EPA suggested.\43\ These comments are discussed in more detail in
section IX of this preamble and in Chapter 8 of the Response to
Comments Document located in the docket for this rulemaking.
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    \43\ The commenters objected to the EPA's interpretation of
other CAA provisions, of legislative history, and of other
provisions of CAA section 111, as well as the EPA's interpretations
of CAA section 111 in earlier administrative actions. We discuss
these comments in the Response to Comments Document located in the
public docket of this final rulemaking.
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3. Final Action
    The EPA is finalizing the position that CAA section 111 requires,
or at least authorizes the Administrator to require a pollutant-
specific SCF as a predicate for promulgating a standard of performance
for that air pollutant. The EPA bases this position primarily on a
refinement of the interpretation of CAA section 111, described above,
on which it solicited comment. Specifically, the EPA interprets the CAA
section 111(b)(1)(B) requirement that the Administrator propose to
``establish[ ] . . . standards of performance'' and then finalize
``such standards with such modifications as he deems appropriate,'' in
light of both the CAA section 111(a)(1) definition of ``standard of
performance'' as a ``standard for emissions of air pollutants,'' and
CAA section 111(b)(1)(A), which requires the Administrator to list a
source category only ``if in his judgment it causes, or contributes
significantly to [dangerous] air pollution.'' Read in this context, CAA
section 111(b)(1)(B) is best understood not to require the
Administrator to promulgate standards for emissions of all air
pollutants but only to require him or her to promulgate standards for
the emissions of air pollutants that the Administrator has determined
``cause or contribute significantly'' to the ``air pollution'' that the
Administrator determined to be dangerous when listing the source
category. Under this interpretation, if the Administrator did not, in
listing the source category, determine that a particular air pollutant
causes or contributes significantly to the dangerous air pollution,
section 111 requires the Administrator to make--or, at least,
authorizes the Administrator to require--a pollutant-specific SCF as a
predicate to regulating that air pollutant.\44\
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    \44\ Although this interpretation is a refinement of the
interpretation for which the EPA solicited comment in the 2019
Proposal, it is rooted in the Proposal. As noted in the summary
above, in supporting the interpretation that CAA section
111(b)(1)(A) requires or authorizes the EPA to require a pollutant-
specific SCF, the EPA made numerous references to CAA sections
111(a)(1) and 111(b)(1)(B), and made clear that those three
provisions must be read together. The EPA made other references as
well to the need to make a pollutant-specific SCF in order to
promulgate standards of performance, which is the thrust of the
interpretation described in this final action. See Id. at 50262-63.
The rational basis approach was an interpretation of CAA section
111(b)(1)(B). That is, under this approach, the EPA interpreted that
provision to authorize standards of performance for those air
pollutants for which the EPA had a rational basis, but not
necessarily standards for all air pollutants. See 81 FR 35842 (2016
Rule), cited in 84 FR 50262 (2019 Proposal). This approach is
similar to the pollutant-specific SCF approach. By the same token,
the EPA's discussions in the 2019 Proposal of the legislative
history, CAA section 111(f), and previous statements the EPA made in
support documents all contain references to a pollutant-specific SCF
as a predicate for promulgating standards of performance. 84 FR
50263 through 67.

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4. Legal Interpretation of CAA Sections 111(a)(1), (b)(1)(B), and
(b)(1)(A) and the Pollutants Subject to Regulation
    The EPA interprets CAA sections 111(b)(1)(B), in light of CAA
sections (b)(1)(A) and (a)(1), to require, or at least to authorize the
Administrator to require, a pollutant-specific SCF as a predicate for
promulgating a standard of performance for that air pollutant. The EPA
bases this interpretation on a close reading of these provisions in the
context of CAA section 111. CAA section 111 directs the EPA to
regulate, through a multi-step process, air pollutants from categories
of stationary sources. CAA section 111(b)(1)(A) requires the initial
action, which is that the Administrator must ``publish . . . a list of
categories of stationary sources. He shall include a category of
sources in such list if in his judgment it causes, or contributes
significantly to, air pollution which may reasonably be anticipated to
endanger public health or welfare.'' This provision does not by its
terms require the Administrator, in listing a source category, to
identify particular air pollutants of concern that are emitted from the
source category, but it does make clear that the Administrator must
identify air pollution that is of concern and must make a finding that
this air pollution, in our shorthand, is dangerous.
    CAA section 111(b)(1)(B) then directs the EPA to propose
regulations ``establishing Federal standards of performance'' for new
sources within the source category, then to allow public comment, and
then to ``promulgate . . . such standards with such modifications as he
deems appropriate.'' CAA section 111(a)(1) defines the term ``standard
of performance'' as ``a standard for emissions of air pollutants which
[the Administrator is required to determine through a specified
methodology].'' This definition makes clear that the standards of
performance that CAA section 111(b)(1)(A) directs the Administrator to
promulgate must concern air pollutants emitted from the sources in the
source category. However, industrial sources of the type subject to CAA
section 111(b)(1)(A) invariably emit more than one air pollutant and
neither CAA section 111(b)(1)(B) nor 111(a)(1) by its terms specifies
for which of those air pollutants the EPA must promulgate standards of
performance.
    But the statute does provide guidance as to the class of air
pollutants for which the EPA must promulgate standards of performance.
Section 111(b)(1)(A) of the CAA demonstrates that the statutory scheme
of CAA section 111 is aimed at controlling ``air pollution which may
reasonably be anticipated to endanger public health or welfare.'' It
follows that the air pollutants for which the Administrator must
establish standards must, or at least may reasonably, be limited to
those air pollutants which contribute to this dangerous air pollution.
    The Administrator's discretion to limit the class of air pollutants
for which he promulgates standards is supported by his statutory
discretion under CAA section 111(b)(1)(B) to finalize standards ``with
such modifications as he deems appropriate.'' In an exercise of this
discretion, the Administrator deems it appropriate to limit the
standards of performance to those air pollutants that contribute to
dangerous air pollution.
    Several other provisions in CAA section 111 also refer to air
pollutants, including CAA section 111(b)(3), which requires the
Administrator to, ``from time to time, issue information on pollution
control techniques for categories of new sources and air pollutants
subject to the provisions of this section.'' This reference to ``air
pollutants subject to the provisions of this section'' (emphasis added)
implies that some air pollutants may not be subject to CAA section 111;
otherwise, the emphasized phrase would be superfluous.\45\
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    \45\ Similarly, CAA section 111(d)(1)(A) makes clear by its
terms that ``a standard of performance under this section'' need not
govern all pollutants emitted from a regulated source to give effect
to Congress's purpose. The requirements of CAA section 111(d)(1)(A)
apply to only a subset of air pollutants, that is, ``any air
pollutant . . . for which air quality criteria have not been issued
or which is not included on a list published under section 7408(a)
of this title or emitted from a source category which is regulated
under section 7412 of this title but . . . to which a standard of
performance under this section would apply if such existing source
were a new source.''
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    As noted in the 2019 Proposal, in the past, the EPA has interpreted
CAA section 111(b)(1)(B) to authorize it to promulgate standards of
performance for any air pollutant that the EPA identified in listing
the source category and any additional air pollutant for which the EPA
has identified a rational basis for regulation. 81 FR 35843 (2016 Oil &
Gas Methane Rule); ``Standards of Performance for Greenhouse Gas
Emissions from New, Modified, and Reconstructed Stationary Sources:
Electric Utility Generating Units--Final Rule,'' 80 FR 64510 (October
23, 2015) (EGU CO2 NSPS Rule). Inherent in this approach is
the recognition that CAA section 111(b)(1)(A) does not, by its terms,
necessarily require the EPA to promulgate standards of performance for
all air pollutants emitting from the source category. Citizen group
stakeholders and some states have endorsed the rational basis approach.
Some industry stakeholders and other states, however, have advocated a
narrower approach with respect to, at least, the GHG for which the EPA
promulgated standards of performance for the Fossil Fuel-Fired Electric
Utility Generating Units source category and the Crude Oil and Natural
Gas Production source category. The stakeholders argued that under this
narrower approach, the EPA is not authorized to promulgate NSPS for at
least GHG unless it first makes a SCF with respect to that pollutant.
    The EPA interprets the phrase at issue in CAA section 111(b)(1)(B),
``standards of performance,'' and the associated phrase in CAA section
111(a)(1), ``emissions of air pollutants,'' by analogy to the similar
phrase, ``any air pollutant,'' found in the CAA permitting provisions
that the U.S. Supreme Court considered in Utility Air Regulatory Group
v. EPA, 573 U.S. 302 (2014) (UARG). In UARG, the Court interpreted CAA
section 169(1), which provides construction and modification permitting
requirements under the Prevention of Significant Deterioration (PSD)
program, and CAA sections 501(2)(B) and 302(j), which provide the
operating permit requirements of the title V program. The Court
concluded that when read in the context of the permitting provisions,
the phrase ``any air pollutant'' did not encompass GHG, even though
they are air pollutants. The EPA considers that the analytical approach
that the Court adopted in UARG also applies to CAA section
111(b)(1)(B). Under this approach, the provisions in that section that
direct the Administrator to establish ``standards of performance'' for
new sources in the source category, require, or at least reasonably
allow, the Administrator to promulgate standards for only those air
pollutants for which the EPA has made a SCF.
    The EPA considers the same analytical approach to support
interpreting ``emissions of air pollutants'' in CAA section 111(a)(1)
to encompass only those air pollutants for which the EPA has made a
SCF. Under the PSD requirements, no ``major emitting facility'' may be
constructed or

