Document ID: EPA-HQ-RCRA-2003-0004-0414
Agency: epa
Document Type: Proposed Rule
Title: Hazardous Waste Management System: Identification and Listing of Hazardous Waste: Conditional Exclusion From Hazardous Waste and Solid Waste for Solvent-Contaminated Industrial Wipes
Posted Date: 2009-10-27T04:00Z

[Federal Register: October 27, 2009 (Volume 74, Number 206)]
[Proposed Rules]               
[Page 55163-55168]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr27oc09-30]                         

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 261

[EPA-HQ-RCRA-2003-0004; FRL-8973-2]
RIN 2050-AE51

 
Hazardous Waste Management System: Identification and Listing of 
Hazardous Waste: Conditional Exclusion From Hazardous Waste and Solid 
Waste for Solvent-Contaminated Industrial Wipes

AGENCY: Environmental Protection Agency.

ACTION: Data availability, management approaches, and request for 
comment.

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SUMMARY: This notice of data availability (NODA) invites comments on a 
revised risk analysis supporting the Environmental Protection Agency's 
(EPA) proposed revisions to the Resource Conservation Recovery Act 
(RCRA) hazardous waste regulations governing the management of solvent-
contaminated wipes. The revised analysis addresses public comments 
received on the risk screening analysis conducted on EPA's 2003 Federal 
Register proposal to exclude solvent-contaminated wipes from the RCRA 
definitions of solid and hazardous waste. To address these comments, 
EPA updated the data, models, and approach used in the risk analysis 
and then had the product peer reviewed by outside experts. The revised 
risk analysis, as well as the peer review comments and our response to 
those comments are available in the docket for this NODA. The NODA also 
invites comment on specific issues in light of the results of the 
revised risk analysis.

DATES: Comments must be received within December 28, 2009.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
RCRA-2003-0004 by one of the following methods:
     http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: rcra-docket@epa.gov, Attention Docket No. EPA-HQ-
RCRA-2003-0004.
     Fax: 202-566-9744, Attention Docket No. EPA-HQ-RCRA-2003-
0004.
     Mail: Environmental Protection Agency, EPA Docket Center 
(EPA/DC), Resource Conservation and Recovery Act (RCRA) Docket, 2822T, 
1200 Pennsylvania Avenue, NW., Washington, DC 20460, Attention Docket 
No. EPA-HQ-RCRA-2003-0004. Please include 2 copies.
     Hand Delivery: Public Reading Room, EPA West, Room 3334, 
1301 Constitution Ave., NW., Washington, DC, Attention Docket No. EPA-
HQ-RCRA-2003-0004. Such deliveries are only accepted during the 
docket's normal hours, and special arrangements should be made for 
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-RCRA-
2003-0004. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not send information you 
consider CBI or that is otherwise protected through http://
www.regulations.gov or e-mail. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment direct to EPA without going 
through http://www.regulations.gov, your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
send an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you send. If EPA cannot read your comment because of 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For more information about EPA's public docket, 
visit the EPA Docket Center homepage at http://www.epa.gov/epahome/
dockets.htm.
    Docket: All documents in the docket are listed in the http://
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Resource 
Conservation and Recovery Act (RCRA) Docket, EPA/DC, EPA West, Room 
3334, 1301 Constitution Ave., NW., Washington, DC. The Public Reading 
Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, 
excluding legal holidays. The telephone number for the Public Reading 
Room is (202) 566-1744, and the telephone number for the RCRA Docket is 
(202) 566-0270.

FOR FURTHER INFORMATION CONTACT: Teena Wooten, Office of Resource 
Conservation and Recovery (ORCR), (703) 308-8751, wooten.teena@epa.gov. 
Direct mail inquiries to the U.S. Environmental Protection Agency, 
Office of Resource Conservation and Recovery, (Mailstop 5304P), 1200 
Pennsylvania Avenue, NW., Washington, DC 20460.

