Expansion plans that will double the size of the Bull Mountain coal mine in Montana were unanimously approved by the state’s land board. The expansion of the state-owned property will allow Signal Peak Energy to add nine years of life to the underground coal mine, the Missoulian reported.

The expansion plan covers about 7,160 acres which includes 640 acres of state coal reserves. Officials said it would bring in $127.2 million from taxes and royalties.

Opponents asked the board to reject the plan in part because of pollution that will be generated from burning the coal. Board member Attorney General Tim Fox countered the opposition by citing the mine's positive contributions to the local economy.

"Those 325 people who work at Bull Mountain combined make about $40 million a year," Fox said. "That's money that is spent in local stores and is important to the economy."

Elected officials from Musselshell County and representatives of the coal industry had urged approval.

The state Department of Environmental Quality signed off on the mine expansion last October. The federal Bureau of Land Management approved the leasing of federal coal reserves involved in the expansion in 2012.

Signal Peak produced 8.7 million tons of coal from the mine last year.

The Land Board is also composed of Gov. Steve Bullock, Fox, Secretary of State Linda McCullough, State Auditor Monica Lindeen and State Superintendent of Public Instruction Denise Juneau.