[Federal Register Volume 83, Number 245 (Friday, December 21, 2018)]
[Rules and Regulations]
[Pages 65878-65924]
[FR Doc No: 2018-27160]

Vol. 83

Friday,

No. 245

December 21, 2018

Part III

Environmental Protection Agency

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40 CFR Part 52

Determination Regarding Good Neighbor Obligations for the 2008 Ozone
National Ambient Air Quality Standard; Final Rule

Federal Register / Vol. 83 , No. 245 / Friday, December 21, 2018 /
Rules and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-HQ-OAR-2018-0225; FRL-9987-86-OAR]
RIN 2060-AT92

Determination Regarding Good Neighbor Obligations for the 2008
Ozone National Ambient Air Quality Standard

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action finalizes the Environmental Protection Agency's
(EPA) determination that the existing Cross-State Air Pollution Rule
Update for the 2008 Ozone National Ambient Air Quality Standards
(NAAQS) (CSAPR Update) fully addresses certain states' obligations
under the good neighbor provision of the Clean Air Act (CAA) regarding
interstate pollution transport for the 2008 ozone NAAQS. The CSAPR
Update, published on October 26, 2016, promulgated Federal
Implementation Plans (FIPs) for 22 states in the eastern U.S. In the
final CSAPR Update, based on information available at that time, the
EPA could not conclude that the rule fully addressed these CAA section
obligations for 21 of the 22 CSAPR Update states. As a result, the EPA
has an outstanding obligation to fully address the requirements of this
Clean Air Act provision for these states. Based on information and
analysis that became available after the CSAPR Update was finalized,
this action finalizes a determination that the existing CSAPR Update
fully addresses the CAA's good neighbor provision for the 2008 ozone
NAAQS for all remaining CSAPR Update states. Specifically, EPA is
finalizing a determination that 2023 is an appropriate future analytic
year to evaluate remaining good neighbor obligations and that, for the
purposes of addressing good neighbor obligations, there will be no
remaining nonattainment or maintenance receptors with respect to the
2008 ozone NAAQS in the eastern U.S. in that year. Therefore, with the
CSAPR Update fully implemented, these remaining CSAPR Update states are
not expected to contribute significantly to nonattainment in, or
interfere with maintenance of, any other state with regard to the 2008
ozone NAAQS. In accord with this finding, the EPA has no outstanding,
unfulfilled obligation to establish additional requirements for
emission sources in these states to further reduce transported ozone
pollution under the good neighbor provision for the 2008 ozone NAAQS.
As a result of this finding, this action finalizes minor revisions to
the existing CSAPR Update regulations to reflect that the CSAPR Update
FIPs fully address this CAA provision. This determination applies to
states currently subject to CSAPR Update FIPs as well as any states for
which EPA has approved replacement of CSAPR Update FIPs with CSAPR
Update state implementation plans (SIPs).

DATES: This final rule is effective on February 19, 2019.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2018-0225. All documents in the docket are
listed on the www.regulations.gov website. Although listed in the
index, some information may not be publicly available, e.g., CBI or
other information whose disclosure is restricted by statute. Certain
other material, such as copyrighted material, is not placed on the
internet and will be publicly available only in hard copy form.
Publicly available docket materials are available either electronically
through www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: David Risley, Clean Air Markets
Division, Office of Atmospheric Programs, U.S. Environmental Protection
Agency, MC 6204M, 1200 Pennsylvania Avenue NW, Washington, DC 20460;
telephone number:<PHONE_NUMBER>; email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Regulated Entities. Entities regulated under the CSAPR Update are
fossil fuel-fired boilers and stationary combustion turbines that serve
generators producing electricity for sale, including combined cycle
units and units operating as part of systems that cogenerate
electricity and other useful energy output. Regulated categories and
entities include:

------------------------------------------------------------------------
                                 NAICS*       Examples of potentially
           Category               code         regulated industries
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Industry.....................     221112  Fossil fuel-fired electric
                                           power generation
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* North American Industry Classification System.

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated. To
determine whether your facility is affected by this action, you should
carefully examine the applicability provisions in 40 CFR 97.804. If you
have questions regarding the applicability of the CSAPR Update to a
particular entity, consult the person listed in the FOR FURTHER
INFORMATION CONTACT section above.
    Outline. The following outline is provided to aid in locating
information in this preamble.

I. General Information
    A. Summary of Proposal in Relation to the Final Determination
    B. States Covered by This Action
II. Background and Legal Authority
    A. Ground-level Ozone Pollution and Public Health
    B. The EPA's Statutory Authority for This Final Action
    C. Good Neighbor Obligations for the 2008 Ozone NAAQS
    D. Summary of the CSAPR Update
III. Final Determination Regarding Good Neighbor Obligations for the
2008 Ozone NAAQS
    A. Analytic Approach
    B. Selection of a Future Analytic Year
    1. Attainment Dates for the 2008 Ozone NAAQS
    2. Feasibility of Control Strategies to Further Reduce Ozone
Season NOX Emissions
    3. Focusing on 2023 for Analysis
    C. Air Quality Analysis
    1. Overview of Air Quality Modeling Platform
    2. Emission Inventories
    3. Definition of Nonattainment and Maintenance Receptors
    4. Air Quality Modeling to Identify Nonattainment and
Maintenance Receptors
    5. Pollutant Transport from Upwind States
    D. Final Determination
IV. Statutory Authority and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review, and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulations and Controlling
Regulatory Costs
    C. Paperwork Reduction Act
    D. Regulatory Flexibility Act
    E. Unfunded Mandates Reform Act
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination with
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children from
Environmental Health and Safety Risks
    I. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    J. National Technology Transfer Advancement Act
    K. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    L. Congressional Review Act
    M. Determinations Under CAA Section 307(b)(1) and (d)

I. General Information

    Within this document ``we,'' ``us,'' or ``our'' should be
interpreted to mean the U.S. EPA.
    Where can I get a copy of this document and other related
information?
    The EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2018-0225 (available at http://www.regulations.gov).
Information related to this final action is available at the website:
https://www.epa.gov/airtransport.

A. Summary of Proposal in Relation to the Final Determination

    On July 10, 2018, the EPA issued its proposed Determination
Regarding Good Neighbor Obligations for the 2008 Ozone National Ambient
Air Quality Standard. 83 FR 31915 (July 10, 2018). In that action, the
agency proposed to determine that the existing CSAPR Update fully
addressed certain states' obligations under CAA section
110(a)(2)(D)(i)(I) with respect to the 2008 ozone NAAQS. The proposed
determination was based upon a finding that 2023 was a reasonable
future analytic year in which to further evaluate air quality with
respect to remaining good neighbor obligations, considering relevant
attainment dates for the 2008 ozone NAAQS and the time necessary to
further mitigate nitrogen oxide (NOX) emissions through
regional assessment of state-of-the-art post-combustion controls within
the CSAPR Update region. The agency's analysis of projected 2023 ozone
concentrations indicated that there would be no remaining monitors
expected to have difficulty attaining or maintaining the 2008 ozone
NAAQS, and the EPA therefore proposed to determine that the existing
regulation--the CSAPR Update--fully addressed states' obligations under
this Clean Air Act provision for this NAAQS. The agency solicited
comment on that proposal with the comment period ending on August 31,
2018. The agency also held a public hearing on August 1, 2018. This
final action was developed considering comments received on the
proposal. Generally, the agency's final action herein remains
consistent with the proposal with respect to its determination
regarding good neighbor obligations for the 2008 ozone NAAQS and its
underlying rationale.

B. States Covered by This Action

    In the CSAPR Update, 81 FR 74504 (Oct. 26, 2016), the EPA
promulgated FIPs affecting 22 eastern states that at least partially
addressed obligations under CAA section 110(a)(2)(D)(i)(I), also known
as the ``good neighbor provision,'' with respect to the 2008 ozone
NAAQS. The good neighbor provision requires upwind states to control
their emissions that significantly contribute to air quality problems
in downwind states. Based on information available when the CSAPR
Update was finalized, the EPA was unable to determine at that time that
the FIPs fully addressed good neighbor obligations under this NAAQS for
21 of the 22 states.\1\ The EPA has subsequently finalized approval of
a SIP that fully addresses the good neighbor obligation for one of
these states--Kentucky. 83 FR 33730 (July 17, 2018). Consistent with
the EPA's July 2018 proposed determination, in this action, the EPA
finalizes a determination that with CSAPR Update implementation the 20
remaining states' good neighbor obligations for the 2008 ozone NAAQS
are fully addressed. In accord with this determination, the EPA has no
further obligation under CAA section 110(c) to establish requirements
for power plants or any other emission sources in these states to
further reduce transported ozone pollution under CAA section
110(a)(2)(D)(i)(I) with regard to this NAAQS. See Table I.A-1 for a
list of states covered by this final action.
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    \1\ The EPA determined in the final CSAPR Update that
implementation of the emissions budget for Tennessee would fully
eliminate the state's significant contribution to downwind
nonattainment and interference with maintenance of the 2008 ozone
NAAQS because the downwind air quality problems to which the state
was linked were projected to be resolved after implementation of the
CSAPR Update. 81 FR 74540.

 Table I.A-1--States Covered by This Final Determination Regarding Good
              Neighbor Obligations for the 2008 Ozone NAAQS
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------------------------------------------------------------------------
                                  State
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Alabama                           Missouri
Arkansas                          New Jersey
Illinois                          New York
Indiana                           Ohio
Iowa                              Oklahoma
Kansas                            Pennsylvania
Louisiana                         Texas
Maryland                          Virginia
Michigan                          West Virginia
Mississippi                       Wisconsin
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II. Background and Legal Authority

A. Ground-level Ozone Pollution and Public Health

    Ground-level ozone causes a variety of negative effects on human
health, vegetation, and ecosystems. In humans, acute and chronic
exposure to ozone is associated with premature mortality and a number
of morbidity effects, such as asthma exacerbation. In ecosystems, ozone
exposure causes visible foliar injury in some plants, decreases growth
in some plants, and affects ecosystem community composition.\2\
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    \2\ For more information on the human health and welfare and
ecosystem effects associated with ambient ozone exposure, see the
EPA's October 2015 Regulatory Impact Analysis of the Final Revisions
to the National Ambient Air Quality Standards for Ground-Level Ozone
(EPA-452/R-15-007) in the docket for this action and also found in
the docket for the 2015 ozone NAAQS, Docket No. EPA-HQ-OAR-2013-
0169-0057.
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    In this final action, consistent with EPA's proposal and with
previous rulemakings described in section II.B, the EPA relies on
analysis that reflects the regional nature of transported ground-level
ozone pollution. Ground-level ozone is not emitted directly into the
air, but is a secondary air pollutant created by chemical reactions
between NOX, carbon monoxide (CO), methane (CH4),
and non-methane volatile organic compounds (VOCs) in the presence of
sunlight. Emissions from mobile sources, electric generating units
(EGUs), industrial facilities, gasoline vapors, and chemical solvents
are some of the major anthropogenic sources of ozone precursors. The
potential for ground-level ozone formation increases during periods
with warmer temperatures and stagnant air masses. Therefore, ozone
levels are generally higher during the summer months.\3 4\ Ground-level
ozone concentrations and temperature are highly correlated in the
eastern U.S., with observed ozone increases of 2-3 parts per billion
(ppb) per degree Celsius reported.\5\
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    \3\ Rasmussen, D.J. et al. (2011). Ground-level ozone-
temperature relationships in the eastern US: A monthly climatology
for evaluating chemistry-climate models. Atmospheric Environment 47:
142-153.
    \4\ High ozone concentrations have also been observed in cold
months, where a few areas in the western U.S. have experienced high
levels of local VOC and NOX emissions that have formed
ozone when snow is on the ground and temperatures are near or below
freezing.
    \5\ Bloomer, B.J., J.W. Stehr, C.A. Piety, R.J. Salawitch, and
R.R. Dickerson (2009). Observed relationships of ozone air pollution
with temperature and emissions, Geophys. Res. Lett., 36, L09803.
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    Precursor emissions can be transported downwind directly or, after
transformation in the atmosphere, as ozone. Studies have established
that ozone formation, atmospheric residence, and transport occur on a
regional scale (i.e., hundreds of miles) over much of the eastern U.S.
As a result of ozone transport, in any given location, ozone pollution
levels are affected by a combination of local emissions and

