Regulators continue to probe dam breach at Duke Energy's coastal plant

Duke Energy says the breach of a cooling pond adjacent to coal ash basins along the Cape Fear River has not impacted water quality, but environmental groups and state regulators say they're doing their own testing for potential hazards in the wake of Hurricane Florence.

The energy company announced Friday that the dam at its Sutton Plant near Wilmington breached in several places as the swollen river inundated Sutton Lake. The lake is used as a cooling reservoir and does not store coal ash, but it's separated from two decades-old ash ponds by less than 200 feet in some places, as well as an unfinished landfill storing excavated ash from the basins.

The landfill breached a week earlier, when Florence's torrential rainfall was still pounding the southeastern part of the state. About 2,000 cubic yards of soil, water and ash – enough to fill two-thirds of an Olympic-sized pool – escaped the impoundment and into a perimeter ditch, but the company did not know how much of it entered Sutton Lake.

Coal ash is the byproduct of coal power production and contains heavy metals like mercury and arsenic.

The Cape Fear Public Utility Authority, which supplies water to 200,000 residents in the Wilmington area, said there's no threat to the quality of treated water, since the intake for its treatment plant is located 20 miles away.

Test results show 'no harm'

Duke Energy said several days of sampling up- and downstream of the site shows little impact on the river's water quality. The company used a state-certified lab to test for 17 different contaminants. Ten had regulatory water quality standards, and none of them were exceeded.

"Those samples tell us there's no harm to the Cape Fear River from the release from the cooling pond," Duke Energy spokesperson Paige Sheehan said.

At a press conference on Monday, DEQ Secretary Michael Regan said staff from three divisions of the agency – along with the EPA – were on site sampling water, examining dam safety and looking at the integrity of the ash landfill.

The agency expects water sampling results to be available by the end of the week, DEQ spokesperson Bridget Munger said.

Environmental advocates are also waiting on results of sampling gathered as they inspected the area near the Sutton Plant over the weekend. Pete Harrison, a staff attorney with EarthJustice who was on the site with others from the Waterkeeper Alliance Friday, said he still has questions about the company's test results so far.

Duke Energy's initial battery of tests did not include boron or sulfate, which company spokespeople have in the past called common tracers of coal ash. Both are among the three-dozen materials the state Department of Environmental Quality tests for through groundwater monitoring near the plant.

Testing for either of those contaminants, Sheehan said Monday, wouldn't provide much information. She said sulfates are common and can have multiple sources. And testing for boron could yield false positives because it's present in salt water and might be found in the brackish river, still under the tidal influence of the nearby sea.

"I've never heard them even mention this issue at that site," Harrison said. "They've done water quality monitoring at that site for years and they've included boron."

Monday evening, Duke did release separate sampling results for a single site downstream of the dam breach that included a test for boron, which couldn't be detected in the samples. Those results did not include a test for sulfate.

Skepticism from environmental groups

Harrison said the comparison of Duke Energy's testing from up and downstream shows potential areas for concern.

"If you do look at these results and give them the benefit of the doubt that these are legitimate sample locations, you do see several parameters that have pretty consistent and substantial differences," Harrison said.

He's particularly wary of the suspended solids showing up in the river below the lake. Sampling shows they more than doubled on some days compared to results upstream, even though the concentration of suspended solids is still less than one-third the permitted limit. But Harrison said that could cause problems downstream if the solids contain coal ash laced with heavy metals, which could leach out over time.

"It's really complicated chemistry going on out there," Harrison said.

Just how much coal ash made it into Sutton Lake – or the Cape Fear River – is hard to say.

Video captured by the Waterkeeper Alliance shows a layer of light gray muck on the surface of the flooded river, which environmental groups point to as evidence of coal ash contamination. It could have originated from the breach of the landfill or the flooding of a separate 50-year-old, vegetation-covered ash dump on site that flooded during the storm.

Duke Energy says this floating scum is made up of "cenospheres" – light, hollow beads that are among the byproducts of burning coal.

"The advocacy groups refer to them as coal ash. We do not," Sheehan said. "Neither does EPA."

A similar debate emerged after Hurricane Matthew, when a dam breach at the company's Lee Plant near Goldsboro released a truck-sized load of coal ash into the Neuse River.

Sheehan said cenospheres are inert and harmless.

But an analysis from samples environmental groups took after Matthew showed otherwise, Harrison said.

"They are caked with the same toxic heavy metals you worry about with any coal ash particle," Harrison said. "It's an extremely misleading argument."

Sheehan acknowledged that the company manages cenospheres like they do coal ash, and the release of the lightweight material may be responsible for the slight increase in contaminants like arsenic downstream of the plant. But she reiterated that water quality levels are still well below permitted concentrations and accused critics of fearmongering.

"The water testing is really the key," Sheehan said. "If it does not show harm, that's really what we need to go by."

As for the breached dam, she said crews will focus on repairing the south side of the cooling pond to stop the escape of water into the river, now that the flooding is beginning to subside.

She said the site is relatively stable, and the breaches in Sutton Lake have been relatively unchanged since the weekend. Duke Energy crews have already begun inspecting the natural gas plant shut down last week as floodwaters rose, eventually leaving 12 inches of water in the facility.

When the Cape Fear River is finally back in its banks, Harrison said, Duke will also need to monitor the water quality of Sutton Lake, which remains a public recreation area.

"It seems to me Duke will have a very substantial cleanup effort on its hands," he said.

WRAL statehouse reporter Travis Fain contributed to this report.

Editor's note: Earlier in the week DEQ said they expect test results from the water quality sampling at the Sutton plant to be available Wednesday. The agency said Wednesday morning that the results should actually be available Thursday or Friday. The story has been updated to reflect the new information.