Formatted Title
Source Identification and Mitigation of PFAS in Stormwater at Gerald Ford International Airport
Background/Objectives
As one of the few states that has established numeric surface water quality criteria for PFAS, Michigan has been requiring NPDES permit holders that are suspected PFAS sources to test permitted discharges for PFAS. This includes Part 139 airports, where the Federal Aviation Administration (FAA) has historically required the use of aqueous film-forming foam (AFFF) for firefighting as part of the airports’ operating certifications. FAA-required firefighter training and equipment testing, as well as aircraft emergency responses, has resulted in the release of PFAS-containing AFFF at many airports. In 2019, the State required the Gerald R. Ford International Airport (GFIA) in Grand Rapids to sample stormwater at one of their outfalls for PFAS (Outfall 011). When the initial sample results showed a PFOS concentration above the Michigan surface water quality criterion of 12 ng/L, the State ordered GFIA to “reduce or eliminate” PFAS in stormwater.” This presentation documents the effort to identify the primary source of PFAS to that specific outfall and to reduce the concentration of PFAS being discharged.
Approach/Activities
The two main alternatives to reduce PFAS at Outfall 011 were to either eliminate the exposure of stormwater to PFAS-impacted materials or to treat the stormwater. Because of the ongoing investigation of PFAS in soil and groundwater at GFIA, at least three historical AFFF release locations within the 860-acre Outfall 011 drainage area had been identified, so the main source of PFAS at the outfall was not obvious. Our solution was to conduct a program of iterative sampling and verification testing in the stormwater network, with chemical “fingerprinting” to identify which historical AFFF release location was the primary source of PFAS at Outfall 011. Once identified, the Airport began a testing program to evaluate soil stabilization methods to eliminate the source of PFAS in stormwater. And although in-line treatment of stormwater upstream of Outfall 011 would be potentially expensive and logistically challenging, the Airport decided to undertake the investigation of that option as well.
Results/Lessons Learned
The source identification effort successfully identified which of the three historical AFFF release areas was primarily responsible for the PFAS at Outfall 011. This effort shows that a carefully designed and executed sampling program, along with relatively straightforward data interpretation, can effectively differentiate sources of PFAS. Evaluation of source mitigation alternatives started in 2022, funded through an FAA research grant. Bench studies are complete, and a field pilot study began in 2023. Bench testing of a flow-through, in-line treatment alternative is also complete, and field pilot testing is planned to begin in 2024. All bench testing and pilot test results will be described in the presentation, along with a discussion of how they inform the development of a full-scale remedy.