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08 October 2003 AGE-NC Project No. 98-0504 Page"3 of 7 2.5. PREVIOUS SITE ASSESSMENTS On 31 July 2002,three soil probe boring(B3,B4 and B5)were advanced east and north-west of the former UST excavation,and north of the former dispenser area.Discrete soil samples were collected at 5-foot intervals,beginning at 10 feet bsg,to the total depth of the wells at between 35 and 40 feet bsg. In addition, a grab ground water sample was collected from each well at total depth. TPH-g and BTEX compounds were not detected in soil samples collected. MTBE was detected by EPA method 8260 in three soil samples at concentrations of 0.016 mg/kg (B3-30), 0.008 mg/kg (B4-20)and 0.006 mg/kg(B4-30).Analytical results of soil samples are summarized in Appendix A. "TPH-g was detected in the grab ground water samples from boring B3,B4 and B5 at concentrations of 240 gg/l, 3001Cg/l and 180 �ig/l, respectively. BTEX compounds were not detected, but MTBE and 1,2-DCA were detected by EPA method 8260 in each of the ground water samples at maximum concentrations of 200 µg/1 (B4) and 13 µg/1 (35). The distribution of dissolved MTBE is depicted in Figure 4, and analytical results from ground water samples are summarized in Appendix A. 3.0. GROUND WATER MONITORING WELL INSTALLATION On 03 and 04 April 2003, three soil borings MW-1 though MW-3 were advanced utilizing a hollow stem auger drill rig for the collection and analysis of soil samples and installation of ground water monitoring wells(Figure 2). Soil boring MW-1 was advanced approximately 10 feet northwest the former dispenser area,boring MW-2 was advanced south of the former UST excavation and boring MW-3 was established sixty feet east.of the former UST excavation. Field work was preformed as described in the AGE-prepared Monitoring Well Installation Work Plan,dated 06 February 2003,as amended and approved by the San Joaquin Country Environmental Health Department (EHD)by letter dated 24 February 2003. 3.1. SOIL SAMPLE COLLECTION Soil borings were advanced using a truck-mounted CME 75-HT or CME 95 drill rig equipped with 8-inch continuous flight hollow-stem augers; the drill rig and two-man crew were supplied by Cascade Drilling of Rancho Cordova,California.Soil borings MW-1 through MW-3 were advanced to a depth of 45 feet bsg to be completed as ground water monitoring well. Auger returns generated by drilling were containerized in properly labeled DOT-approved model 17H 55-gallon drums and was stored on-site. Advanced GmEnvironmental,Inc.