Ninety-three percent of wells have tested positive in North Carolina for toxic heavy metals, such as vanadium, lead and hexavalent chromium. The state Department of Environment and Natural Resources (DENR) has now advised residents near the coal and ash pits owned by Duke Energy to avoid drinking or cooking with well water but did not provide advice about bathing in the water.

Over 150 wells near the dump sites did not pass groundwater standards set by the state, or almost 95 percent of the 163 wells tested so far. This is an update to test results reported last month, when 87 private wells in the vicinity of eight Duke coal-fired power plants failed to meet standards.

Coal ash is a result of the burning of coal to create electricity and contains many chemical compounds harmful to life. In early 2014, 30,000 – 82,000 tons of coal ash burst from a Duke Energy impoundment area at its closed Dan River Power Station near the town of Eden. Wastewater in the amount of 27 million gallons also ran into the river. In the wake of this disaster, North Carolina enacted a law requiring tests of all wells within 1.000 feet of Duke Energy’s 32 dump sites.

Duke did not immediately respond to requests for comment but spokesmen for the company previously said such contaminations could be naturally occurring. It keeps more than 150 million tons of coal ash in 32 dump sites in North Carolina.

Duke Energy’s headquarters is in Charlotte, North Carolina and is the largest generator of electricity in the United States. It also has facilities in Canada and Latin America.