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Proposed Rule2026-01844

Interstate Transport Plan Review for the 2015 Ozone NAAQS

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Published

January 30, 2026

Issuing agencies

Environmental Protection Agency

Abstract

Pursuant to the Clean Air Act (CAA), the U.S. Environmental Protection Agency (EPA) is proposing to approve State Implementation Plan (SIP) submissions from eight States--Alabama, Arizona, Kentucky, Minnesota, Mississippi, Nevada, New Mexico, and Tennessee--regarding interstate transport for the 2015 8-hour ozone National Ambient Air Quality Standards (NAAQS). This action also explains why the EPA anticipates withdrawing previously proposed EPA error-correction actions related to interstate transport obligations for Iowa and Kansas and withdrawing previously proposed SIP disapproval actions for Tennessee, New Mexico, and Arizona. 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. If finalized as proposed, this action would resolve these 10 States' obligations to eliminate significant contribution to nonattainment or interference with maintenance of the 2015 8-hour ozone NAAQS in other States.

Full Text

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<title>Federal Register, Volume 91 Issue 20 (Friday, January 30, 2026)</title>
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[Federal Register Volume 91, Number 20 (Friday, January 30, 2026)]
[Proposed Rules]
[Pages 4026-4045]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-01844]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-HQ-OAR-2025-0192; FRL-12716-01-OAR]
RIN 2060-AW63

Interstate Transport Plan Review for the 2015 Ozone NAAQS

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; reconsideration of final rule.

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SUMMARY: Pursuant to the Clean Air Act (CAA), the U.S. Environmental
Protection Agency (EPA) is proposing to approve State Implementation
Plan (SIP) submissions from eight States--Alabama, Arizona, Kentucky,
Minnesota, Mississippi, Nevada, New Mexico, and Tennessee--regarding
interstate transport for the 2015 8-hour ozone National Ambient Air
Quality Standards (NAAQS). This action also explains why the EPA
anticipates withdrawing previously proposed EPA error-correction
actions related to interstate transport obligations for Iowa and Kansas
and withdrawing previously proposed SIP disapproval actions for
Tennessee, New Mexico, and Arizona. 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. If finalized as proposed,
this action would resolve these 10 States' obligations to eliminate
significant contribution to nonattainment or interference with
maintenance of the 2015 8-hour ozone NAAQS in other States.

DATES: Comments must be received on or before March 2, 2026.

ADDRESSES: Comments: You may send comments, identified by Docket ID No.
EPA-HQ-OAR-2025-0192, by any of the following methods:
<bullet> Federal eRulemaking Portal: <a href="http://www.regulations.gov">www.regulations.gov</a> (our
preferred method). Follow the online instructions for submitting
comments.
<bullet> Email: <a href="/cdn-cgi/l/email-protection#13723e727d773e613e777c70787667537663723d747c65">[email&#160;protected]</a>. Include Docket ID No. EPA-
HQ-OAR-2025-0192 in the subject line of the message.
<bullet> Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2025-0192, Mail Code 28221T, 1200
Pennsylvania Avenue NW, Washington, DC 20460.
<bullet> Hand Delivery or Courier: EPA Docket Center, WJC West
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004.
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except Federal holidays).
Instructions: All submissions received must include the Docket ID
No. for this proposed rulemaking. Comments received may be posted
without change to <a href="http://www.regulations.gov">www.regulations.gov</a>, including personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the ``Public Participation''
heading of the SUPPLEMENTARY INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: For information about this proposed
rule, contact Gwyndolyn Sofka, Air Quality Planning Division, Office of
State Air Partnerships (C539-04), Environmental Protection Agency, 109
TW Alexander Drive, Research Triangle Park, NC 27711; telephone number
(919) 541-5121; email address: <a href="/cdn-cgi/l/email-protection#87f4e8e1ece6a9e0f0fee9e3e8ebfee9c7e2f7e6a9e0e8f1">[email&#160;protected]</a> OR Thomas Uher,
Air Quality Planning Division, Office of State Air Partnerships (C539-
04), Environmental Protection Agency, 109 TW Alexander Drive, Research
Triangle Park, NC 27711; telephone number: (919) 541-5534; email
address: <a href="/cdn-cgi/l/email-protection#d5a0bdb0a7fba1bdbab8b4a695b0a5b4fbb2baa3">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION:
Docket. The EPA established a docket for this action under Docket
ID No. EPA-HQ-OAR-2025-0192. All documents in the docket are listed in
<a href="http://www.regulations.gov/">www.regulations.gov/</a>. Although listed, some information is not publicly
available, e.g., 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 as PDF versions that can only be
accessed on the EPA computers in the docket office reading room.
Certain databases and physical items cannot be downloaded from the
docket but may be requested by contacting the docket office at 202-566-
1744. The docket office has up to 10 business days to respond to these
requests. With the exception of such material, publicly available
docket materials and a plain language summary of the proposed rule are
available electronically at <a href="http://www.regulations.gov">www.regulations.gov</a>.
Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2025-0192. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at <a href="http://www.regulations.gov">www.regulations.gov</a>, including any personal information
provided, unless the comment includes information claimed to be CBI or
other information whose disclosure is restricted by statute. Do not
submit electronically to <a href="http://www.regulations.gov">www.regulations.gov</a> any information that you
consider to be CBI or other information whose disclosure is restricted
by statute. This type of information should be submitted as discussed
below.
The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web,

[[Page 4027]]

cloud, or other file sharing system). For additional submission
methods, the full EPA public comment policy, information about CBI or
multimedia submissions, and general guidance on making effective
comments, please visit <a href="http://www.epa.gov/dockets/commenting-epa-dockets">www.epa.gov/dockets/commenting-epa-dockets</a>.
The <a href="http://www.regulations.gov/website">www.regulations.gov/website</a> allows you to submit your comment
anonymously, which means the EPA will not know your identity or contact
information unless you provide it in the body of your comment. If you
send an email comment directly to the EPA without going through
<a href="http://www.regulations.gov">www.regulations.gov</a>, your email address will be automatically captured
and included as part of the comment that is placed in the public docket
and made available on the internet. If you submit an electronic
comment, the EPA recommends that you include your name and other
contact information in the body of your comment and with any digital
storage media you submit. If the EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, the
EPA may not be able to consider your comment. Electronic files should
not include special characters or any form of encryption and should be
free of any defects or viruses. For additional information about the
EPA's public docket, visit the EPA Docket Center homepage at
<a href="http://www.epa.gov/dockets">www.epa.gov/dockets</a>.
Submitting CBI. Do not submit information containing CBI to the EPA
through <a href="http://www.regulations.gov">www.regulations.gov</a>. Clearly mark the part or all of the
information that you claim to be CBI. For CBI information on any
digital storage media that you mail to the EPA, note the docket ID,
mark the outside of the digital storage media as CBI, and identify
electronically within the digital storage media the specific
information that is claimed as CBI. In addition to one complete version
of the comments that includes information claimed as CBI, you must
submit a copy of the comments that does not contain the information
claimed as CBI directly to the public docket through the procedures
outlined in Instructions above. If you submit any digital storage media
that does not contain CBI, mark the outside of the digital storage
media clearly that it does not contain CBI and note the docket ID.
Information not marked as CBI will be included in the public docket and
the EPA's electronic public docket without prior notice. Information
marked as CBI will not be disclosed except in accordance with
procedures set forth in 40 Code of Federal Regulations (CFR) part 2.
Our preferred method to receive CBI is for it to be transmitted
electronically using email attachments, File Transfer Protocol (FTP),
or other online file sharing services (e.g., Dropbox, OneDrive, Google
Drive). Electronic submissions must be transmitted directly to the
Office of State Air Partnerships (OSAP) CBI Office at the email address
<a href="/cdn-cgi/l/email-protection#345b554544476b57565d745144551a535b42">[email&#160;protected]</a> and, as described above, should include clear CBI
markings and note the docket ID. If assistance is needed with
submitting large electronic files that exceed the file size limit for
email attachments, and if you do not have your own file sharing
service, please email <a href="/cdn-cgi/l/email-protection#f69997878685a995949fb6938697d8919980">[email&#160;protected]</a> to request a file transfer
link. If sending CBI information through the postal service, please
send it to the following address: U.S. EPA, Attn: OAQPS Document
Control Officer, Mail Drop: C404-02, 109 T.W. Alexander Drive, P.O. Box
12055, Research Triangle Park, North Carolina 27711, Attention Docket
ID No. EPA-HQ-OAR-2025-0192. The mailed CBI material should be double
wrapped and clearly marked. Any CBI markings should not show through
the outer envelope.
Preamble acronyms and abbreviations. Throughout this preamble the
use of ``we,'' ``us,'' or ``our'' is intended to refer to the EPA. We
use multiple acronyms and terms in this preamble. While this list may
not be exhaustive, to ease the reading of this preamble and for
reference purposes, the EPA defines the following terms and acronyms
here:

2016v1 2016 Version 1 Emissions Modeling Platform
2016v2 2016 Version 2 Emissions Modeling Platform
2016v3 2016 Version 3 Emissions Modeling Platform
CAA Clean Air Act
CAIR Clean Air Interstate Rule
CBI Confidential Business Information
CFR Code of Federal Regulations
CSAPR Cross-State Air Pollution Rule
EGU Electric Generating Unit
EHD Environmental Health Department
EPA United States Environmental Protection Agency
FIP Federal Implementation Plan
LADCO Lake Michigan Air Directors Consortium
NAAQS National Ambient Air Quality Standards
NDEP Nevada Division of Environmental Protection
NMED New Mexico Environment Department
NO<INF>X</INF> Nitrogen Oxides
OMB United States Office of Management and Budget
ppb parts per billion
ppm parts per million
PRA Paperwork Reduction Act
RFA Regulatory Flexibility Act
SIP State Implementation Plan
TSD Technical Support Document
UMRA Unfunded Mandates Reform Act
VOCs Volatile Organic Compounds
WOE Weight of Evidence

Organization of this document. The information in this preamble is
organized as follows:

I. Executive Summary
II. General Information
A. Does this action apply to me?
B. What action is the EPA taking?
C. What is the EPA's authority for taking this action?
III. Background and Approach for Evaluation
A. Description of Statutory, Regulatory, and Judicial Background
B. Description of the EPA's 4-Step Interstate Transport
Regulatory Framework
C. The EPA's Approach To Evaluating Interstate Transport for the
2015 8-Hour Ozone NAAQS
1. Selection of Analytic Year
2. Step 1 of the 4-Step Interstate Transport Framework
3. Step 2 of the 4-Step Interstate Transport Framework
4. Choice of Modeling to Inform Steps 1 and 2
5. Step 3 of the 4-Step Interstate Transport Framework
6. Step 4 of the 4-Step Interstate Transport Framework
IV. SIP Submissions Addressing Interstate Transport of Air Pollution
for the 2015 8-Hour Ozone NAAQS
A. SIP Summaries and the EPA's Evaluation
1. Alabama
a. Prior Notices Related to Alabama's SIP Submission
b. Summary of Alabama's Submission
c. Evaluation of Alabama's Submission
2. Arizona
a. Prior Notices Related to Arizona's SIP Submission
b. Summary of Arizona's Submission
c. Evaluation of Arizona's Submission
3. Iowa
a. Prior Notices Related to Iowa's SIP Submission
b. Summary of Iowa's Submission
c. Evaluation of Iowa's Submission
4. Kansas
a. Prior Notices Related to Kansas' SIP Submission
b. Summary of Kansas' Submission
c. Evaluation of Kansas' Submission
5. Kentucky
a. Prior Notices Related to Kentucky's SIP Submission
b. Summary of Kentucky's Submission
c. Evaluation of Kentucky's Submission
6. Minnesota
a. Prior Notices Related to Minnesota's SIP Submission
b. Summary of Minnesota's Submission
c. Evaluation of Minnesota's Submission
7. Mississippi
a. Prior Notices Related to Mississippi's SIP Submission
b. Summary of Mississippi's Submission
c. Evaluation of Mississippi's Submission
8. Nevada

[[Page 4028]]

a. Prior Notices Related to Nevada's SIP Submission
b. Summary of Nevada's Submission
c. Evaluation of Nevada's Submission
9. New Mexico
a. Prior Notices Related to New Mexico's SIP Submission
b. Summary of New Mexico's Submission
c. Evaluation New Mexico's Submission
10. Tennessee
a. Prior Notices Related to Tennessee's SIP Submission
b. Summary of Tennessee's Submission
c. Evaluation of Tennessee's Submission
B. CAA Section 110(l)
V. Summary of Changes to Existing Regulatory Text
VI. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
B. Executive Order 14192: Unleashing Prosperity Through
Deregulation
C. Paperwork Reduction Act (PRA)
D. Regulatory Flexibility Act (RFA)
E. Unfunded Mandates Reform Act (UMRA)
F. Executive Order 13132: Federalism
G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use
J. National Technology Transfer and Advancement Act

I. Executive Summary

On October 1, 2015, the EPA revised the primary and secondary 8-
hour standards for ozone to 70 parts per billion (ppb) in the final
rule entitled ``National Ambient Air Quality Standards for Ozone''
(``2015 8-hour ozone NAAQS'').\1\ States were required to provide ozone
infrastructure SIP submissions to fulfill interstate transport
obligations for the 2015 8-hour ozone NAAQS by October 1, 2018.\2\
Pursuant to the ``good neighbor'' or ``interstate transport'' provision
of CAA section 110, the SIP submissions were required to include
provisions sufficient to prevent emissions within the State that
``contribute significantly to nonattainment in, or interfere with
maintenance by, any other State with respect to [the NAAQS].'' \3\
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\1\ 80 FR 65292 (Oct. 26, 2015).
\2\ See 42 U.S.C. 7410(a)(1).
\3\ Id. 7410(a)(2)(D)(i)(I).
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In a series of memoranda released in 2018, the EPA provided
guidance to States on the content of SIP submissions that address the
interstate transport provision for the 2015 ozone NAAQS. In March 2018,
we released modeling results that use a 2011 base year and a 2023
analytical year (``March 2018 memorandum'').\4\ In August 2018, we
issued further guidance advising that it ``may be reasonable and
appropriate for states to use a 1 ppb contribution threshold, as an
alternative to a 1 percent threshold.'' (``August 2018
memorandum'').\5\ Many States, including States covered by this
rulemaking, submitted SIP submissions that relied on the modeling and
analysis in the March 2018 and August 2018 memoranda.
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\4\ 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. The version of 2023 contribution
modeling referenced in the March 2018 memorandum may also be
referred to as 2011-base year modeling. The memo is available in the
docket (Docket ID No. EPA-HQ-OAR-2025-0192) and at <a href="http://www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips">www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips</a>.
\5\ 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 at 3, available in the docket
and at <a href="http://www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips">www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips</a>.
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When acting on certain submissions in 2023, however, the EPA
interpreted the March 2018 and August 2018 memoranda as allowing EPA to
give greater weight to the EPA's latest modeling results (referred to
as ``2016v3'') when it showed linkages not identified in the March 2018
memorandum modeling and to apply a 1 percent of the NAAQS contribution
threshold. Based on the SIP submissions, the EPA's interpretation of
its memoranda, and the 2016v3 modeling, the EPA disapproved the SIP
submissions from Alabama, Kentucky, Minnesota, Mississippi, Nevada, and
16 other States in ``Air Plan Disapprovals; Interstate Transport of Air
Pollution for the 2015 8-Hour Ozone National Ambient Air Quality
Standards'' (``SIP Disapproval Action'').\6\ Using the same approach,
the EPA also proposed to disapprove the SIP submissions from Arizona,
New Mexico, and Tennessee, and proposed to error correct the previous
approval of the SIPs from Iowa and Kansas to disapprovals in
``Supplemental Air Plan Actions: Interstate Transport of Air Pollution
for the 2015 8-Hour Ozone National Ambient Air Quality Standards and
Supplemental Federal `Good Neighbor Plan' Requirements for the 2015 8-
Hour Ozone National Ambient Air Quality Standards'' (``Proposed
Supplemental Air Plan Action'').\7\
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\6\ See 88 FR 9336 (Feb. 13, 2023).
\7\ See 89 FR 12666 (Feb. 16, 2024).
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Many of the EPA's disapprovals were challenged in regional circuit
courts and stayed.\8\ The Fifth Circuit vacated and remanded the EPA's
disapproval of Mississippi's SIP submission concluding that the EPA
failed to recognize or reasonably explain its decision to consider the
updated modeling in an ``outcome determinative'' way.\9\ The Sixth
Circuit vacated and remanded the EPA's disapproval of Kentucky's SIP in
part for failing to address reliance interests Kentucky had in guidance
provided by EPA to Kentucky, including specific feedback on a draft
version of Kentucky's submission.\10\ The challenges against the
disapprovals of the SIP submissions from Alabama, Minnesota, and Nevada
remain pending, but in abeyance, pending the EPA's reconsideration.\11\
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\8\ See, e.g., Alabama et al. v. EPA, No. 23-11173, ECF No. 33
(11th Cir. August 17, 2023) (Alabama); Allete, Inc. et al. v. EPA,
No. 23-1776, ECF No. 5292580 (8th Cir. July 5, 2023) (Minnesota).
\9\ Texas v. EPA, 132 F.4th 808, 860-862 (5th Cir. 2025). The
Fifth Circuit has withheld the mandate pending the resolution of
pending petitions for rehearing en banc, which are focused on the
portion of the opinion upholding the EPA's disapproval of Texas's
SIP submission. See Texas et al. v. EPA, No. 23-60069 ECF No. 588
(5th Cir. May 22, 2025).
\10\ Kentucky v. EPA, 123 F.4th 447, 468-471 (6th Cir. 2024).
See Sections III.C.3 and III.C.4 for further discussion of the Sixth
Circuit's decision.
\11\ See Alabama et al. v. EPA, No. 23-11173 (11th Cir.);
Alabama Power Company v. EPA, No. 23-11196 (11th Cir.); Allete, Inc.
et al. v. EPA, No. 23-1776 (8th Cir.); Nevada Cement Co. LLC, v.
EPA, No. 23-682 (9th Cir.).
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In light of the Fifth and Sixth Circuit judicial decisions and upon
further review, the EPA now proposes to evaluate the relevant SIP
submissions under policies related to the contribution threshold and
choice of modeling consistent with the Fifth and Sixth Circuits'
interpretation of the March 2018 and August 2018 memoranda. This
proposed rule, if finalized, would approve the portion of SIP
submissions addressing interstate transport for the 2015 8-hour ozone
NAAQS of eight States. Additionally, at the final stage of this
rulemaking, the EPA anticipates withdrawing the proposed error
correction of the EPA's past approvals for two additional States and
withdrawing the proposed partial disapproval of SIP submissions for
three States included in the EPA's Proposed Supplemental Air Plan
Action under CAA section 110(a)(2)(D)(i)(I), referred to as the ``good
neighbor'' or the ``interstate transport'' provision of the CAA, for
the 2015 8-hour ozone NAAQS.
The EPA proposes to find that interstate transport of ozone
precursor emissions from eight upwind States (Alabama, Arizona,
Kentucky, Mississippi, Minnesota, Nevada, New

