Richardson Flat Tailings sits in Summit County, Utah, near Park City. Silver, gold, lead, and zinc mining ran there from 1875 to 1982, leaving roughly 7 million tons of mine tailings behind. The site is proposed for the National Priorities List, a federal registry of the country's most serious contaminated sites, but has not yet been formally added. Cleanup is divided into four operable units, each covering a different geographic area.
EPA has identified 14 contaminants of concern at the site. They include metals such as arsenic, lead, cadmium, zinc, aluminum, copper, mercury, and nickel. These metals turned up in solid waste, surface water, and sediment. Heavy metals spread through water into Silver Creek and downstream, and exposed tailings with little vegetation are vulnerable to wind and rain erosion.
The main tailings impoundment, Operable Unit 1, covers 258 acres and is largely cleaned up. It is capped and stabilized, with native plants and wildlife returning. A small portion still needs a final cap, which will be added later. Remedial action there began in February 2008 and is estimated to continue through February 2028. EPA's current focus is a roughly six-mile stretch of Silver Creek, covered by Operable Units 2 and 3, spanning about 2,711 acres. An Engineering Evaluation and Cost Analysis for that stretch was recently finalized. Cleanup will move in phases, starting where tailings are exposed at the surface. About 17 to 18 million dollars in settlement funds are available. Prospector Drain, Operable Unit 4, has a removal action estimated for June through August 2028. The most recent five-year review across all units was completed in September 2023.
Human exposure is currently under control at the site, meaning EPA has determined no unacceptable exposure pathways exist. Physical construction of the cleanup is not yet complete, and the site is not ready for its anticipated use. Part of the site is managed by the Bureau of Land Management, and a former railroad right-of-way is now operated by the Utah Division of Parks and Recreation as a recreation area.
Community members can review the Engineering Evaluation and Cost Analysis in the Site Documents and Data section. Public comments were accepted through June 8, 2026. EPA Region 8 and the Utah Department of Environmental Quality hosted a public open house on Monday, May 11, 2026 at the Park City Library Community Room, 1255 Park Avenue, Park City, UT 84060. Site records can also be viewed at the Park City Library or at the EPA Superfund Records Center in Denver, Colorado.
