Air Plan Approval; California; State Implementation Plan Revision for Chico, Modesto, and Stockton Carbon Monoxide Maintenance Areas

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R09-OAR-2024-0473; FRL-12323-01-R9]</DEPDOC> <SUBJECT>Air Plan Approval; California; State Implementation Plan Revision for Chico, Modesto, and Stockton Carbon Monoxide Maintenance Areas</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 California state implementation plan (SIP) that removes carbon monoxide (CO) contingency measures and monitoring requirements from the maintenance plan for three CO maintenance areas: Chico Urbanized Area, Modesto Urbanized Area, and Stockton Urbanized Area. We are proposing to approve the revision under the Clean Air Act (CAA or “Act”). We are taking comments on this proposal and plan to follow with a final action. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Comments must be received on or before April 30, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R09-OAR-2024-0473 at <E T="03">https://www.regulations.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 <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, 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 or multimedia submissions, and general guidance on making effective comments, please visit <E T="03">https://www.epa.gov/dockets/commenting-epa-dockets.</E> If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Julia Leo, EPA Region IX, 75 Hawthorne St., San Francisco, CA 94105; phone: (213) 244-1862; email: <E T="03">leo.julia@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. Background</FP> <FP SOURCE="FP-2">II. Requirements of CAA Section 110(l)</FP> <FP SOURCE="FP-2">III. The State's Submittal and Evaluation for Compliance With SIP Revision Procedural Requirements</FP> <FP SOURCE="FP1-2">A. The State's Submittal</FP> <FP SOURCE="FP1-2">B. Evaluation for Compliance With SIP Revision Procedural Requirements</FP> <FP SOURCE="FP-2">IV. The EPA's Evaluation and Action</FP> <FP SOURCE="FP1-2">A. How is the EPA evaluating the SIP revision?</FP> <FP SOURCE="FP1-2">B. Does the SIP revision meet the evaluation criteria?</FP> <FP SOURCE="FP1-2">C. Proposed Action and Public Comment</FP> <FP SOURCE="FP-2">V. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Background</HD> The CAA requires the EPA to set national ambient air quality standards (NAAQS or “standards”) for carbon monoxide (CO) as one of six “criteria” air pollutants. In 1971, the EPA established primary and secondary NAAQS for CO at 9 parts per million (ppm), averaged over an 8-hour period, and at 35 ppm, averaged over a 1-hour period. <SU>1</SU> <FTREF/> <FTNT> <SU>1</SU>  36 FR 8186 (April 30, 1971). </FTNT> In 1991, the EPA designated 11 areas in California as nonattainment for the 9 ppm CO standard: Bakersfield Metropolitan Area, Chico Urbanized Area, Fresno Urbanized Area, Lake Tahoe North Shore Area, Lake Tahoe South Shore Area, Los Angeles-South Coast Air Basin Area, Modesto Urbanized Area, Sacramento Area, San Diego Area, San Francisco-Oakland-San Jose Area, and Stockton Urbanized Area. <SU>2</SU> <FTREF/> <FTNT> <SU>2</SU>  56 FR 56694, 56723-56726 (November 6, 1991). </FTNT> In 1996, the California Air Resources Board (CARB) submitted a redesignation request and maintenance plan (“1996 CO Maintenance Plan”)  <SU>3</SU> <FTREF/> demonstrating continued maintenance of the CO NAAQS in ten of these areas, <SU>4</SU> <FTREF/> including the Chico Urbanized Area, the Modesto Urbanized Area, and the Stockton Urbanized Area, through 2010. The EPA approved the 1996 CO Maintenance Plan as a revision to the California SIP and redesignated the ten areas to attainment effective June 1, 1998. <SU>5</SU> <FTREF/> In 2004, CARB submitted the “2004 Revision to the California State Implementation Plan for Carbon Monoxide, Updated Maintenance Plan for Ten Federal Planning Areas” (“2004 CO Second Maintenance Plan”)  <SU>6</SU> <FTREF/> that provided a ten-year update to the 1996 CO Maintenance Plan and demonstrated that the areas would maintain the CO NAAQS through 2018. On November 30, 2005, the EPA approved the 2004 CO Second Maintenance Plan as a revision to the California SIP. <SU>7</SU> <FTREF/> The Chico Urbanized Area, Modesto Urbanized Area, and Stockton Urbanized Area have completed their 20-year maintenance periods (from 1998 to 2018) as required under CAA section 175A. <FTNT> <SU>3</SU>  CARB, “Final Carbon Monoxide Redesignation Request and Maintenance Plan for Ten Federal Planning Areas (“1996 CO Maintenance Plan”) (April 26, 1996). </FTNT> <FTNT> <SU>4</SU>  The 2004 CO Second Maintenance Plan did not include Los Angeles. The EPA redesignated Los Angeles-South Coast Air Basin to attainment for CO in 2007. 