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0 <br /> David Wang, P.E. , Chief <br /> Page 11 <br /> March 6, 1991 <br /> d. Water levels cannot be averaged over time. <br /> 12 . Page 7-10, Overall Operational Strategy <br /> The report states "Figures 6. 1-9 through 6 . 1-11 (see <br /> Section 6. 1. 1. 1) illustrate the treatment system not only <br /> captures the 100 ug/L plume but apparently has captured <br /> the entire plume in the South Balloon Area. " The figures <br /> do not illustrate capture of the plumes. <br /> Recommendation: The figures should be amended as <br /> discussed above. <br /> 13 . Page 7-10, Additional Extraction Well <br /> After claiming to have captured the entire plume (see <br /> above) , the report refers to chemistry data and concludes <br /> " . . .that a portion of the C-zone plume was not being <br /> captured by the existing wells. " <br /> i <br /> Recommendation: The report presents inconsistent <br /> conclusions and should be clarified. The cause may be a <br /> combination of misinterpretation of the ground water <br /> elevation contour maps and inaccuracy of the maps. <br /> CONCLUSION <br /> Interpretations made from this data is limited by its quality and <br /> usefulness. Based on the concerns expressed here and in previous <br /> reviews, the presentations and interpretations based upon the <br /> earlier data may be of lesser quality. However, the cost to <br /> benefit ratio of securing additional data may be too close or <br /> exceeded. Therefore, the benefit of securing additional data must <br /> be considered. The Department recognizes the limits of the data <br /> and risks in using it. We recommend that decisions made regarding <br /> the use of current data interpretations be evaluated during the FS <br /> and if necessary the five (5) year review. <br /> (9 - C� <br /> - 0161 <br /> Jim Pinasco <br /> Waste Management Engineer <br /> Site Mitigation Branch <br />