[Federal Register Volume 88, Number 29 (Monday, February 13, 2023)]
[Rules and Regulations]
[Pages 9336-9384]
[FR Doc No: 2023-02407]

Vol. 88

Monday,

No. 29

February 13, 2023

Part II

 Environmental Protection Agency

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 40 CFR Part 52

Air Plan Disapprovals; Interstate Transport of Air Pollution for the
2015 8-Hour Ozone National Ambient Air Quality Standards; Final Rule

Federal Register / Vol. 88 , No. 29 / Monday, February 13, 2023 /
Rules and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-HQ-OAR-2021-0663; EPA-R02-OAR-2021-0673; EPA-R03-OAR-2021-0872;
EPA-R03-OAR-2021-0873; EPA-R04-OAR-2021-0841; EPA-R05-OAR-2022-0006;
EPA-R06-OAR-2021-0801; EPA-R07-OAR-2021-0851; EPA-R08-OAR-2022-0315;
EPA-R09-OAR-2022-0394; EPA-R09-OAR-2022-0138; FRL-10209-01-OAR]

Air Plan Disapprovals; Interstate Transport of Air Pollution for
the 2015 8-Hour Ozone National Ambient Air Quality Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule; final agency action.

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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the
Environmental Protection Agency (EPA or the Agency) is finalizing the
disapproval of State Implementation Plan (SIP) submissions for 19
states regarding interstate transport and finalizing a partial approval
and partial disapproval of elements of the SIP submission for two
states for the 2015 8-hour ozone national ambient air quality standards
(NAAQS). The ``good neighbor'' or ``interstate transport'' provision
requires that each state's SIP 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.
Disapproving a SIP submission establishes a 2-year deadline for the EPA
to promulgate Federal Implementation Plans (FIPs) to address the
relevant requirements, unless the EPA approves a subsequent SIP
submission that meets these requirements. Disapproval does not start a
mandatory sanctions clock. The EPA is deferring final action at this
time on the disapprovals it proposed for Tennessee and Wyoming.

DATES: The effective date of this final rule is March 15, 2023.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2021-0663. Additional supporting materials
associated with this final action are included in certain regional
dockets. See the memo ``Regional Dockets Containing Additional
Supporting Materials for Final Action on 2015 Ozone NAAQS Good Neighbor
SIP Submissions'' in the docket for this action. All documents in the
dockets are listed on the https://www.regulations.gov website. Although
listed in the index, some information is not publicly available, i.e.,
confidential business information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available through https://www.regulations.gov or please
contact the person identified in the FOR FURTHER INFORMATION CONTACT
section for additional information.

FOR FURTHER INFORMATION CONTACT: General questions concerning this
document should be addressed to Mr. Thomas Uher, Office of Air Quality
Planning and Standards, Air Quality Policy Division, Mail Code C539-04,
109 TW Alexander Drive, Research Triangle Park, NC 27711; telephone
number:<PHONE_NUMBER>; email address: [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document ``we,'' ``us,'' and
``our'' refer to the EPA.
    References to section numbers in roman numeral refer to sections of
this preamble unless otherwise specified.

I. General Information

A. How can I get copies of this document and other related information?

    The EPA established a Headquarters docket for this action under
Docket ID No. EPA-HQ-OAR-2021-0663 and several regional dockets. All
documents in the docket are listed in the electronic indexes, which,
along with publicly available documents, are available at https://www.regulations.gov. Publicly available docket materials are also
available in hard copy at the Air and Radiation Docket and Information
Center, EPA/DC, William Jefferson Clinton West Building, Room 3334,
1301 Constitution Avenue NW, Washington, DC. Some information in the
docket may not be publicly available via the online docket due to
docket file size restrictions, such as certain modeling files, or
content (e.g., CBI). For further information on the EPA Docket Center
services and the current status, please visit us online at https://www.epa.gov/dockets.
    The EPA also established dockets in each of the EPA Regional
offices to help support the proposals that are now being finalized in
this national action. These include all public comments, technical
support materials, and other files associated with this final action.
Each regional docket contains a memorandum directing the public to the
headquarters docket for this final action. While all documents in
regional dockets are listed in the electronic indexes at https://www.regulations.gov, some information may not be publicly available via
the online dockets due to docket file size restrictions, such as
certain modeling files, or content (e.g., CBI). Please contact the EPA
Docket Center Services for further information.

B. How is the preamble organized?

Table of Contents

I. General Information
    A. How can I get copies of this document and other related
information?
    B. How is the preamble organized?
    C. Where do I go if I have state-specific questions?
II. Background and Overview
    A. Description of Statutory Background
    B. Description of the EPA's 4-Step Interstate Transport
Framework
    C. Background on the EPA's Ozone Transport Modeling Information
    D. The EPA's Approach to Evaluating Interstate Transport SIPs
for the 2015 8-Hour Ozone NAAQS
III. The EPA's Updated Air Quality and Contribution Analysis
    A. Description of Air Quality Modeling for the Final Action
    B. Air Quality Modeling To Identify Nonattainment and
Maintenance Receptors
    C. Air Quality Modeling To Quantify Upwind State Contributions
IV. Summary of Bases for Disapproval
    A. Alabama
    B. Arkansas
    C. California
    D. Illinois
    E. Indiana
    F. Kentucky
    G. Louisiana
    H. Maryland
    I. Michigan
    J. Minnesota
    K. Mississippi
    L. Missouri
    M. Nevada
    N. New Jersey
    O. New York
    P. Ohio
    Q. Oklahoma
    R. Texas
    S. Utah
    T. West Virginia
    U. Wisconsin
V. Response to Key Comments
    A. SIP Evaluation Process
    B. Application of the 4-Step Interstate Transport Framework
    C. Good Neighbor Provision Policy
VI. Statutory and Executive Orders Reviews
    A. Executive Orders 12866: Regulatory Planning and Executive
Order 13563:

Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act of 1995 (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution or Use
    I. National Technology Transfer and Advancement Act (NTTAA)
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act (CRA)
    L. Judicial Review

C. Where do I go if I have state-specific questions?

    The following table identifies the states covered by this final
action along with an EPA Regional office contact who can respond to
questions about specific SIP submissions.

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                Regional offices                          States
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EPA Region 2: Kenneth Fradkin, Air and Radiation  New Jersey, New York.
 Division/Air Programs Branch, EPA Region 2, 290
 Broadway, 25th Floor, New York, NY 10007.
EPA Region 3: Mike Gordon, Planning and           Maryland, West
 Implementation Branch, EPA Region III, 1600 JFK   Virginia.
 Boulevard, Philadelphia, Pennsylvania 19103.
EPA Region 4: Evan Adams, Air and Radiation       Alabama, Kentucky,
 Division/Air Planning and Implementation          Mississippi.
 Branch, EPA Region IV, 61 Forsyth Street SW,
 Atlanta, Georgia 30303.
EPA Region 5: Olivia Davidson, Air & Radiation    Indiana, Illinois,
 Division/Air Programs Branch, EPA Region V, 77    Michigan, Minnesota,
 W. Jackson Boulevard, Chicago, Illinois 60604-    Ohio, Wisconsin.
 3511.
EPA Region 6: Sherry Fuerst, Air and Radiation    Arkansas, Louisiana,
 Division, EPA Region 6, 1201 Elm Street, Suite    Oklahoma, Texas.
 500, Dallas, Texas 75270.
EPA Region 7: William Stone, Air and Radiation    Missouri.
 Division, Air Quality Planning Branch, EPA
 Region VII, 11201 Renner Boulevard, Lenexa,
 Kansas 66219.
EPA Region 8: Adam Clark, Air and Radiation       Utah.
 Division, EPA, Region VIII, Mailcode 8ARD-IO,
 1595 Wynkoop Street, Denver, Colorado 80202.
EPA Region 9: Tom Kelly, Air and Radiation        California, Nevada.
 Division, EPA Region IX, 75 Hawthorne St., San
 Francisco, California 94105.
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II. Background and Overview

    The following provides background for the EPA's final action on
these SIP submissions related to the interstate transport requirements
for the 2015 8-hour ozone NAAQS (2015 ozone NAAQS).

A. Description of Statutory Background

    On October 1, 2015, the EPA promulgated a revision to the ozone
NAAQS (2015 ozone NAAQS), lowering the level of both the primary and
secondary standards to 0.070 parts per million (ppm) for the 8-hour
standard.\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 \2\ meeting the applicable requirements of section
110(a)(2).\3\ 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). The 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).\4\
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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\ The terms ``submission,'' ``revision,'' and ``submittal''
are used interchangeably in this document.
    \3\ 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
CAA section 110(a)(2) are referred to as infrastructure
requirements.
    \4\ See North Carolina v. EPA, 531 F.3d 896, 909-11 (D.C. Cir.
2008) (North Carolina).
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    On February 22, 2022, the EPA proposed to disapprove 19 good
neighbor SIP submissions from the States of Alabama, Arkansas,
Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, Minnesota,
Mississippi, Missouri, New Jersey, New York, Ohio, Oklahoma, Tennessee,
Texas, West Virginia, and Wisconsin.\5\ On May 24, 2022, the EPA
proposed to disapprove four additional good neighbor SIP submissions
from the States of California, Nevada, Utah, and Wyoming.\6\ On October
25, 2022, the EPA proposed to disapprove a new good neighbor SIP
submission from Alabama submitted on June 21, 2022.\7\ The EPA is
deferring action on the proposals related to the good neighbor SIP
submissions from Tennessee and Wyoming at this time. As explained in
the notifications of proposed disapproval, the EPA's justification for
each of these proposals applies uniform, nationwide analytical methods,
policy judgments, and interpretation with respect to the same CAA
obligations, i.e., implementation of good neighbor requirements under
CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS for states
across the country. The EPA's final action is likewise based on this
common core of determinations. As indicated at proposal, the EPA is
taking a consolidated, single final action

on the proposed SIP disapprovals.\8\ Included in this document is final
action on 2015 ozone NAAQS interstate transport SIPs addressing CAA
section 110(a)(2)(D)(i)(I) for Alabama, Arkansas, California, Illinois,
Indiana, Kentucky, Louisiana, Maryland, Michigan, Minnesota,
Mississippi, Missouri, Nevada, New Jersey, New York, Ohio, Oklahoma,
Texas, Utah, West Virginia, and Wisconsin. The 2015 ozone NAAQS
interstate transport SIP submissions addressing CAA section
110(a)(2)(D)(i)(I) for Tennessee and Wyoming will be addressed in a
separate action.
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    \5\ 87 FR 9545 (February 22, 2022) (Alabama, Mississippi,
Tennessee); 87 FR 9798 (February 22, 2022) (Arkansas, Louisiana,
Oklahoma, Texas); 87 FR 9838 (February 22, 2022) (Illinois, Indiana,
Michigan, Minnesota, Ohio, Wisconsin); 87 FR 9498 (February 22,
2022) (Kentucky); 87 FR 9484 (February 22, 2022) (New Jersey, New
York); 87 FR 9463 (February 22, 2022) (Maryland); 87 FR 9533
(February 22, 2022) (Missouri); 87 FR 9516 (February 22, 2022) (West
Virginia).
    \6\ 87 FR 31443 (May 24, 2022) (California); 87 FR 31485 (May
24, 2022) (Nevada); 87 FR 31470 (May 24, 2022) (Utah); 87 FR 31495
(May 24, 2022) (Wyoming).
    \7\ 87 FR 64412 (October 25, 2022) (Alabama). Alabama withdrew
its original good neighbor SIP submission on April 21, 2022. Id. at
64419.
    \8\ In its proposals, the EPA stated ``The EPA may take a
consolidated, single final action on all the proposed SIP
disapproval actions with respect to obligations under CAA section
110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. Should EPA take a
single final action on all such disapprovals, this action would be
nationally applicable, and the 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.'' E.g.,
87 FR 9463, 9475 n.51.
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B. Description of the EPA's 4-Step Interstate Transport Framework

