[Federal Register Volume 71, Number 3 (Thursday, January 5, 2006)]
[Rules and Regulations]
[Pages 654-786]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 06-4]



[[Page 653]]

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Part II





Environmental Protection Agency





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40 CFR Parts 9, 141, and 142



National Primary Drinking Water Regulations: Long Term 2 Enhanced 
Surface Water Treatment Rule; Final Rule

  Federal Register / Vol. 71, No. 3 / Thursday, January 5, 2006 / Rules 
and Regulations  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9, 141, and 142

[EPA-HQ-OW-2002-0039; FRL-8013-1]
RIN 2040--AD37


National Primary Drinking Water Regulations: Long Term 2 Enhanced 
Surface Water Treatment Rule

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is promulgating National Primary Drinking Water 
Regulations that require the use of treatment techniques, along with 
monitoring, reporting, and public notification requirements, for all 
public water systems that use surface water sources. The purposes of 
the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) are to 
protect public health from illness due to Cryptosporidium and other 
microbial pathogens in drinking water and to address risk-risk trade-
offs with the control of disinfection byproducts.
    Key provisions in the LT2ESWTR include the following: source water 
monitoring for Cryptosporidium, with a screening procedure to reduce 
monitoring costs for small systems; risk-targeted Cryptosporidium 
treatment by filtered systems with the highest source water 
Cryptosporidium levels; inactivation of Cryptosporidium by all 
unfiltered systems; criteria for the use of Cryptosporidium treatment 
and control processes; and covering or treating uncovered finished 
water storage facilities.
    EPA believes that implementation of the LT2ESWTR will significantly 
reduce levels of infectious Cryptosporidium in finished drinking water. 
This will substantially lower rates of endemic cryptosporidiosis, the 
illness caused by Cryptosporidium, which can be severe and sometimes 
fatal in sensitive subpopulations (e.g., infants, people with weakened 
immune systems). In addition, the treatment technique requirements of 
this regulation will increase protection against other microbial 
pathogens like Giardia lamblia.

DATES: This final rule is effective on March 6, 2006. The incorporation 
by reference of certain publications listed in the rule is approved by 
the Director of the Federal Register as of March 6, 2006. For judicial 
review purposes, this final rule is promulgated as of January 5, 2006.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-HQ-OW-2002-0039. All documents in the docket are listed on the 
www.regulations.gov Web site. Although listed in the index, some 
information is not publicly available, i.e., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, is not placed on the Internet and will be 
publicly available only in hard copy form. Publicly available docket 
materials are available either electronically through 
www.regulations.gov or in hard copy at the Water Docket, EPA/DC, EPA 
West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The 
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the Water 
Docket is (202) 566-2426.

FOR FURTHER INFORMATION CONTACT: Daniel C. Schmelling, Standards and 
Risk Management Division, Office of Ground Water and Drinking Water (MC 
4607M), Environmental Protection Agency, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460; telephone number: (202) 564-5281; fax number: 
(202) 564-3767; e-mail address: [email protected]. For general 
information, contact the Safe Drinking Water Hotline, telephone number: 
(800) 426-4791. The Safe Drinking Water Hotline is open Monday through 
Friday, excluding legal holidays, from 9 a.m. to 5 p.m., Eastern time.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Who Is Regulated by This Action?

    Entities potentially regulated by the LT2ESWTR are public water 
systems (PWSs) that use surface water or ground water under the direct 
influence of surface water (GWUDI). Regulated categories and entities 
are identified in the following chart.

------------------------------------------------------------------------
                Category                  Examples of regulated entities
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Industry...............................  Public Water Systems that use
                                          surface water or ground water
                                          under the direct influence of
                                          surface water.
State, Local, Tribal or Federal          Public Water Systems that use
 Governments.                             surface water or ground water
                                          under the direct influence of
                                          surface water.
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    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 
could potentially be regulated by this action. Other types of entities 
not listed in this table could also be regulated. To determine whether 
your facility is regulated by this action, you should carefully examine 
the definition of public water system in Sec.  141.3 of Title 40 of the 
Code of Federal Regulations and applicability criteria in Sec.  
141.700(b) of today's rule. If you have questions regarding the 
applicability of the LT2ESWTR to a particular entity, consult one of 
the persons listed in the preceding section entitled FOR FURTHER 
INFORMATION CONTACT.

Abbreviations Used in This Document

ASTM American Society for Testing and Materials
AWWA American Water Works Association
[deg]C Degrees Centigrade
CDC Centers for Disease Control and Prevention
CFE Combined Filter Effluent
CFR Code of Federal Regulations
COI Cost-of-Illness
CT The Residual Concentration of Disinfectant (mg/L) Multiplied by the 
Contact Time (in minutes)
CWS Community Water Systems
DAPI 4',6-Diamindino-2-phenylindole
DBPs Disinfection Byproducts
DBPR Disinfectants/Disinfection Byproducts Rule
DE Diatomaceous Earth
DIC Differential Interference Contrast (microscopy)
EA Economic Analysis
EPA United States Environmental Protection Agency
GAC Granular Activated Carbon
GWUDI Ground Water Under the Direct Influence of Surface Water
HAA5 Five Haloacetic Acids (Monochloroacetic, Dichloroacetic, 
Trichloroacetic, Monobromoacetic and Dibromoacetic Acids)
ICR Information Collection Rule (also Information Collection Request)
ICRSS Information Collection Rule Supplemental Surveys

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ICRSSM Information Collection Rule Supplemental Survey of Medium 
Systems
ICRSSL Information Collection Rule Supplemental Survey of Large Systems
IESWTR Interim Enhanced Surface Water Treatment Rule
Log Logarithm (common, base 10)
LRAA Locational Running Annual Average
LRV Log Removal Value
LT1ESWTR Long Term 1 Enhanced Surface Water Treatment Rule
LT2ESWTR Long Term 2 Enhanced Surface Water Treatment Rule
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
MG Million Gallons
M-DBP Microbial and Disinfectants/Disinfection Byproducts
MF Microfiltration
NPDWR National Primary Drinking Water Regulation
NTTAA National Technology Transfer and Advancement Act
NTU Nephelometric Turbidity Unit
OMB Office of Management and Budget
PE Performance Evaluation
PWS Public Water System
QC Quality Control
QCRV Quality Control Release Value
RAA Running Annual Average
RFA Regulatory Flexibility Act
RO Reverse Osmosis
SAB Science Advisory Board
SBAR Small Business Advocacy Review
SDWA Safe Drinking Water Act
SWAP Source Water Assessment Program
SWTR Surface Water Treatment Rule
TCR Total Coliform Rule
TTHM Total Trihalomethanes
UF Ultrafiltration
UMRA Unfunded Mandates Reform Act

Table of Contents

I. General Information
    A. Who Is Regulated by This Action?
II. Summary of the Final Rule
    A. Why Is EPA Promulgating the LT2ESWTR?
    B. What Does the LT2ESWTR Require?
    1. Source water monitoring
    2. Additional treatment for Cryptosporidium
    3. Uncovered finished water storage facilities
    C. Will This Regulation Apply to My Water System?
III. Background Information
    A. Statutory Requirements and Legal Authority
    B. Existing Regulations for Microbial Pathogens in Drinking 
Water
    1. Surface Water Treatment Rule
    2. Total Coliform Rule
    3. Interim Enhanced Surface Water Treatment Rule
    4. Long Term 1 Enhanced Surface Water Treatment Rule
    5. Filter Backwash Recycle Rule
    C. Concern with Cryptosporidium in Drinking Water
    1. Introduction
    2. What is Cryptosporidium?
    3. Cryptosporidium health effects
    4. Efficacy of water treatment processes on Cryptosporidium
    5. Epidemic and endemic disease from Cryptosporidium
    D. Specific Concerns Following the IESWTR and LT1ESWTR
    E. New Information on Cryptosporidium Risk Management
    1. Infectivity
    2. Occurrence
    3. Analytical methods
    4. Treatment
    F. Federal Advisory Committee Recommendations
IV. Explanation of Today's Action
    A. Source Water Monitoring Requirements
    1. Today's rule
    a. Sampling parameters and frequency
    b. Sampling location
    c. Sampling schedule
    d. Plants operating only part of the year
    e. Failing to monitor
    f. Providing treatment instead of monitoring
    g. Grandfathering previously collected data
    h. Ongoing watershed assessment
    i. Second round of monitoring
    j. New source monitoring
    2. Background and analysis
    a. Sampling parameters and frequency
    b. Sampling location
    c. Sampling schedule
    d. Plants operating only part of the year
    e. Failing to monitor
    f. Grandfathering previously collected data
    g. Ongoing watershed assessment
    h. Second round of monitoring
    3. Summary of major comments
    a. Sampling parameters and frequency
    b. Sampling location
    c. Sampling schedule
    d. Plants operating only part of the year
    e. Failing to monitor
    f. Providing treatment instead of monitoring
    g. Grandfathering previously collected data
    h. Ongoing watershed assessment
    i. Second round of monitoring
    j. New source monitoring
    B. Filtered System Cryptosporidium Treatment Requirements
    1. Today's rule
    a. Bin classification
    b. Bin treatment requirements
    2. Background and analysis
    a. Basis for targeted treatment requirements
    b. Basis for bin concentration ranges and treatment requirements
    3. Summary of major comments
    C. Unfiltered System Cryptosporidium Treatment Requirements
    1. Today's rule
    a. Determination of mean Cryptosporidium level
    b. Cryptosporidium treatment requirements
    c. Use of two disinfectants
    2. Background and analysis
    a. Basis for Cryptosporidium treatment requirements
    b. Basis for requiring the use of two disinfectants
    c. Filtration avoidance
    3. Summary of major comments
    D. Options for Systems to Meet Cryptosporidium Treatment 
Requirements
    1. Microbial toolbox overview
    2. Watershed control program
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    3. Alternative source
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    4. Pre-sedimentation with coagulant
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    5. Two-stage lime softening
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    6. Bank filtration
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    7. Combined filter performance
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    8. Individual filter performance
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    9. Demonstration of performance
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    10. Bag and cartridge filtration
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    11. Membrane filtration
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    12. Second stage filtration
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    13. Slow sand filtration
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    14. Ozone and chlorine dioxide
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    15. Ultraviolet light
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    E. Disinfection Benchmarking for Giardia lamblia and Viruses
    1. Today's rule
    2. Background and analysis
    3. Summary of major comments
    F. Requirements for Systems with Uncovered Finished Water 
Storage Facilities
    1. Today's rule

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    2. Background and analysis
    a. Types and sources of contaminants in open reservoirs
    b. Regulatory approaches to reduce risk from contamination in 
open reservoirs
    c. Definition of uncovered finished water storage facility
    3. Summary of major comments
    G. Compliance Schedules
    1. Today's rule
    2. Background and analysis
    3. Summary of major comments
    H. Public Notice Requirements
    1. Today's rule
    2. Background and analysis
    3. Summary of major comments
    I. Reporting Source Water Monitoring Results
    1. Today's rule
    2. Background and analysis
    3. Summary of major comments
    J. Analytical Methods
    1. Analytical methods overview
    2. Cryptosporidium methods
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    3. E. coli methods
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    4. Turbidity methods
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    K. Laboratory Approval
    1. Cryptosporidium laboratory approval
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    2. E. coli laboratory approval
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    3. Turbidity analyst approval
    a. Today's rule
    b. Background and analysis
    c. Summary of major comments
    L. Requirements for Sanitary Surveys Conducted by EPA
    1. Today's rule
    2. Background and analysis
    3. Summary of major comments
    M. Variances and Exemptions
    1. Variances
    2. Exemptions
V. State Implementation
    A. Today's Rule
    1. Special State primacy requirements
    2. State recordkeeping requirements
    3. State reporting requirements
    4. Interim primacy
    B. Background and Analysis
    C. Summary of Major Comments
VI. Economic Analysis
    A. What Regulatory Alternatives Did the Agency Consider?
    B. What Analyses Support Today's Final Rule?
    C. What Are the Benefits of the LT2ESWTR?
    1. Nonquantified benefits
    2. Quantified benefits
    a. Filtered PWSs
    b. Unfiltered PWSs
    3. Timing of benefits accrual (latency)
    D. What Are the Costs of the LT2ESWTR?
    1. Total annualized present value costs
    2. PWS costs
    a. Source water monitoring costs
    b. Filtered PWSs treatment costs
    c. Unfiltered PWSs treatment costs
    d. Uncovered finished water storage facilities
    e. Future monitoring costs
    f. Sensitivity analysis--influent bromide levels on technology 
selection for filtered plants
    3. State/Primacy agency costs
    4. Non-quantified costs
    E. What Are the Household Costs of the LT2ESWTR?
    F. What Are the Incremental Costs and Benefits of the LT2ESWTR?
    H. Are there Increased Risks From Other Contaminants?
    I. What Are the Effects of the Contaminant on the General 
Population and Groups within the General Populations that Are 
Identified as Likely to be at Greater Risk of Adverse Health 
Effects?
    J. What Are the Uncertainties in the Risk, Benefit, and Cost 
Estimates for the LT2ESWTR?
    K. What Is the Benefit/Cost Determination for the LT2ESWTR?
    L. Summary of Major Comments
    1. Cryptosporidium occurrence
    a. Quality of the ICR and ICRSS data sets
    b. Treatment of observed zeros
    2. Drinking water consumption
    3. Cryptosporidium infectivity
    4. Valuation of benefits
    a. Valuation of morbidity
    b. Valuation of lost time under the enhanced cost of illness 
(COI) approach
VII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions that Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations or Low-Income 
Populations
    K. Consultations with the Science Advisory Board, National 
Drinking Water Advisory Council, and the Secretary of Health and 
Human Services
    L. Plain Language
    M. Analysis of the Likely Effect of Compliance with the LT2ESWTR 
on the Technical, Financial, and Managerial Capacity of Public Water 
Systems
    N. Congressional Review Act
VIII. References

II. Summary of the Final Rule

A. Why Is EPA Promulgating the LT2ESWTR?

    EPA is promulgating the Long Term 2 Enhanced Surface Water 
Treatment Rule (LT2ESWTR) to further protect public health against 
Cryptosporidium and other microbial pathogens in drinking water. 
Cryptosporidium is a protozoan parasite that is common in surface water 
used as drinking water sources by public water systems (PWSs). In 
drinking water, Cryptosporidium is a particular concern because it is 
highly resistant to chemical disinfectants like chlorine. When 
ingested, Cryptosporidium can cause acute gastrointestinal illness, 
which may be severe and sometimes fatal for people with weakened immune 
systems. Cryptosporidium has been identified as the cause of a number 
of waterborne disease outbreaks in the United States (details in 
section III.C).
    The LT2ESWTR supplements existing microbial treatment regulations 
and targets PWSs with higher potential risk from Cryptosporidium. 
Existing regulations require most PWSs using surface water sources to 
filter the water, and those PWSs that are required to filter must 
remove at least 99 percent (2-log) of the Cryptosporidium (details in 
section III.B). As explained in the proposal for today's rule (68 FR 
47640, August 11, 2003) (USEPA 2003a), new data on the occurrence, 
infectivity, and treatment of Cryptosporidium in drinking water 
indicate that existing regulations are sufficient for most PWSs. A 
subset of PWSs with greater vulnerability to Cryptosporidium, however, 
requires additional treatment.
    In particular, recent national survey data show that the level of 
Cryptosporidium in the sources of most filtered PWSs is lower than 
previously estimated, but also that Cryptosporidium levels vary widely 
from source to source. Accordingly, a subset of filtered PWSs has 
relatively high levels of source water Cryptosporidium contamination. 
In addition, data from human health studies indicate that the potential 
for Cryptosporidium to cause infection is likely greater than 
previously recognized (details in section III.E). These findings have 
led EPA to conclude that existing requirements do not provide adequate 
public health protection in filtered PWSs with the highest source water 
Cryptosporidium levels. Consequently, EPA is establishing risk-targeted 
additional treatment requirements for such filtered PWSs under the 
LT2ESWTR.

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    For PWSs that use surface water sources and are not required to 
filter (i.e., unfiltered PWSs), existing regulations do not require any 
treatment for Cryptosporidium. New survey data suggest that typical 
Cryptosporidium levels in the treated water of unfiltered PWSs are 
higher than in the treated water of filtered PWSs (USEPA 2003a). Thus, 
Cryptosporidium treatment by unfiltered PWSs is needed to achieve 
comparable public health protection (details in section III.E). 
Further, results from recent treatment studies have allowed EPA to 
develop standards for the inactivation of Cryptosporidium by ozone, 
ultraviolet (UV) light, and chlorine dioxide (details in section IV.D). 
Based on these developments, EPA is establishing requirements under the 
LT2ESWTR for all unfiltered PWSs to treat for Cryptosporidium, with the 
required degree of treatment depending on the source water 
contamination level.
    Additionally, the LT2ESWTR addresses risks in uncovered finished 
water storage facilities, in which treated water can be subject to 
significant contamination as a result of runoff, bird and animal 
wastes, human activity, algal growth, insects, fish, and airborne 
deposition (details in section IV.F). Existing regulations prohibit the 
building of new uncovered finished water storage facilities but do not 
deal with existing ones. Under the LT2ESWTR, PWSs must limit potential 
risks by covering or treating the discharge of such storage facilities.
    Most of the requirements in today's final LT2ESWTR reflect 
consensus recommendations from the Stage 2 Microbial and Disinfection 
Byproducts (M-DBP) Federal Advisory Committee. These recommendations 
are set forth in the Stage 2 M-DBP Agreement in Principle (65 FR 83015, 
December 29, 2000) (USEPA 2000a).

B. What Does the LT2ESWTR Require?

1. Source Water Monitoring
    The LT2ESWTR requires PWSs using surface water or ground water 
under the direct influence (GWUDI) of surface water to monitor their 
source water (i.e., the influent water entering the treatment plant) to 
determine an average Cryptosporidium level. As described in the next 
section, monitoring results determine the extent of Cryptosporidium 
treatment requirements under the LT2ESWTR.
    Large PWSs (serving at least 10,000 people) must monitor for 
Cryptosporidium (plus E. coli and turbidity in filtered PWSs) for a 
period of two years. To reduce monitoring costs, small filtered PWSs 
(serving fewer than 10,000 people) initially monitor just for E. coli 
for one year as a screening analysis and are required to monitor for 
Cryptosporidium only if their E. coli levels exceed specified 
``trigger'' values. Small filtered PWSs that exceed the E. coli 
trigger, as well as all small unfiltered PWSs, must monitor for 
Cryptosporidium for one or two years, depending on the sampling 
frequency (details sections IV.A).
    Under the LT2ESWTR, specific criteria are set for sampling 
frequency and schedule, sampling location, using previously collected 
data (i.e., grandfathering), providing treatment instead of monitoring, 
sampling by PWSs that use surface water for only part of the year, and 
monitoring of new plants and sources (details in section IV.A). The 
LT2ESWTR also establishes requirements for reporting of monitoring 
results (details in section IV.I), using analytical methods (details in 
section IV.J), and using approved laboratories (details in section 
IV.K).
    The date for PWSs to begin monitoring is staggered by PWS size, 
with smaller PWSs starting at a later time than larger ones (details in 
section IV.G). Today's rule also requires a second round of monitoring 
to begin approximately 6.5 years after the first round concludes in 
order to determine if source water quality has changed to a degree that 
should affect treatment requirements (details in section IV.A).
2. Additional Treatment for Cryptosporidium
    The LT2ESWTR establishes risk-targeted treatment technique 
requirements to control Cryptosporidium in PWSs using surface water or 
GWUDI. These treatment requirements supplement those established by 
existing regulations, all of which remain in effect under the LT2ESWTR.
    Filtered PWSs will be classified in one of four treatment 
categories (or ``bins'') based on the results of the source water 
Cryptosporidium monitoring described in the previous section. This bin 
classification determines the degree of additional Cryptosporidium 
treatment, if any, the filtered PWS must provide. Occurrence data 
indicate that the majority of filtered PWSs will be classified in Bin 
1, which carries no additional treatment requirements. PWSs classified 
in Bins 2, 3, or 4 must achieve 1.0- to 2.5-log of treatment (i.e., 90 
to 99.7 percent reduction) for Cryptosporidium over and above that 
provided with conventional treatment. Different additional treatment 
requirements may apply to PWSs using other than conventional treatment, 
such as direct filtration, membranes, or cartridge filters (details in 
section. IV.B). Filtered PWSs must meet the additional Cryptosporidium 
treatment required in Bins 2, 3, or 4 by using one or more treatment or 
control processes from a ``microbial toolbox'' of options (details in 
section. IV.D).
    The LT2ESWTR requires all unfiltered PWSs to provide at least 2-log 
(i.e., 99 percent) inactivation of Cryptosporidium. If the average 
source water Cryptosporidium level exceeds 0.01 oocysts/L based on the 
monitoring described in the previous section, the unfiltered PWS must 
provide at least 3-log (i.e., 99.9 percent) inactivation of 
Cryptosporidium. Further, under the LT2ESWTR, unfiltered PWSs must 
achieve their overall inactivation requirements (including Giardia 
lamblia and virus inactivation as established by earlier regulations) 
using a minimum of two disinfectants (details in section IV.C).
3. Uncovered Finished Water Storage Facilities
    Under the LT2ESWTR, PWSs with uncovered finished water storage 
facilities must take steps to address contamination risks. Existing 
regulations require PWSs to cover all new storage facilities for 
finished water but do not address existing uncovered finished water 
storage facilities. Under the LT2ESWTR, PWSs using uncovered finished 
water storage facilities must either cover the storage facility or 
treat the storage facility discharge to achieve inactivation and/or 
removal of 4-log virus, 3-log Giardia lamblia, and 2-log 
Cryptosporidium on a State-approved schedule (details in section. 
IV.F).

C. Will This Regulation Apply to My Water System?

    The LT2ESWTR applies to all PWSs using surface water or GWUDI, 
including both large and small PWSs, community and non-community PWSs, 
and non-transient and transient PWSs. Wholesale PWSs must comply with 
the requirements of today's rule based on the population of the largest 
PWS in the combined distribution system. Consecutive PWSs that purchase 
treated water from wholesale PWSs that fully comply with the monitoring 
and treatment requirements of the LT2ESWTR are not required to take 
additional steps for that water under today's rule.

III. Background Information

    The sections in this part provide summary background information 
for

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today's final LT2ESWTR. Individual sections address the following 
topics: (A) Statutory requirements and legal authority for the 
LT2ESWTR; (B) existing regulations for microbial pathogens in drinking 
water; (C) the problem with Cryptosporidium in drinking water; (D) 
specific public health concerns addressed by the LT2ESWTR; (E) new 
information for Cryptosporidium risk management in PWSs; and (F) 
recommendations from the Stage 2 M-DBP Advisory Committee for the 
LT2ESWTR. For additional information on these topics, see the proposed 
LT2ESWTR (USEPA 2003a) and supporting technical material where cited.

A. Statutory Requirements and Legal Authority

    The Safe Drinking Water Act (SDWA or the Act), as amended in 1996, 
requires EPA to publish a maximum contaminant level goal (MCLG) and 
promulgate a national primary drinking water regulation (NPDWR) with 
enforceable requirements for any contaminant that the Administrator 
determines may have an adverse effect on the health of persons, is 
known to occur or has a substantial likelihood of occurring in public 
water systems (PWSs) with a frequency and at levels of public health 
concern, and for which, in the sole judgement of the Administrator, 
regulation of such contaminant presents a meaningful opportunity for 
health risk reduction for persons served by PWSs (section 1412 
(b)(1)(A)).
    MCLGs are non-enforceable health goals and are to be set at a level 
at which no known or anticipated adverse effects on the health of 
persons occur and which allows an adequate margin of safety (sections 
1412(b)(4) and 1412(a)(3)). EPA established an MCLG of zero for 
Cryptosporidium under the Interim Enhanced Surface Water Treatment Rule 
(IESWTR) (63 FR 69478, December 16, 1998) (USEPA 1998a). In today's 
rule, the Agency is not making any changes to the current MCLG for 
Cryptosporidium.
    The Act also requires each NPDWR for which an MCLG is established 
to specify a maximum contaminant level (MCL) that is as close to the 
MCLG as is feasible (sections 1412(b)(4) and 1401(1)(C)). The Agency is 
authorized to promulgate an NPDWR that requires the use of a treatment 
technique in lieu of establishing an MCL if the Agency finds that it is 
not economically or technologically feasible to ascertain the level of 
the contaminant (sections 1412(b)(7)(A) and 1401(1)(C)). The Act 
specifies that in such cases, the Agency shall identify those treatment 
techniques that would prevent known or anticipated adverse effects on 
the health of persons to the extent feasible (section 1412(b)(7)(A)).
    The Agency has concluded that it is not currently economically or 
technologically feasible for PWSs to determine the level of 
Cryptosporidium in finished drinking water for the purpose of 
compliance with a finished water standard. As described in section 
IV.C, the LT2ESWTR is designed to protect public health by lowering the 
level of infectious Cryptosporidium in finished drinking water to less 
than 1 oocyst/10,000 L. Approved Cryptosporidium analytical methods, 
which are described in section IV.K, are not sufficient to routinely 
determine the level of Cryptosporidium at this concentration. 
Consequently, the LT2ESWTR relies on treatment technique requirements 
to reduce health risks from Cryptosporidium in PWSs.
    When proposing an NPDWR that includes an MCL or treatment 
technique, the Act requires EPA to publish and seek public comment on 
an analysis of health risk reduction and costs. This includes an 
analysis of quantifiable and nonquantifiable costs and health risk 
reduction benefits, incremental costs and benefits of each alternative 
considered, the effects of the contaminant upon sensitive 
subpopulations (e.g., infants, children, pregnant women, the elderly, 
and individuals with a history of serious illness), any increased risk 
that may occur as the result of compliance, and other relevant factors 
(section 1412(b)(3)(C)). EPA's analysis of health benefits and costs 
associated with the LT2ESWTR is presented in the Economic Analysis of 
the LT2ESWTR (USEPA 2005a) and is summarized in section VI of this 
preamble. The Act does not, however, authorize the Administrator to use 
a determination of whether benefits justify costs to establish an MCL 
or treatment technique requirement for the control of Cryptosporidium 
(section 1412(b)(6)(C)).
    Finally, section 1412(b)(2)(C) of the Act requires EPA to 
promulgate a Stage 2 Disinfectants and Disinfection Byproducts Rule 
within 18 months after promulgation of the LT1ESWTR, which occurred on 
January 14, 2002. Consistent with statutory requirements for risk 
balancing (section 1412(b)(5)(B)), EPA is finalizing the LT2ESWTR in 
conjunction with the Stage 2 DBPR to ensure parallel protection from 
microbial and DBP risks.

B. Existing Regulations for Microbial Pathogens in Drinking Water

    This section summarizes existing rules that regulate treatment for 
pathogenic microorganisms by PWSs using surface water sources. The 
LT2ESWTR supplements these rules with additional risk-targeted 
requirements, but does not withdraw any existing requirements.
1. Surface Water Treatment Rule
    The Surface Water Treatment Rule (SWTR) (54 FR 27486, June 29, 
1989) (USEPA 1989a) applies to all PWSs using surface water or ground 
water under the direct influence (GWUDI) of surface water as sources 
(i.e., Subpart H PWSs). It established MCLGs of zero for Giardia 
lamblia, viruses, and Legionella, and includes the following treatment 
technique requirements to reduce exposure to pathogenic microorganisms: 
(1) Filtration, unless specific avoidance criteria are met; (2) 
maintenance of a disinfectant residual in the distribution system; (3) 
removal and/or inactivation of 3-log (99.9%) of Giardia lamblia and 4-
log (99.99%) of viruses; (4) maximum allowable turbidity in the 
combined filter effluent (CFE) of 5 nephelometric turbidity units (NTU) 
and 95th percentile CFE turbidity of 0.5 NTU or less for plants using 
conventional treatment or direct filtration (with different standards 
for other filtration technologies); and (5) watershed protection and 
source water quality requirements for unfiltered PWSs.
2. Total Coliform Rule
    The Total Coliform Rule (TCR) (54 FR 27544, June 29, 1989) (USEPA 
1989b) applies to all PWSs. It established an MCLG of zero for total 
and fecal coliform bacteria and an MCL based on the percentage of 
positive samples collected during a compliance period. Coliforms are 
used as an indicator of fecal contamination and to determine the 
integrity of the water treatment process and distribution system. Under 
the TCR, no more than 5 percent of distribution system samples 
collected in any month may contain coliform bacteria (no more than 1 
sample per month may be coliform positive in those PWSs that collect 
fewer than 40 samples per month). The number of samples to be collected 
in a month is based on the number of people served by the PWS.
3. Interim Enhanced Surface Water Treatment Rule
    The Interim Enhanced Surface Water Treatment Rule (IESWTR) (63 FR 
69478, December 16, 1998) (USEPA 1998a) applies to PWSs serving at 
least 10,000 people and using surface water or

[[Page 659]]

GWUDI sources. Key provisions established by the IESWTR include the 
following: (1) An MCLG of zero for Cryptosporidium; (2) Cryptosporidium 
removal requirements of 2-log (99 percent) for PWSs that filter; (3) 
more stringent CFE turbidity performance standards of 1.0 NTU as a 
maximum and 0.3 NTU or less at the 95th percentile monthly for 
treatment plants using conventional treatment or direct filtration; (4) 
requirements for individual filter turbidity monitoring; (5) 
disinfection benchmark provisions to assess the level of microbial 
protection that PWSs provide as they take steps to comply with new DBP 
standards; (6) inclusion of Cryptosporidium in the definition of GWUDI 
and in the watershed control requirements for unfiltered PWSs; (7) 
requirements for covers on new finished water storage facilities; and 
(8) sanitary surveys for all surface water systems regardless of size.
    The IESWTR was developed in conjunction with the Stage 1 
Disinfectants and Disinfection Byproducts Rule (Stage 1 DBPR) (63 FR 
69389, December 16, 1998) (USEPA 1998b), which reduced allowable levels 
of certain DBPs, including trihalomethanes, haloacetic acids, chlorite, 
and bromate.
4. Long Term 1 Enhanced Surface Water Treatment Rule
    The Long Term 1 Enhanced Surface Water Treatment Rule ( LT1ESWTR) 
(67 FR 1812, January 14, 2002) (USEPA 2002a) builds upon the microbial 
control provisions established by the IESWTR for large PWSs through 
extending similar requirements to small PWSs. The LT1ESWTR applies to 
PWSs that use surface water or GWUDI as sources and that serve fewer 
than 10,000 people. Like the IESWTR, the LT1ESWTR established the 
following: 2-log (99 percent) Cryptosporidium removal requirements by 
PWSs that filter; individual filter turbidity monitoring and more 
stringent combined filter effluent turbidity standards for conventional 
and direct filtration plants; disinfection profiling and benchmarking; 
inclusion of Cryptosporidium in the definition of GWUDI and in the 
watershed control requirements for unfiltered PWSs; and the requirement 
that new finished water storage facilities be covered.
5. Filter Backwash Recycle Rule
    The Filter Backwash Recycling Rule (FBRR) (66 FR 31085, June 8, 
2001) (USEPA 2001a) requires PWSs to consider the potential risks 
associated with recycling contaminants removed during the filtration 
process. The provisions of the FBRR apply to all PWSs that recycle, 
regardless of population served. In general, the provisions include the 
following: (1) PWSs must return certain recycle streams to a point in 
the treatment process that is prior to primary coagulant addition 
unless the State specifies an alternative location; (2) direct 
filtration PWSs recycling to the treatment process must provide 
detailed recycle treatment information to the State; and (3) certain 
conventional PWSs that practice direct recycling must perform a one-
month, one-time recycling self assessment.

C. Concern With Cryptosporidium in Drinking Water

1. Introduction
    EPA is promulgating the LT2ESWTR to reduce the public health risk 
associated with Cryptosporidium in drinking water. This section 
describes the general basis for this public health concern through 
reviewing information in several areas: the nature of Cryptosporidium, 
health effects, efficacy of water treatment processes, and the 
incidence of epidemic and endemic disease. Further information about 
Cryptosporidium is available in the following documents: 
Cryptosporidium: Human Health Criteria Document (USEPA 2001b), 
Cryptosporidium: Drinking Water Advisory (USEPA 2001c), and 
Cryptosporidium: Risks for Infants and Children (USEPA 2001d).
2. What Is Cryptosporidium?
    Cryptosporidium is a protozoan parasite that lives and reproduces 
entirely in one host. Ingestion of Cryptosporidium can cause 
cryptosporidiosis, a gastrointestinal (GI) illness. Cryptosporidium is 
excreted in feces. Transmission of cryptosporidiosis occurs through 
consumption of water or food contaminated with feces or by direct or 
indirect contact with infected persons or animals (Casemore 1990).
    In the environment, Cryptosporidium is present as a thick-walled 
oocyst containing four organisms (sporozoites); the oocyst wall 
insulates the sporozoites from harsh environmental conditions. Oocysts 
are 4-5 microns in length and width. Upon a host's ingestion of 
oocysts, enzymes and chemicals produced by the host's digestive system 
cause the oocyst to excyst, or break open. The excysted sporozoites 
embed themselves in the surfaces of the epithelial cells of the lower 
small intestine. The organisms then begin absorbing nutrients from 
their host cells. When these organisms sexually reproduce, they produce 
thick- and thin-walled oocysts. The host excretes the thick-walled 
oocysts in its feces; thin-walled oocysts excyst within the host and 
contribute to further host infection.
    The exact mechanism by which Cryptosporidium causes GI illness is 
not known. Factors may include damage to intestinal structure and 
cells, changes in the absorption/secretion processes of the intestine, 
toxins produced by Cryptosporidium or the host, and proteins that allow 
Cryptosporidium to adhere to host cell surfaces (Carey et al. 2004).
    Upon excretion, Cryptosporidium oocysts may survive for months in 
various environmental media, including soil, river water, seawater, and 
human and cattle feces at ambient temperatures (Kato et al. 2001, 
Pokorny et al. 2002, Fayer et al. 1998a and 1998b, and Robertson et al. 
1992). Cryptosporidium can also withstand temperatures as low as -20 
[deg]C for periods of a few hours (Fayer and Nerad 1996) but are 
susceptible to desiccation (Robertson et al. 1992).
    Cryptosporidium is a widespread contaminant in surface water used 
as drinking water supplies. For example, among 67 drinking water 
sources surveyed by LeChevallier and Norton (1995), 87 percent had 
positive samples for Cryptosporidium. A more recent survey of 80 medium 
and large PWSs conducted by EPA detected Cryptosporidium in 85 percent 
of water sources (USEPA 2003a). Cryptosporidium contamination can come 
from animal agriculture, wastewater treatment plant discharges, 
slaughterhouses, birds, wild animals, and other sources of fecal 
matter.
    Because different species of Cryptosporidium are very similar in 
morphology, researchers have focused on genetic differences in trying 
to classify them. However, discussion on Cryptosporidium taxonomy is 
complicated by the fact that even within species or strains, there may 
be differences in infectivity and virulence. Cryptosporidium parvum (C. 
parvum) has been the primary species of concern to humans. Until 
recently, some researchers divided C. parvum into two primary strains, 
genotype 1, which infects humans, and genotype 2, which infects both 
humans and cattle (Carey et al. 2004). In 2002, Morgan-Ryan et al. 
proposed that genotype 1 be designated a separate species, C. hominis. 
Additional Cryptosporidium species infecting other mammals, birds, and 
reptiles have been documented. In some cases, these species can infect 
both immunocompromised (having weakened immune systems) and

[[Page 660]]

otherwise healthy humans (Carey et al. 2004).
3. Cryptosporidium Health Effects
    Cryptosporidium infection is characterized by mild to severe 
diarrhea, dehydration, stomach cramps, and/or a slight fever. 
Incubation is thought to range from 2 to 10 days (Arrowood 1997). 
Symptoms typically last from several days to 2 weeks, though in a small 
percentage of cases, the symptoms may persist for months or longer in 
otherwise healthy individuals.
    Symptoms may be more severe in immunocompromised persons (Frisby et 
al. 1997, Carey et al. 2004). Such persons include those with AIDS, 
cancer patients undergoing chemotherapy, organ transplant recipients 
treated with drugs that suppress the immune system, and patients with 
autoimmune disorders (e.g., Lupus). In AIDS patients, Cryptosporidium 
has been found in the lungs, ear, stomach, bile duct, and pancreas in 
addition to the small intestine (Farthing 2000). Immunocompromised 
patients with severe persistent cryptosporidiosis may die (Carey et al. 
2004). Besides the immunocompromised, children and the elderly may be 
at higher risk from Cryptosporidium than the general population 
(discussed in section VII.G).
    Studies with human volunteers have demonstrated that a low dose of 
C. parvum (e.g., 10 oocysts) is sufficient to cause infection in 
healthy adults, although some strains are more infectious than others 
(DuPont et al. 1995, Chappell et al. 1999, Okhuysen et al. 2002). 
Studies of immunosuppressed adult mice have demonstrated that a single 
viable oocyst can induce C. parvum infections (Yang et al. 2000, 
Okhuysen et al. 2002). The lowest dose tested in any of the human 
challenge studies was 10 oocysts. Because drinking water exposures are 
generally projected to be at lower levels (e.g., 1 oocyst), statistical 
modeling is necessary to project the effects of such exposure. 
Following the advice of its Science Advisory Board (SAB), EPA has 
developed a range of models to predict effects of exposure to low doses 
of Cryptosporidium. These models are discussed in section VI and in the 
LT2ESWTR Economic Analysis (USEPA 2005a).
    The degree and duration of the immune response to Cryptosporidium 
is not well characterized. In a study by Chappell et al. (1999), 
volunteers with IgG Cryptosporidium antibodies in their blood were 
immune to low doses of oocysts. The ID50 (the dose that infects 50 
percent of the challenged population) was 1,880 oocysts for those 
individuals compared to 132 oocysts for individuals that tested 
negative for those antibodies. However, earlier studies did not observe 
a correlation between the development of antibodies after 
Cryptosporidium infection and subsequent protection from illness 
(Okhuysen et al. 1998).
    No cure for cryptosporidiosis is known. Medical care usually 
involves treatment for dehydration and nutrient loss. Certain 
antimicrobial drugs like Azithromycin, Paromomycin, and nitazoxanide, 
the only drug approved for cryptosporidiosis in children, have been 
partially effective in treating immunocompromised patients (Rossignol 
et al. 1998). Therapies used to treat retroviruses can be helpful in 
fighting cryptosporidiosis in people with AIDS and are more effective 
when used in conjunction with antimicrobial therapy. The effectiveness 
of antiretroviral therapy is thought to be related to the associated 
increase in white blood cells rather than the decrease in the amount of 
virus present.
4. Efficacy of Water Treatment Processes on Cryptosporidium
    EPA is particularly concerned about Cryptosporidium because, unlike 
pathogens such as bacteria and most viruses, Cryptosporidium oocysts 
are highly resistant to standard disinfectants like chlorine and 
chloramines (Korich et al. 1990, Ransome et al. 1993, Finch et al. 
1997). Consequently, control of Cryptosporidium in most treatment 
plants is dependent on physical removal processes. However, due to 
their size (4-5 microns), oocysts can sometimes pass through filters.
    Monitoring data on finished water show that Cryptosporidium is 
sometimes present in filtered, treated drinking water (LeChevallier et 
al. 1991, Aboytes et al. 2004). For example, Aboytes et al. (2004) 
analyzed 1,690 finished water samples from 82 plants. Of these, 22 
plants had at least one positive sample for infectious Cryptosporidium 
(1.4 percent of all samples were positive). All positive samples 
occurred at plants that met existing regulatory standards and many had 
very low turbidity.
    Waterborne outbreaks of cryptosporidiosis have occurred even in 
areas served by filtered surface water supplies (Solo-Gabriele and 
Neumeister, 1996). In some cases, outbreaks were attributed to 
treatment deficiencies, but in others, the treatment provided by the 
water system met the regulatory requirements in place at that time. 
These data indicate that even surface water systems that filter and 
disinfect can still be vulnerable to Cryptosporidium, depending on the 
source water quality and treatment effectiveness.
    Certain alternative disinfectants can be more effective in treating 
for Cryptosporidium. Both ozone and chlorine dioxide have been shown to 
inactivate Cryptosporidium, albeit at doses much higher than those 
required to inactivate Giardia, which has typically been used to set 
disinfectant doses (summarized in USEPA 2003a). Studies have also 
demonstrated a synergistic effect of treatment using ozone followed by 
chlorine or monochloramine (Rennecker et al. 2000, Driedger et al. 
2001). Significantly, UV light has recently been shown to achieve high 
levels of Cryptosporidium inactivation at feasible doses (summarized in 
USEPA 2003a).
    Other processes that can help reduce Cryptosporidium levels in 
finished water include watershed management programs, pretreatment 
processes like bank filtration, and additional clarification and 
filtration processes during water treatment. Further, optimizing 
treatment performance and achieving very low levels of turbidity in the 
finished water has been shown to improve Cryptosporidium removal in 
treatment plants (summarized in USEPA 2003a).
5. Epidemic and Endemic Disease From Cryptosporidium
    Cryptosporidium has caused a number of waterborne disease outbreaks 
since 1984 when the first was reported in the United States. Data from 
the Centers for Disease Control and Prevention (CDC) include ten 
outbreaks caused by Cryptosporidium in drinking water between 1984 and 
2000, with approximately 421,000 cases of illness (CDC 1993, 1996, 
1998, 2000, and 2002). The most serious outbreak occurred in 1993 in 
Milwaukee; an estimated 403,000 people became sick (MacKenzie et al. 
1994), and at least 50 Cryptosporidium-associated deaths occurred among 
the severely immunocompromised (Hoxie et al. 1997). Further, a study by 
McDonald et al. (2001) using blood samples from Milwaukee children 
suggests that Cryptosporidium infection was more widespread than might 
be inferred from the illness estimates by MacKenzie et al. (1994).
    The number of identified and reported outbreaks in the CDC database 
is believed to substantially understate the actual incidence of 
waterborne disease outbreaks and cases (Craun and Calderon 1996, 
National Research Council 1997). This under reporting is

[[Page 661]]

due to a number of factors. Many people experiencing gastrointestinal 
illness do not seek medical attention. Where medical attention is 
provided, the pathogenic agent may not be identified through routine 
testing. Physicians and patients often lack sufficient information to 
attribute gastrointestinal illness to any specific origin, such as 
drinking water, and few States have an active outbreak surveillance 
program. In addition, if drinking water is investigated as the source 
of an outbreak, oocysts may not be detected in water samples even if 
they are present, due to limitations in analytical methods. 
Consequently, outbreaks may not be recognized in a community or, if 
recognized, may not be traced to a drinking water source.
    In addition, an unknown but probably significant portion of 
waterborne disease is endemic (i.e., isolated cases not associated with 
an outbreak) and, thus, is even more difficult to recognize. In an 
outbreak, if the pathogen has been identified, medical providers and 
public health investigators know what to look for. In endemic disease, 
there is no investigation, so the illness may never be identified, or 
if it is, it may not be linked to a source (e.g., drinking water, 
person-to-person transmission). In addition, where a pathogen is 
identified, lab results may not be reported to public health agencies.
    Because of this under reporting, the actual incidence of 
cryptosporidiosis associated with drinking water is unknown. However, 
indications of this incidence rate can be roughly extrapolated from 
different sources. Mead et al. (1999) estimated approximately 300,000 
total cases of cryptosporidiosis annually that result in a physician 
visit, with 90 percent of these attributed to waterborne (drinking 
water and recreational water) and secondary transmission. This estimate 
is based on the percentage of stools that test positive for 
Cryptosporidium and applying this percentage to the approximately 15 
million physician visits for diarrhea each year. While the fraction of 
cryptosporidiosis cases that result in a physician visit is unknown, 
Corso et al. (2003) reported that during the 1993 outbreak in 
Milwaukee, medical care was sought in approximately 12 percent of all 
cryptosporidiosis cases.
    Surveillance data from the CDC for 2001 show an overall incidence 
of 1.5 laboratory diagnosed cases of cryptosporidiosis per 100,000 
population (CDC, 2002). Although the fraction of all cryptosporidiosis 
cases that are laboratory confirmed is unknown, during the 1993 
Milwaukee outbreak, 739 cases from an estimated 403,000 cases total 
were confirmed by a laboratory (MacKenzie et al., 1994). These data 
indicate a ratio of 1 laboratory confirmed case per 545 people 
estimated to be ill with cryptosporidiosis.
    A few studies have attempted to determine exposure in certain areas 
by measuring seroprevalence of Cryptosporidium antibodies (the 
frequency at which antibodies are found in the blood). Detection of 
such antibodies (seropositivity), however, does not mean that the 
person actually experienced symptoms of cryptosporidiosis. An 
individual can be asymptomatically infected and still excrete oocysts. 
Seroprevalence, though, is still a method for estimating the exposure 
to Cryptosporidium that has occurred within a limited time period (the 
antibodies may last only a few months).
    Frost et al. (2001) conducted a paired city study, in which the 
serological response of blood donors in a city using ground water as 
its water source was compared to that of donors in a city using surface 
water as its source. Rates of seropositivity were higher (49 vs. 36 
percent) in the city with the surface water source. A similar study in 
two other cities (Frost et al. 2002) showed a seropositivity rate of 54 
percent in the city served by surface water compared to 38 percent in 
the city served by ground water. These studies suggest that drinking 
water from surface sources may be a factor in the higher rates of 
seropositivity.

D. Specific Concerns Following the IESWTR and LT1ESWTR

    In the LT2ESWTR, EPA is addressing a number of public health 
concerns that remain following implementation of the IESWTR and 
LT1ESWTR. These are as follows:
     The need for filtered PWSs with higher levels of source 
water Cryptosporidium contamination to provide additional risk-based 
treatment for Cryptosporidium beyond IESWTR or LT1ESWTR requirements;
     The need for unfiltered PWSs to provide risk-based 
treatment for Cryptosporidium to achieve equivalent public health 
protection with filtered PWSs; and
     The need for PWSs with uncovered finished water storage 
facilities to take steps to reduce the risk of contamination of treated 
water prior to distribution to consumers.
    EPA and stakeholders identified each of these issues as public 
health concerns during development of the IESWTR (USEPA 1994, 1997). 
However, the Agency was unable to address these concerns in those 
regulations due to data gaps in the areas of health effects, 
occurrence, analytical methods, and treatment. Consequently, EPA 
followed a two-stage strategy for microbial and disinfection byproducts 
rules. Under this strategy, the IESWTR and LT1ESWTR were promulgated to 
provide an initial improvement in public health protection in large and 
small PWSs, respectively, while additional data to support a more 
comprehensive regulatory approach were collected.
    Since promulgating the IESWTR and LT1ESWTR, EPA has worked with 
stakeholders to collect and analyze significant new information to fill 
data gaps related to Cryptosporidium risk management in PWSs. The next 
section presents EPA's evaluation of these data and their implications 
for both the risk of Cryptosporidium in filtered and unfiltered PWSs 
and the feasibility of steps to limit this risk. In addition, the 
Agency has evaluated additional data related to mitigating risks with 
uncovered finished water storage facilities, which are presented in 
section IV.F.

E. New Information on Cryptosporidium Risk Management

    EPA and stakeholders determined during development of the IESWTR 
that in order to establish risk-based treatment requirements for 
Cryptosporidium, additional information was needed in the following 
areas: (1) The risk associated with a given level of Cryptosporidium 
(i.e., infectivity); (2) the occurrence of Cryptosporidium in PWS 
sources; (3) analytical methods that would suffice for making site-
specific source water Cryptosporidium density estimates; and (4) the 
use of treatment technologies to achieve specific levels of 
Cryptosporidium disinfection (USEPA 1997).
    In today's final LT2ESWTR, EPA is promulgating risk-based 
Cryptosporidium treatment requirements for filtered and unfiltered 
PWSs. The Agency believes that the critical data gaps in the areas of 
infectivity, occurrence, analytical methods, and treatment that 
prevented the adoption of such an approach under earlier regulations 
have been addressed. The new information that the Agency and 
stakeholders evaluated in each of these areas and its significance for 
today's LT2ESWTR are summarized as follows. See section VI.L for a 
summary of public comments on EPA's use of Cryptosporidium infectivity 
and

[[Page 662]]

occurrence data in assessing benefits of the LT2ESWTR.
1. Infectivity
    Infectivity relates the probability of infection to the number of 
Cryptosporidium oocysts that a person ingests. It is used to predict 
the disease burden associated with a particular Cryptosporidium level 
in drinking water. Information on Cryptosporidium infectivity comes 
from dose-response studies where healthy human volunteers ingest 
different numbers of oocysts (i.e., the ``dose'') and are subsequently 
evaluated for signs of infection and illness (i.e., the ``response'').
    Prior to the IESWTR, data from a human dose-response study of one 
Cryptosporidium isolate (IOWA) had been published (DuPont et al. 1995). 
Following IESWTR promulgation, a study of two additional isolates (TAMU 
and UCP) was completed and published (Okhuysen et al. 1999). This 1999 
study also reanalyzed the IOWA study results. The measured infectivity 
of Cryptosporidium oocysts varied over a wide range in the Okhuysen et 
al. (1999) study. The UCP oocysts were much less infective than the 
IOWA oocysts, and the TAMU oocysts were much more infective.
    EPA analyzed these new data for the proposed LT2ESWTR using two 
different dose-response models. This analysis suggested that the 
overall infectivity of Cryptosporidium is greater than was estimated 
for the IESWTR (USEPA 2003a). Specifically, EPA estimated the mean 
probability of infection from ingesting a single infectious oocyst 
ranges from 7 to 10 percent. This infection rate is approximately 20 
times higher than the estimate of 0.4 percent used in the IESWTR.
    Since the publication of the proposed LT2ESWTR, EPA has evaluated 
three additional studies of Cryptosporidium infectivity. EPA also 
received a recommendation from the SAB that it analyze Cryptosporidium 
infectivity data using a wider range of models. Accordingly, EPA re-
estimated Cryptosporidium infectivity using the new data and six 
different dose-response models, including the two models used at 
proposal. Estimates from the new data and models for the probability of 
infection from ingesting a single infectious oocyst range from 4 to 16 
percent. A detailed discussion of the models and their varying 
assumptions is provided in the LT2ESWTR Economic Analysis (USEPA 
2005a).
    As is apparent from these results, substantial uncertainty about 
the infectivity of Cryptosporidium remains in several areas. These 
include the variability in host susceptibility, response at very low 
oocyst doses typical of drinking water ingestion, and the relative 
infectivity and occurrence of different Cryptosporidium isolates in the 
environment. To address this uncertainty, EPA conducted its health risk 
reduction and benefits analyses using a representative range of model 
results. In the summary tables for these analyses, three sets of 
estimates are presented: A ``high'' estimate based on the model that 
showed the highest mean baseline risk; a ``medium'' estimate, based on 
the models and data used at proposal, which also happens to be in the 
middle of the range of estimates produced by the six models using the 
newly available data; and a ``low'' estimate, based on the model that 
showed the lowest mean baseline risk.
    These estimates should not be construed as upper and lower bounds 
on illnesses avoided and benefits. For each model, a distribution of 
effects is estimated, and the ``high'' and ``low'' estimates show only 
the means of these distributions for two different model choices. The 
detailed distribution of effects is presented for the proposal model in 
the Economic Analysis (USEPA 2005a). Further, the six dose-response 
models used in this analysis do not cover all possible variations of 
models that might have been used with the data, and it is possible that 
estimates with other models would fall outside the range presented. 
However, as discussed in the Economic Analysis, EPA believes that the 
models used in the analyses reflect a reasonable range of results based 
on important dimensions of model choice.
    Regardless of which model is chosen, the available infectivity data 
suggest that the risk associated with a given concentration of 
Cryptosporidium is most likely higher than EPA had estimated for the 
IESWTR. This finding supports the need for increased treatment for 
Cryptosporidium as required under the LT2ESWTR.
2. Occurrence
    Information on the occurrence of Cryptosporidium oocysts in 
drinking water sources is a critical parameter for assessing risk and 
the need for additional treatment for this pathogen. For the IESWTR, 
EPA had no national survey data on Cryptosporidium occurrence and 
relied instead on several studies that were local or regional. After 
promulgating the IESWTR, EPA obtained data from two national surveys, 
the Information Collection Rule (ICR) and the ICR Supplemental Surveys 
(ICRSS), which were designed to provide improved estimates of 
occurrence on a national basis.
    The ICR included monthly sampling for Cryptosporidium and other 
water quality parameters from the sources of approximately 350 large 
PWSs over 18 months. The ICRSS involved twice-per-month Cryptosporidium 
sampling from the sources of a statistically random sample of 40 large 
and 40 medium PWSs over 12 months. In addition, the ICRSS required the 
use of an improved analytical method for Cryptosporidium analysis that 
had a higher method recovery (the likelihood that an oocyst present in 
the sample will be counted) and enhanced sample preparation procedures.
    EPA analyzed ICR and ICRSS data using a statistical model to 
account for factors like method recovery and sample volume analyzed. As 
described in more detail in EPA's Occurrence and Exposure Assessment 
for the LT2ESWTR (USEPA 2005b), the ICR and ICRSS results demonstrate 
two main differences for filtered PWSs in comparison to Cryptosporidium 
occurrence data used for the IESWTR:

    (1) The occurrence of Cryptosporidium in many drinking water 
sources is lower than was indicated by the data used in IESWTR. For 
example, median Cryptosporidium levels for the ICR and ICRSS data 
are approximately 0.05/L, which is nearly 50 times lower than the 
median IESWTR estimates of 2.3 oocysts/L (USEPA 1998a).
    (2) Cryptosporidium occurrence is more variable from location to 
location than was shown by the data considered for the IESWTR. This 
finding demonstrates that, although median occurrence levels are 
below those estimated for the IESWTR, a subset of PWSs contains 
Cryptosporidium levels that are considerably greater than the 
median.

    These results, therefore, indicate that Cryptosporidium levels are 
relatively low in most water sources, but a subset of sources with 
relatively higher concentrations may require additional treatment. 
These findings support a risk-targeted approach for the LT2ESWTR 
wherein additional Cryptosporidium treatment is required only for 
filtered PWSs with the highest source water pathogen levels.
    Only the ICR provided data to evaluate Cryptosporidium occurrence 
in unfiltered PWS sources. The median Cryptosporidium level among 
unfiltered PWS sources was 0.0079 oocysts/L. This level is 
approximately 10 times lower than the median level for filtered PWS 
sources.
    When the Cryptosporidium removal that filtered PWSs achieve is 
taken into account, these occurrence data suggest that unfiltered PWSs 
typically have

[[Page 663]]

higher concentrations of Cryptosporidium in their treated water than 
filtered PWSs. EPA has estimated that on average, conventional 
filtration plants remove around 99.9 percent (3-log) of the 
Cryptosporidium present in the source water. Most unfiltered PWSs, 
however, provide no treatment for Cryptosporidium. If an unfiltered PWS 
had a source water Cryptosporidium level 10 times lower than a filtered 
PWS and the filtered PWS achieved 3-log Cryptosporidium removal, then 
the Cryptosporidium level in the treated water of the unfiltered PWS 
would be 100 times higher than in the filtered PWS.
    These results suggest that to achieve public health protection 
equivalent to that provided by filtered PWSs, unfiltered PWSs must take 
additional steps. Thus, this finding supports the need for 
Cryptosporidium treatment requirements for unfiltered PWSs under the 
LT2ESWTR.
3. Analytical Methods
    To establish risk-targeted treatment requirements, analytical 
methods must be available to estimate the contaminant densities in PWS 
sources. These density estimates are used to determine the level of 
treatment that is needed at a particular site.
    When EPA developed the IESWTR, the best available method for 
measuring Cryptosporidium was the Information Collection Rule Protozoan 
Method (ICR Method). The ICR Method provided a quantitative measurement 
of Cryptosporidium oocysts, but typically undercounted the actual 
occurrence due to low method recovery. For example, in a spiking study 
(studies in which known quantities of oocysts are added to water 
samples) conducted during the ICR survey, the mean recovery of spiked 
Cryptosporidium oocysts was only 12 percent (Scheller et al. 2002). EPA 
concluded that the ICR Method was adequate for making national 
occurrence estimates in the ICR survey but would not suffice for making 
estimates of Cryptosporidium levels at specific sites.
    Subsequent to promulgating the IESWTR, EPA developed an improved 
Cryptosporidium method, EPA Method 1622 (and later, 1623), to achieve 
higher recovery rates and lower inter- and intra-laboratory variability 
than previous methods. Methods 1622 and 1623 incorporate improvements 
in the concentration, separation, staining, and microscope examination 
procedures. During the ICRSS, which required the use of Method 1622 or 
1623, a spiking study demonstrated a mean Cryptosporidium recovery of 
43 percent (Connell et al. 2000). Thus, mean Cryptosporidium recovery 
with Methods 1622 and 1623 was more than 3.5 times higher compared to 
the ICR Method performance in the earlier spiking study. In addition, 
the relative variation in recovery from sample to sample was lower with 
Methods 1622 and 1623.
    As described in section IV of this preamble, EPA has concluded that 
a monitoring program using Methods 1622 or 1623 can be effective in 
characterizing PWSs source water Cryptosporidium levels for purposes of 
determining the need for additional treatment requirements. This 
finding supports the feasibility of risk-targeted treatment 
requirements under the LT2ESWTR.
4. Treatment
    To establish risk-targeted Cryptosporidium treatment requirements, 
feasible treatment processes must be available that allow PWSs to 
inactivate or remove Cryptosporidium. PWSs may then implement these 
treatment processes to comply with additional treatment requirements.
    During development of the IESWTR, EPA recognized that chlorine, the 
most commonly used disinfectant, is ineffective for inactivating 
Cryptosporidium. Studies suggested that other disinfectants like ozone 
and chlorine dioxide could be effective against Cryptosporidium. 
However, EPA concluded that data available at that time were not 
sufficient to define how any disinfectant could be applied to achieve a 
specific level of Cryptosporidium inactivation (USEPA 1997). This 
conclusion was due in part to methodological inconsistencies and 
shortcomings in the available studies.
    With the completion of major studies since promulgation of the 
IESWTR, EPA has acquired the data necessary to establish standards for 
Cryptosporidium inactivation by several disinfectants. For ozone and 
chlorine dioxide, EPA reviewed new studies by Rennecker et al. (1999), 
Owens et al. (1999, 2000), Oppenheimer et al. (2000), Ruffell et al. 
(2000), and Li et al. (2001). Collectively, these studies cover a wide 
range of both natural and laboratory water conditions. Based on these 
studies, EPA has developed tables that specify the product of ozone or 
chlorine dioxide concentration and time of exposure (i.e., CT tables) 
needed to achieve up to 3-log Cryptosporidium inactivation. Section 
IV.D of this preamble shows these tables.
    Most significantly, many recent studies have demonstrated that UV 
light is efficient for inactivating high levels of Cryptosporidium. 
These studies include Clancy et al. (1998, 2000, 2002), Bukhari et al. 
(1999), Craik et al. (2000, 2001), Landis et al. 2000), Sommer et al. 
(2001), Shin et al. (2001), and Oppenheimer et al. (2002). Using 
results from these studies, EPA has defined the UV light intensity and 
exposure time required for up to 4-log Cryptosporidium inactivation. 
Section IV.D presents these values. EPA has determined that UV light is 
a feasible technology for PWSs of all sizes to inactivate 
Cryptosporidium.
    EPA has also developed standards for processes that physically 
remove Cryptosporidium contamination. These processes include river 
bank filtration, sedimentation basins, bag filters, cartridge filters, 
and membranes. Section IV.D presents design and operational standards 
for these processes, along with a summary of supporting studies.
    The development of these standards for Cryptosporidium inactivation 
and removal processes overcomes a significant limitation that existed 
when EPA developed the IESWTR. These standards will allow PWSs to 
implement cost-effective strategies to comply with additional 
Cryptosporidium treatment requirements under the LT2ESWTR.

F. Federal Advisory Committee Recommendations

    EPA convened the Stage 2 M-DBP Federal Advisory Committee in March 
1999 to evaluate new information and develop recommendations for the 
LT2ESWTR and Stage 2 DBPR. The Committee was comprised of 
representatives from EPA, State and local public health and regulatory 
agencies, local elected officials, Indian Tribes, drinking water 
suppliers, chemical and equipment manufacturers, and public interest 
groups. A technical workgroup provided analytical support for the 
Committee's discussions.
    Committee members signed an Agreement in Principle in September 
2000 stating consensus recommendations of the group. The Agreement was 
published in a December 29, 2000 Federal Register notice (USEPA 2000a). 
For the LT2ESWTR, the consensus recommendations of the Committee are 
summarized as follows:
    (1) Supplemental risk-targeted Cryptosporidium treatment by 
filtered PWSs with higher source water contaminant levels as shown by 
monitoring results;
    (2) Cryptosporidium inactivation by all unfiltered PWSs, which must 
meet

[[Page 664]]

overall treatment requirements using a minimum of 2 disinfectants;
    (3) A ``toolbox'' of treatment and control processes for PWSs to 
comply with Cryptosporidium treatment requirements;
    (4) Reduced monitoring burden for small filtered PWSs;
    (5) Future monitoring to confirm or revise source water quality 
assessments;
    (6) Development of guidance for UV disinfection and other toolbox 
components; and
    (7) Cover or treat existing uncovered finished water reservoirs 
(i.e., storage facilities) or implement risk mitigation plans.
    These recommendations reflect a Committee judgement that, based on 
available information, additional risk-based Cryptosporidium treatment 
requirements for filtered and unfiltered PWSs are appropriate and 
feasible under the LT2ESWTR. Much of today's final LT2ESWTR reflects 
the Committee's recommendations. The next part of this preamble 
describes specific requirements of the rule.

IV. Explanation of Today's Action

A. Source Water Monitoring Requirements

    Today's rule requires PWSs using surface water or GWUDI sources to 
monitor their source water to assess the level of Cryptosporidium. 
Monitoring results assign a PWS to a Cryptosporidium treatment bin, 
which determines the extent of additional Cryptosporidium treatment 
requirements (sections IV.B and IV.C described treatment requirements 
for filtered and unfiltered PWSs, respectively).
    Source water monitoring under the LT2ESWTR is designed to ascertain 
the mean level of Cryptosporidium in the influent to a surface water 
treatment plant. Requirements differ by PWS size (above or below 10,000 
people served) and treatment plant type (filtered or unfiltered PWS). 
This section describes monitoring requirements for sampling parameters 
and frequency, sampling location, sampling schedule, monitoring plants 
that operate only part of the year, failing to monitor, providing 
treatment instead of monitoring, grandfathering previously collected 
data, ongoing watershed assessment, second round of monitoring, and new 
source monitoring.
    Other sections of this preamble describe additional requirements 
related to monitoring, including compliance schedules (section IV.G), 
reporting of monitoring results (section IV.I), use of approved 
analytical methods, including minimum sample volume (section IV.J), and 
use of approved laboratories (section IV.K). As described in section 
IV.G, monitoring compliance dates under the LT2ESWTR are staggered: 
smaller PWSs begin monitoring after larger PWSs.
    For additional information, see Source Water Monitoring Guidance 
Manual for Public Water Systems under the Long Term 2 Enhanced Surface 
Water Treatment Rule. This document provides guidance on sampling 
location, procedures for collecting and shipping samples, contracting 
with laboratories, and related topics to assist PWSs in complying with 
LT2ESWTR monitoring requirements. It may be acquired from EPA's Safe 
Drinking Water Hotline, which can be contacted as described under FOR 
FURTHER INFORMATION CONTACT at the beginning of this document.
1. Today's Rule
    a. Sampling parameters and frequency. Requirements for the source 
water parameters that PWSs must measure under the LT2ESWTR, as well as 
the sampling frequency and duration, are stated as follows for large 
and small PWSs, including both filtered and unfiltered plants:

Large Filtered PWSs

    Filtered PWSs serving at least 10,000 people must sample at least 
monthly for Cryptosporidium, E. coli, and turbidity for a period of two 
years. Sampling may be conducted at a higher frequency (e.g., twice-
per-month, once-per-week) but the sampling must be evenly spaced 
throughout the monitoring period. As described in section IV.B, 
filtered PWSs that sample at least twice-per-month over two years use a 
different calculation, which is less conservative, to determine their 
treatment bin classification under the LT2ESWTR.

Large Unfiltered PWSs

    Unfiltered PWSs serving at least 10,000 people must also sample for 
Cryptosporidium at least monthly for a period of 2 years. No E. coli or 
turbidity monitoring is required for unfiltered PWSs. Unfiltered PWSs 
may choose to sample more frequently; however, as described in section 
IV.C, a higher sampling frequency does not change the calculation used 
to determine unfiltered PWS Cryptosporidium treatment requirements.

Small Filtered PWSs

    Filtered PWSs serving fewer than 10,000 people (i.e., small PWSs) 
monitor under the LT2ESWTR using a two-phase strategy that begins with 
an indicator screening analysis. Small filtered PWSs must initially 
sample for E. coli at least once every two weeks for a period of one 
year. Cryptosporidium monitoring is required of these PWSs only if the 
indicator monitoring results meet one of the following conditions:
    (1) For PWSs using lake/reservoir sources, the annual mean E. coli 
concentration is greater than 10 E. coli/100 mL.
    (2) For PWSs using flowing stream sources, the annual mean E. coli 
concentration is greater than 50 E. coli/100 mL.
    PWSs using ground water under the direct influence of surface water 
must comply with the requirement to monitor for Cryptosporidium based 
on the E. coli level that applies to the nearest surface water body. If 
no surface water body is nearby, the PWS must comply based on the 
requirements that apply to PWSs using lake/reservoir sources.
    The State may approve small filtered PWSs to monitor for an 
indicator other than E. coli. The State also may approve an alternative 
E. coli concentration to trigger Cryptosporidium monitoring. This 
approval must be in writing and must be based on a State determination 
that the alternative indicator and/or trigger level will more 
accurately identify whether a PWS will exceed the Bin 1 Cryptosporidium 
level of 0.075 oocysts/L, as stated in section IV.B.1 of this preamble. 
EPA will issue guidance to States on alternative indicators and trigger 
levels, if warranted, based on large PWS monitoring results.
    Small filtered PWSs may elect to skip E. coli monitoring if they 
notify the State that they will monitor for Cryptosporidium. PWSs must 
notify the State no later than three months prior to the date the PWS 
is required to begin monitoring (see section IV.G for specific dates).
    Small filtered PWSs that are required to monitor for 
Cryptosporidium must conduct this monitoring using either of two 
frequencies: (1) Sample at least twice-per-month for a period of one 
year or (2) sample at least once-per-month for a period of two years. 
Note that the same treatment compliance dates apply to the PWS 
regardless of which Cryptosporidium sampling frequency is used (i.e., 
selecting the two-year Cryptosporidium sampling frequency does not 
extend Cryptosporidium treatment compliance deadlines).

Small Unfiltered PWSs

    All unfiltered PWSs serving fewer than 10,000 people must monitor 
for Cryptosporidium. The E. coli screening analysis used by small 
filtered PWSs is not applicable to small unfiltered PWSs. Small 
unfiltered PWSs must use either

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of the same two Cryptosporidium sampling frequencies available to small 
filtered PWSs: (1) Sample twice-per-month for one year or (2) sample 
once-per-month for two years. As with small filtered PWSs, the same 
treatment compliance dates apply to the PWS regardless of which 
Cryptosporidium sampling frequency is used.
    b. Sampling location. PWSs must collect source water samples for 
each plant that treats a surface water or GWUDI source. However, where 
multiple plants receive all of their water from the same influent, such 
as plants that draw water from the same intake or pipe, the State may 
approve one set of monitoring results to be applied to all plants.
    PWSs must collect source water samples prior to chemical treatment, 
such as coagulants, oxidants, and disinfectants, unless the following 
condition is met: The State may approve a system to collect a sample 
after chemical treatment if the State determines that collecting a 
sample prior to chemical treatment is not feasible and that the 
chemical treatment is unlikely to have a significant adverse effect on 
the analysis of the sample. PWSs that recycle filter backwash must 
collect samples prior to the point of filter backwash addition due to 
the likely presence of coagulant and other treatment chemicals in the 
backwash. See section IV.D.6 for directions on sampling location for 
PWSs using bank filtration.
    For plants that use multiple water sources at the same time, PWSs 
must collect samples from a tap where the sources are combined prior to 
treatment, if available. If a blended source tap is not available, PWSs 
must collect samples from each source and either analyze a weighted 
composite (blended) sample or analyze samples from each source 
separately and determine a weighted average of the results. The 
weighting of sources must reflect the relative usage of the different 
sources by the treatment plant at the time the sample is collected.
    PWSs must submit a description of their proposed sampling 
location(s) to the State no later than three months prior to the date 
the PWS must begin monitoring (see section IV.G for specific dates). 
This description must address the position of the sampling location in 
relation to the PWS's water source(s) and treatment processes, 
including points of chemical addition and filter backwash recycle. If 
the State does not respond to a PWS regarding sampling location(s), the 
PWS must begin sampling at the reported location. See Source Water 
Monitoring Guidance Manual for Public Water Systems under the Long Term 
2 Enhanced Surface Water Treatment Rule, which can be acquired as 
stated previously, for guidance on sampling location descriptions.
    c. Sampling schedule. PWSs must collect samples in accordance with 
a schedule that the PWS develops and reports prior to initiating 
monitoring. The sampling schedule must specify the calendar dates when 
the PWS will collect each required sample in a particular round of 
monitoring. Scheduled sampling dates must be evenly distributed 
throughout the monitoring period, but may be arranged to accommodate 
holidays, weekends, and other events when collecting or analyzing a 
sample would be problematic (e.g., a PWS is not required to schedule 
samples on the same calendar date each month).
    PWSs must submit sampling schedules no later than three months 
prior to the date the PWS must begin a round of monitoring (see section 
IV.G for specific dates). Unless the State approves an alternative 
procedure, large PWSs (serving at least 10,000 people) must report 
their sampling schedule for initial source water monitoring to EPA 
using the LT2ESWTR electronic data reporting and review system 
described in section IV.I. Schedules for initial monitoring by small 
PWSs and for the second round of monitoring by all PWSs must be 
reported to the State. PWSs should verify that their laboratory can 
accommodate the scheduled sampling dates before submitting the 
schedule.
    EPA will not formally approve sampling schedules but will notify a 
PWS if its sampling schedules does not meet the requirements of today's 
rule (e.g., does not include the required number of samples). If a PWS 
does not receive notification from the State or EPA regarding the 
sampling schedule, the PWS must begin monitoring according to the 
reported sampling schedule.
    PWSs must collect samples within two days before or two days after 
the dates indicated in their sampling schedules (i.e., within a 5-day 
period around the schedule date) unless one of the following two 
conditions applies:
    (1) If an extreme condition or situation exists that may pose 
danger to the sample collector, or that cannot be avoided and causes 
the PWS to be unable to sample in the scheduled 5-day period, the PWS 
must sample as close to the scheduled date as is feasible unless the 
State approves an alternative sampling date. The PWS must submit an 
explanation for the delayed sampling date to the State concurrent with 
the shipment of the samples to the laboratory.
    (2) If a PWS is unable to report a valid analytical result for a 
scheduled sampling date due to equipment failure, loss of or damage to 
the sample, failure to comply with the analytical method requirements, 
or the failure of an approved laboratory to analyze the sample, then 
the PWS must collect a replacement sample. Collection of the 
replacement sample must occur within 21 days of the PWS receiving 
information that an analytical result cannot be reported for the 
scheduled date unless the PWS demonstrates that collecting a 
replacement sample within this time frame is not feasible or the State 
approves an alternative resampling date. The PWS must submit an 
explanation for the resampling date to the State concurrent with the 
shipment of the sample to the laboratory.
    Failure to collect a required sample within the 5-day period around 
a scheduled date that does not meet one of these two conditions is a 
monitoring violation. PWSs must revise their sampling schedules to add 
dates for collecting all missed samples and must submit the revised 
schedule to the State for approval prior to when the PWS begins 
collecting the missed samples.
    d. Plants operating only part of the year. Some PWSs operate 
surface water treatment plants for only part of the year. This includes 
PWSs that provide water for only a fraction of the year (e.g., resorts 
open only in the summer) and PWSs that use a surface water plant to 
supplement another source only during periods of high demand.
    Most LT2ESWTR monitoring, treatment, and implementation schedule 
requirements apply to such plants. Monitoring requirements, however, 
differ in two respects:
    (1) PWSs must conduct sampling only during months of the 2 year 
monitoring period when the plant operates unless the State specifies 
another monitoring period based on plant operating practices; and
    (2) For plants that operate less than six months per year and where 
Cryptosporidium monitoring is required, PWSs must collect at least six 
Cryptosporidium samples per year during each of two years of 
monitoring.
    e. Failing to monitor. Today's rule requires PWSs to provide a Tier 
3 public notice for violation of monitoring and testing procedure 
requirements, including the failure to collect one or two source water 
Cryptosporidium samples. If a PWS fails to collect three or more 
Cryptosporidium samples, other than in specifically exempted situations 
(see section IV.A.1.c), the PWS must

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provide a Tier 2 special public notice. Violations for failing to 
monitor persist until the State determines that the PWS has begun 
sampling on a revised schedule that includes dates for the collection 
of missed samples. Section IV.H provides further details on public 
notice requirements of the LT2ESWTR.
    PWSs must report their bin classification (or mean Cryptosporidium 
level for unfiltered PWSs) no later than six months after the end of 
the scheduled monitoring period (specific dates in section IV.G). 
Failure by a PWS to collect the required number of Cryptosporidium 
samples to report its bin classification or mean Cryptosporidium level 
by the compliance date is a treatment technique violation and the PWS 
must provide a Tier 2 special public notice (unless the PWS has already 
provided a Tier 2 public notice for missing three sampling dates and is 
successfully meeting a State-approved schedule for sampling). The 
treatment technique violation and public notice requirements persist 
until the State determines that the PWS is implementing a State-
approved monitoring plan to allow bin classification or will install 
the highest level of treatment required under the rule, as described 
next.
    f. Providing treatment instead of monitoring. PWSs are not required 
to conduct source water monitoring under the LT2ESWTR for plants that 
will provide the highest level of treatment required under the rule. 
This applies both to plants that provide this level of treatment at the 
time the plant would otherwise begin source water monitoring and to 
plants that commit to install technology to achieve this level of 
treatment by the applicable compliance date for meeting Cryptosporidium 
treatment requirements under the LT2ESWTR.
    Filtered PWSs are not required to monitor at plants that will 
provide a total of at least 5.5-log of treatment for Cryptosporidium, 
equivalent to meeting the treatment requirements of Bin 4 as discussed 
in section IV.B. Unfiltered PWSs are not required to monitor for plants 
that will provide a total of at least 3-log of Cryptosporidium 
inactivation, equivalent to meeting the treatment requirements for 
unfiltered PWSs with source water Cryptosporidium levels above 0.01 
oocysts/L as discussed in section IV.C.
    PWSs that intend to provide this level of treatment rather than 
initiate monitoring must notify the State no later than three months 
prior to the month the PWS must otherwise begin monitoring. PWSs submit 
this notification in lieu of submitting a sampling schedule. In 
addition, a PWS may choose to stop sampling at any point after it has 
initiated monitoring if it notifies the State that it will provide the 
highest level of treatment. In both cases, the PWSs must install and 
operate technologies to achieve this level of treatment no later than 
the applicable Cryptosporidium treatment compliance date for the PWS as 
specified in section IV.G. Failure to provide this treatment by the 
compliance date is a treatment technique violation.
    g. Grandfathering previously collected data. If the State approves, 
PWSs may comply with the initial source water monitoring requirements 
of today's rule by using (i.e., grandfathering) sample results 
collected before the PWS is required to begin monitoring. PWSs may 
grandfather monitoring results either in lieu of or in addition to 
conducting new monitoring under the rule. To be eligible for 
grandfathering, monitoring results must be equivalent in data quality 
to monitoring PWSs conduct under today's rule and the PWS must comply 
with reporting requirements. Details of these requirements follow.

Grandfathered Data Quality Requirements

     Analysis of E. coli samples must meet the analytical 
method and approved laboratory requirements for source water monitoring 
under today's rule. PWSs are not required to report E. coli and 
turbidity data in order to grandfather Cryptosporidium monitoring 
results, although EPA requests that PWSs report these data if they are 
available. PWSs that grandfather Cryptosporidium data without 
associated E. coli and turbidity data are not required to conduct 
separate monitoring for these parameters when they have satisfied 
Cryptosporidium monitoring requirements.
     Analysis of Cryptosporidium samples must meet the criteria 
of a validated version of EPA Method 1622 or 1623, which are described 
in USEPA 1999a, USEPA 1999b, USEPA 2001e, USEPA 2001f, USEPA 2005c, and 
USEPA 2005d. The volume analyzed for each sample must meet the criteria 
described in section IV.J, which are at least 10 L of sample or at 
least 2 mL of packet pellet volume or as much volume as two approved 
filters can accommodate before clogging.
     The sampling location must meet the criteria for LT2ESWTR 
monitoring, as described previously.
     For Cryptosporidium samples, the sampling frequency must 
be at least monthly and on a regular schedule. The collection of 
individual samples may deviate from a regular schedule under the same 
criteria that apply to deviation from LT2ESWTR sampling schedules, as 
described previously. Additionally, deviations in the sampling 
frequency of previously collected data are allowed under the following 
conditions: (1) PWSs may grandfather data where there are gaps in the 
sampling frequency if the State approves and if the PWS conducts 
additional monitoring when specified by the State to ensure the data 
used for bin classification are seasonally representative and unbiased; 
and (2) PWSs may grandfather data where the sampling frequency varies 
(e.g., one year of sampling monthly and one year of sampling twice-per-
month); monthly average sample concentrations must be used to calculate 
the bin classification, as described in section IV.B.

Grandfathered Data Reporting Requirements

    PWSs that request to grandfather previously collected monitoring 
results must report the following information by the applicable dates 
listed in this section. PWSs serving at least 10,000 people must report 
this information to EPA unless the State approves an alternate 
procedure for reporting. PWSs serving fewer than 10,000 people must 
report this information to the State.
    PWSs must report that they intend to submit previously collected 
monitoring results for grandfathering. This report must specify the 
number of previously collected results the PWS will submit, the dates 
of the first and last sample, and whether a PWS will conduct additional 
source water monitoring for initial bin classification. PWSs must 
report this information no later than three months prior to the date 
the PWSs is required to start monitoring, as shown in section IV.G.
    PWSs must report previously collected monitoring results for 
grandfathering, along with the required documentation listed in this 
section, no later than two months after the month the PWS is required 
to start monitoring, as shown in section IV.G.
     For each sample Cryptosporidium or E. coli result, PWSs 
must report the applicable data elements in section IV.I.1.
     PWSs must certify to EPA or the State that the reported 
monitoring results include all results the PWS generated during the 
time period beginning with the first reported result and ending with 
the final reported result. This applies to samples that were collected 
from the sampling location specified for source water monitoring

[[Page 667]]

under this subpart, not spiked, and analyzed using the laboratory's 
routine process for the analytical methods listed in this section.
     PWSs must certify to EPA or the State that the samples 
were representative of a plant's source water(s) and the source 
water(s) have not changed. PWSs must submit to EPA a description of the 
sampling location(s) for each water treatment plant, which must address 
the position of the sampling location in relation to the PWS's water 
source(s) and treatment processes, including points of chemical 
addition and filter backwash recycle.
     For Cryptosporidium samples, the laboratory or 
laboratories that analyzed the samples must provide a letter certifying 
that the quality control criteria specified in the methods listed in 
this section were met for each sample batch associated with the 
reported results. Alternatively, the laboratory may provide bench 
sheets and sample examination report forms for each field, matrix 
spike, initial precision and recovery (IPR), ongoing precision and 
recovery (OPR), and method blank sample associated with the reported 
results.
     If the State determines that a previously collected data 
set submitted for grandfathering was generated during source water 
conditions that were not normal for the PWS, such as a drought, the 
State may disapprove the data. Alternatively, the State may approve the 
previously collected data if the PWS reports additional source water 
monitoring data, as determined by the State, to ensure that the overall 
data set used for bin classification represents average source water 
conditions for the PWS.
    If a PWS submits previously collected data that fully meet the 
number of samples required for initial source water monitoring and some 
of the data are rejected due to not meeting the requirements of this 
section, PWSs must conduct additional monitoring to replace rejected 
data on a schedule the State approves. PWSs are not required to begin 
this additional monitoring until at least two months after notification 
that data have been rejected and additional monitoring is necessary.
    h. Ongoing watershed assessment. Today's rule includes provisions 
to assess changes in a PWS's source water quality following initial bin 
classification. As required by 40 CFR 142.16(b)(3)(i), source water is 
one of the components that States must address during the sanitary 
surveys that are required for surface water PWSs. These sanitary 
surveys must be conducted every 3 years for community PWSs and every 5 
years for non-community PWSs. Under today's rule, if the State 
determines during the sanitary survey or an equivalent source water 
assessment that significant changes have occurred in the watershed that 
could lead to increased contamination of the source water by 
Cryptosporidium, the PWS must take actions specified by the State to 
address the contamination. These actions may include additional source 
water monitoring and/or implementing options from the microbial toolbox 
discussed in section IV.D.
    i. Second round of monitoring. PWSs must begin a second round of 
source water monitoring beginning six years after initial bin 
classification (see compliance dates in section IV.G). If EPA does not 
modify LT2ESWTR requirements by issuing a new regulation prior to the 
second round of monitoring, PWSs must carry out this monitoring 
according to the requirements that apply to the initial round of source 
water monitoring. PWSs will then be reclassified in LT2ESWTR treatment 
bins based on the second-round monitoring result. However, if EPA 
changes the LT2ESWTR treatment bin structure to reflect a new 
analytical method or new risk information, PWSs will undergo a risk 
characterization in accordance with the revised rule.
    j. New source monitoring. A PWS that begins using a new surface 
water source after the date the PWS is required to conduct source water 
monitoring under the LT2ESWTR must monitor the new source on a schedule 
approved by the State. This applies to both new plants that begin 
operation and previously operating plants that bring a new source on-
line after the required monitoring date for the PWS. The State may 
determine that monitoring should be conducted before a new plant or 
source is brought on-line or initiated within some time period 
afterward. The new source monitoring must meet all LT2ESWTR 
requirements as specified previously in this section. The PWS must also 
determine its treatment bin classification and comply with any 
additional Cryptosporidium treatment requirements based on the 
monitoring results on a schedule approved by the State.
2. Background and Analysis
    Monitoring requirements in today's rule are designed to ascertain 
Cryptosporidium levels with suitable accuracy for making treatment bin 
classifications and in a time frame that does not delay the 
installation of Cryptosporidium treatment where needed. The following 
discussion summarizes the basis for monitoring requirements with 
respect to sampling parameters and frequency, sampling location, 
sampling schedule, monitoring plants that operate for only part of the 
year, failing to monitor, grandfathering previously collected data, 
ongoing watershed assessment, and the second round of monitoring. Most 
of these requirements were part of the August 11, 2003, proposal for 
today's final rule, and supporting analyses are presented in greater 
detail in the proposal (USEPA 2003a). Differences from proposed 
requirements are noted in the following discussion where applicable.
    a. Sampling parameters and frequency. The requirements in today's 
final rule for the parameters and frequency of source water monitoring 
are unchanged from those in the proposed rule (USEPA 2003a), with the 
exception of an additional option for lower frequency Cryptosporidium 
sampling by small PWSs. These requirements reflect recommendations by 
the Stage 2 M-DBP Advisory Committee. They are designed to ensure a low 
potential for misclassification in assigning PWSs to Cryptosporidium 
treatment bins. The supporting analyses are summarized as follows for 
Cryptosporidium and indicator (E. coli) monitoring:

Cryptosporidium Monitoring

    EPA analyzed bin misclassification rates for different 
Cryptosporidium monitoring programs by evaluating the likelihood of two 
types of errors:
    (1) A PWS with a true mean Cryptosporidium concentration of 0.5-log 
(i.e., factor of 3.2) above a bin boundary is incorrectly assigned to a 
lower bin (false negative) and
    (2) A PWS with a true mean concentration of 0.5-log below a bin 
boundary is incorrectly assigned to a higher bin (false positive).
    The first type of error, a false negative, could lead to PWSs not 
providing an adequate level of treatment while the second type of 
error, a false positive, could lead to PWSs incurring additional costs 
for unnecessary treatment.
    EPA evaluated false positive and false negative rates for 
monitoring programs that differed based on the number of samples 
collected and the calculation used to determine the bin classification. 
The analysis accounted for the sample volume assayed, variation in 
source water Cryptosporidium occurrence, variation in analytical method 
recovery, and other factors.
    Results of this analysis indicate that PWSs must collect at least 
24 samples in order to keep the likelihood of both false positives and 
false negatives at five

[[Page 668]]

percent or less. Under a monitoring program involving fewer samples, 
such as eight or twelve, a very conservative calculation for bin 
classification would be required to achieve a low false negative rate 
(e.g., bin classification based on the maximum or second highest sample 
concentration). However, such an approach would result in false 
positive rates in the range of 50 to 70 percent. Conversely, collecting 
more than 24 samples can further reduce false positive and false 
negative rates, albeit to a small degree. See the proposed LT2ESWTR for 
additional details on this analysis (USEPA 2003a).
    Based on the results of this analysis, EPA concluded that PWSs 
operating year-round should collect at least 24 samples when they 
monitor for Cryptosporidium. This number of samples ensures a high 
likelihood of appropriate bin classification. Today's rule does not 
allow bin classification based on fewer samples (except in the case of 
PWSs operating only part of the year) as this would involve 
unacceptably high false positive or false negative rates and would, 
therefore, be an inappropriate basis to determine Cryptosporidium 
treatment requirements. EPA believes, though, that PWSs should have the 
choice to collect more than 24 samples to further improve the accuracy 
of bin classification, and today's rule allows this.
    In regard to the time frame for LT2ESWTR monitoring, the Agency 
considered the trade-off between monitoring over a long period to 
better capture temporal fluctuations and the desire to prescribe 
additional treatment quickly to PWSs with higher Cryptosporidium 
levels. Today's rule requires large PWSs to evaluate their source water 
Cryptosporidium levels using two years of monitoring. This will account 
for some degree of yearly variability, without significantly delaying 
additional public health protection where needed.
    Because many small PWSs will monitor for E. coli for one year 
before monitoring for Cryptosporidium, today's rule allows two options. 
Small PWSs can collect 24 Cryptosporidium samples over just one year 
(resulting in a total of two years of source water monitoring when E. 
coli monitoring is considered) or they can spread their 24 
Cryptosporidium samples over two years. Spreading the Cryptosporidium 
monitoring over two years will reduce the monitoring costs a PWS incurs 
in a single year but will not push back the treatment compliance 
deadline. This allowance for small PWSs to monitor for Cryptosporidium 
over two years is a change from the proposal (USEPA 2003a). It stems 
from recognition of the benefit this approach will provide to some 
small PWSs in budgeting for monitoring.

