practices to maximize gas collection. Two commenters from state
agencies agreed with removing the operational standards, and agreed
with retaining monthly monitoring of temperature and nitrogen/oxygen
and retaining the corresponding monitoring data.
    Several commenters suggested that certain monitoring data should be
reported on a semi-annual basis so that agencies can identify or
prevent fires. For example, state agency commenters suggested that the
EPA require semi-annual reporting of wellhead readings above 5 percent
oxygen and 130 degrees Fahrenheit, which was supported by supplemental
comments received from the industry and industry trade organizations.
One commenter also suggested reporting of any subsurface fire. One
regional agency wanted the results to be reported if temperature
exceeds 150[emsp14][deg]F and also suggested reporting any methane to
carbon dioxide ratio less than 1.
    Commenters that supported removal of the operational standards for
temperature and nitrogen/oxygen also contended that the nitrogen/oxygen
and temperature wellheads parameters are poor indicators of landfill
fires or inhibited decomposition and that landfill owners or operators
already have their own incentive to prevent landfill fires. Commenters
added that expanding the LFG collection system by drilling new wells
may introduce more air into the landfill, which can exacerbate a fire
and actually increase oxygen content. Commenters (0451-0178, 0451-0167,
0215-0191, 0215-0121) that favored retaining the operational standards
for temperature and nitrogen/oxygen contend that temperature and
nitrogen/oxygen data are essential to inform regulators of the presence
of the potential for a landfill fire.
    Response: After carefully considering public comments and available
data, the EPA is removing the operational standards (i.e., the
requirement to meet operating limits) for nitrogen/oxygen, but not
temperature. Landfill owners or operators must continue to monitor
nitrogen/oxygen on a monthly basis, however, to ensure that the GCCS is
well maintained and operated, collects the most LFG, and minimizes
losses of LFG through the surface of the landfill. Landfill owners or
operators must maintain records of this monthly monitoring and make
these records available to the Administrator upon request. The EPA is
requiring monthly monitoring and recordkeeping for these wellhead
monitoring parameters (i.e., oxygen, nitrogen, temperature, and
pressure), since these are key indicators that are already being
monitored by landfill owner or operators to determine how well the
landfill is being operated, including the capturing and destroying
landfill gas, promoting efficient anaerobic decomposition and/or
preventing landfill fires.
    Because of concerns regarding fire hazards, the EPA is retaining
the operational standard for temperature. Landfill owners or operators
must electronically submit, as part of their annual report, all
readings that show LFG temperatures greater than 55 degrees Celsius
(131 degrees Fahrenheit), and document the root cause and corrective
action taken to correct for this exceedance, as discussed in section
VI.A.2 of this preamble. While several commenters supported removing
the temperature parameter, other commenters were concerned with fire
risks if the parameter was removed. In addition, given the EPA
experience with consent decrees and other enforcement actions involving
elevated temperature values, the EPA has decided to retain temperature
as an operating standard in the final rule. This overall approach will
reduce the number of requests for higher operating values and
alternative timeliness for nitrogen/oxygen parameters. In addition,
note that regulatory agencies can request data records of oxygen,
nitrogen, or temperature monitoring, as measured on a monthly basis, at
any time.
    Landfills are subject to 40 CFR part 60, subpart A. These
provisions require landfill owners or operators, to the extent
practicable, to maintain and operate any affected facility including
associated air pollution control equipment in a manner consistent with
good air pollution control practice for minimizing emissions. Due to
the extreme environmental consequences of a subsurface landfill fire,
these provisions obligate landfill owners or operators to take all
practical steps necessary to avoid landfill fires. While this action
removes requirements to meet operational standards for nitrogen/oxygen
at wellheads and to make corrective actions, landfill owners or
operators must continue all due diligence to ensure that the GCCS is
not overdrawn, thereby creating a flammable subsurface environment.
    Because the corrective action requirements for certain parameters
have been retained, the EPA is reaffirming its provisions for HOVs. The
HOV provisions were originally enacted to address variations in
temperature between landfills and between wells. With a sufficient
demonstration (i.e., supporting data showing the elevated parameter
does not cause fires or significantly inhibit anaerobic decomposition
by killing methanogens), an HOV may be established for temperature,
nitrogen, or oxygen at a particular well. The EPA encourages regulatory
authorities review requests for HOVs in a timely manner and to make use
of these mechanisms where

appropriate.\42\ States may also consider HOVs when developing state
plans.
---------------------------------------------------------------------------

    \42\ The EPA asserts the importance of case specific HOV
requests and approvals. However, to address concerns from HOV
request reviewers and those submitting requests, an example of
regulatory guidance for HOV demonstrations can be found at http://www.epa.ohio.gov/portals/34/document/guidance/gd_1002.pdf.
---------------------------------------------------------------------------

2. Corrective Action
    In a 1998 Federal Register notice (63 FR 32748, June 16, 1998), the
EPA amended the wellhead monitoring provisions of 40 CFR part 60,
subpart WWW, to allow an alternative timeline for correcting wellhead
exceedances to be submitted to the Administrator for approval. The rule
change made the wellhead monitoring provisions consistent with the SEM
provisions, which allow an alternative remedy and corresponding
timeline for correcting an exceedance to be submitted to the
Administrator for approval. The EPA noted in the 1998 preamble that any
timeline extending more than 120 days must be approved by the
regulating agency. Since 1998, questions have been raised about the
timing of correcting wellhead exceedances and whether a landfill needs
agency approval for corrective action timelines that exceed 15 calendar
days but are less than the 120 days allowed for expanding the GCCS.
    In the 2015 Emission Guidelines proposal, the EPA clarified its
intent and outlined a corresponding timeline for correcting positive
pressure at a wellhead. The EPA proposed that a landfill must submit an
alternative corrective action timeline request to the Administrator for
approval if the landfill cannot restore negative pressure within 15
calendar days of the initial failure to maintain negative pressure and
the landfill is unable to (or does not plan to) expand the gas
collection system within 120 days of the initial exceedance. The EPA
explained in the preamble that it did not specify a schedule in the
proposed rule language by when a landfill would need to submit
alternative timeline requests because the EPA determined that
investigating and determining the appropriate corrective action, as
well as the schedule for implementing corrective action, would be site
specific and depend on the reason for the exceedance (80 FR 52126). In
addition, the EPA requested comment (80 FR 52126) on an alternative
timeline that extends the requirement for notification from 15 days to
as soon as practicable, but no later than 60 days from when an
exceedance is identified. In the 2014 ANPRM, the EPA had requested
comment on the same approach, as well as whether 60 days is the
appropriate time to make necessary repairs.
    Comment: The EPA received comments on the proposed changes,
including the time allowed for corrective action and for submitting
alternative timeline requests for approval by the Administrator.
Regarding the timeframe for submitting a request, several state
agencies recommended extending the 15-day timeline for a request to be
submitted and indicated that 15 days is not sufficient time to evaluate
the problem and plan for corrective action, which may often involve
construction activities. There were varied opinions from the state
agencies on what length of time beyond 15 days is appropriate. Two
agencies supported an extension to as soon as practicable but no later
than 60 days, other agencies specified that the request should be
submitted within 30 days from the initial exceedance.
    Industry representatives from private and publicly owned landfills
as well as waste industry consultants opposed the requirement to submit
a request for an alternative corrective action timeline within 15 days.
The commenters were concerned that 15 days is not enough time to assess
the appropriate solution across miles of interconnected piping. In
addition, the commenters were concerned that a 15-day time period would
increase the paperwork for both the landfill and the reviewing
regulatory agency. One commenter indicated that while many repairs can
be completed within 60 days, some repairs, especially in cold weather
climates, may take longer. One industry commenter suggested that a
timeframe of 90 days to complete any adjustments or repairs is
appropriate. If the corrections could not be made within 90 days, the
commenter stated that the landfill would be prepared to have the system
expanded within 120 days.
    Industry commenters raised the issue that the timeline for
corrective action for surface exceedances in the current subpart WWW
regulations, 40 CFR 60.755(c)(4)(v), allows 120 days to install a new
well or other collection device or submit an alternative timeline for
another corrective action. These commenters also indicated that the
1998 NSPS amendments modified the corrective action for wellhead
parameter exceedances to be consistent with the timeframe allowed for
correcting surface exceedances (63 FR 32748, June 16, 1998). The
commenters also noted that the 1998 amendments recognized that
installation of a new well may not always be the appropriate corrective
action for remedying a wellhead exceedance.
    Despite the 1998 rule amendments, several of these industry
commenters note that interpretation and implementation of the 1998
amendments to 40 CFR 60.755(a)(3) have been inconsistent, with some
agencies only requiring the landfill owner or operator to submit
requests if the corrective action will take longer than 120 days. Other
states have taken the position that any exceedances that cannot be
resolved within 15 days must automatically result in a requirement to
expand the GCCS. One commenter referenced determinations that required
landfills to submit an alternative timeline request within 15 days. One
commenter indicated that the original rule never anticipated
notification and a request for an alternative compliance timeline
within 15 days, while another commenter indicated that the state of
Texas requires landfills to submit alternative timelines only if the
corrective action requires more than 120 days to complete.
    In consideration of the 1998 final rule notice, industry commenters
recommended that EPA require landfill owners or operators to submit an
alternative timeline request for approval as soon as practicable and
only in circumstances in which a system expansion or alternative
corrective action will require more than 120 days to complete. One of
the commenters (Republic 0451-0176) suggested that this approach was
consistent with the Petroleum Refineries NSPS (40 CFR part 60, subpart
Ja). The commenter noted that while the Landfills NSPS requires special
approval to avoid the default corrective action of expanding the GCCS,
the Refineries NSPS requires a root cause analysis to identify the
appropriate corrective action, without specifying a default approach.
The Refineries NSPS requires a root cause analysis and a corrective
action analysis for exceedances and requires the facility to implement
the corrective action within 45 days. If the corrective action cannot
be completed in 45 days, the refinery must document and record all
corrective actions completed to date. For actions not fully completed
by day 45, they must develop an implementation schedule, as soon as
practicable, for beginning and completing all corrective action.
    One commenter provided some ideas for landfills to demonstrate good
faith effort to comply with the 120-day corrective action schedule.
They suggested the rules clarify that the landfill owner or operator is
required to submit a notification to the agency that

identifies and describes the diagnosis performed, the results of the
diagnosis, identifies the corrective measure or alternative remedy to
be implemented and reason(s) why system expansion is not appropriate to
correct the exceedance. Under such an approach, corrective measures
other than expansion that take 0-60 days to complete from the initial
exceedance would not require any notification or approval but they
would be documented in the annual compliance report. For corrective
actions other than expansion that take longer than 60 days but less
than 120 days to complete, the landfill owner or operator would notify
the regulatory agency by day 75 from the date of the initial
exceedance. This would allow 45 days for the agency to review and
comment, and such notification would not require agency approval so as
not to delay the site from proceeding with and completing the
corrective action, as long as the corrective actions are completed
within the 120-day timeframe.
    Industry commenters indicated that the timeline for corrective
action is affected by other regulations. Two of these commenters noted
that any corrective action that involves disturbing the final landfill
cover could delay diagnosing the problem. All of these commenters also
noted that a 60-day timeframe is problematic for landfills affected by
the Asbestos NESHAP (40 CFR part 61, subpart M), which requires a 45-
day notification prior to disturbing areas that may have asbestos
containing material.
    Response: The EPA is retaining the corrective action requirements
for temperature in addition to negative pressure. The EPA recognizes
the importance of temperature as a critical indicator of landfill fires
and its effect on methanogens. Further removal of the corrective action
requirements for temperature could have the unintended consequence of
improper operation of a GCCS which could lead to a subsurface fire. Due
to the importance of this parameter, e-reporting requirements for
excessive temperature have also been established to better assess
landfill fires.\43\
---------------------------------------------------------------------------

    \43\ The need to rely on temperature in addition to pressure is
also illustrated in the report titled Subsurface Heating Events at
Solid Waste and Construction and Demolition Debris Landfills: Best
Management Practices at http://www.epa.state.oh.us/Portals/34/document/guidance/gd_1009.pdf.
---------------------------------------------------------------------------