SUPPLEMENTARY INFORMATION: 

I. General Information

A. Does this Action Apply to Me?

    This action may affect up to 164,000 entities in at least 15 
industries involved in the use and handling of solvent-contaminated 
wipes. These industries include, but are not limited to:

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                                Industry
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1. Printing manufacturing.
2. Chemical and allied products manufacturing.
3. Plastics and rubber products manufacturing.
4. Fabricated metal products manufacturing.
5. Industrial machinery and equipment manufacturing.
6. Electronics and computers manufacturing.
7. Transportation equipment manufacturing.
8. Furniture and fixture manufacturing.
9. Auto dealers (retail trade).
10. Publishing (printed matter).
11. Business services.
12. Auto repair and maintenance.
13. Military bases.
14. Solid waste services.
15. Industrial launderers.
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    This list is not intended to be an exhaustive list, but rather 
provides a guide for readers regarding entities likely to be covered by 
this action. This list includes the types of entities that EPA is now 
aware of that could potentially be covered by this action. Other types 
of entities not listed above could also be addressed by this action. If 
you have any questions about the

[[Page 55164]]

applicability of this action to a particular entity or industry, 
consult the individual listed above in the FOR FURTHER INFORMATION 
CONTACT Section.

B. What Should I Consider as I Prepare My Comments for EPA?

    1. Submitting CBI. Do not send CBI information to EPA through 
http://www.regulations.gov or e-mail. Clearly mark the part or all the 
information that you claim to be CBI. For CBI information on a disk or 
CD-ROM that you mail to EPA, mark the disk or CD-ROM as CBI and then 
identify electronically within the disk or CD-ROM the specific 
information that is claimed as CBI. As well as one complete version of 
the comment that includes information claimed as CBI, send a copy of 
the comment that does not contain the information claimed as CBI for 
inclusion in the public docket. Information so marked will not be 
disclosed, except under procedures set forth in 40 CFR part 2.
    2. Tips for Preparing Your Comments. When sending comments, 
remember to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register date and 
page number).
     Follow directions--The agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree, suggest alternatives, 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in enough detail to allow reproduction.
     Provide specific examples to explain your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible.
     Make sure to send your comments by the comment period 
deadline identified.
    The contents of this notice are listed in the following outline:

I. Background
    A. Introduction
    B. November 2003 Proposed Rule Standards and Approach
    C. Comments on the 2003 Proposal
II. Methodology and Results of the Revised Risk Analysis
    A. Introduction
    B. Were the Documents Peer Reviewed Before Issuing this Notice?
    C. How were the Landfill Loadings for Solvent-Contaminated Wipes 
Determined?
    D. How were the Risk-Based Mass Loadings Calculated?
    E. How were the Risk-Based Mass Loadings Compared to the 
Solvent-Quantity Loadings?
    F. What are the Results for the Comparison of the Loading 
Estimates?
    G. Request for Comment
III. Discussion and Request for Comment on Management Approaches and 
Risk Analysis Findings
IV. Conclusion

I. Background

A. Introduction

    A wide variety of industries use wipes (i.e., rags, shop towels, 
disposable wipes and paper towels, collectively called ``wipes'') for 
cleaning and degreasing. The wipes are handled in various ways. For 
example, wipes may be used once or several times before they are thrown 
away, while other wipes are used, laundered, and reused multiple times. 
During cleaning and degreasing operations, these wipes may become 
contaminated with solvents, as well as with other materials (e.g., 
paints, varnishes, waxes, metal shavings, inks, dirt). When discarded, 
spent wipes are considered hazardous waste under the Federal hazardous 
waste regulations if the wipes exhibit a hazardous waste characteristic 
under 40 CFR part 261, subpart C or contain a solvent listed in 40 CFR 
261.31 (that is, the solvents included in RCRA waste codes F001 through 
F005).
    Members of the regulated community petitioned EPA to remove 
solvent-contaminated wipes from the hazardous waste regulations. The 
petitioners argued that when small amounts of solvent are used on each 
wipe, minimal risk occurs from the disposal of such wipes in municipal 
solid waste landfills (MSWLF). Thus, they viewed the required disposal 
of the solvent-contaminated wipes in RCRA Subtitle C hazardous waste 
facilities as overregulation. Industrial laundries presented similar 
arguments and requested that the solvent-contaminated wipes they wash 
before returning them to their customers for reuse be excluded from the 
definition of solid waste. After a review of the petitions, subsequent 
industry requests and information, and internal EPA analysis, the 
Agency decided to propose exclusions from the RCRA definition of solid 
waste for solvent-contaminated wipes sent to a laundry or dry cleaner 
and from the definition of hazardous waste for solvent-contaminated 
wipes sent to a landfill or combustion facility, provided certain 
conditions were met. We published the proposed changes in the November 
20, 2003, Federal Register (68 FR 65586). The result of this proposal, 
if finalized, would reduce the regulatory burden on users and handlers 
of solvent-contaminated wipes. In support of the proposed regulatory 
change, we completed a risk screening analysis to evaluate the 
potential risk at MSWLFs from the disposal of solvent-contaminated 
wipes and industrial laundry sludge.

