PFAS Fingerprinting to Refine the Conceptual Site Model for an Unlined Landfill
Christopher Gurr, PE, PFAS Remedial Investigation Discipline Leader, CDM Smith, Inc.
PFAS is a class of contaminants impacting many communities across the nation. Unlike the “fully emerged” contaminants (like chlorinated solvents) where, for groundwater at least, we typically only have to track just a few contaminants, samples for PFAS can return detections for over 20 compounds per sample. That list continues to grow as analytical methods mature. This is both a challenge and an opportunity. It’s a challenge, because now we have many more compounds to track, evaluate, and communicate risk (not to mention unquantified “suspect” PFAS and precursors). It is an opportunity because the datasets are much larger, with many more variables—which opens the door to more rigorous forensics. In this presentation, I will discuss how PFAS analysis can be used to “fingerprint” sources at contaminated groundwater sites, and why the chemistry allows us to do so. I will present a case study of a contaminated landfill where CDM Smith used a thermal imaging drone to identify seeps around the landfill cap. The distribution, or fingerprint, of PFAS detections in the seeps were comparable to the landfill’s monitoring wells. The fingerprinting served as a strong line of evidence to develop the conceptual site model, particularly groundwater to surface water discharge.
Chris Gurr, PE, is the PFAS Remedial Investigation Discipline Leader for CDM Smith. He specializes in contaminant fate and transport and remediation technology. He is active in multiple PFAS R&D projects, and has been an author on the ITRC PFAS guidance. He has a BS in chemistry from the University of Virginia and MS/ENG degrees in environmental engineering from Stanford University.