UpdatedMon, Apr 26, 2021 at 3:34 pm ET Reply On April 23, this muddy, claylike substance was photographed on the bank of Marsh Creek Lake as the photographer said it was 'seeping up from the ground.' (Ginny Kerslake) CHESTER COUNTY, PA — The Department of Environmental Protection on Earth Day sent investigators to Marsh Creek Lake to collect samples of an unidentified substance reported on the banks of the lake. A DEP spokesperson said the department has taken samples of gray muddy clay deposits showing up in Marsh Creek Lake near the site of a more than 8,000-gallon drilling fluid spill into the wetlands in August 2020. Sunoco's Mariner East 2 pipeline construction was halted after the accident, and an effort has been ongoing to reroute the pipeline around the state parklands. Read that report from August 2020 here.