[[Page 4029]]

Mexico, and Tennessee) do not significantly contribute to nonattainment
or interfere with maintenance of the 2015 8-hour ozone NAAQS in other
States. On that basis, we propose to approve the relevant portions of
these States' SIPs, which do not need to impose additional restrictions
to satisfy obligations under the interstate transport provision. We,
therefore, propose to reconsider the previous full or partial
disapprovals of the 2015 ozone NAAQS SIP submissions from Alabama,
Minnesota, and Nevada included in the SIP Disapproval Action. In
response to the circuit courts' remands of the EPA's disapprovals of
the 2015 ozone NAAQS interstate transport SIP submissions from Kentucky
and Mississippi, we are proposing to approve these SIPs.\12\
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\12\ See Kentucky v. EPA, 123 F.4th 447 (6th Cir. 2024); Texas
v. EPA, 132 F.4th 808 (5th Cir. 2025).
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The EPA previously proposed to partially disapprove the 2015 8-hour
ozone NAAQS interstate transport SIP submissions from Arizona, New
Mexico, and Tennessee.\13\ The EPA also proposed error corrections
related to the prior approval of Iowa and Kansas's 2015 8-hour ozone
NAAQS interstate transport SIPs.\14\ For consistent treatment between
States, the EPA anticipates withdrawing these prior proposals at the
final stage of this rulemaking. For clarification, the EPA notes that
the prior SIP approvals for Iowa and Kansas remain in place.
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\13\ 89 FR 12666 (Feb. 16, 2024).
\14\ Id.
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The EPA previously promulgated 2015 8-hour ozone NAAQS interstate
transport Federal Implementation Plans (FIPs) for Alabama, Kentucky,
Minnesota, Mississippi, and Nevada,\15\ which have been stayed under
the EPA's actions in response to various judicial stays of the SIP
Disapproval Action and to the Supreme Court's stay of the Good Neighbor
Plan.\16\ If this action is finalized as proposed, the EPA would no
longer have the authority or the intention to lift the current stay of
those FIPs, or otherwise attempt to implement those FIPs, for these or
any other States with approved SIPs with respect to the interstate
transport obligations for the 2015 ozone NAAQS.\17\
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\15\ 88 FR 36654 (June 5, 2023) (Good Neighbor Plan).
\16\ 88 FR 49295 (July 31, 2023) (staying the Good Neighbor Plan
FIPs for, inter alia, Kentucky and Mississippi); 88 FR 67102 (Sept.
29, 2023) (staying the Good Neighbor Plan FIPs for, inter alia,
Alabama, Minnesota, and Nevada); 89 FR 87960 (Nov. 6, 2024) (staying
the Good Neighbor Plan as to all subject emissions sources).
\17\ The EPA is not at this time withdrawing the Good Neighbor
Plan FIPs for states with proposed SIP approvals but anticipates
taking that step in a future action for all states that obtain final
SIP approvals for the relevant obligations. Because the Good
Neighbor Plan FIPs are stayed for Alabama, Kentucky, Minnesota,
Mississippi, and Nevada, and the EPA has no current authority to
bring them into effect, leaving the stayed regulatory provisions in
place has no practical or legal effect for any party. We acknowledge
that the removal of regulatory language promulgating such FIPs is a
matter that is important to be resolved quickly to provide certainty
to the relevant states. However, we believe such an action would be
subject to CAA section 307(d) and is beyond the scope of this
action.
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Taken together, these steps, if finalized, will fully resolve the
included States' interstate transport obligations for the 2015 8-hour
ozone NAAQS. The EPA intends to take a subsequent action consistent
with this proposal, subject to further public input, to address
interstate transport obligations for the 2015 8-hour ozone NAAQS for
other States.

II. General Information

A. Does this action apply to me?

This proposed rule is relevant to 10 States. It affects five upwind
States (Alabama, Kentucky, Mississippi, Minnesota, and Nevada) with
prior full or partial disapprovals and three upwind States (Arizona,
New Mexico, and Tennessee) with proposed partial disapprovals of the
portion of their SIP submittals addressing interstate transport for the
2015 8-hour ozone NAAQS by approving their SIPs. The EPA finds that
these States do not significantly contribute to nonattainment or
interfere with maintenance of the 2015 8-hour ozone NAAQS in any other
State. In addition, this proposed rule explains why the EPA anticipates
withdrawing the EPA's prior proposed error correction regarding Iowa
and Kansas' 2015 8-hour ozone NAAQS interstate transport SIPs.\18\ For
clarification, the EPA notes that the prior approvals for Kansas and
Iowa's SIPs remain in place.
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\18\ Id.
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B. What action is the EPA taking?

In this rule, as stated in Section I of this preamble, the EPA is
proposing approval of the portion of SIP submissions addressing
interstate transport for the 2015 8-hour ozone NAAQS of eight States,
including areas of Indian country located within the geographic bounds
of the covered States. As part of these broader actions, the EPA is
proposing to reconsider three prior final SIP actions and respond to
the remand of two SIP actions to the EPA. At the final stage of this
rulemaking, the EPA anticipates withdrawing the EPA's prior proposed
error correction of past approvals for two additional States and
withdrawing the proposed partial disapproval of SIP submissions for
three States included in the Proposed Supplemental Air Plan Action.\19\
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\19\ Id.
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This action does not propose any action on the ``Federal `Good
Neighbor Plan' for the 2015 Ozone National Ambient Air Quality
Standards'' (``Good Neighbor Plan'').\20\ However, the EPA would no
longer have the authority or the intention to lift the current stay of
those FIPs, or otherwise attempt to implement the Good Neighbor Plan
requirements, for these or any other State with approved SIPs with
respect to the interstate transport obligations for the 2015 ozone
NAAQS.
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\20\ 88 FR 36654 (June 5, 2023).
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The EPA intends to address the Good Neighbor Plan, and the
remaining States covered by that action which are not addressed in this
action, in a future action. We anticipate that action will also
address, as relevant, the applicability of any Good Neighbor Plan FIPs
in areas in Indian country.

C. What is the EPA's authority for taking this action?

The statutory authority for this proposed action is provided by the
CAA as amended (42 U.S.C. 7401 et seq.). Specifically, CAA section 110
provides the primary statutory underpinning for this action. The most
relevant portions of CAA section 110 are subsections 110(a)(1),
110(a)(2) (including 110(a)(2)(D)(i)(I)), 110(k)(2), and 110(k)(3). The
EPA has historically referred to SIP submissions made for the purpose
of satisfying the applicable requirements of CAA sections 110(a)(1) and
110(a)(2) as ``infrastructure SIP'' or ``iSIP'' submissions. CAA
section 110(a)(1) addresses the timing and general requirements for
iSIP submissions and CAA section 110(a)(2) provides more details
concerning the required content of these submissions.\21\ CAA section
110(a)(2) includes a list of specific elements that ``[e]ach such
plan'' must address, including the requirements of CAA section
110(a)(2)(D)(i)(I).\22\
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\21\ 42 U.S.C. 7410(a)(2).
\22\ The EPA's general approach to infrastructure SIP
submissions is explained in greater detail in individual documents
acting or proposing to act on state infrastructure SIP submissions
and in guidance. See, e.g., Memorandum from Stephen D. Page on
Guidance on Infrastructure State Implementation Plan (SIP) Elements
under Clean Air Act Sections 110(a)(1) and 110(a)(2) (Sept. 13,
2013) included in the docket for this proposed action, Docket ID No.
EPA-HQ-OAR-2025-0192.
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CAA section 110(a)(2)(D)(i)(I), also known as the ``good neighbor''
or ``interstate transport'' provision,

[[Page 4030]]

provides the primary basis for this proposed action. It requires that
each State's SIP include provisions sufficient to ``prohibit[ ],
consistent with the provisions of this subchapter, any source or other
type of emissions activity within the state from emitting any air
pollutant in amounts which will--(I) contribute significantly to
nonattainment in, or interfere with maintenance by, any other State
with respect to any [NAAQS].'' \23\ The EPA often refers to the
emissions reduction requirements under this provision as ``good
neighbor obligations'' or ``interstate transport obligations'' and
submissions addressing these requirements as ``good neighbor SIPs'' or
``interstate transport SIPs.''
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\23\ 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

CAA section 301(a)(1) gives the Administrator the general authority
to prescribe such regulations as necessary to carry out functions under
the CAA.\24\ Pursuant to this section, the EPA has authority to clarify
the applicability of CAA requirements and undertake other rulemaking
action as necessary to implement CAA requirements.
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\24\ Id. 7601(a)(1).
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CAA section 110(k)(2) gives the Administrator authority to act on a
complete SIP submission in accordance with CAA section 110(k)(3), which
gives the Administrator authority to approve in whole, disapprove, or
approve in part and disapprove in part SIP submissions based on the
EPA's determination whether the submission meets the relevant
requirements of the CAA.\25\ The authority to review and approve or
disapprove submissions, based on the EPA's interpretation of the CAA,
also implicitly includes the authority to reconsider the EPA's previous
action on a SIP submission. Two judicial decisions described in
Sections III.C.3 and 4 of this preamble have caused the EPA to
reconsider key policies related to interstate transport requirements
under CAA section 110(a)(2)(A)(i)(I) for the 2015 8-hour ozone
NAAQS.\26\ The EPA's new understanding is applicable not just to the
States who were the subject of those judicial decisions but to other
States as well.
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\25\ Id. 7410(k)(2)-(3).
\26\ See Kentucky v. EPA, 123 F.4th 447 (6th Cir. 2024); Texas
v. EPA, 132 F.4th 808 (5th Cir. 2025).
---------------------------------------------------------------------------

In addition to the forgoing provisions, the EPA proposes this
action consistent with agencies' authority to reconsider prior
decisions.\27\
---------------------------------------------------------------------------

\27\ See FDA v. Wages & White Lion Invs., LLC, 145 S. Ct. 898
(2025); FCC v. Fox TV Stations, Inc., 556 U.S. 502 (2009); Motor
Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29
(1983); Clean Air Council v. Pruitt, 862 F.3d 1, 8 (D.C. Cir. 2017).
---------------------------------------------------------------------------

III. Background & Approach for Evaluation

A. Description of Statutory, Regulatory, and Judicial Background

On October 1, 2015, the EPA promulgated a revision to the ozone
NAAQS, lowering both the primary and secondary standards to 70 ppb for
the 8-hour standard.\28\ CAA section 110(a)(1) requires States to
submit, within three years after promulgation of a new or revised
standard, SIP submissions meeting the applicable requirements of CAA
section 110(a)(2).\29\ One of these applicable requirements is found in
CAA section 110(a)(2)(D)(i)(I), which generally requires that SIPs
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).\30\
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\28\ Although the level of the standard is specified in the
units of ppb, ozone concentrations are also described in parts per
million (ppm). For example, 70 ppb is equivalent to 0.070 ppm.
\29\ SIP submissions that are intended to meet the applicable
requirements of CAA 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.
\30\ See North Carolina v. EPA, 531 F.3d 896, 909-11 (D.C. Cir.
2008).
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On January 31, 2023, the EPA signed final disapprovals for 19 SIP
submissions and partially approved and partially disapproved two SIP
submissions addressing the good neighbor provision for the 2015 ozone
NAAQS, including from Alabama, Kentucky, Minnesota, Mississippi, and
Nevada.\31\ On March 15, 2023, the EPA promulgated FIPs for Alabama,
Kentucky, Minnesota, Mississippi, and Nevada in the Good Neighbor Plan,
which were later stayed. On February 16, 2024, the EPA proposed partial
disapproval of SIP submissions from Arizona, New Mexico, and Tennessee;
proposed error corrections to change past approvals to partial
disapprovals for Iowa and Kansas; and proposed FIPs for all five
States.\32\
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\31\ 88 FR 9336 (Feb. 13, 2023).
\32\ 89 FR 12666 (Feb. 16, 2024).
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In Ohio v. EPA, the Supreme Court stayed enforcement of FIPs
promulgated in the Good Neighbor Plan as to certain parties pending
judicial review.\33\ The EPA complied with that order by staying the
FIPs as to all sources in all the remaining 23 States not already under
stays.\34\ The EPA's disapprovals of the SIP submissions from Kentucky
and Mississippi were later vacated and remanded back to the EPA by
circuit courts, which means that the EPA has an outstanding duty to act
on those SIP submissions consistent with the court
opinions.35 36
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\33\ Ohio v. EPA, 603 U.S. 279 (2024).
\34\ 89 FR 87960 (Nov. 6, 2024) (staying the Good Neighbor Plan
as to all subject emissions sources); see also 88 FR 49295 (July 31,
2023); 88 FR 67102 (Sept. 29, 2023).
\35\ Kentucky v. EPA, 123 F.4th 447 (6th Cir. 2024); Texas v.
EPA, 132 F.4th 808 (5th Cir. 2025).
\36\ Texas petitioners' petitions for rehearing en banc of Texas
remain pending. See Texas et al. v. EPA, No. 23-60069, ECF Nos. 582,
583 (5th Cir. May 9, 2025).
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B. Description of the EPA's 4-Step Interstate Transport Regulatory
Process

