With 92% of Coal Ash Still Coating North Carolina River Bed, Duke Energy Declares Cleanup Complete

River coal ash leak
Coal ash is a heavy metal-laden and possibly radioactive by-product of coal plants. N.C. Department of Environment and Natural Resources via YouTube.com

Last February, around 39,000 tons of toxic coal slurry gushed into a major North Carolina river. Now, having cleaned up around 3,000 tons worth, the company behind the spill and state regulators say their work is done.

With 92 percent of the original heavy metal-laden and possibly radioactive coal ash still coating 70 miles of river bottom, river advocates are frustrated.

"This stuff is not just going to go to the bottom and stay there and not harm the environment," Brian Williams of the Dan River Basin Association told the Charlotte Observer. "It will be an issue for many, many years to come."

Duke Energy and state regulators say they will continue to patrol the river to find and test deposits of sediment and ash, but that it could "do more damage trying to remove all the ash than leaving it in place," said Dianne Reid, water sciences chief for the NC Division of Water Resources, told the Observer. Continuing to dredge the river would stir up the sediment on the bottom, risking the release of more preexisting toxins, like mercury and PCBs, into the water column, the state argues. The situation highlights the difficulty of remediation in river environments--once a spill happens, rehabilitating the environment is a delicate and arduous task.

Most of the coal ash is now buried under a layer of sediment. But river advocates and scientists say that doesn't mean it will always stay there. Under certain circumnstances, like major storm or during warmer weather, metals covered by sediment can be re-released into the water column, be eaten by organisms, and work their way up the food chain.

The Dan River is especially prone to that type of re-mixing, because of surges of water released from a hydroelectric dam located upstream, according to Williams.

Arsenic is among the contaminants of concern from the Duke Energy spill; a few weeks after the original coal ash pond collapsed, causing the release into the river, regulators released video of another Duke Energy pipe leaking arsenic-laden water into the river.

Federal prosecutors launched a criminal investigation of the NC Department of Environment and Natural Resources following the spill, amid questions of lax regulatory enforcement.