The U.S. Environmental Protection Agency notified the state of Wisconsin this week that it was starting an investigation into 15 publically owned power plants to determine if they were violating clean air laws. The EPA sent a letter to the state Department of Administration asking for information about the plants “to determine whether the emission sources at these facilities are complying with the Clean Air Act.” The EPA letter comes after Doyle?s administration acknowledged that as many as eight state-run plants have violated the Clean Air Act in recent years. The state is already spending more than $250 million to convert a coal-fired plant that powers the University of Wisconsin-Madison to run on natural gas and biomass after a federal judge agreed with the Sierra Club that it was violating the Clean Air Act.