emissions from upwind sources. Numerous observational studies have
demonstrated the transport of ozone and its precursors and the impact
of upwind emissions on high concentrations of ozone pollution. \6\
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    \6\ For example, Bergin, M.S. et al. (2007). Regional air
quality: local and interstate impacts of NOX and
SO2 emissions on ozone and fine particulate matter in the
eastern United States. Environmental Sci & Tech. 41: 4677-4689.
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    The EPA concluded in several previous rulemakings (summarized in
section II.B) that interstate ozone transport can be an important
component of peak ozone concentrations during the summer ozone season
and that NOX control strategies are effective for reducing
regional-scale ozone transport. Model assessments have looked at
impacts on peak ozone concentrations after potential emission reduction
scenarios for NOX and VOCs for NOX-limited and
VOC-limited areas. For example, Jiang and Fast concluded that
NOX emission reduction strategies are effective in lowering
ozone mixing ratios in urban areas and Liao et al. showed that
NOX reductions result in lower peak ozone concentrations in
non-attainment areas in the Mid-Atlantic.\7 8\ Assessments of ozone
conducted for the October 2015 Regulatory Impact Analysis of the Final
Revisions to the National Ambient Air Quality Standards for Ground-
Level Ozone (EPA-452/R-15-007) also show the importance of
NOX emissions on ozone formation. This analysis is in the
docket for this action and also can be found in the docket for the 2015
ozone NAAQS regulatory impact analysis, Docket No. EPA-HQ-OAR-2013-0169
(document ID EPA-HQ-OAR-2013-0169-0057).
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    \7\ Jiang, G.; Fast, J.D. (2004). Modeling the effects of VOC
and NOX emission sources on ozone formation in Houston
during the TexAQS 2000 field campaign. Atmospheric Environment 38:
5071-5085.
    \8\ Liao, K. et al. (2013) Impacts of interstate transport of
pollutants on high ozone events over the Mid-Atlantic United States.
Atmospheric Environment 84, 100-112.
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    Studies have found that NOX emission reductions can be
effective in reducing ozone pollution as quantified by the form of the
2008 ozone standard, 8-hour peak concentrations. Specifically, studies
have found that NOX emission reductions from EGUs, mobile
sources, and other source categories can be effective in reducing the
upper-end of the cumulative ozone distribution in the summer on a
regional scale.\9\ Analysis of air quality monitoring data trends shows
reductions in summertime ozone concurrent with implementation of
NOX reduction programs.\10\ Gilliland et al. examined the
NOX SIP Call, discussed in more detail later, and presented
reductions in observed versus modeled ozone concentrations in the
eastern U.S. downwind from major NOX sources.\11\ The
results showed significant reductions in ozone concentrations (10-25
percent) from observed measurements (CASTNET and AQS) \12\ between 2002
and 2005, linking reductions in EGU NOX emissions from
upwind states with ozone reductions downwind of the major source
areas.\13\ Additionally, G[eacute]go et al. showed that ground-level
ozone concentrations were significantly reduced after implementation of
the NOX SIP Call.\14\ Thus, these studies support the EPA's
continued focus on regional and seasonal NOx control strategies to
address regional interstate ozone pollution transport.
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    \9\ Hidy, G.M. and Blanchard C.L. (2015). Precursor reductions
and ground-level ozone in the Continental United States. J. of Air &
Waste Management Assn. 65, 10.
    \10\ Simon, H. et al. (2015). Ozone trends across the United
States over a period of decreasing NOX and VOC emissions.
Environmental Science & Technology 49, 186-195.
    \11\ Gilliland, A.B. et al. (2008). Dynamic evaluation of
regional air quality models: Assessing changes in O3
stemming from changes in emissions and meteorology. Atmospheric
Environment 42: 5110-5123.
    \12\ CASTNET is the EPA's Clean Air Status and Trends Network.
AQS is the EPA's Air Quality System.
    \13\ Hou, Strickland & Liao. ``Contributions of regional air
pollutant emissions to ozone and fine particulate matter-related
mortalities in eastern U.S. urban areas''. Environmental Research,
Feb. 2015. Available at https://ac.els-cdn.com/S0013935114004113/1-s2.0-S0013935114004113-main.pdf?_tid=78c88101-fa6e-4e75-a65c-f56746905e7d&acdnat=1525175812_0e62553b83c9ffa1105aa306a478e8bb.
    \14\ G[eacute]go et al. (2007). Observation-based assessment of
the impact of nitrogen oxides emission reductions on O3
air quality over the eastern United States. J. of Applied
Meteorology and Climatology 46: 994-1008.
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B. The EPA's Statutory Authority for This Final Action

    The statutory authority for this final action is provided by the
CAA as amended (42 U.S.C. 7401 et seq.). Specifically, sections 110 and
301 of the CAA provide the primary statutory underpinnings for this
action. The most relevant portions of section 110 are subsections
110(a)(1), 110(a)(2) (including 110(a)(2)(D)(i)(I)), and 110(c)(1).
    Section 110(a)(1) provides that states must make SIP submissions
``within 3 years (or such shorter period as the Administrator may
prescribe) after the promulgation of a national primary ambient air
quality standard (or any revision thereof),'' and that these SIP
submissions are to provide for the ``implementation, maintenance, and
enforcement'' of such NAAQS.\15\ The statute directly imposes on states
the duty to make these SIP submissions, and the requirement to make the
submissions is not conditioned upon the EPA taking any action other
than promulgating a new or revised NAAQS.\16\
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    \15\ 42 U.S.C. 7410(a)(1).
    \16\ See EPA v. EME Homer City Generation, L.P., 134 S. Ct.
1584, 1601 (2014).
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    The EPA has historically referred to SIP submissions made for the
purpose of satisfying the applicable requirements of CAA sections
110(a)(1) and 110(a)(2) as ``infrastructure SIP'' submissions. Section
110(a)(1) addresses the timing and general requirements for
infrastructure SIP submissions, and section 110(a)(2) provides more
details concerning the required content of these submissions. It
includes a list of specific elements that ``[e]ach such plan''
submission must address.\17\ All states, regardless of whether the
state includes areas designated as nonattainment for the relevant
NAAQS, must have SIPs that meet the applicable requirements of section
110(a)(2), including provisions of section 110(a)(2)(D)(i)(I),
described later, that are the focus of this action.
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    \17\ The EPA's general approach to infrastructure SIP
submissions is explained in greater detail in individual notices
acting or proposing to act on state infrastructure SIP submissions
and in guidance. See, e.g., Memorandum from Stephen D. Page on
Guidance on Infrastructure State Implementation Plan (SIP) Elements
under Clean Air Act Sections 110(a)(1) and 110(a)(2) (Sept. 13,
2013).
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    Section 110(c)(1) requires the Administrator to promulgate a FIP at
any time within two years after the Administrator: (1) Finds that a
state has failed to make a required SIP submission; (2) finds a SIP
submission to be incomplete pursuant to CAA section 110(k)(1)(C); or
(3) disapproves a SIP submission. This obligation applies unless the
state corrects the deficiency through a SIP revision that the
Administrator approves before the FIP is promulgated.\18\
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    \18\ 42 U.S.C. 7410(c)(1).
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    Section 110(a)(2)(D)(i)(I), also known as the ``good neighbor
provision,'' provides the primary basis for this action. It requires
that each state SIP include provisions sufficient to ``prohibit[ ],
consistent with the provisions of this subchapter, any source or other
type of emissions activity within the State from emitting any air
pollutant in amounts which will--(I) contribute significantly to
nonattainment in, or interfere with maintenance by, any other State
with respect to any [NAAQS].'' \19\ The EPA

often refers to the emission reduction requirements under this
provision as ``good neighbor obligations'' and submissions addressing
these requirements as ``good neighbor SIPs.''
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    \19\ 42 U.S.C. 7410(a)(2)(D)(i)(I).
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    The EPA has previously issued four rules interpreting and
clarifying the requirements of section 110(a)(2)(D)(i)(I) for states in
the eastern United States. These rules, and the associated court
decisions addressing these rules, summarized here, provide important
direction regarding the requirements of section 110(a)(2)(D)(i)(I).
    The NOX SIP Call, promulgated in 1998, addressed the
good neighbor provision for the 1979 1-hour ozone NAAQS.\20\ The rule
required 22 states and the District of Columbia to amend their SIPs to
reduce NOX emissions that contribute to ozone nonattainment
in downwind states. The EPA set ozone season NOX budgets for
each state, and the states were given the option to participate in a
regional allowance trading program, known as the NOX Budget
Trading Program (NBP), to achieve all or most of the required emission
reductions.\21\ The United States Court of Appeals for the District of
Columbia Circuit (D.C. Circuit) largely upheld the NOX SIP
Call in Michigan v. EPA, 213 F.3d 663 (D.C. cir. 2000), cert. denied,
532 U.S. 904 (2001).
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    \20\ 63 FR 57356 (Oct. 27, 1998). As originally promulgated, the
NOX SIP Call also addressed good neighbor obligations
under the 1997 8-hour ozone NAAQS, but the EPA subsequently stayed
the rule's provisions with respect to that standard. 40 CFR
51.121(q).
    \21\ ``Allowance Trading'' sometimes referred to as ``cap and
trade'' is an approach to reducing pollution that has been used
successfully to protect human health and the environment. Allowance
trading programs have two key components: Emissions budgets (the sum
of which provide a cap on emissions), and tradable allowances equal
to the budgets that authorize allowance holders to emit a specific
quantity (e.g., one ton) of the pollutant. This approach ensures
that the environmental goal is met while the tradable allowances
provide flexibility for individual participants to establish and
follow their own compliance path. Because allowances can be bought
and sold in an allowance market, these programs are often referred
to as ``market-based.''
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    The EPA's next rule addressing the good neighbor provision, the
Clean Air Interstate Rule (CAIR), was promulgated in 2005 and addressed
both the 1997 fine particulate matter (PM2.5) NAAQS and 1997
ozone NAAQS.\22\ CAIR required SIP revisions in 28 states and the
District of Columbia to reduce emissions of sulfur dioxide
(SO2) and/or NOX--important precursors of
regionally transported PM2.5 (SO2 and annual
NOX) and ozone (summer-time NOX). As in the
NOX SIP Call, states were given the option to participate in
regional allowance trading programs to achieve the reductions. When the
EPA promulgated the final CAIR in 2005, the EPA also issued findings
that states nationwide had failed to submit SIPs to address the
requirements of CAA section 110(a)(2)(D)(i) with respect to the 1997
PM2.5 and 1997 ozone NAAQS.\23\ The states were required by
the CAA to have submitted good neighbor SIPs for those standards by
July 2000 (i.e., three years after the standards were finalized).\24\
These findings of failure to submit triggered a two-year clock for the
EPA to issue FIPs to address interstate transport,\25\ and on March 15,
2006, the EPA promulgated FIPs to implement the emission reductions
required by CAIR.\26\ CAIR was remanded to the EPA by the D.C. Circuit
in North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008), modified on
reh'g, 550 F.3d 1176. For more information on the legal issues
underlying CAIR and the D.C. Circuit's holding in North Carolina, refer
to the preamble of the original CSAPR.\27\
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    \22\ 70 FR 25162 (May 12, 2005).
    \23\ 70 FR 21147 (April 25, 2005).
    \24\ See n.14 and main text, supra.
    \25\ See n.17 and main text, supra.
    \26\ 71 FR 25328 (April 28, 2006).
    \27\ 76 FR 48208, 48217 (Aug. 8, 2011).
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    In 2011, the EPA promulgated the original CSAPR to address the
issues raised by the remand of CAIR. CSAPR addressed the two NAAQS at
issue in CAIR and additionally addressed the good neighbor provision
for the 2006 PM2.5 NAAQS.\28\ CSAPR, as revised, required 28
states to reduce SO2 emissions, annual NOX
emissions, and/or ozone season NOX emissions that
significantly contribute to other states' nonattainment or interfere
with other states' abilities to maintain these air quality
standards.\29\ To align implementation with the applicable attainment
deadlines, the EPA promulgated FIPs for each of the 28 states covered
by CSAPR. The FIPs implement regional allowance trading programs to
achieve the necessary emission reductions. Each state can submit a good
neighbor SIP at any time that, if approved by the EPA, would replace
the CSAPR FIP for that state.\30\ CSAPR was the subject of an adverse
decision by the D.C. Circuit in August 2012.\31\ However, this decision
was reversed in April 2014 by the Supreme Court,\32\ which largely
upheld the rule, including EPA's approach to addressing interstate
transport in CSAPR. The rule was remanded to the D.C. Circuit to
consider other claims not addressed by the Supreme Court. EPA v. EME
Homer City Generation, L.P., 134 S. Ct. 1584 (2014) (EME Homer City).
In July 2015 the D.C. Circuit affirmed the EPA's interpretation of
various statutory provisions and the EPA's technical decisions. EME
Homer City Generation, L.P. v. EPA, 795 F.3d 118 (2015) (EME Homer City
II). However, the court also remanded the rule without vacatur for
reconsideration of the EPA's emissions budgets for certain states,
which the court found may over-control those states' emissions with
respect to the downwind air quality problems to which the states were
linked. Id. at 129-30, 138. For more information on the legal
considerations of CSAPR and the court's decisions in the EME Homer City
litigation, refer to the preamble of the CSAPR Update.\33\
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    \28\ 76 FR 48208.
    \29\ CSAPR was revised by several rulemakings after its initial
promulgation in order to revise certain states' budgets and to
promulgate FIPs for five additional states addressing the good
neighbor obligation for the 1997 ozone NAAQS. 76 FR 80760 (Dec. 27,
2011); 77 FR 10324 (Feb. 21, 2012); 77 FR 34830 (June 12, 2012).
    \30\ The EPA has already approved SIPs fully replacing the
original CSAPR FIPs for Alabama, 81 FR 59869 (Aug. 31, 2016);
Georgia, 82 FR 47930 (Oct. 13, 2017); South Carolina, 82 FR 47936
(Oct. 13, 2017); and Indiana (signed Nov. 27, 2018; publication in
the Federal Register forthcoming).
    \31\ On August 21, 2012, the D.C. Circuit issued a decision in
EME Homer City Generation, L.P. v. EPA, 696 F.3d 7 (D.C. Cir. 2012)
(EME Homer City I), vacating CSAPR. The EPA sought review with the
D.C. Circuit en banc and the D.C. Circuit declined to consider the
EPA's appeal en banc. EME Homer City Generation, L.P. v. EPA, No.
11-1302 (D.C. Cir. January 24, 2013), ECF No. 1417012 (denying the
EPA's motion for rehearing en banc).
    \32\ On January 23, 2013, the Supreme Court granted the EPA's
petition for certiorari. EPA v. EME Homer City Generation, L.P., 133
S. Ct. 2857 (2013) (granting the EPA's and other parties' petitions
for certiorari).
    \33\ 81 FR 74511.
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    In 2016, the EPA promulgated the CSAPR Update to address interstate
transport of ozone pollution with respect to the 2008 ozone NAAQS.\34\
The final rule generally updated the CSAPR ozone season NOX
emissions budgets for 22 states to achieve cost-effective and
immediately feasible NOX emission reductions from EGUs
within those states.\35\ To align implementation with relevant
attainment dates, the CSAPR Update implemented these budgets through
FIPs requiring sources to participate in a revised CSAPR ozone season
NOX allowance trading program beginning with the 2017 ozone
season. As discussed in more detail later in this preamble, the 2017
deadline was intended to ensure that the emission reductions from the
rule would be made prior to the July 20, 2018 moderate attainment
deadline. As under the

