Document ID: EPA-HQ-OAR-2021-0663-0020
Agency: epa
Document Type: Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards
Posted Date: 2023-02-13T05:00Z

[Federal Register Volume 88, Number 29 (Monday, February 13, 2023)]
[Rules and Regulations]
[Pages 9336-9384]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-02407]

[[Page 9335]]

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  

[[Page 9336]]

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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: (919) 541-5534; 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:

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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

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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

[[Page 9339]]

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

[[Page 9340]]

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.

[[Page 9341]]

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).
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    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\
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    \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

[[Page 9342]]

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.
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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

[[Page 9343]]

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

[[Page 9344]]

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).
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    \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.
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    \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.
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    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.
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    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

[[Page 9345]]

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

[[Page 9346]]

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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[[Page 9347]]

    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

[[Page 9348]]

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.
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    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

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\
---------------------------------------------------------------------------

    \74\ See 86 FR 23078-79.
    \75\ EME Homer City II, 795 F.3d at 136.
---------------------------------------------------------------------------

    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.

[[Page 9349]]

    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.
---------------------------------------------------------------------------

    \76\ EME Homer City II, 795 F.3d at 136.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

[[Page 9350]]

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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

[[Page 9351]]

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
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                           2016 centered   2016 centered
             Monitor ID                 State             County              average         maximum      2023 average    2023 maximum        2021
--------------------------------------------------------------------------------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                           2016 centered   2016 centered
             Monitor ID                 State             County              average         maximum      2023 average    2023 maximum        2021
--------------------------------------------------------------------------------------------------------------------------------------------------------
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
170310001...........................         IL  Cook...................            73.0              77            68.2            71.9              71
170314201...........................         IL  Cook...................            73.3              77            68.0            71.5              74
170317002...........................         IL  Cook...................            74.0              77            68.5            71.3              73
350130021...........................         NM  Dona Ana...............            72.7              74            70.8            72.1              80
350130022...........................         NM  Dona Ana...............            71.3              74            69.7            72.4              75
350151005...........................         NM  Eddy...................            69.7              74            69.7            74.1              77
350250008...........................         NM  Lea....................            67.7              70            69.8            72.2              66
480391004...........................         TX  Brazoria...............            74.7              77            70.4            72.5              75
481210034...........................         TX  Denton.................            78.0              80            69.8            71.6              74
481410037...........................         TX  El Paso................            71.3              73            69.8            71.4              75
482010055...........................         TX  Harris.................            76.0              77            70.9            71.9              77
482011034...........................         TX  Harris.................            73.7              75            70.1            71.3              71
482011035...........................         TX  Harris.................            71.3              75            67.8            71.3              71
530330023...........................         WA  King...................            73.3              77            67.6            71.0              64
550590019...........................         WI  Kenosha................            78.0              79            70.8            71.7              74
551010020...........................         WI  Racine.................            76.0              78            69.7            71.5              73
--------------------------------------------------------------------------------------------------------------------------------------------------------

    In total, in 2023 there are a total of projected 33 modeling-based 
receptors nationwide including 14 nonattainment receptors in 9 
different counties and 19 maintenance-only receptors in 13 additional 
counties (Harris County, TX, has both nonattainment and maintenance-
only receptors).
    As shown in Table III.B-3 of this action, there are 49 monitoring 
sites that are identified as ``violating-monitor'' maintenance-only 
receptors in 2023.As noted earlier in this section, the EPA uses the 
approach of considering ``violating-monitor'' maintenance-only 
receptors as confirmatory of the proposal's identification of receptors 
and does not implicate additional linked states in this final action, 
Rather, using this approach serves to strengthen the analytical basis 
for our Step 2 findings by establishing that many upwind states covered 
in this action are also projected to contribute above 1 percent of the 
NAAQS to these additional ``violating monitor'' maintenance-only 
receptors.

[[Page 9352]]

    Table III.B-3--Average and Maximum 2023 Base Case 8-Hour Ozone, and 2021 and Preliminary 2022 Design Values (ppb) and 4th High Concentrations at
                                                                  Violating Monitors a
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                2023         2023                                2021  4th   2022 P  4th
              Monitor ID                 State             County             average      maximum        2021        2022 P        high         high
--------------------------------------------------------------------------------------------------------------------------------------------------------
40070010.............................         AZ  Gila....................         67.9         69.5           77           76           75           74
40130019.............................         AZ  Maricopa................         69.8         70.0           75           77           78           76
40131003.............................         AZ  Maricopa................         70.1         70.7           80           80           83           78
40131004.............................         AZ  Maricopa................         70.2         70.8           80           81           81           77
40131010.............................         AZ  Maricopa................         68.3         69.2           79           80           80           78
40132001.............................         AZ  Maricopa................         63.8         64.1           74           78           79           81
40132005.............................         AZ  Maricopa................         69.6         70.5           78           79           79           77
40133002.............................         AZ  Maricopa................         65.8         65.8           75           75           81           72
40134004.............................         AZ  Maricopa................         65.7         66.6           73           73           73           71
40134005.............................         AZ  Maricopa................         62.3         62.3           73           75           79           73
40134008.............................         AZ  Maricopa................         65.6         66.5           74           74           74           71
40134010.............................         AZ  Maricopa................         63.8         66.9           74           76           77           75
40137020.............................         AZ  Maricopa................         67.0         67.0           76           77           77           75
40137021.............................         AZ  Maricopa................         69.8         70.1           77           77           78           75
40137022.............................         AZ  Maricopa................         68.2         69.1           76           78           76           79
40137024.............................         AZ  Maricopa................         67.0         67.9           74           76           74           77
40139702.............................         AZ  Maricopa................         66.9         68.1           75           77           72           77
40139704.............................         AZ  Maricopa................         65.3         66.2           74           77           76           76
40139997.............................         AZ  Maricopa................         70.5         70.5           76           79           82           76
40218001.............................         AZ  Pinal...................         67.8         69.0           75           76           73           77
80013001.............................         CO  Adams...................         63.0         63.0           72           77           79           75
80050002.............................         CO  Arapahoe................         68.0         68.0           80           80           84           73
80310002.............................         CO  Denver..................         63.6         64.8           72           74           77           71
80310026.............................         CO  Denver..................         64.5         64.8           75           77           83           72
90079007.............................         CT  Middlesex...............         68.7         69.0           74           73           78           73
90110124.............................         CT  New London..............         65.5         67.0           73           72           75           71
170310032............................         IL  Cook....................         67.3         69.8           75           75           77           72
170311601............................         IL  Cook....................         63.8         64.5           72           73           72           71
181270024............................         IN  Porter..................         63.4         64.6           72           73           72           73
260050003............................         MI  Allegan.................         66.2         67.4           75           75           78           73
261210039............................         MI  Muskegon................         67.5         68.4           74           79           75           82
320030043............................         NV  Clark...................         68.4         69.4           73           75           74           74
350011012............................         NM  Bernalillo..............         63.8         66.0           72           73           76           74
350130008............................         NM  Dona Ana................         65.6         66.3           72           76           79           78
361030002............................         NY  Suffolk.................         66.2         68.0           73           74           79           74
390850003............................         OH  Lake....................         64.3         64.6           72           74           72           76
480290052............................         TX  Bexar...................         67.1         67.8           73           74           78           72
480850005............................         TX  Collin..................         65.4         66.0           75           74           81           73
481130075............................         TX  Dallas..................         65.3         66.5           71           71           73           72
481211032............................         TX  Denton..................         65.9         67.7           76           77           85           77
482010051............................         TX  Harris..................         65.3         66.3           74           73           83           72
482010416............................         TX  Harris..................         68.8         70.4           73           73           78           71
484390075............................         TX  Tarrant.................         63.8         64.7           75           76           76           77
484391002............................         TX  Tarrant.................         64.1         65.7           72           77           76           80
484392003............................         TX  Tarrant.................         65.2         65.9           72           72           74           72
484393009............................         TX  Tarrant.................         67.5         68.1           74           75           75           75
490571003............................         UT  Weber...................         69.3         70.3           71           74           77           71
550590025............................         WI  Kenosha.................         67.6         70.7           72           73           72           71
550890008............................         WI  Ozaukee.................         65.2         65.8           71           72           72           72
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ 2022 preliminary design values are based on 2022 measured MDA8 concentrations provided by state air agencies to the EPA's Air Quality System (AQS),
  as of January 3, 2023.

C. Air Quality Modeling To Quantify Upwind State Contributions

    This section documents the procedures the EPA used to quantify the 
impact of emissions from specific upwind states on ozone design values 
in 2023 for the identified downwind nonattainment and maintenance 
receptors. The EPA used CAMx photochemical source apportionment 
modeling to quantify the impact of emissions in specific upwind states 
on downwind nonattainment and maintenance receptors for 8-hour ozone. 
CAMx employs enhanced source apportionment techniques that track the 
formation and transport of ozone from specific emissions sources and 
calculates the contribution of sources and precursors to ozone for 
individual receptor locations. The benefit of the photochemical model 
source apportionment technique is that all modeled ozone at a given 
receptor location in the modeling domain is tracked back to specific 
sources of emissions and boundary conditions to fully characterize 
culpable sources.
    The EPA performed nationwide, state-level ozone source 
apportionment modeling using the CAMx Ozone Source Apportionment 
Technology/Anthropogenic Precursor Culpability Analysis (OSAT/APCA) 
technique \79\ to quantify the contribution of 2023 NOX and 
VOC emissions from all sources in each state to the corresponding 
projected ozone design values in 2023 at

[[Page 9353]]

air quality monitoring sites. The CAMx OSAT/APCA model run was 
performed for the period May 1 through September 30 using the projected 
future base case emissions and 2016 meteorology for this time period. 
In the source apportionment modeling the Agency tracked (i.e., tagged) 
the amount of ozone formed from anthropogenic emissions in each state 
individually as well as the contributions from other sources (e.g., 
natural emissions).
---------------------------------------------------------------------------

    \79\ As part of this technique, ozone formed from reactions 
between biogenic VOC and NOX with anthropogenic 
NOX and VOC are assigned to the anthropogenic emissions.
---------------------------------------------------------------------------

    In the state-by-state source apportionment model run, the EPA 
tracked the ozone formed from each of the following tags:
     States--anthropogenic NOX emissions and VOC 
emissions from individual state (emissions from all anthropogenic 
sectors in a given state were combined);
     Biogenics--biogenic NOX and VOC emissions 
domain-wide (i.e., not by state);
     Boundary Concentrations--concentrations transported into 
the air quality modeling domain;
     Tribes--the emissions from those tribal lands for which 
the Agency has point source inventory data emissions modeling platform 
(EPA did not model the contributions from individual tribes);
     Canada and Mexico--anthropogenic emissions from those 
sources in the portions of Canada and Mexico included within the 
modeling domain (the EPA did not model the contributions from Canada 
and Mexico separately);
     Fires--combined emissions from wild and prescribed fires 
domain-wide (i.e., not by state); and
     Offshore--combined emissions from offshore marine vessels 
and offshore drilling platforms within the modeling domain.
    The contribution modeling provided contributions to ozone from 
anthropogenic NOX and VOC emissions in each state, 
individually. The contributions to ozone from chemical reactions 
between biogenic NOX and VOC emissions were modeled and 
assigned to the ``biogenic'' category. The contributions from wildfire 
and prescribed fire NOX and VOC emissions were modeled and 
assigned to the ``fires'' category. That is, the contributions from the 
``biogenic'' and ``fires'' categories are not assigned to individual 
states nor are they included in the state contributions.
    For the Step 2 analysis, the EPA calculated a contribution metric 
that considers the average contribution on the 10 highest ozone 
concentration days (i.e., top 10 days) in 2023 using the same approach 
as the EPA used in the proposed action and in the Revised CSAPR 
Update.\80\ This average contribution metric is intended to provide a 
reasonable representation of the contribution from individual states to 
projected future year design values, based on modeled transport 
patterns and other meteorological conditions generally associated with 
modeled high ozone concentrations at the receptor. An average 
contribution metric constructed in this manner ensures the magnitude of 
the contributions is directly related to the magnitude of the ozone 
design value at each site.
---------------------------------------------------------------------------

    \80\ The use of daily contributions on the top 10 concentration 
days for calculating the average contribution metric is designed to 
be consistent with the method specified in the modeling guidance in 
terms of the number of days to use when projecting future year 
design values.
---------------------------------------------------------------------------

    The analytic steps for calculating the contribution metric for the 
2023 analytic year are as follows:
    (1) Calculate the 8-hour average contribution from each source tag 
to individual ozone monitoring site for the time period of the 8-hour 
daily maximum modeled concentrations in 2023;
    (2) Average the contributions and average the concentrations for 
the top 10 modeled ozone concentration days in 2023;
    (3) Divide the average contribution by the corresponding average 
concentration to obtain a Relative Contribution Factor (RCF) for each 
monitoring site;
    (4) Multiply the 2023 average design value by the 2023 RCF at each 
site to produce the average contribution metric values in 2023; \81\
---------------------------------------------------------------------------

    \81\ Note that a contribution metric value was not calculated 
for any receptor at which there were fewer than 5 days with model-
predicted MDA8 ozone concentrations greater than or equal to 60 ppb 
in 2023. Eliminating from the Step 2 evaluation any receptors for 
which the modeling does not meet this criterion ensures that upwind 
state contributions are based on the days with the highest ozone 
projections. This criterion is consistent with the criterion for 
projecting design values, as recommended in the EPA's modeling 
guidance. In the modeling for this final action, the monitoring site 
in Seattle, Washington (530330023), was the only receptor that did 
not meet this criterion.
---------------------------------------------------------------------------

    (5) Truncate the average contribution metric values to two digits 
to the right of the decimal for comparison to the 1 percent of the 
NAAQS screening threshold (0.70 ppb)
    The resulting contributions from each tag to each monitoring site 
in the U.S. for 2023 can be found in the docket for this final action. 
Additional details on the source apportionment modeling and the 
procedures for calculating contributions can be found in the AQM TSD. 
The EPA's response to comments on the method for calculating the 
contribution metric can be found in the RTC document for this final 
action.
    The largest contribution from each state that is the subject of 
this final action to modeled 8-hour ozone nonattainment and modeling-
based maintenance receptors in downwind states in 2023 are provided in 
Table III.C-1 of this action. The largest contribution from each state 
to the additional ``violating monitor'' maintenance-only receptors is 
provided in Table III.C-2 of this action. All states that are linked to 
one or more nonattainment or maintenance-only receptors are also linked 
to one or more violating monitor maintenance receptors, except for 
Minnesota.

  Table III.C-1--Largest Contribution by State to Downwind 8-Hour Ozone
          Nonattainment and Maintenance Receptors in 2023 (ppb)
------------------------------------------------------------------------
                                         Largest            Largest
                                    contribution to a  contribution to a
           Upwind state                  downwind           downwind
                                      nonattainment     maintenance-only
                                         receptor           receptor
------------------------------------------------------------------------
Alabama...........................               0.75               0.65
Arkansas..........................               0.94               1.21
California........................              35.27               6.31
Illinois..........................              13.89              19.09
Indiana...........................               8.90              10.03
Kentucky..........................               0.84               0.79
Louisiana.........................               9.51               5.62

[[Page 9354]]

 
Maryland..........................               1.13               1.28
Michigan..........................               1.59               1.56
Minnesota.........................               0.36               0.85
Mississippi.......................               1.32               0.91
Missouri..........................               1.87               1.39
Nevada............................               1.11               1.13
New Jersey........................               8.38               5.79
New York..........................              16.10              11.29
Ohio..............................               2.05               1.98
Oklahoma..........................               0.79               1.01
Texas.............................               1.03               4.74
Utah..............................               1.29               0.98
West Virginia.....................               1.37               1.49
Wisconsin.........................               0.21               2.86
------------------------------------------------------------------------

Table III.C-2--Largest Contribution to Downwind 8-Hour Ozone ``Violating
               Monitor'' Maintenance-Only Receptors (ppb)
------------------------------------------------------------------------
                                                              Largest
                                                           contribution
                                                           to a downwind
                      Upwind State                           violating
                                                              monitor
                                                           maintenance-
                                                           only receptor
------------------------------------------------------------------------
Alabama.................................................            0.79
Arkansas................................................            1.16
California..............................................            6.97
Illinois................................................           16.53
Indiana.................................................            9.39
Kentucky................................................            1.57
Louisiana...............................................            5.06
Maryland................................................            1.14
Michigan................................................            3.47
Minnesota...............................................            0.64
Mississippi.............................................            1.02
Missouri................................................            2.95
Nevada..................................................            1.11
New Jersey..............................................            8.00
New York................................................           12.08
Ohio....................................................            2.25
Oklahoma................................................            1.57
Texas...................................................            3.83
Utah....................................................            1.46
West Virginia...........................................            1.79
Wisconsin...............................................            5.10
------------------------------------------------------------------------

IV. Summary of Bases for Disapproval

    As explained in Section II, the EPA relies on the 4-step interstate 
transport framework to evaluate obligations under CAA section 
110(a)(2)(D)(i)(I). At proposal, the EPA used this framework to guide 
its evaluation of each state's SIP submission. While the EPA used this 
framework to maintain a nationally consistent and equitable approach to 
interstate transport, the contents of each individual state's 
submission were evaluated on their own merits, and the EPA considered 
the facts and information, including information from the Agency, 
available to the state at the time of its submission, in addition to 
more recent air quality and contribution information. Here we provide a 
brief, high level overview of the SIP submissions and the EPA's 
evaluation and key bases for disapproval. These summaries are presented 
for ease of reference and to direct the public to the most relevant 
portions of the proposals and final rule record for further 
information. The full basis for the EPA's disapprovals is available in 
relevant Federal Register notifications of proposed disapproval for 
each state, in the technical support documents informing the proposed 
and final action, and in the responses to comments in Section V and the 
RTC document. In general, except as otherwise noted, the comments and 
updated air quality information did not convince the Agency that a 
change from proposal was warranted for any state. The exceptions are 
that the EPA is deferring action at this time on the proposed 
disapprovals for Tennessee and Wyoming. Further, the EPA is finalizing 
partial approvals of prong 1 (``significant contribution to 
nonattainment'') for Minnesota and Wisconsin because they are linked 
only to maintenance-only receptors; the EPA is finalizing a partial 
disapproval with respect to prong 2 (``interference with maintenance'') 
obligations for these two states.

