Rule
Determination of Attainment by the Attainment Date and Clean Data Determination for the 2012 Annual Fine Particulate Standard; Plumas County, California
The full text was pulled automatically from the official source and is not Threadline News reporting; the annotations alongside it are.
Agency
Environmental Protection Agency (EPA).
Action
Final rule.
Summary
The Environmental Protection Agency (EPA) is finalizing our determination that the Portola nonattainment area in Plumas County, California, attained the 2012 annual fine particulate matter ("PM2.5") national ambient air quality standard (NAAQS or "standard") by the December 31, 2025 "Serious" area attainment date. This determination is based on ambient air quality monitoring data from 2023 through 2025. We are also finalizing a clean data determination (CDD) based on the 2023 through 2025 data and our evaluation of preliminary air quality monitoring data from 2026.
Dates
This rule is effective September 14, 2026.
Addresses
The EPA has established a docket for this action under Docket ID No. EPA-R09-OAR-2026-2608. All documents in the docket are listed on the https://www.regulations.gov website. Although listed in the index, some information is not publicly available, e.g., Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available through https://www.regulations.gov, or please contact the person identified in the FOR FURTHER INFORMATION CONTACT section for additional availability information. 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 FOR FURTHER INFORMATION CONTACT section.
For further information contact
Lindsay Wickersham, Planning Section (AIR-2-1), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; telephone number: (415) 947-4192; email address: [email protected].
I. Summary of the Proposed Action
On May 14, 2026, the EPA proposed to determine, based on complete (or otherwise validated), quality-assured, and certified data, meeting the requirements of 40 CFR part 50, appendix N for 2023 through 2025, that the Portola PM2.5 nonattainment area attained the 2012 annual PM2.5 NAAQS by its December 31, 2025 attainment date.\1\
\1\ 91 FR 27224 (May 14, 2026).
In accordance with 40 CFR 51.1015, we also proposed to issue a CDD for the Portola PM2.5 nonattainment area for the 2012 annual PM2.5 NAAQS based on the 2023-2025 data.\2\
\2\ Id.
The EPA's proposal explained that if we were to finalize the CDD, the requirements for the area to submit attainment planning provisions to meet the requirements for an attainment plan for the 2012 annual PM2.5 NAAQS, including an attainment demonstration, reasonable further progress plan, quantitative milestones, quantitative milestone reports, and contingency measures, would be suspended until such time as: (1) the area is redesignated to attainment, after which such requirements are permanently discharged; or (2) the EPA determines that the area has re-violated the PM2.5 NAAQS, at which time the state shall submit such attainment plan elements for the Serious nonattainment area by a future date to be determined by the EPA and announced through publication in the Federal Register at the time the EPA determines the area is violating the 2012 PM2.5 NAAQS.\3\ The requirements to submit emissions inventories, best available control measures, including control technologies, and a nonattainment new source review permitting program for the Serious nonattainment area will remain in effect.
\3\ 40 CFR 51.1015(b).
Finally, the EPA's proposal explained that the CDD does not constitute a redesignation to attainment. The Portola PM2.5 nonattainment area will remain designated nonattainment for the 2012 annual PM2.5 NAAQS until such time as the EPA determines, pursuant to sections 107 and 175A of the Clean Air Act (CAA), that the Portola PM2.5 nonattainment area meets the CAA requirements for redesignation to attainment, including an approved maintenance plan showing that the area will continue to meet the 1997 annual PM2.5 NAAQS for 10 years.\4\
\4\ Id.
Please see our May 14, 2026 proposed rulemaking for additional background and a detailed explanation of the rationale for our proposed action.\5\
\5\ 91 FR 27724 (May 14, 2026).
II. Public Comment
The public comment period for the proposed rulemaking opened on May 14, 2026,\6\ the date of its publication in the Federal Register, and closed on June 15, 2026. During this period, the EPA received one comment submission that discussed diesel generator exhaust associated with data centers around the nation. As this action only concerns the Portola PM2.5 nonattainment Area, and because there are no data centers in this area, this comment is not germane to our action and does not require a response. The comment is included in the docket for this action.
\6\ Id.
III. Final Action
For the reasons discussed in detail in our proposed action, the EPA is finalizing our determination that the Portola PM2.5 nonattainment area has attained the 2012 annual PM2.5 NAAQS by the December 31, 2025 attainment date, based on complete, quality- assured, and certified ambient air quality monitoring data for the 2023-2025 monitoring period.\7\ The EPA is taking this final action pursuant to CAA section 179(c)(1).
\7\ EPA AQS Design Value Report, AMP480, dated March 31, 2026. (Report Request ID: 2367374).
Preliminary data available in the EPA's Air Quality System (AQS) for 2026 (January through March) indicate that the Portola nonattainment area continues to show concentrations consistent with attainment of the 2012 annual PM2.5 NAAQS; \8\ therefore, as provided in 40 CFR 51.1015, we are also finalizing a CDD. Consequently, the requirements for the state to submit any SIP revisions related to attainment of the 2012 annual PM2.5 NAAQS for this
area, including an attainment demonstration, reasonable further progress plan, quantitative milestones, quantitative milestone reports, and contingency measures, will be suspended for so long as the area continues to attain this NAAQS. This final determination that the Portola nonattainment area has attained the 2012 annual PM2.5 NAAQS does not constitute a redesignation of the area to attainment. The designation status of the Portola nonattainment area will remain "Serious" nonattainment for the 2012 annual PM2.5 NAAQS until such time as the EPA determines, pursuant to sections 107 and 175A of the CAA, that the area meets the CAA requirements for redesignation to attainment, including an approved maintenance plan showing that the area will continue to meet the standard for 10 years.
\8\ EPA, AQS Design Value Report, AMP480, dated June 23, 2026. (Report Request ID: 2390857). Although the Q1 mean of 19.32 [micro]g/m\3\ exceeds the NAAQS, the means for Q2 and Q3 are expected to be significantly lower, because Q1 corresponds with the winter months, when PM2.5 concentrations in the area peak due to bowl-shaped topography, cold stagnant winters, and extensive use of residential wood stoves. Q1 2026 concentrations are consistent with the historic trend of data years that have recorded annual averages attaining the NAAQS. See 83 FR 64774, 64788.
IV. Statutory and Executive Order Reviews
Additional information about these statutes and Executive Orders can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.
A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review
This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget (OMB) for review.