The Berkeley Pit is a terminal sink, the remains of an Anaconda Company open pit copper mine that ceased operations in 1982. The pit began as a silver mine in 1880. Its Irish immigrant owner Marcus Daly soon discovered copper filled the mine, and in two years Anaconda was the world’s leading copper company.

Anaconda converted the mine to an open pit operation in 1955 after underground mining became less profitable. As copper was connected to America’s consumer culture and used in household products and automobiles, Anaconda promoted the mine as a tourist attraction in the 1950s and 1960s. Mining continued 24 hours a day, and one and a half billion tons of matter was removed from the pit.

The pit reached 1,780 feet in depth and four miles in circumference. Waste piles covered fifteen thousand homes, three churches, and seven schools in the Butte area. A drop in copper prices caused the mine to cease operations, including shutdown of the water pumps. Groundwater and surface run-off collect in the terminal sink at the rate of two and a half million gallons per day, combining with sulfur and bacteria in the pool. Bedrock currently encases the toxic pool, but scientists predict the water level will surpass the bedrock layer and seep into alluvial soil in 2023, potentially contaminating the Columbia River.

The Berkeley Pit is a Superfund site, and an EPA- constructed water treatment plant will be activated once the pit water reaches its predicted critical level.

Researched, written, and narrated by University of West Florida Public History Student Jeremy Hatcher.