    The EPA used a 4-step interstate transport framework (or 4-step
framework) to evaluate each state's implementation plan submission
addressing the interstate transport provision for the 2015 ozone NAAQS.
The EPA has addressed the interstate transport requirements of CAA
section 110(a)(2)(D)(i)(I) with respect to prior NAAQS in several
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,\9\ the Cross-State Air Pollution Rule Update (CSAPR Update)
\10\ and the Revised CSAPR Update, both of which addressed the 2008
ozone NAAQS.\11\
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    \9\ See Federal Implementation Plans: Interstate Transport of
Fine Particulate Matter and Ozone and Correction of SIP Approvals,
76 FR 48208 (August 8, 2011).
    \10\ Cross-State Air Pollution Rule Update for the 2008 Ozone
NAAQS, 81 FR 74504 (October 26, 2016).
    \11\ In 2019, the United States Court of Appeals for the
District of Columbia Circuit (D.C. Circuit) remanded 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) (Wisconsin). The Revised CSAPR Update for
the 2008 Ozone NAAQS, 86 FR 23054 (April 30, 2021), responded to the
remand of 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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    Shaped through the years by input from state air agencies \12\ and
other stakeholders on EPA's prior interstate transport rulemakings and
SIP actions,\13\ as well as a number of court decisions, the EPA has
developed and used 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 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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    \12\ See 63 FR 57356, 57361 (October 27, 1998).
    \13\ 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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    The general steps of this framework allow for some methodological
variation, and this can be seen in the evolution of the EPA's
analytical process across its prior rulemakings. This also means states
have some flexibility in developing analytical methods within this
framework (and may also attempt to justify an alternative framework
altogether). The four steps of the framework simply provide a
reasonable organization to the analysis of the complex air quality
challenge of interstate ozone transport. As discussed further
throughout this document, the EPA has organized its evaluation of the
states' SIP submissions around this analytical framework (including the
specific methodologies within each step as evolved over the course of
the CSAPR rulemakings since 2011), but where states presented
alternative approaches either to the EPA's methodological approaches
within the framework, or organized their analysis in some manner that
differed from it entirely, we have evaluated those analyses on their
merits or, in some cases, identified why even if those approaches were
acceptable, the state still does not have an approvable SIP submission
as a whole.

C. Background on the EPA's Ozone Transport Modeling Information

    In general, the 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 at
Step 1. To quantify the contribution of emissions from specific upwind
states on 2023 ozone design values for the identified downwind
nonattainment and maintenance receptors at Step 2, the EPA performed
nationwide, state-level ozone source apportionment modeling for 2023.
The source apportionment modeling projected contributions to ozone at
receptors from precursor emissions of anthropogenic nitrogen oxides
(NOX) and volatile organic compounds (VOCs) in individual
upwind states.
    The EPA has released several documents containing projected design
values, contributions, and information relevant to air agencies for
evaluating interstate transport with respect to the 2015 ozone NAAQS.
First, on January 6, 2017, the 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.\14\ In the NODA, the 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 ozone NAAQS.\15\ On October 27, 2017, the 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 was intended to provide information to assist
states' efforts to develop SIP submissions to address interstate
transport obligations for the 2008 ozone NAAQS.\16\ On March 27, 2018,
the 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 ozone NAAQS at
Step 1 of the 4-step interstate transport framework.\17\ 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 ozone NAAQS under Step 2 of
the 4-step interstate transport framework.\18\ The EPA subsequently
issued two more memoranda in August and October 2018, providing
additional information to states developing interstate transport SIP
submissions for the 2015 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.\19\
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    \14\ 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).
    \15\ See 82 FR 1733, 1735 (January 6, 2017).
    \16\ 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.
    \17\ 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.
    \18\ 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.''
March 2018 memorandum at 2.
    \19\ 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''); 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 or
at https://www.epa.gov/airmarkets/memo-and-supplemental-information-regarding-interstate-transport-sips-2015-ozone-naaqs.
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    Following the release of the modeling data shared in the March 2018
memorandum, the 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.\20\ This collaborative project was a multi-year
joint effort by the EPA, MJOs, and states to develop a new, more recent
emissions platform for use by the EPA and states in regulatory modeling
as an improvement over the dated, 2011-based platform that the EPA had
used to project ozone design values and contribution data provided in
the 2017 and 2018 memoranda. The 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, the EPA released and accepted public comment on 2023 modeling
that used the 2016v1 emissions platform.\21\ Although the Revised CSAPR
Update addressed transport for the 2008 ozone NAAQS, the projected
design values and contributions from the 2016v1 platform were also
useful for identifying downwind ozone problems and linkages with
respect to the 2015 ozone NAAQS.\22\
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    \20\ The results of this modeling, as well as the underlying
modeling files, are included in Docket No. EPA-HQ-OAR-2021-0663.
    \21\ See 85 FR 68964, 68981 (October 30, 2020).
    \22\ 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 final Revised CSAPR Update, the EPA made further
updates to the 2016-based emissions platform to include updated onroad
mobile emissions from Version 3 of the EPA's Motor Vehicle Emission
Simulator (MOVES) model (MOVES3) \23\ 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 inventory improvements. The construct of the
updated emissions platform, 2016v2, is described in the ``Technical
Support Document (TSD): Preparation of Emissions Inventories for the
2016v2 North American Emissions Modeling Platform,'' hereafter known as
the 2016v2 Emissions Modeling TSD, and is included in Docket No. EPA-
HQ-OAR-2021-0663. The EPA performed air quality modeling using the
2016v2 emissions to provide projections of ozone design values and
contributions in 2023 that reflect the effects on air quality of the
2016v2 emissions platform. The results of the 2016v2 modeling were used
by the EPA as part of the Agency's evaluation of state SIP submissions
with respect to Steps 1 and 2 of the 4-step interstate transport
framework at the proposal stage of this action. By using the 2016v2
modeling results, the EPA used the most current and technically
appropriate information for the proposed rulemakings that were issued
earlier in 2022.
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    \23\ 86 FR 1106. 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.
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    The EPA invited and received comments on the 2016v2 emissions
inventories and modeling that were used to support proposals related to
2015 ozone NAAQS interstate transport. (The EPA had earlier published
the emissions inventories on its website in September of 2021 and
invited initial feedback from states and other interested
stakeholders.\24\) In response to these comments, the EPA made a number
of updates to the 2016v2 inventories and model design to construct a
2016v3 emissions platform which was used to update the air quality
modeling. The EPA made additional updates to its modeling in response
to comments as well. The EPA is now using this updated modeling to
inform its final action on these SIP submissions. Details on the air
quality modeling and the methods for projecting design values and
determining contributions in 2023 are described in Section III and in
the TSD titled ``Air Quality Modeling TSD for the 2015 8-hour ozone
NAAQS Transport SIP Final Actions'', hereafter known as the Final
Action AQM TSD.25 26 Additional details related to the
updated 2016v3 emissions platform are located in the TSD titled
``Preparation of Emissions Inventories for the 2016v3 North American
Emissions Modeling Platform,'' hereafter known as the 2016v3 Emissions
Modeling TSD, included in Docket ID No. EPA-HQ-OAR-2021-0663.\27\
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    \24\ https://www.epa.gov/air-emissions-modeling/2016v2-platform.
    \25\ See Final Action AQM TSD in Docket ID No. EPA-HQ-OAR-2021-
0663
    \26\ References to section numbers in roman numeral refer to
sections of this preamble unless otherwise specified, and references
to section numbers in numeric form refer to the Response to Comments
document for this final action included in the docket.
    \27\ See 2016v3 Emissions Modeling TSD in Docket ID No. EPA-HQ-
OAR-2021-0663.
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D. The EPA's Approach To Evaluating Interstate Transport SIPs for the
2015 Ozone NAAQS

