Upper Missouri Waterkeeper, Inc. watchdogs new mining applications in Southwest and West-Central Montana because, more often than not, hardrock mining creates acid mine drainage.
Acid mine drainage is one of mining’s most serious threats to water. A mine draining acid can devastate rivers, streams, and aquatic life for hundreds, and under the “right” conditions, thousands of years.
How does it form?
At metal mines, the target ore (like gold, silver, copper, etc) is often rich in sulfide minerals. When the mining process exposes the sulfides to water and air, together they form sulfuric acid. This acid can and often does dissolve other harmful metals and metalloids (like arsenic) in the surrounding rock.
Many river systems and former mine sites are totally inhospitable to aquatic life, with the exception of “extremophile” bacteria. Additionally, heightened acidity reduces the ability of streams to buffer against further chemical changes.
Acid mine drainage can be released anywhere on the mine where sulfides are exposed to air and water — including waste rock piles, tailings, open pits, underground tunnels, and leach pads.
Harm to fish & other aquatic life
Acid mine drainage can have severe impacts on fish, animals and plants. Many impacted streams have a pH of 4 or lower — similar to battery acid.
Acid mine drainage is especially harmful because it can occur indefinitely — long after mining has ended. Hardrock mines across the western United States may require water treatment in perpetuity. For example, government officials have determined that acid drainage at the Golden Sunlight mine in Montana will continue for thousands of years.
Water treatment can be a significant economic burden if a company files for bankruptcy or refuses to cover water treatment costs. For example, acid runoff from the Summitville Mine in Colorado killed all biological life in a 17-mile stretch of the Alamosa River. The site was designated a federal Superfund site, and the EPA is spending $30,000 a day to capture and treat acid runoff.
Montana’s Smith River is threatened by mining today!
Did you know that the spectacular Smith River, one of Montana’s crown jewels, is at risk from a proposed copper mine? Take action and learn more by clicking here – help us Save Our Smith!