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07 March 2002 <br /> AGE-NC Project No 99-0637 <br /> Page 3 of 6 <br /> Upon soil sample retrieval, the brass sleeves were removed from the sampler The ends of the <br /> leading brass sleeve were immediately covered with Teflon sheets, sealed with plastic end caps, <br /> secured with tape and Immediately placed in a chilled container for transportation to MAI, a <br /> California DHS-certified laboratory The sample sleeve was labeled with the location, boring <br /> designation, depth, time, date and sampler's Initials The soil sample was analyzed for <br /> • TPH-g and TPH-d in accordance with EPA Method 8015-modified, <br /> • BTEX in accordance with EPA Method 8020, and <br /> • MTBE, DIPE, ETBE, TAME, TBA, EDB and 1,2-DCA in accordance with EPA Method <br /> 8260M <br /> 3.0. FINDINGS <br /> Soil descriptions and CPT data Interpretations were utilized to construct the vertical and lateral soil <br /> model,the contaminant Impact to soil ground water was assessed from the laboratory analytical data <br /> Iobtained from the Investigation <br /> I31 STRATIGRAPHY <br /> Based on the findings from the CPT soil boring, cross sections A-A' and B-B' were constructed to <br /> depict general lithology beneath the site (Figures 3 and 4) Generally, fine grained silts and clays <br /> were encountered at depths between surface grade and 10 feet bsg,20 and 30 feet bsg,45 and 60 feet <br /> bsg and 80 feet bsg to the total depths of the borings Gravelly sand, sand and silty sand were <br /> observed at all other depths CPT computer-generated boring logs are Included In Appendix A <br /> 3 2 HYDROGEOLOGICAL MODEL <br /> Based on the CPT results and comparison with soil descriptions from borings previously advanced <br /> on the site, AGE has developed a preliminary subsurface model of the site soil stratigraphy <br /> comprised of six Informal zones, a vadose (unsaturated) zone and five hydrological units <br /> Hydrological units maybe defined as significant vertical intervals of soil having significant lateral <br /> extent and Inferred to have 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 /> Ihydrologic unit characterized by significantly greater hydraulic conductivity values than overlying <br /> . and underlying units A flow unit is capable of serving as a preferred migration route, and could <br /> potentially allow migration of large contaminant masses over great distances <br /> Advanced GeoEnvironmental,Inc <br />