    The EPA is applying a consistent set of policy judgments across all
states for purposes of evaluating interstate transport obligations and
the approvability of interstate transport SIP submissions for the 2015
ozone NAAQS under CAA section 110(a)(2)(D)(i)(I). These policy
judgments conform with relevant case law and past agency practice as
reflected in CSAPR and related rulemakings. Employing a nationally
consistent 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
to ensure an ``efficient and equitable'' approach. See EPA v. EME Homer
City Generation, LP, 572 U.S. 489, 519 (2014) (EME Homer City). Some
comments on EPA's proposed SIP disapprovals claim the EPA is imposing
non-statutory requirements onto SIPs or that the EPA must allow states
to take inconsistent approaches to implementing good neighbor
requirements. Both views are incorrect; the EPA's use of its
longstanding framework to evaluate these SIP submissions reflects a
reasonable and consistent approach to implementing the requirements of
CAA section 110(a)(2)(D)(i)(I), while remaining open to alternative
approaches states may present. These comments are further addressed in
Section V and the Response to Comment (RTC) document contained in the
docket for this action, Docket ID No. EPA-HQ-OAR-2021-0663.
    In the March, August, and October 2018 memoranda, the EPA
recognized that states may be able to establish alternative approaches
to addressing their interstate transport obligations for the 2015 ozone
NAAQS that vary from a nationally uniform framework. The 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 submission.\28\ In general,
the 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 CAA
obligations and relevant case law. Where states submitted SIP
submissions that rely on any such potential concepts as the EPA or
others may have identified or suggested in the past, the EPA evaluated
whether the state adequately justified the technical and legal basis
for doing so. For example, the EPA has considered the arguments put
forward by Alabama, Missouri, Ohio, Oklahoma, Texas, and Utah related
to alternative methods of identifying receptors.\29\ The EPA also has
considered the arguments attempting to justify an alternative
contribution threshold at Step 2 pursuant to the August 2018 memorandum
made by Alabama, Arkansas, Illinois, Indiana, Kentucky, Louisiana,
Michigan, Mississippi, Missouri, Oklahoma, and Utah,\30\ as well as
criticisms of the 1 percent of the NAAQS contribution threshold made by
Nevada and Ohio.\31\ These topics are further addressed in Section V.B
as well as the RTC document.
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    \28\ March 2018 memorandum at 3 (``EPA also notes that, in
developing their own rules, states have flexibility to follow the
familiar four-step transport framework (using EPA's analytical
approach or somewhat different analytical approaches within this
steps) or alternative framework, so long as their chosen approach
has adequate technical justification and is consistent with the
requirements of the CAA.''); August 2018 memorandum at 1 (``The EPA
and air agencies should consider whether the recommendations in this
guidance are appropriate for each situation.''); October 2018
memorandum at 1 (``Following the recommendations in this guidance
does not ensure that EPA will approve a SIP revision in all
instances where the recommendations are followed, as the guidance
may not apply to the facts and circumstances underlying a particular
SIP.'').
    \29\ 87 FR 64421-64422 (Alabama); 87 FR 9540-9541 (Missouri); 87
FR 9869-9870 (Ohio); 87 FR 9820-9822 (Oklahoma); 87 FR 9826-9829
(Texas); and 87 FR 31480-31481 (Utah).
    \30\ 87 FR 64423-64424 (Alabama); 87 FR 9806-9807 (Arkansas); 87
FR 9852-9853 (Illinois); 87 FR 9855-9856 (Indiana); 87 FR 9509-9510
(Kentucky); 87 FR 9815-9816 (Louisiana); 87 FR 9861-9862 (Michigan);
87 FR 9557 (Mississippi); 87 FR 9541-9544 (Missouri); 87 FR 9819
(Oklahoma); 87 FR 31478 (Utah).
    \31\ 87 FR 31492 (Nevada); 87 FR 9871 (Ohio).
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    The 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
interstate transport obligations for the 2015 ozone NAAQS. Attachment A
to the March 2018 memorandum identified a ``Preliminary List of
Potential Flexibilities'' that could potentially inform SIP
development. However, the EPA made clear in both the March 2018
memorandum \32\ and in Attachment A that the list of ideas was not
endorsed by the Agency but rather ``comments provided in various
forums'' on which the EPA sought ``feedback from interested
stakeholders.'' \33\ 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 are we specifically
recommending that states use these approaches.'' \34\ 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 one or
more of these ideas in support of their SIP submissions, the EPA
reviewed their technical and legal justifications for doing so.\35\
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    \32\ ``In addition, the memorandum is accompanied by Attachment
A, which provides a preliminary list of potential flexibilities in
analytical approaches for developing a good neighbor SIP that may
warrant further discussion between EPA and states.'' March 2018
memorandum at 1.
    \33\ March 2018 memorandum, Attachment A at A-1.
    \34\ Id.
    \35\ E.g., 87 FR 64423-64425 (Alabama); 87 FR 31453-31454
(California); 87 FR 9852-9854 (Illinois); 87 FR 9859-9860 (Indiana);
87 FR 9508, 9515 (Kentucky); 87 FR 9861-9862 (Michigan); 87 FR 9869-
9870 (Ohio); 87 FR 9798, 9818-9820 (Oklahoma); 87 FR 31477-31481
(Utah); 87 FR 9526-9527 (West Virginia).
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    The remainder of this section describes the EPA's analytical
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 the 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).\36\ 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, 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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    \36\ For attainment dates for the 2015 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 the 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 the EPA's denial of a petition under CAA
section 126(b) Maryland v.

EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020) (Maryland). 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). The 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 applicable
attainment date,\37\ which at the time of EPA's proposed and final
actions on the SIPs addressed in this action is the Moderate area
attainment date under CAA section 181 for ozone nonattainment. The
Moderate area attainment date for the 2015 ozone NAAQS is August 3,
2024.\38\ Thus, 2023 is now the appropriate year for analysis of
interstate transport obligations for the 2015 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 ozone NAAQS.
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    \37\ The EPA notes that the court in Maryland did not have
occasion to evaluate circumstances in which the 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.
    \38\ 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).
---------------------------------------------------------------------------

    The EPA recognizes that the attainment date for nonattainment areas
classified as Marginal for the 2015 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 the EPA's modeling of the year 2023, and no state provided an
alternative analysis using a 2021 analytic year (or the prior 2020
ozone season). However, the EPA must act on SIP submissions using the
information available at the time it takes such action, and it is now
past 2021. In this circumstance, the 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 (rejecting Delaware's argument that the EPA should have used an
analytic year of 2011 instead of 2017). Consequently, in this proposal
the 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
ozone NAAQS.
2. Step 1 of the 4-Step Interstate Transport Framework
    In Step 1, the EPA identifies monitoring sites that are projected
to have problems attaining and/or maintaining the NAAQS in the 2023
analytic year. Where the 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 the EPA's 4-step
interstate transport framework. For sites that are identified as a
nonattainment or maintenance receptor in 2023, the EPA proceeds to the
next step of the 4-step interstate transport framework by identifying
which upwind states contribute to those receptors above the
contribution threshold.
    The EPA's approach to identifying ozone nonattainment and
maintenance receptors in this action 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.\39\
---------------------------------------------------------------------------

    \39\ See North Carolina, 531 F.3d at 910-11 (holding that the
EPA must give ``independent significance'' to each prong of CAA
section 110(a)(2)(D)(i)(I)).
---------------------------------------------------------------------------

    The 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 the EPA defined
nonattainment receptors as those areas that both currently measure
nonattainment and that the EPA projects will be in nonattainment in the
analytic year (i.e., 2023).\40\
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    \40\ 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 25241,
25249 (January 14, 2005); see also North Carolina, 531 F.3d at 913-
14 (affirming as reasonable the EPA's approach to defining
nonattainment in CAIR).
---------------------------------------------------------------------------

    In addition, the 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) (EME Homer City II).\41\ Specifically, the 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. The 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). The EPA also recognizes
that previously experienced meteorological conditions (e.g., dominant
wind direction, temperatures, air mass patterns) promoting ozone
formation that led to maximum concentrations in the measured data may
reoccur in the future. 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.
---------------------------------------------------------------------------

    \41\ 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, the 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
earlier, the 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.
    As discussed further in Section III.B., in response to comments,
the Agency has also taken a closer look at measured ozone levels at
monitoring sites in 2021 and 2022 for the purposes of informing the
identification of additional receptors in 2023. We find there is a
basis to consider certain sites with elevated ozone levels that are not
otherwise identified as receptors to be an additional type of
maintenance-only receptor given the likelihood that ozone levels above
the NAAQS could persist at those locations through at least 2023. We
refer to these as violating-monitor maintenance-only receptors
(``violating monitors''). For purposes of this action, we use this
information only in a confirmatory way for states that are otherwise
found to be linked using the modeling-based methodology. The EPA
intends to take separate action to address states that are linked only
to one or more violating-monitor receptors.
3. Step 2 of the 4-Step Interstate Transport Framework
    In Step 2, the 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 ozone NAAQS), the upwind state is not ``linked''
to a downwind air quality problem, and the EPA, therefore, concludes
that the state does not contribute significantly 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 pursuant to the
requirements of CAA section 110(a)(2)(D)(i)(I).
    In this final action, the EPA relies 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 ozone NAAQS (i.e., 0.70
ppb) at downwind receptors. This is consistent with the Step 2 approach
that the EPA applied in CSAPR for the 1997 ozone NAAQS, which has
subsequently been applied in the CSAPR Update and Revised CSAPR Update
when evaluating interstate transport obligations for the 2008 ozone
NAAQS, and in the EPA's proposals for this action. The EPA continues to
find 1 percent to be an appropriate threshold. For ozone, as the EPA
found in the CAIR, CSAPR, and CSAPR Update, a portion of the
nonattainment problems from anthropogenic sources in the U.S. result
from the combined impact of relatively small contributions, typically
from multiple upwind states and, in some cases, substantially larger
contributions from a subset of particular upwind states, along with
contributions from in-state sources. The EPA's analysis shows that much
of the ozone transport problem being analyzed in this action is still
the result of the collective impacts of contributions from 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 the EPA (and states) to apply a consistent framework to evaluate
interstate emissions transport under the interstate transport provision
from one NAAQS to the next. See 81 FR 74518; see also 86 FR 23085
(reviewing and explaining rationale from CSAPR, 76 FR 48237-38, for
selection of 1 percent threshold).
    The EPA's August 2018 memorandum recognizes 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 in their SIP submission, and where that
state determined that it was not linked at Step 2 using the alternative
threshold, the EPA evaluated 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. The states covered by
this action that rely on a contribution threshold other than 1 percent
of the NAAQS in their 2015 ozone NAAQS good neighbor SIP submission are
Alabama, Arkansas, Illinois, Indiana, Kentucky, Louisiana, Michigan,
Mississippi, Missouri, Oklahoma, and Utah. Ohio also criticized the 1
percent of the NAAQS threshold, though it acknowledged it was linked
above either a 1 percent of the NAAQS or 1 ppb contribution threshold.
Nevada also criticized the 1 percent of the NAAQS contribution
threshold, but ultimately relied on it to support its submission.
    In the proposals for this action, the EPA evaluated each states'
support for the use of an alternative threshold at Step 2 (e.g., 1
ppb), and additionally shared its experience since the issuance of the
August 2018 memorandum regarding use of alternative thresholds at Step
2. The EPA solicited comment on the subject as it considered the
appropriateness of rescinding the memorandum.\42\ The EPA received
numerous comments related to both the EPA's evaluation of SIP
submissions relying on an alternative threshold, and the EPA's
experience with alternative thresholds. The EPA is not, at this time
rescinding the August 2018 memorandum; however, for purposes of
evaluating contribution thresholds for the 2015 ozone NAAQS, the EPA
continues to find the use of an alternative threshold problematic for
the reasons stated at proposal. Regardless of the EPA's position on the
August 2018 memorandum, the EPA continues to find that the arguments
put forth in the SIP submissions of by Alabama, Arkansas, Illinois,
Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri,
Oklahoma, and Utah, as well as arguments in comments received on these
actions, to be inadequate. See Section V.B.7 and the RTC Document for
additional detail.
---------------------------------------------------------------------------

