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amec— <br /> TECHNICAL <br /> ATTACHMENT B.3 <br /> Groundwater Recirculation Feasibility Assessment <br /> Nestle USA, Inc.- Ripon, CA <br /> 1.0 INTRODUCTION <br /> On behalf of Nestle USA Inc., AMEC has assessed the feasibility of groundwater recirculation <br /> (extraction and above ground treatment with re-injection) for treating groundwater affected <br /> primarily by TCE and its daughter products (DCE and vinyl chloride), hereafter, referred to as <br /> constituents of concern (COCs) that may have historically been discharged at the City of <br /> Ripon Wastewater Treatment Plant (WWTP). The feasibility of groundwater recirculation is <br /> evaluated in this document in terms of its potential effectiveness, implementability, and cost. <br /> Section 2.0 provides an overview of the technology; the potential effectiveness, <br /> implementability and cost of groundwater recirculation is evaluated in Section 3.0. Section 4.0 <br /> summarizes conclusions from the feasibility analysis and Section 5.0 includes a list of <br /> references used for this assessment. <br /> 2.0 TECHNOLOGY DESCRIPTION <br /> Groundwater recirculation is basically "pump-and-treat" where the treated groundwater is <br /> discharged back to the aquifer via a series of injection wells. There are several potential <br /> advantages to subsurface discharge of treated groundwater (as opposed to surface <br /> discharge), including (EPA, 2007): <br /> • Return of groundwater to the subsurface can be used to augment hydraulic <br /> containment or flush a contaminant source. <br /> • Return of treated water to the subsurface may conserve groundwater as a natural <br /> resource which is particularly beneficial in areas such as Ripon, where groundwater <br /> serves as a sole source for drinking water. <br /> Potential disadvantages of subsurface reinjection were also described in EPA (2007), <br /> including: <br /> • Re-injection may compromise plume capture if not carefully modeled and controlled. <br /> • Injection wells typically require more extensive maintenance compared to extraction <br /> wells. This would be a problem near the WWTP as clogging could be a substantial <br /> burden since injection wells would likely clog at a higher rate. <br /> • There is a potential to discharge contaminants that are not CDCs but are present in <br /> groundwater and are not readily treated by the employed treatment technologies. <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 133-1 <br />