Montana - Butte - Copper

State: Montana
Description: The Berkeley Pit is a former open pit copper mine located in Butte, Montana. The old mine shafts started flooding when mining there ended in 1982, sending contaminated water into the Berkeley Pit. It's been slowly filling up ever since. It is one mile long by half a mile wide and is filled to a depth of about 900 feet with heavily acidic water and dangerous heavy metals. The pit contains so much dissolved metal that some material is mined directly from the water.


Over the active lifespan of the Berkeley, approximately 320 million tons of ore and over 700 million tons of waste rock were mined from the Pit. Put another way, "The Richest Hill on Earth" produced enough copper to pave a four-lane highway four inches thick from Butte to Salt Lake City and 30 miles beyond .The pit and its water present a serious environmental problem and the mine has become one of the largest federal Superfund Sites.

When the pit water level eventually reaches the natural water table, estimated to occur by around 2020, the pit water will reverse flow back into surrounding groundwater, polluting into Silver Bow Creek which is the headwaters of the Clark Fork River. in 2016, thousands of migrating geese landed in the pit, killing at least 3,000 of them. Residents of the mining city saw this as a wake-up call, raising question about how to prevent the heavily acidic, metal-laden water from contaminating other waterways and the ground water.

One of the developments in the clean-up has been the construction of a treatment plant to treat and divert water coming in to the pit and to additionally treat the existing Berkeley Pit water.

For more information on the Berkely Pit, visit