iterations have provided differing outcomes and are therefore
unreliable, this is not what the overall record indicates. Rather, in
general, although the specifics of states' linkages may change
slightly, our modeling overall has provided consistent outcomes
regarding which states are linked to downwind air quality problems. For
example, the EPA's modeling shows that most states that were linked to
one or more receptors using the 2011-based platform (i.e., the March
2018 data release) are also linked to one or more receptors using the
newer 2016-based platform. Because each platform uses different
meteorology (i.e., 2011 and 2016) it is not at all unexpected that an
upwind state could be linked to different receptors using 2011 versus
2016 meteorology.
    In addition, although a state may be linked to a different set of
receptors, states are often linked to receptors in the same area that
has a persistent air quality problem. These differing results regarding
receptors and linkages can be affected by the varying meteorology from
year to year, but this does not indicate that the modeling or the EPA
or the state's methodology for identifying receptors or linkages is
inherently unreliable. Rather, for many states these separate modeling
runs all indicated: (i) that there would be receptors in areas that
would struggle with nonattainment or maintenance in the future, and
(ii) that the state was linked to some set of these receptors, even if
the receptors and linkages differed from one another in their specifics
(e.g., a different set of receptors were identified to have
nonattainment or maintenance problems, or a state was linked to
different receptors in one modeling run versus another).
    The EPA interprets this common result as indicative that a state's
emissions have been substantial enough to generate linkages at Step 2
to varying sets of downwind receptors generated under varying
assumptions and meteorological conditions, even if the precise set of
linkages changed between modeling runs. Under these circumstances, we
think it is appropriate to proceed to a Step 3 analysis to determine
what portion of a particular state's emissions should be deemed
``significant.'' We also note that only four states included in the
proposed disapprovals went from being unlinked to being linked between
the 2011-based modeling provided in the March 2018 memorandum and the
2016v2-based modeling--Alabama, Minnesota, Nevada, and Tennessee.
5. Cooperative Federalism and the EPA's Authority
    Comment: Many comments point to the concept of cooperative
federalism as embodied in the CAA to make various arguments as to why
the EPA cannot or should not be allowed to exercise its independent
judgment in evaluating the arguments presented by the states in the SIP
submissions, and some also argue that the EPA must approve each state's
submission in deference to how states choose to interpret the CAA
requirements they must meet.
    EPA Response: The CAA establishes a framework for state-Federal
partnership to implement the NAAQS based on cooperative federalism.
Under the general model of cooperative federalism, the Federal
Government establishes broad standards or goals, states are given the
opportunity to determine how they wish to achieve those goals, and if
states choose not to or fail to adequately implement programs to
achieve those goals, a Federal agency is empowered to directly regulate
to achieve the necessary ends. Under the CAA, once the EPA establishes
or revises a NAAQS, states have the obligation and opportunity in the
first instance to develop an implementation plan under CAA section 110
and the EPA will approve SIP submissions under CAA section 110 that
fully satisfy the requirements of the CAA. This sequence of steps is
not in dispute.
    The EPA does not, however, agree with the comments'
characterization of the EPA's role in the state-Federal relationship as
being ``secondary'' such that the EPA must defer to state choices
heedless of the substantive objectives of the Act; such deference would
be particularly inappropriate in the context of addressing interstate
pollution. The EPA believes that the comments fundamentally
misunderstand or inaccurately describe this action, as well as the
```division of responsibilities' between the states and the federal
government'' they identify in CAA section 110 citing the Train-Virginia
line of cases \291\ and other cases.\292\

Those cases, some of which pre-date the CAA amendments of 1990
resulting in the current Good Neighbor Provision,\293\ stand only for
the proposition that the EPA must approve state plans if they meet the
applicable CAA requirements. But these cases say nothing about what
those applicable requirements are. The EPA is charged under CAA section
110 with reviewing states' plans for compliance with the CAA and
approving or disapproving them based on EPA's determinations. Thus, the
EPA must ultimately determine whether state plans satisfy the
requirements of the Act or not. Abundant case law reflects an
understanding that the EPA must evaluate SIP submissions under the CAA
section 110(k)(2) and (3).\294\ If they are deficient, the EPA must so
find, and become subject to the obligation to directly implement the
relevant requirements through a Federal implementation plan under CAA
section 110(c), unless EPA approves an applicable SIP first.\295\
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    \291\ See Virginia v. EPA, 108 F.3d 1397, 1407 (D.C. Cir. 1997)
(Virginia) (quoting Train v. Natural Resources Defense Council,
Inc., 421 U.S. 60, 79 (1975) (Train)). The ``Train-Virginia line of
cases'' are named for the U.S. Supreme Court case Train, 421 U.S.
and to the D.C. Circuit case Virginia, 108 F.3d. The D.C. Circuit
has described these cases as defining a ``federalism bar'' that
generally recognizes states' ability to select emissions control
measures in their SIPs so long as CAA requirements are met. See,
e.g., Michigan v. EPA, 213 F.3d 663, 687 (D.C. Cir. 2000)
(Michigan).
    \292\ Union Elec. Co. v. EPA, 427 U.S. 246 (1976), Am. Elec.
Power Co. v. Connecticut, 565 U.S. 410 (2011), Fla. Power & Light v.
Costle, 650 F.2d 579 (5th Cir. 1981), Bethlehem Steel Corp. v.
Gorsuch, 742 F.2d 1028 (7th Cir. 1984), Concerned Citizens of
Bridesburg v. EPA, 836 F.2d 777 (3d Cir. 1987), North Carolina, 531
F.3d 896, Luminant, 675 F.3d 917 (5th. Cir. 2012), Luminant Co. LLC
v. EPA, 714 F.3d 841 (5th. Cir. 2013), North Dakota v. EPA, 730 F.3d
750 (8th. Cir. 2013), EME Homer City II, 795 F.3d 118 (D.C. Cir.
2015), and Texas v. USEPA, 829 F.3d 405 (5th. Cir. 2016).
    \293\ The 1970 version of the Act required SIPs to include
``adequate provisions for intergovernmental cooperation'' concerning
interstate air pollution. CAA section 110(a)(2)(E), 84 Stat. 1681,
42 U.S.C. 1857c-5(a)(2)(E). In 1977, Congress amended the Good
Neighbor Provision to direct States to submit SIP submissions that
included provisions ``adequate'' to ``prohibi[t] any stationary
source within the State from emitting any air pollutant in amounts
which will . . . prevent attainment or maintenance [of air quality
standards] by any other State.'' CAA section 108(a)(4), 91 Stat.
693, 42 U.S.C. 7410(a)(2)(E) (1976 ed., Supp. II). Congress again
amended the Good Neighbor Provision in 1990 to its current form.
    \294\ See, e.g., Virginia, 108 F.3d at 1406. See also, e.g.,
Westar Energy v. EPA, 608 Fed. App'x 1, 3 (D.C. Cir. 2015) (``EPA
acted well within the bounds of its delegated authority when it
disapproved of Kansas's proposed [good neighbor] SIP.'') (emphasis
added); Oklahoma, 723 F.3d at 1209 (upholding the EPA's disapproval
of ``best available retrofit technology'' (BART) SIP, noting BART
``does not differ from other parts of the CAA--states have the
ability to create SIPs, but they are subject to EPA review'').
    \295\ EME Homer City Generation, 572 U.S. at 508-510.
---------------------------------------------------------------------------

    The EPA responds in greater detail to these comments in the RTC
document.
6. Availability of Guidance for SIP Submissions
    Comment: Comments contend the EPA failed to issue guidance in a
timely fashion by releasing its August 2018 memorandum 31 days prior to
when SIPs addressing interstate ozone transport were due and issuing
the October 2018 memorandum 18 days after those SIPs were due. Some
comments additionally claim that it is unreasonable for the EPA to
disapprove SIP submissions based on standards that were not defined,
mandated, or required by official guidance.
    EPA Response: Comments' contention is unsupported by the statute or
applicable case law. Regarding the need for the EPA's guidance in
addressing good neighbor obligations, in EME Homer City, the Supreme
Court clearly held that ``nothing in the statute places the EPA under
an obligation to provide specific metrics to States before they
undertake to fulfill their good neighbor obligations.'' \296\
---------------------------------------------------------------------------

    \296\ EME Homer City, 572 U.S. at 510.
---------------------------------------------------------------------------

    Nonetheless, as comments point out, the EPA issued three
``memoranda'' in 2018 to provide some assistance to states in
developing these SIP submissions. In acting on the SIP submissions in
this action, the EPA is neither rescinding nor acting inconsistently
with the memoranda--to the extent the memoranda constituted agency
guidance (not all the information provided did constitute guidance),
information or ideas in the memoranda had not at that time been
superseded by case law developments, and the memoranda's air quality
and contribution data had not at that time been overtaken by updated
modeling and other updated air quality information. While comments
specific to each of those memoranda are addressed elsewhere in this
record, we note in brief that each memorandum made clear that the EPA's
action on SIP submissions would be through a separate notice-and-
comment rulemaking process and that SIP submissions seeking to rely on
or take advantage of any information or concepts in these memoranda
would be carefully reviewed against the relevant legal requirements and
technical information available to the EPA at the time it would take
such rulemaking action.

B. Application of the 4-Step Interstate Transport Framework

1. Analytic Year
    Comment: One comment asserted that 2023 is not an appropriate
analytical year because, according to the commenter, the EPA and at
least some downwind states have not in fact implemented mandatory
emissions control requirements associated with their nonattainment
areas, and North Carolina and Wisconsin require that upwind and
downwind state obligations must be implemented ``on par.'' The comment
also characterizes the EPA's invocation of Maryland as an inappropriate
shifting of regulatory burden to upwind states.
    EPA Response: This is an incorrect interpretation of the D.C.
Circuit's holdings in North Carolina, Wisconsin, and Maryland, which
held that the EPA and the states must align good neighbor obligations
to the extent possible with the downwind areas' attainment dates. These
are set by the statute and remain fixed regardless of whether downwind
areas are delayed in implementing their own obligations. It would be
unworkable to expect that upwind states' obligations could be perfectly
aligned with each downwind area's actual timetable for implementing the
relevant emissions controls, and no court has held that this is the
EPA's or the states' obligation under the good neighbor provision.
Further, this ignores the fact that upwind states must also address
their interference with maintenance of the NAAQS, as well as the
Maryland court's holding that good neighbor obligations should be
addressed by the Marginal area attainment date for ozone under subpart
2 of part D of title I of the CAA. Both circumstances may involve
situations in which the home state for an identified downwind receptor
does not have a specific obligation to plan for and implement specific
emissions controls while an upwind state may nonetheless be found to
have good neighbor obligations. But, as the Maryland court recognized,
the absence of specific enumerated requirements does not mean the
downwind state does not have a statutorily binding obligation subject
to burdensome regulatory consequences: ``Delaware must achieve
attainment `as expeditiously as practicable,''' and ``an upgrade from a
marginal to a moderate nonattainment area carries significant
consequences . . . .'' Maryland, 958 F.3d at 1204.
    Further, where any downwind-state delays are unreasonable or
violate statutory timeframes, the CAA provides recourse to compel the
completion of such duties in CAA section 304, not to defer the
elimination of significant contribution and thereby expose the public
in downwind areas to the elevated pollution levels caused in part by
upwind states' pollution. Regardless, in this action, 2023 aligns with
the Moderate area attainment date in 2024, and all of the downwind
nonattainment areas corresponding to receptor locations identified at
Step 1 in this action are already classified as being in Moderate
nonattainment or have been reclassified to Moderate and the relevant
states face obligations to submit

SIP submissions and implement reasonably available control technologies
(RACT) by January 1, 2023. See 87 FR 60897, 60899 (October 7, 2022).
The EPA further responds to this comment in the RTC document.
2. Attachment A to the March 2018 Memorandum
    Comment: Comments state that states conducted their analyses based
on the flexibilities listed in Attachment A of the March 2018
Memorandum. Comments cite the part of the memorandum where the EPA
notes that ``in developing their own rules, states have flexibility to
follow the familiar four-step transport framework (using [the] EPA's
analytical approach or somewhat different analytical approaches within
these steps) or alternative frameworks, so long as their chosen
approach has adequate technical justification and is consistent with
the requirements of the CAA.'' Comments state that the EPA's
disapproval of SIP submissions that took advantage of the flexibilities
is arbitrary and capricious because the EPA has changed, without
communication, its consideration of what is deemed to be the
``necessary provisions'' required for an approvable SIP submission too
late in the SIP submission process and because, in disapproving these
SIPs, the EPA is applying a consistent set of policy judgments across
all states.
