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1 <br /> 1.0 INTRODUCTION <br /> This report documents the results of soil remediation confirmation sampling performed on <br /> June 3, 1993, and groundwater monitoring conducted on June 21, 1993, by Aegis <br />' Environmental, Inc (Aegis), at the former Exxon Company, U S A (Exxon), service <br /> station located at 909 West Hammer Lane in Stockton, California (Figure 1) Three soil <br />' borings, SB-8 through SB-10 (Figure 2), were drilled to assess the presence of petroleum <br /> hydrocarbons in the soil following 10 months of soil vapor extraction The groundwater <br /> monitoring included collection of depth-to-groundwater measurements and groundwater <br />' samples from five wells, MW-1, MW-2, MW-5, MW-6, and MW-8, on site (Figure 2) This <br /> report is based, in part, on information supplied to Aegis by Exxon Based on the <br /> sampling results and site history, justification for site closure is also included <br /> 1 <br /> 1 2 0 SITE DESCRIPTION <br />' The site is a vacant lot at the northwest corner of the intersection of Hammer Lane and <br /> Lower Sacramento Road, in a commercial area of Stockton (Figure 1) The site is a <br /> former Exxon service station that retailed gasoline The station's former facilities included <br />' a service building, three dispenser islands, and four underground storage tanks (UST) <br /> with associated piping The UST were located at the south central portion of the site <br /> The layout of the former service station's surface and subsurface structures is shown in <br /> Figure 2 <br /> 30 BACKGROUND <br /> The former Exxon service station is currently vacant and no structures remain The UST, <br /> Iservice building, and fuel dispensers were removed in February 1986, after the fuel lines <br /> failed a tightness test The piping was removed in August 1990 <br /> • In February 1986, Groundwater Technology, Inc (GTI), of Concord, California, <br /> collected soil samples from the excavated UST basin (Figure 3) Laboratory <br /> analytical reports indicated petroleum hydrocarbons in the soil at concentrations <br /> up to 4,600 parts-per-million (ppm) GTI drilled several soil borings (SB-1 through <br /> SB-4) and installed groundwater monitoring wells MW-1 through MW-5 in 1986 and <br /> 1987 (Figure 2) Soil samples from SB-1 through SB-4, MW-1, and MW-2 were <br /> screened for petroleum hydrocarbons using a photoionization detector Petroleum <br /> hydrocarbons were apparently not detected and no samples were analyzed <br /> I Analytical results for samples collected from MW-3 through MW-5 are summarized <br /> in Table 4 <br /> • In 1987, EA Engineering, Science and Technology (EA) of Lafayette, California, <br /> conducted a soil vapor survey at the site <br /> 93 0058 QMR <br />