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' Bank of Stockton Cutter Lumber Site Page 6 Autumn Quarter Groundwater Monitoring Report ' Project No 102 2 • 20 January 1999 ' 3.0 DISCUSSION ' 3.1 Discussion of Data Field and analytical data results are summarized in Tables 1 and 2 and ' illustrated in Figures 3 through 7 At the request of the LOP case officer, soil analytical data from past soil borings has also been attached as Table 3 The locations of these borings are depicted in figures 8 and 9 1 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 fallen about 3 feet ' 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 I The analytic data from peripheral wells suggest that the down gradient limit of '• the gasoline plume in the shallow groundwater has been partially defined The presence of gasoline hydrocarbons in the deeper groundwater as determined by well MW-8A continues to persist 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 decreased by a factor of at least two One exception to this is MW-11, the most distant well from the point of release Levels of TPH-G and BTEX have fluctuated considerably, but there is no clear trend of reducing 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 Quarterly groundwater monitoring and sampling should continue The depth to ' groundwater should be checked monthly for at least the next quarter It is now appropriate to consider what additional work may be needed The presence of 2937 Veneman Ave ,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293 I