As discussed for the single wellhead only and multi-wellhead only
well site analyses, the EPA modeled OGI monitoring programs for both a
1.0 percent and 0.5 percent leak generation rate and compared the
resulting modeled emissions to the same empirical study data to
determine which model was more representative of the emissions at this
type of well site. The baseline emissions resulting from FEAST for this
model plant were 15.40 tpy methane and 8.51 tpy methane at 1.0 percent
and 0.5 percent leak generation rate, respectively. The highest average
site emissions were calculated at 3.3 tpy methane for large natural gas
sites and 4.0 tpy methane for large oil sites in the U.S. DOE marginal

well study, which the EPA anticipates is similar to the model plant
with major production and processing equipment. The EPA next applied
the emissions factors from the Rutherford, et al. study to the
equipment counts in our model plant, resulting in emissions of 7.1 tpy
methane. These emissions suggest the 0.5 percent leak generation rate
is more appropriate for consideration of the costs of control and
appropriate OGI monitoring frequency for well sites and centralized
production facilities with major production and processing equipment.

       Table 13--Summary of Emission Reductions and Cost-Effectiveness: OGI Monitoring at Well Sites With Major Production or Processing Equipment
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Cost-effectiveness         Incremental cost-
                                                                              Methane        VOC     --------------------------       effectiveness
                     Monitoring frequency                      Annual cost    emission     emission                            -------------------------
                                                               ($/yr/site)   reduction    reduction   Methane ($/  VOC ($/ton)  Methane ($/
                                                                             (tpy/site)   (tpy/site)      ton)                      ton)     VOC ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Well Sites and Centralized Production Facilities: 0.5 percent leak generation rate Single Pollutant Approach
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baseline.....................................................  ...........         8.51         2.37  ...........  ...........  ...........  ...........
Annual.......................................................       $2,162         3.99         1.11         $542       $1,951  ...........  ...........
Semiannual...................................................        2,588         5.73         1.59          452        1,624         $244         $879
Quarterly....................................................        3,440         6.61         1.84          520        1,872          969        3,487
Bimonthly....................................................        4,292         6.97         1.94          616        2,217        2,398        8,625
Monthly......................................................        6,848         7.26         2.02          943        3,393        8,676       31,212
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       Well Sites and Centralized Production Facilities: 0.5 percent leak generation rate Multipollutant Approach
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baseline.....................................................  ...........         8.51         2.37  ...........  ...........  ...........  ...........
Annual.......................................................        2,162         3.99         1.11          271          975  ...........  ...........
Semiannual...................................................        2,588         5.73         1.59          226          812          122          439
Quarterly....................................................        3,440         6.61         1.84          260          936          485        1,744
Bimonthly....................................................        4,292         6.97         1.94          308        1,108        1,199        4,313
Monthly......................................................        6,848         7.26         2.02          472        1,697        4,338       15,606
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based on the information summarized in Table 13 for the 0.5 percent
leak generation rate, under the single pollutant approach where all
costs are assigned to methane and zero cost to VOC, all frequencies
appear reasonable for methane emissions; where all costs are assigned
to VOC and zero cost to methane, all frequencies appear reasonable for
VOC emissions. Similarly, under the multipollutant approach where the
costs are divided equally between the two pollutants, all frequencies
appear reasonable when compared directly to a baseline of no OGI
monitoring.
    The EPA next evaluated the incremental cost associated with
advancing to each more frequent monitoring schedule. As shown in Table
13 for the single pollutant approach, the incremental costs of going
from quarterly to bimonthly monitoring for these larger well sites are
$2,398/ton methane and $8,625/ton of VOC. These incremental costs are
outside the range of costs the EPA has found reasonable for this source
category (i.e., $2,165/ton methane and $5,540/ton VOC). Under the
multipollutant approach, the incremental costs of going from quarterly
to bimonthly monitoring are $1,199/ton methane and $4,313/ton VOC,
which is within the range the EPA has found reasonable for this source
category.
    Next the EPA evaluated the costs of a combined program for well
sites and centralized production facilities, using quarterly OGI as a
baseline with AVO inspections added at bimonthly, and monthly
frequencies to determine if this combined program would be as effective
as, but less expensive than, bimonthly OGI. The EPA did not evaluate
annual, semiannual, or quarterly AVO inspection frequencies because
those would occur at the same time as at least one of the OGI surveys
if the EPA were to require quarterly OGI monitoring for well sites and
centralized production facilities with major production and processing
equipment. However, the EPA is soliciting comment on the costs and
effectiveness of a combined program of quarterly OGI surveys in
combination with quarterly AVO inspections that are offset by one
month, such that eight total fugitive surveys would take place over the
course of a year. Further, the EPA determined that some costs
associated with the AVO inspections would be less than those provided
in Table 9 because those costs are also included in the OGI monitoring
costs in Table 8. For example, there would be no additional costs to
read the rule, travel for inspections that overlap with OGI monitoring
surveys, or additional recordkeeping system costs. Table 14 summarizes
the results of this combined program for well sites and centralized
production facilities with major production and processing equipment.

 Table 14--Summary of Emissions Reductions and Cost-Effectiveness: Combined OGI Monitoring and AVO Inspections at Well Sites and Centralized Production
                                                                       Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Cost-effectiveness         Incremental cost-
                                                                              Methane        VOC     --------------------------       effectiveness
                     Monitoring frequency                      Annual cost    emission     emission                            -------------------------
                                                               ($/yr/site)   reduction    reduction   Methane ($/  VOC ($/ton)  Methane ($/
                                                                             (tpy/site)   (tpy/site)      ton)                      ton)     VOC ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                     Well Sites and Centralized Production Facilities: Assumes no additional travel costs Single Pollutant Approach
--------------------------------------------------------------------------------------------------------------------------------------------------------
Quarterly OGI................................................       $3,440         6.61         1.84         $520       $1,872  ...........  ...........

OGI + Bimonthly AVO..........................................        4,232         6.93         1.93          611        2,198        2,497        8,981
OGI + Monthly AVO............................................        5,021         7.10         1.97          707        2,545        4,616       16,608
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Well Sites and Centralized Production Facilities: Assumes no additional travel costs Multipollutant Approach
--------------------------------------------------------------------------------------------------------------------------------------------------------
Quarterly OGI................................................        3,440         6.61         1.84          260          936  ...........  ...........
OGI + Bimonthly AVO..........................................        4,232         6.93         1.93          305        1,099        1,248        4,491
OGI + Monthly AVO............................................        5,021         7.10         1.97          354        1,272        2,308        8,304
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Under the single pollutant approach, a combined program of
quarterly OGI and bimonthly or monthly AVO are reasonable for methane
and VOC emissions individually. When incremental costs are considered,
the costs of going from bimonthly to monthly AVO inspections is not
reasonable for either pollutant under the single pollutant approach.
Under the multipollutant approach, all combinations appear reasonable
when evaluated against a baseline of no monitoring. The multipollutant
incremental costs are not reasonable for a combined program of
quarterly OGI and monthly AVO. However, the EPA finds it is reasonable
to consider either a bimonthly OGI monitoring program alone or a
combination of quarterly OGI and bimonthly AVO as cost-effective
measures to reduce fugitive emissions from well sites and centralized
production facilities that include major production and processing
equipment.
    Finally, the EPA compared the emissions reductions achieved by the
combined quarterly OGI and bimonthly AVO program to a bimonthly OGI
program with no AVO inspections. While both programs appear cost-
effective, the combined program achieves comparable emissions
reductions to the bimonthly OGI program (6.93 tpy of methane and 1.93
tpy of VOC for the combined program, compared to 6.97 tpy of methane
and 1.94 tpy of VOC for the bimonthly OGI program) at a comparable cost
($4,232 for the combined program compared to $4,292 for the bimonthly
OGI program), and results in more total visits to the well site or
centralized production facility. Specifically, a total of four OGI
surveys and four AVO inspections would be completed, for a total of
eight surveys at the site each year (two of the bimonthly AVO
inspections would occur at the same time as two of the OGI surveys)
whereas bimonthly OGI would result in six surveys of the site each
year. Additional visits to the site create more opportunities to find
and fix fugitive emissions, including the large emissions that can be
detected by AVO inspections. Therefore, the EPA finds that the BSER for
well sites and centralized production facilities with major production
and processing equipment is quarterly OGI surveys combined with
bimonthly AVO inspections and therefore is proposing this combined
program as the standard for reducing fugitive emissions at these sites.
The EPA solicits comment on this proposed standard, including the basis
for the decision to propose quarterly OGI monitoring with bimonthly AVO
inspections rather than bimonthly OGI monitoring.
    Because the EPA finds that the combination of quarterly OGI
monitoring and bimonthly AVO inspections are reasonable, the EPA is
proposing this combination of monitoring frequencies and methods as the
BSER for well sites and centralized production facilities with major
production and processing equipment. The EPA is specifically proposing
to require this combination program for fugitive emissions components
affected facilities located at well sites or centralized production
facilities that contain the following major production and processing
equipment:
     One or more controlled storage vessels or tank batteries,
     One or more control devices,
     One or more natural gas-driven pneumatic controllers or
natural gas-driven pneumatic pumps, or
     Two or more pieces of major production and processing
equipment not otherwise specified.\77\
---------------------------------------------------------------------------

    \77\ Major production and processing equipment includes
centrifugal and reciprocating compressors, separators, glycol
dehydrators, heater/treaters, and storage vessels.
---------------------------------------------------------------------------

    The EPA is proposing to define this subcategory as well sites with
one or more controlled storage vessels, control devices, or natural
gas-driven pneumatic controllers because those sources individually are
known sources of super-emitter emissions events (see section IV.C) and
are subject to quarterly OGI for compliance assurance (storage vessels
and pneumatic controllers) or are subject to other continuous
monitoring requirements (control devices). Further, the EPA is defining
this subcategory as well sites with two or more other major production
and processing equipment because the model plant includes two
separators, which are another source that can contribute to large
emissions when combined with a storage tank. As explained previously
related to small well sites, the EPA is proposing an additional
subcategory of well sites to recognize that this model plant may
overstate the fugitive emissions from well sites that have only one
piece of major production and processing equipment that is not a
controlled storage vessel, control device, pneumatic controller, or
pneumatic pump. Consistent with comments received on the November 2021
proposal, the EPA understands that the industry is aware that this
specific equipment (controlled storage vessels, control devices, and
natural gas-driven pneumatic controllers) is more prone to emissions
and that fugitive surveys using OGI present an opportunity to identify
these emissions. However, the EPA is not expanding the definition of
fugitive emissions component to include controlled tank batteries,
control devices, or natural gas-driven pneumatic controllers as
explained earlier in this section because those sources are subject to
separate requirements that are intended to ensure proper operation
(including regular inspections, in the case of controlled tank
batteries and natural gas-driven pneumatic controllers).
    In summary, the EPA is proposing that the BSER for well sites with
major

production and processing equipment and centralized production
facilities, is a combination program consisting of bimonthly AVO
inspections and quarterly OGI monitoring and the closed and sealed
requirement for thief hatches (as explained in the discussion on small
well sites).
    Well closure plans. The EPA is proposing that owners and operators
of each well site or centralized production facility may stop the
required fugitive emissions monitoring and repair for that site when
the well site has been properly closed because in that event there
should not be any equipment or other fugitive components onsite for
monitoring. This would also help address concerns cited by many
stakeholders regarding continuing emissions from orphaned wells and
unplugged idled wells. In the November 2021 proposal, the EPA solicited
comment and information on idled and unplugged wells due to the EPA's
understanding and concern that these non-producing oil and natural gas
wells are generally unmanned and many are in disrepair. 86 FR 63240
(November 15, 2021). The EPA notes that ``some states and NGOs also
have elevated concerns about the potential number of wells that could
be abandoned in the near future as they reach the end of their
productive lives.'' Id.
    In addition, since promulgation of NSPS OOOOa, the EPA has received
various questions from owners and operators related to when fugitive
emissions monitoring applies if a well is shut-in, idled, or
permanently closed. The Agency is therefore proposing specific
requirements in NSPS OOOOb to ensure clarity for well sites and
centralized production facilities subject to the rule. Studies have
shown that idled wells can have fugitive emissions, and in some cases
these emissions can be very large.78 79 The EPA finds that
these data demonstrate the importance of continued fugitive emissions
monitoring on a routine basis to ensure that fugitive emissions
continue to be addressed throughout the life of the well site, even
during periods when the wells at the site are shut-in or idled and
could be put back into production at a later date.
---------------------------------------------------------------------------

