How does mine waste impact streams, groundwater, and animal and human health?
Due to the composition of the Butte ore body, significant acid mine drainage occurred in the Upper Clark Fork. Butte ore is high in fool’s gold, or iron pyrite, a compound of iron and sulfur. When exposed to water and air, pyrite oxidizes, leading to rust (iron) and sulfuric acid. As the sulfuric acid mixes with surface water, streams and groundwater, the acidity also causes the metals present in Butte ore (copper, lead, cadmium, zinc, to name a few) to dissolve in the water in high concentrations. The resulting acidic water, with high concentrations of toxic heavy metals, poses extreme risks for fish and other aquatic life, vegetation, and humans. The mobile nature of water can cause the contimation to spread, as in the case of the Clark Fork River, where contamination spread 120 miles downstream from the sources in Butte and Anaconda to the Milltown Dam near Missoula.
