[Federal Register Volume 83, Number 246 (Wednesday, December 26, 2018)]
[Proposed Rules]
[Pages 66210-66223]
[FR Doc No: 2018-27748]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 258

[EPA-HQ-RCRA-2015-0354; FRL-9988-41-OLEM]
RIN 2050-AG86

Revisions to the Criteria for Municipal Solid Waste Landfills To
Address Advances in Liquids Management

AGENCY: Environmental Protection Agency (EPA).

ACTION: Advance Notice of Proposed Rulemaking.

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SUMMARY: The Environmental Protection Agency (EPA) is considering
whether to propose revisions to the criteria for Municipal Solid Waste
Landfills (MSWLFs) to support advances in effective liquids management.
To this end, EPA is seeking information relating to: Removing the
prohibition on the addition of bulk liquids to MSWLFs; defining a
particular class of MSWLF units (i.e., bioreactor landfill units) to
operate with increased moisture content; and establishing revised MSWLF
criteria to address additional technical considerations associated with
liquids management, including waste stability, subsurface reactions,
and other important safety and operational issues. This Advance Notice
of Proposed Rulemaking (ANPRM) also discusses the results of related
research conducted to date, describes EPA's preliminary analysis of
that research, and seeks additional scientific studies, data, and
public input on issues that may inform a future proposed rule. The EPA
is not reopening any existing regulations through this ANPRM.

DATES: Comments must be received on or before March 26, 2019. If
necessary, EPA may convene a public meeting to collect more information
on this issue after the close of the public comment period. The EPA
would provide notice

and details of such a meeting on its website.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
RCRA-2015-0354 to the Federal eRulemaking Portal: http://www.regulations.gov. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or withdrawn. The
EPA may publish any comment received to its public docket. Do not
submit electronically any information you consider to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. If you need to include CBI as part of your
comment, please visit http://epa/gov/dockets/comments.html for
instructions. Multimedia submissions (audio, video, etc.) must be
accompanied by a written comment. The written comment is considered the
official comment and should include discussion of all points you wish
to make. For additional submission methods, the full EPA public comment
policies, and general guidance on making effective comments, please
visit http://www.epa.govdockets/comments.html.
    The EPA's policy is that all comments received will be included in
the public docket without change including any personal information
provided, unless the comment includes profanity, threats, information
claimed to be CBI or other information whose disclosure is restricted
by statute.

FOR FURTHER INFORMATION CONTACT: For questions regarding this ANPRM,
contact Craig Dufficy or John Sager, Materials Recovery and Waste
Management Division of the Office of Resource Conservation and Recovery
(mail code 5304P), U.S. Environmental Protection Agency, 1200
Pennsylvania Avenue NW, Washington, DC 20460; Craig Dufficy telephone:
703-308-9037; email<EMAIL_ADDRESS>John Sager telephone: 703-
308-7256; email<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: The following outline is provided to aid in
locating information in this preamble.

I. Does this action apply to me?
II. What action is EPA contemplating?
III. Regulatory Background
    A. RCRA Subtitle D MSWLF Regulations
    B. RCRA MSWLF RD&D Rule
    C. Air Emissions Regulations
IV. Bioreactor Landfill Research History
    A. Project XL and CRADAs
    B. Report: Bioreactor Landfills, State of the Practice Review
    C. Report: Permitting of Landfill Bioreactor Operations: Ten
Years After the RD&D Rule
    D. RCRA MSWLF RD&D Annual Reports
V. Potential Environmental Benefits, Cost Savings, and Environmental
Considerations
    A. Potential Environmental Benefits
    B. Potential Cost Savings
    C. Environmental Considerations
    1. Groundwater Considerations
    2. Air Emissions Considerations
VI. Additional Technical Considerations
VII. Characteristics of Bioreactor Landfill Units and Wet Landfill
Units
VIII. Universe of MSWLFs Potentially Affected by This ANPRM
IX. Relationship to Organics Diversion and Composting Programs
X. What information is EPA seeking?
    A. Information on Benefits and Risks of Bioreactor Landfill
Units and Wet Landfill Units
    B. Questions on Characteristics of Bioreactor Landfill Units and
Wet Landfill Units
    C. Questions on Operations and Post-Closure Care
    D. Questions on Potential Risks
    E. Questions on Potential Costs and Benefits
XI. Statutory and Executive Order Review
XII. Conclusion

I. Does this action apply to me?

    Entities potentially affected by a future rulemaking on liquids
management in Municipal Solid Waste Landfills (MSWLFs), including
public or private owners or operators of MSWLF units, may be interested
in commenting on this ANPRM. Potentially affected categories and
entities include the following:

           Table 1--Categories of Potential Affected Entities
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                Category                   Example of affected entities
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Federal Government.....................  Agencies procuring waste
                                          services.
State Governments......................  Regulatory agencies and
                                          agencies operating landfills.
Industry...............................  Owners or operators of
                                          municipal solid waste
                                          landfills.
Municipalities, including Tribal         Owners or operators of
 Governments.                             municipal solid waste
                                          landfills.
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    The potentially affected entities may also fall under the North
American Industry Classification System (NAICS) code 924110, Sanitation
engineering agencies, government; or 562212, Solid Waste Landfill. The
industry sector(s) identified above may not be exhaustive; other types
of entities not listed may also be affected. If you have any questions
regarding the applicability of a future final rule to a particular
entity, contact the person listed in the following section.

II. What action is EPA contemplating?

    The EPA is considering whether to propose revisions to the criteria
in 40 CFR part 258 to support advances in effective liquids management.
The purpose of this ANPRM is to solicit data and information to inform
our thinking on this potential action.
    First, EPA is evaluating whether to propose easing current
restrictions on the addition of liquids in order to promote accelerated
biodegradation of the waste. Time-limited variances for liquids
addition are currently allowed at facilities with Research, Development
and Demonstration (RD&D) permits authorized under 40 CFR 258.4. The EPA
is considering whether it would be appropriate to propose removing the
prohibition on the addition of bulk (i.e., non-containerized) liquids
and providing for the operation of bioreactor landfill units outside of
the current RD&D program.
    Second, future revisions could also include defining a new class of
MSWLF units with specific requirements for how liquids may be managed
in such units. For example, bioreactor landfill units were described in
the preamble to the 2004 RD&D rule as units in which the controlled
addition of non-hazardous liquid wastes or water accelerates
biodegradation and landfill gas (LFG) generation.\1\ A future proposed
definition under the Resource Conservation and Recovery Act (RCRA)
could also be quantitative in nature, such as by employing a specified
percentage of moisture content or more by weight as a threshold
criterion. Any future proposed definition might also include other
factors such as the average amount of annual precipitation in an area;
whether liquids are added intentionally for any purpose other than
cleaning, maintenance, and wetting of daily cover; whether leachate is
recirculated; and the magnitude of the

first-order biodegradation constant (k) discussed later in this
document. Relatedly, EPA also believes that there may be some MSWLFs
operating at high levels of moisture content (so-called ``wet landfill
units'') that can be distinguished from bioreactor landfill units to
which liquids are purposefully added. \2\ Specific characteristics that
may be considered in developing a RCRA definition for a bioreactor
landfill unit or a wet landfill unit are discussed later in Section VII
of this ANPRM. As in the 2004 RD&D rule preamble, bioreactor landfill
units are generally characterized by the intentional addition of
liquids to accelerate biodegradation, while the term wet landfill unit,
which does not have a RCRA regulatory definition, is generally used to
describe landfill units with a high moisture content, whether
intentional or not. The intent of this ANPRM is to draw a distinction
between these terms and consider possible revisions to Part 258.
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    \1\ 69 FR 13251, March 22, 2004, Research, Development and
Demonstration Permits Rule for MSWLFs.
    \2\ The terms ``wet,'' ``leachate recirculation,'' and
``bioreactor'' are sometimes used interchangeably in technical and
popular literature to describe a landfill operated under conditions
of elevated in-situ moisture content. The EPA also defines
bioreactor landfills under the Clean Air Act NESHAP for MSWLFs.
Unless otherwise noted, in this ANPRM the term ``bioreactor landfill
unit'' refers to those units meeting the description contained in
the 2004 RD&D preamble, and ``wet landfill unit'' refers to MSWLFs
with elevated moisture content under consideration for possible
revisions to Part 258.
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    Third, EPA is also considering whether other revisions to Part 258
may be necessary for MSWLFs operating as bioreactor landfill units or
wet landfill units. These issues include whether to revise the design
and operating criteria under Part 258 to address important safety and
operational issues related to leachate collection, waste stability,
subsurface reactions, and other issues. These are discussed in Section
VI below. For informational purposes, Section IV of this ANPRM also
discusses the results of related research conducted to date and
describes EPA's preliminary analysis of that research.
    Any revisions to Part 258 in a subsequent, proposed rulemaking
could be narrowly tailored to focus on facilities that choose to add
bulk liquids or otherwise operate as bioreactor landfill units.
Alternatively, such revisions could be broadly applicable to address
liquids management practices at all facilities. The EPA is not making
any specific proposal through this ANPRM and plans to evaluate the data
and comments received in response to this ANPRM before proposing any
specific action.
    With this notice, EPA is seeking public input on key issues at this
preliminary stage to inform its thinking on any future proposed
rulemaking. The EPA is not reopening any existing regulations through
this ANPRM. The EPA anticipates that any revisions would be proposed
under the authority of RCRA sections 1008, 2002, 4004, 4005 and 4010,
42 U.S.C. 6907, 6912, 6944, 6945, and 6949a. At that time, EPA would
take public comment on those proposed revisions.