    \78\ Amy Townsend-Small and Jacob Hoschouer. ``Direct
measurements from shut-in and other abandoned wells in the Permian
Basin of Texas indicate some wells are a major source of methane
emissions and produced water.'' 2021 Environ. Res. Lett. 16 054081.
https://iopscience.iop.org/article/10.1088/1748-9326/abf06f.
    \79\ Eric D. Lebel, Harmony S. Lu, Lisa Vielst[auml]dte, Mary
Kang, Peter Banner, Marc L. Fischer, and Robert B. Jackson.
``Methane Emissions from Abandoned Oil and Gas Wells in
California.'' Environmental Science & Technology 2020 54 (22),
14617-14626. DOI: 10.1021/acs.est.0c05279.
---------------------------------------------------------------------------

    However, there is a point at the end of a well site's useful life
where the EPA does anticipate the cessation of fugitive emissions
monitoring is appropriate, when all wells at the well site have been
permanently plugged and all equipment has been removed. To demonstrate
that a well site has reached that point where it is appropriate to
cease fugitive monitoring, the EPA is proposing to require owners and
operators to develop and submit a well closure plan within 30 days of
the cessation of production from all wells at the well site or
centralized production facility. The plan would include: (1) The steps
necessary to close all wells at the well site, including plugging of
all wells; (2) the financial requirements and disclosure of financial
assurance to complete closure; and (3) the schedule for completing all
activities in the closure plan. The EPA is also proposing to require
that owners and operators submit a notification to the Agency 60 days
before beginning well closure activities. The EPA solicits comment on
additional provisions that could be added, including, for example,
automatic consequences for missed monitoring reports, as a means of
assuring that companies remain engaged with the site, including
conducting monitoring, until all the wells at the site are properly
closed.
    Finally, the EPA is proposing that when the well closure activities
have been completed, prior to ceasing regular monitoring, the owner or
operator would be required to conduct a survey of the well site using
OGI. The purpose of this survey is to ensure there are no emissions
identified with OGI. If any emissions are identified, the owner or
operator would be required to take steps to eliminate those emissions
and resurvey. The EPA is proposing that once the OGI survey indicates
no emissions are present, the well site would be considered closed and
no further fugitive emissions monitoring would be required.
    The EPA finds that the requirements described above not only would
allow owners and operators of well sites and centralized production
facilities to stop fugitive emissions monitoring at a clearly defined
point where fugitive emissions are no longer a concern at the site,
these proposed requirements would also prevent well sites from becoming
orphaned or left in an idled and unplugged state with no form of
emissions monitoring and repair. The EPA assesses the continued
monitoring of well sites will help identify emissions and maintain the
well site such that it does not fall into disrepair. The EPA is
soliciting comment on these planning and monitoring requirements.
Lastly, because a well site could have a long useful life, during which
there may be different owners or operators, the EPA is proposing to
require owners and operators to report, through the annual report, any
changes in ownership at individual well sites so that it is clear who
the responsible owners and operators are until the site is plugged and
closed and fugitive emissions monitoring is no longer required. We
propose this reporting requirement as an important step in maintaining
transparency for the responsible owner or operator and will also
prevent well sites from becoming orphaned in the future. The EPA
solicits comment on this additional reporting requirement, including
other mechanisms for obtaining this information.
iii. Summary of Proposed Standards
    Definition of fugitive emissions component. Based on changes made
and discussed under section IV.A.1.a.ii of this preamble, the EPA is
proposing to define fugitive emissions component as any component that
has the potential to emit fugitive emissions of methane or VOC at a
well site, centralized production facility, or compressor station,
including valves, connectors, pressure relief devices, open-ended
lines, flanges, covers and CVS not subject to 40 CFR 60.5411b, thief
hatches or other openings on a storage vessel not subject to 40 CFR
60.5395b, compressors, instruments, meters, and yard piping.
    Monitoring requirements. The EPA is proposing the following
requirements for each subcategory of well sites not located on the
Alaska North Slope.
     Single wellhead only well sites and small well sites:
Quarterly AVO inspections.
     Multi-wellhead only well sites: Semiannual OGI (or EPA
Method 21) monitoring and quarterly AVO inspections at wellhead only
well sites with two or more wellheads.
     Well sites with major production and processing equipment
and centralized production facilities: Quarterly OGI (or EPA Method 21)
monitoring and bimonthly AVO inspections at well sites and centralized
production facilities with: (1) One or more controlled storage vessels
or tank batteries; (2) one or more control devices; (3) one or more
natural gas-driven pneumatic controllers; or (4) two or more pieces of
major production or processing equipment not listed in items (1)
through (3).
    Where semiannual monitoring is proposed, subsequent semiannual

monitoring would occur at least 4 months apart and no more than 7
months apart. Where quarterly monitoring is proposed, subsequent
quarterly monitoring would occur at least 60 days apart and quarterly
monitoring may be waived when temperatures are below 0 degrees
Fahrenheit ([deg]F) for two of three consecutive calendar months of a
quarterly monitoring period.
    When fugitive emissions are identified through AVO inspections, the
EPA is proposing to require that repairs be completed within 15 days
after the first attempt. The EPA is proposing a 15-day repair timeframe
so that the monthly AVO inspections do not overlap the repair schedule.
When fugitive emissions are identified through OGI surveys, the EPA is
proposing to require a first attempt at repair within 30 days of
detecting the fugitive emissions, with final repair, including resurvey
to verify repair, completed within 30 days after the first attempt,
consistent with the November 2021 proposal. Finally, we are proposing
to require owners and operators to develop a fugitive emissions
monitoring plan that covers all the applicable requirements for the
fugitive emissions components located at a well site or centralized
production facility. This monitoring plan would also include specific
procedures, defined by the owner or operator, to ensure consistency in
surveys conducted with either OGI or EPA Method 21, and to ensure that
these surveys are conducted appropriately for identifying fugitive
emissions from components at the site.
    Monitoring (AVO and OGI) surveys would be required to continue
until the owner or operator permanently closes the well site. Closure
includes completing well closure activities specified by the owner or
operator in a well closure plan. A final OGI survey of the well site
would be required to ensure there are no emissions following plugging
all of the wells at the site and completing closure activities. If
emissions are identified during this OGI survey, the rule would require
eliminating those emissions within the same timeline as required for
regular OGI surveys (first attempt within 30 days of identification,
with final repair within 30 days of the first attempt) and a resurvey
of the whole site to verify emissions have been addressed.
    Recordkeeping and Reporting Requirements. Specific recordkeeping
and reporting requirements would also apply for each fugitive emissions
affected facility. Sources would be required to report the designation
of the type of site (i.e., well site, centralized production facility,
or compressor station) at which the fugitive emissions components
affected facility is located. In addition, for each fugitive emissions
components affected facility that becomes an affected facility during
the reporting period, the date of the startup of production or the date
of the first day of production after modification would be required for
well sites or centralized production facility. Each fugitive emissions
components affected facility at a well site would also be required to
specify in the annual report what type of site it is (i.e., a single
wellhead only well site, small well site, a multi-wellhead only well
site, or a well site with major production and processing equipment).
    For fugitive emissions components affected facilities complying
with the requirement to conduct surveys using AVO, the annual report
would require the date of the survey, the total number and type of
equipment for which leaks were identified, or, if no leaks were
detected, a statement that there were no leaks on the day of
inspection, the total number and type of equipment for which leaks
identified were repaired within 15 calendar days, the total number and
type of equipment for which no repair attempt was made within 15 days
of the leaks being identified, and the total number and type of
equipment placed on the delay of repair.
    For fugitive emissions components affected facilities complying
with the requirement to monitor for fugitive emissions using OGI on a
semiannual or quarterly basis, the following information would be
required to be included in the annual report:
     Date of the survey,
     Monitoring instrument used,
     Any deviations from key monitoring plan elements or a
statement that there were no deviations from these elements of the
monitoring plan,
     Number and type of components for which fugitive emissions
were detected,
     Number and type of fugitive emissions components that were
not repaired,
     Number and type of fugitive emission components (including
designation as difficult-to-monitor or unsafe-to-monitor, if
applicable) on delay of repair and explanation for each delay of
repair, and
     Date of planned shutdown(s) that occurred during the
reporting period if there are any components that have been placed on
delay of repair.
b. EG OOOOc
    In section XII.A.2 of the November 2021 proposal preamble (86 FR
63196; November 15, 2021), the EPA proposed BSER for EG OOOOc for
reducing methane emissions from existing well sites that was the same
as that proposed for new well sites, with a site-wide emissions
threshold used to determine OGI monitoring frequency. However, as
explained for new, modified, and reconstructed well sites and
centralized production facilities in the previous section, the EPA has
changed approaches for evaluating the BSER for fugitive emissions
components, which also affects the determinations for BSER for existing
sources under EG OOOOc.
    The EPA did not identify any factors specific to existing sources
that would alter the analysis performed for new sources to make that
analysis different for existing well sites. Therefore, the EPA has
evaluated the presumptive standards in EG OOOOc using the same approach
as that for the proposed standards in NSPS OOOOb, specifically
evaluating both the total cost-effectiveness of each monitoring option
against a baseline of no monitoring and the incremental costs of
increasing stringency between monitoring options. The EPA has
determined that the methods for identifying fugitive emissions (i.e.,
AVO, OGI, and EPA Method 21), methane emissions reductions, costs, and
cost effectiveness related to the single pollutant approach for methane
emissions discussed above for the fugitive emissions components
affected facility at new well sites are also applicable for the
fugitive emissions components affected facility at existing well sites.
Further, the fugitive emissions requirements do not require the
installation of controls on existing equipment or the retrofit of
equipment, which can generally be an additional factor for
consideration when determining the BSER for existing sources.
Therefore, the EPA is proposing that it is appropriate to use the
analysis developed for the proposed NSPS OOOOb to also determine the
BSER and proposed presumptive standards for the EG OOOOc. Additionally,
the EPA is proposing the same requirement that thief hatches must be
closed and sealed at all times, in addition to the requiring fugitive
emissions monitoring continue until all of the wells at an existing
well site or centralized production facility are permanently closed and
the owner or operator has completed the same requirements for well
closure and submitted a well closure report meeting the same
requirements described for new sources.
    Single wellhead only and small well sites. Table 15 summarizes the
costs associated with AVO inspections at existing single wellhead only
well sites

and existing small well sites. Based on the information summarized in
Table 15, and the explanation provided for new single wellhead only
well sites and new small well sites, the semiannual, quarterly, and
bimonthly inspection frequencies are all reasonable. When examining the
incremental costs of going from quarterly to bimonthly AVO inspections,
the costs are not reasonable at $3,618/ton methane. Therefore, the EPA
proposes that the BSER for existing single wellhead only well sites is
quarterly AVO inspections, and the BSER for existing small sites
includes quarterly AVO inspections and the closed and sealed
requirement for thief hatches (as explained in the discussion above on
new, modified and reconstructed small well sites).

