PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)

Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) Monitored Retention (PMR) is an approach for managing PFAS-affected sites that relies on natural retention processes that can lessen the migration and maximum concentrations of many PFAS at impacted sites. Because PFAS have not yet been shown to degrade to harmless end products by natural abiotic or biological actions, these retention processes (e.g., sorption, matrix diffusion) are expected to be the primary factors that dictate how PFAS behave and move in the environment (ITRC, 2023; Newell et al., 2021a; Newell et al., 2021b, Adamson et al., 2022; Brusseau et al., 2018; Guelfo et al., 2021; Guo et al., 2020), and they form the basis for PMR. The PMR concept has been incorporated into a framework that can help users determine the suitability of PMR at a specific site or identify the highest priorities among a portfolio of PFAS-affected groundwater sites. This framework provides guidance on collecting different types of data (lines of evidence) to support a PMR evaluation. It also describes enhanced retention strategies known as PFAS Enhanced Retention (PER) that may be applicable for management of sites where natural retention is insufficient on its own but more active remediation such as excavation of soils may not be necessary to protect downgradient receptors.