Researchers detect coal ash beneath five NC lakes, including a Charlotte water source
Scientists have detected coal ash in sediment at the bottom of five North Carolina lakes, evidence that it can reach bodies of water in previously unknown ways.
Sediments beneath Mountain Island Lake, a drinking water source in and near Charlotte, was one spot where ash was detected. The study did not conclude that the waste is a risk to people or wildlife, but recommends more research.
Experts had thought that coal ash polluted ground and surface waters primarily by leaking from pits and ponds where power companies traditionally stashed it. Duke Energy is excavating 80 millions tons of coal ash across the state to reduce that threat, with 5.4 million tons once stored close to Mountain Island Lake already removed.
But researchers from Duke and Appalachian State universities found that airborne ash particles fell directly into lake waters over the past 40 to 70 years, especially before pollution controls were installed. And that ash particles that dropped to the ground also washed into the lakes, especially during extreme weather.
“We thought that the majority of the coal ash is restricted to coal ash ponds and landfills,” said Avner Vengosh, a professor at Duke’s Nicholas School of the Environment. “Now we see it’s already in the open environment.”
All the work underway to prevent seepage from the ponds dedicated to coal ash storage doesn’t account for the two other coal ash contamination processes that the study uncovered, said Vengosh, who has studied coal ash for years.
“Although coal is being replaced by natural gas for power generation, environmental challenges posed by the accumulation of coal ash and its inadequate disposal over decades” persists, the study states.
The study
Backed by funding from the National Science Foundation, researchers from the two universities sliced cylindrical cores from sediment at the bottom of the five man-made lakes created adjacent to current and former coal-powered power plants.
Mountain Island Lake waters once helped cool Riverbend Steam Station in Gaston County. Duke Energy retired coal-powered units there in 2013. It dug up the last of 5.4 million tons of coal ash stored on the property more recently.
Because sediment settles in layers beneath lakes over time, the researchers noted, each core offers glimpses into how ash deposits into the lakes changed over time.
In Hyco Lake in Person County, for example, researchers divided the coal ash release into three periods.
Before the Clean Air Act passed in 1970, they noted a significant amount of ash in the sediment. From the 1970s through the 1990s when the law required some ash to be stored in ponds, the amount decreased.
And since the 1990s, according to the paper, ash releases have decreased again as disposal methods shifted from wet surface impoundments to dry landfills.
Duke Energy spokesperson Bill Norton said the company has tested surface waters around its plants regularly since 1959, and have found no indication of danger to humans. And the energy corporation has retired two-thirds of its coal plants, Riverbend included, in the Carolinas, North said.
“Most of the extremely small amount of ash found by the researchers occurred prior to the extensive air quality controls that have been in place for decades at our remaining coal plants,” Norton said, “so customers will remain protected as we continue our transition to cleaner energy.
Why track coal ash?
Coal ash is a concern because it contains potentially hazardous contaminants such as mercury, cadmium and arsenic, according to the EPA.
Vengosh told The Charlotte Observer he got the idea for the study in 2018, when floodwaters from Hurricane Florence spilled into a Duke Energy coal ash storage pond.
“The fact that we have coal ash in this proximity, it’s happened for decades; it’s not new,” Vengosh stressed.
Vengosh said the researchers have not brought the results of their study, published in Science of the Total Environment Monday morning, to North Carolina officials charged with monitoring water safety.
Charlotte Water, which supplies drinking water in and near Mecklenburg County, says it has downstream buoys that take readings of the lake water every few minutes. Staff also pull samples regularly, spokesperson Jennifer Frost said.
Any weather that floods or churns a water supply is liable to introduce more ash, the study found.
The other lake bottoms where coal ash was detected in sediment include Mayo Lake, also in Person County; Belews Lake, which extends into Rockingham, Forsyth and Stokes counties; and Lake Sutton, in Brunswick County.
This story was originally published October 3, 2022 at 9:12 AM.
