Acidity Decline of Above-Drainage Underground Mines in West Virginia
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Extensive underground mining has taken place in West Virginia since the late 1800s, and West Virginia researchers estimated an area of about 610,000 hectares with underground mining beneath the surface in this state alone. This legacy of mining has changed groundwater quality, by introducing acid mine drainage, and quantity, due to intercepting and changing underground water flow paths. In areas of northern Appalachia where high sulfur coal exists and no limestone units are present for neutralization, the greatest environmental impact from underground mines has been on surface water quality from acid mine drainage. The effects on surface water include high levels of acidity and metals that have detrimental effects on aquatic organisms, low pH conditions that accelerate weathering and release of aluminum and other toxic elements from minerals, and orange-colored stream sediments from iron hydroxide precipitation.
Data from water quality studies in 1968 were found for more than 100 underground mine discharges in northern West Virginia. We located those sites and took water samples from 37 of them. We found after measuring the water quality that the average acidity of Upper Freeport underground mines was 1,422 milligrams per liter in 1968 and 306 milligrams per liter in 2006, which shows a significant improvement in regional water quality from above-drainage underground mines during the last 50 to 70 years. A similar trend was found for Pittsburgh underground mines: acidity was 2,548 milligrams per liter in 1968 and 496 milligrams per liter in 2006. These declines in acidity give hope that water quality will continue to improve over time in these watersheds, and the rate of improvement helps to predict treatment strategies and costs.