On Feb. 2, a Duke employee noticed a large sinkhole in the ash pond; engineers quickly determined that a 48-inch concrete storm pipe running underneath had ruptured. Researchers from Wake Forest University, who flew a remote-controlled drone over the plant weeks after the spill, estimated that as much as 20 million gallons of toxic slurry was forced through the hole in the pipe and out into the river on the first day alone.
That ash is now glued to the sides and bottom of the river and to low-hanging trees along it. Swaths of its banks are coated in thick, sooty black, with silvery sparkles catching the sunlight. Even brief contact with the sandy shore can leave glistening metallic traces on a hand.
It took Duke six days to plug the leak, delayed in part by high river levels and a large snowstorm that blasted the area days after the spill, according to a timeline provided by the North Carolina Department of Environment and Natural Resources (DENR). As scrutiny grew, the company acknowledged a second storm pipe had also ruptured; that one was plugged Feb. 19, though North Carolina officials said on Feb. 28 that the plug in the smaller drain was still not entirely set. The ash lined 70 miles of the riverbed, in some places up to five feet deep, the U.S. Fish and Wildlife Service told reporters.
Environmental advocates believe that the ash and toxic chemicals may have been leaking for years before the spill was discovered — and are likely still leaching into the river from several other locations.
On Friday, North Carolina officials notified the company that it had failed to apply for proper wastewater permits and properly maintain the ash pond, and recommended fines. That day, regulators announced the discovery of a gallon-per-minute leak of emergency drainage from a Duke Energy plant near Asheville, N.C.
Reached for comment Friday, Duke Energy spokesman Tom Williams said all the leaks at the Dan River site have been plugged. He denied that any further spillage continued there.