Air Plan Approval; Indiana; Huntington County 2010 Sulfur Dioxide Redesignation and Maintenance Plan

<RULE> ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Parts 52 and 81</CFR> <DEPDOC>[EPA-R05-OAR-2024-0378; FRL-12933-02-R5]</DEPDOC> <SUBJECT>Air Plan Approval; Indiana; Huntington County 2010 Sulfur Dioxide Redesignation and Maintenance Plan</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) finds that Huntington Township in Huntington County, Indiana (hereafter referred to as “Huntington area”) is attaining the 2010 sulfur dioxide (SO <E T="52">2</E> ) National Ambient Air Quality Standard (NAAQS). EPA is approving Indiana's request to redesignate the Huntington area from nonattainment to attainment for the 2010 SO <E T="52">2</E> NAAQS because the request meets the statutory requirements for redesignation under the Clean Air Act (CAA). EPA is also approving Indiana's maintenance plan for the area as part of Indiana's federally enforceable State Implementation plan (SIP). </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This final rule is effective on January 9, 2026. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> EPA has established a docket for this action under Docket ID No. EPA-R05-OAR-2024-0378. All documents in the docket are listed on the <E T="03">https://www.regulations.gov</E> website. Although listed in the index, some information is not publicly available, <E T="03">i.e.,</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 <E T="03">https://www.regulations.gov</E> or at the Environmental Protection Agency, Region 5, Air and Radiation Division, 77 West Jackson Boulevard, Chicago, Illinois 60604. This facility is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding Federal holidays. We recommend that you telephone Cecilia Magos, at (312) 886-7336 before visiting the Region 5 office. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Cecilia Magos, Air and Radiation Division (AR-18J), Environmental Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago, Illinois 60604, (312) 886-7336, <E T="03">magos.cecilia@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA. <HD SOURCE="HD1">I. Background</HD> On January 9, 2018 (83 FR 1098), EPA designated Huntington Township, a partial area of Huntington County, Indiana, as nonattainment for the 2010 SO <E T="52">2</E> NAAQS. Section 191 of the CAA, 42 U.S.C. 7514, directs States to submit a SIP for an area designated as nonattainment demonstrating that the area will achieve the NAAQS as expeditiously as practicable, but no later than five years from the effective date of designation. EPA approved Indiana's plan for attaining the 2010 SO <E T="52">2</E> NAAQS for the Huntington area on August 14, 2025 (90 FR 39130), and found that Indiana satisfied other applicable requirements for nonattainment areas. EPA published its proposed approval on September 25, 2025 (90 FR 46124), for the Huntington area. The public comment period for this proposal closed on October 27, 2025. <HD SOURCE="HD1">II. Response to Public Comments</HD> EPA received two supportive comments and three adverse comments. Summaries of the adverse comments and EPA's responses are provided below. All comments submitted during the public comment period are available in the docket of this action. <E T="03">Comment:</E> The commenter requests EPA withdraw the direct final rule approving the Huntington County area redesignation and maintenance plan. Additionally, they request EPA re-propose the action as a “standard notice-and-comment process” and provide a 60-day comment period pursuant to the Administrative Procedure Act (APA) and the CAA with all the key technical materials in the docket the commenter suggests are missing. <E T="03">Response:</E> EPA notes the commenter mischaracterizes the action published. EPA did not publish a direct final rule approving the redesignation to attainment for the 2010 SO <E T="52">2</E> NAAQS and maintenance plan of the Huntington County area. EPA published a proposed approval of the redesignation and maintenance plan on September 25, 2025 (90 FR 46124), and opened a public comment period for 30-days as required by the APA and CAA. Additionally, EPA has made all appropriate documentation available in the docket of this action. Therefore, EPA will not repropose the approval of the 2010 SO <E T="52">2</E> NAAQS redesignation and maintenance plan for the Huntington area. <E T="03">Comment:</E> Commenter states that under the APA, EPA did not include the appropriate or sufficient technical materials necessary for meaningful comment. To summarize, the commenter requests additional modeling and technical support materials related to AERMOD, AERMET, BPIPPRM, receptor