[Federal Register Volume 87, Number 35 (Tuesday, February 22, 2022)]
[Proposed Rules]
[Pages 9498-9516]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-02947]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2021-0841; EPA-HQ-OAR-2021-0663; FRL-9423-01-R4]


Air Plan Disapproval; Kentucky; Interstate Transport Requirements 
for the 2015 8-Hour Ozone National Ambient Air Quality Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the 
Environmental Protection Agency (EPA or Agency) is proposing to 
disapprove a State Implementation Plan (SIP) submittal from the 
Kentucky Energy and Environment Cabinet, Department of Environmental 
Quality (DAQ) (herein after referred to as Kentucky or the 
Commonwealth) regarding the interstate transport requirements for the 
2015 8-hour ozone national ambient air quality standards (NAAQS or 
standard). The ``Good Neighbor'' or ``Interstate Transport'' provision 
requires that each state's implementation plan contain adequate 
provisions to prohibit emissions from within the state from 
significantly contributing to nonattainment or interfering with 
maintenance of the NAAQS in other states. This requirement is part of 
the broader set of ``infrastructure'' requirements, which are designed 
to ensure that the structural components of each state's air quality 
management program are adequate to meet the state's responsibilities 
under the CAA. This disapproval, if finalized, will establish a 2-year 
deadline for EPA to promulgate a Federal Implementation Plan (FIP) to 
address the relevant interstate transport requirements, unless EPA 
approves a subsequent SIP submittal that meets these requirements. 
Disapproval does not start a mandatory sanctions clock.

DATES: Comments must be received on or before April 25, 2022.
    Withdrawals: As of February 22, 2022, the proposed rule published 
in December 30, 2019, at 84 FR 71854, is withdrawn.

ADDRESSES: You may submit comments, identified by Docket No. EPA-R04-
OAR-2021-0841, through the Federal eRulemaking Portal at https://www.regulations.gov following the online instructions for submitting 
comments.
    Instructions: All submissions received must include the Docket No. 
EPA-R04-OAR-2021-0841 for this rulemaking. Comments received may be 
posted without change to https://www.regulations.gov/, including any 
personal information provided. For detailed instructions on submitting 
comments and additional information on the rulemaking process, see the 
``Public Participation'' heading of the SUPPLEMENTARY INFORMATION 
section of this document. Out of an abundance of caution for members of 
the public and staff, the EPA Docket Center and Reading Room are open 
to the public by appointment only to reduce the risk of transmitting 
COVID-19. The Docket Center staff also continues to provide remote 
customer service via email, phone, and webform. For further information 
on EPA Docket Center services and the current status, please visit EPA 
online at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: Evan Adams of the Air Regulatory 
Management Section, Air Planning and Implementation Branch, Air and 
Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 
Forsyth Street SW, Atlanta, Georgia 30303-8960. Mr. Adams can be 
reached by telephone at (404) 562-9009, or via electronic mail at 
[email protected].

SUPPLEMENTARY INFORMATION: Public Participation: Submit your comments, 
identified by Docket No. EPA-R04-OAR-2021-0841, at https://www.regulations.gov. Once submitted, comments cannot be edited or 
removed from the docket. EPA may publish any comment received to its 
public docket. Do not submit to EPA's docket at https://www.regulations.gov any information you consider to be Confidential 
Business Information (CBI) or other information whose disclosure is 
restricted by statute. Multimedia submissions (audio, video, etc.) must 
be accompanied by a written comment. The written comment is considered 
the official comment and should include discussion of all points you 
wish to make. EPA will generally not consider comments or comment 
contents located outside of the primary submission (i.e., on the web, 
cloud, or other file sharing system).

[[Page 9499]]

    There are two dockets supporting this action, EPA-R04-OAR-2021-0841 
and EPA-HQ-OAR-2021-0663. Docket No. EPA-R04-OAR-2021-0841 contains 
information specific to Kentucky, including this notice of proposed 
rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional 
modeling files, emissions inventory files, technical support documents, 
and other relevant supporting documentation regarding interstate 
transport of emissions for the 2015 8-hour ozone NAAQS which are being 
used to support this action. All comments regarding information in 
either of these dockets are to be made in Docket No. EPA-R04-OAR-2021-
0841. For the full EPA public comment policy, information about CBI or 
multimedia submissions, and general guidance on making effective 
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health concerns related to COVID-19, the EPA 
Docket Center and Reading Room are open to the public by appointment 
only. The Docket Center staff also continues to provide remote customer 
service via email, phone, and webform. For further information and 
updates on EPA Docket Center services, please visit EPA online at 
https://www.epa.gov/dockets.
    EPA continues to carefully and continuously monitor information 
from the Centers for Disease Control and Prevention (CDC), local area 
health departments, and Federal partners so that EPA can respond 
rapidly as conditions change regarding COVID-19.
    The indices to Docket No. EPA-R04-OAR-2021-0841 and Docket No. EPA-
HQ-OAR-2021-0663 are available electronically at www.regulations.gov. 
While all documents in each docket are listed in their respective 
index, some information may not be publicly available due to docket 
file size restrictions or content (e.g., CBI).

Table of Contents

I. Background
    A. Description of Statutory Background
    B. Description of EPA's Four Step Interstate Transport 
Regulatory Process
    C. Background on EPA's Ozone Transport Modeling Information
    D. EPA's Approach to Evaluating Interstate Transport SIPs for 
the 2015 8-Hour Ozone NAAQS
II. Summary of Kentucky's 2015 8-Hour Ozone Interstate Transport SIP 
Submission
    A. Information Related to Emission Trends From Kentucky Sources
    B. Information Related to Connecticut Monitors Provided by 
Kentucky
    C. Information Related to the Harford, Maryland Monitor Provided 
by Kentucky
    D. Summary of Conclusions From Kentucky
    E. Summary of Midwest Ozone Group TSD Appended to Kentucky's 
Submittal
III. EPA's Evaluation of Kentucky's 2015 8-Hour Ozone Interstate 
Transport SIP Submission
    A. Results of EPA's Step 1 and Step 2 Modeling and Findings for 
Kentucky
    B. Evaluation of Information Provided by Kentucky Regarding Step 
1
    C. Evaluation of Information Provided by Kentucky Regarding Step 
2
    D. Evaluation of Information Provided by Kentucky Regarding Step 
3
    E. Evaluation of Information Provided by Kentucky Regarding Step 
4
    F. Conclusion
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

    The following provides background for EPA's proposed action related 
to the interstate transport requirements for the 2015 8-hour ozone 
NAAQS for the Commonwealth of Kentucky.

A. Description of Statutory Background

    On October 1, 2015, EPA promulgated a revision to the ozone NAAQS 
(2015 8-hour ozone NAAQS), lowering the level of both the primary and 
secondary standards to 0.070 parts per million (ppm).\1\ Section 
110(a)(1) of the CAA requires states to submit, within 3 years after 
promulgation of a new or revised standard, SIP submissions meeting the 
applicable requirements of section 110(a)(2).\2\ One of these 
applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), 
otherwise known as the ``good neighbor'' or ``interstate transport'' 
provision, which generally requires SIPs to contain adequate provisions 
to prohibit in-state emissions activities from having certain adverse 
air quality effects on other states due to interstate transport of 
pollution. There are two so-called ``prongs'' within CAA section 
110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain 
adequate provisions prohibiting any source or other type of emissions 
activity within the state from emitting air pollutants in amounts that 
will significantly contribute to nonattainment of the NAAQS in another 
state (prong 1) or interfere with maintenance of the NAAQS in another 
state (prong 2). EPA and states must give independent significance to 
prong 1 and prong 2 when evaluating downwind air quality problems under 
CAA section 110(a)(2)(D)(i)(I).\3\
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    \1\ National Ambient Air Quality Standards for Ozone, Final 
Rule, 80 FR 65292 (October 26, 2015). Although the level of the 
standard is specified in the units of ppm, ozone concentrations are 
also described in parts per billion (ppb). For example, 0.070 ppm is 
equivalent to 70 ppb.
    \2\ SIP revisions that are intended to meet the applicable 
requirements of section 110(a)(1) and (2) of the CAA are often 
referred to as infrastructure SIPs and the applicable elements under 
section 110(a)(2) are referred to as infrastructure requirements.
    \3\ See North Carolina v. EPA, 531 F.3d 896, 909-11 (D.C. Cir. 
2008).
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B. Description of EPA's Four Step Interstate Transport Regulatory 
Process

    EPA is using the 4-step interstate transport framework (or 4-step 
framework) to evaluate the states' implementation plan submittals 
addressing the interstate transport provision for the 2015 8-hour ozone 
NAAQS. EPA has addressed the interstate transport requirements of CAA 
section 110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several 
regional regulatory actions, including the Cross-State Air Pollution 
Rule (CSAPR), which addressed interstate transport with respect to the 
1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter 
standards,\4\ the Cross-State Air Pollution Rule Update (CSAPR Update) 
\5\ and the Revised CSAPR Update, both of which addressed the 2008 
ozone NAAQS.\6\
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    \4\ See Federal Implementation Plans: Interstate Transport of 
Fine Particulate Matter and Ozone and Correction of SIP Approvals, 
76 FR 48208 (August 8, 2011).
    \5\ Cross-State Air Pollution Rule Update for the 2008 Ozone 
NAAQS, 81 FR 74504 (October 26, 2016).
    \6\ In 2019, the United States Court of Appeals for the District 
of Columbia Circuit (D.C. Circuit) remanded the CSAPR Update to the 
extent it failed to require upwind states to eliminate their 
significant contribution by the next applicable attainment date by 
which downwind states must come into compliance with the NAAQS, as 
established under CAA section 181(a). Wisconsin v. EPA, 938 F.3d 
303, 313 (D.C. Cir. 2019). The Revised CSAPR Update for the 2008 
Ozone NAAQS, 86 FR 23054 (April 30, 2021), responded to the remand 
of the CSAPR Update in Wisconsin and the vacatur of a separate rule, 
the ``CSAPR Close-Out,'' 83 FR 65878 (December 21, 2018), in New 
York v. EPA, 781 F. App'x. 4 (D.C. Cir. 2019).
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    Through the development and implementation of the CSAPR rulemakings 
and prior regional rulemakings pursuant to the interstate transport 
provision,\7\ EPA, working in partnership with states, developed the 
following 4-step interstate transport framework to evaluate a state's 
obligations to eliminate interstate transport emissions under the 
interstate transport provision for the ozone NAAQS: (1) Identify 
monitoring sites that are projected to have problems attaining and/or 
maintaining the NAAQS (i.e., nonattainment and/or maintenance 
receptors); (2) identify

[[Page 9500]]

states that impact those air quality problems in other (i.e., downwind) 
states sufficiently such that the states are considered ``linked'' and 
therefore warrant further review and analysis; (3) identify the 
emissions reductions necessary (if any), applying a multifactor 
analysis, to eliminate each linked upwind state's significant 
contribution to nonattainment or interference with maintenance of the 
NAAQS at the locations identified in Step 1; and (4) adopt permanent 
and enforceable measures needed to achieve those emissions reductions.
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    \7\ In addition to CSAPR rulemakings, other regional rulemakings 
addressing ozone transport include the ``NOX SIP Call,'' 
63 FR 57356 (October 27, 1998), and the ``Clean Air Interstate 
Rule'' (CAIR), 70 FR 25162 (May 12, 2005).
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C. Background on EPA's Ozone Transport Modeling Information

    In general, EPA has performed nationwide air quality modeling to 
project ozone design values which are used in combination with measured 
data to identify nonattainment and maintenance receptors. To quantify 
the contribution of emissions from specific upwind states on 2023 ozone 
design values for the identified downwind nonattainment and maintenance 
receptors, EPA performed nationwide, state-level ozone source 
apportionment modeling for 2023. The source apportionment modeling 
provided contributions to ozone at receptors from precursor emissions 
of anthropogenic nitrogen oxides (NOX) and volatile organic 
compounds (VOCs) in individual upwind states.
    EPA has released several documents containing projected design 
values, contributions, and information relevant to evaluating 
interstate transport with respect to the 2015 8-hour ozone NAAQS. 
First, on January 6, 2017, EPA published a notice of data availability 
(NODA) in which the Agency requested comment on preliminary interstate 
ozone transport data including projected ozone design values and 
interstate contributions for 2023 using a 2011 base year platform.\8\ 
In the NODA, EPA used the year 2023 as the analytic year for this 
preliminary modeling because that year aligns with the expected 
attainment year for Moderate ozone nonattainment areas for the 2015 8-
hour ozone NAAQS.\9\ On October 27, 2017, EPA released a memorandum 
(October 2017 memorandum) containing updated modeling data for 2023, 
which incorporated changes made in response to comments on the NODA, 
and noted that the modeling may be useful for states developing SIPs to 
address interstate transport obligations for the 2008 ozone NAAQS.\10\ 
On March 27, 2018, EPA issued a memorandum (March 2018 memorandum) 
noting that the same 2023 modeling data released in the October 2017 
memorandum could also be useful for identifying potential downwind air 
quality problems with respect to the 2015 8-hour ozone NAAQS at Step 1 
of the 4-step interstate transport framework.\11\ The March 2018 
memorandum also included the then newly available contribution modeling 
data for 2023 to assist states in evaluating their impact on potential 
downwind air quality problems for the 2015 8-hour ozone NAAQS under 
Step 2 of the 4-step interstate transport framework.\12\ EPA 
subsequently issued two more memoranda in August and October 2018, 
providing additional information to states developing interstate 
transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, 
respectively, potential contribution thresholds that may be appropriate 
to apply in Step 2 of the 4-step interstate transport framework, and 
considerations for identifying downwind areas that may have problems 
maintaining the standard at Step 1 of the 4-step interstate transport 
framework.\13\
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    \8\ See Notice of Availability of the Environmental Protection 
Agency's Preliminary Interstate Ozone Transport Modeling Data for 
the 2015 8-hour Ozone National Ambient Air Quality Standard (NAAQS), 
82 FR 1733 (January 6, 2017).
    \9\ See 82 FR 1733, 1735 (January 6, 2017).
    \10\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2008 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), October 27, 2017 (``October 2017 memorandum''), 
available in Docket No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
    \11\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), March 27, 2018 (``March 2018 memorandum''), 
available in Docket No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
    \12\ The March 2018 memorandum, however, provided, ``While the 
information in this memorandum and the associated air quality 
analysis data could be used to inform the development of these SIPs, 
the information is not a final determination regarding states' 
obligations under the good neighbor provision. Any such 
determination would be made through notice-and-comment rulemaking.''
    \13\ See Analysis of Contribution Thresholds for Use in Clean 
Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards, August 31, 2018) (``August 2018 
memorandum''), and Considerations for Identifying Maintenance 
Receptors for Use in Clean Air Act Section 110(a)(2)(D)(i)(I) 
Interstate Transport State Implementation Plan Submissions for the 
2015 Ozone National Ambient Air Quality Standards, October 19, 2018 
(``October 2018 memorandum''), available in Docket No. EPA-HQ-OAR-
2021-0663 for this action or at https://www.epa.gov/airmarkets/memo-and-supplemental-information-regarding-interstate-transport-sips-2015-ozone-naaqs.
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    Since the release of the modeling data shared in the March 2018 
memorandum, EPA performed updated modeling using a 2016-based emissions 
modeling platform (i.e., 2016v1). This emissions platform was developed 
under the EPA/Multi-Jurisdictional Organization (MJO)/state 
collaborative project.\14\ This collaborative project was a multi-year 
joint effort by EPA, MJOs, and states to develop a new, more recent 
emissions platform for use by EPA and states in regulatory modeling as 
an improvement over the dated 2011-based platform that EPA had used to 
project ozone design values and contribution data provided in the 2017 
and 2018 memoranda. EPA used the 2016v1 emissions to project ozone 
design values and contributions for 2023. On October 30, 2020, in the 
Notice of Proposed Rulemaking for the Revised CSAPR Update, EPA 
released and accepted public comment on 2023 modeling that used the 
2016v1 emissions platform.\15\ Although the Revised CSAPR Update 
addressed transport for the 2008 ozone NAAQS, the projected design 
values and contributions from the 2016v1 platform are also useful for 
identifying downwind ozone problems and linkages with respect to the 
2015 8-hour ozone NAAQS.\16\
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    \14\ The results of this modeling, as well as the underlying 
modeling files, are included in Docket No. EPA-HQ-OAR-2021-0663.
    \15\ See 85 FR 68964, 68981 (October 30, 2020).
    \16\ See the Air Quality Modeling Technical Support Document for 
the Final Revised Cross-State Air Pollution Rule Update, included in 
Docket No. EPA-HQ-OAR-2021-0663.
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    Following the Revised CSAPR Update final rule, EPA made further 
updates to the 2016 emissions platform to include mobile emissions from 
EPA's Motor Vehicle Emission Simulator (MOVES) model \17\ and updated 
emissions projections for electric generating units (EGUs) that reflect 
the emissions reductions from the Revised CSAPR Update, recent 
information on plant closures, and other sector trends. The construct 
of the updated emissions platform, 2016v2, is described in the 
Preparation of Emissions Inventories for the 2016v2 North American 
Emissions Modeling Platform technical support document (TSD) for this 
proposed rule and is included in Docket No. EPA-HQ-OAR-2021-0663. EPA 
performed air quality modeling of the 2016v2 emissions using the most 
recent public release version of the Comprehensive Air Quality Modeling 
with Extensions (CAMx) photochemical modeling,