III. Regulatory Background

A. RCRA Subtitle D MSWLF Regulations

    Under RCRA Subtitle D, as amended by the Hazardous and Solid Waste
Amendments of 1984, 42 U.S.C. 6941-6949a, EPA promulgated minimum
national standards in 1991 \3\ for owners and operators of MSWLFs at 40
CFR part 258, subparts A through G. The EPA has revised Part 258 on
several occasions since 1991.\4\ The regulations specifically include
seven subparts: (1) General provisions, including RD&D permits; (2)
location restrictions; (3) operating criteria; (4) design criteria; (5)
groundwater monitoring and corrective action; (6) closure and post-
closure care; and (7) financial assurance.
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    \3\ 56 FR 50978 (October 9, 1991), 40 CFR parts 257 and 258,
Solid Waste Disposal Facility Criteria, Final Rule.
    \4\ https://www.epa.gov/landfills/municipal-solid-waste-landfills.
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    Under RCRA Subtitle D, approved states are to have permitting
programs or other systems of prior approval to ensure that all MSWLFs
in the state meet the federal minimum criteria. The EPA reviews and
approves state permit programs in accordance with 40 CFR part 239. Upon
EPA approval, a state program may provide flexibility for owners and
operators of MSWLF units, as allowed by Part 258. For example, an
approved state program may allow an owner/operator to use an
alternative material or an alternative thickness for daily cover.
    When promulgated in 1991, EPA's MSWLF regulations were intended to
have the effect of keeping the contents of the unit as dry as possible.
While EPA recognized at the time that moisture was necessary to promote
biodegradation and waste stabilization,\5\ there was concern that the
risk of liner leakage and groundwater contamination increased as the
moisture content increased. Based on data available at that time, EPA
believed that minimizing the amount of liquid in a landfill was
necessary to reduce the possibility of groundwater contamination
resulting from the leakage of leachate; reduce possible damage to the
liner and final cover of the unit resulting from waste subsidence; and
reduce the buildup of hydrostatic pressure on the liner due to the
``bathtub'' \6\ effect, when the combined rate of liquids addition and
infiltration outpaced the leachate removal rate. To address these
risks, the regulations prohibit disposal of bulk liquids in MSWLFs and
require low permeability final cover systems. The design criteria in
258.40 indicate that, unless an alternative is approved, new units and
lateral expansions are to be operated with a composite liner and
leachate collection system that is designed and constructed to maintain
a maximum allowable hydraulic head on the liner of 30 cm. The resulting
design has accordingly come to be referred to as a ``dry-tomb
landfill.'' \7\
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    \5\ 56 FR 51055 (October 9, 1991), 40 CFR parts 257 and 258,
Solid Waste Disposal Facility Criteria, Final Rule.
    \6\ See 53 FR 33356 (August 30, 1988), 40 CFR parts 257 and 258,
Solid Waste Disposal Facility Criteria, Proposed Rule; the
``bathtub'' effect is an analogy used to describe filling up a
landfill with liquids faster than the the leachate collection system
can remove them.
    \7\ 81 FR 28720, May 10, 2016, Revision to the Research,
Development and Demonstration Permits Rule for MSWLFs.
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B. RCRA MSWLF RD&D Rule

    In 2004, EPA promulgated the RD&D rule at 40 CFR 258.4 \8\ to
expand research into liquids addition and other innovative landfill
practices. The RD&D rule enables the director of an approved state
waste management program to issue time-limited RD&D permits for the use
of innovative methods that can vary the liquids restrictions in 40 CFR
258.28(a) and the run-on/run-off control systems in 40 CFR
258.26(a)(1), provided that the MSWLF unit has a leachate collection
system designed and constructed to maintain less than 30 cm of leachate
on the liner. The RD&D permits can also vary the final cover criteria
of Sec.  258.60(a)(1), (a)(2) and (b)(1), provided that the owner/
operator demonstrates that the infiltration of liquid through the
alternative cover system will not cause contamination of groundwater or
surface water, or cause leachate depth on the liner to exceed 30 cm.
All RD&D permits issued under 40 CFR 258.4 are required to include
terms and conditions as protective as the MSWLF criteria in Part 258 to
assure protection of human health and the environment. After the
initial permit term of three years, owner/operators may apply to the
director of an approved state program to renew the RD&D permit for an
additional three-

year term. The initial RD&D rule allowed three renewals for a maximum
permit term of 12 years. In 2016, EPA amended the RD&D rule to extend
the maximum permit term to 21 years.\9\
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    \8\ 69 FR 13242, March 22, 2004, Research, Development and
Demonstration Permits Rule for MSWLFs.
    \9\ 81 FR 28720, May 10, 2016, Revision to the Research,
Development and Demonstration Permits Rule for MSWLFs.
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    As shown in Table 2, 16 states have approved RCRA Subtitle D RD&D
programs. Among these states, EPA believes there are 35 facilities
operating bioreactor landfill units with RD&D permits providing
variances allowing liquids additions. The EPA has also issued a site-
specific rule for the Salt River Landfill facility in Indian Country
that authorizes, in part, the operation of a research, development, and
demonstration bioreactor landfill.\10\ All facilities with RD&D permits
are required to submit annual performance reports to their state waste
management programs demonstrating progress toward project goals. The
EPA's site-specific rule for the Salt River Landfill also requires
annual reports to EPA. The most recent annual reports available to EPA
are shown in Table 2. The EPA provides information on its preliminary
review of this information in Section IV.4 below.
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    \10\ 74 FR 11677, March 19, 2009, Final Determination to Approve
Research, Development, and Demonstration Request for the Salt River
Landfill.

                                       Table 2--RD&D Permitted Facilities
----------------------------------------------------------------------------------------------------------------
                                         Date program                                               Date latest
                 State                    approved by        Listing of permitted facilities       annual report
                                           EPA \11\                                               available \12\
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Alaska................................            2011  Anchorage Regional Landfill, Eagle River            2009
                                                        Central Peninsula Landfill, Soldotna....            2017
                                                        Fairbanks North Star Borough Landfill,              2018
                                                         Fairbanks.
                                                        Palmer Central Landfill, Palmer.........            2014
California............................            2007  CWM Kettleman Hills Facility, Kettleman             2010
                                                         City.
                                                        Yolo County Central Landfill, Woodland..            2005
Illinois..............................            2006  River Ben Prairie Landfill, Cook County.            2018
Indiana...............................            2005  None....................................             N/A
Iowa..................................            2009  None....................................             N/A
Kansas................................            2009  Barton County Landfill, Great Bend......            2016
                                                        Johnson County Landfill, Shawnee........            2017
                                                        Plumb Thicket Landfill, Harper..........            2016
                                                        Seward County Landfill, Liberal.........            2015
                                                        Western Plains Landfill, Finney County..            2017
Massachusetts.........................            2013  None....................................             N/A
Michigan..............................            2006  Midland City Landfill, Midland..........            2016
                                                        Smiths Creek Landfill, St. Clair........            2016
Minnesota.............................            2005  Spruce Ridge Landfill, Plymouth.........            2015
Missouri..............................            2006  City of Columbia Landfill, Columbia.....            2017
Nebraska..............................            2008  None....................................             N/A
New Hampshire.........................            2010  None....................................             N/A
Ohio..................................            2011  None....................................             N/A
Oregon................................            2013  Columbia Ridge Landfill, Arlington......            2018
                                                        Finley Buttes Regional Landfill,                    2016
                                                         Boardman.
Virginia..............................            2009  Maplewood Landfill, Amelia County.......            2010
Wisconsin.............................            2006  Cranberry Creek Landfill, Wood County...            2017
                                                        Deer Track Park Landfill, Watertown.....            2017
                                                        Emerald Park Landfill, Waukesha County..            2017
                                                        Glacier Ridge Landfill, Horicon.........            2017
                                                        Hickory Meadows Landfill, Hilbert.......            2017
                                                        La Crosse County Landfill, La Crosse                2017
                                                         County.
                                                        Lake Area Landfill, Sarona..............            2017
                                                        Mallard Ridge Landfill, Walworth County.            2017
                                                        Metro Landfill, Franklin................            2017
                                                        Orchard Ridge Landfill, Menomonee Falls.            2017
                                                        Pheasant Run Landfill, Paris............            2017
                                                        Ridgeview Landfill, Whitelaw............            2017
                                                        Seven Mile Creek Landfill, Eau Claire...            2017
                                                        Timberline Trail Landfill, Stubbs.......            2017
                                                        Valley Trail Landfill, Berlin...........
Salt River Pima-Marcopa Indian           Site-specific  Salt River landfill, Phoenix                        2011
 Community (Arizona).                             rule   Metropolitan Area.
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C. Air Emissions Regulations

