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5.0 GROUNDWATER EXTRACTION AND CAPTURE ZONE <br /> ANALYSES <br /> Prior reports (including LSCE, 2003 and 2004)have described the coordination of <br /> groundwater remediation efforts with onsite uses of extracted salt-affected groundwater for <br /> facility operations. Groundwater quality impacts have occurred primarily in the shallow <br /> zone in the vicinity of the ponds. Figure 3-1 illustrates the estimated extent of the shallow <br /> zone impact through isocontours of chloride concentrations. The deep groundwater zone is <br /> minimally affected with chloride concentrations ranging from 90 to 96 mg/L in the <br /> immediate vicinity of the ponds as exhibited by MW313 (Figure 3-2). <br /> The Closure Plan calls for an enhanced landfill cover, including improvements to the existing <br /> surface water drainage system (Golder, 2005). In accordance with WDR No. R5-2004-0157, <br /> ` closure of both ponds will occur during Summer to Fall 2005; final closure documentation <br /> will be submitted to the RWQCB by October 31, 2005. Pond closure actions will mitigate <br /> migration of the salt residual in the unsaturated zone to groundwater. Therefore, this <br /> corrective action program focuses on remediation of salt-impacted groundwater in the <br /> shallow zone. <br /> v <br /> 5.1 Groundwater Cleanup Objective <br /> Corrective actions are undertaken to achieve the following goals (Section 20430 (b) of Title <br /> 27): "to remediate releases from the Unit; to ensure that the discharger achieves compliance <br /> with the Water Standard adopted under §20390 for that Unit."The "Unit' at this site entails <br /> the two evaporation ponds. <br /> The(WQPS) for the constituents of concern (chloride and TDS) are 89 mg/L and 600 mg/L, <br /> respectively, for the shallow zone. As discussed above, chloride has served as a useful <br /> • indicator for evaluating the impact of plant operations on groundwater quality. Thus, the <br /> groundwater corrective action program is based on capturing salt-affected groundwater as <br /> delineated by elevated chloride concentrations. Specifically, the cleanup objective is to <br /> restore chloride concentrations in shallow groundwater to a level below the WQPS of 89 <br /> mg/L. Figure 5-1 shows the perimeter of the salt-affected area with an outer chloride <br /> isocontour of the 100 mg/L contour, or essentially at the WQPS. <br /> © LUHDORFF & SCALMANINI <br /> CONSULTING ENGINEERS 7 <br />