[[Page 9501]]

version 7.10.\18\ EPA proposes to primarily rely on modeling based on 
the updated and newly available 2016v2 emissions platform in evaluating 
these submissions with respect to Steps 1 and 2 of the 4-step 
interstate transport framework. By using the updated modeling results, 
EPA is using the most current and technically appropriate information 
for this proposed rulemaking. Section III of this notice and the Air 
Quality Modeling TSD included in Docket No. EPA-HQ-OAR-2021-0663 for 
this proposal contain additional detail on the modeling performed using 
the 2016v2 emissions modeling.
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    \17\ Additional details and documentation related to the MOVES3 
model can be found at https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves.
    \18\ Ramboll Environment and Health, January 2021, www.camx.com.
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    In this notice, EPA is accepting public comment on this updated 
2023 modeling, which uses the 2016v2 emissions platform. Details on the 
air quality modeling and the methods for projecting design values and 
determining contributions in 2023 are described in the Air Quality 
Modeling TSD for 2015 8-hour Ozone NAAQS Transport SIP Proposed 
Actions. Comments on EPA's air quality modeling should be submitted in 
Docket No. EPA-R04-OAR-2021-0841. Comments are not being accepted in 
Docket No. EPA-HQ-OAR-2021-0663.
    States may have chosen to rely on the results of EPA modeling and/
or alternative modeling performed by states or Multi-Jurisdictional 
Organizations (MJOs) to evaluate downwind air quality problems and 
contributions as part of their submissions. In section III, EPA 
evaluates how Kentucky used air quality modeling information in its 
submission.

D. EPA's Approach to Evaluating Interstate Transport SIPs for the 2015 
8-Hour Ozone NAAQS

    EPA proposes to apply a consistent set of policy judgments across 
all states for purposes of evaluating interstate transport obligations 
and the approvability of interstate transport SIP submittals for the 
2015 8-hour ozone NAAQS. These policy judgments reflect consistency 
with relevant case law and past Agency practice as reflected in CSAPR 
and related rulemakings. Nationwide consistency in approach is 
particularly important in the context of interstate ozone transport, 
which is a regional-scale pollution problem involving many smaller 
contributors. Effective policy solutions to the problem of interstate 
ozone transport going back to the NOX SIP Call have 
necessitated the application of a uniform framework of policy judgments 
in order to ensure an ``efficient and equitable'' approach. See EME 
Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).
    In the March, August, and October 2018 memoranda, EPA recognized 
that states may be able to establish alternative approaches to 
addressing their interstate transport obligations for the 2015 8-hour 
ozone NAAQS that vary from a nationally uniform framework. EPA 
emphasized in these memoranda, however, that such alternative 
approaches must be technically justified and appropriate in light of 
the facts and circumstances of each particular state's submittal. In 
general, EPA continues to believe that deviation from a nationally 
consistent approach to ozone transport must be substantially justified 
and have a well-documented technical basis that is consistent with 
relevant case law. Where states submitted SIPs that rely on any such 
potential concepts as may have been identified or suggested in the 
past, EPA will evaluate whether the state adequately justified the 
technical and legal basis for doing so.
    EPA notes that certain potential concepts included in an attachment 
to the March 2018 memorandum require unique consideration, and these 
ideas do not constitute Agency guidance with respect to transport 
obligations for the 2015 8-hour ozone NAAQS. Attachment A to the March 
2018 memorandum identified a ``Preliminary List of Potential 
Flexibilities'' that could potentially inform SIP development.\19\ 
However, EPA made clear in that attachment that the list of ideas were 
not suggestions endorsed by the Agency but rather ``comments provided 
in various forums'' on which EPA sought ``feedback from interested 
stakeholders.'' \20\ Further, Attachment A stated, ``EPA is not at this 
time making any determination that the ideas discussed below are 
consistent with the requirements of the CAA, nor [is EPA] specifically 
recommending that states use these approaches.'' \21\ Attachment A to 
the March 2018 memorandum, therefore, does not constitute agency 
guidance, but was intended to generate further discussion around 
potential approaches to addressing ozone transport among interested 
stakeholders. To the extent states sought to develop or rely on these 
ideas in support of their SIP submittals, EPA will thoroughly review 
the technical and legal justifications for doing so.
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    \19\ March 2018 memorandum, Attachment A.
    \20\ Id. at A-1.
    \21\ Id.
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    The remainder of this section describes EPA's proposed framework 
with respect to analytic year, definition of nonattainment and 
maintenance receptors, selection of contribution threshold, and 
multifactor control strategy assessment.
1. Selection of Analytic Year
    In general, the states and EPA must implement the interstate 
transport provision in a manner ``consistent with the provisions of 
[title I of the CAA].'' See CAA section 110(a)(2)(D)(i). This requires, 
among other things, that these obligations are addressed consistently 
with the timeframes for downwind areas to meet their CAA obligations. 
With respect to ozone NAAQS, under CAA section 181(a), this means 
obligations must be addressed ``as expeditiously as practicable'' and 
no later than the schedule of attainment dates provided in CAA section 
181(a)(1).\22\ Several D.C. Circuit court decisions address the issue 
of the relevant analytic year for the purposes of evaluating ozone 
transport air-quality problems. On September 13, 2019, the D.C. Circuit 
issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to 
the extent that it failed to require upwind states to eliminate their 
significant contribution by the next applicable attainment date by 
which downwind states must come into compliance with the NAAQS, as 
established under CAA section 181(a). See 938 F.3d 303, 313.
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    \22\ For attainment dates for the 2015 8-hour ozone NAAQS, refer 
to CAA section 181(a), 40 CFR 51.1303, and Additional Air Quality 
Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective August 3, 2018).
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    On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. 
EPA that cited the Wisconsin decision in holding that EPA must assess 
the impact of interstate transport on air quality at the next downwind 
attainment date, including Marginal area attainment dates, in 
evaluating the basis for EPA's denial of a petition under CAA section 
126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The 
court noted that ``section 126(b) incorporates the Good Neighbor 
Provision,'' and, therefore, ``EPA must find a violation [of section 
126] if an upwind source will significantly contribute to downwind 
nonattainment at the next downwind attainment deadline. Therefore, the 
agency must evaluate downwind air quality at that deadline, not at some 
later date.'' Id. at 1204 (emphasis added). EPA interprets the court's 
holding in Maryland as requiring the states and the Agency, under the 
good neighbor provision, to assess downwind air quality as 
expeditiously as practicable and no later than the next

[[Page 9502]]

applicable attainment date,\23\ which is now the Moderate area 
attainment date under CAA section 181 for ozone nonattainment. The 
Moderate area attainment date for the 2015 8-hour ozone NAAQS is August 
3, 2024.\24\ EPA believes that 2023 is now the appropriate year for 
analysis of interstate transport obligations for the 2015 8-hour ozone 
NAAQS, because the 2023 ozone season is the last relevant ozone season 
during which achieved emissions reductions in linked upwind states 
could assist downwind states with meeting the August 3, 2024, Moderate 
area attainment date for the 2015 8-hour ozone NAAQS.
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    \23\ EPA notes that the court in Maryland did not have occasion 
to evaluate circumstances in which EPA may determine that an upwind 
linkage to a downwind air quality problem exists at Steps 1 and 2 of 
the interstate transport framework by a particular attainment date, 
but for reasons of impossibility or profound uncertainty the Agency 
is unable to mandate upwind pollution controls by that date. See 
Wisconsin, 938 F.3d at 320. The D.C. Circuit noted in Wisconsin that 
upon a sufficient showing, these circumstances may warrant 
flexibility in effectuating the purpose of the interstate transport 
provision.
    \24\ See CAA section 181(a); 40 CFR 51.1303; Additional Air 
Quality Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective August 3, 2018).
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    EPA recognizes that the attainment date for nonattainment areas 
classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 
2021. Under the Maryland holding, any necessary emissions reductions to 
satisfy interstate transport obligations should have been implemented 
by no later than this date. At the time of the statutory deadline to 
submit interstate transport SIPs (October 1, 2018), many states relied 
upon EPA modeling of the year 2023, and no state provided an 
alternative analysis using a 2021 analytic year (or the prior 2020 
ozone season). However, EPA must act on SIP submittals using the 
information available at the time it takes such action. In this 
circumstance, EPA does not believe it would be appropriate to evaluate 
states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an 
attainment date that is wholly in the past, because the Agency 
interprets the interstate transport provision as forward looking. See 
86 FR 23054, 23074; see also Wisconsin, 938 F.3d at 322. Consequently, 
in this proposal EPA will use the analytical year of 2023 to evaluate 
each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect 
to the 2015 8-hour ozone NAAQS.
2. Step 1 of the 4-Step Interstate Transport Framework
    In Step 1, EPA identifies monitoring sites that are projected to 
have problems attaining and/or maintaining the NAAQS in the 2023 
analytic year. Where EPA's analysis shows that a site does not fall 
under the definition of a nonattainment or maintenance receptor, that 
site is excluded from further analysis under EPA's 4-step interstate 
transport framework. For sites that are identified as a nonattainment 
or maintenance receptor in 2023, EPA proceeds to the next step of the 
4-step interstate transport framework by identifying the upwind state's 
contribution to those receptors.
    EPA's approach to identifying ozone nonattainment and maintenance 
receptors in this action is consistent with the approach used in 
previous transport rulemakings. EPA's approach gives independent 
consideration to both the ``contribute significantly to nonattainment'' 
and the ``interfere with maintenance'' prongs of CAA section 
110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in 
North Carolina v. EPA.\25\
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    \25\ See North Carolina v. EPA, 531 F.3d 896, 910-11 (D.C. Cir. 
2008) (holding that EPA must give ``independent significance'' to 
each prong of CAA section 110(a)(2)(D)(i)(I)).
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    For the purpose of this proposal, EPA identifies nonattainment 
receptors as those monitoring sites that are projected to have average 
design values that exceed the NAAQS and that are also measuring 
nonattainment based on the most recent monitored design values. This 
approach is consistent with prior transport rulemakings, such as the 
CSAPR Update, where EPA defined nonattainment receptors as those areas 
that both currently measure nonattainment and that EPA projects will be 
in nonattainment in the future analytic year (i.e., 2023).\26\
---------------------------------------------------------------------------

    \26\ See 81 FR 74504 (October 26, 2016). This same concept, 
relying on both current monitoring data and modeling to define 
nonattainment receptor, was also applied in CAIR. See 70 FR at 
25241, 25249 (January 14, 2005); see also North Carolina, 531 F.3d 
at 913-14 (affirming as reasonable EPA's approach to defining 
nonattainment in CAIR).
---------------------------------------------------------------------------

    In addition, in this proposal, EPA identifies a receptor to be a 
``maintenance'' receptor for purposes of defining interference with 
maintenance, consistent with the method used in CSAPR and upheld by the 
D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 
136 (D.C. Cir. 2015).\27\ Specifically, EPA identified maintenance 
receptors as those receptors that would have difficulty maintaining the 
relevant NAAQS in a scenario that takes into account historical 
variability in air quality at that receptor. The variability in air 
quality was determined by evaluating the ``maximum'' future design 
value at each receptor based on a projection of the maximum measured 
design value over the relevant period. EPA interprets the projected 
maximum future design value to be a potential future air quality 
outcome consistent with the meteorology that yielded maximum measured 
concentrations in the ambient data set analyzed for that receptor 
(i.e., ozone conducive meteorology). EPA also recognizes that 
previously experienced meteorological conditions (e.g., dominant wind 
direction, temperatures, air mass patterns) promoting ozone formation 
that led to maximum concentrations in the measured data may reoccur in 
the future. The maximum design value gives a reasonable projection of 
future air quality at the receptor under a scenario in which such 
conditions do, in fact, reoccur. The projected maximum design value is 
used to identify upwind emissions that, under those circumstances, 
could interfere with the downwind area's ability to maintain the NAAQS.
---------------------------------------------------------------------------

    \27\ See 76 FR 48208 (August 8, 2011). The CSAPR Update and 
Revised CSAPR Update also used this approach. See 81 FR 74504 
(October 26, 2016) and 86 FR 23054 (April 30, 2021).
---------------------------------------------------------------------------

    Recognizing that nonattainment receptors are also, by definition, 
maintenance receptors, EPA often uses the term ``maintenance-only'' to 
refer to those receptors that are not nonattainment receptors. 
Consistent with the concepts for maintenance receptors, as described 
above, EPA identifies ``maintenance-only'' receptors as those 
monitoring sites that have projected average design values above the 
level of the applicable NAAQS, but that are not currently measuring 
nonattainment based on the most recent official design values. In 
addition, those monitoring sites with projected average design values 
below the NAAQS, but with projected maximum design values above the 
NAAQS are also identified as ``maintenance-only'' receptors, even if 
they are currently measuring nonattainment based on the most recent 
official design values.
3. Step 2 of the 4-Step Interstate Transport Framework
    In Step 2, EPA quantifies the contribution of each upwind state to 
each receptor in the 2023 analytic year. The contribution metric used 
in Step 2 is defined as the average impact from each state to each 
receptor on the days with the highest ozone concentrations at the 
receptor based on the 2023 modeling. If a state's contribution value 
does not equal or exceed the threshold of 1 percent of the NAAQS (i.e., 
0.70 ppb for the 2015 8-hour ozone NAAQS), the upwind state is not 
``linked'' to a

