Brice said he will appear Tuesday in Rockingham County Superior Court to alert court officials that a settlement has been reached.

A byproduct of burning coal for the creation of electricity, coal ash is a veritable cocktail of toxic and carcinogenic materials, including elements of arsenic, hexavalent chromium, selenium, vanadium, and other toxic substances that can be harmful to human health, studies show.

After the spill, elevated levels of the chemicals were found in the Dan in violation of federal regulations, Brice said.

To put toxicity levels in perspective, Brice said the release of a single pound of arsenic into a waterway is enough to “trigger a violation” of federal guidelines. In the 2014 spill, Duke Energy released more than 3,500 pounds of arsenic into the Dan River, Brice said.

With their home less than a mile from the Duke facility, the Overbys saw firsthand what tons of toxic waste looks like — a thick gray sludge that settled ash on the river bottom some 70 miles downstream from the spill.

“You could see it in the water, you know, but I had no idea what it was at that time,’’ Overby said.