Air Plan Approval; Kentucky; Louisville Area Limited Maintenance Plan for the 1997 8-Hour Ozone NAAQS

Issuing agencies

Abstract

The U.S. Environmental Protection Agency (EPA or Agency) is approving a State Implementation Plan (SIP) revision submitted by the Commonwealth of Kentucky through the Energy and Environment Cabinet (Cabinet) on behalf of the Louisville Metro Air Pollution Control District (District) via a letter dated June 3, 2024. The SIP revision consists of a Limited Maintenance Plan (LMP) for the Kentucky portion of the bi-state Louisville, Kentucky-Indiana 1997 8-hour ozone maintenance area (the "bi-state Louisville Area"). The Kentucky portion of the bi-state Louisville Area is comprised of Bullitt, Jefferson, and Oldham Counties in Kentucky (the "Louisville Area"). The EPA is approving the Louisville Area's LMP because it provides for the maintenance of the 1997 8-hour ozone National Ambient Air Quality Standards (NAAQS) within the bi-state Louisville Area through the end of the second 10-year portion of the maintenance period. The effect of this action is to make certain commitments related to maintenance of the 1997 8-hour ozone NAAQS in the Louisville Area federally enforceable as part of the Kentucky SIP.

Full Text

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<title>Federal Register, Volume 91 Issue 194 (Thursday, October 8, 2026)</title>
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[Federal Register Volume 91, Number 194 (Thursday, October 8, 2026)]
[Rules and Regulations]
[Pages 64297-64301]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-20641]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2024-0295; FRL-13322-02-R4]


Air Plan Approval; Kentucky; Louisville Area Limited Maintenance 
Plan for the 1997 8-Hour Ozone NAAQS

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The U.S. Environmental Protection Agency (EPA or Agency) is 
approving a State Implementation Plan (SIP) revision submitted by the 
Commonwealth of Kentucky through the Energy and Environment Cabinet 
(Cabinet) on behalf of the Louisville Metro Air Pollution Control 
District (District) via a letter dated June 3, 2024. The SIP revision 
consists of a Limited Maintenance Plan (LMP) for the Kentucky portion 
of the bi-state Louisville, Kentucky-Indiana 1997 8-hour ozone 
maintenance area (the ``bi-state Louisville Area''). The Kentucky 
portion of the bi-state Louisville Area is comprised of Bullitt, 
Jefferson, and Oldham Counties in Kentucky (the ``Louisville Area''). 
The EPA is

[[Page 64298]]

approving the Louisville Area's LMP because it provides for the 
maintenance of the 1997 8-hour ozone National Ambient Air Quality 
Standards (NAAQS) within the bi-state Louisville Area through the end 
of the second 10-year portion of the maintenance period. The effect of 
this action is to make certain commitments related to maintenance of 
the 1997 8-hour ozone NAAQS in the Louisville Area federally 
enforceable as part of the Kentucky SIP.

DATES: This rule is effective November 9, 2026.

ADDRESSES: The EPA has established a docket for this action under 
Docket Identification No. EPA-R04-OAR-2024-0295. All documents in the 
docket are listed on the <a href="http://regulations.gov">regulations.gov</a> website. Although listed in 
the index, some information may not be publicly available, i.e., 
Confidential Business Information or other information whose disclosure 
is restricted by statute. Certain other material, such as copyrighted 
material, is not placed on the internet and will be publicly available 
only in hard copy form. Publicly available docket materials are 
available either electronically through <a href="https://www.regulations.gov">https://www.regulations.gov</a> or 
in hard copy at the Air Regulatory Management Section, Air Planning and 
Implementation Branch, Air and Radiation Division, U.S. Environmental 
Protection Agency, Region 4, 61 Forsyth Street, SW, Atlanta, Georgia 
30303-8960. The EPA requests that if at all possible, you contact the 
person listed in the FOR FURTHER INFORMATION CONTACT section to 
schedule your inspection. The Regional Office's official hours of 
business are Monday through Friday 8:30 a.m. to 4:30 p.m., excluding 
Federal holidays.

FOR FURTHER INFORMATION CONTACT: Nelsha Athauda, Multi-Air Pollutant 
Coordination Section, Air Planning and Implementation Branch, Air and 
Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 
Forsyth Street SW, Atlanta, Georgia 30303-8960. The telephone number is 
(404) 562-9360. Ms. Athauda can also be reached via electronic mail at 
<a href="/cdn-cgi/l/email-protection#c9a8bda1a8bcada8e7a7aca5baa1a889acb9a8e7aea6bf"><span class="__cf_email__" data-cfemail="e081948881958481ce8e858c938881a0859081ce878f96">[email&#160;protected]</span></a>.

