Acid Mine Drainage (AMD) is currently the main pollutant of surface water in the mid-Atlantic region. AMD is caused when water flows over or through sulfur-bearing materials forming solutions of net acidity. AMD comes mainly from abandoned coal mines and currently active mining. AMD degrades more than 4,500 stream miles in the mid-Atlantic region with the loss of aquatic life, and restricts stream use for recreation, public drinking water and industrial water supplies.
What is Mine Drainage?
Mine drainage is metal-rich water formed from chemical reaction between water and rocks containing sulfur-bearing minerals. The runoff formed is usually acidic and frequently comes from areas where ore or coal mining activities have exposed rocks containing pyrite, a sulfur bearing mineral. Metal-rich drainage can also occur in mineralized areas that have not been mined.
Mines built as early as the 1800s were developed in a manner which utilized gravity drainage, to avoid excessive water accumulation in the mines. As a result, water polluted by acid, iron, sulfur and aluminum drained away from the mines and into streams.
How does Mine Drainage Occur?
Mine drainage is formed when pyrite, an iron sulfide, is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Some or all of this iron can precipitate to form the red, orange, or yellow sediments in the bottom of streams containing mine drainage . The acid runoff further dissolves heavy metals such as copper, lead, mercury into ground or surface water
Problems Associated with Mine Drainage
Contaminated drinking water
Disrupted growth and reproduction of aquatic plants and animals
Corroding effects of acid on parts of infrastructure such as bridges
Economic Concerns Resulting from Acid Mine Drainage
A region impacted by acid mine drainage often has a decline in valued recreational fish species such as trout as well as a general decline in outdoor recreation and tourism along with contamination of groundwater drinking supplies