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Quarterly Momtonng and Sampling Report(Q3 2001} 5 Ranch Market 23569 Santa Fe Road Riverbank California August 9 2001 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 Sampling 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, Califomia The water samples were analyzed for TPHg, BTEX, 1,2-DCA, EDB, and five oxygenates using EPA method 8260B Groundwater Analytical Results Historical and recent groundwater laboratory analytical results are summarized in Table 3 The highest TPHg and benzene concentrations were detected in monitoring well MW-1 at 35,000 . parts per billion (ppb) and in MW-2 at 6,800 ppb, respectively (Figure 5) The highest MtBE and TBA concentrations were detected in monitoring well MW-1 at 900 ppb and MW-5 at 11 ppb, respectively TBA was also reported in monitoring well MW-6 at a concentration of 5 9 ppb 1,2-DCA was reported in MW-3, MW-5, and MW-7 at concentrations of 11 ppb, 2 0 ppb, and 0 68 ppb No other oxygenates or EDB were reported above the laboratory detection 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, and the monthly samples collected from DW-1, did not contain detectable concentrations of TPHg, BTEX, oxygenates, 1,2-DCA, or EDB MtBE was detected in domestic well DW-4 at a concentration of 1 1 ppb Due to the reported presence of MtBE in DW-4, the RWQCB requested SECOR resample DW-4 to verify the sample results SECOR field personnel resampled DW-4 on August 1, 2001 The DW-4 water sample did not contain detectable concentrations of TPHg, BTEX, 1,2-DCA, EDB, or oxygenates, including MtBE Copies of the laboratory analytical reports and chain-of-custody manifests are included in Attachment 4 Conclusion Ten groundwater monitoring wells and four domestic water wells were sampled this quarter Groundwater elevation declined an average 13 feet since April 2001 Referring to Table 3, an increase in the concentration of benzene, TPHg, and MtBE was observed in wells MW-1 and File Ranch MarketlReport\Riverbank 01-3Q