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I <br /> Bank of Stockton- Cutter Lumber Site Page 6 <br /> Quarterly Groundwater Monxtonng Report <br /> Project No 102 2 <br /> 17 February 2000 <br /> 1 <br /> 3.0 DISCUSSION <br />' 3.1 Discussion of Data <br />' Field and analytical data results are summarized in Tables 1 and 2 and <br /> illustrated in Figures 3 through 5 <br />' The map of groundwater gradient (Figure 3) suggests that the flow of <br /> groundwater 1s to the northeast The water table has risen about one foot since <br /> the monitoring event in October of last year The direction and gradient of flow <br />' have remained generally consistent over this entire time the wells have been <br /> monitored <br />' A glance at the analytic data shows that the bailer blanks and the trip blank <br /> contained detectable xylene This concentration on all blanks is at or near 0 6 <br />' ppb Upon questioning, the sample technician reported that all bailer blanks <br /> and the trip blank were originally from the same jug of distilled water which <br /> was purchased at a retail outlet The circumstances would seem to suggest that <br /> the water used to make up blank samples was contaminated by a low level of <br /> xylene, rather than caused by a dirty sample bailer The fact that one sample of <br /> formation water did not contain detectable xylene would seem to confirm this <br />' Based on the available information, it is interpreted that the existence of xylene <br /> in blank samples is not reflective of sampling techniques, but is merely due to a <br /> trace of contaminant in the source water container <br />' The analytic data suggest that contaminant levels are generally consistent to <br /> somewhat decreasing <br />' sample from the dee <br /> Although traces of benzene and toluene were found in the sa p e p <br />' monitoring well, MW-8A, gasoline range hydrocarbons and BTEX compounds 1n <br /> the deeper groundwater as determined by well MW-8A have gradually fallen to <br /> trace or non-detectable levels except for xylene which persists at a level slightly <br />' over the minimum detection limit The gasoline range hydrocarbons formerly <br /> detectable in sample from this well appear to have been the result of cross <br /> contamination during drilling We therefor propose that MW-8A be abandoned <br />' by pressure grouting it to the surface with neat cement <br /> 2937 Veneman Ave ,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 <br /> Modesto, CA 95356 Fax (209) 569-0293 <br />