This project is intended to understand the practical implications of per- and polyfluoroalkyl substance (PFAS) migration from concrete impacted by historical use(s) of aqueous film-forming foam (AFFF) to potential receptors such as natural waters (e.g., stormwater, groundwater, surface water) and inform decisions on the necessity for and selection of optimized passive management. Based on existing data from concrete core samples, PFAS concentrations have been observed at 10s to 100s of micrograms per liter in leachate compared to a low nanograms per liter screening criteria and therefore, impacted concrete could represent an ongoing secondary source that may necessitate removal resulting in additional waste generation and management.
The overall objectives of this project are to 1) compare an established leaching test method for intact concrete cores to an adapted method that considers PFAS chemistry and permeability of intact concrete and 2) evaluate field-scale application of commercial sealants to manage and mitigate PFAS leaching from concrete and associated waste streams.
The technology to mitigate PFAS leaching from impacted concrete is commercially available sealants. Novel components of this work include comparing an established leaching method to those developed by the team for the purposes of evaluating PFAS leaching from concrete and investigation of concrete infrastructure potentially representing a risk to the Department of Defense (DoD). Based on observed leaching, a practical mass flux evaluation of PFAS leachability will be considered to evaluate if management is required and how management could assist with source control as part of an overall site management and remediation strategy. The project will also attempt to validate the durability and PFAS leaching mitigation of commercially available sealants, with success measured by sustained mitigation of PFAS in runoff samples and holistic mass flux of PFAS to natural waters when exposed to field conditions over the period of performance. The field-scale sealant evaluation is contingent upon characterizing concrete infrastructure at multiple sites to evaluate whether passive management is necessary.
There are few comprehensive evaluations pertaining to the magnitude of PFAS leaching from impacted concrete and its potential risk to natural water. Developing regulatory attention and criteria within the nanogram per liter range may result in the need DoD to potentially manage ongoing PFAS leaching from concrete infrastructure via costly and disruptive removal and/or transition of waste debris to a landfill.
The overall expected benefits of this project include evaluating the potential risk of PFAS leaching from concrete, mitigating a potential ongoing contributing source to natural water via passive management, and reducing future concerns of a potential secondary source. By mitigating PFAS leachability from concrete infrastructure the potential prolonged discharge of PFAS to natural waters is reduced without physical removal. Further, decreasing the PFAS mass flux to the environment will reduce costs associated with managing potentially impacted natural waters via treatment (e.g., extraction/collection treatment systems). If the durability of the sealant applied to the impacted concrete is determined to be sufficiently robust, it may also reduce the risk associated with potential off-site disposal of the concrete infrastructure. Lastly, establishing a logical way to evaluate PFAS leaching from concrete and the associated influence on natural water will enable mitigation of potential secondary sources and allow for development of a pragmatic approach to holistic site management for PFAS. (Anticipated Project Completion - 2025)