A Practical Guide for Airports to Differentiate PFAS Sources

April 22, 2024

Airports now have a practical, data-driven approach to build lines of evidence as to whether activities at the airport, or from other sources, may have contributed to PFAS found on or near the airport property.

Published in the summer of 2023, the PFAS Source Differentiation Guide for Airports is intended primarily for airports with commercial air service, particularly Part 139 certificated airports that are required by the FAA to maintain and annual certify aircraft rescue and firefighting capabilities and equipment functionality.

For these airports, the FAA has required the use of aqueous film-forming foam (AFFF) that conforms to military specifications. Until the fall 2023, only AFFF products containing PFASs were approved by the FAA to satisfy required specification. The above research focused on “PFAS of Relevance” and its association with AFFF. Releases of AFFF at airports are the greatest “PFAS of Relevance” concern given the volume that is used and the direct pathways AFFF releases have to sensitive receptors (soil, water, etc.).

New and pending government regulations

Until recently, the U.S. Environmental Protection Agency’s former drinking water standard health advisory threshold to limit PFAS exposure was just that, an advisory. On April 10, 2024, EPA announced requirements that municipal water systems remove six PFAS chemical compounds present in U.S. drinking water.

The mandate does not directly affect airports, except in a rare instance where they also function as a public water drinking supplier. However, the implication is significant that municipal water systems, if they have PFAS impacts that exceed the new maximum contaminant levels (MCLs), will be looking for contributing sources of PFAS. Airports will be at the top of the easy list of potential PFAS sources.

In addition, EPA action in April 2024 designated two widely used PFAS as hazardous substances under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), also known as Superfund. The listing and “polluter pays” strict liability scheme will likely have a significant impact on airport environmental programs and other activities such as property sale/acquisition and soil management plans for airport construction projects.

The beginning of PFAS

Certain PFAS chemical compounds are used in AFFF to enhance extinguishing performance on fires fueled by flammable liquids and gases. These types of fires have a lower ignition temperature and spread rapidly once ignited. The U.S. Department of Defense (DOD) required the inclusion of certain PFAS in its

AFFF specification from the late 1960s until 2019. The FAA had required commercial airports certified under Part 139 to use AFFF that meet this military specification since 2006.

ACRP authorizes research

Under the auspices of the National Academy of Science Engineering in Medicine and the Transportation Research Board, the Airport Cooperative Research program issued a request for research on the development of an approach for airports to use when facing questions about whether activities at the airport or from nearby sources may have contributed to observed PFAS in local environmental media.

As the Guide states, “Often the first reaction by the public, media and local community when per- and polyfluoroalkyl substances (PFAS) are found near an airport is to conclude that the airport is the sole PFAS source; in fact, off-airport sources may be involved.”

To advance the understanding and use of PFAS source differentiation techniques, there was a need to consolidate available research and best practices into an easy-to-use guide and screening tool.

Led by contributors Janet Anderson, Dan Schneider, Mat Knutson and Zachary Puchacz, the team used machine learning to gather 800,000 publicly available data points of PFAS sampling results from throughout the U.S. and consolidated the research. Recommended practices that use a data-driven approach were then identified based on the research.

A three-step approach to PFAS source differentiation methodology

There is no ”silver bullet” for PFAS source differentiation today. However, these steps can help airports better understand potential PFAS sources and help build a lines-of-evidence approach regarding source differentiation.

1. Desktop review

It can be tempting to start with environmental sampling, but it is essential to first build an inventory of sites where PFAS may have been used at the airport and nearby in the community.

The desktop review is the collection of available information – through interviews, records search, news clippings and the like – that will produce a thorough understanding of potential on- and off-airport PFAS sources and geologic site characteristics that could indicate PFAS migration pathways. This first step can be carried out without environmental sampling but will inform a follow-on sampling rationale in a data-driven, lines-of-evidence approach.

2. Conventional sampling

The next step uses standard PFAS analytical methods available from most commercial laboratories. These analytical results can undergo a screening level forensic review to further build lines of evidence regarding potential PFAS sources. The ACRP research provides discussion on methods to screen and evaluate resulting data for source differentiation clues.

3. Advanced analysis

This third step, which includes advanced forensics to further differentiate and potentially identify PFAS sources, may be called for in some instances. It would involve laboratory methods that are of significantly higher cost than standard PFAS analytical methods.

The guide lays out the process by which airports can navigate these steps for source differentiation which it summarizes as:

· Understand readily ascertainable on-airport sources of relevant PFAS to the extent feasible, including historical and current potential sources.

· Evaluate areas near the airport, especially those that are hydraulically upgradient, to determine whether there are industries that use (or have used) PFAS or PFAS-containing products that could potentially contribute to PFAS environmental impacts.

· Develop a detailed understanding of site conditions: geological, hydrogeological, soil, and surface water runoff.

· Analyze environmental samples for PFAS when appropriate to assess relevant on-airport PFAS occurrence and concentration. Sampling may include upgradient and downgradient samples to investigate onsite PFAS migration onto the airport and the extent of any PFAS groundwater plume.

· Evaluate standard PFAS analytical data as a screening step to determine whether any source differentiation trends are evident.

· Conduct advanced PFAS source forensics on selected samples as appropriate to develop additional lines of evidence to further potentially differentiate PFAS sources.

The Guide, presented in a reader-friendly manner, is content rich and offers everything from a “PFAS 101” and “Frequently Asked Questions” to “How PFAS Move and Transform” and “PFAS Sampling Protocols and Best Practices”. It will help equip any affected airport operator to build lines of evidence related to PFAS source identification found on or near the airport property.

About the Author

Daniel F. Schneider

Daniel F. Schneider, P.E., CHMM, is a senior principal and National Director - Site Investigation and Remediation at Terracon. He has more than 34 years of experience in environmental, geotechnical, and remedial construction management engineering and leads Terracon’s PFAS Professional Network