A. Alabama

    In the 2016v3 modeling, Alabama is projected to be linked above 1 
percent of the NAAQS to one nonattainment receptor. It is also linked 
to one violating-monitor maintenance-only receptor. Its highest-level 
contribution is 0.75 ppb to Galveston County, Texas (AQS Site ID 
481671034).\82\ A full summary of Alabama's June 21, 2022, SIP 
submission, as well as Alabama's previous submission history, was 
provided in the proposed SIP submission disapproval.\83\ In its 
submission, Alabama advocated for discounting maintenance receptors 
through use of historical data trends. The EPA finds Alabama's approach 
is not adequately justified.\84\ The EPA disagrees with Alabama's 
assessment of the 2016v2 modeling,\85\ and further responds to comments 
on model performance in Section III. The EPA disagrees with Alabama's 
arguments for application of a higher contribution threshold than 1 
percent of the NAAQS at Step 2,\86\ and further addresses the relevance 
of ``significant impact levels'' within the Prevention of Significant 
Deterioration program (``PSD SILs'') in Section V.B.6. The EPA found 
technical flaws in Alabama's back trajectory analysis.\87\ The State 
did not conduct an adequate Step 3 analysis, and the EPA identified 
several unsupported assertions in the SIP submission.\88\ Alabama also 
argued in its SIP submission that it had already implemented all cost-
effective controls. However, the State included an insufficient 
evaluation of additional emissions control opportunities to support 
such a conclusion.\89\ The EPA further addresses arguments related to

[[Page 9355]]

mobile sources in Section V.C.1.\90\ Additionally, as explained in 
Section V.B.9,\91\ reliance on prior transport FIPs such as the CSAPR 
Update is not a sufficient analysis at Step 3. The State included no 
permanent and enforceable emissions controls in its SIP submission.\92\ 
We provide further response to comments regarding Alabama's SIP 
submission in the RTC document. The EPA is finalizing disapproval of 
Alabama's interstate transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \82\ The highest-magnitude downwind contribution from each state 
is based on the contributions to modeling-based receptors and does 
not consider the contributions to violating-monitor maintenance-only 
receptors. Each state's maximum contribution to downwind violating-
monitor maintenance-only receptors is available in the Final Action 
AQM TSD.
    \83\ 87 FR 64419-64421.
    \84\ Id. at 64421-64422.
    \85\ Id. at 64422-64423.
    \86\ Id. at 64423-64424.
    \87\ Id. at 64424-64425.
    \88\ Id. at 64425-64426.
    \89\ Id.
    \90\ See also id. at 64425-64426.
    \91\ See also id. at 64426.
    \92\ Id.
---------------------------------------------------------------------------

B. Arkansas

    In the 2016v3 modeling, Arkansas is projected to be linked above 1 
percent of the NAAQS to one nonattainment receptor and five 
maintenance-only receptors. It is also linked to seven violating-
monitor maintenance-only receptor. Its highest-level contribution is 
1.21 ppb to Brazoria County Texas (AQS Site ID 480391004). A full 
summary of Arkansas's October 10, 2019, SIP submission was provided in 
the proposed SIP submission disapproval.\93\ The EPA disagrees with 
Arkansas's arguments for application of a higher contribution threshold 
than 1 percent of the NAAQS at Step 2, and further addresses the 
relevance of PSD SILs in Section V.B.6.\94\ The EPA also found 
technical flaws in Arkansas's ``consistent and persistent'' claims and 
back trajectory analysis,\95\ and legal flaws in the state's arguments 
related to relative contribution.\96\ The State did not conduct an 
adequate Step 3 analysis.\97\ Arkansas argued in its SIP submission 
that it had already implemented all cost-effective controls. However, 
the State included an insufficient evaluation of additional emissions 
control opportunities to support such a conclusion.\98\ Further, the 
State's reliance on the cost-effectiveness thresholds in the CSAPR and 
CSAPR Update is insufficient for the more protective 2015 ozone 
NAAQS.\99\ The State included no permanent and enforceable controls in 
its SIP submission.\100\ We provide further response to comments 
regarding Arkansas's SIP submission in the RTC document. The EPA is 
finalizing disapproval of Arkansas's interstate transport SIP 
submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \93\ 87 FR 9798, 9803-9806 (February 22, 2022).
    \94\ Id. at 9806-9807.
    \95\ Id. at 9808-9809.
    \96\ Id. at 9809-9810.
    \97\ Id. at 9809-9810.
    \98\ Id. at 9810.
    \99\ Id.
    \100\ Id. at 9811.
---------------------------------------------------------------------------

C. California

    In the 2016v3 modeling, California is projected to be linked above 
1 percent of the NAAQS to eight nonattainment receptors and four 
maintenance-only receptors. It is also linked to 26 violating-monitor 
maintenance-only receptor. Its highest-level contribution is 35.27 ppb 
to the nonattainment receptor located on the Morongo Band of Missions 
Indians reservation (AQS Site ID 060651016).\101\ A full summary of 
California's October 1, 2018, SIP submission was provided in the 
proposed SIP submission disapproval.\102\ The EPA found technical and 
legal flaws in California's geographic, meteorological, wildfire, and 
trajectories analysis, and the State's arguments related to local, 
international, and non-anthropogenic emissions.\103\ The EPA further 
addresses the topic of international emissions in Section V.C.2. The 
State did not conduct an adequate Step 3 analysis.\104\ California in 
its SIP submission argued that it had already implemented all cost-
effective controls. However, California provided an insufficient 
evaluation of additional control opportunities to support such a 
conclusion.\105\ Further, the State's reliance on the cost-
effectiveness threshold in the CSAPR Update is insufficient for the 
more protective 2015 ozone NAAQS.\106\ California included no permanent 
and enforceable emissions controls in its SIP submission \107\ and 
argued that interstate transport is fundamentally different in the 
western U.S. than in the eastern U.S., to which the EPA responds in 
Section V.C.3.\108\ We provide further response to comments regarding 
California's SIP submission in the RTC document. The EPA is finalizing 
disapproval of California's interstate transport SIP submission for the 
2015 ozone NAAQS.
---------------------------------------------------------------------------

    \101\ We note that, consistent with the EPA's prior good 
neighbor actions in California, the regulatory ozone monitor located 
on the Morongo Band of Mission Indians (``Morongo'') reservation is 
a projected downwind receptor in 2023. See monitoring site 060651016 
in Table V.D-1. of this action. We also note that the Temecula, 
California, regulatory ozone monitor is a projected downwind 
receptor in 2023 and in past regulatory actions has been deemed 
representative of air quality on the Pechanga Band of Luise[ntilde]o 
Indians (``Pechanga'') reservation. See, e.g., Approval of Tribal 
Implementation Plan and Designation of Air Quality Planning Area; 
Pechanga Band of Luise[ntilde]o Mission Indians, 80 FR 18120, at 
18121-18123 (April 3, 2015); see also monitoring site 060650016 in 
Table V.D-1. of this action. The presence of receptors on, or 
representative of, the Morongo and Pechanga reservations does not 
trigger obligations for the Morongo and Pechanga Tribes. 
Nevertheless, these receptors are relevant to the EPA's assessment 
of any linked upwind states' good neighbor obligations. See, e.g., 
Approval and Promulgation of Air Quality State Implementation Plans; 
California; Interstate Transport Requirements for Ozone, Fine 
Particulate Matter, and Sulfur Dioxide, 83 FR 65093 (December 19, 
2018). Under 40 CFR 49.4(a), tribes are not subject to the specific 
plan submittal and implementation deadlines for NAAQS-related 
requirements, including deadlines for submittal of plans addressing 
transport impacts. We also note that California's maximum 
contribution to a downwind state receptor is 6.31 ppb in Yuma 
County, Arizona (AQS Site ID 040278011).
    \102\ 87 FR 31448-31452.
    \103\ Id. at 31454-31457, 31460.
    \104\ Id. at 31458-31461.
    \105\ Id. at 31458.
    \106\ Id. at 31458-31459.
    \107\ Id. at 31461.
    \108\ See also id. at 31453.
---------------------------------------------------------------------------

D. Illinois

    In the 2016v3 modeling, Illinois is projected to be linked above 1 
percent of the NAAQS to two nonattainment receptors and three 
maintenance-only receptors. It is also linked to six violating-monitor 
maintenance-only receptor. Its highest-level contribution is 19.09 ppb 
to Kenosha County, Wisconsin (AQS Site ID 550590019). A full summary of 
Illinois's May 21, 2019, SIP submission was provided in the proposed 
SIP submission disapproval.\109\ The EPA disagrees with Illinois's 
arguments for application of a higher contribution threshold than 1 
percent of the NAAQS at Step 2.\110\ The state did not conduct an 
adequate Step 3 analysis.\111\ The State included an insufficient 
evaluation of additional emissions control opportunities in its SIP 
submission.\112\ The EPA also found technical and legal flaws in 
Illinois' arguments related to ``on-the-way'' controls, participation 
in the Lake Michigan Air Directors Consortium (LADCO), and 
international contributions.\113\ The EPA further addresses the topic 
of international contribution in Section V.C.2. Further, as explained 
in Section V.B.9., states may not rely on non-SIP measures to meet SIP 
requirements, and reliance on prior transport FIPs such as the CSAPR 
Update is not a sufficient analysis at Step 3.\114\ The State included 
no permanent and enforceable controls in its SIP submission.\115\ We 
provide further response to comments regarding Illinois's SIP 
submission in the RTC document. The EPA is finalizing disapproval of 
Illinois's interstate

[[Page 9356]]

transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \109\ Id. at 9845.
    \110\ Id. at 9852-9853.
    \111\ Id. at 9853-9855.
    \112\ Id. at 9853.
    \113\ Id. at 9853-9854.
    \114\ See also id. at 9854.
    \115\ Id. at 9855.
---------------------------------------------------------------------------

E. Indiana

    In the 2016v3 modeling, Indiana is projected to be linked above 1 
percent of the NAAQS to four nonattainment receptors and six 
maintenance-only receptors. It is also linked to 10 violating-monitor 
maintenance receptors. Its highest-level contribution is 10.03 ppb to 
Racine County, Wisconsin (AQS Site ID 551010020). A full summary of 
Indiana's November 2, 2018, SIP submission was provided in the proposed 
SIP submission disapproval.\116\ The EPA disagrees with Indiana's 
arguments for application of a higher contribution threshold than 1 
percent of the NAAQS at Step 2.\117\ The State did not conduct an 
adequate Step 3 analysis.\118\ The EPA found technical and legal flaws 
in Indiana's arguments related to ozone concentration and design value 
trends, the timing of expected source shutdowns, local emissions, 
international and offshore contributions, Indiana's portion of 
contribution, and Indiana's back trajectory analysis.\119\ The EPA 
further addresses the topic of international emissions in Section 
V.C.2. Indiana argued that it would not be cost-effective to implement 
controls on non-EGUs. However, the State included an insufficient 
evaluation of additional emissions control opportunities, for any type 
of source, to support that conclusion.\120\ The EPA also confirmed that 
EGU shutdowns identified by Indiana were included in the 2016v2 
modeling,\121\ and if they were valid and not included in the 2016v2 
modeling, then they were incorporated into the 2016v3 modeling as 
explained in Section III and the 2016v3 Emissions Modeling TSD. 
Further, in Section V.B.9., states may not rely on non-SIP measures to 
meet SIP requirements.\122\ The State included no permanent and 
enforceable emissions controls in its SIP submission.\123\ We provide 
further response to comments regarding Indiana's SIP submission in the 
RTC document. The EPA is finalizing disapproval of Indiana's interstate 
transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \116\ Id. at 9845-9847.
    \117\ Id. at 9855-9856.
    \118\ Id. at 9857-9861.
    \119\ Id. at 9858-9861.
    \120\ Id. at 9857-9858.
    \121\ Id. at 9858-9859.
    \122\ See also id. at 9861.
    \123\ Id.
---------------------------------------------------------------------------

F. Kentucky

    In the 2016v3 modeling, Kentucky is projected to be linked above 1 
percent of the NAAQS to two nonattainment receptors and one 
maintenance-only receptor. It is also linked to four violating-monitor 
maintenance-only receptor. Its highest-level contribution based on the 
2016v3 modeling is 0.84 ppb to Fairfield County, Connecticut (AQS Site 
ID 090019003). A full summary of Kentucky's January 11, 2019, SIP 
submission was provided in the proposed SIP submission 
disapproval.\124\ Although the EPA's 2016v3 modeling indicated a 
highest-level contribution below 1 ppb, the EPA disagrees with 
Kentucky's arguments for application of a higher contribution threshold 
than 1 percent of the NAAQS at Step 2.\125\ Further, Kentucky is linked 
above 1 ppb to a violating-monitor receptor. The EPA addresses the 
relevance of the PSD SILs in Section V.B.6. The Commonwealth did not 
conduct an adequate Step 3 analysis.\126\ The EPA found technical and 
legal flaws in Kentucky's arguments related to the level and timing of 
upwind versus downwind-state responsibilities, NOX emissions 
trends and other air quality information, and back-trajectory 
analyses.\127\ The EPA also found technical and legal flaws in certain 
State-level comments submitted by Midwest Ozone Group and attached to 
Kentucky's submission, including arguments related to international 
emissions.\128\ The EPA further addresses the topics of international 
emissions in Section V.C.2. Kentucky in its SIP submission also argued 
that it had already implemented all cost-effective controls. However, 
the Commonwealth included an insufficient evaluation of additional 
emissions control opportunities to support such a conclusion.\129\ As 
explained in Section V.B.9., states may not rely on non-SIP measures to 
meet SIP requirements, and reliance on prior transport FIPs such as the 
CSAPR Update is not a sufficient analysis at Step 3.\130\ The EPA also 
confirmed in the proposed SIP submission disapproval that EGU shutdowns 
identified by Kentucky were included in the 2016v2 modeling, and yet 
Kentucky was still linked in that modeling.\131\ Kentucky in its SIP 
submission advocated for lower interstate ozone transport 
responsibility for states linked only to maintenance-only receptors. 
The EPA finds Kentucky's arguments in this regard inadequately 
supported.\132\ The Commonwealth included no permanent and enforceable 
emissions controls in its SIP submission.\133\ We provide further 
response to comments regarding Kentucky's SIP submission in the RTC 
document. The EPA is finalizing disapproval of Kentucky's interstate 
transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \124\ 87 FR 9498, 9503-9507 (February 22, 2022).
    \125\ Id. at 9509-9510.
    \126\ Id. at 9511-9515.
    \127\ Id. at 9512-9514.
    \128\ Id. at 9508, 9515. The state also did not explain its own 
views regarding the relevance of these materials to its submission. 
Id.
    \129\ Id. at 9511-9512.
    \130\ See also id. at. 9512.
    \131\ Id. at 9511-9512.
    \132\ Id. at 9514-9515.
    \133\ Id. at 9515.
---------------------------------------------------------------------------

G. Louisiana

    In the 2016v3 modeling, Louisiana is projected to be linked above 1 
percent of the NAAQS to two nonattainment receptors and five 
maintenance-only receptors. It is also linked to 10 violating-monitor 
maintenance-only receptor. Its highest-level contribution is 9.51 ppb 
to Galveston County Texas (AQS Site ID 481671034). A full summary of 
Louisiana's November 13, 2019, SIP submission was provided in the 
proposed SIP submission disapproval.\134\ The EPA disagrees with 
Louisiana's arguments for application of a higher contribution 
threshold than 1 percent of the NAAQS and disagrees with Louisiana's 
criticisms of a 1 percent of the NAAQS contribution threshold at Step 
2.\135\ The EPA further addresses technical comments on the 1 percent 
of the NAAQS contribution threshold in Section V.B.4. Louisiana did not 
conduct an adequate Step 3 analysis.\136\ The State included an 
insufficient evaluation of additional emissions control opportunities 
in its SIP submission.\137\ The EPA also found technical flaws in 
Louisiana's ``consistent and persistent'' claims, assessment of 
seasonal weather patterns, surface wind directions, and back trajectory 
analysis.\138\ The State included no permanent and enforceable controls 
in its SIP submission.\139\ We provide further response to comments 
regarding Louisiana's SIP submission in the RTC document. The EPA is 
finalizing disapproval of Louisiana's interstate transport SIP 
submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \134\ Id. at 9811-9812.
    \135\ Id. at 9812, 9815-9816.
    \136\ Id. at 9814-9816.
    \137\ Id. at 9814. 9816.
    \138\ Id. at 9814-9816.
    \139\ Id. at 9816.