    After carefully considering the comments received and evaluating
the available data, the EPA is finalizing corrective action
requirements that generally give owners or operators 60 days to
investigate and determine the appropriate corrective action and then
implement that action. The EPA has retained the requirements for
temperature and positive pressure, in that if positive pressure or
temperature exceedances exist, action must be initiated to correct the
exceedances within 5 calendar days. This requirement has been retained
to ensure the landfill takes prompt action to ensure the GCCS remains
well-operated. The EPA recognizes, however, that the appropriate
corrective action, as well as a schedule to implement it, is site-
specific and depends on the reason for the exceedance. Therefore, for
corrective action that takes longer than 60 days after the initial
exceedance to implement, the EPA is providing flexibility for the
landfill to determine the appropriate course of action based on a root
cause analysis. Specifically, if the owner or operator cannot achieve
negative pressure or temperature of 55 degrees Celsius (131 degrees
Fahrenheit) at the GCCS wellhead within 15 days, then the owner or
operator must conduct a root cause analysis and correct the exceedance
as soon as practicable, but no later than 60 days after positive
pressure or temperature of 55 degrees Celsius (131 degrees Fahrenheit)
was first measured. An implementation schedule is required for
exceedances that will take longer than 60 days to correct. A root cause
analysis is an assessment conducted through a process of investigation
to determine the primary cause, and any other contributing cause(s), of
positive pressure at a wellhead or temperature above 55 degrees Celsius
(131 degrees Fahrenheit). The root cause analysis and documentation of
the corrective action taken to restore negative pressure or temperature
of 55 degrees Celsius (131 degrees Fahrenheit) must be kept on site as
a record, but they do not have to be submitted or approved.
    If negative pressure or temperature of 55 degrees Celsius (131
degrees Fahrenheit) cannot be achieved within 60 days, then the owner
or operator must develop an implementation schedule to complete the
corrective action(s) as soon as practicable, but no more than 120 days
following the positive pressure or temperature reading. The owner or
operator must also notify the Administrator within 75 days. The
implementation schedule, root cause analysis, and documentation of the
corrective action taken to restore negative pressure or temperature of
55 degrees Celsius (131 degrees Fahrenheit) must be submitted in the
facility's next annual report, but these items do not have to be
approved.
    If the exceedance cannot be corrected (or is not expected to be
corrected) within 120 days, then the owner or operator must submit the
root cause analysis, plan for corrective action to restore negative
pressure or temperature of 55 degrees Celsius (131 degrees Fahrenheit),
and the corresponding implementation timeline to the Administrator. The
Administrator must approve the plan for corrective action and the
corresponding timeline. The owner or operator must submit the proposed
corrective action and timeline to the Administrator for approval as
soon as practicable but no later than 75 days after the initial
exceedance. Requiring approval by the Administrator for corrective
action timelines that extend beyond 120 days is consistent with the
corrective action timeline for surface emissions in 40 CFR
60.36f(c)(4)(v). This approach also prevents the landfill owner or
operator from delaying submittals for corrective action requests until
day 120. Once the negative pressure has been restored, the facility
must document the corrective actions taken in the facility's next
annual report.
    For corrective action required to address positive pressure or
temperature, the owner or operator must keep a record of the root cause
analysis conducted, including a description of the recommended
corrective action(s); the date for corrective action(s) already
completed following the positive pressure reading and; and for
action(s) not already completed within 60 days of the initial positive
pressure reading, a schedule for implementation, including proposed
commencement and completion dates. For corrective actions taking longer
than 60 days to correct the exceedance, the owner or operator would
also include in the annual report the root cause analysis, recommended
corrective action(s), date corrective actions were completed, and
schedule for implementing corrective actions. The owner or operator
must also notify the Administrator within 75 days. For corrective
actions taking longer than 120 days to correct the exceedance, the
owner or operator would include, in a separate notification submitted
to the Administrator for approval as soon as practicable, but no later
than 75 days after the initial positive pressure or elevated
temperature reading, the root cause analysis, recommended corrective
action(s), date corrective actions taken to date were completed, and
proposed schedule for implementing corrective actions.

3. Landfills Recirculating Leachate or Adding Other Liquids
    In the ANPRM and proposed Emission Guidelines, the EPA solicited
input on whether additional action should be taken to address emissions
from wet landfills (i.e., landfills that recirculate leachate or add
liquids). Commenters differed on whether the EPA should require
separate thresholds or different lag times for landfills that
recirculate leachate or add liquids. (The lag time is the time period
between when the landfill exceeds the emission rate threshold and when
controls are required to be installed and started up.)
    Comments: Commenters supported more environmentally protective
requirements for wet landfills and asserted that wet landfills produce
more methane but actually collect less. Commenters said that the EPA
should shorten the lag time for installing controls for these
landfills. Other commenters opposed separate requirements for wet
landfills and contended that additional requirements for wet landfills
would achieve minimal emission reductions and would result in a
significant additional burden for landfills that recirculate leachate.
One commenter said that the EPA should focus on potential emission
reductions at landfills that recirculate leachate.
    Commenters also differed on what methane generation rate (k-value)
should be used in the landfill Emission Guidelines for wet landfills.
One commenter indicated that they have previously provided several
studies on k-values for wet landfills to EPA and urged the EPA to
update the emission factors for wet landfills based on this literature
prior to adjusting the control requirements at landfills recirculating
leachate or adding other liquids. Another commenter asked the EPA to
use higher, more representative k-values, or perhaps a sensitivity
analysis for a range of k-values to estimate the impacts of controlling
emissions from wet landfills in the landfills Emission Guidelines.
    Response: Based on the diverse nature of the feedback provided and
several other outstanding EPA actions affecting the control
requirements and emission factors for wet landfills, the EPA is not
creating separate emission threshold or lag time requirements for wet
landfills in this action. Instead, the EPA believes it is appropriate
to further assess emissions from wet landfills prior to taking
additional action on control requirements or changes to the k-values.
As a result, the EPA is finalizing additional electronic reporting
requirements for wet landfills with a design capacity of 2.5 million Mg
or greater to inform potential future action on wet landfills. The
final rule is limiting reporting of these additional data to wet
landfills that meet the current size threshold of 2.5 million Mg of
design capacity to be consistent with the universe of landfills that
are affected by the rule.
    Specifically, the final Emission Guidelines require annual
electronic reporting of the volume of leachate recirculated (gallons
per year) and the volume of other liquids added (gallons per year), as
well as the surface area over which the leachate is recirculated (or
sprayed), and the surface area (acres) over which any liquids are
applied. The quantity of leachate recirculated or liquids added should
be based on company records or engineering estimates. The initial
report will collect historical data for the 10 years preceding the
initial annual reporting year, to the extent the data are available in
on-site records, along with data corresponding to the initial reporting
year. After the initial report, the other annual electronic reports
will include only the quantities of leachate recirculated and/or added
liquid and their corresponding surface areas for each the subsequent
reporting year. The EPA believes many landfills, especially those
operating with a Research, Development, and Demonstration (RD&D)
permit, already keep records and may submit reports containing
quantities of liquids added. So, the effort to track these additional
data is expected to be minimal. RD&D permits are issued through
Resource Conservation and Recovery Act (RCRA) subtitle D, part 258
regulations for MSW landfills. The EPA is also aware of some state
rules that require reporting of leachate or added liquids outside of
the Clean Air Act reporting requirements. Consolidating these data in
an electronic format in a central repository can help inform how
leachate or added liquids affect LFG generation and collection whether
air emission standards should be adjusted for wet landfills.
    The EPA is also requiring the landfill to report the total waste
disposed (Mg) in the area with recirculated leachate and/or added
liquids, as well as the annual waste acceptance rates (Mg/yr) in those
same areas. Recognizing that the waste quantities may be tracked at the
scale house entry to the landfill and not the specific cell where the
liquids are added, the EPA is allowing the landfill to report data
based on on-site records or engineering estimates.
    The EPA is exempting landfills in the closed landfill subcategory
from this wet landfill report recognizing that this information would
be difficult to obtain from this subcategory of landfills, these
landfills are unlikely to still be adding liquids if closed, and also
because the gas generation from these landfills is on the downward side
of their gas generation curve. In addition, for similar reasons the EPA
is allowing owners or operators of landfills to discontinue annual
reporting of the wet landfill report after the landfill has submitted
its closure report.
    The EPA is also aware of annual LFG collected and annual LFG
generation data electronically reported to 40 CFR part 98, subpart HH,
of the GHGRP and therefore the EPA is not requesting reporting of these
data in this rule to avoid duplicative requests. However, the EPA may
link the wet landfill practices data collected under the landfills NSPS
with the annual gas collected data under subpart HH in order to inform
how liquids addition affects LFG emissions. Similarly, the EPA
understands that precipitation may affect gas generation. However,
since precipitation data are readily available through the National
Weather Service, the EPA is not requiring reporting of this parameter.
Instead, the EPA will use existing electronic data already available to
link up with data collected under this final rule. These additional
data will be used to assess the appropriateness of potential future
action on wet areas of landfills.
    The Paperwork Reduction Act (PRA) requires each federal agency to
obtain OMB approval before undertaking a collection of information
directed to 10 or more people. The PRA applies whether a ``collection
of information is mandatory, voluntary, or required to obtain or retain
a benefit.'' The EPA believes the additional data on wet landfills will
be beneficial for evaluating whether separate thresholds for wet
landfills are appropriate when revising future MSW landfill standards.
Because the EPA understands that many of the data elements in the wet
landfill report, including quantities of leachate or other liquids
added and the surface areas over which those liquids are added are
tracked at a state level as part of a leachate management or RDD
permit, the EPA does not anticipate these data. Additionally, the EPA
is allowing landfill owners or operators to report the data elements in
the wet landfill monitoring report using either engineering estimates
or on-site records to minimize the burden on respondents, depending on
the types of records the landfill owner/operator may keep.
    This is a new rule and a new collections submitted to OMB under

EPA ICR number 2522.02. This collection is similar to collections for
subpart Cc. Thus, many of the line item burden estimates in this ICR
estimate are the same as the burdens submitted to OMB under ICR number
1893.06 for the most recent ICR renewal for subpart Cc.
4. Portable Gas Analyzers
    Commenters on the proposed NSPS (79 FR 41796) requested that the
EPA specify that portable gas composition analyzers are an acceptable
alternative to Methods 3A or 3C, and noted that these devices are
commonly used in practice to measure wellhead parameters and are
calibrated according to the manufacturer's specifications. Currently,
approvals of these analyzers are done on a case-by-case basis.
Therefore, in the preamble for the proposed revisions of the Emission
Guidelines (80 FR 52141), the EPA requested data or information on
using a portable gas composition analyzer according to Method 3A for
wellhead monitoring. The EPA also requested data on other reference
methods used for calibrating these analyzers.
    Comment: Many commenters supported the use of portable gas
composition analyzers and requested that the EPA specify that these
analyzers may be used as an approved alternative monitoring method for
well monitoring. Three state agencies indicated the use of the portable
analyzers is common practice. One of these agencies stated that Method
3A and Method 3C are designed to be used in ``quasi-CEMS'' and/or
``laboratory benchtop'' situations and most landfill operators are not
using this type of equipment to test wellhead LFG; instead, landfill
operators are using handheld-size portable analyzers. Another state
agency stated that portable gas composition analyzers (e.g., Landtec
GEM 2000) are a standard for conducting MSW landfill well monitoring
and the analyzers provide additional information on gas composition
than what the current Emission Guidelines require, which provides
operators with a better understanding of the condition of the landfill.
This commenter said that a primary advantage of portable gas
composition analyzers, for both landfills and regulators, is that these
devices take and record the monitored readings (as well as other
information on gas composition that is not required to be monitored in
the Emission Guidelines), which can then be downloaded into a
spreadsheet and prevent landfills from making data collection mistakes.
The commenter suggested that the EPA and state air pollution control
agencies would benefit if the EPA were to require landfills to submit,
in their semi-annual reports, all of the monitoring data recorded by
portable gas composition analyzers.
    One commenter stated that most portable gas composition analyzers
can be used to measure the oxygen level at the wellhead and can be
calibrated according to Method 3A, but are unlikely to be calibrated
according to Method 3C (to measure oxygen or nitrogen levels) because
such calibration requires the use of gas chromatograph equipment with a
thermal conductivity detector and integrator. The commenter said that
Method 3A is straightforward and does not specify a particular
technology. Several commenters specifically referenced the comments
from an equipment manufacturer that provided specific details on how
its Landtec GEM Series portable analyzers are able to comply with each
specific requirement in Method 3A, including the calibration
requirements. Two of these commenters said that portable gas
composition analyzers should be allowed in both the Emissions
Guidelines and NSPS. Another of these commenters requested that the EPA
add language to the rule to recognize that balance gas is commonly used
as a surrogate for nitrogen.
    With regard to the EPA's request for data on other reference
methods used for calibrating portable gas composition analyzers, one
commenter suggested that the EPA allow ASTM D6522 as an alternative to
Method 3A because an analyzer can easily be calibrated for oxygen alone
following ASTM D6522. The commenter stated that although the QA/QC
procedures in ASTM D6522 are different from Method 3A, they are just as
rigorous as Method 3A. The commenter stated that it has extensive data
available showing portable gas composition analyzers are routinely
calibrated according to ASTM Method D6522 for measuring NOx, CO, and
oxygen during engine testing. This commenter also stated that any
analyzer or device must be calibrated according to an EPA approved
method and not just manufacturer's specifications.
    Response: The EPA appreciates the commenters providing information
regarding the use of portable gas composition analyzers for landfill
monitoring. Commenters provided data showing that their portable gas
composition analyzers are used to monitor the oxygen level at a
wellhead and are capable of meeting the calibration requirements in
Method 3A. Therefore, in this action, we are clarifying the use of
portable gas composition analyzers with Method 3A. A portable gas
composition analyzer may be used to monitor the oxygen level at a
wellhead provided that the analyzer is calibrated and meets all QA/QC
according to Method 3A. Although we did not receive enough information
regarding calibration methods that could be used on a portable gas
composition analyzer to monitor the nitrogen level at a wellhead, any
portable combustion monitor analyzer that uses gas chromatography and
thermal conductivity technology may be used with Method 3C. Other
technologies for the measurement of nitrogen may be used in lieu of
Method 3C through the administrative alternative test method process
outlined in 40 CFR 60.8(b)(2).
    Regarding the suggestion to allow ASTM D6522-11 as an alternative
to Method 3A, the EPA thanks the commenter for their perspective. As
long as all the quality assurance is conducted as required by ASTM
D6522-11, then ASTM D6522-11 may be used as an alternative to Method 3A
for wellhead monitoring (prior to combustion). Examples of quality
assurance required by ASTM D6522-11 include, but are not limited to:
analyzers must have a linearity check, interference check, bias check
using mid-level gases, stability check, and be calibrated before a
test; and a calibration error check and the interference verification
must be conducted after the testing has occurred. Due to a different
sample matrix typically found in post-combustion gas streams as stated
in the applicability of ASTM D6522-11, the interference check must be
done on the oxygen measurement with the appropriate gases (e.g., carbon
dioxide, VOC mixture, and methane) and concentration ranges. The ASTM
D6522-11 method also has calibrations before and calibration checks
after testing. According to Methods 3A, 3C, and ASTM D6522-11, the data
are valid only when they pass the bias check or zero and upscale
calibration error check. The EPA does not believe manufacturers'
specifications are rigorous enough to ensure data are of a proper
quality.
5. More Precise Location Data
    The EPA proposed more specific requirements for reporting the
locations where measured methane surface emissions are 500 ppm above
background (80 FR 52124). Specifically, the EPA proposed to require
landfills to report the latitude and longitude coordinates of each SEM
exceedance using an instrument with an accuracy of at least 3 meters.
This includes surface methane readings above 500 ppm for landfills
conducting quarterly SEM with

