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17 April 2002 <br /> . AGE-NC Project No. 97-0343 <br /> Page 3 of 6 <br /> I boring. Upon soil sample retrieval, the brass sleeves were removed from the sampler. The ends of <br /> the leading brass sleeve were immediately covered with Teflon sheets, sealed with plastic end caps <br /> and secured with tape. Then the sleeve was labeled with the location, boring designation, depth, <br /> I time, date and sampler's initials, and immediately placed in a chilled container for transportation to <br /> BioJet, a California DHS-certified laboratory. The soil sample was analyzed for microbial and <br /> physicochemical enumerations. <br /> 3.0. FINDINGS <br /> Soil descriptions were utilized to construct the vertical and lateral soil model; the contaminant <br /> impact to soil ground water was assessed from the laboratory analytical data obtained from the <br /> Iinvestigation. <br /> 3.1. STRATIGRAPHY <br /> • Based on the findings from the CPT soil borings,cross sections A-A' and B-B' were constructed to <br /> Idepict general lithology beneath the site(Figures 3 and 4).Gravelly sand, sand and sand to silty sand <br /> were encountered at depths between 20 feet bsg and 25 feet bsg and 90 feet bsg to 95 feet bsg. Silty <br /> sand,sandy silt,silt and clay were observed at all other depths. CPT computer-generated boring logs <br /> are included in Appendix A. <br /> 3.2. HYDROGEOLOGICAL MODEL <br />' Based on the CPT results, AGE has developed a preliminary subsurface model of the site soil <br /> stratigraphy comprised of four informal zones, a vadose (unsaturated) zone and three hydrological <br /> units. Hydrological units may be defined as significant vertical intervals of soil having significant <br />' lateral extent and having similar hydrologic characteristics (i.e. hydraulic conductivity, <br /> transmissivity, etc.) over its vertical and horizontal extent. A `flow unit' may be defined as a <br /> hydrologic unit and is characterized by significantly greater hydraulic conductivity values than <br /> overlying and underlying units. A flow unit is capable of serving as a preferred migration route,and <br /> could potentially allow migration of large contaminant masses over great distances. <br />' The model presented is interpretational and will be modified as more data is collected. The four <br /> vertical zones identified are as follows (depths are approximate and can vary by several feet across <br /> the site): <br /> I <br />' Advanced GeoEnvironmental,Inc. <br /> I <br />