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

[[Page 9357]]

H. Maryland

    In the 2016v3 modeling, Maryland is projected to be linked above 1 
percent of the NAAQS to three nonattainment receptors and one 
maintenance-only receptor. It is also linked to three violating-monitor 
maintenance receptors. Its highest-level contribution is 1.28 ppb to 
New Haven County, Connecticut (AQS Site ID 090099002). A full summary 
of Maryland's October 16, 2019, SIP submission was provided in the 
proposed SIP submission disapproval.\140\ The state did not conduct an 
adequate Step 3 analysis.\141\ The State included an insufficient 
evaluation of additional emissions control opportunities in its SIP 
submission.\142\ Further, as explained in Section V.B.9, states may not 
rely on non-SIP measures to meet SIP requirements, and reliance on 
prior transport FIPs such as the CSAPR Update is not a sufficient 
analysis at Step 3.\143\ The EPA also confirmed in the proposed SIP 
submission disapproval that state emissions controls and regulations 
identified by Maryland were generally included in the 2016v2 modeling, 
and yet Maryland was still linked in that modeling.\144\ The State 
included no permanent and enforceable controls in its SIP 
submission.\145\ We provide further response to comments regarding 
Maryland's SIP submission in the RTC document. The EPA is finalizing 
disapproval of Maryland's interstate transport SIP submission for the 
2015 ozone NAAQS.
---------------------------------------------------------------------------

    \140\ Id. at 9469.
    \141\ Id. at 9470-9473.
    \142\ Id. at 9471, 9473.
    \143\ See also id. at 9471, 9473 n.46, 9474.
    \144\ Id. at 9472-9473.
    \145\ Id. at 9473-9474.
---------------------------------------------------------------------------

I. Michigan

    In the 2016v3 modeling, Michigan is projected to be linked above 1 
percent of the NAAQS to four nonattainment receptors and six 
maintenance-only receptors. It is also linked to eight violating-
monitor maintenance receptors. Its highest-level contribution is 1.59 
to Sheboygan County, Wisconsin (AQS Site ID 551170006). A full summary 
of Michigan's March 5, 2019, SIP submission was provided in the 
proposed SIP submission disapproval.\146\ The EPA disagrees with 
Michigan's arguments for application of a higher contribution threshold 
than 1 percent of the NAAQS as well as criticisms of a 1 percent of the 
NAAQS contribution threshold at Step 2.\147\ The EPA further addresses 
technical comments on the 1 percent of the NAAQS contribution threshold 
in Section V.B.4 and addresses comments regarding the relevance of the 
PSD SILs in Section V.B.6. The State did not conduct an adequate Step 3 
analysis.\148\ Michigan argued in its SIP submission that additional 
controls would be premature and burdensome. However, the State included 
an insufficient evaluation of additional emissions control 
opportunities to support such a conclusion.\149\ The EPA found 
technical and legal flaws in Michigan's arguments related to upwind-
state obligations as to maintenance-only receptors, international 
emissions, relative contribution, apportionment, and upwind versus 
downwind-state responsibilities.\150\ The EPA further addresses the 
topics of mobile sources and international emissions in Sections V.C.1 
and V.C.2, respectively. The EPA also confirmed in the proposed SIP 
submission disapproval that the EGU retirements identified by Michigan 
as not included in the 2011-based EPA modeling, as well as various 
Federal rules, were included in the 2016v2 modeling, and yet Michigan 
was still linked in that modeling.\151\ The State included no permanent 
and enforceable emissions controls in its SIP submission.\152\ We 
provide further response to comments regarding Michigan's SIP 
submission in the RTC document. The EPA is finalizing disapproval of 
Michigan's interstate transport SIP submission for the 2015 ozone 
NAAQS.
---------------------------------------------------------------------------

    \146\ Id. at 9847-9848.
    \147\ Id. at 9861-9862.
    \148\ Id. at 9863-9867.
    \149\ Id. at 9864.
    \150\ Id. at 9864-9867.
    \151\ Id. at 9866.
    \152\ Id. at 9867.
---------------------------------------------------------------------------

J. Minnesota

    In the 2016v3 modeling, Minnesota is projected to be linked above 1 
percent of the NAAQS to one maintenance-only receptor. It is not linked 
to a violating-monitor maintenance-only receptor. Its highest-level 
contribution is 0.85 ppb to Cook County, Illinois (AQS Site ID 
170310001). A full summary of Minnesota's October 1, 2018, SIP 
submission was provided in the proposed SIP submission 
disapproval.\153\ Because Minnesota was not projected to be linked to 
any receptor in 2023 in the EPA's 2011-based modeling, comments argued 
that the EPA must approve the SIP submission and not rely on new 
modeling. The EPA responds to these comments in Section V.A.4. Although 
the EPA acknowledges that Minnesota's Step 3 analysis was insufficient 
in part because the State assumed it was not linked at Step 2, this is 
ultimately inadequate to support a conclusion that the State's sources 
do not interfere with maintenance of the 2015 ozone NAAQS in other 
states in light of more recent air quality analysis.\154\ The State 
included no permanent and enforceable emissions controls in its SIP 
submission.\155\ We provide further response to comments regarding 
Minnesota's SIP submission in the RTC document. Although EPA proposed 
to disapprove both prong 1 and prong 2 of Minnesota's SIP submission, 
the present record, including the results of the 2016v3 modeling, 
indicates that Minnesota is not linked to any nonattainment 
receptors.\156\ The EPA is finalizing a partial approval of Minnesota's 
interstate transport SIP submission for the 2015 ozone NAAQS as to 
prong 1 and a partial disapproval as to prong 2.
---------------------------------------------------------------------------

    \153\ Id. at 9867.
    \154\ Id. at 9868-9869.
    \155\ Id. at 9869.
    \156\ The EPA received a comment that it would be arbitrary and 
capricious for the EPA to finalize a full disapproval of Tennessee's 
good neighbor SIP submission (both prong 1 and prong 2) if EPA 
concluded the state is linked only to a maintenance-only receptor 
(prong 2). EPA is deferring final action on Tennessee's good 
neighbor SIP submission, but in reviewing linkages in the 2016v3 
modeling we determined that Minnesota and Wisconsin are not linked 
above 1 percent of the NAAQS to any nonattainment receptors (prong 
1) but are linked to maintenance-only receptors (prong 2); these 
states are receiving partial approvals and partial disapprovals.
---------------------------------------------------------------------------

K. Mississippi

    In the 2016v3 modeling, Mississippi is projected to be linked above 
1 percent of the NAAQS to one nonattainment receptor and two 
maintenance-only receptors. It is also linked to eight violating-
monitor maintenance receptors. Its highest-level contribution is 1.32 
ppb to Galveston County, Texas (AQS Site ID 481671034). A full summary 
of Mississippi's September 3, 2019, SIP submission was provided in the 
proposed SIP submission disapproval.\157\ In its submission, 
Mississippi advocated for discounting receptors through use of 
historical data trends. The EPA finds Mississippi's approach is not 
adequately justified.\158\ In the 2011-based modeling, Mississippi's 
contribution to receptors was above 1 percent of the NAAQS, but below 1 
ppb. The EPA disagrees with Mississippi's arguments for application of 
a higher contribution threshold than

[[Page 9358]]

1 percent of the NAAQS at Step 2,\159\ and further addresses the 
relevance of the PSD SILs in Section V.B.6. The state did not conduct a 
Step 3 analysis.\160\ The State included no evaluation of additional 
emissions control opportunities in its SIP submission.\161\ The State 
included no permanent and enforceable emissions controls in its SIP 
submission.\162\ We provide further response to comments regarding 
Mississippi's SIP submission in the RTC document. The EPA is finalizing 
disapproval of Mississippi's interstate transport SIP submission for 
the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \157\ 87 FR 9554.
    \158\ Id. at 9556.
    \159\ Id. at 9557.
    \160\ Id. at 9558.
    \161\ Id.
    \162\ Id.
---------------------------------------------------------------------------

L. Missouri

    In the 2016v3 modeling, Missouri is projected to be linked above 1 
percent of the NAAQS to one nonattainment receptor and three 
maintenance-only receptors. It is also linked to five violating-monitor 
maintenance receptors. Its highest-level contribution is 1.87 ppb to 
Sheboygan County, Wisconsin (AQS Site ID 551170006). A full summary of 
Missouri's June 10, 2019, SIP submission was provided in the proposed 
SIP submission disapproval.\163\ In its submission, Missouri advocated 
for discounting certain maintenance receptors through use of historical 
data trends. The EPA finds Missouri's approach is not adequately 
justified.\164\ The EPA disagrees with Missouri's arguments for 
application of a higher contribution threshold than 1 percent of the 
NAAQS at Step 2, and further addresses comments regarding the August 
2018 memorandum in Section V.B.7.\165\ The State did not conduct a Step 
3 analysis.\166\ The State included no evaluation of additional 
emissions control opportunities in its SIP submission.\167\ The State 
included no permanent and enforceable emissions controls in its SIP 
submission.\168\ We provide further response to comments regarding 
Missouri's SIP submission in the RTC document. The EPA is finalizing 
disapproval of Missouri's June 10, 2019, interstate transport SIP 
submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \163\ Id. at 9538-9540.
    \164\ Id. at 9540-9541.
    \165\ See also id. at 9541-9544.
    \166\ Id. at 9544.
    \167\ Id.
    \168\ We note that in comments, Missouri indicated its intent to 
submit a new SIP submission to the EPA, which would re-evaluate good 
neighbor obligations based on its 2016v2 linkages and provide an 
analysis that would include emissions reductions requirements. The 
EPA received this submission on November 1, 2022. The EPA explains 
its consideration of this new submission as separate SIP submission 
in the RTC document for this final action.
---------------------------------------------------------------------------

M. Nevada

    In the 2016v3 modeling, Nevada is projected to be linked above 1 
percent of the NAAQS to three nonattainment receptors and one 
maintenance-only receptor. It is also linked to one violating-monitor 
maintenance receptor. Its highest-level contribution is 1.13 ppb to 
Weber County, Utah (AQS Site ID 490570002). A full summary of Nevada's 
October 1, 2018, SIP submission was provided in the proposed SIP 
submission disapproval.\169\ Because Nevada was not projected to be 
linked to any receptor in 2023 in the EPA's 2011-based modeling, 
commenters on the proposed SIP submission disapproval argued that the 
EPA must approve the SIP submission and not rely on new modeling. The 
EPA responds to these comments in Section V.A.4. The EPA also responds 
to technical criticisms of the 1 percent of the NAAQS contribution 
threshold and the relevance of the PSD SILs in Section V.B.4 and in 
Section V.B.6, respectively. The State did not conduct a Step 3 
analysis.\170\ The State included no evaluation of additional emissions 
control opportunities in its SIP submission.\171\ The State included no 
additional emissions controls in its SIP submission.\172\ We provide 
response to comments specific to interstate transport policy in the 
western U.S. in Section V.C.3. We provide further response to comments 
regarding Nevada's SIP submission in the RTC document. The EPA is 
finalizing disapproval of Nevada's interstate transport SIP submission 
for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \169\ 87 FR 31485, 31492-31493 (May 24, 2022).
    \170\ Id. at 31493.
    \171\ Id.
    \172\ Id.
---------------------------------------------------------------------------

N. New Jersey

    In the 2016v3 modeling, New Jersey is projected to be linked above 
1 percent of the NAAQS to three nonattainment receptors and one 
maintenance-only receptor. It is also linked to three violating-monitor 
maintenance receptors. Its highest-level contribution is 8.38 ppb to 
Fairfield County, Connecticut (AQS Site ID 090019003). A full summary 
of New Jersey's May 13, 2019, SIP submission was provided in the 
proposed SIP submission disapproval.\173\ The State did not conduct an 
adequate Step 3 analysis.\174\ New Jersey argued in its SIP submission 
that existing controls were sufficient to address the State's good 
neighbor obligations. However, the State included an insufficient 
evaluation of additional emissions control opportunities to support 
such a conclusion.\175\ The State's reliance on the cost-effectiveness 
threshold in the CSAPR Update is insufficient for a more protective 
NAAQS.\176\ The State included no permanent and enforceable emissions 
controls in its SIP submission.\177\ We provide further response to 
comments regarding New Jersey's SIP submission in the RTC document. The 
EPA is finalizing disapproval of New Jersey's interstate transport SIP 
submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \173\ Id. at 9490-9491.
    \174\ Id. at 9496.
    \175\ Id.
    \176\ Id.
    \177\ Id. at 9496-9497.
---------------------------------------------------------------------------

O. New York

    In the 2016v3 modeling, New York is projected to be linked above 1 
percent of the NAAQS to three nonattainment receptors and one 
maintenance-only receptor. It is also linked to two violating-monitor 
maintenance receptors. Its highest-level contribution is 16.10 ppb to 
Fairfield County, Connecticut (AQS Site ID 090010017). A full summary 
of New York's September 25, 2018, SIP submission was provided in the 
proposed SIP submission disapproval.\178\ The state did not conduct an 
adequate Step 3 analysis.\179\ New York argued in its SIP submission 
that existing controls were sufficient to address the State's good 
neighbor obligations. However, the state included an insufficient 
evaluation of additional emissions control opportunities to support 
such a conclusion.\180\ The State's reliance on the cost-effectiveness 
threshold in the CSAPR Update is insufficient for the more protective 
2015 ozone NAAQS.\181\ The State included no permanent and enforceable 
emissions controls in its SIP submission.\182\ We provide further 
response to comments regarding New York's SIP submission in the RTC 
document. The EPA is finalizing disapproval of New York's interstate 
transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \178\ Id. at 9489-9490.
    \179\ Id. at 9492-9494.
    \180\ Id. at 9493.
    \181\ Id. at 9493-9494.
    \182\ Id. at 9494-9495.
---------------------------------------------------------------------------

P. Ohio

    In the 2016v3 modeling, Ohio is projected to be linked above 1 
percent of the NAAQS to four nonattainment receptors and five 
maintenance-only

[[Page 9359]]

receptors. It is also linked to nine violating-monitor maintenance 
receptors. Its highest-level contribution is 2.05 ppb to Fairfield 
County, Connecticut (AQS Site ID 090019003). A full summary of Ohio's 
September 28, 2018, SIP submission was provided in the proposed SIP 
submission disapproval.\183\ In its submission, Ohio advocated for use 
of the Texas Commission on Environmental Quality (TCEQ)'s definition of 
maintenance receptors. The EPA finds that TCEQ's definition is legally 
and technically flawed,\184\ and as a result Ohio's approach is also 
not adequately justified.\185\ The EPA further evaluates TCEQ's 
technical arguments in a TSD prepared by regional modeling staff.\186\ 
The EPA disagrees with Ohio's arguments for application of a higher 
contribution threshold than 1 percent of the NAAQS at Step 2.\187\ The 
EPA responds to technical criticisms of the 1 percent of the NAAQS 
contribution threshold in Section V.B.4. The State did not conduct an 
adequate Step 3 analysis.\188\ The State included an insufficient 
evaluation of additional emissions control opportunities in its SIP 
submission.\189\ The EPA found technical deficiencies in Ohio's 
unsubstantiated claims that emissions are overestimated.\190\ The EPA 
also confirmed in the proposed SIP submission disapproval that several 
EGU and non-EGUs identified by Ohio were included in the 2016v2 
modeling, and yet Ohio was still linked in that modeling.\191\ The EPA 
summarizes the emissions inventories used in the 2016v3 modeling in 
Section III.A. Further, as explained in Section V.B.9, states may not 
rely on non-SIP measures to meet SIP requirements, and reliance on 
prior transport FIPs such as the CSAPR Update is not a sufficient 
analysis at Step 3.\192\ The EPA finds legal flaws and deficiencies in 
Ohio's arguments related to upwind versus downwind-state 
responsibilities, the role of international emissions, relative 
contribution, and overcontrol.\193\ The EPA discusses international 
emissions in Section V.C.2. The EPA disagrees with Ohio's arguments 
related to mobile sources.\194\ We further address this topic in 
Section V.C.1. Ohio also argued in its SIP submission that it had 
already implemented all cost-effective controls. However, the state 
included no evaluation of additional emissions control opportunities to 
support such a claim.\195\ Further, the State's reliance on the cost-
effectiveness threshold in the CSAPR Update is insufficient for the 
more protective 2015 ozone NAAQS.\196\ The State included no permanent 
and enforceable emissions controls in its SIP submission.\197\ We 
provide further response to comments regarding Ohio's SIP submission in 
the RTC document. The EPA is finalizing disapproval of Ohio's 
interstate transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \183\ Id. at 9849-9851.
    \184\ Id. at 9826-9829.
    \185\ Id. at 9869-9870.
    \186\ 2015 8-Hour Ozone Transport SIP Proposal TSD, in Docket ID 
No. EPA-R06-OAR-2021-0801 (hereinafter Evaluation of TCEQ Modeling 
TSD).
    \187\ Id. at 9871.
    \188\ Id. at 9871-9875.
    \189\ Id. at 9871-9875.
    \190\ Id. at 9872.
    \191\ Id.
    \192\ See also id. at 9874-9875.
    \193\ Id. at 9873-9874.
    \194\ Id.
    \195\ Id. at 9872-9873.
    \196\ Id. at 9874.
    \197\ Id. at 9875.
---------------------------------------------------------------------------

Q. Oklahoma

    In the 2016v3 modeling, Oklahoma is projected to be linked above 1 
percent of the NAAQS to one nonattainment receptor and one maintenance-
only receptor. It is also linked to eight violating-monitor maintenance 
receptors. Its highest-level contribution is 1.01 ppb to Denton County, 
Texas (AQS Site ID 481210034). A full summary of Oklahoma's October 25, 
2018, SIP submission was provided in the proposed SIP submission 
disapproval.\198\ In its submission, Oklahoma advocated for use of 
TCEQ's definition of maintenance receptors and modeling to discount 
receptors in Texas. The EPA finds that TCEQ's definition is legally and 
technically flawed \199\ and, as a result, Oklahoma's approach is also 
not adequately justified.\200\ The EPA further evaluates TCEQ's 
technical arguments in the EPA Region 6 2015 8-Hour Ozone Transport SIP 
Proposal TSD (Evaluation of TCEQ Modeling TSD) prepared by regional 
modeling staff.\201\ Comments argued against the use of updated 
modeling where linkages in the EPA's 2011-based modeling and later 
iterations of EPA modeling differ. The EPA addressed the change in 
identified linkages between the 2011-based modeling and the 2016v2 
modeling in the proposed SIP disapproval,\202\ and further responds to 
comments on the use of updated modeling in Section V.A.4. The EPA 
disagrees with Oklahoma's arguments for application of a higher 
contribution threshold than 1 percent of the NAAQS at Step 2 \203\ and 
further addresses comments regarding the relevance of the PSD SILs in 
Section V.B.6. The State did not conduct an adequate Step 3 
analysis.\204\ Oklahoma argued in its SIP submission that it had 
already implemented all cost-effective controls. However, the State 
included an insufficient evaluation of additional emissions control 
opportunities to support such a conclusion.\205\ As explained in 
Section V.B.9, states may not rely on non-SIP measures to meet SIP 
requirements, and reliance on prior transport FIPs such as the CSAPR 
Update is not a sufficient analysis at Step 3.\206\ Further, the 
State's reliance on the cost-effectiveness threshold in the CSAPR 
Update is insufficient for the more protective 2015 ozone NAAQS.\207\ 
The EPA finds legal flaws in Oklahoma's argument related to collective 
contribution.\208\ The State included no permanent and enforceable 
emissions controls in its SIP submission.\209\ We provide further 
response to comments regarding Oklahoma's SIP submission in the RTC 
document. The EPA is finalizing disapproval of Oklahoma's interstate 
transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \198\ Id. at 9816-9818.
    \199\ Id. at 9826-9829.
    \200\ Id. at 9820-9822.
    \201\ Evaluation of TCEQ Modeling TSD in Docket ID No. EPA-R06-
OAR-2021-0801.
    \202\ 87 FR 9823.
    \203\ Id. at 9819.
    \204\ Id. at 9822-9824.
    \205\ Id. at 9822-9824.
    \206\ See also id. at. 9822-9823.
    \207\ Id.
    \208\ Id. at 9823.
    \209\ Id. at 9824.
---------------------------------------------------------------------------