GCCS in place, as well as landfills that are conducting Tier 4 SEM to
determine the timing of GCCS installation.
    Comments: Several commenters supported and several commenters
opposed the EPA's proposed requirement to report the latitude and
longitude coordinates of each methane surface emissions exceedance
using an instrument with an accuracy of at least 3 meters.
    Of those commenters that supported the requirement, one said that
making global positioning system (GPS) coordinates of each exceedance
available would assist owners or operators in determining the location
and timing of exceedances relative to the GCCS components and would
also assist in inspections and enforcement. This commenter added that
these requirements provided important compliance monitoring assurances
as well as important information to landfill owners or operators
regarding their GCCS effectiveness. Other supportive commenters argued
that all SEM data and GPS coordinates should be recorded, no matter
whether there is an exceedance. One of these commenters, a state
agency, said that the NSPS and Emission Guidelines have historically
required retention of only exceedance data, but GPS data correlated
with SEM readings would be an invaluable addition to the monitoring
procedure. Another commenter said recording all SEM data (rather than
only exceedances) was necessary to show compliance with the monitoring
requirement; and by linking the methane readings with positioning data,
the time required to process the data would be reduced. Commenters said
that by correlating the SEM readings directly with the location of the
reading, facilities and their regulators could easily gain a clear
picture of how the LFG collection system was functioning and anticipate
problems before they arose by tracking trends in the data.
    Of the commenters that opposed the requirement that owners or
operators of landfills report the latitude and longitude coordinates of
each exceedance using an instrument with an accuracy of at least 3
meters, one said it was unclear why coordinate information must be
reported, given that it merely adds burden for sites to collect and
report as well as for agencies to review. Two of these commenters
argued that the added expense to purchase an instrument (i.e., a GPS
device), use that GPS device in the field, and then plot the GPS data
on a map, may provide no additional value to the operator compared to
marking exceedances with marker flags. One of these commenters stated
that 3 meters is too much of an error range such that the use of GPS
alone may not allow the operator to return to the exact spot of the
exceedance, and may still necessitate the use of a marker flag. Another
of these commenters added that the existing approach of marking
exceedances at their exact physical location with a marker flag is
actually more accurate because it does not rely on a technology with
accuracy limitations.
    Some of the commenters that oppose the requirement said that it is
unclear from the docket materials (e.g., the Regulatory Impact
Analysis) whether the EPA evaluated: (1) If GPS equipment can achieve
an accuracy of at least 3 meters; (2) the cost to purchase or rent GPS
equipment; and/or (3) the size and weight of the GPS equipment with
regard to requiring a technician to carry another field monitoring
instrument. One of these commenters added that because GPS equipment is
not typically integrated into other monitoring devices, monitoring
technicians will be required to carry the GPS equipment in addition to
the monitoring equipment, which could be difficult and present a safety
concern.
    Response: The EPA is finalizing a requirement for landfills to
report the latitude and longitude coordinates of each surface emissions
exceedance, as proposed, except the instrument accuracy must be at
least 4 meters instead of 3 meters. GPS technology is readily available
and is currently in use at landfills in California and other landfills
employing electronic LFG data management systems. These GPS devices
have the ability to identify latitude and longitude coordinates in
decimal degrees with at least five decimal places. This level of
accuracy and precision is consistent with the requirements in Petroleum
Refinery Sector Risk and Technology Review and New Source Performance
Standards (80 FR 75250). The EPA is aware of one device that is already
in use by some landfills in California to conduct surface emissions
monitoring and to create a more comprehensive understanding of the
GCCS. The instrument, containing a flame ionization detector (FID), is
linked by Bluetooth wireless technology to a GPS-enabled handheld field
instrument. This instrument has an accuracy of 2-4 meters.
    When reviewing site records on the location of the traversed path
and where surface emission leaks were identified, inspectors will be
able to identify areas of the landfill where surface monitoring
activities may be incomplete, which may assist with targeting
inspections to problem areas of the landfill. In addition, more precise
location data will allow the landfill owner or operator to overlay the
coordinates of surface exceedances against maps of the GCCS to
determine spatial and temporal patterns of exceedances relative to GCCS
components. Both the landfill owner or operator and regulators can use
locational data to gain perspective on how the LFG collection system is
functioning over time and will allow the landfill to track trends in
GCCS performance and cover practices.
    Using GPS locational data will provide a more robust and long-term
record of GCCS performance compared to the short-term practice of
simply marking an exceedance location with a marker flag. Owners or
operators may continue the practice of marking exceedances with a flag,
but GPS data will allow the landfill owner or operator to return
readily to the location of the exceedance to not only take the required
corrective action, but also to track and inform long-term performance
of the GCCS to minimize emissions.
    The EPA included the rental price of a Trimble Integrated Landfill
Gas Solution device, which combines a FID linked by Bluetooth wireless
technology to a GPS-enabled handheld field instrument, in the revised
testing and monitoring cost analysis for both the final Emission
Guidelines and final NSPS. The GPS location is recorded in real time as
the technician traverses the path so the labor involved in gathering
and recording the data with GPS coordinates is expected to be minimal.
In fact, the recording of each surface reading and the corresponding
locational data is automatic, in contrast to the older technology,
which may have involved handwriting an exceedance in a notebook and
then transposing the data to a computer after returning from the field.
Eliminating transposing the data could reduce data entry errors and
improve data accuracy and credibility. The GPS device is already in use
by landfills that maintain an electronic LFG data management system to
map long-term trends in GCCS performance. The GPS device weighs
approximately 21 ounces (including battery weight) and can be clipped
to a belt or attached to a backpack to allow the technician to complete
the monitoring safely.

B. Tier 4

    In the 2015 Emission Guidelines proposal, the EPA proposed Tier 4
as an alternative site-specific emission threshold determination for
when a landfill must install and operate a GCCS (80 FR 52112). For both
Tier 4 SEM for

determining the timing for GCCS installation and SEM to ensure a well
operated GCCS, the EPA considered limiting SEM during windy conditions.
Specifically, in the Emission Guidelines, the EPA proposed that SEM
must be terminated when the average wind speed exceeds 5 mph or the
instantaneous wind speed exceeds 10 mph. However, the EPA also proposed
that the Administrator may approve alternatives to this wind speed
surface monitoring termination for landfills consistently having
measured winds in excess of these specified limits.
    Comments. The EPA received numerous comments on the Tier 4
provisions included in the 2015 Emission Guidelines proposal. The
discussion below includes all comments related to changes since the
2015 proposal; more detailed comments are available in the Response to
Comments document. A summary of the initial comments received in
response to our request for comments for a Tier 4 provision in the 2014
ANPRM was provided in the preamble to the proposal (80 FR 52112).
    Which landfills should qualify. Some commenters believe that the
EPA should limit the types of landfills that qualify for Tier 4. One
commenter opposed the inclusion of a Tier 4 option for new landfills,
stating that it allows a subset of new landfills to delay methane
capture requirements when these landfills will be required to install a
GCCS in the future and should have a GCCS designed and installed during
landfill construction. One commenter encouraged the EPA to ban Tier 4
for landfills with a voluntary (non-regulatory) GCCS because it is
possible that GCCS design, monitoring, recordkeeping, and reporting
requirements could be avoided indefinitely through the use of a non-
regulatory GCCS that may not provide the same level of control as
required by the EPA landfills regulations. Another commenter thinks
that Tier 4 could be conducted at landfills with a GCCS installed, but
that the GCCS should follow typical operational conditions during the
Tier 4 test. In other words, if portions of the site are typically
offline due to decreased gas flow, the commenter (0215-0197) thinks
those portions must remain offline during Tier 4. Further, one
commenter believes that no means of gas control whatsoever should be
employed during the Tier 4 exemption.
    Frequency. There were a variety of opinions on how often SEM should
be conducted for Tier 4. One commenter suggested the SEM should be done
annually instead of quarterly. Two other commenters were concerned with
reducing the frequency to semi-annually unless the landfill no longer
accepted waste. One of these commenters noted that if a landfill has
already crossed the 34 Mg/yr NMOC threshold and the facility continues
to receive solid waste, then the expected gas generation will continue
to increase.
    Windy conditions. Many commenters, including many state agencies,
opposed limiting surface monitoring during windy conditions, stating
that the wind restrictions would be a significant inhibitor to
completing the required monitoring in many regions of the country due
to typical windy conditions. Commenters also stated that it would be
difficult to schedule and reschedule dedicated sampling crews.
    Commenters claimed that climate conditions across the United States
are too variable, that monitoring the wind using an anemometer is not
representative of wind conditions where the surface monitoring is
required (5-10 cm of surface), and that it is difficult to assemble
monitoring team and schedule monitoring events if they may be cancelled
due to wind. One commenter supports the development of a Tier 4 SEM
methodology that is functional during windy conditions. Other
commenters support the removal of the wind speed criteria and
replacement with a requirement that surface monitoring be performed
during typical meteorological conditions. Lastly, one commenter pointed
out that the Tier 4 proposal is inconsistent with the ongoing quarterly
SEM requirements since Tier 4 has wind restrictions and the ongoing
quarterly SEM does not.
    One commenter noted that EPA recognized wind speed can skew the
results of SEM. Another commenter did not submit comments specific to
the wind speed limitations; however, this commenter supported the SEM
approach in the CA LMR, which does include wind speed restrictions.
    Reporting requirement. Commenters supported the notification
requirement; however, one commenter believes landfills should not be
required to reschedule monitoring events based on the availability of
regulatory authorities. Furthermore, two commenters thought the
notification requirement was acceptable but with the existing wind
requirements, coordination with regulators could become even more
challenging. Another commenter did not support the notification
requirement because Tier 4 is voluntary.
    Response: After considering public comments and input from small
entity outreach, the EPA is finalizing Tier 4 SEM procedures for
determining when a landfill must install a GCCS. Tier 4 provides
operational flexibility and allows owners or operators of landfills
that have exceeded the modeled NMOC emission rate threshold to
demonstrate that site-specific surface methane emissions are below a
specific threshold. Commenters raised some valid points, however, and
based on our consideration of that input, we are making some
adjustments to the final rule.
    In response to public comments concerned with implementation of
Tier 4 with wind speed restrictions, the EPA is retaining a wind speed
limitation with allowance of a wind barrier when onsite wind speed
exceeds the limits in the regulation. The EPA is also providing
additional clarifications about probe placement (as described in
sections IV.A.2 and V.B of this preamble) for Tier 4 SEM. In the
proposed NSPS (80 FR 52136), the EPA acknowledged concerns about the
accuracy of SEM under windy conditions. The EPA is including the wind
speed restriction, because air movement can affect whether the monitor
is accurately reading the methane concentration during surface
monitoring. Because Tier 4 is an optional emission threshold
methodology, the EPA believes that wind speed restrictions and the use
of wind barriers are appropriate to ensure the reliability of the
results, which in turn determine the timing of GCCS installation. We
also refined the wind speed criteria to account for gusts up to 10 mph.
The EPA is not finalizing a variance for wind speed, but is allowing
the use of a wind barrier. In the proposed NSPS (80 FR 52136), the EPA
acknowledged concerns about the accuracy of SEM under windy conditions.
The EPA also expressed concern about whether monitors could accurately
read methane concentrations or provide representative results. The EPA
has provided the Tier 4 approach as a flexible alternative to
traditional modeling based approaches; but still asserts the importance
of accurate measurements due to the use of the SEM approach to
determine installation of controls.
    In addition, Tier 4 is allowed only if the landfill owner or
operator can demonstrate that NMOC emissions are greater than or equal
to 34 Mg/yr but less than 50 Mg/yr using Tier 1 or Tier 2 (a landfill
need not model emissions under Tier 3 before using Tier 4). Tier 3 was
not required because tiers 1 and 2 are more commonly used. If both Tier
1 and Tier 2 indicate NMOC emissions of 50 Mg/yr or greater, then Tier
4 cannot be used. This change avoids a

