Results from federally mandated tests: Toxics abundant in groundwater near Duke coal ash ponds

Results from federally mandated tests: Toxics abundant in groundwater near Duke coal ash ponds

- in Environment, Top Story

Policy Watch examination of federally mandated testing reveals chemical contamination near four coal ash sites

Editor’s note: Because of the volume of data — a total of 20,000 pages — this story discusses the results of groundwater testing at and near four Duke Energy coal ponds: Asheville, Belews Creek in Stokes County, HF Lee in Goldsboro and Mayo in Person County. Policy Watch will cover the remaining seven plants over the next week.

Coal ash ponds at the Asheville plant contain high levels of radium, chromium and cobalt. (Map: Duke Energy)

This story has been updated to include clarifications from Duke Energy.

Arsenic. Boron. Selenium. Radium. These toxic contaminants, and many others, are profuse in the groundwater near Duke Energy’s coal ash ponds, proving what environmental advocates, neighbors and scientists have long been asserting: The ponds are leaking. The flow of groundwater cannot be controlled. These contaminants could enter private wells near the plants, potentially posing health risks to those drinking the water. And without a statewide, routine monitoring network of private drinking water wells, it is impossible to know the full extent and nature of the contamination.

Policy Watch analyzed the most recent groundwater results released by Duke Energy in its first annual report as required by federal coal ash rules. In more than 5,500 pages, the data for four plants showed that levels of chemical contamination routinely exceeded state and federal groundwater and drinking water standards in monitoring wells near the plants. The data was collected in 2016 and 2017 and analyzed by independent contractors hired by Duke Energy.

Policy Watch also compared the results to the state’s temporary standard —IMAC for short — that addresses unregulated contaminants.

Avner Vengosh, professor of ocean and earth sciences at Duke University,
has extensively studied coal ash contaminants. (Photo: Duke University)

“What was a surprise was the different types of contamination in the shallow groundwater beneath the ponds,” said Avner Vengosh, who has conducted extensive research on coal ash as professor of earth and ocean sciences at Duke University.

Vengosh had not yet read every report, he said, but of those he had reviewed, “it reinforced that all of them are leaking.”

Duke Energy has acknowledged that its ponds leak. The utility also agrees with the finding that radium-226 and 228 have been found in the groundwater. Duke questions, though, whether those radioactive particles are naturally occurring, and not attributable to the ash ponds.

It is true that in some regions of the state certain geologic conditions produce radioactivity: Stokes and Buncombe counties, for example, where Duke Energy has coal ash ponds. The presence of naturally occurring radium has prompted state health officials to recommend residents of “radon zones” — such as western North Carolina and Wake County northeast to the Virginia border — test their indoor air for the contaminant. (Chronic exposure to radon can cause lung cancer.)

However, Vengosh said that at some of Duke’s coal ash ponds, the radium might not be naturally occurring. Within the groundwater test results, he said radium levels — one as high as 190 picocuries, the unit of measurement for the element — are occurring in the same wells with elevated levels of other contaminants associated with coal ash, such as sulfate. This coincidence suggests that in some situations, the source of the radium is not solely geologic, he said.

Some of the coal ash is being reused in concrete and as fill at the Asheville Regional Airport. The radioactivity in the ash would likely be trapped in the concrete — although it’s unclear what the extent of a release would be should the blocks crack or weather. Using it as airport fill, Vengosh said, is problematic because the material could leach into the subsurface. (To complicate matters, during its 2017 session, the legislature passed a law relaxing regulations on stormwater discharges from airport runways.)

The coal ash pond at HF Lee in Goldsboro is scheduled for excavation. It has high levels of several contaminants, including radium and arsenic. (Map: Duke Energy)

Upper Neuse Riverkeeper Matthew Starr is particularly concerned about the HF Lee plant in Goldsboro, which sits along the Neuse. In addition to radium exceedances — and Goldsboro is not in a radon zone — high levels of arsenic are present. Arsenic is known to cause cancer.

Starr criticized DEQ for not aggressively pursuing a comprehensive, statewide cleanup. Lee’s coal ash pond is scheduled to be “dewatered” and excavated, but, Starr said, “that needs done for all of the plants. The level of inactivity is astonishing.”

