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amec- <br /> 4.0 <br /> CONCLUSIONS <br /> The effectiveness, implementability and cost of a bioaugmentation bio-curtain for treating <br /> dissolved phase contamination near the City of Ripon WWTP Lagoons was evaluated in <br /> Section 3.0. The effectiveness analysis concluded that: <br /> • The effectiveness of groundwater recirculation towards minimizing the risk to <br /> downgradient receptors is low because COC-affected groundwater exists beyond the <br /> alignment of the proposed recirculation system. Intrinsic remediation would be required <br /> to manage the risk of COC impacts to receptors downgradient of the barrier. <br /> Implementation challenges were identified in Section 3.0 of this document are: <br /> • Injection of treated groundwater may be difficult due to well efficiency losses. <br /> • Groundwater treated for CDCs prior to re-injection may still contain TDS and arsenic <br /> above levels established in Waste Discharge Requirements, therefore, it may not be <br /> possible to achieve regulatory approval of such as system. <br /> The total cost for the groundwater recirculation system is estimated to be approximately $59 <br /> million. This approach may not provide an additional reduction in risk towards downgradient <br /> receptors over that which could be obtained with intrinsic remediation. Further, this approach <br /> may not be implementable due to physical limitations and water quality discharge limits <br /> associated with the re-injection of treated groundwater. For these reasons, groundwater <br /> recirculation is not retained for consideration as part of the overall groundwater remedial <br /> action. <br /> 5.0 REFERENCES <br /> EPA, 2007. Options for Discharging Treated Water from Pump and Treat Systems. United <br /> States Environmental Protection Agency. <br /> AMEC Geomatrix, Inc. <br /> \\oad-fs1\doc_safe\9000s\9837.006\4000 REGULATORYTS Assessment_Apx B_012711\Attachment B.3\Attach B-3.docx 133-5 <br />