[[Page 9503]]

downwind air quality problem, and EPA, therefore, concludes that the 
state does not significantly contribute to nonattainment or interfere 
with maintenance of the NAAQS in the downwind states. However, if a 
state's contribution equals or exceeds the 1 percent threshold, the 
state's emissions are further evaluated in Step 3, considering both air 
quality and cost as part of a multi-factor analysis, to determine what, 
if any, emissions might be deemed ``significant'' and, thus, must be 
eliminated under CAA section 110(a)(2)(D)(i)(I).
    EPA is proposing to rely in the first instance on the 1 percent 
threshold for the purpose of evaluating a state's contribution to 
nonattainment or maintenance of the 2015 8-hour ozone NAAQS (i.e., 0.70 
ppb) at downwind receptors. This is consistent with the Step 2 approach 
that EPA applied in CSAPR for the 1997 ozone NAAQS, which has 
subsequently been applied in the CSAPR Update when evaluating 
interstate transport obligations for the 2008 ozone NAAQS. EPA 
continues to find 1 percent to be an appropriate threshold. For ozone, 
as EPA found in the CAIR, CSAPR, and the CSAPR Update, a portion of the 
nonattainment problems from anthropogenic sources in the U.S. result 
from the combined impact of relatively small contributions from many 
upwind states, along with contributions from in-state sources and, in 
some cases, substantially larger contributions from a subset of 
particular upwind states. EPA's analysis shows that much of the ozone 
transport problem being analyzed in this proposed rule is still the 
result of the collective impacts of contributions from many upwind 
states. Therefore, application of a consistent contribution threshold 
is necessary to identify those upwind states that should have 
responsibility for addressing their contribution to the downwind 
nonattainment and maintenance problems to which they collectively 
contribute. Continuing to use 1 percent of the NAAQS as the screening 
metric to evaluate collective contribution from many upwind states also 
allows EPA (and states) to apply a consistent framework to evaluate 
interstate emissions transport under the interstate transport provision 
from one NAAQS to the next. See 81 FR at 74518 (August 8, 2011); see 
also 86 FR at 23085 (April 30, 2021) (reviewing and explaining 
rationale from CSAPR, 76 FR at 48237-38 (August 8, 2011), for selection 
of 1 percent threshold).
    EPA's August 2018 memorandum recognized that in certain 
circumstances, a state may be able to establish that an alternative 
contribution threshold of 1 ppb is justifiable. Where a state relies on 
this alternative threshold, and where that state determined that it was 
not linked at Step 2 using the alternative threshold, EPA will evaluate 
whether the state provided a technically sound assessment of the 
appropriateness of using this alternative threshold based on the facts 
and circumstances underlying its application in the particular SIP 
submission.
4. Step 3 of the 4-Step Interstate Transport Framework
    Consistent with EPA's longstanding approach to eliminating 
significant contribution or interference with maintenance, at Step 3, 
states linked at Steps 1 and 2 are generally expected to prepare a 
multifactor assessment of potential emissions controls. EPA's analysis 
at Step 3 in prior Federal actions addressing interstate transport 
requirements has primarily focused on an evaluation of cost-
effectiveness of potential emissions controls (on a marginal cost-per-
ton basis), the total emissions reductions that may be achieved by 
requiring such controls (if applied across all linked upwind states), 
and an evaluation of the air quality impacts such emissions reductions 
would have on the downwind receptors to which a state is linked; other 
factors may potentially be relevant if adequately supported. In 
general, where EPA's or alternative air quality and contribution 
modeling establishes that a state is linked at Steps 1 and 2, it will 
be insufficient at Step 3 for a state merely to point to its existing 
rules requiring control measures as a basis for approval. In general, 
the emissions-reducing effects of all existing emissions control 
requirements are already reflected in the air quality results of the 
modeling for Steps 1 and 2. If the state is shown to still be linked to 
one or more downwind receptor(s), states must provide a well-documented 
evaluation determining whether their emissions constitute significant 
contribution or interference with maintenance by evaluating additional 
available control opportunities by preparing a multifactor assessment. 
While EPA has not prescribed a particular method for this assessment, 
EPA expects states at a minimum to present a sufficient technical 
evaluation. This would typically include information on emissions 
sources, applicable control technologies, emissions reductions, costs, 
cost effectiveness, and downwind air quality impacts of the estimated 
reductions, before concluding that no additional emissions controls 
should be required.\28\
---------------------------------------------------------------------------

    \28\ As examples of general approaches for how such an analysis 
could be conducted for their sources, states could look to the CSAPR 
Update, 81 FR 74504, 74539-51; CSAPR, 76 FR 48208, 48246-63; CAIR, 
70 FR 25162, 25195-229; or the NOX SIP Call, 63 FR 57356, 
57399-405. See also Revised CSAPR Update, 86 FR 23054, 23086-23116. 
Consistently across these rulemakings, EPA has developed emissions 
inventories, analyzed different levels of control stringency at 
different cost thresholds, and assessed resulting downwind air 
quality improvements.
---------------------------------------------------------------------------

5. Step 4 of the 4-Step Interstate Transport Framework
    At Step 4, states (or EPA) develop permanent and federally 
enforceable control strategies to achieve the emissions reductions 
determined to be necessary at Step 3 to eliminate significant 
contribution to nonattainment or interference with maintenance of the 
NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions 
control measure at Step 3 to address its interstate transport 
obligations, that measure must be included in the state's 
implementation plan so that it is permanent and federally enforceable. 
See CAA section 110(a)(2)(D) (``Each such [SIP] shall . . . contain 
adequate provisions. . . .''). See also CAA section 110(a)(2)(A); 
Committee for a Better Arvin v. EPA, 786 F.3d 1169, 1175-76 (9th Cir. 
2015) (holding that measures relied on by a state to meet CAA 
requirements must be included in the SIP).

II. Summary of Kentucky's 2015 8-Hour Ozone Interstate Transport SIP 
Submission

    On January 11, 2019, Kentucky submitted a SIP revision, a portion 
of which addressed the CAA section 110(a)(2)(D)(i)(I) interstate 
transport requirements for the 2015 8-hour ozone NAAQS. The 
Commonwealth's SIP submission provided Kentucky's analysis of its 
impact to downwind states and concluded that the Commonwealth had met 
the requirements of CAA section l10(a)(2)(D)(i)(I) (i.e., prongs 1 and 
2) because Kentucky's SIP contains adequate provisions to prevent 
sources and other types of emissions activities within the Commonwealth 
from significantly contributing to nonattainment, or interfering with 
the maintenance, of downwind states with respect to the 2015 8-hour 
ozone NAAQS.
    The Commonwealth's submission relied on the results of EPA's 
modeling of the year 2023, contained in the March 2018 memorandum, to 
identify downwind nonattainment and

[[Page 9504]]

maintenance receptors that may be ``linked'' to emissions from sources 
in Kentucky (which correlates to Step 1 of the 4-step framework).\29\ 
The March 2018 modeling indicates that the Commonwealth was linked to 
four nonattainment receptors and one maintenance monitor above 1% of 
the NAAQS. The largest impact from Kentucky sources on any downwind 
nonattainment receptor in the East was projected to be 0.89 ppb at the 
Fairfield County, Connecticut (ID: 90013007) site. The other 
nonattainment receptors to which Kentucky was linked are: a second site 
in Fairfield County (ID: 90019003); Milwaukee, Wisconsin (ID: 
550790085); and Sheboygan, Wisconsin (ID: 551170006). The impact from 
Kentucky sources on the one downwind maintenance-only receptor to which 
it was linked in that modeling was 1.52 ppb at the Harford County, 
Maryland monitor (ID: 240251001).
---------------------------------------------------------------------------

    \29\ EPA notes that Kentucky's SIP submission is not organized 
around EPA's 4-step framework for assessing good neighbor 
obligations, but EPA summarizes the submission using that framework 
for clarity here.
---------------------------------------------------------------------------

    The Commonwealth reviewed EPA's August 2018 memorandum as it 
related to the use of a potential alternative contribution threshold of 
1 ppb and agreed that use of a 1 ppb contribution threshold is 
comparable to the amount of collective contribution captured using a 
threshold equivalent to 1 percent of the NAAQS. Based on the March 2018 
modeling and application of a 1 ppb alternative contribution threshold, 
the Commonwealth found that it would not be linked as a significant 
contributor to the four nonattainment receptors in Connecticut and 
Wisconsin (which correlates to EPA's Step 2), and therefore concluded 
that no further controls were required to address its contribution to 
those four receptors. Thus, the Commonwealth concluded that Kentucky's 
SIP contains adequate provisions to prevent sources and other types of 
emissions activities within the Commonwealth from contributing 
significantly to nonattainment in any other state (i.e., ``prong 1'' of 
CAA section l10(a)(2)(D)(i)(I)) for the 2015 8-hour ozone NAAQS.
    After application of the 1 ppb contribution threshold, Kentucky 
remained linked to the downwind maintenance-only receptor at Harford 
County, Maryland (ID: 240251001) because the Commonwealth's 
contribution of 1.52 ppb to this receptor was greater than the 1 ppb 
alternative threshold. Kentucky's SIP submission asserted that the 
amount of NOX emission reductions required for an upwind 
state should not be the same for a monitor that is already attaining 
the NAAQS as they are for a nonattainment monitor. The Commonwealth 
further asserted that local controls should be implemented before 
requiring upwind states to control their sources. Thus, Kentucky 
concluded that no further reductions other than on-the-books and on-
the-way measures are required to address the Commonwealth's interstate 
transport obligation to eliminate its contribution to the Harford 
County, Maryland maintenance receptor.
    In addition, Kentucky provided information intended to demonstrate 
that Kentucky's SIP contains adequate provisions to prevent sources and 
other types of emissions activities within the Commonwealth from 
significantly contributing to nonattainment, or interfering with the 
maintenance, of downwind states with respect to the 2015 8-hour ozone 
NAAQS, and thus, no additional emissions reductions from Kentucky are 
necessary. Specifically, Kentucky listed existing state, SIP-approved 
regulations and Federal programs for sources in the Commonwealth that 
it concluded address the requirements of CAA 110(a)(2)(D)(i)(I) for the 
2015 8-hour ozone NAAQS.\30\ Kentucky provided more detailed analyses 
related to several specific topics, which are summarized in sections 
below.
---------------------------------------------------------------------------

    \30\ See Kentucky's January 11, 2019, SIP submission, at pages 
20 through 30 for the list of state, SIP-approved regulations and 
Federal programs identified by Kentucky.
---------------------------------------------------------------------------

    The Commonwealth also included documents attached as appendices to 
its submittal. The March 2018 memorandum and the August 2018 memorandum 
were attached at appendices A and B, respectively.\31\ As Appendix C, 
the Commonwealth appended several documents developed and/or submitted 
by the Midwest Ozone Group (a consortium of upwind industries with 
emitting facilities).\32\ This included a modeling analysis developed 
by Alpine Geophysics titled ``Good Neighbor Modeling Technical Support 
Document for the 8-hour Ozone State Implementation Plans,'' dated June 
2018 (Alpine TSD). The Alpine TSD contains alternative modeling of 2023 
performed by Alpine Geophysics sponsored by MOG, as well as additional 
policy suggestions that MOG suggested states could consider in 
developing good neighbor SIP submissions (see section 9 of the Alpine 
TSD).\33\ The Alpine TSD also appended a separate set of MOG comments 
on EPA's March 2018 memorandum.\34\ These comments and Alpine's 
modeling analysis were further summarized in a Microsoft PowerPoint 
Presentation titled ``MOG's Preview of 2015 Ozone NAAQS Good Neighbor 
SIPs.'' EPA also summarizes the materials developed by MOG that the 
Commonwealth included as Appendix C to its submittal, although it is 
unclear that Kentucky intended to rely on all aspects of these 
materials.
---------------------------------------------------------------------------

    \31\ See the following Appendices to Kentucky's January 11, 
2019, submission: Appendix A--Information on the Interstate 
Transport State Implementation Plan Submissions for the 2015 Ozone 
National Ambient Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), March 27, 2018 (``March 2018 memorandum''); 
Appendix B--Analysis of Contribution Thresholds for Use in Clean Air 
Act Section 110(a)(2)(D)(i)(I) Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards, August 31, 2018; and Appendix D--Public 
Hearing & Statement of Consideration.
    \32\ See Appendix C to Kentucky's January 11, 2019, submission--
Midwest Ozone Group Technical Support Document: ``Good Neighbor 
Modeling Technical Support Document for 8-Hour Ozone Implementation 
Plans.''
    \33\ It is unclear whether Kentucky intends to rely on all of 
the data and policy approaches in Appendix C as included in its 
submittal, or if these documents were appended solely to support 
specific policy and technical arguments relied on by Kentucky in its 
submittal.
    \34\ See the following Appendices to Appendix C--Midwest Ozone 
Group Technical Support Document: ``Good Neighbor Modeling Technical 
Support Document for 8-Hour Ozone Implementation Plans of Kentucky's 
January 11, 2019: Appendix A--4km Modeling Results for Mid-Atlantic 
and Lake Michigan Domains Compared to EPA 12 km ``No Water'' Design 
Value Calculations from March 2018 Memorandum; Appendix B--Midwest 
Ozone Group Comments on EPA's March 27, 2018 Memorandum Entitled 
``Information on the Interstate Transport State Implementation Plan 
Submissions for the 2015 Ozone National Ambient Air Quality 
Standards under Clean Air Act Section 110(a)(2)(D)(i)(I); Appendix 
C--Presentation--Midwest Ozone Group Preview of 2015 Ozone NAAQS 
Good Neighbor SIPs.
---------------------------------------------------------------------------

A. Information Related to Emission Trends From Kentucky Sources

    With respect to ozone precursors emitted from Kentucky sources, 
Kentucky focused its analysis on NOX emissions, as it found 
that ozone is far more sensitive to NOX emissions than VOC 
emissions in the Southeastern United States and that controlling 
NOX emissions is a more effective strategy in reducing 
ozone. Kentucky reviewed NOX emissions trends in the 
Commonwealth, comparing annual NOX emissions from 2008 to 
2016, finding that NOX emissions in Kentucky have 
significantly decreased since 2008. The Commonwealth asserted that it 
has significantly lowered NOX emissions between 2008 and 
2017 \35\ and contended that planned shutdowns and

[[Page 9505]]

conversion to natural gas, along with the implementation of Federal and 
State programs, ensure Kentucky's emissions will continue to decrease. 
Based on the 2014 national emission inventory (NEI), Kentucky indicated 
that the major contributor of NOX emissions in the 
Commonwealth are point sources, mainly comprised of electric generating 
units (EGUs).
---------------------------------------------------------------------------

    \35\ Table 2 in Kentucky's SIP provides historic annual 
NOX emissions data for point sources in the state from 
2008 through 2016, however, the associated graph at Chart 1 
indicates annual NOX emissions from 2008 through 2017.
---------------------------------------------------------------------------

    Kentucky asserted that NOX emissions from EGUs in the 
Commonwealth have decreased and would continue to decrease based, in 
part, on the implementation of CAIR, CSAPR, and the CSAPR Update, as 
well as retirements of several EGUs in the Commonwealth. The 
Commonwealth compared Kentucky's NOX ozone season 
allocations to actual EGU emissions in the Commonwealth, concluding 
that Kentucky's NOX ozone season budgets have decreased 
since the implementation of CSAPR and the CSAPR Update and actual ozone 
season NOX emissions are significantly lower than the 
trading program budgets.\36\ The SIP submission summarized coal-fired 
unit retirements, shutdowns, and repowering from 2015 through 2017 as 
well as on-the-way reductions from natural gas conversions and 
retirements from 2017 through 2023.\37\ Kentucky stated that it 
expected emissions will continue to decline in the future due to 
continued implementation of CSAPR, the CSAPR Update, and scheduled 
shutdowns, fuel switches, and retirements of facilities in the 
Commonwealth.
---------------------------------------------------------------------------

    \36\ Kentucky's SIP acknowledged that the CSAPR trading program 
does not address interstate transport for the 2015 standard but 
nonetheless provides NOX emission reductions.
    \37\ See Kentucky's January 11, 2019, submittal located in 
Docket No. EPA-R04-OAR-2021-0841, at pages 32-33 for discussion on 
implementation of CSAPR, the CSAPR Update, EGU retirements, and EGU 
fuel switches.
---------------------------------------------------------------------------

