Air Plan Approval; IA, Muscatine; 2010 1-Hour SO2 Maintenance Plan and Redesignation

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Parts 52 and 81</CFR> <DEPDOC>[EPA-R07-OAR-2025-0818; FRL-12901-01-R7]</DEPDOC> <SUBJECT> Air Plan Approval; IA, Muscatine; 2010 1-Hour SO <E T="0735">2</E> Maintenance Plan and Redesignation </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 redesignate the nonattainment area in Muscatine County, Iowa to attainment for the 2010 1-hour sulfur dioxide (SO <E T="52">2</E> ) National Ambient Air Quality Standard (NAAQS). The EPA is also proposing to approve Iowa's maintenance plan for the 2010 1-hour SO <E T="52">2</E> NAAQS for the Muscatine nonattainment area and approve modifications to source-specific permits in the Iowa State Implementation Plan (SIP). The EPA's proposed approval of this rule revision is being done in accordance with the requirements of the Clean Air Act (CAA). </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Comments must be received on or before September 22, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, identified by Docket ID No. EPA-R07-OAR-2025-0818 to <E T="03">https://www.regulations.gov</E> . Follow the online instructions for submitting comments. <E T="03">Instructions:</E> All submissions received must include the Docket ID No. for this rulemaking. Comments received will be posted without change to <E T="03">https://www.regulations.gov,</E> 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 <E T="02">SUPPLEMENTARY INFORMATION</E> section of this document. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Bethany Olson, Environmental Protection Agency, Region 7 Office, Air Quality Planning Branch, 11201 Renner Boulevard, Lenexa, Kansas 66219; telephone number: (913) 551-7905; email address: <E T="03">olson.bethany@epa.gov</E> . </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document “we,” “us,” and “our” refer to the EPA. <HD SOURCE="HD1">Table of Contents</HD> <EXTRACT> <FP SOURCE="FP-2">I. Written Comments</FP> <FP SOURCE="FP-2">II. What is being addressed in this document?</FP> <FP SOURCE="FP-2">III. Have the requirements for approval of a SIP revision been met?</FP> <FP SOURCE="FP-2">IV. What is the background for the EPA's proposed actions?</FP> <FP SOURCE="FP-2">V. What is the EPA's analysis of the redesignation request and maintenance plan?</FP> <FP SOURCE="FP-2">VI. What is the EPA's analysis of the SIP-approved permit modifications?</FP> <FP SOURCE="FP-2">VII. What action is the EPA proposing to take?</FP> <FP SOURCE="FP-2">VIII. Incorporation by Reference</FP> <FP SOURCE="FP-2">IX. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Written Comments</HD> Submit your comments, identified by Docket ID No. EPA-R07-OAR-2025-0818, at <E T="03">https://www.regulations.gov</E> . Once submitted, comments cannot be edited or removed from <E T="03">Regulations.gov</E> . 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 ( <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> . <HD SOURCE="HD1">II. What is being addressed in this document?</HD> The EPA is proposing to approve a SIP revision and redesignation request submitted on November 17, 2021, by the Iowa Department of Natural Resources (IDNR). The EPA is proposing to take the following three separate but related actions: (1) to add new or revised permits for Muscatine area sources into the Iowa SIP and remove certain air construction permits from the SIP; (2) to approve Iowa's maintenance plan for the 2010 1-hour SO <E T="52">2</E> NAAQS in the Muscatine area and incorporate it into the SIP; and (3) to redesignate the Muscatine area to attainment for the 2010 1-hour SO <E T="52">2</E> NAAQS. The EPA proposes to find that the State's submittal meets the requirements for redesignation under the CAA and the revisions do not interfere with any applicable requirement concerning attainment and reasonable further progress. The full State submission is included in the docket for this action. <HD SOURCE="HD1">III. Have the requirements for approval of a SIP revision been met?