Indicator Monitoring

    Due to the relatively high cost of analyzing samples for 
Cryptosporidium, the Advisory Committee and EPA investigated indicators 
that are less costly to analyze to determine if any could be used in 
place of Cryptosporidium monitoring. No indicators were identified that 
correlated strongly with Cryptosporidium and could fully substitute for 
Cryptosporidium monitoring for determining treatment bin 
classifications. However, this investigation did identify an indicator, 
E. coli, that can be used to identify some of the water sources that 
are unlikely to exceed a Cryptosporidium level of 0.075 oocysts/L--the 
level at which filtered PWSs must provide additional treatment under 
the LT2ESWTR.
    Data from the ICR and ICRSS were used in the investigation of 
indicators. With these data, E. coli performed the best in identifying 
sources with low Cryptosporidium levels. In addition, analyzing plants 
separately based on source water type was necessary due to a different 
relationship between E. coli and Cryptosporidium in reservoir/lake 
sources compared to flowing stream sources.
    The analysis of E. coli concentrations that could trigger 
Cryptosporidium monitoring was based on false negative and false 
positive rates. For this indicator, false negatives occur when sources 
do not exceed the E. coli trigger value but exceed a Cryptosporidium 
level of 0.075 oocysts/L. False positives occur when sources exceed the 
E. coli trigger value but do not exceed a Cryptosporidium level of 
0.075 oocysts/L. The false negative rate is critical because it 
characterizes the ability of the indicator to identify those plants 
with higher Cryptosporidium levels that should conduct Cryptosporidium 
monitoring to determine if additional treatment is needed.
    For plants with flowing stream sources, a mean E. coli trigger 
concentration of 50/100 mL produced zero false negatives for both ICR 
and ICRSS data sets. This means that in these data sets, all plants 
that exceeded mean Cryptosporidium concentrations of 0.075 oocysts/L 
also exceeded the E. coli trigger concentration. The false positive 
rate for this trigger concentration was near 50 percent, meaning it was 
not highly specific in targeting only those plants with high 
Cryptosporidium levels. However, at a higher E. coli trigger 
concentration, such as 100/100 mL, the false negative rate increased 
without a significant reduction in the false positive rate.
    For plants with lake or reservoir sources, a mean E. coli trigger 
of 10/100 mL resulted in a false negative rate of 20 percent with ICR 
data and 67 percent with ICRSS data. While this false negative rate in 
the ICRSS data set appears high, it is based on just three plants in 
this survey that used a reservoir/lake source and had a mean 
Cryptosporidium level above 0.075 oocysts/L. With a lower E. coli 
trigger concentration, such as 5/100 mL, the number of false negatives 
in both data sets decreased by one plant, but the false positive rate 
increased from 20 to 40 percent.
    After evaluating these results, the Advisory Committee recommended 
that all large PWSs monitor for Cryptosporidium, rather than using E. 
coli in a screening analysis. EPA concurred with this recommendation 
because it achieves the highest certainty that these PWSs will be 
classified in the correct Cryptosporidium treatment bin and provide the 
appropriate level of public health protection. In addition, the 
Advisory Committee recommended and today's rule requires that large 
filtered PWSs collect E. coli and turbidity samples along with 
Cryptosporidium. EPA will use these data to confirm or, if necessary, 
further refine the use of E. coli and possibly turbidity as indicators 
for monitoring by small filtered PWSs.
    Cryptosporidium monitoring places a relatively greater economic 
burden on small PWSs, and EPA will have additional E. coli and 
Cryptosporidium data from large PWS monitoring prior to the initiation 
of small PWS monitoring. Based on these considerations and the 
available data on E. coli as an indicator of sources with lower 
Cryptosporidium levels, the Advisory Committee recommended that small 
filtered PWSs initially monitor for E. coli for one year as a screening 
analysis. Biweekly sampling (i.e., 1 sample every two weeks) for E. 
coli is required to achieve high confidence in the results, since no 
additional monitoring is required if the E. coli level is less than the 
trigger value. Mean E. coli concentrations above 10 and 50/100 mL 
trigger Cryptosporidium monitoring in PWSs using reservoir/lake and 
flowing stream sources, respectively.
    EPA concurred with these recommendations by the Advisory Committee 
and believes they achieve an appropriate balance between enhancing

[[Page 669]]

public health protection and reducing the economic impact of today's 
rule on small PWSs. Survey data indicate that approximately 75 to 80 
percent of small PWSs will not exceed the E. coli trigger values and, 
consequently, will not be required to monitor for Cryptosporidium. 
Because E. coli is far less costly to analyze than Cryptosporidium 
(costs listed in USEPA 2005a), this approach will significantly reduce 
the burden of today's rule for these PWSs. Further, EPA will review 
indicator data from large PWS monitoring and, if appropriate, issue 
guidance to States on alternative indicator triggers prior to when 
small PWSs begin monitoring. Today's rule allows States to approve 
alternative approaches to indicator monitoring for small PWSs.
    EPA could not identify an indicator screening analysis for 
unfiltered PWSs. As described in section IV.C, a mean Cryptosporidium 
concentration of 0.01 oocysts/L determines whether unfiltered PWSs are 
required to provide 2- or 3-log Cryptosporidium inactivation. No E. 
coli concentration was effective in determining whether PWSs were 
likely to fall above or below this level. Consequently, today's rule 
requires all unfiltered PWSs to monitor for Cryptosporidium, unless 
they choose to provide 3-log Cryptosporidium inactivation.
    b. Sampling location. The requirements in today's final rule for 
the source water sample collection location are similar to those in the 
proposed rule (USEPA 2003a). They are designed to achieve two 
objectives: (1) Characterize the influent water to the treatment plant 
at the time each sample is collected and (2) ensure that samples are 
not affected by treatment chemicals that could interfere with 
Cryptosporidium analysis.
    The first objective is the basis for requiring PWSs that use 
multiple sources to either analyze a blended source sample or calculate 
a weighted average of sources that reflects the influent at the time of 
sample collection. It is also the reason that PWSs are required to 
sample after certain pretreatment processes like bank filtration 
(described in section IV.D) that do not involve chemical addition.
    The second objective is why PWSs are generally required to sample 
upstream of chemical addition and prior to backwash addition (for PWSs 
that recycle filter backwash). However, EPA recognizes that in some 
situations, sampling prior to chemical addition will not be feasible 
and discontinuing chemical addition for a period of time prior to 
sampling will not be advisable. This situation could occur when a 
treatment chemical is added at an intake that is difficult to access. 
Further, some treatment chemicals may not interfere with 
Cryptosporidium analyses when present at very low levels. Consequently, 
today's rule allows States to approve PWSs sampling after chemical 
addition when the State determines that collection prior to chemical 
treatment is not feasible and the treatment chemical is not expected to 
interfere with the analysis of the sample.
    EPA believes that States should review source water monitoring 
locations for their PWSs. State review of monitoring locations will 
ensure that PWSs collect source water samples at the correct location 
to determine the appropriate level of public health protection. 
Consequently, today's rule requires PWSs to report a description of 
their monitoring location to the State. This requirement is a change 
from the proposed rule, which did not require PWSs to report a 
description of their sampling location (USEPA 2003a). This change 
reflects public comment on the proposal, as described later, which 
strongly supported State review of monitoring locations. If a PWS does 
not hear back from the State by the time it is scheduled to begin 
sampling, it may assume that its monitoring location is acceptable.
    c. Sampling schedule. The requirement in today's final rule that 
PWSs must develop a schedule for sample collection before the start of 
monitoring was part of the proposal (USEPA 2003a). This requirement 
will help to ensure that monitoring determines the mean concentration 
of Cryptosporidium in the treatment plant influent. To achieve this 
objective, the timing of sample collection must not be adjusted in 
response to fluctuations in water quality--for example, the avoidance 
of sampling when the influent water is expected to be of poor quality.
    EPA believes that the 5-day window for sample collection and 
associated allowances for sampling outside this window provide 
sufficient flexibility. If circumstances arise that prevent the PWS 
from sampling within the scheduled 5-day window, such as a weather 
event or plant emergency, the PWS must collect a sample as soon as 
feasible. In this case, feasibility includes both the ability of the 
PWS to safely collect a sample and the availability of an approved 
laboratory to conduct the analysis within method specifications. In 
addition, today's rule allows States to authorize a different date for 
collecting the delayed sample. Such an authorization may be appropriate 
in cases where sampling is significantly delayed and collecting the 
delayed sample during the same time period in the following year of 
monitoring is preferable.
    PWSs that collect a sample as scheduled but are unable to have the 
sample analyzed as required due to problems like shipping or laboratory 
analysis must collect a replacement sample within 21 days of receiving 
information that one is needed, unless the PWS demonstrates that 
collecting a replacement sample within this time frame is not feasible. 
This time frame is a minor change from the proposal, which allowed only 
14 days for resampling (USEPA 2003a), and it provides greater 
flexibility for scheduling replacement samples. Information that 
resampling is needed includes information the PWS acquires directly, as 
well as notice from the shipping company, laboratory, State, or EPA. 
Today's rule allows States to authorize an alternative date for 
collection of the replacement sample. This may be needed for resampling 
to occur during the same conditions as the originally scheduled sample.
    If collecting a sample was feasible but the PWS failed to do so, 
EPA believes that the PWSs must develop a revised sampling schedule and 
submit it to the State. This will allow for State consultation 
regarding the reason for the missed sample(s) and strategies for the 
PWS to complete the required monitoring.
    d. Plants operating only part of the year. The proposed LT2ESWTR 
did not include distinct monitoring requirements for plants that 
operate only part-year. However, EPA requested comment in the proposal 
on an approach to plants that operate only part-year that is similar to 
the requirements in today's final rule (USEPA 2003a).
    Monitoring requirements for plants that operate only part-year 
derive from three considerations: (1) A PWS should sample only during 
the months when a treatment plant operates; (2) the mean 
Cryptosporidium level used for bin classification can be determined 
with fewer samples in plants that operate only part-year because source 
water quality typically varies less during the shorter operating 
period; and (3) a minimum number of samples is necessary to classify 
any plant in an LT2ESWTR bin with high confidence.
    The basis for the first consideration is straightforward. Source 
water monitoring under the LT2ESWTR is used to establish treatment 
requirements, and these should be based

[[Page 670]]

on the water quality when a plant is in operation. The rationale for 
the second and third considerations stems from analyses, similar to 
those described previously, of potential misclassification rates in 
assigning plants to LT2ESWTR treatment bins.
    Source water variability is one factor that influences the number 
of samples needed to accurately classify plants in LT2ESWTR treatment 
bins. As variability increases, more samples are needed to determine 
the mean Cryptosporidium level with high confidence. EPA does not have 
data on source water variability specifically in plants that operate 
only part-year. However, survey data show that pathogen levels vary 
seasonally, and plants operating part-year will generally experience 
less variability during a given year than plants operating year-round. 
Consequently, fewer samples are typically needed to determine the mean 
Cryptosporidium level during the period of operation for a part-year 
plant.
    Nevertheless, even when a plant operates for only a few months per 
year and source water exhibits little variability, a minimum number of 
samples is necessary for bin classification. This is due to the 
relatively low sample volume, variable method recovery, nonhomogeneous 
distribution of Cryptosporidium in water, and other factors that limit 
the accuracy of any individual sample for characterizing the source 
water. Data suggest that for plants operating for six months per year 
or less, collecting a minimum of six samples per year over two years 
may allow bin classification with comparable accuracy to that achieved 
by year-round plants sampling monthly (USEPA 2005a).
    Based on these considerations, today's rule requires similar source 
water monitoring for plants that operate only part-year during their 
months of operation as is required for year-round plants. However, if 
the plant is required to monitor for Cryptosporidium and operates for 
six months or less, the PWS must collect at least six Cryptosporidium 
samples per year over two years.
    e. Failing to monitor. Requirements for PWSs that fail to conduct 
source water monitoring are based on the need for PWSs to determine a 
Cryptosporidium bin classification and provide the appropriate level of 
public health protection within the compliance time frame. The LT2ESWTR 
proposal required PWSs that did not complete all source water 
monitoring requirements to meet the requirements of the highest 
treatment bin (USEPA 2003a). In today's final rule, EPA has 
significantly changed requirements from those in the proposal for PWSs 
that fail to monitor. These changes are intended to give States more 
flexibility in working with PWSs to fulfill monitoring requirements and 
ensure they achieve the appropriate Cryptosporidium treatment level.
    For most monitoring and testing procedure violations under the 
LT2ESWTR, PWSs must provide a Tier 3 public notification, which is 
standard for this type of violation under an NPDWR. However, if a PWS 
fails to collect three or more Cryptosporidium samples, the violation 
is elevated to a Tier 2 special public notice. The reason for elevating 
the public notice at this point is the persistence of the violation and 
the difficulty the PWS will have in collecting the required number of 
samples for bin classification by the compliance date. Section IV.H 
provides further details on public notice requirements of the LT2ESWTR.
    As described in section IV.G, today's rule requires bin 
classification within six months following the end of the monitoring 
period specified for the PWS. This six-month period provides some 
opportunity for collecting and analyzing missed samples. The number of 
samples that can be made up in this period is limited, though, due to 
the need for samples to be evenly distributed throughout the year, as 
well as for PWSs and States to spend time during this period evaluating 
monitoring results to determine bin classification. In consideration of 
these factors, EPA believes that elevating the public notice when a PWS 
has missed three or more Cryptosporidium samples is appropriate. This 
violation will end when the State determines that the PWS has begun 
sampling on a schedule to collect the required number of samples.
    Failure by a PWS to collect the required number of Cryptosporidium 
samples for bin classification by the compliance date is a treatment 
technique violation with a required Tier 2 public notice. This 
violation reflects the inability of the PWS to determine and comply 
with its Cryptosporidium treatment requirements under the LT2ESWTR and 
provide the appropriate level of public health protection. The 
violation ends when the State determines that the PWS is carrying out a 
monitoring plan that will lead to bin classification. A PWS that has 
already provided a Tier 2 public notice for missing three sampling 
dates and is successfully meeting a State-approved sampling schedule is 
not required to issue another public notice for missing the bin 
classification date. Alternatively, the PWS can choose to provide the 
highest level of Cryptosporidium treatment required under the rule, 
which is 5.5-log for filtered PWSs and 3-log for unfiltered PWSs.
    f. Grandfathering previously collected data. Requirements for 
grandfathering previously collected monitoring data in today's final 
rule are similar to those in the proposal (USEPA 2003a). These 
requirements are based on the principle that to be eligible for 
grandfathering, previously collected data must be equivalent in quality 
to data that will be collected under the rule.
    The Stage 2 M-DBP Advisory Committee recommended that EPA accept 
previously collected Cryptosporidium data that are ``equivalent in 
sample number, frequency, and data quality (e.g. volume analyzed, 
percent recovery) to data that would be collected under the LT2ESWTR * 
* * to determine bin classification in lieu of further monitoring'' 
(USEPA 2000a). The Advisory Committee recognized that accepting 
previously collected data could have a number of benefits, including 
early determination of LT2ESWTR compliance needs, increasing laboratory 
capacity, and allowing PWSs to determine their bin classification using 
a larger, and potentially more representative, data set.
    To ensure equivalent data quality, today's rule requires that 
grandfathered data meet the same requirements for analytical methods, 
sampling location, and sample volume as data collected under the rule. 
PWSs must not selectively report monitoring results for grandfathering. 
Further, grandfathered Cryptosporidium data must generally be collected 
at least monthly and on a regular schedule, with the same provisions 
for delayed or replacement samples as allowed for regular monitoring. 
Today's final rule differs from the proposal, however, in making 
allowances for use of previously collected data where irregularities or 
gaps in the sampling frequency occur.
    EPA recognizes that when PWSs collected Cryptosporidium data prior 
to the proposed or final LT2ESWTR, there may have been months when a 
PWS either failed to collect or lost a sample due to problems with 
equipment, transportation, laboratory analysis, or other reasons. If 
the PWS did not collect a replacement sample, gaps in the previously 
collected data set occurred. EPA believes that grandfathering of such a 
data set may be appropriate despite these gaps if the PWS conducts 
additional monitoring, as necessary, to ``fill-in'' gaps and ensure 
that the data set is unbiased. Consequently, today's rule allows 
grandfathering of data with

[[Page 671]]

gaps in the sampling frequency if approved by the State.
    In addition, if the frequency of sampling in a previously collected 
data set varies, EPA believes the data could still be appropriate for 
use in bin classification. For example, a PWS might have sampled for 
Cryptosporidium once per month for a number of months and then 
increased the sampling frequency to twice per month. Today's rule 
allows the use of such a data set. However, to avoid bias, the PWS must 
calculate a monthly average for each month of sampling and then 
determine the bin classification using these monthly averages, rather 
than the individual sample concentrations.
    Today's rule requires PWSs that plan to grandfather monitoring data 
to notify EPA or the State regarding the number and time span of sample 
results no later than three months prior to when the PWS must begin 
monitoring. The timing for submission of this notice is concurrent with 
the submission of a sampling schedule. This notification is necessary 
for the State to determine that a PWS is not required to submit a 
sampling schedule (when a PWS will fully comply with initial monitoring 
through grandfathering) or that a sampling schedule may include less 
than the full number of required samples (when a PWS will conduct new 
monitoring in conjunction with grandfathering to complete a data set). 
Further, this notice will assist EPA and States in determining the 
resources necessary to ensure timely review of grandfathered data.
    PWSs must submit all monitoring results for grandfathering to EPA 
or the State, along with required supporting documentation, no later 
than two months after the PWS is required to begin monitoring. This 
timing will allow a PWS to continue collecting data for grandfathering 
until the month the PWS is required to begin monitoring under today's 
rule, plus an additional two months for sample analysis and compilation 
of the data for submission.
    This reporting deadline for grandfathering monitoring results is a 
change from the proposed rule. In the proposal, a PWS that intended to 
grandfather data in lieu of conducting new monitoring under the rule 
had to submit its grandfathered results no later than four months prior 
to when the PWS was otherwise required to begin monitoring under the 
rule. This proposed approach had the shortcoming that a PWS could not 
complete its monitoring for grandfathering within this four month 
period. In today's final rule, a PWS may continue monitoring for 
grandfathering all the way until the date when the PWS must begin 
monitoring under the rule, if necessary. PWSs that conclude their 
monitoring for grandfathering earlier may submit the data at an earlier 
date.
    g. Ongoing watershed assessment. Treatment requirements under the 
LT2ESWTR are based on source water quality. Consequently, today's rule 
requires watershed assessment and, as described in the next section, a 
second round of monitoring following initial bin classification to 
determine if source water quality has changed to the degree that the 
treatment level should be modified. These requirements are unchanged 
from those in the proposed LT2ESWTR (USEPA 2003a), with the exception 
of an allowance for States to use programs other than the sanitary 
survey to assess changes in the watershed.
    Today's rule leverages the existing requirement for States to 
perform sanitary surveys on surface water PWSs. During the source water 
review in the sanitary survey, today's rule requires States to 
determine if significant changes have occurred in the watershed that 
could lead to increased contamination by Cryptosporidium. The State can 
also choose to make this determination through an equivalent review of 
the source water under a program other than the sanitary survey, such 
as a Source Water Protection Assessment. If the State determines that 
significant changes have occurred, the State may specify that the PWS 
conduct additional source water monitoring or treat the potential 
contamination. This approach allows the PWS and State to respond to a 
significant change in source water quality prior to initiating a second 
round of monitoring or any time thereafter.
    h. Second round of monitoring. A more rigorous reassessment of the 
source water occurs through a second round of monitoring that begins 
six years after initial bin classification. If EPA does not develop and 
finalize modifications to the LT2ESWTR prior to the date when PWSs must 
begin the second round of monitoring, then this second round must 
conform to the same requirements that applied to the initial round of 
monitoring. PWSs may be classified in a different treatment bin, 
depending on the results of the second round of monitoring.
    The Stage 2 M-DBP Advisory Committee recommended that EPA initiate 
a stakeholder process several years prior to the second round of 
monitoring to review new information and determine if today's rule 
should be modified. If the Agency modifies the LT2ESWTR, the second 
round of monitoring would potentially involve a new analytical method 
and a different treatment bin structure.
3. Summary of Major Comments
    Public comment on the August 11, 2003, LT2ESWTR proposal generally 
supported the use of source water monitoring to determine additional 
treatment requirements. The following discussion summarizes major 
comments and EPA's responses in regard to sampling parameters and 
frequency, sampling location, sampling schedule, monitoring plants that 
operate only part-year, failing to monitor, providing treatment instead 
of monitoring, grandfathering previously collected data, ongoing source 
water assessment, second round of monitoring, and new source 
monitoring.
    a. Sampling parameters and frequency. Most commenters supported the 
proposed requirements for large PWSs to sample monthly for 
Cryptosporidium, as well as for E. coli and turbidity in filtered PWSs, 
for 24 months. Alternatives recommended by some commenters included 
ending monitoring after one year if no oocysts are detected, allowing 
large PWSs to use an E. coli screening analysis to determine if 
Cryptosporidium monitoring is necessary, and using watershed data to 
determine treatment needs instead of source water monitoring.
    In response, EPA continues to believe that large PWSs should 
complete 24 months of Cryptosporidium monitoring, regardless of the 
first-year results, in order to capture a degree of annual variability 
in Cryptosporidium occurrence. Moreover, for the reasons discussed 
previously in this preamble, EPA continues to support the Advisory 
Committee recommendation that all large PWSs should monitor for 
Cryptosporidium, rather than use the E. coli screening analysis. EPA is 
not aware of studies that support the use of other watershed data in 
place of Cryptosporidium monitoring to determine treatment needs.
    Regarding requirements for small PWSs, most commenters supported 
the E. coli screening analysis for small filtered PWSs. Several 
commenters recommended more options for Cryptosporidium monitoring by 
small PWSs, such as allowing monitoring to be spread over two years, 
instead of the one year required in the proposal, or allowing fewer 
samples. EPA agrees that budgeting for Cryptosporidium monitoring by 
some small PWSs will be easier if it is spread over two years, and 
today's rule allows this as an option.

[[Page 672]]

However, based on the analysis of false negative and false positive 
rates described previously, EPA continues to believe that at least 24 
Cryptosporidium samples are necessary to determine the appropriate bin 
classification for year-round plants.
    b. Sampling location. With respect to sampling location 
requirements, several commenters recommended that PWSs be allowed to 
collect samples either before or after pretreatment processes. These 
commenters stated that the chemicals used in pretreatment processes are 
unlikely to affect the analysis of Cryptosporidium oocysts at typical 
concentrations. Further, where sampling is conducted prior to a 
pretreatment process like presedimentation, commenters supported 
allowing PWSs to receive additional treatment credit for the process.
    In response, EPA continues to believe that common pretreatment 
chemicals like oxidants and coagulants have the potential to adversely 
affect the performance of Cryptosporidium analytical methods. 
Consequently, today's rule requires that in most cases, PWSs must 
sample upstream of chemical addition. Where PWSs sample prior to 
pretreatment processes like presedimentation with coagulation, they are 
eligible to receive additional treatment credit for the process. 
However, if sampling prior to chemical addition is not feasible for a 
particular plant and the treatment chemical is present at a very low 
level that is unlikely to interfere with sample analysis, the State may 
approve sampling after chemical addition.
    Many commenters recommended that States approve sampling locations 
for their PWSs. Commenters indicated that State review and approval of 
monitoring plans will help to prevent confusion and PWSs potentially 
sampling at an incorrect location. EPA agrees with these commenters and 
has established a requirement in today's rule for PWSs to report a 
description of the sampling location to the State. If a PWS does not 
hear back from the State by the time it is scheduled to begin sampling, 
it may assume that its monitoring location is acceptable.
    c. Sampling schedule. In regard to sampling schedule requirements, 
several commenters requested that PWSs be given a time window larger 
than 5 days around scheduled sampling dates to collect samples. 
Recommended alternatives included a 7 or 9-day window, or only 
requiring that PWSs collect a sample within a specified month. In 
addition, commenters identified situations that interfere with sample 
collection, such as plant interruptions and laboratory or 
transportation problems, and noted that some of these are outside the 
conditions under which the proposal allowed a PWS to collect a delayed 
or replacement sample without penalty.
    In response, EPA continues to believe that for routine sample 
collection, a 5-day window provides sufficient flexibility, given that 
PWSs will pick the sampling days and can schedule around holidays, 
weekends, and other times when sampling would be problematic. However, 
today's rule allows PWSs to sample outside of this window without 
penalty if necessary due to unforeseen conditions. Further, if a PWS 
collects a sample but is unable to have it analyzed due to problems 
with equipment, transportation or the laboratory, today's rule allows 
the PWS to collect a replacement sample without penalty.
    In regard to the time frame for collecting missed or replacement 
samples, commenters recommended a number of approaches. These include 
adding extra sampling days to the original sampling schedule, which a 
PWS could then use in the event of missed sampling dates, and allowing 
PWSs to collect make-up samples either immediately after the scheduled 
sampling date or at the end of the monitoring period.
    In general, EPA considers it preferable for PWSs to collect missed 
or replacement samples as close as is feasible to scheduled sampling 
dates. However, if there is a significant delay with respect to the 
original sampling date, collecting make-up samples at an alternate time 
may be appropriate to ensure that sampling results are seasonally 
representative. Therefore, today's rule requires PWSs to collect a 
missed sample as close as is feasible to the scheduled sampling date, 
and to collect replacement samples within 21 days of receiving 
information that one is needed, unless doing so within this time frame 
is not feasible. However, the State can authorize alternative sampling 
dates so that monitoring is not seasonally biased. This could include 
sampling during the same time in the following year, if the missed 
sample occurred during the first year of monitoring, or sampling after 
the end of the scheduled monitoring period.
    d. Plants operating only part of the year. Commenters on monitoring 
requirements for surface water plants that operate for only part of the 
year generally recommended that sampling occur only during the period 
of operation. However, several different options were put forward for 
how the sampling be conducted. Some commenters recommended a minimum of 
12 samples per year for two years distributed evenly over the period 
that the plant operates. Others suggested allowing the PWS to collect 
the required number of samples over a longer time period in order to 
limit the frequency of required samples when the plant is operating. 
Several commenters said that State input is critical to determining the 
appropriate monitoring period since States may have historical 
knowledge of plant operating practices.
    In response, EPA agrees that monitoring of plants that operate only 
part-year under today's rule should be conducted only during months 
when the plant is operating, unless the State determines that a longer 
monitoring period is appropriate due to historical operating practices. 
Further, plants that operate only part-year should maintain the same 
sampling frequency as plants operating year-round, with the exception 
that plants monitoring for Cryptosporidium must collect at least six 
samples per year to allow for appropriate bin classification. EPA does 
not believe extending monitoring over more years in plants that operate 
only part-year is appropriate, as this would delay the installation of 
additional treatment where needed.
    e. Failing to monitor. Most commenters opposed automatically 
classifying PWSs in the highest treatment bin (Bin 4) if they fail to 
complete required monitoring, as the proposed rule stipulated. 
Commenters suggested alternative approaches, such as giving States the 
flexibility to address missed samples using current enforcement 
mechanisms, classifying a PWS only one level higher than the bin 
determined by the collected data, allowing an additional year of 
sampling, and allowing States to use other information (e.g., sanitary 
surveys, other monitoring data) to aid in the classification. A few 
commenters, however, supported Bin 4 classification for PWSs that fail 
to monitor, on the basis that any other approach would create an 
incentive for PWSs to stop testing if poor water quality is suspected.
    EPA agrees that States should have flexibility in dealing with PWSs 
that fail to monitor. Further, providing the highest level of treatment 
may not be in the best interests of consumers where a PWS has minor 
problems in carrying out source water monitoring. However, EPA also 
believes that violations for monitoring failures must reasonably ensure 
that PWSs complete monitoring as required to determine a bin 
classification within the compliance

[[Page 673]]

date. Failure to do so would potentially compromise public health 
protection.
    Based on these considerations, EPA has not established an automatic 
Bin 4 classification for monitoring failures under today's rule. 
Rather, if a PWS misses three or more Cryptosporidium samples, this 
persistent violation requires a Tier 2 public notice (other violations 
require a Tier 3 notice). Further, if a PWS is unable to determine a 
bin classification by the compliance date due to failure to collect the 
required number of Cryptosporidium samples, this is a treatment 
technique violation with a required Tier 2 public notice (unless the 
PWS has already issued a Tier 2 notice for missing 3 Cryptosporidium 
samples and is monitoring on a State-approved schedule). These 
violations last until the State determines that a PWS has begun 
monitoring on a schedule that will lead to bin classification or the 
PWS agrees to install treatment instead of monitoring.
    f. Providing treatment instead of monitoring. Commenters supported 
the option for a PWS to provide the highest level of Cryptosporidium 
treatment required under today's rule rather than conducting source 
water monitoring. Several commenters recommended that a PWS should be 
allowed to take this option after having initiated monitoring. EPA 
agrees, and today's rule allows a PWS to stop monitoring at any time by 
notifying the State that it will provide 5.5-log Cryptosporidium 
treatment for filtered PWSs or 3-log Cryptosporidium inactivation for 
unfiltered PWSs by the compliance deadline specified in section IV.G.
    g. Grandfathering previously collected data. With respect to 
grandfathering previously collected data, many commenters expressed 
concern with a proposed requirement that samples must have been 
collected in equal time intervals. Commenters stated that although PWSs 
may have sampled on a regular schedule, previously collected data sets 
are likely to have gaps due to samples rejected for method QC 
violations or periods when the PWS was unable to collect a sample. In 
addition, there are instances where PWSs have changed the frequency of 
sampling, such as from monthly to twice per month.
    EPA agrees that if a PWS has collected samples according to a 
regular schedule and met other data quality standards, then rejecting a 
large data set due to isolated gaps in the sampling frequency would be 
inappropriate. Consequently, today's rule allows States to approve 
grandfathering of previously collected data with omissions in the 
sampling interval, provided the PWS conducts additional monitoring if 
required by the State to ensure the data set is seasonally 
representative. Further, PWSs may grandfather previously collected data 
sets in which the sampling frequency varies, as long as samples were 
collected at least monthly. In this situation, PWSs must use monthly 
average concentrations, rather than individual sample concentrations, 
for bin classification.
    With respect to data quality standards, such as meeting analytical 
method QC criteria, sampling at the correct location, and analyzing the 
minimum sample volume, several commenters stated that EPA should apply 
the same acceptance standards to previously collected data as are 
applied to data collected under today's rule. Other commenters, though, 
suggested that States should have the flexibility to accept previously 
collected data that deviate from the data quality standards for 
monitoring under the rule. These commenters stated that such data sets 
might include samples collected over a longer period of time and may 
reflect more worst-case weather events.
    In response, EPA believes that data quality standards should be 
uniformly applied under today's rule, so that previously collected data 
should not be held to a lower standard than new data or evaluated 
differently from State to State. The requirements in today's rule with 
respect to Cryptosporidium analytical methods and minimum sample volume 
reflect recommendations of the Advisory Committee, which also 
recommended that the same data quality standards be applied for 
grandfathering. Further, because today's rule allows PWSs to collect 
make-up samples to address gaps in previously collected data sets, PWSs 
will have the opportunity to collect make-up samples for results that 
are rejected due to data quality standards without losing an entire 
data set.
    In regard to notification of the acceptability of data for 
grandfathering, commenters recommended that if previously collected 
data submitted by a PWS are rejected, the PWS should have at least two 
months between notification and the date new monitoring must be 
initiated. These two months will give the PWS time to address rejection 
of the data and prepare for sampling. EPA agrees with this 
recommendation. Under today's rule, if a PWS properly submits a 
complete data set for grandfathering and the PWS must conduct new 
monitoring due to rejection of the data, the PWS has at least two 
months following notification by the State to initiate sampling.
    h. Ongoing watershed assessment. Commenters asked for greater 
flexibility in the requirement for States to determine whether there 
have been significant changes in the watersheds of their PWSs that 
could lead to increased contamination. The proposed rule specified that 
States must make this determination during sanitary surveys. However, 
several commenters noted that some States perform source water 
protection assessments on the same frequency as sanitary surveys, and 
these detailed assessments might be a better mechanism to monitor 
changes in the watershed. EPA agrees and today's rule allows States to 
determine whether significant changes have occurred in the watershed 
through either a sanitary survey or an equivalent review of the source 
water under another program.
    i. Second round of monitoring. Some commenters supported the 
proposed requirement for a second round of source water monitoring, but 
most opposed requiring it for all PWSs. These commenters recommended 
that States should be authorized to use sanitary surveys, source water 
assessments, ambient water quality data, treatment plant data, and 
other information to determine if a second round of monitoring is 
necessary for a PWS. Some commenters suggested that EPA fund research 
to allow the use of finished water monitoring as the determinant for 
treatment requirements in a second round of monitoring.
    In response, EPA continues to believe that PWSs should conduct a 
second round of monitoring to determine if the level of treatment 
required as a result of the first round of monitoring is still 
appropriate. Consequently, today's rule requires this. However, EPA 
agrees that prior to a second round of monitoring, the Agency should 
evaluate the results of the first round of monitoring, along with 
whatever new information is available on Cryptosporidium analytical 
methods, risk, and other relevant issues. If EPA determines that there 
should be changes to the requirements for a second round of monitoring 
in today's rule, the Agency will issue a new rule establishing those 
changes.
    j. New source monitoring. EPA requested comment in the proposal on 
monitoring requirements for new plants and sources (USEPA 2003a). Most 
commenters recommended that new plants and sources undergo monitoring 
equivalent to that required for existing plants and sources, and 
suggested that States should have discretion to determine when 
monitoring should take place. EPA agrees with these recommendations and 
today's rule requires PWS to conduct source water

[[Page 674]]

monitoring for new plants and sources on a schedule approved by the 
State. This schedule must include dates for the PWS to determine its 
treatment bin classification and, if necessary, comply with additional 
Cryptosporidium treatment requirements.

B. Filtered System Cryptosporidium Treatment Requirements

1. Today's Rule
    Today's rule requires filtered PWSs using surface water or GWUDI 
sources to provide greater levels of treatment if their source waters 
have higher concentrations of Cryptosporidium. Specifically, filtered 
PWSs are classified in one of four treatment bins based on results from 
the source water monitoring described in the previous section. PWSs 
classified in the lowest concentration bin are subject to no additional 
treatment requirements, while PWSs assigned to higher concentration 
bins must reduce Cryptosporidium levels beyond IESWTR and LT1ESWTR 
requirements. All PWSs must continue to comply with the requirements of 
the SWTR, IESWTR, and LT1ESWTR, as applicable.
    This section addresses procedures for classifying filtered PWSs in 
Cryptosporidium treatment bins and the treatment requirements 
associated with each bin. Section IV.D presents the treatment and 
control options, collectively termed the ``microbial toolbox,'' that 
PWSs must use to meet additional Cryptosporidium treatment requirements 
under today's rule.
    a. Bin classification. After completing initial source water 
monitoring, filtered PWSs must calculate a Cryptosporidium bin 
concentration for each treatment plant where Cryptosporidium monitoring 
is required. This Cryptosporidium bin concentration is used to classify 
filtration plants in one of the four treatment bins shown in Table 
IV.B-1.

        Table IV.B-1.--Bin Classification Table for Filtered PWSs
------------------------------------------------------------------------
                                with a Cryptosporidium       The bin
      For PWSs that are:        bin concentration of .   classification
                                          . .               is . . .
------------------------------------------------------------------------
* * * required to monitor for   less than 0.075         Bin 1.
 Cryptosporidium.                oocysts/L.
                                0.075 oocysts/L or      Bin 2.
                                 higher, but less than
                                 1.0 oocysts/L.
                                1.0 oocysts/L or        Bin 3.
                                 higher, but less than
                                 3.0 oocysts/L.
                                3.0 oocysts/L or        Bin 4.
                                 higher.
* * * serving fewer than        NA....................  Bin 1.
 10,000 people and NOT
 required to monitor for
 Cryptosporidium \1\.
------------------------------------------------------------------------
\1\ Filtered PWSs serving fewer than 10,000 people are not required to
  monitor for Cryptosporidium if they monitor for E. coli and
  demonstrate a mean concentration of E. coli less than or equal to 10/
  100 mL for lake/reservoir sources or 50/100 mL for flowing stream
  sources or do not exceed an alternative State-approved indicator
  trigger (see section IV.A.1).

    In general, the Cryptosporidium bin concentration is calculated by 
averaging individual sample results from one or more years of 
monitoring. Specific procedures vary, however, depending on the 
frequency and duration of monitoring. These procedures are as follows:
    (1) For PWSs that collect a total of at least 24 but not more than 
47 Cryptosporidium samples over two or more years, the Cryptosporidium 
bin concentration is equal to the highest arithmetic mean of all sample 
concentrations in any 12 consecutive months of Cryptosporidium 
monitoring.
    (2) For PWSs that collect a total of at least 48 samples, the 
Cryptosporidium bin concentration is equal to the arithmetic mean of 
all sample concentrations.
    (3) For PWSs that serve fewer than 10,000 people and monitor for 
Cryptosporidium for only one year (i.e., collect 24 samples in 12 
months), the Cryptosporidium bin concentration is equal to the 
arithmetic mean of all sample concentrations.
    (4) For PWSs with plants that operate only part-year that monitor 
for less than 12 months per year, the Cryptosporidium bin concentration 
is equal to the highest arithmetic mean of all sample concentrations 
during any year of Cryptosporidium monitoring.
    In data sets with variable sampling frequency, PWSs must first 
calculate an arithmetic mean for each month of sampling and then apply 
one of these four procedures using the monthly mean concentrations. As 
described in section IV.A, PWSs may grandfather previously collected 
Cryptosporidium data where the sampling frequency varies (e.g., one 
year of monthly sampling and one year of twice-per-month sampling).
    Filtered PWSs serving fewer than 10,000 people are not required to 
monitor for Cryptosporidium if they demonstrate a mean E. coli 
concentration less than or equal to 10/100 mL for lake/reservoir 
sources or 50/100 mL for flowing stream sources or do not exceed an 
alternative State-approved indicator trigger. PWSs that meet this 
criterion are classified in Bin 1 as shown in Table IV.B-1.
    When determining the Cryptosporidium bin concentration, PWSs must 
calculate individual sample concentrations as the total number of 
oocysts counted, divided by the volume assayed (see section V.K for 
details). In samples where no oocysts are detected, the result is 
assigned a value of zero for the purpose of calculating the bin 
concentration. Sample analysis results are not adjusted for analytical 
method recovery or the percent of Cryptosporidium oocysts that are 
infectious.
    PWSs must report their treatment bin classification to the State 
for approval following initial source water monitoring (see section 
IV.G for specific compliance dates). The report must include a summary 
of the data and calculation procedure used to determine the bin 
concentration. If EPA does not amend today's rule before the second 
round of monitoring described in section IV.A, PWSs must recalculate 
their bin classification after completing the second round of 
monitoring and report the results to the State for approval. If the 
State does not respond to a PWS regarding its bin classification after 
either report, the PWS must comply with the Cryptosporidium treatment 
requirements of today's rule based on the reported bin classification.
    b. Bin treatment requirements. Table IV.B-2 shows the additional 
Cryptosporidium treatment requirements associated with the four 
treatment bins for filtered PWSs under today's rule. All filtered PWSs 
must comply with these treatment requirements based on their bin 
classification, which must be determined using the procedures just 
described.

[[Page 675]]



                     Table IV.B-2.--Treatment Requirements for LT2ESWTR Bin Classifications
----------------------------------------------------------------------------------------------------------------
                                         And you use the following filtration treatment in full compliance with
                                          the SWTR, IESWTR, and LT1ESWTR (as applicable), then your additional
                                                            treatment requirements are . . .
                                      --------------------------------------------------------------------------
 If your bin classification  is . . .  Conventional filtration
                                            treatment \1\,
                                          diatomaceous earth       Direct filtration      Alternative filtration
                                         filtration, or slow                                   technologies
                                           sand filtration
----------------------------------------------------------------------------------------------------------------
Bin 1................................  No additional treatment  No additional treatment  No additional
                                                                                          treatment.
Bin 2................................  1-log treatment \2\....  1.5-log treatment \2\..  As determined by the
                                                                                          State 2 4
Bin 3................................  2-log treatment \3\....  2.5-log treatment \3\..  As determined by the
                                                                                          State 3 5
Bin 4................................  2.5-log treatment \3\..  3-log treatment \3\....  As determined by the
                                                                                          State 3 6
----------------------------------------------------------------------------------------------------------------
\1\ Applies to a treatment train using separate, sequential, unit processes for coagulation/flocculation,
  clarification, and granular media filtration. Clarification includes any solid/liquid separation process
  following coagulation where accumulated solids are removed during this separate component of the treatment
  system.
\2\ PWSs may use any technology or combination of technologies from the microbial toolbox in section IV.D.
\3\ PWSs must achieve at least 1-log of the required treatment using ozone, chlorine dioxide, UV, membranes, bag
  filtration, cartridge filtration, or bank filtration.
\4\ Total Cryptosporidium removal and inactivation must be at least 4.0 log.
\5\ Total Cryptosporidium removal and inactivation must be at least 5.0 log.
\6\ Total Cryptosporidium removal and inactivation must be at least 5.5 log.

    The total Cryptosporidium treatment required for plants in Bins 2, 
3, and 4 is 4.0-log, 5.0-log, and 5.5-log, respectively. Conventional 
treatment (including softening), slow sand, and diatomaceous earth 
filtration plants in compliance with the IESWTR or LT1ESWTR, as 
applicable, receive a prescribed 3.0-log Cryptosporidium treatment 
credit toward these total bin treatment requirements. Accordingly, 
these plant types must provide 1.0- to 2.5-log of additional treatment 
when classified in Bins 2-4, respectively. Direct filtration plants in 
compliance with existing regulations receive a prescribed 2.5-log 
treatment credit and, consequently, must achieve 0.5-log greater 
treatment to comply with Bins 2-4. Section IV.D describes how States 
may award a level of treatment credit that differs from the prescribed 
credit based on a demonstration of performance by the PWS.
    For PWSs using alternative filtration technologies, such as 
membranes, bag filters, or cartridge filters, no prescribed treatment 
credit is available because the performance of these processes is 
specific to individual products. Consequently, when PWSs using these 
processes are classified in Bins 2-4, the State must determine 
additional treatment requirements based on the credit the State awards 
to a particular technology. The additional treatment requirements must 
ensure that plants classified in Bins 2-4 achieve total Cryptosporidium 
reductions of 4.0- to 5.5-log, respectively. Section IV.D describes 
challenge testing procedures to determine treatment credit for 
membranes, bag filters, and cartridge filters.
    PWSs can achieve additional Cryptosporidium treatment credit 
through implementing pretreatment processes like presedimentation or 
bank filtration, by developing a watershed control program, and by 
applying additional treatment steps like ozone, chlorine dioxide, UV, 
and membranes. In addition, PWSs can receive a higher level of credit 
for existing treatment processes through achieving very low filter 
effluent turbidity or through a demonstration of performance. Section 
IV.D presents criteria for awarding Cryptosporidium treatment credit to 
these and other treatment and control options, which collectively 
comprise the microbial toolbox.
    PWSs in Bin 2 can meet additional Cryptosporidium treatment 
requirements by using any option or combination of options from the 
microbial toolbox. For Bins 3 and 4, PWSs must achieve at least 1-log 
of the additional treatment requirement by using ozone, chlorine 
dioxide, UV, membranes, bag filtration, cartridge filtration, or bank 
filtration.
2. Background and Analysis
    Today's rule will increase protection against Cryptosporidium and 
other pathogens in PWSs with the highest source water contamination 
levels. This targeted approach builds upon existing regulations under 
which all filtered PWSs must provide the same level of treatment 
regardless of source water quality. EPA's intent with today's rule is 
to ensure that PWSs with higher risk source waters achieve public 
health protection commensurate with PWSs with less contaminated 
sources.
    The Cryptosporidium treatment requirements for filtered PWSs in 
today's rule are unchanged from the August 11, 2003 proposal (USEPA 
2003a) and reflect consensus recommendations by the Stage 2 M-DBP 
Advisory Committee (USEPA 2000a). The following discussion summarizes 
the Agency's basis for establishing risk-targeted Cryptosporidium 
treatment requirements and for setting the specific bin concentration 
ranges and treatment requirements that apply to filtered PWSs in 
today's rule.
    a. Basis for targeted treatment requirements. In developing today's 
rule, EPA evaluated the degree to which new information on 
Cryptosporidium warranted moving beyond existing regulations. As 
discussed in section III, the IESWTR established a Cryptosporidium MCLG 
of zero and requires large filtered PWSs to achieve 2-log 
Cryptosporidium removal. The LT1ESWTR extended this requirement to 
small PWSs. After these rules were promulgated, advances were made in 
analytical methods and treatment for Cryptosporidium, and EPA collected 
new information on Cryptosporidium occurrence and infectivity. 
Consequently, EPA assessed the implications of these developments for 
further controlling Cryptosporidium to approach the zero MCLG.
    The risk-targeted approach for filtered PWSs in today's final rule 
stems from four general findings based on new information on 
Cryptosporidium:
    (1) New data on Cryptosporidium infectivity suggest that the risk 
associated with a particular level of Cryptosporidium is most likely 
higher than EPA estimated at the time of earlier rules;
    (2) New data on Cryptosporidium occurrence indicate that levels are 
relatively low in most water sources, but a subset of sources has 
substantially higher concentrations;
    (3) The finding that UV light can readily inactivate 
Cryptosporidium, as well as other technology developments, makes 
achieving high levels of

[[Page 676]]

treatment for Cryptosporidium feasible for PWSs of all sizes; and
    (4) EPA Methods 1622 and 1623 are capable of assessing annual mean 
levels of Cryptosporidium in drinking water sources.
    These findings led EPA to conclude that most filtered PWSs 
currently provide sufficient treatment for Cryptosporidium, but 
additional treatment is needed in those PWSs with the highest source 
water Cryptosporidium levels to protect public health. Further, PWSs 
can characterize Cryptosporidium levels in their source waters with 
available analytical methods and can provide higher levels of treatment 
with available technologies. Consequently, risk-targeted treatment 
requirements for Cryptosporidium based on source water contamination 
levels are appropriate and feasible to implement.
    b. Basis for bin concentration ranges and treatment requirements. 
To establish the risk-targeted treatment requirements in today's rule, 
EPA had to determine the degree of treatment that should be required 
for different source water Cryptosporidium levels to protect public 
health. This determination involved addressing several questions:
     What is the risk associated with Cryptosporidium in a 
drinking water source?
     How much Cryptosporidium removal do filtration plants 
achieve?
     What is the appropriate statistical measure for 
classifying PWSs into treatment bins?
     What degree of additional treatment is needed for higher 
source water Cryptosporidium levels?
     How should PWSs calculate their treatment bin 
classification?
    This section summarizes how EPA evaluated these questions in 
developing today's rule. See the proposed LT2ESWTR for further details 
(USEPA 2003a).

What is the Risk Associated With Cryptosporidium in a Drinking Water 
Source?

    The risk of infection from Cryptosporidium in drinking water is a 
function of exposure (i.e., the dose of oocysts ingested) and 
infectivity (i.e., likelihood of infection as a function of ingested 
dose). Primary (i.e., direct) exposure to Cryptosporidium depends on 
the concentration of oocysts in the source water, the fraction removed 
by the treatment plant, and the volume of water consumed (secondary 
exposure occurs through interactions with infected individuals). Thus, 
the daily risk of infection (DR) is as follows:

DR = (oocysts/L in source water) x (fraction remaining after treatment) 
x (liters consumed per day) x (likelihood of infection per oocyst 
dose).

    Assuming 350 days of consumption per year for people served by 
community water systems (CWSs), the annual risk (AR) of infection is as 
follows:

AR = 1 - (1 - DR) \350\.

    As discussed in section III.E, EPA has estimated the mean 
likelihood of infection from ingesting one Cryptosporidium oocyst to 
range from 4 to 16 percent. Median individual daily water consumption 
is estimated as 1.07 L/day. Figure IV.B-1 illustrates ranges for the 
annual risk of infection by Cryptosporidium in CWSs based on these 
values for different source water infectious oocyst concentrations and 
treatment plant removal efficiencies. The dashed lines represent the 
uncertainty associated with Cryptosporidium infectivity for each log-
removal curve. See Chapter 5 of the LT2ESWTR Economic Analysis for 
details (USEPA 2005a).
BILLING CODE 6560-50-P

[[Page 677]]

[GRAPHIC] [TIFF OMITTED] TR05JA06.000

BILLING CODE 6560-50-C
    The results in Figure IV.B-1 show, for example, that if a treatment 
plant had a concentration of infectious Cryptosporidium in the source 
water of 0.1 oocysts/L and the plant achieved 3-log removal, the mean 
annual risk of

[[Page 678]]

Cryptosporidium infection would range from 0.0017 to 0.0060 (17 to 60 
infections per 10,000 consumers). In comparison, if the same plant had 
a source water infectious Cryptosporidium level of 0.01 oocysts/L, the 
annual infection risk would range from 1.7 to 6 per 10,000 consumers.

How much Cryptosporidium removal do filtration plants achieve?

    The amount of Cryptosporidium removal that filtration plants 
achieve was a key factor in assessing the additional treatment that 
plants with higher source water Cryptosporidium levels should provide. 
To evaluate this factor, EPA reviewed studies of Cryptosporidium 
removal by common treatment processes. As described in the proposal for 
today's rule, these processes were conventional treatment, direct, slow 
sand, and diatomaceous earth filtration, as well as membrane, bag, and 
cartridge filtration (USEPA 2003a).
    The majority of plants treating surface water use conventional 
treatment, which is defined in 40 CFR 141.2 as coagulation, 
flocculation, sedimentation, and filtration. In the proposal, EPA 
reviewed studies of conventional treatment by Dugan et al. (2001), 
Nieminski and Bellamy (2000), McTigue et al. (1998), Patania et al. 
(1999), Huck et al. (2000), Emelko et al. (2000), and Harrington et al. 
(2001). Based on these studies, EPA estimated that conventional 
treatment plants in compliance with the IESWTR or LT1ESWTR typically 
achieve a Cryptosporidium removal efficiency of approximately 3-log. 
Consequently, conventional treatment plants receive 3-log credit toward 
Cryptosporidium treatment requirements under today's rule.
    This 3-log credit for conventional treatment is consistent with the 
Stage 2 M-DBP Agreement in Principle (USEPA 2000a), which states as 
follows:

    ``The additional treatment requirements in the bin requirement 
table are based, in part, on the assumption that conventional 
treatment plants in compliance with the IESWTR achieve an average of 
3 logs removal of Cryptosporidium.''

    The M-DBP Advisory Committee did not recommend a level of 
Cryptosporidium treatment credit for other types of filtration plants.
    EPA also reviewed studies of the performance of clarification 
processes like dissolved air flotation, which can be used in place of 
sedimentation in a conventional treatment train (Gregory and Zabel 
1990, Plummer et al. 1995, Edzwald and Kelley 1998). These studies 
indicate that plants using clarification processes other than 
sedimentation that are located after coagulation and prior to 
filtration can achieve performance equivalent to conventional treatment 
plants. As a result, any treatment train that includes coagulation/
flocculation, clarification, and granular media filtration is regarded 
as conventional treatment for purposes of awarding treatment credit 
under today's rule. The clarification step must be a solid/liquid 
separation process where accumulated solids are removed during this 
separate component of the treatment system.
    Direct filtration plants use coagulation, flocculation, and 
filtration processes just as conventional treatment plants do, but they 
lack a sedimentation basin or equivalent clarification process. In the 
proposal, EPA reviewed studies of sedimentation by Dugan et al. (2001), 
States et al. (1997), Edzwald and Kelly (1998), Payment and Franco 
(1993), Kelly et al. (1995), and Patania et al. (1995). Results from 
these studies demonstrate that sedimentation basins can achieve 0.5-log 
or greater Cryptosporidium removal. In addition, some studies have 
observed that direct filtration achieves less Cryptosporidium removal 
than conventional treatment (Patania et al. 1995) and the incidence of 
Cryptosporidium in the treated water is higher (McTigue et al. 1998). 
Given these findings, EPA has awarded direct filtration plants a 2.5-
log credit towards Cryptosporidium treatment requirements under today's 
rule (i.e., 0.5-log less credit than for conventional treatment).
    Slow sand filtration involves passing raw water through a bed of 
sand at low velocity and without prior coagulation. Diatomaceous earth 
filtration is a process by which a filtration medium is initially 
deposited onto a support membrane and medium is added throughout the 
operation to keep the filter from clogging. In the proposal, EPA 
reviewed slow sand filtration studies by Fogel et al. (1993), Hall et 
al. (1994), Schuler and Ghosh (1991), and Timms et al. (1995) and 
diatomaceous earth filtration studies by Schuler and Gosh (1990) and 
Ongerth and Hutton (1997, 2001). For both processes, these studies 
indicate that a well-designed and properly operated filter can achieve 
Cryptosporidium removal efficiencies similar to those observed for 
conventional treatment plants. Slow sand and diatomaceous earth 
filtration plants, therefore, receive a 3-log credit towards 
Cryptosporidium treatment requirements under today's rule.
    Estimating a typical Cryptosporidium removal efficiency for 
filtration technologies like membranes, bag filters, and cartridge 
filters is not possible because the performance of such filters is 
specific to a particular product. As a result, credit for these devices 
must be determined by the State based on product-specific testing using 
the procedures described in section IV.D or other criteria approved by 
the State.
    Table IV.B-3 summarizes the credits various types of filtration 
plants receive toward Cryptosporidium treatment requirements under 
today's rule. This credit determines the degree of additional treatment 
that plants classified in Bins 2-4 must apply, as shown in Table IV.B-
2.

                Table IV.B-3.--Cryptosporidium Treatment Credit Towards LT2ESWTR Requirements \1\
----------------------------------------------------------------------------------------------------------------
                                     Conventional
                                       treatment                             Slow sand or         Alternative
           Plant type                  (includes       Direct filtration  diatomaceous earth      filtration
                                      softening)                              filtration         technologies
----------------------------------------------------------------------------------------------------------------
Treatment credit................  3.0-log...........  2.5-log...........  3.0-log...........  Determined by
                                                                                               State. \2\
----------------------------------------------------------------------------------------------------------------
\1\ Applies to plants in full compliance with the IESWTR or LT1ESWTR as applicable.
\2\ Credit must be determined through product or site-specific assessment.

    As discussed previously, studies indicate that conventional 
treatment plants producing very low filtered water turbidity can 
achieve a higher level of Cryptosporidium removal than 3-log, and 
today's rule allows such plants to receive additional treatment credit. 
Further, States can award a higher or lower level of credit to an 
individual plant based on a site-specific demonstration of performance. 
Section IV.D provides details on both of these topics.
    The Cryptosporidium removal credits for filtration plants in 
today's rule differ from the amount of credit awarded under the IESWTR 
and LT1ESWTR. As

[[Page 679]]

discussed in section III, those rules require all filtered PWSs to 
achieve 2-log removal of Cryptosporidium. PWSs using conventional 
treatment, or direct, slow sand, or diatomaceous earth filtration are 
in compliance with this requirement if they meet specified filtered 
water turbidity standards. These regulatory criteria were based on 
consideration of the minimum level of removal that all these filtration 
processes will achieve (USEPA 1998a). However, in the risk assessments 
that supported these regulations, EPA estimated that most filtration 
plants will achieve significantly more removal, with median 
Cryptosporidium reductions near 3-log.
    Today's rule will supplement IESWTR and LT1ESWTR requirements by 
mandating additional treatment at certain PWSs based on source-water 
Cryptosporidium levels. When assessing the need for additional 
treatment at potentially higher risk PWSs, EPA believes that 
considering the full removal efficiency achieved by different types of 
treatment plants is appropriate. Because making a site-specific 
assessment of removal efficiency at all treatment plants individually 
is not feasible, establishing prescribed treatment credits based on 
available data is necessary. Accordingly, EPA has concluded that 
available data support the higher levels of prescribed credit towards 
Cryptosporidium treatment requirements for filtration plants 
established by today's rule.

What is the appropriate statistical measure for classifying PWSs into 
treatment bins?

    EPA and the Advisory Committee evaluated different statistical 
measures for characterizing Cryptosporidium monitoring results to 
determine if additional treatment should be required. These measures 
included the arithmetic mean, median, 90th percentile, and maximum.
    EPA concluded, consistent with Advisory Committee recommendations, 
that Cryptosporidium levels should be characterized by an arithmetic 
mean. This conclusion is based on two factors: (1) Available data 
suggest that the mean concentration directly relates to the average 
risk of the exposed population (i.e., drinking water consumers); and 
(2) with a limited number of samples, the mean can be estimated more 
accurately than other statistical measures, such as a 90th percentile 
estimate.

What degree of additional treatment is needed for higher source water 
Cryptosporidium levels?

    Development of the risk-based treatment requirements in today's 
rule involved first determining the threshold source-water 
Cryptosporidium level at which filtered PWSs should provide additional 
treatment to protect public health. The key factors in making this 
determination were the estimations of Cryptosporidium risk and 
treatment plant removal efficiency discussed previously, along with the 
performance of analytical methods for classifying PWSs in different 
treatment bins.
    EPA and Advisory Committee deliberations focused on mean source-
water Cryptosporidium concentrations in the range of 0.01 to 0.1 
oocysts/L as threshold levels for requiring additional treatment. Based 
on the type of risk information shown in Figure IV.B-1, these levels 
are estimated to result in an annual infection risk in the range of 1.7 
x 10-4 to 6.0 x 10-3 (or 1.7 to 60 infections per 
10,000 consumers) for a treatment plant achieving 3-log Cryptosporidium 
removal (the treatment efficiency estimated for conventional plants 
under existing regulations).
    A shortcoming with establishing the threshold for additional 
treatment at 0.01 oocysts/L, however, is that a PWS would exceed this 
concentration with only a very few oocysts being detected. For a PWS 
collecting monthly 10-L samples and bin classification based on the 
maximum running annual average, as required under today's rule, 
detecting two oocysts during one year of monitoring would exceed a mean 
of 0.01 oocysts/L. Given the uncertainty associated with 
Cryptosporidium monitoring, EPA and the Advisory Committee did not 
support requiring additional treatment for filtered PWSs based on so 
few counts. Although this shortcoming could theoretically be addressed 
by a higher sampling frequency, the feasibility of increased sampling 
is limited by the capacity of laboratories and the cost of sample 
analysis.
    A related concern in establishing the threshold concentration for 
requiring additional treatment was bin misclassification. If the 
threshold concentration was set at 0.1 oocysts/L, for example, some 
PWSs with actual mean source-water concentrations greater than this 
level would measure a concentration less than this level and would be 
misclassified in the bin that requires no additional treatment. 
Consequently, they would not provide sufficient public health 
protection. As discussed previously, this type of error is due to the 
limited number and volume of samples that can be analyzed, imperfect 
method recovery, and variability in Cryptosporidium occurrence.
    Based on these considerations, the Advisory Committee recommended 
and today's rule establishes that filtered PWSs must provide additional 
treatment for Cryptosporidium when their mean source-water 
concentration exceeds 0.075 oocysts/L. At this concentration, PWSs 
collecting monthly 10-L samples must count at least nine oocysts in one 
year (9 oocysts per 120 L total sample volume) before additional 
treatment is required. Further, any PWS with a mean source-water 
infectious Cryptosporidium level above 0.1 oocysts/L, which corresponds 
to an estimated infection risk range of 1.7 to 6.0 x 10-3, 
is highly likely to be appropriately classified in a bin requiring 
additional treatment.
    After identifying this first threshold for requiring additional 
treatment, determining the Cryptosporidium concentrations that should 
bound higher treatment bins was necessary. In making these 
determinations, EPA concurred with Advisory Committee recommendations 
that sought to balance the possibility of bin misclassification against 
equitable risk reduction and public health protection.
    Treatment bins that span a wider concentration range result in 
lower bin misclassification rates. The analysis summarized in section 
IV.A shows that the monitoring required under today's rule can 
accurately characterize a PWS's mean Cryptosporidium level within a 
0.5-log margin, but error rates increase for smaller margins (USEPA 
2005a). Conversely, treatment bins that span a narrower concentration 
range provide more equitable protection from risk among different PWSs. 
This is due to identical treatment requirements applying to all PWSs in 
the same bin. In consideration of these issues, today's rule 
establishes two higher treatment bins at Cryptosporidium concentrations 
of 1.0 oocysts/L and 3.0 oocysts/L. These values result in the four 
bins shown in Table IV.B-1. Available occurrence data indicate that few 
PWSs will measure mean Cryptosporidium concentrations greater than 3.0 
oocysts/L, so there is no need to establish a treatment bin above this 
level.
    With respect to the degree of additional Cryptosporidium treatment 
that PWSs in Bins 2-4 must provide, EPA and the Advisory Committee 
considered values of 0.5-log and greater. Today's rule establishes a 1-
log additional treatment requirement for conventional plants in Bin 2. 
Because

[[Page 680]]

the concentration range of Bin 2 spans approximately one order of 
magnitude, this degree of treatment ensures that plants classified in 
Bin 2 will achieve treated water Cryptosporidium levels comparable to 
plants in Bin 1. Conventional plants in Bins 3 and 4 must provide 2.0- 
and 2.5-log of additional treatment, respectively. As recommended by 
the Advisory Committee, these higher additional treatment levels are 
required based on the recognition that plants in Bins 3 and 4 have a 
much greater potential vulnerability to Cryptosporidium. Consequently, 
significantly higher treatment is appropriate to protect public health.
    These additional treatment requirements for conventional treatment 
plants in Bins 2-4 are based on a prescribed 3-log Cryptosporidium 
treatment credit for compliance with the IESWTR or LT1ESWTR, as 
discussed previously. They translate to total Cryptosporidium treatment 
requirements of 4.0-, 5.0-, and 5.5-log for Bins 2, 3, and 4, 
respectively. Plants receiving higher or lower levels of prescribed 
treatment credit are required to provide less or more additional 
treatment if classified in Bins 2-4.
    Plants using slow sand or diatomaceous earth filtration, which also 
receive a 3-log treatment credit, incur the same additional treatment 
requirements as conventional plants if classified in Bins 2-4. Direct 
filtration plants, however, must provide 0.5-log greater additional 
treatment if classified in Bins 2-4 because they receive a 2.5-log 
prescribed credit. EPA expects, though, that most direct filtration 
plants will be classified in Bin 1 because direct filtration is 
typically applied only to higher quality source waters.
    Because EPA is unable to establish a prescribed treatment credit 
for other types of filtration technologies like membranes, bag filters, 
and cartridge filters, today's rule requires that States assign a 
treatment credit to a particular filtration product. This credit then 
determines the amount of additional treatment that a plant using this 
product must provide if classified in Bins 2-4 in order to achieve the 
required total treatment level. Section IV.D provides criteria for 
assigning Cryptosporidium treatment credit to membranes, bag filters, 
and cartridge filters.
    As described in Section IV.D, today's rule establishes a wide range 
of treatment and control options through the microbial toolbox for PWSs 
to meet additional Cryptosporidium treatment requirements. PWSs may 
choose any option or combination of options from the microbial toolbox 
to meet the treatment requirements of plants in Bin 2. For plants in 
Bins 3 or 4, though, PWSs must achieve at least 1-log of the additional 
treatment requirement using UV, ozone, chlorine dioxide, membranes, bag 
filters, cartridge filters, or bank filtration. EPA is establishing 
this provision in today's rule as recommended by the Advisory Committee 
because these processes will serve as significant additional treatment 
barriers for PWSs with the highest levels of pathogens in their 
sources.

How should PWSs calculate their treatment bin classification?

    The specific calculations that PWSs use to determine their bin 
classification are based on analyses of misclassification rates and 
bias. As described in section IV.A, today's rule requires PWSs to 
collect at least 24 samples (except for plants that operate only part-
year) when they monitor for Cryptosporidium. Most PWSs will collect 
these 24 samples over two years, but PWSs may sample at a higher 
frequency and small PWSs may complete this monitoring in one year. 
These differences affect the bin classification calculation.
    PWSs that sample monthly over two years (24 samples total) must use 
the maximum running annual average (Max-RAA) for bin classification 
because this achieves a low false negative rate (the likelihood a PWS 
will be incorrectly classified in a lower bin). In comparison, if such 
PWSs used the mean of all samples over two years for bin 
classification, the false negative rate would be almost four times 
higher (see Table IV.B.4).
    PWSs that choose to sample at least twice per month over two years 
(48 samples total) must use the mean of all 48 samples for their bin 
classification. This approach achieves a low false negative rate 
similar to the Max-RAA for 24 samples and, in addition, reduces the 
false positive rate (the likelihood a PWS will be incorrectly 
classified in higher bin--see Table IV.B.4). Due to the lower false 
positive rate associated with 48 samples, EPA expects that some PWSs 
will choose to sample for Cryptosporidium twice per month.
    Small PWSs (serving fewer than 10,000 people) that complete their 
Cryptosporidium monitoring over one year must use the mean of all 24 
samples for bin classification. This approach has a higher false 
negative rate than the approaches allowed for PWSs that monitor over 
two years. However, it is the only feasible option for PWSs that 
conduct just one year of Cryptosporidium sampling. Averaging sample 
concentrations over less than one year is not appropriate (except in 
the case of plants that operate only part-year that monitor for less 
than one year) as this would bias the bin classification due to 
seasonal variation in water quality.

  Table IV.B-4.--False Positive and False Negative Rates for Monitoring
           and Binning Strategies Considered for the LT2ESWTR
------------------------------------------------------------------------
                                                   False        False
                   Strategy                      positive 1   negative 2
------------------------------------------------------------------------
48 sample arithmetic mean.....................         1.7%         1.4%
24 sample Max-RAA.............................         5.3%         1.7%
24 sample arithmetic mean.....................         2.8%        6.2%
------------------------------------------------------------------------
1 False positive rates calculated for systems with Cryptosporidium
  concentrations 0.5 log below the Bin 1 boundary of 0.075 oocysts/L.
2 False negative rates calculated for systems with Cryptosporidium
  concentrations 0.5 log above the Bin 1 boundary of 0.075 oocysts/L.

    Two additional considerations that relate to characterizing 
Cryptosporidium monitoring results to determine treatment requirements 
are (1) fewer than 100 percent of oocysts in a sample are recovered and 
counted by the analyst and (2) not all the oocysts measured with 
Methods 1622 or 1623 are capable of causing infection. These two 
factors are offsetting, in that oocyst counts not adjusted for recovery 
tend to underestimate the true concentration, while the total oocyst 
count typically overestimates the infectious concentration that 
presents a health risk.
    As described in section III, matrix spike data indicate that 
average recovery of Cryptosporidium oocysts with Methods 1622 or 1623 
in a national monitoring program will be approximately 40 percent. 
Regarding the fraction of oocysts that are infectious, LeChevallier et 
al. (2003) tested natural waters for Cryptosporidium using both Method 
1623 and a method (cell culture-PCR) to test for infectivity. Results 
suggested that 37 percent of the Cryptosporidium oocysts detected by 
Method 1623 were infectious. This finding is consistent with the 
observation that 37 percent of the oocysts counted during the ICRSS 
using Methods 1622 or 1623 had internal structures, which indicate a 
higher likelihood of infectivity (among the remaining oocysts, 47 
percent had amorphous structures and 16 percent were empty).
    While it is not possible to establish a precise value for method 
recovery or the fraction of oocysts that are infectious,

[[Page 681]]

available data suggest that these parameters may be of similar 
magnitude. Consequently, the Advisory Committee recommended that 
monitoring results should not be adjusted to account for either 
recovery or the fraction infectious. EPA concurs with this 
recommendation and today's rule requires that PWSs be classified in 
treatment bins using the total number of Cryptosporidium oocysts 
counted, without further adjustment. The LT2ESWTR treatment bins in 
today's rule are constructed to reflect this approach.
3. Summary of Major Comments
    For filtered PWS treatment requirements in the LT2ESWTR proposal, 
EPA received significant public comment on the risk-based approach to 
requiring additional treatment, the role of States in determining bin 
classification, and the treatment credit for filtration plants. The 
following discussion summarizes comments in these areas and EPA's 
responses.
    Most commenters supported the risk-based approach of the LT2ESWTR 
in which filtered PWSs monitor for microbial contaminants and only 
those PWSs finding higher levels of contamination are required to 
provide additional treatment for Cryptosporidium. Among these comments, 
many stated support for the four treatment bins for filtered PWSs, with 
some noting that future research will indicate whether the bins should 
be restructured in a later rulemaking. Several commenters expressed 
support for EPA's combination of the Stage 2 DBPR and LT2ESWTR as 
essential to creating a balanced approach between DBP control and 
microbial risk.
    A few commenters opposed the expenditure of funds to reduce risk 
from Cryptosporidium on the basis that epidemiological evidence 
suggests this risk is low and most communities have not experienced 
cryptosporidiosis outbreaks. EPA agrees that additional treatment for 
Cryptosporidium in drinking water is not warranted in all communities. 
Under today's rule, most PWSs are expected to be classified in the 
lowest bin, which requires no additional treatment. However, based on 
risk information presented in USEPA (2005a) and summarized in this 
preamble, EPA believes that additional treatment is necessary to 
protect public health in PWSs with the highest Cryptosporidium levels. 
Further, as described in USEPA (2005a), EPA's assessment of 
Cryptosporidium risk in drinking water is consistent with the limited 
available epidemiological data on disease incidence.
    With respect to the role of States in bin classification, most 
commenters recommended that States assign or approve the bin 
classification for their PWSs. Commenters maintained that State 
approval of bin classification is an inherent governmental function and 
will avoid confusion as to the level of treatment each PWS must 
provide. Further, the approval process will provide an opportunity for 
dialog between States and PWSs. EPA agrees with these comments and 
today's rule requires PWSs to submit their calculation of bin 
classification to the State for review. If the PWS does not hear back 
from the State, it must proceed to apply the level of treatment 
appropriate for its calculated bin classification in accordance with 
its applicable compliance schedule.
    In regard to the Cryptosporidium treatment credit that should be 
awarded to filtration plants, many commenters supported the 3-log 
Cryptosporidium removal credit for conventional treatment and slow sand 
filtration. Some comments included data showing that conventional 
treatment can achieve greater than 4-log removal of Cryptosporidium, 
and several commenters stated concerns that EPA has underestimated the 
level of treatment achievable through conventional treatment. 
Commenters supported the inclusion of plants using softening and 
dissolved air flotation for conventional treatment credit and requested 
that EPA extend this credit to similar treatment trains using other 
types of clarification processes.
    EPA recognizes that studies show conventional treatment can achieve 
more than 3-log Cryptosporidium removal under optimal conditions. 
However, studies also demonstrate that removal efficiencies can be 
significantly less for suboptimal plant set-up and operation. EPA does 
not expect that all plants will operate under optimal conditions at all 
times. Consequently, today's rule awards a prescribed 3-log credit to 
conventional plants complying with the IESWTR or LT1ESWTR and allows 
plants to receive higher credit through demonstrating low finished 
water turbidity or through an alternative demonstration of performance, 
as describe in section IV.D. EPA agrees that plants using alternative 
clarification process that involves solids removal between coagulation 
and filtration should qualify for 3-log credit and today's rule 
provides for this.

C. Unfiltered System Cryptosporidium Treatment Requirements

1. Today's Rule
    Today's rule requires all PWSs that use a surface water or GWUDI 
source and are unfiltered to provide treatment for Cryptosporidium. The 
degree of required treatment depends on the level of Cryptosporidium in 
the source water, as determined through required monitoring. Further, 
unfiltered PWSs must meet overall treatment requirements using at least 
two disinfectants and must continue to meet all applicable filtration 
avoidance criteria. Details of these requirements follow.
    a. Determination of mean Cryptosporidium level. Following 
completion of the required initial source water monitoring described in 
section IV.A, each unfiltered PWS must determine the arithmetic mean of 
all its Cryptosporidium sample results generated during the monitoring 
period. As required for filtered PWSs, individual sample results must 
be calculated as the total number of oocysts counted, divided by the 
volume assayed (see section V.K for details). Samples are not adjusted 
for method recovery and, in samples where no oocysts are detected, the 
result is treated as zero.
    Unfiltered PWSs must report their mean Cryptosporidium level to the 
State for approval (see section IV.G for specific reporting dates). The 
report must include a summary of the data used to determine the mean 
concentration. If the State does not respond to a PWS regarding its 
mean Cryptosporidium level, the PWS must comply with the 
Cryptosporidium treatment requirements of today's rule, as described 
next, based on the reported level.
    If EPA does not amend today's rule before the second round of 
monitoring described in section IV.A, unfiltered PWSs must recalculate 
their mean Cryptosporidium level using results from the second round of 
monitoring. Unfiltered PWSs must report this level to the State as 
described for the initial round of monitoring.
    b. Cryptosporidium treatment requirements. Unfiltered PWSs must 
comply with the following treatment requirements based on their mean 
source-water Cryptosporidium level: if the level is less than or equal 
to 0.01 oocysts/L then at least 2-log Cryptosporidium inactivation is 
required; if the level is greater than 0.01 oocysts/L, or if the 
unfiltered PWS chooses not to monitor for Cryptosporidium, then at 
least 3-log Cryptosporidium inactivation is

[[Page 682]]

required. See section IV.G for treatment compliance dates.
    EPA has developed criteria, described in section IV.D, to award 
Cryptosporidium inactivation credit for treatment with chlorine 
dioxide, ozone, or UV light. Unfiltered PWSs may use any of these 
disinfectants to meet their Cryptosporidium inactivation requirements 
under today's rule. Further, unfiltered PWSs must achieve the following 
with respect to disinfection treatment:
    (1) A PWS that uses chlorine dioxide or ozone and fails to achieve 
the required level of Cryptosporidium inactivation on more than one day 
in the calendar month is in violation of the treatment technique 
requirement.
    (2) A PWS that uses UV light and fails to achieve the required 
level of Cryptosporidium inactivation in at least 95 percent of the 
water delivered to the public every month is in violation of the 
treatment technique requirement.
    c. Use of two disinfectants. Unfiltered PWSs must use at least two 
different disinfectants to provide 4-log virus, 3-log Giardia lamblia, 
and 2- or 3-log Cryptosporidium inactivation as required under 40 CFR 
141.72(a) and today's rule. Further, each of two disinfectants must 
achieve by itself the total inactivation required for one of these 
target pathogens. This requirement does not modify the existing 
requirement under 40 CFR 141.72(a) for PWSs to provide a disinfectant 
residual in the distribution system.
2. Background and Analysis
    The intent of the Cryptosporidium treatment requirements for 
unfiltered PWSs in today's final rule is to ensure that they achieve 
public health protection equivalent to that achieved by filtered PWSs. 
These requirements are unchanged from the August 11, 2003 proposal 
(USEPA 2003a), and they reflect consensus recommendations by the Stage 
2 M-DBP Advisory Committee (USEPA 2000a). The following discussion 
summarizes the Agency's basis for establishing risk-targeted 
Cryptosporidium treatment requirements for unfiltered PWSs in today's 
rule and for requiring the use of two disinfectants.
    a. Basis for Cryptosporidium treatment requirements. As described 
in section III, available data suggest that unfiltered PWSs must take 
additional steps to achieve public health protection against 
Cryptosporidium equivalent to that provided by filtered PWSs.
    In occurrence data from the ICR, the median Cryptosporidium level 
in unfiltered PWS sources was 0.0079 oocysts/L, which is approximately 
10 times less than the median level of 0.052 oocysts/L in filtered PWS 
sources. In translating these source water levels to finished water 
concentrations, EPA and the Advisory Committee assumed that 
conventional filtration treatment plants in compliance with the IESWTR 
or LT1ESWTR achieve an average of 3-log (99.9 percent) removal of 
Cryptosporidium. Existing regulations do not require unfiltered PWSs to 
provide any treatment for Cryptosporidium.
    If the median source water Cryptosporidium level in filtered PWSs 
is approximately 10 times higher than in unfiltered PWSs, and filtered 
PWSs achieve 3-log Cryptosporidium removal, then the median finished 
water Cryptosporidium level in filtered PWSs is approximately 100 times 
lower than in unfiltered PWSs. Thus, these data suggest that most 
unfiltered PWSs must provide 2-log Cryptosporidium treatment to ensure 
equivalent public health protection.
    Some unfiltered PWSs must provide greater than 2-log 
Cryptosporidium treatment to ensure equitable protection, depending on 
their source water level. Under today's rule, the Cryptosporidium 
treatment requirements for filtered PWSs, as described in section 
IV.B.1, will achieve mean finished water Cryptosporidium levels of less 
than 1 oocyst/10,000 L. An unfiltered PWS with a mean source water 
Cryptosporidium concentration above 0.01 oocysts/L would have to 
provide at least 3-log inactivation to achieve an equivalent finished 
water Cryptosporidium level.
    As stated earlier, EPA has determined that UV light is a feasible 
technology for PWSs of all sizes, including unfiltered PWSs, to 
inactivate Cryptosporidium. In addition, treating for Cryptosporidium 
using ozone is feasible for some unfiltered PWSs. Inactivating 
Cryptosporidium with chlorine dioxide, while allowed under today's 
rule, does not appear to be feasible for most unfiltered PWSs due to 
regulatory limits on chlorite--a chlorine dioxide byproduct.
    Based on these findings, today's rule requires all unfiltered PWSs 
to provide at least 2-log Cryptosporidium inactivation, and to provide 
at least 3-log inactivation if the mean source water level exceeds 0.01 
oocysts/L. These treatment requirements will ensure that unfiltered 
PWSs achieve public health protection against Cryptosporidium that is 
comparable to filtered PWSs in the finished water that is distributed 
to consumers.
    Available data indicate that no unfiltered PWSs will show measured 
mean source water Cryptosporidium levels of 0.075 oocysts/L or higher--
the level at which a filtered PWS must provide at least 4-log 
Cryptosporidium under today's rule. Consequently, EPA is not 
establishing treatment requirements in today's rule to address 
Cryptosporidium at this higher level. Under existing regulations (40 
CFR 141.171 and 141.521), unfiltered PWSs must maintain a watershed 
control program that minimizes the potential for contamination by 
Cryptosporidium oocysts in the source water. If the measured mean 
Cryptosporidium level in an unfiltered PWS is 0.075 oocysts/L or 
higher, EPA believes the State should critically evaluate the adequacy 
of the watershed control program.
    Under today's rule, unfiltered PWSs using ozone or chlorine dioxide 
to treat for Cryptosporidium must demonstrate the required 2- or 3-log 
inactivation every day the PWS serves water to the public, except any 
one day each month. Existing regulations (40 CFR 141.72(a)(1)) require 
unfiltered PWSs to ensure inactivation of 3-log Giardia lamblia and 4-
log viruses every day except any one day per month. Consequently, 
today's rule extends this compliance standard to Cryptosporidium 
inactivation.
    For unfiltered PWSs that use UV to treat for Cryptosporidium, 
today's rule requires demonstration of the required 2- or 3-log 
inactivation in at least 95 percent of the water delivered to the 
public every month. EPA intends this standard to be comparable to the 
``every day except any one day per month'' standard established for 
ozone and chlorine dioxide. Because UV disinfection systems will 
typically consist of multiple reactors that will be monitored 
continuously, EPA believes that a compliance standard based on the 
percentage of water disinfected to the required level is more 
appropriate than a single daily measurement. Section IV.D describes an 
equivalent standard for filtered PWSs.
    b. Basis for requiring the use of two disinfectants. Unfiltered 
PWSs must use at least two different disinfectants to meet the 
inactivation requirements for Cryptosporidium (2- or 3-log), Giardia 
lamblia (3-log) and viruses (4-log), and each of two disinfectants must 
achieve by itself the total inactivation required for one of these 
target pathogens. For example, a PWS could use UV light to achieve 3-
log inactivation of Giardia lamblia and Cryptosporidium and use 
chlorine to provide 4-log virus inactivation. The use of two 
disinfectants protects public health by creating multiple barriers 
against microbial pathogens. This has two

[[Page 683]]

general advantages over a single barrier: improved reliability and a 
broader spectrum of efficacy.
    Because unfiltered PWSs rely solely on inactivation for microbial 
treatment, an unfiltered PWS using only one disinfectant would provide 
no primary microbial treatment if that disinfection process were to 
fail. While disinfection processes should be designed for a high level 
of reliability, they are not generally 100 percent reliable. Existing 
regulations and today's rule recognize this limitation by allowing 
unfiltered PWSs to fail to achieve required disinfection levels one day 
per month. Consequently, EPA believes that for effective public health 
protection, unfiltered PWSs should use at least two primary 
disinfection processes. If one process fails, a second process will 
provide some degree of protection against pathogens.
    A second advantage of a PWS using multiple disinfectants is that 
this approach will typically be more effective against a broad spectrum 
of pathogens. The efficacy of different disinfectants against different 
types of pathogens varies widely. For example, UV light appears to be 
very effective for inactivating protozoa like Cryptosporidium and 
Giardia lamblia, but is less effective against certain enteric viruses 
like adenovirus. Chlorine, however, is highly effective against enteric 
viruses but less effective against protozoa. As a result, multiple 
disinfectants will generally provide more effective inactivation of a 
wide range of pathogens than a single disinfectant.
    c. Filtration avoidance. Today's rule does not withdraw or modify 
any existing criteria for avoiding filtration under 40 CFR 141.71. 
Accordingly, unfiltered PWSs must continue to comply with all existing 
filtration avoidance criteria. EPA believes these criteria help to 
ensure that watershed protection provides a microbial barrier in those 
PWSs that do not filter.
    Further, today's rule does not establish any new criteria for 
filtration avoidance. In the proposed LT2ESWTR, EPA indicated that 
compliance with DBP standards under the Stage 2 DBPR would be 
incorporated into the criteria for filtration avoidance. However, EPA 
has not done this in today's final rule in order to give States more 
flexibility in working with unfiltered PWSs to comply with the Stage 2 
DBPR.
3. Summary of Major Comments
    EPA received significant public comment on the following treatment 
requirements for unfiltered PWSs in the LT2ESWTR proposal: the 
requirement for all unfiltered PWSs to provide at least 2-log 
Cryptosporidium inactivation, treatment requirements for unfiltered 
PWSs with high Cryptosporidium levels, and the requirement for 
unfiltered PWSs to use at least two disinfectants. A summary of these 
comments and EPA's responses follows.
    Several commenters supported the requirement that all unfiltered 
PWSs achieve at least 2-log inactivation of Cryptosporidium, noting 
that this was part of the Agreement in Principle (USEPA 2000a). Some 
commenters, however, requested that EPA not establish a minimum 
Cryptosporidium treatment level due to the following factors: 
monitoring of unfiltered PWS sources has shown very low levels of 
Cryptosporidium, and some sources may have no Cryptosporidium; the 
Cryptosporidium in an unfiltered PWS source are likely to be of non-
human origin and are less likely to infect humans; and disease 
incidence data have not established a link between unfiltered PWSs and 
cryptosporidiosis in consumers.
    In response, EPA continues to believe that all unfiltered PWSs 
should provide treatment for Cryptosporidium to protect public health. 
Monitoring has shown that unfiltered PWS sources are contaminated with 
Cryptosporidium, and no source is likely to be entirely free of 
Cryptosporidium due to the ubiquity of Cryptosporidium in both human 
and many animal populations. Studies, such as those cited in section 
III, have established that Cryptosporidium from animals can infect 
humans. EPA does not regard the absence of cryptosporidiosis cases 
attributed to drinking water in a particular community as evidence that 
no treatment for Cryptosporidium is needed. As described in section 
III, cryptosporidiosis incidence data generally do not indicate overall 
disease burden because most cases are undetected, unreported, and not 
traced to a particular source.
    Some commenters recommended that EPA require only 1-log 
Cryptosporidium inactivation for unfiltered PWSs that demonstrate 
source water levels below 0.001 oocysts/L. EPA does not support this 
approach, though, due to concerns with the reliability of monitoring to 
establish such an extremely low level of Cryptosporidium. In addition, 
UV light is a feasible technology for unfiltered PWSs of all sizes to 
achieve at least 2-log Cryptosporidium inactivation. For these reasons, 
EPA has concluded that the minimum Cryptosporidium treatment level 
should be 2-log, as recommended by the Advisory Committee.
    In the proposed LT2ESWTR, EPA requested comment on the treatment 
that should be required if an unfiltered PWS measured a Cryptosporidium 
level of 0.075 oocysts/L or higher--the concentration at which a 
filtered PWS must provide at least 4-log treatment. Several commenters 
supported equivalent treatment requirements (i.e., at least 4-log 
reduction) for unfiltered and filtered PWSs with Cryptosporidium at 
this level. Other commenters stated that available data indicate no 
unfiltered PWSs are likely to measure Cryptosporidium at such a high 
level.
    EPA agrees that available data on Cryptosporidium occurrence 
suggest that no unfiltered PWSs will measure a mean level of 0.075 
oocysts/L or higher. Moreover, establishing a 4-log treatment 
requirement on the precautionary basis that an unfiltered PWS might 
measure a high level of Cryptosporidium has a significant cost--it 
would require any unfiltered PWS to provide 4-log, rather than 3-log, 
inactivation to avoid Cryptosporidium monitoring. EPA expects that many 
small unfiltered PWSs will choose to provide 3-log Cryptosporidium 
inactivation rather than monitor for Cryptosporidium. Accordingly, EPA 
has concluded that establishing a 4-log Cryptosporidium treatment 
requirement for unfiltered PWSs that measure a Cryptosporidium level of 
0.075 oocysts/L or higher is unnecessary and inappropriate at this 
time. In the event that an unfiltered PWS does measure Cryptosporidium 
at this level, the State can require the PWS to take steps to reduce 
the contamination under existing watershed control program requirements 
for unfiltered PWSs.
    Some commenters supported the requirement for unfiltered PWSs to 
use at least two disinfectants to meet overall inactivation 
requirements for Cryptosporidium, Giardia lamblia, and viruses and for 
each disinfectant to achieve the total inactivation required for one 
target pathogen. These commenters stated that this requirement will 
improve inactivation against a wide variety of pathogens and increase 
treatment reliability. Other commenters, though, opposed this 
requirement for a number of reasons: it will unnecessarily limit the 
ability of PWSs to minimize DBPs, there is no similar requirement for 
filtered PWSs, the requirement for each disinfectant to achieve the 
total inactivation for one pathogen goes beyond the Agreement in 
Principle, and EPA has not provided a risk analysis to justify the 
requirement.

