On October 3, 2012, environmental groups filed a complaint before the Illinois Pollution Control Board alleging that groundwater pollution leached from coal-ash ponds at four Midwest Generation facilities. Sierra Club, Environmental Law and Policy Center, Prairie Rivers Network, and Citizens Against Ruining the Environment allege that coal-ash ponds at Midwest Generation's facilities in Joliet, Pekin, Waukegan, and Romeoville, Illinois have released contaminants into the groundwater, causing exceedances of state and federal standards for several pollutants including arsenic, boron, and selenium. The environmental groups seek an order requiring Midwest Generation to modify its coal ash disposal practices and remediate groundwater contamination, as well as civil penalties.

The Illinois Environmental Protection Agency ("IEPA") sent notices of alleged violation to Midwest Generation for its facilities in Joliet, Pekin, Waukegan, and Romeoville, Illinois.  These notices included groundwater monitoring data showing concentrations of several pollutants in excess of state standards. However, an IEPA spokeswoman stated that no off-site drinking water wells have been affected by the pollution.

Midwest Generation is required to answer this complaint by December 3, 2012.