Hill Air Force Base sits near Ogden, Utah and has been on the EPA's National Priorities List since July 22, 1987. The base is divided into 19 operable units covering contamination both on the base and in nearby communities including Clearfield, Clinton, Layton, Riverdale, Roy, South Weber, and Sunset. Cleanup has been underway for decades, but physical construction is not yet complete across the entire site.
More than 100 chemicals have been identified as contaminants of concern. Chlorinated solvents are the most widespread, with trichloroethene found in groundwater, soil, soil gas, surface water, and air at multiple locations. Other contaminants include tetrachloroethene, benzene, petroleum-related chemicals, heavy metals like arsenic and chromium, pesticides, and polychlorinated biphenyls (PCBs). Contamination has been found in soil, groundwater, and indoor air. Vapor intrusion, where chemical vapors move from contaminated groundwater into buildings above, is a specific concern for nearby residents and businesses.
The Air Force, EPA, and Utah Department of Environmental Quality (UDEQ) have worked together under a Federal Facility Agreement in place since 1991. Cleanup methods include landfill caps, pump-and-treat systems, soil vapor extraction, bioremediation, and monitored natural attenuation. Records of Decision have been issued for 16 of the 19 operable units. Three units covering demolished buildings and per-fluoro alkyl substances (PFAS) are still in early investigation stages. The most recent five-year review, completed in December 2023, found cleanup work was done as planned. Human exposure is not under control across the full site, and groundwater migration status is uncertain due to insufficient data. The EPA and Air Force cannot yet conclude whether cleanup is fully protective at all areas, partly because of emerging contaminants including PFAS and 1,4-dioxane.
The base will remain an active military facility. A new Interstate 15 interchange along the western edge of the base has prompted adjustments to cleanup work at Operable Unit 5, including completed soil excavation in Spring 2025 and planned relocation of groundwater monitoring wells. Federal land needed for the interstate will transfer to the Utah Department of Transportation.
Community members can get involved through the Restoration Advisory Board (RAB), which meets quarterly in public sessions held in-person or virtually with details available on EPA's official site profile. Meetings are co-chaired by a community member and an Air Force representative, with EPA and UDEQ staff also attending. When a new cleanup plan is developed or an existing one is changed, there is a minimum 30-day public comment period. To join the mailing list or ask questions, contact Barbara Fisher at barbara.fisher.1@us.af.mil or (801) 775-3301. The Air Force also offers public site tours.
