obligation for Illinois, Michigan, Pennsylvania, Virginia, and West
Virginia). The EPA's time to conduct the modeling was additionally
constrained by the court-ordered deadline to take final action
addressing the good neighbor obligation for Kentucky by June 30,
2018. See Order, Sierra Club v. Pruitt, No. 3:15-cv-04328 (N.D. Cal.
May 23, 2017), ECF No. 73. Because the Kentucky action addressed the
same problem of regional interstate ozone transport for the 2008
ozone NAAQS, it was necessary to complete the modeling in time for
the EPA to issue a proposed action for Kentucky in advance of that
deadline.
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    If the EPA had analyzed air quality in 2020 instead of 2023, in
order to strictly adhere to the attainment dates under the Act, as the
commenters suggest, and identified downwind air quality problems in
that year, the agency would not have been able to identify any cost-
effective emission reductions that could be implemented in that year.
As explained earlier, the EPA has already addressed control strategies
that could be implemented in the short term and that were considered to
be cost-effective. If the EPA issued a rule that focused instead only
on the limited amount of emission reductions potentially achievable
from additional control strategies feasible to implement by 2020--i.e.,
from the optimization of SNCR--the EPA is not aware of any information
that would change its analysis of the cost-effectiveness of those
controls, and accordingly believes that those controls would be
unlikely to be implemented. Under these circumstances, any downwind air
quality problems projected in 2020 would remain.
    The EPA believes that a more substantial amount of emission
reductions is likely achievable from the implementation of new controls
(SCR and SNCR) at EGUs or from the implementation of various control
strategies at non-EGUs, but its analysis shows that such control
strategies could not be feasibly implemented by the 2020 attainment
date (or, indeed, for several years thereafter). Thus, if the EPA had
relied on modeling for 2020 to identify downwind air quality issues, as
the commenter urges, the EPA could not ensure that implementation of
the emission reductions achievable with these control strategies
several years later would be justified by continued downwind air
quality problems (a concern justified by the results of the 2023
modeling cited in this action). NOX emissions levels are
expected to decline in the future through the combination of the
implementation of existing local, state, and federal emission reduction
programs and changing market conditions for generation technologies and
fuels.\112\ Therefore, were the EPA to evaluate downwind ozone
concentrations and upwind state linkages in a future year that precedes
the date when actual compliance is anticipated (i.e., the timeframe
within which additional control strategies can feasibly be
implemented), the EPA could not ensure that the emission reductions
will be ``necessary to achieve attainment'' in any downwind area by the
time they were implemented. EME Homer City, 134 S. Ct. at 1608. While
the Supreme Court indicated that the EPA was entitled to ``leeway,''
id. at 1609, the EPA does not believe it would have been consistent
with the EME Homer City decisions to impose substantially greater
emission reductions several years after the modeling year used to
identify downwind air quality problems without ensuring that such
reductions would be necessary by the time that they can reasonably be
anticipated to be implemented, i.e., without ensuring that they would
not over-control relative to downwind air quality. Such an approach
would only replicate the circumstances the D.C. Circuit found
impermissible in CSAPR in EME Homer City II.
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    \112\ Annual Energy Outlook 2018. Electricity Supply,
Disposition, Prices, and Emissions. Reference Case. Department of
Energy, Energy Information Administration.
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    Thus, if the EPA were to rely on only air quality modeling for
2020, the EPA would be faced with a choice between the possibility of
under-control if it promulgated a rule focusing only on the cost-
effective emission reductions achievable by the 2020 ozone season, and
the potential for a significant amount of over-control if it
promulgated a rule requiring substantial emission reductions to be
implemented several years after any downwind ozone problems projected
in 2020. Given the limited availability of potential emission
reductions by the 2020 attainment date, the EPA instead has reasonably
chosen to model downwind air quality in a year associated with a
compliance timeframe consistent with the NOX control
strategies anticipated to result in more meaningful improvements in
downwind areas.
    While the EPA is aware of the modeling conducted by the OTC for
2020, the EPA does not believe that this information demonstrates that
the EPA's decision to model 2023 was unreasonable. As already noted,
the EPA has already implemented all cost-effective control strategies
that could be implemented in the near term under the CSAPR Update, and
does not believe additional cost-effective control strategies can be
implemented by the 2020 ozone season, even if the modeling did
appropriately identify downwind air quality problems in that year.
Moreover, despite asserting that the OTC used ``EPA-approved methods''
for the modeling, the commenter did not provide sufficient information
regarding the inputs and methodology for the modeling such that the EPA
could rely on the OTC modeling for purposes of this action. For the
same reasons described more fully below in section III.C.4 with regard
to the OTC's 2023 projections, the EPA also cannot conclude that the
projections are reliable for all of the areas identified as having
apparent projected air quality problems in 2020. Without reliable
projected design values, the EPA cannot appropriately determine whether
emission reductions implemented in that year (even assuming, contrary
to EPA's conclusions in this action, that any additional control
strategies that could be implemented in that year would be both
feasible and cost-effective) would under- or over-control upwind state
emissions.
    It is worth noting that the EPA was not aware at the time that it
selected the 2023 modeling year that the results would show no
remaining air quality problems in the East. The EPA certainly
anticipated that ozone concentrations would improve over time relative
to the 2017 modeling conducted for the CSAPR Update. However, the EPA
had previously conducted modeling for 2023, released in Janaury 2017
and discussed further in section III.C, that showed at least one
potential maintenance receptor in Tarrant County, Texas. See Notice of
Data

Availability, 82 FR 1733, 1737.\113\ The EPA accepted comments on this
modeling and made adjustments to the emission inventories and other
modeling inputs before running the model for 2023 again for purposes of
this action after determining that 2023 would also be an appropriate
year to evaluate for purposes of the remaining good neighbor
obligations for the 2008 ozone NAAQS. It was only upon completing this
additional modeling run that the EPA could conclude that, for the
purposes of these good neighbor obligations, it projected no further
air quality problems in 2023.
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    \113\ Although the modeling was conducted to evaluate air
quality relative to the more stringent 2015 ozone NAAQS, the data
show that the maximum design value for the Tarrant County, Texas
monitor was also expected to exceed the 2008 ozone NAAQS.
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    Comment: One commenter contends that the EPA's approach to
determining that 2023 is the appropriate analytic year is a reversal of
past agency interpretation regarding the four-step CSAPR framework. The
commenter states that the CSAPR Update, though only a partial remedy
under the good neighbor provision, acknowledged the 2018 attainment
deadline for Moderate nonattainment areas. The commenter asserts that
here, in contrast, the EPA has begun by assessing the feasibility of
installing an arbitrarily narrow set of new controls without regard to
the next attainment date. The commenter contends that this approach
turns the CSAPR framework on its head, unreasonably changing agency
interpretation without explanation and in violation of the Act.
    The commenter notes that control feasibility has played a role in
the past regional ozone rules, but contends that it cannot override the
obligation to prohibit pollution that prevents attainment and
maintenance of the standards, nor can it displace the attainment
deadlines. The commenter further asserts that when the EPA has
considered feasibility in analyzing ozone-related good neighbor
obligations since the North Carolina decision, it has not done so in
the context of selecting an analytic year, but in apportioning the
necessary emission reductions. The commenter explains that, in the
original CSAPR, feasibility of installing SO2 controls did
contribute to selecting two future analytic years, but contends that
the rule linked both analytic years to attainment deadlines, including
analysis of the next upcoming attainment year.
    Response: In the CSAPR Update, the EPA focused its analysis on the
upcoming attainment date and the limited control strategies that could
be implemented within that timeframe with the explicit understanding
that such a limited analysis was unlikely to provide a sufficient basis
to determine that the good neighbor obligation was fully addressed for
all states for the 2008 ozone NAAQS. Here, the EPA is obligated to
conduct an analysis that fully addresses the good neighbor provision
and thus has selected a future analytic year to coincide with the
timeframe in which emission reductions most likely to address that
obligation could be implemented, rather than selecting a year in which
few emission reductions could be implemented. Selection of an analytic
year associated with anticipated future compliance is entirely
consistent with the EPA's four-step framework as applied in prior
rulemakings. See, e.g., NOX SIP Call, 63 FR 57450 (using the
anticipated 2007 compliance year for its analysis); CAIR, 70 FR 25241
(using the years 2009 and 2010, the anticipated compliance years for
the ozone and PM2.5 NAAQS, respectively); CSAPR, 76 FR 48211
(using the 2012 compliance year); CSAPR Update, 81 FR 74537 (using the
2017 compliance year).
    The commenter is also incorrect to suggest that the EPA's approach
is inconsistent with the original CSAPR rulemaking, which addressed
good neighbor obligations for the 1997 ozone NAAQS. While it is true
that the EPA considered attainment dates in its CSAPR analysis, the
commenter fails to acknowledge that the EPA considered the entire suite
of attainment dates for the relevant NAAQS, including the ``maximum''
future attainment dates that CSAPR's later compliance phase was
intended to address. 76 FR 48277-78. Thus, in establishing two phases
of compliance in 2012 and 2014, the EPA considered attainment dates for
the ozone NAAQS between 2007 and 2024, and for the PM2.5
NAAQS, the EPA considered attainment dates ranging from 2010 to 2019.
Id. Moreover, as the commenter acknowledges, the EPA established two
compliance phases in CSAPR based on the feasibility of implementing
certain control strategies. Id. at 48278. In the earlier phase, the EPA
anticipated that the covered EGUs would undertake more easily
implemented control strategies that could be implemented in the short
term, including optimization of existing controls, installation of
relatively simple NOX controls, and generation shifting, see
id. at 48279, the same control strategies already considered and
implemented for the 2008 ozone NAAQS in the CSAPR Update. The EPA
determined that a later compliance phase was justified based on the
need for more time to feasibly implement other controls strategies. Id.
at 48278 (``Given the time needed to design and construct scrubbers at
a large number of facilities, EPA believes the 2014 compliance date is
as expeditious as practicable for the full quantity of SO2
reductions necessary to fully address the significant contribution to
nonattainment and interference with maintenance.''). The EPA's approach
to the 2008 ozone NAAQS has been consistent with ths earlier approach,
except that the EPA has evaluated these two categories of control
strategies in two separate actions (i.e., the CSAPR Update and this
action) rather than in a single rulemaking specifically to ensure that
the first phase of reductions could be implemented as soon as possible.
    To the extent that the commenters suggest that the EPA chose an
earlier analytic year in prior rulemakings, the EPA notes that it has
not done so in all rulemakings. In the NOX SIP Call, the EPA
evaluated air quality in 2007, nine years after the rule was
promulgated. 63 FR 57377 (October 27, 1998). In CAIR, which was
promulgated in 2005, the EPA evaluated air quality in 2009 and 2010,
for the ozone and PM2.5 NAAQS, respectively. 70 FR 25241
(May 12, 2005). Thus, the EPA's approach in this action is not
inconsistent with these prior actions. Although the EPA evaluated
relatively more near-term air quality in CSAPR and CSAPR Update, the
EPA expected that certain cost-effective control strategies could be
implemented in the near term in those actions. Here, the EPA has
already analyzed and implemented those cost-effective control
strategies that could be implemented quickly to address the 2008 ozone
NAAQS through the CSAPR Update. Accordingly, any further emission
reductions that may be required to address the 2008 ozone NAAQS would
necessarily be implemented through control strategies that cannot be
implemented in the near term and require a longer period for
implementation.

