[Federal Register Volume 64, Number 211 (Tuesday, November 2, 1999)]
[Proposed Rules]
[Pages 59246-59378]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-27741]



[[Page 59245]]

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Part II





Environmental Protection Agency





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40 CFR Parts 141 and 142



National Primary Drinking Water Regulations; Radon-222; Proposed Rule

  Federal Register / Vol. 64, No. 211 / Tuesday, November 2, 1999 / 
Proposed Rules  

[[Page 59246]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 141 and 142

[WH-FRL-6462-8]
RIN 2040-AA94


National Primary Drinking Water Regulations; Radon-222

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of proposed rulemaking.

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SUMMARY: In this action, the Environmental Protection Agency (EPA) is 
proposing a multimedia approach to reducing radon risks in indoor air 
(where the problem is greatest), while protecting public health from 
the highest levels of radon in drinking water. Most radon enters indoor 
air from soil under homes and other buildings. Only approximately 1-2 
percent comes from drinking water. The Agency is proposing a Maximum 
Contaminant Level Goal (MCLG) and National Primary Drinking Water 
Regulations (NPDWR) for radon-222 in public water supplies. Under the 
framework set forth in the 1996 amendments to the SDWA, EPA is also 
proposing an alternative maximum contaminant level (AMCL) and 
requirements for multimedia mitigation (MMM) programs to address radon 
in indoor air. Public water systems (PWS) are defined in the Safe 
Drinking Water Act (SDWA). This proposed rule applies to community 
water systems (CWS), a subset of PWSs. Under the proposed rule, CWSs 
may comply with the AMCL if they are in States that develop an EPA-
approved MMM program or, in the absence of a State program, develop a 
State-approved CWS MMM program. This approach is intended to encourage 
States, Tribes, and CWSs to reduce the health risk of radon in the most 
cost-effective way. The Agency is also proposing a maximum contaminant 
level (MCL) for radon-222, to apply to CWSs in non-MMM States that 
choose not to implement a CWS MMM program. The proposal also includes 
monitoring, reporting, public notification, and consumer confidence 
report requirements for radon-222 in drinking water.

DATES: EPA must receive public comments, in writing, on the proposed 
regulations by January 3, 2000.

ADDRESSES: You may send written comments to the Radon-222, W-99-08 
Comments Clerk, Water Docket (MC-4101); U.S. Environmental Protection 
Agency; 401 M Street, SW., Washington, DC 20460. Comments may be hand-
delivered to the Water Docket, U.S. Environmental Protection Agency; 
401 M Street, SW., East Tower Basement, Washington, DC 20460. Comments 
may be submitted electronically to [email protected]. Electronic 
comments must be submitted as an ASCII, WP6.1, or WP8 file avoiding the 
use of special characters and any form of encryption. Electronic 
comments must be identified by the docket number W-99-08. Comments and 
data will also be accepted on disks in WP6.1, WP8, or ASCII format. 
Electronic comments on this action may be filed online at many Federal 
Depository libraries.
    Please submit a copy of any references cited in your comments. 
Facsimiles (faxes) cannot be accepted. EPA would appreciate one 
original and three copies of your comments and enclosures (including 
any references). Commenters who would like EPA to acknowledge receipt 
of their comments should include a self-addressed, stamped envelope.
    The proposed rule and supporting documents, including public 
comments, are available for review in the Water Docket at the address 
listed previously. The Docket also has several of the key supporting 
documents electronically available as PDF files. For information on how 
to access Docket materials, please call (202) 260-3027 between 9 a.m. 
and 3:30 p.m. Eastern Time, Monday through Friday.

FOR FURTHER INFORMATION CONTACT: For general information on radon in 
drinking water, contact the Safe Drinking Water Hotline, phone (800) 
426-4791. The Safe Drinking Water Hotline is open Monday through 
Friday, excluding Federal holidays, from 9 a.m. to 5:30 p.m. Eastern 
Time. For technical inquiries regarding the proposed regulations, 
contact Sylvia Malm, Office of Ground Water and Drinking Water, U.S. 
Environmental Protection Agency (mailcode 4607), 401 M Street, SW, 
Washington DC, 20460. Phone: (202) 260-0417. E-mail: 
[email protected]. For inquiries regarding the proposed multimedia 
mitigation program, contact Anita Schmidt, Office of Radiation and 
Indoor Air, U.S. Environmental Protection Agency, (mailcode 6609J), 401 
M Street, S.W, Washington, DC, 20460. Phone: (202) 564-9452. E-mail: 
[email protected]. For general information on radon in indoor air, 
contact the Radon Hotline at 1-800-SOS-RADON (1-800-767-7236).

SUPPLEMENTARY INFORMATION:

Potentially Regulated Entities

    Potentially regulated entities include community water systems 
using ground water or mixed ground and surface water.
    The following table lists potentially regulated entities. This 
table is not intended to be exhaustive, but rather provides a guide for 
readers regarding entities likely to be regulated by this action. This 
table lists the types of entities that EPA is now aware of that could 
potentially be regulated by this action. Other entities not listed in 
the table could also be regulated. To determine whether your 
organization is affected by this action, you should carefully examine 
the proposed applicability criteria in section 40 CFR parts 
141.20(b)(1) and Section IV of the preamble. If you have questions 
regarding the applicability of this action to a particular entity, 
consult Sylvia Malm who is listed in the preceding FOR FURTHER 
INFORMATION CONTACT section.

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                                               Examples of potentially
                 Category                        regulated entities
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Industry..................................  Privately owned/operated
                                             community water supply
                                             systems using ground water
                                             or mixed ground water and
                                             surface water.
State, Tribal, and Local Government.......  State, Tribal, or local
                                             government-owned/operated
                                             water supply systems using
                                             ground water or mixed
                                             ground water and surface
                                             water.
Federal Government........................  Federally owned/operated
                                             community water supply
                                             systems using ground water
                                             or mixed ground water and
                                             surface water.
------------------------------------------------------------------------

Abbreviations Used in This Proposal

AMCL: Alternative Maximum Contaminant Level
BAT: Best Available Technology
BEIR: Committee on the Biological Effects of Ionizing Radiation. The 
Committee on Health Risks of Exposure on Radon that conducted the 
National Research Council Biological Effects of Ionizing Radiation 
(BEIR) VI Study (NAS 1999a). The committee is formed by the Radiation 
Effect Research/Commission on Life Sciences/National Research Council/
National Academy of Sciences.
CFR: Code of Federal Regulations
CWS: Community Water System
EF: Equilibrium Factor
EPA: U.S. Environmental Protection Agency
FR: Federal Register
GAC: Granular Activated Carbon

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HRRCA: Health Risk Reduction and Cost Analysis
IOC: Inorganic Contaminant
LSC: Liquid Scintillation Counting
MCL: Maximum Contaminant Level
MCLG: Maximum Contaminant Level Goal
MMM: Multimedia Mitigation
NAS: National Academy of Sciences
NAS Radon in Drinking Water Committee: The Committee on Risk Assessment 
of Exposure to Radon of the Drinking Water that conducted the National 
Research Council Risk Assessment of Radon in Drinking Water Study (NAS 
1999b). The committee is formed by the Board of Radiation Effect 
Research of the Commission on Life Sciences of the National Research 
Council, National Academy of Sciences.
NELAC: National Environmental Laboratory Accreditation Conference
NIST: National Institute of Standards and Technology
NIRS: National Inorganics and Radionuclides Survey
NPDWR: National Primary Drinking Water Regulation
NPRM: Notice of Proposed Rulemaking
NTNC: Non-Transient, Non-Community
OGWDW: Office of Ground Water and Drinking Water
OMB: Office of Management and Budget
PBMS: Performance-Based Measurement System
PE: Performance Evaluation
PT: Proficiency Testing
POE: Point-of-Entry
POU: Point-of-Use
PRA: Paperwork Reduction Act
PWS: Public Water System
pCi/L: Picocuries per Liter
RFA: Regulatory Flexibility Act
SAB: Science Advisory Board
SBA: Small Business Administration
SBO: Small Business Ombudsman
SBREFA: Small Business Regulatory Enforcement and Fairness Act
SDWA: Safe Drinking Water Act
SDWIS: Safe Drinking Water Information System
SIRG: State Indoor Radon Grant
SSCT: Small Systems Compliance Technology
SSVT: Small Systems Variance Technology
SMF: Standardized Monitoring Framework
UMRA: Unfunded Mandates Reform Act
URTH: Unreasonable Risks to Health
WL: Working Level
WLM: Working Level Month

Table of Contents

I. Summary: What Does Today's Proposed Rulemaking Mean for My Water 
System?
    A. Why is EPA Proposing to Regulate Radon in Drinking Water?
    B. What is Radon?
    C. What are the Health Concerns from Radon in Air and Water?
    D. Does this Regulation Apply to My Water System?
    E. How Will this Regulation Protect Public Health?
    F. How Will the Multimedia Mitigation (MMM) Program Work?
    G. What are the Proposed Limits for Radon in Drinking Water?
    H. What is the Proposed Best Available Technology (BAT) for 
Treating Radon in Drinking Water?
    I. What Analytical Methods are Recommended?
    J. Where and How Often Must I Test My Water for Radon?
    K. May I Use Point-of-Use (POU) Devices, Point-of-Entry (POE) 
Devices, or Bottled Water to Comply with this Regulation?
    L. May I Get More Time or Use a Cheaper Treatment? Variances and 
Exemptions
    M. What are State Primacy, Record Keeping, and Reporting 
Requirements?
    N. How are Tribes Treated in this Proposal?

Statutory Requirements and Regulatory History

II. What Does the Safe Drinking Water Act Require the EPA to Do When 
Regulating Radon in Drinking Water?
    A. Withdraw the 1991 Proposed Regulation for Radon
    B. Arrange for a National Academy of Sciences Risk Assessment.
    C. Set an MCLG, MCL, and BAT for Radon-222
    D. Set an Alternative MCL (AMCL) and Develop Multimedia 
Mitigation (MMM) Program Plan Criteria
    E. Evaluate Multimedia Mitigation Programs Every Five Years
III. What Actions Has EPA Taken on Radon in Drinking Water Prior to 
This Proposal?
    A. Regulatory Actions Prior to 1991
    B. The 1991 NPRM
    C. 1994 Report to Congress: Multimedia Risk and Cost Assessment 
of Radon
    D. 1997 Withdrawal of the 1991 NPRM for Radon-222
    E. 1998 SBREFA Small Business Advocacy Review Panel for Radon
    F. 1999 HRRCA for Radon in Drinking Water

Requirements

IV. To Which Water Systems Does this Regulation Apply?
V. What is the Proposed Maximum Contaminant Level Goal (MCLG) for 
Radon?
    A. Approach to Setting the MCLG
    B. MCLG for Radon in Drinking Water
VI. What Must a State or Community Water System Have In Its 
Multimedia Mitigation Program Plan?
    A. What are the Criteria?
    B. Why Will MMM Programs Get Risk Reduction Equal or Greater 
Than Compliance with the MCL?
    C. Implementation of an MMM Program in Non-Primacy States
    D. Implementation of the MMM Program in Indian Country
    E. CWS Role in State MMM Programs
    F. Local CWS MMM Programs in Non-MMM States and State Role in 
Approval of CWS MMM Program Plans
    G. CWS Role in Communicating to Customers
    H. How Did EPA Develop These Criteria?
    I. Background on the Existing EPA and State Indoor Radon 
Programs
VII. What are the Requirements for Addressing Radon in Water and 
Radon in Air? MCL, AMCL and MMM
    A. Requirements for Small Systems Serving 10,000 People or Less
    B. Requirements for Large Systems Serving More Than 10,000 
People
    C. State Role in Approval of CWS MMM Program Plans
    D. Background on Selection of MCL and AMCL
    E. Compliance Dates
VIII. What are the Requirements for Testing for and Treating Radon 
in Drinking Water?
    A. Best Available Technologies (BATs), Small Systems Compliance 
Technologies (SSCTs), and Associated Costs
    B. Analytical Methods
    C. Laboratory Approval and Certification
    D. Performance-Based Measurement System (PBMS)
    E. Proposed Monitoring and Compliance Requirements for Radon
IX. State Implementation
    A. Special State Primacy Requirements
    B. State Record Keeping Requirements
    C. State Reporting Requirements
    D. Variances and Exemptions
    E. Withdrawing Approval of a State MMM Program
X. What Do I Need to Tell My Customers? Public Information 
Requirements
    A. Public Notification
    B. Consumer Confidence Report

Risk Assessment and Occurrence

XI. What is EPA's Estimate of the Levels of Radon in Drinking Water?
    A. General Patterns of Radon Occurrence
    B. Past Studies of Radon Levels in Drinking Water
    C. EPA's Most Recent Studies of Radon Levels in Ground Water
    D. Populations Exposed to Radon in Drinking Water
XII. What Are the Risks of Radon in Drinking Water and Air?
    A. Basis for Health Concern
    B. Previous EPA Risk Assessment of Radon in Drinking Water
    C. NAS Risk Assessment of Radon in Drinking Water
    D. Estimated Individual and Population Risks
    E. Assessment by National Academy of Sciences: Multimedia 
Approach to Risk Reduction

Economics and Impacts Analysis

XIII. What is the EPA's Estimate of National Economic Impacts and 
Benefits?
    A. Safe Drinking Water Act (SDWA) Requirements for the HRRCA
    B. Regulatory Impact Analysis and Revised Health Risk Reduction 
and Cost Analysis (HRRCA) for Radon

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    C. Baseline Analysis
    D. Benefits Analysis
    E. Cost Analysis
    F. Economic Impact Analysis
    G. Weighing the Benefits and Costs
    H. Response to Significant Public Comments on the February 1999 
HRRCA
XIV. Administrative Requirements
    A. Executive Order 12866: Regulatory Planning and Review
    B. Regulatory Flexibility Act (RFA)
    C. Unfunded Mandates Reform Act (UMRA)
    D. Paperwork Reduction Act (PRA)
    E. National Technology Transfer and Advancement Act (NTTAA)
    F. Executive Order 12898: Environmental Justice
    G. Executive Order 13045: Protection of Children from 
Environmental Health Risks and Safety Risks
    H. Executive Order on Federalism
    I. Executive Order 13084: Consultation and Coordination with 
Indian Tribal Governments
    J. Request for Comments on Use of Plain Language

Stakeholder Involvement

XV. How has the EPA Provided Information to Stakeholders in 
Development of this NPRM?
    A. Office of Ground Water and Drinking Water Website
    B. Public Meetings
    C. Small Entity Outreach
    D. Environmental Justice Initiatives
    E. AWWA Radon Technical Work Group

Background

XVI. How Does EPA Develop Regulations to Protect Drinking Water?
    A. Setting Maximum Contaminant Level Goal and Maximum 
Contaminant Level
    B. Identifying Best Available Treatment Technology
    C. Identifying Affordable Treatment Technologies for Small 
Systems
    D. Requirements for Monitoring, Quality Control, and Record 
Keeping
    E. Requirements for Water Systems to Notify Customers of Test 
Results if Not in Compliance
    F. Approval of State Drinking Water Programs to Enforce Federal 
Regulations
XVII. Important Technical Terms
XVIII. References

Appendix I to the Preamble: What are the Major Public Comments on the 
1991 NPRM and How has the EPA Addressed Them in this Proposal?

    A. General Issues
    B. Statutory Authority and Requirements
    C. Radon Occurrence
    D. Radon Exposure and Health Effects
    E. Maximum Contaminant Level
    F. Analytical Methods
    G. Treatment Technologies and Cost
    H. Compliance Monitoring

I. Summary: What Does Today's Proposed Rulemaking Mean for My Water 
System?

A. Why Is EPA Proposing To Regulate Radon in Drinking Water?

    The proposed National Primary Drinking Water Regulation (NPDWR) for 
radon in drinking water is based on a multimedia approach designed to 
achieve greater risk reduction by addressing radon risks in indoor air, 
with public water systems providing protection from the highest levels 
of radon in their ground water supplies. The framework for this 
proposal is set out in the Safe Drinking Water Act as amended in 1996 
(SDWA), which provides for a multimedia approach for addressing the 
public health risks from radon in drinking water and radon in indoor 
air from soil. This statutory-based framework reflects the 
characteristics uniquely specific to radon among drinking water 
contaminants: that the relative cost-effectiveness of reducing risk 
from exposure to this contaminant is substantially greater for a non-
drinking water source of exposure--indoor air--than it is from drinking 
water. Accordingly, SDWA directs the Environmental Protection Agency 
(EPA) to promulgate a maximum contaminant level (MCL) for radon in 
drinking water, but also to make available a higher alternative maximum 
contaminant level (AMCL) accompanied by a multimedia mitigation (MMM) 
program to address radon risks in indoor air. Further, in setting the 
MCL, EPA is to take into account the costs and benefits of programs 
that control radon in indoor air (SDWA 1412(b)(13)(E)).

B. What Is Radon?

Radon's Physical Properties
    Throughout this preamble, ``radon'' refers to the specific isotope 
radon-222. Radon is a naturally occurring gas formed from the 
radioactive decay of uranium-238. Low concentrations of uranium and its 
other decay products, specifically radium-226, occur widely in the 
earth's crust, and thus radon is continually being generated, even in 
soils in which there is no man-made radioactive contamination. Radon is 
colorless, odorless, tasteless, chemically inert, and radioactive. A 
portion of the radon released through radioactive decay moves through 
air or water-filled pores in the soil to the soil surface and enters 
the air, while some remains below the surface and dissolves in ground 
water (water that collects and flows under the ground's surface).
    Because radon is a gas, when water that contains radon is exposed 
to the air, the radon will tend to be released into the air. Therefore, 
radon is usually present in only low amounts in rivers and lakes. If 
ground water is supplied to a house, radon in the water will tend to be 
released into the air of the house via various water uses. Thus 
presence of radon in drinking water supplies leads to exposure via both 
oral route (ingesting water containing radon) and inhalation route 
(breathing air containing both radon and radon decay products released 
from water used in the house such as for cooking and washing).
    Radon itself also decays, emitting ionizing radiation in the form 
of alpha particles, and transforms into decay products, or ``progeny'' 
radioisotopes. It has a half-life of about four days and decays into 
short-lived progeny. Unlike radon, the progeny are not gases, and can 
easily attach to and be transported by dust and other particles in air. 
The decay of progeny continues until stable, non-radioactive progeny 
are formed. At each step in the decay process, radiation is released.

C. What Are the Health Concerns From Radon in Air and Water?

    National and international scientific organizations have concluded 
that radon causes lung cancer in humans. The primary risk is lung 
cancer from radon entering indoor air from soil under homes. Tap water 
is a smaller source of radon in air; however, breathing radon released 
to air from household water uses also increases the risk of lung 
cancer, and consumption of drinking water containing radon presents a 
smaller risk of internal organ cancers, primarily stomach cancer.
    In most cases, radon in soil under homes is the biggest source of 
exposure and radon from tap water will be a small source of radon in 
indoor air.
    The U.S. Surgeon General has warned that indoor radon (from soil) 
is the second leading cause of lung cancer (USEPA 1988b). The National 
Academy of Sciences (NAS 1999a) estimates that radon from soil causes 
about 15,000 to 22,000 (using two different approaches) lung cancer 
deaths each year in the U.S. If you smoke and your home has high indoor 
radon levels, your risk of lung cancer is especially high. EPA and the 
U.S. Surgeon General recommend testing all homes below the third floor.
    The NAS report mandated by the 1996 SDWA identifies the same unit 
risk associated with radon in drinking water compared with previous EPA 
analyses. Based on the NAS risk assessment and an updated EPA

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occurrence analysis, the Agency estimates that uncontrolled levels of 
radon in public drinking water supplies cause 168 fatal cancers each 
year in the U.S. However, radon in domestic drinking water generally 
contributes a very small part (about 1-2 percent) of total radon 
exposure from indoor air. The NAS estimated that about 89 percent of 
the fatal cancers caused by radon in drinking water were due to lung 
cancer from inhalation of radon released to indoor air, and about 11 
percent were due to stomach cancer from consuming water containing 
radon (NAS 1999b).

D. Does This Regulation Apply to My Water System?

    The regulation for radon in drinking water and the multimedia 
approach proposed in this action would apply to all community public 
water systems (CWSs) that use ground water or mixed ground and surface 
water. The proposed regulation would not apply to non-transient non-
community (NTNC) public water supplies, nor to transient public water 
supplies.

E. How Will This Regulation Protect Public Health?

    Given the much greater potential for risk reduction in indoor air 
and years of experience with radon mitigation programs, EPA expects 
that greater overall risk reduction will result from this proposal than 
from an approach which solely addresses radon in public drinking water 
supplies. The proposed regulation for radon in drinking water is 
intended to promote a more cost-effective multimedia approach to reduce 
radon risks, particularly for small systems with limited resources, and 
to reduce the highest levels of radon in drinking water. This 
determination to have a strong and effective multimedia radon program 
to address radon in indoor air is consistent with the SDWA framework 
for multimedia radon programs and the SDWA expectation that EPA would 
give significant weight to the risk findings of the NAS report, which 
confirm the health risks of radon in drinking water, and the much 
greater risks from radon in indoor air arising from soil under homes.

F. How Will the Multimedia Mitigation (MMM) Program Work?

    The multimedia mitigation (MMM) program is modeled on the National 
Indoor Radon Program implemented by EPA, States and others. That 
program has achieved substantial risk reduction through voluntary 
public action since the release of the original ``A Citizen's Guide to 
Radon'' in 1986 (USEPA 1986, 1992b) and the U.S. Surgeon General's 
recommendation in 1988 that all homes be tested and elevated levels be 
reduced. The program has been successful in achieving indoor radon risk 
reduction through a variety of program strategies, which form the basis 
for EPA's proposed multimedia mitigation program plan criteria. Based 
on the estimated number of existing homes fixed and the number of new 
homes built radon-resistant since the national program began in 1986, 
EPA estimates that under existing Federal and State indoor radon 
programs, a total of more than 2,500 lives will be saved through indoor 
radon risk reduction efforts expected to take place through the year 
2000. Every year the rate of lives saved increases as more existing 
houses with elevated radon levels are fixed and as more new houses are 
built radon-resistant. For the year 2000, EPA estimates that the rate 
of radon-related lung cancer deaths that will be avoided from 
mitigation of existing homes and from homes built radon-resistant (in 
high radon areas) will be about 350 lives saved per year (USEPA 1999i).
    The MMM/AMCL approach is intended to provide a more cost-effective 
alternative to achieve radon risk reduction, by allowing States (or 
community water systems) to address radon in indoor air from the soil 
source, while reducing the highest levels of radon in drinking water. 
It is EPA's expectation that most States will develop State-wide 
multimedia mitigation programs as the most cost-effective approach. 
Most of the States currently have indoor radon programs that are 
addressing radon risk from soil, and can be used as the foundation for 
development of MMM program plans. EPA expects that State indoor radon 
programs will implement MMM programs under agreements with the State 
drinking water programs. The regulatory expectation of community water 
systems serving 10,000 persons or less is that they meet the 
alternative maximum contaminant level (AMCL) and be associated with an 
approved MMM program plan--either developed by the State and approved 
by EPA or developed by the CWS and approved by the State. Tribal CWS 
MMM programs, as well as those in States and Territories that do not 
have drinking water primacy, will be approved by EPA. The same general 
criteria for State MMM program plans would apply to CWSs in developing 
local MMM programs in States that do not have such a program, albeit 
with a local perspective on such criteria and commensurate with the 
unique attributes of small CWSs. EPA expects that MMM program 
strategies for CWSs will be less comprehensive than those of State MMM 
programs, and will need to reflect the local character of the community 
served by the CWS. Strong public participation in the development of 
the CWS MMM program plans will help to ensure this, as well as 
community support for the MMM program. Figures I.1 and I.2 provide a 
conceptual model for the MCL, AMCL, and MMM programs for small and 
large systems.

BILLING CODE 6560-50-P

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[GRAPHIC] [TIFF OMITTED] TP02NO99.000



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[GRAPHIC] [TIFF OMITTED] TP02NO99.001



BILLING CODE 6560-50-C

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    To meet the requirements of SDWA, the risk reduction benefits 
expected to be achieved by MMM programs are to be equal to or greater 
than risk reduction benefits that would be achieved by CWSs complying 
with the MCL. Under SDWA, this means that if all States implemented MMM 
programs they would be expected to result in about 62 cancer deaths 
averted annually, equal to what would be achieved with universal 
compliance with the MCL at 300 pCi/L. Unlike health risk reduction 
benefits gained through water treatment, which remain constant from one 
year to the next, the rate of health benefits from reducing indoor 
radon is cumulative; that is, it steadily increases every year with 
every additional existing home that is mitigated and with every new 
home built radon-resistant. Therefore, MMM programs will use and build 
on the indoor radon program framework to achieve ``equal or greater'' 
risk reduction, rather than focusing efforts on precisely quantifying 
``equivalency'' to the much more limited risk reduction expected to 
occur if community water systems complied with the MCL.

G. What Are the Proposed Limits for Radon in Drinking Water?

    The proposed regulation provides that States may adopt State-wide 
MMM programs and the alternative maximum contaminant level (AMCL) of 
4000 pCi/L. This is the most effective approach for radon risk 
reduction and the one EPA expects the majority of States to adopt. If a 
State has an EPA-approved MMM program plan, CWSs in that State may 
comply with the AMCL. In the absence of an approved State MMM program 
plan the regulatory expectation for small CWSs (those serving 10,000 or 
fewer) is that they comply with a level of 4000 pCi/L in drinking 
water, and develop and implement a State-approved local MMM program 
plan to reduce indoor radon risks arising from soil and rock under 
homes and buildings. Small CWSs may also choose to comply with the MCL 
of 300 pCi/L (and not develop a local MMM program.)
    The AMCL/MMM approach is EPA's regulatory expectation for small 
CWSs because an MMM program and compliance with the AMCL is a much more 
cost-effective way to reduce radon risk than compliance with the 
maximum contaminant level (MCL) of 300 pCi/L. (While EPA believes that 
the MMM approach is preferable for small systems in a non-MMM State, 
small CWSs may, at their discretion, choose the option of meeting the 
MCL instead of developing a local MMM program). Large CWSs (serving a 
population of more than 10,000) must either comply with the proposed 
MCL or comply with the AMCL and implement a State-approved CWS MMM 
program plan (in the absence of an approved State MMM program plan).
    If a State has an approved MMM program plan, the standard for radon 
in drinking water that the State would adopt in order to obtain primacy 
would be 4000 pCi/L.
    Under the proposed requirements, an MMM program plan must address 
four criteria:

1. Public involvement in development of the MMM program plan
2. Quantitative goals for existing homes fixed and new homes built 
radon-resistant
3. Strategies for achieving goals
4. Plan to track and report results

    CWSs must monitor for radon in drinking water according to the 
requirements described in Section VIII of this preamble, and report 
their results to the State. If the State determines that the radon 
level in a CWS is below 300 pCi/L, the system need only continue to 
meet monitoring requirements and is not covered by the requirements 
described in Section VI of this preamble, regarding MMM programs.

H. What Is the Proposed Best Available Technology (BAT) for Treating 
Radon in Drinking Water?

Proposed BAT for Radon Under Section 1412 of the SDWA
    High-performance aeration, as described in Section VIII.A of this 
preamble, is the BAT for all systems. For systems serving 10,000 
persons or fewer, the BAT is high-performance aeration and the Small 
Systems Compliance Technologies, as described in Section VIII.A.
Proposed BAT for Radon Under Section 1415 of the SDWA
    BAT for purposes of variances is the same as BAT under Section 1412 
of the Act.

I. What Analytical Methods Are Recommended?

    EPA is proposing Liquid Scintillation Counting (Standard Method 
7500-Rn) and de-emanation (``Lucas Cell'') as the approved methods. The 
Liquid Scintillation Counting method designated ``D 5072-92'' by the 
American Society for Testing and Materials (ASTM) is being proposed as 
an alternate method.

J. Where and How Often Must I Test My Water for Radon?

    All CWSs that use ground water must monitor for radon. If your 
system relies on ground water or uses ground water to supplement 
surface water during low-flow periods, you must monitor for radon. If 
you are required to monitor for radon you must collect samples for 
analysis at each entry point to the distribution system, after 
treatment and storage. Initially all CWSs using ground water must 
monitor for radon at each entry point to the distribution system 
quarterly for one year. (See Section VII.E for discussion of compliance 
dates). If the results of analyses show that the average of all first 
year samples at any sample site is above the MCL/AMCL, you must 
continue monitoring quarterly at that sampling site until the average 
of four consecutive quarterly samples is below the MCL/AMCL. If the 
results of analyses show that the average of all first year samples at 
each sample site is below the MCL/AMCL, you may reduce monitoring to 
once a year at State discretion at each sample site. If the results 
indicate that the average of the four quarterly samples are close to 
the MCL/AMCL (as discussed next), the State may require you to continue 
monitoring quarterly.
    The State may allow you to reduce monitoring for radon to a 
frequency of once every three-years, if the average from four 
consecutive quarterly samples is less than \1/2\ the MCL/AMCL and the 
State determines that your system is reliably and consistently below 
the MCL/AMCL. However, if a sample collected while monitoring annually 
or less frequently exceeds the radon MCL/AMCL, the monitoring frequency 
must be increased to quarterly until the average of 4 consecutive 
quarterly samples is less than the MCL/AMCL. The State may require the 
collection of a confirmation sample(s) to verify the result of the 
initial sample. In the case of reduced monitoring, if the analytical 
results from any sampling point are found to exceed \1/2\ the MCL/AMCL, 
the State may require you to collect a confirmation sample at the same 
sampling point. The results of the initial sample and the confirmation 
sample(s) will be averaged and the resulting average will be used to 
determine compliance. States may, at their discretion, disregard 
samples that have obvious sampling errors.
    If, after initial monitoring, the State determines that it is 
highly unlikely that radon levels in your system will be above the MCL/
AMCL, the State may grant a waiver reducing monitoring frequency to 
once every nine years. In granting the waiver, the State must take into 
consideration factors such as the geological area of the source water 
and previous analytical results which demonstrate that radon levels do 
not

[[Page 59253]]

occur above the MCL/AMCL. If you are granted a waiver, it remains in 
effect for a nine year period.
    If you monitor for radon after proposal of this rule, you may use 
the data, at the State's discretion, toward satisfying the initial 
sampling requirements for radon. Your monitoring program and the 
methods used to analyze for radon must satisfy the regulations set out 
in the proposal.

K. May I Use Point-of-Use (POU) Devices, Point-of-Entry (POE) Devices, 
or Bottled Water To Comply With This Regulation?

    POE aeration or granular activated carbon (GAC) would be allowable 
for use to achieve compliance with MCLs. While these POE technologies 
are not considered BAT for large systems, they are considered small 
system compliance technologies (SSCTs), and thus may serve as BAT under 
Sections 1412 and 1415 of the Act for systems serving 10,000 persons or 
fewer. Since POU devices are used to treat water at a single tap, radon 
will be released at unacceptable levels from the other non-treated 
taps, including the shower head. For this reason, POU devices do not 
adequately address radon risks and will not be allowed to be used for 
compliance purposes. Likewise, although bottled water reduces ingestion 
risk from radon, it does not reduce radon-related inhalation risks from 
household water. For this reason, compliance determinations based on 
bottled water consumption cannot be used.

L. May I Get More Time or Use a Cheaper Treatment? Variances and 
Exemptions

Variances and Exemptions (Section 1415.a of the SDWA)
    States and Tribes with primary enforcement responsibility 
(``primacy'') may issue a variance under Section 1415(a)(1)(A) of the 
Act to a CWS that cannot comply with an MCL because of source water 
characteristics on condition that the system install the best available 
technology. Under Section 1416 of the Act, primacy entities may exempt 
a CWS from an NPDWR due to ``compelling factors'', subject to the 
restrictions described in the Act. Primacy entities may require systems 
to implement additional interim control measures such as installation 
of additional centralized treatment or POE devices for each customer as 
measures to reduce the health risk before granting a variance or 
exemption. The primacy entity must find that the variance or exemption 
will not pose an ``unreasonable risk to health'', as determined by the 
State or other primacy entity. Guidance for estimating ``unreasonable 
risk to health'' (URTH) values for contaminants, including radon, is 
being developed by EPA and will result in an upcoming publication (a 
draft of the guidance is expected in the Fall of 1999). Preliminary 
information regarding URTH values may be found elsewhere (Orme-Zavaleta 
1992, USEPA 1998f). States must require CWSs to provide POE devices or 
other means, as appropriate to the risks present (i.e., no POU or 
bottled water for volatile contaminants, such as radon), to reduce 
exposure below unreasonable risk to health values before granting a 
variance or exemption.
``Small Systems Variances'' (Section 1415(e) of the SDWA)
    For NPDWRs proposed after the 1996 Amendments to the Act, EPA is 
required to evaluate the affordability and technical feasibility of 
treatment technologies for use as compliance technologies for small 
systems. Three categories of small systems will be considered: those 
serving: (1) 25-500, (2) 501-3,300, and (3) 3,301-10,000 persons. If 
EPA determines that source water conditions exist for one or more small 
water system size categories such that typical small systems within a 
given category will not be able to afford and/or implement a technology 
capable of achieving compliance, then EPA will designate applicable 
``small systems variance technologies'' (SSVTs) capable of achieving 
contaminant levels that are ``protective of public health''. Primacy 
entities may issue small systems variances to eligible CWSs that 
install and properly maintain a listed SSVT. For a small system to be 
eligible for a small systems variance, the primacy entity must 
determine that the system cannot afford to comply through installing 
treatment, finding an alternate source of water, or restructuring/
consolidating.
    EPA has determined that affordable and technically feasible 
technologies exist for radon removal for all classes of small systems. 
Under the 1996 SDWA, if EPA lists at least one small systems compliance 
technology for a given system size category for all source water 
qualities, then it may not list any small systems variance technologies 
for that size category, i.e., small systems compliance technologies and 
variance technologies are mutually exclusive. For this reason, no small 
system will be eligible for a small systems variance for radon under 
the SDWA (Section 1415(e)). Small systems may be eligible for general 
variances (under Section 1415.a of the Act) and/or exemptions on a case 
by case basis. It is also important to emphasize that the presumptive 
regulatory expectation for small systems is an MMM program (in the 
absence of a State MMM program) and compliance with the AMCL of 4000 
pCi/L. Thus, for the vast majority of small systems (those with radon 
levels below 4000 pCi/L), compliance with this proposed rule will not 
involve any treatment of drinking water.

M. What Are State Primacy, Record Keeping, and Reporting Requirements?

    The proposed Radon Rule requires States to adopt several regulatory 
requirements, including public notification requirements, MCL/AMCL for 
radon, and the requirements of Subpart R in the proposed rule. In 
addition, States and eligible Indian tribes will be required to adopt 
several special primacy requirements for the Radon Rule. The proposed 
rule includes additional reporting requirements for MMM program plans. 
The proposed rule also requires States to keep specific records in 
accordance with existing regulations. These requirements are discussed 
in more detail in Section IX of this preamble.

N. How Are Tribes Treated in This Proposal?

    The proposal provides Tribes the option of seeking ``treatment in 
the same manner as a State'' for the purposes of assuming enforcement 
responsibility for a CWS program, and developing and implementing an 
MMM program (see Section VI.C). If a Tribe chooses not to implement an 
EPA-approved MMM program, any tribal CWS may develop an MMM plan for 
EPA approval, under the same criteria described in Section VI.A.

Statutory Requirements and Regulatory History

II. What Does the Safe Drinking Water Act Require the EPA To Do 
When Regulating Radon in Drinking Water?

    The 1996 Amendments to the Safe Drinking Water Act (PL 104-182) 
establish a new charter for public water systems, States, Tribes, and 
EPA to protect the safety of drinking water supplies. (For an overview 
of the general requirements for all drinking water regulations, see 
Section XVI of this preamble). Among other mandates, Congress amended 
Section 1412 of the SDWA to direct EPA to take the following actions 
regarding radon in drinking water.

[[Page 59254]]

A. Withdraw the 1991 Proposed Regulation for Radon

    Congress specified that EPA should withdraw the drinking water 
standards proposed for radon in 1991 (see discussion in Section III.D).

B. Arrange for a National Academy of Sciences Risk Assessment

    The amendments in Section 1412(b)(13)(B) require EPA to arrange for 
the National Academy of Sciences (NAS) to conduct an independent risk 
assessment for radon in drinking water and an assessment of the health 
risk reduction benefits from various mitigation measures to reduce 
radon in indoor air.

C. Set an MCLG, MCL, and BAT for Radon-222

    Congress specified in Section 1412 (b)(13) that EPA should propose 
a new MCLG and NPDWR for radon-222 by August, 1999. EPA is also 
required to finalize the regulation by August, 2000. As a preliminary 
step, EPA was required to publish a radon health risk reduction and 
cost analysis (HRRCA) for possible radon MCLs for public comment by 
February, 1999. As required by SDWA, this analysis addressed: (1) 
Health risk reduction benefits that come directly from controlling 
radon; (2) health risk reduction benefits likely to come from 
reductions in contaminants that occur with radon; (3) costs; (4) 
incremental costs and benefits associated with each MCL considered; (5) 
effects on the general population and on groups within the general 
population likely to be at greater risk; (6) any increased health risk 
that may occur as the result of compliance; and (7) other relevant 
factors, including the quality and extent of the information, the 
uncertainties in the analysis, and factors with respect to the degree 
and nature of the risk.

D. Set an Alternative MCL (AMCL) and Develop Multimedia Mitigation 
(MMM) Program Plan Criteria

    The amendments in Section 1412(b)(13)(F) introduced two new 
elements into the radon in drinking water rule: (1) An Alternative 
Maximum Contaminant Level (AMCL), and (2) radon multimedia mitigation 
(MMM) programs. If the MCL established for radon in drinking water is 
more stringent than necessary to reduce the contribution to radon in 
indoor air from drinking water to a concentration that is equivalent to 
the national average concentration of radon in outdoor air, EPA is 
required to simultaneously establish an AMCL. The AMCL would be the 
standard that would result in a contribution of radon from drinking 
water to radon levels in indoor air equivalent to the national average 
concentration of radon in outdoor air. If an AMCL is established, EPA 
is to publish criteria for State multimedia mitigation (MMM) programs 
to reduce radon levels in indoor air. Section VI of this preamble 
describes what a State or public water system must have in their 
multimedia mitigation program plan.

E. Evaluate Multimedia Mitigation Programs Every Five Years

    Once the MMM programs are established, EPA must re-evaluate them no 
less than every five years (Section 1412(b)(13)(G)). EPA may withdraw 
approval of programs that are not expected to continue to meet the 
requirement of achieving equal or greater risk reduction.

III. What Actions Has EPA Taken on Radon in Drinking Water Prior to 
This Proposal?

A. Regulatory Actions Prior to 1991

    Section 1412 of the SDWA, as amended in 1986, required the EPA to 
publish Maximum Contaminant Level Goals (MCLGs) and to promulgate 
NPDWRs for contaminants that may cause an adverse effect on human 
health and that are known or anticipated to occur in public water 
supplies. On September 30, 1986, EPA published an advance notice of 
proposed rulemaking (ANPRM) (51 FR 34836) concerning radon-222 and 
other radionuclides. The ANPRM discussed EPA's understanding of the 
occurrence, health effects, and risks from these radionuclides, as well 
as the available analytical methods and treatment technologies, and 
sought additional data and public comment on EPA's planned regulation.
    EPA's Science Advisory Board (SAB) reviewed the ANPRM and the four 
draft criteria documents that supported it prior to publication of the 
ANPRM in the Federal Register. EPA subsequently revised the criteria 
documents and resubmitted them to the SAB for review during the summer 
of 1990. EPA then revised the criteria documents based on this 
additional round of SAB review and presented a summary of the SAB 
comments and the Agency's responses in a 1991 Notice of Proposed 
Rulemaking (NPRM).

B. The 1991 NPRM

    On July 18, 1991 (56 FR 33050), EPA proposed a NPDWR for radon and 
the other radionuclides addressed in the 1986 ANPRM. The 1991 notice, 
which built on and updated the information assembled for the 1986 
ANPRM, proposed an MCLG, an MCL, BAT, and monitoring, reporting, and 
public notification requirements for radon in public water supplies. 
The proposed MCLG was zero, the proposed MCL was 300 pCi/L, and the 
proposed BAT was aeration. Under the proposed rule, all CWSs and 
NTNCWSs relying on ground water would have been required to monitor 
radon levels quarterly at each point of entry to the distribution 
system. Compliance monitoring requirements were based on the arithmetic 
average of four quarterly samples. The 1991 proposed rule required 
systems with one or more points of entry out of compliance to treat 
influent water to reduce radon levels below the MCL or to secure water 
from another source below the MCL.
    The proposed rule was accompanied by an assessment of regulatory 
costs and economic impacts, as well as an assessment of the risk 
reduction associated with implementation of the MCL. EPA estimated the 
following potential impacts from the 1991 proposed MCL:
     An estimated lifetime cancer risk of about two cancers for 
every 10,000 persons exposed to radon in drinking water.
     Avoidance of about 80 cancer cases per year.
     About 27,000 public water systems affected.
     A total annual cost of about $180 million.
    The Agency received substantial comments on the proposal and its 
supporting analyses from States, water utilities, and other stakeholder 
groups. EPA has included in Appendix I of this preamble a summary of 
major public comments on the 1991 NPRM and how EPA subsequently 
addressed those comments.

C. 1994 Report to Congress: Multimedia Risk and Cost Assessment of 
Radon

    In 1992, Congress directed EPA to report on the multimedia risks 
from exposure to radon, the costs to control this exposure, and the 
risks from treating to remove radon. EPA's 1994 Report to Congress 
(USEPA 1994a) estimates the risk, fatal cancer cases, cancer cases 
avoided and costs for mitigating radon in water and in indoor air. The 
Report found that cancer risks from radon in both air and water are 
high. While radon risk in air typically far exceeds that in water, the 
cancer risk from radon in water is higher than the cancer risk 
estimated to result from any other currently regulated drinking water 
contaminant.
    EPA conducted a quantitative uncertainty analysis of the risks 
associated with exposure to radon in

[[Page 59255]]

drinking water. This analysis, reviewed by EPA's SAB at the direction 
of Congress, found that:
     People are exposed to waterborne radon in three ways: (1) 
From ingesting radon dissolved in water; (2) from inhaling radon gas 
released from water during household use; and (3) from inhaling radon 
progeny derived from radon released from water.
     The estimated total U.S. cancer fatalities per year from 
unregulated waterborne radon via all three routes of exposure were 192, 
with a range from about 51 to 620.
     The estimated annual cost was $272 million.
    The 1994 Report to Congress noted that the regulated industry 
estimated considerably higher costs than EPA for a 300 pCi/L MCL. For 
example, in October 1991 the American Water Works Association (AWWA) 
estimated national costs at $2.5 billion/year (for discussion of this 
issue, see Section G of the Appendix to this preamble). The final part 
of the report included the SAB's comments on each analysis presented 
and an EPA discussion of the issues raised by the SAB.

D. 1997 Withdrawal of the 1991 NPRM for Radon-222

    As required by the SDWA as amended, EPA withdrew the MCLG, MCL, and 
monitoring, reporting, and public notification requirements proposed in 
1991 for radon-222 on August 6, 1997 (62 FR 42221). No other provision 
of the 1991 proposal was affected by this withdrawal.

E. 1998 SBREFA Small Business Advocacy Review Panel for Radon

    In 1998, EPA convened a Small Business Advocacy Review Panel to 
address the radon rule, in accordance with the Regulatory Flexibility 
Act (RFA) as amended by the Small Business Regulatory Enforcement 
Fairness Act (SBREFA). The Panel of representatives from EPA, the 
Office of Management and Budget's Office of Information and Regulatory 
Affairs, and the Small Business Administration's Office of Advocacy 
reviewed technical background information related to this rulemaking, 
and reviewed comments provided by small business and government 
entities affected by this rule. The Panel made recommendations in a 
final report to the Administrator which included a discussion of how 
the Agency could accomplish its environmental goals while minimizing 
impacts to small entities. For additional details, see Section XIV.B of 
this proposal.

F. 1999 HRRCA for Radon in Drinking Water

    EPA published the Health Risk Reduction and Cost Analysis required 
by the SDWA on February 26, 1999 (64 FR 9559), and took public comment 
for 45 days. EPA held a one-day public meeting in Washington, D.C. on 
March 16, 1999, to present the HRRCA and the latest MMM framework, and 
discuss stakeholder questions and issues. For details of the contents 
of the HRRCA and EPA's response to significant public comment, see 
Section XIII of this preamble.

Requirements

IV. To Which Water Systems Does This Regulation Apply?

    The SDWA directs EPA to develop national primary drinking water 
regulations (NPDWRs) that apply to public water systems (PWSs). The 
statute defines a PWS as a system that provides water to the public for 
human consumption if such system has at least 15 service connections or 
regularly serves at least 25 individuals (Section 1401(4)(A)). EPA's 
regulations at 40 CFR 141.2 define different types of PWSs. A community 
water system (CWS) serves at least 15 service connections used by year 
round residents or regularly serves at least 25 year-round residents. A 
non-community system does not serve year-round residents; rather, it 
(1) regularly serves at least 25 of the same persons over 6 months of 
the year (a ``non-transient'' system such as a restaurant or church) or 
(2) does not serve at least 25 of the same persons over 6 months of the 
year (a ``transient'' system such as a campground or service station).
    The regulation for radon in drinking water and the multimedia 
approach for reduction of radon in indoor air (MMM program) proposed in 
this notice applies only to CWSs that use ground water or mixed ground 
and surface water (see following discussion regarding ``mixed'' 
supplies). The proposed regulation does not apply to transient water 
systems because most people who use such facilities do so only 
occasionally (e.g., travelers). There is no evidence that such short-
term exposure to radon would cause acute illness. The data on which 
health risks from radon were determined for this rulemaking reflect 
long-term exposure (see chapter 3 of the RIA (USEPA 1999f) HRRCA 
section that discusses calculation of risk). And, as discussed next in 
the context of non-transient non-community systems, even workers at 
transient facilities who regularly drink the water would be expected to 
have much less exposure than persons served by community water systems. 
For these reasons, the proposed rule does not cover transient systems.
    The proposed regulation also does not apply to non-transient non-
community (NTNC) water systems. EPA has determined that the risks posed 
to persons served by NTNC systems (such as factories, hospitals, and 
schools with their own drinking water wells) are substantially less 
than the risks to persons served by community water systems.
    The Agency recently completed a preliminary analysis of radon 
occurrence (using data provided by six States), exposure and risk at 
NTNC public water systems. Results from this preliminary analysis 
indicate that even though radon concentrations are likely to be about 
60 percent higher at NTNC locations than at locations served by a 
community water system, the lifetime average risk to individuals who 
work or attend school in buildings served by a groundwater-based NTNC 
system is probably about 17 percent of the average risk to a worker 
(and 6.7 percent of the average risk to a student) exposed in a home 
served by a community ground water system. The reason that risks are 
lower in the NTNC setting than the residential setting is that people 
who are exposed at NTNC locations spend a smaller fraction of their 
lifetime there than in the home. Further, in the particular case of 
students most do not spend their entire school years in the same 
school. EPA also notes that there is limited data in this area, and 
more information is needed on how water is used in NTNC facilities and 
on the contribution NTNC water use makes to radon inhalation risk. In 
addition, the overall population served by NTNC PWSs is relatively 
small (5.2 million vs. 89.7 million in homes served by CWSs using 
ground water (USEPA 1999b)).
    EPA acknowledges that the SDWA applies to all public water systems. 
However, EPA believes that limiting the applicability of the radon rule 
to community water systems where the risk from radon exposure is the 
greatest meets a major goal of Congress in enacting the 1996 amendments 
to the Act-to focus regulations on the most significant problems. In 
the Conference Report adopting the 1996 amendments, Congress finds that 
``more effective protection of public health requires--a Federal 
commitment to set priorities that will allow scarce Federal, State, and 
local resources to be targeted toward the drinking water problems of 
greatest public health concerns. `` H. Rep. 104-182, Sec. 3. Moreover, 
Congress specifically directed EPA in setting the NPDWRs for radon to 
take into

[[Page 59256]]

consideration the costs and benefits of control programs for radon from 
other sources. EPA has used this authority in this proposal to set the 
MCL at 300 pCi/L and to encourage small systems to implement the MMM 
program and comply with the AMCL. In both circumstances, EPA took into 
account the fact that programs to control radon in indoor air promise 
greater benefits at considerably less cost. EPA believes this cost-
effectiveness factor is also relevant in determining the applicability 
of the radon rule. EPA's preliminary analysis of the risk associated 
with exposure to radon from NTNC systems is that it is much less than 
the risk from exposure from CWSs. For this reason, EPA has determined 
that it is not cost-effective to regulate these systems.
    However, it is important to note that this analysis is based on 
limited occurrence and exposure data. In particular, relatively little 
is known about the transfer factor for release of radon from water into 
indoor air at NTNC locations, or about the equilibrium factor affecting 
the amount of radon in indoor air at such locations. The calculations 
done by EPA to date have assumed that certain values for these 
parameters at NTNC locations are similar to those in homes, although 
the data are limited.
    The EPA is soliciting comment on the proposal to exclude NTNC PWSs 
from the radon regulation. EPA is soliciting comments on the Agency's 
preliminary analysis of radon exposure in NTNC PWSs, as well as any 
additional data on key parameters, including data on the release of 
radon from drinking water in the types of buildings (e.g., restaurants, 
factories, churches, etc.) supplied by NTNC PWSs, and occurrence of 
radon in NTNC PWSs. If information by commenters shows a greater 
opportunity for risk reduction than identified in its initial analysis, 
EPA may make the final radon rule applicable to NTNC PWSs without 
further public comment.
    With regard to systems using mixed ground and surface water, 
current regulations require that all systems that use any amount of 
surface water as a source be categorized as surface water systems. This 
classification applies even if the majority of water in a system is 
from a ground water source. Data currently in SDWIS does not identify 
how many of these mixed systems exist although this information would 
help the Agency to better understand regulatory impacts. To the extent 
that systems correctly classified by SDWIS as surface water systems 
also use ground water that may exceed the MCL/AMCL for radon, the costs 
and benefits of the current proposal will be underestimated.
    EPA is investigating ways to identify how many mixed systems exist 
and how many mix their ground and surface water at the same entry point 
or at separate entry points within the same distribution systems. For 
example, a system may have several plants/entry points that feed the 
same distribution system. One of these entry points may mix and treat 
surface water with ground water prior to its entry into the 
distribution system. Another entry point might use ground water 
exclusively for its source while a different entry point would 
exclusively use surface water. However, all three entry points would 
supply the same system classified in SDWIS as surface water.
    One method EPA could use to address this issue would be to analyze 
Community Water System Survey (CWSS) data then extrapolate this 
information to SDWIS to obtain a national estimate of mixed systems. 
CWSS data, from approximately 1,900 systems, breaks down sources of 
supply at the level of the entry point to the distribution system and 
further subdivides flow by source type. The Agency could use the 
national estimate of mixed systems to regroup surface water systems for 
certain impact analyses when regulations only impact one type of 
source. The Agency requests comment on this methodology and its 
applicability for use in regulatory impact analyses.

V. What Is the Proposed Maximum Contaminant Level Goal for Radon?

A. Approach To Setting the Maximum Contaminant Level Goal (MCLG)

    Under Section 1412(b)(4) of the SDWA, the EPA must establish 
maximum contaminant level goals (MCLG) at the level at which no known 
or anticipated adverse effects on the health of persons occur, and 
which allow an adequate safety margin. Section 1412(b)(13) requires the 
Administrator to set an MCLG for radon in drinking water.

B. MCLG for Radon in Drinking Water

    As described in Section XII of this preamble, radon is a documented 
human carcinogen, classified by EPA as a Group A carcinogen (i.e., 
there is sufficient evidence of a causal relationship between exposure 
to radon and lung cancer in humans). Radon is classified as a known 
human carcinogen based on data from epidemiological studies of 
underground miners. This finding is supported by a consensus of opinion 
among national and international health organizations. The 
carcinogenicity of radon has been well established by the scientific 
community, including the Biological Effects of Ionizing Radiation (BEIR 
VI) Committee of the National Academy of Sciences (NAS 1999a), the 
National Institute of Environmental Health Sciences, U.S. Department of 
Health and Human Services, the World Health Organization's 
International Agency for Research on Cancer (IARC 1988), the 
International Commission on Radiological Protection (ICRP 1987), and 
the National Council on Radiation Protection and Measurement (NCRP 
1984). In addition, the Centers for Disease Control, the American Lung 
Association, the American Medical Association, the American Public 
Health Association and others have recognized radon as a significant 
public health problem.
    Based on the well-established human carcinogenicity of radon, and 
of ionizing radiation in general, the Agency is proposing an MCLG of 
zero for radon in drinking water. This decision is also supported by 
the NAS' current recommendation for a linear non-threshold relationship 
between exposure to radon and cancer in humans. In the BEIR VI report 
(NAS 1999a), the NAS concluded that there is good evidence that a 
single alpha particle (high-linear energy transfer radiation) can cause 
major genomic changes in a cell, including mutation and transformation 
that potentially could lead to cancer. They noted that even if 
substantial repair of the genomic damage were to occur, ``the passage 
of a single alpha particle has the potential to cause irreparable 
damage in cells that are not killed.'' Given the convincing evidence 
that most cancers originate from damage to a single cell, the committee 
went on to conclude that ``On the basis of these [molecular and 
cellular] mechanistic considerations, and in the absence of credible 
evidence to the contrary, the committee adopted a linear non-threshold 
model for the relationship between radon exposure and lung-cancer risk. 
However, the BEIR VI committee recognized that it could not exclude the 
possibility of a threshold relationship between exposure and lung 
cancer risk at very low levels of radon exposure.'' The NAS committee 
on radon in drinking water (NAS 1999b) reiterated the finding of the 
BEIR VI committee's comprehensive review of the issue, that a 
``mechanistic interpretation is consistent with linear non-threshold 
relationship between radon exposure and cancer risk''. The committee 
noted that the ``quantitative

[[Page 59257]]

estimation of cancer risk requires assumptions about the probability of 
an exposed cell becoming transformed and the latent period before 
malignant transformation is complete. When these values are known for 
singly hit cells, the results might lead to reconsideration of the 
linear no-threshold assumption used at present.'' EPA recognizes that 
research in this area is on-going but is basing its regulatory 
decisions on the best currently available science and recommendations 
of the NAS that support use of a linear non-threshold relationship. For 
additional information on this issue see Section XII.C.3. ``Biologic 
Basis of Risk Estimation'' of this preamble.

VI. What Must a State or Community Water System Have in Its 
Multimedia Mitigation Program Plan?

    Today's proposed rule provides States (as defined in Section 1401 
of the SDWA) with alternatives for controlling radon exposure. States 
can develop a MMM program for the reduction of the higher risk of radon 
in indoor air together with an alternative MCL (AMCL) of 4000 pCi/L to 
address the highest levels of exposure from radon in drinking water. If 
a State does not choose this option, the community water systems (CWS) 
in that State must develop and implement local MMM program plans or 
comply with an MCL of 300 pCi/L. See Section VII for information on the 
regulatory expectations for CWSs.

A. What Are the Criteria?

1. Overview
    EPA has identified four criteria that State MMM program plans are 
required to meet to be approved by EPA. MMM program plans developed by 
Indian tribes will be reviewed by EPA, according to these same 
criteria. CWSs developing local MMM programs are also subject to these 
criteria. These four criteria are: public participation, setting 
quantitative goals, strategies for achieving goals, and a plan to track 
and report results.
    The criteria are based on a number of factors. Foremost, the 
criteria reflect the elements found in successful voluntary action 
programs for radon in indoor air that have been underway for more than 
a decade. It is estimated that at the end of the year 2000, voluntary 
programs to test homes and mitigate elevated radon levels in indoor air 
and to encourage the construction of ``radon-resistant'' new homes will 
have saved some 2500 lives; and, there is much more that can be done. 
In the 1999 BEIR VI report (NAS 1999a), NAS concluded that 5,000 to 
7,000 cancer cases (using two different methods) could be avoided 
annually if all homes were below EPA's voluntary radon action level of 
4 pCi/L of air. Incorporating these program elements into the criteria 
required for the MMM programs builds on successful efforts and can be 
expected to result in an even greater number of lives saved as more 
States adopt programs and existing programs are strengthened and 
expanded.
    EPA has developed criteria that allow considerable flexibility for 
those developing and expanding programs. EPA was urged by States and 
other stakeholders to avoid prescribing the specific elements of the 
MMM program in a ``one size fits all'' approach. States and CWSs 
adopting MMM programs will be required to set quantitative goals for 
mitigating elevated levels of radon in indoor air of existing homes and 
building radon-resistant new homes, and to initiate strategies to 
promote and increase these activities. However, there are requirements 
that will be new to many of the State indoor radon programs. Those 
adopting MMM programs will be required to involve the public in a 
number of important (and on-going) ways, and to track and report 
results from the implementation of the programs. With these additional 
elements, both the affected public and EPA will be able to assess the 
success of the MMM programs. Stakeholder input and EPA's experience 
with the national voluntary program and the State indoor radon programs 
led EPA to conclude that these criteria will provide the basis for a 
program that meets the statutory directive for equal or greater risk 
reduction benefits.
    The Agency also considered equity-related issues concerning the 
potential impacts of MMM program implementation. There is no factual 
basis to indicate that minority and low income or other communities are 
more or less exposed to radon in drinking water than the general 
public. However, some stakeholders expressed more general concerns 
about equity in radon risk reduction that could arise from the MMM/AMCL 
framework outlined in SDWA. One concern is the potential for an uneven 
distribution of risk reduction benefits across water systems and 
society. Under the proposed framework for the rule, customers of CWSs 
complying with the AMCL could be exposed to a higher level of radon in 
drinking water than if the MCL were implemented, though this level 
would not be higher than the background concentration of radon in 
ambient air. However, these CWS customers could also save the cost, 
through lower water rates, of installing treatment technology to comply 
with the MCL. Under the proposed regulation, CWSs and their customers 
have the option of complying with either the AMCL (associated with a 
State or local MMM program) or the MCL. EPA believes it is important 
that these issues and choices be considered in an open public process 
as part of the development of MMM program plans. Therefore, EPA has 
incorporated requirements into the proposed rule that provide a 
framework for consideration of equity concerns with the MMM/AMCL. 
First, the proposed rule includes requirements for public participation 
in the development of MMM program plans, as well as for notice and 
opportunity for public comment. EPA believes that the requirement for 
public participation will result in State and CWS program plans that 
reflect and meet their different constituents' needs and concerns and 
that equity issues can be most effectively dealt with at the State and 
local levels with the participation of the public. In developing their 
MMM program plans, States and CWSs are required to document and 
consider all significant issues and concerns raised by the public. EPA 
expects and strongly recommends that States and CWSs pay particular 
attention to addressing any equity concerns that may be raised during 
the public participation process. In addition, EPA believes that 
providing CWS customers with information about the health risks of 
radon and on the AMCL and MMM program option will help to promote 
understanding of the health risks of radon in indoor air, as well as in 
drinking water, and help the public to make informed choices. To this 
end, EPA is requiring CWSs to alert consumers to the MMM approach in 
their State in consumer confidence reports issued between publication 
of the final radon rule and the compliance dates for implementation of 
MMM programs. This will include information about radon in indoor air 
and drinking water and where consumers can get additional information.
    EPA is encouraging the States to elect to develop and implement 
State-wide MMM program plans. Since almost all States currently have 
State indoor radon programs, EPA considers the States to be best 
positioned to develop strong MMM program plans that, when implemented, 
will be expected to achieve equal or greater radon risk reduction when 
compared to compliance with the MCL. For example, a State-wide plan can 
take into account the within-State variations in indoor radon 
potential, the differences in radon

[[Page 59258]]

levels in drinking water, the experienced coalitions and cooperative 
partners that have been working to promote public action on indoor 
radon, the technical expertise of State drinking water and indoor radon 
programs, and many other factors. EPA expects that the States will be 
best positioned to develop MMM program plans that are robust and 
credible in terms of the level of public participation in the 
development and review process, the goals that are to be achieved from 
implementation of MMM, and the program strategies to be used.
    In the development of State MMM program plans meeting EPA's 
criteria and in the implementation of the State's MMM program plan, EPA 
expects and strongly recommends that the State's programs responsible 
for drinking water and for indoor radon coordinate and collaborate on 
their efforts. This is particularly important because of the uniqueness 
of the MMM/AMCL approach which addresses radon risk reduction in 
drinking water and in indoor air in a multimedia manner that is outside 
the normal regulatory structure for drinking water. Both programs have 
important responsibilities and roles in making the AMCL and MMM program 
approach successful in achieving optimal radon risk reduction. To this 
end, EPA has included as a special primacy requirement (see Section 
142.16 of the proposed rule) that States include in their primacy 
revision application for the AMCL a description of the extent and 
nature of coordination between the State's interagency programs (i.e., 
indoor radon and drinking water programs) on development and 
implementation of the MMM program plan, including the level of 
resources that will be made available for implementation and 
coordination between these agencies.
    CWSs developing local MMM program plans are also subject to these 
criteria. CWS MMM program plans developed in the absence of a State 
program are deemed to be approved by EPA if they meet the same criteria 
and are approved by the State. States without a MMM program, as a 
special condition of primacy (see Section 142.16 of the proposed rule), 
will be required to review and approve local CWS MMM program plans and 
to submit their process for approving such plans to EPA. The Agency 
considered an approach under which it would directly review and approve 
CWS MMM program plans. However, for several reasons, EPA is proposing 
that States review local MMM program plans. EPA believes that 
responsibility for such reviews is an appropriate and natural extension 
of the States' primacy responsibilities for oversight and enforcement 
of drinking water regulations. State review and approval of local MMM 
program plans will ensure that all elements of the radon rulemaking--
both the MMM program as well as implementation of the AMCL/MCL--are 
enforced through the State, rather than separating elements of the rule 
between the Federal and State governments. Dividing responsibility in 
such a way may complicate implementation of both elements of the radon 
rule and be confusing to both CWSs and the public. EPA also believes 
that the States are best positioned to assist CWSs, especially small 
systems, in the development of local MMM programs plans to review and 
approve local plans that meet the four criteria. States have a direct 
and ongoing regulatory relationship with CWSs as a part of their 
primacy authorities, as well as a major responsibility for public 
health related policy and programs in the State. In addition, States 
are aware of and sensitive to local public health needs and concerns, 
as well as other issues, that may need to be considered in the 
development and implementation of local MMM programs. For all these 
reasons, EPA is proposing an approach today that would require the 
States to review and approve local MMM program plans in accordance with 
the same criteria used in EPA's review of State MMM program plans. 
However, EPA solicits comments on other approaches, such as EPA review 
and approval of local MMM program plans or other options intermediate 
between sole State or sole Federal responsibility.
    EPA anticipates, and recommends, that States would assist CWSs in 
developing their local MMM program plans and would approve program 
plans that meet the criteria and that reflect local radon 
implementation issues as discussed in Section VI.F. In non-MMM States, 
EPA is also including as a special primacy requirement that States 
include in their primacy revision application for the MCL a description 
of the extent and nature of coordination between interagency programs 
(i.e., indoor radon and drinking water programs) on development and 
implementation of the State's review and approval process for CWS MMM 
program plans, including the level of resources will be made available 
for implementation and coordination between these agencies.
2. Criteria for MMM Program Plans
    The following four criteria are required for approval of State MMM 
program plans by EPA. Local MMM program plans developed by community 
water systems are deemed to be approved by EPA if they meet these 
criteria (as appropriate for the local level) and are approved by the 
State. The term ``State'', as referenced next, includes States, Indian 
tribes and community water systems. EPA is requesting comment on each 
of the criteria for approval of State, and CWS, MMM program plans. In 
particular, EPA is requesting comment on whether the criteria need to 
be more or less stringent, and the supporting rationale for EPA's 
consideration of other potentially credible approaches.
    (a) Description of Process for Involving the Public. (1) States are 
required to involve community water system customers, and other sectors 
of the public with an interest in radon, both in drinking water and in 
indoor air, in developing their MMM program plan. The MMM program plan 
must include:

A description of processes the State used to provide for public 
participation in the development of its MMM program plan, including the 
components identified in the following paragraphs b, c, and d;
A description of the nature and extent of public participation that 
occurred, including a list of groups and organizations that 
participated;
A summary describing the recommendations, issues, and concerns arising 
from the public participation process and how these were considered in 
developing the State's MMM program plan; and,
A description of how the State made information available to the public 
to support informed public participation, including information on the 
State's existing indoor radon program activities and radon risk 
reductions achieved, and on options considered for the MMM program plan 
along with any analyses supporting the development of such options.
    (2) Once the draft program plan has been developed, the State must 
provide notice and opportunity for public comment on the draft plan 
prior to submitting it to EPA.
    (b) Quantitative Goals. (1) States are required to establish and 
include in their plans quantitative goals, to measure the effectiveness 
of their MMM program, for the following:
    (i) Existing houses with elevated indoor radon levels that will be 
mitigated by the public; and,
    (ii) New houses that will be built radon-resistant by home 
builders.
    EPA is proposing to require establishing quantitative goals in 
these

[[Page 59259]]

two areas because they represent the most direct link to the risk 
reduction benefits that are the ultimate objective of the MMM programs. 
In addition, EPA analyses indicate that it is very cost-effective to 
test and mitigate existing homes with elevated indoor radon levels. It 
is also very cost-effective to build new homes radon-resistant, 
especially in higher radon potential areas. In the existing indoor 
radon program, EPA has been encouraging the States to promote testing 
and mitigation in all areas of a State. EPA has also encouraged the 
States to focus on their activities to promote radon-resistant new 
construction on the highest radon potential areas (Zone 1) where 
building homes radon-resistant is most cost-effective. However, it is 
also cost-effective to build homes in medium potential areas (Zone 2), 
as well as in ``hot'' spots found in most lower radon potential areas 
(Zone 3).
    EPA recognizes the States' (and CWSs') need for flexibility in 
designing MMM programs reflecting their needs and circumstances, in 
particular the extent to which opportunities are available for risk 
reduction in mitigation of existing homes with elevated indoor radon 
levels or in construction of new homes built radon-resistant. Some 
States, in particular those with a preponderance of lower radon 
potential areas (and for CWSs in lower radon potential areas), may find 
it preferable to focus more heavily on testing and mitigation of 
existing housing than on radon-resistant new construction.
    EPA is requesting comment on whether there are alternative goals 
that achieve radon risk reduction and the rationale for those goals. 
EPA is also soliciting comments on the goals outlined in paragraph (b), 
in particular on the appropriateness of the goals and whether the goals 
need to be more or less stringent.
    (2) These goals must be defined quantitatively either as absolute 
numbers or as rates. If goals are defined as rates, a detailed 
explanation of the basis for determining the rates must be included.
    EPA is proposing to provide this option, in part, because 
opportunities available for risk reduction in mitigation of existing 
homes with elevated indoor radon levels or in construction of new homes 
built radon-resistant may vary between States and within States. In 
addition, the level of new home construction may vary from year to year 
in different parts of a State or in a local jurisdiction. In this 
situation, it may be more appropriate to set goals for radon-resistant 
new construction as a rate, rather than absolute numbers, to account 
for this variability. This may be especially true for CWS developing 
local MMM program plans where no new home construction is currently 
taking place but may in the future.
    (3) States are required to establish goals for promoting public 
awareness of radon health risks, for testing of existing homes by the 
public, for testing and mitigation of existing schools, and for 
construction of new public schools to be radon-resistant, or to include 
an explanation of why goals were not established in these program 
areas.
    EPA is proposing that States have this option of defining goals as 
absolute numbers or as rates because, while awareness of radon health 
risks is a necessary element and a first step in getting the public to 
take action on indoor radon, public awareness, in and of itself, does 
not constitute radon exposure reduction. It does, however, help to 
facilitate informed choice by the public regarding radon testing and 
mitigation. Since the level of awareness on the health effects of radon 
is already high in many States, EPA is proposing to give flexibility to 
the States on this goal. In the case of radon in schools, many States 
have undertaken a range of activities to address radon in schools and 
some have done extensive testing, in some cases passing State 
legislation requiring the State to test public schools. Therefore, EPA 
is proposing to give States the option of setting these goals for 
schools. Although this approach provides flexibility in goal setting, 
EPA strongly encourages those States which do not have high levels of 
public awareness on radon and where there has been limited testing of 
public schools across the State to set goals in these areas. EPA is 
soliciting comment on whether States should be required to set 
quantitative goals in all or some of these areas in paragraph (b)(3).
    (c) Implementation Plans. (1) States are required to include in 
their MMM program plan implementation plans outlining the strategic 
approaches and specific activities the State will undertake to achieve 
the quantitative goals identified in paragraphs (b)(1) and (b)(2). This 
must include implementation plans in the following two key areas:
    (i) Promoting increased testing and mitigation of existing housing 
by the public through public outreach and education and during 
residential real estate transactions.
    (ii) Promoting increased use of radon-resistant techniques in the 
construction of new homes.
    (2) If a State has included goals for promoting public awareness of 
radon health risks; promoting testing of existing homes by the public; 
promoting testing and mitigation of existing schools; and promoting 
construction of new public schools to be radon resistant, then the 
State is required to submit a description of the strategic approach 
that will be used to achieve the goals.
    (3) States are required to provide the overall rationale and 
support for why their proposed quantitative goals identified in 
paragraphs (b)(1) and (b)(2), in conjunction with their program 
implementation plans, will satisfy the statutory requirement that an 
MMM program be expected to achieve equal or greater risk reduction 
benefits to what would have been expected if all public water systems 
in the State complied with the MCL.
    (d) Plans for Measuring and Reporting Results. (1) States are 
required to include in the MMM plan submitted to EPA a description of 
the approach that will be used to assess the results from 
implementation of the State MMM program, and to assess progress towards 
the quantitative goals in paragraphs (b)(1) and (b)(2). This 
specifically includes a description of the methodologies the State will 
use to determine or track the number of existing homes with elevated 
levels of radon in indoor air that are mitigated and the number or the 
rate of new homes built radon-resistant. This must also include a 
description of the approaches, methods, or processes the State will use 
to make the results of these assessment available to the public.
    (2) If a State includes goals in paragraph (b)(3) for promoting 
public awareness of radon health risks; testing of existing homes by 
the public; testing and mitigation of existing schools; and, 
construction of new public schools to be radon-resistant; the State is 
required to submit a description of how the State will determine or 
track progress in achieving each of these goals. This must also include 
a description of the approaches, methods, or processes the State will 
use to make these results available to the public.

B. Why Will MMM Programs Get Risk Reduction Equal or Greater Than 
Compliance With the MCL?

    The National Indoor Radon Program implemented by EPA, States and 
others, has achieved substantial risk reduction through voluntary 
public action since the release of the original ``A Citizen's Guide to 
Radon'' in 1986 (USEPA 1986) (updated: USEPA 1992b) and the U.S. 
Surgeon General's recommendation in 1988 (US EPA, 1988b) that all homes 
be tested and elevated radon levels be reduced. The program has been

[[Page 59260]]

successful in achieving voluntary risk reduction on indoor radon 
through a variety of program strategies. It is important to keep in 
perspective the comparatively large potential for risk reduction that 
can be achieved if all existing homes with indoor radon levels at or 
above EPA's voluntary action level for indoor radon of 4 pCi/L in the 
U.S. were mitigated (approximately 6 million homes). In addition there 
is the potential for significant risk reduction potential if the 
approximately 1 million new homes built annually in the U.S. were built 
radon-resistant. Based on the estimated number of existing homes fixed 
and the number of new homes built radon-resistant since the national 
program began in 1986, EPA estimates that a total of more than 2,500 
lives will be saved through voluntary indoor radon risk reduction 
efforts expected to take place up through the year 2000. Every year the 
rate of lives saved increases as more existing houses with elevated 
radon levels are fixed and as more new houses are built radon-
resistant. On average this rate of lives that will be saved from these 
risk reduction actions increases by about 30 additional lives per year. 
EPA estimates that for the year 2000, the rate of radon-related lung 
cancer deaths that will be avoided from mitigation of existing homes 
and from homes built radon-resistant in high radon areas will be about 
350 lives saved per year (USEPA 1999i).
    Under the radon provision of SDWA, if all States adopted the AMCL, 
all State MMM programs together must be expected to result in at 
minimum about 62 cancer deaths averted annually; equal to what would be 
achieved with universal compliance with the MCL. Unlike these health 
risk reduction benefits which remain constant from one year to the 
next, the rate of health benefits from reducing radon in indoor air, as 
noted previously, steadily increases every year with every additional 
existing home that is mitigated and with every new home built radon-
resistant. This steady incremental risk reduction offered by mitigation 
of existing homes with elevated indoor radon and building homes radon-
resistant, especially during real estate transactions and through 
builder and consumer education and State and local adoption of radon-
resistant building codes, holds the potential for substantial long-term 
risk reduction. NAS in their 1999 BEIR VI Report, concluded that up to 
one third (i.e., 5,000 to 7,000) of their estimated 15,000 to 22,000 
annual radon-related lung cancer deaths in the U.S. could be avoided if 
all homes were below EPA's voluntary radon action level of 4 pCi/L of 
air (NAS 1999a). This does not include the risk reduction that is 
achieved from new homes built radon-resistant. The one million new 
homes on average being built every year represent a significant radon 
risk reduction opportunity. Therefore, a critical element for MMM is to 
utilize and build on the indoor radon program framework to achieve 
``equal or greater'' risk reduction rather than focusing efforts on 
precisely quantifying the much more limited risk reduction that will 
not occur in community water systems complying with the AMCL (i.e., the 
difference in the risk reduction between the MCL and the AMCL).
C. Implementation of an MMM Program in Non-Primacy States
    A State that does not have primary enforcement responsibility for 
the Public Water System Program under Section 1413 of the SDWA 
(``primacy'') and where EPA administers the CWS program may still 
develop a State-wide MMM program plan. EPA would not expect to develop 
an MMM program plan where the State elects not to develop a State-wide 
MMM program plan. Accordingly, CWSs in such jurisdictions would be 
required to comply with the more stringent MCL or develop local MMM 
program plans for approval by EPA.
    The SDWA authorizes all States to develop and submit a MMM program 
plan to mitigate radon levels in indoor air for approval by the 
Administrator under Section 1412(b)(13)(G). EPA is proposing that 
States that do not have primacy may submit a plan to EPA that meets the 
criteria of 40 CFR 141.302. If the State's plan is approved, the State 
would be subject to all reporting and compliance requirements of 40 CFR 
141.303. Community water systems in States with approved MMM programs 
would comply with the AMCL of 4000 pCi/L, and would be subject to the 
requirements for monitoring and analytical methods in 40 CFR 141.20. 
EPA would continue to administer compliance with the MCL/AMCL, and with 
monitoring and methods requirements.

D. Implementation of the MMM Program in Indian Country

    Under this proposal, States can develop State-wide MMM programs for 
the reduction of radon in indoor air, and community water systems in 
such States can then comply with an AMCL of 4000 pCi/L (rather than an 
MCL of 300 pCi/L). Under Section 1451 of the SDWA, the Administrator of 
EPA is authorized to treat Indian Tribes in the same manner as States. 
The proposal provides tribes the option of seeking ``treatment in the 
same manner as a State'' for the purposes of assuming enforcement 
responsibility for a community water system program, and developing and 
implementing an MMM program. If a tribe does not choose to implement an 
MMM program, any tribal CWS may develop an MMM program plan for EPA 
approval, under the same criteria described previously.
    EPA is proposing to amend the ``treatment as a State'' regulations 
to allow tribes to be treated in the same manner as States for purposes 
of carrying out the MMM program. Under this proposal, a tribe would not 
need to demonstrate that it qualified for treatment in the same manner 
as a State for any other purpose other than the MMM provisions. Tribes 
may want to seek treatment in the same manner as a State for this 
limited purpose to the extent that radon is a significant problem on 
tribal lands because the MMM program provides an opportunity to focus 
resources on reducing the higher risk exposure--indoor air--and 
addressing radon in drinking water at the highest levels of exposure. 
EPA is proposing to amend the treatment in the same manner as State 
regulations (40 CFR 142.72 and 40 CFR 142.78) to obtain treatment as a 
State status solely for the purpose of implementing the MMM 
authorities. Tribes can, of course, always apply to be treated in the 
same manner as a State for primacy over the Public Water Supply Program 
under 40 CFR 142.72.
    A tribe applying for authority to develop and implement an MMM 
program plan that has met the criteria under 40 CFR 142. 72 to be 
treated in the same manner as a State for any purpose will not need to 
reestablish that it meets the first two criteria (40 CFR 142.72 (a) and 
(b)) and needs to provide only information in 40 CFR 142.76 that is 
necessary to demonstrate that the criteria in 40 CFR 142.72 (c) and (d) 
are met for the MMM program plan. A tribe whose application for 
authority to carry out the MMM program is approved must develop and 
implement a MMM program plan in accordance with 40 CFR 141.302 and 
141.303.

E. CWS Role in State MMM Programs

    EPA anticipates that CWSs, especially small systems, would have a 
limited role in State-wide MMM programs. For example, States may 
develop information brochures on radon that could be distributed 
locally by CWSs. EPA expects that States will want to consult with 
CWSs, small and large, in

[[Page 59261]]

making a determination about the nature and scope of the role, if any, 
of CWSs in implementing a State-wide MMM program. During EPA's 
stakeholder process, many States and CWSs agreed that States were best 
positioned to design and implement effective State-wide MMM programs 
and that it was not apparent what role CWSs might take in such a 
program. However, CWSs do have important responsibilities for 
communicating information on radon to their customers (see Section 
VI.G).

F. Local CWS MMM Programs in Non-MMM States and State Role in Approval 
of CWS MMM Program Plans

    The regulatory expectation of small community public water systems 
(CWSs) is that they meet the AMCL and be associated with a MMM program-
either developed by the State and approved by EPA or developed by the 
CWS and approved by the State. EPA strongly recommends that States 
choose to develop and implement State-wide MMM programs as the most 
cost-effective approach to manage the health risks from radon. In those 
cases where States do not elect to do a State-wide MMM program, CWSs 
would need to notify the State of its intention to develop and submit a 
local MMM program plan to the State (4 years after publication of the 
final rule in the Federal Register). EPA believes that, in all cases, 
the regulatory burden of complying with AMCL and implementing a MMM 
program will be considerably less than complying with the more 
stringent regulatory level for radon in drinking water. EPA believes 
that the MMM/AMCL is the appropriate standard for CWSs, especially for 
small systems, because it results in greater radon risk reduction and 
makes better use of limited resources. EPA believes that the four 
criteria for plan approval can be applied to CWS local MMM program 
plans (as appropriate for the local level), commensurate with the 
unique attributes of these CWSs and their service areas. As previously 
discussed in more detail, these four criteria are: public 
participation, setting quantitative goals, strategies for achieving 
goals, and a plan to track and report results.
    In general, EPA expects that CWSs would be able to meet the four 
criteria by carrying out a wide range of diverse activities, many of 
which are well within the expertise of CWSs. However, small CWSs would 
not necessarily be expected to perform some of the activities entirely 
on their own. In carrying out certain activities, small CWSs would be 
expected to seek help from others in order to build upon and take 
advantage of existing CWS and State networks. The existing State indoor 
radon programs, for example, operate in large measure through a network 
of State and local partners such as the American Lung Association, the 
National Association of Counties, the National Environmental Health 
Association, the National Safety Council, consumer advocacy groups, 
non-government organizations, and other local and county governmental 
organizations. CWSs should be able to use the same networks and their 
capabilities, and State radon in indoor air programs should help 
facilitate these contacts. The following provides some additional 
perspective on the four criteria relative to CWS MMM programs.
    Public Participation: Thorough public participation is certainly 
within the capability of CWSs. Systems are often required in the course 
of CWS activities, such as operation, maintenance, water bill 
collection, violation notification, and planning for new facilities, to 
involve, communicate with, inform, and in other ways interact with the 
public. Thus, these systems already engage, to a significant degree, in 
public outreach and communication. EPA expects that such expertise can 
readily be directed toward the particular public participation 
requirements associated with MMM programs. Public participating during 
development of local MMM plans will help ensure greater local support 
for and implementation of the CWS MMM programs.
    Quantitative Goals: EPA notes that the quantitative goals that 
CWSs, especially small CWSs, typically will need to establish may be 
rather modest compared to those that would be expected for State-wide 
programs. The level of risk reduction needed to ensure ``equal or 
greater'' risk reduction be achieved (as if the MCL were being met) 
from a local MMM program plan is a function of and takes into account 
factors such as the size of the population served, level of radon in 
drinking water, and most importantly, the needs and goals of the 
community.
    Strategies for Achieving Goals: EPA recognizes that promoting 
public action in the areas of new homes built radon-resistant and 
mitigation of existing homes with elevated levels of radon in indoor 
air will be entirely new ventures for CWSs. However, EPA believes CWSs, 
including small CWSs, will be capable of conducting various activities 
designed to promote testing and mitigation of existing homes with 
elevated levels of radon in indoor air and building of new homes to be 
radon-resistant. Such activities include public education programs, 
provision of radon test kits, establishing networks with local health 
and government officials to gain their support and involvement in MMM 
implementation, meeting with community leaders, customers, local real 
estate and home building officials and organization, utilizing existing 
information distribution network employed by CWSs, and other types of 
activities to promote public action on indoor radon. EPA expects that 
MMM program strategies for CWSs will be less comprehensive and far 
reaching than those of State MMM programs, and will need to reflect the 
local character of the community served by the CWS.
    Tracking and Reporting of Results: EPA recognizes that assessing or 
tracking progress towards meeting these goals also represents a new 
responsibility for CWSs. However, CWSs may be able to build upon their 
experience and networks for communicating with customers and 
identifying their needs or concerns and find ways to collect 
information about actions taking place in the community. To track homes 
built or modified to be radon resistant, CWSs may be able to obtain 
needed information from various local and State programs and offices 
and other organizations in its network. CWS may also choose to employ 
contractor support or consultant services to obtain this information or 
to help track other MMM related activities. EPA also expects the States 
to provide assistance to CWSs in developing their tracking and 
assessment approach based on State experience in determining the 
results of their State indoor radon programs. EPA recognizes that CWSs' 
options for tracking results may be more limited than those available 
to the States, and that States should consider such limitations in 
their five-year review of local programs.
    CWSs may find it useful to combine efforts with adjacent CWSs for 
purpose of developing and implementing joint MMM programs, thereby 
broadening their combined expertise, local infrastructure and 
institutional bases, and network of partners. EPA also expects that 
privately-owned, as well as publicly owned, CWSs can avail themselves 
of these same kinds of networks, partnership, and consultant services. 
Private systems will generally also be well connected to the municipal 
entities in the jurisdictions in which they operate.
    The report of the Small Business Advocacy Review Panel included a 
discussion of the concept of a ``model MMM program'' for small systems 
which would not be required but could

[[Page 59262]]

provide a workable option for small systems. It might address potential 
concerns of the smallest systems that anticipate they may lack the 
resources and expertise to develop an MMM program. As discussed 
subsequently in Section VI. H., EPA has concerns in general about the 
appropriateness and applicability of a ``one-size-fits-all'' approach 
for MMM programs. A model approach, even for small CWSs, would not 
address the unique, site-specific needs of different CWSs and their 
associated communities. EPA is requesting public comment on the concept 
of a model MMM program for CWSs.
    As noted previously, EPA is strongly recommending that States 
choose to develop and implement State-wide MMM programs as the most 
cost-effective approach to manage the health risks from radon which 
would preclude the need for water systems to develop such programs on 
their own. EPA also believes the States which choose not to do an MMM 
program have an important role, and are the best positioned, to assist 
CWSs in development of local MMM program plans. EPA will also be 
providing guidance to assist CWSs, including small CWSs, in the 
development of local MMM programs. This section has discussed the 
manner in which the four criteria could be applied to CWSs in non-MMM 
States. EPA is requesting comment on approaches to applying these 
criteria to CWSs, especially the smallest CWSs, in view of the 
capabilities of these systems and their ability to get assistance from 
others. EPA is also requesting comment on options that may be available 
to CWSs, particularly, small systems, to develop and implement an MMM 
program plan.
    In summary, EPA recognizes that CWSs do not have the same 
institutional base and infrastructure, legislative authority, 
proportionate resource base, or indoor radon program experience as 
States on which to base development of a local MMM program plan. 
However, EPA believes that the four criteria for approval are equally 
applicable to both States and CWSs, and can be applied to CWSs 
(particularly small CWSs) in a manner that recognizes and accounts for 
these differences. As discussed previously, the manner in which these 
criteria are addressed by CWSs in local MMM program plans, and the 
level and scope of effort, will necessarily differ from that embodied 
in State plans. States should consider these differences in evaluating 
CWS MMM program plans and in their five-year review of CWS MMM program 
implementation. EPA believes that States, in particular, are best 
positioned to assist CWSs, especially small systems, in the development 
of local MMM programs that satisfy the four criteria, and expects them 
to provide such assistance. In evaluating CWS plans, States should 
exercise flexibility in their review and approval process, especially 
for small CWSs, recognizing that they will not have the same 
institutional and resource base or experience and may need to obtain 
assistance from others.
    The Agency expects that most systems in non-MMM States with radon 
levels between 4,000 pCi/L and 300 pCi/L will develop and submit MMM 
program plans. However, the Agency recognizes that some CWSs in non-MMM 
States may elect not to develop a MMM program plan for a variety of 
reasons. In these cases, certain options are available to small CWSs. 
They may consider working with one or more other systems for the 
purposes of developing and implementing an MMM program plan, in order 
to take advantage of greater institutional capabilities. If a system 
does not develop an MMM program plan on its own or together with other 
systems, the system must comply with the MCL of 300 pCi/L through any 
available means (e.g., blending, use of alternate sources, and 
treatment).
    From a risk communication standpoint, EPA wishes to convey to 
customers of small CWSs that its regulatory expectation for these 
systems is that they meet the AMCL and implement an MMM program. 
However, CWSs can choose to meet the MCL rather than take the MMM 
approach. If a CWS opts for the MMM/AMCL approach but is unable to 
develop and successfully implement a State-approved MMM program plan, 
it may be required as part of an enforcement order, to meet the MCL 
rather than comply with the MMM/AMCL. The Agency requests comment on 
this approach for small system MMM programs.
    The SDWA provides that EPA will approve local water system MMM 
program plans and EPA has developed the criteria to be used for 
approving MMM program plans, as discussed in (A). EPA will review and 
approve State MMM program plans. CWS MMM program plans that address the 
criteria and are approved by the State are deemed approved by EPA. The 
proposed rule requires States that do not have a State-wide MMM 
program, as a condition of primacy for the radon regulation, to review 
MMM program plans submitted by CWSs and to approve plans meeting the 
four criteria for MMM program plans discussed in Section VI.A. of this, 
including providing notice and opportunity for public comment on CWS 
MMM program plans. EPA solicits comment on this approach to reviewing 
and approving local MMM plans. Under SDWA, MMM program plans submitted 
by CWSs are to be subject to the same criteria and conditions as State 
MMM program plans. EPA believes that the States are best positioned to 
assist CWSs, especially small systems, in the development and review of 
local MMM program plans that meet the four criteria, and to have public 
health oversight of the progress of the implementation of these local 
radon risk reduction programs. EPA encourages those States not choosing 
to develop a State-wide MMM program plan to exercise flexibility in 
their review and approval of local MMM program plans, especially for 
small CWSs, recognizing that CWSs will not have the same institutional 
base, nor the State's program experience on indoor radon, on which to 
base to local development of a MMM program plan. EPA expects that the 
State drinking water programs and indoor radon programs will work 
collaboratively in assisting CWSs that elect to develop and implement 
local CWS MMM program plans and comply with the AMCL. In non-primacy 
states, EPA will review and approve local CWS MMM program plans and 
oversee compliance with the AMCL if the state chooses not to do a 
state-wide MMM program plan. MMM program plans developed by Indian 
Tribes or tribal community water systems will be reviewed by EPA. The 
specific requirements of a CWS in a State with a State-wide MMM program 
are addressed in Section VI.E. CWSs may choose to meet the MCL.
    For those CWSs (both large and small) in non-MMM States that 
develop local MMM program plans, the State would review the MMM program 
at least once every 5 years and provide progress reports to the EPA in 
keeping with the statutory requirements of the SDWA and this Section. 
(States may also establish interim reporting requirements for the CWS 
under a MMM program to help ensure adequate progress toward the goals 
set forth in the local MMM program plan.) Failure of a CWS to develop 
its MMM program plan by the required regulatory deadline or failure of 
a CWS to implement its approved MMM program plan (5 years and 5\1/2\ 
years, respectively after the final rule is published) would be a 
violation of this regulation unless the CWS is complying with the MCL. 
It is expected that a CWS would be given time to correct any violations 
relating to its MMM program

[[Page 59263]]

through an appropriate enforcement action.

