Determining PFAA Plume Stability Condition Quickly and Efficiently

While petroleum plumes and even many chlorinated solvent plumes stabilize in size on a time scale of a few to several years, perfluoroalkyl and polyfluoroalkyl substances, particularly perfluoroalkyl acids (PFAAs), in groundwater pose a specific challenge for site investigation and remediation due to their recalcitrance, which creates a potential for much longer-term plume expansion. Understanding the plume stability condition (i.e., is the plume expanding, stable, or shrinking) is essential for plume management and remedy selection, but resolving this trend using conventional monitoring methods can take 5 to 10 years or longer at many sites. This paper explores the difficulties in determining plume stability condition and presents four tools for evaluating stability condition more quickly and more efficiently: (1) high-resolution spatial sampling, (2) high-volume sampling, (3) passive integrative samplers, and (4) statistically based high-frequency sampling. By employing these tools, site managers can optimize monitoring strategies to quickly discern if and how much PFAA plume expansion is occurring and make timely informed decisions regarding PFAA plume management.