Air Plan Approval; Kentucky; Emissions Inventory and Nonattainment New Source Review for the Henderson-Webster Sulfur Dioxide Nonattainment Area

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R04-OAR-2025-0023; FRL-12899-01-R4]</DEPDOC> <SUBJECT>Air Plan Approval; Kentucky; Emissions Inventory and Nonattainment New Source Review for the Henderson-Webster Sulfur Dioxide Nonattainment Area</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 two State Implementation Plan (SIP) revisions submitted by the Commonwealth of Kentucky, through the Energy and Environment Cabinet (Cabinet), Division of Air Quality (DAQ) on January 26, 2024, and February 15, 2024, to certify two requirements under the Clean Air Act (CAA or Act). These revisions establish that the Kentucky SIP satisfies the nonattainment new source review (NNSR) and base year emissions inventory requirements for the 2010 1-hour sulfur dioxide (SO <E T="52">2</E> ) national ambient air quality standard (NAAQS) for the Henderson-Webster SO <E T="52">2</E> nonattainment area (hereinafter “Henderson-Webster SO <E T="52">2</E> Nonattainment Area” or “Area”). These actions are being proposed pursuant to the CAA. </SUM> <DATES> <HD SOURCE="HED">DATES:</HD> Comments must be received on or before October 6, 2025. </DATES> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R04-OAR-2025-0023 at <E T="03">regulations.gov.</E> Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">Regulations.gov</E> . 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. 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, the full EPA public comment policy, information about CBI 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> Pearlene Williams-Miles, Multi-Air Pollutant Coordination Section, Air Planning and Implementation Branch, Air and Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia 30303-8960. The telephone number is (404) 562-9144. Ms. Williams-Miles can also be reached via electronic mail at <E T="03">williamsmiles.pearlene@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">I. Background</HD> SO <E T="52">2</E> is a gas that is formed by the burning of fossil fuels from power plants and other industrial facilities, such as extracting metal from ore; natural sources, such as volcanoes; and locomotives, ships, and other vehicles and heavy equipment that burn fuel with a high sulfur content. SO <E T="52">2</E> is the component of greatest concern amongst sulfur oxides (SOx) and is used as the indicator for the larger group of gaseous SOx. Control measures that reduce SO <E T="52">2</E> can generally be expected to reduce people's exposures to all gaseous SOx. On June 2, 2010, EPA revised the primary SO <E T="52">2</E> NAAQS. Specifically, EPA established a 1-hour SO <E T="52">2</E> standard at a level of 75 parts per billion (ppb), based on the 3-year average of the annual 99th percentile of 1-hour daily maximum concentrations. <FTREF/> <SU>1</SU> <E T="03">See</E> 75 FR 35520 (June 22, 2010). The 1-hour standard is met at an ambient air quality monitoring site 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. <E T="03">See</E> 75 FR 35520, codified at 40 CFR 50.17(a)-(b). <FTNT> <SU>1</SU>  This rule became effective on August 23, 2010, and revoked the 24-hour and annual primary SO <E T="52">2</E> standards. </FTNT> Upon promulgation of a new or revised SO <E T="52">2</E> NAAQS, section 107(d) of the CAA requires EPA to designate as nonattainment any area that is violating the NAAQS (or that contributes to ambient air quality in a nearby area that is violating the NAAQS). As part of the designation process for the 2010 1-hour SO <E T="52">2</E> NAAQS, the Henderson-Webster SO <E T="52">2</E> Nonattainment Area was designated as a nonattainment area in the fourth round of designations on December 21, 2020. <E T="51">2 3</E> <FTREF/> These area designations became effective on April 30, 2021. <E T="03">See</E> 86 FR 16055 (March 26, 2021). States with nonattainment areas for the SO <E T="52">2</E> NAAQS must provide nonattainment SIP revisions meeting the applicable requirements of CAA sections 110(a), 172, 191, and 192  <SU>4</SU> <FTREF/> for the SO <E T="52">2</E> NAAQS. EPA's regulations governing nonattainment SIPs are set forth at 40 CFR part 51, with specific procedural requirements and control strategy requirements residing at subparts F and G, respectively. <FTNT> <SU>2</SU>   <E T="03">See</E> Round 4 SO <E T="52">2</E> Designations at <E T="03">https://www.epa.gov/sulfur-dioxide-designations/epa-completes-fourth-round-sulfur-dioxide-designations.