R. Texas

    In the 2016v3 modeling, Texas is projected to be linked above 1 
percent of the NAAQS to one nonattainment receptor and nine 
maintenance-only receptors. It is also linked to ten violating-monitor 
maintenance-only receptor. Its highest-level contribution is 4.74 ppb 
to Dona Ana County, New Mexico (AQS Site ID 350130021). A full summary 
of Texas's August 17, 2018, SIP submission was provided in the proposed 
SIP submission disapproval,\210\ and additional details were provided 
in the Evaluation of TCEQ Modeling TSD. The EPA identified several 
technical flaws in TCEQ's modeling and analysis of modeling 
results.\211\ In its submission, Texas advocated for use of its own 
definition of maintenance receptors and modeling. The EPA finds Texas's 
approach inadequately justified and

[[Page 9360]]

legally and technically flawed.\212\ The EPA further evaluated TCEQ's 
technical arguments in the Evaluation of TCEQ Modeling TSD. In comment 
on the proposal, Texas pointed to differences in linkages in the EPA's 
2011-based modeling and 2016v2 modeling. The EPA addressed the change 
in identified linkages between the 2011-based modeling and the 2016v2 
modeling in the proposed SIP submission disapproval,\213\ and further 
responds to comments on the use of updated modeling in Section V.A.4. 
The State did not conduct an adequate Step 3 analysis.\214\ The State 
included an insufficient evaluation of additional emissions control 
opportunities in its SIP submission.\215\ The EPA found technical flaws 
in Texas's arguments related to ``consistent and persistent'' claims 
and its other assessments, including analysis of back 
trajectories.\216\ The State included no permanent and enforceable 
emissions controls in its SIP submission.\217\ We provide further 
response to comments regarding Texas's SIP submission in the RTC 
document. The EPA is finalizing disapproval of Texas's interstate 
transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \210\ Id. at 9824-9826.
    \211\ Id. at 9829-9830; Evaluation of TCEQ Modeling TSD.
    \212\ 87 FR 9826-9829.
    \213\ Id. at 9831.
    \214\ Id. at 9831-9834.
    \215\ Id. at 9831, 9834.
    \216\ Id. at 9832-9833, Evaluation of TCEQ Modeling TSD.
    \217\ 87 FR 9834.
---------------------------------------------------------------------------

S. Utah

    In the 2016v3 modeling, Utah is projected to be linked above 1 
percent of the NAAQS to three nonattainment receptors and one 
maintenance-only receptor. It is also linked to four violating-monitor 
maintenance receptors. Its highest-level contribution is 1.29 ppb to 
Douglas County, Colorado (AQS Site ID 080350004). A full summary of 
Utah's January 29, 2020, SIP submission was provided in the proposed 
SIP submission disapproval.\218\ In its submission, Utah argued that 
certain receptors in Colorado should not be counted as receptors for 
the purpose of 2015 ozone NAAQS interstate transport, but Utah's 
explanation is insufficient to discount those receptors.\219\ The EPA 
disagrees with Utah's arguments for application of a higher 
contribution threshold than 1 percent of the NAAQS at Step 2.\220\ Utah 
suggested in its SIP submission that interstate transport is 
fundamentally different in the western U.S. than in the eastern U.S., 
an argument we have previously rejected and respond to further in 
Section V.C.3.\221\ The State did not conduct an adequate Step 3 
analysis.\222\ The State included an insufficient evaluation of 
additional emissions control opportunities in its SIP submission.\223\ 
The EPA finds technical and legal flaws in the State's arguments 
related to relative contribution, international and non-anthropogenic 
emissions, and the relationship of upwind versus downwind-state 
responsibilities.\224\ The EPA further addresses the topics of 
international emissions in Section V.C.2 and wildfires in the RTC 
document. The EPA also confirmed in the proposed SIP submission 
disapproval that several anticipated controls identified by Utah were 
included in the 2016v2 modeling, and yet Utah was still linked in that 
modeling.\225\ The State included no permanent and enforceable 
emissions controls in its SIP submission.\226\ We provide further 
response to comments regarding Utah's SIP submission in the RTC 
document. The EPA is finalizing disapproval of Utah's interstate 
transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \218\ Id. at 31475-31477.
    \219\ Id. at 31480-31481.
    \220\ Id. at 31478.
    \221\ See also id. at 31479-31481, 31482.
    \222\ Id. at 31481-31483.
    \223\ Id. at 31482
    \224\ Id. at 31481-31483.
    \225\ Id. at 31483.
    \226\ Id.
---------------------------------------------------------------------------

T. West Virginia

    In the 2016v3 modeling, West Virginia is projected to be linked 
above 1 percent of the NAAQS to three nonattainment receptors and one 
maintenance-only receptor. It is also linked to four violating-monitor 
maintenance receptors. Its highest-level contribution is 1.49 ppb to 
New Haven County, Connecticut (AQS Site ID 090099002). A full summary 
of West Virginia's February 4, 2019, SIP submission was provided in the 
proposed SIP submission disapproval.\227\ The EPA finds technical and 
legal flaws in the State's examination of back trajectories and 
arguments related to mobile sources and international emissions.\228\ 
The EPA further addresses the topics of mobile sources and 
international emissions in Section V.C.1 and in Section V.C.2, 
respectively. The State did not conduct an adequate Step 3 
analysis.\229\ West Virginia argued in its SIP submission that it had 
already implemented all cost-effective controls. However, the State 
included an insufficient evaluation of additional emissions control 
opportunities to support such a conclusion.\230\ The EPA also confirmed 
in the proposed SIP submission disapproval that specific EGU shutdowns 
identified by West Virginia were included in the 2016v2 modeling, which 
continued to show West Virginia was linked at Step 2.\231\ As explained 
in Section V.B.9, a state may not rely on non-SIP measures to satisfy 
SIP requirements, and reliance on prior transport FIPs such as the 
CSAPR Update is not a sufficient analysis at Step 3.\232\ Further, the 
State's reliance on the cost-effectiveness threshold in the CSAPR 
Update is insufficient for a more protective NAAQS.\233\ The State 
included no permanent and enforceable emissions controls in its SIP 
submission.\234\ We provide further response to comments regarding West 
Virginia's SIP submission in the RTC document. The EPA is finalizing 
disapproval of West Virginia's interstate transport SIP submission for 
the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \227\ Id. at 9522-9524.
    \228\ Id. at 9526-9527, 9528.
    \229\ Id. at 9527-9532.
    \230\ Id. at 9528-9529.
    \231\ Id. at 9529-9530.
    \232\ See also id. at 9530-9532.
    \233\ Id. at 9531.
    \234\ Id. at 9532.
---------------------------------------------------------------------------

U. Wisconsin

    In the 2016v3 modeling, Wisconsin is projected to be linked above 1 
percent of the NAAQS to three maintenance-only receptors. It is also 
linked to five violating-monitor maintenance receptors. Its highest-
level contribution is 2.86 ppb to Cook County, Illinois (AQS Site ID 
170314201). A full summary of Wisconsin's September 14, 2018, SIP 
submission was provided in the proposed SIP submission 
disapproval.\235\ The State did not assess in its SIP submission 
whether the state was linked at Step 2,\236\ and did not conduct an 
adequate Step 3 analysis.\237\ The State included an insufficient 
evaluation of additional emissions control opportunities.\238\ Further, 
as explained in Section V.B.9, reliance on prior transport FIPs such as 
the CSAPR Update is not a sufficient analysis at Step 3.\239\ The EPA 
found additional inadequacies and legal flaws in Wisconsin's 
submission.\240\ The State included no permanent and enforceable 
emissions controls in its SIP submission.\241\ We provide further 
response to comments regarding

[[Page 9361]]

Wisconsin's SIP submission in the RTC document. Although EPA proposed 
to disapprove both prong 1 and prong 2 of Wisconsin's SIP submission, 
the present record, including the results of the 2016v3 modeling, 
indicates that Wisconsin is not linked to any nonattainment 
receptors.\242\ The EPA is finalizing a partial approval of Wisconsin's 
interstate transport SIP submission for the 2015 ozone NAAQS as to 
prong 1 and a partial disapproval as to prong 2.
---------------------------------------------------------------------------

    \235\ Id. at 9851.
    \236\ Id. at 9875.
    \237\ Id. at 9875-9876.
    \238\ Id. at 9876.
    \239\ See also id.
    \240\ Id.
    \241\ Id. at 9876-9877.
    \242\ The EPA received a comment that it would be arbitrary and 
capricious for the EPA to finalize a full disapproval of Tennessee's 
good neighbor SIP submission (both prong 1 and prong 2) if EPA 
concluded the State is linked only to a maintenance-only receptor 
(prong 2).The EPA is deferring final action on Tennessee's good 
neighbor SIP submission, but in reviewing linkages in the 2016v3 
modeling we determined that Minnesota and Wisconsin are not linked 
above 1 percent of the NAAQS to any nonattainment receptors (prong 
1) but are linked to maintenance-only receptors (prong 2); these 
States are receiving partial approvals and partial disapprovals.
---------------------------------------------------------------------------

V. Response to Key Comments

    The EPA received numerous comments on the proposed action which are 
summarized in the RTC document along with the EPA's responses to those 
comments in Docket ID No. EPA-HQ-OAR-2021-0663. Each comment in its 
entirety is available in the relevant regional docket(s) for this 
action.\243\ The following sections summarize key comments and the 
EPA's responses.
---------------------------------------------------------------------------

    \243\ 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, for a list 
of all regional dockets.
---------------------------------------------------------------------------

A. SIP Evaluation Process

1. Relationship Between Timing of Proposals To Disapprove SIPs and 
Promulgate FIPs
    Comment: Comments alleged generally that the timing of the EPA's 
proposed actions on the SIP submissions in relation to proposed FIPs 
was unlawful, unfair, or both. Some comments claimed that the sequence 
of the EPA's actions is improper, unreasonable, or bad policy. Several 
commenters asserted that because the EPA proposed FIPs (or, according 
to some, promulgated FIPs, which is not factually correct) prior to 
finalizing disapproval of the state SIP submission, the EPA allegedly 
exceeded its statutory authority and overstepped the states' primary 
role in addressing the good neighbor provision under CAA section 
110.\244\
---------------------------------------------------------------------------

    \244\ The EPA notes the commenters' reference to FIPs is to 
proposed good neighbor FIPs for the 2015 ozone NAAQS that were 
proposed separately from this rulemaking action. 87 FR 20036 (April 
6, 2022).
---------------------------------------------------------------------------

    EPA Response: The EPA disagrees. The EPA has followed the Clean Air 
Act provisions, which prescribe specified maximum amounts of time for 
states to make SIP submissions, for the EPA to act on those 
submissions, and for the EPA to promulgate FIPs if necessary, but do 
not prohibit the EPA from acting before that time elapses. Nothing 
relieves the EPA from its statutory obligation to take final action on 
complete SIP submissions before the Agency within the timeframes 
prescribed by the statute.\245\ The EPA's proposed FIP does not 
constitute the ``promulgation'' of a FIP because the proposed FIP is 
not a final action that imposes any requirements on sources or states. 
And although the EPA's FIP authority is not at issue in this action, 
the EPA notes the Agency has been clear that it will not finalize a FIP 
for any state until predicate authority is established for doing so 
under CAA section 110(c)(1). 87 FR 20036, 20057 (April 6, 2022) (``The 
EPA is proposing this FIP action now to address twenty-six states' good 
neighbor obligations for the 2015 ozone NAAQS, but the EPA will not 
finalize this FIP action for any state unless and until it has issued a 
final finding of failure to submit or a final disapproval of that 
state's SIP submission.''). The EPA strongly disagrees that proposing a 
FIP prior to proposing or finalizing disapproval of a SIP submission 
oversteps the Agency's authority. Indeed, the ability to propose a FIP 
before finalizing a SIP disapproval follows ineluctably from the 
structure of the statute, which, as the Supreme Court recognized in EME 
Homer City, does not oblige the EPA ``to wait two years or postpone its 
[FIP] action even a single day.'' 572 U.S. at 509. If the EPA can 
finalize a FIP immediately upon disapproving a SIP, then surely the EPA 
must have the authority to propose that FIP before taking final action 
on the SIP submission. Accord Oklahoma v. U.S. EPA, 723 F.3d 1201, 1223 
(10th Cir. 2013).
---------------------------------------------------------------------------

    \245\ Although the EPA anticipates responding to comments 
related to the EPA's FIP authority in a separate FIP rulemaking, the 
EPA notes with regard to the procedural timing concerns raised in 
comments on this action that the Supreme Court confirmed in EME 
Homer City Generation, ``EPA is not obliged to wait two years or 
postpone its action even a single day: The Act empowers the Agency 
to promulgate a FIP `at any time' within the two[hyphen]year 
limit.'' 572 U.S. 489 at 509. The procedural timeframes under CAA 
section 110 do not function to establish a norm or expectation that 
the EPA must or should use the full amount of time allotted, 
particularly when doing so would place the Agency in conflict with 
the more ``central'' statutory objective of meeting the NAAQS 
attainment deadlines in the Act. EME Homer City, 572 U.S. 489, 509 
(2014). See also Wisconsin, 938 F.3d at 318, 322; Sierra Club v. 
EPA, 294 F.3d 155, 161 (D.C. Cir. 2002) (Sierra Club).
---------------------------------------------------------------------------

    It is true that the EPA would not be legally authorized to finalize 
a FIP for any state unless and until the EPA formally finalizes a 
disapproval of that state's SIP submission (or makes a finding of 
failure to submit for any state that fails to make a complete SIP 
submission), per CAA section 110(c), but the EPA has not yet finalized 
a FIP for any state for good neighbor obligations for the 2015 ozone 
NAAQS. Further, the sequencing of our actions here is consistent with 
the EPA's past practice in our efforts to timely address good neighbor 
obligations. For example, at the time the EPA proposed the CSAPR Update 
FIPs in December of 2015, we had not yet proposed action on several 
states' SIP submissions but finalized those SIP disapproval actions 
prior to finalization of the FIP.\246\
---------------------------------------------------------------------------

    \246\ The proposed CSAPR Update was published on December 3, 
2015, and included proposed FIPs for Indiana, Louisiana, New York, 
Ohio, Texas, and Wisconsin. 80 FR 75705. At that time, the EPA had 
not yet even proposed action on good neighbor SIP submissions for 
the 2008 ozone NAAQS from Indiana, Louisiana, New York, Ohio, Texas, 
and Wisconsin; however, the EPA subsequently proposed and finalized 
these disapprovals before finalizing the CSAPR Update FIPs, 
published on October 26, 2016 (81 FR 74504). See 81 FR 38957 (June 
15, 2016) (Indiana); 81 FR 53308 (August 12, 2016) (Louisiana); 81 
FR 58849 (August 26, 2016) (New York); 81 FR 38957 (June 15, 2016) 
(Ohio); 81 FR 53284 (August 12, 2016) (Texas); 81 FR 53309 (August 
12, 2016) (Wisconsin).
---------------------------------------------------------------------------

    Additional comments on cooperative federalism are addressed in 
Section V.B.5.
    Further, The D.C. Circuit in Wisconsin held that states and the EPA 
are obligated to fully address good neighbor obligations for ozone ``as 
expeditiously as practical'' and in no event later than the next 
relevant downwind attainment dates found in CAA section 181(a),\247\ 
and states and the EPA may not delay implementation of measures 
necessary to address good neighbor requirements beyond the next 
applicable attainment date without a showing of impossibility or 
necessity.\248\ It is important for the states and the EPA to assure 
that necessary emissions reductions are achieved, to the extent 
feasible, by the 2023 ozone season to assist downwind areas with 
meeting the August 3, 2024, attainment deadline for Moderate 
nonattainment areas. Further, the D.C. Circuit in Wisconsin emphasized 
that the EPA has the authority under CAA section 110 to structure its 
actions so as to ensure necessary reductions are achieved by the 
downwind attainment

[[Page 9362]]

dates,\249\ the next of which for the 2015 ozone NAAQS is now the 
Moderate area attainment date of August 3, 2024.\250\ The court pointed 
out that the CAA section 110 schedule of SIP and FIP deadlines is 
procedural whereas the attainment schedule is ``central to the 
regulatory scheme[.]'' \251\ Thus, the sequence and timing of the EPA's 
action in disapproving these SIP submissions is informed by the need to 
ensure that any necessary good neighbor obligations identified in the 
separate FIP rulemaking are implemented as expeditiously as practicable 
and no later than the next attainment date. As explained in our 
proposed disapproval, analysis (and, if possible, implementation) of 
good neighbor obligations should begin in the 2023 ozone season. See, 
e.g., 87 FR 9798, 9801-02 (Feb. 22, 2022). Indeed, states' and the 
EPA's analysis would have been more appropriately aligned with 2020, 
rather than 2023 (as had been presented in the EPA's March 2018 
memorandum \252\), corresponding with the 2021 Marginal area attainment 
date. However, that clarification in legal obligations was not 
established by case law until 2020. See Maryland, 958 F.3d at 1203-04.
---------------------------------------------------------------------------

    \247\ Wisconsin, 938 F.3d at 313-14 (citing North Carolina, 531 
F.3d at 911-12.
    \248\ See Wisconsin, 938 F.3d at 320.
    \249\ Wisconsin, 938 F.3d at 318 (``When EPA determines a 
State's SIP is inadequate, the EPA presumably must issue a FIP that 
will bring that State into compliance before upcoming attainment 
deadlines, even if the outer limit of the statutory timeframe gives 
the EPA more time to formulate the FIP.'') (citing Sierra Club, 294 
F.3d at 161).
    \250\ 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).
    \251\ Wisconsin, 938 F.3d at 322 (``Delaware's argument leans 
too heavily on the SIP submission deadline. SIP submission 
deadlines, unlike attainment deadlines, are `procedural' and, 
therefore, not `central to the regulatory scheme.' '') (citing 
Sierra Club, 294 F.3d at 161).
    \252\ See March 2018 memorandum.
---------------------------------------------------------------------------

