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3 <br />2 INVESTIGATION SUMMARY <br />2.1 Geologic and HydroQeologic Summary <br />The near -surface geology at this facility, to the maximum <br />explored depth of 75 feet below ground surface (BGS), consists of <br />interbedded, discontinuous sequences of fine-grained sand, silt, <br />and clay. The depths to groundwater in monitoring wells at the <br />facility were approximately 51 to 53 feet BGS on March 23, 1994 and <br />groundwater elevations in the wells ranged from —34.69 to —35.40 <br />feet, relative to MSL. Groundwater flow is northeasterly at a <br />gradient of about 2.5 x 10'3 feet per feet (ft/ft) . <br />2.2 Analytical Summar <br />The analytical summary provided is intended to identify the <br />media and areas which the remediation system will be designed to <br />address. Refer to the December 19, 1991, Problem Assessment Report <br />and the April 24, 1994 Groundwater Monitoring Well Installation <br />Report for analytical details. <br />2.2.1 Soil Sampling Summary <br />Soil samples collected during site investigation activities <br />during March 1994 indicated that only 1 sample of 14 collected <br />contained detectable levels of hydrocarbon compounds. The sample <br />collected from borehole MW -13 at a depth of 60 feet, 3ust below the <br />groundwater surface, contained a benzene concentration of 10 <br />micrograms per kilogram (ug/kg). Based on available soil sample <br />data, the extent of any residual gasoline -impacted soil is limited. <br />Five soil samples were evaluated for total heterotrophic plate <br />count (microbial identification and characterization), and the <br />respective microbes ability to degrade fuel hydrocarbons. Four <br />07/94/1213821125997/Ri:M REP/l July 1, 1994 9 26am <br />