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1 <br /> Working To Restore Nature <br /> The closest surface water to the site is Duck Creek, 113 of a mile to the southeast Mormon <br /> Slough is approximately 1 mile to the north. The piezometnc level of groundwater has been <br /> ' reported to be between 45 and 55 feet below the surface at the site (San Joaquin County Flood <br /> Control and Water Conservation District, 1989 data) <br /> ' There is one water supply well on the subject property All water for the site, including sinks <br /> and restrooms in the office, is supplied by the well The location of the supply well is shown <br /> on Plate 2 Well locations within a 112 mile radius of the site were requested from the <br /> ' Department of Water Resources A well, identified as OlN07E17M, is located approximately <br /> 400 feet east of the project site This well is screened from 144 to 176 feet below grade and <br /> is not expected to be affected by activities associated with this tank closure. <br /> INVESTIGATION HISTORY <br /> Soil Investigation - June 15, 1990 <br /> ' On June 15, 1990, RESNA personnel (formerly WaterWork) advanced two angled soil bonngs <br /> (ASB-1, ASB-2) beneath the existing tank The location and orientation of the borings are <br /> depicted on Plate 3 These borings were advanced at 45° from vertical and terminated beneath <br /> the longitudinal centerline of the tank approximately 5 feet beneath the tank bottom The results <br /> of the initial phase of investigation were presented in a report entitled, "Underground Fuel Tank <br /> ' Abandonment Contaminant Assessment Report," dated July 30, 1990 <br /> ' Analytical results of soil samples collected from Boring ASB-1 showed significant concentrations <br /> of gasoline hydrocarbons at 15 5 and 21 feet along the boring length This corresponds to <br /> approximately 11 and 15 vertical feet below grade, at the fill end of the tank Laboratory <br /> analysis of soil samples collected from ASB-2 at the opposite end of the tank recorded very low <br /> levels of contamination The absence of significant contamination at this end of the tank <br /> indicates that soil contamination is localized at the fill end of the tank Soil contamination at the <br /> site is likely due to overspill during routine filling of the tank Laboratory results are <br /> summarized in Table 1 <br /> Soil and Groundwater Investigation - January 15-16, 1991 <br /> ' On January 15, and 16, 1991 to further define the vertical extent of contamination, two <br /> additional angle soil borings (BJJS-ASB1 and BJJS-ASB2) were advanced beneath the existing <br /> tank utilizing 6-inch hollow stem augers Borings BJJS-ASB1 and BJJS-ASB2 were advanced <br /> at 450 and 600 respectively, from vertical and terminated beneath the longitudinal center-line of <br /> M 11500WREPORTSISR-4894 FNL 2 <br />