G. CWS Role in Communicating to Customers

    At a minimum, CWSs have important responsibilities for 
communicating information on radon to their customers. Under the 
requirements of the Consumer Confidence Rule (CCR), CWSs will be 
required to provide key information on the health effects of radon 
should the level of radon in drinking water exceed the MCL (or AMCL in 
States with MMM programs). Today's action also updates the standard CCR 
rule requirements and adds special requirements that reflect the 
multimedia approach of this rule. The intent of these provisions is to 
assist in clearer communication of the relative risks of radon in 
indoor air from soil and from drinking water, and to encourage public 
participation in the development of the State or CWS MMM program plans. 
Today's action also proposes to require CWSs to add information to the 
mandatory yearly report which would inform their customers on how to 
get involved in developing their State or local CWS MMM program plan. 
This information would include a brief educational statement on radon 
risks, explaining that the principal radon risk comes from radon in 
indoor air, rather than drinking water, and for that reason, radon risk 
reduction efforts may be focused on indoor air rather than drinking 
water. This information will also note that many States and systems are 
in the process of creating programs to reduce exposure to radon, and 
encourage readers to call for more information. This information would 
be provided every year until the compliance date for implementation of 
State MMM programs (or CWS local MMM programs in States without a 
State-wide MMM program. (See Section X of this preamble for more 
information on CCR and public notice requirements for radon). EPA is 
also planning to develop public information materials on radon in 
drinking water and indoor air as ``tools'' to assist CWSs, as well as 
the States, Indian tribes, and others, with the risk communication 
issues associated with the MCL, AMCL, and MMM.

H. How Did EPA Develop These Criteria?

    EPA obtained extensive stakeholder input in developing the 
regulatory criteria for State MMM program plans. Stakeholders 
participating in this process represented many diverse groups and 
organizations with an interest in radon, both from the perspective of 
radon in drinking water and of radon in indoor air. This included State 
drinking water and State radon program representatives, municipal and 
privately owned public water system suppliers, local government 
officials, environmental groups, and organizations representing State 
health officials, county governments, public interest groups, and 
others.
    As part of the process of getting stakeholder input on development 
of MMM guidelines and criteria, EPA presented several conceptual 
framework options for MMM for discussion and consideration. Three 
preliminary approaches were discussed: (1) To set specific numerical 
targets in mitigations of existing houses and houses built radon-
resistant (as surrogates for lives saved) for each State to meet; (2) 
to set a level of effort that States must demonstrate would be achieved 
under their MMM plan; and (3) to set minimum core indoor radon program 
elements required for all plans.
    Under the first approach, specific targets to achieve ``equal'' 
risk reduction could be set using a variety of approaches and tools and 
based on a number of factors, such as the level of radon in the 
drinking water, the number of people served by that system, and other 
factors. It would also require allocating among the States the total 
number of lives saved nationally by universal compliance with the MCL 
(estimated to be about 62 lives saved yearly). The allocation of lives 
saved by States would likely lead to some State targets being fractions 
of a life saved yearly, depending on the number of systems, radon 
levels, and people served. Many stakeholders thought that significant 
attention would need to be paid to the risk communication challenges of 
communicating this approach to the public. Although some stakeholders 
thought this approach might be workable, others did not consider it 
universally applicable or workable and that it might preclude 
flexibility and innovation.
    The second approach, ``level of effort'', would focus more on a 
plan for implementation of risk reduction strategies using a point 
system where different risk reduction strategies (such as public 
education, radon-resistant new construction code adoption, etc.) would 
be assigned a specific number of points based on potential to achieve 
health risk reduction. The number of State-specific points that a MMM 
program plan would have to meet to be approved would require 
determining the number of systems complying with the AMCL rather than 
the MCL, the radon levels in their drinking water, and population 
served. This approach would give States flexibility in choosing the 
combination of indoor radon risk reduction strategies that best meets 
the needs of that State by giving them a menu of approaches from 
different categories of strategies with different assigned points. 
There are two difficulties in implementing this approach that would 
need to be addressed. First, it may be difficult to assign in advance a 
specific quantified value for different strategies in terms of a 
numerical outcome in risk reduction (i.e., in lives saved or in 
existing homes mitigated or houses built radon-resistant). EPA 
requested the National Academy of Sciences (NAS), as part of its 
assessment of radon in drinking water, to ``prepare an assessment of 
the health risk reduction benefits associated with various mitigation 
measures [described in SDWA] to reduce radon levels in indoor air.'' 
Although the NAS included some review of the States' experience with 
public education and risk communication, they did not include a 
quantitative assessment of the ``health risk reduction benefits'' 
associated with specific ``mitigation measures'' referred to by SDWA. 
Second, risk communication research has shown, and many stakeholders 
agreed, that a variety of strategies must be employed simultaneously 
when trying to get voluntary public actions on preventive health and 
safety measures. It is often difficult to single out or characterize, 
for example, the number of people who take voluntary health risk 
reduction actions because of viewing a particular televised public 
service announcement separate from other messages, activities, 
communications, and efforts being implemented by society to reduce that 
particular public health risk.
    Setting specific State risk reduction targets or a level of effort 
point system were considered in part to address language in the SDWA 
radon provision that State plans approved by EPA are expected to 
achieve health risk reduction benefits ``equal to or greater than the 
health risk reduction benefits that would be achieved if each public 
water system in the State complied with the maximum contaminant level 
[MCL]* * *.'' As some stakeholders noted, there are complexities 
associated with determining risk reduction targets (e.g., in pCi/L) for 
indoor radon needed to substitute or ``make-up'' for some very small 
level of risk reduction that would not occur if systems comply with the 
AMCL. Careful attention would need to be paid to ensuring that this

[[Page 59264]]

approach did not produce the unintended effect of narrowly focusing or 
limiting the risk reduction goals of MMM program plans. Some States and 
other stakeholders were concerned that a complex approach, that may be 
difficult to communicate to the public, could hamper voluntary public 
action currently taking place on indoor radon. Some States thought that 
they may have the data and/or tools that would permit such an approach.
    The third conceptual approach was to require MMM program plans to 
include a set of core program elements, without targets or points, to 
be determined by EPA. This would require a set of basic program 
elements that each State MMM program plan would have to incorporate to 
be approved by EPA. In addition, the States could choose to add 
additional program elements from a menu of strategies to be provided by 
EPA. An example of implementation of a core program element might be 
that each State would have to adopt radon-resistant new construction 
standards into their State and local building codes, or require testing 
and mitigation firms to register with the State and report numbers of 
radon tests and mitigations conducted. Many stakeholders were concerned 
that this approach might not provide sufficient flexibility needed by 
the States to reflect their particular needs, including the scope of 
the radon in drinking water and indoor radon problem, and the varying 
extent to which the States have been addressing their indoor radon 
problem through their existing State radon programs.
    EPA is soliciting public comment on these three alternative 
conceptual frameworks for MMM program plans that were examined through 
the stakeholder process and is also requesting public comment on other 
potential frameworks and rationale for why and how these would achieve 
increased radon risk reduction.
    While stakeholders had differing views of the three conceptual 
approaches presented by EPA for discussion purposes, a number of mutual 
concerns and issues integral to formulation of a conceptual framework 
for MMM were identified. The following set of broad issues and concerns 
raised by stakeholders were considered in the development of the 
required criteria that EPA is proposing.
    A uniform approach, that is, a ``one size fits all'' approach to 
MMM might not provide States with the flexibility they need to custom 
tailor their plans to their needs. Every State is different in terms of 
the extent and magnitude of the indoor radon problem, the nature of the 
existing State indoor radon program, the levels of radon in public 
water supplies, and many other factors.
    Because the SDWA framework for radon permits States to choose to 
adopt either the MCL or AMCL/MMM option, some stakeholders believed 
that States might be less inclined to adopt the MMM/AMCL approach if it 
were considered too complex and difficult to implement and communicate 
to the public. The approach needs to be simple and straightforward, 
provide flexibility to accommodate the variety of needs in different 
States, and encourage innovation at the State and local level.
    MMM will be most effective if it is built on and consistent with 
the foundation and infrastructure of the existing State indoor radon 
programs. States are better positioned than public water suppliers to 
achieve radon risk reduction under MMM programs. Most States currently 
have a voluntary radon program. Some States noted the need for some 
consistency between the criteria and objectives for MMM program plans 
and the goals, priorities, and EPA's existing State Indoor Radon Grant 
(SIRG) program guidance.
    States and other stakeholders raised concerns about the potential 
relationship between MMM and the current State indoor radon programs. 
Stakeholders strongly encouraged EPA to carefully identify and consider 
the potential for negative impacts of MMM requirements on current State 
efforts on indoor radon. In particular there were concerns that 
attention and resources might be diverted to the MMM program. States 
might choose not to do a MMM program if the effectiveness or 
infrastructure of their current indoor radon program might be reduced, 
or if it does not help States meet the goals of their voluntary 
programs. This would be counter-productive if it resulted in reduced 
efforts and diminished infrastructure of a State's voluntary program 
already achieving indoor radon risk reduction.
    Some States felt it was important to have extensive public debate 
and examination of any program proposed by the State in order to get 
public support for the AMCL and MMM approach.
    A number of stakeholders noted the need for MMM programs to have 
definable endpoints or goals, show how these endpoints will be 
attained, and describe how results will be determined. Some States 
indicated the importance of demonstrating to the public that the 
program is achieves radon risk reduction.
    Stakeholders noted that the level of risk reduction that can be 
achieved by focusing resources and effort on radon in indoor air is 
significantly greater than what can be achieved by universal compliance 
with the MCL. MCL-based risk reduction targets would also be 
significantly smaller than the risk reduction already being achieved. 
Therefore it is important to focus on the greater risk reduction 
potential for radon in indoor air, and on enhancement of indoor radon 
programs, rather than focus on the smaller risk reduction potential 
from radon in water.
    In developing and deciding on proposed criteria, EPA took into 
account these stakeholder views and concerns, as well as EPA's goals 
for MMM and the current approach used by EPA and the States to get 
indoor radon risk reduction. This information and experience taken 
together led to the proposed MMM criteria that are based upon three 
elements: (1) Involve the public in development of MMM; (2) track the 
level of indoor radon risk reduction that occurs; and, (3) build on the 
existing framework of State indoor radon programs.
    First, stakeholders suggested that extensive public participation 
in the development of a State MMM program plan is important. One 
important approach is to involve various segments of the public, from 
community water system customers to key public health and other 
organizations, the business community, local officials, and many 
others. The public needs to be informed about and participate in the 
MMM development process to ensure that the goals and other elements of 
the plan will be publicly supported, responsive to the needs of the 
various stakeholders, and meet public and State goals for reducing 
indoor radon. Such a process may also result in increased public 
awareness and voluntary action to reduce the levels of indoor radon. 
Stakeholder involvement can help States clearly define goals and design 
the process and strategies for meeting these goals. EPA recognizes that 
there are a variety of non-quantitative and quantitative approaches, 
tools, and types of information that can be used to develop goals, but 
public input is very important to this process. The public involvement 
in development and examination of plans will help to get support and 
buy-in from all stakeholders to a set of goals, program strategies, and 
results measurement, and thus, helps to ensure program success.
    Second, a successful MMM program plan needs to include a provision 
for determining progress on reducing the public's exposure to indoor 
radon, and for reporting back to the public. In the case of indoor 
radon, risk reduction results can be evaluated by tracking or

[[Page 59265]]

in some way determining the level of existing home mitigation and new 
homes built radon-resistant. A few States already track this 
information closely. Many do not. EPA believes that there are a variety 
of approaches currently being used, such as statistically-based 
surveys; State requirements for tracking testing and mitigation by 
radon testing and mitigation companies; voluntary agreement by builders 
to provide information on construction of radon-resistant homes; and 
other approaches. EPA also recognizes the importance of providing 
States the flexibility to craft new and innovative approaches for 
tracking and assessing progress. Through implementation of a State-wide 
MMM/AMCL approach, States may be able to provide new incentives and 
opportunities for gathering the information the State will need to 
demonstrate to the public, and EPA, that progress is being made in 
getting public action to reduce radon risks.
    Third, building MMM on the framework of existing State indoor radon 
programs takes advantage of the existing programs already working to 
get public action on indoor radon. Nearly every State currently has a 
program with existing policies, public outreach and education programs, 
partner networks and coalitions, and other infrastructure. States have 
used the State Indoor Radon Grant (SIRG) funds available under Title 
III of the Toxics Substances Control Act (TSCA) to develop a variety of 
radon strategies, including distributing information materials to 
educate the public, maintaining radon hotlines, conducting training 
programs, providing technical assistance, operating certification 
programs for the radon industry, setting up regulatory requirements for 
industry reporting of testing and mitigation, conducting surveys 
(testing) of homes and schools, working with local governments in high-
risk areas to establish incentive programs for radon-resistant new 
construction, and many other activities. Many of these activities are 
consistent with the findings of the National Academy of Sciences. They 
found three factors were most important for motivating the public to 
test and fix their home: (1) A radon awareness campaign; (2) promoting 
the widespread voluntary testing by the public of indoor radon levels; 
and (3) educating the public about mitigation and ensuring the 
availability of qualified contractors. The reinforcement and 
augmentation of these types of efforts through MMM programs is expected 
to result in increased levels of testing and mitigation of existing 
homes by the public and of homes being built to be radon-resistant.
    The ``mitigation measures'' set forth in the 1996 SDWA are similar 
to those being used in the existing national and State radon programs. 
Section 1412 (b)(13)(G)(ii) provides that State MMM programs may rely 
on a variety of ``mitigation measures'' including ``public education, 
testing, training, technical assistance, remediation grants and loans 
and incentive programs, or other regulatory or non-regulatory 
measures''. These represent many of the same strategies that are 
integral to the indoor radon program strategy, as well as those 
outlined in the 1988 Indoor Radon Abatement Act.
    The risk reduction achieved to date through the national and State 
radon programs has been achieved primarily through a non-regulatory 
approach. The SIRG guidance for implementing a program also outlines 
and recommends indoor radon program priorities, encourages States to 
develop narrative descriptions of how they intend to address the 
priority areas, and encourages the establishment of goals for 
awareness, testing and mitigation of homes and schools, and radon-
resistant new construction. Under SIRG, the States are required to 
submit a list of their activities and workplans for each project that 
will be done under the grant. While EPA's SIRG guidance requires a list 
of program activities, it is not currently a Federal requirement under 
the Indoor Radon Abatement Act of 1988 or under SIRG that State indoor 
radon programs to: (a) publicly set goals for awareness, testing, 
mitigation and new construction; (b) develop and implement a strategic 
plan for action through real estate transactions, new home 
construction, testing and fixing schools, and getting the public to 
test and fix their homes; (c) develop and implement approaches to track 
and measure the results of their strategic plans and activities and 
report those results to the public; and (d) directly involve the public 
in the development of the States' program goals and strategic plans. 
EPA is proposing that, in order to have an approved MMM program plan, 
States now be required to take these steps.
    EPA believes this augmentation of State programs required under the 
criteria will result in an increased level of risk reduction. States 
will develop their plans with direct public participation in setting 
goals, develop strategic plans in key areas, and develop approaches for 
tracking and measuring results against goals. EPA also expects that 
substantial and constructive public participation in the development 
process of the State's MMM program plan is likely to result in a 
program that meets the public's needs and concerns on an important 
public health issue, as well as in greater public awareness of the 
health effects of radon and in increased voluntary action by the public 
to address their risks from indoor radon. Given EPA's estimate of the 
expected increase in the yearly rate of lung cancer deaths avoided from 
the current voluntary program, EPA expects that State MMM program plans 
meeting these four criteria will achieve equal, or much more likely, 
greater health risk reduction benefits.

I. Background on the Existing EPA and State Indoor Radon Programs

    Implementation of EPA's current national strategy to reduce public 
health risks from radon in indoor air has focused on using a 
decentralized management and risk communication approach in partnership 
with States, local governments and a network of national organizations; 
a continuum of risk reduction strategies; and, a strong focus on key 
priorities. Reduction of indoor radon levels has the potential to yield 
very large risk reduction benefits through pursuit of a wide range of 
approaches including the availability of relatively inexpensive 
testing, mitigation, and new construction techniques to reduce the risk 
from indoor radon. National, State, and local efforts continue to 
proactively encourage the public to test and fix their homes, promote 
action on radon in association with real estate transactions, and 
promote the construction of new homes with radon-resistant techniques 
through institutional changes such as local adoption of new 
construction standards and codes.
    Prior to 1985 the federal government and only a few States had 
initiated activities to address indoor radon problems. The initial 
foundation and scope of State programs was determined by the different 
needs of the States. For example, some Western States developed 
programs to assist citizens living on or near uranium mines or mill 
tailings sites. When very high levels of radon in homes in the area 
known as the Reading Prong in the Northeastern U.S. were discovered in 
late 1984, the Agency began to develop and to implement a coordinated 
national radon program. Some Eastern States situated over the Reading 
Prong began to develop strong programs in response to homes being found 
with radon levels in the hundreds and thousands of pCi/L of air. 
However, there was no coordinated government program, or testing and

[[Page 59266]]

mitigation industry, to address the risks posed by radon and only a 
very small fraction of the public was even aware of the problem.
    Since then, there has been significant progress in the nation's 
program to promote voluntary public action to reduce the health risks 
from radon in indoor air. EPA's non-regulatory Radon Program has 
established a partnership between federal, State, local and private 
organizations, as well as private industry, working together on 
numerous fronts to promote voluntary radon risk reduction. This 
partnership initially focused programs on increasing public awareness 
of the problem and providing the public with the necessary resources, 
including a range of technical guidance and information, to enable them 
to reduce their health risks through voluntary actions across the 
nation. Congress endorsed this strategy and strengthened the indoor 
radon program through the Superfund Amendments and Reauthorization Act 
of 1986, and again in 1988 through passage of the Indoor Radon 
Abatement Act. The Superfund Amendments and Reauthorization Act of 1986 
(SARA) authorized EPA to conduct a national assessment of radon in 
residences, schools, and workplaces. The 1988 Indoor Radon Abatement 
Act (IRAA), an amendment to the Toxic Substances Control Act. 
established the overall long-term goal of reducing indoor radon levels 
to ambient outdoor levels, required the development and promotion of 
model standards and techniques for radon-resistant construction, and 
established the State Indoor Radon Grant program (SIRG). IRAA also 
directed EPA to study radon levels in the U.S., evaluate mitigation 
methods to reduce indoor radon, establish proficiency programs for 
radon detection devices and services, develop training centers, provide 
the public with information about radon, and assist States to develop 
and implement programs to address indoor radon.
    Recognizing the importance of working in partnership with the 
States and leading national organizations, EPA developed a 
decentralized system for informing the public about the health risks 
from radon, consisting primarily of State and local governments and key 
national organizations, with their state and local affiliates, who 
serve as sources of radon information and support activities to the 
public. EPA has worked with the States to help establish and enhance 
effective State indoor radon programs and develop basic State 
capabilities needed for assisting the public in reducing their risk 
from indoor radon. EPA developed and transferred technical guidance on 
radon measurement and mitigation to the States, the private sector, and 
the public.
    A key initiative in this effort to build State Radon Programs has 
been the State Indoor Radon Grant (SIRG) Program, which provides 
funding to help States develop and operate effective and self-
sustaining radon programs. As of August 1999, forty-five States are 
currently participating in the SIRG program. These grants have been 
instrumental in establishing State radon programs or in helping States 
expand their radon programs more quickly than they otherwise could 
have.
    EPA, the States and national and local partners are using a mixture 
of diverse strategies that range from the more flexible, such as 
providing information to the public to encourage the public to act, to 
more prescriptive, such as providing incentives that give some 
advantage for taking action, or to adopting policies and requirements 
that mandate certain actions. As a result, many initiatives are 
underway today both to actively encourage and motivate homeowners to 
test and fix their homes as well as to institutionalize risk reduction 
through testing and mitigation during real estate transactions and 
through construction of new homes to be radon-resistant.
    EPA and the States, working with key national and local 
organizations, have developed a wide range of channels for delivering 
information to their members, affiliates and other target audiences. 
Many organizations have their own ``hotlines,'' journals, brochures, 
newsletters, press releases, radio and television programs, national 
conferences, and offer training and continuing education programs. 
These partners collaborate to urge public action on radon though a wide 
variety of strategies including information, motivation, incentives, 
and state and local mandates. The public receives a consistent message 
on radon from EPA, the States, and a number of other key, respected, 
and credible sources. Each target audience, like physicians or school 
nurses or local government officials, becomes in turn a source of 
information for new target audiences like their patients and local 
constituents. This approach is comparable to that used to encourage 
people to take various other voluntary preventive measures to reduce 
their risk of various health and safety risks. Some of the national 
organizations that EPA and the States work with include the American 
Lung Association, the National Association of City and County Health 
Officials, the National Parent Teacher Association, the Asian American 
and Pacific County Health Officials, the Association of State and 
Territorial Health Officials, the National Environmental Health 
Association, the National Association of County Officials, the Consumer 
Research Council of Consumer Federation of America, the National Safety 
Council, and many others.
    Many of the publicly available information materials are 
specialized and designed to encourage specific actions by certain 
groups, e.g., physicians, homebuilders, real estate agents, home 
inspectors, home buyers and sellers, and many others. As a result, for 
example, many home builders are voluntarily using radon resistant new 
construction techniques and some real estate associations are 
voluntarily incorporating the use of radon disclosure forms into their 
regular business practices. Medical and health care professionals are 
being educated about the health risks of radon and are encouraging 
their patients to test their homes for radon as a preventive health 
care measure. Public service announcements by local radio and TV 
stations encourage the public to act. Other public information 
materials provide consumers with information on how to test their homes 
and what options they have for mitigating their radon problem.
    Incentive programs and initiatives, such as free radon test kits, 
and builder rebates when builders build homes radon-resistant, are 
being implemented. States and local jurisdictions are also pursuing a 
variety of regulatory radon initiatives, such as requiring schools to 
be tested for indoor radon, requiring disclosure of elevated radon 
levels in residential real estate transactions, and requiring new homes 
to be built with radon-resistant new construction features through 
building codes. These strategies and many others are being used to 
successfully achieve public action to reduce the health risks from 
indoor radon.
    EPA has consulted with scientists, federal, state and local 
government officials, public health organizations, risk communication 
experts, and others to design this program and focus on radon program 
strategies which have the greatest potential for reducing radon risks 
through long-term institutional change. In developing strategies for 
reducing radon risks, EPA and the States have learned from the 
experience of other successful national public health campaigns, such 
as the campaigns to promote the use of seat belts. These campaigns have 
shown that significant public action to voluntarily

[[Page 59267]]

reduce health risks can be achieved from concerted efforts through a 
variety of diverse strategies and through the combined efforts of State 
and local governments, public health organizations, and other public 
interest groups, grass roots organizations, and the private sector.
    Program priorities have been identified to help concentrate and 
focus efforts of EPA, the States, and local organizations, and others 
on those activities that are most effective in achieving the overall 
mission of indoor radon risk reduction. Working with a broad group of 
stakeholders, EPA established several key priority areas for indoor 
radon. States and cooperative national organizations have been focusing 
many of their efforts and activities in these areas.
1. Targeting Efforts on the Greatest Risks First
    EPA, the States, and many other public health organizations 
recommend that all homes be tested and all homes at or above 4 pCi/L be 
fixed. However, resources have been more heavily focused initially in 
areas where action produces the most substantial risk reduction, such 
as on homes and schools in the high radon potential areas and on the 
increased risk of lung cancer from indoor radon to current and former 
smokers.
2. Promote Radon-Resistant New Construction
    EPA and others encourage programs to promote voluntary adoption of 
radon-resistant building techniques by builders and the adoption of 
radon construction standards into national, State and local building 
codes. Methods (model standards) that establish construction techniques 
for reducing radon entry in new construction have been developed and 
published by EPA in collaboration with the National Association of Home 
Builders. There are currently over 30 major building contractors (some 
are national firms) who design and construct radon resistant new homes. 
It is very cost-effective to build new homes radon-resistant, 
especially in higher radon potential areas. In the existing indoor 
radon program, EPA has been encouraging the States to promote testing 
and mitigation in all areas of a State. EPA has also encouraged the 
States to focus on their activities to promote radon-resistant new 
construction on the highest radon potential areas (Zone 1) where 
building homes radon-resistant is most cost-effective. However, it is 
also cost-effective to build homes in medium potential areas (Zone 2), 
as well as in ``hot'' spots found in most lower radon potential areas 
(Zone 3).
3. Promote Testing and Mitigation During Real Estate Transactions
    Based on the efforts of EPA, the States, and others, there has been 
a steady increase in the number of radon tests and mitigations 
voluntarily done through real estate actions. It is very cost-effective 
to test and mitigate existing homes with elevated indoor radon levels. 
Real estate transactions offer a significant opportunity to achieve 
radon risk reduction. In 1993, EPA published the ``Home Buyer's and 
Seller's Guide to Radon'' (USEPA 1993f). Hundreds of thousands of 
copies of the ``Home Buyer's Guide'' have been distributed to 
consumers. The companion to the ``Home Buyer's Guide'' is the 
``Consumer's Guide to Radon Reduction'' (USEPA 1992d) which provides 
information on how to go about reducing elevated radon levels in a 
home.
    A significant amount of radon testing and mitigation of existing 
homes takes place during real estate transactions through the 
combination of home inspections, real estate transfers, and relocation 
services. Many different groups are in a position to influence buyers 
and sellers to test and mitigate elevated radon levels. This includes 
sales agents and brokers, buyers agents, home inspectors, mortgage 
lenders, secondary mortgage lenders, appraisers, insurance companies, 
State real estate licensing commissions, real estate educators, 
relocation companies, real estate press, and others. There are 
currently no requirements at the federal, State, or local level that a 
house be tested for indoor radon as part of a real estate transaction. 
Many State and local governments, however, have passed laws requiring 
some form of radon disclosure, although the extent and detail of these 
mandatory disclosure laws varies.
4. Promote Individual and Institutional Change through Public 
Information and Outreach Programs
    Because the health risk associated with indoor radon is controlled 
primarily by individual citizens, EPA, the States and others have 
developed a nationwide public information effort to inform the public 
about the health risks from indoor radon and encourage them to take 
action. EPA recommends that the public use EPA-listed or State-listed 
radon test devices and hire a trained and qualified radon contractor to 
fix elevated radon levels. Early on, EPA established voluntary programs 
to evaluate the proficiency of these testing and mitigation service 
companies to provide a mechanism for providing the public with 
information by publishing updated lists of firms that pass all relevant 
criteria. Many States have established their own proficiency programs. 
To help support these efforts, EPA established four self-sustaining 
Regional Radon Training Centers across the country to train testing and 
mitigation contractors, State personnel, and others in radon 
measurement, mitigation, and prevention techniques. In 1998, the 
Conference of Radiation Control Program Directors (CRCPD), representing 
State radiation officials, initiated a pilot program through the 
National Environmental Health Association to establish a privatized 
national proficiency program to replace EPA's proficiency program which 
is terminating.

VII. What Are the Requirements for Addressing Radon in Water and 
Radon in Air? MCL, AMCL and MMM

    A CWS must monitor for radon in drinking water in accordance with 
the regulations, as described in Section VIII of this preamble, and 
report their results to the State. If the State determines that the 
system is in compliance with the MCL of 300 pCi/L, the CWS does not 
need to implement a MMM program (in the absence of a State program), 
but must continue to monitor as required.
    As discussed in Section VI, EPA anticipates that most States will 
choose to develop a State-wide MMM program as the most cost-effective 
approach to radon risk reduction. In this case, all CWSs within the 
State may comply with the AMCL of 4000 pCi/L. Thus, EPA expects the 
vast majority of CWSs will be subject only to the AMCL. In those 
instances where the State does not adopt this approach, the proposed 
regulation provides the following requirements:

A. Requirements for Small Systems Serving 10,000 People or Less

    The EPA is proposing that small CWS serving 10,000 people or less 
must comply with the AMCL, and implement a MMM program (if there is no 
state MMM program). This is the cut-off level specified by Congress in 
the 1996 Amendments to the Safe Drinking Water Act for small system 
flexibility provisions. Because this definition does not correspond to 
the definitions of ``small'' for small businesses, governments, and 
non-profit organizations previously established under the RFA, EPA 
requested comment on an alternative definition of ``small entity'' in 
the preamble to the proposed

[[Page 59268]]

Consumer Confidence Report (CCR) regulation (63 FR 7620, February 13, 
1998). Comments showed that stakeholders support the proposed 
alternative definition. EPA also consulted with the SBA Office of 
Advocacy on the definition as it relates to small business analysis. In 
the preamble to the final CCR regulation (63 FR 4511, August 19, 1998), 
EPA stated its intent to establish this alternative definition for 
regulatory flexibility assessments under the RFA for all drinking water 
regulations and has thus used it for this radon in drinking water 
rulemaking. Further information supporting this certification is 
available in the public docket for this rule.
    EPA's regulation expectation for small CWSs is the MMM and AMCL 
because this approach is a much more cost-effective way to reduce radon 
risk than compliance with the MCL. (While EPA believes that the MMM 
approach is preferable for small systems in a non-MMM State, they may, 
at their discretion, choose the option of meeting the MCL of 300 pCi/L 
instead of developing a local MMM program). The CWSs will be required 
to submit MMM program plans to their State for approval. (See Sections 
VI.A and F for further discussion of this approach).
    SDWA Section 1412(b)(13)(E) directs EPA to take into account the 
costs and benefits of programs to reduce radon in indoor air when 
setting the MCL. In this regard, the Agency expects that implementation 
of a MMM program and CWS compliance with 4000 pCi/L will provide 
greater risk reduction for indoor radon at costs more proportionate to 
the benefits and commensurate with the resources of small CWSs. It is 
EPA's intent to minimize economic impacts on a significant number of 
small CWSs, while providing increased public health protection by 
emphasizing the more cost-effective multimedia approach for radon risk 
reduction.

B. Requirements for Large Systems Serving More Than 10,000 People

    The proposal requires large community water systems, those serving 
populations greater than 10,000, to comply with the MCL of 300 pCi/L 
unless the State develops a State-wide MMM program, or the CWSs 
develops and implements a MMM program meeting the four regulatory 
requirements, in which case large systems may comply with the AMCL of 
4,000 pCi/L. CWSs developing their own MMM plans will be required to 
submit these plans to their State for approval.

C. State Role in Approval of CWS MMM Program Plans

    The SDWA provides that EPA will approve CWS MMM program plans. EPA 
has developed criteria to be used for approving MMM programs. EPA will 
review and approve State MMM program plans. CWS MMM program plans that 
address the criteria and are approved by the State are deemed approved 
by EPA. The proposed rule requires States that do not have a State-wide 
MMM program, as a condition of primacy for the radon regulation, to 
review MMM program plans submitted by CWSs and to approve plans meeting 
the four criteria for MMM programs discussed in Section VI of this 
preamble, including providing notice and opportunity for public comment 
on CWS MMM program plans. Under Section 1412(b)(13)(G)(vi) of SDWA, MMM 
program plans submitted by CWSs are to be subject to the same criteria 
and conditions as State MMM program plans. EPA will review CWS MMM 
program plans in non-primacy States, Tribes and Territories that do not 
have a state-wide MMM program, and approve them if they meet the four 
required criteria.

D. Background on Selection of MCL and AMCL

    The SDWA directs that if the MCL for radon is set at a level more 
stringent than the level in drinking water that would correspond to the 
average concentration of radon in outdoor air, EPA must also set an 
alternative MCL at the level corresponding to the average concentration 
in outdoor air. Consistent with this requirement, EPA is proposing to 
set the AMCL at 4000 pCi/L. This level is based on technical and 
scientific guidance contained in the NAS Report (NAS 1999b) on the 
water-to-air transfer factor of 10,000 pCi/L in water to 1 pCi/L in 
indoor air and the average outdoor radon level of 0.4 pCi/L.
    The SDWA generally requires that EPA set the MCL for each 
contaminant as close as feasible to the MCLG, based on available 
technology and taking costs to large systems into account. The 1996 
amendments to the SDWA added the requirement that the Administrator 
determine whether or not the benefits of a proposed maximum contaminant 
level justify the costs based on the HRRCA required under Section 
1412(b)(3)(C). They also provide new discretionary authority to the 
Administrator to set an MCL less stringent than the feasible level if 
the benefits of an MCL set at the feasible level would not justify the 
costs (SDWA section 1412(b)(6)(A)).
    EPA is proposing to set the MCL at 300 pCi/L, in consideration of 
several factors. First, the Agency considered the general statutory 
requirement that the MCL be set as close as feasible to the MCLG of 
zero (SDWA section 1412(b)(4)), and its responsibility to protect 
public health. In addition, the radon-specific provisions of the 
amendments provide that, in promulgating a radon standard, the Agency 
take into account the costs and benefits of programs to control indoor 
radon (SDWA 1412(b)(13)(E). Although EPA believes that an MCL of 100 
pCi/L would be feasible, EPA believes that consideration of the costs 
and benefits of indoor radon control programs allows the level of the 
MCL to be adjusted to a less stringent level than the Agency would set 
using the SDWA feasibility test. The proposed MCL of 300 pCi/L takes 
into account and relies on the unique conditions of this provision and 
the reality it reflects that the great preponderance of radon risk is 
in air, not water, and the much more cost-effective alternative to 
water treatment is to address radon in indoor air through the MMM 
program. The Agency recognizes that controlling radon in air will 
substantially reduce human health risk in more cost-effective ways than 
spending resources to control radon in drinking water. If most states 
adopted the MMM/AMCL option, EPA estimates the combined costs for 
treatment of water at systems exceeding the AMCL, developing a MMM 
program, and implementing measures to get risk reduction equivalent to 
national compliance with the MCL (62 avoided fatal cancer cases and 4 
avoided non-fatal cancer cases per year) at $80 million, which is 
substantially less than the $407.6 million cost of achieving the MCL. 
EPA expects that most states will adopt the AMCL/MMM program option
    While EPA believes it is appropriate to acknowledge the more cost-
effective control program to a certain extent in setting the MCL, the 
Agency does not believe the cost-effectiveness is the sole determining 
factor. Rather, EPA believes the absolute level of risk to which 
members of the public may be exposed is also a key consideration in 
determining a standard that is protective of public health.
    The Agency proposed an MCL of 300 pCi/L in 1991 based, in part, on 
its assessment of the health risk posed by radon in drinking water. It 
should be noted that the overall magnitude of risk estimated by the 
Agency at that time is in agreement with the overall risk of radon in 
drinking water currently estimated by the National Academy of Sciences 
(NAS 1999b). The Agency has

[[Page 59269]]

a long-standing policy that drinking water standards should limit risk 
to within a range of approximately 10 -4 to 10 -6 
and is thus proposing to use the flexibility provided by the authority 
in 1412(b)(13)(E) to propose an MCL of 300 pCi/L, which is 
approximately at the upper bound of the Agency's traditional risk range 
used for the drinking water program (representing an estimated 2 fatal 
cancers per 10,000 persons).
    As noted earlier, the Administrator must publish a determination as 
to whether the benefits of the proposed MCL justify the costs, based on 
the Health Risk Reduction and Cost Analysis prepared in accordance with 
SDWA Sec. 1412(b)(3)(C). Accordingly, the Administrator has determined 
that the benefits of the proposed MCL of 300 pCi/L justify the costs. 
The benefits of the proposed MCL, include about 62 avoided fatal lung 
cancer cases and 4 avoided non-fatal lung cancer cases annually. EPA 
has used a valuation of $5.8 million ($1997) to value the avoided fatal 
cancers and a valuation of $536,000 ($1997) to value the avoided non-
fatal cancers. Multiplying these valuations by the estimated cancer 
cases avoided (62 fatal, 3.6 non-fatal) yields a benefits estimate of 
$362 million per year. The cost to achieve national compliance with an 
MCL of 300 pCi/L is estimated at $407.6 million per year. EPA expects 
the actual cost of the proposed rule to be significantly lower, since 
the expectation is that most systems will not need to comply with the 
MCL of 300 pCi/L. Costs would be about $80 million per year if the 
AMCL/MMM option is widely adopted by States.
    There are also some potential non-quantified benefits, including 
customer peace of mind from knowing drinking water has been treated for 
radon and reduced treatment costs for arsenic for some water systems 
that have problems with both contaminants, and non-quantified costs, 
including increased risks from exposure to disinfection byproducts, 
permitting and treatment of radon off-gassing, anxiety on the part of 
residents near treatment plants and customers who may not have 
previously been aware of radon in their water, and safety measures 
necessary to protect treatment plant personnel from exposure to 
radiation. However, in this case it is not likely that accounting for 
these non-quantifiable benefits and costs quantitatively would 
significantly alter the overall assessment. Taking both quantified and 
non-quantified benefits into account, EPA has determined that the costs 
are justified by the benefits. Accordingly, the new authority to set a 
less stringent MCL if benefits do not justify costs is not applicable 
and has not been used in this proposal.
    Although the central tendency estimate of monetized costs exceeds 
the central tendency estimate of monetized benefits, the determination 
that benefits justify costs is consistent with the legislative history 
of this provision, which makes clear that this determination whether 
benefits ``justify'' costs is more than a simple arithmetic analysis of 
whether benefits ``exceed'' or ``outweigh'' costs. The determination 
must also ``reflect the non-quantifiable nature of some of the benefits 
and costs that may be considered. The Administrator is not required to 
demonstrate that the dollar value of the benefits are greater (or 
lesser) than the dollar value of the costs.'' [Senate Report 104-169 on 
S. 1316, p. 33] The determination is based on the analysis conducted 
under SDWA Sec. 1412(b)(3)(C), in the Health Risk Reduction and Cost 
Analysis (HRRCA) published for public comment on February 26, 1999 (64 
FR 9559), revised in response to public comment, and available as part 
of the Regulatory Impact Analysis (1999n) in the public docket to 
support this rulemaking. The costs and benefits of the proposed rule, 
and the methodologies used to calculate them, are discussed in detail 
in section XII of this preamble and in the Regulatory Impact Analysis 
(1999n).
    In making this determination, EPA also considered the special 
nature of the radon standard, which provides an alternate MCL of 4000 
pCi/L for states or water systems that adopt a MMM program designed to 
produce equal or greater risk reduction benefits to compliance with the 
MCL by promoting voluntary public action to mitigate radon in indoor 
air. As noted previously, mitigation of radon in indoor air is much 
more cost-effective than mitigation of radon in drinking water. If most 
states adopted the MMM/AMCL option, EPA estimates the combined costs 
for treatment of water at systems exceeding the AMCL, developing a MMM 
program, and implementing measures to get risk reduction equivalent to 
national compliance with the MCL (62 avoided fatal cancer cases and 4 
avoided non-fatal cancer cases per year) at $80 million, which is 
substantially less than the $407.6 million cost of achieving the MCL.
    In its valuation of costs and benefits for the MMM program, EPA has 
assumed that adopting the MMM approach will achieve only benefits 
equivalent to those for meeting the MCL and has calculated the costs 
and benefits of the proposed rule on this basis. However, EPA expects 
that adoption of MMM programs will be widespread as a result of this 
rule and that the actual benefits realized will be far greater than 
those associated with meeting the MCL. In addition, EPA fully expects 
most States to follow the MMM approach, therefore CWSs below the AMCL 
will incur minimal costs and a much smaller subset of CWSs will incur 
costs to meet the AMCL. Thus, costs for meeting the MCL are a 
theoretical worst case scenario which the Agency believes will not 
occur, particularly since the regulatory expectation for water systems 
serving 10,000 people or fewer would be that they meet the 4000 pCi/L 
AMCL, along with implementation of a local MMM program. Although in 
some cases small CWSs may choose to meet the MCL of 300 pCi/L through 
water treatment, this is voluntary and not a requirement of the 
proposed regulation.
    The Agency also considered the costs, benefits, and risk reduction 
potential of radon levels at 100 pCi/l, 500 pCi/L, 1000 pCi/L, 2000 
pCi/L and 4000 pCi/L. As table VII.1 illustrates, the costs and 
benefits increase as the radon level increases. The quantified costs 
somewhat exceed the quantified benefits at each level, but the benefit-
cost ratios are similar. However, the difference between costs and 
benefits becomes somewhat larger as the various MCL options become more 
stringent, with the largest difference at 100 pCi/L. When the 
uncertainty of the estimates is factored in, there is overlap in the 
benefit and cost estimates at all evaluated options. For more 
information on this analysis, please refer to the Regulatory Impact 
Analysis (RIA) for this proposal (USEPA, 1999n).

[[Page 59270]]



                                                        Table VII.1.--Evaluation of Radon Levels
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                       Cost per
                                                Fatal                                                   fatal        Total       Monetized
            Radon level  (pCi/L)                cancer      Individual fatal lifetime cancer risk    cancer case    national   benefits \1\    Benefit-
                                                cases                                                  avoided     costs \1\        $M        cost ratio
                                               avoided                                                   ($M)          $M
--------------------------------------------------------------------------------------------------------------------------------------------------------
4000.......................................          2.9  26.8 in 10,000...........................         14.9         43.1          17.0          0.4
2000.......................................          7.3  13.4 in 10,000...........................          9.5         69.7          42.7          0.6
1000.......................................         17.8  6.7 in 10,000............................          7.3        130.5         103            0.8
500........................................         37.6  3.35 in 10,000...........................          6.8        257.4         219            0.9
300........................................         62.0  2.0 in 10,000............................          6.6        407.6         362            0.9
100........................................        120.0  0.67 in 10,000...........................          6.8        816.2         702           0.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Water Mitigation only; assuming 100% compliance with MCL. Source: revised HRRCA.

    Some commenters recommended that EPA give serious consideration to 
setting an MCL at the AMCL level (4000 pCi/L), or at least at a level 
substantially above 300 pCi/L, in order to control radon levels in 
drinking water at a level more comparable to outdoor background levels. 
This approach was also discussed by the Small Business Advocacy Review 
Panel convened for this rule under the RFA as amended by SBREFA. (A 
copy of the Panel's final report is available in the docket for this 
rule making, (USEPA, 1998c).)
    As noted earlier, EPA's interpretation of the standard-setting 
requirements of the SDWA for radon are that they rely primarily upon 
the general standard-setting provisions for National Primary Drinking 
Water Regulations, with some additional radon-specific provisions. The 
general provisions require that the MCL be set as close as feasible to 
the MCLG. The radon-specific provisions direct the Administrator to 
take into account the costs and benefits of control programs for radon 
from other sources. As discussed, EPA is interpreting these general and 
radon-specific authorities to propose an MCL above the feasible level, 
near the upper end of the risk range traditionally used by the Agency 
in setting drinking water standards. In addition, EPA believes that the 
extensive statutory detail enacted on multimedia mitigation illustrates 
a congressional preference for cost-effective compliance through the 
AMCL/MMM program approach. EPA notes that the equal or greater risk 
reduction required to be achieved through the AMCL/MMM option would be 
diminished as the MCL approaches the AMCL of 4,000 pCi/L and that fewer 
States and CWSs would select this option. Further, the AMCL/MMM 
approach would be eliminated entirely if the MCL were set at the AMCL.
    As noted previously, EPA believes the proposed MCL of 300 pCi/L, in 
combination with the proposed AMCL and MMM approach, accurately and 
fully reflects the SDWA provisions. The Agency recognizes , however, 
that some stakeholders may have strong views about the appropriateness 
of setting an MCL at a higher level. Accordingly, EPA requests comment 
on the option of setting the MCL closer to or at the AMCL level of 4000 
pCi/L. In this connection, the Agency also requests comments on and the 
rationale for how such alternative options could be legally supported 
under the SDWA and in the record for this rulemaking, in light of the 
considerations EPA has applied for the MCL it proposes.
    EPA solicits comment on the proposed MCL and AMCL and the Agency's 
rationale, and on other appropriate MCLs given these considerations, 
and the rationale for alternative levels. In the final rule, the Agency 
may select a higher or lower option from those analyzed in the HRRCA 
for the final radon rule without further public comment.

E. Compliance Dates

    The proposed time line for compliance with the radon rule is 
described next and illustrated in Figure VII.1.

BILLING CODE 6560-60-P

[[Page 59271]]

[GRAPHIC] [TIFF OMITTED] TP02NO99.002



BILLING CODE 6560-50-C

[[Page 59272]]

    States are required to submit their primacy revision application 
packages by two years from the date of publication of the final rule in 
the Federal Register. For States adopting the AMCL, EPA approval of a 
State's primacy revision application is contingent on submission of and 
EPA approval of the State's MMM program plan. Therefore, EPA is 
proposing to require submission of State-wide MMM program plans as part 
of the complete and final primacy revision application. This will 
enable EPA to review and approve the complete primacy application in a 
timely and efficient manner in order to provide States with as much 
time as possible to begin to implement MMM programs. In accordance with 
Section 1413(b)(1) of SDWA and 40 CFR 142.12(d)(3), EPA is to review 
primacy applications within 90 days. Therefore, although the SDWA 
allows 180 days for EPA review and approval of MMM program plans, EPA 
expects to review and approve State primacy revision applications for 
the AMCL, including the State-wide MMM program plan, within 90 days of 
submission to EPA.
    EPA is proposing that CWSs begin their initial monitoring 
requirements (one year of quarterly monitoring) for radon by 3 years 
after publication of the final rule in the Federal Register, except for 
CWSs in States that submit a letter to the Administrator committing to 
develop an MMM program plan in accordance with Section 1412 
(b)(13)(G)(v). For CWSs in these States, one year of quarterly 
monitoring is proposed to begin 4.5 years after publication of the 
final rule. The proposed rule allows systems to use grandfathered data 
collected after the proposal date to satisfy the initial monitoring 
requirements provided the monitoring and analytical methods employed 
satisfy the regulations set forth in the rule and the State approves. 
Systems opting to conduct early monitoring will not be considered in 
violation of the MCL/AMCL until after the initial monitoring period 
applicable to their State (i.e., 4 years after publication of the final 
rule, 5.5 years after publication of the final rule).
    The routine and reduced monitoring requirements were developed to 
be consistent with the Standardized Monitoring Framework (SMF) and the 
Phase II/V monitoring schedule. EPA believes this is valuable for 
States and systems by providing sampling efficiency and organization, 
therefore, EPA has tried to adapt the compliance dates so that States 
and systems can make a smooth transition into the SMF following the 
initial monitoring requirements. The necessity to complete the initial 
monitoring in a timely manner is driven by the need for systems in non-
MMM States to evaluate their compliance options, including development 
of a local MMM program and compliance with the AMCL), and for systems 
in MMM States to ensure compliance with the AMCL.
    EPA feels it is important to set time constraints on implementation 
of the MMM plans to ensure the equal or greater risk reduction 
resulting from multimedia mitigation. Therefore, the rule must allow 
the systems in non-MMM States enough time to develop their MMM program 
plan with technical assistance from the State and submit the plan for 
State approval. In addition, the State must have sufficient time to 
review and approve the local plans. If the compliance determination for 
a system in a non-MMM State exceeds the MCL during the initial 
monitoring period, the proposed rule requires these systems to notify 
the State of their intention to develop a local MMM program at the 
completion of initial monitoring, 4 years after publication of the 
final rule. The local MMM program plans must be submitted to the State 
for approval by 5 years after of publication of the final rule (i.e., 
12 months after the completion of initial monitoring) and the States 
have 6 months from the submittal date to review and approve or 
disapprove the plan. The system will begin implementation of their MMM 
program 5.5 years after publication of the final rule (i.e., 1.5 years 
after the completion of initial monitoring). If the State fails to 
review and disapprove the local MMM program in the time allowed, the 
system will begin implementation of the submitted plan. If the system 
fails to comply with these compliance dates, a MCL violation will apply 
from the date of exceedence. If the compliance determination for a 
system choosing to comply with the MCL exceeds the MCL following the 
completion of the initial monitoring period, the system will have the 
option to submit a local MMM plan to the State within 1 year from the 
date of the exceedence and begin implementation 1.5 years from the date 
of the exceedence or incur a MCL violation.
    Implementation of State-wide MMM programs must begin 3 years after 
publication of the final rule, unless the State submits a letter to the 
Administrator committing to develop an MMM program plan in accordance 
with Section 1412 (b)(13)(G)(v) of the SDWA. States submitting this 
letter must implement their State-wide MMM program plan by 4.5 years 
after publication of the final rule. EPA feels it is extremely 
important that the MMM program plans be completed on a schedule that 
allows States sufficient time to begin implementation by the compliance 
date to ensure that equal or greater risk reduction benefits are 
provided.
    EPA recognizes potential issues may arise as a result of the 
proposed initial monitoring schedule. The potential issues include lab 
capacity and a temporary deviation from the SMF schedule. EPA is 
requesting comment on alternatives to avoid or lessen the impact of 
these issues and other issues not listed here.
    EPA considers the proposed monitoring schedule to be acceptable 
since the proposed rule affects one contaminant and applies to a 
smaller universe of water systems (NTNCWSs, transient systems, and CWSs 
relying solely on surface water are not covered by the rule) which 
decreases the number of systems effected, and therefore lessens the 
impacts of the potential issues. An alternative initial monitoring 
scenario which was considered would specify early monitoring 
requirements for systems serving more than 10,000 people. This scenario 
would put additional burden on the States and systems to monitor early 
and it would not substantially ease the workload since the number of 
systems serving greater than 10,000 that use groundwater or groundwater 
under the direct influence of surface water is relatively small.
    Initial monitoring could be phased in over a period of two or three 
years, but EPA does not feel it is appropriate to extend the initial 
monitoring period due to the necessity to evaluate the need to develop 
and implement local MMM program plans. In MMM States, systems must be 
in compliance with the AMCL in a timely manner to ensure the maximum 
risk reduction.
    In consideration of all these factors, EPA is proposing to require 
the initial monitoring over a one-year period as specified earlier. 
However, systems opting to conduct early monitoring will not be 
considered in violation of the MCL/AMCL until after the initial 
monitoring period applicable to their State (i.e., 4 years after 
publication of the final rule, 5.5 years after publication of the final 
rule). However, CWSs opting to conduct early monitoring will not be 
considered in violation of the MCL/AMCL until after the initial 
monitoring period applicable to their State (i.e., 4 years after 
publication of the final rule, 5.5 years after publication of the final 
rule. It is EPA's strong recommendation that all States choose to adopt 
the AMCL and implement an MMM

[[Page 59273]]

program. But some States may elect to adopt the MCL or may decide later 
to adopt the AMCL/MMM approach. In these states, the initial monitoring 
will be required to begin by 3 years after publication of the final 
rule, whereas in States submitting the 90-day letter committing to 
develop an MMM program plan will begin initial monitoring 4.5 years 
after publication of the final rule.

VIII. What Are the Requirements for Testing for and Treating Radon 
in Drinking Water?

A. Best Available Technologies (BATs), Small Systems Compliance 
Technologies (SSCTs), and Associated Costs

1. Background
    Section 1412(b)(4)(E) of the Act states that each national primary 
drinking water regulation which establishes an MCL shall list the 
technology, treatment techniques, and other means which the 
Administrator finds to be feasible for purposes of meeting the MCL. In 
addition, the Act states that EPA shall list, if possible, affordable 
small systems compliance technologies (SSCTs) that are feasible for the 
purposes of meeting the MCL. In order to fulfill these requirements, 
EPA has identified best available technologies (BAT) and SSCTs for 
radon.
    (a) Proposed BAT. Technologies are judged to be BAT when they are 
able to satisfactorily meet the criteria of being capable of high 
removal efficiency; having general geographic applicability, reasonable 
cost, and a reasonable service life; being compatible with other water 
treatment processes; and demonstrating the ability to bring all of the 
water in a system into compliance. The Agency proposes that, of the 
technologies capable of removing radon from source water, only aeration 
fulfills these requirements of the SDWA for BAT determinations for this 
contaminant. The full range of technical capabilities for this proposed 
BAT is discussed in the EPA Technologies and Costs document for radon 
(USEPA 1999h). Table VIII.A.1 summarizes the BAT findings by EPA for 
the removal of the subject drinking water contaminants, including a 
summary of removal capabilities.

     Table VIII.A.1--Proposed Bat and Associated Contaminant Removal
                              Efficiencies
------------------------------------------------------------------------
 
------------------------------------------------------------------------
High Performance Aeration \1\............  Up to 99.9% Removal.
------------------------------------------------------------------------
Note: (1) High Performance Aeration is defined as the group of aeration
  technologies that are capable of being designed for high radon removal
  efficiencies, i.e., Packed Tower Aeration, Multi-Stage Bubble Aeration
  and other suitable diffused bubble aeration technologies, Shallow Tray
  and other suitable Tray Aeration technologies, and any other aeration
  technologies that are capable of similar high performance.

    Granular activated carbon (GAC) can also remove radon from water, 
and was evaluated as a potential BAT and a potential small systems 
compliance technology for radon. Since GAC removes radon less 
efficiently than it does organic contaminants, it generally requires 
designs that use larger quantities of carbon per volume of water 
treated to remove radon compared to contaminants for which GAC is BAT. 
This requirement for larger carbon amounts translates to much higher 
treatment costs for GAC radon removal. In fact, full-scale application 
of GAC for radon removal has been limited to installations at the 
household point-of-entry and for centralized treatment for very small 
communities (AWWARF 1998a). EPA has determined that the requirements 
for radon removal render it infeasible for large municipal treatment 
systems, and it is therefore not considered a BAT for radon. However, 
GAC and point-of-entry (POE) GAC may be appropriate for very small 
systems under some circumstances, as described next (USEPA 1999h, 
AWWARF 1998a, AWWARF 1998b).
    (b) Proposed Small Systems Compliance Technologies. The 1996 
Amendments to SDWA recognize that BAT determinations may not address 
many of the problems faced by small systems. In response to this 
concern, the Act specifically requires EPA to make technology 
assessments relevant to the three categories of small systems 
respectively for both existing and future regulations. These 
requirements are in addition to EPA's obligation, unchanged by the SDWA 
as amended in 1996, to designate BAT. The three population-served size 
categories of small systems defined by the 1996 SDWA are: 10,000--3,301 
persons, 3,300--501 persons, and 500--25 persons. These evaluations 
include assessments of affordability and technical feasibility of 
treatment technologies for each class of small system. Table VIII.A.2, 
``Proposed Small Systems Compliance Technologies (SSCTs) and Associated 
Contaminant Removal Efficiencies'', lists the proposed small systems 
compliance technologies for radon and summarizes EPA's findings 
regarding affordability and technical feasibility for the evaluated 
technologies. EPA has interpreted the SSCTs as equivalent to BATs under 
Section 1415 of the Act, for the purposes of small systems (those 
serving 10,000 persons or fewer) applying to primacy agencies for 
Section 1415(a) variances.

 Table VIII.A.2.-- Proposed Small Systems Compliance Technologies (SSCTS) \1\ and Associated Contaminant Removal
                                                  Efficiencies
----------------------------------------------------------------------------------------------------------------
                                   Affordable listed                                                Limitations
    Small systems compliance         small  systems     Removal efficiency     Operator level          (see
           technology                categories \2\                             required \3\        footnotes)
----------------------------------------------------------------------------------------------------------------
Packed Tower Aeration (PTA).....  All Size Categories  90- > 99.9% Removal  Intermediate........  (a)
High Performance Package Plant    All Size Categories  90- > 99.9% Removal  Basic to              (a)
 Aeration (e.g., Multi-Stage                                                 Intermediate.
 Bubble Aeration, Shallow Tray
 Aeration).
Diffused Bubble Aeration........  All Size Categories  70 to > 99% removal  Basic...............  (a, b)
Tray Aeration...................  All Size Categories  80 to > 90%........  Basic...............  (a, c)
Spray Aeration..................  All Size Categories  80 to > 90%........  Basic...............  (a, d)
Mechanical Surface Aeration.....  All Size Categories  > 90%..............  Basic...............  (a, e)
Centralized granular activated    May not be           50 to > 99% Removal  Basic...............  (f)
 carbon.                           affordable, except
                                   for very small
                                   flows.

[[Page 59274]]

 
Point-of-Entry (POE) granular     May be affordable    50 to > 99% Removal  Basic...............  (f, g)
 activated carbon.                 for systems
                                   serving fewer than
                                   500 persons..
----------------------------------------------------------------------------------------------------------------
Notes: \1\ The Act (Section 1412(b)(4)(E)(ii)) specifies that SSCTs must be affordable and technically feasible
  for small systems.
\2\ This section specifies three categories of small systems: (i) those serving 25 or more, but fewer than 501,
  (ii) those serving more than 500, but fewer than 3,301, and (iii) those serving more than 3,300, but fewer
  than 10,001.
\3\ From National Research Council. Safe Water from Every Tap: Improving Water Service to Small Communities.
  National Academy Press. Washington, DC. 1997.
Limitations: (a) Pre-treatment to inhibit fouling may be needed. Post-treatment disinfection and/or corrosion
  control may be needed.
(b) May not be as efficient as other aeration technologies because it does not provide for convective movement
  of the water, which reduces the air:water contact. It is generally used in adaptation to existing basins.
(c) Costs may increase if a forced draft is used. Slime and algae growth can be a problem, but may be controlled
  with chemicals, e.g., copper sulfate or chlorine.
(d) In single pass mode, may be limited to uses where low removals are required. In multiple pass mode (or with
  multiple compartments), higher removals may be achieved.
(e) May be most applicable for low removals, since long detention times, high energy consumption, and large
  basins may be required for larger removal efficiencies.
(f) Applicability may be restricted to radon influent levels below around 5000 pCi/L to reduce risk of the build-
  up of radioactive radon progeny. Carbon bed disposal frequency should be designed to allow for standard
  disposal practices. If disposal frequency is too long, radon progeny, radium, and/or uranium build-up may make
  disposal costs prohibitive. Proper shielding may be required to reduce gamma emissions from the GAC unit. GAC
  may be cost-prohibitive except for very small flows.
(g) When POE devices are used for compliance, programs to ensure proper long-term operation, maintenance, and
  monitoring must be provided by the water system to ensure adequate performance.

    (c) Approaches for Listing Small Systems Compliance Technologies 
(SSCTs). EPA has considered several options for the listing of SSCTs in 
the proposed rule for radon. The issue is how to list SSCTs with BAT in 
the rule, while at the same time allowing for flexible and timely 
updates to the list of SSCTs in the future.
    EPA would like to establish a procedure that allows SSCT lists to 
be updated by guidance, rather than through the more resource intensive 
and time-consuming process of rule-making. For example, under today's 
proposal, EPA is including SSCT lists in the rule. This approach fully 
satisfies the requirements in Section 1412(b)(4)E(ii) of the Act, which 
states that EPA shall include SSCTs in lists of BAT for meeting the 
MCL. Since BATs are explicitly listed in rules, it is consistent to 
explicitly list SSCTs. Also, Section 1415(a) of the Act requires that 
BAT be proposed and promulgated with NPDWRs to satisfy the provisions 
for ``general variances'' (variances under Section 1415(a)); therefore, 
SSCTs must be listed in the rule if small systems are to be allowed to 
use them as BAT in satisfying the provisions for general variances.
    Regarding updates to the list of SSCTs, Section 1412(b)(9) of the 
Act states that EPA shall review and revise, as appropriate, all 
promulgated NPDWRs every six years. However, since revisions of NPDWRs 
follow the normal rule-making process of proposing, taking public 
comment, and finalizing the rule, the process can be very time-
consuming. While EPA believes that this six year review cycle is 
sufficient for updates to lists of BAT, it is unlikely to be sufficient 
for updates to lists of SSCTs, since recent improvements in package 
plant technologies, POE/POU devices, and remote monitoring/control 
technologies have been fairly rapid and future improvements seem 
imminent. For this reason, EPA seeks comment on this approach or 
alternate approaches that would allow for more timely updates to the 
list of SSCTs.
    In support of an approach to SSCT list updates that is less formal 
and more expeditious than rulemaking, EPA notes that new Section 
1412(b)(4)(E)(iv) allows the Administrator, after promulgating an 
NPDWR, to ``supplement the list of technologies describing additional 
or new or innovative treatment technologies that meet the requirements 
of this paragraph for categories of small public water systems.'' This 
provision does not contain any reference to or require rulemaking to 
update the SSCT list, in contrast with the earlier 1994 House version 
(in H.R. 3392) of this provision that specifically required revisions 
of the list to be made ``by rule.''
    Under one alternative, EPA would publish only an initial list of 
SSCTs with the BAT list in 40 CFR 141.66. EPA would also state in the 
rule that updates to the list of SSCTs would be done through guidance 
published in the Federal Register or through updates to the SSCT 
guidance manual. This process would be consistent with the process 
already used for listing SSCTs for the currently regulated drinking 
water contaminants (USEPA 1998g). A similar alternative approach would 
simply ``list'' SSCTs in Section 141.66 by referencing EPA guidance, 
which would be published separately and which could be updated 
periodically as needed outside of the normal rule-making process. 
Finally, EPA could publish both the initial list and the updates solely 
in a Federal Register notice or as guidance; however, under this last 
approach, only the promulgated BAT listed in the rule (which would not 
include SSCTs) would be available for small systems seeking a general 
variance under Section 1415(a) of the Act. EPA solicits comments on the 
suggested approaches for the listing of SSCTs and on the equivalency of 
SSCTs with BAT for the purposes of small systems applying for variances 
under Section 1415 of the Act.
    (d) Small Systems Affordability Determinations. The affordability 
determinations that are used for listing SSCTs are discussed in detail 
in recent EPA publications (USEPA 1998i, USEPA 1998e). It should be 
noted that aeration is one of the least expensive treatment 
technologies for drinking water (USEPA 1993d, NRC 1997) and has been 
determined to be affordable for all three small systems size 
categories. For the smallest size category (serving 25 to 500 persons), 
EPA cost estimates indicate that typical annual household

[[Page 59275]]

costs for aeration (80% removal efficiency, with disinfection and 
scaling inhibitor) are $190 per household per year ($/HH/yr). For 
systems installing aeration only, household costs for the smallest 
system size category are $114 per household per year. Case studies 
(n=9, USEPA 1999h) for systems with aeration serving between 25 and 500 
persons showed annual household costs ranging from $5 to $97 per 
household per year, with an average of $45 per household per year. 
Costs reported in these case studies included all pre- and post-
treatments added with aeration. The ``national average per household 
cost'' estimated in the Regulatory Impact Analysis is $260 per 
household per year for 25-500 persons. This average per household cost 
is higher than the estimated per household costs for systems using 
aeration since these average costs include not only aeration, but also 
the more expensive compliance alternatives (GAC, regionalization, and 
``high side'' PTA). Note that the cost for the 25-500 category is a 
weighted average of the per household costs for the 25-100 and 101-500 
categories reported in Table 7-2 of the Regulatory Impact Analysis. 
Also note that monitoring costs of approximately $4.00 per household 
per year ($270 per system) are included in the national average per 
household costs, but not in the aeration treatment per household costs 
reported.
    Granular activated carbon (GAC) may be affordable only for very 
small flows. EPA's GAC-COST model estimates indicate that GAC may not 
be affordable for the smallest size category (25-500 persons served) in 
whole. Annual household costs are estimated to be approximately $800 to 
> $1000 per household per year. However, case studies of small systems 
using GAC to remove radon for very small flows (populations served < 
100 persons) show annual household costs ranging from $46 to $77 per 
household per year. The large discrepancy between modeled costs and 
full-scale case study costs is probably due to the fact that the model 
design assumptions are more typical of larger systems, whereas the 
designs used in the case studies are much simpler. The American Water 
Works Association Research Foundation (AWWARF 1998a) similarly 
concludes that EPA's cost estimates for radon removal by GAC are over-
estimates (ibid., p. 190) and that GAC can be cost competitive with 
aeration for very small systems (ibid., Chapter 8). Examples of 
estimates of POE-GAC capital costs are shown in the next section, 
``Treatment Costs''.
2. Treatment Costs: BAT, Small Systems Compliance Technologies, and 
Other Treatment
    (a) Modeled Treatment Unit Costs. Total production costs associated 
with the various technological options for radon reduction, such as 
packed tower aeration and diffused bubble aeration installations, have 
been examined (USEPA 1999h). For systems that are currently 
disinfecting, ninety-nine percent reduction of radon by PTA is 
estimated to cost from $2.48/kgal (dollars per 1,000 gallons treated) 
for the smallest systems, defined as those serving 100 persons or 
fewer, to $ 0.12/kgal for large systems, defined as those serving up to 
1,000,000 persons. Eighty percent reduction of radon by PTA without 
disinfection is estimated to range from $2.10/kgal to $0.08/kgal for 
the same system sizes. For those systems adding disinfection because of 
the addition of aeration treatment, disinfection treatment costs for 
very small systems are estimated at an additional $1.40/kgal and costs 
for large systems are estimated at an additional $0.07/kgal. Aeration 
production costs have been adjusted to include costs that account for 
the addition of a chemical stabilizer (orthophosphate) by 25 percent of 
small systems (those serving 10,000 persons or fewer) and by 15 percent 
of large systems. In other words, the production costs shown are 
weighted averages that simulate the installation of aeration without 
chemical stabilizers by a fraction of the systems and with chemical 
stabilizers by the remaining fraction. Chemical stabilizers are used to 
minimize fouling from iron and manganese and/or to reduce corrosivity 
to the distribution system. Chemical addition cost estimates include 
capital costs for feed systems and operations and maintenance costs for 
the processes involved. Table VII.A.3 summarizes total production costs 
for system size categorizes for 80 percent radon removal. Further 
details on costing assumptions and breakdown of the unit treatment 
costs can be found in the RIA (USEPA 1999h).

 Table VIII.A.3.--Total Production Cost\1\ of Contaminant Removal by BAT for 80 Percent Radon Removal (Dollars/
                                        1,000 Gallons, Late 1997 Dollars)
----------------------------------------------------------------------------------------------------------------
                                                                Population Served
                               ---------------------------------------------------------------------------------
                                   25-100      100-500     500-1,000   1,000-3,300  3,300-10,000      >10,000
----------------------------------------------------------------------------------------------------------------
Aeration\2\...................         2.06         0.71         0.39         0.22          0.15  0.08-0.10
Aeration + disinfection.......         3.44         1.09         0.69         0.40          0.22  0.09-0.12
Granular Activated Carbon              0.34         2.16         2.16           NA            NA  NA
 (GAC).
GAC + disinfection............         1.71         2.54         2.46           NA            NA  NA
POE GAC + UV disinfection.....        16.99        14.03           NA           NA            NA  NA
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Cost ranges are estimated from cost equations found in the radon Technologies and Costs document (EPA
  1999h), as used in the radon HRCCA (64 FR 9559).
\2\ Aeration costs are weighted to include chemical inhibitor costs (Fe/Mn and corrosion control) for 25 percent
  of small systems and 15 percent of large systems.

    (b) Case Studies of Treatment Unit Costs. Case studies for aeration 
and GAC are reported in detail in the radon Technologies and Costs 
document (USEPA 1999h). Total production costs for aeration case 
studies ranged from an average of $0.82/kgal for systems serving 25--
100 persons (n = 4, standard deviation = $0.32/kgal, average population 
= 58) to $0.19/kgal for systems serving 100--3,300 persons (n = 11, 
standard deviation = $0.22/kgal, average population = 873). Total 
production costs for GAC ranged from $1.50/kgal for systems serving 
fewer than 100 persons (n = 2, standard deviation = $0.48/kgal, average 
population = 55) to $0.40/kgal for a system serving approximately 
23,000 persons. Production costs for two POE GAC installations ranged 
from $0.21/

[[Page 59276]]

kgal to $0.75/kgal. It should be noted that these POE GAC costs do not 
include the additional monitoring costs that would apply in a 
compliance situation. Annual monitoring costs are generally negligible 
compared to annual treatment costs for centralized treatment (<2.5 
percent for very small systems to <1 percent for large systems), and 
may be significant in the case of POE treatment (USEPA 1998g). For this 
reason, the POE GAC case study production costs may under-estimate true 
POE GAC costs. In general, the case studies suggest that EPA's modeled 
unit costs may be conservative for small systems. Since it is true that 
the radon case studies are not necessarily a random sample of all 
systems that will be impacted by the future radon rule, it may be 
argued that the typical reported costs may differ significantly from 
the typical costs of compliance. However, the costs of aeration from 
the radon case studies overlap nicely with the costs reported in the 
VOCs case studies, which should represent typical costs of compliance. 
Given this fact and the large number of case studies used, EPA has 
confidence that the case studies represent a best estimate of costs of 
treatment for compliance purposes. It should be noted that these 
reported case study costs are total costs and include all pre- and 
post-treatments added with the radon treatment process.
    (c) Treatment Cost Assumptions and Methodology. The general 
assumptions used to develop the treatment costs include costs for: 
chemicals and general maintenance, labor, capital amortized over 20 
years at a 7 percent interest rate, equipment housing, associated 
engineering and construction, land for small systems (design flow < 1 
mgd per well), and power and fuel (USEPA 1998h, USEPA 1998g, USEPA 
1999h). Costs were updated to December 1997 dollars using a standard 
construction cost index (Engineering News-Record Construction Cost 
Index). Process capital costs for aeration technologies were calculated 
using updated cost equations from the Packed Tower Column Air Stripping 
Cost Model (USEPA 1993e). Process capital costs for granular activated 
carbon and total capital costs for iron and manganese sequestration/
corrosion control, and disinfection were calculated using standard EPA 
models (as described in USEPA 1998e and USEPA 1999a). Construction, 
engineering, land, permitting, and labor costs were estimated based 
upon recommendations from an expert panel comprised of practicing water 
design and costing engineers from professional consulting companies, 
utilities, State and Federal agencies, and public utility regulatory 
commissions (USEPA 1998i). GAC disposal costs are included in the GAC-
COST O&M model. All cost estimates include capital costs for equipment 
housing and land for small systems (design flows < 1.0 MGD). It was 
assumed that all treatment installations would include disinfection. 
Capital and operating & maintenance costs for iron and manganese (Fe/
Mn) sequestration by the addition of zinc orthophosphate were included 
for 25 percent of small systems and 15 percent of large systems. Pre- 
and post-treatment assumptions are explained in more detail later.
    (d) ``Decision Tree''. Compliance costs were estimated assuming 
that non-compliant water systems would choose from a variety of 
compliance options, including installing a suitable treatment train, 
finding an alternate source of water, purchasing water from a near-by 
water utility, and using best management practices, like blending or 
ventilated storage. The modeled proportions of systems choosing a 
compliance pathway (the ``decision tree'') is based on the assumption 
that systems will choose the most cost-effective alternative, given the 
fact that site-specific factors (e.g., a well located in a suburban 
residential area) may force some systems to choose an option that is 
more expensive than the least cost alternative. The modeled proportions 
were assumed to vary by system size and water quality. More details on 
these assumptions are found in the Health Risk Reduction and Cost 
Analysis supporting this proposal (64 FR 9559).
    (e) Iron and Manganese Assumptions. Treatment costs assume that 25 
percent of small systems and 15 percent of large systems installing 
aeration will need to add an additional chemical inhibitor (e.g., 
orthophosphate, polyphosphates, silicates, etc.) to minimize the 
formation of iron/manganese (Fe/Mn) precipitates and carbonate scale; 
to reduce bio-fouling from the growth of Fe/Mn oxidizing bacteria (See, 
e.g., Faust and Aly 1998); and to reduce water corrosivity. Although 
zinc orthophosphate was assumed to be universally used, this was done 
as a simplifying costing assumption, and should not interpreted as 
suggesting that zinc orthophosphate is the appropriate inhibitor choice 
for all circumstances. Uncertainty analyses were performed in national 
cost estimates to simulate a range of choices of chemical inhibitors by 
systems and to simulate a range in the percentages of systems requiring 
the addition of an inhibitor. It is reiterated that, for the purposes 
of iron/manganese control and corrosion control, other chemical 
inhibitors may be more appropriate than zinc orthophosphate on a case 
by case basis.
    (f) Iron and Manganese Occurrence. Tables VIII.A.4 and VIII.A.5 
show the estimated co-occurrence of radon with dissolved iron and 
manganese in raw ground water for various radon and Fe/Mn levels. It 
can be seen from these tables (based on the U.S. Geological Survey's 
National Water Information System database, ``NWIS'') that the majority 
of ground water systems will be expected to have Fe/Mn source water 
levels below the secondary MCLs (SMCLs) for iron (greater than 85 
percent of GW samples have less than the SMCL of 0.3 mg/L) and 
manganese (greater than 75 percent of GW systems have less than the 
SMCL of 0.05 mg/L). Since Fe/Mn precipitation inhibitors are 
appropriate for treating combined Fe/Mn levels up to around 1-2 mg/L 
(Faust and Aly 1998, USEPA 1999h), this data indicates that the vast 
majority of ground water systems (greater than 95 percent) will be 
expected to be in situations where inhibitors are sufficient for 
handling iron and manganese problems. The cost estimates conservatively 
assume that inhibitors will also be used by systems with source water 
below the SMCLs for iron and manganese. Systems with Fe/Mn levels above 
1-2 mg/L may require oxidation/filtration or a similar removal 
technology. However, it should be noted that Fe/Mn levels this high may 
cause very noticeable nuisance problems, including ``red water'', 
noticeable turbidity, laundry and sink staining, and interference with 
the brewing of tea and coffee. It is likely that many systems with 
source water Fe/Mn levels this high will have already addressed this 
problem.

[[Page 59277]]



     Table VIII.A.4.-- Co-Occurrence of Radon With Dissolved Iron in Raw Ground Water\1\, \2\ (4188 Samples)
----------------------------------------------------------------------------------------------------------------
                                                            Dissolved Fe (mg/L) (percent)
          Radon  (pCi/L)           -----------------------------------------------------------------------------
                                         ND          <0.3       0.3-1.5      1.5-2.5        >2.5        Totals
----------------------------------------------------------------------------------------------------------------
ND................................         0.67         0.36         0.21         0.02         0.31         1.57
<100..............................         2.17         1.72         0.53         0.12         0.48         5.02
100-300...........................         7.55        10.20         2.67         1.34         1.74        23.50
300-1,000.........................        18.89        22.61     \3\ 3.08         0.57         1.31        46.46
1,000-3,000.......................         6.42         9.05         0.74         0.10         0.62        16.93
>3,000............................         2.10         3.82         0.31         0.02         0.26         6.51
                                   -----------------------------------------------------------------------------
    Totals........................        37.80        47.76         7.54         2.17         4.72       100.00
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Based on analyses as described in USEPA 1999c.
\2\ The USGS National Water Information System (NWIS) database was used for this analysis.
\3\ Shaded area denotes region where radon level is above MCL and dissolved iron is above 0.3 mg/L, the
  secondary MCL for iron.


    Table VIII.A.5.--Co-Occurrence of Radon With Dissolved Manganese in Raw Ground Water 1, 2 (4189 Samples)
----------------------------------------------------------------------------------------------------------------
                                                                  Dissolved Mn (mg/L) (percent)
                 Radon  (pCi/L)                 ----------------------------------------------------------------
                                                      ND         <0.02      0.02-0.05      >.050        Totals
----------------------------------------------------------------------------------------------------------------
ND.............................................         0.69         0.26         0.05         0.57         1.57
<100...........................................         2.67         0.84         0.36         1.15         5.02
100-300........................................         8.00         5.97         2.20         7.33        23.50
300-1,000......................................        21.99        11.84         3.17     \3\ 9.48        46.48
1,000-3,000....................................         6.45         5.90         1.24         3.34        16.93
>3,000.........................................         1.43         3.39         0.53         1.17         6.52
                                                ----------------------------------------------------------------
    Totals.....................................        41.23        28.20         7.55        23.04       100.00
----------------------------------------------------------------------------------------------------------------
Notes: \1\ and \2\: See Table VIII.A.4.
\3\ Shaded area denotes region where radon level is above MCL and dissolved manganese is above 0.05 mg/L, the
  secondary MCL for manganese.

    A similar analysis of the National Inorganic and Radionuclides 
Survey (NIRS) database, which sampled finished ground water, suggests 
that greater than 81 percent of GW systems sampled have dissolved Fe/Mn 
levels less than 0.3 mg/L and greater than 97 percent of systems 
sampled have levels less than 1.5 mg/L (USEPA 1999h). Table VIII.A.6 
compares combined Fe/Mn levels predicted by the NIRS database to occur 
in finished ground water with levels predicted by NWIS to occur in raw 
ground water. This table is consistent with expectations that the vast 
majority of ground water systems will have combined Fe/Mn levels below 
1-2 mg/L and that a significant fraction of ground water systems with 
Fe/Mn levels above the SMCL are already taking measures to reduce Fe/Mn 
levels.

  Table VIII.A.6.--Co-Occurrence of Radon With Dissolved Combined Iron and Manganese in Raw and Finished Ground
                                                      Water
----------------------------------------------------------------------------------------------------------------
                                     Percent of samples with dissolved
                                    combined Fe and Mn (mg/L) (percent)
        Ground water type         ---------------------------------------              Data sources
                                          <0.3                <1.5
----------------------------------------------------------------------------------------------------------------
Finished Ground Water............  >81, >93            >97 >99            NIRS,\1\ AWWA Water:/Stats \2\
Raw Ground Water.................  >85, >71            >95 >88            NWIS,\3\ AWWA Water:/Stats
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ ``National Inorganics and Radionuclides Survey'': See USEPA 1999c for references.
\2\ American Water Works Association, ``Water:/Stats, 1996 Survey: Water Quality''.
\3\ USGS, National Water Information System.

    An analysis of the American Water Works Association (AWWA) 
``Water:/ Stats'' database corroborates these conclusions: average Fe/
Mn levels in finished water from 442 ground water systems showed that 
greater than 93 percent of the systems had combined Fe/Mn levels less 
than 0.3 mg/L and greater than 99 percent of systems had combined Fe/Mn 
levels less than 1.5 mg/L (AWWA 1997); average Fe/Mn levels in raw 
ground water from 433 systems showed that greater than 71 percent of 
systems had combined Fe/Mn levels less than 0.3 mg/L and greater than 
88 percent of systems had Fe/Mn levels less than 1.5 mg/L. While this 
analysis does support the conclusions from NIRS and NWIS, it should be 
noted that the AWWA ``Water:/Stats Survey'' is skewed towards large 
ground water systems: only 3.4 percent of the systems surveyed serve 
fewer than 10,000 persons, whereas at the national

[[Page 59278]]

level, greater than 95 percent of ground water systems serve fewer than 
10,000 persons. In comparison, NIRS was designed to be nationally 
representative of contaminant occurrence in CWSs, while NWIS is a 
``data bank'' in which the U.S. Geological Survey stores water 
contaminant data from its various studies. While the data in NWIS was 
not collected as part of a designed national survey (and hence can not 
be claimed to be necessarily nationally representative), it is arguably 
nationally representative based on its large sample size and its wide 
distribution of sample collection locations (USEPA 1999c).
    (g) Disinfection Assumptions. It was assumed that all systems 
adding treatment would include disinfection. Since a significant 
fraction of ground water systems already disinfect, the percentage of 
systems that would have to add disinfection was estimated from a 
``disinfection-in-place baseline'', as described in the Radon Health 
Risk Reduction and Cost Analysis published on February 26, 1999 (64 FR 
9559). It should be noted that this baseline is nationally 
representative. Some States will, of course, have higher proportions of 
ground water systems with disinfection-in-place (e.g., those States 
that require that ground water systems disinfect) and some will have 
lower proportions. Since the cost estimates being calculated are at the 
national level, EPA believes that this assumption is valid since this 
will over-estimate costs for systems in some States and under-estimate 
costs for systems in other States, with the respective cost errors 
tending to cancel at the national level. As a simplifying cost 
assumption, chlorination was assumed for all systems adding 
disinfection. The actual choice of disinfection technology should, of 
course, be made on a case by case basis. The fact that many systems 
will choose disinfection systems other than chlorination and that some 
systems will not add disinfection at all is captured in the uncertainty 
analysis, described later in this section.
    (h) Comparison of Modeled Costs with Real Costs from Case Studies. 
Figure VIII.A.1 compares modeled total capital costs against case 
studies of actual aeration treatment installations for radon and VOCs 
found in the literature and gathered by EPA. It should be noted that 
these case studies include all pre- and post-treatments capital costs 
and costs for land, housing structures, permits, and all other capital 
added with the aeration process. If EPA's assumptions regarding pre- 
and post-treatments were seriously flawed, this comparison would 
demonstrate the fact. As can be seen, EPA's models fit the data fairly 
well and, in fact, Figure VIII.A.2 shows that the ``typical cost 
model'' rather closely approximates a power fit through the capital 
cost data for the larger systems and significantly over-estimates 
capital costs for small systems.
    The ``PTA Cost Model'' represents EPA's best estimate of the costs 
of constructing and operating a PTA system under the associated design 
assumptions (steel shell, below-ground concrete clearwell, structure, 
etc.). This design was intended to be fairly typical of those systems 
serving more than 500 persons and up to 1,000,000 persons. The ``High 
Side PTA Cost Model'' represents EPA's best estimate of the costs of 
constructing and operating a PTA system under the same basic treatment 
design, but including significantly higher land, structure, and 
permitting costs. This model was intended to be fairly typical of 
systems that are ``land-locked'' in suburban or urban areas where land 
costs, building codes, and permitting demands may be much higher than 
for typical situations. The ``Low Side PTA Cost Model'' represents 
EPA's best estimate of the costs of constructing and operating a PTA 
system using designs more typical of very small systems, including 
package plant installations. This model is described in the Radon 
Technologies and Costs Document (USEPA 1999h). As can be seen in Figure 
VIII.A.1, the PTA Cost and High Side PTA Cost models are representative 
of the systems with design flows greater than 0.1 MGD. All of these 
models tend to over-estimate costs for those systems with smaller 
design flows.
    The relative percentages of non-compliant systems modeled by the  
low-, typical-, and high-side costs are shown in the ``decision tree'' 
in Table 7-3 of the Regulatory Impact Assessment supporting this 
proposal. As part of the uncertainty analysis (described later in this 
section), these decision tree percentages were varied significantly. 
The results and assumptions are presented in detail in Section 10.8.3 
of the Regulatory Impact Assessment. Based on a sensitivity analysis of 
the relative impacts of all the cost elements studied, the variance in 
the decision tree percentage values had much less of an impact on 
national costs compared to the variance in the treatment unit costs ($/
kgal).

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    Figure VIII.A.2 compares the EPA aeration capital cost models 
against best fits to aeration capital cost case studies from the Radon 
Technologies and Costs Document (which includes aeration installations 
for VOCs) and to capital costs for radon case studies as reported by 
American Water Works Association Research Foundation (AWWARF 1998b). In 
general, EPA's unit cost estimates are supported by the case studies 
cited previously and by the findings reported by the AWWARF (AWWARF 
1998b).
    Figure VIII.A.3 shows that EPA's modeled operations and maintenance 
(O&M) costs are representative of the case study cost data. It should 
be noted that EPA is modeling incremental O&M aeration costs 
(additional O&M costs due to the addition of radon treatment) and that 
many of the radon case studies and all of the VOCs case studies report 
total O&M costs, which include O&M costs not related to the removal of 
radon. For this reason, the case study O&M costs would be expected to 
be considerably higher than the modeled costs, especially for the 
larger systems (which tend to have other processes in place that 
require substantial O&M costs). For example, most of the case studies 
using disinfection already had disinfection in place before adding 
aeration for radon. Since it is very difficult to separate the 
individual components of O&M costs without detailed site-specific 
information, these disinfection O&M costs are included in the O&M costs 
shown even though they are not related to treatment added for radon. As 
described previously, EPA did model O&M costs for disinfection and 
sequestration for iron and manganese and did include these in its 
national cost estimates. Figure VIII.A.3 compares modeled O&M costs for 
aeration with and without disinfection. Modeled O&M costs for iron/
manganese stabilization and corrosion control are included through a 
weighting procedure that simulates 25 percent of small systems and 15 
percent of large systems adding a chemical inhibitor. EPA solicits 
public comment and data on treatment costs and performance for the 
removal of radon from drinking water.

