Power company officials on Tuesday marked the opening of a new gas-fired power plant in Cheyenne that replaces several old coal-fired plants elsewhere Although Wyoming is the nation's leading coal-producing state, officials say federal regulations now make it effectively impossible to open a new coal-fired plant anywhere in the country. Officials from Cheyenne Light, Fuel and Power and Black Hills Corp. held an opening ceremony for the Cheyenne Prairie Generating Station Tuesday afternoon.