  Table 15--Summary of Methane Emissions Reductions and Cost-Effectiveness: AVO Inspections at Existing Single
                                  Wellhead Only Well Sites and Small Well Sites
----------------------------------------------------------------------------------------------------------------
                                                          Methane
                                      Annual cost ($/    emission          Total cost-        Incremental cost-
        Monitoring frequency             yr/site)     reduction (tpy/ effectiveness ($/ton  effectiveness ($/ton
                                                           site)            methane)              methane)
----------------------------------------------------------------------------------------------------------------
Annual..............................            $296            0.11                $2,579  ....................
Semiannual..........................             417            0.40                 1,048                   429
Quarterly...........................             660            0.56                 1,181                 1,511
Bimonthly...........................             904            0.63                 1,443                 3,618
Monthly.............................           1,633            0.69                 2,367                11,455
----------------------------------------------------------------------------------------------------------------

    Multi-wellhead only well sites. Table 16 summarizes the costs
associated with OGI monitoring at multi-wellhead only well sites and
Table 17 summarizes the costs associated with combined OGI and AVO
surveys at multi-wellhead only well sites. Based on the information
summarized in Table 16, the costs of annual, semiannual, quarterly, and
bimonthly OGI monitoring is reasonable when compared to a baseline of
no monitoring. When examining the incremental costs of going from
semiannual OGI to quarterly OGI, the costs are not reasonable at
$2,620/ton methane reduced. The EPA next evaluated the costs associated
with adding AVO inspections to semiannual OGI monitoring to determine
if additional emission reductions could be achieved at a reasonable
cost. Based on the information summarized in Table 17, all programs
presented are cost-effective when compared to a baseline of no
monitoring. When examining the incremental costs of going from a
combined program of semiannual OGI with quarterly AVO inspections to
one with bimonthly AVO inspections, the costs are not reasonable at
$3,394/ton methane reduced. Because the combined program of semiannual
OGI with quarterly AVO inspections is cost-effective and would result
in more visits to the well site, and thus provide opportunity to
address any emissions detected, the EPA is proposing that the BSER for
existing multi-wellhead only well sites is a combined program of
semiannual OGI with quarterly AVO inspections.

 Table 16--Summary of Emission Reductions and Cost-Effectiveness: OGI Monitoring at Well Sites With Two or More
                                                    Wellheads
----------------------------------------------------------------------------------------------------------------
                                                          Methane
                                      Annual cost ($/    emission          Total cost-        Incremental cost-
        Monitoring frequency             yr/site)     reduction (tpy/     effectiveness         effectiveness
                                                           site)         methane ($/ton)       methane ($/ton)
----------------------------------------------------------------------------------------------------------------
Baseline............................  ..............            2.66  ....................  ....................
Annual..............................          $1,972            1.18                $1,677  ....................
Semiannual..........................           2,327            1.79                 1,300                   578
Quarterly...........................           3,037            2.06                 1,473                 2,620
Bimonthly...........................           3,747            2.15                 1,741                 7,799
Monthly.............................           5,877            2.24                 2,619                23,140
----------------------------------------------------------------------------------------------------------------

    Table 17--Summary of Methane Emissions Reductions and Cost-Effectiveness: Combined OGI Monitoring and AVO
                             Inspections at Existing Multi-Wellhead Only Well Sites
----------------------------------------------------------------------------------------------------------------
                                                          Methane
                                      Annual cost ($/    emission          Total cost-        Incremental cost-
        Monitoring frequency             yr/site)     reduction (tpy/     effectiveness         effectiveness
                                                           site)         methane ($/ton)       methane ($/ton)
----------------------------------------------------------------------------------------------------------------
Semiannual OGI......................          $2,327            1.79                $1,300  ....................
OGI + Quarterly AVO.................           2,651            1.99                 1,331                $1,606
OGI + Bimonthly AVO.................           2,973            2.09                 1,425                 3,394
OGI + Monthly AVO...................           3,671            2.16                 1,822                12,728
----------------------------------------------------------------------------------------------------------------

    Well sites with major production and processing equipment and
centralized production facilities. Table 18 summarizes the costs
associated with OGI monitoring and Table 19 summarizes the costs of
combined OGI and AVO surveys at existing well sites and centralized
production facilities with major production and processing equipment.
The EPA is proposing the same definition for these well sites,
including the specific equipment that

constitutes a well site in this subcategory (e.g., leak-prone
equipment, such as controlled storage vessels). Based on the
information summarized in Table 18, all monitoring frequencies appear
cost-effective when compared to a baseline of no monitoring. When
incremental costs are considered, the costs of going from quarterly to
bimonthly OGI monitoring is not reasonable. The EPA then evaluated if
AVO inspections could be added to the quarterly OGI monitoring at a
reasonable cost. As shown in Table 19, all programs presented are cost-
effective when compared to a baseline of no monitoring. When examining
the incremental costs of going from a quarterly OGI program to a
combined program of quarterly OGI with bimonthly AVO inspections, the
costs are not reasonable at $2,497/ton methane reduced. Therefore, the
EPA is proposing quarterly OGI monitoring for these sites. In sum, the
EPA is proposing that the BSER for existing well sites with major
production and processing equipment and centralized production
facilities consists of quarterly OGI monitoring and the closed and
sealed requirement for thief hatches (as explained above in the
discussion on new, modified or reconstructed small well sites).

    Table 18--Summary of Emission Reductions and Cost-Effectiveness: OGI Monitoring at Well Sites With Major
                                       Production or Processing Equipment
----------------------------------------------------------------------------------------------------------------
                                                          Methane
                                      Annual cost ($/    emission          Total cost-        Incremental cost-
        Monitoring frequency             yr/site)     reduction (tpy/     effectiveness         effectiveness
                                                           site)         methane ($/ton)       methane ($/ton)
----------------------------------------------------------------------------------------------------------------
Baseline............................  ..............            8.51  ....................  ....................
Annual..............................          $2,162            3.99                  $542
Semiannual..........................           2,588            5.73                   452                  $244
Quarterly...........................           3,440            6.61                   520                   969
Bimonthly...........................           4,292            6.97                   616                 2,398
Monthly.............................           6,848            7.26                   943                 8,676
----------------------------------------------------------------------------------------------------------------

    Table 19--Summary of Methane Emissions Reductions and Cost-Effectiveness: Combined OGI Monitoring and AVO
  Inspections at Existing Well Sites With Major Production and Processing Equipment and Centralized Production
                                                   Facilities
----------------------------------------------------------------------------------------------------------------
                                                          Methane
                                      Annual cost ($/    emission          Total cost-        Incremental cost-
        Monitoring frequency             yr/site)     reduction (tpy/     effectiveness         effectiveness
                                                           site)         methane ($/ton)       methane ($/ton)
----------------------------------------------------------------------------------------------------------------
Quarterly OGI.......................          $3,440            6.61                  $520  ....................
OGI + Bimonthly AVO.................           4,232            6.93                   611                $2,497
OGI + Monthly AVO...................           5,021            7.10                   707                 4,616
----------------------------------------------------------------------------------------------------------------

2. OGI Monitoring at Compressor Stations
a. NSPS OOOOb
    In the November 2021 proposal, the EPA proposed that compressor
stations would be required to conduct quarterly OGI or EPA Method 21
monitoring. Where OGI monitoring was used to perform the quarterly
monitoring surveys, the EPA proposed surveys would be conducted
according to the procedures proposed in the November 2021 proposal as
appendix K.
    In this supplemental proposal, the EPA is retaining the proposed
quarterly OGI (or EPA Method 21) monitoring requirement for fugitive
emissions components affected facilities located at compressor stations
(including the requirement that consecutive quarterly monitoring survey
be conducted at least 60 days apart). Also, as in the November 2021
proposal, the supplemental proposal includes the provision in the 2016
NSPS OOOOa that the quarterly monitoring may be waived when
temperatures are below 0 [deg]F for two of three consecutive calendar
months of a quarterly monitoring period.
    In addition, the EPA is proposing to add a requirement to conduct
monthly AVO monitoring at compressor stations. As discussed above for
well sites, the EPA finds these AVO monitoring requirements can be
conducted by any personnel at the site as indications of emissions can
be identified without the need for specialized training. Any
indications of fugitive emissions identified via AVO would be subject
to repair. The EPA specifically received comments on the November 2021
proposal that indicated that ``even though small company compressor
stations are not manned 24 hours a day, they are visited weekly, if not
daily.'' \80\ Therefore, no additional costs are associated with the
proposed monthly AVO inspection requirement for compressor stations.
---------------------------------------------------------------------------

    \80\ See Document ID Nos. EPA-HQ-OAR-2021-0317-0585 and EPA-HQ-
OAR-2021-0317-0814.
---------------------------------------------------------------------------

    While the EPA is maintaining (and strengthening in the case of the
monthly AVO requirement) the November 2021 proposal as it relates to
the collection of fugitive emissions components located at compressor
stations, the EPA is not including the requirement to conduct OGI
monitoring surveys according to the procedures that would become
appendix K. See discussion in section IV.A.1.a.ii on comments received
opposing this requirement. Instead, the EPA is proposing that quarterly
surveys be performed according to the OGI procedures specified in the
proposed regulatory text in NSPS OOOOb or according to EPA Method 21.
b. EG OOOOc
    Based on the analysis presented in section XII.A.2 of the 2021
November proposal preamble (86 FR 63196; November 15, 2021), the
proposed BSER for EG OOOOc for reducing methane emissions from existing
compressor stations was quarterly monitoring (using either OGI or EPA
Method 21).
    Based on the same public comment considerations and reasoning as
explained above (see sections IV.A.2.a.ii

of this preamble) for changes to the proposed NSPS OOOOb for fugitive
emissions at compressor stations, the EPA is proposing the same changes
and requirements under EG OOOOc. The EPA did not identify any factors
specific to existing sources that would alter the analysis performed
for new sources to make that analysis different for existing compressor
stations. The EPA determined that the methods for identifying fugitive
emissions (i.e., AVO, OGI, and EPA Method 21), methane emission
reductions, costs, and cost effectiveness discussed above for the
fugitive emissions components affected facility at new compressor
stations are also applicable for the fugitive emissions components
affected facility at existing compressor stations. The fugitive
emissions requirements do not require the installation of controls on
existing equipment or the retrofit of equipment, which can generally be
an additional factor for consideration when determining the BSER for
existing sources. Therefore, the EPA found it is appropriate to
continue using the analysis developed for the proposed NSPS OOOOb to
also determine the BSER and proposed presumptive standards for the EG
OOOOc.
3. OGI Monitoring at Well Sites and Compressor Stations on the Alaska
North Slope
a. NSPS OOOOb
    In the November 2021 proposal, the EPA proposed an annual
monitoring requirement for well sites and compressor stations located
on the Alaska North Slope, which included a requirement to follow the
procedures outlined in the proposed appendix K where monitoring was
conducted using OGI.
    In this supplemental proposal, the EPA is retaining the proposed
annual monitoring requirement for well sites and compressor stations
located on the Alaska North Slope. Consecutive annual monitoring
surveys would be required at least 9 months apart and no more than 13
months apart. For the reasons discussed in section IV.A.1.a.ii, the EPA
is not including the requirement to follow the proposed procedures in
appendix K when conducting monitoring surveys with OGI. The EPA is
proposing that annual surveys be performed according to the OGI
procedures specified in the proposed regulatory text in NSPS OOOOb or
according to EPA Method 21 of appendix A-7 of this part.
b. EG OOOOc
    Based on the analysis presented in section XII.A.2 of the November
2021 proposal preamble (86 FR 63196; November 15, 2021), the proposed
BSER for EG OOOOc for reducing methane emissions from existing well
sites and compressor stations located on the Alaska North Slope was
annual monitoring.
    In this supplemental proposal, the EPA is retaining the annual
monitoring requirement for existing well sites and compressor stations
located on the Alaska North Slope. As discussed in the November 2021
proposal, the same technical infeasibility issues with weather
conditions exist for existing well sites and compressor stations
located on the Alaska North Slope as for new well sites and compressor
stations. Further, the EPA did not identify any other factors specific
to existing sources located on the Alaska North Slope that would alter
the analysis performed for new sources to make that analysis different
for existing well sites and compressor stations. Therefore, the EPA is
proposing a presumptive standard for reducing methane emissions from
the fugitive emissions components designated facilities located at
existing well sites and compressor stations located on the Alaska North
Slope that is the same as what we are proposing for NSPS OOOOb.

