A damaged drainage pipe has been leaking toxic coal ash into a North Carolina river for at least four days as workers continue to try and repair the breach. According to Duke Energy, around 82,000 tons of coal-ash slurry have leaked into the Dan's River, along with 27 million gallons of contaminated water.

Coal ash is the leftover residue from burning coal, and it is highly toxic, containing lead, mercury, selenium, and arsenic, among others. The gray toxic sludge is reportedly inches deep and coating the riverbank for at least a couple of miles. One anecdote from The Charlotte Observer: "A woman dipped her hand into the water and it came out coated slate gray."

Environmental regulators said that they were testing the water for at least 28 different chemicals. Five towns downstream from the leak that get their drinking water from the river have been filtering it and deemed it safe to use. Duke Energy's own tests said that the levels of lead, arsenic and selenium were below two parts per billion, below EPA regulations. Disputing that, The Waterkeeper Alliance measured arsenic levels ten times higher than Duke's readings.

The plant ceased coal-burning in 2012, but ash ponds from many of Duke's coal-burning plants still remain. There are currently no regulations about how to handle or dispose of coal ash.