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• Reduction of Toxicity, Mobility, and Volume. This criterion establishes preference for an alternative that will produce permanent and significant mass reductions The evaluation ' focuses on the amount of chemicals to be destroyed or treated, the type and quantity of residual chemicals that will remain after treatment, and the effectiveness of the remedial alternatives ' • Technical Feasibility. The evaluation focuses on the possibility of implementation given site constraints, reliability of the technology, and the ability to monitor the performance of an ' alternative Each alternative requires evaluation against site-specific hydrogeologic conditions • Cost. This criterion is used to assess capital and operation and maintenance (O&M) costs on a conceptual level only Capital costs include direct costs, such as equipment purchase and site construction/development, and indirect costs including fees for engineering design and permitting, and startup expenses O&M costs include ongoing labor, materials, repairs, administrative fees, and reporting costs during the operating and monitoring period 4.3 IDENTIFICATION AND SCREENING OF POTENTIALLY APPLICABLE TECHNOLOGIES Potentially applicable technologies for site remediation are identified below lie • Excavation • Enhanced bioremediation • Stearn stripping ' • Air spargmg and soil vapor extraction • Groundwater extraction with In-well air stripping • Ozone sparging • Groundwater pump-and-treat • Monitored natural attenuation • High vacuum dual-phase extraction • In-situ oxidation with Fenton's reagent Site conditions are such that some hydrocarbon mass would be left in place after implementation of each of these remedial alternatives, until the processes of natural attenuation are complete The following discussion of the characteristics, advantages, and disadvantages of these remedial technologies is based on a review of remediation case studies for the technologies, professional judgement, and previous remedial actions conducted at the site • Excavation. This alternative may not be cost effective given the depth of hydrocarbon impacted soils Assuming excavation is performed to a depth of 40 feet bgs onsite over an approximately 80 by 60 foot area, significant dewatering would be required to excavate the lower 20 feet of saturated soil Disposal of large water volumes over the duration of the excavation may not be feasible Dewatering operations would increase the likelihood of further promoting the transport of hydrocarbons and MTBE from the neighboring offsite sources Excavation and dewatering efforts would disrupt equilibrium conditions in the GSProjeM%73942WAS=kWP1WP03031WPLa doc 14