C. Air Quality Analysis

    In this section, the agency describes the air quality modeling
performed, consistent with step 1 of the framework described in section
III.A, to identify locations where it expects nonattainment or
maintenance problems with respect to the 2008 ozone NAAQS in the 2023
analytic year. This section includes information on the air quality
modeling platform used in support of the final determination with a
focus on the base year and future base case emission inventories. The
June 2018 Air

Quality Modeling Technical Support Document (AQM TSD) in the docket for
this action contains more detailed information on the air quality
modeling for 2023 used to support the final determination.\114\
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    \114\ And available online at https://www.epa.gov/airmarkets/proposed-csapr-close-out.
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    In addition to the proposal, 83 FR 31915 (July 10, 2018), the EPA
provided an additional opportunity to comment on the air quality
modeling platform and air quality modeling results that are used in
this determination when it published a Notice of Data Availability (82
FR 1733) on January 6, 2017, which provided the preliminary modeling
results for the 2023 analytic year. Specifically, in the NODA the EPA
requested comment on the data and methodologies related to the 2011 and
2023 emission inventories and the air quality modeling to project 2023
ozone concentrations and ozone contributions. While the EPA issued this
NODA to provide information to assist state interstate transport
planning for the 2015 ozone NAAQS (which is set at 70 ppb), the
modeling approaches and future year projection methods were also
applicable to the 2008 ozone NAAQS (set at 75 ppb). In fact, commenters
explicitly commented on these methods with respect to the 2008 ozone
NAAQS. The EPA considered comments received on the NODA in the
development of the air quality modeling analysis used for proposal. As
discussed below and in the Response to Comments (RTC) in the docket for
this action, we have considered additional comments on emission
inventories and air quality modeling submitted in response to the
proposal for this action for this final determination. However, the EPA
did not find that any of these comments raised concerns with the
modeling discussed at proposal such that additional air quality
modeling was merited. Accordingly, the emission inventories and
modeling discussed in the following sections is the same information
discussed in the EPA's proposed action.
1. Overview of Air Quality Modeling Platform
    The EPA performed nationwide photochemical modeling for 2023 to
identify nonattainment and maintenance receptors relevant for the 2008
ozone NAAQS. For this action, the EPA performed air quality modeling
for two emissions scenarios: (1) A 2011 base year; and (2) the 2023
analytic year (i.e., a business-as-usual scenario in 2023: One without
any additional interstate ozone transport requirements beyond those
imposed by the CSAPR Update). The modeling results for 2023 presented
here were originally released to the public with an accompanying
memorandum on October 27, 2017.\115\
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    \115\ Memorandum from Stephen D. Page, Director, Office of Air
Quality Planning and Standards, to Regional Air Division Directors,
Regions 1-10, Supplemental Information on the Interstate Transport
State Implementation Plan Submissions for the 2008 Ozone National
Ambient Air Quality Standards under Clean Air Act Section
110(a)(2)(D)(i)(I) (Oct. 27, 2017), available at https://www.epa.gov/airmarkets/october-2017-memo-and-supplemental-information-interstate-transport-sips-2008-ozone-naaqs.
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    The 2011 base year has previously been used to support the CSAPR
Update proposal and final rule. The EPA chose to continue using 2011 as
the base year because when EPA's analyses commenced, 2011 was the most
recent emissions modeling platform available that included future year
projected inventories needed for transport analyses. Using 2011 as a
base year also remains appropriate from the standpoint of good modeling
practice. The meteorological conditions during the summer of 2011 were
generally conducive for ozone formation across much of the U.S.,
particularly the eastern U.S. As described in the AQM TSD, the EPA's
guidance for ozone attainment demonstration modeling, hereafter
referred to as the modeling guidance, recommends modeling a time period
with meteorology conducive to ozone formation for purposes of
projecting future year design values.\116\ The EPA therefore believes
that meteorological conditions and emissions during the summer of 2011
provide an appropriate basis for projecting 2023 ozone concentrations.
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    \116\ U.S. Environmental Protection Agency, 2014. Modeling
Guidance for Demonstrating Attainment of Air Quality Goals for
Ozone, PM2.5, and Regional Haze, Research Triangle Park,
NC, available at http://www.epa.gov/ttn/scram/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.pdf.
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    For this rule, the EPA used the Comprehensive Air Quality Model
with Extensions (CAMx) version 6.40 \117\ to simulate pollutant
concentrations for the 2011 base year and the 2023 future year
scenarios. This version of CAMx was the most recent publicly available
version of this model at the time that the EPA performed air quality
modeling for this final rule. CAMx is a grid cell-based, multi-
pollutant photochemical model that simulates the formation and fate of
ozone and fine particles in the atmosphere. The CAMx model applications
were performed for a modeling region (i.e., modeling domain) that
covers the contiguous 48 United States, the District of Columbia, and
adjacent portions of Canada and Mexico using grid cells with a
horizontal resolution of 12 km x 12 km. A map of the air quality
modeling domain is provided in the AQM TSD.
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    \117\ CAMx v6.40 was the most recent public release version of
CAMx at the time the EPA updated its modeling in fall 2017.
Comprehensive Air Quality Model with Extensions version 6.40 User's
Guide. Ramboll Environ, December 2016, available at http://www.camx.com/.
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    The 2011-based air quality modeling platform includes 2011 base
year emissions, 2023 future year projections of these emissions, and
2011 meteorology for air quality modeling with CAMx. In the remainder
of this section, the EPA provides an overview of the 2011 and 2023
emission inventories and the methods for identifying nonattainment and
maintenance receptors along with a list of the receptors in the U.S.
that EPA projected would have nonattainment and maintenance air quality
problems in 2023 (in the business-as-usual scenario).
    To ensure the reliability of its modeling results, the EPA
conducted an operational model performance evaluation of the 2011
modeling platform by comparing the 8-hour daily maximum ozone
concentrations predicted during the May through September ozone season
to the corresponding measured concentrations in 2011. This evaluation
generally followed the approach described in the modeling guidance.
Details of the model performance evaluation are described in the AQM
TSD. The model performance results indicate that the 8-hour daily
maximum ozone concentrations predicted by the 2011 CAMx modeling
platform generally reflect the corresponding magnitude of observed 8-
hour ozone concentrations on high ozone days in the 12-km U.S. modeling
domain. These results provide confidence in the ability of the modeling
platform to provide a reasonable projection of expected future year
ozone concentrations and contributions.\118\
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    \118\ As recommended in the modeling guidance, the acceptability
of model performance was judged by considering the 2011 CAMx
performance results in light of the range of performance found in
recent regional ozone model applications. These other modeling
studies represent a wide range of modeling analyses that cover
various models, model configurations, domains, years and/or
episodes, and chemical mechanisms. Overall, the ozone model
performance results for the 2011 CAMx simulations are within the
range found in other recent peer-reviewed and regulatory
applications. The model performance results, as described in the AQM
TSD, demonstrate that the predictions from the 2011 modeling
platform correspond to measured data in terms of the magnitude,
temporal fluctuations, and spatial differences for 8-hour daily
maximum ozone.

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2. Emission Inventories
    The EPA developed emission inventories for this rule, including
emissions estimates for EGUs, non-EGU point sources, stationary
nonpoint sources, onroad mobile sources, nonroad mobile sources,
wildfires, prescribed fires, and biogenic emissions. The EPA's air
quality modeling relies on this comprehensive set of emission
inventories because emissions from multiple source categories are
needed to model ambient air quality and to facilitate comparison of
model outputs with ambient measurements.
    To prepare the emission inventories for air quality modeling, the
EPA processed the emission inventories using the Sparse Matrix Operator
Kernel Emissions (SMOKE) Modeling System version 3.7 to produce the
gridded, hourly, speciated, model-ready emissions for input to the CAMx
air quality model. Additional information on the development of the
emission inventories and on datasets used during the emissions modeling
process for this final rule is provided in the October 2017 Technical
Support Document ``Additional Updates to Emission Inventories for the
Version 6.3, 2011 Emissions Modeling Platform for the Year 2023''
(Emissions Modeling TSD).\119\
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    \119\ This TSD is also available in the docket for this final
action and at https://www.epa.gov/air-emissions-modeling/additional-updates-2011-and-2023-emissions-version-63-platform-technical.
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    As noted earlier, the emission inventories, methodologies, and data
used for the air quality modeling discussed in this final rule are the
same as the inventories discussed at proposal as no new modeling was
performed following the proposal. The inventories incorporate comments
received on the January 2017 NODA along with improved data and methods
that became available after the NODA modeling was completed. The
inventories are documented in the Emissions Modeling TSD. The January
2017 NODA itself was developed after taking into account the several
iterations of comments on the data and methods used in the 2011
emissions modeling platform.\120\
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    \120\ The initial modeling platform based on the 2011 National
Emissions Inventory (NEI) was first released for public comment in
November 2013 through a NODA (78 FR 70935). In developing the CSAPR
Update, the EPA subsequently updated the base year 2011 emission
inventory as well as future year inventories for that rulemaking and
took comment on those updates. Notice of Data Availability, 79 FR
2437 (January 2014); CSAPR Update proposal, 80 FR 46271 (August
2015); CSAPR Update final, 81 FR 74527 (September 2016). Technical
support documents are available for each iteration of the
inventories on EPA's emissions modeling website: https://www.epa.gov/air-emissions-modeling/2011-version-6-air-emissions-modeling-platforms.
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    As noted above, the EPA uses emissions data from the year 2011 in
its base year air quality modeling. The 2011 NOX and
SO2 EGU emissions are based primarily on reported data from
continuous emissions monitoring systems (CEMS). Other EGU pollutants in
the 2011 emission inventories are estimated using emissions factors and
annual heat input data reported to the EPA. For EGUs without CEMS, the
EPA used data submitted to the National Emissions Inventory (NEI) by
the states. The 2011 inventories also include some updates to 2011 EGU
stack parameters and emissions made in response to comments on the
January 2017 NODA. For more information on the details of how the 2011
EGU emissions were developed and prepared for air quality modeling, see
the Emissions Modeling TSD.
    In developing the 2023 emission inventory, the EPA did not
incorporate any new interstate transport emission reductions beyond the
CSAPR Update, but the 2023 projected emission inventory does reflect
expected changes in activity and emission reductions from on-the-books
actions, including planned emission control installations and
promulgated federal measures that affect anthropogenic emissions. The
emission inventories for air quality modeling include some emissions
categories that are held constant between the base and future years,
such as biogenic emissions and emissions from agricultural, wild, and
prescribed fires.\121\ The emission inventories used for Canada were
received from Environment and Climate Change Canada in April 2017 and
were provided for the years 2013 and 2025. This was the first time that
future year projected inventories for Canada were provided directly by
Environment and Climate Change Canada and the new inventories are
thought to be an improvement over inventories projected by EPA. The EPA
used the Canadian emission inventories without adjusting the emissions
to the represented year because the EPA lacks specific knowledge
regarding Canadian emissions trends and because the interval of years
(i.e., 12) was the same as that used for the U.S. modeling which relied
on a 2011 to 2023 interval. For Mexico, onroad mobile source inventory
data were based on 2011 and 2023 runs of MOVES-Mexico. For area,
nonroad, and point source emissions in Mexico, EPA used the Inventario
Nacional de Emisiones de Mexico using 2018 and 2025 data projections to
interpolate 2023 estimates.
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    \121\ Biogenic emissions and emissions from wildfires and
prescribed fires were held constant between 2011 and 2023 because:
(1) These emissions are tied to 2011 meteorological conditions and
(2) the focus of this action is on the contribution from
anthropogenic emissions to projected ozone nonattainment and
maintenance.
---------------------------------------------------------------------------

    As noted in the October memo, the EPA projected EGU emissions for
the 2023 emission inventory based on an approach that combines the
latest reported operational data with known and anticipated fleet and
pollution controls changes. The EPA begins with the most recent
reported ozone season data available at the time of the EPA's
analysis--in this case, 2016 SO2 and NOX data
from units reporting under the Acid Rain and CSAPR programs under 40
CFR part 75. The EPA then updated the 2016 reported emissions with
unit-specific adjustments to account for upcoming announced
retirements, post-combustion control retrofits, coal-to-gas
conversions, combustion controls upgrades, new units, and on-the-books
reductions such as CSAPR Update compliance, state rules, and Best
Available Retrofit Technology (BART) requirements under the regional
haze program of the CAA.\122\ The EPA implemented reductions associated
with the CSAPR Update in its emission projection, because the 2016
reported data did not reflect the implementation of this rule, by
assuming each SCR-controlled unit in the CSAPR Update region not
already emitting at or below 0.10 lb/mmBtu would do so beginning in
2017. For emissions from EGUs not reporting under 40 CFR part 75, the
EPA largely relied on unadjusted 2011 NEI data for its 2023
assumptions.\123\ We note that the EPA's approach to projecting 2023
EGU emissions is consistent with the approach the EPA used in the CSAPR
Update to project the future EGU emissions baseline from which to
estimate reduction potential. 81 FR 74543.\124\ Additional details
about the EPA's future year EGU emissions projections are provided in
the Emissions Modeling TSD.
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    \122\ The EPA uses the U.S. EIA Form 860 as a source for
upcoming controls, retirements, and new units.
    \123\ Available at https://www.epa.gov/air-emissions-modeling/2011-version-63-platform.
    \124\ Also see the Ozone Transport Policy Analysis Final Rule
Technical Support Document. EPA. August 2016. Available at https://www.epa.gov/sites/production/files/2017-05/documents/ozone_transport_policy_analysis_final_rule_tsd.pdf.
---------------------------------------------------------------------------

