ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study high COC concentrations at the Site appears to be acting as a continual source of dilute CDCs downgradient of the Site. Containing or reducing COC concentrations at the Site would allow natural processes to progress toward restoring groundwater quality. The following sections discuss the general response actions, associated technologies, and, process technologies that are remedial options for mitigating the high COC concentrations area and dilute COCs in groundwater. 5.1 Soil TCE and daughter products (cis-1,2-DCE and VC) are the COCs remaining in soil. Past SVE remediation has removed substantial COC mass from the vadose zone. However, CDCs in groundwater can volatilize and migrate into soil gas, posing a potential exposure route via indoor air intrusion. To address this issue, vadose zone remediation by SVE was employed in the Study Area. Direct exposure to remaining soil sources of CDCs is not likely because Nestle has already remediated all shallow source areas of COCs that were identified. 5.2 Air All the COCs listed in Section 5 can potentially volatilize from shallow soil or groundwater to indoor air. The California Environmental Protection Agency (Cal- EPA) established California Human Health Screening Levels (CHHSLs) for 54 chemicals in soil or soil gas as thresholds of acceptable risk to human health.X" CHHSLs for indoor air and soil gas address the following COCs listed in the CAO: • 1,2-dichloroethane (DCA), • Cis-1,2-DCE, • Trans-1,2-dichloroethene (trans-1,2-DCE), • PCE, • 1,1,1-trichloroethane (TCA), • TCE, and • VC. Based on these CHHSLs, Nestle's soil gas investigations have shown no harmful impacts to indoor air and minimal impacts in shallow soil vapors' The final remediation must adequately protect indoor air. However, current conditions already are protective of indoor air quality and this exposure pathway will not drive remediation requirements. 11