EPA Superfund Site

F.E. WARREN AIR FORCE BASE

WY | EPA ID WY5571924179

About this site’s exposure pathways: As of September 2025, the F.E. Warren Air Force Base (Warren) Superfund site is considered Insufficient Data to Make a Human Exposure Evaluation (HEID) because of a newly identified potential exposure pathway and⁄or contaminant(s) known as per-fluor-alkyl substances (PFAS). At least three potential soil source areas were recently identified. PFAS are a group of man-made chemicals that includes perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), GenX, and many other chemicals. The drinking water maximum contaminant level standard for PFOA and PFOS is 4 ppt or 0.004 ug⁄l. Maximum concentrations in environmental media at Warren include soils up to 3,400 ug⁄kg; ground water up to 7,200 ug⁄l and one surface water detection of 112 ug⁄l.
Historic uses of aqueous Fire Fighting Foams are the source of PFAS at the base. The site was previously categorized as Human Exposure Under Control. The concentrations in soil, ground water, and surface water need to be delineated and assessed for potential exposure risks. EPA uses this Human Exposure status when there is a lack of evidence to suggest that actual or reasonably anticipated human exposures are occurring, and that those exposures are above acceptable risk-based levels.
As of September 2025, the planned activities to collect sufficient information to evaluate this new potential exposure pathway and⁄or contaminants(s) are to conduct a remedial investigation (RI), which will include a Human Health Risk Assessment (HHRA) and⁄or information about the human interactions with potentially contaminated media. The PFAS contaminants may be co-mingled with contaminants in ground water associated with the fourteen established Operable Units (OUs) on the base. One or more new OUs may be established to facilitate response actions. Direct soil exposure and ingestion of ground pathways must be evaluated. EPA currently anticipates that there will be sufficient data to make a Human Exposure evaluation by December 2026.
In addition, the Air Force is currently conducting RIs at multiple potential source sites and pathways. Sampling suggests PFAS may have migrated off-base in groundwater and/or surface water based on samples adjacent to the Base.