Rocky Mountain Power says proposed federal environmental regulations could close many of its coal-fired power plants in Wyoming early.
Last month, the U.S. Environmental Protection Agency released a revised version of its plan to control regional haze. The latest plan incorporates some parts of a plan from Wyoming regulators but it includes tougher restrictions for some plants.
Rocky Mountain Power, Wyoming's largest power provider, has four coal-fired plants in the state - Jim Bridger, Dave Johnston, Wyodak and Naughton.
Company spokesman Dave Eskelsen declined to tell the Casper Star-Tribune which plants which would be endangered by the proposal.
He said the company is studying the potential effects on each of its units.