modified in certain areas of the U.S. unless it has received a permit
that includes certain conditions and emission limits. CAA section
165(a)(1). In the PSD definitional provisions, CAA section 169(1)
defines the term ``major emitting facility'' as any stationary source
of air pollutants that emits, or has the potential to emit, at least
100 or 250 tpy (depending on the source) of ``any air pollutant.'' See
CAA sections 169(2)(C), 111(a)(4) (defining ``construction'' to include
``modification,'' which in turn is defined to mean, in relevant part, a
certain type of change that increases the amount of ``any air
pollutant'' emitted by the source). Title V makes it unlawful to
operate a ``major source'' without an operating permit that includes
all applicable CAA requirements. Title V defines a ``major source'' by
incorporating the CAA-wide definition of ``major stationary source:'' A
stationary source that emits or has the potential to emit at least 100
tons per year of ``any air pollutant.'' CAA section 501(2)(B), 302(j).
    In a 2010 rule, ``Prevention of Significant Deterioration and Title
V Greenhouse Gas Tailoring Rule,'' 75 FR 31514 (June 3, 2010)
(Tailoring Rule), the EPA took the position that the phrase ``any air
pollutant'' in these provisions necessarily included GHG, based on the
2007 decision by the U.S. Supreme Court that the CAA-wide definition of
``air pollutant,'' CAA section 302(g), encompasses GHG. Massachusetts
v. EPA, 549 U.S. 497 (2007). The EPA's interpretation, however, created
practical problems, which the Agency recognized in the Tailoring Rule:
It would cause numerous commercial and small industrial sources to
become subject to the permitting requirements, which were burdensome
and which Congress designed to apply only to large industrial sources
that were equipped to carry those burdens. UARG, 573 U.S. at 310-11
(citing 73 FR 44355, 44498 and 99).
    UARG held that the EPA's interpretation of the PSD and title V
provisions was unreasonable, and that the phrase ``any air pollutant''
in these provisions did not include GHG. The Court adopted a two-step
analysis. First, the Court found that the fact that the CAA-wide
definition of ``air pollutant'' included GHG did not mean that all the
references to ``air pollutant'' in the CAA's operative provisions
necessarily include GHG; rather, whether the term included GHG was
dependent on the context of the particular operative provision. 573
U.S. at 316. The Court found support for this position in the fact that
``where the term `air pollutant' appears in the Act's operative
provisions, EPA has routinely given it a narrower, context-appropriate
meaning.'' Id. The Court explained that the EPA had already interpreted
``any air pollutant'' in the permitting provisions to be limited to
``regulated'' air pollutants, which the Court described as ``a
reasonable, context-appropriate meaning.'' Id. at 316-17. The Court
identified several other provisions ``where EPA has inferred from
statutory context that a generic reference to air pollutants does not
encompass every substance falling within the Act-wide definition.'' For
example, and of particular significance here, the Court noted that CAA
section 111(a)(4), read together with CAA sections 111(a)(2) and
(b)(1)(B), applies NSPS requirements to a source that undergoes a
physical or operational change that increases its emission of ``any air
pollutant,'' but the EPA interprets this provision as limited to air
pollutants for which the EPA has promulgated standards of performance.
573 U.S. at 317. Similarly, the Court noted that CAA sections
169A(b)(2)(A) and (g)(7) require a certain type of source that
interferes with visibility to retrofit if it has the potential to emit
250 tpy of ``any pollutant,'' but that the EPA interprets this
provision as limited to visibility-impairing air pollutants. 573 U.S.
at 318. The Court emphasized that Massachusetts did not call these
interpretations into question; rather, according to the Court,
``Massachusetts does not foreclose the Agency's use of statutory
context to infer that certain of the Act's provisions use `air
pollutant' to denote not every conceivable airborne substance, but only
those that may sensibly be encompassed within the particular regulatory
program.'' 573 U.S. at 319. Therefore, in this first step, the Court
concluded that the CAA did not compel the EPA to interpret the phrase
``any air pollutant'' in the permitting provisions to include GHG.
    Second, the Court found that the EPA did not have the discretion to
interpret this phrase to include GHG, because it was unreasonable to do
so in light of the permitting provisions. The Court explained that
including GHG would expand the permitting programs to large numbers of
small sources, but that ``a brief review of the relevant statutory
provisions leaves no doubt that the PSD program and Title V are
designed to apply to, and cannot rationally be extended beyond, a
relative handful of large sources capable of shouldering heavy
substantive and procedural burdens.'' Id. at 322. The Court went on to
describe the various PSD and title V statutory requirements that are
resource-intensive and time-consuming, and, therefore, incompatible
with application to large numbers of small sources. Id. at 322-23.
    The EPA is adopting UARG's two-step analytical approach to conclude
that, in light of its context, CAA section 111(b)(1)(B) does not
mandate, and cannot reasonably be read to authorize, the EPA to
promulgate standards of performance for an air pollutant for which the
EPA has not made a SCF. At a minimum, even if these provisions are not
read to preclude the EPA from promulgating standards of performance
without first making a pollutant-specific SCF, it is reasonable to
interpret these provisions as authorizing the EPA to decline to
promulgate standards without first making such a SCF. UARG was explicit
that provisions of CAA section 111 are subject to its analytical
approach. As noted above, the Court endorsed the EPA's interpretation
that, notwithstanding the reference to ``any air pollutant'' in CAA
section 111(a)(4), the requirements concerning a ``modification'' in
CAA section 111(b)(1)(B), which is at issue here, and CAA sections
111(a)(2) and (4) do not require the EPA to promulgate standards for
every pollutant that a modified source emits, because those provisions
must be understood in context to embrace a limited set of air
pollutants. 573 U.S. at 317.
    As is clear from the EPA's summary above of the CAA section 111
rulemaking process, the first action that the EPA must take, specified
in CAA section 111(b)(1)(A), is to list a source category for
regulation on the basis of a determination that the category
contributes significantly to dangerous air pollution, and it is this
provision that establishes the context that is relevant for present
purposes. This provision makes clear that although Congress designed
CAA section 111 to apply broadly to source categories of all types
wherever located, Congress also imposed a constraint: The EPA is
authorized to regulate only sources that it finds cause or contribute
significantly to air pollution that the EPA finds to be dangerous.
    Congress' direction to EPA to promulgate standards of performance
for the sources in the category, under CAA section 111(b)(1)(B), must
be viewed in this context. Congress did not specify which air
pollutants the standards of performance must address, stating only, as
noted above, in the definitional provisions of CAA section 111 that the
term ``standard of performance'' means a standard for

``emissions of air pollutants.'' This phrase is substantially similar
to the phrase ``any air pollutant'' in the PSD and Title V provisions
addressed in UARG. In fact, ``emissions of air pollutants'' appears to
be less encompassing than ``any air pollutant.'' As the U.S. Supreme
Court has noted, ``Read naturally, the word `any' has an expansive
meaning, that is, `one or some indiscriminately of whatever kind.'
Webster's Third New International Dictionary 97 (1976).'' United States
v. Gonzales, 520 U.S. 1, 4, 1997), quoted in Department of Housing and
Urban Development v. Rucker, 535 U.S. 125, 131 (2002), cited in
Massachusetts, 549 U.S. at 529 n.25.
    Under the analytical approach of UARG, because the regulatory scope
of the CAA's ``operative provisions,'' such as CAA sections
111(b)(1)(B) and 111(a)(1), must be understood in context, their
reference to ``standards of performance'' and ``emissions of air
pollutants'' cannot be read to mandate promulgation of standards of
performance for each and every air pollutant emitted from the source
category. In addition, because Congress limited the EPA to regulating
only stationary sources in a category that the Administrator must first
determine to cause or contribute significantly to dangerous air
pollution, it is not reasonable to read ``air pollutants'' to refer to
any of the source category's air pollutants for which the EPA has not
made a SCF. At the very least, it is reasonable to interpret that
phrase more narrowly. As noted in the 2019 Proposal, interpreting the
CAA section 111 provisions to authorize the EPA to regulate any air
pollutant, even ones that the EPA did not consider in listing the
source category, creates the risk that the EPA may regulate air
pollutants emitted in small quantities or otherwise having little
adverse effect.\46\
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    \46\ As should be clear from this discussion immediately above,
this interpretation of CAA sections 111(b)(1)(B) and (a)(1) differ
from the interpretation of CAA section 111(b)(1)(A) that the EPA
described in the 2019 Proposal. See 84 FR 50263 (stating that
interpreting CAA section 111(b)(1)(B), the EPA was mindful that an
Agency ``[may] avoid a literal interpretation at Chevron step one .
. . [by] show[ing] either that, as a matter of historical fact,
Congress did not mean what it appears to have said, or that, as a
matter of logic and statutory structure, it almost surely could not
have meant it'' (citation omitted)).
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    It is true that, recently, the EPA has adopted the approach of
regulating additional air pollutants that it did not address in the
listing determination only after determining that it has a rational
basis for doing so, and in making that determination, has considered
the same factors as it would in making a SCF. 81 FR 35843 (2016 Rule).
However, this approach is a creature of Agency practice and, therefore,
is not as firmly established as statutory requirements. As noted in the
2019 Proposal, interpreting CAA section 111 to require only a
pollutant-specific rational basis standard, and not a SCF, could lead
to potentially anomalous results when the Agency, after listing a
source category on grounds that its emissions taken together contribute
significantly to dangerous air pollution, proceeds to promulgate NSPS
for individual air pollutants. EPA stated that, as an example, under
the rational basis interpretation, the EPA could list a source category
on grounds that it emits numerous air pollutants that, taken together,
significantly contribute to air pollution that may reasonably be
anticipated to endanger public health or welfare, and proceed to
regulate each of those pollutants, without ever finding that each (or
any) of those air pollutants by itself causes or contributes
significantly to--or, in terms of the text of other provisions, causes
or contributes to--air pollution that may reasonably be anticipated to
endanger public health or welfare. 84 FR 50263. As further noted in the
2019 Proposal, CAA section 111(b)(1)(A) does not provide or suggest any
criteria to define the rational basis approach, the EPA has not
articulated any criteria in its previous applications in the EGU
CO2 NSPS and the 2016 subpart OOOOa rules, and in instances
before those rules in which the EPA has relied on the ``rational
basis'' approach, the EPA has done so to justify not setting a standard
for a given pollutant, rather than to justify setting such a standard.
Id. Thus, the rational basis test allows the EPA virtually unfettered
discretion in determining which air pollutants to regulate. As a
result, the rational basis standard creates the possibility that the
EPA could seek to promulgate NSPS for pollutants that may be emitted in
relatively minor amounts, as the EPA noted in the 2019 Proposal. 84 FR
50263. As noted in section IX below, numerous commenters reiterated
these concerns.
    In contrast, CAA section 111(b)(1)(A) is clear that the EPA may
list a source category for regulation only if the EPA determines that
the source category ``causes or contributes significantly'' (emphasis
added) to dangerous air pollution. In light of the stringency of this
statutory requirement for listing a source category, it would be
unreasonable to interpret CAA section 111(b)(1)(B) to allow the Agency
to regulate air pollutants from the source category merely by making an
administrative determination under the open-ended and undefined
rational basis test. Rather, it is logical to interpret CAA section
111(b)(1)(B) to require that the Agency apply the same degree of rigor
in determining which air pollutants to regulate as it does in
determining which source categories to list for regulation.
    For these reasons, the EPA concludes that in the context of CAA
section 111, the requirement that the EPA promulgate ``standards of
performance,'' (CAA section 111(b)(1)(B)), defined as ``standard[s] for
emissions of air pollutants'' (CAA section 111(a)(1)), must be
interpreted to require a pollutant-specific SCF (CAA section
111(b)(1)(A)) as a predicate for promulgating standards of performance.
At a minimum, the Agency considers this interpretation to be reasonable
and, accordingly, adopts it. Requiring a pollutant-specific SCF
establishes a clearer framework for assessing which air pollutants
merit regulatory attention that will require sources to bear control
costs. This promotes regulatory certainty for stakeholders and
consistency in the EPA's identification of which air pollutants to
regulate and reduces the risk that air pollutants that do not merit
regulation will nevertheless become subject to regulation due to an
unduly vague standard.
    In the 2019 Proposal, the EPA solicited comment on whether to
interpret CAA section 111(b)(1)(A) to require a determination that the
pollutant causes or contributes significantly to dangerous air
pollution (the SCF) or instead, to interpret it to require a
determination that the pollutant simply causes or contributes to
dangerous air pollution. 84 FR 50261. The same issue arises with
respect to CAA sections 111(b)(1)(B) and (a)(1), but the EPA has
concluded that interpreting these provisions to require a SCF as the
pollutant-specific finding is consistent with the source-category SCF
in CAA section 111(b)(1)(A). That is, in light of Congress' clearly
expressed intent in CAA section 111(b)(1)(A) that the EPA base its
listing of a source category on a finding that the emissions from the
source category contribute significantly to dangerous air pollution,
the EPA concludes that CAA sections 111(b)(1)(B) and (a)(1) require the
EPA to base its regulation of a pollutant on a similarly rigorous
finding that the pollutant contributes significantly to dangerous air
pollution. If, in the alternative, the statute is ambiguous in this
regard, the EPA exercises its

discretion to interpret it to require a pollutant-specific SCF.
    In the 2019 Proposal, the EPA noted that interpreting CAA section
111 to require a pollutant-specific SCF as a predicate to regulation
``need not result in duplicative SCFs (or duplicative associated
endangerment findings). That is, the EPA would not need to make
separate SCFs (and associated endangerment findings) for both the
source category and each pollutant emitted by the source category that
the EPA seeks to regulate.'' 84 FR 50266. The EPA continues to hold
this view. In identifying any new source categories under CAA section
111(b)(1)(A), the EPA could identify each air pollutant of concern and
make a SCF, as appropriate, for emissions of each of those pollutants
from the source category, and, in that same action, make the SCF for
the source category itself. In addition, in the 2019 Proposal, the EPA
solicited comment on what implications interpreting CAA section 111 to
require a pollutant-specific SCF would give rise to for already
promulgated standards of performance. Id. The EPA believes that
standards of performance will generally not be affected by this
requirement because generally, the EPA identified and analyzed the air
pollutants of concern when the EPA listed a source category, or
initiated promulgation of standards of performance at the same time or
shortly after listing the source category, and, therefore, in
association with the significance determination the Agency made in that
listing. For example, as noted elsewhere, the EPA followed that process
when it listed the Crude Oil and Natural Gas Production source
category, that is, it identified and analyzed the air pollutants of
concern at that time in the supporting documents. Importantly, the EPA
relied on its analyses of those air pollutants as the basis for
determining that the source categories' emissions contribute
significantly to dangerous air pollution.\47\
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    \47\ The EPA also took the approach in the 2016 Rule that it is
revising here, when it attempted to expand the Crude Oil and Natural
Gas Production source category. It discussed the pollutant
emissions, including GHG, VOC, and SO2, made a SCF for
those emissions, and, on the basis of that SCF, listed the expanded
source category. 81 FR 35837 through 40.
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B. Flaws in the 2016 Rule's Significant Contribution Finding

