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M <br /> 28 April 2004 <br /> • AGE-NC Project No 99-0570 <br />' Page 3 of 6 <br /> , <br />' tertiary-amyl methyl ether(TAME), tertiary butanol (TBA), ethylene dlbromide(EDB)and <br /> 1,2-drehloroethane(1,2-DCA) in accordance with EPA Methods 8020 and 8260-Modified <br />' All nnseate generated during drilling activities was containerized In properly labeled DOT-approved <br /> 55-gallon drums, and was stored on-site In an area lacking public access The twinned soil borings <br />' were backfilled over Its entire depth with a portland cement grout mix <br />' 3.0. FINDINGS <br /> The computer-generated CPT llthologic logs were Integrated with previous subsurface soil <br />' descriptions to construct the subsurface geological model, the hydrocarbon Impact to ground water <br /> was quantified by laboratory analysis of the grab ground water as presented below <br />' 31 STRATIGRAPHY <br />' . Based on the findings from the CPT soil borings and existing monitoring well and soil borings,the <br /> cross sections A-A' and B-B' were constructed to depict general lithology beneath the site(Figures <br /> 3 and 4) <br />' Dominantly fine-grained soil conslstrng,of silty clay to clay, poorly graded sand with silt and silty <br /> sand were encountered at depths from the near surface to approximately 10 feet bsg Silty sand and <br />' sand with gravel layers were encountered from-10 or 15 feet to approximately 55 feet across the site <br /> A laterally continuous silt and clay unit was encountered from 55 feet to 80 or locally 85 feet bsg, <br /> alternating layers of laterally continuous silty sand and poorly graded sand with silt were <br />' encountered — <br /> Alternating layers of silty sand, poorly graded sand and silty clay were encountered from 80 or 85 <br />' feet to total depth 110 feet bsg CPT computer-generated boring logs are Included In Appendix A <br /> 5� vss VYW <br /> I3 2 HYDROGEOLOGICAL MODEL <br /> Based on the CPT results, AGE has developed a preliminary subsurface model of the site sediment <br /> stratigraphy comprised of four informal zones,a vadose(unsaturated)zone and three hydrogeologrc <br /> units Hydrogeologrc or hydrostrati graphic units(HUs)are defined as a body of rock or sediment that <br /> has hydrogeologrc characteristics(I e hydraulic conductivity,pore pressure,etc )that make It distinct <br /> from surrounding bodies of rock or sediment(Sanders, 1998),or a part of a body of rock that forms <br /> • a distinct hydrologic unit with respect to the flow of ground water(Maxey, 1964) A`flow unit'may <br /> Advanced GeoEnvironmental,Inc <br /> I <br />