    In short, nothing in the language of CAA section 110(c) prohibits 
the EPA from proposing a FIP as a backstop, to be finalized and 
implemented only in the event that a SIP submission is first found to 
be deficient and final disapproval action on the SIP submission is 
taken. Such an approach is a reasonable and prudent means of assuring 
that the statutory obligation to reduce air pollution affecting the 
health and welfare of those living in downwind states is implemented 
without delay, either via a SIP, or where such plan is deficient, via a 
FIP. The sequencing of the EPA's actions here is therefore reasonably 
informed by its legal obligations under the CAA, including in 
recognition of the fact that the implementation of necessary emissions 
reductions to eliminate significant contribution and thereby protect 
human health and welfare is already several years delayed. The EPA 
shares additional responses related to the timing of 2015 ozone NAAQS 
good neighbor actions in Section V.A.
    Comment: Some comments allege the EPA is depriving States of the 
opportunity to target specific emissions reductions opportunities, or 
the opportunity to revise their submissions at any point in the future.
    EPA Response: The EPA disagrees. The EPA has repeatedly emphasized 
that states have the freedom at any time to develop a revised SIP 
submission and submit that to the EPA for approval, and this remains 
true. See 87 FR 20036, 20051 (April 6, 2022); 86 FR 23054, 23062 (April 
30, 2021); 81 FR 74504, 74506 (Oct. 26, 2016). In the proposed FIPs, as 
in prior transport actions, the EPA discusses a number of ways in which 
states could take over or replace a FIP, see 87 FR 20036, 20149-51 
(Section VII.D: ``Submitting A SIP''); see also id. at 20040 (noting as 
one purpose in proposing the FIP that ``this proposal will provide 
states with as much information as the EPA can supply at this time to 
support their ability to submit SIP revisions to achieve the emissions 
reductions the EPA believes necessary to eliminate significant 
contribution''). If, and when, the EPA receives a SIP submission that 
satisfies the requirements of CAA section 110(a)(2)(D)(i)(I), the 
Agency will take action to approve that SIP submission.
    Comment: Some commenters assert that the EPA is disapproving SIP 
submissions for the sole purpose of pursuing an alleged objective of 
establishing nation-wide standards in FIPs. Other commenters point to 
the proposed FIPs to make arguments that the EPA's decision to finalize 
disapproval of the SIPs is an allegedly foregone conclusion or that the 
EPA has allegedly failed to provide the opportunity for meaningful 
public engagement on the proposed disapproval of the SIPs.
    EPA Response: The EPA disagrees as the facts do not support this 
assertion. To date, the EPA has approved 24 good neighbor SIPs for the 
2015 ozone NAAQS: Alaska,\253\ Colorado,\254\ Connecticut,\255\ 
Delaware,\256\ District of Columbia,\257\ Florida,\258\ Georgia,\259\ 
Hawaii,\260\ Idaho,\261\ Iowa,\262\ Kansas,\263\ Maine,\264\ 
Massachusetts,\265\ Montana,\266\ Nebraska,\267\ New Hampshire,\268\ 
North Carolina,\269\ North Dakota,\270\ Oregon,\271\ Rhode Island,\272\ 
South Carolina,\273\ South Dakota,\274\ Vermont,\275\ and 
Washington.\276\
---------------------------------------------------------------------------

    \253\ 84 FR 69331 (December 18, 2019).
    \254\ 87 FR 61249 (October 11, 2022).
    \255\ 86 FR 71830 (December 20, 2021).
    \256\ 85 FR 25307 (May 1, 2020).
    \257\ 85 FR 5570 (January 31, 2020).
    \258\ 86 FR 68413 (December 2, 2021).
    \259\ Id.
    \260\ 86 FR 73129 (December 27, 2021).
    \261\ 85 FR 65722 (October 16, 2020).
    \262\ 87 FR 22463 (April 15, 2022).
    \263\ 87 FR 19390 (April 4, 2022).
    \264\ 86 FR 45870 (August 17, 2021).
    \265\ 85 FR 5572 (January 31, 2020).
    \266\ 87 FR 21578 (April 12, 2022).
    \267\ 85 FR 21325 (April 17, 2020).
    \268\ 86 FR 45870 (August 17, 2021).
    \269\ 86 FR 68413 (December 2, 2021).
    \270\ 85 FR 20165 (April 10, 2020).
    \271\ 84 FR 22376 (May 17, 2019).
    \272\ 86 FR 70409 (December 10, 2021).
    \273\ 86 FR 68413 (December 2, 2021).
    \274\ 85 FR 67653 (October 26, 2020).
    \275\ 85 FR 34357 (June 4, 2020).
    \276\ 83 FR 47568 (September 20, 2018).
---------------------------------------------------------------------------

    The policy judgments made by the EPA in all actions on 2015 ozone 
NAAQS good neighbor SIP submissions, including approval actions, 
reflect consistency with relevant good neighbor case law and past 
agency practice implementing the good neighbor provision as reflected 
in the original CSAPR, CSAPR Update, Revised CSAPR Update, 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 
dating back to the NOX SIP Call [63 FR 57356 (October 27, 
1998)] have necessitated the application of a uniform framework of 
policy judgments to ensure an ``efficient and equitable'' approach. See 
EME Homer City, 572 U.S. at 519. In any case, the approach of the 
proposed transport FIP is not the subject of this SIP disapproval. This 
rulemaking does not impose any specific emissions control measures on 
the states. Nor is the EPA disapproving these SIP submittals because 
they did not follow exactly the control strategies in the proposed 
FIP--the EPA has repeatedly indicated openness to alternative 
approaches to addressing interstate pollution obligations, but for 
reasons explained elsewhere in the rulemaking record, the EPA finds 
that none of the states included in this action submitted approvable 
approaches to addressing those obligations.
    The EPA disputes the contentions that the FIP proposal itself 
indicates that the EPA did not earnestly examine the SIP submissions 
for compliance with the CAA or have an appropriate rationale

[[Page 9363]]

for proposing to disapprove certain SIP submissions. The EPA also 
disputes that the FIP proposal indicates that the EPA did not intend to 
consider comments on the proposed disapprovals. Comments making claims 
the EPA did not follow proper administrative procedure have been 
submitted utilizing the very notice and comment process these comments 
claim the EPA is skipping, and these claims are factually unsupported. 
Comments related to the length of the comment period and claims of 
``pretext'' are addressed in the RTC document.
    Comment: Several comments pointed out how hard many states have 
worked to develop an approvable SIP submission.
    EPA Response: The EPA acknowledges and appreciates states' efforts 
to develop approvable SIPs. Cooperative federalism is a cornerstone of 
CAA section 110, and the EPA strives to collaborate with its state 
partners. The timing of the EPA's 2015 ozone NAAQS good neighbor 
actions is not in any way intended to call into question any state's 
commitment to develop approvable SIPs. The EPA evaluated each SIP 
submission on its merits. The EPA relies on collaboration with state 
air agencies to ensure SIP submissions are technically and legally 
defensible, and the Agency's action here is in no way meant to 
undermine that collaboration between state and Federal partners 
respecting SIP development.
    Comment: Several comments make various arguments about when the EPA 
can finalize FIPs. Some commenters argue that CAA section 110(c)(1) 
guarantees states an additional two years to correct their SIP 
submissions before the EPA finalizes a FIP. Others argue that the 
notice and comment requirements of the Administrative Procedures Act 
mandate that the EPA finalize a SIP submission disapproval before 
proposing a FIP. One commenter suggested that a state must be allowed 
to fully exhaust its judicial remedies to challenge a SIP submission 
disapproval before the EPA can promulgate a FIP. Commenters also raise 
concerns about the analysis and requirements in the proposed FIPs.
    EPA Response: Comments opining on when the EPA is legally 
authorized to propose or finalize a FIP are outside the scope of this 
action. While the EPA acknowledges that the Agency has no obligation or 
authority to finalize a FIP until finalizing a disapproval of a SIP 
submission or determining that a state failed to submit a complete SIP 
submission (CAA section 110(c)(1)), this action is limited to 
determining whether the covered SIP submissions meet the requirements 
of CAA section 110(a)(2)(D)(i)(I). For the same reason, comments 
criticizing specific substantive requirements or implementation 
timelines in the proposed FIPs are beyond the scope of this action.
2. Requests for Additional Time To Revise SIP Submissions
    Comment: Some commenters argue that the EPA must or should delay 
action on these SIP submissions so that states can reexamine and 
resubmit SIP submissions. Other commenters argue that states must be 
given more time to re-examine and resubmit their SIP submission for 
various reasons, including the substantive requirements in the proposed 
FIPs.
    EPA Response: The EPA notes that there is no support in the Clean 
Air Act for such a delay. CAA section 110(a)(1) requires states to 
adopt and submit SIP submissions meeting certain requirements including 
the requirements of CAA section 110(a)(2)(D)(i)(I), ``within 3 years 
(or such shorter period as the Administrator prescribe) after the 
promulgation of a national primary ambient air quality standard (or any 
revision thereof).'' CAA section 110(a)(1). The submission deadline 
clearly runs from the date of promulgation of the NAAQS, which for the 
2015 ozone NAAQS was October 1, 2015. 80 FR 65291 (Oct. 26, 2015). In 
addition, while the Administrator is given authority to prescribe a 
period shorter than three years for the states to adopt and submit such 
SIP submissions, the Act does not give the Administrator authority to 
lengthen the time allowed for CAA section 110(a)(2) submissions. And 
the EPA would be in violation of court-ordered deadlines if it deferred 
taking final action beyond January 31, 2023, for all but two of the 
states covered by this action.\277\
---------------------------------------------------------------------------

    \277\ The EPA has no court-ordered deadline to take final action 
on the good neighbor SIP submission from Alabama dated June 21, 
2022, or Utah's good neighbor SIP submission.
---------------------------------------------------------------------------

    Comments asserting that the EPA must give more time to states to 
correct deficiencies and re-submit conflict with the controlling 
caselaw in that they would elevate the maximum timeframes allowable 
within the procedural framework of CAA section 110 over the attainment 
schedule of CAA section 181 that the D.C. Circuit has now held multiple 
times must be the animating focus in the timing of good neighbor 
obligations. The D.C. Circuit in Wisconsin held that states and the EPA 
are obligated to fully address good neighbor obligations for ozone ``as 
expeditiously as practical'' and in no event later than the next 
relevant downwind attainment dates found in CAA section 181(a),\278\ 
and the EPA may not delay implementation of measures necessary to 
address good neighbor requirements beyond the next applicable 
attainment date without a showing of impossibility or necessity.\279\ 
Further, the court pointed out that the CAA section 110 schedule of SIP 
and FIP deadlines is procedural, and while the EPA has complied with 
the mandatory sequence of actions required under section 110 here, we 
are mindful of the court's observation that, as compared with the 
fundamental substantive obligations of title I of the CAA to attain and 
maintain the NAAQS, the maximum timeframes allotted under section 110 
are less ``central to the regulatory scheme[.]'' \280\
---------------------------------------------------------------------------

    \278\ Wisconsin, 938 F.3d at 313-14 (citing North Carolina, 531 
F.3d at 911-12). On May 19, 2020, the D.C. Circuit in Maryland, 
applying the Wisconsin decision, held that the EPA must assess 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, 958 F.3d at 1203-
04.
    \279\ See Wisconsin, 938 F.3d at 320.
    \280\ Wisconsin, 938 F.3d at 322 (``Delaware's argument leans 
too heavily on the SIP submission deadline. SIP submission 
deadlines, unlike attainment deadlines, are `procedural' and 
therefore not `central to the regulatory scheme.''') (citing Sierra 
Club, 294 F.3d at 161).
---------------------------------------------------------------------------

    Comment: Other comments take the position that states are owed a 
second opportunity to submit SIP submissions before the EPA takes final 
action for various reasons, including claims that the EPA failed to 
issue adequate guidance or is otherwise walking back previously issued 
guidance. They allege that a state cannot choose controls to eliminate 
significant contribution until the EPA quantifies the contribution. 
Other comments argue that the EPA should not or cannot base the 
disapprovals on alleged shifts in policy that occurred after the Agency 
received the SIP submissions.
    EPA Response: The EPA disagrees that the Agency was required to 
issue guidance or quantify individual states' level of significant 
contribution for 2015 ozone NAAQS good neighbor obligations, because as 
noted in EME Homer City, the Supreme Court clearly held that ``nothing 
in the statute places EPA under an obligation to provide specific 
metrics to States before they undertake to fulfill their good neighbor 
obligations.'' \281\ The Agency issued three memoranda in 2018 to 
provide modeling results and some ideas to states in the development of 
their SIP submissions. However, certain aspects of those discussions 
were specifically

[[Page 9364]]

identified as not constituting agency guidance (especially Attachment A 
to the March 2018 memorandum, which comprised an unvetted list of 
outside stakeholders' ideas). Further, states' submissions did not meet 
the terms of the August or October 2018 memoranda addressing 
contribution thresholds and maintenance receptors, respectively. (See 
Section V.B for further discussion of these memoranda.) We acknowledge 
that the EPA reassessed air quality and states' contribution levels 
through additional modeling before proposing action on these SIP 
submissions. But that is not in any way an effort to circumvent the 
SIP/FIP process; rather it is an outcome of the reality that the EPA 
updated its modeling platform from a 2011 to a 2016 base year and 
updated its emissions inventory information along with other updates. 
There is nothing improper in the Agency improving its understanding of 
a situation before taking action, and the Agency reasonably must be 
able to act on SIP submissions using the information available at the 
time it takes such action. Those updates have not uniformly been used 
to disapprove SIPs--the new modeling for instance supported the 
approval of Montana's and Colorado's SIPs.\282\ Nor has the new 
modeling prevented states from submitting new SIP submissions based on 
that modeling. For instance, the State of Alabama withdrew its prior 
submission in April of 2022, following our proposed disapproval, and 
submitted a new submission (further updated in June of 2022) analyzing 
the 2016v2 modeling used at proposal. The EPA is acting on that new 
submission and evaluating the new arguments the State developed 
regarding the more recent modeling. Nonetheless, as explained in the 
EPA's proposed disapproval of Alabama's new submission and in Section 
IV.A, the new arguments that Alabama has presented in its more recent 
submission do not lead the EPA to a contrary conclusion that its SIP 
submission should be approved.\283\ This demonstrates two points 
contrary to commenters' contentions: first, the EPA is following the 
science and is making nationally consistent determinations at Steps 1 
and 2, based on its review of each state's submission; and second, the 
fact that states made submissions based on the 2011-based modeling 
results presented in the March 2018 memorandum rather than on the most 
recent modeling results is not prejudicial to the outcome of the EPA's 
analysis, as our action on Alabama's more recent submission evaluating 
the State's arguments with respect to the newer, 2016-based modeling 
makes clear.
---------------------------------------------------------------------------

    \281\ EME Homer City, 572 U.S. at 510.
    \282\ 87 FR 6095, 6097 at n. 15 (February 3, 2022) (Montana 
proposal); 87 FR 27050, 27056 (May 6, 2022) (Colorado, proposal), 87 
FR 61249 (October 11, 2022) (Colorado, final).
    \283\ 87 FR 64412 (October 25, 2022).
---------------------------------------------------------------------------

    Contrary to commenters' arguments, the EPA had no obligation to 
issue further guidance, define obligations, or otherwise clarify or 
attempt to interpret states' responsibilities since the issuance of the 
2018 memoranda, prior to acting on these SIP submissions. States 
themselves were aware or should have been aware of the case law 
developments in Wisconsin and in Maryland, which called into question 
the EPA's use of 2023 as the analytical year in the March 2018 
memorandum. Those decisions were issued in 2019 and 2020 respectively, 
yet no state moved to amend or supplement their SIP submissions with 
analysis of an earlier analytical year or to otherwise bring their 
analyses into conformance with those decisions (e.g., through fuller 
analysis of non-EGU emissions reduction potential or through treatment 
of international contribution). Given the Supreme Court's 2014 holding 
in EME Homer City, 572 U.S. at 508-510, which reversed a D.C. Circuit 
holding that the EPA was obligated to define good neighbor 
obligations,\284\ states had no reason to expect the EPA would be 
obligated to issue further guidance to clarify requirements in the wake 
of those decisions. The EPA agrees with those commenters who point out 
that states have the first opportunity to assess and address 
obligations in implementing the NAAQS, but with that understanding in 
mind, it is notable that prior to the proposed disapprovals in February 
of 2022, no state moved to amend or supplement their SIP submission as 
the case law on good neighbor obligations evolved or in response to new 
modeling information as it became available.
---------------------------------------------------------------------------

    \284\ EME Homer City Generation, L.P. v. EPA, 696 F.3d 7 (D.C. 
Cir. 2012) (EME Homer City I).
---------------------------------------------------------------------------

    Further, the EPA has evaluated state SIP submissions on the merits 
of what is contained in the submission, not the use of any particular 
modeling platform. The EPA disagrees with commenters' assertions that 
the EPA has proposed disapproval of a state's proposed SIP due to the 
use of a particular modeling platform. As noted previously, the EPA 
approved state SIP submissions that have used the earlier modeling. The 
EPA did not reach its conclusion to disapprove states' SIP submissions 
based on the use of the 2016v2 emissions platform standing alone. Use 
of that platform, or any other modeling platform, is not ipso facto 
grounds for disapproval at all. As evident in the proposed disapprovals 
and summarized in Section IV, the EPA evaluated the SIP submissions 
based on the merits of the arguments put forward in each SIP 
submission.
3. Alleged Harm to States Caused by Time Between SIP Submission and the 
EPA's Action
    Comment: Many comments pointed to the EPA's statutory deadlines to 
take action on the SIP submissions to argue that the EPA's delay harmed 
the upwind state's interests because now the EPA may conclude they need 
to reduce their emissions to satisfy their good neighbor obligations in 
the separate FIP rulemaking whereas had the EPA acted by statutory 
deadlines using the older modeling, they might have had their SIP 
submissions approved. Some commenters suggest that the EPA never gave 
the state SIP submissions the appropriate review or suggest that the 
EPA's review of the SIP submissions was prejudiced by the FIP it had 
proposed.
    EPA Response: The EPA acknowledges that the Agency's statutory 
deadlines to take final action on these SIP submissions generally fell 
in 2020 and 2021. However, the delay in acting caused no prejudice to 
the upwind states. First, this action to disapprove SIP submissions 
itself will not impose any requirements or penalties on any state or 
sources within that state. Second, these delays have primarily had the 
effect of deferring relief to downwind states and their citizens from 
excessive levels of ozone pollution under the good neighbor provision. 
Further, the EPA has generally had a practice of correcting its action 
on good neighbor SIP submittals if later information indicates that a 
prior action was in error--thus, it is not the case that simply having 
obtained an approval based on earlier modeling would have meant a state 
would be forever insulated from later being subject to corrective or 
remedial good neighbor actions. See, e.g.,86 FR 23056, 23067-68 (April 
30, 2021) (error correcting Kentucky's approval to a disapproval and 
promulgating FIP addressing Kentucky's outstanding 2008 ozone NAAQS 
good neighbor obligations); 87 FR 20036, 20041 (April 6, 2022) 
(proposing error correction for Delaware's 2015 ozone NAAQS SIP 
approval to a disapproval based on updated air quality modeling). 
Finally, there is no basis in the CAA to use the Agency's own delay as 
a basis to nullify

