[Federal Register Volume 64, Number 223 (Friday, November 19, 1999)]
[Proposed Rules]
[Pages 63382-63461]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-29067]



[[Page 63381]]

_______________________________________________________________________

Part II





Environmental Protection Agency





_______________________________________________________________________



40 CFR Part 261



Hazardous Waste Identification Rule (HWIR): Identification and Listing 
of Hazardous Wastes; Proposed Rule

  Federal Register / Vol. 64, No. 223 / Friday, November 19, 1999 / 
Proposed Rules  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 261

[FRN-6469-9]
RIN 2050-AE07


Hazardous Waste Identification Rule (HWIR): Identification and 
Listing of Hazardous Wastes

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule and request for comments.

-----------------------------------------------------------------------

SUMMARY: Today's action proposes to retain and amend the mixture rule 
and the derived-from rule in the Resource Conservation and Recovery Act 
(RCRA). The mixture and derived-from rules ensure that hazardous wastes 
that are mixed with other wastes or that result from the treatment, 
storage or disposal of hazardous wastes do not escape regulation and 
thereby cause harm to human health and the environment.
    EPA is proposing two revisions to the mixture and derived-from 
rules. These revisions would narrow the scope of the mixture and 
derived-from rules, tailoring the rules to more specifically match the 
risks posed by particular wastes. The first is an exemption for 
mixtures and/or derivatives of wastes listed solely for the 
ignitability, corrosivity, and/or reactivity characteristics. The 
second is a conditional exemption from the mixture and derived-from 
rules for ``mixed wastes'' (that is, wastes that are both hazardous and 
radioactive).
    Today's document also discusses an implementation framework for an 
exemption from hazardous waste management for wastes that meet 
chemical-specific exemption levels, also known as the Hazardous Waste 
Identification Rule (HWIR) exemption. The HWIR exemption would identify 
a broad set of listed hazardous waste that could be safely managed in 
nonhazardous waste management units. The current version of the model 
that could be used to derive the exemption levels is designed to 
evaluate simultaneous exposures across multiple media and pathways in 
order to estimate the resulting health and environmental effects. 
Before using a revised risk assessment to support a final regulatory 
action, we would propose the HWIR exemption, providing public notice 
and the opportunity to comment on the revised risk assessment and 
resulting exemption levels.
    In addition, today's document discusses the possibility of revising 
the Land Disposal Restrictions (LDRs) by replacing technology-based 
treatment standards in the RCRA regulations with risk-based treatment 
standards.

DATES: To make sure we consider your comments on revisions to the 
mixture and derived-from rules (Sections I-IV, Sections XXI-XXVI (as 
applicable) of the preamble and proposed regulatory language amending 
40 CFR part 261), they must be postmarked on or before February 17, 
2000.
    To make sure we consider your comments on the discussed 
concentration-based HWIR exemption and the possible revisions to the 
LDR Treatment Standards (Sections V-XX and Sections XXI-XXVI (as 
applicable) of the preamble), they must be postmarked on or before May 
17, 2000.

ADDRESSES: Please send an original and two copies of your comments 
referencing Docket number F-99-WH2P-FFFFF to (1) if using regular U.S. 
Postal Service mail: RCRA Docket Information Center, Office of Solid 
Waste (5305W), U.S. Environmental Protection Agency Headquarters (EPA, 
HQ), 401 M Street, S.W., Washington, D.C.. 20460, or (2) if using 
special delivery, such as overnight express service: RCRA Docket 
Information Center (RIC), Crystal Gateway One, 1235 Jefferson Davis 
Highway, First Floor, Arlington, Virginia 22202. It would also be 
helpful, although not mandatory, to include an electronic copy by 
diskette or Internet email. In this case, send your comments to the 
RCRA Information Center on labeled personal computer diskettes in ASCII 
(TEXT) format or a word processing format we can convert to ASCII 
(TEXT). Please include on the disk label the name, version, and edition 
of your word processing software as well as your name and docket number 
F-99-WH2P-FFFF. Protect your diskette by putting it in a protective 
mailing envelope. To send a copy by Internet email, address it to: 
[email protected]. Make sure this electronic copy is in an 
ASCII format that doesn't use special characters or encryption. Cite 
the docket Number F-99-WH2P-FFFFF in your electronic file.
    The RCRA Information Center is located at Crystal Gateway One, 1235 
Jefferson Davis Highway, First Floor, Arlington Virginia. If you would 
like to look at and copy supporting information for RCRA rules, please 
make an appointment with the RCRA Information Center by calling (703) 
603-9230. Docket hours are from 9 A.M. to 4 P.M. Monday through Friday, 
except for Federal holidays. You may copy up to 100 pages from any 
regulatory document at no cost. Additional copies cost $0.15 per page.

FOR FURTHER INFORMATION CONTACT: For general information about this 
proposed rule, contact the RCRA Hotline, Office of Solid Waste, U.S. 
Environmental Protection Agency, Washington, DC 20460, (800) 424-9346 
(toll free); TDD (800) 553-7672 (hearing impaired); in the Washington, 
D.C. metropolitan area the number is (703) 412-9810; TDD (703) 486-3323 
(hearing impaired). For technical information on this proposed rule, 
contact Adam Klinger at (703) 308-3267 or Tracy Atagi at (703) 308-
8672; for specific information on the risk modeling system, contact 
David Cozzie at (703) 308-0479. To get copies of the reports or other 
materials referred to in this proposal, contact the RCRA Docket at the 
phone number or address listed above.

SUPPLEMENTARY INFORMATION: The proposal and other material associated 
with this action can be electronically accessed on the Internet at 
http://www.epa.gov/epaoswer/hazwaste/id
    The official record for this rulemaking will be kept in paper form. 
Accordingly, EPA will transfer all comments received electronically 
into paper form and place them in the official record, which will also 
include all comments submitted directly in writing. The official record 
is the record maintained at the address in ADDRESSES at the beginning 
of this document.
    We will respond to submitted comments, whether written or 
electronic, in a notice in the Federal Register or in a response to 
comments document placed in the official record for this rulemaking. We 
will not immediately reply to electronically submitted comments other 
than to seek clarification of comments that may be garbled in 
transmission or during conversion to paper form, as discussed above.

Affected Entities

    Entities potentially affected by this proposed action are 
generators of industrial hazardous waste, and entities that treat, 
store, transport and/or dispose of these wastes. Different sets of 
entities (i.e., industrial and service sectors) are affected by 
different provisions of this regulatory proposal, as displayed below: 
This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be affected by this 
action.

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------------------------------------------------------------------------
                                                    List of potentially
           SIC code                 NAICS code         affected U.S.
                                                    industrial entities
------------------------------------------------------------------------
A. Proposed Revision to 40 CFR
 261.3 RCRA Mixture-and-
 Derived-from Rules:
    2800......................  32xxxx...........  Chemicals & allied
                                                    products
                                                    manufacturing.
    2819......................  Five possible      Industrial inorganic
                                 codes.             chemicals
                                                    manufacturing.
    2821......................  325211...........  Plastics materials &
                                                    resins
                                                    manufacturing.
    2833......................  325411...........  Medicinal chemicals &
                                                    botanicals
                                                    manufacturing.
    2834......................  325412...........  Pharmaceutical
                                                    preparations
                                                    manufacturing.
    2851......................  32551............  Paints & allied
                                                    products
                                                    manufacturing.
    2869......................  Five possible      Industrial organic
                                 codes.             chemicals
                                                    manufacturing.
    2879......................  32532............  Pesticides &
                                                    agricultural
                                                    chemicals
                                                    manufacturing.
    3089......................  Four possible      Plastics products
                                 codes.             manufacturing.
    3241......................  32731............  Hydraulic cement
                                                    products
                                                    manufacturing.
    3479......................  Four possible      Fabricated metal
                                 codes.             coating & allied
                                                    services.
    3711......................  Five possible      Motor vehicle &
                                 codes.             passenger car bodies
                                                    manufacturing.
    4212......................  562111 & 562112..  Local trucking
                                                    services (industrial
                                                    waste shipment).
    4953......................  Five possible      Refuse (industrial
                                 codes.             waste) treatment/
                                                    disposal services.
    7389......................  36 possible codes  Business services.
    7532......................  811121...........  Auto repair & auto
                                                    paint shops.
    9511......................  92411............  Waste management.
    9711......................  811121...........  National security
                                                    (military bases).
------------------------------------------------------------------------
Explanatory Notes:
(1) SIC = 1987 Standard Industrial Classification system (U.S.
  Department of Commerce's traditional code system last updated in
  1987).
(2) NAICS = 1997 North American Industrial Classification System (U.S.
  Department of Commerce's new code system as of 1997).
(3) Refer to the Internet website http://www.census.gov/epcd/www/
naicsdev.htm for additional information and a cross-walk table for the
  SIC and NAICS codes systems.

    This table lists those entities that EPA believes could be affected 
by this proposed action, based on industrial sectors identified in the 
economic analysis in support of this proposal. A total of about 120 
entities are expected to benefit from the proposed revisions to 40 CFR 
261.3 in the 17 industrial sectors listed above, but primarily in the 
chemicals and allied products sector (i.e., SIC code 28, or NAICS code 
325). Other entities not listed in the table also could be affected. To 
determine whether your facility is regulated by this action, you should 
examine 40 CFR parts 260, 261 and 268 carefully in concert with the 
amended rules found at the end of this Federal Register document. If 
you have questions regarding the applicability of this action to a 
particular entity, consult the persons listed in the preceding FOR 
FURTHER INFORMATION CONTACT section.

                                Acronyms
------------------------------------------------------------------------
           Acronym                             Definition
------------------------------------------------------------------------
3MRA.........................  Multimedia, Multipathway and
                                Multireceptor Risk Assessment.
AOI..........................  Area of Interest.
APA..........................  Administrative Procedures Act.
AT...........................  Aerated Tank.
BDAT.........................  Best Demonstrated Available Technology.
CERCLA.......................  Comprehensive Environmental Response,
                                Compensation and Liability Act.
CFR..........................  Code of Federal Regulations.
CMA..........................  Chemical Manufacturers Association.
CWA..........................  Clean Water Act.
DOT..........................  Department of Transportation.
EPA..........................  Environmental Protection Agency.
EPACMTP......................  EPA's Composite Model for Leachate
                                Migration with Transformation Products.
EXAMS........................  Exposure Analysis Modeling System.
EXAMSIO......................  Exposure Analysis Modeling System--Input
                                Output Interface.
FRAMES.......................  Framework for Risk Analysis in Multimedia
                                Environmental Systems.
GIRAS........................  Geographic Information Retrieval and
                                Analysis System.
HEAST........................  Health Effects Assessment Summary Table.
HQ...........................  Hazard Quotient.
HSWA.........................  Hazardous and Solid Waste Amendments of
                                1984.
HWIR.........................  Hazardous Waste Identification Rule.
HWIR99.......................  Hazardous Waste Identification Rule--1999
                                Framework.
ICR..........................  Information Collection Request.
IEUBK........................  Integrated, Exposure, Uptake and
                                BioKinetic Model.
IRIS.........................  Integrated Risk Information System.
ISCST3.......................  Industrial Source Complex Short Term
                                model.
LAU..........................  Land Application Unit.
LCR..........................  Lead and Copper Rule.
LDR..........................  Land Disposal Restriction.
LF...........................  Landfill.
LLMW.........................  Low Level Mixed Wastes.
LLRWDF.......................  FLow Level Radioactive Waste Disposal
                                Facility.
LOEL.........................  Lowest Observed Effects Level.

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MACT.........................  Maximum Achievable Control Technology.
MCL..........................  Maximum Containment Level.
MINTEQA2.....................  Geochemical speciation model; originally
                                a combination of Mineral Equilibrium
                                Model (MINEQL) and the thermodynamic
                                database WATEQ3.
NAPL.........................  Non-Aqueous Phase Liquid.
NOEL.........................  No Observed Effects Level.
NRC..........................  Nuclear Regulatory Commission (NRC).
NTTAA........................  National Technology Transfer and
                                Advancement Act.
OMB..........................  Office of Management and Budget.
ORD..........................  Office of Research and Development.
OIRM.........................  Office of Information and Resources
                                Management.
OSW..........................  Office of Solid Waste.
OSWER........................  Office of Solid Waste and Emergency
                                Response.
PBMS.........................  Performance Based Measurement System.
QA/QCl.......................  Quality Assurance/Quality Control.
RCRA.........................  Resource Conservation Recovery Act.
RfD..........................  Reference Dose.
RfC..........................  Reference Concentration.
RIC..........................  RCRA Docket Information Center.
RMS..........................  Root Mean Square.
SAB..........................  Science Advisory Board.
SAMSON.......................  Solar and Meteorological Surface
                                Observation Network.
SBREFA.......................  Small Business Regulatory Enforcement
                                Fairness Act.
SCIM.........................  Sampled Chronological Input Model.
SI...........................  Surface Impoundment.
SPARC........................  System Performs Automated Reasoning in
                                Chemistry.
SSLs.........................  Soil Screening Levels.
SVOC.........................  Semi-Volatile Organic Compound.
SZM..........................  Saturated Zone Module.
TC...........................  Toxicity Characteristic.
TCLP.........................  Toxicity Characteristic Leaching
                                Procedure.
TDD..........................  Telecommunications Device for the Deaf.
TOC..........................  Total Organic Carbon.
TRI..........................  Toxic Release Inventory.
TSCA.........................  Toxic Substance Control Act.
TSDF.........................  Treatment, Storage, and Disposal
                                Facility.
TSS..........................  Total Suspended Solid.
UMRA.........................  Unfunded Mandates Reform Act.
USLE.........................  Universal Soil Loss Equation.
UTS..........................  Universal Treatment Standards.
VO...........................  Volatile Organics.
VOC..........................  Volatile Organic Compounds.
VZM..........................  Vadose Zone Module.
WMU..........................  Waste Management Unit.
WP...........................  Waste Pile
------------------------------------------------------------------------

Outline

Background

I. Under what legal authority is EPA proposing these regulatory 
changes?
II. What is EPA proposing today and on what other actions is EPA 
seeking comment?

Retaining the Mixture and Derived-From Rules

III. Why is EPA proposing to retain the mixture and derived-from 
rules?

Proposed Revisions to 40 CFR 261.3

IV. How and why is EPA proposing to revise the hazardous waste 
identification regulations for mixtures and derived-from wastes?

HWIR Exemption Options

V. Why is EPA developing a chemical-based HWIR exemption for listed 
hazardous waste (including both mixtures and derived-from waste)?
VI. What options is EPA developing for the HWIR exemption?
VII. What wastes would be eligible for an HWIR exemption?
VIII. What level of governmental review would be needed for an HWIR 
exemption claim?
IX. For the generic HWIR exemption, what steps would I follow before 
my waste could be exempted?
X. Once the waste becomes exempt, what RCRA requirements might still 
apply?
XI. For the generic HWIR exemption, what conditions and requirements 
would I be required to fulfill to maintain the exemption?
XII. What would be the conditions and requirements for the landfill-
only HWIR exemption?
XIII. What would happen if I do not comply with the conditions and 
the requirements of the HWIR exemption?
XIV. What might the regulatory language for the HWIR exemption look 
like?

HWIR Risk Assessment

XV. What is the goal of the HWIR risk assessment?
XVI. How did EPA develop the current version of the HWIR risk 
assessment?
XVII. What are the results of the current version of the risk 
assessment?
XVIII. How was the HWIR exemption list of chemicals developed?
XIX. How would EPA use the results of the risk assessment to set 
HWIR exemption levels?

Possible Revision to LDR Treatment Standards

XX. How might EPA use the results of the HWIR model to revise the 
hazardous waste LDR treatment standards?

Economic Impacts

XXI. What are the economic impacts of today's proposed regulatory 
changes?

[[Page 63385]]

Relationship to Other Programs

XXII. How would the HWIR exemption relate to other programs?
    A. Would HWIR change how you determine if a waste is hazardous?
    B. Could a characteristic hazardous waste be exempt under HWIR?
    C. How would the HWIR exemption differ from the delisting 
process per 40 CFR 260.22?
    D. How would HWIR affect TSDF closure requirements for my 
facility?
    E. How would HWIR affect the Land Disposal Restriction (LDR) 
Program?
    F. How would HWIR relate to the RCRA air emission standards?
    G. Would HWIR affect ``Use Constituting Disposal'' regulations?
    H. Could hazardous waste debris become under HWIR?
    I. Would contaminated media be eligible for an HWIR exemption?
    J. Does the final HWIR-Media Rule impact HWIR?
    K. How would HWIR impact actions under the Superfund program 
(CERCLA)?
    L. How does HWIR relate to the draft Industrial D Voluntary 
Guidance?
    M. How does HWIR relate to the Comparable Fuels Exemption?
    N. How would HWIR affect mixed waste?
    O. How does HWIR relate to the Sewage Sludge Regulatory Program?

State Authorization

XXIII. How would today's proposed regulatory changes be administered 
and enforced in the States?

Administrative Requirements

XXIV. How has EPA fulfilled the administrative requirements for this 
proposed rulemaking?
    A. Executive Order 12866: Determination of Significance
    B. Regulatory Flexibility Act
    C. Paperwork Reduction Act (Information Collection Request)
    D. Unfunded Mandates Reform Act
    E. Executive Orders on Federalism
    F. Executive Order 13084: Consultation and Coordination with 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from 
Environmental Health Risks and Safety Risks
    H. National Technology Transfer and Advancement Act of 1995

References

XXV. What are some key documents containing information supporting 
this notice?

Request for Comment

XXVI. On what issues is EPA specifically seeking public comment?

Background

I. Under What Legal Authority Is EPA Proposing These Regulatory 
Changes?

    These regulations are proposed under the authority of Sections 
2002(a), 3001, 3002, 3004, and 3006 of the Solid Waste Disposal Act of 
1970, as amended by the Resource Conservation and Recovery Act of 1976 
(RCRA), as amended by the Hazardous and Solid Waste Amendments of 1984 
(HSWA), 42 U.S.C. Sec. 6912(a), 6921, 6922, 6924, 6926.

II. What Is EPA Proposing Today and on What Other Actions Is EPA 
Seeking Comment?

A. What Is Included In Today's Notice?
    Today EPA:
    1. Proposes to retain the mixture and derived-from rules, currently 
set forth in 40 CFR 261.3(a)(2)(iii), 261.3(a)(2)(iv) and 
261.3(c)(2)(i). As explained in Section III, these rules, which are 
currently in effect on an emergency basis, regulate wastes that are 
mixed with, or are derived from the treatment, storage, or disposal of, 
listed hazardous wastes.
    2. Proposes to narrow the scope of the mixture and derived-from 
rules by exempting mixtures and derivatives of wastes listed solely for 
the ignitability, corrosivity, and/or reactivity characteristics which 
no longer exhibit any characteristic of hazardous waste and comply with 
land disposal restrictions applicable to characteristic wastes.
    3. Discusses an implementation framework for two exemptions from 
Subtitle C management requirements for wastes meeting a set of 
conditions and procedures. The two options are:
    (a) A ``generic'' exemption that has no specific requirements as to 
how the waste is managed once conditions of the exemption are met; and
    (b) a ``landfill-only'' exemption that limits the subsequent 
management of the exempted waste to disposal in a landfill and 
prohibits placement on the land before disposal;
    4. Discusses the current version of the risk assessment that EPA 
intends to use to create exemption levels to be used in the 
implementation framework; and
    5. Discusses whether to revise the Land Disposal Restrictions by 
replacing the technology-based treatment standards in 40 CFR 268.40 and 
268.48 with risk-based treatment standards.
B. What Related Regulatory Action Is EPA Also Proposing Elsewhere in 
Today's Federal Register?
    In a separate proposal published elsewhere in the Federal Register 
today, we are also proposing to conditionally exempt hazardous waste 
mixed with low-level radioactive wastes (low-level mixed wastes, or 
LLMW) or mixed with Naturally Occurring and/or Accelerator-produced 
Radioactive Material (NARM mixed waste) from the storage, 
transportation, and disposal requirements of RCRA. Treated LLMW and 
NARM mixed waste would be exempt from RCRA hazardous waste 
transportation and disposal facility requirements if it is disposed at 
a low level radioactive waste disposal facility (LLRWDF) regulated by 
the Nuclear Regulatory Commission (NRC). In addition, we are also 
proposing that untreated LLMW and NARM mixed waste generated by the NRC 
licensees may be stored according to NRC regulations instead of RCRA 
hazardous waste storage regulations.
C. What Is EPA's Legal Obligation With Respect to This Proposal?
    Our legal obligation for this proposal stems from EPA's fiscal year 
1993 appropriation act, which required EPA to revise the mixture and 
derived-from rules, 40 CFR 261.3(a)(2)(iv) and 40 CFR 261.3(c)(2)(i), 
by October 1, 1994. (Pub. L. No. 102-389, 106 Stat. 1571). Congress 
made the deadline enforceable under RCRA's citizen suit provision, 
section 7002, 42 U.S.C. Sec. 6972. We did not meet this deadline for 
revisions, and in early October 1994 several groups of waste generating 
and waste managing industries filed suits to enforce the deadline.
    Two of the cases were consolidated and a third was dismissed with 
the plaintiffs being added as intervenors to the consolidated cases. 
Environmental Technology Council v. Browner, C.A. No. 94-2346 
(TFH)(D.D.C.). The U.S. District Court for the District of Columbia 
entered a consent decree resolving the consolidated cases on May 3, 
1993. The consent decree, as subsequently amended, required the 
Administrator to sign a proposal to revise the mixture and derived-from 
rules by November 13, 1995 and a notice of final action on the proposal 
by February 13, 1997. The decree reflects the parties' understanding 
that EPA's leading option was developing a multipathway risk assessment 
to establish constituent-specific, risk-based ``exit levels'' for 
listed hazardous wastes. It does not, however, specify what types of 
revisions EPA needs to propose or promulgate. On November 13, 1995, the 
Administrator signed the proposed Hazardous Waste Identification Rule 
(HWIR) to revise the mixture and derived-from rules. This proposal was 
published in the Federal Register on December 21, 1995. (60 FR 66344). 
It proposed a set of exemption levels for hundreds of hazardous 
constituents. Many of these exemption levels were based on a complex 
multipathway risk assessment. The notice also proposed to revise the 
derived-from rule to provide relief for

[[Page 63386]]

hazardous wastes listed because they exhibited the characteristics of 
ignitability, corrosivity and/or reactivity, and solicited comment on 
the concept of providing a separate exemption for hazardous wastes 
mixed with low level radioactive wastes.
    We received extensive comments, many critical, on the 1995 HWIR 
proposal, particularly with respect to the scientific risk assessment. 
We continued to view risk-based exemption levels based on a 
multipathway risk assessment as our preferred option. We concluded that 
considerable work needed to be done to resolve the complex scientific 
and technical issues raised in the comments. We negotiated with the 
parties to extend the deadlines in the decree to allow us time to 
address these issues. On April 11, 1997, the District Court entered an 
order amending the consent decree in Environmental Technology Council 
v. Browner.
    The amended decree revised the deadlines for a revision to the 
mixture and derived-from rules, with an October 31, 1999 deadline for 
the Administrator to sign a proposal, and an April 30, 2001 deadline to 
sign a notice taking final action. The amended decree also included 11 
different provisos that we are obligated to make our best efforts to 
address. They require EPA to solicit comment on a number of issues 
related to risk assessment and to the implementation scheme we were 
developing for the exemption levels that the risk assessment would 
support. Today's rulemaking, in conjunction with the mixed waste 
proposal, also to be published today, fulfills our obligations under 
the consent decree.
    Specifically, the amended consent decree required EPA to sign a 
notice proposing revisions to the mixture and derived-from rules in 40 
CFR 261.3(a)(2(iv) and (c)(2)(i), and request comment on the 11 
provisos listed in the decree. The consent decree reflected EPA's 
intent to further study three broad areas regarding hazardous 
constituents in hazardous waste and to establish a constituent-based 
exemption from hazardous waste regulation for low-risk wastes currently 
subject to RCRA subtitle C regulation. It also reflected EPA's intent 
to ``make best efforts'' to describe and discuss the items in the 11 
provisos.
    The three areas of study were: (a) Modeling of anaerobic 
biodegradation of hazardous constituents in the saturated zone, (b) the 
physical relationship between waste concentrations and leachate 
concentrations, and of mass limitations in leachate, and (c) the use of 
additional toxicity data from sources outside EPA. Seven of the 11 
provisos concerned particular issues for EPA to study with respect to 
these three areas of study. Three provisos concerned options for 
implementing the exemption levels EPA expected to derive from the 
modeling. Finally, one proviso concerned an exemption from hazardous 
waste regulation for certain radioactive hazardous mixed wastes 
generated by nuclear power plants that are subject to regulation by the 
Nuclear Regulatory Commission (or states authorized to implement those 
regulations).
    As contemplated in the consent decree, we developed a new model to 
analyze hazardous constituents in hazardous waste. We addressed the 
seven modeling-related issues listed in the provisos, either by 
incorporating steps in the model to produce data with respect to those 
issues, or by studying the issues and concluding that it was not 
possible to include them in a model at this time (see Sections XV to 
XIX). We addressed the three implementation-related provisos by 
developing a plan to implement a program to exempt certain waste 
currently regulated as hazardous waste under RCRA subtitle C from full 
hazardous waste regulation, based on meeting risk-based exemption 
levels for hazardous constituents (see Sections V to XIV). Finally, as 
stated above, the mixed waste provision is addressed in a separate 
notice of proposed rulemaking.
    Despite a concerted, sustained effort, we did not succeed in 
developing within the consent decree time frame a risk assessment 
capable of generating reliable exemption levels. We concluded that we 
could not implement our preferred option by the October 31 deadline for 
proposed revisions. Moreover, we were not sure how much additional time 
we would need to address the remaining modeling issues. We concluded 
that we would better serve the public interest and better utilize our 
rulemaking resources by proceeding with the options that were ready for 
proposal rather than seeking another deadline extension for the 
purposes of resolving the complex technical issues presented by the 
risk assessment. Therefore, we decided to propose (1) Revisions to the 
mixture rule for wastes listed because they exhibit the characteristics 
of ignitability, corrosivity, and/or reactivity described in Section IV 
below, and (2) a set of conditional exemptions from various Subtitle C 
regulations (including the mixture and derived-from rules) for certain 
low-level radioactive wastes as described in the separate proposal 
published elsewhere today, including the conditional exemptions from 
the mixture and derived-from rules proposed here today.
D. How Does Today's Notice Relate to the 1995 HWIR Proposal?
    In 1995, we published an HWIR proposal that included revisions to 
the mixture and derived-from rules and a discussion of exemptions 
similar to the HWIR exemption scenarios discussed in today's notice (60 
FR 66344 (December 21, 1995)). Comments we received on the HWIR95 
proposal have been invaluable in crafting today's notice, particularly 
in revising the risk assessment, and we will formally respond to those 
comments, as well as to comments on today's notice, when we promulgate 
a final rule. Today's notice is technically a supplement to HWIR95. 
However, because it has been four years since the 1995 HWIR proposal, 
we have written today's notice as a stand alone proposal. You do not 
have to read the 1995 proposal to understand today's notice.
E. What Other Regulatory Options Have Been Received From EPA 
Stakeholders?
    In August 1999, we received a paper from the Chemical Manufacturers 
Association (CMA) describing five additional regulatory options, 
including suggested regulatory language, for revising the mixture and 
derived-from rules (see Memorandum from Dorothy Kellogg, CMA to 
Elizabeth Cotsworth, Acting Director, Office of Solid Waste, August 
1999). CMA forwarded these options seeking regulatory relief for some 
specific high-volume wastes that they believe are low-risk and feel 
that EPA could propose to exempt with very little delay. Although we 
have not had time to analyze these options, we would like to present 
them here for others to provide their views.
    Three of these options involve exempting from the hazardous waste 
derived-from rule: (1) Residues from the combustion of listed hazardous 
waste, (2) leachate from the land disposal of listed hazardous waste 
(that is subsequently managed in a system regulated under the Clean 
Water Act), and (3) sludges from the biological treatment of listed 
hazardous wastewaters. In each of these cases, CMA argues that the 
wastes are both physically and chemically dissimilar from the wastes 
that were originally listed. In addition, CMA notes that combustion and 
biological treatment can greatly reduce or eliminate organic chemicals. 
Under the options presented in CMA's discussion papers, each of these 
wastes would not be hazardous, even though they are generated from the

[[Page 63387]]

treatment, storage or disposal of hazardous waste, unless they exhibit 
one or more of the hazardous waste characteristics of 40 CFR Part 
261.3.
    CMA's paper does not, however, explicitly address how LDR treatment 
standards would apply to these residues. Especially in the case of the 
ash and wastewater treatment sludge, which would often result from LDR 
treatment, if the wastes do not meet the LDR standards, then there 
would be a question of whether further treatment to meet LDRs would be 
required.
    EPA has already been considering another possible approach for 
addressing combustion residues, which would list these derived-from 
wastes under their own multi-source listing code, similar to multi-
source leachate (F039). This listing would continue to regulate these 
wastes as hazardous, but application of other requirements could be 
tailored to fit the physical and chemical properties of these wastes. 
EPA is developing an Advance Notice of Proposed Rule Making (ANPRM) 
that would discuss the idea of a new listing for combustion residues. 
More information on this ANPRM (SAN No. 4093) can be found in the most 
recent agenda of regulatory and deregulatory actions (64 FR 21987 
(April 26, 1999)).
    In their materials, CMA has forwarded specific changes to 
regulatory language currently in effect and found in the Code of 
Federal Regulations (CFR). EPA has not evaluated this language and 
presents it here to enhance public dialogue on these ideas. CMA 
suggests that we modify 40 CFR 261.3(c)(2)(ii) and add the following 
language:
    ``[1] Wastes derived from burning any listed hazardous waste in a 
permitted or interim status hazardous waste combustion device; [2] 
Leachate derived from landfills or land treatment units containing 
listed hazardous waste, which is managed in a wastewater treatment 
system the discharge of which is subject to regulation under either 
section 402 or section 307(b) of the Clean Water Act (including 
wastewater at facilities which have eliminated the discharge of 
wastewater); [3] Wastes derived from the aggressive biological 
treatment of listed hazardous wastewaters in a wastewater treatment 
systems the discharge of which is subject to regulation under either 
section 402 or section 307(b) of the Clean Water Act (including 
wastewater at facilities which have eliminated the discharge of 
wastewater).''
    The other two options presented in the paper involve specific 
wastes that result from the mixture of hazardous wastes with solid 
wastes. One option involves an expansion of the current ``headworks'' 
exemption in 40 CFR 261.3(a)(2)(iv)(A) and (B). The headworks exemption 
exempts from the mixture rule wastewaters containing small quantities 
of particular F-listed solvents, based on the mass-balance flow of 
these solvents through the headworks of industrial wastewater treatment 
systems. CMA's options paper requests that this exemption be amended in 
three ways.
    First, CMA's suggested revision would allow direct monitoring of 
the actual concentration of spent solvents in untreated wastewater to 
demonstrate compliance. The current requirement is to perform a weekly 
mass balance of the solvents entering the system. Losses due to 
volatilization must be counted in the mass balance determination under 
the current system. We note that CMA's suggested wastewater monitoring 
would provide accurate data at the point the wastewater enters the 
treatment system, but the losses due to volatilization would not be 
counted in this approach.
    Second, under the revised headworks exemption, benzene, 2-
ethoxyethanol, 2-nitropropane, and 1,1,2-trichloroethane would be 
incorporated into the list of chemicals. These four chemicals were 
added to the 261.31 list of spent solvents in 1986 but the exemption 
does not currently include these chemicals.
    Third, under the revised headworks exemption, multi-source leachate 
(F039) derived solely from the disposal of the spent solvents listed in 
40 CFR 261.31 would be eligible for the exemption.
    Again, CMA has forwarded specific changes to regulatory language 
currently in effect and found in the Code of Federal Regulations (CFR). 
EPA has not evaluated this language and presents it here to enhance 
public dialogue on these ideas. CMA suggests that we modify 40 CFR 
261.3(a)(2)(iv)(A) and (B) to read as follows:
    ``40 CFR 261.3(a)(2)(iv)(A). One or more of the following 
solvents listed in Sec. 261.31--carbon tetrachloride, 
tetrachloroethylene, trichloroethylene [add solvents that meet the 
standards to be included in this paragraph], including multi-source 
leachate derived from the disposal of these solvents and no other 
listed hazardous wastes--Provided, That either the actual 
concentration of these solvents or the maximum total weekly usage of 
these solvents (other than the amounts that can be demonstrated not 
to be discharged to wastewater) divided by the average weekly flow 
of wastewater into the headworks of the facility's wastewater 
treatment or pretreatment system does not exceed 1 part per million; 
or * * *
    40 CFR 261.3(a)(2)(iv)(B). One or more of the following solvents 
listed in Sec. 261.31--methylene chloride, 1,1,1-trichloroethane, 
chlorobenzene, o-dichlorobenzene, cresols, cresylic acid, nitrobenzene, 
toluene, methyl ethyl ketone, carbon disulfide, isobutanol, pyridine, 
spent chlorofluorocarbon solvents [add solvents that meet the standards 
to be included in this paragraph], including multi-source leachate 
derived from the disposal of these solvents and no other listed 
hazardous wastes--Provided, That either the actual concentration of 
these solvents or the maximum total weekly usage of these solvents 
(other than the amounts that can be demonstrated not to be discharged 
to wastewater) divided by the average weekly flow of wastewater into 
the headworks of the facility's wastewater treatment or pretreatment 
system does not exceed [25] part per million; or * * *''
    These modifications add 4 chemicals to either paragraph (A) or (B), 
include leachate derived from the disposal of these solvents and no 
other listed hazardous waste and allow for the demonstration by direct 
measurement that concentrations do not exceed the specified levels. 
Note the 25 ppm threshold specified in 40 CFR 261.3(a)(2)(iv)(B) is the 
threshold within current regulations, and we do not believe it was 
CMA's intention to alter this level to 1 ppm, the level stated in their 
materials.
    The other regulatory option involving hazardous waste mixtures 
would be an expansion of a current exemption for ``de minimis'' losses 
that result from the manufacture of commercial chemical product. The 
current exemption, found in 40 CFR 261.3(a)(2)(iv)(D), exempts from the 
mixture rule small losses of a commercial chemical product that can 
result from normal handling of the chemicals during the manufacturing 
process. The existing exemption applies to some but not all hazardous 
wastes listed in 40 CFR 261.33 (see 46 FR 56586). CMA's suggested 
expansion of this option would also exempt small losses from the normal 
handling of all listed hazardous wastes (instead of just the handling 
of commercial chemical products). One rationale for the current ``de 
minimis'' exemption is that a facility has little economic incentive to 
allow spills, leaks or other losses of commercial products. With 
respect to wastes, CMA believes that tank and container and air 
emission management standards of 40 CFR Parts 264 and 265, Subparts I, 
J, BB, and CC serve to encourage safe management of these wastes.

[[Page 63388]]

    Specific changes forwarded by CMA would modify 40 CFR 
261.3(a)(2)(iv)(D). EPA has not evaluated this language and presents it 
here to enhance public dialogue on these suggestions. Their language 
reads as follows:
    ``40 CFR 261.3(a)(2)(iv)(D). One or more hazardous wastes listed 
in Subpart D, arising from de minimis losses of these materials from 
manufacturing and related operations in which these materials are 
generated. For purposes of paragraph (a)(2)(iv)(D), ``de minimis'' 
losses include those from normal material handling operations (e.g., 
spills from the unloading or transfer of materials from bins or 
other containers, leaks from pipes, valves or other devices used to 
transfer materials); minor leaks of process equipment, storage tanks 
or containers; leaks from well maintained pump packings and seals; 
sample purging; relief device discharges; discharges from safety 
showers and rinsing and cleaning of personal safety equipment; and 
rinsate from empty containers or from containers that are rendered 
empty by that rinsing; or''
    Note that the phrase ``One or more hazardous wastes listed in 
Subpart D'' replaces the more narrow eligibility contained in the 
current regulation as ``a discarded commercial chemical product, or 
chemical intermediate listed in 261.33.'' Also note the origin of these 
wastes has been made broader by the inclusion of the term ``generated'' 
replacing the phrase ``used as raw materials or are produced in the 
manufacturing process.''
    We request comment on the merits and drawbacks of all these 
possible revisions to the mixture and derived-from rules and on how LDR 
standards should apply. We also request any data that may help us to 
further evaluate (a) the potential risks to human health and the 
environment, (b) any special or unique technical considerations, and 
(c) the economic effects of each of the possible revisions.

Retaining the Mixture and Derived-From Rules

III. Why Is EPA Proposing To Retain the Mixture and Derived-From Rules?

A. What Are the Mixture and Derived-From Rules?
    The mixture and derived-from rules are a part of the RCRA 
regulations that define which wastes are considered to be hazardous and 
therefore subject to RCRA Subtitle C regulations. The mixture rule 
discussed in today's notice refer specifically to 40 CFR 
261.3(a)(2)(iii) and (iv). Under the mixture rule, a solid waste 
becomes regulated as a hazardous waste if it is mixed with one or more 
listed hazardous wastes The derived-from rule discussed in today's 
notice refers specifically to 40 CFR 261.3(c)(2)(i). Under the derived-
from rule, any solid waste generated from the treatment, storage, or 
disposal of a hazardous waste remains regulated as a hazardous waste. 
These derived-from wastes include wastes such as sludges, spill 
residues, ash, emission control dust, and leachate.
B. What Is the Legal History of the Mixture and Derived-From Rules?
    EPA promulgated the mixture and derived-from rules in 1980 as part 
of the comprehensive ``cradle to grave'' requirements for managing 
hazardous waste. 45 FR 33066 (May 19, 1980). Numerous industries that 
generate hazardous wastes challenged the 1980 mixture and derived-from 
rules in Shell Oil Co. v. EPA, 950 F. 2d 741 (D.C. Cir. 1991). In 
December 1991 the D.C. Circuit Court of Appeals vacated the rules 
because they had been promulgated without adequate notice and 
opportunity to comment. The court, however, suggested that EPA might 
want to consider reinstating the rules pending full notice and comment 
in order to ensure continued protection of human health and the 
environment.
    In response to this decision, we promulgated an emergency rule 
reinstating the mixture and derived-from rules as interim final rules 
without providing notice and opportunity to comment. 57 FR 7628 (March 
3, 1992). We also promulgated a ``sunset provision'' which provided 
that the mixture and derived-from rules would remain in effect only 
until April 28, 1993. Shortly after, we published a proposal containing 
several options for revising the mixture and derived-from rules. See 57 
FR 21450 (May 20, 1992). The May 1992 proposal and the time pressure 
created by the ``sunset provision'' generated significant controversy. 
In response, Congress included in EPA's FY1993 appropriation several 
provisions addressing the mixture and derived-from rules. Pub. L. No. 
102-389, 106 Stat. 1571. First, Congress nullified the sunset provision 
by providing that EPA could not promulgate any revisions to the rules 
before October 1, 1993, and by providing that the reinstated 
regulations could not be ``terminated or withdrawn'' until revisions 
took effect. However, to ensure that we could not postpone the issue of 
revisions indefinitely, Congress also established a deadline of October 
1, 1994 for the promulgation of revisions to the mixture and derived-
from rules. Congress made this deadline enforceable under RCRA's 
citizen suit provision, section 7002.
    On October 30, 1992, we published two notices, one removing the 
sunset provision, and the other withdrawing the May 1992 proposal. (See 
57 FR 49278, 49280). We had received many comments criticizing the May 
1992 proposal. The criticisms were due, in a large part, to the very 
short schedule imposed on the regulation development process itself. 
Commenters also feared that the proposal would result in a 
``patchwork'' of differing State programs because some states might not 
adopt the revisions. This fear was based on the belief that States 
would react in a negative manner to the proposal and refuse to 
incorporate it into their programs if finalized. Finally, many 
commenters also argued that the risk assessment used to support the 
proposed exemption levels failed to provide adequate protection of 
human health and the environment because it evaluated only the risks of 
human consumption of contaminated groundwater and ignored other 
pathways that could pose greater risks. Based on these concerns, and 
based on EPA's desire to work through the individual elements of the 
proposal more carefully, we withdrew the proposal.
    Subsequently, a group of waste generating industries challenged the 
March 1992 action that reinstated the mixture and derived-from rules 
without change. Mobil Oil Corp. v. EPA, 35 F.3d 579 (D.C. Cir. 1994). 
The court rejected this challenge, adopting our argument that the 
appropriations act made the challenge moot because it prevented both us 
and the courts from terminating or withdrawing the interim rules before 
we revised them, even if we failed to meet the statutory deadline for 
the revisions.
    We did not meet Congress' October 1, 1994 deadline for revising the 
mixture and derived-from rules. In early October 1994 several groups of 
waste generating and waste managing industries filed citizen suits to 
enforce the October 1, 1994 deadline for revising the mixture and 
derived-from rules. The U.S. District Court for the District of 
Columbia entered a consent decree resolving the consolidated cases on 
May 3, 1993. Environmental Technology Council v. Browner, C.A. No. 94-
2119 (TFH) (D.D.C. 1994). The consent decree originally required the 
Administrator to sign a proposal to amend the mixture and derived-from 
rules by November 13, 1995 and a notice of final rulemaking by December 
15, 1996, and specified that the deadlines in the appropriations act do 
not apply to any rule revising the

[[Page 63389]]

separate regulations that establish jurisdiction over media 
contaminated with hazardous wastes. On November 13, 1995, the 
Administrator signed the proposed Hazardous Waste Identification Rule 
to revise the mixture and derived-from rules, which was published in 
the Federal Register on December 21, 1995. (60 FR 66344).
    We received extensive comments, many critical, on the 1995 
proposal, particularly with respect to the scientific risk assessment 
supporting the proposed revisions to the mixture and derived-from 
rules. As a result of the comments, we concluded that considerable work 
needed to be done to resolve complex scientific and technical issues 
raised by the risk assessment and the comments received. On April 11, 
1997, the District Court entered an order amending the consent decree 
in Environmental Technology Council v. Browner. The amended decree 
provided us with additional time to perform further scientific risk 
assessment work and requires us to address specific issues and options 
for revising the mixture and derived-from rules. The amended decree 
calls for a notice of proposed rulemaking to revise the mixture and 
derived-from rules, with an October 31, 1999 deadline for the 
Administrator to sign a proposal, and an April 30, 2001 deadline to 
sign a notice of final rulemaking. Until this rule is promulgated, the 
mixture and derived-from rules are considered to remain in effect on an 
``emergency basis.''
C. Why Is EPA Proposing To Retain the Mixture and Derived-From Rules?
    The mixture and derived-from rules are necessary to regulate 
hazardous wastes in a way that protects human health and the 
environment. Mixtures and residuals of hazardous waste represent a 
large and varied universe. Many hazardous wastes continue to be toxic 
after they have been mixed with other waste or have been treated. As 
explained below, without the mixture and derived-from rules, such 
wastes could easily escape coverage of RCRA Subtitle C regulations, 
while nevertheless posing risks to human health and the environment.
    We believe that without the mixture and derived-from rules, some 
generators would alter their waste to the point it no longer meets the 
listing description without detoxifying, immobilizing, or otherwise 
actually treating the waste. For example, without a ``mixture'' rule, 
generators of hazardous wastes could escape regulatory requirements by 
mixing listed hazardous wastes with other hazardous wastes or 
nonhazardous solid wastes to create a ``new'' waste that arguably no 
longer meets the listing description, but continues to pose a serious 
hazard. Similarly, without a ``derived-from'' rule, hazardous waste 
generators could potentially evade regulation by minimally processing 
or managing a hazardous waste and claiming that the resulting residue 
is no longer the listed waste, despite the continued hazards of the 
residue. (See 57 FR 7628). It is therefore necessary for protection of 
human health and the environmental to capture mixtures and derivatives 
of listed hazardous waste in the universe of regulated hazardous 
wastes. A hazardous waste regulatory system that allowed hazardous 
waste to leave the system as soon as it was modified to any degree by 
being mixed or marginally treated would be ineffective and unworkable. 
Such a system could act as a disincentive to adequately treat, store 
and dispose of listed hazardous waste.
    We know that mixtures and residuals of hazardous waste can be 
hazardous based on our experience in identifying and regulating 
hazardous waste. For example, during the listing process, we review 
data on specific waste streams generated from a number of industrial 
processes to determine whether these wastes would pose hazards to human 
health or the environment if mismanaged. Through the listing process, 
we have determined risks arising from the disposal of waste mixtures 
and derived-from wastes. Leachate generated from hazardous wastes is a 
particularly good example of residuals of hazardous wastes that contain 
toxic chemicals that can endanger environmental or human receptors. Our 
risk analyses have shown that multi-source leachate derived from 
hazardous waste landfills can contain very high concentrations of toxic 
organic compounds and metals. (Preliminary Data Summary for the 
Hazardous Waste Treatment Industry, EPA/OW, 1989). Other derived-from 
wastes that, because of their treatment process, can result in higher 
concentrations of chemicals (especially metals) than their parent 
wastes include wastewater treatment sludge and combustor ash. As a 
result of either wastewater treatment or combustion, the wastes would 
have their volumes greatly reduced, but could still contain the same 
amount of inorganic chemicals, thus resulting in a higher concentration 
of chemicals.
    Our experience with delisting petitions also supports the need to 
regulate as hazardous mixtures and residuals of listed hazardous waste 
in order to protect human health and the environment. Generators can 
petition us under 40 CFR 260.22 to exclude a waste produced at a 
particular facility from the definition of hazardous waste. Such 
petitions must demonstrate that the waste does not meet any of the 
criteria for which it was listed nor has other attributes that might 
result in the waste being hazardous. As of March 27, 1995, we have 
denied or dismissed 139 of 809 (17%) of delisting petitions received. 
This estimate does not include 543 petitions (67% of the total) that 
were withdrawn (311), mooted (198) or referred to the State authority 
(34). The chief reason for denying or dismissing most of the 139 
delisting petitions was failure by the petitioner to supply adequate 
information. However, in at least 13 cases, we denied delisting 
petitions for mixtures or residuals of listed waste because risk 
analyses indicated that the toxicity and leaching potential of 
hazardous chemicals in those wastes posed unacceptable risk to human 
health (see Disposition of Delisting Petitions for Derived-From/Mixture 
Wastes, U.S. EPA memorandum, 1992 and Analysis of the Delisting 
Petition Data Management System, U.S. EPA, September 1998). We have 
also identified damage cases associated with mixture and derived-from 
wastes. For example, there are Superfund sites that contain mixture and 
derived-from wastes (See 50 FR 658). In many cases, determining when 
the environmental damage occurs on a site is difficult, but we have 
identified at least nine sites that involve the mismanagement of 
mixture and derived-from wastes. (see ``Releases of Hazardous 
Constituents Associated with Mixture and Derived-from Wastes,'' EPA 
1999). These waste types are also associated with RCRA corrective 
actions where high concentrations of hazardous chemicals were found in 
the vicinity of units that contained a listed waste. (Data on Mixture 
and Derived-from Wastes from Closures and Corrective Action at 
Hazardous Waste Management Facilities, EPA, 1992).
    In addition, through the development of the LDR program, we have 
considered the appropriateness and effectiveness of various hazardous 
waste treatment technologies. Treatments specified within the LDR 
regulations, promulgated under 40 CFR 268, are required for hazardous 
waste to be land disposed. However, technology-based treatment 
standards do not always equate with low risk. In addition, treatment 
that is not performed properly or is not fully optimized may result in 
residues that present some risk. Further discussion and examples of LDR 
treatment are presented in a background

[[Page 63390]]

document entitled Memorandum to the Docket from Larry Rosengrant 
Regarding Section 3004(m) of the Hazardous and Solid Waste Amendments, 
U.S. EPA January 21, 1992. Since treatment standards are based on the 
limits of technology, residuals can still pose sufficient risk to 
warrant continued regulation under RCRA Subtitle C.
D. Does EPA Have the Legal Authority To Retain the Mixture and Derived-
From Rules?
    We have had, and we continue to have the statutory and regulatory 
authority to promulgate the mixture and derived-from rules. The mixture 
and derived-from rules, particularly with the revisions proposed today, 
ensure that hazardous wastes that are mixed with other wastes or 
treated in some fashion do not escape regulation as long as they are 
reasonably likely to threaten human health and the environment. These 
rules retain jurisdiction over listed hazardous wastes and clarify that 
such wastes do not automatically exit the Subtitle C system when they 
are mixed or treated, however minimally.
    The mixture and derived-from rules are valid exercises of our 
authority to list hazardous waste under section 3001 of RCRA. We have 
consistently interpreted section 3001(a) as providing EPA with 
flexibility in deciding whether to list or identify a waste as 
hazardous, that is to consider the need for regulation. Specifically, 
section 3001 requires that EPA, in determining whether to list a waste 
as hazardous waste, or to otherwise identify a waste as hazardous 
waste, decided whether a waste ``should be subject to the requirements 
of Subtitle C.'' Hence, section 3001 authorizes us to determine when 
Subtitle C regulation is appropriate. The statute directs EPA to 
regulate hazardous waste generators (section 3002(a)), hazardous waste 
transporters (section 3003(a)), and hazardous waste treatment, storage, 
and disposal facilities (section 3004(a)) ``as necessary to protect 
human health and the environment.'' By extension, the decision of when 
waste should be subject to the regulatory requirements of Subtitle C is 
essentially a question of whether regulatory controls promulgated under 
sections 3002-3004 are necessary to protect human health and the 
environment. We have therefore consistently interpreted section 3001 to 
give us broad flexibility in fashioning criteria for hazardous wastes 
to enter or exit the Subtitle C regulatory system. See, Military Toxics 
Project v. EPA, 146 F.3d 948, 958 (D.C. Cir. 1998).
    EPA's 1980 criteria authorize the listing of classes of hazardous 
wastes when we have reason to believe that wastes in the class are 
typically or frequently hazardous. See 40 CFR 261.11(b). As discussed 
Section III.C. above, EPA has ample reasons for classifying mixtures 
and residuals of listed hazardous waste as hazardous wastes.
    In addition to providing the context in which the determination of 
whether a waste ``should be subject to the requirements of Subtitle 
C,'' sections 3002-3004 allow us to impose requirements on waste 
handlers until wastes have ``cease[d] to pose a hazard to the public.'' 
Shell Oil Co. v. EPA, 959 F.2d 741, 754 (D.C. Cir. 1991). See also 
Chemical Manufacturers Assoc. v. EPA, 959 F.2d 158, 162-65 (D.C. Cir. 
1990) (EPA may regulate the disposal of nonhazardous wastes in a 
hazardous waste impoundment under section 3004) and Chemical Waste 
Management, Inc. v. EPA, 976 F.2d 2, 8, 13-14 (D.C. Cir. 1992) (EPA may 
require further treatment of wastes under section 3004 even though they 
cease to exhibit a hazardous characteristic).

Proposed Revisions to 40 CFR 261.3

IV. How and Why Is EPA Proposing To Revise the Hazardous Waste 
Identification Regulations for Mixtures and Derived-From Wastes?

A. How and Why Is EPA Proposing To Revise the Hazardous Waste 
Identification Regulations for Wastes That Were Listed Solely for 
Ignitability, Corrosivity and/or Reactivity?
    There are 29 waste codes within the RCRA program listed solely for 
ignitability, corrosivity, and/or reactivity characteristics. 
Currently, 40 CFR 261.3(a)(2)(iii) specifies that a mixture of these 
wastes and a solid waste is no longer a hazardous waste if the mixture 
does not exhibit a hazardous characteristic. These mixtures must still 
meet the LDR requirements of 40 CFR 268.40.
    We believe that wastes listed solely because they exhibit the 
ignitability, corrosivity and/or reactivity characteristics should all 
be treated identically, whether they are mixtures, residuals, or wastes 
meeting the original listing description as generated. For example, ash 
resulting from the combustion of an ignitable listed waste would no 
longer exhibit the characteristic of ignitability. Under the current 
derived-from rule, this ash would not be exempt, however if it were a 
``mixture'' rather than a treatment residual, it would be exempt under 
the current mixture rule. Another example are nitroglycerine patches, 
which when used for medical purposes are not reactive even at the point 
they are manufactured, but are regulated as P081 when discarded. Thus, 
today's proposed revision would expand this exemption which is 
currently in the mixture rule only, so that all these materials would 
be exempt from hazardous waste regulation if they are de-characterized 
and meet the appropriate LDR treatment standards, including treatment 
for all underlying hazardous constituents (as defined in 40 CFR 
268.3(i)). Table 1 presents the 29 wastes codes and the 
characteristic(s) that are the basis for their listing.

Table 1.--Wastes Listed for Ignitability, Corrosivity, and/or Reactivity
------------------------------------------------------------------------
                  Waste code           Description          Hazard code
------------------------------------------------------------------------
1.............  F003            Spent xylene and other     (I)
                                 non-halogenated solvents.
2.............  K044            Wastewater treatment       (R)
                                 sludges from the
                                 manufacturing and
                                 processing of explosives.
3.............  K045            Spent carbon from the      (R)
                                 treatment of wastewater
                                 containing explosives.
4.............  K047            Pink/red water from TNT    (R)
                                 operations.
5.............  P009            Ammonium Picrate.........  (R)
6.............  P081            Nitroglycerine...........  (R)
7.............  P112            Tetranitromethane........  (R)

[[Page 63391]]

 
8.............  U001            Acetaldehyde.............  (I)
9.............  U002            Acetone..................  (I)
10............  U008            Acrylic Acid.............  (I)
11............  U031            n-Butyl alcohol..........  (I)
12............  U020            Benzenesulfonyl chloride.  (C, R)
13............  U055            Cumene...................  (I)
14............  U056            Cyclohexane..............  (I)
15............  U057            Cyclohexanone............  (I)
16............  U092            Dimethylamine............  (I)
17............  U096            Cumene Hydroperoxide.....  (R)
18............  U110            Di-n-propylamine.........  (I)
19............  U112            Ethyl Acetate............  (I)
20............  U113            Ethyl Acrylate...........  (I)
21............  U117            Ethyl Ether..............  (I)
22............  U124            Furan....................  (I)
23............  U125            Furfural.................  (I)
24............  U154            Methanol.................  (I)
25............  U161            Methyl isobutyl ketone...  (I)
26............  U186            1,3 Pentadiene...........  (I)
27............  U189            Sulfur phosphide.........  (R)
28............  U213            Tetrahydrofuran..........  (I)
29............  U239            Xylene...................  (I)
------------------------------------------------------------------------
I=ignitability, C=corrosivity, R=reactivity

    As explained in Section XXI, the majority of the waste which would 
be eligible for this exemption would be F003 (spent xylene and other 
non-halogenated solvents). However, the full listing description for 
F003 in 40 CFR 261.31 includes the following statement: ``and all spent 
solvent mixtures/blends containing, before use, one or more of the 
above non-halogenated solvents, and, a total of ten percent or more (by 
volume) of one or more of those solvents listed in F001, F002, F004, 
and F005 * * *'' Although F003 is listed solely for ignitability, its 
listing description includes references to solvents that were listed 
for toxicity as well. This is one of the reasons that LDR standards 
reference a composite list of chemicals that must be treated for F001, 
F002, F003, F004 and F005. We therefore request comment on whether to 
allow F003 to be eligible for this proposed exemption.
B. How Is EPA Proposing To Revise The Mixture and Derived-From Rules 
for Mixed Waste?
    In the revisions to 40 CFR Part 261.3 that we are proposing today, 
we also include a conditional exemption for mixed waste from the 
mixture and derived-from rules, provided the mixed waste is handled in 
accordance with 40 CFR Part 266, Subpart N.
    The proposed regulatory language in 40 CFR Part 266, Subpart N, 
which we are including in a separate Federal Register notice published 
elsewhere today conditionally exempts hazardous waste mixed with low-
level radioactive wastes (low-level mixed wastes/LLMW), or mixed with 
Naturally Occurring and/or Accelerator-produced Radioactive Material 
(NARM mixed waste) from the storage, treatment in tank, transportation, 
and disposal requirements of RCRA. Nuclear Regulatory Commission (NRC) 
or its Agreement State licensed LLMW generators can store, or treat 
LLMW in storage tanks without RCRA Subtitle C permits if all exemption 
conditions are met. Treated LLMW or NARM mixed waste could be disposed 
at a low level radioactive waste disposal facility (LLRWDF) regulated 
by the NRC or its Agreement State if all exemption conditions are met. 
The rationale for conditionally exempting LLMW from the mixture and 
derived-from rules is the same as that for creating the conditional 
exemption from the RCRA regulatory definition of hazardous waste for 
LLMW. We incorporate by reference the notice of proposed rulemaking for 
the LLMW conditional exemption (EPA Docket Number F-1999-ML2P-FFFFF). 
We request comment on whether to conditionally exempt low level mixed 
wastes from the mixture and derived-from rules.