    EPA Response: Comments mistakenly view Attachment A to the March
2018 memorandum releasing modeling results as constituting agency
guidance. The EPA further disagrees with commenters' characterization
of the EPA's stance regarding the ``flexibilities'' listed (without
analysis) in Attachment A. Attachment A to the March 2018 memorandum
identified a ``Preliminary List of Potential Flexibilities'' that could
potentially inform SIP development.\297\ However, the EPA made clear in
that attachment that the list of ideas were not suggestions endorsed by
the Agency but rather ``comments provided in various forums'' from
outside parties on which the EPA sought ``feedback from interested
stakeholders.'' \298\ Further, Attachment A stated, ``EPA is not at
this time making any determination that the ideas discussed later are
consistent with the requirements of the CAA, nor are we specifically
recommending that states use these approaches.'' \299\ Attachment A to
the March 2018 memorandum, therefore, does not constitute agency
guidance, but was intended to generate further discussion around
potential approaches to addressing ozone transport among interested
stakeholders. The EPA emphasized in this memorandum that any such
alternative approaches must be technically justified and appropriate in
light of the facts and circumstances of each particular state's
submittal.\300\ As stated in the proposed SIP disapprovals,\301\ the
March 2018 memorandum provided that, ``While the information in this
memorandum and the associated air quality analysis data could be used
to inform the development of these SIPs, the information is not a final
determination regarding states' obligations under the good neighbor
provision.'' \302\ In this final SIP disapproval action, the EPA again
affirms that certain concepts included in Attachment A to the March
2018 memorandum require unique consideration, and these ideas do not
constitute agency guidance with respect to transport obligations for
the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \297\ March 2018 memorandum, Attachment A.
    \298\ Id.
    \299\ Id.
    \300\ March 2018 memorandum.
    \301\ E.g., 87 FR 9487.
    \302\ See Information on the Interstate Transport State
Implementation Plan Submissions for the 2015 Ozone National Ambient
Air Quality Standards under Clean Air Act Section
110(a)(2)(D)(i)(I), March 27, 2018, available in docket EPA-HQ-OAR-
2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
---------------------------------------------------------------------------

    In response to comments' claims that since the time transport SIP
submissions were submitted to the EPA for review, the EPA has changed,
without communication, its consideration of what is deemed to be the
``necessary provisions'' required for an approvable SIP submission, the
EPA disagrees. As comments note, and as stated in the proposed
disapproval notifications, the EPA recognizes that states have
discretion to develop their own SIP transport submissions and agrees
that states are not bound to using the 4-step interstate transport
framework the EPA has historically used. However, states must then
provide sufficient justification and reasoning to support their
analytical conclusions and emissions control strategies. See, e.g., 87
FR 9798, 9801. In the SIP submissions being disapproved in this action,
no state provided any enforceable emissions control strategies for
approval into their SIP. The EPA has evaluated the merits of each
state's arguments as to why no additional emissions reduction
requirements are needed to satisfy their obligations under CAA section
110(a)(2)(D)(i)(I) for the more protective 2015 ozone NAAQS. While the
EPA used its own 4-step interstate transport framework as a guide for
its review to ensure a consistent and equitable evaluation of each
states' submissions, the EPA has also considered states' individual
arguments without predetermining the EPA's conclusions about the
state's transport obligations.
    It was never the Agency's intent in sharing Attachment A that
states would invoke one or more of the potential ``flexibilities'' that
outside parties advocated for as a basis for concluding that no
additional emissions controls were necessary to address interstate
transport for the more protective 2015 ozone NAAQS without proper
justification. Nothing in Attachment A suggested that was the Agency's
intended objective. Indeed, where certain approaches identified in
Attachment A might have produced analytical conclusions requiring
upwind states to reduce their emissions, no state invoking Attachment A
followed through with implementing those controls. We observe this
dynamic at work in Kentucky's submission, because Kentucky appended
comments from the Midwest Ozone Group to its submission that
demonstrated that applying a ``weighted'' approach to allocating
upwind-state responsibility at Step 3 would have resulted in an
emissions control obligation on Kentucky's sources, yet the State
offered no explanation in its submittal why it was not adopting that
approach or even what its views on that approach were. See 87 FR 9515.
As another example, Michigan cited Attachment A to the March 2018 in
developing a methodology for calculating significant contribution under
which Michigan would have been responsible for eliminating up to 0.12
ppb of contribution to downwind receptors; however, the State suggested
that uncertainty caused by modeling ``noise'' was too great to either
require emissions reductions or demonstrate that Michigan had any
linkages to receptors at all. See 87 FR 9860-9861. However, this
explanation did not, as an analytical matter, demonstrate a level of
scientific uncertainty which might allow for ignoring the results,\303\

particularly when the Agency has implemented good neighbor requirements
at levels of ``significant contribution'' comparable to or even less
than 0.12 ppb. See Wisconsin, 938 F.3d at 322-23 (rejecting Wisconsin's
argument that it should not face good neighbor obligations for the 2008
ozone NAAQS on the basis that its emission reductions would only
improve a downwind receptor by two ten-thousandths of a part per
billion).
---------------------------------------------------------------------------

    \303\ Scientific uncertainty may only be invoked to avoid
comporting with the requirements of the CAA when ``the scientific
uncertainty is so profound that it precludes . . . reasoned
judgment'' Massachusetts v. EPA, 127 S.Ct. 1438 (2007). See
Wisconsin, 938 F.3d at 318-19 (``Scientific uncertainty, however,
does not excuse EPA's failure to align the deadline for eliminating
upwind States' significant contributions with the deadline for
downwind attainment of the NAAQS.''). See also EME Homer City, 795
F.3d at 135-36 (``We will not invalidate EPA's predictions solely
because there might be discrepancies between those predictions and
the real world. That possibility is inherent in the enterprise of
prediction.'').
---------------------------------------------------------------------------

    The EPA continues to neither endorse the ``flexibilities'' in
Attachment A, nor stakes a position that states are precluded from
relying on these concepts in the development of their good neighbor SIP
submissions, assuming they could be adequately justified both
technically and legally. This has been demonstrated through the EPA's
extensive evaluation of the merits of each states' SIP submissions,
including their attempted use of flexibilities and derivatives of the
EPA's historically applied 4-step interstate transport framework.\304\
---------------------------------------------------------------------------

    \304\ Nor in the course of this evaluation has the EPA uniformly
ruled out the concepts in Attachment A. For example, we noted at
proposal that California's identification of a flexibility in
Attachment A related to excluding certain air quality data
associated with atypical events may be generally consistent with the
EPA's modeling guidance, but this does not affect the ultimate
determination that California's SIP is not approvable. See 87 FR
31454.
---------------------------------------------------------------------------

3. Step 1: October 2018 Memorandum
    Comments: Comments claimed that the EPA is not honoring its October
2018 memorandum, which they claim would allow for certain monitoring
sites identified as maintenance-only receptors in the EPA's methodology
to be excluded as receptors based on historical data trends. They
assert that the EPA is inappropriately disapproving SIP submissions
where the state sufficiently demonstrated certain monitoring sites
should not be considered to have a maintenance problem in 2023.
    EPA Response: The October 2018 memorandum recognized that states
may be able to demonstrate in their SIPs that conditions exist that
would justify treating a monitoring site as not being a maintenance
receptor despite results from our modeling methodology identifying it
as such a receptor. The EPA explained that this demonstration could be
appropriate under two circumstances: (1) the site currently has ``clean
data'' indicating attainment of the 2015 ozone NAAQS based on measured
air quality concentrations, or (2) the state believes there is a
technical reason to justify using a design value from the baseline
period that is lower than the maximum design value based on monitored
data during the same baseline period. To justify such an approach, the
EPA anticipated that any such showing would be based on an analytical
demonstration that: (1) Meteorological conditions in the area of the
monitoring site were conducive to ozone formation during the period of
clean data or during the alternative base period design value used for
projections; (2) ozone concentrations have been trending downward at
the site since 2011 (and ozone precursor emissions of NOX
and VOC have also decreased); and (3) emissions are expected to
continue to decline in the upwind and downwind states out to the
attainment date of the receptor. EPA evaluated state's analyses and
found no state successfully applied these criteria to justify the use
of one of these alternative approaches. The air quality data and
projections in Section III indicate that trends in historic measured
data do not necessarily support adopting a less stringent approach for
identifying maintenance receptors for purposes of the 2015 ozone NAAQS.
In fact, as explained in Section III, the EPA has found in its analysis
for this final action that, in general, recent measured data from
regulatory ambient air quality ozone monitoring sites suggest a number
of receptors with elevated ozone levels will persist in 2023 even
though our traditional methodology at Step 1 did not identify these
monitoring sites as receptors in 2023. Thus, the EPA is not acting
inconsistently with that memorandum--the factual conditions that would
need to exist for the suggested approaches of that memorandum to be
applicable have not been demonstrated as being applicable or
appropriate based on the relevant data.
    We further respond to comments related to the identification of
receptors at Step 1 the RTC document.
4. Step 2: Technical Merits of a 1 Percent of the NAAQS Contribution
Threshold
    Comment: Several comments contend that for technical reasons, the
0.70 ppb threshold is inappropriate for determining whether a state is
linked to a downwind receptor at Step 2 of the 4-step interstate
transport framework. Comments state that the degree to which errors
exist in modeling ozone concentrations and contributions make it
inappropriate for a threshold as low as 0.70 ppb to be used. Some
comments further state that the 0.70 ppb threshold is inappropriate
because the concentration threshold is lower than what monitoring
devices are capable of detecting. Comments reference the reported
precision of Federal reference monitors for ozone and the rounding
requirements found in 40 CFR part 50, appendix U, Interpretation of the
Primary and Secondary National Ambient Air Quality Standards for Ozone,
for support. Comments note that the 1 percent contribution threshold of
0.70 ppb is lower than the manufacturer's reported precision of Federal
reference monitors for ozone and that the requirements found in
appendix U truncates monitor values of 0.70 ppb to 0 ppb.
    EPA Response: The EPA disagrees that a 1 percent of the NAAQS
contribution threshold at Step 2 is ``inappropriate'' for the 2015
ozone NAAQS due to modeling biases and errors. The explanation for how
the 1 percent contribution threshold was originally derived is
available in the 2011 CSAPR rulemaking. See 76 FR 48208, 48236-38 (Aug.
8, 2011). The EPA has effectively applied a 1 percent of the NAAQS
threshold to identify linked upwind states in three prior FIP
rulemakings and numerous state-specific actions. The D.C. Circuit has
declined to establish bright line criteria for model performance. In
upholding the EPA's approach to evaluating interstate transport in
CSAPR, the D.C. Circuit held that it would not ``invalidate EPA's
predictions solely because there might be discrepancies between those
predictions and the real world. That possibility is inherent in the
enterprise of prediction.'' EME Homer City II, 795 F.3d at 135. The
court continued to note that ``the fact that a `model does not fit
every application perfectly is no criticism; a model is meant to
simplify reality in order to make it tractable.' '' Id. at 135-36
(quoting Chemical Manufacturers Association v. EPA, 28 F.3d 1259, 1264
(DC Cir. 1994). See also Sierra Club v. EPA, 939 F.3d 649, 686-87 (5th
Cir. 2019) (upholding the EPA's modeling in the face of complaints
regarding an alleged ``margin of error,'' noting challengers face a
``considerable burden'' in overcoming a ``presumption of regularity''
afforded ``the EPA's choice of analytical methodology'') (citing BCCA
Appeal Grp. v. EPA, 355 F.3d 817, 832 (5th Cir. 2003)).
    Furthermore, it is not appropriate to compare the bias/error
involved in the estimation of total ozone to the potential error in the
estimation of the subset of ozone that is contributed by a single
state.\305\ For example, on a specific day

the modeled versus monitored ozone value may differ by 2 ppb but that
is a relatively small percentage of the total modeled ozone, which for
a receptor of interest would be on the order of 70 ppb. It would be
unrealistic to assign all of the 2 ppb discrepancy in the earlier
example to the estimated impact from a single state because the 2 ppb
error would be the combination of the error from all sources of ozone
that contribute to the total, including estimated impacts from other
states, the home state of the receptor, and natural background
emissions.
---------------------------------------------------------------------------

    \305\ See, e.g., 87 FR 9798 at 9816.