B. November 2003 Proposed Rule Standards and Approach

    To evaluate the appropriate regulatory status for solvent-
contaminated wipes, we considered the risks to the environment and 
public health from the management of solvent-contaminated wipes and 
wastewater treatment sludge from laundries (laundry sludge) in MSWLFs. 
This was done by conducting a screening analysis to determine the 
constituent-specific risks from landfilling wipes and laundry sludge 
contaminated with the F001-F005 listed (40 CFR 261.31) spent solvents. 
Then we estimated the risks from exposure to the 30 F001-F005 listed 
solvents potentially used on wipes, assuming disposal in an unlined 
MSWLF. Specifically, we looked at potential risks from inhalation of 
the spent solvents volatilizing from the landfill, from ingestion of 
groundwater contaminated by the spent solvents leaching from the 
landfill, and from inhalation of the spent solvent vapors released from 
contaminated groundwater during showering and other such uses. Section 
V of the Technical Background Document for the proposed rule [Docket 
EPA-HQ-RCRA-2003-0004] provides details on the risk screening analysis 
conducted for the 2003 proposed rule.

C. Comments on the 2003 Proposal

    During the comment period on the proposed rule, we received 
substantive comments on the risk screening analysis and solvent loading 
calculations from 23 commenters. In addition to public review and 
comment, we received comments from outside peer reviewers. Both the 
public and the peer reviewers questioned the validity of the risk 
screening analysis and the modeling assumptions. These comments are 
available in EPA's Docket No. EPA-HQ-RCRA-2003-0004.

II. Methodology and Results of the Revised Risk Analysis

A. Introduction

    In response to the comments received from the peer reviewers and 
the public on the risk screening analysis used to support the proposed 
rule, we decided to revisit our risk analysis. Based on this

[[Page 55165]]

review, we determined that a more robust risk analysis was required to 
adequately determine the potential risk from disposal of solvent-
contaminated wipes and laundry sludge in MSWLFs, also referred to in 
this NODA as landfills or non-hazardous waste landfills. We have thus 
completed a revised risk analysis which is more robust and more 
sophisticated than the original risk screening analysis. The revised 
risk analysis includes updated data and information, a new model to 
evaluate the behavior of solvents in a landfill, revised fate and 
transport modeling, including additional probabilistic modeling, 
uncertainty and sensitivity analyses, and an improved approach to 
compare the solvent quantity estimates to the risk-based solvent 
levels. Because so much of the revised risk analysis is new, we believe 
it appropriate to make it available for public comment before making 
decisions on the final rule.
    The revised risk analysis estimates the amount of each F-listed 
solvent that is present in solvent-contaminated wipes and laundry 
sludge disposed of in MSWLFs. We compared these amounts to the 
quantities of spent solvents that may be disposed of in MSWLFs without 
presenting unacceptable risks to human health and the environment 
(risk-based mass loadings). The revised risk analysis consists of three 
separate documents, which are described generally in this NODA. The 
documents are:

--``Landfill Loadings Calculations for Disposed Solvent-Contaminated 
Wipes and Laundry Sludge Managed in Municipal Landfills''
--``Risk-Based Mass Loading Limits for Solvents in Disposed Wipes and 
Laundry Sludges Managed in Municipal Landfills''
--``F001-F005 Solvent-Contaminated Wipes and Laundry Sludge: Comparison 
of Landfill Loading Calculations and Risk-Based Mass Loading Limits''

For more details about the revised risk analysis, please see the above 
documents in the Docket (EPA-HQ-RCRA-2003-0004).
    The discussion below summarizes our revised risk analysis for 
disposal of the solvent-contaminated wipes and laundry sludge in 
landfills.