original CSAPR, each state can submit a good neighbor SIP at any time
that, if approved by the EPA, would replace the CSAPR Update FIP for
that state.\36\ The final CSAPR Update also addressed the remand by the
D.C. Circuit of certain states' original CSAPR phase 2 ozone season
NOX emissions budgets in EME Homer City II. The CSAPR Update
is subject to pending legal challenges in the D.C. Circuit. Wisconsin
v. EPA, No. 16-1406 (D.C. Cir. argued Oct. 3, 2018). Further
information about the CSAPR Update can be found in section II.D of this
notice.
---------------------------------------------------------------------------

    \34\ 81 FR 74504.
    \35\ One state, Kansas, was made newly subject to a CSAPR ozone
season NOX requirement by the CSAPR Update. All other
CSAPR Update states were already subject to ozone season
NOX requirements under the original CSAPR.
    \36\ EPA has already approved SIPs fully replacing the CSAPR
Update FIPs for Alabama, 82 FR 46674 (Oct. 6, 2017), and Indiana
(signed Nov. 27, 2018; publication in the Federal Register
forthcoming).
---------------------------------------------------------------------------

    Section 301(a)(1) of the CAA also gives the Administrator the
general authority to prescribe such regulations as are necessary to
carry out functions under the Act.\37\ Pursuant to this section, the
EPA has authority to clarify the applicability of CAA requirements. In
this action, among other things, the EPA is clarifying the
applicability of section 110(a)(2)(D)(i)(I) with respect to the 2008
ozone NAAQS. In particular, the EPA is using its authority under
sections 110 and 301 to make a determination that no further
enforceable reductions in emissions of NOX are required
under this provision with respect to the 2008 ozone NAAQS for the
states covered by this rule. The EPA is making minor revisions to the
existing state-specific sections of the CSAPR Update regulations for
all states covered by this action.
---------------------------------------------------------------------------

    \37\ 42 U.S.C. 7601(a)(1).
---------------------------------------------------------------------------

C. Good Neighbor Obligations for the 2008 Ozone NAAQS

    On March 12, 2008, the EPA promulgated a revision to the NAAQS,
lowering both the primary and secondary standards to 75 ppb. See
National Ambient Air Quality Standards for Ozone, Final Rule, 73 FR
16436 (March 27, 2008). Specifically, the standards require that an
area may not exceed 0.075 ppm (75 ppb) using the 3-year average of the
fourth highest 24-hour maximum 8-hour rolling average ozone
concentration. These revisions of the NAAQS, in turn, triggered a 3-
year deadline for states to submit SIP revisions addressing
infrastructure requirements under CAA sections 110(a)(1) and 110(a)(2),
including the good neighbor provision. Several events affected the
timely application of the good neighbor provision for the 2008 ozone
NAAQS, including reconsideration of the 2008 ozone NAAQS and legal
developments pertaining to the EPA's original CSAPR, which created
uncertainty surrounding the EPA's statutory interpretation and
implementation of the good neighbor provision.\38\ Notwithstanding
these events, the EPA ultimately affirmed that states' good neighbor
SIPs were due on March 12, 2011.
---------------------------------------------------------------------------

    \38\ These events are described in detail in section IV.A.2 of
the CSAPR Update. 81 FR 74515.
---------------------------------------------------------------------------

    The EPA subsequently took several actions that triggered the EPA's
obligation under CAA section 110(c) to promulgate FIPs addressing the
good neighbor provision for several states.\39\ First, on July 13,
2015, the EPA published a rule finding that 24 states failed to make
complete submissions that address the requirements of section
110(a)(2)(D)(i)(I) related to the interstate transport of pollution as
to the 2008 ozone NAAQS. See 80 FR 39961 (effective August 12, 2015).
This finding triggered a two-year deadline for the EPA to issue FIPs to
address the good neighbor provision for these states by August 12,
2017. The CSAPR Update finalized FIPs for 13 of these states (Alabama,
Arkansas, Illinois, Iowa, Kansas, Michigan, Mississippi, Missouri,
Oklahoma, Pennsylvania, Tennessee, Virginia, and West Virginia),
requiring their participation in a NOX emission trading
program. The EPA also determined in the CSAPR Update that the agency
had no further FIP obligation as to nine additional states identified
in the finding of failure to submit because these states did not
contribute significantly to nonattainment in, or interfere with
maintenance by, any other state with respect to the 2008 ozone NAAQS.
81 FR 74506.\40 41\ On June 15, 2016, and July 20, 2016, the EPA
published additional rules finding that New Jersey and Maryland,
respectively, also failed to submit transport SIPs for the 2008 ozone
NAAQS. See 81 FR 38963 (June 15, 2016) (New Jersey, effective July 15,
2016); 81 FR 47040 (July 20, 2016) (Maryland, effective August 19,
2016). The finding actions triggered two-year deadlines for the EPA to
issue FIPs to address the good neighbor provision for Maryland by
August 19, 2018, and for New Jersey by July 15, 2018. The CSAPR Update
also finalized FIPs for these two states.
---------------------------------------------------------------------------

    \39\ This section of the preamble focuses on SIP and FIP actions
for those states addressed in the CSAPR Update. The EPA has also
acted on SIPs for other states not mentioned in this action. The
memorandum, ``Final Action, Status of 110(a)(2)(D)(i)(I) SIPs for
the 2008 Ozone NAAQS,'' more fully describes the good neighbor SIP
status for the 2008 ozone NAAQS and is available in the docket for
this action.
    \40\ The nine states were Florida, Georgia, Maine,
Massachusetts, Minnesota, New Hampshire, North Carolina, South
Carolina, and Vermont.
    \41\ The two remaining states addressed in the findings of
failure to submit (California and New Mexico) were not part of the
CSAPR Update analysis and are not addressed in this action.
---------------------------------------------------------------------------

    In addition to these findings, the EPA finalized disapproval or
partial disapproval actions for good neighbor SIPs submitted by
Indiana, Kentucky, Louisiana, New York, Ohio, Texas, and Wisconsin.\42\
These disapprovals triggered the EPA's obligation to promulgate FIPs to
implement the requirements of the good neighbor provision for those
states within two years of the effective date of each disapproval. The
EPA promulgated CSAPR Update FIPs for each of these states.
---------------------------------------------------------------------------

    \42\ See the following actions: Indiana (81 FR 38957, June 15,
2016); Kentucky (78 FR 14681, March 7, 2013); Louisiana (81 FR
53308, August 12, 2016); New York (81 FR 58849, August 26, 2016);
Ohio (81 FR 38957, June 15, 2016); Texas (81 FR 53284, August 12,
2016); and Wisconsin (81 FR 53309, August 12, 2016).
---------------------------------------------------------------------------

    As discussed in more detail in the next section, in issuing the
CSAPR Update, the EPA did not determine that it had entirely addressed
the EPA's outstanding CAA obligations to implement the good neighbor
provision with respect to the 2008 ozone NAAQS for 21 of 22 states
covered by that rule. Accordingly, the CSAPR Update did not fully
satisfy the EPA's obligation under section 110(c) to address the good
neighbor provision requirements for those states by approving SIPs,
issuing FIPs, or some combination of those two actions. The EPA found
that the CSAPR Update FIP fully addressed the good neighbor provision
for the 2008 ozone NAAQS only with respect to Tennessee.
    The EPA notes that it has separately finalized an action to fully
address Kentucky's good neighbor obligation for the 2008 ozone NAAQS.
On May 23, 2017, the U.S. District Court for the Northern District of
California issued an order requiring the EPA to take a final action
fully addressing the good neighbor obligation for the 2008 ozone NAAQS
for Kentucky by June 30, 2018. See Order, Sierra Club v. Pruitt, No.
3:15-cv-04328 (N.D. Cal.), ECF No. 73. On May 10, 2018, Kentucky
submitted a final SIP to EPA, which the agency finalized approval of
consistent with the court-ordered deadline. 83 FR 33730 (July 17,
2018).
    Subsequent to the promulgation of the CSAPR Update, the EPA
approved SIPs fully replacing the CSAPR Update FIPs for Alabama, 82 FR
46674 (October 6, 2017), and Indiana (signed November 27, 2018;
publication in the Federal Register forthcoming). In those SIP
approvals and consistent with the conclusions of the CSAPR Update, the
EPA found that the SIPs partially satisfy

Alabama's and Indiana's good neighbor obligations for the 2008 ozone
NAAQS. Thus, the EPA continues to have an obligation to fully address
the good neighbor provision requirements for the 2008 NAAQS with
respect to Alabama, stemming from the July 13, 2015 findings notice,
and Indiana, due to the June 15, 2016 disapproval of the state's good
neighbor SIP. Other states have also submitted SIPs, some of which the
EPA has approved and some of which still remain pending. However, these
states are not the subject of this rulemaking and these actions are
therefore not described in detail in this section.
    Table II.C-1 summarizes the statutory deadline for the EPA to
address its FIP obligation under CAA section 110(c) and the event that
activated the EPA's obligation for each of the 20 CSAPR Update states
that are the subject of this final action. For more information
regarding the actions triggering the EPA's FIP obligation and the EPA's
action on SIPs addressing the good neighbor provision for the 2008
ozone NAAQS, see the memorandum, ``Final Action, Status of
110(a)(2)(D)(i)(I) SIPs for the 2008 Ozone NAAQS,'' in the docket for
this action.

