New study suggests coal ash pollution more widespread than previously thought

Updated at 7:15 p.m.

Coal ash pollution may be more widespread in North Carolina than previously thought, according to a new study published Monday by researchers at Duke University and Appalachian State University.

The study found large quantities of coal ash in the sediment, or sand, of five recreational lakes across North Carolina; pollution in four of these lakes were previously unknown. All of these lakes are nearby former or currently operational Duke Energy coal plants.

“The new findings indicate that we have underestimated the environmental impact of coal ash,” said Avner Vengosh, study co-author and a Duke University professor of Environmental Quality. “We thought that the majority of the coal ash [was] restricted to coal ash ponds and landfills. Now we see it’s already in the open environment.”

Duke Energy spokesman Bill Norton said water supplies are well-protected from coal ash impacts.

"We’ve already retired two-thirds of our Carolinas coal plants, and most of the [coal ash this study] found occurred prior to the extensive air quality controls that have been in place for decades at our remaining coal plants, so customers will remain protected as we continue our transition to cleaner energy," Norton said.

The study authors suggest there are three possible ways the coal ash can reach the lakes: atmospheric emissions, climate events such as hurricanes, and leaking from the coal ash ponds.

Coal ash is created as a result of burning coal to generate electricity. The byproduct contains several hazardous metals, including lead and mercury.

Historically, coal ash has been stored in so-called ponds near coal plants. However, that method can contaminate groundwater or lead to spills. In 2014, the coal ash pond at Duke Energy's Dan River Steam Station in Eden collapsed into the Dan River. Approximately 39,000 tons of ash and 27 million gallons of ash pond water were released.

Duke Energy is transitioning away from using coal ash ponds, per a 2020 legal agreement with state officials and environmental groups. The settlement requires Duke Energy to excavate nearly 80 million tons of coal ash at six of its coal plants. The utility company must move the coal ash into on-site lined landfills.

A 2019 study published by Vengosh found coal ash in the sediment of Sutton Lake in Brunswick County.

"[That] was the first time we realized that solid coal ash could be [moved] from storage into an open environment," Vengosh said.

The new study from Monday builds on this previous research, and finds coal ash contamination in four more recreational lakes across North Carolina: Hyco Lake and Mayo Lake in Person County, Belews Lake northwest of Greensboro, and Mountain Island Lake in Mecklenburg County. Mountain Island Lake is a source of drinking water for the city of Charlotte.

“By looking [at samples of sediments under] the microscope, we were able to identify the different types of coal ash that were deposited over time in the lakes “ said Ellen Cowan, a professor of Geology at Appalachian State University and a study co-author.

“At several of the sites, it appears that coal ash was initially just dumped into the nearby lake. Over time... we see changes in the coal ash with higher proportions of small particles.”

There's also evidence that this contamination can cause harmful ecological impacts, especially on fish.

"The sediment quality [in these lakes] has been damaged," said Zhen Wang, lead author of the study. "It has great implications for damaging the health of the aquatic ecosystem."

Duke Energy disputes this.

"Regular tests of surface waters in lakes and streams adjacent to our plants shows water quality remains safe," said Norton. "Water providers around those lakes also confirm water supplies are safe, as shown by thousands of tests annually."

The study authors warn that this is a much larger problem and it will likely only get worse because of climate change.

“We did a very detailed examination of five lakes, but there are numerous lakes or open water reservoirs next to coal plants not only North Carolina, but all over the country,” Vengosh said. “The phenomenon that we discovered probably applies to many other sites across the U.S. All of them are going to be vulnerable to more extreme weather events and flooding that we know is coming from global warming.”

This story has been updated to include Duke Energy's response from spokesman Bill Norton.

Copyright WUNC 2022