Groundwater behaves differently depending on the geology — for example, it moves through limestone more easily because that rock is more porous than clay. Groundwater also travels downhill as well as through fractures in the rock — which can occur because of earthquakes, normal plate shifting and fracking.  (Under the Trump administration, the EPA, though, is now taking public comment on “groundwater connectivity,” essentially questioning the established science of hydrology.)

Duke Energy spokeswoman Erin Culbert

Duke Energy spokeswoman Erin Culbert took issue with a recent press release from the Waterkeeper Alliance pointing out the high radium levels. She accused the “critic groups” of “drawing conclusions at this early stage to simply use this milestone to advance their agenda.”

“They seek to sign up North Carolinians for the most extreme, most disruptive and most expensive way to close basins, Culbert continued. “That’s not prudent for the environment, communities or families’ energy bills.”

(In its recent requests for rate increases, Duke Energy has asked that the North Carolina Utilities Commission allow the utility to pass along the cost of coal ash cleanup to ratepayers. So far, the NCUC has deferred that decision for future cleanup costs.)

Culbert said Duke’s modeling studies show that at the Allen and Marshall plants, the groundwater actually flows away from drinking water wells. However, competing studies commissioned by environmental groups contradict those findings.

“People who live there need more sound evidence then modeling,” Vengosh said. “We need a network of wells between the coal ash ponds and the drinking water to detect early signs of contamination. Once it’s in there, it’s too late.”

Culbert said Duke performs on-the-ground testing to determine groundwater flow; the utility uses modeling as a tool to predict how groundwater might respond to different scenarios in the future.

Vengosh recommends establishing a statewide monitoring network of wells placed between the coal ash ponds and private drinking water wells. “It’s problematic to evaluate private wells without regular monitoring,” he said. However, such an endeavor would require enormous political will by both regulators and lawmakers which is unlikely. It would also cost millions of dollars that DEQ doesn’t have, and the legislature has proven itself loathe to appropriate.


Culbert said the next phase of study will be to systematically assess the background levels of the compounds, including radium, and compare them with results from monitoring wells. This could provide insight as to the level of existing contamination and to determine what portion Duke believes it is responsible for.

Likewise, DEQ officials told Policy Watch that the Division of Water Resources is reviewing the data to determine what contaminants could be naturally occurring. “Once established, DEQ will be in a better position to identify impacts to water resources that are associated with the coal ash impoundments,” said spokesman Jamie Kritzer. “DEQ is committed to ensuring compliance is achieved as quickly as possible.”

So far, background results vary widely, and they have to yet to undergo statistical analysis. But initial data from the Lee plant show that cobalt levels in the samples from background wells ranged from 1.43 parts per billion to 15.3 ppb. Monitoring wells showed a range of 1.15 ppb to 39 ppb. Interim safety standards for cobalt set a maximum of 1 ppb.

Arsenic and boron are among the toxic contaminants at Belews Creek in Stokes County (Map: Duke Energy)

At Belews Creek, selenium was detected in seven background samples above maximum levels — an average of 28.9 ppb; exceedances were found in an equal number of samples from regular monitoring wells — but at a higher average, 48.9 ppb, The maximum allowable level is 20 ppb.

Arsenic levels at Belews Creek were also very high — nearly 10 times the maximum allowable level, as were cobalt and boron. There were also elevated levels of radium.

Despite these exceedances and the fact that contamination has migrated through the groundwater offsite, Belews Creek is not scheduled for excavation; Duke plans to cap the material in a lined landfill instead.

Amy Adams of Appalachian Voices

Amy Adams, North Carolina program manager for Appalachian Voices, said the differences in contaminants among the plants is likely because of the different types of coal that was burned at the plants over time. And the presence of radium in coal ash isn’t new. “What is new is the scope of the problem,” Adams said.

Ironically, just last week the EPA announced it is revisiting its CCRs, short for coal combustion residual rules. The proposal would relax regulations on the utility industry for the purpose of saving power producers money.

“These current rules give us the scope of the problem,” Adams said, “so the EPA is saying, ‘Let’s remove the rules.’”


Once the contaminants have entered the groundwater, they can be very difficult to remove. Over decades, radium decays, but it does not dilute, as would water contaminated with arsenic for example. Water and soil contaminated with radium must by physically excavated or pumped out. Then the contaminated material has to be properly disposed of in a hazardous waste landfill or other special facility.

Under the state’s Coal Ash Management Act, Duke Energy must provide alternative water, such as filtration systems or water lines, to households within a half-mile of the “compliance boundaries.”