B. Advanced Methane Detection Technologies

    As discussed in section XI.A.5 of the November 2021 proposal
preamble (86 FR 63175; November 15, 2021), the EPA proposed an
alternative screening option that would allow the use of advanced
measurement technologies as an alternative to the use of ground based
OGI surveys and AVO inspections to identify emissions from the
collection of fugitive emissions components located at well sites,
centralized production facilities, and compressor stations. In the
November 2021 proposal, the EPA stated that we did not have enough
information to determine how the proposed alternative standard (i.e.,
bimonthly screening using advanced measurement technologies) compared
to the proposed BSER of OGI monitoring in that notice. Further we
stated that information provided through comments to the November 2021
proposal may be used to reevaluate BSER for fugitive emissions
components at well sites and compressor stations through a supplemental
proposal.\81\ As described below, commenters overwhelmingly supported
the concept of an alternative screening option that would allow owners
and operators to take advantage of advanced measurement technologies to
detect fugitive emissions. Commenters also provided helpful information
and input on how the alternative screening option could be made more
useful and effective, including flexibilities that could be
incorporated into the program design to enable the use of a wider
variety of advanced measurement technologies. While there was
widespread support of the concept of an alternative screening option,
the EPA still does not have enough information to conduct the requisite
BSER analysis \82\ for any specific advanced measurement technology to
determine whether it would qualify as the BSER for detecting fugitive
emissions (either in lieu of or in addition to OGI). The EPA, however,
does anticipate that through this alternative screening option, if
finalized as proposed and utilized by the industry, the Agency would
gain additional information that could be used to reevaluate the BSER
in a future rulemaking.
---------------------------------------------------------------------------

    \81\ 86 FR 63177 (November 15, 2021).
    \82\ Please see CAA section 111(a)(1) for a list of factors,
including costs, that the EPA must take into account when
determining whether an emission reduction system would qualify as
the BSER.
---------------------------------------------------------------------------

    In response to this feedback, the EPA is proposing a number of
changes to the alternative screening option that are intended to
support the deployment and utilization of a broader spectrum of
advanced measurement technologies and, ultimately, enable more cost-
effective reductions in emissions. These changes include a proposed
``matrix'' which would specify several different screening frequencies
corresponding to a range of minimum detection levels, in contrast to
the single screening frequency and detection level permitted under the
November 2021 proposal. In addition, we are proposing to allow owners
and operators the option of using continuous monitoring technologies as
an alternative to periodic screening and are proposing long- and short-
term emissions rate thresholds that would trigger corrective action as
well as monitoring plan requirements for owners and operators that
choose this approach.
    Lastly, we are proposing to establish a clear and streamlined
pathway for technology developers and other entities to seek the EPA's
approval for the use of advanced measurement technologies under this
alternative screening option. Under this pathway, entities would seek
approval for alternative test methods to demonstrate the performance of

alternative technologies, which would replace the use of OGI and AVO
for fugitive emissions monitoring and the use of OGI for no
identifiable emissions monitoring of covers and CVS (see section IV.K
of this preamble) in both the proposed NSPS OOOOb and EG OOOOc. Once an
alternative test method is approved by the EPA according to the
proposed process, which is described in more detail below in Section
IV.B.3, owners and operators would be able to utilize the advanced
methane detection technology/technique in accordance with the
alternative test method without the need for additional approval.
Section IV.B.1 of this preamble discusses the use of advanced
measurement technology in an alternative periodic screening approach.
Section IV.B.2 of this preamble discusses the use of advanced
measurement technologies in a continuous monitoring approach as a
second alternative approach to the fugitive emissions monitoring and
repair program and no identifiable emissions monitoring of covers and
CVS in NSPS OOOOb and EG OOOOc. Section IV.B.3 of this preamble
discusses the requirements for applying for an alternative test method,
including who can submit an application for an alternative test method.
Once an alternative test method is approved by the EPA, owners and
operators would be able to utilize the advanced methane detection
technology/technique in accordance with the alternative test method
without the need for additional approval.
1. Alternative Periodic Screening
a. Summary of November 2021 Proposal
    The EPA proposed an alternative fugitive emissions monitoring and
repair program for new, modified, or reconstructed fugitive emissions
sources (i.e., collection of fugitive emissions components located at
well sites, centralized production facilities, and compressor stations)
that included bimonthly screening for large emissions events using
advanced measurement technologies coupled with ground based OGI
monitoring at least annually at each site. Specifically, the EPA
proposed to allow owners and operators to comply with this alternative
fugitive emissions standard instead of the ground-based quarterly or
(co-proposed) semiannual OGI surveys for regulated sources, so long as
owners and operators chose this alternative for all affected well
sites, centralized production facilities, and compressor stations
within a company-defined area and the methane detection technology used
for the bimonthly screening surveys had a demonstrated minimum
detection threshold of 10 kg/hr.
    In the November 2021 proposal, the EPA sought comment on this
minimum detection threshold for the advanced measurement technologies
used in the alternative screening approach and solicited data on the
current detection sensitivity of commercially available methane
detection technologies as deployed, as well as other data that could be
used to support consideration of a different minimum detection
threshold. The EPA also solicited comment on development of a survey
matrix for the alternative screening approach option, where instead of
prescribing one detection threshold and screening frequency, the
frequency of screening surveys would be based on the sensitivity of the
technology (i.e., screening surveys performed with technologies with
the lower detection thresholds would need to be performed less
frequently than screening surveys performed with technologies with
higher detection thresholds).
    The November 2021 proposal also included a requirement for owners
and operators to include information specific to the alternative
screening approach in their fugitive emissions monitoring plan. This
would include information on which sites are utilizing this alternative
screening option; a description of the measurement technology used for
screenings; verification of the methane detection threshold, with
supporting data to support the verification; procedures for daily
verification of sensitivity under field conditions; standard operating
procedures; and methodology for conducting the screening. The EPA
solicited comment on when notifications would be required for sites
where the alternative standard is applied and whether submission of the
monitoring plan and/or Agency approval before utilizing the alternative
standard was necessary to ensure consistency in screening survey
procedures in the absence of finalized methods or procedures.
    When fugitive emissions are detected through a periodic screening
survey, the EPA proposed to require a ground based OGI survey of all
fugitive emissions components at the site within 14 days of the
screening survey. Due to the significance of the emissions events
detected through screening, an expeditious timeframe was proposed, but
the EPA requested additional information to fully evaluate the
appropriateness of this proposed 14-day deadline for a follow-up OGI
survey. Further, the EPA proposed to require repair of all fugitive
emissions identified during the follow-up OGI survey in accordance with
the same repair deadlines as those for regular fugitive surveys (i.e.,
a first attempt at repair within 30 days of the OGI survey and final
repair completed within 30 days of the first attempt). However, because
large emissions events, especially those identified during the
screening surveys, contribute disproportionately to emissions, the EPA
solicited comment on creating a tiered repair deadline requirement that
would be based on the severity of the fugitive emissions identified.
The EPA also noted that some equipment types with large emissions
warrant a requirement for a root cause analysis rather than simply
requiring the equipment to be repaired and solicited comment on how a
root cause analysis with corrective action approach could be applied in
the proposed alternative screening approach.
b. Changes to Proposal and Rationale
    The EPA received overwhelming support for the inclusion of an
option to use advanced technologies for periodic screenings as an
alternative to the fugitive emissions monitoring and repair program
proposed in NSPS OOOOb and EG OOOOc. However, commenters remarked that
the Agency failed to provide sufficient supporting evidence for the
proposed minimum detection threshold of 10 kg/hr. Commenters provided
alternative minimum detection thresholds and/or monitoring frequencies;
many of these commenters provided supporting evidence for equivalency
to the proposed fugitive emission monitoring and repair program in NSPS
OOOOb and EG OOOOc, including results from LDAR program effectiveness
models, such as FEAST. However, the results of these models varied
widely, and as such, it was difficult to compare the different
thresholds and frequencies presented by commenters. Additionally, one
commenter suggested the EPA should investigate the role of modeling in
equivalency demonstrations because the modeling outputs are highly
impacted by the model inputs and assumptions made in the models.\83\
Commenters also encouraged the EPA to adopt a survey matrix for the
alternative screening approach option that would allow owners and
operators to vary the frequency of periodic screening surveys based on
the detection sensitivity of the screening survey technology.
Commenters stated that the EPA should

use existing publicly available LDAR program effectiveness models \84\
to determine a matrix of survey frequencies and detection thresholds
that would provide a demonstration of equivalency between the
alternative screening and the standard fugitive emissions monitoring
and repair program.
---------------------------------------------------------------------------

    \83\ See Document ID No. EPA-HQ-OAR-2021-0317-0747.
    \84\ Currently, the free publicly available simulation models
are Fugitive Emissions Abatement Simulation Toolkit (FEAST) and Leak
Detection and Repair Simulator (LDAR-Sim).
---------------------------------------------------------------------------

    Based on these comments and subsequent discussions with
commenters,\85\ the EPA decided that the best course of action for
determining equivalency between different fugitive emission programs
would be to run one of the leak detection and repair program
effectiveness models with a set of standardized model inputs. For this
effort, the EPA chose to conduct the modeling using FEAST so we could
directly compare alternatives to the results of the OGI fugitive
emissions program proposed as the BSER described in section IV.A of
this preamble.\86\
---------------------------------------------------------------------------

    \85\ See February 18, 2022, memorandum, Summary of Meeting with
American Petroleum Institute, and February 28, 2022, memorandum,
Summary of Meeting with Environmental Defense Fund located at Docket
ID No. EPA-HQ-OAR-2021-0317.
    \86\ The EPA used FEAST version 3.1 to model the various
programs. While the EPA used FEAST in this modeling exercise, the
EPA would expect other available modeling simulation tools to
produce similar results.
---------------------------------------------------------------------------

    Based on recent aerial and satellite studies,\87\ \88\ a primary
advantage of more frequent screening with advanced technologies is to
quickly identify large emission events (commonly referred to as
``super-emitters''). These super-emitters may be the result of large
leaks from fugitive emissions components, but may also result from
other sources, such as unlit flares or process malfunctions. Therefore,
for this equivalency assessment, the EPA included emissions from other
sources beyond fugitive emissions components that contribute to these
super-emitters. This emissions distribution was developed using aerial
study data from Cusworth, et al.,\89\ and supplemented to include
additional leaks between the lower limits of detection of the aerial
surveys (about 15 to 20 kg/hr) and high-flow samplers commonly used in
ground-level quantification studies (maximum quantification limit of
about 9 kg/hr). The EPA assumed the small model plants (Model Plants 1
and 2) have one potential super-emitter source and that the larger
model plant (Model Plant 4) has two potential super-emitter sources.
The EPA evaluated the impact of different super-emitter frequencies but
conducted the equivalency modeling using the 1.0 percent leak
generation rate based on data from Zavala-Araiza, et al.\90\
Additionally, the EPA performed a sensitivity analysis where we assumed
a 1.0 percent leak generation rate for larger emissions sources
commonly identified using aerial screening technologies (>26 kg/hr) and
a 0.5 percent leak generation rate for fugitive emissions components
consistent with the analysis for OGI and AVO programs described in
section IV.A. More detail on the FEAST modeling assumptions and
simulations is provided in the Supplemental TSD for this action located
at Docket ID No. EPA-HQ-OAR-2021-0317. The EPA solicits comment on the
use of LDAR effectiveness models in the development of the requirements
for the alternative screening approach, specifically on the
appropriateness of the inputs and assumptions used in the EPA's FEAST
modeling simulations.
---------------------------------------------------------------------------