B. Information Related to Connecticut Monitors Provided by Kentucky

    EPA's March 2018 modeling showed Kentucky linked to the two 
receptors located in Fairfield County, Connecticut, which is part of 
the New York-Northern New Jersey-Long Island, NY-NJ-CT (New York Metro 
Area) core based statistical area (CBSA).\38\ Kentucky applied an 
alternative contribution threshold of 1 ppb, and thus determined that 
Kentucky was no longer linked to the Connecticut receptors. In 
addition, Kentucky provided information intended to demonstrate that 
emissions from local sources in the area surrounding the monitors 
contribute significantly to the continued nonattainment issues, and 
thus, that local controls should be implemented before requesting 
upwind states to control facilities.
---------------------------------------------------------------------------

    \38\ EPA's designations for the 2015 8-hour ozone standard 
divided the state into two areas, Greater Connecticut, CT, with a 
marginal classification, and New York-Northern New Jersey-Long 
Island, NY-NJ-CT (New York Metro Area), with a moderate 
classification. See https://www.epa.gov/ozone-designations/additional-designations-2015-ozone-standards.
---------------------------------------------------------------------------

    In particular, Kentucky's SIP submission claims that the Westport 
Sherwood, Fairfield, Connecticut (ID: 90019003) and Stratford Point 
Lighthouse, Fairfield County (ID: 90013007) monitors are located less 
than three miles from the I-95 interstate highway corridor and over 500 
miles from Kentucky. Kentucky asserted these monitors have a consistent 
pattern of violating the 2015 8-hour ozone NAAQS from 2007 to 2016. 
Kentucky also pointed out that it is not linked in the modeling to two 
other nonattainment receptors (the Greenwich Point Park and Criscuolo 
Park monitoring sites) that are in relatively close proximity to the 
Westport and Stratford monitors. Kentucky compared the distances 
between these sites with the distances of the sites to Kentucky's 
nearest border.
    Kentucky's SIP submission also provided information related to the 
New York Metro Area, citing the 2014 NEI to state that the on-road 
source sector contributed the highest amount of NOX 
emissions and that the nonpoint source sector contributed the highest 
amount of VOC emissions in that area. The Commonwealth further provided 
information about high vehicle miles traveled (VMT) and commuting 
patterns in the New York Metro Area, as well as information regarding 
violating monitors along the I-95 corridor and outlying monitors that 
show attainment.
    Additionally, Kentucky's SIP submission includes Hybrid Single 
Particle Lagrangian Integrated Trajectory (HYSPLIT) model back 
trajectory analysis to the two Connecticut receptors,\39\ asserting 
that the HYSPLIT analysis indicates that the monitors are downwind of 
nonattainment areas in New York, New Jersey, Pennsylvania, and 
Maryland. The Commonwealth also asserted there is a consistent pattern 
of violating monitors located along the I-95 corridor. In addition, 
Kentucky asserted that pollutants are trapped in the marine boundary 
layer and then transported inland to coastal Connecticut receptors due 
to conditions on Long Island Sound.
---------------------------------------------------------------------------

    \39\ According to Kentucky, the HYSPLIT analysis were generated 
using EPA's 2015 Ozone Designation Mapping Tool, available at 
https://www.epa.gov/ozone-designations/ozone-designations-guidance-
and-
data#:~:text=The%20ozone%20designations%20mapping%20tool,for%20the%20
2015%20Ozone%20NAAQS.
---------------------------------------------------------------------------

    The Commonwealth's SIP submission also discussed point sources in 
the New York Metro Area, providing information regarding the largest 
point sources in that area. In addition, Kentucky provided 
NOX and VOC emission information for 13 counties in the New 
York Metro Area that have NOX and VOC emission totals above 
10,000 tpy, finding that three counties that surround Fairfield County 
(Suffolk, Queens, and Nassau Counties) had the highest NOX 
emissions.
    Kentucky further evaluated high electric demand days in New York, 
discussing a New York Department of Environmental Conservation (NYDEC) 
determination that peaking units operating on peak electricity demand 
days are a major contributor of NOX (particularly units 
installed before 1987), and that such units can contribute 4.8 ppb of 
ozone on high ozone days.\40\ Kentucky concluded NOX 
emission reductions from these EGUs point sources would have a 
significant impact on ozone levels in the New York Metro Area.
---------------------------------------------------------------------------

    \40\ Kentucky references NYDEC emission analysis entitled 
``Background, High Electric Demand Day (HEDD) Initiative'', New York 
Department of Environmental Conservation.
---------------------------------------------------------------------------

C. Information Related to the Harford, Maryland Monitor Provided by 
Kentucky

    Kentucky acknowledged that EPA's March 27, 2018 modeling shows the 
potential for Kentucky emissions to significantly contribute to the 
Edgewood, Harford County, Maryland (ID: 240251001) maintenance-only 
monitor (Edgewood monitor) in 2023. However, Kentucky provided air 
quality data designed to demonstrate that emissions from local sources 
in the area surrounding the monitors contribute significantly to the 
continued air quality issues and concluded that there are local 
controls that should be implemented before requesting upwind states to 
control facilities.
    Kentucky provided additional information with respect to the 
Edgewood Monitor, which is located 3 miles from the I-95 corridor and 
approximately 350 miles from Kentucky. Kentucky provided data to show 
that the Edgewood monitor consistently violated the 2015 8-hour ozone 
standard from 2007 to 2016. Kentucky also provided information related 
to other nonattainment monitors located in Baltimore County and Harford 
County.
    The Commonwealth's SIP submission provided data related to the 
Baltimore-

[[Page 9506]]

Columbia-Towson, MD CBSA (Baltimore Area), citing to the 2014 NEI to 
state that the on-road source sector contributed the highest amount of 
NOX emissions and that the nonpoint source sector 
contributed the highest amount of VOC emissions in that area. Kentucky 
further provided information about VMTs and commuting patterns in the 
Baltimore Area, as well as information regarding violating monitors 
along the I-95 corridor and outlying monitors that show attainment. The 
SIP submission asserted that local mobile emissions are a key 
contributor to the Edgewood monitor, which is also located in close 
proximity to the 1-95 corridor. Kentucky further cited to a 
presentation and remarks by Maryland officials, discussing programs to 
reduce emissions from local sources, specifically focusing on mobile 
source NOX reduction programs.
    Kentucky cited a 2010 case study in the Chesapeake Bay that 
suggests the transport of pollution from nearby urban areas accumulates 
over the Bay and becomes stagnant, creating a bay breeze which is 
pushed by southerly winds northward towards the Edgewood monitor. 
Additionally, Kentucky's SIP submission also provided HYSPLIT model 
back trajectory analysis to the Edgewood receptor,\41\ asserting that 
the HYSPLIT indicates that the monitors are downwind of nonattainment 
areas in Baltimore County, Baltimore City, Arlington County, and the 
District of Columbia. Kentucky also asserted that higher altitude 
particles from the northwest of Baltimore combine with lower-level 
particles from the south and southeast.
---------------------------------------------------------------------------

    \41\ According to Kentucky, the HYSPLIT analysis were generated 
using EPA's 2015 Ozone Designation Mapping Tool, available at 
https://www.epa.gov/ozone-designations/ozone-designations-guidance-
and-
data#:~:text=The%20ozone%20designations%20mapping%20tool,for%20the%20
2015%20Ozone%20NAAQS.
---------------------------------------------------------------------------

    Kentucky's submission used information on local mobile emissions 
along the I-95 corridor and coastal air pollution formation and 
accumulation along the Maryland coast to support its conclusion that 
local air quality problems are the source of ozone violations at these 
monitors.
    Additionally, Kentucky asserted that the implementation of local 
programs to reduce emissions should be sufficient for monitors in the 
Maryland area to attain the 2015 8-hour ozone NAAQS. Kentucky cited 
claims by MOG (appended to the submittal in Appendix C) that the 
modeling in EPA's March 2018 memorandum does not account for additional 
retirements, conversions, and modifications or emission control 
programs expected to be implemented before 2023. Kentucky concluded 
that because the Edgewood monitor is a maintenance receptor, the 
Commonwealth believes that no further reductions from Kentucky sources 
other than on-the-books controls should be required because maintenance 
receptors should be treated differently than nonattainment receptors in 
terms of upwind requirements. The Commonwealth also asserted that 
states linked to maintenance receptors should be held to less stringent 
standards of emissions reductions as compared to states linked to a 
nonattainment receptor.
    The Commonwealth also asserted that local emission controls should 
be implemented before upwind states are required to control their 
facilities, which is based on Kentucky's concurrence with statements 
from MOG. The Commonwealth cited MOG's comments on local controls 
stating: ``When an area is measuring nonattainment of a NAAQS, as is 
the case with the areas linked to Kentucky, the CAA requires that the 
effects and benefits of local controls on all source sectors be 
considered first, prior to pursuing controls of sources in upwind 
states.'' \42\ The Commonwealth concluded that the emissions reductions 
resulting from on-the-books and on-the-way measures are adequate to 
prohibit emissions within Kentucky from interfering with the 
maintenance of downwind states with respect to the 2015 8-hour ozone 
NAAQS.
---------------------------------------------------------------------------

    \42\ Kentucky's SIP references MOG's comments that cite CAA 
sections 107(a) and 110(a)(1).
---------------------------------------------------------------------------

D. Summary of Conclusions From Kentucky

    In summary, based on Kentucky's reliance on the modeling results in 
EPA's March 2018 memorandum, the Commonwealth found that emissions from 
Kentucky sources were potentially linked to four nonattainment monitors 
in Connecticut and Wisconsin and one maintenance receptor in Harford 
County, Maryland. However, after utilizing a 1 ppb alternative 
contribution threshold, the Commonwealth concluded that it was no 
longer linked to the four nonattainment monitors, and thus, that the 
Kentucky SIP contains adequate provisions to prevent sources and other 
types of emissions activities within the State from contributing 
significantly to nonattainment in any other state (i.e., ``prong 1'' of 
CAA section 110(a)(2)(D)(i)(I)) for the 2015 8-hour ozone NAAQS. 
Although modeling results indicated that Kentucky remained linked to 
the maintenance-only receptor in Harford County, Maryland, even after 
the application of the 1 ppb alternative threshold, Kentucky asserted 
that states should not be required to apply the same degree of 
reductions for maintenance receptors as nonattainment areas, and 
determined that additional NOX emission reductions other 
than those that are on-the-books or on-the-way are not required to 
address its downwind contribution to that receptor. Kentucky further 
provided an assessment of local sources in the vicinity of the 
Connecticut and Maryland monitors and concluded that local 
(particularly mobile) emissions, high VMTs and commuting patterns, and 
weather patterns are the primary cause of violating monitors in these 
areas. Therefore, Kentucky concluded that its SIP has adequate 
provisions to prohibit emissions from interfering with maintenance in 
another state (i.e., ``prong 2'' of CAA section 110(a)(2)(D)(i)(I)) 
with respect to the 2015 8-hour ozone NAAQS.

E. Summary of Midwest Ozone Group TSD Appended to Kentucky's Submittal

    Kentucky attached several materials developed by MOG to its 
submittal as Appendix C, which included a document titled `` `Good 
Neighbor' Modeling Technical Support Document for 8-Hour Ozone State 
Implementation Plans'' prepared by Alpine Geophysics.\43\ The Alpine 
Geophysics document also attached the following documents: 4 kilometer 
(km) modeling results for mid-Atlantic and Lake Michigan domains 
compared to EPA 12 km ``No Water'' Design Value Calculations from March 
2018 memorandum (Appendix A); MOG comments on EPA's March 2018 
memorandum (Appendix B); and a Microsoft PowerPoint presentation from 
MOG previewing 2015 8-hour ozone NAAQS good neighbor SIPs (Appendix C). 
EPA notes a number of modeling results and technical and policy 
arguments provided in the MOG attachments are not explicitly discussed 
in Kentucky's SIP submission narrative. Therefore, it is unclear 
whether Kentucky intended to rely on Alpine's modeling or MOG's policy 
argument to support the Commonwealth's overall transport SIP 
conclusions. To ensure review of all potentially relevant technical and 
policy issues identified in Kentucky's SIP package, this section 
summarizes key arguments presented in

[[Page 9507]]

Appendix C. However, in EPA's evaluation of the SIP submittal in 
section III, EPA will differentiate between those positions clearly 
adopted by the Commonwealth and those where it is unclear and therefore 
a position espoused by MOG cannot be attributed to Kentucky.
---------------------------------------------------------------------------

    \43\ See Appendix C of Kentucky's January 11, 2019, transport 
SIP submission.
---------------------------------------------------------------------------

    Appendix C included modeling results performed by Alpine Geophysics 
as presented in the Alpine TSD. The Alpine modeling results identified 
the Harford, Maryland receptor as a nonattainment receptor, with 
Kentucky emissions contributing 2.07 ppb. In addition, the Alpine 
modeling results identified Kentucky linkages above 1 percent to the 
following maintenance-only receptors: Gloucester, New Jersey (ID: 
340150002), with a Kentucky contribution of 1.69 ppb; Richmond, New 
York (ID: 360850067), with a Kentucky contribution of 0.93; and 
Philadelphia, Pennsylvania (ID: 421010024), with a Kentucky 
contribution of 1.53. (While MOG asserts in separate comments that 
emission reductions not accounted for in EPA's modeling suggests there 
will be no receptors by 2023, this is not consistent with Alpine's 
modeling.)
    The Alpine TSD also evaluated additional approaches and 
flexibilities that states could apply in SIP revisions, based on the 
potential concepts provided in Appendix A of EPA's March 2018 
memorandum.\44\ These included reliance on alterative modeling data, 
evaluation of international contributions (both anthropogenic 
contribution and as an additional percentage of boundary conditions), 
alternate contribution thresholds, proportional control of upwind 
emissions by level of upwind state contribution, and addressing 
interference with maintenance obligations through use of 10-year 
projections.
---------------------------------------------------------------------------

    \44\ See Section 9.0--Selected SIP Revision Approaches in 
Appendix C--MOG's TSD of Kentucky's January 11, 2019 transport SIP 
submission.
---------------------------------------------------------------------------

    MOG suggested states should be allowed to select multiple sources 
of modeling data rather than a single modeling simulation if such 
information is considered equally credible when making policy decisions 
related to the development of good neighbor SIPs.
    With respect to international emissions, MOG cited to an attachment 
to EPA's 2018 memorandum and asserts that EPA's and Alpine's 
contribution modeling tracks and reports the relative impact 
contributions of anthropogenic emissions located within the 36 km 
modeling domain. Considering this information, MOG concluded that 
states seeking to avoid overcontrol may wish to consider removing that 
portion of the projected design value that is explicitly attributed to 
international anthropogenic contribution, which may be enough to 
demonstrate attainment with the 2008 or 2015 8-hour ozone NAAQS at 
multiple monitors in the U.S.
    With respect to potential use of alternative contribution 
thresholds, MOG pointed to states raising concerns that the 1 percent 
threshold is more stringent than the 2016 EPA Significant Impact level 
(SIL) guidance of 1 ppb, which is designed as an individual source or 
group of sources' contribution limit (in the context of prevention of 
significant deterioration (PSD) permitting).\45\ MOG suggested that 
states could submit SIP revisions citing the SIL of 1 ppb as an 
acceptable total state anthropogenic contribution threshold under Step 
2 of the 4-step process, and request relief from the 1 percent 
threshold in lieu of using an alternate value.
---------------------------------------------------------------------------

    \45\ MOG cited to the Georgia Environmental Protection 
Division's comment on EPA's March 2018 Memorandum to support this 
claim. See Section 9.0--Selected SIP Revision Approaches in Appendix 
C--MOG's TSD of Kentucky's January 11, 2019 transport SIP 
submission, citing Boylan, J. W. (May 4, 2018). Georgia EPD Comments 
on EPA's March 27, 2018 Interstate Transport Memo [Memorandum].
---------------------------------------------------------------------------

    MOG presented an alternative approach to how upwind-state emission 
reduction obligations could be allocated. Specifically, MOG proposed 
that upwind reductions could be allocated in proportion to the size of 
their contribution to downwind nonattainment. To illustrate this 
approach, MOG determined a proportional reduction requirement 
associated with the relative contribution from each upwind state to the 
Harford County, Maryland monitor. Under this analysis, MOG's approach 
indicated that Kentucky would be responsible for a 0.02 ppb reduction 
at the monitor and ``would then need to craft a [good neighbor SIP] 
revision to generate reductions associated with this proportional 
amount.''
    With respect to ``interference with maintenance'' obligations, MOG 
suggested that an upwind state could choose to indicate that no 
additional controls would be needed to address a maintenance monitor if 
the upwind state can show that either the monitor is likely to remain 
in attainment for a period of 10 years or that the upwind state's 
emissions will not increase for 10 years after the attainment date.

