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t <br /> �I <br />' 09 July 2002 <br /> AGE-NC Project No 00-0769 <br />' Page 4 of 5 <br />' 4.0. SUMMARY AND CONCLUSIONS <br /> _ The findings of the May 2002 site investigation event include the following <br />' • Ground water elevation was approximately 14 feet below MSL in the shallow screened wells <br /> (MW-1, MW-2B and MW-3B) during the May 2002 monitoring event Ground water was <br /> within the screened interval of monitoring wells MW-2B and MW-3B and was <br />' approximately 5 0 feet above the screened interval of MW-1 <br />' • Ground water was approximately 0 13 feet and 0 50 feet lower in the deeper screened <br /> monitonng wells (MW-2A and MW-3A) than in the shallow screened wells during the <br /> second quarter 2002 monitoring event <br />' • TPH-g and BTEX compounds were detected in ground water samples collected from four <br /> ofthe five on site monitonng wells(MW-1,MW-2B,MW-3A and MW-3B) Concentrations <br /> as high as 140,000 µg/1 TPH-g, 36,000 gg/1 benzene, 48,000 gg/l toluene, 2,400 µg/1 <br />' ethylbenzene and 12,000 µg/1 total xylenes were detected, in sample MW-1 <br /> • 1,2-DCA was detected in ground water samples collected from monitoring wells MW-1, <br /> MW-2A, MW-2B and MW-3B at concentrations as high as 2,500 µtg/l (MW-1), which <br /> exceeds California's Maximum Contaminant Level (MCL) of 0 5 gg/1 in drinking water <br />' • TBA was detected In sample MW-2B at a concentration of 280 pg/l, which exceeds the <br /> California drinking water action level of 12 gg/1 <br /> • Concentrations of contamination have remained relatively stable in monitoring wells MW-1, <br />' MW-2B,MW-3A and MW-3B since groundwater monitoring began in May 1998 However, <br /> contaminant concentrations have steadily decreased In MW-2A during the same period <br />' The horizontal and vertical extent of contamination related to an unauthorized release from <br /> the former UST has not yet been defined in soil or ground water <br /> 5,0. RECOMMENDATIONS <br />' Based on the results of this and previous investigations AGE recommends <br />' Continued quarterly ground water monitoring The next ground water monitoring event <br /> should be scheduled for August 2002 <br /> • Completion of the scope of work proposed In the AGE-prepared Additional Subsurface <br />' Investigation WorkPlan,dated 19 Apnl 2001 Work to be completed includes advancing soil <br /> i <br />' Advanced GcoEnvironmental,Inc <br />