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QUARTERLY MONITORING REPORT JANUARY ]997 CANEPA S CAR WASH I 6290 Pacific Avenue Stockton CA January 27, ]997 monitoring reports to explain this apparent local recharge with a potentially leaky sewer line I Hydrographs of monitor wells MW-1 through MW-8, presented in Figure 4, Appendix A, illustrate the fluctuation of the groundwater table Historical groundwater measurements are provided in the accompanying Hydrograph Table IThe results of the laboratory analyses Indicate that TPH-G, BTEX, and MTBE were detected in groundwater samples collected during the sampling event Benzene concentrations detected in MW- 1, MW-2, and SV-1 exceed the maximum contaminant level (MCL) for benzene (1 0 µg/L) in drinking water (California Code of Regulations, Title 22, Drinking Water Regulatory Criteria) No MCL has yet been established for MTBE The California Department of Health Services has set an action level of 35 µg/L for MTBE in drinking water, however MTBE concentrations detected in j groundwater samples from MW-1, MW-2, and SV-1 exceed that level Analytical results for the January, 1997, sampling are generally consistent with historical analytical results TPH-G, BTEX, and MTBE concentrations in the samples from MW-I and MW-2, however, are generally at their lowest historical levels In addition, the sample from MW-6 did not contain either TPH-G or BTEX constituents for the first time in Its history Most of the other monitor wells have generally experienced a decline In TPH-G and BTEX concentrations relative to 1994 and 1995 results This cannot necessarily be attributed to natural attenuation because the water level in the • wells has been above or very near the top of the well screens during the August and October, 1996, Iand January, 1997, monitoring The historical groundwater analytical data for the site are presented in Table A, Appendix B Floating product was not observed in any of the wells during the January, 1997, quarterly sampling Strong petroleum hydrocarbon odor was noted in MW-1 and SV-1 A moderate gasoline odor was noted in MW-2 Floating product has not been reported in previous groundwater monitoring Ifrom June, 1994 through October, 1996 The next quarterly monitoring event is scheduled for April, 1997 If you need additional information or have any questions, please contact us at (209) 668-9234 Respectfully submitted, �QVESSI Condor Earth Technologies, Inc OQ P F'L 51592 !rte Exp 6-30-98 I Donald F Kresse Robert J Job, California Registered California R ist d>, CIVIL �Q- Geologist #6430 Professional Engine4 �IYI rp1 951592 ICAN 1 QT 97 • IPage -5- It� CONDOR