A coalition of conservation groups sued the federal government Wednesday to keep a proposed natural gas pipeline out of three roadless areas on national forest land near the town of Silt, 185 mi west of Denver.

The environmental groups say a 100-ft-wide construction corridor for the Bull Mountain pipeline violates the 2001 federal roadless rule, a policy that limits road building on designated public lands.

The U.S. Forest Service and Bureau of Land Management approved the 25.5-mi peipeine route in January. It would cross the 120,000-acre Clear Fork Divide roadless area, which connects the Grand and Battlement mesas to the West Elk Mountains.

The proposed route would follow a 1980s-era pipeline and connect to existing underground pipelines on its way north to merge with a main gas pipeline along Interstate 70. The route approved by the federal agencies cuts through eight mi of the Clear Creek, East Willow and Baldy Mountain roadless areas.