Greensboro officials seeking the source of a potentially harmful, drinking water contaminant are focused on a relatively small area that includes Piedmont Triad International Airport and its immediate surroundings.
Although months of additional study remain before they draw any final conclusions, water managers Steve Drew and Mike Borchers say that a major source of the pollutant PFOS appears to be training drills and actual emergencies at or near PTI during which firefighters deployed a highly effective, synthetic foam used to squelch fuel-based blazes.
“They are legacy sites that have been used for firefighting training over the decades,” said Drew, director of Greensboro’s department of water resources. “We don’t always know where they are ... I would say that predominantly our findings are pointing to years and years of firefighting training activities.”
Assistant director Borchers said the city has joined with airport officials, as well as with Guilford County emergency and public health agencies, to pinpoint places where past PFOS-based, fire retarding foam might have been left to evaporate or drain into the soil.
“It’s like putting the pieces of a puzzle together, that’s the way I describe it,” said Borchers, who is supervising the search effort on behalf of city government.
In addition to training drills, instances where the foam might have accumulated in that area include crashes involving tanker trucks and long forgotten industrial fires or spills.
Meanwhile, the airport itself still could be contributing fresh sources of contamination: PTI conducts fire-training drills using firefighting foam once a year on its runway in the Greensboro watershed without cleaning up afterward, creating a possibility that additional PFOS is making its way into a nearby stream or ground water.
“We do not currently have a cleanup protocol, as this has not been a regulated chemical,” PTI executive director Kevin Baker said recently of the firefighting foam. “Obviously if the city's analysis shows that these tests are contributory in any more than a de minimis amount, and everyone believes it is necessary to clean, we will work with them to develop something if possible and practical.”
Margin of safety
The stakes potentially are high. Scientists differ about what constitutes a safe PFOS level in drinking water. But they generally agree too much might trigger certain forms of cancer, high cholesterol, thyroid disease and other injuries to human health.
PFOS is scientific shorthand for “perfluorooctane sulfonate,” a distant and likely more harmful relative of the GenX chemical that has caused so much concern for drinking water safety to Greensboro’s southeast in the Cape Fear River basin.
After their commercial development about 70 years ago, PFOS and other so-called “perfluorinated compounds” became popular components in a variety of consumer goods where resistance to water, stains or grease was required, everything from carpeting to Teflon cooking surfaces, pizza cartons and microwave popcorn bags.
PFOS carved out a special niche in fire-retardant foams, making a soapy mixture with the capacity to both smother fuel-based fires and the toxic vapors that often emanate from exposed gasoline or similar flammable substances.
Foams are indispensible when firefighters confront, for example, a raging gasoline fire or an overturned tanker truck on Interstate 40, said Battalion Chief Jim Robinson of the Greensboro Fire Department.
The stuff works
The foam can snuff out in 10 minutes a fuel fire that otherwise might require several hours to stop, he said.
“The stuff does work, that’s why it’s so expensive,” Robinson said, noting that the cost runs about $35 a gallon for a liquid base that then is blended with 100 gallons of water to make the sudsy mixture.
But chemical manufacturers began phasing out domestic production of PFOS and its sister chemicals about 15 years ago after researchers built a solid case that these artificial substances could harm human health and that they had accumulated in the blood serum of 99 percent of the American populace.
Scientists have even found PFOS in the brain tissue of polar bears roaming the arctic reaches of East Greenland.
Today, PFOS is what environmental officials call an unregulated, emerging contaminant. In practical terms, that means no hard and fast limits prohibit its presence in drinking water, but it is deemed undesirable and generally acknowledged as a health threat.
A recent scientific study asserted that “civilian airports” nationwide are a significant source of contamination by the so-called PFAS class of chemicals that includes PFOS.
“Many civilian airports and military fire training areas have been contaminated by PFASs contained in aqueous film-forming foams that are widely used during firefighting training activities,” said the team of scientists that included researchers from Harvard University and the National Exposure Research Laboratory in Research Triangle Park.
The study noted that surface waters and groundwater near some of these sites have been contaminated by “concentrations that are 3-to-4 orders of magnitude higher than the U.S. EPA health advisory level for drinking water."
Location, location ...
