The US Environmental Protection Agency (EPA) has revoked a permit for the mountaintop-removal of one of the largest coal mining projects in West Virginia.

The agency said that Mingo Logan Coal’s Spruce No 1 coal mine would lead to unhealthy levels of salinity and toxic levels of selenium.

The permit for the 9.3 million square meter operation has been revoked under Section 404 of the Clean Water Act.

The EPA’s decision could affect dozens of other mining projects across Appalachia, where firms have been blasting the peaks off mountains for years to reach coal, reports the Washington Post.