The U.S. Environmental Protection Agency has approved a plan for the Salt River Project to curtail a unit at its coal-fired Coronado power plant a few months each year to comply with regional haze requirements.
EPA Administrator Scott Pruitt on Oct. 6 said the federal agency approved an Arizona regional haze state implementation plan and a withdrawal of a federal implementation plan for the two-unit plant. Pruitt, who announced the decision during a visit with Gov. Doug Ducey, said the state "delivered a thorough plan" that seeks to improve visibility and reduce haze-causing emissions.
"Our goal at EPA is not to use a one-size-fits-all approach to addressing state environmental problems, but to empower our state partners to make their own plans to address their individual environmental needs," he said in a statement.
Working with the state of Arizona, Salt River Project in 2016 offered an alternative to installing a selective catalytic reduction, or SCR, system at unit 1 of the plant by December 2017, something favored by the U.S. EPA at the time. The public power utility said doing so would cost $110 million, while the alternative would allow the unit to meet regional haze requirements, save customers money and provide operational flexibility.
The Coronado plant is in Apache County, Ariz., and has an operating capacity of 762 MW, according to S&P Global Market Intelligence data. It began operating late 1979. Salt River Project has already installed an SCR system on unit 2.
Ducey said the state welcomed news of the EPA's decision.
"Arizonans should chart their own destiny, rather than being forced to comply with one-size-fits-all policies from the federal government," he said in a statement.
The proposal filed by the Arizona Department of Environmental Quality in December 2016 consists of an interim operating strategy that takes effect on Dec. 5 this year and lasts through Dec. 31, 2025, and a final operating strategy that takes effect on Jan. 1, 2026. In April, the EPA proposed to find that the best available retrofit technology, or BART, alternative for the plant would provide greater reasonable progress toward natural visibility conditions than BART.
Salt River Project spokesman Scott Harelson said the finalized revision to the state implementation plan incorporated Salt River Project's Better-than-BART strategy for Coronado. The strategy allows Salt River Project to annually select a curtailment period for unit 1 based on emissions performance for that year.
The curtailment periods occur in the fall and winter months when plant emissions may be most impactful to visibility, Harelson said.
The revision also requires Salt River Project to make a decision in December 2022 whether to install SCR technology or close unit 1 by December 2025.
"The EPA Final Rule is important for [Salt River Project] customers and the state of Arizona as it reduces the plant's impact on regional haze while maintaining its ability to provide affordable and reliable power to our more than 1 million customers in the Valley," Harrelson said.