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Nestle USA, Inc.—Ripon, CA January 28, 2011 <br /> 2011 Revised Feasibility Study <br /> The problems posed for disposal of treated groundwater disposal is a serious <br /> obstacle to success, as with Alternative 2. The significant volume of groundwater <br /> that would need to be disposed combined with naturally occurring TDS <br /> concentrations beyond current permit levels limits viable disposal options. No <br /> long-term solutions are known for this issue" <br /> This alternative reduces toxicity by in-situ chemical treatment, which reduces <br /> COCs to inert compounds in place, and by removing and treating groundwater. <br /> The pump-and-treat process transfers CDCs to a different medium, such as <br /> granular activated carbon. The spent carbon then must be disposed of as a <br /> waste. Toxicity is permanently removed in place for the higher concentration <br /> areas. This alternative will reduce toxicity of groundwater to below RAOs. <br /> Implementability of this alternative is moderate, with problems occurring primarily <br /> with treated water disposal and well efficiency degradation. Also, finding suitable <br /> locations for extraction wells and treatments systems will be problematic. <br /> Implementability of the extensive in-situ chemical treatment in the Intermediate <br /> Aquifer would be difficult due to dispersal of utilities and injection points over a <br /> larger area. Attempting to inject chemical treatment to the source area below <br /> and adjacent to the NPC and WWTP lagoons is problematic due to the high <br /> vertical and horizontal groundwater gradients. Pilot studies will likely be required <br /> as part of this alternative in order to assess the technical feasibility of injection <br /> technologies such as chemical oxidation or in-situ bioremediation. <br /> 10.1.4 Alternative 4 <br /> Alternative 4 involves the use of existing pump and treat activities in the Upper <br /> Aquifer at the Site. This includes ongoing groundwater extraction and treatment <br /> from the upper A-zone (at wells EU-3 and EU-4) and the lower A-zone (at well <br /> EI-1), followed by monitoring COC concentrations beneath the Site within the <br /> next 3 years, and then in-situ chemical treatment at any remaining high <br /> concentration areas identified from monitoring (see Figure 10). <br /> 10.1.4.1 Description <br /> Alternative 4 continues the current groundwater extraction in the Upper Aquifer <br /> source area at the Site. Pump-and-treat is employed for up to three years, to be <br /> followed by a post-remediation assessment of the area of historical high <br /> concentrations in the Upper Aquifer at the Site"". Current mass removal and <br /> concentration trends at Upper Aquifer monitoring wells have shown effective <br /> reductions in concentrations, and current proposed changes in the operation of <br /> this remediation system are intended to improve mass removal efficiency and <br /> assess the likelihood of VOC mass remaining in this area of the subsurface. Two <br /> additional Upper Aquifer monitoring wells were installed in December 2009 in this <br /> area to assist in these future assessments of groundwater impacts beneath the <br /> Sitev. As mass removal rates reach minimal and asymptotic levels, termination <br /> of groundwater extraction from Upper Aquifer wells will be proposed and <br /> implemented, following regulatory approval. <br /> 43 <br />