Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Williams Air Force Base
EPA #: AZ7570028582
Congressional District: 01
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Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 07/14/89
Final Date: 11/21/89
The 4,043-acre Williams Air Force Base (WAFB) site was commissioned as a flight training school in 1941. Contaminants from base activities include organic solvents and paint strippers, petroleum spills, metal plating wastes, hydraulic fluids, pesticides, and radiological wastes. Discharges and disposal at WAFB have resulted in soil and groundwater contamination. Thirteen sub-sites have been identified as potentially contaminated areas including: two fire training areas, a fuel storage area , two surface storm drainage areas, a hazardous material storage area, a landfill, a pesticide burial pit, a radiological disposal area, and four underground storage tanks. In 1992, several new sub-sites were discovered at the base which were added to the investigation. To date 3,856 acres have been transferred for reuse by Phoenix-Mesa Gateway Airport authority and Arizona State University. However, the most wide-spread and complex remaining cleanup remedy at Williams remains to be implemented. Up to twelve million gallons of jet fuel have contaminated an aquifer considered by the State of Arizona as a protected drinking water source. In October 2008, Air Force initiated a Thermal Enhanced Extraction pilot test utilizing steam injection to extract the most toxic and mobile constituents from the plume.
Contaminants and Risks
- Soil and Sludges
Groundwater contains LNAPL and volatile organic compounds (VOCs). Soils contain various VOCs, PCBs, and pesticides from past disposal practices. Accidental ingestion of contaminated soil and groundwater is a potential health hazard.
Who is Involved
This site is being addressed by the United States Air Force through a Federal Facilities Agreement with the U.S. Environmental Protection Agency, the Arizona Department of Environmental Quality and the Arizona Department of Water Resources. The Air Force community contact for Williams Air Force Base is
Public Affairs Officer
Air Force Real Property Agency Western Region
3411 Olson St.
McClellan CA 95652-1003
(916) 643-6420, ext. 109
Investigation and Cleanup Activities
Williams Air Force Base is participating in the Installation Restoration Program, a specially funded program established by the Department of Defense (DOD) in 1978 to identify, investigate, and control the migration of hazardous contaminants at military and other DOD facilities. This site is being addressed in six operable units employing both short and long-term remedial actions as described below.
Initial Actions: A portion of the Southwest Drainage System was stabilized in 1988 by installing a soil, cement, and concrete cap on the ditch. In 1991, a small pesticide drum burial site was excavated and disposed of off site. Radiological materials were removed from another burial site and disposed of in late 1992. The removal of approximately 20 underground storage tanks at the liquid fuels storage area was conducted during late 1990 and early 1991, eliminating the source of liquid fuel leaks.
Operable Unit 1: Under EPA oversight, the Air Force completed an investigation of the nature and extent of the contamination at all impacted areas of the base. In 1994 a remedy was chosen that included installation of a permeable river rock cap over the main landfill of the former base, Site LF004 and long term groundwater monitoring.
Monitoring of the groundwater at Landfill LF-004 eventually revealed increasing concentrations of TCE and PCE, along with a rising water table. In 1997 groundwater monitoring identified contaminants (TCE and PCE) leaching out of the landfill and migrating off-site. A supplemental investigation in 2000 was unsuccessful in determining the exact source of the leaching. Meanwhile contaminated concentrations decreased. However, in 2004 contaminant levels began to climb above regulatory levels again. The plume of contamination is undefined and appears to be moving off-site. The Air Force has installed additional monitoring wells off site to help delineate the leading edge of contamination. Soil gas investigations have been conducted to identify sources of groundwater contamination within the area of the landfill. Soil gas survey data to date indicates a potential remediable source area. There is evidence that dissolved TCE and PCE are migrating off Air Force property in concentration exceeding drinking water standards. In May 2013, the Air Force solicited public comments on a proposed remedy for soil vapor extraction to treat vadose zone soils and in well air stripping technology to treat the groundwater plume. No public comments were received. The Air Force is now preparing the Record of Decision.
Operable Unit 2: Liquid Fuels Storage Area: In 1990, an investigation into the type and extent of contamination was initiated at the waste liquids storage area. At the conclusion of the investigation in late 1992, a remedy was chosen that involves pumping and treating the groundwater contamination, with reinjection of the treated groundwater. Treatability tests have indicated that pump treat technology may not be feasible. A Focused Feasibility Study (FFS) report was completed and submitted to the regulatory agencies in 1999 which recommended monitored natural attenuation with future studies to evaluate new technologies as they become available. Both the USEPA and the State of Arizona rejected the FFS report. To avoid a formal dispute resolution phase, the Air Force agreed to add Thermally Enhanced Extraction as a component of the groundwater remedy to enhance effectiveness and feasibility of the selected remedy to address LNAPL and dissolved phase contamination. From 2002 to 2005, the Air Force spent over 3 million dollars in the design and construction of this remedy. In a turn-around of events, on February 1, 2005 the Air Force notified EPA that funding to operate the remedy was not approved. Furthermore, the Air Force explained that it unilaterally amended their funding criteria which removed the Liquid Fuel Storage Area from funding eligibility. Following formal dispute resolution, in February 2006, Air Force agreed to fund the operation of the TEE pilot, and if successful, expand it to a scaled up final remedy. As of February 2010, the pilot test have been concluded, after having successfully removed 118,331 pounds of petroleum hydrocarbons and 3,652 pounds of benzene from the subsurface. The pilot was operated on a schedule due to funding constraints. Free product was still being recovered as operations ceased. The intent of the pilot was to demonstrate the removal effectiveness. In September 2013, the Air Force and the regulatory agencies signed a Record of Decision to complete the steam enhanced extraction remedy that had begun under the pilot. The remedy is currently in Design and Construction and is anticipated to resume operations in Fall 2014. The treatment is anticipated to run approximately 400 days. Following the steam treatment, enhanced bioremediation treatment will continue to treat residual contamination to meet regulatory standards. The Air Force has already completed a Finding of Suitability to Transfer the surface property of the ST-12 site.
