The three-judge panel ruled unanimously that land bureau officials “acted reasonably” in considering whether more Antelope Coal mining would affect pollution levels in the basin or greenhouse gas emissions before agreeing to open lands adjacent to the company’s existing mine near Douglas, Wyo.

The ruling clears the way for Cloud Peak to expand operations at its Antelope facility, one of the nation’s top-producing mines. The company sought permission from the U.S. Department of Interior to extract a further 430 million tons of coal from areas adjacent to the existing site, which houses the world’s top deposits of low-sulfur subbituminous coal for electric power generation.