Williams Air Force Base (Former)

Williams Air Force Base was a United States Air Force flight-training installation on the eastern edge of Mesa, in Maricopa County, Arizona, roughly 30 miles southeast of Phoenix. Established in 1941, the base grew to cover approximately 4,043 acres and became one of the Air Force's leading pilot-training facilities, training a substantial share of the service's pilots over its operating life. During World War II it prepared bomber crews, and in the postwar decades it shifted to jet pilot training and specialized programs for allied air forces. The base closed on September 30, 1993, and the property has since been redeveloped, most visibly as the Phoenix-Mesa Gateway Airport, along with educational and industrial uses. Cleanup of legacy contamination has continued at the site since closure.

Decades of flight training, fuel handling, fire-training exercises, and waste disposal left a range of contaminants in soil and groundwater at the former base. Investigators have documented an impacted groundwater plume that extends a short distance beyond the former base boundary, and several of the substances of concern have been associated with health effects in other settings, which has prompted concerns about potential exposure among those who lived or worked there.

1. PFAS (per- and polyfluoroalkyl substances): These are long-lasting synthetic chemicals that were a key ingredient in firefighting foams. At the former Williams Air Force Base, PFAS have been detected in soil and groundwater, and the use of AFFF firefighting foam at the installation has been identified as a likely source. PFAS exposure has been associated in some studies with a range of health concerns, which is why their presence is closely monitored.
2. Solvents (TCE and PCE): Industrial solvents such as trichloroethylene and perchloroethylene were widely used for degreasing and equipment maintenance. Monitoring at the base found increasing concentrations of TCE and PCE that were beginning to move off site within the groundwater plume. These volatile organic compounds have been associated with potential health effects, and concerns about exposure relate mainly to contaminated groundwater.
3. PCBs (polychlorinated biphenyls): These are manmade chemical mixtures once common in electrical equipment and other industrial applications. PCBs have been documented among the soil contaminants at the former base. PCBs are persistent in the environment and have been associated with potential health concerns, which is one reason they are tracked during site cleanup.
4. Heavy metals: Metals were present in soil at the site as a result of various base operations and waste-handling activities. Certain metals can persist in soil and have been associated with potential health effects depending on the level and route of exposure, prompting their inclusion in site monitoring and remediation.
5. Jet fuel and petroleum hydrocarbons: Aviation fuel storage and handling left fuel-related hydrocarbons in soil and groundwater, including light non-aqueous phase liquid (free product) tied to aviation fuel. Petroleum constituents and the volatile compounds associated with them have raised concerns about potential exposure, and large quantities of hydrocarbons have been the focus of extensive treatment efforts.

The former Williams Air Force Base was placed on the EPA National Priorities List, the federal Superfund program, on November 21, 1989. The Air Force has organized cleanup into multiple operable units addressing the landfill, fuel storage area, fire-training area, and other zones. Remedies have included landfill caps and annual inspections, soil vapor extraction, in-well air stripping, steam-enhanced and bioremediation methods for fuel-related contamination, chemical oxidant injections, institutional controls, and ongoing groundwater monitoring. Cleanup remains active, and the site is reviewed periodically under the Superfund process.

Veterans and family members who served at or lived near the former Williams Air Force Base may wish to stay informed as monitoring and cleanup continue and as scientific understanding of these contaminants develops. Anyone with questions about possible exposure or related health concerns is encouraged to speak with the U.S. Department of Veterans Affairs about benefits, screening, and any programs for which they may be eligible.