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<br /> Fourth Quarter 2005
<br /> Thnfty#172
<br /> Page 2
<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 lead to the analyses of all
<br /> wells Since the samples were analyzed by EPA Method 8260B, 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 /> Thnfty 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 Thnfty's request to add soluble lead only to the sample from well MW-11
<br /> Thnfty began to analyze soluble lead in the sample from well MW-11 for the first quarter 2005
<br /> 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 (37,100 ug/L,
<br /> 11,700 ug/L, and 367 ug/L, respectively)
<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, Thrifty has analyzed for oxygenates di-isopropyl ether(DIPE),
<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 TBA in wells MW-3 (75 ug/L), MW-6 (22 ug/L) and MW-7 (15 ug/L) In a letter
<br /> dated December 9, 2004, the SJCEHD indicated that methanol may be discontinued as a
<br /> sampling requirement, but that ethanol must continue to be analyzed for since it is a fuel additive
<br /> at the site The SJCEHD further required that ethanol must be analyzed by EPA Method 8015
<br /> Ethanol was not detected using EPA Method 8015M Dissolved lead was not detected above
<br /> 0 002 mg/L 1n well MW-11 The action level for lead in drinking water is 0 015 mg/L
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