    When the Administrator listed the oil and natural gas industry as a
source category in 1979, he did not determine that methane emissions
from the source category cause or contribute significantly to dangerous
air pollution. In this rulemaking, the EPA is taking the position that
the EPA must make that determination as a predicate to promulgating
standards of performance for methane from this source category. The
Administrator did determine in the 2016 Rule that methane from the
source category contributes significantly to dangerous air pollution,
but that determination was flawed and must be rescinded for two
reasons: (1) The Administrator made that determination on the basis of
methane emissions from the production, processing, and transmission and
storage segments, instead of just the production and processing
segments; and (2) the Administrator failed to support that
determination with either established criteria or some type of
reasonably explained and intelligible standard or threshold for
determining when an air pollutant contributes significantly to
dangerous air pollution.
1. Improper Scope of Source Category
    In the 2016 Rule, the Administrator made the significant
contribution finding on the basis of assessing methane emissions from
the source category as defined to include the production, processing,
and transmission and storage segments. In the present action, we are
removing the transmission and storage segment, leaving only the
production and processing segments. Because the 2016 Rule did not
assess whether methane emissions from the production and processing
segments alone cause or contribute significantly to dangerous air
pollution, we find that the Rule's determination is not adequate and,
therefore, we are rescinding it. Until the EPA makes an appropriate
determination that methane emissions from the Oil and Natural Gas
source category, properly calculated, contribute significantly to
dangerous air pollution, it does not have authority to promulgate
standards of performance for methane from these sources under CAA
section 111(b)(1)(b).
2. Lack of Criteria or Standard for Determining Significant
Contribution
    In the 2019 Proposal, the EPA ``solicit[ed] comment on the question
of whether the SCF in the 2016 . . . [R]ule can be considered
appropriate given that nowhere in the course of developing and
promulgating that rule did the EPA set forth the standard by which the
`significance' of the contribution of the methane emissions from the
source category (as revised) was to be assessed.'' 84 FR 50267. The EPA
elaborated that it was asking for comment on whether, as a matter of
law, under CAA section 111, the EPA is obligated to identify the
standard by which it determines whether a source category's emissions
``contribute significantly,'' and whether, if not so obligated, the EPA
nevertheless fails to engage in reasoned decision-making by not
identifying that standard. Id. The EPA cited Motor Vehicle Mfrs. Assn.
of United States, Inc. v. State Farm Mut. Automobile Ins. Co., 463 U.S.
29, 43 (1983), which states, ``Normally, an agency rule would be
arbitrary and capricious if the agency has . . . entirely failed to
consider an important aspect of the problem.''. Id. See Department of
Homeland Security v. Regents of Univ. of Cal., No. 18-587, slip op. at
18 (U.S. June 18, 2020) (executive action to rescind the Deferred
Action for Childhood Arrivals program failed to provide a reasoned
explanation when it failed to consider certain ``conspicuous issues'').
For the reasons that follow, the EPA concludes that the failure to
identify any such standard or any established set of criteria for the
2016 Rule's SCF for methane emissions from the source category is
unreasonable and requires rescinding the 2016 Rule's SCF.
    As the EPA noted in the 2019 Proposal, the ``contributes
significantly'' provision in CAA section 111(b)(1)(A) is ambiguous. See
84 FR 50267-68 (citing EPA v. EME Homer City Generation, L.P., 572 U.S.
489 (2014) (holding that a similar provision in CAA section
110(a)(2)(D)(i), often termed the ``good neighbor'' provision, is
ambiguous)). Accordingly, the EPA has authority to interpret that
provision. Id. at 50268. As noted above, the EPA reads CAA section
111(b)(1)(B) in light of CAA sections 111(b)(1)(A) and (a)(1) to
incorporate the ``contributes significantly'' standard in connection
with promulgating NSPS for particular air pollutants. The EPA has
concluded that to allow the EPA to distinguish between a contribution
and a significant contribution to dangerous pollution, some type of
(reasonably explained and intelligible) standard and/or established set
of criteria that can be consistently applied is necessary. Without at
least one or the other, it is impossible to evaluate whether the SCF is
well reasoned. Therefore, the lack of a standard or established set of
criteria for the 2016 Rule's SCF renders the finding arbitrary and
capricious. A supporting basis for this conclusion can be found in the
EPA's analysis of the ``contribute significantly'' provisions of CAA
section 189(e), concerning major stationary sources of PM with a
diameter of 10 micrometers or less (PM10). This provision
requires that the

control requirements applicable to major stationary sources of
PM10 also apply to major stationary sources of
PM10 precursors ``except where the Administrator determines
that such sources [of precursors] do not contribute significantly to
PM10 levels which exceed the standard in the area.'' As the
EPA noted in the 2019 Proposal, in CAA section 189(e), Congress
intended that, in order to be subject to regulation, the emissions must
have a greater impact than a simple contribution not characterized as a
significant contribution. However, Congress did not quantify how much
greater. Therefore, the EPA developed criteria for identifying whether
the impact of a particular precursor would ``contribute significantly''
to a NAAQS exceedance. 84 FR 50268. These criteria included numerical
thresholds. Id.
    The EPA has concluded similarly that, under CAA section 111(b), a
standard or an established set of a criteria, or perhaps both, are
necessary to identify what is significant and what is not. Moreover,
without either, any determination of significance is arbitrary and
capricious because it does not identify a reasoned basis for that
determination.\48\ This is evident in the flawed significance finding
in the 2016 Rule. There, the EPA determined that ``the collective GHG
emissions from the oil and natural gas source category are
significant'' and based that determination on several facts concerning
the amount of methane emissions from the Oil and Gas source category,
in comparison to other domestic and global emissions. Specifically, the
EPA stated that oil and gas GHG emissions are significant, whether the
comparison is (i) ``domestic'' (noting that this sector is ``the
largest source of methane emissions, accounting for 32 percent of
United States methane and 3.4 percent of total United States emissions
of all GHG''), (ii) ``global'' (noting that this sector, ``while
accounting for 0.5 percent of all global GHG emissions, emits more than
the total national emissions of over 150 countries, and combined
emissions of over 50 countries''), or (iii) ``when both the domestic
and global GHG emissions comparisons are viewed in combination.'' 81 FR
35840. The EPA did add a qualitative assessment of those facts. It
noted that ``no single GHG source category dominates on the global
scale,'' noted further that the oil and natural gas source category,
``like many (if not all) individual GHG source categories, could appear
small in comparison to total emissions,'' and asserted that
nevertheless, ``in fact, it is a very important contributor in terms of
both absolute emissions, and in comparison to other source categories
globally or within the United States.'' Id. However, the EPA did not
identify any set of criteria by which to evaluate those facts and to
ensure that those facts constituted the comprehensive set of data for
determining significance. In contrast, when the EPA determines whether
an area should be designated nonattainment on grounds that it
``contributes'' to ambient air quality problems in a nearby area, the
EPA applies an established set of criteria that identify the relevant
sets of data to analyze and explain how to analyze them. See Catawba
Cty. v. EPA, 571 F.3d 20, 39-40 (DC Cir. 2009) (Catawba) (holding that
in determining whether an area ``contributes'' to downwind ozone air
quality problems, the EPA, ``[t]o be reasonable . . . must . . . define
and explain the criteria the agency is applying''; explaining that the
EPA adopted a set of nine criteria that it defined and explained ``in
spades''). These criteria help ensure that the EPA's decision-making is
well-reasoned and consistent. The EPA considers it particularly
important to develop a set of criteria and/or a standard in order to
determine when a significant contribution occurs, in order, as noted
above, to distinguish it from a simple contribution. A contribution can
be greater or lesser and remain a contribution, but a significant
contribution determination necessarily involves a judgment about the
degree of the contribution that rises to the level of significance. For
such a judgment to be meaningful (and to be understood by regulated
parties and by the public), the Agency must identify the criteria it
will use to determine significance. In the 2016 Rule's significance
finding, the EPA did not identify such criteria.
---------------------------------------------------------------------------

    \48\ As noted in the 2019 Proposal, in a 1994 rule concerning
CAA section 213(a), which requires the EPA to make a finding that
air pollutant emissions from new and existing nonroad engines and
vehicles are ``significant contributors'' to dangerous air
pollution, the EPA determined that it is not necessary to establish
a ``specific numerical standard'' for determining significance. 84
FR 50268 (citing 59 FR 31306 and 31308 (June 17, 1994)). However,
more recently, as further noted in the 2019 Proposal, the EPA
promulgated criteria to interpret and apply ``contribute
significantly'' in the ``good neighbor'' provision, CAA section
110(a)(2)(D)(i). 84 FR 50267 and 68 (discussing the criteria and the
EPA's use of them in the Cross State Air Pollution Rule, which the
U.S. Supreme Court upheld in EPA v. EME Homer City Generation, LP.,
572 U.S. 489 (2014)). In Coalition for Responsible Regulation v. EPA
(CRR), the Court considered a challenge to the EPA's 2009
determination under CAA section 202(a) that GHG air pollution may
reasonably be anticipated to endanger public health and welfare (the
GHG Endangerment Finding) on grounds that the EPA had failed to
quantify a threshold amount of GHG air pollution that would be safe
and that, as a result, the EPA had no basis for concluding that the
current amount may endanger. 684 F.3d 102, 122-23 (DC Cir. 2012),
aff'd in part and rev'd in part on other grounds sub nom. Utility
Air Regulatory Group v. EPA, 573 U.S. 302 (2014). The Court upheld
the GHG Endangerment Finding, concluding that the EPA based it on an
overall assessment of risk--accounting for ``the precautionary
thrust of the CAA and the multivariate and sometimes uncertain
nature of climate science''--for which no quantitative threshold is
necessary. Id. at 123. That case is distinguishable because it
focused on the endangerment finding for GHG air pollution, not on
the amount of contribution that GHG emissions make to that air
pollution. In any event, the contribution requirement of section
202(a)(1) requires only a simple contribution determination, not a
significant contribution.
---------------------------------------------------------------------------

    Nor did the EPA identify any threshold against which to compare the
cited facts concerning methane emissions, and thereby assess their
importance, much less explain why a contribution above such a threshold
should be deemed significant while a contribution below it should not.
Thus, for example, although the EPA justified the significance
determination, in part, on grounds that the source category's emissions
constitute 3.4 percent of total U.S. GHG emissions and 0.5 percent of
all global GHG emissions, the EPA did not explain why either of those
facts supports the significance determination. Because the EPA did not
identify a threshold or criteria for evaluating the oil and gas
industry's percentage of domestic or global GHG emissions, the EPA
could not justify the 2016 Rule's SCF. As a result, that determination
cannot be considered the result of reasoned and appropriate decision-
making.\49\ The EPA intends to begin

rulemaking shortly to identify thresholds and/or criteria and to apply
them in future significance determinations.
---------------------------------------------------------------------------

    \49\ In the EGU CO2 NSPS Rule, the EPA determined, in
the alternative, that CO2 emissions from fossil fuel-
fired EGUs contribute significantly to dangerous air pollution. The
EPA explained that fossil fuel-fired EGUs ``emit almost one-third of
all U.S. GHG emissions, and are responsible for almost three times
as much as the emissions from the next ten stationary source
categories combined.'' The EPA added that ``[t]he CO2
emissions from even a single new coal-fired power plant may amount
to millions of tons each year,'' and that ``the CO2
emissions from even a single NGCC unit may amount to one million or
more tons per year.'' The EPA also asserted that in that rulemaking,
``[i]t is not necessary'' for the EPA ``to decide whether it must
identify a specific threshold for the amount of emissions from a
source category that constitutes a significant contribution.'' The
EPA explained that ``under any reasonable threshold or definition,
the emissions from combustion turbines and steam generators are a
significant contribution.'' 80 FR 64531. In 2018, the EPA proposed
to revise the EGU CO2 NSPS Rule, and solicited comment on
whether a SCF for GHG emissions from fossil fuel-fired EGUs was a
necessary predicate for promulgating a NSPS for those emissions.
``Review of Standards of Performance for Greenhouse Gas Emissions
From New, Modified, and Reconstructed Stationary Sources: Electric
Utility Generating Units--Proposed Rule, 83 FR 65424, 65432 n.25
(December 20, 2018). While the EPA has not taken final action for
that rule, the unique CO2 emissions profile of fossil
fuel-fired EGUs should be noted: The volume of emissions from EGUs
dwarfs the amount of GHG emissions from every other source category.
---------------------------------------------------------------------------

    Commenters objected that the 2016 Rule's SCF should not be
considered invalid due to the lack of a standard by which to assess
significant contribution, citing Mississippi Commission on Envtl.
Quality v. EPA, 790 F.3d 138 (D.C. Cir. 2015) (Mississippi), the most
recent decision in the line of cases that includes Catawba, noted
above. In that line of cases, the Court upheld the EPA's approach to
determining whether, under CAA section 107(d)(1)(A)(i), an upwind area
should be treated as nonattainment because it ``contributes'' to
downwind air quality problems. See Mississippi, 790 F.3d at 150 (citing
Catawba, 571 F.3d at 39-40). The Court held that the EPA was not
required to establish a threshold level of impact for determining
whether an upwind area ``contributes'' to a downwind area. The
Mississippi Court cited Catawba, 571 F.3d at 39-40), which commenters,
in turn, cite to argue that such a threshold is not necessary for
determining a significant contribution under CAA section 111(b).
However, as noted above, the EPA had ``define[d] and explain[ed]'' a
set of criteria for determining whether an upwind area ``contributes,''
and in the cited case law, the Court found that these criteria
facilitated the reasonableness of the EPA's decision-making. Catawba,
571 F.3d at 39-40. In any event, this case law is distinguishable
because it concerns the EPA's determination under CAA section
107(d)(1)(A)(i) of a simple contribution, whereas CAA section 111(b)
requires the EPA to determine a significant contribution. As noted
above, the EPA considers it particularly important to develop a set of
criteria and/or a standard in order to determine when a significant
contribution occurs, in order to distinguish it from a simple
contribution.