Operable Unit 3: Site FT002. At this fire training site, all structures, piping, and 117 cubic yards of surface soil were removed and transported to approved off-site disposal areas. In addition, contaminant concentrations in 25,000 cubic feet of contaminated subsurface soil were reduced through bioventing. Bioventing didn't bring the contamination in deeper soil to levels that would allow unrestricted use.
The Air Force submitted a Draft Record of Decision Amendment to EPA with land use controls as part of the remedy. The Air Force then prepared and public noticed a Proposed Plan which removed the land use controls from the remedy. The EPA did not concur with the remedy without inclusion of land use controls, and Air Force subsequently formalized their land use control requirements with the State of Arizona. Recent sampling indicates contamination still remains in deep soils above remediation goals. The Air Force is now proposing to install a soil vapor extraction system to complete the remedy. Still to be completed are the finalization of the the ROD amendment and transfer of the property.
Operable Unit 4: the Record of Decision for Operable Unit 4 was signed in 1999 to address the former skeet ranges at South Desert Village, and site SS20 along with 8 other facilities. The ROD selected a six inch soil cap for the South Desert village housing area affected by the former skeet range, along with land use restrictions and long term maintenance and monitoring. At the SS- 20 skeet range the ROD specified removal of lead contaminated soils from firing range berm. In addition, institutional controls were specified for sites SS-16, former electroplating and chemical cleaning shop and building 1010 (site SS-24), and no further action was recommended for the other 4 sites.
Operable Unit 5 addressed nine facilities: ST-25 airfield underground storage tanks, WP27 Paint Shop Leach Field, DP-28 Sewage Sludge Trenches, SS-29 Prime Beef Yard, SS-31 Course Maintenance Area, SS-32 Building 1070, SS-34 Munitions Incinerator, LF 26 Concrete Hardfill Drum Removal Area, Area 26 Sewage Sludge Stockpile Area. Removal Actions were completed for these sites in 1995, and the OU-5 ROD was signed recommending no further action for these sites in 1998.
Operable Unit 6 addressed Site SS-17 the former Pesticide Paint shop recommending excavation of dieldrin contaminated soils, and no further action for for the investigative waste facility (IWF) and decontamination pad at building 1069. The excavated dieldrin contaminated soils from SS-17 were amended and stockpiled at another location on base in an unsuccessful attempt at bioremediation. In November 2007 the biotreatment piles were removed and disposed of , and Air Force has completed verification sampling of the soils around the biotreatment piles. A final report of completion of excavations was submitted to the agencies in April 2010. In 2011, the Air Force solicited public comments on a final remedy comprising institutional controls and ongoing groundwater monitoring. The Record of Decision is on hold as the Air Force is now questioning the need for institutional controls.
Parcel N Debris Area -- a vacant lot near the landfill still remaining to be transferred has been identified as having potential waste disposal and small arms munitions issues. Air Force is investigating this site due to evidence of possible releases and munitions.
Cleanup Results to Date
Cleaning the Southwest Drainage System and removing pesticide drums, radiological materials, and underground storage tanks have reduced the potential for exposure to contaminated materials at the Williams Air Force Base site while studies are taking place and cleanup activities are being implemented.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
The Air Force is finalizing cleanup plans to address the source of contamination at the landfill and to address the groundwater contamination at the ST-12 Fuels Spill site.
Documents and Reports
No documents found
Public Meetings: The Williams Restoration Advisory Board (RAB) meets quarterly at the Arizona State University Polytechnic Campus, Peralta Hall Room #132, 7171 E. Sonoran Arroyo Mall, Mesa, AZ 85212. For more information about RAB activities contact Amber Cargile at (480) 239-6269 or firstname.lastname@example.org
Public Information Repositories
The public information repositories for the site are at the following locations:
Government Records Section (3rd floor)
Arizona State University
300 East Orange Mall
Tempe, AZ 85281
Government Records Reference Desk: (480) 965-3390
The Air Force maintains the administrative record (AR) for the site. Documents are available via the Air Force Real Property Agency (AFRPA) Web Site.
Newsletters and fact sheets are available on the AFRPA Williams Web Site.
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