III. EPA's Evaluation of Kentucky's 2015 8-Hour Ozone Interstate 
Transport SIP Submission

    EPA is proposing to find that Kentucky's January 11, 2019, SIP 
submission does not meet the Commonwealth's obligations with respect to 
prohibiting emissions that contribute significantly to nonattainment or 
interfere with maintenance of the 2015 8-hour ozone NAAQS in any other 
state based on EPA's evaluation of the SIP submission using the 4-step 
interstate transport framework, and therefore EPA is proposing to 
disapprove Kentucky's SIP submission.

A. Results of EPA's Step 1 and Step 2 Modeling and Findings for 
Kentucky

    As described in section I, EPA performed updated air quality 
modeling to project design values and contributions for 2023. These 
data were examined to determine if Kentucky contributes at or above the 
threshold of 1 percent of the 2015 8-hour ozone NAAQS (0.70 ppb) to any 
downwind nonattainment or maintenance receptor. As shown in Table 1, 
the data \46\ indicate that in 2023, emissions from Kentucky contribute 
greater than 1 percent of the standard to nonattainment or maintenance-
only receptors in Bucks County, Pennsylvania (ID: 420170012), New Haven 
County, Connecticut (ID: 90099002), and Fairfield County, Connecticut 
(ID: 90019003 and 90013007).\47\
---------------------------------------------------------------------------

    \46\ The ozone design values and contributions at individual 
monitoring sites nationwide are provided in the file 
``2016v2_DVs_state_contributions.xlsx'' which is included in Docket 
No. EPA-HQ-OAR-2021-0663.
    \47\ These modeling results are consistent with the results of a 
prior round of 2023 modeling using the 2016v1 emissions platform 
which became available to the public in the fall of 2020 in the 
Revised CSAPR Update, as noted in section I. That modeling showed 
that Kentucky had a maximum contribution greater than 0.70 ppb to at 
least one nonattainment or maintenance-only receptor in 2023. These 
modeling results are included in the file ``Ozone Design Values And 
Contributions Revised CSAPR Update.xlsx'' in Docket No. EPA-HQ-OAR-
2021-0663.

[[Page 9508]]



                                          Table 1--Kentucky Linkage Results Based on EPA Updated 2023 Modeling
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                           2023 average    2023  maximum     Kentucky
            Receptor ID                     Location                County             Nonattainment/      design value    design value    contribution
                                                                                        maintenance            (ppb)           (ppb)           (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
420170012..........................  Pennsylvania.........  Bucks................  Maintenance..........            70.7            72.2            0.88
90099002...........................  Connecticut..........  New Haven............  Nonattainment........            71.8            73.9            0.83
90019003...........................  Connecticut..........  Fairfield............  Nonattainment........            76.1            76.4            0.82
90013007...........................  Connecticut..........  Fairfield............  Nonattainment........            74.2            75.1            0.77
--------------------------------------------------------------------------------------------------------------------------------------------------------

B. Evaluation of Information Provided by Kentucky Regarding Step 1

    At Step 1 of the 4-step interstate transport framework, Kentucky 
relied on EPA modeling released in the March 2018 memorandum to 
identify nonattainment and maintenance receptors in 2023 and also 
included results from modeling performed by Alpine. As described 
previously in this notice, EPA has recently updated its 2023 modeling 
using the most current and technically appropriate information. EPA 
proposes to rely on EPA's most recent modeling to identify 
nonattainment and maintenance receptors in 2023. However, even using 
EPA modeling available to Kentucky at the time of its SIP submittal, 
three nonattainment receptors and one maintenance-only receptor were 
projected in 2023 to which Kentucky was linked above 1 percent of the 
NAAQS. In addition, the Alpine modeling that Kentucky appended to its 
submittal also indicated that Kentucky was linked to several receptors 
in 2023.\48\ Kentucky appended comments from MOG arguing that states 
should be allowed to select multiple sources of modeling data rather 
than a single modeling simulation if such information is considered 
equally credible when making policy decisions related to the 
development of good neighbor SIPs. Whether EPA's most recent 2023 
modeling is relied on, or whether it is considered in conjunction with 
its older 2023 modeling and/or the Alpine modeling, the results 
consistently identify several nonattainment or maintenance receptors to 
which Kentucky is linked above 1 percent of the 2015 8-hour ozone 
NAAQS.
---------------------------------------------------------------------------

    \48\ The Alpine modeling results identified the Harford, 
Maryland receptor as a nonattainment receptor, with Kentucky 
emissions contributing 2.07 ppb. In addition, the Alpine modeling 
results identified Kentucky linkages above 1 percent to the 
following maintenance-only receptors: Gloucester, New Jersey (ID: 
340150002), with a Kentucky contribution of 1.69 ppb; Richmond, New 
York (ID: 360850067), with a Kentucky contribution of 0.93; and 
Philadelphia, Pennsylvania (ID: 421010024), with a Kentucky 
contribution of 1.53.
---------------------------------------------------------------------------

    As discussed in section II.E, Kentucky attached documents from MOG 
that discussed international transport of emissions and their 
contribution to U.S. ozone monitors, and argued that states could 
remove that portion of the projected design value explicitly attributed 
to international anthropogenic contribution. MOG asserted that 
excluding the international anthropogenic contributions could result in 
attainment with the 2008 or 2015 8-hour ozone NAAQS at ozone monitors 
in the United States, thus potentially eliminating 2023 receptors. 
Kentucky did not explicitly discuss in its SIP submittal MOG's 
arguments regarding contributions from international emissions and 
therefore it is unclear if the Commonwealth intended to rely on this 
argument to support their conclusion, however, EPA is providing its 
analysis related to these arguments.
    EPA disagrees that excluding international contribution (whether 
from North American international anthropogenic, boundary conditions, 
or other international sources) from the projected design value of 
receptors is acceptable under the CAA.\49\ The good neighbor provision 
requires states and EPA to address interstate transport of air 
pollution that contributes to downwind states' ability to attain and 
maintain NAAQS. Whether emissions from other states or other countries 
also contribute to the same downwind air quality issue is irrelevant in 
assessing whether a downwind state has an air quality problem, or 
whether an upwind state is significantly contributing to that problem. 
States are not obligated under CAA section 110(a)(2)(D)(i)(I) to reduce 
emissions sufficient on their own to resolve downwind receptors' 
nonattainment or maintenance problems. Rather, states are obligated to 
eliminate their own ``significant contribution'' or ``interference'' 
with the ability of other states to attain or maintain the NAAQS.
---------------------------------------------------------------------------

    \49\ To the extent that MOG cited Attachment A to EPA's March 
2018 memorandum as suggesting support for this approach, this is 
incorrect. As discussed in section I.D, the attachment summarized 
ideas from outside stakeholders, and EPA did not endorse such 
approaches as technically or legally appropriate. Further, nothing 
in Attachment A suggested that international contribution could 
simply be subtracted from a downwind receptor's projected design 
value.
---------------------------------------------------------------------------

    Indeed, the D.C. Circuit in Wisconsin specifically rejected 
petitioner arguments suggesting that upwind states should be excused 
from good neighbor obligations on the basis that some other source of 
emissions (whether international or another upwind state) could be 
considered the ``but-for'' cause of downwind air quality problem. See 
938 F.3d at 323-324. The court viewed petitioners' arguments as 
essentially an argument ``that an upwind State `contributes 
significantly' to downwind nonattainment only when its emissions are 
the sole cause of downwind nonattainment.'' See 938 F.3d at 324. The 
court explained that ``an upwind State can `contribute' to downwind 
nonattainment even if its emissions are not the but-for cause.'' Id. at 
324-325. See also Catawba County v. EPA, 571 F.3d 20, 39 (D.C. Cir. 
2009) (rejecting the argument ``that `significantly contribute' 
unambiguously means `strictly cause' '' because there is ``no reason 
why the statute precludes EPA from determining that [an] addition of 
[pollutant] into the atmosphere is significant even though a nearby 
county's nonattainment problem would still persist in its absence''); 
Miss. Comm'n on Envtl. Quality v. EPA, 790 F.3d 138, 163 n.12 (D.C. 
Cir. 2015) (observing that the argument that ``there likely would have 
been no violation at all . . . if it were not for the emissions 
resulting from [another source]'' is ``merely a rephrasing of the but-
for causation rule that we rejected in Catawba County.''). Therefore, a 
state is not excused from eliminating its significant contribution on 
the basis that international emissions also contribute some amount of 
pollution to the same receptors to which the state is linked.

C. Evaluation of Information Provided by Kentucky Regarding Step 2

    At Step 2 of the 4-step interstate transport framework, Kentucky 
relied on EPA modeling released in the March 2018 memorandum to 
identify upwind state linkages to nonattainment and maintenance 
receptors in 2023 and included results from modeling run by

[[Page 9509]]

Alpine. Both EPA's modeling released in the March 2018 memorandum as 
well as Alpine's modeling indicate that Kentucky is linked to downwind 
monitors.\50\ As Kentucky attached Alpine's modeling without discussing 
it in the narrative of the submittal, it is unclear whether Kentucky 
intended to rely on Alpine's modeling in its submittal.
---------------------------------------------------------------------------

    \50\ Although the various modeling runs (EPA's March 2018 
modeling, Alpine's modeling and EPA's updated modeling) indicate 
that Kentucky is linked to different receptors and with differing 
amounts of contribution, all three sets of modeling are consistent 
in that each indicates linkages between Kentucky and downwind 
receptors.
---------------------------------------------------------------------------

    As described in section I.C of this notice, EPA has recently 
updated modeling to identify upwind state contributions to 
nonattainment and/or maintenance receptors in 2023. In this notice, EPA 
proposes to rely on the Agency's most recently available modeling to 
identify upwind contributions and ``linkages'' to downwind air quality 
problems in 2023 using a threshold of 1 percent of the NAAQS. See 
section I.D for a general explanation of the use of 1 percent of the 
NAAQS.
    As shown in Table 1, updated EPA modeling identifies Kentucky's 
maximum contribution to a downwind nonattainment or maintenance 
receptor is greater than 1 percent of the standard (i.e., 0.70 ppb).
    Kentucky, however, argued in its SIP submittal for the use of an 
alternative 1 ppb contribution threshold at Step 2 to attempt to 
demonstrate that it was no longer ``linked'' to projected downwind 
nonattainment receptors. Specifically, Kentucky cited EPA's August 2018 
memorandum as supporting the use of a 1 ppb alternative contribution 
threshold at Step 2 to assert that the Commonwealth was no longer 
``linked'' to projected downwind nonattainment receptors, while 
conceding that even under this alternative threshold, it was linked 
above 1 ppb to the projected Harford, Maryland maintenance-only 
receptor. EPA's most recent modeling of 2023 no longer identifies the 
Harford, Maryland monitoring site as either a maintenance or 
nonattainment receptor. Nonetheless, Kentucky is linked above 1 percent 
of the NAAQS but less than 1 ppb to the four receptors in EPA's most 
recent modeling. Therefore, whether Kentucky's use of an alternative 1 
ppb contribution threshold is approvable is potentially a dispositive 
question in EPA's evaluation.
    EPA proposes to find that Kentucky's reliance on an alternative 
contribution threshold of 1 ppb at Step 2 is not approvable. EPA 
acknowledges that the August 2018 memorandum generally recognized that 
a 1 ppb threshold may be appropriate for states to use, but also made 
clear that this guidance would be applied under the facts and 
circumstances of each particular SIP submittal.\51\ However, Kentucky 
did not provide a technical analysis to sufficiently justify use of an 
alternative 1 ppb threshold at the linked, downwind monitors. 
Kentucky's SIP submission simply stated that the Commonwealth agrees 
with EPA's rationale set out in the August 2018 memorandum that the 
amount of upwind collective contribution captured with the 1 percent 
and 1 ppb thresholds was generally comparable. But the guidance 
anticipated that states would evaluate whether the alternative 
threshold was appropriate under their specific facts and circumstances, 
not that the use of the alternative threshold would be automatically 
approvable.\52\ With respect to the assertion that 1 ppb was generally 
comparable to 1 percent, Kentucky did not provide discussion or 
analysis containing information specific to Kentucky or a receptor 
analysis for the affected monitors, as anticipated in the 2018 
memorandum, to evaluate whether the alternative threshold was 
appropriate to apply with respect to the monitors to which Kentucky was 
linked. Such state-specific information is necessary to thoroughly 
evaluate the state-specific circumstances that could support approval. 
Given the absence of technical analysis to support the use of a 1 ppb 
threshold under the facts and circumstances relevant to Kentucky and 
its linked receptors, EPA proposes that the use of 1 ppb as a 
contribution threshold is not approvable.\53\ (As discussed in section 
III.C.1 below, EPA no longer intends to dedicate resources to 
supplement state submittals with insufficient analysis in this regard, 
and also has identified other policy and programmatic concerns with 
attempting to recognize alternative thresholds at Step 2 or otherwise 
deviating from its historical, consistent practice since CSAPR of 
applying a threshold of 1 percent of the NAAQS at Step 2.)
---------------------------------------------------------------------------

    \51\ See August 2018 memorandum at 1.
    \52\ As an example of the type of analysis that EPA anticipated 
states might conduct under the guidance, in one instance, EPA itself 
attempted to conduct a state- and receptor-specific analysis that 
could support approval of the use of a 1 ppb threshold. See Air Plan 
Approval; Iowa; Infrastructure State Implementation Plan 
Requirements for the 2015 Ozone National Ambient Air Quality 
Standard, 85 FR 12232 (March 2, 2020). The Agency received adverse 
comment on this proposed approval and has not taken final action 
with respect to this proposal.
    \53\ Kentucky applied the 1 ppb contribution threshold to the 
Connecticut, Wisconsin, and Maryland receptors, as the Commonwealth 
found that Kentucky was linked to these receptors based on the 
modeling released with the March 2018 memorandum. Under EPA's 
updated modeling, Kentucky is no longer linked to the Wisconsin and 
Maryland receptors and is linked to receptors in Pennsylvania and 
New Haven, Connecticut. See Table 1. However, as Kentucky did not 
provide any state-specific information, the rationale is also 
applicable to the Pennsylvania and New Haven, Connecticut linkages.
---------------------------------------------------------------------------

    The MOG materials appended to Kentucky's submission argued that a 
2016 EPA SIL guidance could be cited as acceptable to support a 1 ppb 
contribution threshold. As an initial matter, Kentucky appears not to 
have relied on this rationale. In EPA's comments on Kentucky's draft 
SIP submittal, EPA stated, ``EPA has not made a determination that the 
SIL, developed for source-specific (PSD) purposes, could be considered 
an appropriate threshold to use when assessing contribution from an 
entire state.'' \54\ Kentucky stated in response that it ``concurs with 
the comment'' and had adjusted its SIP submittal accordingly.\55\ 
Further, even if the State had attempted to rely on the SIL as support 
for a 1 ppb threshold, the basis supplied by MOG is inadequate. The SIL 
is an analytical metric used in the context of PSD permitting, a part 
of the CAA's ``prevention of significant deterioration'' program, which 
generally is applicable in areas that designated attainment \56\ or 
unclassifiable for the NAAQS. Good neighbor analysis for the ozone 
NAAQS, by contrast, addresses the degree of significant contribution to 
nonattainment and interference with maintenance of the NAAQS resulting 
at downwind receptors from the collective contribution of many upwind 
sources. Further, it is not correct to conflate the