SUPPLEMENTARY INFORMATION: The EPA uses multiple abbreviations and 
terms in this rule. While this list may not be exhaustive, for ease of 
reading and for reference purposes, the EPA defines the following terms 
and acronyms here:

CAA Clean Air Act
EPA Environmental Protection Agency
LMP Limited Maintenance Plan
NAAQS National Ambient Air Quality Standard or Standards
NPRM Notice of Proposed Rulemaking
SIP State Implementation Plan

Table of Contents

I. Executive Summary
II. Background
III. Response to Comments
IV. Statutory and Executive Order Reviews

I. Executive Summary

    Under CAA sections 110(k) and 175A, the EPA is approving the 
Louisville Area LMP for the 1997 8-hour ozone NAAQS, submitted by the 
Cabinet on June 3, 2024, as a revision to the Kentucky SIP. The EPA is 
approving the Louisville Area LMP because it includes an acceptable 
update of the various elements of the 1997 8-hour ozone NAAQS 
maintenance plan approved by the EPA for the first 10-year period--
including an emissions inventory, assurance of adequate monitoring and 
verification of continued attainment, and contingency provisions.
    The EPA finds that the Louisville Area qualifies for the LMP option 
and that, therefore, the Louisville Area LMP adequately demonstrates 
maintenance of the 1997 8-hour ozone NAAQS through documentation of 
monitoring data showing design values well below the NAAQS and 
continuation of existing control measures. The EPA believes that the 
Louisville Area's 1997 8-hour ozone LMP is sufficient to provide for 
maintenance of the 1997 8-hour ozone NAAQS in the bi-state Louisville 
Area over the remainder of the second 10-year maintenance period, 
through 2027, and thereby satisfies the requirements for such a plan 
under CAA section 175A(b).

II. Background

    On April 30, 2004, the bi-state Louisville Area--which is comprised 
of Bullitt, Jefferson, and Oldham Counties in Kentucky; and Clark and 
Floyd Counties in Indiana--was designated as nonattainment for the 1997 
8-hour ozone NAAQS.\1\ Subsequently, on September 29, 2006, the Cabinet 
submitted a redesignation request and the first 10-year maintenance 
plan for the Louisville Area. In 2007, the EPA approved the maintenance 
plan and redesignated the Louisville Area to attainment for the 1997 8-
hour ozone NAAQS.\2\
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    \1\ See 69 FR 23858 (Apr. 30, 2004).
    \2\ See 72 FR 36601 (July 5, 2007).
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    Through a notice of proposed rulemaking (NPRM) published on August 
27, 2026,\3\ the EPA proposed to approve the Louisville Area LMP for 
the 1997 8-hour ozone NAAQS, which is designed to maintain the 1997 8-
hour ozone NAAQS within the Louisville Area through the end of the 
second 10-year portion of the maintenance period beyond redesignation. 
The details of the Cabinet's June 3, 2024, submittal as well as the 
EPA's rationale for approval are described in more detail in the August 
27, 2026, NPRM. Comments on the August 27, 2026, NPRM were due on or 
before September 17, 2026. The EPA received two sets of comments from 
two separate individuals. The first set of comments provides feedback 
on the proposal and the plan, and concludes by stating that the 
feedback is not ``a case against approving Kentucky's submission.'' The 
second set of comments recommends approval of the LMP but makes some 
requests for clarification. Overall, EPA acknowledges the comments 
received and a brief response is provided below. The commenters did not 
provide new technical data or legal arguments demonstrating that the 
proposed approach is unreasonable. Consequently, EPA is finalizing the 
action as proposed without modifications.
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    \3\ See 91 FR 55294 (Aug. 27, 2026).
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III. Response to Comments

