ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

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Nestle USA, Inc.—Ripon, CA January 28, 2011 2011 Revised Feasibility Study 9.3.2 In-situ Chemical/Biological Treatment A wide variety of treatment processes are available for in-situ chemical/biological treatment. In-situ chemical/biological treatment involves injecting reagents that enhance degradation of COCs either through chemical or biological processes. The reagents are typically injected into high COC concentration areas to transform the COC mass into benign end products. The degradation processes can be either by oxidative or reductive mechanisms, and may or may not involve native or injected microbes. These processes may also occur naturally; however, reagent injection can be designed to enhance these natural processes. 9.3.2.1 Reductive Dehalogenation The addition of organic substrates and engineered microbial cultures to saturated soils for promoting the destruction of chlorinated compounds such as TCE and cis-1,2-DCE, has proven to be an effective in-situ remedial technology at many field sites, where the native or injected microbial populations have utilized the injected substrates to reduce TCE and cis-1,2-DCE to environmentally benign compounds (ethene and chloride) by a process called reductive dehalogenation. The treatment process for reductive dehalogenation is as follows: During microbiologically-mediated reductive dechlorination, chlorine atoms are removed sequentially to yield less chlorinated VOCs in a step-wise reduction requiring the addition of 2 electrons from the electron donor (carbohydrate) for each dechlorination step (2 electrons for each chlorine atom removed). PCE + 2e- + H+—> TCE + CI- TCE + 2e- + H+—> cis-1,2-DCE + CI- cis-1,2-DCE + 2e- +H+—> VC + CI- VC + 2e- + H+—> ethene +CI- Electrons are supplied by the in-situ fermentation of organic compounds such as carbohydrate by naturally occurring subsurface microorganisms. The PCE —> TCE —> cis-1,2-DCE dechlorination steps occur readily in many anaerobic environments, but further reduction to ethene often requires special site-specific geochemical and microbiological conditions (hence the need for a pilot test). The relative success of reductive dechlorination can be assessed by the abundance of non-chlorinated reduction products (ethene and ethane). Other microbiological reactions occur that consume carbohydrate by reducing naturally occurring groundwater constituents such as sulfate and ferric iron. This approach has several general advantages, including: • Cost effectiveness: inexpensive food grade substances can be added to create subsurface treatment zones • High water solubility and geochemical stability: organic substrates such as carbohydrates have high aqueous solubilities and can persist for longer 32