Air Plan Approval; Indiana; Second Maintenance Plan for 2008 Ozone NAAQS

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R05-OAR-2025-0167; FRL-12839-01-R5]</DEPDOC> <SUBJECT>Air Plan Approval; Indiana; Second Maintenance Plan for 2008 Ozone NAAQS</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is proposing to approve a revision to the Indiana State Implementation Plan (SIP). On April 1, 2025, the Indiana Department of Environmental Management (IDEM) submitted a revision to the State's plan for maintaining the 2008 ozone National Ambient Air Quality Standard (NAAQS or standard) in the Indiana portion of the Cincinnati, Ohio-Kentucky-Indiana area. EPA is proposing to approve this maintenance plan because it provides for the maintenance of the 2008 ozone NAAQS for the area for 10 additional years as required by the Clean Air Act (CAA). EPA is also initiating the adequacy review process for motor vehicle emission budgets (Budgets) for the area. This action, if finalized, would make certain commitments related to maintenance of the 2008 ozone NAAQS in this area federally enforceable as part of the Indiana SIP. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Comments must be received on or before December 22, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R05-OAR-2025-0167 at <E T="03">https://www.regulations.gov,</E> or via email to <E T="03">langman.michael@epa.gov.</E> For comments submitted at <E T="03">Regulations.gov,</E> follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from the docket. EPA may publish any comment received to its public docket. Do not submit to EPA's docket at <E T="03">https://www.regulations.gov</E> any information you consider to be Confidential Business Information (CBI), Proprietary Business Information (PBI), 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. EPA will generally not consider comments or comment contents located outside of the primary submission ( <E T="03">i.e.,</E> on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. For the full EPA public comment policy, information about CBI, PBI, or multimedia submissions, and general guidance on making effective comments, please visit <E T="03">https://www.epa.gov/dockets/commenting-epa-dockets.</E> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Delaney Kilgour, Air and Radiation Division (AR18J), Environmental Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago, Illinois 60604, (312) 886-1493, <E T="03">kilgour.delaney@epa.gov.</E> The EPA Region 5 office is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding Federal holidays. </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA. This <E T="02">SUPPLEMENTARY INFORMATION</E> section is arranged as follows: <EXTRACT> <FP SOURCE="FP-2">I. Summary of EPA's Proposed Action</FP> <FP SOURCE="FP-2">II. Background</FP> <FP SOURCE="FP-2">III. EPA's Evaluation of Indiana's SIP Submittal</FP> <FP SOURCE="FP1-2">A. Second Maintenance Plan</FP> <FP SOURCE="FP1-2">B. Transportation Conformity</FP> <FP SOURCE="FP-2">IV. What action is EPA taking?</FP> <FP SOURCE="FP-2">V. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Summary of EPA's Proposed Action</HD> EPA is proposing to approve, as a revision to the Indiana SIP, the 2008 ozone NAAQS maintenance plan for the Indiana portion of the Cincinnati, Ohio-Kentucky-Indiana area. The Cincinnati area includes Lawrenceburg Township in Dearborn County in Indiana; Butler, Clermont, Clinton, Hamilton, and Warren Counties in Ohio; and parts of Boone, Campbell, and Kenton Counties in Kentucky. The maintenance plan is designed to keep the Cincinnati area in attainment of the 2008 ozone NAAQS through 2037. <HD SOURCE="HD1">II. Background</HD> Ground-level ozone is formed when nitrogen oxides (NO <E T="52">X</E> ) and volatile organic compounds (VOC) react in the presence of sunlight. These two pollutants are referred to as ozone precursors. Scientific evidence indicates that adverse public health effects occur following exposure to ozone. On March 12, 2008, under section 109 of the CAA, EPA promulgated a revised primary and secondary 8-hour ozone NAAQS of 0.075 parts per million (ppm). <E T="03">See</E> 73 FR 16436 (March 27, 2008). Under EPA's regulations at 40 CFR part 50, the 2008 ozone NAAQS is attained in an area when the 3-year average of the annual fourth highest daily maximum 8-hour average concentration is equal to or less than 0.075 ppm, when truncated after the thousandth decimal place, at all of the ozone monitoring sites in the area. <E T="03">See</E> 40 CFR 50.15 and appendix P to 40 CFR part 50. Following promulgation of a new