Judge John Kane ruled that the planned expansion does not comply with the National Environmental Policy Act (NEPA), and would create toxic mercury pollution from burning the mined coal at Four Corners Power Plant.
Western Environmental Law Center’s Shiloh Hernandez said: "The court’s ruling now gives OSM the opportunity to tell the whole truth about coal impacts and to rectify the legacy of pollution from the Navajo Mine and Four Corners complex."
The Four Corners Power Plant, which sources coal exclusively from the Navajo mine, provides electricity to California, Arizona, New Mexico and Texas.
Navajo Transitional Energy, a wholly-owned liability company of the Navajo Nation, had filed an application with Office of Surface Mining Reclamation and Enforcement (OSMRE) for the planned expansion project in 2012.
OSMRE carried out environmental review and approved the project.
The local conservation groups opposed the project, which would allow strip-mining of 12.7 million tons of coal, and initiated legal proceedings against OSMRE for approving the expansion.
San Juan Citizens Alliance’s Mike Eisenfeld said: "With this decision, we hope OSM seizes the opportunity to address the legacy of pollution from the Navajo Mine and Four Corners Power Plant."