B. Were the Documents Peer Reviewed before Issuing this Notice?

    The revised risk analysis will be used to support EPA's rulemaking 
to the RCRA hazardous waste regulations governing the management of 
solvent-contaminated wipes. Under our peer review policy, risk analyses 
used to support rulemaking decisions are influential scientific 
information. Therefore, we conducted an external peer review in 
accordance with both EPA's peer review policy and the Office of 
Management and Budget's (OMB's) Final Information Quality Bulletin for 
Peer Review. We asked the peer reviewers to conduct a comprehensive 
review of the risk analysis. The peer reviewers were asked to respond 
to a set of questions, which are included in the public docket for this 
NODA addressing the technical basis of the approaches we used and to 
prepare a report highlighting their comments and recommendations. The 
peer reviewers suggested clarifications in several sections of the 
``Landfill Loadings Calculations for Disposed Solvent-Contaminated 
Wipes and Laundry Sludge Managed in Municipal Landfills'' document. One 
reviewer questioned the method chosen to determine the uncertainty/
variability distribution, while two reviewers asked for more 
information on determining the number of generators using wipes. The 
reviewers also suggested that EPA review its discussion on sensitivity 
analysis. For the ``Risk-Based Mass Loading Limits for Solvents in 
Disposed Wipes and Laundry Sludges Managed in Municipal Landfills'' 
document, the reviewers recommended more data and discussion on the 
model methodology and results. EPA revised these documents 
incorporating the peer reviewers' comments, where necessary and 
appropriate. The docket contains the individual peer reviewer reports, 
EPA's response to the peer reviewers' comments, and supporting 
documents for the peer reviews.\1\ For more information about the peer 
review process, see EPA's Peer Review Handbook at http://www.epa.gov/
iris/Peer_Review_Handbook_2006_3rd_edition.pdf.
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    \1\ The ``F001-F005 Solvent-Contaminated Wipes and Laundry 
Sludge: Comparison of Landfill Loading Calculations and Risk-Based 
Mass Loading Limits'' document was developed after completion of the 
peer reviews.
---------------------------------------------------------------------------

C. How were the Landfill Loadings for Solvent-Contaminated Wipes 
Determined?

    We began the evaluation by looking at the 30 solvents listed in 40 
CFR 261.31 (F001-F005). Through literature review and site visits, we 
eliminated 10 of these 30 solvents \2\ from the analysis. Of the 10 
eliminated solvents, 5 are ozone-depleting or present other serious 
hazards and are therefore banned or restricted from use. The other 5 
solvents eliminated from the analysis may have been used on wipes in 
the past; however, our research found that these solvents are currently 
not used or are used only in limited quantities in conjunction with 
wipes. The Agency solicits comment on this finding.
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    \2\ Carbon tetrachloride, 1,1,1-Trichloroethane, 
Trichlorofluoromethane, Dichlorodifluoromethane, 1,1,2-
Trichlorotrifluorethane (ozone depleting substances), Carbon 
disulfide, ethyl ether, Nitrobenzene, 2-Nirtopropane, Pyridine (not 
know to be used as solvents in wipes applications). For the 
discussion on the solvents, see the ``Landfill Loadings Calculations 
for Disposed Solvent-Contaminated Wipes and Laundry Sludge Managed 
in Municipal Landfills'' Section 1.2.1 and 1.2.2.
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    After identifying the remaining 20 solvents \3\ to evaluate, we 
used both deterministic (point-value) and Monte Carlo (probabilistic) 
methods in the analysis. We estimated the number of generators and the 
number of wipes used by those generators. Few generators have the same 
solvent use practices or use the same number of wipes. To account for 
these differences, our revised risk analysis included an assessment of 
the uncertainty using empirical data-based probability distributions in 
a Monte Carlo analysis. We conducted a separate sensitivity analysis to 
assess the influence that each input parameter has on the result. These 
results identify the most and least influential assumptions. We 
estimated the amount of solvent that could be on a wipe or in laundry 
sludge before disposal and then estimated the number of generators 
potentially disposing of solvent-contaminated wipes or laundry sludge 
into a single MSWLF. Through our calculations, we derived estimated 
landfill loadings for the solvents. The full report, ``Landfill 
Loadings Calculations For Disposed Solvent-Contaminated Wipes and 
Laundry Sludge Managed in Municipal Landfills'' describes the 
assumptions made, methodologies used, and the results of the analysis. 
The Docket (EPA-HQ-RCRA-2003-0004) for this NODA contains this 
document.
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    \3\ Acetone, benzene, butanol, chlorobenzene, cresols (total), 
cyclohexanone, dichlorobenzene, 1, 2-ethoxyethanol, 2-ethyl acetate, 
ethyl benzene, isobutanol, methanol, methyl ethyl ketone, methyl 
isobutyl ketone, methylene chloride, tetrachloroethylene, toluene, 
trichloroethane, 1,1,2-trichloroethylene, xylene (mixed isomers).
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D. How were the Risk-Based Mass Loadings Calculated?

