Raleigh, N.C. a The largest U.S. electric company and the Obama administration said Thursday they are settling a 15-year-old legal case over claims that Duke Energy violated federal clean air laws by modifying coal-fired power generators without required air pollution control equipment. The proposed settlement with the U.S. Environmental Protection Agency and the Justice Department requires Duke Energy to pay a civil penalty of $975,000, shut down one coal-burning unit and spend $4.4 million on environmental mitigation projects.