# Air Plan Approval; Missouri; Control of NOX Emissions From Large Stationary Internal Combustion Engines > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2026-14260 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** July 15, 2026 - **Citation:** 91 FR 43351 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-R07-OAR-2026-4819; FRL-13460-01-R7] Air Plan Approval; Missouri; Control of NO X Emissions From Large Stationary Internal Combustion Engines AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The Environmental Protection Agency (EPA) is proposing to approve revisions to the Missouri State Implementation Plan (SIP) related to Control of Nitrogen Oxide (NO X ) Emissions From Large Stationary Internal Combustion Engines. The revisions reformat and revise reporting, recordkeeping, and compliance requirements; incorporate other state rules by reference; add definitions specific to the rule; revise unnecessarily restrictive or duplicative language; and make administrative wording changes. The revisions also add an exemption for certain spark-ignited internal combustion engines. The EPA's proposed approval is pursuant to, and consistent with, the requirements of the Clean Air Act (CAA). DATES: Comments must be received on or before August 14, 2026. ADDRESSES: You may send comments, identified by Docket ID No. EPA-R07-OAR-2026-4819 to https://www.regulations.gov. Follow the online instructions for submitting comments. Instructions: All submissions received must include the Docket ID No. for this rulemaking. Comments received will be posted without change to https://www.regulations.gov, including any personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the “Written Comments” heading of the SUPPLEMENTARY INFORMATION section of this document. FOR FURTHER INFORMATION CONTACT: William Stone, Environmental Protection Agency, Region 7 Office, Air Quality Planning Branch, 11201 Renner Boulevard, Lenexa, Kansas 66219; telephone number: (913) 551-7714; email address: stone.william@epa.gov. SUPPLEMENTARY INFORMATION: Throughout this document “we,” “us,” and “our” refer to the EPA. Table of Contents I. Written Comments II. What is being addressed in this document? III. Have the requirements for approval of a sip revision been met? IV. What action is the EPA taking? V. Incorporation by Reference VI. Statutory and Executive Order Reviews I. Written Comments Submit your comments, identified by Docket ID No. EPA-R07-OAR-2026-4819, at https://www.regulations.gov. Once submitted, comments cannot be edited or removed from Regulations.gov. The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. 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, 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 https://www.epa.gov/dockets/commenting-epa-dockets. II. What is being addressed in this document? The EPA is proposing to approve Missouri's SIP revisions submitted on March 7, 2019, and June 10, 2021, which update Title 10 Code of State Regulations (CSR) 10-6.390 “Control of NO X Emissions From Large Stationary Internal Combustion Engines.” The purpose of these regulations 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. The primary revision to this regulation was to add an exemption to 10 CSR 10-6.390 for existing spark ignition (SI) stationary engines that emit twenty-five (25) tons or less of NO X during the ozone season (May 1 through September 30). Stationary SI engines that meet the criteria for the exemption will no longer have to meet the general provisions of this rule, including emission limits, or the testing requirements of section (5)(A). The new exemption is similar to the exemption currently in the rule for compression ignition (CI) IC engines and was approved into the Missouri SIP in 2015 (80 FR 55545). The EPA has reviewed the State's analysis and finds that the 25-ton NO X exemption in 10 CSR 10-6.390 will not adversely impact air quality, nor will it affect the State's ability to meet its NO X SIP Call budget obligations. The 25-ton NO X exemption in 10 CSR 10-6.390 applies to both new and existing SI engines. New stationary SI engines that qualify for the exemption will be subject to the more stringent NO X emission limits in the New Source Performance Standards in 40 CFR part 60, subpart JJJJ. The Kennett Generating Station (Kennett) in Kennett, MO is the only facility with existing SI engines that qualify for the 25-ton exemption. NO X emissions at Kennett have consistently been less than six tons per ozone season per year. The small amount of NO X emissions from the Kennett SI engines has a minimal impact on the 2015 ozone NAAQS within Missouri and neighboring states. The St. Louis, MO-IL nonattainment is the nearest nonattainment area and is more than 100 miles from Kennett. Because ozone design values in the St. Louis area are driven by typical urban emissions, a small