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1 Consent Decree Exhibit C 7.0 Future Conditions: Cleanup Action Alternatives and Justification The following sections summarize the alternative cleanup actions for future conditions that were considered in the BFS, and describe the justification under MTCA for selecting the proposed cleanup actions described in Chapter 6.0. Proposed cleanup actions were selected from a list of alternatives and evaluated according to MTCA [WAC 173-340-360(2) and (3)]. Refer to Chapter 5.0 for a detailed description of the criteria. As stated previously, all evaluated alternatives for all pathways meet the threshold criteria of WAC 173-340-360(2). Justification for cleanup action selection for each environmental exposure pathway is organized by the three criteria from WAC 173-340-360(3) and presented in the following sections. 7.1 CLEANUP ACTION ALTERNATIVES FOR GAS In addition to the proposed cleanup action for gas, which includes institutional controls, compliance monitoring and phased active landfill gas controls, the following alternatives were evaluated: • Institutional controls, compliance monitoring, contingent active venting for buildings, and passive venting for pavement and open space • Institutional controls, compliance monitoring, contingent active venting for buildings, pavement and open space • Institutional controls, compliance monitoring, and area -wide landfill gas collection system ' 7.2 JUSTIFICATION OF PROPOSED CLEANUP ACTION FOR GAS 7.2.1 Permanent Solutions to the Maximum Extent Practicable All alternatives provide overall protectiveness to human health and the environment. All are effective in reducing the risk of fire and explosion from the accumulation of methane. The proposed cleanup action and the alternative with an area -wide landfill gas collection system provide further protection from the accumulation of toxic pollutants in the interior of buildings by maintaining a continuous vacuum beneath the buildings. The alternatives are effective in the long term. No development would occur on -site without first implementing the technology options from the selected alternative. The technology options of all alternatives except for the area -wide landfill gas collection system alternative would be designed and constructed as an integral part of each component of development. This coordination of design and construction of the technology options for building landfill gas control with the design and construction of the building itself generally provides higher quality and more reliable system performance. The area -wide landfill gas collection system would be more FINAL - March 2001 7-1 Everett Landfill Tire Fire Site Cleanup Action Plan L