RALEIGH — North Carolina officials say they will retest seven residential wells near Duke Energy coal ash dumps for contamination after homeowners were prematurely assured their water is safe to drink.
The homeowners were sent letters by the North Carolina Department of Health and Human Services in recent weeks saying water from their wells met all state health screening levels. Agency spokeswoman Alexandra Lefebvre now says the tests performed by the commercial laboratory that processed the samples weren’t sensitive enough to measure potentially harmful chemicals down to the state screening levels.
The decision to retest the wells was made late last month after The Associated Press questioned the validity of the results.
“Well sampling and resampling is an ongoing process and our goal remains to help residents make the most health protective choices for their families,” Lefebvre said Tuesday.
The state required all residential wells within 1,000 feet of one of Duke Energy’s coal ash pits to be tested by independent labs as a result of a new law passed last year after a massive spill of coal ash at the company’s Dan River Steam Station.
Of the 207 wells sampled so far, more than 90 percent failed to meet state groundwater standards for such toxic heavy metals as lead, vanadium and hexavalent chromium. Though all of those chemicals can be found in the waste left behind when coal is burned to generate electricity, Duke has insisted the contamination found in the residential wells near its dumps is likely naturally occurring. Still, the company has agreed to deliver bottled water to the homes where letters were sent warning that their water isn’t safe to use for drinking or cooking.
The wells now being retested were among the handful where state health officials had sent letters saying they were in the clear.
At issue are the method detection limits, typically referred to as MDLs, for the tests performed on the samples when screening for chemicals.
For example, the test performed for hexavalent chromium could detect concentrations down to 2.5 parts per billion. However, the state’s health screening level for hexavalent chromium, which studies have suggested can cause cancer when ingested in even tiny amounts, is 0.07 parts per billion — 35 times less than the MDL of the lab that tested the samples.
When first asked about the discrepancy on May 20, state health officials told AP the issue was far more complex than “simply looking at a number on a piece of paper” to see if a particular well met the agency’s own screening levels.
“It is absolutely necessary to collaborate with (the state Department of Environment and Natural Resources) and the lab to get a whole picture of the lab results,” Lefebvre responded in an email. “Similarly, this is why each water sample is assessed on an individual basis and takes into account not just each individual contaminant, but the combination of contaminants, which can sometimes compound the potential health impact.”
Lefebvre said Tuesday the agency is in the process of contacting the homeowners to collect new samples from the seven wells, which will be tested at a different lab capable of testing at MDLs at or below the health screening levels.
DJ Gerken, a lawyer at the Southern Environmental Law Center who has sued Duke over its coal ash pollution, said people have the right to expect state agencies to provide accurate information — especially when it involves the safety of drinking water.
“Contaminants from coal ash can be unhealthy even in very small amounts. You can’t tell families their drinking water is safe until you look hard enough to know that is true,” he said.