potential conflict between what is required under the Emission
Guidelines and what is required by the landfills NESHAP for landfills
with modeled NMOC emissions greater than 50 Mg/yr. It also ensures that
landfills with modeled NMOC emissions at 50 Mg/yr or more continue to
be required to install controls at an NMOC level and on a schedule that
is at least as stringent as the current NSPS (40 CFR part 60, subpart
WWW). To demonstrate that NMOC emissions are less than 50 Mg/yr
according to Tier 1 and Tier 2, landfill owners or operators will
continue to calculate the NMOC emission rate and report results
annually.
    Regarding frequency of monitoring, the EPA is finalizing an
approach where quarterly SEM is required for Tier 4 indefinitely unless
the landfill is closed. Closed landfills would be able to reduce the
frequency of surface emission monitoring to annually after four
quarters of no surface exceedances. Landfills that are closed are on
the downside of their gas generation profile.
    Regarding landfills equipped with a non-regulatory GCCS, the EPA is
allowing the non-regulatory GCCS to be in operation during the Tier 4
SEM demonstration, but only if the non-regulatory GCCS has operated for
at least 75 percent of the hours the 12 months leading up to the Tier 4
SEM demonstration (6,570 hours), as discussed below. The EPA recognizes
that many landfills have acted early to control their emissions and
installed a GCCS before surpassing the size and NMOC emission
thresholds in the landfills regulations in order to recover and utilize
LFG methane for beneficial use, flare for carbon credits, control
odors, or meet state-specific regulations that may be more stringent
than the federal NSPS standards. Thus, during the SEM demonstration,
the non-regulatory GCCS must continue to operate as it normally would
to collect and control as much LFG as possible. Although these
landfills do not operate their GCCS under the landfills NSPS, they
employ the same technology that would be applied to comply with the
landfills NSPS. Many of these non-regulatory GCCSs are located at sites
that are likely to eventually exceed the NSPS size and NMOC emissions
thresholds and thus if no exceedances are identified during a Tier 4
SEM, the system is operating at a level consistent with the landfills
NSPS collection and control requirements and operational standards at a
point in time earlier than when federal regulations would require.
These near-term methane reductions from non-regulatory GCCS are
beneficial to the environment and the goal of achieving short-term
emission reductions of methane, a potent greenhouse gas. In addition,
landfill owners or operators have incentive to operate the GCCS as
efficiently as possible to collect and control LFG to avoid surface
exceedances, as it would reduce paperwork requirements associated with
the compliance provisions of the landfills NSPS. The non-regulatory
GCCS would have to be robust to keep readings below 500 ppm methane
during an SEM demonstration.
    To not allow the Tier 4 demonstration while a non-regulatory GCCS
is in operation under these circumstances would create a disincentive
for landfill owners or operators to install control systems voluntarily
before emissions reach the regulatory threshold for review. The
requirement to operate the GCCS at least 75 percent of the hours during
the 12 months leading up to the Tier 4 SEM demonstration (described
below) will ensure that the non-regulatory GCCS is in regular use and
thus represents accurate operation of the facility.
    The landfill owner or operator is allowed to operate the non-
regulatory GCCS during the Tier 4 demonstration, but only if the non-
regulatory GCCS has operated for at least 75 percent of the hours
during the 12 months leading up to the Tier 4 SEM demonstration (6,570
of 8,760 hours). To demonstrate that the non-regulatory GCCS operated
at least 75 percent of the hours during the 12 months leading up to the
Tier 4 SEM demonstration, landfill owners or operators must keep
records of the total operating hours of the gas collection system as
measured for each destruction device (i.e., at the flare, engine, or
other destruction device), as well as the annual operating hours where
active gas flow was sent to each destruction device. If the non-
regulatory GCCS has not operated at least 75 percent of the hours
during the 12 months leading up to the Tier 4 SEM demonstration, then
the landfill is not eligible for Tier 4. The EPA seeks to encourage use
of voluntary non-regulatory GCCS systems for early gas collection
before emissions reach the regulatory threshold for review, while still
allowing landfill owners and operators to use Tier 4 surface emissions
monitoring approach to determine if a GCCS is required. We believe that
requiring the operation of the non-regulatory GCCS at least 75 percent
of the hours during the 12 months leading up to the Tier 4 SEM
demonstration (described below) will ensure that the non-regulatory
GCCS is in regular use and thus results would be representative of the
operation of the landfill.
    Regarding other recordkeeping and reporting requirements associated
with Tier 4, landfill owners or operators choosing Tier 4 would
continue to calculate the NMOC emission rate and report results in the
annual report to demonstrate that NMOC emissions are less than 50 Mg/
yr. Once there is any measured concentration of methane of 500 ppm or
greater from the surface of the landfill, the EPA is requiring a GCCS
to be installed and operated within 30 months of the most recent NMOC
emission rate report in which the calculated NMOC emission rate equals
or exceeds 34 Mg/yr according to Tier 2. Starting the 30 months from
the most recent NMOC emission rate report ensures that a GCCS is
installed in a timely manner. The EPA believes that if a landfill owner
or operator chooses to use Tier 4 SEM, it is appropriate to require the
installation and operation of a GCCS when any reading of 500 ppm or
greater is detected during the quarterly SEM event. Since Tier 4 is
allowed only if the landfill owner or operator can demonstrate that
NMOC emissions are greater than or equal to 34 Mg/yr NMOC, but less
than 50 Mg/yr using Tier 1 or Tier 2, we would expect the methane
emissions at the landfill to be below the 500 ppm threshold. If an
exceedance of the threshold is detected, it would be indicative of
higher emissions than would normally be expected at a landfill.
    The EPA is also finalizing a recordkeeping requirement to take and
store digital photographs of the instrument setup. The photographs must
be time and date-stamped and taken at the first sampling location prior
to sampling and at the last sampling location after sampling at the end
of each sampling day, for the duration of the Tier 4 monitoring
demonstration. The EPA believes these records will help provide
credibility to the Tier 4 sampling results.
    The EPA is also finalizing a requirement to notify delegated
authorities 30 days prior to the Tier 4 test so that officials can be
present to observe the SEM. This notification is consistent with other
notification requirements for stack testing. This notification
requirement will also mitigate concerns that the SEM is being conducted
incorrectly and ensure transparency of results achieved during the SEM
approach. In the event the Tier 4 SEM is postponed due to weather
conditions or other unforeseen events, the EPA is requiring the owner
or operator to notify the delegated authority to arrange a rescheduled
Tier 4 SEM date.

    Emerging Measurement Technologies. This rulemaking provides certain
MSW landfill owners or operators the option of using either modeling or
the Tier 4 SEM approach to determine whether controls are required to
be installed at specific landfills. Current modeling approaches, which
rely on the decomposition rate of different waste streams buried in a
landfill, are prone to uncertainties due to inaccuracies in input data
and often unverifiable assumptions. Current surface emission
measurement methodologies can also have associated uncertainties.
    New methane emissions measurement methodologies are emerging that
are anticipated to provide landfill methane emission rates (mass per
unit time) over time, thereby reducing significantly the uncertainty
associated with current modeling and emission measurements approaches.
Two promising examples of new methane measurement methodologies being
used by research groups to quantify landfill methane emissions are
mobile tracer correlation (TC) 44 45 46 47 and discrete area
source eddy covariance (DASEC).\48\
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    \44\ Development of a mobile tracer correlation method for
assessment of air emissions from landfills and other area sources,
Foster-Wittig, T.A.; Thoma, E.D.; Green, R.B.; Hater, G.R.; Swan,
N.D.; Chanton, J.P. Atmos. Environ. 2015, 102 (0), 323-330.
    \45\ Quantification of methane emissions from 15 Danish
landfills using the mobile tracer dispersion method, M[oslash]nster,
J.; Samuelsson, J.; Kjeldsen, P.; Scheutz, C. Waste Manage. 2015, 35
(0), 177-186.
    \46\ Methane Emissions Measured at Two California Landfills by
OTM-10 and an Acetylene Tracer Method, Green, R.B., Hater, G.R.,
Thoma, E.D., DeWees, J., Rella, C.W., Crosson, E.R., Goldsmith,
C.D., Swan, N., Proceedings of the Global Waste Management
Symposium, San Antonio, TX, October 3-6, 2010.
    \47\ Development of Mobile Measurement Method Series OTM 33;
Thoma, E.D.; Brantley, H.L.; Squier, B.; DeWees, J.; Segall, R.;
Merrill, R.; Proceedings of the Air and Waste Management Conference
and Exhibition, Raleigh, NC, June 22-25, 2015.
    \48\ Using Eddy Covariance to Quantify Methane Emissions from a
Dynamic Heterogeneous Area, Xu, L., Lin, X., Amen, J., Welding, K.
and McDermitt, D. Impact of changes in barometric pressure on
landfill methane emission. Global Biogeochemical Cycles 2014, 28(7),
pp. 679-695.
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    1. Mobile tracer correlation. This methodology provides a ``snap-
shot in time'' assessment of whole facility methane emissions using on-
site release of atmospheric tracer gases. It provides a total mass
emission rate of methane (or other gas) per unit of time. An
instrumented vehicle driving 1 km to 4 km downwind of the landfill
simultaneously measures the emitted landfill methane plume along with
the superimposed tracer gas release. The landfill methane emission rate
is determined through a simple ratio to the known tracer gas release
rate. The technique has been demonstrated using a variety of tracer
gases and instruments by a number of groups to investigate emissions
from landfills and other sources. The mobile tracer correlation
approach is under development by the EPA as a Category C ``other test
method (OTM)'' with potential posting in 2017 (https://www3.epa.gov/ttnemc01/prelim.html).
    2. Eddy covariance (EC). This micrometeorological method estimates
the source emission rate from the vertical wind speed and gas
concentration above the emitting surface. This technique measures the
emissions flux in mass of methane (or other gas) per unit area. The
technique is well-established for measurement of emission fluxes from
spatially-extended homogenous sources, such as very large, flat fields.
Discrete area source eddy covariance (DASEC) is an application of EC to
finite, heterogeneous area sources. This application of EC has been
recently demonstrated on landfills, although method development
questions on the effects of topography and variable observational foot
print remain. DASEC provides the potential for long term (near
continuous) measurements of discrete sections of a landfill using
solar-powered on-site instrumentation. Development of this type of long
term measurement capability is critical to better understand and *track
changes in landfill emissions overtime that may be caused by both site
management and atmospheric factors.
    In sum, as noted above, these techniques are still being
investigated and additional work will be needed before the EPA can deem
them ready for use in this application. Once additional research is
completed, we believe that DASEC used in combination with mobile TC
will provide a characterization of methane landfill emissions with
significantly reduced uncertainty over current models or measurement
techniques.

