"The problem here — and this is the insidious part of abandoned mine lands — is that mines are not well mapped in this country," said Chris Holmes, a spokesman for the Office of Surface Mining Reclamation and Enforcement (OSMRE).
The agency does maintain a database of abandoned coal mines, listing their relative degree of hazard, but even that requires frequent updates. "You'd think the database would be fairly static, but that's not true," Holmes said. Instead, he said, mines are often found by happenstance or accident and added to the list.
Unfortunately for would-be subterranean entrepreneurs, old coal mines, although plentiful, often aren't good candidates for reuse, so much of the reuse of old coal mines takes place on the surface. Companies don't want to risk stumbling across acid mine drainage, as the polluted water is called, or an explosive methane pocket deep within a coal seam.
In addition to pollution and explosion threats, many are prone to collapse.
"Coal mines are notorious for being unstable, and that's because they're all in sedimentary rock," said Alfred Whitehouse, a consultant on mining and environmental issues and former administrator of the Abandoned Mine Land Program at Office of Surface Mining Reclamation and Enforcement. "It's more complicated because on land when you frame a building, you can see what you're doing. When you're underground you're not quite sure what's above you," such as weak zones or fractures in the rock.