---------------------------------------------------------------------------

    To address comments that compare the 0.70 ppb threshold to the
Federal reference monitors for ozone and the rounding requirements
found in 40 CFR part 50, appendix U, the EPA notes that the comment is
mistaken in applying criteria related to the precision of monitoring
data to the modeling methodology by which we project contributions when
quantifying and evaluating interstate transport at Step 2. Indeed,
contributions by source or state cannot be derived from the total
ambient concentration of ozone at a monitor at all but must be
apportioned through modeling. Under our longstanding methodology for
doing so, the contribution values identified from upwind states are
based on a robust assessment of the average impact of each upwind
state's ozone-precursor emissions over a range of scenarios, as
explained in the Final Action AQM TSD. This analysis is in no way
connected with or dependent on monitoring instruments' precision of
measurement. See EME Homer City II, 795 F.3d 118, 135-36 (```[A] model
is meant to simplify reality in order to make it tractable.''').
5. Step 2: Justification of a 1 Percent of the NAAQS Contribution
Threshold
    Comment: Comments contend that the EPA has not provided enough
basis for reliance on the 0.70 ppb threshold, claiming that its use is
therefore arbitrary and capricious.
    EPA Response: The EPA is finalizing its proposed approach of
consistently using a 1 percent of the NAAQS contribution threshold at
Step 2. This approach ensures both national consistency across all
states and consistency and continuity with our prior interstate
transport actions for other NAAQS. Comments have not established that
this approach is either unlawful or arbitrary and capricious.
    The 1 percent threshold is consistent with the Step 2 approach that
the EPA applied in CSAPR for the 1997 ozone NAAQS, which has
subsequently been applied in the CSAPR Update and revised CSAPR Update
when evaluating interstate transport obligations for the 2008 ozone
NAAQS. The EPA continues to find 1 percent to be an appropriate
threshold. For ozone, as the EPA found in the CAIR, CSAPR, and CSAPR
Update, a portion of the nonattainment and maintenance problems in the
U.S. results from the combined impact of relatively small contributions
from many upwind states, along with contributions from in-state sources
and other sources. The EPA's analysis shows that much of the ozone
transport problem being analyzed for purposes of evaluating 2015 ozone
NAAQS SIP obligations is still the result of the collective impacts of
contributions from many upwind states. Therefore, application of a
consistent contribution threshold is necessary to identify those upwind
states that should have responsibility for addressing their
contribution to the downwind nonattainment and maintenance problems to
which they collectively contribute. Where a great number of
geographically dispersed emissions sources contribute to a downwind air
quality problem, which is the case for ozone, EPA believes that, in the
context of CAA section 110(a)(2)(D)(i)(I), a state-level threshold of 1
percent of the NAAQS is a reasonably small enough value to identify
only the greater-than-de minimis contributers yet is not so large that
it unfairly focuses attention for further action only on the largest
single or few upwind contributers. Continuing to use 1 percent of the
NAAQS as the screening metric to evaluate collective contribution from
many upwind states also allows the EPA (and states) to apply a
consistent framework to evaluate interstate emissions transport under
the interstate transport provision from one NAAQS to the next. See 81
FR 74504, 74518. See also 86 FR 23054, 23085 (reviewing and explaining
rationale from CSAPR, 76 FR 48208, 48236-38, for selection of 1 percent
threshold).
    Further, the EPA notes that the role of the Step 2 threshold is
limited and just one step in the 4-Step interstate transport framework.
It serves to screen in states for further evaluation of emissions
control opportunities applying a multifactor analysis at Step 3. Thus,
as the Supreme Court has recognized, the contribution threshold
essentially functions to exclude states with ``de minimis'' impacts.
EME Homer City, 572 U.S. at 500.
    Comment: Commenters contend that the EPA cannot use the 1 percent
threshold as a determination for significance.
    EPA Response: To clarify, the EPA does not use the 1 percent of the
NAAQS threshold as the definition of ``significance.'' Rather, where a
state's contribution equals or exceeds the 1 percent of the NAAQS
threshold, the EPA expects states to further evaluate their emissions
to determine whether their emissions constitute significant
contribution or interference with maintenance. The contribution
threshold is a screening threshold to identify states which may be
``contributing'' to an out of state receptor. The EPA has maintained
this interpretation of the relevant statutory language across many
rulemakings, though commenters continue to confuse the Step 2 threshold
with a determination of ``significance,'' which it is not. See EME
Homer City, 572 U.S. at 500-502 (explaining the difference between the
``screening'' analysis at Steps 1 and 2 whereby the EPA ``excluded as
de minimis any upwind State that contributed less than one percent of
the . . . NAAQS'' and the ``control'' analysis at Step 3 whereby the
EPA determined ``cost thresholds'' to define significance).
    Further, the EPA's air quality and contribution modeling for ozone
transport is based on application of the model in a relative sense
rather than relying upon absolute model predictions. All models have
limitations resulting from uncertainties in inputs and scientific
formulation. To minimize the effects of these uncertainties, the
modeling is anchored to base period measured data in the EPA's guidance
approach for projecting design values. Notably, the EPA also uses our
source apportionment modeling in a relative sense when calculating the
average contribution metric (used to identify linkages). In this method
the magnitude of the contribution metric is tied to the magnitude of
the projected average design value which is tied to the base period
average measured design value. The EPA's guidance has recommended
against applying bright-line criteria for judging whether statistical
measures of model performance constitute acceptable or unacceptable
model performance.
    The Agency continues to find that this method using the CAMx model
to evaluate contributions from upwind states to downwind areas is
reliable. The agency has used CAMx routinely in previous notice and
comment transport rulemakings to evaluate contributions relative to the
1 percent threshold for both ozone and PM2.5. In fact, in
the original CSAPR, the EPA found that ``[t]here was wide support from
commenters for the use of CAMx as an

appropriate, state[hyphen]of[hyphen]the science air quality tool for
use in the [Cross[hyphen]State Air Pollution] Rule. There were no
comments that suggested that the EPA should use an alternative model
for quantifying interstate transport.'' 76 FR 48229 (August 8, 2011).
In this action, the EPA has taken a number of steps based on comments
and new information to ensure to the greatest extent the accuracy and
reliability of its modeling projections at Step 1 and 2, as discussed
elsewhere in this document.
6. Step 2: Prevention of Significant Deterioration Significant Impact
Levels
    Comment: Several comments insist that when identifying an
appropriate linkage threshold at Step 2 of the 4-step framework, the
EPA should consider or rely on the 1 ppb significant impact level (SIL)
for ozone used as part of the prevention of significant deterioration
PSD permitting process. Comments reference the EPA's April 17, 2018,
guidance memorandum, ``Significant Impact Levels for Ozone and Fine
Particles in the Prevention of Significant Deterioration Permitting
Program'' (SIL guidance), as well as the EPA's March 2018 memorandum's
Attachment A flexibilities to lend support to their opinion that the 1
ppb SIL should also be used to determine linkages at Step 2.
    EPA Response: The EPA's SIL guidance relates to a different
provision of the Clean Air Act regarding implementation of the
prevention of significant deterioration (PSD) permitting program. This
program applies in areas that have been designated attainment of the
NAAQS and is intended to ensure that such areas remain in attainment
even if emissions were to increase as a result of new sources or major
modifications to existing sources located in those areas. This purpose
is different than the purpose of the good neighbor provision, which is
to assist downwind areas (in some cases hundreds or thousands of miles
away) in resolving ongoing nonattainment of the NAAQS or difficulty
maintaining the NAAQS through eliminating the emissions from other
states that are significantly contributing to those problems. In
addition, as discussed earlier, the purpose of the Step 2 threshold
within the EPA's interstate transport framework for ozone is to broadly
sweep in all states contributing to identified receptors above a de
minimis level in recognition of the collective-contribution problem
associated with regional-scale ozone transport. The threshold used in
the context of PSD SIL serves an entirely different purpose, and so it
does not follow that they should be made equivalent. Further, comments
incorrectly associate the EPA's Step 2 contribution threshold with the
identification of ``significant'' emissions (which does not occur until
Step 3), and so it is not the case that the EPA is interpreting the
same term differently.
    The EPA has previously explained this distinction between the good
neighbor framework and PSD SILs. See 70 FR 25162, 25190-25191 (May 12,
2005); 76 FR 48208, 48237 (August 8, 2011). Importantly, the
implication of the PSD SIL threshold is not that single-source
contribution below this level indicates the absence of a contribution
or that no emissions control requirements are warranted. Rather, the
PSD SIL threshold addresses whether further, more comprehensive, multi-
source review or analysis of air quality impacts are required of the
source to support a demonstration that it meets the criteria for a
permit. A source with estimated impacts below the PSD SIL may use this
to demonstrate that it will not cause or contribute (as those terms are
used within the PSD program) to a violation of an ambient air quality
standard, but is still subject to meeting applicable control
requirements, including best available control technology, designed to
moderate the source's impact on air quality.
    Moreover, other aspects of the technical methodology in the SIL
guidance compared to the good neighbor framework make a direct
comparison between these two values misleading. For instance, in PSD
permit modeling using a single year of meteorology the maximum single-
day 8-hour contribution is evaluated with respect to the SIL. The
purpose of the contribution threshold at Step 2 of the 4-step good
neighbor framework is to determine whether the average contribution
from a collection of sources in a state is small enough not to warrant
any additional control for the purpose of mitigating interstate
transport, even if that control were highly cost effective. Using a 1
percent of the NAAQS threshold is more appropriate for evaluating
multi-day average contributions from upwind states than a 1 ppb
threshold applied for a single day, since that lower value of 1 percent
of the NAAQS will capture variations in contribution. If EPA were to
use a single day reflecting the maximum amount of contribution from an
upwind state to determine whether a linkage exists at Step 2, comments'
arguments for use of the PSD SIL might have more force. However, that
would likely cause more states to become linked, not less. And in any
case, consistent with the method in our modeling guidance for
projecting future attainment/nonattainment, the good neighbor
methodology of using multiple days provides a more robust approach to
establishing that a linkage exists at the state level than relying on a
single day of data.
7. Step 2: August 2018 Memorandum
    Comment: Comments assert that in the August 2018 memorandum the EPA
committed itself to approving SIP submissions from states with
contributions below 1 ppb, and so now the EPA should or must approve
the good neighbor SIP submission from any state with a contribution
below 1 ppb, either based on modeling available at the time of the
state's SIP submission or at any time.
    EPA Response: These comments mischaracterize the content and the
EPA's application of August 2018 memorandum. Further, the EPA disputes
that the EPA misled states or that the EPA has not appropriately
reviewed SIP submissions from states that attempted to rely on an
alternative contribution threshold at Step 2.
    Specifically, the EPA's August 2018 memorandum provided an analysis
regarding ``the degree to which certain air quality threshold amounts
capture the collective amount of upwind contribution from upwind
states.'' \306\ It interpreted ``that information to make
recommendations about what thresholds may be appropriate for use in''
SIP submissions (emphasis added).\307\ Specifically, the August 2018
memorandum said, ``Because the amount of upwind collective contribution
capture with the 1 percent and the 1 ppb thresholds is generally
comparable, overall, we believe it may be reasonable and appropriate
for states to use a 1 ppb contribution threshold, as an alternative to
a 1 percent threshold, at Step 2 of the 4-step framework in developing
their SIP revisions addressing the good neighbor provision for the 2015
ozone NAAQS.'' (emphasis added).\308\ Thus, the text of the August 2018
memorandum does not guarantee that any state with a contribution below
1 ppb has an automatically approvable good neighbor SIP. In fact, the
August 2018 memorandum indicated that ``[f]ollowing these
recommendations does not ensure that EPA will approve a SIP revision in
all instances where the recommendations are followed, as the guidance
may not apply to the facts and circumstances underlying a particular
SIP. Final decisions by the EPA to approve a particular SIP revision
will

only be made based on the requirements of the statute and will only be
made following an air agency's final submission of the SIP revision to
the EPA, and after appropriate notice and opportunity for public review
and comment.'' \309\ The August 2018 memorandum also stated, ``EPA and
air agencies should consider whether the recommendations in this
guidance are appropriate for each situation.'' \310\ The EPA's
assessment of every SIP submission that invoked the August 2018
memorandum considered the particular arguments raised by the
state.\311\
---------------------------------------------------------------------------

    \306\ August 2018 memorandum, page 1.
    \307\ August 2018 memorandum, page 1.
    \308\ August 2018 memorandum, page 4.
    \309\ August 2018 memorandum, page 1.
    \310\ August 2018 memorandum, page 1.
    \311\ 87 FR 64423-64424 (Alabama); 87 FR 9806-9807 (Arkansas);
87 FR 9852-9853 (Illinois); 87 FR 9855-9856 (Indiana); 87 FR 9508-
9511 (Kentucky); 87 FR 9812-9813 (Louisiana); 87 FR 9861-9862
(Michigan); 87 FR 9557 (Mississippi); 87 FR 9541-9543 (Missouri); 87
FR 31492 (Nevada); 87 FR 9870-9871 (Ohio); 87 FR 9818-9820
(Oklahoma); 87 FR 31477-31451 (Utah).