    As will be seen in the discussion of bioreactor landfill research
in the next section of this notice, one of the primary characteristics
of bioreactor landfill units is that the rate of LFG generation is
accelerated. Should EPA propose in a subsequent rulemaking to move
bioreactor landfill operations outside of RD&D permits, EPA intends to
evaluate changes to the RCRA regulations to ensure that LFG gas
emissions are properly controlled in compliance with existing emissions
regulations. Air emissions from MSWLFs are regulated under the RCRA
Subtitle D regulations as well as EPA regulations issued pursuant to
two Clean Air Act (CAA)

programs, the National Emission Standards for Hazardous Air Pollutants
(NESHAP), and the New Source Performance Standards (NSPS). The RCRA
rules impose standards to limit methane generation to a level below the
Lower Explosive Limit (LEL) to prevent landfill fires and explosions
that can kill or injure and damage containment structures and thereby
cause emissions of toxic fumes.\13\ By contrast, the CAA regulations
for air emissions principally address hazardous air pollutants (HAP)
and LFG, and they do not explicitly address methane. Yet, methane
comprises close to 50% of LFG \14\ on average, and EPA understands that
adding liquids increases the rate of LFG generation. Thus, EPA plans to
examine whether an increase in methane surface emissions may also
result in exceedances of the current explosive gas limits in Part 258.
Consequently, in any proposal to amend the RCRA rules to allow bulk
liquids addition, EPA expects the need to consider the implications of
enhanced methane generation at such units.
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    \11\ Date listed is when the state RD&D Program was approved.
    \12\ Date listed is most recent report available to EPA; ``N/A''
means that EPA is not aware of any permitted facility in a state
that is approved to issue an RD&D permit.
    \13\ 56 FR 51051-52.
    \14\ See https://www.epa.gov/lmop/basic-information-about-landfill-gas.
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    As mentioned, the RCRA Subtitle D standards for MSWLFs address
explosive gas control. Section 258.23 of those rules specifies that the
concentration of methane generated by a MSWLF must not exceed 25% of
the lower explosive limit (LEL) in facility structures, and it must not
exceed the LEL for methane at the property boundary. The rules also
require a routine methane monitoring program to ensure those standards
are met. (40 CFR 258.23(b).) If methane levels exceed the standards,
the owner or operator must immediately take all necessary steps to
ensure protection of human health and safety and notify the regulatory
authority; place in the operating record information on the gas levels
detected and steps taken to protect human health; and implement a
remediation plan. (40 CFR 258.23(c))
    The MSWLF NESHAP was promulgated in 2003 and is scheduled for a
Residual Risk and Technology Review (RTR) due in 2020. Bioreactor
landfill units are defined in the NESHAP to be a MSWLF or portion of a
MSWLF to which any liquid other than leachate (leachate includes LFG
condensate) is added in a controlled fashion into the waste mass (often
in combination with recirculating leachate) to reach a minimum average
moisture content of 40% by weight to accelerate or enhance the
anaerobic (without oxygen) biodegradation of the waste. The NESHAP
requires bioreactor landfill units to install and operate LFG
collection systems within six months of reaching the 40% moisture
content threshold. The MSWLF NSPS and Emission Guidelines (EG) were
promulgated in 1996, followed by a revised NSPS/EG in 2016. The NSPS/EG
rules, currently under reconsideration, require LFG collection 30
months after emissions reach a threshold of 34 metric tons (revised
from a 50 metric ton threshold in the 1996 rules) of non-methane
organic compounds (NMOCs) or more per year.

IV. Bioreactor Landfill Research History

    After promulgation of the Part 258 standards in 1991, EPA
increasingly became aware that landfill technology was evolving and
that alternative designs and operations could benefit from further
study through research and demonstration projects. Research initiated
in the 1970s and 1980s by the University of Wisconsin--Madison \15\ and
Georgia Institute of Technology \16\ contributed to EPA's understanding
of the potential benefits of liquids addition. The EPA has been
researching \17\ bioreactor landfill units and liquids addition since
2001.
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    \15\ Ham & Bookter, 1982; Barlaz et al., 1987 as referenced in
``Bioreactor Landfills State-Of-The Practice Review,'' U.S.
Environmental Protection Agency, Washington, DC, EPA/600/R-09/071.
    \16\ Pohland, 1975; Pohland & Harper, 1986 as referenced in
``Bioreactor Landfills State-Of-The Practice Review,'' pages iv-vi,
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
071.
    \17\ As used in this ANPRM, the term ``EPA research'' is used to
describe EPA cooperative efforts with and analysis of data from
facilities with variances for liquids addition granted through the
Project XL, CRADA, and RD&D programs. Variances were granted with
the understanding that performance data would be shared with EPA and
the states. The EPA is not the owner/operator of these facilities
where full-scale landfill operations are taking place.
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    That year, EPA's Office of Research and Development (ORD) began
conducting research through EPA's Project XL program and the use of
Cooperative Research and Development Agreements (CRADAs). Project XL,
which stands for ``eXcellence and Leadership,'' was a national pilot
program that allowed state and local governments, businesses and
federal facilities to work with EPA to develop innovative technologies
and more cost-effective ways of achieving environmental and public
health protection. As part of these partnerships, EPA issued
regulatory, program, policy, or procedural flexibilities to conduct the
work. Beginning in 2001, four bioreactor landfills were accepted into
Project XL, including those in Buncombe County, North Carolina; Yolo
County, California; King George County, Virginia; and the Maplewood
facility in Amelia Country, Virginia.
    The use of CRADAs was a means for EPA to promote collaborative
research between EPA's ORD and external parties. Bioreactor landfill
units operating with CRADAs \18\ included the Outer Loop Landfill in
Louisville, Kentucky, and the Polk County Landfill in Florida. The
purpose of the research conducted at these Project XL and CRADA sites
was to allow the landfills to add non-hazardous and non-containerized
liquids and investigate the impact on waste biodegradation and
stabilization.
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    \18\ See EPA Docket # EPA-HQ-RCRA-2015-0354 for summaries of the
Outer Loop, Buncomb County, and Yolo County landfills.
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    In 2004, EPA promulgated the RD&D rule as described in Section
III.2 above. The EPA believes there are 35 facilities with RD&D permits
involving variances for liquids management including the addition of
bulk liquids. The EPA has also issued a site-specific rule for the Salt
River Landfill facility in Indian Country that in part authorizes
operation of a research, development, and demonstration bioreactor
landfill.
    In preparing this ANPRM, EPA has reviewed and made a preliminary
analysis of data from approximately 41 landfill facilities with
variances for liquids addition granted through the Project XL, CRADA
and RD&D research programs. Data analysis from the Project XL and CRADA
facilities draws extensively from the 2007 ``Bioreactor Landfills
State-Of-The Practice Review'' published by ORD. Data analysis from the
35 RD&D-permitted facilities, along with additional data analysis from
the Project XL and CRADA facilities, draws extensively from the 2014
ORD report ``Permitting of Landfill Bioreactor Operations: Ten Years
after the RD&D Rule.'' The EPA also compiled and reviewed the most
recent annual reports available from the facilities identified in Table
2 above.\19\ The EPA presents examples of these data in the sub-
sections below. Later, in Section V, EPA discusses potential benefits
and environmental considerations associated with bioreactor landfill
units based on preliminary analysis of the data now available to it.
Should EPA determine after further analysis to proceed with a
rulemaking proposal,

that proposal will be based on additional risk evaluation.
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    \19\ These reports and other citations for this ANPRM are
accessible via http://www.regulations.gov (Federal eRulemaking
Portal) using ID No. EPA-HQ-RCRA-2015-0354.
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A. Project XL and CRADAs

    Summary data from the Outer Loop facility in Kentucky, the Yolo
County landfill in California, and the Buncombe County facility in
North Carolina are presented below. The data as presented are intended
to be illustrative but not a comprehensive summary of the operation and
performance of these facilities.
1. Outer Loop Landfill
    The Outer Loop Landfill Bioreactor (OLLB) project in Louisville, KY
\20\ studies solid waste decomposition, moisture balance, LFG
generation, and leachate quality to evaluate the effect of bioreactor
landfill operations on municipal solid waste (MSW) decomposition.
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    \20\ ``Landfill Bioreactor Performance: Second Interim Report
Outer Loop Recycling and Disposal Facility,'' EPA/600/R-07/060,
September, 2006.
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Operations
    The OLLB study evaluates three types of landfill cells: (i) Control
cells, in which no liquids were added; (ii) cells in which liquids were
added after the cell had been completely filled with waste (the
Retrofit cells); and (iii) cells in which liquids and air were added as
the waste was placed in the landfill (the As-Built cells).
Reported Results
     The results of the moisture balance calculations indicate
an increase in moisture content of six to seven percent in the As-Built
cells, an increase of approximately one percent in the Retrofit cells
and a slight decrease in the Control cells during the 2000-2005 study
period.
     Data regarding leachate head in the sump, which was used
as an indirect indicator of leachate head on the liner, indicated that
operating a landfill as a bioreactor caused an overall increase in
leachate head in the sump compared to the Control cells. However, in
all three cases, the average leachate level on the liner was well below
the 30 cm maximum allowable head.
     Based on data evaluated in the 2006 Outer Loop Second
Interim Report, there is no indication that the bottom liner system of
the test cells was compromised while installing liquid application
features, or while applying liquid through those features.
     While variable, the rate of LFG generation in the As-Built
bioreactor landfill cell was greater than that of the Control cell,
potentially providing a greater rate of energy production if collection
occurred early and consistently.
     The LFG decay constant (k value \21\) for As-Built
bioreactor landfill cells was evaluated to be 0.16 yr-1 while the
Retrofit cells and the Control cells had a k valueof approximately
0.061 yr-1.
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    \21\ The ``k'' value is a biodegradation constant; the higher
the k value, the higher the rate of biodegradation. See https://www3.epa.gov/ttn/chief/ap42/ch02/index.html for further discussion
of k values. Also see ``Impact of Accelerated Biodegradation'' in a
memo to the docket for this ANPRM by John Sager, USEPA, September
24.
---------------------------------------------------------------------------

    Although the concentration (ppmv) of non-methane organic carbon
(NMOC) in the collected LFG did not appear to be higher in the
bioreactor landfill cells compared to the Control cells, the
overallproduction was higher because of the higher gas flow rate.
     Evaluation of the biochemical oxygen demand to chemical
oxygen demand ratio (which is generally an indicator of organic solids
decomposition) revealed that waste decomposition in the As-Built
bioreactor landfill cells may have been accelerated compared to the
Control cells.
     Overall, the analysis of the data collected during the
first five years indicate that the addition of liquids accelerated
waste degradation based on leachate quality and solid waste
decomposition data. The LFG quantity data indicate that the decay rate
was highest in the As-Built cell and lowest in the Control cell.
2. Yolo County Central Landfill, California
    The goal of the Yolo County Central landfill project \22\ is to
manage landfill solid waste for rapid waste decomposition, maximum LFG
generation and capture, and minimum long-term environmental
consequences.
---------------------------------------------------------------------------

