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rSecond Quarter 2005 Groundwater Monitoring Report <br /> Boyett Petroleum,419 S.Main,Manteca,CA <br /> Page 3 <br />' Table 2: Laborator Analytical Results June 30 2005 <br /> • Other <br />' B T E X TPH-G MTBE Oxygenates/ <br /> Additives <br /> Detection 0.5 0.5 0.5 1.0 0.05 0.5 0.5-5.0 <br /> Limits: pg/L gg/L gg/L µg/L mg/L pg/L pg/L, <br /> Analytical Method: 8260B 8260B 8260E 8260B 8015M 8260B 8260B <br /> Sample I.D. Well I.D. <br /> MW2 MW-2 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> MW3 MW-3 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> tMW4R MW-4R <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> MW6 MW-6 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> MW7 MW-7 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> MW8 MW-8 <0.5 <0.5 <0.5 1 <1.0 <0.05 <0,5 <0.5-5.0 <br />' MW9 MW-9 <0.5 <0.5 <0.5 <1.0 <0.05 1.1 <0.5-5.0 <br /> MW10 MW-10 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> MW 11 MW-11 <0.5 <0.5 <0.5 <1.0 <0.05 3.1 <0.5-5.0 <br /> EWI EW-1 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 <br /> Unit Conversions: Analytical <br /> µg/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(DIPS), <br /> ethyl iertiary-butyl ether(ETRE), tertiary-amyl methyl ether(TAME), 1,2-dichloroethane(1,2- <br /> x1!'4) anA 0-ha-n-'PnnR <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 monitoring wells. MTBE was detected in the groundwater <br /> samples collected from MW-9 and MW-11. MTBE was not detected at or above the laboratory reported <br />' detection limit of 0.5 gg/L in the groundwater samples collected from MW-2, MW-3, MW-4R, MW-6, <br /> MW-7, MW-8, MW-10, and EW-1. <br />' DISCUSSION AND RECOMMENDATIONS <br /> Laboratory analytical results for the groundwater samples collected from the Site monitoring wells on <br /> June 30, 2005, indicate that MTBE was detected at concentrations below the California Department of <br />' Health Services Maximum Contaminant Level (MCL) of 13 gg/L in the groundwater samples collected <br /> from MW-9 and MW-11. MTBE was not detected at or above the laboratory reported detection limit in <br /> the groundwater samples collected from the other monitoring wells at the Site. <br /> Concentrations of MTBE in groundwater at the Site have decreased significantly during the last two <br /> years, as shown on the graph in Figure 5, attached. There has also been a corresponding reduction in the <br />' estimated size of the MTBE plume during the same time period. The decrease in concentrations and the <br />' t� CONDOR <br />