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

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Parts 52 and 81</CFR> <DEPDOC>[EPA-R05-OAR-2024-0378; FRL-12933-01-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> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is proposing to find that Huntington Township, Indiana (referred to in this proposed rule as the Huntington County, Indiana area) is attaining the 2010 sulfur dioxide (SO <E T="52">2</E> ) National Ambient Air Quality Standard (NAAQS) and to propose approval of Indiana's request to redesignate the area 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 proposing to approve Indiana's maintenance plan for the area, which, once approved, will become part of Indiana's federally enforceable State Implementation Plan (SIP). </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Comments must be received on or before October 27, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R05-OAR-2024-0378 at <E T="03">https://www.regulations.gov,</E> or via email to <E T="03">arra.sarah@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> Abigail Teener, Air and Radiation Division (AR-18J), Environmental Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago, Illinois 60604, (312) 353-7314, <E T="03">teener.abigail@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> <HD SOURCE="HD1">I. Background and Redesignation Requirements</HD> On June 22, 2010 (75 FR 35520), EPA published a new SO <E T="52">2</E> NAAQS of 75 parts per billion (ppb), which is met at an ambient air quality monitoring site (or in the case of dispersion modeling, at an ambient air quality receptor location) when the 3-year average of the annual 99th percentile of daily maximum 1-hour average concentrations does not exceed 75 ppb, as determined in accordance with appendix T of 40 CFR part 50. 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 with an effective date of April 9, 2018, based on air quality modeling information which showed that Isolatek International (Isolatek), formerly known as U.S. Mineral Wool, may have been contributing to violations of the 2010 SO <E T="52">2</E> NAAQS. Section 191 of the CAA directs States to submit a SIP for an area designated as nonattainment for the 2010 SO <E T="52">2</E> NAAQS to EPA within 18 months of the effective date of the designation. The SIP must demonstrate that the State will achieve the NAAQS for the nonattainment area as expeditiously as practicable, but no later than five years from the effective date of designation. On November 6, 2023, Indiana submitted Commissioner's Order 2023-Air-01, containing SO <E T="52">2</E> emission limits for Isolatek, along with a revision to the Indiana SIP that provides for attainment of the 2010 SO <E T="52">2</E> NAAQS in the Huntington County area. The revision included an Attainment Demonstration, Reasonably Available Control Measures/Reasonably Available Control Technology (RACM/RACT) requirements, Reasonable Further Progress (RFP) provisions, Contingency Measures, Emissions Inventories for the 2017 Base Year and 2023 Attainment Year, and NSR Certification. On February 12, 2024, Indiana submitted a supplemental SIP revision including Commissioner's Order 2023-Air-02, effective March 1, 2024, which revised Commissioner's Order 2023-Air-01 and established compliance requirements for the SO <E T="52">2</E> emission limits. Commissioner's Order 2023-Air-02 is included as attachment C of Indiana's July 30, 2024, redesignation request. On August 14, 2025 (90 FR 39130), EPA approved Indiana's plan for attaining the 2010 SO <E T="52">2</E> NAAQS for the Huntington County area and for meeting other nonattainment area planning requirements of CAA sections 110, 172, 179 and 192. EPA approved Indiana's demonstration that these requirements provide for attainment of the 2010 SO <E T="52">2</E> NAAQS in Huntington County and that Indiana had satisfied the other applicable requirements for nonattainment areas. <HD SOURCE="HD1">II. Evaluation of Indiana's Redesignation Request and Maintenance Plan</HD> On July 30, 2024, Indiana submitted a redesignation request and maintenance plan for the Huntington County nonattainment area for the 2010 SO <E T="52">2</E> NAAQS, and on September 17, 2024, submitted supplemental information. Under section 107(d)(3)(E) of the CAA, EPA may promulgate a redesignation of a nonattainment area provided that: 1. EPA has determined that the area has attained the NAAQS; 2. EPA has fully approved the applicable implementation plan for the area under section 110(k) of the CAA; 3. EPA has determined that improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable implementation plan and applicable Federal air pollution control regulations and other permanent and enforceable reductions; 4. EPA has fully approved a maintenance plan for the area under section 175A of the CAA; and 5. The State containing such area has met all requirements applicable to the area under section 110 of the CAA and part D. EPA's evaluation of Indiana's redesignation request and maintenance plan was based on consideration of the five redesignation criteria provided under CAA section 107(d)(3)(E) and is described in the remainder of this section. <HD SOURCE="HD2"> A. Criterion (1)—The Huntington County SO <E T="54">2</E> Nonattainment Area Has Attained the 2010 SO <E T="54">2</E> NAAQS </HD> CAA section 107(d)(3)(E)(i) requires EPA to determine that an area has attained the applicable NAAQS in order for EPA to redesignate the area from nonattainment to attainment. If dispersion modeling is used to make this determination, an area is attaining the 2010 SO <E T="52">2</E> NAAQS when the modeled concentration is at or below the one-hour SO <E T="52">2</E> NAAQS of 196.4 micrograms per cubic meter (or 75 ppb). As detailed in EPA's April 23, 2014, <E T="03">Guidance for 1-Hour SO</E> <E T="54">2</E> <E T="03"> Nonattainment Area SIP Submissions</E> (“April 2014 SO <E T="52">2</E> Guidance”), there are generally two methods available to support an attainment determination. The first component relies on air quality monitoring data. For SO <E T="52">2,</E> any available monitoring data would need to indicate that all monitors in the affected area are meeting the standard in 40 CFR 50.17. The second component relies on air quality modeling data. If there are no air quality monitors in the area, a further analysis using air quality dispersion modeling will generally be needed to estimate SO <E T="52">2</E> concentrations throughout the nonattainment area to demonstrate that the entire area is attaining the applicable NAAQS, based on current actual emissions or the fully implemented control strategy. <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> The April 2014 SO <E T="52">2</E> Guidance states that 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. Attainment demonstrations for the 2010 SO <E T="52">2</E> NAAQS should demonstrate future attainment and maintenance of the NAAQS in the entire area designated as nonattainment ( <E T="03">i.e.,</E> not just at the violating monitor) by using air quality dispersion modeling ( <E T="03">see</E> appendix W to 40 CFR part 51) to show that the mix of sources and enforceable control measures and emission rates in an identified area will not lead to a violation of the 2010 SO <E T="52">2</E> NAAQS. For a short-term ( <E T="03">i.e.,</E> 1-hour) standard, EPA believes that dispersion modeling, using allowable emissions and addressi ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 37k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━