HWIR Exemption Options

V. Why Is EPA Developing a Chemical-Based HWIR Exemption for Listed 
Hazardous Waste (Including Both Mixtures and Derived-From Waste)?

A. What Issue Would the HWIR Exemption Address?
    The HWIR exemption would refine the regulation of hazardous wastes 
by improving identification of lower risk hazardous wastes, while 
ensuring that the health of our nation's citizens and environment is 
not compromised. Wastes are hazardous and subject to RCRA Subtitle C 
regulations if they exhibit certain characteristics (``characteristic 
wastes'') or if they have been placed on certain lists by EPA (``listed 
wastes'').
    Once a waste is identified as a listed hazardous waste, it remains 
regulated as hazardous, even if it has been treated to remove all 
hazardous chemicals, unless the wastes are formally delisted. Delisting 
under 40 CFR 260.22 requires a formal rulemaking process under the 
Administrative Procedures Act (APA). Delistings are waste stream 
specific, with close government review of sampling procedures, 
analytical test results, and the accompanying quality assurance and 
quality control (QA/QC) data. This process has the advantage of 
tailoring the delisting determination to the specific waste, but it is 
also resource intensive and time consuming for both the petitioner and 
the government. Such costs could discourage a generator from

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exploring the use of pollution prevention and new waste treatment 
technologies to detoxify his waste. By offering a self-implementing 
alternative, the HWIR exemption would exempt low-risk wastes more 
quickly and at less cost than the current delisting process.
B. How Would the HWIR Exemption Affect the Regulation of Hazardous 
Waste?
    Under this approach, wastes that have been designated as listed 
hazardous wastes under Subpart D of 40 CFR Part 261 (or are mixed with, 
derived from, or contain listed hazardous wastes) would no longer be 
subject to the full ``cradle to grave'' RCRA Subtitle C hazardous waste 
management requirements, if the chemicals of concern in the wastes are 
below risk-based exemption levels. The waste would instead be managed 
under RCRA Subtitle D nonhazardous waste management requirements, which 
better match the risks posed by this low-risk waste. The HWIR approach 
would be self-implementing, and therefore less burdensome both to the 
generator and the overseeing agency than the current delisting process.
C. How Would the Exemption Continue To Ensure Protection of Human 
Health and the Environment?
    HWIR would continue to ensure protection of human health and the 
environment by establishing numerical risk levels that are based on a 
multi-media approach to environmental protection. The risk models that 
would underlie the exemption levels in the HWIR exemption predict the 
potential release of hazardous chemicals from waste management units to 
the air, land, surface water, and groundwater. If wastes contain these 
chemicals at concentrations greater than these levels, they would 
remain regulated as hazardous under RCRA Subtitle C. On the other hand, 
those wastes that no longer contain these chemicals or that can be 
demonstrated to contain these chemicals below these levels, would no 
longer be considered hazardous under RCRA Subtitle C, but would still 
be subject to State nonhazardous waste regulations. The HWIR exemption 
would also include testing and documentation requirements to ensure 
that the exemption levels have been and continue to be met.

VI. What Options Is EPA Developing for the HWIR Exemption?

    We are developing two options for the HWIR exemption: (1) The 
``generic'' HWIR exemption, and (2) the ``landfill-only'' HWIR 
exemption. As discussed in Section XVII of this preamble, we are not 
proposing the HWIR exemption because of technical difficulties in 
developing chemical-specific exemption levels from the model. Before we 
would promulgate an HWIR exemption, we would first publish an HWIR 
proposal that would include specific exemption levels and give the 
public an opportunity to comment. Therefore, our discussion consists of 
a ``framework'' for the two HWIR exemption options. In this discussion, 
``you'' refers to the person who would wish to claim an exemption for a 
waste under these options.
A. What Is the Generic HWIR Exemption option?
    Under the generic HWIR exemption option, your listed hazardous 
waste would no longer be hazardous once the risk-based exemption levels 
have been satisfied, and you fulfill the conditions and requirements 
discussed in Section IX of this preamble. The exemption levels would be 
listed in a new appendix to 40 CFR Part 261 (Appendix X), found in 
Table 2, in Section XIV of this preamble. You would have to continue to 
meet specific waste testing requirements to ensure that the waste 
remains below the HWIR exemption levels.
    This option is based on the premise that the HWIR exemption levels 
would be protective in all reasonable waste disposal scenarios. 
Therefore, there would be no limits to where an HWIR waste could be 
disposed under this option, except for existing State requirements that 
apply to all nonhazardous industrial wastes. A discussion of the risk 
assessment model supporting this option can be found in Sections XV 
through XIX of today's preamble.
B. What Is the Landfill-Only HWIR Exemption?
    Under the landfill-only HWIR exemption, your waste would have to 
meet a different set of HWIR exemption levels, found in Table 2, in 
Section XIV of this preamble, and you would be required to dispose of 
the waste in a landfill. A landfill is a land-based unit where non-
liquid wastes are placed for permanent disposal, and is not a land 
application unit (where wastes are incorporated into the soil). This 
landfill would not need to be a hazardous waste landfill, but 
nonhazardous landfills are still regulated under existing State 
requirements, which would help ensure that it is protective of human 
health and the environment. This landfill disposal requirement is in 
addition to the other requirements described under the generic HWIR 
exemption option.
    In addition, under the landfill-only exemption, you would also be 
required to fulfill waste tracking requirements to ensure that the 
waste does arrive at a landfill, and until the waste is disposed, you 
would not be allowed to place it on the land. We are concerned about 
the temporary placement of these wastes in waste piles or other such 
intermediate land-based destinations, because exemption levels for the 
landfill-only option (unlike the levels for the generic option) would 
not consider such risks. See Section XII of this preamble for 
discussion of these additional conditions and requirements.
    We believe that restricting wastes to landfills and customizing the 
exemption levels to that unit focuses the HWIR exemption on the lowest-
risk and most likely disposal scenario for non-liquids. Management in a 
landfill helps reduce air release and overland transport of hazardous 
chemicals. This option could allow for less conservative exemption 
levels, thus reducing regulatory costs while continuing to protect 
human health and the environment.
C. What Implementation Options Are in Both the 1995 HWIR Proposal and 
Today's Notice?
    In our 1995 HWIR proposal, we developed a number of options for 
exempting low risk wastes from RCRA Subtitle C hazardous waste 
regulation. Under a proposed ``base national option,'' generators would 
be required to demonstrate that constituent concentrations within a 
waste did not exceed risk-based HWIR exemption levels. Conceptually, 
the base national option from 1995 is the same as today's generic 
option discussed in Section VI.A of this preamble. We also proposed 
several ``contingent management'' options, under which generators were 
required to meet alternate exemption levels, provided that they met 
additional waste management requirements. The landfill-only option 
discussed in Section VI.B of this preamble is similar to one of the 
contingent management options proposed in 1995.
    When we developed today's notice, we considered all of the options 
discussed or proposed in 1995, plus an additional contingent management 
option that would require waste to be stabilized and then disposed in a 
landfill. (see Evaluation of Contingent Management Options, U.S. EPA, 
1999). One of the most pervasive comments on the 1995 HWIR proposal was 
related to the number and complexity of alternatives, which made it 
difficult for readers to understand and comment on the proposal. We 
have decided to

[[Page 63393]]

develop only the two options we have deemed most viable: the base 
national option and the contingent management national option 1 
(disposal in a landfill). As discussed above, these two options are 
called the generic HWIR option and the landfill-only HWIR option.
    The 1999 HWIR options differ from their 1995 counterparts. The 
biggest changes are to the risk assessment we are developing to support 
the options. Instead of modeling each exposure pathway separately as we 
did in 1995, the current version of the model takes into account 
simultaneous exposures via multiple pathways. See Sections XV through 
XIX of this preamble for a discussion of the current version of the 
model. In the 1995 HWIR proposal we included more than 350 exemption 
levels. About half of these levels were based on risk modeling, while 
the other have were based on an extrapolation methodology that we have 
since discarded. As explained in Section XVII, today's discussion does 
not include any specific exemption levels because of technical 
difficulties in the risk modeling. Instead, we discuss the framework of 
the exemption and ask for comment on the modeling approach. Before we 
would promulgate an HWIR exemption, we would first publish an HWIR 
proposal that would include specific exemption levels and give the 
public an opportunity to comment.
    In addition to modeling changes, we have also revised the 
discussion of some of the implementation requirements. We have scaled 
back the testing requirements so that facilities would not have to 
document why chemicals would not be in their waste (essentially proving 
a negative). Instead, under today's options, facilities would only have 
to test for chemicals ``reasonably expected'' to be in their waste; the 
guidelines for determining what chemicals we would ``reasonably 
expect'' to be in a waste are discussed in Section IX of this preamble. 
Also, for the generic option, we have developed three categories of 
wastes (liquids, semi-solids, and solids) rather than the two proposed 
in 1995 (wastewaters and nonwastewaters). These categories are 
discussed in more detail in Section XIX.C. Finally, for the landfill-
only option, we would require tracking requirements to ensure that the 
waste arrives at its intended destination. These requirements are 
discussed in Section XII.B.
D. Why Did We Decide Not To Go Forward With Two of the National 
Contingent Management Approaches Discussed in the 1995 HWIR Proposal?
    The 1995 HWIR options included three approaches that required a 
generator to meet national exemption levels. After carefully evaluating 
these options and reviewing the input we received from our 
stakeholders, we determined that, except for the landfill-only national 
contingent management option (analogous to the first national 
contingent management option from 1995), it would not be feasible and/
or desirable to develop and implement the other approaches at this 
time.
    Under the second national contingent management option for 1995 
HWIR proposal, we considered establishing exemption levels for each 
type of waste management unit: landfill, waste pile, land application 
unit, tank, and surface impoundment. Upon further review, however, we 
determined that setting exemption levels for waste piles, land 
application units, tanks or surface impoundments was not a desirable 
option for several reasons.
    First, waste piles and tanks are intermediate disposal 
destinations. It is not appropriate to exempt wastes based on exposures 
from just these units and no others, since the final disposition of the 
waste is most important for determining long-term risk. Second, we 
found in 1995 that the land application unit drove most of the non-
liquid exemption levels and therefore separate land application unit 
levels would be no different from levels established for the generic 
option. Similarly, a surface impoundment option would be expected to be 
similar to levels for liquids established under the generic option, and 
we do not believe that separate exemption levels are warranted. Given 
that the generic option has fewer requirements and similar exemption 
levels, we decided a contingent management option for land application 
units and surface impoundments would add unnecessary complexity to the 
rule.
    Under the third national contingent management option, we 
considered setting exemption levels for waste management units with 
specific design or operating controls that would allow for less 
conservative exemption levels. Although specific public comment on the 
national contingent management options was limited, representatives 
from industry indicated a support for options that allowed the 
consideration of site-specific factors. Therefore, in addition to 
evaluating the approach of developing separate exemption levels for 
each type of waste management unit, we considered developing exemption 
levels based upon engineering controls in place at certain units.
    However, when we evaluated the unit control option, we found it 
difficult to quantitatively attribute a set of risk protection levels 
to specific engineering and management controls, especially over a long 
period of time. Also, in order to enforce such an option, we would need 
to make complex judgements regarding whether the required unit controls 
were being used correctly. Such determinations would be more 
appropriately made under the oversight of a permitting authority, 
rather than as a condition of a self-implementing exemption under HWIR.
E. Why Did We Decide Not To Go Forward With the State Contingent 
Management Approaches Discussed in the 1995 HWIR proposal?
    In 1995, we proposed that qualified States would be allowed to 
manage listed waste in their nonhazardous waste management programs 
under certain conditions. We included three different State-based 
approaches. These three approaches differed in terms of (1) the risk-
based criteria (10-5 versus 10-4 cancer risk, for 
example) that would be used to identify the set of wastes that could be 
managed under an approved State program; (2) the type of State program 
review that we would conduct to identify qualified State programs 
(qualitative and/or quantitative); and (3) the breadth of the State 
program that we would review and qualify. For example, we could have 
reviewed the entire State nonhazardous program, or only that portion 
related to the HWIR exemption.
    As we considered the above State program approaches to contingent 
management, we recognized that State industrial nonhazardous waste 
programs have improved significantly since the early days of the RCRA 
Subtitle C hazardous waste program. A well-developed State program 
could offer a continuum of management for waste of varying risks and 
allow more local judgements and ongoing oversight of HWIR exemptions. 
Waste generators have also expressed support for State program 
approaches to contingent management, because site-specific or regional 
specific parameters could be considered to a larger extent in State 
risk assessments. However, after further consideration of the State 
program options, as well as review of the input we received from our 
stakeholders, we decided that the implementation of these options would 
be difficult.
    Although the States recognize that relying upon State programs 
could be a

[[Page 63394]]

preferable alternative for the regulated community than a national 
approach (in terms of less conservative exemption levels for example), 
they expressed concern about resource implications, should they be 
required to independently develop exemption criteria. The States would 
have to perform risk assessments, which are resource-intensive and 
require specialized expertise. From an implementation perspective, some 
States would prefer for EPA to develop exemption levels for the States 
to implement and enforce within their Subtitle D versus Subtitle C 
programs. (see Overview: State-Based Contingent Management Case Study 
Project, Discussion Draft for April 1-2, 1998 Joint ASTSWMO Task Force 
Meeting, March 9, 1998).
    Furthermore, the transfer of jurisdiction over HWIR-exempt wastes 
from the Federal to the State governments would entail some type of EPA 
review of the quality of State Subtitle D programs. One State 
association indicated it would be inappropriate for EPA to evaluate 
State Subtitle D programs as part of authorizing states to use the 
contingent management options.
    Finally, State program approaches would result in a variety of 
disposal standards across the States. States and the regulated 
community would have to devote additional resources to ensure that 
waste streams generated and exiting under contingent management 
standards in neighboring States meet applicable transportation and 
disposal standards in the receiving States. A representative of the 
waste management industry expressed concern over the interstate 
transport ramifications of these approaches. For these reasons, we have 
decided not to pursue a State contingent management implementation 
option.
F. What Other HWIR Implementation Option Has EPA Considered?
    We also considered another contingent management option which would 
establish HWIR exemption levels for stabilized wastes when managed in a 
landfill. This approach was based upon the notion that different risks 
are posed by the same chemicals in different waste forms. More 
specifically, the physical nature of stabilized wastes, their ability 
to reduce the mobility of chemicals in the environment and the 
requirement to manage such waste in a landfill could provide additional 
protection. For example, stabilizing the waste and managing it in a 
landfill would help reduce or eliminate certain releases, such as 
windblown dust. By taking this additional protection into account, we 
could develop specific exemption levels that would be less stringent 
than those developed for the national generic option or the landfill-
only option, but equally protective. The focus on stabilized waste 
forms was partially derived from a screening study that has been placed 
in the docket (see Waste Forms Technical Background Document, U.S. EPA, 
September 1998).
    As explained in the background document, we decided not to further 
develop a stabilized waste option because of complications in defining 
which stabilized forms are appropriate and technical difficulties in 
determining what are the appropriate reductions in mobility from these 
forms.

VII. What Wastes Would Be Eligible for an HWIR Exemption?

    A listed hazardous waste would be eligible for this exemption once 
all the HWIR exemption levels are achieved. Even though the wastes 
might still contain chemicals for which they were originally listed, 
concentrations at HWIR exemption levels would pose very low risk to 
human health and the environment. However, wastes which exhibit any of 
the hazardous characteristics would continue to be regulated as 
hazardous wastes until the characteristic is removed, even if HWIR 
exemption levels are achieved.
    As discussed in Section XVIII of this preamble, we might not 
develop HWIR exemption levels for all ``chemicals of concern'' (HWIR 
exemption chemicals). Those wastes that would reasonably be expected to 
contain HWIR exemption chemicals without exemption levels would not be 
eligible for the exemption even if those chemicals are not detected in 
the waste. Chemicals can pose risk below levels capable of being 
detected by analytical methods. If a chemical does not have a risk-
based HWIR level to compare against, we cannot evaluate whether it 
poses a risk below detection. Therefore, we believe that any waste that 
would be reasonably expected to contain an HWIR exemption chemical that 
does not have an exemption level should be ineligible for the HWIR 
exemption, regardless of test results. See Section IX.A for further 
discussion of this issue.

VIII. What Level of Governmental Review Would Be Needed for an HWIR 
Exemption Claim?

    For both the generic and the landfill-only alternatives, the HWIR 
exemption would be self-implementing. Self-implementing means that no 
prior governmental approval or review of documentation is required 
before wastes are exempted from RCRA hazardous waste regulation. The 
use of a self-implementing mechanism is consistent with most other 
hazardous waste exemptions and exclusions, such as exemptions from the 
mixture and derived-from rules found in 40 CFR 261.3(c)(2)(ii) and 
exclusions from the definition of hazardous waste found in 40 CFR 
261.4(b).
    Self-implementation has several advantages: (1) The exemption can 
take effect quickly, (2) the generator's burden in claiming the 
exemption is reduced, and (3) the burden for the overseeing agency (the 
authorized State or an EPA Region) is also reduced. Most of the 
commenters to the 1995 HWIR proposal, including a majority of States, 
favored self-implementation.
    Self-implementation would not prevent the overseeing agency from 
having a role in the HWIR exemption. As a condition of claiming an HWIR 
exemption, you would be required to provide specific information to the 
overseeing agency (see Section IX.D). In addition, you would be 
required to keep and retain records in order to maintain an exemption 
(see Section XI.C). This information would be available to the 
overseeing agency in an inspection and for an enforcement action, if 
needed. Because HWIR waste would be some of the lowest-risk industrial 
wastes, and the overseeing agency would still have authority to enforce 
against an improperly claimed exemption, we believe that there would be 
little benefit to requiring prior governmental approval before the 
exemption takes place.
    In addition, your waste would only become exempt upon your 
receiving written confirmation that the notification package had been 
received by the overseeing agency. Examples of confirmation include 
certified mail return receipt, or written confirmation of delivery from 
a commercial delivery service. Upon receipt that the notification 
package has been delivered successfully, you would be allowed to manage 
the HWIR waste as nonhazardous. Confirmation that the overseeing agency 
has received the package would not imply, however, that the package has 
been reviewed or approved.
    As noted above, since our preferred option is to make the HWIR 
exemption self-implementing, the overseeing agency would not be 
required to make a decision regarding the waste prior to exemption. We 
do not believe that requiring a waiting period (for example, 30 or 60 
days) before the exemption becomes effective is necessary. Most of the 
commenters to the 1995 HWIR

[[Page 63395]]

proposal, including representatives of industry, federal and state 
government agencies, utility associations, industry associations and 
waste management associations opposed the idea of a waiting period. 
They felt that such a waiting period could create undue expense, 
administrative burden, and numerous legal and practical complications 
(such as storage space issues).
    Some of the commenters on the 1995 HWIR proposal, including some 
State governments, favored having the option of requiring prior 
approval and a waiting period. One possible approach would to require a 
waiting period which could be used by the overseeing authority to 
review the notification package. This review would be discretionary. If 
the overseeing authority takes no action during this waiting period, 
then the exemption would be approved. Commenters on the 1995 HWIR 
proposal who favored a waiting period felt that it would allow the 
overseeing agency time to screen notifications and obtain additional 
information as necessary. Waiting period recommendations ranged from 30 
days to 90 days.
    We request comment on whether HWIR should be self-implementing, and 
whether there should be a waiting period before the exemption take 
effect.

IX. For the Generic HWIR Exemption, What Steps Would I Follow Before My 
Waste Could Be Exempted?

    You would be required to complete the following steps before your 
waste could be exempted:
    (a) Determine which HWIR exemption chemicals of concern your waste 
is reasonably expected to contain. (see Section IX.A below)
    (b) Develop a waste sampling and analysis plan (see Section 
IX.B.1).
    (c) Determine that the concentrations of the chemicals reasonably 
expected to be present in your waste are at or below the appropriate 
exemption levels (see Section IX.B.1).
    (d) Determine that the waste does not exhibit any of the hazardous 
waste characteristics of Subpart C of 261.
    (e) Notify the overseeing agency that you are claiming an exemption 
under this Subpart for your waste (see Section IX.D).
    Once you receive confirmation that your notification was received 
by the overseeing agency, then your waste is exempt. Figure 1 provides 
an overview of this process, which is described in more detail in the 
sections that follow.

BILLING CODE 6560-50-P

[[Page 63396]]

[GRAPHIC] [TIFF OMITTED] TP19NO99.000



BILLING CODE 6560-50-C

[[Page 63397]]

A. For Which Chemicals Would I Have To Analyze To Obtain an HWIR 
Exemption?
    To claim the HWIR exemption for your candidate waste (``HWIR 
waste''), you would have to determine for which chemicals listed in the 
new 40 CFR Part 261 Appendix X (found in Table 2, in Section XIV of 
this preamble) you would have to analyze. You would have to test your 
HWIR waste for all chemicals reasonably expected to be present, which 
includes the following:
    1. Chemicals identified as the basis for listing the waste. (For F 
and K listed waste, these chemicals are found in Appendix VII of 40 CFR 
261. For P and U listed waste, these are the chemicals named in the 
specific listings found in 40 CFR 261.33);
    2. Chemicals listed in the table ``Treatment Standards for 
Hazardous Wastes'' contained in 40 CFR 268.40 as regulated hazardous 
chemicals for LDR treatment of the waste;
    3. Chemicals detected in any previous analysis of the waste;
    4. Chemicals introduced into the process that generates the waste; 
and
    5. Chemicals that are known to result from side reactions or are 
byproducts of the process that generates the waste.
    You would not be required to test for every chemical found in the 
new 40 CFR Part 261 Appendix X (which contains the broad set of 
chemicals ``of concern'' discussed in XVII.A of this preamble). You 
could use process knowledge to determine if a chemical other than those 
included in the five categories referenced above might be present in 
the waste. If you were to determine that the chemical is not reasonably 
expected to be present in the waste, you do not need to test for it. 
However, you would be responsible for ensuring that the waste meets all 
HWIR exemption levels. If at any time the waste fails to meet the 
levels, then the waste stream is not exempt. Additionally, you would be 
also responsible for determining whether your waste exhibits one of the 
hazardous waste characteristics set out in Subpart C of part 261.
    We request comment on the above guidance for determining which 
chemicals are ``reasonably expected to be present.'' In particular, we 
request comment on whether and how to adjust this definition for some 
of the broader waste listings, such as electroplating operations (RCRA 
waste code F006) or spent solvents (RCRA waste codes F001-F005). These 
listings represent multiple processes, and any particular process would 
not necessarily contain all the chemicals for which the broad waste 
code was listed. For example, a chrome plating waste might not 
necessarily contain nickel, even though nickel is one of the chemicals 
associated with F006 wastes.
    In addition, as discussed in Section XVII of this preamble, we 
might not develop exemption levels for all HWIR chemicals. If your 
waste would reasonably be expected to contain HWIR exemption chemicals 
that do not have levels, that waste would not be eligible for the 
exemption even if that chemical is not detected in your waste. The 
reason we believe that such wastes should be ineligible is that 
chemicals can pose risk below analytical method detection limits.
    If a chemical does not have a risk-based HWIR level to compare 
against, we cannot evaluate whether a waste poses a risk below its 
analytical detection limit. Therefore, any waste that would be 
reasonably expected to contain an HWIR chemical that does not have an 
exemption level would not be exempted, regardless of test results. 
Unlike the 1995 HWIR proposal, under this approach you would only be 
required to test chemicals that are or have historically been 
associated with the waste (either through the original listing, the LDR 
requirements, or generator knowledge). Therefore, we believe it is 
reasonable that for those chemicals, an absence of a risk-based 
standard would prevent the associated waste from becoming exempt.
    We did not encounter this issue in our 1995 HWIR proposal because 
we assigned every chemical an exemption level either through modeling 
or through an extrapolation methodology. We have subsequently discarded 
the extrapolation methodology because both the public comments and our 
own internal review indicated that it did not have a firm enough 
scientific basis. We request comment on this policy to exclude from 
HWIR eligibility those wastes are reasonably expected to contain 
chemicals that do not have HWIR exemption levels.
B. How Would I Have To Sample and Analyze My Waste Stream When Seeking 
an Exemption Under HWIR?
    Under today's approach, you would have to sample and analyze for 
all chemicals that you determined are reasonably expected to be present 
in your waste stream. In addition to the initial testing described 
below, you would also be required to retest your waste stream after it 
is exempted to ensure ongoing compliance. It remains your 
responsibility to ensure that a waste stream always meets the exemption 
requirements for all HWIR exemption chemicals, regardless of which 
chemicals you would be required to test, how many samples you consider, 
or how often you retest.
    The discussion that follows explores, in some depth, a number of 
issues related to the characterization of your waste stream and the 
determination of compliance with the HWIR exemption's testing 
requirements. For each waste stream that you seek to exempt, you would 
have to develop and follow a written plan for sampling and analyzing 
your waste stream. This plan is discussed in Section IX.B.1. You must 
analyze at least four samples and must document the results from all 
samples analyzed. Waste stream characterization and appropriate methods 
are discussed in the remaining parts of Section IX.B. For every 
chemical tested, each sample must show that the total concentration is 
at or below the exemption level. This standard of compliance is 
discussed in Section IX.B.2. Possible alternatives to this standard of 
compliance are discussed in Section IX.C. Together, these elements form 
the core testing requirements for a generator initially seeking 
exemption. Subsequent testing requirements and the frequency of such 
testing are discussed later in Section XI.A of this preamble.
    1. Waste sampling and analysis plan. The waste sampling and 
analysis plan is a planning document used to define the necessary 
criteria and quality control requirements for sampling, analysis, and 
data assessment. We recommend that these plans be developed consistent 
with the guidance provided in the applicable sections of ``Test Methods 
for Evaluating Solid Waste, Physical/Chemical Methods'' (SW-846). More 
specifically, chapters within this document that should be helpful to 
you include Chapter One that describes basic quality assurance and 
quality control procedures, Chapter Nine which provides guidance on 
sampling strategy, and sampling techniques, and Chapter Two that 
identifies appropriate methods for samples based upon sample matrix and 
the analytes to be analyzed.
    You would be required to develop a waste sampling and analysis plan 
prior to testing your hazardous waste stream for compliance with the 
HWIR exemption levels. Your waste sampling and analysis plan would be 
required to contain the following information:
    a. The chemicals for which each waste stream will be analyzed and 
the rationale for the selection of those chemicals;
    b. Sampling strategy, and methods used to obtain representative 
samples of the waste stream to be analyzed;
    c. The sample preparation, clean-up, if necessary, and test 
determinative

[[Page 63398]]

methods used to analyze for these chemicals; and
    d. Sufficient sampling procedures and locations to characterize the 
entire waste stream.
    You might already have a waste sampling and analysis plan in place 
because of general facility standards for treatment, storage or 
disposal facilities (see 40 CFR 264.13 and 265.13), or because of land 
disposal requirements (see 40 CFR 268.7(a)). The key elements of an 
HWIR waste sampling and analysis plan are consistent with these other 
waste analysis plans (See Waste Analysis at Facilities that Generate, 
Treat, Store and Dispose of Hazardous Waste, U.S. EPA April 1994). You 
can create a separate waste sampling and analysis plan for your HWIR 
exemption or you could modify existing plans to fulfill both HWIR and 
LDR requirements. Be aware that a modification to your existing waste 
sampling and analysis plan could require a permit modification.
    2. Waste stream characterization and demonstration of compliance 
with the HWIR exemption levels. You would have to obtain representative 
samples and analyze your waste stream to ensure that it is properly 
characterized. Such samples should be collected in an unbiased manner, 
that is, one which gives all samples an equal chance of appearing to 
represent the population. Analysis of such samples should statistically 
represent concentrations in the waste stream in terms of averages and 
variation. Finally, such samples should preserve the waste's 
composition and to prevent contamination or changes in concentration of 
the parameters to be analyzed.
    You would also have to evaluate your waste stream using the maximum 
detected concentrations based upon the complete extraction of HWIR 
exemption chemicals. If any sample contains a chemical at a 
concentration greater than its specified exemption level, then the 
waste stream would be ineligible for the HWIR exemption.
    The specific exemption levels your waste must meet depend on the 
regulatory option under which you seek to exempt your waste (generic 
and landfill-only options). The two regulatory options, which are 
discussed in Section VI, would have separate exemption levels. In 
addition, the different waste form categories within the generic option 
(liquid, semi-solid, solid) would have separate exemption levels. (See 
Section XIX.C for a discussion of this waste form categories). The 
format of the exemption levels table is presented in Table 3 found in 
Section XIV of this preamble. Meeting the appropriate exemption level 
requires that the concentration of each sample be at or below that 
exemption level.
    Because any sample above the HWIR exemption levels would disqualify 
the waste stream from the exemption, this could provide an incentive to 
take as few samples as possible. To have adequate confidence that the 
waste stream is properly exempt, today's approach would require a 
minimum number of samples. In constructing this requirement, we do not 
want to overprescribe sampling in cases in which you seek to exempt a 
homogeneous waste stream whose true average concentrations are 
substantially below the exemption level.
    We believe that a minimum of four samples at each testing event is 
reasonable. This minimum number of samples conforms to the requirements 
developed for the delisting program and established in its guidance 
(see Petitions to Delist Hazardous Wastes: A Guidance Manual, U.S. EPA 
March 1993). In addition, at least four samples are often used to 
characterize your waste stream using common statistical measures of 
average concentration (sample mean) and variability (standard 
deviation), and can be used to determine if additional samples are 
appropriate.
    This minimum number of samples should not be assumed to be the same 
as an appropriate number of samples. The appropriate number of samples 
should be consistent with the characterization of the waste stream and 
the distribution of concentrations recorded as a result of the samples 
taken. As specific requirements for the HWIR exemption, you would have 
to take at least four samples and to characterize your waste stream.
    The number of samples you would have to take would have to be 
sufficient to represent variability throughout the waste stream and 
across time. We recognize that solid wastes are often not homogeneous 
and are by nature generally heterogeneous. Solids are also frequently 
difficult to completely mix. Thus, more than four samples might be 
needed. You should use your knowledge of the process generating the 
waste stream to help determine the appropriate number of samples. The 
greater the variability within the waste, the more difficult it is to 
determine whether your samples are representative of the entire waste 
stream. One way to improve sampling precision is to increase the number 
of samples. In addition, you can improve your information on the 
variability of chemical concentrations within the waste stream by 
analyzing grab samples.
    Because generators of many different kinds of waste streams might 
seek exemption under HWIR, we have no preconceived notions on how 
variable your particular waste stream might be. Sampling of a 
heterogeneous waste with highly variable concentrations would require a 
greater number of samples, as contrasted with relatively homogeneous 
wastes with mean concentrations well below the exemption levels. In 
addition, the longer the time period over which you might need to 
establish the variability of the waste stream, the greater the number 
of samples you should take. For waste streams that experience wide 
variability in chemical concentrations over time, you should discuss, 
in your waste sampling and analysis plan, how your sampling strategy 
addresses such variability.
    You still would continue to be responsible for ensuring that your 
waste streams always meet the appropriate exemption levels. We discuss, 
in a background document, estimates regarding numbers of samples. This 
document explores sample sizes for different waste streams, for the 
not-to-exceed compliance standard (the preferred approach) as well as 
alternative compliance standards discussed later under subsection C of 
this part of the preamble (see Estimates of Sample Sizes Required for a 
Generator to Demonstrate a Waste Qualifies for Exemption Under HWIR, 
U.S. EPA, May 1999).
    We request comment on both the need for a minimum number of samples 
and what that minimum number should be.
    Allowing no samples to exceed the HWIR exemption level provides a 
clear standard against which both you and the overseeing authority can 
refer for compliance and enforcement purposes. Such clarity is 
especially important in the context of a self-implementing regulatory 
mechanism, because the overseeing agency would not scrutinize the waste 
sampling and analysis plan in advance to determine if such 
methodologies were chosen and applied correctly.
    As noted in the 1995 HWIR proposal, enforcement authorities prefer 
the practicality of a strict maximum standard. Inspectors seek to 
independently collect samples for analysis over a short time span. An 
exceedance by any sample during an inspection could constitute a 
violation.
    In some cases, you might also be required to demonstrate compliance 
with LDR sampling and analysis requirements. For example, wastes that 
become exempt after the point they are generated would have to still 
fulfill LDR requirements. To demonstrate

[[Page 63399]]

compliance for the LDR program, ``all portions of the waste must meet 
the applicable treatment standards, that is, no portion may exceed the 
regulatory limit.'' (63 FR 28556, 28567 (May 26, 1998)). Thus requiring 
that all samples be at or below the exemption levels would be 
consistent with the approach used in the LDR program.
    We recognize limitations to the strict maximum standard. As noted 
by commenters to the 1995 proposal, you would have to effectively meet 
a much lower average concentration level to maintain confidence that no 
sample would exceed the HWIR exemption level. However, as the purpose 
of HWIR is to exempt only waste streams that are clearly nonhazardous, 
imposing a strict maximum makes continued compliance more certain for 
wastes with chemical concentrations far below the exemption levels. 
Wastes with chemical concentrations near the exemption level, 
especially wastes with some significant degree of variability, may not 
be the most appropriate candidates for a self-implementing HWIR 
exemption.
    However, unlike the development of the LDR regulatory standards and 
its implementation of a strict maximum, the HWIR model as designed 
would not incorporate variability into the exemption levels. Within the 
LDR standards, we set a maximum acceptable chemical level for a 
particular waste treatability group, based on the performance of the 
Best Demonstrated Available Technologies (BDAT). This maximum 
incorporates fluctuations in performance for well-designed and well-
operated treatment systems and thereby ``builds in'' variability into 
the standard itself. This maximum is calculated as the mean of 
individual performance values multiplied by variability and recovery 
factors.
    In developing LDR concentration based treatment standards, we did 
not believe that incorporating variability relaxed the requirements of 
Section 3004(m), but rather represented a response to ``normal 
variations in treatment processes. As a practical matter, facilities 
will have to incorporate variability factors into process design to 
ensure performance that is more stringent than the standard to ensure 
continuous compliance with the standard.'' (see BDAT Background 
Document for QA/QC Procedures and Methodology dated October 23, 1991). 
In contrast, for the purposes of the HWIR exemption levels, there were 
no data or estimates of concentration variability within wastes. 
Therefore, adjustments to the HWIR exemption levels would not have the 
same informational basis available for incorporating variability into 
the regulatory standard.
    We request comment on the strict maximum standard against which to 
evaluate a waste stream for an HWIR exemption. Alternatives to the 
strict maximum are discussed in Section IX.C below.
    3. Selection of a reliable analytical method to test your waste 
stream. We would not specify which method you would use to evaluate 
chemical concentrations in waste; you may select any reliable 
analytical method. However, you would have to establish and document 
that the performance of the selected method demonstrates that the HWIR 
exemption level was achieved.
    You would also have to demonstrate that the analysis could have 
detected the presence of a chemical at or below the specified exemption 
level. We would consider that the HWIR exemption level was achieved if 
you indicate that the chemical concentration of a spiked sample is at 
or below some fraction of the exemption level within analytical method 
performance limits (for example, sensitivity, bias and precision). To 
determine the performance limits for a method, we recommend following 
the quality control (QC) guidance provided in Chapters One and Two of 
SW-846, and the additional QC guidance provided in the individual 
methods. As discussed in the 1995 HWIR proposal, detection at, but not 
below, the exemption level may not be sufficient to establish a 
reliable method, because such detection would not demonstrate the 
absence of the chemical with sufficient confidence (60 FR 66377). At a 
method's limit of quantitation, results may be obtained with a specific 
degree of confidence, generally with an uncertainty of plus or minus 
30% in the measured value (see Keith, L.H., Environmental Sampling: A 
Practical Guide, 1992). The relative uncertainty would be expected to 
be much lower as the concentrations increase above a method's 
quantitation limit. Again, quality control guidance found within SW-846 
and associated with the individual methods should assist in identifying 
the necessary performance.
    Your method would also have to attain acceptable recovery for the 
chemicals under analysis. Such recovery is dependent upon the waste 
matrix being analyzed and has ranged from 80-120% for method 
development activities, volatile organics (using relative recoveries), 
and for inorganics in almost all matrices. Analyses of certain other 
chemicals (extractable organics) can achieve slightly smaller 
recoveries (70%+), and for a few ``difficult'' matrices, we have 
considered sample preparation appropriate if it generates recovery of 
50% or greater. These issues are discussed within a recent Agency 
memorandum (see Appropriate Selection and Performance of Analytical 
Methods for Waste Matrices Considered to be `Difficult to Analyze', 
U.S. EPA memorandum, January, 1996). In the development of LDRs, 
methods with less than 20 percent recovery have been discarded from the 
calculation of treatment standards (see BDAT Background Document for 
QA/QC Procedures and Methodology, U.S. EPA, October 23, 1991).
    If you have trouble meeting these acceptable levels of recovery, 
you may be using an inappropriate method, may not have pursued 
appropriate alternative methods (consistent with guidance on method 
modification), or may be faced with the lack of an existing, validated 
method. In the case in which an existing method or appropriate 
alternative will not achieve acceptable recoveries, we request comment 
on correcting such analyses for the bias introduced by these 
deficiencies in recovery. Bias introduced by partial recoveries refers 
to the systematic deviation of analytical results due to matrix 
effects. It can be assessed by comparing measurements to an accepted 
reference value in a sample of known concentration or by determining 
the recovery of a known amount of contaminant spiked into a sample 
(that is, a matrix spike). Given the potential for using different 
methods, adjustments with respect to recovery can make the results from 
different methods more comparable.
    We specifically request comment on the option of requiring that 
analytical protocols achieve a minimum of 20% recovery, and that 
analytical results with analytical spike recovery of less than 100% be 
corrected for the percent recovery determined for that waste before 
being compared to the HWIR exemption level. This adjustment would allow 
the greatest flexibility in the choice of analytical procedures, 
provide equivalency between different procedures, and allow those 
matrices that are difficult to analyze to be considered for exemption.
    Finally, we seek to address potential technical limitations of 
analytical methods in quantitating to concentrations identified through 
the HWIR risk modeling. In the 1995 HWIR proposal, we suggested the use 
of detection limits to serve as exemption levels in cases where the 
exemption

[[Page 63400]]

levels fell below proposed ``exemption quantitation criteria'' or EQCs. 
Such EQCs were defined as the lowest levels that can be reliably 
measured within acceptable limits of precision and accuracy during 
routine laboratory operating conditions using appropriate methods (60 
FR 66377). For chemicals that had modeled or extrapolated levels below 
their EQCs, we set the exemption level for these chemicals at the EQC 
and required the application of LDR treatment standards, regardless of 
whether the waste was to be land disposed. We also discussed the 
alternative of making wastes containing chemicals with analytical 
limitations ineligible for an exemption, but expressed concerns about 
the impact such a policy would have on eligible waste volumes.
    We continue to harbor concerns about the impact that technical 
limitations might have on waste eligibility, but are equally interested 
in creating continuing incentives for generators to improve their 
analytical methods and quantitate to levels selected on the basis of 
risk. We have historically noted and continue to recognize increased 
sensitivity of analytical methods over time. Levels of quantitation are 
also driven by market demands, and by setting exemption levels on the 
outer reaches of current methods, we seek to have the market modify and 
develop methods to reach these levels. Commenters to the 1995 rule 
encouraged the continued pursuit of analytical methods, possibly 
through revisiting such EQC determinations over time.
    We are also interested in bolstering the relationship of the 
exemption levels to the underlying risk assessment and therefore, seek 
to avoid the adoption of levels not related to risk; established 
quantitation levels (for example, EQCs) and LDR treatment standards are 
not based on risk assessment and therefore are not ideal for 
identifying HWIR waste as non-hazardous. Therefore, in seeking 
exemption under HWIR, you would have to use and modify, as necessary, 
reliable analytical methods to determine if concentrations in your 
waste meet the exemption levels.
    In 1995, we received comments both supporting our application of 
EQCs as exemption levels and rejecting such usage as not associated 
with risk. Under another alternative, we could use the detection limit 
in place of the risk-based level, if the risk associated with the 
detection level concentration is judged to be within an acceptable 
range of risk (even if not meeting the primary risk objectives). We 
request comment on the option of using the detection limit in place of 
the HWIR exemption level when the detection limit is higher, but still 
within an acceptable level of risk.
C. What Alternatives Has EPA Considered for Demonstrating Compliance 
With the Exemption Levels?
    1. EPA requests comment on alternative standards for compliance. As 
explained previously, we would require all samples to have 
concentrations at or below the HWIR exemption level. However, we did 
consider alternative standards for compliance. These alternative 
standards would allow the mean chemical concentration within the HWIR 
waste to be closer, yet still at or below the HWIR exemption level. 
Such alternatives would allow greater variability in sample 
concentrations near the exemption level and, to a modest extent, allow 
chemical concentrations from individual samples to exceed the HWIR 
exemption level, while maintaining the mean to be below the exemption 
level.
    We believe that it might be appropriate to consider alternatives 
that would allow chemical concentrations from individual samples to 
exceed the HWIR exemption level because of the nature of the risk 
assessment used to set those levels. The HWIR risk assessment considers 
only chronic risk. Therefore, the levels are based on average exposure 
to a chemical over a lifetime, not on one-time events. In addition, the 
current version of the risk modeling does not consider variations in 
waste concentrations within a calendar year.
    Specifically, we request comment on three alternative regulatory 
standards: (1) The upper confidence limit associated with the estimated 
mean concentration in the waste would have to be at or below the HWIR 
exemption level at some level of confidence; (2) the estimated mean 
chemical concentration within the candidate waste would have to be at 
or below the HWIR exemption levels, and the concentration of individual 
samples would be required to be at or below some multiple of the 
exemption level; and (3) the estimated mean concentration would have to 
be at or below the HWIR exemption level, and the upper confidence limit 
associated with the estimated mean (at some level of confidence) would 
have to be at or below some multiple of the exemption level.
    Within the upper confidence level approach under alternative (1), 
you would have to demonstrate that the upper confidence limit around 
the estimated mean concentration in the waste is below the HWIR 
exemption level at some specified level of confidence. This approach 
was used in the comparable fuels rule which required the upper 
confidence limit at 95% confidence to be below the exclusion level (see 
63 FR 33782).
    An upper confidence limit approach has advantages in that it allows 
for a degree of variation in the concentration of individual samples in 
the waste. The mean would be required to be below the HWIR exemption 
levels; however, occasional values above the exemption level would be 
tolerated. The approach is self-implementing in the determination of 
the number of samples required and it is consistent with the way RCRA 
wastes are often assessed for the toxicity characteristic.
    An upper confidence limit approach also provides continuing 
incentives to better characterize the wastes. Within the strict maximum 
approach, the more samples you take, the greater the likelihood that 
one sample would fail. With an upper confidence limit approach, the 
more samples that you take, the better that you can establish the upper 
confidence limit associated with the mean (that is, the more precise 
your estimate is of the mean). With an upper confidence limit approach, 
wastes with mean concentrations near but below the exemption level 
could be exempted by taking enough samples to bring the upper 
confidence limit below the exemption level. You would need to determine 
whether the value of the exemption justifies the cost of sampling.
    Specifically requiring a minimum number of samples is unnecessary 
with an upper confidence limit approach. The number of samples is 
directly calculable from the confidence level chosen, the standard 
deviation of the distribution, and the distance between the mean and 
the exemption levels.
    An upper confidence limit would provide the maximum flexibility in 
selecting the sampling, analytical and statistical methods for 
establishing an HWIR exemption. Although an upper confidence limit is a 
statistically based performance criterion, that does not mean you would 
have to perform a large number of chemical analyses nor employ complex 
statistics.
    However, we are concerned about prescribing statistical methods for 
evaluation of HWIR compliance. Inspectors would still have the right to 
enforce based on grab samples, and inspectors would find it difficult 
and resource intensive to replicate the type of sampling needed to 
construct a statistically based upper confidence limit. Therefore, 
disagreements between you as the generator and inspectors could 
engender involved statistical comparisons as well as increased costs in 
resolving compliance status.

[[Page 63401]]

    The second alternative requires both the average chemical 
concentration to be below the HWIR exemption levels, and the 
concentration of individual samples to be below some multiple of the 
exemption level. Requiring all individual samples to be below a 
multiple of the exemption level restricts the potential variability of 
the waste. Only wastes with modest variation (and/or the ability to 
maintain lower average levels) are likely to meet HWIR exemption 
levels.
    Consistent with the no exceedance approach, a minimum number of 
samples would need to be required under this alternative. There would 
be a similar incentive not to test your waste, because the more samples 
you take, the greater the probability of finding an individual sample 
that would fail.
    This alternative could be of benefit to both you and enforcement 
officials. Enforcement officials would have one concentration level 
against which to evaluate compliance, and you would have a standard 
that would tolerate some variation in the waste around the exemption 
level and permit individual samples to exceed the exemption level.
    Making assumptions about the underlying distribution and ranges of 
waste stream concentrations and adopting the same approach that we used 
to develop variability factors under the LDR program, we suggest a 
multiple for this evaluative standard of 2.8. Note that we do not 
adjust the regulatory standard below which the average concentration in 
the waste stream would have to reside, but rather are suggesting a 
ceiling for any individual sample be based upon a similar kind of 
adjustment as the one used in the LDR program. Whereas the LDR 
adjustment was based on data from specific treatment processes, the 
multiple applied to the exemption level to derive this ceiling is 
established based on assumed characteristics of the underlying 
distribution of concentration in waste. Actual concentrations across a 
wide range of real waste streams will vary much more considerably. The 
specific derivation of this multiple can be found in the background 
document entitled ``Estimates of Samples Sizes Required for a Generator 
to Demonstrate a Waste Qualifies for Exemption Under HWIR.'' We request 
comment on the multiple of 2.8 and invite the suggestion of 
alternatives.
    The third alternative combines elements of the first two 
alternatives discussed. The generator would calculate an upper 
confidence limit similar to alternative (1), but that limit would be 
required to be at or below some multiple of the exemption level rather 
than the exemption level itself. We would need to derive a basis for 
this multiple, consistent with the discussion of alternative (2).
    This third approach would permit greater variability in the waste 
stream as compared to either the lead option in which no samples may 
exceed the exemption level and as compared to alternative (1) in which 
only a few samples falling outside the confidence interval could exceed 
the exemption level. Similar to alternative (1), we express concerns 
about prescribing statistical methods for evaluating HWIR compliance--
disagreements can ensue in situations where the generator has 
established a confidence limit below the multiple of the exemption 
level, and, at the same time, the inspector finds an individual sample 
above this multiple of the exemption level.
    Finally, and as implied by the use of confidence intervals within 
alternatives (1) and (3), either the generator or EPA would have to 
establish with what confidence theses statistical measures are 
evaluated. We believe that we should select the appropriate level of 
confidence. We recognize, however, that the use of confidence limits 
could rely on a fixed level of confidence for all waste streams or we 
could vary the specified level of confidence and require larger waste 
volumes to have greater confidence in the estimation of the mean than 
smaller streams. For example, we could require large, medium and small 
waste streams to achieve 98 percent, 95 percent, and 90 percent 
confidence, respectively.
    We request comment on all three alternative approaches and 
specifically on the use of statistical measures and their consequences 
for enforcement, on the basis for establishing limits (for example, 
multipliers to the exemption levels) to which individual samples or 
confidence limits would have to comply, and on the selection of 
confidence limits and the appropriateness of varying such limits based 
on waste volume.
    2. EPA requests comment on the use of grab or composite sampling, 
where appropriate, to demonstrate compliance. We are also considering 
whether to allow composite sampling as well as grab sampling for 
demonstrating compliance; our lead option presumes the use of grab 
samples. Composite sampling is a strategy in which multiple individual 
or ``grab'' samples (from different locations or times) are physically 
combined and mixed into a single sample so that a physical (rather than 
mathematical) averaging takes place. Composite samples provide average 
concentrations of a waste stream and, in contrast with grab samples, 
might reduce the number of samples needed to gain an accurate 
representation of a waste. Composite samples, though, are difficult for 
volatile organic compounds (VOCs) where analyte could be lost in the 
process of compositing.
    To the extent that composite sampling achieves the goal of 
representing average concentrations in the waste, then the evaluation 
of composite samples for the purposes of HWIR compliance could be 
appropriate. This position was discussed in the 1995 HWIR proposal (60 
FR 66386). In addition, the delisting program guidance suggests the use 
of composite samples. Both grab and composite sampling are used for the 
purposes of determining LDR compliance. Grab samples are required for 
all non-wastewaters and several wastewater streams, while composite 
samples taken over any one day are used for remaining wastewaters (see 
40 CFR 268.40(b)).
    Grab sampling is the preference of EPA and State enforcement 
officials. Grab sampling provides information about a waste's 
variability and the bounds of a chemical's concentration within a 
heterogeneous waste, while composite sampling yields information about 
average concentration. The resources necessary for enforcement to take 
composites over extended time periods is considered prohibitive. 
Furthermore, the use of composite samples for the purposes of HWIR 
compliance could create confusion if an enforcement official finds a 
grab sample that exceeds the HWIR exemption criteria while you found 
all composite samples to meet the HWIR levels.
    Related to the concept of compositing is the size of each sample 
you may select for analysis. Currently, there is no specific guidance 
on the size of each sample to determine compliance with HWIR, and the 
selection of a very large grab sample would have a similar effect of 
physically averaging the concentration of a chemical within that 
sample. Greater physical sample size could also improve precision.
    We request comment on the consideration of composite samples, 
particularly spatial composites, in evaluating a waste stream for HWIR 
compliance. We also request comment on the need to specify the size of 
samples taken to evaluate your waste stream.

[[Page 63402]]

D. What Information Would I Have To Include In the Notification Package 
to the Overseeing Authority?
    Before managing any waste as exempt under HWIR, you would first 
have to send a notice to the Director of the State or EPA Regional 
authority that has jurisdiction over the facility generating the waste. 
We envision this notice as a tool for the overseeing agency to document 
and track exemptions, not as a means to review and verify exemption 
claims.
    The overseeing agency would be under no obligation to undertake a 
review of exemption claims prior to the exemption becoming effective. 
However, failure to undertake such prior review would not preclude a 
subsequent enforcement action, should the exemption claim later be 
determined to be inaccurate or otherwise invalid.
    For this reason, we prefer to keep information requirements in the 
notification package to a minimum and to require that specific 
information documenting individual exemption claims (such as the 
sampling and analysis information) be kept on-site at the generating 
facility.
    The notification package would have to be sent by certified mail or 
other mail service that provides written confirmation of delivery. You 
would be required to include the following in the notification package:
    (a) The name, address, and RCRA ID number of the facility claiming 
the exemption;
    (b) The applicable EPA Hazardous Waste Code of the exempted waste 
and the narrative description associated with the listing from Part 
261, subpart D;
    (c) A brief, general description of the process that produces the 
waste;
    (d) An estimate of the average monthly, maximum monthly, and annual 
quantities of the exempted waste (we are suggesting a simple check box 
system);
    (e) A statement that you are claiming the HWIR exemption for the 
waste;
    (f) A certification--signed by you or your authorized 
representative--that the information in your notice is true, accurate 
and complete.
    To give you an idea of what this notification package would look 
like, we have included a sample form in the docket (see Sample 
Notification Form for Waste Claiming Exemption Under the Hazardous 
Waste Identification Rule (HWIR), U.S., EPA July 1999). We request 
comment on this form of notification and alternatives such as 
electronic submission.
    We also request comment on whether to require additional 
information in the notification package, such as the list of chemicals 
found in the waste and a summary of results for each sample analyzed. 
The implementing agency could find such summary information helpful in 
planning and prioritizing inspections.
E. What Is the Role of the Public in the HWIR Exemption Process?
    In recognition that issues surrounding hazardous waste management 
often arouse public sentiments, EPA developed a framework for public 
participation under RCRA. This public participation framework seeks to 
both formalize responsibilities of facility owners and operators under 
RCRA, and to enhance citizen opportunity for involvement in local 
environmental decision making. Regulations, such as the permit 
modifications procedures in 40 CFR 270.42 (52 FR 35838) and the changes 
to 40 CFR Part 124 (procedures for processing permit applications) 
codified in the ``RCRA Expanded Public Participation'' rule (60 FR 
63417-34, December 11, 1995), have made facility owners and operators 
responsible for a number of public participation activities (such as 
public notices, public meetings, and information repositories).
    In addition to the statutory and regulatory requirements cited 
above, EPA has published the ``RCRA Public Participation Manual'' 
(EPA530-R-96-007). This manual outlines public participation procedures 
and guidance to staff in EPA and RCRA-authorized state programs, to 
assist them with ensuring that the public has an early and meaningful 
role in the RCRA permitting process. This manual also provides public 
participation guidance to regulated industries and the communities that 
interact with them.
    Finally, EPA has also established several mechanisms in addition to 
the RCRA Information Center (the Docket) for promoting public access to 
information regarding RCRA, including a citizens' RCRA hotline, an 
Internet Web site, and a searchable database of all RCRA related policy 
documents (``RCRA Online'').
    In the 1995 HWIR proposal, we proposed requiring the HWIR waste 
generator to notify the public of exemption claims, through publication 
of newspaper notices local to facilities that generate and/or dispose 
of HWIR waste. However, other types of hazardous waste determinations 
do not require such notices. Because the HWIR exemptions levels would 
be based upon a nationally protective risk analysis, we do not believe 
that site-specific public notices of exemption claims are necessary. We 
believe that the existing mechanisms discussed above provide 
opportunity for interested parties to become informed and involved and 
to influence RCRA program development and implementation.
    We also understand that on the State level, many environmental 
agencies have mechanisms in place, such as telephone hotlines, print or 
electronic media, to answer questions about public safety and 
environmental issues. State environmental agencies would have the 
option of making information contained in notification packages from 
each generating facility in the respective State available to the 
public. Depending upon the structure of State programs, the State 
agencies could decide to keep the information available at State 
offices, or to delegate the information-sharing role down to the local 
level at public libraries, schools, or fire stations. As discussed in 
the previous section, today's notice, unlike the 1995 HWIR proposal, 
does not advocate requiring the submission of testing information as 
part of the notification package. Under this approach, however, the 
information that the States could share with the public would not 
contain the testing results.
    Another possible approach to this issue is to keep the exemption 
self-implementing except when there are adverse public comments on the 
exemption. Under this approach, you, as the person claiming the 
exemption, would publish a notice in a local paper explaining the 
exemption. If you receive no adverse comments, then you would send a 
certification to this effect to the overseeing agency with the 
notification package. When you receive the written confirmation that 
the notification package has been received, then the waste would be 
exempt.
    On the other hand, if you do receive adverse comments, then you 
would forward those to the overseeing agency with the notification 
package. The waste would not be exempt until the overseeing agency 
approved the package. This approach would have the advantage of 
targeting the overseeing agency's resources toward reviewing those 
exemptions that are of most public concern, and also giving the person 
claiming the exemption assurance that the overseeing agency supports 
the claim.
    We are taking comment on these issues of public notification and 
access to information related to HWIR exemption claims. Specifically, 
we request comment on (1) whether existing mechanisms for information 
sharing, including access via the Internet, are sufficient to provide 
the public with information relative to

[[Page 63403]]

individual HWIR exemption claims asserted in each State, (2) whether it 
is instead appropriate to notify the public of HWIR exemption claims 
through such mechanisms as newspaper notices at either the waste 
generating or the disposal facility prior to having the exemption 
claims become effective, and (3) whether the receipt of adverse public 
comments should trigger review of the package by the overseeing agency. 
We also request comment on whether to include testing results 
information in the notification package for the purpose of greater 
public access to this information.

