Region 8

Richardson Flat Tailings

Richardson Flat Tailings site location map Site Type: Proposed NPL
City: Park City
County: Summit
Street Address: NW 1/4 SEC 1 T2S R 4E
ZIP Code: 84060
EPA ID: UTD980952840
SSID: 0894
Site Aliases: Richard Flats
Congressional District: 1

Site Description

The Richardson Flat Tailings site covers about 160 acres in a small valley 1½ miles northeast of Park City, Utah. The site consists of a tailings dam and impoundment that were used to capture and hold mill tailings from the Ontario Mine near Park City. Hazardous substances at the site include heavy metals such as arsenic cadmium, copper, lead, mercury, silver, and zinc.

Historic aerial photos show that a tailings pile existed as early as 1953. The most recent tailings disposal in the area occurred from 1975 to 1981, when the site owner, United Park City Mines (UPCM), leased it's mining operations to Noranda Mining and Park City Ventures.

The site is located next to Silver Creek, which is classified by the state of Utah as a cold-water fishery. In 1989, EPA and State of Utah officials observed mine tailings at the site sinking into an on-site diversion ditch and Silver Creek. Surface water coming from a diversion ditch surrounding the site is contaminated with heavy metals. This ditch empties into wetlands below the tailings dam and flows into Silver Creek. Groundwater below the site is also contaminated with heavy metals.

Map of site boundary and operable units, January 22, 2015

The primary concerns are the site's effect on surface water and groundwater quality in the area, and the potential for people or wildlife to come into direct contact with the tailings or contaminated soils.

Cleanup activities at the site are being conducted by UPCM, in cooperation with the Upper Silver Creek Watershed Group. The Upper Silver Creek Watershed Group is comprised of federal, state, and local agencies, local elected officials, and community representatives who have been working together since 1999 to address environmental contamination in the watershed left behind from historical mining activities.

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Site Risk

Media Affected Contaminants Source of Contamination
groundwater, surface water, air arsenic, cadmium, copper, lead, mercury, silver and zinc mining and milling operations

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Cleanup Progress

High-volume air sampling at the site in 1986 found that arsenic, cadmium, lead and zinc were released to the air. The site was proposed for the National Priorities List (NPL) in 1992. EPA also conducted a removal assessment in 1992 and concluded that no immediate response actions were required while investigations continued. During the 1990s, UPCM performed some voluntary work at the site, including covering most of the tailings pile with clean, low-permeability soil and reseeding the site. The diversion ditch was also improved. Together, these steps have minimized the potential for direct contact with the tailings and contaminated soils, and have helped to reduce the amount of water infiltrating through the pile.

In October 2000, EPA and UPCM signed an Administrative Order on Consent for UPCM to conduct a focused Remedial Investigation/Feasibility Study (RI/FS) of the site. The RI/FS was completed in fall 2004 and focused on evaluating the existing condition of the tailings pile, as well as any other actions considered necessary to further stabilize the site. A proposed cleanup plan was then issued with various cleanup alternatives. EPA received public comment on the proposal for 30 days and held a public comment meeting before making a final cleanup decision. The final decision is detailed in the Record of Decision (ROD), issued in 2005.

The entire Silver Creek watershed is also being investigated by EPA, the state of Utah and UPCM through a cooperative, community-based stakeholder group. The eventual goal is to minimize the effects of more than 100 years of mining on the Silver Creek watershed and to return Silver Creek to a safe, productive condition.

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Site Documents

Record of Decision (PDF), July 6, 2005 (96 pp, 846 K, about PDF)

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Kathryn Hernandez
Remedial Project Manager
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (8EPR-SR)
Denver, CO 80202-1129
800-227-8917 ext. 312-6101 (toll free Region 8 only)

Site Information Repositories:

Park City Library
1255 Park Avenue
Park City, UT 84060

EPA Superfund Records Center
1595 Wynkoop Street
Denver, CO 80202-1129
To request copies of administrative record documents call:
800-227-8917 ext. 312-7273 (toll free Region 8 only)


Muhammad Slam
Environmental Engineer - CERCLA
Utah Department of Environmental Quality
Environmental Response & Remediation Division
195 North 1950 West
Salt Lake City, UT 84116

Dave Allison
Community Involvement Specialist
Utah Department of Environmental Quality
Environmental Response & Remediation Division
195 North 1950 West
Salt Lake City, UT 84116

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The following links exit the site Exit

Utah Department of Environmental Quality

Summit County Utah

Park City, Utah

Park City Library

Silver Creek Watershed

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