Coal ash is the common name for Coal Combustion Residuals (CCRs), a term the Environmental Protection Agency uses to describe several waste products produced by power plants that burn coal to generate electricity. These facilities are referred to as "coal-fired" power plants.
Midwest Generation, former owner and operator of the Joliet #9 Generating Station, has a permit from EPA for dumping coal ash into Joliet's Lincoln Stone Quarry. The quarry, located on the south side of the Des Plaines River, is unlined. Even with Midwest Generation's existing control systems, contaminates are migrating toward local waterways and leaching into the area groundwater.
References and Further Reading
Coal ash basics. (2017, April 26). Retrieved September 30, 2017, from https://www.epa.gov/coalash/coal-ash-basics