[[Page 684]]

    In response, EPA believes that the benefits of both redundancy and 
a broad spectrum of microbial protection justify requiring the use of 
two disinfectants. Further, requiring each disinfectant to achieve the 
full inactivation of one target pathogen establishes a minimal 
performance level so that each disinfectant will serve as a substantive 
barrier. In most cases, PWSs will comply with this requirement by using 
UV or ozone to inactivate Giardia lamblia and Cryptosporidium and using 
chlorine to inactivate viruses.

D. Options for Systems To Meet Cryptosporidium Treatment Requirements

1. Microbial Toolbox Overview
    Today's rule includes a variety of treatment and control options, 
collectively termed the ``microbial toolbox,'' that PWSs can implement 
to comply with additional Cryptosporidium treatment requirements. 
Options in the microbial toolbox include source protection and 
management programs, prefiltration processes, treatment performance 
programs, additional filtration components, and inactivation 
technologies. The Stage 2 M-DBP Advisory Committee recommended the 
microbial toolbox to provide PWSs with broad flexibility in selecting 
cost-effective LT2ESWTR compliance strategies.
    Most options in the microbial toolbox carry prescribed credits 
toward Cryptosporidium treatment requirements. PWSs receive these 
credits by demonstrating compliance with required design and 
operational criteria, which are described in the sections that follow. 
In addition, States may award treatment credits other than the 
prescribed credit through a ``demonstration of performance,'' which 
involves site-specific testing by a PWS with a State-approved protocol. 
Under a demonstration of performance, a State may award credit to a 
treatment plant or to a unit process of a treatment plant that is 
higher or lower than the prescribed credit. This option also allows 
States to award credit to a unit process that does not meet the design 
and operational criteria in the microbial toolbox for prescribed 
credit.
    To be eligible for treatment credit for a microbial toolbox option, 
PWSs must initially report compliance with design criteria, where 
required, to the State (some options do not require design criteria). 
Thereafter, for most options, PWSs must report compliance with required 
operational criteria to the State each month (the watershed control 
program option requires yearly reporting). Failure by a PWS in any 
month to demonstrate treatment credit equal to or greater than its 
Cryptosporidium treatment requirements under today's rule is a 
treatment technique violation. This violation lasts until the PWS 
demonstrates that it is meeting criteria for sufficient treatment 
credit to satisfy its Cryptosporidium treatment requirements.
    As described in section IV.B, filtered PWSs may use any option or 
combination of options from the microbial toolbox to comply with the 
additional Cryptosporidium treatment requirements of Bin 2. PWSs in 
Bins 3 or 4 must achieve at least 1-log of the additional 
Cryptosporidium treatment requirement by using ozone, chlorine dioxide, 
UV, membranes, bag filtration, cartridge filtration, or bank 
filtration.
    If allowed by the State, PWSs may use different microbial toolbox 
options in different months to comply with Cryptosporidium treatment 
requirements under today's rule. For example, a PWS in Bin 2, which 
requires 1-log additional Cryptosporidium treatment, could comply with 
this requirement in one month using ``individual filter performance,'' 
which carries a 1-log credit; in a subsequent month, this PWS could use 
``combined filter performance'' and ``presedimentation basin with 
coagulation,'' which each carry 0.5-log credit. This approach is 
intended to provide greater operational flexibility to PWSs. It allows 
a PWS to receive treatment credit for a microbial toolbox option in any 
month the PWS is able to meet required operational criteria, even if 
the PWS does not meet these criteria during all months of the year.
    Table IV.D-1 summarizes prescribed treatment credits and associated 
design and operational criteria for microbial toolbox options. The 
sections that follow describe each toolbox option in detail. In 
addition, EPA has developed three guidance documents to assist PWSs 
with selecting and implementing microbial toolbox options: Toolbox 
Guidance Manual, UV Disinfection Guidance Manual, and Membrane 
Filtration Guidance Manual. Each may be acquired from EPA's Safe 
Drinking Water Hotline, which can be contacted as described under FOR 
FURTHER INFORMATION CONTACT at the beginning of this notice.

     Table IV.D-1.--Microbial Toolbox: Options, Credits and Criteria
------------------------------------------------------------------------
                                      Cryptosporidium treatment credit
          Toolbox option            with design and operational criteria
                                                     \1\
------------------------------------------------------------------------
            Source Protection and Management Toolbox Options
------------------------------------------------------------------------
Watershed control program.........  0.5-log credit for State-approved
                                     program comprising required
                                     elements, annual program status
                                     report to State, and regular
                                     watershed survey. Unfiltered PWSs
                                     are not eligible for credit.
Alternative source/intake           No prescribed credit. PWSs may
 management.                         conduct simultaneous monitoring for
                                     treatment bin classification at
                                     alternative intake locations or
                                     under alternative intake management
                                     strategies.
-----------------------------------
                      Prefiltration Toolbox Options
------------------------------------------------------------------------
Presedimentation basin with         0.5-log credit during any month that
 coagulation.                        presedimentation basins achieve a
                                     monthly mean reduction of 0.5-log
                                     or greater in turbidity or
                                     alternative State-approved
                                     performance criteria. To be
                                     eligible, basins must be operated
                                     continuously with coagulant
                                     addition and all plant flow must
                                     pass through basins.
Two-stage lime softening..........  0.5-log credit for two-stage
                                     softening where chemical addition
                                     and hardness precipitation occur in
                                     both stages. All plant flow must
                                     pass through both stages. Single-
                                     stage softening is credited as
                                     equivalent to conventional
                                     treatment.
Bank filtration...................  0.5-log credit for 25-foot setback;
                                     1.0-log credit for 50-foot setback;
                                     horizontal and vertical wells only;
                                     aquifer must be unconsolidated sand
                                     containing at least 10 percent
                                     fines (as defined in rule); average
                                     turbidity in wells must be less
                                     than 1 NTU. PWSs using existing
                                     wells followed by filtration must
                                     monitor the well effluent to
                                     determine bin classification and
                                     are not eligible for additional
                                     credit.
-----------------------------------

[[Page 685]]

 
                  Treatment Performance Toolbox Options
------------------------------------------------------------------------
Combined filter performance.......  0.5-log credit for combined filter
                                     effluent turbidity less than or
                                     equal to 0.15 NTU in at least 95
                                     percent of measurements each month.
Individual filter performance.....  0.5-log credit (in addition to 0.5-
                                     log combined filter performance
                                     credit) if individual filter
                                     effluent turbidity is less than or
                                     equal to 0.15 NTU in at least 95
                                     percent of samples each month in
                                     each filter and is never greater
                                     than 0.3 NTU in two consecutive
                                     measurements in any filter.
Demonstration of performance......  Credit awarded to unit process or
                                     treatment train based on a
                                     demonstration to the State with a
                                     State-approved protocol.
-----------------------------------
                  Additional Filtration Toolbox Options
------------------------------------------------------------------------
Bag and cartridge filters.........  Up to 2-log credit with
                                     demonstration of at least 1-log
                                     greater removal in a challenge test
                                     when used singly. Up to 2.5-log
                                     credit with demonstration of at
                                     least 0.5-log greater removal in a
                                     challenge test when used in series.
Membrane filtration...............  Log credit equivalent to removal
                                     efficiency demonstrated in
                                     challenge test for device if
                                     supported by direct integrity
                                     testing.
Second stage filtration...........  0.5-log credit for second separate
                                     granular media filtration stage if
                                     treatment train includes
                                     coagulation prior to first filter.
Slow sand filters.................  2.5-log credit as a secondary
                                     filtration step; 3.0-log credit as
                                     a primary filtration process. No
                                     prior chlorination.
-----------------------------------
                      Inactivation Toolbox Options
------------------------------------------------------------------------
Chlorine dioxide..................  Log credit based on measured CT in
                                     relation to CT table.
Ozone.............................  Log credit based on measured CT in
                                     relation to CT table.
UV................................  Log credit based on validated UV
                                     dose in relation to UV dose table;
                                     reactor validation testing required
                                     to establish UV dose and associated
                                     operating conditions.
------------------------------------------------------------------------
\1\ Table provides summary information only; refer to following preamble
  and regulatory language for detailed requirements.

2. Watershed Control Program

a. Today's Rule
    Filtered PWSs can receive 0.5-log credit toward Cryptosporidium 
treatment requirements under today's rule for implementing a State-
approved watershed control program designed to reduce the level of 
Cryptosporidium. To be eligible to receive this credit initially, PWSs 
must perform the following steps:
     Notify the State of the intent to develop a new or 
continue an existing watershed control program for Cryptosporidium 
treatment credit no later than two years prior to the date the PWS must 
comply with additional Cryptosporidium treatment requirements under 
today's rule.
     Submit a proposed watershed control plan to the State for 
approval no later than one year prior to the date the PWS must comply 
with additional Cryptosporidium treatment requirements under today's 
rule. The watershed control plan must contain these elements:
    (1) The designation of an ``area of influence'' in the watershed, 
which is defined as the area outside of which the likelihood of 
Cryptosporidium contamination affecting the treatment plant intake is 
not significant;
    (2) The identification of both potential and actual sources of 
Cryptosporidium contamination, including a qualitative assessment of 
the relative impact of these contamination sources on water quality at 
the treatment plant intake;
    (3) An analysis of control measures that could mitigate the sources 
of Cryptosporidium contamination, including the relative effectiveness 
of control measures in reducing Cryptosporidium loading to the source 
water and their feasibility; and
    (4) A statement of goals and specific actions the PWS will 
undertake to reduce source water Cryptosporidium levels, including a 
description of how the actions will contribute to specific goals, 
watershed partners and their roles, resource requirements and 
commitments, and a schedule for plan implementation.
    If the State approves the watershed control plan for 
Cryptosporidium treatment credit, PWSs must perform the following steps 
to be eligible to maintain the credit:
     Submit an annual watershed control program status report 
to the State no later than a date specified by the State. The status 
report must describe the following: (1) how the PWS is implementing the 
approved watershed control plan; (2) the adequacy of the plan to meet 
its goals; (3) how the PWS is addressing any shortcomings in plan 
implementation; and (4) any significant changes that have occurred in 
the watershed since the last watershed sanitary survey.
     Notify the State prior to making any significant changes 
to the approved watershed control plan. If any change is likely to 
reduce the planned level of source water protection, the PWS must 
include in this notification a statement of actions that will be taken 
to mitigate this effect.
     Perform a watershed sanitary survey no less frequently 
than the PWS must undergo a sanitary survey under 40 CFR 
142.16(b)(3)(i), which is every three to five years, and submit the 
survey report to the State for approval. The State may require a PWS to 
perform a watershed sanitary survey at an earlier date if the State 
determines that significant changes may have occurred in the watershed 
since the previous sanitary survey. A person approved by the State must 
conduct the watershed sanitary survey and the survey must meet 
applicable State guidelines. The watershed sanitary survey must 
encompass the area of influence as identified in the State-approved 
watershed control plan, assess the implementation of actions to reduce 
source water Cryptosporidium levels, and identify any significant new 
sources of Cryptosporidium.
    PWSs are eligible to receive Cryptosporidium treatment credit under 
today's rule for preexisting watershed control programs (e.g., programs 
in place at the time of rule promulgation).

[[Page 686]]

To be eligible for credit, such programs must meet the requirements 
stated in this section and the watershed control plan must address 
future actions that will further reduce source water Cryptosporidium 
levels.
    If the State determines that a PWS is not implementing the approved 
watershed control plan (i.e., the PWS is not carrying out the actions 
on the schedule in the approved plan), the State may revoke the 
Cryptosporidium treatment credit for the watershed control program. 
Failure by a PWS to demonstrate treatment credit at least equal to its 
Cryptosporidium treatment requirement under today's rule due to such a 
revocation of credit is a treatment technique violation. The violation 
lasts until the State determines that the PWS is implementing an 
approved watershed control plan or is otherwise achieving the required 
level of Cryptosporidium treatment credit.
    PWSs must make the approved watershed control plan, annual status 
reports, and watershed sanitary surveys available to the public upon 
request. These documents must be in a plain language style and include 
criteria by which to evaluate the success of the program in achieving 
plan goals. If approved by the State, the PWS may withhold portions of 
these documents based on security considerations.
    Unfiltered PWSs are not eligible to receive Cryptosporidium 
treatment credit for a watershed control program under today's rule. 
Under existing regulations (40 CFR 141.71), unfiltered PWSs must 
maintain a watershed control program that minimizes the potential for 
contamination by Cryptosporidium as a condition for avoiding 
filtration.

b. Background and Analysis

    Cryptosporidium enters drinking water through fecal contamination 
of PWS source waters. Implementing a watershed control program that 
reduces or treats sources of fecal contamination in PWS sources will 
benefit public health by lowering the exposure of drinking water 
consumers to Cryptosporidium and other pathogenic microorganisms. In 
addition, a watershed control program may enhance treatment plant 
management practices through generating knowledge of the sources, fate, 
and transport of pathogens.
    The Stage 2 M-DBP Advisory Committee recommended 0.5-log 
Cryptosporidium treatment credit for a watershed control program (USEPA 
2000a), and the August 11, 2003 proposal included criteria for PWSs to 
receive this credit (USEPA 2003a). The following discussion summarizes 
the basis for this credit and for differences in associated 
requirements between the proposal and today's final rule.
    The efficacy of a watershed control program in reducing levels of 
Cryptosporidium and other microbial pathogens depends on the ability of 
a PWS to identify and control sources of fecal contamination. The fecal 
sources that are significant in a particular watershed and the control 
measures that will be effective in mitigating these sources are site 
specific. Consequently, EPA believes that States should determine 
whether a watershed control program developed by a PWS to reduce 
Cryptosporidium contamination warrants 0.5-log treatment credit. 
Accordingly, today's rule requires State approval of watershed control 
programs for PWSs to receive credit.
    If a PWS intends to implement a watershed control program to comply 
with Cryptosporidium treatment requirements under today's rule, EPA 
believes the PWS should notify the State at least two years prior to 
the required treatment compliance date. This notification will give the 
State an opportunity to communicate with the PWS regarding site-
specific considerations for a watershed control program. Further, the 
PWS should submit the proposed watershed control plan to the State for 
approval at least one year prior to the treatment compliance date. This 
schedule will give the State time to evaluate the program for approval 
and, if necessary, allow the PWS to make modifications necessary for 
approval. Thus, today's rule establishes these reporting deadlines.
    The required elements for a watershed control plan in today's rule 
are the minimum necessary for a program that will be effective in 
reducing levels of Cryptosporidium and other pathogens in a treatment 
plant intake. These elements include defining the area of the watershed 
where contamination can affect the intake water quality, identifying 
sources of contamination within this area, evaluating control measures 
to reduce contamination, and developing an action plan to implement 
specific control measures.
    EPA encourages PWSs to leverage other Federal, State, and local 
programs in developing the elements of their watershed control plans. 
For example, SDWA section 1453 requires States to carry out a source 
water assessment program (SWAP) for PWSs. Depending on how a State 
implements this program, the SWAP may be used to define the area of 
influence in the watershed and identify actual and potential 
contamination sources. In 2002, EPA launched the Watershed Initiative 
(67 FR 36172, May 23, 2002) (USEPA 2002b), which will provide grants to 
support watershed-based approaches to preventing, reducing, and 
eliminating water pollution. In addition, EPA recently promulgated 
regulations for Concentrated Animal Feeding Operations that will limit 
discharges that contribute microbial pathogens to watersheds.
    Many PWSs do not control the watersheds of their sources of supply. 
Their watershed control plans should involve partnerships with 
watershed landowners and government agencies that have authority over 
activities in the watershed that may contribute Cryptosporidium to the 
water supply. Stakeholders that control activities that could 
contribute to Cryptosporidium contamination include municipal 
government and private operators of wastewater treatment plants, 
livestock farmers and persons who spread manure, individuals with 
failing septic systems, logging operations, and other government and 
commercial organizations.
    After a State approves a watershed control plan for a PWS and 
initially awards 0.5-log Cryptosporidium treatment credit, the PWS must 
submit a watershed control program status report to the State each 
year. These reports are required for States to exercise oversight and 
ensure that PWSs implement the approved watershed control plan. They 
also provide a mechanism for PWSs to work with the States to address 
any shortcomings or necessary modifications in watershed control plans 
that are identified after plan approval.
    In addition, PWSs must undergo watershed sanitary surveys every 
three to five years by a State-approved party. These surveys will 
provide information to PWSs and States regarding significant changes in 
the watershed that may warrant modification of the approved watershed 
control plan. Also, they allow for an assessment of watershed control 
plan implementation.
    The proposed rule required watershed sanitary surveys annually, but 
EPA has reduced the frequency to every three to five years in today's 
final rule. This frequency is consistent with existing requirements for 
PWS sanitary surveys. EPA is establishing this longer frequency on the 
basis that most watersheds will not undergo significant changes over 
the course of a single year. If significant changes in the watershed do 
occur, however, PWSs must identify these changes in their annual 
program status reports. In addition, States have

[[Page 687]]

the authority to require that a watershed sanitary survey be conducted 
at an earlier date if the State determines that significant changes may 
have occurred in the watershed since the previous survey.
    In the proposed rule, approval of a watershed control program 
expired after a PWS completed the second round of source water 
monitoring, and the PWS had to reapply for program approval. Today's 
final rule, however, does not include this requirement. Instead, 
today's rule gives States authority to revoke Cryptosporidium treatment 
credit for a watershed control program at any point if a State 
determines that a PWS is not implementing the approved watershed 
control plan. EPA believes this approach is preferable to the automatic 
expiration of credit in the proposed rule for two reasons: (1) It 
assures PWSs that if they implement the approved watershed control 
plan, they will maintain the treatment credit; and (2) it gives States 
the authority to ensure PWSs implement watershed control programs for 
which they receive treatment credit and to take action at any time if a 
PWS does not.
    EPA believes that PWSs should be eligible to receive 
Cryptosporidium treatment credit for watershed control programs that 
are in place prior to the treatment compliance date. The same 
requirements for watershed control program treatment credit apply 
regardless of whether the program is new or existing at the time the 
PWS submits the watershed control plan for approval. In the case of 
existing programs, the watershed control plan must list future 
activities the PWS will undertake that will reduce source water 
contamination.
    The Toolbox Guidance Manual lists programmatic resources and 
guidance available to assist PWSs in building partnerships and 
implementing watershed protection activities. It also incorporates 
information on the effectiveness of different control measures to 
reduce Cryptosporidium levels and provides case studies of watershed 
control programs. This guidance is intended to assist both PWSs in 
developing watershed control programs and States in assessing and 
approving these programs.
    In addition to this guidance and other technical resources, EPA 
provides funding for watershed and source water protection through the 
Drinking Water State Revolving Fund (DWSRF) and Clean Water State 
Revolving Fund (DWSRF). Under the DWSRF program, States may fund source 
water protection activities by PWSs, including watershed management and 
pathogen source reduction plans. CWSRF funds can be used for 
agricultural best management practices to reduce pathogen loading in 
receiving waters and for the replacement of failing septic systems.

c. Summary of Major Comments

    Public comments on the August 11, 2003, LT2ESWTR proposal supported 
the concept of awarding credit towards Cryptosporidium treatment 
requirements for an effective watershed control program. Commenters 
expressed concerns, however, with specific criteria for awarding this 
credit, including annual watershed sanitary surveys, re-approval of 
watershed control programs, standards for existing watershed control 
programs, and public availability of documents related to the watershed 
control program. A summary of these comments and EPA's responses 
follows.
    Regarding the proposed requirement for annual watershed sanitary 
surveys, commenters stated that this frequency is too high because 
activities to reduce Cryptosporidium contamination in the watershed 
will often take many years to implement. These commenters recommended 
that watershed sanitary surveys be performed every three to five years 
in conjunction with PWSs sanitary surveys or longer. In contrast, other 
commenters supported annual watershed sanitary surveys as being 
necessary to allow proper responses to new sources of contamination 
that can occur quickly in watersheds. Such sources can occur through 
development, new recreation programs, fires, unauthorized activities, 
and other factors.
    While EPA believes that regular watershed sanitary surveys are 
necessary to identify new sources of contamination and allow States to 
properly oversee watershed control programs, EPA agrees that 
significant changes typically will not occur over one year. Therefore, 
today's final rule requires PWSs that receive Cryptosporidium treatment 
credit for a watershed control program to undergo watershed sanitary 
surveys every three to five years, rather than every year. To address 
the concern that new sources of watershed contamination can arise 
quickly, today's rule requires PWSs to identify any significant changes 
that have occurred in their watersheds in their annual program status 
reports. States can then require a watershed sanitary survey at an 
earlier date if significant changes have occurred since the previous 
survey.
    Many commenters opposed the proposed requirement for PWSs to 
reapply for approval of their watershed control programs after 
completing the second round of source water monitoring. The concern was 
that this requirement would discourage PWSs from pursuing watershed 
control programs because they would be uncertain about whether they 
would continue to receive treatment credit for their programs in the 
future. As an alternative, commenters recommended that States monitor 
the progress of PWSs in implementing watershed control programs through 
the watershed sanitary surveys and annual status reports. A State could 
then deny treatment credit to a PWS if it failed to demonstrate 
adequate commitment to its approved watershed control plan.
    EPA agrees with these comments and today's final rule does not 
include a requirement for re-approval of the watershed control program 
after the second round of monitoring. Instead, PWSs must submit annual 
program status reports to the State and undergo regular watershed 
sanitary surveys. If the State determines that a PWS is not 
implementing its approved watershed control plan on the basis of these 
measures, it can withdraw the treatment credit associated with the 
program. PWSs that implement their approved watershed control plans, 
however, can maintain the associated treatment credit indefinitely 
under today's rule.
    Several commenters stated that PWSs with existing watershed control 
programs should be eligible for Cryptosporidium treatment credit under 
the same standards that apply to new programs. EPA agrees that both 
existing and new watershed control programs should be eligible for 
Cryptosporidium treatment credit under the same standards, and today's 
rule allows this. As is required for new programs, PWSs with existing 
watershed control programs must submit a watershed control plan that 
details future activities the PWS will implement to reduce source water 
contamination. As with new programs, States will have the discretion to 
approve the proposed watershed control plan for 0.5-log Cryptosporidium 
treatment credit.
    With respect to a proposed requirement that the watershed control 
plan, annual status reports, and watershed sanitary surveys be made 
available to the public, commenters stated that homeland security 
concerns are associated with these documents. Homeland security 
concerns apply to information on the location of treatment plant 
intakes and other structures. EPA agrees that there are security 
concerns associated with watershed control program documents. EPA also 
believes, though, that the public should be allowed to learn about the 
actions PWSs

[[Page 688]]

plan to take to address Cryptosporidium contamination and the progress 
of PWSs in implementing these actions. Consequently, today's rule 
requires PWSs to make the approved watershed control plan, annual 
status reports, and watershed sanitary surveys available to the public. 
However, PWSs may withhold portions of these documents that raise 
security concerns with State approval.
3. Alternative Source
a. Today's Rule
    If approved by the State, a PWS may determine its Cryptosporidium 
treatment requirements under today's rule using additional source water 
monitoring results for an alternative treatment plant intake location 
or an alternative intake operational strategy. By meeting the 
requirements of this option, which are described as follows, a PWS may 
reduce its Cryptosporidium treatment requirements under today's rule.
     Monitoring for an alternative intake location or 
operational strategy, termed ``alternative source monitoring,'' may 
only be performed in addition to monitoring the existing plant 
intake(s) (i.e., the intake(s) the PWS uses when it must begin 
monitoring under today's rule).
     Alternative source monitoring must meet the sample number, 
sample frequency, and data quality requirements that apply to source 
water monitoring for bin classification, as described in section IV.A.
     PWSs that perform alternative source monitoring must 
complete this monitoring by the applicable deadline for treatment bin 
classification under today's rule, as described in section IV.G. Unless 
a PWS grandfathers monitoring data for the existing plant intake, 
alternative source monitoring must be performed concurrently with 
monitoring the existing intake.
     PWSs must submit the results of alternative source 
monitoring to the State, along with supporting information documenting 
the location and/or operating conditions under which the alternative 
source monitoring was conducted. If a PWS fulfills these requirements, 
the PWS may request that the State classify the PWS in a treatment bin 
under today's rule using the alternative source monitoring results.
     If the State approves bin classification for a PWS using 
alternative source monitoring results, the PWS must relocate the plant 
intake or implement the intake operational strategy to reflect the 
alternative source monitoring. The PWS must complete these actions no 
later than the applicable date for the PWS to comply with 
Cryptosporidium treatment requirements under today's rule. The State 
may specify reporting requirements to verify operational practices.
    Failure by a PWS that is classified in a treatment bin using 
alternative source monitoring to relocate the intake or implement the 
new intake operational strategy, as required, by the applicable 
treatment compliance deadline is a treatment technique violation. This 
violation lasts until the State determines that the PWS has carried out 
required changes to the intake location or operation or is providing 
the level of Cryptosporidium treatment required for the existing intake 
location and operation.
b. Background and Analysis
    Plant intake refers to the works or structures at the head of a 
conduit through which water is diverted from a source (e.g., river or 
lake) into a treatment plant. Plants may be able to reduce influent 
Cryptosporidium levels by changing the intake placement (either within 
the same source or to an alternate source) or managing the timing or 
level of withdrawal.
    The Stage 2 M-DBP Advisory Committee recommended that PWSs be 
allowed to modify their plant intakes to comply with today's rule, and 
the August 11, 2003 proposal included this option (USEPA 2000a). The 
requirements for this option in today's final rule are unchanged from 
the proposal. The following discussion summarizes the basis for these 
requirements.
    The effect of changing the location or operation of a plant intake 
on influent Cryptosporidium levels can only be ascertained through 
monitoring. Consequently, EPA is not establishing a prescriptive credit 
for this option. Rather, if a PWS expects that Cryptosporidium levels 
from a current plant intake will result in a bin classification 
requiring additional treatment under today's rule, the PWS may conduct 
additional Cryptosporidium monitoring reflecting a different intake 
location or operational strategy (alternative source monitoring). The 
PWS may then request that the State approve bin classification for the 
plant based on alternative source monitoring results, provided the PWS 
will implement the corresponding changes to the intake location or 
operation.
    PWSs that conduct alternative source monitoring must also monitor 
their existing plant intakes. Monitoring the existing intake is 
required for the State to determine a treatment bin classification for 
a plant in the event the PWS does not modify the intake (to reflect 
alternative source monitoring) prior to the treatment compliance 
deadline under today's rule.
    Further, PWSs must conduct alternative source monitoring within the 
applicable time frame for source water monitoring under today's rule. 
This approach is required for the State to determine a bin 
classification for the plant based on alternative source monitoring by 
the bin classification deadline. In addition, this timing will allow 
the PWS to modify the intake or implement additional treatment, if 
necessary, by the treatment compliance deadline. This requirement 
means, however, that unless a PWS meets the requirement for monitoring 
its existing intake through grandfathering, the PWS must perform 
alternative source monitoring concurrently with existing intake 
monitoring, although it does not have to be on exactly the same 
schedule.
    Because alternative source monitoring will be used for bin 
classification, this monitoring must comply with all applicable 
requirements for source water monitoring that are described in section 
IV.A. Further, the PWS must provide the State with supporting 
information documenting the conditions, such as the source location, 
under which the alternative source monitoring was conducted. This 
documentation is required so that if bin classification is based on 
alternative source monitoring results, the State can ensure the PWS 
implements the corresponding modifications to the intake.
c. Summary of Major Comments
    Public comments on the August 11, 2003, LT2ESWTR proposal supported 
allowing PWSs to determine treatment bin classification by monitoring 
for an alternative intake location or operational strategy. Several 
commenters stated they were unsure if this option would be widely used 
due to the burden of performing Cryptosporidium monitoring at both the 
current intake and the alternative source. Commenters also recommended 
that PWSs first conduct source water assessments or watershed sanitary 
surveys to evaluate intake management strategies to reduce 
Cryptosporidium levels in the plant influent.
    In response, EPA believes that PWSs who choose alternative source 
monitoring must also monitor their current intake so that the State can 
determine the appropriate bin classification if the PWS does not

[[Page 689]]

subsequently modify its intake. While few PWSs may choose to pursue 
alternative source monitoring, EPA believes this option should be 
available for PWSs that elect to do so. EPA agrees that it is 
appropriate for PWSs to assess contamination sources in the watershed 
when considering whether to relocate or change the operation of their 
intakes. The Toolbox Guidance Manual provides direction to PWSs on 
conducting these assessments.
    EPA requested comment on whether representative Cryptosporidium 
monitoring can be performed prior to implementation of a new intake 
strategy (e.g., monitoring a new source prior to constructing a new 
intake structure). Commenters stated that there may be situations where 
allowing Cryptosporidium monitoring to demonstrate a reduction in 
oocyst levels prior to implementation of a new intake strategy is 
appropriate. Incurring costs for constructing a new intake before 
determining whether the strategy will reduce oocyst levels is not cost 
effective. EPA agrees with this comment and today's rule allows PWSs to 
conduct alternative source monitoring prior to constructing a new 
intake and to base their bin classification on these monitoring results 
with State approval.
4. Pre-Sedimentation With Coagulant
a. Today's Rule
    Presedimentation is a preliminary treatment process used to remove 
gravel, sand and other particulate material from the source water 
through settling before the water enters the primary clarification and 
filtration processes in a treatment plant. PWSs receive 0.5-log credit 
towards Cryptosporidium treatment requirements under today's rule for a 
presedimentation process that meets the following conditions:
     Treats all flow reaching the treatment plant;
     Continuously adds a coagulant to the presedimentation 
basin;
     Achieves one of the following two performance criteria:
    (1) Demonstrates at least 0.5-log mean reduction of influent 
turbidity. This reduction must be determined using daily turbidity 
measurements in the presedimentation process influent and effluent and 
must be calculated as follows: log10 (monthly mean of daily 
influent turbidity)--log10 (monthly mean of daily effluent 
turbidity).
    (2) Complies with State-approved performance criteria that 
demonstrate at least 0.5-log mean removal of micron-sized particulate 
material, such as aerobic spores, through the presedimentation process.
    PWSs may receive treatment credit for a presedimentation process 
during any month the process meets these conditions. To be eligible for 
credit, PWSs must report compliance with these conditions to the State 
each month. PWSs may earn presedimentation treatment credit for only 
part of the year if the process does not meet these conditions year-
round. In this situation, PWSs must fully meet their Cryptosporidium 
treatment requirements under today's rule using other microbial toolbox 
options during those months when the PWS does not receive treatment 
credit for presedimentation.
    Alternatively, PWSs may apply to the State for Cryptosporidium 
treatment credit for presedimentation processes using a demonstration 
of performance, as described in section IV.D.9. Demonstration of 
performance provides an option for PWSs with presedimentation processes 
that do not meet these prescribed conditions for treatment credit and 
for PWSs who seek greater than 0.5-log Cryptosporidium treatment credit 
for their presedimentation processes.
    PWSs are not eligible for Cryptosporidium treatment credit for a 
presedimentation process if their sampling point for the source water 
Cryptosporidium monitoring used for bin classification was after (i.e., 
downstream of) the presedimentation process. In this case, the removal 
achieved by the presedimentation process will be reflected in the 
monitoring results and bin classification.
b. Background and Analysis
    Presedimentation involves passing raw water through retention 
basins in which particulate material is removed through settling. PWSs 
use presedimentation to reduce and stabilize particle concentrations 
prior to the primary clarification and filtration processes in a 
treatment plant. Presedimentation is often operated at higher hydraulic 
overflow rates than conventional sedimentation (the sedimentation 
process that directly precedes filtration in a conventional treatment 
plant) and may not involve coagulant addition. PWSs may operate a 
presedimentation process only during periods of high raw water 
turbidity.
    As a process for removing particles, presedimentation can reduce 
Cryptosporidium levels to some degree. In addition, presedimentation 
can improve the performance of subsequent treatment processes by 
dampening variability in raw water quality. The efficacy of 
presedimentation in removing particles, including Cryptosporidium, is 
influenced by the use of coagulant, the hydraulic loading rate, water 
quality parameters like temperature and turbidity, and physical 
characteristics of the sedimentation basin.
    The Stage 2 M-DBP Advisory Committee recommended 0.5-log 
Cryptosporidium treatment credit for presedimentation with coagulation 
(USEPA 2000a). The August 11, 2003 proposal included criteria, which 
were similar to those in today's final rule, for PWSs to receive this 
credit (USEPA 2003a). The following discussion summarizes the basis for 
this credit and for differences in associated requirements between the 
proposal and today's final rule.
    In the proposal, EPA reviewed published studies of Cryptosporidium 
removal through conventional sedimentation processes by Payment and 
Franco (1993), Kelly et al. (1995), Patania et al. (1995), States et 
al. (1997), Edzwald and Kelly (1998), and Dugan et al. (2001). These 
studies included bench-, pilot-, and full-scale processes, and the 
reported levels of Cryptosporidium removal varied widely, ranging from 
0.4- to 3.8-log. In addition, these studies also supported two other 
significant findings:

    (1) Proper coagulation significantly improves Cryptosporidium 
removal through sedimentation. In Dugan et al. (2001), for example, 
average Cryptosporidium removal across a sedimentation basin was 
1.3-log with optimal coagulation and decreased to 0.2-log when the 
coagulant dose was insufficient.
    (2) The removal of aerobic spores correlates well with the 
removal of Cryptosporidium when a coagulant is present. This 
indicates that aerobic spores, which are naturally present in 
surface waters, may be used as an indicator of Cryptosporidium 
removal in coagulated full-scale sedimentation processes.

    Cryptosporidium removal efficiencies in conventional sedimentation 
may be higher than in presedimentation due to differences in hydraulic 
loading rates, coagulant doses, and other factors. EPA identified no 
published studies of Cryptosporidium removal through presedimentation 
processes. In the proposal, however, EPA evaluated data on the removal 
of aerobic spores in the presedimentation processes of three PWSs as an 
indicator of Cryptosporidium removal (USEPA 2003a). All three PWSs 
added a coagulant (polymer, metal salts, or recycled sludge) to the 
presedimentation process. The mean removal of aerobic spores through 
presedimentation in the three PWSs ranged from 0.5- to 1.1-log over 
time

[[Page 690]]

spans ranging from several months to several years.
    These data support the finding that full-scale presedimentation 
processes can achieve Cryptosporidium removals of 0.5-log and greater 
under routine operating conditions and over an extended time period. 
Accordingly, EPA concluded that 0.5-log Cryptosporidium treatment 
credit for presedimentation processes is appropriate under certain 
conditions. Today's rule establishes three conditions for PWSs to 
receive this credit.
    The first condition for presedimentation to receive 0.5-log 
Cryptosporidium treatment credit is that the process must treat all 
flow reaching the treatment plant. Presedimentation cannot reduce the 
Cryptosporidium level entering a treatment plant by 0.5-log or greater 
on a continuous basis if the process is operated intermittently or 
treats only a fraction of the plant flow. EPA recognizes that for some 
PWSs, operating a presedimentation process intermittently in response 
to high turbidity levels is preferable to continuous operation. By 
establishing a requirement for continuous operation as a condition for 
treatment credit, EPA is not recommending against intermittent 
operation of presedimentation processes. Rather, EPA is only 
identifying one of the conditions under which a 0.5-log Cryptosporidium 
treatment credit for presedimentation appears to be justified.
    A second condition for presedimentation treatment credit is that 
the process must operate with coagulant addition. Available data 
support awarding 0.5-log Cryptosporidium treatment credit to a 
presedimentation process only when a coagulant is present. The full-
scale presedimentation data reviewed in the proposal involved coagulant 
addition, and literature studies indicate that Cryptosporidium removal 
through sedimentation can be substantially lower in the absence of 
sufficient coagulant. Further, the Stage 2 M-DBP Advisory Committee 
specifically recommended 0.5-log Cryptosporidium treatment credit for 
presedimentation with coagulation (USEPA 2000a). Based on these 
factors, EPA concluded that coagulation is a necessary condition for 
PWSs to receive treatment credit for presedimentation.
    The third condition for awarding treatment credit to 
presedimentation is that the process must achieve a monthly mean 
turbidity reduction of at least 0.5-log or meet alternative State-
approved performance criteria. This requirement stems from a 
recommendation by the SAB, which reviewed data for awarding treatment 
credit to presedimentation under the LT2ESWTR. In their report, the SAB 
concluded that available data were minimal to support 0.5-log 
prescribed credit for presedimentation and recommended that performance 
criteria other than overflow rate be included if credit is given for 
presedimentation (SAB 2003).
    In response to this recommendation by the SAB, EPA analyzed the 
relationship between removal of aerobic spores (as an indicator of 
Cryptosporidium removal) and reduction in turbidity in the full-scale 
presedimentation processes of three PWSs. The results of this analysis, 
which are shown in Table IV.D-2, suggest that presedimentation 
processes achieving a monthly mean reduction in turbidity of at least 
0.5-log have a high likelihood of reducing mean Cryptosporidium levels 
by 0.5-log or more. Consequently, EPA concluded that turbidity 
reduction is an appropriate performance criterion for awarding 
Cryptosporidium treatment credit to presedimentation basins. The Agency 
believes this performance criterion addresses the concern raised by the 
SAB.

  Table IV.D-2.--Relationship Between Mean Turbidity Reduction and the
     Percent of Months When Mean Spore Removal Was at Least 0.5 Log
------------------------------------------------------------------------
                                                            Percent of
                                                          months with at
                                                           least 0.5 Log
        Log reduction in turbidity (monthly mean)         Mean Reduction
                                                             in spores
                                                             (percent)
------------------------------------------------------------------------
at least 0.1-log........................................              64
at least 0.2-log........................................              68
at least 0.3-log........................................              73
at least 0.4-log........................................              78
at least 0.5-log........................................              89
at least 0.6-log........................................              91
at least 0.7-log........................................              90
at least 0.8-log........................................              89
at least 0.9-log........................................              95
at least 1.0-log........................................             96
------------------------------------------------------------------------
 Source: Data from Cincinnati Water Works, Kansas City Water Services
  Department, and St. Louis Water Division.

    The proposed rule required PWSs to achieve at least 0.5-log 
turbidity reduction through presedimentation in at least 11 of the 12 
previous consecutive months to be eligible for presedimentation 
treatment credit. EPA recognizes, however, that some PWSs will not be 
able to demonstrate at least 0.5-log turbidity reduction through 
presedimentation during months when raw water turbidity is lower. As a 
result, these PWSs would not be able to achieve treatment credit for 
their presedimentation basins. To provide more options for these PWSs, 
EPA has modified this requirement in today's final rule in two 
respects.
    The first modification is that in today's final rule, PWSs must 
demonstrate compliance with the conditions for presedimentation 
treatment credit on a monthly, rather that a yearly basis. This 
requirement allows treatment credit for presedimentation in any month a 
PWS can demonstrate at least 0.5-log turbidity reduction, even if the 
PWS cannot achieve this level of turbidity reduction in all months of 
the year.
    A PWS that meets the conditions for presedimentation treatment 
credit for only part of the year must implement other microbial toolbox 
options to comply with Cryptosporidium treatment requirements in the 
remainder of the year. Nevertheless, achieving presedimentation 
treatment credit for even part of the year may benefit certain PWSs. 
For example, a PWS may be able to reduce the level of disinfection it 
provides during the months it receives presedimentation treatment 
credit, or this treatment credit may provide a margin of safety to 
ensure compliance with Cryptosporidium treatment requirements.
    The second modification is the allowance for States to approve 
alternative performance criteria to turbidity reduction that 
demonstrate at least 0.5-log mean removal of micron-sized particulate 
material through the presedimentation process. EPA believes that 
aerobic spores are an appropriate alternative criterion. As described 
earlier, studies support the use of aerobic spores as an indicator of 
Cryptosporidium removal in coagulated sedimentation processes. If 
approved by the State, a PWS could receive 0.5-log treatment credit for 
presedimentation by demonstrating at least 0.5-log reduction in aerobic 
spores. The Toolbox Guidance Manual provides information on analytical 
methods for measuring aerobic spores. This may provide an option for 
PWSs that are not able to demonstrate 0.5-log turbidity reduction but 
have a sufficient concentration of aerobic spores in their raw water. 
PWSs may work with States to identify other alternative criteria, as 
well as appropriate monitoring to support use of the criteria.
c. Summary of Major Comments
    Public comments on the August 11, 2003, LT2ESWTR proposal supported 
allowing PWSs to achieve 0.5-log credit towards Cryptosporidium 
treatment requirements for presedimentation with

[[Page 691]]

coagulation. Some commenters also supported the proposed operational, 
monitoring, and performance conditions required for PWSs to receive 
this credit. Other commenters, however, opposed the proposed 
requirement for turbidity reduction as a condition for receiving 
presedimentation treatment credit. A summary of these commenters' 
concerns and EPA's responses follows.
    Commenters who opposed requiring turbidity reduction for 
presedimentation treatment credit were concerned that PWSs cannot 
achieve this criterion during periods when raw water turbidity is low. 
Further, these commenters stated that turbidity removal does not 
reflect the overall benefits of presedimentation, which improves the 
performance of the primary treatment train by equalizing water quality. 
Some commenters also provided data showing the reduction in turbidity 
and aerobic spore levels in the presedimentation processes of several 
PWSs and stated that turbidity removal may not be an appropriate 
indicator of acceptable performance for presedimentation basins. 
Several commenters suggested that EPA establish a limit on hydraulic 
overflow rate in place of a turbidity removal requirement.
    In response, EPA continues to believes that 0.5-log turbidity 
reduction is an appropriate performance indicator for 0.5-log 
Cryptosporidium reduction in presedimentation processes. EPA has 
reviewed the additional data submitted by commenters on the removal of 
turbidity and aerobic spores (as an indicator of Cryptosporidium 
removal) in full-scale presedimentation basins. These data are 
consistent with data reviewed for the proposal in showing that when 
turbidity removal was below 0.5-log, removal of aerobic spores was also 
usually below 0.5-log. Conversely, when turbidity reduction exceeded 
0.5-log, aerobic spore removal was typically higher than 0.5-log. 
Consequently, while there is not a one-to-one relationship between 
reduction in turbidity and reduction in aerobic spores, 0.5-log 
turbidity reduction is a reasonable indicator of when Cryptosporidium 
removal is likely to be at least 0.5-log.
    EPA recognizes, though, that 0.5-log turbidity reduction through 
presedimentation will not be feasible for some PWSs when raw water 
turbidity is low. Today's final rule contains several provisions to 
address this concern. First, PWSs can receive credit for 
presedimentation during any month the process achieves 0.5-log 
turbidity removal. Thus, PWSs that cannot achieve 0.5-log turbidity 
reduction year-round may receive credit for presedimentation in those 
months when they can meet this condition. Today's rule also allows PWSs 
to receive presedimentation credit using State-approved performance 
criteria other than turbidity reduction. If approved by the State, a 
PWS may receive credit for presedimentation by demonstrating, for 
example, 0.5-log reduction in aerobic spores. Finally, if 
presedimentation improves treatment plant performance by reducing and 
equalizing particle loading, a PWS can receive additional treatment 
credit under today's rule for achieving lower filtered water turbidity 
(see section IV.D.7).
5. Two-Stage Lime Softening
a. Today's Rule
    Lime softening in drinking water treatment involves the addition of 
lime and other chemicals to remove hardness (calcium and magnesium) 
through precipitation. In single-stage softening, chemical addition and 
hardness precipitation occur in a single clarification process prior to 
filtration. In two-stage softening, chemical addition and hardness 
precipitation occur in each of two sequential clarification processes 
prior to filtration. In some water treatment plants, a portion of the 
raw water bypasses a softening process (i.e., split softening) in order 
to achieve a desired pH and alkalinity level in the treated water.
    Under today's rule, single-stage softening with filtration receives 
a prescribed 3.0-log credit towards Cryptosporidium treatment 
requirements, which is equivalent to conventional treatment (see 
section IV.B). Two-stage softening receives an additional 0.5-log 
Cryptosporidium treatment credit during any month a PWS meets the 
following conditions:

    (1) Chemical addition and hardness precipitation occur in two 
separate and sequential softening stages prior to filtration; and
    (2) Both softening stages treat the entire plant flow taken from 
surface water sources or GWUDI (i.e., no portion of the plant flow 
from a surface water source may bypass either softening stage).

    Alternatively, PWSs may apply to the State for Cryptosporidium 
treatment credit for softening processes using a demonstration of 
performance, as described in section IV.D.9. Demonstration of 
performance provides an option for PWSs with softening processes that 
do not meet these conditions for prescribed treatment credit and for 
PWSs who seek greater than the prescribed Cryptosporidium treatment 
credit for their softening processes.
b. Background and Analysis
    Lime softening is a common practice that PWSs use to reduce water 
hardness, which is primarily calcium and magnesium. The addition of 
lime elevates the pH of the raw water. Elevation to pH 9.4 or higher 
causes precipitation of calcium carbonate and further elevation to pH 
10.6 or higher causes precipitation of magnesium hydroxide. Soda ash 
may be added with lime to precipitate non-carbonate hardness. Removal 
of the precipitate occurs through clarification (e.g., sedimentation 
basin) and filtration processes. Coagulants and recycled softening 
sludge are often used to enhance removal. In two-stage softening, the 
second stage is commonly used to precipitate magnesium, along with 
increased levels of calcium.
    In addition to reducing hardness, softening processes remove 
particulate material present in the raw water, including microbial 
pathogens like Cryptosporidium. Particulate material flocculates with 
the softening precipitate and is removed through the clarification and 
filtration processes, similar to a conventional treatment plant. The 
degree of Cryptosporidium removal will depend on the amount of 
precipitate formation, the use of coagulants, the raw water quality, 
and other factors. Available data indicate that the elevated pH used in 
softening does not inactivate Cryptosporidium or Giardia (Logsdon et 
al. 1994, Li et al. 2001), though it does inactivate some 
microorganisms like viruses (Battigelli and Sobsey, 1993, Logsdon et 
al. 1994).
    The Stage 2 M-DBP Advisory Committee recommended that lime 
softening be eligible for up to 1.0-log additional Cryptosporidium 
treatment credit based on a site-specific demonstration of performance, 
but did not recommend any prescribed credit for this process (USEPA 
2000a). After reviewing available data, however, EPA included a 
prescribed 0.5-log Cryptosporidium treatment credit for two-stage lime 
softening in the August 11, 2003 proposal (USEPA 2003a). This approach 
reflected a recommendation by the SAB, which supported an additional 
0.5-log treatment credit for two-stage lime softening if all the water 
passes through both stages (SAB 2003). The proposal also allowed for 
greater treatment credit through a demonstration of performance. The 
following discussion summarizes the basis for the lime softening 
treatment credit in today's final rule and differences with the 
proposal.
    In the proposal, EPA reviewed a study by Logsdon et al. (1994) that 
evaluated

[[Page 692]]

Cryptosporidium removal in full-scale lime softening plants. 
Cryptosporidium was detected in the raw water at 5 plants: one single-
stage plant and four two-stage plants. Based on measured levels, the 
removal of Cryptosporidium across the softening clarification 
(sedimentation) stages was 1.0-log in the single stage plant and ranged 
from 1.1-to 2.3-log in the two-stage plants. Cryptosporidium reductions 
from raw to filtered water were 0.6- and 2.2-log in the single stage 
plant and ranged from greater than 2.67- to greater than 3.85-log in 
the two-stage plants.
    EPA also evaluated data collected by PWSs on the removal of aerobic 
spores in full-scale lime softening plants. As discussed earlier, 
studies have shown the removal of aerobic spores to be an indicator for 
Cryptosporidium removal, and one pilot-scale study of a softening plant 
found significantly greater removal of Cryptosporidium than aerobic 
spores under similar treatment conditions (Clark et al., 2001). For the 
full-scale plants, average reductions in aerobic spores across the 
softening clarification stages were 2.4- and 2.8-log for two plants 
that practice two-stage softening and were 1.6- and 2.4-log for two 
plants that practice single-stage softening (USEPA 2003a).
    The Cryptosporidium removal data from Logsdon et al. (1994) and the 
aerobic spore removal data provided by PWSs indicate that a lime 
softening clarification stage can achieve greater than 0.5-log 
Cryptosporidium removal during routine operation. Consequently, EPA 
agrees with the SAB recommendation to award an additional 0.5-log 
Cryptosporidium treatment credit for two-stage softening. Today's rule 
establishes two-conditions for PWSs to receive this credit.
    The first condition for 0.5-log treatment credit for two-stage 
softening is that chemical addition and hardness precipitation must 
occur in two separate and sequential softening stages prior to 
filtration. The purpose of this condition is to ensure that plants 
receiving additional credit for two-stage softening actually have 
softening and associated particle removal occurring in each of two 
sequential clarification stages. Plants with other types of 
clarification processes in series with a softening stage are not 
eligible for two-stage softening credit. Such plants may, however, be 
eligible for additional treatment credit for other microbial toolbox 
options, such as presedimentation, or may achieve additional credit 
through a demonstration of performance.
    The second condition for two-stage softening treatment credit is 
that both softening stages must treat the entire plant flow taken from 
a surface water source or GWUDI. The SAB recommended this condition, 
which reflects the understanding that a softening stage is unlikely to 
reduce overall Cryptosporidium levels by 0.5-log or more if it treats 
only a fraction of the plant flow.
    EPA recognizes that some PWSs using softening will bypass a 
softening stage in order to maintain a desired pH and alkalinity level 
in the treated water, and EPA is not recommending against this practice 
generally. Rather, the restriction on bypassing a softening stage in 
today's rule applies only to PWSs that seek additional treatment credit 
for softening. Additionally, plants that soften both surface water and 
ground water are eligible for softening treatment credit if they bypass 
a softening stage only with ground water that is not under the direct 
influence of surface water.
    The proposal also required that a coagulant be present in both 
clarifiers for a PWS to be eligible for additional treatment credit for 
two-stage softening. EPA is not establishing this requirement in 
today's final rule. While many PWSs that practice softening add 
coagulants to improve the removal of precipitates and other particles, 
the SAB did not recommend coagulant addition as a condition for 
receiving treatment credit. Further, available data do not indicate 
that additional coagulant is necessary to achieve at least 0.5-log 
Cryptosporidium removal across a softening clarification stage if 
hardness precipitation is occurring.
c. Summary of Major Comments
    Public comments on the August 11, 2003, LT2ESWTR proposal supported 
awarding additional Cryptosporidium treatment credit for lime softening 
processes. EPA received specific comments on the types of lime 
softening processes eligible for additional treatment credit, the 
amount of additional treatment credit awarded, and the need for a 
coagulant. A summary of these commenters' concerns and EPA's responses 
follows.
    In regard to the types of lime softening processes eligible for 
treatment credit, commenters recommended that EPA better define two-
stage softening. Commenters stated that two-stage softening involves 
two separate reaction chambers with the addition of the softening 
chemical at the beginning of each chamber. Some commenters recommended 
that eligibility for additional treatment credit should be based on the 
level of softening precipitate formed or the settled water turbidity 
and not on whether a plant practices single- or two-stage softening. 
Another commenter recommended that any plant designs with multiple, 
continuously operated clarification processes in series should be 
eligible for additional treatment credit.
    In response, EPA has refined the definition of two-stage softening 
in today's final rule, which requires that softening processes employ 
chemical addition and hardness precipitation in two sequential stages 
to be eligible for the prescribed additional treatment credit. EPA 
agrees with commenters that the level of precipitate formation will 
influence the degree of Cryptosporidium removal. Available data, 
however, indicate that two-stage softening will generally achieve more 
Cryptosporidium removal than single-stage softening. Consequently, EPA 
believes that two-stage softening should be eligible for the additional 
prescribed 0.5-log treatment credit. Plants with single-stage softening 
may receive additional treatment credit under today's rule through a 
demonstration of performance. Similarly, plants that employ multiple 
clarification process other than softening in series may receive 
additional treatment credit either as presedimentation or through a 
demonstration of performance.
    With respect to the amount of additional Cryptosporidium treatment 
credit for two-stage softening, most commenters supported awarding 3.0-
log treatment credit to single-stage lime softening, equivalent to a 
conventional treatment plant, and an additional prescribed 0.5-log 
treatment credit for two-stage lime softening. A few commenters 
requested that two-stage lime be granted an additional Cryptosporidium 
treatment credit of 1.0-log, based on the level of aerobic spore 
removal measured across softening clarifiers.
    EPA agrees with most commenters and the SAB that 0.5-log is an 
appropriate level of additional prescribed Cryptosporidium treatment 
credit for two-stage softening. Where plants are able to demonstrate a 
significantly higher level of removal of Cryptosporidium or an 
indicator like aerobic spores, they may apply for additional treatment 
credit through a demonstration of performance.
    Commenters stated that achieving particle removal in lime softening 
is not dependent on a coagulant like a metal salt or organic polymer. 
Some commenters recommended that coagulant be defined to include 
softening chemicals like lime and magnesium hydroxide (a softening

[[Page 693]]

precipitate). EPA agrees that available data do not demonstrate the 
need for a traditional metal salt or organic coagulant for effective 
particle removal in softening. Accordingly, today's final rule does not 
require the use of a coagulant as a condition for additional treatment 
credit in two-stage softening. Instead, each stage must involve 
chemical addition and hardness precipitation. EPA intends this 
requirement to ensure that softening and associated particle removal 
occur in each stage if a plant is to receive additional treatment 
credit for two-stage softening.
6. Bank Filtration
a. Today's Rule
    Bank filtration is a water treatment process that uses one or more 
pumping wells to induce or enhance natural surface water infiltration 
and to recover that surface water from the subsurface after passage 
through a river bed or bank(s). Under today's rule, bank filtration 
that serves as pretreatment to a filtration plant is eligible for 
Cryptosporidium treatment credit if it meets the following criteria:
     Wells with a ground water flow path of at least 25 feet 
receive 0.5-log treatment credit; wells with a ground water flow path 
of at least 50 feet receive 1.0-log treatment credit. The ground water 
flow path must be determined as specified in this section.
     Only wells in granular aquifers are eligible for treatment 
credit. Granular aquifers are those comprised of sand, clay, silt, rock 
fragments, pebbles or larger particles, and minor cement. A system must 
characterize the aquifer at the well site to determine aquifer 
properties. Systems must extract a core from the aquifer and 
demonstrate that in at least 90 percent of the core length, grains less 
than 1.0 mm in diameter constitute at least 10 percent of the core 
material.
     Only horizontal and vertical wells are eligible for 
treatment credit.
     For vertical wells, the ground water flow path is the 
measured distance from the edge of the surface water body under high 
flow conditions (determined by the 100 year floodplain elevation 
boundary or by the floodway, as defined in Federal Emergency Management 
Agency flood hazard maps) to the well screen. For horizontal wells, the 
ground water flow path is the measured distance from the bed of the 
river under normal flow conditions to the closest horizontal well 
lateral screen.
     Systems must monitor each wellhead for turbidity at least 
once every four hours while the bank filtration process is in 
operation. If monthly average turbidity levels, based on daily maximum 
values in the well, exceed 1 NTU, the system must report this result to 
the State and conduct an assessment within 30 days to determine the 
cause of the high turbidity levels in the well. If the State determines 
that microbial removal has been compromised, the State may revoke 
treatment credit until the system implements corrective actions 
approved by the State to remediate the problem.
     Springs and infiltration galleries are not eligible for 
treatment credit under this section, but are eligible for credit under 
the demonstration of performance provisions described in section 
IV.D.9.
    Alternatively, PWSs may apply to the State for Cryptosporidium 
treatment credit for bank filtration using a demonstration of 
performance. States may award greater than 1.0-log Cryptosporidium 
treatment credit for bank filtration based on a site-specific 
demonstration. For a bank filtration demonstration of performance 
study, today's rule establishes the following criteria:
     The study must follow a State-approved protocol and must 
involve the collection of data on the removal of Cryptosporidium or a 
surrogate for Cryptosporidium and related hydrogeologic and water 
quality parameters during the full range of operating conditions.
     The study must include sampling both from the production 
well(s) and from monitoring wells that are screened and located along 
the shortest flow path between the surface water source and the 
production well(s).

The Toolbox Guidance Manual provides guidance on conducting site-
specific bank filtration studies, including analytical methods for 
measuring aerobic and anaerobic spores, which may serve as surrogates 
for Cryptosporidium removal.
    PWSs using existing bank filtration as pretreatment to a filtration 
plant at the time the PWS must begin source water Cryptosporidium 
monitoring under today's rule must sample the well for the purpose of 
determining bin classification. These PWSs are not eligible to receive 
additional treatment credit for bank filtration. In these cases, the 
performance of the bank filtration process in reducing Cryptosporidium 
levels will be reflected in the monitoring results and bin 
classification.
    PWSs using bank filtration without additional filtration must 
collect source water samples in the surface water (i.e., prior to bank 
filtration) to determine bin classification unless the State approves 
an alternative monitoring location. This applies to systems using bank 
filtration to meet the Cryptosporidium removal requirements of the 
IESWTR or LT1ESWTR under the provisions for alternative filtration 
demonstration in 40 CFR 141.173(b) or 141.552(a). Bank filtration 
criteria for Cryptosporidium removal credit under today's rule do not 
apply to existing State actions regarding alternative filtration 
Cryptosporidium removal credit for IESWTR or LT1ESWTR compliance. PWSs 
using GWUDI sources must collect samples from the well (i.e., the 
ground water).
b. Background and Analysis
    Bank filtration is a water treatment process that makes use of 
surface water that has naturally infiltrated into ground water through 
a river bed or bank and is recovered via a pumping well. River bed 
infiltration is typically enhanced by the pumping action of nearby 
wells. Bank filtrate is water that is drawn into a pumping well from a 
nearby surface water source after having traveled through the 
subsurface (i.e., aquifer) and mixing with other ground water. In bank 
filtration, microorganisms and other particles are removed by contact 
with the aquifer materials.
    The Stage 2 M-DBP Advisory Committee recommended a prescribed 
Cryptosporidium treatment credit of 1.0-log for bank filtration with 
the option for PWSs to receive greater treatment credit through a site-
specific demonstration of performance (USEPA 2000a). The August 11, 
2003 proposal included criteria, similar to those in today's final 
rule, for PWSs to receive prescribed treatment credits of 0.5- and 1.0-
log (USEPA 2000a). The following discussion summarizes the basis for 
these credits and for differences in associated requirements between 
the proposal and today's final rule.
    Directly measuring the removal of Cryptosporidium through bank 
filtration is difficult due to the relatively low oocyst concentrations 
typically present in surface and ground water. In the proposal, EPA 
reviewed bank filtration field studies that measured the removal of 
Cryptosporidium surrogates, specifically aerobic and anaerobic 
bacterial endospores (Havelaar et al. 1995, Rice et al. 1996, Pang et 
al. 1998, Arora et al. 2000, Medema et al. 2000, and Wang et al. 2001). 
These microorganisms are suitable surrogates because they are resistant 
to inactivation in the subsurface, similar in size and shape to 
Cryptosporidium, and present in both surface and ground water at 
concentrations that allow calculation of log removal across the surface 
water-

[[Page 694]]

ground water interface and within the aquifer. In addition, EPA 
reviewed studies of the transport of Cryptosporidium through soil 
materials in laboratory column studies (Harter et al. 2000).
    Based on these studies, EPA concluded that bank filtration 
processes can achieve significant Cryptosporidium removal and that 
prescribed Cryptosporidium treatment credits of 0.5-log and 1.0-log are 
appropriate under certain conditions. These conditions are as follows: 
Only wells located in unconsolidated, predominantly sandy aquifers are 
eligible
    The bank filtration removal process performs most efficiently when 
the aquifer is comprised of granular materials with open pore-space for 
water flow around the grains. In these granular porous aquifers, the 
flow path is meandering, thereby providing ample opportunity for 
microorganisms to come into contact with and attach to a grain surface. 
Accordingly, only wells located in unconsolidated, granular aquifers 
are eligible for bank filtration treatment credit.
    Granular aquifers are those comprised of sand, clay, silt, rock 
fragments, pebbles or larger particles and minor cement. Specifically, 
a PWS must extract a core from the aquifer and demonstrate that in at 
least 90 percent of the core length, grains less than 1.0 mm in 
diameter constitute at least 10 percent of the core material. 
Laboratory column studies of Cryptosporidium transport (Harter et al., 
2000) and field studies of aerobic bacterial endospore passage in the 
subsurface (Pang et al., 1998) support these criteria.

Only Horizontal and Vertical Wells Are Eligible

    A number of devices are used for the collection of ground water 
including horizontal and vertical wells, spring boxes, and infiltration 
galleries. Among these, only horizontal and vertical wells are eligible 
for log removal credit because spring boxes and infiltration galleries 
are components of engineered systems designed to speed transport 
through or by-pass the naturally protective riverbed or bank.

Wells Must be Located 25 Feet From the Surface Water Source To Be 
Eligible for 0.5-Log Credit and Located at Least 50 Feet From the 
Surface Water Source To Be Eligible for 1.0-Log Credit

    A vertical or horizontal well located adjacent to a surface water 
body is eligible for bank filtration credit if there is sufficient 
ground water flow path length to effectively remove oocysts. 
Specifically, the ground water flow path must be at least 25 feet and 
50 feet for 0.5-log and 1.0-log Cryptosporidium treatment credit, 
respectively. The ground water flow path to a vertical well is the 
measured distance from the edge of the surface water body under high 
flow conditions (determined by the 100 year floodplain elevation 
boundary or floodway, as defined in Federal Emergency Management Agency 
flood hazard maps) to the wellhead. The ground water flow path to a 
horizontal well is the measured distance from the bed of the river 
under normal flow conditions to the closest horizontal well lateral.
    These required flow path distances for Cryptosporidium treatment 
credit are based on pathogen and surrogate monitoring data from bank 
filtration field studies (Wang et al. 2001, Havelaar et al. 1995, 
Medema et al. 2000). Results from these studies show that significant 
removal of anaerobic and aerobic spores can occur during passage across 
the surface water--ground water interface, with lesser removal 
occurring during ground water transport within the aquifer away from 
that interface. The ground water--surface water interface is usually 
comprised of finer grained material that lines the bottom of the 
riverbed. Typically, the thickness of the interface is small, ranging 
from a few inches to a foot.
    These results suggest that during normal and low surface water 
elevations, the surface water-ground water interface will perform 
effectively to remove microbial contamination like Cryptosporidium. 
During short periods of flooding, substantially lower removal rates may 
occur due to scouring of the riverbed and removal of the protective, 
fine-grained material. Assessing the mean Cryptosporidium removal that 
a bank filtration process will achieve over the period of a year 
requires consideration of both high and low removal periods. By 
considering all time intervals with differing removal rates over the 
period of a year, EPA concluded that 0.5-log removal over 25 feet and 
1.0-log removal over 50 feet are appropriate estimates of the mean 
performance of a bank filtration process (USEPA 2003a).

Wells Must Be Continuously Monitored for Turbidity

    Similar pathogen removal mechanisms are expected to occur in slow 
sand filtration and bank filtration. Under the 40 CFR 141.73(b)(1), the 
turbidity level of slow sand filtered water must be 1 NTU or less in 95 
percent of the measurements taken each month. Turbidity sampling is 
required once every four hours, but may be reduced to once per day 
under certain conditions. Just as turbidity monitoring is used to 
provide assurance that the removal credit assigned to a slow sand 
filter is being realized, today's rule requires turbidity monitoring at 
least once every 4 hours for all bank filtration wells that receive 
treatment credit.
    If monthly average turbidity levels (based on daily maximum values 
in the well) exceed 1 NTU, the PWS must report this result to the State 
and conduct an assessment to determine the cause of the high turbidity 
levels in the well. If the State determines that microbial removal has 
been compromised, the State may revoke treatment credit until the PWS 
implements corrective actions to remediate the problem.

Demonstration of Performance

    EPA recognizes that some bank filtration processes may achieve mean 
Cryptosporidium removal greater than 1-log. Consequently, today's rule 
allows PWSs to receive greater than 1.0-log Cryptosporidium treatment 
credit for bank filtration through a State-approved demonstration of 
performance study. This allowance is a change from the proposed rule, 
which did not explicitly recognize demonstration of performance for 
bank filtration (USEPA 2003a). This change reflects EPA's agreement 
with public comment, described next, which recommended that EPA 
explicitly recognize the option to conduct a bank filtration 
performance study for greater than 1.0-log treatment credit.
    A demonstration of performance study must involve the collection of 
data on the removal of Cryptosporidium or surrogates and related 
hydrogeologic and water quality parameters during the full range of 
operating conditions. PWSs must sample from both the production well(s) 
and one or more monitoring wells that are screened and located along 
the shortest flow path between the surface water and the production 
well(s). This will allow determination of the removal efficiency of the 
aquifer.
    Because directly measuring Cryptosporidium removal will not be 
feasible for most PWSs, today's rule allows PWSs to sample for a State-
approved indicator, such as aerobic bacterial endospores. Research has 
shown that aerobic spores can be very mobile in the subsurface 
environment (Pang et al. 1998), and data collected by Wang et al. 
(2001) indicate that aerobic spores are present in some surface waters 
in sufficient quantity to allow measurement of log removal values.
    EPA has provided guidance on conducting site-specific bank 
filtration

[[Page 695]]

studies in the Toolbox Guidance Manual. This guidance discusses data 
needs and analysis for a performance demonstration so that the State 
may tailor the study plan to meet site-specific hydrogeological and 
operational conditions.
    In summary, EPA believes that full-scale field data support 
prescribed Cryptosporidium treatment credit up to 1.0-log for bank 
filtration under the required conditions for set-back distance, aquifer 
material, collection device type, and turbidity monitoring. 
Demonstration of performance provides an appropriate opportunity for 
States to award higher Cryptosporidium treatment credit for bank 
filtration on a site-specific basis.
    For PWSs using bank filtration when they must conduct source water 
monitoring for bin classification, the required sampling locations 
reflect the intent for this monitoring to capture the level of 
Cryptosporidium entering a PWS's primary filtration treatment process. 
Where bank filtration serves as pretreatment to a filtration plant, 
PWSs must collect source water samples after bank filtration but prior 
to the filtration plant. In this case, the Cryptosporidium removal that 
bank filtration achieves will be reflected in the monitoring results 
and bin classification for the filtration plant. In contrast, where 
bank filtration is the primary filtration process, meaning that a PWS 
uses bank filtration to comply with the Cryptosporidium treatment 
requirements of the IESWTR or LT1ESWTR, PWSs must collect samples in 
the surface water source (e.g, the river).
c. Summary of Major Comments
    Public comments on the August 11, 2003, LT2ESWTR proposal supported 
awarding Cryptosporidium treatment credit for bank filtration. Many 
commenters, however, stated that the proposed levels of credit (0.5- 
and 1.0-log) were insufficient. To address this issue, commenters 
supported allowing PWSs to obtain greater treatment credit by 
performing a site-specific study of bank filtration removal efficiency. 
Commenters recommended that site-specific bank filtration studies 
involve the measurement of surrogates for Cryptosporidium removal using 
monitoring wells located along the shortest flow path between the 
surface water and the production well.
    EPA agrees that some bank filtration sites may achieve greater than 
1.0-log Cryptosporidium removal. Today's rule establishes the proposed 
bank filtration Cryptosporidium treatment credits of 0.5- and 1.0-log 
and allows PWSs to apply to the State for higher levels of credit 
through a site-specific demonstration of performance. In such a study, 
PWSs must measure the removal of Cryptosporidium or a State-approved 
surrogate using monitoring wells located along the flow path, as 
recommended by commenters.
    Some commenters cited research addressing appropriate surrogate 
organisms for estimating Cryptosporidium removal in surface water 
treatment plants and bank filtration sites. Commenters recommended that 
EPA recognize aerobic endospores as a surrogate measure in 
Cryptosporidium removal studies, including those for bank filtration.
    EPA agrees that based on available information, aerobic spores are 
suitable Cryptosporidium removal surrogates for bank filtration 
processes due to their size, resistance to inactivation, and 
concentration in surface and ground waters. Data from several bank 
filtration sites on the use of aerobic spores as a Cryptosporidium 
removal surrogate are available. The Toolbox Guidance Manual identifies 
aerobic spores as suitable in conjunction with other hydrogeologic data 
for making site-specific determinations for additional Cryptosporidium 
removal credit.
    In guidance, EPA suggests that where feasible, PWSs measure diatom 
species in conjunction with aerobic spores in bank filtration studies 
because Cryptosporidium oocysts are intermediate in size between the 
two surrogate groups. Further, EPA recognizes the current uncertainties 
and limitations in available information on surrogates for bank 
filtration and will update guidance as warranted by new information.
7. Combined Filter Performance
a. Today's Rule
    For water treatment plants that use filtration, the turbidity of 
the filtered water is an indicator of how effectively the plant is 
removing particulate matter, including microbial pathogens, from the 
raw water. PWSs using conventional filtration treatment or direct 
filtration receive an additional 0.5-log Cryptosporidium treatment 
credit during any month the PWS meets the following standard:
     The turbidity level of representative samples of a PWS's 
filtered water (i.e., the combined filter effluent) is less than or 
equal to 0.15 NTU in at least 95 percent of the measurements taken each 
month. PWSs must continue to measure turbidity as specified in 40 CFR 
141.74(a) and (c), which generally require sampling at least every four 
hours using approved methods.

PWSs using other types of filtration processes, including slow sand, 
diatomaceous earth, membranes, bag, or cartridge filtration, are not 
eligible for this treatment credit.
b. Background and Analysis
    Turbidity is a method defined parameter that is based on measuring 
the amount of light scattered by suspended particles in a solution. 
This measure can detect the presence of a wide variety of particles in 
water, including microorganisms, but cannot provide specific 
information on particle type, number, or size. In filtered water, the 
turbidity level indicates how well the filtration and other upstream 
clarification processes have performed in removing particles from the 
raw water, with lower turbidity indicating better particle removal. 
Thus, lower filtered water turbidity is associated with a decreased 
likelihood that microbial pathogens like Cryptosporidium have passed 
through the filtration plant and into the water distributed to 
consumers.
    Under existing regulations, PWSs that filter must monitor turbidity 
in the combined filter effluent (CFE) at least every four hours using 
approved methods, although States may reduce this frequency to once per 
day for PWSs serving 500 people or fewer (40 CFR 141.74(a) and (c)). 
For PWSs using conventional or direct filtration, at least 95 percent 
of the CFE turbidity measurements must be less than or equal to 0.3 
NTU, and the turbidity must never exceed 1 NTU (40 CFR 141.173(a) and 
141.551(a)-(b)).
    The Stage 2 M-DBP Advisory Committee recommended an additional 0.5-
log Cryptosporidium treatment credit for PWSs that achieve a CFE 
turbidity less than or equal to 0.15 NTU in at least 95 percent of 
measurements per month (USEPA 2000a). This 95th percentile turbidity 
standard is one half the level required under existing regulations for 
PWSs using conventional or direct filtration, as stated earlier. The 
August 11, 2003 proposal included this treatment credit for PWSs using 
conventional or direct filtration (USEPA 2003a), and EPA is 
establishing it in today's final rule with no changes from the 
proposal. The following discussion summarizes the basis for this 
treatment credit.
    In the proposal, EPA analyzed the improvement in Cryptosporidium 
removal that conventional and direct filtration plants realize when 
operating at lower effluent turbidity levels. For this analysis, EPA 
estimated that PWSs

[[Page 696]]

complying with the existing 95th percentile CFE turbidity standard of 
0.3 NTU will typically operate with filter effluent turbidity between 
0.1-0.2 NTU; PWSs complying with a CFE standard of 0.15 NTU were 
estimated to operate with filter effluent turbidity less than 0.1 NTU. 
Accordingly, EPA compared Cryptosporidium removal efficiencies when 
effluent turbidity was below 0.1 NTU with those when effluent turbidity 
was in the range of 0.1-0.2 NTU.
    Studies by Patania et al. (1995), Emelko et al. (1999), and Dugan 
et al. (2001) observed the average removal of Cryptosporidium to be 
0.5-to 1.2-log greater when filter effluent turbidity was less than 0.1 
NTU in comparison to removal with effluent turbidity between 0.1-0.2 
NTU. These studies, therefore, indicate that PWSs complying with a 
filter effluent turbidity standard of 0.15 NTU will achieve at least 
0.5-log greater Cryptosporidium removal than PWSs complying with the 
existing 0.3 NTU standard. Based on this finding, EPA concluded that an 
additional 0.5-log Cryptosporidium treatment credit is appropriate for 
PWSs using conventional or direct filtration that meet a 95th 
percentile CFE turbidity standard of 0.15 NTU.
    Other types of filtration processes, such as slow sand, 
diatomaceous earth, membranes, bag, or cartridge filtration, are not 
eligible for this treatment credit. These filtration processes remove 
Cryptosporidium through different mechanisms than those operative in 
rapid granular media filtration, which is used in conventional and 
direct filtration. Available data do not establish a similar 
relationship between lower filter effluent turbidity and improved 
Cryptosporidium removal efficiency for these other filtration 
processes.
    The SAB reviewed the proposed additional Cryptosporidium treatment 
credit for PWSs that operate with very low filtered water turbidity. In 
their report, the SAB stated that further lowering of turbidity would 
result in further reductions in Cryptosporidium in the effluent from 
filtration processes, but available data were limited in showing the 
exact removal that can be achieved. Based on the data provided, the SAB 
recommended that no additional treatment credit be given to plants that 
demonstrate a CFE turbidity of 0.15 NTU or less (SAB 2003).
    In addressing this SAB recommendation, EPA recognizes that 
precisely quantifying the increase in Cryptosporidium removal that a 
particular filtration plant will realize when operating at lower filter 
effluent turbidity is not generally feasible. Available data, though, 
consistently show that removal of Cryptosporidium is at least 0.5-log 
greater when filter effluent turbidity reflects compliance with a 0.15 
NTU standard in comparison to a 0.3 NTU standard. Further, treatment 
plants operating at lower filter effluent turbidity will achieve 
increased removal of other microbial pathogens present in the raw 
water. In consideration of these factors, EPA believes that PWSs should 
receive an additional 0.5-log Cryptosporidium treatment credit when at 
least 95 percent of CFE turbidity measurements are less than or equal 
to 0.15 NTU.
    Another key issue in establishing additional treatment credit based 
on low filtered water turbidity is the performance of analytical 
instruments (turbidimeters) to accurately measure turbidity at low 
levels. In the proposal, EPA reviewed studies of low level turbidity 
measurements by EPA (1998c), Sadar (1999), and Letterman et al. (2001). 
Among the significant findings of these studies are the following:

    (1) On-line turbidimeters typically had a positive bias (i.e., a 
higher turbidity reading) in comparison to bench-top turbidimeters. 
EPA expects that most PWSs that receive additional treatment credit 
for low filter effluent turbidity will use on-line turbidimeters. 
This finding suggests that the error in turbidimeter readings may be 
generally conservative, so that PWSs will operate at lower than 
required turbidity levels.
    (2) Different turbidimeters did not agree well when used to 
measure low level turbidity, which may be due to differences in 
instrument design. This finding suggests that low level turbidity 
measurements may be viewed as a relative indicator of water quality 
improvement at a particular PWS but may be less applicable for 
making comparisons among different PWSs.

