U.S. EPA orders ARCO to complete investigation for Leviathan Mine ...

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U.S. EPA orders ARCO to complete investigation for Leviathan Minecleanup
Release date: 06/26/2008
Contact Information: Wendy Chavez, 415/947-4248,chavez.wendy@epa.gov


Investigation to help determine cleanup actions
SAN FRANCISCO – The U.S. Environmental Protection Agency recently orderedthe Atlantic Richfield Company to complete a comprehensiveinvestigation of the Leviathan Mine Superfund Site to determinelong-term cleanup actions at the former mine located in AlpineCounty, Calif. near the California-Nevada border.

Since the site was added to the EPA’s NationalPriority’s List in 2000, the agency has continued to focus oncontrolling and cleaning up the acid mine drainage from LeviathanMine, which is upstream from lands of the Washoe Tribe of Nevadaand California. The EPA has been successful in requiring thecapture and treatment of the acid mine drainage during the summer months when access to thesite is not affected by snow. The EPA will evaluate how to expandthe collection and treatment system to a year-round system.

“Completing the investigation and cleanup evaluation for thissite is the next step toward a long-term solution for this minesite,” said Keith Takata, the Superfund Division director theEPA’s Pacific Southwest region. “The EPA will work withthe affected states, tribes, and communities to determine a finalcleanup action.”

The EPA’s evaluation will include assessing potential risksfrom surface waters, groundwater, sediments, soils, and flora andfauna impacted by mine run-off. The assessment will includespecific Washoe Tribal cultural uses of that area’s resourcesaffected by the mine.

The open-pit mining of sulfur from the site left wastes andunderground conduits that result in acid mine drainage into theLeviathan Creek/Bryant Creek watershed, which drains into the EastFork of the Carson River -- a major source of water supply and ahabitat for fish. Unless treated, the releases contain elevatedconcentrations of metals and metalloids, most notably arsenic, aswell as iron, aluminum, chromium, cobalt, copper, nickel and zinc.The low pH and high metals content of the acid mine drainagehistorically limited most aquatic life in Leviathan Creek andportions of Bryant Creek downstream of the mine until responseactivities were initiated.

The site was initially developed as an underground mine for gold,copper and copper sulfate, starting in 1863. From 1954 through1962, Anaconda Copper Mining Company conducted open pit mining,which later was acquired by Atlantic Richfield. In 1984, the stateof California acquired approximately 495 acres of the mine to cleanup and abate water quality problems associated with historicmining. The Lahontan Regional Water Quality Control Board, whichwas delegated authority over the mine property, constructedevaporation ponds in an attempt to reduce the impact from some ofthe mine releases.