EPA Approves Arizona's Plan to Fix Hayden SO2 Pollution
Published Date: 8/20/2026
Rule
Summary
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 (SO<INF>2</INF>) national ambient air quality standards (NAAQS or "standards") in the Hayden SO<INF>2</INF> nonattainment area. These SIP revisions, collectively referred to as the "Hayden SO<INF>2</INF> 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.
Analyzed Economic Effects
3 provisions identified: 2 benefits, 0 costs, 1 mixed.
State Smelter Limits Become Federally Enforceable
On September 21, 2026, four Arizona rules become part of the federal State Implementation Plan (SIP) and are fully federally enforceable. The rules are R18-2-B1302 (Limits on SO2 Emissions from the Hayden Smelter, revised January 2, 2026), Appendix 14 (Procedures for Sulfur Dioxide and Lead Fugitive Emissions Studies for the Hayden Smelter, revised January 2, 2026), R18-2-715, and R18-2-715.01 (both revised April 7, 2017).
Termination of Federal Sanctions and FIP Obligation
All federal sanctions that were triggered by EPA's November 5 and November 10, 2020 actions are terminated on the effective date of this rule (September 21, 2026). The Federal Implementation Plan (FIP) obligation tied to the earlier finding and the consent decree in Center for Biological Diversity et al. v. Regan is also terminated when this approval becomes effective.
Plan Finalized to Attain SO2 Standards
EPA has finalized approval of Arizona's 2023 Hayden SO2 Plan and its supplement, finding that the submissions provide for attainment of the 1971 and 2010 SO2 national ambient air quality standards in the Hayden nonattainment area. As of the effective date of this rule (September 21, 2026), EPA states the Hayden Plan meets the Clean Air Act requirements for attainment demonstration, reasonable further progress, RACM/RACT, emissions inventories, NSR, enforceable emission limits, and contingency measures; the 1971 SO2 NAAQS will no longer apply to the Hayden area when the approval is effective.
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