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1 <br /> Shell 3 - March 29, 2012 <br /> j <br /> Site Description <br /> The Site is located at 620 Charter Way in Stockton, California and is an active retail gasoline <br /> station. The Site is bounded by an off ramp to 1-5 to the west, West Charter Way to the north <br /> and a business to the east and south. The surrounding land use is commercial. <br /> Site History/Assessments <br /> In July 1989, soil contamination was identified by an environmental investigation. To date, 20 <br /> monitoring wells have been installed and monitored regularly. A Site map showing the location <br /> of the current USTs, monitoring wells and groundwater level contours is provided at the end of <br /> this five year summary. <br /> Remediation Summary <br /> • Free Product: Free product is noted in MW-2 (up to 0.37 feet), MW-3, MW-4 (up to 0.18 <br /> feet), MW-7 and MW-16-50 (up to 0.05 feet). Free product continues (MW-16-50) in <br /> 2011. <br /> • Soil Excavation: Unknown <br /> • In-Situ Soil Remediation: Soil vapor extraction, conducted from September 1992 <br /> through November 1996 removed approximately 17,628.pounds of TPHg. <br /> • Groundwater Remediation: No groundwater remediation has been conducted. <br /> General Site Conditions <br /> Geology;and Hydrogeology: The Site is underlain by interbedded and intermixed sand, <br /> silt and clay. The depth to groundwater varies between 15 and 19 feet bgs and the <br /> groundwater gradient is variable, southeast at approximately 0.001 ft/ft. <br /> • Estimate of Hydrocarbon Mass in Soil: Following remediation, Conestoga-Rovers & <br /> Associates estimated that 4,275 pounds of TPHg remains beneath the site. <br /> • Groundwater Trends: There are more than 22 years of groundwater monitoring data for <br /> this Site. Benzene trends are shown below, "source area (MW-16-50), near down <br /> gradient!(MW-4). and far down gradient (MW-5) <br /> A Benzene Trend for MW-16-50 <br /> 2500 _ <br /> J <br /> 2000 — <br /> `e1500 <br /> y <br /> e � <br /> 1000 <br /> CO <br /> r 500 — <br /> '. 0 <br /> lb 1\�\ti <br />