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Peter MacNicholl <br /> February 23, 2005 <br /> Page 3 of 4 <br /> Recommendation <br /> For all future Annual Progress Report's, the GSU recommends following the <br /> forthcoming USEPA guidance on capture zone analyses for pump-and-treat <br /> systems. <br /> SPECIFIC COMMENTS AND RECOMMENDATIONS <br /> 1) Figure 5.3-1A (Extraction Well Capture Zones for the Upper Hydrologic Zone Third <br /> Quarter 2004): Based on a review of this figure, the GSU has the following comments <br /> regarding adequacy of capture of the contaminant plumes. It appears that the dieldrin <br /> plume located near monitoring well LM174AU is not being adequately captured. The <br /> northwest portion of the dieldrin plume located near groundwater extraction well <br /> EW040A does not appear to be captured, however this plume may be captured further <br /> downgradient by extraction well EW-021A. The GSU is not convinced that the <br /> tetrachloroethylene (PCE) and trichloroethylene (TCE) plumes located downgradient of <br /> extraction well EW045AU are being completely captured. However, capture of these <br /> plumes may be accomplished further downgradient in extraction wells EW041AU and <br /> EW021AU. In addition, there appears to be inadequate capture for the following <br /> plumes: the small TCE plume near monitoring well LM147A, the large TCE plume near <br /> extraction wells EW018A, EW019A, and EW020A, and the small TCE plume adjacent <br /> monitoring well LM157A. <br /> Recommendation <br /> The GSU recommends revising the Draft 2004 Annual Monitoring Report to <br /> include a more specific discussion of the adequacy of capture for each of the <br /> contaminant plumes mentioned above, as well as a discussion of whether, and if <br /> necessary what, changes in the existing groundwater extraction system are <br /> required to address capture of these plumes. <br /> 2) Page 5-7, Section 5.8.1 (Conclusions, Conclusions): The GSU concurs with the <br /> conclusions presented here, with the following exception. With regards to bulleted <br /> comment number 3, the GSU reiterates its recommendation presented in Specific <br /> Comment number 1 above, specifically as to whether the PCE plume in the area of <br /> extraction well EW045AU is being captured as is stated here by the USACOE. <br /> Recommendation <br /> See the GSU's recommendation presented in Specific Comment number 1, above, <br /> regarding the adequacy of capture of the PCE plume in the area of extraction well <br /> EW045AU. <br /> Tracy DDD_URS121704_DraftWellMonitoringProg2004AnnualRpt.doc <br />