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3 0 PROJECT RESULTS <br /> ' 31 Geology and Hydrogeology <br /> ' Consistent with previous investigations, the uppermost 30 feet of soil at MW-5 and MW-6 consists <br /> of a massive sandy soil sequence interbedded with intervals of clay, silt and fine sand mixtures <br /> The descriptions of soil observed during the drilling of MW-5 and MW-6 are included on the <br /> ' monitoring well logs (Appendix D) <br /> Based on previous CPT borings, the soil between 30 and 150 feet consists of a massive <br /> sequence of clay and silt soils interrupted by several discontinuous intervals of sand and gravel <br /> soils The distribution of the sand and gravel intervals is interpreted in cross-section (Figure 4) <br /> Duringh - <br /> the drilling a#MW 5 and MW-6, groundwater was first encountered at a depth of between <br /> ' 20 5 and 21 1 feet bgs On December 19, 2002, the static depth to the groundwater table, as <br /> measured in the six monitoring wells, ranged from 19 23 feet bgs in MW-6 to 21 11 feet bgs in <br /> MW-4 The corresponding groundwater surface elevations ranged from a high of 17 57 feet <br /> ' above mean sea level (msl) at MW-1 to a low of 16 56 feet above msl at MW-5 The resulting <br /> groundwater surface appears as an irregular plane dipping to the northeast at a gradient of <br /> approximately 0 0071 foot/foot A groundwater surface contour map is included as Figure 5 The <br /> well construction details and groundwater monitoring data are summarized in Table 8 <br /> ' 32 Analytical Results <br /> The sod samples collected at 20 and 30 feet from MW-5 and MW-6 did not contain detectable <br /> concentrations of gasoline compounds These soil sample analytical results are summarized in <br /> Table 5, and the laboratory report is included in Appendix E <br /> From the six monitoring wells, the groundwater sample collected from MW-2 contained the <br /> ' highest concentrations of gasoline compounds 510 pg/I of TPH-as-gasoline, 12 µg/l of benzene, <br /> 16 pg/l of toluene 49 µg/l of ethylbenzene, 37 µg/l of xylenes, and 10 µg/l of MTBE The only <br /> other detectable concentrations of gasoline compounds were 53 µg11 of TPH-as-gasoline to MW-1 <br /> rand 55 µg/l of TPH-as-gasoline in MW-3 The distribution of MTBE at the groundwater table is <br /> shown on Figure 6 The groundwater sample collected from the on-site water supply well did not <br /> ' contain detectable concentrations of gasoline compounds The groundwater sample analytical <br /> results are summarized in Table 7, and the laboratory reports are included in Appendix E <br /> ' 11 <br />