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Former Manna Pro Site Page 6 Quarterly Groundwater Monitoring Report ' Project No 207 2 . July 11, 2001 3.0 DISCUSSION ' 3.1 Discussion of Data ' Field and analytical data results are summarized in Summary Table 1 and illustrated 1n Figures 3 through 5 ' The map of groundwater gradient (Figure 3) suggests that the flow of groundwater is to the northeast The water table has fallen about 14 feet since the last monitoring event in March The analytic data suggest that contaminant levels are generally consistent with what has been observed in past monitoring events The more distal areas appear to display a gradual degradation of the contaminant plume, but little natural attenuation is occurring in the core area ' In the December 2000 groundwater monitoring event, a dramatically reduced contaminant concentration in the groundwater sample from MW-6 was noted 1. Over the past 8 years, this well has typically produced samples with TPH-G concentrations of 15,000 ppb or more The lowest concentration previously recorded prior to December 2000 was 3380 ppb in January of 2000 These concentrations contrast sharply with the December sample result 858 ppb In the sample from the March 2001 event, the TPH-G concentration was 2,750 ppm The level for this current event has once again decreased to 824 ppm ' The reason for these fluctuations is not known, but may be associated with local hydrocarbon degradation resulting from the ORC material placed in boring ORC-1 in the spring of 2000. ' 3.2 Future Work Schedule ' A recently submitted Corrective Action Plan has been approved by the San Joaquin County PHS-EHD and pre-approval of the associated costs has been ' granted the California UST Cleanup Fund Preliminary work for implementation of the CAP has commenced and field work will commence in the near future 2937 Veneman Ave ,#B240 Geo-Phase Environmental Inc Phone (209)569-0293 Modesto, CA 95356 Fax(209) 569-0293 t