Rule2026-18334
Air Plan Approvals; Indiana; Prong 4 (Visibility) for the 2015 Ozone National Ambient Air Quality Standard
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
September 9, 2026
Effective
October 9, 2026
Issuing agencies
Environmental Protection Agency
Abstract
The U.S. Environmental Protection Agency (EPA) is approving a portion of Indiana's State Implementation Plan (SIP) submission regarding the infrastructure requirements in Clean Air Act (CAA) section 110 for the 2015 ozone National Ambient Air Quality Standards (NAAQS). The infrastructure requirements are designed to ensure that the structural components of each State's air quality management program are adequate to meet the State's responsibilities under the CAA. The EPA finds that Indiana's infrastructure submission fulfills CAA requirements for a State's SIP to contain adequate provisions prohibiting emissions that will interfere with required visibility protection measures in any other State's SIP. The EPA proposed to approve this action on April 10, 2026, and received no adverse comments.
Full Text
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<title>Federal Register, Volume 91 Issue 173 (Wednesday, September 9, 2026)</title>
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[Federal Register Volume 91, Number 173 (Wednesday, September 9, 2026)]
[Rules and Regulations]
[Pages 57262-57265]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-18334]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R05-OAR-2018-0788; FRL-13249-02-R5]
Air Plan Approvals; Indiana; Prong 4 (Visibility) for the 2015
Ozone National Ambient Air Quality Standard
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: The U.S. Environmental Protection Agency (EPA) is approving a
portion of Indiana's State Implementation Plan (SIP) submission
regarding the infrastructure requirements in Clean Air Act (CAA)
section 110 for the 2015 ozone National Ambient Air Quality Standards
(NAAQS). The infrastructure requirements are designed to ensure that
the structural components of each State's air quality management
program are adequate to meet the State's responsibilities under the
CAA. The EPA finds that Indiana's infrastructure submission fulfills
CAA requirements for a State's SIP to contain adequate provisions
prohibiting emissions that will interfere with required visibility
protection measures in any other State's SIP. The EPA proposed to
approve this action on April 10, 2026, and received no adverse
comments.
DATES: This final rule is effective on October 9, 2026.
ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R05-OAR-2018-0788. All documents in the docket are
listed on the <a href="https://www.regulations.gov">https://www.regulations.gov</a> website. Although listed in
the index, some information is not publicly available, i.e.,
Confidential Business Information (CBI), Proprietary Business
Information (PBI), 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
through <a href="https://www.regulations.gov">https://www.regulations.gov</a> or please contact the person
identified in the FOR FURTHER INFORMATION CONTACT section for
additional information.
FOR FURTHER INFORMATION CONTACT: Matt Rau, Air and Radiation Division
(AR-18J), Environmental Protection Agency, Region 5, 77 West Jackson
Boulevard, Chicago, Illinois 60604, telephone number: (312) 886-6524,
email address: <a href="/cdn-cgi/l/email-protection#3e4c5f4b10535f4a4a565b497e5b4e5f10595148"><span class="__cf_email__" data-cfemail="9fedfeeab1f2feebebf7fae8dffaeffeb1f8f0e9">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean the EPA.
Acronyms
CAA Clean Air Act
CBI Confidential Business Information
EPA U.S. Environmental Protection Agency
LADCO Lake Michigan Air Directors Consortium
NAAQS National Ambient Air Quality Standards
PBI Proprietary Business Information
RPO Regional Planning Organization
SIP State Implementation Plan
I. Executive Summary
A. What action is the EPA taking?
The EPA is finalizing an approval of Indiana's November 2, 2018,
interstate transport infrastructure SIP submission as satisfying the
requirements related to visibility protection contained in CAA section
110(a)(2)(D)(i)(II), also known as Prong 4, for the 2015 ozone NAAQS.
B. What is the legal authority and requirements?
The EPA proposed to approve Indiana's submission into the SIP on
April 10, 2026, 91 FR 18347. In this action, EPA is finalizing an
approval of Indiana's submittal as meeting the visibility protection
requirements of CAA section 110(a)(2)(D)(i)(II) for the 2015 ozone
NAAQS.
