As a result of widespread use of aqueous film-forming foam (AFFF), many millions of tons of per- and polyfluoroalkyl substances (PFAS)-impacted paving materials potentially exist at fire training areas, runways, taxiways, and stockpiles resulting from runway renewal (e.g., resurfacing, regrooving), or infrastructure upgrades. These impacted paving materials may serve as persistent source zones for PFAS in ground and surface water due to slow release of PFAS. Stockpiled paving materials from maintenance and construction activities also may serve as PFAS sources. Limited mechanistic understanding of PFAS release from impacted paving materials as well as absence of standardized tools to rapidly assess this release limit development of viable options for disposal and reuse. Field managers need a practical and scenario-specific toolkit that provides test methods, assessment protocols, and guidance integrated into a “how-to” approach for evaluating leaching from PFAS-impacted pavements and recycled paving materials as well as to assess efficacy of treatment methods.

The overall goal of this project is to assess the role of fundamental phenomena in the leaching of PFAS from impacted concrete and asphalt through development and demonstration of laboratory leaching protocols coupled with field validation of laboratory leaching tests. Specific objectives are to:

1. characterize and verify fundamental phenomena that control PFAS leaching from concrete and asphalt;
2. adapt and demonstrate methods of the United States Environmental Protection Agency (USEPA) Leaching Evaluation Assessment Framework (LEAF) test methods for evaluating PFAS-impacted paving materials;
3. develop and validate practical calculation methodologies that allow for screening and scenario-specific estimation of PFAS leaching; and
4. provide comparisons and quantify uncertainty when using laboratory test methods for field leaching estimates.

The project objectives will be achieved through a combination of bench-scale, field-scale, and modeling efforts. Specifically, methods will be adapted for assessing PFAS content in concrete and asphalt. LEAF Method 1315, which evaluates diffusion from consolidated materials, will be developed and demonstrated for use with a wide range of PFAS-impacted concrete and asphalt (Objectives 1, 2). Field sampling and instrumentation will be used to evaluate PFAS leaching from concrete and asphalt at the field scale, and this data will be used to validate laboratory leaching assessments and resulting transport models (Objectives 3, 4). Models will be parameterized and calibrated using data generated in bench-scale assessments of leaching using LEAF methods, and the validated models will be used to assess different leaching scenarios, including leaching under varied management scenarios. A key advantage of these objectives is that they dovetail with initial work underway in Australia and ongoing work under existing SERDP project ER20-1126, which focuses on development and demonstration of LEAF for use with impacted soils and a limited number of consolidated materials.

The overarching benefit of this work will be the generation of techniques that can be used to support the prioritization and management of intact and stockpiled AFFF-impacted concrete and asphalt at DoD facilities, thus reducing the overall risks to human health and the environment due to PFAS exposure. This will be achieved through the development of pragmatic tools for understanding and evaluating PFAS leaching and mobility from impacted paving materials, which is essential for screening assessments, detailed risk assessments, and evaluation of treatment alternatives. A key advantage of this project will be coordination with SERDP, the Australian Department of Defence, and USEPA. Study results are targeted for incorporation into the USEPA LEAF program. Coordination of this work across U.S. and Australian agencies will result in methods that are broadly accepted in the U.S. and internationally. (Anticipated Project Completion - 2026)