Evidence of Multiple Unmonitored Coal Ash Spills Found in NC Lake

High levels of coal ash solids in sediments from North Carolina’s Sutton Lake suggest it has been contaminated by multiple coal ash spills,
most of them apparently unmonitored and unreported. (Image: Avner Vengosh, Duke Univ)
High levels of coal ash solids in sediments from North Carolina’s Sutton Lake suggest it has been contaminated by multiple coal ash spills, most of them apparently unmonitored and unreported. (Image: Avner Vengosh, Duke Univ)

Coal ash solids found in sediments collected from Sutton Lake in 2015 and 2018 suggest the eastern North Carolina lake has been contaminated by multiple coal ash spills, most of them apparently unmonitored and unreported until now. Avner Vengosh, professor of geochemistry and water quality at Duke University’s Nicholas School of the Environment, who led the research, said:

Sutton Lake served as an impoundment for a Duke Energy coal-fired power plant from the 1970s until the plant was retired and replaced with a natural gas-powered plant in 2013. It is located on the Cape Fear River about 11 miles upstream from the city of Wilmington, and is now widely used for recreational boating and fishing.

In September 2018, floodwaters from Hurricane Florence inundated the lake and an adjacent coal ash landfill before flowing back into Cape Fear. Coal ash has long been known to contain high levels of toxic and carcinogenic elements that can pose ecological and human health risks if they leak into the environment.

Power plants in the United States generate about 100 million tons of the ash a year. About half of it is stored in landfills or impoundments, in most cases adjacent to waterways. Vengosh said:

While several lines of evidence suggest the coal ash solids found in Sutton Lake originate from multiple spills, further analysis will be needed to determine the timeline of these events and if similar unmonitored spills have also happened in other lakes near coal ash ponds in North Carolina, Vengosh said.

The spills could have been caused by floods, he noted, but other causes, such as accidental release or past dumping practices, cannot be ruled out. He and his colleagues published their peer-reviewed study in the journal Science of the Total Environment.

To do the study, they conducted four independent sets of laboratory tests on bottom sediments collected in October 2018 from seven sites in Sutton Lake and three sites in the adjacent Cape Fear River. They also analyzed three sediment samples collected from Sutton Lake in 2015 and three more collected that same year from nearby Lake Waccamaw, which has never served as a coal ash impoundment.

The researchers analyzed each sample using four different methods for detecting and measuring the possible presence of coal ash solids — magnetic susceptibility, visual observation of microscopic coal ash particles, trace element distributions, and strontium isotope ratios.

The tests revealed high levels of coal ash solids mixed with natural sediments in the samples collected from Sutton Lake in both 2018 and 2015. Among the contaminants detected were many metals — including arsenic, selenium, and thallium, once used as rat poison — that have toxic impacts at elevated levels. The metals are naturally found in coal and are enriched in coal-ash residuals when the coal is burned.

Past studies by Vengosh’s lab have shown that some of these metals, such as arsenic, can be released from coal ash solids into water trapped between grains of sediment at the lake’s bottom, where they build up and, over time, bioaccumulate up the local food web.

A 2017 study by Duke University Ph.D. student Jessica Brandt revealed that 85 percent of all fish tissue samples collected from Sutton Lake still contained selenium at levels that exceeded Environmental Protection Agency standards four years after the coal-fired power plant there was retired.

Another study showed that strontium isotope ratios in the inner ears of fish from Sutton Lake now mirror the ratios found in coal ash. Vengosh said:

Provided by: Tim Lucas, Duke University [Note: Materials may be edited for content and length.]

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