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iFourth Quarter 2004
<br /> Thrifty#172
<br /> January 19, 2004
<br /> Page 2
<br /> total petroleum hydrocarbons as gasoline(TPHg) by EPA Method 8015M Ethanol and
<br /> methanol were analyzed by ASTM Method D285 EMC field sampling forms are provided in
<br /> Appendix A
<br /> In a letter dated September 1, 2004, the San Joaquin County Environmental Health Department
<br /> (SJCEHD) requested that Thrifty add 1,2-DCA, EDB, and soluble Iead to the analyses of all
<br /> wells Since the samples were analyzed by EPA Method 826013, Thrifty was able to report 1,2-
<br /> DCA and EDB, but due to the fact that sampling was previously conducted on August 11, 2004,
<br /> soluble lead was not added for the third quarter 2004 event In a letter dated October 6, 2004,
<br /> Thrifty requested that soluble lead not be added to the list of analytes due to lead being detected
<br /> at low concentrations in soil or being non detect Thrifty further requested that if the SJCEHD
<br /> still required lead to be added, that it only be required for well MW-11, the well with the highest
<br /> TPHg, benzene, and MTBE concentrations at the site In a letter dated December 15, 2004, the
<br /> SJCEHD granted Thrifty's request to add soluble lead only to the sample from well MW-11
<br /> Thrifty will analyze soluble lead in the sample from well MW-11 during sampling for the first
<br /> quarter 2005 sampling event
<br /> TPHg, BTEX, and MTBE concentrations appear in Table 1, while historical oxygenate and
<br /> alcohol results are presented in Table 2 Copies of groundwater laboratory reports and chain-of-
<br /> custody documents are included in Appendix B TPHg, benzene, and MTBE isoconcentration
<br /> maps are presented as Figures 3, 4, and 5, respectively The highest concentrations of TPHg,
<br /> benzene, and MTBE in groundwater were found in monitoring well MW-11 (221,000 ug/L,
<br /> 26,500 ug/L, and 776 ug/L, respectively) The remaining site wells have very Iow to non-
<br /> detectable constituent concentrations
<br /> During the current quarter, TPHg, benzene, and MTBE were not detected in offsite well MW-9
<br /> During the third quarter 2004, TPHG, benzene, and MTBE were detected in well MW-9 The
<br /> reason for the appearance and disappearance of these constituents is uncertain Thrifty will
<br /> continue to monitor well MW-9
<br /> Since the third quarter of 1997, Thnfly has analyzed for oxygenates di-isopropyl ether(DIPE),
<br /> I
<br /> ethyl-tert butyl ether (ETBE), tert-amyl methyl ether(TAME), and tert-butanol (TBA), and
<br /> MTBE by method 8260B The alcohols (ethanol and methanol) were analyzed by ASTM
<br /> standard D285 The SJCEHD requested these analyses Laboratory results indicate no alcohols
<br /> or oxygenates (besides MTBE) were detected above the laboratory detection limit, with the
<br /> exception of TAME in wells MW-7 (12 ug/L) and MW-9 (12 ug/L) The detections limits for
<br /> TAME and TBA were significantly elevated in well MW-ll Ina letter dated December 9, 2004,
<br /> the SJCEHD indicated that methanol may be discontinued as a sampling requirement, but that
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