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March 18, 1993 Page 7 Remedial Action The general response actions necessary to achieve the soil- and groundwater-based remedial objectives are: (1) delineate the vertical and lateral extent of petroleum hydrocarbon impact, (2) monitor dissolved-phase plume movement, and (3) reduce the mass of petroleum hydrocarbons in the capillary fringe and vadose zone, satu- rated soils, and groundwater. Current remedial activity constitutes response actions 1 and 2; therefore, only response action 3 is developed here. Initially, the focus will be on petroleum hydrocarbon mass removal. Several reme- diation technologies were screened for this purpose and applicable technologies were used to construct remedial alternatives. Because the site is the location of an operating bulk terminal, only in-situ technologies were considered. Technologies were eliminated from further consideration on the basis of technical imple- mentability. Three technologies: soil vapor extraction, liquid-phase extraction, and bio-stimulation were found suitable and were used in formulating alternatives. Alternatives were designed to mitigate nuisance conditions, reduce risk of fire or explosion, and protect beneficial uses of water. Alternatives are outlined below. o Alternative 1: Initially,use soil vapor extraction to remove petroleum hydrocarbon mass. Once petroleum hydrocarbon mass has been significantly diminished, use air sparging in conjunction �., with soil vapor extraction to further reduce hydrocarbon mass in the capillary fringe and groundwater through biostimulation. Complete impact delineation; identify and monitor possible expo- sure pathways (continue groundwater monitoring). o Alternative 2: Use liquid-phase extraction to remove petroleum hydrocarbon mass and stabilize the plume area. Complete impact delineation; identify and monitor possible exposure pathways (continue groundwater monitoring). Technical,institutional, environmental protection, and economic criteria were used to evaluate the alternatives. Overlapping components of each alternative were not considered; therefore, comparing mass removal technologies was central to evaluation process. A soil vapor extraction feasibility test was completed prior to preparation of this document and data from the test was considered in the eval- uation process. For the purpose of technology comparison, the radius of influence for each extrac- tion application was assumed to be equal. The results of the evaluation process are briefly outlined below. �` 3100104/TRAP