---------------------------------------------------------------------------

    Comment: Some comments allege that the EPA representatives led the
states to believe that their SIP submission would be approved on the
basis of a 1 ppb contribution threshold. The comments further claim
that the EPA has now since reversed course on its August 2018
memorandum and imposed new requirements on states that were not
included in the EPA's guidance. One comment suggested EPA switched
position without explanation from the August 2018 guidance to its
proposed disapprovals, which it viewed as unlawful under FCC v. Fox TV
Stations, Inc., 556 U.S. 502 (2009).
    EPA Response: As an initial matter, we note that the salience of
these comments is limited to only a handful of states. The August 2018
memorandum made clear that the Agency had substantial doubts that any
threshold greater than 1 ppb (such as 2 ppb) would be acceptable, and
the Agency is affirming that a threshold higher than 1 ppb would not be
justified under any circumstance for purposes of this action. No
comment provided a credible basis for using a threshold even higher
than 1 ppb. So this issue is primarily limited to the difference
between a 0.70 ppb threshold and a 1.0 ppb threshold. Therefore, we
note that this issue is only relevant to a small number of states whose
only contributions to any receptor are above 1 percent of the NAAQS but
lower than 1 ppb. Under the 2016v3 modeling of 2023 being used in this
final action, those states with contributions that fall between 0.70
ppb and 1 ppb included in this action are Alabama, Kentucky, and
Minnesota.
    The EPA disagrees with comments' claims that the Agency has
reversed course on applying the August 2018 memorandum. In line with
the memorandum, the EPA evaluated every justification put forward by
every state covered by this SIP disapproval action that attempted to
justify an alternative threshold under the August 2018 memorandum,
which are Alabama,\312\ Arkansas,\313\ Illinois,\314\ Indiana,\315\
Kentucky,\316\ Louisiana,\317\ Michigan,\318\ Mississippi,\319\
Missouri,\320\ and Oklahoma,\321\ and Utah.\322\ The EPA also addressed
criticisms of the 1 percent of the NAAQS contribution threshold made by
Ohio \323\ and Nevada.\324\ (The topic of the EPA's input during
state's SIP-development processes is further discussed in the RTC
document.)
---------------------------------------------------------------------------

    \312\ 87 FR 64423-64424.
    \313\ 87 FR 9806-9807.
    \314\ 87 FR 9852-9853.
    \315\ 87 FR 9855-9856.
    \316\ 87 FR 9508-9511.
    \317\ 87 FR 9812-9813.
    \318\ 87 FR 9861-9862.
    \319\ 87 FR 9557.
    \320\ 87 FR 9541-9543.
    \321\ 87 FR 9818-9820.
    \322\ 87 FR 31477-31451.
    \323\ 87 FR 9870-9871.
    \324\ 87 FR 31492.
---------------------------------------------------------------------------

    For this reason, the EPA disagrees with comment that case law
reviewing changes in agency positions as articulated in FCC v. Fox TV
Stations, Inc., is applicable to this action. The Agency has not
imposed a requirement that states must use a 1 percent of the NAAQS
threshold (which would reflect a change in position from the August
2018 memorandum). Rather, under the terms of the August 2018
memorandum, the Agency has found that Alabama, Arkansas, Illinois,
Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Nevada,
Ohio, Oklahoma, and Utah have not made a sufficient showing that the
use of an alternative contribution threshold is justified for those
States. Even if it were found that the Agency's position had
fundamentally changed between this rulemaking action and the August
2018 memorandum (which we do not concede to be the case), we do not
believe that any state had a legitimate reliance interest that would be
sufficient to overcome the countervailing public interest that is
served in declining to approve a state's use of the 1 ppb threshold
where the state did not have adequate technical justification. First,
neither states nor the emissions sources located in those states have
incurred any compliance costs based on the August 2018 memorandum.
Second, it is not clear that any states invested much of their own
public resources in developing state-specific arguments in support of a
1 ppb threshold. As the EPA observed at proposal, in nearly all
submittals, the states did not provide the EPA with analysis specific
to their state or the receptors to which its emissions are potentially
linked. In one case, the EPA's proposed approval of Iowa's SIP
submittal, ``the EPA expended its own resources to attempt to
supplement the information submitted by the state, in order to more
thoroughly evaluate the state-specific circumstances that could support
approval.'' E.g., 87 FR 9806-07 (emphasis added). The EPA emphasizes
again that it was the EPA's sole discretion to perform this analysis in
support of the state's submittal, and the Agency is not obligated to
conduct supplemental analysis to fill the gaps whenever it believes a
state's analysis is insufficient. Id.
    We acknowledge that certain states may have assumed the EPA would
approve SIP submissions from states whose contribution to any receptor
was below 1 ppb, but that assumption reflected a misunderstanding of
the August 2018 memorandum, and in any case, an assumption is not, as a
legal matter, the same thing as a reliance interest.
    The EPA is not formally rescinding the August 2018 memorandum in
this action or at this time, but since guidance memoranda are not
binding in the first place, it is not required that agencies must
``rescind'' a guidance the moment it becomes outdated or called into
question. As the Agency made clear in the August 2018 memorandum, all
of EPA's proposals for action on interstate transport SIP submissions
are subject to rulemaking procedure, including public notice and
comment, before the EPA makes a final decision.
    Although the EPA is not formally revoking the August 2018
memorandum at this time, and we have separately found that no state
successfully established a basis for use of a 1 ppb threshold, we also
continue to believe, as set forth in our proposed disapprovals, that
national ozone transport policy associated with addressing obligations
for the 2015 ozone NAAQS is not well-served by allowing for less
protective thresholds at Step 2. Furthermore, the EPA disagrees that
national consistency is an inappropriate consideration in the context
of interstate ozone transport. The Good Neighbor provision, CAA section
110(a)(2)(D)(i)(I), requires to a unique degree of concern for
consistency, parity, and equity across

state lines.\325\ For a regional air pollutant such as ozone,
consistency in requirements and expectations across all states is
essential. Based on the EPA's review of good neighbor SIP submissions
to-date and after further consideration of the policy implications of
attempting to recognize an alternative Step 2 threshold for certain
states, the Agency now believes the attempted use of different
thresholds at Step 2 with respect to the 2015 ozone NAAQS raises
substantial policy consistency and practical implementation concerns.
The availability of different thresholds at Step 2 has the potential to
result in inconsistent application of good neighbor obligations based
solely on the strength of a state's SIP submission at Step 2 of the 4-
step interstate transport framework. From the perspective of ensuring
effective regional implementation of good neighbor obligations, the
more important analysis is the evaluation of the emissions reductions
needed, if any, to address a state's significant contribution after
consideration of a multifactor analysis at Step 3, including a detailed
evaluation that considers air quality factors and cost. While
alternative thresholds for purposes of Step 2 may be ``similar'' in
terms of capturing the relative amount of upwind contribution (as
described in the August 2018 memorandum), nonetheless, use of an
alternative threshold would allow certain states to avoid further
evaluation of potential emissions controls while other states with a
similar level of contribution would proceed to a Step 3 analysis. This
can create significant equity and consistency problems among states.
---------------------------------------------------------------------------

    \325\ The EPA notes that Congress has placed on the EPA a
general obligation to ensure the requirements of the CAA are
implemented consistently across states and regions. See CAA section
301(a)(2). Where the management and regulation of interstate
pollution levels spanning many states is at stake, consistency in
application of CAA requirements is paramount.
---------------------------------------------------------------------------

    One comment suggested that the EPA could address this potentially
inequitable outcome by simply adopting a 1 ppb contribution threshold
for all states. However, the August 2018 memorandum did not conclude
that 1 ppb would be appropriate for all states, and the EPA does not
view that conclusion to be supported at present. The EPA recognized in
the August 2018 memorandum that on a nationwide basis there was some
similarity in the amount of total upwind contribution captured between
1 percent and 1 ppb. However, while this may be true in some sense,
that is hardly a compelling basis to move to a 1 ppb threshold for
every state. Indeed, the 1 ppb threshold has the disadvantage of losing
a certain amount of total upwind contribution for further evaluation at
Step 3 (e.g., roughly 7 percent of total upwind state contribution was
lost according to the modeling underlying the August 2018 memorandum;
in the EPA's 2016v2 and 2016v3 modeling, the amount lost is 5 percent).
Further, this logic has no end point. A similar observation could be
made with respect to any incremental change. For example, should the
EPA next recognize a 1.2 ppb threshold because that would only cause
some small additional loss in capture of upwind state contribution as
compared to 1 ppb? If the only basis for moving to a 1 ppb threshold is
that it captures a ``similar'' (but actually smaller) amount of upwind
contribution, then there is no basis for moving to that threshold at
all. Considering the core statutory objective of ensuring elimination
of all significant contribution to nonattainment or interference with
maintenance of the NAAQS in other states as well as the broad, regional
nature of the collective contribution problem with respect to ozone, we
continue to find no compelling policy reason to adopt a new threshold
for all states of 1 ppb.
    It also is unclear why use of a 1 ppb threshold would be
appropriate for all states under a more protective NAAQS when a 1
percent of the NAAQS contribution threshold has been used for less
protective NAAQS. To illustrate, a state contributing greater than 0.75
ppb but less than 1 ppb to a receptor under the 2008 ozone NAAQS was
``linked'' at Step 2 using the 1 percent of the NAAQS contribution
threshold, but if a 1 ppb threshold were used for the 2015 ozone NAAQS,
then that same state would not be ``linked'' to a receptor at Step 2
under a NAAQS that is set to be more protective of human health and the
environment. Consistency with past interstate transport actions such as
CSAPR, and the CSAPR Update and Revised CSAPR Update rulemakings (which
used a Step 2 threshold of 1 percent of the NAAQS for two less
protective ozone NAAQS), is an important consideration. Continuing to
use a 1 percent of NAAQS approach ensures that if the NAAQS are revised
and made more protective, an appropriate increase in stringency at Step
2 occurs, to ensure an appropriately larger amount of total upwind-
state contribution is captured for purposes of fully addressing
interstate transport obligations. See 76 FR 48208, 48237-38.
    One comment identified that if the EPA were to use a 1 percent of
the NAAQS contribution threshold, the EPA would be obligated to seek
feedback on that contribution threshold through a public notice and
comment process. The EPA's basis and rationale for every SIP submission
covered by this final SIP disapproval action, including the use of a 1
percent of the NAAQS contribution threshold, was in fact presented for
public comment. The EPA received, and is addressing in this action,
many detailed comments about contribution thresholds. Further, the
EPA's application of a 1 percent of the NAAQS threshold has been
consistently used in notice-and-comment rulemakings beginning with the
CSAPR rulemaking in 2010-2011 and including both FIP actions (CSAPR
Update and Revised CSAPR Update) and numerous actions on ozone
transport SIP submissions. In each case, the 1 percent of the NAAQS
threshold was subject to rigorous vetting through public comment and
the Agency's response to those comments, including through analytical
evaluations of alternative thresholds. See, e.g., 81 FR 74518-19. By
contrast, the August 2018 memorandum was not issued through notice-and-
comment rulemaking procedures, and the EPA was careful to caveat its
utility and ultimate reliability for that reason.
    Comment: Some comments claim that the EPA is applying the August
2018 memorandum inconsistently based on the EPA's actions with regard
to action good neighbor SIP submissions from Iowa and Oregon for the
2015 ozone NAAQS and Arizona's good neighbor SIP submission for the
2008 ozone NAAQS.
    EPA Response: The EPA disagrees that there is any such
inconsistency. The EPA withdrew a previously proposed approval of
Iowa's SIP submission where the Agency had attempted to substantiate
the use of a 1 ppb contribution threshold, and re-proposed and
finalized approval of that SIP based on a different rationale using a 1
percent of the NAAQS contribution threshold. 87 FR 9477 (Feb. 22,
2022); 87 FR 22463 (April 15, 2022). As explained earlier in this
section, this experience of the EPA attempting to justify 1 ppb for a
state through additional air quality analysis, where the state had not
conducted an analysis the Agency considered to be sufficient is part of
the reason the Agency is moving away from attempting to justify use of
this alternative contribution threshold.
