BILLINGS (AP) – The U.S. Interior Department should not have approved the expansion of a southeastern Montana coal mine without taking a closer look at its effect on the environment, a federal judge said Oct. 26 about a lawsuit arguing the government ignored coal’s contributions to climate change.

Environmental groups sued the Interior Department after it approved an expansion of the Spring Creek Coal mine in 2012. The case marks the second time conservationists have used worries over climate change to successfully challenge approval of a coal mine after it had been granted.

But unlike in the previous case involving Colorado mines, U.S. Magistrate Judge Carolyn Ostby did not explicitly name climate change as a factor in her decision. She referred more broadly to air quality and environmental concerns, saying the government had failed to explain its thinking on the issue before granting approval and failed to seek public input.

Ostby said work at the mine near Decker, Mont. will not be shut down immediately. Rather, the judge recommended that federal officials reconsider the environmental effects of the expansion by Wyoming-based Cloud Peak Energy. The mine, which employs about 260 people, is allowed to continue operating in the meantime.

The judge gave the government 180 days to complete its analysis and get public comment before the mine’s approval would be vacated. U.S. District Judge Susan Watters will have the final decision.

The 2,042-acre expansion of the Spring Creek Coal mine added 117 million tons of coal that could be mined, which would allow it to operate through at least 2022, according to court documents. Mining on those parcels already has begun.

Spokesman Rick Curtsinger said the company was disappointed in the judge’s decision and planned to work with federal officials to defend the expansion.

“Spring Creek Mine is an important part of America’s energy supply and Montana’s economy,” Curtsinger said.

The Interior Department’s Office of Surface Mining and Reclamation is the lead defendant in the case. The agency was reviewing the judge’s recommendations, spokesman Christopher Holmes said.

A similar case in which federal officials reconsidered mining plans that were already approved involved the Colowyo and the Trapper mines, both in Colorado. After a re-examination of the Colowyo mine, Interior officials determined that burning coal to produce electricity there had “insignificant impacts” on national greenhouse gas emissions and moderate effects on emissions in Colorado.

A plaintiff in both cases, New Mexico-based WildEarth Guardians, has mounted an aggressive legal campaign against the coal industry in recent years, challenging decisions affecting 11 mines in five states through a spate of lawsuits.

A decision is pending in a case involving the San Juan coal mine in New Mexico. In September, lawyers for the group contested federal approval of mine plans and coal leases in four states: the Antelope and Black Thunder mines in Wyoming’s Powder River Basin, the El Segundo Mine in New Mexico, the Bowie No. 2 Mine in Colorado and the Skyline Mine in Utah.

WildEarth Guardians’ Jeremy Nichols said Ostby’s recommendation offers “another solid sign that Interior’s coal program is completely off the rails.

“The greenhouse gas emissions do matter, and they need to come up with solutions to limit those emissions,” Nichols said. “In the long term, that’s going to mean keeping coal in the ground.”

Cloud Peak mined more than 17 million tons of coal from Spring Creek last year, including about 4 million tons exported to Asian markets though ports in British Columbia, according to the company’s regulatory filings.

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