When evaluating interstate transport obligations, the EPA
consistently utilizes the 4-step interstate transport framework (the
``Framework''), which was developed to explicate the critical statutory
terms in CAA section 110(a)(2)(D)(i)(I) and to provide a reasonable
organization to the analysis of the complex air quality challenge of
interstate ozone transport. The EPA addressed the interstate transport
requirements of CAA section 110(a)(2)(D)(i)(I) with respect to
implementation of prior NAAQS using the Framework in several regulatory
actions, including the original Cross-State Air Pollution Rule
(CSAPR),\37\ which addressed interstate transport with respect to the
1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter
standards, and the CSAPR Update \38\ and the Revised CSAPR Update,\39\
which addressed the 2008 ozone NAAQS.\40\ For the 2015 8-

[[Page 4031]]

hour ozone NAAQS, the EPA used this framework in evaluating SIP
submissions (while considering any alternative approaches States may
have put forth in the submission) and applied this framework in the
Good Neighbor Plan.\41\
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\37\ See Federal Implementation Plans: Interstate Transport of
Fine Particulate Matter and Ozone and Correction of SIP Approvals;
76 FR 48208 (Aug. 8, 2011) (CSAPR).
\38\ Cross-State Air Pollution Rule Update for the 2008 Ozone
NAAQS; 81 FR 74504 (Oct. 26, 2016).
\39\ Revised Cross-State Air Pollution Rule Update for the 2008
Ozone NAAQS; 86 FR 23054 (Apr. 30, 2021).
\40\ In 2019, the D.C. Circuit Court of Appeals remanded the
CSAPR Update to the extent it failed to require upwind states to
eliminate their significant contribution by the next applicable
attainment date by which downwind states must come into compliance
with the NAAQS, as established under CAA section 181(a). Wisconsin
v. EPA, 938 F.3d 303, 313 (D.C. Cir. 2019). The Revised CSAPR Update
responded to the remand of the CSAPR Update in Wisconsin and the
vacatur of a separate rule, the ``CSAPR Close-Out,'' 83 FR 65878
(Dec. 21, 2018), in New York v. EPA, 781 F. App'x. 4 (D.C. Cir.
2019).
\41\ 88 FR 9338; 88 FR 36671.
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Shaped by input from State air agencies \42\ and other stakeholders
on the EPA's prior interstate transport rulemakings and SIP submission
actions,\43\ as well as several court decisions,\44\ the EPA developed
and used the Framework to evaluate States' obligations to eliminate
interstate transport emissions under the interstate transport provision
for the ozone NAAQS:
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\42\ 63 FR 57356, 57361 (Oct. 27, 1998).
\43\ In addition to CSAPR rulemakings, other regional
rulemakings addressing ozone transport include the ``NO<INF>X</INF>
SIP Call;'' 63 FR 57356 (Oct. 27, 1998), and the ``Clean Air
Interstate Rule'' (CAIR); 70 FR 25162 (May 12, 2005).
\44\ See, e.g., EPA v. EME Homer City Generation, L.P., 572 U.S.
489 (2014) (EME Homer City).
---------------------------------------------------------------------------

(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 to ``contribute'' (i.e., are considered ``linked'') to those
receptors and whose emissions, 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.
The EPA does not require States to use the Framework in interstate
transport SIP submissions, but it is a useful organizational tool that
has been upheld by the Supreme Court as ``permissible, workable, and
equitable.'' \45\
---------------------------------------------------------------------------

\45\ EME Homer City, 572 U.S. at 524.
---------------------------------------------------------------------------

C. The EPA's Approach To Evaluating Interstate Transport for the 2015
Ozone NAAQS

1. Selection of Analytic Year
In this section, the EPA describes the process for identifying an
appropriate analytic year for this proposed rule. Every State covered
by this proposed rule utilized an analytic year of 2023. The EPA is
retaining the 2023 analytical year used to inform past action on
States' interstate transport SIP submissions, to ensure consistency and
equitable treatment of all States, and to give consideration to the
information and data available to States at the time they developed
these SIP submissions. In the EPA's March 2018 memorandum, the EPA
provided air quality information that States could use to identify
receptors in Step 1 and evaluate interstate contributions in Step 2
using a 2023 analytic year.\46\ The EPA selected the year 2023 because
it was the last full ozone season before the August 3, 2024, Moderate
area attainment date for the 2015 ozone NAAQS.\47\ Ozone seasons for
purposes of interstate transport obligations run each year from May 1-
September 30.\48\ To demonstrate attainment by these deadlines,
downwind States would be required to rely on design values calculated
using ozone data from 2021 through 2023.\49\ Areas that do not attain
by the deadline may be ``bumped up'' to a higher nonattainment
classification level per CAA sections 181 and 182, thereby incurring
additional ongoing obligations. Thus, consistent with prior interstate
transport rulemakings, the EPA's analysis focuses on the last full
ozone season before the attainment dates (i.e., 2023). The later
versions of the EPA's modeling (2016v2, 2016v3) also used a 2023
analytic year.
---------------------------------------------------------------------------

\46\ See March 2018 memorandum. The version of 2023 contribution
modeling referenced in the March 2018 memorandum may also be
referred to as 2011-base year modeling. The memo is available in the
docket (Docket ID No. EPA-HQ-OAR-2025-0192) and at <a href="http://www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips">www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips</a>.
\47\ See CAA section 181(a); 40 Code of Federal Regulations
(CFR) 51.1303; 83 FR 25776 (June 4, 2018, effective Aug. 3, 2018).
\48\ See 40 CFR 52.38(b)(1), 52.40(c)(1)).
\49\ The ozone design value for a monitoring site for the 2015
ozone NAAQS is the 3-year average of the annual fourth-highest daily
maximum 8-hour average ozone concentrations at the site. 40 CFR part
50, appendix U, section 4(a).
---------------------------------------------------------------------------

The EPA recognizes that in applying the EPA's 2023 analytics to
inform this action, see Section III.C.4 of this preamble, the EPA may
be perceived as acting inconsistently with the EPA's previous policy of
considering a future analytic year from the standpoint of the timing of
the EPA's rulemaking action. The EPA's general policy has been to use
forward-looking projections associated with a future analytic year,
consistent with its interpretation that the interstate transport
provision is a forward-looking statute.\50\ Courts have generally
upheld that interpretation.\51\ However, no court has ruled (nor has
the EPA interpreted) that the statute compels the EPA to always use a
future analytic year from the standpoint of every particular interstate
transport rulemaking. Here, the EPA proposes that several important,
overriding considerations warrant retaining the 2023 analytic year in
this rulemaking. Were the EPA to consider air quality information tied
to year(s) after 2023,\52\ the EPA would separately evaluate these
States using different data than that which informed our prior
evaluation of the State submissions, solely as a result of the timing
of the EPA's action on these States.
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\50\ See, e.g., 86 FR 23054, 23074 (April 30, 2021).
\51\ See North Carolina v. EPA, 531 F.3d 896, 913-14 (D.C. Cir.
2008).
\52\ The EPA used an analytic year of 2023 in previously
promulgated FIPs for the 2015 ozone NAAQS. The EPA also used a 2026
analytic year, but the additional analysis for 2026 was conducted
for purposes of the Agency's Step 3 analysis in that rulemaking. See
88 FR at 36694.
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Where the need for parity among States or other jurisdictions in
like circumstances warrants it, courts have recognized that it may be
appropriate for the EPA to rely on a unified dataset to ensure
consistency in treatment.\53\ Here, for two States, the EPA is acting
on remand following adverse court rulings, and the EPA is otherwise
conducting reconsideration as to the other States included in this
action, taking those adverse decisions into account. Comparable to the
situation in Weld County, it makes sense to conduct this re-evaluation
using the existing information in the record, rather than become
trapped in a cycle of constantly shifting analysis and output. Indeed,
the court in Kentucky faulted the EPA for failing to consider States'
reliance interests when switching to updated analytics in our
disapproval of Kentucky's SIP submission, rather than evaluating the
submission according to the EPA's March 2018 memorandum modeling, which
was provided to States for use in drafting their plans if they
chose.\54\
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\53\ See Bd. Cnty. Comm'rs of Weld Cnty. v. EPA, 72 F.4th 284,
290 (D.C. Cir. 2023) (``Weld County'') (upholding as reasonable the
EPA's determination that ``greater parity among counties and faster
turnaround make the original data a better choice than partial
updating'').
\54\ See Kentucky, 123 F.4th 447, 469-70.

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[[Page 4032]]

In addition, the EPA recognizes that the Agency provided
information to States for use in the development of these SIP
submissions including air quality projections for the analytic year
2023 as released in the March 2018 memorandum. In this respect, we find
it appropriate to use the same analytic year as the one the EPA's
guidance communicated to States (i.e., 2023) during SIP development.
Therefore, when evaluating the SIP submissions for the 2015 8-hour
ozone NAAQS included in this action, the EPA proposes to rely solely on
projected air quality data for the 2023 analytic year. In doing so, the
EPA is mindful of the unique and case-specific reliance interests the
March 2018 memorandum may have engendered in State air agencies, since
that memorandum said States ``may consider using this [2023 modeling
data] to develop SIPs that address requirements of [CAA section
110(a)(2)(D)(i)(I)] for the 2015 ozone NAAQS'' and did not address the
use of air quality information for an analytic year after 2023.\55\
This determination is not being made, and should not be understood, to
extend to any other CAA requirements or situations. In addition, as
described in Section III.C.4. of this preamble, the EPA's proposed
approach for evaluating air quality information in this action is to
first rely on information provided in the March 2018 memorandum, as
included by States in their SIP submissions, and then consider more
recent EPA modeling information only if necessary to determine whether
any linkages are still projected to persist.
---------------------------------------------------------------------------

\55\ March 2018 memorandum at 4.
---------------------------------------------------------------------------

2. Step 1 of the 4-Step Interstate Transport Framework
In Step 1, a State (or the EPA in the context of a FIP) identifies
monitoring sites that are projected to have problems attaining and/or
maintaining the NAAQS in the 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 Framework. For sites that are identified as a
nonattainment or maintenance receptor in 2023, the EPA proceeds to the
next step of the Framework by identifying which upwind States
contribute above the threshold to those receptors.
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.\56\
---------------------------------------------------------------------------

\56\ 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, based on air quality modeling, 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
sites that both currently measure nonattainment and that the EPA
projects will be in nonattainment in the analytic year (i.e.,
2023).\57\
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\57\ 81 FR 74504 (Oct. 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 (Jan. 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 as 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).\58\ Specifically, the EPA identifies 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 is
determined by evaluating the projected ``maximum'' design value at each
monitoring site. These future year maximum design values are derived
from model projections of the maximum measured design value during the
relevant base year time 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.
---------------------------------------------------------------------------

\58\ 76 FR 48208 (Aug. 8, 2011). The CSAPR Update and Revised
CSAPR Update also used this approach. See 81 FR 74504 (Oct. 26,
2016) and 86 FR 23054 (Apr. 30, 2021).
---------------------------------------------------------------------------

Recognizing that nonattainment receptors are also, by definition,
maintenance receptors, the EPA often uses the term ``maintenance-only''
to refer to those receptors that are not nonattainment receptors.
Consistent with the concepts for maintenance receptors, as described
earlier, the EPA identifies ``maintenance-only'' receptors as those
monitoring sites that have projected average design values above the
level of the applicable NAAQS but that are not currently measuring
nonattainment based on the most recent official design values. In
addition, those monitoring sites with projected average design values
below the NAAQS, but with projected maximum design values above the
NAAQS, are also identified as ``maintenance-only'' receptors, even if
they are currently measuring nonattainment based on the most recent
official design values.
3. Step 2 of the 4-Step Interstate Transport Framework
In Step 2, a State (or the EPA in the context of a FIP) uses air
quality modeling to quantify the impacts of emissions from each upwind
State to each receptor in the 2023 analytic year. The EPA then
evaluates these impacts with respect to an air quality screening
threshold. Emissions impacts above that threshold are considered to
constitute a ``contribution'' to that receptor, whether a nonattainment
or maintenance receptor. Emissions impacts below that threshold are
considered de minimis and so categorically are excluded from being
considered ``contribution'' (or, for purposes of Prong 2, are
categorically not considered ``interference with maintenance''). The
CAA does not define ``contribution'' or ``interference'' as used in the
interstate transport provision, and this approach gives technical
meaning to these statutory terms through screening out de minimis
impacts. States with emissions impacts above the contribution threshold
proceed to Step 3 analysis, where both air quality and cost factors are
considered as part of a multi-factor analysis, to determine what, if
any, emissions might be deemed ``significant'' and, thus, must be

[[Page 4033]]

eliminated pursuant to the requirements of CAA section
110(a)(2)(D)(i)(I).\59\
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\59\ Note that upwind states that are linked to a downwind
receptor at Step 2 may nevertheless be found to not significantly
contribute to nonattainment or interfere with maintenance at the
receptor depending on the outcome of the Step 3 analysis. See 81 FR
74553.
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A relatively low contribution threshold has historically been used
for ozone NAAQS considering the collective contribution problem posed
by interstate ozone pollution.\60\ The contribution metric used in Step
2 is defined as the average impact from each State to each receptor on
the days in 2023 with the highest ozone concentrations at the receptor,
based on the future year modeling.\61\ To quantify the contribution of
emissions from individual upwind States to projected 2023 ozone design
values for the identified downwind nonattainment and maintenance
receptors in Step 2, the EPA performed nationwide, State-level ozone
source apportionment modeling. The source apportionment modeling
provides contributions to ozone at receptors from precursor emissions
of anthropogenic nitrogen oxides (NO<INF>X</INF>) and volatile organic
compounds (VOCs) in individual upwind States. The EPA released
contribution modeling results for 2023 with the March 2018 memorandum,
which uses a base year of 2011.\62\ The EPA later released contribution
modeling results for 2023 using a 2016 base year.\63\
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\60\ See 88 FR at 9342.
\61\ See Air Quality Modeling Final Rule Technical Support
Document--2015 Ozone NAAQS Good Neighbor Plan in Docket ID No. EPA-
HQ-OAR-2025-0192 (``2016v3 Technical Support Document (TSD)'').
\62\ For an explanation of how the base year is used, see the
2016v3 TSD in the docket for this proposed action.
\63\ 88 FR 9352-9354 (Feb. 13, 2023).
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Determining an appropriate screening threshold is a critical
component of designing and applying Step 2. The assessment completed in
the August 2018 memorandum \64\ used data and air quality analyses that
were specifically applicable to the NAAQS being considered and the
relevant air quality conditions (e.g., pollutant concentrations and the
magnitude of interstate transport). As a result, conclusions made with
respect to one NAAQS are not by default applicable to another NAAQS. In
previous actions, the EPA's analysis of collective contribution
concluded that a screening threshold equivalent to 1 percent of the
1997 and 2008 ozone NAAQS was appropriate in Step 2.\65\
---------------------------------------------------------------------------

\64\ August 2018 memorandum, available in the docket and at
<a href="http://www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips">www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips</a>.
\65\ In CSAPR, the EPA used 0.80 ppb as the threshold, which is
1 percent of the 1997 ozone NAAQS. 76 FR 48208, 48238 (Aug. 8,
2011). In the CSAPR Update, the EPA used 0.75 ppb as the threshold,
which is 1 percent of the 2008 ozone NAAQS. 81 FR 74504, 74518 (Oct.
26, 2016).
---------------------------------------------------------------------------

In the August 2018 memorandum, the EPA evaluated data pertinent to
several alternative thresholds that could be applicable to the
development of SIP revisions to address transport for the 2015 8-hour
ozone NAAQS. This evaluation compared the 1 percent of the 8-hour ozone
NAAQS threshold (1-percent threshold), which is 0.70 ppb, and two
potential alternative thresholds, 1 ppb and 2 ppb. The purpose of that
analysis was to examine the amount of collective upwind contribution
(i.e., the sum of contributions from upwind States that are linked to
each receptor) that would be captured at each of these alternative
thresholds nationwide. The EPA's conclusion in that memorandum was that
a threshold of 1 ppb may be appropriate for States to use and develop
SIP revisions addressing the interstate transport provision for the
2015 8-hour ozone NAAQS because, nationwide, the difference in the
amount of total upwind contribution captured using a 1-ppb threshold is
relatively small compared to the amount captured using a 1-percent
threshold (roughly a 7 percentage point difference). The August 2018
memorandum also indicated a 2-ppb threshold may be insufficient to
address collective upwind State contribution to downwind air quality
problems.\66\
---------------------------------------------------------------------------