    Non-EGU point source emissions in the 2011 inventory are generally
based on the 2011 NEI version 2.\125\ However,

the NEI emission inventories must be processed into a format that is
appropriate for the air quality model to use. Details on the
development and processing of the emissions for 2011 are available in
the Emissions Modeling TSD. The TSD also describes the EPA's
methodology for developing the non-EGU emissions for the 2023 emission
inventory. Projection factors and percent reductions used to estimate
2023 emissions in this final rule reflect comments received through the
January 2017 NODA, along with emission reductions due to national and
local rules, control programs, plant closures, consent decrees, and
settlements. The Emissions Modeling TSD contains details on the factors
used and on their respective impacts on the emission inventories.
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    \125\ For more information on the 2011 National Emissions
Inventory version 2, see https://www.epa.gov/air-emissions-inventories/2011-national-emissions-inventory-nei-technical-support-document.
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    As noted in the proposal, the EPA updated its methodology for
estimating point and nonpoint 2023 emissions from the oil and gas
sector after the release of the January 2017 NODA. The projection
factors used in the updated 2023 oil and gas emission inventory
incorporate state-level factors based on historical growth from 2011-
2015 and region-specific factors that represent projected growth from
2015 to 2023. The 2011-2015 state-level factors were based on
historical state oil and gas production data published by the U.S.
Department of Energy's Energy Information Administration (EIA), while
the 2015-2023 factors are based on projected oil and gas production in
EIA's 2017 Annual Energy Outlook (AEO) Reference Case without the Clean
Power Plan for the six EIA supply regions. The 2017 AEO was the latest
available at the time the modeling was performed. Details on the
revised methodology that the EPA used to project oil and gas emissions
to 2023, as well as changes to the base year 2011 and future year 2023
emission inventories for other sectors, can be found in the Emissions
Modeling TSD.
    The EPA developed the onroad mobile source emissions for both the
2011 and 2023 inventories using the EPA's Motor Vehicle Emissions
Simulator, version 2014a (MOVES2014a). The agency computed these
emissions within SMOKE by multiplying the MOVES-based emissions factors
with activity data appropriate to each inventory year. MOVES2014a
reflects projected changes to fuel usage and onroad mobile control
programs finalized as of March 2014, which include emission reductions
expected to occur into the future. Therefore, for the 2011 inventory,
those rules that were in effect in 2011 are reflected at a level that
corresponds to the extent to which each rule had penetrated the fleet
and fuel supply by that year, and similarly for the 2023 inventory.
Local control programs such as the California Low Emission Vehicle
(LEV) III program, also implemented in states other than California
that have adopted California's program pursuant to CAA section 177, are
included in the onroad mobile source emissions. Activity data for
onroad mobile sources, such as the expected vehicle miles traveled in
2023, were projected for future year using trends identified in AEO
2016.
    The commercial marine category 3 vessel (``C3 marine'') emissions
in the 2011 emission inventory for this rule are equivalent to those in
the 2011NEIv2 with the inclusion of updated emissions for California.
These emissions reflect reductions associated with the Emissions
Control Area proposal to the International Maritime Organization
control strategy (EPA-420-F-10-041, August 2010); reductions of
NOX, VOC, and CO emissions for new C3 engines that went into
effect in 2011; and fuel sulfur limits that went into effect as early
as 2010. The cumulative impacts of these rules, which will achieve
additional reductions through 2023, are incorporated in the 2023
projected emissions for C3 marine sources. For this modeling, the
larger C3 marine sources are treated with plume rise, thereby putting
the emissions into model layers higher than ground-level. This was done
because the ships have stacks that release emissions higher than the
20-meter threshold for the ground-level layer in the air quality model.
The height at which the emissions are inserted into the model impacts
how the emissions are transported within the model. The emissions from
the smaller category 1 (C1) and category 2 (C2) vessels are still
released into the ground-level layer of the model.
    To develop the nonroad mobile source emission inventories other
than C3 marine for the modeling platform, the EPA used monthly, county,
and process-level emissions output from the National Mobile Inventory
Model (NMIM) (http://www.epa.gov/otaq/nmim.htm). The nonroad mobile
emissions control programs include reductions in emissions from
locomotives, diesel engines, and marine engines, along with standards
for fuel sulfur content and evaporative emissions. A comprehensive list
of control programs included for mobile sources is available in the
Emissions Modeling TSD.
    The emissions for stationary nonpoint sources in the 2011 emission
inventory are generally derived from the 2011 NEI version 2. For more
information on nonpoint source emissions in the 2011 emission
inventory, see the Emissions Modeling TSD and the 2011NEIv2 TSD. 2023
emissions for stationary nonpoint sources were projected using a
variety of factors, including AEO 2017 projections for 2023 and state
projection factors using EIA data from 2011-2015. The 2023 emission
inventory in the EPA's proposal and this final rule also incorporate
information from states about projected control measures or changes in
nonpoint source emissions provided in comments to the January 2017
NODA. These changes were limited and are discussed in the Emissions
Modeling TSD.
    Comment: While some commenters agreed with the reasonableness of
the EPA's projections, others contend that the EPA's EGU emission
projections are unreasonable for a variety of reasons. These commenters
assert that actual 2023 emissions may be higher than modeled due to low
CSAPR Update allowance prices or natural gas price uncertainty. They
suggest that the 0.10 lb/mmBtu average used by EPA for SCR-controlled
units covered by the CSAPR Update is not reasonable because some units
may operate at higher levels in the future, and they also suggest that
EPA should have incorporated impacts of the proposed repeal of the
Clean Power Plan and the proposed Affordable Clean Energy (ACE) rule
into its emissions projections.
    Response: The EPA disagrees with the suggestion that its 2023 EGU
emission projections and the underlying methodology to generate those
projections are unreasonable. As with all projections, there is
inherent uncertainty, but with respect to EGU NOX emissions,
the EPA's 2023 projections likely reflect a more conservative (i.e.,
higher) NOX emissions estimate than comparable alternative
methods for projecting future EGU emissions. As explained above, the
EPA's 2023 EGU emissions projections used reported 2016 data, adjusting
that data based only on currently known changes in the power sector and
a change in emission rate to reflect implementation of the CSAPR Update
after 2017. As such, the EPA's approach does not account for changes
that would be estimated to occur due to economic and other
environmental policy factors. Trends in historic emissions data and
emission projections using a variety of methods and models suggest that
inclusion of these factors would likely further reduce future
NOX emission projections. To illustrate the potential for
additional NOX reductions when considering further factors,
we note that

nationwide 2023 EGU NOX emission projections using various
modeling approaches estimate lower NOX emission futures than
the methodology EPA applied here. The EPA's EGU emissions projection
methodology estimates that 2023 NOX emissions will be 20%
below 2016 levels whereas EIA estimates that 2023 NOX
emissions will be 21% to 32% below 2016 levels and EPA's Integrated
Planning Model estimates that 2023 NOX emissions will be 28%
below 2016 levels.126 127
---------------------------------------------------------------------------

    \126\ EIA 2018 Annual Energy Outlook, Reference Case and High
Oil and Gas Resource and Technology side case. Table 8 ``Electricity
Supply, Disposition, Prices, and Emissions,'' available at https://www.eia.gov/outlooks/aeo/.
    \127\ IPM Version 6--Initial Run, available at https://www.epa.gov/airmarkets/clean-air-markets-power-sector-modeling.
---------------------------------------------------------------------------

    The EPA neither intends nor expects to be able to predict future
emissions from each of thousands of EGUs.\128\ And it does not expect
each of these SCR-controlled units to emit at the fleet-wide
technology-specific average emission rate that it uses in its EGU
emissions projections. Some of the units will over-perform and some of
the units will under-perform in comparison to this average rate, but
the average rate nevertheless reflects both a reasonable compliance
pathway in response to the CSAPR Update and a reasonable fleet average
for that compliance pathway. Predicting each unit's individual emission
rate is an exercise in increased uncertainty, and the use of an average
technology-specific fleet emission rate for each unit reduces that
uncertainty. Moreover, in a trading program with state-specific caps,
sources are permitted the flexibility to emit in a variety of ways
provided the state and regional caps are met. The compliance success is
not gauged on unit-level operation and emissions, but rather state and
regional operation and emission levels. (The same holds true for
gauging the reasonableness and accuracy of projections for such
programs.) This compliance mechanism promotes more cost-effective
attainment of the emissions and air quality goals. Therefore, it is
plausible--and entirely consistent with EPA projections--that sources
in each state would find an alternative compliance pathway that
achieves commensurate emission reductions in equally relevant parts of
the upwind airshed.
---------------------------------------------------------------------------

    \128\ EPA-HQ-OAR-2018-0225-0042 at 98; EPA-HQ-OAR-2009-0491-4512
(RTC at 4).
---------------------------------------------------------------------------

    The EPA's EGU assumptions for 2023 reflected ozone-season emission
levels that were approximately 10 percent lower than the CSAPR Update
budgets. 2017 ozone-season data reflected emissions that were already 7
percent below the CSAPR Update budgets, reflecting a 21 percent drop
from the prior year, a pace of reduction that would, if continued, put
actual emissions well below 2023 assumptions. Preliminary 2018 data
suggest continuing reductions, and indicate that the CSAPR Update
region is already in 2018 emitting at or near the EPA-assumed 2023
emission level. In other words, the emission levels that commenters
suggest are unreasonable for 2023 may well already have been achieved
or nearly achieved in 2018--five years ahead of the analytic year. In
order for emissions in 2023 to be at the levels commenters prefer that
the EPA model (e.g., only emission levels that can be ensured via
enforceable limits), a decade-long decline in ozone-season emissions
would have to not only cease but reverse. Moreover, this would have to
occur during a time period where significantly more high-emitting coal
generation capacity has announced plans to retire and significantly
more zero- or lower-emitting generation capacity is expected to come
online. In particular, since the EPA in 2017 made EGU projections for
2023 (in which the EPA only assumed retirements that had already been
planned and announced at the time it made the projections), many
additional high emitting coal units have announced their plans to
retire by 2023. 5.9 gigawatts (GW) of coal capacity retirements were
announced and planned for 2019-2022 based on the June 2017 EIA 860m
Form, but that same form a year later (June 2018 EIA Form 860m) shows
10.2 GW of coal retirements for that same period, reflecting a near
doubling of coal retirement announcements occurring over a one-year
period. For instance, Conesville Units 4, 5, and 6 in Ohio have
announced their retirement prior to 2023. The EPA in its 2017
projections had assumed these units would be operating and collectively
emitting 1,502 tons of NOX in the 2023 ozone season. These
additional retirements announced subsequent to the EPA's analysis
further bolster the conclusion that the EPA's emission estimates are
conservative (i.e., that they may overpredict 2023 emissions). The
magnitude of coal retirements like this, announced after the EPA's
analysis, but scheduled to occur prior to 2023, suggests the emissions
trend will continue downward. Moreover, the commenters' assertion that
an assumed increase would be a more reasonable projection is not
supported by compelling analysis or economic modeling: It contradicts
the recent historical data, the most recent announcements on
retirements and newly built capacity, and the widely used power sector
models' outlook for 2023. The EPA believes, supported by the most
recent reported data, that its 2023 EGU projections are reasonable and
conservative. To the extent that actual 2023 emissions may differ from
these projections, they are more likely to be even lower than the
assumptions used in the EPA's modeling.
    The utility and the reasonableness of the EPA's EGU projections
hinge on state-level and regional-level EGU emission projections, not
projections for individual units or groups of units within a state.
Nonetheless, the EPA notes that the assumed average emission rate for
units with SCR optimization potential was quite consistent with the
observed compliance measures. That is, the most recent historical data
reported by unit operation, discussed in more detail in section
III.B.2, bears out EPA assumptions in the CSAPR Update that these units
would lower their emission rates in response to that rule, as they did
in fact lower their emission rate 45 percent in the first year of the
program.
    The EPA also disagrees with the assertion that that low allowance
prices necessarily mean that emissions will be higher than the EPA's
EGU projections. In a scenario where all other elements of the power
sector and allowance market are held constant, the commenters
observation would likely be realized. However, it is the EPA's
experience with trading programs that those other variables do not
remain constant over time. In most cases, lower allowance prices
reflect the market's expectation that future emissions will be lower
than anticipated, rather than higher, as other market forces continue
to drive down emissions, thus decreasing demand for allowances
authorizing those emissions. The commenters' claim is therefore not
consistent with observed historical emission patterns over successive
years of an allowance trading program's implementation. For example,
regional emissions under the Acid Rain Program and CSAPR have
consistently been below the sum of emission budgets, despite relatively
low allowance prices.\129\ The commenters' claim is also not consistent
with forward-looking emissions projections in power sector models.
There are a variety of policy and market forces at work beyond CSAPR
Update allowance prices that are

