The objective of this project is to facilitate regulatory stakeholder adoption of stabilization and/or solidification (S/S) as a defensible and practical technology for managing solids impacted with aqueous film-forming foam. Numerous in situ and ex situ demonstrations of S/S will be compiled into a referenceable science-based, performance compilation. The information within the compilation will then guide the selection of sites to investigate long-term performance of S/S technology, support a predictive tool capable of simulating long-term performance of S/S, and develop a Technology Evaluation Framework. Specific technical project objectives include:

1. Compile a referenceable database of S/S implementations across different soils and regional conditions.
2. Characterize leaching from field-aged per- and polyfluoroalkyl substances (PFAS)-stabilized solids.
3. Identify influential parameters to predict PFAS leachability over time.
4. Develop a Technology Evaluation Framework around the application, long-term monitoring, and validation of the S/S technology to provide a framework for regulatory acceptance and widespread industry adoption.

The S/S technology is designed to mitigate PFAS leaching from solids. S/S for PFAS-impacted solids can prevent potential PFAS transport to natural waters and reduce risks to biota. For stabilization, chemical reagents (e.g., sorbents, fixants, stabilizers, etc.) are uniformly distributed and mixed throughout PFAS-impacted solids. These chemical reagents discourage the solubility of PFAS in water by either sorbing PFAS to sparingly soluble sorbents or imparting the surface of the impacted solids with a greater affinity for PFAS sorption. A variety of commercially available products have been proposed, developed, and tested for their ability to reduce PFAS leaching (and bioavailability) with varying degrees of effectiveness across a range of PFAS (e.g., granulated activated carbon, RemBind®, FluoroSorb®, and recycled waste materials). These sorbents primarily function by increasing the available surface area to support hydrophobic and/or electrostatic surface interactions with PFAS as well as substrates upon which supramolecular structures may form. To further reduce water infiltration into treated soils, solidification using binders (e.g., portland cement, bentonite, native clays, etc.) may be used, and the resulting solid matrix creates a low permeability monolith that limits infiltration and leachability. In some instances, surface compaction of stabilized soils may be implemented, or a low permeable cap may be placed over stabilized soils to redirect precipitation runoff and discourage vertical infiltration through the stabilized soil.

Based on the large magnitude of PFAS-impacted solids likely requiring some form of in situ or ex situ management in the coming years, there are significant benefits to have access to as many management strategies as possible. Specifically, S/S offers a potentially sustainable and cost-favorable management technology for PFAS-impacted solids. Further, investments have already been made in field-scale S/S to address PFAS leachability. To maximize the return on those investments, this work aims to compile a dataset, build a predictive tool to support the design and implementation of S/S, and develop a Technology Evaluation Framework on sample collection and leaching approaches for evaluating S/S long-term performance to build regulatory confidence in S/S. Through this structured and data-driven approach, the project aims to substantiate S/S as a viable and cost-effective technology for managing PFAS-impacted solids, ultimately supporting its broader adoption and regulatory acceptance. (Anticipated Project Completion - 2028)