In a notice sent Wednesday to Deseret Power President and CEO Kimball Rasmussen, WildEarth Guardians and the tribe said they will go to court over what they say are 35,000 ongoing federal Clean Air Act violations at Bonanza.
The 30-year-old plant generates 500-megawatts of electricity on the reservation in northeastern Utah near the Colorado line, and it spews more than 3.5 million of tons of air pollution from a 600-foot smokestack, according to the critics.
Rasmussen had no comment about the threatened suit.
And the U.S. Environmental Protection Agency, which has oversight responsibility for pollution on the reservation, was not prepared Wednesday to discuss violations at the plantif there are any.
However, Carl Daly in the EPA's Denver regional office noted that his agency is currently reviewing Deseret's over-arching air-quality permit, one that would require the plant to comply with a variety of monitoring and reporting standards.
"It hasn't been finalized yet," Daly said. "It's been on hold."
Jeremy Nichols, with WildEarth Guardians, noted that the Uinta Basin has been struggling with wintertime smog in recent years, bucking the conventional wisdom about what is normally a summer pollution problem by logging some of the nation's highest ozone levels in the nation in two of the past three years.
"We're honored to be able to work side by side with the Ute tribe to rein in this rogue coal-fired power plant," said Nichols. "With air pollution on the rise, we need relief, we need clean-air solutions."
Ground-level ozone can trigger asthma, scar lungs and cause premature death, and many suspect emissions from the region's booming oil and gas industry are playing a role.
Meanwhile, controlling emissions from the Bonanza plant, which adds nitrogen oxides that are key to creating ozone pollution, are also important in addressing overall pollution in the basin, the tribe and the environmental group say.