Environmental law firm Earthjustice, on behalf of the conservation groups High Country Citizens’ Alliance and WildEarth Guardians, filed a suit in federal court Wednesday to overturn Bureau of Land Management and US Forest Service decisions authorizing leasing and exploration in the western Colorado forest.

“Protecting our public forests is good for wildlife, for recreation, for clean water and our economy,” Earthjustice attorney Ted Zukoski said.

“Bulldozing roads and scraping well pads for coal exploration and mining will significantly degrade these values to benefit a dirty fuel source.”

The BLM announced last week it had approved the Sunset Trail area coal exploration plan, submitted by Ark Land Co on behalf of Mountain Coal Co. Both are subsidiaries of Arch Coal.

“Current reserves at the West Elk mine are estimated to last nine to 11 years,” BLM said in the announcement.

“Exploration will provide additional data regarding the amount and quality of coal.

“The data is used to determine whether any additional mineable reserves are in the lease modification areas within the federal coal lease boundaries.”

The exploration plan will be conducted in 2013-14 and involve drilling 10 wells to collect core samples within the lease area.

Road upgrades needed to get a drilling rig into the area will take about two weeks to build, following which construction, drilling and reclamation activities will begin and are expected to take an average of 16 days per well.

The BLM said it had limited disturbance to about half an acre.

The groups are seeking a temporary restraining order to prevent Arch from conducting the exploration, which could begin as early as next week.

The groups’ lawsuit challenges the BLM and Forest Service on a number of grounds, including that the agencies failed to analyze and assess air pollution impacts and impacts to the Sunset roadless area.

“The Sunset roadless area is a 5800-acre area of undeveloped aspen and spruce forests, beaver ponds and streams that hugs the west flank of 12,700-foot Mount Gunnison and the West Elk Wilderness in western Colorado,” the groups said in the suit.

“These roadless lands, managed by the US Forest Service, are home to elk, black bear and goshawk and is enjoyed by hunters and hikers.”

The suit also challenges the validity of the Colorado Roadless Rule, which exempted roadless areas in the North Fork Valley of Colorado from protection.

“Absent adoption of the Colorado Roadless Rule, the Forest Service could not have adopted a decision authorizing road construction for the West Elk mine in the Sunset roadless area.”

The West Elk longwall mine sold 5.7 million tons of thermal coal in 2011, according to the company’s website.