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East Bay Municipal Utility District <br /> Stockton Service Center <br /> 18 1995 <br /> Groundwater Remediation <br /> CAMENTAL HEAL` <br /> _,,,MiT/SERVICES <br /> Executive Summary <br /> The Stockton Service Center is an East Bay Municipal Utility District (District) <br /> maintenance facility located at 1804 West Main Street, Stockton, California. <br /> Between 1987 and 1989, three underground storage tanks containing gasoline were <br /> removed from the site. Evidence of leakage was observed during the removal of the <br /> first tank in 1987. Groundwater monitoring wells were installed between 1989 and <br /> 1993, and soil and groundwater samples were collected to determine the extent of <br /> the contamination. Petroleum hydrocarbons were detected in the groundwater in the <br /> vicinity of the 1987 underground storage tank removal. The District has submitted <br /> quarterly groundwater sampling results since 1991. The groundwater is 10 feet below <br /> ground surface and is not considered a source of drinking water. <br /> The District evaluated several cleanup alternatives based on implementability, <br /> effectiveness, and cost. The results of the sampling and the evaluation of cleanup <br /> alternatives were reported to the San Joaquin County Public Health Services <br /> Environmental Health Division in the December 1993 Additional Site Assessment <br /> Remedial Options Report. Bioremediation was selected to cleanup the groundwater <br /> at the Stockton Service Center. A Remedial Action Plan detailing the <br /> implementation of the bioremediation was submitted to the San Joaquin County <br /> Public Health Services Environmental Health Division and the Central Valley <br /> Regional Water Quality Control Board in September 1994. <br /> Bioremediation is ' the process in which bacteria are used to breakdown <br /> compounds into carbon dioxide, water, and other non-hazardous compounds. <br /> Bacteria produce enzymes and biosurfactants to assist in the breakdown process. <br /> These enzymes and biosurfactants have been isolated and concentrated so that they <br /> will speed up the breakdown of the petroleum hydrocarbons when added to the <br /> groundwater. The proposed bioremediation uses bacteria already present in the <br /> groundwater at the Stockton Service Center and enhances the process through the <br /> addition of enzymes and biosurfactants. This system consists of pumping <br /> groundwater from a well near the center of the contaminated groundwater plume <br /> into a mixing tank, adding an enzyme complex and biosurfactants to the tank, and <br /> 95R2 East Bay Municipal Utility District <br /> 40429601\execsum.rem i Stockton Service Center-Remediation <br />