    \87\ Chen, Yuanlei, et al. 23 Mar 2022, https://doi.org/10.1021/acs.est.1c06458.
    \88\ Irakulis-Loitxate, Itziar, et al. 30 June 2021, https://doi.org/10.1126/sciadv.abf4507.
    \89\ Cusworth, Daniel, et al. 2 June 2021, https://pubs.acs.org/doi/10.1021/acs.estlett.1c00173.
    \90\ Zavala-Araiza, Daniel, et al. 16 Jan 2017, https://doi.org/10.1038/ncomms14012.
---------------------------------------------------------------------------

    In this action, the EPA is revising the proposal for the
alternative screening approach to provide additional flexibility to
owners and operators to show that the advanced technology for which
they are seeking approval would reduce fugitive emissions at least
equivalent to the reduction under the proposed fugitive emission
monitoring and repair program in NSPS OOOOb and EG OOOOc, as well as
the proposed covers and CVS requirements in NSPS OOOOb and EG OOOOc.
Instead of requiring a fixed screening survey frequency for all
technologies, the EPA is proposing a survey matrix, where the minimum
detection threshold of the screening technology determines the
frequency of screening surveys and whether an annual OGI ground-based
survey is needed as a supplement to the periodic screening surveys.
Tables 20 and 21 present the details of the screening matrix for
facilities required to conduct quarterly and semiannual OGI ground-
based monitoring under the proposed fugitive emissions monitoring and
repair program in NSPS OOOOb and EG OOOOc, respectively. Based on the
FEAST modeling the EPA performed, technologies with a minimum detection
threshold above 30 kg/hr could not be deemed equivalent to the proposed
fugitive emissions monitoring and repair program in NSPS OOOOb and EG
OOOOc at any screening survey frequency, even when coupled with an
annual OGI ground-based survey. As such, the alternative periodic
screening approach is limited to technologies with a minimum detection
threshold less than or equal to 30 kg/hr.

 Table 20--Survey Matrix for Alternative Periodic Screening Approach for
        Affected Facilities Subject to Quarterly OGI Monitoring a
------------------------------------------------------------------------
                                                            Minimum
                                                           detection
             Minimum screening frequency                  threshold of
                                                           screening
                                                         technology \b\
------------------------------------------------------------------------
Quarterly + Annual OGI...............................          <=1 kg/hr
Bimonthly............................................          <=2 kg/hr
Monthly..............................................          <=4 kg/hr
Bimonthly + Annual OGI...............................         <=10 kg/hr
Monthly + Annual OGI.................................         <=30 kg/hr
------------------------------------------------------------------------
\a\ Well sites with major production and processing equipment,
  controlled storage vessels, natural gas-driven pneumatic controllers,
  associated covers and closed vent systems, and control devices,
  centralized production facilities, and compressor stations.
\b\ Based on a probability of detection of 90 percent.

 Table 21--Survey Matrix for Alternative Periodic Screening Approach for
        Single and Multi-Wellhead Only Sites and Small Well Sites
------------------------------------------------------------------------
                                                            Minimum
                                                           detection
             Minimum screening frequency                  threshold of
                                                           screening
                                                         technology \a\
------------------------------------------------------------------------
Semiannual...........................................          <=1 kg/hr
Triannual............................................          <=2 kg/hr
Triannual + Annual OGI...............................          <=5 kg/hr
Quarterly + Annual OGI...............................         <=15 kg/hr
Monthly + Annual OGI.................................         <=30 kg/hr
------------------------------------------------------------------------
\a\ Based on a probability of detection of 90 percent.

    These survey matrices will provide owners and operators who choose
to implement the alternative periodic screening approach a wider
selection of methane detection technologies from which to choose. The
matrices also provide clear goals for vendors interested in the
development of future technologies for methane detection. The EPA
solicits comments on the survey matrices developed for the alternative
periodic screening approach. Specifically, the EPA is interested in
comments regarding the applicability of this matrix to both currently
available technologies and those currently in development. Further,
where specific technologies may not easily work within the context of
the proposed matrix, we are soliciting detailed information on how
those specific technologies work, including empirical data that would
allow for additional evaluation of parameters in the proposed matrix;
how emissions reduction equivalency can be demonstrated for those
technologies compared with the standard OGI work practice; and changes
that would be needed to the proposed matrix and the basis for those
changes. Finally, we are soliciting feedback from owners and operators
on ways to improve and further incentivize use of the proposed matrix
approach to ensure they are comfortable utilizing any approved
alternative technologies and test methods.
    To reflect changes made to the proposed alternative periodic
screening approach, the EPA is also modifying the proposed requirements
for site-specific monitoring plans. The EPA is proposing to allow
owners and operators to develop a site-specific monitoring plan or to
develop a monitoring plan that covers multiples sites. At a minimum,
the monitoring plan would need to contain the following information:
(1) Identification of each site that will be monitored through periodic
screening, including latitude and longitude coordinates; (2)
identification of the test method(s) used for the periodic screening;
(3) identification and contact information for the entity performing
the periodic screening; (4) frequency for conducting periodic
screenings; (5) procedures for conducting ground-based monitoring
surveys in response to confirmed emission detection events from
periodic screening surveys; (6) procedures and timing for identifying
and repairing fugitive emissions components, covers, and CVS; (7)
procedures and timing for verifying repairs for fugitive emissions
components, covers, and CVS, and (8) recordkeeping and retention
requirements.
    The EPA is also clarifying the timeframes for when owners and
operators must conduct the initial periodic screening survey when
complying with the alternative periodic screening standard. In the
November 2021 proposal, the EPA did not include timeframes for
initiating periodic monitoring. The EPA is proposing that, for the
initial periodic screening survey must be conducted within 90 days of
the startup of production for each fugitive emissions components
affected facility and/or storage vessel affected facility located at a
new, modified, or reconstructed well site or centralized production
facility and have not begun any fugitive monitoring; within 90 days of
startup for each fugitive emissions components affected facility and
storage vessel affected facility located at a new compressor station;
and within 90 days of modification for each fugitive emissions
components affected facility and storage vessel affected facility
located at a modified compressor station. This 90-day initial screening
requirement is the same as that required for the OGI-based fugitive
emissions surveys. Additionally, the EPA is proposing that the initial
periodic screening survey must be conducted no later than the date of
the next required OGI fugitive emissions survey for any affected
facility that was previously complying with the proposed fugitive
emissions monitoring and repair program and proposed covers and CVS
requirements in NSPS OOOOb and EG OOOOc. The EPA solicits comment on
the proposed timing to perform the initial periodic screening survey,
including information to support different timeframes.
    When the periodic screening survey identifies emissions, the EPA is
proposing to require a ground-based survey using OGI to identify the
source of the emissions and any other fugitive emissions present. Any
fugitive emissions identified during this ground-based survey would be
subject to repair requirements. For fugitive emissions components, the
EPA is proposing to require a completion of repairs within 30 days of
the screening survey. The EPA is proposing that if the ground-based
survey confirms that emissions were caused by a failure of a control
device, the owner or operator must initiate a root cause analysis and
determine appropriate corrective action within 24 hours of the ground-
based survey. Because a failure of a control device would likely result
in violations of the standards, the EPA is proposing appropriate
corrective action should be taken as soon as possible to address these
failures. Similarly, for covers and CVS, which are either fugitive
components or are subject to the proposed cover and CVS requirements,
the EPA is proposing to require repair within 30 days of the screening
survey. The EPA is also proposing that if a leak or defect in a cover
or CVS is identified, the owner or operator would be required to
perform a root cause analysis to determine the cause of emissions from
the cover or CVS within five days of completing the ground-based
inspection, in addition to requiring repair within 30 days of the
screening survey. The root cause analysis should include a
determination as to whether the system was operated outside of the
engineering design analyses and

whether updates are necessary for the system. Because covers and CVS
are required to be designed and operated with no identifiable
emissions, indications of emissions from these sources could result in
violations of the CVS requirements where the CVS is not a fugitive
emissions component. Therefore, the EPA is proposing that appropriate
corrective actions should be taken to resolve the emissions and ensure
that the no detectable emissions standard is continuously met. Examples
of corrective actions might include replacement of gaskets with a
material more suitable for the composition of materials in the storage
vessel or redesign of the entire CVS to ensure pressure setpoints are
appropriate for relief devices on storage vessels. The EPA understands
that the length of time necessary to complete corrective actions will
vary based on the specific action taken. Therefore, we are soliciting
comment on an appropriate deadline by which all corrective actions
should be completed that would account for variability in complexity
for such actions.
2. Alternative Continuous Monitoring Systems
a. Summary of November 2021 Proposal
    In the November 2021 proposal, the EPA recognized that the
alternative screening approach as outlined above may not be well suited
to continuous monitoring technologies, such as sensors or open-path
technology, even though these technologies may meet the minimum methane
detection threshold (86 FR 63176; November 15, 2021). To incentivize
these continuous monitoring technologies, which could be valuable tools
in quickly detecting large emissions events, as well as identifying
when emissions at the site begin to rise, the EPA requested information
that could be used in an equivalence demonstration and would allow for
the development of a flexible framework that could cover multiple types
of continuous monitoring technologies and be used as a second
alternative approach to the fugitive emissions monitoring and repair
program in NSPS OOOOb and EG OOOOc. Specifically, the EPA requested
information on the number of continuous monitors needed on a site,
placement criteria for these monitors, response factors, minimum
detection levels, frequency of data readings, how to interpret the
monitor data to determine the difference between detected emissions and
baseline emissions, how to determine allowable emissions versus leaks,
the meteorological data criteria, measurement systems data quality
indicators, calibration requirements and frequency of calibration
checks, how downtime should be handled, and how to handle situations
where the source of emissions cannot be identified even when the
monitor registers a leak.
b. Changes to Proposal and Rationale
    In response to the solicitation for comment on the development of a
framework for continuous monitoring technologies in the November 2021
proposal, the EPA received comments from vendors, trade groups,
industry, and environmental groups in support of developing a framework
for these technologies. Many of these commenters discussed the benefits
of continuous monitoring systems including the low detection
sensitivities of the technologies, the potential savings involved in
identifying the largest leaks in near real time, and the potential to
repair leaks on a much quicker timeframe. The EPA is proposing a
framework for continuous monitoring technologies that is akin to the
fenceline monitoring work practice promulgated by the EPA in 2015 as
part of the National Emissions Standards for Hazardous Air Pollutants
(NESHAP) for the petroleum refinery sector (80 FR 75178; December 1,
2015). Under this proposed approach, an owner or operator utilizing
continuous monitoring technologies would conduct a root cause analysis
and corrective action whenever a methane emission rate action-level is
exceeded at the boundary of a facility.
    The EPA is proposing methane emissions rate (i.e., kg/hr) based
action levels instead of methane concentration (e.g., ppmv) based
action levels (as in the Refineries NESHAP) in order to: (1) Account
for upwind contributions from other sites and meteorological effects
and (2) allow the Agency to evaluate the methane emissions reductions
achieved by this framework, thus providing for a metric to demonstrate
equivalency with the proposed fugitive emissions monitoring and repair
program and proposed covers and CVS requirements in NSPS OOOOb and EG
OOOOc. Through the comments received and subsequent discussions with
commenters,\91\ the EPA has gathered information on how these
continuous monitoring systems have been applied and how owners and
operators use the information from these systems to initiate a response
to identify and repair leaks. The application of these systems appears
to vary widely across the industry, with no consistent standard
currently employed. This is especially true for how sources initiate
identification of the cause of a leak. To standardize the use of these
systems across the industry, the EPA is proposing two action levels in
this alternative continuous monitoring approach: (1) A long-term action
level to limit emissions over time and (2) a short-term action level to
identify large leaks and malfunctions. Both action levels would apply
to all owners and operators choosing to use this alternative, and a
root cause analysis and corrective action would be triggered when
either action level is exceeded. The proposed long-term action levels
are developed from the same FEAST Model used for the development of the
proposed survey matrix for periodic screening and the action-levels are
based on the annual emissions (including super-emitters) of our Model
Plant 2 and Model Plant 3 discussed in section IV.A.2 of this preamble.
Based on this data, the EPA is proposing an action-level of 1.2 kg/hr
\92\ for sites consisting of only wellheads and 1.6 kg/hr \93\ for all
other well sites and compressor stations with equipment. This long-term
action level would be based on a rolling 90-day average, where the 90-
day average would be recalculated each day. The EPA is also proposing a
short-term action-level of 15 kg/hr for sites consisting of only
wellheads and 21 kg/hr for other well sites and compressor stations.
These action levels are based on the same magnitude of emissions as the
long-term action level; however, the rates are defined over the period
of seven days. The short-term action level would be based on a rolling
7-day average, where the 7-day average would be recalculated each day.
The EPA solicits comment on the proposed short-term and long-term
action levels. The EPA is also aware of industry led efforts \94\ to
minimize methane emissions through the entirety of the value chain
using the percentage of intensity or production as a metric. The EPA is
soliciting comment on the potential use of intensity or production in
the development of action levels, including appropriate thresholds for
setting such action levels on both a short-term and long-term basis.
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    \91\ See memorandum, Summary of Meetings on Alternative
Screening and Continuous Monitoring Systems located at Docket ID No.
EPA-HQ-OAR-2021-0317.
    \92\ 11.6 tons per year methane.
    \93\ 15.5 tons per year methane.
    \94\ One Future Coalition.
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    The EPA is aware of other continuous monitoring systems using
technologies that are not designed to quantify a site-level methane
emissions rate (e.g.,