    \42\ See, e.g., 87 FR 9551.
---------------------------------------------------------------------------

4. Step 3 of the 4-Step Interstate Transport Framework
    Consistent with the EPA's longstanding approach to eliminating
significant contribution and interference with maintenance, at Step 3,
a multifactor assessment of potential emissions controls is conducted
for states linked at Steps 1 and 2. The 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 the EPA's or state-provided
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 SIP approval. In general, the emissions-
reducing effects of all existing emissions control requirements are
already reflected in the future year projected 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) despite these existing
controls, but that state believes it has no outstanding good neighbor
obligations, the EPA expects the state to provide sufficient
justification to support a conclusion by the EPA that the state has
adequate provisions prohibiting ``any source or other type of emissions
activity within the State from emitting any air pollutant in amounts
which will'' ``contribute significantly to nonattainment in, or
interfere with maintenance by,'' any other State with respect to the
NAAQS. See CAA section 110(a)(2)(D)(i)(I). While the EPA has not
prescribed a particular method for this assessment, as many commenters
note, the 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.\43\ The EPA responds to comment
on issues related to Step 3 in Section V.B.8. and in the RTC document.
---------------------------------------------------------------------------

    \43\ Because no state included new enforceable emissions control
measures in the submissions under review here, we focus our analysis
on whether states justified that no additional controls were
required. As examples of general approaches for how a Step 3
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, the 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 the 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.\44\ 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 SIP 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).
---------------------------------------------------------------------------

    \44\ The EPA notes that any controls included in an approved SIP
are federally-enforceable.
---------------------------------------------------------------------------

III. The EPA's Updated Air Quality and Contribution Analysis

    As noted in Section II, the EPA relied in part on its 2016v2
emissions platform-based air quality modeling to support its proposed
interstate transport actions taken in 2022. Following receipt of
comments, the EPA updated this modeling, incorporating new information
received to create the 2016v3 emissions inventory and making additional
updates to improve model performance. Using the 2016v3 emissions
inventory, the EPA evaluated modeling projections for air quality
monitoring sites and considered current ozone monitoring data at these
sites to identify receptors that are anticipated to have problems
attaining or maintaining the 2015 ozone NAAQS.
    This section presents a summary of the methodology and results of
the 2016v3 modeling of 2023, along with the application of the EPA's
Step 1 and Step 2 methodology for identifying receptors and upwind
states that contribute to those receptors. We also explain that current
measured ozone levels based on data for 2021 and preliminary data for
2022 at other monitoring sites (i.e., monitoring sites that are not
projected to be receptors in 2023 based on air quality modeling)
confirm the likely continuation of elevated ozone levels in 2023 at
these locations and confirm that nearly all upwind states in this
action are also linked above 1 percent of the NAAQS to one or more of
these monitors.
    While all of this information compiled by the EPA (both the
modeling and monitoring data) plays a critical role in the basis for
this final action, the EPA has also thoroughly evaluated the modeling
information and other analyses and arguments presented by the upwind
states in their SIP submittals. Our evaluation of the states' analyses
was generally set forth in the proposals, and the EPA in this final
action has responded to comments on our evaluation of the various
information and arguments made by states. The EPA's final decision to
disapprove these states' SIP submittals is based on our evaluation of
the entire record, recognizing that states possess the authority in the
first instance to propose how they would address their significant
contribution to air quality problems in other states. Nonetheless, as
explained in the proposals, and in this document and supporting
materials in the docket, we conclude that no state included in this
action effectively demonstrated that it will not be linked to at least
one air quality receptor in 2023, and none of these states' various
arguments for alternative approaches ultimately present a satisfactory
basis for the EPA to approve these states' SIP submissions.

A. Description of Air Quality Modeling for the Final Action

    In this section, the Agency describes the air quality modeling
performed consistent with Steps 1 and 2 of the 4-step interstate
transport framework to (1) Identify locations where it expects
nonattainment or maintenance problems with respect to the 2015 ozone
NAAQS for the 2023 analytic year, and (2) quantify the contributions
from anthropogenic emissions from upwind states to downwind ozone
concentrations at monitoring sites projected to be in nonattainment or
have maintenance problems for the 2015 ozone NAAQS in 2023. This
section includes information on the air quality modeling platform used
in support of the final SIP disapproval action with a focus on the base
year and future base case emissions inventories. The EPA also provides
the projection of 2023 ozone concentrations and the interstate
contributions for 8-hour ozone. The Final Action AQM TSD in Docket ID
No. EPA-HQ-OAR-2021-0663 contains more detailed information on the air
quality modeling aspects supporting our final action on these SIP
submissions.
1. Public Review of Air Quality Modeling Information for the Proposed
Action
    The EPA provided several opportunities to comment on the emissions
modeling platform and air quality modeling results that were used for
the proposed SIP submission actions. On September 20, 2021, the EPA
publicly released via our web page updated emissions inventories
(2016v2) and requested comment from states and

MJOs on these data.\45\ In January 2022, the EPA released air quality
modeling results including projected ozone design values and
contributions from 2023 based on the 2016v2 emissions. At that time the
EPA indicated its intent to use these data to support upcoming
transport rulemakings. Then, on February 22, 2022, the EPA published
proposed disapprovals for 19 interstate transport SIP submissions using
the modeling data released in January 2022 and the emissions
inventories shared in September 2021.\46\ The EPA provided a 60-day
comment period on these proposals. On May 24, 2022, the EPA proposed
disapprovals for an additional four states' interstate transport SIP
submissions using the same modeling platform, and provided a 62-day
comment period.\47\ The EPA provided a 30-day comment period beginning
on October 25, 2022, on the proposed disapproval of Alabama's June 21,
2022, SIP submission, which relied on the same modeling platform as the
other noted proposals.\48\ In addition to its proposed disapprovals,
the EPA also proposed approval of Iowa's, Arizona's, and Colorado's SIP
submissions using the 2016v2 modeling and provided 30-day comment
periods. 87 FR 9477 (February 22, 2022) (Iowa); 87 FR 37776 (June 24,
2022) (Arizona); and 87 FR 27050 (May 6, 2022) (Colorado).
---------------------------------------------------------------------------

    \45\ https://www.epa.gov/air-emissions-modeling/2016v2-platform.
    \46\ These proposals are listed in footnote 5 of this action.
    \47\ The EPA also relied on this same modeling data to support
proposed Federal Implementation Plans (FIPs) resolving interstate
transport obligations for 27 states for the 2015 ozone NAAQS. 87 FR
20036 (April 6, 2022). The EPA allowed 60 days to receive comments
on the proposed FIP rule, including acceptance of comment on the
2016v2 emissions inventory-based modeling platform. The EPA then
allowed for an additional 15 days via an extension of the comment
period. 87 FR 29108 (May 12, 2022).
    \48\ 87 FR 64412, 64413.
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2. Overview of Air Quality Modeling Platform
    The EPA used version 3 of the 2016-based modeling platform (i.e.,
2016v3) for the air quality modeling for this final SIP disapproval
action. This modeling platform includes 2016 base year emissions from
anthropogenic and natural sources and future year projected
anthropogenic emissions for 2023.\49\ The emissions data contained in
the 2016v3 platform represent an update to the 2016 version 2
inventories used for the proposal modeling.
---------------------------------------------------------------------------

    \49\ The 2016v3 platform also includes projected emissions for
2026. However, the 2026 data are not applicable and were not used in
this final action.
---------------------------------------------------------------------------

    The air quality modeling for this final disapproval action was
performed for a modeling region (i.e., modeling domain) that covers the
contiguous 48 states using a horizontal resolution of 12 x 12 km. The
EPA used the CAMx version 7.10 for air quality modeling which is the
same model that the EPA used for the proposed rule air quality
modeling.\50\ Additional information on the 2016-based air quality
modeling platform can be found in the Final Action AQM TSD.
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    \50\ Ramboll Environment and Health, January 2021, https://www.camx.com.
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    Comments: Commenters noted that the 2016 base year summer maximum
daily average 8-hour (MDA8) ozone predictions from the proposal
modeling were biased low compared to the corresponding measured
concentrations in certain locations. In this regard, commenters said
that model performance statistics for a number of monitoring sites,
particularly those in portions of the West and in the area around Lake
Michigan, were outside the range of published performance criteria for
normalized mean bias (NMB) and normalized mean error (NME) of less than
plus or minus 15 percent and less than 25 percent, respectively.\51\
Comments say the EPA must investigate the factors contributing to low
bias and make necessary corrections to improve model performance in the
modeling supporting final SIP actions. Some commenters said that the
EPA should include NOX emissions from lightning strikes and
assess the treatment of other background sources of ozone to improve
model performance for the final action. Additional information on the
comments on model performance can be found in the RTC document for this
final SIP disapproval action.
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    \51\ Christopher Emery, Zhen Liu, Armistead G. Russell, M. Talat
Odman, Greg Yarwood & Naresh Kumar (2017) Recommendations on
statistics and benchmarks to assess photochemical model performance,
Journal of the Air & Waste Management Association, 67:5, 582-598,
DOI: 10.1080/10962247.1265027.
---------------------------------------------------------------------------

    EPA Response: In response to these comments the EPA examined the
temporal and spatial characteristics of model under prediction to
investigate the possible causes of under prediction of MDA8 ozone
concentrations in different regions of the U.S. in the proposal
modeling. The EPA's analysis indicates that the under prediction was
most extensive during May and June with less bias during July and
August in most regions of the U.S. For example, in the Upper Midwest
region model under prediction was larger in May and June compared to
July through September. Specifically, the normalized mean bias for days
with measured concentrations greater than or equal to 60 ppb improved
from a 21.4 percent under prediction for May and June to a 12.6 percent
under prediction in the period July through September. As described in
the AQM TSD, the seasonal pattern in bias in the Upper Midwest region
improves somewhat gradually with time from the middle of May to the
latter part of June. In view of the seasonal pattern in bias in the
Upper Midwest and in other regions of the U.S., the EPA focused its
investigation of model performance on model inputs that, by their
nature, have the largest temporal variation within the ozone season.
These inputs include emissions from biogenic sources and lightning
NOX, and contributions from transport of international
anthropogenic emissions and natural sources into the U.S. Both biogenic
and lightning NOX emissions in the U.S. dramatically
increase from spring to summer.52 53 In contrast, ozone
transported into the U.S. from international anthropogenic and natural
sources peaks during the period March through June, with lower
contributions during July through September.54 55 To
investigate the impacts of the sources, the EPA conducted sensitivity
model runs which focused on the effects on model performance of adding
NOX emissions from lightning strikes, using updated biogenic
emissions, and using an alternative approach (described in more detail
later in this section) for quantifying transport of ozone and precursor
pollutants into the U.S. from international anthropogenic and natural
sources. In the air quality modeling for proposal, the amount of
transport from international sources was based on a simulation of the
hemispheric version of the Community Multi-scale Air Quality

