The latest rounds of water testing showed a high level of PFOS at another Issaquah well, according to a new report released by Geosyntec, the firm the city hired to conduct water testing.

Monitoring Well No. 6 showed a level of perfluorooctane sulfonate (PFOS) at 2.2 parts per billion in a test conducted Oct. 17. This is nearly 31 times the Environmental Protection Agency’s advisory level, which recommends that water have no more than 0.07 parts per billion of PFOS and perfluorooctanoic acid (PFOA) combined.

The tests also showed Monitoring Wells 3 and 5 to have levels of PFOS above EPA standards.

Monitoring Wells 1 through 5 were installed in May of this year, while Monitoring Wells 6 and 7 were installed in October.

PFOS is part of a family of compounds known as perfluorinated compounds (PFCs). PFCs have been used in the production of teflon, water-resistant clothing and firefighting foams.

The Geosyntec report named the Eastside Fire and Rescue headquarters, located at 175 Newport Way NW, as a probable source of the contaminants.

“PFOS concentrations increase markedly between [Monitoring Well No. 5] and [Monitoring Well No. 6], which is located about 500 feet downgradient of 175 Newport Way NW, where PFOS was detected in soil,” the report stated. “Historic use of firefighting foams at 175 Newport Way NW, the presence of PFOS in soil and the high PFOS detection at [Monitoring Well No. 6] located just downgradient of this property, indicates this property is a source of PFCs to groundwater that should be investigated further.”

Previously, Bob Anderson of Geosyntec had told the Issaquah City Council at its Sept. 19 meeting that Eastside Fire and Rescue was a likely source of the PFOS, after the chemical compound had been found in three soil samples taken on the fire department’s property on Sept. 8.

“We’re aware of it and working with Issaquah cooperatively … We’re going to work on it and figure out where to go from here,” Eastside Fire and Rescue Chief Jeff Clark said, noting that the fire department has hired its own consultant to study the water.

“We do know that, in the past, PFOS was found in firefighting foams,” Clark said. “In the history of Eastside Fire and Rescue, I’m confident that the foam was used here.”

However, it has been some time since Eastside Fire has used these types of foams. Clark said that foams containing PFOS stopped being produced in the mid-2000s, and that “we believe sometime around 2005 or sometime thereafter, we stopped buying foams with PFOS.”

He also noted that the only foams containing PFOS were Class B foams, used for fighting flammable liquid fire. The fire department has always used Class A foams, designed for wood fires, far more frequently.

Currently, the fire department is going through old buying records to determine when foams containing PFOS might have been purchased. Clark said that this process may take a while, as these records are not digital, but on paper.

In the meantime, Clark said, it’s important to note that “the [drinking] water is safe, and there are no products we currently use that are dispensing PFOS.”

“The city of Issaquah is very committed to partnering with both Sammamish Plateau Water and Eastside Fire and Rescue on next steps,” said Autumn Monahan, assistant to the city administrator. “Safety is our top priority — Issaquah meets all standards for safe drinking water.”

Since the spring, the city has been treating City Well No. 4 to remove PFCs from the water. Monahan said that this filtration system has been successful.

In high amounts, PFCs have been linked to a variety of health issues, such as cancer, thyroid problems, a weakened immune system, high cholesterol and pregnancy complications such as preeclampsia.

Geosyntec will present its new report on PFOS findings at the Dec. 19 council meeting.

Bob Anderson of Geosyntec did not respond for comment.