C. Changes To Address Closed or Non-Productive Areas

1. Closed Landfill Subcategory
    In the 2015 Emission Guidelines proposal, the EPA proposed a
separate subcategory for landfills that closed before August 27, 2015.
These landfills would be subject to an NMOC emission threshold of 50
Mg/yr NMOC for determining when controls must be installed or removed,
rather than the 34 Mg/yr NMOC emission threshold (or corresponding Tier
4 emission threshold) that would apply to open landfills. In addition,
the EPA requested comments on extending the subcategory of closed
landfills to those that close no later than 13 months after publication
of the final Emission Guidelines in the Federal Register.
    Comment: Commenters generally favored the creation of a closed
landfill subcategory and believe it was appropriate for closed
landfills to be categorized separately. One commenter agreed that a
separate category is appropriate, but only if EPA decides to lower the
NMOC emission threshold thus ensuring that closed landfills with low
emissions are not burdened with a requirement to install a GCCS.
Another commenter suggested that the EPA exempt closed landfills from
40 CFR part 60, subpart Cf, entirely since facilities that no longer
have income from waste acceptance have financially planned for closure.
The commenter believes that if these landfills were included in the new
rule, it would cause financial burden.
    Many commenters, including one state agency, support the expansion
of the closed landfill subcategory to include those facilities that
closed no later than 13 months of publication of the Emission
Guidelines. Commenters believe it is critical that landfills that are
planning to close are given the necessary time to meet all criteria and
file required documentation to achieve closed status. Another commenter
believes the EPA should provide the opportunity for landfills to be
closed under the Emission Guidelines until the state or federal
regulations implementing the revised Emission Guidelines are effective
(i.e., through a revised state or federal plan). This would allow more
landfills nearing the end of their useful lifetime with little ability
to change their fees or plan for longer GCCS operation the chance to
close and remain under current regulations.
    Response: After considering public comments, the EPA is finalizing
the subcategory for closed landfills and is expanding the subcategory
to include those landfills that close on or before September 27, 2017.
Landfills in the closed landfill subcategory continue to be subject to
a 50 Mg/yr NMOC emission rate threshold for installing a GCCS,
consistent with the NMOC threshold in 40 CFR part 60, subparts Cc and
WWW.
    The EPA recognizes that after landfills stop accepting waste and
close, LFG flows decline as well as the corresponding ability to
achieve additional reductions. Many of these closed landfills are
subject to the emission control requirements in the current Emission
Guidelines (40 CFR part 60, subpart Cc, or corresponding state or
federal plan) or the current

NSPS (40 CFR part 60, subpart WWW) and have achieved significant
reductions. However, commenters report that declining gas flows make it
difficult to operate a GCCS according to the landfills regulations and
many closed landfills must use supplemental fuel to properly operate
control devices such as flares for example. In addition, many closed
landfills no longer have income from tipping fees, and have either
decommissioned their GCCS or are in process of doing so. Thus, the EPA
recognizes that it could be financially burdensome for landfills that
are already closed to restart or expand their GCCS. For these reasons,
the EPA is finalizing the subcategory of closed landfills.
    To give closed landfills or landfills that are planning to close
more time to complete the steps to reach closure, the EPA is expanding
the closed landfill subcategory to include those landfills that close
on or before September 27, 2017. Closed landfills must submit a closure
report to the Administrator within 30 days of waste acceptance
cessation. The Administrator may request additional information as may
be necessary to verify that permanent closure has taken place in
accordance with the closure requirements under RCRA (40 CFR 258.60).
Closure criteria include a requirement to prepare a written closure
plan and to install a final cover system that is designed to minimize
infiltration and erosion.
    Landfills in the closed landfill subcategory of the Emission
Guidelines would be exempt from initial reporting requirements in
subpart Cf, provided that the landfill already met these requirements
under subparts Cc or WWW of 40 CFR part 60.
    For landfills that are expected to close after September 27, 2017,
the EPA understands that gas quality will remain a concern and has
revised the GCCS removal criteria, as discussed in section IV.A.5 of
this preamble.
2. Criteria for Removing or Decommissioning a GCCS
    The proposed revisions to the Emission Guidelines in 2015 modified
the criteria that allow a landfill owner or operator to cap or remove
the GCCS. Specifically, the proposal refined the 15-year criterion by
allowing a landfill owner or operator to demonstrate that the GCCS will
be unable to operate for 15 years due to declining gas flows. In
addition, the EPA tightened the NMOC emissions criterion, requiring the
controls until the NMOC emissions were below 34 Mg/yr for three
consecutive quarters to be consistent with the emission threshold for
installing controls. For closed landfills, the NMOC emissions criterion
remained at 50 Mg/yr to be consistent with the emission threshold for
the closed landfill subcategory. Finally, the proposed Emission
Guidelines added an alternative removal criterion based on site-
specific SEM of methane. This alternative would allow the owner or
operator to demonstrate for four consecutive quarters that there are no
surface emissions of 500 ppm or greater from the closed landfill or
area of an open landfill that is closed. The EPA received numerous
comments on the revised set of GCCS removal criteria.
    Comment: Commenters did not agree on the proposed alternative to
allow an SEM demonstration as a criterion for removing a GCCS.
Commenters in favor of an SEM demonstration for GCCS removal agreed
with the flexibility that the approach would offer, but commenters that
opposed the criterion expressed concern about emissions once the GCCS
was no longer operating.
    Some commenters opposed SEM procedures for determining removal or
decommissioning of the GCCS. One commenter expressed concerns with
relying on surface emission testing because the intervals are too far
apart to detect localized high emissions and low surface emission
readings during a dormant period could lead to uncontrolled emissions
at a later period. The commenter (0215-0121) added that even in a
closed landfill the decay process is not complete and gas collection
systems should stay in place. Another commenter opposed SEM
specifically at closed areas of open landfills due to gas migration
concerns and difficulty in defining these areas.
    Several commenters representing industry and state agency interests
supported the use of SEM procedures to help determine the removal or
decommissioning of existing GCCS. Commenters supported the use of SEM
to allow the flexibility to confirm when a closed landfill or area of
an open landfill that is closed is no longer producing gas in
significant quantities could remove or decommission all or a portion of
the GCCS. Several of these commenters referenced a rationale similar to
the one they provided for supporting the use of Tier 4 SEM for
determining GCCS installation as discussed in section VI.B of this
preamble.
    Commenters that supported an SEM demonstration for GCCS removal
presented several options on how to implement the SEM procedure.
Several commenters requested that the EPA provide a ``step-down''
procedure for scaling down GCCS operations in nonproducing areas and
allowing a GCCS to be removed from rule applicability. Two commenters
made recommendations on SEM procedures for GCCS removal or
decommissioning, which included shutting down the GCCS for 30 days
following a Tier 2 test showing NMOC emissions below the threshold,
then relying on subsequent SEM demonstrations and corrective action to
determine whether the GCCS could remain off. Other commenters also
stated that when considering SEM for removing the GCCS, quarterly SEM
should be performed at steady state conditions. As LFG generation
declines, one commenter suggested that some wells may be removed from
service; however, such wells must not be turned on in order to pass
quarterly SEM and subsequently turned back off for the remainder of the
quarter. Another commenter suggested that EPA not rely solely on
surface emissions when defining a closed landfill in arid areas, but
instead should consider the gas quality being collected (methane,
carbon dioxide, negative pressure, or nitrogen/oxygen content) when
determining when a GCCS can be removed.
    Regarding the 15-year criterion in the 2015 Emission Guidelines,
several commenters noted that the provision to allow landfills to
demonstrate the GCCS could not be operated for 15 years due to
declining flow was vague, and more guidance was needed to provide
instructions to landfills on how to demonstrate this to regulators.
    Response: After considering public comments, the EPA is finalizing
criteria for capping, removing, or decommissioning the GCCS that are
similar to the criteria in 40 CFR part 60, subpart Cc, but have been
adjusted to reflect the NMOC emission threshold in the final rule and
to provide flexibility on the requirement to operate the GCCS for 15
years. The final criteria are: (1) The landfill is a closed landfill,
(2) the GCCS has been in operation for 15 years or the landfill owner
or operator can demonstrate that the GCCS will be unable to operate for
15 years due to declining gas flows, and (3) three successive tests for
NMOC emissions are below the NMOC emission threshold of 34 Mg/yr for
open landfills and below 50 Mg/yr NMOC for closed landfills. The three
successive tests for NMOC emissions makes the threshold for removing a
GCCS consistent with the threshold for installing a GCCS. The EPA is
not finalizing an alternative set of criteria for capping, removing, or
decommissioning a GCCS that includes a SEM demonstration.
    While a SEM approach has been allowed for installation of controls,
the

EPA believes it is not appropriate to allow SEM demonstrations for
capping, removing, or decommissioning a control system. The EPA
recognizes the unique emissions profile for landfills including the
ability of these sources to release emissions for decades. For these
reasons, the EPA believes it is appropriate to ensure that controls are
installed and properly maintained for the appropriate period of time.
The EPA believes sufficient flexibility has been added to the control
removal approach by allowing a demonstration of the system's inability
to operate for 15 years due to declining gas flows and a calculation of
the NMOC emission rate. Further, during the comment period, concerns
were raised about changes in the waste mass over time and how the SEM
approach could inadvertently allow landfills whose emissions were in a
period of dormancy, rather than a decline in their emissions profile,
to remove controls. Agency enforcement personnel are also aware of
situations where the installation of additional wells led to additional
gas capture at sites asserting declining emissions. The EPA understands
the importance of gas capture from landfills and believes the SEM
approach for control removal may have the unintended consequence of
allowing controls to be removed when significant gas capture is still
possible. As a result, the EPA is not finalizing the SEM approach for
removal.
    Several commenters noted that the provision provided in the 2015
Emission Guidelines to allow landfills to demonstrate the GCCS could
not be operated for 15 years due to declining flow was vague, and more
guidance was needed to provide instructions to landfills on how to
demonstrate this to regulators.
    Regarding the 15-year criterion, the EPA is retaining the
requirement to operate the GCCS for 15 years, but is providing
flexibility to address declining gas flow in areas where the GCCS has
not operated for 15 years. If the landfill is closed and the NMOC
emission rate is less than 34 Mg/yr, but the GCCS has not operated for
15 years, the landfill owner or operator can demonstrate that the GCCS
will be unable to operate for 15 years due to declining gas flows. The
EPA is providing this flexibility to address areas of declining gas
flows due to the age of the waste, arid climate, or low organic
content. Given that there are unique situations that could cause low
gas flow, or low gas quality which would cause a GCCS to be unable to
operate for 15 years, the EPA is not providing prescriptive criteria
for how a landfill owner or operator can demonstrate that a GCCS could
not operate for 15 years and will proceed with a site-specific approach
for handling these unique cases. Some examples of data elements that
could be used to demonstrate a GCCS is unable to operate may include
supplemental fuel use at the flare to sustain operations or LFG quality
sample measurements showing methane content lower than what is viable
for combustion in the destruction device.