    We also developed a methodology to estimate the amount of hazardous 
spent solvents that could be disposed of in MSWLFs (unlined and 
composite lined), and be protective of human health and the environment 
at the point of exposure. These ``allowable amounts'' are risk-based 
mass loading rates expressed in kg of each spent solvent

[[Page 55166]]

that can be added to a landfill in a given year. These risk-based mass 
loading rates were derived from modeling scenarios defined in terms of 
the solvent, landfill type (e.g., lined or unlined), exposure pathway 
(e.g., ambient air inhalation), contact media (e.g., groundwater), and 
receptor (e.g., child or adult). Mass loading rates were estimated for 
each solvent such that the exposure at the 50th and 90th percentiles of 
the risk distribution would not exceed the identified risk target 
criteria, if these materials were disposed of in a MSWLF. The 50th and 
90th percentiles are typically used by the Agency to characterize risk. 
The 90th percentile represents a ``high end'' estimate of individual 
risk, while the 50th percentile results reflect the central tendency 
estimate of the risk distribution.\4\ For this analysis, the risk 
criteria were selected so that either 50 or 90 percent of the 
hypothetical individuals living near a landfill will not be exposed to 
solvent releases resulting in an excess lifetime cancer risk above 1 
chance in 10,000 (10-4) through 1 chance in 1,000,000 
(10-6).\5\ For noncancer health effects, we used a hazard 
quotient (HQ) of one as our risk criterion (the noncancer HQ is defined 
as the ratio of predicted intake levels to safe intake levels).
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    \4\ Guidance for Risk Characterization, U.S. Environmental 
Protection Agency, 1995.
    \5\ These risk criteria are consistent with those discussed in 
EPA's hazardous waste listing determination policy (see December 22, 
1994; 59 FR 66072). Also see 40 CFR 300.430(e)(2)(i)(A)(2), which 
establishes a cancer risk range of 10-4 to 
10-6 in the National Oil and Hazardous Substances 
Pollution Contingency Plan (NCP) for responding to releases of 
hazardous substances under Superfund.
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    We identified the following exposure pathways based on the 
solubility and volatility of the 20 spent solvents included in the 
analysis, as well as the operating practices of nonhazardous waste 
landfills:
    (1) Inhalation of ambient air containing spent solvents emitted 
from the landfill at residential dwellings;
    (2) Ingestion of spent solvents that leach from the landfill and 
migrate through groundwater to residential drinking water wells;
    (3) Inhalation of spent solvents during showering and bathing with 
solvent-contaminated groundwater; and
    (4) Dermal contact of spent solvents during showering and bathing 
with solvent-contaminated groundwater.
    A probabilistic approach was used to develop national mass loading 
rates because landfills that receive solvent-contaminated wipes and 
laundry sludge could be of varying geometry and located in many 
different parts of the country. The approach primarily addresses the 
variability in waste management practices (that is, unlined and 
composite lined landfills), environmental settings, and exposure-
related parameters. We also developed a landfill source model to 
simulate the solvent-specific air emissions and leachate releases from 
landfills. The quantity of solvent releases to the air and groundwater 
were then used as inputs to the air and groundwater fate and transport 
models.
    For each solvent, we calculated risk estimates assuming a unitized 
mass loading rate (1 kg per year) for each liner type, exposure 
pathway, and receptor, as well as for the combined exposures associated 
with groundwater uses. The risk results provide insight into the 
relative nature of exposures and potential risks that could be 
associated with the solvent-contaminated wipes disposed of in MSWLFs.
    For unlined landfills, the groundwater pathways were always 
associated with the highest predicted risks at the 50th and 90th 
percentiles of the distributions. For composite lined landfills, 
groundwater exposures were associated with the highest risks at the 
90th percentile, except for methylene chloride and methyl ethyl ketone, 
which showed higher risks for the ambient air inhalation pathway. At 
the 50th percentile, the highest predicted risks were associated with 
the ambient air inhalation pathway for 16 of the 20 solvents; however, 
for unlined landfill disposal, the predicted risks were associated more 
with drinking water.
    From this information, we developed solvent-specific risk-based 
mass loading rates (in kg/yr) that could be disposed of in a MSWLF and 
meet specific risk criteria and be protective of human health and the 
environment. The risk-based mass loading rates do not provide direct 
insight into the potential impacts associated with current management 
practices. The full report, ``Risk-Based Mass Loading Limits for 
Solvents in Disposed Wipes and Laundry Sludges Managed in Municipal 
Landfills'' describes the assumptions made, methodologies used, and the 
results of the analysis. The Docket for this NODA (EPA-HQ-RCRA-2003-
0004) contains this document.