    The EPA also disputes the claim that Oregon and Arizona were the
only states ``allowed'' to use a 1 ppb threshold. The EPA approved
Oregon's SIP submission for the 2015 ozone NAAQS on May 17,

2019, and both Oregon and the EPA relied on a 1 percent of the NAAQS
contribution threshold. 84 FR 7854, 7856 (March 5, 2019) (proposal); 84
FR 22376 (May 17, 2019) (final). In our FIP proposal for the 2015 ozone
NAAQS, the EPA explained it was not proposing to conduct an error
correction for Oregon even though updated modeling indicated Oregon
contributed above 1 percent of the NAAQS to monitors in California,
because the specific monitors in California are not interstate ozone
transport ``receptors'' at Step 1. See 87 FR 20036, 20074-20075 (April
6, 2022). The EPA solicited public comment on its approach to Oregon's
contribution to California receptors as part of the 2015 ozone NAAQS
transport FIP development, and the Agency has not yet taken final
action on that FIP. In 2016, the EPA previously approved Arizona's good
neighbor SIP for the earlier 2008 ozone NAAQS based on a similar
rationale with regard to certain monitors in California in 2016. 81 FR
15200 (March 22, 2016) (proposal); 81 FR 31513 (May 19, 2016) (final
rule). The Agency's view with respect to its evaluation of both Arizona
and Oregon is that specific monitors in California are not interstate
ozone transport ``receptors'' at Step 1. The EPA has not approved or
applied an alternative Step 2 threshold for any state.
    Comments related to the specific circumstances of an individual
state and/or its arguments put forth in its SIP submission as it
pertains to the August 2018 Memorandum are further addressed in the RTC
document.
8. Step 3: States' Step 3 Analyses for the 2015 Ozone NAAQS
    Comment: Comments state that the EPA has not provided any guidance
on what an appropriate Step 3 analysis would entail, and therefore any
decision where the Agency rejects a Step 3 analysis is arbitrary and
capricious. One comment claims that not a single state has successfully
made a Step 3 demonstration leading to an approvable interstate
transport SIP for the 2015 ozone NAAQS. Comments note that there is no
requirement in the CAA that states must complete an analysis similar to
the EPA's, and the EPA cannot substitute its own judgment for that of
the state's in crafting a SIP. Rather, the EPA is obligated to defer to
state choices. One comment asserts that the EPA is required to
interpret the term ``significant contribution'' in a manner ``which
ties contribution to an amount which contributes significantly to
downwind maintenance or nonattainment problems.'' Another comment
claims the EPA is intentionally exploiting the Supreme Court decision
in EME Homer City to justify any requirements it deems necessary to
further Federal policy decisions. Some comments identify that some
states did not conduct a Step 3 analysis in their submitted SIPs
because, using the flexibilities provided in the 2018 memoranda, these
states concluded in Step 1 and Step 2 that no controls were required.
One comment suggests that the EPA propose an 18-month period to allow
these states to proceed with Steps 3 and 4.
    EPA Response: The EPA disagrees that it is obligated to defer to
states' choices in the development of good neighbor SIP submissions. As
required by the Act, the EPA has evaluated each of the SIP submissions
for compliance with the CAA, including whether an adequate Step 3
analysis was conducted--or whether states had offered an approvable
alternative approach to evaluating their good neighbor obligations--and
found in each case that what these states submitted was not approvable.
The Supreme Court has recognized that the EPA is not obligated to
provide states with guidance before taking action to disapprove a SIP
submission. EME Homer City, 572 U.S. at 508-10. Nonetheless, throughout
the entire history of the EPA's actions to implement the good neighbor
provision for ozone, starting with the 1998 NOX SIP Call, we
have consistently adopted a similar approach at Step 3 that evaluates
emissions reduction opportunities for linked states applying a
multifactor analysis. States could have performed a similar analysis of
emissions control opportunities. The EPA has not directed states that
they must conduct a Step 3 analysis in precisely the manner the EPA has
done in its prior regional transport rulemakings; however, SIPs
addressing the obligations in CAA section 110(a)(2)(D)(i)(I) must
prohibit ``any source or other type of emissions activity within the
State'' from emitting air pollutants which will contribute
significantly to downwind air quality problems. Thus, States seeking to
rely on an alternative approach to defining ``significance'' must use
an approach that comports with the statute's objectives to determine
whether and to what degree emissions from a state should be
``prohibited'' to eliminate emissions that will ``contribute
significantly to nonattainment in, or interfere with maintenance of''
the NAAQS in any other state. Further, the approach selected must be
reasonable and technically justified. Therefore, while the EPA does not
direct states to use a particular framework, nonetheless, each state
must show that its decision-making was based on a ``technically
appropriate or justifiable'' evaluation.
    Further, the Agency has a statutory obligation to review and
approve or disapprove SIP submittals according to the requirements of
the Clean Air Act. See CAA section 110(k)(3). And the Agency is
empowered to interpret those statutory requirements and exercise both
technical and policy judgment in acting on SIP submissions. Indeed, the
task of allocating responsibility for interstate pollution particularly
necessitates Federal involvement. See EME Homer City, 572 U.S. at 514
(``The statute . . . calls upon the Agency to address a thorny
causation problem: How should EPA allocate among multiple contributing
upwind States responsibility for a downwind State's excess
pollution?''); see also Wisconsin, 938 F.3d at 320. Further, we have
consistently disapproved states' good neighbor SIP submissions
addressing prior ozone NAAQS when we have found those states linked
through our air quality modeling and yet the state failed to conduct an
analysis of emissions control opportunities, or such analysis was
perfunctory or otherwise unsatisfactory. We have been upheld in our
judgment that such SIPs are not approvable. See Westar Energy v. EPA,
608 Fed. App'x 1, 3 (DC Cir. 2015) (``EPA acted well within the bounds
of its delegated authority when it disapproved of Kansas's proposed
SIP.'') (emphasis added).
    With respect to the assertion that no state has successfully
avoided a FIP with an approvable Step 3 analysis, we note first that at
this time, no final FIP addressing the 2015 ozone NAAQS has been
promulgated. More directly to the point, no state submission that is
the subject of this disapproval action offered any additional emissions
control measures. While it is conceivable that a Step 3 analysis may
result in a determination that no additional controls are needed, EPA
expects that such circumstances will generally be rare, else the CAA's
interstate transport provisions are rendered ineffective. For example,
the EPA determined in the CSAPR Update that even though the District of
Columbia and Delaware were linked to out of state receptors at Steps 1
and 2 of the 4-step interstate transport framework, no additional
control measures were required of either jurisdiction. As to the
District of Columbia, we found that there were no affected EGU sources
that would fall under the CSAPR Update's control program. For Delaware,
we found that

there were no emissions reductions available from any affected sources
for any of the emissions control stringencies that were analyzed. See
81 FR 74504, 74553. No state's submission covered in this action
contained an emissions control analysis that would allow for these
types of conclusions to be reached for all of its sources.\326\ States
generally did not conduct any comparative analysis of available
emissions control strategies--nor did they prohibit any additional
ozone-precursor emissions.
---------------------------------------------------------------------------

    \326\ We note that California's SIP submission is not approvable
at Step 3, despite the fact that the EPA has not identified
NOX emissions control opportunities at the state's EGUs.
Nonetheless, the SIP submission is not approvable because the state
attempted to rely on the CSAPR Update cost threshold to justify a
no-control determination when that threshold was in relation to a
partial remedy for a less protective NAAQS, and even if it could be
reasonably concluded that no emissions reductions are appropriate at
EGUs in California, the SIP submission did not conduct an adequate
analysis of emissions control opportunities at its non-EGU
industrial sources. See 87 FR 31459-60.
---------------------------------------------------------------------------

    We are unclear what another comment intends in asserting that the
EPA is required to interpret ``significant contribution'' in a manner
``which ties contribution to an amount which contributes significantly
to downwind maintenance or nonattainment problems.'' The EPA disagrees
that: (1) It has imposed or mandated a specific approach to Step 3 in
this action, (2) this action established a particular level of
emissions reduction that states were required to achieve, or (3) it
mandated a particular methodology for making such a determination. To
the extent the comment suggests that the Agency cannot mandate that
states use cost as a method of allocating responsibility in their
transport SIPs, first, the Agency has not done so. Further, as to
whether cost could be used as a permissible method of allocating
responsibility, the comment ignores the Supreme Court's holding to the
contrary in EME Homer City, 572 U.S. at 518, and the D.C. Circuit's
earlier holding to the same effect in Michigan, 213 F.3d at 687-88,
both of which upheld the EPA's approach of using uniform cost-
effectiveness thresholds to allocate upwind state responsibilities
under the good neighbor provision for prior NAAQS. While this approach
may be reasonable to apply again for the 2015 ozone NAAQS (and the EPA
has proposed to do so in the proposed FIP action published on April 6,
2022), the EPA did not impose such a requirement on states in
developing SIP submissions, nor is the EPA finding any SIP submission
not approvable based on a failure to use this particular methodology.
    In its March 2018 memorandum, Attachment A, the Agency acknowledged
that there could be multiple ways of conducting a Step 3 analysis. The
Agency did not endorse any particular approach and noted the Attachment
was merely a list of stakeholder ideas that the EPA was not
recommending any state follow. The apparent result of this
``flexibility,'' however, was that no state presented a Step 3 analysis
that resulted in including any enforceable emissions reductions to
address good neighbor obligations for the 2015 ozone NAAQS in their
interstate transport SIP submittals. Likewise, the comment here did not
include information or analysis establishing that any particular
alternative Step 3 approach should have been approved or that any state
performed such an analysis in a manner that would have addressed
``significant contribution'' even in the manner the comment appears to
be suggesting.
    Notably, materials appended to one State's SIP submission,
developed by the Midwest Ozone Group (MOG), did present an analysis
applying an approach to ``significant contribution'' that was based on
calculating a proportional share of each state's contribution to a
downwind receptor, and this methodology would have imposed on that
State's, Kentucky's, sources an obligation to eliminate 0.02 ppb of
ozone at the relevant receptor. See 87 FR 9507. While the EPA does not
endorse or here evaluate the merits of such an approach, it is
noteworthy that the State in that instance did not adopt that approach,
did not impose that obligation on its sources through enforceable
measures by revising its SIP, and offered no explanation for its
decision not to do so. See id. 9516 (``This approach would have imposed
additional emissions reductions for Kentucky sources. Kentucky's final
SIP did not consider MOG's proposal and did not provide an explanation
for why it was rejecting this approach to allocating upwind emissions
reductions, even though it appended this recommendation to its SIP
submittal.'').
9. Step 4: Attempt To Rely on FIPs in a SIP Submission
    Comment: One comment states that FIPs or other Federal emissions
control measures do not have to be incorporated into and enforceable
under state law to be an approvable SIP measure. They view it as
acceptable for a state to rely in its SIP Submission on the emissions
reductions achieved by prior ozone transport FIPs, such as the CSAPR
Update or the Revised CSAPR Update, as a permissible means of achieving
emissions reductions to eliminate significant contribution for the 2015
ozone NAAQS.
    EPA Response: The EPA disagrees. As the EPA has noted on page 16 of
our September 2013 memorandum ``Guidance on Infrastructure State
Implementation Plan (SIP) Elements under Clean Air Act sections
110(a)(1) and 110(a)(2)'' (2013 Infrastructure SIP Guidance): ``a FIP
is not a state plan and thus cannot serve to satisfy the state's
obligation to submit a SIP.'' \327\ Indeed, the general principle that
measures relied on to meet states' CAA obligations must be part of the
SIP has been recognized by courts, such as in Committee for a Better
Arvin, 786 F.3d 1169 (9th Cir. 2015).
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    \327\ Guidance on Infrastructure State Implementation Plan (SIP)
Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2),
September 13, 2013 (available at https://www.epa.gov/sites/default/files/2015-12/documents/guidance_on_infrastructure_sip_elements_multipollutant_final_sept_2013.pdf).
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    This principle is grounded in the recognition that if such measures
are not rendered enforceable within the SIP itself, then they may be
modified or amended in ways that would undermine the basis for the
state's reliance on them, while the approved SIP itself would purport
to have addressed the relevant obligation merely by outdated reference
to that modified or nonexistent control measure residing outside the
SIP. For example, to be credited for attainment demonstration purposes,
requirements that may otherwise be federally enforceable (such as new
source review permit limits or terms in federally enforceable consent
orders), must be in the state's implementation plan so that they could
not later be changed without being subject to the EPA's approval. This
principle is instrumental to ensuring that states cannot take credit
for control measures that might be changed (even by the EPA itself)
without the EPA's required approval action under CAA section 110, which
includes the obligation to ensure there is no interference or
backsliding with respect to all applicable CAA requirements. See CAA
section 110(l). See also Montana Sulfur and Chemical Co. v. EPA, 666
F.3d 1174, 1195-96 (9th Cir. 2012) (``The EPA correctly reads 42 U.S.C.
