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The legal fight over the Montana Department of Environmental Quality’s approval of a central Montana copper mine made an appearance in the Montana Supreme Court Wednesday. During an hour-long hearing, justices dove deep into weedy regulatory issues focusing on the safety of storing mine tailings and how the mine is expected to influence water quality in Sheep Creek, a tributary of the Smith River.

The Black Butte Mine, which is expected to produce 14.5 million tons of high-grade copper over its 13-year operational life, is the focus of the lawsuit. After finishing a multi-year review and producing more than 90,000 pages of administrative records, the DEQ in April of 2020 approved Tintina’s application to move forward with the mine near White Sulphur Springs.

The mine has garnered support from Meagher and Broadwater county officials, who cite its job-creation potential and the property owner’s right to develop the mine. Conservation groups oppose the mine, arguing that Montana regulators shouldn’t treat the Black Butte project as a “guinea pig” for a mine design that’s been untested in this state and that mining operations could impair water quality in Sheep Creek and the Smith River.

DEQ and Tintina are asking the Montana Supreme Court to overturn a lower court’s finding that the state erred in its decision to approve the mine. They say the agency complied with state laws in its analysis of the proposed mine’s environmental impacts and properly evaluated the company’s plan to mitigate those impacts. They also argued that Katherine Bidegeray inappropriately substituted her discretion for the agency’s in the ruling she issued for the Meagher County District Court.

“DEQ gave the mine the most extensive analysis of any mine in Montana’s history,” Dale Schowengerdt, an attorney representing Tintina, told the justices Wednesday. “Literally their goal is to provide for the safest mine in Montana’s history.“

Schowengerdt also argued that the district court exceeded its role and “with respect to the district court,” the DEQ possesses more expertise in the environmental analyses at hand.

na Environmental Information Center, Earthworks and American Rivers countered that DEQ’s analysis of the project relied on an assumption that the mine tailings would remain stable and secure despite studies indicating that oxidation of the tailings would lead to acidification, which can impair surface water and groundwater. Tailings are what’s left over after the valuable material — copper in this case — has been separated from the ore body.

They also argued that Tintina’s water treatment plan doesn’t do enough to protect the water. More specifically, the conservation groups said the mine will produce nitrogen contents four to six times the allowable standard, which could exacerbate the oxygen-depleting algal blooms that the Smith already experiences.

As a result, DEQ has failed its statutory duties to uphold environmental protections, according to Jenny Harbine, an Earthjustice attorney representing the conservation groups in the lawsuit. For instance, the plaintiffs are skeptical that Tintina’s proposal to turn mine tailings into a “cement paste” — rather than leaving them in slurry form, the more commonly used approach to deal with tailings — will protect them from oxidation, acidification and “disaggregation.”

“It’s not enough to say that there’s a pretty good chance that this mine will operate as planned and environmental harm will be avoided,” said Harbine, citing high-profile tailings impoundment failures that inspired the Montana Legislature to write safeguards into statute when it passed the 1971 Metal Mine Reclamation Act. “That’s not what the statute requires, and that’s not good enough for the Smith River or its tributaries, which have irreplaceable values to Montana fisheries and residents alike.”

Tintina’s attorney countered that it is going above and beyond the standards in its application and that it shouldn’t be penalized for seeking an additional form of security for the tailings.

“It’s designed to withstand a doomsday catastrophe: a 1-in-10,000-year earthquake at the same time as a 1-in-10,000-year flood, followed immediately by a 1-in-100-year of snowpack melt,” Schowengerdt said. “The engineer of record for this mine concluded that the factor of safety for this mine is so high and so far exceeds what’s required that it’s not even necessary to analyze what’s going into the [tailings storage facility].”

Burt Hurwitz, an attorney for Meagher County, argued in his brief remarks that two things can be true at once in this case — that the DEQ arrived at protective standards for the Smith and its tributaries, and that the mine can operate in a safe, environmentally sound manner.

He also said the Montana Supreme Court has not heard a case that will have a “more direct and measurable impact” on the residents of Meaghers and Broadwater counties.

A ruling in favor of the conservation groups will uphold the district court’s decision to toss out Black Butte’s permit until DEQ completes a further review. A ruling in favor of Tintina and DEQ would reinstate Black Butte’s mining permit.

Editor’s Note: This story was updated June 21, 2023, to correct an error concerning the plaintiffs’ attorney’s name.