D. Startup, Shutdown, and Malfunction Provisions

    In July 2014, the EPA proposed that the standards in subpart XXX
apply at all times, including periods of startup or shutdown, and
periods of malfunction. In addition, the proposed NSPS included
recordkeeping and reporting requirements for all landfill owners or
operators to estimate emissions during such periods.
    Similarly, the EPA proposed standards that apply at all times in
the August 2015 proposed Emission Guidelines. However, the EPA
considered how the landfill emissions differ from those generated by
industrial or manufacturing sources. Specifically, the EPA noted that
landfill emissions are produced by a continuous biological process that
cannot be stopped or restarted. Therefore, the primary concern related
to SSM is with malfunction of the landfill GCCS and associated
monitoring equipment, not with the startup or shutdown of the entire
source. SSM periods that we have determined should be covered by the
work practice standard are those periods when the landfill GCCS and
associated monitoring equipment are not operating.
    To address these SSM periods, the EPA proposed in the 2015 Emission
Guidelines that in the event the collection or control system is not
operating the gas mover system must be shut down and all valves in the
GCCS contributing to venting of gas to the atmosphere must be closed
within 1 hour of the collection or control system not operating. This
provision is consistent with 40 CFR part 60, subpart WWW. Additionally,
the EPA proposed recordkeeping of combustion temperature, bypass flow,
and periods when the flare flame or the flare pilot flame is out. The
EPA received numerous comments on the 2014 proposed changes to the NSPS
and the additional proposed edits made in the 2015 Emission Guidelines.
A summary of these comments are presented below.
    Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008). Many commenters
stated that the Sierra Club decision applies only to rules with
numerical emission limits and not to rules that are specified as a work
practice. One of these commenters elaborated that Sierra Club applies
to section 111 of the Clean Air Act. Therefore, the commenter concluded
that landfills subject to the NSPS are not bound by the findings of
Sierra Club and instead they are legally allowed to develop a clear and
achievable landfill rule by considering the unique circumstances that a
landfill is a biological process that cannot be stopped or restarted
and that the gas collection and control systems must periodically be
shut down for maintenance, repair, and expansion.
    Retain the 5 day/1-hour exemption for SSM events. Many commenters,
including affected industry commenters and some state agencies,
disagreed with removing the provisions in 40 CFR part 60, subpart WWW,
which allow for exemption periods of 5 days for collection systems and
1 hour for treatment or control devices. These commenters indicated
that by removing this provision, state and local agencies could
misconstrue the rule to require that a landfill must operate the gas
collection system at all times, even during SSM, including periods of
collection system construction, expansion, and repair. These commenters
suggested instead of removing the exemption provision during periods of
SSM, compliance can be maintained as long as the landfill owner or
operator minimizes emissions of LFG by following the applicable work
practices and restores the system to operation as expeditiously as
practicable.
    One of the state agency commenters, suggested that the 5-day and 1-
hour time limitations in subpart WWW are appropriate for most
situations and instead of removing these exemptions, the new subpart
XXX could provide a mechanism for the facility to apply to the
Administration for an extension of those timeframes. On the contrary,
one state agency commenter and an NGO agreed with the standards
applying at all times, including periods of SSM.
    If the 5 day/1-hour exemption is not retained, the EPA should add a
work practice standard for SSM events. One commenter was concerned that
the preamble language for the 2014 proposed Emission Guidelines does
not clarify how a landfill can demonstrate compliance with the standard
during SSM events stating that ``compliance with proposed 40 CFR
60.34f(e) does not constitute compliance with the applicable standards
in proposed 40 CFR 60.36f'' and that ``by shutting down flow to the
flare or other control devices a source is unlikely to be in violation
of

the 98 percent emission reduction requirements since there will be no
gas flowing to the control device'' (see 80 FR 52134-52135). This
commenter stated that EPA must clarify this confusion and specify a
clear set of work practices (e.g., shut down of the gas mover system
and prevention of venting) that constitute compliance during SSM
periods when the collection or control system is not operated. Several
other industry commenters and the U.S. Small Business Administration
also asked that the rule specifically accommodate periods when the
collection system is not operating during activities associated with
construction, expansion, repair, replacement, testing, upgrades, or
other maintenance of the system or its components.
    Reporting requirement to estimate NMOC emissions whenever the
collection system or control system is not operating. Two commenters
representing a state agency and an NGO supported reporting NMOC
emissions during SSM periods. Several industry commenters provided
numerous technical arguments to explain the infeasibility of accurately
estimating NMOC emissions during the short periods of SSM. For example,
methods to estimate LFG emissions are based on site-specific variables
that estimate LFG generation over the life of the landfill, typically
on an annual basis, and cannot be used to estimate hourly or daily
emissions. Accordingly, the commenters contended that it is technically
and practically inappropriate to require landfill owners/operators to
make this estimate for the time periods that the gas collection or
control systems are not operated, given the substantial technical
uncertainties involved in estimating these emissions over discrete,
short-term time periods. Further, other commenters noted that emissions
during SSM are expected to be very low, reporting SSM emissions is an
onerous and meaningless exercise and is likely to overestimate
emissions.
    Two commenters asked that if the reporting requirement is retained,
the EPA should limit the reporting to periods when the flare is free
venting because these are the only emissions that can be estimated
accurately. Several commenters asked EPA to develop guidance on how to
estimate emissions during SSM if this requirement is retained in the
final rule.
    Several commenters stated that because there should be no deviation
from the rule when the work practices of the rule are followed, there
are no excess emissions, and the reported emissions are not relevant to
determining compliance. Commenters are concerned that if estimated NMOC
emissions are reported, states will deem the reported emissions to be
``excess emissions,'' which could be treated as a serious violation.
Therefore, reporting these emissions poses the risk of state or citizen
suits for enforcement, even when a landfill is following all
requirements of the rule.
    Other Comments. Several commenters added that because SSM
provisions apply to numerical emission limitations and a numerical
limitation applies only to the control device (not the collection
devices), commenters stated that SSM provisions should address only
operation of the control devices during periods when LFG is routed from
the collection system.
    Several commenters indicated that EPA must retain an allowance of 5
days/1 hour for downtime events so that states do not file enforcement
actions for downtime events that are shorter than the previously
allowed 5 days/1-hour allowance. These commenters also asked the EPA to
clarify that the 1-hour allowance for shutting vents allows for free
venting for 1 hour such that venting during this time period does not
constitute ``excess emissions'' that can be deemed a serious violation.
    Response: The EPA recognizes that landfills are not typical
affected sources that can be started up or shut down. Landfill
emissions are produced by a continuous biological process that cannot
be stopped or shut down. The EPA also recognizes that the primary
concern is with malfunction of the LFG collection and control system
and associated monitoring equipment, not with the startup, shutdown, or
malfunction of the entire source. The EPA received extensive comments
on the proposed requirements applicable to landfills during SSM events,
as summarized above. Consistent with the recent Court decision that
vacated the exemption in 40 CFR 63.6(f)(1) and (h)(1) for SSM (Sierra
Club v. EPA, 551 F.3d 1019), the EPA has established standards in this
rule that apply at all times.
    The general provisions in 40 CFR part 60 provide that emissions in
excess of the level of the applicable emissions limit during periods of
SSM shall not be considered a violation of the applicable emission
limit unless otherwise specified in the applicable standard (see 40 CFR
60.8(c)) (emphasis added). As reflected in the italicized language, an
individual subpart can supersede this provision.
    The EPA is finalizing a requirement in 40 CFR 60.465(e) whereby the
standards apply at all times, including periods of SSM. However, the
final rule incorporates a work practice during periods of SSM. During
these SSM events, owners or operators must shut down the gas mover
system and close within 1 hour all valves in the GCCS contributing to
venting of the gas to the atmosphere. The landfill owner or operator
must also keep records and submit reports of all periods when the
collection and control device is not operating. The EPA, however, is
not reinstating the 5-day exemption for SSM periods because the
provision provides an exemption from compliance with the standard
during SSM periods, which the EPA does not have the authority to do
under the reasoning of the Sierra Club decision.

E. Other Corrections and Clarifications

1. Test Methods
    In the 2014 proposed NSPS, the EPA did not include EPA Method 18 or
EPA Method 25A. In the 2015 proposed Emission Guidelines, the EPA
proposed to include Method 25A based on public comments received on the
2014 proposed NSPS and the EPA's recognition that the use of Method 25A
is necessary for measuring outlet concentrations less than 50 ppm NMOC.
However, the EPA did not propose to include Method 18 (80 FR 52112)
because the EPA had determined that Method 18 was not appropriate or
cost effective for testing the large number of NMOCs found in landfill
samples. Specifically, 40 target analytes are listed in the current
landfills section of AP-42 and 160 analytes are listed in the draft
landfills section AP-42. The EPA determined that the extensive quality
assurance required by the method makes the method technically and
economically prohibitive for all the potential target analytes.
    Comment: Commenters requested that the EPA retain both Method 18
and 25A in the final rule and cited a number of reasons that the EPA
should retain them, including both technical and legal reasons.
Commenters stated that landfill owners or operators have relied on
these test methods to demonstrate compliance for performance testing of
enclosed flares as a part of EPA policy for over a decade under 40 CFR
60.764 [60.754]. One commenter emphasized the importance of Method 25A
because its use is required for many sources with an outlet
concentration of less than 50 ppmv NMOC as carbon.
    The commenters noted that the majority of LFG destruction devices
show NMOC concentrations below 50 ppmv as carbon. Due to issues with
Methods 25/25C in measuring NMOC

content under this level, commenters observed that the proposed NSPS
rule change effectively removes the ability to accurately measure
compliance with the 20 ppmv outlet standard for a large class of
enclosed combustors. Commenter believes that Method 25A is the superior
testing methodology for certain circumstances and is more commonly used
in practice. Commenters cited limitations of Method 25, including
sensitivity of the test method to water and carbon dioxide and the
inability to measure NMOC content below 50 ppmv as carbon.
    Commenters also contended that the EPA did not provide any
justification for removing these methods. Commenters stated that the
EPA did not provide any factual data, methodology, or any legal or
policy justification for its proposed exclusion of Method 25A or Method
18; thus commenters claimed that the EPA did not satisfy the notice-
and-comment requirements of the CAA.
    Response: After considering public comments, the EPA is including
both EPA Method 25A and Method 18 (on a limited basis, i.e., compound
specific) in the final landfills regulations (40 CFR part 60, subparts
Cf and XXX).
    After reviewing the comments received on the NSPS for new landfills
proposed on July 17, 2014, the EPA recognizes that the use of Method
25A is necessary for measuring outlet concentrations less than 50 ppm
NMOC. EPA Method 25A determines total gaseous organic concentration of
vapor (total organic compounds). Because the rule regulates NMOC, EPA
Method 18 or Method 3C are needed to determine the concentration of
methane in the gas stream. Method 25A, in conjunction with Methods 18
or 3C (for methane), can be used to determine NMOC for the outlet
concentrations less than 50 ppm NMOC as carbon. Note that Method 25A
FIDs are insensitive to formaldehyde.
    While Method 18 may be used in conjunction with Method 25A for
methane or specific compounds of interest, there are limitations on the
number of analytes that can be reasonably quantified in measuring the
sum of all NMOCs. With the possibility of 40 target analytes listed in
the current landfill section of AP-42 (160 analytes in the draft
landfill AP-42), Method 18 is not an appropriate or cost effective
method to test all NMOCs found in landfill samples. The extensive QA
required by the method makes the method technically and economically
prohibitive for all the potential target analytes.
2. Tier 2 Sampling Procedure
    The EPA continues to believe that the number of samples required
per hectare is appropriate for Tier 2. As described in 40 CFR 60.764,
the EPA is reaffirming that the two samples are required per hectare
and if additional samples are taken, all samples must be used in
determining the site-specific NMOC concentration. Landfill owners or
operators must also ensure that the probes are evenly distributed over
the landfill surface. The EPA explored a number of methods, including a
statistical approach, when establishing requirements for the number and
location of Tier 2 samples for the original rule. Public commenters
raised significant concerns with approaches based on equations. As
such, the EPA determined that a simplified method (2 samples per
hectare) was best and received no public comments to the contrary.
3. Non-degradable Waste
    The EPA is reaffirming that all the waste must be included in
calculating the design capacity. Non-degradable waste cannot be
subtracted from the permitted landfill design capacity. However, non-
degradable waste can be subtracted from the mass of solid waste when
calculating the NMOC emission rate because such waste would not produce
NMOC emissions. Non-degradable waste is defined as waste that does not
break down through chemical or microbiological activity. Examples
include concrete, municipal waste combustor ash, and metals. Petroleum
contaminated soils (PCS) and paper mill sludges likely contain organics
that could be emitted as MSW LFG emissions. Therefore, emissions from
PCS and sludges would need to be accounted for in the emission estimate
only. The EPA is also reaffirming that documentation of the nature and
amount of non-degradable waste needs to be maintained when subtracting
the mass of non-degradable waste from the total mass of waste for NMOC
emission rate calculations.

