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Second Quarter Groundwater Monitoring Report June 2003 <br /> Boyett Petroleum,419 S.Main,Manteca,CA <br /> Page 4 <br /> • LABORATORY ANALYTICAL RESULTS <br /> The groundwater samples were analyzed for benzene, toluene, ethyl benzene, and total xylenes (BTEX) <br /> and selected gasoline oxygenates/additives by EPA Method 8260B, and total petroleum hydrocarbons <br /> quantified as gasoline (TPH-G) by Method 8015B by Argon Laboratories, Inc. of Ceres, California. The <br /> selected oxygenates/additives included methyl tertiary-butyl ether (MTBE), ethanol (EtOH), tertiary- <br /> butanol (TBA), di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether <br /> (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB). <br /> Laboratory analytical results for the groundwater samples collected at the site on June 25, 2003, indicate <br /> that BTEX constituents and TPH-G were not detected at or above the laboratory reported detection limits <br /> in any of the groundwater samples collected from the monitor wells. Gasoline oxygenates/additives were <br /> not detected at or above the laboratory reported detection limits in the groundwater samples collected <br /> from MW-3, MW-6, MW-8 and MW-9. MTBE was detected in the groundwater samples collected from <br /> MW-1, MW-2, and MW-7. TAME was detected in the groundwater samples collected from MW-1 and <br /> MW-7. The laboratory analytical results for the June 2003 monitoring event indicate a decrease in the <br /> concentration of MTBE detected in the groundwater sample collected from MW-9, and an increase in the <br /> concentration of MTBE detected in MW-1, MW-2, and MW-7 relative to the previous sampling event <br /> conducted in March 2003. <br /> The laboratory analytical results for the second quarter 2003 quarterly groundwater monitoring event are <br /> presented in Table 4, on the following page. A map representing MTBE isoconcentration contours in <br /> shallow groundwater is included as Figure 5, attached. A graph showing MTBE concentrations versus <br /> time in monitor wells MW-1 and MW-7 is presented as Figure 6, attached. A graph showing MTBE <br /> concentrations and groundwater elevations in monitor wells MW-1 and MW-7 is presented as Figure 7, <br /> • attached. Historical groundwater monitoring data, laboratory certificates of analyses, and chain of custody <br /> record are also attached. <br /> 4 <br /> �1� CONDOR <br />