Model (H-CMAQ) \56\ for 2016. The outputs from this hemispheric
modeling were then used to provide boundary conditions for the national
scale air quality modeling at proposal.\57\ Overall, H-CMAQ tends to
under predict daytime ozone concentrations at rural and remote
monitoring sites across the U.S. during the spring of 2016 whereas the
predictions from the GEOS-Chem global model \58\ were generally less
biased.\59\ During the summer of 2016 both models showed varying
degrees of over prediction with GEOS-Chem showing somewhat greater over
prediction, compared to H-CMAQ. In view of those results, the EPA
examined the impacts of using GEOS-Chem as an alternative to H-CMAQ for
providing boundary conditions for the modeling supporting this final
action.
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    \52\ Guenther, A.B., 1997. Seasonal and spatial variations in
natural volatile organic compound emissions. Ecol. Appl. 7, 34-45.
http://dx.doi.org/10.1890/1051-0761(1997) 007[0034:SASVIN]2.0.CO;2.
Guenther, A., Hewitt, C.N., Erickson, D., Fall, R.
    \53\ Kang D, Mathur R, Pouliot GA, Gilliam RC, Wong DC.
Significant ground-level ozone attributed to lightning-induced
nitrogen oxides during summertime over the Mountain West States. NPJ
Clim Atmos Sci. 2020 Jan 30;3:6. doi: 10.1038/s41612-020-0108-2.
PMID: 32181370; PMCID: PMC7075249.
    \54\ Jaffe DA, Cooper OR, Fiore AM, Henderson BH, Tonnesen GS,
Russell AG, Henze DK, Langford AO, Lin M, Moore T. Scientific
assessment of background ozone over the U.S.: Implications for air
quality management. Elementa (Wash DC). 2018;6(1):56. doi: 10.1525/
elementa.309. PMID: 30364819; PMCID: PMC6198683.
    \55\ Henderson, B.H., P. Dolwick, C. Jang, A., Eyth, J.
Vukovich, R. Mathur, C. Hogrefe, N. Possiel, G. Pouliot, B. Timin,
K.W. Appel, 2019. Global Sources of North American Ozone. Presented
at the 18th Annual Conference of the UNC Institute for the
Environment Community Modeling and Analysis System (CMAS) Center,
October 21-23, 2019.
    \56\ Mathur, R., Gilliam, R., Bullock, O.R., Roselle, S., Pleim,
J., Wong, D., Binkowski, F., and 1 Streets, D.: Extending the
applicability of the community multiscale air quality model to 2
hemispheric scales: motivation, challenges, and progress. In: Steyn
DG, Trini S (eds) Air 3 pollution modeling and its applications,
XXI. Springer, Dordrecht, pp 175-179, 2012.
    \57\ Boundary conditions are the concentrations of pollutants
along the north, east, south, and west boundaries of the air quality
modeling domain. Boundary conditions vary in space and time and are
typically obtained from predictions of global or hemispheric models.
Information on how boundary conditions were developed for modeling
supporting EPA's final SIP actions can be found in the AQM TSD.
    \58\ I. Bey, D.J. Jacob, R.M. Yantosca, J.A. Logan, B.D. Field,
A.M. Fiore, Q. Li, H.Y. Liu, L.J. Mickley, M.G. Schultz. Global
modeling of tropospheric chemistry with assimilated meteorology:
model description and evaluation. J. Geophys. Res. Atmos., 106
(2001), pp. 23073-23095, 10.1029/2001jd000807.
    \59\ Henderson, B.H., P. Dolwick, C. Jang, A., Eyth, J.
Vukovich, R. Mathur, C. Hogrefe, G. Pouliot, N. Possiel, B. Timin,
K.W. Appel, 2022. Meteorological and Emission Sensitivity of
Hemispheric Ozone and PM2.5. Presented at the 21st Annual
Conference of the UNC Institute for the Environment Community
Modeling and Analysis System (CMAS) Center, October 17-19, 2022.
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    For the lightning NOX, biogenics, and GEOS-Chem
sensitivity runs, the EPA reran the proposal modeling using each of
these inputs, individually. Results from these sensitivity runs
indicate that each of the three updates provides an improvement in
model performance. However, by far the greatest improvement in modeling
performance is attributable to the use of GEOS-Chem. In view of these
results the EPA has included lightning NOX emissions,
updated biogenic emissions, and international transport from GEOS-Chem
in the air quality modeling supporting final SIP actions. Details on
the results of the individual sensitivity runs can be found in the AQM
TSD. For the air quality modeling supporting final SIP actions, model
performance based on days in 2016 with measured MDA8 ozone greater than
or equal to 60 ppb is considerably improved (i.e., less bias and error)
compared to the proposal modeling in nearly all regions. For example,
in the Upper Midwest, which includes monitoring sites along Lake
Michigan, the normalized mean bias improved from a 19 percent under
prediction to a 6.9 percent under prediction and in the Southwest
region, which includes monitoring sites in Denver, Las Cruces, El Paso,
and Salt Lake City, normalized mean bias improved from a 13.6 percent
under prediction to a 4.8 percent under prediction.\60\ In all regions,
the normalized mean bias and normalized mean error statistics for high
ozone days based on the modeling supporting final SIP actions are
within the range of performance criteria benchmarks (i.e., less than
plus or minus 15 percent for normalized mean bias and less than 25
percent for normalized mean error).\61\ Additional information on model
performance information is provided in the AQM TSD. In summary, the EPA
included emissions of lightning NOX, as requested by
commenters, and investigated and addressed concerns about model
performance for the modeling supporting final SIP actions.
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    \60\ A comparison of model performance from the proposal
modeling to the final modeling for individual monitoring sites can
be found in the docket for this final action.
    \61\ Christopher Emery, Zhen Liu, Armistead G. Russell, M. Talat
Odman, Greg Yarwood & Naresh Kumar (2017) Recommendations on
statistics and benchmarks to assess photochemical model performance,
Journal of the Air & Waste Management Association, 67:5, 582-598,
DOI: 10.1080/10962247.1265027.
---------------------------------------------------------------------------

3. Emissions Inventories
    The EPA developed emissions inventories to support air quality
modeling for this final action, including emissions estimates for EGUs,
non-EGU point sources (i.e., stationary point sources), stationary
nonpoint sources, onroad mobile sources, nonroad mobile sources, other
mobile sources, wildfires, prescribed fires, and biogenic emissions
that are not the direct result of human activities. The EPA's air
quality modeling relies on this comprehensive set of emissions
inventories because emissions from multiple source categories are
needed to model ambient air quality and to facilitate comparison of
model outputs with ambient measurements.
    Prior to the modeling of air quality, the emissions inventories
must be processed into a format that is appropriate for the air quality
model to use. To prepare the emissions inventories for air quality
modeling, the EPA processed the emissions inventories using the Sparse
Matrix Operator Kernel Emissions (SMOKE) Modeling System version 4.9 to
produce the gridded, hourly, speciated, model-ready emissions for input
to the air quality model. Additional information on the development of
the emissions inventories and on data sets used during the emissions
modeling process are provided in the document titled ``Technical
Support Document (TSD): Preparation of Emissions Inventories for the
2016v3 North American Emissions Modeling Platform,'' hereafter known as
the ``2016v3 Emissions Modeling TSD.'' This TSD is available in the
docket for this action.\62\
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    \62\ See Preparation of Emissions Inventories for the 2016v3
North American Emissions Modeling Platform TSD, also available at
https://www.epa.gov/air-emissions-modeling/2016v3-platform.
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4. Foundation Emissions Inventory
    The 2016v3 emissions platform is comprised of data from various
sources including data developed using models, methods, and source
datasets that became available in calendar years 2020 through 2022, in
addition to data retained from the Inventory Collaborative 2016 version
1 (2016v1) Emissions Modeling Platform, released in October 2019. The
2016v1 platform was developed through a national collaborative effort
between the EPA and state and local agencies along with MJOs. The
2016v2 platform used to support the proposed action included updated
data, models and methods as compared to 2016v1. The 2016v3 platform
includes updates implemented in response to comments along with other
updates to the 2016v2 platform such as corrections and the
incorporation of updated data sources that became available prior to
the 2016v3 inventories being developed. Several commenters noted that
the 2016v2 platform did not include NOX emissions that
resulted from lightning strikes. To address this, lightning
NOX emissions were computed and included in the 2016v3
platform.
    For this final action, the EPA developed emissions inventories for
the base year of 2016 and the projected year of 2023. The 2023
inventories represent changes in activity data and of predicted
emissions reductions from on-the-books actions, planned emissions
control installations, and promulgated Federal measures that affect
anthropogenic emissions. The 2016 emissions inventories for the U.S.
primarily include data derived from the 2017 National Emissions
Inventory (2017