VII. Impacts of This Final Rule

    For most Emission Guidelines, the EPA analyzes the impacts in the
year the standard is implemented. If the Emission Guidelines are
promulgated and published in August 2016, then the implementation year
would be 2017 based on the following: states have 9 months to prepare a
state plan implementing the guidelines (May 2017); the EPA has 4 months
to review the plan (September 2017); and if necessary, the state has an
additional 2 months to revise and submit a corrected plan based on any
comments from the EPA (November 2017). Concurrently, the EPA must
promulgate a federal plan within 6 months after the state plan is due,
consistent with 40 CFR 60.27(d), or November 2017. Thus, the EPA-
approved state plan and updated federal plan implementing the Emission
Guidelines are expected to become effective in November 2017. Although
late 2017 is the estimated implementation year, the reporting and
control timeframe allows 3 months to submit the first NMOC emission
report and then 30 months after reporting the NMOC emission rate
results before the GCCS is required to be installed. Therefore, the
first year that affected landfills could have controls installed under
the final rule will be late 2020.
    Because of the necessarily lengthy implementation process, the EPA
is assessing impacts in year 2025 as a representative year for the
landfills Emission Guidelines. While the year 2025 differs somewhat
from the expected first year of implementation for the Emission
Guidelines (year 2020), the number of existing landfills required to
install controls under the final rule in year 2025 is the same as those
estimated to control in the estimated first year of implementation.
Further, year 2025 represents a year in which several of the landfills
subject to control requirements will have had to expand their GCCS
according the expansion lag times set forth in 40 CFR part 60, subpart
Cf.
    The landfills dataset used for estimating the impacts of the
Emission Guidelines is discussed in detail in the August 27, 2015
proposed revisions to the Emission Guidelines (80 FR 52116-52117). The
EPA made several significant edits to the dataset since the August 2015
proposal, based on public comments received; new data made available
from the landfills reporting 2014 emissions to 40 CFR part 98, subpart
HH, of GHGRP; and consultations with EPA regional offices, and state
and local authorities to identify additional landfills expected to
undergo a modification within the next 5 years. After incorporating all
of the updates to the inventory and removing the landfills expected to
modify, the revised dataset to analyze the impacts of the final rule
now has 1,851 existing landfills that accepted waste after

1987 \49\ and opened prior to 2014.\50\ A detailed discussion of
updates made to the landfill dataset is in the docketed memorandum,
``Summary of Updated Landfill Dataset Used in the Cost and Emission
Reduction Analysis of Landfills Regulations, 2016.''
---------------------------------------------------------------------------

    \49\ November 8, 1987, is the date on which permit programs were
established under the Hazardous and Solid Waste Amendments of RCRA.
This date was also selected as the regulatory cutoff in the Emission
Guidelines for landfills no longer receiving wastes because the EPA
judged states would be able to identify active facilities as of this
date. The data available to EPA include an open year without the
month and so the analysis uses a cutoff year of 1988 for landfill
closure year.
    \50\ July 17, 2014, is the proposal date of the revised NSPS for
MSW landfills in 40 CFR part 60, subpart XXX. A landfill opening or
commencing construction on its modification after this date would
become subject to this new subpart and would not be subject to the
revised Emission Guidelines. The EPA cannot predict the exact month
a model landfill will open so the analysis uses a cutoff year of
2014.
---------------------------------------------------------------------------

    The methodology used for estimating the impacts of the Emission
Guidelines is discussed in detail in the August 27, 2015 proposed
revisions to the Emission Guidelines (80 FR 52116-52117). The EPA made
several significant edits to the methodology since the August 2015
proposal based on public comments and comments on a separate peer
review of the EPA Landfill Gas Energy Cost (LFGcost) model.\51\
Notably, the EPA adjusted its assumption of gas collection efficiency
to an average of 85 percent. The impacts analysis at the proposal did
not apply a collection efficiency assumption. However, in consideration
of public comments received and EPA assumptions in subpart HH of the
GHGRP, and analyses performed for marginal abatement cost curves, the
EPA has included an 85 percent average gas collection efficiency factor
to reflect a more realistic indicator of GCCS performance.\52\ In
addition, Chapter 2.4 of the EPA AP-42 for MSW landfills cites a range
of collection efficiencies for LFG between 60 and 85 percent. The EPA
also adjusted the electricity purchase price and anticipated revenue
estimates using forecasted commercial retail electricity rate data and
forecasted electricity generation price data for different Energy
Information Administration (EIA) Electricity Market Module
regions.53 54
---------------------------------------------------------------------------

    \51\ See the docketed 2016 RIA for additional discussion of
changes made on the methodology for estimating impacts as a result
of the LFGcost peer review.
    \52\ USEPA. Global Mitigation of Non-CO2 Greenhouse
Gases: 2010-2030. EPA-430-R-13-011.
    \53\ See the docketed 2016 RIA for additional discussion of
changes made to electricity pricing assumptions.
    \54\ To map existing landfill sites to EIA's Electricity Market
Module regions, the sites' geospatial coordinates were overlayed on
a map of the EMM regions. The AEO Electricity Market Module regions
are commensurate with the eGRID2012 primary regions for which a
shapefile is available at https://www.epa.gov/energy/download-egrid2012-shapefiles. For expected new landfills within a state the
specific location is unknown, therefore the landfill is located at
the state's centroid for purposes of mapping the site to an EMM
region.
---------------------------------------------------------------------------

    A detailed discussion of the methodology and equations used to
estimate the impacts of the final rule are available in the docketed
memorandum ``Revised Methodology for Estimating Cost and Emission
Impacts of MSW Landfill Regulations, 2016.'' The results of applying
this methodology to the population of existing landfills potentially
subject to the final rule are in the docketed memorandum ``Revised Cost
and Emission Impacts Resulting from the Landfill EG Review, 2016.''
Table 2 of this preamble summarizes the emission reductions and costs
associated with the final rule.

                                                Table 2--Emission Reductions and Costs for Final Rule in Year 2025 at Existing Landfills (2012$)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Number of
                                                               Number of                landfills     Annual                   Annual      Annual
                                          Landfills affected   landfills   Number of    reporting    Net cost  Annual NMOC    methane       CO2e       NMOC Cost     Methane cost    CO2e Cost
                 Option                     by final rule a     affected   landfills     but not     (million   reductions   reductions  reductions  effectiveness  effectiveness  effectiveness
                                                                   b      controlling  controlling    $2012)      (Mg\yr)     (million     (million      ($\Mg)         ($\Mg)        ($\mt) d
                                                                                c                                  Mg\yr)     mt\yr) d
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Baseline (2.5 million Mg design          All.................       1014          638          177        642       58,770          9.3         231         10,900           69.3            2.8
 capacity\50 Mg\yr NMOC).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Incremental values vs. the Baseline
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Final Option (2.5 million Mg design      Open................          0           93         -100     e 54.1        1,810        0.285         7.1         29,900            190            7.6
 capacity/34 Mg/yr NMOC).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
a The final option in this table shows the impacts of reducing the NMOC emission threshold to 34 Mg/yr on open landfills only, and retaining the NMOC threshold of 50 Mg/yr for the closed
  landfill subcategory.
b Landfills are affected by the landfills Emission Guidelines based on design capacity. Once affected, they calculate and report emissions until they exceed the NMOC threshold, which triggers
  control requirements. Since we are not changing the size threshold, there are no incremental landfills affected.
c Since the number of landfills affected remains the same as the baseline, the number of landfills reporting NMOC (but not controlling) decreases since more landfills will control emissions
  under the final rule.
d Results do not include secondary CO[ihel2] impacts.
e The annualized net cost for the final Emission Guidelines is estimated to be $54.1 million (2012$) in 2025, when using a 7 percent discount rate. The annualized costs represent the costs
  compared to no changes to the current Emission Guidelines (i.e., baseline) and include $92.6 million to install and operate a GCCS, as well as $0.76 million to complete the corresponding
  testing and monitoring. These control costs are offset by $39.3 million in revenue from electricity sales, which is incorporated into the net control costs for certain landfills that are
  expected to generate revenue by using the LFG to produce electricity.

A. What are the air quality impacts?

    The EPA estimates that the final rule will achieve nearly an
additional 3 percent reduction in NMOC from existing landfills, or
1,810 Mg/yr, when compared to the baseline, as shown in Table 2 of this
preamble. The final rule would also achieve 0.285 million Mg of methane
reductions (7.1 million mtCO2e) in 2025. These reductions are achieved
by reducing the NMOC threshold from 50 Mg/yr to 34 Mg/yr open
landfills.

B. What are the water quality and solid waste impacts?

    Leachate is the liquid that passes through the landfilled waste and
strips contaminants from the waste as the leachate percolates.
Precipitation generates the vast majority of leachate volume.
Installation of a gas collection system will generate additional
liquid, in the form of gas condensate, and it will be routed to the
same leachate treatment mechanisms in place for controlling
precipitation-based leachate. Collected leachate can be treated on site
or transported off site to wastewater treatment facilities. Some
landfills have received permits allowing for recirculation of leachate
in the landfill, which may further reduce the volume of leachate
requiring treatment. Additional liquid generated from gas condensate is
not expected to be significant and insufficient data are available to
estimate the increases in leachate resulting from expanded gas
collection and control requirements.
    The additional gas collection and control components required by
this final rule have finite lifetimes (approximately 15 years) and
these

pipes and wells will be capped or disposed of at the end of their
useful life. There are insufficient data to quantify the solid waste
resulting from disposal of this control infrastructure.
    Further, the incremental costs of control for the final rule of
$54.1 million in 2025 (7% discount rate, 2012$) are not expected to
have an appreciable market effect on the waste disposal costs, tipping
fees, or the amount of solid waste disposed in landfills because the
costs for gas collection represent a small portion of the overall costs
to design, construct, and operate a landfill. The handling of waste by
the private companies in the industry was estimated to generate $55
billion of revenue in 2011, of which landfilling contributed $13
billion, while a more recent estimate shows the U.S. non-hazardous
solid waste services industry generated about $60 billion in annual
revenues in 2015. These revenue estimates do not include activity
related to publicly owned landfills. For more information, see the
``Regulatory Impact Analysis for the Final Revisions to the Emission
Guidelines for Existing Sources and the New Source Performance
Standards in the Municipal Solid Waste Landfills Sector, 2016''
(hereafter ``2016 RIA'') included in the docket. There also is
insufficient information to quantify the effect increased gas control
costs might have on the amount of solid waste disposed in landfills
versus other disposal mechanisms such as recycling, waste-to-energy, or
composting. Note that elements of this final rule--notably lowering the
NMOC threshold to 34 Mg/yr--provide additional incentives to separate
waste.

C. What are the secondary air impacts?

    Secondary air impacts may include grid emissions from purchasing
electricity to operate the GCCS components, by-product emissions from
combustion of LFG in flares or energy recovery devices, and offsets to
conventional grid emissions from new LFG energy supply.
    The secondary air impacts are presented as net impacts, considering
both the energy demand and energy supply resulting from the final rule.
The methodology used to prepare the estimated secondary impacts for
this preamble is discussed in the docketed memorandum ``Revised
Estimates of Secondary Impacts of the Landfills Emission Guidelines
Review, 2016.''
    While we do expect NOx and sulfur dioxide (SO2) emission
changes as a result of these guidelines, we expect these changes to be
small and these changes have not been estimated. The net impacts were
computed for CO2e. After considering the offsets from LFG
electricity, the impacts of the final rule are expected to reduce
CO2 emissions by 277,000 metric tons per year. These
CO2 emission reductions are in addition to the methane
emission reductions achieved from the direct destruction of methane in
flares or engines presented in Table 2 of this preamble.

D. What are the energy impacts?

    The final rule is expected to have a very minimal impact on energy
supply and consumption. Active gas collection systems require energy to
operate the blowers and pumps and the final rule will increase the
volume of LFG collected. When the least cost control is a flare, energy
may be purchased from the grid to operate the blowers of the LFG
collection system. However, when the least cost control option is an
engine, the engine may provide this energy to the gas control system
and then sell the excess to the grid. Considering the balance of energy
generated and demanded from the estimated least cost controls, the
final rule is estimated to supply 0.51 million megawatt hours (MWh) of
additional renewable LFG energy per year, which will reduce the need
for conventional fossil-based energy sources.

E. What are the cost impacts?

    To meet the final rule emission thresholds, a landfill is expected
to install the least cost control for combusting the LFG. The cost
estimates evaluated each landfill to determine whether a gas collection
and flare or a gas collection with flare and engine equipment would be
least cost, after considering local power buyback rates and whether the
quantity of LFG was sufficient to generate electricity. The control
costs include the costs to install and operate gas collection
infrastructure such as wells, header pipes, blowers, and an enclosed
flare. For landfills for which the least cost control option is an
engine, the costs also include the cost to install and operate one or
more reciprocating internal combustion engines to convert the LFG into
electricity. Revenue from electricity sales was incorporated into the
net control costs using forecasted electricity generation price data
from EIA Electricity Market Module regions. Testing and monitoring
costs at controlled landfills include the cost to conduct initial
performance tests on the enclosed flare or engine control equipment,
quarterly surface monitoring, continuous combustion monitoring, and
monthly wellhead monitoring. At uncontrolled landfills, the testing and
monitoring costs include calculation and reporting of NMOC emission
rates.
    The nationwide incremental annualized net cost for the final rule
is $54.1 million, when using a 7 percent discount rate and 2012$. The
annualized net costs of $54.1 million represent the costs compared to
no changes to the current Emission Guidelines (i.e., baseline) and
include $92.6 million to install and operate a GCCS, as well as $0.76
million to complete the corresponding testing and monitoring. These
control costs are offset by $39.3 million in revenue from electricity
sales, which is incorporated into the net control costs for certain
landfills that are expected to generate revenue by using the LFG to
produce electricity.