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    Figures VIII.A.4 and VIII.A.5 compare the modeled capital costs and 
O&M costs for GAC against actual costs reported in case studies (USEPA 
1999a, AWWARF 1998b). As can be readily seen, EPA's modeled costs are 
significantly higher than the actual costs, especially so for very 
small flows. To account for this discrepancy, EPA used the best fit 
through the case study data to generate a calibrated GAC model for 
capital and O&M costs. EPA calculated GAC treatment costs based on this 
model and did an uncertainty analysis on GAC costs assuming that while 
the modeled costs were typical, they could be as high as the GAC-COST 
predictions. This procedure is described in more detail in the radon 
HRRCA.
    EPA also estimated point-of-entry GAC (POE-GAC) costs for very 
small systems. While capital and standard maintenance costs may be 
affordable ($100-$350 per household per year), monitoring costs can 
make POE-GAC much more expensive. EPA estimates (USEPA 1998g) that 
monitoring costs alone can be as much as $140 per household per year. A 
``high end'' estimate for POE-GAC is $1,000 per household per year. If 
more cost-effective monitoring and maintenance program schemes are 
devised, these costs may be considerably lower.
    In general, treatment costs may vary significantly depending on 
local circumstances. For example, costs of treatment will be less than 
shown if contaminant concentration levels encountered in the raw water 
are lower than those used for the calculations or if an existing 
clearwell can be retrofitted for aeration. However, costs of treatment 
will be higher if oxidation/filtration pre-treatment is required for 
iron and manganese removal or if water must be piped from the well-head 
to an off-site area for treatment.

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    (i) Uncertainty Analysis for Treatment Costs. To estimate the 
uncertainty in national treatment costs, EPA estimated credible ranges 
and distributions of values for the most important factors (inputs) 
affecting costs. Distributions of selected inputs were then used in a 
Monte Carlo analysis to explore the uncertainty in national costs. The 
cost factors that were analyzed include:
     Numbers of systems in the various size categories;
     The distribution of the numbers of sources (wells) per 
system in each size category;
     Distributions of populations served in each size category;
     Annual household water consumption;
     Proportions of systems and wells exceeding radon limits; 
and
     Unit costs of radon treatment technologies (aeration and 
GAC).
    Each of these inputs was modeled using probability distributions 
that reflect the spread in the available data. In some cases, 
(distributions of populations served, daily household water 
consumption, unit costs) variability was estimable from SDWIS, the 
CWSS, or other sources. In the case of the numbers of systems of 
different sizes, the estimated variability was greatest for the 
smallest systems, less for the moderate size systems, and the numbers 
of the largest systems (serving greater than 100,000 customers) was 
assumed to be known with certainty. The variation in the proportions of 
systems and sources above radon limits was estimated based on EPA's 
recent analysis (USEPA 1999l) of inter- and intra-system radon 
variability in radon levels.
    In addition to these inputs, the estimated percentages of systems 
choosing particular treatment technologies (the ``decision tree'') were 
allowed to vary as well. Three decision tree matrices were used, 
corresponding to a central tendency estimate of the proportions of 
systems choosing specific mitigation technologies, and to lower- and 
higher-cost distributions of technology selection. When the simulation 
was run, the central tendency matrix was selected in 80 percent of the 
iterations, and the low- and high-cost decision matrices were selected 
in ten percent of the iterations each.
    The variability in the estimated mitigation costs was examined 
using a conservative test case in which all systems above an MCL of 300 
pCi/L were assumed to mitigate to comply with the MCL. The results of 
the analysis are described in detail in the radon Health Risk Reduction 
and Cost Analysis. In general, the distribution of cost estimates, even 
with all the variables included in the Monte Carlo analysis, is much 
narrower than the corresponding distribution of risk and benefit 
results. For this hypothetical scenario, the fifth percentile cost 
estimate is $455 million per year, while the 95th percentile estimate 
is $599 million per year (only 32 percent higher). The compactness in 
spread in national costs relative to the spread in national benefits is 
primarily due to the fact that the variability in the individual cost 
model inputs is low relative to the variability in some of the inputs 
(e.g., individual risk) to the benefits model.
    (j) Potential Interactions Between the Radon Rule and Upcoming and 
Existing Rules Affecting Ground Water Systems: Aeration and GAC are BAT 
for more than 25 and 50 currently regulated contaminants, respectively. 
Both technologies have been well-demonstrated and the secondary effects 
of each technology are well understood (See, e.g., Cornwell 1990, 
Umphres and Van Wagner 1986, AWWA 1990). These technologies are also 
used to remove other contaminants from drinking water, including taste 
and odor causing compounds. The Community Water System Survey (USEPA 
1997a) indicates that 2 to 5 percent of ground water systems serving 
fewer than 500 persons currently have aeration treatment in place. Of 
systems serving more than 500 persons, 10-25 percent of these systems 
have aeration treatment at one or more entry points.
    In the case of aeration, these secondary effects include carbon 
dioxide release (pH increase), oxygen uptake, and potential bacterial 
density increases, all of which potentially impact other existing and 
future drinking water regulations that pertain to ground water. In the 
case of GAC treatment, potential bacterial density increases are of 
concern. These potential interactions are described in a following 
section. (Concerns that are specific to radon removal and secondary 
effects due to other contaminants, e.g., radium and uranium, are 
discussed in part 3 of this Section.)
    (k) Ground Water Rule: Since the treatment techniques applicable to 
the removal of radon, i.e., aeration, GAC, and/or ventilated storage, 
may result in increases in microbial activity (NAS 1999b, Spencer et 
al. 1999), it is important that water systems determine whether post-
treatment disinfection is necessary. The ``Ten States Standards'' 
(GLUMRB 1997) suggest that disinfection should follow ground water 
exposure to the atmosphere (e.g., aeration or atmospheric storage). The 
Ten State Standards also suggest that systems using GAC treatment 
implement ``provisions for a free chlorine residual and adequate 
contact time in the water following the [GAC] filters and prior to 
distribution.'' While EPA is not requiring that disinfection be used in 
conjunction with any treatment for radon, it is including costs for 
disinfection with treatment in accordance with good engineering 
practice. Cost assumptions for disinfection, including clearwell sizing 
for 5-10 minutes of contact time, are consistent with 4-log viral 
inactivation for ground water, which is expected to be consistent with 
requirements in the upcoming Ground Water Rule.
    It should be noted that air is not a significant pathogen vector 
and thus aeration does not necessarily increase pathogenic risk for 
ground water users. However, bacterial activity can increase upon 
aeration and/or treatment with GAC. In the case of aeration treatment, 
bacteria that oxidize iron and/or sulfide may proliferate because of 
the oxygen increase; in the case of GAC treatment, bacteria may 
proliferate since the GAC surface tends to accumulate organic matter 
and nutrients that support the bacteria. In either case, heterotrophic 
plate count limits may become high enough to be of concern and for this 
reason disinfection may be necessary (USEPA 1999h, NAS 1999b).
    (l) Disinfectants and Disinfection Byproducts (D/DBP) Rule: 
Commonly used disinfection practices for ground water systems include 
chlorination and, especially for small systems with limited 
distribution systems, ultraviolet (UV) radiation. Disinfection is used 
by many ground water systems because it decreases microbial risks from 
microbial contamination of ground water (NAS 1999b). However, there is 
a trade-off between a reduction in microbial risks and the risks 
introduced from disinfection by-products. Various disinfectant by-
products (DBPs) can be formed depending on the disinfectant used, the 
disinfectant concentration and contact time, water temperature, the 
levels of DBP pre-cursors like natural organic materials and bromide, 
etc. For example, chlorination by-products like trihalomethanes can 
result from the interaction between chlorine chemical species and 
naturally occurring organic materials (NOM) and bromate can result from 
the ozonation of waters with sufficiently high levels of naturally 
occurring bromide ion.
    Ground water systems tend to have significantly lower 
trihalomethane (THM) organic precursors than surface waters, although 
this is not always the case. Total organic carbon (TOC) is often

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used as a surrogate for formation of one important class of DBPs, total 
trihalomethanes (THM), since the THM formation potential of chlorinated 
waters correlates with TOC. As reported in the proposed Disinfectants 
and Disinfection Byproducts Rule (July 29, 1994: 59 FR 38668), a survey 
of surface waters showed TOC levels at the 25th, 50th, and 75th 
percentiles of 2.6, 4.0, and 6.0 mg/L, respectively; ground waters 
showed TOC levels at the same percentiles of ``non-detect'', 0.8, and 
1.9 mg/L, respectively. Nationally, typical ground waters have low TOC 
levels. However, some areas of the U.S., e.g., the Southeastern U.S. 
(EPA Region 4), have some aquifers with high TOC levels.
    One approach for the minimization of DBP formation in drinking 
water is to employ a disinfectant other than chlorine. Primary 
disinfection with chloramination, ozonation, or UV radiation are 
examples. However, other considerations may apply. For example, 
ozonation of ground water with sufficiently high bromide levels may 
result in significant levels of the DBP bromate. If a residual is 
required, it may be necessary to add secondary chlorination to maintain 
a residual in the distribution system. Other strategies include 
reducing the precursor concentration prior to chlorination, removal of 
THMs after their formation, and the installation of a second 
chlorination point in the distribution system. This last approach 
allows much lower chlorination levels to be used for primary 
chlorination, which greatly reduces THM formation.
    While these strategies may be employed to minimize the formation of 
DBPs and, thereby reducing potential DBP risks and avoiding MCL 
violations for the DBP rule, there are other reasons to expect minimal 
interactions between the radon rule and the D/DBP rule. Namely, EPA 
expects that the radon rule will not result in a large percentage of 
systems adding disinfection because of the need to treat for radon. 
Since the primary regulatory option for small ground water systems is 
the MCL/MMM option (MCL = 4000 pCi/L) and less than one percent (1%) of 
small systems have radon levels that high, EPA does not expect many 
small systems to add treatment for radon in response to the radon rule, 
resulting in a very small percentage of small systems adding 
disinfection. Roughly half of all small systems already half 
disinfection in place already, further suggesting minimal small system 
impact from the radon rule. While EPA also expects that many large 
systems will also adopt the MCL/MMM option, EPA estimates that 95-97 
percent of large ground water systems are already disinfecting, and 
thus would not have to add disinfection if treating for radon. For the 
expected small minority of systems that do add chlorination 
disinfection with radon treatment, the trade-off between a reduction in 
risks from radon exposure to an increase in risk from disinfection by-
products will need to be carefully considered by the system installing 
treatment and strategies to minimize DBP formation should be 
implemented (NRC 1997, NAS 1999b, Spencer et al. 1999).
    (m) Lead and Copper Rule: For several reasons, it is expected that 
few systems already in compliance with the Lead and Copper Rule will 
experience direct cost impacts because of the Radon Rule. Systems 
serving fewer than 50,000 persons do not have to modify corrosion 
control practices if the lead and/or copper contaminant trigger levels 
are not exceeded. For the reasons explained next, aeration is not 
expected to result in increased lead and copper levels in the vast 
majority of cases. While larger systems will have to include radon 
treatment into their over-all ``optimal corrosion control'' plans as 
they are updated, aeration tends to reduce or maintain corrosivity 
levels and should not result in measures beyond those included in the 
national costs for the proposed radon rule.
    Aeration of ground water for radon treatment tends to raise the pH 
of water (Kinner et al. 1990, as cited by NAS 1999b, Spencer et al. 
1999), since it tends to remove dissolved carbon dioxide, which forms 
carbonic acid when dissolved in water. In a study of VOCs removal by 
aeration, the American Water Works Association (AWWA 1990) reported 
that the net effect of aeration was ``no increase in corrosivity'': The 
reduction in carbon dioxide levels resulted in higher pH and in 
increased stability of carbonate minerals that serve to protect 
distribution systems, negating the corrosive effects of increased 
oxygen levels. The NAS concludes (NAS 1999b and references cited within 
Spencer et al. 1999) that studies suggest that corrosivity tends to 
decrease with aeration, but that a minority of systems that aerate may 
have to add a corrosion inhibitor to stabilize the impacts of the 
increased oxygen levels. As described previously, EPA has assumed in 
its national costs that, of the systems that install aeration, 25 
percent of small systems and 15 percent of large systems will add 
chemical inhibitors for the dual purposes of corrosion control and the 
control of iron and manganese.
    (n) Arsenic Rule: It is expected that there will be no significant 
negative relationships between compliance measures for the Arsenic and 
Radon Rules. In fact, one of the few expected impacts is beneficial: 
aeration plus disinfection may serve to pre-oxidize As(III) to the more 
readily removable As(V) form. However, the benefits estimated in this 
notice do not reflect this potential benefit.
3. Descriptions of Technologies and Issues
    (a) Aeration. Aeration techniques for removal of radon from 
drinking water include active processes such as diffused bubble 
aeration (DBA), packed tower aeration (PTA), simple spray aeration, 
slat tray aeration, and free fall aeration, with or without spray 
aerators. Passive aeration processes such as free-standing, open air 
storage of water for reduction of radon may be effective for systems 
requiring lower removal efficiencies. Additional removal of radon via 
radioactive decay (into the daughter products of radon) may also occur 
in storage tanks and in pipelines which distribute drinking water, 
reducing radon by approximately 10 to 30 percent, within 8 to 30 hour 
detention periods. Although all of these aeration processes may be 
effective, depending on site specific conditions, only active aeration 
processes are considered BAT. Site specific considerations that may 
influence an individual water system's choice of treatment include 
source water quality (including concentrations of radon and other 
contaminants removed or otherwise affected by aeration), institutional 
or labor constraints, wellhead location, seasonal climate (e.g., 
temperature), site-specific design factors, and local preferences. 
Identical treatment designs may achieve different radon removal 
efficiencies at individual water systems, depending upon these factors. 
A design for a technology may be altered to increase the radon removal 
efficiency, e.g., an increase in the technology's air:water ratio (the 
respective flows of air and water being mixed) may increase the radon 
removal efficiency to account for local conditions that depress the 
radon removal efficiency. In some cases, the removal efficiency 
requirement may be high enough that only high performance aeration 
technologies (e.g., packed tower aeration) will achieve the desired 
removals.
    High performance aeration technologies, e.g., packed tower aeration 
(PTA) and package plant aerators with high air:water ratios like 
shallow tray aeration (STA) or multi-stage bubble

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aeration (MSBA), provide the most efficient transfer of radon from 
water to air, with the ability to remove greater than 99 percent of 
radon from water. A supply which requires a smaller reduction of radon, 
e.g., 50 percent, could opt to install one of these technologies and 
treat 50 percent of its source water and subsequently blend the treated 
with raw water, or it may design a shorter packed tower to achieve 
compliance with the MCL, both of which are significantly cheaper than 
treating the entire flow to 99 percent radon removal. Other advantages 
of high performance aeration include: removal of hydrogen sulfide, 
carbon dioxide, and VOCs, and oxidation of iron and manganese. Full-
scale PTA, STA, and MSBA installations have been constructed for the 
removal of radon for very small up to medium sized-systems (AWWARF 
1998b, USEPA 1999a). In addition to these case studies, full-scale 
aeration facilities for VOCs removal for medium to large-sized systems 
have been reported in the literature (AWWA 1990). Since radon is more 
easily air stripped than most volatile organic compounds, and high 
performance aeration technologies have been shown to be efficient forms 
of aeration for VOC removal (Kavanaugh and Trussell 1989, Dyksen et al. 
1995), these technologies are appropriate as BAT for radon.
    Treatment issues regarding aeration have been discussed in the 
literature (e.g., Dihm and Carr 1988, Kinner et al. 1990b, Dell'Orco et 
al. 1998, AWWARF 1998b) and by EPA (USEPA 1999d). These issues include 
the potential for bacteria fouling (e.g., iron/manganese/sulfide 
oxidizing bacteria), iron and manganese chemical precipitation and 
scaling, and corrosivity changes. Bacteria fouling and Fe/Mn scaling 
may clog or otherwise impede operations at an aeration facility, 
requiring preventative maintenance and/or periodic cleaning. Regarding 
corrosivity, the aeration process tends to reduce carbon dioxide levels 
(and raise pH, which tends to decrease corrosivity) and introduce 
oxygen (which tends to increase corrosivity). Whether or not 
corrosivity increases or decreases depends on site specific factors. In 
general, the degree to which these treatment issues may occur depends 
on the source water quality, ambient water and air temperatures, pre- 
and post-treatments added or in place, the type of aeration used, and 
other factors. To account for the cost impacts of dealing with Fe/Mn/
carbonate scaling, EPA has included the capital and operation and 
maintenance costs of pre-treatment with a scalant stabilizer (which 
also may serve as a corrosion inhibitor, depending upon the type of 
corrosivity). Pre-/Post-treatment with a disinfectant to control 
biological fouling and to provide four-log viral deactivation (assuming 
a five minute contact time at 1.0-1.5 mg/L chlorine) has also been 
assumed in cost estimates. EPA assumed that those groundwater systems 
without disinfection already in place will add disinfection when 
aerating.
    The PTA process involves the use of packing materials to create 
pore spaces that greatly increase the air:water contact time for a 
given flow of air into water. In counter-current PTA, the water is 
pumped to the top of the tower, then distributed through the tower with 
spray nozzles or distribution trays. The water flows downward against a 
current of air, which is blown from the bottom of the tower by forced 
or induced draft. The air space at the top of the tower is continually 
refreshed with ventilators. This design results in continuous and 
thorough contact of the water with ambient air. The factors that 
determine the radon removal efficiency are the air:water ratio (the 
ratio of air blown into the bottom of the tower and the water pumped 
into the top of the tower), the type and number of packing material, 
the internal tower dimensions, the water loading rate, the radon level 
in the influent and in the ambient air, and the water and air 
temperatures. A typical packed tower aeration installation consists of: 
(1) the tower: a metal (stainless steel or aluminum), fiber-glass 
reinforced plastic, or concrete tower with internals consisting of 
packing material with supports and distributors, (2) a blower or 
blowers, (3) effluent storage, which is generally provided as a 
concrete clearwell (airwell) below the tower; very small systems may 
use metal or plastic storage tanks, and (4) effluent pumping. Pumping 
into the tower is performed either through modification or replacement 
of the original well pump.
    Commercially available high performance package plant aerators 
(USEPA 1999a, AWWARF 1998b) include multi-stage bubble aerators (MSBA), 
shallow tray aerators (STA), and other high air:water ratio designs. 
MSBA units typically consist of shallow (typically less than 1.5 feet 
deep) high-density polyethylene tanks partitioned into multiple stages 
with stainless steel or plastic dividers. Each stage is provided with 
an aerator, each of which is connected to the air supply manifold. STA 
units typically consist of one to six stacked tray modules (each 18 to 
30 inches deep). Water is pumped through each tray as air is blown 
through diffusers at the bottom of the tray, creating turbulent mixing 
of the air and water. These package plant aerators have several 
distinct advantages: they are low-profile and compact (small 
footprint), are considered straightforward to install, and are 
relatively easy to maintain.
    Other varieties of active aeration include diffused bubble 
aeration, which involves the bubbling of air into the water basin (of 
varying depth and design) via a set of air bubble diffusors. Forms vary 
from designs with shallow depth tanks containing thousands of diffusers 
to ``low technology'' designs involving bubbling air into a storage 
tank via a perforated hose connected to a blower. Some forms of 
diffused bubble aeration can remove up to 99.9 percent of radon from 
drinking water; simpler varieties can remove from 80 to > 90 percent of 
radon. One of the main advantages of diffused bubble aeration is its 
potential for making use of existing basins for the aeration process, 
which substantially reduces construction costs. Even if the aeration 
basin must be newly constructed, this process can be more cost 
effective than PTA for small systems. The disadvantages of diffused 
aeration include the requirement for increased contact time, the 
impracticality of large air-to-water ratios because of air pressure 
drops, and overall less efficient mass transfer of radon from water. 
The level of contact between air and water achievable in a packed tower 
aerator is difficult to obtain in a simple diffused air system (i.e., 
forms like MSBA can achieve comparable contacts).
    The Radon Technology and Cost document (USEPA 1999h) summarizes 
treatability studies for four diffused bubble aeration installations. 
One of the case studies involves a full-scale diffused aeration plant 
in Belstone, England, which provided a long-term radon removal 
efficiency of 97 percent. This plant (design flow of 2.5 mgd) was 
designed with an air:water ratio, using 2,800 air diffusers, each 
designed to supply a maximum of 0.8 cubic feet per minute, and a 24-
minute retention time. In a field test of a diffused bubble aeration 
system, Kinner et al. (1990) report that removals of 90 to 99 percent 
were achieved at air-to-water ratios of 5 and 15, respectively.
    Spray aerators direct water upward, vertically, or at an angle, 
dispersing the water into small droplets, which provide a large 
air:water interfacial area for radon volatilization. In single pass 
mode, depending upon the air:water ratio, removal efficiencies of >50 
to >85 percent can be achieved. In multiple pass mode, 99 percent 
removals can be

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achieved. Most of the advantages cited previously for diffused aeration 
also apply to spray aeration. Disadvantages include the need for a 
large operating area and operating problems during cold weather months 
when the temperature is below the freezing point. Costs associated with 
this option (for all sizes of water treatment plants) have not been 
developed by EPA, but case studies (USEPA 1999a, AWWARF 1998b) indicate 
that it is cost-competitive with other small systems aeration 
technologies.
    EPA has evaluated other, less technology-intensive (``low-
technology''), options which may be suitable for small water systems, 
and which may cost less than the options described previously to 
install and operate (Kinner et al. 1990b, USEPA 1999a, AWWARF 1998b). 
These options include: atmospheric storage, free fall with nozzle-type 
aerator, bubble aerators, blending, and slat tray aerators. Limited 
data concerning these low-technology alternatives are reviewed in USEPA 
1999a and AWWARF 1998b. Case studies show that atmospheric storage with 
a detention time of nine hours resulted in removals of 7-13 percent and 
a detention time of 30 hours in removals of around 35 percent. Dixon 
and Lee (1987) report that blending 6.34 MG of well water with a radon 
level of 1079 pCi/L with 18.34 MG of surface water resulted in effluent 
water with 226 pCi/L. Other storage case studies (detention times 
ranging from 8 to 23 hours) show that free-fall into a tank, free-fall 
with simple bubble aeration, simple spray aeration with free-fall, and 
simple bubble aeration remove 50-70 percent, 85-95 percent, 60-70 
percent, and 80-95 percent of radon, respectively. More detail on an 
example will illustrate the simplicity of the treatment involved: the 
case study for ``free-fall with simple bubble aeration'' cited 
previously involved the introduction of water through two feet of free 
fall into a tank equipped with garden hose (punctured) bubble aerators, 
where the air was supplied by a laboratory air pump. Kinner et al. 
(1990b) concluded that very effective radon reduction can be achieved 
by simple aeration technologies that may be easily applied in small 
communities.
    (i) Evaluation of Radon Off-Gas Emissions Risks. Since this notice 
contains a proposal to reduce radon concentrations in drinking water by 
setting an MCL, and the EPA is proposing aeration as BAT for meeting 
the MCL, the Agency undertook an evaluation of risks associated with 
potential air emissions of radon from water treatment facilities due to 
aeration of drinking water. In the first evaluation (USEPA 1988a, 
1993a), EPA used radon data from 20 drinking water systems in the U.S. 
which, according to the Nationwide Radon Survey (1985), contained the 
highest levels of radon in drinking water and affected the largest 
populations and/or drinking water communities. EPA estimated the 
potential annual emissions (in pCi radon/yr) from these facilities, 
assuming 100 percent radon removal.
    These radon emissions estimates were used as inputs to the AIRDOS-
EPA model, which is a dispersion model that can be used to estimate the 
concentration of radon at a point some distance from the point source 
(e.g., a packed tower vent). This model is the predecessor to the newer 
CAP-88-PC model, which combined AIRDOS with the DARTAB model, which 
estimates the total lifetime risk to individuals and the total health 
impact for populations. The underlying physical models in CAP-88 are 
essentially the same as those underlying AIRDOS and DARTAB (USEPA 
1992c). In fact, the main differences between CAP-88-PC model and its 
predecessors is that CAP-88-PC is intended for wide-spread use in a 
personal computer environment (the CAP-88-PC model and its supporting 
documentation can be downloaded from the EPA homepage, http://
www.epa.gov/rpdweb00/assessment/cap88.html). EPA has made comparisons 
between the AIRDOS-EPA dispersion model results and actual annual-
average ground-level concentrations and found very good agreement. EPA 
has studied the validity of AIRDOS-EPA and concluded that its 
predictions are within a factor of two within actual average ground-
level concentrations, the results of which are as good as any existing 
comparable model (USEPA 1992c).
    Estimates of ground-level radon exposure were made for the 
following parameters: air dispersion of radioactive emissions, 
including radon and progeny isotopes of radon decay; concentrations in 
the air and on the ground; amounts of radionuclides taken into the body 
via inhalation of air and ingestion of meat, milk, and fresh 
vegetables, dose rates to organs and estimates of fatal cancers to 
exposed persons within a 50 kilometer radius of the water treatment 
facilities. Estimates of individual risk and numbers of annual cancer 
cases were completed for each of the 20 water systems, as well as a 
crude estimate of U.S. risks (total national risks) based on a 
projection of results obtained for the 20 water systems. These 
estimates were based on exposure analyses on a limited number of model 
plants, located in urban, suburban and rural settings, which were 
scaled to evaluate a number of facilities. (A similar approach has been 
used by the Agency in assessing risks associated with dispersion of 
coal and oil combustion products.) The risk assessment results for the 
20 systems indicate the following: a highest maximum lifetime risk of 2 
 x  10-\5\ for individuals within 50 km of one of 
these systems, with a maximum incidence at the same location of 0.003 
cancer cases per year; an estimate of annual cancer cases for all 20 
systems of 0.0038 per year; and a crude U.S. estimate of 0.09 fatal 
cancer cases/year due to air emissions if all drinking water supplies 
are treated by aeration to meet an MCL of 300 pCi/L. Two other cases 
were evaluated: (1) Assuming that small drinking water systems are 
treated by aeration to meet the MCL/MMM option of 4000 pCi/L and large 
systems are treated to meet the MCL of 300 pCi/L, the best estimate of 
total national fatal cancer cases per year due to radon off-gas 
emissions is 0.04 cases/year, and (2) Assuming that all systems treat 
by aeration to meet the (A)MCL/MMM option of 4000 pCi/L , the best 
estimate is 0.01 cases/year. These results of the risk assessment for 
potential radon emissions from drinking water facilities are summarized 
in Table VIII.A.7. For all MCL options shown, the maximum lifetime 
individual risks from radon off-gas are much smaller (100 to 70,000 
times smaller) than the average lifetime individual risks from the 
untreated water. Regarding national population risks (fatal cancer 
cases per year), the estimated population risk from radon off-gas is 
850 to 17,000 times smaller than the estimated population risk from the 
untreated water.

[[Page 59290]]



 Table VIII.A.7.--Estimates of Risks at 20 Sites Due to Potential Radon Emissions From Aeration Units and Crude
                                        Projection of Total U.S. Risk \1\
----------------------------------------------------------------------------------------------------------------
                                     Concentration  Emissions from                          Population risk \2\
         Modeling scenario          in water (pCi/   facility (Ci      Maximum lifetime     (fatal cancer cases
                                          L)            Rn/Yr)       individual risk \2\         per year)
----------------------------------------------------------------------------------------------------------------
20 Facilities Modeled:
    1.............................           1,839            2.79  3  x  10-7             7  x  10-5
    2.............................           5,003            6.22  6  x  10-7             2  x  10-4
    3.............................           2,175            2.85  3  x  10-7             9  x  10-5
    4.............................           1,890           20.89  6  x  10-6             1  x  10-4
    5.............................           1,310            1.81  5  x  10-7             9  x  10-7
    6.............................           1,329           91.80  9  x  10-6             1  x  10-3
    7.............................           4,085            2.26  2  x  10-7             3  x  10-5
    8.............................          10,640            1.18  1  x  10-7             1  x  10-5
    9.............................           3,083            0.55  5  x  10-8             7  x  10-6
    10............................           3,270            9.04  2  x  10-5             1  x  10-3
    11............................           2,565            3.54  7  x  10-6             6  x  10-4
    12............................           4,092           13.75  2  x  10-7             3  x  10-5
    13............................          16,135            2.23  2  x  10-7             3  x  10-5
    14............................           3,882            0.27  8  x  10-8             5  x  10-6
    15............................           1,244            1.03  3  x  10-7             2  x  10-5
    16............................           2,437            1.35  4  x  10-7             5  x  10-7
    17............................             996            8.94  9  x  10-7             2  x  10-4
    18............................           7,890            0.87  3  x  10-7             6  x  10-6
    19............................           9,195            1.02  3  x  10-7             1  x  10-5
    20............................           7,500            1.04  3  x  10-7             6  x  10-6
                                   -----------------------------------------------------------------------------
Totals for All 20 Facilities......                             161  .....................  0.004
----------------------------------------------------------------------------------------------------------------
Totals Assuming All U.S. Community                            3700  .....................  0.09
 Water Systems Treat to 300 pCi/L
 \3\, i.e., All Systems Meet MCL
 of 300 pCi/L.
----------------------------------------------------------------------------------------------------------------
Totals Assuming All Small U.S.                                1600  .....................  0.04
 Drinking Water Facilities Treat
 to 4000 pCi/L \3\ and All Large
 U.S. Drinking Water Treat to 300
 pCi/L, i.e., All Small Systems
 Meet MCL of 4000 pCi/L and All
 Large Systems: meet MCL of 300
 pCi/L.
----------------------------------------------------------------------------------------------------------------
Totals Assuming All U.S. Drinking                              240  .....................  0.01
 Water Facilities Treat to 4000
 pCi/L \3\, i.e., All Systems meet
 MCL of 4000 pCi/L.
----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Estimates of Risk Assessment Using AIRDOS-EPA to estimate radon exposure. The total U.S. risk is based on
  the very conservative projection that all CWSs will treat to 200 pCi/L, USEPA 1993b.
\2\ Risks are based on the National Academy of Science's lifetime fatal cancer unit risk or radon in drinking
  water of 6.7 x 10 -\7\.
\3\ USEPA 1999j.

    A second ``worst case'' evaluation was performed using four 
scenarios with high radon influent levels (ranging from 1,323 pCi/L to 
110,000 pCi/L) and/or high flows to further determine whether 
individuals living near water treatment plants would experience 
significant increases in cancer risks due to radon off-gas emissions. 
For this analysis, the MINEDOSE model was used in conjunction with 
radon emissions estimates to estimate lifetime fatal cancer risks for 
individuals living near the modeled facility. Emissions were estimated 
using MINDOSE 1.0 (1989), a predecessor to COMPLY-R (1.2), which can be 
downloaded from the EPA homepage (http://www.epa.gov/rpdweb00/
assessment/comply.html). Comply-R (1.2, radon-specific) is intended for 
demonstrating compliance with the National Emissions Standards for 
Hazardous Air Pollutants (NESHAPS) in 40 CFR 61, Subpart B, which are 
the Federal standards for radon emissions from underground uranium 
mines. While these standards do not apply to drinking water facilities, 
the model can be used to estimate radon exposures from aeration vents 
at drinking water facilities. To check for consistency between MINEDOSE 
and COMPLY-R, several modeling scenarios done in the original analysis 
with MINEDOSE were repeated using COMPLY-R and the results from 
MINEDOSE were found to be conservative with respect to the COMPLY-R 
results, i.e., COMPLY-R predicts lower exposures for the scenarios 
modeled. The MINEDOSE code was originally used instead of the AIRDOS 
code because of its relative ease of use. When modeling the same 
scenarios with MINEDOSE and AIRDOS, the predicted exposures were 
determined to be similar enough to warrant the use of MINEDOSE for this 
work. The results from the MINEDOSE modeling work and subsequent work 
(USEPA 1994a) concluded that even these ``worst case maximum individual 
risks'' from radon off-gas were much smaller (300 to 1,000 times 
smaller) than the average individual risks posed by the untreated 
water.
    (ii) Permitting of Radon Off-Gas from Drinking Water Facilities. 
Radon emissions to ambient air are only Federally regulated under 40 
CFR 61,

[[Page 59291]]

National Emission Standards for Hazardous Air Pollutants (NESHAPs). 
These regulations apply to radon emissions under very specific 
circumstances, including emissions of radon to ambient air from uranium 
mine tailings, phosphogypsum stacks (40 CFR 61, Subpart R), Department 
of Energy storage and disposal facilities for radium-containing 
materials (40 CFR 61, Subpart Q), and underground uranium mines (40 CFR 
61, Subpart B). At present, there are no State or Federal regulations 
that directly apply to radon air emissions from water treatment 
facilities.
    To assess potential procedures (e.g., permit applications, off-gas 
risk modeling) and costs that could be associated with radon off-gas 
from aeration facilities, EPA gathered information from agencies 
responsible for air permitting (USEPA 1999h), using California as a 
case study. California air permitting requirements are expected to be 
more restrictive than most States, and for this reason, it is 
considered a conservative case study. The information gathered is not 
expected to be nationally representative, but is illustrative as a 
``worst case scenario''.
    EPA contacted representatives from nine air districts in California 
via telephone to determine the likely response of their district to 
promulgation of a radon rule with an associated radon MCL requirement 
(USEPA 1999h). The air boards were chosen to represent large, 
metropolitan areas, medium-sized cities, and smaller, more rural areas. 
The representatives responded to the following questions:
     What is the likely response of your permitting board to 
water systems installing aeration treatment to comply with the radon 
rule?
     What are the likely permitting procedures and costs for 
water systems installing aeration for radon? Who would be responsible, 
the permitting board or the water system, for carrying out each 
procedure and paying the costs?
     Will large water systems and small water systems follow 
different procedures, or are procedures uniform regardless of water 
system size (e.g., off-gas volume)? How do permitting costs change with 
the applicant's system size?
     Will water systems be required to perform off-gas risk 
modeling as part of the permitting procedure or will they be required 
to do other environmental impact analyses?
     Would there be annual renewal procedures (e.g., 
reapplication, compliance monitoring) and costs? Who would be 
responsible for carrying our the procedures and bearing the costs?
     Is ongoing monitoring likely to be required?
    Where possible, representatives provided estimates of time and cost 
that could be incurred by water systems and the districts as a result 
of the potential district response to the radon rule.
    Responses to these questions indicated that the likely response to 
a radon rule is similar across the California air districts contacted. 
Most districts indicated they are likely to follow the lead of the 
State. ``Following the State's lead'' means that, if the State includes 
radon on its Toxic Air Contaminants List and establishes potency 
factors (unit risk factors and expected exposure levels for radon), air 
districts will probably regulate drinking water system aeration 
facilities through permits. Permitting procedures are similar across 
air districts and generally do not vary for facilities of different 
sizes. However, permitting costs and who bears those costs can vary 
significantly from air district to air district. Some portion of the 
costs are likely to vary based on facility size or emissions level.
    Currently, ``radionuclides'' (which includes radon) are on the 
Toxic Air Contaminant Identification List developed by the California 
Air Resources Board. Listed contaminants are categorized by priority, 
and depending on what category a substance is in, the substance may or 
may not have ``potency factors'' developed by California's Office of 
Environmental Hazard Health Assessment (OEHHA). At the present time, 
radon is ``Category 4A'', which means that OEHHA is not currently 
planning on publishing values for the radon unit risk factor and 
reference exposure level, indicating that air boards are not likely to 
require permitting for radon off-gas at the present time. However, 
radon has been proposed for elevation in priority to ``Category 3'', 
which means that it could be a candidate for the development potency 
numbers in the future. Since California air quality districts generally 
follow the lead of OEHHA, if OEHHA publishes a unit risk factor and 
reference exposure level for radon in the future, air districts are 
then likely to evaluate whether radon should be considered in their air 
permitting programs. If OEHHA decides not to establish potency factors 
for radon, California air districts are not likely to require 
permitting for radon off-gas from drinking water treatment plants.
    Respondents indicated that typical permitting procedures were: a 
system applies for a permit to construct; the board evaluates the 
application and decides whether or not to issue a permit; a permit may 
then be issued, after which the system may construct the aerator; the 
District conducts an inspection and the system may or may not have to 
perform testing; a public notice is issued if required by risk level 
and proximity of schools; the District issues a permit to operate; 
system must annually renew the permit (no monitoring or inspection 
likely). It is likely that water systems in the more densely populated, 
Metropolitan areas are more likely to need to do a risk assessment and 
perform modeling as part of their permit application. Permitting costs 
ranged from < $500 for simple permitting up to $50,000 for more 
complicated situations, with typical permitting costs reported in the 
$1,000 to $5,000 range. These costs do not include any radon dispersion 
controls or other engineering controls that might be required for the 
permit.
    (b) Centralized Liquid Phase Granular Activated Carbon (GAC) and 
Point-of-Entry GAC. GAC removes radon from water via sorption. 
``Downflow'' designs are used, in which the raw water is introduced at 
the top of the carbon bed and flows under pressure downwards through 
the bed. The treated water may then be disinfected or otherwise post-
treated and piped to the distribution system. Advantages to the use of 
GAC relative to aeration include the lack of a need to break pressure 
(and hence re-pump), the lack of radon off-gas emissions, and, in very 
small systems applications with good water quality, GAC typically has 
no moving parts and requires little maintenance. Details regarding the 
process of radon removal via GAC are provided elsewhere (USEPA 1999h, 
AWWARF 1998a,b). This discussion will focus on potential issues that 
small water systems may face if they choose GAC for radon removal. Of 
these, raw water quality is of paramount concern since it affects radon 
removal efficiency, unit lifetime, and the potential for secondary 
radiation hazards. Radon, iron, uranium, and radium levels are most 
important.
    (i) Radon Influent Levels for POE GAC: Gamma Radiation Hazards. An 
upper limit of 5,000 pCi/L of radon in influent water being treated by 
POE GAC is suggested by Rydell et al. (1989) and Kinner et al. (1990b) 
to protect persons in frequent proximity to the carbon bed (i.e., 
residents) from gamma ray exposures. This influent level is based on a 
residential exposure limit of 170 mRem/year, or 0.058 mR/hour based on 
8 hours/day of maximum exposure, 365 days per year. The 170 mRem/year 
limit was established by the National Council on Radiation

[[Page 59292]]

Protection Bulletin (cited by Rydell et al. 1989). Note that this 
residential exposure limit is less conservative than the EPA 
recommended limit of 100 mRem/year for water treatment plant personnel. 
However, the assumption of 8 hours/day of maximum proximity is 
extremely conservative. The 100 mRem/year limit is achieved if a person 
gets maximum exposure for approximately 5 hours per day or less, 365 
days per year, which is still a conservative assumption.
    Rydell et al. determined this influent limit based on an empirical 
and theoretical relationship between radon influent level and gamma ray 
emissions from the carbon bed. As will be discussed next, based on 
recent work using improved gamma ray detection methodology, Hess et al. 
(1998) report that this limit may be too low by a factor of 2, i.e., 
the suggested radon influent limit may be closer to 10,000 pCi/L. Note 
that these limits are based on assumptions about GAC contact basin 
configurations, type and extent of shielding, length of time and 
proximity of persons to the unit, etc. While the ``rules-of-thumb'' 
described previously are useful, appropriate radon influent limits may 
be higher or lower depending upon site-specific considerations and 
should be determined on a case-by-case basis.
    The University of Maine reported results on the removal of radon 
from drinking water using GAC (Hess et al. 1998). Nine carbon beds (all 
in Maine), which had been in use for more than 10 years by public water 
systems and private homes for radon removal, were studied. Radon 
influent levels ranged from 330 to 107,000 pCi/L, with a mean of 24,500 
pCi/L and a standard deviation of 11,800 pCi/L. Gamma ray emissions 
from the GAC units and accumulated radon progeny, uranium, and radium 
were analyzed. Gamma ray emissions from the GAC surface ranged from 
11.5 uR/h to 301 uR/h, with a mean of 78 uR/h and a standard deviation 
of 82 uR/h, and were 2 to 4 times lower than predicted by theory. The 
authors concluded that the limit of 5,000 pCi/L suggested by Rydell et 
al. (1989) may be too low by a factor of 2 or more.
    (ii) Radon Influent Levels for Centralized GAC: Gamma Radiation 
Hazards. Using the very conservative assumption that a water treatment 
operator will be in close proximity for 40 hours per week, the 100 
mRem/year translates to around 0.05 mR/hour, which also corresponds to 
a maximum of 5,000-10,000 pCi/L of radon for small flows. However, 
since GAC is likely to be used only by very small water systems and 
does not involve intensive O&M, much shorter work weeks are likely. 
Using 10 hours/week, the maximum radon influent level would be higher. 
Again, these are ``rule-of-thumb'' suggestions only. The best means to 
ensure that 100 mRem/year maximum exposure limits are maintained is to 
implement appropriate monitoring of gamma levels in the treatment 
facility and to ensure that proper shielding and worker proximity 
restraints are engineered to minimize exposures.
    (iii) Other Water Quality Considerations: Naturally-Occurring Iron 
and Dissolved Organic Materials. The adsorption of iron precipitates 
can reduce a unit's radon removal efficiency, so that the raw water may 
need to be pre-treated to stabilize and/or remove the dissolved iron. 
The American Water Works Association Research Foundation (AWWARF 
1998a,b) reports that waters with low iron and low levels of naturally 
occurring organic matter (``total organic carbon'', TOC) can achieve 
good radon steady-state removals (i.e., radon sorption equals radon 
decay), but that the negative effects of iron and TOC on removal 
efficiencies may necessitate pilot testing to ensure proper contactor 
design. For raw water with high iron and/or TOC, pre-filtration or pre-
oxidation/filtration may be required to achieve good steady-state 
removals.
    (iv) Other Water Quality Considerations: Naturally-Occurring 
Uranium and Radium: Uranium and radium raw water levels are also of 
concern since sorption may occur onto the GAC surface, which results in 
uranium and radium occurrence in the GAC filter backwash residuals and 
ultimately may create a final GAC bed disposal problem. Water quality 
(pH, iron levels, natural organic matter levels, alkalinity, etc.) 
determine the extent to which uranium and radium sorb to the GAC 
surface. AWWARF (1998b) reported results from case studies conducted 
over a two year period in New Hampshire, New Jersey, and Colorado, 
including findings regarding loadings of uranium and radium on the GAC 
surface and respective levels in backwash residuals. Radon influent 
levels were 15,000-17,000 pCi/L, 2,220 pCi/L, and <7,500 pCi/L at the 
New Hampshire, New Jersey, and Colorado sites, respectively. In the New 
Hampshire pilot study, backwash residuals contained 200 
pCi/g uranium and 50 to 60 pCi/g radium. For water 
treatment residuals with uranium levels between 75 and 750 pCi/g, EPA 
suggests that disposal measures be determined on a case-by-case basis 
(USEPA 1994b). In general, disposal in a controlled landfill 
environment may be necessary. The GAC bed itself accumulated less than 
the limit of 75 pCi/g for all but one of the five GAC columns in New 
Hampshire. For the New Jersey and Colorado pilot plants, uranium, 
radium, and radon progeny levels were low enough in the backwash 
residuals and the GAC bed that special disposal considerations were not 
an issue. It should be noted that State disposal restrictions may be 
more stringent than EPA's suggestions, which may make GAC a less 
attractive alternative in these States.
    (v) GAC Disposal Issues. Radon progeny (e.g., Pb-210, a beta 
emitter) accumulation is also related to radon influent level. If radon 
influent levels are high, the GAC unit lifetime may decrease 
significantly, where this lifetime is defined as the length of time 
between start-up and when an unacceptable accumulation of radioactive 
Pb-210 occurs. While no Federal agency currently has the legislative 
authority to regulate the disposal of wastes generated by water 
treatment facilities on the basis of naturally occurring radioactive 
materials (NORM), EPA (USEPA 1994b) suggests that NORM solid wastes 
with radioactivity above 2,000 pCi/g be disposed of in appropriate low-
level radioactive waste facilities. Furthermore, given the prohibitive 
expense and burden of disposing of low-level radioactive waste, EPA 
would suggest that water treatment facilities avoid situations where 
such high waste levels would expected to potentially occur. In the case 
of wastes containing Pb-210, EPA suggests that case-by-case 
determinations be made for determining appropriate disposal. In 
summary, for higher radon influent levels, shorter bed lifetimes may be 
appropriate to reduce Pb-210 build-up.
    Hess et al. (1998), cited previously, also studied several methods 
of cleaning the GAC bed by removing Pb-210 and radium from the spent 
GAC with various chemical cleaning solutions (e.g., solutions of 
hydrochloric acid, nitric acid, sodium hydroxide, etc.). Disposal of 
the cleaned GAC and the much smaller volume of concentrated radon 
progeny and radium is expected to be cheaper in some cases than 
disposal of the contaminated GAC bed to a controlled disposal-facility. 
The authors concluded that several of the cleaning solutions 
(hydrochloric acid at 1 mole/liter, nitric acid at 0.5 mole/liter, and 
acetic acid 0.5 mole/liter in quantities of 150 mL solution per 100 
grams of carbon) show promise. Precipitates on the GAC surface 
(including iron oxides, sorbed radium

[[Page 59293]]

and radon progeny, including Pb-210) were effectively removed. Removal 
efficiencies for Pb-210 ranged from 30 percent to 70 percent and radium 
removals from 70 to 90 percent. This work indicates that a viable 
system of collecting and cleaning spent GAC material may be feasible, 
potentially making GAC a more attractive small systems alternative. 
Work supporting programs of this type deserves further consideration.
    (vi) The American Water Works Association Research Foundation 
Report on Radon Removal Using GAC. The American Water Works Association 
Research Foundation (AWWARF 1998a,b) has recently reported on radon 
removal by GAC. AWWARF suggests that water systems with design flows 
below 70 gallons per minute may want to evaluate GAC and POE GAC as 
potential radon removal technologies (AWWARF 1999a), but warns that 
they appear to be attractive technologies only for very small systems 
with radon influent levels below 5,000 pCi/L, iron and manganese levels 
low enough not to warrant pre-treatment, and uranium and radium levels 
low enough not to accumulate to levels of concern on the GAC bed (USEPA 
1994b). These findings are generally consistent with EPA's findings.

B. Analytical Methods

1. Background
    The SDWA directs EPA to set a contaminant's MCL as close to its 
MCLG as is ``feasible'', the definition of which includes an evaluation 
of the feasibility of performing chemical analysis of the contaminant 
at standard drinking water laboratories. Specifically, SDWA directs EPA 
to determine that it is economically and technologically feasible to 
ascertain the level of the contaminant being regulated in water in 
public water systems (Section 1401(1)(C)(i)). NPDWRs are also to 
contain ``criteria and procedures to assure a supply of drinking water 
which dependably complies with such [MCLs]; including accepted methods 
for quality control and testing procedures to insure compliance with 
such levels. * * *'' (Section 1401(1)(D)).
    To comply with these requirements, EPA considers method performance 
under relevant laboratory conditions, their likely prevalence in 
certified drinking water laboratories, and the associated analytical 
costs. A critical part of the method performance evaluation involves an 
analysis of inter-laboratory collaborative study data. This analysis 
allows EPA to confirm that the method provides reliable and repeatable 
results when used within a given laboratory and when used 
``identically'' in other standard laboratories. Other technical 
limitations, e.g., sampling and sample preservation requirements, 
requirements for non-standard apparatus, and hazards from wastestreams, 
are also considered.
    In particular, the reliability of analytical methods at the maximum 
contaminant level is critical to the implementation and enforcement of 
the NPDWR. Therefore, each analytical method considered was evaluated 
for accuracy, recovery (lack of bias), and precision (good 
reproducibility over the range of MCLs considered). The primary purpose 
of this evaluation is to determine:
     Whether currently available analytical methods measure 
radon in drinking water with adequate accuracy, bias, and precision;
     If any newly developed analytical methods can measure 
radon in drinking water with acceptable performance;
     Reasonable expectations of technical performance for these 
methods by analytical laboratories conducting routine analysis at or 
near the MCL levels (interlaboratory studies); and
     Analytical costs. The selection of analytical methods for 
compliance with the proposed regulation includes consideration of the 
following factors:
    (a) Reliability (i.e., Precision/ accuracy of the analytical 
results over a range of concentrations, including the MCL);
    (b) Specificity in the presence of interferences;
    (c) Availability of adequate equipment and trained personnel to 
implement a national compliance monitoring program (i.e., laboratory 
availability);
    (d) Rapidity of analysis to permit routine use; and
    (e) Cost of analysis to water supply systems.
2. Analytical Methods for Radon in Drinking Water
    (a) Proposed Analytical Methods for Radon. The analytical methods 
described here are the testing procedures EPA identified and evaluated 
to insure compliance with the MCL and AMCL. Two analytical methods for 
radon in water that fit EPA's criteria for acceptability as compliance 
monitoring methods were identified: Liquid Scintillation Counting (LSC) 
and the de-emanation method. The LSC method is here defined as Standard 
Method 7500-Rn, SM 1995; the de-emanation method is described in the 
report, ``Two Test Procedures for Radon in Drinking Water, 
Interlaboratory Study'' (USEPA 1987). EPA believes these methods are 
technically sound, economical, and generally available for radon 
monitoring, and is proposing their use for monitoring to determine 
compliance with the MCL or AMCL. The reliability of these methods has 
been demonstrated by a history of many years of use by State, Federal, 
and private laboratories. Both methods have undergone interlaboratory 
collaborative studies (multi-laboratory testing), demonstrating 
acceptable accuracy and precision. Thirty-six laboratories participated 
in the interlaboratory study for Standard Method 7500-Rn and sixteen 
labs in the de-emanation study. The American Society for Testing and 
Materials (ASTM) has also published an LSC method (ASTM 1992). Although 
its collaborative study (15 participating laboratories) was conducted 
at radon sample concentrations greater than 1,500 pCi/L, it is 
substantially equivalent to Standard Method (SM) 7500-Rn. EPA is 
proposing that ASTM D-5072-92 serve as an alternate method for radon 
for both the MCL and AMCL, under the restriction that the quality 
controls from SM 7500-Rn are met; namely, that the relative percent 
differences between duplicate analyses are less than the 95 percent 
confidence level counting uncertainty, as defined in SM 7500-Rn. Table 
VIII.B.1 summarizes the proposed analytical methods for radon in 
drinking water.

[[Page 59294]]



                    Table VIII.B.1.--Proposed Analytical Methods for Radon in Drinking Water
----------------------------------------------------------------------------------------------------------------
                                                               References (method or page number)
                    Method                     -----------------------------------------------------------------
                                                     SM          ASTM                       EPA
----------------------------------------------------------------------------------------------------------------
Liquid Scintillation Counting.................   7500-Rn\1\    D 5072-92  ......................................
                                                                     \2\
De-emanation..................................  ...........  ...........  EPA 1987 \3\
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Standard Methods for the Examination of Water and Wastewater. 19th Edition Supplement. Clesceri, L., A.
  Eaton, A. Greenberg, and M. Franson, eds. American Public Health Association, American Water Works
  Association, and Water Environment Federation. Washington, DC. 1996.
\2\ American Society for Testing and Materials (ASTM). Standard Test Method for Radon in Drinking Water.
  Designation: D 5072-92. Annual Book of ASTM Standards. Vol. 11.02. 1996.
\3\ Appendix D, Analytical Test Procedure, ``The Determination of Radon in Drinking Water''. In ``Two Test
  Procedures for Radon in Drinking Water, Interlaboratory Collaborative Study''. EPA/600/2-87/082. March 1987.
  p. 22.

    Other analytical methods were evaluated, but they failed at least 
one of the criteria described previously. These methods included an 
``activated charcoal passive radon collector'', a ``de-gassing Lucas 
Cell'' technique (a variant of the de-emanation method), the ``electret 
ionization chamber system'', and a ``delay-coincidence liquid 
scintillation counting system''. All of these methods are described and 
evaluated elsewhere (USEPA 1999g). As described next, if EPA implements 
the ``Performance Based Measurement System'' (PBMS) program, then any 
method that performs according to specified criteria may be used for 
compliance monitoring.
    (b) Summary of Methods. Analysis of radon in drinking water by the 
LSC method involves preparation of the water sample (ca. 20 mL), which 
includes the selective partitioning of radon from the water sample into 
a water-immiscible mineral-oil scintillation cocktail and allowance for 
equilibration of radon-222 with its progeny. The prepared sample is 
then analyzed with an alpha-particle counting system that is optimized 
for detecting radon alpha particles. Scintillation counting methods are 
discussed later. One of the advantages of transferring the radon from 
the water sample into the water-immiscible cocktail is that potential 
interferents (other alpha emitters) are left behind in the water phase.
    The de-emanation method involves bubbling radon-free helium or aged 
air (low background radon) through the water sample into an evacuated 
scintillation chamber. After equilibrium is reached (3 to 4 hours), 
this chamber is placed in a counter and the resulting scintillations 
are counted. This method generally allows measurement of lower level of 
radon than does low volume direct liquid scintillation. However, this 
method is more difficult to use, requiring specialized glassware and 
skilled technicians. Regions of the country with high radon levels in 
water (e.g., New Hampshire and Maine) may experience problems with this 
method, since the high radon levels in the samples can cause high 
backgrounds in the Lucas cell, forcing retirement of the cell for 
extended periods.
    (c) Alpha Particle Counting Methods for Radon-222. One of the 
distinct characteristics of alpha particles is that they exhibit an 
intense loss of energy as they pass through matter, due to strong 
interactions between the alpha particles and the surrounding atoms. 
This intense loss of energy is used in differentiating alpha 
radioactivity from other types. Some of the alpha particle's energy 
loss is due to its ionization of atoms with which it comes in contact. 
Alpha particle detection is based on this phenomenon: when alpha 
particles ionize the phosphor coating of a detector, the energized 
phosphor ``scintillates'' (or emits light). The resulting light (or 
scintillations) are then detected and quantified with an appropriate 
detector that is calibrated to determine the concentration of the alpha 
emitter of interest. There are variants of detectors that measure these 
interactions, but this discussion will focus on the type relevant to 
the LSC and Lucas Cell methods.
    In scintillation counting, the alpha particle transfers energy to a 
scintillator medium, e.g., a phosphor dissolved in a solvent 
``cocktail'', which is enclosed within a ``light-tight'' container to 
reduce background light. The scintillation cocktail serves two roles: 
it contains the phosphor which is involved in quantifying the radon 
activity (concentration) and it selectively extracts the radon from the 
water sample, leaving behind other alpha emitters that may interfere 
with the analysis. The transfer of energy from the radon-derived alpha 
particles to the phosphor dissolved in the scintillator medium results 
in the production of light (scintillation) of energies characteristic 
of the phosphor and with an intensity proportional to the energy 
transmitted from the alpha particles, which are the ``signature'' of 
radon-222. A ``counter'' records the individual amplified pulses which 
are proportional to the number of alpha particles striking the 
scintillation detector, which is ultimately proportional to the radon 
activity in the original sample. The scintillation cell system used for 
the liquid scintillation method is as described previously. The system 
used for the de-emanation method is similar, with the exception that a 
scintillation flask (``Lucas Cell'', a 100-125 ml metal cup coated on 
the inside with a zinc sulfide phosphor and having a transparent 
window) replaces the liquid scintillation medium described. A counting 
system compatible with the scintillation flask is incorporated to 
quantify the radon concentration in the sample. Since radon has a short 
decay period (half-life of 3.8 days), correction methods are employed 
to account for the radon that decayed between the time of sample 
collection and the end of the analysis.
    (d) Sampling Collection, Handling, and Preservation. In order to 
ensure that samples arriving at laboratories for analysis are in good 
condition, EPA is proposing requirements for sample collection, 
handling and preservation.
    When sampling for dissolved gases like radon, special attention to 
sample collection is required. Either the sample collection method 
described in SM 7500-Rn, the VOC sample collection method, or one of 
the methods described in ``Two Test Procedures for Radon in Drinking 
Water, Interlaboratory Collaborative Study'' (USEPA 1987) should be 
used. In addition, because dissolved radon tends to accumulate at the 
interface between a water sample and some types of plastic containers, 
glass bottles with teflon lined caps must be used. Finally, EPA's 
assessment of laboratory performance is premised on the assumption that 
sample analysis occurs no later than 4 days after collection. 
Laboratories unable to comply with this holding time limit may have 
difficulty performing within the estimated precision and accuracy 
bounds. EPA solicits public comment on the proposed sample collection 
procedures for radon in drinking water.

[[Page 59295]]

    In discussions between EPA and the water utility industry, concerns 
have been expressed about the difficulties in collecting samples and 
the requisite skills that may be required. EPA emphasizes that the 
skills required to sample for radon are the same as those required to 
sample for other currently regulated drinking water contaminants, 
namely volatile organic contaminants. In addition, the 1992 EPA 
collaborative study mentioned earlier evaluated four sample collection 
techniques and found them all capable of providing equivalent results. 
Supplementing this study, EPA has reviewed a sampling protocol for 
radon in water developed by the Department of Health Services Division 
of Drinking Water and Environmental Management (CA DHS 1998). This 
protocol employs one of the four techniques evaluated by EPA, the 
immersion technique.
    Using the immersion technique, the well is purged for 15 minutes by 
running the sampling tap, to ensure that a representative sample is 
collected. After the purging period, a length of flexible plastic 
tubing is attached to the spigot, tap, or other connection, and the 
free end of the tubing is placed at the bottom of a small bucket. The 
water is allowed to fill the bucket, slowly, until the bucket 
overflows. The bucket is emptied and refilled at least once.
    Once the bucket has refilled, a glass sample container of an 
appropriate size is opened and slowly immersed into the bucket in an 
upright position. Once the bottle has been placed on the bottom of the 
bucket, the tubing is placed into the bottle to ensure that the bottle 
is flushed with fresh water. After the bottle has been flushed, the 
tubing is removed while the bottle is resting on the bottom of the 
bucket. The cap is placed back on the bottle while the bottle is still 
submerged, and the bottle is tightly sealed. As noted in the California 
protocol cited earlier, the choice of the sample container is dependent 
on the laboratory that will perform the analysis, and will be a 
function of the liquid scintillation counter that is employed. If 
bottles are supplied by the laboratory, there is no question of what 
container to employ.
    Once the sealed sample bottle is removed from the bucket, it is 
inverted and checked for bubbles that would indicate headspace. If 
there are no visible air bubbles, the outside of the sealed bottle is 
wiped dry and cap is sealed in place with electrical tape, wrapped 
clockwise. After the sample bottle is sealed, a second (duplicate) 
sample is collected in the same fashion from the same bucket. The date 
and time of the sample collection is recorded for each sample.
    As can be surmised from the description, the sample collection 
procedures are not particularly labor intensive. Most of the time is 
spent allowing the water to overflow the bucket. Likewise, there are no 
significant manual skills required.
    (e) Skill Considerations for Laboratory Personnel. While neither of 
these techniques is difficult relative to standard drinking water 
methods, a discussion of the skills required to employ the methods is 
appropriate. Given the long history of successful use of the liquid 
scintillation counting technique (it has been used in medical 
laboratories and environmental research laboratories for well over 30 
years), EPA feels confident that State drinking water laboratories will 
be able to adequately use these methods. The skills required are 
primarily the ability to transfer and mix aliquots of the sample to a 
sealed container for further analysis. The counting process is highly 
automated and the equipment runs unattended for days, if needed.
    The de-emanation process requires somewhat more manual skill. As 
noted in the 1991 proposed rule, EPA expects that this technique would 
require greater efforts be made to train technicians than for the 
liquid scintillation technique. The technique requires that the 
counting cell be evacuated to about 10 mTorr pressure and then a series 
of stopcocks or valves are manipulated to transfer the radon that is 
purged from the sample into the counting cell. Potential problems with 
the analysis, such as a high background level of radon that can develop 
over the course of the day, or aspirating water into the counting cell, 
can be minimized by a well-trained analyst. However, as EPA concluded 
in 1991, the Lucas cell technique is not expected to form the sole 
basis of a compliance monitoring program for radon in drinking water.
    (f) Cost of Performing Analyses. The actual costs of performing 
analysis may vary with laboratory, analytical technique selected, the 
total number of samples analyzed by a lab, and by other factors. Based 
upon information collected in 1991, the average sample cost for radon 
in water was estimated to be $50 per sample. EPA recently updated this 
cost estimate to $57 per sample (USEPA 1999b) by conducting a similar 
survey of drinking water laboratories. The data from the 1991 and 1998 
surveys and the descriptive statistics are summarized in Table 
VIII.B.2. There was no clear correlation between the estimated price 
and the method cited by the laboratory. The 1998 range of prices 
brackets those collected by EPA in 1991. It is expected that the 
``market forces'' generated by a radon regulation will tend to lower 
per sample costs, especially in light of the fact the LSC is very 
amenable to automation, with feed capacities of more than 50 samples/
load possible. However, as will be discussed later, there may be short-
term laboratory capacity issues that resist a lowering of per sample 
prices.

                                                                           Table VIII.B.2. Radon Sample Cost Estimate
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Cost      Year data
           Arbitrary lab No.              estimate    collected                                                   Descriptive statistics for 1991
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1.....................................          $30         1991  Mean, $49.80; Median, $47.00; Std. Dev., $18.80; Range, $45; Minimum, $30; Maximum, $75.
2.....................................           44         1991
3.....................................           50         1991
4.....................................           75         1998
                                                                                                               Descriptive Statistics for 1998 Data
5.....................................           75         1998  Mean, $56.88; Median, $52.50; Std. Dev., $15.80; Range, $35; Minimum, $40; Maximum, $75.
6.....................................           50         1998
7.....................................           40         1998
8.....................................           75         1998
9.....................................           45         1998
10....................................           55         1998
11....................................           75         1998
12....................................           40         1998
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 59296]]

    These cost data are preliminary and may be different in practice 
for the following reasons: (a) As the number of experienced 
laboratories increases, the costs can be expected to decrease; (b) 
analytical costs are determined, to some extent, by the quality control 
efforts and quality assurance programs adhered to by the analytical 
laboratory; (c) per-sample costs are influenced by the number of 
samples analyzed per unit time. EPA solicits comments on its cost 
estimates from laboratories experienced in performing these analyses.
    (g) Method Detection Limits and Practical Quantitation Levels. 
Method detection limits (MDLs) and practical quantitation levels (PQLs) 
are two performance measures used by EPA to estimate the limits of 
performance of analytic chemistry methods for measuring contaminants in 
drinking water. An MDL is the lowest level of a contaminant that can be 
measured by a specific method under ideal research conditions. EPA 
usually defines the MDL as the minimum concentration of a substance 
that can be measured and reported with 99 percent confidence that the 
true value is greater than zero. The term MDL is used interchangeably 
with minimum detectable activity (MDA) in radionuclide analysis, which 
is defined as that amount of activity which in the same counting time, 
gives a count which is different from the background count by three 
times the standard deviation of the background count. A PQL is the 
level at which a contaminant can be ascertained with specified methods 
on a routine basis (such as compliance monitoring) by accredited 
laboratories, within specified precision and accuracy limits.
    The feasibility of implementing an MCL at a particular level is in 
part determined by the ability of analytical methods to ascertain 
contaminant levels with sufficient precision and accuracy at or near 
the MCL. The proposed methods demonstrate good reproducibility and 
accuracy at radon concentrations in the range of 150-300 pCi/L (half of 
the proposed MCL up to the proposed MCL), as demonstrated in the 
results from inter-laboratory studies. In inter-laboratory studies (or 
Performance Evaluation studies), prepared samples of known 
concentration are distributed for analysis to participating labs, which 
have no information on the concentrations of the samples. The results 
of the analyses by the participants are compared with the known value 
and with each other to estimate the precision and accuracy of both the 
methods used and the lab's proficiency in using the method. Table 
VIII.B.3 summarizes the statistical results of these inter-laboratory 
studies for the proposed methods.
    In the 1991 proposed rule, EPA proposed using both the MDL and PQL 
as measures of performance for radon analytical methods. EPA also 
proposed acceptance limits based on the PQLs that were derived from 
these performance evaluation studies. The use of acceptance limits was 
confusing to commenters for various reasons. The important issue is the 
observation that true analytical method performance is related to 
within-laboratory conditions (including counting times in the case of 
radiochemicals) and that acceptance limits are based on multi-
laboratory Performance Evaluation studies. For non-radiochemical 
contaminants this issue is less troublesome because their PQLs tend to 
be ``fixed'' since the MDLs to which they are related reflect optimized 
conditions for standard laboratory equipment, whereas for radiochemical 
contaminants, counting times can always be increased to increase the 
sensitivity and hence lower the appropriate acceptance limits. While 
the fifty minute counting time in Standard Method 7500-Rn reflects a 
balanced trade-off between time of analysis (and hence the cost of 
analysis) and sensitivity, it can obviously be adjusted as needed to 
adjust sensitivity. For this reason, commenters objected to the use of 
acceptance limits (and, relatedly, PQLs) for radiochemical 
contaminants.
    EPA agrees that these comments have merit and has decided to seek 
comment on two proposals regarding the use of acceptance limits and 
PQLs for radon. The first proposal, and the preferred option, is to not 
use acceptance limits or PQL for radon, and to adopt the detection 
limit as the measure of sensitivity, as done in the 1976 Radionuclides 
rule. The existing definition of the detection limit takes into account 
the influence of the various factors (efficiency, volume, recovery 
yield, background, counting time) that typically vary from sample to 
sample. Thus, the detection limit applies to the circumstances specific 
to the analysis of an individual sample and not to an idealized set of 
measurement parameters, as with acceptance limits and PQLs. The 
proposed detection limit is 12 +/- 12 pCi/L, which is based on the 
detection limit described in SM 7500-Rn (50 minute counting time, 6 cpm 
background, 2.7 cpm/dpm efficiency, and under the energy window 
optimization procedure as described in the method). This detection 
limit should be applicable to all three approved methods.
    One of the reasons for setting a sensitivity standard is to ensure 
that laboratories will perform acceptably well on a routine basis at 
contaminant levels near the MCL. Internal quality control/quality 
assurance procedures are of paramount importance. In addition, 
Proficiency Tests are administered by laboratory certifying authorities 
to ensure that laboratory performance is acceptable. Currently, the 
system for administering proficiency tests and certifying laboratories 
is in a state of transition. Up to the recent past, all primacy 
entities evaluated laboratory performance based on EPA's Performance 
Evaluation (PE) studies program, the National Exposure Research 
Laboratory (NERL-LV) Performance Evaluation (PE) Studies program for 
radioactivity in drinking water. Currently, the Proficiency Testing 
(PT) program for radionuclides is being privatized, i.e., operated by 
an independent third party provider accredited by the National 
Institute of Standards and Technology (NIST). A lack of uniformity in 
state PT requirements may limit laboratory availability for a given 
public water system to laboratories that use PT samples approved by the 
state. It should be noted that this issue is general and is not 
specific to the proposed radon regulation. Efforts to encourage 
uniformity in state PT requirements are described in more detail in the 
laboratory capacity section.
    Under the alternative of using the MDL as the measure of 
sensitivity, standard statistical procedures would be used to ensure 
that a laboratory has analyzed PT samples acceptably. Since the 
national PT program will still be overseen by EPA, the exact procedures 
for determining acceptable performance will be developed by EPA and 
NIST as the PT program develops. The respective roles of EPA and NIST 
in the PT program and discussed further in the Laboratory Approval and 
Certification section.
    The second proposal is to use the concepts of the acceptance limit 
and PQL for radon. Using the standard relationship that PQLs are equal 
to 5 to 10 times the MDL yields a PQL for radon in the range of 60 to 
240 pCi/L. EPA is proposing a PQL of 100 pCi/L and is seeking comment 
on this value. The proposed acceptance limit for a single sample is 
5 %. The proposed acceptance limits for triplicate analyses 
at the 95th and 99th percent confidence intervals are 6 % 
and 9 %, respectively. All of these acceptance limits are 
based on the inter-laboratory studies used for the precision and 
accuracy results reported in Table

[[Page 59297]]

 VIII.B.3. EPA seeks comments on the relative merits between the first 
option (the preferred option) of using only an MDL as the measure of 
sensitivity and the second option of using a PQL with prescribed 
acceptance limits.

          Table VIII.B.3.--Inter-laboratory Performance Data for Proposed Radon Analytical Methods \1\
----------------------------------------------------------------------------------------------------------------
                                              Sample
                  Method                   Conc.  pCi/  Accuracy  %  Repeatability  Reproducibility    Bias  %
                                                L                         pCi/L          pCi/Ls
----------------------------------------------------------------------------------------------------------------
SM 7500-Rn...............................          111      101-102             9              12        0.7-2.3
SM 7500-Rn...............................          153      102-103            10           16-18        2.3-3.4
De-Emanation.............................          111          114            16              23           14.5
De-Emanation.............................          153          114            17              28           13.7
ASTM D5072-92............................        1,622           97         2,217           3,541           -2.6
ASTM D5072-92............................       16,324           95        14,950          44,400           -4.7
ASTM D5072-92............................       66,324           94        49,190         210,350          -6.0
----------------------------------------------------------------------------------------------------------------
Notes: (1) All results are reported in methods citations found in Table VIII.B.1.

    (h) Accuracy and Precision of the Proposed Methods. While SM 7500-
Rn has the best over-all results in precision and accuracy, the de-
emanation method also shows acceptable performance. The ASTM method 
shows similar accuracy and bias, but much larger errors in 
repeatability (operator precision) and reproducibility (between-lab 
precision). Given this inferior demonstration of precision and the 
higher concentrations used in the intra-laboratory studies, it may be 
argued that this method should not be proposed as a drinking water 
method. However, EPA maintains that the method is similar enough in 
substance to SM 7500-Rn that it may serve as an alternate method if the 
laboratories use the appropriate quality control measures, i.e., ensure 
that the relative percent difference between results on duplicate 
samples is within the counting uncertainty 95% confidence interval, 
where at least 10% of daily samples are duplicates. This procedure is 
described in the 4th edition of the Manual for the Certification of 
Laboratories Analyzing Drinking Water, Criteria and Procedures Quality 
Assurance (EPA 1997). EPA requests comment on including ASTM D5072-92 
as an alternate test method.

C. Laboratory Approval and Certification

1. Background
    The ultimate effectiveness of the proposed regulations depends upon 
the ability of laboratories to reliably analyze contaminants at 
relatively low levels. The Drinking Water Laboratory Certification 
Program is intended to ensure that approved drinking water laboratories 
analyze regulated drinking water contaminants within acceptable limits 
of performance. The Certification Program is managed through a 
cooperative effort between EPA's Office of Ground Water and Drinking 
Water and its Office of Research and Development. The program 
stipulates that laboratories analyzing drinking water compliance 
samples must be certified by U.S. EPA or the State. The program also 
requires that certified laboratories must analyze PT samples, use 
approved methods, and States must also require periodic on-site audits.
    External checks of performance to evaluate a laboratory's ability 
to analyze samples for regulated contaminants within specific limits is 
one of the means of judging lab performance and determining whether to 
grant certification. Under a PT program, laboratories must successfully 
analyze PT samples (contaminant concentrations are unknown to the 
laboratory being reviewed) that are prepared by an organization that is 
approved by the primacy entity. Successful annual participation in the 
PT program is prerequisite for a laboratory to achieve certification 
and to remain certified for analyzing drinking water compliance 
samples. Achieving acceptable performance in these studies of known 
test samples provides some indication that the laboratory is following 
proper practices. Unacceptable performance may be indicative of 
problems that could affect the reliability of the compliance monitoring 
data.
    EPA's previous PE sample program and the approaches to determine 
laboratory performance requirements are discussed in 63 FR 47097 
(September 3, 1998, ``1998 methods update''). In that notice, EPA 
amended the regulations to adopt the universal requirement for 
laboratories to successfully analyze a PE sample at least once each 
year, addressing the fact that the Agency has not specified PE test 
frequency requirements in its current drinking water regulations. 
Though not specified in the methods update regulation, PE samples may 
be provided by EPA, the State, or by a third party with the approval of 
the State or EPA. Under the developing PT program, NIST has accredited 
a list of PT sample providers, including a radionuclides PT samples 
which will apply to radon.
    In addition, guidance on minimum quality assurance requirements, 
conditions of laboratory inspections, and other elements of laboratory 
certification requirements for laboratories conducting compliance 
monitoring measurements are detailed in the 4th edition of the Manual 
for the Certification of Laboratories Analyzing Drinking Water, 
Criteria and Procedures Quality Assurance (EPA 1997), which can be 
downloaded via the internet at ``http://www.epa.gov/OGWDW/
labindex.html''.
2. Laboratory Capacity--Practical Availability of the Methods
    In order to determine the practical availability of the methods, 
EPA considered three major factors. First, the availability of the 
major instrumentation was reviewed. Secondly, several laboratories 
performing drinking water analyses were contacted to determine their 
potential capabilities to perform radon analyses. Lastly, EPA has 
reviewed the current status of the privatized Performance Evaluation 
studies program and the on-going measure to implement a uniform 
program, highlighting the potential impacts on short-term and long-term 
laboratory capacity for radon.
3. Laboratory Capacity: Instrumentation
    Regarding instrumentation availability, the major instrumentation 
required for LSC is the liquid scintillation counter. Automated 
counters capable of what that method terms ``automatic spectral 
analysis'' are available from at least a dozen suppliers. The de-
emanation Lucas cell apparatus is the same apparatus that has been used 
for radium analyses for many years. In light of the wide availability 
and the long history of accessibility of the proper instrumentation, 
EPA believes that instrument availability should not be an issue for 
radon analytical methods.

[[Page 59298]]

4. Laboratory Capacity: Survey of Potential Laboratories
    In order to evaluate the availability of laboratory capacity to 
perform radon analyses, EPA contacted the drinking water certification 
authorities in the States of California, Maryland, and Pennsylvania. 
These states were chosen based both on estimated radon occurrence and 
the overall status of the programs. Ultimately, EPA collected 
information on the availability and relative costs of radon analyses 
for drinking water from a total of nine commercial laboratories.
    Eight of the nine laboratories that were contacted do perform radon 
analyses. All the laboratories were certified in one or more states to 
perform radiochemical analyses. When asked what specific methods were 
used, the laboratories responded with either the technique (liquid 
scintillation counting) or a specific method citation. EPA Method 913 
(which later was revised to become SM 7500-Rn) was cited by two of the 
laboratories. EPA Method ``EERF Appendix B'' was cited by another 
laboratory. The remaining laboratories indicated that they performed 
liquid scintillation analyses and could accommodate requests for 
methods employing that technique.
    When asked about capacity, the laboratories indicated that they 
each perform between 100 and 12,000 analyses per year. The latter 
figure came from a laboratory that is currently involved in a large 
ground water monitoring project in the western United States. The next 
largest estimate was 300 samples per year. However, EPA expects that 
like any other type of environmental analysis, given a regulatory 
``driver'' to perform the analysis, and given the ability of LSC 
analysis to be automated, the laboratory capacity will develop in a 
timely manner.
    EPA's 1992 Annual Report on Radiation Research and Methods 
Validation reports the results of a collaborative study on radon 
analysis (EPA 1993) and is another useful source of information 
regarding potential radon laboratory capacity. This study employed 51 
laboratories with the capability to perform liquid scintillation 
analyses. This suggests that at that time there already existed a 
substantial capacity for these analyses.
    Further, the liquid scintillation apparatus is used for other 
radiochemical analyses, including tritium. Information from EPA 
regarding the performance evaluation program for tritium analyses 
suggests that there are approximately 100-200 laboratories with the 
necessary equipment. Much of the capacity for tritium analyses could 
also be used for radon (EPA 1997). As of September 1997, 136 of 171 
participating laboratories achieved acceptable results for tritium. 
While the total number of participants and the number achieving 
acceptable results vary between studies, the data indicate that there 
is a substantial capability for liquid scintillation analysis 
nationwide.
5. Laboratory Capacity: Laboratory Certification and Performance 
Evaluation Studies
    The availability of laboratories is also dependent on laboratory 
certification efforts in the individual states with regulatory 
authority for their drinking water programs. Until June of 1999, a 
major component of many of these certification programs was their 
continued participation in the current EPA Water Supply WS performance 
evaluation (PE) program, which included radiochemistry PE studies. Due 
to resource limitations, EPA has recently privatized EPA's PE programs, 
including the Water Supply studies. EPA has addressed this topic in 
public stakeholders meetings and in some recent publications, including 
Federal Register notices and its June 1997 ``Labcert Bulletin'', which 
can be downloaded from the Internet at ``http://www.epa.gov/OGWDW/
labcert3.html''. The decision to privatize the PE studies programs was 
announced in the Federal Register on June 12, 1997 (62 FR 32112). This 
notice indicated that in the future the National Institute of Standards 
and Technology (NIST) would develop standards for private sector PT 
sample providers and would evaluate and accredit these providers, while 
the actual development and manufacture of PT samples would fall to the 
private sector. Further information regarding the respective roles of 
EPA and NIST in the privatized PT program can be downloaded from NIST's 
homepage at ``http://ts.nist.gov/ts/htdocs/210/210.htm''. EPA believes 
that this program will ensure the continued viability of the existing 
PT programs, while maintaining government oversight.
    This externalized proficiency testing program is in the process of 
becoming operational. Under the externalized PT program:
     EPA issues standards for the operation of the program,
     NIST administers a program to accredit PT sample 
providers,
     Non-EPA PT sample providers develop and manufacture PT 
sample materials and conduct PT studies,
     Environmental laboratories purchase PT samples directly 
from PT Sample Providers (approved by NIST or the State), and
     Certifying authorities certify environmental laboratories 
performing sample analyses in support of the various water programs 
administered by the States and EPA under the Safe Drinking Water Act.
    NIST is in the process of approving a provider for PT samples for 
radionuclides, including radon. States also have the option of 
approving their own PT sample providers. At this time, it is difficult 
to speculate to what degree this externalization of the PT program will 
affect short-term and long-term laboratory capacity for radon. EPA 
recognizes that initial implementation problems may arise because of 
the potential for near-term limited availability of radon PT samples. 
EPA also recognizes that insufficient laboratory capacity may lead to a 
short-term increase in analytical costs. In the absence of definitive 
information regarding the future PT program, EPA solicits public 
comment on this matter.
6. Efforts To Ensure a Uniform Proficiency Testing Program: NELAC
    The National Environmental Laboratory Accreditation Conference 
(NELAC) is also evaluating the issues surrounding privatization of the 
SDWA PT program through its proficiency testing committee. NELAC serves 
as a voluntary national standards-setting body for environmental 
laboratory accreditation, and includes members from both state and 
Federal regulatory and non-regulatory programs having environmental 
laboratory oversight, certification, or accreditation functions. One of 
the goals for the re-designed SDWA PT program is to be consistent with 
NELAC's recommendations.
    The members of NELAC meet bi-annually to develop consensus 
standards through its committee structure. These consensus standards 
are adopted by participants for use in their own programs in pursuit of 
a uniform national laboratory accreditation program in which 
environmental testing laboratories will be able to receive one annual 
accreditation that is accepted nationwide. As part of its accreditation 
program, NELAC is developing standards for a proficiency testing 
program that addresses all fields of testing, including drinking water. 
Recent meetings of the Proficiency Testing Committee of NELAC have 
reviewed several important issues, including State selection of PT 
sample providers and reciprocity between States.

[[Page 59299]]

These issues are described in more detail elsewhere (NELAC 1999a). The 
NELAC Proficiency Testing Committee is currently drafting requirements 
for radiochemical proficiency testing under SDWA. The June 15, 1999 
draft (NELAC 1999b) of its radiochemical proficiency testing 
requirements describes radiochemical PT sample designs, acceptance 
limits, and other information.
    The intent of the NELAC standards setting process is to ensure that 
the needs of EPA and state regulatory programs are satisfied in the 
context of a uniform national laboratory accreditation program. EPA 
recognizes that cooperating with NELAC is an important part of the re-
design of the Proficiency Testing (PT) program for drinking water, 
since NELAC provides a means for states, environmental testing 
laboratories, and PT study providers to have direct input into the 
process. It is hoped that this mutual effort will minimize the 
potential disruption in the process of moving from the old EPA PE 
program towards the new privatized PT program. EPA shares NELAC's goal 
of encouraging uniformity in standards between primacy States regarding 
laboratory proficiency testing and accreditation.
7. Laboratory Capacity: Holding Time
    The short holding time for radon, 4 days in Method 7500-Rn, 
presents concerns relative to the practical availability of laboratory 
capacity as well. The 4-day holding time was also the focus of a number 
of comments that EPA received in response to the 1991 proposed rule. 
Many commenters were concerned that if a local laboratory is not 
available, the only alternative will be to send the samples by 
overnight delivery to a laboratory elsewhere. However, this situation 
is not unique to the analysis of radon. As evidenced during the data 
gathering pursuant to the Disinfection By-Products Information 
Collection Rule (DBP ICR), several large commercial laboratories 
already account for a sizable share of the market for SDWA analyses for 
non-radon parameters, including organics, for which the holding times 
are often 7 days. Given that a day would be required for shipping the 
samples, only three days would remain for the laboratory to perform the 
radon analysis (the day on which the sample is collected being ``day 
zero''). Some commenters argued that for a large commercial laboratory 
serving the water utilities, this short holding time will make it 
difficult if not impossible to perform the necessary analyses within 
the holding time. However, through common sense scheduling efforts 
between the utility and the laboratory, such as not collecting samples 
on Thursdays and Fridays, the holding time issue should be able to be 
accommodated in light of the ability of the LSC method to be highly 
automated.

D. Performance-Based Measurement System (PBMS)

    On October 6, 1997, EPA published a Notice of the Agency's intent 
to implement a Performance Based Measurement System (PBMS) in all of 
its programs to the extent feasible (62 FR 52098). EPA is currently 
determining how to adopt PBMS in its drinking water program, but has 
not yet made final decisions. When PBMS is adopted in the drinking 
water program, its intended purpose will be to increase flexibility in 
laboratories in selecting suitable analytical methods for compliance 
monitoring, significantly reducing the need for prior EPA approval of 
drinking water analytical methods. Under PBMS, EPA will modify the 
regulations that require exclusive use of Agency-approved methods for 
compliance monitoring of regulated contaminants in drinking water 
regulatory programs. EPA will probably specify ``performance 
standards'' for methods, which the Agency would derive from the 
existing approved methods and supporting documentation. A laboratory 
would then be free to use any method or method variant for compliance 
monitoring that performed acceptably according to these criteria. EPA 
is currently evaluating which relevant performance characteristics 
should be specified to ensure adequate data quality for drinking water 
compliance purposes. After PBMS is implemented, EPA may continue to 
approve and publish compliance methods for laboratories that choose not 
to use PBMS. After EPA makes final determinations to implement PBMS in 
programs under the Safe Drinking Water Act, EPA would then provide 
specific instruction on the specified performance criteria and how 
these criteria would be used by laboratories for radon compliance 
monitoring.

E. Proposed Monitoring and Compliance Requirements for Radon

1. Background
    The monitoring regulation for radon proposed in 1991 by EPA 
required that groundwater systems monitor for radon at each entry point 
to the distribution system quarterly for one year initially. Monitoring 
could be reduced to one sample annually per entry point to the 
distribution system if the average of all first quarterly samples was 
below the MCL. States could allow systems to reduce monitoring to once 
every three years if the system demonstrated that results of all 
previous samples collected were below the MCL. The proposal also 
allowed States to grant waivers to groundwater systems to reduce the 
frequency of monitoring, up to once every 9 years, if States determined 
that radon levels in drinking water were consistently and reliably 
below the MCL. Comments made in response to the proposed monitoring 
requirements for radon were mainly concerned that the proposed 
monitoring requirements including number of samples and the frequency 
of monitoring did not adequately take into account the effect of 
seasonal variations in radon levels on determining compliance. Other 
commenters felt that sampling at the entry point of the distribution 
system was not representative of exposure to radon, and they suggested 
that sampling for radon should be done at the point of use.
    Since the 1991 proposal EPA has obtained additional information 
from States, the waterworks industry and academia on the occurrence of 
radon, including data on the temporal variability of radon. Utilizing 
this additional data, the Agency performed extensive statistical 
analyses to predict how temporal, analytical variations and variations 
between individual wells may affect exposure to radon. The results of 
these analyses are described in detail in the report ``Methods, 
Occurrence and Monitoring Document for Radon'' in the docket for this 
rule (USEPA 1999g). As a result of the new information available, EPA 
was able to refine the requirements for monitoring and address the 
concerns expressed by the commenters on the 1991 proposal.
    The proposed monitoring requirements for radon are consistent with 
the monitoring requirements for regulated drinking water contaminants, 
as described in the Standardized Monitoring Framework (SMF) promulgated 
by EPA under the Phase II Rule of the National Primary Drinking Water 
Regulations (NPDWR) and revised under Phases IIB and V. The goal of the 
SMF is to streamline the drinking water monitoring requirements by 
standardizing them within contaminant groups and by synchronizing 
monitoring schedules across contaminant groups. A summary of monitoring 
requirements in this proposal, the SMF and the 1991 proposal are 
provided in Table VIII.E.1.