NEI) \63\ and data specific to the year of 2016. The following sections
provide an overview of the construct of the 2016v3 emissions and
projections. The fire emissions were unchanged between the 2016v2 and
2016v3 emissions platforms. For the 2016v3 platform, the biogenic
emissions were updated to use the latest available versions of the
Biogenic Emissions Inventory System and associated land use data to
help address comments related to a degradation in model performance in
the 2016v2 platform as compared to the 2016v1 platform. Details on the
construction of the inventories are available in the 2016v3 Emissions
Modeling TSD. Details on how the EPA responded to comments related to
emissions inventories are available in the RTC document for this
action.
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    \63\ https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-technical-support-document-tsd.
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    Development of emissions inventories for annual NOX and
sulfur dioxide (SO2) emissions for EGUs in the 2016 base
year inventory are based primarily on data from continuous emissions
monitoring systems (CEMS) and other monitoring systems allowed for use
by qualifying units under 40 CFR part 75, with other EGU pollutants
estimated using emissions factors and annual heat input data reported
to the EPA. For EGUs not reporting under part 75, the EPA used data
submitted to the NEI by state, local, and tribal agencies. The final
action inventories include updates made in response to comments on the
proposed actions including the proposed SIP submission disapprovals and
the proposed FIP. The Air Emissions Reporting Rule, (80 FR 8787;
February 19, 2015), requires that Type A point sources large enough to
meet or exceed specific thresholds for emissions be reported to the EPA
via the NEI every year, while the smaller Type B point sources must
only be reported to EPA every 3 years. In response to comments,
emissions data for EGUs that did not have data submitted to the NEI
specific to the year 2016 were filled in with data from the 2017 NEI.
For more information on the details of how the 2016 EGU emissions were
developed and prepared for air quality modeling, see the 2016v3
Emissions Modeling TSD.
    The EPA projected 2023 baseline EGU emissions using version 6 of
the Integrated Planning Model (IPM) (www.epa.gov/airmarkets/powersector-modeling). IPM, developed by ICF Consulting, is a state-of-
the-art, peer-reviewed, multi-regional, dynamic, deterministic linear
programming model of the contiguous U.S. electric power sector. It
provides forecasts of least cost capacity expansion, electricity
dispatch, and emissions control strategies while meeting energy demand
and environmental, transmission, dispatch, and reliability constraints.
The EPA has used IPM for over two decades to better understand power
sector behavior under future business-as-usual conditions and to
evaluate the economic and emissions impacts of prospective
environmental policies. The model is designed to reflect electricity
markets as accurately as possible. The EPA uses the best available
information from utilities, industry experts, gas and coal market
experts, financial institutions, and government statistics as the basis
for the detailed power sector modeling in IPM. The model documentation
provides additional information on the assumptions discussed here as
well as all other model assumptions and inputs.\64\ The EPA relied on
the same model platform as in the proposals but made substantial
updates to reflect public comments on near-term fossil fuel market
price volatility and updated fleet information reflecting Summer 2022
U.S. Energy Information Agency (EIA) 860 data, unit-level comments, and
additional updates to the National Electric Energy Data System (NEEDS)
inventory.
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    \64\ Detailed information and documentation of the EPA's Base
Case, including all the underlying assumptions, data sources, and
architecture parameters can be found on the EPA's website at:
https://www.epa.gov/airmarkets/power-sector-modeling.
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    The IPM version 6--Updated Summer 2021 Reference Case incorporated
recent updates through the summer 2022 to account for updated Federal
and state environmental regulations (including Renewable Portfolio
Standards (RPS), Clean Energy Standards (CES) and other state
mandates), fleet changes (committed EGU retirements and new builds),
electricity demand, technology cost and performance assumptions from
recent data for renewables adopting from National Renewable Energy Lab
(NREL's) Annual Technology Baseline 2020 and for fossil sources from
the EIA's Annual Energy Outlook (AEO) 2020. Natural gas and coal price
projections reflect data developed in fall 2020 but updated in summer
2022 to capture near-term price volatility and current market
conditions. The inventory of EGUs provided as an input to the model was
the NEEDS fall 2022 version and is available on the EPA's website.\65\
This version of NEEDS reflects announced retirements and under
construction new builds known as of early summer 2022. This projected
base case accounts for the effects of the final Mercury and Air Toxics
Standards rule, CSAPR, the CSAPR Update, the Revised CSAPR Update, New
Source Review enforcement settlements, the final Effluent Limitation
Guidelines (ELG) Rule, the Coal Combustion Residual (CCR) Rule, and
other on-the-books Federal and state rules (including renewable energy
tax credit extensions from the Consolidated Appropriations Act of 2021)
through early 2021 impacting emissions of SO2,
NOX, directly emitted particulate matter, carbon dioxide
(CO2), and power plant operations. It also includes final
actions, up through the Summer 2022, the EPA has taken to implement the
Regional Haze Rule and best available retrofit technology (BART)
requirements. Documentation of IPM version 6 and NEEDS, along with
updates, is in Docket ID No. EPA-HQ-OAR-2021-0663 and available online
at https://www.epa.gov/airmarkets/power-sector-modeling.
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    \65\ Available at https://www.epa.gov/airmarkets/national-electric-energy-data-system-needs-v6.
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    Non-EGU point source emissions are mostly consistent with those in
the proposal modeling except where they were updated in response to
comments. Several commenters mentioned that point source emissions
carried forward from 2014 NEI were not the best estimates of 2017
emissions. Thus, emissions sources in 2016v2 that had been projected
from the 2014 NEI in the proposal were replaced with emissions based on
the 2017 NEI. Point source emissions submitted to the 2016 NEI or to
the 2016v1 platform development process specifically for the year 2016
were retained in 2016v3.
    The 2023 non-EGU point source emissions were grown from 2016 to
2023 using factors based on AEO 2022 and reflect emissions reductions
due to known national and local rules, control programs, plant
closures, consent decrees, and settlements that could be computed as
reductions to specific units by July 2022.
    Aircraft emissions and ground support equipment at airports are
represented as point sources and are based on adjustments to emissions
in the January 2021 version of the 2017 NEI. The EPA developed and
applied factors to adjust the 2017 airport emissions to 2016 and 2023
based on activity growth projected by the Federal Aviation
Administration Terminal Area Forecast 2021,\66\ the latest available
version at the time the factors were developed.
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    \66\ https://www.faa.gov/data_research/aviation/taf/.

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    Emissions at rail yards were represented as point sources. The 2016
rail yard emissions are largely consistent with the 2017 NEI rail yard
emissions. The 2016 and 2023 rail yard emissions were developed through
the 2016v1 Inventory Collaborative process. Class I rail yard emissions
were projected based on the AEO freight rail energy use growth rate
projections for 2023 with the fleet mix assumed to be constant
throughout the period.
    The EPA made multiple updates to point source oil and gas emissions
in response to comments. For the 2016v3 modeling, the point source oil
and gas emissions for 2016 were based on the 2016v2 point inventory
except that most 2014 NEI-based emissions were replaced with 2017 NEI
emissions. Additionally, in response to comments, state-provided
emissions equivalent to those in the 2016v1 platform were used for
Colorado, and some New Mexico emissions were replaced with data
backcast from 2020 to 2016. To develop inventories for 2023 for the
2016v3 platform, the year 2016 oil and gas point source inventories
were first projected to 2021 values based on actual historical
production data, then those 2021 emissions were projected to 2023 using
regional projection factors based on AEO 2022 projections. This was an
update from the 2016v2 approach in which actual data were used only
through the year 2019, because 2021 data were not yet available.
NOX and VOC reductions resulting from co-benefits to New
Source Performance Standards (NSPS) for Stationary Reciprocating
Internal Combustion Engines (RICE) are reflected, along with Natural
Gas Turbine and Process Heater NSPS NOX controls and Oil and
Gas NSPS VOC controls. In some cases, year 2019 point source inventory
data were used instead of the projected future year emissions except
for the Western Regional Air Partnership (WRAP) states of Colorado, New
Mexico, Montana, Wyoming, Utah, North Dakota, and South Dakota. The
WRAP future year inventory \67\ was used in these WRAP states in all
future years except in New Mexico where the WRAP base year emissions
were projected using the EIA historical and AEO forecasted production
data. Estimated impacts from the recent oil and gas rule in the New
Mexico Administrative code 20.2.50 \68\ were also included. Details on
the development of the projected point and nonpoint oil and gas
emissions inventories are available in the 2016v3 Emissions Modeling
TSD in Docket ID No. EPA-HQ-OAR-2021-0663.
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    \67\ http://www.wrapair2.org/pdf/WRAP_OGWG_2028_OTB_RevFinalReport_05March2020.pdf.
    \68\ https://www.env.nm.gov/air-quality/ozone-draft-rule/ and
https://www.srca.nm.gov/parts/title20/20.002.0050.html.
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    Onroad mobile sources include exhaust, evaporative, and brake and
tire wear emissions from vehicles that drive on roads, parked vehicles,
and vehicle refueling. Emissions from vehicles using regular gasoline,
high ethanol gasoline, diesel fuel, and electric vehicles were
represented, along with buses that used compressed natural gas. The EPA
developed the onroad mobile source emissions for states other than
California using the EPA's Motor Vehicle Emissions Simulator (MOVES).
MOVES3 was released in November 2020 and has been followed by some
minor releases that improved the usage of the model but that do not
have substantive impacts on the emissions estimates. For 2016v2, MOVES3
was run using inputs provided by state and local agencies through the
2017 NEI where available, in combination with nationally available data
sets to develop a complete inventory. Onroad emissions were developed
based on emissions factors output from MOVES3 run for the year 2016,
coupled with activity data (e.g., vehicle miles traveled and vehicle
populations) representing the year 2016. The 2016 activity data were
provided by some state and local agencies through the 2016v1 process,
and the remaining activity data were derived from those used to develop
the 2017 NEI. The onroad emissions were computed within SMOKE by
multiplying emissions factors developed using MOVES with the
appropriate activity data. Prior to computing the final action
emissions for 2016, updates to some onroad inputs were made in response
to comments and to implement corrections. Onroad mobile source
emissions for California were consistent with the updated emissions
data provided by the state for the final action.
    The 2023 onroad emissions reflect projected changes to fuel
properties and usage, along with the impact of the rules included in
MOVES3 for each of those years. MOVES emissions factors for the year
2023 were used. A comprehensive list of control programs included for
onroad mobile sources is available in the 2016v3 Emissions Modeling
TSD. Year 2023 activity data for onroad mobile sources were provided by
some state and local agencies, and otherwise were projected to 2023 by
first projecting the 2016 activity to year 2019 based on county level
vehicle miles traveled (VMT) from the Federal Highway Administration.
The VMT were held flat from 2019 to 2021 to account for pandemic
impacts, and then projected from 2021 to 2023 using AEO 2022-based
factors.\69\ Recent updates to inspection and maintenance programs in
North Carolina and Tennessee were reflected in the MOVES inputs for the
modeling supporting this final action. The 2023 onroad mobile emissions
were computed within SMOKE by multiplying the respective emissions
factors developed using MOVES with the year-specific activity data.
Prior to computing the final action emissions for 2023, the EPA made
updates to some onroad inputs in response to comments and to implement
corrections.
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    \69\ VMT data for 2020 were the latest available at the time of
final rule data development but were heavily impacted by the
pandemic and unusable to project to 2023; in addition, it was
determined that chaining factors based on AEO 2020 and AEO2021
obtain the needed factors led to unrealistic artifacts, thus only
AEO 2022 data were used.
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    The commercial marine vessel (CMV) emissions in the 2016 base case
emissions inventory for this action were based on those in the 2017
NEI. Factors were applied to adjust the 2017 NEI emissions backward to
represent emissions for the year 2016. The CMV emissions are consistent
with the emissions for the 2016v1 platform CMV emissions released in
February 2020 although, in response to comments, the EPA implemented an
improved process for spatially allocating CMV emissions along state and
county boundaries for the modeling supporting this final action.
    The EPA developed nonroad mobile source emissions inventories
(other than CMV, locomotive, and aircraft emissions) for 2016 and 2023
from monthly, county, and process level emissions output from MOVES3.
Types of nonroad equipment include recreational vehicles, pleasure
craft, and construction, agricultural, mining, and lawn and garden
equipment.\70\ The nonroad emissions for the final action were
unchanged from those at the proposal. The nonroad mobile emissions
control programs include reductions to locomotives, diesel engines, and
recreational marine engines, along with standards for fuel sulfur
content and evaporative emissions. A comprehensive list of

control programs included for mobile sources is available in the 2016v3
Emissions Modeling TSD.
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    \70\ Line haul locomotives are also considered a type of nonroad
mobile source but the emissions inventories for locomotives were not
developed using MOVES3. Year 2016 and 2023 locomotive emissions were
developed through the 2016v1 process, and the year 2016 emissions
are mostly consistent with those in the 2017 NEI. The projected
locomotive emissions for 2023 were developed by applying factors to
the base year emissions using activity data based on AEO freight
rail energy use growth rate projections along with emissions rates
adjusted to account for recent historical trends.
---------------------------------------------------------------------------