    Comment 1a: The commenter states that the Louisville Area LMP 
``ties its maintenance demonstration to a design-value screening 
threshold of 85 percent of the ozone NAAQS'' and that one monitor in 
Jefferson County does not meet this threshold. The commenter alleges 
that the EPA's ``stress test loses its precision'' by adding the 
largest area-wide design-value increase, 0.008 parts per million (ppm) 
recorded at the Clark County, Indiana monitor, to the highest current 
design value in the area. The commenter states that the math ``is 
conservative in form, but borrows its volatility figure from a monitor 
that is not under stress and applies it to one that already shows its 
own multi-period climb.'' The commenter further states that a 
projection built from the trajectory of the monitor with the highest 
design value, ``rather than an area-wide maximum increase pulled from 
elsewhere, would test the monitor that actually needs testing.''
    Response 1a: The EPA evaluates each LMP on a case-by-case basis, 
taking into consideration the weight of evidence (WOE) of the 
information presented in the SIP submittal. The EPA evaluated the level 
of the bi-state Louisville Area's air quality design values as part of 
its WOE along with a measure of the stability of the ozone design 
values and concluded that the probability of the bi-state Louisville 
Area violating the standard during the second maintenance period is 
low. The EPA's

[[Page 64299]]

evaluation is discussed in the NPRM and further described below.
    Regarding the comment concerning the ``NPRM's stress test,'' 
several kinds of analyses can be performed to assess whether an area 
has had relatively stable or consistently improving air quality levels 
over the long term such that the probability of the area violating the 
standard in the future would be low. One approach is to take the most 
recent design value for the area \4\ and add the maximum design value 
increase, over one or more consecutive years, that has been observed in 
the area over the past several years.\5\ For this maintenance plan, the 
EPA assessed the design value data to determine whether adding the 
maximum design value increase over the 14-year timeframe between 2012 
and 2025 to the most recent design value for the bi-state Louisville 
Area would result in a value below the 0.084 ppm threshold to attain 
the 1997 8-hour ozone NAAQS.
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    \4\ The design value for an area is the highest design value at 
any monitor in the area.
    \5\ See EPA's Resource Document for 1997 Ozone NAAQS Areas: 
Supporting Information for States Developing Maintenance Plans, 
November 20, 2018, pp. 6-7.
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    The EPA's analysis showed that adding the maximum design value 
increase in any monitor over the entire 14-year timeframe--0.008 ppm--
to the maximum most recent design value at any monitor in the area--
0.075 ppm--would result in a design value attaining the 1997 8-hour 
ozone NAAQS. According to the commenter, the EPA should have instead 
considered the trajectory at the monitor with the 0.075 ppm design 
value. However, the design values at this monitor did not change 
between 2024 and 2025, and the difference between the highest and 
lowest design value at this monitor over the 14-year timeframe was 
lower--0.006 ppm--which would produce a value of 0.081 ppm, which is 
also below the NAAQS. Thus, when the EPA applies its understanding of 
the commenter's approach, this appears to reinforce the EPA's 
conclusion that the probability of the bi-state Louisville Area 
violating the standard during the second maintenance period is low.
    Comment 1b: The commenter points out that deciding which of the ten 
listed contingency measures to adopt ``rests on the Division's 
judgment.'' The commenter states that there is no ``minimum stringency 
floor'' or opportunity for the EPA or public to review the choice 
before it becomes part of the SIP. The commenter states that 
``attaching a stringency standard, or a defined concurrence step, to 
that selection would let the contingency plan ``provide a prompt, 
predictable response rather than a discretionary one.''
    Response 1b: The EPA acknowledges the comments and offers some 
clarifications in this response. CAA section 175A(d) only requires that 
maintenance plans contain contingency provisions that ``the 
Administrator deems necessary to assure that the State will promptly 
correct any violation of the standard which occurs after the 
