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' Former Manna Pro Site Page 5 <br /> Quarterly Groundwater Monitoring Report <br />' Protect No 1012 <br /> • January 17,2001 <br />' 3,0 DISCUSSION <br />' 3.1 Discussion of Data <br /> Field and analytical data results are summarized in Summary Table 1 and illustrated in <br /> Figures 3 through 5 <br /> The map of groundwater gradient (Figure 3) suggests that the flow of groundwater is to the <br /> northeast The water table has fallen almost two feet since the last monitonng event in <br /> July <br />' The analytic data suggest that contaminant levels are generally consistent with what has <br /> been observed in past monitoring events The more distal areas appear to display a gradual <br />' degradation of the contaminant plume, but little natural attenuation is occurring in the core <br /> area <br />' One notable development in this event is the dramatically reduced contaminant <br /> concentrations in the groundwater sample from MW-6 Over the past 8 years, this well has <br /> typically produced samples with TPH-G concentrations of 15,000 ppb or more The lowest <br /> concentration previously recorded was 3380 ppb in January of 2000 These concentrations <br /> contrast sharply with the 858 ppb concentration recorded in this current event If this <br /> sample is representative, it may be reflective of influence of the Oxygen Release <br /> Compound (ORC) which was introduced in a nearby up-gradient boring (ORC-1) in May <br /> of 2000 The dissolved oxygen levels have not risen appreciably in MW-6, but the sharply <br /> reduced TPH level may represent the leading edge of influence from the ORC boring <br />' The contaminant levels in the sample from MW-11, the deep well, have fallen to non- <br /> detectable levels It appears the gasoline-impacted samples first collected in this well were <br /> rcross-contaminated by invasion of drilling mud filtrate during the drilling process We <br /> recommend that monitoring of this well be terminated and that it be considered for <br /> abandonment <br /> 3.2 Future Work Schedule <br /> A Corrective Action Plan is currently being prepared, and should be submitted soon <br />' Monitoring of the existing wells should continue <br /> 2937 Veneman Ave,#5240 Geo-Phase Environmental Inc Phone(209)569-0293 <br /> Modesto,CA 95356 Fax(209)569-0293 <br />