Levels of perfluorooctane sulfonate, also known as PFOS, will likely increase at a City of Issaquah production well, according to experts hired by the city, after high concentrations of the chemical were found in a newly drilled monitoring well.

After soil samples taken from Eastside Fire and Rescue’s headquarters at 175 Newport Way Northwest were found to contain trace amounts of PFOS, the city drilled monitoring wells north and south of EFR in early October.

Results from Monitoring Well No. 6, located near the junction of Newport Way Northwest and Northwest Dogwood north of EFR, detected PFOS at a level of 2,200 part per trillion — more than 31 times higher than the Environmental Protection Agency’s lifetime advisory benchmark of 70 parts per trillion for PFOS and perfluorooctanoic acid, also known as PFOA, combined. PFOA was detected at 80 parts per trillion in Monitoring Well No. 6.

Monitoring Well No. 7, drilled at Northwest Alder Court and Newport Way, was found to contain 7.9 parts per trillion of PFOS and PFOA combined.

According to Geosyntec Consultants, a Seattle-based company contracted by the city to determine the source of the PFOS, groundwater in Issaquah flows north, meaning Monitoring Well No. 6 is “downstream” of EFR headquarters. Continuing testing has seen higher concentrations of PFOS in Monitoring Well No. 6 than other monitoring wells located further north.

Consultants have concluded that EFR’s headquarters “is the primary source of PFOS contributing the plume that intersects the City’s Well 4 (Gilman Well No. 4).”

PFOS was originally detected in Gilman Well No. 4 at 600 parts per trillion in 2013. Since June 2016, water from that well has been run through a treatment system and currently shows no detectable level of PFOS.

“The high concentrations of PFOS at MW06, relative to the downgradient (similar to downstream) monitoring wells, suggest that PFOS concentrations will likely increase at the City’s Well 4 before they decrease,” according to a report from Geosyntec.

“We are potentially a source,” EFR Chief Jeff Clark said. “We’re not going to say we are the primary source. There is an awful lot of testing that’s needed to be done.”

PFOS is frequently associated with firefighting foam, specifically the Class B “aqueous film-forming foam” first developed by 3M and the U.S. Navy in the 1960s.

EFR officials told The Issaquah Press that firefighting foam containing PFOS had been the standard in the industry until 2000. 3M stopped all production of its Class B firefighting foam in 2002.

Clark said 99 percent of firefighting foam is used off-site, when trucks are out on calls.

The city declined to comment.

Geosyntec has already ruled out the 2002 tanker truck fire on Interstate 90 as the source of PFOS found in Gilman Well No. 4 because PFOS was not found in monitoring wells directly adjacent to the incident site.

PFOS has also been found three Sammamish Plateau Water production wells and in

Issaquah’s Gilman Well No. 5, all below EPA advisory limits.

In October, trace amounts of PFOS were found in water tested by Sammamish Plateau Water in Issaquah Creek. Minute amounts were found both in the main stem, near the fish hatchery, and in the North Fork. However, surface water tests carried out by the City of Issaquah have not detected PFOS.

PFOS is known to cause liver damage and birth defects in lab animals. Research on its effects on humans is still evolving.

Lizz Giordano covers Issaquah and Sammamish for The Issaquah Press and Sammamish Review.

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