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I23 September 2002 <br /> AGE-NC Project No 95-0128 <br />' Page 6 of 7 <br />' The hydrocarbon mass removal calculations and the concentrations ofthe influent samples over time <br /> are displayed in Appendix D <br /> 5.0. SUMMARY AND CONCLUSIONS <br />' The following conclusions were drawn from the results of this quarterly investigation <br /> • Ground-water elevations measured during the May 2002 monitoring event ranged between <br />' 18 52 and 19 82 feet below MSL, ground water flow direction at the site was inferred to be <br /> northeast towards a well-defined cone of depression at extraction well EW-1 <br /> • Dissolved petroleum hydrocarbons quantified as TPH-g,TPH-d and BTEX compounds were <br />' detected in ground water samples MW-4, MW-5 and VW-1, collected within the <br /> northeastern portion of the site <br />' • The highest concentrations of BTEX compounds were detected in sample MW-5,the BTEX <br /> concentrations of 370µg/1 benzene,280µg/l'toluene, 1,600µg/1 ethylbenzene and 5,500µg/1 <br /> xylenes were well above the DHS' Maximum Contaminant Levels (MCLS) in drinking <br /> liewater <br /> • The highest concentration of MTBE detected in the ground water samples (1,100 µg/1) <br />' occurred in monitoring well MW-5, adjacent to extraction well EW-1 Lower or non- <br /> detectable MTBE concentrations in the down-gradient and cross gradient wells defined the <br /> dissolved MTBE plume toward the north and west,however,the dissolved MTBE plume has <br />' not been defined east or south of the site (Figure 4) <br /> The lead scavenger 1,2-DCA was detected in sample MW-3 at 1 5 µg/l, slightly above the <br /> MCL of 0 5 µg/1 <br /> 1 Approximately 0 42 kg or 0 93 lbs of MTBE, 0 28 kg or 0 62 lbs of BTEX, 5 6 kg or 12 lbs <br /> of TPH-g and 0 67 kg or 1 5 lbs of TPH-d were removed and treated by the ground water <br />' extraction system <br /> c n 'n U d"f%1%41%/rL 1*,T"A TT"kTC <br /> Based on the results of this and previous investigations, AGE recommends <br /> • Continued quarterly ground water monitoring of the site concurrently with the Pacific Car <br /> Wash site (4405 Pacific Avenue), the next monitoring event is tentatively scheduled for <br /> September 2002 <br /> . Continued interim ground water extraction and treatment as a remedial measure <br />' Advanced GeoEnvzronmenta!Inc <br />