EPA Greenlights Arizona's Sulfur Dioxide Cleanup Plan in Hayden
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.
Personalized for You
How does this regulation affect your finances?
Personalize government policy and PRIA will tell you what this federal register document means for your household, plus every other regulation we track. PRIA reads each provision against your financial profile to show you exactly what matters to your wallet.
Key Dates
Department and Agencies
Related Federal Register Documents
2026-19071, Partial Repeal of the Carbon Pollution Standards for Fossil Fuel-Fired Electric Generating Units
The EPA is rolling back most of the 2024 rules that limited carbon pollution from fossil fuel power plants. This change affects coal and gas plants by easing some strict limits on emissions and carbon capture technology. The new rules kick in on November 16, 2026, potentially saving money for power plants but raising questions about pollution control.
2026-19072, Rescission of the Greenhouse Gas Findings for Fossil Fuel-Fired Power Plants and Repeal of Regulations for Power Plant Greenhouse Gas Emissions Under Clean Air Act Section 111
The EPA is proposing to cancel all greenhouse gas rules for fossil fuel power plants, saying the law doesn’t let them regulate these emissions for climate reasons. This change affects power plants across the U.S. and could impact future pollution limits and costs. Comments on this proposal are open until November 2, 2026, so now’s the time to speak up!
2026-18317, Updated Definition of “Waters of the United States”
The purpose of this supplemental notice of proposed rulemaking is for the U.S. Environmental Protection Agency (EPA) and the Department of the Army ("the agencies") to supplement and seek additional comment on certain aspects of an earlier proposal, published on November 20, 2025, to revise the regulations defining the scope of waters federally covered under the Clean Water Act in light of the U.S. Supreme Court's 2023 decision in Sackett v. Environmental Protection Agency. As stated in the agencies' November 20, 2025 Notice of Proposed Rulemaking (NPRM), the agencies intend for this rulemaking to provide greater regulatory certainty and increase Clean Water Act program predictability and consistency by clarifying the definition of "waters of the United States." After consideration of the public comments received on the NPRM, the agencies are issuing this notice to supplement the NPRM with additional regulatory options on certain aspects of the proposed rule.
2026-14112, Amendments and Nonconformance Penalties for Model Year 2027 and Later Heavy-Duty Highway Engines and Amendments to Inducement Provisions for SCR-Equipped Diesel Engines
Starting with model year 2027, the EPA is updating rules for big truck engines to make sure they last longer and pollute less. They’re also letting engine makers pay penalties if their engines don’t meet standards, and tightening rules for special pollution-control systems on diesel engines. These changes affect truck and engine makers and kick in soon, with public feedback due by August 29, 2026.
2026-13667, Minor New Source Review Program Air Permitting Public Participation Requirements for State Implementation Plans
The EPA wants to give states more freedom to decide how much public input is needed when approving small air pollution sources or changes. This means local air agencies can tailor public participation to fit their community’s needs while still protecting air quality. If you’re involved in air permits, watch for comment deadlines and possible virtual hearings this summer!
2026-13263, Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems
The EPA is rolling out the sixth Unregulated Contaminant Monitoring Rule (UCMR 6) to check for new, sneaky chemicals in public drinking water. Big water systems serving 3,300+ people and some smaller ones will test for 30 different contaminants, including certain PFAS and pesticides, to keep our water safe. Comments and feedback are open until late August 2026, and the EPA will host fun online meetings to chat about the plan!
Previous / Next Documents
Previous: 2026-16988, Deletion From the National Priorities List
The Environmental Protection Agency (EPA) announces the deletion of six sites and the partial deletion of two sites, from the Superfund National Priorities List (NPL). The NPL, created under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended, is an appendix of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). In accordance with the NCP, sites may be deleted from the NPL where no further response is appropriate. The EPA and the applicable states, through their designated state agency, have determined that all appropriate response actions under CERCLA have been completed. However, this deletion does not preclude future actions under Superfund.
Next: 2026-16990, Air Plan Approval; SC; Department Name Change
The EPA is giving a thumbs-up to South Carolina’s update that splits one big department into two: the Department of Public Health and the Department of Environmental Services. This change updates air pollution rules to match the new department names and kicks in on September 21, 2026. If you live or work in South Carolina, this keeps air quality rules clear and official—no extra costs or delays involved!