“GREENSBORO — Greensboro water supervisors are considering the next step after test wells at Piedmont Triad International Airport produced inconsistent results that have dimmed hopes for pinpointing a major source of the problem chemical PFOS, a harmful compound once heavily used in firefighting foam.

City water administrators have been seeking a ‘ground zero’ for PFOS contamination at or near the airport after tracking its source upstream from Lake Brandt to the industrial zone that includes PTI, the fossil-fuel tank farm and other industries.

But tests of 10 monitoring wells at a former hazardous waste site on airport grounds showed a variety of concentrations for PFOS and its sister chemical, PFOA. They ranged from “none detected” to a high reading of 1,001 parts per trillion (ppt) near a former US Airways hangar, said Mike Borchers, an assistant director of the city Department of Water Resources.

‘Investigation and sampling have shown the sources are more widespread — multiple sources — and treatment has the potential to be more problematic,’ Borchers said…

A high-profile, draft report released by the federal government last week suggested that recently lowered safety limits for PFOS and PFOA should be dropped even further. The report by the U.S. Agency for Toxic Substances and Disease Registry raised concerns that the 2-year-old recommended limit of 70 ppt for PFOS in drinking water should be about 10 times lower.

‘As more research is done, we are finding that these substances are toxic at smaller and smaller doses,’ said Olga Naidenko, senior science adviser at the nonprofit Environmental Working Group in Washington.

Noting that Greensboro’s most recent test results showed drinking water from the Mitchell Water Treatment Plant containing PFOS at 57 ppt, she said more vulnerable residents might want to think about additional filtering…

The outcome of the recent PTI testing has left Borchers and other water officials reassessing the original hope that they could track the chemical back upstream through the watershed to a central point, where the water system’s PFOS problems might be eliminated before getting into the stream network that feeds the municipal reservoirs in Greensboro’s northern sector.

Recent tests confirmed that soil and ground water in the PTI area are contaminated. But instead of just one or a few major ‘hotspots,’ the problem appears to be more spread out and the result of many different occurrences at different sites over a long period of time, Borchers said.

That leaves city officials looking toward additional treatment technology to help the Mitchell Water Treatment Plant, which has had the biggest problem with the synthetic chemical that lingers as an environmental hazard even though industry stopped using it years ago.”

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