    \22\ ``Full Scale Landfill Bioreactor Project at the Yolo County
Central Landfill,'' Yazdani, Kieffer, Akau, 2002; ``Full Scale
Bioreactor Landfill for Carbon Sequestration and Greenhouse Gas
Emission Control, Final Technical Progress Report,'' Yazdani,
Kieffer, Sananikone, Augenstein, March 2006, D.O.E. Award Number DE-
FC26-01NT41152; and ``Controlled Bioreactor Landfill Program at the
Yolo County Central Landfill,'' Yazdanie, Kieffer, Sananikone,
Methane to Markets Partnership Expo, Beijing, China, November, 2007.
---------------------------------------------------------------------------

Operations
     Waste decomposition is accelerated by improving conditions
for either the aerobic or anaerobic biological processes and involves
circulating controlled quantities of liquid (leachate, groundwater,
gray water, etc.), and, in the aerobic process, large volumes of air.
     Cover cells with surface membrane for high-efficiency gas
capture; and liquid addition to the first (enhanced) cell, but not the
second (control) cell.
     The gas capture cover system was installed before liquid
addition was initiated.
Reported Results
     Over five-fold acceleration of methane production.
     Reduction of fugitive methane emissions to <5% of
generated LFG.
     Rapid and extensive volume reduction in the enhanced cell
compared to the control cell.
     Waste stabilization (indicated by methane recovery, air-
space volume loss and other indicators) compared to the dry-tomb
control.
     Observed leachate head over the base liner was 2 inches,
and less than 20% of the 30 cm maximum hydraulic head allowed under
Part 258.
     Settlement in the 3.5-acre study enhanced cell averaged
8.5% of the waste mass, and settlement in the 6-acre control cell
averaged 4% of the waste mass.
     Landfill stabilization and completed LFG generation are
estimated to be complete at 15 years for full-scale cells.
3. Buncombe County, North Carolina Landfill
    The Buncombe County bioreactor landfill \23\ is a full-scale
implementation of a bioreactor landfill system performed in two phases.
---------------------------------------------------------------------------

    \23\ USEPA PROJECT XL Buncombe County Bioreactor Project, 2011
and 2014 Progress Reports, CDM Smith.
---------------------------------------------------------------------------

Operations
     Phase 1 is a retro-fit system; the trenches were installed
after the landfill cells were filled to capacity. The Phase 1 Retrofit
System was installed in Cells 1-5 and has been in operation since April
2007.
     Phase 2 is a build-as-you-go, full-scale bioreactor
landfill system; the infrastructure was installed in stages as the
waste was being placed. The build-as-you-go approach provides more
extensive wetting of the waste and earlier capture of LFG.
     This project was granted regulatory flexibility to apply
liquids other than leachate to the waste. As of 2011, only leachate had
been used since there was adequate leachate available onsite to meet
the needs of the project.
     In 2011, the County completed construction of a 1.4 MW
landfill gas-to-energy project at the site. Part of the project
included the installation of 25 vertical gas wells in Cells 1-5 in the
Retrofit System, and the gas collection component of the Phase 1
Retrofit System was removed. It was decided

that dedicating the bioreactor landfill cell trenches to leachate
recirculation and using the vertical wells for gas collection would be
simpler to operate and provide a more consistent flow of LFG to the
generator.
Reported Results
     Cumulatively, 4 million gallons of leachate were
recirculated, resulting in an estimated 803 fewer truck trips to the
wastewater treatment plant and $306,758 in hauling cost savings.
     Significant settlement occurred in the closed landfill
cells receiving leachate recirculation, leading to a more stable ground
surface layer, while adding the equivalent of 5 months of capacity
valued at nearly $2 million.
     Landfill stabilization and completed LFG generation are
estimated to be complete at 15 years for the full-scale cells.
     A surface cover geomembrane was used as a temporary cover
(when no cell activity) to prevent gas emissions to the atmosphere and
confine gas to the conductive layer just below the surface.
     No downgradient groundwater contamination has been
identified through 2017 from groundwater monitoring.\24\
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    \24\ The ``2017 Environmental Monitoring and Reporting Form''
submitted to the North Carolina Department of Environmental Quality
suggested possible groundwater exceedances; these were identified as
background contamination in telephone communication November 20,
2017, USEPA and NCDEQ.
---------------------------------------------------------------------------

B. Report: Bioreactor Landfills, State of the Practice Review

    In 2009, ORD published the report ``Bioreactor Landfills, State of
the Practice Review'' (State of the Practice report) \25\. The State of
the Practice report includes the following summary conclusions:
---------------------------------------------------------------------------

    \25\ C. Benson, M. Barlaz, and T. M. Tolaymat. ``Bioreactor
Landfills State-Of-The Practice Review,'' pages iv-vi, U.S.
Environmental Protection Agency, Washington, DC, EPA/600/R-09/071.
---------------------------------------------------------------------------

     Conventional containment systems (liners, covers, and
leachate collection systems) employed for conventional landfills
function effectively for bioreactor landfills.
     Action leakage rates were never exceeded and flow rates
were similar between conventional and bioreactor landfill cells where
comparisons were possible.
     Concentrations of heavy metals and organic compounds are
similar in bioreactor landfills and conventional landfills, and leakage
rates for conventional and bioreactor landfills are comparable.
     Bioreactor landfill operations employing conventional
containment technologies (including alternative liners) do not impose
greater risk to groundwater than conventional landfills.
     Methane generation at bioreactor landfills is accelerated
relative to predicted rates.
     There is no indication that gas production increases
appreciably as the moisture content increases above 40%.
    In addition to these findings, another finding of the study was
that insufficient data were being collected at commercial and municipal
landfills to fully evaluate whether bioreactor landfill methods used in
practice are effective in enhancing waste degradation, stabilization,
and gas generation. Future studies should include more detailed
monitoring and evaluation schemes that can be used to form definitive
conclusions regarding the effectiveness of bioreactor landfill
operational methods.

C. Report: Permitting of Landfill Bioreactor Operations: Ten Years
After the RD&D Rule

    In 2014, ORD published ``Permitting of Landfill Bioreactor
Operations: Ten Years After the RD&D Rule.'' \26\ The report found
that, since promulgation of EPA's MSWLF criteria in 1991, a growing
number of landfill sites have practiced leachate recirculation as well
as addition of bulk free liquids, generally under ad hoc state-level
research and development programs (e.g., the Florida Bioreactor
Demonstration Project) or site-specific permitting mechanisms
administered in association with EPA, such as described above. The
report identifies a number of associated economic and environmental
benefits, including: The acceleration of LFG generation; minimization
of the need for leachate treatment and offsite disposal; more rapid
reduction in concentration of leachate constituents of concern; and an
increase in the rate of landfill settlement. The report also concludes
that bioreactor landfill unit operations require increased levels of
engineering design, operational control, and monitoring to safely
achieve the benefits of accelerated LFG generation and meet EPA's goals
for protection of human health and the environment. Additional
challenges for bioreactor landfill management that are identified in
the report include issues with temperature control and increased LFG
collection and associated control. The study also identified that
buildup of saturated conditions and rapid waste settlement from
accelerated waste decomposition can compromise the structural stability
of the waste mass.
---------------------------------------------------------------------------

    \26\ Tolaymat, T. AND J. Morris. ``Permitting of Landfill
Bioreactor Operations: Ten Years after the RD&D Rule.'' U.S.
Environmental Protection Agency, Washington, DC, EPA/600/R-14/335,
2014.
---------------------------------------------------------------------------

D. RCRA MSWLF RD&D Annual Reports

    Research at MSWLFs with RD&D permits is ongoing, and as discussed
above, facilities with RD&D permits are required to submit annual
performance reports to their state waste management programs
demonstrating progress toward project goals. The EPA conducted a
preliminary review of these reports in 2018 looking specifically for
evidence of exceedances of groundwater protection standards, and we
found no evidence of significant exceedances resulting from bioreactor
landfill unit operations. For example, we found evidence of exceedances
of state action limits and other parameters that were attributed in the
reports we examined to background concentrations, activities at non-
bioreactor landfill cells, and normal variations.
    The EPA presents the following data from one 2016 annual report
\27\ as illustrative of the information and data in the reports. The
data as presented are not intended to be a comprehensive summary of the
operation and performance of this facility. In that report, the report
authors state the following:
---------------------------------------------------------------------------

    \27\ 2016 RD&D Annual Report, City of Midland, Michigan MSWLF;
CTI and Associates, Novi, Michigan; June, 2017.
---------------------------------------------------------------------------

     A total of 865,800 gallons has been added to the
bioreactor landfill unit since sludge acceptance began in August, 2014.
     The sludge application did not result in any odor issues
during the reporting period.
     The overall quality of leachate generated by the
bioreactor landfill unit does not appear to have been impacted by
sludge addition during the reporting period. Some of the components,
such as organic and suspended solids, were adequately treated by the
bioreactor landfill unit.
     Temperature of the waste mass was within a suitable range
for the development of microbial activity, therefore indicating the
addition of sludge did not have a negative impact on waste temperature.
     The predicted gas generation volume was in general
agreement with the measured data using the selected methane generation
parameters, including the relationship between the sludge addition and
the first order decay coefficient.
     The overall results of this analysis show that wastewater
digested sludge

can be safely received, transported, and applied to accelerate solid
waste decomposition.
    The EPA continues to analyze these reports and additional data and
information that are provided to the agency. As it does so, EPA will
consider questions such as those presented in Section X. Interested
stakeholders may thus use those questions as a guide in submitting data
and information in response to this ANPRM. The EPA notes that the
following questions are of particular importance in the evaluation of
site data to distinguish the potential risks of bioreactor landfill
units as compared to landfill units with lower moisture content,
including whether the addition of some kinds of bulk liquids may pose
greater risk than other kinds of bulk liquids:
    (1) What type and what quantity of bulk liquids were added to the
waste mass?
    (2) Is there evidence of groundwater contamination, air emissions
violations or other liquids management problems?
    (3) Was LFG collection required in the RD&D permit, and if so, when
was gas collection required in relation to the timing of liquids
addition?
    (4) Was gas collection infrastructure required to be installed
early in the construction of new cells, or were vertical wells inserted
at some point after cells were being filled?