camera based continuous systems). While the EPA believes these systems
could be useful in a methane mitigation program, they are not suitable
for the proposed alternative continuous monitoring approach because
they are not capable of quantifying site-level methane emissions, which
is the basis for the equivalency demonstration of the proposed
alternative continuous monitoring approach. That said, the EPA solicits
comment on how these types of systems could fit within the alternative
continuous monitoring approach, what action levels should be applied to
a non-emission rate based continuous monitoring system, and data to
support those action levels in order to conduct an equivalency
demonstration. The EPA also solicits comment on whether a different
type of approach should be used for these other types of continuous
monitoring systems, and if so, what that approach would look like and
how equivalency could be demonstrated between the approach and the
proposed fugitive emissions monitoring and repair program and proposed
covers and CVS requirements in NSPS OOOOb and EG OOOOc.
    The EPA is proposing that owners and operators must initiate a root
cause analysis within 5 calendar days of an exceedance of either the
short-term or long-term action level. Additionally, the EPA is
proposing that the initial corrective action identified must be
completed within five calendar days of an exceedance of the short-term
action level and within 30 calendar days of an exceedance of the long-
term action level. If, upon completion of the initial corrective
actions, the continuous monitor readings remain above an action level,
or if all identified corrective action measures require more than 30
days to complete, the owner or operator would be required to develop a
corrective action plan and submit it to the Administrator within 60
calendar days of the initial action level exceedance. The EPA is
soliciting comment on the proposed requirements for the root cause
analysis and corrective action, the timeframes for conducting these
activities, and the requirement for corrective action plan submittals.
    In order to ensure that the continuous monitoring systems used in
the alternative continuous monitoring approach are sensitive enough to
trigger at the proposed action levels, the EPA is proposing that the
continuous monitoring systems must have a detection level an order of
magnitude less than the proposed action level and that the system must
produce a valid mass emissions rate (i.e., kg/hr) from the site at
least once every twelve hours. The EPA is also proposing requirements
related to operability of the monitors within the continuous monitoring
system. Specifically, the EPA is proposing that the operational
downtime of the continuous monitoring system, or the time that any
monitor fails to collect or transmit quality assured data, must be less
than or equal to 10 percent on a 12-month rolling average, where the
12-month average is recalculated each month. We are soliciting comment
on this approach to addressing downtime and other ways to address
system downtime and the consequences of that downtime.
    Similar to the alternative periodic screening approach, owners and
operators who choose to implement the alternative continuous monitoring
approach must develop a monitoring plan. The monitoring plan can either
be a site-specific monitoring plan or cover multiples sites. At a
minimum, the monitoring plan would need to contain the following
information: (1) Identification of each site that will be monitored
through periodic screening, including latitude and longitude
coordinates; (2) identification of the test method(s) used for the
continuous monitoring; (3) identification and contact information for
the entity performing the continuous monitoring if the continuous
monitoring system is administered through a third-party provider; (4)
number and location of monitors; (5) system calibration procedures and
schedules; (6) identification of critical components and procedures for
their repairs; (7) procedures for out of control periods; (8)
procedures for determining when a fugitive emissions event is detected
by the continuous monitoring technology; (9) procedures and timing for
identifying and repairing fugitive emissions components, covers, and
CVS; (10) procedures and timing for verifying repairs for fugitive
emissions components, covers, and CVS, and (11) recordkeeping and
retention requirements.
    The EPA is proposing that owners and operators who choose to comply
with the alternative continuous monitoring approach must install and
begin conducting monitoring with the continuous monitoring system
within 120 days of the startup of production for each fugitive
emissions components affected facility or storage vessel affected
facility located at a new, modified, or reconstructed well site or
centralized production facility; within 120 days of startup for each
fugitive emissions components affected facility and storage vessel
affected facility located at a new compressor station; and within 120
days of modification for each fugitive emissions components affected
facility and storage vessel affected facility located at a modified
compressor station. Additionally, the EPA is proposing the continuous
monitoring system must begin monitoring no later than the date of the
next scheduled OGI monitoring survey for any affected facility that was
previously complying with the proposed fugitive emissions monitoring
and repair program and proposed covers and CVS requirements in NSPS
OOOOb and EG OOOOc. The EPA solicits comment on the proposed timing to
install and begin conducting monitoring with the continuous monitoring
system, including information to support different timeframes.
    The EPA is soliciting comment on this proposed alternative
continuous monitoring approach, especially the use of site-level
methane emissions as a surrogate for VOC emissions, the practicality of
implementing the proposed framework, and any additional data on how
continuous monitoring technologies have been deployed at well sites,
centralized production facilities, and compressor stations. The EPA
proposes to use the continuous monitoring system to confirm the
effectiveness of the corrective action and has proposed additional
repair and notification requirements for when corrective action is
delayed or when the corrective action is ineffective.
3. Alternative Test Method Approval
a. Summary of November 2021 Proposal
    The EPA solicited comment on whether owners and operators choosing
to comply with the alternative periodic screening approach would need
to submit their monitoring plan to the delegated authority and whether
Agency approval was necessary before the owner or operator could
implement the alternative. The EPA proposed that EPA approval may be
necessary to ensure consistency in screening survey procedures in the
absence of finalized methods and procedures.
b. Changes to Proposal and Rationale
    The EPA received comments from industry, state agencies, and non-
governmental organizations acknowledging that review and approval of
individual monitoring plans increases the burden on industry.
Additionally, the review of these monitoring plans increases the burden
on delegated authorities to evaluate the alternative technologies and
may result

in inconsistent application or variable approvals for the same
technology between different states. The EPA also received direct
comment \95\ from one state that expressed that the EPA should serve as
the clearinghouse for approving these advanced measurement techniques.
---------------------------------------------------------------------------

    \95\ See Document ID No. EPA-HQ-OAR-2021-0317-0763.
---------------------------------------------------------------------------

    The EPA continues to find that, prior to implementation, approval
of the technologies used in the alternative periodic screening approach
and the alternative continuous monitoring approach is necessary due to
the lack of standard methods and performance specifications for these
types of systems. Approval of these systems will allow a wider range of
methane detection techniques to be applied, but also allow the Agency
to provide more specific guidance on the proper operation of these
systems. Based on the comments received, the EPA is proposing to
require these systems to be approved by the Administrator under the
alternative test method provisions in 40 CFR 60.8(b)(3) instead of
owners and operators seeking approval of these systems through site-
specific monitoring plans. The use of the alternative test method
provisions has typically been applied to the approval of alternative
test methods used to conduct performance testing to demonstrate
compliance with a numerical emission standard. While work practice
standards are not numerical emission standards, there is precedent for
approving alternative test methods within work practice standards, so
long as the change in the testing or monitoring method or procedure
will provide a determination of compliance status at the same or higher
stringency as the method or procedure specified in the applicable
regulation.96 97 The EPA is soliciting comment on the use of
this provision at 40 CFR 60.8(b)(3) for the approval of the alternative
test method for an alternative technology for measurements within the
proposed alternative periodic screening approach and the proposed
alternative continuous monitoring approach.
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    \96\ In amendments to the approval of state programs and
delegation of federal authorities, the EPA clarified that certain
provisions within work practices, such as those related to
compliance and enforcement provisions, are delegable provisions. In
particular, the EPA stated that monitoring requirements are
delegable. See 65 FR 55810 (September 14, 2000).
    \97\ The fenceline monitoring work practice in 40 CFR part 63
subpart CC allows owners and operators to seek an alternative test
method for use of technologies other than the prescribed sorbent
tube monitoring with Method 325 A and B of appendix A to 40 CFR part
63. See 40 CFR 63.658(k)(1).
---------------------------------------------------------------------------

    Once an alternative test method for an alternative technology has
been approved, if it is broadly applicable, the EPA will post it to the
Emission Measurement Center website.\98\ Any owner or operator who
meets the specific applicability for the alternative test method, as
outlined in the alternative test method, may use the alternative test
method to comply with the alternative periodic screening approach or
alternative continuous monitoring approach. The owner or operator would
be required to notify the Administrator of adoption of the alternative
periodic screening approach or alternative continuous monitoring
approach in the first annual report following implementation of the
alternative standard. The owner or operator's fugitive emissions
monitoring plan would identify the approved alternative test method(s)
the owner or operator is using the alternative periodic screening
approach or alternative continuous monitoring approach.
---------------------------------------------------------------------------

    \98\ https://www.epa.gov/emc/oil-andgas-approved-alternative-test-methods.
---------------------------------------------------------------------------

    In an effort to streamline the approval process and reduce the time
needed for processing these request for alternative test methods, the
EPA is proposing the following pre-qualifications for those requesting
approval of their technology: (1) Requestors are limited to any
individual or organization located in or that has representation in the
U.S.; (2) requestor must have direct knowledge of the design,
operation, and characteristics of the underlying technology; (3) the
underlying technology must have been applied to methane measurements in
the oil and gas production, processing, and/or transmission and storage
sectors either domestically or internationally; (4) the technology must
be a commercial product, meaning it has been sold, leased, or licensed,
or offered for sale, lease, or license, to the general public. While
the EPA has based these pre-qualifications on comments received from
vendors or advanced methane detection technologies, the EPA solicits
comments on how we have characterized the pre-qualifications in this
proposal and whether any additional pre-qualifications may be
appropriate.
    In an effort to streamline the approval of these requests by
ensuring adequate information is received in the request to allow a
full evaluation of the alternative technology, the EPA is proposing
that any application for an alternative test method contain the
following information at a minimum: (1) The desired applicability of
the technology (i.e., site-specific, basin-specific or broadly
applicable across the sector); (2) a description of the measurement
systems; (3) supporting information verifying that the technology meets
the desired detection threshold(s) as applied in the field; (4) a
detailed description of the alternative testing procedure(s), including
data quality objectives to ensure the detection threshold(s) are
maintained and procedures for a daily verification check of the
measurement sensitivity under field conditions, and; (5) standard
operating procedures consistent with the EPA's guidance and including
safety considerations, measurement limitations, personnel
qualification/responsibilities, equipment and supplies, data and record
management, and quality assurance/quality control. The EPA solicits
comment on the proposed information required to be submitted with the
application of an alternative test method and whether the EPA should
consider requiring any additional information.
    The EPA is proposing a defined timeframe for review and
determination of alternative test method requests by the Agency. The
EPA is proposing to issue either an approval or disapproval in writing
to the requestor within 270 days of receipt of the request, with a
number of milestones for acknowledgement of receipt and initial
reviews. The EPA is also proposing a mechanism to allow a conditional
approval of a submitted alternative test method in the event a
determination is not made by the Agency within 270 days. Finally, the
EPA is maintaining the authority to rescind any previous approval if we
find it reasonable to dispute the results of any alternative test
method used to demonstrate compliance with either the alternative
periodic screening approach or the alternative continuous monitoring
approach. The EPA proposes to make these approvals and the supporting
information available to the public on an EPA supported website. The
EPA solicits comments on the proposed timeframe to review and approve
alternative test methods and whether alternative timelines should be
considered.