[[Page 59300]]



         Table VIII.E.1.--Comparison of Monitoring Requirements
------------------------------------------------------------------------
                    Monitoring requirements for radon
-------------------------------------------------------------------------
                                  1999 Proposal--MCL/   SMF for IOCs in
          1991 Proposal                  AMCL             groundwater
------------------------------------------------------------------------
                     Initial Monitoring Requirements
------------------------------------------------------------------------
Four consecutive quarters of      Four consecutive    Four consecutive
 monitoring at each entry point    quarters of         quarters of
 for one year. Initial             monitoring at       monitoring at
 monitoring was proposed to have   each entry point.   each entry point
 been completed by January 1,      Initial             for sampling
 1999.                             monitoring must     points initially
                                   begin by three      exceeding MCL.
                                   years from date
                                   of publication of
                                   the final rule in
                                   Federal Register
                                   of 4.5 years from
                                   date of
                                   publication of
                                   the final rule in
                                   Federal Register
                                   (depending on
                                   effective date
                                   applicable to the
                                   State).
------------------------------------------------------------------------
                     Routine Monitoring Requirements
------------------------------------------------------------------------
One sample annually if average    One sample          One sample at each
 from four consecutive quarterly   annually if         sample point
 samples taken initially is less   average from four   during the
 than MCL.                         consecutive         initial 3 year
                                   quarterly samples   compliance period
                                   is less than MCL/   for groundwater
                                   AMCL, and at the    systems for
                                   discretion of       sampling points
                                   State.              below MCL.
------------------------------------------------------------------------
          1991 Proposal           1999 Proposal--MCL    SMF for IOCs in
                                                          Groundwater
------------------------------------------------------------------------
                     Reduced Monitoring Requirements
------------------------------------------------------------------------
State may allow groundwater       State may allow     State may allow
 systems to reduce the frequency   CWS using           groundwater
 of monitoring to once every       groundwater to      systems to reduce
 three years provided that they    reduce monitoring   monitoring
 have monitored quarterly in the   frequency to:.      frequency to:
 initial year and completed       Once every three    Once every three
 annual testing in the second      years if average    years if samples
 and third year of the first       from four           subsequently
 compliance period. Groundwater    consecutive         detects less than
 systems must demonstrate that     quarterly samples   MCL and
 all previous analytical samples   is less than \1/    determined by
 were less than the MCL.           2\ the MCL/AMCL,    State to be
                                   provided no         ``reliably and
                                   samples exceed      consistently
                                   the MCL/AMCL. and   below MCL.''
                                   if the system is
                                   determined by
                                   State to be
                                   ``reliably and
                                   consistently
                                   below MCL/AMCL ''.
------------------------------------------------------------------------
                    Monitoring Requirements for Radon
------------------------------------------------------------------------
          1991 Proposal           1999 Proposal--MCL/   SMF for IOCs in
                                          AMCL            Groundwater
------------------------------------------------------------------------
                    Increased Monitoring Requirements
------------------------------------------------------------------------
Systems monitoring annually or    Systems monitoring  If the MCL is
 once per three year compliance    annually would be   exceeded in a
 period exceed the radon MCL in    required to         single sample,
 a single sample would be          increase            the system
 required to revert to quarterly   monitoring if the   required to begin
 monitoring until the average of   MCL/AMCL for        sampling
 4 consecutive samples is less     radon is exceeded   quarterly until
 than the MCL. Groundwater         in a single         State determines
 systems with unconnected wells    sample, the         that it is
 would be required to conduct      system would be     ``reliably and
 increased monitoring only at      required to         consistently''
 those wells exceeding the MCL.    revert to           below MCL.
The State may require more         quarterly
 frequent monitoring than          monitoring until
 specified.                        the average of 4
Systems may apply to the State     consecutive
 to conduct more frequent          samples is less
 monitoring than the minimum       than the MCL/AMCL.
 monitoring frequencies           Systems monitoring
 specified.                        once every three
                                   years would be
                                   required to
                                   monitor annually
                                   if the radon
                                   level is less
                                   than MCL/AMCL but
                                   above \1/2\ MCL/
                                   AMCL in a single
                                   sample. Systems
                                   may revert to
                                   monitoring once
                                   per three years
                                   if the average of
                                   the initial and
                                   three consecutive
                                   annual samples is
                                   lees than \1/2\
                                   MCL/AMCL.
                                  CWS using
                                   groundwater with
                                   un-connected
                                   wells would be
                                   required to
                                   conduct increased
                                   monitoring only
                                   at those well
                                   which are
                                   affected.
------------------------------------------------------------------------
 
[[Page 59301]]

 
                    Monitoring Requirements for Radon
------------------------------------------------------------------------
          1991 Proposal           1999 Proposal--MCL    SMF for IOCs in
                                                          Groundwater
------------------------------------------------------------------------
                          Confirmation Samples
------------------------------------------------------------------------
Where the results of sampling     Systems may         Where the results
 indicate an exceedence of the     collect             sampling indicate
 maximum contaminant level, the    confirmation        an exceedence of
 State may require that one        samples as          the maximum
 additional sample be collected    specified by the    contaminant
 as soon as possible after the     State. The          level, the State
 initial sample was taken [but     average of the      may require that
 not to exceed two weeks] at the   initial sample      one additional
 same sampling point. The          and any             sample be
 results of the of the initial     confirmation        collected as soon
 sample and the confirmation       samples will be     as possible after
 sample shall be averaged and      used to determine   the initial
 the resulting average shall be    compliance.         sample was taken
 used to determine compliance.                         [but not to
                                                       exceed two weeks]
                                                       at the same
                                                       sampling point.
                                                       The results of
                                                       the initial
                                                       sample and the
                                                       confirmation
                                                       sample shall be
                                                       averaged and the
                                                       resulting average
                                                       shall be used to
                                                       determine
                                                       compliance.
------------------------------------------------------------------------
                          Grandfathering of Data
------------------------------------------------------------------------
If monitoring data collected      If monitoring data  States may allow
 after January 1, 1985 are         collected after     previous sampling
 generally consistent with the     proposal of the     data to satisfy
 requirements specified in the     rule are            the initial
 regulation, than the State may    consistent with     sampling
 allow the systems to use those    the requirements    requirements
 data to satisfy the monitoring    specified in the    provided the data
 requirements for the initial      regulation, then    were collected
 compliance period.                the State may       after January 1,
                                   allow the systems   1990.
                                   to use those data
                                   to satisfy the
                                   monitoring
                                   requirements for
                                   the initial
                                   compliance period.
------------------------------------------------------------------------
                    Monitoring Requirements for Radon
------------------------------------------------------------------------
          1991 Proposal           1999 Proposal--MCL    SMF for IOCs in
                                                          Groundwater
------------------------------------------------------------------------
                                 Waivers
------------------------------------------------------------------------
State may grant waiver to         The State may       The State may
 groundwater systems to reduce     grant a             grant waiver to
 the frequency of monitoring, up   monitoring waiver   groundwater
 to nine years. If State           to systems to       systems after
 determines that radon levels in   reduce the          conducting
 drinking water are ``reliably     frequency of        vulnerability
 and consistently'' below the      monitoring to up    assessment to
 MCL.                              to one sample       reduce the
                                   every nine years    frequency of
                                   based on previous   monitoring, up to
                                   analytical          nine years, if
                                   results,            State determines
                                   geological          that radon levels
                                   characteristics     in drinking water
                                   of source water     are ``reliably
                                   aquifer and if a    and
                                   State determines    consistently''
                                   that radon levels   below the MCL.
                                   in drinking water  System must have
                                   are ``reliably      three previous
                                   and                 samples.
                                   consistently''      Analytical
                                   below the MCL/      results of all
                                   AMCL.               previous samples
                                  Analytical results   taken must be
                                   of all previous     below MCL.
                                   samples taken
                                   must be below \1/
                                   2\ the MCL/AMCL.
------------------------------------------------------------------------

    In developing the proposed compliance monitoring requirements for 
radon, EPA considered:
    (1) The likely source of contamination in drinking water;
    (2) The differences between ground water and surface water systems;
    (3) The collection of samples which are representative of consumer 
exposure;
    (4) Sample collection and analytical methods;
    (5) The use of appropriate historical data to identify vulnerable 
systems and to specify monitoring requirements for individual systems;
    (6) The analytical, temporal and intra-system variance of radon 
levels;
    (7) The use of appropriate historical data and statistical analysis 
to establish reduced monitoring requirements for individual systems; 
and
    (8) The need to provide flexibility to the States to tailor 
monitoring requirements to site-specific conditions by allowing them 
to:

--Grant waivers to systems to reduce monitoring frequency, provided 
certain conditions are met.
--Require confirmation samples for any sample exceeding the MCL/AMCL.
--Allow the use of previous sampling data to satisfy initial sampling 
requirements.
--Increase monitoring frequency.
--Decrease monitoring frequency.
2. Monitoring for Surface Water Systems
    CWSs relying exclusively on surface water as their water source 
will not be required to sample for radon. Systems that rely in part on 
ground water would be considered groundwater systems for purposes of 
radon monitoring. Systems that use ground water to supplement surface 
water during low-flow periods will be required to monitor for radon. 
Ground water under the influence of surface water would be considered 
ground water for this regulation.
3. Sampling, Monitoring Schedule and Initial Compliance for CWS Using 
Groundwater
    EPA is retaining the quarterly monitoring requirement for radon as 
proposed initially in the 1991 proposal to account for variations such 
as sampling, analytical and temporal variability in radon levels. 
Results of analysis of data obtained since 1991, estimating 
contributions of individual sources of variability to overall variance 
in the radon data sets evaluated, indicated that sampling and 
analytical variance contributes less than 1 percent to the overall 
variance. Temporal variability within single wells accounts

[[Page 59302]]

for between 13 and 18 percent of the variance in the data sets 
evaluated, and a similar proportion (12-17 percent) accounts for 
variation in radon levels among wells within systems. (USEPA 1999g)
    The Agency performed additional analyses to determine whether the 
requirement of initial quarterly monitoring for radon was adequate to 
account for seasonal variations in radon levels and to identify non-
compliance with the MCL/AMCL. Results of analysis based on radon levels 
modeled for radon distribution for ground water sources (USEPA 1999g) 
and systems (USEPA 1998a) in the U.S. show that the average of the 
first four quarterly samples provides a good indication of the 
probability that the long-term average radon level in a given source 
would exceed an MCL or AMCL. Tables VIII.E.2 and VIII.E.3 show the 
probability of the long-term average radon level exceeding the MCL and 
AMCL at various averages obtained from the first four quarterly samples 
from a source.

 Table VIII.E.2.--The Relationship Between the First-Year Average Radon
  Level and the Probability of the Long-Term Radon Average Radon Levels
                            Exceeding the MCL
------------------------------------------------------------------------
                                          Then the probability that the
    If the average of the first four      long-term average radon level
   quarterly samples from a source is    in that source exceeds 300 pCi/
                                                       L is
------------------------------------------------------------------------
Less than 50 pCi/L.....................  0 percent.
Between 50 and 100 pCi/L...............  0.5 percent.
Between 100 and 150 pCi/L..............  0.4 percent.
Between 150 and 200 pCi/L..............  7.2 percent.
Between 200 and 300 pCi/L..............  26.8 percent.
------------------------------------------------------------------------


 Table VIII.E.3.--The Relationship Between the First-Year Average Radon
  Level and the Probability of the Long-Term Radon Average Radon Levels
                           Exceeding the AMCL
------------------------------------------------------------------------
                                          Then the probability that the
    If the average of the first four      long-term average radon level
   quarterly samples from a source is    in that source exceeds 4000 pCi/
                                                       L is
------------------------------------------------------------------------
Less than 2,000 pCi/L..................  Less than 0.1 percent.
Between 2,000 and 2,500 pCi/L..........  9.9 percent.
Between 2,500 and 3,000 pCi/L..........  15.1 percent.
Between 3,000 and 4,000 pCi/L..........  32.9 percent.
------------------------------------------------------------------------

    The Agency proposes that systems relying wholly or in part on 
ground water will be required to initially sample quarterly for radon 
for one year at each well or entry point to the distribution system. 
All samples will be required to be of finished water, as it enters the 
distribution system after any treatment and storage. If the average of 
the four quarterly samples at each well is below the MCL/AMCL, 
monitoring may be reduced to once a year at State discretion. Systems 
may be required to continue monitoring quarterly in instances where the 
average of the quarterly samples at each well is below but close to the 
MCL/AMCL. The reason for this is that in such cases, there is a good 
chance for the long-term average radon level to exceed the MCL/AMCL.
    Systems already on-line must begin initial monitoring for 
compliance with the MCL/AMCL by the compliance dates specified in the 
rule (i.e., 3 years after the date of promulgation or 4.5 years after 
the date of promulgation). Monitoring requirements for new sources will 
be determined by the State. The compliance dates are discussed in 
detail in Section VII.E, Compliance Dates.
    The Agency is retaining the requirement as proposed in 1991 to 
sample at the entry point to the distribution system. Sampling at the 
entry point allows the system to account for radon decay during storage 
and removal during the treatment process. The reason for not allowing 
sampling at the point of use is that this approach would not take into 
account higher exposure levels that may be encountered at locations 
upstream from the sampling site. In addition, sampling at the entry 
point will make it easier to identify and isolate possible contaminant 
sources within the system. The sample collection sites at each entry 
point to the distribution system and the monitoring schedule requiring 
sampling for four consecutive quarters proposed herein is consistent 
with the SMF. This approach streamlines monitoring since the same 
sampling points can be used for the collection of samples for other 
source-related contaminants.
    EPA specifically requests comments on the following aspects of the 
proposed monitoring requirements:
     The appropriateness of the proposed initial monitoring 
period.
     The availability and capabilities of laboratories to 
analyze radon samples collected during the initial compliance period. 
The Agency recognizes that short-term implementation problems may arise 
to meet the initial monitoring deadline because of the potential 
limited availability of radon performance evaluation (PE) samples used 
to evaluate and certify laboratories.
     The appropriateness of the proposed number and frequency 
of samples required to monitor for radon.
     The designation of sampling locations at the entry point 
to the distribution system which is located after any treatment and 
storage. Comments are also solicited on the definition of sampling 
points that are representative of consumer exposure.
     Designating sampling locations and frequencies that permit 
simultaneous monitoring for all regulated contaminants, whenever 
possible and advantageous. The proposed sampling locations would be 
such that the same sampling locations could be used for the collection 
of samples for other source-related contaminants such as the volatile 
organic chemicals and inorganic chemicals, which would simplify sample 
collection efforts.
    EPA also solicits comments on whether the monitoring requirements 
should include additional monitoring for radon as a source of consumer 
exposure from the distribution system. Results of investigations in 
Iowa indicate that in some instances, pipe scale deposited in the 
distribution system can be a source of exposure to radon. Community 
ground water systems could be required to collect an additional sample 
from the distribution system during the initial year of monitoring, at 
the same time the entry point sample is collected, and continue to 
collect samples from the distribution system annually if it is shown 
that exceedence of the MCL/AMCL is caused by the release of radon from 
deposited scale in the interior of the distribution system. Results 
obtained from distribution samples could provide information on the 
extent and frequency

[[Page 59303]]

of occurrence of radon originating from distribution systems.
4. Increased/Decreased Monitoring Requirements
    Initial compliance with the MCL/AMCL will be determined based on an 
average of four quarterly samples taken at individual sampling points 
in the initial year of monitoring. Systems with averages exceeding the 
MCL/AMCL at any sampling point will be deemed to be out of compliance. 
Systems in a non-MMM State exceeding the MCL will have the option to 
develop and implement a local MMM program in accordance with the 
timeframe discussed in Section VII.E, Compliance Dates without 
receiving a MCL violation.
    Systems exceeding the MCL/AMCL will be required to monitor 
quarterly until the average of four consecutive samples is less than 
the MCL/AMCL. Systems will then be allowed to collect one sample 
annually if the average from four consecutive quarterly samples is less 
than the MCL/AMCL and if the State determines that the system is 
reliably and consistently below the MCL/AMCL.
    Systems will be allowed to reduce monitoring frequency to once 
every three years (one sample per compliance period) per well or 
sampling point, if the average from four consecutive quarterly samples 
is less than \1/2\ the MCL/AMCL and the State determines that the 
system is reliably and consistently below the MCL/AMCL. As shown in 
Tables VIII.E.2 and VIII.E.3, EPA believes that there is sufficient 
margin of safety to allow for this since there is a small probability 
that long term average radon levels will exceed the MCL/AMCL.
    Systems monitoring annually that exceed the radon MCL/AMCL in a 
single sample will be required to revert to quarterly monitoring until 
the average of four consecutive samples is less than the MCL/AMCL. 
Community ground water systems with unconnected wells will be required 
to conduct increased monitoring only at those wells exceeding the MCL/
AMCL. Compliance will be based on the average of the initial sample and 
three consecutive quarterly samples.
    Systems monitoring once per compliance period or less frequently 
which exceed \1/2\ the MCL/AMCL (but do not exceed the MCL/AMCL) in a 
single sample would be required to revert to annual monitoring. Systems 
may revert to monitoring once every three years if the average of the 
initial and three consecutive annual samples is less than \1/2\ the 
MCL/AMCL. Community ground water systems with unconnected wells will be 
required to conduct increased monitoring only at those wells exceeding 
the MCL/AMCL.
    States may grant a monitoring waiver reducing monitoring frequency 
to once every nine years (once per compliance cycle) provided the 
system demonstrates that it is unlikely that radon levels in drinking 
water will occur above the MCL/AMCL. In granting the monitoring waiver, 
the State must take into consideration factors such as the geological 
area where the water source is located, and previous analytical results 
which demonstrate that radon levels do not occur above the MCL/AMCL. 
The monitoring waiver will be granted for up to a nine year period. 
(Given that all previous samples are less than \1/2\ the MCL/AMCL, then 
it is highly unlikely that the long-term average radon levels would 
exceed the MCL/AMCL.)
    If the analytical results from any sampling point are found to 
exceed the MCL/AMCL (in the case of routine monitoring) or \1/2\ the 
MCL/AMCL (in the case of reduced monitoring), the State may require the 
system to collect a confirmation sample(s). The results of the initial 
sample and the confirmation sample(s) shall be averaged and the 
resulting average shall be used to determine compliance.
    EPA specifically requests comments on the following aspects of the 
proposed monitoring requirements :
     Allowing systems at State discretion, to reduce monitoring 
frequencies as long as the system demonstrates that its radon levels 
are maintained below the MCL/AMCL. For example, all community ground 
water systems would be required to collect one sample from each entry 
point to the distribution system (located after any treatment and 
storage) quarterly at first and annually after compliance is 
established. MCL/AMCL exceedence would trigger reverting to quarterly 
sampling until compliance with the MCL/AMCL is reestablished. 
Compliance is reestablished when the average of four consecutive 
quarterly samples is below the MCL/AMCL.
     Allowing States to reduce monitoring requirements to not 
less than once every three years if the average radon levels from four 
consecutive quarterly samples is less than \1/2\ the MCL/AMCL, and the 
State determines that the radon levels in the drinking water are 
reliably and consistently below \1/2\ the MCL/AMCL. A single sample 
exceeding \1/2\ the MCL/AMCL would trigger reverting to sampling 
annually. Comments are solicited on the criteria allowing the utility 
to revert to monitoring once every three years if the average of the 
initial and three consecutive annual samples is less than \1/2\ the 
MCL/AMCL.
     Factors affecting State discretion to grant waivers. In 
addition, the Agency solicits comments on the advisability of reducing 
the monitoring frequency up to nine years between samples. Comments are 
solicited on the requirement that all previous samples (that might be 
used to identify systems which are very unlikely to exceed the MCL/
AMCL) must be below \1/2\ the MCL/AMCL in order for a system to qualify 
for a waiver.
     Allowing States to require the collection of confirmation 
samples to verify initial sample results as specified by the State, and 
to use the average of the initial sample and the confirmation samples 
to determine compliance.
5. Grandfathering of Data
    At a State's discretion, sampling data collected since the proposal 
could be used to satisfy the initial sampling requirements for radon, 
provided that the system has conducted a monitoring program and used 
analytical methods that meet proposal requirements. The Agency wants to 
provide water suppliers with the opportunity to synchronize their radon 
monitoring program with monitoring for other contaminants and to get an 
early start on their monitoring program if they wish to do so.
    The Agency solicits comments on the advisability of allowing the 
use of monitoring data obtained since the proposal to satisfy the 
initial monitoring requirements.

IX. State Implementation

    This section describes the regulations and other procedures and 
policies States have to adopt, or have in place, to implement today's 
proposed rule. States must continue to meet all other conditions of 
primacy in 40 CFR part 142.
    Section 1413 of the SDWA establishes requirements that a State must 
meet to obtain or maintain primacy enforcement responsibility (primacy) 
for its public water systems. These include: (1) Adopting drinking 
water regulations that are no less stringent than Federal NPDWRs in 
effect under Section 1412(b) of the Act; (2) adopting and implementing 
adequate procedures for enforcement; (3) keeping records and making 
reports available on activities that EPA requires by regulation; (4) 
issuing variances and exemptions (if allowed by the State) under 
conditions no less stringent than allowed by Sections 1415 and 1416; 
(5) adopting

[[Page 59304]]

and being capable of implementing an adequate plan for the provision of 
safe drinking water under emergency situations; and (6) adopting 
authority for administrative penalties.
    40 CFR part 142 sets out the specific program implementation 
requirements for States to obtain primacy for the public water supply 
supervision (PWSS) program, as authorized under SDWA 1413 of the Act. 
In addition to meeting the basic primacy requirements, States may be 
required to adopt special primacy provisions pertaining to a specific 
regulation. States are required by 40 CFR 142.12 to include these 
regulation-specific provisions in an application for approval of their 
program revisions. To maintain primacy for the PWS program and to be 
eligible for interim primacy enforcement authority for future 
regulations, States must adopt today's rule, when final, along with the 
special primacy requirements discussed next. Interim primacy 
enforcement authority allows States to implement and enforce drinking 
water regulations once State regulations are effective and the State 
has submitted a complete and final primacy revision application. Under 
interim primacy enforcement authority, States are effectively 
considered to have primacy during the period that EPA is reviewing 
their primacy revision application.

A. Special State Primacy Requirements

    In addition to adopting drinking water regulations at least as 
stringent as the regulations described in the previous sections, EPA 
requires that States adopt certain additional provisions related to 
this regulation, in order to have their drinking water program revision 
application approved by EPA. States have two options when implementing 
this rule. States may adopt the AMCL and implement a State-wide MMM 
program plan or States may adopt the MCL. If a State chooses to adopt 
the MCL, CWSs in that State have the option to develop and implement a 
State-approved local MMM program plan and comply with the AMCL.
    To ensure that the State program includes all the elements 
necessary for a complete enforcement program, EPA is proposing that 40 
CFR part 142 be amended to require the following in order to obtain 
primacy for this rule:
    (1) Adoption of the promulgated Radon Rule, and
    (2) One of the following, depending on which regulatory option the 
State chooses to adopt:
    (a) If a State chooses to develop and implement a State-wide MMM 
program plan and adopt the AMCL, the primacy application must contain a 
copy of the State-wide MMM program plan meeting the four criteria in 40 
CFR Part 141 Subpart R and the following: a description of how the 
State will make resources available for implementation of the State-
wide MMM program plan, and a description of the extent and nature of 
coordination between interagency programs (i.e., indoor radon and 
drinking water programs) on development and implementation of the MMM 
program plan, including the level of resources that will be made 
available for implementation and coordination between interagency 
programs (i.e., indoor air and drinking water programs).
    (b) If a State chooses to adopt the MCL, the primacy application 
must contain a description of how the State will implement a program to 
approve local CWS MMM program plans prepared to meet the criteria 
outlined in 40 CFR Part 141 Subpart R. In addition, the primacy 
application must contain a description of how the State will ensure 
local CWS MMM program plans are implemented and the extent and nature 
of coordination between interagency programs (i.e., indoor radon and 
drinking water programs) on development and implementation of the MMM 
program, including the level of resources that will be made available 
for implementation and coordination between interagency programs (i.e., 
indoor air and drinking water programs), as well as, a description of 
the reporting and record keeping requirements for the CWSs.
    States are required to submit their primacy revision application 
packages by two years from the date of publication of the final rule in 
the Federal Register. For States adopting the AMCL, EPA approval of a 
State's primacy revision application is contingent on submission of and 
EPA approval of the State's MMM program plan. Therefore, EPA is 
proposing to require submission of State-wide MMM program plans as part 
of the complete and final primacy revision application. This will 
enable EPA to review and approve the complete primacy application in a 
timely and efficient manner in order to provide States with as much 
time as possible to begin to implement MMM programs. In accordance with 
Section 1413(b)(1) of SDWA and 40 CFR 142.12(d)(3), EPA is to review 
primacy applications within 90 days. Therefore, although the SDWA 
allows 180 days for EPA review and approval of MMM program plans, EPA 
expects to review and approve State primacy revision applications for 
the AMCL, including the State-wide MMM program plan, within 90 days of 
submission to EPA.
    EPA is proposing that States notify CWSs of their decision to adopt 
the MCL or AMCL at the time they submit their primacy application 
package to EPA (24 months after publication of the final rule). If a 
State adopts the MCL, CWSs choosing to implement a local CWS MMM 
program and comply with the AMCL will be required to have completed 
initial monitoring, notify the State of their intention, and begin 
developing a plan 4 years after the rule is final. EPA is particularly 
concerned that these CWSs have sufficient time to develop MMM program 
plans with local input and allow for State approval. Therefore, it is 
EPA's expectation that States will be submitting complete and final 
primacy revision applications by 24 months from the date of publication 
of the final rule in Federal Register. In reviewing any State requests 
for extensions of time in submitting primacy revision applications, EPA 
will consider whether sufficient time will be provided to CWSs to 
develop and get State approval of their local MMM program plans prior 
to implementation.

B. State Record Keeping Requirements

    Today's rule does not include changes to the existing recordkeeping 
provisions required by 40 CFR 142.14. MMM record keeping requirements 
will be addressed in each State's primacy revision application 
submission to meet the special primacy requirements for radon (40 CFR 
142.16).

C. State Reporting Requirements

    Currently States must report to EPA information under 40 CFR 142.15 
regarding violations, variances and exemptions, enforcement actions and 
general operations of State public water supply programs.
    In accordance with the Safe Drinking Water Act (SDWA), EPA is to 
review State MMM programs at least every five years. For the purposes 
of this review, the States with EPA-approved MMM program plans shall 
provide written reports to EPA in the second and fourth years between 
initial implementation of the MMM program and the first 5-year review 
period, and in the second and fourth years of every subsequent 5-year 
review period. EPA will review these programs to determine whether they 
continue to be expected to achieve risk reduction of indoor radon using 
the information provided in the two biennial reports. EPA requests 
comment on this approach. These reports are required to include the 
following information:

[[Page 59305]]

     A quantitative assessment of progress towards meeting the 
required goals described in Section VI. A., including the number or 
rate of existing homes mitigated and the number or rate of new homes 
built radon-resistant since implementation of the States' MMM program: 
and
     A description of accomplishments and activities that 
implement the program strategies outlined in the implementation plan 
and in the two required areas of promoting increased testing and 
mitigation of existing homes and promoting increased use of radon-
resistant techniques in construction of new homes.
     If goals were defined as rates, the State must also 
provide an estimate of the number of mitigations and radon-resistant 
new homes represented by the reported rate increase for the two-year 
period.
     If the MMM program plan includes goals for promoting 
public awareness of the health effects of indoor radon, testing of 
homes by the public; testing and mitigation of existing schools; and 
construction of new public schools to be radon-resistant, the report is 
also required to include information on results and accomplishments in 
these areas.
    EPA will use this information in discussions and consultations with 
the State during the five-year review to evaluate program progress and 
to consider what modifications or adjustments in approach may be 
needed. EPA envisions this review process will be one of consultation 
and collaboration between EPA and the States to evaluate the success of 
the program in achieving the radon risk reduction goals outlined in the 
approved programs. If EPA determines that a MMM program in not 
achieving progress towards its goals, EPA and the State shall 
collaborate to develop modifications and adjustments to the program to 
be implemented over the five year period following the review. EPA will 
prepare a summary of the outcome of the program evaluation and the 
proposed modification and adjustments, if any, to be made by the State.
    States that submit a letter to the Administrator by 90 days after 
publication of the final rule committing to develop an MMM program 
plan, must submit their first 2-year report by 6.5 years from 
publication of the final rule. For States not submitting the 90-day 
letter, but choosing subsequently to submit an MMM program plan and 
adopt the AMCL, the first 2-year report must be submitted to EPA by 5 
years from publication of the final rule. States shall make available 
to the public each of these two-year reports, as well as the EPA 
summaries of the five-year reviews of a State's MMM program, within 90 
days of completion of the reports and the review.
    In primacy States without a State-wide MMM program, the States 
shall provide a report to EPA every five-years on the status and 
progress of CWS MMM programs towards meeting their goals. The first of 
such reports would be due 5 years after CWSs begin implementing a local 
MMM program which is 5.5 years from publication of the final rule.

D. Variances and Exemptions

    Section 1415 of the SDWA authorizes the State to issue variances 
from NPDWRs (the term ``State'' is used in this preamble to mean the 
State agency with primary enforcement responsibility, or ``primacy,'' 
for the public water supply system program or EPA if the State does not 
have primacy). The State may issue a variance under Section 1415(a) if 
it determines that a system cannot comply with an MCL due to the 
characteristics of its source water, and on condition that the system 
install BAT. Under Section 1415(a), EPA must propose and promulgate its 
finding identifying the best available technology, treatment 
techniques, or other means available for each contaminant, for purposes 
of Section 1415 variances, at the same time that it proposes and 
promulgates a maximum contaminant level for such contaminant. EPA's 
finding of BAT, treatment techniques, or other means for purposes of 
issuing variances may vary, depending upon the number of persons served 
by the system or for other physical conditions related to engineering 
feasibility and costs of complying with MCLs, as considered appropriate 
by the EPA. The State may not issue a variance to a system until it 
determines among other things that the variance would not pose an 
unreasonable risk to health (URTH). EPA has developed draft guidance, 
``Guidance in Developing Health Criteria for Determining Unreasonable 
Risks to Health'' (USEPA 1990) to assist States in determining when an 
unreasonable risk to health exists. EPA expects to issue final guidance 
for determining when URTH levels exist later this year. When a State 
grants a variance, it must at the same time prescribe a schedule for 
(1) compliance with the NPDWR and (2) implementation of such additional 
control measures as the State may require.
    Under Section 1416(a), the State may exempt a public water system 
from any MCL and/or treatment technique requirement if it finds that 
(1) due to compelling factors (which may include economic factors), the 
system is unable to comply or develop an alternative supply, (2) the 
system was in operation on the effective date of the MCL or treatment 
technique requirement, or, for a newer system, that no reasonable 
alternative source of drinking water is available to that system, (3) 
the exemption will not result in an unreasonable risk to health, and 
(4) management or restructuring changes cannot be made that would 
result in compliance with this rule. Under Section 1416(b), at the same 
time it grants an exemption the State is to prescribe a compliance 
schedule and a schedule for implementation of any required interim 
control measures. The final date for compliance may not exceed three 
years after the NPDWR effective date except that the exemption can be 
renewed for small systems for limited time periods.
    EPA will not list ``small systems variance technologies'', as 
provided in Section 1415(e)(3) of the Act, since EPA has determined 
that affordable treatment technologies exist for all applicable system 
sizes and water quality conditions. As stated in this Section of the 
Act, if the Administrator finds that small systems can afford to comply 
through treatment, alternate water source, restructuring, or 
consolidation, according to the affordability criteria established by 
the Administrator, then systems are not eligible for small systems 
variances. Small systems will, however, still be able to apply for 
``regular'' variances and exemptions, pursuant to Sections 1415 and 
1416 of the Act.

E. Withdrawing Approval of a State MMM Program

    If EPA determines that a State MMM program is not achieving 
progress towards its MMM goals, and the State repeatedly fails to 
correct, modify and adjust implementation of its MMM program after 
notice by EPA, EPA may withdraw approval of the State's MMM program 
plan. The State will be responsible for notifying CWSs of the 
Administrator's withdrawal of approval of the State-wide MMM program 
plan. The CWSs in the State would then be required to comply with the 
MCL within one year from date of notification, or develop a State-
approved CWS MMM program plan. EPA will work with the State to develop 
a State process for review and approval of CWS MMM program plans that 
meet

[[Page 59306]]

the required criteria and establish a time frame for submittal of 
program plans by CWSs that choose to continue complying with the AMCL. 
The review process will allow for local public participation in 
development and review of the program plan.

X. What Do I Need To Tell My Customers? Public Information 
Requirements

A. Public Notification

    Sections 1414(c)(1) and (c)(2) of the SDWA, as amended, require 
that public water systems notify persons served when violations of 
drinking water standards occur. EPA recently proposed to revise the 
current public notification regulations to incorporate new statutory 
provisions enacted under the 1996 SDWA amendments (64 FR 25963, May 13, 
1999). The purpose of public notification is to alert customers in a 
timely manner to potential risks from violations of drinking water 
standards and the steps they should take to avoid or minimize such 
risks.
    Today's regulatory action would add violation of the radon NPDWR to 
the list of violations requiring public notice under the May 13, 1999, 
proposed public notification rule. Today's action would make three 
changes to the proposed public notification rule.
     First, Appendix A to Subpart Q would be modified to 
require a Tier 2 public notice for violations of the MCL and AMCL for 
all community water systems. Under the proposed rule, Tier 2 public 
notices would be required for violations and situations with potential 
to have serious adverse effects on human health. Tier 2 public notices 
must be distributed within 30 days after the violation is known, and 
must be repeated every three months until the violation is resolved.
     Second, Appendix A would also be modified to require a 
Tier 3 public notice for all radon monitoring and testing procedure 
violations and for violations of the Multimedia Mitigation (MMM) 
Program Plan. Tier 3 public notices must be distributed within a year 
of the violation and could, at the water system's option, be included 
in the annual Consumer Confidence Report (CCR).
     Third, Appendix B to Subpart Q would be modified to add 
standard health effects language, which public water systems are 
required to use in their notices when violations of the AMCL or MMM 
occur. EPA proposes that the standard health effects language for these 
violations, to be included in CCR annual reports and public notices. 
The language for violation of the (A)MCL would be as follows: ``People 
who use drinking water containing radon in excess of the (A)MCL for 
many years may have an increased risk of getting lung and stomach 
cancer.'' The language for violation of the MMM would be as follows: 
``Your water system is not complying with requirements to promote the 
reduction of lung cancer risks from radon in indoor air, which is a 
problem in some homes. Radon is a naturally occurring radioactive gas 
which may enter homes from the surrounding soil and may also be present 
in drinking water. Because your system is not complying with applicable 
requirements, it may be required to install water treatment technology 
to meet more stringent standards for radon in drinking water. The best 
way to reduce radon risk is to test your home's indoor air and, if 
elevated levels are found, hire a qualified contractor to fix the 
problem. For more information, call the National Safety Council's Radon 
Hotline at 1-800-SOS-RADON.'' The standard health effects language 
public water systems are to use in their public notice would be 
identical to that used in the annual CCR.
    The final public notification rule is expected to be published 
around December, 1999, well in advance of the August, 2000, deadline 
for the final radon regulation. The final public notification 
requirements for radon, therefore, will be published with the final 
radon rule. The Agency will republish the tables in Appendices A and B 
to Subpart Q of Part 141 with all necessary changes in the final rule.

B. Consumer Confidence Report

    Section 1414(d) of the SDWA requires that all community water 
systems provide annual water quality reports (or consumer confidence 
reports (CCRs)) to their customers. In their reports, systems must 
provide, among other things, the levels and sources of all detected 
contaminants, the potential health effects of any contaminant found at 
levels that violate EPA or State rules, and short educational 
statements on contaminants of particular interest.
    Today's action updates the standard CCR rule requirements in 
subpart O and adds special requirements that reflect the multimedia 
approach of this rule. The intent of these provisions is to assist in 
clearer communication of the relative risks of radon in indoor air from 
soil and from drinking water, and to encourage public participation in 
the development of the State or CWS MMM program plans. Systems that 
detect radon at a level that violates the A/MCL would have to include 
in their report a clear and understandable explanation of the violation 
including: the length of the violation, actions taken by the system to 
address the violation, and the potential health effects (using the 
language proposed today for Appendix C to subpart O: ``People who use 
drinking water containing radon in excess of the (A)MCL for many years 
may have an increased risk of getting lung and stomach cancer''). This 
approach is comparable to that used for other drinking water 
contaminants.
    In addition, recognizing the novelty of the MMM approach and the 
interest that consumers may have in participating in the design of the 
MMM program, today's action also proposes that any system that has 
ground water as a source must include information in its report in the 
years between publication of the final rule and the date by which 
States, or systems, will be required to implement an MMM program. This 
information would include a brief educational statement on radon risks, 
explaining that the principal radon risk comes from radon in indoor 
air, rather than drinking water, and for that reason, radon risk 
reduction efforts may be focused on indoor air rather than drinking 
water. This information will also note that many States and systems are 
in the process of creating programs to reduce exposure to radon, and 
encourage readers to call the Radon Hotline (800-SOS-RADON) or visit 
EPA's radon web site (www.epa.gov/iaq/radon) for more information. A 
system would be able to use language provided in the proposed rule by 
EPA or could chose to tailor the wording to its specific local 
circumstances in consultation with the primacy agency. EPA recognizes 
that this creates a slight additional burden on community water system 
operators, but believes that the value of strong public support for, 
and participation in, the creation of the MMM program outweighs this 
burden. EPA also recognizes that this notice may provoke some 
confusion, since CCRs would alert consumers to the risks presented by a 
contaminant which most systems have never monitored in their water, 
although the notice would state that the system would be testing and 
would provide customers with the results. EPA is requesting comment on 
this proposed notice.
    Finally, the Agency will republish the tables in Appendices A, B, 
and C to Subpart O of Part 141 with all necessary changes in the final 
rule.

[[Page 59307]]

 Risk Assessment and Occurrence

XI. What Is EPA's Estimate of the Levels of Radon in Drinking 
Water?

A. General Patterns of Radon Occurrence

    Radon levels in ground water in the United States are generally 
highest in New England and the Appalachian uplands of the Middle 
Atlantic and Southeastern States. There are also isolated areas in the 
Rocky Mountains, California, Texas, and the upper Midwest where radon 
levels in ground water tend to be higher than the United States 
average. The lowest ground water radon levels tend to be found in the 
Mississippi Valley, lower Midwest, and Plains States. The following map 
shows the general patterns of radon occurrence in those States for 
which data are available.

BILLING CODE 6560-50-P

[[Page 59308]]

[GRAPHIC] [TIFF OMITTED] TP02NO99.008



BILLING CODE 6560-50-C

[[Page 59309]]

    In addition to large-scale regional variation, radon levels in 
ground water vary significantly over a smaller area. Local differences 
in geology tend to greatly influence the patterns of radon levels 
observed at specific locations. (This means, for example, that not all 
radon levels in New England are high and not all radon levels in the 
Gulf Coast region are low). Over small distances, there is often no 
consistent relationship between radon levels in ground water and 
uranium or other radionuclide levels in the ground water or in the 
parent bedrock (Davis and Watson 1989). Similarly, no significant 
geographic correlation has been found between radon levels in 
groundwater systems and the levels of other inorganic contaminants. 
Radon may be found in groundwater systems where other contaminants (for 
example, arsenic) also occur. However, finding a high (or low) level of 
radon does not indicate that a high (or low) level of other 
contaminants will also be found. Similarly, there is little evidence 
that radon occurrence is correlated with the presence of organic 
pollutants. In estimating the costs of radon removal, EPA has taken 
into account the fact that other contaminants, such as iron and 
manganese, may also be present in the water. High levels of iron and 
manganese may complicate the process of radon removal and increase the 
costs of mitigation.
    Radon is released rapidly from surface water. Therefore, radon 
levels in supplies that obtain their water from surface sources (lakes 
or reservoirs) are very low compared to groundwater levels.
    Because of its short half life, there are relatively few man-made 
sources of radon exposure in ground water. The most common man-made 
sources of radon ground water contamination are phosphate or uranium 
mining or milling operations and wastes from thorium or radium 
processing. Releases from these sources can result in high ground water 
exposures, but generally only to very limited populations; for 
instance, to persons using a domestic well in a contaminated aquifer as 
a source of potable water (USEPA 1994a).

B. Past Studies of Radon Levels in Drinking Water

    A number of studies of radon levels in drinking water were 
undertaken in the 1970s and early 1980s. Most of these studies were 
limited to small geographic areas, or addressed systems that were not 
representative of community systems throughout the U.S. The first 
attempt to develop a comprehensive understanding of radon levels in 
public water supplies was the National Inorganics and Radionuclides 
Survey (NIRS), which was undertaken by the EPA in 1983-1984. As part of 
NIRS, radon samples were analyzed from 1,000 community groundwater 
systems throughout the United States. The size distribution of systems 
sampled was the same as the size distribution of groundwater systems in 
U.S., and the geographic distribution was approximately consistent with 
the regional distribution of systems. Because of the limited number of 
samples, however, the number of radon measurements in some States was 
quite small. Table XI.B.1 summarizes the regional patterns of radon in 
drinking water supplies as seen in the NIRS database.

               Table XI.B.1.--Radon in Community Ground Water Systems by Region (All System Sizes)
----------------------------------------------------------------------------------------------------------------
                                                                                                   Geometric
                         Region                           Arithmetic mean     Geometric mean        standard
                                                              (pCi/L)            (pCi/L)       deviation (pCi/L)
----------------------------------------------------------------------------------------------------------------
Appalachian............................................              1,127                333               4.76
California.............................................                629                333               3.09
Gulf Coast.............................................                263                125               3.38
Great Lakes............................................                278                151               3.01
New England............................................              2,933              1,214               3.77
Northwest..............................................                222                161               2.23
Plains.................................................                213                132               2.65
Rocky Mountains........................................                607                361              2.77
----------------------------------------------------------------------------------------------------------------
 Source: USEPA 1999g.
Note: These distributions are described in two ways. First, the arithmetic means (average values) are given. In
  addition, the geometric mean and geometric standard deviation are given. This approach is taken because the
  distributions of radon in groundwater systems are not ``normal'' bell-shaped curves. Instead, like many
  environmental data sets, it was found that the logarithms of the radon concentrations were normally
  distributed (``lognormal distribution.'') The geometric mean corresponds to the center of a bell-shaped
  ``normal'' distribution when radon concentrations are expressed in logarithms. The geometric standard
  deviation is a measure of the spread of the bell-shaped curve, expressed in logarithmic form.

    The NIRS has the disadvantage that the samples were all taken from 
within the water distribution systems, making estimation of the 
naturally occurring influent radon levels difficult. In addition, the 
NIRS data provide no information to allow analysis of the variability 
of radon levels over time or within individual systems. Thus, while the 
NIRS data provide statistically valid estimates of radon levels in the 
systems that were sampled, they do not adequately represent radon 
levels in some individual States, especially in large systems.
    The NIRS data formed the basis for EPA's first estimates of the 
levels of radon in community groundwater systems in the United States 
(Wade Miller 1990). They formed the basis for estimating the impacts of 
EPA's 1991 Proposed Rule. These estimates were updated in 1993, using 
improved statistical methods to estimate the distributions of radon in 
different size systems (Wade Miller 1993.)

C. EPA's Most Recent Studies of Radon Levels in Ground Water

    EPA's current re-evaluation of radon occurrence in ground water 
(USEPA 1999g) uses data from a number of additional sources to 
supplement the NIRS information and to develop estimates of the 
national distribution of radon in community ground water systems of 
different sizes. EPA gathered data from 17 States where radon levels 
were measured at the wellhead, rather than in the distribution systems. 
The Agency then evaluated the differences between the State (wellhead) 
data and the NIRS (distribution system) data. These differences were 
then used to adjust the NIRS data to make them more representative of 
ground water radon levels in the States where no direct

[[Page 59310]]

measurements at the wellhead had been made. EPA solicits any additional 
data on radon levels in community water systems, particularly in the 
largest size categories.
    Table XI.C.1 summarizes EPA's latest estimates of the distributions 
of radon levels in ground water supplies of different sizes. It also 
provides information on the populations exposed to radon through 
community water systems (CWS). In this table, radon levels and 
populations are presented for systems serving population ranges from 25 
to greater than 100,000 customers. The CWSs are broken down into the 
following system size categories:
     Very very small systems (25-500 people served), further 
subdivided into 25-100 and 101-500 ranges, in response to comments 
received on the 1991 proposal;
     Very small systems (501-3,300 people);
     Small systems (3,301-10,000 people);
     Medium systems (10,001-100,000 people); and
     Large systems (greater than 100,000 people).

                       Table XI.C.1.--Radon Distributions in Community Groundwater Systems
----------------------------------------------------------------------------------------------------------------
                                                        System Size (Population Served)
                             -----------------------------------------------------------------------------------
                                 25-100        101-500      501-3,300   3,301-10,000     >10,000     All systems
----------------------------------------------------------------------------------------------------------------
Total Systems...............     14,651        14,896         10,286         2,538         1,536        43,907
Geometric Mean Radon Level,         312           259            122           124           132           232
 pCi/L......................
Geometric Standard Deviation          3.0           3.3            3.2           2.3           2.3           3.0
Arithmetic Mean.............        578           528            240           175           187           442
Population Served (Millions)          0.87          3.75          14.1          14.3          55.0          88.1
Radon Level, pCi/L..........                Proportions of Systems Exceeding Radon Levels (percent)
100.........................         84.7          78.7           56.9          60.4          62.9          74.0
300.........................         51.4          45.1           22.1          14.3          16.2          39.0
500.........................         33.6          29.1           11.4           4.6           5.5          24.2
700.........................         23.4          20.3            6.8           1.8           2.3          16.5
1000........................         14.7          12.9            3.6           0.6           0.8          10.2
2000........................          4.7           4.4            0.8           0.0           0.1           4.9
4000........................          1.1           1.1            0.1           0.0           0.0           0.8 
----------------------------------------------------------------------------------------------------------------
Sources: USEPA 1999g; Safe Drinking Water Information System (1998).

    Systems were broken down in this fashion because EPA's previous 
analyses have shown that the distributions of radon levels are 
different in different size systems. In the updated occurrence 
analysis, insufficient data were available to accurately assess radon 
levels in various subcategories of largest systems. Thus, data from the 
two largest size categories were pooled to develop exposure estimates.

D. Populations Exposed to Radon in Drinking Water

    Based on data from the Safe Drinking Water Information System 
(SDWIS), the Agency estimates that approximately 88.1 million people 
were served by community ground water systems in the United States in 
1998. Using the data in Table XI.C.1, systems serving more than 500 
people account for approximately 95 percent of the population served by 
community ground water systems, even though they represent only about 
33 percent of the total active systems. The largest systems (those 
serving greater than 10,000 people) serve approximately 62.5 percent of 
the people served by community ground water systems, even though they 
account for only 3.5 percent of the total number of systems.
    As noted previously, the average radon levels vary across the 
system size categories. As shown in Table XI.C.1, the average system 
geometric mean radon levels range from approximately 120 pCi/L for the 
larger systems to 312 pCi/L for the smallest systems. The average 
arithmetic mean values for the various system size categories range 
from 175 pCi/L to 578 pCi/L, and the population-weighted arithmetic 
mean radon level across all the community ground water supplies is 213 
pCi/L (calculations not shown). The bottom panel of Table XI.C.1 shows 
the proportions of the systems with average radon levels greater than 
selected values.
    Table XI.D.1 presents the total populations in homes served by 
community ground water systems at different radon levels, broken down 
by system size category. These data show that approximately 20 percent 
of the total population served by community ground water systems are 
served by systems where the average radon levels entering the system 
exceed 300 pCi/L and 64 percent of this population are served by 
systems with average radon levels above 100 pCi/L. Less than one-tenth 
of one percent of the population is served by systems obtaining their 
water from sources with radon levels above 4,000 pCi/L.

                     Table XI.D.1.--Population Exposed Above Various Radon Levels by Community Ground Water System Size (Thousands)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Very very small       Very Small      Small        Medium         Large
                   Radon level  (pCi/L)                   ---------------------------------------------------------------------------------     Total
                                                              25-100      101-500     501-3,300     3,301-10K     10K-100K        >100K
--------------------------------------------------------------------------------------------------------------------------------------------------------
4,000....................................................          9.4           46           20           0.2           0.9           0.4          77.2
2,000....................................................           41          183          119           5.7          21.7          11.0         381
1,000....................................................          128          541          513          85.5         289           147         1,695
700......................................................          202          848          962         267           859           436         3,558
500......................................................          290        1,210        1,620         672         2,070         1,050         6,893
300......................................................          445        1,880        3,140       2,080         6,060         3,070        16,641
100......................................................          733        3,290        8,080       8,760        23,400        11,900        56,054
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 59311]]

XII. What Are the Risks of Radon in Drinking Water and Air?

A. Basis for Health Concern

    The potential hazard of radon was first identified in the 1940s 
when an increased incidence of lung cancer in Bohemian underground 
miners was shown to be associated with inhalation of high levels of 
radon-222 in the mines. By the 1950s, the hazard was shown to be due 
mainly to the short half-life progeny of radon-222. Based on a clear 
relationship between radon exposure and risk of lung cancer in a number 
of studies in miners, national and international health organizations 
have concluded that radon is a human carcinogen. In 1988, the 
International Agency for Research on Cancer (IARC 1988) convened a 
panel of world experts who agreed unanimously that sufficient evidence 
exists to conclude that radon causes cancer in humans and in 
experimental animals. The Biological Effects of Ionizing Radiation 
(BEIR) Committee (NAS 1988, NAS 1999a), the International Commission on 
Radiological Protection (ICRP 1987), and the National Council on 
Radiation Protection and Measurement (NCRP 1984) also have reviewed the 
available data and agreed that radon exposure causes cancer in humans. 
EPA has concurred with these determinations and classified radon in 
Group A, meaning that it is considered by EPA to be a human carcinogen 
based on sufficient evidence of cancer in humans. After smoking, radon 
is the second leading cause of lung cancer deaths in the United States 
(NAS 1999a).
    Most of the radon that people are exposed to in indoor and outdoor 
air comes from soil. However, radon in ground water used for drinking 
or other indoor purposes can also be hazardous. When radon in water is 
ingested, it is distributed throughout the body. Some of it will decay 
and emit radiation while in the body, increasing the risk of cancer in 
irradiated organs (although this increased risk is significantly less 
than the risk from inhaling radon). Radon dissolved in tap water is 
released into indoor air when it is used for showering, washing or 
other domestic uses, or when the water is stirred, shaken, or heated 
before being ingested. This adds to the airborne radon from other 
sources, increasing the risk of lung cancer (USEPA 1991, 1994a; NAS 
1999b).

B. Previous EPA Risk Assessment of Radon in Drinking Water

1. EPA's 1991 Proposed Radon Rule
    Because initial information on the cancer risks of radon came from 
studies of underground miners exposed to very high radon levels, not 
much consideration was given to non-occupational radon exposure until 
recently. As new miner groups at lower radon exposure levels were added 
to the data base, it became evident that radon exposures in indoor air, 
outdoor air, and drinking water might be important sources of risk for 
the U.S. population. In 1991, as part of developing a regulation for 
radionuclides and radon in water as required by the 1986 Safe Drinking 
Water Act, EPA drafted the Radon in Drinking Water Criteria Document 
(USEPA 1991) to assess the ingestion and inhalation risk associated 
with exposure to radon in drinking water. EPA estimated that a person's 
risk of fatal cancer from lifetime use of drinking water containing one 
picocurie of radon per liter (1 pCi/L) is close to 7 chances in 10 
million (7  x  10--7). Based on this and other 
considerations, EPA proposed a rule for regulating radon levels in 
public water systems (56 FR 33050).
2. SAB Concerns Regarding the 1991 Proposed Radon Rule
    The Radiation Advisory Committee of EPA's Science Advisory Board 
(SAB) reviewed EPA's draft criteria document and proposed rule and 
identified a number of issues that had not been adequately addressed, 
including: (a) Uncertainties associated with the models, model 
parameters, and final risk estimates; (b) high exposure from water at 
the point of use (e.g., shower); (c) risks from the disposal of 
treatment byproducts; and (d) occupational exposure due to regulation 
and removal of radon in drinking water. The SAB recommended that EPA 
investigate these issues before finalizing the radon rule. The EPA 
considered SAB's recommendations in developing the current proposal.
3. 1994 Report to Congress
    In 1992, Congress passed Public Law 102-389 (the Chafee-Lautenberg 
Amendment to EPA's Appropriation Bill). This law directs the 
Administrator of the EPA to report to Congress on EPA's findings 
regarding the risks of human exposure to radon and their associated 
uncertainties, the costs for controlling or mitigating that exposure, 
and the risks posed by treating water to remove radon.
    In response to the SAB's comments and the Chafee-Lautenberg 
Amendment, EPA drafted a report entitled Uncertainty Analysis of Risks 
Associated with Radon in Drinking Water (USEPA 1993b) and presented it 
to the SAB in February 1993. This document evaluated the variability 
and uncertainty in each of the factors needed to calculate human cancer 
risk from water-borne radon in residences served by community 
groundwater systems, and used Monte Carlo simulation techniques to 
derive quantitative confidence bounds for the risk estimates for each 
of the exposure routes to water-borne radon. In addition, the report 
summarized the risk estimates from exposure to radon in indoor and 
outdoor air.
    Based on the data available at the time, EPA estimated that the 
total number of fatal cancers that will occur as a result of exposure 
to water-borne radon in homes supplied by community groundwater systems 
was 192 per year. EPA noted that the risk from water-borne radon is 
small compared to the risk of soil-derived radon in indoor air (13,600 
lung cancer cases per year) or in outdoor air (520 lung cancer deaths 
per year) (USEPA 1992b, 1993b).
    The EPA included the findings of this uncertainty analysis with the 
SAB review comments in the Report to the United States Congress on 
Radon in Drinking Water: Multimedia Risk and Cost Assessment of Radon 
(USEPA 1994a). This report also included an assessment of the risk from 
exposure to radon at drinking water treatment facilities. The SAB 
reviewed the report prepared by EPA, and commended the EPA's 
methodologies employed in the uncertainty analysis and the exposure 
assessment of radon at the point of use (e.g. showering). However, the 
SAB stated that the estimates of risk from ingested radon may have 
additional uncertainties in dose estimation and in the use of primarily 
the atomic bomb survivor exposure (gamma emission with low linear 
energy transfer) in deriving the organ-specific risk per unit dose for 
from radon and progeny (alpha particle emission with high linear energy 
transfer). The SAB also questioned EPA's estimates of the number of 
community water supplies affected, and the extrapolation of the risk of 
lung cancer associated with the high radon exposures of uranium miners 
to the low levels of exposure experienced in domestic environments. The 
SAB recommended that the Agency use a relative risk orientation as an 
important consideration in making risk reduction decisions on all 
sources of risks attributable to radon. Based on the

[[Page 59312]]

comments and recommendations of the SAB, EPA revised several of the 
distributions used in the Monte Carlo analysis and finalized the 
Uncertainty Analysis of Risks Associated with Exposure to Radon in 
Drinking Water (USEPA 1995).

C. NAS Risk Assessment of Radon in Drinking Water

1. NAS Health Risk and Risk-Reduction Benefit Assessment Required by 
the 1996 Amendments to the Safe Drinking Water Act
    The 1996 amendments to the Safe Drinking Water Act required EPA to 
arrange with the National Academy of Sciences (NAS) to conduct a risk 
assessment of radon in drinking water and an assessment of the health-
risk reduction benefits associated with various measures to reduce 
radon concentrations in indoor air. The law also directed EPA to 
promulgate an alternative maximum contaminant level (AMCL) if the 
proposed MCL is less than the concentration of radon in water 
``necessary to reduce the contribution of radon in indoor air from 
drinking water to a concentration that is equivalent to the national 
average concentration of radon in outdoor air.''
2. Charge to the NAS Committee
    In accordance with the requirements of the 1996 amendments to the 
SDWA, in February 1997, EPA funded the NAS National Research Council to 
establish a multidisciplinary committee of the Board of Radiation 
Effects Research. This Committee on Risk Assessment of Exposure to 
Radon in Drinking Water (the NAS Radon in Drinking Water committee) was 
charged to use the best available data and methods to provide the 
following:
    (a) The best estimate of the central tendency of the transfer 
factor for radon from water to air, along with an appropriate 
uncertainty range,
    (b) Estimates of unit cancer risk (i.e., the risk from lifetime 
exposure to water containing 1 pCi/L) for the inhalation and ingestion 
exposure routes, both for the general population and for subpopulations 
within the general population (e.g., infants, children, pregnant women, 
the elderly, individuals with a history of serious illness) that are 
identified as likely to be at greater risk due to exposure to radon in 
drinking water than the general population,
    (c) Unit cancer risks from inhalation exposure for people in 
different smoking categories,
    (d) Descriptions of any teratogenic and reproductive effects in men 
and women due to exposure to radon in drinking water,
    (e) Central estimates for a population-weighted average national 
ambient (outdoor) air concentration for radon, with an associated 
uncertainty range.
    The NAS Radon in Drinking Water committee was also asked to 
estimate health risks that might occur as the result of compliance with 
a primary drinking water regulation for radon. The committee was to 
assess the health risk reduction benefits associated with various 
mitigation measures to reduce radon levels in indoor air.
3. Summary of NAS Findings
    The NAS completed its charge and issued a report entitled ``Risk 
Assessment of Radon in Drinking Water'' (NAS 1999b). The NAS report 
provides detailed descriptions of the methods and assumptions employed 
by the NAS Radon in Drinking Water committee in completing its 
evaluation. The following text provides a summary of the NAS report.
    (a) National Average Ambient Radon Concentration. Because radon 
levels in outdoor air vary from location to location, the NAS Radon in 
Drinking Water committee concluded that available data are not 
sufficiently representative to calculate a population-weighted annual 
average ambient radon concentration. Based on the data that are 
available, the NAS Radon in Drinking Water committee concluded that the 
best estimate of an unweighted arithmetic mean radon concentration in 
ambient (outdoor) air in the United States is 15 Bq/m3 
(equal to 0.41 pCi/L of air), with a confidence range of 14 to 16 Bq/
m3 (0.38-0.43 pCi/L air).
    (b) Transfer Factor. The relationship between the concentration of 
radon in water and the average indoor air concentration of water-
derived radon is described in terms of the transfer factor (pCi/L in 
air per pCi/L in water). Most researchers who have investigated this 
variable in residences find that it can be described as a lognormal 
distribution of values, most conveniently characterized by the 
arithmetic mean (AM) and the standard deviation (Stdev), or by the 
geometric mean (GM) and the geometric standard deviation (GSD). The NAS 
Radon in Drinking Water committee performed an extensive review of both 
measured and calculated values of the transfer factor in residences, 
with the results summarized in the following Table XII.1:

                               Table XII.1.--Measured and Modeled Transfer Factors
----------------------------------------------------------------------------------------------------------------
            Approach                      AM                 Stdev                GM                  GSD
----------------------------------------------------------------------------------------------------------------
Measured.......................  0.87  x  10-4        1.2  x  10-4        0.38  x  10-4       3.3
Modeled........................  1.2  x  10-4         2.4  x  10-4        0.55  x  10-4       3.5
----------------------------------------------------------------------------------------------------------------
a Calculated from, GM and GSD.

    The committee concluded that there is reasonable agreement between 
the average value of the transfer factor estimated by the two 
approaches, and identified 1 in 10,000 (1.0 x 10-4) as the 
best central estimate of the transfer factor for residences, with a 
confidence bound of about 0.8 to 1.2 x 10-4. This central 
tendency value is the same as has been used in previous assessments 
(USEPA 1993b, 1995).
    Based on this transfer factor, the NAS committee concluded that the 
AMCL for radon in drinking water would be 150,000 Bq/m3 ( 
about 4,000 pCi/L). That is, a concentration of 4,000 pCi/L of radon in 
water is expected to increase the concentration of radon in indoor air 
by an amount equal to that in outdoor air.
    (c) Biologic Basis of Risk Estimation. Both the BEIR VI Report (NAS 
1999a) and their report on radon in drinking water (NAS 1998b) 
represent the most definitive accumulation of scientific data gathered 
on radon since the 1988 NAS BEIR IV (NAS 1988). These committees' 
support for the use of linear non-threshold relationship for radon 
exposure and lung cancer risk came primarily from their review of the 
mechanistic information on alpha-particle-induced carcinogenesis, 
including studies of the effect of single versus multiple hits to cell 
nuclei.
    The NAS BEIR VI Committee (NAS 1999a) conducted an extensive review 
of information on the cellular and molecular mechanism of radon-induced 
cancer in order to help support the assessment of cancer risks from low 
levels of radon exposure. In the BEIR VI

[[Page 59313]]

report (NAS 1999a), the NAS concluded that there is good evidence that 
a single alpha particle (high-linear energy transfer radiation) can 
cause major genomic changes in a cell, including mutation and 
transformation that potentially could lead to cancer. Alpha particles, 
such as those that are emitted from the radon decay chain, produce 
dense trails of ionized molecules when they pass through a cell, 
causing cellular damage. Alpha particles passing through the nucleus of 
a cell can damage DNA. In their report, the BEIR VI Committee noted 
that even if substantial repair of the genomic damage were to occur, 
``the passage of a single alpha particle has the potential to cause 
irreparable damage in cells that are not killed''. Given the convincing 
evidence that most cancers originate from damage to a single cell, the 
Committee went on to conclude that ``On the basis of these [molecular 
and cellular] mechanistic considerations, and in the absence of 
credible evidence to the contrary, the Committee adopted a linear non-
threshold model for the relationship between radon exposure and lung-
cancer risk. The Committee also noted that epidemiological data 
relating to low radon exposures in mines also indicate that a single 
alpha track through the cell may lead to cancer. Finally, while not 
definitive by themselves, the results from residential case-control 
studies provide some direct support for the conclusion that 
environmental levels of radon pose a risk of lung cancer. However, the 
BEIR VI Committee recognized that it could not exclude the possibility 
of a threshold relationship between exposure and lung cancer risk at 
very low levels of radon exposure.
    The NAS Committee on radon in drinking water (NAS 1999b) reiterated 
the finding of the BEIR VI Committee's comprehensive review of the 
issue, that a ``mechanistic interpretation is consistent with linear 
non-threshold relationship between radon exposure and cancer risk''. 
The committee noted that the ``quantitative estimation of cancer risk 
requires assumptions about the probability of an exposed cell becoming 
transformed and the latent period before malignant transformation is 
complete. When these values are known for singly hit cells, the results 
might lead to reconsideration of the linear no-threshold assumption 
used at present.@ EPA recognizes that research in this area is on-going 
but is basing its regulatory decisions on the best currently available 
science and recommendations of the NAS that support use of a linear 
non-threshold relationship. EPA recognizes that research in this area 
is on-going but is basing its regulatory decisions on the best 
currently available science and recommendations of the NAS that support 
use of a linear non-threshold relationship.
    (d) Unit Risk from Inhalation Exposure to Radon Progeny. The 
calculation of the unit risk from inhalation of radon progeny derived 
from water-borne radon depends on four key variables: (1) The transfer 
factor that relates the concentration of radon in air to the 
concentration in water, (2) the equilibrium factor (the level of radon 
progeny present compared to the theoretical maximum amount), (3) the 
occupancy factor (the fraction of full time that a person spends at 
home) and (4) the risk of lung cancer per unit exposure (the risk 
coefficient). The values utilized by NAS for each of these factors are 
summarized next.
Transfer Factor
    The NAS Radon in Drinking Water committee (NAS 1999b) reviewed 
available data and concluded that the best estimate of the transfer 
factor is 1.0  x  10-4 pCi/L air per pCi/L water.
Equilibrium Factor
    At radiological equilibrium, 1 pCi/L of radon in air corresponds to 
a concentration of 0.010 Working Levels (WL) of radon progeny. One WL 
is defined as any combination of radioactive chemicals that result in 
an emission of 1.3  x  105 MeV of alpha particle energy. One 
WL is approximately the total amount of energy released by the short-
lived progeny in equilibrium with 100 pCi of radon. Under typical 
household conditions, processes such as ventilation and plating out of 
progeny prevent achievement of equilibrium, and the level of radon 
progeny present is normally less than 0.010 WL. The equilibrium factor 
(EF) is the ratio of the alpha energy actually present in respirable 
air compared to the theoretical maximum at equilibrium. Based on a 
review of measured values in residences, USEPA (1993b, 1995) identified 
a value of 0.4 as the best estimate of the mean, with a credible range 
of 0.35 to 0.45. NAS (1999a, 1999b) reviewed the data and also selected 
a value of 0.4 as the most appropriate point estimate of EF.
Occupancy Factor
    The occupancy factor (the fraction of time that a person spends at 
home) varies with age and occupational status. Studies on the occupancy 
factor have been reviewed by EPA (USEPA 1992b, 1993b, 1995), who found 
that a value of 0.75 is the appropriate point estimate of the mean with 
a credible range of 0.65-0.80. Based on a review of available data, 
both the BEIR VI committee (NAS 1999a) and the NAS Radon in Drinking 
Water committee (NAS 1999b) identified an occupancy factor of 0.7 as 
the best estimate to employ in calculation of the inhalation unit risk 
from inhalation of radon progeny.
Risk of Lung Cancer Death per Unit Exposure (Risk Coefficient)
    There are extensive data on humans (mainly from studies of 
underground miners) establishing that inhalation exposure to radon 
progeny causes increased risk of lung cancer (NAS 1999a, 1999b). The 
basic approach used by NAS to quantify the risk of fatal cancer 
(specifically death from lung cancer) from inhalation of radon progeny 
in air was to employ empirical dose-response relationships derived from 
studies of humans exposed to radon progeny in the environment. The most 
recent quantitative estimate of the risk of lung cancer associated with 
inhalation of radon progeny has been conducted by the BEIR VI committee 
(NAS 1999a), and this analysis was employed by the NAS Radon in 
Drinking Water committee (NAS 1999b). The BEIR VI committee reviewed 
all of the most current data from studies of humans exposed to radon, 
including cohorts of underground miners and residents exposed to radon 
in their home, as well as studies in animals and in isolated cells. 
Because of differences in exposure level and duration, studies of 
residential radon exposure would normally be preferable to studies of 
miners for quantifying risk to residents from radon progeny in indoor 
air. However, the BEIR VI committee found that the currently available 
epidemiological studies of residents exposed in their homes are not 
sufficient to develop reliable quantitative exposure-risk estimates 
because (a) the number of subjects is small, (b) the difference between 
exposure levels is limited, and (c) cumulative radon exposure estimates 
are generally incomplete or uncertain. Therefore, the BEIR VI committee 
focused their analysis on studies of radon-exposed underground miners.
    The method used by the BEIR VI committee was essentially the same 
as used previously by the BEIR IV committee (NAS 1988), except that the 
database on radon risk in underground miners is now much more 
extensive, including 11 cohorts of underground miners, which, in all, 
include about 2,700 lung cancers among 68,000

[[Page 59314]]

miners, representing nearly 1.2 million person-years of observations. 
Details of these 11 cohorts are presented in the NAS BEIR VI Report 
(NAS 1999a). For historical reasons, the measure of exposure used in 
these studies is the Working Level Month (WLM), which is defined as 170 
hours of exposure to one Working Level (WL) of radon progeny.
    Based on evidence that risk per unit exposure increased with 
decreasing exposure rate or with increasing exposure duration (holding 
cumulative exposure constant), the BEIR VI committee modified the 
previous risk model to include a term to account for this ``inverse 
dose rate'' effect. Because the adjustment could be based on either the 
concentration of radon progeny or the duration of exposure, there are 
two alternative forms of the preferred model--the ``exposure-age-
concentration'' model, and the ``exposure-age-duration'' model. For 
brevity, these will generally be referred to here as the 
``concentration'' and ``duration'' models.
    Mathematically, both models can be represented as:

RR=1+ERR=1+(5-14+15-24
15-24+25+ 
25+)
    (1)

Where:

RR=relative risk of lung cancer in a person due to above-average radon 
exposure compared to the average background risk for a similar person 
in the general population
ERR=Excess relative risk (the increment in risk due to the above-
average exposure to radon)
=exposure-response parameter (excess relative risk per WLM)
5-14=exposures (WLM) incurred from 5-14 years 
prior to the current age
15-24=exposures (WLM) incurred from 15-24 years 
prior to the current age
25+=exposures (WLM) incurred 25 or more years 
prior to the current age
15-24=time-since-exposure factor for risk from 
exposures incurred 15-24 years or more before the attained age
25+=time-since-exposure factor for risk from 
exposures incurred 25 or more years or more before the attained age
=effect-modification 
factor for attained age
=effect-modification factor for exposure 
rate or exposure duration

    The BEIR VI committee used a two-stage approach for combining 
information from the 11 miner studies to derive parameters for the 
concentration and duration risk models. First, estimates of model 
parameters were derived for each study cohort, and then population-
weighted averages of the parameters were calculated across studies to 
derive an overall estimate that takes variation between and within 
cohorts into account. The results of the pooled analysis of all of the 
miner data indicated that, for a given level of exposure to radon, the 
excess relative risk of lung cancer decreases with increasing time 
since exposure, decreases as a function of increased attained age, 
increases with increasing duration of exposure, and decreases with 
increasing exposure rate (the inverse dose rate effect).
    The BEIR VI committee applied the risk models to 1985-89 U.S. 
mortality data to estimate individual and population risks from radon 
in air. At the individual level, the committee estimated the lifetime 
excess relative risk (ERR), which is the percent increase in the 
lifetime probability of lung cancer death from indoor radon exposure. 
For population risks, the committee estimated attributable risk (AR), 
which indicates the proportion of lung-cancer deaths that theoretically 
may be reduced by reduction of indoor radon concentrations to outdoor 
levels.
Extrapolation From Mines to Homes
    Because of a number of potential differences between mines and 
homes, exposures to equal levels of radon progeny may not always result 
in equal doses to lung cells. The ratio of the dose to lung cells in 
the home compared to that in mines is described by the K factor. Based 
on the best data available at the time, NAS (1991) had previously 
concluded that the dose to target cells in the lung was typically about 
30 percent lower for a residential exposure compared to an equal WLM 
exposure in mines (i.e., K = 0.7). The BEIR VI committee re-examined 
the issue of the relative dosimetry in homes and mines. In light of new 
information regarding exposure conditions in home and mine 
environments, the committee concluded that, when all factors are taken 
into account, the dose per WLM is nearly the same in the two 
environments (i.e., a best estimate for the K-factor is about 1) (NAS 
1999a). The major factor contributing to the change was a downward 
revision in breathing rates for miners. Thus, for calculation of risks 
from residential exposures, Equation 1 can be applied directly without 
adjustment.
Combined Effect of Smoking and Radon
    Because of the strong influence of smoking on the risk from radon, 
the BEIR VI committee (NAS 1999a) evaluated risk to ever-smokers and 
never-smokers separately. The committee had information on 5 of the 
miner cohorts, from which they concluded that the combined effects of 
radon and smoking were more than additive but less than multiplicative. 
As a best estimate the committee determined that never-smokers should 
be assigned a relative risk coefficient () about twice that 
for ever-smokers, in each of the two models defined previously. This 
means that the attributable risk, or the proportion of all lung cancers 
attributable to radon, is about twice as high for never-smokers as 
ever-smokers. Nevertheless, because the incidence of lung cancer is 
much greater for ever-smokers than never-smokers, the probability of a 
radon induced lung cancer is still much higher for ever-smokers. This 
higher risk in ever-smokers arises from the synergism between radon and 
cigarette smoke in causing lung cancer.
    Based on the BEIR VI lifetime relative risk results, the NAS Radon 
in Drinking Water committee (NAS 1999b) calculated the lifetime risk 
(per Bq/m3 air) for each of the two models using the 
following basic equation:

Excess lifetime risk=(Baseline risk)* (LRR-1)
Where LRR=lifetime relative risk
    Baseline lung cancer risk values used by the NAS Radon in Drinking 
Water committee (NAS 1999b) are summarized in Table XII.2.

                 Table XII.2.--Baseline Lung Cancer Risk
------------------------------------------------------------------------
                                     Smoking       Ever-        Never-
              Gender                prevalence  smokers \1\    smokers
------------------------------------------------------------------------
Male.............................         0.58        0.116       0.0091
Female...........................         0.42        0.068       0.0059
------------------------------------------------------------------------
\1\ Ever-smokers were defined as persons who had smoked at least 100
  cigarettes in their entire life (CDC 1995).


[[Page 59315]]

    The NAS Radon in Drinking Water committee (NAS 1999b) adopted the 
average of the results from each of the two models as the best estimate 
of lifetime risk from radon progeny.
Results: Inhalation Unit Risk for Water-Borne Radon Progeny
    Based on the inputs and approaches summarized in the previous 
sections, NAS calculated the inhalation unit risk for radon progeny, by 
smoking category, with the results described in Table XII.3:

                                                            Table XII.3.--Lifetime Unit Risk
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                      Inhalation risk
         Smoking category             per Bq/m \3\ in air     per pCi/L in water        Lifetime  (yrs)        Annual unit risk      coefficient  (per
                                                                                                             (per pCi/L in water)           WLM)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Combined..........................  1.6 x 10-4              5.93 x 10-7             74.9                    7.92 x 10-9            5.49 x 10-4
Ever Smokers......................  2.6 x 10-4              9.63 x 10-7             73.7                    1.31 x 10-8            9.07 x 10-4
Never Smokers.....................  0.5 x 10-4              1.85 x 10-7             76.1                    2.43 x 10-9            1.68 x 10-4
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The NAS Radon in Drinking Water committee (NAS 1999b) estimated 
that the uncertainty around the inhalation risk coefficient for radon 
progeny can be characterized by a lognormal distribution with a GSD of 
1.2 (based on the duration model) to 1.3 (based on the concentration 
model). This corresponds to an uncertainty range for the combined 
population of about 3.4  x  10-4 to 8.1  x  10-4 lung cancer deaths per 
person per WLM.
Inhalation Risks to Subpopulations, Including Children
    The NAS Radon in Drinking Water committee concluded that, except 
for the lung-cancer risk to smokers, there is insufficient information 
to permit quantitative evaluation of radon risks to susceptible sub-
populations such as infants, children, pregnant women, elderly and 
seriously ill persons.
    The BEIR VI committee (NAS 1999a) noted that there is only one 
study (tin miners in China) that provides data on whether risks from 
radon progeny are different for children, adolescents, and adults. 
Based on this study, the committee concluded that there was no clear 
indication of an effect of age at exposure, and the committee made no 
adjustments in the lung cancer risk model for exposures received at 
early ages.
    (e) Unit Risk for Ingestion Exposure. The calculation of the unit 
risk from ingestion of radon in water depends on three key variables: 
(1) The amount of radon-containing water ingested, (2) the fraction of 
radon lost from the water before ingestion, and (3) the risk to the 
tissues per unit of radon absorbed into the body (risk coefficient). 
The values utilized by NAS for each of these factors are summarized 
next.
Water Ingestion Rate
    EPA (USEPA 1993b, 1995) performed a review of available data on the 
amount of water ingested by residents. In brief, water ingestion can be 
divided into two categories: direct tap water (that which is ingested 
as soon as it is taken from the tap) and indirect tap water (water used 
in cooking, for making coffee, etc.). Available data indicate nearly 
all radon is lost from indirect tap water before ingestion, so only 
direct tap water is of concern. Based on available data (Pennington 
1983; USEPA 1984; Ershow and Cantor 1989, USEPA 1993b, USEPA 1995) 
scientists estimated that the mean of the direct tap water ingestion 
rate was 0.65 liters per day (L/day), with a credible range of about 
0.57 to 0.74 L/day. Based mainly on this analysis, NAS (1999b) 
identified 0.6 L/day as the best estimate of direct tap water intake, 
and utilized this value in the calculation of the unit risk from radon 
ingestion. This value includes direct tap water ingested at all 
locations, and so includes both residential and non-residential 
exposures.
    The analysis conducted for radon in drinking water uses radon-
specific estimates of water consumption, based on guidance from the NAS 
Radon in Drinking Water committee. Based on radon's unique 
characteristics, this approach is different from the Agency's approach 
to other drinking water contaminants.
    In general, in calculating the risk for all other water 
contaminants, EPA uses 2 liters per day as the average amount of water 
consumed by an individual. For radon, the Agency used 0.6 liters per 
day to estimate the risks of radon ingestion. The NAS ingestion risk 
number is derived from an average risk/radiation coefficient, an 
average drinking water ingestion rate, and an average life expectancy. 
NAS chose to use an ingestion rate of 0.6 liter per day, based on an 
assumption that only 0.6 liters of the ``direct'' water will retain 
radon. Since radon is very readily released during normal household 
water use, we assume that radon in water used for indirect purposes 
(cooking, making coffee, etc) is released before drinking. Only direct 
water (drinking from tap directly) is used to estimate ingestion risk.
    The Agency solicits comments on this approach to estimating the 
ingestion risk of radon in drinking water, particularly the assumption 
of 0.6 liters per day direct consumption.
Fraction of Radon Remaining During Water Transfer From the Tap
    Because radon is a gas, it tends to volatilize from water as soon 
as the water is discharged from the plumbing system into any open 
container or utensil. As would be expected, the fraction of radon 
volatilized before consumption depends on time, temperature, surface 
area-to-volume ratio, and degree of mixing or aeration. A previous 
analysis by EPA (USEPA 1995) identified a value of 0.8 as a reasonable 
estimate of the mean fraction remaining before ingestion, with an 
estimated credibility interval about the mean of 0.7 to 0.9. Because 
data are so sparse, and in order to be conservative, NAS assumed a 
point estimate of 1.0 for this factor (NAS 1999b).
Risk per Unit of Radon Absorbed (Risk Coefficient)
    The NAS Radon in Drinking Water committee reviewed a number of 
publications on the risk from ingestion of radon, and noted that there 
was a wide range in the estimates, due mainly to differences and 
uncertainties in the way radon is assumed to be absorbed across the 
gastrointestinal tract. Therefore, the committee developed new 
mathematical models of the diffusion of radon in the stomach and the 
behavior of radon dissolved in blood and other tissues to calculate the 
radiation dose absorbed by tissues following ingestion of radon 
dissolved in water (NAS 1999b).
    NAS determined that the stomach wall has the largest exposure (and 
hence the largest risk of cancer) following oral exposure to radon in 
water, but that

[[Page 59316]]

there is substantial uncertainty on the rate and extent of radon entry 
into the wall of the stomach from the stomach contents. The ``base 
case'' used by NAS assumed that diffusion of radon from the stomach 
contents occurs through a surface mucus layer and a layer of non-
radiosensitive epithelial cells before coming into proximity with the 
radiosensitive stem cells. Below this layer, diffusion into capillaries 
was assumed to remove radon and reduce the concentration to zero. Based 
on this model, the concentration of radon near the stem cells was about 
30 percent of that in the stomach contents.
    The distribution of absorbed radon to peripheral tissues was 
estimated by NAS using a physiologically-based pharmacokinetic (PBPK) 
model based on the blood flow model of Leggett and Williams (1995). The 
committee's analysis considered that each radioactive decay product 
formed from radon decay in the body exhibited its own behavior with 
respect to tissues of deposition, retention, and routes of excretion 
with the ICRP's age-specific biokinetic models The computational method 
used by the NAS Radon in Drinking Water committee to calculate the age-
and gender-averaged cancer death risk from lifetime ingestion of radon 
is described in EPA's Federal Guidance Report 13 (USEPA 1998d).
Results: Ingestion Unit Risk
    The NAS Radon in Drinking Water committee estimated that an age- 
and gender-averaged cancer death risk from lifetime ingestion of radon 
dissolved in drinking water at a concentration of 1 Bq/L probably lies 
between 3.8  x  10-7 and 4.4  x  10-6, with 1.9 
x  10-6 as the best central value. This is equivalent to a 
lifetime risk of 7.0  x  10-8 per pCi/L, with a credible 
range of 1.4  x  10-8 to 1.6  x  10-7 per pCi/L. 
This uncertainty range is based mainly on uncertainty in the estimated 
dose to the stomach and in the epidemiologic data used to estimate the 
risk (NAS 1999b), and does not include the uncertainty in exposure 
factors such as average daily direct tap water ingestion rates or radon 
loss before ingestion. The lifetime risk estimate of 7.0  x  
10-8 per pCi/L corresponds to an ingestion risk coefficient 
of 4.29  x  10-12 per pCi ingested.
Ingestion Risk to Children
    NAS (1999b) performed an analysis to investigate the relative 
contribution of radon ingestion at different ages to the total risk. 
This analysis considered the age dependence of: radon consumption, 
behavior of radon and its decay products in the body, organ size, and 
risk. The results indicated that even though water intake rates are 
lower in children than in adults, dose coefficients are higher in 
children because of their smaller body size. In addition, the cancer 
risk coefficient for ingested radon is greater for children than for 
adults. Based on dose and stomach cancer risk models, NAS (1999b) 
estimated that about 30% of lifetime ingestion risk was due to 
exposures occurring during the first 10 years of life. However, the NAS 
found no direct epidemiological evidence to suggest that any sub-
population is at increased risk from ingestion of radon. In addition, 
ingestion risk as a whole accounts for only 11% of total risk from 
radon exposure from drinking water for the general population, with 
inhalation accounting for the remaining 89%. The NAS did not identify 
children, or any other groups except smokers, as being at significantly 
higher overall risk from exposure to radon in drinking water.
    (f) Summary of NAS Lifetime Unit Risk Estimates. Table XII.4 
summarizes the lifetime average unit risk estimates derived by the NAS 
Radon in Drinking Water committee.

Table XII.4.--Nas Radon in Drinking Water Committee Estimate of Lifetime Unit Risk Posed by Exposure to Radon in
                                                 Drinking Water
----------------------------------------------------------------------------------------------------------------
                                                                       Gender-averaged lifetime unit risk
           Exposure route                  Smoking status     --------------------------------------------------
                                                                Risk per Bq/L in water   Risk per pCi/L in water
----------------------------------------------------------------------------------------------------------------
Inhalation..........................  Ever...................  2.6  x  10-5              9.6  x  10-7
                                      Never..................  0.50  x  10-5             1.9  x  10-7
                                      All....................  1.6  x  10-5              5.9  x  10-7
Ingestion...........................  All....................  0.19  x  10-5             7.0  x  10-8
                                     ---------------------------------------------------------------------------
    Total Risk (inhalation +          All....................  1.8  x  10-5              6.6  x  10-7
     ingestion).
----------------------------------------------------------------------------------------------------------------

    (g) Other Health Effects. The NAS Radon in Drinking Water committee 
was asked to review teratogenic and reproductive risks from radon. The 
committee concluded there is no scientific evidence of teratogenic and 
reproductive risks associated with either inhalation or ingestion of 
radon.
    (h) Relative Magnitude of the Risk from Radon in Water. The NAS 
Radon in Drinking Water committee concluded that radon in water 
typically adds only a small increment to the indoor air concentration. 
The committee estimated the cancer deaths per year due to radon in 
indoor air (total), radon in outdoor air, radon progeny from waterborne 
radon, and ingestion of radon in water are 18, 200, 720, 160, and 23, 
respectively. However, the committee recognized that radon in water is 
the largest source of cancer risk in drinking water compared to other 
regulated chemicals in water.

D. Estimated Individual and Population Risks

    Based on the findings and recommendations of the NAS Radon in 
Drinking Water committee, EPA has performed a re-evaluation of the 
risks posed by radon in water (USEPA 1999b). This assessment relied 
upon the inhalation and ingestion unit risks derived by NAS (1999b), 
and calculated risks to individuals and the population by combining the 
unit risks derived by NAS with the latest available data on the 
occurrence of radon in public water systems (USEPA 1999g).
    In brief, the risk to a person from exposure to radon in water is 
calculated by multiplying the concentration of radon in the water (pCi/
L) by the unit risk factor (risk per pCi/L) for the exposure pathway of 
concern (ingestion, inhalation). The population risk (the total number 
of fatal cancer cases per year in the United States due to radon 
ingestion in water) is estimated by multiplying the average annual 
individual risk (cases per person per year) by the total number of 
people exposed. Data which EPA used to

[[Page 59317]]

calculate individual risks and population risks are summarized next.
Radon Concentration in Community Water Systems
    The EPA has recently completed a detailed review and evaluation of 
the latest available data on the occurrence of radon in community water 
systems (USEPA 1999g; see Section XI). In brief, the concentration of 
radon in drinking water from surface water sources is very low, and 
exposures from surface water systems can generally be ignored. However, 
radon does occur in most groundwater systems, with the concentration 
values tending to be highest in areas where groundwater is in contact 
with granite. In addition, radon concentrations tend to vary as a 
function of the size of the water system, being somewhat higher in 
small systems than in large systems (USEPA 1999g). Based on EPA's 
analysis, the population-weighted average concentration of radon in 
community ground water systems is estimated to be 213 pCi/L, with a 
credible range of about 190 to 240 pCi/L (USEPA 1999g).
Total Exposed Population
    Based on data available from the Safe Drinking Water Information 
System (SDWIS), EPA estimates that 88.1 million people (about one-third 
of the population of the United States) are served in their residence 
by community water supply systems using ground water (USEPA 1998a).
    Based on these data on radon occurrence and size of the exposed 
population, EPA calculated the risks from water-borne radon to people 
exposed at residences served by community groundwater systems. EPA also 
calculated revised quantitative uncertainty analysis of the risk 
estimates at residential locations, incorporating NAS estimates of the 
uncertainty inherent in the unit risks for each pathway. In addition, 
EPA performed screening level estimates of risk to people exposed to 
water-borne radon in various types of non-residential setting. EPA's 
findings are summarized next.
1. Risk Estimates for Ingestion of Radon in Drinking Water
    Table XII.5 presents EPA's estimate of the mean individual risk 
(fatal cancer cases per person per year) for the people who ingest 
water from community ground water systems. This includes exposures that 
occur both in the residence and in non-residential settings (the 
workplace, restaurants, etc). The lower and upper bounds around the 
best estimate were estimated using Monte Carlo simulation techniques 
(USEPA 1999b).

    Table XII.5.--Estimated Risk from Radon Ingestion at Residential and Non-residential Locations Served by
                                             Community Water Systems
----------------------------------------------------------------------------------------------------------------
              Parameter                      Lower bound             Best  estimate            Upper bound
----------------------------------------------------------------------------------------------------------------
Mean Annual Individual Risk (cancer   3.2  x  10-8              2.0  x  10-7             4.3  x  10-7
 deaths per person per year).
Population Risk (cancer deaths per    3                         18                       38
 year).
----------------------------------------------------------------------------------------------------------------

2. Risk Estimates for Inhalation of Radon Progeny Derived From 
Waterborne Radon
    (a) Inhalation Exposure to Radon Progeny in the Residential 
Environment. Table XII.6 presents the EPA's best estimate of the mean 
individual risk and population risk of lung cancer fatality due to 
inhalation of radon progeny derived from water-borne radon at 
residences served by community groundwater systems. Lower and upper 
bounds on the individual and population risk estimates were derived 
using Monte Carlo simulation techniques.

