WILLIAMS AFB
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. As of 2014, most of the identified contaminated areas have been addressed. The most significant remaining areas are include the ST-12 Fuels Spill Site and the LF-004 Landfill Site. At the ST-12 Fuels Spill Site jet fuel from leaking storage tanks and pipelines has contaminated an aquifer considered by the State of Arizona as a potential drinking water source not currently being used. 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. Following successful completion of the pilot, Air Force amended the Record of Decision in September 2013 to select full scale Steam Enhanced Extraction (SEE) combined with enhanced bioremediation as the final remedy for the site. The SEE system was constructed in 2014 and began operation in October, and will continue to operate for approximately 420 days until removal of as much of the mass of fuel product as practicable is complete. Enhanced Bioremediation will follow to further degrade residual contamination. The final remedy for the LF004 landfill was selected in April of 2014. The original Record of Decision selected a permeable cap of river rock to address direct contact concerns with elevated beryllium in surface soils, and required monitoring of the groundwater. Low levels of industrial solvents Perchloroethylene (PCE) and Trichloroethylene (TCE) were subsequently discovered in the groundwater. The Record of Decision was amended to include soil vapor extraction of shallow sources in the landfill area, In Well Air Stripping (IWAS), and chemical oxidation to treat the ground water.
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