Foam use by the South Dakota Air National Guard and Sioux Falls Fire Department is the cause.
City engineer Tim Stefanich, who oversees the water system, conceded “there was a little bit of time in between” finding the contamination, determining its source and deciding to shut off affected wells.
In 2014, the city tested for PFAS as part of an EPA-mandated water sampling program.
Today, the 19 offline wells are no longer sampled, but water leaving the city’s purification plant is sampled monthly.
But unlike Box Elder, where training, testing and emergency response activities at Ellsworth Air Force Base led to contamination, two culprits are responsible for the contamination in Sioux Falls.
Of the 17 wells sampled for PFOA/PFOS, 12 had concentrations above the EPA level, including one well 3,500 times that level.
Six of the 10 municipal wells with PFOA/PFOS above the EPA level are marked in the Air Guard’s report.
Lubbers and Stefanich balked at providing the exact location of the other four wells, but Stefanich described one well as north of the airport terminal, and the three others as west and northwest of well 10, which had detections 200 times the EPA advisory level.
With no PFAS detections in raw water entering the treatment plant since 2016, Lubbers and Stefanich believe they have the situation under control.
The Lewis and Clark Regional Water system, a nonprofit, wholesale provider of treated water that Sioux Falls uses for the other half of its drinking water needs, is also tested and has no reported detections.

Contamination from banned chemicals in firefighting foam at levels above safe drinking water guidelines has been found in streams around Palmerston North airport.
Photo: 123RF Seven surface water samples have all tested above the guidelines for the [www.pncc.govt.nz/pfas banned chemical PFOS.]
Streams around Palmerston North airport are contaminated with firefighting foam chemicals at between three and 12 times the safe drinking water guidelines.
A group with representatives from Palmerston North Airport, Horizons Regional Council, Palmerston North City Council, and MidCentral DHB Public Health Services has been set up to handle the PFOS contamination.
The airport was working on a disposal plan of PFOS foam, which would be replaced with fluorine-free firefighting foam, airport chief executive David Lanham said.
More bores will begin to be drilled next week for more tests, to assess if contaminated groundwater was moving off the airport site, Mr Lanham said.
"There are no formal requirements for landowners or regulatory authorities to notify [the public of] the results of investigations," the ministry said in a statement today.
PFASs were not included in the drinking-water standards, only in interim guidelines, so district health boards and the Ministry of Health do not need to be told if they were found, it said.
"Currently there is no consistent evidence that environmental exposures at the low levels New Zealanders are generally exposed to will cause harmful health effects," the ministry said.
"The interim guidance levels for PFOS and PFOA in drinking water were derived from effects found at certain doses in animal studies.

Foam used in 1996 crash may have contaminated Bulls’ water 19 Jul, 2018 11:00am 2 minutes to read Groundwater around the site of a 1996 Skyhawk crash is being tested to see if the firefighting foam used could have contaminated the Bulls water supply.
The Royal New Zealand Air Force plane crashed at Kakariki, near Halcombe and north of Bulls, in 1996.
The pilot ejected safely and no one was hurt.
But firefighting foam used at the scene more than 20 years ago may be the source of PFAS substances contaminating the Bulls water supply.
If not, contamination could have come from landfills, wastewater or industrial activity.
How it has happened is a mystery.
PFAS substances in firefighting foams have also been found in water around the Ohakea Air Force Base, but the direction of water flow would not take them to the Bulls water supply.
The results will be provided to the landowners, local councils and to the Government group responding to instances of PFAS contamination.
The testing will determine whether a one-off event like using foam in the crash could be affecting groundwater 20 years later.
The NZDF says the foams it uses have contained only trace amounts since 2002.

