Air Plan Approval; Guam; Base Year Emissions Inventory for the 2010 1-Hour Sulfur Dioxide National Ambient Air Quality Standard for the Piti-Cabras Nonattainment Area

<RULE> ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R09-OAR-2025-0268; FRL-12868-02-R9]</DEPDOC> <SUBJECT>Air Plan Approval; Guam; Base Year Emissions Inventory for the 2010 1-Hour Sulfur Dioxide National Ambient Air Quality Standard for the Piti-Cabras Nonattainment Area</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Direct final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is taking direct final action to approve a revision to Guam's State Implementation Plan (SIP) under section 110(k)(3) of the Clean Air Act (CAA or “the Act”). This revision concerns the base year emissions inventory for the Piti-Cabras, Guam sulfur dioxide (SO <E T="52">2</E> ) nonattainment area (“Piti-Cabras area” or NAA) for the 2010 1-hour SO <E T="52">2</E> National Ambient Air Quality Standard (NAAQS, “standard,” or “2010 SO <E T="52">2</E> NAAQS”). </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This rule is effective October 14, 2025 without further notice, unless the EPA receives adverse comments by August 15, 2025. If we receive such comments, we will publish a timely withdrawal in the <E T="04">Federal Register</E> to notify the public that this direct final rule will not take effect. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R09-OAR-2025-0268 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> Khoi Nguyen, Geographic Strategies and Modeling Section, Planning & Analysis Branch, Air & Radiation Division, EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; telephone number: 415-947-4120; email address: <E T="03">Nguyen.Khoi@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. Guam EPA's Base Year Emissions Inventory for the Piti-Cabras Nonattainment Area</FP> <FP SOURCE="FP-2">III. The EPA's Evaluation</FP> <FP SOURCE="FP-2">IV. Public Comment and Final Action</FP> <FP SOURCE="FP-2">V. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. Background</HD> On June 22, 2010, the EPA published in the <E T="04">Federal Register</E> a strengthened, primary 1-hour SO <E T="52">2</E> NAAQS, establishing a new standard at a level of 75 parts per billion (ppb), based on the 3-year average of the annual 99th percentile of daily maximum 1-hour average concentrations of SO <E T="52">2</E> . <SU>1</SU> <FTREF/> Following promulgation of a new or revised NAAQS, the EPA is required to designate all areas of the country as either “attainment,” “nonattainment,” or “unclassifiable.”  <SU>2</SU> <FTREF/> On December 21, 2017, the EPA signed a notice designating six areas in three States and two territories as nonattainment in the third round of SO <E T="52">2</E> designations, effective April 9, 2018. <SU>3</SU> <FTREF/> With that action, the EPA designated as nonattainment the portion of Guam within a 6.074-km radius centered on UTM Easting 249,601.60 m, and UTM Northing 1,489,602.00 m (UTM Zone 55N). <SU>4</SU> <FTREF/> <FTNT> <SU>1</SU>  On June 2, 2010, the EPA signed the final rule titled, “Primary National Ambient Air Quality Standard for Sulfur Dioxide,” 75 FR 35520 (June 22, 2010), codified at 40 CFR part 50. </FTNT> <FTNT> <SU>2</SU>  CAA section 107(d)(1). </FTNT> <FTNT> <SU>3</SU>  83 FR 1098 (January 9, 2018). </FTNT> <FTNT> <SU>4</SU>  For designations technical discussions, see the Technical Support Document, Chapter 11: Intended Round 3 Area Designations for the 2010 1-Hour SO <E T="52">2</E> Primary National Ambient Air Quality Standard for Guam. EPA Office of Air and Radiation, December 2017, Section 3, 6-26, available in the docket for this action. </FTNT> The Piti-Cabras area is located on the western side of the island of Guam, centered on the Piti and Cabras power plants, which are both owned by Guam Power Authority (GPA). The Piti facility (also referred to as Marianas Energy Company (MEC) by Guam) consists of two baseload electric generating units (8 and 9). Piti 8 and 9 are two 45.2 megawatt (MW) diesel engines. The