E. How were the Risk-Based Mass Loadings Compared to the Solvent-
Quantity Loadings?

    To perform a comparison, EPA evaluated a 90th percentile risk 
criterion for the risk-based mass loading limit to be protective of 90 
percent of hypothetically exposed individuals across all of the 
landfill sites in the United States (Guidance for Risk 
Characterization, U.S. Environmental Protection Agency, 1995; 
accessible at http://www.epa.gov/OSA/spc/pdfs/rcguide.pdf, which states 
that ``For the Agency's purposes, high end risk descriptors are 
plausible estimates of the individual risk for those persons at the 
upper end of the risk distribution,'' or conceptually, individuals with 
``exposure above about the 90th percentile of the population 
distribution''). As recommended in the Guidance, EPA also evaluated the 
50th percentile results as the central tendency estimate of that risk 
distribution. Thus, we compared the 90th percentile estimate of 
landfill loading rates (ELLRs) to the 90th percentile of the risk-based 
mass loading levels (RB-MLLs) to determine whether the ELLRs in 
landfills that can be attributed to solvent-contaminated wipes and 
laundry sludge exceeds the RB-MLLs that correspond to selected health-
based limits. A similar comparison was conducted at the 50th 
percentile.

F. What are the Results for the Comparison of the Loading Estimates?

    The results for both the ELLR and the RB-MLL are generated from a 
probabilistic analysis. The results from these two separate 
calculations are given by a distribution of values. The theoretical 
risk distribution provides the basis for calculating risk-based mass 
loading rates for any percentile of that distribution. Based on the 
risk criteria that EPA evaluated for the wipes analysis, the RB-MLL was 
identified at the 50th and 90th percentiles of the distribution. These 
levels represent the allowable mass loading rate (in kg per year) for 
management of solvent-containing wipes and laundry sludges in a MSWLFs 
anywhere in the country in any given year.
    The comparisons of the ELLRs and RB-MLLs are expressed as ratios, 
i.e., the 90th percentile ELLRs (kg solvent per year) are divided by 
the 90th percentile RB-MLLs (kg solvent per year) for a specific 
solvent to yield ratios. The ELLR is an estimate of the mass loading 
into the landfill and the RB-MLL is an estimate of the mass loading 
that would correspond to an exposure equivalent to the chosen risk 
criterion, or risk ``target.'' Therefore, if the ratio exceeds one, 
this indicates the degree to which the ELLR exceeds the evaluation 
criteria used to establish the RB-MLLs (i.e., a cancer risk of 1 x 
10-5 and an HQ of 1 for noncarcinogenic risk).
    The comparison of the 90th percentile values of the ELLRs and the 
RB-MLLs

[[Page 55167]]

