Many aqueous film forming foam (AFFF) delivery systems in aircraft hangars and firefighting vehicles may require thorough cleaning to avoid ongoing environmental impacts from residual per- and polyfluoroalkyl substances (PFAS) within those systems. Though replacement AFFF formulations are being introduced, existing residuals and legacy impact within these AFFF delivery systems are likely to continue to discharge PFAS. Anecdotal and vendor supplied cleaning methods exist, but they can be insufficient for the ultra-trace levels of concern. Thus, current operational parameters may need to be adjusted to meet the challenges presented by PFAS. Currently, no framework is available for evaluating the cost and environmental impact of cleanup compared to the costs of replacing components and systems.

The primary goal of this project is to provide data and information to refine existing cleanup guidance for firefighting systems, specifically hangar systems and Aircraft Rescue and Firefighting (ARFF) vehicles impacted by PFAS. The working hypotheses and/or assumptions are:

1. The two options for dealing with firefighting systems are cleanup to remove PFAS and/or replacement of PFAS-impacted components.
2. Cleanup (e.g., flushing) protocols exist but may not be sufficient to remove PFAS to the desired levels.
3. Replacement of components is intrusive and costly, but this can be minimized by understanding why components may be sources of PFAS and design strategies to better clean those without replacement.
4. Cleanup, if not performed thoughtfully, can generate large volumes of waste.
5. Protocols can be optimized by modeling the hydraulics of piping systems and the sorptive behaviors of PFAS to the firefighting systems.
6. If sampling protocols for verifying cleanup efficacy are not well designed, this will lead to false assurance of cleanliness.

The overall technical effort involves providing data, information, and best practices on the efficacies of cleanup techniques for firefighting systems. Operational details of those techniques will be informed by PFAS-specific experimental studies of material-specific persistence and modeling of the firefighting piping systems. The studies would be aimed at components of the firefighting systems (e.g., hangar systems and ARFF equipment) considered the mostly likely points to act as PFAS reservoirs, keeping in mind the multitude of systems in existence of varying ages, resulting in site- and vehicle-specific cleanup challenges. A second goal of the cleanup techniques would be to minimize the production of PFAS-containing cleanup solutions. These experiments and demonstrations for cleaning firefighting systems and managing cleanup solutions, along with the phenomenological and hydraulic modeling of piping systems, will allow the results to be applied to many situations.

The project’s data and demonstrations will refine existing practices for cleaning firefighting systems and managing the waste produced by the operations. This study will provide data to support whether the firefighting system are inherently resistant to adequate cleanup thereby requiring replacement of specific components or entire systems. While replacement might be warranted for impacted components, replacement could also be warranted if the costs associated with managing the residuals are high. The overall benefit of this project will be the development of a standardized cleanup framework based on a toolbox of options utilized across the DoD and civilian aviation firefighting community which could potentially lead to substantial cost savings. (Anticipated Project Completion - 2023)