DEP spokesman John Poister said the agency doesn't want to comment until it can carefully review the lawsuit.
Among other things, the lawsuit contends that runoff and other pollution from the mining is fouling the South Fork Tenmile Creek, along with other Monongahela tributaries.
The South Fork is designated by the DEP as a "high quality warm water fishery" upstream of the mine and a "warm water fishery" below the mine. But the lawsuit contends the DEP's 2012 Draft Water Quality Monitoring Report lists the South Fork as "impaired and not attaining its aquatic life use."
"As an already impaired water body, it is essentially that no further strain from industrial and other pollutants be placed on the South Fork," the lawsuit said.