  Table XII.6.--Estimated Risks from Inhalation of Water-Borne Radon Progeny in Residences Served by Community
                                           Ground Water Supply Systems
----------------------------------------------------------------------------------------------------------------
              Parameter                      Lower bound             Best  estimate            Upper bound
----------------------------------------------------------------------------------------------------------------
Mean Annual Individual Risk (lung     7.9  x  10-7              1.7  x  10-6             3.0  x  10-6
 cancer deaths per person per year).
Population Risk (lung cancer deaths   70                        148                      263
 per year).
----------------------------------------------------------------------------------------------------------------

    Of the total number of lung cancer deaths due to water-borne radon, 
most (about 84 percent) are expected to occur in ever-smokers, with the 
remainder (about 16 percent) occurring in never-smokers.
Analysis of Peak Exposures and Risks Due to Showering
    Both NAS and EPA have paid special attention to the potential 
hazards associated with high exposures to radon that may occur during 
showering. High exposure occurs during showering because a large volume 
of water is used, release of radon from shower water is nearly 
complete, and the radon enters a fairly small room (the shower/
bathroom). However, both NAS (1999b) and USEPA (1993b, 1995) concluded 
that the risk to humans from radon released during showering was likely 
to be small. This is because the inhalation risk from radon is due 
almost entirely to radon progeny and not to radon gas itself, and it 
takes time (several hours) for the radon progeny to build up from the 
decay of the radon gas released from the water. For example, in a 
typical shower scenario (about 10 minutes), the level of progeny builds 
up to only 2 to 4 percent of its maximum possible value. Thus, 
showering is one of many indoor water uses that contribute to the 
occurrence of radon in indoor air, but hazards from inhalation of radon 
during showering are not of special concern.
    (b) Inhalation Exposure to Radon Progeny in the Non-Residential 
Environment. The results summarized to this point relate to exposures 
which occur in homes. However, on average, people spend about 30 
percent of their time at other locations. Surveys of human activity 
patterns reveal that time outdoors or in cars accounts for about 13 
percent of the time (USEPA 1996), and about 17 percent of the time, on 
average across the entire population (including both workers and non-
workers), is spent in non-residential structures. Such non-residential 
buildings are presumably all served with water, so exposure to radon 
and radon progeny is expected to occur, at least in buildings served by 
groundwater. Because data needed to quantify exposure at non-
residential locations are limited, EPA has performed only a screening

[[Page 59318]]

level evaluation to date. This evaluation may be revised in the future, 
depending on the availability of more detailed and appropriate input 
data.
    As with exposures in the home, the largest source of exposure and 
risk from water-borne radon in non-residential buildings is inhalation 
of radon progeny. Limited data were found on measured transfer factors 
in non-residential buildings, so values were estimated for several 
different types of buildings based on available data on water use 
rates, building size, and ventilation rate, based on the following 
basic equation:

TF = (We)/(V)

Where:

W = Water use (L/person/day)
e = Use-weighted fractional release of radon from water to air
V = Building volume (L/person)
 = Ventilation rate (air changes/day)

    The resulting transfer factor values varied as a function of 
building type, based on limited data, but the average across all 
building types was about 1  x  10-4 (the same as for 
residences). Very few data were located for the equilibrium factor in 
non-residential buildings, so a value of 0.4 (the same as in a 
residence) was assumed (USEPA 1999b).
    Based on an estimated average transfer factor of 1  x  
10-4 and assuming an average occupancy factor of 17 percent 
at non-residential locations, the estimated lifetime and annual risks 
of death from lung cancer due to exposure per unit concentration of 
radon (1pCi/L) in water are 1.4  x  10-7 per pCi/L and 1.9 
x  10-9 per pCi/L, respectively.
    Assuming a mean radon concentration in water of 213 pCi/L, these 
unit risks correspond to lifetime and annual individual risks of 3.1 
x  10-5 and 4.1  x  10-7 lung cancer deaths per 
person. Assuming the same population size of 88.1 million population 
exposed to radon through community ground water supplies, EPA's best 
estimate of the number of fatal cancer cases per year resulting from 
the inhalation of radon progeny in non-residential environments is 36 
lung cancer deaths per year (USEPA 1999b) (from the population of 
individuals exposed in non-residential settings served by community 
ground water supplies).
    (c) Analysis of Risk Associated with Exposure at NTNC Locations. A 
subset of the water systems serving non-residential populations are the 
non-transient non-community (NTNC) systems. Statistics from SDWIS 
indicate there are about 5.2 million individuals exposed at buildings 
served by NTNC groundwater systems (USEPA 1999b).
    Data on radon exposures at locations served by NTNC systems are 
limited. However, data are available for water used and population size 
at each of 40 strata of NTNC systems (USEPA 1998a). Assuming (a) the 
exposure at NTNC locations is occupational in nature with about 8 hr/
day, 250 days/yr, and 25 years per lifetime for workers and 8 hr/day, 
180 days/yr, and 12 years per lifetime for students, (b) the same 
transfer factor (1  x  10-4) and equilibrium factor (0.4) 
assumed for other non-residential buildings apply at NTNC locations, 
and (c) the concentration of radon in water at NTNC locations is about 
60 percent higher than in community water systems (mean concentration = 
341 pCi/L) (see Section XI of this preamble), then the estimated 
population-weighted average individual annual and lifetime lung cancer 
risks are 2.6  x  10-7 and 2.0  x  10-5, 
respectively.
3. Risk Estimates for Inhaling Radon Gas
    NAS (1999b) did not derive a unit risk factor for inhalation of 
radon gas, but provided in their report a set of annual effective doses 
to tissues (liver, kidney, spleen, red bone marrow, bone surfaces, 
other tissues) from continuous exposure to 1Bq/m3 of radon 
in air. These doses to internal organs from the decay of radon gas 
absorbed across the lung and transported to internal sites were based 
on calculations by Jacobi and Eisfeld (1980). Based on these dose 
estimates, EPA estimated a unit risk value using an approach similar to 
that used by NAS to derive the unit risk for ingestion of radon gas in 
water. The organ-specific doses reported by Jacobi and Eisfeld were 
multiplied by the lifetime-average organ-specific and gender-specific 
risk coefficients (risk of fatal cancer per rad) from Federal Guidance 
Report No. 13 (USEPA 1998d). Based on an average transfer factor of 1 
x  10-4, and assuming 70 percent occupancy, the estimated 
annual average unit risk is 8.5  x  10-11 cancer deaths per 
pCi/L in water. This corresponds to a lifetime average unit risk of 6.3 
 x  10-9 per pCi/L. This unit risk excludes the risk of lung 
cancer from inhaled radon gas, since this risk is already included in 
the unit risk from radon progeny. Based on the population-weighted 
average radon concentration of 213 pCi/L, the lifetime average 
individual risk is 1.35  x  10-6 cancer deaths per person, 
and the average annual individual risk is 1.8  x  10-8 
cancer deaths per person per year. Based on an exposed population of 
88.1 million people, the annual population risk is about 1.6 cancer 
deaths/year. The uncertainty range around this estimate, derived using 
Monte Carlo simulation techniques, is about 1.0 to 2.7 cancer deaths 
per year (USEPA 1999b).
4. Combined Fatal Cancer Risk
    The best estimates of fatal cancer risks to residents from 
ingesting radon in water, inhalation of waterborne progeny, and 
inhalation of radon gas are presented in Table XII.7. As seen, EPA 
estimates that an individual's combined fatal cancer risk from lifetime 
residential exposure to drinking water containing 1 pCi/L of radon is 
slightly less than 7 chances in 10 million (7  x  10-7), and 
that the population risk is about 168 cancer deaths per year 
(uncertainty range = 80 to 288 per year). Of this risk, most (88 
percent) is due to inhalation of radon progeny, with 11 percent due to 
ingestion of radon gas, and less than 1 percent due to inhalation of 
radon gas.

  Table XII.7.--Summary of Unit Risk, Individual Risk and Population Risk Estimates for Residential Exposure to
                                     Radon in Community Groundwater Supplies
----------------------------------------------------------------------------------------------------------------
                                                                                                       Annual
                                            Lifetime unit risk  (fatal    Annual individual risk     population
             Exposure pathway                 cancer cases per person     (fatal cancer cases per   risk  (fatal
                                                    per pCi/L)               person per year)       cancer cases
                                                                                                      per year)
----------------------------------------------------------------------------------------------------------------
Radon Gas Ingestion.......................               7.0  x  10-8                2.0  x  10-7            18
Radon Progeny Inhalation..................               5.9  x  10-7                1.7  x  10-6           148

[[Page 59319]]

 
Radon Gas Inhalation......................               6.3  x  10-9                1.8  x  10-8           1.6
                                           ---------------------------------------------------------------------
    Total (credible bounds)...............  6.7  x  10-7 (3.6  x  10-7  1.9  x  10-6 (0.9  x  10-6  168 (80-288)
                                                      - 9.7  x  10-7)             - 3.3  x  10-6)
----------------------------------------------------------------------------------------------------------------

    EPA believes that radon in community groundwater water systems also 
contributes exposure and risk to people when they are outside the 
residence (e.g., at school, work, etc.). Although data are limited, a 
screening level estimate suggests that this type of exposure could be 
associated with about 36 additional lung cancer deaths per year.
Request for Comment
    EPA solicits public comments on its assessment of risk from radon 
in drinking water. In particular, EPA requests comment and 
recommendations on the best data sources and best approaches to use for 
evaluating ingestion and inhalation exposures that occur for members of 
the public (including both workers and non-workers) at non-residential 
buildings (e.g. restaurants, churches, schools, offices, factories, 
etc).

E. Assessment by National Academy of Sciences: Multimedia Approach to 
Risk Reduction

    The NAS report, ``Risk Assessment of Radon in Drinking Water,'' 
summarized several assessments of possible approaches relating 
reduction of radon in indoor air from soil gas to reduction of radon in 
drinking water. The NAS Report provided useful perspectives on 
multimedia mitigation issues that EPA used in developing the proposed 
criteria and guidance for multimedia mitigation programs. The NAS 
Committee focused on how the multimedia approach might be applied at 
the community level and defined a series of scenarios, assuming that 
multimedia programs would be implemented by public water systems. The 
report may provide useful perspectives of interest to public water 
systems if their State does not develop an EPA-approved MMM program.
    For most of the scenarios, the Committee chose primarily to focus 
on how to compare the risks posed by radon in indoor air from soil gas 
to the risks from radon in drinking water in a home in a local 
community. They assessed the feasibility of different activities based 
on costs, radon concentrations, different assumptions about risk 
reduction actions that might be taken, and other factors.
    Overall, the Committee suggested that reduction of indoor radon can 
be an alternative and more effective means of reducing the overall risk 
from radon. They went on to conclude that mitigation of airborne radon 
to achieve equal or greater radon risk reduction ``makes good sense 
from a public health perspective.'' They also noted that non-economic 
issues, such as equity concerns, could factor into a community's 
decision whether to undertake a multimedia mitigation program.
    The Committee also discussed the role of various indoor air 
mitigation program strategies, or ``mitigation measures'' as they are 
described in SDWA. The Committee concluded that an education and 
outreach program is important to the success of indoor radon risk 
reduction programs, but would not in and of itself be sufficient to 
claim that risk reduction took place. Based on an assessment of several 
State indoor radon programs, they found that States with effective 
programs had several factors in common in the implementation of their 
programs. They concluded that the effectiveness of these State programs 
were the result of: (1) Promoting wide-spread testing of homes, (2) 
conducting radon awareness campaigns, (3) providing public education on 
mitigation, and (4) ensuring the availability of qualified contractors 
to test and mitigate homes.
    These views are consistent with the examples of indoor radon 
activities that Congress set forth in the radon provision in SDWA on 
which State Multimedia Mitigation programs may rely. These include 
``public education, testing, training, technical assistance, 
remediation grants and loans and incentive programs, or other 
regulatory or non-regulatory measures.'' These measures also represent 
many of the same strategies that are integral to the current national 
and State radon programs, as well as those outlined in the 1988 Indoor 
Radon Abatement Act, sections 304 to 307 (15 U.S.C. 2664-2667).
    EPA recognizes, as does the National Academy of Sciences, that 
these activities and strategies are important to achieving public 
awareness and action to reduce radon, but that these actions are not in 
and of themselves actual risk reduction. Therefore, EPA has determined 
that State MMM plans will need to set and track actual risk reduction 
goals. However, the criteria and guidance for States to use in 
designing MMM program plans provides extensive flexibility in choosing 
strategies that reflect the needs of individual States.
    The Committee discussed the effectiveness of various indoor radon 
control technologies and recommended that active sub-slab 
depressurization techniques are most effective for controlling radon in 
the mitigation of elevated radon levels in existing buildings and in 
the prevention of elevated levels in new buildings. (Active systems 
rely on mechanically-driven techniques (powered fans) to create a 
pressure gradient between the soil and building interior and thus, 
prevent radon entry.) The Committee expressed concern over the adequacy 
of the scientific basis for ensuring that such methods can be used 
reliably as a consistent outcome of normal design and construction 
methods. The Committee also noted the limited amount of data available 
to quantify the reduction in indoor radon levels expected when such 
techniques were used.
    The Committee found that much of the comparative data available on 
the impact of the passive radon-resistant new construction features is 
confined to the impact of the passive thermal stack on radon levels and 
not on the other features of the passive radon-resistant new 
construction system, such as eliminating leakage paths, sealing utility 
penetrations, and prescribing the extent and quality of aggregate 
beneath the

[[Page 59320]]

foundation. The Committee found that the passive stack alone yielded 
reductions in radon levels as great as 90%, that reductions in radon 
levels of about 40% are more typical, and that the effect of the 
passive stack may be considerably less in slab-on-grade houses that in 
houses with basements. However, the Committee also stated that the 
other features in the passive radon-resistant new construction system 
contribute to reducing radon levels. EPA notes that there are 
substantial difficulties in gathering good comparative data on these 
other features because of the significant variability of radon 
potential across building sites, even within a small area. In addition 
it is impractical to test the same house with and without radon 
resistant features. However, based on the Committee's discussion of the 
contributions of these other features to reducing radon levels, it is 
reasonable to expect that passive systems as a whole achieve greater 
reductions in radon than the passive stack alone.
    EPA agrees with the Committee's perspective that active radon-
reduction systems, while slightly more expensive, assure the greatest 
risk reduction in not only the mitigation of existing homes, but also 
in the construction of new homes. EPA also agrees with the Committee's 
perspective that more data on passive new construction systems would 
allow for more precise estimation of average expected reductions in 
radon levels in new homes from application of passive radon-resistant 
new construction techniques. However, EPA believes there is sufficient 
data and application experience to have a reasonable assurance that the 
passive techniques when used in new homes reduce indoor radon levels by 
about 50% on average. Further, these techniques have been adopted by 
the home construction industry into national model building codes and 
by many State and local jurisdictions into their building codes. EPA 
recommends that new homes built with passive radon-resistant new 
construction features be tested after occupancy and if elevated levels 
still exist, the passive systems be converted to active ones. For these 
reasons, EPA believes it is appropriate to consider passive radon-
resistant new construction techniques for new homes as one means of 
achieving risk reduction through new construction in multimedia 
mitigation programs.

Economics and Impacts Analysis

XIII. What Is the EPA's Estimate of National Economic Impacts and 
Benefits?

A. Safe Drinking Water Act (SDWA) Requirements for the HRRCA

    Section 1412(b)(13)(C) of the SDWA, as amended, requires EPA to 
prepare a Health Risk Reduction and Cost Analysis (HRRCA) to be used to 
support the development of the radon NPDWR. EPA was to publish the 
HRRCA for public comment and respond to significant comments in this 
preamble. EPA published the HRRCA in the Federal Register on February 
26, 1999 (64 FR 9559). Responses to significant comments on the HRRCA 
are provided in Section XIII.H.
    The HRRCA addresses the requirements established in Section 
1412(b)(3)(C) of the amended SDWA, namely: (1) Quantifiable and non-
quantifiable health risk reduction benefits for which there is a 
factual basis in the rulemaking record to conclude that such benefits 
are likely to occur as the result of treatment to comply with each 
level; (2) quantifiable and non-quantifiable health risk reduction 
benefits for which there is a factual basis in the rulemaking record to 
conclude that such benefits are likely to occur from reductions in co-
occurring contaminants that may be attributed solely to compliance with 
the MCL, excluding benefits resulting from compliance with other 
proposed or promulgated regulations; (3) quantifiable and non-
quantifiable costs for which there is a factual basis in the rulemaking 
record to conclude that such costs are likely to occur solely as a 
result of compliance with the MCL, including monitoring, treatment, and 
other costs, and excluding costs resulting from compliance with other 
proposed or promulgated regulations; (4) the incremental costs and 
benefits associated with each alternative MCL considered; (5) the 
effects of the contaminant on the general population and on groups 
within the general population, such as infants, children, pregnant 
women, the elderly, individuals with a history of serious illness, or 
other subpopulations that are identified as likely to be at greater 
risk of adverse health effects due to exposure to contaminants in 
drinking water than the general population; (6) any increased health 
risk that may occur as the result of compliance, including risks 
associated with co-occurring contaminants; and (7) other relevant 
factors, including the quality and extent of the information, the 
uncertainties in the analysis, and factors with respect to the degree 
and nature of the risk.
    The HRRCA discusses the costs and benefits associated with a 
variety of radon levels. Summary tables and figures are presented that 
characterize aggregate costs and benefits, impacts on affected 
entities, and tradeoffs between risk reduction and compliance costs. 
The HRRCA serves as a foundation for the Regulatory Impact Analysis 
(RIA) for this proposed rule.

B. Regulatory Impact Analysis and Revised Health Risk Reduction and 
Cost Analysis (HRRCA) for Radon

    Under Executive Order 12866, Regulatory Planning and Review, EPA 
must estimate the costs and benefits of the proposed radon rule in a 
Regulatory Impact Analysis (RIA) and submit the analysis to the Office 
of Management and Budget (OMB) in conjunction with the proposed rule. 
To comply with the requirements of E.O. 12866, EPA has prepared an RIA, 
a copy of which is available in the public docket for this proposed 
rulemaking. The revised HRRCA is now included as part of the RIA (USEPA 
1999f). This section provides a summary of the information from the RIA 
for the proposed radon rule.
1. Background: Radon Health Risks, Occurrence, and Regulatory History
    Radon is a naturally occurring volatile gas formed from the normal 
radioactive decay of uranium. It is colorless, odorless, tasteless, 
chemically inert, and radioactive. Uranium is present in small amounts 
in most rocks and soil, where it decays to other products including 
radium, then to radon. Some of the radon moves through air or water-
filled pores in the soil to the soil surface and enters the air, and 
can enter buildings through cracks and other holes in the foundation. 
Some radon remains below the surface and dissolves in ground water 
(water that collects and flows under the ground's surface). Due to 
their very long half-life (the time required for half of a given amount 
of a radionuclide to decay), uranium and radium persist in rock and 
soil.
    Exposure to radon and its progeny is believed to be associated with 
increased risks of several kinds of cancer. When radon or its progeny 
are inhaled, lung cancer accounts for most of the total incremental 
cancer risk. Ingestion of radon in water is suspected of being 
associated with increased risk of tumors of several internal organs, 
primarily the stomach. As required by the SDWA, as amended, EPA 
arranged for the National Academy of Sciences (NAS) to assess the 
health risks of radon in drinking

[[Page 59321]]

water. The NAS released the pre-publication draft of the ``Report on 
the Risks of Radon in Drinking Water,'' (NAS Report) in September 1998 
and published the Report in July 1999 (NAS 1999b). The analysis in this 
RIA uses information from the 1999 NAS Report (see Section XII.C of 
this preamble). The NAS Report represents a comprehensive assessment of 
scientific data gathered to date on radon in drinking water. The 
report, in general, confirms earlier EPA scientific conclusions and 
analyses of radon in drinking water.
    NAS estimated individual lifetime unit fatal cancer risks 
associated with exposure to radon from domestic water use for ingestion 
and inhalation pathways (Table XIII.1). The results show that 
inhalation of radon progeny accounts for most (approximately 88 
percent) of the individual risk associated with domestic water use, 
with almost all of the remainder (11 percent) resulting from directly 
ingesting radon in drinking water. Inhalation of radon progeny is 
associated primarily with increased risk of lung cancer, while 
ingestion exposure is associated primarily with elevated risk of 
stomach cancer.

   Table XIII.1.--Estimated Radon Unit Lifetime Fatal Cancer Risks in
                         Community Water Systems
------------------------------------------------------------------------
                                                             Proportion
                                              Cancer unit     of total
             Exposure pathway               risk per pCi/L      risk
                                               in water       (percent)
------------------------------------------------------------------------
Inhalation of radon progeny \1\...........      5.9 x 10-7            88
Ingestion of radon \1\....................      7.0 x 10-8            11
Inhalation of radon gas \2\...............      6.3 x 10-9             1
                                           -----------------------------
    Total.................................      6.7 x 10-7           100
------------------------------------------------------------------------
\1\ Source: NAS 1998B.
\2\ Source: Calculated by EPA from radiation dosimetry data and risk
  coefficients provided by NAS (NAS 1998B).

    The NAS Report confirmed that indoor air contamination arising from 
soil gas typically accounts for the bulk of total individual risk due 
to radon exposure. Usually, most radon gas enters indoor air by 
diffusion from soils through basement walls or foundation cracks or 
openings. Radon in domestic water generally contributes a small 
proportion of the total radon in indoor air.
    The NAS Report is one of the most important inputs used by EPA in 
the RIA. EPA has used the NAS's assessment of the cancer risks from 
radon in drinking water to estimate both the health risks posed by 
existing levels of radon in drinking water and also the cancer deaths 
prevented by reducing radon levels.
    In updating key analyses and developing the framework for the cost-
benefit analysis presented in the RIA, EPA has consulted with a broad 
range of stakeholders and technical experts. Participants in a series 
of stakeholder meetings held in 1997, 1998, and 1999 included 
representatives of public water systems, State drinking water and 
indoor air programs, Tribal water utilities and governments, 
environmental and public health groups, and other Federal agencies.
    The RIA builds on several technical components, including estimates 
of radon occurrence in drinking water, analytical methods for detecting 
and measuring radon levels, and treatment technologies. Extensive 
analyses of these issues were undertaken by the Agency in the course of 
previous rulemaking efforts for radon and other radionuclides. Using 
data provided by stakeholders, and from published literature, the EPA 
has updated these technical analyses to take into account the best 
currently available information and to respond to comments on the 1991 
proposed NPDWR for radon.
    The analysis presented in the RIA uses updated estimates of the 
number of active public drinking water systems obtained from EPA's Safe 
Drinking Water Information System (SDWIS). Treatment costs for the 
removal of radon from drinking water have also been updated. The RIA 
follows current EPA policies with regard to the methods and assumptions 
used in cost and benefit assessment.
    As part of the regulatory development process, EPA has updated and 
refined its analysis of radon occurrence patterns in ground water 
supplies in the United States (USEPA 1998l). This new analysis 
incorporates information from the EPA's 1985 National Inorganic and 
Radionuclides Survey (NIRS) of approximately 1000 community ground 
water systems throughout the United States, along with supplemental 
data provided by the States, water utilities, and academic research. 
The new study also addressed a number of issues raised by public 
comments in the previous occurrence analysis that accompanied the 1991 
proposed NPDWR, including characterization of regional and temporal 
variability in radon levels, and the impact of sampling point for 
monitoring compliance.
    In general, radon levels in ground water in the United States have 
been found to be the highest in New England and the Appalachian uplands 
of the Middle Atlantic and Southeastern States. There are also isolated 
areas in the Rocky Mountains, California, Texas, and the upper Midwest 
where radon levels in ground water tend to be higher than the United 
States average. The lowest ground water radon levels tend to be found 
in the Mississippi Valley, lower Midwest, and Plains States. When 
comparing radon levels in ground water to radon levels in indoor air at 
the States level, the distributions of radon concentrations in indoor 
air do not always mirror distributions of radon in ground water.
2. Consideration of Regulatory Alternatives
    (a) Regulatory Approaches. The RIA evaluates MCL options for radon 
in ground water supplies of 100, 300, 500, 700, 1000, 2000, and 4000 
pCi/L. As Table VII.1 in Section VII of the preamble illustrates, the 
costs and benefits increase as the radon level decreases and the 
benefit-cost ratios are very similar at each level. The RIA also 
presents information on the costs and benefits of implementing 
multimedia mitigation (MMM) programs. The scenarios evaluated are 
described in detail in Sections 9 and 10 of the RIA (USEPA 1999f). 
Based on the analysis shown in the report, the selected regulatory 
alternative discussed next has a significant multimedia mitigation 
component. For more information on this analysis, please refer to the 
RIA.
    (b) Selected Regulatory Alternatives. A CWS must monitor for radon 
in drinking water in accordance with the regulations, as described in 
Section VIII of this preamble, and report their results to the State. 
If the State determines that

[[Page 59322]]

the system is in compliance with the MCL of 300 pCi/L, the CWS does not 
need to implement a MMM program (in the absence of a State program), 
but must continue to monitor as required.
    As discussed in Section VI, EPA anticipates that most States will 
choose to develop a State-wide MMM program as the most cost-effective 
approach to radon risk reduction. In this case, all CWSs within the 
State may comply with the AMCL of 4000 pCi/L. Thus, EPA expects the 
vast majority of CWSs will be subject only to the AMCL. In those 
instances where the State does not adopt this approach, the proposed 
regulation provides the following requirements:
    (i) Requirements for Small Systems Serving 10,000 People or Less. 
The EPA is proposing that small CWSs serving 10,000 people or less must 
comply with the AMCL, and implement a MMM program (if there is no state 
MMM program). This is the cut-off level specified by Congress in the 
1996 Amendments to the Safe Drinking Water Act for small system 
flexibility provisions. Because this definition does not correspond to 
the definitions of ``small'' for small businesses, governments, and 
non-profit organizations previously established under the RFA, EPA 
requested comment on an alternative definition of ``small entity'' in 
the preamble to the proposed Consumer Confidence Report (CCR) 
regulation (63 FR 7620, February 13, 1998). Comments showed that 
stakeholders support the proposed alternative definition. EPA also 
consulted with the SBA Office of Advocacy on the definition as it 
relates to small business analysis. In the preamble to the final CCR 
regulation (63 FR 4511, August 19, 1998), EPA stated its intent to 
establish this alternative definition for regulatory flexibility 
assessments under the RFA for all drinking water regulations and has 
thus used it for this radon in drinking water rulemaking. Further 
information supporting this certification is available in the public 
docket for this rule.
    EPA's regulation expectation for small CWSs is the MMM and AMCL 
because this approach is a much more cost-effective way to reduce radon 
risk than compliance with the MCL. (While EPA believes that the MMM 
approach is preferable for small systems in a non-MMM State, they may, 
at their discretion, choose the option of meeting the MCL of 300 pCi/L 
instead of developing a local MMM program). The CWSs will be required 
to submit MMM program plans to their State for approval. (See Sections 
VI.A and F for further discussion of this approach).
    SDWA Section 1412(b)(13)(E) directs EPA to take into account the 
costs and benefits of programs to reduce radon in indoor air when 
setting the MCL. In this regard, the Agency expects that implementation 
of a MMM program and CWS compliance with 4000 pCi/L will provide 
greater risk reduction for indoor radon at costs more proportionate to 
the benefits and commensurate with the resources of small CWSs. It is 
EPA's intent to minimize economic impacts on a significant number of 
small CWSs, while providing increased public health protection by 
emphasizing the more cost-effective multimedia approach for radon risk 
reduction.
    (ii) Requirements for Large Systems Serving More Than 10,000 
People. The proposal requires large community water systems, those 
serving populations greater than 10,000, to comply with the MCL of 300 
pCi/L unless the State develops a State-wide MMM program, or the CWS 
develops and implements a MMM program meeting the four regulatory 
requirements, in which case large systems may comply with the AMCL of 
4,000pCi/L. CWSs developing their own MMM plans will be required to 
submit these plans to their State for approval.
    (c) Background on the Selection of the MCL and AMCL. For a 
description of EPA's process in selecting the MCL and AMCL, see Section 
VII.D of today's preamble.

C. Baseline Analysis

    Data and assumptions used in establishing baselines for the 
comparison of costs and benefits are presented in the next section. 
While the rule as proposed does not require 100 percent compliance with 
an MCL, an analysis of these full compliance scenarios are required by 
the SDWA, as amended, and were an important feature in the development 
of the NPDWR for radon.
1. Industry Profile
    Radon is found at appreciable levels only in systems that obtain 
water from ground water sources. Thus, only ground water systems would 
be affected by the proposed rule. The following discussion addresses 
various characteristics of community ground water systems that were 
used in the assessment of regulatory costs and benefits. Table XIII.2 
shows the estimated number of community ground water systems in the 
United States. This data originally came from EPA's Safe Drinking Water 
Information System (SDWIS) and are summarized in EPA's Drinking Water 
Baseline Handbook (USEPA, 1999c). EPA estimates that there were 43,908 
community ground water systems active in December 1997 when the SDWIS 
data were evaluated. Approximately 96.5 percent of the systems serve 
fewer than 10,000 customers, and thus fit EPA's definition of a 
``small'' system (see 63 FR 44512 at 44524-44525, August 19, 1998). 
Privately-owned systems comprise the bulk of the smaller size 
categories, whereas most larger systems are publicly owned.

                                                        Table XIII.2.--Number of Community Ground Water Systems in the United States \1\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                     System size category
                  Primary source/ownership                  ------------------------------------------------------------------------------------------------------------------------------------
                                                               25-100    101-500   501-1,000  1,001-3,301  3,301-10,000  10,001-50,000  50,001-100,000  100,001-1,000,000  >1,000,000    Total
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total......................................................     14,232     15,070      4,739       5,726         2,489         1,282             139               70               2     43,908
Public.....................................................      1,202      4,104      2,574       3,792         1,916           997             113               52               2     14,764
Private....................................................     12,361      9,776      1,705       1,531           459           243              24               14               0     26,252
Purchased-Public...........................................        114        427        265         272            84            36               1                4               0      1,203
Purchased-Private..........................................        171        347        101          79            13             3               1                0               0        718
Other......................................................        384        416         94          52            17             3               0                0               0       971
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Source: USEPA 1999c.

    In addition to the number of affected systems, the total number of 
sources (wells) is an important determinant of potential radon 
mitigation costs. Larger systems tend to have larger numbers of sources 
than small ones, and it has been

[[Page 59323]]

conservatively assumed in the mitigation cost analysis that each source 
out of compliance with the MCL or AMCL would need to install control 
equipment.
    Table XIII.3 summarizes the estimated number of wells per ground 
water system. Both the number of wells and the variability in the 
number of wells increases with the number of customers served. These 
characteristics of community ground water sources are included in the 
mitigation cost analysis discussed in Section 7 of the RIA (USEPA 
1999f).
2. Baseline Assumptions
    In addition to the characteristics of the ground water suppliers, 
other important ``baseline'' assumptions were made that affect the 
estimates of potential costs and benefits of radon mitigation. Two of 
the most important assumptions relate to the distribution of radon in 
ground water sources and the technologies that are currently in place 
for ground water systems to control radon and other pollutants.
    As noted in Section 3 of the RIA (USEPA 1999f), EPA has recently 
completed an analysis of the occurrence patterns of radon in 
groundwater supplies in the United States (USEPA 1999g). This analysis 
used the NIRS and other data sources to estimate national distributions 
of groundwater radon levels in community systems of various sizes. The 
results of that analysis are summarized in Table XIII.4. These 
distributions are used to calculate baseline individual and population 
risks, and to predict the proportions of systems of various sizes that 
will require radon mitigation.

                                       Table XIII.3.--Estimated Average Number of Wells Per Groundwater System \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   System size category
                                 -----------------------------------------------------------------------------------------------------------------------
                                     25-100        101-500      501-1,000    1001-3,301   3,301-10,000  10,001-50,000  50,001-100,000  100,001-1,000,000
--------------------------------------------------------------------------------------------------------------------------------------------------------
Average Number of Wells             1.5 (0.2)     2.0 (0.2)     2.3 (0.2)     3.1 (0.3)     4.6 (1.1)      9.8 (1.8)     16.1 (2.2)       49.9 (12.7)
 (Confidence Interval)..........
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Source: USEPA 1999c.


                     Table XIII.4.--Distribution of Radon Levels in U.S. Groundwater Sources
----------------------------------------------------------------------------------------------------------------
                                                                      Population served
                 Statistic                 ---------------------------------------------------------------------
                                               25-100        101-500      501-3,300   3,301-10,000     >10,000
----------------------------------------------------------------------------------------------------------------
Geometric Mean, pCi/L.....................        312           259           122           124           132
Geometric Standard Deviation, pCi/L.......          3.04          3.31          3.22          2.29          2.31
Arithmetic Mean...........................        578           528           240           175           187
----------------------------------------------------------------------------------------------------------------

    The costs of radon mitigation are affected to some extent by the 
treatment technologies that are currently in place to mitigate radon 
and other pollutants, and by the existence of pre- and post-treatment 
technologies that affect the costs of mitigation. EPA has conducted an 
extensive analysis of water treatment technologies currently in use by 
groundwater systems. Table XIII.5 shows the proportions of ground water 
systems with specific technologies already in place, broken down by 
system size (population served). Many ground water systems currently 
employ disinfection, aeration, or iron/manganese removal technologies. 
This distribution of pre-existing technologies serves as the baseline 
against which water treatment costs are measured. For example, costs of 
disinfection are attributed to the radon rule only for the estimated 
proportion of systems that would have to install disinfection as a 
post-treatment because they do not already disinfect. The cost analysis 
assumes that any system affected by the rule will continue to employ 
pre-existing radon treatment technology and pre- and post-treatment 
technologies in their efforts to comply with the rule. Where pre- or 
post-treatment technologies are already in place it is assumed that 
compliance with the radon rule will not require any upgrade or change 
in the pre- or post-treatment technologies. Therefore, no incremental 
cost is attributed to pre- or post-treatment technologies. This may 
underestimate costs if pre- or post-treatment technologies need to be 
changed (e.g., a need for additional chlorination after the 
installation of packed tower aeration). The potential magnitude of this 
cost underestimation is not known, but is likely to be a very small 
fraction of total treatment costs.

              Table XIII.5.--Estimated Proportions of Groundwater Systems With Water Treatment Technologies Already in Place (Percent) \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   System Size (Population Served)
                                           -------------------------------------------------------------------------------------------------------------
  Water treatment  technologies in place                                                                                                       100,001
                                               25-100      101-500     501-1,000   1,001-3,300  3,301-10,000  10,001-50,000  50,001-100,000   1,000,000
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fe/Mn removal & aeration & disinfection...          0.4          0.2          1.2          0.6           2.9           2.2             3.1           2
Fe/Mn removal & aeration..................          0            0.1          0.2          0.1           0.4           0.1             0.4           0.1
Fe/Mn removal & disinfection..............          2.1          5.1          8.3          3             7.8           7.4             9.7           6.8
Fe/Mn removal.............................          1.9          1.5          1.5          1             1.1           0.4             1.1           0.2
Aeration & disinfection only..............          0.9          3.2          9.8         13.7          20.9          19.7            18.6          19.9
Aeration only.............................          0.8          1            1.8          2.9           2.9           1               2.1           0.6
Disinfection only.........................         49.6         68.2         65           65            56.3          66              58.3          68.3

[[Page 59324]]

 
None......................................         44.3         20.7         12.2         13.7           7.7           3.2             6.7           2.1 
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\. Source: EPA analysis of data from the Community Water System Survey (CWSS), 1997, and Safe Drinking Water Information System (SDWIS), 1998.

    The treatment baseline assumptions shown in Table XIII.5 were used 
in the initial analysis for the development of the NPDWR for radon. 
These assumptions were used to establish the costs of 100 percent 
compliance with an MCL. Another analysis, which portrays the costs of 
the rule as recommended in this proposed rulemaking, is provided in the 
results section of this summary and also in Section 9 of the RIA.

D. Benefits Analysis

11. Quantifiable and Non-Quantifiable Health Benefits
    The quantifiable health benefits of reducing radon exposures in 
drinking water are attributable to the reduced incidence of fatal and 
non-fatal cancers, primarily of the lung and stomach. Table XIII.6 
shows the health risk reductions (number of fatal and non-fatal cancers 
avoided) and the residual health risk (number of remaining cancer 
cases) at various radon in water levels.

          Table XIII.6.--Residual Cancer Risk and Risk Reduction from Reducing Radon in Drinking Water
----------------------------------------------------------------------------------------------------------------
                                                                                          Risk          Risk
                                                             Residual      Residual     reduction     reduction
                                                           fatal cancer   non-fatal      (fatal      (non-fatal
              Radon Level  (pCi/L in water)                risk  (cases  cancer risk     cancers       cancers
                                                             per year)    (cases per   avoided per   avoided per
                                                                            year)       year)\1\      year)\1\
----------------------------------------------------------------------------------------------------------------
(Baseline)...............................................         168            9.7           0             0
4,0002 \2\...............................................         165            9.5           2.9           0.2
2,000....................................................         160            9.4           7.3           0.4
1,000....................................................         150            8.8          17.8           1.1
700......................................................         141            8.3          26.1           1.5
500......................................................         130            7.6          37.6           2.2
300......................................................         106            6.1          62.0           3.6
100......................................................          46.8          2.8         120             7.0 
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Risk reductions and residual risk estimates are slightly inconsistent due to rounding.
\2\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on SDWA provisions of Section 1412(b)(13).

    Since preparing the prepublication edition of the NAS Report, the 
NAS has reviewed and slightly revised their unit risk estimates. EPA 
uses these updated unit risk estimates in calculating the baseline 
risks, health risk reductions, and residual risks. Under baseline 
assumptions (no control of radon exposure), approximately 168 fatal 
cancers and 9.7 non-fatal cancers per year are associated with radon 
exposures through CWSs. At a radon level of 4,000 pCi/L, approximately 
2.9 fatal cancers and 0.2 non-fatal cancers per year are prevented. At 
300 pCi/L, approximately 62.0 fatal cancers and 3.6 non-fatal cancers 
are prevented each year.
    The Agency has developed monetized estimates of the health benefits 
associated with the risk reductions from radon exposures. The SDWA, as 
amended, requires that a cost-benefit analysis be conducted for each 
NPDWR, and places a high priority on better analysis to support 
rulemaking. The Agency is interested in refining its approach to both 
the cost and benefit analysis, and in particular recognizes that there 
are different approaches to monetizing health benefits. In the past, 
the Agency has presented benefits as cost per life saved, as in Table 
XIII.7.
    The costs of reducing radon to various levels, assuming 100 percent 
compliance with an MCL, are summarized in Table XIII.7, which shows 
that, as expected, aggregate radon mitigation costs increase with 
decreasing radon levels. For CWSs, the costs per system do not vary 
substantially across the different radon levels evaluated. This is 
because the menu of mitigation technologies for systems with various 
influent radon levels remains relatively constant and are not sensitive 
to percent removal.

                 Table XIII.7.--Estimated Annualized National Costs of Reducing Radon Exposures
                                                [$Million, 1997]
----------------------------------------------------------------------------------------------------------------
                                                                      Central
                                                                     tendency          Total      Total cost per
                       Radon level (pCi/L)                          estimate of     annualized     fatal cancer
                                                                    annualized    national costs   case avoided
                                                                     costs \2\          \3\
----------------------------------------------------------------------------------------------------------------
4000 \1\........................................................            34.5            43.1            14.9
2000............................................................            61.1            69.7             9.5

[[Page 59325]]

 
1000............................................................           121.9           130.5             7.3
700.............................................................           176.8           185.4             7.1
500.............................................................           248.8           257.4             6.8
300.............................................................           399.1           407.6             6.6
100.............................................................           807.6           816.2            6.8
----------------------------------------------------------------------------------------------------------------
\1\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
 
\2\ Costs include treatment, monitoring, and O&M costs only.
\3\ Costs include treatment, monitoring, O&M, recordkeeping, reporting, and state costs for administration of
  water programs.

    An alternative approach presented here for consideration as one 
measure of potential benefits is the monetary value of a statistical 
life (VSL) applied to each fatal cancer avoided. Since this approach is 
relatively new to the development of NPDWRs, EPA is interested in 
comments on these alternative approaches to valuing benefits, and will 
have to weigh the value of these approaches for future use.
    Estimating the VSL involves inferring individuals' implicit 
tradeoffs between small changes in mortality risk and monetary 
compensation. In the HRRCA, a central tendency estimate of $5.8 million 
(1997$) is used in the monetary benefits calculations. This figure is 
determined from the VSL estimates in 26 studies reviewed in EPA's 
recent draft guidance on benefits assessment (USEPA 1998e), which is 
currently under review by the Agency's Science Advisory Board (SAB) and 
the Office of Management and Budget (OMB).
    It is important to recognize the limitations of existing VSL 
estimates and to consider whether factors such as differences in the 
demographic characteristics of the populations and differences in the 
nature of the risks being valued have a significant impact on the value 
of mortality risk reduction benefits. Also, medical care or lost-time 
costs are not separately included in the benefits estimate for fatal 
cancers, since it is assumed that these costs are captured in the VSL 
for fatal cancers.
    For non-fatal cancers, willingness to pay (WTP) data to avoid 
chronic bronchitis is used as a surrogate to estimate the WTP to avoid 
non-fatal lung and stomach cancers. The use of such WTP estimates is 
supported in the SDWA, as amended, at Section 1412(b)(3)(C)(iii): ``The 
Administrator may identify valid approaches for the measurement and 
valuation of benefits under this subparagraph, including approaches to 
identify consumer willingness to pay for reductions in health risks 
from drinking water contaminants.''
    A WTP central tendency estimate of $536,000 is used to monetize the 
benefits of avoiding non-fatal cancers (Viscusi et al. 1991). The 
combined fatal and non-fatal health benefits are summarized in Table 
XIII.8. The annual health benefits range from $17.0 million for a radon 
level of 4000 pCi/L to $702 million at 100 pCi/L.

 Table XIII.8.--Estimated Monetized Health Benefits from Reducing Radon
                            in Drinking Water
------------------------------------------------------------------------
                                                             Monetized
                                                              health
                                                             benefits,
                                                              central
                   Radon level (pCi/L)                       tendency
                                                           (annualized,
                                                            $millions,
                                                             1997)\1\
------------------------------------------------------------------------
4,000 \2\...............................................            17.0
2,000...................................................            42.7
1,000...................................................             103
700.....................................................             152
500.....................................................             219
300.....................................................             362
100.....................................................            702
------------------------------------------------------------------------
Notes:
\1\ Includes contributions from fatal and non-fatal cancers, estimated
  using central tendency estimates of the VSL of $5.8 million (1997$),
  and a WTP to avoid non-fatal cancers of $536,000 (1997$).
\2\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on
  SDWA provisions of Section 1412(b)(13).

    Reductions in radon exposures might also be associated with non-
quantifiable benefits. EPA has identified several potential non-
quantifiable benefits associated with regulating radon in drinking 
water. These benefits may include any customer peace of mind from 
knowing drinking water has been treated for radon. In addition, if 
chlorination is added to the process of treating radon via aeration, 
arsenic pre-oxidation will be facilitated. Neither chlorination nor 
aeration will remove arsenic, but chlorination will facilitate 
conversion of Arsenic (III) to Arsenic (V). Arsenic (V) is a less 
soluble form that can be better removed by arsenic removal 
technologies. In terms of reducing radon exposures in indoor air, it 
has also been suggested that provision of information to households on 
the risks of radon in indoor air and available options to reduce 
exposure may be a non-quantifiable benefit that can be attributed to 
some components of a MMM program. Providing such information might 
allow households to make more informed choices than they would have in 
the absence of an MMM program about the need for risk reduction given 
their specific circumstances and concerns. In the case of the proposed 
radon rule, it is not likely that accounting for these non-quantifiable 
benefits would significantly alter the overall assessment.
    The benefits calculated for this proposal are assumed to begin to 
accrue on the effective date of the rule and are based on a calculation 
referred to as the ``value of a statistical life'' (VSL), currently 
estimated at $5.8 million. The VSL is an average estimate derived from 
a set of 26 studies estimating what people are willing to pay to avoid 
the risk of premature mortality. Most of these studies examine 
willingness to pay in the context of voluntary acceptance of higher 
risks of immediate accidental death in the workplace in exchange for 
higher wages. This value is sensitive to differences in population 
characteristics and perception of risks being valued.
    For the present rulemaking analysis, which evaluates reduction in 
premature mortality due to carcinogen exposure, some commenters have 
argued that the Agency should consider an assumed time lag or latency 
period in these calculations. Latency refers to the difference between 
the time of initial exposure to environmental carcinogens and the onset 
of any resulting cancer. Use of such an approach might reduce 
significantly the present value estimate.

[[Page 59326]]

The BEIR VI model and U.S. vital statistics, on which the estimate of 
lung cancers avoided is based, imply a probability distribution of 
latency periods between inhalation exposure to radon and increased 
probability of cancer death. EPA is interested in receiving comments on 
the extent to which the presentation of more detailed information on 
the timing of cancer risk reductions would be useful in evaluating the 
benefits of the proposed rule.
    Latency is one of a number of adjustments or factors that are 
related to an evaluation of potential benefits associated with this 
rule, how those benefits are calculated, and when those economic 
benefits occur. Other factors which may influence the estimate of 
economic benefits associated with avoided cancer fatalities include (1) 
A possible ``cancer premium'' (i.e., the additional value or sum that 
people may be willing to pay to avoid the experiences of dread, pain 
and suffering, and diminished quality of life associated with cancer-
related illness and ultimate fatality); (2) the willingness of people 
to pay more over time to avoid mortality risk as their income rises; 
(3) a possible premium for accepting involuntary risks as opposed to 
voluntary assumed risks; (4) the greater risk aversion of the general 
population compared to the workers in the wage-risk valuation studies; 
(5) ``altruism'' or the willingness of people to pay more to reduce 
risk in other sectors of the population; and (6) a consideration of 
health status and life years remaining at the time of premature 
mortality. Use of certain of these factors may significantly increase 
the present value estimate. EPA therefore believes that adjustments 
should be considered simultaneously. The Agency also believes that 
there is currently neither a clear consensus among economists about how 
to simultaneously analyze each of these adjustments nor is there 
adequate empirical data to support definitive quantitative estimates 
for all potentially significant adjustment factors. As a result, the 
primary estimates of economic benefits presented in the analysis of 
this rule rely on the unadjusted $5.8 million estimate. However, EPA 
solicits comment on whether and how to conduct these potential 
adjustments to economic benefits estimates together with any rationale 
or supporting data commenters wish to offer. Because of the complexity 
of these issues, EPA will ask the Science Advisory Board (SAB) to 
conduct a review of these benefits transfer issues associated with 
economic valuation of adjustments in mortality risks. In its analysis 
of the final rule, EPA will attempt to develop and present an analysis 
and estimate of the latency structure and associated benefits transfer 
issues outlined previously consistent with the recommendations of the 
SAB and subject to resolution of any technical limitations of the data 
and models.

E. Cost Analysis

1. Total National Costs of Compliance with MCL Options
    Table XIII.9 summarizes the estimates of total national costs of 
compliance with the range of potential MCLs considered. The table is 
divided into two major groupings; the first grouping displays the 
estimated costs to systems and the second grouping displays the 
estimated costs to States. State costs, presented in Table XIII.9, were 
developed as part of the analyses to comply with the Unfunded Mandates 
Reform Act (UMRA) and also the Paperwork Reduction Act (PRA). 
Additional information on State costs is provided in Section 8 of the 
RIA and also in Section VIII of this preamble.

 Table XIII.9.--Summary of Estimated Costs Under the Proposed Radon Rule Assuming 100% Compliance With an MCL of
                                                    300 pCi/L
                                                [$ Millions] \1\
----------------------------------------------------------------------------------------------------------------
                                                                                                    10 percent
                                                                  3 percent cost  7 percent cost      cost of
                                                                     of capital     of capital        capital
----------------------------------------------------------------------------------------------------------------
                                             Costs to Water Systems
----------------------------------------------------------------------------------------------------------------
      Total Capital Costs (20 years, undiscounted)..............           2,463           2,463           2,463
----------------------------------------------------------------------------------------------------------------
                                                  Annual Costs
----------------------------------------------------------------------------------------------------------------
Annualized Capital..............................................           165.6           232.5           289.4
Annual O&M......................................................           152.4           152.4           152.4
                                                                 -----------------------------------------------
      Total Annual Treatment....................................           318.0           385.0           441.8
                                                                 -----------------------------------------------
Monitoring Costs................................................            14.1            14.1            14.1
Recordkeeping and Reporting Costs \2\...........................             6.1             6.1             6.1
                                                                 -----------------------------------------------
      Total Annual Costs to Water Systems \3\...................           338.2           405.1           461.6
----------------------------------------------------------------------------------------------------------------
                                                 Costs to States
----------------------------------------------------------------------------------------------------------------
Administration of Water Programs................................             2.5             2.5             2.5
                                                                 -----------------------------------------------
      Total Annual State Costs..................................             2.5             2.5             2.5
      Total Annual Costs of Compliance \4\......................           340.6           407.6          464.4
----------------------------------------------------------------------------------------------------------------
1.  Assumes no MMM program implementation costs (e.g., all systems comply with 300 pCi/L).
2.  Figure represents average annual burden over 20 years.
3.  Costs include treatment, monitoring, O&M, recordkeeping, and reporting costs to water systems.
4.  Totals have been rounded. Costs include treatment, monitoring, O&M, recordkeeping, reporting, and state
  costs for administration of water programs.


[[Page 59327]]

2. Quantifiable and Non-quantifiable Costs
    The capital and operating and maintenance (O&M) costs of mitigating 
radon in Community Water Systems (CWSs) were estimated for each of the 
radon levels evaluated. The costs of reducing radon in community ground 
water to specific target levels were calculated using the cost curves 
discussed in Section 7.5 and the matrix of treatment options presented 
in Section 7.6 of the RIA. For each radon level and system size 
stratum, the number of systems that need to reduce radon levels by up 
to 50 percent, 80 percent and 99 percent were calculated. Then, the 
cost curves for the distributions of technologies dictated by the 
treatment matrix were applied to the appropriate proportions of the 
systems. Capital and O&M costs were then calculated for each system, 
based on typical estimated design and average flow rates. These flow 
rates were calculated on spreadsheets using equations from EPA's 
Baseline Handbook (USEPA 1999e). The equations and parameter values 
relating system size to flow rates are presented in Appendix C of the 
RIA. The technologies addressed in the cost estimation included a 
number of aeration and granular activated carbon (GAC) technologies 
described in Section 7.2 of the RIA, as well as storage, 
regionalization, and disinfection as a post-treatment. To estimate 
costs, water systems were assumed, with a few exceptions to simulate 
site-specific problems, to select the technology that could reduce 
radon to the selected target level at the lowest cost. CWSs were also 
assumed to treat separately at every source from which water was 
obtained and delivered into the distribution system.
    EPA has attempted to note potential non-quantifiable benefits when 
the Agency believes they might occur, as in the case of peace-of-mind 
benefits from radon reduction. The Agency recognizes that there may 
also be non-quantifiable disbenefits, such as anxiety on the part of 
those near aeration plants or those who find out that their radon 
levels are high. It is not possible to determine whether the net 
results of such psychological effects would be positive or negative. 
The inclusion of non-quantifiable benefits and costs in this analysis 
are not likely to alter the overall results of the benefit-cost 
analysis for the proposed radon rule.

F. Economic Impact Analysis

    A summary analysis of the impacts on small entities is shown in 
Section XIV.B of this preamble (Regulatory Flexibility Act). An 
analysis of the impacts on State, local, and tribal governments is 
shown in Section XIV.C (Unfunded Mandates Reform Act). For information 
on how this proposed rulemaking may impact Indian tribal governments, 
see Section XIV.I of today's preamble. Information on the types of 
information that States will be required to collect, as well as EPA's 
estimate of the burden and reporting requirements for this proposed 
rulemaking, is shown in Section XIV.D (Paperwork Reduction Act). EPA's 
assessment of the impacts that this proposed rulemaking may have on 
low-income and minority populations, as well as any potential concerns 
regarding children's health, are shown in Section XIV.F (Environmental 
Justice) and Section XIV.G (Protection of Children from Environmental 
Health Risks and Safety Risks) of today's preamble.

G. Weighing the Benefits and Costs

1. Incremental Costs and Benefits of Radon Removal

  Table XIII.10.--Estimates of the Annual Incremental Risk Reduction, Costs, and Benefits of Reducing Radon in Drinking Water Assuming 100% Compliance
                                                                       With an MCL
                                                                    [$ Millions 1997]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   Radon Level, pCi/L
                                                              ------------------------------------------------------------------------------------------
                                                                 4000 \1\       2000         1000         700          500          300          100
--------------------------------------------------------------------------------------------------------------------------------------------------------
Incremental Risk Reduction, Fatal Cancers Avoided Per Year...          2.9          4.4         10.5          8.4         11.5         24.4         58.4
Incremental Risk Reduction, Non-Fatal Cancers Avoided Per              0.2          0.3          0.6          0.4          0.8          1.3          3.5
 Year........................................................
Annual Incremental Monetized Benefits, $ Million Per Year....         17.0         25.7         61.0         48.7         67.1          142          341
Annual Incremental Radon Mitigation Costs, $ Million Per Year         34.5         26.6         60.8         54.9         72.0        150.3       408.5
 \2\.........................................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
\2\ Costs include treatment, monitoring, and O&M costs only.

2. Impacts on Households
    The cost impact of reducing radon in drinking water at the 
household level was also assessed. As expected, costs per household 
increase as system size decreases as shown in Table XIII.11.

   Table XIII.11.--Annual Costs per Household for Community Water Systems to Treat to Various Radon Levels \1\
                                                    [$, 1997]
----------------------------------------------------------------------------------------------------------------
                                    VVS (25-    VVS (101-     VS (501-     S (3301-     M (10,001-
       Radon level (pCi/L)            100)         500)        3300)         10K)         100K)       L (> 100K)
----------------------------------------------------------------------------------------------------------------
                    Households Served by PUBLIC Systems Above Radon Level by Population Served
----------------------------------------------------------------------------------------------------------------
4000 \2\........................        256.5         91.0         22.7         14.3           6.2           4.5
2000............................        259.0         92.8         23.5         14.9           7.1           5.2
1000............................        262.5         94.8         24.6         15.4           8.6           6.4
700.............................        264.4         96.0         25.2         15.9           9.6           7.2
500.............................        266.3         97.1         25.9         16.4          10.6           8.1

[[Page 59328]]

 
300.............................        269.5         99.3         26.9         17.4          12.4           9.5
100.............................        278.8        107.1         29.1         20.1          16.2          12.8
----------------------------------------------------------------------------------------------------------------
                   Households Served by PRIVATE Systems Above Radon Level by Population Served
----------------------------------------------------------------------------------------------------------------
4000 \2\........................        372.4        141.1         30.3         22.8           6.6           4.4
2000............................        375.8        143.7         31.2         23.7           7.5           5.1
1000............................        380.5        146.3         32.6         24.7           9.1           6.3
700.............................        383.1        147.8         33.4         25.4          10.1           7.1
500.............................        385.6        149.4         34.2         26.2          11.2           7.9
300.............................        389.8        152.2         35.5         27.7          13.1           9.4
100.............................        401.5        162.4         37.9         32.1          17.1         12.6
----------------------------------------------------------------------------------------------------------------
\1\ Reflects total household costs for systems to treat down to these levels. Because EPA expects that most
  systems will comply with the AMCL/MCL, most systems will not incur these household costs.
\2\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).

    Costs to households are higher for households served by smaller 
systems than larger systems for two reasons. First, smaller systems 
serve far fewer households than larger systems and, consequently, each 
household must bear a greater percentage share of the capital and O&M 
costs. Second, smaller systems tend to have higher influent radon 
concentrations that, on a per-capita or per-household basis, require 
more expensive treatment methods (e.g., one that has an 85 percent 
removal efficiency rather than 50 percent) to achieve the applicable 
radon level.
    To further evaluate the impacts of these household costs, the costs 
per household were compared to median household income data for each 
system-size category. The results of this calculation, presented in 
Table XIII.12 for public and private systems, indicate a household's 
likely share of average incremental costs in terms of the median 
income. Actual costs for individual households will reflect higher or 
lower income shares depending on whether they are above or below the 
median household income (approximately $30,000 per year) and whether 
the water system incurs above average or below average costs for 
installing treatment. For all system sizes but very very small private 
systems, average household costs as a percentage of median household 
income are less than one percent for households served by either public 
or private systems. Average impacts exceed one percent only for 
households served by very very small private systems, which are 
expected to face average impacts of 1.12 percent at the 4,000 pCi/l 
level and 1.35 percent at the 300 pCi/l level and for households served 
by very very small public systems at the 300 pCi/l level, whose average 
costs barely exceed one percent. Similar to the average cost per 
household results on which they are based, average household impacts 
exhibit little variability across radon levels.

                    Table XIII.12.--Per Household Impact by Community Groundwater Systems as a Percentage of Median Household Income
                                                                        [Percent]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                         Average Impact to Households Served by Public Systems    Average Impact to Households Served by Private Systems
                                                        Exceeding Radon Levels                                    Exceeding Radon Levels
          Radon level, pCi/L          ------------------------------------------------------------------------------------------------------------------
                                       VVS (25-  VVS (101-                                       VVS (25-  VVS (101-
                                         100)       500)       VS       S        M         L       100)       500)       VS       S        M        L
--------------------------------------------------------------------------------------------------------------------------------------------------------
4000 \1\.............................      0.86      0.30      0.13     0.06     0.03     0.02       1.12      0.35      0.16     0.07     0.04     0.02
2000.................................      0.92      0.36      0.12     0.05     0.02     0.01       1.19      0.42      0.16     0.09     0.02     0.01
1000.................................      0.96      0.38      0.13     0.05     0.02     0.01       1.24      0.44      0.16     0.09     0.03     0.01
700..................................      0.98      0.38      0.13     0.06     0.03     0.02       1.27      0.45      0.17     0.09     0.03     0.01
500..................................      1.00      0.39      0.13     0.06     0.03     0.02       1.30      0.45      0.17     0.09     0.03     0.01
300..................................      1.05      0.40      0.14     0.06     0.03     0.02       1.35      0.47      0.18     0.10     0.04     0.02
100..................................      1.17      0.44      0.15     0.07     0.05     0.03       1.51      0.51      0.19     0.12     0.05    0.02
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).

3. Summary of Annual Costs and Benefits
    Table XIII.13 reveals that at a radon level of 4000 pCi/L 
(equivalent to the AMCL estimated in the NAS Report), annual costs of 
100 percent compliance with an MCL are approximately twice the annual 
monetized benefits. For radon levels of 1000 pCi/L to 300 pCi/L, the 
central tendency estimates of annual costs are above the central 
tendency estimates of the monetized benefits.

[[Page 59329]]



   Table XIII.13.--Estimated National Annual Costs and Benefits \1\ of Reducing Radon Exposures Assuming 100%
                                Compliance with an MCL--Central Tendency Estimate
                                               [$ Millions, 1997]
----------------------------------------------------------------------------------------------------------------
                                                   Annualized         Total                           Annual
              Radon level  (pCi/L)                  treatment      annualized    Cost per fatal     monetized
                                                    costs \2\       costs \3\    cancer avoided      benefits
----------------------------------------------------------------------------------------------------------------
4000 \4\.......................................            34.5            43.1            14.9             17.0
2000...........................................            61.1            69.7             9.5             42.7
1000...........................................           121.9           130.5             7.3            103
700............................................           176.8           185.4             7.1            152
500............................................           248.8           257.4             6.8            219
300............................................           399.1           407.6             6.6            362
100............................................           807.6           816.2             6.8           702
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ Benefits are calculated for stomach and lung cancer assuming that risk reduction begins immediately.
  Estimates assume a $5.8 million value of a statistical life and willingness to pay of $536,000 for non-fatal
  cancers.
\2\ Costs are annualized over twenty years using a discount rate of seven percent. Costs include treatment,
  monitoring, and O&M costs.
\3\ Costs include treatment, monitoring, O&M, recordkeeping, reporting, and state costs for administration of
  water programs.
\4\ 4000 pCi/L is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).

    Because the costs of compliance with an MCL for small systems 
outweigh the benefits at each radon level (Table XIII.14), the MMM 
option was recommended for small systems to alleviate some of the 
financial burden to these systems and the households they serve and to 
realize equivalent or greater benefits at much lower costs. The results 
of the benefit-cost analyses for MMM implementation scenarios are shown 
at the end of this section and also in Section 9 of the RIA.

                           Table XIII.14.-- Estimated Annual Costs and Benefits for 100% Compliance With an MCL by System Size
                                                                    [$Millions, 1997]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                          System size
         Radon level (pCi/l)                   Parameter \1\         -----------------------------------------------------------------------------------
                                                                         25-100        101-500      501-3300     3301-10,000   10,001-100K      >100K
--------------------------------------------------------------------------------------------------------------------------------------------------------
4000.................................  Benefits.....................          0.16          0.79           2.7           2.8           7.0           3.6
                                       Costs........................          7.8          14.3            6.3           2.9           2.7           0.5
2000.................................  Benefits.....................          0.41          2.0            6.8           6.9          17.7           9.0
                                       Costs........................         13.2          22.7           11.6           5.7           6.3           1.6
1000.................................  Benefits.....................          1.0           4.8           16.3          16.7          42.6          21.6
                                       Costs........................         23.1          36.5           24.7          13.4          18.9           5.3
700..................................  Benefits.....................          1.5           7.1           24.1          24.6          62.9          31.9
                                       Costs........................         30.6          46.5           36.3          21.1          32.8           9.5
500..................................  Benefits.....................          2.1          10.2           34.7          35.4          90.6          45.9
                                       Costs........................         39.4          57.9           50.8          32.0          53.0          15.6
300..................................  Benefits.....................          3.5          16.9           57.3          58.6         150            75.9
                                       Costs........................         55.6          79.3           78.8          56.1          99.3          26.9
100..................................  Benefits.....................          7.2          32.7          111           113           290           147
                                       Costs........................         93.4         134            147           122           238            73.5 
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Costs do not include recordkeeping, reporting, or state costs for administration of water programs. Recordkeeping and reporting costs are estimated
  at $6.1 million for all system sizes and State administration costs for water programs are estimated at $2.5 million.

    Total costs to public and private water systems, by size, were also 
evaluated in the RIA. Table XIII.15 presents the total annualized costs 
for public and private systems by system size category for all radon 
levels evaluated in the RIA. The costs are comparable for public and 
private systems across system sizes for all options. This pattern may 
be due in large part to the limited number of treatment options assumed 
to be available to either public or private systems in mitigating 
radon.

                                                     Table XIII.15.--Average Annual Cost Per System
                                                                   [$Thousands, 1997]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                       Average costs to public systems exceeding radon levels    Average costs to private systems exceeding radon levels
                                     -------------------------------------------------------------------------------------------------------------------
         Radon Level (pCi/l)           VVS (25-  VVS (101-                                       VVS (25-  VVS (101-
                                         100)       500)       VS       S        M        L        100)       500)       VS       S        M        L
--------------------------------------------------------------------------------------------------------------------------------------------------------
4000................................        8.2       12.4     18.5     49.3     82.3    484.9        7.6       10.1     15.6     43.7     72.1    468.5
2000................................        8.3       12.6     19.1     51.3     94.1    560.7        7.7       10.3     16.2     45.5     82.4    541.8
1000................................        8.4       12.9     26.6     60.1    115.9    693.4        7.8       10.5     16.8     47.3    100.2    670.2
700.................................        8.5       13.0     27.2     61.9    129.0    758.3        7.9       10.6     17.1     48.7    111.7    752.7
500.................................        8.5       13.2     27.8     63.7    143.2    847.8        7.9       10.7     17.5     50.3    123.9    841.6
300.................................        8.6       13.5     28.8     67.4    167.1   1000.4        8.0       10.9     18.1     53.3    144.7    992.9
100.................................        8.9       14.6     31.0     77.2    219.1   1345.3        8.2       11.6     19.1     61.8    189.6   1333.1
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 59330]]

 
                                   Annual Per System Cost for those Systems Below Radon Levels: Monitoring Costs Only
--------------------------------------------------------------------------------------------------------------------------------------------------------
All.................................        0.3        0.3      0.4      0.6      1.1      2.6        0.3        0.3      0.4      0.6      1.1      2.6
--------------------------------------------------------------------------------------------------------------------------------------------------------

4. Benefits From the Reduction of Co-Occurring Contaminants
    The occurrence patterns of industrial pollutants are difficult to 
clearly define at the national level relative to a naturally occurring 
contaminant such as radon. Similarly, the Agency's re-evaluation of 
radon occurrence has revealed that the geographic patterns of radon 
occurrence are not significantly correlated with other naturally 
occurring inorganic contaminants that may pose health risks. Thus, it 
is not likely that a clear relationship exists between the need to 
install radon treatment technologies and treatments to remove other 
contaminants. On the other hand, technologies used to reduce radon 
levels in drinking water have the potential to reduce concentrations of 
other pollutants as well. Aeration technologies will also remove 
volatile organic contaminants from contaminated ground water. 
Similarly, granular activated carbon (GAC) treatment for radon removal 
effectively reduces the concentrations of organic (both volatile and 
nonvolatile) chemicals and some inorganic contaminants. Aeration also 
tends to oxidize dissolved arsenic (a known carcinogen) to a less 
soluble form that is more easily removed from water. The frequency and 
extent that radon treatment would also reduce risks from other 
contaminants has not been quantitatively evaluated.
5. Impacts on Sensitive Subpopulations
    The SDWA, as amended, includes specific provisions in Section 
1412(b)(3)(C)(i)(V) to assess the effects of the contaminant on the 
general population and on groups within the general population such as 
children, pregnant women, the elderly, individuals with a history of 
serious illness, or other subpopulations that are identified as likely 
to be at greater risk of adverse health effects due to exposure to 
contaminants in drinking water than the general population. The NAS 
Report concluded that there is insufficient scientific information to 
permit separate cancer risk estimates for potential subpopulations such 
as pregnant women, the elderly, children, and seriously ill persons. 
The NAS Report did note, however, that according to the NAS model for 
the cancer risk from ingested radon, which accounts for 11 percent of 
the total fatal cancer risk from radon in drinking water, approximately 
30 percent of the fatal lifetime cancer risk is attributed to exposure 
between ages 0 to 10.
    The NAS Report identified smokers as the only group that is more 
susceptible to inhalation exposure to radon progeny (NAS 1999b). 
Inhalation of cigarette smoke and radon progeny result in a greater 
increased risk than if the two exposures act independently to induce 
lung cancer. NAS estimates that ``ever smokers'' (more than 100 
cigarettes over a lifetime) may be more than five times as sensitive to 
radon progeny as ``never smokers'' (less than 100 cigarettes over a 
lifetime). Using current smoking prevalence data, EPA's preliminary 
estimate for the purposes of the HRRCA is that approximately 85 percent 
of the cases of radon-induced cancer will occur among current and 
former smokers. This population of current and former smokers, which 
consists of 58 percent of the male and 42 percent of the female 
population, will also experience the bulk of the risk reduction from 
radon exposure reduction in drinking water supplies.
6. Risk Increases From Other Contaminants Associated With Radon 
Exposure Reduction
    As discussed in Section 7.2 of the RIA, the need to install radon 
treatment technologies may require some systems that currently do not 
disinfect to do so. Case studies (US EPA 1998j) of twenty-nine small to 
medium water systems that installed treatment (24 aeration, 5 GAC) to 
remove radon from drinking water revealed only two systems that 
reported adding disinfection (both aeration) with radon treatment (the 
other systems either had disinfection already in place or did not add 
it). In practice, the tendency to add other disinfection with radon 
treatment may be much more significant than these case studies 
indicate. EPA also realizes that the addition of chlorination for 
disinfection may result in risk-risk tradeoffs, since, for example, the 
disinfection technology reduces potential for infectious disease risk, 
but at the same time can result in increased exposures to disinfection 
by-products (DBPs). This risk-risk trade-off is addressed by the 
recently promulgated Disinfectants and Disinfection By-Products NPDWR 
(63 FR 69390). This rule identified MCLs for the major DBPs, with which 
all CWSs and NTNCWSs must comply. These MCLs set a risk ceiling from 
DBPs that water systems adding disinfection in conjunction with 
treatment for radon removal could face. The formation of DBPs 
correlates with the concentration of organic precursor contaminants, 
which tend to be much lower in ground water than in surface water. In 
support of this statement, the American Water Works Association's 
WATERSTATS survey (AWWA 1997) reports that more than 50% of the ground 
water systems surveyed have average total organic carbon (TOC) raw 
water levels less than 1 mg/L and more than 80% had TOC levels less 
than 3 mg/L. On the other hand, WATERSTATS reports that less than 6% of 
surface water systems surveyed had raw water TOC levels less than 1 mg/
L and more than 50% had raw water TOC levels greater than 3 mg/L. In 
fact, this survey reports that more than 85% of surface water systems 
had finished water TOC levels greater than 1 mg/L.
    The NAS Report addressed several important potential risk-risk 
tradeoffs associated with reducing radon levels in drinking water, 
including the trade-off between risk reduction from radon treatment 
that includes post-disinfection with the increased potential for DBP 
formation (NAS 1999b). The report concluded that, based upon median and 
average total trihalomethane (THM) levels taken from a 1981 survey, 
ground water systems would face an incremental individual lifetime 
cancer risk due to chlorination

[[Page 59331]]

byproducts of 5  x  10-5. It should be emphasized that this 
risk is based on average and median Trihalomethane (THM) occurrence 
information that does not segregate systems that disinfect from those 
that do. It should also be noted that this survey pre-dates the 
promulgation of the Stage I Disinfection Byproducts Rule by almost 
twenty years. Further, the NAS Report points out that this average DBP 
risk is smaller than the average individual lifetime fatal cancer risk 
associated with baseline radon exposures from ground water (untreated 
for radon), which is estimated at 1.2  x  10-4 using a mean 
radon concentration of 213 pCi/L.
    While this risk comparison is instructive, a more meaningful 
relationship for the proposed radon rule would be to compare the trade-
off between radon risk reduction from radon treatment and introduced 
DBP risk from disinfection added along with radon treatment. EPA 
emphasizes that this risk trade-off is only of concern to the small 
minority (<1%) of small ground water systems with radon levels above 
the AMCL of 4000 pCi/L and to the small minority of large ground water 
systems that are not already disinfecting. Presently, approximately 
half of all small community ground water systems already have 
disinfection in place, as shown in Table XIII.5. The proportion of 
systems having disinfection in place increases as the system's size 
increases; >95% of large ground water systems currently disinfect. In 
terms of the populations served, 83% of persons served by small 
community ground water systems (those serving 10,000 persons or fewer) 
already receive disinfected drinking water and 95% of persons served by 
large ground water systems already receive disinfected drinking water. 
As shown in Tables XIII.16 and XIII.17, even for those ground water 
systems adding both radon treatment and disinfection, this risk-risk 
trade-off tends to be very favorable, since the risk reduction from 
radon removal greatly outweighs the added risk from DBP formation.
    An estimate of the risk reduction due to treatment of radon in 
water for various removal percentages and finished water concentrations 
is provided in Table XIII.16. These risk reductions are much greater 
than NAS's estimate of the average lifetime risk from DBP exposure for 
ground water systems, by factors ranging from 3.5 for low radon removal 
efficiencies (50%) to more than 130 for higher radon removal 
efficiencies (>95%).

  Table XIII.16.--Radon Risk Reductions Resulting from Water Treatment
------------------------------------------------------------------------
                                     Required     Reduced lifetime risk
Radon Influent (Raw Water) level,    removel      resulting from Water
              pCi/L                 efficiency   Treatment for Radon in
                                    (percent)      Drinking Water \1\
------------------------------------------------------------------------
500..............................           52  1.7  x  10 -\4\
750..............................           68  3.4  x  10 -\4\
1000.............................           76  5.1  x  10 -\4\
2500.............................           90  1.5  x  10 -\3\
4000.............................           94  2.5  x  10 -\3\
10000............................           98  6.5  x  10 -\3\
------------------------------------------------------------------------
\1\ Assumes that water is treated to 80% of the radon MCL.

    Table XIII.17 demonstrates the risk-risk trade-off between the risk 
reduction from radon removal and the risks introduced from total 
trihalomethanes (TTHM) for two scenarios: (1) the resulting TTHM level 
is 0.008 mg/L (10% of the TTHM MCL) and (2) the resulting TTHM level is 
0.080 mg/L (the TTHM MCL). The table demonstrates that the risk-risk 
trade-off is favorable for treatment with disinfection, even for 
situations where radon removal efficiencies are low (50%) and TTHM 
levels are present at the MCL. While accounting quantitatively for the 
increased risk from DBP exposure for systems adding chlorination in 
conjunction with treatment for radon may somewhat decrease the 
monetized benefits estimates, disinfection may also produce additional 
benefits from the reduced risks of microbial contamination.

   Table XIII.17.--Radon Risk Reduction from Treatment Compared to DBP
                                  Risks
------------------------------------------------------------------------
                                   Estimated risk ratios: (lifetime risk
                                     reduction from radon removal \1\ /
                                    lifetime average risk from TTHMs in
                                          chlorinated groundwater)
 Radon influent (Raw Water) level --------------------------------------
              pCi/L                                TTHMs
                                                 present at     TTHMs
                                    (NAS) \2\   10% of TTHM   present at
                                                 MCL (0.080      MCL
                                                 mg/L) \3\
------------------------------------------------------------------------
500..............................            4           30            3
750..............................            7           60            6
1000.............................           10           90            9
2500.............................           30          300           30
4000.............................           50          500           50
10000............................          130         1200         120
------------------------------------------------------------------------
Notes: \1\ From Table XIII.16.
\2\ From Appendix D in: National Research Council, Risk Assessment of
  Radon in Drinking Water, National Academy Press, Washington, DC. 1999.
  DBP concentrations are from a 1981 study and therefore pre-date the
  Stage 1 DBP NPDWR.
\3\ US EPA Regulatory Impact Analysis for the Stage 1 Disinfectants/
  Disinfection Byproducts Rule. Prepared by The Cadmus Group. November
  12, 1998. Analysis is based on the 95% upper confidence interval value
  from the Integrated Risk Information System (IRIS) lifetime unit risks
  for each THM. TTHM is assumed to comprised by 70% chloroform, 21%
  bromodichloromethane, 8% dibromochloromethane, and 1% bromoform.
\4\ US EPA. Regulatory Impact Analysis for the Stage 1 Disinfectants/
  Disinfection Byproducts Rule. Based on the 95% upper confidence
  interval value from the Integrated Risk Information System (IRIS) for
  the lifetime unit risk for dibromochloromethane (2.4  x  10 -\6\ risk
  of cancer case over 70 years of exposure).


[[Page 59332]]

7. Other Factors: Uncertainty in Risk, Benefit, and Cost Estimates
    Estimates of health benefits from radon reduction are uncertain. 
EPA is including an uncertainty analysis of radon in drinking water 
risks in Section XII of the preamble to the proposed radon rule. A 
brief discussion on the uncertainty analysis is also shown in Section 
10 of the RIA (USEPA 1999f) for radon in drinking water. Monetary 
benefit estimates are also affected by the VSL estimate that is used 
for fatal cancers. The WTP valuation for non-fatal cancers has less 
impact on benefit estimates because it contributes less than 1 percent 
to the total benefits estimates, due to the fact that there are few 
non-fatal cancers relative to fatal cancers and they receive a much 
lower monetary valuation.
8. Costs and Benefits of Multimedia Mitigation Program Implementation 
Scenarios
    In addition to evaluating the costs and benefits across a range of 
radon levels, EPA has evaluated five scenarios that reduce radon 
exposure through the use of MMM programs. The implementation 
assumptions for each scenario are described in the next section. These 
five scenarios are described in detail in Section 9 of the RIA. For the 
MMM implementation analysis, systems were assumed to mitigate water to 
the 4,000 pCi/L Alternative Maximum Contaminant Level (AMCL), if 
necessary, and that equivalent risk reduction between the AMCL and the 
radon level under evaluation would be achieved through a MMM program. 
Therefore, the actual number of cancer cases avoided is the same for 
the MMM implementation scenarios as for the water mitigation only 
scenario. A complete discussion on why MMM is expected to achieve equal 
or greater risk reduction is shown in Section VI.B of the preamble for 
the proposed radon rule.
    For the RIA, EPA used a simplified approach to estimating costs of 
mitigating indoor air radon risks. A point estimate of the average cost 
per life saved under the current voluntary radon mitigation programs 
served as the basis for estimating the costs of risk reduction under 
the MMM options. The Agency has estimated the average screening and 
mitigation cost per fatal lung cancer avoided to be approximately 
$700,000, assuming the current distribution of radon in indoor air, 
that all homes would be tested for radon in indoor air, and that all 
homes at or above EPA's voluntary action level of 4 pCi/L would be 
mitigated. This value was originally derived based on data gathered in 
1991. The same value has been used in the RIA, without adjustment for 
inflation, after discussions with personnel from EPA's Office of 
Radiation and Indoor Air indicated that screening and mitigation costs 
have not increased since 1991.
9. Implementation Scenarios
    EPA evaluated the annual cost of five MMM implementation scenarios 
that span the range of participation in MMM programs that might occur 
when a radon NPDWR is implemented. Each scenario assumes a different 
proportion of States will comply with the AMCL and implement MMM 
programs. It has been assumed that ``50 percent of States'' implies 50 
percent of systems in the U.S; ``60 percent of States'' implies 60 
percent of systems, and so on.

Scenario A: 50 percent of States implement MMM programs.
Scenario B: 60 percent of States implement MMM programs.
Scenario C: 70 percent of States implement MMM programs.
Scenario D: 80 percent of States implement MMM programs.
Scenario E: 95 percent of States implement MMM programs.

    States that do not implement MMM programs instead must review and 
approve any system-level MMM programs prepared by community water 
systems. In these States, regardless of scenario, 90 percent of systems 
are assumed to comply with the AMCL and to implement a system-level MMM 
program and 10 percent are assumed to comply with the MCL. EPA requests 
comment on whether this is an appropriate assumption.
10. Costs and Benefits of MMM Implementation Scenarios
    Table XIII.18 shows the total annual system-level and State-level 
costs for each MMM scenario, assuming an MCL of 300 pCi/L and AMCL of 
4,000 pCi/L. Additional MMM scenario cost and benefit tables for MCL 
levels of 100, 500, 700, 1000, 2000, and 4000 pCi/L are shown in 
Appendix E of the RIA. System, State, and MMM mitigation costs decrease 
from $121.1 million to $60.4 million as the percentage of States 
implementing MMM programs increases from 50 to 95 percent. System-level 
costs decrease from $104 million to $47 million as the percentage of 
States implementing MMM programs increases from 50 to 95 percent. Costs 
for actual mitigation of radon in indoor air rise from $3.9 million to 
$4.1 million as the percentage of States implementing MMM programs 
rises from 50 to 95 percent. Note that these mitigation costs are 
relatively flat because all scenarios assume that 95 percent or more of 
the risk reduction will be achieved through MMM at either the State or 
local level.
    Table XIII.19 represents the ratios of benefits to costs of MMM 
programs for each scenario, by system size. Only the ratios in the 
bottom row of the table include costs to the States. The balance of the 
numbers presented here represent local benefits and costs only and as 
such, somewhat overstate the net benefits of the scenarios. Benefit-
cost ratios are generally less than one for the smallest system size 
category (systems serving less than 500 people), but greater than one 
for larger systems under all five scenarios. For larger systems, 
benefit-cost ratios range from 2.6 for systems serving 501-3,300 people 
under Scenario A to approximately 41.4 for systems serving 10,001 to 
100,000 people under Scenario E. Overall benefit-cost ratios are over 
one for all five scenarios. This pattern is seen primarily because a 
larger proportion of smaller systems have influent radon levels 
exceeding 4000 pCi/L. A larger proportion of small systems versus large 
systems therefore, incur water mitigation costs to comply with the 
AMCL.
    Table XIII.20 shows the net benefits (benefits minus costs) of the 
various MMM implementation scenarios. As would be expected from the 
benefit-cost ratios shown in Table XIII.19, all systems serving more 
than 500 people realize net positive benefits under all five scenarios. 
By far the largest proportion of net benefits is realized by systems 
serving 10,001 to 100,000 people.

[[Page 59333]]



  Table XIII.18 (A).--Annual System--Level and State--Level Costs Associated with the Multimedia Mitigation and
                                                   AMCL Option
                                        [$ Millions/Year] [MCL=300 pCi/L]
----------------------------------------------------------------------------------------------------------------
                                    Scenario A      Scenario B      Scenario C      Scenario D    Scenario E  5%
                                   45% implement   36% implement   27% implement   18% implement     implement
                                   system-level    system-level    system-level    system-level    system-level
                                   MMM program;    MMM program;    MMM program;    MMM program;    MMM program;
                                    5% mitigate     4% mitigate     3% mitigate     2% mitigate     5% mitigate
           System size             water to 300    water to 300    water to 300    water to 300    water to 300
                                  piC/L MCL; 95%  piC/L MCL; 96%  piC/L MCL; 97%  piC/L MCL; 98%    piC/L MCL;
                                  mitigate water  mitigate water  mitigate water  mitigate water  99.5% mitigate
                                   to 4000 piC/L   to 4000 piC/L   to 4000 piC/L   to 4000 piC/L   water to 4000
                                       AMCL            AMCL            AMCL            AMCL         piC/L AMCL
----------------------------------------------------------------------------------------------------------------
                               System Costs for Water Mitigation ($ millions/year)
----------------------------------------------------------------------------------------------------------------
25-100..........................            10.2             9.7             9.3             8.8             8.1
101-500.........................            17.6            16.9            16.3            15.6            14.6
501-3300........................             9.9             9.2             8.5             7.7             6.7
3301-10,000.....................             5.5             5.0             4.5             3.9             3.1
10,001-100,000..................             7.5             6.6             5.6             4.6             3.2
>100,000........................             2.0             1.7             1.4             1.1             0.7
                                 -------------------------------------------------------------------------------
    Total CWS Water Mitigation              52.7            49.1            45.4            41.8            36.3
     Costs......................
----------------------------------------------------------------------------------------------------------------
                               Water System Administration Costs ($ millions/year)
----------------------------------------------------------------------------------------------------------------
25-100..........................            17.0            14.0            11.0             8.0             3.7
101-500.........................            17.4            14.3            11.3             8.2             3.8
501-3300........................            12.0             9.9             7.8             5.7             2.6
3301-10,000.....................             3.0             2.5             1.9             1.4             0.6
10,001-100,000..................             1.7             1.4             1.1             0.8             0.4
>100,000........................             0.1             0.1             0.1             0.0             0.0
                                 -------------------------------------------------------------------------------
    Total CWS Administrative                51.2            42.1            33.1            24.1            11.1
     Costs......................
                                 ===============================================================================
        Total CWS Water                    104.0            91.2            78.5            65.9            47.4
         Mitigation and
         Administrative Costs...
----------------------------------------------------------------------------------------------------------------


                               Table XIII.18 (B).--State MMM Administrative Costs
                                                [$ millions/year]
----------------------------------------------------------------------------------------------------------------
                                  Scenario A 50%  Scenario B 60%  Scenario C 70%  Scenario D 80%
                                     of states       of states       of states       of states    Scenario E 95%
                                     implement       implement       implement       implement       of states
                                  state-wide MMM  state-wide MMM  state-wide MMM  state-wide MMM     implement
                                   programs; 45%   program; 35%    program; 25%    program; 15%   state-wide MMM
                                      of CWS          of CWS          of CWS          of CWS      program; 5% of
                                     implement       implement       implement       implement     CWS implement
                                   system-level    system-level    system-level    system-level    system-level
                                    MMM program     MMM program     MMM program     MMM program     MMM program
----------------------------------------------------------------------------------------------------------------
   State costs associated with State-wide MMM program administration, reviewing system-level MMM programs, and
    reviewing system-level water mitigation requirements are not distributable across different system sizes.
----------------------------------------------------------------------------------------------------------------
State Administration Costs for               2.5             2.5             2.5             2.5             2.5
 Water Mitigation...............
State Administration Costs for               2.9             3.5             4.1             4.7             5.6
 State-Level MMM Mitigation.....
State Administration Costs for               7.8             6.1             4.4             2.6             0.9
 System-Level MMM Mitigation....
                                 -------------------------------------------------------------------------------
        Total State                         13.2            12.1            10.9             9.8             8.9
         Administration Costs...
----------------------------------------------------------------------------------------------------------------


                              Table XIII.18 (C).--MMM Testing and Mitigation Costs
                                                [$ million/year]
----------------------------------------------------------------------------------------------------------------
                                    Scenario A      Scenario B      Scenario C      Scenario D      Scenario E
----------------------------------------------------------------------------------------------------------------
CWS MMM Costs...................             1.9             1.5             1.1             0.7             0.2
State MMM Costs.................             2.1             2.5             2.9             3.3             3.9
                                 -------------------------------------------------------------------------------
    Total MMM Costs.............            3.91            3.95            3.99            4.03            4.12
                                 ===============================================================================

[[Page 59334]]

 
        Total Costs (From Tables           121.1           107.3            93.4            79.7            60.4
         XIII.18 A, B, and C)...
----------------------------------------------------------------------------------------------------------------


                              Table XIII.19.--Ratio of Benefits and Costs by System Size for Each Scenario (MCL=300 pCi/L)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      System size                          Benefits, $M     Scenario A      Scenario B      Scenario C      Scenario D      Scenario E
--------------------------------------------------------------------------------------------------------------------------------------------------------
25-100.................................................              3.5            0.13            0.14            0.17            0.21            0.30
101-500................................................             16.9            0.48            0.53            0.61            0.70            0.92
501-3,300..............................................             58.0            2.59            2.98            3.51            4.27            6.23
3,301-10,000...........................................             59.2            6.87            7.85            9.16            11.0           15.61
10,001-100,000.........................................            147.3           15.82           18.35           21.84           26.96           41.43
>100,000...............................................             76.7           37.16           43.70           53.04           67.44          113.68
                                                        ------------------------------------------------------------------------------------------------
        OVERALL........................................            361.6            2.98            3.37            3.87            4.54            5.99
--------------------------------------------------------------------------------------------------------------------------------------------------------


                                            Table XIII.20.--Net Benefits by System Size for Each Scenario \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       System size                         Benefits, $M     Scenario A      Scenario B      Scenario C      Scenario D      Scenario E
--------------------------------------------------------------------------------------------------------------------------------------------------------
25-100..................................................             3.5          (24.3)          (20.7)          (17.1)          (13.5)           (8.3)
101-500.................................................            16.9          (18.7)          (14.8)          (11.0)           (7.1)           (1.6)
501-3,300...............................................            58.0           35.6            38.6            41.5            44.4            48.7
3,301-10,000............................................            59.2           50.6            51.7            52.7            53.8            55.4
10,001-100,000..........................................           147.3          138.0           139.3           140.6           141.8           143.7
>100,000................................................            76.7           74.6            74.9            75.3            75.6            76.0
                                                         -----------------------------------------------------------------------------------------------
        OVERALL.........................................           361.6          240.5           254.3           268.2           281.9           301.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Parentheses indicate negative numbers.

