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5.0 DISCUSSION OF RESULTS <br /> Data obtained during this assessment indicates the subsurface sediments consist primarily of <br /> interbedded silty clay, sandy clay, clay, clayey silt, sandy silt and silt extending from ground <br /> surface to a depth of approximately 50 feet bgs and silty sand, clayey sand and sand <br /> extending from approximately 50 feet to 60 feet bgs <br /> Boring logs were used to develop a cross section of the subsurface geology of the site The <br /> cross section location is shown in Figure 2 Geologic cross section AW showing the mayor <br /> lithologic units underlying the site is included as Figure 3. <br /> Groundwater was encountered during drilling activities at a depth of approximately 44 to 50 <br /> feet bgs Groundwater was measured later at depths ranging from 42 80 to 44 80 feet below <br /> the top of casing in these monitoring wells on August 14, 1996, and from 42 12 to 43 79 <br /> feet below the top of well casings Groundwater elevations are plotted and contoured on the <br /> groundwater elevation contour maps generated for data collected on August 14, 1996 (Figure <br /> 4) and November 26, 1996 (Figure 5) Groundwater appears as a mound with a relatively <br /> flat portion centrally located beneath the site and flowing radially away from this portion at <br /> a gradient of approximately 0 006 to 0.01 feet per foot as measured on August 14, 1996 and <br /> 0 025 to 0 038 feet per foot as measured on November 26, 1996 <br /> Laboratory analysis of all soil samples collected from the sort borings of wells VW-4, VW-5 <br /> and MW-10 detected TPH and Benzene at maximum concentrations of 220 mg/kg and 2 4 <br /> mg/kg, respectively <br /> TPH concentrations ranged from 900 mg/kg to 4,900 mg/kg in the samples collected from <br /> the 20 to 40-foot depth intervals in VW-2 while benzene concentrations ranged from 6.7 <br /> mg/kg to 67 mg/kg. <br /> TPH concentrations ranged from 480 mg/kg to 6,600 mg/kg in the samples collected from <br /> the 25 to 40-foot depth intervals in VW-6 while benzene concentrations ranged from 0 36 <br /> mg/kg to 4 8 mg/kg <br /> TPH concentrations ranged from 300 mg/kg to 3,500 mg/kg m the samples collected from <br /> the 20 to 55-foot depth intervals in MW-11 while benzene concentrations ranged from 2 7 <br /> mg/kg to 44 mg/kg. <br /> MTBE was detected at maximum concentrations of 9 8 mg/kg, 0 15 mg/kg, 0 032 mg/kg, <br /> 43 mg/kg, 0 027 mg/kg and 16, mg/kg in soil samples collected from wells VW-2, VW-4, <br /> VW-5, VW-6, MW-10 and MW-11, respectively. <br /> 6 <br />