of PFAS could help municipalities in this instance. Fortunately, there is a guide and screening tool to accomplish this. Developed for a wide spectrum of users, including lay people, the PFAS Source Differentiation Guide for Airports presents a lines-of-evidence approach to help differentiate between PFAS sources. Federally funded research, led by contributors Janet Anderson, Dan Schneider, Mat Knutson and Zachary Puchacz, used machine learning to gather 800,000 publicly available data points in PFAS sampling results throughout the U.S., and consolidated the research. Recommended practices that use a data-driven lines of evidence approach were then identified based on the research. Although the research focused on airports, municipalities impacted by PFAS contamination levels could follow a similar lines of evidence approach to collaboratively obtain relevant PFAS data, analyze potential contributing PFAS sources, and pursue more detailed site analysis or determination of treatment options and assignment of PFAS liability. Reader friendly, the guide presents a wealth of information from PFAS 101 to PFAS Sampling Protocols and Best Practices. The lines of evidence approach are summarized in three steps: 1. DESKTOP REVIEW This is just what it sounds like—a search of news clippings, records and more that begins to tell the story of likely PFAS sources and geologic factors that suggest potential PFAS migration pathways. This work informs the next step. 2. CONVENTIONAL SAMPLING The PFAS Source Differentiation Guide offers options on screening methods and data evaluation using standard PFAS analysis available in most commercial laboratories. Results from sampling further builds lines of evidence regarding PFAS sources. 3. ADVANCED ANALYSIS Should it be necessary, advanced forensic methods to identify potential PFAS sources would involve additional laboratory methods and forensic analyses. These tend to be less standardized and widely accepted since they are more costly and take longer timeframes to complete than typical PFAS laboratory analyses. Many local governments lack the resources in expertise, tools and personnel to comply with EPA’s 2024 PFAS drinking water standard. Knowing how to access funding to help fill these gaps and methods to generate evidence-based data, if needed, that informs on PFAS source differentiation, are two steps any municipality can begin implementing today. the consultants can participate in the competitive bid response. THE RATIONALE FOR PFAS SOURCE DIFFERENTIATION As to enforcement, EPA has indicated that significant contributors to PFAS release in the environment will be its focus. In its PFAS Enforcement Discretion and Settlement Policy under CERCLA memo, EPA stated: “EPA does not intend to pursue entities where equitable factors do not support seeking response actions or costs under CERCLA, including, but not limited to, community water systems and publicly owned treatment works, municipal separate storm sewer systems, publicly owned/operated municipal solid waste landfills, publicly owned airports and local fire departments…” However, absent legislative protections, parties found responsible for PFAS contamination could move to include other parties—like local government water, wastewater and solid waste operations—into CERCLA’s “polluter pays” model. Developing data that provides evidence of different sources 10 CIVIL AND MUNICIPAL VOLUME 05, ISSUE 10
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