II. Background
On November 2, 2018, Indiana submitted an infrastructure SIP
revision for the 2015 ozone NAAQS addressing the fourth component of
CAA section 110(a)(2)(D)(i)(II), also known as ``Prong 4.'' Prong 4
requires that a State's SIP contain adequate provisions prohibiting any
source or other type of emissions activity within the State from
emitting any air pollutant in amounts which will interfere with
measures required to be included in the applicable SIP for any other
State to protect visibility.
Indiana is a member of the Lake Michigan Air Directors Consortium
(LADCO) regional planning organization (RPO) and participated in the
RPO's regional approach to identifying emission reduction measures
necessary to make reasonable progress towards the national visibility
goal in LADCO Class I areas. That process also included consultations
with States in other RPOs. Indiana responded to requests from non-LADCO
States and another RPO to consider additional measures to address
visibility impairment in Class I areas outside the LADCO States.
III. CAA Section 110(a)(2)(D)(i)(II)--Visibility Protection
CAA section 110(a)(2)(D)(i)(II), Prong 4, requires SIPs to contain
adequate provisions to prohibit emissions in amounts that will
interfere with measures required to be included in the applicable
implementation plan for any other state under part C of the Act to
protect visibility. The EPA issued guidance on infrastructure SIPs in a
September 13, 2013, memorandum titled ``Guidance on Infrastructure
State Implementation Plan (SIP) Elements
[[Page 57263]]
under Clean Air Act sections 110(a)(1) and 110(a)(2)'' (``2013
Guidance''). The 2013 Guidance states that these Prong 4 requirements
can be satisfied by approved SIP provisions that the EPA has found to
adequately address any contribution of that State's sources that impact
the visibility program requirements in other States.\1\
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\1\ 2013 Guidance at pages 32 through 33. A copy of this
guidance can be found in the docket of this rulemaking.
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The 2013 Guidance lays out how a State's infrastructure SIP may
satisfy Prong 4. In the second planning period, confirmation that a
State has a fully approved regional haze SIP that fully meets the
requirements of 40 CFR 51.308 will satisfy the requirements of Prong
4.\2\ A fully approved regional haze SIP \3\ will ensure that emissions
from sources under an air agency's jurisdiction are not interfering
with measures required to be included in other air agencies' plans to
protect visibility.
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\2\ The EPA acknowledges that in the 2013 Guidance, we indicated
that the EPA may find it appropriate to supplement the guidance
regarding the relationship between regional haze SIPs and prong 4
after second implementation period SIPs become due, which occurred
on July 31, 2021. After a review of the 2013 Guidance and the second
implementation period regional haze requirements, the EPA maintains
the interpretation that a fully approved regional haze SIP satisfies
prong 4 requirements in the second implementation period.
\3\ Since second implementation period SIPs became due, a
``fully approved regional haze SIP'' would necessarily include fully
approved first and second implementation period regional haze SIPs.
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In the second planning period, the EPA's Regional Haze regulations
under 40 CFR 51.308(f) require that a State consider the emission
reduction measures identified by other States as being necessary to
make reasonable progress towards meeting the national visibility goal
in Class I Federal areas. Specifically, the regulations require a State
to include in its Regional Haze SIP all measures agreed to during that
process or measures that will provide equivalent visibility improvement
(See 40 CFR 51.308(f)(2)(ii)). Thus, in meeting the requirements of 40
CFR 51.308(f), an approved regional haze SIP meeting the requirements
of 40 CFR 51.308(f)(2)(ii) will ensure that emissions from sources
under an air agency's jurisdiction are not interfering with measures
required to be included in other air agencies' plans to protect
visibility and will, therefore, satisfy Prong 4.
III. Summary of Public Comments and the EPA's Responses
The EPA received one comment during the comment period for the
proposed rule. The commenter did not object to the EPA's proposed
action, but rather suggested that the EPA include additional
information supporting the determinations of the proposal in the final
rule. EPA has provided this additional information in the background
section of this final action, and we are finalizing our action as
proposed.
