The state Department of Environment and Natural Resources says owners of 20 wells were warned against drinking the water because of the levels of heavy metals. Twenty-four wells were tested near three coal-burning power plants in the Charlotte region. The wells drew groundwater from deposits separated from water beneath coal ash pits at the Allen, Buck and Marshall Steam Stations.
Duke Energy says the results show that some coal ash pollutants can occur naturally in groundwater.
DENR says many factors can affect the findings.
A Southern Environmental Law Center spokeswoman says they're skeptical because DENR hasn't released critical information about the tests.