    In addition, the American Society for Testing and Materials (ASTM) 
has issued standard test methods for measurement of turbidity below 5 
NTU by on-line (ASTM 2001) and static (ASTM 2003) instruments. These 
methods specify that the instrument should permit detection of 
turbidity differences of 0.01 NTU or less in waters having turbidities 
of less than 1.00 NTU (ASTM 2001) and 5.0 NTU (ASTM 2003), 
respectively.
    After reviewing these studies and the ASTM methods, EPA concluded 
that currently available monitoring equipment can reliably measure 
turbidity at levels of 0.15 NTU and lower. Rigorous calibration and 
maintenance of turbidity monitoring equipment is necessary, however. 
EPA has developed guidance on proper calibration, operation, and 
maintenance of turbidimeters (USEPA 1999c).
c. Summary of Major Comments
    Public comment on the August 11, 2003, LT2ESWTR proposal supported 
awarding additional Cryptosporidium treatment credit for PWSs that 
achieve lower filtered water turbidity. Commenters raised specific 
concerns with the criteria for PWSs to receive this credit, the 
available data that support this credit, and the performance of 
turbidimeters for measuring turbidity at very low levels. A summary of 
these comments and EPA's responses follows.
    Most commenters supported awarding 0.5-log additional 
Cryptosporidium treatment credit for PWSs that achieve at least 95 
percent of CFE turbidity measurements less than or equal to 0.15 NTU. A 
few commenters, however, recommended that PWSs only receive additional 
treatment credit for demonstrating this level of turbidity performance 
in each individual filter effluent (IFE), rather than the CFE. In 
addition, one commenter stated that PWSs should be required to monitor 
CFE turbidity every 15 minutes, rather than every four hours as 
required under current regulations.
    In response, EPA agrees with the recommendation of most commenters 
and has established additional Cryptosporidium treatment credit based 
on meeting a 95th percentile turbidity level of 0.15 NTU in the CFE. 
EPA recognizes, however, that achieving low turbidity in each IFE may 
represent a higher level of performance than achieving low turbidity in 
the CFE. As described in the next section, EPA has also established 
standards for additional Cryptosporidium treatment credit based on low 
IFE turbidity in today's rule. EPA does not have data indicating that 
PWSs should monitor the CFE turbidity at a higher frequency than every 
four hours, as required under existing regulations. Consequently, EPA 
is not changing the frequency of required CFE turbidity monitoring as a 
condition for PWSs to receive additional treatment credit under today's 
rule.
    One commenter summarized additional studies that provide data on 
the improvement in Cryptosporidium removal efficiency at lower filter 
effluent turbidity levels. According to this commenter, these studies 
demonstrate that lowering filter effluent turbidity from 0.3 to 0.15 
NTU translates to an improvement in Cryptosporidium removal of more 
than 1.5-log, with individual studies showing a range of >0.7-log to 
>3-log based on median removal. EPA finds that these studies bolster 
the conclusion that PWSs operating to meet 0.15 NTU in the filter 
effluent will achieve at least 0.5-

[[Page 697]]

log greater Cryptosporidium removal than PWSs operating to meet 0.3 
NTU. Thus, they support the additional 0.5-log Cryptosporidium 
treatment credit under today's rule for PWSs meeting 0.15 NTU at the 
95th percentile in the CFE.
    In regard to the measurement of low level turbidity, some 
commenters raised concerns that turbidimeters used by the U.S. water 
supply industry do not agree when used to measure turbidity in the 0.01 
to 0.5 NTU range. Further, these differences are independent of the 
calibration method used and can be significant when comparing 
instruments by different manufacturers. Other commenters stated that 
turbidimeters can accurately reflect turbidity values less than 0.15 
NTU if properly calibrated, and some commenters cited the ASTM method 
development process to support this assessment. In addition, commenters 
suggested that available guidance on turbidity measurement provides 
quality assurance measure that can reduce analytical uncertainty.
    EPA agrees with commenters that available methods and instruments 
are adequate to demonstrate compliance with a 0.15 NTU turbidity level. 
In particular, EPA believes that monitoring low level turbidity can be 
effective for demonstrating water quality improvements at individual 
plants, but also recognizes that the performance of turbidimeters used 
at different plants may vary. Further, calibration and maintenance of 
turbidity monitoring equipment is critical, and EPA has developed 
guidance on these procedures (USEPA 1999c).
8. Individual Filter Performance
a. Today's Rule
    PWSs using conventional filtration treatment or direct filtration 
receive an additional 0.5-log Cryptosporidium treatment credit during 
any month the PWS meets the following criteria:
     The filtered water turbidity for each individual filter is 
less than or equal to 0.15 NTU in at least 95 percent of the 
measurements recorded each month; and
     No individual filter has a measured turbidity level 
greater than 0.3 NTU in two consecutive measurements taken 15 minutes 
apart.
PWSs must continue to monitor turbidity for each individual filter 
continuously and record the results every 15 minutes, as required under 
40 CFR 141.174 and 141.560.
    PWSs that receive this 0.5-log Cryptosporidium treatment credit for 
individual filter performance also receive 0.5-log treatment credit for 
combined filter performance, as described in section IV.D.7, for a 
total additional treatment credit of 1.0-log. Conversely, PWSs are not 
required to pursue individual filter performance credit to remain 
eligible for combined filter performance credit.
    If a PWS has received credit for individual filter performance to 
comply with its Cryptosporidium treatment requirements and fails to 
meet the required criteria for this credit during any month, the PWS 
will not incur a treatment technique violation if the State determines 
the following:
     The failure to meet the required criteria for individual 
filter performance treatment credit was due to unusual and short-term 
circumstances that could not reasonably be prevented through optimizing 
treatment plant design, operation, and maintenance; and
     The PWS has experienced no more than two such failures in 
any calendar year.
    This treatment credit is not applicable to other types of 
filtration processes, including slow sand, diatomaceous earth, 
membranes, bag, or cartridge filtration.
b. Background and Analysis
    Awarding additional treatment credit for individual filter 
performance is based on the expectation that achieving low filtered 
water turbidity in each individual filter will provide increased 
protection against microbial pathogens. Most treatment plants have 
multiple filters. Moderately elevated turbidity in the effluent from a 
single filter may not significantly affect the turbidity of the 
combined filter effluent, but may indicate a reduction in the overall 
pathogen removal efficiency of the filtration process. Consequently, a 
primary goal in optimizing water treatment plant performance is 
ensuring that each filter always produces very low turbidity water.
    The criteria for PWSs to achieve the additional 1.0-log 
Cryptosporidium treatment credit for individual filter performance 
reflect goals of Phase IV of the Partnership for Safe Water 
(Partnership). The Partnership is a voluntary cooperative program 
involving PWSs, professional associations, and Federal and State 
regulatory agencies that seeks to increase protection against microbial 
contaminants by optimizing water treatment plant performance. The Stage 
2 M-DBP Advisory Committee recommended 1.0-log treatment credit for 
PWSs that successfully participate in a peer review program and 
identified Phase IV of the Partnership as a program where such credit 
would be appropriate (USEPA 2000a).
    At the time of the Advisory Committee recommendation, the 
performance goals for Phase IV of the Partnership reflected those of 
the EPA Composite Correction Program (USEPA 1991a) and involved an on-
site evaluation by a third-party team. Phase IV performance goals for 
individual filters included filtered water turbidity less than 0.1 NTU 
at least 95 percent of the time based on daily maximum values and a 
maximum measurement of 0.3 NTU. The purpose of the on-site evaluation 
was to confirm that a PWS had met Phase IV performance goals or had 
achieved the highest level of performance given its unique raw water 
quality.
    After the Stage 2 M-DBP Agreement in Principle was signed in 
September 2000, the Partnership eliminated on-site third-party 
evaluation as a component of Phase IV. Instead, Phase IV required 
completion of an Optimization Assessment Spreadsheet in which the PWS 
entered water treatment data to demonstrate that it had achieved Phase 
IV performance levels. The application also required narratives related 
to the administrative support and operational capabilities necessary to 
sustain performance long-term.
    The August 11, 2003 LT2ESWTR proposal included a 1.0-log 
Cryptosporidium treatment credit for PWSs that met the individual 
filter performance goals of Phase IV of the Partnership (i.e., 95 
percent of daily maximum values below 0.1 and no values above 0.3 NTU) 
(USEPA 2003a). Rather than requiring an application package with 
historical data and narratives, however, the proposed rule required 
PWSs to report filter effluent turbidity data to the State each month 
to demonstrate compliance with these filter performance goals.
    The Partnership modified the Phase IV goals for individual filter 
performance in 2003. A revised goal is filtered water turbidity less 
than 0.10 NTU at least 95 percent of the time based on values recorded 
at 15 minute time intervals. Thus, where the earlier goal was based on 
daily maximum values for each filter, the revised goal is based on all 
values for each filter--a less stringent approach. The Partnership made 
this modification after finding that none of the water treatment plants 
that had been evaluated could consistently meet the 0.1 NTU goal using 
daily maximum values and, further, that this goal was biased against 
plants with more filters.
    In today's final rule, EPA has adjusted the criteria from the 
proposal for PWSs

[[Page 698]]

to receive additional treatment credit based on individual filter 
effluent turbidity. These adjustments are in response to the changes 
the Partnership made to Phase IV individual filter performance goals. 
Under today's rule, PWSs receive 1.0-log additional Cryptosporidium 
treatment credit if effluent turbidity from each filter is less than or 
equal to 0.15 NTU at least 95 percent of the time and never exceeds 0.3 
NTU in two consecutive measurements taken 15 minutes apart.
    EPA expects that PWSs will operate at less than 0.1 NTU in order to 
comply with a regulatory limit of 0.15 NTU. Further, EPA believes that 
assessing individual filter compliance with a maximum turbidity level 
of 0.3 NTU based on two consecutive measurements taken 15 minutes apart 
is appropriate. This approach allows for brief fluctuations in 
turbidimeter readings that may not indicate a degradation in filtered 
water quality to occur without penalizing a PWS, but it should catch 
filters that significantly exceed 0.3 NTU over the course of a month. 
EPA applied this approach to individual filter monitoring under the 
IESWTR and LT1ESWTR. Consequently, EPA regards these criteria as 
comparable to the revised Partnership Phase IV standards for individual 
filter performance.
    In addition, today's rule gives States authority to determine 
whether to issue a treatment technique violation for PWSs that exceed 
individual filter performance limits. This authority applies in the 
case where a PWS receives credit for individual filter performance to 
meet the treatment requirements of today's rule and fails to achieve 
the criteria to receive this credit during a month. If the State 
determines that this failure was due to unusual and short-term 
circumstances that could not reasonably be prevented through treatment 
optimization, the State may choose not to issue a treatment technique 
violation, which the PWS otherwise will incur. Because this authority 
should be applied only to unusual plant circumstances, a State cannot 
make this determination if a PWS has experienced more than two such 
failures in any calendar year.
    EPA is granting States this authority because PWSs that 
consistently meet the criteria for individual filter performance 
treatment credit may occasionally experience short-term deviations from 
these criteria due to circumstances largely beyond the PWS's control. 
An example of such a circumstance may be malfunctioning equipment that 
a PWS quickly removes from service, but that nevertheless prevents the 
PWS from fully meeting individual filter performance criteria in a 
particular month. EPA believes that States should only apply this 
authority in cases where PWSs have consistently achieved the criteria 
for individual filter performance treatment credit in previous months.
    The approach in today's final rule for valuing individual filter 
performance treatment credit differs from the approach in the proposal. 
EPA's intent in both the proposal and today's rule is to award an 
additional 1.0-log Cryptosporidium treatment credit to PWSs that meet 
the criteria for individual filter performance. In the proposal, 
however, PWSs could receive 1.0-log additional treatment credit 
specifically for meeting the individual filter performance criteria, 
but were then not eligible to receive any treatment credit under the 
combined filter performance option. In today's rule, PWSs receive 0.5-
log credit for the individual filter performance option and also 
receive an additional 0.5-log treatment credit for the combined filter 
performance option (discussed in section IV.D.7), resulting in 1.0-log 
total additional credit. EPA has made this modification so that if a 
PWS fails in an attempt to achieve individual filter performance 
credit, the PWS is clearly still eligible to received combined filter 
performance credit.
    In a review of a draft LT2ESWTR proposal, the SAB recommended that 
PWSs receive 0.5-log, rather than 1.0-log, additional Cryptosporidium 
treatment credit for achieving individual filter effluent turbidity 
below 0.15 NTU at the 95th percentile (SAB 2003). In response to this 
SAB recommendation, today's rule requires additional individual filter 
performance criteria to support 1.0-log total additional treatment 
credit. Specifically, today's rule incorporates the Partnership Phase 
IV performance goal that individual filter effluent turbidity never 
exceed 0.3 NTU (as described earlier, EPA concluded that determining 
compliance with this standard based on two consecutive measurements 
taken 15 minutes is appropriate and consistent with existing 
regulations). Thus, EPA believes that these criteria, in conjunction 
with the expectation that controlling effluent turbidity at all filters 
individually rather than just the combined filter effluent will 
generally result in lower microbial risk, justify 1.0-log additional 
treatment credit.
c. Summary of Major Comments
    Public comment on additional treatment credit for individual filter 
performance in the August 11, 2003 proposal raised a number of issues: 
changes in the Partnership Phase IV criteria and achievability of the 
proposed criteria for this credit, credit for participating in peer 
review programs, and a review process for data that exceed regulatory 
limit. A summary of these comments and EPA's responses follows.
    Several commenters stated that PWSs could not consistently achieve 
the proposed individual filter effluent turbidity criterion of 95 
percent of daily maximum measurements less than or equal to 0.1 NTU. 
Commenters provided data on turbidity levels in PWSs to support this 
assertion and indicated that the Partnership modified this criterion in 
the Phase IV individual filter performance goals because PWSs could not 
meet it. Alternatives recommended by commenters for the final rule 
included the use of the revised Partnership Phase IV goals for 
individual filter effluent turbidity or a more stringent criterion for 
combined filter effluent turbidity.
    In response, EPA agrees that current Partnership Phase IV goals 
provide appropriate criteria for awarding 1.0-log total additional 
Cryptosporidium treatment credit. Today's rule grants this total credit 
to PWSs that meet a 95th percentile individual filter effluent 
turbidity limit of 0.15 NTU, and EPA expects that PWSs complying with 
this limit will operate under the Partnership goal of 0.10 NTU. EPA 
does not support awarding a higher level of additional treatment credit 
for a more stringent combined filter effluent turbidity criterion, 
beyond the 0.5-log credit available under combined filter performance 
(see section IV.D.7). The purpose of the individual filter performance 
toolbox option is to recognize the higher pathogen removal PWSs will 
likely achieve by maintaining very low effluent turbidity for each 
individual filter.
    A few commenters suggested that as an alternative to establishing 
numerical criteria for individual filter performance, today's rule 
should award additional treatment credit for PWSs that successfully 
participate in a peer review program. In addition to the Partnership, 
commenters listed the Area Wide Optimization Program and the Texas 
Optimization Program as examples of programs that will provide for 
comprehensive improvements in treatment performance.
    EPA agrees that participation in peer review programs is beneficial 
for PWSs. Further, such programs may assist PWSs in meeting the 
filtration performance criteria in today's rule for additional 
Cryptosporidium treatment credit. EPA does not believe, however, that 
mere participation in a peer review program

[[Page 699]]

is an appropriate basis for awarding additional treatment credit. 
Rather, to ensure national consistency in standards for compliance with 
treatment requirements, EPA has concluded that additional treatment 
credit should be based on PWSs meeting specified criteria for enhanced 
treatment performance.
    Another significant issue raised by commenters is the need for a 
review process for deviations from the criteria for individual filter 
performance due to circumstances that cannot be prevented through plant 
optimization. An example given by several commenters is a filter that 
malfunctions and is taken out of service, but that may have exceeded 
the individual filter performance turbidity criteria for a short period 
when the filter was operating.
    EPA agrees that circumstances may occur that are beyond the PWS's 
control and that prevent the PWS from fully meeting the criteria for 
individual filter performance in a particular month. If a PWS relies on 
individual filter performance treatment credit to meet the treatment 
requirements of today's rule and the PWS fails to meet all criteria for 
this credit in a given month, the State may review the reasons for this 
failure. If the State finds that the failure was due to circumstances 
that could not be prevented through plant optimization, the State may 
choose not to issue a treatment technique violation on up to two such 
occasions in a calendar year.
9. Demonstration of Performance
a. Today's Rule
    A demonstration of performance is a site-specific test that 
assesses the Cryptosporidium removal efficiency of a water treatment 
plant or a treatment process within a plant. Under today's rule, PWSs 
may undertake demonstration of performance testing for the following 
purposes:

    (1) To establish a Cryptosporidium treatment credit that is 
higher than the prescribed treatment credit in today's rule for a 
water treatment plant or a treatment process in the microbial 
toolbox; or
    (2) To establish a Cryptosporidium treatment credit for a 
treatment process that is not included in the microbial toolbox or 
that does not meet the design or operational criteria for prescribed 
treatment credit in the microbial toolbox.

    The specific requirements that apply to demonstration of 
performance testing are as follows:
     PWSs may receive Cryptosporidium treatment credit for a 
water treatment plant or a treatment process within a plant that is 
based on a site-specific demonstration of Cryptosporidium removal 
efficiency. This demonstration of performance treatment credit may be 
greater than or less than any prescribed treatment credit in today's 
rule.
     The site-specific demonstration of Cryptosporidium removal 
efficiency must follow a State-approved protocol and may involve the 
use of surrogates rather than Cryptosporidium.
     The State must approve through written notification any 
treatment credit based on a demonstration of performance. As a 
condition of approval, the State may designate monitoring and treatment 
performance criteria the PWS must meet and report on an ongoing basis 
to remain eligible for the credit. The State may designate such 
criteria to verify that the PWS maintains the operating conditions 
under which the State approved the demonstration of performance 
treatment credit.
     PWSs are not eligible for prescribed treatment credit for 
any treatment process that is included in a demonstration of 
performance credit.
b. Background and Analysis
    The prescribed Cryptosporidium treatment credits in today's rule 
for water treatment plants and for treatment processes in the microbial 
toolbox are based on conservative estimates of mean Cryptosporidium 
removal efficiencies. Due to site-specific conditions, however, some 
PWSs will achieve greater Cryptosporidium removal than reflected in the 
prescribed treatment credits. In addition, some PWSs will have 
treatment processes that are not included in the microbial toolbox or 
that do not meet microbial toolbox criteria for prescribed treatment 
credit. In all these cases, PWSs have the option to undertake 
demonstration of performance testing to establish an appropriate level 
of Cryptosporidium treatment credit for the treatment plant or 
treatment process.
    The option for demonstration of performance testing in today's rule 
reflects a recommendation by the Stage 2 M-DBP Advisory Committee. 
Specifically, the Committee stated that the LT2ESWTR should allow site-
specific testing both to establish Cryptosporidium treatment credit 
above the prescribed credit for microbial toolbox processes and to 
demonstrate Cryptosporidium removal for technologies not listed in the 
microbial toolbox. The August 11, 2003 LT2ESWTR proposal included the 
demonstration of performance option (USEPA 2003a), and EPA is 
establishing it in today's final rule.
    Demonstration of performance testing will be specific to a 
particular site and will depend on the treatment processes being 
tested, water quality, plant infrastructure, PWS resources, and other 
factors. Consequently, today's rule does not establish specific 
protocols for demonstration of performance testing. Rather, today's 
rule gives States the authority to approve testing protocols developed 
by PWSs and to determine what level of Cryptosporidium treatment credit 
is appropriate. The Toolbox Guidance Manual provides recommendations to 
PWSs and States on conducting demonstration of performance testing, 
including analytical methods for measuring aerobic and anaerobic 
spores.
    In general, demonstration of performance testing should encompass 
the full range of expected operating conditions and should 
conservatively assess the degree of Cryptosporidium removal that a 
treatment process can reliably achieve. Directly quantifying the 
removal of Cryptosporidium typically is not feasible in full-scale 
testing due to limitations in source water concentrations and 
analytical method performance. Consequently, demonstration of 
performance testing that is conducted at full-scale may involve the use 
of surrogates, such as aerobic spores, that have been shown to 
correlate with the removal of Cryptosporidium. PWSs and States may also 
consider the use of pilot-scale studies in conjunction with full-scale 
studies for demonstration of performance testing.
    As a condition of approving a demonstration of performance credit, 
the State may designate treatment performance criteria the PWS must 
meet on an ongoing basis to remain eligible for the credit. For 
example, if a PWS conducts a demonstration of performance study while 
operating with very low filtered water turbidity, the State may 
establish as a condition of approving treatment credit based on the 
study that the PWS must continue operating at the low filtered water 
turbidity. EPA believes this condition is necessary because, in this 
example, if the PWS were to begin operating at a higher filtered water 
turbidity level, the demonstration of performance study results might 
no longer represent the PWSs actual performance.
    PWSs are not eligible for prescribed treatment credit for any 
treatment process that is included in a demonstration of performance 
credit. For example, if a PWS receives a demonstration of performance 
treatment credit of 4-log for Cryptosporidium removal through a 
conventional treatment plant (i.e., coagulation/sedimentation/
filtration), the PWS is not

[[Page 700]]

also eligible for additional treatment credit for combined filter 
performance. In this case, the demonstration of performance testing 
accounts for the removal achieved by filtration.
c. Summary of Major Comments
    Public comment on the August 11, 2003 LT2ESWTR proposed supported 
inclusion of the demonstration of performance option to award site-
specific treatment credit to PWSs. Commenters stated that many well-run 
surface water treatment plants achieve significantly greater 
Cryptosporidium removal than the prescribed treatment credit, and 
demonstration of performance testing is needed to award an appropriate 
level of credit in such cases. Two aspects of this option that received 
significant public comment are the provision for States to award less 
than the prescribed treatment credit if indicated by testing results 
and the need for guidance on demonstration of performance testing. 
These comments and EPA's responses are summarized as follows.
    Several commenters recommended that EPA eliminate the provision 
that allows States to award less than the prescribed treatment credit 
based on demonstration of performance testing. These commenters stated 
that pilot- and full-scale testing is conservative and challenging to 
implement and that for past regulations, States generally have not 
awarded lower treatment credit based on a site-specific study. If this 
provision remains in the regulation, commenters suggested that EPA 
provide criteria addressing how it should be applied. Such criteria 
should recognize the conservative nature of testing with surrogates for 
Cryptosporidium removal and the potential for misleading or flawed 
testing results.
    In response, EPA believes that States should have the discretion to 
award either more or less treatment credit than the prescribed credit 
on a case-by-case basis where a State has site-specific information 
that an alternative credit is appropriate. Today's rule allows this. 
EPA recognizes, however, that demonstration of performance testing 
should be designed to provide a conservative estimate of treatment 
efficiency and, as such, is not generally intended to reduce the level 
of treatment credit a PWS receives. Further, results from demonstration 
of performance testing should be rigorously evaluated for flaws and 
bias prior to being used to support either a higher or lower treatment 
credit. The Toolbox Guidance Manual identifies approaches States may 
wish to consider in awarding higher or lower treatment credit.
    Many commenters stated that EPA should provide thorough guidance on 
demonstration of performance testing. Topics for this guidance 
suggested by commenters include approaches to demonstrating treatment 
credit, minimum duration of testing, the use of safety factors, and 
periodic reconfirmation of testing results. Some commenters recommended 
that guidance address both full-scale testing with surrogates like 
aerobic spores and pilot-scale testing with Cryptosporidium or 
surrogates. Other commenters recommended that testing should be limited 
to full-scale processes and that testing with pilot-scale 
representations of full-scale equipment should be discouraged.
    In the Toolbox Guidance Manual, EPA provides direction on 
procedures for demonstration of performance testing that addresses 
issues raised by commenters. These issues include surrogates for full-
scale testing, potential roles for pilot-scale testing in conjunction 
with full-scale testing, minimum duration of testing to capture the 
full range of operating conditions, the analysis of data from testing 
to establish treatment credit, and routine monitoring to verify that 
the conditions under which demonstration of performance credit is 
awarded are maintained during routine operation. EPA believes that this 
guidance will assist PWSs and States with implementing demonstration of 
performance testing appropriately.
10. Bag and Cartridge Filtration
a. Today's Rule
    Under today's rule, PWSs may receive Cryptosporidium treatment 
credit of up to 2.0-log for an individual bag or cartridge filter and 
up to 2.5-log for two or more bag or cartridge filters operated in 
series. To be eligible for this treatment credit, filters must meet the 
definition of a bag or cartridge filter and must undergo challenge 
testing to demonstrate removal efficiency with an applied safety 
factor, as described in this section.
    Today's rule defines bag and cartridge filters as pressure driven 
separation processes that remove particulate matter larger than 1 
micrometer using an engineered porous filtration media through either 
surface or depth filtration. Bag filters are constructed of a non-
rigid, fabric filtration media housed in a pressure vessel in which the 
direction of flow is from the inside of the bag to the outside. 
Cartridge filters are typically constructed as rigid or semi-rigid, 
self-supporting filter elements housed in a pressure vessel in which 
flow is from the outside of the cartridge to the inside.
    Today's rule treats bag and cartridge filters equivalently, with 
the following exception: If a cartridge filter meets the definition of 
a membrane filtration process and can be direct integrity tested 
according to the criteria specified in section IV.D.11, a PWS has the 
option to seek greater treatment credit for the filter as a membrane. 
Section IV.D.11 describes criteria for awarding treatment credit to 
membranes.
    Today's rule requires challenge testing to establish 
Cryptosporidium treatment credit for bag and cartridge filters. This 
challenge testing is product-specific and not site-specific. Once 
challenge testing is performed on a specific bag or cartridge 
filtration product, PWSs that install the specific filtration product 
are not required to repeat challenge testing at individual sites. For a 
PWS to receive Cryptosporidium treatment credit for a bag or cartridge 
filter, challenge testing must meet the following criteria:
     Challenge testing must be conducted on full-scale filters 
that match the filters the PWS will use in materials, construction, and 
associated housing or pressure vessel. If treatment credit will be 
based on filters operated in series then challenge testing must be 
performed on the filters in series.
     Challenge testing must involve measuring the removal by 
the filter of either Cryptosporidium or a surrogate that is removed no 
more efficiently than Cryptosporidium (i.e., the ``challenge 
particulate'').
     The analytical method used to measure removal in the 
challenge test must discretely quantify the specific challenge 
particulate. The maximum allowable feed water concentration of the 
challenge particulate used during a challenge test is 10,000 times the 
analytical method detection limit of the challenge particulate in the 
filtrate.
     During challenge testing, filters must be operated at the 
maximum design flow rate and for a duration sufficient to reach the 
maximum design pressure drop (i.e., ``terminal pressure drop''). PWSs 
may not operate bag or cartridge filters outside of these design 
parameters during routine use. In order to achieve terminal pressure 
drop during challenge testing, adding particulate matter, such as fine 
carbon test dust or bentonite clay particles, to the test water is 
allowed and may be necessary.
     In each challenge test, the removal of the challenge 
particulate must be measured during three periods over the

[[Page 701]]

filtration cycle: (1) Within two hours of start-up of a new filter, (2) 
when the pressure drop is between 45 and 55 percent of the terminal 
pressure drop, and (3) when the pressure drop has reached 100 percent 
of the terminal pressure drop. A log removal value (LRV) must be 
calculated for each of these periods as follows: LOG10 
(filter influent challenge particulate level) - LOG10 
(filter effluent challenge particulate level). For each filter tested, 
the LRV for the filter (LRVfilter) is equal to the minimum 
of these three LRVs.
     The LRVfilter values for each filter that is 
tested are used to determine the removal efficiency that is assigned to 
the specific bag or cartridge filter product (i.e., a filter product 
line) or combination of filters in series. If fewer than twenty filters 
are tested, the removal efficiency of the filter product line is equal 
to the lowest LRVfilter among the filters tested (today's 
rule does not specify a minimum number of filters to test). If twenty 
or more filters are tested, the removal efficiency of the filter 
product line is equal to the 10th percentile of the 
LRVfilter values among the filters tested.
     The Cryptosporidium treatment credit assigned to an 
individual bag or cartridge filter is equal to the removal efficiency 
established during challenge testing minus a 1.0-log factor of safety, 
up to a maximum treatment credit of 2.0-log (e.g., if challenge testing 
demonstrates a removal efficiency of 3.0-log or greater, the filter is 
eligible to receive 2.0-log Cryptosporidium treatment credit).
     The Cryptosporidium treatment credit assigned to 
configurations of two or more bag or cartridge filters operated in 
series is equal to the removal efficiency established during challenge 
testing minus a 0.5-log factor of safety, up to a maximum treatment 
credit of 2.5-log (e.g., if challenge testing demonstrates a removal 
efficiency of 3-log or greater, the filter receives 2.5-log 
Cryptosporidium treatment credit).
    If a previously tested bag or cartridge filter is modified in a 
manner that could change the removal efficiency of the filter product 
line, a new removal efficiency must be established for the modified 
filter through challenge testing. If approved by the State, data from 
challenge testing conducted prior to promulgation of today's rule may 
be considered in lieu of additional testing. However, the prior testing 
must have been conducted in a manner that demonstrates a removal 
efficiency for Cryptosporidium commensurate with the treatment credit 
awarded to the filter.
b. Background and Analysis
    Bag and cartridge filters are widely used by very small PWSs and in 
point-of-entry applications to remove particulate material from raw 
water, including microbial pathogens like Cryptosporidium. Depending on 
water quality and treatment plant infrastructure, these filters may be 
used as the sole filtration step or as a polishing filter that follows 
primary filtration processes. A critical aspect of bag and cartridge 
filters as defined in today's rule is that they cannot undergo direct 
integrity testing, which is used to detect leaks that could result in 
contamination of the treated water. Cartridge filters that meet the 
definition of a membrane process and can be direct integrity tested are 
considered membranes under today's rule, and these are described in 
section IV.D.11.
    The Stage 2 M-DBP Advisory Committee recommended Cryptosporidium 
treatment credits of 1.0- and 2.0-log for bag and cartridge filters, 
respectively (USEPA 2000a), and the August 11, 2003 LT2ESWTR proposal 
included criteria for PWSs to receive these treatment credits. The 
proposed criteria required challenge testing and the application of a 
1.0-log factor of safety to establish treatment credit. In today's 
final rule, EPA has modified these criteria to allow both bag and 
cartridge filters to be eligible for 2.0-log credit and to allow 2.5-
log credit with a 0.5-log factor of safety for bag or cartridge filters 
operated in series. The following discussion summarizes the basis for 
these criteria and for differences between the proposal and today's 
final rule.
    In the proposal, EPA reviewed bag and cartridge filtration studies 
by Long (1983), Schaub et al. (1993), Goodrich et al. (1995), Ciardelli 
(1996a and 1996b), Li et al. (1997), Roessler (1998), Enriquez et al. 
(1999), NSF (2001a and 2001b), and Cornwell and LeChevallier (2002). 
Results from these studies indicated that both bag and cartridge 
filters exhibit variable removal efficiency, ranging from 0.5- to 3.6-
log. No correlation between the pore size rating established by the 
manufacturer and the removal efficiency of the filter was apparent. 
Additionally, available data did not indicate a strong relationship 
between commonly used process monitoring parameters, such as turbidity 
and pressure drop, and Cryptosporidium removal efficiency.
    Due to this lack of correlation between either design criteria or 
process monitoring and removal efficiency, today's rule requires 
challenge testing of filters to establish Cryptosporidium treatment 
credit. Challenge testing must measure the removal across the filter of 
Cryptosporidium or a surrogate, like polystyrene microspheres, that is 
removed no more efficiently than Cryptosporidium (Long 1983, Li et al. 
1997, NSF 2002b). Further, because studies have shown the removal 
efficiency of some bag and cartridge filters to decrease over the 
course of a filtration cycle (Li et al. 1997, NSF 2001a,b), challenge 
testing must assess removal efficiency during three periods: within two 
hours of startup of a new filter, between 45-55 percent of terminal 
pressure drop, and at the end of the run after terminal pressure drop 
is realized.
    Bag and cartridge filter challenge testing is product-specific and 
not site-specific since the intent of this testing is to demonstrate 
the removal capabilities of the filtration device rather than evaluate 
the feasibility of implementing the technology at a specific plant. 
Challenge testing must be conducted using full-scale filter elements to 
assess the performance of the entire unit, including the filtration 
media, seals, filter housing and other components integral to the 
filtration system. To be eligible for treatment credit when operated in 
series, filters must be tested in series. Multiple filters of the same 
type can be tested to provide a better statistical basis for estimating 
removal efficiency. The Toolbox Guidance Manual provides information on 
bag and cartridge filter challenge testing.
    Today's rule establishes the proposed requirement that a 1.0-log 
factor of safety be applied to the removal efficiency established 
during challenge testing for individual bag or cartridge filters when 
determining treatment credit. Thus, to receive a 2.0-log treatment 
credit, a removal efficiency of at least 3.0-log must be demonstrated 
during challenge testing. EPA believes that this factor of safety is 
necessary because integrity testing with bag and cartridge filters is 
not possible (note: under today's rule, cartridge filters that can be 
integrity tested are classified as membranes and no safety factor is 
required; see section IV.D.11).
    Challenge testing provides an estimate of the removal efficiency of 
a bag or cartridge filter product line but does not involve testing 
every filter. Further, it does not fully capture the variation in 
filter performance that will occur over time during routine use. For 
membranes, the use of direct integrity tests, such as a pressure hold 
test, that is correlated to removal efficiency addresses this problem. 
With bag and cartridge filters, however, EPA is aware

[[Page 702]]

of no equivalent test, and parameters like turbidity and pressure 
differential that may be monitored with these filters have not been 
shown to correlate with Cryptosporidium removal efficiency. 
Consequently, a safety factor is necessary to account for variation in 
individual filter performance relative to challenge test results.
    Individual bag and cartridge filters are eligible for a maximum 
Cryptosporidium treatment credit of 2.0-log. EPA proposed this level of 
credit for cartridge filters but proposed a 1.0-log maximum credit for 
bag filters, as recommended by the Advisory Committee. However, after 
further reviewing available data, EPA has concluded that treatment 
studies do not support establishing different limits on treatment 
credit for bag and cartridge filters. Accordingly, today's rule treats 
bag and cartridge filters equivalently. EPA continues to believe that 
2.0-log is an appropriate maximum treatment credit for a single bag or 
cartridge filter, based on available data on the removal of 
Cryptosporidium and surrogates by these processes and the absence of a 
direct integrity test.
    Today's rule also establishes criteria for awarding treatment 
credit to bag or cartridge filters operated in series. EPA believes 
that the use of these filters in series provides clear advantages in 
comparison to operation of a single filter. Series operation will 
achieve both greater removal efficiency and improved reliability by 
lessening the impact of variation in the performance of a single 
filter. In consideration of these factors, bag or cartridge filters 
operated in series are eligible for a higher Cryptosporidium treatment 
credit of 2.5-log and require a lower safety factor of 0.5-log applied 
to challenge test results when determining treatment credit.
c. Summary of Major Comments
    In response to the August 11, 2003 proposal, EPA received 
significant public comment on the following issues related to bag and 
cartridge filtration: the allowable treatment credit, the factor of 
safety applied to challenge testing results to determine treatment 
credit, and the procedure for determining the removal efficiency. A 
summary of these comments and EPA's responses follows.
    In regard to the proposed treatment credits, several commenters 
recommended that bag and cartridge filters should be eligible for up to 
2.0- and 2.5-log credit, respectively, if supported by the challenge 
test results. Others commented that filters should be allowed to 
qualify for removal credits at or below the 1.0- and 2.0-log credits in 
the proposal. EPA agrees that additional flexibility should be provided 
with respect to the removal credit awarded to bag and cartridge 
filters. After reviewing these comments and reassessing data presented 
in the proposal on the removal efficiencies of bag and cartridge 
filters, EPA revised the proposal to allow up to 2.0-log treatment 
credit for either a single bag or cartridge filter. In addition, 
today's rule allows up to 2.5-log credit for bag or cartridge filters 
operated in series.
    With respect to the 1.0-log safety factor applied to challenge test 
results to determine treatment credit, some commenters supported this 
approach, while others recommended a reduced safety factor. In 
response, EPA continues to believe that a 1.0-log safety factor is 
appropriate to address variability in individual filter performance and 
in the absence of a direct integrity test for bag and cartridge 
filters. Where filters are operated in series, however, EPA agrees that 
the safety factor should be reduced. Series operation provides an 
intrinsic process safety and will dampen some of the variability in 
removal efficiency observed for individual filters. Thus, EPA is 
reducing the factor of safety to 0.5-log for configurations consisting 
of two or more filters in series.
    Commenters requested that EPA clarify the procedure used to 
determine the removal efficiency of bag and cartridge filters. In 
response, expanded and clarified guidance on conducting challenge tests 
to determine removal efficiency for bag and cartridge filters has been 
included in the Toolbox Guidance Manual.
11. Membrane Filtration
a. Today's Rule
    Today's final rule establishes criteria for awarding 
Cryptosporidium treatment credit to membrane filtration processes. To 
receive removal credit, filters must meet the definition of a membrane 
filtration process and undergo challenge testing to establish removal 
efficiency; PWSs must periodically verify system integrity through 
direct integrity testing and perform continuous indirect integrity 
monitoring during use. The removal credit awarded to a membrane process 
is based on the removal efficiency demonstrated during challenge 
testing and the sensitivity of the direct integrity test.
    For the purpose of today's rule, membrane filtration is defined as 
a pressure or vacuum driven separation process in which particulate 
matter larger than 1 micrometer is rejected by an engineered barrier, 
primarily through a size-exclusion mechanism, and which has a 
measurable removal efficiency of a target organism that can be verified 
through the application of a direct integrity test.

Membrane Challenge Testing

    Any membrane filter used to meet the treatment requirements of 
today's rule must undergo challenge testing to determine its 
Cryptosporidium removal efficiency. Challenge testing establishes the 
maximum Cryptosporidium treatment credit a membrane filtration process 
is eligible to receive, provided this value is less than or equal to 
the sensitivity of the direct integrity test, as described later in 
this section. Challenge testing for membranes is product-specific, and 
PWSs that install membranes that have successfully undergone challenge 
testing are not required to repeat testing at their sites. Membrane 
challenge testing must meet the following criteria:
     Challenge testing must be conducted on either an identical 
full-scale module or a smaller-scale module identical in material and 
similar in construction to the membrane modules the PWS will use. A 
module is the smallest component of a membrane unit in which a specific 
membrane surface area is housed in a device with a filtrate outlet 
structure.
     Either Cryptosporidium or a surrogate that is removed no 
more efficiently than Cryptosporidium must be used as the challenge 
particulate during challenge testing.
     The analytical method used to measure removal in the 
challenge test must discretely quantify the specific challenge 
particulate. The maximum allowable feed water concentration used during 
a challenge test is 6.5-log (3.16 x 10\6\) times the detection limit of 
the challenge particulate in the filtrate.
     Challenge testing must be conducted under representative 
hydraulic conditions at the maximum design flux and maximum design 
process recovery as specified by the manufacturer for the membrane 
filtration process. Flux is defined as the throughput of a pressure 
driven membrane process expressed as flow per unit of membrane area. 
Recovery is defined as the volumetric percent of feed water that is 
converted to filtrate over the course of an operating cycle 
uninterrupted by events such as chemical cleaning or a solids removal 
process (i.e., backwashing).
     The removal efficiency for the membrane is determined from 
the results of the challenge test, expressed as a log removal value 
(LRV). A LRV must be calculated for each membrane module evaluated 
during the challenge

[[Page 703]]

test based on the feed and filtrate concentrations of the challenge 
particulate for that module. The individual LRVs for each module are 
used to determine the overall removal efficiency of the membrane 
product. If fewer than twenty modules are tested, the overall removal 
efficiency is assigned a value equal to the lowest of the 
representative LRVs for the various modules tested. If twenty or more 
modules are tested, then the overall removal efficiency is assigned a 
value equal to the 10th percentile of the representative LRVs for the 
various modules tested.
     As part of the challenge test, a quality control release 
value (QCRV) must be established for a non-destructive performance test 
(e.g., bubble point test, diffusive airflow test, pressure/vacuum decay 
test) that demonstrates the Cryptosporidium removal capability of the 
membrane module. The non-destructive performance test must be applied 
to each membrane module a PWS uses in order to verify Cryptosporidium 
removal capability. Membrane modules that do not meet the established 
QCRV are not eligible for the Cryptosporidium removal credit 
demonstrated during challenge testing.
    If a previously tested membrane product is modified in a manner 
that could change the removal efficiency of the membrane or the 
applicability of non-destructive performance test and associated QCRV, 
the modified membrane filter must be challenge tested to establish the 
removal efficiency and QCRV. If approved by the State, data from 
challenge testing conducted prior to promulgation of today's rule may 
be considered in lieu of additional testing. However, the prior testing 
must have been conducted in a manner that demonstrates a removal 
efficiency for Cryptosporidium commensurate with the treatment credit 
awarded to the filter.

Membrane Direct Integrity Testing

    In order to receive Cryptosporidium treatment credit for a membrane 
filtration process, PWSs must conduct direct integrity testing in a 
manner that demonstrates a removal efficiency equal to or greater than 
the removal credit awarded to the membrane filtration process. A direct 
integrity test is defined as a physical test applied to a membrane unit 
in order to identify and isolate integrity breaches (i.e., one or more 
leaks that could result in contamination of the filtrate).
    Each membrane unit must be independently direct integrity tested, 
where a membrane unit is defined as a group of membrane modules that 
share common valving which allows the unit to be isolated from the rest 
of the system for the purpose of integrity testing or other 
maintenance. The direct integrity test must be applied to the physical 
elements of the entire membrane unit including membranes, seals, 
potting material, associated valving and piping, and all other 
components which under compromised conditions could result in 
contamination of the filtrate.
    Common direct integrity tests include those that apply pressure or 
vacuum (such as the pressure decay test and diffusive airflow test) and 
those that measure the rejection of a particulate or molecular marker 
(such as spiked particle monitoring). Today's final rule does not 
stipulate the use of a particular direct integrity test. Instead, the 
direct integrity test must meet performance criteria for resolution, 
sensitivity, and frequency.
    ``Resolution'' is defined as the smallest leak that contributes to 
the response from a direct integrity test. Any direct integrity test 
applied to meet the requirements of this rule must have a resolution of 
3 micrometers or less. The manner in which resolution is determined 
will depend on the type of direct integrity test used (i.e., pressure-
based versus marker-based tests).
    ``Sensitivity'' is defined as the maximum LRV that can be reliably 
verified by the direct integrity test. The sensitivity of the direct 
integrity test applied to a membrane filtration process to meet the 
Cryptosporidium treatment requirements of this rule must be equal to or 
greater than the removal credit awarded to the membrane filtration 
process. Furthermore, the increased concentration of suspended solids 
that occurs on the high pressure side of the membrane in some module 
designs must be considered in the sensitivity determination (i.e., the 
scouring action of some membrane designs keeps the accumulated solids 
in suspension where they may pass through an integrity breach). 
Specifically, the sensitivity of the direct integrity test is reduced 
by a factor that quantifies the increased concentration of suspended 
solids relative to the feed concentration.
    The ``frequency'' of direct integrity testing specifies how often 
the test is performed over an established time interval. Direct 
integrity tests available at the time of promulgation are applied 
periodically and must be conducted on each membrane unit at a frequency 
of not less than once per day that the unit is in operation, unless the 
State determines that less frequent testing is acceptable. If 
continuous direct integrity test methods become available that also 
meet the sensitivity and resolution criteria described earlier, such a 
continuous test may be used in lieu of periodic testing.
    PWSs must establish a direct integrity test control limit that is 
indicative of an integral membrane unit capable of meeting the 
Cryptosporidium removal credit awarded to the membrane. If the control 
limit for the direct integrity test is exceeded, the membrane unit must 
be taken off-line for diagnostic testing and repair. The membrane unit 
may only be returned to service after the repair has been completed and 
confirmed through the application of a direct integrity test. A monthly 
report must be submitted to the State summarizing all direct integrity 
test results above the control limit and the corrective action that was 
taken in each case.

Continuous Indirect Integrity Monitoring

    Available direct integrity test methods are applied periodically 
since the membrane unit must be taken out of service to conduct the 
test. In order to provide some measure of process performance between 
direct integrity testing events, PWSs must perform continuous indirect 
integrity monitoring on each membrane unit. Continuous indirect 
integrity monitoring is defined as monitoring some aspect of filtrate 
water quality that is indicative of the removal of particulate matter 
at a frequency of at least once every 15 minutes. If a continuous 
direct integrity test is implemented that meets the resolution and 
sensitivity criteria described previously in this section, continuous 
indirect integrity monitoring is not required.
    Unless the State approves an alternative parameter, continuous 
indirect integrity monitoring must include continuous filtrate 
turbidity monitoring. If the filtrate turbidity readings are above 0.15 
NTU for a period greater than 15 minutes, the PWS must perform direct 
integrity testing on the associated membrane unit.
    If the State approves an alternate parameter for continuous 
indirect integrity monitoring, the State must approve a control limit 
for that parameter. If the parameter exceeds the control limit for a 
period greater than 15 minutes, the PWS must perform direct integrity 
testing on the associated membrane unit.
    PWSs must submit a monthly report to the State summarizing all 
continuous indirect integrity monitoring results triggering direct 
integrity testing and the corrective action that was taken in each 
case.
    EPA has developed the Membrane Filtration Guidance Manual to assist

[[Page 704]]

systems with implementation of these requirements. This guidance may be 
requested from EPA's Safe Drinking Water Hotline, which may be 
contacted as described under FOR FURTHER INFORMATION CONTACT in the 
beginning of this notice.
b. Background and Analysis
    In the August 11, 2003 proposed LT2ESWTR, EPA proposed to establish 
criteria for awarding credit to membrane filtration processes for 
removal of Cryptosporidium (USEPA 2003g). The Agency based these 
criteria on data demonstrating the Cryptosporidium removal efficiency 
of membrane filtration processes, a critical evaluation of available 
integrity monitoring techniques, and study of State approaches to the 
regulation of membrane filtration for pathogen removal. This 
information is summarized in the report Low-Pressure Membrane 
Filtration for Pathogen Removal: Application, Implementation, and 
Regulatory Issues (USEPA 2001g).
    As summarized in this report, a number of studies demonstrate the 
ability of membrane filtration processes to remove pathogens, including 
Cryptosporidium, to below detection levels (USEPA 2001g). In some 
studies that used Cryptosporidium seeding, measured removal 
efficiencies were as high as 7-log (Jacangelo, et al., 1997; Hagen, 
1998; Kachalsky and Masterson, 1993). In other studies, removal 
efficiencies ranged from 4.4- to 6.5-log and were only limited by the 
seeded concentration of Cryptosporidium oocysts (Dwyer, et al. 1995, 
Jacangelo et al. 1989, Trussel, et al. 1998, NSF 2000a-g, Olivieri 
1989). Collectively, these results demonstrate that an integral 
membrane module (i.e., a membrane module without any leaks or defects, 
with an exclusion characteristic smaller than Cryptosporidium) is 
capable of removing this pathogen to below detection in the filtrate, 
independent of the influent concentration.
    The 2003 proposal included a provision for challenge testing 
membranes to demonstrate the removal efficiency of Cryptosporidium. EPA 
believes this requirement is necessary due to the proprietary nature of 
these products and the lack of any uniform design criteria for 
establishing the exclusion characteristic of a membrane. Guidance on 
the design and conduct of a challenge test to meet the requirements of 
this rule is presented in the Membrane Filtration Guidance Manual.
    Challenge testing is required on a product-specific basis, rather 
than a site-specific basis; thus, modules used in full-scale facilities 
will generally not be directly challenge tested. The removal capability 
of production membrane modules is verified through the application of a 
non-destructive performance test, such as a bubble point test. A 
quality control release value (QCRV) for the non-destructive 
performance test can be related to the results of the challenge test 
and used to demonstrate the ability of production modules to achieve 
the Cryptosporidium removal efficiency demonstrated during challenge 
testing. Most membrane manufacturers have adapted some form of non-
destructive testing for the purpose of product quality control and have 
established a QCRV that is indicative of an acceptable product. It may 
be possible to apply these existing practices to meet the requirements 
of today's final rule.
    While challenge testing demonstrates the removal efficiency of an 
integral membrane module, defects or leaks in the membrane or other 
system components can result in contamination of the filtrate unless 
they are identified, isolated, and repaired. In order to verify 
continued performance of a membrane system, today's final rule requires 
direct integrity testing of membrane filtration processes used to meet 
the Cryptosporidium treatment requirements of this rule.
    An evaluation of available direct integrity tests indicates that 
pressure-based tests are widely applied and sufficiently sensitive to 
provide verification of removal efficiencies in excess of 4-log. 
Marker-based direct integrity tests are also available, and new direct 
integrity tests may be developed that present an improvement over 
existing tests. Rather than specify a particular direct integrity test, 
today's final rule defines performance criteria for direct integrity 
testing. These criteria are resolution, sensitivity, and frequency, as 
previously described. EPA believes that this approach will provide 
flexibility for the development and implementation of future 
innovations in direct integrity testing while ensuring that any test 
applied to meet the requirements of this rule will achieve the required 
level of performance.
    Since available direct integrity tests require taking the membrane 
unit out of service to conduct the test, today's rule establishes a 
minimum test frequency for direct integrity testing. Currently, there 
is no standard frequency for direct integrity testing that has been 
adopted by all States and membrane treatment facilities. In a 2000 
survey, the required frequency of integrity testing was found to vary 
from once every four hours to once per week; however, the most common 
frequency for conducting a direct integrity test was once every 24 
hours (USEPA 2001g). Specifically, 10 out of 14 States that require 
periodic direct integrity testing specify a frequency of once per day. 
Furthermore, many membrane manufacturers of systems with automated 
integrity test systems set up the membrane units to automatically 
perform a direct integrity test once per day.
    EPA believes that daily direct integrity testing is appropriate for 
most membrane filtration installations, but under some circumstances, 
less frequent testing may be adequate. Thus, EPA is allowing States to 
approve less frequent direct integrity testing on the basis of 
demonstrated process reliability, use of multiple barriers effective 
for Cryptosporidium, or reliable process safeguards.
    Due to the periodic nature of direct integrity testing, today's 
rule includes a provision for continuous indirect integrity monitoring. 
While indirect monitoring is not as sensitive as direct testing, it 
provides an indication of process performance to ensure that a major 
failure has not occurred between application of direct integrity tests.
c. Summary of Major Comments
    In response to the 2003 proposal, the Agency received significant 
comments on the following issues related to membrane filtration: the 
frequency of direct integrity testing; the procedure necessary to 
determine removal credit for membrane filtration; and the requirement 
for continuous indirect integrity monitoring.
    The 2003 proposal requested comment on the proposed minimum direct 
integrity test frequency of once per day. Some commenters supported the 
daily frequency and commented that many states have already adopted 
this standard. Others commented that direct integrity testing once per 
day is too frequent, citing the lack of data in the proposal 
documenting the rate of membrane failure, as well as the loss in 
production that occurs when the membrane unit is taken off-line for 
testing.
    While EPA recognizes these concerns, a critical factor in 
establishing a testing frequency is the amount of time that water from 
a compromised membrane unit is supplied to the public before the 
integrity breach is detected. EPA believes that this factor is most 
important to public health protection and that daily direct integrity 
testing is appropriate for the majority of membrane systems. However, 
EPA also acknowledges that there may be

[[Page 705]]

circumstances under which less frequent testing may provide adequate 
public health protection, and has revised the rule to allow States to 
permit less frequent direct integrity testing based on demonstrated 
process reliability, use of multiple barriers effective for 
Cryptosporidium, or reliable process safeguards.
    Several commenters expressed concern with the process needed to 
determine appropriate removal credit for membrane filtration. However, 
many commenters also supported the flexibility provided to States in 
determining the appropriate removal credit for membrane filtration 
based on the criteria defined in the 2003 proposal. EPA believes that 
the proposed approach for awarding Cryptosporidium removal credit to 
membrane filtration is supported by the available data and analysis, 
and will allow higher removal credits to be considered on a 
scientifically sound basis. EPA recognizes that the flexibility 
provided in the regulation does increase the complexity of determining 
removal credits for membrane filtration. To address this issue, EPA has 
developed extensive guidance to support the implementation of 
requirements for membrane filtration.
    EPA received comment that continuous indirect integrity monitoring 
is unnecessary due to the poor sensitivity of currently available 
methods. EPA acknowledges that currently available indirect monitoring 
methods are less sensitive than available direct integrity tests. 
However, EPA believes that continuous indirect integrity monitoring is 
necessary to protect public health. Specifically, continuous monitoring 
may alert a system of potentially severe integrity breaches that could 
result in bypass of unfiltered water around the membrane filtration 
process and pose a risk to public health. Furthermore, EPA has provided 
States with the flexibility to permit use of more sensitive continuous 
indirect monitoring methods and/or to establish lower control limits. 
Also, implementation of continuous direct integrity testing would 
preclude the need to implement any form of indirect integrity 
monitoring.
12. Second Stage Filtration
a. Today's Rule
    PWSs may receive 0.5-log credit towards the Cryptosporidium 
treatment requirements of today's rule for a second filtration stage. 
To be eligible for this credit, the second-stage filtration must meet 
the following criteria:
     The filter must be a separate second stage of granular 
media filtration, such as sand, dual media, or granular activated 
carbon (GAC), that follows a first stage of granular media filtration 
(e.g., follows a conventional treatment or direct filtration plant).
     The first filtration stage must be preceded by a 
coagulation process.
     Both filtration stages must treat 100 percent of the 
treatment plant flow.
     The State must approve the treatment credit based on an 
assessment of the design characteristics of the filtration process.
    This microbial toolbox option does not apply to bag filters, 
cartridge filters, membranes, or slow sand filters, which are addressed 
separately in the microbial toolbox. Further, this options does not 
apply to roughing filters, which are pretreatment processes that 
typically consist of coarse media and are not preceded by coagulation. 
States may consider awarding treatment credit to roughing filters under 
a demonstration of performance.
    PWSs may not receive additional treatment credit for both second-
stage filtration and lower filter effluent turbidity (i.e., combined or 
individual filter performance) that is based on turbidity levels 
following the second filtration stage. PWSs may receive credit for both 
options based on turbidity following the first filtration stage.
b. Background and Analysis
    The Stage 2 M-DBP Advisory Committee recommended a 0.5-log 
Cryptosporidium treatment credit for a roughing filter with the 
stipulation that EPA identify the design and operational conditions 
under which such credit is appropriate. After reviewing available data, 
however, EPA was unable to determine conditions under which a roughing 
filter is likely to achieve at least 0.5-log removal of 
Cryptosporidium. Roughing filters consist of coarse media like gravel 
and usually are not preceded by coagulation. They are used to remove 
sediment and large particulate matter from raw water prior to the 
primary treatment processes. EPA identified no studies indicating that 
roughing filters would be effective for removal of Cryptosporidium 
(USEPA 2003a).
    In contrast, numerous studies have demonstrated that granular media 
filtration can be effective for removing Cryptosporidium when preceded 
by coagulation (Patania et al. 1995, Nieminski and Ongerth 1995, 
Ongerth and Pecoraro 1995, LeChevallier and Norton 1992, LeChevallier 
et al. 1991, Dugan et al. 2001, Nieminski and Bellamy 2000, McTigue et 
al. 1998, Patania et al. 1999, Huck et al. 2000, Emelko et al. 2000). 
PWSs may implement a second granular media filtration stage to achieve 
various water quality objectives, such as increased removal of organic 
material in biologically active filters or removal of inorganic 
contaminants. Consequently, EPA believes that consideration of 
additional Cryptosporidium treatment credit for a second granular media 
filtration stage is appropriate.
    The August 11, 2003 LT2ESWTR proposal included an additional 0.5-
log Cryptosporidium treatment credit for PWSs that use a second 
separate filtration stage consisting of rapid sand, dual media, GAC, or 
other fine grain media. A cap, such as GAC, on a single stage of 
filtration did not qualify. In addition, the proposal required the 
first stage of filtration to be preceded by a coagulation step and both 
stages had to treat 100 percent of the plant flow. Today's final rule 
establishes this treatment credit with minimal changes from the 
proposal. The basis for this credit and for changes from the proposed 
rule are summarized in the following discussion.
    While the studies of Cryptosporidium removal by granular media 
filtration cited previously evaluated only a single stage of 
filtration, the same removal mechanisms will be operative in a second 
stage of granular media filtration. Secondary filters may remove 
Cryptosporidium that were destabilized but not trapped in primary 
filters or that were trapped but subsequently detached from primary 
filters prior to backwash. Thus, EPA believes these studies are 
supportive of additional removal credit for a second filtration stage.
    An important finding of these studies is that coagulation is 
necessary to achieve significant Cryptosporidium removal by granular 
media filtration (does not apply to slow sand filtration, which is 
addressed in the next section). Consequently, today's rule requires 
that the first filtration stage be preceded by coagulation for a PWS to 
receive treatment credit for second-stage filtration. This requirement 
is necessary to ensure that both filtration stages are effective for 
Cryptosporidium removal. PWSs will already comply with this requirement 
where a second filtration stage is applied after conventional treatment 
or direct filtration.
    In the proposal, EPA also reviewed data provided by a PWS on the 
removal of aerobic spores through GAC filters (i.e., contactors) 
following conventional treatment. As discussed earlier, studies have 
demonstrated that aerobic spores can serve as an indicator of 
Cryptosporidium removal by granular

[[Page 706]]

media filtration (Dugan et al. 2001, Emelko et al. 1999 and 2000, Yates 
et al. 1998, Mazounie et al. 2000). Over a two year period, the mean 
removal of aerobic spores across the GAC filters exceeded 0.5-log. 
These results support the finding that a second stage of granular media 
filtration can reduce Cryptosporidium levels by 0.5-log or greater.
    Today's rule does not establish design criteria such as filter 
depth or media size for second-stage filters to be eligible for 
treatment credit. While filter design will influence Cryptosporidium 
removal efficiency, EPA recognizes that appropriate filter designs will 
vary depending on the application. States have traditionally provided 
oversight for treatment process designs in PWSs. Accordingly, today's 
rule requires State review and approval of second-stage filter design 
as a condition for PWSs to receive additional treatment credit for this 
process. The Microbial Toolbox Guidance Manual addresses second-stage 
filtration for Cryptosporidium treatment credit.
c. Summary of Major Comments
    Public comment on the August 11, 2003 LT2ESWTR proposal generally 
supported additional treatment credit for second-stage filtration. 
Commenters raised specific concerns with EPA establishing design 
requirements for filtration, the sufficiency of data to support 
prescribed treatment credit, and the expansion of this credit to 
include other filtration technologies. These comments and EPA's 
responses are summarized as follows.
    In the proposal, EPA requested comment on whether a minimum filter 
depth should be required for PWSs to receive treatment credit for a 
second filtration stage. All commenters opposed EPA setting regulatory 
design standards for filters on the basis that PWSs and States need the 
flexibility to determine appropriate treatment designs. In response, 
EPA agrees that effective filter designs will vary depending on the 
application. Consequently, EPA is not establishing filter design 
criteria in today's rule, but is requiring that States approve designs 
for PWSs to receive treatment credit for second-stage filtration.
    Many commenters stated that available data support the prescribed 
0.5-log Cryptosporidium treatment credit for second-stage filtration. 
Some commenters provided additional data on the removal of aerobic 
spores through GAC filters following conventional treatment that showed 
a mean reduction greater than 1-log. In contrast, other commenters were 
concerned about the lack of data to support increased removal through a 
second filtration stage. These commenters recommended that treatment 
credit for second-stage filtration should be awarded only on a site-
specific basis through a demonstration of performance.
    EPA has concluded that available data are sufficient to support the 
prescribed 0.5-log treatment credit for second-stage filtration. 
Studies of granular media filtration demonstrate high levels of 
Cryptosporidium removal and one study has shown greater than 1.0-log 
removal through secondary GAC filters. Secondary filters can remove 
Cryptosporidium that pass through or detach from the primary filters. 
This added removal will help to stabilize finished water quality by 
providing a barrier during periods of the filtration cycle when the 
primary filters are not performing optimally. Therefore, EPA is 
establishing this credit in today's rule.
    Several commenters recommended that EPA expand the second-stage 
filtration option to include membranes, bag filters, and DE filtration. 
EPA notes that today's rule establishes prescribed treatment credits 
specifically for bag and cartridge filters and membranes as microbial 
toolbox options, and prescribed credit for DE filtration is addressed 
in section IV.B. PWSs may seek treatment credit for other filtration 
technologies through a demonstration of performance under today's rule.
13. Slow Sand Filtration
a. Today's Rule
    PWSs may receive a 2.5-log credit towards the Cryptosporidium 
treatment requirements in today's rule for implementing slow sand 
filtration as a secondary filtration stage following a primary 
filtration process. To be eligible for this credit, the slow sand 
filtration must meet the following criteria:
     The slow sand filter must be a separate second stage of 
filtration that follows a first stage of filtration like conventional 
treatment or direct filtration;
     There must be no disinfectant residual in the influent 
water to the slow sand filtration process;
     Both filtration stages must treat 100 percent of the 
treatment plant flow from a surface water or GWUDI source; and
     The State must approve the treatment credit based on an 
assessment of the design characteristics of the filtration process.
    Slow sand filtration used as a primary filtration process receives 
a prescribed 3-log Cryptosporidium treatment credit, as described in 
section IV.B.
b. Background and Analysis
    Slow sand filtration is a process involving passage of raw water 
through a bed of sand at low velocity (generally less than 0.4 m/h), 
resulting in substantial particulate removal. Several studies have 
demonstrated that slow sand filtration can achieve significant 
Cryptosporidium removal (Schuler and Ghosh, 1991, Timms et al. 1995, 
Hall et al. 1994). Slow sand filtration is typically used as a primary 
filtration process, usually in small systems, rather than as a 
secondary filtration stage following conventional treatment or another 
primary filtration process. EPA expects, however, that slow sand 
filtration would be effective for Cryptosporidium removal in such an 
application, which warrants consideration of treatment credit under 
today's rule.
    The Stage 2 M-DBP Advisory Committee recommended that slow sand 
filtration receive 2.5-log or greater Cryptosporidium treatment credit 
when used in addition to existing treatment that achieves compliance 
with the IESWTR or LT1ESWTR. The August 11, 2003 LT2ESWTR proposal 
included 2.5-log treatment credit for slow sand as a secondary 
filtration process, with the only associated condition being no 
disinfectant residual in the water influent to the filter. In today's 
rule, EPA is establishing this treatment credit with minimal changes 
from the proposal. The following discussion summarizes the basis for 
this credit and for changes from the proposal.
    Removal of microbial pathogens in slow sand filters is complex and 
is believed to occur through a combination of physical, chemical, and 
biological mechanisms, both on the surface and in the interior of the 
filter bed. In particular, biological activity in the upper layers of 
the filter is believed to promote microbial removal. Based on 
previously cited studies demonstrating greater than 4-log removal of 
Cryptosporidium through slow sand filtration, today's rule awards a 
prescribed 3-log Cryptosporidium removal credit to slow sand filtration 
as a primary filtration process.
    The effectiveness of slow sand as a secondary filtration process is 
more uncertain. In general, EPA expects that the same microbial removal 
mechanisms will be operative. However, due to the quality of treated 
water following a primary filtration process, filter ripening and 
development of the biologically active layer in a secondary slow sand 
filter may be inhibited. One study that evaluated Cryptosporidium 
removal by slow sand filtration alone

[[Page 707]]

and slow sand filtration preceded by a rapid sand filter observed 
similar removal levels in the two treatment trains (Hall et al. 1994). 
Because of the uncertainty regarding the performance of slow sand as a 
secondary filtration step and in consideration of the Advisory 
Committee recommendation, today's rule establishes a 2.5-log additional 
Cryptosporidium treatment credit for this application.
    Due to the importance of biological activity to slow sand filter 
performance, PWSs may not receive the prescribed treatment credit if 
the influent water to the slow sand filter contains a disinfectant 
residual. EPA is not establishing design standards for slow sand 
filters in today's rule. Studies have shown, however, that design 
deficiencies in slow sand filters may lead to poor Cryptosporidium 
removal (Fogel et al. 1993). Consequently, States must approve slow 
sand filter designs as a secondary filtration stage for PWSs to receive 
treatment credit under today's rule.
c. Summary of Major Comments
    Public comment on the August 11, 2003 proposal focused on the 
question of whether the 2.5-log Cryptosporidium treatment credit for 
slow sand as a secondary filtration process is appropriate. Many 
commenters supported the proposed treatment credit. These commenters 
cited studies demonstrating greater than 4-log Cryptosporidium removal 
by slow sand filtration and concluded that the data justify a 2.5-log 
treatment credit for slow sand filtration added to a clarification and 
filtration treatment train.
    Several commenters, however, stated that this treatment credit is 
not justified due to the lack of data on the performance of slow sand 
as a secondary filtration step. Available studies on slow sand filter 
performance for Cryptosporidium removal have mostly been conducted on 
raw (i.e., unfiltered) water. These commenters were concerned that if 
slow sand filtration is applied following a primary filtration process, 
the filter ripening period and other factors will be significantly 
affected. As a result, the slow sand filtration may provide only 
limited removal over a long ripening period.
    In response, EPA recognizes that little testing has been conducted 
on the performance of slow sand filtration specifically as a second 
filtration stage in a treatment train. However, available data do not 
indicate that slow sand filtration would be substantially less 
effective when used in this capacity. Slow sand filtration is 
recommended only for higher quality source waters, and water quality 
following a primary filtration process would be well within recommended 
design limits for slow sand filtration (USEPA 1991a). EPA agrees that 
filter ripening is critical to slow sand filtration achieving its full 
performance level, and this process may require more time when slow 
sand filtration follows a primary filtration process. However, this 
effect may be counterbalanced by very long filter run times between 
cleaning the filter due to the high quality influent water. 
Consequently, EPA believes that 2.5-log Cryptosporidium treatment 
credit for slow sand as a secondary filtration process is warranted.
14. Ozone and Chlorine Dioxide
a. Today's Rule
    PWSs may use ozone and chlorine dioxide to meet Cryptosporidium 
treatment requirements under today's rule. To receive treatment credit, 
PWSs must measure the water temperature, disinfectant contact time, and 
residual disinfectant concentration at least once each day and 
determine the log inactivation credit using the tables in this section. 
Specific criteria are as follows:
     The temperature of the disinfected water must be measured 
at least once per day at each residual disinfectant concentration 
sampling point.
     The disinfectant contact time(s) (``t'') must be 
determined for each day during peak hourly flow.
     The residual disinfectant concentration(s) (``C'') of the 
water before or at the first customer must be measured each day during 
peak hourly flow.
     Tables IV.D-3 or IV.D-4 must be used to determine 
Cryptosporidium log inactivation credit for ozone or chlorine dioxide, 
respectively, based on the water temperature and the product of 
disinfectant concentration and contact time (CT).

                                   Table IV.D-3.--CT Values for Cryptosporidium Inactivation by Ozone \1\ (mg/L x min)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                      Water temperature, [deg]C
                Log credit                 -------------------------------------------------------------------------------------------------------------
                                              <=0.5       1         2         3         5         7        10        15        20        25        30
--------------------------------------------------------------------------------------------------------------------------------------------------------
0.25......................................       6.0       5.8       5.2       4.8       4.0       3.3       2.5       1.6       1.0       0.6      0.39
0.5.......................................      12        12        10         9.5       7.9       6.5       4.9       3.1       2.0       1.2      0.78
1.0.......................................      24        23        21        19        16        13         9.9       6.2       3.9       2.5      1.6
1.5.......................................      36        35        31        29        24        20        15         9.3       5.9       3.7      2.4
2.0.......................................      48        46        42        38        32        26        20        12         7.8       4.9      3.1
2.5.......................................      60        58        52        48        40        33        25        16         9.8       6.2      3.9
3.0.......................................      72        69        63        57        47        39        30        19        12         7.4      4.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ PWSs may use this equation to determine log credit between the indicated values: Log credit = (0.0397 x (1.09757) Temp) x CT.


                             Table IV.D-4.--CT Values for Cryptosporidium Inactivation by Chlorine Dioxide \1\ (mg/L x min)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                      Water temperature, [deg]C
                Log credit                 -------------------------------------------------------------------------------------------------------------
                                              <=0.5       1         2         3         5         7        10        15        20        25        30
--------------------------------------------------------------------------------------------------------------------------------------------------------
0.25......................................     159       153       140       128       107        90        69        45        29        19       12
0.5.......................................     319       305       279       256       214       180       138        89        58        38       24
1.0.......................................     637       610       558       511       429       360       277       179       116        75       49
1.5.......................................     956       915       838       767       643       539       415       268       174       113       73
2.0.......................................    1275      1220      1117      1023       858       719       553       357       232       150       98
2.5.......................................    1594      1525      1396      1278      1072       899       691       447       289       188      122
3.0.......................................    1912      1830      1675      1534      1286      1079       830       536       347       226      147
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ PWSs may use this equation to determine log credit between the indicated values: Log credit = (0.001506 x (1.09116) Temp) x CT.


[[Page 708]]

    PWSs may have several disinfection segments in sequence along the 
treatment train, where a disinfectant segment is defined as a treatment 
unit process with a measurable disinfectant residual level and a liquid 
volume. In determining the total log inactivation, the PWS may 
calculate the CT for each disinfection segment and use the sum of these 
values to determine the log inactivation achieved through the plant. 
The Toolbox Guidance Manual provides information on recommended 
methodologies for determining CT values for different disinfection 
reactor designs and operations.
    Alternatively, the State may approve alternative CT values to those 
specified in Tables IV.D-3 or IV.D-4 based on a site-specific study a 
PWSs conducts following a State-approved protocol. The Toolbox Guidance 
Manual describes recommended approaches for making such demonstrations.
b. Background and Analysis
    Ozone and chlorine dioxide are chemical disinfectants that have 
been shown to be effective for inactivating Cryptosporidium. The Stage 
2 M-DBP Advisory Committee recommended that EPA develop criteria for 
PWSs to achieve Cryptosporidium inactivation credit with these 
disinfectants. The August 11, 2003 LT2ESWTR proposal included CT values 
for 0.5- to 3-log Cryptosporidium inactivation credit by ozone or 
chlorine dioxide at temperatures ranging from less than 0.5 C to 25 C, 
along with daily required monitoring (USEPA 2003a). Today's final rule 
establishes these criteria with no changes from the proposed rule, but 
expands the CT tables down to 0.25-log inactivation and up to a water 
temperature of 30 C. The following discussion summarizes the basis for 
these criteria.
    The requirements for at least daily monitoring of the water 
temperature, residual disinfectant concentration, and contact time 
during peak hourly flow to determine a daily inactivation level reflect 
existing requirements for Giardia inactivation by chemical disinfection 
in 40 CFR 141.74. EPA expects that in practice, many PWSs using ozone 
or chlorine dioxide will monitor more frequently and for multiple 
disinfectant segments. In the Toolbox Guidance Manual, EPA provides 
information on recommended approaches for monitoring and calculating CT 
values for ozone and chlorine dioxide reactors.
    The CT values for both ozone and chlorine dioxide are based on 
analyses by Clark et al. (2002a,b), with additional procedures to 
assess confidence bounds. Clark et al. (2002a,b) developed predictive 
equations for Cryptosporidium inactivation through evaluating studies 
on ozone by Rennecker et al. (1999), Li et al. (2001), Owens et al. 
(2000), and Oppenheimer et al. (2000) and on chlorine dioxide by Li et 
al. (2001), Owens et al. (1999) and Ruffell et al. (2000). EPA applied 
confidence bounds to these predictive equations to ensure that PWSs 
operating at a given CT value are likely to achieve at least the 
corresponding log inactivation level in the CT table.
    In identifying confidence bounds for CT values, EPA was primarily 
concerned with uncertainty in the estimations by Clark et al. (2002a,b) 
of the linear relationship between log inactivation and CT (i.e., 
uncertainty in the regression) and with real variability in the 
inactivation rate. Such real variability could be associated with 
different populations of oocysts and different water matrices. In 
contrast, variability associated with experimental error, such as the 
assays used to measure loss of infectivity, was a lessor concern. The 
purpose of the CT tables is to ensure a given level of inactivation and 
not to predict the measured result of an individual experiment.
    For developing earlier CT values, EPA has used bounds for 
confidence in prediction, which account for both real variability and 
experimental error. EPA believes that this approach was appropriate due 
to limited inactivation data and uncertainty in the sources of 
variability in the data. However, the high doses of ozone and chlorine 
dioxide necessary to inactivate Cryptosporidium create an offsetting 
concern with the formation of DBPs (e.g., bromate and chlorite). In 
consideration of this concern, EPA has employed a less conservative 
method to calculate confidence bounds for the ozone and chlorine 
dioxide CT values in today's rule; specifically, EPA has attempted to 
exclude experimental error from the confidence bounds.
    In order to estimate confidence bounds that exclude experimental 
error, EPA assessed the relative contribution of experimental error to 
the variance observed in the Cryptosporidium inactivation data sets. 
This assessment was done by comparing variance among data points with 
consistent experimental conditions, which was attributed to 
experimental error, with the total variance in a data set. By this 
analysis, EPA estimated that 87.5 and 62 percent of the variance in the 
Cryptosporidium inactivation data for ozone and chlorine dioxide, 
respectively, could be ascribed to experimental error (Sivaganesan 
2003, Messner 2003). EPA then applied these estimates to the predictive 
equations developed by Clark et al. (2002a,b) using a modified form of 
a formula for calculating a 90 percent confidence bound (Messner 2003).
    This analysis produced the CT values shown in tables IV.D-3 and 
IV.D-4 for ozone and chlorine dioxide, respectively. CT values are 
provided for inactivation as low as 0.25-log. Such a low inactivation 
level may be used by PWSs applying ozone in combination with other 
disinfectants. Available data do not support the determination of 
conditions for inactivation greater than 3-log, so the CT values in 
today's rule do not go beyond this level. The temperature range of CT 
values in today's rule goes to 30 C (86 F), which will accommodate most 
natural waters. If the water temperature is higher than 30 C, 
temperature should be set to 30 C for the log inactivation calculation. 
PWSs may use the equations provided as footnotes to tables IV.D-3 and 
IV.D-4 to interpolate between CT values.
    EPA recognizes that inactivation rates may be sensitive to water 
quality and operational conditions at individual PWSs. To reflect this 
potential, PWSs are allowed to perform a site-specific inactivation 
study to determine CT requirements. The State must approve the 
protocols or other information used to derive alternative CT values. 
EPA has provided guidance for such studies in the Toolbox Guidance 
Manual.
c. Summary of Major Comments
    Public comment on the August 11, 2003 LT2ESWTR proposal supported 
the inclusion of ozone and chlorine dioxide in the microbial toolbox 
for Cryptosporidium inactivation. Commenters stated concerns with the 
required criteria for achieving Cryptosporidium treatment credit, 
including the conservatism EPA applied in developing the CT tables, the 
ability of PWSs with different types of source waters to use these 
disinfectants, and the range of conditions covered by the CT tables. 
Commenters also made recommendations for guidance. These comments and 
EPA's responses are summarized as follows.
    Some commenters supported the proposed CT tables, but others stated 
that the statistical approach used to calculate the confidence bounds 
from which the CT values are derived is overly conservative. These 
commenters were concerned that this approach will increase capital and 
operating costs and lead to higher byproduct levels.
    In response, EPA believes that the confidence bounds used for the 
ozone and chlorine dioxide CT tables in today's rule are appropriate 
and

[[Page 709]]

necessary to ensure that PWSs achieve intended levels of 
Cryptosporidium inactivation. They account only for uncertainty in the 
regression of inactivation data and for variability in inactivation 
data that cannot be attributed to experimental error. This approach is 
significantly less conservative than the approaches used in CT tables 
for earlier rules. EPA employed this less conservative approach in 
recognition of the high disinfectant doses necessary for 
Cryptosporidium inactivation and concern with byproducts.
    Commenters were concerned that due to the relatively high ozone and 
chlorine dioxide doses necessary for Cryptosporidium inactivation, some 
PWSs will be unable to use these disinfectants to achieve required 
levels of Cryptosporidium treatment. In particular, using ozone for 
high Cryptosporidium inactivation levels will be difficult in areas 
where cold water temperatures would necessitate especially high doses 
or where high source water bromide levels would cause problems with 
bromate formation. The use of chlorine dioxide for Cryptosporidium 
inactivation may be difficult due to chlorite formation.
    EPA recognizes that the use of ozone and chlorine dioxide to 
achieve Cryptosporidium inactivation will depend on source water 
factors and will not be feasible for all PWSs. Due to the availability 
of UV, which EPA has determined to be a feasible technology for 
Cryptosporidium inactivation by all PWS sizes, the feasibility of 
today's rule does not depend on the widespread use of ozone or chlorine 
dioxide for compliance. In assessing the impact of today's rule on 
PWSs, EPA used ICR survey data to estimate the fraction of PWSs that 
could use ozone or chlorine dioxide to achieve different levels of 
Cryptosporidium inactivation without exceeding DBP MCLs (see Economic 
Analysis for the LT2ESWTR). While EPA expects that some PWSs will use 
these disinfectants, the microbial toolbox provides many other options 
for PWSs to comply with the Cryptosporidium treatment requirements of 
today's rule.
    Commenters recommended that EPA expand the range of conditions 
encompassed in the CT tables. Specifically, commenters asked that CT 
tables include values for water temperatures above 25 C and supported 
this request by providing data showing temperature profiles for water 
sources with maximum temperatures near 30 C. Commenters also requested 
CT values for Cryptosporidium inactivation levels below 0.5-log for 
PWSs that will use multiple disinfectants to meet the treatment 
requirements in today's rule. In addition, commenters suggested that 
EPA provide equations that PWSs can use to interpolate between the 
listed CT values.
    EPA has addressed these recommendations in today's final rule. The 
CT tables for ozone and chlorine dioxide include values for a water 
temperature of 30 C and for 0.25-log inactivation. Footnotes to these 
tables contain equations that PWSs can use to calculate log 
inactivation credit for conditions between those provided in the 
tables. PWSs may use these equations in their process control systems.
    Commenters made recommendations for guidance on the use of ozone 
and chlorine dioxide to comply with today's rule. These recommendations 
concern topics like monitoring disinfection reactors, procedures for 
calculating disinfectant concentration and contact time, site specific 
studies, and synergistic effects of multiple disinfectants. EPA has 
addressed these topics in the Toolbox Guidance Manual.
15. Ultraviolet Light
a. Today's Rule
    PWSs may use ultraviolet (UV) light to comply with Cryptosporidium 
treatment requirements in today's rule, as well as Giardia lamblia and 
virus treatment requirements in existing regulations. To receive 
treatment credit, PWSs must operate UV reactors validated to achieve 
the required UV dose, as shown in the table in this section, and 
monitor their UV reactors to demonstrate operation within validated 
conditions. Specific criteria are as follows:

Required UV Doses

     UV dose (fluence) is the product of the UV intensity over 
a surface area (fluence rate) and the exposure time. PWSs must use 
validation testing to demonstrate that a UV reactor achieves the UV 
doses shown in Table IV.D-5 in order to receive the associated 
inactivation credit.

     Table IV.D-5.--UV Dose Requirements for Cryptosporidium, Giardia lamblia, and Virus Inactivation Credit
----------------------------------------------------------------------------------------------------------------
                                                Cryptosporidium UV     Giardia lamblia UV    Virus UV dose (mJ/
                 Log credit                       dose (mJ/cm2)          dose (mJ/cm2)              cm2)
----------------------------------------------------------------------------------------------------------------
0.5.........................................                    1.6                    1.5                    39
1.0.........................................                    2.5                    2.1                    58
1.5.........................................                    3.9                    3.0                    79
2.0.........................................                    5.8                    5.2                   100
2.5.........................................                    8.5                    7.7                   121
3.0.........................................                   12                     11                     143
3.5.........................................                   15                     15                     163
4.0.........................................                   22                     22                     186
----------------------------------------------------------------------------------------------------------------

     The dose values in Table IV.D-5 are for UV light at a 
wavelength of 254 nm as delivered by a low pressure mercury vapor lamp. 
However, PWSs may use this table to determine treatment credits for 
other lamp types through validation testing, as described in the UV 
Disinfection Guidance Manual. The dose values in Table IV.D-5 apply to 
post-filter applications of UV in filtration plants and to PWSs that 
meet all applicable filtration avoidance criteria.

UV Reactor Validation Testing

     The validation test may be reactor-specific or site-
specific. Unless the State approves an alternative approach, this 
testing must involve the following: (1) Full scale testing of a reactor 
that conforms uniformly to the UV reactors used by the PWS, and (2) 
inactivation of a test microorganism whose dose response 
characteristics have been quantified with a low pressure mercury vapor 
lamp.
     Validation testing must identify ranges for parameters the 
PWS can monitor to ensure that the required UV dose is delivered during 
operation. These parameters must include flow rate, UV intensity as 
measured by UV sensors, and UV lamp status.
     The operating parameters determined by validation testing 
must

[[Page 710]]

account for the following factors: (1) UV absorbance of the water, (2) 
lamp fouling and aging, (3) measurement uncertainty of UV sensors, (4) 
dose distributions arising from the flow velocity profiles through the 
reactor, (5) failure of UV lamps or other critical system components, 
and (6) inlet and outlet piping or channel configurations of the UV 
reactor. In the UV Disinfection Guidance Manual, EPA describes 
recommended approaches for reactor validation that address these 
factors.