anticipated to continue to drive generation shifting from higher-
emitting to lower-emitting sources. These include changes such as:
Sustained, lower natural gas prices that make lower-emitting natural
gas combined cycle units more economic to build and dispatch; state
energy policy and technology advancements which have made renewable
energy (e.g., solar and wind) more competitive compared to higher-
emitting fossil-fuel fired generation; and the aging of the coal fleet
which is leading many companies to conclude that a significant number
of higher-emitting plants are reaching the end of their useful economic
life. The EPA's experience implementing prior allowance trading
programs shows that emissions from covered sources generally trend
downwards (regardless of allowance price) as time extends further from
the initial compliance year. Both the Acid Rain Program and CSAPR
SO2 allowance banks grew in 2017 from their 2016 levels,
indicating that sources are collectively adding to the bank by emitting
below state budgets rather than drawing down the bank because of the
availability of low-cost allowances. This supports the EPA's belief
that the assumptions underlying its projection of 2023 ozone-season
NOX levels for EGUs are reasonable and appropriate.
---------------------------------------------------------------------------

    \129\ See 2016 Program Progress--Cross-State Air Pollution Rule
and Acid Rain Program available at https://www3.epa.gov/airmarkets/progress/reports/index.html.
---------------------------------------------------------------------------

    To the extent that commenters assert that the EPA cannot in its
projections perfectly predict future natural gas prices, the EPA
agrees. Projections are inherently uncertain, and the EPA believes it
has made reasonable and conservative estimates regarding the role of
natural gas prices in generation shifting and lower future emission
reductions. The EPA's EGU projection method for this action started
with existing data and only assumed generation shifting in instances
where retirements were scheduled to occur and newly built capacity was
scheduled to come online. In other words, the generation shifting
assumed for 2023 reflects concrete, planned actions. The agency's
applied projection method would suggest that the EPA's 2023 projections
are conservative and that more, not less, generation shifting is likely
to occur as we remain in a low natural gas price environment that is
complemented by debottlenecking of Marcellus region natural gas
production through significant new pipeline and pipeline capacity
expansion in the 2017-2023 timeframe.
    With regard to comments stating that the EPA should factor the
proposed ACE rule into its 2023 outlook, the EPA notes it has not done
so as the ACE rule is not final. Moreover, it has not factored the
Clean Power Plan into its projections given the stay of that rule
issued by the Supreme Court. Both of these assumptions are reasonable
and consistent with EPA analytic precedents and OMB Circular A-4
guidance (requiring that regulatory baselines should reflect the future
effect of current government programs and policies).130 131
---------------------------------------------------------------------------

    \130\ Regulatory Impact Analysis for the Proposed Emission
Guidelines for Greenhouse Gas Emissions from Existing Electric
Utility Generating Units; Revisions to Emission Guideline
Implementing Regulations; Revisions to New Source Review Program.
EPA. Table ES-8. August 2018. Available at https://www.epa.gov/sites/production/files/2018-08/documents/utilities_ria_proposed_ace_2018-08.pdf.
    \131\ Regulatory Impact Analysis for the Proposed Emission
Guidelines for Greenhouse Gas Emissions from Existing Electric
Utility Generating Units; Revisions to Emission. Table ES-8.
Available at https://www.epa.gov/sites/production/files/2018-08/documents/utilities_ria_proposed_ace_2018-08.pdf.
---------------------------------------------------------------------------

    Comment: For mobile source and non-EGU emissions, commenters
suggest that emissions projections for these sectors could be
unreliable due to the EPA's planned rulemaking actions including the
proposed repeal of regulations with respect to so-called ``glider''
vehicles, engines, and kits, 82 FR 53442 (Nov. 16, 2017) (proposing to
repeal the Greenhouse Gas Emissions and Fuel Efficiency Standards for
Medium- and Heavy-Duty Engines and Vehicles--Phase 2); the proposed
Safer Affordable Fuel Efficient (SAFE) Vehicles Rule for Model Years
2021-2026 Passenger Cars and Light Trucks, 83 FR 42986 (Aug. 24, 2018)
(proposing to repeal the Corporate Average Fuel Economy (CAFE)
standards); and the proposed withdrawal of Control Techniques
Guidelines (CTG) for the Oil and Natural Gas Industry, 83 FR 10478
(Mar. 9, 2018).
    Response: The EPA disagrees that its 2023 projections are
unreliable because of potential changes to other regulations. The EPA
first notes any potential regulatory changes to the ``glider''
regulations, the SAFE vehicle rules, and the oil and gas CTG have not
been finalized. In general, the mobile source and non-EGU emission
inventories do not reflect rulemakings finalized in calendar year 2016
or later, nor do they reflect any rules proposed but not yet finalized
since 2016, as only finalized rules are reflected in modeling
inventories. The EPA's normal practice is to only include changes in
emissions from final regulatory actions in its modeling because, until
such rules are finalized, any potential changes in NOX or
VOC emissions are speculative.
    In addition, even if emissions were to change as a result of any
such final rules, commenters have not indicated how and whether these
additional emissions would affect downwind ozone concentrations. The
model year 2017-2025 GHG regulations for cars and light trucks were
projected to yield small but measurable criteria and toxic emission
reductions from vehicles.\132\ Because the vehicles affected by the
2017-2025 GHG standards would still need to meet applicable criteria
pollutant emissions standards (e.g., the Tier 3 emissions standards; 79
FR 23414), the regulatory impact analysis that accompanied the proposed
revision to the GHG standards estimated a very limited impact on
criteria and toxic pollutant emissions (increases in upstream emissions
and decreases in tailpipe emissions). Moreover, the proposed SAFE
Vehicles Rule specifically notes that none of the regulatory
alternatives considered ``would noticeably impact net emissions of
smog-forming or other `criteria' or toxic air pollutants.'' 83 FR
42996. As to glider kits in particular, we note that the ``no action
assurance'' provided by then-Administrator Pruitt via memorandum of
July 6, 2018, was subsequently rescinded via a memorandum signed by
Acting Administrator Wheeler on July 26, 2018, and that the EPA has not
taken any further final action that would change any requirements for
glider vehicles, glider engines, or glider kits.
---------------------------------------------------------------------------

    \132\ See Table 4.3-19 in EPA Regulatory Impact Analysis for
EPA's Final Rulemaking for 2017-2025 Light-Duty Vehicle Greenhouse
Gas Emission Standards and Corporate Average Fuel Economy Standards
(EPA-420-R-12-016, August 2012).
---------------------------------------------------------------------------

    Finally, with regard to the proposed withdrawal of the oil and gas
CTG, we also note that impacts of the CTGs were not included in the
modeled inventories, so their withdrawal would not change the results
of the modeling.
3. Definition of Nonattainment and Maintenance Receptors
    In this action, the EPA is continuing to apply the CSAPR Update
approach to identifying nonattainment and maintenance receptors for the
2008 ozone NAAQS in the 2023 analytic year. The EPA here describes the
analytical approach pursued in the CSAPR Update with regard to the good
neighbor requirements for the 2008 ozone NAAQS. For consistency's sake,
the analysis and discussion underlying and presented in this action
adheres to that analytical approach.
    To give independent effect to both the ``contribute significantly
to nonattainment'' and the ``interfere with maintenance'' prongs of
section 110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS, consistent with
the D.C. Circuit's opinion in North Carolina, 531

F.3d at 910-11, the EPA has separately identified downwind areas
expected to be in nonattainment of the 2008 ozone NAAQS and downwind
areas expected to have problems maintaining the 2008 ozone NAAQS.
    Specifically, the EPA has identified as nonattainment receptors
those monitors that both currently measure nonattainment based on
measured 2014-2016 design values and that the EPA projects will be in
nonattainment for the 2008 ozone NAAQS in 2023 (i.e., are projected to
have average design values that exceed the NAAQS).
    The EPA has identified maintenance receptors as those receptors
that would have difficulty maintaining the relevant NAAQS in a scenario
that accounts for historical variability in air quality at that
receptor. The variability in air quality was determined by evaluating
the ``maximum'' future design value at each receptor based on a
projection of the maximum measured design value over the relevant base-
year period. The EPA defines the projected maximum future design value
as a potential future air quality outcome consistent with the
meteorology that yielded maximum measured concentrations in the ambient
data set analyzed for that receptor. The EPA also recognizes that
previously experienced meteorological conditions (e.g., dominant wind
direction, temperatures, air mass patterns) promoting ozone formation
that led to maximum concentrations in the measured data may reoccur in
the future. Therefore, the maximum design value gives a reasonable
projection of future air quality at the receptor under a scenario in
which such conditions do, in fact, reoccur. The projected maximum
design value is used to identify downwind areas where emissions from
upwind states could therefore interfere with the area's ability to
maintain the NAAQS. The EPA therefore assessed the magnitude of the
maximum projected design value for 2023 at each receptor in relation to
the 2008 ozone NAAQS. Where that value exceeded the NAAQS, the EPA
determined that receptor to be a ``maintenance'' receptor for purposes
of defining interference with maintenance, consistent with the method
used in CSAPR and upheld by the D.C. Circuit in EME Homer City II.\133\
That is, monitoring sites with a maximum projected design value that
exceeds the NAAQS in 2023 are considered to have a maintenance problem
in 2023.
---------------------------------------------------------------------------

    \133\ See 795 F.3d at 136.
---------------------------------------------------------------------------