</E> <SU>3</SU>  The Henderson-Webster SO <E T="52">2</E> Nonattainment Area is comprised of a portion of Henderson County and a portion of Webster County. EPA designated the Henderson-Webster SO <E T="52">2</E> Nonattainment Area in 2020 based on a violating ambient air monitor—the Sebree data requirements rule (DRR) monitor (Air Quality System ID: 21-101-1011)—sited to characterize the maximum 1-hour SO <E T="52">2</E> concentrations in the area. (The DRR may be found at 40 CFR 51.1205). The extent of the partial county Henderson-Webster SO <E T="52">2</E> Nonattainment Area was defined based on air dispersion modeling during round 4 SO <E T="52">2</E> designations in 2020. <E T="03">See</E> 40 CFR 81.318. </FTNT> <FTNT> <SU>4</SU>  Section 191(a) of the CAA directs states to submit SIPs for areas designated as nonattainment for the SO <E T="52">2</E> NAAQS to EPA within 18 months of the effective date of the designation. Under CAA section 192(a) these SIPs are required to demonstrate that their respective areas will attain the NAAQS as expeditiously as practicable, but no later than 5 years from the effective date of designation. In addition, sections 110(a) and 172(c), as well as EPA regulations at 40 CFR part 51, set forth substantive elements each SIP must contain to be approved by EPA. </FTNT> Section 172(c) directs states with nonattainment areas to submit a SIP that contains an attainment demonstration showing that the affected area will attain the relevant standard as expeditiously as practicable, but no later than the applicable statutory attainment date (April 30, 2026, for the Henderson-Webster SO <E T="52">2</E> Nonattainment Area). <SU>5</SU> <FTREF/> On April 23, 2014, EPA issued guidance for meeting the statutory requirements in SO <E T="52">2</E> SIPs under the 2010 revised NAAQS in a document entitled “Guidance for 1-Hour SO <E T="52">2</E> Nonattainment Area SIP Submissions”  <SU>6</SU> <FTREF/> (hereinafter referred to as “2014 SO <E T="52">2</E> Nonattainment Guidance”) which describes the statutory requirements for nonattainment at CAA section 172(c), including an accurate inventory of actual emissions from all sources in nonattainment areas; an attainment demonstration; a demonstration of reasonable further progress; implementation of Reasonably Available Control Measures (RACM) (including Reasonably Available Control Technologies (RACT)); NNSR; enforceable emissions limitations and control measures; and adequate contingency measures for the affected area. For EPA to fully approve a SIP revision as meeting the requirements of CAA sections 110, 172, and 191-192 and EPA's regulations at 40 CFR part 51, the SIP for the affected area must demonstrate to EPA's satisfaction that each of the requirements have been met. State air agencies with nonattainment areas for the 2010 1-hour primary SO <E T="52">2</E> NAAQS are required to submit a SIP revision that addresses these requirements within 18 months after an area is designated nonattainment (no later than October 30, 2022, for the Henderson-Webster SO <E T="52">2</E> Nonattainment Area). <SU>7</SU> <FTREF/> Kentucky's January 26, 2024, and February 15, 2024, SIP revisions address the air agency's NNSR permitting and emissions inventory obligations pursuant to section 172(c)(5) and 172(c)(3) of the Act, respectively. <FTNT> <SU>5</SU>  Soon after the 1990 amendments to the CAA were enacted by Congress, EPA issued comprehensive guidance on SIPs in a document entitled the “General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990,” published in the <E T="04">Federal Register</E> at 57 FR 13498 (April 16, 1992) (General Preamble). Among other things, the General Preamble addressed SO <E T="52">2</E> SIPs and fundamental principles for SIP control strategies. <E T="03">Id.</E> at 13545-49, 13567-68. </FTNT> <FTNT> <SU>6</SU>   <E T="03">See https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf</E> . </FTNT> <FTNT> <SU>7</SU>   <E T="03">See</E> CAA section 191(a). ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 40k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━