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I Canepa's Car Wash 6230 Pacific Avenue,Stockton,CA Fourth Quarter Groundwater Morutortng Report,October 2005 Page 4 of 9 • ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2- dtbromoethane (EDB) Groundwater samples collected from the SVE wells (SV-1 through SV-9) on September 12, 2005 and from SV-4 on October 13, 2005 indicate that concentrations of BTEX,MTBE, or TPH-G were detected at or above the laboratory detection limits in SVE wells SV-1 through SV-9, which is consistent with historic results for those wells The laboratory analytical results from the fourth quarter of 2005 were compared to the results from samples collected on July 2, 2002 The comparison indicated that concentrations in the southern SVE wells, SV-7 through SV-9, as well as SVE wells SV-2 and SV-5, have decreased, whereas contaminant concentrations detected in SV-1 located to the northwest have increased Groundwater sample analytical results for SVE wells SV-3, SV-4, and SV-6 are generally consistent with the historic results for those wells Current groundwater sample laboratory analytical results indicate that none of the constituents of concern were detected at or above the laboratory detection limits in monitor wells MW-4, MW-9, or MW-12D, which is consistent with historic results for those wells Since monitoring well MW-1 was designated the primary pumping well for the on-site treatment system in October 2004, contaminant concentrations have remained at historic highs (with the exception of concentrations detected in the groundwater samples collected during the December 1994 and June 1995 monitoring events) EDB was detected for the first time at the site in MW-1 at a concentration of 4 $ pg/L Current groundwater sample laboratory analytical results for monitor well MW-3 are general consistent with historic results with the exception of MTBE, which has been detected at increasing concentrations since the January 2005 monitoring event Benzene and MTBE iso-concentration contour maps are included as Figures 4 and 5 (Attachment A), respectively Historic laboratory analytical results from groundwater samples collected from MW-3 indicate a trend of increasing MTBE concentrations since April 11, 2001 (Figure 6, Attachment A) Groundwater sample laboratory analytical results for the current monitoring event are provided in Table 3, on the following page Laboratory certificates of analyses and chain of custody records are included in Attachment F • �� CONDOR