    All nonattainment receptors also, by definition, meet EPA's
criteria for identifying maintenance receptors--i.e., in addition to
currently measuring nonattainment and having projected average design
values that exceed the NAAQS, the receptors also would have difficulty
maintaining the NAAQS accounting for variability in air quality at the
receptor. The EPA refers to maintenance receptors that are not also
nonattainment receptors as ``maintenance-only'' receptors. Maintenance-
only receptors therefore include those sites where the projected
maximum design value exceeds the NAAQS, but the projected average
design value is at or below the NAAQS. In addition, those sites that
are currently measuring clean data (i.e., are at or below the 2008
ozone NAAQS), but are projected to be in nonattainment based on the
average design value (and that, by definition, are projected to have a
maximum design value above the standard) are also identified as
maintenance-only receptors. Unlike nonattainment receptors, the EPA did
not disqualify potential maintenance receptors based on current clean
monitored data in order to account for the possibility that certain
areas would fail to maintain the NAAQS in the future, even though they
may be currently attaining the NAAQS. See North Carolina, 531 F.3d at
910-11 (finding that failure to give independent significance to the
maintenance prong ``provides no protection for downwind areas that,
despite EPA's predictions, still find themselves struggling to meet
NAAQS due to upwind interference'').
    For further details regarding the EPA's identification of receptors
in the CSAPR Update, see 81 FR 74526.
4. Air Quality Modeling To Identify Nonattainment and Maintenance
Receptors
    The following summarizes the procedures for projecting future-year
8-hour ozone average and maximum design values to 2023 to determine
nonattainment and maintenance receptors. Consistent with the EPA's
modeling guidance, the agency uses the air quality modeling results in
a ``relative'' sense to project future concentrations. That is, the
ratios of future year model predictions to base year model predictions,
i.e., the ``relative response factor'' or relative (percent) change in
model predictions for each location, are used to adjust monitored
ambient ozone design values to generate future year projected design
values. The modeling guidance recommends using measured ozone
concentrations for the 5-year period centered on the base year as the
air quality data starting point for future year projections. This
average design value is used to dampen the effects of inter-annual
variability in meteorology on ozone concentrations and to provide a
reasonable projection of future air quality at the receptor under
``average'' conditions. In addition, the EPA uses the projection of the
maximum base period design value to provide a projection of future year
air quality during meteorological conditions more favorable for ozone
formation than on average. Because the base year for this analysis is
2011, the EPA is using the base period 2009-2013 ambient ozone design
value data to project 2023 average and maximum design values in a
manner consistent with the modeling guidance.
    The approach for projecting future ozone design values involved the
projection of an average of up to three design value periods, which
include the years 2009-2013 (design values for 2009-2011, 2010-2012,
and 2011-2013). The 2009-2011, 2010-2012, and 2011-2013 design values
are accessible at www.epa.gov/airtrends/values.html. The average of the
three design values creates a ``5-year weighted average'' value. The 5-
year weighted average values were then projected to 2023. To project 8-
hour ozone design values, the agency used the 2011 base year and 2023
future base-case model-predicted ozone concentrations to calculate
relative response factors (RRFs) for the location of each monitoring
site. The RRFs were then applied to actual monitored data, i.e., the
2009-2013 average ozone design values (to generate the projected
average design values) and the individual design values for 2009-2011,
2010-2012, and 2011-2013 (to generate potential maximum design values).
Details of this approach are provided in the AQM TSD.
    The EPA considers projected design values that are greater than or
equal to 76.0 ppb to be violating the 2008 ozone NAAQS in 2023.\134\ As
noted previously, nonattainment receptors are those sites that both
have projected average design values greater than the 2008 ozone NAAQS
and are also

violating the NAAQS based on the most recent measured air quality data.
Therefore, as an additional step, for those sites that are projected to
be violating the NAAQS based on the average design values in 2023, the
EPA examined the most recent measured design value data to determine if
the site was currently violating the NAAQS. For the proposal, the
agency examined ambient data for the 2014-2016 period, which form the
basis for the most recent available, certified measured design values
at the time of proposal. Certified measured design value data for 2015-
2017 are now available and have been included in the analysis of
projected receptor. The 2015-2017 design values can be found in a
spreadsheet file in the docket for this rule. Considering the 2015-2017
measured design values does not change the determination regarding
nonattainment and maintenance receptors in 2023 for the 2008 NAAQS.
---------------------------------------------------------------------------

    \134\ From 40 CFR 50.15(b): ``The 8-hour primary and secondary
ambient air quality standards are met at an ambient air quality
monitoring site when the 3-year average of the annual fourth-highest
daily maximum 8-hour average O3 concentration is less
than or equal to 0.075 ppm, as determined in accordance with
appendix P to this part.'' The agency's use of 76.0 ppb (or 0.076
parts per million) to identify violations of the 2008 Ozone NAAQS in
this action is consistent the 2008 ozone NAAQS regulation. From
section 2.2 of appendix P to 40 CFR part 50: ``The computed 3-year
average of the annual fourth-highest daily maximum 8-hour average
O3 concentrations shall be reported to three decimal
places (the digits to the right of the third decimal place are
truncated, consistent with the data handling procedures for the
reported data).''
---------------------------------------------------------------------------

    As discussed above, maintenance-only receptors include both: (1)
Those sites with projected average and maximum design values above the
NAAQS that are currently measuring clean data; and (2) those sites with
projected average design values below the level of the NAAQS, but with
projected maximum design values of 76.0 ppb or greater.
    In projecting these future year design values, the EPA applied its
own modeling guidance,\135\ which recommends using model predictions
from the ``3 x 3'' array of grid cells surrounding the location of the
monitoring site to calculate the relative response factors and identify
future areas of nonattainment. In addition, in light of comments on the
January 2017 NODA and other analyses, the EPA also projected 2023
design values based on a modified version of this approach for those
monitoring sites located in coastal areas. In brief, in the alternative
approach, the EPA eliminated from the design value calculations those
modeling data in grid cells not containing a monitoring site that are
dominated by water (i.e., more than 50 percent of the land use in the
grid cell is water).\136\ For each individual monitoring site, the EPA
is providing the base period 2009-2013 average and maximum design
values, 2023 projected average and maximum design values based on both
the 3 x 3 approach and the alternative approach affecting coastal
sites, and 2014-2016 measured design values.
---------------------------------------------------------------------------

    \135\ U.S. Environmental Protection Agency, 2014. Modeling
Guidance for Demonstrating Attainment of Air Quality Goals for
Ozone, PM2.5, and Regional Haze. http://www.epa.gov/ttn/scram/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.pdf.
    \136\ A model grid cell is identified as a ``water'' cell if
more than 50 percent of the grid cell is water based on the 2006
National Land Cover Database. Grid cells that meet this criterion
are treated as entirely over water in the Weather Research Forecast
(WRF) modeling used to develop the 2011 meteorology for EPA's air
quality modeling.
---------------------------------------------------------------------------

    Tables III.C-1 and III.C-2 contain the ambient 2009-2013 base
period average and maximum 8-hour ozone design values, the 2023
projected baseline average and maximum design values, and the ambient
2014-2016 design values for the air quality monitors that were
identified in the CSAPR Update as having remaining problems attaining
or maintaining the 2008 ozone NAAQS in 2017, even with CSAPR Update
implementation. The tables present the projected design values under
both the 3x3 approach and the alternative approach. Table III.C-1
contains data for the monitors identified as remaining nonattainment
receptors in 2017 in the CSAPR Update and Table III.C-2 contains data
for the monitors identified as remaining maintenance-only receptors in
2017 in the CSAPR Update.\137\ The design values for all monitoring
sites in the contiguous U.S. are provided in the docket. According to
the EPA's modeling, there are no remaining nonattainment or maintenance
receptors in the eastern U.S. in 2023 regardless of which approach to
projecting design values is used.
---------------------------------------------------------------------------

    \137\ The EPA recognizes that the modeling results indicate a
substantial projected improvement in ozone air quality (compared to
current measured ozone levels) at several locations, including three
monitors in Connecticut located near the sea--i.e., on the order of
10-12 ppb.

 Table III.C-1--Base Period, Current (2014-2016), and 2023 Projected Design Values (ppb) for Monitors Identified as Remaining Nonattainment Receptors in
                                                                2017 in the CSAPR Update
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                2009-2013    2009-2013                   2023en       2023en    2023en ``No  2023en ``No
     Monitor ID              State               County            Avg          Max       2014-2016   ``3x3'' Avg  ``3x3'' Max  Water'' Avg  Water'' Max
--------------------------------------------------------------------------------------------------------------------------------------------------------
090019003...........  Connecticut........  Fairfield.........         83.7           87           85         72.7         75.6         73.0         75.9
090099002...........  Connecticut........  New Haven.........         85.7           89           76         71.2         73.9         69.9         72.6
480391004...........  Texas..............  Brazoria..........         88.0           89           75         74.0         74.9         74.0         74.9
484392003...........  Texas..............  Tarrant...........         87.3           90           73         72.5         74.8         72.5         74.8
484393009...........  Texas..............  Tarrant...........         86.0           86           75         70.6         70.6         70.6         70.6
551170006...........  Wisconsin..........  Sheboygan.........         84.3           87           79         70.8         73.1         72.8         75.1
--------------------------------------------------------------------------------------------------------------------------------------------------------

 Table III.C-2--Base Period, Current (2014-2016), and 2023 Projected Design Values (ppb) for Monitors Identified as Remaining Maintenance-Only Receptors
                                                               in 2017 in the CSAPR Update
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                2009-2013    2009-2013                   2023en       2023en    2023en ``No  2023en ``No
     Monitor ID              State               County            Avg          Max       2014-2016   ``3x3'' Avg  ``3x3'' Max  Water'' Avg  Water'' Max
--------------------------------------------------------------------------------------------------------------------------------------------------------
090010017...........  Connecticut........  Fairfield.........         80.3           83           80         69.8         72.1         68.9         71.2
090013007...........  Connecticut........  Fairfield.........         84.3           89           81         71.2         75.2         71.0         75.0
240251001...........  Maryland...........  Harford...........         90.0           93           73         71.4         73.8         70.9         73.3
260050003...........  Michigan...........  Allegan...........         82.7           86           75         69.0         71.8         69.0         71.7
360850067...........  New York...........  Richmond..........         81.3           83           76         71.9         73.4         67.1         68.5
361030002...........  New York...........  Suffolk...........         83.3           85           72         72.5         74.0         74.0         75.5
481210034...........  Texas..............  Denton............         84.3           87           80         69.7         72.0         69.7         72.0
482010024...........  Texas..............  Harris............         80.3           83           79         70.4         72.8         70.4         72.8
482011034...........  Texas..............  Harris............         81.0           82           73         70.8         71.6         70.8         71.6
482011039...........  Texas..............  Harris............         82.0           84           67         71.8         73.6         71.8         73.5
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Comment: The EPA received several comments regarding its projection
of 2023 ozone design values. The commenters suggest that certain
monitoring sites in the New York City area will continue to have
nonattainment and/or maintenance problems for the 2008 NAAQS in 2023, a
claim which is contrary to the results of the EPA's modeling which
shows that nonattainment and maintenance problems will be resolved in
all areas outside of California by 2023. The assertion by the
commenters is based on their examination of measured design values for
2017 and modeling-based projected design values for 2017 and 2023.
First, some commenters compared the projected design values for 2017
based on modeling by the OTC using the Community Multi-scale Air
Quality Model (CMAQ) to the 2017 design values projected by the EPA
using the CAMx model. Those commenters point out that the 2017 CMAQ-
based design values are higher than the EPA CAMx design values by up to
9.2 ppb at certain sites in the Northeast. Commenters also point to
data showing that the greatest difference between the OTC CMAQ and EPA
CAMx 2017 design values is at coastal monitoring sites, such as the
Susan Wagner site in New York and the Westport site in Connecticut.
Second, commenters compared the 2017 OTC CMAQ and EPA CAMx design
values to the corresponding 2017 measured design values and contend
that the CMAQ-based 2017 design values compare favorably to the
measured data and that the CAMx-based design values under-predict the
measured data. One commenter identified eight sites in Connecticut that
are currently measuring nonattainment based on 2015-2017 design values
which the EPA's CAMx modeling predicts will be in attainment in 2017.
Third, commenters point to OTC CMAQ-based design values for 2023 which
indicate that there will be two monitoring sites in Connecticut with
design values that exceed the 2008 NAAQS in that year. Fourth, the
commenters note that the design values based on OTC CAMx modeling for
2023 are comparable in magnitude to the corresponding 2023 design
values based on EPA's 2023 CAMx modeling. Commenters use this
information to contend that the CAMx model provides a forecast that is
too optimistic and that the EPA should rely upon the higher projected
design values for 2023 from the OTC CMAQ modeling.
    Some of the commenters point out that the EPA's 2023 modeling
projects a maximum design value of 75.9 ppb at Westport site and
contend that, before the EPA can conclude that areas will attain by
2023 with only the narrowest of margins (i.e., 0.1 ppb), the EPA must
conduct its own analysis of the emission response differences between
CMAQ and CAMx. Similarly, some commenters said that the EPA must
address the demonstrated tendency of its methodology to under-predict
real-world ozone levels in many downwind locations and that the EPA's
modeling is not sufficiently conservative to give confidence that
attainment is assured even as late as 2023.
    Response: The EPA does not agree that the modeling provided by
commenters should affect the EPA's reliance on its own 2023 modeling.
First, the commenters focused on projected average design values and
completely ignore the EPA's projected maximum design values when
comparing modeled to measured design values for 2017.\138\ The
projected maximum design values are intended to represent future ozone
concentrations when meteorological conditions are more conducive to
ozone formation than on average. Analysis of meteorological conditions
for the summers of 2015, 2016, and 2017 indicate that meteorology was
more conducive than average for ozone formation during these summers in
the Northeast.\139\ Comparing both the 2017 modeled average design
values and maximum projected design values from the EPA's modeling to
the 2017 measured design values indicates that the projected maximum
design values are, in most cases, closer in magnitude to the 2017
measured design values than the 2017 model-projected average design
values, particularly for the Susan Wagner and Westport sites cited by
commenters. Specifically, the 2017 measured design value and the EPA's
modeled maximum design value at the Susan Wagner site are 76 ppb and
77.8 ppb, respectively. At the Westport site the 2017 measured design
value and the EPA's modeled maximum design value are 83 ppb and 79.5
ppb, respectively. At the site in Philadelphia County, Pennsylvania the
modeled 2017 maximum design value was 1.1 ppb lower than the
corresponding measured value (78 ppb), and at the site in Harford
County, Maryland, the modeled value was higher, not lower, than the
measured 2017 design value (75 ppb). As part of our response to the
commenters' concerns about the EPA's modeling we also compared the 2017
measured design values to the EPA's projected 2017 maximum design
values for 81 sites in the Northeast that had both a 2009 to 2013 base
period measured maximum design value exceeding the 2008 NAAQS and valid
2017 measured design values. As a result of this analysis we found that
the 2017 projected maximum design values are only 0.5 ppb higher than
the corresponding 2017 measured design values, on average across these
81 sites, and the median difference is -0.9 ppb. Thus, while the EPA
recognizes that there are uncertainties in the modeling, the results
for sites in the Northeast do not, on balance, show a notable bias in
the EPA's design value projections. It is not unreasonable that there
may be some differences in terms of over- and under-estimates between
the modeling-based projections for a future year and the measured data
in part because the meteorology of the future year cannot be known in
advance. For instance, the degree of ozone conducive meteorology in a
particular region can vary from year to year such that some years are
more conducive then others. Since it is not possible to forecast
meteorology for analytic years in the future, the EPA chose to model
meteorological conditions from a historical time-period when
meteorology was generally conducive for ozone formation, as recommended
in the EPA's modeling guidance.
---------------------------------------------------------------------------

