ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

Home Browse Search

Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study The use of chemical reagents may require a more extensive network of injection wells and multiple applications. 9.3.2.1.3 Relative Cost The most significant costs are related to the initial installation and operation of the chosen process. Reducing the COC concentrations appreciably will shorten the overall life of the project and reduce long-term project costs associated with the other technologies. Application of this technology, specifically bioaugmentation, to treat groundwater at the Site and near the WWTP, is estimated to cost approximately $53,000,000 (see Appendix D and Attachment B.2). 9.3.2.1.4 Conclusion In-situ chemical/biological technology is retained for further evaluation for reducing or removing CDCs at the Site within the Upper Aquifer. 9.3.2.2 Aerobic Biodegradation and Cometabolism Although VC can be directly oxidized in the presence of aerobic bacteria and oxygen, TCE is not susceptible to direct aerobic biodegradation"". Therefore, as discussed in Attachment B.1, biosparging by oxygen or air injection would not be a feasible approach for treating groundwater impacted by TCE. Studies have shown that the aerobic bioremediation of TCE, cis-1,2-DCE and VC is possible by an aerobic co-metabolic pathway""". The aerobic co-metabolic pathway involves the addition of a carbon-containing substrate such as methane, propane, toluene, phenol, etc. and oxygen to stimulate the growth of aerobic bacteria in the subsurfacexly". Enzymes existing within the aerobic bacteria for oxidizing the substrate fortuitously catalyze the oxidation of the TCE and cis-1,2- DCE, among several other VOCs, to carbon dioxide. The aerobic process is primarily limited by the ability to deliver and disperse dissolved oxygen and the carbon substrate in the subsurface. The aerobic co-metabolic process is only applicable to low concentrations of dissolved TCE (less than 1,000 pg/L) and would not be suitable for in-situ treatment of groundwater beneath the site. As discussed in Attachment B.1, this approach would not be implementable or cost-effective for treating groundwater in the vicinity of the WWTP. 9.3.2.3 Effectiveness Aerobic cometabolism would not be effective for treating groundwater within the Upper Aquifer (B-zone and Upper A-zone) beneath the Site where TCE concentrations exceed 1,000 µg/L. This process could theoretically be effective for treating low concentrations of dilute CDCs (TCE, cis-1,2-DCE, and VC) in the lower A-zone, and Intermediate Aquifer within the Study Area, if implementable. 9.3.2.4 Implementability Much of the research to date has focused on using chemicals such as toluene, phenol, or alkanes as co-metabolic inducers. The addition of toluene and/or phenol as inducers is clearly undesirable because of the potential to introduce new chemicals to the subsurface which themselves would cause degradation of 34