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i QUARTERLY MONITORING REPOR f,lily 1998 CANEPA S CAR WASH 6230 Pacific Avenue,Stockton,CA August 24 1998 ' Page -2 Prior to granting unconditional approval of Installation of a new SVE system, the Underground Storage Tank Clean-Up Fund has indicated the need for additional Investigation Condor has conducted the mstallation and sampling of two soil borings adjacent to the SVE well array The investigation included soil vapor screening using the Simulprobe sampling device in soil vapor collection mode The results indicated high levels of volatile organic compounds are present in the soil vapor at the site The results of the laboratory analysis of the soil and groundwater samples collected during the investigation are included in Report—Soil and Groundwatei Investigation, dated June 12, 1998 A detailed Site History is included in Appendix B 3 0 QUARTERLY GROUNDWATER MONITORING -JULY, 1998 ' On July 21 and 22, 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 locations) In addition, at the request of Mr Rowe of the PHS/EHD, a groundwater sample was also collected from soil vapor ' eatiaction well SV-4 The order of sampling was MW-5, MW-4, MW-8, MW-6, MW-7, MW-3, MW-2, SV-4, and MW-1 ' 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 clean, single-use, polypropylene, 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, however Strong petroleum hydrocarbon odors were noted in the groundwater samples collected from MW-I and SV-4, and a moderate odor was detected in MW-2 No odor was noted in any of the other groundwater samples collected ' All of the monitor wells, except MW-1 were purged using new, disposable bailers Monitor well MW-1 was purged with an electric submersible pump At least 3 casing volumes of water were purged from each well (see the Groundwater Monitoring Field Forins 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 two 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 4 1 GROUNDWATER ELEVATION CONTOURS ' On July 21, 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 35 4 feet below thakWll ' La CONDOR