Field Demonstration of In Situ Stabilization (ISS) of Per- and Polyfluoroalkyl Substances in Soil with RemBind®

A field study was completed to assess the effectiveness of in-situ soil stabilization (ISS) to immobilize per- and polyfluoroalkyl substances (PFAS) impacted soil, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), in a former burn pit at the Cavalier Space Force Station, North Dakota. Only a few field ISS studies have been published to-date and this work provides important practical considerations and performance data. Based on the results of a laboratory treatability study, RemBind® 100X, which consists of an aluminum hydroxide/carbon blend (amorphous aluminum hydroxide, kaolinite clay, and activated carbon), was applied at 3 percent by dry weight as a stabilizing material (or fixant) to impacted soil to reduce PFAS leaching from soil to groundwater. The fixant was distributed and mixed over a 3-foot vertical zone across a 100- x 100-foot area gridded into 18 test cells. Four performance monitoring events were completed throughout 19 months, during which soil samples were collected to assess PFAS leaching using Leaching Environmental Assessment Framework (LEAF) analysis, and vadose zone moisture was monitored using downhole nuclear magnetic resonance (NMR) imaging and in-situ moisture probes. For all PFAS analyzed, leachate concentrations following leachate testing, were reduced by at least 95 percent (±5.1%) for each of the four sampling events and concentrations were measured at levels less than the United States Environmental Protection Agency’s (USEPA’s) regional screening levels (OSD 2023) and maximum contaminant levels (EPA 2024) for PFOS, PFOA, perfluorobutanoic acid (PFBA), perfluorobutanesulfonic acid (PFBS), perfluorononanoic acid (PFNA), perfluorohexanoic acid (PFHxA), perfluorohexanesulfonic acid (PFHxS), and hexafluoropropylene oxide dimer acid (HFPO-DA). Furthermore, the approach was effective at reducing leaching from the stabilized soils, while still allowing infiltration of precipitation. Overall, this study confirms the efficacy of this technology and therefore should be consideration at other similar PFAS-impacted sites.