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rAW 15 4 ,, ',y., �,' a 4�_ � °5� •,, - .I.�'�¢ s ...sex t.�-_ - ��,'y"• risy s�"*�'�e` Criterion 5. : All of the approaches are comparable in terms of short term effectiveness, although excavation would result in some increased exposure or release of hydrocarbons due to physically exposing soils to the atmosphere. In terms of time to cnmplete remediation the excavation approaches will probably require 2-4 weeks to complete while vapor extraction or soil bioremediation could require years. An engineered cap could be comple,ad 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 withira the capillary zone the potential for introducing hydrocarbons into the shallow groundwater is high since the groundwater and capillary zone are in contact. Alternatives 2 and 4, soil excavation with removal to a licensed landfill and site capping would also be effective. Soil entails the enhancement of the natural processes eof deg adationiof contaminants would be only moderately effective because soils at the site are of vary low permeability. T} significantly enhance oxygen and nutrient levelsi� theasoils bilitwilto l. severely limit this approach. Similary sideration limit the applicability of so?l vapor extr ction?iVapornextraction is ideally suited for soils with relatively high permeabilities (fl darcy) and which are above the saturated zone. The soils rpt this site are clayey silt to silty e12y with permeabilities of 10'6 to 10' darcys, and contaminated soils are located within and above the capillary fringe, which contains water filled pare spaces held by surface tension. Criterion 7. : The excavation alternatives have certain imple:mentability difficulties associated with the structures on site (Figure 3, Dames & Moore, Nov, 1989). 11: is unliKel.y that ;.III of the contaminated material can be removed without risking damage to structures on site. Criterion 8. : It is believed that all five approaches ca Tof he achieve regulatory and community acceptance. dogreadisruption (visual, traffic, odors, noise) in the immediate aito a�reatiis significantly greater for the excavation alternatives, however, this would be axpected to last only 2-4 weeks tit most. ':he ever, disruptive alternative would be soil capping. Etowever it is not anticipated that this temporary disruption would, result in lass of community acceptance. Criterion 9, : The three alternatives are all Comparable irl terms of impacts upon water conservation.