C. Criteria for Making a Significant Contribution Finding Under CAA
Section 111

    In the 2019 Proposal, the EPA solicited comment regarding criteria
for the Agency to consider in making a SCF. 84 FR 50267. The
solicitation for comment was not on the factors the Agency should
consider in determining whether air pollution may reasonably be
anticipated to endanger public health or welfare, but rather the
factors that should be considered when determining under CAA section
111 whether a pollutant from a source category significantly
contributes to that air pollution. Several commenters recommend that
the EPA defer any action on SCF criteria and suggest the EPA undertake
these questions in a separate future rulemaking. Some commenters
suggest specific criteria the EPA could consider.
    The EPA made clear in the 2019 Proposal that it would not finalize
criteria in this rulemaking, but rather would conduct a separate
rulemaking to do so. 84 FR 50267. There is no need for the EPA to
promulgate criteria at this time because this rule rescinds NSPS. The
EPA expects that in the future, it will promulgate criteria before
promulgating additional NSPS.
    It should be noted that several commenters contend that oil and gas
methane emissions are too small to be considered ``significant.'' For
example, some commenters cite as support that the contribution of oil
and gas methane to total U.S. GHG emissions is only about 3 percent,
that U.S. methane emissions are only about 7 percent of global methane
emissions, and that U.S. methane emissions are only about 1 percent of
global GHG emissions. The EPA appreciates the commenters' views
concerning the amounts and impacts of methane emissions from the
transmission and storage segment, as well as the production and
processing segments. The EPA acknowledges that depending on the
criteria that it adopts to support a SCF in the future, such a
relatively small contribution to the national and global pool of
methane emissions may not be deemed significant. But until the EPA
itself reviews and assesses those amounts of emissions according to the
criteria that it eventually adopts, the EPA cannot make a determination
as to whether methane emissions from the production and processing
segments contribute significantly to dangerous air pollution.

VII. Implications for Regulation of Existing Sources

    As discussed in section VII of the proposal preamble, the EPA
recognizes that by rescinding the applicability of the NSPS, issued
under CAA section 111(b), to methane emissions for the sources in the
Crude Oil and Natural Gas Production source category that are currently
covered by the NSPS, existing sources of the same type in the source
category will not be subject to regulation under CAA section 111(d).
This is a legal consequence that results from the application of the
CAA section 111 requirements. Comments were received that both agreed
and disagreed with the proposed decision and reflected varying opinions
on the implications for regulation of existing sources. These comments
are provided, along with the EPA's responses, in section X of this
preamble and in Chapter 9 of the Response to Comments Document. None of
the comments received resulted in a material change in the EPA's
rationale and conclusions from proposal. The following provides a
summary of the EPA's legal interpretation of CAA section 111(d)(1) and
rationale for why the lack of regulation of existing sources under CAA
section 111(d) will have a limited environmental impact.

A. Existing Source Regulation Under CAA Section 111(d)

    As the EPA stated at proposal (see section VII of the 2019 Proposal
preamble), CAA section 111(d) authorizes the regulation of existing
sources in a source category for particular air pollutants to which a
standard of performance would apply if those existing sources were new
sources. By legal operation of the terms of CAA section 111(d), certain
existing sources in the Crude Oil and Natural Gas Production source
category will no longer be subject to regulation under CAA section
111(d) as a result of this final rule. Under CAA section 111(d)(1)(A),
CAA section 111(d) applies only to air pollutants (1) for which air
quality criteria have not been issued, and which are not on the EPA's
list of air pollutants issued under CAA section 108(a) (commonly
referred to as the ``CAA 108(a) exclusion''), and (2) which are not HAP
emitted from a source category regulated under CAA section 112
(commonly referred to as the ``CAA 112 exclusion''). See 42 U.S.C.
7411(d)(1)(A) (CAA section 111(d) applies to ``any air pollutant (i)
for which air quality criteria have not been issued or which is not
included on a list published under section 7408(a) of this title or
emitted from a source category which is regulated under section 7412 of
this title'').
    For reasons set out in the proposal preamble, the EPA has concluded
that VOC fall within the CAA 108(a) exclusion and, thus, are not the
type of air pollutant that, if subjected to a standard of performance
for new sources, would trigger the application of CAA section 111(d).
VOC are not expressly listed as CAA section 108(a) pollutants, but they
are precursors to photochemical oxidants (e.g., ozone) and PM, both of
which are listed CAA section 108(a) pollutants. As provided in CAA
section 302(g), the term ``air pollutant'' is defined to include

precursors ``to the extent that the Administrator has identified such
precursor or precursors for the particular purpose for which the term
`air pollutant' is used.'' For the following reasons, it is appropriate
to consider VOC within the scope of photochemical oxidants and PM,
which are listed CAA section 108(a) pollutants, for the particular
purpose of applying the CAA section 108 exclusion in CAA section
111(d).
    First, VOC are regulated through the CAA's NAAQS implementation
program established under CAA section 110, as a result of the inclusion
of ozone and PM on the CAA section 108(a) list, because VOC are
precursors to those two listed pollutants. See, e.g., CAA section
182(b)(2) (establishing ``reasonably available control technology''
requirements for VOC sources in moderate ozone attainment areas); CAA
section 182(c)(2)(b) (requiring serious ozone areas to submit a
reasonable further progress demonstration that will account for a set
amount of VOC emissions reductions); CAA section 182(d)(2) (requiring
specific VOC reductions to satisfy the offset requirement for severe
areas); CAA section 182(e)(1) (requiring specific VOC reductions to
satisfy the offset requirement for extreme areas). Indeed, the
regulation of ozone precursors is the means of addressing ozone in the
ambient air, because ozone levels in the ambient air are the result of
photochemical reactions of precursors (VOC and NOX), as
opposed to being directly emitted from sources.
    Second, as explained in the proposal preamble, excluding VOC from
regulation under CAA section 111(d) makes sense within the CAA's three-
part structure for addressing emissions from stationary sources. As the
EPA has discussed in past rulemakings, the CAA sets out a comprehensive
scheme for air pollution control, addressing three general categories
of pollutants emitted from stationary sources: (1) Criteria pollutants
(which are addressed in CAA sections 108 through 110); (2) hazardous
pollutants (which are addressed under CAA section 112); and (3)
``pollutants that are (or may be) harmful to public health or welfare
but are not or cannot be controlled under [CAA] sections 108-110 or
112.'' ``Carbon Pollution Emission Guidelines for Existing Stationary
Sources: Electric Utility Generating Units: Final Rule,'' 80 FR 64661,
64711 (October 23, 2015) (quoting 40 FR 53340 (November 17, 1975)).
Within this three-part structure, CAA section 111(d) is properly
understood as a ``gap-filling'' measure to address pollutants that are
not addressed under either the criteria pollutant and NAAQS
implementation provisions in CAA sections 108 through 110 or the HAP
provisions in CAA section 112. Because VOC are regulated as precursors
to ozone and PM2.5 under CAA sections 108 through 110, they
are properly excluded from regulation under CAA section 111(d) because
the ``gap-filling'' function of CAA section 111(d) is not needed.
    Third, reading the phrase ``included on a list published under [CAA
section 108(a)]'' as including precursors is reasonable in light of the
provision in CAA section 112(b)(2) that restricts what pollutants may
be listed as CAA section 112 HAP.
    Finally, as discussed in detail in the proposal preamble, the fact
that precursors are not always treated as CAA section 108(a) listed
pollutants under all contexts across the CAA does not undermine the
conclusion that they should be excluded under the CAA section 108
exclusion in CAA section 111(d).

B. Impact of Lack of Regulation of Existing Oil and Natural Gas Sources
Under CAA Section 111(d)

    The EPA maintains its position from the proposed rule that the lack
of regulation of existing sources under CAA section 111(d) through an
Emission Guideline (EG) will have limited impact. This is because there
are several factors that will continue to contribute to the downward
trend of total methane emissions from oil and natural gas existing
sources even in the absence of an EG.
    First, as the EPA stated in the 2019 Proposal preamble, the 2016
Rule includes a definition and approach to determining new source
applicability that are very broad, and in the specific context of the
oil and natural gas production industry, can be anticipated to result
in wide applicability of the NSPS to existing sources due to the
frequency with which such sources can be reasonably expected to engage
in ``modification'' activity. Specifically, it would take at least 7
years from date of promulgation of an EG for requirements to be fully
implemented.\50\ During this time, the EPA expects that a percentage of
existing sources will shut down or undertake modification which will
result in them becoming subject to regulation under CAA section 111(b).
However, based on limited information that commenters submitted, the
EPA acknowledges there may be some existing sources that have never
been modified and accepts that these are examples of existing sources
that have continued to operate for long periods of time without being
reconstructed or modified. The EPA did not prepare and include a
quantitative analysis that estimates the levels at which source
modification/equipment turnover may occur. However, the EPA maintains
that this is one factor (among other factors) that in the absence of an
EG will continue to contribute to the downward trend of total methane
emissions from oil and natural gas existing sources.
---------------------------------------------------------------------------

    \50\ This estimation considers the development of states' plans
and the Federal plan. Unlike NSPS, EG are not directly enforceable;
thus, these mechanisms are critical for implementation.
---------------------------------------------------------------------------

    Secondly, there are market incentives for the oil and natural gas
industry to capture as much natural gas (and, by extension, methane) as
is cost effective. Depending on the future trajectories of natural gas
prices and the costs of natural gas capture and emission reductions,
market incentives may continue to drive emission reductions, even in
the absence of specific regulatory requirements applicable to methane
emissions from existing sources. Assessing the relationship of methane
emissions and natural gas production, overall natural gas gross
withdrawals have increased about 50 percent from 1990 to 2018, while
aggregate methane emissions from the NSPS subpart OOOOa-relevant
industry segments have stayed relatively flat (Figure 1). This trend
indicates decreasing aggregate methane emissions intensity for these
segments over this period (Figure 1). These trends are likely driven by
a combination of economic and technical advances.
---------------------------------------------------------------------------

    \51\ Methane emissions from Table 3-37 (Petroleum Systems) and
Table 3-57 (Natural Gas Systems) in U.S. EPA. 2020. Inventory of
U.S. Greenhouse Gas Emissions and Sinks: 1990-2018. EPA 430-R-20-
002. Available at: https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2018. Accessed July 1, 2020.
U.S. Energy Information Administration (EIA) data on natural gas
gross withdrawals available at: https://www.eia.gov/dnav/ng/ng_prod_sum_a_EPG0_FGW_mmcf_a.htm. Accessed July 1, 2020.