indicates that 8 of the 20 spent solvents could pose potential risks 
above EPA's evaluated criteria at some risk levels for unlined 
landfills. The 90th percentile risks for benzene (using the high end 
cancer risk value only), 1,1,2-trichloroethane, methylene chloride, 
tetrachloroethylene, and trichloroethylene exceeded the 10-5 
cancer risk criteria. The 90th percentile risks for chlorobenzene, 
toluene, and xylenes exceeded the criteria for non-cancer health 
effects (HQ = 1). As expected, the predicted risks for the unlined 
landfill analysis were always greater than those for the composite-
lined landfill analysis. Using the comparison of the 90th percentile 
results, the potential risks from all solvents examined in the 
composite-liner scenario, except for tetrachloroethylene, were well 
below (generally <0.1) the health-based criteria used in this analysis. 
The value for tetrachloroethylene was 1.1 using the higher end cancer 
risk value and 0.9 using the lower end cancer risk value. For a more 
detailed explanation of how the ELLR and RB-MLL were compared, see the 
``F001-F005 Solvent-Contaminated Wipes and Laundry Sludge: Comparison 
of Landfill Loading Calculations and Risk Based Mass Loading Limits'' 
document in the docket for this NODA.
    A comparison of the ELLR and RB-MLL central tendency values (50th 
percentiles), showed that tetrachloroethylene is the only solvent in 
the unlined landfill scenario that produced a ratio of ELLR to RB-MLL 
greater than one (using a cancer risk of 1 x 10-5 and an HQ 
of 1) and this value was 1.4 using the higher end cancer risk value; 
using the lower end cancer risk value, the ratio was 1.2. For the 
composite liner scenario, all ratios of the 50th percentile ELLRs and 
RB-MLLs are well below one using these risk criteria.
    The ratios from a comparison of the ELLRs and the RB-MLLs for the 
constituents with carcinogenic risk would change if the RB-MLLs were 
calculated using a risk criterion different from the 1 x 
10-5 criterion. If a target risk level of 1 x 
10-4 were used for calculating the RB-MLLs, the carcinogenic 
risk for the carcinogens (1,1,2-trichloroethane, benzene, methylene 
chloride, tetrachloroethylene, and trichloroethylene) would be lower by 
a factor of ten. Alternatively, if a target risk level of 1 x 
10-6 were used, the cancer risks for these constituents 
would be higher by a factor of ten. A comparison of the ELLR and RB-MLL 
values using the 10-4 risk criterion for the no-liner 
scenario would have the effect of lowering the ratios; however, the 
ratios of 7 of the 8 solvents of potential concern would remain above 
one at the 90th percentile (the ratio for benzene would be less than 
one). Using the 10-4 criterion at the 50th percentile, the 
ratios for all the solvents would be below one. Using the 
10-6 risk criterion would have the effect of raising the 
ratios in the unlined landfill scenario for carcinogens, such that the 
ratios for all these 8 solvents for the 90th percentile results would 
exceed one by a wider margin. Using the 10-6 risk criterion, 
the ratios from the 50th percentile results would increase for the 
carcinogenic solvents, such that the ratios for tetrachloroethylene and 
trichloroethylene would exceed one at the 50th percentiles.
    For the composite-liner scenario, the ratios for all solvents would 
be below one (including tetrachloroethylene) at both the 90th and 50th 
percentiles using the 10-4 risk criterion. Using the 
10-6 criterion, the ratios for tetrachloroethylene and 
trichloroethylene at the 90th percentile are above one.
    These results differ from our original risk screening analysis for 
the proposed rule in the following ways:
     The number of solvents that show a potential risk for 
disposal in an unlined landfill in our risk screening analysis 
increased by 2 in the revised analysis and the solvents indicating a 
potential risk also changed.\6\
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    \6\ Solvents in the proposal indicating a potential risk in 
unlined landfill scenario: Methyl ethyl ketone, methyl isobutyl 
ketone, nitrobenzene, pyridine, methylene chloride, 2-nitroproane. 
Solvents from revised risk analysis indicating a potential risk in 
unlined landfill scenario: benzene, 1,1,2-trichloroethane, 
chlorobenzene, methylene chloride, tetrachloroethylene, toluene, 
trichloroethylene, and xylene.
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     In the original risk screening analysis, we did not 
consider risks from lined landfills. The revised risk analysis does 
consider risks from composite lined non-hazardous waste landfills.
     In the original risk screening analysis, we did not 
identify any solvents of concern from laundry sludge. Our revised risk 
analysis indicates that tetrachloroethylene may be a concern in both 
solvent-contaminated wipes and laundry sludge disposed of in unlined 
and composite lined landfills.

G. Request for Comment

    We are seeking comment on all aspects of the revised risk analysis 
(landfill loading calculations, risk based mass loading levels, 
comparison document). In particular, we are seeking comment on:
    --The assumptions used;
    --Whether the uncertainties are properly acknowledged and 
mitigated, as appropriate;
    --The data used;
    --The methodology used; and
    --How the agency should consider using the results of the revised 
risk analysis in its decision-making.

