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SITE CLOSURE REQUEST REPORT <br /> Former Exxon Service Station No.7-3330 <br /> 1 3128 West Benjamin Holt Drive <br /> 1 Stockton,California <br /> Delta Project No. D093-810 <br /> Page 4 <br /> (Johnson, 1989). The current interrelationships of topography,pumping, and artificial recharge can cause <br /> local ground water flow to be complicated and difficult to predict. <br /> 2.4 Local Water Supply <br /> Public water supply in the area has been from surface water and ground water. The City of Stockton <br /> Municipal Utilities District is the major supplier of ground water. Most of the water supply wells draw <br /> ground water from the Laguna Formation at depths from 150 to 600 feet. The closest City water supply <br /> well is City of Stockton Well No. 10 located approximately 900 feet east-northeast from the Exxon <br /> property (Figure 2). The Stockton East Water District is the supplier of surface water. The Stockton <br /> East Water District Treatment Plant is located in eastern Stockton. Water is drawn from New Hogan <br /> Reservoir, located approximately 30 miles east-northeast of Stockton. <br /> Private water supply wells in the Stockton area draw ground water from depths of less than 150 feet. <br /> I . The closest private water supply wells are believed to be located 2,500 to 3,000 feet west and southwest <br /> of the Exxon property and are only used to fill an artificial lake (Lincoln Lake) in a residential area <br /> (Engineering-Science, Inc., 1991). <br /> 2.5 Initial Soil and Ground Water Investigations <br /> Three soil borings were advanced at the site in March 1991 by Engineering-Science, Inc. and completed <br /> as ground water monitoring wells. The initial three borings are identified as SB-01, SB-02, and S13-03, <br /> and were subsequently identified as monitoring wells MW-1, MW-2, and MW-3, respectively(Figure 3). <br /> Soil samples were collected from the borings and submitted for laboratory analysis of benzene, toluene, <br /> ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons (TPH) using EPA Methods 8020 <br /> and 418.1, respectively. Sample depths and soil sample analytical results from samples collected from <br /> the soil borings are included in Table 1. Results of Engineering-Science Inc. work was presented in a <br /> 1991 report entitled Sensitive Receptors-Risk Assessment, Site Survey and Literature Research. <br /> The initial soil and ground water investigation indicated that soil beneath the site predominantly consists <br /> of clay with intermittent sand lenses (ranging in thicknesses of four to six feet) at depths from 10 to 22 <br /> RPT001.810 <br />