Air Plan Approval; Arizona; Attainment Plan for the Hayden SO2 Nonattainment Area for the 1971 and 2010 Sulfur Dioxide National Ambient Air Quality Standards
Key claim: EPA has formally approved Arizona’s plan to bring the Hayden area into compliance with federal sulfur dioxide air-quality standards, locking in the state’s emissions limits and control measures for that area.
Abstract
(Rule · Environmental Protection Agency) The Environmental Protection Agency (EPA) is finalizing approval of revisions to the Arizona state implementation plan (SIP) for attaining the 1971 and 2010 sulfur dioxide (SO2) national ambient air quality standards (NAAQS or “standards”) in the Hayden SO2 nonattainment area. These SIP revisions, collectively referred to as the “Hayden SO2 Plan” or “Plan,” include Arizona’s attainment demonstration and other elements required under Clean Air Act (CAA or “Act”) sections 110, 172, 191, and 192. In addition to an attainment demonstration, the revisions address the requirements for meeting reasonable further progress (RFP) toward attainment of the NAAQS, reasonably available control measures and reasonably available control technology (RACM/RACT), base-year and projection-year emissions inventories, nonattainment new source review, emissions limitations necessary to provide for attainment, and contingency measures. The EPA is approving the SIP revisions as meeting the CAA requirements. This action is being taken under the CAA.
Why this matters
Final approval of Arizona’s Hayden SO2 attainment plan converts state emission limits and control measures into federally enforceable requirements, affecting compliance obligations for local SO2 sources (primarily copper smelting) and providing a template for how EPA closes out legacy SO2 nonattainment designations. The practical effects include locked-in operating constraints on emitters and continued monitoring to demonstrate NAAQS compliance, with public-health implications for the surrounding community.