</HD> The State submission has met the public notice requirements for SIP submissions in accordance with 40 CFR 51.102. The submission also satisfied the completeness criteria of 40 CFR part 51, appendix V. The State provided public notice on this SIP submission from August 20, 2021, to September 20, 2021, and held a public hearing on September 20, 2021. IDNR received and responded to written comments from two sources, and included the comments and responses in its submission. In addition, as explained above and in more detail in the technical support document (TSD) which is part of this document, the revision meets the substantive SIP requirements of the CAA, including section 110 and implementing regulations. <HD SOURCE="HD1">IV. What is the background for the EPA's proposed actions?</HD> <HD SOURCE="HD2">A. Nonattainment Designation</HD> On June 2, 2010 (75 FR 35520), the EPA signed the revised the primary SO <E T="52">2</E> NAAQS, establishing a new 1-hour standard of 75 parts per billion (ppb). Under the EPA's regulations at 40 CFR part 50, the 2010 1-hour SO <E T="52">2</E> NAAQS is met at a monitoring site when the 3-year average of the annual 99th percentile of daily maximum 1-hour average concentrations is less than or equal to 75 ppb (based on the rounding convention in 40 CFR part 50, appendix T). <SU>1</SU> <FTREF/> Ambient air quality monitoring data for the 3-year period must meet a data completeness requirement. A year meets data completeness requirements when all four quarters are complete, and a quarter is complete when at least 75 percent of the sampling days for each quarter have complete data. A sampling day has complete data if 75 percent of the hourly concentration values, including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator, are reported. <SU>2</SU> <FTREF/> <FTNT> <SU>1</SU>   <E T="03">See</E> 40 CFR 50.17. </FTNT> <FTNT> <SU>2</SU>  40 CFR part 50, appendix T, section 3(b). </FTNT> Following promulgation of a new or revised NAAQS, the EPA is required by CAA section 107(d) to designate areas throughout the nation as attaining or not attaining the NAAQS, or as unclassifiable. On August 5, 2013, the EPA designated a portion of Muscatine County, Iowa, as nonattainment for the 2010 primary 1-hour SO <E T="52">2</E> NAAQS (78 FR 47191), effective October 4, 2013. The designation was based on air quality monitoring data from 2009-2011 showing violations of the NAAQS. Pursuant to CAA sections 172(a)(2) and 192(a), this action established an attainment date five years after the effective date of the final action designating the area as nonattainment for the 2010 SO <E T="52">2</E> NAAQS ( <E T="03">i.e.,</E> by October 4, 2018). <HD SOURCE="HD2">B. Relevant Historical SIP Actions</HD> The EPA's 2013 SO <E T="52">2</E> nonattainment designation triggered an obligation for Iowa to submit a SIP for the Muscatine SO <E T="52">2</E> nonattainment area (NAA) addressing the requirements of CAA sections 110, 172(c) and 191-192 within 18 months following the October 4, 2013, effective date of designation ( <E T="03">i.e.,</E> by April 4, 2015). The EPA did not receive an attainment SIP revision for the Muscatine NAA by the April 6, 2015 deadline and subsequently on March 18, 2016, the EPA published a finding of failure to submit indicating that Iowa did not submit the required SO <E T="52">2</E> attainment plan (81 FR 14736). Iowa submitted the required attainment plan submittal on May 26, 2016. The EPA proposed approval of Iowa's attainment plan on August 24, 2017 (82 FR 40086). The EPA published a supplemental notice of proposed rulemaking (SNPRM) on January 9, 2018, and included additional information in the docket in response to public comments suggesting that insufficient information was provided in the docket to allow the reviewer to fully evaluate the attainment plan and the EPA's proposed approval (83 FR 997). The EPA published a second SNPRM on June 22, 2020, to provide additional detail regarding the technical support and policy rationale for approving the attainment demonstration and control strategy, as well as the underlying state permits as the enforceable mechanism of the control strategy (85 FR 37405). The EPA issued a final approval of Iowa's attainment plan on November 17, 2020 (85 FR 73218). Iowa's approved 2016 attainment plan provided a modeled attainment demonstration and satisfied the required nonattainment planning requirements mentioned above for the Muscatine NAA. In accordance with CAA title I, part D, subpart 1, the revision included a 2011 base-year and projection-year emissions inventories ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 104k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━