The United States, Sierra Club and several Wisconsin electric utilities have lodged a settlement agreement to resolve allegations that the generators violated the Clean Air Act (CAA). United States v. Wis. Power & Light Co., No. 13-cv-266 (W.D. Wis. filed 4/22/13). The settlement calls for the retirement of three units by the end of 2015 and either retirement or refueling of another unit. Defendants will also install new emission controls at specified locations; commit to meet specific nitrogen oxide, sulfur dioxide and particulate matter limits; and install new monitoring systems. The settlement also includes a $2.4- million civil penalty and $8.5 million in environmental mitigation projects.