Two energy companies demanding the continued operation of a coal-fired power plant in Colstrip are asking the U.S. Supreme Court to block the implementation of a federal emissions standard.
Talen Montana and NorthWestern Energy this week asked the Supreme Court to stop a rule issued by the U.S. Environmental Protection Agency in April. to limit the release of air pollutants from coal combustion to generate electricity.
The companies argue that complying with the EPA rule, combined with another rule to limit climate-warming carbon dioxide emissions, would lead to the plant’s closure.
“These two rules – taken together – impose an unbearable burden on Colstrip,” the complaint says, adding that Talen, the plant’s operator, and NorthWestern Energy, which owns the plant along with utilities in Washington and Oregon that are moving away from coal-fired power, face a “tough choice.”
NorthWestern and Talen wrote that they could shut down the plant by July 2027 or invest $350 million to meet mercury and air pollutant limits. Even if the companies upgrade Colstrip, they said they would be forced to close the plant by 2031, when greenhouse gas limits take effect.
“Any decision is irreversible and has serious consequences for Colstrip, its owners and Montana,” the appeal states. “Without a stay of the final ruling, Colstrip’s owners are forced to make this decision without knowing the full circumstances. … Colstrip’s future should not depend on a hasty decision-making process while this case is pending. A stay can avoid potentially catastrophic consequences.”
The companies argue that closing Colstrip, which they say is the largest coal-fired power plant west of the Mississippi, will threaten grid reliability and increase costs for Northwestern Energy’s hundreds of thousands of customers. While the required cost of the MATS upgrade is estimated at $350 million, according to the filing, Talen previously suggested the cost could exceed $600 million.
The companies are asking the Supreme Court to stay the MATS rule while a lower court examines the merits of the numerous lawsuits brought by states and industry groups.
Environmental and health groups support the EPA’s new emissions standards, calling them long overdue and designed to protect Montana residents who live near and downwind of Colstrip.
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In an email to the Montana Free Press, Anne Hedges, co-director of the Montana Environmental Information Center, called NorthWestern and Talen “shameless.”
“They use outdated technology to prevent toxic air pollution instead of adhering to industry standards. They whine about having to do what every other similar facility has already done to protect the public from lead, arsenic and other harmful pollutants,” she wrote. “They should have installed the technology decades ago when it was cheaper, but they have chosen profits over public health.”
NorthWestern and Talen argue in their complaint that the expected public health benefits of the stricter standard are small and that the existing standard is well within the human and environmental health agency’s safety margin. They claim the plant has been in compliance with the existing standard for “filterable particulate matter” — soot — since a 2018 incident that was remedied after a plant upgrade.
“Colstrip’s future should not depend on a hasty decision-making process while this case is pending. A delay can avoid potentially catastrophic consequences.”
Colstrip operator Talen and co-owner NorthWestern Energy
These arguments are not understandable to Robert Byron, a retired internist who is involved with Montana Health Professionals for a Healthy Climate. Byron said the MATS rule is based on science and will provide “almost immediate health benefits” to surrounding communities.
Reducing heavy metals such as the neurotoxin mercury and the carcinogen arsenic should be a public health priority, Byron said, adding that particulate matter exposure has been linked to strokes, heart attacks and negative outcomes for pregnant mothers and their young children.
“We didn’t used to know much about the impact of air pollutants on human health. Now there is clear evidence of it, and if we can do something about it, we should do it rather than just ignore it for profit,” Byron said.
The Montana Department of Justice has joined 22 other Republican states and a coalition of energy and mining associations in calling for a stay of the MATS rule in a separate Supreme Court case.
In their motion, the states argue that the EPA estimated the likely cost of complying with the rule – $860 million – without demonstrating “whether any public health benefits would result.”
The uncertainty surrounding the MATS and greenhouse gas rules has also translated into uncertainty about the plant’s ownership. Late last month, NorthWestern announced an agreement with Puget Sound Energy, a Washington-based utility, to acquire its share of Colstrip’s power generation effective Jan. 1, 2026. With this increased ownership comes a larger share of the expenses associated with maintaining the nearly 40-year-old plant.