X. Once the Waste Becomes Exempt, What RCRA Requirements Might Still 
Apply?

A. Where Could HWIR Waste Be Treated or Disposed?
    Under the generic HWIR exemption, there would be no conditions 
imposed on the management of the exempted waste. The waste would no 
longer be subject to regulation as a hazardous waste under Subtitle C, 
and therefore would be treated and disposed in accordance with State 
regulations governing the management of other nonhazardous industrial 
waste.
    Under the contingent management HWIR exemption, HWIR waste would 
have to be disposed of in a landfill. This landfill does not need to be 
a hazardous waste landfill, but it would be regulated under existing 
State requirements for nonhazardous waste landfills, which would help 
ensure that it is protective of human health and the environment.
    Under both options, the waste might also have to meet LDR 
requirements (see Section X.C).
B. Would a Manifest Be Needed To Track Where the HWIR Waste Was Shipped 
Off-Site?
    For exemptions using the generic option, we do not believe that 
tracking is necessary, since the levels for the exemption are based on 
modeling destinations for appropriately managed nonhazardous industrial 
waste. This judgement is consistent with existing State nonhazardous 
waste programs, which do not require a specific tracking mechanism as 
nonhazardous waste travels from the generator to its point of disposal. 
We request comment on whether under the HWIR generic exemption we 
should require that paperwork accompany the waste in order to track the 
waste and provide notice to the receiving facility that the waste is 
HWIR-exempt.
    For exemptions using the landfill-only option, we believe that 
tracking of some sort might be needed to ensure that the waste is, in 
fact, disposed in a landfill. The landfill-only HWIR exemption levels 
are based on disposal in a landfill; other destinations might not meet 
our risk protection criteria. We evaluated a number of options for 
tracking landfill-only HWIR exempt wastes, including requiring the use 
of a uniform hazardous waste manifest, which is required for hazardous 
waste generators shipping waste off-site. However, instead of requiring 
uniform hazardous waste manifest tracking, we suggest an alternative 
tracking requirement for the landfill-only exemption (See Section XII.B 
for further discussion of the alternatives.)
C. How Would Land Disposal Restriction (LDR) Requirements Apply to the 
HWIR Waste?
    Wastes that have been shown to have met the HWIR exemption levels 
at the point of generation would be considered by EPA to have never 
been hazardous and, therefore, would have no LDR obligation. Wastes 
that have met the HWIR exemption levels after the point of generation, 
however, would still be subject to LDRs even after they become exempt 
from the definition of hazardous waste, because LDRs apply to wastes 
that are hazardous or have ever been hazardous.
    HWIR wastes that are subject to LDRs are also subject to the ban 
against using dilution to achieve LDRs (40 CFR 268.3). However, HWIR 
wastes that are not subject to LDRs would not be subject to this ban. 
For example, wastewaters managed solely in tanks and discharged under 
the Clean Water Act (CWA) are not managed on the land and therefore not 
subject to the LDR dilution ban.
    We considered whether to specifically prohibit the use of dilution 
to achieve the HWIR exemption levels. Our intention in developing HWIR 
is to exempt wastes that are low risk due to pollution prevention or 
treatment, not to encourage dilution. Dilution would be inconsistent 
with the Congressional purpose of encouraging waste minimization. The 
legislative history of RCRA indicates that a prohibition on dilution 
``is particularly important where regulations are based on 
concentrations of hazardous constituents'' (H.R. Rep. no. 198, Part I, 
98th Congress, 1st Session 38 (1983)).
    Since HWIR wastes that would be subject to LDRs would also be 
subject to the ban against using dilution to achieve LDRs, adding a 
specific dilution ban for HWIR could be redundant for all wastes 
subject to the land disposal restrictions. However, HWIR wastes that 
are not subject to LDRs would not be subject to this ban, and are 
identified as (1) wastes with chemical concentrations below LDR levels 
but above HWIR levels, and (2) wastes that are not managed or disposed 
on the land.
    For example, wastewaters managed solely in tanks and discharged 
under the Clean Water Act (CWA) are not managed on the land and 
therefore not subject to the LDR dilution ban. For such wastewaters 
managed in tanks, it might be difficult in some cases to determine if 
intentional dilution is occurring. Combining wastewaters for treatment 
purposes before discharge under the Clean Water Act is often the most 
efficient and effective way of treating them.
    Generally, we oppose the dilution of waste consistent with stated 
waste minimization policies to reduce the volume and toxicity of wastes 
(see Section 1003 of RCRA), but we also recognize that the aggregation 
of wastes amenable to the same type of treatment is legitimate and 
desirable, even though chemical concentrations within such wastes might 
decrease. In promulgating regulations under the LDR program, we 
provided guidance regarding such aggregation as permissible dilution, 
despite the overall dilution ban. Aggregation is considered legitimate 
if all wastes are amenable to the same type of treatment and this 
method of treatment is utilized for the aggregated wastes (55 FR 
22666). Several commenters to the 1995 HWIR proposal, while supportive 
of an HWIR dilution ban, felt that aggregation for purposes of transfer 
and treatment in wastewater systems should not be considered 
impermissible dilution. By adopting similar guidance for HWIR, we could 
prevent inappropriate dilution, but allow for appropriate aggregation 
for the purposes of treatment.
    We request comment on whether to specifically prohibit dilution as 
a means of attaining the HWIR exemption levels. We also request comment 
on the appropriateness of considering as permissible dilution 
aggregated waste streams directed towards centralized treatment for the 
purpose of meeting HWIR exemption levels.

XI. For the Generic HWIR Exemption, What Conditions and Requirements 
Would I Be Required to Fulfill To Maintain the Exemption?

A. Would I Have To Retest the Exempted Waste Stream?
    Yes. Unless you only generate one batch of waste, you would have to 
periodically test the exempted waste stream as a condition of the 
exemption.

[[Page 63404]]

Failure to test and maintain documentation of this testing in 
accordance with the requirements under 40 CFR 261.57 would revoke the 
exemption. Post-exemption testing is needed to check for the continued 
compliance of the waste stream with the HWIR exemption levels and to 
maintain accurate characterizations of the waste stream. Note that a 
batch of waste would represent the amount generated prior to the next 
scheduled testing event (see Section XI.A.2 for discussion of testing 
frequency).
    We would require the same sampling and analysis approach for 
subsequent testing as that required for the initial exemption (see 
Section IX.B of this preamble), and we request comment on the 
advantages and disadvantages of requiring the same testing scheme for 
both initial and subsequent sampling and analysis.
    We also considered methodologies in which the data derived during 
the course of initial testing could be used as the basis for subsequent 
testing. A prediction limit derived from initial testing data could be 
used to evaluate continued compliance with the HWIR exemption. 
Prediction limits are designed to set an upper bound on the range of 
individual measurements that you would be likely to observe and still 
remain in compliance. If, during subsequent testing, any of the 
individual samples exceeded the prediction limit, there would be 
statistically significant evidence that the average concentration of 
the waste stream had changed and now exceeded the exemption level.
    Although the prediction limit requires some statistical analysis, 
such prediction intervals are no more complicated to calculate than 
upper confidence intervals and are used in other parts of the RCRA 
program (see RCRA groundwater monitoring program 40 CFR 264.97). The 
use of prediction limits could also necessitate the collection of fewer 
samples over time to achieve the same amount of confidence that the 
waste stream remains appropriately exempt. However, because these 
prediction limits would be specific to a particular waste stream, 
compliance determinations would be more difficult and involved for the 
enforcing Agency.
    We request comment on the potential use of prediction limits and 
other such techniques for the purposes of subsequent testing.
    1. For which chemicals would I have to retest the waste stream? You 
would have to retest for all chemicals meeting the criteria for 
mandatory testing, unless the results of your testing demonstrated 
that, over the course of a year, the chemical was below the HWIR 
exemption level by an order of magnitude or more. In other words, if 
all samples taken during a twelve month period showed that a chemical 
was below one tenth of the HWIR exemption level, then no further 
testing for that chemical would be required. You continue to be 
responsible for the presence of these chemicals in your waste. Also, 
consistent with the previous discussion on reliable analytical methods, 
you would have to demonstrate that the analysis could have detected the 
presence of each chemical at or below one-tenth of the specified 
exemption levels.
    The exception to this approach, as explained in Section XI.A.3 of 
this preamble, occurs when you have a change in the process generating 
your waste that introduces a new chemical or changes the concentration 
of existing chemicals. Then you would be required to test for all 
chemicals which are likely to be present, as explained in Section IX.A.
    We request comment on the appropriateness of removing testing 
requirements for chemicals consistently detected less than one-tenth of 
the exemption level and whether this reduced testing obligation should 
occur after fewer or more testing events than those undertaken in one 
year. As currently structured, removing the obligation to test for 
certain chemicals after one testing event could mean as few as four 
samples having concentrations below an order of magnitude of the 
exemption level. Finally, we request comment on whether no further 
testing is appropriate for waste streams in which all chemicals are 
found to be below one-tenth of their exemption levels.
    2. How often would I have to retest the waste stream? Retesting 
frequency would depend on the annual volume of the waste and whether it 
is a liquid or a non-liquid. Each year, you should document your annual 
generation of waste becoming exempt under HWIR for the purpose of 
establishing your retesting frequency.

------------------------------------------------------------------------
    If your waste is a liquid and it is      Then you would have to test
          generated in quantities                 your waste stream
------------------------------------------------------------------------
Less than 35,000 tons/year................  Every 12 Months.
Between 35,000 and 500,000 tons/year......  Every 6 Months.
Over 500,000 tons/year....................  Every 3 Months.


------------------------------------------------------------------------
 If your waste is a non-liquid (that is, a
 solid or semi-solid) and it is generated    Then you would have to test
               in quantities                      your waste stream
------------------------------------------------------------------------
Less than 2,000 tons/year.................  Every 12 Months.
Between 2,000 and 10,000 tons/year........  Every 6 Months.
Over 10,000 tons/year.....................  Every 3 Months.
------------------------------------------------------------------------

    We believe it is appropriate to vary the testing frequency based on 
both form and volume, because liquids are generally more homogeneous 
and therefore easier to characterize than solids. In addition, liquids 
are generated in significantly greater quantities. To require the same 
retesting frequencies for liquids and solids would mean relatively 
small quantities of liquids being retested often or relatively large 
volumes of solids becoming exempt without retesting.
    Larger amounts of waste have the potential of greater environmental 
risk than smaller amounts. Therefore, we believe it is reasonable to 
require generators of larger waste streams to retest more frequently 
than generators of smaller waste streams. We would require testing at 
particular time intervals throughout the year, rather than allowing a 
generator to choose when such tests would be conducted. We do not want 
to provide a flexibility to generators that they could use to ``game 
the system,'' that is, choose most favorable sampling times within a 
calendar year. The development of these particular volume thresholds 
and their testing frequency is described in a background document to 
this notice (see Background Document on Retesting Frequency, U.S. EPA, 
July 1999).
    Retesting frequency might also vary depending upon whether the 
generator seeking exemption is a small business. Small businesses and 
small generators are not necessarily the same `` small businesses, 
particularly those potentially affected by this exemption, are 
typically characterized by the number of employees at a firm (less 
frequently by the firm's annual receipts). To the extent that small 
businesses are not small generators, diminished retesting frequency 
based on smaller annual volumes would not apply. In order to reduce 
burden on small businesses, EPA could also consider reducing testing 
frequency for small business regardless of whether they produce 
comparatively small or large volumes of waste. Such reduced 
requirements would still need to ensure that the generator continues to 
be

[[Page 63405]]

accountable for compliance with the exemption levels.
    Suggestions were also made that the retesting frequency be 
established based either on the variability of the waste stream or on 
the amount of difference between the exemption levels and the 
concentrations detected in the waste. Alternatively, retesting could be 
required after the production of a set amount of waste rather than 
based on elapsed time. We believe that such alternatives could be made 
workable for this exemption, but would certainly be more involved. As 
far as identifying which chemicals to retest, we have relied on the 
observed concentrations in the waste stream to suggest that chemicals 
below one-tenth of the exemption level do not require retesting. (See 
Section XI.A.1 of this preamble).
    In the 1995 HWIR proposal, we proposed that the frequency of 
retesting would diminish over time. In today's notice, however, the 
frequency remains the same. Instead of diminishing the testing 
frequency, we would require retesting for those chemicals that are 
within an order of magnitude (above one-tenth) of the exemption levels. 
We believe this formulation will help reduce the burden of retesting 
and focus on those chemicals that are most likely to exceed the 
exemption levels due to waste stream variability. We request comment on 
these retesting provisions and particularly on whether retesting 
frequency should be diminished because of lower annual volumes or less 
variability in the waste stream. EPA also requests comments on whether 
to reduce testing frequency for generators who are small businesses 
that may or may not generate large annual volumes of waste.
    3. If the process generating my waste stream changes, would I have 
to retest? If a significant process change occurs, then you would have 
to retest the waste stream. A significant process change is one that 
has the potential to change the exempt status of the HWIR waste. 
Establishing retesting for process change is consistent with other EPA 
guidance and regulation (examples include recommendations within our 
Ash Sampling Guidance, July 1995 and within the LDR program as 
discussed at 51 FR 40597). We request comment on whether to require 
retesting after a significant process change.
B. What Would Happen If My Waste Stream No Longer Meets the Exemption 
Levels?
    If your waste stream no longer meets the HWIR exemption levels, it 
would no longer be exempt under this regulatory provision and would be 
a hazardous waste, subject to all hazardous waste management 
requirements. Once the waste is determined to be hazardous, it would 
remain hazardous until the waste stream met the exemption levels and 
the notification package requirements were fulfilled again. Compliance 
with HWIR exemption levels would be determined from the last available 
test data or from the latest sample taken from the waste in question. 
Testing which shows chemical concentration levels above exemption 
levels would not affect wastes previously generated under a valid claim 
of exemption.
    One issue is whether there should be additional requirements if a 
wastestream loses its HWIR exempt status because it no longer meets the 
exemption levels or does not meet one of the other conditions of the 
exemption. For example, should there be a mandatory waiting period 
before the exemption can be reinstated? Such a waiting period would 
give the overseeing agency a chance to inspect the documentation of the 
original exemption and would prevent a generator from exempting a 
wastestream shipment by shipment (instead of determining if the entire 
wastestream is clearly nonhazardous). We request comment on whether we 
should require such a waiting period or impose other requirements 
needed before a waste stream can regain its exempt status.
C. What Records Would I Have To Maintain On-Site and for How Long?
    You would have to maintain, on-site, a copy of the notification 
package sent to the overseeing agency, and a copy of the waste sampling 
and analysis plan for as long as the HWIR exemption continues to be 
active, and for the three years that follow. You would also have to 
maintain a record of all test results for three years after each waste 
testing event occurs. In addition, you would be required to maintain 
any specific documentation relied on in making process knowledge 
determinations, such as the Material Data Safety Sheet (MSDS), product 
labels, or information provided by manufacturers of the processing 
equipment. You would have to be able to explain any process knowledge 
determinations if requested by the overseeing agency.
D. How Would the Overseeing Agency Access These Records?
    You would be required to make all records relating to the HWIR 
exemption, including any information claimed as Confidential Business 
Information, immediately available to an overseeing agency during an 
inspection. In addition, you would have to provide a copy of the 
records directly to the overseeing agency within five business days of 
receiving a written request.
E. What Would Happen If the Information I Submitted in the Notification 
Package Changes?
    If any of the information in your notification package changes, you 
would have to provide a revised package to the overseeing agency within 
30 days of that change.

XII. What Would Be the Conditions and Requirements for the Landfill-
Only HWIR Exemption?

A. Which Conditions and Requirements Would Be the Same for the Generic 
HWIR Exemption and the Landfill-Only HWIR Exemption?
    The landfill-only HWIR exemption would include all the same 
implementation conditions and requirements as the generic HWIR 
exemption, including waste sampling and analysis plans, notification, 
follow-up testing and recordkeeping and reporting.
B. What Additional Conditions and Requirements Would I Have to Meet for 
the Landfill-Only HWIR Exemption?
    Because the exemption levels for the landfill-only HWIR exemption 
would be conditioned on disposal of this waste in a landfill, we 
believe that additional conditions and requirements are needed to 
ensure that the waste arrives at the landfill in a timely manner. The 
landfill-only exemption levels could not be considered protective of 
other waste management scenarios (including storage in a waste pile, 
which was modeled separately). The following three additional 
conditions and requirements for the landfill-only exemption would help 
address these concerns.
    (1) You would have to dispose of this waste in a landfill.
    (2) You would not be allowed to place this waste on the land, prior 
to disposal in a landfill. We are concerned about the temporary 
placement of these wastes in waste piles or other such intermediate 
land-based destinations, because exemption levels for the landfill-only 
option (unlike the levels for the generic option) would not consider 
such risks. We are particularly concerned about the potential of 
significant releases of particulate releases to air, as well as 
releases through erosion and runoff, since risks from these pathways 
are either not applicable or significantly reduced for the landfill 
scenario, but could be considerable for other scenarios.

[[Page 63406]]

    To ensure that the HWIR waste exempted under the landfill-only 
option is eventually disposed in a landfill, we are requesting comment 
on whether to restrict storage time of these wastes to one year. You 
would also only be allowed to store the waste in non-land-based units, 
such as tanks, containers or containment buildings. This storage 
requirement is similar to one imposed on restricted wastes under the 
LDR program (40 CFR 268.50). 40 CFR 268.50(b) allows waste handlers to 
store restricted wastes for up to one year, unless EPA demonstrates 
that such storage is not solely for the purpose of accumulation for 
proper recovery, treatment, or disposal.
    (3) You would have to track the arrival of your HWIR exempt waste 
at a landfill, and keep records of the shipments. Since the exemption 
levels for the landfill-only HWIR exemption would be based solely on 
assessing risks associated with disposal of this waste in a landfill, 
we want to ensure that the waste is, in fact, disposed at such a 
destination in a timely manner. We are asking for comment on three 
alternatives for tracking the landfill-only exempted waste.
    Under the first alternative, you would have to directly notify the 
designated landfill of the shipment of landfill-only HWIR exempt waste. 
Specifically, this notification would include the date of shipment, the 
carrier(s) used, the destination facility, and volume and general 
description of the waste. This notification does not need to accompany 
the waste, since you notify the disposal facility directly.
    You should receive a certification from the landfill operator that 
the waste arrived. You would have to keep a copy of this certification 
for three years. We also request comment on whether to require the 
destination landfill owner/operator to keep copies of this 
certification for three years as well. If you have not received a 
certification that the waste shipment arrived at the landfill 45 days 
after the date of shipment, then you would have to report this to the 
overseeing agency. If the waste has not reached the landfill within 60 
days after the date of shipment, then on the 61st day, the waste stream 
would not be exempt from RCRA Subtitle C and is now a hazardous waste. 
You (the generator), as the person identified on the HWIR notification 
form, would be the generator of this hazardous waste and must comply 
with 40 CFR Part 262.
    A second alternative, which we would like to receive comment on, 
would use the existing manifest system to track the conditionally 
exempt HWIR waste. The uniform hazardous waste manifest (40 CFR 262.20 
and 49 CFR 172.205) is prepared and signed by the waste generator and 
accompanies the waste shipment as it moves among the waste carriers, 
until it reaches the designated facility that is permitted to receive 
the waste. The receiving facility must sign the manifest and return it 
to the hazardous waste generator. The generator, carrier(s), and 
receiving facility must retain copies of the signed manifests for three 
years. This cradle-to-grave tracking system is intended to ensure that 
hazardous waste is properly managed and to allow generators and their 
overseeing agencies the ability to track their hazardous wastes.
    However, we are concerned that requiring nonhazardous materials 
transporters and waste management facilities to comply with manifest 
requirements could create considerable burden for nonhazardous 
facilities that become subject to these requirements. Furthermore, in 
many States, regulations prohibit Subtitle D facilities from receiving 
manifested wastes, and current federal regulations limit the use of the 
manifest to handlers that have EPA RCRA identification numbers.
    On the other hand, we are planning in a separate action to propose 
revisions to the Uniform Hazardous Waste Manifest regulations in 
response to many requests for a streamlined, up-to-date, and less 
burdensome hazardous waste tracking system. Under the proposed 
revisions to the existing manifest system, we are developing a standard 
manifest form with fewer State optional boxes and are proposing to 
automate the manifest paperwork. Therefore, although we are not 
proposing to require uniform hazardous waste manifest tracking, we 
recognize that the revised manifest system might be perceived by 
industry and the states as a less burdensome alternative than creating 
an entirely new tracking system for HWIR exempt wastes. We request 
comment on using the revised manifest system for HWIR exempt wastes.
    Under a third alternative, which we would like to receive comment 
on, we considered using Department of Transportation (DOT) shipping 
papers (49 CFR 173 Subpart C) to track the waste. Under this option, 
the shipping papers would need to include additional information, 
including the date of the shipment, the carrier used, and the 
destination facility. The generator would be required to provide the 
transporter with a copy of the shipping papers, which would identify 
the destination facility. The initial transporter, and any subsequent 
transporters, would be required to return to you a copy of each 
shipping paper, with a notation indicating the identification of the 
disposal facility (and/or the subsequent transporter). There would be 
no record keeping requirements placed upon the transporter or disposal 
facility, however, you would be required to keep copies of these 
records for three years.
    However, the representatives from DOT were uncomfortable with this 
option for a number of reasons. First, although it serves to reduce 
burden on the landfill owner/operator, it increases the burden on the 
transporter in terms of having to send copies to generators with each 
change of custody. In addition, some wastes would fall out of DOT's 
jurisdiction without manifest coverage. DOT regulates ``hazardous 
materials,'' and waste accompanied by a hazardous waste manifests are 
automatically defined as a hazardous material. If the manifest is no 
longer required, then some wastes would no longer meet the definition 
of hazardous material. Therefore, we believe that the benefits provided 
by this option might be outweighed by the complexity of implementation. 
However, we would be interested in receiving public comment on this 
notion of using shipping papers or other alternative documents to track 
HWIR exempt wastes.
    Regardless of which option we pursue, interstate transport of HWIR 
wastes would be an issue. If your State were to adopt an HWIR 
exemption, your HWIR waste would be nonhazardous only within your State 
or other States with the HWIR exemption. Thus, HWIR exempt wastes 
shipped to or through a State where the HWIR exemption had not been 
adopted would have to comply with the applicable hazardous waste 
requirements. Commentors to the 1995 HWIR proposal remarked on this 
patchwork of State programs as an important HWIR issue, but offered 
little way of specific guidance or suggestions for resolving this 
issue. We request further comment on this issue in today's notice.

XIII. What Would Happen if I Do Not Comply With the Conditions and the 
Requirements of the HWIR Exemption?

A. What Is the Difference Between an HWIR Condition and a Requirement?
    A condition is an obligation you or your waste must meet in order 
for your waste to become and to remain exempt from hazardous waste 
regulations. If a condition is not fulfilled, then the waste is 
hazardous and subject to RCRA Subtitle C requirements. A requirement is 
an obligation whose violation would not affect the exempt status of the 
HWIR

[[Page 63407]]

waste, but would be a violation under RCRA.
B. What Are the Conditions for the Two HWIR Options, and What Would 
Happen if I Do Not Meet Them?
    We are considering three conditions for meeting the generic HWIR 
waste exemption: (1) meeting the appropriate HWIR exemption levels (2) 
testing and retesting of the waste, which documents that exemption 
levels have been met; and (3) notification to the overseeing agency 
that you are managing the waste as exempt. The landfill-only 
alternative has four conditions: (1) meeting the appropriate HWIR 
exemption levels (2) testing and retesting of the waste, which 
documents that exemption levels have been met; (3) notification to the 
overseeing agency that you are managing the waste as exempt; and (4) 
waste arrival at the landfill facility within the 60 day time period.
    Failure to meet any of these conditions would have the effect of 
rendering the waste back into regulation under RCRA Subtitle C. For 
example, under the landfill-only alternative, if a waste no longer met 
the exemption levels, or if the overseeing agency was not properly 
notified, or if the required testing was not performed, or if the waste 
did not arrive at the designated landfill within 60 days of shipment, 
then the waste stream would be considered hazardous and subject to all 
provisions of RCRA Subtitle C.
C. What Would HWIR Tracking Requirements Be, and What Would Happen if I 
Do Not Meet Them?
    The HWIR tracking requirements would only apply to waste exempted 
under the landfill-only alternative. HWIR waste tracking requirements 
would be imposed on both generators and landfill operators.
    As discussed in Section XII.B of this preamble, HWIR waste 
generators would have to notify the designated landfill of the shipment 
of conditionally exempt HWIR waste. The landfill operators receiving 
the waste must certify in writing to the generator confirming that the 
waste arrived at the landfill. The HWIR generator must keep copies of 
these records for three years from the shipment date, and we are 
requesting comment on whether the landfill operator must also keep 
copies of these records.
    These tracking requirements would be under the authority of 
Sections 3007 and 2002 of RCRA Subtitle C and therefore are not 
conditions of the exemption. Section 3007 gives us the authority to 
compel anyone who generates, stores, treats, transports, disposes of or 
otherwise handles or has handled hazardous wastes to ``furnish 
information related to such wastes'' and make such information 
available to the government for ``the purposes of...enforcing the 
provisions of this chapter.'' Section 2002 gives the Administrator the 
authority to promulgate such regulations as are necessary to carry out 
the functions of the statute. Failure to comply with these tracking 
requirements would not affect the exempt status of the waste, but the 
landfill's failure to send back the certification would constitute a 
violation of RCRA.
    Although the paperwork that tracks the arrival of the waste 
shipment at the landfill is a requirement, the arrival of the waste at 
the landfill within 60 days would be a condition. Thus if the waste 
arrived at the landfill within 60 days, but the landfill did not send 
back the certification of arrival, the waste would maintain its exempt 
status. (Although, as noted above, the landfill's failure to send back 
the certification would be a violation of RCRA). However, if the waste 
did not arrive at the landfill within 60 days of shipment, it would 
lose its exempt status and would be subject to all RCRA Subtitle C 
requirements.

XIV. What Might the Regulatory Language for the HWIR Exemption Look 
Like?

    Below is draft language that shows what the HWIR exemption 
regulatory language might look like. As explained in Section XVII, , we 
are not proposing the HWIR exemption because of technical difficulties 
in developing chemical-specific exemption levels from the model. Before 
we would go final with an HWIR exemption, we would first publish an 
HWIR proposal that would include specific exemption levels and give the 
public an opportunity to comment. We are including this draft language 
for discussion to help you give us more targeted comments on the 
implementation provisions that we have discussed in previous preamble 
sections.

Purpose and Scope of the HWIR Exemption

A. What Is the Purpose of This Exemption?

    (1) The HWIR exemption outlines the conditions and procedures that 
a facility can use to exempt a listed hazardous waste from the 
requirements of 40 CFR Parts 262-266, 270, and under certain 
circumstances, also from 40 CFR Part 268. A waste may be exempted 
when--preferably through pollution prevention or otherwise through 
treatment--the chemicals in the waste are at or below the exemption 
levels listed in Table 2.
    (2) The rule sets exemption levels for two disposal alternatives. 
One allows unrestricted management of exempted wastes. The other 
requires exempted wastes be disposed only in a landfill.

B. What Is the Scope of This Exemption?

    (1) Wastes meeting all requirements of the HWIR exemption are 
exempt from all requirements of 40 CFR Parts 262-266 and 270.
    (2) Wastes meeting the requirements described in Section are not 
subject to the land disposal restrictions of 40 CFR Part 268.
    (3) Wastes containing a chemical listed in Table 2 for which there 
is no exemption level in Table 3 are ineligible for this exemption.

C. What Definitions Apply?

    Chemicals reasonably expected to be present means:
    (1) Chemicals identified as the basis for listing the waste you 
wish to exempt. (For F and K listed waste, these chemicals are 
identified in Appendix VII of 40 CFR Part 261. For P and U listed 
waste, these are chemicals are found in 40 CFR 261.33),
    (2) Chemicals listed in the table ``Treatment Standards for 
Hazardous Wastes'' contained in 40 CFR 268.40 as regulated hazardous 
chemicals for land disposal restriction (LDR) treatment of the waste,
    (3) Chemicals detected in any previous analysis of the same waste,
    (4) Chemicals introduced into the process that generates the waste, 
and
    (5) Chemicals that are byproducts of the process that generates the 
waste.
    Overseeing agency means the state or EPA regional authority that 
administers the exemption.
    Waste form means at the point of exemption, the waste form is 
liquid, semi-solid, or solid, as defined below (for the purposes of the 
HWIR exemption only):
    (1) Liquid means a waste contains total suspended solids less than 
1% by weight.
    (2) Semi-solid means a waste contains total suspended solids of 1% 
or more by weight but no more than 30% by weight.
    (3) Solid means a waste contains total suspended solids more than 
30% by weight.

[[Page 63408]]

Obtaining an Exemption

D. What Steps Must I Follow To Establish My Waste as Exempt?

    You must take the following steps to establish that your waste 
meets the requirements of the HWIR exemption:
    (1) Determine whether your waste is reasonably expected to contain 
any chemical listed in Table 2, using the criteria described in Section 
XIV.E.

    Note: If your waste is reasonably expected to contain any 
chemical listed in Table 2 for which there is no exemption level in 
Table 3, your waste cannot be exempt under the HWIR exemption even 
if you do not detect the chemical.

    (2) Determine the form of your waste (liquid, semi-solid, or solid) 
and under which regulatory alternative (unrestricted management or 
landfill-only) you will be claiming the exemption (see Section XIV.F).
    (3) Determine the concentration of each Appendix X chemical 
reasonably expected to be present in your waste (see Sections XIV.G, H, 
and I).
    (4) Determine whether the concentrations of all the Appendix X 
chemicals in your waste are at or below the exemption levels 
established for your waste form and disposal alternative (see Section 
XIV.J).
    (5) Notify the overseeing agency that you are claiming an exemption 
under the HWIR exemption for your waste (see Section XIV.K).
    (6) For the landfill-only alternative, notify the receiving 
landfill (see Section XIV.M).

E. What Wastes Are Eligible for this Exemption?

    To be eligible for this exemption, your waste must meet the 
following conditions:
    (1) Your waste must exhibit none of the characteristics of 
hazardous waste set out in subpart C of 40 CFR Part 261. If your waste 
does exhibit a hazardous waste characteristic, it must be de-
characterized before it can be exempt.
    (2) Your waste must meet one or more of the following descriptions:
    (a) Any listed hazardous waste described in 40 CFR 261.31 (non-
specific sources), 40 CFR 261.32 (specific sources), and 40 CFR 261.33 
(discarded commercial chemical products).
    (b) Any mixture of a listed hazardous waste with a solid waste 
under 40 CFR 261.3(a)(2)(iii) or (iv).
    (c) Any waste derived from the treating, storing, or disposing of a 
listed hazardous waste under 40 CFR 261.3(c)(2)(i).
    (d) Any media or debris contaminated with a listed hazardous waste, 
a mixture containing a listed hazardous waste, or a waste derived from 
a listed hazardous waste.
    (3) All chemicals reasonably expected to be present in your waste 
must have exemption levels listed in Table 2, and be at or below those 
exemption levels. Chemicals reasonably expected to be present in your 
waste are those chemicals in Table 3 that meeting the following:
    (a) Chemicals identified as the basis for listing the waste you 
wish to exempt. (For F and K listed waste, these chemicals are 
identified in Appendix VII of 40 CFR Part 261. For P and U listed 
waste, these are chemicals are found in 40 CFR 261.33).
    (b) Chemicals listed in the table ``Treatment Standards for 
Hazardous Wastes'' contained in 40 CFR 268.40 as regulated hazardous 
chemicals for land disposal restriction (LDR) treatment of the waste.
    (c) Chemicals detected in any previous analysis of the same waste.
    (d) Chemicals introduced into the process that generates the waste.
    (e) Chemicals that are byproducts of the process that generates the 
waste.

F. What Chemical Concentration Levels Must My Waste Meet To Become 
Exempt?

    To become exempt your waste must meet the chemical concentration 
levels specified in Table 3. These exemption levels depend on the form 
of your waste (liquid, semi-solid, or solid) and the type of exemption 
you intend to pursue (unrestricted management or landfill only).
    (1) To use the unrestricted-management alternative, the chemicals 
in your waste must be at or below the exemption levels in Table 3 for 
unrestricted management. Under this alternative, you must determine 
your waste form and meet the exemption level for that form. The waste 
form depends on the total suspended solids (TSS) in the waste (see 
definitions, Section XIV.C):

------------------------------------------------------------------------
      If your waste contains TSS in a
             concentration of                  Then it is defined as a
------------------------------------------------------------------------
Less than 1%..............................  Liquid.
Between 1% and 30%........................  Semi-solid.
Greater than 30%..........................  Solid.
------------------------------------------------------------------------

    (2) To use the landfill-only alternative then the chemicals in your 
waste must be at or below the exemption levels in Table 3 for landfill 
only.

G. For Which Chemicals Must I Test in My Waste?

    (1) You must test your waste for each chemical reasonably expected 
to be present in your waste, as identified in Section XIV.E.
    (2) For chemicals listed in Table 2 other than those reasonably 
expected to be present in your waste, you may either test for any such 
chemical or use your knowledge of the production process that generated 
the waste to determine that it is not present.

H. At What Point Must I Sample My Waste?

    You may sample your waste at any point between its point of 
generation and its point of disposal. However, your waste will be 
subject to land disposal restrictions in 40 CFR Part 268 unless your 
waste meets all applicable concentration levels at its point of 
generation.

I. How Must I Sample and Analyze My Waste?

    (1) For each waste you seek to exempt you must develop and follow a 
written plan for sampling and analyzing wastes. The plan must contain 
the following:
    (a) The chemicals for which you will analyze each waste and the 
rationale for choosing those chemicals.
    (b) Your methods for collecting a representative sample of the 
waste to be analyzed.
    (c) Your preparation and test methods for analyzing these 
chemicals.
    (d) Sampling procedures and locations for characterizing the waste 
stream.
    (2) You must analyze at least 4 samples. You must also document the 
results from all samples analyzed.

J. What Must My Analysis Show?

    (1) For every chemical tested, each sample must show that the total 
concentration in the waste is at or below the exemption level 
appropriate to your waste form and type of exemption.
    (2) You must document your ability to analyze a sample spiked at or 
below the exemption level. Such documentation would consist of 
analytical results from a sample spiked at or below exemption level 
concentrations.

K. What Information Must I Submit to the Overseeing Agency?

    Before managing any waste as exempt under the HWIR exemption, you 
must send a notice to the overseeing agency by certified mail or other 
mail service that confirms delivery in writing. This notice of your 
exemption claim must include all of the following:

[[Page 63409]]

    (1) Your facility's name, address, and RCRA ID number.
    (2) The applicable EPA hazardous waste code of your exempted waste 
and the narrative description associated with the listing from subpart 
D of 40 CFR Part 261.
    (3) A brief, general description of how you manufactured, treated, 
or otherwise produced the waste.
    (4) An estimate of the annual quantities of the exempted waste.
    (5) A statement that you are claiming the HWIR exemption for the 
waste.
    (6) A certification--signed by you or your authorized 
representative--that the information in your notice is true, accurate, 
and complete.

L. When Does the Exemption Take Effect?

    The exemption--whether unrestricted management or landfill only--
takes effect when you receive written confirmation of delivery to the 
overseeing agency. At that time you may begin managing your waste under 
this exemption.

M. Must I Track My Waste Exempted Under the HWIR Exemption?

    (1) Waste meeting the exemption levels for unrestricted management 
require no tracking.
    (2) For waste meeting the exemption levels for landfill-only:
    (a) You must send written notice to the landfill receiving your 
waste and include the following:
    (i) The date of the shipment.
    (ii) The volume and form of the waste.
    (iii) A general description of the exempt waste.
    (iv) The shipper(s) used to transport the waste.
    (v) A signed certification that your waste meets the exemption 
levels for landfill-only.
    (b) You must receive a certification from the landfill owner or 
operator that the waste shipment reached the landfill within 60 days of 
shipment. If you do not receive this certification within 45 days of 
the shipment date, you must notify the overseeing agency in writing 
that you have not received the certification.
    (c) You must keep a copy of the notification you sent to the 
landfill and a copy of the certification you received from the landfill 
(and/or the notification you sent to the overseeing agency that you did 
not receive the certification from the landfill) for three years.
    (d) If your waste does not arrive at the landfill within 60 days of 
shipment, the waste that you claimed as exempt is no longer exempt on 
the 61st day and is now a hazardous waste. You, as the person 
identified on the HWIR notification form, are the generator of this 
hazardous waste and must comply with 40 CFR Part 262.

N. Must my waste meet 40 CFR Part 268--Land Disposal Requirements?

    Your waste must meet all applicable requirements in 40 CFR Part 
268, unless each waste sample is at or below the exemption levels at 
the point of generation.

O. Where May I Dispose of My Exempt Waste?

    (1) For the unrestricted management alternative, you may dispose of 
this waste in any destination that can legally accept nonhazardous 
waste.
    (2) For the landfill-only alternative, you must dispose of this 
waste directly in a landfill licensed or permitted by the state or 
federal government under Subtitle C or D of RCRA. The waste must not be 
placed on the land before final disposal.

Maintaining an Exemption

P. What If the Information I Submitted Changes?

    You must submit to the head of the overseeing agency any change in 
any information submitted as describe in Section XIV.K within 30 
business days of learning of the change.

Q. What Retesting Must I Do?

    (1) You must retest for all chemicals reasonably expected to be in 
your waste on the following schedule, based on waste form and annual 
quantity of the waste produced. However, you do not need to retest for 
the chemical if after twelve months of testing, your analysis has shown 
concentrations uniformly below one-tenth of the applicable exemption 
level.

------------------------------------------------------------------------
   If you generate the following annual
     quantity of liquid waste (tons):           Then you must retest
------------------------------------------------------------------------
0-35,000..................................  Every 12 months.
35,000-500,000............................  Every 6 months.
Over 500,000..............................  Every 3 months.


------------------------------------------------------------------------
   If you generate the following annual
   quantity of semi-solid or solid waste        Then you must retest
                  (tons)
------------------------------------------------------------------------
0-2,000...................................  Every 12 months.
2,000-10,000..............................  Every 6 months.
Over 10,000...............................  Every 3 months.
------------------------------------------------------------------------

    (2) You must follow a waste sampling and analysis plan meeting the 
requirements described in Section XIV.I for retesting.
    (3) If at any time the process generating the exempt waste changes 
significantly, you must retest the waste for all chemicals reasonably 
expected to be present. A significant change is one that could affect 
the exempt status of the waste under consideration. For example, a 
change that adds new chemicals or increases chemical concentrations is 
a significant change.

R. What Records Must I Maintain On-Site, and for How Long?

    You must keep records of the following in your files on-site for 
three years after the date of the relevant test:
    (1) The waste sampling and analysis plans for initial testing (as 
described in Section XIV.I) and retesting (as described in Section 
XIV.Q).
    (2) Results from the waste sampling and analysis including quality 
control analyses from initial testing or retesting.
    (3) All volume determinations made to decide on the frequency of 
retesting as described in Section XIV.Q.
    (4) Any information submitted to the overseeing agency either as 
part of the initial notice (see Section XIV.K) or for later changes 
(see Section XIV.P).
    (5) Any specific documentation relied on in making process 
knowledge determinations, such as the Material Data Safety Sheet 
(MSDS), product labels, or information provided by manufacturers of the 
processing equipment.
    (6) Documentation of compliance with the LDR requirements of 40 CFR 
268.
    (7) For the landfill-only alternative, notification that the waste 
was shipped to a landfill and certification that the waste shipment 
reached the landfill (see Section XIV.M).

Consequences of Not Meeting the Exemption

S. How Will the Overseeing Agency Verify an Exemption?

    (1) The overseeing agency may conduct inspections and audits to 
verify your exemption claim. Such inspections could include sampling of 
the exempt waste stream. Exceedances of the exemption levels determined 
by single grab samples would be sufficient to demonstrate non-
compliance with the requirements of the exemption.
    (2) You must make all records relating to the exemption immediately 
available to the overseeing agency performing an inspection. You must 
provide a copy of the records to the overseeing agency within 5 
business days of receiving a written request.
    (3) You must be able to explain any process knowledge 
determinations if requested by the overseeing agency.
    (4) In an enforcement action, the burden of proof to establish 
compliance

[[Page 63410]]

with the requirements of the HWIR exemption is on the person claiming 
the exemption.

T. What Is the Status of My Waste if I Don't Meet or Maintain the 
Exemption?

    Failure to satisfy any of the exemption conditions [except those 
described in Sections XIV.M(2)(a)-XIV.M(2)(c)] voids the exemption and 
requires that you manage the exempted waste stream has hazardous waste.
    Failure to satisfy the requirements described in Sections 
XIV.M(2)(a)-XIV.M(2)(c) for the landfill-only alternative (in other 
words, the tracking requirements) would not affect the exempt status of 
the waste, but would constitute a violation of RCRA.

              Table 2.--Appendix X HWIR Exemption Chemicals
------------------------------------------------------------------------
   Chemical name [alternate names]       CASRN              Note
------------------------------------------------------------------------
A2123 [Ethanimidothioic acid, 2-       30558-43-1  .....................
 (dimethylamino) -N-hydroxy-2-oxo-
 ,methyl ester].
Acenaphthene........................      83-32-9  b
Acenaphthylene [Acenaphthalene].....     208-96-8  b
Acetaldehyde [Ethanal]..............      75-07-0  .....................
Acetone [2-Propanone]...............      67-64-1  .....................
Acetonitrile [Ethanenitrile]........      75-05-8  .....................
Acetophenone........................      98-86-2  .....................
2-Acetylaminofluorene [2-AAF].......      53-96-3  b
Acrolein [2-Propenal]...............     107-02-8  .....................
Acrylamide [Propenaminde]...........      79-06-1  .....................
Acrylic acid........................      79-10-7  .....................
Acrylonitrile [2-Propenenitrile]....     107-13-1  .....................
Aldicarb............................     116-06-3  .....................
Aldicarb sulfone....................    1646-88-4  .....................
Aldrin..............................     309-00-2  .....................
Allyl alcohol.......................     107-18-6  .....................
Allyl chloride [3-Chloropropylene]       107-05-1  .....................
 [3-Chloropropene].
4-Aminobiphenyl.....................      92-67-1  .....................
5-Aminomethyl-3-isoxazolol              2763-96-4  .....................
 [Muscimol].
4-Aminopyridine.....................     504-24-5  b
Amitrole............................      61-82-5  .....................
Ammonium picrate....................     131-74-8  .....................
Aniline.............................      62-53-3  .....................
Anthracene..........................     120-12-7  b
Antimony [Antimony, total]..........    7440-36-0  b, c
Aramite.............................     140-57-8  .....................
Arsenic [Arsenic, total]............    7440-38-2  b, c
Auramine............................     492-80-8  .....................
Azaserine...........................     115-02-6  .....................
Barban..............................     101-27-9  .....................
Barium [Barium, total]..............    7440-39-3  b, c
Bendiocarb..........................   22781-23-3  .....................
Bendiocarb phenol...................   22961-82-6  .....................
Benomyl.............................   17804-35-2  .....................
Benz[c]acridine.....................     225-51-4  b
Benz[a]anthracene...................      56-55-3  b
Benzene.............................      71-43-2  .....................
Benzenesulfonyl chloride............      98-09-9  .....................
Benzidine...........................      92-87-5  .....................
Benzo[b]fluoranthene................     205-99-2  b
Benzo[j]fluoranthene................     205-82-3  b
Benzo[k]fluoranthene................     207-08-9  b
Benzo[g,h,i]perylene................     191-24-2  b
Benzo[a]pyrene......................      50-32-8  b
Benzyl alcohol......................     100-51-6  .....................
Benzyl chloride.....................     100-44-7  .....................
Beryllium [Beryllium, total]........    7440-41-7  b, c
Bromoacetone........................     598-31-2  .....................
Bromodichloromethane                      75-27-4  b
 [Dichlorobromomethane].
Bromoform [Tribromomethane].........      75-25-2  b
Bromomethane [Methyl bromide].......      74-83-9  b
4-Bromophenyl phenyl ether [p-           101-55-3  .....................
 Bromodiphenyl ether].
Brucine [2,3-Dimethoxy strychnidin-      357-57-3  .....................
 10-one].
n-Butyl alcohol [n-Butanol].........      71-36-3  .....................
Butylate............................    2008-41-5  .....................
Butyl benzyl phthalate..............      85-68-7  b
Cadmium [Cadmium, total]............    7440-43-9  b, c
Carbaryl............................      63-25-2  .....................
Carbendazim.........................   10605-21-7  .....................
Carbofuran..........................    1563-66-2  .....................
Carbofuran phenol...................    1563-38-8  .....................
Carbon disulfide....................      75-15-0  .....................
Carbon tetrachloride................      56-23-5  b

[[Page 63411]]

 
Carbosulfan.........................   55285-14-8  .....................
Chlorambucil........................     305-03-3  .....................
Chlordane [Chlordane, alpha and           57-74-9  a
 gamma isomers].
Chlornaphazin.......................     494-03-1  .....................
Chloroacetaldehyde..................     107-20-0  .....................
4-Chloroaniline [p-Chloroaniline]...     106-47-8  .....................
Chlorobenzene [Monochlorobenzene]...     108-90-7  b
Chlorobenzilate.....................     510-15-6  .....................
p-Chloro-m-cresol...................      59-50-7  b
Chloroethane [Ethyl chloride].......      75-00-3  b
bis-(2-Chloroethoxy) methane             111-91-1  .....................
 [Dichloromethoxy ethane].
bis-(2-Chloroethyl) ether                111-44-4  b
 [Dichloroethyl ether] [1,1'-
 Oxybis(2-chloroethane)].
Chloroform [Trichloromethane].......      67-66-3  b
bis-(2-Chloroisopropyl) ether [2,2'-     108-60-1  b
 Oxybis(1-chloropropane)] [Bis-(2-
 Chloro-1-methylethyl) ether].
Chloromethane [Methyl chloride].....      74-87-3  b
bis-(Chloromethyl) ether                 542-88-1  b
 [Dichloromethyl ether].
2-Chloronaphthalene [beta-                91-58-7  b
 Chloronaphthalene].
2-Chlorophenol [o-Chlorophenol].....      95-57-8  b
4-Chlorophenyl phenyl ether [p-         7005-72-3  b
 Chlorodiphenyl ether].
1-(o-Chlorophenyl) thiourea.........    5344-82-1  .....................
Chloroprene [2-Chloro-1,3-butadiene]     126-99-8  .....................
3-Chloropropionitrile...............     542-76-7  .....................
4-Chloro-o-toluidine hydrochloride..    3165-93-3  .....................
Chromium [Chromium, total]..........    7440-47-3  b, c
Chrysene............................     218-01-9  b
Citrus red No. 2....................    6358-53-8  .....................
Cobalt [Cobalt, total]..............    7440-48-4  e
Copper [Copper, total]..............    7440-50-8  c
Copper dimethyldithiocarbamate......     137-29-1  .....................
o-Cresol [2-Methyl phenol]..........      95-48-7  a
--Cresol [3-Methyl phenol]..........     108-39-4  a
p-Cresol [4-Methyl phenol]..........     106-44-5  a
Crotonaldehyde [trans-2-Butenal]        4170-30-3  .....................
 [beta-Methylacrolein].
Cumene [Isopropyl benzene]..........      98-82-8  .....................
--Cumenyl methylcarbamate...........      64-00-6  .....................
Cyanides, amenable..................      57-12-5  b, d
Cyanides, total.....................      57-12-5  b, d
Cycasin.............................   14901-08-7  .....................
Cycloate............................    1134-23-2
Cyclohexane.........................     110-82-7  .....................
Cyclohexanone.......................     108-94-1  .....................
2-Cyclohexyl-4,6-dinitrophenol......     131-89-5  b
Cyclophosphamide....................      50-18-0  .....................
2,4-D [2,4-Dichlorophenoxyacetic          94-75-7  d
 acid].
Daunomycin..........................   20830-81-3  .....................
Dazomet.............................     533-74-4  .....................
o,p'-DDD............................      53-19-0  a
p,p'-DDD............................      72-54-8  a
o,p'-DDE [o,p' TDE].................    3424-82-6  a
p,p'-DDE [p,p'-TDE].................      72-55-9  a
o,p'-DDT............................     789-02-6  a
p,p'-DDT............................      50-29-3  a
Diallate............................    2303-16-4  .....................
Dibenz[a,h]acridine.................     226-36-8  b
Dibenz[a,j]acridine.................     224-42-0  b
Dibenz[a,h]anthracene...............      53-70-3  b
7H-Dibenzo[c,g]carbazole............     194-59-2  b
Dibenzofuran........................     132-64-9  .....................
Dibenzo[a,e]pyrene..................     192-65-4  b
Dibenzo[a,h]pyrene..................     189-64-0  b
Dibenzo[a,i]pyrene..................     189-55-9  b
Dibromochloromethane                     124-48-1  b
 [Chlorodibromomethane].
1,2-Dibromo-3-chloropropane.........      96-12-8  .....................
Di-n-butyl phthalate................      84-74-2  b
1,2-Dichlorobenzene [o-                   95-50-1  a, b
 Dichlorobenzene].
1,3-Dichlorobenzene [m-                  541-73-1  a, b
 Dichlorobenzene].
1,4-Dichlorobenzene [p-                  106-46-7  a, b
 Dichlorobenzene].
3,3'-Dichlorobenzidine..............      91-94-1  .....................
cis-1,4-dichloro-2-butene...........    1476-11-5  a
trans-1-4-Dichloro-2-butene.........     110-57-6  a
Dichlorodifluoromethane [CFC-12]....      75-71-8  b
1,1-Dichloroethane [Ethylidene            75-34-3  b
 dichloride].

[[Page 63412]]

 
1,2-Dichloroethane [Ethylene             107-06-2  b
 dichloride].
1,1-Dichloroethylene [Vinylidene          75-35-4  b
 chloride].
cis-1,2-Dichloroethylene............     156-59-2  a, b
trans-1,2-Dichloroethylene..........     156-60-5  a, b
2,2'-Dichloroisopropyl ether [2,2'-    39638-32-9  b
 Oxybis(2-chloropropane)].
2,4-Dichlorophenol 120-83-2 b 2,6-        87-65-0  b
 Dichlorophenol.
1,1-Dichloropropane [Propylidene          78-99-9  a, b
 chloride].
1,2-Dichloropropane [Propylene            78-87-5  a, b
 dichloride].
1,3-Dichloropropanol................   26545-73-3  a, b
Dichloropropene [Dichloropropylene]    26952-23-8  b
 [Dichloro-1-Propene].
cis-1,3-Dichloropropene [cis-1,3-      10061-01-5  a, b
 Dichloropropylene].
trans-1,3-Dichloropropene [trans-1,3-  10061-02-6  a, b
 Dichloropropylene].
Dieldrin............................      60-57-1  .....................
1,2,3,4-Diepoxybutane [2,2'-            1464-53-5  .....................
 Bioxirane].
Diethylene glycol, dicarbamate......    5952-26-1  .....................
O,O-Diethyl-S-methyl dithiophosphate    3288-58-2  b
Diethyl-p-nitrophenyl phosphate.....     311-45-5  .....................
Diethyl phthalate...................      84-66-2  b
Diethylstilbestrol..................      56-53-1  .....................
Dihydrosafrole......................      94-58-6  .....................
Dimethoate [O,O-Dimethyl S-               60-51-5  b
 methylcarbamoylmethyl
 phosphorodithioate].
3,3'-Dimethoxybenzidine.............     119-90-4  .....................
Dimethylamine [N-Methyl methanamine]     124-40-3  .....................
p-Dimethylaminoazobenzene [4-             60-11-7  .....................
 Dimethylaminoazobenzene].
7,12-Dimethylbenz[a]anthracene......      57-97-6  b
3,3'-Dimethylbenzidine..............     119-93-7  .....................
2,4-Dimethyl phenol.................     105-67-9  b
Dimethyl phthalate..................     131-11-3  b
Dimethyl sulfate....................      77-78-1
Dimetilan...........................     644-64-4
1,3-Dinitrobenzene [m-                    99-65-0  b
 Dinitrobenzene].
1,4-Dinitrobenzene [p-                   100-25-4  b
 Dinitrobenzene].
4,6-Dinitro-o-cresol [4,6-Dinitro-2-     534-52-1  d
 methyl phenol].
2,4-Dinitrophenol...................      51-28-5  b
2,4-Dinitrotoluene..................     121-14-2
2,6-Dinitrotoluene..................     606-20-2
Dinoseb [2-sec-Butyl-4,6-                 88-85-7  b
 dinitrophenol].
Di-n-octyl phthalate................     117-84-0  b
1,4-Dioxane [1,4-Diethylene dioxide]     123-91-1
Diphenylamine [N,N-Diphenylamine]...     122-39-4
1,2-Diphenylhydrazine...............     122-66-7
Di-n-propylamine [Dipropylamine]....     142-84-7
Disulfiram [Tetraethylthiuram             97-77-8
 disulfide].
Disulfoton [O,O-Diethyl S-(2-            298-04-4  b
 (ethylthio)ethyl)phosphorodithioate
 ].
Dithiobiuret........................     541-53-7
Endosulfan I [alpha-Endosulfan].....     959-98-8  a
Endosulfan II [beta-Endosulfan].....   33213-65-9  a
Endosulfan sulfate..................    1031-07-8
Endothall...........................     145-73-3
Endrin..............................      72-20-8
Endrin aldehyde.....................    7421-93-4  b
Endrin ketone.......................   53494-70-5  b
Epichlorohydrin [1-Chloro-2,3-           106-89-8
 epoxypropane].
Epinephrine.........................      51-43-4
2-Ethoxyethanol [Ethylene glycol         110-80-5  b
 monoethyl ether] [Cellosolve].
Ethyl acetate.......................     141-78-6
Ethyl acrylate......................     140-88-5
Ethyl benzene.......................     100-41-4
Ethyl carbamate [Urethane] [Carbamic      51-79-6
 acid, ethyl ester].
S-Ethyl dipropylthiocarbamate [EPTC]     759-94-4
Ethylenebisdithiocarbamic acid......     111-54-6  d
Ethylene dibromide [1,2-                 106-93-4
 Dibromoethane].
Ethylene oxide......................      75-21-8
Ethylene thiourea [2-                     96-45-7
 Imidazolidinethione].
Ethyl ether [Ethane 1,1' oxybis]....      60-29-7
bis-(2-Ethylhexyl) phthalate [Di-2-      117-81-7  b
 ethylhexyl phthalate].
Ethyl methacrylate..................      97-63-2
Ethyl methanesulfonate..............      62-50-0
Ethyl Ziram.........................   14324-55-1
Famphur.............................      52-85-7
Ferbam..............................   14484-64-1
2-Fluoracetamide....................     640-19-7

[[Page 63413]]

 
Fluoranthene........................     206-44-0  b
Fluorene............................      86-73-7  b
Fluoride............................   16984-48-8  c
Fluoroacetic acid, sodium salt            62-74-8
 [Sodium fluoroacetate].
Formaldehyde........................      50-00-0
Formetanate hydrochloride...........   23422-53-9
Formic Acid.........................      64-18-6
Formparanate........................   17702-57-7
Furan...............................     110-00-9
Furfural [ 2-Furancarboxaldehyde]...      98-01-1
Heptachlor..........................      76-44-8
Heptachlor epoxide, alpha, beta, and    1024-57-3  a
 gamma isomers.
1,2,3,4,6,7,8-Heptachlorodibenzo-p-    35822-46-9  a
 dioxin.
1,2,3,4,6,7,8-                         67562-39-4  a
 Heptachlorodibenzofuran.
1,2,3,4,7,8,9-                         55673-89-7  a
 Heptachlorodibenzofuran.
Hexachlorobenzene...................     118-74-1  b
Hexachloro-1,3-butadiene                  87-68-3
 [Hexachlorobutadiene].
alpha-Hexachlorocyclohexane [alpha-      319-84-6  a
 BHC].
beta-Hexachlorocyclohexane [beta-        319-85-7  a
 BHC].
delta-Hexachlorocyclohexane [delta-      319-86-8  a
 BHC].
gamma-Hexachlorocyclohexane [gamma-       58-89-9  a
 BHC] [Lindane].
Hexachlorocyclopentadiene...........      77-47-4
1,2,3,4,7,8 Hexachlorodibenzo-p-       39227-28-6  a
 dioxin.
1,2,3,6,7,8 Hexachlorodibenzo-p-       57653-85-7  a
 dioxin.
 1,2,3,7,8,9-Hexachlorodibenzo-p-      19408-74-3  a
 dioxin.
1,2,3,4,7,8 Hexachlorodibenzofuran..   70648-26-9  a
1,2,3,6,7,8 Hexachlorodibenzofuran..   57117-44-9  a
1,2,3,7,8,9 Hexachlorodibenzofuran..   72918-21-9  a
 2,3,4,6,7,8-Hexachlorodibenzofuran.   60851-34-5  a
Hexachloroethane....................      67-72-1  b
Hexachlorophene.....................      70-30-4
Hexachloropropene                       1888-71-7
 [Hexachloropropylene].
Hexaethyl tetraphosphate............     757-58-4
2-Hexanone..........................     591-78-6
Indeno[1,2,3-cd]pyrene..............     193-39-5  b
Iodomethane [Methyl iodide].........      74-88-4  b
3-Iodo-2-propynyl N-butylcarbamate..   55406-53-6
Isobutyl alcohol [isobutanol].......      78-83-1  .....................
Isodrin.............................     465-73-6  .....................
Isolan [Isopropyl methyl pyrazolyl       119-38-0  .....................
 dimethylcarbamate].
Isophorone..........................      78-59-1  .....................
Isosafrole..........................     120-58-1  .....................
Kepone [Chlordecone]................     143-50-0  .....................
Lasiocarpine........................     303-34-1  .....................
Lead [Lead,total]...................    7439-92-1  b, c
Maleic hydrazide....................     123-33-1  .....................
Malononitrile [Propanedinitrile]....     109-77-3  .....................
Manganese dimethyldithiocarbamate...   15339-36-3  .....................
Melphalan...........................     148-82-3  .....................
Mercury [Mercury, total]............    7439-97-6  b, c
Metam Sodium........................     137-42-8  .....................
Methacrylonitrile [2-Methyl-2-           126-98-7  .....................
 propenenitrile].
Methanol [Methyl alcohol]...........      67-56-1  .....................
Methapyrilene.......................      91-80-5  .....................
Methiocarb..........................    2032-65-7  .....................
Methomyl............................   16752-77-5  .....................
Methoxychlor........................      72-43-5  .....................
3-Methylcholanthrene................      56-49-5  b
4-Methylene bis-(2-chloroaniline)...     101-14-4  .....................
Methylene bromide [Dibromomethane]..      74-95-3  b
Methylene chloride [Dichloromethane]      75-09-2  b
Methyl ethyl ketone [2-Butanone]          78-93-3  .....................
 [MEK].
Methyl isobutyl ketone [Hexone] [4-      108-10-1  .....................
 Methyl-2-pentanone].
2-Methyllactonitrile [Acetone             75-86-5  .....................
 cyanohydrin].
Methyl methacrylate.................      80-62-6  .....................
Methyl methanesulfonate.............      66-27-3  .....................
2-Methylnaphthalene.................      91-57-6  b
Methyl parathion [O,O-Dimethyl O-p-      298-00-0  b
 nitrophenyl phosphorothioate].
2-Methyl pyridine [alpha-Picoline]       109-06-8  b
 [2-Picoline].
Methylthiouracil....................      56-04-2  .....................
Metolcarb...........................    1129-41-5  .....................
Mexacarbate.........................     315-18-4  .....................