UV Reactor Monitoring

     PWSs must monitor for the parameters necessary to 
demonstrate operation within the validated conditions of the required 
UV dose. These parameters must include flow rate, UV intensity as 
measured by UV sensors, and UV lamp status. PWSs must check the 
calibration of UV sensors and recalibrate in accordance with a protocol 
approved by the State.
     For PWSs using UV light to meet microbial treatment 
requirements, at least 95 percent of the water delivered to the public 
every month must be treated by UV reactors operating within validated 
conditions for the required UV dose.
b. Background and Analysis
    Numerous studies have demonstrated that UV light is effective for 
inactivating Cryptosporidium, Giardia lamblia, and other microbial 
pathogens at relatively low doses (Clancy et al. 1998, 2000, 2002, 
Bukhari et al. 1999, Craik et al. 2000, 2001, Landis et al. 2000, 
Sommer et al. 2001, Shin et al. 2001, and Oppenheimer et al. 2002). EPA 
has determined that UV light is a feasible technology for PWSs of all 
sizes to inactivate Cryptosporidium. Accordingly, EPA expects that UV 
is one of the primary technologies PWSs will use to comply with 
Cryptosporidium treatment requirements in today's rule.
    The Stage 2 M-DBP Advisory Committee recommended that EPA establish 
standards for the use of UV to comply with drinking water treatment 
requirements. These standards include the UV doses necessary for 
different levels of Cryptosporidium, Giardia lamblia, and virus 
inactivation and a protocol for validating the disinfection performance 
of UV reactors. The Committee also directed EPA to develop a UV 
disinfection guidance manual to familiarize States and PWSs with 
important design and operational issues for UV installations.
    The August 11, 2003 LT2ESWTR proposal included UV doses for PWSs to 
achieve treatment credit of up to 3-log for Cryptosporidium and Giardia 
lamblia and up to 4-log for viruses, along with associated reactor 
validation and monitoring requirements. The proposal also required 
unfiltered PWSs using UV to achieve the UV dose for the required level 
of Cryptosporidium inactivation in at least 95 percent of the water 
delivered to the public every month (USEPA 2003a).
    Today's final rule establishes these criteria with no changes from 
the proposed rule. However, EPA has expanded the UV dose table to 
include 4-log inactivation of Cryptosporidium and Giardia lamblia and 
has expanded the 95 percent compliance requirement to include filtered 
PWSs and to cover Giardia lamblia and virus inactivation. The following 
discussion summarizes the basis for these criteria.
    The UV dose values in Table IV.D-5 are based on meta-analyses of UV 
inactivation studies with Cryptosporidium parvum, Giardia lamblia, 
Giardia muris, and adenovirus (Qian et al. 2004, USEPA 2003a). EPA has 
expanded the dose values for Cryptosporidium and Giardia lamblia from 
3- to 4-log inactivation because available data support criteria for 
this level of treatment. Neither today's rule nor any existing 
regulations require PWSs to provide Cryptosporidium inactivation above 
this level, so EPA has not expanded the UV dose tables further. While 
today's rule requires up to 5.5-log Cryptosporidium treatment by 
filtered PWSs, at least 2.0-log of this treatment must be achieved by 
physical removal.
    The required UV doses for inactivation of viruses are based on the 
dose-response of adenovirus because among waterborne pathogenic viruses 
that have been studied, it appears to be the most UV resistant. As 
summarized in Embrey (1999), adenoviruses have been identified as the 
second most important agent of gastroenteritis in children and can 
cause significant adverse health effects, including death, in persons 
with compromised immune systems. They are associated with fecal 
contamination in water and have been implicated in waterborne disease 
outbreaks.
    EPA used data from studies performed with low pressure mercury 
vapor lamps on water with turbidity representative of filtered water to 
derive the UV dose values in Table IV.D-5. Studies with low pressure 
mercury vapor lamps were selected because they allow the UV dose to be 
accurately quantified (see USEPA 2003a for specific studies). The UV 
dose values in Table IV.D-5 can be applied to medium pressure mercury 
vapor lamps and other lamp types through UV reactor validation testing, 
as described in the UV Disinfection Guidance Manual. Due to the 
potential for particulate matter to interfere with UV disinfection, the 
application of these dose values is limited to post-filtration in 
filtered PWSs and to unfiltered PWSs.
    Flow-through UV reactors deliver a distribution of doses due to 
variations in light intensity and particle flow path through the 
reactor. To best account for the dose distribution, the validation test 
must use a challenge microorganism to determine the degree of 
inactivation achieved by the UV reactor. This level of performance must 
then be associated to the UV dose requirements in Table IV.D-5 through 
known dose-response relationships for the challenge microorganism and 
target pathogen in order to assign disinfection credit to the UV 
reactor. States may approve an alternative basis for awarding UV 
disinfection credit.
    Today's rule requires full-scale testing of UV reactors to validate 
the operating conditions under which the reactors can deliver a 
required UV dose. EPA believes this testing is necessary due to the 
uncertainty associated with predicting reactor disinfection performance 
entirely through modeling or through reduced-scale testing. Under 
today's rule, EPA intends UV reactor validation testing to be reactor-
specific and not site-specific. This means that once a UV reactor has 
been validated for a range of operating conditions, the validation test 
results can be applied by all PWSs that will operate within those 
conditions without the need for retesting at each individual site.
    Validation testing must account for factors that will influence the 
dose delivered by UV reactors during routine operation. These factors 
include UV absorbance, lamp fouling, lamp aging, the performance of UV 
intensity sensors, hydraulic flow path and residence time 
distributions, UV lamp failure, and reactor inlet and outlet 
hydraulics. The successful outcome of validation testing is the 
determination of acceptable operating ranges for parameters the PWSs 
can monitor to ensure delivery of the required UV dose during 
treatment. The specific parameters will vary depending on the reactor 
control strategy. In all cases, however, PWSs must monitor UV intensity 
within the reactor as measured by UV sensors, the flow rate, and the 
status of lamps. EPA believes that any effective UV reactor control 
strategy will involve monitoring for these parameters.
    Today's rule requires all PWSs using UV for disinfection compliance 
to treat

[[Page 711]]

at least 95 percent of the water distributed to the public each month 
with UV reactors operating within validated conditions for the required 
UV dose. EPA views this 95 percent limit as a feasible minimum level of 
performance for PWSs to achieve, while ensuring the desired level of 
health protection is provided. For purposes of design and operation, 
PWSs should strive to deliver the required UV dose at all times during 
treatment.
    EPA developed these requirements and the associated UV Disinfection 
Guidance Manual solely for public water systems using UV light to meet 
drinking water disinfection standards established under SDWA. EPA has 
not addressed and did not consider the extension of these requirements 
and guidance to other applications, including point of entry or point 
of use devices for residential water treatment that are not operated by 
public water systems to meet SDWA disinfection standards.
c. Summary of Major Comments
    Public comment on the August 11, 2003 LT2ESWTR proposal supported 
the inclusion of UV light in the microbial toolbox for Cryptosporidium 
inactivation. EPA received significant comment on the UV dose tables, 
the use of adenovirus as the basis for virus UV dose requirements, UV 
compliance standards for filtered systems, and safety factors 
associated with draft guidance. These comments and EPA's responses are 
summarized as follows.
    Commenters generally supported the proposed UV dose values for 
Cryptosporidium and Giardia lamblia inactivation and recommended that 
EPA incorporate these values into the final rule. Several commenters 
requested that EPA provide values for 3.5-, 4.0- or higher log 
inactivation of Cryptosporidium and Giardia lamblia because available 
dose-response data include this range. Due to factors like tailing and 
censoring in the underlying dose-response data, some commenters stated 
that the proposed UV dose values are conservative and advised EPA to 
consider this conservatism when recommending additional safety factors 
in guidance.
    In response, EPA has extended the UV dose table in today's rule to 
cover 3.5- and 4.0-log Cryptosporidium and Giardia lamblia 
inactivation. None of EPA's regulations require inactivation of 
Cryptosporidium or Giardia lamblia above these levels, so EPA has not 
established UV dose requirements for inactivation above 4-log. EPA 
believes that the statistical analysis used to determine the required 
UV doses appropriately accounts for variability, tailing, and censoring 
in the underlying dose-response data. However, the required UV dose 
values do not account for bias and uncertainty associated with UV 
reactor validation and monitoring, which are addressed in guidance.
    Several commenters were concerned with the use of adenovirus to set 
UV dose requirements for virus inactivation because the resulting dose 
values are several times higher than typical UV doses for drinking 
water disinfection. These high dose values impact the feasibility of 
PWSs using UV to fully meet virus treatment requirements, which will 
hinder the use of UV to reduce DBPs and for point-of-entry treatment. 
Commenters requested that EPA consider waterborne viruses that are more 
UV-sensitive, such as rotavirus or hepatitus, when setting UV dose 
requirements. Commenters noted that adenovirus commonly causes 
infections of the lung or eye, which are not transmitted through water 
consumption, and that no drinking water outbreaks associated with 
adenovirus have been reported in the United States.
    EPA recognizes that the UV doses for virus inactivation in today's 
rule are relatively high and that this will limit the degree to which 
PWSs can use UV for virus treatment. Based on occurrence and health 
effects, however, EPA continues to believe that UV dose requirements 
should be protective for adenovirus. The existing requirement for 4-log 
virus treatment, as established under the SWTR, applies to all 
waterborne viruses of public health concern in PWSs. Adenovirus is 
consistently found in water subject to fecal contamination and can be 
transmitted through consumption of or exposure to contaminated water. 
It is a common cause of diarrheal illness, particularly in children, 
and fecal shedding is prevalent in asymptomatic adults. While illness 
from adenovirus is typically self-limiting, severe health effects, 
including death, can occur. Consequently, EPA regards adenovirus as a 
potential health concern in PWSs and has established UV dose 
requirements to address it.
    Many commenters recommended that EPA establish a compliance 
standard for the operation of UV reactors within validated conditions 
by filtered PWSs, similar to the 95 percent standard proposed for 
unfiltered PWSs. Commenters were concerned that without a clear 
compliance standard in the rule, filtered PWSs would be held to 
inconsistent and unclear standards, which would impede the design and 
implementation of UV systems. Some commenters recommended that filtered 
PWSs by held to the same 95 percent standard as unfiltered PWSs, while 
others recommended a lower 90 percent standard on the basis that 
filtered PWSs have more barriers of protection.
    EPA agrees that establishing a clear compliance standard for the 
use of UV to meet inactivation requirements is appropriate. For 
filtered PWSs using UV to meet microbial treatment requirements, 
today's final rule requires at least 95 percent of the water 
distributed to consumers to be treated by UV reactors operating within 
validated conditions. This is the same standard that applies to 
unfiltered PWSs. EPA believes that a 95th percentile standard is 
feasible for all PWSs and represents the minimum level of performance 
that should be achieved. During routine operation, PWSs should endeavor 
to maintain UV reactors within validated conditions for the required UV 
dose at all times.

E. Disinfection Benchmarking for Giardia lamblia and Viruses

1. Today's Rule
    The purpose of disinfection benchmarking under today's rule is to 
ensure that PWSs maintain protection against microbial pathogens as 
they implement the Stage 2 DBPR and LT2ESWTR. If a PWS proposes to make 
a significant change in disinfection practice, the PWS must perform the 
following:
     Develop a disinfection profile for Giardia lamblia and 
viruses. A disinfection profile consists of documenting Giardia lamblia 
and virus log inactivation levels at least weekly over a period of at 
least one year. PWSs that operate for less than one year must profile 
only during the period of operation. The calculated log inactivation 
levels must include the entire treatment plant and must be based on 
operational and water quality data, such as disinfectant residual 
concentration(s), contact time(s), temperature(s), and, where 
necessary, pH. PWSs may create profiles by conducting new weekly (or 
more frequent) monitoring and/or by using previously collected data. A 
PWS that created a Giardia lamblia disinfection profile under the 
IESWTR or LT1ESWTR may use the operational data collected for the 
Giardia lamblia profile to create a virus disinfection profile.
     Calculate a disinfection benchmark, using the following 
procedure: (1) Determine the calendar month with the lowest log 
inactivation; (2) The lowest month becomes the critical period for that 
year; (3) If acceptable data from

[[Page 712]]

multiple years are available, the average of critical periods for each 
year becomes the benchmark; (4) If only one year of data is available, 
the critical period for that year is the benchmark.
     Notify the State before implementing the significant 
change in disinfection practice. The notification to the State must 
include a description of the proposed change, the disinfection profiles 
and inactivation benchmarks for Giardia lamblia and viruses, and an 
analysis of how the proposed change will affect the current 
inactivation benchmarks.
    For the purpose of these requirements, significant changes in 
disinfection practice are defined as (1) moving the point of 
disinfection (this is not intended to include routine seasonal changes 
already approved by the State), (2) changing the type of disinfectant, 
(3) changing the disinfection process, or (4) making other 
modifications designated as significant by the State. The Disinfection 
Profiling and Benchmarking Guidance Manual provides information to PWSs 
and States on the development of disinfection profiles, identification 
and evaluation of significant changes in disinfection practices, and 
considerations for setting an alternative benchmark (USEPA 1999d).
2. Background and Analysis
    A goal in the development of rules to control microbial pathogens 
and disinfection byproducts (DBPs) is the balancing risks between these 
two classes of contaminants. EPA established disinfection profiling and 
benchmarking under the IESWTR and LT1ESWTR, based on a recommendation 
by the Stage 1 M-DBP Advisory Committee, to ensure that PWSs maintained 
adequate protection against pathogens as they reduced risk from DBPs. 
EPA is extending profiling and benchmarking requirements to the 
LT2ESWTR for the same objective.
    Some PWSs will make significant changes in their current 
disinfection practice to meet TTHM and HAA5 requirements under the 
Stage 2 DBPR and to provide additional treatment for Cryptosporidium 
under the LT2ESWTR. To ensure that these PWSs maintain disinfection 
that is effective against a broad spectrum of microbial pathogens, EPA 
believes that PWSs and States should evaluate the effects of 
significant changes in disinfection practice on current microbial 
treatment levels. Disinfection profiling and benchmarking serves as a 
tool for making such evaluations.
    The August 11, 2003 LT2ESWTR proposal included disinfection 
profiling and benchmarking requirements. Under the proposal, profiling 
for Giardia lamblia and viruses was required if a PWS was required to 
monitor for Cryptosporidium or, in the case of small PWSs, exceeded 80 
percent of the TTHM or HAA5 MCL based on a locational running annual 
average. Under this approach, most large PWSs and a significant 
fraction of small PWSs were required to develop profiles. The proposal 
also included a schedule for disinfection profile development. Those 
PWSs that developed profiles were then required to calculate a 
disinfection benchmark and notify the State if they proposed to make a 
significant change in disinfection practice.
    In today's final rule, EPA has significantly modified the 
applicability requirements for disinfection profiling. PWSs are only 
required to develop a disinfection profile if they propose to make a 
significant change in disinfection practice after completing the first 
round of source water monitoring. EPA has made this change from the 
proposal because under the LT2ESWTR and Stage 2 DBPR, most PWSs will 
not be required to make significant changes to their disinfection 
practice. Consequently, most PWSs will not need a disinfection profile. 
EPA believes that disinfection profiling requirements should be 
targeted to those PWSs that will make significant disinfection changes.
    EPA has also eliminated the scheduling requirements for development 
of the disinfection profile in order to provide more flexibility to 
PWSs and States. Today's rule only requires that PWSs notify States 
prior to making a significant change in their disinfection practice and 
that this notification include the disinfection profiles and 
benchmarks, along with an analysis of how the proposed change will 
affect the current benchmarks. EPA believes that PWSs should collect 
the operational data needed to develop disinfection profiles, such as 
disinfectant residual, water temperature, and flow rate, as part of 
routine practice. PWSs that do not have current disinfection profiles 
should record this operational information at least weekly for one year 
so that they can use it to develop disinfection profiles if required.
    Today's rule retains the proposed requirement that when 
disinfection profiling is required, PWSs must develop profiles for both 
Giardia lamblia and viruses. EPA believes that profiling for both 
target pathogens is appropriate because the types of treatment changes 
that PWSs will make to comply with the Stage 2 DBPR or LT2ESWTR could 
lead to a significant change in the inactivation level for one pathogen 
but not the other. For example, a PWS that switches from chlorine to UV 
light to meet Giardia lamblia inactivation requirements is likely to 
maintain a high level of treatment for this pathogen. The level of 
treatment for viruses, however, may be significantly reduced. In 
general, viruses are much more sensitive to chlorine than Giardia but 
are more resistant to UV. The situation for a PWS switching to 
microfiltration is similar. The same operational data are used to 
develop disinfection profiles for both Giardia lamblia and viruses.
    As was the case with the IESWTR and LT1ESWTR, the disinfection 
benchmark under today's rule is not intended to function as a 
regulatory standard. Rather, the objective of these provisions is to 
facilitate interactions between the States and PWSs to assess the 
impact on microbial risk of proposed changes to disinfection practice. 
Final decisions regarding levels of disinfection for Giardia lamblia 
and viruses beyond the minimum required by regulation will continue to 
be left to the States and PWSs. To ensure that the level of treatment 
for both protozoan and viral pathogens is appropriate, States and PWSs 
should consider site-specific factors such as source water 
contamination levels and the reliability of treatment processes.
3. Summary of Major Comments
    EPA received significant public comment on disinfection profiling 
and benchmarking requirements in the August 11, 2003 proposal. A few 
commenters supported the proposed requirements but most raised concerns 
with the burden and usefulness of disinfection profiling and requested 
greater flexibility. These comments and EPA's responses are summarized 
as follows.
    Commenters stated that disinfection profiling diverts PWS and State 
resources from other public health protection activities and presents 
an incomplete picture of the information that should be considered when 
evaluating disinfection changes. Further, some States can only require 
the level of treatment specified in regulations (e.g., the SWTR, 
IESWTR, LT1ESWTR) and cannot use a disinfection benchmark to enforce a 
higher treatment standard. Some commenters also disagreed with 
requiring a disinfection profile for viruses, since current 
disinfection practices targeting Giardia lamblia typically achieve much 
greater virus inactivation than required.

[[Page 713]]

    To address these concerns, commenters requested that profiling only 
be required for PWSs prior to switching disinfectants or that States be 
allowed to grant waivers from disinfection profiling requirements. 
Commenters also recommended that States be given flexibility to 
determine the appropriate time for PWSs to develop disinfection 
profiles, if necessary. In regard to virus profiling, some commenters 
suggested that it only be required for PWSs that have not developed 
profiles for Giardia lamblia or that are switching disinfectants to UV.
    In response, EPA has modified the proposed requirements for 
disinfection profiling and benchmarking from the proposal to 
significantly reduce the burden on PWSs and States. In today's final 
rule, profiling is only required for PWSs that propose to make a 
significant change in disinfection practice. EPA projects that most 
PWSs will not be required to make treatment changes to comply with the 
LT2ESWTR and Stage 2 DBPR and, as a result, will not be required to 
develop disinfection profiles. Further, today's rule gives PWSs and 
States flexibility to determine the timing for developing disinfection 
profiles and only requires that the profiles and benchmarks be included 
in a notification to the State before a PWS implements a significant 
change in disinfection practice. For PWSs that have not developed 
disinfection profiles, EPA recommends recording the necessary 
operational data at least weekly over one year so that a profile can be 
prepared if needed.
    For PWSs that propose to make a significant change in disinfection 
practice, today's rule maintains the proposed requirement for a 
disinfection profile for viruses. EPA recognizes that current 
disinfection practices with chlorine typically achieve far more virus 
inactivation than required. However, the types of treatment changes 
that PWSs will make to comply with the Stage 2 DBPR or LT2ESWTR, such 
as implementing UV or microfiltration, are likely to maintain high 
levels of treatment for Giardia lamblia but may result in a significant 
decrease in treatment for viruses. Consequently, EPA believes that 
States and PWSs should consider whether such a decrease in virus 
treatment will occur when evaluating proposed treatment changes.
    Moreover, developing a virus disinfection profile does not require 
the collection of operational data beyond that necessary to develop a 
Giardia lamblia disinfection profile. Therefore, today's rule allows 
PWSs to use previously developed Giardia lamblia disinfection profiles 
and allows the operational data that underlie the Giardia lamblia 
profile to be used for a virus disinfection profile.

F. Requirements for Systems With Uncovered Finished Water Storage 
Facilities

1. Today's Rule
    Today's rule requires PWSs that store treated water in an open 
reservoir (i.e., use uncovered finished water storage facilities) to do 
either of the following:
     Cover the finished water storage facility; or
     Treat the discharge of the uncovered finished water 
storage facility that is distributed to consumers to achieve 
inactivation and/or removal of 4-log virus, 3-log Giardia lamblia, and 
2-log Cryptosporidium.
    PWSs must notify the State if they use uncovered finished water 
storage facilities no later than April 1, 2008. PWSs must either meet 
the requirements of today's rule for covering or treating each facility 
or be in compliance with a State-approved schedule for meeting these 
requirements no later than April 1, 2009.
    Today's rule revises the definition of an uncovered finished water 
storage facility as follows: uncovered finished water storage facility 
is a tank, reservoir, or other facility used to store water that will 
undergo no further treatment to reduce microbial pathogens except 
residual disinfection and is directly open to the atmosphere.
2. Background and Analysis
    The requirements in today's rule for PWSs that use uncovered 
finished water storage facilities (open reservoirs) are based on an 
assessment of the types and sources of contaminants in open reservoirs, 
the efficacy and feasibility of regulatory approaches to reduce risks 
from this contamination, and comments on the August 11, 2003 proposal. 
The following discussion summarizes this assessment.
    a. Types and sources of contaminants in open reservoirs. The 
storage of treated drinking water in open reservoirs can lead to 
significant water quality degradation and health risks to consumers 
(USEPA 1999e). Examples of such water quality degradation include 
increases in algal cells, coliform bacteria, heterotrophic plate count 
bacteria, turbidity, particulates, DBPs, metals, taste and odor, insect 
larvae, Giardia, Cryptosporidium, and nitrate (USEPA 1999e). 
Contamination of open reservoirs occurs through surface water runoff, 
bird and animal wastes, human activity, algal growth, insects and fish, 
and airborne deposition. Additional information on these sources of 
contamination follows.
    If a reservoir receives surface water runoff, the SWTR requires 
that it be treated as raw water storage, rather than a finished water 
reservoir (40 CFR 141.70(a)). Nevertheless, many uncovered finished 
water reservoirs have been found to be affected by surface water 
runoff, which may include agricultural fertilizers, pesticides, 
microbial pathogens, automotive fluids and residues, sediment, 
nutrients, natural organic matter, and metals (USEPA 1999e, 
LeChevallier et al. 1997).
    Birds are a significant cause of contamination in open reservoirs, 
and bird feces may contain coliform bacteria, viruses, and other human 
pathogens, including vibrio cholera, Salmonella, Mycobacteria, Typhoid, 
Giardia, and Cryptosporidium (Geldreich and Shaw 1993). Birds can 
ingest pathogens at landfills or wastewater treatment plants prior to 
visiting a reservoir and have been shown to carry and pass infectious 
Cryptosporidium parvum (Graczyk et al. 1996). Five to twenty percent of 
birds are estimated to be periodically infected with human pathogens 
like Salmonella (USEPA 1999e). A 1993 Salmonella outbreak in Gideon, MO 
that resulted in seven deaths was traced to pigeons roosting in a 
finished water storage tank.
    Animals that are either known or suspected to contaminate open 
reservoirs include dogs, cats, deer, rats, mice, opossums, squirrels, 
muskrats, raccoons, beavers, rabbits, and frogs. Some animals are 
infected with human pathogens like Cryptosporidium, which can be 
discharged to the reservoirs in feces or transmitted by direct contact 
between animals and the water (Fayer and Unger 1986, Current 1986, 
USEPA 1999e).
    Open reservoirs are exposed to contamination through human 
activities. Pesticides and fertilizers can enter open reservoirs 
through runoff and airborne drifts from spray applications. Swimming in 
reservoirs can result in pathogens being passed from the feces, shedded 
skin, and mucus membranes of infected persons. PWSs routinely find a 
great variety of items that have been thrown into open reservoirs, 
despite the use of high fences and set-back distances. Such items 
include baby carriages, beer bottles, bicycles, bullets, dead animals, 
dog waste bags, fireworks, garbage cans, a pay phone, shoes, and 
shovels (USEPA 1999e). These items are a potential source of pathogens 
and toxic substances and clearly indicate the

[[Page 714]]

susceptibility of open reservoirs to intentional contamination.
    Algal growth is common in open reservoirs and can lead to aesthetic 
problems like color, taste, and odor, and may generate cyanobacterial 
toxins, which cause headaches, fever, diarrhea, abdominal pain, nausea, 
and vomiting. In addition, algae can increase other contaminants like 
DBPs by increasing biomass within reservoirs, and corrosion products 
like lead, through causing significant pH fluctuations. Algae have been 
shown to shield bacteria from the effects of disinfection (Geldreich 
and Shaw 1993).
    Open reservoirs may be infested with the larvae of insects such as 
midge flies, water fleas, and gnats, which can be carried through the 
distribution system from the reservoir (USEPA 1999e). Chlorination is 
ineffective against midge fly larvae. Fly outbreaks may increase the 
presence of insect-eating birds, which present another source of 
contamination as described earlier. Some open finished water reservoirs 
have been found to support fish populations.
    Open reservoirs also are subject to airborne deposition of 
contaminants, such as industrial pollutants, automobile emissions, 
pollen, dust, particulate matter, and bacteria. Deposition occurs 
during all types of weather conditions, but is likely to be accelerated 
during precipitation events as air pollutants are transported from the 
air column above the reservoir by rain or snow.
    b. Regulatory approaches to reduce risk from contamination in open 
reservoirs. For many decades, public health agencies and professional 
associations like the American Public Health Association, the U.S. 
Public Health Service, and the American Water Works Association have 
recommended that all finished water reservoirs be covered (USEPA 
1999e). In the IESWTR and LT1ESWTR, EPA prohibited the construction of 
new uncovered finished water reservoirs (40 CFR 141.170(c) and 
141.511). These regulations did not address existing uncovered finished 
water reservoirs, however. In the preamble to the IESWTR, EPA stated 
that a requirement to cover existing reservoirs would be considered 
when data to develop national cost estimates were available.
    EPA has now collected the necessary data to estimate costs 
associated with regulatory control strategies for uncovered finished 
water reservoirs. The August 11, 2003 LT2ESWTR proposal included three 
options for PWSs with uncovered finished water reservoirs to reduce 
risk: (1) cover the reservoir, (2) treat the discharge to achieve 4-log 
virus inactivation, or (3) implement a State-approved risk mitigation 
plan (USEPA 2003a). These options reflected recommendations from the 
Stage 2 M-DBP Advisory Committee (USEPA 2000a). Today's final rule 
includes the first option to cover, modifies the second option to also 
require 3-log Giardia and 2-log Cryptosporidium treatment, and does not 
establish an option for a risk mitigation plan. The following 
discussion describes the basis for these changes.
    As described earlier, studies have shown that small mammals and 
birds that live near water may be infected with Cryptosporidium and 
Giardia and may shed infectious oocysts and cysts into the water 
(Graczyk et al. 1996, Fayer and Unger 1986, Current 1986). LeChevallier 
et al. (1997) evaluated Cryptosporidium and Giardia levels in six 
uncovered finished water reservoirs. The geometric mean concentration 
of Cryptosporidium was 1.2 oocysts/100 L in the inlet samples and 8.1 
oocysts/100 L in the effluent samples (i.e., 600 percent increase in 
the reservoir). For Giardia, the geometric mean concentrations in the 
inlet and effluent samples were 1.9 and 6.1 cysts/100 L, respectively 
(i.e., 200 percent increase in reservoir).
    Most, if not all, PWSs would treat to achieve 4-log virus 
inactivation with chlorine. Based on EPA guidance, the dose of chlorine 
necessary for 4-log virus inactivation would not achieve even 0.5-log 
Giardia inactivation and would produce no inactivation of 
Cryptosporidium (USEPA 1991b). Consequently, PWSs treating for viruses 
in open reservoirs, as proposed, would provide very little protection 
against contamination by Giardia and Cryptosporidium.
    Due to the demonstrated potential for contamination by Giardia and 
Cryptosporidium in open reservoirs and the ineffectiveness of virus 
treatment against these pathogens, today's rule requires PWSs to treat 
for Giardia and Cryptosporidium in addition to viruses if they do not 
cover their finished water reservoirs. Specifically, today's rule 
specifies the same baseline treatment as required for a raw unfiltered 
source, which is 4-log virus, 3-log Giardia, and 2-log Cryptosporidium 
reduction.
    EPA believes that requiring treatment for viruses, Giardia, and 
Cryptosporidium in uncovered finished water reservoirs is consistent 
with SDWA section 1412(b)(7)(A), which authorizes the use of a 
treatment technique to prevent adverse health effects to the extent 
feasible if measuring the contaminant is not feasible. Monitoring for 
these pathogens at the very low levels that would cause public health 
concern and at the frequency necessary to detect contamination events 
is not feasible with available analytical methods. EPA has determined 
that with the availability of technologies like UV, treating for 
Giardia, Cryptosporidium, and viruses is feasible for all PWS sizes.
    Today's rule does not allow PWSs to implement a risk mitigation 
plan as an alternative to covering a reservoir or treating the 
discharge because EPA does not believe that a risk mitigation plan 
would provide equivalent public health protection. Consequently, a risk 
mitigation plan would not meet the statutory provision for a treatment 
technique to prevent adverse health effects from pathogens like Giardia 
and Cryptosporidium to the extent feasible (SDWA section 
1412(b)(7)(A)).
    As discussed earlier, open reservoirs are subject to contamination 
from many sources, including runoff, birds, animals, humans, algae, 
insects, and airborne deposition. Control measures can provide a degree 
of protection against some of these sources (e.g., bird deterrent 
wires, security fences with setback distances). All PWSs are 
significantly constrained, however, in the degree to which they can 
implement such measures with existing open reservoirs due to factors 
like the size of the reservoir, the location of the reservoir (e.g., 
within residential communities or parks), and the existing 
infrastructure. For example, many open finished water reservoirs are 
impacted by runoff, despite the fact that this has been prohibited for 
many years under existing regulations (USEPA 1999e). EPA has concluded 
that implementing control measures that would be highly effective 
against all sources of contamination of open reservoirs would not be 
feasible for PWSs. Accordingly, today's rule does not allow this 
option.
    c. Definition of uncovered finished water storage facility. The 
IESWTR established the following definition for an uncovered finished 
water storage facility: uncovered finished water storage facility is a 
tank, reservoir, or other facility used to store water that will 
undergo no further treatment except residual disinfection and is open 
to the atmosphere.
    In the August 11, 2003, proposed LT2ESWTR, EPA requested comment on 
whether this definition should be revised. EPA was concerned that it 
would not include certain cases in which water is stored in an open 
reservoir after a PWS completes treatment to reduce microbial

[[Page 715]]

pathogens. Such a case would be a PWS that applies a corrosion 
inhibitor to the effluent of an open reservoir where water is stored 
after filtration and primary disinfection. In this case, the PWS could 
claim that the corrosion inhibitor constitutes additional treatment 
and, consequently, the open reservoir does not meet EPA's definition of 
an uncovered finished water storage facility. However, the water stored 
in the open reservoir would be subject to microbial contamination from 
the sources described in this section and would undergo no further 
treatment for this contamination.
    Today's rule revises the definition of an uncovered finished water 
storage facility in two ways: (1) The phrase ``to reduce microbial 
pathogens'' is inserted following the word ``treatment;'' and (2) the 
word ``directly'' is inserted prior to ``open to the atmosphere.'' The 
first change ensures that an open reservoir where water is stored after 
a PWS has completed filtration (where required) and primary 
disinfection will be appropriately classified as an uncovered finished 
water storage facility. Whether a PWS applies corrosion control or 
other treatment to maintain water quality in the distribution system 
will not affect this determination.
    The second change clarifies that covered reservoirs with air vents 
or overflow lines are not uncovered finished water storage facilities. 
Such air vents and overflow lines are open to the atmosphere but are 
usually hooded or screened to prevent contamination of the water. 
Consequently, these reservoirs are not directly open to the atmosphere 
and are not subject to the requirements of today's rule for uncovered 
finished water storage facilities.
3. Summary of Major Comments
    EPA received significant public comment on requirements for 
uncovered finished water storage facilities in the August 11, 2003 
proposal. Major issues raised by commenters include whether to require 
all reservoirs to be covered, requiring treatment for Giardia and 
Cryptosporidium, support for the proposed options, and revising the 
definition of an uncovered finished water storage facilities. A summary 
of these comments and EPA's responses follows.
    Several commenters recommended that EPA require all finished water 
reservoirs to be covered. These commenters stated that making an 
uncovered reservoir equal in quality to a covered reservoir is not 
possible--open reservoirs will always be contaminated by fecal material 
from birds and small mammals, as well as increased DBPs due to algae 
and other aquatic organisms, airborne contaminants, and sediment 
stirred up by wind. Commenters were also concerned that uncovered 
reservoirs are a major vulnerability for PWS security (i.e., 
intentional contamination). Some commenters cited the fact that there 
are hundreds of thousands of covered finished water reservoirs in 
comparison to approximately 100 uncovered finished water reservoirs as 
evidence that the public health risks of open reservoirs are widely 
recognized.
    EPA agrees that storing treated water in open reservoirs presents a 
risk to public health. With today's final rule, EPA expects that many 
PWSs will cover or eliminate uncovered finished water reservoirs. For 
reservoirs where covering is not feasible, EPA believes that treating 
the water for Giardia, Cryptosporidium, and viruses will provide 
protection against the range of pathogens likely to contaminate the 
reservoir.
    Many commenters supported requiring treatment for Giardia and 
Cryptosporidium for PWSs that treat the reservoir discharge. Commenters 
stated that reservoirs should either be covered or treated as 
unfiltered sources (meaning 3-log Giardia, 2-log Cryptosporidium, and 
4-log virus treatment). The LeChevallier et al. (1997) study was cited 
as demonstrating increases in Giardia and Cryptosporidium in uncovered 
finished water reservoirs, and commenters noted that treatment for 
viruses would not be effective against these protozoa. EPA agrees with 
these comments and today's rule requires treatment for Giardia and 
Cryptosporidium, as well as viruses, by PWSs that do not cover their 
reservoirs.
    Some commenters expressed support for the proposed options, 
including allowing risk mitigation plans as an adequate remedy for an 
uncovered reservoir. These commenters characterized the proposal as 
providing reasonable alternatives to the substantial costs involved in 
covering reservoirs or providing alternative storage. Commenters stated 
that strategies included in a risk management plan could address the 
range of microorganisms for which treatment is necessary, depending on 
site-specific circumstances.
    EPA recognizes that covering or finding alternative storage for 
uncovered finished water reservoirs can be costly. While EPA believes 
that covering finished water reservoirs is the most effective approach 
to protecting public health, today's rule allows PWSs to provide 
treatment for Giardia, Cryptosporidium, and viruses as a feasible 
alternative. As described earlier, EPA does not believe that providing 
treatment only for viruses, as proposed, would be protective against 
the range of pathogens that contaminate open reservoirs. Further, EPA 
has concluded that implementing a risk mitigation plan that would 
provide equivalent protection to covering or treating a reservoir is 
not feasible. This is due to the many potential sources of 
contamination and the significant limitations that all PWSs have in the 
control measures they can implement for existing open reservoirs.
    Commenters supported revising the definition of uncovered finished 
water storage facilities to include situations where PWSs apply a 
treatment like corrosion control to water stored in an open reservoir 
after the water has undergone filtration, where required, and primary 
disinfection. In addition, commenters recommended that EPA clarify that 
``open to the atmosphere'' in the definition does not include vents and 
overflow lines in covered reservoirs. EPA agrees with these comments 
and today's rule is consistent with them.

G. Compliance Schedules

1. Today's Rule
    This section specifies compliance dates for the monitoring and 
treatment technique requirements in today's rule. As described in 
sections IV.A through IV.F of this preamble, today's rule requires PWSs 
to carry out the following activities:
     Conduct initial source water monitoring on a reported 
schedule. PWSs may grandfather previously collected monitoring results 
and may elect to provide the maximum Cryptosporidium treatment level of 
5.5-log for filtered PWSs or 3.0-log for unfiltered PWSs instead of 
monitoring.
     Determine a treatment bin classification (or mean 
Cryptosporidium level for unfiltered PWSs) based on monitoring results.
     For filtered PWSs in Bins 2-4 and all unfiltered PWSs, 
provide additional treatment for Cryptosporidium by selecting 
technologies from the microbial toolbox.
     Report disinfection profiles and benchmarks prior to 
making a significant change in disinfection practice.
     Report the use of uncovered finished water storage 
facilities and cover or treat the discharge of such reservoirs on a 
State-approved schedule.

[[Page 716]]

     Conduct a second round of source water monitoring 
approximately six years after initial bin classification.
    Compliance dates for these activities vary by PWS size. Tables 
IV.G-1 and IV.G-2 specify source water monitoring and treatment 
compliance dates for large and small PWSs, respectively. Table IV.G-3 
shows compliance dates for PWSs using uncovered finished water storage 
facilities. Wholesale PWSs must comply with the requirements of today's 
rule based on the population of the largest PWS in the combined 
distribution system.

        Table IV.G-1.--Monitoring and Treatment Compliance Dates for PWSs Serving at Least 10,000 People
----------------------------------------------------------------------------------------------------------------
                                                              Compliance dates by PWS Size
                                      --------------------------------------------------------------------------
             Requirement                                         PWSs serving at least    PWSs serving at least
                                        PWSs serving at least     50,000 but less than     10,000 but less than
                                            100,000 people           100,000 people           50,000 people
----------------------------------------------------------------------------------------------------------------
Report sampling schedule and sampling  No later than July 1,    No later than January    No later than January
 location description for initial       2006..                   1, 2007.                 1, 2008.
 source water monitoring for
 Cryptosporidium (plus E. coli and
 turbidity at filtered PWSs) 1, 2.
Report notice of intent to
 grandfather previously collected
 Cryptosporidium data, if applicable.
Report intent to provide the maximum
 Cryptosporidium treatment level in
 lieu of monitoring, if applicable
 \1\.
Begin initial source water monitoring  No later than the month  No later than the month  No later than the month
 for Cryptosporidium (plus E. coli      beginning October 1,     beginning April 1,       beginning April 1,
 and turbidity at filtered PWSs) 1,2.   2006.                    2007.                    2008.
Submit previously collected            No later than December   No later than June 1,    No later than June 1,
 Cryptosporidium data and required      1, 2006.                 2007..                   2008.
 documentation for grandfathering, if
 applicable.
Report Cryptosporidium treatment bin   No later than the month  No later than the month  No later than the month
 classification (or mean                beginning April 1,       beginning October 1,     beginning October 1,
 Cryptosporidium concentration for      2009.                    2009.                    2010.
 unfiltered PWSs) and supporting data
 for approval.
Report disinfection profiles and             Prior to making a significant change in disinfection practice.
 benchmarks, if applicable.
Comply with additional                 No later than April 1,   No later than October    No later than October
 Cryptosporidium treatment              2012 \3\.                1, 2013 \3\.             1, 2012 \3\.
 requirements based on treatment bin
 classification (or mean
 Cryptosporidium concentration for
 unfiltered PWSs) \3\.
Report sampling schedule and sampling  No later than January    No later than July 1,    No later than July 1,
 location description for second        1, 2015.                 2015..                   2016.
 round of source water monitoring for
 Cryptosporidium (plus E. coli and
 turbidity at filtered PWSs) \1\.
Report intent to provide maximum
 Cryptosporidium treatment level in
 lieu of monitoring, if applicable
 \1\.
Begin second round of source water     No later than the month  No later than the month  No later than the month
 monitoring for Cryptosporidium (plus   beginning April 1,       beginning October 1,     beginning October 1,
 E. coli and turbidity at filtered      2015.                    2015.                    2016.
 PWSs) \1\.
Report Cryptosporidium treatment bin   No later than the month  No later than the month  No later than the month
 classification (or mean                beginning October 1,     beginning April 1,       beginning April 1,
 Cryptosporidium concentration for      2017.                    2018.                    2019.
 unfiltered PWSs) and supporting data
 from second round of monitoring for
 approval.
Comply with additional                                     On a schedule the State approves.
 Cryptosporidium treatment
 requirements if bin classification
 (or mean Cryptosporidium
 concentration for unfiltered PWSs)
 changes based on second round of
 monitoring.
----------------------------------------------------------------------------------------------------------------
\1\ PWS are not required to conduct source water monitoring if they submit a notice of intent to provide the
  maximum Cryptosporidium treatment level: 5.5-log for filtered PWSs or 3.0-log for unfiltered PWSs.
\2\ Not required if PWS grandfathers at least 2 years of Cryptosporidium data.
\3\ States may grant up to an additional 2 years for systems making capital improvements.


    Table IV.G-2.--Monitoring and Treatment Compliance Dates for PWSs
                    Serving Fewer Than 10,000 People
------------------------------------------------------------------------
              Requirement                        Compliance dates
------------------------------------------------------------------------
   Indicator (E. coli) Monitoring Requirements for Filtered PWSs Only
------------------------------------------------------------------------
Report sampling schedule and sampling    No later than July 1, 2008.
 location description for initial
 source water monitoring for E. coli or
 alternative State-approved indicator1
 2.
Report notice intent to grandfather      ...............................
 previously collected E. coli data, if
 applicable.
Report intent to provide the maximum     ...............................
 Cryptosporidium treatment level in
 lieu of monitoring, if applicable \1\.
Begin initial source water monitoring    No later than the month
 for E. coli1 2.                          beginning October 1, 2008.
Report E. coli data for grandfathering,  No later than December 1, 2008.
 if applicable.

[[Page 717]]

 
Report sampling schedule and sampling    No later than July 1, 2017.
 location description for second round
 of source water monitoring for E. coli
 \1\.
Report intent to provide the maximum     ...............................
 Cryptosporidium treatment level in
 lieu of monitoring, if applicable \1\.
Begin second round of source water       No later than the month
 monitoring for E. coli \1\.              beginning October 1, 2017.
------------------------------------------------------------------------


 
                                   Compliance dates by monitoring option
                                 ---------------------------------------
           Requirement              PWSs monitoring     PWSs monitoring
                                    twice-per-month      monthly for 2
                                      for 1 year             years
------------------------------------------------------------------------
  Cryptosporidium Monitoring Requirements for Filtered PWSs That Exceed
  Indicator (E. coli) Trigger Concentration \3\ and All Unfiltered PWSs
------------------------------------------------------------------------
Report sampling schedule and      No later than January 1, 2010.
 sampling location description
 (if not reported previously)
 for initial source water
 monitoring for Cryptosporidium
 1 4.
 Report notice of intent to
 grandfather previously
 collected Cryptosporidium data,
 if applicable.
Begin initial source water        No later than the month beginning
 monitoring for Cryptosporidium    April 1, 2010.
 1 4.
Submit previously collected       No later than June
 Cryptosporidium data and          1, 2010.
 required documentation for
 grandfathering, if applicable.
Report Cryptosporidium treatment  No later than the   No later than the
 bin classification (or mean       month beginning     month beginning
 Cryptosporidium concentration     October 1, 2011.    October 1, 2012.
 for unfiltered PWSs) and
 supporting data for approval.
Report disinfection profiles and  Prior to making a significant change
 benchmarks, if applicable.        in disinfection practice.
Comply with additional            No later than
 Cryptosporidium treatment         October 1, 2014
 requirements based on treatment   \5\.
 bin classification (or mean
 Cryptosporidium concentration
 for unfiltered PWSs) \5\.
Report sampling schedule          No later than than
 sampling location description     January 1, 2019.
 (if not reported previously)
 for second round of source
 water Cryptosporidium
 monitoring \1\.
Begin second round of source      No later than the
 water monitoring for              month beginning
 Cryptosporidium \1\..             April 1, 2019.
Report Cryptosporidium treatment  No later than the   No later than the
 bin classification (or mean       month beginning     month beginning
 Cryptosporidium concentration     October 1, 2020.    October 1, 2021.
 for unfiltered PWSs) and
 supporting data from second
 round of monitoring for
 approval.
Comply with additional            On a schedule the State approves.
 Cryptosporidium treatment
 requirements if bin
 classification (or mean
 Cryptosporidium concentration
 for unfiltered PWSs) changes
 based on second round of
 monitoring.
------------------------------------------------------------------------
\1\ PWS are not required to conduct source water monitoring if they
  submit a notice of intent to provide the maximum Cryptosporidium
  treatment level: 5.5-log for filtered PWSs or 3.0-log for unfiltered
  PWSs.
\2\ Not required if PWS grandfathers at least 1 year of E. coli data.
\3\ Filtered PWSs must conduct Cryptosporidium monitoring if the E. coli
  annual mean concentration exceeds 10/100 mL for PWSs using lake or
  reservoir sources or exceeds 50/100 mL for PWSs using flowing stream
  sources or a trigger value for an alternative State-approved indicator
  is exceeded.
\4\ Not required if PWS grandfathers at least 1 year of twice-per-month
  or 2 years of monthly Cryptosporidium data.
\5\ States may grant up to an additional 2 years for PWSs making capital
  improvements.


 Table IV.G-3.--Compliance Dates for PWSs Using Uncovered Finished Water
                           Storage Facilities
------------------------------------------------------------------------
 
------------------------------------------------------------------------
Report the use of uncovered finished     No later than April 1, 2008.
 water storage facilities, if
 applicable.
Either comply with requirement to cover  No later than April 1, 2009.
 or treat uncovered finished water
 storage facilities or comply with
 State-approved schedule to meet this
 requirement.
------------------------------------------------------------------------

2. Background and Analysis
    The compliance schedule in today's final rule stems from its risk-
targeted approach, wherein PWSs initially conduct monitoring to 
determine additional treatment requirements. A primary objective of 
this schedule is to ensure that PWSs provide additional treatment 
without delay for higher risk sources. This is especially important 
with a risk-targeted rule, given the significant time required for 
initial monitoring. However, the compliance schedule balances this 
objective with the need to provide PWSs and States with time to prepare 
for implementation activities.
    SDWA section 1412(b)(10) states that a drinking water regulation 
shall take effect 3 years from the promulgation date unless the 
Administrator determines that an earlier date is practicable. Today's 
rule requires PWSs to begin monitoring prior to 3 years from the 
promulgation date. Based on EPA's assessment and recommendations of the 
Advisory Committee, as described in this section, EPA has determined 
that these monitoring start dates are practicable and appropriate.

[[Page 718]]

    In general, PWSs serving at least 10,000 people conduct two years 
of source water monitoring for Cryptosporidium (as well as E. coli and 
turbidity in filtered PWSs). At the conclusion of this monitoring, 
these PWSs have six months to analyze monitoring results and report 
their treatment bin classification to the State for approval. Where 
required, PWSs must provide the necessary level of additional 
Cryptosporidium treatment within three years of bin classification, 
though States may allow an additional two years for PWSs making capital 
improvements. A second round of source water monitoring must be 
initiated six years after initial bin classification.
    For PWSs serving at least 10,000 people, the timing of monitoring 
and treatment activities in today's rule partially reflects 
recommendations by the Stage 2 M-DBP Advisory Committee and the 
schedule in the August 11, 2003 proposed LT2ESWTR. EPA has modified the 
proposed compliance schedule to stagger monitoring start dates for PWSs 
serving 10,000 to 99,999 people. The following discussion addresses 
these changes from the proposal.
    The proposed rule required all PWSs serving at least 10,000 people 
to begin source water monitoring six months after the rule was 
established, as recommended by the Advisory Committee. Under today's 
final rule, PWSs serving at least 100,000 people maintain this 
schedule. The monitoring start date for PWSs serving 50,000 to 99,999 
people is staggered by six months and begins 12 months after the rule 
is effective. For PWSs serving 10,000 to 49,999, the monitoring start 
date is staggered by 18 months and begins 24 months after the rule is 
effective. Dates to comply with additional treatment requirements are 
staggered accordingly.
    This staggering of monitoring start dates for PWSs serving 10,000 
to 99,999 people is advantageous in several respects:
     Provides more time for PWSs that have not monitored for 
Cryptosporidium previously to prepare for monitoring (PWSs serving at 
least 100,000 people monitored for Cryptosporidium under the ICR). PWSs 
can use this time to develop budgets, establish contracts with 
Cryptosporidium laboratories, identify appropriate sampling locations, 
and learn sampling procedures.
     Provides more time for Cryptosporidium analytical 
laboratories to build capacity as needed to accommodate the sample 
analysis needs of PWSs.
     Spreads out the transactional demand for regulatory 
oversight. EPA anticipates that the period of greatest transactional 
demand for States and EPA that oversee monitoring will be when PWSs 
begin monitoring. The staggered schedule will allow States and EPA to 
provide more assistance to individual PWSs.
     Eliminates the gap between the end of large PWS monitoring 
and the start of small PWS monitoring (under the proposed rule 
schedule, a gap of 18 months existed between the time that large PWSs 
completed and small PWSs started Cryptosporidium monitoring). Such a 
gap could create difficulties with maintaining Cryptosporidium sampling 
and laboratory analysis expertise to support monitoring by small PWSs.
    The timing of monitoring and treatment activities in today's rule 
for PWSs serving fewer than 10,000 people is nearly identical to the 
schedule in the August 11, 2003 proposed LT2ESWTR and reflects 
recommendations by the Advisory Committee. The only change is allowing 
these PWSs the option to spread their Cryptosporidium monitoring over 
two years in order to facilitate budgeting for this monitoring. 
However, this change does not affect the treatment compliance dates for 
these PWSs.
    Specifically, filtered PWSs serving fewer than 10,000 people 
initially conduct one year of source water monitoring for E. coli or an 
alternative indicator if approved by the State, beginning 30 months 
after the rule is effective. At the conclusion of this monitoring, 
these PWSs have six months to prepare for Cryptosporidium monitoring, 
if required based on their indicator monitoring results. Filtered PWSs 
that exceed the indicator trigger value and all unfiltered PWSs serving 
fewer than 10,000 people must begin Cryptosporidium monitoring 48 
months after the rule is effective. This Cryptosporidium monitoring may 
consist of sampling twice-per-month for one year or once-per-month for 
two years. PWSs must report their bin classification to the State for 
approval within six months of the scheduled completion of 
Cryptosporidium monitoring.
    Regardless of the Cryptosporidium sampling frequency, PWSs serving 
fewer than 10,000 people must comply with any additional 
Cryptosporidium treatment requirements within 102 months (8.5 years) 
after the rule is effective. States may allow an additional two years 
for PWSs making capital improvements. PWSs must begin a second round of 
source water monitoring for E. coli or an alternative State-approved 
indicator within 11.5 years (138 months) after the rule is effective 
(six years after the bin classification date for PWSs that sampled for 
Cryptosporidium twice-per-month during initial source water 
monitoring).
    In summary, the compliance schedule for today's rule maintains the 
earliest compliance dates recommended by the Advisory Committee for 
PWSs serving at least 100,000 people. These PWSs serve the majority of 
people that consume water from surface sources. The schedule also 
maintains the latest compliance dates the Advisory Committee 
recommended, which apply to PWSs serving fewer than 10,000 people. EPA 
has staggered compliance schedules for PWSs between these two size 
categories in order to facilitate implementation of the rule.
3. Summary of Major Comments
    EPA received significant public comment on the compliance schedule 
in the August 11, 2003 proposal. Major issues raised by commenters 
include providing more time for PWSs to prepare for monitoring, giving 
States more time to oversee monitoring, ensuring that laboratory 
capacity can accommodate the compliance schedule, and establishing 
consistent schedules for consecutive PWSs. A summary of these comments 
and EPA's responses follows.
    Commenters were concerned that some PWSs, in particular PWSs 
serving 10,000 to 50,000 people, would need more than the three months 
allowed under the proposed rule to report sampling schedules for 
monitoring. In order to develop sampling schedules, PWSs must establish 
contracts with laboratories, which may involve using municipal 
procurement procedures. For smaller PWSs, budgeting for this expense 
may require substantial time and planning.
    EPA recognizes this concern and today's final rule provides 
significantly more time for many PWSs to submit sampling schedules. 
Specifically, PWSs serving 50,000 to 99,999 people and those serving 
10,000 to 49,999 people must submit sampling schedules 9 and 21 months 
after the rule is effective, respectively. EPA believes that these PWSs 
will have sufficient time to develop sampling schedules with these 
compliance dates. Today's rule still requires PWSs serving at least 
100,000 people to submit sampling schedules 3 months after the rule is 
effective. Because these PWSs have monitored for Cryptosporidium 
previously, however,

[[Page 719]]

EPA believes that this compliance date is feasible for these PWSs.
    Several commenters recommended that States, rather than EPA, 
oversee monitoring due to States' existing relationships with and 
knowledge of their PWSs. Commenters were concerned that some States 
will not participate in early implementation activities and indicated 
that States would prefer monitoring to begin 24 months after rule 
promulgation. States need sufficient time to become familiar with the 
rule, train their staff, prepare primacy packages, and train PWSs.
    In general, EPA would prefer that States oversee monitoring by 
their PWSs and will work with States to facilitate their involvement 
with rule implementation. Where States are unable to implement today's 
rule, however, EPA is prepared to oversee implementation. Moreover, EPA 
believes that the staggered compliance schedule in today's final rule 
will enhance States' ability to implement the rule.
    While EPA does not consider waiting until 24 months after rule 
promulgation to start monitoring for all PWSs to be appropriate, most 
PWSs will not begin monitoring until this time or later under today's 
rule. Among large PWSs (i.e., those serving at least 10,000 people), 
the majority are in the 10,000 to 49,999 person size category and these 
PWSs do not begin monitoring until 24 months after rule promulgation. 
Further, all PWSs serving fewer than 10,000 people do not begin 
monitoring until 30 months after rule promulgation. These smaller PWSs 
are likely to need the most assistance from States. By staggering 
monitoring start dates, today's rule also reduces the number of PWSs 
that will begin monitoring at any one time, when the most assistance 
from regulatory agencies will be required.
    Many commenters were concerned that the capacity at Cryptosporidium 
analytical laboratories would not be sufficient for the proposed 
implementation schedule. Commenters noted that the proposed rule 
schedule had a break of 18 months between the end of large PWS 
Cryptosporidium monitoring and the start of small PWS Cryptosporidium 
monitoring and thought that this break would discourage laboratories 
from making investments to improve capacity. Other commenters stated 
that excess laboratory capacity exists and that upon indication that a 
final rule is imminent, commercial laboratories will hire staff to 
handle the expected number of samples. Laboratories will, however, need 
time to train analysts.
    EPA recognizes the concern with ensuring that capacity at 
Cryptosporidium laboratories will be sufficient. Through EPA's 
laboratory approval program (described in section IV.K), the Agency has 
evaluated capacity at Cryptosporidium laboratories. Based on 
information provided by laboratories, EPA believes that current 
capacity at Cryptosporidium laboratories will be sufficient for the 
monitoring that PWSs serving at least 100,000 people will begin six 
months after the rule is effective. EPA expects that commercial 
laboratories will increase capacity as needed to serve the demand of 
smaller PWSs that begin monitoring later. Approximately six months are 
required to train Cryptosporidium analysts. Consequently, the staggered 
compliance schedule should allow time for laboratories to hire and 
train staff as necessary. In addition, with the compliance schedule in 
today's final rule, no break exists between the time that large PWSs 
end and small PWSs begin Cryptosporidium monitoring. Thus, EPA has 
eliminated this potential disincentive to laboratories investing in 
capacity.
    However, EPA will continue to monitor laboratory capacity and the 
ability of PWSs to contract with laboratories to meet their monitoring 
requirements under the LT2ESWTR. The Agency will assist with 
implementation of the rule to help maximize the use of available 
laboratory capacity by PWSs. If evidence emerges during implementation 
of the rule that PWSs are experiencing problems with insufficient 
laboratory capacity, the Agency will undertake appropriate action at 
that time.
    In regard to consecutive PWSs (i.e., PWSs that buy and sell treated 
water), commenters recommended that compliance schedules in the Stage 2 
DBPR and LT2ESWTR should be consistent. Some commenters also suggested 
that where a small PWS sells water to a large PWS, the small PWS should 
comply on the large PWS schedule. In response, today's final rule 
requires PWSs that sell treated drinking water to other PWSs to comply 
according to the schedule that applies to the largest PWS in the 
combined distribution system. This approach will ensure that PWSs have 
the same compliance schedule under both the LT2ESWTR and Stage 2 DBPR.

H. Public Notice Requirements

1. Today's Rule
    Today's rule establishes the following public notice requirements:
     For violations of treatment technique requirements, which 
today's rule establishes for Cryptosporidium treatment and for covering 
or treating uncovered finished water reservoirs, PWSs must issue a Tier 
2 public notice and must use existing health effects language (except 
as provided below) for microbiological contaminant treatment technique 
violations, as stated in 40 CFR 141 Subpart Q, Appendix B.
     For violations of monitoring and testing procedure 
requirements, including the failure to collect one or two source water 
Cryptosporidium samples, PWSs must issue a Tier 3 public notice. If the 
State determines that a PWS has failed to collect three or more 
Cryptosporidium samples, the PWS must provide a Tier 2 special public 
notice. Violations for failing to monitor continue until the State 
determines that the PWS has begun sampling on a revised schedule that 
includes dates for collection of missed samples. This schedule may also 
include a revised bin determination date where necessary.
     PWSs must report their bin classification no later than 
six months after the end of the scheduled monitoring period (specific 
dates in section IV.G.). Failure by a PWS to collect the required 
number of Cryptosporidium samples to report its bin classification by 
the compliance date is a treatment technique violation and the PWS must 
provide a Tier 2 public notice. The treatment technique violation 
persists until the State determines that the PWS is implementing a 
State-approved monitoring plan to allow bin classification or will 
install the highest level of treatment required under the rule. If the 
PWS has already provided a Tier 2 special public notice for missing 3 
sampling dates and is successfully meeting a State-approved schedule 
for sampling and bin determination, it need not provide a second Tier 2 
notice for missing the bin determination deadline in today's rule.
2. Background and Aalysis
    In 2000, EPA published the Public Notification Rule (65 FR 25982, 
May 4, 2000) (USEPA 2000b), which revised the general public 
notification regulations for PWSs in order to implement the public 
notification requirements of the 1996 SDWA amendments. This regulation 
established the requirements that PWSs must follow regarding the form, 
manner, frequency, and content of a public notice. Public notification 
of violations is an integral part of the public health protection and 
consumer right-to-know

[[Page 720]]

provisions of the 1996 SDWA Amendments.
    Owners and operators of PWSs are required to notify persons served 
when they fail to comply with the requirements of a NPDWR, have a 
variance or exemption from the drinking water regulations, or are 
facing other situations posing a risk to public health. The public 
notification requirements divide violations into three categories (Tier 
1, Tier 2 and Tier 3) based on the seriousness of the violations, with 
each tier having different public notification requirements.
    EPA has limited its list of violations and situations routinely 
requiring a Tier 1 notice to those with a significant potential for 
serious adverse health effects from short term exposure. Tier 1 
violations contain language specified by EPA that concisely and in non-
technical terms conveys to the public the adverse health effects that 
may occur as a result of the violation. States and water utilities may 
add additional information to each notice, as deemed appropriate for 
specific situations. A State may elevate to Tier 1 other violations and 
situations with significant potential to have serious adverse health 
effects from short-term exposure, as determined by the State.
    Tier 2 public notices address other violations with potential to 
have serious adverse health effects on human health. Tier 2 notices are 
required for the following situations:
     All violations of the MCL, maximum residual disinfectant 
level (MRDL) and treatment technique requirements, except where a Tier 
1 notice is required or where the State determines that a Tier 1 notice 
is required; and
     Failure to comply with the terms and conditions of any 
existing variance or exemption. Tier 3 public notices include all other 
violations and situations requiring public notice, including the 
following situations:
     A monitoring or testing procedure violation, except where 
a Tier 1 or 2 notice is already required or where the State has 
elevated the notice to Tier 1 or 2; and
     Operation under a variance or exemption.
    The State, at its discretion, may elevate the notice requirement 
for specific monitoring or testing procedures from a Tier 3 to a Tier 2 
notice, taking into account the potential health impacts and 
persistence of the violation.
    As part of the IESWTR, EPA established health effects language for 
violations of treatment technique requirements for microbiological 
contaminants. EPA believes this language, which was developed with 
consideration of Cryptosporidium health effects, is appropriate for 
violations of some Cryptosporidium treatment requirements under the 
LT2ESWTR. However, for persistent monitoring violations and missing the 
deadline for bin determination, EPA is promulgating alternative 
language that better informs consumers of the nature and potential 
health consequences of the violation.
    As described in section IV.C, EPA proposed automatically 
classifying PWSs in the highest treatment bin (Bin 4) if they fail to 
complete required monitoring. For today's final rule, EPA has 
determined that providing more flexibility to States in dealing with 
PWSs that fail to monitor is appropriate. EPA also believes, however, 
that responses to monitoring failures must reasonably ensure that PWSs 
complete monitoring as required to determine a bin classification 
within the compliance date, or as soon thereafter as possible. 
Moreover, consistent with the public health protection and consumer 
right-to-know provisions of the 1996 SDWA Amendments, consumers should 
be informed of these monitoring failures.
    Instead of the proposed automatic Bin 4 classification for 
monitoring failures under today's rule, PWSs must provide a Tier 3 
public notice for monitoring violations including up to two missed 
Cryptosporidium samples. If a PWS misses three or more Cryptosporidium 
samples (other than the specifically exempted situations described in 
section IV.A.1.c), this persistent violation requires a Tier 2 public 
notice. This elevated public notice level reflects significant concern 
that persistent failure to collect required samples will result in the 
PWS being unable to determine its Cryptosporidium treatment bin 
classification and the corresponding required treatment level by the 
compliance date.
    Further, if a PWS is unable to determine a bin classification by 
the compliance date due to failure to collect the required number of 
Cryptosporidium samples, this is a treatment technique violation that 
also requires a Tier 2 public notice, unless the system is already 
complying with an alternate State-approved schedule for monitoring and 
bin determination. A PWS that does not determine its bin classification 
by the required date may not be able to comply with the Cryptosporidium 
treatment technique requirements of today's rule by the required date 
and provide the appropriate level of public health protection.
3. Summary of Major Comments
    In the August 11, 2003, proposal, EPA requested comment on whether 
violations of the treatment requirements for Cryptosporidium under the 
LT2ESWTR should require a Tier 2 public notice and whether the proposed 
health effects language is appropriate (USEPA 2003a). Most commenters 
supported requiring a Tier 2 public notice for violations of 
Cryptosporidium treatment requirements under the LT2ESWTR and agreed 
that no new health effects language is needed for this notification. 
One commenter stated that a failure to meet Cryptosporidium removal 
requirements under LT2ESWTR should require Tier 1 public notice.
    Today's final rule reflects the views of most commenters and is 
consistent with existing regulations in requiring a Tier 2 public 
notice for Cryptosporidium treatment technique violations. A State may 
elevate a violation to Tier 1 if the State determines that the 
violation creates significant potential for serious adverse health 
effects from short-term exposure.
    Another commenter agreed that Tier 2 notice was appropriate but 
recommended that the LT2ESWTR and any associated guidance be more 
explicit as to when a treatment technique violation occurs with the use 
of microbial toolbox options. As described in section IV.D, EPA has 
stated in today's final rule that failure by a PWS in any month to 
demonstrate treatment credit with microbial toolbox options equal to or 
greater than its Cryptosporidium treatment requirements is a treatment 
technique violation. This violation lasts until the PWS demonstrates 
that it is meeting criteria for sufficient treatment credit to satisfy 
its Cryptosporidium treatment requirements.

I. Reporting Source Water Monitoring Results

    This section presents specific reporting requirements that apply to 
source water monitoring under today's rule, including EPA's data system 
for reporting and reviewing monitoring results. For related 
requirements, see section IV.A for monitoring parameters frequency, 
section IV.J for required analytical methods, and section IV.K for 
approved laboratories. General reporting requirements under today's 
rule and associated compliance dates are shown in section IV.G.
1. Today's Rule
    PWSs must report results from the required source water monitoring

[[Page 721]]

described in section IV.A no later than 10 days after the end of the 
first month following the month when the sample is collected. For 
Cryptosporidium analyses, PWSs must report the data elements specified 
in Table IV.I-1. For samples in which at least 10 L is filtered and all 
of the sample volume is analyzed, only the sample volume filtered and 
the number of oocysts counted must be reported. Table IV.I-2 presents 
the data elements that PWSs must report for E. coli and turbidity 
analyses. PWSs, or approved laboratories acting as the PWSs' agents, 
must retain results from Cryptosporidium and E. coli monitoring until 
36 months after bin determination for the particular round of 
monitoring.

       Table IV.I-1.--Cryptosporidium Data Elements To Be Reported
------------------------------------------------------------------------
              Data element                   Reason for data  element
------------------------------------------------------------------------
Identifying information:
    PWSID..............................  Needed to associate plant with
                                          public water system.
    Facility ID........................  Needed to associate sample
                                          result with facility.
    Sample collection point............  Needed to associate sample
                                          result with sampling point.
    Sample collection date.............  Needed to determine that
                                          utilities are collecting
                                          samples at the frequency
                                          required.
    Sample type (field or matrix spike)  Needed to distinguish field
     \1\.                                 samples from matrix samples
                                          for recovery calculations.
Sample results:
    Sample volume filtered (L), to       Needed to verify compliance
     nearest \1/4\ L \2\.                 with sample volume
                                          requirements.
    Was 100% of filtered volume          Needed to calculate the final
     examined? \3\.                       concentration of oocysts/L and
                                          determine if volume analyzed
                                          requirements are met.
    Number of oocysts counted..........  Needed to calculate the final
                                          concentration of oocysts/L.
------------------------------------------------------------------------
\1\ For matrix spike samples, sample volume spiked and estimated number
  of oocysts spiked must be reported. These data are not required for
  field samples.
\2\ For samples in which <10 L is filtered or <100% of the sample volume
  is examined, the number of filters used and the packed pellet volume
  must also be reported to verify compliance with LT2ESWTR sample volume
  analysis requirements. These data are not required for most samples.
\3\ For samples in which <100% of sample is examined, the volume of
  resuspended concentrate and volume of this resuspension processed
  through IMS must be reported to calculate the sample volume examined.
  These data are not required for most samples.


    Table IV.I-2.--E. coli and Turbidity Data Elements To Be Reported
------------------------------------------------------------------------
                                            Reason for collecting data
              Data element                           element
------------------------------------------------------------------------
Identifying Information:
    PWS ID.............................  Needed to associate analytical
                                          result with public water
                                          system.
    Facility ID........................  Needed to associate plant with
                                          public water system.
    Sample collection point............  Needed to associate sample
                                          result with sampling point.
    Sample collection date.............  Needed to determine that
                                          utilities are collecting
                                          samples at the frequency
                                          required.
    Analytical method number...........  Needed to associate analytical
                                          result with analytical method.
    Method Type........................  Needed to verify that an
                                          approved method was used and
                                          call up correct web entry
                                          form.
    Source water type..................  Needed to assess
                                          Cryptosporidium indicator
                                          relationships.
    E. coli/100 mL.....................  Sample result (although not
                                          required, the laboratory also
                                          will have the option of
                                          entering primary measurements
                                          for a sample into the LT2ESWTR
                                          internet-based database to
                                          have the database
                                          automatically calculate the
                                          sample result).
Turbidity Information:
    Turbidity result...................  Needed to assess
                                          Cryptosporidium indicator
                                          relationships.
------------------------------------------------------------------------

    PWSs serving at least 10,000 people must submit sampling schedules 
(described in section IV.A) and monitoring results for the initial 
source water monitoring to EPA electronically at the following Internet 
site: https://intranet.epa.gov/lt2/. These PWSs should instruct their 
laboratories to electronically enter results at this site using web-
based manual entry forms or by uploading XML files (extensible markup 
language files--a standard format that enables information exchange 
between different systems) from laboratory information management 
systems (LIMS). After laboratories enter sample results, PWSs must 
review the results on-line at this site. The State may approve an 
alternative approach for reporting source water monitoring schedules 
and sample results if, for example, a PWS or laboratory does not have 
the capability to report data electronically.
    If a PWS believes that its laboratory entered a sample result into 
the data system erroneously, the PWS may notify the laboratory to 
rectify the entry. In addition, if a PWS believes that a result is 
incorrect, the PWS may electronically mark the result as contested and 
petition the State to invalidate the sample. If a PWS contests a sample 
result, the PWS should submit a rationale to the State, including a 
supporting statement from the laboratory, providing a justification. 
PWSs may arrange with laboratories to review their sample results prior 
to the results being entered into the EPA data system.
    PWSs serving fewer than 10,000 people must submit sampling 
schedules and monitoring results for the initial round of source water 
monitoring to the State. Further, all PWSs must submit sampling 
schedules and monitoring results for the second round of

[[Page 722]]

monitoring to the State. Regardless of the reporting process used, PWSs 
must report an analytical monitoring result to the State no later than 
10 days after the end of the first month following the month when the 
sample was collected.
2. Background and Analysis
    The reporting requirements for source water monitoring in today's 
final rule reflect those in the August 11, 2003 proposed LT2ESWTR 
(USEPA 2003a). The data elements that PWSs must report for 
Cryptosporidium and E. coli analyses are the minimum necessary to 
identify the sample, determine the sample concentration, and verify 
that the PWS complied with rule requirements like minimum sample volume 
and approved analytical methods. PWSs or laboratories must keep bench 
sheets and slide reports for Cryptosporidium analyses for three years 
after bin determination for the particular round of monitoring, at 
which time PWSs must be in compliance with any additional 
Cryptosporidium treatment requirements based on the monitoring results.
    Due to the early implementation schedule, EPA expects to partner 
with States to implement initial source water monitoring by large PWSs 
under today's rule. EPA has developed an Internet-based data system to 
allow electronic reporting and review of source water monitoring 
results by laboratories, PWSs, States, and EPA. States may use this 
data system to oversee monitoring by their PWSs. Where States are 
unable to provide this oversight, the data system will allow EPA to 
implement today's rule. Accordingly, PWSs serving at least 10,000 
people must use this data system to report sampling schedules and 
sample results for the initial round of source water monitoring unless 
the State approves an alternative method for reporting.
    EPA expects laboratories to report analytical results for 
Cryptosporidium, E. coli, and turbidity analyses directly to the data 
system using web forms and software that are available free of charge. 
The data system will perform logic checks on data entered and will 
calculate results from primary data where necessary. This is intended 
to reduce reporting errors and limit the time involved in 
investigating, checking, and correcting errors at all levels. The 
LT2ESWTR proposal describes the analysis functions of the data system 
in more detail (USEPA 2003a).
    In general, EPA expects that States will implement the initial 
source water monitoring by small PWSs and the second round of 
monitoring by all PWSs. Thus, PWSs must submit sampling schedules and 
monitoring results for this monitoring to the State. Note that where 
States do not assume primacy for the rule, however, EPA will act as the 
State.
3. Summary of Major Comments
    EPA received significant public comment on the following aspects of 
reporting requirements for source water monitoring in the August 11, 
2003 proposed LT2ESWTR: the deadline for reporting sample results, 
EPA's electronic data system, and reporting results to EPA rather than 
the State. A summary of these comments and EPA's responses follows.
    Some commenters were concerned with requiring PWSs to report sample 
results no later than the 10th of the second month after the month when 
the sample is collected. Commenters stated that this will cause most 
PWSs to sample in the first part of the month, which will exacerbate 
laboratory capacity problems. As an alternative, commenters recommended 
that PWSs be required to report sample results 72 days after 
collection. This approach would give all PWSs the same time period to 
report sample results regardless of the collection date and would 
facilitate PWSs and laboratories scheduling sample collection dates 
more uniformly throughout the month.
    In response, EPA believes that requiring PWSs to report monitoring 
results by the 10th of the second month after sample collection is 
appropriate. This will maintain consistency with existing drinking 
water regulations, which typically require monitoring results to be 
reported by the 10th of the following month. Thus, specifying this 
reporting date under today's rule will avoid causing PWSs and States to 
develop different reporting dates for different regulations. Due to the 
time required for laboratories to analyze Cryptosporidium samples, 
today's rule gives PWSs an extra month to report monitoring results; 
i.e., the minimum time PWSs have to report results is approximately 40 
days (one month plus 10 days). This time frame, however, is greater 
than what is necessary for laboratories to analyze samples and for PWSs 
to review results. Consequently, EPA does not believe that PWSs will 
benefit by collecting a sample at the start of a month in comparison to 
the end of a month.
    Many commenters expressed concern with the readiness of the 
electronic data system for reporting and reviewing monitoring results 
under today's rule. Commenters stated that PWSs have experienced 
significant problems with data systems that supported earlier rules, 
such as the Information Collection Rule and the Unregulated Contaminant 
Monitoring Rule. Commenters recommended that the data system be in 
place and fully tested prior to finalization of the rule and that EPA 
provide training for users. If the data system is not available when 
the rule is finalized, commenters asked that the monitoring be delayed 
as specified in the Agreement in Principle (USEPA 2000a).
    EPA has ensured that the LT2 data system has been fully tested and 
deployed prior to finalizing the rule. During development of the data 
system, EPA has involved stakeholders in a joint requirements 
workgroup, which has made recommendations for data system 
characteristics and has participated in data system testing. EPA has 
developed guidance and other training materials for PWSs, States, and 
laboratories on how to use the data system and will provide technical 
assistance on a ongoing basis to data system users. EPA believes these 
steps will help to avoid problems that stakeholders experienced with 
data systems for earlier rules.
    Some commenters expressed concerns about large PWSs reporting 
monitoring results to EPA. Commenters stated that implementation of the 
rule should be administered by States, due to the existing 
relationships States have with the PWSs they regulate. For States that 
will implement the rule, commenters recommended allowing PWSs to report 
to States, rather than EPA. Commenters also requested that EPA provide 
copies of all monitoring data and PWS correspondence to States when 
they assume primacy.
    EPA will work with States to implement today's rule and to help 
States assume as much responsibility for implementation as they can. 
Through the LT2ESWTR data system, States will have full access to 
monitoring results reported by their PWSs. Today's rule also allows 
States to direct their PWSs to report monitoring results directly to 
them, rather than EPA. Further, States may require PWSs to submit 
descriptions of monitoring locations for approval. In general, EPA will 
seek to involve States in any communications with and decisions for 
their PWSs and will allow States to take responsibility for these 
activities if they choose to do so. However, because monitoring for the 
largest systems begins before States will have had time to assume 
primacy, EPA must be prepared to oversee monitoring for these PWSs 
where States are unable to do so.

[[Page 723]]

J. Analytical Methods

1. Analytical Methods Overview
    Today's final rule requires public water systems to conduct 
LT2ESWTR source water monitoring using approved methods for 
Cryptosporidium, E. coli, and turbidity analyses. PWSs must meet the 
quality control criteria stipulated by the approved methods and 
additional method-specific requirements, as stated in this section. 
Related requirements for reporting source water monitoring results and 
using approved laboratories are discussed in sections IV.I and IV.K, 
respectively.
    EPA has developed guidance for sampling and analyses under the 
LT2ESWTR. The Source Water Monitoring Guidance Manual for Public Water 
Systems under the LT2ESWTR provides recommendations on activities like 
collecting samples and setting up contracts with laboratories. The 
Microbial Laboratory Manual for the LT2ESWTR provides information for 
laboratories that conduct analyses. These guidance documents may be 
requested from EPA's Safe Drinking Water Hotline, which may be 
contacted as described in the FOR FURTHER INFORMATION CONTACT section 
in the beginning of this notice, and are available on the Internet at 
www.epa.gov/safewater/disinfection/lt2.
2. Cryptosporidium Methods
a. Today's Rule
    Cryptosporidium analysis for source water monitoring under today's 
rule must be conducted using either Method 1622: Cryptosporidium in 
Water by Filtration/IMS/FA (EPA 815-R-05-001, USEPA 2005c) or Method 
1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA (EPA 
815-R-05-002, USEPA 2005d). Additional method requirements for today's 
rule include the following:
     For each Cryptosporidium sample, at least a 10-L sample 
volume must be analyzed unless a PWS meets one of the two exceptions 
stated in this section. PWSs may collect and analyze greater than a 10-
L sample volume.
     The first exception to the sample volume requirement stems 
from sample turbidity. If a sample is very turbid, it may generate a 
large packed pellet volume upon centrifugation (a packed pellet refers 
to the concentrated sample after centrifugation has been performed in 
EPA Methods 1622 and 1623). Samples resulting in large packed pellets 
must have the sample concentrate aliquoted into multiple ``subsamples'' 
for independent processing through IMS, staining, and examination. PWSs 
are not required to analyze more than 2 mL of packed pellet volume per 
sample.
     The second exception to the sample volume requirement 
stems from filter clogging. In cases where the filter clogs prior to 
filtration of 10 L, the PWS must analyze as much sample volume as can 
be filtered by 2 filters, up to a packed pellet volume of 2 mL. This 
condition applies only to filters that have been approved by EPA for 
nationwide use with Methods 1622 and 1623--the Pall Gelman 
EnvirochekTM and EnvirochekTM HV filters, the 
IDEXX Filta-MaxTM foam filter, and the Whatman 
CrypTestTM cartridge filter.
     Methods 1622 and 1623 include fluorescein isothiocyanate 
(FITC) as the primary antibody stain for Cryptosporidium detection, 
DAPI staining to detect nuclei, and DIC to detect internal structures. 
Under today's rule, PWSs must report total Cryptosporidium oocysts as 
detected by FITC as determined by the color (apple green or alternative 
stain color approved for the laboratory under the Lab QA Program 
described in section IV.K), size (4-6 micrometers) and shape (round to 
oval). This total includes all of the oocysts identified as described 
here, less any atypical organisms identified by FITC, DIC, or DAPI 
(e.g., possessing spikes, stalks, appendages, pores, one or two large 
nuclei filling the cell, red fluorescing chloroplasts, crystals, 
spores, etc.).
     As required by Method 1622 and 1623, PWSs must have 1 
matrix spike (MS) sample analyzed for each 20 source water samples. The 
volume of the MS sample must be within ten percent of the volume of the 
unspiked sample that is collected at the same time, and the samples 
must be collected by splitting the sample stream or collecting the 
samples sequentially. The MS sample and the associated unspiked sample 
must be analyzed by the same procedure. MS samples must be spiked and 
filtered in the laboratory. However, if the volume of the MS sample is 
greater than 10 L, the PWS is permitted to filter all but 10 L of the 
MS sample in the field, and ship the filtered sample and the remaining 
10 L of source water to the laboratory. In this case, the laboratory 
must spike the remaining 10 L of water and filter it through the filter 
that was used to collect the balance of the sample in the field.
     Laboratories must use flow cytometer-counted spiking 
suspensions for spiked QC samples.
b. Background and Analysis
    The M-DBP Advisory Committee recommended the use of Methods 1622 or 
1623 and a minimum sample volume of 10 L for source water 
Cryptosporidium analyses under the LT2ESWTR. The August 11, 2003 
proposed rule reflected these recommendations, with associated QC 
requirements and exceptions to the minimum sample volume for samples 
that are highly turbid or cause significant filter clogging (USEPA 
2003a). Today's final rule is unchanged from the proposal in these 
respects.
    Today's rule requires the use of methods 1622 or 1623 because they 
are the best available methods that have undergone full validation 
testing. As described in section III.E, these methods were used during 
the ICRSS, where MS samples indicated a mean recovery and relative 
standard deviation of 43 and 47 percent, respectively (Connell et al. 
2000). EPA expects that PWSs will achieve comparable performance with 
these methods during source water monitoring under today's rule. With 
the minimum sample volume and QC requirements in today's rule, this 
level of performance will be sufficient to assign PWSs to 
Cryptosporidium treatment bins and realize the public health goals 
intended by EPA and the Advisory Committee for the LT2ESWTR. EPA has 
also approved these methods for ambient water monitoring under a 
separate rulemaking (68 FR 43272, July 21, 2003) (USEPA 2003b).
    The proposed LT2ESWTR required the use of April 2001 versions of 
Methods 1622 or 1623 and requested comment on approving revised 
versions of these methods in the final rule (USEPA 2003a). The revised 
methods were included in the proposal as draft June 2003 versions. The 
revisions in these versions included increased flexibility in some QC 
requirements, clarification of certain method procedures, an increase 
in the allowable sample storage temperature to 10[deg]C, the addition 
of several approved analysis modifications, and other refinements (see 
the proposed rule for details)(USEPA 2003a).
    Today's rule requires the use of the revised versions of Methods 
1622 and 1623. In the versions of these methods finalized with today's 
rule, the upper temperature limit for sample receipt has been increased 
to 20[deg]C. This change responds to public comment and recent 
publications (Ware and Schafer 2005, Francy et al. 2004, Nichols et al. 
2004). As described in section IV.A, PWSs may grandfather data 
generated with earlier approved versions of these methods (i.e., 1999 
or 2001 versions).

[[Page 724]]

c. Summary of Major Comments
    Public comment on the August 11, 2003 proposed LT2ESWTR supported 
approval of the revised versions of Methods 1622 and 1623, which 
today's rule establishes for source water Cryptosporidium monitoring. 
EPA also received comment regarding the lack of viability and 
infectivity information with these methods and requirements for 
analyzing QC samples.
    Several commenters were concerned that Methods 1622 and 1623 do not 
indicate whether a Cryptosporidium oocyst is viable and infectious. 
While EPA recognizes that these methods do not provide information on 
Cryptosporidium infectivity, EPA's analysis indicates that they can 
perform effectively for identifying those PWSs that should provide 
additional Cryptosporidium treatment (USEPA 2005a). This analysis is 
based on the actual performance of these methods in the ICRSS. Further, 
EPA and the M-DBP Advisory Committee, which recommended Methods 1622 
and 1623, accounted for this lack of information on infectivity when 
designing the Cryptosporidium treatment bins in today's rule. EPA has 
not identified any feasible methods for quantifying Cryptosporidium 
infectivity in a national monitoring program.
    Several commenters suggested that laboratories should only be 
required to perform one OPR test per day instead of one for every 20 
samples, as Methods 1622 and 1623 require. EPA believes, however, that 
the frequency of one OPR test per 20 samples is appropriate for 
identifying and correcting problems. For example, if an OPR test is 
performed once per day for a laboratory that processes 60 samples per 
day, a problem that occurs at sample 10 will be continued through the 
next 50 samples. If an OPR test is performed once per 20 samples, a 
problem that occurs at sample 10 would only affect 10 additional 
samples. Consequently, EPA is maintaining the current QC criteria in 
Methods 1622 and 1623.
3. E. coli Methods
a. Today's Rule
    For enumerating source water E. coli density under the LT2ESWTR, 
EPA is approving the same methods that are currently approved for 
ambient water monitoring under 40 CFR 136.3. EPA established these 
methods through the rulemaking ``Guidelines Establishing Test 
Procedures for the Analysis of Pollutants; Analytical Methods for 
Biological Pollutants in Ambient Water'' (USEPA 2003b). Table IV.J-1 
summarizes these methods. Method identification numbers are provided 
for applicable standards published by EPA and voluntary consensus 
standards bodies including Standard Methods, American Society of 
Testing Materials (ASTM), and the Association of Analytical Chemists 
(AOAC).

                                            Table IV.J-1.--List of Approved Analytical Methods for E. coli 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             Standard Methods 18th,
               Method                          EPA               19th, 20th Ed.               ASTM                   AOAC                  Other
--------------------------------------------------------------------------------------------------------------------------------------------------------
MPN 2 3 4, multiple tube...........  ......................  9221B.1/9221F 5 6 7...
Multiple tube/multiple well........  ......................  9223B 5 8.............  .....................  991.15 9.............  Colilert[supreg] 8
                                                                                                                                    10, Colilert-
                                                                                                                                    18[supreg] 8 10 11.
MF 2 3 12 13 14 two step, or.......  1103.1 16.............  9222B/9222G5 15 9213D   D5392-93 17..........
                                                              5.
Single step........................  1603 18, 1604 19......  ......................  .....................  .....................  mColiBlue 24 20.
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Recommended for enumeration of E. coli in ambient water only, number per 100 ml.
2 Tests must be conducted to provide organism enumeration (density). Select the appropriate configuration of tubes/filtrations and dilutions/volumes to
  account for the quality, character, consistency, and anticipated organism density of the water sample.
3 To assess the comparability of results obtained with individual methods, it is suggested that side-by-side tests be conducted across seasons of the
  year with the water samples routinely tested in accordance with the most current Standard Methods for the Examination of Water and Wastewater or EPA
  alternate test procedure (ATP) guidelines.
4 Samples shall be enumerated by the multiple-tube or multiple-well procedure. Using multiple-tube procedures, employ an appropriate tube and dilution
  configuration of the sample as needed and report the Most Probable Number (MPN). Samples tested with Colilert[supreg] may be enumerated with the
  multiple-well procedures, Quanti-tray[supreg], or Quanti-tray[supreg] 2000, and the MPN calculated from the table provided by the manufacturer.
5 APHA. 1998, 1995, 1992. Standard Methods for the Examination of Water and Wastewater. American Public Health Association. 20th, 19th, and 18th
  Editions. Amer. Publ. Hlth. Assoc., Washington, DC.
6 The multiple-tube fermentation test is used in 9221.B.1. Lactose broth may be used in lieu of lauryl tryptose broth (LTB), if at least 25 parallel
  tests are conducted between this broth and LTB using the water samples normally tested, and this comparison demonstrates that the false-positive rate
  and false-negative rate for total coliform using lactose broth is less than 10 percent. No requirement exists to run the completed phase on 10 percent
  of all total coliform-positive tubes on a seasonal basis.
7 After prior enrichment in a presumptive medium for total coliform using 9221B.1, all presumptive tubes or bottles showing any amount of gas, growth or
  acidity within 48 3 h of incubation shall be submitted to 9221F. Commercially available EC-MUG media or EC media supplemented in the
  laboratory with 50 [mu]g/ml of MUG may be used.
8 These tests are collectively known as defined enzyme substrate tests, where, for example, a substrate is used to detect the enzyme glucuronidase
  produced by E. coli.
9 AOAC. 1995. Official Methods of Analysis of AOAC International, 16th Edition, Volume 1, Chapter 17. Association of Official Analytical Chemists
  International. 481 North Frederick Avenue, Suite 500, Gaithersburg, Maryland 20877-2417.
10 Descriptions of the Colilert[supreg], Colilert-18[supreg], Quanti-Tray[supreg] and Quanti-Tray[supreg] 2000 may be obtained from IDEXX Laboratories,
  Inc., One IDEXX Drive, Westbrook, Maine 04092.
11 Colilert-18[supreg] is an optimized formulation of the Colilert[supreg] for the determination of total coliforms and E. coli that provides results
  within 18 h of incubation at 35 [deg]C rather than the 24 h required for the Colilert[supreg] test and is recommended for marine samples.
12 A 0.45 [mu]m membrane filter (MF) or other pore size certified by the manufacturer to fully retain organisms to be cultivated and to be free of
  extractables which could interfere with their growth.
13 Because the MF technique usually yields low and variable recovery from chlorinated wastewaters, the Most Probable Number method will be required to
  resolve any controversies.
14 When the MF method has not been used previously to test ambient water with high turbidity, large number of noncoliform bacteria, or samples that may
  contain organisms stressed by chlorine, a parallel test should be conducted with a multiple-tube technique to demonstrate applicability and
  comparability of results.
15 Subject total coliform positive samples as determined by 9222B or other membrane filter procedure to 9222G using NA-MUG media.
16 USEPA. 2002c. Method 1103.1: Escherichia coli (E. coli) In Water By Membrane Filtration Using membrane-Thermotolerant Escherichia coli Agar (mTEC).
  U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-821-R-02-020.
17 ASTM. 2000, 1999, 1996. Annual Book of ASTM Standards--Water and Environmental Technology. Section 11.02. American Society for Testing and Materials.
  100 Barr Harbor Drive, West Conshohocken, PA 19428.