                       Table II.C-1--Actions That Activated EPA's Statutory FIP Deadlines
----------------------------------------------------------------------------------------------------------------
                                                 Type of action (Federal Register citation,      Statutory FIP
                    State                                     publication date)                   deadline 43
----------------------------------------------------------------------------------------------------------------
Alabama......................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Arkansas.....................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Illinois.....................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Indiana......................................  SIP disapproval (81 FR 38957, 6/15/2016)......          7/15/2018
Iowa.........................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Kansas.......................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Louisiana....................................  SIP disapproval (81 FR 53308, 8/12/2016)......          9/12/2018
Maryland.....................................  Finding of Failure to Submit (81 FR 47040, 7/           8/19/2018
                                                20/2016).
Michigan.....................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Mississippi..................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Missouri.....................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
New Jersey...................................  Finding of Failure to Submit (81 FR 38963, 6/           7/15/2018
                                                15/2016).
New York.....................................  SIP disapproval (81 FR 58849, 8/26/2016)......          9/26/2018
Ohio.........................................  SIP disapproval (81 FR 38957, 6/15/2016)......          7/15/2018
Oklahoma.....................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Pennsylvania.................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Texas........................................  SIP disapproval (81 FR 53284, 8/12/2016)......          9/12/2018
Virginia.....................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
West Virginia................................  Finding of Failure to Submit (80 FR 39961, 7/           8/12/2017
                                                13/2015).
Wisconsin....................................  Partial SIP disapproval as to prong 2 (81 FR            9/12/2018
                                                53309, 8/12/2016).
----------------------------------------------------------------------------------------------------------------

    An August 12, 2017 statutory deadline has passed for the EPA to act
with respect to good neighbor obligations under the 2008 ozone NAAQS
for 12 CSAPR Update states. The EPA is subject to a court-ordered
deadline to promulgate a final action fully addressing the good
neighbor obligations under the 2008 ozone NAAQS for five of these
states by no later than December 6, 2018.\44\ The statutory deadlines
for the EPA to act with respect to good neighbor obligations under the
2008 ozone NAAQS for eight other CSAPR Update states passed between
July 15, 2018, and September 26, 2018.
---------------------------------------------------------------------------

    \43\ The FIP deadline is two years from the effective date of
the SIP disapproval or Finding of Failure to Submit, which generally
trails the publication date by 30 days.
    \44\ Order, New York v. Pruitt, No. 1:18-cv-00406-JGK (S.D.N.Y.
June 12, 2018), ECF No. 34. The five states are Illinois, Michigan,
Pennsylvania, Virginia, and West Virginia.
---------------------------------------------------------------------------

D. Summary of the CSAPR Update

    On October 16, 2016, the EPA finalized the CSAPR Update. The
purpose of the CSAPR Update was to protect public health and welfare by
reducing interstate pollution transport that will significantly
contribute to nonattainment, or interfere with maintenance, of the 2008
ozone NAAQS in the eastern U.S. As discussed in section II.C, the EPA
finalized a FIP for each of the 22 states subject to the rule,\45\
either having previously found that those states failed to submit a
complete good neighbor SIP (15 states) or having issued a final rule
disapproving their good neighbor SIP submittals (seven states). For the
22 states covered by the CSAPR Update, the EPA promulgated EGU ozone
season NOX emissions budgets, implemented through a regional
allowance trading program, to reduce interstate ozone transport for the
2008 ozone NAAQS during the ozone season (May-September), beginning
with the 2017 ozone season.
---------------------------------------------------------------------------

    \45\ Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas,
Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, New
Jersey, New York, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas,
Virginia, West Virginia, and Wisconsin.
---------------------------------------------------------------------------

    To establish and implement the CSAPR Update emissions budgets, the
EPA followed a four-step analytic process that has been used in each of
the agency's regional interstate transport rulemakings. The four-step
interstate transport framework is described in more detail in section
III.A. To summarize, in step 1, the agency identified downwind
locations, referred to as receptors, that were expected to have
problems attaining or maintaining the NAAQS. In step 2, the EPA
examined, using a contribution threshold of one percent of the NAAQS,
which upwind states contributed to the nonattainment or maintenance
receptors identified in step 1. In step 3, the EPA quantified the
upwind emissions that significantly contributed to nonattainment or
interfered with maintenance and established emission budgets that
reflected removal of those emissions. Finally, in step 4, the agency
provided for implementation of the budgets through an allowance trading
program.
    The EPA aligned its analysis of air quality and upwind state
contributions in steps 1 and 2, as well as implementation of the
trading program in step 4 with relevant attainment dates for the 2008
ozone NAAQS. The EPA's final 2008 Ozone NAAQS SIP Requirements Rule
established the attainment deadline of July 20, 2018, for ozone
nonattainment areas classified as

Moderate.\46\ Because the attainment date fell during the 2018 ozone
season, the 2017 ozone season was the last full season from which data
could be used to determine attainment of the NAAQS by that date.
Therefore, consistent with the court's instruction in North Carolina to
harmonize implementation of emission reductions under the good neighbor
provision with downwind attainment dates, 531 F.3d at 912, the EPA
established and implemented emissions budgets starting with the 2017
ozone season. 81 FR 74507. The establishment of 2017 as the CSAPR
Update's analytic year and compliance timeframe was further supported
by an assessment that certain control strategies to mitigate ozone
pollution transport were feasible in that timeframe.
---------------------------------------------------------------------------

    \46\ 80 FR 12264, 12268 (Mar. 6, 2015); 40 CFR 51.1103. Ozone
nonattainment areas are classified as either Marginal, Moderate,
Serious, Severe, or Extreme, based on the severity of the air
quality problem in the area. Areas with more acute air quality
problems are required to implement more stringent control
requirements and are provided additional time to attain the NAAQS.
See CAA sections 181 and 182, 42 U.S.C. 7511, 7511a.
---------------------------------------------------------------------------

    As to step 3, in particular, the EPA quantified emissions from
upwind states that would significantly contribute to nonattainment or
interfere with maintenance by first evaluating various levels of
uniform NOX control stringency, each represented by an
estimated marginal cost per ton of NOX reduced. The EPA then
applied a multi-factor test to evaluate cost, available emission
reductions, and downwind air quality impacts to determine the
appropriate level of uniform NOX control stringency that
addressed the impacts of interstate transport on downwind nonattainment
or maintenance receptors. The EPA used this multi-factor assessment to
gauge the extent to which emission reductions should be implemented in
the future compliance year (i.e., 2017) and to evaluate the potential
for over- and under-control of upwind state emissions.
    Within the multi-factor test, the EPA identified a ``knee in the
curve,'' i.e., a point at which the cost-effectiveness of the emission
reductions was maximized, so named for the discernable turning point
observable in a multi-factor (i.e., multi-variable) curve. See 81 FR
74550. The EPA concluded that this was at the point where emissions
budgets reflected a uniform NOX control stringency
represented by an estimated marginal cost of $1,400 per ton of
NOX reduced. In light of this multi-factor test, EPA
determined this level of stringency in emissions budgets represented
the level at which incremental EGU NOX reduction potential
and corresponding downwind ozone air quality improvements were
maximized--relative to other control stringencies evaluated--with
respect to marginal cost. That is, the ratio of emission reductions to
marginal cost and the ratio of ozone improvements to marginal cost were
maximized relative to the other levels of control stringency evaluated.
The EPA found that feasible and cost-effective EGU NOX
reductions were available to make meaningful and timely improvements in
downwind ozone air quality to address interstate ozone transport for
the 2008 ozone NAAQS for the 2017 ozone season. 81 FR 74508. Further,
the agency's evaluation showed that emissions budgets reflecting the
$1,400 per ton cost threshold did not over-control upwind states'
emissions relative to either the downwind air quality problems to which
they were linked or the one percent contribution threshold in step 2
that triggered their further evaluation in step 3. Id. at 74551-52. As
a result, the EPA finalized EGU ozone season NOX emissions
budgets developed using uniform control stringency represented by
$1,400 per ton. These budgets represented emissions remaining in each
state after elimination of the amounts of emissions that the EPA
identified would significantly contribute to nonattainment or interfere
with maintenance of the 2008 ozone NAAQS in downwind states.
    To implement the CSAPR Update's emission budgets, the EPA
promulgated FIPs requiring power plants in covered states to
participate in the CSAPR NOX Ozone Season Group 2 allowance
trading program starting in 2017.\47\ CSAPR's trading programs and the
EPA's prior emissions trading programs (e.g., CAIR and the
NOX Budget Trading Program) have provided a proven
implementation framework for achieving emission reductions. In addition
to providing environmental certainty (i.e., a cap on emissions), these
programs also provide regulated sources with flexibility in choosing
compliance strategies. By using the CSAPR allowance trading programs,
the EPA applied an implementation framework that was shaped by notice
and comment in previous rulemakings and reflected the evolution of
these programs in response to court decisions and practical experience
gained by states, industry, and the EPA.
---------------------------------------------------------------------------

    \47\ The ozone season NOX allowance trading program
created under the original CSAPR was renamed the CSAPR
NOX Ozone Season Group 1 Trading Program and now applies
only to sources in Georgia. In the CSAPR Update, the EPA found that
Georgia did not contribute to interstate transport with respect to
the 2008 ozone NAAQS, but the state has an ongoing ozone season
NOX requirement under the original CSAPR with respect to
the 1997 ozone NAAQS.
---------------------------------------------------------------------------

    Based on information available at the time of its promulgation, the
EPA was unable to conclude that the CSAPR Update fully addressed most
of the covered states' good neighbor obligations for the 2008 ozone
NAAQS. 81 FR 74521. Information available at the time indicated that,
even with CSAPR Update implementation, several downwind receptors were
expected to continue having problems attaining and maintaining this
NAAQS and that emissions from upwind states were expected to continue
to contribute greater than or equal to one percent of the NAAQS to
these areas during the 2017 ozone season. Id. at 74551-52. Further, the
EPA could not conclude at that time whether additional EGU and non-EGU
reductions implemented on a longer timeframe than 2017 would be
necessary, feasible, and cost-effective to address states' good
neighbor obligations for this NAAQS.
    As noted, the EPA premised its conclusion that the CSAPR Update may
not fully address states' good neighbor obligations in part on the
agency's assessment that air quality problems would persist at downwind
receptors in 2017 even with CSAPR Update implementation. The EPA's
assessment of CSAPR Update implementation using the Air Quality
Assessment Tool (AQAT) indicated that certain eastern air quality
monitors would continue to have problems attaining and maintaining the
2008 ozone NAAQS in 2017. 81 FR 74550-52. Specifically, projected
nonattainment receptors remained in Connecticut, Texas, and Wisconsin,
while projected maintenance-only receptors remained in Connecticut,
Maryland, Michigan, New York, and Texas.\48\ See Table II.D-1 for a
list of remaining nonattainment receptors and Table II.D-2 for a list
of remaining maintenance-only receptors. (The EPA's approach to
defining nonattainment and maintenance-only receptors is explained in
section III.C.1 below.)
---------------------------------------------------------------------------

    \48\ Projected AQAT design values for the $1400/ton policy case
are available in Tables D-6 and D-7 of the CSAPR Update ``Ozone
Transport Policy Analysis Final Rule TSD'' (August 2016), Docket ID
No. EPA-HQ-OAR-2015-0500-0555.

  Table II.D-1--Remaining 2017 Projected Nonattainment Receptors in the
                              Eastern U.S.
------------------------------------------------------------------------
      Monitor ID                  State                   County
------------------------------------------------------------------------
090019003.............  Connecticut.............  Fairfield.
090099002.............  Connecticut.............  New Haven.
480391004.............  Texas...................  Brazoria.
484392003.............  Texas...................  Tarrant.
484393009.............  Texas...................  Tarrant.
551170006.............  Wisconsin...............  Sheboygan.
------------------------------------------------------------------------

Table II.D-2--Remaining 2017 Projected Maintenance-Only Receptors in the
                              Eastern U.S.
------------------------------------------------------------------------
      Monitor ID                  State                   County
------------------------------------------------------------------------
090010017.............  Connecticut.............  Fairfield.
090013007.............  Connecticut.............  Fairfield.
240251001.............  Maryland................  Harford
260050003.............  Michigan................  Allegan.
360850067.............  New York................  Richmond.
361030002.............  New York................  Suffolk.
481210034.............  Texas...................  Denton.
482010024.............  Texas...................  Harris.
482011034.............  Texas...................  Harris.
482011039.............  Texas...................  Harris.
------------------------------------------------------------------------

    The EPA's analysis also showed that 21 of the 22 CSAPR Update
states would continue to contribute equal to or greater than one
percent of the 2008 ozone NAAQS to at least one remaining nonattainment
or maintenance receptor in 2017.\49\ The EPA did not, at that time,
evaluate whether the projected air quality problems would persist and
whether upwind states would continue to contribute to these receptors
in years beyond 2017. Thus, for those 21 states, the EPA could not,
based on information available in the CSAPR Update rulemaking, make an
air quality-based conclusion that the CSAPR Update would fully resolve
states' good neighbor obligations with respect to the 2008 ozone NAAQS.
(For one state, Tennessee, the EPA determined that the CSAPR Update
fully resolved its good neighbor obligation.)
---------------------------------------------------------------------------

    \49\ See EPA's Air Quality Assessment Tool from the CSAPR Update
in the docket for this action.
---------------------------------------------------------------------------

