PUBLIC HEALTH ASSESSMENT
WILLIAMS AIR FORCE BASE
MESA, MARICOPA COUNTY, ARIZONA
Williams Air Force Base (Williams AFB) is in Mesa, Maricopa County, Arizona, approximately 30 miles southeast of Phoenix and just east of Chandler. Williams AFB, constructed in 1941, operated primarily as a flight training school from 1942 until the base closed on September 30, 1993. A variety of hazardous wastes have been handled, stored, and disposed of at Williams AFB, resulting in soil and groundwater contamination at a number of locations.
The Air Force has identified 32 areas of potential concern at Williams AFB. These sites include landfills, fire protection training areas, pesticide burial areas, former skeet ranges and firing ranges, and hazardous materials storage areas. The Agency for Toxic Substances and Disease Registry (ATSDR) conducted a site visit in February 1997. ATSDR staff examined all 32 areas for potential exposure pathways but identified only one potential exposure pathway of concern associated with Williams AFB--exposure to soil at the Former Skeet Range (Site SS-19). This public health assessment (PHA) focuses on the evaluation of this pathway.
Potential Exposure to Contaminated Soil at the Former Skeet Range
The Former Skeet Range does not pose a current public health hazard because people are unable to access areas that contain high lead concentrations (greater than 400 milligrams per kilogram [mg/kg]) and therefore are not exposed to contaminated soil. Future exposures will not pose a public health hazard because corrective activities will (1) reduce contaminant concentrations and (2) ensure that exposures to soil with lead at concentrations above 400 mg/kg are prevented. ATSDR has further ensured the safety of future residents by preparing an educational fact sheet that will inform future residents of the area's former use and actions being taken to clean up the area. Past exposures to lead-containing soil at the Former Skeet Range are unlikely because the area was covered by lawns, foundations, roadways, and sidewalks.
Exposure to the Other 31 Sites
An analysis of available information for the other 31 sites at Williams AFB indicates that these sites are not associated with past, current, or future public health hazards because (1) no site-related contaminants are present, (2) contaminant concentrations detected are too low to pose a public health hazard, (3) past and current exposures have been prevented by strict security measures, or (4) affected areas have been or will be remediated.
Williams Air Force Base (Williams AFB) is in Mesa, Maricopa County, Arizona, approximately 30 miles southeast of Phoenix and just east of Chandler (see Figure 1). A variety of hazardous wastes have been handled, stored, and disposed of at Williams AFB, resulting in soil and groundwater contamination at a number of locations. Thirty-two potentially contaminated sites have been identified at Williams AFB (see Figure 2).
Williams AFB, constructed in 1941, operated primarily as a flight training school from 1942 until the base closed on September 30, 1993. Additional training programs for bombardiers, bomber pilots, instrument bombing specialists, and fighter gunnery were also housed on base. A variety of activities, such as maintenance of aircraft (e.g., T-36, T-38, and F-5 planes) and firefighter training involved the use of hazardous materials (IT, 1989). Industrial solvents, jet fuels, oils, lubricants, plating rinse waters, aircraft washing solutions, paint strippers, caustics, and pesticides were used at the base. Many of these materials contain volatile organic compounds (VOCs) (e.g., benzene, toluene, xylene, methyl ethyl ketone [MEK], and trichloroethylene [TCE]); semi-volatile organic compounds (SVOCs) (e.g., polynuclear aromatic hydrocarbons [PAHs]); metals (e.g., lead, zinc, and copper); and total petroleum hydrocarbons (TPHs) (AFBCA, 1994; IT, 1990, 1996a).
Remedial and Regulatory History
The U.S. Air Force (USAF) began evaluating Williams AFB in 1983 through its Installation Restoration Program (IRP). The IRP is designed to identify, evaluate, and clean up environmental contamination resulting from past waste management practices. Investigators discovered soil and groundwater contamination during these investigations. As a result, Williams AFB was placed on the Environmental Protection Agency's (EPA) National Priorities List (NPL) on November 21, 1989. The USAF, the EPA, the Arizona Department of Environmental Quality (ADEQ), and the Arizona Department of Water Resources entered a federal facilities agreement (FFA) on September 21, 1990. The FFA prioritizes and schedules investigation and remedial activities, establishes a cooperative relationship between federal and state agencies, defines the roles and responsibilities of the different agencies, and resolves disputes (AFBCA, 1994; IT, 1996c).