emissions increase at a source of that distance will not interfere with attainment or maintenance of the ozone NAAQS. In addition, total NO X emissions from all sources subject to the NO X SIP Call continue to remain below Missouri's NO X SIP call budget and have been trending downward for the last 5 years. Any increase in emissions related to this exemption at Kennett is unlikely to negatively impact this trend. In addition to the new exemption for stationary SI engines, definitions specific to the rule were added that match the definitions of the same terms in 10 CSR 10-6.020, which is approved into the Missouri SIP, or match the same terms found in 40 CFR 60.4219. The reporting, recordkeeping, and test method requirements have also been reformatted and can be found in sections (4)(A) and (5) of the rule. The revisions also correct incorrect references to other state and federal rule citations caused by prior revisions. For the above reasons, and as discussed in more detail in the technical support document (TSD) included in the docket for this action, the EPA concludes that, in accordance with CAA section 110(l), the 25-ton NO X exemption in 10 CSR 10-6.390 and the other revisions will not interfere with any applicable requirement concerning attainment, reasonable further progress (RFP), or any other applicable requirement of the CAA. The full text of the rule revisions can be found in the state submittals included in this docket. III. Have the requirements for approval of a sip revision been met? The State submissions have met the public notice requirements for SIP submissions in accordance with 40 CFR 51.102. The submissions also satisfied the completeness criteria of 40 CFR part 51, appendix V. The State provided public notice on these SIP revisions 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 above 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, RFP, or any other applicable requirement of the CAA. IV. What action is the EPA taking? The EPA is proposing to amend the Missouri SIP by approving the State's request to revise 10 CSR 10-6.390 “Control of NO X Emissions From Large Stationary Internal Combustion Engines.” We are processing this as a proposed action because we are soliciting comments on this proposed action. Final rulemaking will occur after consideration of any comments. V. Incorporation by Reference In this document, the EPA is proposing to include regulatory text in an EPA final rule that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is proposing to finalize the incorporation by reference of Missouri rule 10 CSR 10-6.390 discussed in section II. of this preamble and as set forth below in the proposed 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 https://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). 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 under Executive Order 12866 (58 FR 51735, October 4, 1993); • Is not an Executive Order 14192 (90 FR 9065, February 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 in Executive Order 13132 (64 FR 43255, August 10, 1999); • Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a state program; • Is not a significant regulatory action subject to Executive 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 (65 FR 67249, November 9, 2000). List of Subjects in 40 CFR Part 52 Environmental protection, Air pollution control, Incorporation by reference, Intergovernmental relations, Nitrogen Oxides, Ozone, Reporting and recordkeeping requirements. Dated: July 6, 2026. James Macy, Regional Administrator, Region 7. For the reasons stated in the preamble, the EPA proposes to amend 40 CFR part 52 as set forth below: PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS 1. The authority citation for part 52 continues to read as follows: Authority: 42 U.S.C. 7401 et seq. Subpart AA—Missouri 2. In § 52.1320, the table in paragraph (c) is amended by revising the entry “10-6.390” to read as follows: § 52.1320 Identification of plan. (c) * * * EPA—Approved Missouri Regulations Missouri citation Title State effective date EPA approval date Explanation Missouri Department of Natural Resources *         *         *         *         *         *         * Chapter 6—Air Quality Standards, Definitions, Sampling and Reference Methods, and Air Pollution Control Regulations for the State of Missouri *         *         *         *         *         *         * 10-6.390 Control of NO X Emissions From Large Stationary Internal Combustion Engines 5/30/2020 [Date of publication of the final rule in the Federal Register ], 91 FR [ Federal Register page where the document begins of the final rule] *         *         *         *         *         *         * [FR Doc. 2026-14260 Filed 7-14-26; 8:45 am] BILLING CODE 6560-50-P --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2026-14260. Public record. Not legal advice.