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Case Summary: EPA Recovers Over $30 million for Past Costs at the Gilt Edge Superfund Site

On October 9, 2012, EPA, the State of South Dakota, and several mining companies reached agreement for the payment of $30.2 million to settle their liabilities at the Gilt Edge Superund Site in South Dakota. The companies are: Cyprus Mines Corporation, Cyprus Amax Minerals Company, Inc., Blue Tee Corp. and Homestake Mining Company of California The agreement was filed with the United States District Court of South Dakota.

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Information about the Companies

Blue Tee Corp. is the corporate successor to Azcon Corporation. Azcon was involved at the site from February 1976 until July 1977, approximately 18 months, as a joint venture partner of Cyprus Mines.

Cyprus Mines Corporation was active in operations at the site for approximately eight years from January 1975 to June 1983.  Cyprus Mines also had a property interest in mining claims at the site until 1986 and possibly longer based upon lease assignments.

Cyprus Amax Minerals Company, Inc. is the corporate successor to Amoco.  Amoco was active in operations at the aite from 1980, shortly after it acquired Cyprus Mines, until 1983 when Cyprus Mines transferred its interests to Lacana.

CoCa Mines was acquired by Hecla Limited in 1991. In 1975, Congdon & Carey, Ltd (Congdon & Carey), a Colorado partnership, formed a joint venture (Cyprus Joint Venture) with Cyprus Mines Corporation (Cyprus Mines) to explore developing the production of gold or other minerals at the site. In February 1976, Cyprus Mines entered into another joint venture agreement (Azcon Joint Venture), with Azcon Corporation (Azcon) whereby Azcon joined the Cyprus Joint Venture. The Azcon Joint Venture was terminated eighteen months later in July 1977 and Azcon’s connection to the site ended.  In June 1983, Cyprus Mines and CoCa Mines, Inc., (CoCa), the successor to Congdon & Carey, entered into a Mining Agreement with Lacana Mining, Inc. (Lacana).

Homestake Mining Company of California was first formed in 1877, it is now a holding company and a subsidiary of Barrick Gold Corporation.

aerial view of the Gilt Edge Mine site
Aerial view of the Gilt Edge Mine site

Information about the Gilt Edge Superfund Site

The Gilt Edge Superfund Site is a 360-acre site that encompasses a former open pit gold mine and a cyanide heap-leach operation. The site is located about 6.5 miles east of Lead, S.D. at the headwaters of the cold-water fisheries and municipal water supplies of the northern Black Hills in South Dakota. In the late 1990s the mine operator, Brohm Mining Company (BMC), became insolvent. In doing so, they left 150 million gallons of acidic heavy-metal-laden water in three open pits, as well as millions of cubic yards of acid-generating waste rock that requires cleanup and long-term treatment.

Mining operations for gold, copper and tungsten were conducted in this small mining district starting in 1876. About a century ago, a series of small mines began dumping metals-laden mill tailing into Strawberry Creek and Bear Butte Creeks. By 1986, when BMC began conducting larger-scale open-pit mining, off-site waters were already contaminated.

Operable Unit (OU) 3 addresses acid rock drainage coming from the Ruby Gulch Waste Rock Repository. The Ruby Gulch Waste Rock Repository is a large acid rock drainage source on the Gilt Edge Mine site. Beginning in 2001, the EPA addressed this threat by reducing the volume of contaminated materials exposed, reducing water infiltration that produced large quantities of acid rock drainage, and containing waste materials. At the completion of that work in 2003, EPA began ongoing performance monitoring and operations and maintenance activities in this area.

Additional information is available from the Gilt Edge Mine Superfund Site web page.

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Pollutants and Environmental Effects

Sulfide waste rock and exposed ore zones (which generate leachates to surface and ground water) contain heavy metals, including arsenic, cadmium, chromium, copper, lead, nickel, silver and zinc. Elevated nitrates and sulfates are also present in heap leach residues. Copper, cadmium and zinc appear to be the metals contaminating the habitats of Strawberry and Bear Butte Creeks. Acid rock drainage generated from the sulfide-bearing wastes within the dump, if not reduced and contained, pose a major threat of contamination and release into the Ruby Gulch drainage and Bear Butte Creek.

Summary of the Consent Decree

The settlement agreement requires the companies to pay a combined $30.2 million to settle their liability at the Site:

  • Cyprus Mines Corporation, Cyprus Amax Minerals Company, Inc., and Blue Tee Corp. will pay a total of $26 million.
  • Homestake Mining Company of California will pay $4.2 million.

Contact Information

For additional information please contact

Amelia Piggott
General Attorney
Region 8
U.S. Environmental Protection Agency
1595 Wynkoop St.,
Denver CO 80202
(303) 312-6410