The commenter stated, ``EPA should strengthen the final rule in
three ways.'' A synopsis of each comment is given before the response.
The comment letter is included in the docket for this rulemaking.
Comment: The commenter suggests that the EPA identify the specific
findings from the regional haze plan approval that it believes satisfy
prong 4. The commenter contends that the proposal does not explain
which findings from the January 26, 2026, approval demonstrate that
Indiana emissions will not interfere with the visibility protection
measures required in other States' SIPs.
Response: In the proposed rule, the EPA confirms that Indiana has a
fully approved regional haze SIP meeting the requirements of 40 CFR
51.308 to satisfy Prong 4. According to the 2013 Guidance, a State's
infrastructure SIP may satisfy Prong 4 for any relevant NAAQS through
an air agency's confirmation that the State has a fully approved
regional haze SIP meeting the requirements of 40 CFR 51.308. Since
second implementation period SIPs became due, a ``fully approved
regional haze SIP'' would necessarily include fully approved first and
second implementation period regional haze SIPs. Therefore, simply
confirming the EPA's approval of Indiana's second implementation period
regional haze plan satisfies the requirement.
The Regional Haze Rule's consultation requirement of 40 CFR
51.308(f)(2)(ii) requires a State to consult with other States that
also have emissions that are reasonably anticipated to contribute to
visibility impairment in each Class I area. The EPA's approval of
Indiana's second implementation period regional haze plan confirms it
has engaged in consultation to consider the emission reduction measures
identified by other States for their sources as being necessary to make
reasonable progress in the mandatory Class I Federal area (See 91 FR
3057, January 26, 2026).
Comment: The commenter suggests that the EPA explain the sequencing
of the EPA's approvals of Indiana's 2015 ozone standard infrastructure
SIP submission made on November 2, 2018. As the Prong 4 portion of the
submittal was not included in the EPA's June 29, 2022, approval, the
commenter suggests that the EPA state what changed and why that change
is sufficient to resolve the previously open Prong 4 issue.
Response: This is the third EPA rulemaking on Indiana's November 2,
2018, submission addressing the 2015 ozone NAAQS. First, the EPA
approved most elements of Indiana's submission on November 2, 2022 (87
FR 66091), which addressed the applicable infrastructure requirements
in CAA section 110(a)(1) and (2) for the 2015 ozone NAAQS related to
the interstate transport element preventing significant deterioration
of air quality from CAA section 110(a)(2)(D)(i)(II) (``Prong 3''). The
proposed rule details the background, including an analysis of each
element (See 87 FR 38693, June 29, 2022). In this rulemaking, EPA did
not act on the other interstate transport elements, Prongs 1, 2, and 4.
Second, the EPA acted on the Prongs 1 and 2 interstate transport
elements. On February 13, 2023 (88 FR 9336), the EPA disapproved the
CAA section 110(a)(2)(D)(i)(I) elements for Indiana and other States.
Prongs 1 and 2 require 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. The EPA found that a portion
of Indiana's submission did not meet the State's interstate transport
obligations, because it did not contain the necessary provisions to
eliminate emissions that would contribute significantly to
nonattainment or interfere with maintenance of the 2015 ozone NAAQS in
any other State. The proposed rulemaking further details the analysis
used in evaluating each State's interstate transport provision for the
2015 ozone NAAQS implementation plan submission, including Indiana (See
87 FR 9838, February 22, 2022).
Third, the EPA is approving the Prong 4 element of CAA section
110(a)(2)(D)(i)(II), with this rule. The EPA finds that Indiana's
infrastructure submission fulfills CAA requirements for a State's SIP
to contain adequate provisions prohibiting emissions that will
interfere with required visibility protection measures in any other
State's SIP. The 2013 Guidance confirms a State's infrastructure SIP
may satisfy Prong 4 \4\ for any relevant NAAQS
[[Page 57264]]
through the States's confirmation that it has a fully approved regional
haze SIP \5\ meeting the requirements of 40 CFR 51.308. The EPA
approved Indiana's regional haze plan for the second implementation
period (See 91 FR 3057, January 26, 2026).