[[Page 9510]]

use of the term ``significance'' as used in the SIL guidance, with the 
term ``contribution,'' which is the appliable statutory term that EPA 
applies at Step 2 of the 4-step interstate transport framework. 
(``Significance'' within the 4-step framework is evaluated at Step 3 
through a multifactor analysis, for those states that are determined to 
``contribute'' to downwind receptors at Steps 1 and 2. See section 
I.D.4.) Given the fundamentally different statutory objectives and 
context, EPA disagrees with MOG's contention that the SIL guidance is 
applicable in the good neighbor context.
---------------------------------------------------------------------------

    \54\ See Kentucky's January 11, 2019, submission, Appendix D, 
Summary of Comments and Responses, at 6-7.
    \55\ Id. at 7. EPA directed Kentucky instead to the August 2018 
memorandum if it wished to rely on a 1 ppb threshold; however, EPA's 
comments noted that this memorandum was only a ``part'' of the 
rationale the Commonwealth should develop. Id. at 6.
    \56\ Pursuant to section 107(d) of the CAA, EPA must designate 
areas as either ``nonattainment,'' ``attainment,'' or 
``unclassifiable.'' Historically for ozone, the EPA has designated 
most areas that do not meet the definition of nonattainment as 
``unclassifiable/attainment.'' This category includes areas that 
have air quality monitoring data meeting the NAAQS and areas that do 
not have monitors but for which the EPA has no evidence that the 
areas may be violating the NAAQS or contributing to a nearby 
violation. In the designations for the 2015 ozone NAAQS, the EPA 
reversed the order of the label to be ``attainment/unclassifiable'' 
to better convey the definition of the designation category and so 
that the category is more easily distinguished from the separate 
unclassifiable category. An ``attainment'' designation is reserved 
for a previous nonattainment area that has been redesignated to 
attainment as a result of the EPA's approval of a CAA section 175A 
maintenance plan submitted by the state air agency.
---------------------------------------------------------------------------

1. EPA's Experience With Alternative Step 2 Thresholds
    EPA here shares further evaluation of its experience since the 
issuance of the August 2018 memorandum regarding use of alternative 
thresholds at Step 2. This experience leads the Agency to now believe 
it may not be appropriate to continue to attempt to recognize 
alternative contribution thresholds at Step 2. The August 2018 
memorandum stated that ``it may be reasonable and appropriate'' for 
states to rely on an alternative threshold of 1 ppb threshold at Step 
2.\57\ (The memorandum also indicated that any higher alternative 
threshold, such as 2 ppb, would likely not be appropriate.) However, 
EPA also provided that ``air agencies should consider whether the 
recommendations in this guidance are appropriate for each situation.'' 
Following receipt and review of 49 good neighbor SIP submittals for the 
2015 8-hour ozone NAAQS, EPA's experience has been that nearly every 
state that attempted to rely on a 1 ppb threshold did not provide 
sufficient information and analysis to support a determination that an 
alternative threshold was reasonable or appropriate for that state.
---------------------------------------------------------------------------

    \57\ See August 2018 memorandum at 4.
---------------------------------------------------------------------------

    For instance, in nearly all submittals, the states did not provide 
EPA with analysis specific to their state or the receptors to which its 
emissions are potentially linked. In one case, the proposed approval of 
Iowa's SIP submittal, EPA expended its own resources to attempt to 
supplement the information submitted by the state, in order to more 
thoroughly evaluate the state-specific circumstances that could support 
approval.\58\ It was at EPA's sole discretion to perform this analysis 
in support of the state's submittal, and the Agency is not obligated to 
conduct supplemental analysis to fill the gaps whenever it believes a 
state's analysis is insufficient. The Agency no longer intends to 
undertake supplemental analysis of SIP submittals with respect to 
alternative thresholds at Step 2 for purposes of the 2015 8-hour ozone 
NAAQS.
---------------------------------------------------------------------------

    \58\ Air Plan Approval; Iowa; Infrastructure State 
Implementation Plan Requirements for the 2015 Ozone National Ambient 
Air Quality Standard, 85 FR 12232 (March 2, 2020). The Agency 
received adverse comment on this proposed approval and has not taken 
final action with respect to this proposal.
---------------------------------------------------------------------------

    Furthermore, EPA's experience since 2018 is that allowing for 
alternative Step 2 thresholds may be impractical or otherwise 
inadvisable for a number of additional policy reasons. For a regional 
air pollutant such as ozone, consistency in requirements and 
expectations across all states is essential. Based on its review of 
submittals to-date and after further consideration of the policy 
implications of attempting to recognize an alternative Step 2 threshold 
for certain states, the Agency now believes the attempted use of 
different thresholds at Step 2 with respect to the 2015 8-hour ozone 
NAAQS raises substantial policy consistency and practical 
implementation concerns.\59\ The availability of different thresholds 
at Step 2 has the potential to result in inconsistent application of 
good neighbor obligations based solely on the strength of a state's 
implementation plan submittal at Step 2 of the 4-step interstate 
transport framework. From the perspective of ensuring effective 
regional implementation of good neighbor obligations, the more 
important analysis is the evaluation of the emissions reductions 
needed, if any, to address a state's significant contribution after 
consideration of a multifactor analysis at Step 3, including a detailed 
evaluation that considers air quality factors and cost. Where 
alternative thresholds for purposes of Step 2 may be ``similar'' in 
terms of capturing the relative amount of upwind contribution (as 
described in the August 2018 memorandum), nonetheless, use of an 
alternative threshold would allow certain states to avoid further 
evaluation of potential emission controls while other states must 
proceed to a Step 3 analysis. This can create significant equity and 
consistency problems among states.
---------------------------------------------------------------------------

    \59\ EPA notes that Congress has placed on EPA a general 
obligation to ensure the requirements of the CAA are implemented 
consistently across states and regions. See CAA section 301(a)(2). 
Where the management and regulation of interstate pollution levels 
spanning many states is at stake, consistency in application of CAA 
requirements is paramount.
---------------------------------------------------------------------------

    Further, it is not clear that national ozone transport policy is 
best served by allowing for less stringent thresholds at Step 2. EPA 
recognized in the August 2018 memorandum that there was some similarity 
in the amount of total upwind contribution captured (on a nationwide 
basis) between 1 percent and 1 ppb. However, EPA notes that while this 
may be true in some sense, that is hardly a compelling basis to move to 
a 1 ppb threshold. Indeed, the 1 ppb threshold has the disadvantage of 
losing a certain amount of total upwind contribution for further 
evaluation at Step 3 (e.g., roughly 7 percent of total upwind state 
contribution was lost according to the modeling underlying the August 
2018 memorandum; \60\ in EPA's updated modeling, the amount lost is 5 
percent). Considering the core statutory objective of ensuring 
elimination of all significant contribution to nonattainment or 
interference of the NAAQS in other states and the broad, regional 
nature of the collective contribution problem with respect to ozone, 
there does not appear to be a compelling policy imperative in allowing 
some states to use a 1 ppb threshold while others rely on a 1 percent 
of the NAAQS threshold.
---------------------------------------------------------------------------

    \60\ See August 2018 memorandum at 4.
---------------------------------------------------------------------------

    Consistency with past interstate transport actions such as CSAPR, 
and the CSAPR Update and Revised CSAPR Update rulemakings (which used a 
Step 2 threshold of 1 percent of the NAAQS for two less stringent ozone 
NAAQS), is also important. Continuing to use a 1 percent of NAAQS 
approach ensures that as the NAAQS are revised and made more stringent, 
an appropriate increase in stringency at Step 2 occurs, so as to ensure 
an appropriately larger amount of total upwind-state contribution is 
captured for purposes of fully addressing interstate transport. See 76 
FR 48208, 48237-38 (August 8, 2011).
    Therefore, notwithstanding the August 2018 memorandum's recognition 
of the potential viability of alternative Step 2 thresholds, and in 
particular, a potentially applicable 1 ppb threshold, EPA's experience 
since the issuance of that memorandum has revealed substantial 
programmatic and policy difficulties in attempting to implement this 
approach. Nonetheless, EPA is not at this time rescinding the August 
2018 memorandum. The basis for disapproval of Kentucky's SIP submission 
with respect to the Step 2 analysis is, in the Agency's view, warranted 
even under the terms of the August 2018 memorandum. EPA invites comment 
on this broader discussion of issues associated with alternative 
thresholds at Step 2. Depending on comment and further evaluation of 
this issue, EPA may determine to rescind the August 2018 memorandum in 
the future.

[[Page 9511]]

    In summary, EPA's updated modeling indicates that emissions from 
Kentucky sources are linked to downwind receptors identified in Table 
1, and application of 1 ppb alternative threshold is not supported by 
Kentucky's SIP submission. Thus, EPA preliminarily finds that Kentucky 
is linked to downwind nonattainment and maintenance receptors, and 
proceeds to Step 3 of the 4-step framework.

D. Evaluation of Information Provided by Kentucky Regarding Step 3

    At Step 3 of the 4-step interstate transport framework, a state's 
emissions are further evaluated, in light of multiple factors, 
including air quality and cost considerations, to determine what, if 
any, emissions significantly contribute to nonattainment or interfere 
with maintenance and, thus, must be eliminated under CAA section 
110(a)(2)(D)(i)(I).
    To effectively evaluate which emissions in the state should be 
deemed ``significant'' and therefore prohibited, states generally 
should prepare an accounting of sources and other emissions activity 
for relevant pollutants and assess potential, additional emissions 
reduction opportunities and resulting downwind air quality 
improvements. EPA has consistently applied this general approach (i.e., 
Step 3 of the 4-step interstate transport framewor46k) when identifying 
emissions contributions that the Agency has determined to be 
``significant'' (or interfere with maintenance) in each of its prior 
Federal, regional ozone transport rulemakings, and this interpretation 
of the statute has been upheld by the Supreme Court. See EME Homer 
City, 572 U.S. 489, 518-520 (2014). While EPA has not directed states 
that they must conduct a Step 3 analysis in precisely the manner EPA 
has done in its prior regional transport rulemakings, state 
implementation plans addressing the obligations in CAA section 
110(a)(2)(D)(i)(I) must prohibit ``any source or other type of 
emissions activity within the State'' from emitting air pollutants 
which will contribute significantly to downwind air quality problems. 
Thus, states must complete something similar to EPA's analysis (or an 
alternative approach to defining ``significance'' that comports with 
the statute's objectives) to determine whether and to what degree 
emissions from a state should be ``prohibited'' to eliminate emissions 
that will ``contribute significantly to nonattainment in, or interfere 
with maintenance of'' the NAAQS in any other state. Kentucky did not 
conduct such an analysis in its SIP submission.
    Kentucky did not include a comprehensive accounting of facilities 
in the Commonwealth and did not include a sufficient analysis of 
potential NOX emissions control technologies, their 
associated costs, estimated emissions reductions, and downwind air 
quality improvements for the purpose of identifying what additional 
emission controls may be necessary to eliminate their significant 
contribution. Rather, Kentucky's SIP included air quality analysis 
related to downwind receptors and relied on existing NOX 
emission measures in the Commonwealth without any rationale to show how 
or why existing measures would eliminate the Kentucky's downwind 
contribution. Further, the Commonwealth provided information related to 
programs that it asserted were responsible for a 10-year decline in 
ozone season NOX emissions in Kentucky, such as regulations 
and Federal programs (including the CSAPR Update), EGU shutdowns, 
retirements, and fuel switches. However, Kentucky did not quantify the 
NOx emission reduction potential of on-the-books regulations or Federal 
programs or on-the-way measures for 2023, nor does the submission 
consider cost-effectiveness of potential emissions controls, the total 
emissions reductions that may be achieved by requiring these controls, 
or an evaluation of the air quality impacts such emissions reductions 
would have on the downwind receptors to which Kentucky is linked. 
Identifying a range of on-the-books emissions control measures that 
have been or may be enacted at the state or local level, without 
analysis of the impact of those measures on the downwind receptors, is 
not a sufficient analysis.
    Furthermore, the emissions-reducing effects of on-the-books 
emissions control requirements are already reflected in the air quality 
results of EPA's modeling under Steps 1 and 2 of the 4-step framework. 
Kentucky, and MOG in the materials it submitted to Kentucky, maintain 
that there were additional emission reductions that have occurred that 
were not accounted for in EPA's 2023 modeling as presented in the March 
2018 memorandum. Kentucky cites the 2019 retirement of units 1 and 2 at 
the E.W. Brown coal-fired power plant (see Appendix D, Response to 
Comments, at 5), and MOG claims a variety of unidentified changes not 
accounted for in EPA's emissions inventory at the time of the modeling 
in the March 2018 memorandum, as well as certain downwind state 
measures apparently under consideration but not adopted, and certain 
changes in the Wisconsin EGU fleet (see Alpine TSD, Appendix B, at 
pages B-5, B-6). In general, any changes in the emissions inventory and 
on-the-books controls relevant to emissions in 2023 have now been 
incorporated into EPA's most recent modeling of 2023. This includes 
changes in Kentucky EGU emissions.
    As previously discussed, EPA's updated modeling indicates sources 
in Kentucky are linked to downwind air quality problems for the 2015 8-
hour ozone standard. However, Kentucky's SIP submittal did not include 
a sufficient accounting of emissions sources or activity in the 
Commonwealth, along with an analysis of potential NOX 
emissions control technologies, associated costs, estimated emissions 
reductions, and downwind air quality improvements to eliminate the 
Kentucky's downwind contribution.
    EPA therefore propose to find that Kentucky was required to analyze 
emissions from the sources and other emissions activity from within the 
Commonwealth to determine whether its contributions were significant, 
and EPA proposes to disapprove its submission because Kentucky failed 
to do so.
    The subsections below contain additional detail with respect to 
arguments made by the Commonwealth in its SIP submission.\61\
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    \61\ These subsections provide brief summaries of the issues as 
presented in Kentucky's SIP as context; please see section II of 
this notice for additional detail on the contents of Kentucky's SIP.
---------------------------------------------------------------------------

1. Evaluation of Kentucky's Reliance on Existing and Future 
NOX Emission Reductions
    The Commonwealth's SIP submission does not contain a Step 3 
analysis regarding future emissions reduction opportunities beyond 
pointing to NOX emission reductions from expected 
retirements, fuel switching, and shutdowns. While the Commonwealth 
claimed there would be an estimated 471 tons of NOX 
emissions from potential shutdown of units at the E.W. Brown Generating 
Station facility in Harrodsburg, Kentucky, the Commonwealth did not 
clarify how these planned reductions would resolve the Commonwealth's 
downwind contribution to the Harford County, Maryland maintenance-only 
receptor by 2023. (Nor did the Commonwealth evaluate whether emissions 
may increase at other sources whose generation would replace that lost 
at E. W. Brown.) Further, the E.W. Brown facility retired coal-fired 
units 1 and 2

[[Page 9512]]

in February 2019,\62\ the units' retirement is included in the recently 
updated modeling for Steps 1 and 2, and yet emissions from Kentucky 
sources remain linked to one or more downwind receptors.
---------------------------------------------------------------------------

