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Firefighters have practiced extinguishing fuel-based fires at fire training areas (FTAs) by applying aqueous film forming foam (AFFF), which contains per- and polyfluoroalkyl substances (PFAS). These compounds can persist in the environment for centuries. FTAs have become a significant source of PFAS to groundwater. The U.S. Environmental Protection Agency (EPA) has designated some PFAS compounds as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Therefore, there is great interest in remediating PFAS-impacted soil and groundwater.
Remediating FTAs can be challenging, as they often are paved with concrete or asphalt. Besides contaminating those materials, PFAS usually impacts the surrounding soils and underlying vadose zone. Also, runoff may result in PFAS spreading to the surrounding areas, such as swales or lowlands.
The TRS Group Solution
TRS Group (TRS), a Parsons company, has patented a robust solution. The method allows TRS to treat all soil types, including clay, asphalt, concrete and other debris. These materials are often found at FTAs and construction sites. TRS heats the soil and debris, either in situ or ex situ, using thermal conduction heating (TCH). This process can achieve soil temperatures greater than 400 degrees Celsius (°C), volatilizing and desorbing PFAS off the impacted materials. Vapor treatment occurs at the surface.
Suggested Remediation Approach
After a consulting engineering firm determines the depths and areal extent of impacted soils, debris, concrete and asphalt requiring treatment, a contractor would excavate the nearby impacted areas. The contractor would then place the soil on top of the FTA, building a treatment cell. TRS then would install its TCH heaters and vapor extraction screens in the constructed cell. Additionally, it would insulate the cell to minimize heat losses. Thereafter, TRS would connect the heaters and vapor collection system to the power and surface treatment equipment.
TRS estimates that typical remediation duration to be three to six months. This duration includes the thermal desorption, capture and treatment of the PFAS.
PFAS Remediation Experience: Joint Base Elmendorf-Richardson (JBER) In Anchorage, Alaska
Funded by the Department of War’s (DOW) Environmental Security Technology Certification Program (ESTCP), TRS has applied its method at three sites. The first two were small demonstration projects. However, the third involved remediating a 2,000 cubic yard soil pile at Joint Base Elmendorf-Richardson (JBER) in Anchorage, Alaska.
At JBER, TRS heated the soil pile for 89 days and achieved an average temperature of 638°C. The independent laboratory, using EPA Method 1633, reported non-detects for all 40 method analytes in the composite sample.
Adopting such an approach, property owners can minimize groundwater impacts and reduce their long-term liability.