When underground coal mining began in the 1700s in the U.S., many of the mines were located far away from developing city infrastructure. There was little thought of potential expansion over these mined-out areas or the effects of long-term subsidence. Until the 1970s, most mine design was essentially done by rule of thumb and focused on short-term operational needs. As cities began to expand into mined-out areas, city infrastructure became exposed to the risk of damage caused by mine subsidence. There are presently 17 states which have active and abandoned underground coal mines that require significant expenditures each year to address mine subsidence risk and damage. …