\66\ August 2018 Memorandum at 4.
---------------------------------------------------------------------------

Subsequent case law reviewing the EPA's disapproval of Kentucky's
SIP submission interpreted the August 2018 memorandum as establishing a
presumptively approvable Step 2 threshold of 1 ppb. The Sixth Circuit
determined that the ``August 2018 memorandum treated the 1 ppb
threshold as presumptively acceptable unless a state's unique facts
made the threshold improper[.]'' \67\ Further, the Sixth Circuit found
that the August 2018 memorandum, together with feedback provided by the
EPA during Kentucky's SIP development process, established an EPA
policy that Kentucky could apply a 1-ppb contribution threshold in Step
2 in its SIP submission for the 2015 ozone NAAQS without further
justification.\68\
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\67\ Kentucky, 123 F.4th. at 469.
\68\ Id. at 468-469.
---------------------------------------------------------------------------

The Fifth Circuit reached a similar result in vacating and
remanding the EPA's disapproval of Mississippi's SIP submission.\69\
The Fifth Circuit found that the EPA had improperly dismissed
Mississippi's use of a 1-ppb threshold as ``inconsequential'' to the
EPA's disposition of the SIP, which was incorrect when considered in
conjunction with the choice of modeling used.\70\ The Court found that
the EPA had failed to provide an adequate explanation for the EPA's
disapproval of Mississippi's SIP.\71\ In reviewing this decision on
remand, the EPA notes that in reaching this conclusion, the Fifth
Circuit necessarily found unpersuasive the EPA's explanations
concerning why a 1-ppb threshold was inappropriate for States to use
without adequate justification.\72\ The EPA cited and discussed this
analysis in its merits brief.\73\ The EPA believes it prudent to
implement a policy more consistent with the Sixth Circuit's
interpretation of the August 2018 memorandum in Kentucky, which is that
1 ppb is a ``presumptively acceptable'' threshold for all States.\74\
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\69\ Texas, 132 F.4th at 860-62.
\70\ Id. at 861.
\71\ Id. at 862.
\72\ See 88 FR at 9371-73; see also id. at 9357-58.
\73\ See EPA Resp. Br. at 138-46, No. 23-60069 (5th Cir. filed
Aug. 15, 2023); see also id. at 34, 42-43, 124-29.
\74\ Kentucky, 123 F.4th. at 469.
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Thus, in response to these opinions and in light of the 2018 August
Memorandum and any reliance interests it may have engendered in State
air agencies, the EPA is proposing to determine that a 1-ppb threshold
is the appropriate Step 2 threshold to rely on in the first instance
for the 2015 ozone NAAQS for all States in this action and any future
actions related to the 2015 ozone NAAQS.\75\ As noted in the August
2018 memorandum, nationally the 1-ppb threshold captures a generally
comparable amount of total upwind contributions overall (70 percent
using 1 ppb versus 77 percent using 1 percent (0.70 ppb))--when
considering all receptors. Further, in the EPA's latest modeling, 2016
Version 3 Emissions Platform Modeling (``2016v3''), the difference in
the amount of total upwind contributions captured is even less,
identifying a difference of only 5

[[Page 4034]]

percentage points.\76\ By relying on a 1-ppb threshold rather than a 1-
percent threshold, the EPA continues to provide the potential, in Step
3, for meaningful emissions reductions in remaining linked upwind
States to aid downwind States with attainment and maintenance of the
2015 ozone NAAQS, while also focusing the EPA's efforts on areas that
are more likely to have impactful outcomes should any emissions
reductions be deemed appropriate. In this proposal, the EPA also
solicits comment on the use of thresholds other than the 1-percent or
1-ppb thresholds discussed in this action, such as a 5-percent
threshold or a 2-ppb threshold, including a basis for relying on any
suggested alternative threshold.
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\75\ The EPA is identifying the 1 ppb threshold as acceptable
based on the specific facts and circumstances associated with this
reconsideration of interstate transport obligations for the 2015
ozone NAAQS. Previously identified thresholds used in interstate
transport analysis associated with other NAAQS, which were based on
their own unique records, are not affected or intended to be
affected. In addition, the use of a 1 ppb threshold does not
undermine the basis for prior approvals of interstate transport SIPs
for the 2015 ozone NAAQS that had used the 1 percent threshold. Any
SIP that was approved under that threshold, which translates to .7
ppb, would be approvable under the 1 ppb threshold.
\76\ 88 FR 9336, 9374 (Feb. 13, 2023).
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The EPA recognizes that not all States elected to rely on the 1-ppb
threshold when developing their SIP submissions, either because the
State did not consider an alternative threshold due to the facts and
circumstances available at the time of submission (e.g., the State was
linked above or below both the 1-percent and 1-ppb threshold), or they
found it appropriate to rely on the 1-percent threshold. However, the
EPA finds it appropriate to presumptively apply a 1-ppb contribution
threshold for the consistent treatment of all States. The availability
of different thresholds in Step 2 has the potential to result in
inconsistent application of interstate transport obligations based
solely on the decisions of a State in Step 2 of the Framework. 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 omit some States from 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 consistency problems among States. Finally, the August 2018
memorandum cautioned that contribution thresholds higher than 1 ppb,
such as 2 ppb, would capture ``notably less [upwind contribution] at
most receptors than the amount captured with either a 1 ppb or 1
percent threshold, and therefore emission reductions from states linked
at that higher threshold may be insufficient to address collective
upwind state contribution to downwind air quality problems.'' \77\ The
EPA is not currently aware of information that would support a
threshold other than 1 ppb for any state.
---------------------------------------------------------------------------

\77\ August 2018 memorandum at 4.
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4. Choice of Modeling To Inform Steps 1 and 2
The EPA released the October 2017 memorandum \78\ containing
updated modeling data for 2023, which incorporated changes made in
response to comments on the January 6, 2017, Notice of Data
Availability,\79\ and was intended to provide information to assist
States' efforts to develop SIP submissions to address interstate
transport obligations for the 2008 ozone NAAQS. The March 2018
memorandum noted that the same 2011 base-year modeling data released in
the October 2017 memorandum could also be useful for identifying
potential downwind air quality problems with respect to the 2015 ozone
NAAQS in Step 1 of the Framework. The March 2018 memorandum also
included newly available contribution modeling data for 2023 to assist
States in evaluating their impact on potential downwind air quality
problems for the 2015 8-hour ozone NAAQS under Step 2 of the
Framework.\80\
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\78\ 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 the docket for this proposed action.
\79\ 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),
(``Notice of Data Availability''); 82 FR 1733 (Jan. 6, 2017).
\80\ The March 2018 memorandum stated ``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.
---------------------------------------------------------------------------

Following the release of the March 2018 memorandum modeling,
through a collaborative multi-year joint effort by the EPA, multi-
jurisdictional organizations, and States, the EPA developed an updated
air quality modeling platform with base year emissions for 2016 and
projected emissions for 2023 (i.e., 2016 Version 1 Emissions Platform
Modeling (``2016v1'')).\81\ 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'') \82\ and updated emissions projections for electric
generating units (EGUs) that reflected the emissions reductions from
the Revised CSAPR Update, recent information on plant closures, and
other inventory improvements (i.e., 2016 Version 2 Emissions Platform
Modeling (``2016v2'')).\83\ The EPA's latest version of air quality
modeling incorporated additional feedback, and was released in early
2023 (``2016v3 modeling'').\84\
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\81\ See the Air Quality Modeling Technical Support Document for
the Final Revised Cross-State Air Pollution Rule Update, included in
the docket for this proposed action, Docket ID No. EPA-HQ-OAR-2025-
0192.
\82\ Additional details and documentation related to the MOVES3
model can be found at <a href="http://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves">www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves</a>.
\83\ The construct of the 2016v2 emissions platform is described
in the ``Technical Support Document (TSD): Preparation of Emissions
Inventories for the 2016v2 North American Emissions Modeling
Platform,'' and is included in the docket for this proposed action.
See also, ``Air Quality Modeling Technical Support Document for the
Federal Implementation Plan Addressing Regional Ozone Transport for
the 2015 Ozone National Ambient Air Quality Standards Proposed
Rulemaking,'' (``2016v2 TSD'') also included in the docket.
\84\ Details on the 2016v3 air quality modeling and the methods
for projecting design values and determining contributions in 2023
and 2026 based on this platform are described in 2016v3 TSD included
in the docket for this proposed action.
---------------------------------------------------------------------------

In the final SIP Disapproval Action, the EPA explained that in
evaluating all SIP submissions, the EPA considered the entire record
before the EPA, including updated modeling and other air quality
analytics, even if such information was not available to States at the
time they developed their submissions.\85\ The EPA explained that, in
our view, we had the authority and responsibility in evaluating
interstate transport obligations to consider the best available
information.\86\ However, the Fifth Circuit found that the EPA had
inappropriately applied the 2016v3 modeling in an outcome-determinative
way in the EPA's evaluation of Mississippi's SIP submission.\87\ In
addition, the Sixth Circuit found that in disapproving Kentucky's SIP
submission, the EPA inappropriately failed to acknowledge the reliance
interests Kentucky had in the March 2018 memorandum modeling as the EPA
stated in the March 2018 memorandum that States could use such modeling
in developing their interstate transport SIPs.88 89
Therefore, the EPA is reconsidering the EPA's approach regarding
States' choice of modeling for evaluating interstate transport SIP

[[Page 4035]]

submissions for the 2015 ozone NAAQS in Steps 1 and 2.
---------------------------------------------------------------------------

\85\ 88 FR at 9343.
\86\ Id. at 9365-67.
\87\ Texas, 132 F.4th at 861-62.
\88\ Kentucky, 123 F.4th at 468-69.
\89\ EPA Resp. Br. at 185-211, No. 23-60069, ECF No. 397 (5th
Cir. filed Aug. 15, 2023); EPA Resp. Br. at 76-95, No. 23-3216, ECF
No. 73 (6th Cir. filed Jan. 29, 2024).
---------------------------------------------------------------------------

When acting on several SIP submissions in 2023, including those
from five States covered by this proposal, the EPA looked at the
modeling relied upon by States but also relied in a ``primary'' way on
the results of the 2016v3 modeling, which identifies receptors and
contributions in 2023, using a 2016 base year; one reviewing court
observed that the effect of this approach was ``outcome determinative''
for some States such as Mississippi.\90\ As noted above, compared to
the March 2018 memorandum modeling, the 2016v3 modeling uses more
recent emissions data and incorporates other technical updates to the
modeling platform.\91\ The differences between the March 2018
memorandum modeling and 2016v3 modeling, depending on the contribution
threshold, result in differences in receptor classification (e.g.,
nonattainment versus maintenance-only) and/or the magnitude of downwind
contributions. In the final SIP Disapproval Action and the Proposed
Supplemental Air Plan Action, the EPA considered whether a State
identified itself as linked based on whichever modeling it chose but
ultimately relied on the 2016v3 modeling for determining whether a
State was linked in Step 2 because the 2016v3 was the most-up-to-date
information at the time.\92\
---------------------------------------------------------------------------

\90\ 88 FR 9380-9381; Texas, 132, F.4th at 860-62. The Texas
court also recognized that for other States this was not the case,
and the EPA's more recent modeling was merely confirmatory. Id. at
861.
\91\ See 2016v3 TSD and ``Air Quality Modeling Technical Support
Document for the 2015 Ozone NAAQS Preliminary Interstate Transport
Assessment'' in the docket for this proposed action.
\92\ 87 FR 9343, 9380.
---------------------------------------------------------------------------

The Fifth and Sixth Circuits did not determine that the EPA may not
consider updated information in taking action on these SIP submissions
or any other types of SIP submissions.\93\ Instead, as described above,
these courts viewed the EPA as having failed to explain the EPA's
reasoning, considering the unique circumstances associated with the
history of the 2015 ozone NAAQS interstate transport obligations and
how the EPA had interpreted the March 2018 memorandum and the August
2018 memorandum in its disapprovals of Kentucky and Mississippi's SIP
submissions.\94\ The EPA's approach here is limited to this
reconsideration of certain 2015 ozone NAAQS good neighbor SIP actions
and does not reflect a broader legal or policy judgment concerning the
EPA's authority to consider information more generally under the
interstate transport provision or other provisions of the CAA. In
general, the EPA views the choice of which information to consider or
rely on to involve consideration of case-specific circumstances.
Further, in the context of this proposed action, the EPA believes it is
appropriate to apply a common approach to evaluate interstate transport
obligations among States for parity. Therefore, to respond to the Fifth
and Sixth Circuits' remands concerning how the EPA previously applied
the 2016v3 modeling to Kentucky and Mississippi (and to apply those
precedents in a consistent manner in its reconsideration of its 2015
ozone NAAQS transport actions \95\), to acknowledge and accommodate
reliance interests States may have had in the March 2018 memorandum
modeling, and to treat States' interstate transport obligations
consistently for the 2015 8-hour ozone NAAQS, the EPA is proposing to
approach the choice of modeling in Steps 1 and 2 in the following way:
the EPA will rely first on the modeling the State used in its SIP
submission to identify receptors and the magnitude of contributions to
those receptors.\96\ If that modeling indicates a State is not linked
in the 2023 analytic year to any receptors above 1 ppb, the EPA will
approve that submission. If, however, the modeling a State used
indicates that a State is linked above 1 ppb to at least one receptor,
the EPA will consider the best available modeling (i.e., the 2016v3
modeling) to determine whether any linkages above 1 ppb are still
anticipated to persist in 2023.\97\ If no linkages persist, the EPA
will consider that State to have resolved its linkages and will approve
such submissions under these circumstances. This approach ensures that
full consideration is given to the modeling available to the States at
the time they develop their interstate transport SIP submissions,
whether that be developed by the EPA or otherwise, which is consistent
with the cooperative-federalism framework of NAAQS implementation.
---------------------------------------------------------------------------

\93\ Texas, 132 F.4th at 860, 862; Kentucky, 123 F.4th at 472.
\94\ Texas, 132 F.4th at 860-861; Kentucky, 123 F.4th at 468-
471.
\95\ The EPA's regulations provide that the EPA need not
necessarily revise provisions of a rule meant to maintain national
uniformity in response to one or more regional circuit decisions
arising from actions that are locally or regionally applicable. See,
e.g., 40 CFR 56.4(c). However, we believe it is ``essential'' to
have national consistency in the implementation of interstate ozone
obligations, see, e.g., 87 FR at 9373-74, and so we propose to apply
the logic of these judicial decisions more broadly to the EPA's
national policies for interstate transport obligations for the 2015
8-hour ozone NAAQS to avoid any unfairness that could result from
the uneven application of judicial rulings from different regional
circuits.
\96\ The EPA has the statutory authority to evaluate the
sufficiency of States' modeling and technical analyses in their SIP
submissions. See Texas v. EPA, 156 F.4th 523, 542-43 (5th Cir.
2025). In this instance, the EPA finds that the photochemical grid
modeling the States covered by this proposal used was technically
sufficient for the purpose of evaluating interstate contribution for
the 2015 ozone NAAQS.
\97\ Under this proposed approach, we note that the EPA is also
not considering the novel ``violating monitor maintenance-only''
approach to maintenance receptor identification that was developed
for the final SIP Disapproval Action. This approach gave greater
consideration to more recent monitoring data when identifying
receptors at Step 1 of the Framework. The monitoring information
used in this approach (measured 2021-2022 air quality monitoring
data) post-dates the information available to States when they
developed their 2015 8-hour ozone NAAQS interstate transport SIPs.
Further, the EPA has not applied that methodology in an ``outcome-
determinative'' way to date for any State.
---------------------------------------------------------------------------

For the purposes of this action, as further explained in Section IV
of this preamble, this approach to choice of modeling, in conjunction
with the use of a 1-ppb threshold, supports proposing approval of eight
States' SIP submissions (Alabama, Arizona, Kentucky, Mississippi,
Minnesota, Nevada, New Mexico, and Tennessee) and withdrawing prior
proposed error corrections for two other States (Iowa and Kansas).
5. Step 3 of the 4-Step Interstate Transport Framework
In Step 3 of the Framework, a State (or the EPA in the context of a
FIP) further evaluates a State's emissions, considering multiple
factors, including air quality and cost, to determine what, if any,
emissions significantly contribute to nonattainment or interfere with
maintenance and, thus, must be eliminated under CAA section
110(a)(2)(D)(i)(I). Because all States included in this proposal can be
approved in Steps 1 and 2, there is no need to further discuss Step 3.
6. Step 4 of the 4-Step Interstate Transport Framework
In Step 4, a State (or the EPA in the context of a FIP) develop
control strategies to achieve the emissions reductions determined to be
necessary in Step 3 to eliminate significant contribution to
nonattainment or interference with maintenance of the NAAQS, which
become permanent and enforceable when adopted. Because all States
included in this proposal can be approved in Steps 1 and 2, there is no
need to further discuss Step 4.