    \138\ Note that the analysis of modeled ozone design values
described in this response are based on the ``3x3'' method to be
consistent with the modeling data submitted by the commenter.
    \139\ See the Appendix in to the Considerations for Identifying
Maintenance Receptors Memo (signed on October 19, 2018).
---------------------------------------------------------------------------

    For 2023, the modeling results show that the EPA and OTC CAMx-based
2023 average design value projections are consistent on an individual
site basis for all sites in the Northeast.\140\ Both the EPA and OTC
CAMx modeling indicate that there will be no sites with design values
that exceed the 2008 NAAQS by 2023.
---------------------------------------------------------------------------

    \140\ The OTC did not provide data on projected future year
maximum design values based on their modeling.
---------------------------------------------------------------------------

    Moreover, the OTC CMAQ 2023 design values are, in fact, fairly
consistent with both the OTC and EPA CAMx-based 2023 projections at
nearly all sites. As an example, the average and median differences
between the OTC CMAQ and EPA CAMx 2023 design values for sites in the
Northeast are 0.15 ppb and 0.70 ppb, respectively. However, while the
EPA and OTC CAMx modeling both indicate that all sites in the Northeast
will be clean for the 2008 NAAQS by 2023, the OTC CMAQ modeling
projects that two sites will have average design values above the 2008
NAAQS by 2023. The two sites projected to exceed the 2008 NAAQS in

2023 with OTC CMAQ modeling are the Westport and the Susan Wagner site.
The CMAQ projected design values for these two sites are not only
inconsistent with the CAMx modeling, but they are also inconsistent
with the CMAQ modeling for other nearby sites in Connecticut, New York,
and New Jersey. For example, based on the OTC CMAQ modeling, ozone at
the Susan Wagner site is projected to decline by only 5 percent between
2011 and 2023, whereas at a site in nearby Bayonne, New Jersey, ozone
is projected to decline by 13 percent over this same time period.
Similarly, ozone at the Westport site is projected to decline by only 3
percent between 2011 and 2023 with CMAQ, but at other sites along the
Connecticut coastline (i.e., sites in Greenwich, Stratford, and
Madison), ozone is projected to decline by 10 to 19 percent. In
addition, the OTC CMAQ results for these two sites (i.e., Westport and
Susan Wagner) are inconsistent with ozone reductions predicted by CMAQ
at other sites in the New York City area which range from 11 to 18
percent. In contrast, the EPA's 2023 modeling shows that ozone is
projected to decline by 13 percent at the Westport site which is an
amount far greater than the 3 percent predicted by OTC's CMAQ modeling.
The EPA's predicted ozone reductions at Westport, however, are
consistent with the predicted reductions at other coastal sites in
Greenwich, Madison, and Stratford, all of which are in the range of 13
to 18 percent. Similarly, ozone at the Susan Wagner site is projected
to decline by 12 percent between 2011 and 2023 based on the EPA's CAMx
modeling which is consistent with the 15 percent reduction predicted at
the nearby site in Bayonne, New Jersey. Thus, the change in ozone from
2011 to 2023 predicted by the EPA's CAMx modeling is much more
spatially consistent within the New York City area than OTC's CMAQ
modeling which predicts spatially anomalous results at two sites (i.e.,
Westport and Susan Wagner).
    While it is possible ozone levels in 2023 at the Westport and/or
Susan Wagner sites may be higher than at other sites in the New York
City area, the commenter fails to provide any explanation regarding the
large difference in the CMAQ-based model response to emission
reductions compared to the response at nearby sites and to other sites
in the New York City area. Based on the complicated photochemistry in
this area, it is possible that ozone monitoring sites closest to the
large NOX emissions in New York City may be less responsive
to NOX controls compared to sites further downwind. Due to
non-linear chemistry, sites very close to the city may experience
increases in ozone or less reduction than other nearby sites on some
days in response to local emission reductions in NOX. Thus,
we might expect that monitoring sites in Connecticut that are closer to
New York City would show less reduction in ozone than sites in
Connecticut that are further downwind. However, as noted above, in the
OTC CMAQ modeling, the closest downwind Connecticut site (Greenwich)
has a 10-percent modeled ozone reduction, while the Westport site,
which is slightly farther downwind, has only a 3-percent modeled ozone
reduction. The commenter did not provide any information to explain why
the OTC CMAQ modeling results for the Westport and Susan Wagner
monitoring sites are dissimilar to other nearby sites or why the
commenters believe that the OTC CMAQ modeling provides a more
representative ozone projection for these two sites compared to the EPA
and OTC CAMx-based modeling.
    Information in the OTC air quality modeling technical support
document (OTC TSD) provides some insight into why their CMAQ and CAMx
modeling shows a dramatic difference in model response in New York City
and coastal Connecticut.\141\ First, the OTC's comparison of CMAQ and
CAMx 2011 base year model predictions to the corresponding measured
data indicate that the CAMx 2011 predictions have lower error and
higher correlation with measured data (i.e., better model performance)
than the CMAQ 2011 predictions for the 8 monitoring sites in
Connecticut and New York that are included in Table 6-6 of the OTC TSD.
Second, examining the 2011 modeled data for the top-10 days used to
calculate the site-specific RRF indicates that the CMAQ 2011
predictions are not representative of ozone concentrations at the
location of high ozone coastal sites in New York City and coastal
Connecticut for which data are provided in the OTC TSD. For example,
Figures 6-81 through 6-90 in the OTC TSD provide time series plots of
measured and CMAQ and CAMx-modeled ozone data for the days used to
calculate the RRF at each of 5 monitoring sites in the Northeast (2
sites in coastal Connecticut, 2 sites in New York City, and 1 site in
Maryland). These figures show several types of data including (1) the
2011 measured and corresponding model-predicted hourly ozone
concentrations at the monitoring site and (2) the highest 2011 and 2017
modeled 8-hour daily maximum ozone concentrations in the 3 x 3 array of
grid cells including and surrounding the monitoring site.\142\ The
latter set of data are used in the calculation of the RRF which, in
turn, is used to project the future year design value at each site. It
is expected that the highest modeled ozone values based on the 3 x 3
approach for calculating RRFs will be equal to or greater than the
modeled value in the grid cell containing the monitor. However, as
evident from the figures in the OTC TSD, the 2011 and 2017 ozone
concentrations used for projecting design values based on OTC's CMAQ
modeling overstate the modeled values at the coastal monitoring sites
by a notably larger amount than the corresponding 2011 predictions from
OTC's CAMx modeling. The clearest example of this is at the Queens
College site in New York City where the CMAQ-based 2011 and 2017 data
for the ten days used for the RRF calculation appear to be 50 to 60 ppb
above the highest hourly measured concentrations at the location of the
monitoring site. In contrast, the CAMx data used for the RRF
calculation appear to be within 20 ppb of the highest hourly measured
data on all ten days at this site. Overall, the OTC CAMx 2011 ozone
concentrations used to calculate the RRF align closely with the model
predictions and measured data at the monitoring sites for which data
are provided in the OTC TSD. Thus, the CAMx-based projections are more
likely to be representative than OTC's CMAQ modeling of the expected
ozone response to emissions reductions at the location of the
monitoring site.
---------------------------------------------------------------------------

    \141\ Ozone Transport Commission/Mid-Atlantic Northeastern
Visibility Union 2011 Based Modeling Platform Support Document,
October 18, 2018. This document can be found in the docket for this
action.
    \142\ In Figures 6-81 through 6-90 of the OTC TSD the highest
modeled ozone concentration in the 3 x 3 array of grid cells is
referred to as the ``9-Grid 8HMX'' value.
---------------------------------------------------------------------------

    Typically, the highest modeled concentrations near coastal
monitoring sites are found in adjacent over-water grid cells. Ozone can
be higher over water than over land because mixing of the air is more
limited over water and titration (i.e., removal) by chemical reaction
of ozone with fresh NO emissions is less prevalent. Thus, it is
possible that the apparent anomalous 2017 design values at the Westport
and Susan Wagner sites derived from OTC's CMAQ modeling may be the
result of using predicted ozone values in the RRF calculations that are
not representative of concentrations at the monitoring site. This
hypothesis is supported by the

OTC's own analysis in which the OTC applied an approach that limits the
use of over-water ozone predictions in the calculation of projected
design values (i.e., Land Water Mask or LWMASK). When the OTC applied
the LWMASK approach, the projected 2017 design values at the Westport
and Susan Wagner sites were lowered significantly. Specifically, the
2017 OTC CMAQ design value at Westport drops from 83 ppb to 76 ppb and
from 78 ppb to 72 ppb at Susan Wagner by limiting the amount of over
water grid cells used in the projections. Thus, the concerns with the
OTC's application of CMAQ for 2017, as described above, call into
question the validity of their CMAQ modeling for other future years.
    Regarding the comment that the EPA's modeling predicts attainment
in 2017 at eight monitors in Connecticut that are currently measuring
nonattainment, it is entirely reasonable to project that these sites
will be in attainment by 2023 as a result of the roughly 19 percent
reduction in aggregate ozone season NOX emissions that is
expected to occur between 2017 and 2023 for the states covered by the
CSAPR Update. Despite large regional and local NOX emission
reductions, ozone has remained stubbornly high at sites in Connecticut.
Larger ozone reductions are expected at these sites in the future as
NOX emissions continue to go down, and the local ozone
chemistry becomes more responsive to NOX reductions. That
is, because of the high NOX emissions in the New York City
area and the non-linear chemistry associated with ozone formation, the
benefits of NOX emission reductions may not have been fully
realized to date at downwind sites in Connecticut. More notable
reductions in ozone at these sites are expected as NOX
emissions decline further, in response to existing control programs and
other factors influencing emissions. Large, short-term reduction in
ozone is not unprecedented at historically high-ozone sites in other
parts of the Northeast Corridor. Specifically, the measured design
values at the Edgewood monitoring site in Harford County, Maryland,
which is downwind of the Baltimore/Washington, DC urban area, declined
by nearly 20 percent between 2012 and 2014 and have been below the
level of the 2008 NAAQS since 2014, as shown by the data in Table
III.C-3, below. Thus, the EPA disagrees that the monitored and OTC CMAQ
modeling data cited by the commenter indicate that the EPA modeling
projections for 2023 are not reliable.

