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1 • 3.0 RESULTS OF THE INVESTIGATION 31 Geology and Hydrogeology ' Soils observed to the total drilling depth of 35 feet bgs consisted of clay and silt mixtures Intervals of sandy sods were not observed Detailed soil descriptions are included on the monitoring well logs (Appendix E) ' During drilling on July 11 and 12, 2002, saturated soil was first encountered in the four monitoring well borings at approximately 18 5 to 19 0 feet bgs On July 24, 2002, the static depth to the groundwater table, as measured in the four completed groundwater monitoring wells, ranged from 22 20 feet below grade in MW-1 to 23 54 feet below street grade in MW-3 The groundwater surface elevation in the four wells ranged from a high of 11 07 feet below mean sea level (msl) at ' MW-1 to a low of 11 77 feet below msl at MW-3 The resulting groundwater surface appears as an irregular plane dipping to the east-southeast at a gradient of approximately 0 029 foot/foot A groundwater surface contour map is included as Figure 4 The well construction details, wellhead elevations and groundwater monitoring data are summarized in Table 3 32 Analytical Results A total of 7 of the 12 soil samples collected during the drilling contained detectable concentrations of gasoline hydrocarbons The soil samples collected at 15 and 35 feet from MW-1, and all five soil samples collected from MW-2 (15, 20, 25, 30, and 35 feet bgs) contained detectable ' concentrations of TPH-as-gasoline and at least one of the BTEX compounds The soil sample collected at 15 feet from MW-2 contained the highest concentrations 8,000 mg/kg of TPH-as- gasoline, 63 mg/kg of benzene, 52 mg/kg of toluene, 130 mglkg of ethylbenzene, and 210 mg/kg of xylenes TPH-as-diesel, TPH-as-motor oil, oxygenates and 1,2-DCA were not detected in any of the sod samples analyzed The soil sample analytical results are summarized in Table 1, the ' concentrations of gasoline compounds in soil are shown in cross-section (Figure 5), and the laboratory reports are included in Appendix F The groundwater samples collected from MW-1, MW-2 and MW-3 contained detectable concentrations of gasoline hydrocarbons, including TPH-as-gasoline, BTEX and 1,2-DCA The ' groundwater sample collected from MW-4 was free of gasoline compounds MTBE, TPH-as- diesel and TPH-as-motor oil were not detected in any of the four groundwater samples The groundwater sample analytical results are summarized in Table 2, the distribution of gasoline in groundwater is shown on Figure 6, and the laboratory reports are included in Appendix F ' 12 y