[[Page 4036]]

IV. SIP Submissions Addressing Interstate Transport of Air Pollution
for the 2015 8-Hour Ozone NAAQS

A. SIP Summaries and the EPA's Evaluation

As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous final and proposed actions on the SIP submissions from
Alabama, Arizona, Kentucky, Minnesota, Mississippi, Nevada, New Mexico,
and Tennessee and anticipates withdrawing the prior proposed error
corrections related to Iowa and Kansas's SIPs.\98\ This section
summarizes and evaluates the submissions from these 10 States. As
explained throughout Section IV of this preamble, the EPA is proposing
to find that these 10 States are screened out from further review after
determining their contributions fall below the contribution threshold,
and so the EPA need not examine the additional information contained in
the submissions despite having done so in previous Federal Register
notices. This proposed action, if finalized, would replace the EPA's
previous final actions disapproving the SIP submissions from Alabama,
Minnesota, and Nevada.
---------------------------------------------------------------------------

\98\ 88 FR 9336 (Feb. 13, 2023) (Alabama, Kentucky, Minnesota,
Mississippi, and Nevada); 89 FR 12666 (Arizona, Iowa, Kansas, New
Mexico, and Tennessee) (Feb. 16, 2024).
---------------------------------------------------------------------------

The EPA acknowledges that there are other States in the SIP
Disapproval Action that are not included in this proposal, which is
limited to those states for which proposed approval is warranted on the
basis of the policies explained in Section III.C. The EPA intends to
reconsider the SIP Disapproval Action, and/or the basis for
disapproval, as to other states, including but not necessarily limited
to Arkansas, Missouri, Oklahoma, Utah, and West Virginia, in a
separate, upcoming rulemaking.
1. Alabama
a. Prior Notices Related to Alabama's SIP Submission
On June 21, 2022, the Alabama Department of Environmental
Management submitted a SIP addressing CAA section 110(a)(2)(D)(i)(I)
interstate transport requirements for the 2015 ozone NAAQS for the
State of Alabama.\99\ The EPA's proposed disapproval of Alabama's
submission was published on October 25, 2022,\100\ and later finalized
on January 31, 2023.\101\ However, the EPA is reconsidering the policy
decisions made in our prior actions addressing interstate transport
obligations for the 2015 8-hour ozone NAAQS following the remand and
vacatur of the EPA's disapproval of Kentucky's and Mississippi's SIP
submissions by the Sixth and Fifth Circuits, respectively, as described
in Section III.C. of this preamble. As a result, the EPA now proposes
to reconsider the disapproval and proposes to approve Alabama's SIP
submission.
---------------------------------------------------------------------------

\99\ See ``AL-127 6.21.2022 Submittal For Ozone 2015 ISIP''
(``Alabama's SIP submission'') in the docket for this proposed
action, Docket ID No. EPA-HQ-OAR-2025-0192.
\100\ 87 FR 64412 (Oct. 25, 2022).
\101\ 88 FR 9336 (Feb. 13, 2023).
---------------------------------------------------------------------------

b. Summary of Alabama's Submission
Alabama's SIP submission provides the State's evaluation of its
impact on downwind States and concludes that emissions from the State
will not significantly contribute to nonattainment or interfere with
maintenance of the 2015 8-hour ozone NAAQS in other States in 2023.
Alabama relies on the results of the EPA's 2016v2 modeling to identify
downwind nonattainment and maintenance receptors that may be impacted
by emissions from sources in the State in Steps 1 and 2 of the
Framework.\102\
---------------------------------------------------------------------------

\102\ Alabama's SIP submission at Part E.
---------------------------------------------------------------------------

Alabama's SIP submission also identifies existing SIP-approved
regulations and Federal programs that regulate ozone precursor
emissions from sources in the State, including the CSAPR trading
programs.\103\ Alabama's SIP submission acknowledges that CSAPR does
not address interstate transport for the 2015 8-hour ozone standard but
does provide residual NO<INF>X</INF> emissions reductions. Alabama
notes that the implementation of the existing SIP-approved regulations
and Federal programs provides for a decline in ozone precursor
emissions in the State. Alabama also notes there are no nonattainment
or maintenance areas in Alabama and that ozone precursor emissions will
continue to decline in the State.
---------------------------------------------------------------------------

\103\ Id.
---------------------------------------------------------------------------

Alabama's SIP submission also includes a ``weight of evidence''
(WOE) analysis evaluating the EPA's 2016v2 emissions modeling platform,
which showed that Alabama is projected to contribute above 0.70 ppb to
one nonattainment monitor and one maintenance monitor.\104\ In support
of its WOE analysis, Alabama cites the EPA's October 2018
memorandum,\105\ which discusses alternative methods to identifying
maintenance receptors, as well as the March and August 2018 memoranda
as supporting Alabama's use of a 1-ppb threshold.
---------------------------------------------------------------------------

\104\ Id.
\105\ See 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 the docket and at <a href="http://www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips">www.epa.gov/Cross-State-Air-Pollution/memo-and-supplemental-information-regarding-interstate-transport-sips</a>.
---------------------------------------------------------------------------

Alabama's WOE analysis includes a Hybrid Single Particle Lagrangian
Integrated Trajectory model back trajectory analysis to receptors in
Denton County and Harris County, Texas. Alabama concludes that, based
on the back trajectories, monitored exceedances at the Texas receptors
are locally driven. Alabama also notes that the design values for the
two Texas monitors have been stagnant, while design values in Alabama
continue to trend downward.
Finally, Alabama provides a review of the State's NO<INF>X</INF>
emissions for point and mobile sources. Alabama indicates that the
highest contributor of NO<INF>X</INF> emissions in the State are from
mobile sources but that NO<INF>X</INF> emissions from this source
category have decreased and will continue to decrease.
Based on this information, Alabama's SIP submission states that
emissions from Alabama do not contribute above 1 ppb of the 2015 8-hour
ozone NAAQS to any projected nonattainment or maintenance receptors in
Step 2 of the Framework.
c. Evaluation of Alabama's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous disapproval of the SIP submission from Alabama. As stated
previously, Alabama's SIP submission uses the EPA's 2016v2 modeling.
This modeling showed that Alabama's projected maximum contribution is
0.88 ppb to a nonattainment receptor (receptor ID 482010055 in Harris
County, Texas) and 0.71 ppb to a maintenance receptor (receptor ID
481210034 in Denton County, Texas).\106\ Both contributions from the
State's chosen modeling are below the 1-ppb threshold. Thus, in
accordance with the policies articulated in Section III.C. of this
preamble, the EPA proposes to find that Alabama does not impact
downwind air quality problems such that the State should be considered
``linked'' in Step 2 of the Framework and, therefore, further

[[Page 4037]]

review and analysis in Steps 3 and 4 is not warranted. Therefore, the
EPA is proposing to approve Alabama's SIP submission because the State
will not contribute significantly to nonattainment or interfere with
maintenance of the 2015 8-hour ozone NAAQS in any other State.\107\
This proposed action, if finalized, would replace the EPA's previous
final action disapproving the SIP submission from Alabama.\108\
---------------------------------------------------------------------------

\106\ 2016v2 TSD, Appendix C.
\107\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
\108\ 88 FR 9336.
---------------------------------------------------------------------------

2. Arizona
a. Prior Notices Related to Arizona's SIP Submission
On September 24, 2018, the Arizona Department of Environmental
Quality submitted a SIP addressing the ``infrastructure'' requirements
of CAA section 110(a)(2), including the interstate transport
requirements under CAA section 110(a)(2)(D)(i)(I), for the 2015 8-hour
ozone NAAQS.\109\ On June 24, 2022, the EPA's proposed approval of
Arizona's SIP submission was published.\110\ The EPA then withdrew the
2022 proposed approval of Arizona's SIP submission with respect to CAA
section 110(a)(2)(d)(i)(I) and proposed to partially disapprove
Arizona's SIP submission as to Prong 2 in the Proposed Supplemental Air
Plan Action.\111\ However, the EPA is reconsidering the policy
decisions made in our prior actions addressing interstate transport
obligations under the 2015 8-hour ozone NAAQS following the remand and
vacatur of the EPA's disapproval of Kentucky's and Mississippi's SIP
submissions by the Sixth and Fifth Circuits, respectively, as described
in Section III.C. of this preamble. As a result, the EPA is proposing
to fully approve Arizona's SIP submission.
---------------------------------------------------------------------------

\109\ See ``Arizona State Implementation Plan Revision under
Clean Air Act Sections 110(a)(1) and 110(a)(2) for the 2015 Ozone
National Ambient Air Quality Standards'' (``Arizona's SIP
submission'') in the docket for this proposed action, Docket ID No.
EPA-HQ-OAR-2025-0192.
\110\ 87 FR 37776 (June 24, 2022).
\111\ 89 FR 12666 (Feb. 16, 2024).
---------------------------------------------------------------------------

b. Summary of Arizona's Submission
Arizona's SIP submission relies on the March 2018 memorandum
modeling to identify downwind nonattainment and maintenance receptors
that may be impacted by emissions from sources in the State in Steps 1
and 2 of the Framework.\112\ Arizona further relies on the 1-percent
threshold in Step 2.\113\ Arizona notes that the March 2018 memorandum
modeling shows that Arizona does not contribute greater than 1 percent
of the NAAQS to any of the modeled nonattainment or maintenance
receptors in other States.\114\ Therefore, Arizona finds that the State
does not contribute significantly to nonattainment or maintenance
receptors in other States and that it is not necessary to identify
emissions reductions or adopt any permanent or enforceable controls
under the interstate transport provision for the 2015 8-hour ozone
NAAQS.\115\ Arizona also states that Arizona's SIP submission contains
adequate provisions to ensure that emissions from the State will not
significantly contribute to nonattainment or interfere with maintenance
of the 2015 8-hour ozone NAAQS in any other State in the future.\116\
---------------------------------------------------------------------------

\112\ Arizona's SIP submission at 12-13.
\113\ Id. at 13.
\114\ Id.
\115\ Id.
\116\ Id. at 14.
---------------------------------------------------------------------------

c. Evaluation of Arizona's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous proposed disapproval of the SIP submission from Arizona.
Arizona's SIP submission uses the EPA's March 2018 memorandum modeling.
This modeling showed that Arizona's projected maximum contribution is
0.49 ppb to a nonattainment receptor (receptor ID 80590006 in Jefferson
County, Colorado) and 0.49 ppb to a maintenance receptor (receptor ID
81230009 in Weld County, Colorado).\117\ Arizona is not linked above
the 1-ppb threshold to any downwind receptor in the State's chosen
modeling. Thus, in accordance with the policies articulated in Section
III.C. of this preamble, the EPA proposes to find that Arizona does not
impact downwind air quality problems such that the State should be
considered ``linked'' in Step 2 of the Framework and, therefore,
further review and analysis in Steps 3 and 4 is not warranted.
Therefore, the EPA is proposing to approve Arizona's SIP submission
because the State will not contribute significantly to nonattainment or
interfere with maintenance of the 2015 8-hour ozone NAAQS in any other
State.\118\ If finalized, the EPA will withdraw the prior proposed
partial disapproval.
---------------------------------------------------------------------------

\117\ See Attachment C to the EPA's March 2018 Memorandum.
\118\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

3. Iowa
a. Prior Notices Related to Iowa's SIP Submission
On November 30, 2018, Iowa submitted a SIP revision addressing CAA
section 110(a)(2)(D)(i)(I) interstate transport requirements for the
2015 8-hour ozone NAAQS.\119\ On March 2, 2020, the EPA's proposed
approval of the portion of Iowa's SIP submission addressing CAA section
110(a)(2)(D)(i)(I) was published.\120\ This proposed approval was later
withdrawn,\121\ and the EPA issued a new approval for Iowa's SIP
submission, which was published on April 15, 2022.\122\ The EPA then
proposed an error correction of our previous approval to partially
disapprove Iowa's SIP submission in the Proposed Supplemental Air Plan
Action.\123\ However, the EPA is now reconsidering the policy decisions
made in prior actions addressing interstate transport obligations under
the 2015 8-hour ozone NAAQS following the remand and vacatur of the
EPA's disapproval of Kentucky's and Mississippi's SIP submissions by
the Sixth and Fifth Circuits, respectively, as described in Section
III.C. of this preamble. As a result, the EPA anticipates withdrawing
the proposed error correction of the April 15, 2022, final approval of
Iowa's SIP submission.
---------------------------------------------------------------------------

\119\ See ``Iowa State Implementation Plan Revision for the 2015
Ozone National Ambient Air Quality Standards'' (``Iowa's SIP
submission'') in the docket for this proposed action, Docket ID No.
EPA-HQ-OAR-2025-0192.
\120\ 85 FR 12232 (Mar. 2, 2020).
\121\ 87 FR 9477 (Feb. 22, 2022).
\122\ 87 FR 22463 (Apr. 15, 2022).
\123\ 89 FR 12666 (Feb. 16, 2024).
---------------------------------------------------------------------------

b. Summary of Iowa's Submission
Iowa relies on the EPA's March 2018 memorandum modeling to identify
downwind nonattainment and maintenance receptors that may be impacted
by emissions from sources in Iowa and concludes that the State does not
contribute significantly to nonattainment or interfere with maintenance
of the 2015 8-hour ozone NAAQS in any other State.\124\ Iowa references
the August 2018 memorandum as a basis to use a 1-ppb threshold when
evaluating the State's contribution to downwind receptors in Step 2.
Iowa identifies projected contributions greater than 1 percent of the
NAAQS to two downwind receptors: a nonattainment receptor in Milwaukee
County, Wisconsin (Milwaukee receptor), and a maintenance-only

[[Page 4038]]

receptor in Allegan County, Michigan (Allegan receptor).\125\
---------------------------------------------------------------------------

\124\ Iowa's SIP submission at 7.
\125\ Id.
---------------------------------------------------------------------------

Iowa notes that, of the contribution greater than 1 percent of the
NAAQS, application of the 1-ppb threshold captures 83 percent of the
upwind contribution at the Milwaukee receptor and 94 percent of the
upwind contribution at the Allegan receptor.\126\ Based on these data,
Iowa concludes that the 1-ppb threshold is therefore an appropriate
contribution threshold with respect to the 2015 8-hour ozone NAAQS
because it captures a ``substantial portion'' of the upwind
contribution when compared to the 1-percent threshold at both
receptors.\127\ Because Iowa's impact on both receptors is projected to
be below the 1-ppb threshold, Iowa concludes that the State's emissions
will not contribute significantly to nonattainment or interfere with
maintenance of the 2015 8-hour ozone NAAQS at either receptor.
---------------------------------------------------------------------------

\126\ Id. at 8.
\127\ Id.
---------------------------------------------------------------------------

c. Evaluation of Iowa's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous proposed error correction of the previous approval of Iowa's
SIP. Iowa's SIP submission uses the EPA's March 2018 memorandum
modeling. This modeling showed that Iowa's projected maximum
contribution is 0.79 ppb to a nonattainment receptor (receptor ID
550790085 in Milwaukee County, Wisconsin) and 0.77 ppb to a maintenance
receptor (receptor ID 260050003 in Allegan County, Michigan).\128\ Both
contributions from the State's chosen modeling are below the 1-ppb
threshold. Thus, in accordance with the policies articulated in Section
III.C. of this preamble, the EPA proposes to find that Iowa does not
impact downwind air quality problems such that the State should be
considered ``linked'' in Step 2 of the Framework and, therefore,
further review and analysis in Steps 3 and 4 is not warranted.
Therefore, the EPA anticipates withdrawing the proposed error
correction of the April 15, 2022, final approval of Iowa's SIP
submission.\129\ For clarification, the EPA notes that the previous
approval of Iowa's SIP remains in place.
---------------------------------------------------------------------------

