A Duke University study has found high levels of coal ash contaminants in rivers and lakes downstream from coal-fired power plants. Mountain Island Lake, which provides drinking water to the Charlotte area, is one of the lakes tested that show the highest amounts of arsenic.
The study tested 11 North Carolina lakes and rivers, and it found smaller ones like Mountain Island had the highest levels of coal ash toxins.
"If you're discharging wastewater from coal ash ponds into small lakes the effect is much larger," says Avner Vengosh, a scientist who contributed to the study.
The section of the lake that receives water from the ash ponds of Duke Energy's River Bend power plant had arsenic levels more than four times above the federal drinking water standard. Soil taken from the bottom of the lake also had high concentrations of arsenic. The rest of the lake had low levels.
"I don't think there is a direct danger for drinking water right now, but if we have changes in the lake hydrology and ecological systems, then one would worry that this could induce changes in the arsenic level of the intake water that Charlotte takes for drinking water," says Vengosh.
He says those changes could include droughts or even seasonal changes that bring cold water that settles on the lake's bottom to the top. For that reason, Vengosh would like to see continuous monitoring of these lakes.
Duke Energy does routinely test Mountain Island for coal ash contaminants, including arsenic says spokesman Tim Pettit.
"The overall health of the lakes and reservoirs remain good, and fish tissue analysis that we have tells us that arsenic is not accumulating in aquatic life."
David Caldwell a water quality supervisor for the county says the study doesn't surprise him. Charlotte-Mecklenburg Utilities keeps an eye on the lake. It's had five tests since 2009 that showed high arsenic levels in the section of the lake where the water from the ash pond flows in.