C. Super-Emitter Response Program

    Although results vary by basin, many studies have found that the
top five percent of sources contribute over 50 percent of the total
emissions.\99\ There is

wide agreement in the peer-reviewed research that a subset of sources
comprising the very largest emission events, commonly referred to as
super-emitters, is typically caused by abnormal operating conditions or
malfunctions.\100\
---------------------------------------------------------------------------

    \99\ Yuanlei Chen et al., ``Quantifying Regional Methane
Emissions in the New Mexico Permian Basin with a Comprehensive
Aerial Survey,'' Environmental Science and Technology, Vol. 56, No.
7 (March 2022), https://doi.org/10.1021/acs.est.1c06458.
    \100\ Daniel Zavala-Araiza et al., ``Super-emitters in Natural
Gas Infrastructure are Caused by Abnormal Process Conditions,''
Nature Communications Vol. 8 (January 2017), https://doi.org/10.1038/ncomms14012; Ram[oacute]n A. Alvarez et al., ``Assessment of
Methane Emissions from the U.S. Oil and Gas Supply Chain,'' Science,
Vol. 361 (July 2018), https://doi.org/10.1126/science.aar7204;
Daniel H. Cusworth et al., ``Intermittency of Large Methane Emitters
in the Permian Basin,'' Environmental Science and Technology Letters
Vol. 8, No. 7 (June 2021), https://doi.org/10.1021/acs.estlett.1c00173; Jeffrey S. Rutherford et al., ``Closing the
Methane Gap in US Oil and Natural Gas Production Emissions
Inventories,'' Nature Communications Vol. 12 (August 2021), https://doi.org/10.1038/s41467-021-25017-4; Yuanlei Chen et al.,
``Quantifying Regional Methane Emissions in the New Mexico Permian
Basin with a Comprehensive Aerial Survey,'' Environmental Science
and Technology, Vol. 56, No. 7 (March 2022), https://doi.org/10.1021/acs.est.1c06458.
---------------------------------------------------------------------------

    Many of the requirements of this rule, when implemented correctly,
would result in reducing the number of super-emitter emissions events.
For the reasons described below, the EPA is further proposing a super-
emitter response program as a backstop to address the large
contribution of super-emitters to the pollution from this sector. For
purposes of this program, the EPA is proposing to define a super-
emitter emissions event as quantified emissions of 100 kg/hr or greater
of methane, a very high threshold that encompasses the largest
emissions events.
    Recognizing that super-emitter emissions events are a significant
source of methane and VOC emissions, the November 2021 proposal and
this supplemental proposal contain standards and requirements that, if
implemented correctly, would prevent (e.g., via zero-emissions
standards for pneumatic controllers and design and operation
requirements for flares) or detect and mitigate (e.g., via regular
monitoring for fugitive emissions using OGI or advanced detection
technologies) most of these large emissions events.\101\ We note that
the estimated emission reductions in both the November 2021 proposal
and this supplemental proposal likely undercount the emission
reductions that would be achieved by this rule because they might not
fully account for the emissions resulting from all super-emitter
emissions events that would be prevented or quickly corrected as a
result of this rule. Though we are not currently able to quantify the
emissions reductions likely to result from preventing or more quickly
mitigating super-emitter emissions events, we note that the information
presented in appendix D to the RIA for this supplemental proposal
includes model simulations suggesting that covering large emitters
could ``significantly impact[] the expected emissions from the fugitive
emission program.'' \102\
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    \101\ Super-emitter emissions events could also be from
intentional venting as part of normal operations or maintenance. The
proposed super-emitter response program discussed in this section is
not intended to address these events.
    \102\ As stated, some of the model simulations in appendix D to
the RIA for this supplemental proposal suggest that large-emitters
could significantly impact the estimated emissions reductions;
however, those simulations are not directly related to the
definition of ``super-emitter'' included in this proposal, thus the
emissions and emission reductions cannot be used to directly assess
the emissions or emission reductions related to the proposed super-
emitter program. The model simulations relied on information of
large emissions from a single basin (Permian), and available data
suggest that the frequency of these events may vary significantly
across different production basins, which could lead to significant
uncertainty if the emission reductions were applied nationwide.
---------------------------------------------------------------------------

    It is clear from the estimates from the two proposals that these
methods are expected to result in the prevention, detection, and repair
of many current super-emitters. Sites that take advantage of
opportunities for continuous emissions monitoring offered by the
alternative monitoring strategies the EPA has proposed may be
particularly able to quickly identify and timely address these events.
    However, super-emitters' significant impact on the communities
where they are located, as well as their greatly disproportionate
contribution to emissions in total, call for additional measures to
backstop compliance and address the unique characteristics of these
events. The abnormal process conditions that characterize these events
can be persistent or episodic, meaning that while some sources are
consistent super-emitters, many such large emissions events are
intermittent and can occur at different sites over time.\103\ A cost-
effective inspection program can therefore miss some of these super-
emitter events, even if implemented in accordance with the proposed
standards. We further note that oil and gas facilities, in particular
those in remote areas, may not have personnel present when super-
emitter emissions events occur. Given the large number and broad
geographic distribution of affected sources and designated facilities
to be regulated under this rule, the EPA also recognizes that the need
for rigorous compliance assurance will be particularly important in
this source category.
---------------------------------------------------------------------------

    \103\ Daniel Zavala-Araiza et al., ``Super-emitters in Natural
Gas Infrastructure are Caused by Abnormal Process Conditions,''
Nature Communications Vol. 8 (January 2017), https://doi.org/10.1038/ncomms14012; Daniel H. Cusworth et al., ``Intermittency of
Large Methane Emitters in the Permian Basin,'' Environmental Science
and Technology Letters Vol. 8, No. 7 (June 2021), https://doi.org/10.1021/acs.estlett.1c00173.
---------------------------------------------------------------------------

    The same sophisticated research and constantly advancing new
monitoring technologies that have contributed to our understanding of
the serious problem of super-emitters can bolster the other standards
and requirements included in this proposal and serve to help identify
and mitigate any super-emitter emissions events. The super-emitter
response program, which the EPA outlined conceptually in the November
2021 proposal for public comment and which we are now proposing here,
would allow the use of reliable and demonstrated remote sensing
technology deployed by experienced, certified entities or regulatory
authorities to find these large emissions sources. As described in the
November 2021 proposal, this proposed super-emitter response program
builds on the growing use of these advanced technologies by a variety
of entities to identify and mitigate super-emitting events.
    This proposed program establishes a pathway by which an EPA-
approved entity or regulatory authority may provide credible, well-
documented identification of a super-emitter emissions event using one
of several permitted technologies and approaches, and then notify the
responsible owner or operator. Once notified of the event, owners and
operators would be required to perform a root-cause analysis and take
corrective actions to address the emissions source at their individual
well sites, centralized production facilities, and compressor stations.
Upon conducting the root-cause analysis, the owner or operator may
determine that all necessary and appropriate actions have been taken
and that no additional action is needed. However, if the owner or
operator confirms the existence of a super-emitter emissions event that
requires mitigation--either due to a failure to comply with one of the
standards in this rule or due to an upset or malfunction at a source
covered by this rule--then the owner or operator must take prompt steps
to eliminate the super-emitter emissions event and report both its
root-cause analysis and corrective actions to the EPA and the
appropriate state or tribal authority. To ensure this program operates
in a transparent manner, the EPA will make available in a document
repository the notices to operators that the EPA receives, as well as
the reports

sent to the EPA by owners and operators in response, so that notifiers,
communities, and owners and operators have quick access to the
information submitted to the EPA under the super-emitter provisions.
    The EPA believes that the super-emitter response program proposed
here will provide a cost-effective and efficient mechanism for
comprehensively detecting and addressing super-emitter emission events,
complementing and reinforcing the other requirements of this proposal
and securing reductions in methane as well as emissions of VOCs and
other health-harming air pollutants. In response to the November 2021
proposal, the EPA received comments from representatives of communities
affected by air pollution from the oil and natural gas sector,
including communities with environmental justice (EJ) concerns, voicing
concern about the impacts of these emissions and support for enhanced
monitoring efforts. The EPA anticipates that the proposed super-emitter
response program will have important benefits for such communities and
will create opportunities for communities to partner with entities
engaged in remote sensing to monitor nearby sources of emissions. The
EPA also anticipates that the proposed transparency requirements for
notifications and for follow-up actions by owners and operators will
provide valuable information for communities about neighboring sources
of emissions and steps taken to mitigate them.
    This section begins with a description of the November 2021
proposal and the comments received on that proposal, followed by a
description of the specific criteria the EPA is proposing for
notifications to sources of super-emitter events and subsequent
corrective actions taken to eliminate the emissions. The EPA seeks
comment on all aspects of this proposed program.
1. November 2021 Proposal
    As described in the November 2021 proposal, ``industry,
researchers, and NGOs have utilized advanced methane detection systems
to quickly identify large emission sources and target ground based OGI
surveys. state and local governments, industry, researchers, and NGOs
have been utilizing advanced technologies to better understand the
detection of, sources of, and factors that lead to large emission
events.'' See 86 FR 63177 (November 15, 2021). In that proposal, the
EPA solicited comment on a potential program for large emission events
that would take advantage of data from the use of advanced technologies
that could identify super-emitter emissions events; under the program,
if emissions were detected above a defined threshold ``by a community,
a Federal or state agency, or any other third party, the owner or
operator would be required to investigate the event, do a root cause
analysis, and take appropriate action to mitigate the emissions, and
maintain records and report on such events.'' See 86 FR 63177 (November
15, 2021).
2. Rationale for and Summary of Proposed Program
    The EPA received numerous comments from industry, non-industry
groups, states, tribes, and local communities articulating a range of
views on the concept described in the November 2021 proposal. These
comments provided valuable information and input on, among other
issues, the potential benefits of the program and the importance of
comprehensively addressing large emission events; implementation
challenges and concerns that would arise in establishing a system by
which researchers or other third parties could identify these events
and notify owners and operators, including concerns related to ensuring
the accuracy of such notifications and providing for safe and lawful
monitoring of sources; and the EPA's legal authority to promulgate such
a program under CAA section 111.
    The EPA has carefully considered these comments, in conjunction
with various peer-reviewed studies, in designing this proposal for a
super-emitter response program. As described below, the principal
objective of this proposed program is to provide a comprehensive and
effective remedy for large emission events that disproportionately
contribute to methane emissions from the Crude Oil and Natural Gas
source category and can be accompanied by health-harming pollution that
affects nearby communities. However, as comments provided by a wide
range of stakeholders emphasized, it is also imperative that any such
program ensure the safety of entities engaged in monitoring as well as
of owners and operators and their employees; utilize accurate,
reliable, and rigorous methods for identifying large emission events;
and be streamlined and efficient to administer, both for owners and
operators of regulated sources as well as for the EPA and the states.
The proposed program contains key features and safeguards that were
designed with these principles in mind.
    As noted above, the EPA assesses this *COM007*program is important
both because of the significant harm associated with super-emitter
emissions events and the well-documented challenges in identifying
these events. The most widely known sources of unintentional releases
resulting in super-emitter emissions events are from controlled tank
batteries, flares, natural gas-driven pneumatic controllers, and
fugitive emissions components. The standards and requirements included
in the November 2021 proposed rule and this supplemental proposal are
expected to identify and eliminate many super-emitters when implemented
as required. However, a cost-effective inspection program requiring
periodic fugitive emissions surveys cannot immediately detect every
instance of a super-emitter emissions event or quickly identify when
equipment malfunctions occur and therefore may not capture some
intermittent or episodic super-emitter emissions events. Further, it is
not cost-effective to impose additional inspection costs on every
source in hopes of detecting the small percentage of sources that
become super-emitters. The proposed super-emitter response program
would provide a cost-effective backstop to the rest of the regulatory
program by directing operator attention to problems urgently requiring
a remedy and providing useful feedback about the effectiveness of the
other regulatory requirements.
    The EPA faced a similar situation when establishing standards for
petroleum refineries, where cost-effective controls and inspections of
equipment and operations would not have addressed potentially
significant levels of emissions that could occur between regular
inspections.\104\ In that instance, the EPA required additional
monitoring and corrective action to address such high emissions;
specifically, the EPA required fenceline monitoring to ``identify a
significant increase in emissions in a timely manner (e.g., a large
equipment leak or a significant tear in a storage vessel seal), which
would allow corrective action measures to occur more rapidly than it
would if a source relied solely on the traditional infrequent
monitoring and inspection methods.'' 79 FR at 36920.\105\ The EPA is
taking a similar approach in this supplemental proposal to address
super-emitter emissions events in a timely manner. This program

