Des Moines Register: Three Iowa environmental groups are suing a state regulatory agency, saying it has failed to require MidAmerican Energy, the state’s largest electricity provider, to weigh retiring two of its western Iowa coal plants. In the lawsuit, the Iowa Environmental Council, the Environmental Law & Policy Center and the Sierra Club say the Iowa Utilities Board didn’t consider the cost savings that would come from MidAmerican retiring two coal plants near Sergeant Bluff and replacing them with renewable energy sources.