ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

Home Browse Search

Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study 9 Identification, Screening and Evaluation of Technology Types All technologies considered for application in addressing RAOs for the Study Area are assessed in the sections below. Table 1 provides a summary of this process and the results of the assessment process detailed below. Attachment B.1 through Attachment BA provide additional details and assessment of specific treatment technologies considered for the area to the southwest of the Site and in the vicinity of the City of Ripon WWTP. 9.1 No Action No technologies apply to this general response action. "No Action" provides a comparison when assessing other general response actions relative to differences in the time required to reach RAOs across the Study Area. 9.2 Containment 9.2.1 Pump, Treat and Discharge The pump, treat, and discharge technology actively introduces a hydraulic barrier by creating a containment/capture area around the area of COC impact. Groundwater can only flow into this containment/capture area, not away from it. This approach has the advantage of containing both horizontal and vertical migration of COCs from impacted areas. Groundwater flowing through the impacted area will remove additional COC mass after extracted water is treated. Treated effluent would be discharged to the storm sewer, sanitary sewer, or the City of Ripon's NP water line for beneficial use, necessitating compliance sampling and analysis. Groundwater in the Ripon vicinity typically contains high levels of TDS, which limits disposal options. This technology preferentially removes COCs in groundwater (dissolved phase) as opposed to any CDCs adsorbed to soil. 9.2.1.1 Effectiveness In general, pump-and-treat is more effective as a method to limit mobility of dissolved-phase CDCs than as a method to remove COCs adsorbed to soil or to reduce COC extent. Long cleanup times have been associated with sites using pump-and-treat as a stand-alone remedy, often due to the low-aqueous solubility of many organic CDCs including TCE, the presence of geologic heterogeneities (fine-grained layers), ongoing COC sources, or non-aqueous-phases". Pump- and-treat may also be effective as a source removal approach for non-sorbing, high solubility COCs, where the source has been removed completely, and the impacted aquifer is relatively homogeneous". Nestle is currently using this technology to control COC migration and remove mass from the dissolved-phase plume at the Site as part of the Interim Remedial Actions, and is planning to further evaluate the containment and mass-removal effectiveness of pump-and- treat. 24