Oral arguments were heard yesterday in the U.S. EPA’s lawsuit against the Tennessee Valley Authority, the nation’s largest public power provider. Lawyers for the EPA argued that the TVA violated the New Source Review rule of the Clean Air Act by failing to install state-of-the-art pollution-control equipment when upgrading its older coal-burning power plants. Lawyers for TVA, meanwhile, argued that the company had conducted routine repairs, not major overhauls, and that EPA was trying to change its rules mid-game. The utility also noted that compliance with the EPA’s order would cost billions of dollars and force up electricity rates. The outcome of the case could have broad implications for utilities, which want to be able to conduct maintenance at older plants without installing expensive new equipment. The three-judge panel hearing the case is expected to rule this summer; meanwhile, similar cases are pending against several other utility companies.