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Ms Mary Meays Page 3 <br /> July 14, 1991 <br /> was used for decontamination or any other field procedures In the future, <br /> field blanks will be collected by transferring water directly from its original <br /> container into a VOA sample vial <br /> At the laboratory, standard internal QA/QC procedures were followed <br /> Ondinga <br /> A summary of the findings from this second quarter of groundwater <br /> sampling is presented below <br /> FQrmer T nk 69ite #1 <br /> Plotting and contouring groundwater level contours (Figure 1) indicate a <br /> trough centered at MW-5 and oriented towards the southwest During the <br /> previous monitoring activities, groundwater flow directions were oriented <br /> towards the southeast As previously discussed, the variability in flow <br /> direction is probably due to the influence of tide-induced water level <br /> changes in the adjacent Stockton deep water channel Tidal data for the <br /> Stockton area is provided in Table 4 <br /> ERM-West obtained groundwater measurements for all Tank Site #1 wells <br /> within a 20-minute time period This was done to minimize the potential <br /> effect of changing tides on measured elevation data Despite the fact that <br /> the elevation measurements were obtained within a short time period, the <br /> trough was present <br /> The laboratory findings (Table 2) indicate a slight decrease in the <br /> concentration of TPH-G and related petroleum compounds at MW-5 The <br /> measured TPH-G concentrations are at the lowest level observed (4 7 mg/1) <br /> during quarterly monitoring activities BTEX concentrations were <br /> measured in concentrations that were less than half of those observed <br /> during the First Quarter 1992 monitoring <br /> MW-4 also showed very low concentrations quantities of TPH as gasoline <br /> and petroleum compounds These constituent concentrations were <br /> generally consistent with previously observed concentrations for this well <br /> A continued decrease in gasoline and BTEX compounds to nondetectable <br /> concentrations was noted in MW-4 during the previous quarter Thus, it is <br /> probable that MW-4 is situated on the margin of the area affected by <br /> gasoline from the former UST <br /> Wells MW-1, MW-2, and MW-3 showed no detectable quantities of gasoline <br /> and petroleum compounds The absence of gasoline and related <br /> compounds in these wells is consistent with the results from previous <br /> quarterly monitoring <br />