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Peter MacNicholl <br /> January 28, 2005 <br /> Page 5 of 5 <br /> 6) Figure 5.3-2a (B-Zone 3Q04): Hydraulic capture of the PCE plume in the B-Zone <br /> north/northwest of EWNB6 does not appear to be adequate. <br /> Recommendation <br /> The GSU recommends further monitoring the effectiveness of hydraulic capture <br /> in the B-Zone north-northwest of extraction well EWNB6. Additional extraction <br /> wells may be necessary in this area if hydraulic capture is shown not to be <br /> complete. <br /> 7) Figure 5.3-2b (B-Zone 3Q03): The GSU has a question as to the effectiveness of <br /> hydraulic capture of the PCE plume in the North Balloon, as well as the hydraulic <br /> capture of a small TCE plume in the North Balloon near monitoring well MW521B. <br /> Recommendation <br /> The GSU recommends further monitoring the effectiveness of hydraulic capture <br /> in the north-northwest portion of the B-Zone in the North Balloon. Additional <br /> extraction wells may be necessary in this area if hydraulic capture is shown not <br /> to be complete. <br /> 8) Section 5.3.2.4 (Capture Zones): The USACOE refers to Figures 5.3-1 a and 5.3-1 b <br /> through 5.3-3a and 5.3-3b (Estimated Extraction Well Capture) which present the <br /> estimated capture zones for the A, B, and C Zones for 3Q03 and 3Q04. The USACOE <br /> reports that the capture zones in 3Q04 appear smaller and more focused when <br /> compared to the 3Q03 capture zones due to a different drawing method being used. In <br /> addition, it is reported that the system was optimized during 2004 which resulted in <br /> more effective capture. These two statements appear to be contradictory, but taken <br /> together seem to imply that the groundwater extraction system was more effective <br /> during 3Q04 than actually reported in the Draft 2004 Annual Progress Report. <br /> Recommendation <br /> The GSU recommends this section of the Draft 2004 Annual Progress Report be <br /> revised to clarify whether the effectiveness of the capture zones has increased <br /> between 3Q03 and 3Q04, and to what extent the use of different drawing methods <br /> has upon this determination. <br /> If you have any questions, please contact me at 916/255-3695 or at <br /> bduke@dtsc.ca.gov. <br /> Sharpe_U RS 112204_FFAAnnual Report.doc <br />