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' Former Manna Pro Site Page 6 <br /> Quarterly Groundwater Monitoring Report <br />' Project No 2012 <br /> . April 2,2001 <br />' 3.0 DISCUSSION <br />' 3.1 Discussion of Data <br /> i <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 risen about 13 feet since the last monitoring event in <br /> December <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 />' In the most recent groundwater monitoring report, a dramatically reduced contaminant <br /> concentration in the groundwater sample from MW-6 was noted Over the past 8 years, <br /> this well has typically produced samples with TPH-G concentrations of 15,000 ppb or <br /> more The lowest concentration previously recorded prior to December 2000 was 3380 <br /> ppb in January of 2000 These concentrations contrast sharply with the December sample <br /> result 858 ppb In the sample from this current event, the TPH-G concentration is 2,750 <br /> ppm This is still low by historical standards, but the increase does not seem to reflect <br /> efficient hydrocarbon degradation resulting from the ORC material placed in boring ORC- <br /> 1 in the spring of 2000 Moreover, the dissolved oxygen content of the water has remained <br /> rernarkably steady levels below 1 ppm We must conclude that the ORC compound, while <br /> marginally beneficial, is not a cost effective method of reducing contamination in the <br />' periphery of the plume at this site <br /> Sample collection from the deep monitoring well (MWD-11) has been terminated We <br /> recommend that this well be abandoned in accordance with California Well Standards the <br /> next time drilling work is conducted at this site <br /> I3.2 Future Work Schedule <br /> A recently submitted Corrective Action Plan has been approved by the San Joaquin County <br /> PHS-EHD Currently bids are being obtained and a budget is being prepared for <br /> submission to the California UST Cleanup Fund for pre-approval of the costs associated <br /> with the approved remedial program <br /> 2937 Veneman Ave,#B240 Geo-Phase Environmental Inc. Phone(209)569-0293 <br /> Modesto,CA 95356 Fax(209)569-0293 <br />