redesignation of the area as an attainment area.'' The CAA does not 
specify the requisite nature, scope, specificity, or number of 
contingency measures to be included in a maintenance plan. It is for 
the EPA to determine whether a state has given adequate assurance that 
it can promptly correct a violation. Kentucky submitted contingency 
measures that the EPA deems adequate, and the commenter does not argue 
that the contingency measures listed in the June 3, 2024, SIP revision 
are insufficient. Kentucky has committed to promptly correct any future 
violation and has identified measures that are sufficiently specific, 
but which allow for latitude in potential scope. This will enable 
Kentucky to address a range of potential sources and differing degrees 
and types of violations. The EPA believes that the contingency measures 
set forth in the submittal, combined with Kentucky's commitment to an 
expeditious timeline, provide assurance that they will promptly correct 
a future potential violation. Given the uncertainty as to timing, 
degree and nature of any future violation, the EPA believes that the 
contingency measures set forth adequately balance the need for 
flexibility in the scope and type of measure to be implemented with the 
need for expeditious action on the part of the Commonwealth.
    The EPA disagrees that the Agency and the public do not have the 
opportunity to review the selected contingency measure before it 
becomes part of the SIP. The District and the Commonwealth developed 
the LMP with public notice and opportunity for a hearing, and the EPA's 
NPRM provided opportunity for comment on the sufficiency of the 
contingency plan. As discussed above, the EPA has determined that this 
contingency plan is sufficient to assure that the District and the 
Commonwealth will promptly correct any violation of the NAAQS, as 
required by CAA section 175A(d). Further, CAA section 175A(d) gives the 
Administrator discretion to ``require[ ] the State to submit a revised 
[SIP]'' if necessary, and pursuant to CAA section 110(l) and 40 CFR 
part 51, subpart F, any SIP revision must be subject to public notice 
at the State level.
    Comment 1c: The commenter states that the second 10-year 
maintenance period runs through 2027, ``close behind any final action 
on this proposal, and the notice does not describe what happens to the 
Louisville Area's SIP obligations after that date or whether a third 
submission is already underway.'' The commenter asserts that the EPA 
should name ``a submission timeline for the period after 2027 now.''
    Response 1c: CAA section 175A only requires States to submit two 
maintenance plan SIP revisions for areas redesignated from 
nonattainment to attainment. The first maintenance plan SIP revision 
must provide for maintenance of the NAAQS ``for at least ten years 
after the redesignation.'' \6\ Effective August 6, 2007, the EPA 
approved the Louisville Area's first maintenance plan and redesignated 
that area to attainment. The second maintenance plan SIP revision must 
provide for maintenance of the NAAQS for 10 years after the expiration 
of the first 10-year period.\7\ Thus, this second maintenance plan for 
the Louisville Area only provides for maintenance of the NAAQS through 
2027--10 years after the expiration of the first 10-year period. No 
third maintenance plan SIP revision is required; therefore, there is no 
submission timeline and no such SIP revision is underway.
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    \6\ See CAA section 175A(a).
    \7\ See CAA section 175A(b).
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    Comment 2a: This commenter states that EPA should ``approve the 
LMP, but that the final rule'' should ``specifically address'' the 
Jefferson County monitor that produced a design value of 0.075 ppm and 
``confirm that continued monitoring and contingency triggers are 
sufficient to catch any upward trend.'' The commenter asserts that the 
monitor ``warrants explicit attention in the final action rather than 
being subsumed into the overall weight of evidence'' because the 
monitor is ``approaching 90 percent of the standard.''
    Response 2a: Regarding the comment concerning the design value of 
0.075 ppm, see the discussion in Response 1a, above. Regarding the 
comment concerning the detection of an upward trend, the EPA has 
approved the Cabinet's air quality monitoring network in the Louisville 
Area as meeting the requirements of 40 CFR part 58, as noted in the 
NPRM and the EPA's October 28, 2025, response to the 2025 network plan 
for Kentucky and the