7410(a)(2) as requiring states to include enforceable emissions limits
and other control measures in the plan itself.'') (emphasis in
original); 40 CFR 51.112(a) (``Each plan must demonstrate that the
measures, rules, and regulations contained in it are adequate to
provide for the timely attainment and

maintenance of the national standard that it implements.'') (emphasis
added).
    The EPA has applied this same interpretation in implementing other
infrastructure SIP requirements found in CAA section 110(a)(2). For
example, in implementing CAA section 110(a)(2)(C), (D)(i)(II), (D)(ii),
and (J) relating to the permitting program for PSD, the EPA has
developed FIPs that incorporate by reference provisions codified at 40
CFR 51.21, and some states have taken delegation of that FIP to
implement the relevant requirements. But the EPA does not and cannot
approve the state as having met these infrastructure SIP elements, even
by virtue of taking delegation of the FIP. See, e.g., 83 FR 8818, 8820
(March 1, 2018). Likewise, under one of the pathways presented in our
2013 Infrastructure SIP Guidance, the EPA does not approve SIPs
addressing interstate visibility transport obligations under CAA
section 110(a)(2)(D)(i)(II) (``prong 4'') until the state itself has a
fully approved regional haze plan, and states cannot rely on the CSAPR
``better than BART'' FIPs to meet their prong 4 requirements until they
have replaced that FIP with an approved SIP. See, e.g., 84 FR 13800,
13801 (April 8, 2019); 84 FR 43741, 43744 (Aug. 22, 2019).
    The comment does not provide contrary examples where the EPA has
approved, as a SIP-based emissions control program, requirements that
are established through Federal regulation or other types of emissions
control programs that are outside the SIP. It is true that in the first
two steps of the 4-step interstate transport framework, the EPA
conducts air quality modeling based on emissions inventories reflective
of on-the-books state and Federal emissions control requirements, to
make determinations about air quality conditions and contribution
levels that can be anticipated in the baseline in a future analytic
year. If the comment's examples were intended to reference this
consideration of Federal measures in prior actions on SIP submittals,
the EPA agrees that it does consider such measures at these steps of
its analysis, and the EPA has consistently taken this approach
throughout its prior ozone transport actions. But here we are
discussing Step 3 and 4 of the framework, where states that have been
found to contribute to downwind nonattainment and maintenance problems,
e.g., are linked at Steps 1 and 2 to an out of state receptor, would
need to evaluate their continuing emissions to determine what if any of
those emissions should be deemed ``significant'' (e.g., Step 3) and
eliminated through enforceable emissions control requirements (e.g.,
Step 4). The EPA is not aware of any good neighbor SIP submission that
it has approved where a state purported to eliminate its significant
contribution (e.g., satisfy Steps 3 and 4) simply by referring to
Federal measures that were not included in its SIP and enforceable as a
matter of state law. Finally, it bears emphasizing that the EPA's
assessment of the 2015 ozone transport SIPs has already accounted for
the emissions-reducing effects of both the CSAPR Update and the Revised
CSAPR Update in its baseline air quality modeling at Steps 1 and 2, and
so pointing to either of those rules as measures that would eliminate
significant contribution at Step 3, for purposes of the 2015 ozone
NAAQS, would be impermissible double-counting.

C. Good Neighbor Provision Policy

1. Mobile Source Emissions
    Comment: Several comments assert that mobile source emissions
within the home state of the location of receptors are the primary
source of nonattainment problems in downwind areas. Some comments
additionally state that a larger portion of their own upwind state
emissions is from mobile source emissions. These comments request that
the EPA focus on these emissions sources rather than stationary sources
to reduce ongoing nonattainment problems. These comments claim mobile
sources are federally regulated and, therefore, the EPA bears the
responsibility to either take action to reduce mobile source emissions
nationwide or encourage downwind states to implement strategies to
reduce their own local mobile source emissions.
    Response: The EPA recognizes that nationwide, mobile sources
represent a large portion of ozone-precursor emissions and, as such,
would be expected to have a large impact on nonattainment and
maintenance receptors.
    The EPA has been regulating mobile source emissions since it was
established as a Federal agency in 1970 and is committed to continuing
the effective implementation and enforcement of current mobile source
emissions standards and evaluating the need for additional
standards.\328\ The EPA believes that the NOX reductions
from its Federal programs are an important reason for the historical
and long-running trend of improving air quality in the United States.
The trend helps explain why the overall number of receptors and
severity of ozone nonattainment problems under the 1997 and 2008 ozone
NAAQS have declined. As a result of this long history, NOX
emissions from onroad and nonroad mobile sources have substantially
decreased and are predicted to continue to decrease into the future as
newer vehicles and engines that are subject to the more recent and more
stringent standards replace older vehicles and engines.\329\
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    \328\ On December 20, 2022, the EPA finalized more stringent
emissions standards for NOX and other pollutants from
heavy-duty vehicles and engines, beginning with model year 2027. See
https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-and-related-materials-control-air-pollution. The EPA is
also developing new multi-pollutant standards for light- and medium-
duty vehicles as well as options to address pollution from
locomotives.
    \329\ https://gispub.epa.gov/air/trendsreport/2022/#home.
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    The EPA included mobile source emissions in the 2016v2 modeling
used to support the proposal of these SIP disapproval actions to help
determine state linkages at Steps 1 and 2 of the 4-step interstate
transport framework and has done likewise in its 2016v3 modeling.
However, whether mobile source emissions are a large portion of an
upwind or downwind state's NOX emissions, and whether they
represent a large portion of the contribution to downwind nonattainment
and maintenance receptors, does not answer the question regarding the
adequacy of an upwind state's SIP submission. The question is whether
``any source or other type of emissions activity'' (in the collective)
in an upwind state is contributing significantly to downwind receptors,
see CAA section 110(a)(2)(D)(i). A state's transport SIP must include a
technical and adequate justification to support its conclusion that the
state has satisfied its interstate transport obligations for the 2015
ozone NAAQS.
    To the extent that comments argue that mobile source emissions
should be the focus of emissions reductions for the purposes of
resolving interstate transport obligations, states could have provided
such an analysis for how mobile source reductions might achieve
necessary reductions. See, e.g., 70 FR 25209. However, states conducted
no such analysis of methods or control techniques that could be used to
reduce mobile source emissions, instead claiming that states cannot
control mobile source emissions, as this is a federally-regulated
sector, or states cannot reasonably control these emissions. States do
have options, however, to reduce emissions from certain aspects of
their mobile source

sectors, and to the extent a state is attributing its contribution to
out of state receptors to its mobile sources, it could have conducted
an analysis of possible programs or measures that could achieve
emissions reductions from those sources. (For example, a general list
of types of transportation control measures can be found in CAA section
108(f).\330\)
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    \330\ In making this observation, the EPA is not suggesting that
mobile source emissions reductions are necessarily required to
address a state's good neighbor obligations, but merely pointing out
that if the state itself attributes the problem to mobile sources,
then it is reasonable to expect that further analysis of such
control strategies would be explored.
---------------------------------------------------------------------------

    State-specific issues raised by comments are further addressed in
the RTC document.
2. International Contributions
    Comment: Several comments state that international emissions
contribute to nonattainment and maintenance receptors downwind, and
these emissions are not within the jurisdiction of the states. They
advocate for the EPA should considering this when acting on SIP
submissions. Some comments claim that, in the west, international
contributions are even greater than in eastern portions of the U.S. and
support their notion that the EPA's evaluation of interstate transport
should take special consideration of unique regional factors when
determining upwind state obligations, or that the Agency should
otherwise explain why it is still inappropriate to factor in higher
international contributions, as the Agency has done in Oregon's case.
    Response: The EPA responded to similar arguments related to
international emissions included in the SIP submissions of Arkansas,
California, Illinois, Indiana, Kentucky, Michigan, Missouri, Ohio,
Utah, Wyoming, and West Virginia in the proposed disapprovals.\331\ No
comments on the proposed disapprovals provided new information to
indicate the EPA's initial assessment was incorrect. These comments'
reasoning related to international emissions is inapplicable to the
requirements of CAA section 110(a)(2)(D)(i)(I). The good neighbor
provision requires states and the EPA to address interstate transport
of air pollution that significantly contributes to downwind states'
ability to attain and maintain the NAAQS. Whether emissions from other
states or other countries also contribute to the same downwind air
quality issue is typically not relevant in assessing whether a downwind
state has an air quality problem, or whether an upwind state is
significantly contributing to that problem. (Only in rare cases has EPA
concluded that certain monitoring sites should not be considered
receptors at Step 1 due to the very low collective upwind-state
contribution at those receptors. See the RTC document.) States are not
obligated under CAA section 110(a)(2)(D)(i)(I) to act alone to reduce
emissions in amounts sufficient to resolve a downwind receptor's
nonattainment or maintenance problem. Rather, states are obligated to
eliminate their own ``significant contribution'' to that receptor or
``interference'' with the ability of other states to attain or maintain
the NAAQS. The statutory standard is, fundamentally, one of
contribution, not causation.
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    \331\ 87 FR 9798, 9809-9810 (Feb. 22, 2022) (Arkansas); 87 FR
31443, 31460-31461 (May 24, 2022) (California); 87 FR 9854
(Illinois); 87 FR 9859-9860 (Indiana); 87 FR 9498, 9508 (Feb. 22,
2022) (Kentucky); 87 FR 9838, 9865 (Michigan); 87 FR 9533, 9543
(Feb. 22, 2022) (Missouri); 87 FR 9838 at 9874 (Ohio); 87 FR 31470,
31482 (May 24, 2022) (Utah); 87 FR 9516, 9527 (Feb. 22, 2022) (West
Virginia); 87 FR 31495, 31507 (May 24, 2022) (Wyoming).
---------------------------------------------------------------------------

    Indeed, the D.C. Circuit in Wisconsin specifically rejected
petitioner arguments suggesting that upwind states should be excused
from good neighbor obligations on the basis that some other source of
emissions (whether international or another upwind state) could be
considered the ``but-for'' cause of downwind air quality problem. See
Wisconsin, 938 F.3d at 323-324. The court viewed petitioners' arguments
as essentially an argument ``that an upwind state `contributes
significantly' to downwind nonattainment only when its emissions are
the sole cause of downwind nonattainment.'' Id. at 324. The court
explained that ``an upwind state can `contribute' to downwind
nonattainment even if its emissions are not the but-for cause.'' Id. at
324-325. See also Catawba County v. EPA, 571 F.3d 20, 39 (DC Cir. 2009)
(rejecting the argument ``that `significantly contribute' unambiguously
means `strictly cause''' because there is ``no reason why the statute
precludes EPA from determining that [an] addition of [pollutant] into
the atmosphere is significant even though a nearby county's
nonattainment problem would still persist in its absence''); Miss.
Comm'n on Envtl. Quality v. EPA, 790 F.3d 138, 163 n.12 (DC Cir. 2015)
(observing that the argument that ``there likely would have been no
violation at all . . . if it were not for the emissions resulting from
[another source]'' is ``merely a rephrasing of the but-for causation
rule that we rejected in Catawba County''). Therefore, a state is not
excused from eliminating its significant contribution on the basis that
international emissions also contribute some amount of pollution to the
same receptors to which the state is linked.
    To the extent comments compare the influence of international
emissions with the EPA's treatment of receptors in California to which
Oregon contributes greater than 0.70 ppb, the EPA responds to these
comments in the RTC document.
3. Western Interstate Transport Policy
    Comment: Several comments argue that the EPA should consider an
alternative approach to evaluating interstate transport in the western
U.S. Comments assert there are considerations unique to the western
states, such as increased background, international, and wildfire
contributions to ozone concentrations in the west. Some commenters
believe a ``case-by-case'' assessment is more appropriate for
evaluating western states' interstate transport obligations, as they
claim the EPA had done for the 2008 ozone standards. They additionally
argue that the EPA modeling is not able to accurately project ozone
concentrations in the west because of these factors, along with the
west's unique topographical influence on ozone transport.
    Response: The EPA disagrees that either its nationwide
photochemical grid modeling or the 4-step interstate transport
framework for ozone cannot generally be applied to states in the
western region of the U.S. and has maintained that position
consistently throughout numerous actions.\332\ Though at times the EPA
has found it appropriate to examine more closely discreet issues for
some western states,\333\ the 4-step interstate transport framework
itself is appropriate for assessing good neighbor obligations of
western states in the absence of those circumstances. The EPA evaluated
the contents of the western states' SIP submissions covered by this
action on the merits of the information the states provided. As
described at proposal and reiterated in Section IV, the EPA is
finalizing its disapproval of California,

Nevada, and Utah's SIP submissions. This final determination is based
on these evaluations, as well as the EPA's 2016v2 and 2016v3 modeling
following stakeholder feedback.
