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LEP Bank of Stockton - Cutter Lumber Site Page 6 Winter Quarter Groundwater Monitoring Report Project No. 102.2 20 April 1999 3.0 DISCUSSION 3.1 Discussion of Data `r Field and analytical data results are summarized in Tables 1 and 2 and illustrated in Figures 3 through 7. The maps (figures 3,4 & 5) of groundwater gradient suggest that the flow of groundwater is to the east by northeast. The water table has risen about two ,.. feet since the monitoring event in December of 1998 and it is less than one foot lower since the monitoring wells MW-6 through MW-11 were constructed in March of 1998. The direction and gradient of flow have remained generally �• consistent over this entire time. The slight variation of depth to groundwater between MW-8A and MW-8B suggests the deeper well, which is completed opposite a permeable sand layer, may be responding more quickly to water '-' recharge from an off-site recharge area. The analytic data suggest that contaminant levels have generally been decreasing, although samples from MW-8B, the nearest well down-gradient from Nampo the point of release does not appear to follow this pattern. The presence of gasoline hydrocarbons in the deeper,r g y p groundwater as determined by well MW-8A continues to persist, although at diminishing levels. The lateral and vertical extent of this deep plume has not yet been fully defined. Detectable levels of gasoline range hydrocarbons and BTEX compounds continue to persist in the water samples from all wells in the northerly release area �• except in MW-10. A review of the analytical data presented in Table 2 suggests the contaminant levels have generally been decreasing since the wells were originally constructed. In most wells the measured contaminant levels have L. decreased by a factor of at least two since the initial round of sampling. One exception to this is MW-11, the most distant well from the point of release, r`. which continues to exhibit low, but persistent contaminant levels. 3.2 Future Work Schedule Based on the data collected during the course of this investigation, Geo-Phase Environmental Inc. anticipates the following work be completed in the future. La Quarterly groundwater monitoring and sampling should continue. The monthly depth to groundwater check will be suspended. The San Joaquin County ti• PHS/EHD has issued a directive to submit a Work Plan to further characterize the vertical and lateral extent of the deeper portions of the hydrocarbon +� 2937 Veneman Ave.,#B240 Geo-Phase Environmental Inc. Phone (209) 569-0293 Modesto, CA 95356 Fax (209)569-0293