[[Page 63414]]

 
Molinate............................    2212-67-1  .....................
Naphthalene.........................      91-20-3  .....................
1,4-Naphthoquinone..................     130-15-4  .....................
1-Naphthylamine [alpha-                  134-32-7  .....................
 Naphthylamine].
2-Naphthylamine [beta-Naphthylamine]      91-59-8  .....................
1-Naphthyl-2-thiourea [alpha-             86-88-4  .....................
 Naphthylthiourea].
Nickel [Nickel, total]..............    7440-02-0  b, c
Nicotine............................      54-11-5  d
2-Nitroaniline [o-Nitroaniline] [2-       88-74-4  .....................
 Nitrobenzenamine].
3-Nitroaniline [m-Nitroaniline] [3-       99-09-2  .....................
 Nitrobenzenamine].
4-Nitroaniline [p-Nitroaniline] [4-      100-01-6  .....................
 Nitrobenzenamine].
Nitrobenzene........................      98-95-3  .....................
Nitroglycerine......................      55-63-0  .....................
2-Nitrophenol [o-Nitrophenol].......      88-75-5  b
4-Nitrophenol [p-Nitrophenol].......     100-02-7  b
2-Nitropropane......................      79-46-9  .....................
4-Nitroquinoline-1-oxide............      56-57-5  .....................
N-Nitrosodi-n-butylamine............     924-16-3  b
N-Nitrosodiethanolamine.............    1116-54-7  b
N-Nitrosodiethylamine...............      55-18-5  b
N-Nitrosodimethylamine..............      62-75-9  b
N-Nitrosodiphenylamine                    86-30-6  b
 [Diphenylnitrosamine].
N-Nitrosodi-n-propylamine [Di-n-         621-64-7  b
 propylnitrosamine].
N-Nitroso-N-ethylurea...............     759-73-9  b
N-Nitroso-N-methylethylamine........   10595-95-6  b
N-Nitroso-N-methylurea..............     684-93-5  b
N-Nitroso-N-methylurethane..........     615-53-2  b
N-Nitrosomethylvinylamine...........    4549-40-0  b
N-Nitrosomorpholine.................      59-89-2  b
N-Nitrosonornicotine................   16543-55-8  b
N-Nitrosopiperidine.................     100-75-4  b
N-Nitrosopyrrolidine................     930-55-2  b
N-Nitrososarcosine..................   13256-22-9  b
5-Nitro-o-toluidine [2-Methyl-5-          99-55-8  .....................
 nitroaniline].
Octachlorodibenzo-p-dioxin [OCDD]...    3268-87-9  a
Octachlorodibenzofuran [OCDF].......   39001-02-0  a
Octamethylpyrophosphoramide.........     152-16-9  .....................
Osmium..............................    7440-04-2  c
Oxamyl..............................   23135-22-0  .....................
Paraldehyde.........................     123-63-7  .....................
Parathion [O,O-Diethyl O-p-               56-38-2  b
 nitrophenyl phosphorothioate].
Pebulate............................    1114-71-2  .....................
Pentachlorobenzene..................     608-93-5  b
1,2,3,7,8-Pentachlorodibenzo-p-        40321-76-4  a
 dioxin.
1,2,3,7,8-Pentachlorodibenzofuran...   57117-41-6  a
2,3,4,7,8-Pentachlorodibenzofuran...   57117-31-4  a
Pentachloroethane...................      76-01-7  b
Pentachloronitrobenzene [PCNB]            82-68-8
 [Quintobenzene] [Quintozene].
Pentachlorophenol [PCP].............      87-86-5  b, c
1,3-Pentadiene......................     504-60-9
bis-(Pentamethylene) thiuram             120-54-7
 tetrasulfide.
Phenacetin..........................      62-44-2
Phenanthrene........................      85-01-8  b
Phenol..............................     108-95-2  b
Phentermine [alpha,alpha-                122-09-8
 Dimethylphenethylamine].
1,2-Phenylenediamine [o-                  95-54-5  a
 Phenylenediamine].
1,3-Phenylenediamine [m-                 108-45-2  a
 Phenylenediamine].
1,4-Phenylenediamine [p-                 106-50-3  a
 Phenylenediamine].
Phenylthiourea......................     103-85-5
Phorate [O,O-Diethyl S-                  298-02-2  b
 (ethylthio)methyl
 phosphorodithioate].
o-Phthalic acid.....................      88-99-3
p-Phthalic acid [Terephthalic acid]      100-21-0
 [1,4-Benzenedicarboxylic acid].
Physostigmine.......................      57-47-6
Physostigmine salicylate............      57-64-7
Polychlorinated biphenyls, total        1336-36-3  e
 [PCBs, total].
Potassium dimethyldithiocarbamate...     128-03-0
Potassium N-hydroxymethyl N-           51026-28-9
 methyldithiocarbamate.
Potassium N-methyldithiocarbamate...     137-41-7
Promecarb...........................    2631-37-0
Pronamide...........................   23950-58-5
Propanenitrile [Propionitrile]           107-12-0
 [Ethyl cyanide].
1,3-Propane sultone.................    1120-71-4

[[Page 63415]]

 
Propargyl alcohol [2-Propyn-1-ol]...     107-19-7
Propham.............................     122-42-9
Propoxur [Baygon] [2-(1-                 114-26-1
 Methylethoxy)-phenol,
 methylcarbamate].
n-Propyl amine [1-Propanamine]......     107-10-8
1,2-Propyleneimine [2-                    75-55-8
 Methylaziridine].
Propylthiouracil [6-Propyl-2-             51-52-5
 thiouracil].
Prosulfocarb........................   52888-80-9
Pyrene..............................     129-00-0  b
Pyridine............................     110-86-1  b
Quinone [p-Benzoquinone]............     106-51-4
Reserpine...........................      50-55-5
Resorcinol [1,3-Benzenediol]........     108-46-3
Saccharin...........................      81-07-2  d
Safrole.............................      94-59-7
Selenium [Selenium, total]..........    7782-49-2  b, c
Selenium,                                144-34-3
 tetrakis(dimethyldithiocarbamate)
 [Selenium dimethyldithiocarbamate].
Silver [Silver, total]..............    7440-22-4  b, c
Silvex [2,4,5-                            93-72-1  b
 Trichlorophenoxypropionic acid]
 [2,4,5-TP].
Sodium azide........................   26628-22-8
Sodium dibutyldithiocarbamate.......     136-30-1
Sodium diethyldithiocarbamate.......     148-18-5
Sodium dimethyldithiocarbamate......     128-04-1
Streptozotocin......................   18883-66-4
Strychnine..........................      57-24-9  d
Styrene [Vinyl benzene]                  100-42-5
 [Phenylethylene].
Sulfallate..........................      95-06-7
Sulfide.............................   18496-25-8  c
Sulfotepp                               3689-24-5  b
 [Tetraethyldithiopyrophosphate].
Tetrabutylthiuram disulfide.........    1634-02-2
Tetramethylthiuram monosulfide [Bis-      97-74-5
 (dimethylthiocarbamoyl)sulfide].
1,2,4,5-Tetrachlorobenzene..........      95-94-3  a, b
2,3,7,8-Tetrachlorodibenzo-p-dioxin     1746-01-6  a
 [2,3,7,8-TCDD].
2,3,7,8-Tetrachlorodibenzofuran        51207-31-9  a
 [2,3,7,8-TCDF].
1,1,1,2-Tetrachloroethane...........     630-20-6  a
1,1,2,2-Tetrachloroethane...........      79-34-5  a, b
Tetrachloroethylene                      127-18-4
 [Perchloroethylene].
2,3,4,6-Tetrachlorophenol...........      58-90-2  a, b, c
Tetrahydrofuran.....................     109-99-9
Tetranitromethane...................     509-14-8
Thallium [Thallium, total]..........    7440-28-0  b, c
Thioacetamide.......................      62-55-5
Thiodicarb..........................   59669-26-0
Thiofanox...........................   39196-18-4
Thiomethanol [Methyl mercaptan]           74-93-1
 [Methanethiol].
Thionazin [O,O,-Diethyl O-pyrazinyl      297-97-2  b
 phosphorothioate].
Thiophanate-methyl..................   23564-05-8
Thiophenol [Benzenethiol]...........     108-98-5
Thiosemicarbazide...................      79-19-6
Thiourea............................      62-56-6
Thiram [Thiuram] [Tetramethylthiuram     137-26-8
 disulfide].
Tin [Tin, total]....................    7440-31-5  e
Tirpate.............................   26419-73-8
Toluene [Methylbenzene].............     108-88-3
2,4-Toluene diisocyanate............     584-84-9  a
2,6-Toluene diisocyanate............      91-08-7  a
2,4-Toluenediamine [2,4-                  95-80-7  a
 Diaminotoluene] [Toluene-2,4-
 diamine].
2,6-Toluenediamine [2,6-                 823-40-5  a
 Diaminotoluene].
3,4-Toluenediamine [3,4-                 496-72-0  a
 Diaminotoluene].
o-Toluidine [2-Methylaniline].......      95-53-4  c
p-Toluidine [4-Methylaniline].......     106-49-0  .....................
Toxaphene [Chlorinated camphene]....    8001-35-2  .....................
Triallate...........................    2303-17-5  .....................
2,4,6-Tribromophenol................     118-79-6  .....................
1,2,4-Trichlorobenzene..............     120-82-1  a, b
1,1,1-Trichloroethane [Methyl             71-55-6  a, b
 chloroform].
1,1,2-Trichloroethane [Vinyl              79-00-5  a, b
 trichloride].
Trichloroethylene...................      79-01-6  .....................
Trichlorofluoromethane                    75-69-4  b
 [Trichloromonofluoromethane] [CFC-
 11].
Trichloromethanethiol...............      75-70-7  .....................
2,4,5-Trichlorophenol...............      95-95-4  a, b
2,4,6-Trichlorophenol...............      88-06-2  a, b
2,4,5-Trichlorophenoxyacetic acid         93-76-5  b
 [2,4,5,-T].

[[Page 63416]]

 
1,2,3-Trichloropropane..............      96-18-4  a
1,1,2-Trichloro-1,2,2-                    76-13-1  b
 trifluoroethane [Freon 113].
Triethylamine.......................     121-44-8  .....................
O,O,O-Triethylphosphorothioate......     126-68-1  b
1,3,5-Trinitrobenzene [sym-               99-35-4  .....................
 Trinitrobenzene].
Tris-(1-azridinyl) phosphine sulfide      52-24-4  .....................
Tris-(2,3 -dibromopropyl) phosphate.     126-72-7  .....................
Trypan blue.........................      72-57-1  .....................
Vanadium [Vanadium, total]..........    7440-62-2  c
Vernolate [Vernam]..................    1929-77-7  .....................
Vinyl chloride [Chloroethylene]           75-01-4  .....................
 [Ethylene chloride].
Vinyl acetate.......................     108-05-4  .....................
Warfarin............................      81-81-2  d
o-Xylene............................      95-47-6  a
m-Xylene............................     108-38-3  a
p-Xylene............................     106-42-3  a
Zinc [Zinc,total]...................    7440-66-6  c
Ziram...............................     137-30-4  .....................
------------------------------------------------------------------------
(a) These chemicals are isomers that have been chosen to represent
  either mixtures of isomers or where isomers were not specified (e.g.,
  ortho-, meta-, and para-Xylene are all isomers and therefore,
  represent Xylenes, isomers not specified). These chemicals may be used
  in industry as single isomers or as a mixture of isomers. While the
  CASRN for mixtures of isomers are not the same as those for the
  individual isomers, the mixtures are regulated by inclusion of these
  isomers on the list.
(b) These chemicals have been chosen to represent the various classes of
  chemicals that are regulated as ``multi-chemical classes'' under RCRA
  (e.g., Endrin aldehyde and Endrin ketone have been chosen as
  representatives of Endrin Metabolites, which is regulated under RCRA.)
  Other chemicals with this note specifically represent those ``multi-
  chemical classes'' that are regulated under RCRA using an ``N.O.S.''
  designation. N.O.S. stands for ``Not Otherwise Specified'' (e.g., 2-
  Chloronaphthalene has been chosen to represent Chlorinated
  naphthalene, N.O.S.) For some chemicals all the isomers were already
  listed in RCRA regulations, for others only the commercially available
  isomers were listed.
(c) These chemicals have been chosen to represent specific RCRA-
  regulated chemical salts or compounds that cannot be measured
  directly. By analyzing for the chemicals listed with this footnote,
  the other RCRA-regulated chemicals are therefore covered (e.g.,
  Arsenic acid, Arsenic Trioxide, and other arsenic compounds can be
  measured in wastes by measuring for Arsenic, total.)
(d) These chemicals have been chosen to represent RCRA-regulated
  ``groups'' of chemicals (e.g., salts) that are directly derived-from
  the chemical on the list (e.g., Nicotine salts are derived-from
  Nicotine.) The salts are typically converted back to the parent
  compound or a related compound during analysis of wastes. The
  individual salts can not typically be measured directly. All salts,
  esters, and other compounds that are measured by analyzing for this
  chemical are also regulated by this rule; i.e., one can not escape
  regulation by claiming that the salt is not listed on Appendix X for
  the chemicals with this footnote.
(e) All compounds with PCBs, Cobalt and Tin are covered when present in
  RCRA listed wastes (i.e., F, K, U and P wastes) as therefore, are
  considered to be part of the HWIR Exemption List.


                                   Table 3.--Appendix X HWIR Exemption Levels
                                                    [Example]
----------------------------------------------------------------------------------------------------------------
                                                              Unrestricted Management Exemption       Landfill-
                                                                           Levels                       Only
             CASRN                    Chemical Name      ------------------------------------------   Exemption
                                    [Alternate Names]     Liquid  (mg/   Semi-solid    Solid (mg/   Levels  (mg/
                                                               l)          (mg/kg)         kg)           kg)
----------------------------------------------------------------------------------------------------------------
00-000-00......................  Chemical A.............        0.00X         0.00X          0.0X          0.0X
----------------------------------------------------------------------------------------------------------------

HWIR Risk Assessment

XV. What Is the Goal of the HWIR Risk Assessment?

    The goal of the HWIR risk assessment is to identify wastes 
currently listed as hazardous that could be eligible for exemption from 
hazardous waste management requirements. The HWIR risk assessment 
estimates chemical-specific potential risks to human and ecological 
receptors living in the vicinity of industrial nonhazardous waste sites 
that could manage HWIR exempted wastes. We would use these risk 
estimates, along with other information, to identify the chemical-
specific concentrations for exempted waste that would be protective of 
human health and the environment according to selected sets of risk 
protection criteria. As explained in Section XIX of the preamble, we 
developed four protection measure scenarios to capture the likely range 
of public protection measures.
    We are not proposing exemption levels based on the results of the 
current version of the risk assessment. As explained in Section XVII, 
we believe that the model requires further evaluation before it can be 
used to generate regulatory levels. We are describing our methodology 
in detail, and we request comment on our risk assessment approach. We 
remain committed to the modeling effort, and hope that these comments 
will help us to revise our model and produce risk-based exemption 
levels. Before we would promulgate an HWIR exemption, we would first 
publish an HWIR proposal that would include specific exemption levels 
and give the public an opportunity to comment.

XVI. How Did EPA Develop the Current Version of the HWIR Risk 
Assessment?

A. What Is the Basic Approach of the Risk Assessment Used To Set Risk-
Based Levels?
    The risk assessment developed for the HWIR exemption is an 
integrated, multimedia, multipathway, and multireceptor risk assessment 
(3MRA) that evaluates impacts to human and ecological receptors. The 
national scale assessment evaluates risks that might occur from the 
long-term, multimedia

[[Page 63417]]

release of a chemical from HWIR exempted waste that is managed in 
facilities typically expected to handle exempted waste. We designed the 
assessment to provide flexibility in producing a distribution of risk 
outputs to describe the range of individual risks across the nation 
from potential exposures to HWIR exempt waste. The HWIR risk assessment 
has three principle components: (1) The assessment strategy, (2) the 
3MRA model, which includes the chemical release, fate, exposure, and 
risk modules, and (3) the input data for the modules (for example, 
environmental setting, chemical, and meteorological data).
    1. Assessment Strategy. The 3MRA strategy (U.S. EPA, 1999-b) 
describes the overall direction for the assessment. The assessment is a 
forward-calculating analysis that evaluates the multiple exposure 
pathway risks to human and ecological receptors. A forward-calculating 
analysis starts with a chemical concentration in a waste management 
unit, estimates the release and transport of the chemical in various 
environmental media, and predicts the exposure and risk that result 
from those concentrations. The strategy describes several different 
analytical levels that the assessment could follow depending on 
available resources and the amount and quality of available data. 
However, because of resource and data constraints, we did not implement 
the strategy to its fullest extent. The strategy describes the 
probabilistic approach to the assessment and explains how the results 
provide an estimate of risk on a national scale. A probabilistic 
analysis calculates risk or hazard by allowing some of the parameters 
to have more than one value, consequently producing a distribution of 
risk or hazard for each receptor. A parameter is any one of a number of 
inputs or variables (such as food ingestion rates and soil 
characteristics) required for the model that we developed to assess 
risk.
    The assessment begins with a range of concentrations for a chemical 
in waste (five concentrations for HWIR) and estimates the associated 
hazards and risks to human and ecological receptors. By evaluating a 
range of waste concentrations and using a probabilistic approach to 
select many of the input parameters, we would be able to identify 
chemical-specific concentrations in waste that match our risk 
protection criteria (that is, our chosen level of protectiveness to 
human health and the environment). The risk protection criteria we 
selected are: cancer risk level, human health and ecological hazard 
quotients, population protection, and probability of site protection. 
The results would represent national distributions of receptor impacts 
near the waste management units typically expected to manage exempted 
waste over a 10,000 year period. For more information on the risk 
assessment approach, see the 3MRA background document (U.S. EPA, 1999-
b).
    2. The 3MRA Model. The 3MRA model automates the assessment 
strategy. The model consists of 18 media-specific pollutant fate, 
transport, exposure, and risk modules; six data processors to manage 
the information transfer within the system; and three databases that 
contain the data required to estimate risk.
    The modeling protocol looks at the movement of a chemical in the 
environment from a variety of chemical and physical processes: release 
from a waste management unit; transport of the chemical through the 
environment; exposure to the chemical from multiple pathways to humans, 
animals, and plants; and estimates the resulting risks or hazards posed 
by the exposures. Modules evaluate a chemical's release from aerated 
tanks, landfills, land application units, surface impoundments, and 
waste piles; movement through the air, groundwater, soil, watersheds, 
rivers, lakes, and wetlands; concentration at drinking water wells, 
residential soils, and farms; bioaccumulation in plants and animals 
(both on land and in waterbodies); and exposures and risks to humans 
and animals through ingestion of contaminated materials such as food 
and soil, inhalation of air (human only), and direct contact with 
contaminated media (ecological only). We invite comment on the approach 
used in the risk assessment that integrates the direct and indirect 
exposure pathways leading to a receptor.
    The 3MRA model application will assess risks to receptors 
temporally over a 10,000 year period. This will be accomplished by 
selecting each year from the present until 10,000 years from now, and 
assessing risks associated with constituent releases from a randomly 
selected waste unit at a randomly selected waste site location. Thus, 
10,000 model runs will occur, with each model run representing a 
different year in the future. As discussed in Section XVI.A.3, each 
waste management unit is assumed to have different operational 
lifetimes (between 20-50 years) and different lengths of time during 
which constituents are assumed to be released from the unit (between 
30-200 years). The model continues simulating releases until less than 
one percent of the initial mass is left or for the maximum time 
constituents are assumed to be released from the unit, whichever occurs 
first. The model balances chemical mass across exposure pathways, and 
reports a total chemical-specific concentration in waste that meets our 
protection criteria.
    The model assesses risks to human and ecological receptors who 
might live within 2 kilometers of a waste management unit. At each 
location where there is a receptor, the model calculates the 
simultaneous exposures and resulting risks for that receptor, by adding 
the appropriate series of pathway-specific risks. Some of the modeled 
receptors might be exposed through several pathways, some might only be 
exposed through one pathway, and some might not be exposed at all to 
any pathway. From this information, the model generates, for each 
chemical across all sites, a distribution of risk for each receptor 
type (and also for all receptor types). This distribution of risk is 
also calculated for each of three radial distances (500 meters, 1000 
meters and 2000 meters) from the center of the waste management units. 
An overview of the 3MRA Model is provided in U.S. EPA (1999-c). EPA 
directive #2182 (U.S. EPA, 1997-b) provides the system design 
development guidance.
    Under this site-based approach, the chemical-specific distributions 
of risks or hazards would include all of the receptors living in the 
vicinity of industrial waste sites that are exposed through one or more 
exposure pathways as well as any receptors not exposed. For example, 
the distributions present the risk and hazard estimated for all 
receptors using groundwater at a site for drinking or showering. This 
includes receptors using groundwater from both wells located within the 
contaminated plume and the receptors outside of the plume. The 
receptors located outside of the contaminated plume have no risk or 
hazard through the groundwater pathway.
    We have also designed the model to have the capability to estimate 
risk and hazard to only those receptors that are exposed to a chemical 
through one or more pathways. With respect to receptors using 
groundwater for drinking or showering, the distributions would reflect 
only the risk and hazard to the receptors located within the 
groundwater plume. The receptors using groundwater as a source of 
drinking or showering and located outside of the plume would not be 
included in the distribution of risk and hazard in this additional 
analysis.
    The number of wells within the groundwater plume will vary

[[Page 63418]]

significantly by site, by chemical, and by waste management unit type. 
For the chemical (acrylonitrile) that we are providing results in the 
Risk Characterization Background Document (US EPA, 1999-as), we 
estimate that nationally up to about a quarter of the groundwater wells 
would be located inside the plumes at industrial Subtitle D landfill 
sites. It is possible that some chemical and waste management 
combinations would have no wells within the groundwater plume.
    The extent of a plume depends on the concentration and mass of a 
chemical constituent in the waste management unit, physical and 
chemical properties of the waste, characteristics of the waste 
management unit, site hydrogeological characteristics and the site 
climate. Because these are variable factors, the extent of the plume 
for the contaminant varies. We estimated the number of wells inside a 
contaminant plume for a chemical constituent at a site by first 
estimating the extent of the plume at that site. The plume extent is 
characterized by approximate stream surfaces that separate the fluid 
emanating from the waste management unit and the ambient ground-water 
flow field, and the transverse dispersion normal to the stream 
surfaces.
    For a given distance from the source (or the waste management 
unit), the lateral extent of the plume is defined as a cross-section 
normal to the flow field where the receptor well concentration has the 
probability of more than 99.74 percent of being greater than 0.001 of 
the maximum concentration at the center of the plume at that 
longitudinal distance from the waste management unit. We estimated the 
extent of the plume based on the assumption that the ground-water flow 
field is steady-state. The derivation of the plume's extent are 
described in Appendix D of the background document for the vadose zone 
and aquifer modules (US EPA, 1999-aa). We request comment on the 
estimates of wells inside and outside the plume of contamination 
developed to date, and our approach in calculating these estimates. We 
also request comment on our approach in measuring the degree of risk 
posed at receptor wells located within the modeled plume of 
contamination and at those wells located outside the plume.
    3. Input data. The 3MRA Model requires over 700 input parameters 
covering a wide range of general data categories including: waste 
management unit characteristics; meteorological data, surface water and 
watershed characteristics; soil properties; aquifer properties; food 
chain or food web characteristics; human and ecological exposure 
factors; types and locations of human and ecological receptors and 
habitats surrounding the waste management unit; and chemical-specific 
properties and toxicity values. We implemented the assessment on a 
national scale but based the analysis on a regional, site-based 
approach. In this approach, site-based data are used when available as 
inputs to the model. When site-based data are not available, then data 
collected on a regional level, followed by data collected on a national 
level, are used for the evaluation. We collected a large amount of data 
to better describe and model plausible exposure scenarios from 
chemical-specific releases from the waste management units. Examples of 
the types of data collected to identify site-based characteristics 
include facility location and the physical and environmental 
characteristics of the sites and surrounding areas (for example, land 
use, human receptor locations, and ecological habitats). Examples of 
regional data we collected were meteorological data, soils 
characteristics, aquifer data, and types of ecological receptors. Data 
collected at the national level included human exposure factors, 
ecological exposure factors, human health toxicity values, and 
ecological toxicity values. We have made available what data were 
collected, where the data were obtained, how the data were collected 
and processed, and issues and uncertainties associated with the data 
collected for the database of the 3MRA model in the docket (U.S. EPA, 
1999-d through -r).
    We assessed the potential human health and ecological impacts at 
201 individual nonhazardous industrial waste management sites. The 
sites were selected to be representative of the management sites found 
in EPA's Screening Survey of Industrial Subtitle D Establishments (U.S. 
EPA, December, 1987). We selected the 201 sites from a survey of 
approximately 2,700 facilities representing a total population of 
nearly 150,000 facilities across 17 industrial sectors that managed 
waste on-site and had one or more of four types of waste management 
units (landfill, waste pile, land application unit, and surface 
impoundment). We drew a simple random sample of 201 facilities from 
each of the 17 industrial sectors in the same proportion as each sector 
in the Subtitle D survey. For example, if the organic chemicals 
industry sector had three percent of the facilities in the survey, we 
randomly selected three percent (that is, six facilities) of the 201 
facilities to be from the organic chemicals industry sector. The 
methodology for the selection of the 201 sites is explained in a 
background document (U.S. EPA, 1999-s). The 201 sites were used to 
collect site, regional, and national data to parameterize the model. We 
request comment on the selection methodology for the 201 sites to 
represent the national population of industrial Subtitle D facilities 
and whether to use sampling weights in future efforts.
    We used measured, calculated, and estimated chemical-specific data 
to generate all relevant chemical-specific thermodynamic and kinetic 
data for the HWIR assessment. The lack of reliable measured 
thermodynamic data necessitated the use of data generated by 
computational methods. The SPARC (System Performs Automated Reasoning 
in Chemistry) model, which is a computational method based on 
fundamental chemical structure theory, was the primary tool for 
calculating the thermodynamic constants. The process of assembling 
kinetic constants for degradation pathways (hydrolysis, anaerobic 
biodegradation and aerobic biodegradation) focused on finding, 
evaluating, and summarizing measured data. Due to the complex nature of 
biodegradation processes, only a limited amount of measured kinetic 
constants were available for chemicals and are included in the HWIR 
chemical database. We grouped these kinetic data according to reaction 
conditions (that is, pH, temperature, and redox conditions). However, 
because the rate constant for metabolism is unavailable for most 
constituents given the general paucity of data on metabolic rate 
constants in fish, the metabolic rate constant was set to a default of 
zero until data can be developed for a larger universe of hydrophobic 
organic chemicals. We have provided the information on chemical 
properties in a database placed in the docket (U.S. EPA, 1999-ai) and 
we request comments on the information contained in the chemical 
database. We also request any additional information on the chemicals.
    We have incorporated anaerobic biodegradation in the model for 
simulating the fate and transport of chemicals through the saturated 
zone. We conducted a workshop on the use of available anaerobic 
biodegradation rates and also invited industrial groups to provide 
available information. We reviewed all available information on the 
anaerobic biodegradation rates for organic chemicals in the saturated 
zone. The criteria used for the review and results of our review are 
presented in the background document (U.S. EPA, 1998-b). We invite 
comments on the inclusion of these data, our criteria for

[[Page 63419]]

evaluating the data, and any additional data on anaerobic 
biodegradation of organic chemicals.
    We used several types of human health toxicity values for the 
purpose of describing the toxicological dose-responses for the 
chemicals evaluated. For human health effects, the toxicity values 
include: cancer slope factors (CSFs), in units of (mg/kg/day) 
-1 for oral exposure to carcinogenic chemicals; reference 
doses (RfDs), in units of mg/kg/day, for oral exposure to 
noncarcinogenic chemicals; inhalation CSFs, derived from Unit Risk 
Factors (URFs), in units of (mg/kg/day) -1 for inhalation 
exposure to carcinogenic chemicals; and reference concentrations 
(RfCs), in units of mg/m3 for inhalation exposure to 
noncarcinogenic chemicals.
    There are a number of sources available for toxicity values that 
attempt to determine the most sensitive health effects associated with 
the chemicals and express the relationship between dose and effect in 
quantitative terms. We established an order of preference for the 
sources of health toxicity values as follows (from most preferred to 
least preferred): (1) the Integrated Risk Information System (IRIS) 
online database of verified health benchmarks (U.S. EPA 1998-g); (2) 
the Health Effects Assessment Summary Tables (HEAST; U.S. EPA 1997-e); 
and (3) EPA's National Center for Environmental Assessment (NCEA) 
provisional values.
    Although we used only these three sources for the toxicity values 
in the analysis, we received toxicity data submitted during the 1995 
HWIR proposal for 32 chemicals that we evaluated in the 1995 HWIR 
proposal. These data included data that were peer-reviewed and 
published as well as data that were neither peer-reviewed nor 
published. EPA summarized and evaluated all of these comments with 
respect to their potential impact on the current toxicity values. A 
complete description of the comments and EPA's preliminary 
recommendations can be found in Report on Consistency of Hazardous 
Waste Identification Rule (HWIR) Benchmarks With Current Agency Values 
and Guidelines (U.S. EPA, 1997-e) and Response to Comments on Hazardous 
Waste Identification Rule (HWIR) Benchmarks (RTI, 1998). In addition, 
we developed a tiered approach for developing interim human toxicity 
values that includes using peer-reviewed, published toxicity data 
submitted to us and other toxicity data used by other Federal agencies 
in the development of their benchmarks. The methodology is described in 
Conceptual Approach to Establishing Interim Human Health Benchmarks 
(U.S. EPA, 1999-aw). We request comment on the use of toxicity data 
from other Federal agencies' benchmark development, our preliminary 
recommendations to use peer-reviewed, published data submitted in 
comments, and the draft methodology to develop interim benchmarks.
    RfDs and RfCs are defined as ``an estimate (with uncertainty 
spanning perhaps an order of magnitude or greater) of a daily exposure 
level for the human population, including sensitive subpopulations, 
that is likely to be without an appreciable risk of deleterious effects 
during a lifetime'' (U.S. EPA, 1998-g). RfDs and RfCs are developed 
using a methodology that is designed to generate protective exposure 
estimates of indeterminate probability. CSFs are used to evaluate 
cancer risks for ingestion and inhalation exposures, respectively. 
Unlike RfDs and RfCs, CSFs do not represent ``safe'' exposure levels, 
rather, they are derived mathematically as the 95% upper confidence 
limit of the slope of the linear portion of the dose-response curve. 
That is, they relate levels of exposure with a probability of effect or 
risk.
    We developed at least one ecological toxicity value for 35 
chemicals. We gathered the data to develop these benchmarks from peer-
reviewed literature and Agency-developed criteria (for example, Ambient 
Water Quality Criteria). The data sources for the ecological benchmarks 
developed for each of the chemicals are available in the technical 
background document (U.S. EPA, 1999-p).
    We developed two types of toxicity values for this analysis. The 
first values are population-level values and are expressed as an 
applied dose in mg/kg-day. The ecological benchmarks are relevant to 
mammals, birds, amphibians, and reptiles. The second set of toxicity 
values are chemical stressor concentration limits (CSCL) that are 
expressed as media concentrations (for example, mg/L). These are 
community-level benchmarks and are relevant for terrestrial and aquatic 
plants, aquatic organisms, benthos, and soil organisms.
    In identifying appropriate studies to develop ecological 
benchmarks, we developed a series of study selection criteria to ensure 
consistency in the interpretation of ecotoxicological data and to 
satisfy relevant data quality objectives. The study selection criteria 
address the desire for consistency across EPA programs, the 
appropriateness of the study data given the management goals and 
assessment endpoints for HWIR, and the quality of the study with 
respect to endpoint selection, dose-response information, and 
appropriate use of extrapolation techniques (e.g., tools for 
statistical inference). In order of importance, the study selection 
criteria included the following: (1) relevance of study endpoints to 
population-level effects, (2) adequate data to demonstrate the dose-
response relationship, (3) appropriateness of study design with respect 
to the exposure route (e.g., gavage versus dietary exposure) and 
exposure duration, (4) quality of the study as determined by the use of 
appropriate dosing regimes, and statistical tools and (5) consistency 
with other EPA programs such as the Office of Water and Superfund.
    With the exception of amphibian populations, the CSCLs are intended 
to represent de minimis levels of effect to communities of organisms. 
For amphibians, the extensive database on acute and subchronic aqueous 
exposures to developing organisms was used to derive CSCLs for surface 
water contact. For other receptor groups such as the soil and sediment 
communities, the study selection criteria included the following: (1) 
Acceptance of a benchmark by other EPA programs (e.g., Great Lakes 
Water Quality Initiative), (2) consistency with EPA guidelines on study 
selection for aquatic toxicity data, (3) relevance of study to species 
presumed to be key functional elements of the community, (4) relevance 
of study endpoints to address community-level effects (e.g., growth, 
survival), (5) adequacy of data to demonstrate dose-response 
relationship, and (6) quality of the study data with respect to the 
design (e.g., field versus laboratory) and appropriate use of 
statistical tools to characterize effects (for example, confidence 
levels). The methodology for the development of these benchmarks is 
described in Data Requirements and Confidence Indicators for Ecological 
Benchmarks Supporting Exit Criteria for the Hazardous Waste 
Identification Rule (HWIR99) (U.S. EPA, 1999-ax).
B. How Does This Effort Compare With Past HWIR Risk Assessments?
    Unlike previous HWIR risk assessment efforts (57 FR 21450 and 60 FR 
66344), which considered groundwater and non-groundwater pathways 
separately, the HWIR99 3MRA Model evaluates simultaneous exposures 
across multiple media and pathways to estimate the resulting health and 
environmental effects. For example, instead of looking at the risks of 
a person drinking contaminated groundwater, breathing contaminated air, 
and eating contaminated food

[[Page 63420]]

separately, and at potentially different points in time, we estimated 
the risk from the simultaneous exposure from multiple pathways, where 
appropriate, across time.
    To estimate the integrated and simultaneous exposures to receptors, 
we developed the 3MRA Model that balances chemical mass across 
pathways, and reports a total chemical-specific concentration in waste 
that meets our protection criteria over time. This approach is unlike 
the 1995 HWIR proposal, which modeled each pathway separately and 
assumed for each that all the mass went to that pathway. As a result, 
the 1995 HWIR proposal reported regulatory levels as both as total 
concentration (for the non-groundwater pathways) and as leach levels 
(for the groundwater pathways). Because we integrate the pathways in 
the 1999 HWIR risk assessment, the revised levels would be reported 
only as the total concentration of the chemical in the waste. We 
request comment on the revised approach to establish regulatory levels 
based only on the chemical-specific total concentration in the waste, 
rather than regulating on both total and leachate levels.
    The model incorporates interacting modules that include:
     The source modules, which estimate the simultaneous 
chemical mass losses to the different media and maintains chemical mass 
balance of the releases from the waste management unit into the 
environment over time;
     The fate/transport modules that receive calculated 
releases from waste management units and distribute the mass through 
each of the media to determine the chemical concentrations in air, 
groundwater, soil and surface water across space and time;
     The food chain modules that receive the outputs from the 
fate and transport modules and estimate the uptake of chemicals in 
various plants and animals;
     The exposure modules that use the media concentrations 
from the fate and transport modules to determine the exposure to human 
and ecological receptors from inhalation (for humans only), direct 
contact (for ecological receptors only) and ingestion (for both 
receptor types); and
     The risk module that predicts the risk/hazard quotient for 
each receptor of concern.
    The HWIR99 risk assessment uses a probabilistic approach to develop 
chemical-specific national distributions of risks. The ``Data 
Collection'' background document (U.S. EPA, 1999-d through r) discusses 
which parameters were probabilistically assessed and the quality of the 
data associated with each probabilistic distribution. We implemented 
the analysis focusing on evaluating inter-site variability across waste 
management unit and environmental setting characteristics. For the 
input parameters with probabilistic distributions, we randomly selected 
a value from the distribution corresponding to each parameter for each 
setting. The model generates a distribution of risk outputs that 
describe the range of individual risks across the nation. Additional 
discussion of the probabilistic approach can be found in the 3MRA 
document (U.S. EPA, 1999-b).
    Another difference between the HWIR99 risk assessment and previous 
efforts is the use of an integrated and tiered approach for using site-
based, regional, and national data to operate the 3MRA Model. We 
collected a large amount of data to better describe and model plausible 
exposure scenarios from chemical-specific releases from the waste 
management units. Examples of the types of data collected to identify 
site-based characteristics include facility locations; the physical and 
environmental characteristics of the sites and surrounding areas (for 
example, land use, human receptor locations, and ecological habitats). 
Examples of regional data we collected were: meteorological data, soils 
characteristics, aquifer data, and types of ecological receptors. Data 
collected at the national level included human exposure factors, 
ecological exposure factors, human health toxicity values, and 
ecological toxicity values.
    In addition, our approach to the ecological risk assessment has 
evolved considerably since the 1995 proposal. Since the 1995 proposal, 
we have published a document titled Guidelines for Ecological Risk 
Assessment (U.S. EPA, April 1998-a) that provides a framework for 
conducting ecological risk assessments. A key component of these 
guidelines is the problem formulation phase of the assessment in which 
the assessor and manager discuss the goal of the risk assessment. Based 
on this guidance, we have better defined our objectives for the 
ecological risk assessment and more clearly stated our management goal 
and assessment endpoints. These objectives are further discussed in 
Section XVI.F.2 of this preamble.
C. What Peer Review Has EPA Conducted on the HWIR Risk Assessment and 
What Were the Results?
    We are pursuing two separate levels of peer review activities to 
support the development of the HWIR risk assessment. The first level of 
peer review activity involved the ORD/OSW Integrated Research and 
Development Plan for the Hazardous Waste Identification Rule or simply 
the ``Research Plan'' (U.S. EPA, 1998-f). The Research Plan defines the 
overall risk assessment strategy. The second level of peer review 
activity addresses internal supporting databases and modules (for 
example, the chemical properties database, certain fate and transport 
modules). We have not completed the independent peer review of all 
support databases and modules and have not yet addressed all of the 
comments received for those modules peer reviewed. The peer review 
comments received to date are in the docket for today's proposed rule. 
When we publish a revised risk assessment for public notice, we will 
also give notice of any further peer review comments and how we address 
those comments.
    Peer Review of the Research Plan. The Research Plan was prepared in 
part as a response to comments on the HWIR 1995 risk assessment. The 
plan responded to comments from the Science Advisory Board (SAB) (SAB, 
1996), comments from the U.S. EPA's Office of Research and Development 
(ORD) and other internal EPA commenters, and the public. A joint task 
force between the Office of Solid Waste (OSW) and ORD was formed in 
order to build a ``good science'' HWIR assessment strategy and 
implementation technology. The Research Plan is the embodiment of six 
guiding principles:
    1. Requiring a risk-based assessment strategy;
    2. Requiring a site-based multimedia, multipathway, and 
multireceptor risk model;
    3. Requiring the necessary assessment databases;
    4. Requiring a computer-based technology;
    5. Requiring a sound science foundation; and,
    6. Conducting the necessary peer reviews.
    We sought to particularly address comments resulting from the 
HWIR95 SAB review. In addition, we conducted a peer review of the 
Research Plan through an independent evaluation by national experts 
outside of EPA (Small, Cohen, and Deisler, 1998).
    In general, the comments on the Research Plan were favorable. All 
the reviewers indicated that we had made many improvements recommended 
by the SAB, resulting in a product superior to that of HWIR95. The 
reviewers were also pleased with the layout and detail presented in the 
documentation. The reviewers, however, did have comments

[[Page 63421]]

on the current effort. One set of comments was directed at the complex 
nature of the multi-module system and suggested that a simpler system 
might be the more appropriate tool, in light of varying model 
sophistication and data quality. While the reviewers applauded the 
efforts for the establishment of parameter distributions through Monte 
Carlo, they expressed their concern as to its transparency to both the 
scientific and public communities. A complete set of peer review 
comments on the Research Plan is available in the docket.
    As we implemented the strategy set out in the Research Plan, we 
found that practical limitations forced us to simplify the approach 
laid out in the plan. A discussion of some of those limitations is 
found in Section XVII of this preamble and in the technical background 
document (U.S. EPA, 1999-at).
    Peer Review of the HWIR99 3MRA Model. The HWIR99 Model is an 
integrated system of databases, system processors, and modules. The 
three databases and six processors that were developed are new and 
specific to the HWIR99 rulemaking effort. The modules used are a 
combination of existing models (for example, ISCST3, an air dispersion 
model) and newly developed models. An extensive external peer review is 
planned to review all 27 model components (18 modules, three databases, 
and six processors). As with the Research Plan peer review, each model 
component was or will be reviewed by a group of independent experts in 
that respective field. These reviewers are charged with specific 
scientific concerns unique to each component. Because of the large 
number of components developed and the timing of their development, 
this activity has been phased over time and is on-going. Copies of the 
peer review charges that we have sent out and the peer review comments 
we have received are available in the docket.
    In response to the peer review comments received so far, we have 
made specific technical modifications to many of the model components, 
and have worked to improve the transparency and clarity of the 
documentation. We will continue to review and address the peer review 
comments and comments from the public as we refine the model in 
preparation for the final HWIR rulemaking.
D. Which Waste Management Units Did EPA Model?
    We modeled five waste management units that represent typical 
management scenarios that are likely disposal destinations for exempted 
wastes. The modeled units include landfills, waste piles, land 
application units, surface impoundments, and aerated tanks. For the 
landfill, waste pile, land application unit, and surface impoundment, 
we extracted data related to the location and size of each of these 
units from the EPA survey of industrial Subtitle D establishments in 
the U.S. (U.S. EPA, 1987). For the aerated tanks, we extracted size 
data from Hazardous Waste TSDF--Background Information for Proposed 
RCRA Air Emission Standards (U.S. EPA, 1991-b). Because we had no 
location data for aerated tanks, we assumed that aerated tanks could be 
located at any location where a surface impoundment currently exists. 
Each of the units is discussed below and the release pathways are 
summarized in Table 4.
    Within each type of waste management unit, we sought to maintain 
mass balance. We begin with a total mass of chemical and partition the 
mass among volatile, liquid, and sorbed phases. Mass released via each 
phase is no longer available for partitioning to and release through 
other phases. The partitioning algorithms and media coefficients that 
we used are described in the two technical background documents for the 
modules for the sources (U.S. EPA, 1999-t and -u) and module 
verifications are described in U.S. EPA (1999-ad and -ae).
    We are presenting an approach in the HWIR 3MRA model to address the 
physical relationship between waste concentrations and leachate 
concentrations, and mass limitations in the leachate. In the 3MRA model 
we start with a specified concentration of a chemical constituent and 
the total mass in a waste management unit, partition the constituent in 
the waste unit into various environmental media. The partitioning takes 
into consideration the physical and chemical characteristics of the 
chemical and the characteristics of the media. The relationship in the 
model, between the concentration of a chemical constituent in the waste 
and its concentration in the leachate, depends on these physical and 
chemical characteristics. The initial chemical mass in the waste 
management unit depletes with time due to partitioning, degradation and 
transport. The 3MRA model assumes the initial mass to be finite and 
then depletes. The concentration of a chemical constituent in a 
downgradient well is initially zero, gradually reaches a maximum and 
then declines as the mass released from the waste management unit 
passes the receptor well area. The details of the partitioning of the 
chemical mass based on the relationships between the waste and the 
leachate depend on the physical characteristics of the chemical 
constituent and the environment. For example, the relationship for 
organic chemicals depends on the fraction of organic carbon in the 
waste and other factors. For metals, the relationship depends on the 
pH, the presence of other inorganic and organic species, temperature, 
and other factors. This is further described in the various waste 
management units being modeled in the 3MRA model for HWIR99 (U.S. EPA, 
1999-t and -u). We request comments on this approach for establishing 
an association between the chemical concentration in the waste, the 
chemical concentration in the leachate, and mass limitations in 
leachate.
    Landfill: We designed the landfill module to simulate the gradual 
filling of an active landfill and the long-term releases from the 
active and closed landfills. The design assumes that the landfill is 
composed of a series of vertical cells of equal volume that are filled 
sequentially. We assumed that each cell requires one year to be filled. 
The formulation of the landfill module is based on the assumption that 
the contaminant mass in the landfill cells might be linearly 
partitioned into the aqueous, vapor, and solid phases. The partitioning 
coefficients are based on those reported in the literature (U.S. EPA, 
1999-aq). The model simulates the active lifetime of the landfill (30 
years) and continues simulating releases until less than one percent of 
the initial mass is left or for a total of 200 years, whichever occurs 
first.
    We assumed the landfill had minimal controls and was constructed 
below grade. In particular, we assumed that the unit has no liner; the 
cover at closure is a soil cover that still permits volatilization and 
particle emissions; and the below grade design prevents runoff and 
erosion.
    Based on the design assumptions above, we simulated the annual 
release of chemical mass by leaching to the unsaturated zone underneath 
the landfill, volatilization to the air pathway, and particle emissions 
to the air pathway during the active lifetime. Because we assumed the 
unit was designed below grade, we did not simulate releases through 
runoff and erosion. In addition, we simulated losses of mass through 
anaerobic biodegradation and hydrolysis within the landfill.
    The module incorporates other assumptions intended to improve the 
efficiency of the model and are described in the technical background 
document (U.S. EPA, 1999-t). These

[[Page 63422]]

include the lack of lateral transport between cells, simulation of only 
a single cell and then aggregation of results based on the time each 
cell is filled, and the assumption that waste is added at a constant 
concentration at a constant rate.
    Waste pile: We designed the waste pile module to simulate the 
management of wastes in a pile situated above grade, with the releases 
of chemicals occurring during the operating lifetime of the pile. The 
unit is described fully in the technical background document (U.S. EPA 
1999-t). We assume that the waste pile is a set height and constant 
area, and that waste in the waste pile is refreshed on an annual basis. 
At the end of the active period, which is 30 years in this simulation, 
the waste pile is removed.
    Based on the design assumptions, we simulated annual releases of 
leachate to the unsaturated zone underneath the pile, volatiles to the 
air, particles to the air, particles through erosion and runoff, and 
dissolved chemicals through runoff. In addition, we simulated losses 
through hydrolysis and aerobic degradation in the surface layer and 
hydrolysis and anaerobic degradation in the subsurface waste pile 
layers.
    The waste pile design did not incorporate management controls. 
However, we assumed the waste pile was situated in a local watershed 
basin, such that run-on of uncontaminated soil to the management unit 
did not occur and soil released from the waste pile mixed with the 
surficial watershed runoff.
    Land application unit: We designed the land application unit module 
to simulate the disposal of wastes in an open field for the purpose of 
degradation or treatment of chemicals. This module is described fully 
in the technical background document (U.S. EPA, 1999-t).
    The model assumes that waste is applied to the surface soil 
periodically and then tilled into the top layer of the soil. Waste is 
applied during each of the 40 years of operation. We simulated releases 
during the active phase and up to 200 years after the land application 
unit is closed or when less than one percent of the total mass remains. 
The waste is applied on a wet weight basis and the water content of the 
waste is used to calculate the total infiltration to the unsaturated 
zone. We also assumed that the characteristics of the waste did not 
alter the characteristics of the native soil. Other than tilling into 
the soil, we did not assume management controls were present that might 
limit releases from the land application unit.
    Based on the design assumptions, we simulated annual releases of 
leachate to the unsaturated zone, volatiles to the air, particulate 
matter to the air, particles through runoff and erosion, and dissolved 
chemicals in runoff. In addition, we considered chemical losses through 
hydrolysis and aerobic biodegradation. Also, because these waste 
management units are on the land surface, they are integral land areas 
in their respective watersheds and, consequently, are not only affected 
by runoff and erosion from upslope land areas, but also affect 
downslope land areas through runoff and erosion. Indeed, after some 
period of time during which runoff and erosion have occurred from a 
waste management unit, the downslope land areas will have been 
contaminated and their surface concentrations could approach (or 
conceivably even exceed) the residual chemical concentrations in the 
waste management unit at that point in time. Thus, after extensive 
runoff and erosion from a waste management unit, the entire downslope 
surface area can be considered a ``source'' and it becomes important to 
consider these ``extended source'' areas in the risk assessment. It is 
for this reason that a holistic modeling approach was taken with the 
waste pile and land application unit source models to incorporate them 
into the watershed of which they are a part.
    The land application unit is fully integrated in the local 
watershed and is simulated as one part of the local watershed. Thus, 
soils from watershed areas above the land application unit might run-on 
to the source and mix with the surficial soils of the land application 
unit. Surface impoundment: We designed the surface impoundment module 
to simulate the disposal of liquid wastes in an earthen material pit 
and the releases of chemicals during the lifetime of the unit. The 
module is described fully in the technical background document (U.S. 
EPA, 1999-u). We assumed that the impoundment was a sink in the 
watershed. We assumed that no liner other than native soils was 
present, no cover was present, and that the unit was comprised of two 
well-mixed phases: liquid and sediment. We also simulated the changes 
at the bottom of the impoundment over time as settled solids fill pore 
space in native soils and impact chemical transport to underlying soils 
and groundwater. In addition, a fraction of each surface impoundment is 
aerated, which enhances biodegradation and increases volatilization of 
some chemicals. The surface impoundment is assumed to operate 50 years 
and then undergo clean closure (that is, all waste is removed from the 
unit).
    Based on the design assumptions, the surface impoundment module 
simulates annual release of leachate to the unsaturated zone and 
volatile emissions to air. Because the surface impoundment is assumed 
to be a sink, overland runoff was not modeled. Also, the redeposition 
of volatiles into the unit through precipitation was not simulated. The 
model accounts for several biological, chemical, and physical processes 
including hydrolysis, volatilization, sorption as well as settlement, 
resuspension, growth and decay of solids, activated aerobic 
biodegradation in the liquid phase (that is, a higher rate based on the 
amount of biomass present) and hydrolysis and anaerobic biodegradation 
in the sediments.
    The migration of contaminants from the surface impoundments to the 
subsurface has not been addressed rigorously in the past versions of 
this module. This is primarily due to lack of understanding on the 
processes related to bottom sediment layers in surface impoundments. We 
enhanced the surface impoundment module for the HWIR99 analyses by 
adding the formation and characterization of the bottom layers.
    Aerated Tank: We designed the aerated tank module to simulate 
releases from aerated tanks used for the treatment of wastewaters 
during the operating lifetime of the aerated tank. We chose to focus on 
aerated tanks because such aerated tanks would have more rapid 
volatilization and therefore present more air risks. The module is 
described fully in the technical background document (U.S. EPA, 1999-
u).
    We selected aerated tanks from the Hazardous Waste TSDF--Background 
Information for Proposed RCRA Air Emission Standards (U.S. EPA, 1991-b) 
to populate the database of unit characteristics. We further limited 
the aerated tanks in our database by not including aerated tanks that 
were the size of a drum or smaller because such units are more likely 
to be short-term units and would also present lower risks. We also 
assumed that an aerated tank would operate as long as the surface 
impoundment and therefore selected 50 years as the operating time for 
an aerated tank. However, we assumed each aerated tank only had a 
maximum lifetime of 20 years, and therefore, the operating lifetime 
would include the replacement of the aerated tank every 20 years. 
Finally, we assumed that the aerated tanks did not

[[Page 63423]]

fail or leak for the purposes of the long-term exposure scenario.
    Based on the design assumptions, we simulated annual volatile 
emissions to air. Because we did not model failures of the aerated 
tanks, we did not simulate leaching to the unsaturated zone or overland 
runoff. We did estimate losses through hydrolysis and activated aerobic 
biodegradation. Finally, we did not estimate redeposition of 
contaminants in to the aerated tank from rainfall. We request comments 
and suggestions on the methodologies used for modeling the 
environmental releases for HWIR99, and the data and methodologies used 
to support the overall modeling framework.

