Wyoming gets nearly 90% of its electricity from coal-fired power plants. A series of new regulations from the Environmental Protection Agency requires those plants to install new pollution controls - its either install, or close down. Nearly half of the electricity currently generated by coal in Wyoming is now either in compliance with mercury rules, or racing towards a compliance deadline. It is an expensive job. For Inside Energy, Reid Frazier of the Allegheny Front takes us inside a plant being retrofitted in Pennsylvania.