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QUARTFRLY MONITORING REPORT January, 1998 CANEPA S CAR WASH 6230 Paufic Avenue Stockton CA February 10, 1998 Page -3 ' 3 0 QUARTERLY GROUNDWATER MONITORING-JANUARY, 1998 On January 20 and 21, 1998, Condor personnel made field observations and collected groundwater samples from the eight monitor wells at the site (see Figure 2, Appendix A for well Iocations) In addition, at the request of Mr Rowe, PI-IS/EHD, a groundwater sample was also collected from soil vapor extraction well SV-8 The order of sampling was MW-5, MW-4, MW-8, MW-6, MW-3, MW-7, MW-2, MW-1, and SV-8 3 1 GROUNDWATER MONITORING OBSERVATIONS AND PARAMETERS The static water level in each well was measured to the nearest 0 01-foot with a battery-operated, flat tape, water-level meter A disposable bailer was lowered into each well to check for floating product, petroleum odors, and sheen Floating product was not observed in any of the monitor wells during the groundwater sampling Water levels in the wells were above the top of the well screens in the wells, however Slight and moderate petroleum hydrocarbon odors were noted in the groundwater samples collected from MW-2 and SV-8, respectively No odor was noted in any of the other wells at the site MW-1 was purged using a small submersible pump All other wells were each purged using new, disposable bailers At least 3 casing volumes of water were purged from each well (see the Groundwater Monitoring Field Forms in Appendix B ) The purged water from each well was placed in a plastic, 55- gallon drum and left on site pending analytical results 3 2 GROUNDWATER SAMPLING Each well was allowed to recover to at least 80% of its pre-purge water level before sampling The groundwater samples were collected directly from disposable bailers Each water sample consisted of three 40-m1 glass, volatile organic analyses (VOA) vials The VOAs were labeled and placed in a cooler chilled with ice The groundwater samples were delivered, under chain-of-custody procedures, to GeoAnalytical Laboratories, Inc, in Modesto,California, on the day of collection 4 0 GROUNDWATER MONITORING RESULTS 41 GROUNDWATER ELEVATION CONTOURS ' On January 20, 1998,the depth to groundwater was measured in each monitor well prior to the collection of groundwater samples The average depth to groundwater was approximately 39 1 feet below the ground surface (bgs) at the site The average depth to groundwater has decreased approximately 2 2 feet since October, 1997 The groundwater elevation ranged from 26 68 to 25 67 feet below sea level (bmsl) The groundwater elevation contour map (Figure 3, Appendix A) indicates groundwater mounding in the center of the site in the vicinity of MW-1 and MW-2 See Table 1, below, for groundwater elevation data A lrydrograph of groundwater elevations is included as Figure 4, Appendix A �� CONDOR