\128\ See Attachment C to the EPA's March 2018 memorandum.
\129\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

4. Kansas
a. Prior Notices Related to Kansas' SIP Submission
On September 27, 2018, Kansas submitted a SIP revision addressing
CAA section 110(a)(2)(D)(i)(I) interstate transport requirements for
the 2015 8-hour ozone NAAQS.\130\ The EPA's proposed approval of
Kansas' SIP submission was published on February 8, 2022,\131\ and the
EPA's final approval was published on April 4, 2022.\132\ The EPA then
proposed an error correction of the past approval to partially
disapprove Kansas' SIP in the Proposed Supplemental Air Plan
Action.\133\ However, the EPA is now reconsidering policy decisions
made in our prior actions addressing interstate transport obligations
for the 2015 8-hour ozone NAAQS following the remand and vacatur of the
EPA's disapproval of Kentucky's and Mississippi's SIP submissions by
the Sixth and Fifth Circuits, respectively, as described in Section
III.C. of this preamble. As a result, the EPA anticipates withdrawing
the proposed error correction of the April 4, 2022, final approval of
Kansas' SIP submission.
---------------------------------------------------------------------------

\130\ See ``Kansas Air Quality State Implementation Plan
Revision for the Implementation, Maintenance, and Enforcement of the
2015 Ozone (O<INF>3</INF>) National Ambient Air Quality Standards''
(``Kansas' SIP submission'') in the docket for this proposed action,
Docket ID No. EPA-HQ-OAR-2025-0192.
\131\ 87 FR 7071 (Feb. 8, 2022).
\132\ 87 FR 19390 (Apr. 4, 2022).
\133\ 89 FR 12666 (Feb. 16, 2024).
---------------------------------------------------------------------------

b. Summary of Kansas' Submission
Kansas relies on the EPA's March 2018 memorandum modeling to
identify downwind nonattainment and maintenance receptors that may be
impacted by emissions from sources in Kansas in the year 2023.\134\
Kansas notes that the State's greatest contribution to a projected
nonattainment or maintenance receptor is 0.77 ppb, which is between 0.7
ppb and 1 ppb.\135\ Because Kansas's maximum contribution to receptors
in downwind States is between 1 percent of the NAAQS and 1 ppb, the
State cites the EPA's August 2018 memorandum to rely on a 1-ppb
threshold.\136\ Therefore, Kansas concludes that emissions from sources
within the State will not significantly contribute to nonattainment or
interfere with maintenance of the 2015 8-hour ozone NAAQS in any other
State.
---------------------------------------------------------------------------

\134\ Attachment A to Kansas' SIP submission at 24-26.
\135\ Id.
\136\ Id.
---------------------------------------------------------------------------

c. Evaluation of Kansas' Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous proposed error correction of the approval of Kansas' SIP.
Kansas' SIP submission uses the EPA's March 2018 memorandum modeling.
This modeling showed that Kansas' projected maximum contribution is
0.69 ppb to a nonattainment receptor (receptor ID 484392003 in Tarrant
County, Texas) and 0.77 ppb (receptor ID 260050003 in Allegan County,
Michigan) \137\ This contribution from the State's chosen modeling is
below the 1-ppb threshold. Thus, in accordance with the policies
articulated in Section III.C. of this preamble, the EPA proposes to
find that Kansas does not impact downwind air quality problems such
that the State should be considered ``linked'' in Step 2 of the
Framework and, therefore, further review and analysis in Steps 3 and 4
is not warranted. Therefore, the EPA anticipates withdrawing the
proposed error correction of the April 4, 2022, final approval of
Kansas's SIP submission.\138\ For clarification, the EPA notes that the
previous approval of Kansas' SIP remains in place.
---------------------------------------------------------------------------

\137\ See Attachment C to the EPA's March 2018 memorandum.
\138\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

5. Kentucky
a. Prior Notices Related to Kentucky's SIP Submission
On January 9, 2019, the Commonwealth of Kentucky submitted a SIP
revision, a portion of which addressed CAA section 110(a)(2)(D)(i)(I)
interstate transport requirements for the 2015 8-hour ozone NAAQS.\139\
The EPA's proposed disapproval of Kentucky's SIP submission was
published on February 22, 2022,\140\ and the EPA's final disapproval
was published on February 13, 2023.\141\ The Sixth Circuit vacated and
remanded that disapproval to the EPA.\142\ Additionally, the EPA is now
reconsidering policy decisions made in our prior actions addressing
interstate transport obligations for the 2015 8-hour ozone NAAQS
following Kentucky and the remand and vacatur of the EPA's disapproval
of Mississippi's SIP

[[Page 4039]]

submission by the Fifth Circuit, as described in Section III.C. of this
preamble. As a result, the EPA now proposes to approve Kentucky's SIP
submission.
---------------------------------------------------------------------------

\139\ See ``Final Kentucky Infrastructure State Implementation
Plan,'' Element D (``Kentucky's SIP submission'') included in the
docket for this proposed action, Docket ID No. EPA-HQ-OAR-2025-0192.
\140\ 87 FR 9498 (Feb. 22, 2022).
\141\ 88 FR 9336 (Feb. 13, 2023).
\142\ Kentucky, 123 F.4th at 473.
---------------------------------------------------------------------------

b. Summary of Kentucky's Submission
Kentucky's SIP submission provides the Commonwealth's analysis of
its impact to downwind States and concludes that the Commonwealth meets
the requirements of CAA section 110(a)(2)(D)(i)(I) because Kentucky's
SIP submission contains adequate provisions to prevent sources and
other types of emissions activities within the Commonwealth from
significantly contributing to nonattainment, or interfering with the
maintenance, of downwind States with respect to the 2015 8-hour ozone
NAAQS.
Kentucky's SIP submission relies on the results of the EPA's March
2018 memorandum modeling to identify downwind nonattainment and
maintenance receptors that may be ``linked'' to emissions from sources
in Kentucky.\143\ Kentucky notes that these modeling results showed
Kentucky is projected to be linked to four nonattainment receptors and
one maintenance receptor above 1 percent of the NAAQS.
---------------------------------------------------------------------------

\143\ Kentucky's SIP submission at 18-19.
---------------------------------------------------------------------------

Kentucky relies on the EPA's August 2018 memorandum to apply a 1-
ppb threshold and finds that the Commonwealth is no longer projected to
be linked to the four nonattainment receptors.\144\ Kentucky,
therefore, concludes that no further controls are required to address
the Commonwealth's contribution to those four receptors and that
Kentucky's SIP submission contains adequate provisions to prevent
sources and other types of emissions activities within the Commonwealth
from contributing significantly to nonattainment in any other State
(i.e., ``Prong 1'' of CAA section 110(a)(2)(D)(i)(I)) for the 2015 8-
hour ozone NAAQS).\145\
---------------------------------------------------------------------------

\144\ Id. at 19.
\145\ Id. at 45.
---------------------------------------------------------------------------

After application of the 1-ppb contribution threshold, Kentucky
notes it contributes over 1 ppb to one maintenance receptor in Harford
County, Maryland (``Harford receptor'').\146\ Kentucky's SIP submission
states that emissions reductions required for an upwind State should
not be the same for a monitor that is projected to be attaining the
NAAQS under average conditions as for a nonattainment monitor. Kentucky
further maintains that local controls should be implemented before
requiring upwind States to control their sources.
---------------------------------------------------------------------------

\146\ Id. at 19.
---------------------------------------------------------------------------

Kentucky also reviews NO<INF>X</INF> emissions trends in the
Commonwealth, comparing annual NO<INF>X</INF> emissions from 2008 to
2016 and finding that NO<INF>X</INF> emissions in Kentucky have
significantly decreased since 2008.\147\ Kentucky indicates that
scheduled shutdowns, fuel switches, and retirements of facilities in
the Commonwealth mean Kentucky's emissions will continue to decrease.
In addition, Kentucky lists existing State, SIP-approved regulations
and Federal programs for sources in the Commonwealth that it concluded
address the requirements of CAA 110(a)(2)(D)(i)(I) for the 2015 8-hour
ozone NAAQS.\148\ Thus, Kentucky concludes that no further reductions
other than existing and anticipated measures are required to address
the Commonwealth's interstate transport obligation to eliminate its
contribution to the Harford receptor (Prong 2).
---------------------------------------------------------------------------

\147\ Id. at 30-31.
\148\ See Kentucky's SIP submission, at 20-30 for the list of
state, SIP-approved regulations and Federal programs identified by
Kentucky.
---------------------------------------------------------------------------

c. Evaluation of Kentucky's Submission
The Sixth Circuit vacated and remanded the EPA's prior disapproval
of Kentucky's SIP submission on the grounds that the disapproval was
arbitrary and capricious for improperly departing from past
policy.\149\ In particular, the Sixth Circuit found that the EPA had
ignored Kentucky's reliance interests in the modeling results released
with the March 2018 memorandum and that the August 2018 memorandum,
together with feedback provided by the EPA during Kentucky's SIP
submission development process, established that Kentucky could apply a
1-ppb contribution threshold in Step 2 in its SIP submission for the
2015 ozone NAAQS without further justification.\150\
---------------------------------------------------------------------------

\149\ Kentucky, 123 F.4th at 468.
\150\ Id. at 468-469.
---------------------------------------------------------------------------

On remand, the EPA is reevaluating Kentucky's submission in
accordance with the court's identification of the EPA's previous
missteps. As described in Section III.C.3. of this preamble, the EPA is
applying a 1-ppb contribution threshold. Furthermore, as described in
Section III.C.4. of this preamble, to accommodate Kentucky's reliance
interests, the EPA is referring in the first instance to the State's
chosen modeling. When the modeling a State relies on in its SIP
submission shows a contribution over 1 ppb to at least one receptor in
2023, the EPA will confirm whether any linkages are projected to exist
in the EPA's updated modeling. Though not explicitly endorsed by the
court, the Sixth Circuit suggested this approach could be a possible
route for the EPA on remand.\151\ Kentucky's SIP submission uses the
EPA's March 2018 memorandum modeling. This modeling showed that
Kentucky's projected maximum contribution is 0.89 ppb to a
nonattainment receptor (receptor ID 90013007 in Fairfield County,
Connecticut) and 1.52 ppb to a maintenance receptor (receptor ID
240251001 in Harford County, Maryland).\152\ The EPA's 2016v3 modeling
shows a maximum contribution of 0.84 ppb to a nonattainment receptor
(receptor ID 90013007 in Fairfield County, Connecticut) and 0.79 ppb to
a maintenance receptor (receptor ID 90099002 in New Haven County,
Connecticut).\153\ Thus, in accordance with the policies articulated in
Section III.C. of this preamble, the EPA proposes to find that Kentucky
does not impact downwind air quality problems such that the
Commonwealth should be considered ``linked'' in Step 2 of the
Framework, and therefore further review and analysis at Steps 3 and 4
is not warranted. Therefore, the EPA is proposing to approve Kentucky's
SIP submission because the Commonwealth will not contribute
significantly to nonattainment or interfere with maintenance of the
2015 8-hour ozone NAAQS in any other State.\154\ This proposed action,
if finalized, will respond to the Sixth Circuit's vacatur and remand of
the previous disapproval of Kentucky's SIP submission.
---------------------------------------------------------------------------

\151\ Id. at 472.
\152\ See Attachment C to the EPA's March 2018 memorandum.
\153\ 2016v3 TSD, Table 4-1.
\154\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

6. Minnesota
a. Prior Notices Related to Minnesota's SIP Submission
On October 1, 2018, the Minnesota Pollution Control Agency
submitted a SIP revision to address CAA section 110(a)(2)(D)(i)(I)
interstate transport requirements for the 2015 8-hour ozone NAAQS.\155\
The EPA's proposed partial disapproval of Minnesota's SIP submission
was published on February 22, 2022,\156\ and the EPA's final partial
disapproval (as to Prong 2) was published on February 13, 2023.\157\

[[Page 4040]]

However, the EPA is now reconsidering the policy decisions made in our
prior actions addressing interstate transport obligations under the
2015 8-hour ozone NAAQS following the remand and vacatur of the EPA's
disapproval of Kentucky's and Mississippi's SIP submissions by the
Sixth and Fifth Circuits, respectively, as described in Section III.C.
of this preamble. As a result, the EPA now proposes to reconsider the
February 13, 2023, partial disapproval of Minnesota's SIP submission
and is proposing to fully approve Minnesota's SIP submission.
---------------------------------------------------------------------------

\155\ See ``Infrastructure/110(a) requirements for the 2015
Ozone National Ambient Air Quality Standard'' (``Minnesota's SIP
submission'') available in the docket for this proposed action,
Docket ID No. EPA-HQ-OAR-2025-0192.
\156\ 87 FR 9838 (Feb. 22, 2022).
\157\ 88 FR 9336 (Feb. 13, 2023).
---------------------------------------------------------------------------

b. Summary of Minnesota's Submission
Minnesota's SIP submission cites both the EPA's March 2018
memorandum modeling and modeling conducted by the Lake Michigan Air
Directors Consortium (LADCO).\158\ In Step 1 of the Framework,
Minnesota identifies monitoring sites that are projected to have
problems attaining and/or maintaining the 2015 8-hour ozone NAAQS in
2023 according to LADCO modeling, which used the Eastern Regional
Technical Advisory Committee (ERTAC) EGU Tool version 2.7 \159\ and the
EPA's March 2018 modeling.\160\ LADCO performed a modeling
demonstration like that of the EPA's 2018 transport modeling, except
with use of the ERTAC EGU Tool to supplement State-specific EGU
information.
---------------------------------------------------------------------------

\158\ See Minnesota's SIP submission at 1.
\159\ Information about the ERTAC EGU tool can be found at
<a href="https://marama.org/technical-center/ertac-egu/">https://marama.org/technical-center/ertac-egu/</a>.
\160\ Minnesota's SIP submission at Tables 2 and 3, pages 8-9.
---------------------------------------------------------------------------

In Step 2, Minnesota's SIP submission presents the State's
projected 2023 ozone contributions to maintenance and nonattainment
receptors identified by both LADCO modeling and the EPA's March 2018
modeling.\161\ Minnesota's SIP submission notes there were differences
in identified receptors between the two modeling results, and the LADCO
results overall yielded slightly lower projected contributions to
downwind receptors from Minnesota sources than the EPA's modeling.\162\
---------------------------------------------------------------------------

\161\ Id.
\162\ Id. at 7.
---------------------------------------------------------------------------

Minnesota relies on the 1-percent threshold to define linkages.
Both the LADCO modeling and the EPA's March 2018 modeling showed that
Minnesota contributes less than 1 percent of the NAAQS to all downwind
receptors. Minnesota shows in Table 2 of the State's SIP submission
that the highest projected contribution to a receptor in 2023 is 0.40
ppb, based on the EPA's March 2018 modeling, or 0.45 ppb, based on
LADCO modeling, to a receptor in Milwaukee County, Wisconsin.\163\
Minnesota concludes that the State is not linked above 1 percent of the
NAAQS to any downwind receptor and therefore does not contribute to
nonattainment or interference with maintenance in other States with
respect to the 2015 8-hour ozone NAAQS.
---------------------------------------------------------------------------

\163\ Id. at 8-9.
---------------------------------------------------------------------------

Although Minnesota concludes it is not linked in Step 2, Minnesota
proceeds with a Step 3 analysis. Minnesota provides air quality data to
demonstrate that no additional emissions reductions are necessary to
satisfy the State's transport obligations, including evidence of
decreasing ambient ozone concentrations in the State from the mid-1990s
through 2017 as well as decreasing NO<INF>X</INF> and VOC emissions
from the State from 2002 through 2015.\164\ Minnesota concludes that
decreasing emissions in the State make it unlikely for the State to
contribute significantly to nonattainment or interference with
maintenance of the 2015 8-hour ozone NAAQS in downwind States.
---------------------------------------------------------------------------

\164\ Id. Figures 1-3, pages 10-11.
---------------------------------------------------------------------------

