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two 08 June 2003 <br /> AGE-NC Project No.02-0961 <br /> Page 2of5 <br /> The Modesto, Riverbank and Turlock Lake Formations and.overlying Recent alluvium are the <br /> principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground <br /> Water Basin(Basin 5-22). The estimated depth to ground water at the site is 20 feet below surface <br /> grade (bsg) based on information from Lines of Equal Depth of Water Wells Fall 1999, published <br /> by the San Joaquin County Flood Control District and Water Conservation District- FCD&WCD. <br /> Based on the map titled Lines ofEqual Elevation of Groundwater Spring 1999 also published by the <br /> San Joaquin County FCD&WCD, the site is in an area where ground water appears to flow to the <br /> `' north to northeast. One domestic well is located on the property,approximately 100 feet north of the <br /> USTs location. <br /> Le <br /> 2.2. DISPENSER AND PRODUCT LINE UPGRADE <br /> Underground product lines to the existing gasoline and diesel underground storage tanks and the fuel <br /> dispensers were upgraded on 18 September 2002.During the upgrade activities,AGE collected nine <br /> soil samples from the product line trenches and former dispenser locations. Laboratory analytical <br /> results detected total petroleum hydrocarbons quantified as diesel(TPH-d)and gasoline(TPH-g)and <br /> low concentrations of ethylbenzene and xylenes.Based upon the analytical results,the EHD required <br /> the preparation of a work plan to define the lateral and vertical extent of contamination in soil and <br /> ground water. <br /> 3.0. PROCEDURES <br /> La The field work reported herein was performed in accordance with procedures outlined in the AGE- <br /> prepared Preliminary Site Assessment Work Plan, dated 10 December 2002, and approved by the <br /> EHD by letter dated 13 December 2002. <br /> 3.1. DRILLING <br /> On 11 and 12 March 2003, soil probe borings B1 though B5 were advanced to a depth of 30 feet <br /> below surface grade (bsg), utilizing a van-mounted Geoprobe 5400 direct-push probing unit <br /> equipped with 1.25-inch probing rods. The soil borings were advanced in the following locations: <br /> • BI was advanced ten feet northwest of the furthest west dispenser location; <br /> • B2 was advanced 12 feet southeast of the furthest west dispenser location; <br /> • B3 was advanced 20 feet north of the furthest west dispenser location; <br /> • B4 was advanced 30 feet northwest of the furthest east dispenser location; and <br /> La Advanced GeoEnvlronmenta[,Inc. <br /> V - <br />