                                Table 4.--HWIR Unit Types and Release Mechanisms
----------------------------------------------------------------------------------------------------------------
                                                Leaching to                                         Runoff and
                                                groundwater     Volatilization  Wind-blown dust      erosion
----------------------------------------------------------------------------------------------------------------
Landfill....................................               X                X                X   ...............
Waste Pile..................................               X                X                X                X
Land Application Unit.......................               X                X                X                X
Surface Impoundment.........................               X                X   ...............  ...............
Aerated Tanks...............................  ...............               X   ...............  ...............
----------------------------------------------------------------------------------------------------------------

E. What Types of Environmental Releases Did EPA Consider When 
Determining How Chemicals Move Through the Environment?
    We modeled four environmental media into which chemicals could 
enter after release from a waste management unit : (1) Atmosphere, 
which includes modeling of dispersion of volatiles and particles from 
waste management units, (2) watershed, which includes modeling the 
response of watersheds to runoff from waste management units, (3) 
surface water, which includes modeling of migration of chemicals in 
surface water, and (4) groundwater, which includes modeling of the 
migration of chemicals in the subsurface. We also modeled three food 
chain pathways that could contribute to a receptor's exposure. These 
were the farm food chain for human receptors, the terrestrial food web 
for the ecological receptors, and the aquatic food web for human and 
ecological receptors.
    We have attempted to use state-of-the-science procedures to model 
the fate and transport of chemicals. However, because of the national 
scale of the assessment and the complexity of probabilistic multimedia 
modeling, we had to select or simplify our modules to make them 
computationally efficient yet maintain a strong science-based 
assessment. The modules described here are presented in more detail in 
the technical background documents that are cited. We request comments 
and suggestions on the methodologies used for modeling the 
environmental fate and transport for HWIR99, and the data and 
methodologies used to support the overall modeling framework. The 
uncertainties associated with each of the modules of 3MRA are described 
below, and additional uncertainties are discussed in Section XVII of 
this preamble.
    1. Atmospheric Modeling: The HWIR99 atmospheric modeling provides 
an annual average estimate of air concentration of dispersed chemicals 
and annual deposition rate estimates for vapors and particles at 
various receptor points in the area of interest. The area of interest 
is defined by a 2 km radius measured from the edge of the largest area 
source at the site. The chemicals are assumed to be in the form of 
volatilized gases or fugitive dust emitted from area sources. The 
atmospheric module simulates the transport and diffusion of the 
chemical. The simulated air concentrations are used to estimate 
biological uptake from plants and human exposures due to direct 
inhalation. The predicted deposition rates are used to determine 
chemical loadings to watershed soils, farm crop areas, and surface 
waters. The details of the atmospheric modeling are presented in the 
atmospheric modeling background documents (U.S. EPA, 1999-v through -
x).
    The atmospheric concentration and deposition of chemicals were 
determined through a steady-state Gaussian plume modeling approach 
using the Industrial Source Complex-Short Term (ISCST3) model. This 
model, which was tailored to the HWIR99 risk assessment, uses hourly 
meteorological data and provides estimates of contaminant 
concentration, dry deposition (particles only) and wet deposition 
(particles and gases) for user-specified averaging periods (annual for 
HWIR99).
    Our preliminary model runs indicated that it was not 
computationally feasible to run ISCST3 on an hourly basis for the 
lifetime of the unit. To reduce the computational burden, we made 
several simplifications to air modeling. One simplification was to use 
a long-term estimate of the concentration and deposition. We ran ISCST3 
using normalized emissions from the units to produce annual average 
concentration and deposition estimates. These estimates were converted 
to yearly estimates by multiplying the normalized-concentration and 
annual deposition predictions by the emission rate for each year. 
Annual averages were then divided by 365.25 to provide predictions in 
the required daily average units.
    A second simplification was to model a fraction of the hours in a 
year. We used the Sampled Chronological Input Model (SCIM) to sample 
the long term meteorological record at regular, user-specified 
intervals and scale the model results at the end to produce the annual 
average estimates. We conducted a study to determine the optimum 
sampling interval (U.S. EPA, 1998-c). The study showed that for dry 
deposition, sampling every 193rd hour from a 5-year database produced 
results essentially the same as those obtained when using the full 
meteorological record. However, this simple sampling scheme 
significantly underestimated wet deposition, particularly at sites with 
infrequent precipitation. For wet deposition, we included an additional 
sampling interval (every eighth hour) during hours with precipitation. 
This resulted in estimates that were not significantly different than 
those obtained from the full record.
    A third simplification involved deposition of gases. Currently, 
there are no air models that contain algorithms specifically designed 
to model the dry deposition of gases. In place of algorithms, we used a 
transfer coefficient to model the dry deposition of gases. A concern 
with this approach is that deposition would be calculated outside the 
model, which precludes the consideration of the deposition in the 
amount of material depleted from the plume. This results in non-
conservation of the mass in the system.
    A final simplification is the use of a scavenging coefficient for 
all gases that is based on approximating the gases as

[[Page 63424]]

very small particles. This approach eliminates the need for running 
ISCST3 for each specific chemical, thus reducing the overall runtime. 
This simplification might lead to under-prediction of wet deposition 
for some gases and over-prediction for others depending on the Henry's 
Law coefficient for the gas.
    2. Watershed modeling: The watershed module is based on conceptual 
and mathematical models that are very similar to those used for the 
land application unit and waste pile sources, that is, the combined 
``local watershed/soil column'' algorithm described in Section 3.4 of 
U.S. EPA (1999-y). As implemented in the watershed module, the model is 
a dynamic, one-dimensional (vertical), fate and transport model that 
also includes hydrological functionality. Each watershed is independent 
of other watersheds and is simulated individually. Each watershed is 
conceptualized as a ``soil column'' with chemical loads being deposited 
on its surface from aerial deposition. The deposited loads are in the 
form of a varying annual average time series. The vertical distribution 
of the chemical as a function of time is then simulated by the model.
    Fate and transport processes simulated by the watershed module are 
volatilization, leaching, runoff, erosion, infiltration and biological 
and/or chemical degradation. Hydrological functionality includes storm 
event-specific runoff estimates, based on the Soil Conservation 
Service's ``curve number'' method, storm event-specific soil erosion 
losses, based on the (modified) Universal Soil Loss Equation, and 
infiltration/recharge estimates based on daily runoff, 
evapotranspiration, and soil moisture modeling. The theoretical 
background and the implementation of the watershed module are presented 
in the background document (U.S. EPA, 1999-y).
    The chemical loads to a waterbody simulated by the watershed module 
are indirect loads only. The sole source of chemical is aerial 
deposition. Chemical loads to the waterbody resulting from direct 
runoff and erosion from a waste management unit are simulated by the 
appropriate source module (land application unit or waste pile). 
Similarly, if a receptor is located in a buffer area between a waste 
management unit and the downslope waterbody (that is, in the ``local 
watershed''), the total surficial soil concentration that the receptor 
is exposed to is the aerial deposition-related concentration simulated 
by the watershed module plus the runoff/erosion-related concentration 
simulated by the relevant source module.
    Because the surface-transport processes in the watershed module are 
hydrologically related, the land areas surrounding the waste management 
unit are disaggregated on a watershed basis, and each watershed 
delineated is modeled independently. A watershed can vary in size from 
a sheet flow-only ``hillside,'' similar to the ``local watershed'' 
construct of the land application unit and waste pile, to much larger 
areas encompassing regional stream or river networks. In all cases, a 
given watershed is modeled as a single, homogeneous area with respect 
to soil characteristics, runoff and erosion characteristics, and 
chemical concentrations in soil. No spatial disaggregation below the 
watershed level is made, that is, no spatial chemical concentration 
gradients are simulated across the ground surface of a given watershed.
    There are a number of limitations of the watershed module that are 
imposed by the overall HWIR objectives and system design, for example, 
the practical inability to calibrate models to site-specific data. In 
addition, the hydrology submodels (the curve number method for runoff 
and the use of the Universal Soil Loss Equation) are relatively 
simplistic methodologies intended to yield planning-level estimates.
    Another limitation is the possibility of spatial dilution of hot 
spots from atmospheric deposition. Because each watershed is modeled as 
a single, homogeneous area with an annual atmospheric loading based on 
the overall watershed average, any relative hot spot falling in a much 
larger watershed will become spatially diluted, and associated risks to 
humans or ecological receptors will be underestimated if those 
receptors spend most or all of their exposure duration within the hot 
spot itself.
    Uncertainties of the watershed module pertain both to uncertainties 
in assumed functional forms of submodels (for example, first order 
reaction kinetic assumptions, relationship of runoff to precipitation) 
as well as uncertainties in parameter values. Parameter uncertainties 
are mitigated by the use of probabilistic sampling methods for these 
parameters. However, given the very limited number of realizations that 
are available, these parameter uncertainties are not completely 
quantified.
    3. Groundwater modeling: The groundwater pathway consists of two 
components: flow and transport in the vadose zone (that is, the 
unsaturated zone directly below the unit), and flow and transport in 
the saturated zone. The modules for these two components are based on 
the flow and transport modules in EPA's Composite Model for Leachate 
Migration with Transformation Products (EPACMTP) (U.S. EPA, 1996-a and 
-b and 1997-c). The vadose-zone module (VZM) simulates moisture 
migration and transport of contaminants between the waste management 
unit and the water table. The saturated zone module (SZM) simulates 
flow and transport of contaminant in the aquifer over which the waste 
management unit is located, and determines contaminant concentrations 
at receptor wells, and mass fluxes to nearby downgradient surface water 
bodies. Details of the two modules are provided below.
    Vadose Zone Module (VZM). Flow in the vadose zone is modeled as 
steady-state and one-dimensional (vertical) from underneath the source 
and the surficial soil outside the unit toward the water table. The 
lower boundary of the vadose zone is the water table. The flow in the 
vadose zone is predominantly gravity-driven, and therefore the vertical 
flow component accounts for most of the fluid flux between the source 
and the water table. The flow rate is determined by the long-term 
average infiltration rate through the waste management unit. 
Contaminant is transported in the vadose zone by advection and 
dispersion. Initially, the vadose zone is assumed to be contaminant-
free and contaminants are assumed to migrate vertically downward. The 
technical details on the VZM are provided in the background documents 
for the vadose zone (U.S. EPA, 1999-aa and -ac).
    The VZM receives the net rate of vertical downward percolation from 
the waste management unit through the unsaturated zone and to the water 
table. Infiltration rates and contaminant mass fluxes emanating from 
the unit are provided as a time series of annual average rates. The VZM 
require an effective steady state infiltration rate and annual average 
contaminant concentrations. In calculating the effective infiltration 
rate, the VZM conserves mass and uses the full time series of annual 
average rates.
    The output of the VZM are a time series of contaminant 
concentrations, the times at which the concentrations are reported, the 
effective infiltration rate, and the duration of the source boundary 
condition.
    The module includes the following limitations:
     Transient effects of the flow are not considered.

[[Page 63425]]

    Multi-phase flow and transport are not permissible. Non-Aqueous 
Phase Liquid (NAPL) flow and transport are not permissible. (For more 
information on NAPLs please see Section XVII.D.3.)
     Vapor-phase diffusion is not allowed.
     Fingering effects in the vadose zone are excluded.
     Clay lenses or potential flow and transport barriers in 
the vadose zone are not considered.
     Decay is limited to first-order. Lag time for decay is not 
considered.
     The transport domain in the saturated zone is kept 
constant. Effects due to mounding caused by infiltration from waste 
management units are not considered. These effects would decrease the 
depth of the flow and transport domain in the vadose zone.
    Saturated Zone Module (SZM). For HWIR 99, the SZM simulates 
groundwater flow using a one-dimensional steady-state solution for 
predicting hydraulic head and Darcy velocities. The aquifer is assumed 
to be of uniform thickness, subject to recharge along the top of the 
aquifer with a regional hydraulic gradient. The saturated zone 
transport module simulated the advective-dispersive transport of 
dissolved one dimension with the other two dimensions added 
analytically (pseudo three dimensional). The technical details on the 
SZM are provided in the background document for the saturated zone 
(U.S. EPA, 1999-aa, U.S. EPA, 1999-ab).
    In implementing, the SZM we set the initial contaminant 
concentration to zero. The concentration gradient along the downstream 
boundary is zero, and the lower aquifer boundary is taken to be 
impermeable. A zero concentration condition is used for the upstream 
aquifer boundary. Contaminants enter the saturated zone through a patch 
source on the upper aquifer boundary directly beneath the source. 
Recharge of contaminant-free infiltration water occurs along the upper 
aquifer boundary outside the patch source. Transport mechanisms 
considered are advection, dispersion, linear or nonlinear equilibrium 
adsorption, and first-order decay.
    The major simplifying assumptions used to simulate contaminant 
transport in the saturated zone are:
     The flow field is at steady state.
     The aquifer is homogeneous and initially contaminant free.
     Adsorption onto the solid phase is described by an 
equilibrium isotherm.
     Chemical and/or biochemical degradation of the contaminant 
can be described as a first-order process.
     The contaminants exist in two phases: solids and liquids. 
The liquid phase is considered a dilute solution of the contaminant.
     The flow field is not affected by traversing streams, nor 
by extraction wells.
     Mass lost to streams located between the wells and the 
waste management units is assumed to be small compared with the bulk of 
the contaminant mass in the saturated zone. All the surface waters are 
assumed to be gaining surface waters; in other words, groundwater is 
always assumed to flow from the aquifer into the stream or other 
surface water body. Down-gradient wells beyond the streams or surface 
waters are assumed to be unaffected by the presence of surface waters.
    The module requires the input of an effective, steady-state 
recharge rate from the VZM. The primary outputs of the SZM are annual 
average concentrations at observation/receptor well locations for all 
chemicals and annual average mass fluxes to surface waters or all 
chemicals.
    Although we did not implement this feature because of time 
constraints, the saturated zone module (SZM) can factor the effects of 
fractures in porous media into the modeling. Similarly, we also have 
the ability to incorporate effects of heterogeneity in aquifers (U.S. 
EPA-ag), but did not implement this feature due to time constraints. 
Both of these capabilities are discussed further in the technical 
background document (U.S. EPA, 1999-aa) We request comments on 
implementing these features in the future.
    The uncertainties in the modeling results are associated with the 
following limitations of the SZM module.
     Transient effects of the flow, recharge, and infiltration 
are not considered.
     Spatially varied recharge is not considered.
     Source geometry is limited to an idealized square, with 
two opposite sides parallel to the flow direction.
     Multi-phase flow and transport are not modeled. Non-
Aqueous Phase Liquid (NAPL) flow and transport are not modeled (For 
more information on NAPLs, please see Section XVII.D.3.)
     Contribution of contaminant to the saturated zone via 
vapor-phase diffusion above the water table is not modeled.
     Karst conditions are not modeled.
     Decay is limited to first-order. Lag time for decay is not 
considered.
     The presence of different hydrogeologic zones in the flow 
and transport domain is not considered.
     The transport domain in the saturated zone is kept 
constant. Effects due to significant mounding caused by infiltration 
from waste management units are not considered.
     Domain geometry is limited to the idealized rectangular 
shape. Other geometries are not considered.
     Only flow to the gaining surface waters, with axes normal 
to the groundwater flow direction, is modeled. Effects of streams on 
the flow field are not considered.
     Only receptor wells with small extraction rates are 
considered. Effects of extraction on the groundwater flow field are not 
considered.
    Metals Transport. The mobility of metals in the subsurface is 
dependent on the geochemical properties of the soil and groundwater. To 
account for the metal-specific interactions with various subsurface 
environments, we used national distributions of key geochemical 
parameters. In this methodology, we used the MINTEQA2 metals speciation 
code to generate non-linear adsorption isotherms for each metal. We 
produced a set of isotherms for each metal reflecting the range of 
geochemical environments that is expected to be encountered at waste 
sites across the nation. We then used this set of isotherms to generate 
two subsets of isotherms for each metal: one for the vadose zone, the 
other for the saturated zone. Within the Generalized Soil Column Model 
within the source models for non-wastewater waste management units, 
adsorption isotherm values were approximated by treating the input 
adsorption isotherms for metals as a random variable in the sampling 
scheme. We recognize that this ignores the possible dynamic effects of 
aqueous phase contaminant concentration, precipitation, dissolution, 
adsorption/desorption, and the geochemistry of media (e.g., oxidation-
reduction conditions) on the value of the adsorption isotherms and the 
fate and transport behavior of metals in general.
    There are many sources of uncertainty associated with the 
distribution coefficients generated by MINTEQA2. These can be 
categorized as: (1) Uncertainty arising from model input parameters, 
(2) uncertainty in database equilibrium constants, and (3) uncertainty 
due to application of the model. The details of methodology and data 
used are provided in the technical background documents on metals 
transport (U.S. EPA, 1991-a; 1996-a; 1998-d; 1998-e and 1999-ah).
    4. Surface Water Modeling: Chemical mass released from a waste 
management unit can enter the local surface waterbody network in runoff 
and erosion directly from the waste

[[Page 63426]]

management unit, from atmospheric deposition to the water surface, in 
runoff and erosion from adjoining watershed subbasins, and by 
interception of contaminated groundwater. The chemical is then subject 
to transport and transformation processes occurring within the 
waterbody network, resulting in variable chemical concentrations in the 
water column and in the underlying sediments. These chemical 
concentrations are the basis for direct exposure to ecological 
receptors and indirect exposure through uptake in the aquatic food web.
    The HWIR Surface Water Module takes the loadings calculated by the 
source, atmospheric, watershed, and groundwater modules, along with 
data on meteorology, hydrology, environmental conditions, and chemical 
reactivity, and calculates the dissolved and suspended chemical 
concentrations throughout the waterbody network over time. The Surface 
Water Module consists of the core model EXAMS II (U.S. EPA, 1982 and 
1997-a) and the interface module EXAMSIO (U.S. EPA, 1999-au). EXAMS is 
a general surface water fate model for organic chemicals. This 
compartment model has been used routinely by both EPA and industry 
analysts for the analysis of expected pesticide concentrations in 
generically defined environments, such as farm ponds. It has also been 
used for site-specific analysis of pesticide concentrations in various 
waterbodies around the world. The interface module EXAMSIO was 
developed specifically for HWIR. It reads data from other HWIR modules 
and databases, and builds EXAMS input files describing the waterbody 
environment and chemical properties, along with the command file that 
specifies the chemical loading history and controls the EXAMS 
simulation. Control is passed to EXAMS, which conducts the simulation 
and produces intermediate results files. EXAMSIO then processes the 
intermediate files and passes the output data back to the proper HWIR 
databases.
    The surface water module as implemented by EXAMSIO and EXAMS 
employs several simplifications in order to meet HWIR project 
requirements and constraints. The project design calls for repeated 
long simulations (200 to 10,000 years) executed quickly (seconds to 
minutes). This requirement limits the temporal resolution at which 
simulations can be conducted. Another important constraint is limited 
site-specific surface water data. This constraint limits the accuracy 
with which a particular site can be described. The major model 
simplifications made in response to these project constraints include 
the use of annual average hydrological and loading inputs, the use of 
national distributions to specify some site-specific environmental 
conditions, and the use of a simple solids balance with no settling and 
burial. For sites that experience periodic drying, a small positive 
flow equivalent to 5 mm/year of direct precipitation onto the waterbody 
surface was assumed in order to keep the model functioning.
    These simplifications could lead to a degree of model error in the 
calculated concentrations. Using annual average loadings and flows 
rather than daily loadings and flows will lead to calculated annual 
average concentrations that are biased somewhat high, depending on the 
correlation between flow and loading at a particular site. This bias is 
somewhat mitigated for reactive and volatile chemicals where the loss 
rate is proportional to the concentration. The use of national 
distributions rather than site-specific environmental data could cause 
calculated concentrations to be low or high at a given location, with 
no known general bias. The simple solids balance will overestimate 
suspended solids concentrations slightly in streams and more 
significantly in ponds, wetlands, and lakes. Calculated total water 
column chemical concentrations will be high, while the dissolved 
chemical fraction will be low. The net result for dissolved water 
column chemical concentrations, which are used for fish exposure, is 
not expected to be biased significantly high or low.
    The effect of assuming a small positive flow equivalent to 5 mm/
year of direct precipitation onto the waterbody in order to prevent 
drying is more difficult to evaluate. This procedure conducts chemical 
loads downstream within a remnant aquatic reach rather than within 
runoff over a dry bed. While the mass balance is maintained, the 
chemical and solids concentrations will tend to be elevated within the 
remnant reach. These elevated concentrations are probably realistic for 
years in which evaporation exceeds all hydrologic inflows.
    Organic chemical simulations account for ionization and sorption as 
equilibrium reactions, and volatilization, hydrolysis, biodegradation, 
and reduction as first-order kinetic reactions. Metals are simulated as 
conservative chemicals that partition to suspended and benthic solids; 
partition coefficients are based on a literature survey that summarizes 
metals partitioning behavior in surface water and sediments. Mercury is 
simulated as three interacting components subject to methylation, 
demethylation, reduction, and volatilization, as well as partitioning 
to suspended and benthic solids.
    5. Food chain modeling: We estimated chemical concentrations in 
fruits and vegetables, beef and dairy products, and fish (for human 
receptors) and in prey and plant food items (for ecological receptors) 
by simulating uptake from the air, water, and/or soil and transport in 
these food items. This uptake and transport modeling uses empirical 
biotransfer factors. These factors are based on the methodologies and 
equations in the April 1997 internal review draft of the Methodology 
for Assessing Health Risks Associated with Multiple Exposure Pathways 
to Combustor Emissions (U.S. EPA, 1997-f), commonly referred to as the 
Indirect Exposure Methodology (IEM). The food chain methodologies and 
equations as implemented for HWIR99 are described in the docket (US 
EPA, 1999-al, 1999-am, and 1999-ap).
F. Which Receptors Did EPA Model When Assessing Exposure to the HWIR 
Exempt Waste?
    1. Which human receptors did EPA model? We modeled four receptor 
types: residents, home gardeners, farmers (beef and dairy) and 
recreational fishers. Some of these receptor types overlap; a resident, 
gardener, or farmer could also be a recreational fisher, and the farmer 
could be a beef farmer, dairy farmer, or both. For each receptor type, 
we evaluated exposures to four age cohorts: ages 1-5; ages 6-12; ages 
13-19; and older than age 19.
    Some of the modeled receptors might be exposed through several 
pathways, some might only be exposed through one pathway, and some 
might not be exposed at all to any pathway. Receptor are evaluated for 
exposures with respect to chemicals present in ambient air (both vapors 
and particles), soils, groundwater, fruits and vegetables, beef and 
dairy products, and fish. Annual exposures are chemical and 
environmental setting specific and are estimated to occur for up to 
10,000 years or when the chemical concentration in a particular media 
(for example, groundwater) decreases to less than one percent of the 
maximum concentration for that media.
    Residents breathe contaminated air and ingest contaminated soil (as 
an incidental contamination of hands or foods). A subset of residents 
have private drinking water wells and are exposed to contaminated 
groundwater through both direct drinking water ingestion and inhalation 
through showering. Those on public water

[[Page 63427]]

supply are assumed to have treated water that meets all drinking water 
standards. We used the 1990 U.S. Census block survey data to estimate 
the number of residents and their ages within two kilometers of each of 
the 201 sites evaluated.
    Home gardeners are residents who are also exposed to contaminated 
homegrown fruits and vegetables. We estimated the percentage of the 
entire population within two kilometers of the waste management unit 
that are home gardeners based on national data presented in EPA's 
Exposure Factors Handbook (EFH) (U.S. EPA, 1997-d).
    Farmers are exposed through inhalation of ambient air, inhalation 
of shower air, ingestion of groundwater, ingestion of soil, and 
ingestion of fruits and vegetables. In addition, beef farmers are 
exposed through ingestion of beef and dairy farmers are exposed through 
ingestion of milk. We estimated the numbers and types of farms and 
farmers within the two-kilometer area of interest from a combination of 
the 1990 Census data (U.S. Bureau of the Census, 1990), Geographic 
Information Retrieval and Analysis System (GIRAS) land use data, and 
county-level census agricultural data (U.S. EPA, 1994). We averaged the 
1987 and 1992 Census of agricultural data to approximate 1990 (for 
consistency with the population census).
    Recreational fishers have the same exposures as either the 
resident, the home gardener or the farmer, but are also exposed through 
fish ingestion. The number of recreational fishers at each site was 
estimated from the 1990 Census data (U.S. Bureau of the Census, 1990) 
and state-level information from the U.S. Fish and Wildlife Service 
National Wildlife Survey (U.S. F&WS, 1991).
    Infants are assumed to be exposed through mother's contaminated 
breastmilk. For infant exposure through breastmilk, the maternal 
exposure through all pathways was summed. The mother is assumed to be 
an adult (as opposed to a teenager) for the purpose of calculating 
maternal dose in the infant breastmilk pathway. The current methodology 
for infant exposure would apply only to dioxin and dioxin-like 
chemicals. We invite comment on this approach and whether it should be 
applied to other chemicals in the assessment.
    For each of the receptor types, we estimated carcinogenic risks 
assuming a nine-year exposure duration based on average exposure during 
this period. Nine years is the median residence duration of the 
distribution for all ages as reported in the Exposure Factors Handbook 
(U.S. EPA, 1997-d). That is, half the population would be exposed for 
less than nine years and half for greater than nine years. Aging of 
cohorts into subsequent cohort age classes, and their differing 
exposures, is included. For each receptor location, human risk is 
estimated by aggregating exposure pathways, when appropriate. The aging 
of a cohort into the subsequent cohort age category(s), and the 
resulting differences in exposure, is included in this average 
calculation. For non-cancer risk calculations, exposure is assumed to 
vary annually; we did not use a longer averaging period. Therefore, a 
single high year of maximum exposure would not be ``diluted'' by a 
multi-year averaging period. That is, we estimated non-cancer hazard 
quotients based on the maximum annual average concentration. This is a 
conservative approach which might overestimate risks. The exposure and 
risk methodologies are described in the Background Document for the 
Human Exposure Module for the HWIR99 3MRA Model (U.S. EPA, 1999-aj) and 
Background Document for the Human Risk Module for the HWIR99 3MRA Model 
(U.S. EPA, 1999-ak), respectively.
    The use of the maximum one year concentration for estimation of 
non-cancer hazard quotients introduces a potential bias when exposure 
to the constituent is associated with chronic effects from long-term 
exposure. The annual average concentration will tend to overestimate 
risk, as RfDs and RfCs for chronic effects are based on lifetime 
average exposure. On the other hand, use of the annual average 
concentration will tend to underestimate risk for developmental 
toxicity. In this case, annual average concentrations might mask higher 
short-term peak exposures resulting in an underestimation of the 
effective HQ (primarily for women of child-bearing age). EPA's 
noncancer toxicity assessment methodology, however, tends not to attach 
a great deal of significance to specific endpoints observed in test 
animals, as a general concordance of effects among species has not been 
demonstrated. The entire body of evidence must be evaluated in each 
case in order to determine whether specific effects are likely in 
humans.
    We estimated exposures for residential receptors (residents and 
home gardeners) at a single location in each of the census blocks in 
the 2-kilometer study area, and for farmers at a single farm in each of 
the census block groups in the 2-kilometer study area. Recreational 
fisher exposures are calculated and averaged across up to three 
randomly selected waterbodies over the entire study area. The random 
selection of waterbodies is made once for recreational fishers who are 
residential receptors, and once for recreational fishers who are 
farmers. We assumed that human receptors both reside and work at the 
receptor location identified for them during site characterization. 
This assumption might overestimate or underestimate exposure to an 
unknown degree and bias, because it is possible that individuals might 
reside at the identified location within the study area, but commute to 
work areas outside of the study area, or could commute to more highly 
contaminated areas within the study area.
    For each receptor type, we estimated only the incremental 
exposures, risks, and hazards quotients for a chemical. We did not 
consider background exposures from natural or other man-made sources. 
For cancer risks, we assumed lifetime exposure risks are in direct 
proportion to the fraction of a lifetime actually exposed (that is, 350 
of 365 days per year (15 days away per year) for each year of the 
exposure duration. We did not consider additive, synergistic, or 
antagonistic effects among multiple chemicals. This assumption might 
overestimate or underestimate exposure to an unknown degree and bias. 
In addition, we did not consider age-specific differences in exposure 
responses; that is, we did not vary cancer slope factors with cohort 
age.

                                                  Table 5.-- HWIR Receptor Types and Exposure Pathways
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Resident           Home  gardener            Farmer                Fisher              Infants
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inhalation..................................  X...................  X...................  X...................  X..................
Soil Ingestion..............................  X...................  X...................  X...................  X..................
Groundwater Ingestion.......................  X (subset)..........  X (subset)..........  X (subset)..........  X (subset).........
Inhalation during showering.................  X (subset)..........  X (subset)..........  X (subset)..........  X (subset).........
Fruit and vegetable ingestion...............  ....................  X...................  X...................  X (subset).........

[[Page 63428]]

 
Beef and/or milk Ingestion..................  ....................  ....................  X...................  X (subset).........
Fish ingestion..............................  ....................  ....................  ....................  X..................
Breast milk ingestion.......................  ....................  ....................  ....................  ...................  X.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    2. How were human exposures estimated? We estimated the contaminant 
exposure that human receptors incur (mass of contaminant per mass of 
body weight) based on simulated concentrations in the various 
environmental media or food items, pathway-specific ingestion or 
inhalation rates, and receptor cohort-specific body weights. Exposure 
factors (for example, intake rates, residence duration) were fixed for 
all receptors of a given type and age at each site. With the exception 
of the shower inhalation exposure, the methodologies and equations used 
for the exposure calculations are from the Methodology for Assessing 
Health Risks Associated with Multiple Exposure Pathways to Combustor 
Emissions (U.S. EPA, 1997-f). The shower inhalation algorithm was 
adapted from McKone (McKone, 1987). All methodologies and equations as 
implemented for HWIR99 are fully described in the technical background 
document: Human Exposure Module: Background and Implementation for the 
HWIR99 Multimedia, Multipathway and Multireceptor Risk Assessment 
(3MRA) Model (U.S. EPA, 1999-aj).
    3. Which ecological endpoints did EPA model? We defined several 
ecological assessment endpoints to evaluate, based on the management 
goal of protecting terrestrial and aquatic ecosystems from HWIR 
exempted waste. The assessment endpoints that we chose to evaluate are 
shown in Table 6. These endpoints represent the general trophic levels 
within a food web and are broad enough to characterize the 
functionality and trophic level interactions within most habitats. In 
addition, these assessment endpoints generally capture the significant 
biota of most habitats.

                  Table 6.--Assessment Endpoints Considered for the HWIR Ecological Assessment
----------------------------------------------------------------------------------------------------------------
                                      Assessment
     Ecological significance           endpoints            Example         Characteristic    Measure of  effect
----------------------------------------------------------------------------------------------------------------
Upper trophic level consumers;    Viable mammalian    Deer mouse, meadow  Reproductive and    Chronic or
 Top recipients of                 wildlife            vole, red fox.      developmental       subchronic
 bioaccumulative chemicals;        populations.                            success.            NOAEL(s) or
 Represent species with large                                                                  LOAEL(s) for
 foraging ranges; Represent                                                                    developmental and
 species with longer life spans.                                                               reproductive
                                                                                               effects.
                                  Viable avian        Red-tailed hawk,    Reproductive and    Chronic or
                                   wildlife            northern bobwhite.  developmental       subchronic
                                   populations.                            success.            NOAEL(s) or
                                                                                               LOAEL(s) for
                                                                                               developmental and
                                                                                               reproductive
                                                                                               effects.
Species represent unique habitat  Viable amphibian    Frog, newt, snake,  Reproductive and    Chronic or
 niches  (e.g., partially          and reptile         turtle.             developmental       subchronic
 aquatic and terrestrial); Some    wildlife                                success.            NOAEL(s) or
 species are sensitive to          populations                                                 LOAEL(s) for
 contaminant exposure.             (``herps'').                                                developmental and
                                                                                               reproductive
                                                                                               effects.
Represents base food web in       Sustainable soil    Nematodes, soils    Growth, survival,   95% of species
 terrestrial systems; Habitat      community           mites,              and reproductive    below no effects
 vital to decomposers and soil     structure and       springtails,        success.            concentration at
 aerators; Proper soil community   function.           annelids,                               50th percentile
 function related to nutrient                          arthropods.                             confidence
 cycling.                                                                                      interval.
Primary producers of energy in    Maintain primary    Soy beans,          Growth, yield,      10th percentile
 ecosystems; Act as food base      terrestrial         alfalfa, rye        germination.        from LOEC data
 for herbivores; Able to           producers (plant    grass.                                  distribution.
 sequester some contaminants;      community).
 Can act as vectors to
 bioaccumulation; Constitute a
 large fraction of the earth's
 biomass.
Highly exposed receptors from     Sustainable         Fish (salmonids),   Growth, survival,   Ambient water
 constant contact with             aquatic community   aquatic             reproductive        quality criteria
 contaminated media Act as         structure and       invertebrates       success.            (AWQC) for
 vectors to transfer               function.           (daphnids).                             aquatic life (95%
 contaminants to terrestrial                                                                   species
 species.                                                                                      protection).
Provide habitat for reproductive  Sustainable         Protozoa, flat      Growth, survival,   10th percentile
 lifestages (e.g., eggs, larval    benthic community   worms, ostracods.   reproductive        from LOEC data
 forms); Habitat for key           structure and                           success.            distribution.
 invertebrate species; Act to      function.
 process nutrients and decompose
 organic matter.
Primary producers of energy in    Maintain primary    Algae and vascular  Growth, mortality,  EC20 for algae;
 the aquatic system; Base food     aquatic producers   aquatic plants.     biomass, root       lowest LOEC for
 source in the aquatic system;     (algal & plant                          length.             aquatic plants.
 Can act to sequester              community).
 contaminants from the water
 column; Act as substrate for
 other organisms in the water
 column (e.g., periphyton).
----------------------------------------------------------------------------------------------------------------


[[Page 63429]]

    Our first step for selecting ecological receptors was to identify 
the habitats that might exist near a site. We collected GIRAS land use 
maps, National Wetland Inventory maps, and National Wildlife Refuge 
maps to plot the types of land uses around the sample sites. We then 
delineated habitats within two kilometers of the waste management unit 
to identify the habitats around the site. We identified subclasses of 
terrestrial habitats, aquatic habitats, and wetlands based on the 
regional location of the site. A detailed description of the subclasses 
considered is found in the background document (US EPA, 1999-an). We 
then used the habitat description and regional location to identify 
potential receptors for each site-based habitat.
    The second step in the process was to assign receptors. Based on 
the ecological assessment endpoints, we sought to capture the range of 
organisms that might reside in a specific habitat and represent the 
functions and trophic levels typically present in that habitat. Thus, 
we modeled a suite of receptors that represent various trophic levels 
within terrestrial, aquatic, and wetland habitats. The receptors that 
we evaluated included: soil communities, terrestrial plant communities, 
mammalian populations, and avian populations for terrestrial habitats; 
and sediment communities, aquatic plant communities, aquatic 
communities, amphibian populations, mammalian populations, and avian 
populations for aquatic habitats. For wetlands, we assigned groups of 
these aquatic and terrestrial receptors based on the type of wetland 
present at a site. In an effort to make the assessment site-based, we 
used information on the location of the site to identify the receptors 
that might occupy different functions or trophic levels. The list of 
receptors by habitat is found in the background document (U.S. EPA, 
1999-an). The description of the ecological risk methodologies are 
described fully in the Background Document for the Ecological Risk 
Module for the HWIR99 3MRA Model (U.S. EPA, 1999-ao).
    4. How were ecological exposures estimated? Similar to estimating 
human receptor exposures, we estimated ecological receptor exposures 
based on simulated contaminant concentrations in the various 
environmental media and food items, pathway-specific ingestion rates, 
and receptor type-specific body weights. An inhalation pathway was not 
considered for ecological receptors. The methodologies and equations 
used for exposure estimates are fully described in the technical 
background documents: Ecological Exposure Module: Background and 
Implementation for the HWIR99 Multimedia, Multipathway and 
Multireceptor Risk Assessment (3MRA) Model (U.S. EPA, 1999-an).

XVII. What Are the Results of the Current Version of the Risk 
Assessment?

    The risk assessment is designed to produce chemical-specific 
distributions of cancer risks or hazards to humans and ecological 
receptors living in the vicinity of industrial waste sites that could 
manage HWIR exempted wastes throughout their operating life. For each 
site and waste concentration, the model can generate risks for each 
receptor location and then sums the number of receptors that fall 
within a specified risk range (bin) to get the distribution of risks 
for the population at each site. We can use the distribution of risks 
at a site to determine whether a site is protected based on the 
percentage of the population protected, a specified cancer risk or 
hazard level, and the initial concentration in waste. The model then 
uses these data to generate a percentile distribution based on the 
number sites protected at a specified risk level for each waste 
concentration to generate the national distribution.
    These results are evaluated over a 10,000 year period of exposure. 
This time frame applies mainly to the groundwater pathway, since 
receptors are exposed to chemicals via other pathways much sooner. 
Evaluating peak doses over this time horizon allows the model to 
capture the slow movement of certain chemicals through the subsurface. 
Although the time frame for such travel might be long, such 
contamination could be a serious problem when the chemical reaches the 
receptor wells (see, for example, the discussion at 63 FR 42157).
    Many of the commenters to the 1995 HWIR proposal felt that it would 
be more reasonable to use a 1,000 year time frame because of the 
uncertainty involved in modeling so far into the future. Land use 
patterns, climate, environmental, other exposure assumptions and 
technology would be expected to change over 10,000 years, but we cannot 
predict what the world will be like then.
    Other commenters to the 1995 proposal felt that uncertainty 
surrounding the modeling effort should lead EPA to choose a time period 
on the order of 10,000 years to ensure that human health is protected. 
Particularly for chemicals that do not degrade, the issue is less which 
generation would bear the risk of exposure to a chemical than the 
magnitude of risk that would be experienced once the contamination does 
reach a drinking water well. A comparison of results from the 1995 
modeling effort suggests, for certain chemicals, a difference in 
exemption concentrations of over an order of magnitude depending upon 
whether 1,000 or 10,000 years was chosen (60 FR 66373). Modeling for 
other hazardous waste identification purposes has found peak 
concentrations of dioxin and arsenic to occur 1,500 and 8,800 years 
after the assumed operating life of the disposal unit (64 FR 46492 and 
64 FR 46507). There might also be some uncertainty regarding when the 
peak concentration occurs, and the selection of a longer time frame 
increases the chance that peaks are considered in the assessment. We 
request comment on the time period over which exposure at a receptor 
should be evaluated.
    The risk assessment is also designed to generate results that allow 
risk managers the flexibility to consider the results based on several 
risk descriptors. The risk descriptors for the human health risk and 
ecological risk are discussed below.
    For the human health assessment, the model calculates the aggregate 
risk or hazard from multiple exposure pathways that occur 
simultaneously at the receptor location to generate the distribution of 
individual risks. For carcinogenic effects, we chose seven risk bins 
ranging from less than 1 x 10-8 to greater than 
1 x 10-4 to generate the distribution. For human health 
hazard quotients, we chose four hazard bins ranging from less than 0.1 
to greater than 10. The model can generate results for three distance 
rings, including within 500 meters, within 1000 meters, and within 2000 
meters. The model can also generate results for 12 exposure pathways, 
including total ingestion and inhalation, total ingestion, total 
inhalation, total groundwater ingestion and shower inhalation, air 
inhalation, shower inhalation, groundwater ingestion, soil ingestion, 
crop ingestion, beef ingestion, dairy ingestion, and fish ingestion. In 
addition, the model can disaggregate the results by five receptor 
types: all receptors, residents, gardeners, farmers, and fishers. 
Finally, the results can be queried by three age cohorts: all ages, 
children 12 and under, and adults 13 and over.
    For the ecological assessment, we calculate impacts to ecological 
receptors using the same general methodology, but we evaluate impacts 
to populations or communities of ecological receptors rather than to 
individuals. For each site, the model generates a distribution of 
hazard quotients (HQ) by receptor and sorts the receptors into one of 
four hazard bins, ranging from less than 0.1 to greater than 10. The 
model uses the

[[Page 63430]]

receptor results to evaluate impacts to several attributes of habitats, 
including three habitat groups (terrestrial, aquatic, and wetland), 11 
habitat types (for example, forest, lake, river), nine receptor groups 
(for example, mammals, aquatic biota, terrestrial plants), and five 
trophic levels (for example, producers, top predators). The model 
generates results for each of the attributes by three distance 
categories: within 1000 meters, between 1000 and 2000 meters, and 
within 2000 meters. In addition, the model also generates results for 
the evaluation of some combinations of these attributes, including 
impacts by habitat group and trophic level, and by habitat group and 
receptor group.
    Numerical results for acrylonitrile are presented in the risk 
characterization technical background document as an example of the 
types of results the model will generate (U.S. EPA, 1999-as). At this 
time, we have not completed final testing of the software system. 
Therefore, the use and interpretation of the results must be limited. 
The results should be viewed as representing the capabilities of the 
model with respect to the types of information that the model can 
produce. The numbers are likely to change after additional diagnostic 
testing and final testing of the software system.
    The software system has been designed and implemented with a strong 
focus on Quality Assurance and Quality Control (QA/QC). The software 
system is comprised of three primary components; the site-based 
databases, the system software, and the modules for performing the 
required exposure and risk assessments. The system software organizes 
the waste site information and prepares individual datasets that are 
used to simulate contaminant release, multimedia fate and transport, 
and human and ecological exposure and risk. The system software also 
manages the execution of the numerous modules that simulate specific 
steps in the risk assessment process (e.g., source release, surface 
water fate and transport, ecological risk). The software development 
steps that we followed (and that address QA/QC) include:
     Software system design is based on detailed and peer 
reviewed HWIR Assessment Methodology.
     Software system is designed using object-oriented design 
principles and utilizing existing EPA models (ISCST, EXAMS, EPACMTP).
     Detailed system specifications are documented and reviewed 
before software coding is initiated.
     Data dictionaries are developed to fully define (and 
constrain) each data item that is shared within the system.
     Database development is designed and executed in close 
coordination with software system development.
     Individual developers design and conduct first level 
testing of all code before assimilation into the larger software 
system.
     System software and component modules are assimilated into 
a unified system with extensive testing of information flow and related 
data integrity.
     Execution of an initial ``technical'' verification (i.e., 
tracking the actual numbers through the system) of the software system 
using a single combination of waste site, chemical, and waste unit 
type.
     Execution of limited ``production'' runs using a subset of 
the total number of waste site/chemical/waste unit type combinations. 
Production runs are oriented toward producing exemption levels.
     Execution of initial full scale production runs (i.e., 
using all site/chemical/waste unit type) combinations.
     Execution and documentation of final tests for individual 
components of the software system. (This step has been delayed due to 
the extended nature of the development process and overall project 
schedule.)
     Execution of second full scale production runs (i.e., the 
runs that would produce the exemptions levels).
    We are providing the entire software system (with documentation) 
and a list of software errors that we have identified in the docket. We 
request comment on the system, including the specifics of any errors 
that are identified.
A. What Are The Major Strengths of the Risk Assessment?
    The HWIR risk assessment has several major strengths. These 
strengths are associated with the development of the 3MRA Model and 
associated components, the data collection approach selected to 
implement the regional site-based approach, and the testing and quality 
assurance process followed during both the developmental and 
implementation phases of the assessment in order to ensure the accuracy 
and usefulness of the information produced.
    A key strength of the risk assessment is the 3MRA Model. The model, 
when fully operational, will represent a state-of-the-art software 
system designed to implement our assessment strategy. The model is an 
integrated, multimedia, multiple exposure pathway, and multiple 
receptor risk assessment tool that evaluates impacts to human and 
ecological receptors. The model addresses concerns raised with earlier 
efforts in the following ways: implementing a probabilistic approach to 
develop chemical-specific national distributions of risks; maintaining 
mass balance partitioning within each source; incorporating fate and 
transport components that manage chemical loadings simultaneously from 
multiple environmental media; evaluating a receptor's exposure through 
multiple pathways simultaneously; evaluating ecological impacts at a 
suite of representative habitats for terrestrial, aquatic, and wetland 
systems; and accounting for various degradation losses, including 
hydrolysis, aerobic, anaerobic, and activated solids biodegradation.
    In selecting the fate and transport models incorporated into the 
3MRA Model, we considered which state-of-the-science models would be 
appropriate for this national scale assessment. For example, the air 
models that we considered ranged in complexity from regional-scale to 
simple, local-scale, box models. Currently available regional-scale 
models do not provide estimates at a fine enough scale for use in our 
assessment. On the other hand, box models tend to be sensitive to the 
size of the box and do not provide any spatial resolution in the 
estimates. The air model we ultimately selected, the Industrial Source 
Complex-Short Term (ISCST3) model, is a steady-state, Gaussian plume 
model with an area source algorithm appropriate for the types of 
sources included in the analysis. This model has undergone peer review 
and various versions have been used in a large number of our regulatory 
analyses. Similar decisions were made for the groundwater and surface 
water modules.
    In addition to existing state-of-the-science media transport 
models, we developed new modeling approaches for the sources included 
in our analysis. These models were designed to address comments 
received from the public and the SAB on the HWIR95 source models. We 
believe the models provide a more accurate simulation of contaminant 
release to all media. For example, we incorporated the following 
features into our models: estimating chemical mass losses through 
different pathways simultaneously, which allows a true, multipathway 
exposure and risk estimate; maintaining mass balance; estimating 
chemical concentrations as a function of time and depth; including

[[Page 63431]]

chemical mass losses such as volatilization, leaching, biodegradation, 
and hydrolysis; and simulating the effects of sediment accumulation on 
the infiltration rate in surface impoundments is modeled.
    We also developed a set of food chain models that reflect the 
current state-of-the-science in plant uptake and bioaccumulation of 
chemicals in plants and animals. Although the farm food chain and 
terrestrial food web are similar to those used in HWIR95, each has been 
updated to reflect the current thinking with regard to specific 
chemical classes. The aquatic food web model is also newly developed 
and reflects the latest thinking with regard to bioaccumulation and 
biomagnification of different types of chemicals in aquatic systems.
    Some of the major improvements made in the area of the human 
exposure and risk include: GIS applications for receptor locations and 
characteristics; management of exposure time series including 
discontinuous exposures across multiple pathways; aging across cohorts 
based on exposure durations; and determination of critical risk time 
periods. These areas have improved our ability to characterize national 
scale risks.
    We have also made improvements in our ecological assessment. The 
resolution of the assessment goes beyond the generic systems used in 
HWIR95 and now includes a suite of representative habitats for 
terrestrial, aquatic, and wetland systems. The habitats are intended to 
reflect the variability of ecological systems across the United States 
and provide a context for selecting appropriate receptors at each site. 
Each habitat is characterized by site-based data such as habitat 
boundaries and ``common'' species and communities associated with that 
habitat. Over 50 representative species of birds, mammals, amphibians, 
and reptiles are included. In addition, simple food webs are 
constructed that indicate the major trophic levels and functional 
groups expected in each type of habitat.
    Also, although the comments from the independent expert peer 
reviewers of the HWIR 3MRA model have not yet been addressed, EPA has 
reviewed those comments and they appear to be generally supportive of 
the overall modeling methodology and approach. The independent expert 
peer reviewer comments received to date are in the docket for today's 
proposed rule. Both the peer review comments and the public comments 
will be addressed prior to a final rulemaking.
    Another strength for HWIR99 is the use of an overall database that 
provides site-based and regional specific data for a statistically 
representative set of industrial sites across the U.S. By selecting a 
statistical sample, we can use this subset of facilities to extrapolate 
our results to all the industrial facilities that have the types of the 
waste management units we evaluated. These data provide us a more 
realistic, rather than hypothetical, insight with respect to location 
of human and ecological receptors in the vicinity of the facilities. 
For humans, we also have data on the number of people at various 
locations, their age distribution, and a variety of other 
characteristics. However, as noted in the preamble discussions on data 
uncertainties (Section XVII.B) and the surface water module (Section 
XVI.E.4), we recognize that we were not able to directly measure many 
facility/site characteristics (for example, depth to groundwater; 
aquifer thickness; hydraulic conductivity; location of wells; type of 
ecological receptors; behavioral characteristics of receptors) at each 
representative site to estimate risk. We addressed these limitations by 
using regional and national data that might underestimate or 
overestimate a chemical's movement through the environment and the 
resulting exposures and risks, with no known general bias.
    We undertook a number of steps during the development and 
implementation phases of the model and examined supporting data to 
ensure the model would produce useful information. We developed the 
model under a documented quality assurance process beginning with an 
understanding of how the model must perform to meet the needs of the 
risk assessment, and continuing through the design of the model, its 
testing, and implementation. We ensured that all components of the 
model interacted appropriately by specifying requirements that each 
component had to meet, including consistency of assumptions and data 
transfer between components. Each component was thoroughly tested and 
documented by the developer. We revised program code, documentation, 
and design specifications to resolve issues found during testing. We 
had or will have each component, as well as the overall model, 
independently tested to ensure that the model functions as the 
developer intended. Finally, all of the databases and underlying data 
went through a quality assurance protocol to ensure that data were 
correctly obtained from the original source, entered in the appropriate 
database, and properly transferred to the 3MRA model prior to 
implementation.
B. What Are the Major Limitations of The Risk Assessment?
    The risk assessment has inherent limitations because of the 
complexity associated with simulating the behavior of a chemical moving 
through the environment from disposal in a management unit, to exposure 
media, and subsequent impacts on receptors. As explained below, 
limitations also result from the amount, type, and quality of the data 
used in our assessment, the set of exposure pathways evaluated, and the 
types of waste management units considered. In addition, both 
computational and resource constraints experienced during the 
development and implementation of the assessment limited our effort. We 
did not evaluate the impacts from either one-time or intermittent 
disposal of a waste, or the catastrophic release of potentially exempt 
waste from the failure of a management unit. We were not able to 
directly measure facility/site characteristics (for example, unit area 
and volume; depth to groundwater; aquifer thickness; hydraulic 
conductivity; location of wells; type of ecological receptors; 
behavioral characteristics of receptors) at each representative site to 
estimate risk. Finally, we were not able to calibrate or validate our 
model with known data sets. We present below the major limitations 
related to resource constraints, risk modeling, and the data used for 
the modeling.
    1. What are the major limitations resulting from computational and 
resource constraints? 
    During the implementation phase of the 3MRA Model, we were limited 
to running a single ``iteration'' of the model for each chemical at a 
waste management unit/site combination to develop the distribution of 
protected populations and sites over a range of five waste 
concentrations. This means that for parameters for which we had 
distributions, we selected a random value for each parameter for each 
setting. The combination of the selected values defined what the 
characteristics of the setting were for the estimation of the hazard 
and risk distributions. Each parameter value at the setting remained 
fixed during the iteration over the range of concentrations evaluated. 
While only a single calculation was performed at each setting, we 
evaluated multiple settings for each chemical. In this manner, we 
account for uncertainty and variability across the representative

[[Page 63432]]

settings of possible waste management units and sites.
    Because of computational constraints (that is, the limited amount 
of time to run the model during the implementation phase of the risk 
assessment), we had to limit the duration of the chemicals release from 
a waste unit to a maximum of 200 years. (However, once released from 
the unit, the chemicals are modeled for 10,000 years or until the 
chemical concentration decreases to one percent of the maximum 
concentration in each media, whichever comes first.) This constraint 
affects only the landfill and land application units. The waste pile is 
assumed to be removed after 30 years, surface impoundments are assumed 
to be clean closed after 50 years (that is no further release after 
closure) and aerated tanks are assumed to be properly maintained to 
prevent any leakages from occurring during their operation.
    We believe that this assumption would have little impact on the 
potential hazard and risk results for most chemicals that are highly 
mobile in environmental media and do not bioaccumulate in the food 
chain. For less mobile chemicals, for example most metals, we would 
likely underestimate the amount of the chemicals released from the 
unit. Based on preliminary sensitivity analyses for a less mobile 
chemical (arsenic), less than one-quarter of the peak mass in a 
landfill or land application unit is predicted to move from the unit 
after 1,000 years. For a land application unit, the peak surface water 
load was not attained even after 1,000 years, even though the surficial 
soil concentration in the unit begins to decrease immediately after the 
end of the operating life (40 years).
    2. What are the major uncertainties of the risk modeling? 
Uncertainty analysis is very complicated when conducted on multimedia 
assessment modeling efforts. The issues associated with how to conduct 
such analyses, whether to conduct quantitative vs. qualitative 
uncertainty analyses, and other related issues are currently being 
debated within the scientific community.
    Sources of uncertainty in toxicological benchmarks include one or 
more of the following: extrapolation from laboratory animal data to 
humans, variability of response within the human population, 
extrapolation of responses at high experimental doses under controlled 
conditions to low doses under highly variable environmental conditions, 
and adequacy of the database (number of studies available, toxic 
endpoints evaluated, exposure routes evaluated, sample sizes, length of 
study, etc.). Toxicological benchmarks are designed to be conservative 
(that is, overestimate risk) because of the uncertainties and 
challenges associated with condensing toxicity data into a single 
quantitative expression.
    Another important area of uncertainty involves estimates of risks 
to children from carcinogenic compounds. We estimated the risk of 
developing cancer from the estimated lifetime average daily dose and 
the slope of the dose-response curve. A cancer slope factor is derived 
from either human or animal data and is taken as the upper bound on the 
slope of the dose-response curve in the low-dose region, expressed as a 
lifetime excess cancer risk per unit exposure. However, individuals 
exposed to carcinogens in the first few years of life might be at 
increased risk of developing cancer. We modified the exposure factors 
for children to account for differences between adult and child 
receptors (for example, body weight, exposure duration). We did not 
adjust the cancer slope factors to account for age-specific differences 
in exposure assumptions (e.g., body weight). However, we recognize that 
significant uncertainties and unknowns exist regarding the estimation 
of lifetime cancer risks in children. Methodologies for estimating 
environmental threats to children's health are relatively new. They are 
currently being debated within the scientific community, and will 
continue to evolve. The underlying assumption in our assessment that 
cancer risks for children can be calculated the same as cancer risks 
for adults has not been peer reviewed.
    Non-cancer effects in children is also an area of uncertainty. Non-
cancer reference doses and reference concentrations for children are 
based on comparing childhood exposure, for which we have age-specific 
data, with adult toxicity measures, where adequate age-specific dose-
response data is lacking. This mismatch results in a large amount of 
uncertainty in the estimation of hazard quotients for children. This 
would sometimes result in an overestimation of children's risk and 
sometimes in an underestimation. This issue is still under 
investigation in the scientific community and no consensus has been 
reached.
    The use of the highest annual average concentration for estimation 
of non-cancer hazard quotients introduces a potential upward bias on 
the hazard quotient, as most non-cancer toxicity benchmarks are based 
on lifetime average exposure. The HWIR methodology should be considered 
to be conservative in this respect. An exception is when exposure to 
the chemical is associated with developmental effects, which can result 
from very short-term exposure. In this case, annual average 
concentrations might mask higher short-term peak exposures resulting in 
an underestimation of the effective HQ (primarily for women of child-
bearing age). The EPA's non-cancer toxicity assessment methodology, 
however, tends not to attach a great deal of significance to specific 
endpoints observed in test animals, as a general concordance of effects 
among species has not been demonstrated. The entire body of evidence 
must be evaluated in each case in order to determine whether specific 
effects are likely in humans.
    Another uncertainty is the impact of inter-individual variability 
in exposure. Exposure variables (for example, media intake rates, 
residence duration) are fixed for all receptors of a given type and age 
and are not allowed to vary. These variables do vary across waste 
sites. Preliminary simulations suggest that this variability might not 
be too large given the large variability of media concentrations 
nationally. However, with further regionalization and refinement of 
environmental fate and source characterization model inputs, inter-
individual variability in exposure could become a significant factor in 
model output in the future.
    Another important area of uncertainty is the transformation of 
chemicals and the changes in the species of metals that can occur 
either in the waste management unit or in environmental media. Once 
chemicals are placed in a waste management unit or released to the 
environment, various processes such as biodegradation and hydrolysis 
act to change the chemical. These changes result in what we call 
transformation products. Often the transformation from one chemical to 
another results in a less toxic chemical; however, for a few chemicals, 
the resultant transformation products can be more toxic. For metals, an 
analogous transformation takes place as the pH of the waste or media 
can change the state of the metal, sometimes to a less toxic form and 
sometimes to a more toxic form. The HWIR99 analysis does not model 
transformation products or changes in metal species except for mercury 
in surface water.
    Also, because the rate constant for metabolism is unavailable for 
most constituents given the general paucity of data on metabolic rate 
constants in fish, the metabolic rate constant was set to a default 
zero until data can be developed for a larger universe of hydrophobic 
organic chemicals.
    The 3MRA model does include hydrolysis, aerobic biodegradation,

[[Page 63433]]

anaerobic biodegradation, and activated aerobic biodegradation. Each of 
these processes result in lower concentrations of the parent chemical 
and results in the formation of daughter products. Although the 3MRA 
can simulate the formation and transport of daughter products, we did 
not implement this capability in today's risk assessment because of the 
technical difficulties. To evaluate daughter products, we would need to 
track the ratio of the amounts of daughter product to parent chemical 
in the waste management unit. This ratio would vary considerably 
depending on the age of the waste management unit. Such data are not 
readily available. Alternatively, we could model the parent and 
daughter products separately assuming the waste management unit 
contains only the parent chemical or daughter product and select the 
lower waste concentration of these two numbers.
    We request comment on (1) our decision to model degradation 
processes, including hydrolysis, aerobic biodegradation, anaerobic 
biodegradation, and activated aerobic biodegradation, (2) our approach 
for considering the daughter products in the regulatory framework, (3) 
the toxicity, if any, of the daughter products that might be generated, 
and (4) the physical conditions under which each of these degradation 
processes occurs. We also request information that might be available 
to help us factor the ratios of parent chemical to daughter product in 
the modeling in order to address the issue of the toxicity of daughter 
products.
    Although we used a regional, site-based approach for this analysis, 
two features related to complex terrain were not modeled. First, in 
modeling the dispersion and deposition of chemicals in ambient air, the 
surrounding terrain was assumed to be relatively flat. We made this 
assumption to simplify the modeling and data collection effort. The 
area of interest for the analysis was limited to 2 kilometers from the 
waste management unit. We did not think it unreasonable to assume the 2 
km study area was relatively flat. Complex terrain is quite important 
for stack sources where emissions are coming out of elevated stacks and 
being widely dispersed. However, all of the units in this analysis are 
either in the ground or slightly elevated such as a waste pile. 
Generally, the plumes will be close to the ground and those living 
closest to the waste management unit will receive the highest air 
exposures. By not using complex terrain in areas that are complex, the 
model might slightly under or overestimate exposures from these 
sources. A second type of feature we did not address is complex 
hydrogeology such as karst or highly fractured aquifers. Some fraction 
of the groundwater settings in this analysis have fractured flow. In 
general, fractured flow in groundwater can channel the contaminant 
plume, thus allowing it to move faster and more concentrated than in 
nonfractured flow environment. This would result in higher 
concentrations in the groundwater.
    However, this analysis is conducted using site-based receptor 
information. Thus, even though the groundwater plume might move faster 
and be more concentrated, whether this would result in higher risk to 
receptors depends on where the receptors are located. For example, 
there might be no wells in the plume. By not modeling fractured flow in 
this analysis, additional uncertainty is added but the magnitude of 
this uncertainty cannot be described at this time.
    Another uncertainty in the modeling methodology involves assessing 
risks to receptors temporally over a 10,000 year period. There are 
significant uncertainties regarding how exposure and environmental 
assumptions will change over time, and the modeling methodology does 
not change these assumptions over this 10,000 year period.
    In addition, the modeling methodology itself is another source of 
uncertainty, because models and their mathematical expressions are 
simplifications of reality that are used to approximate real-world 
conditions and processes, and their relationships. The sources of model 
uncertainty include relationship errors and modeling errors. Models do 
not include all parameters or equations necessary to express reality 
because of the inherent complexity of the natural environment, and the 
lack of sufficient data to describe the natural environment. 
Consequently, models are based on numerous assumptions and 
simplifications, and reflect an incomplete understanding of natural 
processes.
    We selected the models used in this risk assessment based on 
science, policy, and professional judgment. These models were selected 
because they provide the information needed for this analysis and 
because we generally consider them to be state-of-the-science. Even 
though some of the models used in the risk analyses are used widely and 
have been accepted for numerous applications, they each retain 
significant sources of uncertainty. Section XVI.E of this preamble, and 
each of the background documents associated with the different models, 
discuss some examples of these uncertainties. Evaluated as a whole, the 
sources of model uncertainty in our analysis could result in either an 
overestimation or underestimation of risk.
    Also, EPA did not conduct a sensitivity analysis which would 
identify the most sensitive parameters in the model. Sensitivity 
analyses and the identification of the most important parameters, such 
as certain source term assumptions, would allow us to better 
characterize the uncertainty in the risk assessment. EPA recognizes 
that the source term assumptions associated with each waste management 
unit are likely to be uncertain, because the data associated with 
developing these assumptions were generally limited.
    In addition to the uncertainties discussed here, there are also 
uncertainties associated with each of the risk assessment modules, as 
discussed in Section XVII.E.
    3. What are the limitations of the data collected to support the 
risk assessment? Under ideal conditions, the risk assessment would be 
based on actual site data using measured input data at every facility 
for all the site-specific variables needed, including facility 
location, waste management unit area, waste volume, location of 
drinking water wells, depth to groundwater, groundwater flow direction, 
meteorological conditions, number and location of receptors, land use 
patterns and types of ecological habitats. However, we did not consider 
this approach because of the time and high costs associated with its 
implementation. Instead, we collected only a part of the model input 
data at the site level. We were not able to directly measure many of 
the facility/site characteristics (for example; depth to groundwater; 
aquifer thickness; hydraulic conductivity; location of wells; type of 
ecological receptors; behavioral characteristics of receptors) at each 
representative site to estimate risk. The model inputs that did not 
have site-based data were characterized through regional and national 
databases. As a result, the data used have several limitations. 
Overall, the use of regional and national input data rather than site-
based facility and environmental data could cause estimated 
concentrations to be low or high at a given location, with no known 
general bias. Below is an overview of some of these limitations. A more 
detailed discussion on the limitations of the data types used in the 
risk assessment are presented in U.S. EPA, 1999-a through -r.

