The proposal would reduce haze-causing nitrogen oxide emissions at the 2,250-megawatt plant by 84 percent, or 28,500 tons per year. It doesn't mandate a specific technology for cleaning up the power plant but acknowledges that installation of selective catalytic reduction, like catalytic converters on an automobile, would meet the limits.
The Salt River Project, which operates the plant, has argued that requiring anything beyond the low nitrogen oxide burners already on the three generating units would result in negligible improvements to air quality.
Owners of the generating station will have until 2023 to make the upgrades under the EPA proposal.
"The EPA's proposal would give everyone more time, but still fails to strike the appropriate balance since the anticipated air quality improvements would not even be visible to the naked eye," said Arizona Department of Environmental Quality Director Henry Darwin.
Some Navajo community groups were happy to hear the news of a pollution control plan for the power plant.
"It's been so many years of worsening air, water and health in our communities from coal," said Adella Begaye, a registered nurse on the Navajo Nation and a member of Dine Citizens Against Ruining Our Environment. "Coal industry and government leaders have fought against change here for so long, but times have changed. It is a new era."