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    \332\ For a discussion of this history, see for example 87 FR
31480-81 (proposed disapproval of Utah SIP submission) and 87 FR
31453-56 (proposed disapproval of California SIP submission).
    \333\ See, e.g., Approval of Arizona's 2008 ozone NAAQS
interstate transport SIP submission, 81 FR 15200 (March 22, 2016)
(Step 1 analysis concluding certain monitors in California should
not be considered interstate transport receptors for purposes of the
good neighbor provision for the 2008 ozone NAAQS); see also 87 FR
61249, 61254-55 (Oct. 11, 2022) (in approving Colorado's interstate
transport SIP for the 2015 ozone NAAQS, analyzing unique issues
associated with wintertime inversion conditions in certain western
areas).
---------------------------------------------------------------------------

    The EPA continues to find it appropriate to rely on the results of
its nationwide modeling in the western U.S., despite comments
concerning the ability for the EPA's modeling to accurately project
ozone concentrations and contributions in western states, as well as
its ability to support the EPA's 4-step framework for assessing
interstate transport. The EPA's nationwide photochemical grid modeling
considers multiple complex factors, including those raised in comments,
such as terrain complexities, variability in emissions (e.g., wildfire
emissions), meteorology, and topography. While the EPA continues to
believe its 2016v2 modeling performs equally as well in both the west
and the east, the EPA has adjusted its 2016v3 modeling to ensure its
predictions more closely replicate the relative magnitude of
concentrations and day-to-day variability that are characteristic of
observed 8-hour daily maximum ozone concentrations in each region, as
explained in Section III.A and the RTC document. As such, the EPA
continues to find its modeling reliable for characterizing ozone
concentrations and contribution values in the western U.S. Further
responses regarding the reliability of the EPA's modeling in the
western U.S. is provided in the RTC document.
    The EPA disagrees with comments noting that the Agency took an
alternative approach for western states when assessing interstate
transport obligations under the 2008 ozone NAAQS. As explained in our
proposed disapproval of California's 2015 ozone NAAQS interstate
transport SIP submission, while the EPA has in limited circumstances
found unique issues associated with addressing ozone transport in
western states, the EPA has consistently applied the 4-step interstate
transport framework in western states, as it has done here, and has
identified ozone transport problems in the west that are similar to
those in the east.334 335 At proposal, the EPA addressed
states' arguments regarding the impact of unique factors such as
topography and, as part of the EPA's evaluation of the contents of the
SIP submission, provided explanation as to why the EPA found the
states' arguments did not support their conclusions regarding long
range transport of ozone in the west.\336\
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    \334\ 87 FR 31443, 31453.
    \335\ 81 FR 74503, 74523.
    \336\ See, e.g., 87 FR 31443, 31457. The EPA evaluated
California's qualitative consideration of unique topographic factors
that may influence the transport of emissions from sources within
the state to downwind receptors in Colorado and Arizona. The EPA
concluded that the State's arguments do not present sufficient
evidence that called into question the results of the EPA's
modeling.
---------------------------------------------------------------------------

    While comments point to relatively higher level of contributions
from non-anthropogenic, local, or international contributions in the
west as reason for evaluating interstate transport differently in the
west, a state is not excused from eliminating its significant
contribution due to contributions from these sources, where the data
shows that anthropogenic emissions from upwind states also contribute
collectively to identified receptors at levels that indicate there to
be an interstate contribution problem as well. As stated in Section
V.C.2, a state is not excused from eliminating its significant
contribution on the basis that international emissions also contribute
some amount of pollution to the same receptors to which the state is
linked. This same principle applies broadly to other arguments as to
which emissions are the ``cause'' of the problem; the good neighbor
provision established a contribution standard, not a but-for causation
standard. See Wisconsin, 938 F.3d at 323-25.

VI. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive orders
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Orders 12866: Regulatory Planning and Executive Order
13563: Improving Regulation and Regulatory Review

    This action is not a significant regulatory action and was,
therefore, not submitted to the Office of Management and Budget for
review.

B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under
the provisions of the Paperwork Reduction Act. This final action does
not establish any new information collection requirement apart from
what is already required by law. This finding relates to the
requirement in the CAA for states to submit SIPs under CAA section
110(a)(2)(D)(i)(I) addressing interstate transport obligations
associated with the 2015 ozone NAAQS.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. This
action will not impose any requirements on small entities. This action
is disapproving SIP submissions for not containing the necessary
provisions to satisfy interstate transport requirements under CAA
section 110(a)(2)(D)(i)(I).

D. Unfunded Mandates Reform Act of 1995 (UMRA)

    This action does not contain any unfunded mandate as described in
UMRA 2 U.S.C. 1531-1538 and does not significantly or uniquely affect
small governments. The action imposes no enforceable duty on any state,
local or tribal governments or the private sector.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the National Government and the states, or on the distribution of power
and responsibilities among the various levels of government.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    This action has tribal implications. However, this action does not
impose substantial direct compliance costs on federally recognized
tribal governments, nor preempt tribal law. This action includes
disapproving the portion of Oklahoma's SIP submission addressing the
state's good neighbor obligations under CAA section 110(a)(2)(D)(i)(I)
for the 2015 ozone NAAQS and applies to certain areas of Indian country
as discussed in Section IV.C of the proposed action, ``Air Plan
Disapproval; Arkansas, Louisiana, Oklahoma, and Texas; Interstate
Transport of Air Pollution for the 2015 Ozone National Ambient Air
Quality Standards'' (87 FR 9798 at 9824, February 2, 2022). However,
this action does not impose substantial direct compliance costs on
federally recognized tribal governments because no actions will be
required of tribal governments. This action will also not preempt
tribal law as no Oklahoma tribe implements a regulatory program under
the CAA, and thus does not have applicable or related tribal laws. The
EPA consulted with tribal officials under the EPA Policy on
Consultation and Coordination with Indian Tribes early in the process
of developing this regulation to permit them to have meaningful and
timely input into its development. A summary of that

consultation is provided in the file ``2015 Ozone Transport OK Tribal
Consultation Meeting Record 3-3-2022,'' in the docket for this action.

G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern health or safety risks that the EPA has
reason to believe may disproportionately affect children, per the
definition of ``covered regulatory action'' in section 2-202 of the
Executive order. This action is not subject to Executive Order 13045
because it merely disapproves SIP submissions as not containing the
necessary provisions to satisfy interstate transport requirements under
CAA section 110(a)(2)(D)(i)(I).

H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution or Use

    This action is not subject to Executive Order 13211, because it is
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations, 59 FR 7629,
Feb. 16, 1994) directs Federal agencies to identify and address
``disproportionately high and adverse human health or environmental
effects'' of their actions on minority populations and low-income
populations to the greatest extent practicable and permitted by law.
The EPA defines environmental justice (EJ) as ``the fair treatment and
meaningful involvement of all people regardless of race, color,
national origin, or income with respect to the development,
implementation, and enforcement of environmental laws, regulations, and
policies.'' The EPA further defines the term fair treatment to mean
that ``no group of people should bear a disproportionate burden of
environmental harms and risks, including those resulting from the
negative environmental consequences of industrial, governmental, and
commercial operations or programs and policies.''
    Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the Act and applicable
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in
reviewing SIP submissions, the EPA's role is to review state choices,
and approve those choices if they meet the minimum criteria of the Act.
As articulated in this final action, the EPA is determining that
certain SIPs do not meet certain minimum requirements, and the EPA is
disapproving those SIPs. Specifically, this action disapproves certain
SIP submissions as not containing the necessary provisions to satisfy
``good neighbor'' requirements under CAA section 110(a)(2)(D)(i)(I).
The EPA did not perform an EJ analysis and did not consider EJ in this
action. The CAA and applicable implementing regulations neither
prohibit nor require such an evaluation. In a wholly separate
regulatory action, the EPA will fully address the CAA ``good neighbor''
requirements under section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS
as it regards the SIP disapprovals included in this final action.
Consideration of EJ is not required as part of this action, and there
is no information in the record inconsistent with the stated goal of
E.O. 12898 of achieving EJ for people of color, low-income populations,
and Indigenous peoples.

K. Congressional Review Act (CRA)

    This action is subject to the CRA, and the EPA will submit a rule
report to each House of the Congress and to the Comptroller General of
the United States. This action is not a ``major rule'' as defined by 5
U.S.C. 804(2).

L. Judicial Review

    Section 307(b)(1) of the CAA governs judicial review of final
actions by the EPA. This section provides, in part, that petitions for
review must be filed in the D.C. Circuit: (i) when the agency action
consists of ``nationally applicable regulations promulgated, or final
actions taken, by the Administrator,'' or (ii) when such action is
locally or regionally applicable, but ``such action is based on a
determination of nationwide scope or effect and if in taking such
action the Administrator finds and publishes that such action is based
on such a determination.'' For locally or regionally applicable final
actions, the CAA reserves to the EPA complete discretion whether to
invoke the exception in (ii).\337\
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    \337\ In deciding whether to invoke the exception by making and
publishing a finding that an action is based on a determination of
nationwide scope or effect, the Administrator takes into account a
number of policy considerations, including his judgment balancing
the benefit of obtaining the D.C. Circuit's authoritative
centralized review versus allowing development of the issue in other
contexts and the best use of agency resources.
---------------------------------------------------------------------------

    This rulemaking is ``nationally applicable'' within the meaning of
CAA section 307(b)(1). In this final action, the EPA is applying a
uniform legal interpretation and common, nationwide analytical methods
with respect to the requirements of CAA section 110(a)(2)(D)(i)(I)
concerning interstate transport of pollution (i.e., ``good neighbor''
requirements) to disapprove SIP submissions that fail to satisfy these
requirements for the 2015 ozone NAAQS. Based on these analyses, the EPA
is disapproving SIP submittals for the 2015 ozone NAAQS for 21 states
located across a wide geographic area in eight of the ten EPA Regions
and ten Federal judicial circuits. Given that on its face this action
addresses implementation of the good neighbor requirements of CAA
section 110(a)(2)(D)(i)(I) in a large number of states located across
the country and given the interdependent nature of interstate pollution
transport and the common core of knowledge and analysis involved in
evaluating the submitted SIPs, this is a ``nationally applicable''
action within the meaning of CAA section 307(b)(1).
    In the alternative, to the extent a court finds this action to be
locally or regionally applicable, the Administrator is exercising the
complete discretion afforded to him under the CAA to make and publish a
finding that this action is based on a determination of ``nationwide
scope or effect'' within the meaning of CAA section 307(b)(1). In this
final action, the EPA is interpreting and applying section
110(a)(2)(D)(i)(I) of the CAA for the 2015 ozone NAAQS based on a
common core of nationwide policy judgments and technical analysis
concerning the interstate transport of pollutants throughout the
continental U.S. In particular, the EPA is applying here the same,
nationally consistent 4-step interstate transport framework for
assessing obligations for the 2015 ozone NAAQS that it has applied in
other nationally applicable rulemakings, such as CSAPR, the CSAPR
Update, and the Revised CSAPR Update. The EPA is relying on the results
from nationwide photochemical grid modeling using a 2016 base year and
2023 projection year as the primary basis for its assessment of air
quality conditions and pollution contribution levels at Step 1 and Step
2 of that 4-step framework and applying a nationally uniform approach
to the identification of nonattainment and

maintenance receptors across the entire geographic area covered by this
final action.\338\ The EPA has also evaluated each state's arguments
for the use of alternative approaches or alternative sets of data with
an eye to ensuring national consistency and avoiding inconsistent or
inequitable results among upwind states (i.e., those states for which
good neighbor obligations are being evaluated in this action) and
between upwind and downwind states (i.e., those states that contain
receptors signifying ozone nonattainment or maintenance problems).
---------------------------------------------------------------------------

    \338\ In the report on the 1977 Amendments that revised section
307(b)(1) of the CAA, Congress noted that the Administrator's
determination that the ``nationwide scope or effect'' exception
applies would be appropriate for any action that has a scope or
effect beyond a single judicial circuit. See H.R. Rep. No. 95-294 at
323, 324, reprinted in 1977 U.S.C.C.A.N. 1402-03.
