Many streams and creeks in southwestern Pennsylvania have a bright orange color. This orange color is due to abandoned mine drainage (AMD). When old underground coal mines were abandoned long ago, they naturally filled with groundwater. The groundwater became contaminated as it dissolved minerals. Natural pressure forces this contaminated water to the surface through openings in the earth called discharges. As these discharges flow into our creeks and streams, they carry the dissolved pollutants with them. Pyrite dissolves in water and when agitated or mixed with air turns into a rusty sludge called iron oxide. This rusty sludge coats stream bottoms and turns them bright orange. Aluminum discharges on the other hand are milky white. AMD significantly degrades a streams quality often making areas of it devoid of aquatic life.