V. Potential Environmental Benefits, Cost Savings, and Environmental
Considerations

A. Potential Environmental Benefits

    Based on research conducted at facilities with RD&D, Project XL and
CRADA-based permits discussed in Section IV above, the data from these
facilities and EPA analysis of the data suggest the following potential
environmental benefits from controlled liquids addition to MSWLFs:
     Acceleration of LFG generation rate, thereby decreasing
the duration of LFG generation potential and limiting the post-closure
care period during which air emissions can occur;
     Acceleration of LFG generation rate, thereby decreasing
the duration of LFG generation potential and limiting the post-closure
care period during which air emissions can occur;
     Minimization and potentially elimination of the need for
leachate treatment and offsite disposal, thereby decreasing the risk of
spills during transport and decreasing potential releases to the
environment during off-site treatment and disposal;
     More rapid reduction in concentrations of biodegradable
organic compounds, potentially limiting the post-closure care period
required for leachate control and decreasing the risk of releases of
contaminants to the air and groundwater during post-closure care;
     An increase in the rate of waste settlement and
compaction, thereby promoting more efficient utilization of permitted
landfill capacity;
     Enhanced opportunities for beneficial reuse of the
landfill property.
    The available data also suggest that bioreactor landfill units,
when compared to conventional dry-tomb MSWLF units, may offer the
potential for reduced long-term risk through decreased release of gas
emissions to the environment, faster waste subsidence and
stabilization, decreased transport and treatment of leachate, and
potentially a shorter period of time for post-closure care. The
economic benefits that may accrue include decreased costs for leachate
treatment and increased revenue from the use or sale of captured LFG
and acceptance of bulk liquid wastes. The EPA requests public comment
on our analysis of these potential benefits and on the related
questions found in Section X.

B. Potential Cost Savings

    Based on research conducted at facilities with RD&D, Project XL and
CRADA-based permits, the data from these facilities and EPA analysis of
the data suggest the following potential cost savings to owners and
operators of MSWLFs:
     Acceleration of LFG generation rate thereby: Increasing
opportunities for economically viable energy utilization options, such
as on-site co-generation of electricity or sale of LFG for use off-
site; extending the period over which capture of LFG is economically
viable; and limiting the post-closure period required for LFG control
and associated costs;
     Decrease in transport costs and the need to rely on
publicly owned treatment works (POTWs) due to minimizing or eliminating
the need for leachate treatment and offsite disposal;
     Reduction in post-closure care costs associated with
maintenance and emission monitoring due to more rapid reduction in
concentrations of biodegradable organic compounds;
     Increased utilization of permitted landfill capacity
resulting from increased waste settlement and compaction;
     Reductions in the scope, duration, and associated costs
for post-closure care.

C. Environmental Considerations

    Due to the nature of bioreactor landfill operations, which are
based on adding liquids to accelerate biodegradation, EPA is
particularly interested in further examination of three categories of
potential adverse effects to human health and the environment: (1) The
potential for release of contaminants to the groundwater due to
increased moisture content and the potential for increased hydrostatic
pressure on the liner; (2) the potential for release of contaminants to
the air resulting from accelerated biodegradation and LFG generation;
and (3) the potential for liquids management practices within the
current regulatory framework to magnify any potentially adverse impact
of bioreactor landfill operations, including releases to the
environment due to the presence of additional liquids, resultant
subsurface heating events, or waste stability issues. The EPA thus
expects to consider, among other things, the following factors as it
considers proposed design and operating criteria including whether:
     Increased engineering design requirements and more complex
construction would be necessary;
     Higher levels of oversight and operator skill would be
necessary due to increased complexity of conducting day-to-day
operations;
     Issues with temperature control, particularly in aerobic
bioreactor landfill units, may be present;
     There are potential waste compatibility issues associated
with adding liquids to unknown MSW constituents; and
     There are potential waste stability issues and the
potential for lateral leachate seeps.
1. Groundwater Considerations
    The EPA intends to carefully examine the potential for increased
risk of groundwater contamination from liquids addition and bioreactor
landfill units as part of its evaluation of the existing liquids
restrictions. The information available to EPA to date has not
identified evidence of significant differences between groundwater
contamination at bioreactor landfill units compared to conventional
units. The ORD ``State of the Practice'' report,\28\ for example,
provides a summary of data comparing the impact

of bioreactor landfill and conventional units, including that:
---------------------------------------------------------------------------

    \28\ C. Benson, M. Barlaz, and T. M. Tolaymat. ``Bioreactor
Landfills State-Of-The Practice Review,'' pages iv-vi, U.S.
Environmental Protection Agency, Washington, DC, EPA/600/R-09/071.
---------------------------------------------------------------------------

     Conventional containment systems (liners, covers, and
leachate collection systems) employed for conventional landfills
function effectively for bioreactor landfills.
     Liner leakage rates for conventional and bioreactor
landfills are comparable.
     For the landfills evaluated, the action leakage rates
(i.e., the rates at which remedial action should be taken) were not
exceeded and flow rates were similar between conventional and
bioreactor cells where comparisons were possible.
     The evaluated bioreactor landfill unit operations
employing conventional containment technologies do not impose greater
risk to groundwater than conventional landfills.
    The EPA requests any monitoring data that may demonstrate an
increased risk of groundwater contamination resulting from the
operation of bioreactor landfill units or from liquids addition as
compared to conventional landfill units. See Section X for additional
questions.
2. Air Emissions Considerations
    The EPA also expects to carefully consider the potential for
releases of LFG and other non-methane organic compound air emissions
associated with liquids addition to MSWLF units. The information
available to EPA described above indicates strongly that the rate of
LFG generation is accelerated with the addition of liquids, and that
the potential exists for methane and other HAPs to be released if LFG
is not properly controlled. Accelerated emission of odors may also
begin after liquids addition due to the possible formation of sulfur
compounds, terpenes and aldehydes. Again, as described above, the
``State of the Practice'' report indicates:
     Methane generation at bioreactor landfill units is
accelerated relative to rates predicted using AP-42 default values \29\
for conventional bioreactor landfill units. Accordingly, gas collection
should be initiated as soon as possible after waste burial or
potentially prior to liquid introduction. Design and analysis of gas
collection systems should also account for the higher rate of LFG
produced over a shorter duration.
---------------------------------------------------------------------------

    \29\ See https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors.
---------------------------------------------------------------------------

     There is no indication that gas production increases
appreciably when the wet weight water content of a bioreactor landfill
reaches 40%, which is the metric for the current bioreactor landfill
regulatory framework under the 2003 CAA NESHAP regulations. Metrics
other than wet weight water content, such as those described in Section
VII, should be considered as thresholds to require installation of gas
collection systems.
    The EPA thus requests data and information concerning the risk of
air emissions from bioreactor landfill units, including data concerning
the correlation between moisture content and LFG generation rates. The
EPA also intends to examine LFG collection requirements in RD&D permits
and requests information about additional LFG collection requirements
in those permits, including early gas collection, over and above
requirements for non-bioreactor landfill units. Examples of data that
may be helpful include the results of air emissions testing and other
operations reports that correlate LFG emissions with moisture content.
See Section X for additional questions.

VI. Additional Technical Considerations

    In addition to considerations associated with potential releases to
groundwater and air, EPA is interested in evaluating the following
design and operating characteristics \30\ as they pertain to effective
liquids management in bioreactor landfill units:
---------------------------------------------------------------------------

    \30\ For a comprehensive discussion of design and operating
characteristics associated with bioreactor landfill units, see
``Sustainable Practices for Landfill Design and Operation,'' by
Townsend, Powell, Jain, Xu, Tolaymat (USEPA/ORD) and Reinhart,
Springer Science and Business Media, New York, 2015.
---------------------------------------------------------------------------