H. Response to Significant Public Comments on the February 1999 HRRCA

    To provide the public with opportunities to comment on the Health 
Risk Reduction and Cost Analysis (HRRCA) for radon in drinking water, 
the Agency published the HRRCA in the Federal Register on February 26, 
1999 (64 FR 9559). The HRRCA was published six months in advance of 
this proposal and illustrated preliminary cost and benefit estimates 
for various MCL options under consideration for the proposed rule. The 
comment period on the HRRCA ended on April 12, 1999, and EPA received 
approximately 26 written comments from a variety of stakeholders, 
including the American Water Works Association, the National Rural 
Water Association, the National Association of Water Companies, the 
Association of Metropolitan Water Agencies, State departments of 
environmental protection, State health departments, State water 
utilities and local water utilities.
    Significant comments on the HRRCA addressed the topics of radon 
occurrence, exposure pathways, sensitive sub-populations and the risks 
to smokers, risks from existing radon exposures, risks associated with 
co-occurring contaminants, risk increases associated with radon 
removal, the benefits of reduced radon exposures, the costs of radon 
treatment measures, the cost and benefit results, and the Multimedia 
Mitigation (MMM) program. The following discussion outlines the 
significant comments received on the HRRCA and the Agency's response to 
these comments.
1. Radon Occurrence
    Several commenters had concerns related to EPA's analysis of radon 
occurrence. Two commenters felt that the radon levels in Table 3.1 of 
the HRRCA were too low and not representative of radon occurrence in 
their regions. A California water utility indicated that due to 
limitations of the NIRS, EPA should conduct a new national radon 
survey, with special emphasis on determining radon levels in the 
largest systems, before promulgating the rule. Two commenters from 
Massachusetts expressed concerns about radon occurrence. One suggested 
that additional analysis of radon variability in individual wells was 
required, and another indicated that the effects of storage and 
residence time on radon levels in supply systems needed to be taken 
into account. One commenter indicated that EPA should more strongly 
consider that most risk reductions predicted in the HRRCA come from 
reductions in radon levels in the small proportions of systems with 
initial very high radon levels.
EPA Response 1-1
    As part of the regulatory development process, EPA updated and 
refined its analysis of radon occurrence patterns in ground water 
supplies in the United States. This new analysis incorporated 
information from the EPA 1995 National Inorganic and Radionuclides 
Survey (NIRS) of 1000 community ground water systems throughout the 
United States, along with supplemental data provided by States, water 
utilities, and academic researchers. EPA's current re-evaluation used 
data from 17 States to determine the differences between radon levels 
in ground water and radon levels in distribution systems in the same 
regions. The results of these comparisons were used to estimate 
national distributions of radon occurrence in ground water. EPA 
believes that the existing NIRS data, along with the Agency's updates 
to this data, currently provide the most comprehensive national-level 
analysis of radon occurrence patterns in ground water supplies. This 
analysis is not intended for the estimation of radon occurrence at the 
state-level.

[[Page 59335]]

    Variability within the NIRS radon occurrence data was analyzed for 
several important contributing factors: within-well (temporal) 
variability, sampling and analytical (methods) variability, intra-
system variability (variability between wells within a single system), 
and inter-system variability (variability between wells in different 
systems). Several important conclusions were drawn from this analysis. 
First and foremost is the conclusion that the NIRS data do capture the 
major sources of radon occurrence variability and thus can be used 
directly, without any additional correction for temporal or sampling 
and analytical variability, to provide reasonable national estimates of 
radon levels and variability levels in ground water drinking supplies. 
In addition, EPA analyzed the additional data sets provided from 
stakeholders (described previously) in conjunction with the NIRS radon 
data to estimate the magnitudes of the variability sources. Based on 
all of these analyses, EPA has concluded that the variability between 
systems dominates the over-all variability (it comprises approximately 
70 percent of the over-all variability). Temporal variability (13-18 
percent), sampling and analytical variability (less than 1 percent), 
and intra-system variability (12-17 percent) are relatively minor by 
comparison. These results are discussed in detail elsewhere (USEPA 
1999b).

    Note: These estimates of variability sources apply to national-
level radon occurrence estimates: individual regions may have 
systems that show variability sources that deviate significantly 
from these values.

This analysis of variability was incorporated into EPA's estimates of 
nation-wide radon occurrence and was used in its estimates of the 
effects of uncertainty in occurrence information on total national 
costs of compliance.
    In response to the comment that ``most risk reductions predicted in 
the HRRCA come from reductions in radon levels in the small proportions 
of systems with initial very high radon levels'', EPA agrees that a 
system with high radon levels would benefit more from water mitigation 
than a system with much lower initial radon levels, but the vast 
majority of the national water mitigation benefits come from systems 
that are above the MCL, but not that high above it (e.g., 80 percent 
removal required for the system to be at the MCL). This is true since 
radon is approximately log-normally distributed (i.e., a much higher 
percentage of water systems can be expected to have relatively low 
radon levels than relatively high radon levels) and hence most systems 
fall into this category. For this reason, the summation of these 
smaller per system benefits enjoyed by the large number of systems 
nearer the MCL greatly outweigh summation of the larger per system 
benefits enjoyed by the minority of systems with very high radon 
levels. This is demonstrated in Table 6-2 of the HRRCA (``Estimated 
Monetized Benefits from Reducing Radon in Drinking Water''), in which 
the central tendency estimate of monetized benefits associated with an 
MCL of 500 pCi/L is 212 million dollars and the benefits associated 
with an MCL of 100 pCi/L is 673 million dollars. This means that, in 
the latter case, 461 million dollars of the benefits come just from the 
systems with radon levels between 100 and 500 pCi/L (80 percent removal 
required), while the remaining benefits (212 million dollars) come from 
the systems with radon levels from 500 pCi/L up to the highest radon 
levels.
    Five commenters indicated that the estimates of the numbers of 
entry points per system used in the HRRCA were incorrect, in that large 
systems had far more entry points than the numbers given in Table 5.4 
of the HRRCA. Several of these commenters cited data from the Community 
Water System Survey (CWSS), showing higher numbers of wells per system 
in each system size category than were used for cost calculations in 
the HRRCA.
EPA Response 1-2
    The relevant distribution for costing out non-centralized treatment 
is the number of entry points, not the number of wells. A given entry 
point (the point at which treatment is applied) may be fed by several 
wells, and hence there is a discrepancy in numbers between the HRRCA, 
which reported a distribution of entry points, and Table 1-5 of the 
Community Water System Survey (CWSS), which reported the average number 
of wells per system. These numbers are related, but not directly 
comparable. In general, the average number of entry points for a class 
of ground water systems would be expected to be smaller than the 
average number of wells. In the HRRCA, the distribution of entry points 
per system was estimated from a statistical analysis (``bootstrap 
analysis'') of the well and entry point data from the CWSS. This 
statistically-calculated distribution was then used to estimate the 
percentage of systems within a system size category having a given 
number of entry points. However, as part of its uncertainty analysis, 
EPA has used the 95% confidence upper bound of the site distribution in 
the national cost estimates supporting this proposal. The average 
number of entry points per system is roughly 10% higher using this 
upper bound analysis. In addition, to test the effects of varying this 
distribution on the national costs of compliance, the per system costs, 
and the per household costs, EPA conducted an uncertainty analysis 
(Monte Carlo analysis including sensitivity) on the distribution by 
simultaneously varying both the percentages of systems estimated to 
have a particular number of sites and the estimated number of sites. 
The results of this analysis are reported both in this notice and in 
the Regulatory Impact Analysis. It should be noted that the treatment 
unit costs and total number of systems dominated the cost uncertainty 
and that the entry point distribution was a relatively minor 
contributor to the overall cost uncertainty.
2. Exposure Pathways
    A number of issues related to radon exposure pathways were raised. 
Several commenters indicated that the risks associated with the build-
up of radon in carbon filters needed to be addressed in HRRCA. Concerns 
were also expressed about general population exposures to radon in air 
released from aeration facilities and exposures to workers at water 
utilities. Another commenter said that EPA should discuss the 
persistence of radon in the body after ingestion.
EPA Response 2-1
    The risks from radon build-up in carbon filters and radon off-gas 
emissions are discussed in some detail in this notice, including an 
evaluation of risks, a discussion of references, and responses from a 
survey of air permitting boards about the permitting of radon off-gas.
EPA Response 2-2
    The persistence of radon in the body following ingestion has been 
investigated and the results have been presented in the Criteria 
Document for Radon (USEPA 1999b). In brief, radon ingested in water is 
well-absorbed from the stomach and small intestine into the bloodstream 
and transported throughout the body. Radon is rapidly (within 
approximately one hour) excreted from the body via the lungs, so only 
about 1 percent of ingested radon undergoes radioactive decay while in 
the body. The risks from the retained radon and its decay products in 
various organs are calculated by NAS and adopted by EPA in the proposed 
rule.

[[Page 59336]]

3. Nature of Health Impacts
    No comments were made concerning the general nature of adverse 
effects associated with radon exposure. Comments concerning specific 
aspects of health impact evaluation are summarized in the following 
sections.
    (a) Sensitive subpopulations, risks to smokers, non-smokers. 
Comments on these sections are addressed together because the majority 
of the comments had to do with the characterization of smokers as a 
sensitive population. Several commenters noted that most risk reduction 
from reducing radon exposure occurs among smokers, and took the 
position that EPA should not include risk reductions to smokers in its 
benefits assessment, because smoking can be viewed as a voluntary risk. 
One commenter suggested that the smokers' willingness to pay for 
cigarettes also indicated a willingness to face the risk of smoking.
EPA Response 3-1
    The term, ``groups within the general population'' is addressed, 
but not comprehensively defined, in the 1996 amendments to the Safe 
Drinking Water Act (SDWA, Sec. '1412(b)(3)(C)). The definition of 
sensitive subpopulations is an issue for discussion and debate, and EPA 
is interested in input from stakeholders. The National Academy of 
Sciences (NAS) Radon in Drinking Water Committee, as part of their 
assessment of the risks of radon in drinking water, has considered 
whether groups within the general population, including smokers, may be 
at increased risk. The NAS Committee has indicated, in their Risk 
Assessment of Radon in Drinking Water report, that smokers are the only 
group within the general population that is more susceptible to 
inhalation exposure to radon progeny, but did not specifically identify 
smokers as a sensitive subpopulation.
    In this proposal, EPA is basing its risk management decision on 
risks to the general population. The general population includes 
smokers as well as former smokers. The risk assessments for radon in 
air and water are based on an average member of the population, which 
includes smokers, former smokers, and non-smokers. A more complete 
discussion on the risks of radon in drinking water and air is presented 
in the NAS's risk assessment report and in Section XII of this 
preamble.
    (b) Risk reduction model, risks from existing radon exposures. 
Commenters raised only one concern associated with the risk model used 
to estimate radon reduction benefits. Three commenters suggested that 
EPA should consider adopting a threshold-based model for radon 
carcinogenesis, and that EPA's current (non-threshold) approach 
overestimates radon risks. In support, the commenters cited a recently 
published paper (Miller et al, 1999) as providing evidence that a 
single alpha particle ``hit'' typical in low-level radon may not be 
sufficient to cause cell transformation leading to cancer.
EPA Response 3-2
    There are a number of papers that have recently examined the 
effects of a single alpha particle on a cell nucleus of mammalian cells 
in culture. The authors of this study concluded that cells were more 
likely to be transformed to cancer causing cells if there were multiple 
alpha particle hits to their nuclei. However, another study, Hei et al. 
(1997), using a similar methodology, found direct evidence that a 
single ``particle traversing a cell nucleus will have a high 
probability of resulting in a mutation'' and concluded that their work 
highlighted the need for radiation protection at low doses. Moreover, 
follow-up microbeam experiments described by Miller et al. at the 1999 
International Congress of Radiation Research demonstrated that one 
alpha particle track through the nucleus was indeed sufficient to 
induce transformation under some experimental conditions. 
Epidemiological data relating to low radon exposures in mines also 
indicate that a single alpha track through the cell may lead to cancer. 
Finally, while not definitive by themselves, the results from 
residential case-control studies provide some direct support for the 
conclusion that environmental levels of radon pose a risk of lung 
cancer. EPA has based its current risk estimates for radon in drinking 
water on the findings of the National Academy of Sciences. Rather than 
focus on the results of any one study, the NAS committees based their 
conclusions on the totality of data on radon--a weight-of-evidence 
approach.
    Both the BEIR VI Report (NAS 1999a) and their report on radon in 
drinking water (NAS 1998b) represent the most definitive accumulation 
of scientific data gathered on radon since the 1988 NAS BEIR IV (NAS 
1988). These committees' support for the use of linear-non-threshold 
relationship for radon exposure and lung cancer risk came primarily 
from their review of the mechanistic information on alpha-particle-
induced carcinogenesis, including studies of the effect of single 
versus multiple hits to cell nuclei.
    In the BEIR VI report (NAS 1999a), the NAS concluded that there is 
good evidence that a single alpha particle (high-linear energy transfer 
radiation) can cause major genomic changes in a cell, including 
mutation and transformation that potentially could lead to cancer. They 
noted that even if substantial repair of the genomic damage were to 
occur , ``the passage of a single alpha particle has the potential to 
cause irreparable damage in cells that are not killed.'' Given the 
convincing evidence that most cancers originate from damage to a single 
cell, the committee went on to conclude that ``on the basis of these 
[molecular and cellular] mechanistic considerations, and in the absence 
of credible evidence to the contrary, the committee adopted a linear-
nonthreshold model for the relationship between radon exposure and 
lung-cancer risk. However, the BEIR VI committee recognized that it 
could not exclude the possibility of a threshold relationship between 
exposure and lung cancer risk at very low levels of radon exposure.'' 
The NAS committee on radon in drinking water (NAS 1999b) reiterated the 
finding of the BEIR VI committee's comprehensive review of the issue, 
that a ``mechanistic interpretation is consistent with linear, non-
threshold relationship between radon exposure and cancer risk''. The 
committee noted that the ``quantitative estimation of cancer risk 
requires assumptions about the probability of an exposed cell becoming 
transformed and the latent period before malignant transformation is 
complete. When these values are known for singly hit cells, the results 
might lead to reconsideration of the linear no-threshold assumption 
used at present.'' EPA recognizes that research in this area is on-
going but is basing its regulatory decisions on the best currently 
available science and recommendations of the NAS that support use of a 
linear non-threshold relationship.
    (c)Risk and risk reduction associated with co-occurring 
contaminants. Several commenters addressed the issue of risks 
associated with co-occurring contaminants. Other commenters indicated a 
need to include risks and risk reductions from co-occurring 
contaminants.
EPA Response 3-3
    The contaminants that may co-occur with radon that are of main 
concern are those that can cause fouling of aeration units (or 
otherwise impede treatment) and those that are otherwise affected by 
the aeration process in such a way as to increase risks. Measures and 
costs to avoid aeration fouling are discussed in

[[Page 59337]]

this notice and in the references cited. Arsenic co-occurrence may be 
relevant since some systems may have to treat for both, but the 
treatment processes are not incompatible. In fact, the only side-effect 
of the aeration process that may impact the removal of arsenic would be 
the potential oxidation of some fraction of less easily removed As(IV) 
form to the more easily removed As(VI) form. There would be no 
additional costs due to this effect, and in fact, there may be cost 
savings involved. The potential for increased risks due to potential 
disinfectant by-product formation after disinfection, is discussed 
next.
    (d) Risk increases associated with radon removal. Five commenters 
said that EPA should include quantitative estimates of the risk 
increases associated with increased exposure to disinfection byproducts 
(DBPs) in the risk and cost-benefit analyses of the HRRCA. One 
commenter said that risks should be apportioned appropriately between 
the proposed radon rule and the Groundwater rule. Another commenter 
maintained that, contrary to the assertion in the HRRCA, there would be 
no reduction in microbial risks due to the increased disinfection 
associated with the radon rule because most groundwater sources 
currently present no microbial risks.
EPA Response 3-4
    EPA would like to highlight that the AMCL/MMM option is the 
preferred option for all drinking water systems, which would result in 
very few water treatment systems adding disinfection. EPA expects the 
radon rule to result in a minority of ground water systems choosing the 
MCL option, and of those, many will be larger systems. Since very few 
small systems are expected to choose the MCL option , very few systems 
are above the AMCL of 4000 pCi/L, and most large ground water systems 
already disinfect their water, few systems are expected to add 
disinfection in response to the radon rule, i.e., increased risk due to 
disinfection by-product formation should not be a significant issue. 
However, EPA does evaluate this risk-risk trade-off in this notice for 
that minority of systems that will be expected to add disinfection with 
treatment for radon. For that minority of systems, the trade-off 
between decreased risks from radon and increased risks from 
disinfection-by-products is favorable.
4. Benefits of Reduced Radon Exposure
    The majority of the comments related to the estimation of benefits 
focused on the methods used to monetize reductions in cancer risks. 
There were also a few comments on non-quantifiable benefits, and on 
several other topics. The previous comments pertaining to risk 
reductions to smokers and that benefits from these risk reductions 
should be excluded from the HRRCA apply here as well.
    (a) Nature of regulatory benefits. There were few comments on this 
section, most of which pertained to non-quantifiable benefits. One 
commenter indicated that the peace-of-mind non-quantifiable benefit 
from radon reduction would be offset by the anxiety of those living 
near aeration plants. Another noted that peace-of-mind benefits were 
not easy to quantify for non-threshold pollutants like radon and, in 
fact, that the regulation of radon might actually increase anxiety by 
drawing attention to the risks associated with radon exposures. 
Commenters also noted that claiming arsenic reduction as a benefit from 
aeration is questionable because there is no demonstrated correlation 
between the levels of radon and arsenic in groundwater systems.
EPA Response 4-1
    By definition, non-quantifiable benefits cannot be measured and 
have not been measured in the HRRCA analysis. Thus, comparisons of 
types of such benefits are not very meaningful. EPA attempts to note 
these potential benefits when the Agency believes they might occur, as 
in the case of peace-of-mind benefits from radon reduction. There may 
also be non-quantifiable costs that may offset any non-quantifiable 
benefits. These include anxiety on the part of residents near treatment 
plants and customers who may not have previously been aware of radon in 
their water. As noted elsewhere in this preamble, EPA believes it 
unlikely that accounting for these non-quantifiable benefits and costs 
quantitatively would significantly alter the overall assessment.
    (b) Monetization of benefits. Comments related to risk reduction 
have been discussed in previous responses, so are not discussed further 
here. Commenters addressed all three approaches to monetizing benefits: 
the value of statistical life; the costs of illness; and willingness-
to-pay. A number of commenters suggested the use of Quality-Adjusted 
Life Years (QALY) as an alternative approach to the valuation of health 
benefits. One commenter indicated that the use of QALYs was a good way 
to avoid having to monetize health outcomes. Two commenters indicated 
that QALYs had the advantage of being able to take into account the 
delayed onset of cancer, as well as reduced incidence. One organization 
suggested QALYs as a superior method for combining the benefits from 
fatal and non-fatal illness over different time periods; which would be 
particularly useful in the case of smokers, whose cancers are likely to 
be delayed, but not necessarily prevented, by reductions in radon 
exposure.
EPA Response 4-2
    The use of QALYs has been extensively discussed within EPA and also 
before the Environmental Economics Advisory Committee of EPA's Science 
Advisory Board. At this time, current Agency policy is to use Value of 
Statistical Life (VSL) estimates for the monetization of risk reduction 
benefits. EPA believes QALY calculations to be experimental and not 
well established for the types of analyses performed by the Agency.
    (c) Value of statistical life (VSL). Several commenters questioned 
the use of, or the value selected for, the value of statistical life as 
a measure of benefits. Other commenters indicated that the large range 
of uncertainty associated with the estimates of risk reduction called 
the VSL (and the willingness-to-pay) methods into question, and 
indicated that EPA needed to better justify the central-tendency VSL 
value selected for use in the HRRCA. They maintained that the VSL 
approach would only be appropriate if the VSL estimates were derived 
from ``similar scenarios'' to those being evaluated in the HRRCA. 
Another commenter suggested that using the VSL was inappropriate in 
that the VSL dollars did not represent (as do compliance costs) actual 
resource losses to society that could be spent on other programs (e.g. 
pollution reduction). Thus, the comparison of compliance costs to VSL 
costs is not valid. They strongly recommend the use of compliance cost 
per life saved as an appropriate measure for judging radon control 
options. One commenter indicated that the use of the VSL approach 
resulted in greatly over-estimated benefits of radon exposure 
reduction, particularly because the VSL for smokers is the same as for 
non-smokers and does not account for the age at which mortality is 
avoided. Another questioned the validity of the mean VSL value used in 
the HRRCA, and indicated that VSL estimates should only come from the 
peer-reviewed scientific literature or from Agency documents that had 
been subject to public comment.

[[Page 59338]]

EPA Response 4-3
    The VSL value, currently recommended by Agency guidance, is derived 
from a statistical distribution of the values found in twenty-six VSL 
studies, which were chosen as the best such studies available from a 
larger body of studies. This examination of studies was undertaken by 
EPA's Office of Air and Radiation in the course of its Clean Air Act 
retrospective analysis. EPA believes the VSL estimate ($5.8 million, 
1997 dollars) to be the best estimate at this time, and is recommending 
that this value be used by the various program offices within the 
Agency. This estimate may, however, be updated in the future as 
additional information becomes available to assist the Agency in 
refining its VSL estimate. The VSL estimate is consistent with current 
Agency economic analysis guidance, which was recently peer reviewed by 
EPA's Science Advisory Board.
    d. Costs of illness (COI). Two commenters suggested that EPA should 
further review the literature on the costs of illness and develop 
better cost measures for the illnesses addressed in the HRRCA.
EPA Response 4-4
    EPA believes that the COI data is the most complete analysis of 
this type currently underway. The cost of illness (COI) data shown in 
the HRRCA were presented as a comparison to Willingness to Pay (WTP) to 
avoid chronic bronchitis. The Agency did not use the COI data to 
estimate risk reduction valuations for non-fatal cancers because these 
estimates can be seen as underestimating the total WTP to avoid non-
fatal cancers. COI may understate total WTP because of its failure to 
account for many effects of disease such as pain and suffering, 
defensive expenditures, lost leisure time, and any potential altruistic 
benefits. It is important to note that the proportion of benefits 
attributable to non-fatal cancer cases accounts for less than one 
percent of the total benefits in the HRRCA.
    (e) Willingness-to-pay. Several commenters questioned EPA's use of 
the willingness-to-pay (WTP) approach for monetizing non-fatal cancer 
risk reductions. Another suggested that a WTP value for victims of non-
fatal cancers should have been used, instead of the WTP estimates for 
chronic bronchitis. It was also suggested that WTP measures would vary 
within the general population, and that use of a constant value was 
inappropriate.
EPA Response 4-5
    EPA believes that the WTP estimates to avoid chronic bronchitis are 
the best available surrogate for WTP estimates to avoid non-fatal 
cancers. WTP estimates were used in the HRRCA as opposed to COI to 
value non-fatal cancer cases. EPA believes that COI may understate 
total WTP because of its failure to account for many effects of disease 
such as pain and suffering, defensive expenditures, lost leisure time, 
and any potential altruistic benefits. It is important to note that the 
proportion of benefits attributable to non-fatal cancer cases accounts 
for less than one percent of the total benefits in the HRRCA.
    (f) Treatment of benefits over time. Many commenters objected to 
EPA's assumption that cancer risk reduction, and hence benefits, would 
begin to accrue immediately upon the reduction of radon exposures. In 
addition, they felt that the failure to discount health benefits 
resulted in an overestimation of the benefits. One commenter suggested 
that a ``gradual phase-in'' of risk reduction should be incorporated 
into the HRRCA benefits calculation. It was also suggested that an 
alternative to immediate benefits accrual be used, and that the effects 
of the immediate benefits accrual assumption be discussed in detail 
with regard to the uncertainties it introduces into the benefits 
estimates. One commenter identified the assumption of immediate 
benefits as a major source of benefits overestimation. Another comment 
asked that EPA provide better justification for assuming immediate 
benefits accrual, and suggests instead that a linear phase-in of risk 
reduction over 70 years would be more appropriate. Three commenters 
also indicate that the failure to take latency of risk reduction into 
account and to discount benefits appropriately, greatly biases the 
benefits estimates in the upward direction. One commenter indicated 
that the failure to discount benefits resulted in a five- to ten-fold 
over-estimation.
EPA Response 4-6
    These comments address the issue of latency, the difference between 
the time of initial exposure to environmental carcinogens and the onset 
of any resulting cancer. Qualitative language has been added to the 
preamble regarding adjustments, including latency, that could be made 
to benefits calculations. This qualitative discussion notes that 
latency is one of a number of adjustments related to an evaluation of 
potential benefits associated with this rule. EPA believes that such 
adjustments should be considered simultaneously. For further 
discussion, see section XIII.D of the preamble.
5. Costs of Radon Treatment Measures
    (a) Drinking water treatment technologies and costs. All of the 
commenters had concerns related to EPA's assumptions and analyses of 
costs of radon treatment measures. In fact, one commenter suggested 
that the entire section was oversimplified by EPA. Most of the 
commenters, however, provided more specific comments which are outlined 
next.
EPA Response 5-1
    Most, if not all, commenters assumed that EPA would propose that 
the risks from radon would be best addressed by drinking water systems 
attempting to meet the MCL. Under this scenario, many small systems 
would be in situations where they faced very difficult treatment 
issues, often with technically difficult and/or expensive solutions. 
However, EPA is suggesting that the risks from radon are best addressed 
by the combined use of the AMCL with a multi-media mitigation (MMM) 
program. Since the proposal also includes a regulatory expectation of 
adoption of the AMCL by small systems, EPA believes that many of the 
comments received are less applicable to this proposal than if the MCL 
were the preferred route of compliance.
    (b) Aeration. Several commenters expressed concerns related to 
aeration costs. One major concern was EPA's failure to address worker 
safety issues, and the associated cost of occupational safety programs, 
at treatment plants. A reference to earlier studies of increased risk 
to neighbors is provided, but details are not included to evaluate 
these studies. Concern was expressed that costs for permitting and 
control of radon emissions from treatment plants were not included, and 
that the public might react strongly to the presence of a local 
treatment plant even if analysis showed the risk to be minimal. Three 
commenters noted that the HRRCA failed to consider quantifiable 
corrosion control costs associated with aeration. Installation of 
aeration for radon removal may also affect lead/copper levels in the 
water distribution system, resulting in additional treatment 
modifications and costs. Many systems will have to develop a different 
corrosion control strategy to comply with the lead and copper rule due 
to the radon regulation.
EPA Response 5-2
    Worker safety issues for aeration treatment of radon in drinking 
water are discussed in today's notice (Section

[[Page 59339]]

VIII.A.3) and are discussed in more detail in other sources (USEPA 
1994b, USEPA 1998h). Radon exposure to workers in drinking water 
treatment plants has been discussed in the literature (e.g., Fisher et 
al. 1996, Reichelt 1996). In fact, these discussions usually apply to 
situations where radon is NOT the contaminant being purposely removed, 
since there is currently no regulatory driver to do so. When ground 
water is exposed to air during treatment for any contaminant, radon may 
be released and may accumulate in the treatment facility. The National 
Research Council (NAS 1999b) suggests that the air in all groundwater 
facilities treating for any contaminant should be monitored for radon 
and that ventilation should be investigated as a means of reducing 
worker exposure. In support of this position, EPA would further 
strongly suggest that systems that attempt to meet the MCL (i.e., that 
are in States that do not adopt the AMCL or otherwise choose to meet 
the MCL) by installing aeration treatment should take the appropriate 
measures to monitor and ventilate the treatment facilities. For those 
small systems that choose GAC treatment, other precautions should be 
taken to monitor and control gamma exposure. GAC treatment issues are 
discussed later in this notice and are discussed in detail elsewhere 
(USEPA 1994b, AWWARF 1998 and 1999).
    EPA has suggested that occupational exposures be limited to 100 
mRem/year, a level well below the upper limit of 5000 mRem/year 
approved in by the President in 1987 (``Radiation Exposure Guidance to 
Federal Agencies for Occupational Exposure'', as cited in USEPA 1994b). 
Based on limited data, it appears that 100 mRem/year is a maintainable 
objective within water treatment plants treating for radon or other 
contaminants. Exposure level monitoring and mitigation through a 
combination of air monitoring and ventilation has been demonstrated to 
be feasible and relatively inexpensive (e.g., Reichelt 1996).
    Regarding the effects on water corrosivity and the impacts of costs 
of corrosion control measures, this notice presents much more detail on 
EPA's assumptions. Corrosion control measures are included in national 
cost estimates and are discussed in this notice. Case study information 
on corrosion control costs associated with aeration are included in the 
Radon Technologies and Costs document (USEPA 1999h).
    (c) GAC. Two commenters noted that the option for use of granular 
activated carbon (GAC) did not address potential problems with 
radioactivity buildup in the carbon. In consideration of treatment 
methods the two commenters saw no mention of the cost of disposal of 
GAC used for radon removal. If not replaced in time it will become a 
low level radioactive waste because of Lead 210 and will become 
difficult to dispose of. Other issues that need to be addressed 
include: will the unit require special shielding; may the charcoal bed 
be required to have a radioactive materials license from the State; and 
how may radioactive carbon be disposed of?
EPA Response 5-3
    Special considerations regarding GAC operations, maintenance, and 
ultimate GAC unit disposal are discussed in some detail in Section 
VIII.A of this notice, including discussions of the radiation hazards 
involved and steps that can be taken to ameliorate these hazards. GAC 
disposal costs are included in the operations and maintenance costs in 
the model used for cost estimates. Comparisons of modeled GAC capital 
and operations & maintenance cost estimates to actual costs reported in 
case studies are included in Section VIII of this notice. EPA would 
like to strongly emphasize that carbon bed lifetimes (carbon bed 
replacement rates) should be designed to preclude situations where 
disposal becomes prohibitively expensive or technically infeasible.
    Recently, the American Water Works Association Research Foundation 
has published a study on the use of GAC for radon removal, which 
includes discussions of the issues described previously, that concludes 
that GAC is a tenable treatment strategy for small systems when used 
properly under the appropriate circumstances (AWWARF 1998a). AWWARF 
also reviewed the proper use of GAC for radon removal in its recent 
review of general radon removal strategies (AWWARF 1998b). When the 
final radon rule is promulgated, a guidance manual will be published 
describing technical issues and solutions for small systems installing 
treatment.
    One commenter suggested that the costs for GAC seemed to be too 
high. The figures used in the analysis could be two orders of magnitude 
above the costs actually seen by the systems.
EPA Response 5-4
    EPA agrees that its GAC cost estimates seem to be very high, as 
compared to case studies (USEPA 1999h, AWWARF 1998b). EPA agrees with 
others (e.g., AWWARF 1998a and b) that GAC will probably be cost-
effective for very small systems or in a point-of-entry mode. This 
issue is addressed in the preamble (Section VIII.A) and GAC will be 
included as a small systems compliance technology.
    (d) Regionalization. Two commenters questioned a cost of $280,000 
as the single cost for regionalization. Assuming $100/foot for an 
interconnection, these costs would equate to an interconnection of 2800 
feet which seems low. Systems are usually separated by more than one-
half mile. A range of costs may need to be considered rather than a 
single number. Smaller systems will have smaller costs, while large 
systems will have larger costs. Thus, the charge for regionalization 
should vary by systems size. Also, EPA should clarify whether or not 
regionalization charges include yearly operation and maintenance costs.
EPA Response 5-5
    EPA agrees that the costs of regionalization would be expected to 
change with water system size, but, as indicated in the assumptions 
outlined in the February 26, 1999 HRRCA, EPA assumed that only very 
small systems (those serving fewer than 500) would resort to 
regionalization in response to the radon rule. Given that the proposed 
rule involves a multi-media approach that greatly encourages small 
systems to choose the AMCL of 4000 pCi/L in conjunction with a multi-
media mitigation program, EPA expects that very few systems would 
choose regionalization as an option. EPA believes that the assumption 
that 1 out of 100 small systems that choose the MCL option would 
regionalize is conservative and would only be exercised if 
regionalization were cost-competitive with other options, except under 
very unusual circumstances. Since the estimate of $250,000 is much more 
expensive than any other option modeled for those size categories, this 
assumption supports the situation where small systems may be expected 
to entertain this option, i.e., where regionalization does not involve 
piping water over great distances. This figure is based on a simple 
estimate using the cost of installed cast iron pipe at $44 per linear 
foot (an average cost for several pipe relevant pipe diameters) from 
the 1998 Means Plumbing Cost Data and applying 20 percent for fittings, 
excavation, and other expenses to arrive at an estimate of $53 per 
linear foot, or $280,000 per linear mile. Purchased water costs ($/
kgal) were assumed to equal the pre-regionalization costs of production 
($/kgal), merely as a modeling convenience. In some cases, purchased 
water costs may be higher, in

[[Page 59340]]

some cases lower. Although EPA does not have many case studies to 
support this assumption, it does have information on a Wisconsin case 
study in which a small water system (serving 375 persons) regionalized 
to connect to a near-by city water supply in 1995, partly in response 
to a radium violation. The capital costs for this regionalization case 
study was $225,000. There were no reported operations costs associated 
with the purchased water. EPA makes no claims that this case study is 
typical, but rather that this is the best assumption that it could make 
based on the available information. Since this is a minor part of the 
over-all national costs and since a more extensive modeling of the 
costs of regionalization would necessitate a much more detailed 
modeling of the additional benefits of regionalization (which were not 
included), this assumption is maintained in the Regulatory Impact 
Assessment for this proposed rule.
    One commenter also questioned the feasibility of regionalization 
for many systems. There are very few locations where this is possible 
and just hooking up to a larger supplier is not practical. Many have 
systems that are not acceptable to a larger supplier and many larger 
suppliers won't accept the liability involved in taking over the small 
system.
EPA Response 5-6
    Since most small systems are expected to adopt the AMCL/MMM option, 
EPA's regionalization assumption (1 percent of the minority of small 
systems that choose the MCL option) is consistent with this commenter's 
concern. Nevertheless, administrative regionalization is often 
feasible, in particular when this does not require new physical 
connections, and may be an important element of the long term 
compliance strategy for a number of systems.
    (e) Pre-treatment to reduce iron/manganese levels. The majority of 
the commenters disagreed with EPA's assumptions on the removal of Fe/
Mn. It was assumed that essentially all systems with high Fe/Mn levels 
are likely to already be treating to remove or sequester these metals. 
Therefore, costs of adding Fe/Mn treatment to radon removal were not 
included in the February, 1999 HRRCA (64 FR 9560). Commenters suggested 
that this is a poor cost assumption, in that there are many systems 
above the secondary MCL for Fe/Mn that do not treat. Of those that 
sequester, commenters suggested that existing treatment is ineffective 
once Fe/Mn has been oxidized. Therefore, filtration as well as 
disinfection would be required for that type of system at a significant 
additional cost that needs to be considered when reviewing the HRRCA.
    If Fe/Mn is present in the source water, removal treatment will be 
necessary to prevent fouling of the radon removal system. Disposal for 
the Fe/Mn residuals also presents a special problem with its associated 
costs. One commenter noted that by not including the costs of Fe/Mn 
removal, EPA is making a poor assumption and may be underestimating 
costs.
EPA Response 5-7
    EPA recognized that not quantifying the costs associated with the 
control of dissolved iron and manganese (Fe/Mn) was potentially a poor 
assumption, and indicated that this assumption would be revisited for 
the Regulatory Impact Analysis supporting this proposed rule. However, 
EPA also indicated that national costs and average per system costs 
would probably not be significantly affected in addressing this issue. 
While EPA's current modeling results support this conclusion, EPA has 
included the costs of adding chemical stabilizers (which minimize Fe/Mn 
precipitation and also provide for corrosion control in some cases) by 
25 percent of small systems that treat and 15 percent of large systems 
that treat. A more detailed discussion on the inclusion of Fe/Mn 
treatment costs is provided in Section VIII of the preamble.
    To further support its position on Fe/Mn control, EPA has also (1) 
analyzed case studies of systems aerating, which include Fe/Mn control 
measures for a small minority of the systems, (2) performed an analysis 
of the co-occurrence of radon with Fe/Mn in ground water, and (3) 
performed an uncertainty analysis on costs, which includes a simulation 
of more expensive control measures for Fe/Mn. All of these results are 
also discussed in Section VIII of the preamble.
    (f) Post treatment-disinfection. Many commenters stated that EPA's 
assumption that the majority of groundwater systems already disinfect 
is false. Some commenters felt this is inconsistent with the Ground 
Water Rule estimates. Commenters suggested that analyses supporting the 
proposed groundwater rule estimate that only 50 percent of CWSs and 
only 25 percent of NTNCWSs disinfect, while Table 5-2 of the HRRCA 
suggests that the majority of water systems using groundwater already 
disinfect and that 20 percent of all water systems serving 3,300 or 
greater have aeration or disinfection in place.
EPA Response 5-8
    The cited analyses supporting the Ground Water Rule (GWR) were 
conducted using occurrence estimates at the level of individual entry 
points at water systems. The February 1999 Radon HRRCA was conducted 
using occurrence estimates at the level of water systems. The GWR and 
radon analyses use the same data source for estimating their respective 
disinfection-in-place baselines, the 1997 Community Water System Survey 
(USEPA 1997a), the only source of information of this type that is 
based on a survey that was designed to be statistically representative 
of community water systems at the national level. The GWR used a 
disinfection-in-place baseline for entry points and the radon HRRCA 
used a disinfection-in-place baseline for water systems.
    The most desirable level of analysis is at the entry point, but the 
only nationally representative data source for radon, the National 
Inorganics and Radionuclides Survey, was conducted at the water system 
level (samples were taken at the tap), which provides no information 
about radon occurrence at individual entry points within water systems. 
Radon intrasystem (within system) occurrence variability studies were 
not available for the analyses supporting the February 1999 radon 
HRRCA. In the interim between publishing the radon HRRCA and today's 
proposal, EPA has conducted radon intrasystem variability studies 
(based on studies other than NIRS) and has used the results of this 
study to estimate radon occurrence at the entry point level. The 
current Regulatory Impact Analysis supporting the Radon rule was 
conducted at the entry point level, consistent with the Ground Water 
Rule.
EPA Response 5-9
    The additional costs to which this commenter is referring, namely 
the costs of storage for contact time, are included in the costs of the 
clearwell, which are included in the costs of the aeration process. In 
the scenarios in which disinfection is assumed, EPA does NOT assume 
that the systems have a clearwell in place and does include the costs 
of adding a clearwell for collection of water after aeration and for 
five minutes of disinfection contact time, which EPA believes to be 
sufficient for 4-log viral de-activation.
    (g) Monitoring costs. One commenter expressed concerns regarding 
EPA's calculation of monitoring costs. The commenter suggested that EPA 
grossly underestimated the number of wells per

[[Page 59341]]

different water system size in Table 5.4 of the HRRCA (64 FR 9585), 
page 9585 and in Appendix D of the HRRCA. As a result, monitoring costs 
need to be recalculated by EPA.
EPA Response 5-10
    See EPA Response 1-2 for EPA's approach to determining the number 
of wells per system.
    (h) Choice of treatment responses. As noted previously in Section 
G, one commenter questioned whether chlorination would always be the 
disinfection technology of choice, as well as EPA's assumption that 
existing chlorination practices would not have to be augmented if 
aeration were installed. Other commenters on cost issues questioned the 
feasibility and practicability of some technologies on cost grounds.
EPA Response 5-11
    EPA assumed that chlorination would be the ``typical'' disinfection 
technology chosen to model the ``average treatment costs'' (or 
``central tendency costs''). There is no way to know beforehand exactly 
how the universe of water systems will behave in response to a given 
situation, so EPA believes that the best way to model national 
compliance costs is to estimate these central tendency costs, then to 
use statistical tools to capture the fact that ``real world costs'' 
will spread around the central tendency costs, rather than being 
equivalent to them. By estimating the central tendency costs and using 
statistical uncertainty to capture ``real world'' variability 
(including variability in disinfection costs), EPA believes that this 
modeling technique allows for the fact that real systems will behave in 
a variety of ways, including things like choosing different 
disinfection technologies.
    (i) Site and system costs. A number of issues were raised 
concerning site and system cost estimates. Several commenters suggested 
that the HRRCA severely underestimated the number of sites per system, 
citing the difference between the CWSS data and HRRCA assumptions. 
Several commenters noted that the numbers of sources per system in 
Table 5-4 of the HRRCA for systems serving 10,001--50,000 were too low. 
One commenter maintained that the number of sources per system could 
have a significant impact on national treatment costs.
EPA Response 5-12
    EPA agrees that the distribution of the number of sites per system 
was underestimated and has revised its estimate to be consistent with 
the CWSS. However, it should be noted that while the distribution of 
the sites per system actually does have an impact on national treatment 
costs, this impact is significantly mitigated by the fact that the flow 
per well being treated decreases proportionally as the estimated number 
of wells per system increases.
    (j) Aggregated national costs. Several commenters agreed that the 
national average costs masked significant impacts on small systems. 
When small systems are considered, the financial impact is large; in 
some cases, water bills could double or triple. Providing individual 
system costs is critical so that utilities can explain to their 
customers the specific costs and benefits for that specific system.
EPA Response 5-13
    EPA estimates household impacts for small systems that install 
treatment (per household costs) by estimating the costs that small 
systems would face (per system costs), then spreading these costs over 
the customer base (population served). As demonstrated in the HRRCA, 
household costs for small systems are expected to be many times higher 
for very small systems than for larger systems. In listing small 
systems compliance technologies for radon, EPA estimated the impacts on 
small systems by estimating the per system costs and the per household 
costs and comparing them to affordability criteria, as described in 
this notice and in the references cited. However, it should also be 
noted that the vast majority of small systems are expected to comply 
with the AMCL/MMM option, rather than the MCL option. Under these 
circumstances, less than 1 percent of small systems would have to take 
measures to reduce radon levels in their drinking water.
    (k) Costs to CWSs. Small systems will bear a significant percentage 
of the costs for implementing a radon MCL, but will only accrue a small 
proportion of the benefits. At the 300 pCi/L, the two categories of 
smallest systems combined would receive 5.6 percent of the benefits at 
this level, but would pay 42 percent of the total costs. Several 
commenters indicated that the benefit-cost ratio for small systems was 
thus highly unfavorable.
EPA Response 5-14
    EPA recognizes that small systems experience similar benefits per 
customer as large systems, but, due to economies of scale (higher 
treatment costs per gallon treated), experience much higher costs per 
customer compared to large systems. This, of course, leads to higher 
costs at the same level of benefits. However, EPA has also recognized 
that radon is a multi-media problem in which most of the risk is 
presented from sources other than drinking water and has addressed this 
fact by designating the AMCL/MMM option as the preferred option for 
small systems. This will greatly lower the per customer costs faced by 
small systems and may lead to greater total benefits that accrue to 
small systems.
    (l) Costs to consumers/households. One commenter thought that the 
household consumption presented in the HRRCA (83,000 gal/year) is too 
low. This is an understatement because treatment would be required for 
all water produced, not just water consumed by households.
EPA Response 5-15
    EPA does not assume that per system costs are based only on 
residential water use and so does not miscalculate water prices in the 
way described by the commenter. To determine the price of water, EPA 
calculates per system costs based on both residential and non-
residential consumers (which is the main reason EPA calculates costs 
for privately-owned and publically-owned separately, i.e., because they 
have different ratios of residential to non-residential consumption). 
These per system costs determine the costs per gallon treated (not per 
gallon consumed) to determine the water price. The water price may then 
be used in conjunction with the household consumption to estimate the 
water bills faced by households, since they do pay by the gallon 
consumed (and not by the gallon treated).
    (m) Application of radon related costs to other rules. Several 
commenters addressed the need to include the cumulative impact of 
regulations in the RIA. The incremental costs of the regulations for 
radon, arsenic, and groundwater systems could substantially change the 
affordability analysis for small systems. Thus, treatment decisions 
need to be made with an understanding of all the requirements that must 
be met so that treatment systems can be designed to meet all 
requirements. One commenter suggested a multi-rule cost and benefit 
analysis to capture the true costs incurred by these systems.
EPA Response 5-16
    The cumulative effects of rules are captured in EPA's 
``affordability criteria'', which are described in the publicly 
available 1998 EPA document, ``National-Level Affordability Criteria 
Under the 1996 Amendments to the Safe

[[Page 59342]]

Drinking Water Act'' (USEPA 1998e). These small system affordability 
criteria take into account how much consumers are currently paying for 
typical water bills. Since the upcoming regulations will affect these 
amounts, the cumulative effect of the costs of the rules will be 
explicitly considered in the affordability determinations for small 
systems as new rules are issued. EPA recognizes that its method of 
basing affordability determinations on average costs does not address 
the situation of systems that have significantly above average costs 
because they must treat for a number of contaminants simultaneously. 
EPA believes this approach is consistent with the requirements of SDWA 
for identifying affordable small system technologies and notes that 
other SDWA mechanisms may be used to address situations where systems 
incur considerably higher costs.
6. Cost and Benefit Results
    The main concern of many of the comments regarding this section 
suggested that the costs of controlling radon in drinking water far 
outweighed possible benefits, especially for small systems. Controlling 
indoor air radon was identified as a better use of regulatory and 
economic resources by several commenters. Commenters also had concerns 
regarding how national total costs, benefits, and economic impacts were 
calculated, and regarding the uncertainties in costs and benefits 
estimates.
    (a) Overview of analytical approach. Many commenters indicated that 
the cost-benefit analysis was skewed toward overestimating benefits, 
and/or omitted important cost elements. One concern shared by many of 
these commenters was that the cost-benefit calculations were biased 
because mitigation costs, but not health benefits, were discounted. A 
commenter also indicated that too many assumptions had been used to 
derive cost and benefit estimates.
EPA Response 6-1
    The radon cost benefit analysis was performed according to EPA 
guidelines, in an attempt to fairly portray both costs and benefits, 
and not leave out important categories of either costs or benefits.
    Annual mitigation costs are compared to annual benefits for the 
cost benefit comparisons. Annual mitigation costs consist of annualized 
capital costs plus yearly operating costs. Annualized costs are 
computed under the assumption that capital expenditure are made up 
front, with borrowed funds, and the payments are then annualized over a 
period of twenty years. Changes in the rate of interest used in the 
annualization process will change the annual cost, just like a mortgage 
will change with different rates of interest. Adding yearly operating 
costs for one year to annualized capital costs for one year gives the 
total annual cost for the year. The issue of discounting of benefits is 
discussed in Section XIII.D.
    In any modeling process, assumptions must be made. To model costs 
and benefits, assumptions about those costs and benefits must be made. 
The number of assumptions needed depends on the complexity of the 
problem addressed, and the time and information available to address 
it. We would be interested in information that might inform our 
modeling, particularly addressing improvements that could be made to 
specific assumptions.
    (b) MCL decision-making criteria. A commenter requested that EPA 
define explicit decision-making criteria for setting MCL levels, to 
assure that the net benefit to society is positive.
    Another commenter indicated that, because drinking water radon 
accounts for a small portion of total risks, EPA should consider the 
relative costs and benefits of mitigation on a case-by-case basis at 
individual systems before making regulatory decisions. A commenter 
suggested that if the latency of cancer risk reduction and benefits 
were discounted properly, the national cost-benefit ratios for radon 
mitigation would be between 5:1 and 9:1. They stated that EPA should 
not promulgate a rule with net negative benefits, especially in light 
of the large economic impacts on small systems.
    A commenter indicated that the cost-benefit ratios in Table 6-13 of 
the HRRCA imply that regulation of radon in ground water is not 
justified. They point out that systems serving 25-3,300 people incur at 
least 56 percent of the costs and generate at most 21 percent of the 
total benefits at all MCLs. They say that justifying radon control in 
drinking water by adding in the benefits of MMM programs is not 
justified. Another commenter also maintained that the small, localized 
benefits of controlling radon exposures do not come near to justifying 
the costs of mitigation.
    One commenter said that the decision to set an MCL must take into 
account the level of uncertainty in cost and benefit estimates. Another 
commenter suggested that the Agency undertake a quantitative 
uncertainty analysis of the cost and benefit estimates. Two commenters 
said that the closeness of the cost and benefit estimates should be 
considered in setting a regulatory level; if uncertainty is large, a 
less stringent MCL would be justified.
EPA Response 6-2
    EPA has included a detailed discussion on its decision-making 
criteria for setting the MCL for radon in drinking water in the 
preamble for the proposed rulemaking (see Section VII.D).
    (c) National costs of radon mitigation. Two commenters indicated 
that the national cost estimates obscured the high costs that would be 
borne by individual systems. One commenter indicated that radon 
variability in individual wells increases the uncertainty in the cost 
estimates. Another commenter said that cost estimates should include 
the costs of more frequent lead and copper exceedences brought about by 
increased aeration. Other comments on specific cost elements were 
summarized in Section 5. One commenter requested that EPA regionally 
disaggregate cost and benefit estimates because of structural and 
operational differences among water systems. Another commenter 
suggested that EPA should conduct a more comprehensive analysis of 
costs and benefits, including cost elements not currently addressed, 
such as waste management.
EPA Response 6-3
    The national costs include an uncertainty analysis which captures 
the regional spread in treatment costs. In addition, EPA has estimated 
total national costs by assuming that most systems will face ``typical 
costs'', but that some will face ``high side'' and some ``low side'' 
treatment costs. These ``high side'' and ``low side'' cost differences 
are largely based on regional considerations, like the costs of land, 
structure, and permitting.
    (d) Incremental costs and benefits. One commenter indicated that 
the incremental costs and benefits of the various MCL options should be 
presented in the HRRCA. They question the affordability of radon 
mitigation for small systems.
EPA Response 6-4
    EPA has provided an analysis of the incremental costs and benefits 
of each MCL option in the HRRCA. See Table 6-7, Estimates of the Annual 
Incremental Costs and Benefits of Reducing Radon in Drinking Water, in 
the February 1999 HRRCA.
    (e) Costs to community water systems. One commenter said that a 
more accurate picture of costs and impacts (inclusive of State and 
local costs) would be needed to make a reasonable

[[Page 59343]]

risk management decision. Another commenter suggested that EPA should 
consider the cumulative costs of all drinking water regulations on 
drinking water systems.
EPA Response 6-5
    See EPA Response 5-14 for EPA's approach to determining the costs 
to CWSs. Administrative costs to States were not included in the 
February 1999 HRRCA, but have been added in the RIA for the proposed 
rule.
    (f) Costs and impacts on households. One commenter asked that EPA 
explain how it determined what was an ``acceptable'' percentage of 
household income that would go to radon mitigation. Another commenter 
indicated that household costs should be compared to benefits at the 
local, rather than national, level, because benefits and costs are 
realized locally. A commenter indicated the median household incomes 
for households served by different system sizes are not shown; they 
also suggested that household costs as a percentage of income were 
underestimated in Table 6-11 of the HRRCA. One commenter said that 
expressing household impacts as a proportion of annual income 
trivializes it and that costs could more meaningfully be compared to 
other types of household expenses (i.e., food, rent). Several 
commenters also noted the significant impact the costs could have on 
customer water bills for small systems.
EPA Response 6-6
    See EPA Response 5-15 for EPA's approach to determining the costs 
to households.
    (g) Summary of costs and benefits. Comments from one organization 
regarding the cost-benefit comparison for radon mitigation were typical 
of those received from other sources. They cited the NRC/NAS report as 
indicating that only two percent of population risk came from drinking 
water and questioned whether the high costs of the rule could justify 
the small benefits obtained. They said that the cost-benefit comparison 
did not justify regulating radon in ground water, especially in small 
systems, where costs were highest and benefits lowest. Another 
commenter also pointed out that it would be more cost-effective to 
regulate radon in indoor air than in drinking water and further 
maintained that spending resources to mitigate radon in water could 
actually result in reduced public health protection. They point out 
that the cost-benefit ratios for the smallest systems range from 20:1 
to 50:1, and suggest that these ratios, rather than the greater 
aggregate costs to large systems, should be persuasive in regulatory 
decision making. Other commenters suggested the high cost-benefit 
ratios did not justify the regulation of small systems.
EPA Response 6-7
    The 1996 Safe Drinking Water Act Amendments require EPA to propose 
a regulation for radon in drinking water by August 1999. The options 
for small systems, proposed for public comment in this rulemaking, 
represents EPA's efforts to address stakeholder comments concerning 
small systems.
7. Multimedia Mitigation Programs
    (a) Multimedia programs. Two commenters indicated that setting the 
AMCL at 4,000 pCi/L was justifiable. They suggested that EPA should 
utilize on MMM approach as the primary tool for reducing radon risks, 
and not use the SDWA to force the States to develop MMM programs.
    Several commenters noted that the MCL EPA selects should be 
justifiable on cost-benefit grounds, with the MMM program serving as a 
supplemental program to allow States to achieve greater risk reduction 
at less cost. Another commenter suggested the multimedia approach 
allowed under the 1996 amendments to the SDWA should not be used with 
regard to radon-222 in water.
EPA Response 7-1
    The requirement for implementation of an EPA-approved MMM program 
in conjunction with State adoption of the AMCL is consistent with the 
statutory framework outlined by Congress in the SDWA provision on 
radon. As proposed, States may choose either to adopt the MCL or the 
AMCL and an MMM program. EPA recommends that small systems comply with 
an AMCL of 4,000 pCi/L and implement a MMM program. See section VII.D 
for background on the selection of the MCL and AMCL.
    Two commenters believe the radon regulation may result in 
litigation against water utilities, local, and State governments if 
systems comply with the AMCL rather than the MCL. As a result, some 
water utilities could choose to comply with the more stringent MCL 
rather than face potential litigation for meeting a ``less stringent 
standard,'' regardless of the increased public health protection. 
According to one commenter, problems will arise when both the AMCL and 
the MCL are required to appear on the annual Consumer Confidence 
Report. The public will view the AMCL as an attempt by the water 
industry to get around the MCL. This will leave the water utility 
vulnerable to toxic tort lawsuits. Because of these problems, the 
concept of an MMM program/AMCL is not as attractive as it once 
appeared.
EPA Response 7-2
    EPA is aware of this concern and the risk communication challenges 
of two regulatory limits for radon in drinking water. However, the SDWA 
framework requires EPA to set an alternative maximum contaminant limit 
for radon if the proposed MCL is more stringent than the level of radon 
in outdoor air. It is important to recognize that in State primacy 
applications for oversight and enforcement of the drinking water 
program, States choosing the MMM approach will be adopting 4,000 pCi/L 
as their MCL. In addition, as part of the proposed rule, EPA will be 
amending the Consumer Confidence Reporting Rule to reflect the proposed 
regulation for radon. Under Sec. 141.153 of the proposed radon rule, a 
system operating under an approved multimedia mitigation program and 
subject to an Alternative MCL (AMCL) for radon must report the AMCL 
instead of the MCL whenever reporting on the MCL is required.
    Another commenter questioned the need for regulating radon in water 
below 3,000 pCi/L, and maintained that there is no conceivable reason 
to regulate it at 100 pCi/L, with or without an MMM program.
EPA Response 7-3
    See EPA Response 6-2 for EPA's decision criteria for setting an 
MCL.
    (b) Implementation scenarios evaluated. One commenter feels that a 
``desk top review'' of States likely to adopt an MMM program would give 
more useful estimates of MMM acceptance than the HRRCA assumptions of 
zero, 50 percent, and 100 percent adoption of MMM programs. This 
commenter felt that for an MMM program to be productive, two things are 
necessary: (1) relatively high radon concentration in water and (2) 
relatively high radon in indoor air.
EPA Response 7-4
    For the purposes of the HRRCA, EPA made these assumptions as a 
straight forward approach for assessing overall cost implications of 
MMM. States are not required to make their determinations on whether to 
adopt the MMM approach until after the rule is final in August 2000. 
Therefore, EPA did not have this information available when developing 
the HRRCA, nor does EPA have this information at this time. However, 
discussions with many State

[[Page 59344]]

drinking water and radon program staff suggest that many States are 
seriously considering the MMM approach.
    EPA expects that MMM programs will be able to achieve indoor radon 
risk reduction even in areas of low radon potential. It is important to 
keep in mind that the only way to know if a house has elevated indoor 
radon levels is to test it. Many homes in low radon potential areas 
have been found with levels well above EPA's action level of 4 pCi/L, 
often next door to houses with very low levels. EPA estimates that 
about 6 million homes in the U.S. of the 83 million homes that should 
test are at or above 4 pCi/L. To date only about 11 million homes have 
been tested. In addition, EPA is not requiring State MMM program plans 
to precisely quantify equivalency in risk reduction between radon in 
drinking water and radon in indoor air.
    (c) Multimedia mitigation cost and benefit assumptions. Two 
commenters indicated that, even if it is not known how the MMM programs 
will be funded, the costs of administering such programs should be 
included in the HRRCA. Several commenters expressed concerns regarding 
the estimated cost of $700,000 per fatal cancer averted. One commenter 
felt that using this value is far too optimistic, indicating that the 
cost of radon risk reduction under State-mandated MMM programs will 
significantly exceed present costs under the voluntary system. To get 
the greatest risk reductions at the lowest costs, MMM program should 
focus on the houses with the highest radon concentrations. Another 
commenter recommended that EPA develop an MMM program that is better 
than the existing voluntary programs and further reduces the cost per 
fatal cancer avoided. The commenter also requested that EPA supply 
background information supporting use of this single MMM program cost 
estimate.
EPA Response 7-5
    EPA is required under the UMRA to assess the costs to States of 
implementing and administering both the MCL and the MMM/AMCL. EPA has 
addressed these costs in the preamble of the rule.
    EPA believes that the criteria for EPA approval of State MMM 
program plans will augment and build on existing State indoor radon 
programs and will result in an increased level of risk reduction.
    As part of developing the 1992 ``A Citizen's Guide to Radon,'' EPA 
analyzed the risk reductions and costs of various radon testing and 
mitigation options (USEPA 1992b). Based on these analyses, a point 
estimate of the average cost per life saved of the current national 
voluntary radon program was used as the basis for the cost estimate of 
risk reduction for the MMM option. EPA had previously estimated that 
the average cost per fatal lung cancer avoided from testing all 
existing homes in the U.S. and mitigation of all those homes at or 
above EPA's voluntary action level of 4 pCi./L is approximately 
$700,000. This value was originally estimated by EPA in 1991. Since 
that time there has been an equivalent offset between a decrease in 
testing and mitigation costs since 1992 and the expected increase due 
to inflation in the years 1992-1997.
    One commenter stated that experiences in Massachusetts showed that 
the costs of incorporating passive radon resistant construction 
techniques is about the same as current prices for marginal quality 
(active) radon mitigation in existing buildings, and disputed the HRRCA 
statement that passive techniques are much less expensive. The 
commenter supported the NAS findings that the effectiveness of these 
techniques in normal construction practice is uncertain.
EPA Response 7-6
    Builders have reported costs as low as $100 to install radon 
resistant new construction features which is significantly less than 
the $350--$500 that was derived in EPA's cost-effectiveness analysis of 
the radon model standards. The cost of materials alone for the passive 
system will always be less than the cost for an active system which 
includes the cost of a fan. In many areas, the majority of the features 
for radon-resistant new construction are already required by code or 
are common building practice, such as an aggregate layer, ``poly'' 
sheeting, and sealing and other weatherization techniques. The only 
additional cost is associated with the vent stack consisting of PVC 
pipe and fittings. In those areas where gravel is not commonly used, 
builders can use a drain tile loop or other alternative less costly 
than gravel to facilitate communication under the slab. EPA estimates 
that the cost to mitigate an existing home ranges from $800 to $2,500 
with an average cost of $1,200.
    (d) Annual costs and benefits of MMM program implementation. 
Several concerns were raised regarding the costs and benefits 
associated with MMM program implementation. One commenter suggested 
that the MMM program description in the HRRCA provides essentially no 
guidance on the point from which additional risk reduction due to MMM 
will be measured.
EPA Response 7-7
    The HRRCA was not intended to include a discussion and description 
of the criteria for EPA approval of State MMM programs. Rather, 
proposed criteria are presented in this proposed rule. EPA's proposed 
criteria do not entail a determination by the State of the level of 
indoor radon risk reduction that has already occurred (``baseline'') as 
the basis for determining how much more risk reduction needs to take 
place. Rather States, with public participation, are required to set 
goals that reflect State and local needs and concerns.
    Another commenter states that EPA has underestimated the benefits 
of an MMM program. The HRRCA registers only the benefits gained in 
relation to water being treated to the MCL. However, according to EPA's 
figures, MMM benefits are expected to be much higher than those 
achieved by mitigating water alone.
EPA Response 7-8
    EPA anticipates that MMM programs will result in sufficient risk 
reduction to achieve ``equal or greater'' risk reduction. A complete 
discussion on why MMM is expected to achieve equal or greater risk 
reduction is shown in Section VI.B of today's preamble. For the 
purposes of the HRRCA analyses, EPA made the conservative assumption 
that the level of risk reduction would at least be ``equal'' to that 
achieved by universal compliance with the MCL.
8. Other Key Comments
    (a) Omission of non-transient non-community water systems 
(NTNCWSs). Eleven commenters criticized EPA's failure to include 
NTNCWSs in the HRRCA. Three commenters indicate that failure to include 
NTNCWSs grossly underestimates costs of radon mitigation. Another 
commenter also suggests that NTNCWSs should be included in the HRRCA, 
to provide a better picture of both costs and benefits. Two commenters 
would also like NTNCWSs included because impacts on these systems are 
likely to be high. Other commenters maintain that excluding NTNCWSs 
skews benefit-cost analyses in favor of regulation. Another commenter 
indicates that NTNCWSs, because of the type of wells and aquifers that 
they draw from, will be most affected by a radon rule.
EPA Response 8-1
    Partly as a result of concerns raised by commenters, and partly as 
a result of its own preliminary analysis of exposure and risk, EPA is 
not proposing that NTNCWSs be covered by this rule. A more complete 
discussion of this issue

[[Page 59345]]

is included in the preamble for the proposed rule. EPA has conducted a 
preliminary analysis on exposure and risks to NTNCWSs and is asking for 
public comment on this preliminary analysis and on the proposed 
exclusion of NTNCWSs. An analysis of the potential benefits and costs 
of radon in drinking water for NTNCWSs is included in the docket for 
this proposed rulemaking. (USEPA 1999m)

XIV. Administrative Requirements

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866, ``Regulatory Planning and Review'' (58 
FR 51,735 (October 4, 1993)), the Agency must determine whether the 
regulatory action is ``significant'' and therefore subject to OMB 
review and the requirements of the Executive Order. The Order defines 
``significant regulatory action'' as one that is likely to result in a 
rule that may:
    (1) have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal governments or 
communities;
    (2) create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    Pursuant to the terms of E.O. 12866, it has been determined that 
this rule is a ``significant regulatory action''. As such, this action 
was submitted to OMB for review. Changes made in the proposal in 
response to OMB suggestions or recommendations will be documented in 
the public record.

B. Regulatory Flexibility Act (RFA)

1. Today's Proposed Rule
    Under the Regulatory Flexibility Act (RFA), 5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA), EPA generally is required to conduct a regulatory flexibility 
analysis describing the impact of the regulatory action on small 
entities as part of rulemaking. Today's proposed rule may have 
significant economic impact on a substantial number of small entities 
and EPA has prepared an Initial Regulatory Flexibility Analysis (IRFA). 
In addition, when preparing an IRFA, EPA must convene a Small Business 
Advocacy Review (SBAR) Panel. A discussion of the Panel's 
recommendations and EPA's response to their recommendations is shown in 
Section 6.
2. Use of Alternative Small Entity Definition
    The EPA is proposing that small CWS serving 10,000 people or less 
must comply with the AMCL, and implement a MMM program (if there is no 
state MMM program). This is the cut-off level specified by Congress in 
the 1996 amendments to the Safe Drinking Water Act for small system 
flexibility provisions. Because this definition does not correspond to 
the definitions of ``small'' for small businesses, governments, and 
non-profit organizations previously established under the RFA, EPA 
requested comment on an alternative definition of ``small entity'' in 
the Preamble to the proposed Consumer Confidence Report (CCR) 
regulation (63 FR 7620, February 13, 1998). Comments showed that 
stakeholders support the proposed alternative definition. EPA also 
consulted with the SBA Office of Advocacy on the definition as it 
relates to small business analysis. In the preamble to the final CCR 
regulation (63 FR 4511, August 19, 1998), EPA stated its intent to 
establish this alternative definition for regulatory flexibility 
assessments under the RFA for all drinking water regulations and has 
thus used it for this radon in drinking water rulemaking. Further 
information supporting this certification is available in the public 
docket for this rule.

3. Background and Analysis

    The RFA requires EPA to address the following when completing an 
IRFA: (1) describe the reasons why action by the Agency is being 
considered; (2) state succinctly the objectives of, and legal basis 
for, the proposed rule; (3) describe, and where feasible, estimate the 
number of small entities to which the proposed rule will apply; (4) 
describe the projected reporting, record keeping, and other compliance 
requirements of the rule, including an estimate of the classes of small 
entities that will be subject to the requirements and the type of 
professional skills necessary for preparation of reports or records; 
(5) identify, to the extent practicable, all relevant Federal rules 
that may duplicate, overlap, or conflict with the proposed rule; and 
(6) describe any significant alternatives to the proposed rule that 
accomplish the stated objectives of applicable statutes while 
minimizing any significant economic impact of the proposed rule on 
small entities. EPA has considered and addressed all of the previously 
described requirements. The following is a summary of the IRFA.
    The first and second requirements are discussed in Section II of 
this Preamble. The third, fourth, and sixth requirements are summarized 
as follows. The fifth requirement is discussed under Section VIII.A.2 
of this Preamble in a subsection addressing potential interactions 
between the radon rule and upcoming and existing rules affecting ground 
water systems.
4. Number of Small Entities Affected
    EPA estimates that 40,863 ground water systems are potentially 
affected by the proposed radon rule, with 96 percent of these systems 
serving less than 10,000 persons. Of the 39,420 small systems 
potentially affected, EPA estimates that 1,761 (4.4 percent) small 
systems will have to modify treatment (install treatment technology) to 
comply with the AMCL. The proposed rule recommends that small systems 
meet the 4,000 pCi/L AMCL and implement a multimedia mitigation (MMM) 
program if their State does not implement a MMM program. Small systems 
may also choose to comply with the MCL rather than implement an MMM 
program. As Table XIV.1 indicates, water mitigation administration 
costs for small systems remain the same under any State MMM program 
adoption scenario. However, small systems located in States that do not 
implement a MMM program must develop and implement their own MMM 
program for the population they serve (unless they choose to comply 
with the MCL), thus increasing their costs. Additional MMM 
implementation scenarios have been analyzed in the RIA (USEPA 1999f) 
which is included in the docket for this proposed rulemaking.

[[Page 59346]]



  Table XIV.1.--Annual Water Mitigation and MMM Program Costs to Small
                                 Systems
                            [$Millions, 1997]
------------------------------------------------------------------------
                                          100% of states   50% of states
            Cost description                 adopt MMM       adopt MMM
------------------------------------------------------------------------
Water Mitigation Costs \1\
    Total Capital Costs.................           118.5           194.1
    Total Annual Costs \2\..............            31.3            43.2
Water Mitigation Administration Costs...             5.8             5.8
Multimedia Mitigation Program Costs \3\.               0            43.3
Total Small System Costs per Year.......            37.1           92.4
------------------------------------------------------------------------
Notes:
\1\ Costs to small systems to mitigate water to the AMCL of 4,000 pCi/L.
 
\2\ Includes annual capital costs, monitoring costs, and operation and
  maintenance costs.
\3\ Does not include the costs of testing and mitigating homes.

5. Proposed Rule Reporting Requirements for Small Systems
    The proposed radon rule requires small systems to maintain records 
and to report radon concentration levels at point-of-entry to the water 
system's distribution system. Small systems are also required to 
provide radon information in the Consumer Confidence Report, and if the 
system is implementing its own MMM program, reports on progress to the 
goals outlined in the system's MMM program plan. Radon monitoring and 
reporting for water mitigation will be required on a quarterly basis 
for at least one year, but thereafter the frequency may be reduced to 
annually or once every three years depending on the level of radon 
present (see Section VIII.E). Other existing information and reporting 
requirements, such as Consumer Confidence Reports and (proposed) public 
notification requirements, will be marginally expanded to encompass 
radon along with other contaminants (see Section X). As is the case for 
other contaminants, required information on system radon levels must be 
provided by affected systems and is not considered to be confidential. 
The professional skills necessary for preparing the reports are the 
same skill level required by small systems for current reporting and 
monitoring requirements.
    The classes of small entities that are subject to the proposed 
radon rule include public groundwater systems serving less than 10,000 
people. Small systems are further classified into very very small 
systems (serving 25-500 persons), very small systems (serving 501-3,300 
persons, and small systems (serving 3,301-10,000 persons).
6. Significant Regulatory Alternatives and SBAR Panel Recommendations
    In response to the SBAR Panel's recommendations and other small 
entity concerns, EPA has included several requirements to help reduce 
the impacts of the proposed radon rule on small entities. These 
requirements include: (1) Recommendation of small system compliance 
with the MMM/AMCL option; (2) less routine monitoring; (3) State 
granting of waivers to ground water systems to reduce monitoring 
frequency; and (4) encouraging and providing information about the use 
of low maintenance treatment technologies. A more complete discussion 
of the SBAR Panel recommendations and EPA's responses follow here. EPA 
also believes small systems can in some cases reduce their economic 
burden by a variety of means, including using the State revolving fund 
loans to offset compliance costs. In the development of this proposed 
rulemaking, EPA considered several regulatory alternatives to the 
proposed requirements for small systems. The proposal includes the 
regulatory expectation that they comply with the AMCL of 4,000 pCi/L 
and be associated with either a state or local MM program. EPA believes 
that this option will provide equivalent or greater health protection 
while reducing economic burdens to small systems. For a more detailed 
description of the alternatives considered in the development of the 
proposed rule see the RIA (USEPA 1999f) or the discussion of regulatory 
alternatives in Section XIV.C (Unfunded Mandates Reform Act).
    In addition to being summarized here, the public docket for this 
proposed rulemaking includes the SBAR Panel's report on the proposed 
radon regulation, which outlines background information on the proposed 
radon rule and the types of small entities that may be subject to the 
proposed rule; a summary of EPA's outreach activities; and the comments 
and recommendations of the small entity representatives (SERs) and the 
Panel.
    (a) Consultations. Consistent with the requirements of the RFA as 
amended by SBREFA, EPA has conducted outreach directly to 
representatives of small entities that may be affected by the proposed 
rule. Anticipating the need to convene a SBAR Panel under Section 609 
of the RFA/SBREFA, in consultation with the Small Business 
Administration (SBA), EPA identified 23 representatives of small 
entities that were most likely to be subject to the proposal. In April, 
1998, EPA prepared an outreach document on the radon rule titled 
``Information for Small Entity Representatives Regarding the Radon in 
Drinking Water Rule'' (USEPA 1998b). EPA distributed this document to 
the small entity representatives (SERs), as well as stakeholder meeting 
discussion documents and the executive summary of the February 1994 
document ``Report to the United States Congress on Radon in Drinking 
Water: Multimedia Risk and Cost Assessment of Radon'' (EPA 1994a).
    On May 11, 1998, EPA held a small entity conference call from 
Washington DC to provide a forum for small entity input on key issues 
related to the planned proposal of the radon in drinking water rule. 
These issues included: (1) Issues related to the rule development, such 
as radon health risks, occurrence of radon in drinking water, treatment 
technologies, analytical methods, and monitoring; and (2) issues 
related to the development and implementation of the multimedia 
mitigation program guidelines. Thirty people participated in the 
conference call, including 13 SERs from small water systems from 
Arizona, California, Nebraska, New Hampshire, Utah, Washington, 
Alabama, Michigan, Wyoming, and New Jersey.
    Efforts to identify and incorporate small entity concerns into this 
rulemaking culminated with the convening of a SBAR Panel on July 9, 
1998, pursuant to Section 609 of RFA/SBREFA. The four person Panel was 
headed by EPA's Small Business Advocacy Chairperson and included the 
Director of the Standards and Risk Management Division within EPA's

[[Page 59347]]

Office of Ground Water and Drinking Water, the Administrator of the 
Office of Information and Regulatory Affairs with the Office of 
Management and Budget, and the Chief Counsel for Advocacy of the SBA. 
For a 60-day period starting on the convening date, the Panel reviewed 
technical background information related to this rulemaking, reviewed 
comments provided by the SERs, and met on several occasions. The Panel 
also conducted its own outreach to the SERs and held a conference call 
on August 10, 1998 with the SERs to identify issues and explore 
alternative approaches for accomplishing environmental protection goals 
while minimizing impacts to small entities. Details of the Panel 
process, along with summaries of the conference calls with the SERs and 
the Panel's findings and recommendations, are presented in the 
September 1998 document ``Final Report of the SBREFA Small Business 
Advocacy Review Panel on EPA's Planned Proposed Rule for National 
Primary Drinking Regulation: Radon'' (USEPA 1998c).
    (b) Recommendations and Actions.--Today's notice incorporates all 
of the recommendations on which the Panel reached consensus. In 
particular, the Panel made a number of recommendations regarding the 
MMM program guidelines, including that the guidelines be user-friendly 
and flexible and provide a viable and realistic alternative to meeting 
the MCL, for both States and CWSs. The Panel also agreed that provision 
of information to the public and equity are important considerations in 
the design of an MMM program.
    In response to the Panel's recommendations and concerns heard from 
other stakeholders, EPA has developed specific criteria that MMM 
programs must meet to be approved by EPA. EPA believes these criteria 
are simple and straightforward and provide the flexibility States and 
public water systems need to develop programs to meet their different 
needs and concerns. The criteria permit States, with public 
participation and input, to determine their own prospective indoor 
radon risk reduction goals and to design the program strategies they 
determine are needed to achieve these goals. The criteria build on the 
existing framework of State indoor radon programs that are already 
working to get indoor radon risk reduction. EPA also believes that 
equity issues can be most effectively discussed and resolved with the 
public's participation and involvement in development of goals and 
strategies for an MMM program. Providing customers of public water 
systems with information about the health risks of radon and on the 
AMCL and MMM program option will help to promote understanding of the 
significant public health risks from radon in indoor air and help the 
public to make informed choices. Section VI of this Preamble discusses 
the MMM program in greater detail.
    Following is a summary of the other Panel recommendations and EPA's 
response to these recommendations, by subject area:
    Occurrence: The Panel recommended that EPA continue to refine its 
estimates of the number of affected wells. The occurrence section of 
the preamble contains an expanded description in regard to how EPA 
refined the estimates of the number of affected water supply wells (See 
Section XI.C ``EPA's Most Recent Studies of Radon Levels in Ground 
Water'').
    Water Treatment: The Panel recommended the following: provide clear 
guidance for when granular activated carbon (GAC) treatment may be 
appropriate as a central or point-of-entry unit treatment technology; 
consider and include in its regulatory cost estimates, to the extent 
possible, the complete burden and benefits; and carefully consider 
effects of radon-off- gassing from aeration towers and potential 
permitting requirements in developing regulations or guidance related 
to aeration.
    In response to these recommendations, the treatment section of the 
preamble contains an expanded description regarding conditions under 
which granular activated carbon (GAC) treatment may be appropriate as a 
central or point-of-entry unit treatment technology (See Section 
VIII.A.3 ``Centralized GAC and Point-of-entry GAC''); the RIA and the 
treatment sections of the preamble describe the components which 
contribute to the regulatory economic analysis (See Section VIII.A.2 
``Treatment Costs: BAT, Small Systems Compliance Technologies, and 
Other Treatment''); high-end treatment cost estimates have been revised 
to include scenarios where air-permitting costs are much higher than 
typical cases (see Sections VIII.A.2 ``Treatment Cost Assumptions and 
Methodology'' and ``Comparison of Modeled Costs with Real Costs from 
Case Studies''); and information and rationale has been added to 
support EPA's belief that permitting requirements from off-gassing from 
aeration towers will not preclude installation of aeration treatment 
(see Section VIII.A.3 ``Evaluation of Radon Off-Gas Emissions Risks'').
    In addition, the Panel recommended that EPA fully consider the 
relationship of the Radon in Drinking Water Rule with other rules 
affecting the same small entities. In response, the treatment section 
of the preamble, the Treatment and Cost Document, and the RIA have been 
expanded to discuss the relationship of treatment for radon with other 
drinking water rules including the Ground Water Rule, Lead and Copper 
Rule, and the Disinfection By-Products Rules (see Section VIII.A.2 
``Potential Interactions Between the Radon Rule and Upcoming and 
Existing Rules Affecting Ground Water Systems'').
    Analytical Methods and Monitoring: The Panel recommended the 
following: fully consider the availability and capacity of certified 
laboratories for radon analysis and consider the costs of monitoring; 
consider applying the VOCs sampling method to radon to reduce the need 
for additional training; reduce the frequency of monitoring after 
initial determination of compliance and consider providing waivers from 
monitoring requirements when a system is not at risk of exceeding the 
MCL; and develop monitoring requirements that are simple and easy to 
interpret to facilitate compliance by small systems.
    In response, the analytical methods section of the preamble 
includes discussion of the availability and capacity of certified 
laboratories for radon analysis (see Section VIII.C ``Laboratory 
Capacity--Practical Availability of the Methods''); and a clarification 
that the radon sampling method is the same as for the volatile organic 
carbons sampling method (see Section VIII.B.2 ``Sampling Collection, 
Handling and Preservation''). The RIA and the preamble include more 
detailed discussion of regulatory costs estimates including the 
monitoring costs estimated (see Section VIII.B.2 ``Cost of Performing 
Analysis''). The monitoring section proposed rule provides for a 
reduced monitoring frequency to once every three years if the average 
of four quarterly samples is less than 1/2 MCL/AMCL, provided that no 
sample exceeds the MCL/AMCL (see Section VIII.E.4 ``Increased/decreased 
monitoring requirements'' and Section 141.28(b) of the proposed rule). 
Section VIII.E.5 ``Grandfathering of Data'' and Section 141.28(b) of 
the proposed rule describes the allowance of grandfathered data, i.e., 
data collected after proposal of the rule, that meet specified 
requirements. Section VIII.E.4 ``Increased/decreased monitoring 
requirements'' of this Preamble discusses the allowance for States to 
grant waivers to ground water systems to reduce the frequency of 
monitoring, i.e., up to a 9 year

[[Page 59348]]

frequency. Section VIII.E, Table VIII.E.1 of this Preamble also 
describes monitoring requirements to facilitate interpretation of the 
requirements.
    General: The Panel recommended that EPA explore options for 
providing technical assistance to small entities to clearly communicate 
the risks from radon in drinking water and indoor air, the rationale 
supporting the regulation, and actions consumers can take to reduce 
their risks. Therefore, this Preamble has been written to clarify to 
the public the risks from radon in drinking water and radon in indoor 
air, and the rationale supporting the proposed regulation (see Sections 
I through V of this Preamble).
    Areas in which Panel did not reach consensus: There were also a 
number of issues discussed by the Panel on which consensus was not 
reached. These included the appropriateness of the Agency's 
affordability criteria for determining if affordable small system 
compliance technologies are available, the appropriate level at which 
to set the MCL, whether EPA should provide a ``model'' MMM program for 
use by small systems in states that do not adopt state-wide MMM 
programs, and whether information on the risks of radon and options for 
reducing it provides ``health risk reduction benefits'' (as referenced 
in the SDWA) independent of whether homes are actually mitigated or 
built radon resistant. A detailed discussion of these issues is 
included in the Panel report. EPA is requesting comment on some of 
these issues in other parts of the preamble. To read the full 
discussion of the issues on which EPA is requesting comment, see 
Sections VII.A ``Requirements for Small Systems Serving 10,000 People 
or Less'', VII.D ``Background on Selection of MCL and AMCL'', and VI.F 
``Local CWS MMM Programs in Non-MMM States and State Role in Approval 
of CWS MMM Program Plans.''

C. Unfunded Mandates Reform Act (UMRA)

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), P.L. 
104-4, establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on State, local, and tribal 
governments and the private sector. Under UMRA Section 202, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with ``Federal mandates'' that 
may result in expenditures to State, local, and tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
one year. Before promulgating an EPA rule, for which a written 
statement is needed, Section 205 of the UMRA generally requires EPA to 
identify and consider a reasonable number of regulatory alternatives 
and adopt the least costly, most cost-effective or least burdensome 
alternative that achieves the objectives of the rule. The provisions of 
Section 205 do not apply when they are inconsistent with applicable 
law. Moreover, Section 205 allows EPA to adopt an alternative other 
than the least costly, most cost-effective or least burdensome 
alternative if the Administrator publishes with the final rule an 
explanation on why that alternative was not adopted.
    Before EPA establishes any regulatory requirements that may 
significantly or uniquely affect small governments, including tribal 
governments, it must have developed, under Section 203 of the UMRA, a 
small government agency plan. The plan must provide for notification to 
potentially affected small governments, enabling officials of affected 
small governments to have meaningful and timely input in the 
development of EPA regulatory proposals with significant Federal 
intergovernmental mandates and informing, educating, and advising small 
governments on compliance with the regulatory requirements.
1. Summary of UMRA Requirements
    EPA has determined that this rule contains a Federal mandate that 
may result in expenditures of $100 million or more for State, local, 
and tribal governments, in the aggregate, or the private sector in any 
one year. Accordingly, EPA has prepared, under Section 202 of the UMRA, 
a written statement addressing the following areas: (1) Authorizing 
legislation; (2) cost-benefit analysis including an analysis of the 
extent to which the costs to State, local, and tribal governments will 
be paid for by the Federal government; (3) estimates of future 
compliance costs; (4) macro-economic effects; and (5) a summary of 
EPA's consultation with State, local, and tribal governments, a summary 
of their concerns, and a summary of EPA's evaluation of their concerns. 
A summary of this analysis follows and a more detailed description is 
presented in EPA's Regulatory Impact Analysis (RIA) of the Radon Rule 
(USEPA 1999f) which is included in the docket for this proposed 
rulemaking.
    (a) Authorizing legislation. Today's proposed rule is proposed 
pursuant to Section 1412(b)(13) of the 1996 amendments to the SDWA 
which requires EPA to propose and promulgate a national primary 
drinking water regulation for radon, establishes a statutory deadline 
of August 1999 to propose this rule, and establishes a statutory 
deadline of August 2000 to promulgate this rule.
    (b) Cost-benefit analysis. Section XIII.B of this preamble, 
describing the Regulatory Impact Analysis (RIA) and Revised Health Risk 
Reduction and Cost Analysis (HRRCA) for radon, contains a detailed 
cost-benefit analysis in support of the radon rule. Today's proposed 
rule is expected to have a total annualized cost of approximately $121 
million with a range of potential impacts from $60.4 to $407.6 million, 
depending on how many States and local PWSs adopt MMM programs and 
comply with the AMCL. This total annualized cost consists of total 
annual impacts on State, local, and tribal governments, in aggregate, 
of approximately $53.5 million and total annual impacts on private 
entities of approximately $67.6 million (Note: these estimates are 
based on Scenario A which assumes 50 percent of States implement MMM 
programs with the remaining 50 percent of States implementing system-
level MMM programs or complying with the MCL. Under Scenario E, total 
costs are approximately $60.4 million. Total national costs of full 
compliance with an MCL are approximately $407.6 million. Detailed 
descriptions of the national costs and MMM scenarios are shown in 
Section XIII of this preamble and Sections 9 and 10 of the RIA (USEPA 
1999f).
    The RIA includes both qualitative and monetized benefits for 
improvements in health and safety. EPA estimates the proposed radon 
rule will have annual monetized benefits of approximately $17.0 million 
if the MCL were to be set at 4,000 pCi/L and $362 million if set at 300 
pCi/L. The monetized health benefits of reducing radon exposures in 
drinking water are attributable to the reduced incidence of fatal and 
non-fatal cancers, primarily of the lung and stomach. Under baseline 
assumptions (no control of radon exposure), 168 fatal cancers and 9.7 
non-fatal cancers per year are associated with radon exposures through 
CWSs. At a radon level of 4,000 pCi/L, an estimated 2.9 fatal cancers 
and 0.2 non-fatal cancers per year are prevented. At a level 300 pCi/L, 
62.0 fatal and 3.6 non-fatal cancers per year are prevented. The Agency 
believes that compliance with an AMCL of 4,000 pCi/L and implementation 
of a MMM program would result in health benefits equal to or greater 
than those achieved by complying with the proposed MCL (300 pCi/L).

