As a result of a detailed site investigation, per- and polyfluoroalkyl substances (PFAS) were identified in several environmental media and ecological receptors near the firefighting training grounds of a Canadian airport. Records showed that three fire training areas (FTA) operated in different locations at this airport: one in the 1950s, one between 1960 and early 1990s, and an active FTA which was constructed in 1993 and remains in use to date. The active FTA was reportedly constructed with a double liner system, complete with interstitial monitoring piping. Perfluorooctane sulfonate (PFOS)-based aqueous film-forming foams (AFFFs) were used in the active FTA until 2001-02, before switching to fluorotelomer-based AFFFs. Since the FTA was rarely cleaned, it was interpreted that residues from AFFF use accumulated over time in sludge and liquid at the bottom of the facility. Liquid overflow was observed from one of the manholes associated with the FTA and direct spraying of AFFF outside the FTA’s containment was also documented. Some of these shortcomings were rectified by upgrading the FTA or modifying firefighting training practices in recent years, but a critical question remained: “Is the active FTA still an ongoing source of PFAS to the environment?” This question was successfully answered by using the results of a water balance calculation along with PFAS signature analysis. The presentation will provide an overview of the practical approach that was followed for this assessment and share insights on how this approach can be used to assess contaminant contribution at FTAs or PFAS sources at other sites, and design upgrades that can successfully address the issue.

Stefano Marconetto, Associate, Senior Environmental Engineer, Golder
Stefano Marconetto is Golder’s global PFAS practice leader with 10 years of experience with the characterization and remediation of PFAS impacted sites. Stefano’s technical focus is primarily on detailed site characterization, fate & transport assessment and conceptual site model development, but his expertise also includes remedial options evaluation, feasibility assessment, remedial action plan development and implementation at military bases, firefighting training facilities, airports, manufacturing plants, power plants and waste disposal sites in North America and abroad. He has also provided technical training as well as support to clients in their liaison with project stakeholders on PFAS related issues. He authored presentations and guidance documents on PFAS, is currently an active member of the Interstate Technology & Regulatory Council (ITRC) PFAS team and is involved in several research projects in collaboration with prestigious universities and industrial partners on PFAS fate & transport and remediation.

It can be challenging to develop a robust conceptual site model (CSM) for federal sites with per- and polyfluoroalkyl substances (PFAS). There are multiple aspects to PFAS sites that differ from more often encountered contaminants, which may substantially increase the effort and associated cost to achieve a robust CSM that supports site-management decision making. This presentation will focus on three PFAS site characterization challenges and approaches to overcoming these challenges. Challenges include: a) source identification; b) estimating total PFAS mass and type; and, c) unsaturated zone mass.

The first challenge is identifying the source(s) of PFAS present at a site, and distinguishing site-related PFAS from potential external sources. PFAS have become widely distributed in the environment, and not all PFAS at a site may originate from releases or activities at the site. For example, identifying other potential sources is particularly important when PFAS are found either in surface water bodies or near landfills, airports, agricultural areas with biosolids application, or large industrial facilities.

The second challenge is quantifying the total mass and types of PFAS present. Over 3,000 PFAS have been commercially produced; therefore potentially many and varied PFAS may be present at a site. Accurately assessing PFAS types and total PFAS mass is critical for developing the CSM, site management strategy, evaluation of potential pathways and associated risks, and identifying and designing a remedial strategy. For example, not all PFAS may be effectively or equally treated by a given technology, including common methods such as sorption to granular activated carbon in pump and treat systems.

The third challenge is assessing the mass of PFAS in the unsaturated zone. Many PFAS releases result in a considerable portion of mass being present in the unsaturated zone, which over time infiltrates with successive precipitation and infiltration events. Characterizing the unsaturated zone mass is important for predicting future groundwater plume footprints and concentrations. Additionally, PFAS-specific infiltration dynamics need to be considered, for example transport of some PFAS are retarded by surfactant interactions in the unsaturated zone.

This presentation will discuss approaches to address these challenges including techniques such as PFAS forensics, specialized analytical capabilities, and robust site media characterization.

Matt Vanderkooy, Contaminant Geoscientist, Geosyntec Consultants
Matt Vanderkooy is a Contaminant Geoscientist with over nine years of experience evaluating sites in Canada and the United States. Matt focuses on building robust conceptual site models with the goal of supporting informed project decision making, including remedial selection and design. Matt specializes in characterizing and remediating sites involving contaminants at the groundwater-surface interface, in contaminated sediments, and identifying pathways PFAS reach receptors through multiple media.