[[Page 63434]]

a. Site-Based Data
    We used a variety of data sources with differing ``snapshots in 
time'' to describe the waste management unit and the surrounding 
environment. We relied on the survey of RCRA Subtitle D industrial 
waste management units (U.S. EPA, 1987) to represent potential 
facilities that would manage and dispose HWIR exempted waste. Although 
over 10 years old, this survey represents the largest consistent set of 
data available on facility locations and waste management unit 
dimensions. A sample of 201 facilities was selected from the survey to 
represent the types and geographical locations of waste management 
units at which exempt waste could be disposed. We then used other data 
sources for other site-based data needs, such as the environmental 
conditions and the number and types of human receptors in the vicinity 
of these 201 facilities. For example, facility location and land use 
patterns were from the late 1970's to mid-1980's (U.S. EPA, 1994) and 
human receptor type and location data were from the 1990 Census Data. 
It is likely that at some of the 201 facilities there have been waste 
management unit additions or closures, land use pattern shifts, or 
demographic changes since the surveys were conducted. However, we 
consider using relatively current land use and population data to be 
preferable to developing and evaluating hypothetical exposure 
scenarios.
    To identify wetlands in the vicinity of the 201 facilities, EPA 
used the 1995 National Wetlands Inventory (U.S. FWS, 1995). Complete 
nationwide coverage is not yet available using this data source. 
Therefore, we also used other data sources (U.S. EPA, 1994-a, U.S. EPA, 
1994-b) to help identify wetland habitats in the vicinity of the 201 
sites.
b. Regional Data
    Due to limited computational times for which we had to generate 
risk-based concentration levels, we modeled only a fraction of the 
hourly meteorological data at regular intervals rather than the 
complete period of record for the meteorological stations (for example, 
30 years). This method, the Sampled Chronological Input Model (SCIM), 
allowed the model to run more quickly while producing long-term 
averages comparable to those obtained from the full data set. Different 
SCIM levels were applied for dry deposition (1 hour of data selected 
for every 193 hours) and wet deposition (1 hour of data selected for 
every 8 hours).
    Another parameter for which we had limited data was the hourly 
precipitation at the meteorological stations found in the Solar and 
Meteorological Surface Observation Network (SAMSON), which we used for 
inputs to the ISCST3 air model. We developed a method in which the 
amount of daily precipitation was scaled from a separate climatological 
data set to hourly levels.
c. National Data
    The 1985 survey of RCRA Subtitle D industrial waste management 
units (U.S. EPA 1987) only included information on landfills, land 
application units, surface impoundments and waste piles. The survey 
contained no information on the presence or design of aerated tanks, 
which are the fifth type of units included in today's risk assessment. 
We assumed that aerated tanks were located at the same facilities that 
operated surface impoundments. We used specific design and operating 
parameters for uncovered aerated tanks developed in the Hazardous Waste 
TSDF--Background Information for Proposed RCRA Air Emission Standards 
(U.S. EPA, 1991-b). We assumed that the characteristics of aerated 
tanks managing hazardous waste would be similar to aerated tanks that 
will manage HWIR exempted waste.
    Site-based and regional datasets are not available for many of the 
human exposure inputs, and in those cases we used national datasets. 
However, some inputs, such as food ingestion rates and exposure 
duration data, are available by regions of the country. We decided that 
national exposure data were appropriate for the national scale 
assessment and did not expend additional time and resources on 
developing these data in to regional-level distributions. Rather we 
relied on national-scale data available in the Exposure Factors 
Handbook (EFH) (U.S. EPA, 1997-d) for the input parameters. In 
developing distributions for today's assessment, we fit selected 
statistical models to the percentile data presented in the Exposure 
Factors Handbook and used goodness-of-fit techniques to select 
distribution types rather than collecting and using all of the raw data 
for each exposure parameter.
d. Uncertainty in the Chemical Database
    The HWIR assessment tracks individual chemicals from specific waste 
streams disposed of in a waste management unit into the surrounding 
multimedia environment at a series of locations around the country. A 
variety of transport processes, including volatilization, leaching, 
runoff, erosion, advection, dispersion, and deposition, move chemicals 
from the waste management units through the multimedia environment to 
locations where human and ecological receptors are likely to be 
exposed. A set of chemical-specific data are required for the 
environmental simulation models that are used to calculate chemical 
fate and characterize the resulting exposures and risks.
    Some of the chemical properties such as the ionization constants 
are not expected to vary among the sites. Values for these properties 
are entered into the HWIR database (U.S. EPA, 1999-ai) as constants, 
and are reported as such to the environmental models for all sites. 
Other chemical properties such as solubility and effective hydrolysis 
rate constants will vary with temperature and pH. We used regression 
techniques or chemical equations to provide proper values for given 
temperature and pH conditions. Values for the regression coefficients 
or chemical constants are entered into the HWIR database as constants. 
The values for these properties reported to the environmental models 
vary with the temperature and pH assumed for a particular medium at a 
particular site. Still other chemical properties are expected to vary 
among sites in response to a host of unknown or unmeasured 
environmental conditions. Examples include biodegradation and reduction 
rate constants and metals partition coefficients. These properties are 
entered into the HWIR database as distributions with minima, maxima, 
and sometimes central-tendency values. The values for these properties 
reported to the environmental models are random functions of the 
specified distributions.
    The uncertainties associated with the chemical database clearly 
vary with chemical property. For some properties, the uncertainty is 
associated with the thermodynamic and kinetic constants for each 
specific chemical. For other properties, the total uncertainty includes 
not only the uncertainty in the specification of the basic constants, 
but also the uncertainty in the equations and classification schemes 
used in the application of these constants to various environmental 
conditions (for example, temperature, pH, and redox conditions). The 
uncertainty associated with the thermodynamic and kinetic constants 
will of course be dependent on the specific chemical and the nature of 
constants (measured versus calculated). The uncertainty resulting from 
the assumptions concerning environmental conditions results from a 
paucity of data describing conditions at hazardous waste sites and the 
requirement to conduct the HWIR assessment on a national basis.

[[Page 63435]]

    All of the data needs cannot be satisfied with measured values 
because the environmental conditions within which the contaminants find 
themselves are simply too varied and have not been studied sufficiently 
to enable known values to be used. Thus, we used other means of 
developing the required data (for example, chemical modeling and expert 
judgment leading to simplifying yet environmentally protective 
assumptions). To generate all relevant chemical-specific data needed 
for the HWIR assessment, we used a combination of measured, calculated 
and estimated data. Although measured data were preferred, the absence 
or scarcity of reliable measured data required the use of data that had 
been generated by computational methods. The SPARC computational 
method, which is based on fundamental chemical structure theory, was 
the primary tool for calculating the thermodynamic constants in the 
HWIR chemical database (Karickhoff et al, 1991). Although rigorous 
testing for SPARC's Chemical Reactivity Models is still in progress, 
comparison of SPARC calculated pKas with measured values for 
a large number of chemicals demonstrates the reliability of this 
computational approach.
    The process of assembling kinetic constants for degradation 
pathways (that is, hydrolysis, anaerobic biodegradation, and aerobic 
biodegradation) focused on finding, evaluating, and summarizing 
measured data. Measured hydrolysis rate constants were found for most 
of the compounds of interest. When hydrolysis data were not available, 
a team of expert scientists provided rate constants based on the team's 
experience with similar compounds, their knowledge of the theory of 
these processes, and their understanding of structure-activity 
relationships. Due to the complex nature of biodegradation processes, 
only measured kinetic constants for a select group of high-volume 
chemicals were entered into the HWIR chemical database. These kinetic 
data were grouped according to reaction conditions (that is, pH, 
temperature, and redox conditions). Each study for a particular 
chemical was given equal weight despite differences in how the study 
was carried out. As a consequence, the uncertainty associated with the 
range of kinetic data in the database is expected to vary by chemical.
    4. What situations are not covered in the risk modeling? a. 
Combustion. In the development of the HWIR exemption, we did not model 
combustion scenarios. We considered possible risk introduced into the 
environment from the combustion of already exempted waste and concluded 
that such risks were more appropriately considered under regulations 
promulgated or to be promulgated under the Clean Air Act.
    More specifically, we recognize that the technological basis of the 
Maximum Achievable Control Technology (MACT) standards currently being 
developed under the Clean Air Act (particularly under Sections 112 and 
129) will help reduce risk from air emissions at nonhazardous 
combustors. Because the risks associated with combustion have as much 
to do with combustor unit design, emissions controls and unit operation 
as they do with the concentration of chemicals in the feed, we did not 
believe it practical or even possible to develop a methodology for 
predicting smokestack emissions, in particular the formation of 
products of incomplete combustion, based solely on the chemical 
composition of wastes that could be combusted. This judgement is 
consistent with our discussion in the comparable fuels exclusion, which 
considered a much narrower universe of waste than the wide variety of 
waste being considered for exemption under HWIR (63 FR 33784).
    In addition, we do not believe that there will be much incentive 
for HWIR exempt waste to be combusted, although a few commenters to the 
1995 proposal suggested otherwise. Waste meeting HWIR exemption levels 
should have a low Btu value, and, therefore, such waste would not be 
particularly attractive for fuel use. Conceivably, a generator seeking 
an exemption after the point of generation could, through combustion, 
avoid land disposal requirements, although combustion is generally more 
expensive than land disposal. Also, such treatment savings presume that 
the exemption concentration levels would be higher than LDR levels. 
Under such circumstances, as discussed in Section XX of this preamble, 
we discuss raising these LDR standards to conform with the HWIR 
exemption levels. The adoption of this minimize threat approach could 
decrease any incentive to combust HWIR exempt waste.
    Some commenters requested that we consider the exemption of 
hazardous waste contingent upon the combustion of these wastes in a 
nonhazardous waste combustor. We believe that the design of such a 
regulatory option would require not only the specification of 
concentration levels of chemicals in the feed, but also operational 
parameters associated with the combustor. Such requirements would 
either make the incoming waste approach waste that could become exempt 
under the generic option or make the operational design associated with 
the combustor approach requirements for hazardous combustors. Again, 
limitations in our ability to precisely model and track the 
transformation, creation and destruction of chemicals through the 
combustion process would severely limit our ability to construct such 
an option.
    We ask for comment on our consideration of risks from combustion 
and alternative regulatory provisions related to the HWIR exemption. 
One alternative is an absolute prohibition on combustion of already 
exempt HWIR waste. A second alternative is a more targeted restriction 
based on chemical content. Some persistent, bioaccumulative and toxic 
chemicals such as mercury are of special concern for combustion, even 
at levels that might allow such waste to become exempt under HWIR. 
Under this second alternative, HWIR wastes containing such chemicals 
could not be combusted.
    A third alternative would structure a prohibition on combustion 
similar to the one designed to prevent the combustion of metal-bearing 
waste within the LDR program (40 CFR 268.3(c)). Such restrictions 
generally require the wastes to have some appreciable organic content 
or heating value, unless the waste is co-generated with a waste 
requiring combustion or unless other Federal or State requirements 
necessitated the reduction of organics. Having met HWIR exemption 
levels for organics might reduce waste eligible for post-exemption 
combustion, under this alternative, to practically zero. We request 
comment on these alternatives, including information that might trigger 
a combustion prohibition, and on any other alternatives for addressing 
risks from the combustion of HWIR wastes.
    b. Beneficial uses. We selected the landfill, waste pile, surface 
impoundment and land application units to model because according to an 
EPA industrial waste screening study, these are the most likely 
destinations for industrial nonhazardous waste (EPA 1987). We also 
modeled aerated tanks because, since the screening study was done, 
there has been a shift away from surface impoundment to aerated tanks 
for managing hazardous waste. If an aerated tank-based hazardous waste 
becomes exempt, it is likely that it would still be managed in that 
aerated tank.
    However, there are many other possible management destinations 
besides these five units, such as using the wastes as road bed, 
construction fill, and cement aggregate. These practices are often 
collectively referred to as

[[Page 63436]]

beneficial use. See the background document entitled Consideration of 
Beneficial Use as an HWIR Waste Management Scenario (EPA, 1999) for a 
discussion of beneficial uses of industrial waste.
    State programs that regulate beneficial use of industrial waste 
would provide some protection against risks posed by this practice. 
However, State regulatory programs vary greatly regarding the level of 
regulation for these wastes. See the background document entitled 
States' Use of Waste and By-Product Materials (ASTSWMO, 1996) for a 
survey of states' beneficial use programs.
    Some of these beneficial uses, particularly uses that involve 
direct exposure to the waste, could pose a greater risk than management 
in the five units that we modeled. We request comment which beneficial 
uses are especially problematic, and whether to prohibit beneficial 
uses of HWIR exempted wastes.
    c. Non-aqueous phase liquids (NAPLs). Fate and transport modeling 
embedded in the HWIR risk assessment does not account for the potential 
of non-aqueous phase liquids (NAPLs) to migrate to the groundwater 
beneath the waste units. NAPLs in the groundwater provide a source of 
contaminants which might move away from the original release location. 
Even if the migrating NAPL phase contains insufficient organic liquid 
to reach a receptor in the free phase, the groundwater zone will still 
contain a zone of laterally distributed NAPL. This zone of NAPL can 
exist substantially beyond the bounds of the waste unit and can act as 
a new source of contamination beyond the unit boundaries, effectively 
reducing the distance between the source and the receptors.
    The NAPL will dissolve into groundwater flowing through it. This 
could lead to chemical concentrations in the groundwater zone that are 
higher than the scenarios modeled in the HWIR risk assessment. The 
combination of reduced distance between receptors and source and the 
higher initial concentrations can significantly increase chemical 
concentrations at receptor locations.
    To augment the analysis and assumptions in the HWIR risk 
assessment, we developed a methodology to consider the potential for 
HWIR exempt waste to form free phase liquids. This methodology involved 
comparing the exemption levels derived for chemicals of specific 
concern for NAPL formation with a calculated ``saturation level'' of 
the chemical to see if a free phase could form. In the case of aqueous 
wastes, this is a simple comparison of the exemption levels to chemical 
specific water solubility limits. Where the exemption level exceeds the 
solubility limit, a separate organic liquid phase could be anticipated. 
The case of free phase flow from waste in a semi-solid or a solid form 
is somewhat more complicated. See the Analysis of NAPL Formation 
Potential and Cosolvency Effect (EPA, 1999-ar) for data, calculations 
and methodology for these comparisons. We request comment on how to 
minimize the potential for NAPL contamination of groundwater due to the 
formation of free-phase liquids in landfills.
    The subject of co-solvency and facilitated transport is a 
considerably more difficult phenomenon to predict and regulate. A co-
solvent is an organic chemical that is partially or completely miscible 
in water, and can change the properties of other chemicals, increasing 
their mobility. Facilitated transport is a chemical or physical process 
that has the potential of improving the transport of a chemical in soil 
or groundwater. Facilitated transport can be significant at co-solvent 
concentrations above a few percent. See Analysis of NAPL Formation 
Potential and Cosolvency Effect (EPA, 1999-ar) for more information. 
EPA is soliciting comment on how to minimize the possible impacts of 
co-solvency on the migration of contaminants.
    d. Sludges generated from HWIR-exempted liquid wastes. In modeling 
the risk posed by liquid wastes, we only looked at the risks posed by 
the liquid itself as it is managed in an aerated tank or surface 
impoundment. Because of the complexity of the processes involved, we 
did not estimate the risk posed by the sludges that would be generated 
from the post-exemption management of these liquid wastes. These 
sludges, which would normally be regulated as hazardous due to the 
derived-from rule, would no longer be subject to the listing code 
because the parent waste had met the HWIR exemption. This would be true 
even when the sludges themselves did not meet the HWIR exemption 
levels, which might happen due to the concentrating effects of de-
watering.
    However, if the sludges retained a high level of metals or other 
regulated chemicals, they might be hazardous due to the toxicity 
characteristic and, therefore, would continue to be regulated under 
RCRA Subtitle C. We request comment on whether sludges from HWIR 
exempted liquids would exceed the HWIR exemption levels, and whether 
the toxicity characteristic is adequate to capture the risks from 
wastes derived from exempt liquids.
    e. Surface impoundments with wastes left in place. In modeling 
surface impoundments, we assumed that at the time of closure, all the 
remaining waste in the surface impoundment is removed, and therefore no 
source of contamination remains (beyond the chemicals that had already 
left the unit). If HWIR waste were to be disposed in a surface 
impoundment that was closed with the waste left in place, then the risk 
assessment could underestimate the risk posed by such waste, especially 
for slow-moving chemicals. We request comment whether the assumption 
that surface impoundments have waste removed at the time of closure is 
likely to have a significant impact on the risk assessment.

XVIII. How Was the HWIR Exemption List of Chemicals Developed?

A. How Did EPA Select the Chemicals That Might Be of Concern in HWIR 
Waste?
    We focused on those chemicals that are likely to be found in listed 
hazardous waste, to be toxic, and to be of concern if released to the 
environment. This list of chemicals was gathered from Appendices VII 
and VIII of 40 CFR 261, Appendix IX of 40 CFR 264, the chemicals listed 
in 40 CFR 261.33 (e) and (f) (the P and U listings) and the chemicals 
listed in 40 CFR 268.40 (LDR treatment standards).
    Part 261 Appendix VII contains the chemicals that were used as the 
basis of listing wastes from specific and nonspecific sources (F and K 
listings). However, it is not meant to be a complete list of hazardous 
chemicals found in those wastes. Part 261 Appendix VIII is a more 
comprehensive list of hazardous chemicals that could be used as a basis 
for listing a waste [see 40 CFR 261.11(a)(3)]. Part 264 Appendix IX is 
the list of chemicals to be analyzed for groundwater monitoring 
purposes. It includes hazardous chemicals that have been found at 
contaminated sites under the Superfund program, and could, therefore, 
be of concern in mismanaged industrial wastes. 40 CFR 261.33 lists 
chemical products that are hazardous when discarded. 40 CFR 268.40 
includes a list of chemicals with treatment requirements for each 
hazardous waste code.
    From these sources, EPA created a ``master list'' of over 600 
chemicals. This list is larger than the one developed in 1995 because 
of the inclusion of chemicals contained in 40 CFR 261.33 and 40 CFR 
268.40, and because of chemicals added to Appendix VIII as a result of 
the carbamate listing (62 FR 32978).

[[Page 63437]]

    To derive the list of chemicals that we would include in the HWIR 
exemption (referred to as HWIR Exemption Chemicals), a number of 
chemicals were deleted from the master list. Some entries were deleted 
because they are analyzed as a different chemical (for example, lead 
compounds are analyzed as lead, therefore only lead is included). Other 
chemicals were deleted because they represented a chemical class where 
a specific chemical within that class was already on the list (for 
example, the class of tetrachlorobenzenes is represented by 1,2,4,5 
tetrachlorobenzene). Finally, some chemicals, although they might pose 
an immediate hazard, were thought to degrade rapidly in the environment 
due to hydrolysis or other processes. Other efforts within the Office 
of Solid Waste could enhance our ability to identify additional 
chemicals that do not persist in the environment and should not 
necessarily be evaluated for the HWIR exemption (for example, ongoing 
waste minimization efforts on chemical persistence have evolved from a 
draft list of chemicals made available in a recent Federal Register 
notice (see 63 FR 60332)).
    Removing chemicals from the master list for the reasons stated 
above reduces the number to 442, which comprises the list of HWIR 
exemption chemicals. This list of chemicals is not the list of 
chemicals for which you would be required to test as described in 
Section IX.A of this preamble; however, this list represents chemicals 
that you would have to certify are not present in your waste. These 
chemicals would be listed in a new appendix to 40 CFR Part 261 that can 
be found in Table 2 in Section XIV. For more information on how this 
list was developed and on the lists of chemicals removed from 
consideration, see Background Document on HWIR Exemption Chemicals, 
U.S. EPA, July 1999-as.
    We request comment on the chemicals considered for the HWIR 
exemption.
B. What Chemicals Has EPA Modeled Using the 3MRA Model?
    In developing the model , we selected a limited group of chemicals 
to produce exemption levels. Two primary factors influenced our 
selection of which chemicals and how many chemicals to model in the 
risk assessment: (1) Adequate chemical-specific toxicity data and (2) 
computational limitations. Our criterion for adequate toxicity data was 
that each chemical had at least one human health toxicological 
benchmark. We relied primarily on toxicity values available on EPA's 
Integrated Risk Information System (IRIS) and presented in the Office 
of Research and Development's Health Effects Assessment Summary Tables 
(HEAST). In addition, we evaluated other Agency toxicity information 
and toxicity information submitted in comments on the HWIR 1995 
proposal. (see Section XVI.A.3) The list of these chemicals with 
benchmarks and criteria for evaluating other information is found in 
Report on the Consistency of HWIR Benchmarks with Current Agency Values 
and Guidelines, (U.S. EPA, 1997-e) and Response to Comments on 
Hazardous Waste Identification Rule (HWIR) Benchmarks (RTI, 1998). We 
request comment on the use of these sources of toxicity data.
    The second factor, computational limitations, further reduced the 
list to 42 chemicals which we attempted to model. These 42 chemicals 
are listed in Table 7 below. This number of chemicals was based on our 
decision to design the software system for assessing multi-media, 
multiple pathway, and multiple receptor risk on a PC-based platform. We 
chose this platform rather than more advanced computers to maximize the 
public dissemination of the risk assessment model and results that 
underlie the risk-based concentration levels. This PC-based platform 
limited the number of chemicals EPA was capable of evaluating for this 
notice due to computer processing speed and data storage limitations. 
To provide an example of the model outputs, the results for 
acrylonitrile managed in a landfill are present in a background 
document (U.S. EPA, 1999-as).
C. How Did EPA Choose the Initial Subset of the 42 Chemicals to Model?
    To select the initial set of chemicals to evaluate, we developed 
criteria to select chemicals from the list of chemicals with at least 
one benchmark. The chemicals with benchmarks were sorted into 16 groups 
of similar chemical and/or physical properties. The specific properties 
used to establish these groups included: (1) The degree of aromaticity 
(the number and arrangement of benzene rings); (2) similarities in 
volatility (for example, low molecular weight hydrocarbons all tend to 
be relatively volatile); (3) the presence of halogens, such as bromine 
and chlorine; (4) the presence of other key elements such as oxygen, 
nitrogen, sulfur and/or phosphorus; (5) commonalities in the use of the 
chemical (for example, pesticides); (6) the presence of organic 
functional groups such as phenols and carbamates; and (7) similarities 
in ionic behavior (for example, anionic metals).
    We then selected candidate chemicals from each of these 16 groups. 
A team of EPA scientists with collective experience in toxicology, fate 
and transport modeling, waste chemistry and programmatic policy then 
reviewed the candidates and selected 42 representative chemicals. The 
chemical selection process involved considerations such as: (1) The 
total number of chemicals within a group (for example, some groups had 
up to 50 chemicals within the group and therefore more candidates were 
examined); (2) the range of expected toxicity of the chemicals within 
the group (for example, benzene is considered to be more toxic than 
toluene); (3) whether the chemical and physical property data and 
analytical methods for each candidate were readily available and 
verifiable; (4) whether there were significant differences in chemical 
structures within the group; (5) the differences in degree or type of 
halogenation (chlorinated or brominated); (6) whether the toxicity data 
represented a mix of isomers; (7) whether the chemical was a common and 
relatively toxic degradation product; (8) whether the chemicals were 
significant to other EPA programs or were traditionally chosen as 
representatives (for example, 2,3,7,8-TCDD is typically chosen as the 
representative for all the isomers of halogenated dioxins and furans); 
and (9) the frequency or expectation of finding the chemical in many 
process waste streams rather than for just one listing. Further details 
on the chemicals groupings and the specific factors used to select each 
representative chemical can be found in the Background Document on the 
Selection of Initial Chemicals. U.S. EPA, October 1999-at. Based on 
these criteria, we selected 42 chemicals to evaluate within the HWIR 
risk assessment model and to develop risk-based levels (see Table 7).

[[Page 63438]]



  Table 7.--Initial List of 1999 HWIR Chemicals Selected for Evaluation
------------------------------------------------------------------------
 Chemical name [alternate name]       CASRN        Representative class
------------------------------------------------------------------------
Acetonitrile...................         75-05-8  organonitrogen.
Acrylonitrile..................        107-13-1  organonitrogen.
Aniline........................         62-53-3  organonitrogen.
Antimony.......................       7440-36-0  oxoanion metal.
Arsenic........................       7440-38-2  oxoanion metal.
Barium.........................       7440-39-3  cationic metal.
Benzene........................         71-43-2  aromatic hydrocarbon.
Benzo[a]pyrene.................         50-32-8  polynuclear aromatic.
Beryllium......................       7440-41-7  cationic metal.
Bis-(2-ethylhexyl)phthalate [Di-       117-81-7  carbon/hydrogen/oxygen.
 (2-ethylhexyl)phthalate].
Cadmium........................       7440-43-9  cationic metal.
Carbon disulfide...............         75-15-0  organosulfur.
Chlorobenzene..................        108-90-7  chlorinated aromatic.
Chloroform.....................         67-66-3  chlorinated
                                                  hydrocarbon.
Chromium.......................       7440-47-3  oxoanion metal.
Dibenz[a,h]anthracene..........         53-70-3  polynuclear aromatic.
2,4-Dichlorophenoxyacetic acid.         94-75-7  chlorinated pesticide.
Ethylene dibromide [1,2-               106-93-4  brominated hydrocarbon.
 Dibromoethane].
Hexachloro-1,3-butadiene.......         87-68-3  miscellaneous
                                                  halogenated.
Lead...........................       7439-92-1  cationic metal.
Mercury........................       7439-97-6  cationic metal.
Methoxychlor...................         72-43-5  chlorinated pesticide.
Methyl ethyl ketone............         78-93-3  carbon/hydrogen/oxygen.
Methylene chloride                      75-09-2  chlorinated
 [Dichloromethane].                               hydrocarbon.
Methyl methacrylate............         80-62-6  carbon/hydrogen/oxygen.
Nickel.........................       7440-02-0  cationic metal.
Nitrobenzene...................         98-95-3  organonitrogen.
Pentachlorophenol..............         87-86-5  chlorinated phenol.
Phenol.........................        108-95-2  nonhalogenated
                                                  phenolic.
Pyridine.......................        110-86-1  organonitrogen.
Selenium.......................       7782-49-2  oxoanion metal.
Silver.........................       7440-22-4  cationic metal.
2,3,7,8-Tetrachlorodibenzo-p-         1746-01-6  dioxin/furan.
 dioxin.
Tetrachloroethylene............        127-18-4  chlorinated
                                                  hydrocarbon.
Thallium.......................       7440-28-0  oxoanion metal.
Thiram.........................        137-26-8  carbamate group.
Toluene........................        108-88-3  aromatic hydrocarbon.
1,1,1-Trichloroethane..........         71-55-6  chlorinated
                                                  hydrocarbon.
Trichloroethylene..............         79-01-6  chlorinated
                                                  hydrocarbon.
Vanadium.......................       7440-62-2  oxoanion metal.
Vinyl chloride.................         75-01-4  chlorinated
                                                  hydrocarbon.
Zinc...........................       7440-66-6  cationic metal.
------------------------------------------------------------------------

    All but one of the 42 chemicals have available toxicological data 
in developing HWIR exemption levels through the HWIR risk assessment. 
In the case of lead, we would not develop a human health-based number 
from the HWIR '99 risk assessment because lead does not have the same 
type of toxicological value used for the other chemicals. Instead, we 
would refer to levels developed for other regulatory programs within 
EPA, which include the Superfund program, the Safe Drinking Water 
Program and the Lead Hazard Control Program.
    Over the past four years, we developed a ``no action'' 
concentration for lead in soil of 400 mg/kg for three separate 
programs: Superfund Site Cleanup under CERCLA (Comprehensive 
Environmental Response, Compensation and Liability Act), Corrective 
Action under RCRA and Lead Hazard Control under TSCA (Toxic Substance 
Control Act). This level is based on protecting children from neuro-
behavioral toxicity effects from multi-media exposures of lead. 
Historically, we have been particularly concerned about lead poisoning 
in children between the age of six months and seven years, and 
therefore have focused on these effects for our regulations. For the 
soil lead guidance determination under these programs, we considered 
risks to children from exposure to lead in air, in soil and dust, in 
their diet and in their drinking water (see OSWER directives #9200.4-
27P and #9355.4-12 regarding RCRA and CERCLA and Risk Analysis to 
Support Standards in Lead in Paint, Dust, and Soil, (EPA 747-R-97-006), 
June 3, 1998, regarding TSCA). These determinations are based on the 
Integrated, Exposure, Uptake and BioKinetic (IEUBK) Model and assume 
that the child lives amongst the contamination (that is, on-site 
exposure).
    We also considered lead levels considered safe under the Safe 
Drinking Water Regulations (40 CFR 141). Although we have not set a 
Maximum Contaminant Level (MCL) for lead in drinking waste systems, we 
have required water systems to reduce the levels of lead at the tap to 
as close to zero as possible (see the Lead and Copper Rule (LCR) under 
40 CFR 141.80). In addition to requiring water systems to optimize 
corrosion control, the LCR also requires that water systems that exceed 
15 ug/L lead in more than 10% of the taps tested meet certain other 
treatment requirements where appropriate. Also, guidance from EPA's 
Office of Drinking Water strongly recommends that source water 
treatment be installed if the concentrations of lead in source water 
exceeds 5 ug/L.

[[Page 63439]]

    We are considering the 400 mg/kg as an appropriate and protective 
human health limit to exempt waste under HWIR. This level considers 
multiple exposures, not just exposures from drinking contaminated 
water, and even for the groundwater ingestion pathway, the 400 mg/kg 
level is based on a default value of 4 ug/L, more stringent than both 
the 15 ug/L and 5 ug/L levels considered within the drinking water 
regulations.
    Hence, we request comment on setting the exemption level for lead 
as the lower of two values: the 400 mg/kg level for human health risks 
and the modeled ecological risk results. (See Section XVI for 
additional discussion of ecological risk assessment performed for 
HWIR). We request comment on this approach for developing an exemption 
level for lead.
    Although we intended to model all 42 chemicals listed above, we 
identified several errors within the system during initial production 
runs. These errors included exceeding solubility limits for one or more 
waste concentrations, failing to account for sites in the results for 
one or more waste concentrations, and generating the distribution of 
results for only the exposed population. The time required to diagnose 
the errors and reprogram the potential fixes to the system and modules 
resulted in a limited time frame for generating the results for this 
notice. Therefore, we included the results for acrylonitrile managed in 
a landfill as an example.
    These results are presented in the technical background document 
Risk Characterization Report for the HWIR99 Multimedia, Multipathway 
and Multireceptor Risk Assessment (3MRA), U.S. EPA, July 1999-as. We 
plan to update the model to address system errors. In addition, we 
expect to place in the docket results for additional chemicals and 
waste management unit combinations from an updated model.
    Because we have not fully tested recent revisions to the model, we 
are not proposing these results as HWIR exemption levels at this time. 
For further discussion please see Section XVII of this preamble.
D. Which Additional Chemicals Might We Model in the Future?
    To help us prioritize possible future exemption level development 
beyond the 42 chemicals in Table 5, we first focused on chemicals 
reasonably expected to be present in major waste streams. For a waste 
stream to be eligible for this exemption, those chemicals reasonably 
expected to be present in the waste stream would have to have exemption 
levels. Developing exemption levels for these chemicals would therefore 
allow more waste to become eligible for an HWIR exemption. For listed 
waste from specific and non-specific sources (that is, F and K wastes 
found in 40 CFR 261.31 and 261.32), this set of chemicals would include 
those chemicals found in Appendix VII of 40 CFR Part 261 (hazardous 
chemicals for which the waste was listed) and those chemicals found in 
40 CFR 268.40 (regulated hazardous constituents under the LDR program).
    We also focused our prioritization efforts on waste streams most 
likely to take advantage of the HWIR exemptions. By analyzing data on 
historic cost savings and the prevalence of chemicals within both large 
and small waste streams, we identified an additional 29 chemicals that 
with exemption levels could greatly increase the number of RCRA waste 
codes, facilities and volumes of waste eligible for the HWIR exemption. 
(The identification of these 29 chemicals is discussed further in 
Background Document on Additional HWIR Chemicals, U.S. EPA, October 
1999-au). These chemicals are listed in Table 8.

  Table 8.--Candidates for Additional HWIR Exemption Level Development
------------------------------------------------------------------------
                  CAS No.                    Chemical name
------------------------------------------------------------------------
1...........         67-64-1  Acetone [2-Propanone]
2...........         98-86-2  Acetophenone
3...........         79-06-1  Acrylamide
4...........         79-10-7  Acrylic Acid
5...........         56-23-5  Carbon tetrachloride
6...........       7440-50-8  Copper
7...........        108-94-1  Cyclohexanone
8...........         95-50-1  Dichlorobenzene [ortho-Dichlorobenzene],
                               1,2-
9...........        107-06-2  Dichloroethane [Ethylene dichloride], 1,2-
10..........        110-80-5  Ethoxyethanol [Ethylene glycol monoethyl
                               ether][Cellosolve], 2-
11..........        141-78-6  Ethyl acetate
12..........        100-41-4  Ethylbenzene
13..........         60-29-7  Ethyl ether [Ethane, 1,1'-oxybis]
14..........         64-18-6  Formic Acid
15..........        118-74-1  Hexachlorobenzene
16..........         67-72-1  Hexachloroethane
17..........         78-83-1  Isobutyl alcohol [2-methyl-1-propanol]
                               [isobutanol]
18..........        108-39-4  meta-Cresol [3-Methyl phenol]
19..........         67-56-1  Methanol [Methyl alcohol]
20..........        108-10-1  Methyl isobutyl ketone [Hexone][4-Methyl-2-
                               pentanone]
21..........         71-36-3  n-Butyl alcohol [n-Butanol]
22..........         79-46-9  Nitropropane, 2-
23..........         95-48-7  ortho-Cresol [2-Methyl phenol]
24..........        106-44-5  para-Cresol [4-Methyl phenol]
25..........        109-99-9  Tetrahydrofuran
26..........         76-13-1  Trichloro-1,2,2-trifluoroethane [Freon
                               113], 1,1,2-
27..........         79-00-5  Trichloroethane [Vinyl trichloride], 1,1,2-
 
28..........         75-69-4  Trichlorofluoromethane
                               [Trichloromonofluoromethane][CFC-11]
29..........       1330-20-7  Xylenes, mixed isomers (ortho-, meta-,
                               para-) [Xylenes, total]
------------------------------------------------------------------------

    Just as there are good candidates for additional exemption levels, 
there are other chemicals that are less attractive for exemption level 
development. The following types of chemicals might be of lower 
priority simply because they are

[[Page 63440]]

not found in most process wastes generated today. These chemicals 
include: (1) Chemicals no longer produced in the United States; (2) 
chemicals produced infrequently or in small quantities; (3) chemicals 
used exclusively as pesticides or herbicides; and (4) chemicals found 
exclusively within discarded chemical products (that is, many of the 
RCRA P and U listed wastes found in 40 CFR 261.33). Consistent with 
this prioritization, we do not believe that we need to develop 
exemption levels for all chemicals listed in Section XIV, to make the 
HWIR exemption available to a broad segment of the waste universe.
    These lower priority chemicals are unlikely to be prevalent in 
newly generated wastes, although they can appear in site clean-up 
wastes or contaminated media (for example, contaminated soil). While 
clean-up wastes and contaminated media may become exempt under HWIR by 
meeting the stated requirements, the main focus of today's rule is 
process wastes. Other regulatory mechanisms exist within the RCRA and 
CERCLA programs to direct the appropriate management of these wastes.
    Another consideration for the development of exemption levels for 
chemicals is whether we have sufficient toxicological data and they do 
not present any other technical issues. Many chemicals, because of a 
lack of human health benchmarks or other technical difficulties, are 
problematic for developing exemption levels. Such technical 
difficulties include analytical challenges in measuring chemical 
concentrations in waste matrices or difficulties representing the 
behavior of the chemical through our modeling framework.
    One such chemical with toxicological information, but which 
presents other technical difficulties is cyanide. Cyanide has 
traditionally been of particular interest because of its high 
prevalence in hazardous waste streams. We have not pursued the 
development of cyanide numbers for generic waste streams using the HWIR 
risk assessment model because of technical concerns that include: (1) 
The presence of cyanide in various forms, which change with waste 
matrix pH, the presence of metals and cyanide concentration; (2) the 
complex chemistry of cyanide, both in the waste and in its 
environmental transport; and, (3) cyanide degradation, such as its 
oxidation to carbon dioxide, nitrogen and water. Further, the chemical 
analysis of cyanide is complicated by significant interferences and the 
reporting of various cyanide forms, including total, free and weak acid 
dissociable forms. We ask for comment on which wastes would be impacted 
by the absence of an HWIR exemption level for cyanide, and for comments 
on how to set HWIR exemption levels for cyanide, given its complex 
chemistry.
    We also request comment on which particular chemicals and waste 
streams are especially suited to an HWIR exemption. We believe that 
direct input from waste generators specifically identifying candidate 
waste streams would be the most useful and targeted means of selecting 
additional chemicals for exemption level development.

XIX. How Would EPA Use the Results of the Risk Assessment To Set HWIR 
Exemption Levels?

    As discussed in Section XVII, we have identified an inconsistency 
in the model results, which we believe demonstrates that the model is 
not performing as designed. In addition, we have not completed final 
testing of the software system. Therefore, we are not proposing HWIR 
exemption levels based on these modeling results. This section explains 
the methodology we would use to set HWIR exemption levels when the 
final modeling results are available. Before we would promulgate an 
HWIR exemption, we would first publish an HWIR proposal that would 
include specific exemption levels and give the public an opportunity to 
comment. We request comment on this methodology for generating HWIR 
exemption levels from the risk assessment results.
A. What Risk Protection Criteria Would EPA Use To Generate HWIR 
Exemption Levels?
    The HWIR exemption levels would be generated based on five 
different types of risk protection criteria: (1) Cancer risk level, (2) 
human health hazard quotient (HQ), (3) ecological hazard quotient, (4) 
population percentile, and (5) probability of protection. By setting a 
value for each of these criteria, we would identify the chemical-
specific waste concentrations that would be protective at those values. 
Each risk criterion is explained in more detail below and summarized in 
Table 9. For each of the risk protection criteria, we would select 
specific levels from a range of values for each protection criterion 
from which we developed HWIR exemption levels. We invite comment on 
which values we should select for each of the risk protection measures.
    1. Cancer Risk level. The cancer risk level refers to a person's 
increased chance of developing cancer over a lifetime due to potential 
exposure to a specific chemical. A risk of 1 x 10-6 
translates as an increased chance of one in a million of developing 
cancer during a lifetime. EPA generally sets regulations at risk levels 
between 10-6 and 10-4 (in other words, from one 
in a million to one in ten thousand increased chance of developing 
cancer during a lifetime). In the RCRA hazardous waste listing program, 
a 10-6 risk is usually the presumptive ``no list'' level, 
while 10-5 is often (used to determine which wastes are 
considered initial candidates for listing (see, for example, the 
petroleum listing at 63 FR 42117). For HWIR, we would evaluate the 
exemption levels that result from both the 10-6 and the 
10-5 risk levels.
    We do not intend to evaluate a risk higher than 10-5 for 
an HWIR exemption, because using higher levels would mean that waste 
could exit the RCRA hazardous waste regulatory system at a higher risk 
than it typically enters the system. In the 1995 HWIR proposal, we did 
consider using higher risk levels for our modeling under the State-
based contingent management approaches, but this was contingent on 
having in place a State nonhazardous waste program approved by EPA, 
which would reduce the overall risk to 10-6 or 
10-5. Given that the HWIR exemption discussed today is 
designed to be self-implementing, with no direct governmental oversight 
of the exemption claims and no EPA review of State nonhazardous waste 
programs, we believe that using a cancer risk level of 10-4 
or higher would be inappropriate.
    2. Hazard Quotient (HQ). The HQ refers to the likelihood that 
exposure to a specific chemical would result in a non-cancer health 
problem (for example, neurological effects). The hazard quotient is 
developed by dividing the estimated exposure to a chemical by the 
reference dose (RfD) for oral ingestion pathways or reference 
concentration (RfC) for inhalation pathways. The RfD and RfC are 
estimates of the highest dose or concentration that might be considered 
safe. An HQ of one or lower indicates that the given exposure is 
unlikely to result in adverse health effects. Some programs, such as 
the drinking water program, set the HQ target at less than one to 
provide a safety factor against exposure to a chemical from other 
sources. For example, the drinking water program has used 20% of the 
RfD in setting drinking water standards (see, for example, 57 FR 
31776). Within the Office of Solid Waste, we have used 25% of the RfD 
in setting standards for Boilers and Industrial Furnaces (BIFs) (56 FR 
7134). For HWIR, we would evaluate the exemption levels that result

[[Page 63441]]

from both an HQ of 0.1 and an HQ of one.
    3. Ecological hazard quotient. The ecological hazard quotient is 
analogous to the human health HQ, except that the estimated exposure is 
compared with an ecological toxicity value rather than the human health 
RfD or RfC. For this analysis, we developed two types of toxicity 
values: (1) an ecological benchmark that is analogous to the human 
health HQ using a RfD; and (2) chemical stressor concentration limit 
(CSCL) that is analogous to the human health HQ using an RfC. The 
ecological hazard quotient protects ecological health at the population 
or community level, and therefore focuses on reproductive and 
developmental effects, rather than the mortality of individual 
organisms. In developing ecological toxicity values for this risk 
assessment, we used the geometric mean between a No Observed Effects 
Level (NOEL) and a Lowest Observed Effects Level (LOEL). (Human health 
reference doses are based on NOELs.) This approach is similar to the 
approach used for developing Ambient Water Quality Criteria, where the 
assumption is that most, but not all, of the aquatic species and 
animals are protected (U.S. EPA, 1985). For HWIR, we would evaluate the 
exemption levels that result from both an ecological hazard quotient of 
one and ten.
    4. Population percentile. The population percentile is the 
percentage of the population protected at the specified risk levels and 
hazard quotients for a single environmental setting. A setting is a 
specific unit at a specific site, and is defined by combining site-
based information (such as unit size, and unit placement) with variable 
environmental information (such as rainfall and exposure rates) 
generated from regional and national data. For HWIR, we would evaluate 
the exemption levels that result from population protection percentiles 
of 99% and 95%.
    Although the risk percentiles are meant to represent the proportion 
of the population protected (or, conversely, at risk), the data used to 
define population variability and to interpret the 99th individual risk 
percentile may be both quantitatively and qualitatively limited. First, 
there might not be a sufficient number of observations for a given 
input for adequately defining an upper percentile (for example, the 
99th percentile) within the range of observations, which introduces 
uncertainty when extrapolating in the tails. Second, efforts to 
describe the variability are often confounded by uncertainties 
introduced as a bias. The bias may over-or underestimate the results to 
an unknown degree.
    5. Probability of protection. The probability of protection is 
defined as the percentage of settings that meet the population 
percentile criteria. These distributions reflect the uncertainty and 
the variability of the model and underlying data required by the model. 
We generally describe a probability of protection as ``high end'' when 
it focuses on individual risk to those people at the upper end of the 
distribution, generally above the 90th percentile (%). For HWIR, we 
would evaluate the exemption levels that result from both 95% and 90% 
probabilities of protection.
    By evaluating different values for each risk protection criteria, 
we would generate potential HWIR exemption levels for four different 
risk protection groups (See Table 9) . The risk protection groups are 
two-dimensional in nature. For example, with respect to the Group 2 
criteria the interpretations for cancer and non-cancer risks are 
respectively:

--99% of the population are subject to cancer risks of less than 
10-6 across 90% of the environmental settings;
--99% of the population experience exposure levels below an HQ of 1 
across 90% of the environmental settings.
    The combinations in Table 9 capture a range of protection levels, 
from most conservative (Group 1) to least conservative (Group 4). These 
groups are not an exhaustive look at all possible combinations of 
potential risk protection criteria; we could choose a different 
combination altogether. These groups were chosen to help bound the 
possible values. We request comment on which risk protection criteria 
to use, and in which combination.

                    Table 9.--Risk Protection Combinations Evaluated for HWIR Risk Assessment
----------------------------------------------------------------------------------------------------------------
                                                   Group 1 (most                                  Group 4 (least
                                                   conservative)      Group 2         Group 3      conservative)
----------------------------------------------------------------------------------------------------------------
Risk Level......................................            10-6            10-6            10-5            10-5
Human Health HQ.................................             0.1               1               1               1
Eco HQ..........................................               1               1               1              10
Population Percentile...........................              99              99              99              95
Probability of Protection.......................              95              90              90              90
----------------------------------------------------------------------------------------------------------------

B. How Would EPA Aggregate the Human Health and Ecological Risk 
Information?
    The risk assessment produces separate results for the protection of 
human receptors and the protection of ecological receptors. We would 
select the lower (more conservative) of these values. Thus, the 
resulting number would be protective of both sets of receptors.
C. How Would EPA Aggregate the Chemical Concentrations at Each Waste 
Management Unit Into HWIR Exemption Levels?
    The risk assessment produces separate results for each of the five 
waste management units being modeled (surface impoundment, aerated 
tank, land application unit, waste pile, and landfill). To apply these 
results to real-world practices under the generic HWIR exemption, we 
defined the categories of wastes that would most likely match the 
scenarios we modeled.
    To match the HWIR exempted wastes to their likely destinations, we 
would tailor the HWIR exemption levels to three broad waste form 
categories: (1) Liquids; (2) semi-solids; and (3) solids. These 
categories are identified by a waste's total suspended solids (TSS) 
content, which is defined as the particles that can be removed from a 
solution by filtration. Liquids are wastes that have less than 1% TSS 
by weight; semi-solids are wastes with a TSS content between 1 and 30%; 
and solids are waste with a TSS content greater than 30%.
    We chose the 1% and 30% thresholds by examining available data on 
wastewater treatment and sludge processing and by considering water 
saturation for a ``typical'' waste passing

[[Page 63442]]

the paint filter test. More detailed discussion of these data sources 
can be found in the background document entitled Correlation between 
Liquid, Sludge, and Solid Waste Forms and Surface Impoundment, Land 
Application Unit, and Landfill Disposal Options (U.S. EPA, 1999-a).
    We would group the unit-specific results to construct HWIR 
exemption levels for each waste category as follows:

                                   Table 10.--HWIR Exemption Level Categories
----------------------------------------------------------------------------------------------------------------
                                                       Semi-Solids (1%TSS30%) (mg/kg)            Solids  (TSS > 30%)
                                         (mg/l)                                                     (mg/kg)
----------------------------------------------------------------------------------------------------------------
Surface Impoundment.............  Evaluate...........  Evaluate.
Aerated Tank....................  Evaluate...........  Evaluate.
Land Application Unit...........  ...................  Evaluate.
Waste Pile......................  ...................  ....................................  Evaluate.
Landfill........................  ...................  ....................................  Evaluate.
----------------------------------------------------------------------------------------------------------------

    As Table 10 suggests, HWIR exemption levels for liquids would be 
derived from releases evaluated at surface impoundments and aerated 
tanks. Exemption levels for semi-solids would be based on releases 
evaluated at surface impoundments, aerated tanks and land application 
units. Solids use risk-based numbers would be based on the releases 
evaluated at waste piles and landfills.
    The exemption levels for each waste form would be determined for 
each waste management unit by selecting the lowest (most stringent) 
chemical concentration from the units evaluated. For example, the 
liquid exemption level would be based on the lower of the surface 
impoundment and aerated tank results. In developing the semi-solid 
numbers, we would convert the surface impoundment and aerated tank 
results, which are in mg/l, to mg/kg based on an assumed density of one 
kg/l (the density of water).
    These categories of waste forms group wastes that are expected to 
be managed in similar ways. Some waste forms will not realistically be 
managed in certain management units. For example, it is unlikely that a 
true solid would be managed in an aerated tank system, or that a true 
liquid would be managed in a landfill. The liquid and solid definitions 
distinguish wastes that are clearly and intuitively liquid and clearly 
and intuitively solid from the rest of the waste universe. Creating 
separate exemption levels for these two waste forms should not affect 
the protectiveness of the exemption, and might allow for more 
appropriate exemption levels and greater regulatory relief.
    The semi-solid category, on the other hand, represents a broad and 
varied universe of waste. Wastes between 1% and 30% TSS could in theory 
be managed in any of the five waste management units, although the more 
liquid wastes (for example, 1%-10% TSS) would be less likely to go to 
landfills and waste piles and the more solid wastes (for example, 20-
30% TSS) would be less likely to go to surface impoundments or aerated 
tanks. Wastes going to land application units, however, could contain 
anywhere from 1% to 30% TSS.
    We considered assigning to the category of semi-solids the lowest 
concentration of the results from any of the five waste management 
units. This approach would ensure that the concentration would be 
protective no matter which of the units is the ultimate destination. 
However, after additional consideration, we decided that the risk 
levels derived from the landfill and waste piles were not directly 
comparable to the other units. Risk values for surface impoundments, 
aerated tanks and land application units are derived on a wet basis 
(that is, they consider the volumes of water contained in the waste 
form), whereas the levels derived for landfill and waste piles are 
derived on a dry basis.
    Our approach groups the risk results from surface impoundments, 
aerated tanks and land application units to produce the semi-solid 
exemption levels. To the extent that semi-solids could be disposed in a 
landfill or waste pile, then this formulation does not explicitly 
evaluate such risk. However, for many chemicals, particularly organics, 
risks from a land application unit would be expected to be generally 
greater than risks from a landfill or a waste pile, although such a 
judgement would be case specific. Applying the land application unit 
results to wastes that contain up to 30% TSS should therefore be more 
protective than lowering the 30% TSS threshold and applying the 
landfill or waste pile results.
    In the 1995 HWIR proposal, we pursued a different characterization 
of waste form categories (see 60 FR 66388). In 1995, we distinguished 
between ``wastewaters'' and ``nonwastewaters'' and offered three 
alternatives to define the two categories. These three alternatives 
were based on the LDR definition of wastewaters, a 15% solids 
threshold, and a distinction for free liquids made on the basis of the 
paint filter test.
    Commenters on the 1995 proposal were split in their support of 
these three options for defining wastewaters and nonwastewaters. Many 
commenters supported a distinction at 15% solids, because this 
threshold would, among the three proposed, best identify the way in 
which waste is actually managed and the way in which the results from 
the risk analysis were used in developing the 1995 HWIR exemption 
levels. Equally strong were opinions advocating consistency with the 
LDR definition. Commenters were concerned about multiple definitions of 
waste forms within the RCRA program and the complexity and confusion 
such differences would cause. We believe that the creation of three 
waste form categories will produce categories with appropriate and 
corresponding exemption levels, while at the same time maintaining 
general consistency with the LDR definitions.
    A few commenters suggested the creation of three waste form 
categories at 1% and 15%, labeling waste less than 1% as wastewaters, 
wastes greater than 15% as non-wastewaters, and allowing the generator 
to classify wastes between these thresholds based on how they are 
actually managed. In today's notice, we have adopted this notion of 
three waste categories; however, as explained earlier we have increased 
the upper threshold to 30% in order to protect against risks of land 
applying wastes with 15-30% solids.
    The concept of ``solids'' based on the 30% threshold is intended to 
conform with the historic consideration of wastes that do not have free 
liquids as defined under 40 CFR 260.10. Conceptually, these wastes 
would also pass the paint filter test developed to determine the 
presence of free liquids in either

[[Page 63443]]

containerized or bulk wastes (see 50 FR 18370) that established the 
paint filter test as well as a subsequent Federal Register notice (57 
FR 54454) that retained the paint filter test over a proposed liquid 
release test. Therefore, as an alternative to the threshold of 30% TSS, 
we request comment on the use of the paint filter test to distinguish 
solids without free liquids from other solids for the purpose of the 
HWIR exemption.
    We also do not believe it appropriate in the generic option to 
allow you to choose which of the three exemption levels (liquid, semi-
solid, or solid) should apply to your wastes. Because there are no 
constraints or requirements that waste exempted under the generic 
option be disposed in a particular unit, there would be no way to 
verify that the waste ended up in the destination for which exemption 
levels were evaluated under the risk assessment.
    As discussed in Section X.C. of this preamble, waste becoming 
exempt after the point of generation must comply with LDR requirements. 
The relationship of the waste categories for HWIR and LDR is therefore 
especially important. We believe that although the HWIR definition of 
liquids is different from the LDR definition of wastewater, these 
definitions are appropriate to their respective programs.(See 
discussion of LDR requirements for HWIR exempted waste in Section X of 
this preamble.)
    We sought to conform the HWIR definition of liquids with the 1% 
threshold for TSS found in the LDR definition of wastewaters (see 40 
CFR 268.2(f)). The overlap is especially useful when making any 
comparisons of HWIR and LDR concentration levels (for example, for the 
purposes of meeting treatment standards established to minimize threats 
to human health and the environment (see Section XX of this preamble).
    HWIR, however, did not adopt the 1% total organic content criterion 
used in the LDR program. We thought it unnecessary to cap organic 
content for the purposes of selecting appropriate exemption levels. We 
presume that liquids exempted under HWIR would be managed in surface 
impoundments and aerated tanks independent of the organic content of 
the waste.
    In contrast, the LDR program sought to distinguish wastes on the 
basis of treatment. By instituting a 1% cap on organic content, the LDR 
program could distinguish wastes likely to be treated by distillation 
or combustion from waste containing minimal organics less suited to 
these treatment technologies and more suited to more typical treatments 
for wastewaters (for example, biological degradation) (51 FR 1726). 
Therefore, the criteria based on organic content is more appropriate 
for the consideration of treatment technologies than for disposal 
destinations.
    As a result of these two sets of definitions, there will be wastes 
that would be identified as ``liquid'' for the purposes of the HWIR 
exemption, and as ``nonwastewaters'' for the purposes of LDRs. However, 
``liquid nonwastewaters'' is a meaningful term, representing organic 
liquids, and is generally recognized as a waste category 
distinguishable from more traditional wastewaters, both in terms of 
treatment alternatives and environmental concerns. Once understood, we 
do not believe that the presence of these two sets of terms will create 
difficulties for the regulated community.
    We request comment on the waste form categories discussed for the 
HWIR generic option. Specifically, we request comment on the definition 
of (1) liquid (TSS<1%), (2) semi-solid (1%TSS30%) 
and (3) solid (TSS>30%); on the grouping of risk results based on 
specific waste management units that correspond to the three waste 
forms; and on the use of a conversion factor of one kg/L to convert the 
aerated tank and surface impoundment results (mg/L) for comparison to 
the land application unit results (mg/kg) in the semi-solid category.
    In contrast to the generic option, wastes exempted under the 
landfill-only option would require exemption levels based only on the 
landfill destination and there is no need to segment the waste 
universe. HWIR implementation provisions would require that such waste 
be managed in a landfill. In addition, acceptance criteria at the 
landfill (such as the general prohibition against managing liquids in a 
landfill) combined with adequate waste representation for landfills in 
the HWIR modeling, help ensure that the landfill specific risk levels 
would be appropriate for these waste forms.