    \62\ See Retired Unit exemption forms for E.W. Brown Generating 
station in Docket No.: EPA-R04-OAR-2021-0841.
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    While the Commonwealth generally asserted that on-the-books or on-
the-way regulations and programs may provide future emissions 
reductions, Kentucky did not quantify these reductions in a meaningful 
way or demonstrate that the downwind improvements from these 
regulations and programs would be sufficient to eliminate the 
Commonwealth's significant contribution or interference with 
maintenance. In addition, the SIP submission did not evaluate or even 
attempt to identify additional control measures for EGUs or non-EGUs, 
nor did it include a determination of emission reduction potential for 
these potential additional controls or consider their cost-
effectiveness or downwind air quality effects. This is not a sufficient 
Step 3 analysis.
2. Evaluation of Kentucky's Reliance on Prior Transport FIPs
    The 10-year emission reductions discussed by Kentucky relies in 
part on the implementation of CAIR, CSAPR, and the CSAPR Update. 
Kentucky's SIP relied on its EGUs being subject to the CSAPR Update 
(which reflected a stringency at the nominal marginal cost threshold of 
$1,400/ton (in 2011 dollars) for the 2008 8-hour ozone NAAQS) to argue 
that it has already implemented all cost-effective emissions reductions 
to support its conclusion that additional NOX emission 
reductions are not necessary from sources in Kentucky. Kentucky did not 
conduct a comprehensive Step 3 analysis or provide any justification 
for reliance on the CSAPR Update beyond identifying the NOX 
emission reductions that the Commonwealth believes are the source of 
the 10-year decline in NOX emissions at EGUs in the 
Commonwealth and noting that the actual emissions from EGUs in the 
Commonwealth are well below the CSAPR Update NOX ozone 
season trading budget.
    EPA disagrees with the Commonwealth. Reliance on the CSAPR Update 
(or the subsequent Revised CSAPR Update, which fully resolved 
Kentucky's good neighbor obligations for the 2008 ozone NAAQS, 86 FR 
23056-57), is insufficient because those policies addressed section 
110(a)(2)(D)(i)(I) only for the 2008 ozone NAAQS. Additionally, 
reliance on an alleged cost-threshold stringency from the CSAPR Update 
is insufficient without additional Step 3 analysis and justification. 
First, the CSAPR Update did not regulate non-EGUs, and thus this 
analysis would have been incomplete, even with respect to obligations 
under the 2008 ozone NAAQS. See Wisconsin, 938 F.3d at 318-20. Second, 
relying on the CSAPR Update's (or any other CAA program's) 
determination of cost-effectiveness without further Step 3 analysis is 
not approvable. Cost-effectiveness must be assessed in the context of 
the specific CAA program; assessing cost-effectiveness in the context 
of ozone transport should reflect a more comprehensive evaluation of 
the nature of the interstate transport problem under the relevant 
NAAQS, the total emissions reductions available at alternative cost 
thresholds, and the air quality impacts of the reductions at downwind 
receptors. While EPA has not established a benchmark cost-effectiveness 
value for 2015 8-hour ozone NAAQS interstate transport obligations, 
because the 2015 8-hour ozone NAAQS is a more stringent and more 
protective air quality standard, it is reasonable to expect control 
measures or strategies to address interstate transport under this NAAQS 
to reflect higher marginal control costs. As such, the marginal cost 
threshold of $1,400/ton for the CSAPR Update (which addresses the 2008 
ozone 8-hour NAAQS and is in 2011 dollars) is not an appropriate cost 
threshold and cannot be approved as a benchmark to use for interstate 
transport SIP submissions for the 2015 8-hour ozone NAAQS.
    In addition, the updated EPA modeling captures all existing CSAPR 
trading programs in the baseline, and that modeling confirms that these 
control programs were not sufficient to eliminate the Kentucky's 
linkage at Steps 1 and 2 under the 2015 8-hour ozone NAAQS. Kentucky 
was therefore obligated at Step 3 to assess additional control measures 
using a multifactor analysis.
    Finally, relying on a FIP at Step 3 is per se not approvable if the 
state has not adopted that program into its SIP and instead continues 
to rely on the FIP. States may not rely on non-SIP measures to meet SIP 
requirements. See CAA section 110(a)(2)(D) (``Each such [SIP] shall . . 
. contain adequate provisions. . . .''). See also CAA section 
110(a)(2)(A); Committee for a Better Arvin v. U.S. E.P.A., 786 F.3d 
1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by state 
to meet CAA requirements must be included in the SIP). Kentucky has not 
adopted the Group 3 NOX Ozone Season Trading Program 
promulgated in the Revised CSAPR Update into its SIP.
3. Evaluation of Kentucky's Analysis of Air Quality and Emission 
Reductions Near the Linked Monitors
    Kentucky's SIP also evaluated air quality in the vicinity of the 
Fairfield County, Connecticut (IDs: 090013007 and 090019003) and 
Harford County, Maryland (ID: 240251001) monitors for which the 
Commonwealth is linked based on EPA's modeling in the March 2018 
memorandum. Kentucky's submission asserts that the primary cause of 
nonattainment problems at the Connecticut and Maryland monitors are due 
to local emissions of ozone precursors (particularly NOX) 
and meteorological conditions.
    Kentucky's SIP submittal argues against control requirements on 
Kentucky sources to address the two nonattainment receptors in 
Fairfield, Connecticut (IDs: 090013007, 090019003) and the maintenance-
only monitor in Harford County, Maryland monitor, claiming that 
additional emission reductions from Kentucky EGUs (the only Kentucky 
source category discussed in the submittal) are not necessary. Kentucky 
concludes that local emissions reductions should be applied before 
requiring Kentucky to control its sources, and that the implementation 
of local programs to reduce emissions should be sufficient for monitors 
in the area to attain the 2015 8-hour ozone NAAQS.\63\
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    \63\ The Commonwealth's submission cites to MOG's statements 
regarding controls on local sources ``When an area is measuring 
nonattainment of a NAAQS, as is the case with the areas linked to 
Kentucky, the CAA requires that the effects and benefits of local 
controls on all source sectors be considered first, prior to 
pursuing controls of sources in upwind states.''
---------------------------------------------------------------------------

    With respect to the information Kentucky provided that is related 
to local emissions and the impact on air quality at the Connecticut and 
Maryland receptors, this information is insufficient to approve 
Kentucky's SIP submission. Regardless of whether local emissions are 
the largest contributor to a specific nonattainment or maintenance 
receptor, the good neighbor provision requires that upwind states 
prohibit emissions that contribute significantly to nonattainment or 
interfere with maintenance of the NAAQS in downwind states. EPA 
evaluates a state's obligations to eliminate interstate transport 
emissions under the interstate transport provision according to EPA's 
4-step process, and EPA's updating modeling at Steps 1 and

[[Page 9513]]

2 has identified a linkage between emission from Kentucky sources and 
downwind nonattainment and maintenance receptors.
    Further, EPA disagrees with Kentucky's claims that local emissions 
reductions from the jurisdiction where the downwind receptor is located 
must first be implemented and accounted for before imposing obligations 
on upwind states under the interstate transport provision. There is 
nothing in the CAA that supports that position, and it does not provide 
grounds on which to approve Kentucky SIP submission. The D.C. Circuit 
has held on five different occasions that the timing framework for 
addressing interstate transport obligations must be consistent with the 
downwind areas' attainment schedule. In particular, for the ozone 
NAAQS, the states and EPA are to address interstate transport 
obligations ``as expeditiously as practicable'' and no later than the 
attainment schedule set in accordance with CAA section 181(a). See 
North Carolina, 531 F.3d at 911-13; Wisconsin, 938 F.3d at 313-20; 
Maryland, 958 F.3d at 1204; New York v. EPA, 964 F.3d 1214, 1226 (D.C. 
Cir. 2020); New York v. EPA, 781 Fed. App'x 4, 6-7 (D.C. Cir. 2019). 
The court in Wisconsin explained its reasoning in part by noting that 
downwind jurisdictions often may need to heavily rely on emissions 
reductions from upwind states in order to achieve attainment of the 
NAAQS, 938 F.3d at 316-17; such states would face increased regulatory 
burdens including the risk of bumping up to a higher nonattainment 
classification if attainment is not reached by the relevant deadline. 
Maryland, 958 F.3d at 1204. The statutory framework of the CAA and 
these cases establish clearly that states and EPA must address 
interstate transport obligations in line with the attainment schedule 
provided in the Act in order to timely assist downwind states in 
attaining and maintain the NAAQS, and this schedule is ``central to the 
regulatory scheme.'' Wisconsin, 938 F.3d at 316 (quoting Sierra Club v. 
EPA, 294 F.3d 155, 161 (D.C. Cir. 2002)).
    In addition, Kentucky's SIP does not provide a technical 
justification to support its conclusion that local emissions reductions 
at the receptors will achieve attainment without upwind reductions from 
sources within Kentucky. Specifically, Kentucky does not provide any 
information to support its claim that the implementation of local 
programs alone will address the air quality problems at the Connecticut 
and Maryland monitors. Even with the consideration of on-the-books 
control measures to reduce mobile source emissions, EPA's modeling 
projects that the total contribution from upwind states is a 
substantial part of the ozone problem at the nonattainment and 
maintenance receptors to which Kentucky is linked. To illustrate this, 
at the four receptors to which Kentucky is linked in EPA's latest 2023 
modeling, the total percent of U.S. anthropogenic emissions from upwind 
states is 55 percent (Bucks Co., Pennsylvania), 90 percent (New Haven 
Co., Connecticut), 90 percent (Fairfield Co.--Stratford, Connecticut), 
and 94 percent (Fairfield Co.--Westport, Connecticut) of the total 
design values at these receptors. Clearly, emissions reductions from 
upwind states would have an impact on the design values at the 
identified receptors.\64\
---------------------------------------------------------------------------

    \64\ In contrast to the receptors to which Kentucky is linked, 
EPA has found that certain receptors are so heavily impacted by 
local emissions that they should not be considered ``transport'' 
receptors for purposes of the ozone NAAQS. Typically, in such cases, 
only one state is linked above 1 percent to that receptor and the 
total upwind state contribution is on the order of 2 percent to 4 
percent of the receptor's DV. See, e.g., 81 FR 15200 (March 22, 
2016), 81 FR 31513 (May 19, 2016), and 81 FR 36179 (June 6, 2016) 
(approving Arizona's transport SIP on basis that certain California 
receptors should not be considered impacted by interstate ozone 
transport).
---------------------------------------------------------------------------

    Additionally, the SIP submission does not assess whether the 
Commonwealth's own emissions contributed to nonattainment or interfered 
with maintenance at the linked receptors, or rather substantiate that 
emissions from the Commonwealth's sources were not interacting with 
these monitors. Consequently, the application of local emission 
reduction measures does not absolve upwind states and sources from the 
responsibility of addressing their significant contribution. Moreover, 
Kentucky still has an obligation under the Act to address its downwind 
contribution to ozone nonattainment or interference with maintenance 
regardless of the emission reduction potential for local control 
measures. Furthermore, given that EPA's updated modeling indicates that 
Kentucky is linked to nonattainment and maintenance receptors at Step 2 
including the same Fairfield County, Connecticut nonattainment 
receptors as were linked in the modeling released with the March 2018 
memorandum, EPA disagrees with Kentucky's claims regarding the 
application of local emission reduction measures with respect to its 
downwind linkages in the most recent modeling.
4. Evaluation of Kentucky's HYSPLIT Analysis
    Kentucky's SIP submittal also included HYSPLIT model back 
trajectory analysis, which Kentucky used to emphasize the local nature 
of the ozone precursor emissions at the two Connecticut receptors, 
mobile sources along the I-95 Corridor, and the proximity of large 
point sources and ozone nonattainment areas in New York, New Jersey, 
Pennsylvania, and Maryland. Similarly, Kentucky also evaluated HYSPLIT 
back-trajectory for the Harford County, Maryland monitor and noted 
similar localized emissions impacts with respect to the Maryland 
monitor as discussed previously for the two Fairfield County, 
Connecticut monitors.
    However, the limited information provided by Kentucky is not 
adequate to support approval of Kentucky's SIP on this basis and in the 
absence of a more complete Step 3 evaluation. Kentucky's SIP submittal 
did not address that the HYSPLIT back-trajectories indicate that ozone 
precursor emissions sources in Kentucky are upwind of the linked 
nonattainment receptors in Connecticut (regardless of the existence of 
other upwind nonattainment areas that may also be contributing to those 
receptors). Additionally, the HYSPLIT trajectory information provided 
by Kentucky was developed by EPA to inform the 2015 8-hour ozone NAAQS 
area designations and was not intended to evaluate long-distance 
interstate transport.\65\
---------------------------------------------------------------------------

    \65\ See Area Designations for the 2015 Ozone National Ambient 
Air Quality Standards memorandum from Janet G. McCabe to EPA 
Regional Administrators, February 25, 2016 (2015 ozone Area 
Designations memorandum).
---------------------------------------------------------------------------

    Attachment 3 of the 2015 8-hour ozone Area Designations memorandum 
states that the line thickness displayed on trajectory plots ``does not 
imply coverage other than to represent the centerline of an air 
parcel's motion calculated to arrive at the starting location at the 
starting time. Uncertainties are clearly present in these results and 
these uncertainties change with trajectory time and distance traveled. 
One should avoid concluding a region is not along a trajectory's path 
if the center line of that trajectory missed the region by a relatively 
small distance.'' \66\
---------------------------------------------------------------------------

    \66\ See id. It is important to understand that HYSPLIT back 
trajectory analyses use archived meteorological modeling that 
includes actual observed data (surface, upper air, airplane data, 
etc.) and modeled meteorological fields to estimate the most likely 
route of an air parcel transported to a receptor at a specified 
time. The method essentially follows a parcel of air backward in 
hourly steps for a specified length of time. HYSPLIT estimates the 
central path in both the vertical and horizontal planes. The HYSPLIT 
central path represents the centerline with the understanding that 
there are areas on each side horizontally and vertically that also 
contribute to the end point at the monitor. The horizontal and 
vertical areas from the centerline grow wider the further back in 
time the trajectory goes. Therefore, a HYSPLIT centerline does not 
have to pass directly over emissions sources or emission source 
areas but merely relatively near emission source areas.

