The operation, which mines 6 million tonnes of coal per annum, has already received federal environmental clearance to incorporate 1700 acres of additional property holding some 10Mt of recoverable coal.

The administrative appeal filed by Earthjustice on behalf of a group of environmental activists asserts that the mine expansion violates laws meant to protect wildlife, air quality and forest lands.

The action follows two environmental grants for the expansion from the US Forest Services, one of which was overturned on grounds that the approval failed to explain landslide risks and weakened protections for lynx and bald eagles.

In June, the US Bureau of Land Management decided West Elk expansion would have no significant environmental impacts and identified more than 83,000 acres in the area suitable for further leasing consideration.

Earthjustice said Arch’s plan to bulldoze 6.5 miles of road and add 48 natural gas drilling pads in the area would turn a scenic area adjacent to the West Elk Wilderness into an industrial zone.

“The Sunset roadless area is a real gem, a beautiful forest of aspen and giant spruce, beaver lodges and meadows, a home for elk and bear,” Earthjustice staff attorney Ted Zukoski said.

“This is a place the Forest Service should be protecting for all Coloradoans, not sacrificing to appease special interests.”

The conservationists said loopholes in Colorado law made the state’s environmental protection for roadless areas particularly vulnerable to industrial development.

For its part, Arch has maintained a consistently positive reputation for environmental responsibility at West Elk, which has operated for more than 12 years without a state environment violation.

As recently as March 2012, the mine received an environmental excellence award from the state reclamation, mining and safety division.

Since 2000, West Elk has won 17 pollution prevention and reclamation awards.