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[GRAPHIC] [TIFF OMITTED] TR14SE20.004

    While environmental performance is a challenging concept to
quantify in monetary terms, improving such performance is increasingly
important for firms that seek to maintain a ``social license to
operate.'' Generally speaking, the social license to operate means that
the firm's employees, investors, customers, and the general public find
that the firm's business activities and operations are acceptable to
continue to freely participate in the marketplace. Maintaining the
social license by improving environmental performance, such as reducing
emissions, can help firms respond to the complex environment within
which they operate in ways that are favorable to their longer-term
business interests.
    Third, the EPA maintains, and has received a substantial amount of
comments confirming its position that participation in the various
voluntary methane emissions mitigation programs is one factor (among
other factors) that in the absence of an EG that will continue to
contribute to the downward trend of total methane emissions from oil
and natural gas existing sources. Owners and operators of facilities in
the oil and natural gas industry participate in voluntary programs that
reduce their methane emissions. Specifically, many owners and operators
of facilities participate in two EPA partnership programs: The Natural
Gas STAR Program \52\ and the Methane Challenge Program.\53\ Owners and
operators also participate in voluntary programs that are not
administered by the EPA, such as the Environmental Partnership \54\ and
the Climate and Clean Air Coalition (CCAC) Oil & Gas Methane
Partnership.\55\ Firms might participate in voluntary environmental
programs for a variety of reasons, including attracting customers,
employees, and investors who value more environmentally responsible
goods and services; finding approaches to improve efficiency and reduce
costs; and reducing pressures for potential new regulations or helping
shape future regulations.56 57 The EPA does acknowledge that
the industry as a whole is not uniformly meeting voluntary measures at
the same level of control and that some companies may not be
participating in cited voluntary methane emissions programs at all.
This makes it difficult to verify the impacts on emissions as a result
of voluntary program participation. Additional time will be needed to
allow these programs to further develop and to be fully implemented to
better quantify the impacts the varied programs have on

reducing emissions from oil and natural gas industry sources.
---------------------------------------------------------------------------

    \52\ The Natural Gas STAR Program started in 1993 and seeks to
achieve methane emission reductions through cost-effective best
practices and technologies. Partner companies document their
voluntary emission reduction activities and report their
accomplishments to the EPA annually. Natural Gas STAR includes over
100 partners across the natural gas value chain and has eliminated
nearly 1.39 trillion cubic feet of methane emissions since 1993.
    \53\ The Methane Challenge Program, started in 2016 and designed
for companies that want to adopt more ambitious actions for methane
reductions, expands the Natural Gas STAR Program through specific,
ambitious commitments; transparent reporting; and company-level
recognition of commitments and progress. This program includes more
than 50 companies from production, gathering and boosting,
transmission and storage, and distribution.
    \54\ The Environmental Partnership is composed of various
companies of different sizes and includes commitments to replace all
high-bleed pneumatic controllers with low-bleed controllers (i.e.,
controllers with a bleed rate less than 6 scfh) within 5 years,
require operators to be on-site or nearby when conducting liquids
unloading, and require initial monitoring for fugitive emissions at
all sites within 5 years, with repairs completed within 60 days of
fugitive emissions detection. https://theenvironmentalpartnership.org/.
    \55\ The CCAC Oil and Gas Methane Partnership is a technical
partnership between oil and natural gas companies, the Environmental
Defense Fund, the EPA Natural Gas STAR Program, and the Global
Methane Initiative that provides technical documents on a wide
variety of opportunities for reducing methane emissions and requires
annual progress reports from its participants. Yearly data on the
progress being made by participants is available on the CCAC
website. http://ccacoalition.org/en/content/oil-and-gas-methane-partnership-reporting.
    \56\ Borck, J.C. and C. Coglianese (2009). ``Voluntary
Environmental Programs: Assessing Their Effectiveness.'' Annual
Review of Environment and Resources. 34(1): 305-324.
    \57\ Brouhle, K., C. Griffiths, and A. Wolverton (2009).
``Evaluating the role of EPA policy levers: An examination of a
voluntary program and regulatory threat in the metal-finishing
industry.'' Journal of Environmental Economics and Management.
57(2): 166-181.
---------------------------------------------------------------------------

    Fourth, several major oil and natural gas producing states have
established regulations on oil and natural gas sector emissions. The
EPA recognizes that state requirements vary in stringency and that only
a subset of states include requirements for sources that the EPA could
potentially define as existing sources. However, states that have
standards applicable to existing sources include California, Colorado,
Utah, Wyoming (in the Upper Green River Basin ozone non-attainment
area), and Texas, and account for a substantial portion of oil \58\ and
natural gas production \59\ in the United States. Furthermore, current
state regulations (and permits) controlling VOC emissions will
concurrently reduce methane emissions from the oil and natural gas
industry. For example, areas that are designated Moderate nonattainment
and above for certain ozone NAAQS, and states within the Ozone
Transport Region, are required to adopt and implement VOC controls for
oil and gas sources covered by the EPA's 2016 Control Techniques
Guidelines.\60\ These controls, which the EPA will address through the
state implementation plan (SIP) approval process, will concurrently
reduce methane emissions.
---------------------------------------------------------------------------

    \58\ Approximately 52 percent of crude oil production in 2019
according to https://www.eia.gov/dnav/pet/pet_crd_crpdn_adc_mbblpd_a.htm.
    \59\ Approximately 35 percent of natural gas production in 2019
according to https://www.eia.gov/dnav/ng/ng_prod_sum_a_EPG0_VGM_mmcf_a.htm.
    \60\ On October 27, 2016, the EPA provided notice of the
availability of a final control techniques guideline document titled
Control Techniques Guidelines for the Oil and Natural Gas Industry
(EPA 453/B-16-001). 81 FR 74798 (October 27, 2016).
---------------------------------------------------------------------------

    As with other factors cited by the EPA, existing source state
requirements are one factor (among others) that in absence of an EG
will continue to contribute to the downward trend of total methane
emissions from oil and natural gas existing sources. Further detail
regarding comments received on the potential for limiting emissions
from existing sources can be found in section X of this preamble.

VIII. Summary of Major Comments and Responses

    In this section, we respond to many of the major comments made on
the 2019 Proposal. In the Response to Comments Document in the docket,
we provide additional discussion for some of these comments, and
respond to additional comments.

A. Revision of the Source Category To Remove Transmission and Storage
Segment

1. History of Scope of Oil and Natural Gas Source Category
    Comment: Commenters assert that language in CAA section 111
demonstrates that Congress contemplated that source categories would be
broad and encompass a variety of different types of emission sources.
The commenters disagree that the 1979 listing did not include the
natural gas transmission and storage segment, and add that, in 1980,
the Agency explained: ``Source categories are intended to be broad
enough in scope to include all processes associated with the particular
industry.'' Commenters state that, in practice, the EPA has long listed
broad source categories, covering an entire industry or a source that
may be found in numerous industries, and sometimes establishing
different subcategories within source categories, including electric
utilities, non-metallic mineral processing, and compressor engines. The
commenters contend that the EPA's treatment of other source categories
soon after the priority listing process consistently recognized the
interrelatedness of facilities or of emissions controls for those
facilities and that this helps determine what sources to include in
each source category. Although petroleum refineries are a separate
source category under CAA section 111, the commenters note that the EPA
previously explained that the source category for the asphalt roofing
industry ``encompasses not only asphalt roofing plants but certain
production units at oil refineries and asphalt processing plants which
were not included on the Priority List promulgated on August 21,
1979.'' 45 FR 76405.
    Response: The EPA has generally exercised discretion in identifying
the scope of any particular industry, including which industrial
processes it includes, for purposes of treating it as a source category
under CAA section 111.\61\ The EPA acknowledges that some of the listed
source categories were broad in scope. However, the EPA has also listed
source categories that are relatively narrow in scope--they have
distinct facility boundaries that encompass a particular process that,
in turn, follows a linear path and results in a specific product.
Examples of narrowly defined source categories include the following.
---------------------------------------------------------------------------

    \61\ The EPA has not relied on particular formulations, such as
standard industrial classification, to identify an industry for
purposes of classifying it.
---------------------------------------------------------------------------

     Primary Copper Smelting, Subpart P: A primary copper
smelter is any installation or any intermediate process engaged in the
production of copper from copper sulfide ore concentrates through the
use of pyrometallurgical techniques. The affected facilities in primary
copper smelters are dryers, roasters, smelting furnaces, and copper
converters.
     Nitric Acid Plants, Subpart G and Ga: A nitric acid plant
is a nitric acid production unit, which, in turn, is any facility
producing weak nitric acid by either the pressure or atmospheric
pressure process.
     Kraft Pulp Mills, Subparts BB and BBa: A kraft pulp mill
is any stationary source which produces pulp from wood by cooking
(digesting) wood chips in a water solution of sodium hydroxide and
sodium sulfide (white liquor) at high temperature and pressure.
Regeneration of the cooking chemicals through a recovery process is
also considered part of the kraft pulp mill. The affected sources are
digester systems, brown stock washer systems, evaporator systems,
condensate stripper systems, recovery furnaces, smelt dissolving tanks,
and lime kilns at kraft pulp mills.
     Sulfuric Acid Plants, Subpart H: The affected sources are
sulfuric acid production units. These are defined as any facility
producing sulfuric acid by the contact process by burning elemental
sulfur, alkylation acid, hydrogen sulfide, organic sulfide and
mercaptans, or acid sludge, but do not include facilities where
conversion to sulfuric acid is utilized primarily as a means of
preventing emissions to the atmosphere of sulfur dioxide or other
sulfur compounds.
    If the EPA does not originally include in a listing certain
processes, and subsequently seeks to include those processes, the EPA
must make the requisite statutory findings in order to do so. The
action that the commenters cite supports this point. In the original
1979 Priority List, the EPA listed the Asphalt Roofing Plants source
category. Subsequently, based on studies on the asphalt roofing
industries, the EPA determined that the initial processing of asphalt
for roofing manufacture may take place at sources other than asphalt
roofing plants. Accordingly, the EPA, through rulemaking, amended the
1979 source category listing to include additional locations such as
asphalt processing plants and asphalt storage tanks at oil refineries.
See 45 FR 76427 and 28. In doing so, the EPA provided a specific
rationale for broadening the source category. The present situation

requires a similar analytical framework: (1) The original source
category listing for Crude Oil and Natural Gas Production was not
broadly defined to include transmission and storage, and (2) the
requisite statutory findings have not been made to expand the category
to include it.
    Comment: Several commenters assert that nothing in the 1979 listing
decision supports the EPA's claim that the Agency at the time viewed
facilities used in natural gas transmission and storage (e.g.,
stationary pipeline compressor engines) as a separate source category.
    Another commenter asserts that the omission in the 1979 listing of
a source in the transmission and storage segment that had been included
in the 1978 technical document suggests that this source was
incorporated into the Crude Oil and Natural Gas Production source
category. The commenter states that, while the EPA studied Stationary
Pipeline Compressor Engines, which are found in the transmission and
storage segment, as a potential independent source category in the 1978
technical document,\62\ this source was not listed as a major or minor
source in the 1979 Listing.\63\ The commenter states that, while the
Agency argues that the source was included in the Stationary Internal
Combustion Engines listing, the EPA supports this proposition only by
citing to a 2008 rule, which does not expressly include stationary
pipeline compressor engines within the Stationary Internal Combustion
Engines source category.\64\ The commenter notes that the EPA cites to
a page stating that ``[c]ategories and entities potentially regulated
by this action'' include ``[a]ny manufacturer that produces or any
industry using a stationary internal combustion engine as defined in
the final rule.'' 73 FR 3568 and 69. The preamble contains a list of
``[e]xamples of regulated entities'' that includes ``[n]atural gas
transmission.'' 73 FR 3569. However, according to the commenter, the
applicability criteria of the final rule contains no explicit reference
to stationary pipeline compressor engines.
---------------------------------------------------------------------------

    \62\ U.S. EPA. Priorities for New Source Performance Standards
Under the Clean Air Act Amendments of 1977. April 1978. EPA-450/3-
78-019. p. 33.
    \63\ 44 FR 49222 through 49226.
    \64\ 73 FR 3568, 3569 (January 18, 2008).
---------------------------------------------------------------------------

