The Environmental Protection Agency has formally denied Salt River Project’s (SRP) request to keep operating an unlined evaporation pond that stores coal combustion residuals at Coronado Generating Station in St. Johns, Apache County. In a Jan. 16, 2025 final determination, the EPA concluded SRP did not demonstrate that the surface impoundment meets federal criteria under 40 C.F.R. § 257.71(d)(1) for groundwater protections, liner performance and monitoring.

SRP submitted the alternate‑liner demonstration application for the Coronado pond on Nov. 30, 2020, and the EPA determined the application complete on Jan. 11, 2022. The agency proposed denial on Jan. 25, 2023 and moved to a final denial two years later; the facility’s status is listed as “Denied” on the EPA’s Coal Combustion Residuals (CCR) Part B implementation webpage. Separately, on March 20, 2025, the EPA granted SRP an extension to delay ceasing use of the pond because of grid reliability concerns, pushing any mandated cessation or closure actions out at least until Sept. 30, 2026.

The denial is significant for Apache County because Coronado’s evaporation pond holds coal ash — a byproduct of coal‑fired power generation — in an unlined surface impoundment. The EPA’s documents identify the central technical failures as SRP’s inability to show adequate groundwater monitoring and to substantiate the pond’s soil and engineering characteristics against federal standards. Where liners and effective monitoring are absent or deficient, coal ash can leach metals and other contaminants. The in‑depth notes accompanying the decision list arsenic, lithium, boron and cadmium among substances of concern that can migrate into groundwater and potentially affect drinking supplies.

Local stakeholders encompass more than the plant operator and regulator. Residents of St. Johns, county water users and nearby tribal communities have a shared interest in groundwater protections and transparent remediation plans. The denial raises immediate questions for those stakeholders: what are the short‑term protections for drinking water wells; what monitoring will be required and made public; and what timetable will govern final closure, capping or removal of ash from the pond?

Several practical matters remain unresolved. Public records and agency postings do not yet aggregate the full local picture of any existing contamination, the specific remediation or closure plan SRP will pursue now that the application is denied, or whether state regulators and the company have communicated directly with affected communities. The March 2025 extension for grid reliability delays enforcement action but does not negate the EPA’s finding that the application failed to meet federal standards.

For Apache County residents this episode underscores the intersection of energy infrastructure, environmental regulation and water security. The EPA denial puts new pressure on SRP and state agencies to clarify near‑term actions and on county and tribal leaders to seek testing data and timelines. Local reporters and public agencies may have additional information not yet consolidated in federal filings, and the decision presents an opening for more detailed local coverage and community engagement on groundwater monitoring and public health safeguards.