                                                  Table III.C-3--Design Values (ppb) at Edgewood Site in Harford County, MD, 2007 Through 2017
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                            Year                                 2007        2008        2009        2010        2011        2012        2013        2014        2015        2016        2017
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Design Value................................................         94          91          87          89          92          93          85          75          71          73          75
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    As the commenters have suggested, the EPA did perform an analysis
comparing model response of ozone to emissions between CMAQ and CAMx
and found that both models give very similar responses when both models
are run with similar inputs (e.g., emissions, meteorology, and boundary
concentrations) and similar technical constructs (e.g., vertical layer
structure and vertical mixing method).\143\ The results of that study
are further supported by a more recent comparison by the EPA of
projected CAMx and CMAQ ozone design values using the EPA's version 6.2
of the 2011 emissions platform \144\ with 2025 as the future
year.145 146 For the two sites in the New York City area
that are the focus of the comments (i.e., Westport and Susan Wagner),
the EPA's analysis shows that both models predict a comparable
reduction at each of these sites. Specifically, at the Westport site
the 2009 to 2013 base period ozone design values were projected to
decline by 9 percent with CMAQ and by 11 percent with CAMx. This
difference in model response equates to only a 1.8 ppb difference in
projected 2025 design values at this site, which is far less than the
9.2 ppb difference between CMAQ and CAMx seen in the OTC's analysis of
2023 modeling results. Similarly, at the Susan Wagner site the base
period ozone design value was projected to decline by 11.2 percent with
CMAQ and 11.7 percent with CAMx in EPA's modeling. The difference in
model response at the Susan Wagner site equates to only a 0.4 ppb
difference in the projected 2025 design, which is far less than the 5.8
ppb difference between CMAQ and CAMx in OTC's 2023 analysis.\147\
Furthermore, a study sponsored by the Texas Commission on Environmental
Quality also found that CAMx and CMAQ provide a comparable response to
the same amount of NOX and VOC emission reductions.\148\ In
summary, based on the EPA's analysis of its own data and the data
available from commenters, we disagree with the commenter's contention
that the EPA's CAMx-based modeling does not provide a credible
projection of 2023 ozone design values.
---------------------------------------------------------------------------

    \143\ Baker, K., S. Phillips, and B. Timin. ``Operational
Evaluation and Model Response Comparison of CAMx and CMAQ for Ozone
and PM2.5'', 7th Annual Community Modeling & Analysis
System Conference, October 2008.
    \144\ See the Technical Support Document (TSD): Preparation of
Emissions Inventories for the Version 6.2, 2011 Emissions Modeling
Platform, EPA, August 2015.
    \145\ A description of the CAMx modeling can be found in the
Regulatory Impact Analysis of the Final Revisions to the National
Ambient Air Quality Standards for Ground-Level Ozone, EPA-452/R-15-
007, September 2015.
    \146\ A description of the EPA CMAQ modeling can be found in the
docket.
    \147\ An Excel file containing the differences in projected
design values between EPA's CMAQ and CAMx modeling for sates along
the Northeast Corridor from Washington, DC to Connecticut can be
found in the docket for this final action.
    \148\ Final Report: Three-Dimensional Performance Comparison of
CAMx and CMAQ Using the 2013 DISCOVER-AQ Field Study Data Base.
Prepared by Ramboll under contract to the Texas Commission on
Environmental Quality, August 2015.
---------------------------------------------------------------------------

5. Pollutant Transport From Upwind States
    Although the EPA has conducted nationwide contribution modeling for
2023, the EPA does not believe this information is necessary for
evaluating remaining good neighbor obligations for the 2008 ozone NAAQS
because there are no ozone monitoring sites in the eastern U.S. that
are expected to have problems attaining or maintaining the 2008 ozone
NAAQS in 2023. Nonetheless, the results of the EPA's state-by-state
ozone contribution modeling were released in a memorandum on March 27,
2018, and are also available in the docket for this action.\149\ The
EPA notes that, while the air quality modeling did identify potential
remaining problem receptors in California in 2023, none of the EPA's
prior analysis nor its current contribution modeling have linked any of
the CSAPR Update states in the eastern U.S., whose good neighbor
obligations for the 2008 ozone NAAQS

are the subject of this action, to any of those potential remaining
problem receptors. Therefore, the EPA does not believe there is a need
to further evaluate the contributions of the 20 CSAPR Update states to
any downwind receptors identified in the EPA's 2017 modeling conducted
for the CSAPR Update.
---------------------------------------------------------------------------

    \149\ 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). EPA Memorandum to Regional Air Division
Directors. March 27, 2018. Available at https://www.epa.gov/sites/production/files/2018-03/documents/transport_memo_03_27_18_1.pdf.
---------------------------------------------------------------------------

D. Final Determination

    Consistent with the proposed action, the EPA has determined that,
with CSAPR Update implementation, 20 eastern states' good neighbor
obligations for the 2008 ozone NAAQS are fully addressed.\150\ The
states covered by this action are listed in table III.D-1. The EPA's
determination is based on findings that: (1) 2023 is a reasonable
future analytic year for evaluating ozone transport problems with
respect to the 2008 ozone NAAQS; and (2) for the purposes of interstate
ozone transport, air quality modeling projections for 2023 indicate
that no further air quality problems will remain in the east in 2023.
---------------------------------------------------------------------------

    \150\ The EPA has also already separately finalized an approval
of Kentucky's SIP submittal demonstrating that the CSAPR Update is a
full remedy for Kentucky's good neighbor obligation for the 2008
ozone NAAQS. 83 FR 33730 (July 17, 2018).
---------------------------------------------------------------------------

    As explained in more detail in section III.B, the EPA's selection
of 2023 as a reasonable future analytic year is supported by an
assessment of attainment dates for the 2008 ozone NAAQS and feasibility
of implementing control strategies to reduce NOX in CSAPR
Update states. The EPA's NOX control strategy feasibility
assessment prioritizes NOX control strategies in CSAPR
Update states that would be additional to those strategies that were
already quantified into CSAPR Update emissions budgets. The EPA finds:
(1) That 2023 is an appropriate future analytic year, taking into
consideration relevant attainment dates, because it is the first ozone
season for which significant new controls to reduce NOX
could be feasibly installed across the CSAPR Update region and thus
represents the timeframe that is as expeditious as practicable for
upwind states to implement additional emission reductions.
    Furthermore, as described in section III.C, the EPA finds: (2) That
its analysis of ozone concentrations in step 1 for the 2023 analytic
year indicates that there are no monitoring sites in the east that are
projected to have nonattainment or maintenance problems with respect to
the 2008 ozone NAAQS in 2023. Together, these two findings lead to
EPA's final determination that--with CSAPR Update implementation--CSAPR
Update states are not expected to significantly contribute to
nonattainment or interfere with maintenance of the 2008 ozone NAAQS in
downwind states in 2023.
    As a result of this final determination, the EPA finds that the
promulgation of the CSAPR Update fully satisfies the requirements of
the good neighbor provision for the 2008 ozone NAAQS for these states,
and therefore also satisfies the agency's obligation pursuant to CAA
section 110(c) for these states. Accordingly, the EPA has no remaining
obligation to issue FIPs, nor are the states required to submit SIPs,
that would further reduce transported ozone pollution beyond the
existing CSAPR Update requirements with regard to the 2008 ozone NAAQS.

 Table III.D-1--States Covered by the Final Determination Regarding Good
              Neighbor Obligations for the 2008 Ozone NAAQS
------------------------------------------------------------------------
                               State name
-------------------------------------------------------------------------
Alabama
Arkansas
Illinois
Indiana
Iowa
Kansas
Louisiana
Maryland
Michigan
Mississippi
Missouri
New Jersey
New York
Ohio
Oklahoma
Pennsylvania
Texas
Virginia
West Virginia
Wisconsin
------------------------------------------------------------------------

    Consistent with this final determination, this action also
finalizes minor revisions to the existing state-specific sections of
the CSAPR Update regulations for states other than Kentucky and
Tennessee. The revisions will remove the current statements indicating
that the CSAPR Update FIP for each such state only partially addresses
the state's good neighbor obligation under CAA section
110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS. Because states can replace
the CSAPR Update FIPs with SIPs, these revisions will also mean that a
SIP that is approved through notice-and-comment rulemaking to fully
replace the CSAPR Update FIP for one of these states would also fully
address the state's good neighbor obligation for this NAAQS. In
particular, the EPA finalizes findings that the agency's previous
approvals of CSAPR Update SIPs for Alabama (82 FR 46674) and Indiana
(signed November 27, 2018; publication in the Federal Register
forthcoming) \151\ fully satisfy those states' good neighbor
obligations for the 2008 ozone NAAQS. Thus, Alabama and Indiana have no
obligation to submit any additional SIP revisions addressing these good
neighbor obligations.
---------------------------------------------------------------------------

    \151\ In this action, the EPA proposed to find that Alabama's
previously approved CSAPR Update SIP would now fully satisfy its
good neighbor obligation for the 2008 ozone NAAQS. Subsequent to the
proposal, the EPA finalized its approval of Indiana's CSAPR Update
SIP. As discussed earlier, the EPA found that Indiana's SIP approval
only partially satisfied its good neighbor obligation for the 2008
ozone NAAQS for the same reasons that the EPA found that Alabama's
SIP approval only partially satisfied that state's good neighbor
obligation. Although the EPA did not propose in this action to find
that Indiana's SIP would now fully satisfy its good neighbor
obligation, the EPA did propose to find that the state's CSAPR
Update FIP would fully satisfy its obligation. Because Indiana's
approved SIP is commensurate with its prior CSAPR Update FIP such
that Indiana is therefore now situated identically to Alabama, the
EPA believes it is a logical outgrowth of the proposal to finalize a
finding that Indiana's approved CSAPR Update SIP also now fully
satisfies its good neighbor obligation for the 2008 ozone NAAQS.
---------------------------------------------------------------------------

IV. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders
can be found at http://www2.epa.gov/laws-regulations/laws-and-executive-orders.

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

    This action is a significant regulatory action that was submitted
to the Office of Management and Budget (OMB) for review. Any changes
made in response to OMB recommendations have been documented in the
docket.

B. Executive Order 13771: Reducing Regulations and Controlling
Regulatory Costs

    This action is not subject to Executive Order 13771 because this
final rule is expected to result in no more than de minimis costs.

C. Paperwork Reduction Act

    This action does not impose any new information collection burden
under the Paperwork Reduction Act. The OMB has previously approved the
information collection activities contained in the existing regulations
and has assigned OMB control number 2060-0667. The minor revisions to
the FIP provisions finalized in this action have no impact on
monitoring, recordkeeping, and reporting requirements for affected

EGUs in the CSAPR NOX Ozone Season Group 2 Trading Program.

D. Regulatory Flexibility Act

    I certify that this action will not have a significant economic
impact on a substantial number of small entities under the Regulatory
Flexibility Act. In making this determination, the impact of concern is
any significant adverse economic impact on small entities. An agency
may certify that a rule will not have a significant economic impact on
a substantial number of small entities if the rule relieves regulatory
burden, has no net burden, or otherwise has a positive economic effect
on the small entities subject to the rule. This action makes a minor
modification to existing CSAPR Update FIPs and does not impose new
requirements on any entity. The EPA has therefore concluded that this
action will have no net regulatory burden for all directly regulated
small entities.

