Duke Energy’s assurance that the Cape Fear River is not contaminated by coal ash is being met with skepticism from some scientists.
They say that the Charlotte-based power company’s limited sample of surface water — in two locations daily since Sept. 18 — is not enough to produce valid test results.
Doubts about the value of Duke’s testing are coming in advance of Cape Fear River test results expected Friday from the N.C. Department of Environmental Quality. The agency tested the water and sediment in the river over several days, starting Sept. 20. The agency says it will continue taking daily samples for the foreseeable future.
Two scientists with expertise in water quality told The N&O that the most important testing for coal ash would analyze river-bottom sediment, where coal ash residue is most likely to be found.
“The reality is the drip drip drip of those places matter most,” said David Buchwalter, a professor of environmental toxicology at N.C. State University. “If they (the heavy metals) don’t get buried, they’ll make their way downstream.”
Coal ash, the byproduct of burning coal in power plants for decades, is not listed as a hazardous waste by the Environmental Protection Agency. But it contains elements, such as mercury, arsenic and selenium, that are considered toxic in high concentrations and over a prolonged period of time. The elements in coal ash don’t break down or die like sewage or bacteria, but could enter the food chain, and work their way up through fish and eventually into human beings, potentially increasing the risk of cancer and reproductive problems.
Duke Energy officials said Sunday, the company had tested the waters of the Cape Fear River where the flooded Sutton Lake was breached and also one mile downstream from a coal ash pond that had flooded at the L.V. Sutton power plant in Wilmington. It’s not clear at this point if any ash flowed out with flood waters and moved downstream, because the coal ash is still covered by water, but Duke said that the water samples show that the presence of ash in the river was negligible and it was not harming the quality of the water.
Duke spokeswoman Paige Sheehan said the company has prepared a long-term water quality testing plan for review by the N.C. Department of Environmental Quality.
“These were initial test results that we wanted to share with the public,” Sheehan said of the water tests. “The water entered at the top and came back out. We don’t believe it displaced ash.”
As seen from Duke’s test results, elements contained in ash increased only slightly day by day in the Cape Fear River. Over several days, however, Duke’s lab results show that the presence of some elements, like aluminum, chromium, copper and silicon, doubled and tripled in the river.
Duke’s approach to testing for coal ash can be contrasted with that of the Santee Cooper power company in South Carolina, whose coal ash pond was in danger of being flooded by the Waccamaw River. The company tested the surface water in two locations: 1/4 mile downstream and 1.5 mile downstream. Santee Cooper also tested sediments in 13 downstream locations, starting at the ash pond and extending 45 miles down the river.
The distances were set by consulting with South Carolina regulators and consultants, and based on river flow conditions, Santee Cooper spokeswoman Mollie Gore said in an email to The N&O. The cresting river did not flood the ash pond, which was protected by an inflatable AquaDam, silt fencing and a floating containment boom.
Avner Vengosh, a professor of geochemistry and water quality at Duke University, noted that Duke’s test results from Sept. 18 through Sept. 25, do not list boron, the element that is typically tracked for coal ash contamination. Boron is the “ultimate tracer” because it is soluble in water, not affected by chemical conditions in the water, and can be reliably measured, Vengosh said.
Vengosh was among the researchers who tested for coal ash after the 2008 coal ash spill in Tennessee that released 5.4 million cubic yards of ash that ended up in the Emory River. The researchers took samples over 18 months and published several papers. The river bottom was later dredged to remove the ash.
Duke includes boron in a Sept. 22 test result but not the other days. Duke defended its testing protocols.
“Boron is a good indicator of coal ash constituents in groundwater but we’re testing surface water here,” Sheenah said in an email. “Because there is the potential for brackish water at Sutton, we can get false positives for boron because it is present in seawater.”
Vengosh said Duke Energy is “playing games” with the lab results. He said a river at flood stage will dilute the presence of contaminants.
He said that the only way to know for sure if coal ash got into the Cape Fear River is to wait for the flood stage to recede, to assess whether the ash is left in the ash pond, and to assess sediments at the river bottom.
“The fact that you’re looking in the middle of the flood and see nothing doesn’t mean anything,” he said.