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n a, Canepa's Car Wash 6230 Pacific Avenue,Stockton,CA Fourth Quarter Groundwater Monitoring Report,November 2003 Page 4 of 6 SLABORATORY ANALYTICAL RESULTS The groundwater samples collected from the monitor wells and SV-4 were analyzed for TPH-G by Method 8015M and BTEX and selected gasoline oxygenates/additives by EPA Method 8260B by Excelchem Laboratories, Inc. of Roseville, California (Excelchem). The selected oxygenates/additives included methyl tert butyl ether (MTBE), ethanol, tertiary-butanol (TBA), di-isopropyl ether (DIPE), ethyl-tert butyl ether (ETBE), tert-amyl methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2- dibromoethane (EDB). The current groundwater sample analytical results presented in Table 3, on the next page, are generally consistent with the historical results (Attachment C) although the limited amount of full gasoline oxygenate analyses (four recent monitoring events) makes historical comparison difficult. None of the contaminants of concern were detected at or above the laboratory reported detection limits in monitor wells MW-4 and MW-9. None of the contaminants of concern were detected at or above the laboratory reported detection limits in deep monitor well MW-12D; this is the second consecutive quarter that has occurred. Monitor well MW-12D has historically shown a decrease in contaminate concentration each quarter since monitoring of the deep aquifer began in October of 2001 (Table A, attached). TBA was detected in the sample collected from monitor well MW-1 for the first time at a concentration of 72 µg/L. Laboratory analytical results indicate a significant increase in BTEX, MTBE, and TPH-G concentrations detected in monitor well MW-1 compared to the July 2003 monitoring event. Laboratory analytical results also indicate a significant increase in BTEX and TPH-G concentrations in monitor well MW-2 compared to the July 2003 monitoring event. TBA and TAME were detected in the sample collected from monitor well MW-3 for the second consecutive quarter (45 and 1.8 pg/L, respectively), along with 1,2-DCA which has historically been detected in the well. The concentration of MTBE detected in the groundwater sample collected from monitor well MW-3 nearly doubled and is consistent with an increasing trend for that contaminant in that well (Figure 6, Attachment A). TBA, MTBE, and TPH-G were detected at low concentrations in the sample collected from monitor well MW-11. Benzene and MTBE iso-concentration contour maps are included as Figures 4 and 5, respectively, in Attachment A. Laboratory certificates of analyses and chain of custody record are included in Attachment E. • �� CONDOR