or revised NAAQS, EPA is required by the CAA to designate areas throughout the nation as attaining or not attaining the NAAQS. On May 21, 2012 (77 FR 30088), EPA designated areas for the 2008 ozone NAAQS, including the Cincinnati, Ohio-Kentucky-Indiana area as nonattainment. These designations became effective on July 20, 2012. Under the CAA, States are also required to adopt and submit SIPs to implement, maintain, and enforce the NAAQS in designated nonattainment areas and throughout the State. When a nonattainment area has three years of complete, certified air quality data that has been determined to attain the 2008 ozone NAAQS, and the area has met other required criteria described in section 107(d)(3)(E) of the CAA, the State can submit to EPA a request to be redesignated to attainment, referred to as a “maintenance area.”  <SU>1</SU> <FTREF/> One of the criteria for redesignation is to have an approved maintenance plan under section 175A of the CAA. The maintenance plan must demonstrate that the area will continue to maintain the standard for the period extending 10 years after redesignation, and it must contain such additional measures as necessary to ensure maintenance and such contingency provisions as necessary to ensure that violations of the standard will be promptly corrected. At the end of the eighth year after the effective date of the redesignation, the State must also submit a second maintenance plan to ensure ongoing maintenance of the standard for an additional 10 years. <E T="03">See</E> CAA section 175A. <FTNT> <SU>1</SU>  Section 107(d)(3)(E) of the CAA sets out the requirements for redesignation. They include attainment of the NAAQS, full approval of the SIP under section 110(k) of the CAA, determination that improvement in air quality is a result of permanent and enforceable reductions in emissions, demonstration that the State has met all applicable section 110 and part D requirements, and a fully approved maintenance plan under CAA section 175A. </FTNT> EPA has published long-standing guidance for States on developing maintenance plans. <SU>2</SU> <FTREF/> The Calcagni Memorandum provides that States may generally demonstrate maintenance by either performing air quality modeling to show that the future mix of sources and emission rates will not cause a violation of the NAAQS or by showing that future emissions of a pollutant and its precursors will not exceed the level of emissions during a year when the area was attaining the NAAQS ( <E T="03">i.e.,</E> attainment year inventory). <E T="03">See</E> Calcagni Memorandum at 9. <FTNT> <SU>2</SU>  “Procedures for Processing Requests to Redesignate Areas to Attainment,” Memorandum from John Calcagni, Director, Air Quality Management Division, September 4, 1992 (the “Calcagni Memorandum”). </FTNT> On February 23, 2016, IDEM submitted a request to EPA to redesignate the Indiana portion of the Cincinnati nonattainment area to attainment for the 2008 ozone NAAQS. This submittal included a plan to maintain the 2008 ozone NAAQS in the Cincinnati area through 2030 as a revision to the Indiana SIP. EPA approved the Cincinnati maintenance plan and the State's request to redesignate the Indiana portion of the area to attainment for the 2008 ozone NAAQS on April 7, 2017 (82 FR 16940). Under section 175A(b) of the CAA, States must submit a revision to the first maintenance plan eight years after redesignation to provide for maintenance of the NAAQS for 10 additional years following the end of the first 10-year period. IDEM submitted a second maintenance plan on April 1, 2025, and supplemented the submission on October 8, 2025. The second maintenance plan shows attainment of the 2008 ozone NAAQS for Cincinnati through 2037, <E T="03">i.e.,</E> through the end of the full 20-year maintenance period for the area. <HD SOURCE="HD1">III. EPA's Evaluation of Indiana's SIP Submittal</HD> <HD SOURCE="HD2">A. Second Maintenance Plan</HD> Section 175A of the CAA sets forth the elements of a maintenance plan for areas seeking redesignation from nonattainment to attainment. Under section 175A, the maintenance plan must demonstrate continued attainment of the NAAQS for at least 10 years after the Administrator approves a redesignation to attainment. Eight years after the redesignation, the State must submit a revised maintenance plan which demonstrates that attainment of the NAAQS will continue for an additional 10 years beyond the initial 10-year maintenance period. To address the possibility o ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 38k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━