Possible Revision to LDR Treatment Standards

XX. How Might EPA Use the Results of the HWIR Model To Revise the 
Hazardous Waste LDR Treatment Standards?

A. What Is the Statutory Basis for the RCRA LDR Treatment standards?
    The statutory requirement for LDR treatment standards is to 
``substantially diminish the toxicity of the waste or substantially 
reduce the likelihood of migration of hazardous constituents from the 
waste so that short term and long term threats to human health and the 
environment are minimized.'' [RCRA Section 3004(m)]. Before we could 
use the risk-based results of the HWIR model to revise the hazardous 
waste treatment requirements under the RCRA land disposal restrictions 
(LDR) program, we would have to determine if the results ``minimize 
threat'' to human health and the environment as required by the 
statute.
    Our implementation of this requirement has evolved through a long 
series of rulemakings (51 FR 1611). The first LDR treatment standards 
were largely based on what technology could achieve. To avoid 
unnecessary treatment, however, we had also proposed to ``cap'' the 
technology based standards with risk-based screening levels. These 
levels were based on human health toxicity thresholds for individual 
hazardous constituents and modeling of the groundwater route for 
exposure. (51 FR 1611-13.)
    In the final initial LDR rule, we promulgated only the technology-
based standards. We explained that although we believed we had the 
authority to promulgate risk-based standards, we were not promulgating 
the proposed risk-based caps, because of extensive comments raising 
concerns about the scientific uncertainties of the risk analyses 
performed to date (51 FR 40578). Members of industry challenged the 
final standards, claiming that they required treatment to 
concentrations below ``minimize threat'' levels. On review, the Court 
held that section 3004(m) authorized both technology-based and risk-
based standards, but remanded the rule to EPA for a fuller explanation 
of our decision to rely on technology-based standards alone. (Hazardous 
Waste Treatment Council v. EPA, 886 F. 2d 355 (D.C. Circ. 1989). 
(``HWTC III'').) The court also held that EPA was not obligated to 
adopt either the RCRA characteristic test levels or the Safe Drinking 
Water Act Maximum Contaminant levels (MCLs) as ``minimize threat'' 
levels, because neither ``purports to establish a level at which safety 
is assured or 'threats to human health and the environment are 
minimized'.'' (886 F. 2d at 363.)
    In our response to the remand, we stated that the best way to 
fulfill the requirements of section 3004(m) would be to ensure that 
technology-based treatment standards did not require treatment of 
hazardous chemicals that posed only insignificant risks. (55 FR 6641, 
Feb. 26,1991). We explained, however, that we were not yet able to 
promulgate such levels. We believed that we lacked a reliable 
predictive model for groundwater exposure; needed to assess exposure 
scenarios for

[[Page 63444]]

air pathways; needed to consider impacts on ecological receptors; 
needed to develop additional analytic methods for hazardous chemicals; 
and needed to develop an approach for chemicals with threshold effect 
levels lower than detection limits. (Id. at 6642.)
    In the same notice, we noted that the ``minimize threat'' language 
of section 3004(m) could reasonably be interpreted to require more 
protection than the ``normal subtitle C command that standards be those 
necessary to protect human health and the environment.'' (Id. at 6641.) 
We found that the many portions of the 1984 amendments stressing the 
inherent uncertainties of land disposal buttressed this interpretation. 
[See RCRA sections 1002(b)(7), 3004 (d)(1)(A), 3004 (e)(i)(A), 
3004(g)(5)]. We also found support in the LDR legislative history. For 
example, the Senate amendment containing the ``minimize threat'' 
standards replaced a committee bill that only would have required 
treatment to be ``protective of human health and the environment.'' 
[See S. 757, Section 3004(b)(7), printed at S. Pep. No. 284, 98th 
Cong., 2nd Session 86].
    Further, we noted that the levels we had been using in site-
specific and waste stream specific contexts, such as clean closures, 
delistings, and no-migration petitions, would not necessarily be 
appropriate for generally applicable standards required to minimize 
threats to human health and the environment. (55 FR 6641, note 1.) We 
took the position that section 3004(m) does not require the elimination 
of every conceivable threat posed by land disposal of hazardous waste, 
citing a statement by Senator Chaffee that ``[i]t is not intended that 
every waste receive repetitive levels of treatment, nor must all 
inorganic constituents be reclaimed.'' 130 Cong. Rec. S.9179 (daily 
ed., July 25, 1984). (55 FR 6641, note 1.) Clearly we did not interpret 
the minimize threat language to require the elimination of all threats.
    Since the outset of the LDR program, we have continued to develop 
and refine the risk assessments that are the basis of our regulatory 
decisions with respect to waste identification. In addition, the 
increased sensitivity of analytical methods has lowered achievable 
detection limits and more extensive biological data are available for 
development of benchmark criteria for assessing ecological risk. As a 
result, the universe of available health-based and ecological data has 
grown significantly, and the reliability of this information has 
improved. In developing the HWIR risk assessment, we now believe that, 
for some chemicals, we might soon have enough data and the necessary 
tools to establish risk-based levels on a national level that minimize 
threats to human health and the environment.
B. Why Do We Believe That the HWIR Risk Assessment Results Could Be 
Used To Revise the Waste Treatment Standards?
    The HWIR risk assessment could be used to develop risk-based LDR 
levels for several reasons. First, the HWIR risk assessment 
significantly expands our ability to evaluate human and ecological risk 
as compared to our historic capability. For example, unlike previous 
analyses that focused solely on groundwater, the HWIR risk assessment 
evaluates the potential for waste chemical migration through the most 
significant environmental fate and transport pathways. Second, the 1999 
HWIR risk assessment looks at the total impact of all those pathways, 
not just at each pathway individually. Finally, the HWIR risk 
assessment also includes the greatest number of ecological benchmarks 
ever used in regulatory development under RCRA. These factors suggest 
that the tools and analyses now exist to properly evaluate when threats 
to human health and the environment are minimized.
C. How Might the Risk-Based LDR levels Be Implemented?
    Generally, an HWIR exemption level would replace an LDR numerical 
treatment standard (``LDR level'') if it is less stringent than the 
existing LDR level. In this case, we could directly use the new risk-
based levels to replace existing LDR levels found in waste-specific 
treatment requirements listed in the table at Sec. 268.40 and the 
Universal Treatment Standard (UTS) levels listed in the table at 
Sec. 268.48. Setting risk-based LDR levels could help simplify the HWIR 
exemption. For those chemicals for which HWIR exemption levels replace 
LDRs, meeting the HWIR exemption would simultaneously satisfy LDR 
treatment requirements for those chemicals. This does not necessarily 
mean, however, that all of the applicable LDR treatment requirements 
would have been met for that waste code. LDRs could regulate more 
chemicals than those with revised risk-based standards. Before a waste 
can be land disposed, all chemicals identified in the LDR standards for 
that waste code must meet applicable LDR treatment standards.
    For some chemicals, however, the HWIR exemption levels might be 
more stringent than the existing LDR numerical standards. In this 
situation, the LDR standards would not be replaced by the HWIR level. 
Otherwise, if HWIR exemption levels were mandated, generators would 
have to treat their waste below levels that are achievable using the 
best demonstrated and available technology, which is the basis for the 
LDR standards. If the waste meets the LDR levels but not the HWIR 
exemption levels, then LDR requirements would be satisfied, but the 
waste would remain hazardous.
    This section reviews and addresses key issues within the LDR 
program that will influence how the HWIR risk assessment results would 
be specifically integrated with the LDR waste treatment standards. For 
instance: (1) HWIR identifies liquid, semi-solid, and solid exemption 
levels while the LDR program identifies wastewater and nonwastewater 
treatability groups; (2) HWIR risk numbers are based on totals analysis 
while LDR levels are based on totals analysis and the Toxicity 
Characteristic Leaching Procedure, or TCLP; and (3) HWIR exemption 
levels that replace existing LDR levels for certain chemicals might 
potentially impact other wastes subject to LDRs.
    Waste Treatment Standards--Treatability Groups. When prohibiting a 
waste stream from land disposal, the LDR program identifies chemicals 
of concern that potentially pose a threat to human health and the 
environment. The LDR numerical treatment standards represent wastewater 
and nonwastewater \1\ chemical levels that technologies can achieve 
when treating specific waste streams. As discussed in section XIX of 
this preamble, HWIR numbers apply to liquids, semi-solids, and solids, 
which is a related but not identical scheme of classification.
---------------------------------------------------------------------------

    \1\ For purposes of implementing the LDR treatment standards, as 
defined in Sec. 268.2, wastewaters are wastes that contain less than 
1% by weight total organic carbon (TOC) and less than 1% by weight 
total suspended solids (TSS). Nonwastewaters are wastes that do not 
meet the criteria for wastewaters.
---------------------------------------------------------------------------

    To attempt to resolve this potential difference and to simplify 
implementation, we could use the HWIR ``liquid'' number for the LDR 
wastewater number, and the lower of the ``semi-solid'' and ``solid'' 
numbers for the nonwastewater LDR number. As discussed in more detail 
below, this type of simple substitution scheme assumes that the HWIR 
exemption levels are higher than the current numerical LDR waste 
treatment standards to which they would be compared.
    Some methodological issues will need to be addressed in pursuing 
this type of approach (or potentially in any similar

[[Page 63445]]

approach). For example, the LDR definition of ``wastewater'' (less than 
1% Total Suspended Solids (TSS) and less than 1% Total Organic Content 
(TOC)) does not precisely match the HWIR definition of ``liquid'' (less 
that 1% TSS). This means that some wastes with less than 1%TSS and 
greater than 1%TOC would be liquids under the HWIR definition but 
nonwastewaters under the LDR definition. We would need to resolve this 
type of translational issue and others that might arise during detailed 
analysis. We note, for this particular case, that ``liquid 
nonwastewater'' is a meaningful term that describes certain types of 
existing waste--organic liquids.
    Waste Treatment Standards--Totals and TCLP Analysis. HWIR risk 
numbers are based solely on totals analysis while the LDR levels are 
based on both totals analysis (most organics) or the TCLP (metals). In 
cases where the current LDR levels and the results of the HWIR model 
are directly comparable (in other words, both sets of numerical 
standards are based on total concentrations), an existing LDR numerical 
standards could be replaced by the appropriate HWIR number if it is 
less stringent than the existing LDR standard. As discussed above, this 
change would be reflected in tables Sec. 268.40 and Sec. 268.48.
    For the chemicals (such as metals, cyclohexanone, methanol, carbon 
disulfide) that have LDR requirements based on the TCLP, the comparison 
of HWIR exemption levels and LDR numerical treatment standards involves 
another level of complexity. This arises because the HWIR exemption 
levels would be based on total chemical concentrations in the waste, 
whereas the LDR treatment standards are based only on what leaches out 
of the treated waste matrix using the TCLP test. For metals treatment 
standards that are based on stabilization, the TCLP test is typically 
used because the chemicals are not destroyed by treatment; they are 
only immobilized. The route of exposure is via leaching over time, 
which is measured by the TCLP. A totals test is not valuable for 
determining the leaching potential of these metals because it would 
also measure the chemicals that are immobilized.
    To address this issue, we could give the hazardous waste generator 
the choice of meeting either the current leachate or the new totals 
number to satisfy LDRs. If a waste meets current leach numbers, but 
cannot meet the totals number, then it would meet LDRs, but it would 
not be eligible for an HWIR exemption. Table 11 below summarizes how we 
would integrate HWIR exemption levels (totals analysis) with LDR waste 
treatment standards (totals and TCLP analysis). We request comments on 
this suggested approach.

  Table 11.--Integrating HWIR Exemption Levels With LDR Waste Treatment
                                Standards
------------------------------------------------------------------------
     If the existing LDR                                Then the LDR
 treatment requirement for a     And if the HWIR          treatment
particular chemical is based   exemption level for  requirement for that
             on                 that chemical is          chemical
------------------------------------------------------------------------
Totals analysis.............  More stringent than   Would remain the
                               existing LDR level.   existing LDR level.
                              Less stringent than   Would be revised to
                               existing LDR level.   the HWIR exemption
                                                     level.
TCLP........................  Either more or less   Would be satisfied
                               stringent (that is,   if either the
                               it doesn't matter     existing LDR level
                               which).               (TCLP) or the HWIR
                                                     risk level (totals)
                                                     is met.
------------------------------------------------------------------------

    Waste Treatment Standards--Applying Risk-Based LDR Levels. In cases 
where the current LDR levels and the results of the HWIR model are 
directly comparable, the appropriate HWIR number would become the LDR 
treatment standard for a chemical if it is less stringent than the 
existing LDR treatment standard. As stated earlier, this change would 
be specified in the waste-specific treatment requirements at 
Sec. 268.40 as well as the UTS table at Sec. 268.48. Therefore, these 
chemical-specific, risk-based LDR levels would apply to all hazardous 
wastes that must meet LDRs before they are land disposed.
    This approach would alter treatment requirements for some 
characteristic wastes and underlying hazardous chemicals whose 
standards are based on totals analysis and that must meet UTS before 
land disposal. It would not affect wastes for which the LDR 
requirements are non-numerical and specify a treatment technology. This 
approach would also not affect any of the other LDR requirements, such 
as notification. Because HWIR is being handled on a chemical basis, the 
resulting suite of LDR numerical treatment standards could be a mix of 
original UTS and risk-based levels. One implementation question is 
whether there is a need to indicate which treatment standards have 
changed due to HWIR (for example, by asterisks in the part 268 tables).
    Waste Treatment Standards and HWIR Exemption Requirements--
Compliance Issues. We expect that some wastes can be treated to achieve 
more stringent levels than the existing LDR levels. The numerical UTS 
standards were calculated with a variability factor to take into 
account process variability on a national basis (see 51 FR 40591, 
November 7, 1986). We designed the variability factor to ensure that 
the LDR treatment standard was achievable in a wide variety of 
settings. However, on a site-specific or waste-specific basis, a 
generator might be able to achieve more stringent HWIR exemption levels 
if their own process variability is less than we have presumed in 
setting national standards. Thus, one issue is whether and how to 
develop the regulatory scheme when an HWIR level is more stringent than 
an LDR level for certain chemicals. If a generator could meet the more 
stringent HWIR exemption levels, and the generator fulfills the other 
requirements of the HWIR exemption, then the waste would become exempt 
from RCRA Subtitle C. Table 12 illustrates how a waste stream could 
satisfy HWIR exemption levels and LDR requirements simultaneously.

    Table 12.--Application of HWIR Exemption Levels and LDR Treatment
                                Standards
------------------------------------------------------------------------
                                And all chemicals
 If all chemicals identified    regulated in the
   in a listed waste code      listed waste code's     Then the waste
                                 LDR prohibition
------------------------------------------------------------------------
Meet HWIR exemption levels    Meet applicable LDR   Would be exempt from
 and the generator fulfills    treatment standards.  Subtitle C
 the other requirements of                           regulation.
 the HWIR exemption.

[[Page 63446]]

 
Meet HWIR exemption levels    Do not meet any       Would not be a
 and the generator fulfills    applicable LDR        hazardous waste but
 the other requirements of     treatment standards.  must meet LDR
 the HWIR exemption.                                 treatment standards
                                                     before it can be
                                                     land disposed.
Do not meet HWIR exemption    Meet applicable LDR   Would satisfy LDR
 levels or other               treatment standards.  treatment
 requirements of the HWIR                            requirements but
 exemption.                                          still be a
                                                     hazardous waste and
                                                     would have to be
                                                     managed in a
                                                     Subtitle C unit.
Do not meet HWIR exemption    Do not meet           Would have to be
 levels or other               applicable LDR        treated to at least
 requirements of the HWIR      treatment standards.  meet LDR treatment
 exemption.                                          standards and be
                                                     managed in a
                                                     Subtitle C unit.
------------------------------------------------------------------------

    This regulatory approach only applies when the HWIR waste does not 
meet the exemption levels at the point of generation. As explained in 
section X.C, wastes that meet the HWIR exemption requirements at the 
point of generation are considered to never have been hazardous and 
therefore LDR requirements do not apply.
D. What Other Issues Would EPA Consider Before Setting Risk-Based LDR 
Standards?
    Assuming that the methodological issues discussed above can be 
resolved satisfactorily, several other issues would need to be 
considered and resolved before we could set risk-based LDR treatment 
standards. Three issues relate directly to the ``minimize threat'' 
standard underlying the LDR treatment standards. These issues are: (1) 
Which risk protection criteria to use, (2) how to consider ecological 
data, and (3) how to consider inhalation and ingestion data. A fourth 
issue is how these changes to the UTS would affect the alternative soil 
LDR treatment standards.
    As explained in Section XIX.A. of this preamble, we are evaluating 
four different combinations of values for the five different risk 
protection criteria. The five risk protection criteria are (1) risk 
level, (2) human health hazard quotient (HQ), (3) ecological hazard 
quotient, (4) population percentile, and (5) probability of protection. 
The final HWIR numbers could be based on any of the four combinations, 
or on another combination altogether.
    If we were to use the results of the HWIR risk assessment to revise 
the LDRs, we would have to make sure that the risk protection criteria 
we choose are appropriate for both purposes, i.e., met the risk 
protection criteria for HWIR and the minimize threat standard for LDR 
treatment standards. Although it is technically possible to chose 
separate criteria for the HWIR exemption and the LDR standards, much of 
the utility of setting risk-based LDR levels would be lost if they were 
set at a different level than the HWIR exemption.
    The second issue, the need to address ecological risk, is one of 
the major gaps that we identified in our response to the court remand 
regarding the choice of risk-based or technology-based treatment 
standards (55 FR 6641). As explained in Section XVI.F of this preamble, 
the HWIR risk assessment includes a thorough evaluation of ecological 
effects for those chemicals with ecological health benchmarks. However, 
not all chemicals have ecological health benchmarks available. Some of 
these chemicals, which are not very persistent or bioaccumulative, 
would probably not be driven by ecological risk, while others would 
have an unknown effect on ecological receptors. For those chemicals 
that do not have readily available ecological data, we would need to 
decide if we should proceed with setting risk-based LDR levels using 
human health data and then revise them in the future when and if 
ecological data are available.
    The third issue, the need to address risks from the air pathway in 
addition to the traditional groundwater ingestion pathway, is another 
gap we identified in our response to the court. As explained in Section 
XVI.E of this preamble, we have thoroughly evaluated the air pathways, 
both direct and indirect, for chemicals that have inhalation 
benchmarks. Unfortunately, not all chemicals have inhalation 
benchmarks, but some of these chemicals are not volatile, or have data 
showing negligible inhalation risk. Before setting risk-based LDR 
levels, we would have to decide how to deal with chemicals that lack 
inhalation risk benchmarks.
    A fourth issue is how a change to the UTS tables to incorporate 
HWIR exemption levels would affect the alternative LDR soil treatment 
standards. Our alternative LDR treatment standards for soil allow 
regulated chemicals in soil to meet either a final concentration of (1) 
10 times the current UTS, or (2) 90 percent reduction of the regulated 
chemical's initial concentration. (See 63 FR 28751, May 26, 1998) These 
alternative soil treatment standards are not mandatory--contaminated 
soils may still meet treatment standards developed for process wastes--
but they are expected to provide greater flexibility when cleaning up 
contaminated soils subject to LDRs. For instance, the alternative soil 
treatment standards take into account (1) the matrix effect of the 
soil, which makes treatment difficult, and (2) the need to encourage 
clean-ups, thus minimizing the overall risk of the contaminated soil at 
the clean-up site. In fashioning this rule, we are seeking to maintain 
the benefits from the alternative soil standards and to create an 
implementation scheme that is simple and effective. We request comment 
on whether and how to use the results of the HWIR model to revise LDR 
treatment standards for soils, and on any implementation impacts 
flowing from our suggested approach.
    Several issues arise when determining how a change in the UTS table 
due to HWIR exemption levels would impact the effectiveness and 
applicability of the alternative soil treatment standards. For 
instance:
     How should we integrate the HWIR exemption levels with the 
alternative soil treatment standards if the HWIR risk-based number is 
(1) greater than the UTS but less than 10xUTS and (2) greater than both 
the UTS and 10xUTS?
     How should we consider the HWIR exemption levels in for 
contaminated soil--for example, should we just apply the same 10x 
multiplication factor to the HWIR risk-based number? If so, is this 
consistent with the risk basis of the HWIR exemption levels? If not, 
will the HWIR exemption levels deter clean ups, which itself has the 
potential to minimize risks in a more global sense?
    We would integrate the HWIR exemption levels with the soil 
treatment standards in a manner that preserves the advantages of the 
alternative soil treatment standards adopted in the recent Phase IV 
rule (63 FR 28751, May

[[Page 63447]]

26, 1998). We presume, strictly for purposes of presenting this 
discussion, that existing UTS numerical standards for process waste 
would be modified by HWIR exemption levels and that the result would be 
a set of revised UTS levels. Therefore, for purposes of this 
discussion, ``current UTS'' refers to existing technology-based UTS 
while ``revised UTS'' refers to UTS levels that would already have been 
modified to reflect HWIR risk-based exemption levels.
    Under this scenario, when applying the soil treatment standards to 
treat constituents of concern present in contaminated soil, the 
constituents of concern may meet (1) the revised UTS, (2) 10 times the 
current UTS, or (3) 90% reduction of initial constituent concentration, 
whichever is greater.
    This would not change implementation of the current soil treatment 
standards. Rather, it would make the soil treatment standards somewhat 
more flexible by providing that contaminated soils can meet the revised 
UTS LDR treatment standard in the case where the revised UTS is higher 
than 10 times UTS or 90% reduction. To implement this, we would add a 
table to the soil treatment standards with the chemicals and the 
specific alternative UTS levels (either the revised UTS or, if higher, 
10x current UTS) for those chemicals.
    We would not raise the current soil treatment standards to 10 times 
the HWIR exemption levels because such levels would no longer be 
minimize threat levels and could be greater than demonstrated 
performance levels. As mentioned earlier, if the HWIR exemption levels 
are below both the UTS and 10xUTS, we would not consider lowering the 
UTS. Lowering the UTS in this case would require generators to treat 
below levels that are achievable using the best demonstrated and 
available technology, which is the basis for the LDR standards.
    Finally, when addressing the potential impacts of HWIR exemption 
levels on contaminated soils subject to LDRs, we would consider how the 
HWIR exemption levels could affect (1) the site-specific, contained-in 
determination, and (2) the site-specific, risk-based treatability 
variance developed specifically for contaminated soils (referred to as 
the risk-based soils variance). Both the contained-in determination and 
the risk-based soils variance apply site-specific risk-based numbers in 
their decision-making process. The potential might exist to compare 
national HWIR risk-based exemption levels to the site-specific risk-
based numbers generated for a contained-in determination or risk-based 
soils variance. However, we intend that national HWIR exemption levels 
should not affect site-specific risk-based levels determined for either 
the contained-in determination or the site-specific risk-based 
treatability variance.
    The contained-in policy is the basis for EPA's longstanding 
interpretation regarding application of RCRA Subtitle C requirements to 
mixtures of contaminated media and hazardous wastes. Under this policy, 
EPA requires that soil (and other environmental media), although not 
wastes themselves, be managed as if they were hazardous waste if they 
``contain'' hazardous waste. Environmental media may contain hazardous 
waste if it is contaminated by a listed waste or exhibits a 
characteristic of hazardous waste. In practice, EPA has applied the 
contained-in principle to determine, on a site-specific level, that 
environmental media should no longer be regulated as hazardous waste 
because it does not ``contain'' hazardous waste.\2\ This determination, 
referred to as a contained-in determination, is made by a regulatory 
agency and reflects conservative, health-based levels derived assuming 
direct exposure pathways. (See 63 FR 28621-28622). We expect that this 
tailored, site-specific determination would have precedence over 
national HWIR exemption levels.
---------------------------------------------------------------------------

    \2\ Environmental media (e.g., soil) no longer contains 
hazardous waste when a site-specific determination is made that 
concentrations of hazardous constituents in any given volume of 
environmental media are low enough to determine that the media does 
not contain hazardous waste. Typically, these ``contained-in'' 
determinations do not mean that no hazardous constituents are 
present in environmental media but simply that the concentrations of 
hazardous constituents present do not warrant management of the 
media as hazardous waste.
---------------------------------------------------------------------------

    Similarly, the risk-based treatability variance provides a way to 
establish alternative LDR treatment standards based on site-specific 
risk-based levels that are approved through the variance process. These 
risk-based levels reflect site-specific conditions, including 
information on (1) constituents of concern, (2) potential human and 
environmental receptors, and (3) potential routes of exposure. Again, 
we expect that this tailored, site-specific determination would have 
precedence over national HWIR exemption levels.

Economic Impacts

XXI. What Are the Economic Impacts of Today's Proposed Regulatory 
Changes?

A. What Are the Economic Impacts of the Revisions to the Mixture and 
Derived-From Rules?
    Today's proposal involves two revisions to the mixture and derived-
from rules. The first applies an existing exemption for mixtures to 
waste derivatives and any hazardous waste that is listed solely because 
it exhibits one or more of the characteristics of ignitability, 
corrosivity, or reactivity. The second involves a conditional exemption 
for mixed radioactive hazardous waste managed under a new regulation 
being proposed in a separate Federal Register notice today. The 
economic impacts of the separate proposed mixed waste regulation are 
discussed in that Federal Register notice published elsewhere today.
    The economic impact of the revision to the mixture and derived-from 
rules concerning wastes listed solely for a characteristic is discussed 
here. Additional information can be found in the Economic Assessment of 
the U.S. EPA's 1999 Proposed Hazardous Waste Identification Rule 
(HWIR). As discussed in Section IV of this preamble, there are 
currently 29 hazardous waste codes within the RCRA program listed 
solely for ignitability (I), corrosivity (C), and/or reactivity (R) 
characteristics. Today's proposed rule would exempt these wastes from 
RCRA Subtitle C regulation, if such wastes are de-characterized and 
meet the associated LDR treatment standards.
    To estimate the potential economic impact of exempting these 29 
characteristically-listed RCRA waste codes, we analyzed the type and 
quantity of industrial hazardous wastes contained in the two databases 
that underlie the HWIR Economic Model: the 1986 ``Generator Survey'', 
and the 1996 ``National Hazardous Waste Constituent Survey''. This 
model and these two databases are described in the Economic Assessment 
background document.
    This exemption is expected to benefit the relevant segment of the 
RCRA regulated community by reducing the cost of shipping and disposing 
these de-characterized wastes. This potential cost savings is modeled 
in this study as consisting of two components:
    (1) The difference between the cost for disposal of treatment 
residuals from these 29 waste codes in hazardous landfills (i.e., 
current or ``baseline'' practice), compared to the cost for

[[Page 63448]]

disposal in nonhazardous landfills under this exemption.
    (2) The reduction in burden hours and associated burden cost for no 
longer requiring preparation, transmitting and filing of truck shipment 
hazardous waste manifests (EPA Form 8700-22) for these potentially 
exempt wastes.
    The database extractions, computations and findings of the impact 
analysis are presented in the Economic Assessment background document. 
The highlights of U.S. EPA's estimated economic impacts for this HWIR 
provision are as follows:

--236 applicable industrial hazardous waste streams, totaling 3.6 
million tons in annual generation by an estimated 120 US facilities.
--As generated, these waste streams consist of 87% wastewaters and 13% 
non-wastewaters.
--The 3.6 million annual tons quantity of applicable waste, represents 
1.4% of the total RCRA hazardous waste universe (1993 BRS large 
generator total quantity = 258 million tons).
--Approximately 75% of the potentially exempt waste streams are 
identified by waste code F003 (spent non-halogenated solvents) plus a 
characteristic waste code (for example, D001), and 19% are identified 
by waste code F003 only.
--Applicable waste streams are located in 17 four-digit level SIC code 
industry sectors. 146 (62%) of the 236 applicable waste streams are 
generated by industries in SIC 28 (i.e. NAICS code 325).
--There are 51 different hazardous chemical constituents in the 
wastestreams; prevalent ones include: ethylbenzene, toluene, methyl 
ethyl ketone, methanol, ethyl acetate, xylenes, acetone, methylene 
chloride, and n-butyl alcohol.
--After RCRA Subtitle C treatment (mainly incineration), the 236 
wastestreams result in the annual disposal of about 57,400 tons of 
treatment residuals, primarily in the form of incineration ash.
--Potential annual industry waste treatment residual, disposal cost 
savings is estimated at $4.593 million, while annual reduction in truck 
shipment manifesting cost is estimated at $0.455 million (i.e. 54,700 
tons/yr divided by 20 tons/shipment = 2,870 manifests per year; 1.3 
hours per manifest x $122 per hour x 2,870 manifests = $0.455 million). 
These two cost savings components represent a total annual cost savings 
estimate of $5.048 million. Applying -15% to +30% cost estimation 
uncertainty to this point-estimate (as explained in the background 
document), produces the associated cost savings estimation uncertainty 
range of $4.29 to $6.56 million per year.
B. How Would EPA Assess the Impacts of the HWIR Exemption?
    Because we have not developed exemption levels, we have not 
estimated the potential economic cost impacts of the HWIR exemption. In 
addition, because the HWIR exemption is deregulatory by design, it will 
provide cost savings to industries with HWIR-eligible wastestreams. 
Before we would go final with an HWIR exemption, we would first publish 
an HWIR proposal that would include specific exemption levels and give 
the public an opportunity to comment. We would provide estimates of 
potential industry cost savings at that time as well.
    The Economic Assessment describes a computer-based economic model 
we developed for the purpose of systematically estimating potential (a) 
type and quantities of HWIR eligible wastestreams, (b) industry 
implementation costs, and (c) net industry cost savings, once HWIR 
exemption levels are developed. [see Economic Assessment of the U.S. 
EPA's 1999 Proposed Hazardous Waste Identification Rule (HWIR)].
    The Economic Assessment report describes the databases and 
decision-rules imbedded in this model, which includes a new database of 
industrial hazardous waste constituent identities and concentrations, 
based on 1996 survey questionnaires received from a sample of 156 
hazardous industrial waste generator and handler facilities (reporting 
constituent data on 1,020 waste streams), administered by U.S. EPA's 
Office of Solid Waste (OSW). The data and findings of this ``National 
Hazardous Waste Constituent Survey'' (NHWCS) are also described and 
referenced in the Economic Assessment background document, as well as 
available for public review from the RCRA Docket in support of this 
proposal. The model integrates OSW's 1986 National Survey of Hazardous 
Waste Generators, and Treatment, Storage, Disposal, and Recycling 
Facilities, containing sample data for 8,016 industrial wastestreams 
associated with 4,036 facilities, with the new database.
    Depending upon the types and number of constituent exemption levels 
developed, net cost savings are expected from industry switching the 
current management of low-risk wastestreams as RCRA hazardous wastes, 
to nonhazardous waste management practices after HWIR exemption, after 
netting-out industry HWIR implementation costs. Under the specific 
paperwork preparation and reporting requirements, and waste sampling/
testing requirements outlined in this preamble (and as itemized in the 
Economic Assessment report), we estimate that the cost to industry for 
implementing HWIR will range from about $6,000 to over $50,000 per 
facility, depending upon the size and number of hazardous waste streams 
per facility and the number of HWIR-applicable constituents. This 
implementation cost estimate is based upon a preliminary average annual 
burden of 15 hours per facility for HWIR-related paperwork and 
reporting and a U.S. national average unit cost for waste sampling 
ranging from $150 to $900 per sampling event and per chemical (cost 
depends upon the chemical analyzed). These implementation costs would 
be offset with the potential cost savings and burden reduction of 
reduced waste management and disposal costs, as well as other RCRA 
hazardous waste related paperwork burden. As we move forward with HWIR, 
we will characterize the full economic impacts and Information 
Collection Request (ICR) burden of that proposal.
C. How Would EPA Assess the Impacts of the Possible LDR Revisions?
    In Section XXI of this preamble, we discuss replacing the existing, 
technology-based LDR standards with HWIR exemption levels. Most of the 
LDRs prescribe constituent concentration non-exceedance thresholds, 
while some prescribe allowable treatment technologies (40 CFR 268.40 & 
268.48). Without actual HWIR exemption levels to compare with the 
existing LDR levels, the potential economic effect (i.e. net decrease 
in average annual waste management costs to industry) is indeterminate. 
Costs savings from avoided treatment requirements would be highly 
variable, depending on which treatments are involved. Treatment costs 
are further discussed in the Economic Assessment document. As we move 
forward and propose the HWIR exemption, we will characterize the 
economic impacts of these regulatory provisions.

Relationship to Other Programs

XXII. How Would the HWIR Exemption Relate to Other Programs?

    Today's notice discusses specific conditions and exemption criteria 
that would exempt listed hazardous wastes, including waste mixtures and 
derived-

[[Page 63449]]

from wastes, from RCRA Subtitle C regulation. A discussion of how these 
changes would affect other relevant RCRA regulatory programs is 
presented below.
A. Would HWIR Change How You Determine if a Waste Is Hazardous?
    No, the HWIR exemption applies to listed hazardous wastes meeting 
exemption criteria, and it does not change the general requirements 
that you use to determine if a waste is hazardous. Under current RCRA 
regulations, if you generate a solid waste, you would have to determine 
if it is a hazardous waste as explained in 40 CFR 262.11 (Hazardous 
Waste Determination). You would have to first determine if your waste 
is excluded from regulation under 40 CFR 261.4 (Exclusions). Then you 
would have to determine whether your waste is listed in Subpart D of 40 
CFR Part 261 (Lists of Hazardous Wastes), and/or the waste exhibits a 
characteristic defined in Subpart C of 40 CFR Part 261.
B. Could a Characteristic Hazardous Waste Be Exempt Under HWIR?
    No. A waste that met all the HWIR exemption levels could 
nevertheless still be hazardous for a characteristic. You would have to 
still determine whether the waste exhibits any of the ignitability, 
corrosivity, reactivity or toxicity characteristics of a hazardous 
waste as specified in 40 CFR 261.21 through 261.24. If so, your waste 
continues to be hazardous until it no longer exhibits any hazardous 
waste characteristic.
C. How Would the HWIR Exemption Differ From the Delisting Process per 
40 CFR 260.22?
    In the delisting process, you would submit information to the State 
or Regional authority that your specific listed hazardous waste does 
not meet the criteria for which it was listed, and that the waste is 
not hazardous for any other reason (see 40 CFR 260.22). Until the State 
or Region makes an affirmative decision that your waste is delisted, 
your waste remains hazardous. In contrast, the purpose of the HWIR 
exemption is to establish a self-implementing rule where the hazardous 
waste generator, rather than the State or EPA, determines whether a 
listed waste would have to continue to be managed as a hazardous waste.
    The evaluation criteria used for delisting vary from today's 
exemption criteria for the following three reasons: (1) Delisting is an 
interactive process with considerable oversight by us or authorized 
State agencies. In delisting, we evaluate the processes generating a 
specific waste stream to determine the chemicals likely to be present, 
as well as the potential variability in the waste. We closely review 
sampling procedures, analytical test results, and the accompanying QA/
QC data. (2) Delisting is specific to one waste stream. For example, in 
a delisting petition you will typically provide the annual waste 
generation volume. Using a specific waste volume as an input to various 
models could result in delisting levels that are higher than the levels 
that would be developed with the HWIR model, which is based on a 
distribution of waste volumes that includes very large waste streams. 
We believe that it is reasonable to use higher exemption levels for the 
smaller waste volumes in delisting petitions, since these volumes pose 
less total risk than larger volumes of waste. (3) Delisting also 
considers the applicability of available groundwater monitoring data 
from land-based waste management units that have received the 
petitioned waste. Such data are typically required under permitting 
regulations for hazardous waste facilities. If any groundwater 
contamination appears to be due to chemicals from the petitioned waste, 
we will consider this as a basis to deny the petition.
    We might also require special testing regimes when making delisting 
determinations to ensure waste consistently meets delisting criteria. A 
facility that accepts and treats waste from diverse sources would 
typically have frequent testing requirements. In other cases, the 
testing requirements for some initial period will be extensive, but the 
subsequent testing might be reduced.
    Delisting petitions for wastes that contain chemical concentrations 
which exceed HWIR exemption levels, would continue to be accepted and 
reviewed by us after promulgation of today's rule. We do not anticipate 
any changes in the current review of delisting petitions as a result of 
the implementation of today's exemption.
D. How Would HWIR Affect TSDF Closure Requirements for My Facility?
    If your TSDF accepts HWIR waste, the closure requirements might 
change, depending upon the waste management unit and the waste. If your 
hazardous waste management unit receives only waste that is exempt 
under today's proposal, it would no longer be receiving hazardous waste 
upon the effective date of the exemption. Thus, at that point in time, 
your TSDF would normally become subject to RCRA Subtitle C closure 
requirements, which are triggered by the final receipt of hazardous 
waste by the unit. You would be required to complete closure activities 
within 180 days after receiving the final volume of hazardous waste. 
(See Time Allowed for Closure in 40 CFR 264.113(b) and 265.113(b).)
    However, RCRA closure requirements would allow you to delay closure 
of your waste management units, while continuing to receive HWIR waste, 
if you meet certain conditions. You may delay closure of landfills, 
land treatment units, and surface impoundments in cases where your unit 
stops receiving hazardous waste if you wish to continue using the unit 
to manage only nonhazardous waste. These requirements are outlined in 
40 CFR 264.113(d) and (e) and 265.113(d) and (e). If you wish to delay 
closure, you would have to request a permit modification at least 120 
days prior to final receipt of hazardous wastes, or, if the facility is 
in interim status, submit an amended part B application at least 180 
days prior to the final receipt of hazardous wastes. The request for a 
permit modification or the amended part B application must include 
demonstrations that your unit has the existing design capacity to 
manage nonhazardous wastes, and that the nonhazardous wastes are 
compatible with any wastes in the unit. In addition, you must update 
facility information, including the waste analysis plan, groundwater 
monitoring plans, closure and post-closure plans, cost estimates, and 
financial assurance demonstrations, as necessary to account for receipt 
of only nonhazardous waste.
    The delay of closure regulations apply only to landfills, land 
treatment units, and surface impoundments. In the case of other RCRA 
units such as tanks and waste piles, we do not believe that the delay-
of-closure regulations are necessary for these units to receive only 
nonhazardous wastes. The closure requirements in 40 CFR Part 264 
Subpart G (Closure and Post-Closure) for these units include removal or 
decontamination of waste residues, containers, liners, bases and 
contaminated soils, equipment, and other containment system components. 
These closure requirements are compatible with the reuse of these units 
for receipt of only nonhazardous waste. Once the unit has been emptied 
of all hazardous wastes and decontaminated, it could receive 
nonhazardous waste.
    Delay of closure regulations do not, however, remove the final 
obligation for ensuring that a closed unit is protective of human 
health and the environment. For the 1995 HWIR proposal, we received 
comments requesting that we

[[Page 63450]]

allow units that have received only exempt wastes during the lifetime 
of the unit, including the time period prior to the effective date of 
HWIR, to be exempt from RCRA requirements, including closure. In 
effect, this would retroactively exempt the unit. Applying the HWIR 
exemption to waste that has already been disposed could, in theory, 
remove the RCRA Subtitle C closure requirements for that unit, because 
that unit would no longer contain hazardous waste.
    However, we do not feel such an application of the HWIR exemption 
would be appropriate or practical considering the self-implementing 
nature of this rule. Ensuring that the already-disposed waste has been 
properly sampled and analyzed and is below the exemption levels in all 
cases would be problematic and would best be done with direct 
government oversight, as is done in delistings. Closure regulations 
provide important protections, such as evaluation of soil and 
groundwater contamination, that should not be lost because of a self-
implementing waste identification rule.
E. How Would HWIR Affect the Land Disposal Restriction (LDR) Program?
    Today's rule contains two important areas of overlap with the RCRA 
LDR program. First, we are asking comment on whether certain of the 
HWIR exemption levels should replace existing technology-based LDR 
standards, if the exemption levels are less stringent than the current 
LDR values.
    Second, if your listed waste is below the HWIR exemption 
concentrations where the waste is first generated (the point where your 
waste first meets the listing description), then a hazardous waste is 
never generated and the LDR requirements do not attach to the waste. In 
contrast, once a listed waste is generated and managed, the LDR 
requirements attach, and remain even after the waste is exempted from 
RCRA Subtitle C under today's exemption.
    In addition to these two areas of overlap, there is also the issue 
of whether you as an HWIR waste generator can ``partially exempt'' your 
waste, removing one or more waste codes, and thus simplifying LDR 
treatment while continuing to manage it as a hazardous waste. In 
concept, you would be able to demonstrate that concentrations for a 
subset of chemicals within your waste met HWIR exemption levels. By 
doing so, you would be able to remove one or more hazardous waste codes 
from your waste. Such ``partially exempted'' waste would continue to be 
managed as hazardous, but in some cases might have fewer LDR 
requirements or might have more disposal options (such as disposal in a 
unit whose permit restricts which waste codes can be accepted).
    We have concerns about the feasibility of this approach and believe 
that the concentration-based exemption as discussed in this notice 
might not be well-suited to partial exemptions. A ``partial exemption'' 
would be difficult to implement using the self-implementing HWIR 
process. We designed the exemption to be a yes/no decision--if all 
concentrations of HWIR chemicals are at or below exemption levels, only 
then would waste be nonhazardous. Under this yes/no approach, we would 
not need a strict accounting of which hazardous chemical in the waste 
is associated with which waste code. In addition, we did not design the 
notification and other HWIR implementation requirements to take into 
account a ``partial exemption'' approach.
    We are also concerned about possible confusion with respect to LDR 
requirements for a waste stream that has become ``partially exempt.'' 
Such waste is still considered hazardous and must meet LDR requirements 
if placed on the land. This gives rise to other questions. For example, 
if an individual waste code is removed, would the LDR treatment 
requirements associated with that waste code, including Universal 
Treatment Standards (UTS), continue to apply? Would compliance with LDR 
be a condition of such partial exemption? These and other 
implementation questions would need to be addressed.
    Finally, we do not believe that any process removing hazardous 
waste codes should substitute for the exemption process as outlined in 
this notice. For example, a waste stream with one waste code could not 
pursue this partial exemption. We would want to ensure that a listed 
waste stream would still be regulated as hazardous until all the HWIR 
chemicals of concern were below risk-based concentrations, no matter 
from which waste stream they originated. We request comments on whether 
the HWIR exemption process could be adapted to allow the generator to 
removes specific waste codes from a waste that continues to be 
hazardous, and how such an adaptation would overcome implementation 
difficulties.
F. How Would HWIR Relate to the RCRA Air Emission Standards?
    Currently, air emissions from units managing hazardous waste are 
regulated under 40 CFR Parts 264 and 265, Subparts AA, BB and CC. 
However, once your hazardous waste satisfies the HWIR exemption 
criteria (including any chemical-specific exemption concentrations for 
volatile organics, or VOs), it would be exempt from RCRA Subtitle C 
regulations, including these air emission standards. In other words, 
once a waste is no longer regulated as hazardous, any unit in which the 
waste is managed (assuming no other hazardous waste is managed in the 
unit) is no longer subject to RCRA Subtitle C regulations, including 40 
CFR Parts 264 and 265, Subparts AA, BB, and CC.
    However, we still would have to ensure that air emissions risks 
from HWIR wastes are adequately addressed. The final rule establishing 
air emission controls for tanks, surface impoundments, containers, and 
miscellaneous units (the ``Subpart CC'' regulations--see 40 CFR 
264.1082) contains provisions whereby a hazardous waste is not subject 
to Subpart CC air emission controls requirements if the facility owner/
operator demonstrates that VO concentration of the hazardous waste is 
below 500 ppmw (parts per million by weight).
    Because exemption levels for specific volatile organics could in 
theory exceed the 500 ppmw threshold of the Subpart CC standards, we 
are requesting comment on whether the exemption would adequately 
address the air emission concerns of RCRA Section 3004(n) in allowing 
waste to become exempt from RCRA Subtitle C. One approach to address 
this concern would be to include an overall maximum cap for the sum of 
all VOs. Since Subpart CC doesn't apply to landfills, another approach 
would be to include a VO cap for the generic HWIR exemption, but not 
for the landfill-only HWIR exemption. We request comment on whether, to 
avoid undercutting the requirements of subpart CC, we should require 
HWIR waste to be below 500 ppmw for VO to address risks from volatile 
organics, and if so, whether this cap should be applied to the 
landfill-only HWIR exemption.
G. Would HWIR Affect ``Use Constituting Disposal'' Regulations?
    The current 40 CFR 266.20 requirements for wastes used in a manner 
constituting disposal would not be changed due to the HWIR exemption at 
this time. Such a change is beyond the scope of our mandate to revise 
the mixture and derived from rules.
    However, we are requesting comment on whether, in the future, we 
should revise 40 CFR 266.20 to make it more congruent to the HWIR 
exemption. Currently, 40 CFR 266.20(b) states that hazardous waste-
derived products that

[[Page 63451]]

are legitimately recycled by being land-applied are exempt from RCRA 
Subtitle C regulation provided they satisfy three conditions: (1) the 
recyclable materials undergo a chemical reaction so as not to be 
separable by physical means, (2) the product must be produced for the 
general public's use, and (3) LDR standards for every hazardous waste 
in the hazardous waste-derived product must be satisfied. (The 
shorthand for this type of recycling is ``use in a manner constituting 
disposal.'' See 40 CFR 261.2(c)(1).)
    The LDR standards, however, are technology-based rather than risk-
based, and, for metal hazardous chemicals, only control leachable 
amounts of the metal. Yet in some situations, total metal levels might 
be more important than leach levels because of the possibility of 
direct contact through inhalation of abraded or wind-dispersed 
contaminants, or surface runoff. On the other hand, HWIR exemption 
levels would be risk-based and consider some of the exposure pathways 
similar to those relevant in analyzing uses constituting disposal (for 
example, inhalation of particles).
    We solicit comment as to the appropriateness of applying HWIR 
exemption levels to hazardous wastes used in a manner constituting 
disposal. One approach would be to replace the requirement to meet LDR 
treatment standards with a requirement to meet the HWIR exemption 
levels. This approach should assure that exemption levels for hazardous 
wastes used in a manner constituting disposal are never less stringent 
than exemption levels for hazardous wastes placed in confined units. We 
request comment on the reasonableness of this approach.
H. Could Hazardous Waste Debris Become Exempt Under HWIR?
    Hazardous debris that contains listed hazardous wastes would be 
eligible for the HWIR exemption. We note, however, that certain 
exemptions already exist relating to hazardous debris. On August 18, 
1992, we published a final rule, Land Disposal Restrictions for Newly 
Listed Wastes and Hazardous Debris (57 FR 37194). In that rule, we 
required that hazardous debris be treated prior to land disposal, using 
treatment technologies from the treatment categories of extraction, 
destruction, or immobilization specified in 40 CFR 268.45, Table 1. We 
also added a conditional exemption at Sec. 261.3(f) for non-
characteristic hazardous debris (that is, debris that is hazardous 
solely because it contains listed hazardous wastes). Section 
261.3(f)(1) exempts debris from RCRA Subtitle C regulation provided 
that the debris is treated using one of the extraction or destruction 
technologies specified in Table 1 of Sec. 268.45. Alternatively, non-
characteristic hazardous debris can be exempt under Sec. 261.3(f)(2) if 
the Regional Administrator determines that it is no longer hazardous, 
after considering the extent of contamination of the debris, (in other 
words, after a ``contained-in'' determination is made). However, non-
characteristic hazardous debris that is treated by a specified 
immobilization technology is not eligible for the conditional exemption 
in Sec. 261.3(f)(1) and, therefore, remains subject to RCRA Subtitle C 
regulation after treatment.
    We would not change the current exemption under Sec. 261.3(f). 
Therefore, non-characteristic hazardous debris that requires LDR 
treatment by extraction or destruction technologies will be exempt from 
RCRA Subtitle C regulation, once treated. As was explained more 
thoroughly in the final rule for hazardous debris, we gave careful 
consideration to many factors before exempting certain treated debris, 
including whether each debris/ contaminant type would be effectively 
treated by each BDAT technology to levels that would no longer pose a 
hazard to human health or the environment (57 FR 37240). We would also 
not change the contained-in exemption under Sec. 261.3(f)(2) for 
hazardous debris. That is, the Regional Administrator may continue to 
determine on an individual basis that hazardous debris no longer 
contains listed hazardous waste, and should therefore be exempt from 
RCRA RCRA Subtitle C.
I. Would Contaminated Media Be Eligible for an HWIR Exemption?
    Listed hazardous wastes generated from the remediation of 
contaminated sites are eligible for exemption under this rule. However, 
due to difficulty in characterizing the origin of these wastes, we 
request comment whether to require testing of an expanded list of 
chemicals for these wastes. We feel that generators might not have 
adequate knowledge of the history of these wastes to apply generator 
knowledge to determine which chemicals would reasonably be expected to 
be in such a waste. Also, field screening techniques used to identify 
contaminants might not detect chemicals at HWIR exemption levels. One 
option would be to require initial testing for all HWIR exemption 
chemicals.
J. Does the Final HWIR-Media Rule Impact HWIR?
    No, although the HWIR-waste and the HWIR-media rules are often 
discussed together, and contaminated media are potentially affected by 
both rules, they are two separate rulemaking efforts on separate 
schedules. The HWIR-media rule does not address at what point wastes 
and media should become exempt from the RCRA Subtitle C regulatory 
system. Instead, HWIR media rule addresses other waste management 
issues, including permits, the storage of remediation wastes during 
cleanup and state authorization. The final HWIR-media rule was signed 
on November 30, 1998 (63 FR 65873).
K. How Would HWIR Impact Actions Under the Superfund Program (CERCLA)?
    All RCRA F, K, P and U wastes are included under the definition of 
hazardous substances in CERCLA Section 101(14)(C). Under CERCLA Section 
103(a), any person in charge of a vessel or facility must, immediately 
notify the National Response Center as soon as he or she has knowledge 
of the release, within a 24-hour period, of a reportable quantity (RQ) 
of any CERCLA hazardous substance. (See 40 CFR 302 for a list of these 
hazardous substances and their RQs.) If your waste met the HWIR 
exemption criterion, it would not be a hazardous waste and therefore 
not a hazardous substance as defined in CERCLA 101(14)(C). However, 
CERCLA does require a person in charge to notify the National Response 
Center of a release of the RCRA exempted waste if the waste or any of 
the chemicals of the waste are CERCLA hazardous substances by virtue of 
CERCLA Sections 101(14)(A), (B), (D), (E), or (F) or 40 CFR 302.4(b), 
and the waste or any of its chemicals that are hazardous substances are 
released in amounts greater than their RQs within a 24-hour period.
    HWIR exemption levels may also be applicable to the CERCLA program 
where RCRA listed hazardous waste has been disposed at the site. CERCLA 
section 121(d) requires that CERCLA actions comply with, or justify a 
waiver of, applicable or relevant and appropriate requirements (ARARs) 
under federal and state environmental laws. The HWIR exemption could 
affect the legal applicability of federal RCRA requirements to 
remediation wastes generated at Superfund sites. They may also be 
considered in determining whether RCRA is relevant and appropriate in 
cases where it is not applicable.