     Leachate collection and removal systems (LCRS);
     Waste stability;
     Waste compatibility;
     Cumulative loading of constituents of concern; and
     Elevated temperature landfills (ETLFs).
    Foremost among these issues is that bioreactor landfill units need
to be designed and operated to handle high moisture content and high
leachate volume. For landfills with elevated moisture content, either
as result of purposeful liquids addition, stormwater management
practices, or incoming waste properties, the LCRS must be designed and
operated to handle higher volumes of leachate. The use of liquids
addition or leachate recirculation at a site can influence LCRS design
in three primary ways. First, the leachate impingement rate (flow of
leachate intercepted by the liner and LCRS) requires more flow removal
capacity. Second, the increased unit weight of the waste, as a result
of the elevated moisture levels, results in greater overburden stress
being placed on the landfill foundation, which can in turn result in
greater differential settlement over the sloped base of the landfill.
Third, the potential for clogging the LCRS must be considered. While it
is possible to retrofit a landfill unit to become a bioreactor landfill
unit, ideally liquids addition infrastructure is installed at the
outset, with similar infrastructure also in place to collect LFG.
    The impact of high moisture content on waste stability is another
important factor for consideration. If the LCRS is insufficiently
designed or improperly operated, liquids can mound on the bottom liner,
resulting in the development of increased pore-water pressures at the
base of the landfill and raising concerns about slope stability. The
key design and operational challenge to minimizing potential slope
concerns is to avoid excessive buildup of pore pressure. This can be
accomplished by maintaining and monitoring the LCRS, avoiding the
creation of low permeability zones within the landfill where leachate
can become perched, and allowing appropriate time in between large
pressure liquids addition events.
    Waste compatibility and the potential for cumulative loading from
the application of liquid industrial wastes are additional factors that
EPA intends to consider in association with any change to the current
prohibition on the addition of bulk liquids. The EPA is interested in
examining the potential for application of such wastes to introduce
constituents that would not otherwise be in the unit. The potential
risk could be due to constituents in those liquid wastes impacting
biodegradation or forming products of concern in the unit. With respect
to cumulative loading, the potential risk could arise from the presence
of constituents in liquid industrial wastes at concentrations that,
while below toxicity characteristic leaching procedure (TCLP)
thresholds for hazardous wastes at the time of application, could
nevertheless build up over time within the unit. For example, if the
constituents are at concentrations just below the TCLP (e.g., mercury-
bearing liquid wastes with [Hg] = 0.19 mg/L; and lead-bearing liquid
waste with [Pb] = 4.9 mg/L), EPA is interested in the potential to
exceed the TCLP once introduced to the landfill unit. The EPA requests
comment to identify specific bulk liquids that have the potential to
cause waste compatibility problems or could pose problems due to
cumulative loading.

    The possibility of subsurface reactions or heating events (known as
elevated temperature landfills (ETLFs)) is also present in landfill
units with increased levels of liquids. ETLFs pose significant
challenges including (1) changes in gas and leachate quality and
quantity which adversely impact the ability to manage these emissions
effectively; (2) rapid waste settlement with implications for slope
stability; and (3) recorded gas and waste temperatures as high as 300
[deg]C, which can compromise parts of the internal landfill
infrastructure.
    While current research and data \31\ suggest that ETLFs may be
caused by many factors, one factor that EPA believes contributes to
their development is high moisture content, possibly due in some
instances to either perched water tables or large volumes of leachate
head buildup on the bottom landfill liner in ETLF-affected areas. While
it is not clear at this time if the abundance of liquids is the cause
or the result of these subsurface heating reactions, it is important to
recognize that the head on liners (HOL) is a regulatory requirement
(see 40 CFR 258.40(a)(2)) which provides an upper limit for the head on
the bottom liner and which EPA is not considering altering at this
time. In the context of bioreactor landfill units, proper leachate
drainage and conveyance from the waste mass are needed to prevent
exceedances of the HOL limit.
---------------------------------------------------------------------------

    \31\ Ohio EPA (2011). Subsurface Heating Events at Solid Waste
and Construction and Demolition Debris Landfills: Best Management
Practices. Guidance Document #1009. October 14, 2011. (http://www.epa.ohio.gov/portals/34/document/guidance/subsurface%20heating%20events.1009.pdf).
    Ohio EPA (2016). Higher Operating Value Demonstrations. Division
of Air Pollution Control Engineering Guide #78. Division of
Materials and Waste Management Guidance Document #1002. (http://epa.ohio.gov/Portals/34/document/guidance/gd_1002.pdf).
    Palmiotto, M., Fattore, E., Paiano, V., Celeste, G., Colombo,
A., & Davoli, E. (2014). Influence of a municipal solid waste
landfill in the surrounding environment: Toxicological risk and odor
nuisance effects. Environment international, 68, 16-24. DOI:
10.1016/j.envint.2014.03.004.
    West Lake landfill, https://www.epa.gov/mo/west-lake-landfill;
Stony Hollow landfill, http://stonyhollowlandfill.com/; and Rumpke
landfill, http://epa.ohio.gov/Portals/47/pic/Rumpke%20Landfill%20factsheet.pdf?ver=2014-07-08-103928-983.
---------------------------------------------------------------------------

    To address concerns from ETLFs, EPA expects that particular
attention will need to be given to landfill units that are proposed to
be retrofitted for leachate injection to enhance waste stabilization.
Retrofitting landfill cells to handle increased moisture content is
complicated by the need to install the necessary infrastructure with
the waste mass already in place, and because of the reduced hydraulic
conductivity of aged wastes and soils with high overburden pressures.
The EPA requests comment on the possibility of establishing different
regulatory requirements for new vs. retrofitted bioreactor landfill
units.

VII. Characteristics of Bioreactor Landfill Units and Wet Landfill
Units

    If it proceeds to a future proposed rule, EPA will need to identify
those units which are subject to revised requirements. The EPA is
therefore also seeking public input on how it most appropriately may
define a ``bioreactor landfill unit.'' The EPA has identified and is
seeking public comment on two possible approaches to defining these
units that reflect EPA's understanding of the information it has
assembled to date.
    One approach to define a bioreactor landfill unit in RCRA
regulations is by moisture content.\32\ Should EPA take such an
approach, EPA is considering whether a 30% moisture threshold may be
appropriate as a quantitative characteristic of a bioreactor landfill
unit. Thirty percent represents a point above the 20-25% \33\ moisture
content range in which MSWLFs typically operate, and at which
biodegradation may be accelerated on as a consequence of the addition
of liquids.
---------------------------------------------------------------------------

    \32\ See EPA-456/R-05-004, ``Example Moisture Balance
Calculations for Bioreactor Landfills'' for a discussion of methods
to calculate moisture content.
    \33\ Solid Waste Association of North America, ``Manager of
Landfill Operations Training Manual,'' page 1-12, January, 2003.
---------------------------------------------------------------------------

    Alternatively, a bioreactor landfill unit may be characterized
qualitatively, as a MSWLF unit to which liquids have been intentionally
added for any purpose other than cleaning, maintenance, and wetting of
daily cover. This qualitative approach to defining a bioreactor
landfill unit is consistent with the understanding that liquids need to
be added for normal maintenance, including cleaning and wetting of
daily cover, while additional liquids may serve only to accelerate
biodegradation. The EPA solicits comment on the impact of increased
moisture content in the range of 25-40% and above, and whether there
are factors governing moisture content for which EPA should account,
other than normal maintenance and accelerated biodegradation.
    The EPA is also interested in obtaining public comment on whether
to regulate wet landfill units as a distinct group under the RCRA
regulations and as a possible alternative to defining and regulating
bioreactor landfill units. Increased moisture content has a similar
effect on biodegradation whether it is added intentionally (as in
bioreactor landfill research projects) or not, and thus EPA is
exploring whether increased moisture content from any or all sources
may pose similar technical issues that warrant special regulatory
treatment.
    The EPA therefore solicits comment on the following characteristics
which it is considering to identify which MSWLF units may be
appropriately identified as ``wet landfill units.'' The EPA also
requests comment on whether these factors should be considered
individually or in combination with one another to identify such units,
including whether:
     Liquids are recirculated or added for any purpose other
than cleaning, maintenance, and wetting of daily cover;
     The unit is located in a region with 40 inches or more of
annual precipitation;
     The unit has a k value of 0.057 or more;
     Precipitation plus leachate recirculation is greater than
55 inches per year; or
     The unit is a bioreactor landfill unit.

Another measure that may be appropriate to identify a bioreactor
landfill unit or a wet landfill unit is the rate of leachate
collection. Leachate collection data are generally available at MSWLFs,
and these data could be used as a surrogate measure of the amount of
liquid in a unit.
    In considering the merits of defining a new class of bioreactor
landfill units or wet landfill units, EPA is motivated to improve the
management of liquids at MSWLFs based on advances since the Part 258
standards were promulgated in 1991. As currently used, EPA believes the
term bioreactor landfill may unnecessarily connote a small class of
research facilities, the benefits of which may not be recognized as
practicable in wider use. The EPA solicits input on the options for
defining bioreactor landfill units or wet landfill units presented here
and whether a new RCRA definition for one or the other may contribute
to the advancement of liquids management practices at MSWLFs.

VIII. Universe of MSWLFs Potentially Affected by This ANPRM

    In addition to potentially defining a new RCRA class of bioreactor
landfill units or wet landfill units, EPA is also considering how to
address existing bioreactor landfill units, such as those with RD&D
permits, in future proposed rules. As discussed previously, EPA is
aware of 35 facilities with RD&D

permits. Because the RD&D authorization is time-limited, bioreactor
landfill units operating under RD&D permits will have to suspend
operations authorized under their RD&D permit no later than 21 years
after they began, unless EPA makes nationwide regulatory changes or
issues a site-specific rule to authorize the unit's continued
operation. The EPA understands some RD&D permits may reach the end of
the 21-year maximum permit term as soon as 2024.
    The EPA believes that regulatory changes to allow the addition of
bulk liquids to MSWLF units as a revised minimum criterion in 40 CFR
258, or as a variance under which state directors could approve bulk
liquids addition on a site-specific basis, would enable a larger group
of facilities to pursue bioreactor landfill operations or liquids
addition practices. Anecdotally, EPA has learned that some facilities
would like to develop bioreactor landfill units, but only if EPA were
to allow bulk liquid addition outside of the temporary RD&D permit
process. The 35 facilities with RD&D permits are a small portion of the
open MSWLFs in the US.
    As discussed in Section V, there are many potential environmental
and economic benefits that may motivate a landfill owner or operate to
pursue construction and operation of a bioreactor landfill unit. Due to
the significant impact on LFG generation from the addition of liquids,
EPA believes that information in its Landfill Methane Outreach Program
(LMOP) database may serve as a good predictor for the potential impact
of developing a RCRA definition and regulations for bioreactor landfill
units or wet landfill units. Of the estimated 1,221 open MSWLFs \34\ in
the EPA Landfill Methane Outreach Program (LMOP) database, there are
approximately 565 MSWLFs that currently provide LFG to one or more or
more operational LFG energy projects (LFG electricity projects, LFG
direct-use projects, and upgraded LFG projects) for a total of 623
operational LFG projects. The EPA plans to explore whether some of
these 565 MSWLFs may be able to achieve better environmental and
economic results if EPA were to remove the prohibition on the addition
of bulk liquids and define bioreactor landfill units or wet landfill
units as a class of facilities that can get standard RCRA Subtitle D
permits in approved states.
---------------------------------------------------------------------------