[[Page 725]]

 
18 USEPA. 2002. Method 1610: Escherichia coli (E. coli) In Water By Membrane Filtration Using Modified membrane-Thermotolerant Escherichia coli Agar
  (modified mTEC). U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-821-R-02-023.
19 Preparation and use of MI agar with a standard membrane filter procedure is set forth in the article, Brenner et al. 1993. ``New Medium for the
  Simultaneous Detection of Total Coliform and Escherichia coli in Water.'' Appl. Environ. Microbiol. 59:3534-3544 and in USEPA. 2002. Method 1604:
  Total Coliforms and Escherichia coli (E. coli) in Water by Membrane Filtration by Using a Simultaneous Detection Technique (MI Medium). U.S.
  Environmental Protection Agency, Office of Water, Washington, DC. EPA-821-R-02-024.
20 A description of the mColiBlue24 test, Total Coliforms and E. coli, is available from Hach Company, 100 Dayton Ave., Ames, IA 50010.

    For most PWSs, the time from sample collection to initiation of 
analysis (i.e., the holding time) for source water E. coli samples may 
not exceed 30 hours for all approved E. coli methods. However, if the 
State determines on a case-by-case basis that analyzing an E. coli 
sample within 30 hours is not feasible, the State may approve the 
holding of an E. coli sample for up to 48 hours between collection and 
initiation of analysis. E. coli samples held between 30 to 48 hours 
must be analyzed by the Colilert reagent version of Standard Method 
9223B as listed in 40 CFR 136.3. All E. coli samples must be maintained 
below 10[deg] C and not allowed to freeze.
    The E. coli sample holding time established for source water 
monitoring under the LT2ESWTR does not apply to E. coli sample holding 
time requirements that have been established under other programs and 
regulations.
b. Background and Analysis
    In the August 11, 2003 proposed LT2ESWTR, EPA planned to approve 
the same E. coli methods that the Agency had proposed for ambient water 
monitoring in an earlier rulemaking, ``Guidelines Establishing Test 
Procedures for the Analysis of Pollutants; Analytical Methods for 
Biological Pollutants in Ambient Water'' (USEPA 2001h). EPA selected 
these methods based on data generated by EPA laboratories, submissions 
to the EPA alternate test procedures program and voluntary consensus 
standards bodies, peer reviewed journal articles, and publicly 
available study reports.
    On July 21, 2003, EPA finalized ``Guidelines Establishing Test 
Procedures for the Analysis of Pollutants; Analytical Methods for 
Biological Pollutants in Ambient Water'' (USEPA 2003b). The only method 
from the proposal of this rule that was not included in the final rule 
was Colisure, which was excluded due to insufficient data on its 
performance with surface water. For the other methods, EPA revised 
certain titles and added method numbers to be consistent with other 
microbiological methods, but the technical content of these methods in 
the final rule did not change from the versions included in the 
proposed rule.
    EPA is approving these same E. coli methods for analyses under the 
LT2ESWTR. The source water E. coli analyses that PWSs will conduct 
under the LT2ESWTR are similar to the ambient water analyses for which 
EPA approved E. coli methods under ``Guidelines Establishing Test 
Procedures for the Analysis of Pollutants; Analytical Methods for 
Biological Pollutants in Ambient Water'' (USEPA 2003b). EPA continues 
to support the findings of this rule and believes that the E. coli 
methods approved therein have the necessary sensitivity and specificity 
to meet the data quality objectives of the LT2ESWTR.
    An important aspect of monitoring for E. coli is the allowable 
sample holding time (i.e., the time between sample collection and 
initiation of analysis). Existing regulations, such as 40 CFR 141.74, 
limit the holding time for E. coli samples to 8 hours. However, for 
PWSs that must ship E. coli samples to an off-site laboratory for 
analysis, meeting an 8 hour holding time is generally not feasible. For 
example, during the ICRSS, all of the PWSs that shipped samples off-
site for E. coli analysis exceeded an 8 hour holding time, and 12 
percent of these samples had holding times in excess of 30 hours.
    While most large PWSs that will monitor for E. coli under the 
LT2ESWTR will conduct these analyses on-site, most small PWSs must ship 
samples off-site to an approved laboratory. To address the concern that 
PWSs using off-site laboratories cannot meet an 8-hour holding time, 
EPA participated in studies to assess the effect of increased sample 
holding time on E. coli analysis results. These studies are summarized 
in the proposed rule (USEPA 2003a) and are described in detail in Pope 
et al. (2003). Based on these studies, EPA has concluded that the 
holding time for E. coli samples can be extended beyond 8 hours prior 
to analysis without compromising the data quality objectives of 
LT2ESWTR monitoring.
    In the proposed LT2ESWTR, EPA required analysis of E. coli samples 
to be initiated within 24 hours of sample collection and required that 
samples be kept below 10[deg] C and not allowed to freeze (USEPA 
2003a). These proposed requirements were based on data showing that 
most samples maintained within these temperature conditions were not 
significantly different at 24 hours than at the standard holding time 
of 8 hours. The proposal also noted that data indicated no significant 
sample degradation after longer time periods, such as 30 or 48 hours, 
for certain methods. Accordingly, EPA requested comment on establishing 
a longer E. coli holding time in the final rule.
    For today's final rule, EPA is establishing a holding time of 30 
hours for all approved E. coli methods. After reviewing public comment 
on this issue, which is summarized in the following section, and 
reassessing the studies described in the proposed rule, EPA has 
concluded that a 30 hour holding time limit for E. coli samples is 
appropriate and consistent with the data quality objectives of LT2ESWTR 
source water monitoring. Further, EPA believes that meeting a 30 hour 
holding time is feasible for most PWSs that must ship E. coli samples 
to an off-site laboratory for analysis. This longer holding time, 
however, does not apply to E. coli monitoring conducted under other 
programs and regulations.
    EPA recognizes that in rare cases, having an E. coli sample 
analyzed within 30 hours may not be feasible for a PWS due to distance 
to an approved laboratory and limited transportation options. In these 
cases, today's rule allows the State to approve up to a 48 hour holding 
time for E. coli samples. Samples held between 30 to 48 hours must be 
analyzed by the Colilert reagent version of Standard Method 9223B. This 
is the only method evaluated in Pope et al. (2003) where no significant 
sample degradation occurred at 48 hours.
    PWSs must maintain samples below 10[deg]C and not allow them to 
freeze. EPA has developing guidance for PWSs on packing and shipping E. 
coli samples to maintain these temperature conditions. See the overview 
at the beginning of this section for information on how to access this 
guidance.
c. Summary of Major Comments
    In the August 11, 2003 LT2ESWTR proposal, EPA requested comment on 
whether the E. coli methods proposed for approval under the LT2ESWTR 
are appropriate and whether there are additional methods not proposed 
that should be considered. EPA also requested comment on the proposal 
to extend the holding time for E. coli

[[Page 726]]

samples to 24 hours; whether EPA should limit the extended holding time 
to only those E. coli analytical methods that were evaluated in the 
holding time studies described in the proposal; and whether EPA should 
increase the source water E. coli holding time to 30 or 48 hours for 
samples evaluated by one method, ONPG-MUG, and retain a 24-hour holding 
time for samples analyzed by other methods.
    Most commenters stated that the proposed E. coli analytical methods 
are appropriate. Commenters also agreed with the proposal to extend the 
holding time for source water E. coli samples, but recommendations 
about the maximum holding time and the methods to which the extended 
holding time should apply differed among commenters. Some suggested 
that EPA increase the holding time to 30 hours for the ONPG-MUG method, 
but retain a 24-hour holding time for the other methods. Other 
commenters recommended a 48-hour holding time for some or all methods. 
Several commenters advised that holding times for all methods should be 
the same to limit confusion. Some commenters were concerned that a 30-
hour holding time would not be sufficient for small PWSs in remote 
areas to ship samples to distant laboratories.
    After consideration of the comments received, as well as the 
holding time study data presented in the proposed rule and the time 
required to ship samples off-site for analysis as evidenced in the 
ICRSS, EPA has concluded that allowing a 30-hour holding time for all 
E. coli methods approved under today's final rule is appropriate. Data 
indicate that a 30-hour holding time for E. coli samples will not 
adversely impact the data quality objectives of LT2ESWTR monitoring. 
Further, establishing the same holding time for all methods will limit 
confusion, and a 30-hour holding time will allow most PWSs that ship 
samples off site for analysis to meet the holding time requirements. 
Today's rule also allows the State to authorize a 48-hour holding time 
for rare cases where a 30-hour holding time is not feasible.
4. Turbidity Methods
a. Today's Rule
    Today's rule requires PWSs to use the analytical methods that have 
been previously approved by EPA for analysis of turbidity in drinking 
water, as listed in 40 CFR 141.74. These are Method 2130B as published 
in Standard Methods for the Examination of Water and Wastewater (APHA 
1992), EPA Method 180.1 (USEPA 1993), Great Lakes Instruments Method 2 
(Great Lakes Instruments 1992), and Hach FilterTrak Method 10133.
b. Background and Analysis
    As stated in section IV.A, today's rule requires filtered PWSs 
serving at least 10,000 people to monitor for turbidity when they 
conduct source water monitoring. EPA may use these data to modify the 
indicator criteria that trigger Cryptosporidium monitoring by small 
filtered PWSs, as recommended by the M-DBP Advisory Committee (USEPA 
2000a). In addition, PWSs using conventional or direct filtration may 
achieve additional Cryptosporidium treatment credit by demonstrating 
very low turbidity in the combined filter effluent, as described in 
section IV.D.7, or the individual filter effluent, as described in 
section IV.D.8.
    The August 11, 2003 proposed LT2ESWTR required PWSs to use 
turbidity methods that EPA had previously approved under 40 CFR 141.74 
for analyzing drinking water (USEPA 2003a). These are EPA Method 180.1 
and Standard Method 2130B, which are based on a comparison of the 
intensity of light scattered by the sample with the intensity of light 
scattered by a standard reference suspension; Great Lakes Instruments 
Method 2, which is a modulated four beam infrared method using a 
ratiometric algorithm to calculate the turbidity value from the four 
readings that are produced; and Hach FilterTrak (Method 10133), which 
is a laser-based method used to analyze finished drinking water.
    Today's final rule is unchanged from the proposal in regard to 
analytical methods for turbidity. Hence, PWSs must use methods 
currently approved in 40 CFR 141.74 for turbidity analysis. EPA 
believes the currently approved methods are appropriate for turbidity 
analyses that will be conducted under the LT2ESWTR. PWSs must use 
turbidimeter instruments as described in the EPA-approved methods, 
which may be either on-line or bench top instruments. If a PWS chooses 
to use on-line instruments for monitoring turbidity, the PWS must 
validate the continuous measurements for accuracy on a regular basis 
using a protocol approved by the State, as required in 40 CFR 141.74.
c. Summary of Major Comments
    EPA received public comment on the turbidity methods required in 
the August 11, 2003 proposed LT2ESWTR. While commenters, in general, 
agreed that currently approved turbidity methods are adequate to meet 
the requirements of the rule, several commenters were concerned with 
turbidity measurement variation among different instruments. One 
commenter suggested voluntary third party testing, while another 
recommended more rigorous calibration and verification processes.
    As described in section IV.D.7, EPA has reviewed studies of low 
level turbidity measurements, as well as standard test methods for 
measurement of turbidity below 5 NTU. After reviewing this information, 
EPA concluded that currently available monitoring equipment can 
reliably measure turbidity at levels of 0.15 NTU and lower. However, 
EPA agrees that rigorous calibration and maintenance of turbidity 
monitoring equipment is necessary for PWSs pursuing the low filtered 
water turbidity performance options in the microbial toolbox. EPA has 
developed guidance on proper calibration, operation, and maintenance of 
turbidimeters (USEPA 1999c).
    A few commenters stated that the LT2ESTWR does not recognize 
advancements in turbidity measurement and newly developed turbidity 
measurement technologies. In response, EPA has not received information 
that supports approval of analytical methods for turbidity in addition 
to those currently approved under 40 CFR 141.74, which are also 
approved for turbidity monitoring under today's rule. If other 
turbidity methods are approved and added to 40 CFR 141.74 in the 
future, these methods will also be approved under the LT2ESWTR.
    One commenter requested that the LT2ESWTR specifically address 
turbidity measurements in plants that practice lime softening. EPA 
notes that additional treatment credit for combined filter effluent 
turbidity is based on measurements collected under 40 CFR 141.173 or 40 
CFR 141.551 (the IESWTR or LT1ESWTR). These regulations allow PWSs that 
use lime softening to acidify samples prior to analysis in order to 
address the effects of lime softening on turbidity measurements. In 
regard to treatment credit based on individual filter effluent 
turbidity, EPA does not believe that acidifying samples while measuring 
turbidity every 15 minutes at each individual filter, as the IESWTR and 
LT1ESWTR require, is feasible. However, PWSs that practice lime 
softening could use the demonstration of performance toolbox option to 
demonstrate that a plant is achieving removal efficiencies equivalent 
to the additional credit allowed for individual filter performance.

[[Page 727]]

K. Laboratory Approval

    Given the potentially significant implications for PWSs and 
drinking water consumers of microbial monitoring under the LT2ESWTR, 
laboratory analyses for Cryptosporidium, E. coli, and turbidity should 
be accurate and reliable within the limits of approved methods. 
Therefore, today's final rule requires PWSs to use laboratories that 
have been approved to conduct analyses for these parameters by EPA or 
the State.
1. Cryptosporidium Laboratory Approval
a. Today's Rule
    Analysis of samples for Cryptosporidium under today's rule must be 
conducted by a laboratory that is approved under EPA's Laboratory 
Quality Assurance Evaluation Program (Lab QA Program) for Analysis of 
Cryptosporidium in Water (described in 67 FR 9731, March 4, 2002, USEPA 
2002d). A list of laboratories that are approved under this program is 
available on the Internet at www.epa.gov/safewater/disinfection/lt2. If 
a State adopts an equivalent approval process under a State laboratory 
certification program, then PWSs can use laboratories approved by the 
State.
b. Background and Analysis
    Because States do not currently approve laboratories for 
Cryptosporidium analyses, EPA has assumed initial responsibility for 
Cryptosporidium laboratory approval. EPA initiated the Cryptosporidium 
Lab QA Program prior to LT2ESWTR promulgation to ensure that adequate 
analytical capacity will be available at approved laboratories to 
support required monitoring, which begins 6 months after rule 
promulgation. The August 11, 2003 proposed LT2ESWTR required PWSs to 
have Cryptosporidium samples analyzed by laboratories approved under 
the EPA Lab QA Program. Today's final rule is unchanged from the 
proposal with respect to this requirement.
    Laboratories seeking approval under the EPA Lab QA Program for 
Cryptosporidium analysis must submit an interest application to EPA, 
successfully analyze a set of initial performance testing samples, and 
undergo an on-site evaluation. Laboratories that pass the quality 
assurance evaluation are approved for Cryptosporidium analysis under 
the LT2ESWTR. To maintain approval, laboratories must successfully 
analyze a set of three ongoing proficiency testing samples 
approximately every four months. The Lab QA Program is described in 
detail in USEPA (2002d) and additional information can be found on the 
Internet at www.epa.gov/safewater/disinfection/lt2.
    EPA tracks the Cryptosporidium sample analysis capacity of approved 
laboratories through the Lab QA Program. Using information provided by 
laboratories, EPA expects that existing capacity should be sufficient 
to support initial source water monitoring by large PWSs under the 
LT2ESWTR. Further, the implementation schedule for today's rule, which 
is described in section IV.G, provides time for laboratories to 
increase capacity through steps like training new analysts as the 
demand for sample analysis grows.
c. Summary of Major Comments
    In regard to approval of laboratories for Cryptosporidium analysis, 
major comments on the August 11, 2003 proposal addressed the following 
issues: laboratory capacity, State approval programs, and analyst 
experience criteria. Comments regarding Cryptosporidium laboratory 
capacity are summarized in section IV.G, while those on the other 
issues are summarized as follows.
    EPA requested comment on States approving Cryptosporidium 
laboratories. Most commenters, however, recommended that EPA maintain 
the Lab QA Program, due to the specialized nature of the work. EPA 
intends to maintain the Lab QA Program, but today's rule does allow 
States to certify Cryptosporidium laboratories by setting up an 
equivalent program.
    EPA also requested comment on the experience criteria that Methods 
1622 and 1623 include for Cryptosporidium analysts. Some commenters 
recommended lowering analyst training and experience requirements, 
while others recommended no change or an increase in microscopy 
training. After evaluating these comments, EPA has concluded that the 
analyst criteria included in Methods 1622 and 1623 are reasonable for 
ensuring that analysts have the experience to evaluate source water 
samples under today's rule. Consequently, EPA has not altered these 
criteria from the approved methods.
2. E. coli Laboratory Approval
a. Today's Rule
    PWSs must have E. coli samples analyzed by a laboratory that has 
been certified by EPA, the National Environmental Laboratory 
Accreditation Conference (NELAC) or the State for total coliform or 
fecal coliform analysis in drinking water under 40 CFR 141.74. The 
laboratory must use the same technique for E. coli analysis under 
today's rule that the laboratory is certified to use for drinking water 
under 40 CFR 141.74 (e.g., membrane filtration, multiple-well, 
multiple-tube).
b. Background and Analysis
    The August 11, 2003 proposed LT2ESWTR required PWSs to have E. coli 
samples analyzed by laboratories that are certified to conduct total or 
fecal coliform analyses in drinking water (i.e., under 40 CFR 141.74) 
by EPA, NELAC or the State. The proposal required laboratories to use 
the same E. coli analytical technique that they are certified to use 
for coliform analyses in drinking water. Today's final rule is 
unchanged from the proposal in regard to these requirements. EPA 
believes that laboratories that are certified to conduct coliform 
analyses in drinking water have the expertise to conduct E. coli 
analyses under today's rule, provided they use the analytical technique 
for which they are certified.
c. Summary of Major Comments
    Two commenters on the August 11, 2003 proposal suggested that 
laboratories should be certified specifically for quantitative analyses 
of total or fecal coliform in a source water matrix. However, the 
methods approved for source water E. coli analyses under today's rule 
are also approved under the drinking water certification program. EPA 
believes that analysts certified for these methods under the drinking 
water certification program have the capability to perform the same 
methods for a source water matrix, even though additional steps may be 
required (such as dilutions). EPA has revised the Laboratory 
Certification Manual to suggest Performance Evaluation (PE) samples for 
source water matrix analyses and States have the option to require PE 
samples as needed in their State laboratory certification programs.
3. Turbidity Analyst Approval
a. Today's Rule
    Under today's rule, measurements of turbidity must be made by a 
party approved by the State.
b. Background and Analysis
    The August 11, 2003 proposed LT2ESWTR required that measurements of 
turbidity be made by a party approved by the State. This reflects 
existing requirements in 40 CFR 141.74 for measurement of turbidity in 
drinking water. Today's final rule is unchanged from the proposal in 
this respect.

[[Page 728]]

c. Summary of Major Comments
    Commenters on requirements for turbidity analyst approval in the 
August 11, 2003 proposal agreed that turbidity analyses should be 
consistent with 40 CFR 141.74. Specifically, any person that is 
currently approved to conduct turbidity analysis under existing 
drinking water regulations should be approved to conduct turbidity 
analyses under the LT2ESWTR. EPA agrees with this comment and it is 
reflected in today's final rule.

L. Requirements for Sanitary Surveys Conducted by EPA

1. Today's Rule
    Today's final rule establishes requirements for PWSs to respond to 
significant deficiencies identified in sanitary surveys that EPA 
conducts. These requirements give EPA authority equivalent to that 
exercised by States under existing regulations to ensure that PWSs 
address significant deficiencies.
     For sanitary surveys conducted by EPA under SDWA section 
1445 or other authority, PWSs must respond in writing to significant 
deficiencies outlined in sanitary survey reports no later than 45 days 
after receipt of the report, indicating how and on what schedule the 
PWS will address significant deficiencies noted in the survey.
     PWSs must correct significant deficiencies identified in 
sanitary survey reports according to the schedule approved by EPA, or 
if there is no approved schedule, according to the schedule the PWS 
reported if such deficiencies are within the control of the PWS.
     A sanitary survey, as conducted by EPA, is an onsite 
review of the water source (identifying sources of contamination by 
using results of source water assessments where available), facilities, 
equipment, operation, maintenance, and monitoring compliance of a PWS 
to evaluate the adequacy of the PWS, its sources and operations, and 
the distribution of safe drinking water. A significant deficiency 
includes a defect in design, operation, or maintenance, or a failure or 
malfunction of the sources, treatment, storage, or distribution system 
that EPA determines to be causing, or has the potential for causing the 
introduction of contamination into the water delivered to consumers.
2. Background and Analysis
    As established by the IESWTR in 40 CFR 142.16(b)(3), primacy States 
must conduct sanitary surveys for PWSs using surface water sources 
every three or five years. The sanitary survey is an onsite review of 
the following: (1) Source, (2) treatment, (3) distribution system, (4) 
finished water storage, (5) pumps, pump facilities, and controls, (6) 
monitoring, reporting, and data verification, (7) system management and 
operation, and (8) operator compliance with State requirements.
    Under the IESWTR, primacy States must have the authority to assure 
that PWSs respond in writing to significant deficiencies identified in 
sanitary survey reports no later than 45 days after receipt of the 
report, indicating how and on what schedule the system will address the 
deficiency (40 CFR 142.16(b)(1)(ii)). Further, primacy States must have 
the authority to assure that systems take necessary steps to address 
significant deficiencies identified in sanitary survey reports if such 
deficiencies are within the control of the system and its governing 
body (40 CFR 142.16(b)(1)(iii)).
    EPA conducts sanitary surveys under SDWA section 1445 for PWSs not 
regulated by primacy States (e.g., Tribal systems, Wyoming). However, 
the authority required of primacy States under 40 CFR 142 to ensure 
that PWSs address significant deficiencies identified during sanitary 
surveys does not extend to EPA. Consequently, the sanitary survey 
requirements established by the IESWTR created an unequal standard. 
PWSs regulated by primacy States are subject to the States' authority 
to require correction of significant deficiencies noted in sanitary 
survey reports, while PWSs for which EPA has direct implementation 
authority did not have to meet an equivalent requirement.
    In the August 11, 2003 proposal, EPA requested comment on 
establishing requirements under 40 CFR 141 for PWSs to correct 
significant deficiencies identified in sanitary surveys conducted by 
EPA. The requirements in today's final rule follow closely on the 
language presented in the proposal. Today's rule ensures that PWSs in 
non-primacy States are subject to comparable requirements for sanitary 
surveys as PWS regulated by States with primacy.
3. Summary of Major Comments
    Most public comment on the August 11, 2003 proposal supported 
requiring PWSs to correct significant deficiencies identified in 
sanitary surveys conducted by EPA. Commenters stated that requirements 
for sanitary surveys should be consistent for PWSs and should not 
depend on the primacy agency. EPA believes the requirements in today's 
final rule will establish this consistency.
    One commenter requested that EPA include a process for PWSs to 
appeal a significant deficiency determination. EPA expects that PWSs 
will raise any concerns regarding significant deficiency determinations 
with the primacy agency, either the State or EPA, that conducts the 
sanitary survey. States or EPA may withdraw or amend their significant 
deficiency determinations as appropriate. The IESWTR did not establish 
a separate appeal process for sanitary surveys conducted by States, and 
EPA has not established such a process for sanitary surveys conducted 
by EPA under today's rule.

M. Variances and Exemptions

    SDWA section 1415 allows States to grant variances from national 
primary drinking water regulations under certain conditions; section 
1416 establishes the conditions under which States may grant exemptions 
to MCL or treatment technique requirements. These conditions and EPA's 
view on their applicability to the LT2ESWTR are summarized as follows:
1. Variances
    Section 1415 specifies two provisions under which general variances 
to treatment technique requirements may be granted:

    (1) A State that has primacy may grant a variance to a PWS from 
any requirement to use a specified treatment technique for a 
contaminant if the PWS demonstrates to the satisfaction of the State 
that the treatment technique is not necessary to protect public 
health because of the nature of the PWS's raw water source. EPA may 
prescribe monitoring and other requirements as conditions of the 
variance (section 1415(a)(1)(B)).
    (2) EPA may grant a variance from any treatment technique 
requirement upon a showing by any person that an alternative 
treatment technique not included in such requirement is at least as 
efficient in lowering the level of the contaminant (section 
1415(a)(3)).

    EPA does not believe that the first variance provision is 
applicable to filtered PWSs under today's rule. Filtered PWSs are 
required to implement additional treatment under the LT2ESWTR only when 
source water monitoring demonstrates higher levels of Cryptosporidium 
contamination. Thus, this treatment technique requirement accounts for 
the nature of the PWS's raw water source. Unfiltered PWS treatment 
requirements also account for the nature of a PWS's raw water source 
with respect to whether 2-or 3-log Cryptosporidium inactivation is 
required.
    In theory, the first variance provision could be applied to the 
requirement that all unfiltered PWSs provide at least 2-

[[Page 729]]

log Cryptosporidium inactivation. If an unfiltered PWS could show a raw 
water Cryptosporidium level 3-log lower than the Bin 1 cutoff for 
filtered PWSs (i.e., below 0.075 oocysts/1,000 L), this could 
demonstrate that no treatment for Cryptosporidium is necessary. The 
unfiltered PWS would already be achieving public health protection 
against Cryptosporidium equivalent to filtered PWSs due to the nature 
of the raw water source.
    In practice, EPA has not identified an approach that is 
economically or technologically feasible for a PWS to demonstrate such 
a low level of Cryptosporidium to support granting a variance. This is 
due to the extremely large volume and number of samples that would be 
necessary to make such a demonstration with confidence. However, 
unfiltered PWSs may choose to pursue the development and implementation 
of monitoring programs to apply for a variance from Cryptosporidium 
inactivation requirements based on the nature of the raw water source. 
A sufficient monitoring program may be feasible in site-specific 
circumstances or with the use of innovative approaches.
    The second provision for granting a variance is not applicable to 
the LT2ESWTR because the rule provides broad flexibility in how PWSs 
achieve the required level of Cryptosporidium reduction through the 
microbial toolbox. Moreover, the microbial toolbox contains an option 
for Demonstration of Performance, under which States can award 
treatment credit based on the demonstrated efficiency of a treatment 
process in reducing Cryptosporidium levels. Thus, there is no need for 
this type of variance under the LT2ESWTR.
    SDWA section 1415(e) describes small PWS variances, but these 
cannot be granted for a treatment technique for a microbial 
contaminant. Hence, small PWS variances are not allowed for the 
LT2ESWTR.
2. Exemptions
    Under SDWA section 1416(a), a State may exempt any PWS from a 
treatment technique requirement upon a finding that (1) Due to 
compelling factors (which may include economic factors such as 
qualification of the PWS as serving a disadvantaged community), the PWS 
is unable to comply with the requirement or implement measures to 
develop an alternative source of water supply; (2) the PWS was in 
operation on the effective date of the treatment technique requirement, 
or for a PWS that was not in operation by that date, no reasonable 
alternative source of drinking water is available to the new PWS; (3) 
the exemption will not result in an unreasonable risk to health; and 
(4) management or restructuring changes (or both) cannot reasonably 
result in compliance with the Act or improve the quality of drinking 
water.
    EPA believes that granting an exemption to the Cryptosporidium 
treatment requirements of the LT2ESWTR would result in an unreasonable 
risk to health. As described in section III.C, Cryptosporidium causes 
acute health effects, which may be severe in sensitive subpopulations 
and include risk of mortality. Moreover, the additional Cryptosporidium 
treatment requirements of the LT2ESWTR are targeted to PWSs with the 
highest degree of risk. Due to these factors, EPA does not support the 
granting exemptions from the LT2ESWTR.

V. State Implementation

A. Today's Rule

    This section describes the regulations and other procedures and 
policies States must adopt to implement today's rule. States must 
continue to meet all other conditions of primacy in 40 CFR Part 142. To 
implement the LT2ESWTR, States must adopt revisions to the following 
sections:

Sec.  141.2--Definitions
Subpart Q--Public Notification
New Subpart W--Additional treatment technique requirements for 
Cryptosporidium
Sec.  142.14--Records kept by States
Sec.  142.15--Reports by States
Sec.  142.16--Special primacy requirements
1. Special State primacy requirements
    To ensure that a State program includes all the elements necessary 
for an effective and enforceable program under today's rule, a State 
primacy application must include a description of how the State will 
perform the following:
     Approve an alternative to the E. coli levels that trigger 
Cryptosporidium monitoring by filtered systems serving fewer than 
10,000 people (see section IV.A.1);
     Approve watershed control programs for the 0.5 log 
watershed control program credit in the microbial toolbox (see section 
IV.D.2);
     Assess significant changes in the watershed and source 
water as part of the sanitary survey process and determine appropriate 
follow-up action (see section IV.A); and
     Approve protocols for treatment credit under the 
Demonstration of Performance toolbox option (see section IV.D.9), for 
site specific chlorine dioxide and ozone CT tables (see section 
IV.D.14), and for alternative UV reactor validation testing (see 
section IV.D.15).
    A State program can be more, but not less, stringent than Federal 
regulations. As such, some of the elements listed here may not be 
applicable to a specific State program.
2. State Recordkeeping Requirements
    Today's rule requires States to keep additional records of the 
following, including all supporting information and an explanation of 
the technical basis for each decision:
     Results of source water E. coli and Cryptosporidium 
monitoring for not less than 1 year;
     Cryptosporidium treatment bin classification for each 
filtered PWS after the initial and after the second round of source 
water monitoring. Also, any change in treatment requirements for 
filtered systems due to watershed assessment during sanitary surveys;
     Determination of whether each unfiltered PWS has a mean 
source water Cryptosporidium level above 0.01 oocysts/L after the 
initial and after the second round of source water monitoring;
     The treatment processes or control measures that each PWS 
employs to meet Cryptosporidium treatment requirements under the 
LT2ESWTR, including measures that systems may use for only part of the 
year; and
     A list of PWSs required to cover or treat the effluent of 
an uncovered finished water storage facilities.
3. State Reporting Requirements
    Today's rule requires States to report the following information:
     The Cryptosporidium treatment bin classification for each 
filtered PWS after the initial and after the second round of source 
water monitoring. Also, any change in treatment requirements for 
filtered systems due to watershed assessment during sanitary surveys; 
and
     The determination of whether each unfiltered PWS has a 
mean source water Cryptosporidium level above 0.01 oocysts/L after the 
initial and after the second round of source water monitoring.
4. Interim Primacy
    States that have primacy (including interim primacy) for every 
existing NPDWR already in effect may obtain interim primacy for this 
rule, beginning on the date that the State submits the application for 
this rule to USEPA, or the effective date of its revised regulations, 
whichever is later. A State that wishes to obtain interim primacy

[[Page 730]]

for future NPDWRs must obtain primacy for today's rule. As described in 
Section IV.A, EPA expects to work with States to oversee the initial 
source water monitoring that begins six months following rule 
promulgation.

B. Background and Analysis

    SDWA establishes requirements that a State or eligible Indian Tribe 
must meet to assume and maintain primary enforcement responsibility 
(primacy) for its PWSs. These requirements include the following 
activities: (1) Adopting drinking water regulations that are no less 
stringent than Federal drinking water regulations; (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 under SDWA; and 
(5) adopting and being capable of implementing an adequate plan for the 
provisions of safe drinking water under emergency situations.
    40 CFR part 142 sets out the specific program implementation 
requirements for States to obtain primacy for the public water supply 
supervision program as authorized under SDWA section 1413. In addition 
to adopting basic primacy requirements specified in 40 CFR Part 142, 
States may be required to adopt special primacy provisions pertaining 
to specific regulations where implementation of the rule involves 
activities beyond general primacy provisions. States must include these 
regulation specific provisions in an application for approval of their 
program revision.
    The current regulations in 40 CFR 142.14 require States with 
primacy to keep various records, including the following: analytical 
results to determine compliance with MCLs, MRDLs, and treatment 
technique requirements; PWS inventories; State approvals; enforcement 
actions; and the issuance of variances and exemptions. Today's final 
rule requires States to keep additional records, including all 
supporting information and an explanation of the technical basis for 
decisions made by the State regarding today's rule requirements. EPA 
currently requires in 40 CFR 142.15 that States report to EPA 
information such as violations, variance and exemption status, and 
enforcement actions, and today's rule adds additional reporting 
requirements related to monitoring and treatment requirements.
    On April 28, 1998, EPA amended its State primacy regulations at 40 
CFR 142.12 to incorporate the new process identified in the 1996 SDWA 
Amendments for granting primary enforcement authority to States while 
their applications to modify their primacy programs are under review 
(63 FR 23362, April 28, 1998) (USEPA 1998c). The new process grants 
interim primary enforcement authority for a new or revised regulation 
during the period in which EPA is making a determination with regard to 
primacy for that new or revised regulation. This interim enforcement 
authority begins on the date of the primacy application submission or 
the effective date of the new or revised State regulation, whichever is 
later, and ends when EPA makes a final determination. However, this 
interim primacy authority is only available to a State that has primacy 
(including interim primacy) for every existing NPDWR in effect when the 
new regulation is promulgated. States that have primacy for every 
existing NPDWR already in effect may obtain interim primacy for this 
rule and a State that wishes to obtain interim primacy for future 
NPDWRs must obtain primacy for this rule.

C. Summary of Major Comments

    Public comment generally supported the special primacy requirements 
in the August 11, 2003 proposal, and many commenters expressed 
appreciation for the flexibility the special primacy requirements 
provided to States. One commenter expressed concern that a State that 
adopted this rule by reference would lose the flexibility intended in 
the proposal. In response, EPA recognizes that some States may be 
limited by their statutes in applying the flexibility allowed under 
today's rule. However, EPA believes that providing flexibility for 
States to approve site-specific approaches that achieve the public 
health goals of the LT2ESWTR is appropriate and will benefit some 
States and PWSs.
    A few commenters were concerned that the special primacy 
requirement to assess changes in watersheds as part of the sanitary 
survey process would be difficult to meet due to a lack of resources or 
large watersheds that overlap State boundaries. In response, EPA notes 
that States are required to evaluate PWS sources under the existing 
sanitary survey requirements (40 CFR 142.16(b)(3)). If a State 
determines during a sanitary survey that significant changes have 
occurred in the watershed that could lead to increased contamination of 
the source by Cryptosporidium, today's rule gives the State the 
authority to require the PWS to take actions to mitigate or treat the 
contamination. Because the treatment requirements in today's rule 
depend on the degree of source water contamination, EPA believes that 
this assessment of changes in a PWS's source water following initial 
bin classification is necessary.
    EPA also received comments on State approval processes for 
laboratories analyzing for Cryptosporidium to meet LT2ESWTR 
requirements. Most commenters stated that EPA should maintain a 
national certification program for laboratories approved for 
Cryptosporidium analysis for LT2ESTWR compliance. Commenters indicated 
that requiring States to approve laboratories for Cryptosporidium 
analysis placed too great a demand on State resources. Today's rule 
does not include a State primacy requirement for laboratory 
certification for Cryptosporidium analysis.
    Some commenters were concerned with the data tracking and review 
burden on States from the reporting requirements for the individual 
toolbox components. EPA agrees with commenters that, in some cases, 
allowing PWSs to report summaries or to self-certify that the PWS met 
the performance requirements for microbial toolbox treatment credit may 
be appropriate. Today's rule allow States to modify the level of 
reporting required for toolbox components and specifically, permit PWSs 
to self-certify to the State that a toolbox component has met its 
performance requirements.

VI. Economic Analysis

    This section summarizes the economic analysis (EA) for the final 
LT2ESWTR. The EA is an assessment of the benefits, both health and 
nonhealth-related, and costs to the regulated community of the final 
regulation, along with those of regulatory alternatives that the Agency 
considered. EPA developed the EA to meet the requirement of SDWA 
section 1412(b)(3)(C) for a Health Risk Reduction and Cost Analysis 
(HRRCA), as well as the requirements of Executive Order 12866, 
Regulatory Planning and Review, under which EPA must estimate the costs 
and benefits of the LT2ESWTR. The full EA is presented in Economic 
Analysis for the Long Term 2 Enhanced Surface Water Treatment Rule 
(USEPA 2005a), which includes additional details and discussion on the 
topics presented throughout this section of the preamble.
    The LT2ESWTR is the second in a staged set of rules that address 
public health risks from microbial contamination of surface and GWUDI 
drinking water supplies and, more specifically, prevent Cryptosporidium

[[Page 731]]

from reaching consumers. As described in section III, EPA promulgated 
the IESWTR and LT1ESWTR to provide a baseline of protection against 
Cryptosporidium in large and small PWSs, respectively. Today's final 
rule will achieve further reductions in Cryptosporidium exposure for 
PWSs with the highest vulnerability. This EA considers only the 
incremental reduction in exposure beyond the two previously promulgated 
rules (IESWTR and LT1ESWTR) from the alternatives evaluated for the 
LT2ESWTR.

A. What Regulatory Alternatives Did the Agency Consider?

    Regulatory alternatives considered by the Agency for the LT2ESWTR 
were developed through the deliberations of the Stage 2 M-DBP Federal 
Advisory Committee (described in section III). The Advisory Committee 
considered several general approaches for reducing the risk from 
Cryptosporidium in drinking water. These approaches included both 
additional treatment requirements for all PWSs and risk-targeted 
treatment requirements for PWSs with the highest vulnerability to 
Cryptosporidium following implementation of the IESWTR and LT1ESWTR. In 
addition, the Advisory Committee considered related issues such as 
alternative monitoring strategies.
    After considering these general approaches, the Advisory Committee 
focused on four regulatory alternatives for filtered PWSs (see Table 
VI.A-1). With the exception of Alternative 1, which requires all PWSs 
to provide additional treatment for Cryptosporidium, these alternatives 
incorporate a risk-targeting approach in which PWSs are classified in 
different treatment bins based on the results of source water 
monitoring. Additional Cryptosporidium treatment requirements are 
directly linked to the treatment bin classification. Accordingly, these 
rule alternatives are differentiated by two criteria: (1) The 
Cryptosporidium concentrations that define the bin boundaries and (2) 
the degree of treatment required for each bin.
    The Advisory Committee reached consensus regarding additional 
treatment requirements for unfiltered PWSs without formally identifying 
regulatory alternatives other than requiring no treatment for 
Cryptosporidium (i.e., no new regulation).

   Table VI.A-1.--Summary of Regulatory Alternatives for Filtered PWSs
------------------------------------------------------------------------
     Mean source water Cryptosporidium          Additional treatment
       monitoring result (oocysts/L)              requirements \1\
------------------------------------------------------------------------
                             Alternative A1
------------------------------------------------------------------------
               2.0-log inactivation required for all PWSs
------------------------------------------------------------------------
                             Alternative A2
------------------------------------------------------------------------
< 0.03....................................  No additional treatment.
>= 0.03 and < 0.1.........................  0.5-log.
>= 0.1 and < 1.0..........................  1.5-log.
>= 1.0....................................  2.5-log.
-------------------------------------------
                   Alternative A3--Today's Final Rule
------------------------------------------------------------------------
< 0.075...................................  No additional treatment.
>= 0.075 and < 1.0........................  1-log.
>= 1.0 and < 3.0..........................  2-log.
>= 3.0....................................  2.5-log.
-------------------------------------------
                             Alternative A4
------------------------------------------------------------------------
< 0.1.....................................  No additional treatment.
>= 0.1 and < 1.0..........................  0.5-log.
>=1.0.....................................  1.0-log.
------------------------------------------------------------------------
\1\ Note: ``Additional treatment requirements'' are in addition to
  levels already required under existing rules (e.g., the IESWTR and
  LT1ESWTR) for PWSs using conventional treatment or equivalent.

B. What Analyses Support Today's Final Rule?

    EPA has quantified benefits and costs for each of the filtered PWS 
regulatory alternatives in Table VI.A-1 and for unfiltered PWS 
requirements. Quantified benefits stem from estimated reductions in the 
incidence of cryptosporidiosis resulting from the regulation. To make 
these estimates, the Agency employed Monte Carlo modeling to account 
for uncertainty and variability in key parameters like Cryptosporidium 
occurrence, infectivity, and treatment efficiency. Costs result largely 
from the installation of additional treatment, with lesser costs due to 
monitoring and other implementation activities.
    Cryptosporidium occurrence significantly influences the estimated 
benefits and costs of regulatory alternatives. As discussed in section 
III.E, EPA analyzed data collected under the ICR, the ICR Supplemental 
Surveys of medium PWSs (ICRSSM), and the ICR Supplemental Surveys of 
large PWSs (ICRSSL) to estimate the national occurrence distribution of 
Cryptosporidium in surface water. EPA evaluated these distributions 
independently when assessing benefits and costs for different 
regulatory alternatives.
    Another parameter that significantly influences estimated benefits 
is Cryptosporidium infectivity (i.e., the likelihood of infection after 
exposure to a given dose of Cryptosporidium). As discussed in section 
III.E, EPA considered results from human volunteer feeding studies and 
applied six different model forms to estimate dose-response 
relationships.
    To address uncertainty in these estimates, benefits are presented 
for three different dose response models: A ``high'' estimate based on 
the model that showed the highest mean baseline risk, a ``medium'' 
estimate based on the model and data used at proposal, which is in the 
middle of the range of estimates produced by the six models, and a 
``low'' estimate, based on the model that showed the lowest mean 
baseline risk. These estimates are not upper and lower bounds. For each 
model, a distribution of effects is estimated, and the ``high'' and 
``low'' estimates show only the means of these distributions for two 
different model choices.
    Both benefits and costs are determined as annualized present 
values, which allows comparison of cost and benefit streams that are 
variable over time. The time frame used for both benefit and cost 
comparisons is 25 years. The Agency uses social discount rates of both 
3 percent and 7 percent to calculate present values from the stream of 
benefits and costs and also to annualize the present value estimates 
over 25 years (see EPA's Guidelines for Preparing Economic Analyses 
(USEPA 2000c) for a discussion of social discount rates).
    Results of these analyses are summarized in this section of the 
preamble. Detailed results and descriptions of the supporting analyzes 
are shown in the LT2ESWTR EA (USEPA 2005a).
    In evaluating the regulatory alternatives shown in Table VI.A-1, 
EPA and the Advisory Committee were concerned with the following 
questions: (1) Do the treatment requirements adequately control 
Cryptosporidium concentrations in finished water? (2) How many PWSs 
will be required to add treatment? and (3) What is the likelihood that 
PWSs will be misclassified in higher or lower treatment bins through 
monitoring?
    Consistent with the consensus recommendation of the Advisory 
Committee, EPA selected Alternative A3 for today's final rule. EPA has 
determined that this alternative will significantly reduce the 
incidence of cryptosporidiosis due to drinking water

[[Page 732]]

in vulnerable PWSs and is feasible for PWSs to implement.
    Alternative A1 (across-the-board 2-log inactivation) was not 
selected because it would impose costs but provide few benefits to PWSs 
with relatively low Cryptosporidium risk. EPA was also concerned about 
the feasibility of requiring every surface water treatment plant to 
install additional treatment processes (e.g., UV) for Cryptosporidium. 
With Alternative A2, EPA was concerned with the feasibility of 
accurately classifying PWSs in treatment bins at a Cryptosporidium 
concentration of 0.03 oocysts/L. EPA does not believe that Alternative 
A4 would reduce risks from Cryptosporidium in vulnerable PWSs to the 
extent feasible, as required under SDWA section 1412(b)(7)(A), because 
of the low levels of treatment required.

C. What Are the Benefits of the LT2ESWTR?

    EPA has quantified and monetized health benefits for reductions in 
endemic cryptosporidiosis due to the LT2ESWTR. In addition, today's 
rule is expected to provide additional health and nonhealth-related 
benefits that EPA was unable to quantify. Table VI.C-1 summarizes these 
unquantified benefits.
1. Nonquantified Benefits

                                Table VI.C-1.--Summary of Nonquantified Benefits
----------------------------------------------------------------------------------------------------------------
              Benefit type                     Potential effect on benefits                  Comments
----------------------------------------------------------------------------------------------------------------
Reducing outbreak risks and response      Increase.............................  Some human or equipment
 costs.                                                                           failures may occur even with
                                                                                  the requirements of today's
                                                                                  rule; however, by adding
                                                                                  barriers of protection for
                                                                                  some PWSs, the rule will
                                                                                  reduce the possibility of such
                                                                                  failures leading to outbreaks.
Reducing averting behavior (e.g.,         Increase/No Change...................  Consumers in PWSs that cease
 boiling tap water or purchasing bottled                                          using uncovered finished water
 water).                                                                          reservoirs (through covering
                                                                                  or taking such reservoirs off-
                                                                                  line) may have greater
                                                                                  confidence in water quality.
                                                                                  This may result in less
                                                                                  averting behavior that reduces
                                                                                  both out-of-pocket costs
                                                                                  (e.g., purchase of bottled
                                                                                  water) and opportunity costs
                                                                                  (e.g., time to boil water).
Improving aesthetic water quality.......  Increase.............................  Some technologies installed for
                                                                                  this rule (e.g., ozone) are
                                                                                  likely to reduce taste and
                                                                                  odor problems.
Reducing risk from co-occurring and       Increase.............................  Although focused on removal of
 emerging pathogens.                                                              Cryptosporidium from drinking
                                                                                  water, PWSs that change
                                                                                  treatment processes will also
                                                                                  increase removal of pathogens
                                                                                  that the rule does not
                                                                                  specifically regulate.
Increased source water monitoring.......  Increase.............................  The greater understanding of
                                                                                  source water quality that
                                                                                  results from monitoring may
                                                                                  enhance the ability of plants
                                                                                  to optimize treatment
                                                                                  operations in ways other than
                                                                                  those addressed in this rule.
Reduced contamination due to covering or  Increase.............................  Contaminants introduced through
 treating finished water storage                                                  uncovered finished water
 facilities.                                                                      storage facilities will be
                                                                                  reduced, which will produce
                                                                                  positive public health
                                                                                  benefits.
Change in the levels of disinfection      Increase/Decrease....................  PWSs that install ozone to
 byproducts.                                                                      comply with the LT2ESWTR may
                                                                                  experience an increase in
                                                                                  certain DBPs. PWSs that
                                                                                  install UV or microfiltration
                                                                                  may reduce the use of chlorine
                                                                                  and experience a decrease in
                                                                                  DBPs.
----------------------------------------------------------------------------------------------------------------
 Source: Chapter 5 of the LT2ESWTR Economic Analysis (USEPA 2005a).

2. Quantified Benefits
    In quantifying benefits for the LT2ESWTR based on reductions in the 
risk of endemic cryptosporidiosis, EPA considered several categories of 
monetized benefits. First, EPA estimated the number of cases expected 
to result in premature mortality (primarily for members of sensitive 
subpopulations such as AIDS patients). The mortality estimate was 
developed using data from the Milwaukee cryptosporidiosis outbreak of 
1993 (described in section III), with adjustments to account for the 
subsequent decrease in the mortality rate among people with AIDS and 
for the difference between the portion of people living with AIDS in 
1993 in Milwaukee and the current and projected national levels. EPA 
estimated a mortality rate of 26.3 deaths per 100,000 illnesses for 
those served by unfiltered PWSs and a mortality rate of 16.7 deaths per 
100,000 illnesses for those served by filtered PWSs. These different 
rates are associated with the incidence of AIDS in populations served 
by unfiltered and filtered PWSs. A complete discussion on how EPA 
derived these rates can be found in subchapter 5.2 of the LT2ESWTR EA 
(USEPA 2005a).
    Reductions in mortalities were monetized using EPA's standard 
methodology for monetizing mortality risk reduction. This methodology 
is based on a distribution of value of statistical life (VSL) estimates 
from 26 labor market and stated preference studies. The mean VSL is 
$7.4 million in 2005 with a 5th to 95th percentile range of $1.2 to 
$16.9 million. A more detailed discussion of these studies and the VSL 
estimate can be found in EPA's Guidelines for Preparing Economic 
Analyses (USEPA 2000c). A real income growth factor was applied to 
these estimates of approximately 1.9 percent per year for the 20-year 
time span following implementation. Income elasticity for VSL was 
estimated as a triangular distribution that ranged from 0.08 to 1.00, 
with a mode of 0.40. VSL values for the 20-year span are shown in the 
LT2ESWTR EA in Exhibit 5.24 (USEPA 2005a).
    The substantial majority of cases are not expected to be fatal and 
the Agency separately estimated the value of non-fatal illnesses 
avoided that would result from the LT2ESWTR. For these, EPA first 
divided projected cases into three categories, mild, moderate, and 
severe, and then calculated a monetized value per case avoided for each 
severity level. These were then combined into a weighted average value 
per case based on the relative frequency of each severity level. 
According to a study conducted by Corso et al. (2003), the majority of 
illness fall into the mild category (88 percent). Approximately 11 
percent of illness fall into the moderate category, which is defined as 
those who seek medical treatment but are not hospitalized. The final 1 
percent have severe symptoms that result in hospitalization. EPA 
estimated different medical expenses and time losses for each category.
    Benefits for non-fatal cases were calculated using a cost-of-
illness (COI)

[[Page 733]]

approach. Traditional COI valuations focus on medical costs and lost 
wages, and leave out significant categories of benefits, specifically 
the reduced utility from being sick (i.e., lost personal or non-work 
time, including activities such as child care, homemaking, community 
service, time spent with family, recreation, and pain and suffering), 
although some COI studies also include an estimate for unpaid labor 
(household production) valued at an estimated wage rate designed to 
reflect the market value of such labor (e.g., median wage for household 
domestic labor). Ideally, a comprehensive willingness to pay (WTP) 
estimate would be used that includes all categories of loss in a single 
number. However, a review of the literature indicated that the 
available studies were not suitable for valuing cryptosporidiosis; 
hence, estimates from this literature are inappropriate for use in this 
analysis. Instead, EPA presents two COI estimates: A traditional 
approach that only includes valuation for medical costs and lost work 
time (including some portion of unpaid household production); and an 
enhanced approach that also factors in valuations for lost unpaid work 
time for employed people, reduced utility (or sense of well-being) 
associated with decreased enjoyment of time spent in non-work 
activities, and lost productivity at work on days when paid workers are 
ill but go to work anyway.
    Table VI.C-2 shows the various categories of loss and how they were 
valued for each estimate for a ``typical'' case in 2003 (weighted 
average based on severity level).

Table VI.C-2.--Traditional and Enhanced COI for Cryptosporidiosis, 2003$
                    [Weighted average cost per case]
------------------------------------------------------------------------
          Loss category               Traditional COI      Enhanced COI
------------------------------------------------------------------------
Direct Medical Costs.............  $106.91                        106.91
Lost Paid Work Days..............  120.13                         120.13
Lost Unpaid Work Days \1\........  24.32                           48.64
Lost Leisure Time \2\............  not included                   217.79
Lost Caregiver Days \3\..........  22.98                           61.50
Lost Leisure Productivity \4\....  not included                   162.98
Lost Productivity at Work........  not included                   126.29
----------------------------------
    Total........................  274.34                         844.24
------------------------------------------------------------------------
\1\ Assigned to 39.7% of the population not engaged in market work;
  assumes 40 hr. unpaid work week, valued at $6.23/hr in traditional COI
  and $12.46/hr in enhanced COI. Does not include lost unpaid work for
  employed people and may not include all unpaid work for people outside
  the paid labor force.
\2\ Includes child care and homemaking (to the extent not covered in
  lost unpaid work days above), time with family, and recreation for
  people within and outside the paid labor force, on days when subject
  is too sick to work.
\3\ Values lost work or leisure time for people caring for the ill.
  Traditional approach does not include lost leisure time. Detail may
  not calculate to totals due to independent rounding; Source: Appendix
  L in LT2ESWTR EA (USEPA 2005a)
\4\ Analogous to lost productivity at work. Includes reduced
  productivity in unpaid work and reduced enjoyment of recreation on
  days when subject is sick but engages in unpaid work or leisure
  activities anyway.

    The various loss categories were calculated as follows: Medical 
costs are a weighted average across the three illness severity levels 
of actual costs for doctor and emergency room visits, medication, and 
hospital stays. Lost paid work represents missed work time of paid 
employees, valued at the median pre-tax wage, plus benefits, of $20.82 
hour. The average number of lost work hours per illness day is 3.4 
(this assumes that 60 percent of the population is in the paid labor 
force and the loss is averaged over 7 days). The weighted average 
number of lost work days per case is 1.7 days. Medical costs and lost 
work days reflect market transactions. Medical costs are always 
included in COI estimates and lost work days are usually included in 
COI estimates.
    In the traditional COI estimate, an equivalent amount of lost 
unpaid work time was assigned to the 40 percent of the population that 
are not in the paid labor force. This includes homemakers, students, 
children, retires, and unemployed persons. This estimate attempts to 
capture market-like work (e.g., homemaking, volunteer work) that is 
unpaid. EPA did not attempt to calculate what percent of cases falls in 
each of these five groups, or how many hours per week each group works, 
but rather assumed an across-the-board 40 hour unpaid work week. For 
this reason, it likely overstates the value of unpaid, market-like 
work, but EPA does not have data on this. This time is valued at $6.23 
per hour, which is one half the median post-tax wage (since work 
performed by these groups is not taxed). This is also approximately the 
median wage for paid household domestic labor.
    In the enhanced COI estimate, an estimate of lost unpaid work days 
for people outside the paid labor force was made by assigning the value 
of $12.46 per hour to the same number of unpaid work hours valued in 
the traditional COI approach (i.e., 40 unpaid work hours per week). 
Lost unpaid work for employed people and any unpaid labor beyond 40 
hours per week for those not in the labor market is shown as lost 
leisure time in Table VI.C-2 for the enhanced approach and is not 
included in the traditional approach.
    In the enhanced approach, all time other than paid and market-like 
work and sleep (8 hours per work day and 16 hours per non-work day) is 
valued at the median after tax wage, or $12.46 per hour. This includes 
lost unpaid personal work (e.g., chores, errands, housework) and 
leisure time for people within and outside the paid labor force. The 
average number of unpaid work hours per illness day is 2.3 (40 hours 
per week averaged over 7 days x 40 percent of the population). Implicit 
in this approach is that people would pay the same amount not to be 
sick during their leisure time as they require to give up their leisure 
time to work (i.e., the after tax wage). In reality, people might be 
willing to pay either more than this amount (if they were very sick and 
suffering a lot) or less than this amount (if they were not very sick 
and still got some enjoyment out of activities such as resting, 
reading, and watching TV), not to be sick. Multiplying 10.3 hours by 
$12.46 gives a value of about $128 for a day of ``lost'' unpaid 
personal work and leisure (i.e., lost utility of being sick). The 
weighted average number of lost leisure days per case is the same as 
the weighted average number of lost work days (1.7 days per case).

[[Page 734]]

    In addition, for days when an individual is well enough to work but 
is still experiencing symptoms, such as diarrhea, the enhanced estimate 
also includes a 30 percent loss of work and leisure productivity, based 
on a study of giardiasis illness (Harrington et al. 1985), which is 
similar to cryptosporidiosis. Appendix P in the EA describes similar 
productivity losses for other illnesses such as influenza (35%-73% 
productivity losses). In the traditional COI analysis, productivity 
losses are not included for either work or nonwork time. The weighted 
average number of reduced productivity days per case, for both work and 
leisure, is 1.3 days.
    EPA believes that losses in productivity and lost leisure time are 
unquestionably present and that these categories have positive value; 
consequently, the traditional COI estimate understates the true value 
of these loss categories. EPA notes that these estimates should not be 
regarded as upper and lower bounds. In particular, the enhanced COI 
estimate may not fully incorporate the value of pain and suffering, as 
people may be willing to pay more than $228 (the sum of the valuation 
of lost work and leisure) to avoid a day of illness. The traditional 
COI estimate may not be a lower bound because it includes a valuation 
for a lost 40 hour work week for all persons not in the labor force, 
including children and retirees. This may be an overstatement of lost 
productivity for these groups, which would depend on the impact of such 
things as missed school work or volunteer activities that may be 
affected by illness.
    As with the avoided mortality valuation, the real wages used in the 
COI estimates were increased by a real income growth factor that varies 
by year, but is the equivalent of about 1.9 percent over the 20 year 
period. This approach of adjusting for real income growth was 
recommended by the SAB (USEPA 2000d) because the median real wage is 
expected to grow each year (by approximately 1.9 percent). 
Correspondingly, the real income growth factor of the COI estimates 
increases by the equivalent of 1.9 percent per year (except for medical 
costs, which are not directly tied to wages). This approach gives a 
total COI valuation per case in 2010 of $306 (undiscounted) for the 
traditional COI estimate and $985 (undiscounted) for the enhanced COI 
estimate; the valuation in 2029 is $381 (undiscounted) for the 
traditional COI estimate and $1,316 (undiscounted) for the enhanced COI 
estimate. There is no difference in the methodology for calculating the 
COI over this 20 year period of implementation; the change in valuation 
is due to the underlying change in projected real wages.
    Table VI.C-3 summarizes the annual cases of cryptosporidiosis 
illness and associated deaths avoided due to the LT2ESWTR proposal. 
Today's rule, on average, is expected to reduce 89,375 to 1,459,126 
illnesses and 20 to 314 deaths annually after full implementation 
(range based on the ICRSSL, ICRSSM, and ICR data sets and model choice 
for Cryptosporidium infectivity).
[GRAPHIC] [TIFF OMITTED] TR05JA06.001

    Tables VI.C-4a and VI.C-4b show the monetized present value of the 
benefit for reductions in endemic cryptosporidiosis estimated to result 
from the LT2ESWTR for the enhanced and traditional COI values, 
respectively. Estimates are given for the ICR, ICRSSL, and ICRSSM 
occurrence data sets and for the three infectivity models.
    With the enhanced COI and a 3 percent discount rate, the annual 
present value of the mean benefit estimate ranges from $177 million to 
$2.8 billion; at a 7 percent discount rate, the mean estimate ranges 
from $144 million to $2.3 billion. With the traditional COI, the 
corresponding mean benefit estimate at a 3 percent discount rate ranges 
from $130 million to $2.0 billion; for a 7 percent discount rate, the 
mean estimate ranges from $105 million to $1.7 billion. None of these 
values include the unquantified and nonmonetized benefits listed in 
Table VI.C-1.
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BILLING CODE 6560-50-C
    a. Filtered PWSs. Benefits to the approximately 168 million people 
served by filtered surface water and GWUDI PWSs range from 34,000 to 
702,000 reduction in mean annual cases of endemic illness based on 
three infectivity models and ICRSSL, ICRSSM, and ICR data sets. In 
addition, premature mortality is expected to be reduced by an average 
of 6 to 116 deaths annually.
    b. Unfiltered PWSs. The 10 million people served by unfiltered 
surface water or GWUDI PWSs will see a significant reduction in 
cryptosporidiosis as a result of the LT2ESWTR. In this population, the 
rule is expected to reduce approximately 55,000 to 758,000 cases of 
illness and 14 to 197 premature deaths annually.
    For unfiltered PWSs, only the ICR data set is used to directly 
calculate illness reduction because it is the only data set that 
includes sufficient information on unfiltered PWSs. Illness reduction 
in unfiltered PWSs was estimated for the ICRSSL and ICRSSM

[[Page 736]]

data sets by multiplying the ICR unfiltered PWS result by the ratio, 
for the quantity estimated, between filtered PWS results from the 
supplemental survey data set (SSM or SSL) and filtered PWS results from 
the ICR.
3. Timing of Benefits Accrual (latency)
    In previous rulemakings, some commenters have argued that the 
Agency should consider an assumed time lag or latency period in its 
benefits calculations. The Agency has not conducted a latency analysis 
for this rule because cryptosporidiosis is an acute illness; therefore, 
very little time elapses between exposure, illness, and mortality. 
However, EPA does account for benefits and costs that occur in future 
years by converting these to present value estimates.

D. What Are the Costs of the LT2ESWTR?

    In order to estimate the costs of today's rule, the Agency 
considered impacts on PWSs and on States (including territories and EPA 
implementation in non-primacy States). Summary information on these 
costs follows, with more detailed information in chapter 6 of the 
LT2ESWTR EA (USEPA 2005a). A detailed discussion of the requirements of 
today's rule is located in section IV of this preamble.
1. Total Annualized Present Value Costs
    Tables VI.D-1 summarizes the annualized present value cost 
estimates for the LT2ESWTR at 3 percent and 7 percent discount rates. 
The mean annualized present value costs of the LT2ESWTR are estimated 
to range from approximately $93 to $133 million using a 3 percent 
discount rate and $107 to $150 million using a 7 percent discount rate. 
This range in mean cost estimates is associated with the different 
Cryptosporidium occurrence data sets. In addition to mean estimates of 
costs, the Agency calculated 90 percent confidence bounds by 
considering the uncertainty in Cryptosporidium occurrence estimates and 
the uncertainty around the mean unit technology costs (USEPA 2005a).
    PWSs will incur approximately 99 percent of the rule's total 
annualized present value costs. States incur the remaining rule costs. 
Table VI.D-2 shows the undiscounted initial capital and one-time costs 
broken out by rule component. A comparison of annualized present value 
costs among the rule alternatives considered by the Agency is located 
in section VI.F of this preamble.
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[[Page 738]]


[GRAPHIC] [TIFF OMITTED] TR05JA06.004

BILLING CODE 6560-50-C

[[Page 739]]

2. PWS Costs
    Table VI.D-3 shows the number of filtered and unfiltered PWSs that 
will incur costs by rule provision. All PWSs that treat surface water 
or GWUDI (i.e., nonpurchased PWSs) will incur one-time costs that 
include time for staff training on rule requirements. PWSs will incur 
monitoring costs to assess source water Cryptosporidium levels, though 
monitoring requirements vary by PWS size (large vs. small) and PWS type 
(filtered vs. unfiltered). Some PWSs will incur costs for additional 
Cryptosporidium treatment, where required, and for covering or treating 
uncovered finished water reservoirs.
[GRAPHIC] [TIFF OMITTED] TR05JA06.005

    a. Source water monitoring costs. Source water monitoring costs are 
structured on a per-plant basis. There are three types of monitoring 
that plants may be required to conduct--turbidity, E. coli, and 
Cryptosporidium. Source water turbidity is a common water quality 
parameter used for plant operational control. Also, to meet SWTR, 
LT1ESWTR, and IESWTR requirements, most PWSs have turbidity analytical 
equipment in-house and operators are experienced with turbidity 
measurement. Thus, EPA assumes that the incremental turbidity 
monitoring burden associated with the LT2ESWTR is negligible.
    Filtered plants in small PWSs initially will be required to conduct 
1 year of biweekly E. coli source water monitoring. These plants will 
be required to monitor for Cryptosporidium if E. coli levels exceed 10 
E. coli/100 mL for lakes and reservoir sources or 50 E. coli/100 mL for 
flowing stream sources. EPA estimated the percent of small plants that 
would be triggered into Cryptosporidium monitoring as being equal to 
the percent of large plants that would fall into any bin requiring 
additional treatment.
    Estimates of laboratory fees, shipping costs, labor hours for 
sample collection, and hours for reporting results were used to predict 
PWS costs for initial source water monitoring under the LT2ESWTR. Table 
VI.D-4 summarizes the present value of monitoring costs for initial bin 
classification. Total present value monitoring costs for initial bin 
classification range from $45 million to $59 million depending on the 
occurrence data set and discount rate. Appendix D of the LT2ESWTR EA 
provides a full explanation of how these costs were developed (USEPA 
2005a).
    b. Filtered PWSs treatment costs. The Agency calculated treatment 
costs by estimating the number of plants that will add treatment 
technologies and coupling these estimates with unit costs ($/plant) of 
the selected technologies. Table VI.D-5 shows the number of plants 
estimated to select different treatment technologies; Table VI.D-6 
summarizes the present value treatment costs and annualized present 
value costs for both filtered and unfiltered PWSs.

[[Page 740]]

[GRAPHIC] [TIFF OMITTED] TR05JA06.006

    To estimate the number of filtered plants that would select a 
particular treatment technology, EPA followed a two step process. 
First, the number of plants that will be assigned to treatment bins 
requiring additional treatment was estimated. Second, the treatment 
technologies that plants will choose to meet these requirements was 
estimated using a ``least-cost decision tree.'' In this estimate, EPA 
assumed that PWSs will select the least expensive technology or 
combination of technologies to meet the log removal requirements of a 
given treatment bin. Technology selections were constrained by maximum 
use percentages, which recognize that some plants will not be able to 
implement certain technologies because of site-specific conditions. In 
addition, certain potentially lower cost components of the microbial 
toolbox, such as changes to the plant intake, were not included because 
EPA lacked data to estimate the number of plants that could select it. 
These limitations on technology use may result in an overestimate of 
costs. An in-depth discussion of the technology selection methodology 
and unit cost estimates can be found in Appendices E and F of the 
LT2ESWTR EA (USEPA 2005a).
[GRAPHIC] [TIFF OMITTED] TR05JA06.007

    c. Unfiltered PWSs treatment costs. The LT2ESWTR requires all 
unfiltered PWSs to achieve 2-log of inactivation if their mean source 
water Cryptosporidium concentration is less than or equal to 0.01 
oocysts/L and 3-log of inactivation if it is greater than 0.01 oocysts/
L. For most PWSs, UV appears to be the least expensive technology that 
can achieve these levels of Cryptosporidium inactivation, and EPA 
expects UV to be widely used by unfiltered PWSs to meet today's rule 
requirements. However, as with filtered PWSs, EPA estimated that a 
small percentage of plants would elect to install a technology more 
expensive than UV due to the configuration of

[[Page 741]]

existing equipment or other factors. Ozone is the next least expensive 
technology that will meet the inactivation requirements for some PWSs 
and EPA estimated that it will be used by plants that do not use UV.
    All unfiltered PWSs must meet requirements of the LT2ESWTR; 
therefore, 100 percent of unfiltered PWSs are estimated to add 
technology. This assumes that no unfiltered PWSs currently use these 
additional treatment technologies. For this cost analysis, EPA assumed 
that all very small unfiltered PWSs will use UV; for all other 
unfiltered PWS sizes, EPA estimated that 90 percent will install UV and 
10 percent will add ozone. Treatment costs for unfiltered PWSs are 
included in Table VI.D-6.
[GRAPHIC] [TIFF OMITTED] TR05JA06.008

    d. Uncovered finished water storage facilities. As part of the 
LT2ESWTR, PWSs with uncovered finished water storage facilities must 
either cover the storage facility or treat the discharge to achieve 
inactivation and/or removal of at least 2-log Cryptosporidium, 3-log 
Giardia lamblia, and 4-log viruses. To develop national cost estimates 
for PWSs to comply with these provisions, unit costs for each 
compliance alternative and the percentage of PWSs selecting each 
alternative were estimated for the inventory of uncovered finished 
water storage facilities. From a recent survey of EPA Regions, EPA 
estimates that there are currently 81 uncovered finished water storage 
facilities for which PWSs must take steps to comply with the LT2ESWTR. 
A full description of the unit costs and other assumptions used in this 
analysis is presented in Chapter 6 and Appendix I of the LT2ESWTR EA 
(USEPA 2005a).
    To comply with the treatment requirements, EPA determined that the 
least-cost treatment option is a combination of chlorine and UV. For 
PWSs with uncovered storage facility capacities of 5 million gallons 
(MG) or less, covering the storage facilities is the least expensive 
alternative. Although disinfection is the least expensive alternative 
for the remaining PWSs, the ability of a PWS to use booster 
chlorination depends on their current residual disinfectant type. 
Somewhat less than half of all surface water PWSs are predicted to use 
chloramination following implementation of the Stage 2 DBPR. Adding 
chlorine to water that has been treated with chloramines is not a 
feasible alternative; therefore, the fraction of PWSs projected to add 
UV and booster chlorination to the effluent from the uncovered storage 
facility was estimated at 50 percent, with the remaining 50 percent 
projected to add covers.
    Table VI.D-7 summarizes total annualized present value costs for 
the uncovered finished water storage facility requirements using both 3 
and 7 percent discount rates. EPA estimates the total annualized 
present value cost for covering or treating the water from uncovered 
finished water storage facilities to be approximately $10 million at a 
3 percent discount rate and $13 million at a 7 percent discount rate.

[[Page 742]]

[GRAPHIC] [TIFF OMITTED] TR05JA06.009

    e. Future monitoring costs. Six years after initial bin 
classification, filtered and unfiltered PWSs must conduct a second 
round of monitoring to assess whether source water Cryptosporidium 
levels have changed significantly. EPA will evaluate new analytical 
methods and surrogate indicators of microbial water quality in the 
interim. While the costs of monitoring are likely to change in the 9 
years following rule promulgation, it is difficult to predict how they 
will change. In the absence of any other information, EPA assumed that 
the laboratory costs will be the same as for the initial monitoring.
    All PWSs that conducted initial monitoring were assumed to conduct 
the second round of monitoring, except for those PWSs that installed 
treatment that achieves a total of 5.5-log or greater treatment for 
Cryptosporidium as a result of the rule. These PWSs are exempt from 
monitoring under the LT2ESWTR. EPA estimates that the cost of the 
second round of source water monitoring will range from $21 million to 
$36 million, depending on the occurrence data set and discount rate 
used in the estimate. Appendix D of the EA provides further details 
(USEPA 2005a).
    f. Sensitivity analysis-influent bromide levels on technology 
selection for filtered plants. One concern with the ICR data set is 
that it may not reflect influent bromide levels in some PWSs during 
droughts. High influent bromide levels (the precursor for bromate 
formation) limits ozone use because some PWSs would not be able to meet 
the MCL for bromate. EPA conducted a sensitivity analysis to estimate 
the impact that higher influent bromide levels would have on technology 
decisions. The sensitivity analysis assumed influent bromide 
concentrations of 50 parts per billion (ppb) above the ICR 
concentrations. Results of the analysis indicate that this higher 
bromide level has a minimal impact on costs.
3. State/Primacy Agency Costs
    EPA estimates that States (including primacy agencies) will incur 
an annualized present value cost of $1.1 to 1.2 million using a 3 
percent discount rate and $1.4 million at 7 percent. State 
implementation activities include regulation adoption, program 
implementation, training State staff, training PWS staff, providing 
technical assistance to PWSs, and updating management systems. To 
estimate implementation costs to States, the number of full-time 
employees (FTEs) per activity is multiplied by the number of labor 
hours per FTE, the cost per labor hour, and the number of States and 
Territories.
    In addition to implementation costs, States will also incur costs 
associated with managing monitoring data. Because EPA will directly 
manage reporting, approval, and analysis of results from the initial 
round of monitoring by large PWSs (serving at least 10,000 people), 
States are not predicted to incur costs for these activities. States 
will, however, incur costs associated with small PWS monitoring. This 
is a result of the later start of small PWS monitoring, which will mean 
that some States will assume primacy for small PWS monitoring. In 
addition, States will review the second round of monitoring results. 
States will also incur costs for reviewing technology compliance data 
and consulting with PWSs regarding disinfection benchmarking (for PWSs 
that change their disinfection procedures to comply with today's rule). 
Appendix D of the LT2ESWTR EA provides more information about the State 
cost analysis (USEPA 2005a).
4. Non-Quantified Costs
    EPA has quantified all the major costs for this rule and has 
provided uncertainty analyses to bound the over or underestimates in 
the costs. There are some costs that EPA has not quantified, however, 
because of lack of data. For example, some PWSs may merge with 
neighboring PWSs to comply with this rule. Such changes have both costs 
(legal fees and connecting infrastructure) and benefits (economies of 
scale). Likewise, PWSs would incur costs for procuring a new source of 
water that may result in lower overall treatment costs.
    In addition, the Agency was unable to predict the usage or estimate 
the costs of several options in the microbial toolbox. These options 
include intake management and demonstrations of performance. They have 
not been included in the quantified analysis because data are not 
available to estimate the number of PWSs that may use these toolbox 
options to comply with the LT2ESWTR. Not including these generally 
lower-cost options may result in overestimation of costs.

E. What Are the Household Costs of the LT2ESWTR?

    Another way to assess a rule's impact is to consider how it may 
impact residential water bills. This analysis considers the potential 
increase in a household's water bill if a CWS passed the entire cost 
increase resulting from this rule on to its customers. This serves as a 
tool to gauge potential impacts and should not be construed as precise 
estimates of potential changes to individual water bills.
    Included in this analysis are all PWS costs, including rule 
implementation, initial and future monitoring for bin classification, 
additional Cryptosporidium treatment, and treating

[[Page 743]]

or covering uncovered finished water storage facilities. Costs for 
Cryptosporidium monitoring by small PWSs, additional Cryptosporidium 
treatment, and uncovered finished water storage facilities are assigned 
only to the subset of PWSs expected to incur them. Although 
implementation and monitoring represent relatively small, one-time 
costs, they have been included in the analysis to provide a complete 
distribution of the potential household cost. A detailed description of 
the derivation of household costs is in Chapter 6 and Appendix J of the 
LT2ESTWR EA (USEPA 2005a).
    For PWSs that purchase treated water (i.e., purchased PWSs) from 
larger nonpurchased PWSs, the households costs are calculated based on 
the unit treatment costs of the larger PWS but included in the 
distribution for the size category of the purchased PWS. Households 
costs for these purchased PWSs are based on the household usage rates 
appropriate for the retail PWS and not the PWS selling (wholesaling) 
the water. This approach for purchased PWSs reflects the fact that 
although they will not face increased costs from adding their own 
treatment, whatever costs the wholesale PWS incurs will likely be 
passed on as higher water costs.
    Table VI.E-1 shows the results of the household cost analysis. In 
addition to mean and median estimates, EPA calculated the 90th and the 
95th percentiles. EPA estimates that all households served by surface 
and GWUDI sources will face some increase in household costs due to 
implementation of the LT2ESWTR. Of all the households subject to the 
rule, from 22 to 41 percent are projected to incur costs for adding 
treatment, depending on the Cryptosporidium occurrence data set used.
    Approximately 92 percent of the households potentially subject to 
the rule are served by PWSs serving at least 10,000 people and 99.8 
percent are served by PWSs serving at least 500 people; these PWSs 
experience the lowest increases in costs due to significant economies 
of scale. Over 95 percent of all households are estimated to face an 
annual cost increase of less than $12. Households served by small PWSs 
that install advanced technologies will face the greatest increases in 
annual costs. EPA expects that the model's projections for these PWSs 
are, in some cases, overstated. Some PWSs are likely to find 
alternative treatment techniques such as other toolbox options not 
included in this analysis, or sources of water (ground water, purchased 
water, or consolidating with another PWS) that would be less costly 
than installing more expensive treatment technologies.
[GRAPHIC] [TIFF OMITTED] TR05JA06.010


[[Page 744]]



F. What Are the Incremental Costs and Benefits of the LT2ESWTR?

    Incremental costs and benefits are those that are incurred or 
realized in reducing Cryptosporidium exposures from one regulatory 
alternative to the next. Estimates of incremental costs and benefits 
are useful in considering the economic efficiency of different 
regulatory alternatives evaluated by EPA. Generally, the goal of an 
incremental analysis is to identify the most efficient regulatory 
alternative. However, this analysis is incomplete because some benefits 
from this rule are unquantified and not monetized. Incremental analyses 
should consider both quantified and unquantified (where possible) 
benefits and costs.
    Usually an incremental analysis implies increasing levels of 
stringency along a single parameter, with each alternative providing 
all the protection of the previous alternative, plus additional 
protection. However, the regulatory alternatives evaluated for the 
LT2ESWTR vary by multiple parameters (e.g., treatment bin boundaries, 
treatment requirements). The comparison between any two alternatives 
is, therefore, between two separate sets of benefits, in the sense that 
they may be distributed to somewhat different population groups.
    The regulatory alternatives, however, do achieve increasing levels 
of benefits at increasing levels of costs. As a result, displaying 
incremental net benefits from the baseline and alternative to 
alternative is possible. Tables VI.F-1a and VI.F-1b show incremental 
costs, benefits, and net benefits for the four regulatory alternatives, 
A1-A4, shown in Table VI.A-1, using the enhanced and traditional COI, 
respectively. All values are annualized present values expressed in 
Year 2003 dollars. The displayed values are the mean estimates for each 
occurrence distribution and infectivity model.
    With the enhanced COI, incremental costs are generally closest to 
incremental benefits for A2, a more stringent alternative than A3, 
which is today's final rule. For the traditional COI, incremental costs 
most closely equal incremental benefits for A3 under the majority of 
conditions evaluated.

G. Are There Benefits From the Reduction of Co-Occurring Contaminants?

    While the quantified and monetized benefits for the LT2ESWTR 
includes only reductions in illness and mortality attributable to 
Cryptosporidium, today's rule will reduce exposure to and disease from 
other microbial pathogens and, in some cases, chemical contaminants.

[[Page 745]]

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[[Page 746]]


[GRAPHIC] [TIFF OMITTED] TR05JA06.012

    All of the options in the microbial toolbox that PWSs will 
implement to comply with today's rule will also reduce levels of other 
microbial pathogens. For example, watershed control programs and intake 
relocation

[[Page 747]]

will cut overall pathogen levels by reducing fecal contamination in the 
source water. Membrane, bag, and cartridge filters will remove 
pathogenic protozoa like Giardia lamblia that are similar in size to or 
larger than Cryptosporidium. Lowering finished water turbidity from 
conventional and direct filtration will improve removal of pathogens 
across a broad size range, including viruses, bacteria, and protozoa. 
Inactivation technologies like ozone and UV are highly effective 
against a large number of different pathogen types.
    Some membrane technologies that PWSs may install to comply with the 
LT2ESWTR can also reduce or eliminate chemical contaminants including 
arsenic, DBPs, and atrazine. The use of UV for inactivation of 
Cryptosporidium may reduce the chlorine dosage that some PWSs must 
apply, which can reduce levels of DBPs. EPA has recently finalized a 
rule to further control arsenic levels in drinking water and is 
concurrently establishing the Stage 2 DBPR to address DBP control.
    The extent to which the LT2ESWTR can reduce the overall risk from 
other contaminants has not been quantitatively evaluated because EPA 
lacks sufficient data on the co-occurrence among Cryptosporidium and 
other microbial pathogens and contaminants. Further, due to the 
difficulties in establishing which PWSs would have multiple problems, 
such as microbial contamination, arsenic, and DBPs or any combination 
of the three, no estimate was made of the potential cost savings from 
addressing more than one contaminant simultaneously.

H. Are There Increased Risks From Other Contaminants?

    It is unlikely that the LT2ESWTR will result in a significant 
increase in risk from other contaminants for most PWSs. Many of the 
options that PWSs will select to comply with the LT2ESWTR, such as UV, 
additional or improved filtration, and watershed control, do not form 
DBPs. Ozone, another technology that is effective against 
Cryptosporidium, does form DBPs (e.g., bromate). However, bromate is 
currently regulated under the Stage 1 DBPR, and PWSs will have to 
comply with this regulation if they implement ozone to meet the 
LT2ESWTR.

I. What Are the Effects of the Contaminant on the General Population 
and Groups Within the General Populations That Are Identified as Likely 
To be at Greater Risk of Adverse Health Effects?

    Section III of this preamble discusses the health effects 
associated with Cryptosporidium on the general population as well as 
the effects on other sensitive sub-populations. In addition, health 
effects associated with children and pregnant women are discussed in 
greater detail in section VII.G of this preamble.

J. What Are the Uncertainties in the Risk, Benefit, and Cost Estimates 
for the LT2ESWTR?

    For today's final rule, EPA has modeled the current baseline risk 
from Cryptosporidium exposure through drinking water, along with the 
reduction in risk and the cost for various rule alternatives. There is 
uncertainty in the risk calculation, the benefit estimates, the cost 
estimates, and the interaction with other regulations. The LT2ESWTR EA 
has an extensive discussion of relevant uncertainties (USEPA 2005a), 
and a brief summary of the major uncertainties follows.
    In regard to the risk estimates, the most significant areas of 
uncertainty are Cryptosporidium occurrence, treatment, and infectivity. 
Among the three available occurrence data sets, the ICR plant-mean data 
were higher than the ICRSSM or ICRSSL plant-mean data at the 90th 
percentile. The reasons for these differing results are not well 
understood but may stem from year-to-year variation in occurrence and 
differences in the sampling and measurement methods employed. The 
ICRSSM and ICRSSL data sets use a newer, more reliable sampling method 
but include fewer plants and a shorter time frame. Additional 
uncertainty is associated with estimating finished water occurrence 
because the analysis is based on estimates of treatment plant 
performance in removing Cryptosporidium.
    EPA has addressed some of the uncertainty in occurrence by 
evaluating benefits and costs for regulatory alternatives with each 
Cryptosporidium data set. Further, in the 2-dimensional Monte Carlo 
simulation models used to estimate risk, key parameters like occurrence 
and treatment efficiency are treated as both variable and uncertain. 
This approach is intended to account for the limitations in available 
data and the recognized variability in these parameters among PWSs.
    EPA has also considered occurrence data from additional sources. 
For example, the LT2ESWTR EA discusses a study of infectious 
Cryptosporidium in the finished water of 82 filtration plants by 
Aboytes et.al, 2004. The mean level of infectious Cryptosporidium 
measured in this study is higher than EPA has estimated using the ICR, 
ICRSSM, or ICRSSL data sets. This result suggests that Cryptosporidium 
occurrence at these plants may have exceeded levels during the ICR and 
ICRSS surveys or that EPA may have overestimated the efficiency of 
treatment plants in removing Cryptosporidium.
    In regard to Cryptosporidium infectivity, EPA evaluated data from 
human feeding studies conducted with different Cryptosporidium 
isolates. The measured infectivity of these isolates varied widely, 
however, and how well these isolates represent Cryptosporidium that 
causes disease in PWSs is uncertain. In addition, extrapolating from 
the higher Cryptosporidium dosing levels used in the human feeding 
studies to the exposure levels typical for drinking water (e.g., one 
oocyst) is uncertain. Another source of uncertainty is differences that 
exist among populations groups, such as individuals that are more 
sensitive (e.g., children, immunocompromised) or less sensitive 
(previously infected adults).
    EPA accounted for some of this uncertainty in infectivity by 
treating the human feeding study results for different Cryptosporidium 
isolates as random samples from a larger and unknown environmental 
distribution of Cryptosporidium infectivity. EPA used a variety of 
models for this analysis, as recommended by the SAB, and presents 
results for a range of models to account for uncertainty in model 
selection. In addition, limited data on levels of Cryptosporidium in 
the 1993 Milwaukee outbreak and associated disease incidence suggest 
that the infectivity of the Cryptosporidium responsible for that 
outbreak is within the range EPA has estimated for the risk assessment 
in today's rule.
    Unquantified benefits from the reduction of co-occurring microbial 
pathogens, as described earlier, are a significant source of 
uncertainty in the estimate of benefits for the LT2ESWTR. EPA is also 
uncertain about the monetization of avoided disease from 
Cryptosporidium and has addressed this uncertainty through the use of 
both traditional and enhanced COI values for benefits estimates.
    While all of the significant costs of today's rule have been 
identified by

[[Page 748]]

EPA, there are uncertainties in the estimates. Occurrence is the most 
significant source of uncertainty in costs, and EPA has attempted to 
account for this uncertainty through the use of different occurrence 
data sets and Monte Carlo modeling as described previously. EPA has 
also estimated uncertainty in unit process costs for treatment 
technologies. In addition, the cost assessment for today's rule 
includes sensitivity analyses, such an assessment of the impact of 
influent bromide levels on technology selection. Chapter 6 of the 
LT2ESWTR EA provides a fuller description of uncertainties in the cost 
estimates (USEPA 2005a).
    Last, EPA has recently finalized or is currently finalizing new 
regulations for arsenic, radon, Cryptosporidium in small surface water 
PWSs, filter backwash recycling, microbial pathogens in PWSs using 
ground water, and DBPs. These rules may have overlapping impacts on 
some PWSs, but the extent is not possible to estimate due to lack of 
information on co-occurrence. However, PWSs may choose treatment 
technologies that will address multiple contaminants. Therefore, while 
the total cost impact of these drinking water rules is uncertain, it is 
most likely less than the estimated total cost of all individual rules 
combined.

