The Berkeley Pit: A Toxic Lake That Keeps Killing

The platform where visitors stand overlooks what may be the most consequential hole in the American West. The Berkeley Pit is one mile long, half a mile wide, and seventeen hundred eighty feet deep. It holds approximately fifty billion gallons of water that is the color of rust and the acidity of vinegar, loaded with arsenic, cadmium, zinc, copper sulfate, and a dozen other heavy metals dissolved from twenty-seven years of open-pit mining. Pumps run around the clock. The water level rises approximately one foot every month. If it ever reaches what federal regulators call the critical water level, it will contaminate the regional aquifer that supplies drinking water to this part of Montana. The pumps are not optional.

Anaconda Copper Mining Company dug the pit beginning in nineteen fifty-five and closed it in nineteen eighty-two when copper prices collapsed. By then the pit had consumed most of historic Butte, including whole neighborhoods. The company that built it became Atlantic Richfield, which became BP, which inherited the cleanup obligation under a federal consent decree. The cleanup has no projected end date.

In November of nineteen ninety-five, a migrating flock of snow geese landed on the pit during a storm. Three hundred forty-two were found dead. The company installed cannon-and-light deterrent systems to keep birds off the water. In November of twenty sixteen, a larger storm pushed a much larger flock down: estimates ran as high as sixty thousand birds landed, and three to four thousand were confirmed dead.

The Berkeley Pit is one of the largest active Superfund sites in the United States. The viewing platform you can visit today charges a small fee. The sign at the entrance explains the chemistry. The pit itself is past the sign, still rising, still being pumped, still waiting for a solution that does not yet exist.