network, background concentration, stack parameters, source shutdown or curtailment documentation for the demonstration of attainment and emissions growth projections for the maintenance period, verification of the maintenance plan's monitoring/verification commitments, and quality assurance and quality control documentation be made available for meaningful evaluation of the attainment demonstration and maintenance plan for Huntington County. <E T="03">Response:</E> As noted in the proposed rulemaking, EPA's April 23, 2024, “Guidance for 1-Hour SO <E T="52">2</E> Nonattainment Area SIP Submissions” (“April 2014 SO <E T="52">2</E> Guidance”)  <SU>1</SU> <FTREF/> states EPA may make determinations of attainment based on the modeling, using allowable emissions, from the attainment demonstrations for the applicable SIP for the affected area. The April 2014 SO <E T="52">2</E> Guidance also notes that a separate actuals-based modeling to support a redesignation request is not necessary if an attainment determination was made based on allowables-based modeling and a demonstration of a fully implemented control strategy has been provided. <SU>2</SU> <FTREF/> EPA's redesignation proposal relies on enforceable limits, previously approved as part of the area's attainment plan action and a report included in the redesignation request containing results from stack testing demonstrating compliance with enforceable SO <E T="52">2</E> emission limits. These stack test results were included in the docket of this action. Modeling requirements and Indiana's modeling analysis, as requested by the commenter, may be found in EPA's proposed attainment plan approval (see 90 FR 25968, June 18, 2025) and therefore, EPA does not find the comment to warrant any changes to this action. <FTNT> <SU>1</SU>  EPA's <E T="03">Guidance for 1-Hour Sulfur Dioxide (SO</E> <E T="54">2</E> <E T="03">) Nonattainment Area State Implementation Plans (SIP) Submissions</E> can be found at <E T="03">https://www.epa.gov/so2-pollution/guidance-1-hour-sulfur-dioxide-so2-nonattainment-area-state-implementation-plans-sip.</E> </FTNT> <FTNT> <SU>2</SU>  April 2014 Guidance, pg. 63. </FTNT> Regarding the comments related to the maintenance plan, such as emission growth projections, verification of monitoring, and the availability of quality assurance and quality control documentation of the attainment demonstration and maintenance plan for Huntington County area, EPA finds that Indiana has appropriately fulfilled its maintenance plan obligations as required under CAA section 175A, 42 U.S.C. 7505A. To further clarify, the docket of this action contains Indiana's redesignation request, which outlines Indiana's requirements for verification of continued attainment and the requirements for maintenance demonstration under section 175A. EPA determines that Indiana adequately fulfilled these requirements through commitments to annual emissions submittals that verify continued attainment of the 2010 SO <E T="52">2</E> NAAQS and review of the projected emissions inventory for the Huntington area. As noted above, EPA adequately fulfilled its requirements under the APA, included all appropriate documentation, and provided adequate time for public comment. <E T="03">Comment:</E> Regarding the maintenance plan, two commenters note that it does not: “specify objective, near-term triggers tied to monitored and/or modeled indicators”; identify or define concrete contingency measures to take effect upon triggers; contain corrective actions and deadlines including specific numeric concentrations or emissions thresholds that would initiate enforcement; nor does it commit to verification of continued ambient air quality monitoring to detect local SO <E T="52">2</E> hotspots, or contain a schedule for periodic inventories or public reporting. <E T="03">Response:</E> EPA does not agree with the submitted comments. Unlike CAA section 172(c)(9), 42 U.S.C. 7502(c)(9), section 175A of the CAA does not explicitly require that contingency measures must take effect without further action by the air agency in order for the maintenance plan to be approved. However, the maintenance plan's contingency plan would become an enforceable part of the SIP and should ensure that contingency measures are adopted and implemented as expeditiously as practicable once they are triggered. <SU>3</SU> <FTREF/> In the “General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990,” published on April 16, 1992 (57 FR 13498), EPA provides further discussion of contingency measures for SO <E T="52">2</E> . This guidance states that in man ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 28k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━