Montana November 18, 2016
The Story Behind Montana’s Acid Lake Will Fascinate You
Did you know Montana has something that’s often called an “acid pit of doom?”
The Berkeley Pit is a former open pit copper mine located in Butte. It’s filled with water that is heavily acidic, laden with heavy metals, rich with dangerous chemicals, and just a real problem in general.
The mine was opened in 1955, operated by Anaconda Copper and then by the Atlantic Richfield Company.
But when the mine closed in 1982, the trouble started.
When the pit was closed, the water pumps in the nearby Kelly shaft were turned off. Groundwater from the surrounding aquifers began to fill the pit slowly, rising at a rate of about one foot per month.
Since the pit closure of 1982, the levels have risen to within 150 feet of the natural groundwater level.
This presents a major environmental problem. The water, with dissolved oxygen, makes the minerals in the ore and wall rocks decay. This releases the acid.
The water in the Berkeley Pit has a pH level of 2.5. Anything below a 7.0 is considered acidic.
The water has the acidity of cola or lemon juice.
The pit water is expected to rise to the natural water table by 2020.
This will reverse flow back into surrounding groundwater, polluting Silver Bow Creek, the headwaters of the Clark Fork River. Needless to say, this would be a disaster.
Once, several hundred geese made the unfortunate choice of resting on the lake during their migration.
Sadly, they died horribly, and that’s when it was discovered that the water was acidic enough to eat away at the intestines of anything that drank enough of it.
The Berkeley Pit is currently a Montana tourist attraction.
For $2, you can step out on a viewing platform and see it for yourself.
The Berkeley Pit is a small part of Butte’s fascinating history. When you’re there, make sure to check out the World Museum of Mining.