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' Former Manna Pro Site Page 6 Quarterly Groundwater Monitoring Report Project No 207 2 . December 11, 2001 ' 3.0 DISCUSSION ' 3.1 Discussion of Data Field and analytical data results are summarized in Summary Table 1 and ' illustrated in 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 3 feet since the last monitoring event in June A local groundwater high of about 0 4 feet ' persists in the vicinity of MW-6 The reason for this feature is not known, although the location seems to correspond with the area where an oxygen release compound (ORC) was placed in boring ORC-1 the spring of 2000 ' 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 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 3,380 ppb in January of 2000 In the three monitoring events since December of 2000, the contaminant concentrations have remained at relatively low levels 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 The first phase vapor extraction / air sparge remedial system has been constructed and is ready for start-up pending receipt of an air emissions permit from the local APCD Recently, the State of California implemented an "Electronic Data Filing" (EDF) requirement for groundwater monitoring associated with underground tank sites Getting the system implemented has resulted in the somewhat late ' 2937 Veneman Ave,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293