— A state judge on Monday questioned why environmental regulators granted permits for Duke Energy to dump coal ash from its power plants into open-pit clay mines in Chatham and Lee counties.

The state Department of Environmental Quality in June approved the sites to accept coal ash as "engineered structural fill." Duke started moving ash to the Brickhaven mine near Moncure in October and is expected to start dumping ash at the Colon site near Sanford next year.

Coal ash is the material left after coal is burned for fuel. While the bulk of it is inert, it does contain heavy metals and other toxins, including arsenic, chromium, selenium and mercury, that can harm fish, wildlife and people.

After a ruptured stormwater line under an ash pit in Eden dumped tons of sludge into the Dan River last year, lawmakers ordered Duke to close all of its ash pits statewide by 2029 and created a state commission to oversee the process.

"This is just one step of many over many years that will be taken to take care of the entire problem," Edward Mussler, solid waste permitting supervisor of DEQ's Division of Waste Management, said of burying ash in the clay mines.

Chatham Citizens Against Coal Ash Dump and Blue Ridge Environmental Defense League challenged the legality of the state permits, arguing that the clay mines are more akin to solid waste landfills than mine reclamation projects and should meet the stiffer design, construction and operational regulations of a landfill.

"It will affect the community with their wells and the property values," Sanford resident Keely Puricz said Monday. "Who wants to be living next to a five-story toxic dump? That’s what it is. Let’s call it what it is. It is a dump."

"We know that the people living near the site have seen these clouds of coal ash. When they dump it, there’s coal ash in the air," Moncure resident Judy Hogan said.

Administrative Law Judge Melissa Owens Lassiter said she needs more information on why the state granted permission for ash to be put in the mines as a "beneficial use," saying she wants to know what that benefit is expected to be.

DEQ officials said the ash will fill the mines, leveling the ground so it could be developed later. Officials also disputed environmentalists' claims that the ash would pollute the water and air nearby.

"It would provide a nice, open space. It is designed where somebody could build something on top of it," Mussler said.

The groups say that nothing can be built on top of the mines because of the need for lines to contain the ash and because of the grade of the sites above the surrounding land.

The hearing is expected to continue Tuesday, and there is no timetable for Lassister to issue a ruling in the case.