Massey Energy which was cited in the lawsuit was taken over by Alpha in a $US7.1 billion acquisition.

The deal was reportedly struck in the days leading up to a trial scheduled to begin June 12.

Though the confidential terms of the agreement prohibited Alpha spokespersons or negotiating parties from sharing details about the settlement, plaintiffs’ attorney Roger Decanio told the Associated Press that “the fact that we were there to pick a jury” probably helped seal the deal for the local residents.

“There's an old saying in this field that if both parties walk out and neither is happy nor completely sad, then it's a good deal,” he was quoted as saying.

“I think that's probably the best description.”

Following complaints that slurry from Massey operations caused discolored, foul-smelling water and community health problems, Decanio consolidated 155 medical monitoring lawsuits involving about 350 people.

While state environmental officials said they found no link between slurry disposal and contaminated water, West Virginia’s State Journal reported that West Virginia University research found government environmental monitoring standards inadequate.

The legal action compounded Alpha’s environmental woes in the Appalachian state where a another lawsuit was filed in May regarding possibly illegal water toxicity levels due to mining activities in Boone and Raleigh counties.

Both counts of litigation involve slurry discharges including underground injection of liquid coal waste in Boone County and Raleigh County’s billion-gallon Bushy Fork slurry impoundment which the Sierra Club described as “the largest earthen dam in the western hemisphere.”