More than 100 potentially contaminated areas have been investigated at Williams AFB. Characterization studies (e.g., an initial assessment study, remedial investigations, a facilities assessment study, and an evaluation/assessment study) have been conducted to determine whether these sites are actually contaminated, and, if so, the extent of the contamination. Based on the results of these investigations, concern over the majority of sites was quickly eliminated (IT, 1993). Thirty-four sites (the IRP sites) were considered to pose potential hazards and were investigated more extensively. Today, there are 32 IRP sites; 1 noncontiguous site (ST-14) was transferred to Luke AFB, Arizona, and another site (SD-15) has been incorporated into IRP Site SD-09 (USAF, 1996b). The 32 IRP sites (listed in Appendix A) have been investigated under 6 operable units. Many of these sites contained contamination at concentrations requiring remedial action. Remedial activities have been completed at the majority of sites and are ongoing at others.
Before its 1993 closure, Williams AFB supported a staff of approximately 870 to 1,600 civilian employees and 3,029 military personnel, 2,700 of whom lived on site (AFBCA, 1994; EPA, 1992; IT, 1990, 1996c).
The Agency for Toxic Substances and Disease Registry (ATSDR) used 1990 census data to compile demographic information in Tables 2 and 3. The census tract that surrounds the base covers over 119 square miles, but it had only 107 persons per square mile in 1990. The base, which has since closed, had a density of 419 persons per square mile. The somewhat higher proportion of males in both areas is typical of locations near military sites. The high percentage of persons of Hispanic origin in the nearby area is also typical for Arizona, due largely to its proximity to the Mexican border. There are relatively high percentages of children under age 10 and very low percentages of persons age 65 and older in both areas (See Figure 3).
Only one household in the base area was owner occupied in 1990, while more than three-quarters off site were owner occupied; a high percentage of owner-occupied households suggests a relatively stable, nontransient population. More than 20% of households off site were mobile homes, which is quite high. The median value of off-site owner-occupied households was relatively high at more than $126,000, while median rent was considerably more moderate.
Upon closing, Williams AFB was transferred to the Air Force Base Conversion Agency (AFBCA) (IT, 1996a). AFBCA assumed responsibilities for the restoration and reuse of the base and is working with the Restoration Advisory Board and Williams redevelopment partnership to maximize reuse. For redistribution purposes, the base has been divided into 42 parcels (USAF, 1996a). To date, 77% of the base's 4,043 acres have been transferred for reuse (USAF, 1996a)--mostly to the Williams Gateway Airport Authority and Arizona State University (ASU). Land has also been transferred to the Maricopa County Community College District, Maricopa County Accommodation School District, the Department of Health and Human Services, and the U.S. Army Reserve Center.
AFBCA will make additional transfers to ASU, the National Weather Service, the City of Mesa, the Salt River Project, the Gila River Indian Community, and the Maricopa County Flood Control District in the future. The USAF will retain several on-base buildings (USAF, 1996a).
Williams AFB is in a valley that has a long history of intensive agricultural use. Predominant crops are citrus, cotton, and alfalfa (EPA, 1992). Over the next 25 years, proposed commercial and residential development plans could dramatically alter the demographics and land use of areas surrounding the base. The East Mesa Subarea Plan proposes to develop portions of Mesa, Gilbert, Apache Junction, and land to the north of Williams AFB. Under this plan, land would be developed within 2 miles of the base's southern border, but areas developed to the north of the base would be more than 4 miles away. The Queen Creek-Chandler Heights Plan proposes to develop land immediately adjacent to the base's southern border (IT, 1996a).
In February 1997, ATSDR staff members conducted a site visit at Williams AFB. They toured the base and met with personnel from Williams AFB, Brooks AFB, ADEQ, and the Arizona Department of Health Services. ATSDR staff did not identify any community health concerns during the site visit. ATSDR identified the Former Skeet Range (Site SS-19) as the only area that poses a potential health concern (ATSDR, 1997a). Exposure to contaminated soil at the Former Skeet Range will be evaluated and discussed in this public health assessment (PHA). Appendix A describes the remaining 31 IRP sites.
In preparing this PHA, ATSDR relied on the information provided in the referenced documents and contacts. The agency assumes adequate quality assurance and control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analyses and conclusions drawn in this document are determined by the availability and reliability of the referenced information.