[[Page 59349]]

    In addition to quantifiable benefits, EPA has identified several 
potential non-quantifiable benefits associated with reducing radon 
exposures in drinking water. These potential benefits are difficult to 
quantify because of the uncertainty surrounding their estimation. Non-
quantifiable benefits may include any peace-of-mind benefits specific 
to reduction of radon risks that may not be adequately captured in the 
Value of Statistical Life (VSL) estimate. In addition, if chlorination 
is added to the process of treating radon via aeration, arsenic pre-
oxidization will be facilitated. Neither chlorination nor aeration will 
remove arsenic, but chlorination will facilitate conversion of Arsenic 
(III) to Arsenic (V). Arsenic (V) is a less soluble form that can be 
better removed by arsenic removal technologies. In terms of reducing 
radon exposures in indoor air, provision of information to households 
on the risks of radon in indoor air and the availability of options to 
reduce exposure may be a non-quantifiable benefit that can be 
attributed to some components of a MMM program. Providing such 
information might allow households to make more informed choices about 
the need for risk reduction given their specific circumstances and 
concerns than they would have in the absence of a MMM program.
    (i) State and Local Administrative Costs. States will incur a range 
of administrative costs with the MCL and MMM/AMCL options in complying 
with the radon rule. Administrative costs associated with water 
mitigation can include costs associated with program management, 
inspections, and enforcement activities. EPA estimates the total annual 
costs of administrative activities for compliance with the MCL to be 
approximately $2.5 million.
    Additional administrative costs will be incurred by those States 
who comply with the AMCL and develop an MMM program plan. In this case, 
States will need to satisfy the four criteria for an acceptable MMM 
program which include: (1) Involve the public in developing the MMM 
program plan; (2) set quantitative State-wide goals for reducing radon 
levels in indoor air; (3) submit and implement plans on existing and 
new homes; and (4) develop and implement plans for tracking and 
reporting results. The administrative costs will consist of the various 
activities necessary to satisfy these four criteria. Because EPA is 
unable to specify the number of States that will implement an MMM 
program, administrative costs were estimated under two assumptions: (1) 
50 percent of States (all water systems in those States) implement an 
MMM program; and (2) 100 percent of States implement an MMM program, 
since we expect that most States will choose this option.
    If a State does not develop an MMM program plan, any local water 
system may chose to meet the AMCL and prepare an MMM program plan for 
State approval. Administrative costs to the State would consist 
primarily of reviewing local program plans and overseeing compliance. 
However, local water systems would bear administrative costs that 
resemble the State costs to administer an MMM program. To estimate 
costs for local water systems in these States, EPA assumed that all 
local systems that exceeded 300 pCi/L but were less than 4,000 pCi/L 
would choose to administer an MMM program rather than achieve the 300 
pCi/L level through water mitigation. It is assumed that, on average, 
water mitigation costs will exceed MMM program administrative costs for 
local water systems.
    EPA estimates that total annual costs of approximately $13.2 
million are expected if half the States elect to administer an MMM 
program and all local water systems in the remaining States undertake 
MMM programs. In this case, costs to 50 percent of the States to 
administer the MMM program ($2.9 million), and costs to 50 percent of 
the States to approve MMM programs developed by local water systems 
($7.8 million) are added to water mitigation costs ($2.5 million). In 
this latter case there would also be costs to local water systems of 
$45 million to develop and implement local MMM programs. This is the 
total cost per year across all system sizes to develop and implement 
system-level MMM programs and assumes approximately 45 percent of CWSs 
will do a system-level MMM plan. The total costs across all system 
sizes under Scenario E for system-level MMM programs is approximately 
$5 million.
    Various Federal financial assistance programs exist to help State, 
local, and tribal governments comply with this rule. To fund 
development and implementation of a MMM program, States have the option 
of using Public Water Systems Supervision (PWSS) Program Assistance 
Grant funds [SDWA Section 1443(a)(1)] and Program Management Set-Aside 
funds from the Drinking Water State Revolving Fund (DWSRF) program. 
Infrastructure funding to provide the equipment needed to ensure 
compliance is available from the DWSRF program and may be available 
from other Federal agencies, including the Housing and Urban 
Development's Community Development Block Grant Program or the 
Department of Agriculture's Rural Utilities Service.
    EPA provides funding to States that have a primary enforcement 
responsibility for their drinking water programs through the PWSS 
grants program. States may use PWSS grant funds to establish and 
administer new requirements under their primacy programs, including MMM 
programs. PWSS grant funds may be used by a State to set-up and 
administer a State MMM program.
    States may also ``contract'' to other State agencies to assist in 
the development or implementation of their primacy program, including 
an MMM program for radon. However, States may not use grant funds to 
contract to regulated entities (i.e., water systems) for MMM program 
implementation.
    An additional source of EPA funding to develop and implement a MMM 
program is through the DWSRF program. The program awards capitalization 
grants to States, which in turn use funds to provide low cost loans and 
other types of assistance to eligible public water systems to assist in 
financing the costs of infrastructure needed to achieve or maintain 
compliance with SDWA requirements. The DWSRF program also allows a 
State to set aside a portion of its capitalization grant to support 
other activities that result in protection of public health and 
compliance with the SDWA. The State Program Management set-aside (SDWA 
Section 1452(g)(2)) allows a State to reserve up to ten percent of its 
DWSRF allotment to assist in implementation of the drinking water 
program. States must match expenditures under this set-aside dollar for 
dollar. DWSRF State Program Management set-aside funds can be used to 
fund activities to develop and run an MMM program, similar to those 
eligible for funding from PWSS grant funds.
    States may also use State Indoor Radon Grant (SIRG) funds to assist 
States in funding their MMM programs. The Agency has determined that 
activities that implement MMM activities and that meet current SIRG 
eligibility requirements can be carried out with SIRG funds because the 
goals of the MMM program reinforce and enhance the goals, strategies, 
and priorities of the existing State indoor radon programs that rely on 
funding through the SIRG program. However, expenditure of SIRG will not 
be permitted to fund strictly water-related activities, such as testing 
or monitoring of water by CWSs.

[[Page 59350]]

    (c) Estimates of future compliance costs. To meet the requirement 
in Section 202 of the UMRA, EPA analyzed future compliance costs and 
possible disproportionate budgetary effects of both the MCL and MMM/
AMCL options. The Agency believes that the cost estimates, indicated 
previously and discussed in more detail in Section XIII.B of today's 
preamble accurately characterize future compliance costs of the 
proposed rule.
    (d) Macroeconomic effects. As required under UMRA Section 202, EPA 
is required to estimate the potential macro-economic effects of the 
regulation. These types of effects include those on productivity, 
economic growth, full employment, creation of productive jobs, and 
international competitiveness. Macro-economic effects tend to be 
measurable in nationwide econometric models only if the economic impact 
of the regulation reaches 0.25 percent to 0.5 percent of Gross Domestic 
Product (GDP). In 1998, real GDP was $7,552 billion so a rule would 
have to cost at least $18 billion annually to have a measurable effect. 
A regulation with a smaller aggregate effect is unlikely to have any 
measurable impact unless it is highly focused on a particular 
geographic region or economic sector. The macro-economic effects on the 
national economy from the radon rule should be negligible based on the 
fact that, assuming full compliance with an MCL, the total annual costs 
are approximately $43.1 million at the 4,000 pCi/L level and about 
$407.6 million at the 300 pCi/L level (at a 7 percent discount rate) 
and the costs are not expected to be highly focused on a particular 
geographic region or industry sector.
    (e) Summary of EPA's consultation with State, local, and tribal 
governments and their concerns. Consistent with the intergovernmental 
consultation provisions of section 204 of the UMRA and Executive Order 
12875 ``Enhancing Intergovernmental Partnership,'' EPA has already 
initiated consultations with the governmental entities affected by this 
rule. EPA initiated consultations with governmental entities and the 
private sector affected by this rulemaking through various means. This 
included four stakeholder meetings, and presentations at meetings of 
the American Water Works Association, the Association of State Drinking 
Water Administrators, the Association of State and Territorial Health 
Officials, and the Conference of Radiation Control Program Directors. 
Participants in EPA's stakeholder meetings also included 
representatives from National Rural Water Association, National 
Association of Water Companies, Association of Metropolitan Water 
Agencies, State department of environmental protection representatives, 
State health department representatives, State water utility 
representatives, the Inter Tribal Council of Arizona, and 
representatives of other tribes. EPA also made presentations at tribal 
meetings in Nevada, Alaska, and California. To address the proposed 
rule's impact on small entities, the Agency convened a Small Business 
Advocacy Review Panel in accordance with the Regulatory Flexibility Act 
(RFA) as amended by the Small Business Regulatory Enforcement Fairness 
Act (SBREFA). EPA also held two series of three conference calls with 
representatives of State drinking water and State radon programs. In 
addition to these consultations, EPA made presentations on the proposed 
Radon Rule to the Association of California Water Agencies, the 
National Association of Towns and Townships, the National League of 
Cities, and the National Association of Counties. Several State 
drinking water representatives also participated in AWWA's Technical 
Workgroup for Radon.
    The Agency also notified governmental entities and the private 
sector of opportunities to provide input on the Health Risk Reduction 
and Cost Analysis (HRRCA) for radon in drinking water in the Federal 
Register on February 26, 1999 (64 FR 9559). The HRRCA was published six 
months in advance of this proposal and illustrated preliminary cost and 
benefit estimates for various MCL options under consideration for the 
proposed rule. The comment period on the HRRCA ended on April 12, 1999, 
and EPA received approximately 26 written comments. Of the 26 comments 
received concerning the HRRCA, 42 percent were from States and 4 
percent were from local governments.
    The public docket for this proposed rulemaking contains meeting 
summaries for EPA's four stakeholder meetings on radon in drinking 
water, all comments received by the Agency, and provides details about 
the nature of State, local, and tribal governments' concerns. A summary 
of State, local, and tribal government concerns on this proposed 
rulemaking is provided in the following section.
    In order to inform and involve tribal governments in the rulemaking 
process, EPA staff attended the 16th Annual Consumer Conference of the 
National Indian Health Board on October 6-8, 1998, in Anchorage, 
Alaska. Over nine hundred persons representing Tribes from across the 
country were in attendance. During the conference, EPA conducted two 
workshops for meeting participants. The objectives of the workshops 
were to present an overview of EPA's drinking water program, solicit 
comments on key issues of potential interest in upcoming drinking water 
regulations, and to solicit advice in identifying an effective 
consultative process with tribes for the future.
    EPA, in conjunction with the Inter Tribal Council of Arizona 
(ITCA), also convened a tribal consultation meeting on February 24-25, 
1999, in Las Vegas, Nevada to discuss ways to involve tribal 
representatives, both tribal council members and tribal water utility 
operators, in the stakeholder process. Approximately twenty-five 
representatives from a diverse group of tribes attended the two-day 
meeting. Meeting participants included representatives from the 
following tribes: Cherokee Nation, Nezperce Tribe, Jicarilla Apache 
Tribe, Blackfeet Tribe, Seminole Tribe of Florida, Hopi Tribe, Cheyenne 
River Sioux Tribe, Menominee Indian Tribe, Tulalip Tribes, Mississippi 
Band of Choctaw Indians, Narragansett Indian Tribe, and Yakama Nation.
    The major meeting objectives were to: (1) Identify key issues of 
concern to tribal representatives; (2) solicit input on issues 
concerning current OGWDW regulatory efforts; (3) solicit input and 
information that should be included in support of future drinking water 
regulations; and (4) provide an effective format for tribal involvement 
in EPA's regulatory development process. EPA staff also provided a 
brief overview on the forthcoming radon rule at the meeting. The 
presentation included the health concerns associated with radon, EPA's 
current position on radon in drinking water, the distinction between an 
MCL and AMCL, the multimedia mitigation (MMM) program, and specific 
issues for tribes. The following questions were posed to the tribal 
representatives to begin discussion on radon in drinking water: (1) 
Will tribal governments be interested in substituting MMM for drinking 
water control; (2) what types of MMM could tribes reasonably implement; 
and (3) what resources are available to fund MMM? The summary for the 
February 24-25, 1999, meeting was sent to all 565 Federally recognized 
tribes in the United States.
    EPA also conducted a series of workshops at the Annual Conference 
of the National Tribal Environmental Council which was held on May 18-
20, 1999, in Eureka, California. Representatives from over 50 tribes 
attended all, or part, of these sessions.

[[Page 59351]]

The objectives of the workshops were to provide an overview of 
forthcoming EPA regulations affecting water systems; discuss changes to 
operator certification requirements; discuss funding for tribal water 
systems; and to discuss innovative approaches to regulatory cost 
reduction. Tribal representatives were generally supportive of 
regulations which would ensure a high level of water quality, but 
raised concerns over funding for regulations. With regard to the 
forthcoming proposed radon rule, many tribal representatives saw the 
multimedia mitigation option as highly desirable, but felt that this 
option may not be adapted unless funds were made available for home 
mitigation. Meeting summaries for EPA's tribal consultations are 
available in the public docket for this proposed rulemaking.
    (f) Nature of state, local, and tribal government concerns and how 
EPA addressed these concerns. State and local governments raised 
several concerns, including the high costs of the rule to small 
systems; the high degree of uncertainty associated with the benefits; 
the high costs of including Non-Transient Non-Community Water Systems 
(NTNCWSs); and the inclusion of risks to both smokers and non-smokers 
in the proposed regulation. Tribal governments raised several concerns 
with the MMM program, including where the funding to mitigate homes 
would come from; the number of homes that would require testing; and 
the frequency of home testing.
    EPA understands the State, local, and tribal government concerns 
with the issues described previously. The Agency believes that the 
options for small systems, proposed for public comment in this 
rulemaking, will address stakeholder concerns pertaining to small 
systems and will help to reduce the financial burden to these systems.
    Non-Transient Non-Community Water Systems (NTNCWSs) are not subject 
to this proposed rulemaking. A detailed discussion of the exposure to 
radon in NTNCWSs is shown in Section XII.D of this preamble. EPA has 
conducted a preliminary analysis on exposure and risks to NTNCWSs and 
is soliciting public comment on this preliminary analysis. An analysis 
of the potential benefits and costs of radon in drinking water for 
NTNCWSs is included in the docket for this proposed rulemaking. (USEPA 
1999m)
    EPA has included the risks to both ever-smokers and never-smokers 
in this proposed rulemaking. The Agency is basing this regulation on 
the risks to the general population and is not excluding any particular 
segments of the population. For a more complete discussion on the risks 
of radon in drinking water and air, see Section XII of this preamble.
    EPA understands tribal governments' concerns with funding for the 
MMM program. To assist State, local, and tribal governments with the 
implementation of an MMM program, EPA is making available Public Water 
Supply Supervision (PWSS) Program Assistance Grant Funds, Drinking 
Water State Revolving Fund (DWSRF) funds, and State Indoor Air Grant 
(SIRG) funds. A more complete discussion of the funding available to 
State, local, and tribal governments for MMM program implementation is 
shown in Section XIV.C.1(b) of this preamble.
    (g) Regulatory Alternatives Considered. As required under Section 
205 of the UMRA, EPA considered several regulatory alternatives in 
developing an MCL for radon in drinking water. In preparation for this 
consideration, the Regulatory Impact Analysis and Health Risk Reduction 
and Cost Analysis (HRRCA) for Radon evaluated radon levels of 100, 300, 
500, 700, 1,000, 2,000, and 4,000 pCi/L.
    The Regulatory Impact Analysis and HRRCA also evaluated national 
costs and benefits of MMM implementation, with States choosing to 
reduce radon exposure in drinking water through an Alternative Maximum 
Contaminant Level (AMCL) and radon risks in indoor air through MMM 
programs. Based on the National Academy of Sciences recommendations, 
the AMCL level that was evaluated is 4,000 pCi/L. For further 
discussion on the regulatory alternatives considered in this proposed 
rulemaking, see Section XIII.B of this preamble.
    EPA believes that the regulatory approaches proposed in today's 
notice are the most cost-effective options for radon that achieve the 
objectives of the rule, including strong public health protection. For 
a complete discussion of this issue, see EPA's Regulatory Impact 
Analysis and Revised HRRCA for Radon (USEPA 1999f).
2. Impacts on Small Governments
    In preparation for the proposed radon rule, EPA conducted analysis 
on small government impacts. This rule may significantly impact small 
governments. EPA included small government officials or their 
designated representatives in the rule making process. EPA conducted 
four stakeholder meetings on the development of the radon rule which 
gave a variety of stakeholders, including small governments, the 
opportunity for timely and meaningful participation in the regulatory 
development process. Groups such as the National Association of Towns 
and Townships, the National League of Cities, and the National 
Association of Counties participated in the proposed rulemaking 
process. Through such participation and exchange, EPA notified 
potentially affected small governments of requirements under 
consideration and provided officials of affected small governments with 
an opportunity to have meaningful and timely input into the development 
of the regulatory proposal.
    EPA also held a conference call on May 11, 1998, to consult 
directly with representatives of small entities that may be affected by 
the proposed rule. This conference call provided a forum for Small 
Entity Representative (SER) input on key issues related to the proposed 
radon rule. These issues included: (1) Issues related to the rule 
development, such as radon health risks, occurrence of radon in 
drinking water, treatment technologies, analytical methods, and 
monitoring; and (2) issues related to the development and 
implementation of the MMM program guidelines.
    As required by SBREFA, EPA also convened a Small Business Advocacy 
Review (SBAR) Panel to help further identify and incorporate small 
entity concerns into this proposed rulemaking. For a sixty-day period 
starting in July 1998, the Panel reviewed technical background 
information related to this rulemaking, reviewed comments provided by 
the SERs, and met on several occasions with EPA and on one occasion 
with the SERs to identify issues and explore alternative approaches for 
accomplishing environmental goals while minimizing impacts to small 
entities. The SBAR final report on the proposed radon rule, which 
includes a description of the SBAR Panel process and the Panel's 
findings and recommendations, is available in the public docket for 
this proposed rulemaking. For a more detailed discussion of the Panel 
report, see Section XIV.B of this preamble.
    In addition, EPA will educate, inform, and advise small systems, 
including those run by small governments, about the radon rule 
requirements. One of the most important components of this process is 
the Small Entity Compliance Guide, required by the Small Business 
Regulatory Enforcement Fairness Act of 1996 after the rule is 
promulgated. This plain-English guide will explain what actions a small 
entity must take to comply with the rule. Also, the Agency is 
developing fact sheets that concisely describe various aspects and 
requirements of the radon rule.

[[Page 59352]]

D. Paperwork Reduction Act (PRA)

    The information collection requirements in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. An 
Information Collection Request (ICR) document has been prepared by EPA 
(ICR, No. 1923.01) and a copy may be obtained from Sandy Farmer by mail 
at OP Regulatory Information Division, U.S. Environmental Protection 
Agency (2137), 401 M St., SW, Washington, DC 20460; by email at 
[email protected]; or by calling (202) 260-2740. A copy may also be 
downloaded off the Internet at http://www.epa.gov/icr.
    Two types of information will be collected under the proposed radon 
rule. First, information on individual water systems and their radon 
levels will enable the States and EPA to evaluate compliance with the 
applicable MCL or AMCL. This information, most of which consists of 
monitoring results, corresponds to information routinely collected from 
water systems for other types of drinking water contaminants. Radon 
monitoring and reporting will initially be required on a quarterly 
basis for at least one year, but thereafter the frequency may be 
reduced to annually or once every three years depending on the level of 
radon present (see Section VIII.E). Other existing information and 
reporting requirements, such as Consumer Confidence Reports and 
(proposed) public notification requirements, will be marginally 
expanded to encompass radon along with other contaminants. As is the 
case for other contaminants, required information on system radon 
levels must be provided by affected systems and is not considered to be 
confidential.
    The second type of information relates to the MMM program, which is 
EPA's recommended approach for small systems under the proposed radon 
rule. Information of this type includes MMM plans prepared by States as 
well as MMM plans prepared by community ground water systems in States 
that do not develop a MMM plan. The proposed rule allows States to 
prepare MMM plans regardless of whether they are primacy States with 
respect to drinking water programs. EPA will review the MMM plans 
developed by States, and States will review system-level MMM plans. 
These reviews will help ensure that MMM programs are likely to achieve 
meaningful reductions in human health risks from radon exposure. 
Acceptable MMM plans will include a plan for the collection of data to 
track the progress of the MMM program relative to goals established in 
the plans (e.g., data on the number or rate of mitigated homes and the 
number or rate of new homes built radon resistant). EPA will review 
State-level MMM programs at least every five years, and States will 
review system-level programs at least every five years. Information 
related to MMM programs (i.e., the MMM plans and tracking data) is 
mandatory for States that choose to implement an EPA-approved MMM 
program and enforce the AMCL for radon rather than the MCL. Similarly, 
information related to system-level MMM programs is required only from 
systems that comply with the AMCL rather than the MCL and are in States 
that do not have a MMM program in place.
    EPA believes the information discussed previously, on compliance 
with the MCL or AMCL and on MMM programs, is essential to achieving the 
radon-related health risk reductions anticipated by EPA under the 
proposed rule.
    EPA has estimated the burden associated with the specific record 
keeping and reporting requirements of the proposed rule in an 
accompanying Information Collection Request (ICR), which is available 
in the public docket for this proposed rulemaking. Burden means the 
total time, effort, or financial resources expended by persons to 
generate, maintain, retain, or disclose or provide information to or 
for a Federal agency. This includes the time needed to review 
instructions; develop, acquire, install, and utilize technology and 
systems for the purposes of collecting, validating, and verifying 
information, processing and maintaining information, and disclosing and 
providing information; adjust the existing ways to comply with any 
previously applicable instructions and requirements; train personnel to 
be able to respond to a collection of information; search data sources; 
complete and review the collection of information; and transmit or 
otherwise disclose the information.
    EPA has estimated a range of administrative costs for the proposed 
rule. These costs do not include testing and mitigating water or 
testing and mitigating households in the MMM program. The PRA requires 
that average annual cost and labor for administrative costs be 
calculated over a three-year period. These costs are presented next. 
However, because the full implementation of the proposed rule does not 
occur until later years, average annual cost and labor for a 20-year 
period are also presented. These 20-year average annual costs are 
presented by scenarios defined by the proportions of systems that elect 
to develop system-level MMM programs and the proportions of states that 
elect to implement state-wide MMM programs. These scenarios are 
described in detail in Section XIII.G and Section 9 of the RIA (USEPA 
1999f). Based on these analyses, EPA's burden estimates for the 
proposed rule, in both costs and hours, are as follows:
     Administrative costs to community groundwater systems for 
mitigation-related activities are estimated to be $14.6 million per 
year ($357 per system) or 267,625 hours, distributed by system size as 
shown in Table XIV.2. All 40,863 community groundwater systems will 
bear these costs under all scenarios evaluated.
     In the first three years of the rule, there are no 
administrative costs to community groundwater systems for MMM program 
activities.

Table XIV.2.--Administrative Costs to Community Water Systems Associated
   With Water Mitigation and System-Level MMM Programs (Excluding MMM
                         Testing and Mitigation)
------------------------------------------------------------------------
                                                          Administrative
                                          Administrative     costs of
     System size (customers served)       costs of water   system-level
                                           mitigation ($   MMM programs
                                             per year)     ($ per year)
------------------------------------------------------------------------
VVS (25-100)............................       4,485,485               0
VVS (101-500)...........................       4,958,735               0
VS (501-3,300)..........................       3,430,387               0
S (3,301-10,000)........................         848,487               0
M (10,001-100K).........................         491,944               0

[[Page 59353]]

 
L (>100K)...............................          23,579               0
                                         -------------------------------
        Total For All Systems...........      14,598,617               0
------------------------------------------------------------------------

     Administrative costs to States for water mitigation-
related activities are to be approximately $3 million per year (Table 
XIV.3) and 119,625 hours, or approximately $65,400 per year per state 
and 2,600 hours per year per state. Forty-six states bear these costs 
under all scenarios.
    Table XIV.3 presents the costs if 100 percent of all states were to 
incur the specific administrative costs listed. However, no state will 
bear 100 percent of state-wide MMM program costs and 100 percent of 
system-level MMM program costs. These costs will be borne in an inverse 
relationship; e.g., 95 percent of the states will bear administrative 
costs associated with state-wide MMM programs and 5 percent of states 
will bear administrative costs associated with system-level MMM 
programs.

  Table XIV.3.--State Administrative Costs for Water Mitigation and MMM
                                Programs
------------------------------------------------------------------------
                                                                ($ per
                                                                year)
------------------------------------------------------------------------
Water Mitigation...........................................    3,009,713
State-Wide MMM Programs....................................        6,346
System-Level MMM Programs..................................        5,909
    Total State Administrative Costs.......................    3,021,968
------------------------------------------------------------------------

     State administrative costs associated with state-wide MMM 
programs are estimated up to $6,300 per year and up to 140 hours per 
year for the first three years of the rule.
     State administrative costs to review system-level MMM 
programs and related activities are estimated up to $5,900 per year and 
up to 123 hours per year for the first three years of the rule.
     The total State administrative costs (water mitigation, 
state-wide, and system-level MMM programs) are estimated up to 
approximately $3 million per year and 119,887 hours per year.
    Because much of the activity required under the proposed rule 
occurs in later years, this analysis presents average administrative 
costs borne by systems and states over a 20 year period. Again, these 
costs do not include water testing and mitigation or testing and 
mitigating households in MMM programs. In addition, these costs are 
presented by scenarios that are defined by the proportions of systems 
that elect to develop system-level MMM programs and the proportions of 
states that elect to implement state-wide MMM programs.
     Administrative costs to community groundwater systems for 
mitigation-related activities are estimated to be $8.6 million per year 
($211 per system) or 145,547 hours per year, distributed by system size 
as shown in Table XIV.4. All 40,863 community groundwater systems will 
bear these costs under all scenarios evaluated.
     Under Scenario A, administrative costs to community 
groundwater systems for MMM program activities are approximately $45.1 
million per year ($2,452 per system) or 174,000 hours per year for the 
18,388 systems (45 percent of all community groundwater systems) that 
develop and file an MMM plan. The costs are distributed across the 
system size categories as shown in Table XIV.4. Under Scenario E, 
administrative costs to systems are $5.0 million per year or 19,333 
hours per year. The per-system cost is the same as Scenario A, but only 
five percent of systems (2,042) bear these costs.
      
      

 Table XIV.4.--Administrative Costs to Community Water Systems Associated With Water Mitigation and System-Level
                                                  MMM Programs
                                     [Excluding MMM Testing and Mitigation]
----------------------------------------------------------------------------------------------------------------
                                                                                  Administrative  Administrative
                                                                  Administrative     costs of        costs of
                                                                  costs of water   system-level    system-level
                 System size (customers served)                    mitigation ($   MMM programs    MMM programs
                                                                     per year)    under scenario  under scenario
                                                                                   A ($ per year   E ($ per year
----------------------------------------------------------------------------------------------------------------
VVS (25-100)....................................................       2,857,190      14,978,142       1,664,238
VVS (101-500)...................................................       2,923,970      15,328,217       1,703,135
VS (501-3,300)..................................................       2,022,764      10,603,857       1,178,206
S (3,301-10,000)................................................         500,319       2,622,804         291,423
M (10,001-100K).................................................         290,080       1,520,674         168,964
L (>100K).......................................................          13,904          72,886           8,097
                                                                 -----------------------------------------------
        Total for All Systems...................................       8,608,226      45,126,581       5,014,065
----------------------------------------------------------------------------------------------------------------


[[Page 59354]]

     Total administrative costs to community water systems 
(water mitigation plus MMM programs) range from $11 million per year 
under Scenario E to $51.2 million under Scenario A or 165,000 hours 
under Scenario E to 320,000 hours under Scenario A. The costs are 
distributed across the various system sizes as shown in Table XIV.5.

    Table XIV.5.--Total Administrative Costs Water Mitigation and MMM
                Programs to Community Groundwater Systems
------------------------------------------------------------------------
                                               Total           Total
                                          administrative  administrative
     System size (customers served)         costs under     costs under
                                          scenario A  ($   scenario E ($
                                             per year)       per year)
------------------------------------------------------------------------
VVS (25-100)............................      16,990,791       3,676,887
VVS (101-500)...........................      17,387,906       3,762,824
VS (501-3,300)..........................      11,238,829       1,813,178
S (3,001-10,000)........................       3,412,697       1,081,316
M (10,001-100,000)......................       1,873,106         521,396
L (100,000).............................         256,893         192,105
                                         -------------------------------
        Total for All Systems...........      51,160,223      11,047,707
------------------------------------------------------------------------

     Administrative costs to States for water mitigation-
related activities are estimated to be approximately $2.5 million per 
year (Table XIV.6) or approximately $53,900 per year per state. Total 
state burden is approximately 100,000 hours per year. Forty-six states 
bear these costs under all scenarios.

  Table XIV.6.--State Administrative Costs for Water Mitigation and MMM
                                Programs
                              [$ per year]
------------------------------------------------------------------------
                                            Scenario A      Scenario E
------------------------------------------------------------------------
Water Mitigation........................       2,477,299       2,477,299
State-Wide MMM Programs.................       2,926,691       5,560,713
System-Level MMM Programs...............       7,830,995         870,111
                                         -------------------------------
        Total State Administrative Costs      13,234,985       8,908,123
------------------------------------------------------------------------

     State administrative costs associated with state-wide MMM 
programs are estimated to be $2.9 million dollars ($127,200 per state 
across 23 states) or 123,000 hours per year under Scenario A. Under 
Scenario E, estimated state administrative costs of state-level MMM 
programs are estimated to be $5.6 million (again $126,400 per state, 
but under this scenario, 44 states bear the costs) or 233,000 hours per 
year for all 44 states.
     State administrative costs to review system-level MMM 
programs and related activities are estimated to be $7.8 million per 
year or 316,410 hours per year under Scenario A and approximately 
$870,000 per year or 35,157 hours per year under Scenario E. In both 
cases the cost per state is approximately $371,000 per year, with 21 
states affected under Scenario A and two states affected under Scenario 
E.
     The total State administrative costs (water mitigation, 
state-wide, and system-level MMM programs) are estimated to be $13.2 
million per year or 538,845 hours per year under Scenario A and $8.9 
million per year or 367,878 hours per year under Scenario E.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations are listed in 40 CFR Part 9 and 48 CFR Chapter 15.
    Comments are requested on the Agency's need for this information, 
the accuracy of the provided burden estimates, and any suggested 
methods for minimizing respondent burden, including through the use of 
automated collection techniques. Send comments on the ICR to the 
Director, OP Regulatory Information Division, U.S. Environmental 
Protection Agency (2137), 401 M St., SW., Washington, DC 20460 and to 
the Office of Management and Budget, 725 17th St., NW., Washington, DC 
20503, marked ``Attention: Desk Officer for EPA''. Include the ICR 
number (1923.01) in any correspondence. Since OMB is required to make a 
decision concerning the ICR between 30 and 60 days after November 2, 
1999, a comment to OMB is best assured of having its full effect if OMB 
receives it by December 2, 1999. The final rule will respond to any OMB 
or public comments on the information collection requirements contained 
in this proposal.

E. National Technology Transfer and Advancement Act (NTTAA)

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Public Law 104-113, Sec. 12(d) (15 U.S.C. 272 
note) directs EPA to use voluntary consensus standards in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus standards 
are technical standards (e.g., materials specifications, test methods, 
sampling procedures, and business practices) that are developed or 
adopted by voluntary consensus standard bodies. The NTTAA directs EPA 
to provide Congress, through OMB, explanations when the Agency decides 
not to use available and applicable voluntary consensus standards.
    EPA's process for selecting the analytical test methods is 
consistent with Section 12(d) of the NTTAA. EPA performed literature 
searches to identify analytical methods from industry, academia, 
voluntary consensus standard bodies, and other parties that could be

[[Page 59355]]

used to measure radon in drinking water.
    This proposed rulemaking involves technical standards. EPA proposes 
to use Standard Method 7500-Rn, which is specific for radon 222 (radon) 
in drinking water, for both the MCL and AMCL for radon in drinking 
water. This method meets the objectives of the rule because it 
accurately and reliably detects radon in drinking water below 100 pCi/
L. Standard Method 7500-Rn was approved by the Standard Methods 
Committee in 1996 and is described in the ``Standard Methods for the 
Examination of Water and Wastewater (19th Edition Supplement)'' which 
was prepared and published jointly by the American Public Health 
Association, American Water Works Association, and Water Environment 
Federation. Additional information on this method is shown in Section 
VIII.B.2 of today's preamble.
    EPA is also proposing the use of the American Society for Testing 
and Materials (ASTM) Standard Test Method for Radon in Drinking Water 
(designation: D5072-92) for the AMCL for radon in drinking water. This 
method is specific for radon in drinking water, but has been shown to 
accurately and reliably detect radon only at concentrations above 1,500 
pCi/L and thus is only useful for the AMCL. ASTM's Standard Test Method 
for Radon in Drinking Water was adopted by ASTM in 1992 and is 
described in the Annual Book of ASTM Standards. Additional information 
on this method is shown in Section VIII.B.2 of this preamble.
    As discussed in Section VIII.B (Analytical Methods) of this 
preamble, EPA is in the process of adopting the Performance-Based 
Measurement System (PBMS) to allow greater flexibility in compliance 
monitoring for this proposed rule and for future rules. For further 
information on PBMS, see Section VIII.D.
    EPA welcomes comments on this aspect of the proposed rulemaking 
and, specifically, invites the public to identify potentially-
applicable voluntary consensus standards and to explain why such 
standards should be used in this regulation.

F. Executive Order 12898: Environmental Justice

    Executive Order 12898 ``Federal Actions To Address 
EnviroPopulations and Low-Income Populations,'' 59 FR 7629 (February 
16, 1994) establishes a Federal policy for incorporating environmental 
justice into Federal agency missions by directing agencies to identify 
and address disproportionately high and adverse human health or 
environmental effects of its programs, policies, and activities on 
minority and low-income populations. The Agency has considered 
environmental justice related issues concerning the potential impacts 
of this action and has consulted with minority and low-income 
stakeholders by convening a stakeholder meeting via video conference 
specifically to address environmental justice issues.
    As part of EPA's responsibilities to comply with E.O. 12898, the 
Agency held a stakeholder meeting via video conference on March 12, 
1998, to address various components of pending drinking water 
regulations; and how they may impact sensitive sub-populations, 
minority populations, and low-income populations. Topics discussed 
included treatment techniques, costs and benefits, data quality, health 
effects, and the regulatory process. Participants included national, 
State, tribal, municipal, and individual stakeholders. EPA conducted 
the meeting by video conference call between eleven cities. This 
meeting was a continuation of stakeholder meetings that started in 1995 
to obtain input on the Agency's Drinking Water programs. The major 
objectives for the March 12, 1998, meeting were: (1) Solicit ideas from 
Environmental Justice (EJ) stakeholders on known issues concerning 
current drinking water regulatory efforts; (2) identify key issues of 
concern to EJ stakeholders; and (3) receive suggestions from EJ 
stakeholders concerning ways to increase representation of EJ 
communities in OGWDW regulatory efforts. In addition, EPA developed a 
plain-English guide specifically for this meeting to assist 
stakeholders in understanding the multiple and sometimes complex issues 
surrounding drinking water regulation. A meeting summary for the March 
12, 1998, stakeholder meeting is available in the public docket for 
this proposed rulemaking.
    Stakeholders have raised concerns that this action may have a 
disproportionate impact on low-income and minority populations. The 
rule framework and in particular, the MMM program coupled with a 4,000 
pCi/L AMCL, were discussed with EJ stakeholders at the March 12, 1998, 
meeting. Key issues of concern with the MMM/AMCL approach included: (1) 
The potential for an uneven distribution of benefits across water 
systems and society; (2) the cost of air remediation to apartment 
dwellers; and (3) the concern that the approach could provide water 
systems and State governments a ``loophole'' through which they could 
escape the responsibility of providing appropriate protection from 
radon exposures.
    The Agency considered equity-related issues concerning the 
potential impacts of MMM program implementation. There is no factual 
basis to indicate that minority and low income or other communities are 
more or less exposed to radon in drinking water than the general 
public. However, some stakeholders expressed more general concerns 
about equity in radon risk reduction that could arise from the MMM/AMCL 
framework outlined in SDWA. One concern is the potential for an uneven 
distribution of risk reduction benefits across water systems and 
society. Under the proposed framework for the rule, customers of CWSs 
complying with the AMCL could be exposed to a higher level of radon in 
drinking water than if the MCL were implemented, though this level 
would not be higher than the background concentration of radon in 
ambient air. However, these CWS customers could also save the cost, 
through lower water rates, of installing treatment technology to comply 
with the MCL. Under the proposed regulation, CWSs and their customers 
have the option of complying with either the AMCL (associated with a 
State or local MMM program) or the MCL.
    EPA believes it is important that these issues and choices be 
considered in an open public process as part of the development of MMM 
program plans. Therefore, EPA has incorporated requirements into the 
proposed rule that provide a framework for consideration of equity 
concerns with the MMM/AMCL. The proposed rule includes requirements for 
public participation in the development of MMM program plans, as well 
as for notice and opportunity for public comment. EPA believes that the 
requirement for public participation will result in State and CWS 
program plans that reflect and meet their different constituents needs 
and concerns and that equity issues can be most effectively dealt with 
at the State and local levels with the participation of the public. In 
developing their MMM program plans, States and CWSs are required to 
document and consider all significant issues and concerns raised by the 
public. EPA expects and strongly recommends that States and CWSs pay 
particular attention to addressing any equity concerns that may be 
raised during the public participation process. In addition, EPA 
believes that providing CWS customers with information about the health 
risks of radon and on the

[[Page 59356]]

AMCL and MMM program option will help to promote understanding of the 
health risks of radon in indoor air, as well as in drinking water, and 
help the public to make informed choices. To this end, EPA is requiring 
CWSs to alert consumers to the MMM approach in their State in consumer 
confidence reports issued between publication of the final radon rule 
and the compliance dates for implementation of MMM programs. This will 
include information about radon in indoor air and drinking water and 
where consumers can get additional information.
    The proposed requirements include the following: (1) A description 
of processes the State used to provide for public participation in the 
development of its MMM program plan; (2) a description of the nature 
and extent of public participation that occurred, including a list of 
groups and organizations that participated; (3) a summary describing 
the recommendations, issues, and concerns arising from the public 
participation process and how these were considered in developing the 
State's MMM program plan; (4) a description of how the State made 
information available to the public to support informed public 
participation, including information on the State's existing indoor 
radon program activities and radon risk reductions achieved, and on 
options considered for the MMM program plan along with any analyses 
supporting the development of such options; and (5) the State must 
provide notice and opportunity for public comment on the plan prior to 
submitting it to EPA.
    The public is invited to comment on this aspect of the proposed 
rulemaking and, specifically, to recommend additional methods to 
address EJ concerns with the MMM/AMCL approach for treating radon in 
drinking water.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    Executive Order 13045, ``Protection of Children from Environmental 
Health Risks and Safety Risks,'' 62 FR 19885 (April 23, 1997) applies 
to any rule that: (1) Is determined to be ``economically significant'' 
as defined under E.O. 12866, and (2) concerns an environmental health 
or safety risk that EPA has reason to believe may have a 
disproportionate effect on children. If the regulatory action meets 
both criteria, the Agency must evaluate the environmental health or 
safety effects of the planned rule on children, and explain why the 
planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the Agency.
    This proposed rule is not subject to the Executive Order because 
the Agency does not have reason to believe the environmental health 
risks or safety risks addressed by this action present a 
disproportionate risk to children. Based on the risk assessment for 
radon in drinking water developed by the NAS, children were not 
identified as being disproportionately impacted by radon. The Committee 
on Risk Assessment of Exposure to Radon in Drinking Water that 
conducted the National Research Council Risk Assessment of Radon in 
Drinking Water Study (NAS 1999b) concluded, except for the lung cancer 
risk to smokers, there is insufficient scientific information to permit 
quantitative evaluation of radon risks to susceptible subpopulations 
such as infants, children, pregnant women, elderly, and seriously ill 
persons.
    The National Academy of Sciences Committee on the Biological 
Effects of Ionizing Radiation (BEIR VI) (NAS 1999a) noted that there is 
only one study (tin miners in China) that provides data on whether 
risks from radon progeny are different for children, adolescents, and 
adults. Based on this study, the committee concluded that there was no 
clear indication of an effect of age at exposure, and the committee 
made no adjustments in the model for exposures received at early ages 
(NAS 1999a). Nonetheless, we evaluated the environmental health or 
safety effects of radon in drinking water on children. The results of 
this evaluation are contained in Section XII of this preamble. Copies 
of the documents used to evaluate the environmental health or safety 
effects of radon in drinking water on children, including the NAS 
Reports, have been placed in the public docket for this proposed 
rulemaking.
    The public is invited to submit or identify peer-reviewed studies 
and data, of which EPA may not be aware, that assessed results of early 
life exposure to radon in drinking water.

H. Executive Orders on Federalism

    Under Executive Order 12875, ``Enhancing the Intergovernmental 
Partnership,'' 58 FR 58093 (October 28, 1993) EPA may not issue a 
regulation that is not required by statute and that creates a mandate 
upon State, local, or tribal government, unless the Federal government 
provides the funds necessary to pay the direct compliance costs 
incurred by those governments, or EPA consults with those governments. 
If EPA complies by consulting, E.O. 12875 requires EPA to provide to 
the Office of Management and Budget a description of the extent of 
EPA's prior consultation with representatives of affected State, local, 
and tribal governments, the nature of their concerns, any written 
communications from the governments, and a statement supporting the 
need to issue the regulation. In addition, E.O. 12875 requires EPA to 
develop an effective process permitting elected officials and other 
representatives of State, local, and tribal governments ``to provide 
meaningful and timely input in the development of regulatory proposals 
containing significant unfunded mandates.''
    EPA has concluded that this rule will create a mandate on State, 
local, and tribal governments and the Federal government will not 
provide the funds necessary to pay the direct costs incurred by State, 
local, and tribal governments in complying with the mandate. In 
developing this rule, EPA consulted with State, local, and tribal 
governments to enable them to provide meaningful and timely input in 
the development of this rule.
    As described in Section XIV.C.1.e, EPA held extensive meetings with 
a variety of State and local representatives, who provided meaningful 
and timely input in the development of the proposed rule. Summaries of 
the meetings have been included in the public docket for this proposed 
rulemaking. See Sections XIV.C.1.e and XIV.C.1.f for summaries of the 
extent of EPA's consultation with State, local, and tribal governments; 
the nature of the governments' concerns; and EPA's position supporting 
the need to issue this rule.
    On August 4, 1999, President Clinton issued a new executive order 
on federalism, Executive Order 13132 [64 FR 43255 (August 10, 1999)], 
which will take effect on November 2, 1999. In the interim, the current 
Executive Order 12612 [52 FR 41685 (October 30, 1987)], on federalism 
still applies. This rule will not have a substantial direct effect on 
States, on the relationship between the national government and the 
States, or on the distribution of power and responsibilities among 
various levels of government, as specified in Executive Order 12612. 
``This proposed rule establishes a National Primary Drinking Water 
Regulation (NPDWR) for the control of radon. This regulation is 
required by section 1412(b)(13) of the Safe Drinking Water Act, as 
amended. EPA conducted extensive discussions with States and local 
governments in developing this proposal, and significant flexibility is 
provided in implementing these regulations.''

[[Page 59357]]

I. Executive Order 13084: Consultation and Coordination With Indian 
Tribal Governments

    Under Executive Order 13084, ``Consultation and Coordination with 
Indian Tribal Governments,'' 63 FR 27655 (May 19, 1998) EPA may not 
issue a regulation that is not required by statute, that significantly 
or uniquely affects the communities of Indian tribal governments, and 
that imposes substantial direct compliance costs on those communities, 
unless the Federal government provides the funds necessary to pay the 
direct compliance costs incurred by the tribal governments, or EPA 
consults with those governments. If EPA complies by consulting, E.O. 
13084 requires EPA to provide the Office of Management and Budget, in a 
separately identified section of the preamble to the rule, a 
description of the extent of EPA's prior consultation with 
representatives of affected tribal governments, a summary of the nature 
of their concerns, and a statement supporting the need to issue the 
regulation. In addition, E.O. 13084 requires EPA to develop an 
effective process permitting elected officials and other 
representatives of Indian tribal governments ``to provide meaningful 
and timely input in the development of regulatory policies on matters 
that significantly or uniquely affect their communities.''
    EPA has concluded that this rule will significantly or uniquely 
affect communities of Indian tribal governments. It will impose 
substantial direct compliance costs on such communities, and the 
Federal government will not provide the funds necessary to pay the 
direct costs incurred by the tribal governments in complying with the 
rule. In developing this rule, EPA consulted with representatives of 
tribal governments pursuant to both E.O. 12875 and E.O. 13084. 
Summaries of the meetings have been included in the public docket for 
this proposed rulemaking. EPA's consultation, the nature of the 
governments' concerns, and EPA's position supporting the need for this 
rule are discussed in Section XIV.C.2 of this preamble.

J. Request for Comments on Use of Plain Language

    Executive Order 12866 and the President's memorandum of June 1, 
1998, require each agency to write all rules in plain language. We 
invite your comments on how to make this proposed rule easier to 
understand. For example:
     Have we organized the material to suit your needs?
     Are the requirements in the rule clearly stated?
     Does the rule contain technical language or jargon that 
isn't clear?
     Would a different format (grouping and order of sections, 
use of headings, paragraphing) make the rule easier to understand?
     Would more (but shorter) sections be better?
     Could we improve clarity by adding tables, lists, or 
diagrams?
     What else could we do to make the rule easier to 
understand?

Stakeholder Involvement

XV. How Has the EPA Provided Information to Stakeholders in 
Development of This NPRM?

A. Office of Ground Water and Drinking Water Website

    EPA's Office of Ground Water and Drinking Water maintains a website 
on radon at the following address: http://www.epa.gov/safewater/
radon.html. Documents are placed on the website for public access.

B. Public Meetings

    EPA has consulted with a broad range of stakeholders and technical 
experts. Participants in a series of stakeholder meetings held in 1997 
and 1998 included representatives of public water systems, State 
drinking water and indoor air programs, tribal water utilities and 
governments, environmental and public health groups, and other Federal 
agencies. EPA convened an expert panel in Denver in November, 1997, to 
review treatment technology costing approaches. The panel made a number 
of recommendations for modification to EPA cost estimating protocols 
that have been incorporated into the radon cost estimates. EPA also 
consulted with a subgroup of the National Drinking Water Advisory 
Council (NDWAC) on evaluating the benefits of drinking water 
regulations. The NDWAC was formed in accordance with the Federal 
Advisory Committee Act (FACA) to assist and advise EPA. A variety of 
stakeholders participated in the NDWAC benefits working group, 
including utility company staff, environmentalists, health 
professionals, State water program staff, a local elected official, 
economists, and members of the general public.
    EPA conducted one-day public meetings in Washington, D.C. on June 
26, 1997; in San Francisco, California on September 2, 1997; and in 
Boston, Massachusetts on October 30, 1997, to discuss its plans for 
developing a proposed NPDWR for radon-222. EPA presented information on 
issues related to developing the proposed NPDWR and solicited 
stakeholder comments at each meeting. EPA also held a series of 
conference calls in 1998 and 1999 with State drinking water and indoor 
air programs, to discuss issues related to developing guidelines for 
multiedia mitigation programs. EPA also held a public meeting in 
Washington, DC. on March 16, 1999, to discuss the HRRCA published on 
February 26, 1999, and the multimedia mitigation framework.

C. Small Entity Outreach

    EPA has conducted outreach directly to representatives of small 
entities that may be affected by the proposed rule, as part of SBREFA. 
A full discussion of the small entity outreach is in Section XIV.B.6 
``Significant Regulatory Alternatives and SBAR Panel Recommendations.''

D. Environmental Justice Initiatives

    In order to uphold Executive Order 12898, ``Federal Actions to 
Address Environmental Justice in Minority Populations and Low-Income 
Populations,'' EPA's Office of Ground Water and Drinking Water convened 
a public meeting in Washington, DC in March 1998 to discuss ways to 
involve minority, low-income, and other sensitive subgroups in the 
stakeholder process and to obtain input on the proposed radon rule. The 
meeting was held in a video-conference format linking EPA Regions I 
through IX to involve as many stakeholders as possible. EPA has taken 
the concerns and issues raised by the environmental justice community 
into account while setting the MCL, MCLG, and AMCL for radon. For more 
information on the March 1998 environmental justice meeting, and on EPA 
proposals to address concerns of stakeholders, see Section XIV.F of 
this Preamble.

E. AWWA Radon Technical Work Group

    The American Water Works Association (AWWA) convened a ``Radon 
Technical Work Group,'' in 1998 that provided technical input on EPA's 
update of technical analyses (occurrence, analytical methods, and 
treatment technology), and discussed conceptual issues related to 
developing guidelines for multimedia mitigation programs. Members of 
the Radon Technical Work Group included representatives from State 
drinking water and indoor air programs, public water systems, drinking 
water testing laboratories, environmental groups and the U.S. 
Geological Survey.

[[Page 59358]]

Background

XVI. How Does EPA Develop Regulations to Protect Drinking Water?

A. Setting Maximum Contaminant Level Goal and Maximum Contaminant Level

    EPA sets an MCLG and MCL or treatment technology for each regulated 
contaminant. The MCLG is based on analysis of health effects of the 
contaminant. Based on the carcinogenicity of ionizing radiation, and 
the NAS' current recommendation for a linear, non-threshold 
relationship between exposure to radon and cancer in humans (NAS 
1999a), the Agency is proposing an MCLG of zero for radon in drinking 
water.
    A drinking water MCL applies to finished (treated) drinking water 
as supplied to customers. The SDWA generally requires that EPA set the 
MCL for each contaminant as close as feasible to the corresponding 
MCLG, based on available technology and taking costs into account. For 
example, if the analytical methods will only allow a relatively 
confident measure of a contaminant at a certain level, then the MCL 
cannot practically be set below that level. In addition, the cost of 
water treatment technologies is considered. If treatment capabilities 
are limited then the MCL must be set at a level that is found to be 
feasible. The MCL set by EPA must be protective of public health.
    The 1996 amendments to SDWA require the Administrator to do a cost-
benefit analysis of the MCLs under consideration and to make a 
determination as to whether the benefits of an MCL under consideration 
justify the costs (1412(b)(3)(C)). The Administrator may set an MCL at 
a level less stringent than the feasible level if he/she finds that the 
benefits of the feasible MCL do not justify the costs (1412(b)(6)(A)). 
There are certain exceptions to the use of this authority 
(1412(b)(6)(B) and (C)).

B. Identifying Best Available Treatment Technology

    As discussed also in Section VIII of this preamble, EPA identifies 
one or more water treatment technologies (i.e., best available 
treatment (BAT)) found to be effective in removing the contaminant from 
drinking water and capable of meeting the MCL. There are a number of 
physical, chemical, and other means used by such treatment technologies 
for removing the contaminant, or in some cases destroying the 
contaminant or otherwise changing the contaminant's composition. In 
assessing potential BATs, EPA examines removal efficiency, cost to 
purchase and maintain, compatibility with other processes, and other 
factors. Most of the information cited by EPA in this context is 
gleaned from technical literature, including research studies covering 
pilot or full scale treatments. If some of the treatments identified 
are found to be most efficient, practical and economical, EPA places 
these on the BAT list and on occasion may provide guidance on other 
treatments that may have certain limitations.

C. Identifying Affordable Treatment Technologies for Small Systems

    The 1996 Amendments to the SDWA directed EPA to identify treatment 
technologies that are affordable for small water systems. EPA is 
charged with identifying affordable treatments for three small system 
population categories: systems serving from 25 to 500, 501 to 3,300, 
and 3,301 to 10,000 persons. A designated ``compliance technology'' for 
these small systems may be a technology that is affordable and that 
achieves compliance with the MCL or a treatment technique requirement. 
Possible compliance technologies may include packaged or modular 
systems, and point-of-entry (POE) or point-of-use (POU) type treatment 
units. As with BAT designations, the compliance technology(ies) 
selected by EPA must be based upon available information from technical 
journals and/or qualified research studies.
    EPA must also identify affordable ``variance technologies'' which 
are to be installed by a public water system after the system has 
applied to the responsible primacy agency for a variance, i.e., a 
``small system variance.'' This variance applies only to systems 
serving fewer than 10,000 people. It also applies only in cases where 
an affordable technology is not available to achieve compliance with an 
MCL (or treatment technique requirement) yet still will be protective 
of public health. One of the requirements for systems that have 
obtained a variance is to install and maintain the variance technology 
in accordance with the listing by EPA, which may be specific to system 
size and/or dependent upon source water quality. A small system 
variance may only be obtained if compliance with the MCL through 
alternate source, treatment, or restructuring options are deemed not to 
be affordable for that system.
    Small system variances are not available to meet MCL or treatment 
technique requirements promulgated prior to 1986, nor for regulations 
addressing microbiological contamination of water.

D. Requirements for Monitoring, Quality Control, and Record Keeping

    Water systems are responsible for conducting monitoring of drinking 
water to ensure that it meets all drinking water standards. To do this, 
water systems and States use analytical methods set out in EPA 
regulations.
    EPA is responsible for evaluating analytical methods developed for 
drinking water and approves those methods that it determines meet 
Agency requirements. Laboratories analyzing drinking water compliance 
samples must be certified by the EPA or the State.
    Whether addressing regulated or unregulated contaminants, EPA 
establishes requirements as to how often water systems must monitor for 
the presence of the subject contaminant. Water systems serving larger 
populations generally must conduct more monitoring (temporally and 
spatially) because there is a greater potential human health impact of 
any violation, and because of the physical extent of larger water 
systems (e.g., miles of pipeline carrying water). Small water systems 
can receive variances or exemptions from monitoring in limited 
circumstances. In addition, under certain conditions, a State may have 
the option to modify monitoring requirements on an interim or a 
permanent basis for regulated contaminants, with a few exceptions. 
States may use this flexibility to reduce monitoring requirements for 
systems with low risk of incurring a violation.

E. Requirements for Water Systems to Notify Customers of Test Results 
if Not in Compliance

    Each owner or operator of a public water system must notify 
customers if the system has failed to comply with an MCL or treatment 
technique requirement, or a testing procedure required by EPA 
regulation. A system must notify its customers if the system is subject 
to a variance (due to an inability to comply with an MCL).
    The form of this notification must be readily understood and 
delivered via mail or direct delivery, through an annual report, or in 
the first water billing cycle following such a drinking water 
violation. The notification must also contain important information 
about the contaminant so that consumers will be aware of any particular 
hazards involved; the notification may indicate whether water can/
cannot be consumed or used for bathing, whether boiling drinking water

[[Page 59359]]

will make it safe; or whether storing water before use may be 
advisable.

F. Approval of State Drinking Water Programs to Enforce Federal 
Regulations

    Section 1413 of the SDWA sets requirements that a State or eligible 
Indian tribe must meet in order to maintain primary enforcement 
responsibility (primacy) for its public water systems. These include 
(1) adopting drinking water regulations that are no less stringent than 
Federal NPDWRs; (2) adopting and implementing adequate procedures for 
enforcement; (3) keeping records and making reports available on 
activities that EPA requires by regulation; (4) issuing variances and 
exemptions (if allowed by the State) under conditions no less stringent 
than allowed by Sections 1415 and 1416; (5) adopting and being capable 
of implementing an adequate plan for the provision of safe drinking 
water under emergency situations, and (6) adopting authority for 
administrative penalties.
    In addition to adopting the basic primacy requirements, States may 
be required to adopt special primacy provisions pertaining to a 
specific regulation. These regulation-specific provisions may be 
necessary where implementation of the NPDWR involves activities beyond 
those in the generic rule. States are required by 40 CFR 142.12 to 
include these regulation-specific provisions in an application for 
approval of their program revisions.

XVII. Important Technical Terms

    Adsorption: In the case of the water/solid interface, the 
accumulation of a dissolved chemical species at the interface between a 
solid material (e.g., granular activated carbon) and water.
    Alpha particle: A radioactivity decay product consisting of the 
charged helium-4 nucleus (two protons and two neutrons with a positive 
ionic charge of two, +2). Alpha particles are relatively heavy (8000 
times as heavy as the beta particle) and are quickly absorbed by 
surrounding matter. The properties of alpha particles are such that 
they are only a health hazard if the emitter is in contact with living 
tissue. When outside the body, they do not penetrate the skin and are 
stopped by a few centimeters of air. However, when inside the body 
(breathed in or ingested), the alpha particle may ionize molecules 
within cells or may form ``free radicals'' (an atom or chemical group 
that contains an unpaired electron and which is very chemically 
reactive), either of which may result in the disruption of normal 
cellular metabolism and produce changes that affect cell replication 
which may induce cancerous cellular growth.
    Bq (becquerel): An alternative unit of radioactivity is the Bq, 
which is equal to 1 disintegration per second. One pCi is equal to 
0.037 Bq, and one Bq is equal to 27 pCi.
    cpm/dpm: Counts per minute divided by radioactive disintegrations 
per minute; counting efficiency as determined by the counts per minute 
detected relative to the predicted disintegrations per minute in a 
well-characterized standard.
    Half-life: The time required for one-half of a population of 
radioactive isotopes to decay; in the case of radioactive contaminants 
dissolved in water, it is the time for the concentration of the 
radioactive contaminant to decrease by a factor of two due to 
radioactive decay.
    Heterotrophic Plate Count: A laboratory procedure for estimating 
the total bacterial count in a water sample (or ``bacterial density'').
    Individual Risk: The risk to a person from exposure to radon in 
water is calculated by multiplying the concentration of radon in the 
water (pCi/L) by the unit risk factor (risk per pCi/L) for the exposure 
pathway of concern (ingestion, inhalation).
    Isotopes: Two or more forms of an atomic element having the same 
number of protons, but differing in the number of neutrons. Some 
isotopes are stable (not radioactive) and some are radioactive, 
depending upon the ratio of neutrons and protons.
    Monte Carlo Analysis:: Method of approximating a distribution of 
model solutions by sampling from simulated ``random picks'' from 
distributions of model input values.
    pCi (picocurie):: a unit of radioactivity equal to 0.037 
radioactive disintegrations per second.
    Percentile: For any set of observations, the ``pth percentile 
value'' is the value such that p% of the observations fall below the 
pth percentile value and (100-p)% fall above it.
    pH: Numerical scale for measuring the relative acidity or basicity 
of an aqueous solution; values less than 7 are acidic (becoming 
increasingly so as they decrease) and above 7 are basic (becoming 
increasing so as they increase).
    Radioactivity: The spontaneous disintegration of unstable atomic 
nuclei (central core of an atom), resulting in the formation of new 
atomic elements (daughter products), which may or may not themselves be 
radioactive, and the discharge of alpha particles, beta particles, or 
photons (other decay particles are known, but their parent isotopes do 
not occur in drinking water).
    Removal efficiency: A measure of the ability of a particular water 
treatment process to remove a contaminant of interest; defined as the 
concentration of the contaminant in the treated water (effluent) 
divided by the concentration of the contaminant in the source water 
(influent).
    WL (working level): Any combination of radioactive chemicals that 
result in an emission of 1.3  x  105 MeV of alpha particle 
energy. One WL is approximately the total amount of energy released by 
the short-lived progeny in equilibrium with 100 pCi of radon.
    Working Level Month (WLM): 170 hours of exposure to one Working 
Level (WL) of radon progeny.
    Unit Risk: The risk from lifetime exposure, via the inhalation and 
ingestion exposure routes, to water containing an unit concentration (1 
pCi/L) of radon.

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U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Suggested Guidelines for Disposal of Drinking Water 
Treatment Wastes Containing Radioactivity. Draft. [June 1994] [USEPA 
1994b]
U.S. Environmental Protection Agency, Office of Science and 
Technology, Office of Radiation and Indoor Air, Office of Policy, 
Planning, and Evaluation. Uncertainty Analysis of Risks Associated 
with Exposure to Radon in Drinking Water. EPA 822-R-96-005. 
Washington, DC. [March 1995] [USEPA 1995]
U.S. Environmental Protection Agency, Office of Research and 
Development. Exposure Factors Handbook. Volume III--Activity 
Factors. NCEA-W-0005, Washington, DC. [April 1996] [USEPA 1996]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Community Water System Survey. Volume II: Detailed 
Survey Results Table and Methodology Report. EPA-815-R-97-001b. 
[January 1997] [USEPA 1997a]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Manual for the Certification of Laboratories 
Analyzing Drinking Water. EPA 815-B-97-001. [March 1997] [USEPA 
1997b]
U.S. Environmental Protection Agency. Tritium in Water Performance 
Evaluation Study, A Statistical Evaluation of the August 8, 1997 
Data, EPA/600/R-97/097 [September 1997] [USEPA 1997c]
U.S. Environmental Protection Agency. Model Systems Report (Draft). 
Prepared by Science Applications International Corporation for the 
Office of Ground Water and Drinking Water. [March 1998] [USEPA 
1998a]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Information for Small Entity Representatives 
Regarding the Radon in Drinking Water Rule, Washington, D.C. [April 
1998] [USEPA 1998b]
U.S. Environmental Protection Agency, Small Business Advocacy Review 
Panel for the Radon Rule. Final Report of the SBREFA Small Business 
Advocacy Review Panel on EPA's Planned Proposed Rule for National 
Primary Drinking Water Regulation: Radon, Washington, D.C. 
[September 1998] [USEPA 1998c]
U.S. Environmental Protection Agency, Office of Radiation and Indoor 
Air. Health Risks from Low-Level Environmental Exposure to 
Radionuclides. Federal Guidance Report No. 13. Part I--Interim 
Version. EPA 401/R-97-014. Washington, DC. [1998] [USEPA 1998d]
U.S. Environmental Protection Agency. National-Level Affordability 
Criteria Under the 1996 Amendments to the Safe Drinking Water Act. 
Final Draft Report. Prepared by International Consultants, Inc. for 
EPA. [August 19, 1998] [USEPA 1998e]
U.S. Environmental Protection Agency, Office of Water. Variance 
Technology Findings for Contaminants Regulated before 1996. EPA 815-
R-98-003. Washington, D.C. [September 1998] [USEPA 1998f]
U.S. Environmental Protection Agency. Cost Evaluation of Small 
System Compliance Options: Point-of-Use and Point-of-Entry Treatment 
Units. Prepared by the Cadmus Group for EPA. [September 1998] [USEPA 
1998g]
U.S. Environmental Protection Agency. Guide for Implementing Phase I 
Water Treatment Cost Upgrades. Prepared by Science Applications 
International Corporation for EPA. [September 1998] [USEPA 1998h]
U.S. Environmental Protection Agency, Small System Compliance 
Technology List for the Non-Microbial Contaminants Regulated Before 
1996. EPA 815-R-98-002. [September 1998] [USEPA 1998i]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Evaluation of Full-Scale Treatment Technologies at 
Small Drinking Water Systems: Summary of Available Cost and 
Performance Data. [December 1998] [USEPA 1998j]
U.S. Environmental Protection Agency. Evaluation of Central 
Treatment Options as Small System Treatment Technologies. Prepared 
by Science Applications International Corporation for EPA. [January 
1999] [USEPA 1999a]
U.S. Environmental Protection Agency, Office of Science and 
Technology. Draft Criteria Document for Radon in Drinking Water. 
Washington, DC. [July 1999] [USEPA 1999b]
U.S. Environmental Protection Agency. Co-Occurrence of Drinking 
Water Contaminants. Primary and Secondary Constituents, with two 
sets of appendices:

[[Page 59362]]

Appendices A-D and Appendices E-F (Draft Report). Prepared by 
Science Applications International Corporation for EPA. [May 21, 
1999] [USEPA 1999c]
U.S. Environmental Protection Agency. Co-Occurrence of Drinking 
Water Contaminants: Initial Tables of Statistical Analysis of 
Secondary Constituents. Draft Prepared by Science Applications 
International Corporation for EPA. [February 2, 1999] [USEPA 1999d]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Drinking Water Baseline Handbook (First Edition). 
[March 2, 1999] [USEPA 1999e]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Regulatory Impact Analysis and Revised Health Risk 
Reduction and Cost Analysis for Radon in Drinking Water (Draft). 
[July 1999] [USEPA 1999f]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Methods Occurrence, and Monitoring Document for 
Radon, Draft. [August 6, 1999] [USEPA 1999g]
U.S. Environmental Protection Agency. Technologies and Costs for the 
Removal of Radon from Drinking Water. Prepared by SAIC for EPA. [May 
1999] [USEPA 1999h]
U.S. Environmental Protection Agency. Technical Notes on Estimating 
the Health Risk Reduction from EPA's Indoor Radon Program. Brian 
Gregory, Office of Radiation and Indoor Air. Washington, DC. [May 
1999] [USEPA 1999i]
U.S. Environmental Protection Agency. Projected National Radon Off-
Gas Emissions and Associated Fatal Cancer Risks for Various Radon 
MCL Options. Memorandum from William Labiosa to Sylvia Malm, Office 
of Ground Water and Drinking Water, [May 12, 1999] [USEPA 1999j]
U.S. Environmental Protection Agency, Office of Policy. Guidelines 
for Preparing Economic Analyses (Draft). [June 11, 1999] [USEPA 
1999k]
U.S. Environmental Protection Agency. Issue Paper: Intra System 
Variability in Ground Water Radon Levels. Prepared by ICF 
Incorporated for EPA, Office of Ground Water and Drinking Water 
[August 6, 1999] [USEPA 1999l]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. An Analysis of the Potential Benefits and Costs of 
Radon in Drinking Water for Non-Transient, Non-Community Water 
Systems (NTNCWS). [August 1999] [USEPA 1999m]
Viscusi, W.K., W.A. Magat, and J. Huber. Pricing Environmental 
Health Risks: Survey Assessments of Risk-Risk and Risk-Dollar Trade-
Offs for Chronic Bronchitis. Journal of Environmental Economics and 
Management, 21:32-51 [1991] [Viscusi 1991]
Wade Miller Associates, Inc., Occurrence and Exposure Assessment for 
Radon in Public Water Supplies, prepared for EPA Office of Drinking 
Water [September 25, 1990] [Wade Miller 1990]
Wade Miller Associates, Inc., Addendum to Occurrence and Exposure 
Assessment for Radon, Radium 226, Radium 228, Uranium, and Gross 
Alpha Particle Activity in Public Water Supplies, (Revised 
Occurrence Estimate Based on Comments to the Proposed Radionuclides 
Regulations), Final Draft, prepared for EPA Office of Drinking Water 
[September 1993] [Wade Miller 1993]

Appendix 1 to the Preamble: What Were the Major Public Comments on 
the 1991 NPRM and How Has EPA Addressed Them in This Proposal?

    EPA received more than 600 comments on the Notice of Proposed 
Rulemaking (NPRM) of July 18, 1991 (56 FR 33050). Of the comments 
received, 289 were from public water suppliers, 89 were from 
individuals, 76 were from local governments, 52 were from States, 48 
were from companies, 43 were from trade/professional organizations, 
12 were from Federal agencies, 10 were from health/environmental 
organizations, 3 were from Members of Congress, and 2 were from 
universities. EPA received additional comments at public hearings on 
September 6, 1991, in Washington, DC and on September 12, 1991, in 
Chicago, Illinois.
    Those commenting raised several concerns, including cost of rule 
implementation, especially for small public water systems, and the 
larger risk to public health from radon in indoor air from soil 
under buildings. The next sections summarize major public comments 
on the 1991 NPRM and provide brief responses in the following areas 
of most concern: (1) General issues; (2) statutory authority and 
requirements; (3) radon occurrence; (4) radon exposure and health 
effects; (5) maximum contaminant level; (6) analytical methods; (7) 
treatment technologies and costs; and (8) compliance monitoring. In 
many instances the following sections refer the reader to applicable 
sections in today's preamble where many of the issues have been 
fully discussed.

A. General Issues

    Additional regulation: Some public comments opposed additional 
regulation in general, and additional drinking water regulation in 
particular. Some comments also suggested EPA proceed with a more 
integrated approach to environmental regulation, i.e., that 
mitigation programs be designed to provide control over major 
exposure routes, which in the case of radon must take the soil gas 
source into account.
    EPA Response: At the time of the 1991 proposal, EPA did not have 
authority under SDWA for a broader radon rule. However, the SDWA as 
amended in 1996 provides such authority. In addition to requiring 
EPA to promulgate a regulation for radon in drinking water, the SDWA 
radon provision also includes a less stringent alternative maximum 
contaminant level (AMCL) and a multimedia approach to address radon 
in indoor air. Much of the health threat is associated with radon 
emanating from soil gas into indoor air. Risk from drinking water 
particularly through the inhalation pathway is also a significant 
and preventable risk. Today's proposal addresses all major routes of 
exposure and is intended to promote multimedia mitigation (MMM) 
programs and implementation of the AMCL. Thus, the Agency expects to 
provide more cost-effective reductions in the health risks 
associated with radon.
    Federal funding for compliance and phased implementation: 
Commenters asked the Agency for increased flexibility in complying 
with the proposed regulation through phased compliance; cheaper 
removal technologies; and/or additional Federal funding. Industry 
and other groups also recommended a phased implementation of radon 
removal, focusing first on priority water sources with the highest 
radon levels.
    EPA Response: Today's proposal provides different compliance 
dates for compliance with the MCL and with the AMCL/MMM program, 
such that there will be sufficient time to implement the MMM 
program.
    The Agency recognizes that the SDWA regulations will continue to 
place a significant burden on some small communities with limited 
tax bases and resources with which to attain compliance. The EPA 
drinking water State Revolving Fund provides support to the States 
and public and private water suppliers, in particular to small 
public water suppliers. This fund offers capitalization grants to 
the States for low-interest loans to help water systems comply with 
the SDWA (For more information refer to Section XIV.C.1 of today's 
preamble.)
    In addition, EPA surveys of public and private water suppliers 
have been initiated to understand more clearly their needs in 
particular in terms of funding to support capital improvements in 
the context of implementing SDWA-related plans.

B. Statutory Authority and Requirements

    Applicability to non-transient, non-community (NTNC) systems: 
Ten commenters stated that EPA must provide better justification for 
regulating non-transient, non-community water systems along with 
community water systems. The indoor occupancy factors and exposure 
rates are different for persons in the workplace (i.e., school and 
hospital) than in the home. EPA should state clearly how the final 
rule will apply to this group.
    EPA Response: About one-third of the systems estimated in 1991 
as being affected by the final regulation were NTNC water systems. 
The Agency requested data in 1991 on NTNC system exposure patterns 
but received none; subsequently, the Agency conducted analysis on 
limited data on NTNC occurrence and exposure patterns and found the 
attendant exposures and risks to be relatively small in comparison 
to those estimated for community water supplies. (For more 
information refer to Section XI.D of today's preamble.)
    In keeping with the flexibility accorded the Agency by SDWA to 
focus on areas of cognizable public health risk, EPA proposes that 
NTNC water systems not be required to comply with the proposed radon 
regulation. At the same time, EPA is soliciting comment and data 
related to this issue and has left open its options in terms of the 
final radon regulation.
    State authority: Commenters felt that the Federal drinking water 
regulations should

[[Page 59363]]

not be uniform across the nation's drinking water supply. Many 
drinking water issues, including those which involve unique 
circumstances in the State and the necessary resources to implement 
programs, remain unresolved and perhaps are not resolvable by the 
Federal government. As a result, States will need to carry more of 
the responsibility in regulating drinking water given their 
familiarity with local circumstances.
    EPA Response: The Agency acknowledges the unique circumstances 
faced by State primacy programs and public water systems. According 
to the framework set forth in the SDWA Amendments, States will have 
the option of adopting the MCL or the higher AMCL and the MMM 
program to address radon in indoor air. State programs in this area 
are expected to vary, in part due to radon occurrence patterns 
locally and in part due to State resources as they apply to 
monitoring public water systems; also States will have flexibility 
in MMM program implementation, and through consideration of 
variances and exemptions as allowed under SWDA.

C. Radon Occurrence

    Radon in PWS (Nationwide): The American Water Works Association 
(AWWA) suggested that EPA's 1991 national occurrence estimates for 
radon were low compared to actual levels, i.e., greater than 20 
percent low, resulting in an inaccurate EPA cost impact estimate. 
The Association suggested EPA consider the following changes to the 
radon occurrence analysis:
     Disaggregation of the National Inorganics and 
Radionuclides Survey (NIRS) occurrence data for the smallest public 
systems, i.e., those serving fewer than 500 persons, into two 
subsets of systems;
     An accounting in the radon occurrence analysis for 
geologic conditions in various regions by applying NIRS data in an 
area-specific manner;
     Updating and increasing the inventory (including NTNCs) 
based upon FRDS data;
     Inclusion of State radon data in the national 
occurrence analysis;
     EPA analyses may have underestimated radon in water 
levels because the location of sampling in NIRS was in the 
distribution systems (where natural decay of radon-222 may have been 
significant, thereby lowering occurrence estimates).
    EPA Response: EPA analyses of these issues addressed the 
concerns described previously to the extent feasible (USEPA 1999c). 
The EPA analyses have incorporated the referenced issues as data 
allowed; the analyses also addressed newer data collected and/or 
submitted to EPA.
    The Agency used State radon in drinking water data to refine the 
previous analysis that were based solely on the NIRS data. The 
Agency identified and obtained data from a number of States that 
supplement the geographic coverage, representativeness, and utility 
of the NIRS data in predicting the occurrence of radon in drinking 
water in the U.S. Additional data sets were obtained that, while not 
addressing radon distributions in States or regions, provided 
significant data related to the sampling, analytical, temporal and 
intra-system variability of radon measurements. The data from the 
NIRS and from the supplementary data sources were subjected to 
extensive statistical analysis to characterize their distribution 
and compare data sets.
    These analyses are discussed and referenced in today's preamble 
Section XI.C. The results indicate that: radon levels seen in the 
NIRS data sets were generally slightly lower than those seen in the 
wellhead and point-of-entry data provided by the same States (with 
radon levels being more comparable in the very small systems due to 
short residence times); previous results were verified that radon 
levels in the U.S. are the highest in New England, the Appalachian 
uplands and other Western and Midwest regions; the levels of radon 
seen in the supplemental State data sets were similar to those seen 
in the NIRS data for the same regions; and, due to procedures used 
to adjust the NIRS data, the proportions of systems exceeding the 
various levels in the current study are greater than those seen in 
previous analyses.
    However, best estimates of the numbers of systems exceeding 
regulatory levels in EPA's 1993 estimate for the 1994 EPA Report to 
Congress (USEPA 1994) and the central tendency estimates in the 
current analysis are quite similar. This is because the total 
estimated number of community and non-community non-transient 
systems that are believed to be active in the U.S. has decreased 
approximately 17 percent between 1993 and the Agency's current 
estimates. Part of this difference is due to system consolidation, 
and part may be due to improved methods for differentiating active 
from inactive systems, although the relative importance of these two 
factors is not known.
    Occurrence of radon in California: A California drinking water 
industry association provided a number of resources including the 
following: a survey of its member agencies; a California Department 
of Health Services (DHS) Groundwater Study; and the Metropolitan 
Water District's (MWD) Southern California Radon Survey. The 
commenter produced estimated radon occurrence figures which far 
exceeded EPA's California and national occurrence profiles. The 
commenter's estimate predicted 75 percent to 97 percent of 
California public water systems out of compliance with a radon 
standard of 300 pCi/L. The commenter submitted to EPA additional 
methods and source data necessary for a complete EPA evaluation of 
this comment.
    EPA Response: EPA studied the commenter's methodology for 
determining radon occurrence in California, proposed water system 
categorization scheme, and the sources of radon data (surveys 
mentioned previously), and has concluded the following:
     That sampling in the California surveys biased the 
results towards higher radon levels since data were apparently 
collected at the wellhead;
     The methods used in combining data sources (and in 
substitutions within data sets) resulted in substantial 
overestimation of radon occurrence in California ground water 
supplies.
     The commenter assumed 23 percent more public water 
supplies in California than indicated in then-current EPA FRDS 
records;
     The use of commenter's GIS-predicted radon levels for 
California systems was also problematic (USEPA 1999c).
    EPA believes that EPA NIRS survey did not under represent the 
levels of radon in California. A comparison by EPA of the NIRS-
California data and other California data reveals a similarity in 
results. Furthermore, EPA results are more in accord with California 
State predictions submitted to EPA during the same comment period.
    Variability of radon levels in water: The American Water Works 
Service Company (AWWSC) provided technical information on the issue 
of radon variability in well water. AWWSC said that the variability 
of radon levels in well water is a phenomenon that could affect the 
compliance status of systems. AWWA and the Association of California 
Water Agencies also echoed concerns about the seasonal and diurnal 
variability in groundwater.
    EPA Response: EPA analyzed this issue to determine if radon 
variability may or may not have any influence on national occurrence 
profiles. EPA reviewed the two available sources of information on 
radon variability (Kinner et al. 1990), and data supplied by the 
American Water Works Service Co. (AWWSC). The Kinner report was 
limited to four sites in New Hampshire that exhibited short-term and 
long-term variability of radon. The AWWSC data were drawn from 400 
wells, nationwide, in 1986 and 1987. Kinner's data appear to 
indicate a radon fluctuation of 20 to 50 percent in well water over 
long-term intervals, weekly or biweekly. The short-term variability 
(15 to 180 minute intervals during a three month test at one site) 
showed a fluctuation of 50 percent as observed in the long-term 
test. These studies did not try to correlate any of the variability 
observed with well yield and water table level to account for the 
inconsistent patterns. The data provided were too limited to 
independently analyze factors that may have influenced radon level 
fluctuations. However, EPA notes that the short-term and long-term 
variabilities of radon observed at a single site were similar. This 
suggests that the long-term variability may be a reflection of 
random sampling where short-term influences are influencing radon 
levels.
    The AWWSC analysis of radon in well water included sampling in 
the fall of 1986 and January 1987. A decrease of 29 percent on 
average was found over the two-month period. A change in analytical 
procedure accounted for about 10 percent of that difference. The 
remaining 19 percent difference was not explained. AWWSC also 
conducted a test of the effect of pumping time on radon levels over 
a short period (five days then two days), beginning with an idle 
period. AWWSC inferred that an observed initial increase in radon 
level (about 25 percent) was due to radon decay in water that had 
been sitting near the well casing. According to AWWSC, a subsequent 
decrease (much smaller) over two days was due to the drawing of less 
enriched water from beyond a potential geologic radon source yet 
within the cone of depression.

[[Page 59364]]

    EPA believes that local geologic and operating conditions may 
produce temporal variations in radon levels in ground water sources. 
However, data are too limited to permit drawing of any conclusions. 
Also, since the Kinner and AWWSC reports cited water that generally 
contained radon in the high levels, 2,500 to 200,000 pCi/L, and 
1,200 to 1,700 pCi/L, respectively, EPA cannot draw any conclusions 
on the effect(s) of short or long-term variability on radon in water 
at 300 pCi/L. Because EPA NIRS data represents single, one-time 
values for systems sampled, it produces no basis for a bias 
conclusion (i.e., over- or under-estimates). On the contrary, the 
random nature of the NIRS survey would cancel any differences 
between the NIRS level and the ``true average'' radon level in 
public supplies.
    Radon Emanation from Pipe Scale Deposits: Data received after 
the comment period, and subsequently reviewed by EPA, suggested that 
due to an existing radon source (radium-226) in some systems, levels 
of radon-222 may in some instances increase as water passes through 
water distribution systems.
    EPA Response: A paper by Valentine et al. (Valentine 1992) 
contained data on the phenomenon of radon levels increasing in water 
distribution pipelines. In three of five distribution systems 
studied in Iowa, the paper's authors found what they refer to as 
radon ``hot spots.'' These systems have more radon in delivered 
water than at the entry to distribution. However, more 
geographically diverse data generally show that natural radon decay 
is a more influential factor as water is distributed. In other 
words, without nationally-relevant data to the contrary, it would be 
expected that within-distribution system radon decay supercedes 
radon production, except in very specific circumstances.
    A more recent article by Field et al. (1995) reported that a 
case study of an Iowa water system with an average of 2.2 mg/L 
dissolved iron and 2.5 pCi/L of radium-226. The finished water 
entering the distribution system had a mean radon level of 432 
 54 pCi/L (one standard deviation). Field et al. 
measured radon levels at the taps of 25 homes and measured radon 
levels ranging from 81 pCi/L to 2,675 pCi/L, with a mean of 1,108 
 648 pCi/L. The authors concluded that iron scale 
deposits were sorbing radium-226, the parent of radon-222. In the 
case study reported, greater than 80% of the surface pipe-scale was 
comprised by iron oxides, with traces of scales containing calcium 
and silicon. Since iron oxides have been shown to selectively 
scavenge radium, it is plausible that a co-occurrence of high iron 
and radium levels may result in the production of significant levels 
of radon within the distribution system. Other factors that would 
determine the level of radon produced include concentration of 
radium-226 sorbed to the pipe scale, the quantity, distribution, and 
surface area of the scale, the composition of the scale, all of 
which are determined by the average finished water quality, and the 
length of time the water is in contact with the scale. All case 
studies were confined to the state of Iowa.
    It remains to be shown that the confluence of conditions that 
result in significant radon production within distribution systems 
exists commonly at the national level or is confined to specific 
locales (e.g., areas with high average levels of iron, radium-226, 
and other site-specific factors).
    Regarding this issue, information available at the present time 
does not support a determination as to the extent to which this 
phenomenon may occur in the U.S. The Agency is, however, soliciting 
comments in today's proposal on the advisability of requiring 
additional monitoring for radon as a source of consumer exposure 
from the distribution system, and on other radon occurrence issues.

D. Radon Exposure and Health Effects

    Approximately 400 public comments were submitted on the 
assessments of exposure to and health effects of radon in the 1991 
NPRM. The major issues raised in these comments, including comments 
regarding the proposed MCLG, are addressed next.
    Linear no-threshold dose response model: Many commenters were 
concerned that EPA only used a linear no-threshold dose-response 
model in projecting cancer risk associated with low level exposure 
to radon in the domestic environment.
    EPA Response: The shape of the dose-response curve for radon has 
been evaluated in detail by the NAS (1999a, 1999b), who concluded 
that essentially all available data are consistent with a linear 
non-threshold mechanism. This includes data on the effects of a wide 
range of ionizing radiation, as well as direct dose-response 
relationships observed for radon in animals studies and in studies 
of cohorts of underground miners. The EPA concurs with the NAS 
evaluation and conclusion.
    Age dependence on risk from radon exposure: A few commenters 
stated that EPA should consider the effect of exposure at young 
ages. According to these commenters, the additional risks in 
children were not well addressed.
    EPA Response: Data on the relative sensitivity of children to 
radon are sparse. In general, the NAS Radon in Drinking Water 
Committee concluded that there is insufficient scientific 
information to permit quantitative evaluation of the risks of lung 
cancer death from inhalation exposure to radon progeny in 
susceptible sub-populations such as infants, children, pregnant 
women, and elderly and seriously ill persons. However, the BEIR VI 
committee (NAS 1999a) noted that there is one study (tin miners in 
China) that provides data on whether risks from radon progeny are 
different for children, adolescents, and adults. Based on this 
study, the committee concluded that there was no clear indication of 
an effect of age at exposure, and the committee made no adjustments 
in the model for exposures received at early ages. This indicates 
that children are not an especially susceptible sub-group. With 
respect to cancer risk from ingestion of radon, NAS (1999b) 
performed an analysis to investigate the relative contribution of 
radon ingestion as a child to the total risk. This analysis 
considered the age dependence of water consumption, of the behavior 
of radon and its decay products in the body, of organ size, and of 
risk. The results indicated that dose coefficients are somewhat 
higher in younger people than adults. NAS (1999b) estimated that 
about 30 percent of a lifetime risk was due to exposures occurring 
during the first 10 years of life.
    Uncertainty of radon risk estimates: Several commenters said EPA 
needs to provide a more in-depth discussion of the uncertainty 
associated with the risk estimates for radon.
    EPA Response: EPA has performed a very detailed two-dimensional 
Monte Carlo evaluation of variability and uncertainty in exposure 
and risk from water-borne radon (USEPA 1993, 1995). The methods and 
inputs used by EPA were reviewed by the SAB and by NAS, and the 
results were judged to be appropriate and sound, subject to some 
refinements in the uncertainty bounds on some of the inputs. Based 
on the most recent recommendations from the NAS regarding the 
uncertainty in the risk coefficient for ingestion and inhalation 
exposure, EPA (1999d) has recalculated the uncertainty bounds around 
each risk estimate. In brief, the credible interval around the best 
estimate of individual and population risks from inhalation and 
ingestion exposure pathways are about four-fold and fourteen-fold, 
respectively.
    Extrapolation of high dose in mines to lower dose in homes: Many 
commenters stated that the differences in dose between the mines and 
homes in the 1991 NAS report Comparative Dosimetry of Radon in Mines 
and Homes needs to be incorporated into the Agency's radon progeny 
inhalation risk calculation.
    EPA Response: EPA and NAS both recognize the importance of 
potential differences between dose and risk per unit exposure in 
mines and in homes. The ratio of the dose to lung cells per WLM in 
the home compared to that in a mine is described by the K factor. 
Based on the best data available at the time, NAS (1991) had 
previously concluded that the dose to target cells in the lung was 
typically about 30 percent lower for a residential exposure compared 
to an equal WLM exposure in mines (i.e., K=0.7). The BEIR VI 
committee re-examined the issue of the relative dosimetry in homes 
and mines. In light of new information regarding exposure conditions 
in home and mine environments, the committee concluded that, when 
all factors are taken into account, the dose per WLM is nearly the 
same in the two environments (i.e., a best estimate for the K-factor 
is about 1) (NAS 1999a). The major factor contributing to the change 
was a downward revision in breathing rates for miners. Thus, NAS has 
concluded that the risk coefficient based on miners is appropriate 
for use in residences without adjustment.
    Possible confounding factors in mine studies: Some commenters 
raised questions about the possible confounding factors in the miner 
epidemiological studies EPA used to project lung cancer risks. 
Commenters stated that, besides radon, exposure to other 
contaminants not found at home can produce synergistic effects. Such 
other contaminants could include diesel fumes, excessive dust

[[Page 59365]]

(which may be a problem in poorly constructed mines without adequate 
ventilation), and other radionuclides like uranium in the mine air.
    EPA Response: The effects on radon risk estimates from 
potentially toxic exposures to substances such as silica, uranium 
dust, blasting fumes, and engine exhaust to underground miner 
cohorts were carefully examined in the NAS reports on radon risks 
(NAS 1988, 1999a) and other studies. For example, in the Malmberget 
iron miner study, Radford and St. Clair Renard (1984) investigated 
and determined that the risk from confounders such as tuberculosis, 
dust, silica, diesel exhaust, metals and asbestos is negligible. 
Edling and Axelson (1983) found the Grangeberg mine atmosphere clean 
of arsenic, asbestos and carcinogenic metals. In the Eldorado miner 
cohort (NAS 1988), potential confounders were investigated and 
exposures to silica and diesel exhaust were very low. In the 
Czechoslovakian uranium miners' study, Sevc et al. (1984, 1988) 
found that cigarette smoking was the only risk factor other than 
radon that was a significant exogenic carcinogenic agent. Two of the 
studies (China and Ontario) have quantitative data on arsenic, and 
there was no significant variation in excess relative risk per unit 
radon exposure across different levels of arsenic exposure (NAS 
1999a). Despite the variety of exposures to potentially toxic agents 
other than radon, the dose-response between radon and lung cancer 
death was approximately consistent across the mining cohorts. NAS 
(1988) also noted that animal studies show no evidence of a 
synergistic effect of these agents on lung cancer risk from radon. 
Taken together, these findings indicate that the effect of 
confounding factors on observed lung cancer rates in miners is 
likely to be small.
    Radon-smoking interaction: Several commenters stated that EPA's 
analysis shows that smoking acts synergistically with radon to 
induce lung cancer. The risk from radon is, on average, ten times 
higher for smokers than for the rest of the population, and over 20 
times higher for heavy smokers. Several commenters asked why they 
should spend resources to remove a natural contaminant from water 
while more than \2/3\ of the related cancer risk is attributable to 
the subpopulation who smoke.
    EPA Response: Because of the strong influence of smoking on the 
risk from radon, the BEIR VI committee (NAS 1999a) evaluated risk to 
ever-smokers and never-smokers separately. The BEIR VI committee had 
smoking information on five of the miner cohorts, from which they 
concluded that there was a submultiplicative interaction between 
radon and smoking in causing lung cancer. Based on current smoking 
prevalence rates, it is estimated that about 84 percent of all 
radon-induced lung cancers will occur in ever-smokers, with only 16 
percent in never-smokers. Thus, it is true that a reduction in radon 
exposure will save more cancer cases in the cohort of smokers than 
nonsmokers, but the relative amount of risk reduction is actually 
greater for nonsmokers than smokers.
    Epidemiological studies of lung cancer in the home environment. 
Some commenters stated that in estimating risk associated with 
exposure to radon, EPA should consider health risk data associated 
with the exposure to low levels of radon in the domestic 
environment.
    EPA Response: The NAS (1999a) has recently performed a careful 
analysis of epidemiological data on the risk of cancer in residents 
from radon. The NAS committee concluded that because of numerous 
design and experimental limitations, these studies do not constitute 
an adequate data base from which quantitative risk estimates can be 
derived. However, the data from studies in residents are considered 
to be generally consistent with the predictions based on the miner 
data.
    Lack of experimental or epidemiological data link exposure via 
ingestion to increased cancer rates: Several commenters stated that 
no experimental or epidemiologic data link exposure via ingestion to 
increased cancer rates. The basis for ingestion risk data was a 
surrogate gas, xenon-133, that behaves similarly to radon.
    EPA Response: Although no human or animal data directly 
demonstrate cancer risk from ingestion of radon, it is certain that 
ingested radon is absorbed from the gastrointestinal tract into the 
body, that this absorbed radon is distributed to internal tissues 
which are then irradiated with alpha particles as the radon and its 
progeny undergo decay. That alpha irradiation increases cancer risk 
is well established (UNSCEAR 1988; NAS 1990).
    EPA's ingestion risk estimate is based on the conclusions from 
the NAS Radon in Drinking Water committee (NAS 1999b). The NAS 
committee performed a re-evaluation of the risks from ingestion of 
radon in direct tap water using the basic approach described in 
Federal Guidance Document 13 (USEPA 1998). This involved developing 
a new pharmacokinetic model of the behavior of ingested radon, based 
primarily on observations of the behavior of ingested radon in 
humans, as well as studies using xenon and other noble gases. NAS 
also addressed the uncertainties (within an order of magnitude) of 
the risk estimates for oral exposure associated with dose estimate 
to the stomach and in the epidemiologic data used to estimate the 
risk (NAS 1999b). Because the magnitude of the risk posed by 
ingestion is about 10 percent of the risk from inhalation of radon 
progeny, these uncertainties are not most critical in evaluating the 
overall hazards from water-borne radon.
    Air-water transfer factor and episodic exposure: As for 
inhalation exposure, most commenters supported EPA's proposed radon 
water-to-air transfer ratio of 10,000:1. Two commenters regarded 
this transfer factor as too conservative.
    EPA Response: EPA has performed a detailed evaluation of radon 
gas transfer from water to air (USEPA 1993, 1995). Values are highly 
variable between buildings, with an average value of about 1E-04. 
The NAS has recently performed an independent review of both 
measured and modeled values, and the NAS committee also concluded 
that a value of 1E-04 is the best point estimate available (NAS 
1999b).
    Outdoor versus indoor radon concentrations: Some commenters 
asserted that the concentration of radon in outdoor air is higher 
than the indoor air concentration resulting from the proposed MCL of 
300 
pCi/L.
    EPA Response: EPA agrees. The NAS committee reviewed all the 
ambient radon concentration data that are available, and based on 
these data concluded that the best estimate of the average ambient 
(outdoor) radon concentration in the United States is 0.4 pCi/L of 
air. In contrast, based on a transfer factor of 1 x 10-4, 
the contribution to indoor air from an average radon concentration 
in water (about 213 pCi/L) is only about 0.021 pCi/L. However, some 
groundwater systems have much higher radon concentrations, and 
increments in indoor air from water-borne radon may be much higher 
in those cases. As required by the Congress. EPA is implementing the 
MMM program to address the issue of relative radon risk from water 
and air.
    Direct tap water ingestion rate: Concerning ingestion intake, 
few commenters expressed an opinion on the direct tap water 
ingestion rate of 1 L/day. One commenter suggested that the intake 
assumption should be 0.7 L/day, and another, 0.25 L/day.
    EPA Response: EPA has based its current assessment of this issue 
on reports by the National Academy of Sciences and others. The 
reader is referred to a fuller discussion in the preamble to today's 
proposed radon in drinking water regulation and to references cited 
therein (see Section XII).
    Radon loss via volatilization prior to ingestion: Two commenters 
felt that the 20 percent radon loss from direct tap water before 
ingestion is conservative.
    EPA Response: Data are limited on the amount of radon lost from 
direct tap water before ingestion. Several studies (von Doblin and 
Lindell 1964; Hursh 1965; Suomela and Kahlos 1972; Gesell and 
Prichard 1980; Horton 1982) suggest a value of about 20 percent as 
the central estimate of radon lost before direct ingestion. Because 
of the lack of data, the NAS (1999b) recommended that a value of 0 
percent (i.e., no loss) be assumed. It is important to note that 
this applies only to ``direct tap water'', and that radon loss is 
assumed to be nearly complete from other types of water (coffee, 
juice, that in foods, etc.).
    Concerning the potential additional loss from the stomach prior 
to absorption, EPA believes that radon does not escape from the 
esophagus. An available study (Correia et al. 1987) conducted by the 
Massachusetts General Hospital specifically measured exhaled air 
following ingestion of radioactive xenon in drinking water. Gas did 
not immediately escape through the mouth. However, the absorption 
through the stomach and small intestine transferred xenon to the 
bloodstream and lungs. The pharmacokinetic model used to evaluate 
risk from ingested radon utilizes this absorption mechanism.
    New studies indicating reduced lung cancer risk: Some commenters 
asserted that the lung cancer risk estimates will be reduced based 
on new studies.
    EPA Response: The risk coefficients for lung cancer derived by 
NAS (1999a, 1999b) are based on a detailed analysis of all of the 
currently available studies.

