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National Information |
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Superfund Program
Richardson Flat Tailings
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Site Type: Proposed NPL City: Park City County: Summit Street Address: T2S - R4E Sec 1, NW 1/4 Zip Code: 84060 EPA ID#: UTD980952840 Site ID#: 0800690 Site Aliases: Richard Flats Congressional District(s): 03 |
Site Description
The Richardson Flat Tailings site covers about 160 acres in a small valley 11/2 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. The hazardous substances at Richardson Flat 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 leased their mining operations to Noranda Mining and Park City Ventures.
In 1989, EPA and State of Utah officials observed mine tailings at Richardson Flat sinking into an on-site diversion ditch and Silver Creek. Richardson Flat is located next to Silver Creek, which is classified by the State of Utah as a cold-water fishery. Surface water coming from a diversion ditch surrounding the Richardson Flat 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.
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 Richardson Flat 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.
Site Risk
| Media Affected | Contaminants | Source of Contamination |
| Ground water, surface water, air | Arsenic, cadmium, copper, lead, mercury, silver and zinc | Mining and milling operations |
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 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 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 for Richardson Flat. 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, issued in 2005.
The entire Silver Creek Watershed is also being investigated by EPA, the State of Utah and United Park City Mines 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.
Site Documents
Note: all documents are Adobe PDF documents (About PDF files)-
Record of Decision, July 2005 (public ftp folder contains a LARGE (4 MB) PDF file)
Contacts
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