Investigation and Remediation of AFFF – A Case Study

Background/Objectives

A municipal fire department trained with Aqueous Film Forming Foams (AFFF) on an elementary school’s sports field, on two separate occasions.  An investigation 7 to 13- years later, identified that the soil in one field was impacted with PFAS soil concentrations greater than 500 µg/Kg which was below the applicable direct contact/dermal criteria but exceeded the soil leaching criteria.  Groundwater concentrations below the source reported concentration of PFAS at 17,000 ng/L, exceeding the states criteria of 70 ng/L in both the overburden and bedrock. Abutting residential water supply wells were sample and their concentrations were below the 70 ng/L criteria.     

Site characterization included soil analysis by both total and SPLP and the analysis of TOC. A negotiated cleanup criteria would permit using leaching criteria based on SPLP analyses and not total mass reducing the soil area to be remediated.  A total of 4,000 tons was calculated within the vadose zone to comply with state regulations. Because of the cost to dispose PFAS contaminated soil along with potential future liability was significant, it was agreed by multiple stakeholders that alternative treatment technologies would be evaluated to reduce the project costs while still being protective of the environment.  

Approach/Activities  

It was recommended to stakeholders that remedial bench scale studies be conducted to find an alternative solution to excavation, transportation, and disposal of the 4,000 tons of PFAS contaminated soil. Several technologies were reviewed, and vendor solicitation package developed. Technologies being evaluated including sorption technologies (injection of nano-iron and soil mixing with a carbon amendment), physical encapsulation/stabilization with reuse potential, the application of ozone to destroy the C-F bond and thermal treatment. Initial bench scale studies, using site specific homogenized soil, will be completed by various vendors and subsequent field pilots will be completed prior to full scale implementation, summer 2022.     

Results/Lessons Learned

This presentation will discuss the site characterization and stake holder involvement in the selection of the of the final remedy.  Currently, soil sample are being submitted to vendors and the results and lessons learned from the various bench scale studies will be presented. In addition, a cost benefit analysis will be completed and presented prior to selecting the final remedy.