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Quarterly Monitonng and Sampling Report(Q1 2002) 5 Ranch Market,23569 Santa Fe Road,Riverbank,Cahfomia Apnl 26,2002 Groundwater Sampling Well Purging Groundwater monitoring wells were purged using a submersible pump and disposable bailers until pH, temperature, and conductivity readings had stabilized Temperature, conductivity, and pH readings were recorded in the wells, at regular purge intervals of one casing volume, with a portable instrument that was calibrated before the wells were purged Water purged from the ten groundwater monitoring wells was stored in drums on site, pending characterization and disposal Domestic Well Groundwater Sampling Procedures Domestic wells were purged by turning on the water at the well, thus draining the well's holding tank and filling the tank with fresh water from the aquifer Once the tank has been recharged, water samples were collected directly from a spigot at the holding tank DW-2R, DW-3, and DW-4 are sampled quarterly, and DW-1 is sampled monthly Groundwater Samphng Procedures The groundwater monitoring wells were re-monitored to verify at least 80% recovery prior to sampling Adequate recovery was observed in the purged wells prior to sampling A disposable bailer was used to collect the groundwater samples All samples were collected in appropriate containers, preserved on ice, and transported under chain-of-custody manifest to Kiff Analytical LLC located in Davis, California The water samples were analyzed for TPHg, BTEX, 1,2-DCA, EDB, and five oxygenates using EPA method 8260B Groundwater Analvtical Results Histoncal and recent groundwater laboratory analytical results are summarized in Table 3 The highest benzene and TPHg concentrations were detected in monitoring well MW-3 at 1,200 parts per billion (ppb) and 9,200 ppb, respectively (Figure 5) The highest MtBE concentration was detected in monitoring well MW-4 at 84 ppb 1,2-DCA was reported in MW-5d at a concentration of 0 86 ppb EDB and other oxygenates, including TBA, were not detected above the laboratory reporting limits in samples collected from the monitoring wells Domestic Well Analytical Results The water samples collected from domestic wells DW-2R and DW-3, sampled quarterly, did not contain detectable concentrations of TPHg, BTEX, oxygenates, 1,2-DCA, or EDB SECOR field personnel collected monthly water samples from DW-1 on January 3, February 4, and March 1, 2002 The DW-1 water samples did not contain detectable concentrations of TPHg, BTEX, 1,2- DCA, EDB, or oxygenates Copies of the laboratory analytical reports and chain-of-custody manifests are included in Attachment 4 File Ranch Market\Report\Riverbank-02-1Q