    Response: As a general matter, the Agency has the authority to
revisit its prior categorization determinations. Nonetheless, the EPA,
upon a close read of its prior rules believes that this and certain
other comments on prior Agency determinations are mistaken, as
described further in this section. The EPA notes that while it believes
the 1979 listing did not include the transmission and storage segment
for the reasons described in this final rule, any interpretation
otherwise (i.e., that the listing did include this segment) did not
have any practical effect until the 2012 Rule, when the EPA promulgated
standards for this segment for the first time. Therefore, to the extent
the 1979 listing can be considered to have included the transmission
and storage segment, the EPA is alternatively determining that such
inclusion was incorrect for the same reasons why the 2012 and 2016
Rules incorrectly included the segment as part of the source category.
    The EPA disagrees with the commenter's suggestion that the 1979
listing incorporated stationary pipeline compressor engines into the
Crude Oil and Natural Gas Production source category. This is clearly
evidenced by examining the pollutants which are identified for the
category. For the 1979 listing, the pollutants identified for the Crude
Oil and Natural Gas Production source category were VOC and
SO2. In the 1978 background documentation, the pollutants
identified for stationary pipeline compressor engines were
NOX, SO2, and carbon monoxide (CO). If the EPA
had included stationary pipeline compressor engines in the Crude Oil
and Natural Gas Production source category in 1979, the Agency likely
would have added NOX and CO to the list of pollutants for
the category.
    That the Stationary Internal Combustion Engine rule (40 CFR part
60, subpart IIII) covers engines in the natural gas transmission and
storage segment is further evidenced by the statement from the February
26, 2008, Federal Register document that specifically identifies
engines in natural gas transmission as example entities subject to the
rule. The commenter is incorrect in asserting that the applicability
criteria of the regulations are silent on engines in natural gas
transmission. Those applicability criteria are characteristics of the
engine (e.g., maximum engine power), which are unrelated to the
location of the engine (e.g., in the transmission segment). See Sec.
60.4230 of 40 CFR part 60, subpart JJJJ. Therefore, the lack of
explicit mention of the transmission segment does not mean that engines
in that segment are not included in the category.
    Comment: Several commenters stated that the description of the
Crude Oil and Natural Gas Production source category in the 1984
proposed NSPS for VOC and SO2 emissions made clear that the
category did not include transmission and storage operations. The
commenters pointed to the statement in the preamble that the source
category excluded emission sources related to the ``distribution'' of
products ``to petroleum refineries and gas pipelines'' (citing, e.g.,
49 FR 2636.
    Other commenters disagree. One commenter asserts that the EPA
defined the source category as ``encompass[ing] the operations of
exploring for oil and natural gas products, drilling for these
products, removing them from beneath the earth's surface, and
processing these products from oil and gas fields for distribution to
petroleum refineries and gas pipelines.'' The commenter states that it
is clear that compressor stations within the transmission and storage
segment ``process these products . . . for distribution'' by
compressing the gas and forcing it through the pipelines.
    Response: The EPA does not agree with the commenter's
interpretation of the quotation from the 1984 proposal. Specifically,
the EPA does not agree that the compression of the natural gas along
transmission pipelines constitutes processing of the natural gas.
Natural gas processing has historically been defined by the Agency to
include the extraction of natural gas liquids from field gas,
fractionation of mixed natural gas liquids to natural gas products, or
both. (40 CFR part 60, subpart KKK; 40 CFR part 63, subpart HH). The
EPA maintains that the language in the 1984 proposal, i.e., that the
category includes ``the operations of exploring for oil and natural gas
products, drilling for these products, removing them from beneath the
earth's surface, and processing these products from oil and gas fields
for distribution to petroleum refineries and gas pipelines,'' is not
ambiguous. Following the well-defined ``processing'' operations, the
natural gas enters transmission gas pipelines. These are the gas
pipelines referred to in the 1984 preamble, meaning that the gas leaves
the processing segment of the oil and natural gas production source
category and travels to the next segment, the natural gas transmission
pipelines.
    Comment: One commenter asserts that, within the 1984 definition of
the production segment, the EPA drew a definitional boundary whereby
production consisted of extraction ``and processing [of oil and natural
gas] for distribution to petroleum refineries and gas pipelines.'' The
commenter states that this implies that the boundary at which the
Agency has always historically defined the category as being where
production meets local distribution to pipelines or refineries. The
commenter states that this interpretation of the CAA meant that the

production segment abuts the distribution end of the industry--not an
arbitrarily created ``Transmission and Storage'' segment.
    Response: The EPA's use of the term ``distribution'' in the 1984
preamble was misinterpreted by the commenter. The commenter appears to
interpret ``distribution'' as the distribution segment of the natural
gas industry, and that the source category includes everything up to
that segment. In the context of the 1984 preamble, the EPA's use of the
term ``distribute'' means the transfer to the next segment of the
industry.
    Comment: A commenter asserts that the 1984 proposal serves to
demonstrate that the EPA did not view its listing as constrained to its
literal terms--``Crude Oil and Natural Gas Production''--because the
1985 NSPS regulated the processing, not the production, segment of the
natural gas industry. Specifically, the EPA stated that, with regard to
the discussion of equipment leaks, ``equipment used in crude oil and
natural gas production (not to be confused with natural gas processing)
for equipment leaks of VOC is not appropriate for widely dispersed
equipment.'' 49 FR 2637. The commenter states that, taken to a literal
extreme, the proposal's argument would mean that the 1985 NSPS exceeded
the scope of the source category and was, thus, unlawful.
    Response: The EPA agrees that the language that the commenter
quotes indicates the Agency's view in the 1985 NSPS that the source
category covered both production and processing. However, this does not
in turn mean that the Agency thought that the source category included
the transmission and storage segment as well. As described above, the
1984 proposal acknowledged equipment leaks in the production segment
but declined to set standards for them based on a technical analysis.
This discussion makes clear that the Agency considered production to be
part of the source category. In contrast, as discussed above, the
preamble is silent on equipment leaks in the transmission and storage
segment.
    Comment: Further, the commenter states that the EPA's proposal
appears to concede that the Agency has never been limited to regulating
only those specific sources within the listed category that it
regulated in the first NSPS. The commenter states that, prior to 2012,
the EPA had issued standards for emissions at gas processing plants
only as part of the ``Crude Oil and Natural Gas Production.'' The
commenter notes that in 2012 the EPA regulated VOC from previously
unregulated upstream sources, including well completions, centrifugal
compressors, reciprocating compressors, pneumatic controllers and
storage vessels (citing 77 FR 49490 (Final Rule promulgating 40 CFR
part 60, subpart OOOO)). The commenter states that these sources were
not part of the EPA's analysis in 1979 or 1984 NSPS, yet the proposal
does not suggest that they were improperly regulated in the 2012 Rule.
Specifically, in 2012 the EPA stated: ``[i]n addition to the operations
covered by the existing standards, the newly established standards will
regulate volatile organic compounds from gas wells, centrifugal
compressors, reciprocating compressors, pneumatic controllers and
storage vessels'' (citing 77 FR 49490).
    The commenter also indicates that the EPA's citation to the 1984
NSPS ignores other statements made during other rulemakings for the
source category, including the same 1984 rulemaking, that suggest that
the source category was intended to cover broadly the oil and natural
gas sector, or at least was not limited to production and processing
(citing 84 FR 50256). The commenter states that, in that NSPS, the EPA
felt the need to exclude specifically certain sources found in the
transmission and storage segment from the standards it set, something
that would not have been necessary if the Agency had intended to
exclude these segments themselves from the definition of the source
category. The sources excluded in that NSPS are compressor stations,
dehydration units, sweetening units, underground storage facilities,
and field gas gathering systems, unless the facility is located at an
onshore natural gas processing plant.
    Response: The commenter's representation of the 1984 rulemaking is
not entirely accurate. It is true that the 1984 proposal limits the
sources covered to those at natural gas processing facilities. However,
the EPA does not agree that this rulemaking was an expansion of the
original ``Crude Oil and Natural Gas Production'' source category. The
commenter is implying that natural gas processing operations were not
included in the original source category listing in 1979 but does not
provide any evidence from the 1978/1979 actions to support that
assertion. An alternative interpretation of this text could also be
that the Agency wished to make it sufficiently clear that while sources
in part of the production and processing segment are included in the
source category, the same sources that are part of the transmission and
storage segment are not included in the source category. However, in
the absence of an explanation for this exclusion, the most that can be
taken away from this text is that these sources are not subject to the
1984 NSPS; this text alone is not dispositive on whether these sources
are included in the broader Oil and Natural Gas source category.
Therefore, the commenter extrapolates a conclusion without a basis to
do so. The fact that SO2 was a pollutant identified for the
Crude Oil and Natural Gas Production source category clearly shows that
processing was included, as the sweetening units covered by the 1984
proposed rules are the primary source of SO2 emissions in
the oil and natural gas industry.
    In addition, there are numerous statements made by the EPA
throughout the 1984 proposal that clearly demonstrate consideration of
sources across the entire Crude Oil and Natural Gas Production source
category. The commenter cites the statement in the1984 proposal that
emission points can be divided into three categories and uses this
statement to argue that the source category included transmission and
storage. However, the comment fails to include the remainder of the
paragraph that includes that statement:

    These emission points can be divided into three main categories:
Process, storage, and equipment leaks. Process emission sources
include well systems, field oil and gas separators, wash tanks,
steeling tanks, and other sources. These process sources remove the
crude oil and natural gas from beneath the earth and separate gas
and water from the crude oil. Best demonstrated control technology
has not been identified for these process emission points;
therefore, these sources have not been considered in developing the
proposed standards. 49 FR 2637 (emphasis added).

    This part of the paragraph clarifies two points. First, the EPA
clearly considered the upstream sources (well systems, field oil and
natural gas separators, etc.) as part of the source category but
indicated that since best demonstrated control technology had not been
identified for those sources, no standards were being proposed at that
time. These sources were then addressed in the 2012 rulemaking, when
the best demonstrated technology/BSER had been determined for them.
Second, this discussion did not mention operations in the transmission
segment.
    One commenter also refers to the parenthetical in the 1984 proposal
related to oil and natural gas production and argues that it is proof
that natural gas processing was not included in the Crude Oil and
Natural Gas Production source category. The following provides more of
the discussion to provide the full context.

    Equipment leaks of VOC can occur from pumps, valves,
compressors, opened ended

lines or valves, and pressure relief devices used in onshore crude
oil and natural gas production. These leaks usually occur due to
design or failure of the equipment. Equipment used in crude oil and
natural gas production (not to be confused with natural gas
processing) are widely dispersed over large areas. The analysis
presented in the BID for the principal control technique (leak
detection and repair work practices) for equipment leaks of VOC is
not appropriate for widely dispersed equipment. The costs and
emission reduction numbers for such an analysis are unknown at this
time. Thus, the proposed standards do not apply to equipment
associated with crude oil and natural gas production. The proposed
standards apply only to equipment located at onshore natural gas
processing plants. 49 FR 2637.

    Taking the 1984 preamble excerpt in context illustrates that the
distinction made between production and processing was specifically
related to the application of leak detection and repair work practices
for equipment leaks and not to define the source category. In fact, the
discussion makes it clear that the EPA's definition of the source
category includes production and processing. Again, there is no mention
here of the application of leak detection and repair programs to the
transmission and storage segment.
    Finally, the commenter cites a paragraph from the proposed
regulation, which clarifies that sources not located at a natural gas
processing plant are not affected facilities, as evidence that the
category includes the transmission and storage segment, since
``compressor stations'' are included. This is also not a compelling
argument. It is not uncommon for equipment, other than that used to
extract natural gas liquids from field gas or to fractionate mixed
natural gas liquids to natural gas products, to be located at a natural
gas processing plant. This paragraph--40 CFR 60.630(e)--simply
clarifies that if other operations (i.e., compressor stations,
dehydration units, sweetening units, underground storage facilities,
field gas gathering units, and liquefied natural gas units) are located
at a natural gas processing plant, the associated components are
subject to the leak detection and repair requirements in NSPS subpart
KKK. This list cannot be extrapolated to the conclusion that the EPA
considered all these operations to be in the source category. As
evidence of this note that ``liquefied natural gas units'' are included
in the list. These units, while part of the overall oil and natural gas
industry, have never been contemplated as being part of the Crude Oil
and Natural Gas source category.
2. ``Sufficiently Related'' Test and Whether Transmission and Storage
Operations Are Distinct From Production and Processing
    Comment: Commenters contend that the proposal to amend the source
category definition is fundamentally at cross-purposes with the
proposal to remove standards of performance for methane. The EPA
proposed to justify the latter by finding that regulation of methane
and VOC is redundant because the controls that sources are required to
implement to reduce their VOC emissions will also reduce their methane
emissions, and this is true regardless of the relative amounts of VOC
and methane in their overall emissions. The commenters state that if
methane regulation is redundant on those grounds, then differences in
gas composition cannot be the basis for determining that two distinct
source categories are necessary.
    Response: The commenters conflate the proposal to remove the
transmission and storage segment from the source category with the
proposal to rescind the methane requirements for the remaining
production and processing segment, without acknowledging that while the
substance of each may have technical similarities, each proposal
addresses discrete, stepwise legal aspects of CAA section 111(b). Under
CAA section 111(b), a source category must first be listed before the
EPA can promulgate an NSPS for sources within the category. The EPA
proposed the first action of removing the transmission and storage
segment from the source category, in part based on the conclusion that
the segment was not previously properly added to the source category
because there are distinct differences in operations and differences in
the emissions profiles between the production and processing segments
and the transmission and storage segment. As described further in this
section, based on the sufficiently related test, these distinct
differences in operations and differences in emissions profile means
that the transmission and storage segment requires a separate SCF in
order to be properly regulated under CAA section 111(b).
    However, once a source category is properly listed and defined, as
are the production and processing segments, the inquiry then is what
are the appropriate standards of performance for sources within that
category. This inquiry is separate from and subsequent to the initial
inquiry of whether a source category is properly identified for
regulation under CAA section 111(b). For example, the EPA has
previously identified sources as appropriately subject to regulation
under CAA section 111(b), but then subsequently declined to promulgate
standards of performance based on inadequate data. In proposing VOC
standards for equipment leaks in oil and gas processing, the EPA
declined to apply such standards to equipment in the production
segment, which is clearly part of the source category, because it did
not have data on costs and emission reduction numbers at that time. 49
FR 2637.
    Similarly, here, while the production and processing segments have
been properly identified as subject to regulation under CAA section
111(b) through the 1979 listing of the source category, the EPA must
then contend with how to regulate these segments. Accordingly, the EPA
proposed the second action to rescind the methane requirements for the
production and processing segments based on the fact that VOC and
methane controls are redundant. While the rationales for both actions
are premised partly on differences in gas composition, the legal and
technical inquiry for each action is different, as these are discrete
steps to regulation under CAA section 111(b). Though the findings under
each inquiry are similarly premised on differences in gas composition,
that does not mean that the response to both inquiries must be the
same, as each inquiry is distinctly different from one another (i.e.,
one is whether the transmission and storage segment is properly part of
the source category, the other is whether and how to regulate methane
from the production and processing segments). The rationale for this
second action was also discussed at length in section IV.D of the 2019
Proposal (84 FR 50259 and 50260). The comments received and the EPA
responses on this second action are provided in section VIII.B below.
    Comment: Commenters do not agree that the transmission and storage
segment cannot be included in the Crude Oil and Natural Gas source
category because the gas composition and operations in that segment are
too different from those in the production and processing segments.
These commenters assert that the EPA's own data do not support the
EPA's rationale. The commenters suggest that, while the EPA compares
the average composition of the production segment to the average
composition of the transmission segment, the Agency fails to consider
the extensive overlap in the range of compositions in both segments.
The commenters state that the EPA's 2011 Natural Gas Composition
memorandum data show the wide range of compositions of gas in the
production

and transmission segments.\65\ The commenters contend that the range of
methane compositions in the production segment fully encompasses the
range in the transmission segment, demonstrating the similarity of the
gas composition in the two segments; similarly, there is extensive
overlap between the segments' VOC compositions.
---------------------------------------------------------------------------

