Draft Final Assessment of Appropriate Fuel Hydrocarbon Cleanup Strategies for George Air Force Base, Victorville, California Using a Risk-Based Approach

摘要

In June 1994, the State Water Resource Control Board (SWRCB) contracted with the Lawrence Livermore National Laboratory University of California (LLNL/UC) Leaking Underground Fuel Tank (LUFT) Team to study the cleanup of LUFTs in California. The study consisted of data collection and analysis from LUFT cases and a review of other studies on LUFT cleanups. Two final reports were submitted to the SWRCB in October and November 1995. These reports were entitled: Recommendations To Improve the Cleanup Process for California's Leaking Underground Fuel Tanks (LUFTs), and California Leaking Underground Fuel Tank (LUFT) Historical Case Analysis. The U.S. Environmental Protection Agency (EPA) has reviewed both LLNL/UC reports and issued a fact sheet supporting the findings and recommendations. Data were collected primarily from the alluvial geologic settings typical of the San Francisco Bay Area, Los Angeles Basin, and the Central Valley. These data represent California's highly populated areas where most gas stations are found and most LUFT releases occur. Study results can be applied to similar settings throughout California. The length of dissolved benzene plumes in groundwater at LUFT releases were evaluated over time to determine how plumes behave. Over 1,200 LUFT cases were evaluated. Benzene was analyzed because it is the human carcinogen of greatest concern in fuel. It is relatively soluble in water, and cleanup standards are generally tied to benzene concentrations. Ninety percent of the dissolved benzene plumes were less than 280 ft. in length. Most of these plumes were either stable or shrinking in length. Seventy percent of the plumes in the study sites were found in shallow groundwater, less than 25 ft. below the ground surface. The study concluded that with rare exceptions, petroleum fuel releases will naturally degrade (passive bioremediation) in California's subsurface conditions. Removing the source of the release will speed the cleanup time.