Formatted Title
Using a Multiple Lines of Evidence Approach for Remedial Investigations and Conceptual Site Model Development for Per-and Polyfluoroalkyl Substances (PFAS) Contaminated Sites
Background/Objectives
Background/Objectives: Per-and polyfluoroalkyl substances (PFAS) are very stable synthetic chemicals with properties that allow them to repel both water and oil. There are thousands of PFAS with various chemical groups in the environment. However, approximately 40 PFAS can currently be analyzed and identified by analytical laboratories. Since the use of PFAS-containing materials is widespread, there may be multiple on- and off-site sources contributing to groundwater contamination within a site investigation area. PFAS are often detected in low levels in groundwater samples collected during site investigations in industrial or urban settings where no obvious on-site source exists, and frequently, no background values are available to evaluate the potential contributions from off-site sources.
Approach/Activities
Approach/Activities: Multiple lines of evidence to PFAS remedial investigations can be used on a wide range of PFAS-impacted sites to determine the source(s), via fingerprinting the range of PFAS that are present, both on-site and down-gradient, within soil, groundwater, surface water, and sediment. In order to evaluate and distinguish PFAS impacts from on-site activities and those from off-site, or background sources, the use of multiple lines of evidence is required. Site investigations should begin with a comprehensive review of any available historical environmental data and geologic/hydrogeological maps and reports conducted on a regional scale and the incorporation of these findings into the site-specific data, such as downhole geophysical and borehole profiling data, to develop the conceptual site model (CSM). Other site-specific groundwater geochemistry data, such as pH, specific conductivity, dissolved oxygen, temperature, salinity, and oxidation-reduction potential can provide insight into understanding the fate and transport of PFAS with the environmental media, as well as understanding the migrations pathways of other contaminants that may be present at the site. Iterative data collection is key in developing a defendable CSM, and is also important for supporting a multiple lines of evidence approach when conducting PFAS investigations at complex sites, especially where the use of downhole geophysical profiling and higher resolution site characterization techniques can be used to gain a fundamental understanding of groundwater flow and contaminant transport through discrete aquifer zones, whether in fractured bedrock, between bedding planes, or within the stratigraphic material in an unconsolidated aquifer.
Results/Lessons Learned
Results/Lessons Learned: This poster summarizes some of the specific investigation methods that can be used in site characterization and to visually display the specific PFAS distribution in groundwater that can be used to identify multiple sources at one site. This poster summarizes various tools used to characterize complex sites where multiple on-site sources may be present and/or other off-site sources may be contributing to the groundwater contamination at one site. The use of the multiple lines of evidence approach provides robust data that can be relied upon for site characterization, developing the CSM, and for providing a foundation for determining feasible remedial strategies.