[[Page 64300]]

District.\8\ Two primary objectives of part 58 monitoring networks are 
to evaluate compliance with the NAAQS and to identify data trends.\9\ 
Any changes in the part 58 monitoring network must be approved by the 
EPA.\10\ Furthermore, the contingency plan includes tracking and 
triggering mechanisms to determine when control measures are needed and 
a process for developing and adopting appropriate control measures. In 
addition to a violation trigger, the contingency plan also includes a 
set of ``indicator'' triggers: (1) any 8-hour ozone monitoring reading 
of 0.085 ppm or greater in the Area, or (2) a periodic emissions 
inventory for the Area that shows greater than 10 percent growth in 
either NO<INF>X</INF> or VOC emissions over the attainment year 
inventory. Either of these non-violating, indicator triggers results in 
Kentucky and the District evaluating existing control measures to see 
if any further emission reductions measures should be adopted in an 
effort to avoid a future violation.
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    \8\ The EPA's response letter is included in the docket for this 
action.
    \9\ See 40 CFR part 58, Appendix D, Section 1.1(a)-(c). See also 
71 FR 61236, 61260 (Oct. 17, 2006).
    \10\ See 40 CFR 58.10 and 58.14.
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    Comment 2b: The commenter states that the final rule should 
``clarify that the contingency measures [in the LMP] remain available 
and enforceable through the end of the maintenance period even as the 
area continues to address the 2015 NAAQS.'' The commenter contends that 
the contingency measures should ``remain coordinated with any ongoing 
control strategies for the newer standard so that resources are not 
diluted.''
    Response 2b: The EPA confirms that, with the approval of this SIP 
revision, the LMP's contingency plan for the entirety of the second 
maintenance period will be part of the federally enforceable SIP. 
Regarding the commenter's suggestion that the contingency measures in 
the LMP should be coordinated with the control measures for the 2015 
ozone NAAQS, CAA section 175A requires each State with a maintenance 
area to submit maintenance plans focused on the specific NAAQS for 
which the area was redesignated to attainment.\11\ In this case, the 
LMP is appropriately focused on the 1997 ozone NAAQS. The EPA carefully 
evaluated the LMP's contingency plan and ensured it complies with the 
requirements of CAA section 175A(d).
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    \11\ See CAA section 175A(a) (``Each State which submits a 
request under section 7407(d) of this title for redesignation of a 
nonattainment area for any air pollutant as an area which has 
attained the national primary ambient air quality standard for that 
air pollutant shall also submit a revision of the applicable State 
implementation plan to provide for the maintenance of the national 
primary ambient air quality standard for such air pollutant in the 
area concerned for at least 10 years after the redesignation.'') 
(emphasis added).
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IV. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the CAA and applicable 
Federal regulations.\12\ Thus, in reviewing SIP submissions, the EPA's 
role is to approve State choices, provided that they meet the criteria 
of the CAA. Accordingly, this action merely approves State law as 
meeting Federal requirements and does not impose additional 
requirements beyond those imposed by State law. For that reason, this 
action:
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    \12\ See 42 U.S.C. 7410(k); 40 CFR 52.02(a).
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    <bullet> Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Order 12866 (58 
FR 51735, October 4, 1993);
    <bullet> Is not an Executive Order 14192 (90 FR 9065, February 6, 
2025) regulatory action because this action is not significant under 
Executive Order 12866;
    <bullet> Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
    <bullet> Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
    <bullet> Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
    <bullet> Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
    <bullet> Is not subject to Executive Order 13045 (62 FR 19885, 
April 23, 1997) because it approves a State program;
    <bullet> Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001); and
    <bullet> Is not subject to requirements of section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA.
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where the EPA or an Indian Tribe 
has demonstrated that a Tribe has jurisdiction. In those areas of 
Indian country, the rule does not have Tribal implications and will not 
impose substantial direct costs on Tribal governments or preempt Tribal 
law as specified by Executive Order 13175 (65 FR 67249, November 9, 
2000).
    This action is subject to the Congressional Review Act, and the EPA 
will submit a rule report to each House of the Congress and to the 
Comptroller General of the United States. This action is not a ``major 
rule'' as defined by 5 U.S.C. 804(2).
    Under CAA section 307(b)(1) of the CAA, petitions for judicial 
review of this action must be filed in the United States Court of 
Appeals for the appropriate circuit by December 7, 2026. Filing a 
petition for reconsideration by the Administrator of this final rule 
does not affect the finality of this action for the purposes of 
judicial review nor does it extend the time within which a petition for 
judicial review may be filed, and shall not postpone the effectiveness 
of such rule or action. This action may not be challenged later in 
proceedings to enforce its requirements.\13\
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    \13\ See CAA section 307(b)(2).
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List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Ozone, Reporting and 
recordkeeping requirements, Volatile organic compounds.

    Dated: September 29, 2026.
Kevin McOmber,
Regional Administrator, Region 4.

    For the reasons stated in the preamble, the EPA amends 40 CFR part 
52 as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

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

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

Subpart S--Kentucky

0
2. In Sec.  52.920, in paragraph (e), amend the table by adding an 
entry for ``1997 8-Hour Ozone Second 10-Year Limited Maintenance Plan 
for the Kentucky portion of the bi-state Louisville Area'' at the end 
of the table to read as follows:


Sec.  52.920  Identification of plan.

* * * * *

[[Page 64301]]

    (e) * * *

                                 EPA-Approved Kentucky Non-Regulatory Provisions
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                                         Applicable        State submittal
    Name of non-regulatory SIP          geographic or      date/ effective    EPA approval date    Explanations
             provision               nonattainment area         date
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                                                  * * * * * * *
1997 8-Hour Ozone Second 10-Year    Bullitt, Jefferson,           6/3/2024  10/8/2026, 91 FR
 Limited Maintenance Plan for the    and Oldham Counties.                    [Insert Federal
 Kentucky portion of the bi-state                                            Register page where
 Louisville Area.                                                            the document
                                                                             begins].
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[FR Doc. 2026-20641 Filed 10-7-26; 8:45 am]
BILLING CODE 6560-50-P


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