    For stationary nonpoint sources, some emissions in the 2016 base
case emissions inventory come directly from the 2017 NEI, others were
adjusted from the 2017 NEI to represent 2016 levels, and the remaining
emissions including those from oil and gas, fertilizer, and solvents
were computed specifically to represent 2016. Stationary nonpoint
sources include evaporative sources, consumer products, fuel combustion
that is not captured by point sources, agricultural livestock,
agricultural fertilizer, residential wood combustion, fugitive dust,
and oil and gas sources. The emissions sources derived from the 2017
NEI include agricultural livestock, fugitive dust, residential wood
combustion, waste disposal (including composting), bulk gasoline
terminals, and miscellaneous non-industrial sources such as cremation,
hospitals, lamp breakage, and automotive repair shops. A recent method
to compute solvent VOC emissions was used.\71\
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    \71\ https://doi.org/10.5194/acp-21-5079-2021.
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    Where comments were provided about projected control measures or
changes in nonpoint source emissions, those inputs were first reviewed
by the EPA. Those found to be based on reasonable data for affected
emissions sources were incorporated into the projected inventories for
2023 to the extent possible. Where possible, projection factors based
on the AEO used data from AEO 2022, the most recent AEO at the time
available at the time the inventories were developed. Federal
regulations that impact the nonpoint sources were reflected in the
inventories. Adjustments for state fuel sulfur content rules for fuel
oil in the Northeast were included along with solvent controls
applicable within the northeast ozone transport region (OTR) states.
Details are available in the 2016v3 Emissions Modeling TSD.
    Nonpoint oil and gas emissions inventories for many states were
developed based on outputs from the 2017 NEI version of the EPA Oil and
Gas Tool using activity data for year 2016. Production-related
emissions data from the 2017 NEI were used for Oklahoma, 2016v1
emissions were used for Colorado and Texas production-related sources
to respond to comments. Data for production-related nonpoint oil and
gas emissions in the States of Colorado, Montana, New Mexico, North
Dakota, South Dakota, Utah, and Wyoming were obtained from the WRAP
baseline inventory.\72\ A California Air Resources Board-provided
inventory was used for 2016 oil and gas emissions in California.
Nonpoint oil and gas inventories for 2023 were developed by first
projecting the 2016 oil and gas inventories to 2021 values based on
actual production data. Next, those 2021 emissions were projected to
2023 using regional projection factors by product type based on AEO
2022 projections. A 2017-2019 average inventory was used for oil and
natural gas exploration emissions in 2023 everywhere except for
California and in the WRAP states in which data from the WRAP future
year inventory \73\ were used. NOX and VOC reductions that
are co-benefits to the NSPS for RICE are reflected, along with Natural
Gas Turbines and Process Heaters NSPS NOX controls and NSPS
Oil and Gas VOC controls. The WRAP future year inventory was used for
oil and natural gas production sources in 2023 except in New Mexico
where the WRAP Base year emissions were projected using the EIA
historical and AEO forecasted production data. Estimated impacts from
the New Mexico Administrative Code 20.2.50 were included.
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    \72\ http://www.wrapair2.org/pdf/WRAP_OGWG_Report_Baseline_17Sep2019.pdf.
    \73\ http://www.wrapair2.org/pdf/WRAP_OGWG_2028_OTB_RevFinalReport_05March2020.pdf.
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B. Air Quality Modeling To Identify Nonattainment and Maintenance
Receptors

    This section describes the air quality modeling and analyses that
the EPA performed in Step 1 to identify locations where the Agency
expects there to be nonattainment or maintenance receptors for the 2015
ozone NAAQS in 2023. Where the EPA's analysis shows that an area or
site does not fall under the definition of a nonattainment or
maintenance receptor in 2023, that site is excluded from further
analysis under the EPA's good neighbor framework.
1. Approach for Identifying Receptors
    In the proposed actions, the EPA applied the same approach used in
the CSAPR Update and the Revised CSAPR Update to identify nonattainment
and maintenance receptors for the 2008 ozone NAAQS.\74\ The EPA's
approach gives independent effect to both the ``contribute
significantly to nonattainment'' and the ``interfere with maintenance''
prongs of section 110(a)(2)(D)(i)(I), consistent with the D.C.
Circuit's direction in North Carolina. Further, in its decision on the
remand of CSAPR from the Supreme Court in the EME Homer City II case,
the D.C. Circuit confirmed that the EPA's approach to identifying
maintenance receptors in CSAPR comported with the court's prior
instruction to give independent meaning to the ``interfere with
maintenance'' prong in the good neighbor provision.\75\
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    \74\ See 86 FR 23078-79.
    \75\ EME Homer City II, 795 F.3d at 136.
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    In the CSAPR Update and the Revised CSAPR Update, the EPA
identified 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 NOX SIP Call and CAIR, where the
EPA defined nonattainment receptors as those areas that both currently
monitor nonattainment and that the EPA projects will be in
nonattainment in the future compliance year.
    The Agency explained in the NOX SIP Call and CAIR and
then reaffirmed in the CSAPR Update that the EPA has the most
confidence in our projections of nonattainment for those counties that
also measure nonattainment for the most recent period of available
ambient data. The EPA separately identified maintenance receptors as
those receptors that would have difficulty maintaining the relevant
NAAQS in a scenario that accounts for historical variability in air
quality at that receptor. The variability in air quality was determined
by evaluating the ``maximum'' future design value at each receptor
based on a projection of the maximum measured design value over the
relevant period. The 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). The EPA also recognizes that previously experienced
meteorological conditions (e.g., dominant wind direction, temperatures,
and 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.

    Therefore, applying this methodology for this action, the EPA
assessed the magnitude of the maximum projected design values for 2023
at each receptor in relation to the 2015 ozone NAAQS and, where such a
value exceeds the NAAQS, the EPA determined that receptor to be a
``maintenance'' receptor for purposes of defining interference with
maintenance, consistent with the method used in CSAPR and upheld by the
D.C. Circuit in EME Homer City II.\76\ That is, monitoring sites with a
maximum design value that exceeds the NAAQS are projected to have
maintenance problems in the future analytic years.
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    \76\ EME Homer City II, 795 F.3d at 136.
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    Recognizing that nonattainment receptors are also, by definition,
maintenance receptors, the EPA often uses the term ``maintenance-only''
to refer to receptors that are not also nonattainment receptors.
Consistent with the concepts for maintenance receptors, as described
earlier, the 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 certified design values.\77\
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    \77\ See https://www.epa.gov/air-trends/air-quality-design-values for design value reports. At the time of this action, the
most recent reports of certified design values available are for the
calendar year 2021. The 2022 values are considered ``preliminary''
and therefore subject to change before certification.
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    Comment: The EPA received comments claiming that the projected
design values for 2023 were biased low compared to recent measured
data. Commenters noted that a number of monitoring sites that are
projected to be below the NAAQS in 2023 based on the EPA's modeling for
the proposed action are currently measuring nonattainment based on data
from 2020 and 2021. One commenter requested that the EPA determine
whether its past modeling tends to overestimate or underestimate actual
observed design values. If EPA finds that the agency's model tends to
underestimate future year design values, the commenter requests that
EPA re-run its ozone modeling, incorporating parameters that account
for this tendency.
    EPA Response: In response to comments, the EPA compared the
projected 2023 design values based on the proposal modeling to recent
trends in measured data. As a result of this analysis, the EPA agrees
that current data indicate that there are monitoring sites at risk of
continued nonattainment in 2023 even though the model projected average
and maximum design values at these sites are below the NAAQS (i.e.,
these sites would not be modeling-based receptors at Step 1). While the
EPA has confidence in the reliability of the modeling for projecting
air quality conditions and contributions in future years, it would not
be reasonable to ignore recent measured ozone levels in many areas that
are clearly not fully consistent with certain concentrations in the
Step 1 analysis for 2023. Therefore, the EPA has developed an
additional maintenance-only receptor category, which includes what we
refer to as ``violating monitor'' receptors, based on current ozone
concentrations measured by regulatory ambient air quality monitoring
sites.
    Specifically, the EPA has identified monitoring sites with measured
2021 and preliminary 2022 design values and 4th high maximum daily 8-
hour average (MDA8) ozone in both 2021 and 2022 (preliminary data) that
exceed the NAAQS as having the greatest risk of continuing to have a
problem attaining the standard in 2023. These criteria sufficiently
consider measured air quality data so as to avoid including monitoring
sites that have measured nonattainment data in recent years but could
reasonably be anticipated to not have a nonattainment or maintenance
problem in 2023, in line with our modeling results. Our methodology is
intended only to identify those sites that have sufficiently poor ozone
levels that there is clearly a reasonable expectation that an ozone
nonattainment or maintenance problem will persist in the 2023 ozone
season. Moreover, the 2023 ozone season is so near in time that recent
measured ozone levels can be used to reasonably project whether an air
quality problem is likely to persist. We view this approach to
identifying additional receptors in 2023 as the best means of
responding to the comments on this issue in this action, while also
identifying all transport receptors.
    For purposes of this action, we will treat these violating monitors
as an additional type of maintenance-only receptor. We acknowledge that
the traditional modeling plus monitoring methodology we used at
proposal and in prior ozone transport rules would otherwise have
identified such sites as being in attainment in 2023. Because our
modeling did not identify these sites as receptors, we do not believe
it is sufficiently certain that these sites will be in nonattainment
that they should be considered nonattainment receptors. In the face of
this uncertainty in the record, we regard our ability to consider such
sites as receptors for purposes of good neighbor analysis under CAA
section 110(a)(2)(D)(i)(I) to be a function of the requirement to
prohibit emissions that interfere with maintenance of the NAAQS; even
if an area may be projected to be in attainment, we have reliable
information indicating that there is a clear risk that attainment will
not in fact be achieved in 2023. Thus, our authority for treating these
sites as receptors at Step 1 in 2023 flows from the responsibility in
CAA section 110(a)(2)(i)(I) to prohibit emissions that interfere with
maintenance of the NAAQS. See, e.g., North Carolina, 531 F.3d at 910-11
(failing to give effect to the interfere with maintenance clause
``provides no protection for downwind areas that, despite EPA's
predictions, still find themselves struggling to meet NAAQS due to
upwind interference . . . .'') (emphasis added). Recognizing that no
modeling can perfectly forecast the future, and ``a degree of
imprecision is inevitable in tackling the problem of interstate air
pollution,'' this approach in the Agency's judgement best balances the
need to avoid both ``under-control'' and ``overcontrol,'' EME Homer
City, 572 U.S. at 523. The EPA's analysis of these additional receptors
further is explained in Section III.C.
    However, because we did not propose to apply this expansion of the
basis for regulation under the good neighbor provision receptor-
identification methodology as the sole basis for finding an upwind
state linked, in this action we are only using this receptor category
on a confirmatory basis. That is, for states that we find linked based
on our traditional modeling-based methodology in 2023, we find in this
final analysis that the linkage at Step 2 is strengthened and confirmed
if that state is also linked to one or more ``violating-monitor''
receptors. If a state is only linked to a violating-monitor receptor in
this final analysis, we are deferring taking final action on that
state's SIP submittal. This is the case for the State of Tennessee.
Among the states that previously had their transport SIPs approved for
the 2015 ozone NAAQS, the EPA has also identified a linkage to
violating-monitor receptors for the State of Kansas. The EPA intends to
further review its air quality modeling results and recent measured
ozone levels, and we intend to address these states' good