    Further, it was not feasible for the EPA to complete an emissions
control analysis that may otherwise have been necessary to evaluate
full elimination of each state's significant contribution to
nonattainment or interference with maintenance and also ensure that
emission reductions already quantified in the rule would be achieved by
2017. 81 FR at 74522. Specifically, the EPA was unable to fully
consider both non-EGU ozone season NOX reductions and
further EGU reductions that may have been achievable after 2017. Id. at
74521. The EPA did not quantify non-EGU stationary source emission
reductions to address interstate ozone transport for the 2008 ozone
NAAQS in the CSAPR Update for two reasons. First, the EPA explained
that there was greater uncertainty in the EPA's assessment of non-EGU
NOX mitigation potential, and that more time would be
required for states and the EPA to improve non-EGU point source data
and pollution control assumptions before we could develop emission
reduction obligations based on that data. Id. at 74542. Second, the EPA
explained that we did not believe that significant, certain, and
meaningful non-EGU NOX reductions were feasible for the 2017
ozone season. Id. Many commenters on the CSAPR Update generally agreed
with the EPA that non-EGU emission reductions were not readily
available for the 2017 ozone season, but some advocated that such
reductions should be included as appropriate in future mitigation
actions. Id. at 74521-22. With respect to EGUs, the EPA concluded that
additional control strategies, such as the implementation of new post-
combustion controls, would take several years to implement, which was
beyond the 2017 ozone season targeted in the CSAPR Update. Id. at
74541. Thus, the EPA also could not make an emission reduction-based
conclusion that the CSAPR Update would fully resolve states' good
neighbor obligations with respect to the 2008 ozone NAAQS because the
reductions evaluated and required by the CSAPR Update were limited in
scope (both by technology and sector). Specifically, EPA focused the
policy analysis for the CSAPR Update on reductions available by the
beginning of the 2017 ozone season from EGUs.
    Regardless of these limitations, in promulgating the CSAPR Update
the EPA stated its belief that it was beneficial to implement, without
further delay, EGU NOX reductions that were achievable in
the near term, particularly before the Moderate area attainment date of
July 20, 2018. Notwithstanding that additional reductions may be
required to fully address the states' interstate transport obligations,
the EPA concluded that the EGU NOX emission reductions
implemented by the final rule were needed for upwind states to
eliminate their significant contribution to nonattainment or
interference with maintenance of the 2008 ozone NAAQS and to assist
downwind states with ozone nonattainment areas that were required to
attain the standard by July 20, 2018.
    As a result of the remaining air quality problems and the
limitations on the EPA's analysis, for all but one of the 22 affected
states, the EPA did not determine in the CSAPR Update that the rule
fully addressed those states' downwind air quality impacts under the
good neighbor provision for the 2008 ozone NAAQS. Id. at 74521. For one
state, Tennessee, the EPA determined in the final CSAPR Update that
Tennessee's emissions budget fully eliminated the state's significant
contribution to downwind nonattainment and interference with
maintenance of the 2008 ozone NAAQS because the downwind air quality
problems to which the state was linked were projected to be resolved
with implementation of the CSAPR Update. Id. at 74552.

III. Final Determination Regarding Good Neighbor Obligations for the
2008 Ozone NAAQS

    As described in section II.D, in the CSAPR Update the EPA
promulgated FIPs intended to address the good neighbor provision for
the 2008 ozone NAAQS, but could not at that time determine, based on
information available when the rule was finalized, that those FIPs
would fully address 2008 ozone NAAQS good neighbor obligations for 21
of the 22 CSAPR Update states. As a result, the EPA could not conclude
that the CSAPR Update fully satisfied its obligation to issue FIPs, nor
had the agency otherwise approved SIPs at that time, to address those
states' good neighbor obligations for the 2008 ozone NAAQS. Since the
CSAPR Update, the EPA has approved a SIP revision fully resolving the
remaining 2008 ozone NAAQS good neighbor obligations for Kentucky.\50\
In this notice, the EPA finalizes a determination that, based on
additional information and analysis that has subsequently become
available, the CSAPR Update fully addresses the remaining 20 affected
states' good neighbor obligations for the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \50\ 83 FR 33730 (July 17, 2018).
---------------------------------------------------------------------------

    In particular, the EPA is finalizing a determination that 2023 is
an appropriate future analytic year considering relevant attainment
dates and the time necessary to implement further NOX
controls. This rationale is described within this section, starting
with Section III.A, which provides the EPA's analytic approach. Section
III.B discusses the agency's selection of 2023 as its future analytic
year and Sections III.B.2 provides the EPA's assessment of feasibility
(e.g., timing) to implement further regional NOX control
strategies for EGUs (Section III.B.2.a) and non-EGUs (Section
III.B.2.b). Further, based on the EPA's analysis of projected air

quality in that year, the EPA has determined that, for the purposes of
addressing good neighbor obligations for the 2008 ozone NAAQS, there
will be no remaining nonattainment or maintenance receptors in the
eastern U.S. in the future analytic year of 2023. The agency's analysis
is described in Section III.C. As a result of these determinations, the
EPA finds that, with CSAPR Update implementation, these states will no
longer contribute significantly to nonattainment in, or interfere with
maintenance by, any other state with respect to the 2008 ozone NAAQS.
This rationale is described in Section III.D. The agency includes a
summary of comments and the EPA's response to those comments at the
conclusion of certain sections and subsections therein. The comments
summarized in these sections and the EPA's responses are further
supplemented by the EPA's Response to Comment document in the docket
for this action.

A. Analytic Approach

    Through the development and implementation of several previous
rulemakings, including most recently the CSAPR Update, the EPA, working
in partnership with states, established the following four-step
framework to address regional interstate transport of ozone pollution
under the Clean Air Act's good neighbor provision.\51\ The agency is
evaluating its determination regarding CSAPR Update states' remaining
good neighbor obligations for the 2008 ozone NAAQS by applying this
same approach.\52\ The steps are summarized in the following four
paragraphs.
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    \51\ See Finding of Significant Contribution and Rulemaking for
Certain States in the Ozone Transport Assessment Group Region for
Purposes of Reducing Regional Transport of Ozone (also known as the
NOX SIP Call), 63 FR 57356 (October 27, 1998); Clean Air
Interstate Rule (CAIR) Final Rule, 70 FR 25162 (May 12, 2005); CSAPR
Final Rule, 76 FR 48208 (August 8, 2011); CSAPR Update for the 2008
Ozone NAAQS Final Rule, 81 FR 74504 (October 26, 2016).
    \52\ With respect to the 2015 ozone NAAQS, which is not
addressed in this action, the EPA recently provided information to
states to inform their development of SIPs to address CAA section
110(a)(2)(D)(i)(I). In a memorandum dated March 27, 2018, the agency
noted that, in developing their own plans, states have flexibility
to follow the familiar four-step transport framework (using the
EPA's analytical approach or somewhat different analytical
approaches within these steps) or alternative frameworks, so long as
their chosen approach has adequate technical justification and is
consistent with the requirements of the CAA.
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    Step 1: Identify downwind air quality problems relative to the 2008
ozone NAAQS. The EPA historically (including in the CSAPR Update)
identified downwind areas with air quality problems, or receptors,
using air quality modeling projections for a future analytic year and,
where appropriate, considering monitored ozone data. In the CSAPR
Update, the agency relied on modeled and monitored data to identify
receptors expected to be in nonattainment with the ozone NAAQS in the
future analytic year, and relied on modeled data to identify additional
receptors that may have difficulty maintaining the NAAQS in the future
analytic year, notwithstanding clean monitored data or projected
attainment.
    Step 2: Determine which upwind states contribute to these
identified downwind air quality problems sufficiently to warrant
further analysis to determine whether their emissions violate the good
neighbor provision. These states are referred to as ``linked'' states.
In the CSAPR Update, the EPA identified such upwind states as those
modeled to impact a downwind receptor in the future analytic year at or
above an air quality threshold equivalent to one percent of the 2008
ozone NAAQS.
    Step 3: For states linked to downwind air quality problems,
identify upwind emissions on a statewide basis that will significantly
contribute to nonattainment or interfere with maintenance of a standard
at a receptor in another state. In all of the EPA's prior rulemakings
addressing interstate ozone pollution transport, the agency identified
and apportioned emission reduction responsibility among multiple upwind
states linked to downwind air quality problems considering multiple
factors consistently across the region. Specifically, the agency
considered feasible NOX control strategies and used cost-
based and air quality-based criteria to evaluate regionally uniform
NOX control strategies that were then used to quantify the
amount of a linked upwind state's emissions, if any, that will
significantly contribute to nonattainment or interfere with maintenance
in another state in the future analytic year. The agency then
established emission budgets reflecting remaining emission levels
following the reduction of emissions that significantly contribute to
nonattainment or interfere with maintenance of the NAAQS downwind.
    Step 4: For upwind states that are found to have emissions that
will significantly contribute to nonattainment or interfere with
maintenance of the NAAQS downwind, implement the necessary emission
reductions within the state. In the CSAPR Update, the EPA implemented
the emission budgets for upwind states found to have good neighbor
obligations by requiring EGUs in those states to participate in the
CSAPR NOX Ozone Season Group 2 Trading Program. In virtually
all respects other than the budgets and the starting year, the program
is identical to allowance trading programs used to implement the
emission reductions quantified in the original CSAPR, and it builds on
the experience of both the EPA and states using emission trading
programs to implement other earlier rules.\53\
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    \53\ Affected sources have participated in EPA-administered
allowance trading programs under both SIPs and FIPs.
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    Because this framework provides a reasonable and logical
structuring of the key elements that should be considered in addressing
the requirements of the good neighbor provision and because this action
is evaluating outstanding obligations that remain following the EPA's
application of this framework with respect to the 2008 ozone NAAQS in
the CSAPR Update, the agency believes it is reasonable to apply the
same framework in this final action.
    Within this four-step interstate transport framework, the EPA would
only proceed to higher enumerated (i.e., downstream) steps if states
meet the criteria applied in lower enumerated (i.e., upstream) steps.
For example, the EPA would only proceed to step 4, in which sources in
upwind states are subject to enforceable emissions limitations, if
downwind air quality problems are identified at step 1, an upwind state
is found to be linked to a downwind air quality problem at step 2, and
sources in the linked upwind state are identified at step 3 as having
emissions that significantly contribute to nonattainment or interfere
with maintenance of the NAAQS considering multiple cost, emissions, and
air-quality factors. For the reasons described in the following
paragraphs, the EPA believes this approach is a reasonable
interpretation of the good neighbor provision.
    The good neighbor provision instructs the EPA and states to apply
its requirements ``consistent with the provisions of'' title I of the
CAA. The EPA is therefore interpreting the requirements of the good
neighbor provision, and the elements of its four-step interstate
transport framework, to apply in a manner consistent with the
designation and planning requirements in title I that apply in downwind
states. See North Carolina, 531 F.3d at 912 (holding that the good
neighbor provision's reference to title I requires consideration of
both procedural and substantive provisions in title I). The EPA notes
that this consistency