[[Page 63452]]

    At sites undergoing CERCLA remedial activities where no listed 
hazardous wastes have been identified, we use a site-specific risk 
assessment for chemicals that have no ARARs. In some cases, these 
health-based cleanup levels might be higher than the exemption levels, 
based on a reasonably conservative exposure scenario. In other cases, 
the CERCLA health-based clean-up levels might be lower than exemption 
levels. The CERCLA health-based clean-up levels may also be different 
from exemption levels based on the consideration of site-specific 
factors.
L. How Does HWIR Relate to the Draft Industrial D Voluntary Guidance?
    EPA's Office of Solid Waste issued for comment the draft Guide for 
Industrial Waste Management (the Guide) in June 1999. The draft Guide 
is meant to provide decision-makers with recommendations and user-
friendly tools to manage nonhazardous industrial waste protectively. 
The draft Guide contains reference materials and simple-to-use modeling 
tools to assess potential groundwater and air impacts. It gives 
stakeholders a common technical framework for planning and implementing 
a comprehensive industrial nonhazardous waste management system. The 
draft Guide is intended to be voluntary and non-regulatory. In 
contrast, HWIR will help determine which wastes are hazardous for the 
purposes of Federal regulation. Unit design, unit operation, and other 
aspects of hazardous waste management are mandated under RCRA Subtitle 
C regulatory oversight.
    HWIR-exempt wastes are eligible for disposal in the industrial 
nonhazardous landfills, surface impoundments, waste piles and land 
application units discussed in the draft Guide. The draft Guide 
recommends tailoring protective liner systems to characteristics of the 
wastes and sites where they are managed, using a three-tiered approach 
to groundwater modeling and risk assessment. Each successive tier of 
analysis requires more specific data, from a minimum of waste 
characteristics to full-blown site assessment. The Guide provides user-
friendly models for Tier 1 and 2 analyses. The Tier 1 model evaluates 
three liner scenarios: no-liner, single liner and composite liner. The 
Tier 2 model evaluates no-liner and single liner scenarios.
    Because HWIR and the draft Guide were designed for different 
purposes, the modeling approaches also differ. We expect the greatest 
differences to arise from how the draft Guide handles risk modeling for 
lined impoundments, landfills, and waste piles. The draft groundwater 
model in the Guide incorporates assumptions for on-going liner 
performance that affect movement of leachate from the unit through 
subsurface soils to groundwater. The Guide also places strong emphasis 
on quality assurance/quality control for liners during installation, 
continued operation and maintenance to protect the liner, installation 
of final covers, and post closure care and monitoring. In the draft 
Guide, EPA is specifically requesting comment on how we can best model 
long-term performance of liners and final cover systems to ensure that 
users design systems that are protective of human health and the 
environment. The comment period on the draft Guide does not end until 
December 1999. We have not yet received comments on the draft Guide, as 
potential users are still reviewing the modeling tools and 
documentation.
    HWIR has a different objective, to determine whether wastes are 
hazardous or nonhazardous. Since HWIR-exempt waste could be disposed in 
units without liners or other controls, the units that we model under 
HWIR are assumed to have no such controls. In addition there is 
considerable uncertainty about the long-term performance of controls 
even for units that do have them. Thus our hazardous waste 
identification policy has been to make the conservative assumption that 
such controls are not present for the purposes of risk assessment. We 
believe this is the most appropriate way to determine which wastes are 
low risk and should exit the Subtitle C regulatory program with this 
sort of self-implementing regulation. As we learn more about the long-
term performance of liner and cover systems, EPA may decide to revisit 
this approach.
M. How Does HWIR Relate to the Comparable Fuels Exemption?
    On June 19, 1998, EPA published air emission standards for 
hazardous waste combustion units (63 FR 338781). Under this final rule, 
we excluded, from the regulatory definition of solid waste, hazardous 
waste-derived fuels that meet specification levels comparable to fossil 
fuels for concentrations of hazardous chemicals. The exclusion applies 
to the comparable fuel from the point it is generated and is claimed by 
the generator of the comparable fuel. Fuel generators must comply with 
sampling and analysis, notification and certification, and 
recordkeeping requirements. The exclusion potentially applies to 
gaseous and liquid hazardous waste-derived fuels, but does not apply to 
solids or to used oil, which is subject to special standards under 40 
CFR Part 279. The only allowable treatment or disposal method for a 
comparable fuel is burning.
    Both the Comparable Fuels Exemption and the HWIR exemption require 
compliance with specified chemical concentrations levels, and both have 
similar, although not identical implementation requirements. The 
Comparable Fuels Exemption, however, is applied only to wastes with 
fuel value, and the levels were developed to be equivalent to chemical 
concentrations found in commonly-used fuels. HWIR, on the other hand, 
applies to all listed hazardous waste, and HWIR exemption levels would 
be developed based on a multimedia risk model. HWIR exemption levels 
would represent chemical concentrations that are acceptable to be 
managed in a nonhazardous waste unit. You may determine which exemption 
(if any) most fits your waste.
N. How Would HWIR Affect Mixed Waste?
    Mixed waste is a combination of hazardous and radioactive wastes, 
and is simultaneously covered by RCRA and the Atomic Energy Act. 
Because HWIR would exempt some hazardous wastes from RCRA Subtitle C 
requirements, it might also, through the same process, exempt some 
mixed waste from the RCRA hazardous waste regulations (without 
affecting its status under the Atomic Energy Act) as well.
    However, because of the overlap of federal requirements for mixed 
waste, we are also developing rules specifically related to mixed 
waste. As mentioned in Section II of this preamble, EPA is proposing a 
separate Federal Register notice to conditionally exempt hazardous 
waste mixed with low-level radioactive wastes or mixed with Naturally 
Occurring and/or Accelerator-produced Radioactive Material from the 
storage, treatment in storage tanks, transportation, and disposal 
requirements of RCRA when the waste is managed in accordance to the 
Nuclear Regulatory Commission (NRC) regulations. In addition, we are 
developing a regulation allowing disposal of mixed waste containing 
radionuclides at low activity levels at facilities meeting the design 
requirements for RCRA Subtitle C, with the NRC to be the implementing 
agency of this rule. More information on this proposal can be found in 
the most recent agenda of regulatory and deregulatory actions (64 FR 
21987).

[[Page 63453]]

O. How Does HWIR Relate to the Sewage Sludge Regulatory Program?
    Sewage sludge (biosolids) is a material Federally regulated under 
the authority of Sections 405(d) of the Clean Water Act (CWA), as 
amended (33 U.S.C.A. 1251, et seq.). On February 19, 1993, we published 
regulations to protect public health and the environment from any 
reasonably anticipated adverse effects of certain pollutants that might 
be present in sewage sludge (58 FR 9248). The regulations are codified 
at 40 CFR Part 503 with conforming amendments codified at 40 CFR Parts 
257 and 403. Part 503 allows four means of final use or disposal of 
sewage sludge: land application, surface disposal, incineration in a 
sewage sludge incinerator, and disposal in a solid waste landfill. Part 
503 establishes requirements for land application, i.e., placing sewage 
sludge on the land for a beneficial purpose (including sewage sludge or 
sewage sludge products that are sold or given away for use in home 
gardens), surface disposal, i.e., by placement on surface disposal 
sites (including sewage sludge-only landfills), and incineration. The 
standards for each end use and disposal practice consist of general 
requirements, numerical limits on the pollutant concentrations in 
sewage sludge, management practices and, in some cases, operational 
requirements. The Part 503 Rule also includes monitoring, record 
keeping and reporting requirements. Parts 257 and 258 govern disposal 
of sewage sludge in solid waste landfills.
    The regulations promulgated under section 405(d) of the Clean Water 
Act apply to domestic sewage sludge, defined in Part 503 as ``solid, 
semi-solid, or liquid residue generated during the treatment of 
domestic sewage in a treatment works. Sewage sludge includes, but is 
not limited to, domestic septage; scum or solids removed in primary, 
secondary or advanced wastewater treatment processes; and a material 
derived from sewage sludge.''
    Sewage sludge regulated under section 405 of the Clean Water Act is 
not hazardous waste. Under section 3001 of RCRA, solid wastes are 
``hazardous'' either by being a ``listed'' hazardous waste or by 
exhibiting a ``characteristic'' of hazardous waste. We have not listed 
sewage sludge as a hazardous waste, nor has sewage sludge been found to 
exhibit any hazardous waste characteristic. However, a sewage sludge 
that met the definition of hazardous waste under 40 CFR Part 261 would 
be subject to hazardous waste regulations, and would not be within the 
scope of Part 503. (see 58 FR 9253).
    Both the HWIR exemption and the sewage sludge regulations include 
numerical limits for certain chemicals. However, we do not expect the 
results of the two efforts to be the same, both because of different 
assumptions in the risk assessments and the differences in the physical 
and chemical characteristics of the matrices between sewage sludge and 
process waste-- for example, sewage sludge has a higher organic content 
than process waste, and that tends to immobilize certain chemicals, 
such as metals--and because of the fact that the Part 503 program 
requirements are different. As stated earlier, the sewage sludge 
regulations consist of other requirements beyond numerical limits, 
including management practices and monitoring requirements. For 
additional information on the Part 503 program, the Part 503 
regulation, and the multi-pathway exposure/risk assessment that serves 
as the technical basis of the Part 503 regulation, the reader is 
directed to the following Internet site: http://www.epa.gov/owm.

State Authorization

XXIII. How Would Today's Proposed Regulatory Changes Be Administered 
and Enforced in the States?

    Under section 3006 of RCRA, EPA may authorize qualified States to 
carry out the RCRA hazardous waste program within the State. Following 
authorization, we maintain independent enforcement authority under 
sections 3007, 3008, 3013, and 7003 of RCRA, although authorized States 
have enforcement responsibility. An authorized State could become 
authorized for this proposal's regulatory changes by following the 
approval process described under 40 CFR 271.21. See 40 CFR Part 271 for 
the overall standards and requirements for authorization.
    We are proposing to retain the mixture and derived-from rules. Most 
states have already received authorization for the mixture and derived-
from rules as they currently stand. The rules are already in effect in 
those authorized States. Those states that are already authorized for 
the mixture and derived-from rules would not need to obtain 
authorization for those rules again. We are also proposing to revise 
those rules under the authority of sections 3001(a), 3002(a), and 
3004(a) of RCRA. If promulgated, these revisions would not go into 
effect in authorized States until they adopt the revisions and receive 
authorization from us for the revision to their regulations.
    None of the proposed revisions are more stringent or broaden the 
scope of the existing Federal requirements. Authorized States are not 
required to modify their programs when we promulgate changes to Federal 
requirements that are less stringent than, or that narrow the scope of, 
existing Federal requirements. This is because RCRA section 3009 allows 
the States to impose (or retain) standards that are more stringent than 
those in the Federal program. (See also 40 CFR 271.1(i)). Therefore, 
States would not be required to adopt the revisions to the mixture and 
derived-from rules in today's rule, although EPA would strongly 
encourage their adoption.

Administrative Requirements

XXIV. How Has EPA Fulfilled the Administrative requirements for this 
Proposed Rulemaking?

    Several statutes and executive orders apply to proposed rulemaking. 
Below is an explanation of how to address the requirements in those 
provisions:
A. Executive Order 12866: Determination of Significance
    Under Executive Order 12866 [58 FR 51,735 (Oct. 4, 1993)], EPA must 
determine whether a regulatory action is ``significant'' and, 
therefore, subject to OMB review and the other provisions of the 
Executive Order. The Order defines a ``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 rights and obligations or 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 
Executive Order 12866.
    Pursuant to four term of Executive Order 12866, we have determined 
that this rule is a ``significant regulatory action'' because there are 
novel policy issues arising out of legal mandates. As such, this action 
was submitted to OMB for review. Changes made in response to OMB 
suggestions or recommendations are documented in the docket to today's 
proposal.

[[Page 63454]]

B. Regulatory Flexibility Act
    Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA) of 1996) whenever an agency is required to publish a notice of 
rulemaking for any proposed or final rule, it must prepare and make 
available for public comment a regulatory flexibility analysis that 
describes the effect of the rule on small entities (small businesses, 
small organizations, and small governmental jurisdictions). However, no 
regulatory flexibility analysis is required if the head of an agency 
certifies the rule will not have a significant [adverse] economic 
impact on a substantial number of small entities.
    SBREFA amended the Regulatory Flexibility Act to require Federal 
agencies to provide a statement of the factual basis for certifying 
that a rule will not have a significant economic impact on a 
substantial number of small entities. The following discussion explains 
our determination.
    As discussed in Section XXI, we have prepared an economic analysis 
of the potential effects of this rule, and have determined that the 
rule is expected to have a net beneficial effect on eligible entities, 
in the form of reduced environmental regulatory compliance costs for 
industrial waste management. The economic analysis evaluates the extent 
to which both small quantity and large quantity industrial waste 
generators might be potentially eligible for cost savings under this 
rule. This proposed rule is voluntary, and the overall economic effect 
of this regulation for both small and large entities which are eligible 
to participate, is expected to be a net average annual reduction in 
industry regulatory burden and compliance costs. Consequently, because 
the net economic impacts and effects of this rule are beneficial rather 
than adverse, this rule will not have a significant [adverse] economic 
impact on a substantial number of small entities. I hereby certify that 
this rule will not have a significant economic impact on a substantial 
number of small entities. This rule, therefore, does not require a 
regulatory flexibility analysis.
C. Paperwork Reduction Act (Information Collection Request)
    The information collection requirements in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. An 
Information Collection Request (ICR) document has been prepared by EPA 
(ICR No. 0801.12) and a copy may be obtained from Sandy Farmer by mail 
at OPPE Regulatory Information Division; U.S. Environmental Protection 
Agency (2137); 401 M St., S.W.; Washington, DC 20460, by email at 
[email protected], or by calling (202) 260-2740. A copy may 
also be downloaded off the Internet at http://www.epa.gov/icr.
    Today's proposed revisions of 40 CFR 261.3 do not include any new 
record keeping or reporting requirements. However, the proposed 
revisions could reduce the burden estimate for existing RCRA 
information collection requirements, such as the Uniform Hazardous 
Waste Manifest (Form 8700-22A). As discussed in Section XXII of this 
preamble, today's proposal could exempt approximately 54,700 tons of 
treated waste residuals (mainly incineration ash) per year. Assuming 
that these now-exempt wastes are shipped offsite for disposal, and 
assuming that an average truckload carries about 20 tons (of solids), 
today's proposal could result in approximately 2,870 shipments per year 
that would no longer require Uniform Hazardous Waste Manifest. The RCRA 
Hazardous Waste Manifest System ICR (No. 0801.12.) estimates an annual 
burden of 1.29 hours per shipment of hazardous waste. Therefore, 
today's proposal could reduce the total burden associated with 
manifests by 3,702 hours per year. (The current burden associated with 
manifests is estimated to be 2,920,383 hours per year).
    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 are listed in 40 CFR Part 9 and 48 CFR Chapter 15.
    Comments are requested on EPA's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden, including through the use of 
automated collection techniques. Send comments on the ICR to the 
Director, OPPE Regulatory Information Division; U.S. Environmental 
Protection Agency (2137); 401 M St., S.W.; Washington, DC 20460; and to 
the Office of Information and Regulatory Affairs, Office of Management 
and Budget, 725 17th St., N.W., Washington, DC 20503, marked 
``Attention: Desk Officer for EPA.'' Please refer to EPA ICR No. 801.12 
and OMB Control No. 2050-0039 in any correspondence. Since OMB is 
required to make a decision concerning the ICR between 30 and 60 days 
after November 19, 1999, a comment to OMB is best assured of having its 
full effect if OMB receives it by December 20, 1999. The final rule 
will respond to any OMB or public comments on the information 
collection requirements contained in this proposal.
D. Unfunded Mandates Reform Act
    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Pub. 
L. 104-4, establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on State, local, and tribal 
governments and the private sector. Under section 202 of the UMRA, we 
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, we must have developed under 
section 203 of the UMRA a small government agency plan. The plan must

[[Page 63455]]

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.
    Today's proposed revision to the mixture and derived-from rules is 
voluntary, and because is less stringent than the current regulations, 
State governments are not required to adopt the proposed changes. The 
UMRA generally excludes from the definition of ``Federal 
intergovernmental mandate'' duties that arise from participation in a 
voluntary federal program. The UMRA also excludes from the definition 
of ``Federal private sector mandate'' duties that arise from 
participation in a voluntary federal program. Therefore we have 
determined that today's proposal is not subject to the requirements of 
sections 202 and 205 of UMRA.
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 
proposed regulation. EPA also may not issue a regulation that has 
federalism implications and that preempts State law unless the Agency 
consults with State and local officials early in the process of 
developing the proposed regulation.
    If EPA complies by consulting, Executive Order 13132 requires EPA 
to provide to the Office of Management and Budget (OMB), in a 
separately identified section of the preamble to the rule, a federalism 
summary impact statement (FSIS). The FSIS must include a description of 
the extent of EPA's prior consultation with State and local officials, 
a summary of the nature of their concerns and the agency's position 
supporting the need to issue the regulation, and a statement of the 
extent to which the concerns of State and local officials have been 
met. For final rules subject to Executive Order 13132, EPA also must 
submit to OMB a statement from the agency's Federalism Official 
certifying that EPA has fulfilled the Executive Order's requirements.
    This proposed rule is not subject to Executive Order 13132 because 
it will not 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. This proposed rule will not result in the imposition of any 
additional requirements on any State, local governments or other 
political subdivisions within any State. Accordingly, the requirements 
of Executive Order 13132 do not apply to this proposal.
F. Executive Order 13084: Consultation and Coordination with Indian 
Tribal Governments
    Under Executive Order 13084, we may not issue a regulation that is 
not required by statute, that significantly or uniquely affects the 
communities of Indian tribal governments, and that imposes substantial 
direct compliance costs on those communities, unless the Federal 
government provides the funds necessary to pay the direct compliance 
costs incurred by the tribal governments, or we consult with those 
governments. If we comply by consulting, Executive Order 13084 requires 
us to provide to the Office of Management and Budget, in a separately 
identified section of the preamble to the rule, a description of the 
extent of our prior consultation with representatives of affected 
tribal governments, a summary of the nature of their concerns, and a 
statement supporting the need to issue the regulation. In addition, 
Executive Order 13084 requires us to develop an effective process 
permitting elected officials and other representatives of Indian tribal 
governments ``to provide meaningful and timely input in the development 
of regulatory policies on matters that significantly or uniquely affect 
their communities.''
    Today's proposed rule does not significantly or uniquely affect the 
communities of Indian tribal governments. Because today's proposed 
revision to the mixture and derived-from rules is less stringent than 
the existing program, it would not create any mandate on Indian tribal 
governments. Accordingly, the requirements of section 3(b) of Executive 
Order 13084 do not apply to this rule.
G. Executive Order 13045: Protection of Children from Environmental 
Health Risks and Safety Risks
    ``Protection of Children from Environmental Health Risks and Safety 
Risks'' (62 FR 19885, April 23, 1997) applies to any rule that: (1) is 
determined to be ``economically significant'' as defined under E.O. 
12866, and (2) concerns an environmental health or safety risk that we 
have reason to believe may have a disproportionate effect on children. 
If the regulatory action meets both criteria, we 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 us. This proposed rule is not subject to E.O. 13045 because it is 
not an economically significant rule as defined by E.O. 12866.
H. National Technology Transfer and Advancement Act of 1995
    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Pub L. No. 104-113, Sec. 12(d) (15 U.S.C. 272 
note) directs us to use voluntary consensus standards in our regulatory 
activities unless to do so would be inconsistent with applicable law or 
otherwise impractical. Voluntary consensus standards are technical 
standards (for example, materials specifications, test methods, 
sampling procedures, and business practices) that are developed or 
adopted by voluntary consensus standards bodies. The NTTAA directs EPA 
to provide Congress, through OMB, explanations when we decide not to 
use available and applicable voluntary consensus standards.
    Today's proposals do not involve technical standards. However, the 
HWIR exemption discussed in this notice does involve sampling and 
analysis requirements, but does not contemplate the use of specific, 
prescribed analytical methods. Rather, we would allow the use of any 
method that meets the prescribed performance criteria, consistent with 
our Performance Based Measurement System (PBMS). The PBMS approach is 
intended to be more flexible and cost-effective for the regulated 
community; it is also intended to encourage innovation in analytical

[[Page 63456]]

technology and improved data quality. We would not preclude the use of 
any method, whether it constitutes a voluntary consensus standard or 
not, as long as it meets the requirements and performance criteria 
specified. We welcome comments on this aspect of the notice and, 
specifically, invites the public to identify potentially-applicable 
voluntary consensus standards and to explain why such standards should 
be used.

References

XXV. What Are Some Key Documents Containing Information Supporting This 
Notice?

    The list of references is organized by the following preamble 
super-headings: (1) Background, (2) Retaining the Mixture and 
Derived-From Rules, (2) HWIR Exemption, (3) HWIR Risk Assessment, 
and (4) Economic Impacts. Under each super-heading, the references 
are listed alphabetically by author and chronologically when there 
is more than one document by the same author.
    These references and other supporting information can be found 
in the RCRA Docket Information Center (see contact information under 
ADDRESSES section at the beginning of the preamble).

Background References

Environmental Technology Council v. Browner, C.A. No. 94-2119 (TFH) 
(D.D.C. 1994).
Environmental Technology Council v. Browner, C.A. No. 94-2346 (TFH) 
(D.D.C. 1997).
Memorandum from Dorothy Kellogg, CMA to Elizabeth Cotsworth, Acting 
Director, Office of Solid Waste, August 1999.

Mixture and Derived-From Rules References

U.S. Environmental Protection Agency, Preliminary Data Summary for 
the Hazardous Waste Treatment Industry, 1989.
U.S. Environmental Protection Agency, Data on Mixture and Derived-
from Wastes from Closures and Corrective Action at Hazardous Waste 
Management Facilities, 1992.
U.S. Environmental Protection Agency, Disposition of Delisting 
Petitions for Derived-From/Mixture Wastes, memorandum, 1992.
U.S. Environmental Protection Agency, Memorandum to the Docket from 
Larry Rosengrant Regarding Section 3004(m) of the Hazardous and 
Solid Waste Amendments, January 21, 1992.
U.S. Environmental Protection Agency, Analysis of the Delisting 
Petition Data Management System, September 1998.
U.S. Environmental Protection Agency, Releases of Hazardous 
Constituents Associated with Mixture and Derived from Wastes, 1999.

HWIR Exemption References

Keith, L.H., Environmental Sampling: A Practical Guide, 1992.
U.S. Environmental Protection Agency, BDAT Background Document for 
QA/QC Procedures and Methodology, October 23, 1991.
U.S. Environmental Protection Agency, Petitions to Delist Hazardous 
Wastes: A Guidance Manual, March 1993.
U.S. Environmental Protection Agency, Waste Analysis at Facilities 
that Generate, Treat, Store and Dispose of Hazardous Waste, April 
1994.
U.S. Environmental Protection Agency, Ash Sampling Guidance, July 
1995.
U.S. Environmental Protection Agency, Appropriate Selection and 
Performance of Analytical Methods for Waste Matrices Considered to 
be `Difficult to Analyze', memorandum, January, 1996.
ASTSWMO, Overview: State-Based Contingent Management Case Study 
Project, Discussion Draft for April 1-2, 1998 Joint ASTSWMO Task 
Force Meeting, March 9, 1998.
U.S. Environmental Protection Agency, Waste Forms Technical 
Background Document, September 1998.
U.S. Environmental Protection Agency, Evaluation of Contingent 
Management Options, 1999
U.S. Environmental Protection Agency, Background Document on 
Retesting Frequency, July 1999.
U.S. Environmental Protection Agency, Estimates of Sample Sizes 
Required for a Generator to Demonstrate a Waste Qualifies for 
Exemption Under HWIR, May 1999.
U.S. Environmental Protection Agency, Sample Notification Form for 
Waste Claiming Exemption Under the Hazardous Waste Identification 
Rule (HWIR), July 1999.

HWIR Risk Assessment References

ASTSWMO, States' Use of Waste and By-Product Material, ASTSWMO Solid 
Waste Subcommittee Resource Recovery Task Force, September 30, 1996
Karickhoff, S.W., V.K. McDaniel, C.M. Melton, A.N. Vellino, D.E. 
Nute and L.A. Carriera. ``Predicting Chemical Reactivity by 
Computer,'' Environ. Toxicology and Chemistry. 10:1405-1416, 1991.
McKone, T.E. Human Exposure to Volatile Organic Compounds in 
Household Tap Water; the Indoor Inhalation Pathway. Environ. Sci. 
Technol. 21(12):1194--1201, 1987.
Research Triangle Institute (RTI). Response to Comments on Hazardous 
Waste Identification Rule (HWIR) Benchmarks, August 1998.
Science Advisory Board, An SAB Report: Review of EPA's Composite 
Model for Leachate Migration with Transformation Products (EPACMTP). 
Prepared by the OSWER Exposure Model Subcommittee of the 
Environmental Engineering Committee. EPA-SAB-EEC-95, 1995.
Science Advisory Board, An SAB Report: Review of a Methodology for 
Establishing Human Health and Ecological Based Exit Criteria for the 
Hazardous Waste Identification Rule (HWIR), Prepared by the HWIR 
Subcommittee of the Executive Committee. EPA-SAB-EC-96-002, May 
1996.
Small, Mitchell J.; Yoram Cohen; and Paul F. Deisler, Jr., Review of 
ORD/OSW Integrated Research and Development Plan for the Hazardous 
Waste Identification Rule (HWIR), December, 1998.
U.S. Bureau of the Census. Census of Agriculture. Geographic Area 
Series State and County Data. 1987 and 1992. (http://www.census.gov/
econ/www/ag0100.html)
U.S. Bureau of the Census. TIGER: The Coast-to-Coast Digital Map. 
1990 (GIS coverage--block and block groups, roads, etc.) (http:/
www.census.gov/geo/www.tiger/)
U.S. Bureau of the Census. Census of Population and Housing: Summary 
Tape File (STF) on CD-ROM Technical Documentation. STF 1-B and STF 
3A. 1992. (http:/www.census.gov/mp/www/rom/msrom6ac.html and http:/
www.census.gov/mp/www/rom/msrom6ae.html)
U.S. Environmental Protection Agency, Office of Research and 
Development, Exposure Analysis System (EXAMS): User's Manual and 
System Documentation, EPA-600/3-82-023, 1982.
U.S. Environmental Protection Agency, Office of Research and 
Development. Guidelines for Deriving Numerical National Water 
Quality Criteria for the Protection of Aquatic Organisms and Their 
Uses. PB85-227049. 1985.
U.S. Environmental Protection Agency, Screening Survey of Industrial 
Subtitle D Establishments, conducted by WESTAT, 1987.
U.S. Environmental Protection Agency, Office of Research and 
Development, MINTEQA2/PRODEFA2, A Geochemical Assessment Model for 
Environmental Systems: Version 3.0, User's Manual, EPA/600/3-91/021, 
March1991-a.
U.S. Environmental Protection Agency, Hazardous Waste TSDF--
Background Information for proposed RCRA Air Emission Standards, 
1991-b.
U.S. Environmental Protection Agency. 1:250,000 Scale Quadrangles of 
Landuse/Landcover GIRAS Spatial Data in the United States. Office of 
Information Resources Management (OIRM), 1994-a Available online at: 
http://www.epa.gov/ngispgm3/nsdi/projects/giras.htm.
U.S. Environmental Protection Agency. 1994-b. The U.S. EPA Reach 
File Version 3.0 Alpha Release (RF3-Alpha) Technical Reference, 
First Edition. Office of Wetlands, Oceans, and Watersheds, Office of 
Water, Washington, DC. Available online at: http://www.epa.gov/
owowwtr1/NPS/rf/techref.html
U.S. Environmental Protection Agency, Office of Solid Waste. EPA's 
Composite Model for Leachate Migration with Transformation Products 
(EPACMTP): Background Document, 1996-a.
U.S. Environmental Protection Agency, Office of Solid Waste. EPA's 
Composite Model for Leachate Migration with Transformation Products 
(EPACMTP): User's Guide, 1996-b.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Background Document for EPACMTP, Metals Transport in the Subsurface, 
1996-c.
U.S. Environmental Protection Agency, Office of Research and 
Development, Exposure Analysis System (EXAMS II):

[[Page 63457]]

User's Guide for Version 2.97.5, EPA-600/R-97/047, 1997-a.
U.S. Environmental Protection Agency, Office of Solid Waste, Office 
of Reseach and Development. System Design Development Guidance, 
Directive No. 2182. 1997-b.
U.S. Environmental Protection Agency, Office of Solid Waste. Test 
and Verification of EPA's Composite Model for Leachate Migration 
with Transformation Products (EPACMTP). 1997-c.
U.S. Environmental Protection Agency, Office of Research and 
Development. Exposure Factors Handbook (EFH). EPA/600/P-95/002Fa, 
August, 1997-d.
U.S. Environmental Protection Agency, Report on the Consistency of 
HWIR Benchmarks with Current Agency Values and Guidelines, November 
1997-e.
U.S. Environmental Protection Agency, Office of Research and 
Development. Methodology for Assessing Health Risks Associated with 
Multiple Exposure Pathways to Combustor Emissions, 1997-f.
U.S. Environmental Protection Agency, Risk Assessment Forum. 
Guidelines for Ecological Risk Assessment--Final. EPA/630/R-95/002F. 
April, 1998-a.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Anaerobic Biodegradation Rates of Organic Chemicals in Groundwater: 
A Summary of Field and Laboratory Studies. July, 1998-b.
U.S. Environmental Protection Agency, Testing of the Sampled 
Chronological Input Model (SCIM) option in the enhanced ISCST3 Model 
for use in the Hazardous Waste Identification Rule (HWIR99), 1998-c.
U.S. Environmental Protection Agency, MINTEQA2/PRODEFA2, A 
Geochemical Assessment Model for Environmental Systems: User Manual 
Supplement for Version 4.0, 1998-d.
U.S. Environmental Protection Agency, Diffuse-Layer Sorption 
Reactions for use in MINTEQA2 for HWIR Metals and Metalloids, June 
1998-e.
U.S. Environmental Protection Agency, Office of Research and 
Development/Office of Solid Waste. ORD/OSW Integrated Research and 
Development Plan for the Hazardous Waste Identification Rule (HWIR), 
October 1998-f.
U.S. Environmental Protection Agency, Office of Research and 
Development. Integrated Risk Information System (IRIS) Database. 
Cincinnati, OH, 1998-g.
U.S. Environmental Protection Agency, Consideration of Beneficial 
Use as an HWIR Waste Management Scenario, 1999.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Correlation between Liquid, Sludge, and Solid Waste Forms and 
Surface Impoundment, Land Application Unit, and Landfill Disposal 
Options, February, 1999-a.
U.S. Environmental Protection Agency, Office of Solid Waste. A 
Framework for Finite-Source Multimedia, Multipathway and 
Multireceptor Risk Assessment: 3MRA. July, 1999-b.
U.S. Environmental Protection Agency, Office of Research and 
Development. FRAMES-HWIR Technology Software System for 1999: System 
Overview. July, 1999-c.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 1. 
Introduction. Section 2: Overview/Site Layout. July 1999-d.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 3: 
Waste Management Unit Data. July 1999-e.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 4: 
Meteorological Data. July 1999-f.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 5: 
Watershed and Waterbody Layout. July 1999-g.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 6: 
Surface Water Data. July 1999-h.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 7: 
Soil Data. July 1999-i.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 8: 
Human Exposure Factors. U.S. Environmental Protection Agency, Office 
of Solid Waste. June 1999-j.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 9: 
Human Receptor Data. July 1999-k.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 10: 
Farm Food Chain and Terrestrial Foodweb Data. July 1999-l.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 11: 
Aquatic Food Web Data. July 1999-m.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 12: 
Ecological Exposure Factors. July 1999-n.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 13: 
Ecological Receptors and Habitats. July 1999-o.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 14: 
Ecological Benchmarks. July 1999-p.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 15: 
Human Health Benchmarks. July 1999-q.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Collection for the Hazardous Waste Identification Rule. Section 16: 
Miscellaneous Data. August 1999-r.
U.S. Environmental Protection Agency, Office of Research and 
Development. Site Selection Methodology for HWIR99 Sampling. 1999-s.
U.S. Environmental Protection Agency, Office of Solid Waste. Source 
Modules for Non-Wastewater Waste Management Units (Land Application 
Units, Waste Piles, and Landfills): Background and Implementation 
for the Multimedia, Multipathway and Multireceptor Risk Assessment 
(3MRA) for HWIR99. July 1999-t.
U.S. Environmental Protection Agency, Office of Solid Waste. Source 
Modules for Tanks and Surface Impoundments: Background and 
Implementation for the Multimedia, Multipathway and Multireceptor 
Risk Assessment (3MRA) for HWIR99. July 1999-u.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Documentation for the Air Module for the FRAMES-HWIR System. June 
1999-v.
U.S. Environmental Protection Agency, Office of Solid Waste. Air 
Module Pre-and Post-Processor: Background and Implementation for the 
Multimedia, Multipathway and Multireceptor Risk Assessment (3MRA) 
for HWIR99. July 1999-w.
U.S. Environmental Protection Agency, Office of Solid Waste. User's 
Guide for the Industrial Source Complex (ISC3) Dispersion Models for 
use in the Multimedia, Multipathway and Multireceptor Risk 
Assessment (3MRA) for HWIR99: Description of Model Algorithms, 128 
pages, June 1999-x.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Watershed Module: Background and Implementation for the Multimedia, 
Multipathway and Multireceptor Risk Assessment (3MRA) for HWIR99. 
July 1999-y.
U.S. Environmental Protection Agency, Office of Research and 
Development. Surface-Water Module for the Hazardous Waste 
Identification Rule (HWIR99), 1999-z.
U.S. Environmental Protection Agency, Office of Solid Waste. Vadose 
and Saturated Zone Modules Extracted from EPACMTP for HWIR99. Draft. 
U.S. Environmental Protection Agency, Office of Solid Waste, July, 
1999-aa.
U.S. Environmental Protection Agency, Office of Solid Waste. Pseudo-
Three Dimensional Aquifer Module for HWIR99: Module Verification 
Document. July, 1999-ab.
U.S. Environmental Protection Agency, Office of Solid Waste. Vadose 
Zone Module for HWIR99: Module Verification Document. July, 1999-ac.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Landfill Module for HWIR99: Module Verification Document. July, 
1999-ad.
U.S. Environmental Protection Agency, Office of Solid Waste. Surface 
Impoundment Module for HWIR99: Module Verification Document. July, 
1999-ae.
U.S. Environmental Protection Agency, Office of Solid Waste. A Study 
to Assess

[[Page 63458]]

the Impacts of Fractured Media in Monte-Carlo Simulations, with 
appendices. July, 1999-af.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Incorporation of Heterogeneity into Monte-Carlo Fate and Transport 
Simulations. July, 1999-ag.
U.S. Environmental Protection Agency, Office of Research and 
Development. Changes in the MINTEQA2 Modeling Procedure for 
Estimating Metal Partitioning Coefficients in Groundwater for 
HWIR99. July,1999-ah.
U.S. Environmental Protection Agency, Office of Solid Waste. 1999. 
Chemical Database for HWIR99, July 1999-ai.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Background Document for the Human Exposure Module for HWIR99 
Multimedia, Multipathway and Multireceptor Risk Assessment (3MRA) 
Model, July 1999-aj.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Background Document for the Human Risk Module for HWIR99 Multimedia, 
Multipathway and Multireceptor Risk Assessment (3MRA) Model, July 
1999-ak.
U.S. Environmental Protection Agency, Office of Solid Waste. Farm 
Food Chain Module: Background and Implementation for the Multimedia, 
Multipathway and Multireceptor Risk Assessment (3MRA) Model for 
HWIR99, July 1999-al.
U.S. Environmental Protection Agency, Office of Solid Waste. Aquatic 
Food Web Module: Background and Implementation for the Multimedia, 
Multipathway and Multireceptor Risk Assessment (3MRA) Model for 
HWIR99, July 1999-am.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Ecological Exposure Module: Background and Implementation for the 
Multimedia, Multipathway and Multireceptor Risk Assessment (3MRA) 
Model for HWIR99, July 1999-an.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Ecological Risk Module: Background and Implementation for the 
Multimedia, Multipathway and Multireceptor Risk Assessment (3MRA) 
for HWIR99, July 1999-ao.
U.S. Environmental Protection Agency, Office of Solid Waste. 1999. 
Terrestrial Food Chain Module: Background and Implementation for the 
Multimedia, Multipathway and Multireceptor Risk Assessment (3MRA) 
for HWIR99, July 1999-ap.
U.S. Environmental Protection Agency, Office of Research and 
Development. Partitioning Coefficients for Metals in Surface Water, 
Soil, and Waste for HWIR99, July 1999-aq.
U.S. Environmental Protection Agency, Office of Solid Waste. 1999. 
Analysis of NAPL Formation Potential and Cosolvency Effect, EPA, 
1999-ar.
U.S. Environmental Protection Agency, Office of Solid Waste. 1999. 
Risk Characterization Report for the HWIR99 Multimedia, Multipathway 
and Multireceptor Risk Assessment (3MRA), July 1999-as.
U.S. Environmental Protection Agency, Background Document on HWIR 
Exemption Chemicals, July 1999-at.
U.S. Environmental Protection Agency, Background Document on the 
Selection of Initial HWIR Chemicals, July 1999-au.
U.S. Environmental Protection Agency, Background Document on 
Additional HWIR Chemicals, July 1999-av.
U.S. Environmental Protection Agency, Office of Solid Waste. 
Conceptual Approach to Establish Interim Human Health Benchmarks: 
Peer Review Draft, June 1999-aw.
U.S. Environmental Protection Agency, Office of Solid Waste. Data 
Requirements and Confidence Indicators for Ecological Benchmarks 
Supporting Exit Criteria for the Hazardous Waste Identification Rule 
(HWIR99), September 1999-ax.
U.S. Fish and Wildlife Service. National Wildlife Survey. 1991.
U.S. Fish and Wildlife Service. National Wetlands Inventory (NWI) 
Metadata, 1995. Available online at: ftp://www.nwi.fws.gov/metadata/
nwi__meta.txt.
U.S. Geological Survey (USGS). USGeoData 1:250,000 and 1:100,000 
Scale Land Use and Land Cover and Associated Maps Digital Data, 
1990. Available online: ftp://www-nmd.usgs.gov/pub/ti/LULC/
lulcguide.

Economic Impacts Reference

U.S. Environmental Protection Agency, Economic Assessment of the 
U.S. EPA's 1999 Proposed Hazardous Waste Identification Rule (HWIR), 
1999.

Request for Comment

XXVI. On What Issues Is EPA Specifically Seeking Public Comment?

    In developing this notice, we tried to address the concerns of all 
our stakeholders. Your comments will help us improve this rule. We 
invite you to provide different views on options we discuss, new 
approaches we haven't considered, new data, how this rule may affect 
you, or other relevant information. We welcome your views on all 
aspects of this notice.
    Your comments will be most effective if you follow the suggestions 
below:
     Explain your views as clearly as possible and why you feel 
that way.
     Where possible, provide technical and cost data to support 
your views.
     If you estimate potential costs, explain how you arrived 
at the estimate.
     Tell us which parts you support, as well as those you 
disagree with.
     Provide specific examples to illustrate your concerns.
     Offer specific alternatives.
     Refer your comments to specific sections of the notice, 
such as the section numbers or page numbers of the preamble, or the 
proposed regulatory sections.
    We welcome comments on any and all aspects of the rulemaking, and 
we are particularly interested in receiving comments on the issues 
listed below. For information on how to submit your comments, please 
see the ADDRESSES section towards the beginning of this preamble.
    1. What are merits and drawbacks of the five possible revisions to 
the mixture and derived-from rules submitted to EPA by CMA? 
Specifically, what are (a) the potential risks to human health and the 
environment, (b) any special or unique technical considerations, and 
(c) the economic effects of each of the possible revisions? (Section 
II.E)
    2. Should EPA allow F003 to be eligible for the proposed expansion 
of the 40 CFR 261.3(a)(2)(iii) exemption (although F003 is listed 
solely for ignitability, its listing description includes references to 
solvents that were listed for toxicity as well)? (Section IV.A)
    3. Should EPA conditionally exempt low level radioactive hazardous 
mixed waste from the mixture and derived-from rules, provided the mixed 
waste is handled in accordance with the requirements of a new Part 266, 
Subpart N, which is being simultaneously proposed today? (Section IV.B)
    4. Should EPA propose and finalize the landfill-only exemption 
(based on conditions of management) and the generic exemption (not 
based on conditions of management) from hazardous waste regulation? 
(Section VI)
    5. Should the HWIR exemption be self-implementing? (Section VIII)
    6. Should EPA require a waiting period between the receipt of the 
notification package by the overseeing agency and the time the waste 
becomes exempt (for example 30 to 90 days)? (Section VIII)
    7. Is EPA's definition of ``chemicals reasonably expected to be 
present'' acceptable? In particular, should the definition be adjusted 
for some of the broader waste listings such as spent solvents (RCRA 
waste codes F001-F005)? (Section IX.A)
    8. Is EPA's policy to exclude from HWIR eligibility those wastes 
are reasonably expected to contain chemicals that do not have HWIR 
exemption levels appropriate? If not, what are other options for 
dealing with chemicals that do not have HWIR exemption levels? (Section 
IXA)
    9. Should EPA require a minimum number of samples at each sampling 
event? If so, what should that number be? (Section IX.B.2)
    10. Is the use of the strict maximum standard (i.e., no sample is 
allowed to exceed the HWIR exemption level) appropriate for the 
evaluation of a waste stream for an HWIR exemption? If not, what is the 
preferred alternative? (Section IX.B.2)
    11. Should EPA require that the bias introduced by partial 
recoveries of the chemicals under analysis be corrected in order to 
make results from different

[[Page 63459]]

analytical methods more comparable? (Section IX.B.3)
    12. If EPA requires correction of the bias introduced by partial 
recoveries, should EPA require that analytical protocols achieve a 
minimum of 20% recovery, and that analytical results with analytic 
spike recovery of less than 100% be corrected for the percent recovery 
determined for that sample before being compared to the HWIR exemption 
level? (Section IX.B.3)
    13. Should EPA use the detection limit in place of the HWIR 
exemption level when the detection limit is higher than the exemption 
level, but still within an acceptable level of risk? (Section IX.B.3.)
    14. As an alternative to using the strict maximum standard for 
compliance, should EPA require that the upper confidence limit (set at 
some level of confidence, such as 95 percent) associated with the mean 
concentration in the candidate waste be at or below the HWIR exemption 
level for the waste to be HWIR exempt? (Section IX.C.1)
    15. As a second alternative to using the strict maximum standard 
for compliance, should EPA require that the estimated mean chemical 
concentration within the candidate waste be at or below the HWIR 
exemption levels, and that the concentration of individual samples 
would have to be at or below some multiple of the exemption level? 
(Section IX.C.1)
    16. As a third alternative to using the strict maximum standard for 
compliance, should EPA require that the estimated mean concentration be 
at or below the HWIR exemption level, and the upper confidence limit 
associated with the estimated mean (at some level of confidence) would 
have to be at or below some multiple of the exemption level? (Section 
IX.C.1)
    17. For the regulatory alternatives that allowing individual 
samples to be at or below some multiple of the HWIR exemption levels, 
how should those limits (for example, multipliers to the exemption 
levels) be established? Specifically, should EPA use a multiplier of 
2.8, consistent with the variability factor used in the LDR program? 
(Section IX.C.1)
    18. Should EPA consider the use of composite samples, particularly 
spatial composites, in addition to grab samples, in evaluating a waste 
stream for HWIR compliance? (Section IX.C.2)
    19. Should EPA specify the size of samples taken to evaluate a 
waste stream for HWIR compliance? (Section IX.C.2)
    20. Is the sample notification form included in the docket (titled 
``Sample Notification Form for Waste Claiming Exemption Under the 
Hazardous Waste Identification Rule'') adequate for claiming an HWIR 
exemption? (Section IX.D)
    21. What alternatives to the written notification package should 
EPA consider (such as electronic submissions)? (Section IX.D)
    22. Should EPA require additional information in the notification 
package, such as the list of chemicals found in the waste and a summary 
of results for each sample analyzed? (Section IX.D)
    23. Are existing mechanisms for information sharing, including 
access via the Internet, sufficient to provide the public with 
information relative to individual HWIR exemption claims exerted in 
each respective State? (Section IX.E)
    24. If existing mechanisms are insufficient, should EPA require 
HWIR waste generators to notify the public of HWIR exemption claims 
through a newspaper notices, prior to having the exemption claims 
become effective? (Section IX.E)
    25. If EPA requires public notification through newspaper notices, 
should the receipt of adverse comments by the generator trigger review 
the HWIR exemption package by the overseeing agency? (Section IX.E)
    26. Should EPA require HWIR waste generators to include testing 
results information in the notification package for the purpose of 
greater public access to this information? (Section IX.E)
    27. Should EPA require that paperwork accompany the waste in order 
to track the waste and provide notice to the receiving facility that 
the waste is HWIR-exempt? (Section X.B.)
    28. Should EPA prohibit dilution as a means of attaining the HWIR 
exemption levels? If so, should EPA allow aggregation of waste streams 
for the purpose of treatment in CWA wastewater systems? (Section X.C)
    29. What are the advantages and disadvantages of requiring the same 
testing scheme for both initial and subsequent sampling and analysis of 
HWIR waste? (Section XI.A)
    30. Should EPA allow the use of prediction limits and other such 
techniques for the purpose of subsequent testing? (Section XI.A)
    31. Should EPA allow the removal of testing requirements for 
chemicals consistently detected in concentrations of less than one-
tenth of the exemption level? If so, after how many testing events with 
levels below one-tenth of the exemption level should this reduced 
testing obligation occur? (Section XI.A.1)
    32. Should the retesting frequency depend on (a) the annual volume 
of waste generated, and (b) the physical form of a waste (liquid or 
non-liquid)? Are there other factors EPA should consider when setting 
retesting frequency? (Section XI.A.2)
    33. Should EPA reduce the testing frequency for generators who are 
small businesses (that may or may not generate large annual volumes of 
waste)? (Section XI.A.2)
    34. Should EPA require retesting after a significant process 
change? (Section XI.A.3)
    35. If a wastestream loses its HWIR-exempt status because it no 
longer meets the exemption levels or does not meet one of the other 
conditions of the exemption, should EPA impose additional requirements 
before the exemption can be reinstated? For example, should there be a 
mandatory waiting period before the exemption can be reinstated? 
(Section XII.B)
    36. Should EPA prohibit storage of HWIR waste for longer than one 
year? (Section XII.B.2)
    37. For the landfill-only option, should tracking of HWIR waste be 
limited to: notifying the landfill of the shipment; receiving a 
confirmation from the landfill that the waste arrived; and keeping a 
copy of the arrival confirmation for three years (first alternative)? 
(Section XII.B(3))
    38. Under this first tracking alternative, should the landfill also 
be required to keep a copy of the arrival confirmation for three years 
as well?(Section XII.B(3))
    39. For the landfill-only option, should tracking of HWIR waste 
consist of: using the existing uniform hazardous waste manifest system 
(40 CFR 262.20 and 49 CFR 172.205) to track the conditionally exempt 
HWIR waste (second alternative)? (Section XII.B.3)
    40. For the landfill-only option, should tracking of HWIR waste 
consist of: using modified DOT shipping papers to accompany the waste; 
receiving a copy of the shipping papers documenting that the waste 
arrived at the landfill; and keeping a copy of these documents for 
three years (third alternative)? (Section XII.B.3)
    41. How can EPA address the issue of interstate transport of HWIR 
waste, where waste exempted in one State would still be regulated as 
hazardous as it travels to or through a State that has not adopted the 
HWIR exemption? (Section XII.B.3)
    42. Is the approach EPA has taken to account for mass balance and 
to integrate the calculations of the important direct and indirect risk 
pathways leading to a receptor appropriate? If not, what are 
alternative approaches? (Section XVI.A.2)

[[Page 63460]]

    43. Is EPA's approach to evaluating the exposed and unexposed 
receptors appropriate? (Section XVI.A.2)
    44. Is EPA's approach to modeling risk to humans from groundwater, 
considering the risk posed at receptor wells located within the modeled 
plume of contamination and outside the modeled plume of contamination 
reasonable? (Section XVI.A.2)
    45. Are EPA's estimates of the fraction of the modeled wells 
located within and outside of the modeled plume of contamination 
reasonable? (Section XVI.A.2)
    46. Is the methodology for selecting the 201sites to represent the 
national population of industrial facilities appropriate? If not, what 
are alternative methodologies? (Section XVI.A.3)
    47. Should EPA apply the sampling weights from the Industrial D 
Survey to the sample of 201 sites? (Section XVI.A.3)
    48. Does the information contained in the HWIR chemical database 
reflect the current state of knowledge for the chemical parameters ? 
(Section XVI.A.3)
    49. Is there any additional information on the chemicals that EPA 
should consider? (Section XVI.A.3)
    50. Is our information on anaerobic biodegradation (for example in 
the saturated zone) of organic chemicals sufficient? (Section XVI.A.3)
    51. Is there any additional data on anaerobic biodegradation of 
organic chemicals? (Section XVI.A.3)
    52. Should EPA use toxicity data, in addition to data contained in 
EPA's IRIS and HEAST databases, (a) which other Federal agencies have 
used in establishing regulatory levels or toxicity benchmarks, or (b) 
which have been otherwise peer-reviewed and published? (Section 
XVI.A.3)
    53. If EPA uses toxicity data other than the data contained in 
EPA's IRIS and HEAST databases, is EPA's methodology to develop interim 
benchmarks from this other data appropriate? If not, what are 
alternative methodologies? (Section XVI.A.3)
    54. Is EPA's decision to establish regulatory levels based only on 
the chemical-specific total concentration in the waste, rather than 
requiring wastes to meet both total and leachate levels appropriate?
    55. In terms of establishing a relationship within the model 
between the chemical concentration in the waste and the chemical 
concentration in the leachate, and of mass limitations in leachate, 
should EPA (for each waste management unit) start with a chemical 
concentration in a waste and partition it to the various environmental 
media based on the physical and chemical characteristics of the 
chemical, the waste management unit characteristics, and the 
partitioning algorithms? (Section XVI.D.)
    56. Are the methodologies used for modeling the environmental 
releases for HWIR99 appropriate? If not, what are alternative 
methodologies? (Section XVI.D)
    57. Are the methodologies used for modeling the environmental fate 
and transport for HWIR99 appropriate? If not, what are alternative 
methodologies? (Section XVI.E)
    58. Are the data and methodologies used to support the HWIR overall 
modeling framework appropriate? If not, what alternatives should EPA 
use? (Section XVI.E.1)
    59. Are the methodologies that EPA plans to implement in the 
saturated zone module (SZM) in order to factor the effects of fractures 
in porous media and incorporate effects of heterogeneity in aquifers 
into the modeling appropriate? (Section XVI.E.3.A)
    60. Is EPA's methodology for calculating infant exposure to dioxin 
and dioxin-like chemicals in breastmilk appropriate? If not, what are 
alternative methodologies? (Section XVI.F.1)
    61. Should EPA model infant exposure to chemicals other than dioxin 
and dioxin-like? If so, which chemicals should be considered? (Section 
XVI.F.1)
    62. Over which time period should exposure at a receptor be 
evaluated? (Section XVII)
    63. Are there any revisions to the software system that would 
address identified errors or improve the risk model ? (Section XVII)
    64. Is EPA's decision to model degradation processes, including 
hydrolysis, aerobic biodegradation, anaerobic biodegradation, and 
activated aerobic biodegradation appropriate? (Section XVII.B.2)
    65. Is the toxicity of daughter products that may be generated from 
the degradation process of significant concern? If so, what methodology 
should be used to calculate the ratio of parent to daughter product for 
the purpose of the model? (Section XVII.B2)
    66. Under which physical conditions should EPA assume that each of 
these degradation processes occurs? (Section XVII.B.2)
    67. Should EPA either (a) prohibit the combustion of already exempt 
HWIR waste, or (b) implement a more targeted combustion restriction for 
HWIR exempt waste based on chemical content? If not, are there any 
other alternatives for addressing risks from the combustion of HWIR 
exempt wastes? (Section XVII.D.1)
    68. Should EPA allow HWIR exempt wastes to be eligible for 
beneficial uses? (Section XVII.D.2)
    69. Did EPA use adequate data to consider (a) the possibility that 
wastes with constituent concentrations low enough to qualify for 
exemption could result in free-phase migration of chemical compounds in 
groundwater, including the potential NAPL contamination of groundwater 
due to the formation of free-phase liquids in landfills and (b) the 
possible impacts of co-solvency on the migration of contaminants 
adequate? (Section XVII.D. 4.)
    70. Is the toxicity characteristic adequate for capturing the risks 
from wastes derived from exempt liquids? (Section XVII.D.4)
    71. Is the assumption that surface impoundments have waste removed 
at the time of closure likely to affect the results of the risk 
assessment? (Section XVII.D.5)
    72. Are the chemicals in the new 40 CFR Part 261 Appendix X the 
best set of chemicals to be considered for the HWIR exemption? If not, 
which set of chemicals should be considered? (Section XVIII.A)
    73. Are the sources of toxicity data that EPA considered adequate? 
If not, what other sources should EPA consider? (Section XVIII.B)
    73. Should EPA establish an HWIR exemption level for lead based on 
the lower of two values: 400 mg/kg soil screening level for human 
health risks and on the results from the HWIR ``99 risk assessment for 
ecological risks? If not, what alternative would you recommend? 
(Section XVIII.C)
    74. Which wastes would be impacted by the absence of an HWIR 
exemption level for cyanide? (Section XVIII.D)
    75. How could an HWIR exemption level be set for cyanide, given its 
complex chemistry? (Section XVIII.D)
    76. Which chemicals and waste streams are especially good 
candidates for HWIR exemptions? (Section XVIII.D)
    77. Is the range of values that EPA considered for each of the risk 
protection measures appropriate? If not, what alternative values should 
be considered? (Section XIX.A)
    78. For each of the risk protection measures (cancer risk level, 
human health hazard quotient, ecological hazard quotient, population 
percentile, and probability of protection), which single value is most 
appropriate? (Section XIX.A)
    79. Is the HWIR definition of liquids (i.e., Total Suspended Solids 
(TSS) less than one percent) appropriate? (Section XIX.C)

[[Page 63461]]

    80. Is the HWIR definition of semi-solids (i.e., TSS greater than 
or equal to one percent and TSS equal to or less than 30 percent) 
appropriate? (Section XIX.C)
    81. Is the HWIR definition of solids (i.e., TSS greater than 30 
percent) appropriate? (Section XIX.C)
    82. As an alternative to defining solids as waste containing 
greater than 30% TSS, should the paint filter test be used to define 
the threshold between semi-solids and solids? (Section XIX.C)
    83. Is the use of a conversion factor of one kg/L to convert the 
tank and surface impoundment results (mg/L) for comparison to the land 
application unit results (mg/kg) in the semi-solid category acceptable 
in this context? If not, what is an alternative approach? (Section 
XIX.C)
    84. Should EPA use the results of the HWIR model to revise LDR 
standards? (Section XX.D)
    85. Should HWIR exemption levels replace existing technology-based 
LDR standards, where the exemption levels are less stringent than the 
current LDR values? (Section XX.E)
    86. Are the scope, methodology, assumptions, data sources, and 
other elements of the Economic Assessment background document for this 
proposal, adequate for describing and estimating the potential economic 
effects of HWIR? (Section XXI)
    87. Should EPA require HWIR waste to be below 500 ppmw for volatile 
organics, and, if so, should this cap be applied to waste exempted 
under the landfill-only HWIR exemption as well? (Section XXII.F)
    88. Should EPA in the future revise 40 CFR 266.20 to apply HWIR 
exemption levels to hazardous waste used in a manner constituting 
disposal? (Section XXII.G)
    89. Should EPA required contaminated media to be tested for a 
broader list of HWIR exemption chemicals than that required for other 
wastes? If so, how should this broader list be developed? (Section 
XXII.I)

List of Subjects in 40 CFR Part 261

    Environmental protection, Hazardous waste, Recycling, Waste 
treatment and disposal.

    Dated: October 29, 1999.
Carol M. Browner,
Administrator.

PART 261--IDENTIFICATION AND LISTING OF HAZARDOUS WASTE

    1. The authority citation for part 261 continues to read as 
follows:

    Authority: 42 U.S.C. 6905, 6912(a), 6921, 6922, 6924y, and 6938.

    2. Section 261.3 is amended by:
    A. Removing paragraph (a)(2)(iii);
    B. Redesignating paragraphs (a)(2)(iv) through (a)(2)(v) as 
paragraphs (a)(2)(iii) through (a)(2)(iv);
    C. Revising newly designated paragraph (a)(2)(iii) and the first 
sentence of paragraph (c)(2)(i); and
    D. Adding paragraph (g).


Sec. 261.3  Definition of hazardous waste.

    (a) * * *
    (2) * * *
    (iii) It is a mixture of solid waste and one or more hazardous 
wastes listed in subpart D of this part and has not been excluded from 
paragraph (a)(2) of this section under Secs. 260.20 and 260.22 of this 
chapter, paragraph (g) of this section, or under part 266, subpart N of 
this chapter; however the following mixtures of solid wastes and 
hazardous wastes listed in subpart D of this part are not hazardous 
waste (except by application of paragraph (a)(2)(i) or (ii) of this 
section) if the generator can demonstrate that the mixture consists of 
wastewater the discharge of which is subject to regulation under either 
section 402 or section 307(b) of the Clean Water Act (including 
wastewater at facilities which have eliminated the discharge of 
wastewater) and;
* * * * *
    (c) * * *
    (2) * * *
    (i) Except as otherwise provided in paragraph (c)(2)(ii) or (g) of 
this section or in part 266, subpart N, any solid waste generated from 
the treatment, storage, or disposal of a hazardous waste, including any 
sludge, spill residue, ash emission control dust, or leachate (but not 
including precipitation run-of) is a hazardous waste. * * *
* * * * *
    (g)(1) A hazardous waste that is listed in subpart D of this part 
solely because it exhibits one or more characteristics of ignitability 
as defined under Sec. 261.21, corrosivity as defined under Sec. 261.22, 
or reactivity as defined under Sec. 261.23 is excluded from regulation, 
if the waste no longer exhibits any characteristic of hazardous waste 
identified in subpart C of this part.
    (2) The exclusion described in paragraph (g)(1) of this section 
also pertains to:
    (i) Any mixture of a solid waste and a hazardous waste listed in 
subpart D of this part solely because it exhibits the characteristics 
of ignitability, corrosivity, or reactivity as regulated under 
paragraph (a)(2)(iii) of this section; and,
    (ii) Any solid waste generated from treating, storing, or disposing 
of a hazardous waste listed in subpart D of this part solely because it 
exhibits the characteristics of ignitability, corrosivity, or 
reactivity as regulated under paragraph (c)(2)(i) of this section.
    (3) Wastes excluded under this section are still subject to part 
268 of this chapter, even if they no longer exhibit a characteristic at 
the point of land disposal.

[FR Doc. 99-29067 Filed 11-18-99; 8:45 am]
BILLING CODE 6560-50-P