CHARLOTTE, NC (WBTV) - Mecklenburg County officials confirmed to WBTV that elevated levels of arsenic were found in Charlotte's main water supply during testing last month.
WBTV learned the arsenic came from the Duke Energy Riverbend Steam Station's coal ash pond, where Duke has been decommissioning the basin. Duke officials said in order to remove the coal ash, they have to get the water out.
According to officials with the Land Use and Environmental Services Agency, water tests detected arsenic in Mountain Island Lake on June 20. Mountain Island Lake provides drinking water for over one million residents in Charlotte.
Officials said the arsenic level was 95 ppb, which is nine times the level allowed by the US Environmental Protection Agency (EPA).
A follow up test just a few days later showed the arsenic was back down to extremely low levels, just 5 ppb. The county said there is no threat to the drinking water supply.
The Catawba River Keeper said he's concerned about the dewatering.
"There is a correct way to do that, and that does not include elevating arsenic in the reservoir at this level," said Sam Perkins, with Catawba River Keeper.
He said he's wondering just how high the levels were before the water got out of the basin, and if Duke Energy knew the arsenic levels were high.
We reached out to Duke Energy for comment.
"As a part of our dewatering efforts we have to conduct weekly tests, and so we did notice some elevated levels. While the state is also doing their testing, when we noticed their data was validating our data," a spokesperson for Duke Energy said. "That was when we made the decision to stop the dewatering process."
The spokesperson said the dewatering has been stopped temporarily so they can install water treatment on site.
Officials said sample tests downstream from the basin showed no impact to the drinking water.