72 FR 26718 (May 11, 2007). </FTNT> <FTNT> <SU>5</SU>  63 FR 15305 (March 31, 1998). </FTNT> <FTNT> <SU>6</SU>  CARB, “2004 Revision to the California State Implementation Plan for Carbon Monoxide,” adopted July 22, 2004. </FTNT> <FTNT> <SU>7</SU>  70 FR 71776 (November 30, 2005). </FTNT> <HD SOURCE="HD1">II. Requirements of CAA Section 110(l)</HD> CAA section 110(l) provides that “[t]he Administrator shall not approve a revision of a plan if the revision would interfere with any applicable requirement concerning attainment and reasonable further progress (as defined in [CAA section 171]) or any other applicable requirement of [the CAA].”  <SU>8</SU> <FTREF/> CAA section 110(l) applies to the approval of all revisions to SIPs under the CAA and to all areas, whether attainment, nonattainment, unclassifiable, or maintenance for one or more of the NAAQS. Before the EPA can conclude that the SIP revision is allowed under CAA section 110(l), the EPA must first conclude that the plan revision meets CAA requirements. <FTNT> <SU>8</SU>  42 U.S.C. 7410(l). </FTNT> The EPA interprets CAA section 110(l) as applying to all NAAQS that are in effect, including those for which SIP submissions have not been made; therefore, the EPA considers the impact of the SIP revision on emissions and/or ambient concentrations of any pollutant. Additionally, in certain circumstances, a state may demonstrate non-interference with CAA applicable requirements by substituting equivalent emissions reductions to compensate for any change to a SIP to ensure actual emissions to the air are not increased and thus preserve status quo air quality. <SU>9</SU> <FTREF/> <FTNT> <SU>9</SU>   <E T="03">See also Hall</E> v. <E T="03">EPA,</E> 273 F.3d 1146, nn. 11-12 (9th Cir. 2001) (reasoning that, if there is no relaxation of air quality regulations, a revision to a SIP would not interfere with reasonable further progress or attainment in areas attaining the NAAQS). </FTNT> <HD SOURCE="HD1">III. The State's Submittal and Evaluation for Compliance With SIP Revision Procedural Requirements</HD> <HD SOURCE="HD2">A. The State's Submittal</HD> On April 4, 2024, CARB submitted a SIP revision titled “2023 Revision to the California State Implementation Plan for Carbon Monoxide,”  <SU>10</SU> <FTREF/> and on January 15, 2025, CARB submitted a clarification by email  <SU>11</SU> <FTREF/> (collectively, the “2023 CO SIP Revision” or “submittal”). The submittal proposes to remove CO contingency measures and monitoring requirements for the Chico, Modesto, and Stockton maintenance areas from the 2004 CO Second Maintenance Plan. CARB proposes updating the 2004 CO Second Maintenance Plan to remove the contingency measures section on page 11 and monitoring requirements for the three areas outlined in section II.A.2 on page 6. <SU>12</SU> <FTREF/> To discontinue CO monitoring, CARB must demonstrate that a contingency plan is no longer needed and remove associated contingency measures (that would be triggered by a monitored CO violation) and monitoring requirements from the SIP. CARB submitted the 2023 CO SIP Revision to demonstrate that CO monitoring is no longer needed for a contingency plan in these areas. The proposed revision follows a CO monitor discontinuation request for these locations submitted by CARB in September 2022. <SU>13</SU> <FTREF/> <FTNT> <SU>10</SU>  CARB, “2023 Revision to the California State Implementation Plan for Carbon Monoxide,” February 9, 2024. </FTNT> <FTNT> <SU>11</SU>  Email dated January 15, 2025, from Ayla Moretti, CARB, to Jin Xu ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 23k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━