Foams used to fight a massive 1986 tire fire at Bergey’s Tires in West Rockhill are being eyed as a potential source of area water contamination.
1/4 Hide caption Angela Goodwin, of West Rockhill, has been using bottled water for over a year because of high numbers of PFAS in her well water that she thinks was contaminated by firefighting foam years ago.
But it is another substance that the Pennsylvania Department of Environmental Protection is now investigating in dozens of nearby private drinking water wells: the unregulated chemicals PFOS and PFOA.
“The chief said the fire was too intense and the foam immediately dissolved.” PFOS and PFOA have been found in dozens of drinking water wells in the area, including in that of the Moyers, who live just 200 yards from where the blaze occurred.
One of the shuttered wells is only 100 feet from their property.
He was diagnosed just months after the wells were closed.
Although Perkasie’s water showed only low levels of PFOS and PFOA when last tested in 2016, which is not uncommon, Jameson spent $1,600 on a whole-house carbon filtration system to give her “peace of mind” that their water is chemical-free.
“It could be (linked) one day,” she said.
State records also show the DEP requested various documents from Bergey’s, including a full accounting of any hazardous substances stored at the site, any information the company has regarding the 1986 fire, and a sheet showing its assets and liabilities.
The company also had “no documentation concerning the use of (firefighting foam) by the U.S. Navy or others to respond to fires on the property.” David Budnick, chief financial officer at Bergey’s, said the same in response to questions from this news organization.

Foams used to fight a massive 1986 tire fire at Bergey’s Tires in West Rockhill are being eyed as a potential source of area water contamination.
1/4 Hide caption Angela Goodwin, of West Rockhill, has been using bottled water for over a year because of high numbers of PFAS in her well water that she thinks was contaminated by firefighting foam years ago.
But it is another substance that the Pennsylvania Department of Environmental Protection is now investigating in dozens of nearby private drinking water wells: the unregulated chemicals PFOS and PFOA.
“The chief said the fire was too intense and the foam immediately dissolved.” PFOS and PFOA have been found in dozens of drinking water wells in the area, including in that of the Moyers, who live just 200 yards from where the blaze occurred.
One of the shuttered wells is only 100 feet from their property.
He was diagnosed just months after the wells were closed.
Although Perkasie’s water showed only low levels of PFOS and PFOA when last tested in 2016, which is not uncommon, Jameson spent $1,600 on a whole-house carbon filtration system to give her “peace of mind” that their water is chemical-free.
“It could be (linked) one day,” she said.
State records also show the DEP requested various documents from Bergey’s, including a full accounting of any hazardous substances stored at the site, any information the company has regarding the 1986 fire, and a sheet showing its assets and liabilities.
The company also had “no documentation concerning the use of (firefighting foam) by the U.S. Navy or others to respond to fires on the property.” David Budnick, chief financial officer at Bergey’s, said the same in response to questions from this news organization.

Horsham, Warminster and Warrington will seek millions of dollars in damages from firefighting foam manufacturers whose products they say contaminated drinking water.
The manufacturers of firefighting foam may feel a little crowded, as all three water authorities impacted by PFAS drinking water contamination in Bucks and Montgomery counties are now suing them over the issue.
Although the three suits are separate, Larry Cohan, lead Anapol Weiss attorney on the cases, said they take a similar tack.
The subject of investigation by this news organization, PFAS chemicals do not break down in the environment and quickly spread through and persist in soil and water.
The Horsham, Warrington and Warminster water authorities all previously relied on groundwater to provide drinking water to approximately 70,000 combined customers.
As the military only agreed to pay to filter wells contaminated above a safety limit recommended by the Environmental Protection Agency, the water authorities were on the hook to pay for the plans, which involved buying large quantities of water from the North Wales Water Authority.
Warminster is currently paying about $2.5 million extra a year, while Horsham is paying about $1.2 million, which it passes through to customers as an average surcharge of $73.48.
Cohan said his firm and the water authorities have not yet totaled an exact amount of alleged damages but that it will be “many millions” of dollars.
Through its investigation of the contamination, this news organization obtained several documents that showed some of the foam manufacturers discussing concerns about the firefighting foams in 2001.
At a meeting of a firefighting products industry group that year, a 3M representative said the company was shutting down its perfluorochemical department due to concern about the chemicals’ “proven persistence pervasiveness, and toxicity.” Records show representatives from Ansul, Tyco, Chemguard, and National Foam were in attendance.