    \34\ USEPA, Landfill Methane Outreach Program (LMOP) Database.
Data from the LMOP Database are current as of September 2018. For
information on the LMOP Database including its sources, please see
the LMOP website https://www.epa.gov/lmop.
---------------------------------------------------------------------------

    In addition to those 565 MSWLFs, EPA estimates that there are
approximately 470 additional MSWLFs \35\ that may be good candidates
for development of an LFG energy project. These 470 MSWLFs are those
that are currently accepting waste or have been closed for five years
or less, have at least one million tons of waste, and do not currently
have an operational, under-construction, or planned LFG project. The
EPA intends to explore whether some of these 470 MSWLFs may be able to
achieve better environmental and economic results if EPA were to remove
the prohibition on the addition of bulk liquids and define bioreactor
landfill units or wet landfill units as a class of facilities that can
get standard RCRA permits in approved states. Some of these 470
facilities may ultimately be candidates for developing bioreactor
landfill units upon changes to the RCRA regulations.
---------------------------------------------------------------------------

    \35\ USEPA, Landfill Methane Outreach Program (LMOP) Database.
Data from the LMOP Database are current as of September 2018. For
information on the LMOP Database including its sources, please see
the LMOP website https://www.epa.gov/lmop.
---------------------------------------------------------------------------

    In considering the number of facilities that may be affected, it is
important to note that the primary intent of this ANPRM is to explore
whether regulatory flexibility is warranted for those facilities that
want to add liquids for the purpose of accelerating biodegradation in
the manner of a bioreactor landfill unit. The EPA believes that
bioreactor landfill units may reduce the overall risk to the
environment and have significant economic benefits.

IX. Relationship to Organics Diversion and Composting Programs

    Apart from any future changes to the MSWLF regulations, EPA is
considering how such changes fit into the Agency's broader Sustainable
Materials Management (SMM) approach. Sustainable materials management
is a systemic approach to using and reusing materials more productively
over their entire life cycles. It represents a change in how our
society thinks about the use of natural resources and environmental
protection. As part of this effort, EPA has developed a non-hazardous
materials and waste management hierarchy that recognizes that no single
waste management approach is suitable for managing all materials and
waste streams in all circumstances. The hierarchy ranks the various
management strategies from most to least environmentally preferred. The
hierarchy places emphasis on reducing, reusing, and recycling as key to
sustainable materials management. Consistent with the hierarchy, EPA
supports reducing the landfilling of organic waste through a variety of
policies and programs. While not directly under EPA's SMM approach,
various state and local initiatives described in this section have also
been emerging to divert organics from landfilling operations. As
discussed above, effective bioreactor landfill units depend upon the
performance of biodegredation processes of organic materials in the
unit. As a policy matter, EPA sees the development of appropriately-
regulated bioreactor landfill units or wet landfill units as a
potential complement to diversion programs, with both reducing the
environmental impacts from organics management, albeit under different
management scenarios.
    The EPA data \36\ indicate that organic materials are historically
the largest component of materials landfilled in the MSW stream,
constituting about 51 percent of landfilled material in 2015. Food
waste is the largest component of the organic materials waste stream,
followed by paper and paperboard, wood wastes and yard trimmings.
Recycling and composting have been increasing over time for organic
materials (except rubber and leather). For example, the percentage of
paper and paperboard that is recycled has increased from 16.9 percent
in 1960 to 66.6 percent in 2015. The amount of composted yard trimmings
has increased from a negligible amount in 1960 to 61.3 percent in 2015.
Composted food waste has increased less significantly from negligible
amounts in 1960 to 5.3 percent in 2015. Information available to EPA
further indicates that states and cities with robust recycling and
composting programs may realize an even greater percentage of recycling
and composting.
---------------------------------------------------------------------------

    \36\ www.epa.gov/smm/advancing-sustainable-materials-management-facts-and-figures.
---------------------------------------------------------------------------

    Such organic waste diversion programs are in effect in multiple
U.S. states and cities. These programs also appear to be growing in
number. The EPA expects that as the numbers of households covered by
such programs grows, so will the quantities of materials diverted from
landfilling operations. A survey conducted by BioCycle in fall 2017
\37\ identified 198 curbside collection programs and 67 drop-off
programs. This represented significant growth compared to 42
communities with curbside collection of food waste

in 2007 \38\ representing 752,000 households. In addition, numerous
communities encourage residents to compost food in their backyards. In
some cities, private companies offer food scrap pick-up services for a
fee.
---------------------------------------------------------------------------

    \37\ ``Residential Food Waste Collection Access in the U.S.,''
Virginia Streeter and Brenda Platt, Biocycle, December 2017, Vol.
58, No. 11, p. 20.
    \38\ ``Source Separated Residential Composting,'' Biocycle,
December 2007.
---------------------------------------------------------------------------

    Additionally, several states and cities have statutes, ordinances,
and/or mandates that require organics diversion from landfills.\39\ The
EPA expects that these laws will have an effect on the amount of
organic waste that would otherwise be available for management in
bioreactor landfill units and wet landfill units, at least within the
jurisdictions in which the diversion laws apply. As of 2018, four
states--Connecticut, Massachusetts, Rhode Island, and Vermont --have
adopted bans on organic waste, going to landfills, while one state--
California --has instituted a waste recycling law requiring commercial
generators of organic waste to either compost or anaerobically digest
organic waste. All five of these states prohibit certain entities that
generate specified amounts of food waste from sending this waste to
landfills, subject to exceptions. Each state's ban varies in how it
applies to various entities, how much organic waste an entity must
produce in order to be covered, and whether exceptions exist for
entities located far from a certified recycling or composting facility
that accepts food scraps. For example, as of 2020, Vermont's law will
cover anyone, including residents that generate any amount of food
waste, while the other states' bans cover only certain commercial,
industrial, and institutional entities. City ordinances in New York
City and Portland, Oregon, mandate materials separation from commercial
generators. Ordinances in Seattle and San Francisco extend the
separation mandate to single family dwellings. An ordinance in Austin,
Texas requires restaurants of a certain size to compost food scraps.
---------------------------------------------------------------------------

    \39\ www.chlpi.org/wp-content/uploads/2013/12/Food-Waste-Toolkit_Oct-2016_smaller.pdf.
---------------------------------------------------------------------------

    Other surveys and data also suggest that state- and local-level
organics diversion programs are gaining momentum. The EPA's State
Measurement Program (Program) estimates that, for 2016, 27 states have
reported having 2,666 organics materials management systems, and 11 of
those states have systems that include anaerobic digestion. The Program
also reports that 21 states have yard waste landfill bans. Finally,
Program data indicate that five states have implemented composting
goals, including Arkansas, California, Maryland, Massachusetts, and
Washington.
    The EPA seeks data and information on how organics diversion and
composting programs may interact with, complement, or enhance the
policy goal of reducing the environmental impact of organics management
across management scenarios. In addition, EPA is also interested in
obtaining data and information on how such programs may otherwise
affect the operation or geographic distribution of bioreactor and wet
landfill units.

X. What information is EPA seeking?

A. Information on Benefits and Risks of Bioreactor Landfill Units and
Wet Landfill Units

    The EPA requests information and data on the benefits and risks to
human health and the environment that may result from the addition of
bulk liquids and the construction, operation, and post-closure care of
bioreactor landfill units and/or wet landfill units. This includes
risks that have concerned the EPA in the past such as potential
contamination of groundwater from liner leakage; potential
contamination of the air from accelerated LFG emissions; the impact of
higher temperatures and potential for fire under various landfill
conditions; and any other potential risks EPA has not yet identified.
(See Section V for a discussion of potential benefits and environmental
considerations.) For information about where to submit information and
comments on the following questions, please see the ``Addresses''
section at the beginning of this document. In responding to any
questions in this document, please identify the question(s) to which
you are responding before each response.

B. Questions on Characteristics of Bioreactor Landfill Units and Wet
Landfill Units

    The EPA requests comments and supporting information on the
following questions concerning characteristics that may be used to
define the universe of bioreactor landfill units or wet landfill units.
(See section VII for additional discussion.)
    (1) If EPA should adopt a definition of a new RCRA class of MSWLFs
outside of RD&D permits, is the qualitative definition in Section VII,
i.e., that a bioreactor landfill unit is defined by the intentional
addition of liquids for any purpose other than cleaning, maintenance,
and wetting of daily cover, an appropriate to definition? Or is a
quantitative definition based on moisture content more appropriate?
    (2) If EPA should adopt a quantitative definition of a bioreactor
landfill unit based on moisture content, what is the appropriate
threshold for moisture content?
    (3) Are there factors other than moisture content that should be
used to define a bioreactor landfill unit in a quantitative manner?
    (4) Should EPA include the use of leachate recirculation, run-on
and run-off systems, and alternative cover designs in any new
definition of a bioreactor landfill unit or wet landfill unit?
    (5) If EPA should determine that it is more appropriate to define
and regulate wet landfill units instead of bioreactor landfill units,
what factors should be considered in such a definition?

