The overall objective of this project is to identify and quantify the potential contributions of background concentrations of per- and polyfluoroalkyl substances (PFAS) to support more informed site assessment and management. The goal is to understand the extent of aqueous film forming foam (AFFF) impacted source areas and their contributions to groundwater relative to background sources. The specific objectives of this demonstration include:

• Collecting and compiling data to better document and validate threshold values for differentiating between PFAS in background areas relative to areas with known releases.
• Developing approaches to identify the potential sources of PFAS on a site-specific or regional basis.
• Understanding the relative magnitude of impacts to groundwater and porewater from background sources that could be demonstrated or reasonably expected.
• Developing best practices for evaluating site-specific background contributions.

This project plans to apply a combination of methods that will generate high-resolution PFAS analytical data that are useful for building a framework for assessing PFAS background contributions.

• Task 1 will address how to better identify the likely background sources of PFAS. Subtasks include documenting relevant sources of background PFAS and establishing a sampling/analysis program.
• Task 2 examines how to document and validate threshold values for background PFAS concentrations in various media. Samples of various media across large geographic areas (nationwide sampling) will be collected and statistically evaluated to establish threshold values for individual PFAS with sufficiently robust datasets.
• Task 3 addresses the expected contribution of background sources of PFAS in various media to groundwater. Desktop studies will be performed to understand potential site-specific pathways to groundwater.
• Task 4 will develop best practices for site-specific evaluations of background PFAS. This will be done through a deliverable that identifies key elements for conducting a site-specific background assessment. This will be a technical document that serves educational purposes as a first-level look at these issues, but can also function as general framework for site managers and contractors to follow.

The project will improve site management by showing how PFAS sources besides AFFF may contribute to PFAS observed at sites. Specifically, it supports ongoing efforts to more accurately establish the extent of impacted sites and prioritize remediation efforts accordingly. The goal of the project is to provide remedial project managers and their consultants with clear, concise technical guidance on how to understand the potential contributions of background sources of PFAS, including how to conduct a site-specific assessment of PFAS background as part of their remedial investigation. (Anticipated Project Completion - 2028)