    \65\ Memorandum to Bruce Moore, U.S. EPA from Heather Brown, EC/
R. ``Composition of Natural Gas for use in the Oil and Natural Gas
Sector Rulemaking.'' July 2011. Docket ID Item No. EPA- HQ-OAR-2010-
0505-0084.
---------------------------------------------------------------------------

    Commenters also discussed the EPA's more recent 2018 composition
data,\66\ asserting that it shows even more variation in gas
composition. A commenter asserts that while the EPA recognizes that
variations in the gas composition can occur from basin-to-basin within
each segment, the EPA does not acknowledge that these basin-to-basin
variations can swamp the purported variations on which the EPA relies
to justify a distinction between production and transmission segments.
---------------------------------------------------------------------------

    \66\ Memorandum to U.S. EPA from Eastern Research Group.
``Natural Gas Composition.'' November 13, 2018. Docket ID No. EPA-
HQ-OAR-2017-0757.
---------------------------------------------------------------------------

    One commenter states that its experience with the oil and natural
gas industry operating in Pennsylvania shows that unprocessed field gas
\67\ can range from, by volume, 75-percent to 98-percent methane and
0.1-percent to 10-percent VOC. The commenter states that in a number of
Pennsylvania counties, the county average field gas composition meets
the EPA's pipeline quality gas composition (i.e., is equal to or
greater than 93-percent methane and less than or equal to 1-percent
VOC; HAP data is unavailable). The commenter states that there are
several natural gas well pads that dehydrate the produced gas onsite
and transfer custody directly to an interstate pipeline. The commenter
notes that this reality further blurs the distinction between the
production and the transmission and storage segments. The commenter
contends that, if a well site is required to meet the requirements of
the 2016 Rule, it stands to reason that a transmission compressor
station accepting the same gas should be required to meet the same
requirements.
---------------------------------------------------------------------------

    \67\ Field gas is described earlier in section V.B of this
preamble.
---------------------------------------------------------------------------

    One of the commenters also notes that the 2018 Natural Gas
Composition memorandum did not include any updated data for the
transmission and storage segment. The commenter states that, given the
significant difference in the production segment data from 2011 and
2018, the EPA must collect more current data for the transmission and
storage segment if it seeks to justify any claims about the segment
being sufficiently distinct from production and processing to warrant
revision of the source category.
    Response: The EPA recognizes that the composition of natural gas in
the production segment can vary considerably, and that in some basins/
areas it is possible that the composition can mirror that in the
transmission segment. However, while the commenters stress this overlap
in the gas composition in limited geographical regions in the U.S.,
such as in some parts of Pennsylvania, they seem to discount the
substantial differences in most areas. For example, for Texas, the
EPA's 2011 gas composition analysis showed that the methane content in
the production segment was, on average, 80.1 percent, but ranged from
55.0 percent to 97.8 percent.\68\ Because the NSPS subpart OOOOa is a
nationwide regulation which applies equally across the country, it is
most appropriate to consider the average composition for the segments.
Further, on a nationwide basis, the data clearly reveal a distinction
in the gas composition between the production and processing segments
and the transmission and storage segment.
---------------------------------------------------------------------------

    \68\ Memorandum to Bruce Moore, U.S. EPA from Heather Brown, EC/
R. ``Composition of Natural Gas for use in the Oil and Natural Gas
Sector Rulemaking.'' July 2011. Docket ID Item No. EPA-HQ-OAR-2010-
0505-0084.
---------------------------------------------------------------------------

    The commenter is correct that the 2018 Natural Gas Composition
memorandum did not include data for the transmission and storage
segment. The EPA conducted a new analysis which analyzed average
methane concentrations using 2015 through 2018 data reported under 40
CFR part 98, subpart W (Petroleum and Natural Gas Systems), of the
EPA's GHGRP.\69\ This analysis did include recent data for the
transmission and storage segment. The EPA found that there is a
statistically significant difference between the average methane
concentration in natural gas at either the gas production, gathering
and boosting, or gas processing \70\ industry segments and the average
methane concentration in natural gas at either the transmission
compression or underground storage segment. This difference further
supports the EPA's justification to remove the transmission and storage
segment from this source category.
---------------------------------------------------------------------------

    \69\ Analysis of Average Methane Concentrations in the Petroleum
and Natural Gas Industry Using Data Reported Under 40 CFR part 98
Subpart W. April 6, 2020. Included in Docket ID No. EPA-HQ-OAR-2017-
0757.
    \70\ Methane concentrations at gas processing facilities
evaluated in this study are based on the inlet gas composition (as
received) by the gas processing facilities.
---------------------------------------------------------------------------

    Comment: Several commenters disagree with the EPA's statements in
the 2019 Proposal that equipment and operations in the production and
processing segments were not interrelated with the transmission and
storage facilities. The commenters contend that while the transmission
and storage segment serves a different role than the production,
processing, and distribution segments, it is still part of the overall
oil and natural gas industry and is a necessary element of the source
category because it prepares the recovered gas for distribution. They
add that, as the 2019 Proposal notes, the processes used to remove
impurities (for example, dehydrators) in the production and processing
segments are also used in the transmission and storage segment (citing
84 FR 50258). Commenters noted that the 2016 Rule stated that the
equipment and operations at production, processing, transmission, and
storage facilities are a sequence of functions that are interrelated
and necessary for getting the product ready for distribution (citing 81
FR 35838). Commenters also noted that the 2016 Rule also cited the
increase in natural gas production from hydraulic fracturing and
horizontal drilling as an example of the interrelated nature of the
industry--i.e., increased production resulting in an increase in the
amount of natural gas needing to be processed and moved to market or
stored, which in turn results in increases in emissions across the
entire natural gas industry.
    Response: The EPA agrees with the commenters that production,
processing, transmission and storage are all segments of the oil and
natural gas industry and that the transmission and storage segment is a
part of the industry because it prepares the recovered gas for
distribution.
    However, this does not necessitate that all of the segments belong
in the same source category for regulatory purposes under CAA section
111. As explained in the 2019 Proposal, the primary purposes of each
segment differs. The purposes of the production and processing segments
are to explore, drill, extract, and process crude oil and natural gas
found beneath the earth's surface. Extracting crude oil and field gas
through drilling wells and processing these products for distribution
to petroleum refineries and gas pipelines is an industrial process that
is distinct from the transmission and storage segment, whose primary
purpose is to move to market pipeline quality natural gas through
transmission

pipelines by increasing the pressure and to store the gas underground
along the pipeline.
    The EPA understands that dehydrators are used to remove impurities
from the natural gas in both the production and processing segments and
in the transmission and storage segment. In the latter segment,
dehydrators are occasionally present along transmission pipelines and
at natural gas storage facilities to remove water and other impurities
that condense as a result of temperature and pressure changes as the
gas moves through the pipeline or is stored underground. However, the
different uses of dehydrators illustrate the separate functions that
the segments have in the industry. In the transmission and storage
segment, dehydrators simply remove these impurities as they accumulate
in pipelines. In the production and processing segment, dehydrators are
a part of the process to change the overall composition of the gas. It
is also noteworthy that the EPA included and regulated air toxics
emissions from dehydrators in two separate source categories and in two
different NESHAP. Dehydrators in the production and processing segments
are covered by 40 CFR part 63, subpart HH, and dehydrators in the
natural gas transmission and storage segment are covered by 40 CFR part
63, subpart HHH.
    The EPA continues to assert that the comparison with the petroleum
industry is directly relevant. The commenters insist that the necessary
link between the extraction and processing of the natural gas in the
production and processing segments and the transmission of the natural
gas predetermines that the two segments must be treated as a single
source category. However, this same link exists between the extraction
and processing of oil, condensate (and other liquids from oil and
natural gas wells) in the production segment and the petroleum
refineries and pipelines that refine/process and distribute these
liquids. However, the commenters do not suggest the interrelatedness of
the production and processing sources originally included in the Crude
Oil and Natural Gas Production source category with those in the
petroleum liquid source categories necessitates that Crude Oil and
Natural Gas Production and Petroleum Refineries be combined into one
category and regulated together. The EPA applies the same logic to
conclude that the fact that the transmission and storage segment is
related to the production and processing sources in the Crude Oil and
Natural Gas Production source category does not necessarily result in
the requirement that they be regulated together. In addition, other
instances in which similar source types emitting the same air
pollutants and subject to the same types of controls are included in
different source categories. For example, leaking pumps, valves,
connectors, and other components at a wide variety of types of
facilities that emit VOC and GHG are included in different source
categories.
3. The Authority To Expand Source Categories and the EPA's Alternative
Approach
    Comment: One commenter asserts that, while the 2012 Rule and 2016
Rule expanded the source category, this expansion was appropriate
considering the statutory mandate that the Administrator should from
time to time review the source categories. The commenter states that
the purpose of this review was to assure that the EPA periodically
consider new scientific developments to ensure that the Agency was
continually acting in a way that protected the public health. The
commenter adds that the statute provides no guidance regarding the
proper scope of a source category, and that Congress left that
determination to Agency expertise, so long as the Agency considers the
impacts of the source's emissions on public health. According to the
commenter, the EPA's expansion of the source category in the 2016 Rule
properly considered the source category's impact on the public health.
However, the commenter adds, but the EPA's current effort to rescind
that expansion is based on alleged procedural errors and fails to
consider the public health impacts of the transmission and storage
segment. The commenter states that the transmission and storage segment
does significantly contribute to the deterioration of public health.
The commenter asserts that the natural gas held at storage facilities
contains all of the same toxic air pollutants and hazardous chemicals
as natural gas does at other stages of the production process, and that
the methane and VOC emissions from compressor stations have the same
adverse impact on public health regardless of what segment of the
source category the methane and VOC emissions are coming from. The
commenter suggests that the EPA take this opportunity to do its own
analysis to determine whether methane, VOC, and HAP (air toxic)
emissions from the transmission and storage segment of the source
category adversely impact public health.
    Response: The EPA agrees that the CAA authorizes the EPA to review
and revise source categories, and that its purpose was to ensure that
the Agency was continually acting in a way that protected the public
health. However, the EPA disagrees with the commenters' position on the
EPA's past consideration of public health in the expansion of the Crude
Oil and Natural Gas source category. The EPA's 2015 evaluation of the
impacts of GHG, VOC, and SO2 on public health and welfare
(80 FR 56601) was conducted for crude oil and natural gas production
and processing, along with natural gas transmission and storage. While
it is true, as the commenter points out, that methane and VOC are
emitted from the natural gas transmission and storage segment, the
EPA's 2015 analysis did not separate the impacts of the pollutants
emitted by natural gas transmission and storage to demonstrate that the
emissions from this segment contribute significantly to the overall
impacts. In the 2019 Proposal, the EPA proposed that it was required to
make a finding that the transmission and storage segment, in and of
itself, contributes significantly to air pollution which may reasonably
be anticipated to endanger public health and welfare. Nothing in the
comments provided cause the EPA to change this conclusion.
4. Significant Contribution Finding for Natural Gas Transmission and
Storage
    Comment: Several commenters state that the SCF that the EPA made in
the 2016 Rule, which was for the production, processing,
transportation, and storage segments collectively, was not appropriate
to authorize the EPA to promulgate NSPS for sources in the transmission
and storage segment. The commenters assert that to regulate sources in
that segment, the EPA was required to make a SCF determination for
emissions from that segment itself. Commenters explain that, to
consider otherwise, once the EPA makes a SCF determination for a source
category consisting of certain types of sources, the Agency would then
be able to add into that source category all manner of ancillary
equipment and operations, even if those ancillary equipment and
operations do not in and of themselves significantly contribute to the
previously-identified endangerment. The commenter states that this
would allow the EPA to evade the express listing criteria by lumping
loose associations of nominally related segments of an industry into a
sector.
    Other commenters disagreed, stating that in the 2016 Rule, the EPA
determined that the rulemaking record

