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Gasco . 3 - October 31 , 2011 <br /> Site Description <br /> The Site is located at 749 East Charter Way in Stockton , California and is an active retail <br /> gasoline station . The Site is bounded by a business to the west, a residence to the north , South <br /> Grant Street to the east and Dr. Martin Luther King Boulevard to the south . The surrounding <br /> land use is mixed residential and commercial. <br /> Site History/Assessments <br /> In November 1998 , soil contamination was identified during the removal of USTs . To date , 17 <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: No free product was documented throughout the life of this case <br /> • Soil Excavation : Unknown <br /> • In-Situ Soil/ Groundwater Remediation : Soil vapor extraction , conducted from July 1987 <br /> through July 2003, removed approximately 65, 187 pounds of TPHg . Dual phase <br /> extraction , proposed <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 approximately 28 feet bgs and the groundwater <br /> gradient is easterly at 0. 00095 feet per foot <br /> • Estimate of Hydrocarbon Mass in Soil : Prior to remediation , Apex Envirotech , Inc. <br /> estimated that approximately 47 ,752 pounds of TPHg remained in site soil. <br /> • Groundwater Trends: There are more than 21 years of groundwater monitoring data for <br /> this Site . Benzene trends are shown below, source area (MW-5) and down gradient <br /> (MW8) <br /> BENZENE Results for MW-5 <br /> 7000 <br /> a <br /> SOUD <br /> 4000 <br /> 1000k <br /> 4 .P� <br /> BENZENE Results for MW-8 <br /> 2030 <br /> loss <br /> 1400 <br /> 01200 <br /> o _ — _ — <br />