Ground Collapse Over Abandoned Mines
by Paul E. VanDorpe
Underground coal mines can cause collapse of the land surface, resulting in problems that range from annoying nuisances to serious, costly hazards. These problems in any area depend on various geologic and past mining conditions.
Since 1840, coal mining in Iowa has left approximately 6,000 mines underlying 80,000 acres, 3,800 of which are urban. Most areas with histories of underground mining have experienced some collapse (subsidence) problems. Well documented cases in the Des Moines area resulted in damage to structures and utilities, and periodic problems are likely to continue. In the What Cheer area (Keokuk County), subsidence craters have damaged roads, yards, pastures, row crops, and utilities. Geologic and mining conditions differ in the Centerville area (Appanoose County) and few subsidence incidents are known, though the potential for them exists. In Oskaloosa (Makaska County) the extent of mining is not well documented. Some minor property damage may be attributable to this cause. Subsidence in rural areas affects pasture and row crops, and reduces the land area available for agriculture.
This environmental legacy from our historic use of a geologic resource will be with us for decades to come. We need to be more aware of the problem, document subsidence events when they occur, take remedial action where possible, and utilize available information in land-use planning.
Adapted from Iowa Geology 1992, No. 17, Centennial Edition, Iowa Department of Natural Resources