F. What are the economic impacts?

    Because of the relatively low net cost of the final rule compared
to the overall size of the MSW industry, as well as the lack of
appropriate economic parameters or model, the EPA is unable to estimate
the impacts on the supply and demand for MSW landfill services.
However, because of the relatively low incremental costs, the EPA does
not believe the final rule would lead to substantial changes in supply
and demand for landfill services or waste disposal costs, tipping fees,
or the amount of waste disposed in landfills. Hence, the overall
economic impact of the final rule should be minimal on the affected
industries and their consumers.

G. What are the benefits?

    This final action is expected to result in significant emissions
reductions from existing MSW landfills. By lowering the NMOC emissions
threshold to 34 Mg/yr, these final guidelines would achieve reductions
of more than 1,810 Mg/yr NMOC and 285,000 metric tons of methane (7.1
million mtCO2e). In addition, the guidelines are expected to
result in the net reduction of 277,000 metric tons CO2, due
to reduced demand for electricity from the grid as landfills generate
electricity from LFG.
    This rule is expected to result in significant public health and
welfare benefits resulting from the climate benefits due to anticipated
methane and CO2 reductions. Methane is a potent GHG that,
once emitted into the atmosphere, absorbs terrestrial infrared
radiation that contributes to increased global warming and continuing
climate change. Methane reacts in the atmosphere to form tropospheric
ozone and stratospheric water vapor, both of which also contribute to
global warming. When accounting for the

impacts of changing methane, tropospheric ozone, and stratospheric
water vapor concentrations, the Intergovernmental Panel on Climate
Change (IPCC) 5th Assessment Report (2013) found that historical
emissions of methane accounted for about 30 percent of the total
current warming influence (radiative forcing) due to historical
emissions of greenhouse gases. Methane is therefore a major contributor
to the climate change impacts described in section III.B of this
preamble. The remainder of this section discusses the methane
reductions expected from this proposed rule and the associated
monetized benefits.
    As discussed in section IV of this preamble, this rulemaking
includes several changes to the Emission Guidelines for MSW landfills
that will decrease methane emissions from this sector. Specifically,
the final emission guideline changes are expected to reduce methane
emissions from all landfills in 2025 by about 285,000 metric tons of
methane.
    We calculated the global social benefits of these methane emission
reductions using estimates of SC-CH4, a metric that
estimates the monetary value of impacts associated with marginal
changes in methane emissions in a given year. The SC-CH4
estimates applied in this analysis were developed by Marten et al.
(2014) and are discussed in greater detail below.
    A similar metric, the social cost of CO2 (SC-
CO2), provides important context for understanding the
Marten et al. SC-CH4 estimates.\55\ The SC-CO2 is
a metric that estimates the monetary value of impacts associated with
marginal changes in CO2 emissions in a given year. It
includes a wide range of anticipated climate impacts, such as net
changes in agricultural productivity and human health, property damage
from increased flood risk, and changes in energy system costs, such as
reduced costs for heating and increased costs for air conditioning.
Estimates of the SC-CO2 have been used by the EPA and other
federal agencies to value the impacts of CO2 emissions
changes in benefit cost analysis for GHG-related rulemakings since
2008.
---------------------------------------------------------------------------

    \55\ Previous analyses have commonly referred to the social cost
of carbon dioxide emissions as the social cost of carbon or SCC. To
more easily facilitate the inclusion of non-CO2 GHGs in
the discussion and analysis the more specific SC-CO2
nomenclature is used to refer to the social cost of CO2
emissions.
---------------------------------------------------------------------------

    The SC-CO2 estimates were developed over many years,
using the best science available, and with input from the public.
Specifically, an interagency working group (IWG) that included the EPA
and other executive branch agencies and offices used three integrated
assessment models (IAMs) to develop the SC-CO2 estimates and
recommended four global values for use in regulatory analyses. The SC-
CO2 estimates were first released in February 2010 and
updated in 2013 using new versions of each IAM.
    The 2010 SC-CO2 Technical Support Document (TSD)
provides a complete discussion of the methods used to develop these
estimates and the current SC-CO2 TSD presents and discusses
the 2013 update (including recent minor technical corrections to the
estimates).\56\
---------------------------------------------------------------------------

    \56\ Both the 2010 SC-CO2 TSD and the current TSD are
available at: https://www.whitehouse.gov/omb/oira/social-cost-of-carbon.
---------------------------------------------------------------------------

    The SC-CO2 TSDs discuss a number of limitations to the
SC-CO2 analysis, including the incomplete way in which the
IAMs capture catastrophic and non-catastrophic impacts, their
incomplete treatment of adaptation and technological change,
uncertainty in the extrapolation of damages to high temperatures, and
assumptions regarding risk aversion. Currently, IAMs do not assign
value to all of the important physical, ecological, and economic
impacts of climate change recognized in the climate change literature
due to a lack of precise information on the nature of damages and
because the science incorporated into these models understandably lags
behind the most recent research. Nonetheless, these estimates and the
discussion of their limitations represent the best available
information about the social benefits of CO2 reductions to
inform benefit-cost analysis. The EPA and other agencies continue to
engage in research on modeling and valuation of climate impacts with
the goal to improve these estimates, and continue to consider feedback
on the SC-CO2 estimates from stakeholders through a range of
channels, including public comments received on Agency rulemakings, a
separate Office of Management and Budget (OMB) public comment
solicitation, and through regular interactions with stakeholders and
research analysts implementing the SC-CO2 methodology. See
the docketed 2016 RIA for additional details.
    A challenge particularly relevant to this rule is that the IWG did
not estimate the social costs of non-CO2 GHG emissions at
the time the SC-CO2 estimates were developed. In addition,
the directly modeled estimates of the social costs of non-
CO2 GHG emissions previously found in the published
literature were few in number and varied considerably in terms of the
models and input assumptions they employed \57\ (EPA 2012). In the
past, the EPA has sought to understand the potential importance of
monetizing non-CO2 GHG emissions changes through sensitivity
analysis using an estimate of the GWP of CH4 to convert
emission impacts to CO2 equivalents, which can then be
valued using the SC-CO2 estimates. This approach
approximates the SC-CH4 using estimates of the SC-
CO2 and the GWP of methane.
---------------------------------------------------------------------------

    \57\ U.S. EPA. 2012. Regulatory Impact Analysis Final New Source
Performance Standards and Amendments to the National Emissions
Standards for Hazardous Air Pollutants for the Oil and Natural Gas
Industry. Office of Air Quality Planning and Standards, Health and
Environmental Impacts Division. April. http://www.epa.gov/ttn/ecas/regdata/RIAs/oil_natural_gas_final_neshap_nsps_ria.pdf. Accessed
April 7, 2016.
---------------------------------------------------------------------------

    The published literature documents a variety of reasons that
directly modeled estimates of SC-CH4 are an analytical
improvement over the estimates from the GWP approximation approach.
Specifically, several recent studies found that GWP-weighted benefit
estimates for CH4 are likely to be lower than the estimates
derived using directly modeled social cost estimates for these
gases.\58\ The GWP reflects only the relative integrated radiative
forcing of a gas over 100 years in comparison to CO2. The
directly modeled social cost estimates differ from the GWP-scaled SC-
CO2 because the relative differences in timing and magnitude
of the warming between gases are explicitly modeled, the non-linear
effects of temperature change on economic damages are included, and
rather than treating all impacts over a hundred years equally, the
modeled damages over the time horizon considered (300 years in this
case) are discounted to present value terms. A detailed discussion of
the limitations of the GWP approach can be found in the 2016 RIA.
---------------------------------------------------------------------------

    \58\ See Waldhoff et al. (2011); Marten and Newbold (2012); and
Marten et al. (2014).
---------------------------------------------------------------------------

    In general, the commenters on previous rulemakings strongly
encouraged the EPA to incorporate the monetized value of non-
CO2 GHG impacts into the benefit cost analysis. However,
they noted the challenges associated with the GWP approach, as
discussed above, and encouraged the use of directly modeled estimates
of the SC-CH4 to overcome those challenges.
    Since then, a paper by Marten et al. (2014) has provided the first
set of published SC-CH4 estimates in the peer-reviewed
literature that are consistent with the modeling assumptions

underlying the SC-CO2 estimates.59 60
Specifically, the estimation approach of Marten et al. used the same
set of three IAMs, five socioeconomic-emissions scenarios, equilibrium
climate sensitivity distribution, three constant discount rates, and
aggregation approach used by the IWG to develop the SC-CO2
estimates.
---------------------------------------------------------------------------

    \59\ Marten et al. (2014) also provided the first set of SC-
N2O estimates that are consistent with the assumptions
underlying the IWG SC-CO2 estimates.
    \60\ Marten, A. L., E. A. Kopits, C. W. Griffiths, S. C. Newbold
& A. Wolverton (2014). Incremental CH4 and N2O
mitigation benefits consistent with the U.S. Government's SC-
CO2 estimates, Climate Policy, DOI: 10.1080/
14693062.2014.912981.
---------------------------------------------------------------------------

    The SC-CH4 estimates from Marten, et al. (2014) are
presented in Table 3 of this preamble. More detailed discussion of the
methodology, results, and a comparison to other published estimates can
be found in the 2016 RIA and in Marten, et al.

                                    Table 3--Social Cost of CH4, 2012-2050 a
                           [In 2012$ per metric ton (Source: Marten et al., 2014 \b\]
----------------------------------------------------------------------------------------------------------------
                                                                              SC-CH4
                                                 ---------------------------------------------------------------
                      Year                                                                            3% 95th
                                                    5% Average      3% Average     2.5% Average     percentile
----------------------------------------------------------------------------------------------------------------
2012............................................            $430           $1000           $1400           $2800
2015............................................             490            1100            1500            3000
2020............................................             580            1300            1700            3500
2025............................................             700            1500            1900            4000
2030............................................             820            1700            2200            4500
2035............................................             970            1900            2500            5300
2040............................................            1100            2200            2800            5900
2045............................................            1300            2500            3000            6600
2050............................................            1400            2700            3300            7200
----------------------------------------------------------------------------------------------------------------
\a\ The values are emissions-year specific. Estimates using several discount rates are included because the
  literature shows that estimates of the SC-CO2 (and SC-CH4) are sensitive to assumptions about the discount
  rate, and because no consensus exists on the appropriate rate to use in an intergenerational context (where
  costs and benefits are incurred by different generations). The fourth value is the 95th percentile of the SC-
  CH4 estimates across three models using a 3 percent discount rate. It is included to represent higher-than-
  expected impacts from temperature change further out in the tails of the SC-CH4 distribution.
\b\ The estimates in this table have been adjusted to reflect recent minor technical corrections to the SC-CO2
  estimates. See the Corrigendum to Marten et al. (2014), http://www.tandfonline.com/doi/abs/10.1080/14693062.2015.1070550.

    The application of these directly modeled SC-CH4
estimates from Marten et al. (2014) in a benefit-cost analysis of a
regulatory action is analogous to the use of the SC-CO2
estimates. In addition, the limitations for the SC-CO2
estimates discussed above likewise apply to the SC-CH4
estimates, given the consistency in the methodology.
    In early 2015, the EPA conducted a peer review of the application
of the Marten, et al. (2014) non-CO2 social cost estimates
in regulatory analysis and received responses that supported this
application. See the 2016 RIA for a detailed discussion.
    The EPA also carefully considered the full range of public comments
and associated technical issues on the Marten et al. SC-CH4
estimates received through this rulemaking. The comments addressed the
technical details of the SC-CO2 estimates and the Marten et al. SC-CH4
estimates as well as their application to this rulemaking analysis. One
comment letter also provided constructive recommendations to improve
the SC-CO2 and SC-CH4 estimates in the future. Based on the evaluation
of the public comments on this rulemaking, the favorable peer review of
the Marten et al. application, and past comments urging the EPA to