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EPA settles with Cyprus Tohono Corp. for clean up at mine site

Release Date: 10/16/2006
Contact Information: Wendy L. Chavez, (415) 947-4248,

(San Francisco, Calif. -- 10/16/2006) -- The U.S. Environmental Protection Agency recently reached an agreement with Cyprus Tohono Corporation requiring the company to clean up a portion of its 10,505-acre mine site responsible for contaminating groundwater on the Tohono O’odham Nation, 32 miles southwest of Casa Grande, Ariz.

Under the settlement, the company will clean up a 450-acre area that includes three evaporation ponds, mill tailings impoundment and a vat leach tailings embankment. Contaminated soil will be excavated, placed on a liner, and covered with a soil cap.

Two of the evaporation ponds and the mill tailings impoundment are considered to have contributed to groundwater contamination of an aquifer that was previously the sole source of drinking water for the North Komelik community. Area residents have also reported that in certain wind conditions dust from the mine blows up into North Komelik, creating potential inhalation of particulate contamination.

“Although the village is being provided clean drinking water in the short term, today's action is necessary to protect public health in the long term,” said Keith Takata, the EPA’s Superfund division director for the U.S. EPA's Pacific Southwest region. “The work under the EPA order will minimize further contamination to the aquifer, as well as address exposure from contaminated soil.”

“This agreement has been a long time in coming and will help to protect the health and well being of Tohono O’odham Nation members” said Vivian Juan-Saunders, Chairwoman of the Tohono O’odham Nation. “We appreciate the efforts of all involved in resolving this important issue.”

Sulfate, a primary contaminant, has been found at 19,400 parts per million in these areas, while background concentrations are less than 100 ppm. Uranium, another primary contaminant, has been measured at 7.98 ppm in the evaporation ponds, which are above .08 ppm background levels.