Andrew Horwath

Claims vs. Chemistry: A Forensic Case Study in AFFF Source Attribution

Andrew Horwath, Associate, Langan Engineering and Environmental Services

As regulatory frameworks for Per- and Polyfluoroalkyl Substances (PFAS) tighten, distinguishing between acute releases and ambient background is critical for liability management. This presentation details a forensic investigation at a manufacturing facility following a fire suppression event involving Aqueous Film Forming Foam (AFFF). The case presents a dichotomy of claims versus evidence: the facility claims a "PFAS-free" process and responders indicated that the AFFF  was certified as free of legacy PFOA/PFOS. However, characterization of soils, sediments, and water identified a spectrum of PFAS, including legacy compounds and fluorotelomers, extending on- and off-site.  We will explore the strategies used to unravel these conflicting datasets. The discussion focuses on chemical analysis techniques used to identify the AFFF signatures and differentiate them from anthropogenic background noise. We will present data comparing source zones against derived background concentrations, evaluating potential off-site contributors that complicate the conceptual site model. By examining the relationships of specific analytes, we intend to differentiate the acute release from environmental baselines. This session is vital for technical professionals and legal counsel, demonstrating that effective defense requires a mastery of chemical forensics to accurately assign liability. We will illustrate how data interpretation provides the defensible evidentiary foundation needed to navigate AFFF litigation, distinguishing actual contributions from background noise in an increasingly litigious environment.

Andrew Horwath is an Associate at Langan with over 20 years of experience in environmental engineering, specializing in forensic investigation and remediation design. As a technical expert in legacy and emerging contaminants, Andrew leads complex site characterizations involving PFAS. His recent work involves source attribution and chemical speciation to differentiate acute releases from historical or regional contributors.  Andrew leverages his experience in environmental engineering and education in chemical engineering to provide defensible evidence for liability valuations, insurance claims, and cost-to-closure evaluations in state and federal litigation. He is a licensed Professional Engineer in 14 states and holds a B.S. in Chemical Engineering from Pennsylvania State University.