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Fourth Quarter 2003 Groundwater Monitoring Report Boyett Petroleum,419 S.Main,Manteca,CA Page 6 • The groundwater samples were analyzed for benzene, toluene, ethyl benzene, and total xylenes (BTEX) and selected gasoline oxygenates/additives by EPA Method 8260B, and total petroleum hydrocarbons quantified as gasoline (TPH-G) by Method 8015B by Argon. The selected oxygenates/additives included MTBE, ethanol (EtOH), tertiary-butanol (TBA), di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETRE), tertiary-amyl methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB). The laboratory analytical results for the fourth quarter 2003 quarterly groundwater monitoring event are presented in Table 6, below. Maps representing MTBE isoconcentration contours in groundwater are included as Figure 9, attached. TABLE 6: Laboratory Analytical Results (December 31, 2003) Oxygenates/Additives B T E X TPH-G MTBE Other Oxygenates/Additives Detection 0.5 0.5 0.5 1.0 0.05 0.5 0.5-5.0 Limits: pg/L ltg/L µ€/L µl/L mg/L pg/L Analytical Method: 82608 8260E 8260B 826013 8015B 8260B 82608 Sample I.D. 3761-MW2-12/31/03 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 3761-MW3-12/31/03 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 . 3761-MW4R-12131/03 <0.5 <0.5 <0.5 <1.0 <0.05 22 <0.5-5.0 3761-MW6-12131103 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 3761-MW7-12131/03 <0.5 <0.5 <0.5 <1.0 <0.05 200 TAME-0.8 3761-MW8-12/31/03 <0.5 <0.5 <0.5 <1.0 <0.05 <0.5 <0.5-5.0 3761-MW9-12/31/03 <0.5 <0.5 <0.5 <1.0 <0.05 4.3 <0,5-5.0 3761-MW10-12/31/03 <0.5 <0.5 <0.5 <1.0 <0.05 230 TAME-0.6 3761-MW11-12/31/03 <0.5 <0.5 <0.5 <1.0 <0.05 520 TAME-1.1 3761-EW1-12131/03 1 <0.5 <0.5 <0.5 <1.0 <U5 36 <0.5-5.0 Unit Conversions: Analytical µg/L: parts per billion(ppb) BTEX=benzene,toluene,ethyl benzene,and total xylenes. mg/L: parts per million(ppm) TPH-G=total petroleum hydrocarbons,quantified as gasoline. MTBE=methyl tertiary-butyl ether Other oxygenates/additives = ethanol (EtOH), tertiary-butanol (TBA), di-isopropyl ether(DIPE),ethyl tertiary-butyl ether(ETRE),tertiary-amyl methyl ether(TAME), 1,2-dichloroethane(1,2-DCA),and 1,2-dibromoethane(EDB) Laboratory analytical results indicate that BTEX constituents, gasoline oxygenates/additives other than MTBE and TAME, and TPH-G were not detected at or above the laboratory reported detection limits in the groundwater samples collected from the monitoring wells. MTBE was detected in the groundwater samples collected from MW-4R, MW-7, MW-9, MW-10, MW-11, and EW-1. TAME was detected in the groundwater samples collected from MW-7, MW-10, and MW-11. The concentration of MTBE in the groundwater samples collected from MW-4R and MW-10 increased relative to the previous sampling . event conducted on November 26, 2003. The concentration of MTBE in the groundwater samples collected from MW-9, MW-11, and EW-1 decreased relative to the previous sampling event. 1 �� CONDOR