K. What Is the Benefit/Cost Determination for the LT2ESWTR?

    The Agency has determined that the benefits of the LT2ESWTR justify 
the costs. As discussed in section VII.C, the rule provides a large 
reduction in endemic cryptosporidiosis illness and mortalities. More 
stringent alternatives provide greater reductions but at higher costs. 
Alternative A1 provides the greatest overall reduction in illnesses and 
mortalities but the incremental benefits between this option and 
alternative A3 (today's final rule) are relatively small while the 
incremental costs are significant. In addition, today's rule, unlike 
alternative A1, specifically targets those PWSs whose source water 
requires higher levels of treatment.
    Tables VI.K-1a and VI.K-1b present net benefits for the four 
regulatory alternatives that were evaluated. Generally, analysis of net 
benefits is used to identify alternatives where benefits exceed costs, 
as well as the alternative that maximizes net benefits. However, as 
with the analysis of incremental net benefits discussed previously, the 
usefulness of this analysis in evaluating regulatory alternatives for 
the LT2ESWTR is somewhat limited because many benefits from this rule 
are unquantified and nonmonetized. Analyses of net benefits should 
consider both quantified and unquantified (where possible) benefits and 
costs.
    Also, as noted earlier, the regulatory alternatives considered for 
the LT2ESWTR vary both in the population that experiences benefits and 
costs (i.e., treatment bin boundaries) and the magnitude of the 
benefits and costs (i.e., treatment requirements). Consequently, the 
more stringent regulatory alternatives provide benefits to population 
groups that do not experience any benefit under less stringent 
alternatives.
    As shown by Tables VI.K-1a and VI.K-1b, net benefits are positive 
for all four regulatory alternatives evaluated under most occurrence 
and discount rate scenarios. With both the enhanced COI and traditional 
COI, net benefits are highest for the alternative A3, which is today's 
final rule, under the majority of occurrence distributions and discount 
rates evaluated.
[GRAPHIC] [TIFF OMITTED] TR05JA06.013


[[Page 749]]


[GRAPHIC] [TIFF OMITTED] TR05JA06.014

    In addition to the net benefits of the LT2ESWTR, the Agency used 
several other techniques to compare costs and benefits. For example, 
EPA calculated the cost of the rule per case avoided. Tables VI.K-2a, b 
and c show both the cost of the rule per illness avoided and cost of 
the rule per death avoided. This cost effectiveness measure is another 
way of examining the benefits and costs of the rule but should not be 
used to compare alternatives because an alternative with the lowest 
cost per illness/death avoided may not result in the highest net 
benefits. With the exception of alternative A1, the rule options look 
favorable when the cost per case avoided is compared to both the 
weighted cost of cryptosporidiosis illness ($844 and $274 for the two 
COI approaches) and the mean value of a statistical death avoided--
approximately $7 million dollars. Additional information about this 
analysis and other methods of comparing benefits and costs can be found 
in chapter 8 of the LT2ESWTR EA (USEPA 2005a).

[[Page 750]]

[GRAPHIC] [TIFF OMITTED] TR05JA06.015


[[Page 751]]


[GRAPHIC] [TIFF OMITTED] TR05JA06.016

L. Summary of Major Comments

    EPA received significant public comment on the analysis of benefits 
and costs of the August 11, 2003 proposed LT2ESWTR in the following 
areas: Cryptosporidium occurrence, drinking water consumption, 
Cryptosporidium infectivity (i.e., dose-response), and valuation of 
benefits. The following discussion summarizes public comment in these 
areas and EPA's responses.
1. Cryptosporidium Occurrence
    With respect to the analysis of Cryptosporidium occurrence, two 
areas that received significant public comment are the quality of the 
ICR and ICRSS data sets (i.e., whether the estimates derived from them 
should be regarded as equally plausible) and the treatment of samples 
in which no Cryptosporidium is detected (i.e., observed zeros).
    a. Quality of the ICR and ICRSS data sets. As noted earlier, the 
ICR, ICRSSM, and ICRSSL data sets differ significantly in the high 
concentration portion of the occurrence distribution (e.g., 90th 
percentile). While the measurement method employed in the ICRSS had 
higher recovery and less variable volumes assayed, the ICR produced a 
much greater number of assays and source waters sampled. Lacking a 
technical basis to conclude that one data set provides a better 
estimate, EPA conducted separate analyses of costs and benefits for all 
three data sets. EPA requested comment on this approach.
    The majority of commenters on this issue supported EPA's approach 
of analyzing the three data sets separately to represent uncertainty 
about occurrence. Two commenters suggested that the ICR data would be 
more reliable for estimating national occurrence due to the larger 
number of samples, while two others viewed the ICRSS data as more 
reliable due to the improved analytical method. No commenters provided 
a technical analysis indicating that one data set is more accurate. 
Given these comments, EPA has retained the approach of analyzing costs 
and benefits separately for each occurrence data set in today's final 
rule.
    b. Treatment of observed zeros. One commenter remarked that the 
majority of samples in which no oocysts were detected (i.e., observed 
zeros) likely contained no oocysts in the volume assayed. This 
commenter was concerned with a parameter in EPA's occurrence analysis 
model for ``true zero,'' which characterizes the likelihood that a 
source water is entirely free of Cryptosporidium at all times. In EPA's 
model, the true zero parameter was assigned a value of 0.1 percent. As 
described in USEPA (2005b), EPA based this assumption on the finding 
that intensive sampling of surface waters usually detects 
Cryptosporidium, even in protected watersheds. The commenter concluded, 
however, that the true zero parameter resulted in the model assigning a 
value of at least 1 oocyst to 99.9 percent of samples.
    EPA responds that the true zero parameter in the occurrence 
analysis model does not operate in this way. While the model is set-up 
to estimate mean source water concentrations and not the concentrations 
in individual volumes assayed, the model recognizes that the majority 
of samples in the ICR and ICRSS contained no oocysts. The model does 
assume that few, if any, of the source waters sampled in these surveys 
never contained a single oocyst (the meaning of the true zero 
parameter). EPA has clarified the definition of the true zero parameter 
in USEPA (2005b). EPA has also conducted a sensitivity analysis in 
which the true zero parameter was varied from values of 0 to 50 
percent, with little effect on estimates of risk, benefit, and cost for 
today's rule.
2. Drinking Water Consumption
    Two commenters were concerned with the distribution for drinking 
water consumption that EPA used in the proposed LT2ESWTR. This 
distribution, which was based on a 1994-1996 survey by the United 
States Department of Agriculture (USDA), reflects water consumption 
from all sources. Commenters recommended two modifications to this 
approach: (1) Adjust the distribution to account for factors like 
bottled water and boiled water use; and (2) use an alternative 
distribution from the USDA survey that reflects consumption of 
community water system (CWS) water only.

[[Page 752]]

    In response, EPA agrees that the distribution should be adjusted to 
remove consumption attributable to bottled water. For the consumption 
distribution in today's final rule, EPA subtracted bottled water usage, 
based on information in the USDA survey, which had the effect of 
reducing consumption by approximately 14 percent in comparison to the 
proposal. EPA does not have information on the effectiveness of heating 
water to make coffee or tea for inactivating Cryptosporidium and has 
not modified the consumption distribution on this basis.
    EPA continues to believe that the USDA distribution for consumption 
of water from all sources, minus bottled water consumption, provides 
the best available estimate for consumption of water from CWSs for 
people served by CWSs. The USDA distribution for consumption of CWS 
water only, which a commenter recommended, includes people not served 
by CWSs (e.g., people with private wells). Inclusion these individuals 
has the effect of underestimating the consumption of CWS water for 
people served by CWSs in this distribution. In contrast, the 
distribution for consumption of water from all sources includes people 
not served by CWSs and the sources those people use (e.g., private 
wells). This avoids the problem of underestimating consumption for 
individuals served by CWS. Accordingly, EPA has retained the use of 
this distribution in today's final rule, with the adjustment stated 
previously for bottled water consumption.
3. Cryptosporidium Infectivity
    In regard to Cryptosporidium infectivity (i.e., dose-response 
assessment), EPA received significant comment on limitations in the 
human feeding studies (e.g. representativeness of Cryptosporidium 
isolates used in the studies, numbers of subjects) and uncertainty in 
extrapolating from high study doses to low drinking water doses. EPA 
believes that the statistical analysis of dose-response data, as 
described in USEPA (2005a), properly accounted for these limitations 
and uncertainties.
    The statistical models used by EPA treated the isolates studied as 
a random sample from a larger population of environmental isolates, 
treated the subjects studied as a random sample from the larger 
population of healthy individuals, and treated each individual's 
outcome as a chance event, where the infection probability is a 
function of the challenge dose. Collectively, these uncertainties 
contributed to the significant uncertainty in EPA's estimate of the 
likelihood of infection given one oocyst ingested.
    Since the LT2ESWTR proposal, EPA has reviewed results from 
additional human feeding studies with Cryptosporidium isolates and 
analyzed data from these and the feeding studies considered for the 
proposal with additional dose-response models (USEPA 2005a). As 
described in Chapter 5 and Appendix N of the LT2ESWTR EA, the 
infectivity estimates from the proposal are near the middle of the 
range of estimates derived with the additional feeding study data and 
dose-response models. Further, the mean estimates from these new 
analyses fall within the 90th percentile uncertainty bounds for 
infectivity estimates from the proposal (USEPA 2005a). Consequently, 
EPA believes that the infectivity estimates from the additional feeding 
study data and dose-response models are consistent with and supportive 
of the estimates of infectivity from the proposal. Further, EPA's 
estimates of infectivity are consistent with data on the infectivity of 
Cryptosporidium in the 1993 Milwaukee outbreak (USEPA 2005a).
4. Valuation of Benefits
    In the area of benefits valuation, EPA received significant public 
comment on the valuation of morbidity, valuation of lost time under the 
Enhanced COI approach, and unquantified benefits.
    a. Valuation of morbidity. EPA received a comment that endemic 
cases that do not show up in public health surveillance data may be too 
mild (and perhaps even asymptomatic) to be economically significant. 
EPA believes endemic cases are significant in terms of public health 
risk and economic impacts. As discussed earlier, only a small fraction 
of the millions of cases of gastrointestinal illnesses are traced to a 
specific illness (such as cryptosporidiosis); yet endemic disease 
clearly exists and those illnesses, even if mild, have public health 
consequences and economic impacts (e.g., missed work). For example, the 
benefits model in the EA assumes that 88 percent of all cases are mild, 
and yet those illnesses represent significant impacts nationally. 
Further, the risk assessment model separately computes infections and 
illnesses. Thus, asymptomatic infections are excluded; only avoided 
illnesses are assigned monetary benefits.
    b. Valuation of lost time under the enhanced cost of illness (COI) 
approach. One commenter extensively questioned the approach used to 
value lost leisure and nonwork time under the Enhanced COI approach, 
noting concerns about the relationship of the approach to standard 
economics practices, the plausibility of the resulting values, and the 
extent of peer review. The following discussion summarizes EPA's 
responses on these issues.
    As discussed in detail in the EA (USEPA 2005a), EPA recognizes that 
the preferred approach for valuing health risk reductions is to rely on 
estimates of individual willingness to pay (WTP). In the absence of 
suitable WTP estimates, analysts often rely on approaches similar to 
the Traditional COI approach used for this rule, as noted by the 
commenter. However, empirical research as well as theoretic concerns 
suggest that these types of COI approaches will generally understate 
true WTP.
    EPA designed the Enhanced COI approach to correct for one potential 
source of understatement--the impact of illness on unpaid work and 
leisure time. While the Enhanced COI approach is innovative, it is 
rooted in standard welfare economic theory and builds on approaches 
used to value time in numerous studies in the labor, transportation, 
recreation, and health economics literature. The commenter is 
concerned, however, that the Enhanced COI approach values nonwork time 
at a higher rate than many recreational studies, several of which value 
travel time at one-third of the wage rate. EPA's extensive review of 
the recreational literature suggests, however, that there is no 
consensus regarding the value of travel time, as discussed in the 
Appendix P of the EA (USEPA 2005a). In addition, travel has both 
pleasant and unpleasant aspects and hence may be valued less than other 
leisure activities, many of which may be valued at a rate higher than 
foregone wages.
    To test the plausibility of the results, the commenter compares the 
value of a ``lifetime case'' of cryptosporidiosis to the value of 
statistical life (VSL) and suggests that the results (which show that 
such a case would be roughly 70 percent of VSL) are improbably high. 
However, EPA believes that this comparison is seriously flawed. There 
is no generally accepted standard for determining whether values for 
nonfatal risk reductions are ``reasonable'' compared to values for 
fatal risk reductions. In addition, the calculation of the value of a 
lifetime case of cryptosporidiosis contains several computational 
errors, and represents the loss of all waking time (not just losses 
attributable to cryptosporidiosis) and so is seriously overstated. 
Perhaps most important, the approach used to value

[[Page 753]]

time losses in the Enhanced COI estimate is appropriate only for 
marginal changes in time use; it is not appropriate for the types of 
lifetime changes considered in the comparison.
    The Enhanced COI estimates are based on an approach developed in 
the EPA report, Valuing Time Losses Due to Illness under the 1996 
Amendments to the Safe Drinking Water Act (USEPA 2005e). This report 
has been subject to two rounds of independent peer review. In 
conclusion, EPA believes that including the Enhanced COI in conjunction 
with the Traditional COI is justified theoretically and that including 
both measures increases EPA's ability to understand the impacts of the 
rule.
VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866, [58 FR 51735, (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 Executive Order 12866, it has been 
determined that this rule is a ``significant regulatory action'' 
because it may have an annual effect on the economy of $100 million or 
more (estimated annual costs are $93 to 133 million and $107 to 150 
million at 3 and 7 percent discount rates, respectively). As such, this 
action was submitted to OMB for review. Changes made in response to OMB 
suggestions or recommendations are documented in the public record.

B. Paperwork Reduction Act

    The Office of Management and Budget (OMB) has approved the 
information collection requirements contained in this rule under the 
provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and 
has assigned OMB control number 2040-0266.
    The information collected as a result of this rule will allow the 
States and EPA to determine appropriate requirements for specific PWSs 
and to evaluate compliance with the rule. For the first 3 years after 
LT2ESWTR promulgation, the major information requirements concern 
monitoring activities and compliance tracking. The information 
collection requirements are mandatory (40 CFR part 141) and the 
information collected is not confidential.
    The estimate of annual average burden hours for the LT2ESWTR during 
the first three years following promulgation is 141,295 hours. The 
annual average cost estimate is $4.4 million for labor and $7 million 
per year for operation and maintenance including lab costs (which is a 
purchase of service). The burden hours per response is 0.63 hours and 
the cost per response is $50.35. The frequency of response (average 
responses per respondent) is 90.3, annually. The estimated number of 
likely respondents is 2,503 (the product of burden hours per response, 
frequency, and respondents does not total the annual average burden 
hours due to rounding). Note that the burden hour estimates for the 
first 3-year cycle include some large PWS but not small PWS monitoring. 
Conversely, burden estimate for the second 3-year cycle will include 
remaining monitoring for large systems (those serving between 10,000 
and 49,999 people) and small PWS monitoring, but not for large PWS 
serving 50,000 or more, which will have been completed by then.
    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.
    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 in 40 CFR are listed in 40 CFR part 9. In addition, EPA is 
amending the table in 40 CFR part 9 of currently approved OMB control 
numbers for various regulations to list the regulatory citations for 
the information requirements contained in this final rule.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis for any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or other statute unless the agency certifies that the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations, and small governmental jurisdictions.
    The RFA provides default definitions for each type of small entity. 
Small entities are defined as: (1) a small business as defined by the 
Small Business Administrations's (SBA) regulations at 13 CFR 121.201; 
(2) a small governmental jurisdiction that is a government of a city, 
county, town, school district or special district with a population of 
less than 50,000; and (3) a small organization that is any ``not-for-
profit enterprise which is independently owned and operated and is not 
dominant in its field.'' However, the RFA also authorizes an agency to 
use alternative definitions for each category of small entity, ``which 
are appropriate to the activities of the agency'' after proposing the 
alternative definition(s) in the Federal Register and taking comment. 5 
U.S.C. 601(3)-(5). In addition, to establish an alternative small 
business definition, agencies must consult with SBA's Chief Counsel for 
Advocacy.
    For purposes of assessing the impacts of today's rule on small 
entities, EPA considered small entities to be public water systems 
serving 10,000 or fewer persons. As required by the RFA, EPA proposed 
using this alternative definition in the Federal Register (63 FR 7620, 
February 13, 1998), requested public comment, consulted with the Small 
Business Administration (SBA), and finalized the alternative definition 
in the Consumer Confidence Reports regulation (63 FR 44511, August 19, 
1998). As stated in that Final Rule, the alternative definition is 
applied to this regulation as well.

[[Page 754]]

    After considering the economic impacts of today's final rule on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. The small 
entities directly regulated by this final rule are PWSs serving fewer 
than 10,000 people. We have determined that 152 of the 6,574 small 
PWSs, or 2.3 percent, regulated by the LT2ESWTR will experience an 
impact of 1 percent or greater of average annual revenues; further, 18 
PWSs, which are 0.3 percent of the small PWSs regulated by this rule, 
will experience an impact of 3 percent or greater of average annual 
revenues (see Table VII.C-1).

                            Table VII.C-1.--Annualized Compliance Cost as a Percentage of Revenues for Small Entities (2003$)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                            Average     Systems experiencing      Systems experiencing
                                                                                            annual     costs of >=1% of their    costs of >=3% of their
                                                                Number of    Percent of   estimated           revenues                  revenues
            PWSs by ownership type and system size                small        small       revenues  ---------------------------------------------------
                                                                 systems      systems        per       Number of    Percent of   Number of    Percent of
                                                                                          system($)     systems      systems      systems      systems
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         A            B            C        D=A*E            E        F=A*G            G
--------------------------------------------------------------
Small Government PWSs........................................        2,827           43    2,649,186           65          2.3            8          0.3
Small Business PWSs..........................................        2,452           37    2,555,888           57          2.3            7          0.3
Small Organization PWSs......................................        1,295           20    4,750,838            5          0.4            2          0.1
                                                              --------------
    All Small Entity PWSs....................................        6,574          100    2,981,331          152          2.3           18         0.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: Detail may not add due to independent rounding. Data are based on the means of the highest modeled distributions using Information Collection Rule
  occurrence data set. Costs are discounted at 3 percent, summed to present value, and annualized over 25 years. Source: Chapter 7 and Appendix H of the
  LT2ESWTR EA (USEPA 2005a).

    Although this final rule will not have a significant economic 
impact on a substantial number of small entities, EPA nonetheless has 
tried to reduce the impact of this rule on small entities. The LT2ESWTR 
contains a number of provisions to minimize the impact of the rule on 
PWSs generally, and on small PWSs in particular. The risk-targeted 
approach of the LT2ESWTR will impose additional treatment requirements 
only on the subset of PWSs with the highest vulnerability to 
Cryptosporidium, as indicated by source water pathogen levels. This 
approach will spare the majority of PWSs from the cost of installing 
additional treatment. Also, development of the microbial toolbox under 
the LT2ESWTR will provide both large and small PWSs with broad 
flexibility in selecting cost-effective compliance options to meet 
additional treatment requirements.
    Small PWSs will monitor for E. coli as a screening analysis for 
source waters with low levels of fecal contamination. Cryptosporidium 
monitoring will only be required of small PWSs if they exceed the E. 
coli trigger value. Because E. coli analysis is much cheaper than 
Cryptosporidium analysis, the use of E. coli as a screen will 
significantly reduce monitoring costs for the majority of small PWSs. 
Further, small PWSs will not be required to initiate their monitoring 
until large PWS monitoring has been completed. This will provide small 
PWSs with additional time to become familiar with the rule and to 
prepare for monitoring and other compliance activities.
    Funding may be available from programs administered by EPA and 
other Federal agencies to assist small PWSs in complying with the 
LT2ESWTR. The Drinking Water State Revolving Fund (DWSRF) assists PWSs 
with financing the costs of infrastructure needed to achieve or 
maintain compliance with SDWA requirements. Through the DWSRF, EPA 
awards capitalization grants to States, which in turn can provide low-
cost loans and other types of assistance to eligible PWSs. Loans made 
under the program can have interest rates between 0 percent and market 
rate and repayment terms of up to 20 years. States prioritize funding 
based on projects that address the most serious risks to human health 
and assist PWSs most in need. Congress provided $1.275 billion for the 
DWSRF program in fiscal year 1997, and has provided an additional 
$4.113 billion for the DWSRF program for fiscal years 1999 through 
2003.
    The DWSRF places an emphasis on small and disadvantaged 
communities. States must provide a minimum of 15% of the available 
funds for loans to small communities. A State has the option of 
providing up to 30% of the grant awarded to the State to furnish 
additional assistance to State-defined disadvantaged communities. This 
assistance can take the form of lower interest rates, principal 
forgiveness, or negative interest rate loans. The State may also extend 
repayment terms of loans for disadvantaged communities to up to 30 
years. A State can set aside up to 2% of the grant to provide technical 
assistance to PWSs serving communities with populations fewer than 
10,000.
    In addition to the DWSRF, money is available from the Department of 
Agriculture's Rural Utility Service (RUS) and Housing and Urban 
Development's Community Development Block Grant (CDBG) program. RUS 
provides loans, guaranteed loans, and grants to improve, repair, or 
construct water supply and distribution systems in rural areas and 
towns of up to 10,000 people. In fiscal year 2003, RUS had over $1.5 
billion of available funds for water and environmental programs. The 
CDBG program includes direct grants to States, which in turn are 
awarded to smaller communities, rural areas, and colo[ntilde]as in 
Arizona, California, New Mexico, and Texas and direct grants to U.S. 
territories and trusts. The CDBG budget for fiscal year 2003 totaled 
over $4.4 billion.
    Although not required by the RFA to convene a Small Business 
Advocacy Review (SBAR) Panel because EPA determined that the proposed 
rule would not have a significant economic impact on a substantial 
number of small entities, EPA did convene a panel to obtain advice and 
recommendations from representatives of the small entities potentially 
subject to this rule's requirements. For a description of the SBAR 
Panel and stakeholder recommendations, please see the proposed rule 
(USEPA 2003a).

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public 
Law 104-4, establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on State, local,

[[Page 755]]

and Tribal governments and the private sector. Under section 202 of the 
UMRA, 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 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 notifying 
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.
    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 which is summarized below.
    Table VII.D-1 illustrates the annualized public and private costs 
for the LT2ESWTR.
[GRAPHIC] [TIFF OMITTED] TR05JA06.017

    A more detailed description of this analysis is presented in 
Economic Analysis for the LT2ESWTR (USEPA 2005a).
    As noted in section III, today's final rule is promulgated pursuant 
to section 1412 (b)(1)(A) of the Safe Drinking Water Act (SDWA), as 
amended in 1996, which directs EPA to promulgate a national primary 
drinking water regulation for a contaminant if EPA determines that the 
contaminant may have an adverse effect on the health of persons, occurs 
in PWSs with a frequency and at levels of public health concern, and 
regulation presents a meaningful opportunity for health risk reduction.
    Section VI of this preamble discusses the cost and benefits 
associated with the LT2ESWTR. Details are presented in the Economic 
Analysis for the LT2ESTWR (USEPA 2005a). EPA quantified costs and 
benefits for four regulatory alternatives. The four alternatives are 
described in section VI. Table VII.D-2 summarizes the range of annual 
costs and benefits for each alternative.

[[Page 756]]

[GRAPHIC] [TIFF OMITTED] TR05JA06.018

    To meet the UMRA requirement in section 202, EPA analyzed future 
compliance costs and possible disproportionate budgetary effects. The 
Agency believes that the cost estimates, indicated earlier and 
discussed in more detail in section VI of this preamble, accurately 
characterize future compliance costs of today's rule.
    In analyzing disproportionate impacts, EPA considered the impact on 
(1) different regions of the United States, (2) State, local, and 
Tribal governments, (3) urban, rural and other types of communities, 
and (4) any segment of the private sector. This analysis is presented 
in Chapter 7 of Economic Analysis for the LT2ESWTR (USEPA 2005a).
    EPA has concluded that the LT2ESWTR will not cause a 
disproportionate budgetary effect. This rule imposes the same 
requirements on PWSs nationally and does not disproportionately affect 
any segment. This rule will treat similarly situated PWSs (in terms of 
size, water quality, available data, installed technology, and presence 
of uncovered finished storage facilities) in similar (proportionate) 
ways, without regard to geographic location, type of community, or 
segment of industry. The LT2ESWTR is a rule where requirements are 
proportionate to risk. Although some groups may have differing 
budgetary effects as a result of the LT2ESWTR, those costs are 
proportional to the need for greater information (monitoring) and risk 
posed (degree of treatment required). The variation in cost between 
large and small PWSs is due to economies of scale (a larger PWS can 
distribute cost across more customers). Regions will have varying 
impacts due to the number of affected PWSs.
    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 2003, real GDP was 
$10,398 billion, so a rule would have to cost at least $26 billion 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 
LT2ESWTR should not have a measurable effect because the total annual 
costs for today's rule range from $93 million to $133 million based on 
median Cryptosporidium occurrence distributions from the ICRSSL and 
Information Collection Rule data sets and a discount rate of 3 percent 
($107 to $150 million at a 7 percent discount rate). These annualized 
figures will remain constant over the 25-year implementation period 
that was evaluated, while GDP will probably continue to rise. Thus, the 
LT2ESWTR costs as a percentage of the national GDP will only decline 
over time. Costs will not be highly focused on a particular geographic 
region or sector.
    Consistent with the intergovernmental consultation provisions of 
section 204 of the UMRA, EPA initiated consultations with the 
governmental entities affected by this rule prior to the proposal. A 
description of the consultations is found in the proposed rule (USEPA 
2003a).
    As required under section 205 of UMRA, EPA considered several 
regulatory alternatives to address PWSs at risk for contamination by 
microbial pathogens, specifically including Cryptosporidium. A detailed 
discussion of these alternatives can be found in section VI of the 
preamble and also in the Economic Analysis for the LT2ESWTR (USEPA 
2005a).
    Among the regulatory alternatives considered for the LT2ESWTR, as 
described in section VI, EPA believes the alternative in today's rule 
is the most cost-effective that achieves the objectives of the rule. 
The objective of the LT2ESWTR is to achieve feasible risk reduction 
from Cryptosporidium and other pathogens in vulnerable PWSs where 
current regulations do not provide sufficient protection.
    EPA evaluated a less costly and less burdensome alternative. 
However, that alternative would provide no benefit to several thousand 
consumers who, under the alternative in today's final rule, will 
receive benefits that most likely exceed their costs, based on EPA 
estimates. This is illustrated in the LT2ESWTR Economic Analysis (USEPA 
2005a). By failing to reduce risk for consumers where additional 
treatment requirements would be cost-effective, the less costly 
alternative does not appear to achieve the objectives of the LT2ESWTR.
    The other alternatives considered by the Agency achieve the 
objectives of the rule, but are more costly, more burdensome, and 
potentially less cost-effective. The alternative in today's rule 
targets additional treatment requirements to PWSs with the highest 
vulnerability to Cryptosporidium and maximizes net benefits under a 
broad range of conditions (USEPA 2005a). Consequently, EPA has found 
the alternative in today's rule to be the most cost-effective among 
those that achieve the objectives of the rule.
    EPA has determined that this rule contains no regulatory 
requirements that might significantly or uniquely affect small 
governments. Thus, today's rule is not subject to the requirements of 
section 203 of UMRA. As described in section VII.C, EPA has certified 
that today's rule will not have a significant economic impact on a 
substantial number of small entities. Average annual expenditures for 
small PWSs to comply with the LT2ESWTR range from

[[Page 757]]

$8.1 to $13.4 million at a 3% discount rate and $8.3 to $13.5 million 
at a 7% discount rate. While the treatment requirements of the LT2ESWTR 
apply uniformly to both small and large PWSs, large PWSs bear a 
majority of the total costs of compliance with the rule. This is due to 
the fact that large PWSs treat a majority of the drinking water that 
originates from surface water sources.

E. Executive Order 13132: Federalism

    Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August 
10, 1999), requires EPA to develop an accountable process to ensure 
``meaningful and timely input by State and local officials in the 
development of regulatory policies that have federalism implications.'' 
``Policies that have federalism implications'' is defined in the 
Executive Order to include regulations that have ``substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government.''
    Under Executive Order 13132, EPA may not issue a regulation that 
has federalism implications, that imposes substantial direct compliance 
costs, and that is not required by statute, unless the Federal 
government provides the funds necessary to pay the direct compliance 
costs incurred by State and local governments, or EPA consults with 
State and local officials early in the process of developing the 
regulation.
    EPA has concluded that this final rule may have federalism 
implications, because it may impose substantial direct compliance costs 
on State or local governments, and the Federal government will not 
provide the funds necessary to pay those costs. The final rule may 
result in expenditures by State, local, and Tribal governments, in the 
aggregate of $100 million or more in any one year. Costs are estimated 
to range from $93 to $133 million at a 3 percent discount rate and $107 
to $150 million using a 7 percent discount rate based on the median 
distribution modeled from ICRSSL and Information Collection Rule 
Cryptosporidium occurrence data sets. Accordingly, EPA provides the 
following federalism summary impact statement as required by section 
6(b) of Executive Order 13132.
    EPA consulted with representatives of State and local officials 
early in the process of developing today's rule to permit them to have 
meaningful and timely input into its development. As described in the 
proposed rule (USEPA 2003a), this consultation included State and local 
government representatives on the Stage 2 M-DBP Federal Advisory 
Committee (whose recommendations were largely adopted in today's rule), 
the representatives from small local governments to the SBAR panel, a 
meeting with representatives from the Association of State Drinking 
Water Administrators, the National Governors' Association, the National 
Conference of State Legislatures, the International City/County 
Management Association, the National League of Cities, the County 
Executives of America, and health departments, consultation with Tribal 
governments at four meetings and through the Advisory Committee 
process, and comments from State and local governments on a pre-
proposal draft of the LT2ESWTR.
    Representatives of State and local officials were generally 
concerned with ensuring that drinking water regulations are adequately 
protective of public health and that any additional regulations achieve 
significant health benefits in return for required expenditures. They 
were specifically concerned with the burden of the rule, both in cost 
and technical complexity, giving flexibility to PWSs and States, 
balancing the control of microbial risks and DBP risks, funding for 
implementing new regulations, equal protection for small PWSs, and 
early implementation of monitoring by large PWSs.
    EPA has concluded that the LT2ESWTR is needed to reduce the public 
health risk associated with Cryptosporidium in drinking water. As shown 
in section VI, estimated benefits for the rule are significantly higher 
than costs. Further, EPA believes that today's rule addresses many of 
the concerns expressed by representatives of government officials.
    Under the LT2ESWTR, expenditures for additional treatment are 
targeted to the fraction of PWSs with the highest vulnerability to 
Cryptosporidium, thereby minimizing burden for the majority of PWSs, 
which will not be required to provide additional treatment. The 
microbial toolbox of compliance options will provide flexibility to 
PWSs in meeting additional treatment requirements, and States have the 
flexibility to award treatment credits based on site-specific 
demonstrations. Disinfection profiling provisions are intended to 
ensure that PWSs do not reduce microbial protection as they take steps 
to reduce exposures to DBPs.
    The LT2ESWTR achieves equal public health protection for small 
PWSs. However, the use of E. coli monitoring by small PWSs as a 
screening analysis to determine the need for Cryptosporidium monitoring 
will reduce monitoring costs for most small PWSs. Capital projects 
related to the rule will be eligible for funding from the Drinking 
Water State Revolving Fund, which includes specific funding for small 
communities. EPA is planning to support the initial monitoring by large 
PWSs that takes place within the first few years after rule 
promulgation. This will substantially reduce the burden on States 
associated with early implementation of monitoring requirements.
    In the spirit of Executive Order 13132, and consistent with EPA 
policy to promote communications between EPA and State and local 
governments, EPA specifically solicited comment on the proposed rule 
from State and local officials.
    As required by section 8(a) of Executive Order 13132, EPA included 
a certification from its Federalism Official stating that EPA had met 
the Executive Order's requirements in a meaningful and timely manner, 
when it sent the draft of this final rule to OMB for review pursuant to 
Executive Order 12866. A copy of this certification has been included 
in the public version of the official record for this final rule.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000), 
requires EPA to develop ``an accountable process to ensure meaningful 
and timely input by tribal officials in the development of regulatory 
policies that have tribal implications.'' Under Executive Order 13175, 
EPA may not issue a regulation that has Tribal implications, that 
imposes substantial direct compliance costs, and that is not required 
by statute, unless the Federal government provides the funds necessary 
to pay the direct compliance costs incurred by Tribal governments, or 
EPA consults with Tribal officials early in the process of developing 
the proposed regulation and develops a Tribal summary impact statement.
    EPA has concluded that this final rule may have Tribal 
implications, because it may impose substantial direct compliance costs 
on Tribal governments, and the Federal government will not provide the 
funds necessary to pay those costs. EPA has identified 93 Tribal water 
systems serving a total population of 82,216 that may be subject to the 
LT2ESWTR. They will bear an estimated total annualized cost of $207,105 
at a 3 percent discount rate ($309,583 at 7 percent) to

[[Page 758]]

implement this rule. Estimated mean annualized cost per system ranges 
from $1,944 to $7,068 at a 3 percent discount rate ($2,905 to $10,681 
at 7 percent) depending on PWS size (see Chapter 7 of the LT2ESWTR 
Economic Analysis (USEPA 2005a) for details). Accordingly, EPA provides 
the following Tribal summary impact statement as required by section 
5(b).
    EPA consulted with Tribal officials early in the process of 
developing this regulation to permit them to have meaningful and timely 
input into its development. This consultation is described in the 
proposed rule (USEPA 2003a). Tribal officials were represented on the 
M-DBP Advisory Committee.
    As required by section 7(a), EPA's Tribal Consultation Official has 
certified that the requirements of the Executive Order have been met in 
a meaningful and timely manner. A copy of this certification is 
included in the docket for this rule.

G. Executive Order 13045: Protection of Children From Environmental 
Health 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 Executive Order 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 final rule is subject to the Executive Order because it is an 
economically significant regulatory action as defined in Executive 
Order 12866, and we believe that the environmental health or safety 
risk addressed by this action may have a disproportionate effect on 
children. Accordingly, we have evaluated the environmental health or 
safety effects of Cryptosporidium on children. The results of this 
evaluation are contained in Cryptosporidium: Risk for Infants and 
Children (USEPA 2001d), which is available in the public docket for 
this action, and are summarized in this section of the preamble. 
Further, while available information is not adequate to conduct a 
quantitative risk assessment specifically for children, EPA has 
assessed the risk associated with Cryptosporidium in drinking water for 
the general population, including children. This assessment is 
described in the Economic Analysis for the LT2ESWTR (USEPA 2005a) and 
is summarized in section VI of this preamble.

Children's Environmental Health

    Cryptosporidiosis in children is similar to adult disease (USEPA 
2001d). Diarrhea is the most common symptom. Other common symptoms in 
otherwise healthy (i.e., immunocompetent) children include anorexia, 
vomiting, abdominal pain, fever, dehydration and weight loss.
    The risk of illness and death due to cryptosporidiosis depends on 
several factors, including age, nutrition, exposure, genetic 
variability, disease and the immune status of the individual. Mortality 
resulting from diarrhea generally occurs at a greater rate among the 
very young and elderly (Gerba et al., 1996). During the 1993 Milwaukee 
drinking water outbreak, associated mortalities in children were 
reported. Also, children with laboratory-confirmed cryptosporidiosis 
were more likely to have an underlying disease that altered their 
immune status (Cicirello et al., 1997). In that study, the observed 
association between increasing age of children and increased numbers of 
laboratory-confirmed cryptosporidiosis suggested to the authors that 
the data are consistent with increased tap water consumption of older 
children. Asymptomatic infection can have a substantial effect on 
childhood growth (Bern et al., 2002).
    Cryptosporidiosis appears to be more prevalent in populations, such 
as children, that may not have established immunity against the disease 
and may be in greater contact with environmentally contaminated 
surfaces (DuPont et al., 1995). In the United States, children aged one 
to four years are more likely than adults to have the disease. The most 
recent reported data on cryptosporidiosis shows the occurrence rate 
(for the year 1999) is higher in children ages one to four (3.03 
incidence rate per 100,000) than in any adult age group (CDC, 2001). 
Evidence from blood sera antibodies collected from children during the 
1993 Milwaukee outbreak suggest that children had greater levels of 
Cryptosporidium infection than predicted for the general community 
(based on the random-digit dialing telephone survey method) (McDonald 
et al., 2001).
    Data indicate a lower incidence of cryptosporidiosis infection 
during the first year of life. This is attributed to breast-fed infants 
consuming less tap water and, hence, having less exposure to 
Cryptosporidium, as well as the possibility that mothers confer short 
term immunity to their children. For example, in a survey of over 
30,000 stool sample analyses from different patients in the United 
Kingdom, the one to five year age group suffered a much higher 
infection rate than individuals less than one year of age. For children 
under one year of age, those older than six months of age showed a 
higher rate of infection than individuals aged less than six months 
(Casemore, 1990). Similarly, in the U.S., of 2,566 reported 
Cryptosporidium illnesses in 1999, 525 occurred in ages one to four 
(incidence rate of 3.03 per 100,000) compared with 58 cases in infants 
under one year (incidence rate of 1.42 per 100,000) (CDC, 2001).
    An infected child may spread the disease to other children or 
family members (Heijbel et al., 1987, Osewe et al., 1996). Millard et 
al. (1994) documented greater household secondary transmission of 
cryptosporidiosis from children than from adults to household and other 
close contacts. Children continued to shed oocysts for more than two 
weeks (mean 16.5 days) after diarrhea cessation (Tangerman et al., 
1991).
    While Cryptosporidium may have a disproportionate effect on 
children, available data are not adequate to distinctly assess the 
health risk for children resulting from Cryptosporidium-contaminated 
drinking water. In assessing risk to children when evaluating 
regulatory alternatives for the LT2ESWTR, EPA assumed the same risk for 
children as for the population as a whole.
    Section VI of this preamble presents the regulatory alternatives 
that EPA evaluated for the proposed LT2ESWTR. Among the four 
alternatives the Agency considered, three involved a risk-targeting 
approach in which additional Cryptosporidium treatment requirements are 
based on source water monitoring results. A fourth alternative involved 
additional treatment requirements for all PWSs. The alternative 
requiring additional treatment by all PWSs was not selected because of 
concerns about feasibility and because it imposed costs but provided 
few benefits to PWSs with high quality source water (i.e., relatively 
low Cryptosporidium risk). The three risk-targeting alternatives were 
evaluated based on several factors, including costs, benefits, net 
benefits, feasibility of implementation, and other specific impacts 
(e.g., impacts on small PWSs or sensitive subpopulations).

[[Page 759]]

    The alternative that today's final rule establishes was recommended 
by the M-DBP Federal Advisory Committee and selected by EPA as the 
Preferred Regulatory Alternative because it was deemed feasible and 
provides significant public health benefits in terms of avoided 
illnesses and deaths. EPA's analysis of benefits and costs indicates 
that this alternative ranks highly among those evaluated with respect 
to maximizing net benefits, as shown in the LT2ESWTR Economic Analysis 
(USEPA 2005a). This document is available in the docket for this 
action.
    The result of the LT2ESWTR will be a reduction in the risk of 
illness for the entire population, including children. Because 
available evidence indicates that children may be more vulnerable to 
cryptosporidiosis than the rest of the population, the LT2ESWTR may, 
therefore, result in greater risk reduction for children than for the 
general population.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This rule is not a ``significant energy action'' as defined in 
Executive Order 13211, ``Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use'' (66 FR 28355 
(May 22, 2001)) because it is not likely to have a significant adverse 
effect on the supply, distribution, or use of energy. This 
determination is based on the following analysis.
    The first consideration is whether the LT2ESWTR would adversely 
affect the supply of energy. The LT2ESWTR does not regulate power 
generation, either directly or indirectly. The public and private 
utilities that the LT2ESWTR regulates do not, as a rule, generate 
power. Further, the cost increases borne by customers of water 
utilities as a result of the LT2ESWTR are a low percentage of the total 
cost of water, except for a very few small PWSs that might install 
advanced technologies and then need to spread that cost over a narrow 
customer base. Therefore, the customers that are power generation 
utilities are unlikely to face any significant effects as a result of 
the LT2ESWTR. In sum, the LT2ESWTR does not regulate the supply of 
energy, does not generally regulate the utilities that supply energy, 
and is unlikely to affect significantly the customer base of energy 
suppliers. Thus, the LT2ESWTR would not translate into adverse effects 
on the supply of energy.
    The second consideration is whether the LT2ESWTR would adversely 
affect the distribution of energy. The LT2ESWTR does not regulate any 
aspect of energy distribution. The utilities that are regulated by the 
LT2ESWTR already have electrical service. As derived later in this 
section, the final rule is projected to increase peak electricity 
demand at water utilities by only 0.036 percent. Therefore, EPA 
estimates that the existing connections are adequate and that the 
LT2ESWTR has no discernable adverse effect on energy distribution.
    The third consideration is whether the LT2ESWTR would adversely 
affect the use of energy. Because some drinking water utilities are 
expected to add treatment technologies that use electrical power, this 
potential impact is evaluated in more detail. The analyses that 
underlay the estimation of costs for the LT2ESWTR are national in scope 
and do not identify specific plants or utilities that may install 
treatment in response to the rule. As a result, no analysis of the 
effect on specific energy suppliers is possible with the available 
data. The approach used to estimate the impact of energy use, 
therefore, focuses on national-level impacts. The analysis estimates 
the additional energy use due to the LT2ESWTR, and compares that to the 
national levels of power generation in terms of average and peak loads.
    The first step in the analysis is to estimate the energy used by 
the technologies expected to be installed as a result of the LT2ESWTR. 
Energy use is not directly stated in Technologies and Costs for Control 
of Microbial Contaminants and Disinfection By-Products (USEPA 2003c), 
but the annual cost of energy for each technology addition or upgrade 
necessitated by the LT2ESWTR is provided. An estimate of plant-level 
energy use is derived by dividing the total energy cost per plant for a 
range of flows by an average national cost of electricity of $0.070/kWh 
(USDOE 2004a). These calculations are shown in detail in Chapter 7 of 
the Economic Analysis for the LT2ESWTR (USEPA 2005a). The energy use 
per plant for each flow range and technology is then multiplied by the 
number of plants predicted to install each technology in a given flow 
range. The energy requirements for each flow range are then added to 
produce a national total. No electricity use is subtracted to account 
for the technologies that may be replaced by new technologies, 
resulting in a conservative estimate of the increase in energy use. 
Results of the analysis are shown in Table VII.H-1 for each of the 
modeled Cryptosporidium occurrence distributions. The incremental 
national annual energy usage is estimated at 165 million megawatt-hours 
(mW) based on the modeled Information Collection Rule occurrence 
distribution.

[[Page 760]]

[GRAPHIC] [TIFF OMITTED] TR05JA06.019

    To determine if the additional energy required for PWSs to comply 
with the rule would have a significant adverse effect on the use of 
energy, the numbers in Table VII.H-1 are compared to the national 
production figures for electricity. According to the U.S. Department of 
Energy's Information Administration, electricity producers generated 
3,848 million mW of electricity in 2003 (USDOE 2004b). Therefore, even 
using the highest assumed energy use for the LT2ESWTR, the rule when 
fully implemented would result in only a 0.004 percent increase in 
annual average energy use.
    In addition to average energy use, the impact at times of peak 
power demand is important. To examine whether increased energy usage 
might significantly affect the capacity margins of energy suppliers, 
their peak season generating capacity reserve was compared to an 
estimate of peak incremental power demand by water utilities.
    Both energy use and water use are highest in the summer months, so 
the most significant effects on supply would be seen then. In the year 
of 2003, U.S. generation capacity exceeded consumption by 15 percent, 
or approximately 160,00 mW (USDOE EIA 2004b). Assuming around-the-clock 
operation of water treatment plants, the total energy requirement can 
be divided by 8,760 hours per year to obtain an average power demand of 
19 mW for the modeled Information Collection Rule occurrence 
distribution. A more detailed derivation of this value is shown in 
Chapter 7 of the Economic Analysis for the LT2ESWTR (USEPA 2005a). 
Assuming that power demand is proportional to water flow through the 
plant, and that peak flow can be as high as twice the average daily 
flow during the summer months, about 38 mW could be needed for 
treatment technologies installed to comply with the LT2ESWTR. This is 
only 0.024 percent of the capacity margin available at peak use.
    Although EPA recognizes that not all areas have a 15 percent 
capacity margin and that this margin varies across regions and through 
time, this analysis reflects the effect of the rule on national energy 
supply, distribution, or use. While certain areas, notably California, 
have experienced shortfalls in generating capacity in the recent past, 
a peak incremental power requirement of 38 mW nationwide is not likely 
to significantly change the energy supply, distribution, or use in any 
given area. Considering this analysis, EPA has concluded that LT2ESWTR 
is not likely to have a significant adverse effect on the supply, 
distribution, or use of energy.

I. National Technology Transfer and Advancement Act

    As noted in the proposed rule, Section 12(d) of the National 
Technology Transfer and Advancement Act (``NTTAA'') of 1995, Public Law 
104-113, section 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.
    This rulemaking involves technical standards. EPA has decided to 
use methods previously approved in 40 CFR 136.3 for the analysis of E. 
coli in surface waters. These include several voluntary consensus 
methods that were developed or adopted by the following organizations: 
American Public Health Association in Standard Methods for the 
Examination of Water and Wastewater, 20th, 19th, and 18th Editions, the 
American Society of Testing Materials in Annual Book of ASTM 
Standards--Water and Environmental Technology, and the Association of 
Analytical Chemists in Official Methods of Analysis of AOAC 
International, 16th Edition. EPA has concluded that these methods have 
the necessary sensitivity and specificity to meet the data quality 
objectives of the LT2ESWTR.
    The Agency conducted a search to identify potentially applicable 
voluntary consensus standards for analysis of Cryptosporidium. However, 
we identified no such standards. Therefore,

[[Page 761]]

EPA approves the use of the following methods for Cryptosporidium 
analysis: Method 1623: Cryptosporidium and Giardia in Water by 
Filtration/IMS/FA, 2004, United States Environmental Protection Agency, 
EPA-815-R-05-002 or Method 1622: Cryptosporidium in Water by 
Filtration/IMS/FA, 2004, United States Environmental Protection Agency, 
EPA-815-R-05-001.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations or Low-Income Populations

    Executive Order 12898 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. EPA 
has considered environmental justice related issues concerning the 
potential impacts of this action and consulted with minority and low-
income stakeholders. A description of this consultation can be found in 
the proposed rule (USEPA 2003a).

K. Consultations With the Science Advisory Board, National Drinking 
Water Advisory Council, and the Secretary of Health and Human Services

    In accordance with Section 1412 (d) and (e) of the SDWA, the Agency 
did consult with the Science Advisory Board, the National Drinking 
Water Advisory Council (NDWAC), and the Secretary of Health and Human 
Services on today's rule.
    EPA charged the SAB panel with reviewing the following aspects of 
the LT2ESWTR proposal:
     The analysis of Cryptosporidium occurrence;
     The pre- and post-LT2ESWTR Cryptosporidium risk 
assessment; and
     The treatment credits for the following four microbial 
toolbox components: raw water off-stream storage, pre-sedimentation, 
lime softening, and lower finished water turbidity.
    EPA met with the SAB to discuss the LT2ESWTR on June 13, 2001 
(Washington, DC), September 25-26, 2001 (teleconference), and December 
10-12, 2001 (Los Angeles, CA). The SAB issued its final report for this 
review, Disinfection Byproducts and Surface Water Treatment: A EPA 
Science Advisory Board Review of Certain Elements of the Stage 2 
Regulatory Proposals, in May 2003.
    Comments from the SAB were generally supportive of EPA's analysis 
of Cryptosporidium occurrence and the Cryptosporidium risk assessment 
for today's rule. The SAB recommended some additional quality assurance 
checks for statistical models, improved descriptions of underlying data 
sets, and better characterization of uncertainty for key parameters. 
USEPA 2005a and 2005b provide information on revisions EPA made in 
response to these comments.
    SAB comments on microbial toolbox options and the Agency's 
responses to those comments are described in section IIII.D of this 
preamble. In general, the SAB supported treatment credit for two-stage 
softening, recommended additional performance criteria to award 
treatment credit to presedimentation basins, recommended modifications 
to the treatment credit for combined and individual filter performance, 
and opposed treatment credit for off-stream raw water storage.
    EPA met with the NDWAC on November 8, 2001, in Washington, DC, to 
discuss the LT2ESWTR proposal. EPA specifically requested comments from 
the NDWAC on the regulatory approach taken in the proposed microbial 
toolbox (e.g., proposal of specific design and implementation criteria 
for treatment credits). The Council was generally supportive of EPA 
establishing criteria for awarding treatment credit to toolbox 
components, but recommended that EPA provide flexibility for States to 
address PWS specific situations. EPA believes that the demonstration of 
performance credit, described in section IV.D.9 provides this 
flexibility by allowing States to award higher or lower levels of 
treatment credit for microbial toolbox components based on site 
specific conditions.
    EPA has consulted with the U.S. Department of Health and Human 
Services (HHS) regarding Cryptosporidium health effects and has 
provided HHS with today's rule.

L. Plain Language

    Executive Order 12866 requires each agency to write its rules in 
plain language. Readable regulations help the public find requirements 
quickly and understand them easily. They increase compliance, 
strengthen enforcement, and decrease mistakes, frustration, phone 
calls, appeals, and distrust of government. EPA made every effort to 
write this preamble to the final rule in as clear, concise, and 
unambiguous manner as possible.

M. Analysis of the Likely Effect of Compliance With the LT2ESWTR on the 
Technical, Financial, and Managerial Capacity of Public Water Systems

    Section 1420(d)(3) of SDWA, as amended, requires that in 
promulgating an NPDWR, the Administrator shall include an analysis of 
the likely effect of compliance with the regulation on the technical, 
managerial, and financial capacity of public water systems. This 
analysis can be found in the LT2ESWTR Economic Analysis (USEPA 2005a). 
Analyses reflect only the impact of new or revised requirements, as 
established by the LT2ESWTR; the impacts of previously established 
requirements on system capacity are not considered.
    EPA has defined overall water system capacity as the ability to 
plan for, achieve, and maintain compliance with applicable drinking 
water standards. Capacity encompasses three components: technical, 
managerial, and financial. Technical capacity is the physical and 
operational ability of a water system to meet SDWA requirements. This 
refers to the physical infrastructure of the water system, including 
the adequacy of source water and the adequacy of treatment, storage, 
and distribution infrastructure. It also refers to the ability of 
system personnel to adequately operate and maintain the system and to 
otherwise implement requisite technical knowledge. Managerial capacity 
is the ability of a water system to conduct its affairs to achieve and 
maintain compliance with SDWA requirements. Managerial capacity refers 
to the system's institutional and administrative capabilities. 
Financial capacity is a water system's ability to acquire and manage 
sufficient financial resources to allow the system to achieve and 
maintain compliance with SDWA requirements. Technical, managerial, and 
financial capacity can be assessed through key issues and questions, 
including the following:

------------------------------------------------------------------------
 
------------------------------------------------------------------------
                           Technical Capacity
------------------------------------------------------------------------
Source water adequacy.............  Does the system have a reliable
                                     source of water with adequate
                                     quantity? Is the source generally
                                     of good quality and adequately
                                     protected?

[[Page 762]]

 
Infrastructure adequacy...........  Can the system provide water that
                                     meets SDWA standards? What is the
                                     condition of its infrastructure,
                                     including wells or source water
                                     intakes, treatment and storage
                                     facilities, and distribution
                                     systems? What is the
                                     infrastructure's life expectancy?
                                     Does the system have a capital
                                     improvement plan?
Technical knowledge and             Are the system's operators
 implementation.                     certified? Do the operators have
                                     sufficient knowledge of applicable
                                     standards? Can the operators
                                     effectively implement this
                                     technical knowledge? Do the
                                     operators understand the system's
                                     technical and operational
                                     characteristics? Does the system
                                     have an effective O&M program?
-----------------------------------
                           Managerial Capacity
------------------------------------------------------------------------
Ownership accountability..........  Are the owners clearly identified?
                                     Can they be held accountable for
                                     the system?
Staffing and organization.........  Are the operators and managers
                                     clearly identified? Is the system
                                     properly organized and staffed? Do
                                     personnel understand the management
                                     aspects of regulatory requirements
                                     and system operations? Do they have
                                     adequate expertise to manage water
                                     system operations (i.e., to conduct
                                     implementation, monitor for E. coli
                                     and Cryptosporidium, install
                                     treatment, and cover or disinfect
                                     reservoir discharge to meet the
                                     LT2ESWTR requirements)? Do
                                     personnel have the necessary
                                     licenses and certifications?
Effective external linkages.......  Does the system interact well with
                                     customers, regulators, and other
                                     entities? Is the system aware of
                                     available external resources, such
                                     as technical and financial
                                     assistance?
-----------------------------------
                           Financial Capacity
------------------------------------------------------------------------
Revenue sufficiency...............  Do revenues cover costs?
Creditworthiness..................  Is the system financially healthy?
                                     Does it have access to capital
                                     through public or private sources?
Fiscal management and controls....  Are adequate books and records
                                     maintained? Are appropriate
                                     budgeting, accounting, and
                                     financial planning methods used?
                                     Does the system manage its revenues
                                     effectively?
------------------------------------------------------------------------

    After determining the type and number of systems to which each 
requirement applies, EPA evaluated the capacity impact of each rule 
requirement on large and small systems affected by that particular 
requirement. EPA determined that the overall impacts on small systems' 
technical, managerial, and financial capacity will vary. Monitoring and 
familiarization with new rules will have no significant effects on 
small systems, with the exception of moderate revenue constraints on 
those systems that need to implement monitoring for Cryptosporidium. 
The largest impacts will occur as a result of attaining 2.5 log 
treatment levels, covering uncovered reservoirs, or disinfecting 
reservoir discharge. EPA assumed that large systems will have the 
technical, financial, and managerial capacity to implement LT2ESWTR 
requirements based on the scale and complexity of their operations. The 
nature of their operations generally assures that they have access to 
the technical and managerial expertise to carry out all activities 
required by the LT2ESWTR. It is also generally easier for large systems 
to fund capital improvements than small systems, since costs can be 
spread over a larger customer base, making them smaller on a per-
household basis.
    To meet challenges posed by rule requirements, it is likely that 
some small and medium systems will need to develop or enhance linkages 
with technical and financial assistance providers (including State 
extension agents). Technical and financial assistance providers can 
help systems analyze their needs as well as the trade-offs between cost 
and health protection. In addition, they may be able to assist systems 
in finding the funding necessary to install and operate new equipment. 
The Safe Drinking Water Act, as amended in 1996, established the 
Drinking Water State Revolving Fund to make funds available to drinking 
water systems to finance infrastructure improvements. EPA also works 
closely with organizations such as the National Rural Water Association 
and the American Water Works Association to develop technical and 
managerial tools, materials, and assistance to aid small systems.

N. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this rule and other 
required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A Major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is a ``major rule'' as defined by 5 U.S.C. 
804(2). This rule will be effective March 6, 2006.

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CO.

List of Subjects

40 CFR Part 9

    Reporting and recordkeeping.

40 CFR Part 141

    Environmental protection, Chemicals, Indians-lands, Incorporation 
by reference, 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: December 15, 2005.
Stephen L. Johnson,
Administrator.

0
For the reasons set forth in the preamble, title 40 chapter I of the 
Code of Federal Regulations is amended as follows:

PART 9--[AMENDED]

0
1. The authority citation for part 9 continues to read as follows:

    Authority: 7 U.S.C. 135 et seq., 136-136y; 15 U.S.C. 2001, 2003, 
2005, 2006, 2601-2671; 21 U.S.C. 331j, 346a, 348; 31 U.S.C. 9701; 33 
U.S.C. 1251 et seq., 1311, 1313d, 1314, 1318, 1321, 1326, 1330, 
1342, 1344, 1345 (d) and (e), 1361; Executive Order 11735, 38 FR 
21243, 3 CFR, 1971-1975 Comp. p. 973; 42 U.S.C. 241, 242b, 243, 246, 
300f, 300g, 300g-1, 300g-2, 300g-3, 300g-4, 300g-5, 300g-6, 300j-1, 
300j-2, 300j-3, 300j-4, 300j-9, 1857 et seq., 6901-6992k, 7401-
7671q, 7542, 9601-9657, 11023, 11048.

0
2. In Sec.  9.1 the table is amended as follows:
0
a. Under the heading ``National Primary Drinking Water Regulations 
Implementation'' by adding entries in numerical order for ``Sec.  
141.706-141.710, 141.713-141.714, 141.716-141.723''.
0
b. Under the heading ``National Primary Drinking Water Regulations 
Implementation'' by removing entries Sec.  142.15(c), 142.15(c)(6)-(7) 
and adding entries in numerical order for ``142.14(a)(9), 142.15(c)(6), 
and 142.16(n)'' as follows:


Sec.  9.1  OMB approvals under the Paperwork Reduction Act.

* * * * *

------------------------------------------------------------------------
                   40 CFR citation                      OMB control No.
------------------------------------------------------------------------
 
                              * * * * * * *
------------------------------------------------------
               National Primary Drinking Water Regulations
------------------------------------------------------------------------
 
                              * * * * * * *
141.706-141.710......................................          2040-0266
141.713-141.714......................................          2040-0266
141.716-141.723......................................          2040-0266
------------------------------------------------------
       National Primary Drinking Water Regulations Implementation
------------------------------------------------------------------------
 
                              * * * * * * *
142.14(a)(9).........................................          2040-0266
 
                              * * * * * * *
142.15(c)(6).........................................          2040-0266
 
                              * * * * * * *
142.16(n)............................................          2040-0266
 
                              * * * * * * *
------------------------------------------------------------------------


[[Page 768]]

PART 141--NATIONAL PRIMARY DRINKING WATER REGULATIONS

0
3. 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.


0
4. Section 141.2 is amended by adding, in alphabetical order, 
definitions for ``Bag filters'', ``Bank filtration'', ``Cartridge 
filters'', ``Flowing stream'', ``Lake/reservoir'', ``Membrane 
filtration'', ``Plant intake'', ``Presedimentation'', and ``Two-stage 
lime softening'', and revising the definition for ``Uncovered finished 
water storage facility'' to read as follows:


Sec.  141.2  Definitions.

* * * * *
    Bag filters are pressure-driven separation devices that remove 
particulate matter larger than 1 micrometer using an engineered porous 
filtration media. They are typically constructed of a non-rigid, fabric 
filtration media housed in a pressure vessel in which the direction of 
flow is from the inside of the bag to outside.
    Bank filtration is a water treatment process that uses a well to 
recover surface water that has naturally infiltrated into ground water 
through a river bed or bank(s). Infiltration is typically enhanced by 
the hydraulic gradient imposed by a nearby pumping water supply or 
other well(s).
* * * * *
    Cartridge filters are pressure-driven separation devices that 
remove particulate matter larger than 1 micrometer using an engineered 
porous filtration media. They are typically constructed as rigid or 
semi-rigid, self-supporting filter elements housed in pressure vessels 
in which flow is from the outside of the cartridge to the inside.
* * * * *
    Flowing stream is a course of running water flowing in a definite 
channel.
* * * * *
    Lake/reservoir refers to a natural or man made basin or hollow on 
the Earth's surface in which water collects or is stored that may or 
may not have a current or single direction of flow.
* * * * *
    Membrane filtration is a pressure or vacuum driven separation 
process in which particulate matter larger than 1 micrometer is 
rejected by an engineered barrier, primarily through a size-exclusion 
mechanism, and which has a measurable removal efficiency of a target 
organism that can be verified through the application of a direct 
integrity test. This definition includes the common membrane 
technologies of microfiltration, ultrafiltration, nanofiltration, and 
reverse osmosis.
* * * * *
    Plant intake refers to the works or structures at the head of a 
conduit through which water is diverted from a source (e.g., river or 
lake) into the treatment plant.
* * * * *
    Presedimentation is a preliminary treatment process used to remove 
gravel, sand and other particulate material from the source water 
through settling before the water enters the primary clarification and 
filtration processes in a treatment plant.
* * * * *
    Two-stage lime softening is a process in which chemical addition 
and hardness precipitation occur in each of two distinct unit 
clarification processes in series prior to filtration.
    Uncovered finished water storage facility is a tank, reservoir, or 
other facility used to store water that will undergo no further 
treatment to reduce microbial pathogens except residual disinfection 
and is directly open to the atmosphere.
* * * * *

0
5. Subpart Q of part 141 is amended by adding Sec.  141.211 to read as 
follows:


Sec.  141.211  Special notice for repeated failure to conduct 
monitoring of the source water for Cryptosporidium and for failure to 
determine bin classification or mean Cryptosporidium level.

    (a) When is the special notice for repeated failure to monitor to 
be given? The owner or operator of a community or non-community water 
system that is required to monitor source water under Sec.  141.701 
must notify persons served by the water system that monitoring has not 
been completed as specified no later than 30 days after the system has 
failed to collect any 3 months of monitoring as specified in Sec.  
141.701(c). The notice must be repeated as specified in Sec.  
141.203(b).
    (b) When is the special notice for failure to determine bin 
classification or mean Cryptosporidium level to be given? The owner or 
operator of a community or non-community water system that is required 
to determine a bin classification under Sec.  141.710, or to determine 
mean Cryptosporidium level under Sec.  141.712, must notify persons 
served by the water system that the determination has not been made as 
required no later than 30 days after the system has failed report the 
determination as specified in Sec.  141.710(e) or Sec.  141.712(a), 
respectively. The notice must be repeated as specified in Sec.  
141.203(b). The notice is not required if the system is complying with 
a State-approved schedule to address the violation.
    (c) What is the form and manner of the special notice? The form and 
manner of the public notice must follow the requirements for a Tier 2 
public notice prescribed in Sec.  141.203(c). The public notice must be 
presented as required in Sec.  141.205(c).
    (d) What mandatory language must be contained in the special 
notice? The notice must contain the following language, including the 
language necessary to fill in the blanks.
    (1) The special notice for repeated failure to conduct monitoring 
must contain the following language:

    We are required to monitor the source of your drinking water for 
Cryptosporidium. Results of the monitoring are to be used to 
determine whether water treatment at the (treatment plant name) is 
sufficient to adequately remove Cryptosporidium from your drinking 
water. We are required to complete this monitoring and make this 
determination by (required bin determination date). We ``did not 
monitor or test'' or ``did not complete all monitoring or testing'' 
on schedule and, therefore, we may not be able to determine by the 
required date what treatment modifications, if any, must be made to 
ensure adequate Cryptosporidium removal. Missing this deadline may, 
in turn, jeopardize our ability to have the required treatment 
modifications, if any, completed by the deadline required, (date).
    For more information, please call (name of water system contact) 
of (name of water system) at (phone number).

    (2) The special notice for failure to determine bin classification 
or mean Cryptosporidium level must contain the following language:

    We are required to monitor the source of your drinking water for 
Cryptosporidium in order to determine by (date) whether water 
treatment at the (treatment plant name) is sufficient to adequately 
remove Cryptosporidium from your drinking water. We have not made 
this determination by the required date. Our failure to do this may 
jeopardize our ability to have the required treatment modifications, 
if any, completed by the required deadline of (date). For more 
information, please call (name of water system contact) of (name of 
water system) at (phone number).

    (3) Each special notice must also include a description of what the 
system is doing to correct the violation and when the system expects to 
return to compliance or resolve the situation.

0
6. Appendix A to Subpart Q of part 141 is amended by adding entry 
number 10 under I.A. to read as follows:

Subpart Q--Public Notification of Drinking Water Violations

[[Page 769]]



     Appendix A to Subpart Q of Part 141--NPDWR Violations and Other Situations Requiring Public Notice \1\
----------------------------------------------------------------------------------------------------------------
                                           MCL/MRDL/TT violations \2\         Monitoring & testing procedure
                                        --------------------------------                violations
                                                                        ----------------------------------------
              Contaminant                  Tier of                         Tier of
                                            public         Citation         public
                                            notice                          notice             Citation
                                           required                        required
----------------------------------------------------------------------------------------------------------------
I. Violations of National Primary
 Drinking Water Regulations (NPDWR):
 \3\
    A. Microbiological Contaminants
 
                                                  * * * * * * *
    10. LT2ESWTR violations............            2    141.710-141.720    \22\ 2, 3  141.701-141.705 and
                                                                                       141.708-141.709.
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
\1\ Violations and other situations not listed in this table (e.g., failure to prepare Consumer Confidence
  Reports) do not require notice, unless otherwise determined by the primary agency. Primacy agencies may, at
  their option, also require a more stringent public notice tier (e.g., Tier 1 instead of Tier 2 or Tier 2
  instead of Tier 3) for specific violations and situations listed in this Appendix, as authorized under Sec.
  141.202(a) and Sec.   141.203(a).
\2\ MCL--Maximum contaminant level, MRDL--Maximum residual disinfectant level, TT--Treatment technique.
\3\ The term Violations of National Primary Drinking Water Regulations (NPDWR) is used here to include
  violations of MCL, MRDL, treatment technique, monitoring, and testing procedure requirements.
* * * * * * *
\22\ Failure to collect three or more samples for Cryptosporidium analysis is a Tier 2 violation requiring
  special notice as specified in Sec.   141.211. All other monitoring and testing procedure violations are Tier
  3.


0
7. Part 141 is amended by adding a new subpart W to read as follows:

Subpart W--Enhanced Treatment for Cryptosporidium

General Requirements

Sec.
141.700 General requirements.

Source Water Monitoring Requirements

141.701 Source water monitoring.
141.702 Sampling schedules.
141.703 Sampling locations.
141.704 Analytical methods.
141.705 Approved laboratories.
141.706 Reporting source water monitoring results.
141.707 Grandfathering previously collected data.

Disinfection Profiling and Benchmarking Requirements

141.708 Requirements when making a significant change in 
disinfection practice.
141.709 Developing the disinfection profile and benchmark.

Treatment Technique Requirements

141.710 Bin classification for filtered systems.
141.711 Filtered system additional Cryptosporidium treatment 
requirements.
141.712 Unfiltered system Cryptosporidium treatment requirements.
141.713 Schedule for compliance with Cryptosporidium treatment 
requirements.
141.714 Requirements for uncovered finished water storage 
facilities.

Requirements for Microbial Toolbox Components

141.715 Microbial toolbox options for meeting Cryptosporidium 
treatment requirements.
141.716 Source toolbox components.
141.717 Pre-filtration treatment toolbox components.
141.718 Treatment performance toolbox components.
141.719 Additional filtration toolbox components.
141.720 Inactivation toolbox components.

Reporting and Recordkeeping Requirements

141.721 Reporting requirements.
141.722 Recordkeeping requirements.

Requirements for Sanitary Surveys Performed by EPA

141.723 Requirements to respond to significant deficiencies 
identified in sanitary surveys performed by EPA.

Subpart W--Enhanced Treatment for Cryptosporidium

General Requirements


Sec.  141.700  General requirements.

    (a) The requirements of this subpart W are national primary 
drinking water regulations. The regulations in this subpart establish 
or extend treatment technique requirements in lieu of maximum 
contaminant levels for Cryptosporidium. These requirements are in 
addition to requirements for filtration and disinfection in subparts H, 
P, and T of this part.
    (b) Applicability. The requirements of this subpart apply to all 
subpart H systems, which are public water systems supplied by a surface 
water source and public water systems supplied by a ground water source 
under the direct influence of surface water.
    (1) Wholesale systems, as defined in Sec.  141.2, must comply with 
the requirements of this subpart based on the population of the largest 
system in the combined distribution system.
    (2) The requirements of this subpart for filtered systems apply to 
systems required by National Primary Drinking Water Regulations to 
provide filtration treatment, whether or not the system is currently 
operating a filtration system.
    (3) The requirements of this subpart for unfiltered systems apply 
only to unfiltered systems that timely met and continue to meet the 
filtration avoidance criteria in subparts H, P, and T of this part, as 
applicable.
    (c) Requirements. Systems subject to this subpart must comply with 
the following requirements:
    (1) Systems must conduct an initial and a second round of source 
water monitoring for each plant that treats a surface water or GWUDI 
source. This monitoring may include sampling for Cryptosporidium, E. 
coli, and turbidity as described in Sec. Sec.  141.701 through 141.706, 
to determine what level, if any, of additional Cryptosporidium 
treatment they must provide.
    (2) Systems that plan to make a significant change to their 
disinfection practice must develop disinfection profiles and calculate 
disinfection benchmarks, as described in Sec. Sec.  141.708 through 
141.709.
    (3) Filtered systems must determine their Cryptosporidium treatment 
bin classification as described in Sec.  141.710 and provide additional 
treatment for Cryptosporidium, if required, as described in Sec.  
141.711. All unfiltered systems must provide treatment for 
Cryptosporidium as described in Sec.  141.712. Filtered and unfiltered 
systems must implement Cryptosporidium treatment according to the 
schedule in Sec.  141.713.

[[Page 770]]

    (4) Systems with uncovered finished water storage facilities must 
comply with the requirements to cover the facility or treat the 
discharge from the facility as described in Sec.  141.714.
    (5) Systems required to provide additional treatment for 
Cryptosporidium must implement microbial toolbox options that are 
designed and operated as described in Sec. Sec.  141.715 through 
141.720.
    (6) Systems must comply with the applicable recordkeeping and 
reporting requirements described in Sec. Sec.  141.721 through 141.722.
    (7) Systems must address significant deficiencies identified in 
sanitary surveys performed by EPA as described in Sec.  141.723.

Source Water Monitoring Requirements


Sec.  141.701  Source water monitoring.

    (a) Initial round of source water monitoring. Systems must conduct 
the following monitoring on the schedule in paragraph (c) of this 
section unless they meet the monitoring exemption criteria in paragraph 
(d) of this section.
    (1) Filtered systems serving at least 10,000 people must sample 
their source water for Cryptosporidium, E. coli, and turbidity at least 
monthly for 24 months.
    (2) Unfiltered systems serving at least 10,000 people must sample 
their source water for Cryptosporidium at least monthly for 24 months.
    (3)(i) Filtered systems serving fewer than 10,000 people must 
sample their source water for E. coli at least once every two weeks for 
12 months.
    (ii) A filtered system serving fewer than 10,000 people may avoid 
E. coli monitoring if the system notifies the State that it will 
monitor for Cryptosporidium as described in paragraph (a)(4) of this 
section. The system must notify the State no later than 3 months prior 
to the date the system is otherwise required to start E. coli 
monitoring under Sec.  141.701(c).
    (4) Filtered systems serving fewer than 10,000 people must sample 
their source water for Cryptosporidium at least twice per month for 12 
months or at least monthly for 24 months if they meet one of the 
following, based on monitoring conducted under paragraph (a)(3) of this 
section:
    (i) For systems using lake/reservoir sources, the annual mean E. 
coli concentration is greater than 10 E. coli/100 mL.
    (ii) For systems using flowing stream sources, the annual mean E. 
coli concentration is greater than 50 E. coli/100 mL.
    (iii) The system does not conduct E. coli monitoring as described 
in paragraph (a)(3) of this section.
    (iv) Systems using ground water under the direct influence of 
surface water (GWUDI) must comply with the requirements of paragraph 
(a)(4) of this section based on the E. coli level that applies to the 
nearest surface water body. If no surface water body is nearby, the 
system must comply based on the requirements that apply to systems 
using lake/reservoir sources.
    (5) For filtered systems serving fewer than 10,000 people, the 
State may approve monitoring for an indicator other than E. coli under 
paragraph (a)(3) of this section. The State also may approve an 
alternative to the E. coli concentration in paragraph (a)(4)(i), (ii) 
or (iv) of this section to trigger Cryptosporidium monitoring. This 
approval by the State must be provided to the system in writing and 
must include the basis for the State's determination that the 
alternative indicator and/or trigger level will provide a more accurate 
identification of whether a system will exceed the Bin 1 
Cryptosporidium level in Sec.  141.710.
    (6) Unfiltered systems serving fewer than 10,000 people must sample 
their source water for Cryptosporidium at least twice per month for 12 
months or at least monthly for 24 months.
    (7) Systems may sample more frequently than required under this 
section if the sampling frequency is evenly spaced throughout the 
monitoring period.
    (b) Second round of source water monitoring. Systems must conduct a 
second round of source water monitoring that meets the requirements for 
monitoring parameters, frequency, and duration described in paragraph 
(a) of this section, unless they meet the monitoring exemption criteria 
in paragraph (d) of this section. Systems must conduct this monitoring 
on the schedule in paragraph (c) of this section.
    (c) Monitoring schedule. Systems must begin the monitoring required 
in paragraphs (a) and (b) of this section no later than the month 
beginning with the date listed in this table:

              Source Water Monitoring Starting Dates Table
------------------------------------------------------------------------
                                                     And must begin the
                              Must begin the first     second round of
                                 round of source        source water
  Systems that serve . . .     water monitoring no   monitoring no later
                              later than the month     than the month
                                 beginning . . .       beginning . . .
------------------------------------------------------------------------
(1) At least 100,000 people.  (i) October 1, 2006.  (ii) April 1, 2015.
(2) From 50,000 to 99,999     (i) April 1, 2007...  (ii) October 1,
 people.                                             2015.
(3) From 10,000 to 49,999     (i) April 1, 2008...  (ii) October 1,
 people.                                             2016.
(4) Fewer than 10,000 and     (i) October 1, 2008.  (ii) October 1,
 monitor for E. coli \a\.                            2017.
(5) Fewer than 10,000 and     (i) April 1, 2010...  (ii) April 1, 2019.
 monitor for Cryptosporidium
 \b\.
------------------------------------------------------------------------
\a\ Applies only to filtered systems.
\b\ Applies to filtered systems that meet the conditions of paragraph
  (a)(4) of this section and unfiltered systems.

    (d) Monitoring avoidance. (1) Filtered systems are not required to 
conduct source water monitoring under this subpart if the system will 
provide a total of at least 5.5-log of treatment for Cryptosporidium, 
equivalent to meeting the treatment requirements of Bin 4 in Sec.  
141.711.
    (2) Unfiltered systems are not required to conduct source water 
monitoring under this subpart if the system will provide a total of at 
least 3-log Cryptosporidium inactivation, equivalent to meeting the 
treatment requirements for unfiltered systems with a mean 
Cryptosporidium concentration of greater than 0.01 oocysts/L in Sec.  
141.712.
    (3) If a system chooses to provide the level of treatment in 
paragraph (d)(1) or (2) of this section, as applicable, rather than 
start source water monitoring, the system must notify the State in 
writing no later than the date the system is otherwise required to 
submit a sampling schedule for monitoring under Sec.  141.702. 
Alternatively, a system may choose to stop sampling at any point after 
it has initiated monitoring if it notifies the State in writing that it 
will provide this level of treatment. Systems must install and operate 
technologies to provide this level of treatment by the

[[Page 771]]

applicable treatment compliance date in Sec.  141.713.
    (e) Plants operating only part of the year. Systems with subpart H 
plants that operate for only part of the year must conduct source water 
monitoring in accordance with this subpart, but with the following 
modifications:
    (1) Systems must sample their source water only during the months 
that the plant operates unless the State specifies another monitoring 
period based on plant operating practices.
    (2) Systems with plants that operate less than six months per year 
and that monitor for Cryptosporidium must collect at least six 
Cryptosporidium samples per year during each of two years of 
monitoring. Samples must be evenly spaced throughout the period the 
plant operates.
    (f)(1) New sources. A system that begins using a new source of 
surface water or GWUDI after the system is required to begin monitoring 
under paragraph (c) of this section must monitor the new source on a 
schedule the State approves. Source water monitoring must meet the 
requirements of this subpart. The system must also meet the bin 
classification and Cryptosporidium treatment requirements of Sec. Sec.  
141.710 and 141.711 or Sec.  141.712, as applicable, for the new source 
on a schedule the State approves.
    (2) The requirements of Sec.  141.701(f) apply to subpart H systems 
that begin operation after the monitoring start date applicable to the 
system's size under paragraph (c) of this section.
    (3) The system must begin a second round of source water monitoring 
no later than 6 years following initial bin classification under Sec.  
141.710 or determination of the mean Cryptosporidium level under Sec.  
141.712, as applicable.
    (g) Failure to collect any source water sample required under this 
section in accordance with the sampling schedule, sampling location, 
analytical method, approved laboratory, and reporting requirements of 
Sec. Sec.  141.702 through 141.706 is a monitoring violation.
    (h) Grandfathering monitoring data. Systems may use (grandfather) 
monitoring data collected prior to the applicable monitoring start date 
in paragraph (c) of this section to meet the initial source water 
monitoring requirements in paragraph (a) of this section. Grandfathered 
data may substitute for an equivalent number of months at the end of 
the monitoring period. All data submitted under this paragraph must 
meet the requirements in Sec.  141.707.


Sec.  141.702  Sampling schedules.

    (a) Systems required to conduct source water monitoring under Sec.  
141.701 must submit a sampling schedule that specifies the calendar 
dates when the system will collect each required sample.
    (1) Systems must submit sampling schedules no later than 3 months 
prior to the applicable date listed in Sec.  141.701(c) for each round 
of required monitoring.
    (2)(i) Systems serving at least 10,000 people must submit their 
sampling schedule for the initial round of source water monitoring 
under Sec.  141.701(a) to EPA electronically at https://intranet.epa.gov/lt2/.
    (ii) If a system is unable to submit the sampling schedule 
electronically, the system may use an alternative approach for 
submitting the sampling schedule that EPA approves.
    (3) Systems serving fewer than 10,000 people must submit their 
sampling schedules for the initial round of source water monitoring 
Sec.  141.701(a) to the State.
    (4) Systems must submit sampling schedules for the second round of 
source water monitoring Sec.  141.701(b) to the State.
    (5) If EPA or the State does not respond to a system regarding its 
sampling schedule, the system must sample at the reported schedule.
    (b) Systems must collect samples within two days before or two days 
after the dates indicated in their sampling schedule (i.e., within a 
five-day period around the schedule date) unless one of the conditions 
of paragraph (b)(1) or (2) of this section applies.
    (1) If an extreme condition or situation exists that may pose 
danger to the sample collector, or that cannot be avoided and causes 
the system to be unable to sample in the scheduled five-day period, the 
system must sample as close to the scheduled date as is feasible unless 
the State approves an alternative sampling date. The system must submit 
an explanation for the delayed sampling date to the State concurrent 
with the shipment of the sample to the laboratory.
    (2)(i) If a system is unable to report a valid analytical result 
for a scheduled sampling date due to equipment failure, loss of or 
damage to the sample, failure to comply with the analytical method 
requirements, including the quality control requirements in Sec.  
141.704, or the failure of an approved laboratory to analyze the 
sample, then the system must collect a replacement sample.
    (ii) The system must collect the replacement sample not later than 
21 days after receiving information that an analytical result cannot be 
reported for the scheduled date unless the system demonstrates that 
collecting a replacement sample within this time frame is not feasible 
or the State approves an alternative resampling date. The system must 
submit an explanation for the delayed sampling date to the State 
concurrent with the shipment of the sample to the laboratory.
    (c) Systems that fail to meet the criteria of paragraph (b) of this 
section for any source water sample required under Sec.  141.701 must 
revise their sampling schedules to add dates for collecting all missed 
samples. Systems must submit the revised schedule to the State for 
approval prior to when the system begins collecting the missed samples.


Sec.  141.703  Sampling locations.

    (a) Systems required to conduct source water monitoring under Sec.  
141.701 must collect samples for each plant that treats a surface water 
or GWUDI source. Where multiple plants draw water from the same 
influent, such as the same pipe or intake, the State may approve one 
set of monitoring results to be used to satisfy the requirements of 
Sec.  141.701 for all plants.
    (b)(1) Systems must collect source water samples prior to chemical 
treatment, such as coagulants, oxidants and disinfectants, unless the 
system meets the condition of paragraph (b)(2) of this section.
    (2) The State may approve a system to collect a source water sample 
after chemical treatment. To grant this approval, the State must 
determine that collecting a sample prior to chemical treatment is not 
feasible for the system and that the chemical treatment is unlikely to 
have a significant adverse effect on the analysis of the sample.
    (c) Systems that recycle filter backwash water must collect source 
water samples prior to the point of filter backwash water addition.
    (d) Bank filtration. (1) Systems that receive Cryptosporidium 
treatment credit for bank filtration under Sec.  141.173(b) or Sec.  
141.552(a), as applicable, must collect source water samples in the 
surface water prior to bank filtration.
    (2) Systems that use bank filtration as pretreatment to a 
filtration plant must collect source water samples from the well (i.e., 
after bank filtration). Use of bank filtration during monitoring must 
be consistent with routine operational practice. Systems collecting 
samples after a bank filtration process may not receive treatment 
credit for the bank filtration under Sec.  141.717(c).

[[Page 772]]

    (e) Multiple sources. Systems with plants that use multiple water 
sources, including multiple surface water sources and blended surface 
water and ground water sources, must collect samples as specified in 
paragraph (e)(1) or (2) of this section. The use of multiple sources 
during monitoring must be consistent with routine operational practice.
    (1) If a sampling tap is available where the sources are combined 
prior to treatment, systems must collect samples from the tap.
    (2) If a sampling tap where the sources are combined prior to 
treatment is not available, systems must collect samples at each source 
near the intake on the same day and must follow either paragraph 
(e)(2)(i) or (ii) of this section for sample analysis.
    (i) Systems may composite samples from each source into one sample 
prior to analysis. The volume of sample from each source must be 
weighted according to the proportion of the source in the total plant 
flow at the time the sample is collected.
    (ii) Systems may analyze samples from each source separately and 
calculate a weighted average of the analysis results for each sampling 
date. The weighted average must be calculated by multiplying the 
analysis result for each source by the fraction the source contributed 
to total plant flow at the time the sample was collected and then 
summing these values.
    (f) Additional Requirements. Systems must submit a description of 
their sampling location(s) to the State at the same time as the 
sampling schedule required under Sec.  141.702. This description must 
address the position of the sampling location in relation to the 
system's water source(s) and treatment processes, including 
pretreatment, points of chemical treatment, and filter backwash 
recycle. If the State does not respond to a system regarding sampling 
location(s), the system must sample at the reported location(s).