Cabras facility consists of two baseload electric generating units (1 and 2) that are 66 MW units. These facilities are the primary emitters of SO <E T="52">2</E> in the area. Nearby, the Taiwan Electrical and Mechanical Engineering Services (TEMES) power plant (also referred to as “Piti 7”), <SU>5</SU> <FTREF/> and commercial and United States Navy (“Navy”) marine vessel ports are also significant emitters of SO <E T="52">2</E> . No other sources on or beyond the island were determined to have the potential to cause or contribute to significant impacts within the area of analysis. The Modeling Technical Support Document (TSD) included in the docket for this action accompanied a recent proposed Clean Data Determination for Piti-Cabras and contains more information on the facilities and emissions. <SU>6</SU> <FTREF/> <FTNT> <SU>5</SU>  Piti/TEMES 7 is a 40 MW combustion turbine and is also owned by GPA. </FTNT> <FTNT> <SU>6</SU>  “Technical Support Document (TSD) for the Piti-Cabras, Guam 2010 1-Hour SO <E T="52">2</E> Nonattainment Area Clean Data Determination Modeling Analysis,” EPA Region 9, June 2025. </FTNT> Section 191 of the CAA directs states containing an area designated nonattainment for the 2010 SO <E T="52">2</E> NAAQS to develop and submit a nonattainment area SIP to the EPA within 18 months of the effective date of an area's designation as nonattainment. The nonattainment area SIP revision (also referred to as an attainment plan) must meet the requirements of subparts l and 5 of part D, of Title 1 of the CAA, 42 U.S.C. 7401 <E T="03">et seq.,</E> and provide for attainment of the NAAQS by the applicable statutory attainment date. <SU>7</SU> <FTREF/> To be approved by the EPA, under section 192(a), these nonattainment area SIPs must provide for attainment of the NAAQS as expeditiously as practicable, but no later than five years from the effective date of designation. <FTNT> <SU>7</SU>  See sections 172 and 191-192 of the CAA. </FTNT> The Guam Environmental Protection Agency (Guam EPA) was required to prepare and submit to the EPA a nonattainment area SIP by October 9, 2019, to bring the area into attainment by the attainment date of April 9, 2023. However, Guam EPA failed to submit a complete attainment plan for the area by the October 9, 2019 deadline. On November 3, 2020, the EPA issued a finding that Guam EPA failed to submit the required attainment plan for the Piti-Cabras area. <SU>8</SU> <FTREF/> Pursuant to section 179 of the CAA and 40 CFR 52.31, the November 3, 2020 finding triggered sanctions clocks. More specifically, under 40 CFR 52.31, the offset sanction in CAA section 179(b)(2) would be imposed 18 months after December 3, 2020 effective date of the finding, and the highway funding sanction in CAA section 179(b)(1) would be imposed six months after the offset sanction was imposed, unless the EPA determined that a subsequent SIP submission corrected the identified deficiencies before the applicable deadlines. <SU>9</SU> <FTREF/> <FTNT> <SU>8</SU>  85 FR 69504 (November 3, 2020). </FTNT> <FTNT> <SU>9</SU>  See 40 CFR 52.31(d)(5). </FTNT> The finding also started a two-year clock by which the EPA is required under CAA section 110(c) to promulgate a Federal Implementation Plan (FIP) for the area, unless Guam EPA submits, and the EPA approves, a SIP for the area before December 3, 2022. On December 19, 2024, the EPA issued a finding that the Piti-Cabras nonattainment area failed to attain the 2010 SO <E T="52">2</E> NAAQS by the statutory attainment date of April 9, 2023. <SU>10</SU> <FTREF/> This finding triggered a requirement for Guam EPA to submit a plan demonstrating attainment of the 2010 SO <E T="52">2</E> NAAQS as expeditiously as practicable, but no later than December 19, 2029. <SU>11</SU> <FTREF/> In that action, the EPA noted that the Guam's submission of a complete SO <E T="52">2</E> attainment plan for the new attainment date in response to this finding of failure t ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 27k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━