EPA proposes Silver Creek soil cleanup, seeks public comments near Park City

Toxic soil along Silver Creek could keep exposing Park City’s entry corridor to arsenic, cadmium, lead and zinc if cleanup drags on, while an approved plan would send crews into one of the area’s last major undeveloped parcels near the Historic Union Pacific Rail Trail.

The U.S. Environmental Protection Agency has released its final Engineering Evaluation/Cost Analysis for Operable Units 2 and 3 at the Richardson Flat Tailings Superfund Site, a more than 2,700-acre area about 1.5 miles northeast of Park City. The agency says the contamination traces back to mining operations in the Park City Mining District that continued until about 1969, and that polluted soils, tailings and sediments have affected Silver Creek, Lower Silver Creek, groundwater and habitat.

The site’s worst contamination remains concentrated in tailings with arsenic as high as 2,100 milligrams per kilogram, cadmium up to 598 mg/kg, lead up to 75,000 mg/kg and zinc up to 107,000 mg/kg. EPA’s 2023 five-year review said ecological risks at the site remained substantial from exposure to zinc, cadmium, lead and arsenic.

EPA’s preferred approach would prioritize cleanup in areas near the rail trail, where tailings sit closer to the surface. The agency says a full cleanup along Silver Creek and the rail trail would cost about $69 million, far more than the roughly $17 million it says is available for the project. That funding gap makes the public comment period especially important, because the final remedy will shape how much contamination gets removed, where work starts and how much of the corridor stays exposed in the meantime.

The comment period is open through June 8, 2026. EPA and the Utah Department of Environmental Quality will host a public open house May 11 from 5:30 p.m. to 7:30 p.m. at the Park City Library community room, where residents can review the cleanup study and press the agencies on priorities, costs and the extent of the work.

The new proposal builds on a long cleanup history. EPA selected excavation, capping and related controls in a 2005 Record of Decision for the Richardson Flat Tailings Site, and a 2014 administrative order on consent with United Park City Mines Inc., the Bureau of Land Management, the U.S. Fish and Wildlife Service, Utah DEQ, the Utah Division of Parks and Recreation and the state of Utah Natural Resource Trustee set out engineering evaluation, removal and restoration work across the site.

Silver Creek matters beyond the tailings itself. Utah classifies the waterway as a cold-water fishery, and EPA has said response actions would likely include extensive excavation and removal of contaminated soils, tailings and sediments in and along the creek. With development pressure still building in the Park City entry corridor, the decision now is whether the corridor remains a contaminated seam of ground beside the trail or starts moving toward a cleaner, more usable landscape.