E. Unfunded Mandates Reform Act

    This action does not contain any unfunded mandate as described in
the Unfunded Mandates Reform Act, 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. This action simply updates the existing CSAPR Update
FIPs to establish that no further federal regulatory requirements are
necessary.

F. 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. This
action simply updates the existing CSAPR Update FIPs to establish that
no further federal regulatory requirements are necessary.

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

    This action does not have tribal implications as specified in
Executive Order 13175. It will not have substantial direct effects on
tribal governments, on the relationship between the federal government
and Indian tribes, or on the distribution of power and responsibilities
between the federal government and Indian tribes. This action simply
updates the existing CSAPR Update FIPs to establish that no further
federal regulatory requirements are necessary. Thus, Executive Order
13175 does not apply to this action. Consistent with the EPA Policy on
Consultation and Coordination with Indian Tribes, the EPA consulted
with tribal officials while developing the CSAPR Update. A summary of
that consultation is provided in the preamble for the CSAPR Update, 81
FR 74584 (October 26, 2016). Additionally, the EPA provided an overview
of its proposed determination during a National Tribal Air
Association--EPA Air Policy Update meeting on Thursday July 26, 2018.

H. 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 environmental 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 simply updates the existing CSAPR
Update FIPs to establish that no further federal regulatory
requirements are necessary.
    Comment: One commenter contends that the EPA has inappropriately
failed to identify and assess the health risks to children from its
decision to authorize continued interstate ozone pollution that
contributes to violations of the 2008 and 2015 ozone air quality
standards in downwind states. The commenter states that the EPA has
consistently recognized that children are disproportionately vulnerable
to the environmental health risks of ozone and asserts that by
authorizing continued pollution that will harm children, the EPA has
failed to ensure that its policies, programs, activities, and standards
address these risks. The commenter claims that this rule is subject to
section 2-202 of the Executive Order, which provides that ``covered
regulatory action'' means ``any substantive action in a rulemaking''
that is ``likely to result in a rule that may'' (1) ``adversely affect
in a material way . . . the environment, public health or safety, or
State, local, or tribal governments or communities'' and (2) ``concern
an environmental health risk or safety risk that an agency has reason
to believe may disproportionately affect children.'' The commenter
asserts that ozone pollution above the air quality standards the EPA
has adopted indisputably is a health risk that disproportionately
affects children.
    Response: According to section 2-202, a rulemaking is a ``covered
regulatory action'' and thus subject to the Executive Order if the
action is economically significant under Executive Order 12866 and
involves an environmental health risk or safety risk that the agency
has reason to believe may disproportionately affect children. This
rulemaking does not qualify under either criterion. First, although
this action is considered a significant regulatory action under
Executive Order 12866, the EPA has not determined that the rule is
economically significant under that Order, and the commenter has not
explained whether or why it should be considered economically
significant. To the extent that the commenter cites the standard for
economic significance wherein an action ``would adversely affect in a
material way . . . the environment, public health or safety, or State,
local, or tribal governments or communities,'' the commenter has not
explained how this action, which concludes that air quality problems
will be resolved and therefore does not either impose or repeal any
regulatory requirements, would have an adverse effect.
    Second, the health-based standard at issue in this action has
already been set in a prior rulemaking to promulgate the 2008 ozone
NAAQS, wherein the EPA did consider the effects of the standard under
the Executive Order. 73 FR 16436, 16506-07. Therefore, this action does
not concern an environmental health or safety risk because the EPA is
simply evaluating how to implement an existing health standard.
Moreover, under the good neighbor provision, the EPA's authority to
prohibit emissions from sources in upwind states is constrained by the
obligation to demonstrate that such reductions are necessary to address
a downwind nonattainment or maintenance problem relative to a NAAQS.
See EME Homer City, 134 S. Ct. at 1608. If the EPA's analysis
determines that there are no such downwind air quality problems in the
future, then the EPA cannot demonstrate that further emission
reductions are necessary from an upwind state and the EPA lacks the
authority to prohibit any further emissions. See id.; EME Homer City
II, 795 F.3d at 130. Under such circumstances, there is no health or
safety risk which may disproportionality affect children.

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

    This action is not a ``significant energy action'' because it is
not likely to

have a significant adverse effect on the supply, distribution, or use
of energy. This action simply updates the existing CSAPR Update FIPs to
establish that no further federal regulatory requirements are
necessary.

J. National Technology Transfer Advancement Act

    This rulemaking does not involve technical standards.

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

    Consistent with Executive Order 12898 and the EPA's environmental
justice policies, the EPA considered effects on low-income populations,
minority populations, and indigenous peoples while developing the CSAPR
Update. The process and results of that consideration are described in
the preamble for the CSAPR Update, 81 FR 74585 (October 26, 2016).
Because this action simply updates the existing CSAPR Update FIPs to
establish that no further federal regulatory requirements are necessary
and does not establish a new environmental health or safety standard,
the EPA believes that no further review of this action under Executive
Order 12898 is necessary.
    Comment: One commenter asserts that the EPA has failed either to
identify or to address the disproportionately high and adverse impact
on minority communities of continued interstate ozone pollution that
contributes to violations of both the 2008 and 2015 health-based
standards for ozone and harms human health, in violation of the
Executive Order. The commenter notes that the EPA's modeling conducted
for the CSAPR Update showed that interstate ozone pollution contributes
significantly to downwind states' failure to attain and maintain the
2008 ozone standard and identified the downwind nonattainment and
maintenance areas that receive this pollution. However, the commenter
contends that the EPA conceded the CSAPR Update would achieve only very
small reductions in the pollution and that the EPA expected air quality
problems in downwind areas to persist. Data for the 2017 ozone season
confirms the EPA's projection that these areas would continue to suffer
poor air quality in violation of the 2008 standard. The commenter
asserts that the agency's claim that all Eastern states will be in
compliance with the 2008 ozone standard in 2023 does not negate the
serious harms that will result from unhealthy ozone levels this year,
next year, and in future years. The commenter states that the
populations in downwind areas that continue to experience violations
are disproportionately members of minority racial and ethnic groups,
and that the EPA's decision will expose communities who live near
polluting sources, who are also disproportionally members of racial and
ethnic minorities, to continued high levels of pollution. The commenter
further asserts that people most exposed to power plant pollution are
the least likely to be able to afford the health care costs imposed by
exposure to pollution and are otherwise socially disadvantaged.
    The commenter concludes that the agency's attempt to justify its
failure to identify and address disproportionately high and adverse
impacts on minority populations is contrary to the Executive Order and
arbitrary. The commenter explains that Executive Order 12898 applies to
all ``effects of [EPA's] programs, policies, and activities,'' which
includes effects of the EPA's administration of the Clean Air Act's
good neighbor provision and the decision not to address ongoing air
pollution that contributes to violations of health-based air quality
standards. The commenter contends that there is no basis to conclude
that the Executive Order creates any exception for EPA programs,
policies, or activities that effectively authorize, rather than curtail
pollution, concluding that decisions that result in greater pollution
are most likely to have disproportionately high and adverse impacts on
minority populations.
    Response: The health-based standard at issue in this action was set
in a prior rulemaking to promulgate the 2008 ozone NAAQS, wherein the
EPA did consider the effects of ozone on different populations,
including those identified by the commenter. 73 FR 16436, 16507. As
discussed earlier, the EPA also considered these effects in
promulgating the emission reduction obligations intended to address
downwind nonattainment and maintenance concerns with respect to this
standard in the CSAPR Update. However, under the good neighbor
provision, the EPA's authority to prohibit emission reductions from
sources in upwind states is constrained by the obligation to
demonstrate that such reductions are necessary to address a downwind
nonattainment or maintenance problem relative to a NAAQS. See EME Homer
City, 134 S. Ct. at 1608. If the EPA's analysis demonstrates that there
are no such downwind air quality problems in the future, then the EPA
cannot demonstrate that further emission reductions are necessary from
an upwind state and the EPA therefore lacks the authority to prohibit
any further emissions. See id.; EME Homer City II, 795 F.3d at 130.
Under such circumstances, further review under Executive Order 12898 is
not warranted.

L. Congressional Review Act

    This action is subject to the Congressional Review Act, 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).

M. Determinations Under CAA Section 307(b)(1) and (d)

    Section 307(b)(1) of the CAA indicates which Federal Courts of
Appeal have venue for petitions of review of final actions by the EPA.
This section provides, in part, that petitions for review must be filed
in the Court of Appeals for the District of Columbia Circuit if: (i)
the agency action consists of ``nationally applicable regulations
promulgated, or final action taken, by the Administrator''; or (ii)
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.''
    The EPA finds that this action is ``nationally applicable'' or, in
the alternative, is based on a determination of ``nationwide scope and
effect'' within the meaning of section 307(b)(1). This action addresses
emissions impacts and sources located in 20 States, which are located
in multiple EPA Regions and federal circuits. The final action is also
based on a common core of factual findings and analyses concerning the
transport of pollutants between the different states. Furthermore, the
EPA intends this interpretation and approach to be consistently
implemented nationwide with respect to section 110(a)(2)(D)(i)(I) for
the 2008 ozone NAAQS.
    For these reasons, the Administrator determines that this final
action is nationally applicable or, in the alternative, is based on a
determination of nationwide scope and effect for purposes of section
307(b)(1). Thus, pursuant to section 307(b), any petitions for review
of this final action must be filed in the Court of Appeals for the
District of Columbia Circuit within 60 days from the date this final
action is published in the Federal Register.
    In addition, pursuant to sections 307(d)(1)(C) and 307(d)(1)(V) of
the CAA, the Administrator has determined

that this action is subject to the provisions of section 307(d). CAA
section 307(d)(1)(B) provides that section 307(d) applies to, among
other things, ``the promulgation or revision of an implementation plan
by the Administrator under CAA section 110(c).'' 42 U.S.C.
7407(d)(1)(B). Under section 307(d)(1)(V), the provisions of section
307(d) also apply to ``such other actions as the Administrator may
determine.'' 42 U.S.C. 7407(d)(1)(V). The agency has complied with
procedural requirements of CAA section 307(d) during the course of this
rulemaking.

List of Subjects in 40 CFR Part 52

    Environmental protection, Administrative practice and procedure,
Air pollution control, Incorporation by reference, Intergovernmental
relations, Nitrogen oxides, Ozone, Particulate matter, Regional haze,
Reporting and recordkeeping requirements, Sulfur dioxide.

    Dated: December 6, 2018.
Andrew R. Wheeler,
Acting Administrator.
    For the reasons stated in the preamble, part 52 of chapter I of
title 40 of the Code of Federal Regulations 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.

Sec. Sec.  52.54, 52.184, 52.731, 52.789, 52.840, 52.882, 52.984,
52.1084, 52.1186, 52.1284, 52.1326, 52.1584, 52.1684, 52.1882, 52.1930,
52.2040, 52.2283, 52.2440, 52.2540, and 52.2587   [Amended]

0
2. Part 52 is amended by removing the text ``, provided that because
the CSAPR FIP was promulgated as a partial rather than full remedy for
an obligation of the State to address interstate air pollution, the SIP
revision likewise will constitute a partial rather than full remedy for
the State's obligation unless provided otherwise in the Administrator's
approval of the SIP revision'' from the second sentence in each of the
following paragraphs:
0
a. Section 52.54(b)(2);
0
b. Section 52.184(b);
0
c. Section 52.731(b)(2);
0
d. Section 52.789(b)(2);
0
e. Section 52.840(b)(2);
0
f. Section 52.882(b)(1);
0
g. Section 52.984(d)(2);
0
h. Section 52.1084(b)(2);
0
i. Section 52.1186(e)(2);
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j. Section 52.1284(b);
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k. Section 52.1326(b)(2);
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l. Section 52.1584(e)(2);
0
m. Section 52.1684(b)(2);
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n. Section 52.1882(b)(2);
0
o. Section 52.1930(b);
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p. Section 52.2040(b)(2);
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q. Section 52.2283(d)(2);
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r. Section 52.2440(b)(2);
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s. Section 52.2540(b)(2); and
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t. Section 52.2587(e)(2).

[FR Doc. 2018-27160 Filed 12-20-18; 8:45 am]
 BILLING CODE 6560-50-P