The U.S. Environmental Protection Agency is proposing pollution controls at six facilities in Arizona to improve visibility at national parks and wilderness areas.
The San Francisco-based EPA is proposing a federal plan to limit emissions such as nitrogen oxides and sulfur dioxide tailored to the facilities.
The six are Tucson Electric Power's Sundt Plant in Tucson, Chemical Lime Nelson in Peach Springs, ASARCO's Hayden Smelter, Freeport McMoran's Miami Smelter, Phoenix Cement Company's Clarkdale plant and CalPortland Cement Company's Rillito plant.
EPA estimates the proposal would reduce sulfur dioxide by almost 30,000 tons per year and nitrogen oxides by 3,100 tons annually.
EPA will hold public hearings on Feb. 25 in Phoenix and the following day in Tucson.
A final determination will be made by June 27.