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.] SVE QUARTERLY OPERATION AND PERFORMANCE Equipment Inventory Not applicable (NA) Operating Mode NA SJVUAPCD Permit No NA TPHG Cone at End of Period (lab) NA Benzene Cone End of Period (lab) NA Flow Rate End of Period NA Applied Vacuum This Period NA HC Destroyed This Period (lab) NA Utility Usage (electrical/gas/propane) NA Operating Hours This Period 0 Percent Time Operational 0 percent Number of Auto Shutdowns NA CURRENT SOURCE (BEFORE DILUTION) INFLUENT SUMMARY (LAB) TPHG Cone This Period NA TPHG Conc Last Period N/A Initial TPHG Cone 55,000 mg/m3 (January 24, 1997(following system startup]) Benzene Cone This Period NA Benzene Cone Last Period N/A Initial Benzene Cone 980 mg/m3 (January 24, 1997 [following system startup]) DISCUSSION Results of this groundwater monitoring event indicate that levels of dissolved gasoline hydrocarbons remained generally consistent in wells MW-1 through MW-7 from the previous sampling events Methyl tertiary butyl ether (MTBE) was detected in wells MW-2 and MW-7 at concentrations of 415 ppb and 212 ppb, respectively, using USEPA Method 8020 However, MTBE was below the laboratory detection limit of 2 ppb for wells MW-2 and MW-7 using USEPA Method 8260 The non detect results for MTBE using USEPA Method 8260 indicate a false positive for the USEPA Method 8020 result, as expected due to the elevated TPHG concentrations in these two wells In addition, well MW-4 contained an MTBE concentration of 45 9 ppb, and well MW-1 contained MTBE and di-isopropyl ether concentrations of 24 2 ppb and 6 10 ppb, respectively, using USEPA Method 8260 The groundwater flow direction (east- southeast) and gradient are consistent with previous sampling events Groundwater elevation decreased 1 14 foot from the previous sampling event (August 1998) CP1 E 1ARC0121681QTRLY12168Q498 DOC 981isg 11 ��