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1 Second Quarter 2004 Groundwater Monitoring Report <br /> Boyett Petroleum,419 S.Main,Manteca,CA <br />' Page 4 <br /> iTable 3: Laboratory Analytical Results .Tune 24, 2004 <br /> 1 B T T E X TPH-G MTBE Other Oxygenates/Additives' <br /> Detection 0.5 0.5 0.5 1.0 0.05 0.5 0.5-5,0 <br /> Limits: pg/L µg/L µg/L µg/L mg/L lig/L pg/L <br />' Analytical Method: 8260B 8260B 8260B 8260B 8015B 8260B 8260B <br /> Sample I.D. <br />' 3761-MW2-6/24104 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> 3761-MW3-6124/04 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br />' 3761-MW4R-6/24/04 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> 3761-MW6-6/24104 <0.5 <0.5 <0.5 1 <1.0 <0.05 <0.5 <0.5-5.0 <br /> 3761-MW7-6124104 <0.5 <0.5 <0.5 1 <1.0 <0.05 11 <0.5-5.0 <br /> 3761-MW8-6/24/04 <0.5 <0.5 <0.5 <L0 <0.05 <0.5 <0.5-5.0 <br /> 3761-MW9-6124/04 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br />' 3761-MW 10-6/24104 <0.5 <0.5 <0.5 <1.0 <0.05 8.3 <0.5-.5.0 <br /> 3761-MW 11-6/24/04 <0.5 <0.5 <0.5 1 <1.0 <0.05 66 <0.5-5.0 <br /> 1 3761-EWI-6/24/04 1 <0.5 <0.5 _<O.5 1 <1.0 1 <0.05 <0.5 <0.5-5.0 <br /> Unit Conversions: Analytical <br /> • ug/L:parts per billion(ppb). BTEX=benzene,toluene,ethyl benzene,and total xylenes. <br /> mg/L:parts per million(ppm). TPH-G=total petroleum hydrocarbons,quantified as gasoline. <br /> MTBE=methyl tertiary-butyl ether. <br /> Other oxygenates/additives=ethanol(EtOH),tertiary-butanol(TBA),di-isopropyl ether(D1PE), <br /> ethyl tertiary-butyl ether (ETRE), tertiary-amyl methyl ether (TAME), 1,2-dichloroethane (1,2- <br /> DCA),and 1,2-dibromoethane(EDB). <br /> Laboratory analytical results indicate that BTEX constituents, gasoline oxygenates/additives other than <br /> MTBE, and TPH-G were not detected at or above the laboratory reported detection limits in the <br />' groundwater samples collected from the monitor wells. MTBE was detected in the groundwater samples <br /> collected from MW-7, MW-10, and MW-11. The concentration of MTBE in the groundwater samples <br /> collected from MW-7, MW-10, and MW-11 decreased relative to the previous sampling event conducted <br />' on March 4, 2004. MTBE was not detected at or above the laboratory reported detection limit of 0.5 µg/L <br /> in the groundwater samples collected from MW-3, MW-4R, MW-8, MW-9, and EW-1, which indicates a <br /> decrease from the concentrations detected in the groundwater samples collected from these wells.during <br />' the previous sampling event. <br /> FUTURE WORK/RECOMMENDATIONS <br />' In the Additional Groundwater Investigation, Monitor Well Destruction and Installation, and Interim <br /> Remediation Pump Test Report, dated January 30, 2004, Condor recommended the installation and <br /> operation of a groundwater pump and treat system using MW-11 as a groundwater extraction well to <br /> remediate contaminated groundwater at the site. Due to the reduction of the concentrations of MTBE in <br /> the groundwater samples collected from the monitor wells at the site during this quarterly monitoring <br /> event and the corresponding reduction in the estimated size of the MTBE plume, Condor recommends <br /> delaying the installation or a groundwater pump and treat system. It may be necessary to evaluate the cost <br /> effectiveness of using groundwater pump and treat for remediation of hydrocarbon impacted groundwater <br /> 1 <br />' t.1� CONDOR <br />