GREENSBORO — Confronting a recent spike of a chemical compound in part of the city water supply, officials are continuing their search near the airport for a possible source.
With higher levels of perfluorinated chemicals detected at one of its treatment plants, Greensboro’s water department has collected samples of groundwater from test wells at Piedmont Triad International Airport. Local administrators are looking for the source of problems with perfluorooctane sulfonate, or PFOS, a component of some firefighting foams.
The city took the groundwater samples in late April from 11 monitoring wells at an airport test site on Greensboro’s western outskirts where city officials believe the bulk of their PFOS problem is centered, said Mike Borchers,an assistant director of the city’s Department of Water Resources.
“They have some wells at an old, inactive hazardous waste site,” said Borchers, who has been supervising the search. “We are currently waiting for the results. ... As soon as we get the results, we can figure out how prevalent it is.”
Streams that rise in the airport environs flow to Lake Brandt, which supplies the Mitchell Water Treatment Plant that has produced water with elevated levels of PFOS and a sister chemical.
Results of the groundwater testing should be known any day now, Borchers said.
In the meantime, the most recent analysis of drinking water from the Mitchell plant has raised concerns in municipal government by inching closer to the federal health-advisory level for the combined presence of PFOS and a closely related perfluorinated chemical, PFOA.
The drinking water tests conducted in February showed PFOS at 57 parts per trillion, or ppt, and PFOA at 6.9 ppt — for a combined total of 63.9 ppt. The federal government’s unenforceable advisory limit for health concerns is a combined total of 70 ppt.
That represents an estimate of the threshold for an unacceptable increase in the risk of disease for someone who drinks water with that amount of contamination over the course of a 70-year lifespan.
PFOS is among the compounds known as “emerging contaminants” for which the federal government has not yet set maximum contaminant levels for drinking water.
Some studies suggest that excessive PFOS exposure over time heightens the risk for kidney and testicular cancers as well as possible damage to the liver, immune system and thyroid. The compounds also have been linked to developmental problems in breast-fed infants and fetuses during pregnancy.
The city’s concern with PFOS dates to 2014 when it was detected at relatively high levels in drinking water produced by the Mitchell plant, located at Battleground Avenue and Benjamin Parkway. It was found during a series of tests that the federal government required nationally for PFOS and several other unregulated pollutants.
Water systems had not tested routinely for PFOS before 2014 because of its unregulated status. After the PFOS problem came to light locally, Borchers and others in the city water department began their painstaking search for the source and what to do about it, hiring the consulting firm HDR to help in the effort.
In their hunt for a source, searchers backtracked methodically along Lake Brandt’s tributaries to eventually identify the airport and the industrial area around it as likely playing a major role. That’s because of that area’s legacy of fire-training exercises and emergencies where PFOS-containing foam was used.
Borchers and other officials say water from both the city’s Mitchell and Townsend plants has never been unsafe to drink.
Located at the larger lake it is named after, the Townsend plant produces drinking water with consistently lower PFOS content — 23 ppt in the most recent sampling, and a combined PFOS/PFOA total of 27.7 ppt.
The city’s testing of groundwater at the airport and treated drinking water at its plants takes place against the backdrop of heightened national and statewide concern for PFOS and other perfluorinated chemicals.
In the nation’s capital last month, the U.S. Environmental Protection Agency hosted a two-day summit on perfluorinated chemicals, at which agency head Scott Pruitt said dealing with PFOS and PFOA pollution was a “national priority.”
Pruitt said EPA needs to begin the lengthy process of setting maximum contaminant levels for how much PFOS and PFOA are allowed in drinking water.
Meanwhile, in Raleigh, state legislators from both parties are championing different changes to North Carolina environmental law aimed primarily at dealing with water pollution triggered by GenX, a newer form of perfluorinated chemical that is ostensibly safer than the class of predecessor chemicals that includes PFOS.
Borchers said he and others in the water department are seeking “ground zero” for the city’s lingering problems with PFOS to learn whether it might be eliminated at the source, which could be more efficient than screening it out downstream.
It’s a search that differs from a classic environmental whodunit where regulators or aggrieved neighbors might be on the trail of a giant corporation that has heedlessly discharged problem chemicals into a body of water used elsewhere as a source of drinking water.
Here, Borchers and other city officials believe their problem stems from years of emergency responses and fire-training exercises where responders used PFOS-containing foam to either fight fires or train for such emergencies. Industrial buildings in the area have fire-suppression systems that also rely on such foams.
“We had a fire station out there where they did a lot of training,” Borchers said of the airport area.
The chemical culprit belongs to a family of about 4,000 compounds that is little known to the public by its various scientific acronyms, but which is famous through trademarks such as Teflon, Scotchgard and Stainmaster for the smudge-, heat- , stick- and water-resistance they add to a variety of products.
Neither PFOS nor PFOA are produced any longer in the United States, but they can be found in some imported goods and in such products as firefighting foam produced before substitutes were introduced.
Borchers said the latest drinking water finding at the Mitchell Plant is bothersome as a departure from a trend toward lower PFOS levels in most previous quarterly testing. By comparison with the latest PFOS reading of 57 ppt, drinking water produced at the Mitchell plant last year contained PFOS at 43 ppt in November and 42 ppt in August.
The more recent sampling of ground water at PTI followed an April 13 meeting between the city water department and airport executives, area fire officials and representatives of major airport tenants, including FedEx, HAECO Americas, Honda Aircraft and Textron Aviation.
The monitoring wells are located near a hangar on airport property that is now leased by American Airlines, Borchers said. The hazardous waste problems that led to those test wells being drilled years ago were caused by earlier tenants and have been resolved, he said, but the network of test wells was left in place.
The city is simply taking advantage of those wells drilled for another purpose to now test groundwater in that area for the possibility that it also might be part of a PFOS hot spot, Borchers said.
The group at the April 13 meeting in the airport’s board room expressed support for the department’s efforts, Borchers said.
City officials asked the attendees to check their in-house inventories for any PFOS-containing foams or other substances; to avoid using them and find substitutes, if possible, for such tasks as required fire-safety testing; and to alert the city’s Department of Water Resources when they must use them to extinguish a fire or for some other purpose, he said.
“It’s a good partnership,” he said of the joint efforts.
City water officials also are developing plans for responding if PFOS and PFOA levels from the Mitchell plant can’t be moderated and spike above the health advisory, Borchers said.
The options include “throttling down” the amount of water Mitchell produces and making up the gap by boosting production at the Lake Townsend plant, as well as possibly increasing the amounts of water the city purchases from neighboring communities, he said.
Borchers said the city also could consider upgrading treatment methods at Mitchell to include an activated carbon technology that’s better at removing perfluorinated chemicals. Standard techniques are largely ineffective.
Borchers said that to keep a closer eye on the issue, the city recently switched from quarterly to monthly testing for PFOS and PFOA in its drinking water.
Contact Taft Wireback at 336-373-7100 and follow @TaftWirebackNR on Twitter.