III. Discussion and Request for Comment on Management Approaches and 
Risk Analysis Findings

    The Agency's November 2003 proposal allowed solvent-contaminated 
wipes and laundry sludge that met certain conditions to be sent either 
to a MSWLF or to another nonhazardous waste landfill that meets the 
standards under 40 CFR part 257, subpart B. We did not discuss the 
specific characteristics of MSWLFs receiving solvent-contaminated wipes 
or laundry sludge, specifically whether the landfill would be unlined 
or lined. Because our revised risk analysis indicates that a number of 
solvents show a potential for risk in unlined landfills (using the 90th 
percentile results and a risk criterion of 1 x 10-\5\ for 
cancer risk), we are considering two additional approaches for managing 
solvent-contaminated wipes and laundry sludge in landfills.
    The first approach would allow the disposal of solvents not showing 
a risk in any municipal landfill or nonhazardous waste landfill whether 
lined or unlined. The solvents that indicated a potential risk if 
disposed of in an unlined landfill \7\ could only be disposed in a 
lined municipal landfill or lined non-hazardous waste landfill. This 
could be accomplished by requiring disposal in a Subtitle D municipal 
or industrial landfill unit subject to, or otherwise meeting, the 
landfill requirements in 40 CFR 258.40(a)(2) and (b).8 9 The 
second approach would be to

[[Page 55168]]

establish conditions that allow all solvent-contaminated wipes, no 
matter which solvent they contain, except perhaps tetrachloroethylene, 
to be sent to a Subtitle D municipal or industrial landfill unit 
subject to, or otherwise meeting, the landfill requirements in Sec.  
258.40(a)(2) and (b). This approach could be simpler since the 
generator would not need to separate his wipes and send them to 
separate disposal locations. We are requesting comment on these two 
approaches.
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    \7\ Benzene, 1,1,2-trichloroethane, chlorobenzene, methylene 
chloride, toluene, trichloroethylene, and xylene.
    \8\ 40 CFR 258.40(a)(2) states: ``With a composite liner, as 
defined in paragraph (b) of this section and a leachate collection 
system that is designed and constructed to maintain less than a 30-
cm depth of leachate over the liner. 40 CFR 258.40(b) states ``For 
purposes of this section, composite liner means a system consisting 
of two components; the upper component must consist of a minimum 30-
mil flexible membrane liner (FML), and the lower component must 
consist of at least a two-foot layer of compacted soil with a 
hydraulic conductivity of no more than 1 x 10-\7\cm/sec. 
FML components consisting of high density polyethylene (HDPE) shall 
be at least 60-mil thick. The FML component must be installed in 
direct and uniform contact with the compacted soil component.''
    \9\ Solvent-contaminated wipes, while not required, could also 
be disposed of in a hazardous waste landfill meeting the landfill 
requirements in 40 CFR 264.301 or 265.301.
---------------------------------------------------------------------------

    The risk analysis using 90th percentile results also indicates that 
tetrachloroethylene has a risk potential in both unlined landfills and 
composite lined landfills for both solvent-contaminated wipes and 
laundry sludge (using a cancer risk criterion of 1 x 
10-\5\). Using the higher end cancer risk value in our 
analysis, the ratio of the ELLR to the RB-MLL for tetrachloroethylene 
was 1.1, while using the lower end cancer risk value the ratio was 0.9. 
If we rounded the numbers, the ratios would both be 1.0. Since we 
generally used a conservative approach in the risk analysis, we are 
asking for comment on whether our results represent a risk of concern.
    Even though the risk may be borderline, we are considering 
alternative management conditions for tetrachloroethylene to address 
this potential risk. One approach is to prohibit disposal of 
tetrachloroethylene, either on solvent-contaminated wipes or in laundry 
sludge that exhibits the tetrachloroethylene toxicity characteristic 
(TC) in nonhazardous waste landfills. Another approach could be 
eliminating wipes contaminated with tetrachloroethylene from the scope 
of the final exclusions for solvent-contaminated wipes, or eliminating 
wipes contaminated with tetrachloroethylene that exhibit the TC in the 
scope of the final exclusions for solvent-contaminated wipes. We are 
requesting comment on these approaches or other possible alternatives.

IV. Conclusion

    We will consider comments received on the revised risk analysis and 
then modify the analysis as appropriate. The final risk analysis, 
comments submitted in response to Section III of this notice, and 
comments submitted in response to the November 2003 proposed rule will 
be considered as we develop a final rule for the management of solvent-
contaminated wipes.
    Readers should note that other than the specific issues identified 
in this NODA, no other issues discussed in or related to the November 
20, 2003, proposed rule are open for further comment and the Agency 
will not respond to any comments received on any issues not identified 
in this NODA.

    Dated: October 15, 2009.
Mathy Stanislaus,
Assistant Administrator, Office of Solid Waste and Emergency Response.
[FR Doc. E9-25812 Filed 10-26-09; 8:45 am]

BILLING CODE 6560-50-P