Property owners and local governments face possible severe structural damage and expensive repairs to homes, buildings, roads, and utility lines when abandoned underground mines collapse. According to a Department of Housing and Urban Development contractor, the annual cost of surface subsidence damage (sinking of the ground surface) is estimated at $30 million.

GAO found that there is no federal, state, or local mechanism to obtain comprehensive data on the nature, frequency, and severity of subsidence occurrences. This data would be helpful to better understand subsidence and develop remedies to solve the problem. The Bureau of Mines estimated that over 8 million acres have been undermined in the United States in extracting coal, metals, and nonmetals. Subsidence has affected over 2 million acres, or 25 percent, of the undermined area. The Bureau also estimated that, on the basis of anticipated underground production of coal, metals, and nonmetals and no significant changes in past practices, mining methods, or scientific subsidence controls, an additional 2.5 million acres will be undermined by the year 2000. Underground mine subsidence damage has been most widespread in Pennsylvania and Illinois. Pennsylvania State officials told GAO that only about 3 percent of those living in subsidence prone areas are insured and many subsidence damage incidents have not been reported for fear of loss in property value. Federal, state, and local officials generally agree that active mines will lead to future subsidence, but not necessarily cause subsidence damage. Mine subsidence can be controlled or avoided by not mining the resource, mining the resource using techniques causing subsidence in a planned or calculated manner, or mining the resource and leaving an adequate amount of coal for surface support.