Minnesota therefore concludes that no additional permanent or
enforceable measures are needed to address ozone transport contribution
from Minnesota sources beyond existing control measures. Therefore,
Minnesota did not consider any new permanent and enforceable measures
to reduce emissions as part of the Step 4 analysis.
c. Evaluation of Minnesota's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous disapproval of the SIP submission from Minnesota. In Steps 1
and 2 of the Framework, Minnesota relies on both LADCO modeling and the
EPA's March 2018 memorandum modeling in its SIP submission. The March
2018 memorandum modeling showed that Minnesota's projected maximum
contribution is 0.40 ppb to a nonattainment receptor (receptor ID
550790085 in Milwaukee County, Wisconsin) and 0.31 ppb to a maintenance
receptor (receptor ID 261630019 in Wayne County, Michigan).\165\ LADCO
modeling similarly showed that Minnesota's projected maximum
contribution to any downwind receptor is 0.45 ppb (receptor ID
550790085 in Milwaukee County, Wisconsin).\166\ Minnesota does not
contribute above the 1-ppb threshold to any receptor in its modeling of
choice. Thus, in accordance with the policies articulated in Section
III.C. of this preamble, the EPA proposes to find that Minnesota does
not impact downwind air quality problems such that the State should be
considered ``linked'' in Step 2 of the Framework and, therefore,
further review and analysis at Steps 3 and 4 is not warranted.
Therefore, the EPA is proposing to fully approve Minnesota's SIP
submission because the State will not contribute significantly to
nonattainment or interfere with maintenance of the 2015 8-hour ozone
NAAQS in any other State.\167\ This proposed action, if finalized,
would replace the EPA's previous final action disapproving the SIP
submission from Minnesota.\168\
---------------------------------------------------------------------------

\165\ See Attachment C to the EPA's March 2018 memorandum.
\166\ Minnesota's SIP submission, Table 2 at 8.
\167\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
\168\ 88 FR 9336.
---------------------------------------------------------------------------

7. Mississippi
a. Prior Notices Related to Mississippi's SIP Submission
On September 3, 2019, the Mississippi Department of Environmental
Quality submitted a SIP revision addressing CAA section
110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 8-
hour ozone NAAQS.\169\ The EPA's proposed disapproval of Mississippi's
SIP submission was published on February 22, 2022,\170\ and the EPA's
final disapproval was published on February 13, 2023.\171\ The Fifth
Circuit vacated and remanded that disapproval to the EPA.\172\
Additionally, the EPA is now reconsidering policy decisions made in our
prior actions addressing interstate transport obligations under the
2015 8-hour ozone NAAQS following Texas and the remand and vacatur of
the EPA's disapproval of Kentucky's SIP submission by the Sixth
Circuit, as described in Section III.C. of this preamble. As a result,
the EPA proposes to approve Mississippi's SIP submission.
---------------------------------------------------------------------------

\169\ See ``Mississippi 2015 Ozone Infrastructure SIP Prongs 1 &
2'' (``Mississippi's SIP submission'') included in the docket for
this proposed action, Docket ID No. EPA-HQ-OAR-2025-0192.
\170\ 87 FR 9545 (Feb. 22, 2022).
\171\ 88 FR 9336 (Feb. 13, 2023).
\172\ Texas, 132 F.4th at 863.
---------------------------------------------------------------------------

b. Summary of Mississippi's Submission
Mississippi's SIP submission provides the State's analysis of its
impact to downwind States and concludes that emissions from the State
will not

[[Page 4041]]

significantly contribute to nonattainment or interfere with maintenance
of the 2015 8-hour ozone NAAQS in other States.
Mississippi's SIP submission relies on the EPA's March 2018
memorandum modeling to identify projected downwind nonattainment and
maintenance receptors and contribution linkages in 2023 that may be
impacted by emissions from sources in Mississippi in Steps 1 and 2 of
the Framework, respectively.\173\ Mississippi notes that the modeled
contributions for Mississippi are below 1 percent of the NAAQS for all
nonattainment and maintenance receptors, except the Deer Park
nonattainment receptor in Harris County, Texas (``Deer Park
receptor'').\174\ Mississippi's SIP submission identifies that the
State is projected to contribute 0.79 ppb to the Deer Park
receptor.\175\
---------------------------------------------------------------------------

\173\ Mississippi's SIP submission at 4.
\174\ Id.
\175\ Id. Table 1.
---------------------------------------------------------------------------

Mississippi discusses the EPA's August 2018 memorandum, noting that
0.79 ppb is between 1 percent of the NAAQS and 1 ppb.\176\
Mississippi's SIP submission also states that the Deer Park receptor
design value was projected to be greater than the 2015 8-hour ozone
standards in 2023, but the actual 2015-2017 design value was below the
NAAQS at 68 ppb.\177\ Based on the EPA's March 2018 modeling, along
with application of a 1-ppb threshold and information regarding 2015-
2017 monitored values at the Deer Park receptor, Mississippi concludes
that sources in the State are not linked to downwind nonattainment or
maintenance receptors in Step 2 and, therefore, the State does not
significantly contribute to nonattainment in another State for the 2015
8-hour ozone standards. Further, Mississippi states that the State's
SIP submission contains adequate provisions to prohibit sources and
other types of emissions activities within the State from contributing
to nonattainment (Prong 1) in another State with respect to the 2015 8-
hour ozone NAAQS.
---------------------------------------------------------------------------

\176\ Id. at 6.
\177\ Id. Table 4.
---------------------------------------------------------------------------

In Mississippi's SIP submission, the State treats the Deer Park
receptor as a maintenance receptor because the 2017 design value of 68
ppb was below the level of the NAAQS at this monitor.\178\ Mississippi
cites the EPA's October 2018 memorandum to apply this alternative
definition of a maintenance receptor. Based on the alternative
definition of a maintenance receptor and the application of a 1-ppb
threshold, Mississippi concludes that the State does not significantly
interfere with maintenance (Prong 2) in another State for the 2015 8-
hour ozone standards. c. Evaluation of Mississippi's Submission
---------------------------------------------------------------------------

\178\ Id. at 9.
---------------------------------------------------------------------------

c. Evaluation of Mississippi's Submission
The Fifth Circuit vacated and remanded the EPA's prior disapproval
of Mississippi's SIP submission on the grounds that the disapproval was
arbitrary and capricious for inadequate explanation.\179\ Applying a 1-
percent threshold to 2016v3 modeling results, the EPA found Mississippi
to be linked to at least one out-of-state receptor. The court noted
that the EPA had said that Mississippi's use of a 1-ppb contribution
threshold was ``inconsequential'' to the outcome; however, Mississippi
did not contribute above 1 ppb in the older modeling provided in its
SIP submission and so would not have been linked had the EPA limited
its consideration only to the modeling used in Mississippi's SIP
submission.\180\ Due to this, the court found that the EPA failed to
recognize or reasonably explain its decision to consider the updated
modeling in an ``outcome determinative'' way.\181\
---------------------------------------------------------------------------

\179\ Texas, 132 F.4th at 860-862.
\180\ See id. at 861-862.
\181\ Id. at 862.
---------------------------------------------------------------------------

On remand, the EPA is reevaluating Mississippi's submission in
accordance with the court's identification of the EPA's previous
missteps. As described in Section III.C.4. of this preamble, the EPA
relies in the first instance on the modeling the State chose to use in
its submission and will only consider its updated modeling information
to confirm that at least one linkage above 1 ppb continues to persist.
In Steps 1 and 2 of the Framework, Mississippi relies on the EPA's
March 2018 memorandum modeling to identify nonattainment and
maintenance receptors and identify upwind State linkages to
nonattainment and maintenance receptors.\182\ This modeling showed that
Mississippi's projected maximum contribution is 0.79 ppb to a
nonattainment receptor (receptor ID 482011039 in Harris County, Texas)
and 0.50 ppb to a maintenance receptor (receptor ID 482010024 in Harris
County, Texas).\183\ Mississippi does not contribute above the 1-ppb
threshold to any receptor in its modeling of choice. Thus, in
accordance with the policies articulated in Section III.C. of this
preamble, the EPA proposes to find that Mississippi does not impact
downwind air quality problems such that the State should be considered
``linked'' in Step 2 of the Framework and, therefore, further review
and analysis at Steps 3 and 4 is not warranted. Therefore, the EPA is
proposing to approve Mississippi's SIP submission because the State
will not contribute significantly to nonattainment or interfere with
maintenance of the 2015 8-hour ozone NAAQS in any other State.\184\
Here, the EPA is not using its updated information in an outcome
determinative way as it is not relying on its updated modeling
information to approve Mississippi's submission. This proposal, if
finalized, will respond to the Fifth Circuit's vacatur and remand of
the previous disapproval of Mississippi's SIP submission.
---------------------------------------------------------------------------

\182\ In Step 1, Mississippi also applied an alternative
definition of a maintenance receptor using the EPA's October 2018
Memorandum and 2014 to 2017 Design Values. However, based on the
EPA's conclusions identified in this section, the EPA does not find
it necessary to review in depth the State's application of an
alternative maintenance receptor definition.
\183\ See Attachment C to the EPA's March 2018 memorandum.
\184\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

8. Nevada
a. Prior Notices Related to Nevada's SIP Submission
On September 28, 2018, the Nevada Division of Environmental
Protection (NDEP) submitted Nevada's infrastructure SIP revision for
the 2015 8-hour ozone NAAQS.\185\ The EPA's proposed disapproval of
Nevada's SIP submission was published on May 24, 2022,\186\ and the
final disapproval was published on February 13, 2023.\187\ However, the
EPA is now reconsidering policy decisions made in our prior actions
addressing interstate transport obligations under the 2015 8-hour ozone
NAAQS following the remand and vacatur of the EPA's disapproval of
Kentucky's and Mississippi's SIP submissions by the Sixth and Fifth
Circuits, respectively, as described in Section III.C of this preamble.
As a result, the EPA is proposing to reconsider the February 13, 2023,
disapproval of Nevada's SIP submission and is proposing to approve
Nevada's SIP submission.
---------------------------------------------------------------------------

\185\ See ``The Nevada Division of Environmental Protection
Portion of the Nevada State Implementation Plan for the 2015 Ozone
NAAQS: Demonstration of Adequacy'' (``Nevada's SIP submission'')
included in the docket for this proposed action, Docket ID No. EPA-
HQ-OAR-2025-0192.
\186\ 87 FR 31485 (May 24, 2022).
\187\ 88 FR 9336 (Feb. 13, 2023).

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

[[Page 4042]]

b. Summary of Nevada's Submission
NDEP addresses CAA section 110(a)(2)(D)(i)(I) interstate transport
requirements for the 2015 8-hour ozone NAAQS in Appendix E of Nevada's
SIP submission.\188\ Nevada's SIP submission follows the Framework to
analyze Nevada's impact on other States. In Steps 1 and 2, Nevada
relies on the EPA's March 2018 memorandum modeling.\189\ Further, in
Step 2, Nevada applies a 1-percent threshold.\190\ Based on the EPA's
March 2018 memorandum modeling results, Nevada's SIP submission
concludes that the largest projected contribution from Nevada to a
nonattainment or maintenance receptor in another State is 0.9 percent
of the 2015 8-hour ozone NAAQS.\191\
---------------------------------------------------------------------------

\188\ Nevada's SIP submission also includes information from two
other agencies that regulate air quality in Nevada: the Clark County
Department of Air Quality and the Washoe County Health District Air
Quality Management Division. Though these two county level agencies
provided their own submissions, they do not include their own
separate transport evaluation and instead incorporate Appendix E of
Nevada's SIP verbatim. The individual submissions from Clark County
and Washoe County are included in the docket, and for simplicity in
this section ``Nevada's SIP submission'' refers to the collection of
submissions from NDEP, Clark County, and Washoe County.
\189\ Nevada's SIP submission, at E-2 and E-3.
\190\ Nevada's SIP submission at E-2, E-3, and E-10.
\191\ Id. at E-6 and Attachment A. Specific contributions to
nonattainment and maintenance monitors are contained in Table E-A3.
---------------------------------------------------------------------------

Based on the conclusion that emissions sources in Nevada do not
contribute above 1 percent of the NAAQS to any nonattainment or
maintenance receptors, Nevada's SIP submission concludes that
identification of necessary emissions reductions in Step 3 of the EPA's
Framework is not needed.\192\ Accordingly, Nevada does not consider any
new permanent and enforceable measures to reduce emissions in Step 4 of
the Framework.\193\
---------------------------------------------------------------------------

\192\ Id. at E-11.
\193\ Id.
---------------------------------------------------------------------------

c. Evaluation of Nevada's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous disapproval of the SIP submission from Nevada. In Steps 1 and
2 of the Framework, Nevada relies on the EPA's March 2018 memorandum
modeling to identify nonattainment and maintenance receptors and upwind
State linkages to nonattainment and maintenance receptors in 2023. This
modeling showed that, outside of California, Nevada's projected maximum
contribution is 0.38 ppb to a maintenance receptor (receptor ID 8059001
in Jefferson County, Colorado) and 0.37 ppb to a nonattainment receptor
(receptor ID 80690011 in Larimer County, Colorado).\194\ \195\ Nevada
is not linked to any downwind receptor above the 1-ppb threshold in its
modeling of choice. Thus, in accordance with the policies articulated
in Section III.C. of this preamble, the EPA proposes to find that
Nevada does not impact downwind air quality problems such that the
State should be considered ``linked'' in Step 2 of the Framework and,
therefore, further review and analysis in Steps 3 and 4 is not
warranted. Therefore, the EPA is proposing to approve Nevada's SIP
submission because the State will not contribute significantly to
nonattainment or interfere with maintenance of the 2015 8-hour ozone
NAAQS in any other State.\196\ This proposed action, if finalized,
would replace the EPA's previous final action disapproving the SIP
submission from Nevada.\197\
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\194\ See Attachment C to the EPA's March 2018 memorandum.
\195\ Nevada identified its maximum contribution to be 0.9
percent of the NAAQS (or 0.65 ppb) to a monitoring site in
California. Because this is below the 1 ppb threshold (as well as a
1% of NAAQS threshold), we do not need to resolve whether this
monitoring site should be considered a transport receptor. See 88 FR
at 36718.
\196\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
\197\ 88 FR 9336.
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9. New Mexico
a. Prior Notices Related to New Mexico's SIP Submission
In 2019, the EPA found that New Mexico had failed to submit a
complete interstate transport SIP submission for the 2015 8-hour ozone
NAAQS.\198\ This triggered the EPA's obligation to promulgate a FIP for
New Mexico within two years.\199\ When the EPA did not do so, multiple
parties brought deadline-suit litigation against the EPA. This resulted
in a consent decree deadline of June 1, 2024, for the EPA to either
promulgate a FIP for New Mexico or approve a SIP submission fully
resolving New Mexico's interstate transport obligations.\200\ By
stipulation of the parties, that deadline has now been extended to
February 26, 2026.\201\
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\198\ 84 FR 66612 (Dec. 4, 2019).
\199\ 42 U.S.C. 7410(c)(1)(A).
\200\ WildEarth Guardians v. Zeldin, No. 22-cv-0174-RB-GBW
(D.N.M. Aug. 16, 2022); Sierra Club v. Zeldin, No. 3:22-cv-01992-JD
(N.D. Cal. Jan. 24, 2023).
\201\ Joint Stipulation Extending Consent Decree Deadlines,
WildEarth Guardians v. Zeldin, No. 1:22-cv-0174, ECF No. 20 (D.N.M.
Nov. 25, 2024); Joint Notice of Stipulated Extension of Consent
Decree Deadline, Sierra Club v. Zeldin, No. 3:22-cv-01992-JD, ECF
No. 44 (N.D. Cal. Nov. 25, 2024).
---------------------------------------------------------------------------