The area around PTI plays a pivotal role in the local saga because — from a strictly environmental standpoint — it’s about the worst place an airport could be sited, let alone an airport bordered by one of the nation’s larger tank farms and a variety of other industry.
PTI and its industrial surroundings sit at the crest of the region’s watershed, a part of Guilford County where key feeder streams rise and begin their separate journeys to reservoirs miles apart that supply both Greensboro and High Point with drinking water.
Drew, Borchers and other Greensboro officials grew concerned about PFOS in the local water supply four years ago, after the organic acid was placed on a short list of emerging contaminants that the U.S. Environmental Protection Agency instructed public utilities to include in their routine water-quality testing for a year.
Like other water systems across the nation, Greensboro normally did not monitor for PFOS.
Greensboro drinking-water managers are trying to figure out the source of the chemical PFOS.
Parts per trillion
But in the EPA-ordered testing during the last quarter of 2014, one sample at the Mitchell Water Treatment Plant contained PFOS and a sister chemical at the combined level of 90 parts per trillion in “finished” water leaving the plant for consumer faucets.
EPA’s current health-advisory level for PFOS is 70 ppt, either singly or in combination with the sister compound. The advisory level represents the point at which an unacceptable risk ensues for cancer or other significant harm to a person who consumes 2 quarts of that water daily over the course of a 70-year lifespan.
But in late 2014, the federal agency still was weighing fresh evidence calling PFOS’s safety into question, and the advisory standard at that time was 200 ppt — roughly three times the present advisory that took effect in mid-2016.
So no action was required of Drew and Borchers other than to alert state and federal regulators to their finding, which they did.
Two quarts a day
Both men emphasize that in their professional opinion, the PFOS content never made the city’s water unsafe to drink at any time.
For one thing, the health advisory is a static number, assuming that a person would drink water every day contaminated at the PFOS warning level.
In actuality, water from the Mitchell plant has fluctuated between PFOS levels considered insignificant and those that are more concerning, with higher readings likely to occur after a rainy spell when PFOS-tainted groundwater or runoff presumably flows into Horse Pen Creek and other tributaries of the Lake Brandt municipal reservoir.
PFOS levels at the city’s other water treatment plant on Lake Townsend have not been so problematic. And Drew and Borchers said that they’ve seen nothing close to the advisory limit in continued testing at the Mitchell plant since its 2014 spike.
The city’s most recent round of tests in November found that water from the plant contained PFOS at 43 ppt and its sister compound at 7.2 ppt.
“As long as we can show that the levels are below that level of 70 parts per trillion, the EPA feels that there is no adverse health impact for those compounds,” Drew said.
Searching the watershed
Even so, Drew said, PFOS is not a natural substance and does not belong in a water system’s output.
So the hunt began for the source of Greensboro’s PFOS problem shortly after the 2014 test at the Mitchell plant that found the alarming spike.
“Not too many months after that, we began regular testing throughout our lakes and watershed,” Drew said.
The city hired a consulting firm to help. State and federal regulators were brought into the loop so that Greensboro managers wouldn’t be making their decisions in a vacuum.
Drew said that water department officials also called on the “tribal knowledge” of others in city government.
“Somebody would say, ‘Oh yeah, we used to do firefighting foam drills at that site off West Market Street back in the 1960s,'” he said.
Borchers’ team started collecting samples of raw water, particularly in lakes Higgins and Brandt that supply the Mitchell facility through a pipeline to the plant about 7 miles away, at the intersection of Battleground Avenue and Benjamin Parkway.
The Mitchell plant provides water to a section of the city that goes from downtown to Gate City Boulevard, much of Battleground Avenue, as far west as Westridge Road and eastward to the Latham Park area.
No smoking gun
Borchers said that in beginning their PFOS quest, water officials “tracked back” from the Mitchell Plant’s intake on Lake Brandt “to see where it was coming from by testing the tributaries.”
“Our focus has been on the western side of Greensboro because that is where these activities, what we call legacy activities, have occurred,” he said of past firefighting events.
Their focus was drawn to Horse Pen Creek that rises right next to the airport and flows northeasterly to become one of Lake Brandt’s tributaries. Water sampling proved their instincts correct; samples from that part of the lake averaged 181 ppt, they said.
As they searched, they were hoping perhaps to find an active industrial plant, an abandoned building or maybe an old landfill full of leaking drums holding a PFOS-containing substance.
