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� Asa c WE rw acs's" ,w - ' 1 _ �-� ` y ti X Criterion 5.: All of the approaches are comparable in terms of short ierin elfec4iveness, although excavation would result in some .- increased exposure or release of hydrocarbons due to physically exposing soils to the atmasphere. In terms of time to complete remediation the excavation approaches will probably require 2-4 weeks to complete wh.ie vapor extraction or soil bioremediation could require years. An engineered cap could be completed in 1-3 months. Criterion 6. : Soil excavation and on-site treatment would be the most effective long term remediation technique in so far as soils could be excavated without endangering structures or further contaminating shallow groundwater. In attempting to remove soils ! within the capillary zone the potential for introducing hydrocarbons into the shallow groundwater is high since the groundwater and capillary zone era in contact. Alternatives 2 and 4, soil excavation with removal to a licensed landfill and site capping would also be effective. Soil bioremediation, which entails the enhancement of this natural processes of degradation of contaminants would be only moderately effective because soils at the site are of very low permeability. The inability to significantly enhance oxygen and nutrient levels in the soils will severely limit this approach. Similar permeability consideration limit the applicability of soil vapor extraction. Vapor extraction is ideally suited for soils with relatively high permeabilities (+1 darty) and which are above the saturated zone. The soils at this site are clayey silt to silty clay with permeabilities of 14'6 to lfl'IL darcys, and contaminated soils are located within and above than capillary fringe, which contains water filled pore spaces held by surface tension. Criterion 7. : The excavation alternatives have certain implementability difficulties associated with the structures on site (Figure 3, Dames & Moore, Nov. 1989). It is unlikely that all of the contaminated material can be removed without risking damage to structures on site. Criterion S.: it is believed that all five approaches can achieve regulatory and community acceptance. The degree of disruption (visual, traffic, odors, noise) in the immediate site area is significantly greater for the excavation alternatives, however, this would be expected to last only 2-4 weeks at most. The least disruptive alternative would be soil capping. However it is not anticipated that this temporary disruption would result in loss of community acceptance. Criterion 5. : The three alternatives are all comparable in terms of impacts upon water conservation. H9LR402.wp 4 , ,,1