[[Page 59366]]

    Relative risk of radon from soil versus radon from drinking 
water: Many commenters stated that the risks posed by radon in water 
are small compared to the risk of radon from soil, and that 
regulation of radon in water will have very little effect in 
reducing the total risk of cancer from radon exposure.
    EPA Response: EPA recognizes that the risk to residents 
contributed by radon in household water is a relatively small 
fraction of the risk contributed by radon released into indoor air 
from soil. Based on the most recent quantitative analysis, NAS 
estimates that this fraction is only about 1 percent. Nevertheless, 
it is still true that radon in water is one of the most hazardous 
substances in public water systems, contributing a total of about 
160-170 cancer deaths per year. Thus, regulation of radon in water 
is appropriate.
    Cancer risk posed by radon in drinking water: Radon in drinking 
water is one of the water contaminants with the highest estimated 
cancer risk.
    EPA Response: EPA agrees, and it is for this reason that EPA 
believes that regulation of radon in water is necessary and 
appropriate. By definition, because radon is a known human 
carcinogen, the MCLG is zero.

E. Maximum Contaminant Level

    Opposition to a radon MCL of 300 pCi/L: More than 300 commenters 
representing trade associations, Federal and State agencies, and 
regional and community water suppliers disagreed with a standard of 
300 pCi/L for radon in drinking water. The strongest opposition came 
from California, Nebraska, and the northeastern region of the United 
States. Other commenters suggested the MCL be set at 1,000 pCi/L or 
at 2,000 pCi/L.
    EPA Response: As referenced in Section A of this Appendix, the 
SDWA as amended in 1996 provides EPA authority to utilize an 
alternative approach (AMCL with MMM programs), which is expected to 
significantly allay concerns of stakeholders and commenters on the 
1991 proposal.
    Use of cost-effectiveness in standard setting: Local water 
agencies throughout California and elsewhere in the United States 
insisted that water rates would double, resulting in economic 
problems. State and local water agencies were in almost unanimous 
agreement that the proposed standard may not be cost-effective, 
posing significant financial and administrative burdens on agencies 
and customers.
    EPA Response: In the past, EPA generally limited consideration 
of economic costs under the SDWA to whether a treatment technology 
was affordable for large public water systems. Under the SDWA as 
amended in 1996, the Agency has conducted considerable analysis in 
the areas of cost and technologies for small systems implementing 
the radon MCL and on small system compliance technologies. (For more 
information on related EPA analyses refer to today's proposal.)
    The MCL as proposed in 1991 and in today's action was set within 
the EPA regulatory target range of approximately 10-4 to 
10-6 individual lifetime fatal cancer risk level, to 
ensure the health and safety of the country's drinking water supply. 
Although this level will prevent numerous fatal cancer cases per 
year, the Agency recognizes that this benefit would affect only 
radon in ground water or 5 percent of the total radon exposure. The 
Agency expects the proposed AMCL/ multimedia approach will result in 
greater radon risk reduction at lower cost. (The multimedia 
mitigation program and the projected costs and benefits are 
described in greater detail in today's proposal.)
    Impact on private wells: Several commenters expressed concern 
over the potential impact of the proposed standards on private 
wells.
    EPA Response: The Agency cannot comment on the impact of an 
NPDWR (radon standard) on private wells. EPA currently possesses 
some data from State surveys that indicate relatively high levels of 
radon in private wells. However, the data are distinct from Public 
Water System data collected by EPA and others. The statute regulates 
public water systems that provide piped water for human consumption 
to at least 15 service connections or that serve an average of at 
least 25 people for at least 60 days each year. Public water systems 
can be community; non-transient, non-community; or transient non-
community systems. As a supplement to Federal coverage, some States 
extend their authority by regulating systems serving 10 people or 
fewer.

F. Analytical Methods

    Availability of qualified laboratories and personnel: Commenters 
stressed the impact the proposed regulation may have on requirements 
for analytical laboratory certification and training of laboratory 
technicians. For example, one State wrote that it has no 
certification process through which laboratories can receive State 
certification for radionuclide analyses. Another commenter stressed 
the need for a strategy to work with individual States to ensure 
sufficient certified analytical laboratory capacity.
    EPA Response: The current situation and expected changes in the 
processes governing laboratory approval and certification are 
discussed in some detail in today's preamble (Section VIII.B). One 
of the changes since 1991 is the formation of the National 
Environmental Laboratory Accreditation Conference (NELAC) in 1995. 
NELAC serves as a voluntary national standards-setting body for 
environmental laboratory accreditation, and includes members from 
both state and Federal regulatory and non-regulatory programs having 
environmental laboratory oversight, certification, or accreditation 
functions. The members of NELAC meet bi-annually to develop 
consensus standards through its committee structure. These consensus 
standards are adopted by participants for use in their own programs 
in order to achieve a uniform national program in which 
environmental testing laboratories will be able to receive one 
annual accreditation that is accepted nationwide. The intent of the 
NELAC standards setting process is to ensure that the needs of EPA 
and State regulatory programs are satisfied in the context of a 
uniform national laboratory accreditation program. EPA shares 
NELAC's goal of encouraging uniformity in standards between primacy 
States regarding laboratory proficiency testing and accreditation.
    Four-day holding period between sampling and analysis: Several 
commenters contended that for laboratories to cope with the 
increased number of samples, the holding period should increase to 
eight days. A State agency suggested a holding period of seven days. 
Another commenter stated that the proposed four-day holding period 
was not possible because many ground water systems have sources 
distributed over large areas that may need sampling. Certified 
personnel will collect, record, package, and send the samples to 
analytical laboratories within four days. Also, with a 100-minute 
counting time requirement, commercial laboratories may be ill-
equipped to analyze samples from 28,000 systems. Another State 
commented that the four-day holding period was not compatible with a 
standard work week.
    Response: Standard Method 7500-Rn reports a 50 minute counting 
time (not 100 minutes) and a four day sample holding time. This 
combination of counting time and holding time has been determined to 
be a good trade-off, given the limitation of the 3.8 day half-life 
of radon. Doubling the sample holding time (i.e., eight days) would 
approximately triple the counting time (i.e., to 150 minutes) 
necessary to achieve the same level of certainty in the analytical 
results, which would probably result in much higher analytical 
costs. Since the sample counting procedure is capable of being 
highly automated, EPA believes that certified laboratories will be 
able to process the required samples with a four-day holding time. 
As an example, one laboratory contacted by EPA currently analyzes 
radon in 12,000 water samples per year as part of a ground water 
monitoring study, providing evidence that a demand for radon 
analytical capacity will result in the required laboratory capacity. 
Based on an evaluation of the potential for laboratory 
certification, performance testing, and analytical procedures, which 
included input from stakeholders, the four day holding time has been 
determined to be feasible, and should result in lower analytical 
costs than a longer holding time and a longer counting time.
    Proposed analytical techniques: A commenter representing a group 
of utilities approved of direct, low-volume liquid scintillation for 
measurement of radon as proposed, but recommended the use of Lucas 
Cell de-emanation for measurement of Ra-226 (not also for radon, as 
proposed). According to this commenter, the liquid scintillation 
method for radon measurement is straightforward and efficient 
compared with the Lucas Cell method that requires a high degree of 
specialized skill. Also, equipment cost for the Lucas Cell method 
may be prohibitive. The Conference of Radiation Control Program 
Directors stated that liquid scintillation, while able to detect 
radon in water at low levels, may provide laboratory results that 
are not reliable.
    EPA Response: EPA agrees that LSC has the stated advantages 
relative to de-

[[Page 59367]]

emanation. EPA also expects that the vast majority of nationwide 
radon analysis will be done using LSC. However, some laboratories 
are already equipped to perform the de-emanation method. Since the 
de-emanation method performs acceptably well, there is no reason to 
refuse the possibility of the added laboratory capacity afforded by 
the approval of this method.
    Precision variability: A local water agency and an engineering 
company representative stated that the 30% precision variability is 
inadequate for determining compliance because of the extensive 
natural variability in radon levels over time. The combination of 
counting error, sampling error, and holding time variability demands 
a precision of 20%, which would lead to more consistent 
data.
    EPA Response: EPA agrees that the 1991 proposal of an acceptance 
level of  30%, based on a radon ``practical quantitation 
level'' (PQL) of 300 pCi/L is not supportable. This conclusion is 
based on an extensive collaborative study of the liquid 
scintillation method and the de-emanation method for radon published 
by EPA in 1993, as described in the methods section (VIII.b) of the 
preamble to this proposal. Today's proposal contains several options 
for ensuring that compliance monitoring is performed using radon 
methods with acceptable accuracy and precision. Based on other 
comments to the 1991 radionuclides proposal, EPA's preferred option 
is that the method detection limit (MDL) be used as the measure of 
sensitivity for radon, and not a PQL, consistent with the use of the 
MDL as the basis for sensitivity in the current radionuclides rule. 
EPA is proposing a value of 12  12 pCi/L as the MDL for 
radon.
    Based on the collaborative study data, EPA's best recommendation 
for acceptance limits for performance evaluations is  5% 
for single measurements, and for triplicate measurements, 
 6% at the 95% confidence level, and  9% at 
the 99% confidence level.

G. Treatment Technologies and Cost

    Water Treatment Costs: Industry groups and several utilities 
provided detailed analyses of unit treatment costs for removal of 
radon in water. Water treatment cost estimates prepared by a 
consultant were up to five times the costs estimated by EPA. An 
analysis produced by a consultant showed that among the different 
factors influencing annual compliance costs estimated by them, unit 
treatment costs have the largest impact.
    EPA Response: EPA disagrees that its radon aeration treatment 
estimates supporting the 1991 radionuclides proposal were under-
estimates. EPA analyzed the aeration cost model and the cost 
elements put forward by the industry commenters and summarized the 
major differences between the EPA and industry models. This summary 
may be obtained from the docket supporting today's proposal (USEPA 
1992). While this summary accounts for the differences in cost 
estimates between EPA and the industry and utility estimates, it is 
not necessary to go into detail regarding these differences since 
overwhelming evidence suggests that EPA's 1992 cost estimates were 
much closer to actual unit costs, based on costs reported in case 
studies collected since 1991 (USEPA 1999a, AWWARF 1998a) than the 
commenter's estimates. A comparison of EPA's current unit capital 
cost estimates to actual capital costs reported in published case 
studies can be found in Figure VIII.A.1 of this preamble. The 
consultant's 1991 estimates are compared against case studies and 
against EPA's current estimates in an EPA memorandum dated July 28, 
1999 (USEPA 1999b). In summary, the consultant's estimates over-
estimated the small systems case studies by factors ranging from 
three for small systems with design flows of around 1 MGD down to 
around 0.3 MGD. For the smallest systems case studies (systems 
serving around 0.015 MGD), the consultant's estimates were high by a 
factor of more than twenty. For large systems, the consultant's 
estimates were two to three times higher than the best fit for the 
large system case studies. As can be seen in Figure VIII.A.1 
(``Total Capital Costs: Aeration Cost Case Studies''), EPA's current 
unit capital cost estimates appear to be very conservative compared 
to small systems case studies (systems with design flows less than 1 
MGD) and are typical of case studies for larger flows (design flows 
greater than 1 MGD). It should be noted the costs reported for these 
case studies are total capital costs and include all process costs, 
as well as pre- and post-treatment capital costs, land, buildings, 
and permits. Figures VIII.A.1 through VIII.A.3 shown in the preamble 
provide strong evidence that EPA's assumptions affecting its unit 
cost estimates are realistic for large systems and are conservative 
for small systems.
    Additional Treatment--Disinfection: Commenters asserted that 
some systems may need to add disinfection treatment to protect 
aerated water supplies from biological contamination. It was also 
stated that about 58 percent of small systems and 12 percent of 
large systems may need to add disinfection technology.
    EPA Response: The current cost analysis assumes that all systems 
adding aeration and GAC will disinfect. For those systems not 
already disinfecting (proportions estimated from the EPA 1997 
Community Water System Survey), it was assumed that systems adding 
treatment would also add disinfection.
    Pretreatment for Iron and Manganese: A commenter also challenged 
EPA's position on the minimal pretreatment of a ground water supply 
before air stripping of radon. The commenter presumed that iron and 
manganese fouling will require additional treatment. While the 
comment did not address the costs to pre-treat water for iron and 
manganese removal, it was mentioned this pretreatment would result 
in high potential costs to water systems.
    EPA Response: EPA has re-evaluated its assumptions regarding 
iron and manganese (Fe/Mn) fouling and has included costs for 
chemical stabilization (sequestration) of Fe/Mn for 25% of small 
systems and 15% of large systems. Based on an analysis of the 
occurrence of Fe/Mn in raw and finished ground water, EPA believes 
that this is adequate to account for Fe/Mn control. Data sources for 
this evaluation were: ``National Inorganics and Radionuclides 
Survey'' (NIRS); American Water Works Association, ``Water:/Stats, 
1996 Survey: Water Quality''. and U.S. Geological Survey, ``National 
Water Information System''). This analysis is more fully discussed 
in Section VIII of the preamble. EPA reiterates that if its Fe/Mn 
cost assumptions were invalid, this fact would be demonstrated in 
comparisons of its estimates of capital and O&M costs against those 
reported in the case studies cited in the preamble. As described 
previously, EPA's unit cost estimates are apparently conservative 
for small systems and seem to be typical of large systems.
    Aeration as BAT and Use of Carbon Treatment: A major commenter 
and a city in California asserted that aeration treatment for radon 
could potentially create a problem in air emissions permitting. 
Also, a major commenter commented that systems with high radon 
levels in water could produce high levels of radon in off-gas, 
potentially creating a shift among utilities to activated carbon 
treatment and waste (radioactive) disposal problems.
    EPA Response: EPA discusses this concern in some detail in 
Section VIII of the preamble, including an evaluation of the 
estimates of the potential risks. Results from a survey of nine 
California air permitting agencies regarding permitting requirements 
and costs for radon treatment is also described in the preamble. The 
full text of this survey is reported in EPA 1999a.
    Centralized Treatment Assumption: Commenters from the regulated 
community challenged EPA's cost analysis assumption involving 
centralized water treatment for radon. These associations cited the 
then-current EPA Community Water Supply Survey of 1986 and the then-
current Water Industry Database. They suggested centralized 
treatment facilities were unrealistic and under predicts the costs 
to public water systems. The industry asserted that the number of 
wells and well groupings per system (with numbers increasing with 
increasing system size) will likely determine the number of 
treatment sites. An industry group produced estimated distributions 
of the percent of systems that would require treatment sites.
    EPA Response: Centralized treatment was not assumed in the 
current radon cost analysis. EPA's current estimate of national 
compliance costs for the proposed radon rule uses the distribution 
of wells (treatment sites) per ground water system as a function of 
water system size from the 1997 Community Water System Survey (USEPA 
1997). EPA assumed that a given system's total flow would be evenly 
distributed between the total number of wells at the system. To 
estimate the radon occurrence at a particular well within a system 
with multiple wells, EPA used its evaluation of intra-system 
occurrence variability (the variability of radon occurrence between 
wells within a given system) to estimate individual well radon 
levels. If multiple wells were predicted to be impacted at a given 
system, the cost model assumes that treatment is installed at each 
well requiring treatment.
    Integrated approach to waste management: Three commenters 
declared that compliance with the radionuclides rule will create 
radioactive waste that may or may not be

[[Page 59368]]

disposable. They recommended an integrated environmental management 
approach in addressing this waste issue.
    EPA Response: The Agency used an integrated environmental 
management approach to determine BAT in removing contaminants from 
drinking water. While Packed Tower Aeration (PTA), the BAT for 
radon, does not generate waste requiring disposal, granular 
activated carbon is of concern. While not BAT, granular activated 
carbon may be used by very small systems to remove radon. Waste 
disposal issues regarding GAC treatment for radon are discussed in 
some detail in Section VIII of this preamble. For more information, 
see NAS 1999b and AWWARF 1998a and AWWARF 1998b.

H. Compliance Monitoring

    Sampling location: Four State environmental/health agencies, one 
private non-environmental firm, eight public water suppliers, and 
one water association suggested that radon sampling of the 
distribution system at the point of entry does not allow systems to 
account for decay and aeration of radon during distribution. 
According to these commenters, sampling is more effective closer to 
the point of use.
    EPA Response: EPA's proposal requires sampling at the entry 
points to the distribution system to assure compliance with the MCL 
for the water delivered to every customer. All samples will be 
required to be finished water, as it enters the distribution system 
after any treatment and storage. This approach allows systems to 
account for the decay and aeration of radon during treatment and 
storage before it enters the distribution system and at the same 
time offers maximum protection to the consumer. It is expected that 
radon levels would progressively decrease within the distribution 
system, downstream from the point of entry. Therefore, consumers who 
are located closest to the point of entry are exposed to higher 
levels of radon that those further downstream. In order to assure 
maximum protection to all of the consumers, EPA requires sampling at 
the entry points to the distribution system.
    Compliance period: Clarification concerning the frequency of 
compliance periods, specifically in regards to the specific timing 
for the commencement of water systems monitoring is warranted.
    EPA Response: The proposed monitoring requirements for radon are 
consistent with the monitoring requirements for regulated drinking 
water contaminants, as described in the Standardized Monitoring 
Framework (SMF) promulgated by EPA under the Phase II Rule of the 
National Primary Drinking Water Regulations (NPDWR) and revised 
under Phases IIB and V. The goal of the SMF is to streamline the 
drinking water monitoring requirements by standardizing them within 
contaminant groups and by synchronizing monitoring schedules across 
contaminant groups.
    Systems already on-line must begin initial monitoring for 
compliance with the MCL/AMCL by the compliance dates specified in 
the rule (i.e., 3 years after the date of promulgation or 4.5 years 
after the date of promulgation). New sources connected on-line must 
satisfy initial monitoring requirements.
    Initial compliance with the MCL/AMCL will be determined based on 
an average of 4 quarterly samples taken at individual sampling 
points in the initial year of monitoring. Systems with averages 
exceeding the MCL/AMCL at any well or sampling point will be deemed 
to be out of compliance. Systems exceeding the MCL/AMCL will be 
required to monitor quarterly until the average of 4 consecutive 
samples are less than the MCL/AMCL. Systems will then be allowed to 
collect one sample annually if the average from four consecutive 
quarterly samples is less than the MCL/AMCL and if the State 
determines that the system is reliably and consistently below MCL/
AMCL.
    Systems that primarily use surface water, supplemented with 
ground water: One water association suggested that public water 
systems supplementing their surface water supply with ground water 
are not in violation. Since the actual lifetime risk involved is 
significantly lower than those systems using 100 percent ground 
water supply, an equitable method of compliance for this type of 
combined systems should be administered.
    EPA Response: In today's proposal, systems relying exclusively 
on surface water as their water source are not required to sample 
for radon. Systems that rely in part on ground water during low-flow 
periods about one quarter of the year are considered public ground 
water systems. According to the ground water monitoring 
requirements, systems are subject to monitor finished water at each 
entry point to the distribution system for radon during periods of 
ground water use. For the purpose of determining compliance, systems 
supplementing their surface water during part of the year will use a 
value of \1/2\ the detection limit for radon for averaging purposes 
for the quarters when the water system is not supplemented by ground 
water. The water system having ground water samples supplementing 
surface water with a radon detection level above the MCL would not 
be out of compliance provided that these samples do not cause the 
average to exceed the MCL when averaged with the value of \1/2\ the 
detection limit during the quarters the ground water source is not 
in use.
    Averaging quarterly samples: Commenters recommended clarifying 
the discussion concerning the averaging of initial measurements to 
determine compliance. They stated that averaging the first year 
quarterly samples with the annual second and third compliance years 
will defeat the purpose of quarterly samples detecting signs of 
seasonal variability.
    EPA Response: EPA is retaining the quarterly monitoring 
requirement for radon as proposed initially in the 1991 proposal to 
account for variations such as sampling, analytical and temporal 
variability in radon levels. Results of analysis of data obtained 
since 1991, estimating contributions of individual sources of 
variability to overall variance in the radon data sets evaluated, 
indicated that sampling and analytical variance contributes less 
than 1 percent to the overall variance. Temporal variability within 
single wells accounts for between 13 and 18 percent of the variance 
in the data sets evaluated, and a similar proportion (12-17 percent) 
accounts for variation in radon levels among wells within systems 
(USEPA 1999c).
    For today's proposal, the Agency performed additional analyses 
to determine whether the requirement of initial quarterly monitoring 
for radon was adequate to account for seasonal variations in radon 
levels and to identify non-compliance with the MCL/AMCL. Results of 
analysis based on radon levels modeled for radon distribution for 
ground water sources and systems (USEPA 1999c) in the U.S. show that 
the average of the first four quarterly samples provides a good 
indication of the probability that the long-term average radon level 
in a given source would exceed an MCL or AMCL. Tables A.1 and A.2 
show the probability of the long-term average radon level exceeding 
the MCL and AMCL at various averages obtained from the first four 
quarterly samples from a source.

 Table A.1.--The Relationship Between the First-Year Average Radon Level
     and the Probability of the Long-Term Radon Average Radon Levels
                            Exceeding the MCL
------------------------------------------------------------------------
                                           Then the probability that the
     If the average of the first four      long-term average radon level
   quarterly samples from a source is:       in that source exceeds 300
                                                     pCi/L is:
------------------------------------------------------------------------
Less than 50 pCi/L.......................  0 percent
Between 50 and 100 pCi/L.................  0.5 percent
Between 100 and 150 pCi/L................  0.4 percent
Between 150 and 200 pCi/L................  7.2 percent
Between 200 and 300 pCi/L................  26.8 percent
------------------------------------------------------------------------


 Table A.2.--The Relationship Between the First-Year Average Radon Level
     and the Probability of the Long-Term Radon Average Radon Levels
                           Exceeding the AMCL
------------------------------------------------------------------------
                                           Then the probability that the
     If the average of the first four      long-term average radon level
   quarterly samples from a source is:      in that source exceeds 4000
                                                     pCi/L is:
------------------------------------------------------------------------
Less than 2,000 pCi/L....................  Less than 0.1 percent
Between 2,000 and 2,500        pCi/L.....  9.9 percent
Between 2,500 and 3,000        pCi/L.....  15.1 percent
Between 3,000 and 4,000        pCi/L.....  32.9 percent
------------------------------------------------------------------------


[[Page 59369]]

    Water systems with a history of compliance: EPA has provided for 
the grandfathering of prior monitoring data for granting waivers. 
Monitoring data collected after January 1, 1985, that are generally 
consistent with the requirements of the section, and includes at 
least one sample taken on or after January 1, 1993, may be accepted 
by the State to satisfy the initial monitoring requirements. Many 
systems meeting the current monitoring requirements should qualify 
for this grandfathering provision because each sampling point or 
source water intake will be monitored within the preceding four-year 
period. New sampling points, or sampling points with new sources, 
must take an initial sample within the year the new source or 
sampling point begins operation.
    EPA Response: Today's proposal provides that at a State's 
discretion, sampling data collected after the proposal could be used 
to satisfy the initial sampling requirements for radon, provided 
that the system has conducted a monitoring program not less 
stringent than that specified in the regulation and used analytical 
methods specified in the proposed regulation. The Agency wants to 
provide water suppliers with the opportunity to synchronize their 
monitoring program with other contaminants and to get an early start 
on their monitoring program if they wish to do so.
    The proposed regulation provides for the States to grant 
monitoring waiver reducing monitoring frequency to once every nine 
years (once per compliance cycle) provided the system demonstrates 
that it is unlikely that radon levels in drinking water will occur 
above the MCL/AMCL. In granting the waiver, the State must take into 
consideration factors such as the geological area where the water 
source is located, and previous analytical results which demonstrate 
that radon levels do not occur above the MCL/AMCL. The waiver will 
be granted for up to a nine year period. (Given that all previous 
samples are less than \1/2\ the MCL/AMCL, then it is highly unlikely 
that the long-term average radon levels would exceed the MCL/AMCL.)

References Cited in Appendix 1 to the Preamble

American Water Works Association Research Foundation. Critical 
Assessment of Radon Removal Systems for Drinking Water Supplies, 
Denver, CO. [December 1998] [AWWARF 1998a]
American Water Works Association Research Foundation. Assessment of 
GAC Adsorption for Radon Removal. Final Draft, Denver, CO. [April 
1998] [AWWARF 1998b]
Correia, J.A., Weise, S.B., Callahan, R.J., and Strauss, H.W. The 
Kinetics of Ingested Rn-222 in Humans Determined from Measurements 
with Xe-133. Massachusetts General Hospital, Boston, MA, unpublished 
report (As cited in Crawford-Brown 1990). [1987] [Correia, et al. 
1987]
Crawford-Brown, D.J. Final Report: Risk and Uncertainty Analysis for 
Radon in Drinking Water. American Water Works Association, Denver, 
CO. [1992] [Crawford-Brown 1992]
Edling, C. and Axelson, O. Quantitative Aspects of Radon Daughter 
Exposure and Lung Cancer in Underground Miners, Br. J. Ind. Med. 
(40:182-187) [1983] [Edling and Axelson 1983]
Ershow, A.G. and Cantor, K.P. Total Water and Tapwater Intake in the 
United States: Population-based Estimates of Quantities and Sources. 
Report prepared under National Cancer Institute Order #263-MD-
810264. [1989] [Ershow and Cantor 1989]
Federal Register, Vol. 64, No. 38. Health Risk Reduction and Cost 
Analysis (HRRCA) for Radon in Drinking Water: Notice, Request for 
Comments and Announcement of Stakeholder Meeting. (Feb. 26, 1999) 
9559-9599. [64 FR 9559]
Field, R.W., Fisher, E.L., Valentine, R.L., and Kross, B.C. Radium-
Bearing Pipe Scale Deposits: Implications for National Waterborne 
Radon Sampling Methods. Am.J. Public Health (85:567-570) [April 
1995] [Field et al. 1995]
Gesell, T.F. and Prichard, H.M. The Contribution of Radon in Tap 
Water to Indoor Radon Concentrations. In: Gesell T.F. and W.M. 
Lowder, eds. Natural radiation environment III, Vol. 2. Washington, 
DC: U.S. Department of Energy, Technical Information Center, pp. 
1347-1363. CONF-780422 (Vol. 2). [1980] [Gesell and Prichard 1980]
Horton, T.R. Results of Drinking Water Experiment. Memorandum from 
T.R. Horton of the Environmental Studies Branch to Charles R. 
Phillips. [1982] [Horton 1982]
Hursh, J.B., Morken, D.A. Davis, T.P., and Lovaas, A. The Fate of 
Radon Ingested by Man. Health Phys. (11:465-476). [1965] [Hursh, et 
al. 1965]
Kinner, N.E., Malley, J.P., and Clement, J.A. Radon Removal Using 
Point-of-Entry Water Treatment Techniques. EPA/600/2-90/047. 
Cincinnati, OH: Risk Reduction Engineering Laboratory. [1990] 
[Kinner, et al. 1990]
National Academy of Sciences, National Research Council. Health Risk 
of Radon and Other Internally Deposited Alpha-Emitters: (BEIR IV) 
National Academy Press, Washington, DC. [1988] [NAS 1988]
National Academy of Sciences, National Research Council. Health 
Effects of Exposure to Low Levels of Ionizing Radiation (BEIR V). 
National Academy Press, Washington, DC. [NAS 1990]
National Academy of Sciences, National Research Council. Comparative 
Dosimetry of Radon in Mines and Homes. National Academy Press, 
Washington, DC. [NAS 1991]
National Academy of Sciences, National Research Council. Health 
Effects of Exposure to Radon. (BEIR VI.) National Academy Press, 
Washington, DC. [NAS 1999a]
National Academy of Sciences, National Research Council, Committee 
on the Risk Assessment of Exposure to Radon in Drinking Water, Board 
on Radiation Effects Research. Risk Assessment of Radon in Drinking 
Water. National Academy Press, Washington, DC. [NAS 1999b]
National Institute of Occupational Safety and Health. Criteria for a 
Recommended Standard: Occupation Exposure to Radon Progeny in 
Underground Mines. U.S. Government Printing Office. [1987] [NIOSH 
1987]
Pennington, J.A. Revision of the Total Diet Study Food List and 
Diets. J. Am. Diet. Assoc. (82:166-173) [1983] [Pennington 1983]
Radford, E.P. and St. Clair Renard, K.G. Lung Cancer in Swedish Iron 
Miners Exposed to Low Doses of Radon Daughters. N. Engl. J. Med. 
(310(23):1485-1494) [1984] [Radford and St. Clair Renard 1984]
Sevc J., Kunz, E., Placek, V., and Smid, A. Comments on Lung Cancer 
Risk Estimates. Health Phys. (46: 961-964) [1984] [Sevc, et al. 
1984]
Sevc, J., Kunz, E., Tomasek, L., Placek, V., and Horacek, J. Cancer 
in Man after Exposure to Rn Daughters. Health Phys. (54:27-46) 
[1988] [Svec, et al. 1988]
Suomela M. and Kahlos, H. Studies on the Elimination Rate and the 
Radiation Exposure Following Ingestion of 222-Rn Rich Water. Health 
Phys. (23:641-652) [1972] [Suomela and Kahlos 1972]
United Nations Scientific Committee on the Effects of Atomic 
Radiation. Sources, Effects and Risks of Ionizing Radiation. United 
Nations, NY. [1988] [UNSCEAR 1988]
U.S. Environmental Protection Agency, Office of Radiation Programs. 
An Estimation of the Daily Average Food Intake by Age and Sex for 
Use in Assessing the Radionuclide Intake of Individuals in the 
General Population. EPA 520/1-84-021. [1984] [USEPA 1984]
U.S. Environmental Protection Agency. Examination of Kennedy/Jenks 
Cost Estimates for Radon Removal by Packed Column Air Stripping. 
Memorandum to Marc Parrotta, ODW, from Michael Cummins, ODW. 
[November 23, 1992] [USEPA 1992]
U.S. Environmental Protection Agency, Office of Science and 
Technology, Office of Radiation and Indoor Air, Office of Policy, 
Planning, and Evaluation. Uncertainty Analysis of Risks Associated 
with Exposure to Radon in Drinking Water. TR-1656-3B. [April 30, 
1993] [USEPA 1993]
U.S. Environmental Protection Agency, Office of Water. Report to 
United States Congress on Radon in Drinking Water: Multimedia Risk 
Assessment of Radon. EPA-811-R-94-001. [March 1994] [USEPA 1994]
U.S. Environmental Protection Agency, Office of Science and 
Technology, Office of Radiation and Indoor Air, Office of Policy, 
Planning and Evaluation. Uncertainty Analysis of Risks Associated 
with Exposure to Radon in Drinking Water. EPA 822-R-96-005. [March, 
1995] [USEPA 1995]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Community Water System Survey. Volume II: Detailed 
Survey Result Tables and Methodology Report. EPA 815-R-97-0016. 
[January 1997] [USEPA 1997]
U.S. Environmental Protection Agency, Office of Radiation and Indoor 
Air. Health Risks from Low-Level Environmental Exposure to 
Radionuclides. Federal

[[Page 59370]]

Guidance Report No. 13. Part I--Interim Version. EPA 401/R-97-014. 
[1998] [USEPA 1998]
U.S. Environmental Protection Agency. Technologies and Costs for the 
Removal of Radon from Drinking Water. Prepared by Science 
Applications International Corporation for EPA. [May 1999] [USEPA 
1999a]
U.S. Environmental Protection Agency. EPA's Unit Capital Cost 
Estimates for Aeration for Radon Treatment Versus AWWA and ACWA's 
Estimates from 1992 (Kennedy/Jenks Report) and AWWARF 1995. 
Memorandum to Sylvia Malm, OGWDW, from William Labiosa, OGWDW. [July 
28, 1999] [USEPA 1999b]
U.S. Environmental Protection Agency, Office of Ground Water and 
Drinking Water. Methods, Occurrence and Monitoring Document for 
Radon. Draft. [August 3, 1999] [USEPA 1999c]
U.S. Environmental Protection Agency, Office of Science and 
Technology. Draft Criteria Document for Radon in Drinking Water. 
[June 1999] [USEPA 1999d]
Valentine, R., Stearns, S., Kurt, A., Walsh, D., and Mielke, W. 
Radon and Radium from Distribution System and Filter Media Deposits. 
Presented at AWWA Water Quality Technology Conference, Toronto. 
[November, 1992] [Valentine et al. 1992]
von Dobeln, W. and Lindell, B. Some Aspects of Radon Contamination 
Following Ingestion. Arkiv for Fysik. 27:531-572 [1964] [von Dobeln 
and Lindell 1964]

List of Subjects

40 CFR Part 141

    Environmental protection, Chemicals, Indians--lands, 
Intergovernmental relations, Radiation protection, Reporting and 
recordkeeping requirements, Water supply.

40 CFR Part 142

    Environmental protection, Administrative practice and procedure, 
Chemicals, Indians--lands, Radiation protection, Reporting and 
recordkeeping requirements, Water supply.

    Dated: October 19, 1999.
Carol M. Browner,
Administrator.

    For the reasons set out in the preamble, the Environmental 
Protection Agency proposes to amend 40 CFR parts 141 and 142 as 
follows:

PART 141--NATIONAL PRIMARY DRINKING WATER REGULATIONS

    1. The authority citation for part 141 continues to read as 
follows:

    Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-
5, 300g-6, 300j-4, 300j-9, and 300j-11.

    2. Section 141.2 is amended by adding definitions of ``Alternative 
Maximum Contaminant Level (AMCL)'' and ``Multimedia Mitigation (MMM) 
Program Plan'' in alphabetical order, to read as follows:


Sec. 141.2  Definitions.

* * * * *
    Alternative Maximum Contaminant Level (AMCL) is the permissible 
level of radon in drinking water delivered by a community water system 
in a State with an EPA-approved multimedia mitigation (MMM) program 
plan, or by a community water system with a State-approved local MMM 
program plan.
* * * * *
    Multimedia Mitigation (MMM) Program Plan is a State or community 
water system program plan of goals and strategies developed with public 
participation to promote indoor radon risk reduction. MMM programs for 
radon in indoor air may use a variety of strategies, including public 
education, testing, training, technical assistance, remediation grant 
and loan or incentive programs, or other regulatory or non-regulatory 
measures.
* * * * *
    3. Section 141.6 is amended by adding paragraph (j) to read as 
follows:


141.6  Effective dates.

* * * * *
    (j) The regulations set forth in Subpart R of this part are 
effective [60 days after date of publication of the final rule in the 
Federal Register].

Subpart C--[Amended]

    4. A new Sec. 141.20 is added to Subpart C to read as follows:


Sec. 141.20  Analytical methods, monitoring, and compliance 
requirements for radon.

    (a) Analytical methods. (1) Analysis for radon shall be conducted 
using one of the methods in the following table:

                              Proposed Analytical Methods for Radon in Drinking Water
----------------------------------------------------------------------------------------------------------------
                                                          References (method or page number)
             Methodology             ---------------------------------------------------------------------------
                                                 SM                       ASTM                     EPA
----------------------------------------------------------------------------------------------------------------
Liquid Scintillation Counting.......  7500-Rn\1\..............  D 5072 92\2\...........  .......................
De-emanation........................  ........................  .......................  EPA 1987\3\
----------------------------------------------------------------------------------------------------------------
\1\ Standard Methods for the Examination of Water and Wastewater. 19th Edition Supplement. Clesceri, L., A.
  Eaton, A. Greenberg, and M. Franson, eds. American Public Health Association, American Water Works
  Association, and Water Environment Federation. Washington, DC. 1996.
\2\ American Society for Testing and Materials (ASTM). Standard Test Method for Radon in Drinking Water.
  Designation: D 5072-92. Annual Book of ASTM Standards. Vol. 11.02. 1996.
\3\ Appendix D, Analytical Test Procedure, ``The Determination of Radon in Drinking Water''. In ``Two Test
  Procedures for Radon in Drinking Water, Interlaboratory Collaborative Study''. EPA/600/2-87/082. March 1987.
  p. 22.

    (2) Sample collection for radon shall be conducted using the sample 
preservation, container, and maximum holding time procedures specified 
in the following table.

                       Sampling Methods and Sample Handling, Preservation, and Holding Time
----------------------------------------------------------------------------------------------------------------
                                                                                           Maximum holding time
          Sampling methods                  Preservative            Sample Container            for sample
----------------------------------------------------------------------------------------------------------------
(i) As described in SM 7500-Rn\1\...  Ship sample in an         Glass with teflon-lined  4 days.
                                       insulated package to      septum.
                                       avoid large temperature
                                       changes.

[[Page 59371]]

 
(ii) As described in EPA 1987\2\ ...
----------------------------------------------------------------------------------------------------------------
\1\ Standard Methods for the Examination of Water and Wastewater. 19th Edition Supplement. Clesceri, L., A.
  Eaton, A. Greenberg, and M. Franson, eds. American Public Health Association, American Water Works
  Association, and Water Environment Federation. Washington, DC. 1996.
\2\ ``Two Test Procedures for Radon in Drinking Water, Interlaboratory Collaborative Study''. EPA/600/2-87/082.
  March 1987.

    (b) Monitoring and compliance requirements. Community water systems 
(CWSs) shall conduct monitoring to determine compliance with the 
maximum contaminant level (MCL) or alternate maximum contaminant level 
(AMCL) specified in Sec. 141.66 in accordance with this chapter. The 
monitoring requirements have been developed to be consistent with the 
Phase II/V monitoring schedule.
    (1) Applicability and sampling location. CWSs using a ground water 
source or CWSs using ground water and surface water sources (for the 
purpose of this section hereafter referred to as systems) shall sample 
at every entry point to the distribution system which is representative 
of each well after treatment and/or storage (hereafter called a 
sampling point) under normal operating conditions in accordance with 
paragraph (b)(2) of this section.
    (2) Monitoring--(i) Initial monitoring requirements. (A) Systems 
must collect four consecutive quarterly samples beginning by the date 
specified in Sec. 141.301(b).
    (B) States may allow previous sampling data collected after [60 
days after date of publication of the final rule] to satisfy the 
initial monitoring requirements, provided the system has conducted 
monitoring to satisfy the requirements specified in this section. If a 
system's early monitoring data indicates an MCL/AMCL exceedence, the 
system will not be considered in violation until the end of the 
applicable initial monitoring period specified in Sec. 141.301(b).
    (ii) Routine monitoring requirements. Systems must continue 
quarterly monitoring until the running average of four consecutive 
quarterly samples is less than the MCL/AMCL. If the running average of 
four consecutive quarterly samples is less than the MCL/AMCL then 
systems may conduct annual monitoring at the State's discretion.
    (iii) Reduced monitoring requirements. States may allow systems to 
reduce the frequency of monitoring to once every three years (one 
sample per compliance period) beginning the following compliance period 
provided the systems:
    (A) Demonstrate that the average of four consecutive quarterly 
samples is below \1/2\ MCL/AMCL;
    (B) No individual samples exceed the MCL/AMCL; and
    (C) The States determine that the systems are reliably and 
consistently below the MCL/AMCL.
    (iv) Increased monitoring requirements. (A) Systems which exceed 
the MCL/AMCL shall monitor quarterly beginning the quarter following 
the exceedence. States may allow systems to reduce their monitoring 
frequency if the requirements specified in paragraph (b)(2)(iii) or 
(b)(2)(iv)(B) of this section are met.
    (B) Systems monitoring once every three years, or less frequently, 
which exceed \1/2\ MCL/AMCL shall begin annual monitoring the year 
following the exceedence. Systems may reduce monitoring to once every 
three years if the average of the initial and three consecutive annual 
samples is less than \1/2\ MCL/AMCL and the State determines the system 
is reliably and consistently below the MCL/AMCL.
    (C) If a community water system has a portion of its distribution 
system separable from other parts of the distribution system with no 
interconnections, increased monitoring need only be conducted at points 
of entry to those portions of system.
    (v) Failure to conduct monitoring as described in this section is a 
monitoring violation.
    (3) Monitoring waivers. (i) States may grant a monitoring waiver to 
systems provided that:
    (A) The system has completed initial monitoring requirements as 
specified in paragraph (b)(2)(i) of this section. Systems shall 
demonstrate that all previous analytical results were less than \1/2\ 
MCL/AMCL. New systems and systems using a new ground water source must 
complete four consecutive quarters of monitoring before the system is 
eligible for a monitoring waiver; and
    (B) States determine that the systems are reliably and consistently 
below the MCL/AMCL, based on a consideration of potential radon 
contamination of the source water due to the geological characteristics 
of the source water aquifer.
    (ii) Systems with a monitoring waiver must collect a minimum of 1 
sample every nine-years (once per compliance cycle).
    (iii) A monitoring waiver remains in effect until completion of the 
nine-year compliance cycle.
    (iv) A decision by States to grant a monitoring waiver shall be 
made in writing and shall set forth the basis for the determination.
    (4) Confirmation samples. Systems may take additional samples to 
verify initial sample results as specified by the State. The results of 
the initial and confirmation samples will be averaged for use in 
calculation of compliance.
    (5) Compliance. Compliance with Sec. 141.66 shall be determined 
based on the analytical result(s) obtained at each sampling point. If 
one sampling point is in violation, the system is in violation.
    (i) For systems monitoring more frequently than annually, 
compliance with the MCL/AMCL is determined by a running annual average 
at each sampling point. If the average at any sampling point is greater 
than the MCL/AMCL, then the system is out of compliance with the MCL/
AMCL.
    (ii) If any one quarterly sampling result will cause the running 
average to exceed the MCL/AMCL, the system is out of compliance.
    (iii) Systems monitoring annually or less frequently whose sample 
result exceeds the MCL/AMCL will revert to quarterly sampling 
immediately. The system will not be considered in violation of the MCL/
AMCL until they have completed one year of quarterly sampling.
    (iv) All samples taken and analyzed under the provisions of this 
section must be included in determining compliance, even if that number 
is greater than the minimum required.
    (v) If a system does not collect all required samples when 
compliance is based on a running annual average of

[[Page 59372]]

quarterly samples, compliance will be based on available data.
    (vi) If a sample result is less than the detection limit, zero will 
be used to calculate the annual average.
    (vii) During the initial monitoring period, if the compliance 
determination for a system in a non-MMM State exceeds the MCL, the 
system will incur a MCL violation unless the system notifies the State 
by [four years after date of publication of the final rule in the 
Federal Register] of their intent to submit a local MMM plan, submits a 
local MMM plan to the State within [5 years after date of publication 
of the final rule in the Federal Register] and begins implementation by 
[5.5 years after date of publication of the final rule in the Federal 
Register]. The State shall approve or disapprove a local MMM program 
plan within 6 months from the date of receipt. If the State does not 
disapprove the local MMM program plan during such period, then the CWS 
shall implement the plan submitted to the State for approval. The 
compliance determination will be conducted as described in this 
paragraph.
    (viii) Following the completion of the initial monitoring period, 
if the compliance determination for a system in a non-MMM State exceeds 
the MCL, the system will incur a MCL violation unless the system 
submits a local MMM plan to the State within 1 year from the date of 
the exceedence and begins implementation 1.5 years from the date of the 
exceedence. The State shall approve or disapprove a local MMM program 
plan within 6 months from the date of receipt. If the State does not 
disapprove the local MMM program plan during such period, then the CWS 
shall implement the plan submitted to the State for approval. The 
compliance determination will be conducted as described in this 
paragraph.
    (6) If a community water system has a distribution system separable 
from other parts of the distribution system with no interconnections, 
the State may allow the system to give public notice to only the area 
served by that portion of the system which is out of compliance.
    5. Section 141.28 is revised to read as follows:


Sec. 141.28  Certified laboratories.

    (a) For the purpose of determining compliance with Sec. 141.20 
through 141.27, 141.41, and 141.42, samples may be considered only if 
they have been analyzed by a laboratory certified by the State except 
that measurements for turbidity, free chlorine residual, temperature 
and pH may be performed by any person acceptable to the State.
    (b) Nothing in this part shall be construed to preclude the State 
or any duly designated representative of the State from taking samples 
or from using the results from such samples to determine compliance by 
a supplier of water with the applicable requirements of this part.

Subpart F--[Amended]

    6. A new Sec. 141.55 is added to Subpart F to read as follows:


Sec. 141.55  Maximum contaminant level goals for radionuclides.

    MCLGs are as indicated in the following table:

------------------------------------------------------------------------
                 Contaminant                              MCLG
------------------------------------------------------------------------
Radon-222....................................  Zero.
------------------------------------------------------------------------

Subpart G--[Amended]

    7. A new Sec. 141.66 is added to Subpart G to read as follows:


Sec. 141.66  Maximum contaminant level for radionuclides.

    (a) The maximum contaminant level for radon-222 is as follows: (1) 
A community water system (CWS) using a ground water source or using 
ground water and surface water sources that serves 10,000 or fewer 
people shall comply with the alternative maximum contaminant level 
(AMCL) of 4000 pCi/L, and implement a State-approved multimedia 
mitigation (MMM) program to address radon in indoor air (unless the 
State in which the system is located has a MMM approved by the 
Environmental Protection Agency). These systems may elect to comply 
with the MCL of 300 pCi/L instead of developing a local CWS MMM program 
plan.
    (2) A CWS using a ground water source or using ground water and 
surface water sources that serves more than 10,000 people shall comply 
with the MCL of 300 pCi/L, except that the system may comply with an 
AMCL of 4000 pCi/L where:
    (i) The State in which the CWS is located has adopted an MMM 
program plan approved by EPA; or,
    (ii) The CWS has adopted an MMM program plan approved by the State.
    (3) A CWS shall monitor for radon in drinking water according to 
the requirements in Sec. 141.20, and report the results to the State, 
and continue to monitor as described in Sec. 141.20. If the State 
determines that the CWS is in compliance with the MCL of 300 pCi/L, the 
CWS has met the requirements of this section and is not subject to the 
requirements of subpart R of this part, regarding MMM programs.
    (4) The Administrator, pursuant to section 1412 of the Act, hereby 
identifies, as indicated in the following table, the best technology 
available for achieving compliance with the maximum contaminant levels 
for radon identified in paragraphs (a)(1) and (a)(2) of this section:

BAT for Radon-222

High-Performance Aeration \1\

    (5) The Administrator, pursuant to section 1412 of the Act, hereby 
identifies in the following table the best technology available to 
systems serving 10,000 persons or fewer for achieving compliance with 
the MCL or AMCL. The table addresses affordability and technical 
feasibility for such BAT.
---------------------------------------------------------------------------

    \1\ High Performance Aeration is defined as the group of 
aeration technologies that are capable of being designed for high 
radon removal efficiencies, i.e., Packed Tower Aeration, Multi-Stage 
Bubble Aeration and other suitable diffused bubble aeration 
technologies, Shallow Tray and other suitable Tray Aeration 
technologies, and any other aeration technologies that are capable 
of similar high performance.

   Proposed Small Systems Compliance Technologies (SSCTS) \1\ and Associated Contaminant Removal Efficiencies
----------------------------------------------------------------------------------------------------------------
                                  Affordable for
   Small systems compliance        listed small         Removal           Operator level       Limitations (see
          technology                 systems           efficiency          required \3\           footnotes)
                                  categories \2\
----------------------------------------------------------------------------------------------------------------
Packed Tower Aeration (PTA)...  All Size           90->99.9% Removal  Intermediate..........  (a)
                                 Categories.
High Performance Package Plant  All Size           90-> 99.9%         Basic to Intermediate.  (a)
 Aeration (e.g., Multi-Stage     Categories.        Removal.
 Bubble Aeration, Shallow Tray
 Aeration).
Diffused Bubble Aeration......  All Size           70 to >99%         Basic.................  (a, b)
                                 Categories.        removal.

[[Page 59373]]

 
Tray Aeration.................  All Size           80 to >90%.......  Basic.................  (a, c)
                                 Categories.
Spray Aeration................  All Size           80 to >90%.......  Basic.................  (a, d)
                                 Categories.
Mechanical Surface Aeration...  All Size           >90%.............  Basic.................  (a, e)
                                 Categories.
Centralized granular activated  May not be         50 to >99%         Basic.................  (f)
 carbon.                         affordable,        Removal.
                                 except for very
                                 small flows.
Point-of-Entry (POE) granular   May be affordable  50 to >99%         Basic.................  (f, g)
 activated carbon.               for systems        Removal.
                                 serving fewer
                                 than 500 persons.
----------------------------------------------------------------------------------------------------------------
\1\ Section 1412(b)(4)(E)(ii) of the SDWA specifies that SSCTs must be affordable and technically feasible for
  small systems.
\2\ The Act (ibid.) specifies three categories of small systems: i) those serving 25 or more, but fewer than
  501, ii) those serving more than 500, but fewer than 3,301, and iii) those serving more than 3,300, but fewer
  than 10,001.
\3\ From National Research Council. Safe Water from Every Tap: Improving Water Service to Small Communities.
  National Academy Press. Washington, DC. 1997. Limitations: a) Pre-treatment to inhibit fouling may be needed.
  Post-treatment disinfection and/or corrosion control may be needed. b) May not be as efficient as other
  aeration technologies because it does not provide for convective movement of the water, which reduces the
  air:water contact. It is generally used in adaptation to existing basins. c) Costs may increase if a forced
  draft is used. Slime and algae growth can be a problem, but may be controlled with chemicals, e.g., copper
  sulfate or chlorine. d) In single pass mode, may be limited to uses where low removals are required. In
  multiple pass mode (or with multiple compartments), higher removals may be achieved. e) May be most applicable
  for low removals, since long detention times, high energy consumption, and large basins may be required for
  larger removal efficiencies. f) Applicability may be restricted to radon influent levels below around 5000 pCi/
  L to reduce risk of the build-up of radioactive radon progeny. Carbon bed disposal frequency should be
  designed to allow for standard disposal practices. If disposal frequency is too long, radon progeny, radium,
  and/or uranium build-up may make disposal costs prohibitive. Proper shielding may be required to reduce gamma
  emissions from the GAC unit. GAC may be cost-prohibitive except for very small flows. g) When POE devices are
  used for compliance, programs to ensure proper long-term operation, maintenance, and monitoring must be
  provided by the water system to ensure adequate performance.

Subpart O--[Amended]

    8. Section 141.151 is amended by revising paragraph (d) to read as 
follows:


141.151  Purpose and applicability of this subpart.

* * * * *
    (d) For the purpose of this subpart, detected means: at or above 
the levels prescribed by Sec. 141.23(a)(4) for inorganic contaminants, 
at or above the levels prescribed by Sec. 141.24(f)(7) for the 
contaminants listed in Sec. 141.61(a), at or above the level prescribed 
by Sec. 141.24(h)(18) for the contaminants listed in Sec. 141.61(c), at 
or above the level prescribed by Sec. 141.66 for radon, and at or above 
the levels prescribed by Sec. 141.25(c) for radioactive contaminants.
* * * * *
    9. Section 141.153 is amended by revising paragraph (d)(1)(i); 
removing paragraph (e)(2) and redesignating paragraph (e)(3) as (e)(2); 
redesignating paragraphs (f)(5), (f)(6), and (f)(7) as (f)(6), (f)(7), 
and (f)(8); and adding paragraph (f)(5) to read as follows:


Sec. 141.153  Content of the reports.

* * * * *
    (d) * * *
    (1) * * *
    (i) Contaminants subject to a MCL, AMCL, action level, or treatment 
technique (regulated contaminants);
* * * * *
    (f) * * *
    (5) Local multimedia radon mitigation programs prescribed by 
subpart R of this part.
* * * * *
    10. Section 141.154 is amended by adding paragraph (f) as follows:


Sec. 141.154  Required additional health information.

* * * * *
    (f) In each complete calendar year between [date of publication of 
final rule in the Federal Register] and [4 years after date of 
publication of the final rule in the Federal Register], each report 
from a system that has ground water as a source must include the 
following notice (except that a system developing a local MMM program 
in a non-MMM State needs to include this statement in each calendar 
year between [date of publication of the final rule in the Federal 
Register] and [5 years after date of publication of the final rule in 
the Federal Register] :

    Radon is a naturally-occurring radioactive gas found in soil and 
outdoor air that may also be found in drinking water and indoor air. 
Some people exposed to elevated radon levels over many years in 
drinking water may have an increased risk of getting cancer. The 
main health risk is lung cancer from radon entering indoor air from 
soil under homes. Your water system plans to test for radon by 
[insert date], and if radon is detected your water system will 
provide the results of testing to their customers. The best way to 
reduce the overall risk from radon is to reduce radon levels in 
indoor air. Some States, and water systems, may now be working to 
develop a program to reduce radon exposure in indoor air and 
drinking water. To get more information and to help develop the 
program, call the Radon Hotline (800-SOS-RADON) or visit the web 
site http://www.epa.gov/iaq/radon/.

Subpart Q--[Amended]

    11. In Sec. 141.201, Table 1 proposed on May 13, 1999, at 64 FR 
25964 is amended by revising paragraphs (1) introductory text and 
(1)(i) to read as follows:


Sec. 141.201  General Public Notification Requirements.

* * * * *
    Table 1 to Sec. 141.201--Violation Categories and Other Situations 
Requiring a Public Notice.
    (1) NPDWR violations (MCL/AMCL, local MMM, MRDL, treatment 
technique, monitoring and testing procedure)
    (i) Failure to comply with an applicable maximum contaminant level 
(MCL), alternative maximum contaminant level (AMCL), the local 
multimedia mitigation requirement for small systems in non-MMM States, 
or maximum residual disinfectant level (MRDL).
* * * * *
    12. In Sec. 141.203, Table 1 proposed on May 13, 1999, at 64 FR 
25964 is amended by revising paragraph (1) to read as follows:


Sec. 141.203  Tier 2 Public Notice--Form, manner, and frequency of 
notice.

* * * * *

[[Page 59374]]

    Table 1 to Sec. 141.203. Violation Categories and Other Situations 
Requiring a Tier 2 Public Notice
    (1) All violations of the MCL, AMCL, MRDL, and treatment technique 
requirements not included in the Tier 1 notice category;
* * * * *
    13. In Sec. 141.204, Table 1 proposed on May 13, 1999, at 64 FR 
25964 is amended by adding paragraph (5) to read as follows:


Sec. 141.204.  Tier 3 Public Notice--Form, manner, and frequency of 
notice.

* * * * *
    Table 1 to Sec. 141.204. Violation Categories and Other Situations 
Requiring a Tier 3 Public Notice
    (5) All violations of the MMM requirements not included in the Tier 
1 or 2 notice category;
* * * * *
    14. Section 141.205 proposed on May 13, 1999, at 64 FR 25964 is 
amended by revising paragraph (d)(1), to read as follows:


Sec. 141.205  Content of the public notice.

* * * * *
    (d) * * *
    (1) Standard health effects language for MCL, AMCL, MMM or MRDL 
violations, treatment technique violations, and violations of the 
condition of a variance or exemption. Public water systems must include 
in each public notice the health effects language specified in Appendix 
B to this subpart corresponding to each MCL, AMCL, MMM, MRDL, and 
treatment technique violation listed in Appendix A to this subpart, and 
for each violation of a condition of a variance or exemption.
* * * * *
    15. Part 141 is amended by adding a new Subpart R to read as 
follows:

Subpart R--Reducing Radon Risks In Indoor Air and Drinking Water

Sec.

141.300  Applicability.
141.301  General requirements.
141.302  Multimedia mitigation (MMM) requirements (required elements 
of MMM program plans).
141.303  Multimedia mitigation (MMM) reporting and compliance 
requirements.
141.304  Local multimedia mitigation program plan approval and 
program review.
141.305  States that do not have primacy.

Subpart R--Reducing Radon Risks in Indoor Air and Drinking Water


Sec. 141.300  Applicability.

    (a) The requirements of this subpart constitute national primary 
drinking water regulations for radon. The provisions of this subpart 
apply to community water systems (CWS) using a ground water source or 
using ground water and surface water sources. CWSs must monitor for 
radon in drinking water according to the requirements described in 
Sec. 141.20, and report the results to the State, and continue to 
monitor as described in Sec. 141.20. If the State determines that the 
CWS is in compliance with the MCL of 300 pCi/L, the CWS has met the 
requirements of this section and is not subject to the requirements of 
this subpart.
    (b) These regulations in this subpart establish criteria for the 
development and implementation of program plans to mitigate radon in 
indoor air and drinking water (multimedia mitigation or MMM program 
plan). In general, where a State, CWS, or Tribal MMM program plan is 
approved, CWSs comply with an AMCL of 4000 pCi/L (Sec. 141.66). In 
jurisdictions without an approved MMM program plan, large CWSs (serving 
greater than 10,000 people) must comply with an MCL of 300 pCi/L 
(Sec. 141.66), except they comply with the AMCL of 4000 pCi/L if they 
develop a CWS MMM program plan approved by the State. Small community 
water systems serving 10,000 or fewer people must comply with 4000 pCi/
L and implement a State-approved multimedia mitigation program plan to 
address radon in indoor air (unless the State in which the system is 
located has a multimedia mitigation program plan approved by the 
Environmental Protection Agency); these systems have the option of 
complying with the MCL instead of implementing a MMM program.


Sec. 141.301  General requirements.

    (a) The requirements for the MMM program plan are set out in this 
subpart. The requirements for the MCL are set out in Sec. 141.20(a) 
(analytical methods), Sec. 141.20(b) (monitoring and compliance), 
Sec. 141.66(a) through (c) (requirements for systems, including MCL and 
AMCL), and Sec. 141.66(d) (BAT).
    (b) Compliance dates.--(1) Initial monitoring. (i) For States that 
submit a letter to the Administrator by [90 days after date of 
publication of the final rule in the Federal Register] committing to 
develop an MMM program plan in accordance with section 
1412(b)(13)(G)(v) of the Act, CWSs must begin one year of quarterly 
monitoring for compliance with the AMCL by [4.5 years after date of 
publication of the final rule in the Federal Register].
    (ii) For States not submitting a letter to the Administrator by [90 
days after date of publication of final rule in the Federal Register] 
committing to develop an MMM program plan, CWSs must begin one year of 
quarterly monitoring for compliance with the MCL/AMCL by [3 years after 
date of publication of final rule in the Federal Register].
    (2) State-wide MMM programs. (i) For States that submit a letter to 
the Administrator by [90 days after date of publication of the final 
rule in the Federal Register] committing to develop an MMM program plan 
in accordance with section 1412(b)(13)(G)(v), implementation of the 
State-wide MMM program must begin by [4.5 years after date of 
publication of the final rule in the Federal Register].
    (ii) For States not submitting a letter to the Administrator by [90 
days after date of publication of the final rule in the Federal 
Register] committing to develop an MMM program plan, but which 
subsequently decide to adopt the AMCL, implementation of the State-wide 
MMM program must begin by [3 years after date of publication of the 
final rule in the Federal Register].
    (iii) If EPA-approval of a State MMM program plan is revoked, all 
systems have one year from notification by the State to comply with the 
MCL. If a system chooses to continue complying with the AMCL and 
develop and implement a local MMM program, the State will specify a 
timeframe for compliance.
    (3) Local MMM programs. (i) During the initial monitoring period, 
if the compliance determination for a CWS in a non-MMM State exceeds 
the MCL, the CWS will incur an MCL violation unless the system notifies 
the State by [four years after date of publication of the final rule in 
the Federal Register] of their intent to submit a local MMM plan, 
submits a local MMM plan to the State within [5 years after date of 
publication of the final rule in the Federal Register] and begins 
implementation by [5.5 years after date of publication of the final 
rule in the Federal Register]. The compliance determination will be 
conducted as described in Sec. 141.20(b)(2).
    (ii) Following the completion of the initial monitoring period, if 
the compliance determination for a CWS in a non-MMM State exceeds the 
MCL, the system will incur an MCL violation unless the system submits a 
local MMM plan to the State within 1 year from the date of the 
exceedence and begins implementation 1.5 years from the date of the 
exceedence. The compliance determination will be conducted as described 
in this paragraph.
    (iii) The State shall approve or disapprove a local MMM program 
plan

[[Page 59375]]

within 6 months from the date of receipt. If the State does not 
disapprove the local MMM program plan during such period, the CWS shall 
implement the plan submitted to the State for approval.
    (iv) If the State determines the CWS is not adequately implementing 
the local MMM plan approved by the State, the system shall incur an MMM 
violation.
    (v) During the MMM program 5-year review periods, the system shall 
incur an MMM violation if the State determines the CWS is not meeting 
MMM program plan objectives.


Sec. 141.302  Multimedia mitigation (MMM) requirements (required 
elements of MMM program plans).

    The following are required for approval of State MMM program plans 
by EPA. Local MMM program plans developed by community water systems 
(CWS) are deemed to be approved by EPA if they meet these criteria (as 
appropriate for the local level) and are approved by the State. The 
term ``State'', as referenced next, means any entity submitting an MMM 
program plan for approval, including States, with and without primacy, 
Indian Tribes and community water systems.
    (a) Description of process for involving the public. (1) States are 
required to involve community water system customers, and other sectors 
of the public with an interest in radon, both in drinking water and in 
indoor air, in developing their MMM program plan. The MMM program plan 
must include:
    (i) A description of processes the State used to provide for public 
participation in the development of its MMM program plan, including the 
components identified in paragraphs (b), (c), and (d) of this section;
    (ii) A description of the nature and extent of public participation 
that occurred, including a list of groups and organizations that 
participated;
    (iii) A summary describing the recommendations, issues, and 
concerns arising from the public participation process and how these 
were considered in developing the State's MMM program plan; and
    (iv) A description of how the State made information available to 
the public to support informed public participation, including 
information on the State's existing indoor radon program activities and 
radon risk reductions achieved, and on options considered for the MMM 
program plan along with any analyses supporting the development of such 
options.
    (2) Once the draft program plan has been developed, the State must 
provide notice and opportunity for public comment on the draft plan 
prior to submitting it to EPA.
    (b) Quantitative goals. (1) States are required to establish and 
include in their plans quantitative goals, to measure the effectiveness 
of their MMM program, for the following:
    (i) Existing houses with elevated indoor radon levels that will be 
mitigated by the public; and
    (ii) New houses that will be built radon-resistant by home 
builders.
    (2) These goals must be defined quantitatively either as absolute 
numbers or as rates. If goals are defined as rates, a detailed 
explanation of the basis for determining the rates must be included.
    (3) States are required to establish goals for promoting public 
awareness of radon health risks, for testing of existing homes by the 
public, for testing and mitigation of existing schools, and for 
construction of new public schools to be radon-resistant, or to include 
an explanation of why goals were not established in these program 
areas.
    (c) Implementation Plans. (1) States are required to include in 
their MMM program plan implementation plans outlining the strategic 
approaches and specific activities the State will undertake to achieve 
the quantitative goals identified in paragraph (b) of this section. 
This must include implementation plans in the following two key areas:
    (i) Promoting increased testing and mitigation of existing housing 
by the public through public outreach and education and during 
residential real estate transactions.
    (ii) Promoting increased use of radon-resistant techniques in the 
construction of new homes.
    (2) If a State has included goals for promoting public awareness of 
radon health risks; promoting testing of existing homes by the public; 
promoting testing and mitigation of existing schools; and promoting 
construction of new public schools to be radon resistant, then the 
State is required to submit a description of the strategic approach 
that will be used to achieve the goals.
    (3) States are required to provide the overall rationale and 
support for why their proposed quantitative goals identified in 
paragraph (b) of this section, in conjunction with their program 
implementation plans, will satisfy the statutory requirement that an 
MMM program be expected to achieve equal or greater risk reduction 
benefits to what would have been expected if all community water 
systems in the State complied with the MCL.
    (d) Plans for measuring and reporting results. (1) States are 
required to include in the MMM plan submitted to EPA a description of 
the approach that will be used to assess the results from 
implementation of the State MMM program, and to assess progress towards 
the quantitative goals in paragraph (b) of this section. This 
specifically includes a description of the methodologies the State will 
use to determine or track the number or rate of existing homes with 
elevated levels of radon in indoor air that are mitigated and the 
number or the rate of new homes built radon-resistant. This must also 
include a description of the approaches, methods, or processes the 
State will use to make the results of these assessments available to 
the public.
    (2) If a State includes goals for promoting public awareness of 
radon health risks; testing of existing homes by the public; testing 
and mitigation of existing schools; and construction of new public 
schools to be radon-resistant; the State is required to submit a 
description of how the State will determine or track progress in 
achieving each of these goals. This must also include a description of 
the approaches, methods, or processes the State will use to make these 
results of these assessments available to the public.


Sec. 141.303  Multimedia mitigation (MMM) reporting and compliance 
requirements.

    (a) In accordance with the Safe Drinking Water Act (SDWA), EPA is 
to review State MMM programs at least every five years. For the 
purposes of this review, the States with EPA-approved MMM program plans 
shall provide written reports to EPA in the second and fourth years 
between initial implementation of the MMM program and the first 5-year 
review period, and in the second and fourth years of every subsequent 
5-year review period. States that submit a letter to the Administrator 
by [90 days after date of publication of the final rule in the Federal 
Register] committing to develop an MMM program plan, must submit their 
first 2-year report by 6.5 years from publication of the final rule. 
For States not submitting the 90-day letter, but choosing subsequently 
to submit an MMM program plan and adopt the AMCL, the first 2-year 
report must be submitted to EPA by 5 years from publication of the 
final rule. EPA will review these programs to determine whether they 
continue to be expected to achieve risk reduction of indoor radon using 
the information provided in the two biennial reports.
    (b)(1) These reports are required to include the following 
information:

[[Page 59376]]

    (i) A quantitative assessment of progress towards meeting the 
required goals described in Sec. 141.302(b), including the number or 
rate of existing homes mitigated and the number or rate of new homes 
built radon-resistant since implementation of the States' MMM program, 
and,
    (ii) A description of accomplishments and activities that implement 
the required program strategies, described in Sec. 141.302(c), outlined 
in the implementation plans and in the two required areas of promoting 
increased testing and mitigation of existing homes and promoting 
increased use of radon-resistant techniques in construction of new 
homes.
    (2) If goals were defined as rates, the State must also provide an 
estimate of the number of mitigations and radon-resistant new homes 
represented by the reported rate increase for the two-year period.
    (3) If the MMM program plan includes goals for promoting public 
awareness of the health effects of indoor radon, testing of homes by 
the public; testing and mitigation of existing schools; and 
construction of new public schools to be radon-resistant, the report is 
also required to include information on results and accomplishments in 
these areas.
    (c) If EPA determines that a MMM program is not achieving progress 
towards its goals, EPA and the State shall collaborate to develop 
modifications and adjustments to the program to be implemented over the 
five year period following the review. EPA will prepare a summary of 
the outcome of the program evaluation and the proposed modification and 
adjustments, if any, to be made by the State.
    (d) If EPA determines that a State MMM program is not achieving 
progress towards its MMM goals, and the State repeatedly fails to 
correct, modify and adjust implementation of their MMM program after 
notice by EPA, EPA will withdraw approval of the State's MMM program 
plan. CWSs in the State would then be required to comply with the MCL, 
or develop a State-approved CWS MMM program plan. The State will be 
responsible for notifying CWSs of the Administrator's withdrawal of 
approval of the State-wide MMM program plan. EPA will work with the 
State to establish a State process for review and approval of CWS MMM 
program plans that meet the required criteria, including local public 
participation in development and review of the program plan, and a time 
frame for submission of program plans by CWSs that choose to continue 
complying with the AMCL.
    (e) States shall make available to the public each of these two-
year reports identified in paragraph (a) of this section, as well as 
the EPA summaries of the five-year reviews of a State's MMM program, 
within 90 days of completion of the reports and the review.
    (f) In primacy States without a State-wide MMM program, the States 
shall provide a report to EPA every five-years on the status and 
progress of CWS MMM programs towards meeting their goals. The first of 
such reports would be due by [10.5 years after date of publication of 
the final rule in Federal Register].


Sec. 141.304  Local multimedia mitigation program plan approval and 
program review.

    (a) In States without an EPA-approved MMM program plan, any 
community water system may elect to develop and implement a local MMM 
program plan that meets the criteria in Sec. 141.302 and comply with 
the AMCL in lieu of the MCL. Local CWS MMM program plans must be 
approved by the State.
    (b) CWSs with State-approved MMM program plans shall report to the 
State as required by the State. States shall review such local programs 
at least every five years to determine if CWSs are implementing their 
program plans and making progress towards their goals. If the CWS fails 
to meet those requirements, the State shall require the system to 
comply with the MCL.


Sec. 141.305  States that do not have primacy.

    (a) If a State, as defined in section 1401 of the Act, that does 
not have primary enforcement responsibility for the Public Water System 
Program under section 1413 of the Act chooses to submit an MMM program 
plan to EPA, that program plan must meet the criteria in Sec. 141.301. 
EPA will approve such program plans in accordance with the requirements 
of Sec. 141.302.
    (b) States with EPA-approved MMM program plans shall report to EPA 
in accordance with the requirements of Sec. 141.303.

PART 142--NATIONAL PRIMARY DRINKING WATER REGULATIONS 
IMPLEMENTATION

    1. The authority citation for part 142 continues to read as 
follows:

    Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-
5, 300g-6, 300j-4, 300j-9, and 300j-11.

    2. Section 142.12 is amended by adding new paragraph (b)(4) to read 
as follows:


Sec. 142.12  Revision of State programs.

* * * * *
    (b) * * *
    (4) To be granted an extension for radon regulatory requirements 
included under 40 CFR part 141, subpart R, the State must commit to 
adopt the AMCL and MMM program plan, or MCL.
* * * * *
    3. Section 142.15 is amended by adding new paragraph (c)(6) to read 
as follows:


Sec. 142.15  Reports by States.

* * * * *
    (c) * * *
    (6) In accordance with the Safe Drinking Water Act (SDWA), EPA is 
to review State MMM programs at least every five years. EPA will review 
these programs to determine whether they continue to be expected to 
achieve risk reduction of indoor radon using the information provided 
in the two biennial reports. For the purposes of this review:
    (i)(A) States with EPA-approved MMM program plans shall provide 
written reports to EPA in the second and fourth years between initial 
implementation of the MMM program and the first 5-year review period, 
and in the second and fourth years of every subsequent 5-year review 
period.
    (B) States that submit a letter to the Administrator by [90 days 
after date of publication of the final rule in the Federal Register] 
committing to develop an MMM program plan, must submit their first 2-
year report by [6.5 years after date of publication of the final rule 
in the Federal Register]. For States not submitting the 90-day letter, 
but choosing subsequently to submit an MMM program plan and adopt the 
AMCL, the first 2-year report must be submitted to EPA by [5 years 
after date of publication of the final rule in the Federal Register].
    (ii) These reports are required to include the following 
information:
    (A) A quantitative assessment of progress towards meeting the 
required goals described in Sec. 141.302(b), including the number or 
rate of existing homes mitigated and the number or rate of new homes 
built radon-resistant since implementation of the States' MMM program, 
and
    (B) A description of accomplishments and activities that implement 
the required program strategies, described in Sec. 141.302(c), outlined 
in the implementation plans and in the two required areas of promoting 
increased testing and mitigation of existing homes and promoting 
increased use of radon-resistant techniques in construction of new 
homes.
    (C) If goals were defined as rates, the State must also provide an 
estimate of

[[Page 59377]]

the number of mitigations and radon-resistant new homes represented by 
the reported rate increase for the two-year period.
    (D) If the MMM program plan includes goals for promoting public 
awareness of the health effects of indoor radon, testing of homes by 
the public; testing and mitigation of existing schools; and 
construction of new public schools to be radon-resistant, the report is 
also required to include information on results and accomplishments in 
these areas.
    (iii) States shall make available to the public each of these two-
year reports, as well as the EPA summaries of the five-year reviews of 
a State's MMM program, within 90 days of completion of the reports and 
the review.
    (iv) In primacy States without a State-wide MMM program, the States 
shall provide a report to EPA every five-years on the status and 
progress of CWS MMM programs towards meeting their goals. The first of 
such reports would be due by [10.5 years after date of publication of 
the final rule in the Federal Register].
* * * * *
    4. Section 142.16 is amended by adding new paragraph (i) to read as 
follows:


Sec. 142.16  Special primacy requirements.

* * * * *
    (i) Requirements for States to adopt 40 CFR part 141, subpart R. In 
addition to the general primacy requirements elsewhere in this part, 
including the requirement that State regulations be at least as 
stringent as federal requirements, an application for approval of a 
State program revision that adopts 40 CFR part 141, subpart R, must 
contain a description of how the State will accomplish the program 
requirements for implementation of the AMCL and MMM program plan or the 
MCL as follows:
    (1) If a State chooses to develop and implement a State-wide MMM 
program plan and adopt the AMCL, the primacy application must include 
the following elements:
    (i) A copy of the State-wide MMM program plan prepared to meet the 
criteria outlined in Sec. 141.302 of this chapter.
    (ii) A description of how the State will make resources available 
for implementation of the State-wide MMM program plan.
    (iii) A description of the extent and nature of coordination 
between interagency programs (i.e., indoor radon and drinking water 
programs) on development and implementation of the MMM program plan, 
including the level of resources that will be made available for 
implementation and coordination between interagency programs (i.e., 
indoor air and drinking water programs).
    (2) If a State chooses to adopt the MCL the primacy application 
must contain the following:
    (i) A description of how the State will implement a program to 
approve local CWS MMM program plans prepared to meet the criteria 
outlined in Sec. 141.302 of this chapter and a description of the 
State's authority to implement this program.
    (ii) A description of how the State will ensure local CWS MMM 
program plans are implemented.
    (iii) A description of reporting and record keeping requirements 
for local CWS MMM programs.
    (iv) A description of how the State will review local CWS program 
plans at least every five years to determine if they are implementing 
the MMM program and making progress towards their goals.
    (v) A description of the procedures and schedule the State will use 
in withdrawing State approval of a CWS MMM program plan and notifying 
the CWS that they are required to comply with the MCL.
    (vi) A description of the extent and nature of coordination between 
interagency programs (i.e., indoor radon and drinking water programs) 
on development and implementation of the State process for review and 
approval of CWS MMM program plans. This description includes the level 
of resources that will be made available for implementation and 
coordination between interagency programs (i.e., indoor air and 
drinking water programs).
    (vii) A description of how the State will make required CWS reports 
available to the public.
    5. A new Sec. 142.65 is added to subpart G, to read as follows:


Sec. 142.65.  Variances and exemptions from the maximum contaminant 
level for radon.

    (a) The Administrator, pursuant to section 1415(a)(1)(A) of the 
Act, hereby identifies in the following table as the best technology, 
treatment techniques, or other means available for achieving compliance 
with the maximum contaminant level for radon:
BAT for Radon-222
    1. For all systems: High-Performance Aeration \1\
    2. For systems serving 10,000 persons or fewer: High-Performance 
Aeration \1\ or \2\, Granular Activated Carbon \2\ (GAC), and Point-of-
Entry GAC \2\.
---------------------------------------------------------------------------

    \1\ High Performance Aeration is defined as the group of 
aeration technologies that are capable of being designed for high 
radon removal efficiencies, i.e., Packed Tower Aeration, Multi-Stage 
Bubble Aeration and other suitable diffused bubble aeration 
technologies, Shallow Tray and other suitable Tray Aeration 
technologies, and any other aeration technologies that are capable 
of similar high performance.
    \2\ As defined and described in 40 CFR 141.66 (e).
---------------------------------------------------------------------------

    (b) A State shall require a community water system to install and/
or use any treatment method identified in paragraph (a) of this section 
as a condition for granting a variance, based upon an evaluation 
satisfactory to the State that indicates that alternative sources of 
water are not reasonably available to the system.
    (c) Bottled water and/or granular activated carbon point-of-use 
devices cannot be used as means of being granted a variance or an 
exemption for radon.
    (d) Community water systems that use point-of-entry devices as a 
condition for obtaining a variance or an exemption from NPDWRs must 
meet the following requirements:
    (1) All point-of-entry units shall be owned, controlled, and 
maintained by the community water system or by a person or persons 
under contract with the public water system to ensure proper operation 
and maintenance of the unit under the terms of the variance or 
exemption.
    (2) All point-of-entry units shall be equipped with mechanical 
warning devices to ensure that customers are notified of operational 
problems.
    (3) If the American National Standards Institute has issued product 
standards applicable to a specific type of point-of-entry device for 
radon,

[[Page 59378]]

individual units of that type shall not be accepted under the terms of 
the variance or exemption unless they are independently certified in 
accordance with such standards.
    (4) Before point-of-entry devices are installed, the community 
water system must obtain the approval of a monitoring plan which 
ensures that the devices provide health protection equivalent to 
analogous centralized water treatment.
    (5) The community water system must apply effective technology 
under a State-approved plan. The microbiological safety of the water 
must be maintained at all times.
    (6) The State must require adequate certification of performance, 
field testing, and, if not included in the certification process, a 
rigorous engineering review of the point-of-entry devices.
    (7) The design and application of point-of-entry devices must 
consider the potential for increasing concentrations of heterotrophic 
bacteria in water treated with activated carbon. It may be necessary to 
use frequent backwashing, post-GAC contactor disinfection, and 
Heterotrophic Plate Count monitoring to ensure that the microbiological 
safety of the water is not compromised.
    6. Section 142.72 is amended by removing the introductory text, by 
redesignating paragraphs (a) through (d) as (b)(1) through (b)(4), and 
by adding a new paragraph (a) to read as follows:


Sec. 142.72. Requirements for Tribal eligibility.

    (a) If a Tribe meets the criteria in paragraph (b) of this section, 
the Administrator is authorized to treat an Indian Tribe as eligible to 
apply for:
    (1) Primary enforcement responsibility for the Public Water System 
Program:
    (2) Authority to waive the mailing requirements of 40 CFR 
141.155(a); and
    (3) Authority to develop and implement a radon multimedia 
mitigation program in accordance with 40 CFR part 141, subpart R.
* * * * *
    7. Section 142.78 is amended by revising paragraph (b) to read as 
follows:


Sec. 142.78. Procedure for processing an Indian Tribe's application.

* * * * *
    (b) A Tribe that meets the requirements of Sec. 142.72 is eligible 
to apply for development grants and primary enforcement responsibility 
for a Public Water System and associated funding under section 1443(a) 
of the Act, for primary enforcement responsibility for public water 
systems under section 1413 of the Act, for the authority to waive the 
mailing requirements of 40 CFR 141.155(a), and for the authority to 
develop and implement a radon multimedia mitigation program in 
accordance with 40 CFR part 141, subpart R.
    8. Part 142 is amended by adding a new Subpart L to read as 
follows:

Subpart L--Review of State MMM Programs


Sec. 142.400 Review of State MMM programs and procedures for 
withdrawing approval of State MMM programs.

    (a)(1)At least every five years, the Administrator shall review 
State MMM programs. For the purposes of this review, States with EPA-
approved MMM programs shall provide written reports to the 
Administrator in the second and fourth years between initial 
implementation of the MMM program and the first 5-year review period, 
and in the second and fourth years of every subsequent 5-year review 
period. The written reports will discuss the status and progress of 
their program towards meeting their MMM goals. The Administrator will 
use the information provided in the two biennial reports in discussions 
and consultations with the State to review the programs to determine 
whether they continue to be expected to achieve risk reduction of 
indoor radon.
    (2) If the Administrator determines that a State MMM program is not 
achieving progress towards its MMM goals, the Administrator and the 
State shall collaborate to develop modifications and adjustments to the 
program to be implemented over the five year period following the 
review. EPA will prepare a summary of the outcome of the program 
evaluation and the proposed modification and adjustments, if any, to be 
made by the State.
    (3) If the State repeatedly fails to correct, modify or adjust 
implementation of its MMM program after notice by the Administrator, 
the Administrator shall initiate proceedings to withdraw approval of 
the State's MMM program plan. The Administrator shall notify the State 
in writing that EPA is initiating withdrawing a State-wide MMM program 
plan and shall summarize in the notice the information available that 
indicates that the State is no longer achieving progress towards its 
MMM goals.
    (4) The State notified pursuant to paragraph (a)(3) of this section 
may, within 30 days of receiving the Administrator's notice, submit to 
the Administrator evidence that the State plans to implement 
modifications to the State MMM program.
    (5) After reviewing the submission of the State, if any, made 
pursuant to paragraph (a)(4) of this section, the Administrator shall 
make a final determination either that the State no longer continues to 
achieve progress towards its MMM goals, or that the State continues to 
implement modifications to the State MMM program, and shall notify the 
State of his or her determination. Before a final determination that 
the State no longer continues to achieve progress towards its MMM 
goals, the Administrator shall offer a public hearing and will publish 
a notice in the Federal Register.
    (b) If approval of a State's MMM program is withdrawn, the State 
will be responsible for notifying CWSs of the Administrator's 
withdrawal of approval of the State-wide MMM program plan. The CWSs in 
the State would then be required to comply with the MCL. EPA will work 
with the State to establish a State process for review and approval of 
CWS MMM program plans that meet the required criteria and a time frame 
for submittal of program plans by CWSs that choose to continue 
complying with the AMCL. The review process will allow for local public 
participation in development and review of the program plan.

[FR Doc. 99-27741 Filed 10-25-99; 3:12 pm]
BILLING CODE 6560-50-P