State environmental regulators say early results from a new study of shallow groundwater in Delaware are generally good. But the study also revealed a potential new area of concern for PFAS contamination.
The Delaware Department of Natural Resources and Environmental Control (DNREC) has contracted the U.S. Geological Survey (USGS) to conduct raw water quality testing in the state’s unconfined aquifer— where many private wells draw drinking water— three times in the last two decades.
The state agency recently received preliminary results from the third survey. Steve Smailer, environmental program administrator for DNREC’s Division of Water, says they were generally good.
“We do have isolated concerns, not going to ignore those, but in an overall broad sense, for the hundreds of parameters that were analyzed for, very few of the ones from this study that we’ve seen so far are actually anywhere close to the standards of concern,” he said.
According to DNREC, specific compounds—including nitrates, sodium and iron— were found above standards at a few locations, consistent with the previous studies.
The recent survey tested for a group of industrial chemicals known as PFAS for the first time. USGS found PFAS above the EPA’s health advisory level at a known contaminated site in New Castle, as well as a Tidewater Utility well in the Fenwick Island area, according to DNREC.
Per- and polyfluoroalkyl substances (PFAS) have also been found in drinking water in New Castle, Doverand the Town of Blades. PFAS were long used in consumer products like non-stick pans, as well as firefighting foams used on military bases. Some studies have shown certain PFAS chemicals may increase the risk of cancer and other health problems.
Smailer says the Tidewater well was already offline when the agency received results indicating elevated levels, and that subsequent testing by DNREC of raw water in the well found PFAS at a lower concentration of 12 ppt. He adds Tidewater’s treated drinking water remains below the health advisory level for PFAS.
“We’re tracking it and seeing what goes on there,” said Smailer. “First and foremost, we wanted to make sure that nobody was exposed to it. Tidewater did a great job making sure that they had controls in place moving forward before the well was put back in service.”
Tidewater Utility did not respond to a request for comment.
Smailer says detection of a new possible PFAS contamination concern is exactly what the unconfined aquifer study is for. He points to the discovery of contamination from the gasoline additive methyl tert-butyl ether (MTBE) in the first USGS unconfined aquifer study done in 2000. MTBE was considered an unregulated emerging contaminant at the time, but the state went on to set a drinking water standard for it in 2002. State legislators have called fora state drinking water standard for PFAS.
“One of the reasons why we look at these emerging contaminants going forward is to have some data to not just guess about,” said Smailer.
Smailer says the unconfined aquifer study currently being completed, taken with the previous studies done in 2000 and 2008, gives the state a “valid baseline” for some of the wells.
“One sample is a snapshot. Two samples you can put a line between two points but it doesn’t really mean it’s a trend,” he said. “Now that we’re beginning to get a third data point on here, we actually have the baseline to begin looking at water quality trends going forward. ”
DNREC says the USGS study summarizing the analysis of over 500 compounds should be finished in spring 2020.