instruction follows the requirement that plans ``contain adequate
provisions prohibiting'' certain emissions in the good neighbor
provision. The following paragraphs will therefore explain how the
EPA's interpretation of the circumstances under which the good neighbor
provision requires that plans ``prohibit'' emissions through
enforceable measures is consistent with the circumstances under which
downwind states are required to implement emissions control measures in
nonattainment areas.
    For purposes of this analysis, the EPA notes specific aspects of
the title I designations process and attainment planning requirements
for the ozone NAAQS that provide relevant context for evaluating the
consistency of the EPA's approach to implementing the good neighbor
provision in upwind states. The EPA notes that this discussion is not
intended to suggest that the specific requirements of designations and
attainment planning for downwind states apply to upwind states pursuant
to the good neighbor provision, but rather to explain why the EPA's
approach to interpreting the good neighbor provision is reasonable in
light of relevant, analogous provisions found elsewhere in title I. Cf.
EDF v. EPA, 82 F.3d 451, 457 (D.C. Cir. 1996) (per curiam) (describing
the phrase ``consistent with'' as ``flexible statutory language'' which
does not require ``exact correspondence . . . but only congruity or
compatibility,'' thus requiring a court to defer to reasonable agency
determinations), amended by 92 F.3d 1209 (D.C. Cir. 1996). In
particular, these provisions demonstrate that the EPA's approach is
consistent with other relevant provisions of title I with respect to
what data is considered in the EPA's analysis and when states are
required to implement enforceable measures.
    First, areas are initially designated attainment or nonattainment
for the ozone NAAQS based on actual measured ozone concentrations. See
CAA section 107(d), 42 U.S.C. 7407(d) (noting that an area shall be
designated attainment where it ``meets'' the NAAQS and nonattainment
where it ``does not meet'' the NAAQS (including certain ``nearby''
areas, as explained below)). If an area measures a violation of the
relevant ozone NAAQS, then the area is generally designated
nonattainment, regardless of what specific factors have influenced the
measured ozone concentrations or whether such levels are due to
enforceable emissions limits.\54\ In such cases where the an ozone
nonattainment area is classified as Moderate or higher, the state is
then required to develop an attainment plan, which generally includes
the application of various enforceable control measures to sources of
emissions located in the nonattainment area, consistent with the
requirements in Part D of title I of the Act.\55\ See generally CAA
section 182, 42 U.S.C. 7511a. If, however, an area measures compliance
with the ozone NAAQS, the area is designated attainment (unless it is
included in the boundaries of a nearby nonattainment area due to its
contribution to that area's nonattainment, as discussed below), and
sources in that area generally are not subject to any new enforceable
control measures under Part D.\56\
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    \54\ Policy tools are available to apply to areas experiencing
exceedances of ozone NAAQS that are appreciably impacted by U.S.
background ozone. The tools available for each affected location
will depend on the specific nature of U.S. background ozone in each
area. Some tools would provide relief from a nonattainment
designation; others would only provide relief from some of the CAA-
prescribed nonattainment area requirements.
    \55\ Areas classified as Marginal nonattainment areas are
required to submit emission inventories and implement a
nonattainment new source review permitting program, but are not
generally required to implement controls at existing sources. See
CAA section 182(a), 42 U.S.C. 7511a(a).
    \56\ Clean Air Act section 184 contains the exception to this
general rule: States that are part of the Ozone Transport Region are
required to provide SIPs that include specific enforceable control
measures, similar to those for nonattainment areas, that apply to
the whole state, even for areas designated attainment for the ozone
NAAQS. See generally 42 U.S.C. 7511c.
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    In determining the boundaries of an ozone nonattainment area, the
CAA requires the EPA to consider whether ``nearby'' areas
``contribute'' to ambient air quality in the area that does not meet
the NAAQS. 42 U.S.C. 7407(d). For each monitor or group of monitors
indicating a violation of the ozone NAAQS, the EPA assesses information
related to various factors, including current emissions and emissions-
related data from the areas near the monitor(s), for the purpose of
establishing the appropriate geographic boundaries for the designated
ozone nonattainment areas. A nearby area may be included within the
boundary of the ozone nonattainment area only after assessing area-
specific information, including an assessment of whether current
emissions from that area contribute to the air quality problem
identified at the violating monitor.\57\ If such a determination is
made, sources in the nearby area are also subject to the applicable
Part D control requirements. However, if the EPA determines that the
nearby area does not contribute to the measured nonattainment problem,
then the nearby area is not part of the designated nonattainment area
and sources in that area are not subject to such control requirements.
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    \57\ See Attachment 2 to Area Designations for the 2008 Ozone
National Ambient Air Quality Standards. Memorandum from Robert J.
Meyers, Principal Deputy Assistant Administrator, U.S. EPA to
Regional Administrators. December 4, 2008. Available at https://archive.epa.gov/ozonedesignations/web/pdf/area_designations_for_the_2008_revised_ozone_naaqs.pdf.
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    The EPA's historical approach to addressing the good neighbor
provision via the four-step interstate transport framework, and the
approach the EPA continues to apply here, is consistent with these
title I requirements. That is, in steps 1 and 2 of the framework, the
EPA evaluates whether there is a downwind air quality problem (either
nonattainment or maintenance), and whether an upwind state impacts the
downwind area such that it contributes to and is therefore ``linked''
to the downwind area. The EPA's determination at step 1 of the good
neighbor analysis (that it has not identified any downwind air quality
problems to which an upwind state could contribute) is analogous to the
EPA's determination in the designation analysis that an area should be
designated attainment. Similarly, EPA's determination at step 2 of the
good neighbor analysis (that, while it has at step 1 identified
downwind air quality problems, an upwind state does not sufficiently
impact the downwind area such that the state contributes to that area's
air quality problems and is therefore linked to that area) is analogous
to the EPA's determination in the designation analysis that a nearby
area does not contribute to a NAAQS violation in another area. Under
the good neighbor provision, the EPA can determine at either step 1 or
2, as appropriate, that the upwind state will not contribute to air
quality problems in downwind areas and, thus, that the upwind state
does not significantly contribute to nonattainment or interfere with
maintenance of the NAAQS in other states. See, e.g., CSAPR Update, 81
FR 74506 (determining that emissions from 14 states do not
significantly contribute to nonattainment or interfere with maintenance
of the 2008 ozone NAAQS); CSAPR, 76 FR 48236 (finding that states whose
impacts on downwind receptors are below the air quality threshold do
not significantly contribute to nonattainment or interfere with
maintenance of the relevant NAAQS). Under such circumstances, sources
in the upwind state are not required to implement any control measures
under the good neighbor provision, which is analogous to the fact that
under the designation and attainment regime,

sources located in areas that are designated attainment (because the
area is attaining the NAAQS and not contributing to any nearby
nonattainment areas) generally are not required to implement the
control measures found in Part D of the Act. Cf. EME Homer City II, 795
F.3d at 130 (determining that CSAPR ozone-season NOX budgets
for 10 states were invalid based on determination that modeling showed
no future air quality problems); CSAPR Update, 81 FR 74523-24 (removing
three states from CSAPR ozone season NOX program based on
determination that states are not linked to any remaining air quality
problems for the 1997 ozone NAAQS).
    The EPA acknowledges one distinction between the good neighbor and
designation analyses: The good neighbor analysis relies on future-year
projections of emissions to calculate ozone concentrations and upwind
state contributions, compared to the use of current measured data in
the designation analysis. As described in more detail in section III.B,
this approach is a reasonable interpretation of the term ``will'' in
the good neighbor provision, see North Carolina, 531 F.3d at 913-14,
and interpreting language specific to that provision does not create an
impermissible inconsistency with other provisions of title I. Moreover,
the EPA's approach to conducting future-year modeling in the good
neighbor analysis to identify downwind air quality problems and linked
states is consistent with its use of current measured data in the
designations process. The EPA's future-year air quality projections
consider a variety of factors, including current emissions data,
anticipated future control measures, economic market influences, and
meteorology. These same factors, e.g., current control measures,
economic market influences, and meteorology, can affect the
NOX emissions levels and consequent measured ozone
concentrations that inform the designations process. Like the factors
that affect measured ozone concentrations used in the designations
process, not all of the factors influencing the EPA's modeling
projections are or can be subject to enforceable limitations on
emissions or ozone concentrations. However, the EPA believes that
consideration of these factors contributes to a reasonable estimate of
anticipated future ozone concentrations. See EME Homer City II, 795
F.3d at 135 (declining to invalidate the EPA's modeling projections
``solely because there might be discrepancies between those predictions
and the real world''); Chemical Manufacturers Association v. EPA, 28
F.3d 1259, 1264 (D.C. Cir. 1994) (``a model is meant to simplify
reality in order to make it tractable''). Thus, the EPA's consideration
of these factors in its future-year modeling projections used at steps
1 and 2 of the good neighbor analysis is reasonable and consistent with
the use of measured data in the designation analysis.\58\
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    \58\ The EPA notes that the consideration of projected actual
emissions in the future analytic year--as opposed to allowable
levels--is also consistent with the statute's instruction that
states in their SIPs (or the EPA when promulgating a FIP) prohibit
emissions that ``will'' impermissibly impact downwind air quality.
This term is reasonably interpreted to mean that the EPA should
evaluate anticipated emissions (based on what sources will emit)
rather than potential emissions (based on what sources could emit).
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    The EPA notes that there is a further distinction between the
section 107(d) designations provision and the section 110(a)(2)(D)(i)
good neighbor provision in that the latter provision uses different
terms to describe the threshold for determining whether emissions in an
upwind state should be regulated (``contribute significantly'') as
compared to the standard for evaluating the impact of nearby areas in
the designations process (``contribute''). Thus, at step 3 of the good
neighbor analysis the EPA evaluates additional factors, including cost
and air-quality considerations, to determine whether emissions from a
linked upwind state would violate the good neighbor provision. Only if
the EPA at step 3 determines that the upwind state's emissions would
violate the good neighbor provision will it proceed to step 4 to
require emissions in the upwind state to be controlled so as to address
the identified violation. This approach to steps 3 and 4 is analogous
to the trigger for the application of Part D requirements to sources
upon designation of an area to nonattainment. Thus, the EPA reasonably
interprets the good neighbor provision to not require it or the upwind
state to proceed to step 4 and implement any enforceable measures to
``prohibit'' emissions unless it identifies a violation of the
provision at step 3. See, e.g., 76 FR 48262 (finding at step 3 that the
District of Columbia is not violating the good neighbor provision, and
therefore will not at step 4 be subject to any control requirements in
CSAPR, because no cost-effective emission reduction opportunities were
identified in the District).
    Comment: Several comments received on the EPA's proposal addressed
the EPA's approach to identifying downwind air quality problems at step
1 of the framework. These comments contend that the agency's analysis
relies on projected future emission levels that are not based on
enforceable mechanisms that ensure those emission levels will actually
occur or remain in place in a future year and thus improve air quality
as modeled. The commenters contend that the Act requires that these
emission levels be enforceable in order for modeling relying on such
assumptions to be used to support any determination under the good
neighbor provision.
    One commenter states that the EPA's approach is contrary to the
fundamental principle behind the statutory obligation that SIPs must
``include enforceable emission limitations'' and ``contain adequate
provisions prohibiting'' emissions that unlawfully impact other states,
citing CAA sections 110(a)(2)(A) and (D). The commenter contends that
the EPA subverts the text and meaning of section 110(a)(2) by declaring
that future air quality will attain the NAAQS without ensuring that the
emission levels that informed that prediction are enforceable. The
commenter further contends that enforceability of control measures is a
consistent requirement throughout the CAA, including for redesignation
to attainment under section 107(d)(3)(E)(iii) and for attainment SIPs
under section 172(c)(6).
    In support of this argument, another commenter cites CAA section
110(a)(2)(A), which indicates that SIPs must ``include enforceable
emission limitations and other control measures, means, or techniques .
. . as well as schedules and timetables for compliance.'' The commenter
further cites CAA section 110(a)(2)(C), which indicates that SIPs must
``include a program to provide for the enforcement of the measures
described in subparagraph (A), and regulation of the modification and
construction of any stationary source within the areas covered by the
plan as necessary to assure that national ambient air quality standards
are achieved, including a permit program. . . .''
    Response: As explained in this section, the EPA does not agree that
all assumptions in a model that inform future-year projections must be
subject to enforceable commitments before the EPA can rely on the
modeling for purposes of identifying downwind air quality problems.
    As discussed earlier, within the four-step framework, the EPA
interprets the good neighbor provision to require sources in upwind
states to implement enforceable emission limitations only if: (1)
Downwind air quality problems are identified at step 1, (2) emissions
from an upwind state are linked to a

