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3 0 SITE INVESTIGATION RESULTS <br /> 31 Geology and Hydrogeology <br /> In general, the soils beneath the site consist of massive sands with varying percentages of fine <br /> gravel, silt and clay The specific sand-based soil units do not correlate well between on-site <br /> borings Over most of the site, the uppermost sod consists of a light brown, poorly-graded, fine <br /> to medium sand to a depth of approximately 10 feet bgs Varying amounts of fine rounded <br /> gravel are present in this uppermost soil unit Over most of the site, a gravelly sand is present <br /> from approximately 10 to 15 feet bgs Beneath the gravelly sand is a silty sand to a depth of <br /> approximately 20 feet bgs From approximately 20 feet bgs to the total drilling depth of 25 feet, <br /> soils consist mainly of sandy silt with up to 25% clay <br /> Results of the sod physical parameter testing indicate that a significant permeability difference <br /> exists between the upper sand and sdity sand soils and the lower sandy silt unit The <br /> permeability of the upper sandy unit was measured at approximately 0 48 foot/day compared <br /> with 0 08 foot/day in the lower silty unit The permeability, moisture content, dry density and <br /> porosity data for the two soil samples tested are summarized in Table 5 The geotechnical <br /> • laboratory report is included in Appendix E <br /> During drilling, saturated sod was first encountered between 13 and 19 feet bgs On June 2, <br /> 1998, prior to well purging and sampling, the static depth-to-groundwater ranged from 12 37 feet <br /> bgs in MW-2 to 13 25 feet bgs in MW-3 The groundwater gradient was calculated at <br /> approximately 0 00025 foot/foot in a northerly direction The groundwater flow direction and <br /> gradient are illustrated on the groundwater surface map (Figure 3) The groundwater monitoring <br /> data are summarized in Table 3 <br /> 32 Analytical Results <br /> Based on the investigation results, soil and groundwater beneath the site have been impacted <br /> by diesel and gasoline hydrocarbons The sod sample analytical results are summarized in <br /> Table 1, the groundwater-grab sample analytical results are presented in Table 2 and the <br /> monitoring well groundwater sample analytical results are included in Table 4 The laboratory <br /> reports are included as Appendix E <br /> • 8 <br />