[[Page 9365]]

the authority granted in the Act to address the nation's air pollution 
problems, as the statute itself contains other forms of adequate 
remedy. CAA section 304(a)(2) provides for judicial recourse where 
there is an alleged failure by the agency to perform a nondiscretionary 
duty, and that recourse is for the Agency to be placed on a court-
ordered deadline to address the relevant obligations. Accord Oklahoma, 
723 F.3d at 1223-24; Montana Sulphur and Chemical Co. v. U.S. EPA, 666 
F.3d 1174, 1190-91 (9th Cir. 2012).
    Comment: Some comments contend that the EPA's delay in acting on 
SIP submissions was a deliberate attempt to circumvent the SIP/FIP 
process, unduly burden the states, or to defer making information 
available to states. Comments allege that the EPA intentionally stalled 
an evaluative action until the perceived ``facts'' of the situation 
changed such that the analyses submitted by states were rendered 
outdated.
    EPA Response: The EPA disagrees with both allegations. In this 
respect, it is important to review the recent history of the EPA's 
regulatory actions and litigation with respect to good neighbor 
obligations for both the 2008 and 2015 ozone NAAQS, and in particular, 
the substantial additional workload the Agency took on in the wake of 
the remand of the CSAPR Update in Wisconsin. In 2018, as the EPA issued 
the memoranda cited by commenters and planned to shift its focus to 
implementing the 2015 standards, it also issued the CSAPR Close-out, 
which made an analytical finding that there were no further obligations 
for 21 states for the 2008 standards following the CSAPR Update. 83 FR 
65878 (Dec. 21, 2018). However, contrary to the EPA's understanding 
that it had fully addressed good neighbor obligations for the 2008 
ozone NAAQS, the D.C. Circuit's decisions in Wisconsin (remanding the 
CSAPR Update) and in New York (vacating the CSAPR Close-out), forced 
the Agency to quickly pivot back to addressing remaining obligations 
under the 2008 standards. Wisconsin v. EPA, 938 F.3d 303 (D.C. Cir. 
2019); New York v. EPA, 781 F. App'x. 4 (D.C. Cir. 2019). The EPA was 
subject to renewed deadline suit litigation under CAA section 304, 
which led to a March 15, 2021, deadline to take final action on several 
states whose FIPs had been remanded and were incomplete in the wake of 
the CSAPR Close-out vacatur. New Jersey v. Wheeler, 475 F.Supp.3d 308 
(S.D.N.Y. 2020). Throughout 2020 and 2021, the EPA was therefore 
focused on an unexpected rulemaking obligation to complete good 
neighbor requirements as to the states with remanded CSAPR Update FIPs. 
This led to the EPA proposing and then issuing an economically 
significant, major rule assessing additional EGU emissions reduction 
obligations as well as presenting updated air quality modeling analysis 
using novel techniques and presenting information on a host of non-EGU 
industrial sources for the first time, i.e., the Revised CSAPR Update, 
86 FR 23054 (April 30, 2021). That rule is now currently subject to 
judicial review in the D.C. Circuit, Midwest Ozone Group v. EPA, No. 
21-1146 (D.C. Cir. argued Sept. 28, 2022).\285\ The EPA has also been 
in the process of reviewing and acting upon many states' good neighbor 
SIPs where the available information indicates that an approval of the 
state's submission was appropriate.\286\
---------------------------------------------------------------------------

    \285\ During this time, the EPA also fulfilled its obligations 
to act on several petitions brought by downwind states under section 
126(b) of the CAA. These actions culminated in litigation and 
ultimately adverse decisions in Maryland and New York v. EPA. 
Maryland v, 958 F.3d; New York v. EPA, 964 F.3d 1214, 2020 WL 
3967838 (D.C. Cir. 2020). Further review and action on these remands 
remains pending before the agency.
    \286\ In chronological order: 83 FR 47568 (September 20, 2018) 
(Washington); 84 FR 69331 (December 18, 2019) (Alaska); 84 FR 22376 
(May 17, 2019) (Oregon); 85 FR 5570 (January 31, 2020) (Washington, 
DC); 85 FR 5572 (January 31, 2020) (Massachusetts); 85 FR 20165 
(April 10, 2020) (North Dakota); 85 FR 21325 (April 17, 2020) 
(Nebraska); 85 FR 25307 (May 1, 2020) (Delaware); 85 FR 34357 (June 
4, 2020) (Vermont); 85 FR 65722 (October 16, 2020) (Idaho); 85 FR 
67653 (October 26, 2020) (South Dakota); 86 FR 45870 (August 17, 
2021) (Maine and New Hampshire); 86 FR 68413 (December 2, 2021) 
(Florida, Georgia, North Carolina, and South Carolina); 86 FR 70409 
(December 10, 2021) (Rhode Island); 86 FR 71830 (December 20, 2021) 
(Connecticut); 86 FR 73129 (December 27, 2021) (Hawaii); 87 FR 19390 
(April 4, 2022) (Kansas); 87 FR 21578 (April 12, 2022) (Montana); 87 
FR 22463 (April 15, 2022) (Iowa); and 87 FR 61249 (October 11, 2022) 
(Colorado).
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    Finally, the Agency needed time to review and evaluate the SIP 
submissions in a coordinated fashion to act on all the states' 
submissions in a consistent manner. As the EPA explained in the 
proposed disapproval action, consistency in defining CAA obligations is 
critically important in the context of addressing a regional-scale 
pollutant like ozone. See, e.g., 87 FR 9807 n.48. Through coordinated 
development of the bases for how the Agency could act on the SIP 
submissions, while also evaluating the contours of a potential Federal 
plan to implement obligations where required, the EPA sequenced its 
deliberations and decision making to maximize efficient, consistent, 
and timely action, in recognition of the need to implement any 
necessary obligations ``as expeditiously as practicable.'' \287\ The 
downsides of commenters' policy preference in favor of giving states 
another opportunity to develop SIP submissions, or in first acting on 
each SIP submission before proposing a FIP, are that such a sequence of 
actions would have led to multiple years of additional delay in 
addressing good neighbor obligations. Even if such a choice was 
available to the Agency using the CAA section 110(k)(5) SIP call 
mechanism, it was entirely reasonable for the EPA to decline to use 
that mechanism in this instance. (EPA further addresses comments in 
support of a SIP call approach in the RTC document.)
---------------------------------------------------------------------------

    \287\ CAA section 181(a); Wisconsin, 938 F.3d at 313-14 (citing 
North Carolina, 531 F.3d at 911-12).
---------------------------------------------------------------------------

    In short, commenters' notion that the EPA was deliberately or 
intentionally deferring or delaying action on these SIP submissions to 
circumvent any required legal process or reach any specific result is 
simply incorrect. Commenters have not supplied any evidence to support 
the claim either that any legal process was circumvented or that the 
Agency's conduct was in bad faith. See Biden v. Texas, 142 S.Ct. 2528, 
2546-47 (2022) (presumption of regularity attends agency action absent 
a ``strong showing of bad faith or improper behavior'') (citing 
Citizens to Protect Overton Park v. Volpe, 401 U.S. 302, 420 (1971); 
SEC v. Chenery, 318 U.S. 80, 87 (1943)).
4. Use of Updated Modeling
    Comment: Comments allege that by relying on modeling not available 
at the time of SIP submission development, the EPA ``moved the goal 
post.'' Comments note the timeframes set out for action on SIPs, citing 
section 110 of the Act, and allege that by failing to act on SIP 
submissions in a timely manner and basing such actions on new modeling, 
the EPA imposes an arbitrary and capricious standard. Comments state 
that the EPA should not disapprove a SIP based on data not available to 
states during development of the SIP submissions or to the EPA during 
the period statutorily allotted for the EPA to take final action on SIP 
submissions.
    EPA Response: In response to comments' claims that the EPA has 
inappropriately changed states' obligations for interstate transport by 
relying on updated modeling not available to states at the time they 
prepared their SIP submissions, the EPA disagrees. As an initial 
matter, the EPA disagrees with comment's claiming that the agency 
expected state air agencies to develop a SIP submission based on

[[Page 9366]]

some unknown future data. The EPA recognizes that states generally 
developed their SIP submissions with the best available information at 
the time of their development. As stated in the proposals, the EPA did 
not evaluate states' SIP submissions based solely on the 2016v2 
emissions platform (or the 2016v3 platform, which incorporates comments 
generated during the public comment period on the proposed SIP actions 
and which supports these final SIP disapproval actions). We evaluated 
the SIP submissions based on the merits of the arguments put forward in 
each SIP submission, which included any analysis put forward by states 
to support their conclusions. Thus, we disagree with commenters who 
allege the Agency has ignored the information provided by the states in 
their submissions. Indeed, the record for this action reflects our 
extensive evaluation of states' air quality and contribution analyses. 
See generally Section IV, which summarizes our evaluation for each 
state.
    We disagree with commenters who advocate that the EPA's evaluation 
of these submissions must be limited to the information available to 
states at the time they made their submissions, or information at the 
time of the deadline for the EPA to act on their submissions. It can 
hardly be the case that the EPA is prohibited from taking rulemaking 
action using the best information available to it at the time it takes 
such action. Nothing in the CAA suggests that the Agency must deviate 
from that general principle when acting on SIP submissions. While CAA 
section 110(k)(2) specifies a time period in which the Administrator is 
to act on a state submission, neither this provision nor any other 
provision of the CAA specifies that the remedy for the EPA's failure to 
meet a statutory deadline is to arrest or freeze the information the 
EPA may consider to what was available at the time of a SIP submission 
deadline under CAA section 110. Indeed, in the interstate transport 
context, this would lead to an anomalous result. For example, the D.C. 
Circuit rejected an argument made by Delaware against the CSAPR Update 
air quality analysis that the EPA was limited to reviewing air quality 
conditions in 2011 (rather than 2017) at the time of the statutory 
deadline for SIP submittals. The court explained,

    Delaware's argument leans too heavily on the SIP submission 
deadline. SIP submission deadlines, unlike attainment deadlines, are 
``procedural'' and therefore not ``central to the regulatory 
scheme.'' Sierra Club, 294 F.3d at 161. Nor can Delaware's argument 
be reconciled with the text of the Good Neighbor Provision, which 
prohibits upwind States from emitting in amounts ``which will'' 
contribute to downwind nonattainment. 42 U.S.C. 7410(a)(2)(D)(i) 
(emphasis added). Given the use of the future tense, it would be 
anomalous for EPA to subject upwind States to good neighbor 
obligations in 2017 by considering which downwind States were once 
in nonattainment in 2011.

    Wisconsin, 903 F.3d at 322. By the same token, here, holding the 
EPA to a consideration only of what information states had available 
regarding the 2023 analytic year at the time of their SIP submissions 
or at the time of a deadline under CAA section 110, would likewise 
elevate the ``procedural'' deadlines of CAA section 110 above the 
substantive requirements of the CAA that are ``central to the 
regulatory scheme.'' Doing so here would force the Agency to act on 
these SIP submissions knowing that more recent refined, high quality, 
state-of-the-science modeling and monitoring data would produce a 
different result in our forward-looking analysis of 2023 than the 
information available in 2018. Nothing in the CAA dictates that the EPA 
must be forced into making substantive errors in its good neighbor 
analysis on this basis.
    We relied on CAMx Version 7.10 and the 2016v2 emissions platform to 
make updated determinations regarding which receptors would likely 
exist in 2023 and which states are projected to contribute above the 
contribution threshold to those receptors. As explained in the preamble 
of the EPA's proposed actions and further detailed in the document 
titled ``Air Quality Modeling TSD: 2015 Ozone National Ambient Air 
Quality Standards Proposed Interstate Transport Air Plan Disapproval'' 
and 2016v2 Emissions Inventory TSD, both available in Docket ID no. 
EPA-HQ-OAR-2021-0663, the 2016v2 modeling built off previous modeling 
iterations used to support the EPA's action on interstate transport 
obligations. The EPA continuously refines its modeling to ensure the 
results are as indicative as possible of air quality in future years. 
This includes adjusting our modeling platform and updating our 
emissions inventories to reflect current information.
    Additionally, we disagree with comments claiming that the 2016v2 
modeling results were sprung upon the states with the publication of 
the proposed disapprovals. The EPA has been publishing a series of data 
and modeling releases beginning as early as the publication of the 
2016v1 modeling with the proposed Revised CSAPR Update in November of 
2020, which could have been used to track how the EPA's modeling 
updates were potentially affecting the list of possible receptors and 
linkages for the 2015 ozone NAAQS in the 2023 analytic year. The 2016-
based meteorology and boundary conditions used in the modeling have 
been available through the 2016v1 platform, which was used for the 
Revised CSAPR Update (proposed in November of 2020, 85 FR 68964). The 
updated emissions inventory files used in the current modeling were 
publicly released September 21, 2021, for stakeholder feedback, and 
have been available on our website since that time.\288\ The CAMx 
modeling software that the EPA used has likewise been publicly 
available for over a year. CAMx version 7.10 was released by the model 
developer, Ramboll, in December 2020. On January 19, 2022, we released 
on our website and notified a wide range of stakeholders of the 
availability of both the modeling results for 2023 and 2026 (including 
contribution data) along with many key underlying input files.\289\
---------------------------------------------------------------------------

    \288\ See https://www.epa.gov/air-emissions-modeling/2016v2-platform.
    \289\ See https://www.epa.gov/scram/photochemical-modeling-applications.
---------------------------------------------------------------------------

    By providing the 2016 meteorology and boundary conditions (used in 
the 2016v1 version) in fall of 2020, and by releasing updated emissions 
inventory information used in 2016v2 in September of 2021,\290\ states 
and other interested parties had multiple opportunities prior to the 
proposed disapprovals in February of 2022 to consider how our modeling 
updates could affect their status for purposes of evaluating potential 
linkages for the 2015 ozone NAAQS. Further, by using the updated 
modeling results, the EPA is using the most current and technically 
appropriate information for this rulemaking. This modeling was not 
performed to ``move the goal posts'' for states but meant to provide 
updated emissions projections, such as additional emissions reductions 
for EGUs following promulgation of the Revised CSAPR Update for the 
2008 ozone NAAQS, more recent information on plant closures and fuel 
switches, and sector trends, including non-EGU sectors. The construct 
of the 2016v2 emissions platform is described in the 2016v2 Emissions 
Modeling TSD contained in Docket ID No. EPA-HQ-OAR-2021-0663.
---------------------------------------------------------------------------

    \290\ https://www.epa.gov/air-emissions-modeling/2016v2-platform.
---------------------------------------------------------------------------

    Finally, comments related to the timing of the EPA's action to 
disapprove these SIP submissions are addressed in Section V.A.1. The 
EPA notes the statute provides a separate remedy for agency action 
unlawfully delayed. In section 304 of the CAA, there is a