downwind air quality problem at step 2, and (3) sources in the linked
upwind state are identified at step 3 as having emissions that
significantly contribute to nonattainment and interfere with
maintenance of the NAAQS, considering cost- and air-quality-based
factors. If all three of these steps are not satisfied, then the state
is not required at step 4 to include provisions in its SIP prohibiting
any level of reductions because the EPA has determined that emissions
from the state will not significantly contribute to nonattainment or
interfere with maintenance of the NAAQS downwind and accordingly there
are no emissions the state is obligated to ``prohibit'' under the good
neighbor provision. Thus, the EPA does not agree that modeling used to
evaluate ozone concentrations at step 1 must only consider enforceable
emission levels. Rather, as explained in detail earlier, the EPA's
approach is consistent with other applicable provisions of title I
regarding the designations and planning requirements applicable in
nonattainment areas.
    The fact that certain statutory provisions require imposition of
enforceable measures does not contradict the EPA's interpretation
regarding when the good neighbor provision requires such measures. In
fact, the requirement at section 172(c)(6), which commenters cite, that
attainment plans for designated nonattainment areas include enforceable
measures to bring the area into attainment is consistent with the EPA's
interpretation of the good neighbor provision, because that requirement
only applies once an area has been designated nonattainment. Similarly,
in the EPA's four-step framework, if the EPA identifies a downwind air
quality problem and determines that an upwind state significantly
contributes to nonattainment or interferes with maintenance of the
NAAQS in that downwind area, the EPA would also require, at step 4, the
imposition of enforceable measures to address the upwind state's impact
on the downwind area. Thus, consistent with the terms of the good
neighbor provision, the EPA requires states to ``prohibit'' emissions
upon a determination that such emissions are having the requisite
impact on downwind areas. However, the requirement of section 172(c)(6)
is not a predicate for an attainment designation, as would be the case
by analogy to commenters' suggestion that enforceable limits are a
required predicate for a determination that sources do not violate the
good neighbor provision.
    The citation to the requirements for the redesignation of areas to
attainment under section 107(d)(3) is inapposite. Such requirements
only apply in areas that have at one point been designated
nonattainment under section 107(d)(1). The commenter has not explained
why the requirements for redesignation, which apply at the end of a
process for nonattainment areas that is well after initial area
designations, should be considered relevant to interpreting initial
obligations under the good neighbor provision. For the reasons
described earlier, the EPA believes it is more reasonable to liken the
process for identifying downwind air quality problems under the good
neighbor provision to initial designations, which do not turn on
evaluations of whether or not the measured emission levels informing
the designation are due to enforceable reductions.
    The EPA also does not agree that either section 110(a)(2)(A) or
section 110(a)(2)(C) require the state to include measures to make the
projected emission limitations enforceable in order to address the good
neighbor provision. Section 110(a)(2)(A) states that a SIP should
``include enforceable emission limitations and other control measures,
means, or techniques . . . as may be necessary or appropriate to meet
the applicable requirements'' of the CAA (emphasis added). As described
earlier, a finding at step 1 that there is no downwind air quality
problem supports a conclusion that a state simply will not contribute
significantly or interfere with maintenance of the NAAQS in another
state, and thus that the state need not prohibit any particular level
of emissions under the good neighbor provision. Accordingly, under
section 110(a)(2)(A), no emission limitations would be ``necessary or
appropriate'' to meet the good neighbor provision. Section 110(a)(2)(C)
similarly indicates that SIPs should provide for the enforcement of
measures cited to support the requirements of section 110(a)(2)(A), but
it does not independently require the imposition of additional control
measures.
    For these reasons, the EPA does not agree with the commenters'
conclusion that the statute requires the imposition of enforceable
emission limitations even where the agency has determined that an
upwind state does not significantly contribute to nonattainment or
interfere with maintenance of the NAAQS in a downwind state. See
section III.C.2 of this notice for further discussion regarding the
EPA's air quality analysis used to support this final determination.

B. Selection of a Future Analytic Year

    In this action, consistent with its practice in previous
rulemakings addressing ozone transport, the EPA focuses its analysis on
a future analytic year in light of the forward-looking nature of the
good neighbor obligation in section 110(a)(2)(D)(i)(I) and in
consideration of prior court decisions. With respect to the statutory
language of the good neighbor provision, the statute requires that
states prohibit emissions that ``will'' significantly contribute to
nonattainment or interfere with maintenance of the NAAQS in any other
state. The EPA reasonably interprets this language as permitting states
and the EPA in implementing the good neighbor provision to
prospectively evaluate downwind air quality problems and the need for
further upwind emission reductions. In the EPA's prior regional
transport rulemakings, the agency generally evaluated whether upwind
states ``will'' significantly contribute to nonattainment or interfere
with maintenance based on projections of air quality in the future year
in which any emission reductions would be expected to go into effect.
For the 1998 NOX SIP Call, it used an analytic year of 2007,
and for the 2005 CAIR, it used analytic years of 2009 and 2010 for
ozone and PM2.5, respectively. 63 FR 57450; 70 FR 25241. The
D.C. Circuit affirmed the EPA's interpretation of ``will'' in CAIR,
finding the EPA's consideration of future projected air quality (in
addition to current measured data) to be a reasonable interpretation of
an ambiguous term. North Carolina, 531 F.3d at 913-14. The EPA applied
the same approach in finalizing CSAPR in 2011 and the CSAPR Update in
2016 by evaluating air quality in 2012 and 2017, respectively. 76 FR
48211; 81 FR 74537.
    Consistent with this approach, a key decision that informs the
application of the interstate transport framework is the selection of a
future analytic year. Several court decisions guide the factors that
the EPA considers in selecting an appropriate future analytic year for
this action. First, in North Carolina, the D.C. Circuit held that the
timeframe for implementation of emission reductions required by the
good neighbor provision should be selected by considering the relevant
attainment dates of downwind nonattainment areas affected by interstate
transport of air pollution. 531 F.3d at 911-12. Moreover, the U.S.
Supreme Court and the D.C. Circuit have both held that the EPA may not
over-control upwind state emissions relative to the downwind air
quality problems to which the upwind emissions contribute.
Specifically, the

courts found that the agency may not require emission reductions (at
steps 3 and 4 of the good neighbor framework) from a state that are
greater than necessary to achieve attainment and maintenance of the
NAAQS in all of the downwind areas to which that state is linked. See
EME Homer City, 134 S. Ct. at 1600-01; EME Homer City II, 795 F.3d at
127. In particular, in EME Homer City II, the D.C. Circuit determined
that the CSAPR phase 2 ozone-season NOX budgets for ten
states were invalid because the EPA's modeling showed that the downwind
air quality problems to which these states were linked would be
resolved by 2014, when the phase 2 budgets were scheduled to be
implemented. 795 F.3d at 129-30.\59\ These court decisions therefore
support the agency's choice to use a future analytic year in order to
help ensure that the EPA does not over- or under-control upwind state
emissions at the time that controls will be implemented. Generally,
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 (e.g., fleet penetration of
mobile source programs through fleet turnover) and changing market
conditions for electricity generation technologies and fuels.\60\ As a
result of expected emission reductions and resulting lower ozone
concentrations in the future, the agency is relatively more at risk of
over-controlling emissions were it not to identify an appropriate
future year in which controls could be feasibly implemented to further
reduce emissions and ozone concentrations. Therefore, because further
controls cannot be implemented feasibly for several years, as discussed
further below, and emissions, upwind contributions, and downwind ozone
concentrations will likely be lower at that later point in time due to
continued phase-in of existing regulatory programs, changing market
conditions, and fleet turnover, it is reasonable for the EPA to
evaluate air quality (at steps 1 and 2 of the good neighbor framework)
in a future analytic year. In other words, it is appropriate for the
EPA's evaluation of air quality to focus on a future analytic year that
is aligned with feasible timing for installation of controls in order
to ensure that downwind air quality problems exist (at step 1) and that
upwind states continue (at step 2) to be linked to downwind air quality
problems at a time when any cost-effective emission reductions
(identified at step 3) would be implemented (at step 4) and to ensure
that such reductions do not over-control relative to the identified
ozone problems. Cf. EME Homer City, 134 S. Ct. at 1600-01; EME Homer
City II, 795 F.3d at 127.
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    \59\ The Supreme Court also held that the agency may not over-
control upwind state emissions such that the impact from an upwind
state to all downwind air quality problems is below the contribution
threshold applied at step 2 that ``linked'' the upwind state in the
first place, EME Homer City, 134 S. Ct. at 1600-01, but CSAPR was
not found in EME Homer City II to have violated the prohibition on
this type of over-control.
    \60\ Annual Energy Outlook 2018. Electricity Supply,
Disposition, Prices, and Emissions. Reference Case. Department of
Energy, Energy Information Administration. Available at https://www.eia.gov/outlooks/aeo/data/browser/#/?id=8-AEO2018&cases=ref2018&sourcekey=0.
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    Thus, in determining the appropriate future analytic year for
purposes of assessing remaining interstate transport obligations for
the 2008 ozone NAAQS, the EPA considered two primary factors: (1) The
applicable attainment dates for this NAAQS; and (2) the timing to
feasibly implement new NOX control strategies. These factors
are discussed in the following two sections. The EPA is finalizing its
proposed determination that these factors collectively support the
identification of 2023 as the future analytic year for evaluating
whether further unfulfilled good neighbor obligations for the 2008
ozone NAAQS will remain after implementation of the CSAPR Update.
    Comment: Several commenters challenge the EPA's interpretation of
the term ``will'' in the good neighbor provision to permit the
identification of downwind air quality problems based on evaluating air
quality in a future year. The commenters contend that the EPA's
interpretation is inconsistent with the Clean Air Act for various
reasons.
    One commenter contends that the word ``will'' merely reflects the
temporal dimension of interstate transport of pollutants--i.e., the
fact that an upwind state ``will'' significantly contribute to
nonattainment or interfere with maintenance as soon as its ozone
pollutants are transported in significant amounts into a downwind area
measuring nonattainment or struggling to maintain the NAAQS. The
commenter concedes that the term ``will'' also contemplates impacts in
relevant future compliance years but contends it is not limited to the
distant future. The commenter asserts that section 110's prohibition
against ``emitting'' pollutants that will significantly contribute to
downwind nonattainment (or interfere with downwind maintenance) plainly
indicates that the phrase ``will contribute'' must be read to include
both current and future emissions, citing North Carolina, 531 F.3d at
914. The commenter contends that the EPA's interpretation of ``will''
to encompass future air quality, as affirmed by the D.C. Circuit in the
CAIR litigation, was reasonable only in light of the agency's
complementary consideration of present measured data. The commenter
states that the EPA's proposed interpretation would grant the agency
unfettered discretion, permitting it to find that ``will'' refers to
any future time that the EPA selects, even one only in the distant
future. The commenter contends that the interpretation of ``will'' to
refer to a future year when ``any emission reductions would be expected
to go into effect'' is circular, meaningless, and irrational where the
EPA finds that no further emission reductions are required.
    Another commenter states that Congress specified that
implementation plans must prohibit ``any'' pollution from ``any''
source that will contribute significantly to nonattainment and
interfere with maintenance, and this includes pollution that will
contibute between now and 2023. The commenter states that the fact that
other pollution emitted at some other time allegedly will not
contribute significantly to nonattainment and interfere with
maintenance does not excuse the EPA's failure to prohibit the pollution
that will do so between now and 2023.
    A further commenter contends that the use of the word ``emitting''
in section 110(a)(2)(D)(i) includes protection against current
emissions from upwind sources that are significantly contributing to
downwind areas' inability to attain a NAAQS. The commenter cites CAA
section 126(b), which provides that a state ``may petition the
Administrator for a finding that any major source or group of
stationary sources emits or would emit any air pollutant in violation
of the prohibition of'' section 110(a)(2)(D)(i) (emphasis added). The
commenter states that this clause confirms that current air pollution
transport cannot be ignored. Similarly, one commenter asserts that,
when interpreting the term ``emit'' in other provisions of the Act, the
D.C. Circuit has held that it refers to actual, present emissions, as
opposed to mere potential or future emissions, citing New York v. EPA,
413 F.3d 3, 39-40 (D.C. cir. 2005).
    Response: These commenters are incorrect, for five reasons.
    First, the commenters misconstrue both the facts and the holding of
the D.C. Circuit's decision in North Carolina. In that case, the court
was reviewing a challenge to the EPA's approach to identifying downwind

