CHESTER COUNTY, Pa. - Thousands of gallons of drilling mud spilled into a lake in Chester County from the controversial Mariner East pipeline project, according to the DEP.Boating on the 500-acre Marsh Creek Lake in Chester County is scenic and relaxing but not far from the boat launch at the busy state park, buoys float warning of danger from a spill worrying those who come here for the beauty."I’m very concerned that something as beautiful and this would be damaged like it’s being damaged," one resident said.Thirty acres of the lake used as drinking water locally are off-limits after 8,100 gallons of “drilling mud” spilled Monday from a nearby construction site of the controversial Mariner East pipeline.Environmental activist Ginny.