C. Questions on Operations and Post-Closure Care

    The EPA requests comments, data and supporting information on
appropriate operational requirements associated with the addition of
bulk liquids and the construction, operation, and post-closure care of
bioreactor landfill units and wet landfill units. (See section VI for
additional discussion.)
    (1) Are there any additional facilities with RD&D permit
applications in the process of state approval, of which EPA is not yet
aware (i.e., are not listed in Table 2 above)? If so, please identify
them.
    (2) What other changes to the part 258 criteria may be warranted if
EPA were to regulate bioreactor landfill units or wet landfill units as
a subset of MSWLF units? For example, if EPA were to make changes to
the existing criteria for liquids restrictions, run-on and run-off
control systems, and alternative cover designs for such units, should
EPA consider changes to other 258 criteria to complement those changes?
    (3) Did state permitting authorities impose any additional
groundwater protection or air emission controls in the initial RD&D
permits as a pre-condition for allowing the addition of bulk liquids?
The EPA is aware that Wisconsin, for example, required LFG collection
from the beginning of operations for MSWLFs granted variances to add
bulk liquids.
    (4) What design and operating changes, if any, should be considered
to manage accelerated waste settlement in bioreactor landfill units and
minimize waste instability issues?
    (5) Should the prospect of increased leachate and accelerated LFG
generation require that a Professional Engineer certify that any or all
MSWLF components and subsystems (e.g., leachate collection and storage,
LFG

collection and control) be designed properly to handle the increased
demands at a bioreactor landfill unit or wet landfill unit?
    (6) Are there alternative cover design modifications using RD&D
permits or in other settings that have demonstrated the ability to
optimize biodegradation?
    (7) If the variances contained in the current RD&D rule were to be
made allowable outside of RD&D permits (see Section II), what
additional performance and prescriptive standards, if any, would be
necessary to demonstrate protection of human health and the
environment?

D. Questions on Potential Risks

    The EPA requests comments, data and other supporting information on
the risks to human health and the environment that may result from the
addition of bulk liquids and the construction, operation, and post-
closure care of bioreactor landfill units and wet landfill units. (See
Sections V and VI for additional discussion.)
    (1) Are there current scientific studies or other data available
pertaining to the impact of moisture content on the frequency and rate
of leachate leakage or other types of environmental releases from
landfills?
    (2) Is there evidence of increased groundwater contamination from
bioreactor landfill units as compared to dry-tomb landfill units?
    (3) Should EPA remove or modify the bulk liquids restriction in 40
CFR 258.28? For example, should the addition of liquids be limited to
off-specification consumable liquids or be open to all non-hazardous
liquid waste?
    (4) What specific bulk liquids and in what quantity were added at
RD&D rule bioreactor landfill units?
    (5) Are there restrictions or conditions on liquid waste acceptance
that EPA should consider? For example, are there any properties (e.g.,
pH, ionic strength, biological activity) of specific kinds of liquid
waste (e.g., sewage sludge, grey water, animal feedlot waste) that may
exacerbate releases from co-managed wastes and should be considered for
possible restrictions on liquid waste acceptance? Are there any
properties of the residual solids from these liquids that may pose risk
when managed at the lower water content within the landfill?
    (6) Could increasing the moisture content of the landfill increase
the risk of fire through exothermic chemical reactions? Are there
specific waste types that are appropriately managed in dry-tomb MSWLFs
but could be incompatible with bioreactor landfill units and/or wet
landfill units?
    (7) How might overall leachate quality be affected by:
    a. Management under aerobic, anaerobic, or hybrid conditions?
    b. Saturation of waste and/or recirculation of leachate?
    (8) At what point should LFG collection and control systems be
installed and operating before allowing the addition of liquids in
order to minimize odors, reduce fugitive LFG emissions, and prevent
accumulation of gasses above the lower explosive limit (LEL)?
    (9) When was LFG collection required to be initiated at bioreactor
landfill units as specified in the initial RD&D permit that allowed the
addition of bulk liquids?
    (10) Are there any changes to the part 258 criteria that the EPA
should consider to better ensure the protectiveness of bioreactor
landfill units and wet landfill units in closure and post-closure?
    (11) Are there special types of containment systems or other
preventative measures that should be considered to mitigate risk from
spills or increased leachate circulation?

E. Questions on Potential Costs, Cost Savings and Benefits

    The EPA requests comments, data and supporting information on the
following questions related to the potential costs, cost savings and
benefits associated with the addition of bulk liquids and the
construction, operation, and post-closure care of bioreactor landfill
units and/or wet landfill units.
    (1) The EPA requests information pertaining to the costs or
estimated costs of construction, operation, closure, and post-closure
care of bioreactor landfill units and wet landfill units. How do these
costs compare with the costs associated with dry-tomb MSWLFs?
    (2) How do costs differ for units managed under aerobic, anaerobic,
and hybrid conditions? \40\
---------------------------------------------------------------------------

    \40\ See https://www.epa.gov/landfills/bioreactor-landfills for
a description of aerobic, anaerobic and hybrid bioreactor landfill
units.
---------------------------------------------------------------------------

    (3) What are the costs associated with early installation of LFG
collection systems?
    (4) What are the benefits associated with increased LFG generation
and capture?
    (5) What are the costs, cost savings and benefits associated with
faster settling of waste in bioreactor landfill units and wet landfill
units?
    (6) How might tipping fees (the charges levied for a given quantity
of waste delivered to a landfill) change in response to any additional
costs incurred during the operation and closure of bioreactor landfill
units and wet landfill units (e.g., updated design criteria, waste
handling requirements)?
    (7) How does managing organic waste in bioreactor landfill units
compare, in terms of the cost, cost savings and benefits, to managing
segregated organic wastes through composting or anaerobic digestion?
    (8) For MSWLFs in areas with organic waste diversion programs, have
owners and operators of such units documented reductions in the
proportion of organics received at the unit? Have any such documented
reductions been shown to affect the performance or environmental risks
associated with bioreactor landfill units?
    (9) Are there cost savings associated with the ability to add bulk
liquids to bioreactor landfill units as compared to other treatment,
storage and disposal methods? Please provide the cost savings or the
estimated cost savings associated with the above mentioned methods.
    (10) Would changes to part 258 to provide national operating and
design criteria for bioreactor landfill units or wet landfill units
create an incentive or disincentive to state and local food waste
diversion programs?
    (11) Are there cost savings associated with the ability to add bulk
liquids to bioreactor landfill units as compared to other treatment,
storage and disposal methods?
    (12) What are the capital costs and operation and maintenance costs
associated with operating a bioreactor landfill unit? How do these
costs compare to those of landfills that do not have bioreactors
landfill units?
    (13) In addition to the standard bioreactor landfill unit
infrastructure and practices, are there any bundled engineering
practices (e.g., complimentary requirements for leachate recirculation,
LFG collection, and leak detection) that landfills operating bioreactor
landfill units are likely to invest in? What are the additional or
complementary benefits or risks of these investments?
    (14) Are there any existing bioreactor landfill facilities
operating under RD&D permits, that would cease operations due to
financial and/or operational difficulties without continued operation
as a bioreactor landfill unit?
    (15) Has the temporary status of permits under the RD&D rule
discouraged any owner/operators from otherwise investing in bioreactor
landfill units?

XI. Statutory and Executive Order Review

    Under Executive Order 12866, entitled Regulatory Planning and
Review (58 FR 51735, October 4, 1993), this is a ``significant
regulatory action'' because it relates to a novel approach to
nationwide landfill management. Accordingly, EPA submitted this Advance
Notice of Proposed Rulemaking to the Office of Management and Budget
(OMB) for review under Executive Order 12866 and any changes made in
response to OMB recommendations have been documented in the docket for
this action.
    Because this document does not impose or propose any requirements,
and instead seeks comments and suggestions for the Agency to consider
in possibly developing a subsequent proposed rule, the various other
review requirements that apply when an agency imposes requirements do
not apply to this action. Nevertheless, as part of your comments on
this ANPRM, you may include any comments or information that could help
the Agency: To assess the potential impact of a subsequent regulatory
action on small entities pursuant to the Regulatory Flexibility Act (5
U.S.C. 601 et seq.); to consider voluntary consensus standards pursuant
to section 12(d) of the National Technology Transfer and Advancement
Act (15 U.S.C. 272 note); to consider environmental health or safety
effects on children pursuant to Executive Order 13045, entitled
``Protection of Children from Environmental Health Risks and Safety
Risks'' (62 FR 19885, April 23, 1997); to consider human health or
environmental effects on minority or low-income populations pursuant to
Executive Order 12898, entitled ``Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations'' (59 FR 7629, February 16, 1994); or to consider potential
impacts to state and local governments or tribal governments.

XII. Conclusion

    The information available to EPA to date suggests that liquids
addition in well-managed bioreactor landfill units and/or wet landfill
units may provide reductions in long-term risk and operational costs in
comparison to dry-tomb landfills as a result of accelerated waste
biodegradation. The EPA continues to gather information on this issue,
including the information received in response to this ANPRM. This
information will assist EPA in making a determination concerning what
actions, if any, to take to revise the MSWLF criteria.

List of Subjects in 40 CFR Part 258

    Environmental protection, Reporting and recordkeeping requirements,
Waste treatment and disposal, Water pollution control.

    Dated: December 14, 2018.
Andrew R. Wheeler,
Acting Administrator.
[FR Doc. 2018-27748 Filed 12-21-18; 8:45 am]
 BILLING CODE 6560-50-P