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The groundwater elevation has decreased by an average of 0 54 feet at the three monitor wells since the previous quarterly monitoring round on September 30, 1998 The flow direction is to the south The overall gradient is 0 005 feet/linear foot RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES The results of the certified analyses of groundwater samples collected from the three monitor wells on December 7, 1998 are shown in Table 1 Copies of the laboratory reports are included as Appendix D of this report TPH-G concentrations ranged from a maximum of 18,000 ug/1 at monitor well MW1 to 4,600 ug/1 at monitor well MW2 Benzene concentrations ranged from a maximum of 2900 ug/l at MW3 to 590 ug/l at MW2 MTBE concentrations ranged from a maximum of 110 ug/1 at MW1 to 72 ug/l in MW3 Concentrations of the oxygenant t-Amyl Methyl Ether (TAME) ranged from a maximum of 28 ug/I at MW2 to below the laboratory detection limits of 1 ug/1 at MW3 The remaining three oxygenants, DIPE, TBA, and ETBE, were not present an concentrations above the laboratory detection limits of 5 ug/l in any of the samples from the three monitor wells Figure 5 shows the distribution of TPH-G, BTEX, and MTBE an groundwater and the estimated lateral limits of the TPH-G in groundwater as determined from groundwater samples collected on December 7, 1998 WATER WELL RECORDS REVIEW Western Geo-Engineers reviewed current and historical water well records maintained by the California Division of Water Resources, the San Joaquin County Flood Control District, the City of Stockton, and California Water Services in order to locate potential sensitive receptors in the site vicinity and to determine the historically lowest groundwater elevation at the site between 1965 and the present According to the owner Mr Fowler , the gasoline UST that was removed from the site in 1987 had been in use since 1965 Leaks from the UST and associated piping could have impacted the soil and groundwater at significantly lower elevations than the current groundwater elevation of approximately 12 5 feet below mean sea level WEGE reviewed the available water well records for domestic wells within a half mile radius of the site and for municipal water wells within a one mile radius of the site The record review identified a total of 11 water wells within the search radius The locations of the wells with respect to the site are shown in Figure 6 A list of the wells and their particulars is included as Appendix E of this report 3 Arc Pump QM 10-12 1998