On July 20, 2021, on behalf of the City of Albuquerque
Environmental Health Department (EHD), the New Mexico Environment
Department (NMED) submitted a certification that Albuquerque-Bernalillo
County ``does not cause or contribute to nonattainment or interfere
with maintenance of the 2015 8-hour ozone NAAQS in any other state.''
\202\ On July 27, 2021, NMED then submitted an interstate transport SIP
submission certifying that New Mexico's SIP submission satisfies
interstate transport requirements for the 2015 8-hour ozone NAAQS.\203\
On July 5, 2023, NMED submitted a supplemental letter that contains
additional data for the EPA's consideration in the Agency's review of
the New Mexico SIP submission.\204\ The EPA proposed to partially
disapprove New Mexico's SIP submission as to Prong 2 in the Proposed
Supplemental Air Plan Action.\205\ However, the EPA is now
reconsidering policy decisions made in our prior actions addressing
interstate transport obligations under the 2015 8-hour ozone NAAQS
following the remand and vacatur of the EPA's disapproval of Kentucky's
and Mississippi's SIP submissions by the Sixth and Fifth Circuits,
respectively, as described in Section III.C of this preamble. As a
result, the EPA is proposing full approval of New Mexico's SIP
submission.
---------------------------------------------------------------------------

\202\ See ``New Mexico Good Neighbor State Implementation Plan
Certification for the 2015 Ozone NAAQS, Submitted on Behalf of
Albuquerque-Bernalillo County'' (``EHD SIP submission'') in the
docket for this action, Docket ID No. EPA-HQ-OAR-2025-0192.
\203\ See ``New Mexico's Good Neighbor State Implementation Plan
Certification for the 2015 Ozone National Ambient Air Quality
Standard'' (``NMED's SIP submission'') in the docket for this
action. For simplicity in this section, ``New Mexico's SIP
submission'' refers to the collective information in NMED's
submission and EHD's submission.
\204\ This additional data was included under the heading
``Exhibit A Estimates of Emission Reductions (``Exhibit A'').
\205\ 89 FR 12666 (Feb. 16, 2024).
---------------------------------------------------------------------------

b. Summary of New Mexico's Submission
New Mexico's SIP submission contains what NMED characterizes as a
WOE analysis of New Mexico's contribution to ozone transport receptors.
In Step 1 of the Framework, New Mexico's SIP submission relies on the
EPA's March 2018 memorandum modeling.\206\ In Step 2, New Mexico
identifies that the State contributes above 1 percent of the NAAQS to
one maintenance receptor and one

[[Page 4043]]

nonattainment receptor, both in Colorado.\207\
---------------------------------------------------------------------------

\206\ NMED's Exhibit A acknowledged the EPA's 2016v3 modeling
results and linkages.
\207\ Id. at Table 1, page 4; page 5.
---------------------------------------------------------------------------

New Mexico used a WOE analysis rather than relying on a single,
national standard for identifying linkages and determining whether
contributions from an upwind State are significant.\208\ NMED and EHD
find that New Mexico should not be considered linked to Colorado
receptors in Step 2 because the majority of the contribution to these
receptors comes directly from Colorado. New Mexico's submission also
states that the relative share of in-state versus out-of-state
contribution in Colorado, topographical influences on the transport of
ozone in Colorado, and other air quality information support its WOE
analysis.\209\
---------------------------------------------------------------------------

\208\ New Mexico SIP submission at 5.
\209\ Id. at 5-16.
---------------------------------------------------------------------------

New Mexico concludes it would be unreasonable for the State to take
further actions to address its interstate transport requirements for
the 2015 8-hour ozone NAAQS and therefore do not conduct an analysis of
emissions control opportunities within the State in Step 3. Thus, in
Step 4, NMED and EHD determine that no additional permanent and
enforceable measures are necessary to reduce the State's emissions.
The supplemental information NMED submitted for the EPA's
consideration in 2023 provides more information in response to the
EPA's indication that the EPA may disapprove New Mexico's SIP
submission. To the EPA's knowledge, this letter was not subject to
public notice or rulemaking process at the State level and does not in
itself purport to be a SIP submission or a revision to New Mexico's SIP
submission. As such, the EPA takes the information in the letter under
advisement but does not consider the letter to be a new SIP submission
in its own right or part of New Mexico's SIP submission.
c. Evaluation of New Mexico's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous proposed disapproval of the SIP submission from New Mexico.
New Mexico relies on the EPA's March 2018 memorandum modeling in the
State's SIP submission. This modeling showed that New Mexico's maximum
contribution is 0.77 ppb to a maintenance receptor (receptor ID
81230009 in Weld County, Colorado) and 0.70 ppb to a nonattainment
(receptor ID 80590006 in Jefferson County, Colorado).\210\ Both
contributions in the State's modeling of choice are below the 1-ppb
threshold. Thus, in accordance with the policies articulated in Section
III.C. of this preamble, the EPA proposes to find that New Mexico does
not impact downwind air quality problems such that it should be
considered ``linked'' in Step 2 of the Framework and, therefore,
further review and analysis in Steps 3 and 4 is not warranted.
Therefore, the EPA is proposing to approve New Mexico's SIP submission
because the State will not contribute significantly to nonattainment or
interfere with maintenance of the 2015 8-hour ozone NAAQS in any other
State.\211\ If finalized, the EPA will withdraw the prior proposed
partial disapproval.
---------------------------------------------------------------------------

\210\ See Attachment C to the EPA's March 2018 memorandum.
\211\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

10. Tennessee
a. Prior Notices Related to Tennessee's SIP Submission
On September 13, 2018, the Tennessee Department of Environment and
Conservation submitted a SIP addressing CAA section 110(a)(2)(D)(i)(I)
interstate transport requirements for the 2015 8-hour ozone NAAQS.\212\
The EPA previously proposed approval of Tennessee's SIP submission on
December 30, 2019.\213\ The EPA then withdrew this proposed approval
and proposed to disapprove Tennessee's SIP submission in a notice
published on February 22, 2022.\214\ In the Proposed Supplemental Air
Plan Action, the EPA then withdrew the proposed disapproval and
proposed to partially disapprove Tennessee's SIP submission as to Prong
2.\215\ However, the EPA is now reconsidering policy decisions made in
our prior actions addressing interstate transport obligations under the
2015 8-hour ozone NAAQS following the remand and vacatur of the EPA's
disapproval of Kentucky's and Mississippi's SIP submissions by the
Sixth and Fifth Circuits, respectively, as described in Section III.C.
of this preamble. As a result, the EPA is proposing full approval of
Tennessee's SIP submission.
---------------------------------------------------------------------------

\212\ The September 13, 2018, SIP submission provided by TDEC
was received by the EPA on September 17, 2018. On September 18,
2018, Tennessee submitted multiple SIP submissions under one cover
letter. The EPA is only acting on Tennessee's 2015 8-hour ozone
NAAQS interstate transport SIP requirements in this notice
(``Tennessee's SIP submission'').
\213\ 84 FR 71854 (Dec. 30, 2019).
\214\ 87 FR 9545 (Feb. 22, 2022).
\215\ 89 FR 12666 (Feb. 16, 2024).
---------------------------------------------------------------------------

b. Summary of Tennessee's Submission
Tennessee's SIP submission provides the State's analysis of its
impact to downwind States and concludes that emissions from the State
will not significantly contribute to nonattainment or interfere with
maintenance of the 2015 8-hour ozone NAAQS in other States. Tennessee's
SIP submission relies on the EPA's March 2018 memorandum modeling to
identify downwind nonattainment and maintenance receptors that may be
impacted by emissions from sources in the State in Steps 1 and 2 of the
Framework.\216\ Tennessee summarizes the State's upwind contribution
and notes Tennessee's largest impact on a projected downwind receptor
is 0.31 ppb and 0.65 ppb to a nonattainment and maintenance receptor,
respectively. Tennessee finds that, based on these modeling results,
emissions from Tennessee do not contribute above 1 percent of the NAAQS
or above 1 ppb at any monitors that are projected to be in
nonattainment or maintenance.\217\
---------------------------------------------------------------------------

\216\ Tennessee's SIP submission at 9.
\217\ Id.
---------------------------------------------------------------------------

Tennessee's SIP submission emphasizes a significant reduction in
NO<INF>X</INF> emissions from coal-fired EGUs and other large
NO<INF>X</INF> sources leading to improvements in air quality,
including reductions attributable to previous transport
rulemakings.\218\ Additionally, Tennessee identifies existing SIP-
approved provisions, Federal regulations and programs, court
settlements, and statewide source shutdowns that Tennessee believes
limit ozone precursor emissions in the State.\219\
---------------------------------------------------------------------------

\218\ Tennessee's SIP submission cites Federal and state rules
at pages 9-12.
\219\ See pages 9 through 12 of Tennessee's SIP submission for a
list of SIP-approved state rules and Federal rules.
---------------------------------------------------------------------------

Based on this information, Tennessee concludes that the State does
not significantly contribute to nonattainment or interfere with
maintenance in another State of the 2015 8-hour ozone NAAQS, and the
existing approved SIP, found at 40 CFR part 52, subpart RR, provides
for adequate measures to control ozone precursor emissions.
c. Evaluation of Tennessee's Submission
As described in Section III.C. of this preamble, in light of the
EPA's implementation of policies consistent with the Sixth and Fifth
Circuits' decisions in Kentucky and Texas, the EPA is reconsidering its
previous

[[Page 4044]]

proposed disapproval of the SIP submission from Tennessee. Tennessee
relied on the EPA's March 2018 memorandum modeling to identify
nonattainment and maintenance receptors and upwind State linkages to
nonattainment and maintenance receptors in 2023. Tennessee relies on a
1-ppb threshold in its SIP submission. This modeling showed that
Tennessee's projected maximum contribution is 0.31 ppb to a
nonattainment receptor (receptor ID 551170006 in Sheboygan County,
Wisconsin) and 0.65 ppb to a maintenance receptor (receptor ID
260050003 in Allegan County, Michigan).\220\ Therefore, Tennessee is
not linked to any downwind receptors above the 1-ppb threshold in its
modeling of choice. Thus, in accordance with the policies articulated
in Section III.C. of this preamble, based on the EPA's evaluation of
the information provided in Tennessee's SIP submission, the EPA
proposes to find that Tennessee does not impact downwind air quality
problems such that the State should be considered ``linked'' in Step 2
of the Framework and, therefore, further review and analysis at Steps 3
and 4 is not warranted. Therefore, the EPA is proposing to approve
Tennessee's SIP submission because the State will not contribute
significantly to nonattainment or interfere with maintenance of the
2015 8-hour ozone NAAQS in any other State.\221\ If finalized, the EPA
will withdraw the prior proposed partial disapproval.
---------------------------------------------------------------------------

\220\ See Attachment C to the EPA's March 2018 memorandum.
\221\ See 42 U.S.C. 7410(a)(2)(D)(i)(I).
---------------------------------------------------------------------------

B. CAA Section 110(l)

Under CAA section 110(l), ``the Administrator shall not approve a
revision of a plan if the revision would interfere with any applicable
requirement concerning attainment . . . or any other applicable
requirement of this chapter.'' Section 110(l) applies to all CAA
requirements, including section 110(a)(2)(D) requirements relating to
interstate transport.\222\
---------------------------------------------------------------------------

\222\ Id. 7410(l).
---------------------------------------------------------------------------

For the 2015 8-hour ozone NAAQS, the EPA previously disapproved
interstate transport SIP submissions from, and promulgated interstate
transport FIPs for sources in, Alabama, Kentucky, Minnesota,
Mississippi, and Nevada.\223\ The EPA's predicate authority for the
FIPs as to each of these States was judicially stayed or judicially
vacated.\224\ However, the Ninth Circuit later lifted the stay of
Nevada's SIP submission.\225\ The EPA never promulgated interstate
transport FIPs for Arizona, Iowa, Kansas, New Mexico, or Tennessee.
Therefore, this proposed action, if finalized, will not revise any
existing requirement in any lawfully promulgated implementation plan
for any State included in this proposed action. In the case of Nevada,
even if the Good Neighbor Plan were considered in the baseline (which
is assumed only for the sake of argument, given that the stay of its
SIP disapproval was lifted), the EPA is not aware of any interference
with other requirements of the CAA that would result from this proposed
action.
---------------------------------------------------------------------------

\223\ 88 FR 9336 (Feb. 13, 2023); 88 FR 36654 (June 5, 2023).
\224\ Alabama et al. v. EPA, No. 23-11173, ECF No. 33 (11th Cir.
Aug. 17, 2023) (SIP Disapproval Action as to Alabama stayed);
Kentucky v. EPA, 123 F.4th 447 (6th Cir. 2024) (SIP Disapproval
Action as to Kentucky vacated); Allete, Inc. d/b/a Minnesota Power
et al. v. EPA, No. 23-1776, ECF No. 5292580 (8th Cir. July 5, 2023)
(SIP Disapproval Action as to Minnesota stayed); Texas v. EPA, 132
F.4th 808 (5th Cir. 2025) (SIP Disapproval Action as to Mississippi
vacated); Nevada Cement Co. v. EPA, No. 23-682, ECF No. 27 (9th Cir.
July 3, 2023) (SIP Disapproval Action as to Nevada stayed).
\225\ Nevada Cement Co. v. EPA, No. 23-682, ECF No. 65 (9th Cir.
Dec. 17, 2024).
---------------------------------------------------------------------------

V. Summary of Changes to Existing Regulatory Text

This section describes proposed amendments to the regulatory text
in the CFR to approve and promulgate SIPs for eight States (Alabama,
Arizona, Kentucky, Minnesota, Mississippi, Nevada, New Mexico, and
Tennessee).
The primary CFR amendments that would apply the approval and
promulgation of the SIPs will be made in the respective State's subpart
of 40 CFR part 52. The subparts are as follows: Alabama--subpart B,
Arizona--subpart D, Kentucky--subpart S, Minnesota--subpart Y,
Mississippi--subpart Z, Nevada--subpart DD, New Mexico--subpart GG,
Tennessee--subpart RR. Where appropriate, the approval status for the
2015 8-hour ozone NAAQS will be changed from disapproved to approved,
and, where appropriate, the approval status will be changed to indicate
the SIP has now been approved.

VI. Statutory and Executive Order Reviews

Additional information about these statutes and Executive Orders
can be found at <a href="http://www.epa.gov/laws-regulations/laws-and-executive-orders">www.epa.gov/laws-regulations/laws-and-executive-orders</a>.

A. Executive Order 12866: Regulatory Planning and Review

This action is a significant regulatory action that was submitted
to the Office of Management and Budget (OMB). Any changes made in
response to Executive Order 12866 review have been documented in the
docket for this action.

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

This action is expected to be an Executive Order 14192 deregulatory
action. This proposed rule is expected to provide burden reduction. If
finalized, this action would resolve the interstate transport
obligations of eight States for the 2015 8-hour ozone NAAQS. Therefore,
this action would result in reduced regulatory burden for those States.

C. Paperwork Reduction Act (PRA)

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

D. Regulatory Flexibility Act (RFA)

I certify this action will not have a significant economic impact
on a substantial number of small entities under the RFA. This action
proposes to approve SIP submissions as satisfying interstate transport
requirements under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone
NAAQS, and these SIP submissions do not impose any requirements on
small entities.

E. Unfunded Mandates Reform Act (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.

F. Executive Order 13132: Federalism

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

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

This action does not have Tribal implications as specified in
Executive Order 13175. This proposed rule does not have substantial
direct effects on one or more Indian Tribes, on the relationship
between the Federal government and Indian Tribes, or on the
distribution of power and responsibilities between the Federal
government and Indian Tribes. Thus,

[[Page 4045]]

Executive Order 13175 does not apply to this action.

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

The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that the EPA has reason to believe may disproportionately affect
children, per the definition of ``covered regulatory action'' in
section 2-202 of the Executive Order. Therefore, this action is not
subject to Executive Order 13045 because it merely approves SIP
submissions as containing the necessary provisions to satisfy
interstate transport requirements under CAA section 110(a)(2)(D)(i)(I).
Furthermore, since this action does not concern human health risks,
EPA's Policy on Children's Health also does not apply.

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

This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution, or use of energy. The purpose of this proposed rule is to
resolve the interstate transport requirements for the 2015 8-hour ozone
NAAQS for 10 States. The EPA does not expect these activities to
adversely affect energy suppliers, distributors, or users.

J. National Technology Transfer and Advancement Act

This rulemaking does not involve technical standards.

List of Subjects in 40 CFR Part 52

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

Lee Zeldin,
Administrator.
[FR Doc. 2026-01844 Filed 1-29-26; 8:45 am]
BILLING CODE 6560-50-P

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