supported a revision of the source category listing to include broadly
the entire oil and natural gas industry (i.e., production, processing,
transmission and storage) that, in the Administrator's judgment,
contributes significantly to air pollution which may reasonably be
anticipated to endanger public health or welfare. Commenters add that
CAA section 111(b)(1)(A) grants the Administrator authority to ``from
time to time . . . revise'' the listed categories, and that nothing in
the statutory text or relevant case law suggests that the EPA must,
before revising a source category in a way that expands its scope, make
a SCF determination for the newly added part of the category,
considered alone. The commenter adds that nothing in the statute
indicates that Congress intended for it to be more difficult for the
EPA to add sources to a category than to include those sources in the
category in the first instance. The commenter states that the EPA's
obligation when revising a source category is only to conclude that the
entire category, as revised, can still be deemed to contribute
significantly to pollution that endangers public health or welfare.
    Response: In this action, the EPA is determining that the
transmission and storage segment of the oil and natural gas industry
should not be included with the production and processing segments as a
single source category. For that reason, if, in the future, the EPA
seeks to promulgate standards of performance for any air pollutants
from the transmission and storage segment, it must first list the
segment as a source category and then determine that their emissions
cause or contribute significantly to air pollution reasonably
anticipated to endanger public health or welfare (SCF). Commenters take
different positions on the question of whether the EPA must make a SCF
for the transmission and storage segment as a predicate to adding them
into a source category that already includes the production and
processing segments. However, because the EPA is determining that the
transmission and storage segment was not properly added to the source
category, it is not necessary to resolve that question, and the EPA
does not do so in this action.
    Comment: Several commenters assert that, in order to remove
transmission and storage segment sources from the Oil and Natural Gas
source category, the EPA must affirmatively show that emissions from
the sources do not significantly impact public health.
    Response: The EPA disagrees with this comment. In this action, the
EPA is determining that its previous determinations that the Crude Oil
and Natural Gas source category included the transmission and storage
segment beginning in 1979, or, in the alternative, that the EPA was
justified in expanding the category to include that segment, were
improper. Rather, the EPA is determining that the source category did
not include that segment beginning in 1979 and that the EPA's action in
2012 and 2016 to add this segment into the source category was
improper. These reasons justify the EPA in determining that the proper
scope of the source category is the production and processing segments
alone. There is no requirement under CAA section 111 that the
improperly added segment must remain in the source category until the
EPA determines that they do not cause or contribute significantly to
dangerous air pollution.
5. Whether EPA Must Move To Add/Expand the Source Category and Regulate
Transmission and Storage Emission Sources
    Comment: Several commenters suggest that if the EPA finalizes the
proposal to remove natural gas transmission and storage and rescind the
applicable requirements for this segment, that the EPA should also move
to properly and legally expand the source category and regulate natural
gas transmission and storage emission sources. The commenters state
that, beyond asserting that it might do so in the future, the proposal
fails to explain why it does not take the logical next step and assess
whether the emissions from the transmission and storage segment
contribute significantly to dangerous pollution. The commenters contend
that the current record, as well as the EPA's past findings,
demonstrates that the emissions from the transmission and storage
segment by itself does contribute significantly to dangerous air
pollution.
    Response: The EPA determined that the Agency's past interpretations
and actions related to the inclusion of the transmission and storage
segment in the Crude Oil and Natural Gas Production source category
were in error. This action focuses on the correction of these past
errors and interpretations. The EPA posits that retaining this focus,
in the absence of established SCF criteria for GHG emissions/methane
needed to add/expand the scope of this rulemaking, is necessary and
appropriate, and that doing so provides greater clarity and certainty
for the regulated community.
    The EPA agrees with commenters that if an appropriate assessment of
the emissions from the transmission and storage segment concludes that
emissions from this segment contribute significantly to the
endangerment to public health or welfare, we would need to propose a
separate rulemaking for the regulation of emissions from sources in
this segment. However, the EPA is not, at this time, assessing whether
the emissions from the transmission and storage segment contribute
significantly to the endangerment to public health or welfare.
    Further, the proposal preamble solicited comment regarding
appropriate criteria for the EPA to consider in making a SCF. This
request was made both as a broad matter and with particular reference
to GHG emissions generally, and to methane emissions from the Oil and
Natural Gas source category most particularly. The EPA is evaluating
the responses received to its solicitation and has not yet established
criteria that it would follow to make such a SCF for the transmission
and storage segment as it relates to GHG emissions/methane. Discussion
on comments received on the EPA's solicitation related to SCF criteria
can be found in section VI.C of this preamble.

B. Rescission of the Applicability to Methane of the NSPS for
Production and Processing Segments

    The following summarizes some of the major comments on the EPA's
proposal to rescind the methane NSPS for the production and processing
segments and provides the EPA's responses. Additional discussion and
comments and responses on this topic are provided above, in section
V.B, and in Chapter 6 of the Response to Comments Document.
    Comment: Several commenters do not agree with the proposal that
section 111 of the CAA authorizes the EPA to rescind one pollutant's
standards because another pollutant's standards may capture them. The
EPA claims that it lacked a rational basis for its 2016 action because
the requirements added in 2016 are entirely redundant with the existing
NSPS for VOC. However, commenters indicate that there is not a specific
provision within the CAA that expressly exempts pollutants from
regulation due to overlapping control technology.
    Response: Although it is true that no CAA provision explicitly
authorizes rescinding requirements on the ground that they are
redundant, the EPA's basis for this action is that it erred in the 2016
Rule when it concluded that it had a rational basis to regulate
methane. It is not rational to impose redundant requirements, because
they are not necessary and do not achieve additional

health or environmental protections. This basis for the EPA's action
does not depend on explicit statutory authorization.
    Comment: Multiple commenters support removing methane requirements
for the production and processing segments on the ground that they are
redundant with the existing NSPS for VOC, for the reasons the EPA
stated in the 2019 subparts OOOO and OOOOa Proposal. Another commenter
states that: (1) Methane can be detected more economically than VOC and
detecting VOC typically is 2 to 4 times the cost of detecting methane,
(2) methane is a reliable indicator of VOC, and (3) detecting methane
is safer than detecting VOC. Other commenters disagreed. One commenter
states that, while the release of VOC may always be accompanied by
methane, it does not follow that the release of methane will always be
accompanied by the release of VOC. Some commenters make the case that
the NSPS does not simply duplicate requirements for emission controls;
rather, it allows, but does not require, operators to comply with both
VOC and methane controls using the same practices. Another commenter
states that selective technologies do exist and could be applied to
reduce VOC but not methane emissions if the methane rescission is
finalized. One commenter asserts that it would be arbitrary to regulate
methane and VOC as the same just because the currently chosen control
technologies are the same. Another commenter adds that, while the
sources of VOC and methane leaks may overlap, the two have distinct
pollutant effects. The commenter further adds that the urgency and
stringency of desired reductions may differ considerably for the two
pollutant categories and may change over time, if, for example, the
need for climate change mitigation becomes more acute. The commenter
suggests that the most sensible approach to regulation of emissions
from oil and natural gas operations is, thus, to keep performance
standards for both VOC and methane on the books, and to update those
standards periodically as the science and technology evolve.
    Response: The EPA acknowledges the comments but emphasizes that all
of the requirements in the rule apply independently of emissions of
either methane or VOC. We discussed this redundancy in detail in
section IV.D of the 2019 Proposal (84 FR 50259) and in section V.B of
this preamble. The EPA continues to take the position that standards of
performance for methane emissions from the production and processing
segments are redundant with the existing NSPS for VOC and establish no
additional health protections. As explained, every affected source in
the production and processing segments will continue to be subject to
the same NSPS requirements for VOC as before, and those requirements
will have the same impact in reducing the source's methane emissions as
before the removal of methane requirements. The EPA maintains that
removing the methane NSPS, while retaining the VOC NSPS, will not
affect the amount of methane reductions that those requirements will
achieve.
    One commenter claims that methane can be detected more economically
and more safely than VOC. First, it is important to note that BSER for
leaking equipment is based on the use of OGI equipment, which does not
require the direct measurement of VOC. It is also worthy to note that
this commenter was primarily referring to economic and safety
advantages of methane leak detection technologies deployed via
aircraft, which is not an option currently allowed under the rule.
    Comment: One commenter asserts that removing methane standards
would almost certainly lead to the adoption of less protective
requirements. The commenter notes that in the 2016 Response to Comment
Document (p. 2-61), the EPA stated, ``that direct regulation of GHG
enables the reduction of additional methane emissions beyond what could
be achieved by prior VOC-focused rules.''
    Response: The EPA agrees that, in theory, the direct regulation of
GHG and consideration of the costs in relation to GHG reduction could
result in more stringent standards and more emission reductions than if
decisions were made entirely based on VOC emission reductions. The EPA
also acknowledges that, for the 2016 Rule, the costs were considered
both in relation to the VOC and methane emission reductions. However,
the EPA disagrees with the comment that removing methane standards
would ``almost certainly'' lead to less protective standards. A
separate action amending NSPS subpart OOOOa (EPA-HQ-OAR-2017-0483; FRL-
10013-60-OAR; FR Doc. 2020-18115), which will be finalized in the
Federal Register of Tuesday, September 15, 2020, is an example of how
this assertion by the commenter is incorrect.
    In 2018, the EPA proposed amendments and clarifications to NSPS
subpart OOOOa (83 FR 52056, October 15, 2018) as a result of the
reconsideration of issues raised in petitions on the 2016 Rule. In
2018, the EPA proposed to decrease the monitoring frequency for well
sites with average combined oil and natural gas production for the
wells at the site greater than or equal to 15 barrels of oil equivalent
(boe) per day from semi-annually to annually. The EPA also proposed to
decrease the monitoring frequency at compressor stations from quarterly
to semi-annually. For both of these situations, the standards were both
for VOC and methane and the cost-effectiveness based on both VOC and
methane emission reductions considered. In fact, the ``multi-
pollutant'' cost effectiveness was also considered where the control
costs were split between VOC and methane.
    In a separate action, the EPA is finalizing the reconsideration
amendments to NSPS subpart OOOOa (EPA-HQ-OAR-2017-0483; FRL-10013-60-
OAR; FR Doc. 2020-18115). However, the decisions for these
reconsideration amendments take into account this final policy review
action, which first rescinds the methane standards for production and
processing sources. Therefore, the separate reconsideration amendments
are finalizing ``VOC-only'' standards based on the cost effectiveness
of the reduction in VOC only. These final reconsideration amendments
are more stringent than the proposed reconsideration amendments, which
were based on both VOC and methane standards. Specifically, in the
separate reconsideration action, the EPA is finalizing semi-annual
monitoring for well sites with average combined oil and natural gas
production for the wells at the site greater than or equal to 15 boe
per day and semi-annual monitoring for gathering and boosting
compressor stations. Therefore, in this specific situation, the
elimination of methane standards resulted in more stringent standards.
    Comment: Commenters state that the redundancy rationale does not
consider future BSER evaluations required by CAA section 111(b)(1)(B).
One commenter notes that CAA section 111(b)(1)(B) requires the EPA to
periodically--every 8 years--review and, if appropriate, revise the
standards established under this section (we refer to this as the 8-
year review). Commenters state that removing methane will mean that the
methane requirements will not be subject to this review. One commenter
states that the EPA's claimed redundancy ignores that methane
regulation will have unique impacts on the 8-year review, including how
the Agency considers cost and benefits, which are relevant factors in
the likely stringency of the standards the EPA ultimately adopts.
    A commenter states that, while the BSER is largely the same for
methane