neighbor obligations as expeditiously as practicable in a future
action.
2. Methodology for Projecting Future Year Ozone Design Values
    Consistent with the EPA's modeling guidance, the 2016 base year and
future year air quality modeling results were used in a relative sense
to project design values for 2023.\78\ That is, the ratios of future
year model predictions to base year model predictions are used to
adjust ambient ozone design values up or down depending on the relative
(percent) change in model predictions for each location. The EPA's
modeling guidance recommends using measured ozone concentrations for
the 5-year period centered on the base year as the air quality data
starting point for future year projections. This average design value
is used to dampen the effects of inter-annual variability in
meteorology on ozone concentrations and to provide a reasonable
projection of future air quality at the receptor under average
conditions. In addition, the Agency calculated maximum design values
from within the 5-year base period to represent conditions when
meteorology is more favorable than average for ozone formation. Because
the base year for the air quality modeling used in this final action is
2016, measured data for 2014-2018 (i.e., design values for 2016, 2017,
and 2018) were used to project average and maximum design values in
2023.
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    \78\ U.S. Environmental Protection Agency, 2018. Modeling
Guidance for Demonstrating Attainment of Air Quality Goals for
Ozone, PM2.5, and Regional Haze, Research Triangle Park,
NC. https://www.epa.gov/scram/state-implementation-plan-sip-attainment-demonstration-guidance.
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    The ozone predictions from the 2016 and future year air quality
model simulations were used to project 2016-2018 average and maximum
ozone design values to 2023 using an approach similar to the approach
in the EPA's guidance for attainment demonstration modeling. This
guidance recommends using model predictions from the 3 x 3 array of
grid cells surrounding the location of the monitoring site to calculate
a Relative Response Factor (RRF) for that site. However, the guidance
also notes that an alternative array of grid cells may be used in
certain situations where local topographic or geographical feature
(e.g., a large water body or a significant elevation change) may
influence model response.
    The 2016-2018 base period average and maximum design values were
multiplied by the RRF to project each of these design values to 2023.
In this manner, the projected design values are grounded in monitored
data, and not the absolute model-predicted future year concentrations.
Following the approach in the CSAPR Update and the Revised CSAPR
Update, the EPA also projected future year design values based on a
modified version of the ``3 x 3'' approach for those monitoring sites
located in coastal areas. In this alternative approach, the EPA
eliminated from the RRF calculations the modeling data in those grid
cells that are dominated by water (i.e., more than 50 percent of the
area in the grid cell is water) and that do not contain a monitoring
site (i.e., if a grid cell is more than 50 percent water but contains
an air quality monitor, that cell would remain in the calculation). The
choice of more than 50 percent of the grid cell area as water as the
criteria for identifying overwater grid cells is based on the treatment
of land use in the Weather Research and Forecasting model (WRF).
Specifically, in the WRF meteorological model those grid cells that are
greater than 50% overwater are treated as being 100 percent overwater.
In such cases the meteorological conditions in the entire grid cell
reflect the vertical mixing and winds over water, even if part of the
grid cell also happens to be over land with land-based emissions, as
can often be the case for coastal areas. Overlaying land-based
emissions with overwater meteorology may be representative of
conditions at coastal monitors during times of on-shore flow associated
with synoptic conditions or sea-breeze or lake-breeze wind flows. But
there may be other times, particularly with off-shore wind flow, when
vertical mixing of land-based emissions may be too limited due to the
presence of overwater meteorology. Thus, for our modeling the EPA
projected average and maximum design values at individual monitoring
sites based on both the ``3 x 3'' approach as well as the alternative
approach that eliminates overwater cells in the RRF calculation for
near-coastal areas (i.e., ``no water'' approach). The projected 2023
design values using both the ``3 x 3'' and ``no-water'' approaches are
provided in the docket for this final action. Both approaches result in
the same set of receptors in 2023. That is, monitoring sites that are
identified as receptors in 2023 based on the ``3 x 3'' approach are
also receptors based on the ``no water'' approach.
    Consistent with the truncation and rounding procedures for the 8-
hour ozone NAAQS, the projected design values are evaluated after
truncation to integers in units of ppb. Therefore, projected design
values that are greater than or equal to 71 ppb are considered to be
violating the 2015 ozone NAAQS. For those sites that are projected to
be violating the NAAQS based on the average design values in 2023, the
Agency examined the measured design values for 2021, which are the most
recent official measured design values at the time of this final
action.
    As noted earlier, the Agency proposes to identify nonattainment
receptors in this rulemaking as those sites that are violating the
NAAQS based on current measured air quality through 2021 and have
projected average design values of 71 ppb or greater. Maintenance-only
receptors include both: (1) Those sites with projected average design
values above the NAAQS that are currently measuring clean data (i.e.,
ozone design values below the level of the 2015 ozone NAAQS in 2021)
and (2) those sites with projected average design values below the
level of the NAAQS, but with projected maximum design values of 71 ppb
or greater. In addition to the maintenance-only receptors, ozone
nonattainment receptors are also maintenance receptors because the
projected maximum design values for each of these sites is always
greater than or equal to the average design value. Further, as
explained previously in this section, the EPA identifies certain
monitoring sites as ``violating monitor'' maintenance-only receptors
based on 2021 and 2022 measured ozone levels.
    The monitoring sites that the Agency projects to be nonattainment
and maintenance receptors for the ozone NAAQS in the 2023 base case are
used for assessing the contribution of emissions in upwind states to
downwind nonattainment and maintenance of the 2015 ozone NAAQS as part
of this final action.
3. 2023 Nonattainment and Maintenance-Only Receptors for the Final
Action
    In this section we provide information on modeling-based design
values and measured data for monitoring sites identified as
nonattainment or maintenance-only receptors in 2023 for this final
action. Table III.B-1 of this action contains the 2016-centered base
period average and maximum 8-hour ozone design values, the 2023
projected average and maximum design values and the measured 2021
design values for monitoring sites that are projected to be
nonattainment receptors in 2023. Table III.B-2 of this action contains
this same information for monitoring sites that are projected to be
maintenance-only receptors in 2023, based on air quality modeling.
Table III.B-3 of this action contains the 2023 projected average and
maximum design values and 2021 design values and 4th high

MDA8 ozone concentrations and preliminary 2020 design values and 4th
high MDA8 ozone concentrations for monitoring sites identified as
violating monitor maintenance-only receptors. The design values for all
monitoring sites in the U.S. are provided in the docket for this
action. Additional details on the approach for projecting average and
maximum design values are provided in the AQM TSD.

 Table III.B-1--Average and Maximum 2016-Centered and 2023 Base Case 8-Hour Ozone Design Values and 2021 Design Values (ppb) at Projected Nonattainment
                                                                       Receptors a
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                                                                           2016 centered   2016 centered
             Monitor ID                 State             County              average         maximum      2023 average    2023 maximum        2021
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060650016...........................         CA  Riverside..............            79.0            80.0            72.2            73.1              78
060651016...........................         CA  Riverside..............            99.7             101            91.0            92.2              95
080350004...........................         CO  Douglas................            77.3              78            71.3            71.9              83
080590006...........................         CO  Jefferson..............            77.3              78            72.8            73.5              81
080590011...........................         CO  Jefferson..............            79.3              80            73.5            74.1              83
090010017...........................         CT  Fairfield..............            79.3              80            71.6            72.2              79
090013007...........................         CT  Fairfield..............            82.0              83            72.9            73.8              81
090019003...........................         CT  Fairfield..............            82.7              83            73.3            73.6              80
481671034...........................         TX  Galveston..............            75.7              77            71.5            72.8              72
482010024...........................         TX  Harris.................            79.3              81            75.1            76.7              74
490110004...........................         UT  Davis..................            75.7              78            72.0            74.2              78
490353006...........................         UT  Salt Lake..............            76.3              78            72.6            74.2              76
490353013...........................         UT  Salt Lake..............            76.5              77            73.3            73.8              76
551170006...........................         WI  Sheboygan..............            80.0              81            72.7            73.6              72
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\a\ 2016-centered base period average design values and projected average and maximum design values are reported with 1 digit to the right of the
  decimal, as recommended in the EPA's modeling guidance. The 2016 maximum design values and 2021 design values are truncated to integer values
  consistent with ozone design value reporting convention in appendix U of 40 CFR part 50.

  Table III.B-2--Average and Maximum 2016-Centered and 2023 Base Case 8-Hour Ozone Design Values and 2021 Design Values (ppb) at Projected Maintenance-
                                                                     Only Receptors
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                                                                           2016 centered   2016 centered
             Monitor ID                 State             County              average         maximum      2023 average    2023 maximum        2021
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040278011...........................         AZ  Yuma...................            72.3              74            70.4            72.1              67
080690011...........................         CO  Larimer................            75.7              77            70.9            72.1              77
090099002...........................         CT  New Haven..............            79.7              82            70.5            72.6              82