receptors in CAIR wherein the agency considered only those areas
projected to be in nonattainment in a future year to be downwind
receptors, but not areas projected to be in attainment that were
currently measuring nonattainment. 531 F.3d at 913. The court explained
that the EPA had consistently interpreted ``will'' in both the
NOX SIP Call and CAIR to ``indicate sources that presently
and at some point in the future `will' contribute to nonattainment,''
and noted that both rules relied on projections of nonattainment in the
future year in which the rule would go into effect. Id. at 914. Thus,
contrary to the commenters' assertions, the EPA did not identify
downwind air quality problems in CAIR based on either a current
measured violation or a projected violation of the NAAQS. Rather, in
CAIR the EPA determined that a downwind air quality problem was
required to be addressed under the good neighbor provision only if both
the current measured data and the projected future data demonstrated
there would be an air quality problem in a downwind area.
    The court affirmed the EPA's interpretation, explaining that
``will'' ``can mean either certainty or indicate the future tense'' and
held that it is reasonable for the EPA to give effect to both potential
meanings of the word. Id. Thus, although the court acknowledged that
the term ``will'' could refer to the certainty of an upwind state's
impact on a downwind state (i.e., based on current measured
nonattainment), as one commenter contends it should, the court also
clearly acknowledged the ambiguity of this term and indicated this was
not the only reasonable interpretation. In light of this ambiguity, the
D.C. Circuit affirmed that the EPA's approach, which gives effect to
both meanings, is permissible under the Act. Here, as explained in more
detail later in section III.C.3, the EPA is identifying downwind
nonattainment receptors based on both current measured data and
projected future air quality, just as the EPA did in the CSAPR Update,
as well as CAIR and the NOX SIP Call.\61\
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    \61\ In compliance with a separate holding of the North Carolina
decision, the EPA further evaluates receptors in areas currently
attaining the standard based on projected future air quality in
order to ensure that the ``interfere with maintenance'' clause of
the good neighbor provision is given independent effect. See 531
F.3d at 910-11.
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    Second, the EPA also does not agree that the term ``emitting''
precludes its interpretation of ``will'' in the good neighbor
provision. The relevant clause of the CAA section 110(a)(2)(D)(i)
requires state plans (or federal plans, where the agency is acting in
the state's stead) to ``contain adequate provisions . . . prohibiting .
. . any source or other type of emissions activity within the State
from emitting any air pollution in amounts which will'' improperly
impact downwind areas under the remaining terms of the provision
(emphasis added). Thus, the term ``emitting'' should be read in concert
with the prohibition required in this clause to refer to the limitation
that should be imposed on sources otherwise found to be in violation of
section 110(a)(2)(D)(i)(I); the term ``emitting'' in its statutory
context does not clearly define the temporal requirements for
determining whether such a violation exists in the first instance.
Rather, the good neighbor provision indicates that sources should be
``prohibit[ed] . . . from emitting,'' which is a forward-looking phrase
intended to address limitations on a source's future activity. The
introduction of the phrase ``which will'' at the end of the clause
further serves as a transition from the general obligation to impose a
prohibition to the specific circumstances under which the prohibition
will apply.
    The commenter's reference to the court's interpretation of ``emit''
in New York is therefore an inapt citation for purposes of interpreting
the good neighbor provision requirements. In that case, the court was
evaluating whether the use of the term ``emit'' in certain
nonattainment new source review provisions (a program imposing a
permitting requirement on the construction of new major sources of air
pollutants and major modifications of existing sources) was intended to
refer to actual or allowable emissions when determining whether
modifications to the source trigger a permitting requirement. 413 F.3d
3, 39-40 (D.C. Cir. 2005). The court noted that the statutory
provisions governing new source review use different language to
distinguish between actual emissions (``emit'' or ``emitted'') and
potential emissions (``potential to emit'' or ``emission
limitations''). Id. In the case of the good neighbor provision, the
phrase ``prohibiting . . . sources . . . from emitting'' certain
amounts of pollution is more consistent with the terminology used to
indicate potential emissions, and therefore more reasonably refers to
the emission limitation that would be imposed under the good neighbor
provision if the requisite finding of significant contribution or
interference with maintenance is made. Thus, the statute's use of the
term ``emit'' does not clearly preclude the EPA's interpretation of
``will'' as permitting the analysis of downwind air quality in a future
year to evaluate interstate transport. The new source review
preconstruction permitting program expressly lays out the predicate
trigger for the permitting requirement (and the D.C. Circuit in New
York was considering whether EPA's interpretation and application of
those statutory terms was permissible); the good neighbor provision
does not expressly lay out the methodology (including the termporal
frame of reference) for determining what constitutes a good neighbor
violation (and the D.C. Circuit in North Carolina affirmed EPA's
construction of the governing statutory provision).
    Third, the commenters err in suggesting that the standard for
granting a section 126(b) petition is incorporated into the good
neighbor provision. While section 126(b) cross-references the
prohibition in section 110(a)(2)(D)(i),\62\ the cross-reference is
unidirectional. There is no indication that Congress intended for the
``emits or would emits'' language from section 126(b) to be conversely
incorporated into section 110, and section 110(a)(2)(D)(i) does not
contain any reference to section 126(b). In any event, the commenters
have not offered any explanation regarding how any relevant
interpretation of section 126(b) should inform the EPA's interpretation
of section 110 with respect to current emissions data or projections of
future air quality.
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    \62\ The text of CAA section 126 as codified in the U.S. Code
cross-references CAA section 110(a)(2)(D)(ii) instead of CAA section
110(a)(2)(D)(i). The courts have confirmed that this is a
scrivener's error and the correct cross-reference is to CAA section
110(a)(2)(D)(i). See Appalachian Power Co. v. EPA, 249 F.3d 1032,
1040-44 (D.C. Cir. 2001).
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    Fourth, while the EPA agrees that the references to ``any'' in
section 110(a)(2)(D)(i) means that any source of emissions of any air
pollutant having the requisite impact may be subject to control under
that provision, the commenter does not explain how this term imposes an
obligation to select a specific analytic year when evaluating whether
such emissions are improperly impacting downwind areas and therefore
whether such control is necessary or authorized. Rather, as the
commenters fail to acknowledge, the EPA is only authorized under the
good neighbor provision to require the prohibition of such emissions in
``amounts which will'' improperly impact another state with respect to
the NAAQS. The Supreme Court has held that this language means that any
emission reductions imposed under the good neighbor provision be no
greater than necessary to address downwind

nonattainment and maintenance of the NAAQS, i.e., that the EPA avoid
unnecessary ``over-control'' of emissions from upwind states. See EME
Homer City, 134 S. Ct. at 1608. In interpreting that decision, the D.C.
Circuit declared EPA's emission reduction requirements for certain
states to be invalid under the good neighbor provision where the EPA
had information indicating that there will be no downwind air quality
problems by the time the emission reductions would have been
implemented. See EME Homer City II, 795 F.3d at 130. Thus, the EPA does
not agree that information indicating a current violation necessarily
obligates the EPA to impose additional emission reductions, especially
if additional information indicates there will be no downwind air
quality issues to address by the time such reductions could be in
place. On the contrary, the D.C. Circuit has already spoken to both the
temporal flexibilities and the temporal obligations imposed by the good
neighbor provision. The court has both affirmed the EPA's
interpretation of ``will'' as permitting consideration of projected
future air quality and instructed the EPA to consider relevant downwind
attainment dates in establishing future compliance timeframes. North
Carolina, 531 F.3d at 910-11, 913. The EPA has reasonably aligned these
two considerations to ensure that emission reductions required from
``any source'' within the anticipated compliance timeframes are in fact
necessary to address downwind air quality problems at that time, in
order to avoid potential over-control in contradiction of EME Homer
City.
    Fifth and finally, the EPA does not agree that its interpretation
of ``will'' to permit consideration of projected future air quality
grants the agency unfettered discretion to choose any future analytic
year, however distant, to justify its conclusions. While the EPA does
contend that the statute permits the consideration of air quality in a
future year aligned with anticipated compliance, the EPA concedes that
it must both comply with the holding in North Carolina to appropriately
consider relevant downwind attainment dates and provide a reasonable,
non-arbitrary justification for selecting an appropriate future
analytic year. The EPA provides such an explanation for the selection
of the 2023 analytic year in the following sections of this notice.
1. Attainment Dates for the 2008 Ozone NAAQS
    As previously noted, in determining the appropriate future analytic
year for purposes of assessing remaining interstate transport
obligations for the 2008 ozone NAAQS, the EPA first considers the
downwind attainment dates for the 2008 ozone NAAQS. Many areas
currently have attainment dates of July 20, 2018 for areas classified
as Moderate. However, as noted earlier, the 2017 ozone season was the
last full season from which data could be used to determine attainment
of the NAAQS by that date.\63\ Given that the 2017 ozone season has now
passed, it is not possible to achieve additional emission reductions by
the Moderate area attainment date. It is therefore necessary to
consider what subsequent attainment dates should inform the EPA's
analysis. The next attainment dates for the 2008 ozone NAAQS will be
July 20, 2021, for nonattainment areas classified as Serious, and July
20, 2027, for nonattainment areas classified as Severe.\64\ Because the
various attainment deadlines are in July, which is in the middle of the
ozone monitoring season for all states, data from the calendar year
prior to the attainment date--e.g., data from 2020 for the 2021
attainment date and from 2026 for the 2027 attainment date--are the
last data that can be used to demonstrate attainment with the NAAQS by
the relevant attainment date. Therefore, the EPA considers the control
strategies that could be implemented by 2020 and 2026 in assessing the
2021 and 2027 attainment dates in its subsequent analysis. The EPA has
also considered that, in all cases, the statute provides that areas
should attain as expeditiously as practicable. See CAA section
181(a)(1).
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    \63\ As discussed in Section II.D, emission reductions that were
feasible and cost-effective for the 2017 ozone season were the focus
of the CSAPR Update.
    \64\ While there are no areas (outside of California) that are
currently designated as Serious or Severe for the 2008 ozone NAAQS,
the CAA requires that the EPA reclassify to Serious any Moderate
nonattainment areas that fail to attain by their attainment date of
July 20, 2018. See CAA section 181(b)(2), 42 U.S.C. 7511(b)(2).
Similarly, if any area fails to attain by the Serious area
attainment date, the CAA requires that the EPA reclassify the area
to Severe.
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    Comment: One commenter notes that all of the states burdened by the
interstate pollution addressed by the proposed action are currently
subject to attainment deadlines in 2015, 2016, or 2018, and it is
likely that some states will be determined to have failed to attain and
become subject to more stringent requirements and a new deadline of
July 20, 2021. The commenter notes that no relevant states are subject
to a deadline of 2027, nor will any be subject to a 2027 deadline in
the future unless they fail yet again to attain by 2021. The commenter
therefore contends that the EPA's decision to consider the 2027
attainment deadline is illegal, unexplained, and arbitrary.
    Response: The EPA does not agree that it may not consider any later
attainment dates simply because there are no states currently subject
to that deadline. As the commenter concedes, there are also currently
no areas in the east subject to the 2021 Serious area attainment date,
yet the EPA nonetheless believes it is appropriate to consider both
future attainment dates in selecting a future analytic year, especially
in light of the limitations on additional control strategies available
in the near term, as discussed in more detail later. Moreover, the EPA
was required to select an analytic year before the Moderate area
attainment date had passed in order to provide sufficient time to
conduct air quality modeling before issuing a proposal for the state of
Kentucky by the court-ordered deadline in June 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 at issue in this
action, it was necessary to complete the modeling in time for the EPA
to issue a proposed action for Kentucky in advance of that deadline. At
that time, as the commenter notes, all areas were subject to attainment
dates in 2015, 2016, or 2018, and emission reductions intended to
assist with attainment by those dates would need to be achieved by the
prior year's ozone season. Since all of these dates were effectively in
the past (including one date that fell less than two weeks after the
date of the proposal of this action), the EPA reasonably looked forward
to the next potential attainment dates for purposes of this analysis.
2. Feasibility of Control Strategies To Further Reduce Ozone Season
NOX Emissions
    The EPA's analysis of the feasibility of NOX control
strategies reflects the time needed to plan for, install, test, and
place into operation EGU and non-EGU NOX reduction
strategies regionally--i.e., across multiple states. This regional
analytic approach is consistent with the regional nature of interstate
ozone pollution transport as described in section II.A. As proposed,
the agency adopted this approach for this final action based on
previous interstate ozone transport analyses showing that where eastern
downwind ozone problems are identified, multiple upwind states
typically are linked to

these problems.\65\ Specifically of relevance to this action, as
discussed in section II.C, the EPA's prospective air quality assessment
of CSAPR Update implementation found that 21 states each continued to
contribute greater than or equal to one percent of the 2008 ozone NAAQS
(i.e., 0.75 ppb) to identified downwind nonattainment or maintenance
receptors in multiple downwind states in 2017. Thus, to reasonably
address any remaining ozone transport problems, the EPA must identify
and apportion emission reduction responsibility across multiple upwind
states. In other words, given the breadth of the ozone transport
problem identified in the CSAPR Update and the breadth of the remaining
CAA obligations (i.e., for 20 states), it is reasonable for the EPA's
analysis to be regional. Where such an analysis is needed for multiple
states, the inquiry into the availability and feasibility of control
options is considerably more time-consuming than it would be for a
single facility or state or sector.
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    \65\ 81 FR 74538.
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    Further, the feasibility of new emissions controls should be
considered with regard to multiple upwind source categories to ensure
that the agency properly evaluates NOX reduction potential
and cost-effectiveness from all reasonable control measures.
NOX emissions come from multiple anthropogenic source
categories, such as mobile sources, electric utilities, and stationary
non-EGU sources (e.g., resource extraction industries and industrial
and commercial facilities). Among stationary sources, EGUs in the
eastern U.S. have been the primary subject of regulation to address
interstate ozone pollution transport and have made significant
financial investments to achieve emission reductions. While the EPA
continues to evaluate control feasibility for EGUs in its analysis, the
EPA's recent analyses indicate that non-EGU source categories, which
the EPA has not made subject to new regulations to address interstate
ozone transport since the NOX SIP Call, may also warrant
further assessment of their potential to cost-effectively reduce
NOX relative to EGUs.\66\ Accordingly, the EPA's assessment
of control feasibility focuses on both EGU and non-EGU sources.
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    \66\ See Assessment of Non-EGU NOX Emission Controls,
Cost of Controls, and Time for Compliance Final TSD from the CSAPR
Update (U.S. EPA, August 2016) in the docket for this action.
---------------------------------------------------------------------------

    Although mobile source emissions also influence ozone formation,
transport, and ambient concentrations, the EPA has historically
addressed mobile source emissions through national rulemakings. As a
result, mobile source emissions are already decreasing because of