is likewise motivated by the same types of considerations that led the
EPA to establish a hotline for reporting oil spills and other
environmental releases (e.g., https://www.epa.gov/emergency-response/national-response-center). However, unlike most oil spills, large
releases of methane are not visible to the human eye; identifying them
requires people with specialized equipment and expertise.
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    \104\ Proposed Rule: Petroleum Refinery Sector Risk and
Technology Review and New Source Performance Standards, 79 FR 36880,
36920 (June 30, 2014).
    \105\ This fenceline monitoring requirement is codified at 40
CFR 63.658 of the National Emission Standards for Hazardous Air
Pollutants from Petroleum Refineries, 40 CFR part 63, subpart CC.
---------------------------------------------------------------------------

    The following sections first describe the details of the proposed
super-emitter response program, including the definition of a super-
emitter emissions event under the program, the requirements for any
party that seeks to report a super-emitter emissions event under the
program; and the requirements for owners and operators responding to
such report. It then describes the statutory structure for the program
under CAA section 111.
a. Super-Emitter Response Program Design
    Threshold for a super-emitter emissions event. To clearly define
what emissions events would be subject to the requirements of this
program, the EPA is proposing to define a super-emitter emissions event
as any emissions detected using remote detection methods with a
quantified emission rate of 100 kg/hr of methane or greater. While the
term ``super-emitter'' has been widely used to describe large emissions
events in literature and various other discussions, no specific mass-
based or production-based rates have been formally or consistently
applied to the term. The EPA is proposing to apply a definition, for
purposes of this response program, that focuses on very large emissions
events at an individual well site, centralized production facility,
compressor station, or natural gas processing plant which warrant
immediate investigation.
    This threshold definition of 100 kg/hr of methane takes into
account several factors. First, this proposed super-emitter response
program is intended to provide a mechanism to utilize high quality
remote sensing detection of only the largest, most harmful emissions
events, and not address all the standards and requirements of NSPS
OOOOb and EG OOOOc that are applicable to individual affected
facilities and associated controls. The goal of this program is to
ensure that if, notwithstanding the other requirements in this
proposal, a very large emissions event occurs and is detected by a
regulatory authority or qualified third parties using particular
technologies, that super-emitting event is quickly addressed.
Therefore, the threshold definition of a super-emitter emissions event
needs to be sufficiently high that it does not duplicate other actions
(e.g., leak detection and repair) facilities are undertaking to comply
with the applicable standards in the rule. Second, where compliance is
achieved with the applicable standards, the EPA does not expect
unintentional releases at these very high levels to occur in normal
operations. Thus, the occurrence of an unintentional release at this
emissions rate should be unusual and would clearly warrant immediate
investigation and mitigation. Defining a super-emitter event to
encompass these unusually large events is therefore consistent with the
EPA's objective of establishing a backstop to the other requirements
proposed in this rule. Third, by setting such a high threshold to
capture the largest and most concerning emissions events, the program
would be more feasible to implement and would properly focus resources
on the most significant and potentially harmful sources of emissions.
Such high rates of emissions also mean that it is cost effective to
quickly address these super-emitters, which release more methane in a
single week than the total methane cost-effectively prevented over the
course of an entire year at sources covered by the fugitive emissions
program. Fourth, as discussed immediately below, this threshold allows
the use of remote sensing technologies that are already in use by the
EPA, states, and third parties, which could allow the program to be
readily implemented upon finalizing NSPS OOOOb and the subsequent state
plans required by EG OOOOc.
    Technologies that may be used to detect a super-emitter emissions
event. Various technologies are available for remote methane detection
that would provide a quantified mass emissions rate, including several
that would meet the performance criteria proposed for the alternative
periodic screening or continuous monitoring for fugitive emissions as
described in sections IV.B.1 and IV.B.2 of this preamble. Some
commenters stated that thresholds should be defined that could allow
the use of a range of technologies, without limiting to one specific
class of technologies.\106\ Among these, as discussed in the November
2021 proposal, the EPA described its understanding that ``some
satellite systems are generally capable of identifying emissions above
100 kg/hr with a spatial resolution which could allow identification of
emission events from an individual site.'' See 86 FR 63177 (November
15, 2021). Several commenters agreed that the use of satellites for
detecting super-emitters was appropriate, while noting that this
technology is continuing to advance.\107\ Further, several commenters
raised concerns regarding potential safety or trespassing on sites with
a program using more ground based or close-range detection
methods.\108\
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    \106\ See Document ID Nos. EPA-HQ-OAR-2021-0317-0605, EPA-HQ-
OAR-2021-0317-0769, EPA-HQ-OAR-2021-0317-0811, and EPA-HQ-OAR-2021-
0317-0844.
    \107\ See Document ID Nos. EPA-HQ-OAR-2021-0317-0738, EPA-HQ-
OAR-2021-0317-0753, EPA-HQ-OAR-2021-0317-0769, and EPA-HQ-OAR-2021-
0317-1391.
    \108\ See Document ID Nos. EPA-HQ-OAR-2021-0317-0727, EPA-HQ-
OAR-2021-0317-0730, EPA-HQ-OAR-2021-0317-0749, EPA-HQ-OAR-2021-0317-
0750, EPA-HQ-OAR-2021-0317-0763, EPA-HQ-OAR-2021-0317-0797, EPA-HQ-
OAR-2021-0317-0810, EPA-HQ-OAR-2021-0317-0814, EPA-HQ-OAR-2021-0317-
0817, EPA-HQ-OAR-2021-0317-0924, and EPA-HQ-OAR-2021-0317-0955.
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    The EPA agrees with the commenters that some flexibility is
appropriate in the type of technology that could be utilized for the
detection of super-emitters, provided that the technology can be safely
deployed and will reliably identify super-emitter emissions events as
defined in this proposal. Considering concerns for the safety of
individuals engaged in third-party monitoring and of facility operator
personnel, the purposes of this program as described above, and
feedback from commenters on the performance and characteristics of
various monitoring technologies, the EPA assesses that allowing only
remote-sensing technologies is appropriate. Therefore, we are proposing
to allow the use of remote-sensing aircraft, mobile monitoring
platforms, or satellites to identify super-emitter emissions events.
The EPA is soliciting comment on this list of technology types that
could be applied for the identification of super-emitter emissions
events and the threshold of 100 kg/hr of methane.
    Qualifications and requirements for notification of super-emitter
emissions events. Next, the EPA is proposing specific requirements
related to the notification of a super-emitter emissions event by
regulatory authorities and qualified third-party notifiers. Several
commenters emphasized the importance of assuring the quality and
reliability of the data and suggested that the EPA should have a role
in verifying the information to provide that assurance.\109\ In order
to address concerns about the expertise of the third party identifying
the super-emitter event, the EPA is proposing that any

third party interested in identifying and notifying owners and
operators of super-emitter emissions events must be pre-approved by the
Agency for the notification to be valid. This approval process would
follow submission of a request for approval as a qualified third-party
notifier to the EPA that demonstrates the potential notifier's
technical expertise in the specific technologies and detection
methodologies proposed for the identification of super-emitter
emissions events (i.e., remote-sensing aircraft, mobile monitoring
platforms, or satellite). This demonstration would include technical
expertise in the use of the detection technology and interpretation, or
analysis, of the data collected by the technology. The EPA would
maintain a public list of approved qualified third-party notifiers so
owners and operators can verify approval before being required to act
on a notification. These approved notifiers could be any third party,
including but not limited to technology vendors, industry, researchers,
non-profit organizations, or other parties demonstrating technical
expertise as described. The EPA is soliciting comment on this approval
criteria, including whether additional criteria would be appropriate.
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    \109\ See Document ID Nos. EPA-HQ-OAR-2021-0317-0738, EPA-HQ-
OAR-2021-0317-0938, and EPA-HQ-OAR-2021-0317-0844.
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    Once approved, a qualified notifier would be required to submit
specific information in the notification. Providing actionable data of
known quality to the owner or operator is essential to ensure resources
are focused on swiftly eliminating the super-emitter emissions event.
Therefore, the EPA is proposing that each notification must contain
specific information to help owners and operators verify that the
emissions are correctly linked to their site and aid in a focused
investigation to swiftly identify the source of emissions. Specific
information that would be required in each notification includes: (1)
The location of emissions in latitude and longitude coordinates, (2)
description of the detection technology and sampling protocols used to
identify the emissions, (3) documentation depicting the emissions and
the site (e.g., aerial imaging with emissions plume depicted), (4)
quantified emissions rate, (5) date(s) and time(s) of detection and
confirmation after data analysis that a super-emitter emissions event
was present, and (6) a signed certification that the notifier is an
EPA-approved entity for providing the notification, and the information
was collected and interpreted as described in the notification. The EPA
believes this level of specificity is necessary to provide owners and
operators with credible information, and address the concerns raised by
commenters that owners and operators could experience undue burden
investigating emissions from monitoring data that are not collected in
a rigorous manner. We are soliciting comment on the specific required
elements of the notification, including whether additional requirements
should be added to aid in verifying the credibility of this
information.
    The EPA further proposes that the entity making the report shall
provide a complete copy to the EPA and to any delegated state authority
(including states implementing a state plan) at an address those
agencies shall specify. The EPA would then promptly make such reports
available to the public online. Third parties may also make such
reports available to the public on other public websites. The EPA would
generally not verify or authenticate the information in third party
reports prior to posting.
    The EPA is seeking comment on whether it should establish a
procedure for owners and operators to suggest that EPA reconsider the
approval granted to a third-party notifier. One type of procedure the
EPA has considered would be based on information provided by the owner
or operator that demonstrates they had received more than three notices
at the same site and from the same third party for super-emitter
emissions events which the owner or operator demonstrates, after
opportunity for response by the third party, that the notifications