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The policy gives more specific guidance for each of these criterion. Consideration was <br /> given to this draft policy in the evaluation of remedial alternatives, as it states that these <br /> criteria may also be applicable to AST cases. <br /> 5.3 REMEDIAL ALTERNATIVES DISCUSSION AND APPROACH <br /> The proposed remediation objectives in this CAP are based on a combination of the <br /> above criteria. The CAP objectives are to implement the most cost-effective and <br /> sustainable remedial approach to protect human health, groundwater quality, and other <br /> sensitive receptors. Given the site conditions, the site-specific objectives are to remove <br /> gasoline constituents from the identified source areas as necessary such that WQOs will <br /> be met in a reasonable timeframe relative to the risk to receptors. Remediation <br /> alternatives reviewed in this CAP address this objective. <br /> As previously discussed, GWE and SVE have been implemented at this site with <br /> marginal success at best. Currently, GWE continues from MW-1. The remedial <br /> technologies selected for evaluation include DPE, AS with SVE, excavation, and . <br /> monitored natural attenuation (MNA). Each of these technologies was discussed and <br /> evaluated on the basis of technical feasibility, cost-effectiveness, and environmental <br /> sustainability. <br /> 5.3.1 DPE <br /> 5.3.1.1 DESCRIPTION <br /> DPE is the process of applying high vacuum through an airtight well seal to <br /> simultaneously extract soil vapors from the vadose zone and groundwater from the <br /> saturated zone. Extended dewatering of the saturated zone combined with vapor <br /> extraction can more effectively remediate residual petroleum hydrocarbons in the source <br /> area. In addition, the vacuum applied with DPE can increase the groundwater yield <br /> from wells completed in low permeability formations. Furthermore, groundwater <br /> extraction may provide hydraulic control of the hydrocarbon plume and reduce <br /> contaminant migration. <br /> A positive displacement blower or liquid-ring pump may be used to create the high <br /> vacuum needed to extract groundwater and soil vapors simultaneously. Alternatively,a <br /> submersible groundwater pump can be used to extract groundwater, while a blower or <br /> liquid-ring pump is used solely to extract soil vapors. The extraction device is <br /> 241729(33) 12 CONESTOGA-ROVERS&ASSOCIATES <br />