A U.S. Forest Service hearings officer ruled that a decision to allow a 690 ha (1,700-acre) expansion of the West Elk Coal Mine in Gunnison County, CO did not adequately address endangered species and geological risks, thus blocking the expansion of the West Elk coal mine.

An environmental assessment of the mine expansion by Grand Mesa Uncompahgre and Gunnison National Forest staff had determined that there were no adverse impacts from the proposed expansion. However, that assessment was challenged by environmental groups represented by the environmental law service Earthjustice, the Denver Post reported.

A review by the service’s regional office found the assessment was inadequate and failed to explain why some restrictions in the original lease were modified, said Steve Segin, a forest service spokesman.

The modifications weakened protections for for lynx, bald eagles, and measures to prevent landslides, said Ted Zukoski, an Earthjustice attorney.

The assessment is being sent back to the Montrose office for revisions, Segin said.

About 566 ha (1,400 acres) — more than 80 percent of the expansion — would be in the Sunset Roadless Area and the development would include 48 well pads and 10.5 km (6.5 miles) of road into roadless lands.

The West Elk Mine is operated by St. Louis-based Arch Coal Inc. In 2011, the West Elk Mine was the second largest coal producer in the state with 5.4 Mt (6 million st) of coal. Peabody Energy’s Twentymile Mine, in Routt County, was the biggest producer with 7 Mt (7.7 million st), according to state mining data.

Arch recently invested $29 million in new coal processing facilities in Colorado.