But they came across nothing like that. So they also reached out to other professionals who might have a clue about PFOS sources, including county Emergency Management coordinator Don Campbell.
Campbell said his job “was just to historically help them identify past events that may have led to those readings,” but he wasn’t able to come up with much.
“While we would have loved to have found a smoking gun, I don’t know that we have any,” Campbell said.
Water soluble, fast moving
Campbell said he had heard rumors that firefighters from throughout the area used to train using firefighting foams in that part of the county.
“I also had heard stories of some large tanker truck fires on Market Street back in the 1990s,” Campbell said.
There also had been two, more recent industrial fires in the area where lots of firefighting foam had been used to protect lives and property — a 2010 blaze at the tank farm involving a massive Colonial Pipeline storage tank and a fire three years later in a D.H. Griffin scrap pile.
Both of those sites, however, were on the wrong side of a ridge line through that part of the county and they drained away from Greensboro toward High Point’s reservoir.
So the evidence to date “seems to be pointing toward the airport,” said Ken Carter, assistant director of the county Department of Public Health.
“But we really don’t have enough information yet to make a full assessment,” he said.
PFOS is challenging to trace because “it’s water soluble and capable of moving readily through the soil,” Carter said.
By asking around and checking official records, Borchers’ team identified a dozen spots at or near the airport where firefighters might have used PFOS-containing foam either in training or actual emergencies.
In addition to training sites, the list included reported sites of highway wrecks involving fuel tankers, other industrial fires and spills.
"Right now, we know an event occurred there, we don't know the magnitude," Borchers said of the sites.
In their next phase of study, the city officials plan to check the water quality in test wells that have been drilled in the area. They also will gather soil samples to test for PFOS contamination in the ground.
And in the coming months, the team will expand its search to the Reedy Fork watershed on the airport’s western perimeter and several other areas that they have yet to check out, he said.
Class B foam
The city fire department does not operate on airport grounds. And the Greensboro department has not run practice drills elsewhere using actual foam in recent years, partly because of the expense, Robinson said.
The city fire department still has foam containing PFOS, but it is gradually switching to an alternate blend that uses another foaming agent, he said.
Fire trucks are required to carry a certain amount of firefighting foam on board because it is so useful in “Class B” fires that involve fuel and other flammable liquids, Robinson said. But such fires are only one of several major types that city fire crews regularly confront, he said.
“The time we would use a Class B foam would be if a car caught on fire and gasoline was spilling everywhere,” Robinson said.
By contrast, PTI operates its own fire department that is required by the Federal Aviation Administration to regularly test its foam-spraying proficiency using the real thing, knowing that many emergencies at the airport might require foam to knock down or prevent a fire involving aviation fuel.
PTI director Baker said he and other airport officials “consider it very important to be protective of the natural environment around the airport.”
“If there are best practices that they recommend, then we would work with them provided that it doesn’t impact airport safety,” Baker said of the city’s water managers.
Borchers said he understands that PTI uses relatively small amounts of the foam in its annual, FAA-required runway drill. And he said the test site drains to Brush Creek, which flows into an arm of Lake Brandt where PFOS levels have been comparatively low.
Effective cleanup is possible. For example, when city fire crews use foam in an actual emergency, the fire department does its best to trap the filmy liquid nearby along with any remaining fuel residue, Robinson said.
Firefighters then leave the rest to an environmental cleanup crew, usually a private contractor who removes the remaining foam, fuel and other contaminants under the supervision of Guilford’s health department, he said.
“They want the environment put back the way it was prior to the incident,” Robinson said of health officials.
Drew and Borchers say they believe it will take about six months to complete their work, including sampling wells around the airport and adequately studying the Reedy Fork watershed.
They are testing water quality at a total of 19 sites in that part of the county, recently closing out six checkpoints to PTI’s eastern side so they can add that many on the western side.
It would be great if they could track down one or more sources for most or all of the PFOS and eliminate the problem right there, Drew said.
The other option is adding new equipment to the Mitchell plant that can screen out PFOS and a number of similar compounds, which could be costly.
City officials probably will pursue both strategies, Drew said.
“It’s likely we’ll budget for it,” he said of the additional filtration equipment. “I think we need to have that secondary safeguard in place.”