Reverse osmosis systems, Vengosh said, would remove many of the contaminants, including radium. “But then the wastewater is enriched with it. What do you do with it?”

Nor does that remedy address groundwater that might be used for irrigation. In rural areas, the groundwater can also feed ponds where livestock and wildlife drink. Groundwater also feeds springs, lakes and rivers. That contamination could enter the drinking water supply through those avenues.

Contaminated surface water, Kritzer said, will be addressed through permitting and remediation. These plans will be developed when state regulators finish assessing each coal ash site. Kritzer said the agency will then “direct Duke Energy to address any deficiencies and require the utility to submit corrective action plans” to address the contamination. If previous cleanups are any indication, this process could take years and will likely be legally challenged.

Coal ash, emerging contaminants such as GenX, pesticides and other pollutants: These are statewide water quality problems that demand a statewide response, not a piecemeal one. Vengosh said the contamination of private drinking water wells from coal ash is as much, if not more of, a public health and environmental crisis as GenX. “It’s an interesting psychology, how the state responds to GenX, but is indifferent about the large numbers of contaminants from coal ash,” Vengosh said. “We should have the same energy and reaction for coal ash as we have for GenX.”

The tables below have been updated to reflect the number of samples taken for radium, which are different from the overall sample amounts. In some cases, that changed the percentage of exceedances.

26 wells (including background)212 samples
ContaminantMaximum contaminant level, groundwater and drinking waterRange of exceedances, lowest to highest (ppb)Number of exceedances% of samples that exceeded maximum contaminant levels
Boron700 ppb711 – 385011654.7
Chloride250 ppm220 – 5404119.3
Chromium10 ppb13.1 – 93.3125.6
Cobalt1 ppb1.07 – 58.613764.6
Radionucleides5 ppb (combined Radium 226-228)4.96 – 19022 of 161 samples13.6
Sulfate250 ppm230 – 4802913.6
Selenium20 ppb20.5 – 39.72310.8
Thallium0.2 ppb0.209 – 0.656136.1
Belews Creek    
31 wells sampled (including 4 background wells)242 samples
ContaminantMaximum contaminant level, groundwater and drinking waterRange of exceedances, lowest to highest (ppb)Number of exceedances% of samples that exceeded maximum contaminant levels
Antimony1 part per billion1 – 4.521
Arsenic 10 ppb10.8 – 97 208.2
Beryllium 4 ppb5 – 6.241.6
Boron700 ppb936 – 13,00010041.3
Cadmium 2 ppb2 – 2.762.4
Chloride250 ppm280 –288218.6
Chromium10 ppb10.8 – 62135
Cobalt 1 ppb1.1 – 3797932
Radionucleides5 ppb (combined Radium 226-228)5.06 – 6.913 of 78 samples3
Selenium 20 ppb20.7 – 79166
Thallium 0.2 ppb.14 – .873715
306 samples31 wells, including 5 background
ContaminantMaximum contaminant level, groundwater and drinking waterRange of exceedances, lowest to highest (ppb)Number of exceedances% of samples that exceeded maximum contaminant levels
Arsenic10 ppb12.9 – 6445216.9
Barium700 ppb739 – 74220.06
Boron700 ppb723 -36806420
Chromium 10 ppb15 – 80.441
Cobalt1 ppb1.08 – 39.916252.9
Radionucleides5 ppb (combined Radium 226-228)5.08 –20.037 of 322 samples2
19 wells (including background)174 samples
ContaminantMaximum contaminant level, groundwater and drinking waterRange of exceedances, lowest to highest (ppb)Number of exceedances% of samples that exceeded maximum contaminant levels
Arsenic10 ppb16.421
Chromium10 ppb10.2 – 4395
Cobalt60 ppb1.11 –10.16034.4
Radionucleides5 ppb (combined Radium 226-228)5.12 – 41.0811 of 198 samples5
Sulfate250 ppm250 – 35063.4
The maximum contaminant levels are based on the state’s 2L groundwater rules, as well as EPA drinking water and groundwater regulations.
Beryllium, cobalt and thallium are subject to Interim Maximum Allowable Concentrations (IMAC), as established by state environmental regulators. A final standard has not been established for these contaminants.
Other contaminants were present in the groundwater, but at levels below state and federal standards.
Source: Duke Energy data, provided as required by federal Coal Combustion Residual rules, DEQ groundwater rules, EPA drinking water regulations