This 2002 photo shows the burning Brier Ridge gob pile in Dillonvale, Ohio.

Some gob piles contain millions of tons of waste and have been abandoned by the mining companies that produced them. These piles can trap solar heat and become very hot, which leads to two potential hazards. The first is a lack of plant growth on the surface of the piles. Vegetation helps prevent erosion on the loose-packed waste piles. Without it, erosion can create dangerous unstable slopes. The second hazard is the potential for some of the coal in the pile to begin to burn. When this happens, the piles can burn for years or decades and emit noxious fumes that contain hazardous pollutants. The fires are not always visible on the surface, which can be dangerous for bystanders. The surface of the pile can get very hot; enough to burn skin or damage equipment. The coal under the surface can turn to ash while the surface is still intact, creating a potential “sink-hole” hazard for anyone or anything on top of the pile.

Gob piles can also lead to environmental hazards. Rainwater percolating through the pile can react with pyrite minerals and become acidic. This is similar to acid mine drainage (AMD). The acidic water has the potential to harm fish and wildlife.