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\4\ In the 2013 Guidance, we indicate that it may be appropriate
to supplement the guidance regarding the relationship between
regional haze SIPs and Prong 4 after second implementation period
SIPs become due, which occurred on July 31, 2021. After a review of
the 2013 Guidance and the second implementation period regional haze
requirements, the EPA maintains the interpretation that a fully
approved regional haze SIP satisfies Prong 4 requirements in the
second implementation period.
\5\ Since second implementation period SIPs became due, a
``fully approved regional haze SIP'' would necessarily include fully
approved first and second implementation period regional haze SIPs.
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Comment: The commenter suggests that the EPA make the
administrative record easier to audit for ordinary readers. The
commenter contends that if the Agency's conclusion depends almost
entirely on Indiana's regional haze plan approval, then the final rule
should include a short summary showing how the plan's interstate
visibility findings relate to this Prong 4 determination.
Response: Electronic dockets make the supporting documents readily
available to readers. The referenced documents are in the docket for
this rulemaking.
As noted in the proposed rule and the previous comment response, a
State having a fully approved regional haze plan for the second
implementation period will ensure that emissions from sources under an
air agency's jurisdiction are not interfering with measures required to
be included in other air agencies' plans to protect visibility and
will, therefore, satisfy Prong 4. By meeting the statutory and
regulatory requirements of the regional haze program, including the
interstate consultation requirements in 40 CFR 51.308(f)(2)(ii),
Indiana's SIP adequately prohibits emissions from within the State that
would interfere with visibility protection measures in any other
State's SIP. Thus, now that the EPA has approved Indiana's regional
haze plan for the second implementation period, Indiana satisfies the
requirements of CAA section 110(a)(2)(D)(i)(II) relating to visibility
protection for the 2015 ozone NAAQS, allowing the Prong 4 element of
the infrastructure submission to be approved.
IV. What action is the EPA taking?
The EPA is approving Indiana's November 2, 2018, interstate
transport infrastructure SIP submission as satisfying the requirements
related to visibility protection contained in CAA section
110(a)(2)(D)(i)(II), also known as Prong 4, for the 2015 ozone NAAQS.
V. 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. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 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:
<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), petitions for judicial review of this
action must be filed in the United States Court of Appeals for the
appropriate circuit by November 9, 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 (See CAA section 307(b)(2)).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Nitrogen oxides, Ozone,
Particulate matter, Sulfur oxides.
Dated: August 24, 2026.
Anne Vogel,
Regional Administrator, Region 5.
For the reasons stated in the preamble, 40 CFR part 52 is amended
as follows:
PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS
0
1. The authority citation for part 52 continues to read as follows:
Authority: 42 U.S.C. 7401 et seq.
0
2. In Sec. 52.770, the table in paragraph (e) is amended by removing
the two entries for ``Section 110(a)(2) Infrastructure Requirements for
the 2015 Ozone NAAQS'' adding in their place an entry for ``Section
110(a)(2) Infrastructure Requirements for the 2015 Ozone NAAQS'' to
read as follows:
Sec. 52.770 Identification of plan.
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(e) * * *
[[Page 57265]]
EPA-Approved Indiana Nonregulatory and Quasi-Regulatory Provisions
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Title Indiana date EPA approval Explanation
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Section 110(a)(2) Infrastructure 11/2/2018 9/9/2026, 91 FR [INSERT All CAA infrastructure
Requirements for the 2015 Ozone NAAQS. Federal Register PAGE elements have been
WHERE THE DOCUMENT approved except (D)(i)(I)
BEGINS]. Prongs 1 and 2, which are
disapproved.
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[FR Doc. 2026-18334 Filed 9-8-26; 8:45 am]
BILLING CODE 6560-50-P
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