Proposed rule · 2026-09604

Determination of Attainment by the Attainment Date and Clean Data Determination for the 2012 Annual Fine Particulate Standard; Plumas County, California

The Environmental Protection Agency (EPA) is proposing to determine that the Portola nonattainment area in Plumas County, California, attained the 2012 annual fine particulate matter ("PM<INF>2.5</INF>") national ambient air quality standard (NAAQS or "standard") by the December 31, 2025 "Serious" area attainment date. This proposed determination is based on ambient air quality monitoring data from 2023 through 2025. We are also proposing to make a clean data determination (CDD) based on the 2023 through 2025 data. If we finalize this CDD, certain Clean Air Act (CAA) requirements that apply to the Portola nonattainment area will be suspended for so long as the area continues to meet the 2012 annual PM<INF>2.5</INF> NAAQS. The area would remain designated nonattainment for the 2012 annual PM<INF>2.5</INF> NAAQS, unless and until the State submits, and EPA approves, a redesignation request and maintenance plan for the area. We are taking comments on this proposal and plan to follow with a final action.