The site has produced small explosives and vehicular safety products since 1957. As a result of the historic operations, soil and groundwater at the site has been impacted by perchlorate, trichloroethene (TCE) primarily, and hexavalent chromium (Cr6+).
The site is underlain by alluvial/colluvial deposits consisting of interbedded sand, silt, and clay. There are three water bearing zones at the site; a shallow unconfined aquifer, and two deeper confined aquifers. Groundwater in the shallow aquifer is encountered at approximately 40 feet below land surface (bls) with perched conditions present in some areas. The most significant impacts to groundwater are present in the shallow aquifer. Consequently, much of the remedial effort completed to date has focused on this aquifer. A strategy is currently being developed to address impacts in the deeper aquifers, which extend up to 400 feet bls.
Source area soils have been found to contain perchlorate concentrations as high as 1,500 milligrams per kilogram (mg/kg), TCE as high as 6.5 mg/kg, and Cr6+ as high as 0.084 mg/kg. Concentrations of these same contaminants in shallow groundwater have been detected up to 500 milligrams per liter (mg/L), 90 mg/L, and 0.25 mg/L, respectively.
Previous groundwater remediation efforts have been limited in scope with modest results. A two-well shallow groundwater pump-and-treat system was installed in 1994. Performance data indicates this system is providing marginal mass removal and only localized hydraulic containment. In addition, a bioremediation pilot test was conducted using hydrogen release compound (HRC®) to treat TCE. The HRC® failed to remediate TCE within the test area, but resulted in significant reduction of perchlorate and Cr6+.