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f� 30 SITE INVESTIGATION RESULTS ' 31 Geology and Hydrogeology Soils encountered during cone penetration testing generally consisted of a massive sequence of clay and silt soils interrupted by intervals of sand and gravelly sand Sandy intervals were observed in CPT-1 at approximately 29 to 35 feet, 57 to 62 feet, and 105 to 121 feet bgs, and in CPT-2 at approximately 28 to 32 feet, 54 to 57 feet, 113 to 119 feet, and 128 to 136 feet bgs The distribution of sandy soils is shown in cross-section (Figure 4) On January 31, 2002, the static depth-to-groundwater ranged from 39 95 feet bgs in MW-7 to ' 41 47 feet bgs in MW-1 The corresponding groundwater surface elevation ranged from a high of 21 86 feet below mean sea level (msl) at MW-6 to a low of 22 59 feet below msl at MW-2 The resulting groundwater surface appears as an irregular plane dipping to the east-southeast at a gradient of approximately 0 0025 foot/foot As shown on the groundwater surface contour map (Figure 5), a groundwater depression observed at MW-2 is not consistent with the regional groundwater surface The well construction details, wellhead elevations and groundwater monitoring data are summarized in Table 2 32 Analytical Results ' Consistent with previous results, gasoline compounds were only detected in two of the groundwater table monitoring wells (MW-2 and MW-3) The highest concentrations of gasoline hydrocarbons (140,000 µg/l of TPH-as-gasoline, 4,200 µg/I of benzene, 37,000 µg/l of toluene, ' 3,300 µg/1 of ethylbenzene, 22,000 p.g/I of xylenes, and 500 µg/I of 1,2-DCA) were detected in the groundwater sample collected from MW-2 MTBE was not detected in any of the groundwater ' samples The groundwater sample analytical results are summarized in Table 3, the approximate lateral extent of impacted groundwater at the water table is shown on Figure 6, and the laboratory reports are included in Appendix C Gasoline compounds were also detected in the discrete groundwater samples collected at approximately 60 feet bgs at CPT-1A and CPT-2, 105 feet bgs at CPT-1A, and 115 feet bgs at CPT-2 The sample collected at 130 feet bgs from CPT-2 did not contain gasoline compounds MTBE was not detected in any of the discrete groundwater samples The discrete groundwater sample analytical results are summarized in Table 4, the concentrations of TPH-as-gasoline and benzene are posted on Figure 4, and the laboratory reports are included in Appendix C 12