SUPPLEMENTARY INFORMATION:

Throughout this document “we,” “us,” and “our” refer to the EPA. We use 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

CBI Confidential Business Information

CFR Code of Federal Regulations

CSR Missouri Code of State Regulations

EPA U.S. Environmental Protection Agency

FR Federal Register

IC Internal Combustion

NAAQS National Ambient Air Quality Standards

NO_X  Nitrogen Oxides

SIP State Implementation Plan

TSD Technical Support Document

U.S.C. United States Code

Table of Contents

I. What is being addressed in this document?

II. Have the requirements for approval of a SIP revision been met?

III. The EPA's Response to Comments

IV. What action is the EPA taking?

V. Incorporation by Reference

VI. Statutory and Executive Order Reviews

I. What is being addressed in this document?

The EPA is approving revisions to the Missouri SIP, Title 10 Code of State Regulations (CSR) 10-6.390 “Control of NO_X Emissions From Large Stationary Internal Combustion Engines,” submitted to the EPA on March 7, 2019, and June 10, 2021. The purpose of the State regulation is to control NO_X emissions from large stationary internal combustion (IC) engines and ensure compliance with the Federal NO_X control plan to reduce the interstate transport of air pollutants. Missouri's rule revisions are detailed in the EPA's notice of proposed rulemaking, published on July 15, 2026.^[1] The EPA finds that these revisions meet the requirements of the CAA and do not impact the State's ability to attain or maintain the National Ambient Air Quality Standards (NAAQS). The full text of the rule revisions as well as the EPA's analysis of the revisions can be found in the technical support document (TSD) included in this docket.

II. Have the requirements for approval of a SIP revision been met?

The State's submission has met the public notice requirements for SIP submissions in accordance with 40 CFR 51.102. The submission also satisfied the completeness criteria of 40 CFR part 51, appendix V. The State provided public notice on this SIP revision from August 4, 2018, to October 4, 2018, and from November 1, 2019, to December 10, 2019, and held public hearings on September 27, 2018, and December 3, 2019. The State received five comments during the first public comment period and none in the second comment period. Missouri's official submission adequately addressed the comments. In addition, as explained in the notice of proposed rulemaking and in more detail in the TSD, which is part of this docket, the revisions meet the substantive SIP requirements of the CAA, including section 110 and implementing regulations. The EPA concludes that in accordance with CAA section 110(l), the revisions to 10 CSR 10-6.390 will not interfere with any applicable requirement concerning attainment, reasonable further progress, or any other applicable requirement of the CAA.

III. The EPA's Response to Comments

The public comment period on the EPA's proposed rule opened July 15, 2026, the date of its publication in the Federal Register , and closed on August 14, 2026. During this period, the EPA received one anonymous comment that was not supportive of the proposed action, available in the docket for this rulemaking, but did not raise a relevant, material objection with specificity that would constitute a significant comment requiring a response. See5 U.S.C. 553(c); 42 U.S.C. 7607(d)(6)(B).

IV. What action is the EPA taking?

The EPA is taking final action to amend the Missouri SIP by approving the State's revisions to 10 CSR 10-6.390 “Control of NO_X Emissions From Large Stationary Internal Combustion Engines.” This final action approves these amendments as part of the SIP.

V. Incorporation by Reference

In this document, the EPA is finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is finalizing the incorporation by reference of the Missouri rule 10-6.390 discussed in section I. of this preamble and as set forth below in the amendments to 40 CFR part 52. The rule provides for control of NO_X emissions from large stationary internal combustion engines and includes reporting, recordkeeping, and compliance requirements. The EPA has made, and will continue to make, these materials generally available through www.regulations.gov and at the EPA Region 7 Office. Please contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information.

Therefore, these materials have been approved by the EPA for inclusion in the SIP, have been incorporated by ( printed page 62321) reference by the EPA into that plan, are fully federally enforceable under CAA sections 110 and 113 as of the effective date of the EPA's approval, and will be incorporated by reference in the next update to the SIP compilation.^[2]

VI. 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:

• Is not a significant regulatory action subject to review by the Office of Management and Budget underExecutive Order 12866 (58 FR 51735, Oct. 4, 1993);
• Is not anExecutive Order 14192 (90 FR 9065, Feb. 6, 2025) regulatory action because this action is not significant under Executive Order 12866;
• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
• 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.);
• 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);
• Does not have federalism implications as specified inExecutive Order 13132 (64 FR 43255, Aug. 10, 1999);
• Is not subject toExecutive Order 13045 (62 FR 19885, Apr. 23, 1997) because it approves a State program;
• Is not a significant regulatory action subject toExecutive Order 13211 (66 FR 28355, May 22, 2001); and
• 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.^[3]

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

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 30, 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 section 307(b)(2)).

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

91 FR 62320