ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study treatment process may vary from a simple carbon adsorber to complicated air stripper and oxidizer. The use of an air stripper and oxidizer, as is currently in use at the 519 South Stockton Avenue system, significantly increases costs, and utilizes an energy source like natural gas. It should also be noted that operation of complex treatment systems are often energy intensive and result in offsetting environmental impacts including the use of fossil fuels, electricity and associated air emissions. Also, high TDS concentrations in the Upper Aquifer (between 900 and 1500 parts per million) limit the utility of the effluent water in the NP system. High TDS also causes scale to form on well screens, significantly restricting groundwater flow and reducing yield. Though this technology is effective in limiting migration, it will require a long operation time unless combined with other more aggressive in-situ treatment technologies. Therefore, long-term maintenance of equipment, infrastructure, and wells, needs to be considered for pump-and-treat. Further, the relatively small amount of COC recovery achieved by this process should be weighed against the burden that pump-and-treat places on groundwater resources. 9.2.1.3 Relative Cost The cost to operate this technology in the long-term exceeds that of many other technologies, particularly due to O&M requirements. Capital costs may include construction or upgrade of treatment systems, and installation of extraction wells, pumps, and conveyance piping and utility conduits. On-going O&M costs may include electricity and natural gas to operate systems, GAC management and disposal, water disposal, compliance sampling and reporting, and replacement parts. O&M costs may increase with time as equipment ages, requiring replacement, and as energy becomes more expensive. Based on current system operation at the Site, the O&M costs for 30 years of operation is on the order of $6,800,000 for a system extracting and treating approximately 32 million gallons per year (approximately 60 gpm; see Attachment D). 9.2.1.4 Conclusion Pump-and-treat is suitable as an interim remedy, but must be carefully evaluated for long-term use. Downsides to long-term implementation of pump-and-treat technology include limitations on the disposal of treated effluent, high TDS concentrations, energy use, air emissions, and waste filter generation disposal, and diminishing effectiveness. These factors must be taken into account and weighed against the benefits that pump-and-treat can achieve. Pump-and-treat is a viable option for meeting the RAOs across the Study Area; however, the length of time required to meet all RAOs may be more than 30 26