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• process (aerobic or anaerobic). When only specific VOCs in groundwater require mitigation, bio-engineered microbes (or enzymes) can be considered for treatment. Although laboratory studies performed by Enzien et al. (1994) have shown that PCE can be anaerobically degraded under bulk aerobic conditions, to date the approach has not been demonstrated in field studies and it is assumed herein that anaerobic conditions must be maintained to degrade these constituents. In contrast, degradation of vinyl chloride under aerobic conditions is well documented. Bio-inoculation technology requires pilot testing and careful engineering design and controls to ensure that the remediation process is effective. Commonly, the engineered microbes need periodic replenishment and nutrient addition to maintain this effectiveness. In addition, anaerobic conditions must be maintained to enable biodegradation of PCE and, as a result,the need for injection of nitrogen or methane into the aquifer is anticipated. Limiting factors for implementation of this technology at the CHSL are the relatively low VOC concentrations in groundwater and the aerobic condition of the aquifer. Additional groundwater monitoring wells and frequent sampling may be required to confirm the effectiveness of this technology. Case studies have not shown that chlorinated aliphatic . concentrations can reduce individual VOC concentrations below the levels that are currently measured in groundwater samples at the site. As a result, this technique is considered to be a technically ineffective and,therefore, not viable alternative for the CHSL. Metal Enhanced Reductive Dehalogenation (MERD): Not Viable —This process uses a metal reactant such as iron shavings to induce an ion exchange process that facilitates the degradation of dissolved halogenated organic compounds (chlorinated VOCs) in groundwater. The MERD technology is generally accomplished using a "funnel-gate or treatment-wall' of iron shavings (or other metal compounds) installed across the flow path of impacted groundwater. The treatment wall would be constructed by excavating through the aquifer and keying the wall into the subjacent aquitard. The majority of the treatment wall would a constructed of low permeability materials, such as a cement-bentonite slurry, that would be configured to funnel groundwater toward that portion of the treatment wall backfilled with the reactive MERD media. As groundwater flows through the treatment wall, the halogenated atoms in the contaminated groundwater react to yield dehalogenated and non-toxic end-products such as ethene, methane and chloride. Typical "funnel and gate" treatment walls are limited to depths of about 60 feet. The depth • to groundwater at the point of compliance varies from about 15 feet near well SB-1 to more than 80 feet in the vicinity of well MW-8. While a "funnel and gate"treatment wall might be Engineering Feasibility Study Geo-Logic Page ■ 16 Corral Hollow Sanitary Landfill ASSOCIATE S January 25,2013