Case Studies in the Application of Forensics to Assess Source and Background Concentrations
Olivia Cain, P.E., Environmental Engineer, Geosyntec Consultants, Inc.
USEPA expects to finalize a rule designating two PFAS substances, PFOA and PFOS, as CERCLA hazardous substances in March 2024. The designation of PFOA and PFOS as hazardous substances is significant, as it will allow the USEPA to list PFAS sites on the National Priorities List (NPL) for investigation and remediation as Superfund sites. Additionally, a house and senate bill were recently introduced to the Florida legislature in January 2024 to propose wastewater effluent limits for industrial users and dischargers. Increased regulation of PFAS at the state and federal levels is a reality that will spur accelerated growth in PFAS investigation and remediation activities. As of November 2023, the FDEP has identified 165 Sites with PFAS contamination above Provisional Cleanup Target Levels. Additionally, a total of 414 public water systems in Florida are scheduled to participate in EPA’s Fifth Unregulated Contaminant Monitoring Rule. With these developments and the anticipated costs of addressing PFAS in a variety of environmental media, there is a growing need to better understand the sources of PFAS contamination. Several factors unique to these compounds complicate forensics evaluations, including evolving analytical standards and the changing regulatory landscape. However, fundamental chemical, physical, and statistical forensics techniques remain as valid and valuable as ever. This presentation covers common and developing forensics tools to quantify background contributions and differentiate multiple sources of PFAS. Two case studies will also be discussed. (i) The first is an example of a focused dataset where simple visual-based analyses were applied to assess sources and background and demonstrate to the regulatory agency that the PFAS detected above screening criteria in the assessment area were not the result of previous industrial activities at the subject site but, rather, multiple off-site sources and anthropogenic background concentrations. (ii) The second case study includes a large dataset (>1,000 samples) to investigate whether PFAS from a former AFFF manufacturing facility impacted different regions within the study area. Multiple lines of evidence were considered (including the use of a principal component analysis to assess sources and background signatures) to demonstrate to the regulatory agency that the PFAS within the study area were the result of mixed PFAS sources, including inputs from the manufacturing facility, but could not be attributed to the manufacturing facility alone.
Olivia Cain is a registered professional engineer in Florida based out of Geosyntec’s Clearwater office. Her practice focuses on contaminant assessment, remediation, and engineering design. Ms. Cain’s PFAS practice includes multi-media sampling, identification of potential PFAS sources both on- and off-site, development of conceptual site models, PFAS treatment design, and litigation support. She has managed or supported PFAS assessment, evaluation, and/or treatment at over 35 sites, including over 25 in Florida.
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