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11 <br /> 1� <br /> 'I 3.0 INVESTIGATION RESULTS <br /> ' 31 Geology and Hydrogeology <br /> Soils observed in the 11 sod borings consist of massive sand intervals interrupted by alternating <br /> thinly-bedded sequences of clay, silt and fine sand mixtures The uppermost 12 to 14 feet of soil <br /> consists mostly of a poorly-graded, fine-medium grained, sand sequence, which is relatively <br /> homogeneous and laterally continuous This massive sand interval overlies an approximately 8 <br /> to 10 foot thick interval of interbedded sequences of clay, silt and fine sand mixtures These <br /> interbeds range from approximately one to four feet thick and are laterally discontinuous across <br /> the site Underlying this sequence at a depth of approximately 20 to 25 feet bgs is another sand <br /> sequence of undetermined thickness This lower sand`sequence is less homogeneous than the <br /> upper sand interval It varies from poorly-graded to well-graded fine-medium sand with varying <br /> amounts of silt In the southeast portion of the site, the lower sand interval contains mostly silt <br /> and little or no sand Sod boring logs are included in Appendix C <br /> During drilling, saturated soil was first encountered at approximately 20 feet bgs Groundwater <br /> ' levels measured in each of the soil borings ranged from 17 5 to 19 0 feet bgs Groundwater <br /> does not appear to be confined and recharge was found to be moderately strong <br /> 3.2 ' Analytical Results <br /> Based on the results of the laboratory analyses, soil and groundwater beneath the site have <br /> been impacted by gasoline hydrocarbons Results of the soil sample analyses are summarized <br /> in Table 2 and the results of the groundwater sample analyses are summarized in Table 3 The <br /> Ilaboratory reports are included in Appendix E <br /> 3 2 1 Soil Sample Results <br /> In soil, the samples collected at 25 feet bgs contained the highest concentrations of TPH-as- <br /> d, gasoline, BTEX and oxygenate compounds In the sod samples collected from 25 feet bgs, the <br /> highest concentration of TPH-as-gasoline was detected in SB-3, south of the dispensers, at a <br /> 1 concentration of 280 milligrams per kilogram (mg/kg) The soil sample collected at 25 feet from <br /> J SB-4, east of the dispensers, contained 260 mg/kg of TPH-as-gasoline, 0 0056 mglkg of <br /> benzene, 0 045 mg/kg of MTBE, and 0 021 mg/kg of TBA None of the other 37 sod samples <br /> analyzed contained detectable concentrations of benzene <br /> I� 7 <br /> 12 <br />