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23 lune 2003 , <br /> AGE-NC Project No 00-0769 <br /> Page 6 of 13 - <br /> +Following collection, samples were placed in a chilled container and transported under chain-of- <br /> custody to Cal Tech Environmental Laboratories (CTEL), a California Department of Health <br /> Services-approved laboratory, for analysis The samples were analyzed for the following <br />' a TPH-g in accordance with EPA Method 8015 modified, <br /> • VOCs,including BTEX and the fuel additives MTBE,DIPE,ETBE,TAME,and TBA, EDB ' <br />' and 1,2-DCA in accordance with EPA Method 8260B <br />' 4.0. FINDINGS <br /> Y P Y <br /> Geologic cross sections A-A 'and B-B'(Figures 3 and 4) depicting general lithology beneath the site <br />' were constructed based on the findings from previous CPT soil borings and boring logs recorded <br /> during installation of ground water monitoring wells MW-1 through MW-5 and soil boring B-2 <br /> Ground water elevation, flow direction and gradient were determined from field data collected on <br /> 21 and 22 November 2002 The hydrocarbon-impact to soil and ground water was inferred from <br /> laboratory analysis of soil samples and field observations <br /> 41 STRATIGRAPHY <br /> Generally, alternating, laterally discontinuous intervals of clay, silt and sand were encountered , <br /> between surface grade and approximately 90 to 100 feet bsg Porous intervals containing silt, silty <br /> sand, sandy silt and poorly graded sand were encountered between approximately 112 to 125 feet <br /> bsg, 130 to 165 feet bsg and 180 and 195 feet bsg Fine grained, silt, silty clay, clayey silt and clay <br /> were observed at all other depths Boring logs for MW-4, MW-5 and B-2 are included in <br /> ' Appendix C r <br /> 4 2 HYDROGEOLOGIC UNITS <br /> Based on cross sections A--A' and B-B', AGE informally identified five hydrologic flow units <br />' between first encountered ground water and 199 feet as having significant intervals of apparently <br /> porous, coarser-grained soil separated by intervals of finer-grained, less permeable soil <br /> Hydrogeologic Unit 1 (HU-1)was subdivided into three sub-units(HU-1 Upper Zone,HU-1 Middle <br /> Zone and HU-1 Lower Zone) that may not have significant barriers to vertical migration of <br /> contaminations Generally, HU-1 Upper Zone was identified at depths between 25 feet (first <br /> 1 encountered ground water) and 51 feet bsg, HU-1 Middle Zone was identified at depths between ' <br /> 48 feet and 75 feet bsg, and HU-1 Lower Zone was identified at depths between 60 feet and 90 feet <br /> . bsg, Hydrogeologic Unit 2 (HU-2) was identified at depths between 112 feet and 125 feet bsg, <br /> Advanced GeoEnvironmental,Inc <br /> 1 <br />