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10 February 2006 • AGE-NC Project No 02-0977 Page 9 of 12 4.0. SUMMARY AND CONCLUSIONS The findings of the December 2005 drilling and well installation investigation results are as follows IGenerally,permeable to semi-permeable, silty sands and unconsolidated fine-medium sands were encountered at depths between 5 and 20 feet bsg and between 35 and 40 feet bsg, ' conversely, less permeable, fine sandy silts and clayey silts were encountered at depths between 25 and 30 feet bsg and between 45 and 65 feet bsg At 70 feet bsg, a medium dense to dense, clayey sand was encountered General hthology beneath the site is depicted in ' geologic cross-sectional view C-C' (Figure 3) • Saturated soil was encountered between 60 and 70 feet bsg from B5 through B9 and MW-8, ' the ground water level was measured from MW-8 at approximately 54 feet bsg utilizing a Solmst water level meter(Appendix B) • TPH-g was detected in soil samples collected from B6(VW-2)-30/45/55, from B7(VW-1)- ' 30/40/50 and from B9(VW-4)-40150160 at concentrations as high as 22 mg/kg Ethylbenzene was only detected from B6(V W-1)-55 foot soil sample at a concentration of ' • 0 11 mg/kg • MTBE was detected in soil samples collected from B5-40155/70, from B6(VW-2)- 20/30/45/55/65, from B7(VW-1)-20130140150165170 and from B9(VW-4)-25140150/60 at ' concentrations as high as 21 mg/kg The estimated extent of MTBE-impacted soil is illustrated in cross section view in Figure 11 ' TAME was detected in soil samples collected from B6(VW-2)-55 at a concentration of 0 80 mg/kg and from B7(VW-1)-30/50 at a concentrations of 0 062 mg/kg and 0 33 mg/kg, respectively ' • Field observations,including odor and PID readings, suggest that hydrocarbons were present in all but one boring (MW-8), with more intense field indications encountered from B6 ' (VW-2)between 40 and 55 feet bsg and from B7 (VW-t) and B9(VW-4)between 30 and 45 feet bsg • The analytical data indicates that MTBE is the main contaminant of concern at the site, ' MTBE-impacted soil was primarily detected in borings B-6 (VW-2), B-7 (VW-1) and B-9 (VW-4), located'on the south, southeast and north sides of the UST area with the highest ' concentrations occurring at 55 feet in boring B-6 • From the UST area,the vertical extent of MTBE-impacted soil has been adequately delineated towards the south by boring B8 (VW-3) and toward the north by B9 (VW-4) and does not ' appear to extend beyond 75 feet bsg However,the vertical extent towards the east-southeast is marginally defined due to low MTBE detections at 70 feet bsg from B6 (VW-2)at 65 feet ' Advanced GeoEnvironmental,Inc