[[Page 9367]]

process for filing suit against the EPA for its failure to comply with 
a non-discretionary statutory duty under the CAA. The appropriate 
remedy in such cases is an order to compel agency action, not a 
determination that the agency, by virtue of missing a deadline, has 
been deprived of or constrained in its authority to act. See Oklahoma, 
723 F.3d at 1224 (``[W]hen `there are less drastic remedies available 
for failure to meet a statutory deadline'--such as a motion to compel 
agency action--`courts should not assume that Congress intended the 
agency to lose its power to act.' The Court `would be most reluctant to 
conclude that every failure of an agency to observe a procedural 
requirement voids subsequent agency action, especially when important 
public rights are at stake.''') (cleaned up) (quoting Brock v. Pierce 
County, 476 U.S. 253, 260 (1986)).
    Comment: Comments state that it is inappropriate for the EPA to 
revise its emissions inventory and to conduct new air quality modeling 
without allowing an appropriate opportunity for stakeholder review and 
comment and that the EPA must allow public comment on any updated 
(i.e., 2016v3) modeling prior to use by the EPA in a final action. 
Comments claim that the EPA must withdraw the proposed disapproval and 
provide states time to develop new SIP submissions based on the updated 
information.
    EPA Response: The EPA has evaluated a wide range of technical 
information and critiques of its 2016v2 emissions inventory and 
modeling platform following a solicitation of public feedback as well 
the public comment period on this action (and the proposed FIP action) 
and has responded to those comments and incorporated updates into the 
version of the modeling being used in this final action (2016v3). See 
Section III, the Final Action AQM TSD, and Section 4 of the RTC 
document for further discussion.
    The EPA's development of and reliance on newer modeling to confirm 
modeling used at the proposal stage is in no way improper and is simply 
another iteration of the EPA's longstanding scientific and technical 
work to improve our understanding of air quality issues and causes 
going back decades. Where the 2016v3 modeling produced a potentially 
different outcome for states from proposal, that is reflected in this 
action (e.g., our deferral of final action on Tennessee and Wyoming's 
SIP submissions).
    Comment: Comments allege that EPA's modeling results have been 
inconsistent, questioning the reliability of the results.
    EPA Response: Although some commenters indicate that our modeling 
iterations have provided differing outcomes and are therefore 
unreliable, this is not what the overall record indicates. Rather, in 
general, although the specifics of states' linkages may change 
slightly, our modeling overall has provided consistent outcomes 
regarding which states are linked to downwind air quality problems. For 
example, the EPA's modeling shows that most states that were linked to 
one or more receptors using the 2011-based platform (i.e., the March 
2018 data release) are also linked to one or more receptors using the 
newer 2016-based platform. Because each platform uses different 
meteorology (i.e., 2011 and 2016) it is not at all unexpected that an 
upwind state could be linked to different receptors using 2011 versus 
2016 meteorology.
    In addition, although a state may be linked to a different set of 
receptors, states are often linked to receptors in the same area that 
has a persistent air quality problem. These differing results regarding 
receptors and linkages can be affected by the varying meteorology from 
year to year, but this does not indicate that the modeling or the EPA 
or the state's methodology for identifying receptors or linkages is 
inherently unreliable. Rather, for many states these separate modeling 
runs all indicated: (i) that there would be receptors in areas that 
would struggle with nonattainment or maintenance in the future, and 
(ii) that the state was linked to some set of these receptors, even if 
the receptors and linkages differed from one another in their specifics 
(e.g., a different set of receptors were identified to have 
nonattainment or maintenance problems, or a state was linked to 
different receptors in one modeling run versus another).
    The EPA interprets this common result as indicative that a state's 
emissions have been substantial enough to generate linkages at Step 2 
to varying sets of downwind receptors generated under varying 
assumptions and meteorological conditions, even if the precise set of 
linkages changed between modeling runs. Under these circumstances, we 
think it is appropriate to proceed to a Step 3 analysis to determine 
what portion of a particular state's emissions should be deemed 
``significant.'' We also note that only four states included in the 
proposed disapprovals went from being unlinked to being linked between 
the 2011-based modeling provided in the March 2018 memorandum and the 
2016v2-based modeling--Alabama, Minnesota, Nevada, and Tennessee.
5. Cooperative Federalism and the EPA's Authority
    Comment: Many comments point to the concept of cooperative 
federalism as embodied in the CAA to make various arguments as to why 
the EPA cannot or should not be allowed to exercise its independent 
judgment in evaluating the arguments presented by the states in the SIP 
submissions, and some also argue that the EPA must approve each state's 
submission in deference to how states choose to interpret the CAA 
requirements they must meet.
    EPA Response: The CAA establishes a framework for state-Federal 
partnership to implement the NAAQS based on cooperative federalism. 
Under the general model of cooperative federalism, the Federal 
Government establishes broad standards or goals, states are given the 
opportunity to determine how they wish to achieve those goals, and if 
states choose not to or fail to adequately implement programs to 
achieve those goals, a Federal agency is empowered to directly regulate 
to achieve the necessary ends. Under the CAA, once the EPA establishes 
or revises a NAAQS, states have the obligation and opportunity in the 
first instance to develop an implementation plan under CAA section 110 
and the EPA will approve SIP submissions under CAA section 110 that 
fully satisfy the requirements of the CAA. This sequence of steps is 
not in dispute.
    The EPA does not, however, agree with the comments' 
characterization of the EPA's role in the state-Federal relationship as 
being ``secondary'' such that the EPA must defer to state choices 
heedless of the substantive objectives of the Act; such deference would 
be particularly inappropriate in the context of addressing interstate 
pollution. The EPA believes that the comments fundamentally 
misunderstand or inaccurately describe this action, as well as the 
```division of responsibilities' between the states and the federal 
government'' they identify in CAA section 110 citing the Train-Virginia 
line of cases \291\ and other cases.\292\

[[Page 9368]]

Those cases, some of which pre-date the CAA amendments of 1990 
resulting in the current Good Neighbor Provision,\293\ stand only for 
the proposition that the EPA must approve state plans if they meet the 
applicable CAA requirements. But these cases say nothing about what 
those applicable requirements are. The EPA is charged under CAA section 
110 with reviewing states' plans for compliance with the CAA and 
approving or disapproving them based on EPA's determinations. Thus, the 
EPA must ultimately determine whether state plans satisfy the 
requirements of the Act or not. Abundant case law reflects an 
understanding that the EPA must evaluate SIP submissions under the CAA 
section 110(k)(2) and (3).\294\ If they are deficient, the EPA must so 
find, and become subject to the obligation to directly implement the 
relevant requirements through a Federal implementation plan under CAA 
section 110(c), unless EPA approves an applicable SIP first.\295\
---------------------------------------------------------------------------

    \291\ See Virginia v. EPA, 108 F.3d 1397, 1407 (D.C. Cir. 1997) 
(Virginia) (quoting Train v. Natural Resources Defense Council, 
Inc., 421 U.S. 60, 79 (1975) (Train)). The ``Train-Virginia line of 
cases'' are named for the U.S. Supreme Court case Train, 421 U.S. 
and to the D.C. Circuit case Virginia, 108 F.3d. The D.C. Circuit 
has described these cases as defining a ``federalism bar'' that 
generally recognizes states' ability to select emissions control 
measures in their SIPs so long as CAA requirements are met. See, 
e.g., Michigan v. EPA, 213 F.3d 663, 687 (D.C. Cir. 2000) 
(Michigan).
    \292\ Union Elec. Co. v. EPA, 427 U.S. 246 (1976), Am. Elec. 
Power Co. v. Connecticut, 565 U.S. 410 (2011), Fla. Power & Light v. 
Costle, 650 F.2d 579 (5th Cir. 1981), Bethlehem Steel Corp. v. 
Gorsuch, 742 F.2d 1028 (7th Cir. 1984), Concerned Citizens of 
Bridesburg v. EPA, 836 F.2d 777 (3d Cir. 1987), North Carolina, 531 
F.3d 896, Luminant, 675 F.3d 917 (5th. Cir. 2012), Luminant Co. LLC 
v. EPA, 714 F.3d 841 (5th. Cir. 2013), North Dakota v. EPA, 730 F.3d 
750 (8th. Cir. 2013), EME Homer City II, 795 F.3d 118 (D.C. Cir. 
2015), and Texas v. USEPA, 829 F.3d 405 (5th. Cir. 2016).
    \293\ The 1970 version of the Act required SIPs to include 
``adequate provisions for intergovernmental cooperation'' concerning 
interstate air pollution. CAA section 110(a)(2)(E), 84 Stat. 1681, 
42 U.S.C. 1857c-5(a)(2)(E). In 1977, Congress amended the Good 
Neighbor Provision to direct States to submit SIP submissions that 
included provisions ``adequate'' to ``prohibi[t] any stationary 
source within the State from emitting any air pollutant in amounts 
which will . . . prevent attainment or maintenance [of air quality 
standards] by any other State.'' CAA section 108(a)(4), 91 Stat. 
693, 42 U.S.C. 7410(a)(2)(E) (1976 ed., Supp. II). Congress again 
amended the Good Neighbor Provision in 1990 to its current form.
    \294\ See, e.g., Virginia, 108 F.3d at 1406. See also, e.g., 
Westar Energy v. EPA, 608 Fed. App'x 1, 3 (D.C. Cir. 2015) (``EPA 
acted well within the bounds of its delegated authority when it 
disapproved of Kansas's proposed [good neighbor] SIP.'') (emphasis 
added); Oklahoma, 723 F.3d at 1209 (upholding the EPA's disapproval 
of ``best available retrofit technology'' (BART) SIP, noting BART 
``does not differ from other parts of the CAA--states have the 
ability to create SIPs, but they are subject to EPA review'').
    \295\ EME Homer City Generation, 572 U.S. at 508-510.
---------------------------------------------------------------------------

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

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

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

B. Application of the 4-Step Interstate Transport Framework

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

[[Page 9369]]

SIP submissions and implement reasonably available control technologies 
(RACT) by January 1, 2023. See 87 FR 60897, 60899 (October 7, 2022). 
The EPA further responds to this comment in the RTC document.
2. Attachment A to the March 2018 Memorandum
    Comment: Comments state that states conducted their analyses based 
on the flexibilities listed in Attachment A of the March 2018 
Memorandum. Comments cite the part of the memorandum where the EPA 
notes that ``in developing their own rules, states have flexibility to 
follow the familiar four-step transport framework (using [the] EPA's 
analytical approach or somewhat different analytical approaches within 
these steps) or alternative frameworks, so long as their chosen 
approach has adequate technical justification and is consistent with 
the requirements of the CAA.'' Comments state that the EPA's 
disapproval of SIP submissions that took advantage of the flexibilities 
is arbitrary and capricious because the EPA has changed, without 
communication, its consideration of what is deemed to be the 
``necessary provisions'' required for an approvable SIP submission too 
late in the SIP submission process and because, in disapproving these 
SIPs, the EPA is applying a consistent set of policy judgments across 
all states.
    EPA Response: Comments mistakenly view Attachment A to the March 
2018 memorandum releasing modeling results as constituting agency 
guidance. The EPA further disagrees with commenters' characterization 
of the EPA's stance regarding the ``flexibilities'' listed (without 
analysis) in Attachment A. Attachment A to the March 2018 memorandum 
identified a ``Preliminary List of Potential Flexibilities'' that could 
potentially inform SIP development.\297\ However, the EPA made clear in 
that attachment that the list of ideas were not suggestions endorsed by 
the Agency but rather ``comments provided in various forums'' from 
outside parties on which the EPA sought ``feedback from interested 
stakeholders.'' \298\ Further, Attachment A stated, ``EPA is not at 
this time making any determination that the ideas discussed later are 
consistent with the requirements of the CAA, nor are we specifically 
recommending that states use these approaches.'' \299\ Attachment A to 
the March 2018 memorandum, therefore, does not constitute agency 
guidance, but was intended to generate further discussion around 
potential approaches to addressing ozone transport among interested 
stakeholders. The EPA emphasized in this memorandum that any such 
alternative approaches must be technically justified and appropriate in 
light of the facts and circumstances of each particular state's 
submittal.\300\ As stated in the proposed SIP disapprovals,\301\ the 
March 2018 memorandum provided that, ``While the information in this 
memorandum and the associated air quality analysis data could be used 
to inform the development of these SIPs, the information is not a final 
determination regarding states' obligations under the good neighbor 
provision.'' \302\ In this final SIP disapproval action, the EPA again 
affirms that certain concepts included in Attachment A to the March 
2018 memorandum require unique consideration, and these ideas do not 
constitute agency guidance with respect to transport obligations for 
the 2015 ozone NAAQS.
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    \297\ March 2018 memorandum, Attachment A.
    \298\ Id.
    \299\ Id.
    \300\ March 2018 memorandum.
    \301\ E.g., 87 FR 9487.
    \302\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), March 27, 2018, available in docket EPA-HQ-OAR-
2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
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    In response to comments' claims that since the time transport SIP 
submissions were submitted to the EPA for review, the EPA has changed, 
without communication, its consideration of what is deemed to be the 
``necessary provisions'' required for an approvable SIP submission, the 
EPA disagrees. As comments note, and as stated in the proposed 
disapproval notifications, the EPA recognizes that states have 
discretion to develop their own SIP transport submissions and agrees 
that states are not bound to using the 4-step interstate transport 
framework the EPA has historically used. However, states must then 
provide sufficient justification and reasoning to support their 
analytical conclusions and emissions control strategies. See, e.g., 87 
FR 9798, 9801. In the SIP submissions being disapproved in this action, 
no state provided any enforceable emissions control strategies for 
approval into their SIP. The EPA has evaluated the merits of each 
state's arguments as to why no additional emissions reduction 
requirements are needed to satisfy their obligations under CAA section 
110(a)(2)(D)(i)(I) for the more protective 2015 ozone NAAQS. While the 
EPA used its own 4-step interstate transport framework as a guide for 
its review to ensure a consistent and equitable evaluation of each 
states' submissions, the EPA has also considered states' individual 
arguments without predetermining the EPA's conclusions about the 
state's transport obligations.
    It was never the Agency's intent in sharing Attachment A that 
states would invoke one or more of the potential ``flexibilities'' that 
outside parties advocated for as a basis for concluding that no 
additional emissions controls were necessary to address interstate 
transport for the more protective 2015 ozone NAAQS without proper 
justification. Nothing in Attachment A suggested that was the Agency's 
intended objective. Indeed, where certain approaches identified in 
Attachment A might have produced analytical conclusions requiring 
upwind states to reduce their emissions, no state invoking Attachment A 
followed through with implementing those controls. We observe this 
dynamic at work in Kentucky's submission, because Kentucky appended 
comments from the Midwest Ozone Group to its submission that 
demonstrated that applying a ``weighted'' approach to allocating 
upwind-state responsibility at Step 3 would have resulted in an 
emissions control obligation on Kentucky's sources, yet the State 
offered no explanation in its submittal why it was not adopting that 
approach or even what its views on that approach were. See 87 FR 9515. 
As another example, Michigan cited Attachment A to the March 2018 in 
developing a methodology for calculating significant contribution under 
which Michigan would have been responsible for eliminating up to 0.12 
ppb of contribution to downwind receptors; however, the State suggested 
that uncertainty caused by modeling ``noise'' was too great to either 
require emissions reductions or demonstrate that Michigan had any 
linkages to receptors at all. See 87 FR 9860-9861. However, this 
explanation did not, as an analytical matter, demonstrate a level of 
scientific uncertainty which might allow for ignoring the results,\303\

[[Page 9370]]

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

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

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

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

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

[[Page 9371]]

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

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

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

[[Page 9372]]

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

[[Page 9373]]

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

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

    Comment: Some comments allege that the EPA representatives led the 
states to believe that their SIP submission would be approved on the 
basis of a 1 ppb contribution threshold. The comments further claim 
that the EPA has now since reversed course on its August 2018 
memorandum and imposed new requirements on states that were not 
included in the EPA's guidance. One comment suggested EPA switched 
position without explanation from the August 2018 guidance to its 
proposed disapprovals, which it viewed as unlawful under FCC v. Fox TV 
Stations, Inc., 556 U.S. 502 (2009).
    EPA Response: As an initial matter, we note that the salience of 
these comments is limited to only a handful of states. The August 2018 
memorandum made clear that the Agency had substantial doubts that any 
threshold greater than 1 ppb (such as 2 ppb) would be acceptable, and 
the Agency is affirming that a threshold higher than 1 ppb would not be 
justified under any circumstance for purposes of this action. No 
comment provided a credible basis for using a threshold even higher 
than 1 ppb. So this issue is primarily limited to the difference 
between a 0.70 ppb threshold and a 1.0 ppb threshold. Therefore, we 
note that this issue is only relevant to a small number of states whose 
only contributions to any receptor are above 1 percent of the NAAQS but 
lower than 1 ppb. Under the 2016v3 modeling of 2023 being used in this 
final action, those states with contributions that fall between 0.70 
ppb and 1 ppb included in this action are Alabama, Kentucky, and 
Minnesota.
    The EPA disagrees with comments' claims that the Agency has 
reversed course on applying the August 2018 memorandum. In line with 
the memorandum, the EPA evaluated every justification put forward by 
every state covered by this SIP disapproval action that attempted to 
justify an alternative threshold under the August 2018 memorandum, 
which are Alabama,\312\ Arkansas,\313\ Illinois,\314\ Indiana,\315\ 
Kentucky,\316\ Louisiana,\317\ Michigan,\318\ Mississippi,\319\ 
Missouri,\320\ and Oklahoma,\321\ and Utah.\322\ The EPA also addressed 
criticisms of the 1 percent of the NAAQS contribution threshold made by 
Ohio \323\ and Nevada.\324\ (The topic of the EPA's input during 
state's SIP-development processes is further discussed in the RTC 
document.)
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    \312\ 87 FR 64423-64424.
    \313\ 87 FR 9806-9807.
    \314\ 87 FR 9852-9853.
    \315\ 87 FR 9855-9856.
    \316\ 87 FR 9508-9511.
    \317\ 87 FR 9812-9813.
    \318\ 87 FR 9861-9862.
    \319\ 87 FR 9557.
    \320\ 87 FR 9541-9543.
    \321\ 87 FR 9818-9820.
    \322\ 87 FR 31477-31451.
    \323\ 87 FR 9870-9871.
    \324\ 87 FR 31492.
---------------------------------------------------------------------------

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

[[Page 9374]]

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

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

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

[[Page 9375]]

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

[[Page 9376]]

there were no emissions reductions available from any affected sources 
for any of the emissions control stringencies that were analyzed. See 
81 FR 74504, 74553. No state's submission covered in this action 
contained an emissions control analysis that would allow for these 
types of conclusions to be reached for all of its sources.\326\ States 
generally did not conduct any comparative analysis of available 
emissions control strategies--nor did they prohibit any additional 
ozone-precursor emissions.
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    \326\ We note that California's SIP submission is not approvable 
at Step 3, despite the fact that the EPA has not identified 
NOX emissions control opportunities at the state's EGUs. 
Nonetheless, the SIP submission is not approvable because the state 
attempted to rely on the CSAPR Update cost threshold to justify a 
no-control determination when that threshold was in relation to a 
partial remedy for a less protective NAAQS, and even if it could be 
reasonably concluded that no emissions reductions are appropriate at 
EGUs in California, the SIP submission did not conduct an adequate 
analysis of emissions control opportunities at its non-EGU 
industrial sources. See 87 FR 31459-60.
---------------------------------------------------------------------------

    We are unclear what another comment intends in asserting that the 
EPA is required to interpret ``significant contribution'' in a manner 
``which ties contribution to an amount which contributes significantly 
to downwind maintenance or nonattainment problems.'' The EPA disagrees 
that: (1) It has imposed or mandated a specific approach to Step 3 in 
this action, (2) this action established a particular level of 
emissions reduction that states were required to achieve, or (3) it 
mandated a particular methodology for making such a determination. To 
the extent the comment suggests that the Agency cannot mandate that 
states use cost as a method of allocating responsibility in their 
transport SIPs, first, the Agency has not done so. Further, as to 
whether cost could be used as a permissible method of allocating 
responsibility, the comment ignores the Supreme Court's holding to the 
contrary in EME Homer City, 572 U.S. at 518, and the D.C. Circuit's 
earlier holding to the same effect in Michigan, 213 F.3d at 687-88, 
both of which upheld the EPA's approach of using uniform cost-
effectiveness thresholds to allocate upwind state responsibilities 
under the good neighbor provision for prior NAAQS. While this approach 
may be reasonable to apply again for the 2015 ozone NAAQS (and the EPA 
has proposed to do so in the proposed FIP action published on April 6, 
2022), the EPA did not impose such a requirement on states in 
developing SIP submissions, nor is the EPA finding any SIP submission 
not approvable based on a failure to use this particular methodology.
    In its March 2018 memorandum, Attachment A, the Agency acknowledged 
that there could be multiple ways of conducting a Step 3 analysis. The 
Agency did not endorse any particular approach and noted the Attachment 
was merely a list of stakeholder ideas that the EPA was not 
recommending any state follow. The apparent result of this 
``flexibility,'' however, was that no state presented a Step 3 analysis 
that resulted in including any enforceable emissions reductions to 
address good neighbor obligations for the 2015 ozone NAAQS in their 
interstate transport SIP submittals. Likewise, the comment here did not 
include information or analysis establishing that any particular 
alternative Step 3 approach should have been approved or that any state 
performed such an analysis in a manner that would have addressed 
``significant contribution'' even in the manner the comment appears to 
be suggesting.
    Notably, materials appended to one State's SIP submission, 
