Being from Montana, when you drive through Butte, there is a giant hole. It is the remains from a historical mining site during the copper boom which began in the area in the 1870s. In 1955, everyone left, and all that remained was the giant hole. Keep in mind this hole, is right in the middle of this small town.
The hole in Butte is called the Berkley Pit. Pumps were used to dewater the mines, but then were shut down in the 1980s. After this, the entire pit/hole filled up with 40 billion gallons of acidic water. The hole is full of heavy metals, and is considered a terminal sink now, that is constantly being filled with ground water and contaminated soil.
The soil surrounding the hole was tested, and found to be full of an immense amount of contaminants, including: Aluminum, Antimony, Arsenic, Barium, Beryllium, Cadmium, Calcium, Chromium, Cobalt, Copper, Iron, Lead, Magnesium, Manganese, Mercury, Nickel, Potassium, Selenium, Silver, Sodium, Thallium, Tin, Vanadium, and Zinc. Most of these were also found in the ground and surface water as well.
The ground water gets contaminated when it flows through the old mine shafts, then reacts with oxygen to oxidize the sulfide minerals, making the water acidic.
There have been as many steps towards a remediation effort to ensure ground water in the area keeps clean. In the 1980s it was placed on the 20th on the list of priority from the US Environmental Protection Agency.
Health hazards from the Berkley Pit during the mining days would cause the miners to inhale silica particles, causing lung problems. It is said that people could still be effected by the exposure to the heavy metals, too much of these minerals can cause inflammatory diseases and cardiac disorders. Arsenic can even lead to skin, lung, and bladder cancer and cause the arteries to harden.
Soil contamination is not only a problem that has begun to arise today, but is still an effect from things from long ago that are still trying to be fixed.