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- _ r <br /> 3 <br /> c .. <br /> E IN N1 <br /> I <br /> 1.0 INTRODUCTION/SITE HISTORY <br /> t This report is being submitted in response to a request by <br /> the San Joaquin County Public Health Services <br /> !w additional (SJDHS} for <br /> site investigation of <br /> j ; groundwater contamination at 1140otWest alHammer aLane, <br /> Stockton, CA (Figure 1). The subject property is currently <br /> , vacant, but previously, housed a gas station operation. The <br /> station formerly dispensed diesel fuel in addition to <br /> regular, unleaded and super unleaded gasoline. Six <br /> underground fuel storage tanks were removed from the site <br /> ' during 1987. The tanks consisted of four 6,000 gallon tanks <br /> and two 12,000 gallon tanks. <br /> Initial investigative work was done b j <br /> y Technology Inc. (GTI). GTI drilled three monitoring wells ton <br /> September 24-25, 1987, and eleven sail borings on June 24, <br /> 3.988• The results of these investigations, including soil <br /> and groundwater analyses, and borin <br /> s { � in GTI's reports dated Jul boring/well logs are contained <br /> 1989. <br /> Four additional monitoring wells 9were83 t1 drilled by d February 6 GTI on <br /> January 10, 1989, the drill logs were not <br /> i.; hed in a <br /> report by GTI, but v?ere included in a Wat rWork report <br /> dated November 11, 1989_ <br /> r• <br /> _i On October 12, 1989, four soil borings were drilled at the <br /> site by WaterWork Corporation. These borings were required <br /> rr1 to more accurately assess the site stratigraphy and extent . <br /> of soil. contamination for the <br /> purpose of <br /> remediation plan. Boring logs are C nt inedecifying in Wa erWork's <br /> a sol <br /> report dated November 11, 1989. <br /> On November 11, 19$g" an Interim Groundwater <br /> Report was submitted by S T48terWork to San Joaquin <br /> Monitoring <br /> y <br /> Public Health Services <br /> ( JPHS). This County <br /> report noted ?bc;=• <br /> action levels of benzene in wells MWl and MW4 free product <br /> in well MW5 sad a lack of water in well Mi43. Also the <br /> groundwater gradient was determined to be in the easterly s <br /> y, direction, which is consistent with San Joaquin County Flood <br /> :r Control and Water Conservation District Maps (Spring 1975, <br /> 1984, 1985). <br /> On January 3, 1990 pF <br /> a raximately 3,000 cubic yards of <br /> t contaminatedsoil was excavated and stockpiled on site. <br /> This work was performed by Telic Engineering of Stockton. <br /> Approval to aerate the soil was obtained from the San <br /> Joaquin CountyAir Pollution District. --The soil has been <br /> - - - subsequently aerated to below method detection limits and <br /> has been replaced in the pit and compacted <br /> 90$. to greater than <br /> J <br /> lip 11111111 ININ NiEllialm <br />