---------------------------------------------------------------------------

[[Page 9514]]

    Further, the back trajectories used by Kentucky were limited to 
evaluating transport of air parcels over a relatively short 24-hour 
period, which limits their use for evaluating long-distance transport 
of emissions from Kentucky to the Fairfield, Connecticut receptors and 
the Harford, Maryland receptor. In contrast, EPA's analysis of 
transported emissions as discussed in section III.A uses updated, 
photochemical grid modeling designed to assess ozone transported to 
downwind monitors across the entire region and over extended timeframes 
that fully account for fate and transport of ozone-precursors over 
longer distances.
    Kentucky's SIP submission states that the Fairfield County ozone 
monitors are located in the New York Metro Area, in close proximity to 
the I-95 transportation artery. The Commonwealth's analysis asserts a 
high VMT and number of commuters in the area indicating the presence of 
mobile emissions that could be the cause of violating monitors along 
the I-95 corridor. Kentucky's SIP also mentions two additional coastal 
monitor sites (Westport Sherwood and Stratford Point Lighthouse) 
located less than three miles from the I-95 corridor that also show a 
pattern of ozone violations. Kentucky raises similar points regarding 
the effect of mobile source emissions along the I-95 corridor in 
Maryland near the Edgewood receptor. Further, Kentucky asserts that 
both the Connecticut and Maryland receptor sites may be particularly 
impacted by unique coastal conditions associated with the Long Island 
Sound and the Chesapeake Bay. While it is true that both of these 
monitors are affected by coastal meteorological conditions such as 
complex land-water wind flows and mixing heights, a large portion of 
anthropogenic ozone at these locations is the result of transport from 
upwind states. In addition, as noted above, EPA's most recent modeling 
shows that Kentucky is linked to a receptor in Bucks County, 
Pennsylvania which is inland and not influenced by coastal meteorology.
    The relevance of the points raised by Kentucky regarding the 
HYSPLIT back trajectories related to the evaluation of Kentucky's good 
neighbor obligations is not clear. As already discussed, the statute 
and the case law (particularly the holdings in Wisconsin and Maryland) 
make clear that good neighbor obligations are not merely supplementary 
to or deferable until after local emission reductions are achieved. 
Further, all of the receptors to which Kentucky is linked are heavily 
impacted by upwind state emissions in addition to local sources and 
conditions. The Wisconsin decision's holding regarding international 
contribution (discussed in section III.A) is equally applicable to an 
upwind state's claims that some other state's emissions, or local 
emissions, are ``more to blame'' than its own emissions. See 938 F.3d 
303 at 323-25 (``an upwind State can `contribute' to downwind 
nonattainment even if its emissions are not the but-for cause'').
5. Evaluation of Kentucky's Approach to Maintenance Receptors
    Kentucky's SIP argues that states linked only to maintenance 
receptors should be held to less stringent standards of emissions 
reductions compared to states linked to a nonattainment receptor. Thus, 
as the Edgewood monitor was identified as a maintenance receptor in 
EPA's March 2018 memorandum modeling, the Commonwealth asserts that no 
further reductions from Kentucky sources other than on-the-books 
controls should be required. Although the Harford monitor is no longer 
linked to Kentucky based on EPA's updated modeling,\67\ emissions from 
the Commonwealth are linked to the Bucks County, Pennsylvania (ID: 
420170012) maintenance-only receptor. Additionally, MOG argues that 
states should be absolved from additional emissions controls to address 
a maintenance monitor if the upwind state can show that either the 
monitor is likely to remain in attainment for a period of 10 years or 
that the upwind state's emissions will not increase for 10 years after 
the attainment date.\68\
---------------------------------------------------------------------------

    \67\ See Table 1, shown previously in this notice.
    \68\ Kentucky did not rely on MOG's proposed approach in its SIP 
submittal, therefore EPA does not comprehensively evaluate MOG's 
suggestion. However, EPA's definition of maintenance receptors 
already accounts for, and projects whether, receptors may have 
trouble attaining the NAAQS, through the use of projected maximum 
design values in the relevant analytic year. Further, EPA's modeling 
of the relevant analytic year also already accounts for projected 
emissions trends of the upwind state (among others) and may (and 
often does) identify a linkage to areas that may struggle to 
maintain the NAAQS despite an overall declining emissions trend. 
This is not surprising. First, most maintenance receptors in EPA's 
projections are currently measuring nonattainment, meaning that, 
despite projecting improved air quality in the future analytic year, 
the receptor location is currently, and may continue to be, near the 
level of the NAAQS. Second, ozone levels are influenced by 
meteorological variability and thus high ozone levels may persist 
despite declining emissions as a result of recurring or worsening 
ozone-conducive atmospheric conditions (e.g., higher temperatures). 
It is unclear how MOG's approach would account for this variability 
or ensure that projected emissions reductions from linked states are 
rendered certain and enforceable.
---------------------------------------------------------------------------

    Under the D.C. Circuit's decision in North Carolina, states and EPA 
are required to give independent significance to the ``interference 
with maintenance'' prong of section 110(a)(2)(D)(i)(I). See 531 F.3d at 
910. Since CSAPR, EPA's nationally consistent policy framework for 
addressing interstate ozone transport has given meaning to this prong 
through a separate definition of maintenance receptors at Step 1 of the 
4-step interstate transport framework. For states linked only to those 
receptors, EPA has found it appropriate to apply an emissions control 
solution that is uniform with the strategy applied for states that are 
linked to nonattainment receptors. See 76 FR at 48271. EPA's approach 
to addressing interference with maintenance under prong 2 for ozone 
NAAQS has been upheld twice. See EME Homer City Generation, L.P., 795 
F.3d at 136; Wisconsin, 938 F.3d at 325-27. See also 86 FR at 23054 
(April 30, 2021).\69\
---------------------------------------------------------------------------

    \69\ In the main text of its SIP submittal conclusion regarding 
interstate transport, Kentucky incorrectly attributes statements 
regarding the ``interfere with maintenance'' prong to the U.S. 
Supreme Court. See Submittal at 45-46. A footnote, however, 
correctly attributes this language to the D.C. Circuit's original 
opinion in EME Homer City v EPA, 696 F.3d 7 (D.C. Cir. 2012). This 
decision was reversed and remanded by the Supreme Court, and on 
remand, the D.C. Circuit affirmed EPA's approach to implementing 
prong 2, see 795 F.3d at 136.
---------------------------------------------------------------------------

    Particularly given this context, Kentucky's SIP submission does not 
provide information sufficient to support less stringent standards of 
emissions reductions than would result from EPA's historical approach 
of addressing emissions activities from upwind states that are linked 
to maintenance-only receptors. The Commonwealth does not explain how 
the obligations of upwind states linked to maintenance-only receptors 
should be treated differently than the obligations of upwind states 
linked to nonattainment receptors.
    Further, EPA believes it would be inconsistent with the CAA for EPA 
to identify receptors that are at risk of NAAQS violations given 
certain conditions due to transported upwind emissions and then not 
prohibit the emissions that place the receptor at risk. The Supreme 
Court held that it was a permissible interpretation of the statute to 
apportion responsibility for states

[[Page 9515]]

linked to nonattainment receptors considering ``both the magnitude of 
upwind States' contributions and the cost associated with eliminating 
them.'' EME Homer City, 134 S. Ct. at 1606. It is equally reasonable 
and permissible to use these factors to apportion responsibility among 
upwind states linked to maintenance receptors because the goal in both 
instances is to prohibit the ``amounts'' of pollution that will either 
significantly contribute to nonattainment or interfere with maintenance 
of the NAAQS downwind. EPA's updated modeling indicates that the 
Commonwealth is still linked to downwind nonattainment and maintenance 
receptors for the 2015 8-hour ozone standard. Consequently, EPA 
believes Kentucky's assertion that upwind states linked to maintenance-
only receptors should be held to less stringent standards of emissions 
reductions (as compared to states linked to a nonattainment receptor) 
is also inappropriate for new downwind linkages.
6. Evaluation of Weighted Step 3 Approach
    Although Kentucky did not adopt this approach in its SIP submittal, 
the MOG materials Kentucky appended provided arguments suggesting a 
``weighted'' approach to Step 3 similar to an approach that 
stakeholders had identified to EPA (as listed in Attachment A to EPA's 
March 2018 memorandum). Under this approach, upwind-state emission 
reduction obligations would be allocated in proportion to the size of 
their contribution to downwind nonattainment. MOG determined the 
proportional reduction requirement associated with the relative 
significant contribution from each upwind state to the Harford County, 
Maryland monitor including Kentucky, which resulted in an additional 
emission reduction obligation for Kentucky of 0.02 ppb, as MOG proposed 
would be the appropriate proportion of reductions necessary for 
attainment at the Harford receptor. This approach would have imposed 
additional emissions reductions for Kentucky sources. Kentucky's final 
SIP did not consider MOG's proposal, and did not provide an explanation 
for why it was rejecting this approach to allocating upwind emission 
reductions, even though it appended this recommendation to its SIP 
submittal.
    In summary, EPA has newly available information that confirms 
sources in Kentucky are linked to downwind air quality problems for the 
2015 8-hour ozone standard. Kentucky's SIP submittal did not include an 
accounting of emissions sources and activity in the Commonwealth along 
with an analysis of potential NOX emissions control 
technologies, their associated costs, estimated emissions reductions, 
and downwind air quality improvements. Nor did Kentucky present an 
alternative approach to assess which of its emissions should be deemed 
``significant.'' EPA proposes to find that Kentucky's analysis--
including reliance on on-the-books state and Federal measures 
(including prior CSAPR programs) and claimed on-the-way emission 
reductions, as well as other air quality, emissions, and geographic 
factors--is insufficient to support the Commonwealth's claim that its 
SIP adequately prohibits emissions within Kentucky in a manner 
sufficient to address the State's interstate transport obligations for 
the 2015 8-hour ozone.

E. Evaluation of Information Provided by Kentucky Regarding Step 4

    Step 4 of the 4-step interstate transport framework calls for 
development of permanent and federally enforceable control strategies 
to achieve the emissions reductions determined to be necessary at Step 
3 to eliminate significant contribution to nonattainment or 
interference with maintenance of the NAAQS. Kentucky indicates that 
certain upcoming planned fuel switches or shutdowns at EGUs will occur 
before the end of 2023, for which Kentucky cites a press release and a 
closure plan developed by each plant's parent company.\70\ As discussed 
in section III.D., Kentucky's analysis is insufficient to demonstrate 
that these reductions are sufficient to address the Commonwealth's 
interstate transport obligations; however, the Commonwealth also did 
not provide a separate SIP revision to ensure the reductions were 
permanent and enforceable. As a result, EPA proposes to disapprove 
Kentucky's January 11, 2019, submittal on the separate, additional 
basis that the Commonwealth has not developed permanent and enforceable 
emissions reductions necessary to meet the obligations of CAA section 
110(a)(2)(d)(i)(I).
---------------------------------------------------------------------------

    \70\ Pointing to anticipated upcoming emission reductions, even 
if they were not included in the analysis at Steps 1 and 2, is not 
sufficient as a Step 3 analysis, for the reasons discussed in 
section III.C. In this section, EPA explain that to the extent such 
anticipated reductions are not included in the SIP and rendered 
permanent and enforceable, reliance on such anticipated reductions 
is also insufficient at Step 4.
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F. Conclusion

    Based on EPA's evaluation of Kentucky's SIP submission, EPA is 
proposing to find that the interstate transport portion of Kentucky's 
January 11, 2019, SIP submission addressing CAA section 
110(a)(2)(D)(i)(I) does not meet the Commonwealth's interstate 
transport obligations because it fails to contain the necessary 
provisions to eliminate emissions that will contribute significantly to 
nonattainment or interfere with maintenance of the 2015 8-hour ozone 
NAAQS in any other state.

IV. Proposed Action

    EPA is proposing to disapprove the 2015 8-hour ozone good neighbor 
interstate transport SIP revision from Kentucky, dated January 11, 
2019. Under CAA section 110(c)(1), if finalized, this disapproval would 
establish a 2-year deadline for EPA to promulgate a FIP for Kentucky to 
address the CAA section 110(a)(2)(D)(i)(I) interstate transport 
requirements pertaining to significant contribution to nonattainment 
and interference with maintenance of the 2015 8-hour ozone NAAQS in 
other states, unless EPA approves a SIP that meets these requirements. 
However, under the CAA, a good neighbor SIP disapproval does not start 
a mandatory sanctions clock.

V. Statutory and Executive Order Reviews

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

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

B. Paperwork Reduction Act (PRA)

    This proposed action does not impose an information collection 
burden under the PRA because it does not contain any information 
collection activities.

C. Regulatory Flexibility Act (RFA)

    This action merely proposes to disapprove a SIP submission as not 
meeting the CAA for Kentucky. EPA certifies that this proposed rule 
will not have a significant economic impact on a substantial number of 
small entities under the RFA (5 U.S.C. 601 et seq.).

D. Unfunded Mandates Reform Act (UMRA)

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

[[Page 9516]]

E. Executive Order 13132: Federalism

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

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

    This proposed action does not have tribal implications as specified 
in Executive Order 13175. This proposed action does not apply on any 
Indian reservation land, any other area where EPA or an Indian tribe 
has demonstrated that a tribe has jurisdiction, or non-reservation 
areas of Indian country. Thus, Executive Order 13175 does not apply to 
this action.

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

    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that EPA has reason to believe may disproportionately affect children, 
per the definition of ``covered regulatory action'' in section 2-202 of 
the Executive Order. This proposed action is not subject to Executive 
Order 13045 because it merely proposes to disapprove a SIP submission 
from Kentucky as not meeting the CAA.

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

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

I. National Technology Transfer and Advancement Act

    This proposed rulemaking does not involve technical standards.

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

    EPA believes the human health or environmental risk addressed by 
this action will not have potential disproportionately high and adverse 
human health or environmental effects on minority, low-income or 
indigenous populations. This action merely proposes to disapprove a SIP 
submission as not meeting the CAA.

K. CAA Section 307(b)(1)

    Section 307(b)(1) of the CAA governs judicial review of final 
actions by EPA. This section provides, in part, that petitions for 
review must be filed in the D.C. Circuit: (i) When the agency action 
consists of ``nationally applicable regulations promulgated, or final 
actions taken, by the Administrator,'' or (ii) when such action is 
locally or regionally applicable, if ``such action is based on a 
determination of nationwide scope or effect and if in taking such 
action the Administrator finds and publishes that such action is based 
on such a determination.'' For locally or regionally applicable final 
actions, the CAA reserves to EPA complete discretion whether to invoke 
the exception in (ii).\71\
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    \71\ In deciding whether to invoke the exception by making and 
publishing a finding that an action is based on a determination of 
nationwide scope or effect, the Administrator takes into account a 
number of policy considerations, including his judgment balancing 
the benefit of obtaining the D.C. Circuit's authoritative 
centralized review versus allowing development of the issue in other 
contexts and the best use of agency resources.
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    If EPA takes final action on this proposed rulemaking, the 
Administrator intends to exercise the complete discretion afforded to 
him under the CAA to make and publish a finding that the final action 
(to the extent a court finds the action to be locally or regionally 
applicable) is based on a determination of ``nationwide scope or 
effect'' within the meaning of CAA section 307(b)(1). Through this 
rulemaking action (in conjunction with a series of related actions on 
other SIP submissions for the same CAA obligations), EPA interprets and 
applies section 110(a)(2)(d)(i)(I) of the CAA for the 2015 8-hour ozone 
NAAQS based on a common core of nationwide policy judgments and 
technical analysis concerning the interstate transport of pollutants 
throughout the continental U.S. In particular, EPA is applying here 
(and in other proposed actions related to the same obligations) the 
same, nationally consistent 4-step framework for assessing good 
neighbor obligations for the 2015 8-hour ozone NAAQS. EPA relies on a 
single set of updated, 2016-base year photochemical grid modeling 
results of the year 2023 as the primary basis for its assessment of air 
quality conditions and contributions at Steps 1 and 2 of that 
framework. Further, EPA proposes to determine and apply a set of 
nationally consistent policy judgments to apply the 4-step framework. 
EPA has selected a nationally uniform analytic year (2023) for this 
analysis and is applying a nationally uniform approach to nonattainment 
and maintenance receptors and a nationally uniform approach to 
contribution threshold analysis.\72\ For these reasons, the 
Administrator intends, if this proposed action is finalized, to 
exercise the complete discretion afforded to him under the CAA to make 
and publish a finding that this action is based on one or more 
determinations of nationwide scope or effect for purposes of CAA 
section 307(b)(1).\73\
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    \72\ A finding of nationwide scope or effect is also appropriate 
for actions that cover states in multiple judicial circuits. In the 
report on the 1977 Amendments that revised section 307(b)(1) of the 
CAA, Congress noted that the Administrator's determination that the 
``nationwide scope or effect'' exception applies would be 
appropriate for any action that has a scope or effect beyond a 
single judicial circuit. See H.R. Rep. No. 95-294 at 323, 324, 
reprinted in 1977 U.S.C.C.A.N. 1402-03.
    \73\ EPA may take a consolidated, single final action on all of 
the proposed SIP disapproval actions with respect to obligations 
under CAA section 110(a)(2)(D)(i)(I) for the 2015 8-hour ozone 
NAAQS. Should EPA take a single final action on all such 
disapprovals, this action would be nationally applicable, and EPA 
would also anticipate, in the alternative, making and publishing a 
finding that such final action is based on a determination of 
nationwide scope or effect.
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List of Subjects in 40 CFR Part 52

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

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

    Dated: February 3, 2022.
Daniel Blackman,
Regional Administrator, Region 4.
[FR Doc. 2022-02947 Filed 2-18-22; 8:45 am]
BILLING CODE 6560-50-P


