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0 • <br /> 10. Section 5.3.2.6, Page 5-3 and Figure 5.3-3: The text states that the western contaminant <br /> plume is approximately 33%captured. According to Figure 5.3-3, extraction wells <br /> EW026B and EW027B are located in the portion of the plume that is currently not <br /> captured. Neither the figure nor the text indicates that these extraction wells have an <br /> impact on the groundwater flow and are capturing any portion of the plume. Please revise <br /> the Report to provide an explanation for the lack of hydraulic control from pumping wells <br /> EW026B and EW02713. <br /> 11. Section 5.6.2, Page 5-5: The text recommends shutting down extraction wells EW003, <br /> EW004AU and EW008A because groundwater extracted from these wells contains low <br /> concentrations of contaminants and, therefore, dilutes the influent to the treatment <br /> system. However, the Report does not address the potential hydraulic effects of shutting <br /> down these wells, in particular the possibility that the cessation of pumping from these <br /> wells would reduce the area of the capture zones and reduce the percentage of <br /> contaminant plume capture. Please revise the Report to discuss the possible hydraulic <br /> effects of shutting downs wells EW003, EW004AU and EW008A, and/or steps that will <br /> be taken to monitor the possible post-shutdown effects on hydraulic capture of the <br /> contaminant plumes in the vicinity of these wells. <br /> In addition, as part of EPA's review of the 1999 Annual Monitoring Report, the EPA had <br /> noted that dieldrin had been detected in EW003 and EW004AU, but that carbon units are <br /> not installed at these wellheads to treat dieldrin. According to Appendix E of this report, <br /> the two wells again contained dieldrin at or above the ACL in every quarter, ranging from <br /> 0.050 ug/l to 0.110 ug/l (ACL is 0.05 ug/1). Since dieldrin continues to be detected above <br /> the ACL at EW003 and EW004AU, groundwater contaminated with dieldrin requires <br /> treatment. Please revise the Report to address how dieldrin in groundwater at these wells <br /> will be treated should EW003 and EW004AU be no longer connected to Treatment Plant <br /> #1. One possible solution is to install carbon units at the wellheads to treat dieldrin and to <br /> route the treated water such that it bypasses the stripper tower to join the effluent from the <br /> stripper tower before discharge to the infiltration gallery or the chimney drain. <br /> 12. Figure 5.3-1, Table 5.3-2 and Appendix H: According to Table 5.3-2, extraction well <br /> EW002AU is screened in the Above Upper Horizon and was pumping in 1999/2000. <br /> However, EW002AU is not shown in Figure 5.3-1 and the appropriate figures in <br /> Appendix H. Please revise the Report to explain why EW002AU is not shown in Figure <br /> 5.3-1 and the figures in Appendix H or revise these figures to include EW002AU. <br /> 6 <br />