The Warminster Municipal Authority, which serves about 40,000 water customers in or near the township, intends to soon file suit against the manufacturers of firefighting foams that have contaminated its groundwater supply.
As reported by this news organization, the authority’s board voted unanimously at an April 27 special meeting to enter into an agreement with Anapol Weiss, a Philadelphia law firm, to investigative the possibility of bringing a suit against the manufacturers.
“Anapol Weiss has determined that legal action against certain manufacturers of AFFF (aqueous film-forming foam) is viable and appropriate, and intends to file suit quickly,” Nemeroff wrote.
“The identities of the defendants in the lawsuit will be disclosed once the lawsuit is filed.” Asked about any financial arrangements, Nemeroff wrote the firm has been retained on a contingent fee basis, meaning the authority will not pay any money unless it is awarded money from a settlement or court verdict.
Lead counsel for Anapol Weiss will be Larry Cohan, who Nemeroff wrote has “extensive experience” in environmental exposure and mass tort cases.
He more recently won a $7.4 million settlement for mesothelioma sufferers, according to the site.
Attorneys in those cases are generally charging that the companies knew their products could be harmful but sold them anyway and without proper warning.
The foams were used by the military at several Bucks and Montgomery County bases, where they reached groundwater through larger accidental hangar releases and regular training exercises.
The military has agreed to pay local water authorities for wells contaminated above a safety limit recommended by the Environmental Protection Agency.
However, the military has not agreed to pay for Warminster’s plan to remove all of the chemicals from its drinking water supply.

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.
“They are legacy sites that have been used for firefighting training over the decades,” said Drew, director of Greensboro’s department of water resources.
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.
In 2002 the only major U.S. manufacturer voluntarily agreed to phase out production of PFOS.
So no action was required of Drew and Borchers other than to alert state and federal regulators to their finding, which they did.
PFOS levels at the city’s other water treatment plant on Lake Townsend have not been so problematic.
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.
Sister Chemical PFOS limits are often set in combination with its sister chemical, PFOA (perfluoroctanoic acid) that has been a major component of Teflon cooking surfaces and many other consumer products.
EPA’s 70 ppt health advisory for drinking water applies to both compounds either alone or in combination.
Water sources contaminated by PFOS have been associated with releases from manufacturing sites, industrial sites, fire/crash training areas, and industrial or municipal waste sites where products are disposed of or applied.

The chemicals have been banned in firefighting since 2006 and have been found in some farms in the area.
Farmers said they were are not being told enough and no testing had been done on properties around the air base or for meat, pasture and soil to their knowledge.
Of the 13 properties chemicals above drinking standards were found and five families drank contaminated water.
When water in tanks was low, some farmers topped up house water with bore water.
A Ministry for Primary Industries (MPI) spokesman said farm soils near Ohakea base had been tested by the New Zealand Defence Force.
But no results were known by people farming in the area.
The spokesman said food, including milk and meat, supplied from the area was safe to eat.
"In late 2017 MPI tested milk from dairy farms in the area to check the level of PFAS compounds.
"From these and the water test results we can be confident that the general food supply is safe," said the spokesman.
MPI said stress and compensation was not an MPI issue, and the focus of the government response had been on ensuring the wellbeing of people in the affected areas.

Those chemicals have been in found in some drinking-water wells on Whidbey Island, Issaquah, Joint Base Lewis-McChord and Airway Heights near Fairchild Air Force Base.
If the bill passes both chambers, Washington would become the first state to restrict the sale of firefighting foams with PFAS, said Ivy Sager-Rosenthal of Toxic-Free Future, a group that advocated for the bill.
The bill now heads to the House, where a companion billpassed out of committee.
The foams are used for fighting oil-based fires, but alternative foams without the chemicals also are available.
Sen. Doug Ericksen, R-Ferndale, proposed an unsuccessful amendment to also exempt Washington refineries.
PFAS raises health concerns that include elevated risks for kidney and testicular cancers.
The chemical also has caused concern among firefighters, who have higher rates of cancer than the overall U.S. population, according to a joint study by the National Institute of Occupational Safety and Health Administration and the University of California, Davis.
But in Washington, some fire departments already are switching to foams that don’t include PFAS, according to Michael White, legislative liaison for the Washington State Council of Fire Fighters.
Their personal protective equipment may also contain the chemical, and the legislation would require manufacturers who sell the firefighting personal protective equipment to provide written notice at the time of sale if PFAS are used in this gear.
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