The City of Rhinelander injected tens of thousands of gallons of wastewater sludge into the ground above where two city wells were later located, according to the former director of the Rhinelander-Oneida County Airport.
This year, those wells were shut down after tests showed high levels of PFAS, a contaminant tied to health risks.
From 1988 to 1992, the city took sludge from its wastewater treatment plant and injected it into the ground at the Rhinelander-Oneida County Airport, former airport director Joe Brauer said Friday.
Wells 7 and 8 later started pumping water from near the sludge-spreading area.
“The sludge operation, we were basically looking at maybe two or three thousand gallons a day, four days a week, for four years. If you take the ratios, I would think that that might be the culprit [of PFAS contamination in the water],” Brauer said in a phone interview.
Bart Sexton, a local environmental consultant and former Oneida County Solid Waste Director, said any
municipal sludge, including sludge from a wastewater treatment plant like Rhinelander’s, is a potential source of PFAS.
“Hydrologically speaking, all of the [ground]water on the airport property and around the periphery of it flows from the northwest to the southeast. Basically, from where that sludge was injected to the well is a direct line,” said current airport director Matthew Leitner.
Well 7 was constructed in 2007, and Well 8 was “newly constructed” in 2015, according to Rhinelander’s Wellhead Protection Plan.
On Dec. 9, the DNR sent a letter to Leitner, the city of Rhinelander, and Oneida County, labeling the airport as a “responsible party” for PFAS contamination in city wells. The letter pointed to fire-fighting
foam as a likely source of the contamination. By federal mandate, the foam is stored on airport grounds and a small amount is tested annually.
Leitner originally said he was “confused” by how the DNR drew is conclusion, since the foam has never been used in an active incident, and most of the two-to-four gallons of foam tested annually is collected in a bucket.
“We thought since the beginning of this that the airport foam is not responsible for that contamination,” he said Friday.
Earlier in the day, Leitner had spoken with a group of scientists and engineers from Mead & Hunt, an environmental consulting firm hired by the airport to review potential PFAS sources. The group told him, based on hydrology and quantities of foam used, that it was an unlikely candidate to blame for the contamination.
Leitner said that “unequivocally” strengthened his stance that the foam doesn’t hold responsibility for drinking water contamination.
Brauer, who served as airport director from 1990 to 2018, said the injection of sludge at the airport ended in 1992.
“By putting the sludge operation out there, you’re enriching the soil, which the [Federal Aviation Administration] believed could increase the earthworm population, which then had the potential basically to be an attractant to birds out at the airport,” he said.
More birds at the airport posed a risk to pilots taking off and landing.
“The DNR has heard mention of potential spreading of wastewater treatment plant sludge somewhere on or near the airport, but to this point, the information was less than definitive,” wrote the DNR’s Chris Saari in an email Friday afternoon. “We would certainly like to learn more about this practice, including whether or not any sludge that might have been spread in this area contained PFAS chemicals.”
Saari is the DNR’s Northern Region Program Manager for the Remediation and Redevelopment Program, and he signed the Dec. 9 letter calling the airport a “responsible party” and singling out fire-fighting foam.
On Friday, he did not rule out the foam as a potential source of water contamination.
“The DNR was not aware that the airport had hired an environmental consultant,” he wrote, continuing to say that the agency would like to review the consultant’s initial conclusions.
Wastewater treatment plant sludge is a combination of substances removed from wastewater by municipalities as part of the water purification process. It’s commonly spread on agricultural fields or other open spaces. According to Sexton, sludge may include PFAS compounds, which may enter the wastewater treatment plant from industrial or other sources.
Rhinelander shut down Well 7 in June due to high PFAS levels. In November, as PFAS levels in Well 8 rose, Mayor Chris Frederickson ordered its shutdown. The city is now drawing water from three remaining active wells.