FARMINGTON — A federal judge in Colorado said that health dangers posed by coal mining are too great to allow a planned expansion of strip mining at the Navajo Mine.

On Tuesday, U.S. District Judge John L. Kane ruled that the proposed expansion of 714 acres at the 13,000-acre Navajo Mine violates the National Environmental Policy Act, or NEPA.

The ruling cited concerns over toxic mercury pollution caused by burning coal at the Four Corners Power Plant, which burns coal exclusively from the Navajo Mine, located 15 miles southwest of Farmington.

In 2012, Navajo and environmental groups sued the federal Office of Surface Mining, Reclamation and Enforcement over the plan, which would have allowed strip mining of 12.7 million tons of coal.

"Enough is enough. It is time to move beyond coal and invest in clean energy for the sake of our communities and future generations," said Colleen Cooley of Diné CARE in a press release issued Wednesday. "The Diné people who reside near the power plant and Navajo Mine have suffered the burden of coal impacts for far too long. This is our home, and we cannot just move away from our communities, so we are grateful that the court rejected this plan."

Each year, the Navajo Mine can produce around 8 million tons of coal, reaping $41 million annually for the Navajo Nation. Tribal President Ben Shelly signed a 2013 resolution to buy the mine for $85 million from BHP Billiton.

Mike Eisenfeld of the San Juan Citizens Alliance, a Durango, Colo.-based nonprofit organization concerned with regional environmental issues, said he hopes the OSM deepens its analysis of the environmental and health impacts posed by coal mining in the wake of the court ruling.