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1 1 i First Quarter 2005 Thrifty#172 ' April 26, 2005 Page 2 ' total petroleum hydrocarbons as gasoline (TPHg) by EPA Method 8015M Ethanol and methanol were analyzed by ASTM Method 8015M EMC field sampling forms are provided in Appendix A. ' In a letter dated September 1, 2004, the San Joaquin County Environmental Health Department (SJCEHD) requested that Thnfty add 1,2-DCA, EDB, and soluble lead to the analyses of all wells Since the samples were analyzed by EPA Method 8260B, Thrifty was able to report 1,2- DCA and EDB, but due to the fact that sampling was previously conducted on August 11, 2004, soluble lead was not added for the third quarter 2004 event In a letter dated October 6, 2004, ' Thrifty requested that soluble lead not be added to the list of analytes due to Iead being detected at low concentrations in soil or being non detect Thrifty further requested that if the SJCEHD still required lead to be added, that it only be required for well MW-11, the well with the highest ' TPHg, benzene, and MTBE concentrations at the site In a letter dated December 15, 2004, the SJCEHD granted Thnfty's request to add soluble lead only to the sample from well MW-11 Thrifty analyzed soluble lead in the sample from well MW-lI during sampling for the first quarter 2005 sampling event TPHg, BTEX, and MTBE concentrations appear in Table 1, while historical oxygenate and alcohol results are presented in Table 2 Copies of groundwater laboratory reports and chain-of- custody documents are included in Appendix B TPHg, benzene, and MTBE isoconcentration maps are presented as Figures 3, 4, and 5, respectively The highest concentrations of TPHg, MTBE in groundwater were found in monitoring well MW-3 (130,000 ug/L and 122,000 ug/L, respectively) The highest benzene concentration was detected in well MW-11 at 814 ug/L The ' remaining site wells have very low to non-detectable constituent concentrations During the current quarter, TPHg, benzene, and MTBE were not detected in offsite well MW-9 ' During the third quarter 2004, TPHG, benzene, and MTBE were detected in well MW-9 The reason for the appearance and disappearance of these constituents is uncertain Thnfty will continue to monitor well MW-9 ' Since the third quarter of 1997, Thnfty has analyzed for oxygenates di-isopropyl ether (DIPE), ethyl-tert butyl ether (ETBE), tert-amyl methyl ether (TAME), and ter -butanol (TBA), and ' MTBE by method 8260B The alcohols (ethanol and methanol) were analyzed by ASTM standard D285 The SJCEHD requested these analyses Laboratory results indicate no alcohols or oxygenates (besides MTBE) were detected above the laboratory detection limit, with the ' exception of TAME in wells MW-3 (835 ug/L) and MW-11 (71 ug/L) and TBA in wells MW-6 (20 ug/L) and MW-7 (19 ug/L) In a letter dated December 9, 2004, the SJCEHD indicated that . methanol may be discontinued as a sampling requirement, but that ethanol must continue to be 1 I