MARQUETTE — Recommendations for disposing of biosolids and water contaminated with per- and polyfluoroalkyl substances, or PFAS, at K.I. Sawyer were recently approved by the Marquette County Board of Commissioners for implementation.

Implementing the recommendations from GEI Consultants entails a $2.63 million project to dewater PFAS-contaminated biosolids and blend them with carbon, iron oxide, blast furnace slag, montmorillonite and Portland cement that will be poured into blocks and transported to a standard landfill. The method provides a “solid product that has proven to be very successful in containing the PFAS indefinitely,” according to county board documents.

For the contaminated water, the county will seek funding for carbon filtration decontamination at an additional estimated cost of $329,000. It was selected over a microfiltration process and a reverse osmosis process.

The issue stems from testing at the K.I. Sawyer Waste Water Treatment Plant that indicated elevated levels of PFAS were present in Class C biosolids, which had been historically disposed of through the land application process on county-owned land, officials said. However, the elevated levels of PFAS in the biosolids limit the ability to land apply all biosolids, according to county documents.

“This PFAS problem is believed to have stemmed from multiple sources of contaminations ranging from the Air Force’s discharging of Aqueous Film Forming Foam — AFFF — at and around the airport during their tenure and a small leak from one of the Sawyer fire trucks,” Sawyer Director of Operations Duane DuRay wrote in a letter to Marquette County Administrator Scott Erbisch and Marquette County Finance Manager Anne Giroux. “These past issues have created a sizable problem at the (wastewater treatment plant) by contaminating two 750,000-gallon sludge storage tanks and the pretreatment lagoon of approximately 500,000 gallons.”

Due to this, GEI was selected as an engineering consultant to complete a study of the contaminated biosolids at the wastewater treatment plant and “investigate the most feasible solution for disposal,” DuRay wrote.

The report detailed eight options to dispose of PFAS-contaminated biosoilds and three options to decontaminate water.

“This report is solving the issues specific to the existing sludge,” DuRay told the board at its May 18 meeting. “You approved, as a board previously, what we think will help be the long-term solution for the sludge. And that was the sludge press, where the county acquired a half-of-a-million dollar grant, plus contributes $800,000 roughly of its own money. That should help solve some of that contaminated sludge issue going forward.”

The options for handling contaminated biosolids included:

≤ Belt press dewater and landfill

≤ Centrifuge dewater and landfill

≤ Dewater and incinerate

≤ In situ stabilization

≤ Long-term encapsulation

≤ Blending and diluting

≤ Geotextile bags

≤ Biosolids amendment and landfill

The biosolids amendment and landfill option, which was ultimately selected by the board, is one of the cheaper options at around $2.633 million, officials said.

“The benefits of this method are the relatively low cost, the material is removed from the site and the end product is made inert,” county board documents state. “This method will require some real-world test(ing) with the actual biosolids to provide the landfills the insurance of an inert product. Staff is currently working with GEI to complete those tests.”

In light of the estimated expenditure, Marquette County Board Chairman Gerald Corkin commented: “I want the board to understand we are looking at $5 million to $6 million. We have to hold the Air Force accountable for their share before we start expending that money.”

Katie Segula can be reached at 906-228-2500, ext. 242. Her email address is ksegula@miningjournal.net.