---------------------------------------------------------------------------

    The Administrator finds that this is a matter on which national
uniformity in judicial resolution of any petitions for review is
desirable, to take advantage of the D.C. Circuit's administrative law
expertise, and to facilitate the orderly development of the basic law
under the Act. The Administrator also finds that consolidated review of
this action in the D.C. Circuit will avoid piecemeal litigation in the
regional circuits, further judicial economy, and eliminate the risk of
inconsistent results for different states, and that a nationally
consistent approach to the CAA's mandate concerning interstate
transport of ozone pollution constitutes the best use of agency
resources. The EPA's responses to comments on the appropriate venue for
petitions for review are contained in the RTC document.
    For these reasons, this final action is nationally applicable or,
alternatively, the Administrator is exercising the complete discretion
afforded to him by the CAA and finds that this final action is based on
a determination of nationwide scope or effect for purposes of CAA
section 307(b)(1) and is publishing that finding in the Federal
Register. Under section 307(b)(1) of the CAA, petitions for judicial
review of this action must be filed in the United States Court of
Appeals for the District of Columbia Circuit by April 14, 2023.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
reference, Ozone.

Michael S. Regan,
Administrator.

    For the reasons set forth in the preamble, 40 CFR part 52 is
amended as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

    Authority:  42 U.S.C. 7401 et seq.

Subpart B--Alabama

0
2. Section 52.56 is added to read as follows:

Sec.  52.56   Control strategy: Ozone.

    (a) The state implementation plan (SIP) revision submitted on June
21, 2022, addressing Clean Air Act section 110(a)(2)(D)(i)(I) (prongs 1
and 2) for the 2015 ozone national ambient air quality standards
(NAAQS) is disapproved.
    (b) [Reserved]

Subpart E--Arkansas

0
3. Section 52.174 is amended by adding paragraph (b) to read as
follows:

Sec.  52.174  Control strategy and regulations: Ozone.

* * * * *
    (b) The portion of the SIP submittal from October 10, 2019,
addressing Clean Air Act section 110(a)(2)(D)(i)(I) for the 2015 ozone
national ambient air quality standards (NAAQS) is disapproved.

Subpart F--California

0
4. Section 52.223 is amended by adding paragraph (p)(7) to read as
follows:

Sec.  52.223  Approval status.

* * * * *
    (p) * * *
    (7) The interstate transport requirements for Significant
Contribution to Nonattainment (Prong 1) and Interstate Transport--
Interference with Maintenance (Prong 2) of Clean Air Act (CAA) section
110(a)(2)(D)(i)(I).

0
5. Section 52.283 is amended by adding paragraph (h) to read as
follows:

Sec.  52.283  Interstate Transport.

* * * * *
    (h) 2015 ozone NAAQS. The 2018 Infrastructure SIP Revision,
submitted on October 1, 2018, does not meet the following specific
requirements of Clean Air Act section 110(a)(2)(D)(i)(I) for the 2015
ozone national ambient air quality standards (NAAQS).
    (1) The requirements of CAA section 110(a)(2)(D)(i)(I) regarding
significant contribution to nonattainment of the 2015 ozone NAAQS in
any other State and interference with maintenance of the 2015 ozone
NAAQS by any other State.
    (2) [Reserved]

Subpart O--Illinois

0
6. Section 52.720 is amended in the table in paragraph (e), under the
heading ``Section 110(a)(2) Infrastructure Requirements,'' by revising
the entry for ``2015 Ozone NAAQS Infrastructure Requirements'' to read
as follows:

Sec.  52.720  Identification of plan.

* * * * *
    (e) * * *

                       EPA-Approved Illinois Nonregulatory and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                      Applicable
      Name of SIP provision          geographic or      State submittal    EPA approval date       Comments
                                  nonattainment area         date
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
                                  Section 110(a)(2) Infrastructure Requirements
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
2015 Ozone NAAQS Infrastructure   Statewide.........  5/16/2019 and 9/22/ 2/13/2023, [INSERT  All CAA
 Requirements.                                         2020.               FEDERAL REGISTER    infrastructure
                                                                           CITATION].          elements under
                                                                                110(a)(2) have
                                                                                been approved
                                                                                except (D)(i)(I)
                                                                                Prongs 1, 2,
                                                                                which are
                                                                                disapproved, and
                                                                                no action has
                                                                                been taken on
                                                                                (D)(i)(II) Prong
                                                                                4.
----------------------------------------------------------------------------------------------------------------

Subpart P--Indiana

0
7. Section 52.770 is amended in the table in paragraph (e) by adding an
entry for ``Section 110(a)(2) Infrastructure Requirements for the 2015
Ozone NAAQS'' after the entry for ``Section 110(a)(2) Infrastructure
Requirements for the 2008 8-Hour Ozone NAAQS'' to read as follows:

Sec.  52.770  Identification of plan.

* * * * *
    (e) * * *

                  EPA-Approved Indiana Nonregulatory Provisions and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                             Indiana
                  Title                        date             EPA approval                 Explanation
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
Section 110(a)(2) Infrastructure             11/2/2018  2/13/2023, [INSERT FEDERAL   All CAA infrastructure
 Requirements for the 2015 Ozone NAAQS.                  REGISTER CITATION].          elements have been
                                                                                approved except (D)(i)(I)
                                                                                Prongs 1 and 2, which are
                                                                                disapproved, and no action
                                                                                has been taken on the
                                                                                visibility portion of
                                                                                (D)(i)(II).

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

Subpart S--Kentucky

0
8. Section 52.930 is amended by adding paragraph (n) to read as
follows:

Sec.  52.930   Control strategy: Ozone.

* * * * *
    (n) Disapproval. The state implementation plan (SIP) revision
submitted on January 11, 2019, addressing Clean Air Act section
110(a)(2)(D)(i)(I) (prongs 1 and 2) for the 2015 ozone national ambient
air quality standards (NAAQS) is disapproved.

Subpart T--Louisiana

0
9. Section 52.996 is amended by adding paragraph (b) to read as
follows:

Sec.  52.996  Disapprovals.

* * * * *
    (b) The SIP submittal from November 13, 2019, addressing Clean Air
Act section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS is disapproved.

Subpart V--Maryland

0
10. Section 52.1076 is amended by adding paragraph (gg) to read as
follows:

Sec.  52.1076  Control strategy plans for attainment and rate-of-
progress: Ozone.

* * * * *
    (gg) Disapproval. EPA is disapproving Maryland's October 16, 2019,
State Implementation Plan (SIP) revision intended to address the Clean
Air Act (CAA) section 110(a)(2)(D)(i)(I) interstate transport
requirements for the 2015 8-hour ozone national ambient air quality
standard (NAAQS).

Subpart X--Michigan

0
11. Section 52.1170 is amended in the table in paragraph (e), under the
heading ``Infrastructure,'' by revising the entry for ``Section
110(a)(2) infrastructure requirements for the 2015 ozone NAAQS'' to
read as follows:

Sec.  52.1170  Identification of plan.

* * * * *
    (e) * * *

                       EPA-Approved Michigan Nonregulatory and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                        Applicable          State
    Name of nonregulatory SIP          geographic or      submittal     EPA approval date         Comments
            provision               nonattainment area       date
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
                                                 Infrastructure
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
Section 110(a)(2) infrastructure   Statewide...........     3/8/2019  2/13/2023, [INSERT    Approved CAA
 requirements for the 2015 ozone                                       FEDERAL REGISTER      elements:
 NAAQS.                                                                CITATION].            110(a)(2)(A), (B),
                                                                                (C), (D)(i)(II)
                                                                                Prong 3, D(ii),
                                                                                (E)(i), (F), (G),
                                                                                (H), (J), (K), (L),
                                                                                and (M).
                                                                                Disapproved CAA
                                                                                elements:
                                                                                110(a)(2)(D)(i)(I)
                                                                                Prongs 1 and 2, and
                                                                                110(a)(2)(D)(i)(II)
                                                                                Prong 4. No action
                                                                                on CAA element
                                                                                110(1)(2)(E)(ii).

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

Subpart Y--Minnesota

0
12. Section 52.1220 is amended in the table in paragraph (e) by
revising the entry for ``Section 110(a)(2) Infrastructure Requirements
for the 2015 Ozone NAAQS'' to read as follows:

Sec.  52.1220  Identification of plan.

* * * * *
    (e) * * *

                                 EPA-Approved Minnesota Nonregulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                                            State
                                        Applicable        submittal
    Name of nonregulatory SIP          geographic or        date/       EPA approved date         Comments
            provision               nonattainment area    effective
                                                             date
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
Section 110(a)(2) Infrastructure   Statewide...........    10/1/2018  2/13/2023, [INSERT    Fully approved for
 Requirements for the 2015 Ozone                                       FEDERAL REGISTER      all CAA elements
 NAAQS.                                                                CITATION].            except transport
                                                                                elements of
                                                                                (D)(i)(I) Prong 2,
                                                                                which are
                                                                                disapproved, and no
                                                                                action has been
                                                                                taken on the
                                                                                visibility
                                                                                protection
                                                                                requirements of
                                                                                (D)(i)(II).
----------------------------------------------------------------------------------------------------------------

Subpart Z--Mississippi

0
13. Section 52.1273 is amended by adding paragraph (b) read as follows:

Sec.  52.1273   Control strategy: Ozone.

* * * * *
    (b) Disapproval. The state implementation plan (SIP) revision
submitted on September 3, 2019, addressing Clean Air Act section
110(a)(2)(D)(i)(I) (prongs 1 and 2) for the 2015 ozone national ambient
air quality standards (NAAQS) is disapproved.

Subpart AA--Missouri

0
14. Section 52.1323 is amended by adding paragraph (p) to read as
follows:

Sec.  52.1323  Approval status.

* * * * *
    (p) For the 2015 8-hour ozone NAAQS:
    (1) Disapproval. Missouri state implementation plan (SIP) revision
submitted on June 10, 2019, to address the Clean Air Act (CAA)
infrastructure requirements of section 110(a)(2) for the 2015 8-hour
ozone NAAQS, is disapproved for section 110(a)(2)(D)(i)(I) (prongs 1
and 2).
    (2) [Reserved]

Subpart DD--Nevada

0
15. Section 52.1472 is amended by adding paragraph (k) to read as
follows:

Sec.  52.1472  Approval status.

* * * * *
    (k) 2015 8-hour ozone NAAQS. The SIP submittal from October 1,
2018, is disapproved for Clean Air Act (CAA) section 110(a)(2)(D)(i)(I)
(prongs 1 and 2) for the NDEP, Clark County, and Washoe County portions
of the Nevada SIP submission.

Subpart FF--New Jersey

0
16. Section 52.1586 is amended by adding paragraph (c) and reserved
paragraph (d) to read as follows:

Sec.  52.1586  Section 110(a)(2) infrastructure requirements.

* * * * *
    (c) 2015 8-hour ozone NAAQS--(1) Disapproval. New Jersey SIP
revision submitted on May 13, 2019, to address the CAA infrastructure
requirements of section 110(a)(2) for the 2015 8-hour ozone NAAQS, is
disapproved for section 110(a)(2)(D)(i)(I) (prongs 1 and 2).
    (2) [Reserved]
    (d) [Reserved]

Subpart HH--New York

0
17. Section 52.1683 is amended by adding paragraph (v) to read as
follows:

Sec.  52.1683  Control strategy: Ozone.

* * * * *
    (v) Disapproval. The portion of the SIP revision submitted on
September 25, 2018, addressing Clean Air Act section 110(a)(2)(D)(i)(I)
(prongs 1 and 2) for the 2015 ozone NAAQS is disapproved.

Subpart KK--Ohio

0
18. Section 52.1870 is amended in the table in paragraph (e), under
``Infrastructure Requirements,'' by revising the entry for ``Section
110(a)(2) infrastructure requirements for the 2015 ozone NAAQS'' to
read as follows:

Sec.  52.1870  Identification of plan.

* * * * *
    (e) * * *

                         EPA-Approved Ohio Nonregulatory and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                        Applicable
              Title                    geographic or      State date      EPA approval            Comments
                                    nonattainment area
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
                                           Infrastructure Requirements
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
Section 110(a)(2) infrastructure   Statewide...........    9/28/2018  2/13/2023, [INSERT    Approved CAA
 requirements for the 2015 ozone                                       FEDERAL REGISTER      elements:
 NAAQS.                                                                CITATION].            110(a)(2)(A), (B),
                                                                                (C), (D)(i)(II)