developed by the Midwest Ozone Group (MOG), did present an analysis 
applying an approach to ``significant contribution'' that was based on 
calculating a proportional share of each state's contribution to a 
downwind receptor, and this methodology would have imposed on that 
State's, Kentucky's, sources an obligation to eliminate 0.02 ppb of 
ozone at the relevant receptor. See 87 FR 9507. While the EPA does not 
endorse or here evaluate the merits of such an approach, it is 
noteworthy that the State in that instance did not adopt that approach, 
did not impose that obligation on its sources through enforceable 
measures by revising its SIP, and offered no explanation for its 
decision not to do so. See id. 9516 (``This approach would have imposed 
additional emissions reductions for Kentucky sources. Kentucky's final 
SIP did not consider MOG's proposal and did not provide an explanation 
for why it was rejecting this approach to allocating upwind emissions 
reductions, even though it appended this recommendation to its SIP 
submittal.'').
9. Step 4: Attempt To Rely on FIPs in a SIP Submission
    Comment: One comment states that FIPs or other Federal emissions 
control measures do not have to be incorporated into and enforceable 
under state law to be an approvable SIP measure. They view it as 
acceptable for a state to rely in its SIP Submission on the emissions 
reductions achieved by prior ozone transport FIPs, such as the CSAPR 
Update or the Revised CSAPR Update, as a permissible means of achieving 
emissions reductions to eliminate significant contribution for the 2015 
ozone NAAQS.
    EPA Response: The EPA disagrees. As the EPA has noted on page 16 of 
our September 2013 memorandum ``Guidance on Infrastructure State 
Implementation Plan (SIP) Elements under Clean Air Act sections 
110(a)(1) and 110(a)(2)'' (2013 Infrastructure SIP Guidance): ``a FIP 
is not a state plan and thus cannot serve to satisfy the state's 
obligation to submit a SIP.'' \327\ Indeed, the general principle that 
measures relied on to meet states' CAA obligations must be part of the 
SIP has been recognized by courts, such as in Committee for a Better 
Arvin, 786 F.3d 1169 (9th Cir. 2015).
---------------------------------------------------------------------------

    \327\ Guidance on Infrastructure State Implementation Plan (SIP) 
Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2), 
September 13, 2013 (available at https://www.epa.gov/sites/default/files/2015-12/documents/guidance_on_infrastructure_sip_elements_multipollutant_final_sept_2013.pdf).
---------------------------------------------------------------------------

    This principle is grounded in the recognition that if such measures 
are not rendered enforceable within the SIP itself, then they may be 
modified or amended in ways that would undermine the basis for the 
state's reliance on them, while the approved SIP itself would purport 
to have addressed the relevant obligation merely by outdated reference 
to that modified or nonexistent control measure residing outside the 
SIP. For example, to be credited for attainment demonstration purposes, 
requirements that may otherwise be federally enforceable (such as new 
source review permit limits or terms in federally enforceable consent 
orders), must be in the state's implementation plan so that they could 
not later be changed without being subject to the EPA's approval. This 
principle is instrumental to ensuring that states cannot take credit 
for control measures that might be changed (even by the EPA itself) 
without the EPA's required approval action under CAA section 110, which 
includes the obligation to ensure there is no interference or 
backsliding with respect to all applicable CAA requirements. See CAA 
section 110(l). See also Montana Sulfur and Chemical Co. v. EPA, 666 
F.3d 1174, 1195-96 (9th Cir. 2012) (``The EPA correctly reads 42 U.S.C. 
7410(a)(2) as requiring states to include enforceable emissions limits 
and other control measures in the plan itself.'') (emphasis in 
original); 40 CFR 51.112(a) (``Each plan must demonstrate that the 
measures, rules, and regulations contained in it are adequate to 
provide for the timely attainment and

[[Page 9377]]

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

C. Good Neighbor Provision Policy

1. Mobile Source Emissions
    Comment: Several comments assert that mobile source emissions 
within the home state of the location of receptors are the primary 
source of nonattainment problems in downwind areas. Some comments 
additionally state that a larger portion of their own upwind state 
emissions is from mobile source emissions. These comments request that 
the EPA focus on these emissions sources rather than stationary sources 
to reduce ongoing nonattainment problems. These comments claim mobile 
sources are federally regulated and, therefore, the EPA bears the 
responsibility to either take action to reduce mobile source emissions 
nationwide or encourage downwind states to implement strategies to 
reduce their own local mobile source emissions.
    Response: The EPA recognizes that nationwide, mobile sources 
represent a large portion of ozone-precursor emissions and, as such, 
would be expected to have a large impact on nonattainment and 
maintenance receptors.
    The EPA has been regulating mobile source emissions since it was 
established as a Federal agency in 1970 and is committed to continuing 
the effective implementation and enforcement of current mobile source 
emissions standards and evaluating the need for additional 
standards.\328\ The EPA believes that the NOX reductions 
from its Federal programs are an important reason for the historical 
and long-running trend of improving air quality in the United States. 
The trend helps explain why the overall number of receptors and 
severity of ozone nonattainment problems under the 1997 and 2008 ozone 
NAAQS have declined. As a result of this long history, NOX 
emissions from onroad and nonroad mobile sources have substantially 
decreased and are predicted to continue to decrease into the future as 
newer vehicles and engines that are subject to the more recent and more 
stringent standards replace older vehicles and engines.\329\
---------------------------------------------------------------------------

    \328\ On December 20, 2022, the EPA finalized more stringent 
emissions standards for NOX and other pollutants from 
heavy-duty vehicles and engines, beginning with model year 2027. See 
https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-and-related-materials-control-air-pollution. The EPA is 
also developing new multi-pollutant standards for light- and medium-
duty vehicles as well as options to address pollution from 
locomotives.
    \329\ https://gispub.epa.gov/air/trendsreport/2022/#home.
---------------------------------------------------------------------------

    The EPA included mobile source emissions in the 2016v2 modeling 
used to support the proposal of these SIP disapproval actions to help 
determine state linkages at Steps 1 and 2 of the 4-step interstate 
transport framework and has done likewise in its 2016v3 modeling. 
However, whether mobile source emissions are a large portion of an 
upwind or downwind state's NOX emissions, and whether they 
represent a large portion of the contribution to downwind nonattainment 
and maintenance receptors, does not answer the question regarding the 
adequacy of an upwind state's SIP submission. The question is whether 
``any source or other type of emissions activity'' (in the collective) 
in an upwind state is contributing significantly to downwind receptors, 
see CAA section 110(a)(2)(D)(i). A state's transport SIP must include a 
technical and adequate justification to support its conclusion that the 
state has satisfied its interstate transport obligations for the 2015 
ozone NAAQS.
    To the extent that comments argue that mobile source emissions 
should be the focus of emissions reductions for the purposes of 
resolving interstate transport obligations, states could have provided 
such an analysis for how mobile source reductions might achieve 
necessary reductions. See, e.g., 70 FR 25209. However, states conducted 
no such analysis of methods or control techniques that could be used to 
reduce mobile source emissions, instead claiming that states cannot 
control mobile source emissions, as this is a federally-regulated 
sector, or states cannot reasonably control these emissions. States do 
have options, however, to reduce emissions from certain aspects of 
their mobile source

[[Page 9378]]

sectors, and to the extent a state is attributing its contribution to 
out of state receptors to its mobile sources, it could have conducted 
an analysis of possible programs or measures that could achieve 
emissions reductions from those sources. (For example, a general list 
of types of transportation control measures can be found in CAA section 
108(f).\330\)
---------------------------------------------------------------------------

    \330\ In making this observation, the EPA is not suggesting that 
mobile source emissions reductions are necessarily required to 
address a state's good neighbor obligations, but merely pointing out 
that if the state itself attributes the problem to mobile sources, 
then it is reasonable to expect that further analysis of such 
control strategies would be explored.
---------------------------------------------------------------------------

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

    \331\ 87 FR 9798, 9809-9810 (Feb. 22, 2022) (Arkansas); 87 FR 
31443, 31460-31461 (May 24, 2022) (California); 87 FR 9854 
(Illinois); 87 FR 9859-9860 (Indiana); 87 FR 9498, 9508 (Feb. 22, 
2022) (Kentucky); 87 FR 9838, 9865 (Michigan); 87 FR 9533, 9543 
(Feb. 22, 2022) (Missouri); 87 FR 9838 at 9874 (Ohio); 87 FR 31470, 
31482 (May 24, 2022) (Utah); 87 FR 9516, 9527 (Feb. 22, 2022) (West 
Virginia); 87 FR 31495, 31507 (May 24, 2022) (Wyoming).
---------------------------------------------------------------------------

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

[[Page 9379]]

Nevada, and Utah's SIP submissions. This final determination is based 
on these evaluations, as well as the EPA's 2016v2 and 2016v3 modeling 
following stakeholder feedback.
---------------------------------------------------------------------------

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

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

    \334\ 87 FR 31443, 31453.
    \335\ 81 FR 74503, 74523.
    \336\ See, e.g., 87 FR 31443, 31457. The EPA evaluated 
California's qualitative consideration of unique topographic factors 
that may influence the transport of emissions from sources within 
the state to downwind receptors in Colorado and Arizona. The EPA 
concluded that the State's arguments do not present sufficient 
evidence that called into question the results of the EPA's 
modeling.
---------------------------------------------------------------------------

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

VI. Statutory and Executive Order Reviews

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

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

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

B. Paperwork Reduction Act (PRA)

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

C. Regulatory Flexibility Act (RFA)

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

D. Unfunded Mandates Reform Act of 1995 (UMRA)

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

E. Executive Order 13132: Federalism

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

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

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

[[Page 9380]]

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

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

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

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

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

I. National Technology Transfer and Advancement Act (NTTAA)

    This rulemaking does not involve technical standards.

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

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

K. Congressional Review Act (CRA)

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

L. Judicial Review

    Section 307(b)(1) of the CAA governs judicial review of final 
actions by the EPA. This section provides, in part, that petitions for 
review must be filed in the D.C. Circuit: (i) when the agency action 
consists of ``nationally applicable regulations promulgated, or final 
actions taken, by the Administrator,'' or (ii) when such action is 
locally or regionally applicable, but ``such action is based on a 
determination of nationwide scope or effect and if in taking such 
action the Administrator finds and publishes that such action is based 
on such a determination.'' For locally or regionally applicable final 
actions, the CAA reserves to the EPA complete discretion whether to 
invoke the exception in (ii).\337\
---------------------------------------------------------------------------

    \337\ In deciding whether to invoke the exception by making and 
publishing a finding that an action is based on a determination of 
nationwide scope or effect, the Administrator takes into account a 
number of policy considerations, including his judgment balancing 
the benefit of obtaining the D.C. Circuit's authoritative 
centralized review versus allowing development of the issue in other 
contexts and the best use of agency resources.
---------------------------------------------------------------------------

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

[[Page 9381]]

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

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

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

List of Subjects in 40 CFR Part 52

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

Michael S. Regan,
Administrator.

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

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

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

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

Subpart B--Alabama

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

Sec.  52.56   Control strategy: Ozone.

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

Subpart E--Arkansas

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

Sec.  52.174  Control strategy and regulations: Ozone.

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

Subpart F--California

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

Sec.  52.223  Approval status.

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

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

Sec.  52.283  Interstate Transport.

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

Subpart O--Illinois

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

Sec.  52.720  Identification of plan.

* * * * *
    (e) * * *

                       EPA-Approved Illinois Nonregulatory and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                      Applicable
      Name of SIP provision          geographic or      State submittal    EPA approval date       Comments
                                  nonattainment area         date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
                                  Section 110(a)(2) Infrastructure Requirements
----------------------------------------------------------------------------------------------------------------
 

[[Page 9382]]

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

Subpart P--Indiana

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

Sec.  52.770  Identification of plan.

* * * * *
    (e) * * *

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

Subpart S--Kentucky

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

Sec.  52.930   Control strategy: Ozone.

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

Subpart T--Louisiana

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

Sec.  52.996  Disapprovals.

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

Subpart V--Maryland

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

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

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

Subpart X--Michigan

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

Sec.  52.1170  Identification of plan.

* * * * *
    (e) * * *

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

[[Page 9383]]

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

Subpart Y--Minnesota

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

Sec.  52.1220  Identification of plan.

* * * * *
    (e) * * *

                                 EPA-Approved Minnesota Nonregulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                                            State
                                        Applicable        submittal
    Name of nonregulatory SIP          geographic or        date/       EPA approved date         Comments
            provision               nonattainment area    effective
                                                             date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Section 110(a)(2) Infrastructure   Statewide...........    10/1/2018  2/13/2023, [INSERT    Fully approved for
 Requirements for the 2015 Ozone                                       FEDERAL REGISTER      all CAA elements
 NAAQS.                                                                CITATION].            except transport
                                                                                             elements of
                                                                                             (D)(i)(I) Prong 2,
                                                                                             which are
                                                                                             disapproved, and no
                                                                                             action has been
                                                                                             taken on the
                                                                                             visibility
                                                                                             protection
                                                                                             requirements of
                                                                                             (D)(i)(II).
----------------------------------------------------------------------------------------------------------------

Subpart Z--Mississippi

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

Sec.  52.1273   Control strategy: Ozone.

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

Subpart AA--Missouri

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

Sec.  52.1323  Approval status.

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

Subpart DD--Nevada

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

Sec.  52.1472  Approval status.

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

Subpart FF--New Jersey

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

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

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

Subpart HH--New York

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

Sec.  52.1683  Control strategy: Ozone.

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

Subpart KK--Ohio

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

[[Page 9384]]

Sec.  52.1870  Identification of plan.

* * * * *
    (e) * * *

                         EPA-Approved Ohio Nonregulatory and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                        Applicable
              Title                    geographic or      State date      EPA approval            Comments
                                    nonattainment area
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
                                           Infrastructure Requirements
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Section 110(a)(2) infrastructure   Statewide...........    9/28/2018  2/13/2023, [INSERT    Approved CAA
 requirements for the 2015 ozone                                       FEDERAL REGISTER      elements:
 NAAQS.                                                                CITATION].            110(a)(2)(A), (B),
                                                                                             (C), (D)(i)(II)
                                                                                             prongs 3 and 4,
                                                                                             (E), (F), (G), (H),
                                                                                             (J), (K), (L), and
                                                                                             (M). Elements
                                                                                             (D)(i)(I) prongs 1
                                                                                             and 2 are
                                                                                             disapproved.
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

Subpart LL--Oklahoma

0
19. Section 52.1922 is amended by adding paragraph (c) to read as 
follows:

Sec.  52.1922  Approval status.

* * * * *
    (c) The portion of the SIP submittal from October 25, 2018, 
addressing Clean Air Act section 110(a)(2)(D)(i)(I) for the 2015 ozone 
national ambient air quality standards (NAAQS) is disapproved.

Subpart SS--Texas

0
20. Section 52.2275 is amended by:
0
a. Removing the first paragraph (m); and
0
b. Adding paragraph (o).
    The addition reads as follows:

Sec.  52.2275  Control strategy and regulations: Ozone.

* * * * *
    (o) Disapproval. The portion of the SIP submittal from September 
12, 2018, addressing Clean Air Act section 110(a)(2)(D)(i)(I) for the 
2015 ozone NAAQS is disapproved.

Subpart XX--West Virginia

0
21. Section 52.2520 is amended in the table in paragraph (e) by adding 
the entry ``Section 110(a)(2) Infrastructure Requirements for the 2015 
8-Hour Ozone NAAQS'' at the end of the table to read as follows:

Sec.  52.2520  Identification of plan.

* * * * *
    (e) * * *

----------------------------------------------------------------------------------------------------------------
                                                            State
    Name of non-regulatory SIP          Applicable        submittal     EPA approval date        Additional
             revision                 geographic area        date                                explanation
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Section 110(a)(2) Infrastructure   Statewide...........     2/4/2019  2/13/2023, [INSERT    Disapproval--EPA is
 Requirements for the 2015 8-Hour                                      FEDERAL REGISTER      disapproving West
 Ozone NAAQS.                                                          CITATION].            Virginia's February
                                                                                             4, 2019, State
                                                                                             Implementation Plan
                                                                                             (SIP) revision
                                                                                             intended to address
                                                                                             the CAA section
                                                                                             110(a)(2)(D)(i)(I)
                                                                                             interstate
                                                                                             transport
                                                                                             requirements for
                                                                                             the 2015 8-hour
                                                                                             ozone national
                                                                                             ambient air quality
                                                                                             standard (NAAQS).
----------------------------------------------------------------------------------------------------------------

Subpart YY--Wisconsin

0
22. Section 52.2591 is amended by adding paragraph (l) to read as 
follows:

Sec.  52.2591  Section 110(a)(2) infrastructure requirements.

* * * * *
    (l) Partial approval/disapproval. In a September 14, 2018, 
submission, WDNR certified that the State has satisfied the 
infrastructure SIP requirements of section 110(a)(2)(A) through (H), 
and (J) through (M) for the 2015 ozone NAAQS. For section 
110(a)(2)(D)(i)(I), prong 1 is approved and prong 2 is disapproved. EPA 
did not take action on any other elements. We will address the 
remaining requirements in a separate action.

[FR Doc. 2023-02407 Filed 2-10-23; 8:45 am]
BILLING CODE 6560-50-P