US District Judge Robert Chambers ruled that the Elk Run coal mine in Boone County and the Alex Energy mine in Nicholas County, both owned by Alpha Natural Resources, caused irrefutable harm to aquatic life and river ecosystems as a whole.

Chambers wrote that aquatic life in the streams plummeted after being “unquestionably biologically impaired”

Penalties are yet to be determined.

Environmental groups praised the decision, calling it the first Federal Court ruling acknowledging damage from high conductivity discharges.

Conductivity is the water’s ability to transfer electricity. High conductivity often signals the presence of pollutants including chloride, phosphate and nitrate.

An Alpha spokesman confirmed the company’s plan to appeal the court’s decision.

Since the case began in 2012, environmental groups, such as Sierra Club, have been quick to slam Alpha and the mountaintop mining methods.

Each of the three plaintiffs was reported to be pleased with the judge’s ruling.

“This decision will force mining companies to internalise the enormous treatment costs that they are currently avoiding and imposing on the public," co-counsel in the case and Public Justice environmental enforcement director Jim Hecker told local media.

The true extent of the victory will be seen when penalties are issued at a later date.