Sec.  141.704  Analytical methods.

    (a) Cryptosporidium. Systems must analyze for Cryptosporidium using 
Method 1623: Cryptosporidium and Giardia in Water by Filtration/IMS/FA, 
2005, United States Environmental Protection Agency, EPA-815-R-05-002 
or Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 2005, 
United States Environmental Protection Agency, EPA-815-R-05-001, which 
are incorporated by reference. The Director of the Federal Register 
approves this incorporation by reference in accordance with 5 U.S.C. 
552(a) and 1 CFR part 51. You may obtain a copy of these methods online 
from http://www.epa.gov/safewater/disinfection/lt2 or from the United 
States Environmental Protection Agency, Office of Ground Water and 
Drinking Water, 1201 Constitution Ave., NW, Washington, DC 20460 
(Telephone: 800-426-4791). You may inspect a copy at the Water Docket 
in the EPA Docket Center, 1301 Constitution Ave., NW, Washington, DC, 
(Telephone: 202-566-2426) or at the National Archives and Records 
Administration (NARA). For information on the availability of this 
material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_-register/code--of--federal--regulations/ibr--locations.html.
    (1) Systems must analyze at least a 10 L sample or a packed pellet 
volume of at least 2 mL as generated by the methods listed in paragraph 
(a) of this section. Systems unable to process a 10 L sample must 
analyze as much sample volume as can be filtered by two filters 
approved by EPA for the methods listed in paragraph (a) of this 
section, up to a packed pellet volume of at least 2 mL.
    (2)(i) Matrix spike (MS) samples, as required by the methods in 
paragraph (a) of this section, must be spiked and filtered by a 
laboratory approved for Cryptosporidium analysis under Sec.  141.705.
    (ii) If the volume of the MS sample is greater than 10 L, the 
system may filter all but 10 L of the MS sample in the field, and ship 
the filtered sample and the remaining 10 L of source water to the 
laboratory. In this case, the laboratory must spike the remaining 10 L 
of water and filter it through the filter used to collect the balance 
of the sample in the field.
    (3) Flow cytometer-counted spiking suspensions must be used for MS 
samples and ongoing precision and recovery (OPR) samples.
    (b) E. coli. Systems must use methods for enumeration of E. coli in 
source water approved in Sec.  136.3(a) of this title.
    (1) The time from sample collection to initiation of analysis may 
not exceed 30 hours unless the system meets the condition of paragraph 
(b)(2) of this section.
    (2) The State may approve on a case-by-case basis the holding of an 
E. coli sample for up to 48 hours between sample collection and 
initiation of analysis if the State determines that analyzing an E. 
coli sample within 30 hours is not feasible. E. coli samples held 
between 30 to 48 hours must be analyzed by the Colilert reagent version 
of Standard Method 9223B as listed in Sec.  136.3(a) of this title.
    (3) Systems must maintain samples between 0[deg]C and 10[deg]C 
during storage and transit to the laboratory.
    (c) Turbidity. Systems must use methods for turbidity measurement 
approved in Sec.  141.74(a)(1).


Sec.  141.705  Approved laboratories.

    (a) Cryptosporidium. Systems must have Cryptosporidium samples 
analyzed by a laboratory that is approved under EPA's Laboratory 
Quality Assurance Evaluation Program for Analysis of Cryptosporidium in 
Water or a laboratory that has been certified for Cryptosporidium 
analysis by an equivalent State laboratory certification program.
    (b) E. coli. Any laboratory certified by the EPA, the National 
Environmental Laboratory Accreditation Conference or the State for 
total coliform or fecal coliform analysis under Sec. 141.74 is approved 
for E. coli analysis under this subpart when the laboratory uses the 
same technique for E. coli that the laboratory uses for Sec.  141.74.
    (c) Turbidity. Measurements of turbidity must be made by a party 
approved by the State.


Sec. 141.706  Reporting source water monitoring results.

    (a) Systems must report results from the source water monitoring 
required under Sec. 141.701 no later than 10 days after the end of the 
first month following the month when the sample is collected.
    (b)(1) All systems serving at least 10,000 people must report the 
results from the initial source water monitoring required under Sec.  
141.701(a) to EPA electronically at https://intranet.epa.gov/lt2/.
    (2) If a system is unable to report monitoring results 
electronically, the system may use an alternative approach for 
reporting monitoring results that EPA approves.
    (c) Systems serving fewer than 10,000 people must report results 
from the initial source water monitoring required under Sec.  
141.701(a) to the State.
    (d) All systems must report results from the second round of source 
water monitoring required under Sec.  141.701(b) to the State.
    (e) Systems must report the applicable information in paragraphs 
(e)(1) and (2) of this section for the source water monitoring required 
under Sec.  141.701.
    (1) Systems must report the following data elements for each 
Cryptosporidium analysis:

 
                              Data element.
 
1. PWS ID.
2. Facility ID.

[[Page 773]]

 
3. Sample collection date.
4. Sample type (field or matrix spike).
5. Sample volume filtered (L), to nearest \1/4\ L.
6. Was 100% of filtered volume examined.
7. Number of oocysts counted.
 

    (i) For matrix spike samples, systems must also report the sample 
volume spiked and estimated number of oocysts spiked. These data are 
not required for field samples.
    (ii) For samples in which less than 10 L is filtered or less than 
100% of the sample volume is examined, systems must also report the 
number of filters used and the packed pellet volume.
    (iii) For samples in which less than 100% of sample volume is 
examined, systems must also report the volume of resuspended 
concentrate and volume of this resuspension processed through 
immunomagnetic separation.
    (2) Systems must report the following data elements for each E. 
coli analysis:

 
 
 
Data element.
 
1. PWS ID.
2. Facility ID.
3. Sample collection date.
4. Analytical method number.
5. Method type.
6. Source type (flowing stream, lake/reservoir, GWUDI).
7. E. coli/100 mL.
8. Turbidity.\1\
 
\1\ Systems serving fewer than 10,000 people that are not required to
  monitor for turbidity under Sec.   141.701 are not required to report
  turbidity with their E. coli results.

Sec.  141.707  Grandfathering previously collected data.

    (a)(1) Systems may comply with the initial source water monitoring 
requirements of Sec.  141.701(a) by grandfathering sample results 
collected before the system is required to begin monitoring (i.e., 
previously collected data). To be grandfathered, the sample results and 
analysis must meet the criteria in this section and the State must 
approve.
    (2) A filtered system may grandfather Cryptosporidium samples to 
meet the requirements of Sec.  141.701(a) when the system does not have 
corresponding E. coli and turbidity samples. A system that grandfathers 
Cryptosporidium samples without E. coli and turbidity samples is not 
required to collect E. coli and turbidity samples when the system 
completes the requirements for Cryptosporidium monitoring under Sec.  
141.701(a).
    (b) E. coli sample analysis. The analysis of E. coli samples must 
meet the analytical method and approved laboratory requirements of 
Sec. Sec.  141.704 through 141.705.
    (c) Cryptosporidium sample analysis. The analysis of 
Cryptosporidium samples must meet the criteria in this paragraph.
    (1) Laboratories analyzed Cryptosporidium samples using one of the 
analytical methods in paragraphs (c)(1)(i) through (vi) of this 
section, which are incorporated by reference. The Director of the 
Federal Register approves this incorporation by reference in accordance 
with 5 U.S.C. 552(a) and 1 CFR part 51. You may obtain a copy of these 
methods on-line from the United States Environmental Protection Agency, 
Office of Ground Water and Drinking Water, 1201 Constitution Ave, NW, 
Washington, DC 20460 (Telephone: 800-426-4791). You may inspect a copy 
at the Water Docket in the EPA Docket Center, 1301 Constitution Ave., 
NW, Washington, DC, (Telephone: 202-566-2426) or at the National 
Archives and Records Administration (NARA). For information on the 
availability of this material at NARA, call 202-741-6030, or go to: 
http://www.archives.gov/federal_ register/code--of--federal-- 
regulations/ibr--locations.html.
    (i) Method 1623: Cryptosporidium and Giardia in Water by 
Filtration/IMS/FA, 2005, United States Environmental Protection Agency, 
EPA-815-R-05-002.
    (ii) Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 
2005, United States Environmental Protection Agency, EPA-815-R-05-001.
    (iii) Method 1623: Cryptosporidium and Giardia in Water by 
Filtration/IMS/FA, 2001, United States Environmental Protection Agency, 
EPA-821-R-01-025.
    (iv) Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 
2001, United States Environmental Protection Agency, EPA-821--R-01-026.
    (v) Method 1623: Cryptosporidium and Giardia in Water by 
Filtration/IMS/FA, 1999, United States Environmental Protection Agency, 
EPA-821-R-99-006.
    (vi) Method 1622: Cryptosporidium in Water by Filtration/IMS/FA, 
1999, United States Environmental Protection Agency, EPA-821-R-99-001.
    (2) For each Cryptosporidium sample, the laboratory analyzed at 
least 10 L of sample or at least 2 mL of packed pellet or as much 
volume as could be filtered by 2 filters that EPA approved for the 
methods listed in paragraph (c)(1) of this section.
    (d) Sampling location. The sampling location must meet the 
conditions in Sec.  141.703.
    (e) Sampling frequency. Cryptosporidium samples were collected no 
less frequently than each calendar month on a regular schedule, 
beginning no earlier than January 1999. Sample collection intervals may 
vary for the conditions specified in Sec.  141.702(b)(1) and (2) if the 
system provides documentation of the condition when reporting 
monitoring results.
    (1) The State may approve grandfathering of previously collected 
data where there are time gaps in the sampling frequency if the system 
conducts additional monitoring the State specifies to ensure that the 
data used to comply with the initial source water monitoring 
requirements of Sec.  141.701(a) are seasonally representative and 
unbiased.
    (2) Systems may grandfather previously collected data where the 
sampling frequency within each month varied. If the Cryptosporidium 
sampling frequency varied, systems must follow the monthly averaging 
procedure in Sec.  141.710(b)(5) or Sec.  141.712(a)(3), as applicable, 
when calculating the bin classification for filtered systems or the 
mean Cryptosporidium concentration for unfiltered systems.
    (f) Reporting monitoring results for grandfathering. Systems that 
request to grandfather previously collected monitoring results must 
report the following information by the applicable dates listed in this 
paragraph. Systems serving at least 10,000 people must report this 
information to EPA unless the State approves reporting to the State 
rather than EPA. Systems serving fewer than 10,000 people must report 
this information to the State.
    (1) Systems must report that they intend to submit previously 
collected monitoring results for grandfathering. This report must 
specify the number of previously collected results the system will 
submit, the dates of the first and last sample, and whether a system 
will conduct additional source water monitoring to meet the 
requirements of Sec.  141.701(a). Systems must report this information 
no later than the date the sampling schedule under Sec.  141.702 is 
required.
    (2) Systems must report previously collected monitoring results for 
grandfathering, along with the associated documentation listed in 
paragraphs (f)(2)(i) through (iv) of this section, no later than two 
months after the applicable date listed in Sec.  141.701(c).
    (i) For each sample result, systems must report the applicable data 
elements in Sec.  141.706.
    (ii) Systems must certify that the reported monitoring results 
include all results the system generated during the time period 
beginning with the first reported result and ending with the final 
reported result. This applies to samples that were collected from the

[[Page 774]]

sampling location specified for source water monitoring under this 
subpart, not spiked, and analyzed using the laboratory's routine 
process for the analytical methods listed in this section.
    (iii) Systems must certify that the samples were representative of 
a plant's source water(s) and the source water(s) have not changed. 
Systems must report a description of the sampling location(s), which 
must address the position of the sampling location in relation to the 
system's water source(s) and treatment processes, including points of 
chemical addition and filter backwash recycle.
    (iv) For Cryptosporidium samples, the laboratory or laboratories 
that analyzed the samples must provide a letter certifying that the 
quality control criteria specified in the methods listed in paragraph 
(c)(1) of this section were met for each sample batch associated with 
the reported results. Alternatively, the laboratory may provide bench 
sheets and sample examination report forms for each field, matrix 
spike, IPR, OPR, and method blank sample associated with the reported 
results.
    (g) If the State determines that a previously collected data set 
submitted for grandfathering was generated during source water 
conditions that were not normal for the system, such as a drought, the 
State may disapprove the data. Alternatively, the State may approve the 
previously collected data if the system reports additional source water 
monitoring data, as determined by the State, to ensure that the data 
set used under Sec.  141.710 or Sec.  141.712 represents average source 
water conditions for the system.
    (h) If a system submits previously collected data that fully meet 
the number of samples required for initial source water monitoring 
under Sec.  141.701(a) and some of the data are rejected due to not 
meeting the requirements of this section, systems must conduct 
additional monitoring to replace rejected data on a schedule the State 
approves. Systems are not required to begin this additional monitoring 
until two months after notification that data have been rejected and 
additional monitoring is necessary.

Disinfection Profiling and Benchmarking Requirements


Sec.  141.708  Requirements when making a significant change in 
disinfection practice.

    (a) Following the completion of initial source water monitoring 
under Sec.  141.701(a), a system that plans to make a significant 
change to its disinfection practice, as defined in paragraph (b) of 
this section, must develop disinfection profiles and calculate 
disinfection benchmarks for Giardia lamblia and viruses as described in 
Sec.  141.709. Prior to changing the disinfection practice, the system 
must notify the State and must include in this notice the information 
in paragraphs (a)(1) through (3) of this section.
    (1) A completed disinfection profile and disinfection benchmark for 
Giardia lamblia and viruses as described in Sec.  141.709.
    (2) A description of the proposed change in disinfection practice.
    (3) An analysis of how the proposed change will affect the current 
level of disinfection.
    (b) Significant changes to disinfection practice are defined as 
follows:
    (1) Changes to the point of disinfection;
    (2) Changes to the disinfectant(s) used in the treatment plant;
    (3) Changes to the disinfection process; or
    (4) Any other modification identified by the State as a significant 
change to disinfection practice.


Sec.  141.709  Developing the disinfection profile and benchmark.

    (a) Systems required to develop disinfection profiles under Sec.  
141.708 must follow the requirements of this section. Systems must 
monitor at least weekly for a period of 12 consecutive months to 
determine the total log inactivation for Giardia lamblia and viruses. 
If systems monitor more frequently, the monitoring frequency must be 
evenly spaced. Systems that operate for fewer than 12 months per year 
must monitor weekly during the period of operation. Systems must 
determine log inactivation for Giardia lamblia through the entire 
plant, based on CT99.9 values in Tables 1.1 through 1.6, 2.1 
and 3.1 of Sec.  141.74(b) as applicable. Systems must determine log 
inactivation for viruses through the entire treatment plant based on a 
protocol approved by the State.
    (b) Systems with a single point of disinfectant application prior 
to the entrance to the distribution system must conduct the monitoring 
in paragraphs (b)(1) through (4) of this section. Systems with more 
than one point of disinfectant application must conduct the monitoring 
in paragraphs (b)(1) through (4) of this section for each disinfection 
segment. Systems must monitor the parameters necessary to determine the 
total inactivation ratio, using analytical methods in Sec.  141.74(a).
    (1) For systems using a disinfectant other than UV, the temperature 
of the disinfected water must be measured at each residual disinfectant 
concentration sampling point during peak hourly flow or at an 
alternative location approved by the State.
    (2) For systems using chlorine, the pH of the disinfected water 
must be measured at each chlorine residual disinfectant concentration 
sampling point during peak hourly flow or at an alternative location 
approved by the State.
    (3) The disinfectant contact time(s) (t) must be determined during 
peak hourly flow.
    (4) The residual disinfectant concentration(s) (C) of the water 
before or at the first customer and prior to each additional point of 
disinfectant application must be measured during peak hourly flow.
    (c) In lieu of conducting new monitoring under paragraph (b) of 
this section, systems may elect to meet the requirements of paragraphs 
(c)(1) or (2) of this section.
    (1) Systems that have at least one year of existing data that are 
substantially equivalent to data collected under the provisions of 
paragraph (b) of this section may use these data to develop 
disinfection profiles as specified in this section if the system has 
neither made a significant change to its treatment practice nor changed 
sources since the data were collected. Systems may develop disinfection 
profiles using up to three years of existing data.
    (2) Systems may use disinfection profile(s) developed under Sec.  
141.172 or Sec. Sec.  141.530 through 141.536 in lieu of developing a 
new profile if the system has neither made a significant change to its 
treatment practice nor changed sources since the profile was developed. 
Systems that have not developed a virus profile under Sec.  141.172 or 
Sec. Sec.  141.530 through 141.536 must develop a virus profile using 
the same monitoring data on which the Giardia lamblia profile is based.
    (d) Systems must calculate the total inactivation ratio for Giardia 
lamblia as specified in paragraphs (d)(1) through (3) of this section.
    (1) Systems using only one point of disinfectant application may 
determine the total inactivation ratio for the disinfection segment 
based on either of the methods in paragraph (d)(1)(i) or (ii) of this 
section.
    (i) Determine one inactivation ratio (CTcalc/CT99.9) 
before or at the first customer during peak hourly flow.
    (ii) Determine successive CTcalc/CT99.9 values, 
representing sequential inactivation ratios, between the point of 
disinfectant application and a point before or at the first customer 
during peak hourly flow. The system must

[[Page 775]]

calculate the total inactivation ratio by determining (CTcalc/
CT99.9) for each sequence and then adding the (CTcalc/
CT99.9) values together to determine ([Sigma] (CTcalc/
CT99.9)).
    (2) Systems using more than one point of disinfectant application 
before the first customer must determine the CT value of each 
disinfection segment immediately prior to the next point of 
disinfectant application, or for the final segment, before or at the 
first customer, during peak hourly flow. The (CTcalc/CT99.9) 
value of each segment and ([Sigma] (CTcalc/CT99.9)) must be 
calculated using the method in paragraph (d)(1)(ii) of this section.
    (3) The system must determine the total logs of inactivation by 
multiplying the value calculated in paragraph (d)(1) or (d)(2) of this 
section by 3.0.
    (4) Systems must calculate the log of inactivation for viruses 
using a protocol approved by the State.
    (e) Systems must use the procedures specified in paragraphs (e)(1) 
and (2) of this section to calculate a disinfection benchmark.
    (1) For each year of profiling data collected and calculated under 
paragraphs (a) through (d) of this section, systems must determine the 
lowest mean monthly level of both Giardia lamblia and virus 
inactivation. Systems must determine the mean Giardia lamblia and virus 
inactivation for each calendar month for each year of profiling data by 
dividing the sum of daily or weekly Giardia lamblia and virus log 
inactivation by the number of values calculated for that month.
    (2) The disinfection benchmark is the lowest monthly mean value 
(for systems with one year of profiling data) or the mean of the lowest 
monthly mean values (for systems with more than one year of profiling 
data) of Giardia lamblia and virus log inactivation in each year of 
profiling data.

Treatment Technique Requirements


Sec.  141.710  Bin classification for filtered systems.

    (a) Following completion of the initial round of source water 
monitoring required under Sec.  141.701(a), filtered systems must 
calculate an initial Cryptosporidium bin concentration for each plant 
for which monitoring was required. Calculation of the bin concentration 
must use the Cryptosporidium results reported under Sec.  141.701(a) 
and must follow the procedures in paragraphs (b)(1) through (5) of this 
section.
    (b)(1) For systems that collect a total of at least 48 samples, the 
bin concentration is equal to the arithmetic mean of all sample 
concentrations.
    (2) For systems that collect a total of at least 24 samples, but 
not more than 47 samples, the bin concentration is equal to the highest 
arithmetic mean of all sample concentrations in any 12 consecutive 
months during which Cryptosporidium samples were collected.
    (3) For systems that serve fewer than 10,000 people and monitor for 
Cryptosporidium for only one year (i.e., collect 24 samples in 12 
months), the bin concentration is equal to the arithmetic mean of all 
sample concentrations.
    (4) For systems with plants operating only part of the year that 
monitor fewer than 12 months per year under Sec.  141.701(e), the bin 
concentration is equal to the highest arithmetic mean of all sample 
concentrations during any year of Cryptosporidium monitoring.
    (5) If the monthly Cryptosporidium sampling frequency varies, 
systems must first calculate a monthly average for each month of 
monitoring. Systems must then use these monthly average concentrations, 
rather than individual sample concentrations, in the applicable 
calculation for bin classification in paragraphs (b)(1) through (4) of 
this section.
    (c) Filtered systems must determine their initial bin 
classification from the following table and using the Cryptosporidium 
bin concentration calculated under paragraphs (a)-(b) of this section:

              Bin Classification Table for Filtered Systems
------------------------------------------------------------------------
                                With a Cryptosporidium       The bin
     For systems that are:      bin concentration of .   classification
                                        . .\1\              is . . .
------------------------------------------------------------------------
. . . required to monitor for   Cryptosporidium <0.075  Bin 1.
 Cryptosporidium under Sec.      oocyst/L.
 141.701.
                                 0.075 oocysts/L        Bin 2.
                                 <=Cryptosporidium
                                 <1.0 oocysts/L.
                                 1.0 oocysts/L          Bin 3.
                                 <=Cryptosporidium
                                 <3.0 oocysts/L.
                                 Cryptosporidium >=3.0  Bin 4.
                                 oocysts/L.
. . . serving fewer than        NA....................  Bin 1.
 10,000 people and NOT
 required to monitor for
 Cryptosporidium under Sec.
 141.701(a)(4).
------------------------------------------------------------------------
\1\ Based on calculations in paragraph (a) or (d) of this section, as
  applicable.

    (d) Following completion of the second round of source water 
monitoring required under Sec.  141.701(b), filtered systems must 
recalculate their Cryptosporidium bin concentration using the 
Cryptosporidium results reported under Sec.  141.701(b) and following 
the procedures in paragraphs (b)(1) through (4) of this section. 
Systems must then redetermine their bin classification using this bin 
concentration and the table in paragraph (c) of this section.
    (e)(1) Filtered systems must report their initial bin 
classification under paragraph (c) of this section to the State for 
approval no later than 6 months after the system is required to 
complete initial source water monitoring based on the schedule in Sec.  
141.701(c).
    (2) Systems must report their bin classification under paragraph 
(d) of this section to the State for approval no later than 6 months 
after the system is required to complete the second round of source 
water monitoring based on the schedule in Sec.  141.701(c).
    (3) The bin classification report to the State must include a 
summary of source water monitoring data and the calculation procedure 
used to determine bin classification.
    (f) Failure to comply with the conditions of paragraph (e) of this 
section is a violation of the treatment technique requirement.


Sec.  141.711  Filtered system additional Cryptosporidium treatment 
requirements.

    (a) Filtered systems must provide the level of additional treatment 
for Cryptosporidium specified in this paragraph based on their bin 
classification as determined under Sec.  141.710 and according to the 
schedule in Sec.  141.713.

[[Page 776]]



----------------------------------------------------------------------------------------------------------------
                         And the system uses the following filtration treatment in full compliance with subparts
                         H, P, and T of this part (as applicable), then the additional Cryptosporidium treatment
   If the system bin                                     requirements are . . .
 classification is . . -----------------------------------------------------------------------------------------
           .                 Conventional                                 Slow sand or           Alternative
                         filtration treatment    Direct filtration     diatomaceous earth        filtration
                        (including softening)                              filtration           technologies
----------------------------------------------------------------------------------------------------------------
Bin 1.................  No additional          No additional          No additional         No additional
                         treatment.             treatment.             treatment.            treatment.
Bin 2.................  1-log treatment......  1.5-log treatment....  1-log treatment.....  (\1\)
Bin 3.................  2-log treatment......  2.5-log treatment....  2-log treatment.....  (\2\)
Bin 4.................  2.5-log treatment....  3-log treatment......  2.5-log treatment...  (\3\)
----------------------------------------------------------------------------------------------------------------
\1\ As determined by the State such that the total Cryptosporidium removal and inactivation is at least 4.0-log.
 
\2\ As determined by the State such that the total Cryptosporidium removal and inactivation is at least 5.0-log.
 
\3\ As determined by the State such that the total Cryptosporidium removal and inactivation is at least 5.5-log.

    (b)(1) Filtered systems must use one or more of the treatment and 
management options listed in Sec.  141.715, termed the microbial 
toolbox, to comply with the additional Cryptosporidium treatment 
required in paragraph (a) of this section.
    (2) Systems classified in Bin 3 and Bin 4 must achieve at least 1-
log of the additional Cryptosporidium treatment required under 
paragraph (a) of this section using either one or a combination of the 
following: bag filters, bank filtration, cartridge filters, chlorine 
dioxide, membranes, ozone, or UV, as described in Sec. Sec.  141.716 
through 141.720.
    (c) Failure by a system in any month to achieve treatment credit by 
meeting criteria in Sec. Sec.  141.716 through 141.720 for microbial 
toolbox options that is at least equal to the level of treatment 
required in paragraph (a) of this section is a violation of the 
treatment technique requirement.
    (d) If the State determines during a sanitary survey or an 
equivalent source water assessment that after a system completed the 
monitoring conducted under Sec.  141.701(a) or Sec.  141.701(b), 
significant changes occurred in the system's watershed that could lead 
to increased contamination of the source water by Cryptosporidium, the 
system must take actions specified by the State to address the 
contamination. These actions may include additional source water 
monitoring and/or implementing microbial toolbox options listed in 
Sec.  141.715.


Sec.  141.712  Unfiltered system Cryptosporidium treatment 
requirements.

    (a) Determination of mean Cryptosporidium level. (1) Following 
completion of the initial source water monitoring required under Sec.  
141.701(a), unfiltered systems must calculate the arithmetic mean of 
all Cryptosporidium sample concentrations reported under Sec.  
141.701(a). Systems must report this value to the State for approval no 
later than 6 months after the month the system is required to complete 
initial source water monitoring based on the schedule in Sec.  
141.701(c).
    (2) Following completion of the second round of source water 
monitoring required under Sec.  141.701(b), unfiltered systems must 
calculate the arithmetic mean of all Cryptosporidium sample 
concentrations reported under Sec.  141.701(b). Systems must report 
this value to the State for approval no later than 6 months after the 
month the system is required to complete the second round of source 
water monitoring based on the schedule in Sec.  141.701(c).
    (3) If the monthly Cryptosporidium sampling frequency varies, 
systems must first calculate a monthly average for each month of 
monitoring. Systems must then use these monthly average concentrations, 
rather than individual sample concentrations, in the calculation of the 
mean Cryptosporidium level in paragraphs (a)(1) or (2) of this section.
    (4) The report to the State of the mean Cryptosporidium levels 
calculated under paragraphs (a)(1) and (2) of this section must include 
a summary of the source water monitoring data used for the calculation.
    (5) Failure to comply with the conditions of paragraph (a) of this 
section is a violation of the treatment technique requirement.
    (b) Cryptosporidium inactivation requirements. Unfiltered systems 
must provide the level of inactivation for Cryptosporidium specified in 
this paragraph, based on their mean Cryptosporidium levels as 
determined under paragraph (a) of this section and according to the 
schedule in Sec.  141.713.
    (1) Unfiltered systems with a mean Cryptosporidium level of 0.01 
oocysts/L or less must provide at least 2-log Cryptosporidium 
inactivation.
    (2) Unfiltered systems with a mean Cryptosporidium level of greater 
than 0.01 oocysts/L must provide at least 3-log Cryptosporidium 
inactivation.
    (c) Inactivation treatment technology requirements. Unfiltered 
systems must use chlorine dioxide, ozone, or UV as described in Sec.  
141.720 to meet the Cryptosporidium inactivation requirements of this 
section.
    (1) Systems that use chlorine dioxide or ozone and fail to achieve 
the Cryptosporidium inactivation required in paragraph (b) of this 
section on more than one day in the calendar month are in violation of 
the treatment technique requirement.
    (2) Systems that use UV light and fail to achieve the 
Cryptosporidium inactivation required in paragraph (b) of this section 
by meeting the criteria in Sec.  141.720(d)(3)(ii) are in violation of 
the treatment technique requirement.
    (d) Use of two disinfectants. Unfiltered systems must meet the 
combined Cryptosporidium inactivation requirements of this section and 
Giardia lamblia and virus inactivation requirements of Sec.  141.72(a) 
using a minimum of two disinfectants, and each of two disinfectants 
must separately achieve the total inactivation required for either 
Cryptosporidium, Giardia lamblia, or viruses.


Sec.  141.713  Schedule for compliance with Cryptosporidium treatment 
requirements.

    (a) Following initial bin classification under Sec.  141.710(c), 
filtered systems must provide the level of treatment for 
Cryptosporidium required under Sec.  141.711 according to the schedule 
in paragraph (c) of this section.
    (b) Following initial determination of the mean Cryptosporidium 
level under Sec.  141.712(a)(1), unfiltered systems must provide the 
level of treatment for Cryptosporidium required under Sec.  141.712 
according to the schedule in paragraph (c) of this section.
    (c) Cryptosporidium treatment compliance dates.

[[Page 777]]



            Cryptosporidium Treatment Compliance Dates Table
------------------------------------------------------------------------
                                                  Must comply with
                                              Cryptosporidium treatment
         Systems that serve . . .           requirements no later than .
                                                       . . \a\
------------------------------------------------------------------------
(1) At least 100,000 people...............  (i) April 1, 2012.
(2) From 50,000 to 99,999 people..........  (i) October 1, 2012.
(3) From 10,000 to 49,999 people..........  (i) October 1, 2013.
(4) Fewer than 10,000 people..............  (i) October 1, 2014.
------------------------------------------------------------------------
a States may allow up to an additional two years for complying with the
  treatment requirement for systems making capital improvements.

    (d) If the bin classification for a filtered system changes 
following the second round of source water monitoring, as determined 
under Sec.  141.710(d), the system must provide the level of treatment 
for Cryptosporidium required under Sec.  141.711 on a schedule the 
State approves.
    (e) If the mean Cryptosporidium level for an unfiltered system 
changes following the second round of monitoring, as determined under 
Sec.  141.712(a)(2), and if the system must provide a different level 
of Cryptosporidium treatment under Sec.  141.712 due to this change, 
the system must meet this treatment requirement on a schedule the State 
approves.


Sec.  141.714  Requirements for uncovered finished water storage 
facilities.

    (a) Systems using uncovered finished water storage facilities must 
comply with the conditions of this section.
    (b) Systems must notify the State of the use of each uncovered 
finished water storage facility no later than April 1, 2008.
    (c) Systems must meet the conditions of paragraph (c)(1) or (2) of 
this section for each uncovered finished water storage facility or be 
in compliance with a State-approved schedule to meet these conditions 
no later than April 1, 2009.
    (1) Systems must cover any uncovered finished water storage 
facility.
    (2) Systems must treat the discharge from the uncovered finished 
water storage facility to the distribution system to achieve 
inactivation and/or removal of at least 4-log virus, 3-log Giardia 
lamblia, and 2-log Cryptosporidium using a protocol approved by the 
State.
    (d) Failure to comply with the requirements of this section is a 
violation of the treatment technique requirement.

Requirements for Microbial Toolbox Components


Sec.  141.715  Microbial toolbox options for meeting Cryptosporidium 
treatment requirements.

    (a)(1) Systems receive the treatment credits listed in the table in 
paragraph (b) of this section by meeting the conditions for microbial 
toolbox options described in Sec. Sec.  141.716 through 141.720. 
Systems apply these treatment credits to meet the treatment 
requirements in Sec.  141.711 or Sec.  141.712, as applicable.
    (2) Unfiltered systems are eligible for treatment credits for the 
microbial toolbox options described in Sec.  141.720 only.
    (b) The following table summarizes options in the microbial 
toolbox:

Microbial Toolbox Summary Table: Options, Treatment Credits and Criteria
------------------------------------------------------------------------
                                 Cryptosporidium treatment credit with
        Toolbox Option             design and implementation criteria
------------------------------------------------------------------------
            Source Protection and Management Toolbox Options
------------------------------------------------------------------------
(1) Watershed control program  0.5-log credit for State-approved program
                                comprising required elements, annual
                                program status report to State, and
                                regular watershed survey. Unfiltered
                                systems are not eligible for credit.
                                Specific criteria are in Sec.
                                141.716(a).
(2) Alternative source/intake  No prescribed credit. Systems may conduct
 management.                    simultaneous monitoring for treatment
                                bin classification at alternative intake
                                locations or under alternative intake
                                management strategies. Specific criteria
                                are in Sec.   141.716(b).
------------------------------
                     Pre Filtration Toolbox Options
------------------------------------------------------------------------
(3) Presedimentation basin     0.5-log credit during any month that
 with coagulation.              presedimentation basins achieve a
                                monthly mean reduction of 0.5-log or
                                greater in turbidity or alternative
                                State-approved performance criteria. To
                                be eligible, basins must be operated
                                continuously with coagulant addition and
                                all plant flow must pass through basins.
                                Specific criteria are in Sec.
                                141.717(a).
(4) Two-stage lime softening.  0.5-log credit for two-stage softening
                                where chemical addition and hardness
                                precipitation occur in both stages. All
                                plant flow must pass through both
                                stages. Single-stage softening is
                                credited as equivalent to conventional
                                treatment. Specific criteria are in Sec.
                                  141.717(b).
(5) Bank filtration..........  0.5-log credit for 25-foot setback; 1.0-
                                log credit for 50-foot setback; aquifer
                                must be unconsolidated sand containing
                                at least 10 percent fines; average
                                turbidity in wells must be less than 1
                                NTU. Systems using wells followed by
                                filtration when conducting source water
                                monitoring must sample the well to
                                determine bin classification and are not
                                eligible for additional credit. Specific
                                criteria are in Sec.   141.717(c).
------------------------------
                  Treatment Performance Toolbox Options
------------------------------------------------------------------------
(6) Combined filter            0.5-log credit for combined filter
 performance.                   effluent turbidity less than or equal to
                                0.15 NTU in at least 95 percent of
                                measurements each month. Specific
                                criteria are in Sec.   141.718(a).
(7) Individual filter          0.5-log credit (in addition to 0.5-log
 performance.                   combined filter performance credit) if
                                individual filter effluent turbidity is
                                less than or equal to 0.15 NTU in at
                                least 95 percent of samples each month
                                in each filter and is never greater than
                                0.3 NTU in two consecutive measurements
                                in any filter. Specific criteria are in
                                Sec.   141.718(b).
(8) Demonstration of           Credit awarded to unit process or
 performance.                   treatment train based on a demonstration
                                to the State with a State- approved
                                protocol. Specific criteria are in Sec.
                                 141.718(c).
------------------------------

[[Page 778]]

 
                  Additional Filtration Toolbox Options
------------------------------------------------------------------------
(9) Bag or cartridge filters   Up to 2-log credit based on the removal
 (individual filters).          efficiency demonstrated during challenge
                                testing with a 1.0-log factor of safety.
                                Specific criteria are in Sec.
                                141.719(a).
(10) Bag or cartridge filters  Up to 2.5-log credit based on the removal
 (in series).                   efficiency demonstrated during challenge
                                testing with a 0.5-log factor of safety.
                                Specific criteria are in Sec.
                                141.719(a).
(11) Membrane filtration.....  Log credit equivalent to removal
                                efficiency demonstrated in challenge
                                test for device if supported by direct
                                integrity testing. Specific criteria are
                                in Sec.   141.719(b).
(12) Second stage filtration.  0.5-log credit for second separate
                                granular media filtration stage if
                                treatment train includes coagulation
                                prior to first filter. Specific criteria
                                are in Sec.   141.719(c)
(13) Slow sand filters.......  2.5-log credit as a secondary filtration
                                step; 3.0-log credit as a primary
                                filtration process. No prior
                                chlorination for either option. Specific
                                criteria are in Sec.   141.719(d).
------------------------------
                      Inactivation Toolbox Options
------------------------------------------------------------------------
(14) Chlorine dioxide........  Log credit based on measured CT in
                                relation to CT table. Specific criteria
                                in Sec.   141.720(b)
(15) Ozone...................  Log credit based on measured CT in
                                relation to CT table. Specific criteria
                                in Sec.   141.720(b).
(16) UV......................  Log credit based on validated UV dose in
                                relation to UV dose table; reactor
                                validation testing required to establish
                                UV dose and associated operating
                                conditions. Specific criteria in Sec.
                                141.720(d).
------------------------------------------------------------------------

Sec.  141.716  Source toolbox components.

    (a) Watershed control program. Systems receive 0.5-log 
Cryptosporidium treatment credit for implementing a watershed control 
program that meets the requirements of this section.
    (1) Systems that intend to apply for the watershed control program 
credit must notify the State of this intent no later than two years 
prior to the treatment compliance date applicable to the system in 
Sec.  141.713.
    (2) Systems must submit to the State a proposed watershed control 
plan no later than one year before the applicable treatment compliance 
date in Sec.  141.713. The State must approve the watershed control 
plan for the system to receive watershed control program treatment 
credit. The watershed control plan must include the elements in 
paragraphs (a)(2)(i) through (iv) of this section.
    (i) Identification of an ``area of influence'' outside of which the 
likelihood of Cryptosporidium or fecal contamination affecting the 
treatment plant intake is not significant. This is the area to be 
evaluated in future watershed surveys under paragraph (a)(5)(ii) of 
this section.
    (ii) Identification of both potential and actual sources of 
Cryptosporidium contamination and an assessment of the relative impact 
of these sources on the system's source water quality.
    (iii) An analysis of the effectiveness and feasibility of control 
measures that could reduce Cryptosporidium loading from sources of 
contamination to the system's source water.
    (iv) A statement of goals and specific actions the system will 
undertake to reduce source water Cryptosporidium levels. The plan must 
explain how the actions are expected to contribute to specific goals, 
identify watershed partners and their roles, identify resource 
requirements and commitments, and include a schedule for plan 
implementation with deadlines for completing specific actions 
identified in the plan.
    (3) Systems with existing watershed control programs (i.e., 
programs in place on January 5, 2006) are eligible to seek this credit. 
Their watershed control plans must meet the criteria in paragraph 
(a)(2) of this section and must specify ongoing and future actions that 
will reduce source water Cryptosporidium levels.
    (4) If the State does not respond to a system regarding approval of 
a watershed control plan submitted under this section and the system 
meets the other requirements of this section, the watershed control 
program will be considered approved and 0.5 log Cryptosporidium 
treatment credit will be awarded unless and until the State 
subsequently withdraws such approval.
    (5) Systems must complete the actions in paragraphs (a)(5)(i) 
through (iii) of this section to maintain the 0.5-log credit.
    (i) Submit an annual watershed control program status report to the 
State. The annual watershed control program status report must describe 
the system's implementation of the approved plan and assess the 
adequacy of the plan to meet its goals. It must explain how the system 
is addressing any shortcomings in plan implementation, including those 
previously identified by the State or as the result of the watershed 
survey conducted under paragraph (a)(5)(ii) of this section. It must 
also describe any significant changes that have occurred in the 
watershed since the last watershed sanitary survey. If a system 
determines during implementation that making a significant change to 
its approved watershed control program is necessary, the system must 
notify the State prior to making any such changes. If any change is 
likely to reduce the level of source water protection, the system must 
also list in its notification the actions the system will take to 
mitigate this effect.
    (ii) Undergo a watershed sanitary survey every three years for 
community water systems and every five years for noncommunity water 
systems and submit the survey report to the State. The survey must be 
conducted according to State guidelines and by persons the State 
approves.
    (A) The watershed sanitary survey must meet the following criteria: 
encompass the region identified in the State-approved watershed control 
plan as the area of influence; assess the implementation of actions to 
reduce source water Cryptosporidium levels; and identify any 
significant new sources of Cryptosporidium.
    (B) If the State determines that significant changes may have 
occurred in the watershed since the previous watershed sanitary survey, 
systems must undergo another watershed sanitary survey by a date the 
State requires, which may be earlier than the regular date in paragraph 
(a)(5)(ii) of this section.
    (iii) The system must make the watershed control plan, annual 
status reports, and watershed sanitary survey reports available to the 
public upon

[[Page 779]]

request. These documents must be in a plain language style and include 
criteria by which to evaluate the success of the program in achieving 
plan goals. The State may approve systems to withhold from the public 
portions of the annual status report, watershed control plan, and 
watershed sanitary survey based on water supply security 
considerations.
    (6) If the State determines that a system is not carrying out the 
approved watershed control plan, the State may withdraw the watershed 
control program treatment credit.
    (b) Alternative source. (1) A system may conduct source water 
monitoring that reflects a different intake location (either in the 
same source or for an alternate source) or a different procedure for 
the timing or level of withdrawal from the source (alternative source 
monitoring). If the State approves, a system may determine its bin 
classification under Sec.  141.710 based on the alternative source 
monitoring results.
    (2) If systems conduct alternative source monitoring under 
paragraph (b)(1) of this section, systems must also monitor their 
current plant intake concurrently as described in Sec.  141.701.
    (3) Alternative source monitoring under paragraph (b)(1) of this 
section must meet the requirements for source monitoring to determine 
bin classification, as described in Sec. Sec.  141.701 through 141.706. 
Systems must report the alternative source monitoring results to the 
State, along with supporting information documenting the operating 
conditions under which the samples were collected.
    (4) If a system determines its bin classification under Sec.  
141.710 using alternative source monitoring results that reflect a 
different intake location or a different procedure for managing the 
timing or level of withdrawal from the source, the system must relocate 
the intake or permanently adopt the withdrawal procedure, as 
applicable, no later than the applicable treatment compliance date in 
Sec.  141.713.


Sec.  141.717  Pre-filtration treatment toolbox components.

    (a) Presedimentation. Systems receive 0.5-log Cryptosporidium 
treatment credit for a presedimentation basin during any month the 
process meets the criteria in this paragraph.
    (1) The presedimentation basin must be in continuous operation and 
must treat the entire plant flow taken from a surface water or GWUDI 
source.
    (2) The system must continuously add a coagulant to the 
presedimentation basin.
    (3) The presedimentation basin must achieve the performance 
criteria in paragraph (3)(i) or (ii) of this section.
    (i) Demonstrates at least 0.5-log mean reduction of influent 
turbidity. This reduction must be determined using daily turbidity 
measurements in the presedimentation process influent and effluent and 
must be calculated as follows: log10(monthly mean of daily 
influent turbidity)-log10(monthly mean of daily effluent 
turbidity).
    (ii) Complies with State-approved performance criteria that 
demonstrate at least 0.5-log mean removal of micron-sized particulate 
material through the presedimentation process.
    (b) Two-stage lime softening. Systems receive an additional 0.5-log 
Cryptosporidium treatment credit for a two-stage lime softening plant 
if chemical addition and hardness precipitation occur in two separate 
and sequential softening stages prior to filtration. Both softening 
stages must treat the entire plant flow taken from a surface water or 
GWUDI source.
    (c) Bank filtration. Systems receive Cryptosporidium treatment 
credit for bank filtration that serves as pretreatment to a filtration 
plant by meeting the criteria in this paragraph. Systems using bank 
filtration when they begin source water monitoring under Sec.  
141.701(a) must collect samples as described in Sec.  141.703(d) and 
are not eligible for this credit.
    (1) Wells with a ground water flow path of at least 25 feet receive 
0.5-log treatment credit; wells with a ground water flow path of at 
least 50 feet receive 1.0-log treatment credit. The ground water flow 
path must be determined as specified in paragraph (c)(4) of this 
section.
    (2) Only wells in granular aquifers are eligible for treatment 
credit. Granular aquifers are those comprised of sand, clay, silt, rock 
fragments, pebbles or larger particles, and minor cement. A system must 
characterize the aquifer at the well site to determine aquifer 
properties. Systems must extract a core from the aquifer and 
demonstrate that in at least 90 percent of the core length, grains less 
than 1.0 mm in diameter constitute at least 10 percent of the core 
material.
    (3) Only horizontal and vertical wells are eligible for treatment 
credit.
    (4) For vertical wells, the ground water flow path is the measured 
distance from the edge of the surface water body under high flow 
conditions (determined by the 100 year floodplain elevation boundary or 
by the floodway, as defined in Federal Emergency Management Agency 
flood hazard maps) to the well screen. For horizontal wells, the ground 
water flow path is the measured distance from the bed of the river 
under normal flow conditions to the closest horizontal well lateral 
screen.
    (5) Systems must monitor each wellhead for turbidity at least once 
every four hours while the bank filtration process is in operation. If 
monthly average turbidity levels, based on daily maximum values in the 
well, exceed 1 NTU, the system must report this result to the State and 
conduct an assessment within 30 days to determine the cause of the high 
turbidity levels in the well. If the State determines that microbial 
removal has been compromised, the State may revoke treatment credit 
until the system implements corrective actions approved by the State to 
remediate the problem.
    (6) Springs and infiltration galleries are not eligible for 
treatment credit under this section, but are eligible for credit under 
Sec.  141.718(c).
    (7) Bank filtration demonstration of performance. The State may 
approve Cryptosporidium treatment credit for bank filtration based on a 
demonstration of performance study that meets the criteria in this 
paragraph. This treatment credit may be greater than 1.0-log and may be 
awarded to bank filtration that does not meet the criteria in 
paragraphs (c)(1)-(5) of this section.
    (i) The study must follow a State-approved protocol and must 
involve the collection of data on the removal of Cryptosporidium or a 
surrogate for Cryptosporidium and related hydrogeologic and water 
quality parameters during the full range of operating conditions.
    (ii) The study must include sampling both from the production 
well(s) and from monitoring wells that are screened and located along 
the shortest flow path between the surface water source and the 
production well(s).


Sec.  141.718  Treatment performance toolbox components.

    (a) Combined filter performance. Systems using conventional 
filtration treatment or direct filtration treatment receive an 
additional 0.5-log Cryptosporidium treatment credit during any month 
the system meets the criteria in this paragraph. Combined filter 
effluent (CFE) turbidity must be less than or equal to 0.15 NTU in at 
least 95 percent of the measurements. Turbidity must be measured as 
described in Sec.  141.74(a) and (c).
    (b) Individual filter performance. Systems using conventional 
filtration treatment or direct filtration treatment receive 0.5-log 
Cryptosporidium treatment credit, which can be in

[[Page 780]]

addition to the 0.5-log credit under paragraph (a) of this section, 
during any month the system meets the criteria in this paragraph. 
Compliance with these criteria must be based on individual filter 
turbidity monitoring as described in Sec.  141.174 or Sec.  141.560, as 
applicable.
    (1) The filtered water turbidity for each individual filter must be 
less than or equal to 0.15 NTU in at least 95 percent of the 
measurements recorded each month.
    (2) No individual filter may have a measured turbidity greater than 
0.3 NTU in two consecutive measurements taken 15 minutes apart.
    (3) Any system that has received treatment credit for individual 
filter performance and fails to meet the requirements of paragraph 
(b)(1) or (2) of this section during any month does not receive a 
treatment technique violation under Sec.  141.711(c) if the State 
determines the following:
    (i) The failure was due to unusual and short-term circumstances 
that could not reasonably be prevented through optimizing treatment 
plant design, operation, and maintenance.
    (ii) The system has experienced no more than two such failures in 
any calendar year.
    (c) Demonstration of performance. The State may approve 
Cryptosporidium treatment credit for drinking water treatment processes 
based on a demonstration of performance study that meets the criteria 
in this paragraph. This treatment credit may be greater than or less 
than the prescribed treatment credits in Sec.  141.711 or Sec. Sec.  
141.717 through 141.720 and may be awarded to treatment processes that 
do not meet the criteria for the prescribed credits.
    (1) Systems cannot receive the prescribed treatment credit for any 
toolbox box option in Sec. Sec.  141.717 through 141.720 if that 
toolbox option is included in a demonstration of performance study for 
which treatment credit is awarded under this paragraph.
    (2) The demonstration of performance study must follow a State-
approved protocol and must demonstrate the level of Cryptosporidium 
reduction the treatment process will achieve under the full range of 
expected operating conditions for the system.
    (3) Approval by the State must be in writing and may include 
monitoring and treatment performance criteria that the system must 
demonstrate and report on an ongoing basis to remain eligible for the 
treatment credit. The State may designate such criteria where necessary 
to verify that the conditions under which the demonstration of 
performance credit was approved are maintained during routine 
operation.


Sec.  141.719  Additional filtration toolbox components.

    (a) Bag and cartridge filters. Systems receive Cryptosporidium 
treatment credit of up to 2.0-log for individual bag or cartridge 
filters and up to 2.5-log for bag or cartridge filters operated in 
series by meeting the criteria in paragraphs (a)(1) through (10) of 
this section. To be eligible for this credit, systems must report the 
results of challenge testing that meets the requirements of paragraphs 
(a)(2) through (9) of this section to the State. The filters must treat 
the entire plant flow taken from a subpart H source.
    (1) The Cryptosporidium treatment credit awarded to bag or 
cartridge filters must be based on the removal efficiency demonstrated 
during challenge testing that is conducted according to the criteria in 
paragraphs (a)(2) through (a)(9) of this section. A factor of safety 
equal to 1-log for individual bag or cartridge filters and 0.5-log for 
bag or cartridge filters in series must be applied to challenge testing 
results to determine removal credit. Systems may use results from 
challenge testing conducted prior to January 5, 2006 if the prior 
testing was consistent with the criteria specified in paragraphs (a)(2) 
through (9) of this section.
    (2) Challenge testing must be performed on full-scale bag or 
cartridge filters, and the associated filter housing or pressure 
vessel, that are identical in material and construction to the filters 
and housings the system will use for removal of Cryptosporidium. Bag or 
cartridge filters must be challenge tested in the same configuration 
that the system will use, either as individual filters or as a series 
configuration of filters.
    (3) Challenge testing must be conducted using Cryptosporidium or a 
surrogate that is removed no more efficiently than Cryptosporidium. The 
microorganism or surrogate used during challenge testing is referred to 
as the challenge particulate. The concentration of the challenge 
particulate must be determined using a method capable of discreetly 
quantifying the specific microorganism or surrogate used in the test; 
gross measurements such as turbidity may not be used.
    (4) The maximum feed water concentration that can be used during a 
challenge test must be based on the detection limit of the challenge 
particulate in the filtrate (i.e., filtrate detection limit) and must 
be calculated using the following equation:

Maximum Feed Concentration = 1 x 10 4 x (Filtrate Detection 
Limit)

    (5) Challenge testing must be conducted at the maximum design flow 
rate for the filter as specified by the manufacturer.
    (6) Each filter evaluated must be tested for a duration sufficient 
to reach 100 percent of the terminal pressure drop, which establishes 
the maximum pressure drop under which the filter may be used to comply 
with the requirements of this subpart.
    (7) Removal efficiency of a filter must be determined from the 
results of the challenge test and expressed in terms of log removal 
values using the following equation:

LRV = LOG10(Cf)-LOG10(Cp)

Where:
LRV = log removal value demonstrated during challenge testing; 
Cf = the feed concentration measured during the challenge 
test; and Cp = the filtrate concentration measured during 
the challenge test. In applying this equation, the same units must be 
used for the feed and filtrate concentrations. If the challenge 
particulate is not detected in the filtrate, then the term 
Cp must be set equal to the detection limit.

    (8) Each filter tested must be challenged with the challenge 
particulate during three periods over the filtration cycle: within two 
hours of start-up of a new filter; when the pressure drop is between 45 
and 55 percent of the terminal pressure drop; and at the end of the 
cycle after the pressure drop has reached 100 percent of the terminal 
pressure drop. An LRV must be calculated for each of these challenge 
periods for each filter tested. The LRV for the filter 
(LRVfilter) must be assigned the value of the minimum LRV 
observed during the three challenge periods for that filter.
    (9) If fewer than 20 filters are tested, the overall removal 
efficiency for the filter product line must be set equal to the lowest 
LRVfilter among the filters tested. If 20 or more filters 
are tested, the overall removal efficiency for the filter product line 
must be set equal to the 10th percentile of the set of 
LRVfilter values for the various filters tested. The 
percentile is defined by (i/(n+1)) where i is the rank of n individual 
data points ordered lowest to highest. If necessary, the 10th 
percentile may be calculated using linear interpolation.
    (10) If a previously tested filter is modified in a manner that 
could change the removal efficiency of the filter product line, 
challenge testing to demonstrate the removal efficiency of

[[Page 781]]

the modified filter must be conducted and submitted to the State.
    (b) Membrane filtration. (1) Systems receive Cryptosporidium 
treatment credit for membrane filtration that meets the criteria of 
this paragraph. Membrane cartridge filters that meet the definition of 
membrane filtration in Sec.  141.2 are eligible for this credit. The 
level of treatment credit a system receives is equal to the lower of 
the values determined under paragraph (b)(1)(i) and (ii) of this 
section.
    (i) The removal efficiency demonstrated during challenge testing 
conducted under the conditions in paragraph (b)(2) of this section.
    (ii) The maximum removal efficiency that can be verified through 
direct integrity testing used with the membrane filtration process 
under the conditions in paragraph (b)(3) of this section.
    (2) Challenge Testing. The membrane used by the system must undergo 
challenge testing to evaluate removal efficiency, and the system must 
report the results of challenge testing to the State. Challenge testing 
must be conducted according to the criteria in paragraphs (b)(2)(i) 
through (vii) of this section. Systems may use data from challenge 
testing conducted prior to January 5, 2006 if the prior testing was 
consistent with the criteria in paragraphs (b)(2)(i) through (vii) of 
this section.
    (i) Challenge testing must be conducted on either a full-scale 
membrane module, identical in material and construction to the membrane 
modules used in the system's treatment facility, or a smaller-scale 
membrane module, identical in material and similar in construction to 
the full-scale module. A module is defined as the smallest component of 
a membrane unit in which a specific membrane surface area is housed in 
a device with a filtrate outlet structure.
    (ii) Challenge testing must be conducted using Cryptosporidium 
oocysts or a surrogate that is removed no more efficiently than 
Cryptosporidium oocysts. The organism or surrogate used during 
challenge testing is referred to as the challenge particulate. The 
concentration of the challenge particulate, in both the feed and 
filtrate water, must be determined using a method capable of discretely 
quantifying the specific challenge particulate used in the test; gross 
measurements such as turbidity may not be used.
    (iii) The maximum feed water concentration that can be used during 
a challenge test is based on the detection limit of the challenge 
particulate in the filtrate and must be determined according to the 
following equation:

Maximum Feed Concentration = 3.16 x 106 x (Filtrate 
Detection Limit)

    (iv) Challenge testing must be conducted under representative 
hydraulic conditions at the maximum design flux and maximum design 
process recovery specified by the manufacturer for the membrane module. 
Flux is defined as the throughput of a pressure driven membrane process 
expressed as flow per unit of membrane area. Recovery is defined as the 
volumetric percent of feed water that is converted to filtrate over the 
course of an operating cycle uninterrupted by events such as chemical 
cleaning or a solids removal process (i.e., backwashing).
    (v) Removal efficiency of a membrane module must be calculated from 
the challenge test results and expressed as a log removal value 
according to the following equation:


LRV = LOG10(Cf) x LOG10(Cp)

Where:
LRV = log removal value demonstrated during the challenge test; 
Cf = the feed concentration measured during the challenge 
test; and Cp = the filtrate concentration measured during 
the challenge test. Equivalent units must be used for the feed and 
filtrate concentrations. If the challenge particulate is not detected 
in the filtrate, the term Cp is set equal to the detection 
limit for the purpose of calculating the LRV. An LRV must be calculated 
for each membrane module evaluated during the challenge test.

    (vi) The removal efficiency of a membrane filtration process 
demonstrated during challenge testing must be expressed as a log 
removal value (LRVC-Test). If fewer than 20 modules are 
tested, then LRVC-Test is equal to the lowest of the 
representative LRVs among the modules tested. If 20 or more modules are 
tested, then LRVC-Test is equal to the 10th percentile of 
the representative LRVs among the modules tested. The percentile is 
defined by (i/(n+1)) where i is the rank of n individual data points 
ordered lowest to highest. If necessary, the 10th percentile may be 
calculated using linear interpolation.
    (vii) The challenge test must establish a quality control release 
value (QCRV) for a non-destructive performance test that demonstrates 
the Cryptosporidium removal capability of the membrane filtration 
module. This performance test must be applied to each production 
membrane module used by the system that was not directly challenge 
tested in order to verify Cryptosporidium removal capability. 
Production modules that do not meet the established QCRV are not 
eligible for the treatment credit demonstrated during the challenge 
test.
    (viii) If a previously tested membrane is modified in a manner that 
could change the removal efficiency of the membrane or the 
applicability of the non-destructive performance test and associated 
QCRV, additional challenge testing to demonstrate the removal 
efficiency of, and determine a new QCRV for, the modified membrane must 
be conducted and submitted to the State.
    (3) Direct integrity testing. Systems must conduct direct integrity 
testing in a manner that demonstrates a removal efficiency equal to or 
greater than the removal credit awarded to the membrane filtration 
process and meets the requirements described in paragraphs (b)(3)(i) 
through (vi) of this section. A direct integrity test is defined as a 
physical test applied to a membrane unit in order to identify and 
isolate integrity breaches (i.e., one or more leaks that could result 
in contamination of the filtrate).
    (i) The direct integrity test must be independently applied to each 
membrane unit in service. A membrane unit is defined as a group of 
membrane modules that share common valving that allows the unit to be 
isolated from the rest of the system for the purpose of integrity 
testing or other maintenance.
    (ii) The direct integrity method must have a resolution of 3 
micrometers or less, where resolution is defined as the size of the 
smallest integrity breach that contributes to a response from the 
direct integrity test.
    (iii) The direct integrity test must have a sensitivity sufficient 
to verify the log treatment credit awarded to the membrane filtration 
process by the State, where sensitivity is defined as the maximum log 
removal value that can be reliably verified by a direct integrity test. 
Sensitivity must be determined using the approach in either paragraph 
(b)(3)(iii)(A) or (B) of this section as applicable to the type of 
direct integrity test the system uses.
    (A) For direct integrity tests that use an applied pressure or 
vacuum, the direct integrity test sensitivity must be calculated 
according to the following equation:


LRVDIT = LOG10 (Qp /(VCF x 
Qbreach))

Where:
LRVDIT = the sensitivity of the direct integrity test; 
Qp = total design filtrate flow from the membrane unit; 
Qbreach = flow of water from an

[[Page 782]]

integrity breach associated with the smallest integrity test response 
that can be reliably measured, and VCF = volumetric concentration 
factor. The volumetric concentration factor is the ratio of the 
suspended solids concentration on the high pressure side of the 
membrane relative to that in the feed water.

    (B) For direct integrity tests that use a particulate or molecular 
marker, the direct integrity test sensitivity must be calculated 
according to the following equation:


LRVDIT = LOG10(Cf)-
LOG10(Cp)

Where:
LRVDIT = the sensitivity of the direct integrity test; 
Cf = the typical feed concentration of the marker used in 
the test; and Cp = the filtrate concentration of the marker 
from an integral membrane unit.

    (iv) Systems must establish a control limit within the sensitivity 
limits of the direct integrity test that is indicative of an integral 
membrane unit capable of meeting the removal credit awarded by the 
State.
    (v) If the result of a direct integrity test exceeds the control 
limit established under paragraph (b)(3)(iv) of this section, the 
system must remove the membrane unit from service. Systems must conduct 
a direct integrity test to verify any repairs, and may return the 
membrane unit to service only if the direct integrity test is within 
the established control limit.
    (vi) Systems must conduct direct integrity testing on each membrane 
unit at a frequency of not less than once each day that the membrane 
unit is in operation. The State may approve less frequent testing, 
based on demonstrated process reliability, the use of multiple barriers 
effective for Cryptosporidium, or reliable process safeguards.
    (4) Indirect integrity monitoring. Systems must conduct continuous 
indirect integrity monitoring on each membrane unit according to the 
criteria in paragraphs (b)(4)(i) through (v) of this section. Indirect 
integrity monitoring is defined as monitoring some aspect of filtrate 
water quality that is indicative of the removal of particulate matter. 
A system that implements continuous direct integrity testing of 
membrane units in accordance with the criteria in paragraphs (b)(3)(i) 
through (v) of this section is not subject to the requirements for 
continuous indirect integrity monitoring. Systems must submit a monthly 
report to the State summarizing all continuous indirect integrity 
monitoring results triggering direct integrity testing and the 
corrective action that was taken in each case.
    (i) Unless the State approves an alternative parameter, continuous 
indirect integrity monitoring must include continuous filtrate 
turbidity monitoring.
    (ii) Continuous monitoring must be conducted at a frequency of no 
less than once every 15 minutes.
    (iii) Continuous monitoring must be separately conducted on each 
membrane unit.
    (iv) If indirect integrity monitoring includes turbidity and if the 
filtrate turbidity readings are above 0.15 NTU for a period greater 
than 15 minutes (i.e., two consecutive 15-minute readings above 0.15 
NTU), direct integrity testing must immediately be performed on the 
associated membrane unit as specified in paragraphs (b)(3)(i) through 
(v) of this section.
    (v) If indirect integrity monitoring includes a State-approved 
alternative parameter and if the alternative parameter exceeds a State-
approved control limit for a period greater than 15 minutes, direct 
integrity testing must immediately be performed on the associated 
membrane units as specified in paragraphs (b)(3)(i) through (v) of this 
section.
    (c) Second stage filtration. Systems receive 0.5-log 
Cryptosporidium treatment credit for a separate second stage of 
filtration that consists of sand, dual media, GAC, or other fine grain 
media following granular media filtration if the State approves. To be 
eligible for this credit, the first stage of filtration must be 
preceded by a coagulation step and both filtration stages must treat 
the entire plant flow taken from a surface water or GWUDI source. A 
cap, such as GAC, on a single stage of filtration is not eligible for 
this credit. The State must approve the treatment credit based on an 
assessment of the design characteristics of the filtration process.
    (d) Slow sand filtration (as secondary filter). Systems are 
eligible to receive 2.5-log Cryptosporidium treatment credit for a slow 
sand filtration process that follows a separate stage of filtration if 
both filtration stages treat entire plant flow taken from a surface 
water or GWUDI source and no disinfectant residual is present in the 
influent water to the slow sand filtration process. The State must 
approve the treatment credit based on an assessment of the design 
characteristics of the filtration process. This paragraph does not 
apply to treatment credit awarded to slow sand filtration used as a 
primary filtration process.


Sec.  141.720  Inactivation toolbox components.

    (a) Calculation of CT values. (1) CT is the product of the 
disinfectant contact time (T, in minutes) and disinfectant 
concentration (C, in milligrams per liter). Systems with treatment 
credit for chlorine dioxide or ozone under paragraph (b) or (c) of this 
section must calculate CT at least once each day, with both C and T 
measured during peak hourly flow as specified in Sec. Sec.  141.74(a) 
through (b).
    (2) Systems with several disinfection segments in sequence may 
calculate CT for each segment, where a disinfection segment is defined 
as a treatment unit process with a measurable disinfectant residual 
level and a liquid volume. Under this approach, systems must add the 
Cryptosporidium CT values in each segment to determine the total CT for 
the treatment plant.
    (b) CT values for chlorine dioxide and ozone. (1) Systems receive 
the Cryptosporidium treatment credit listed in this table by meeting 
the corresponding chlorine dioxide CT value for the applicable water 
temperature, as described in paragraph (a) of this section.

                                  CT Values (mg[middot]min/L) for Cryptosporidium Inactivation by Chlorine Dioxide \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                 Water Temperature, [deg]C
                           Log credit                            ---------------------------------------------------------------------------------------
                                                                   <=0.5     1       2       3       5       7      10      15      20      25      30
--------------------------------------------------------------------------------------------------------------------------------------------------------
(i) 0.25........................................................     159     153     140     128     107      90      69      45      29      19      12
(ii) 0.5........................................................     319     305     279     256     214     180     138      89      58      38      24
(iii) 1.0.......................................................     637     610     558     511     429     360     277     179     116      75      49
(iv) 1.5........................................................     956     915     838     767     643     539     415     268     174     113      73
(v) 2.0.........................................................    1275    1220    1117    1023     858     719     553     357     232     150      98
(vi) 2.5........................................................    1594    1525    1396    1278    1072     899     691     447     289     188     122

[[Page 783]]

 
(vii) 3.0.......................................................    1912    1830    1675    1534    1286    1079     830     536     347     226    147
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Systems may use this equation to determine log credit between the indicated values: Log credit = (0.001506 x (1.09116) Temp) x CT.

    (2) Systems receive the Cryptosporidium treatment credit listed in 
this table by meeting the corresponding ozone CT values for the 
applicable water temperature, as described in paragraph (a) of this 
section.

                                        CT Values (mg[middot]min/L) for Cryptosporidium Inactivation by Ozone \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                 Water Temperature, [deg]C
                           Log credit                            ---------------------------------------------------------------------------------------
                                                                   <=0.5     1       2       3       5       7      10      15      20      25      30
--------------------------------------------------------------------------------------------------------------------------------------------------------
(i) 0.25........................................................     6.0     5.8     5.2     4.8     4.0     3.3     2.5     1.6     1.0     0.6    0.39
(ii) 0.5........................................................      12      12      10     9.5     7.9     6.5     4.9     3.1     2.0     1.2    0.78
(iii) 1.0.......................................................      24      23      21      19      16      13     9.9     6.2     3.9     2.5     1.6
(iv) 1.5........................................................      36      35      31      29      24      20      15     9.3     5.9     3.7     2.4
(v) 2.0.........................................................      48      46      42      38      32      26      20      12     7.8     4.9     3.1
(vi) 2.5........................................................      60      58      52      48      40      33      25      16     9.8     6.2     3.9
(vii) 3.0.......................................................      72      69      63      57      47      39      30      19      12     7.4    4.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Systems may use this equation to determine log credit between the indicated values: Log credit = (0.0397 x (1.09757)Temp) x CT.

    (c) Site-specific study. The State may approve alternative chlorine 
dioxide or ozone CT values to those listed in paragraph (b) of this 
section on a site-specific basis. The State must base this approval on 
a site-specific study a system conducts that follows a State-approved 
protocol.
    (d) Ultraviolet light. Systems receive Cryptosporidium, Giardia 
lamblia, and virus treatment credits for ultraviolet (UV) light 
reactors by achieving the corresponding UV dose values shown in 
paragraph (d)(1) of this section. Systems must validate and monitor UV 
reactors as described in paragraphs (d)(2) and (3) of this section to 
demonstrate that they are achieving a particular UV dose value for 
treatment credit.
    (1) UV dose table. The treatment credits listed in this table are 
for UV light at a wavelength of 254 nm as produced by a low pressure 
mercury vapor lamp. To receive treatment credit for other lamp types, 
systems must demonstrate an equivalent germicidal dose through reactor 
validation testing, as described in paragraph (d)(2) of this section. 
The UV dose values in this table are applicable only to post-filter 
applications of UV in filtered systems and to unfiltered systems.

                UV Dose Table for Cryptosporidium, Giardia lamblia, and Virus Inactivation Credit
----------------------------------------------------------------------------------------------------------------
                                                          Cryptosporidium    Giardia lamblia
                       Log credit                           UV dose (mJ/       UV dose (mJ/      Virus  UV dose
                                                               cm\2\)             cm\2\)           (mJ/cm\2\)
----------------------------------------------------------------------------------------------------------------
(i) 0.5................................................                1.6                1.5                 39
(ii) 1.0...............................................                2.5                2.1                 58
(iii) 1.5..............................................                3.9                3.0                 79
(iv) 2.0...............................................                5.8                5.2                100
(v) 2.5................................................                8.5                7.7                121
(vi) 3.0...............................................                 12                 11                143
(vii) 3.5..............................................                 15                 15                163
(viii) 4.0.............................................                 22                 22                186
----------------------------------------------------------------------------------------------------------------

    (2) Reactor validation testing. Systems must use UV reactors that 
have undergone validation testing to determine the operating conditions 
under which the reactor delivers the UV dose required in paragraph 
(d)(1) of this section (i.e., validated operating conditions). These 
operating conditions must include flow rate, UV intensity as measured 
by a UV sensor, and UV lamp status.
    (i) When determining validated operating conditions, systems must 
account for the following factors: UV absorbance of the water; lamp 
fouling and aging; measurement uncertainty of on-line sensors; UV dose 
distributions arising from the velocity profiles through the reactor; 
failure of UV lamps or other critical system components; and inlet and 
outlet piping or channel configurations of the UV reactor.
    (ii) Validation testing must include the following: Full scale 
testing of a reactor that conforms uniformly to the UV reactors used by 
the system and inactivation of a test microorganism whose dose response 
characteristics have been quantified with a low pressure mercury vapor 
lamp.
    (iii) The State may approve an alternative approach to validation 
testing.
    (3) Reactor monitoring. (i) Systems must monitor their UV reactors 
to determine if the reactors are operating within validated conditions, 
as determined under paragraph (d)(2) of this section. This monitoring 
must include UV intensity as measured by a UV sensor, flow rate, lamp 
status, and other parameters the State designates

[[Page 784]]

based on UV reactor operation. Systems must verify the calibration of 
UV sensors and must recalibrate sensors in accordance with a protocol 
the State approves.
    (ii) To receive treatment credit for UV light, systems must treat 
at least 95 percent of the water delivered to the public during each 
month by UV reactors operating within validated conditions for the 
required UV dose, as described in paragraphs (d)(1) and (2) of this 
section. Systems must demonstrate compliance with this condition by the 
monitoring required under paragraph (d)(3)(i) of this section.

Reporting and Recordkeeping Requirements


Sec.  141.721  Reporting requirements.

    (a) Systems must report sampling schedules under Sec.  141.702 and 
source water monitoring results under Sec.  141.706 unless they notify 
the State that they will not conduct source water monitoring due to 
meeting the criteria of Sec.  141.701(d).
    (b) Systems must report the use of uncovered finished water storage 
facilities to the State as described in Sec.  141.714.
    (c) Filtered systems must report their Cryptosporidium bin 
classification as described in Sec.  141.710.
    (d) Unfiltered systems must report their mean source water 
Cryptosporidium level as described in Sec.  141.712.
    (e) Systems must report disinfection profiles and benchmarks to the 
State as described in Sec. Sec.  141.708 through 141.709 prior to 
making a significant change in disinfection practice.
    (f) Systems must report to the State in accordance with the 
following table for any microbial toolbox options used to comply with 
treatment requirements under Sec.  141.711 or Sec.  141.712. 
Alternatively, the State may approve a system to certify operation 
within required parameters for treatment credit rather than reporting 
monthly operational data for toolbox options.

                                    Microbial Toolbox Reporting Requirements
----------------------------------------------------------------------------------------------------------------
                                                    Systems must submit the
                Toolbox option                       following information          On the following schedule
----------------------------------------------------------------------------------------------------------------
(1) Watershed control program (WCP)..........  (i) Notice of intention to        No later than two years before
                                                develop a new or continue an      the applicable treatment
                                                existing watershed control        compliance date in Sec.
                                                program.                          141.713
                                               (ii) Watershed control plan.....  No later than one year before
                                                                                  the applicable treatment
                                                                                  compliance date in Sec.
                                                                                  141.713.
                                               (iii) Annual watershed control    Every 12 months, beginning one
                                                program status report.            year after the applicable
                                                                                  treatment compliance date in
                                                                                  Sec.   141.713.
                                               (iv) Watershed sanitary survey    For community water systems,
                                                report.                           every three years beginning
                                                                                  three years after the
                                                                                  applicable treatment
                                                                                  compliance date in Sec.
                                                                                  141.713. For noncommunity
                                                                                  water systems, every five
                                                                                  years beginning five years
                                                                                  after the applicable treatment
                                                                                  compliance date in Sec.
                                                                                  141.713.
(2) Alternative source/intake management.....  Verification that system has      No later than the applicable
                                                relocated the intake or adopted   treatment compliance date in
                                                the intake withdrawal procedure   Sec.   141.713.
                                                reflected in monitoring results.
(3) Presedimentation.........................  Monthly verification of the       Monthly reporting within 10
                                                following: (i) Continuous basin   days following the month in
                                                operation (ii) Treatment of       which the monitoring was
                                                100% of the flow (iii)            conducted, beginning on the
                                                Continuous addition of a          applicable treatment
                                                coagulant (iv) At least 0.5-log   compliance date in Sec.
                                                mean reduction of influent        141.713.
                                                turbidity or compliance with
                                                alternative State-approved
                                                performance criteria.
(4) Two-stage lime softening.................  Monthly verification of the       Monthly reporting within 10
                                                following: (i) Chemical           days following the month in
                                                addition and hardness             which the monitoring was
                                                precipitation occurred in two     conducted, beginning on the
                                                separate and sequential           applicable treatment
                                                softening stages prior to         compliance date in Sec.
                                                filtration (ii) Both stages       141.713.
                                                treated 100% of the plant flow.
(5) Bank filtration..........................  (i) Initial demonstration of the  No later than the applicable
                                                following: (A) Unconsolidated,    treatment compliance date in
                                                predominantly sandy aquifer (B)   Sec.   141.713.
                                                Setback distance of at least 25
                                                ft. (0.5-log credit) or 50 ft.
                                                (1.0-log credit).
                                               (ii) If monthly average of daily  Report within 30 days following
                                                max turbidity is greater than 1   the month in which the
                                                NTU then system must report       monitoring was conducted,
                                                result and submit an assessment   beginning on the applicable
                                                of the cause..                    treatment compliance date in
                                                                                  Sec.   141.713.
(6) Combined filter performance..............  Monthly verification of combined  Monthly reporting within 10
                                                filter effluent (CFE) turbidity   days following the month in
                                                levels less than or equal to      which the monitoring was
                                                0.15 NTU in at least 95 percent   conducted, beginning on the
                                                of the 4 hour CFE measurements    applicable treatment
                                                taken each month.                 compliance date in Sec.
                                                                                  141.713.
(7) Individual filter performance............  Monthly verification of the       Monthly reporting within 10
                                                following: (i) Individual         days following the month in
                                                filter effluent (IFE )            which the monitoring was
                                                turbidity levels less than or     conducted, beginning on the
                                                equal to 0.15 NTU in at least     applicable treatment
                                                95 percent of samples each        compliance date in Sec.
                                                month in each filter (ii) No      141.713.]
                                                individual filter greater than
                                                0.3 NTU in two consecutive
                                                readings 15 minutes apart.
(8) Demonstration of performance.............  (i) Results from testing          No later than the applicable
                                                following a State approved        treatment compliance date in
                                                protocol.                         Sec.   141.713.
                                               (ii) As required by the State,    Within 10 days following the
                                                monthly verification of           month in which monitoring was
                                                operation within conditions of    conducted, beginning on the
                                                State approval for                applicable treatment
                                                demonstration of performance      compliance date in Sec.
                                                credit.                           141.713.

[[Page 785]]

 
(9) Bag filters and cartridge filters........  (i) Demonstration that the        No later than the applicable
                                                following criteria are met: (A)   treatment compliance date in
                                                Process meets the definition of   Sec.   141.713.
                                                bag or cartridge filtration;
                                                (B) Removal efficiency
                                                established through challenge
                                                testing that meets criteria in
                                                this subpart.
                                               (ii) Monthly verification that    Within 10 days following the
                                                100% of plant flow was filtered.  month in which monitoring was
                                                                                  conducted, beginning on the
                                                                                  applicable treatment
                                                                                  compliance date in Sec.
                                                                                  141.713.
(10) Membrane filtration.....................  (i) Results of verification       No later than the applicable
                                                testing demonstrating the         treatment compliance date in
                                                following: (A) Removal            Sec.   141.713.
                                                efficiency established through
                                                challenge testing that meets
                                                criteria in this subpart; (B)
                                                Integrity test method and
                                                parameters, including
                                                resolution, sensitivity, test
                                                frequency, control limits, and
                                                associated baseline.
                                               (ii) Monthly report summarizing   Within 10 days following the
                                                the following: (A) All direct     month in which monitoring was
                                                integrity tests above the         conducted, beginning on the
                                                control limit; (B) If             applicable treatment
                                                applicable, any turbidity or      compliance date in Sec.
                                                alternative state-approved        141.713.
                                                indirect integrity monitoring
                                                results triggering direct
                                                integrity testing and the
                                                corrective action that was
                                                taken.
(11) Second stage filtration.................  Monthly verification that 100%    Within 10 days following the
                                                of flow was filtered through      month in which monitoring was
                                                both stages and that first        conducted, beginning on the
                                                stage was preceded by             applicable treatment
                                                coagulation step.                 compliance date in Sec.
                                                                                  141.713.
(12) Slow sand filtration (as secondary        Monthly verification that both a  Within 10 days following the
 filter).                                       slow sand filter and a            month in which monitoring was
                                                preceding separate stage of       conducted, beginning on the
                                                filtration treated 100% of flow   applicable treatment
                                                from subpart H sources..          compliance date in Sec.
                                                                                  141.713.
(13) Chlorine dioxide........................  Summary of CT values for each     Within 10 days following the
                                                day as described in Sec.          month in which monitoring was
                                                141.720..                         conducted, beginning on the
                                                                                  applicable treatment
                                                                                  compliance date in Sec.
                                                                                  141.713.
(14) Ozone...................................  Summary of CT values for each     Within 10 days following the
                                                day as described in Sec.          month in which monitoring was
                                                141.720..                         conducted, beginning on the
                                                                                  applicable treatment
                                                                                  compliance date in Sec.
                                                                                  141.713.
(15) UV......................................  (i) Validation test results       No later than the applicable
                                                demonstrating operating           treatment compliance date in
                                                conditions that achieve           Sec.   141.713.
                                                required UV dose.                Within 10 days following the
                                               (ii) Monthly report summarizing    month in which monitoring was
                                                the percentage of water           conducted, beginning on the
                                                entering the distribution         applicable treatment
                                                system that was not treated by    compliance date in Sec.
                                                UV reactors operating within      141.713.
                                                validated conditions for the
                                                required dose as specified in
                                                141.720(d)..
----------------------------------------------------------------------------------------------------------------

Sec.  141.722  Recordkeeping requirements.

    (a) Systems must keep results from the initial round of source 
water monitoring under Sec.  141.701(a) and the second round of source 
water monitoring under Sec.  141.701(b) until 3 years after bin 
classification under Sec.  141.710 for filtered systems or 
determination of the mean Cryptosporidium level under Sec.  141.710 for 
unfiltered systems for the particular round of monitoring.
    (b) Systems must keep any notification to the State that they will 
not conduct source water monitoring due to meeting the criteria of 
Sec.  141.701(d) for 3 years.
    (c) Systems must keep the results of treatment monitoring 
associated with microbial toolbox options under Sec. Sec.  141.716 
through 141.720 and with uncovered finished water reservoirs under 
Sec.  141.714, as applicable, for 3 years.

Requirements for Sanitary Surveys Performed by EPA


Sec.  141.723  Requirements to respond to significant deficiencies 
identified in sanitary surveys performed by EPA.

    (a) A sanitary survey is an onsite review of the water source 
(identifying sources of contamination by using results of source water 
assessments where available), facilities, equipment, operation, 
maintenance, and monitoring compliance of a PWS to evaluate the 
adequacy of the PWS, its sources and operations, and the distribution 
of safe drinking water.
    (b) For the purposes of this section, a significant deficiency 
includes a defect in design, operation, or maintenance, or a failure or 
malfunction of the sources, treatment, storage, or distribution system 
that EPA determines to be causing, or has the potential for causing the 
introduction of contamination into the water delivered to consumers.
    (c) For sanitary surveys performed by EPA, systems must respond in 
writing to significant deficiencies identified in sanitary survey 
reports no later than 45 days after receipt of the report, indicating 
how and on what schedule the system will address significant 
deficiencies noted in the survey.
    (d) Systems must correct significant deficiencies identified in 
sanitary survey reports according to the schedule approved by EPA, or 
if there is no approved schedule, according to the schedule reported 
under paragraph (c) of this section if such deficiencies are within the 
control of the system.

PART 142--NATIONAL PRIMARY DRINKING WATER REGULATIONS 
IMPLEMENTATION

0
8. 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.


0
9. Section 142.14 is amended by adding paragraph (a)(9) to read as 
follows:


Sec.  142.14  Records kept by States.

* * * * *
    (a) * * *

[[Page 786]]

    (9) Any decisions made pursuant to the provisions of part 141, 
subpart W of this chapter.
    (i) Results of source water E. coli and Cryptosporidium monitoring.
    (ii) The bin classification after the initial and after the second 
round of source water monitoring for each filtered system, as described 
in Sec.  141.710 of this chapter.
    (iii) Any change in treatment requirements for filtered systems due 
to watershed assessment during sanitary surveys, as described in Sec.  
141.711(d) of this chapter.
    (iv) The determination of whether the mean Cryptosporidium level is 
greater than 0.01 oocysts/L after the initial and after the second 
round of source water monitoring for each unfiltered system, as 
described in Sec.  141.712(a) of this chapter.
    (v) The treatment processes or control measures that systems use to 
meet their Cryptosporidium treatment requirements under Sec.  141.711 
or Sec.  141.712 of this chapter.
    (vi) A list of systems required to cover or treat the effluent of 
an uncovered finished water storage facility, as specified in Sec.  
141.714 of this chapter.
* * * * *

0
10. Section 142.15 is amended by adding paragraph (c)(6) to read as 
follows:


Sec.  142.15  Reports by States.

    (c) * * *
    (6) Subpart W. (i) The bin classification after the initial and 
after the second round of source water monitoring for each filtered 
system, as described in Sec.  141.710 of this chapter.
    (ii) Any change in treatment requirements for these systems due to 
watershed assessment during sanitary surveys, as described in Sec.  
141.711(d) of this chapter.
    (iii) The determination of whether the mean Cryptosporidium level 
is greater than 0.01 oocysts/L both after the initial and after the 
second round of source water monitoring for each unfiltered system, as 
described in Sec.  141.712(a) of this chapter.
* * * * *

0
11. Section 142.16 is amended by adding paragraph (n) to read as 
follows:


Sec.  142.16  Special primacy conditions.

* * * * *
    (n) Requirements for States to adopt 40 CFR part 141, subpart W. In 
addition to the general primacy requirements elsewhere in this part, 
including the requirements 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 W, must 
contain a description of how the State will accomplish the following 
program requirements where allowed in State programs.
    (1) Approve an alternative to the E. coli levels that trigger 
Cryptosporidium monitoring by filtered systems serving fewer than 
10,000 people, as described in Sec.  141.701(a)(5).
    (2) Assess significant changes in the watershed and source water as 
part of the sanitary survey process and determine appropriate follow-up 
action for systems, as described in Sec.  141.711(d) of this chapter.
    (3) Approve watershed control programs for the 0.5-log treatment 
credit in the microbial toolbox, as described in Sec.  141.716(a) of 
this chapter.
    (4) Approve protocols for demonstration of performance treatment 
credits in the microbial toolbox, as allowed under Sec.  141.718(c) of 
this chapter.
    (5) Approve protocols for alternative ozone and chlorine dioxide CT 
values in the microbial toolbox, as allowed under Sec.  141.720(c) of 
this chapter.
    (6) Approve an alternative approach to UV reactor validation 
testing in the microbial toolbox, as allowed under Sec.  
141.720(d)(2)(iii) of this chapter.
* * * * *
[FR Doc. 06-4 Filed 1-4-06; 8:45 am]
BILLING CODE 6560-50-P