- The Washington Times - Tuesday, March 26, 2002

The government yesterday announced an $87 million settlement with Atlantic Richfield Co. and five other mining firms to control billions of gallons of highly acidic mine drainage that threaten water supplies in Butte, Mont.
The Justice Department, the Environmental Protection Agency and the state of Montana said the settlement will prevent drainage containing arsenic and heavy metals from flowing out of the pit and endangering Butte's water supply.
The Justice Department said Berkeley Pit is part of the Silver Bow Creek/Butte area Superfund site in southwestern Montana. Total costs of cleanup at the pit alone will likely reach $110 million.
The cleanup will be performed by ARCO and five other firms: ASARCO, AR Montana Corporation, Dennis Washington, Montana Resources and Montana Resources, Inc.
The settlement was filed in U.S. District Court in Butte.
Under the agreement, the companies will pump and treat the pit's acidic mine water, which now amounts to more than 30 billion gallons, to keep the water level at a safe point. Absent the EPA's cleanup action, contaminated water from the pit would flow into Silver Bow Creek and area groundwater, endangering people relying on that water for drinking and the fish population.
The Berkeley Pit site encompasses roughly 23 square miles near downtown Butte. Surrounding the pit are more than 3,500 miles of underground mine workings operated by several separate mines since 1865.
Until 1982, the Justice Department said all of the mine workings were dewatered by ARCO and its predecessors through a massive underground pumping system to allow mining to continue in the pit and the other underground mines.
In 1982, the department said, ARCO decided to cease mine operations and shut off the dewatering pumps. Groundwater in the area then started rising back to levels that existed before the mining and dewatering operations began. Justice officials said as the groundwater level rose, the Berkeley Pit rapidly filled with acidic mine drainage from the pit walls, the network of underground mines, waste-rock dumps, and leach pads in the area.
"What was once a regulated mining and dewatering operation has now become a Superfund site with the largest body of contaminated water in the United States," said Deputy Assistant Attorney General John Cruden, of the department's Environment and Natural Resources Division.
Department officials said the mine drainage that exists in the Berkeley Pit is laden with arsenic and heavy metals such as aluminum, cadmium, copper, iron, lead, zinc and sulfate. These same toxic attributes of the pit water also led to the 1995 deaths of 342 snow geese, who mistook the contaminated water for a migratory drinking stop.

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