As usual, sedimentary deposits tell the tale:
"Our results clearly indicate the presence of coal ash at the bottom of Sutton Lake and suggest there have been multiple coal ash spills into the lake from adjacent coal ash storage facilities after, and even before, floodwaters from Hurricane Florence caused major flooding in 2018," said Avner Vengosh, professor of geochemistry and water quality at Duke University’s Nicholas School of the Environment, who led the research.
According to Vengosh and his colleagues from Duke and Appalachian State University, the amount of contaminants was more than what was found in streams following major coal ash spills in Kingston, Tennessee in 2008 and the Dan River in North Carolina in 2014.
Of course Duke Energy is spouting denials and rationalizations left and right, but Avner knows his stuff. This isn't an environmental advocacy org speaking, it's pure science: