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CLEAWWT-ER ' G R O U P Environmental Serwees Remedial Media Remedial Option Affected ITechnologyEvaluated Option 5 Soil Excavation w/Soil Aeration Groundwater Enhanced Bioremediation(iSOC) ' Option 6 Soil Enhanced Bioremediation(iSOC) Groundwater Enhanced Bioremediation(iSOC) ' The technical ment and approximate cost of each remedial technology is discussed below in light of site conditions The costs have not been rigorously determined, but are approximations based on a brief assessment of the equipment and operation involved in each option The costs assume operation for one year, however, operation of an engineered system may extend beyond one year and result in higher operation and maintenance costs Actual costs could be approximately 25% higher or lower Additionally, the costs shown do not account for any additional investigative or groundwater monitoring costs ' 6.2 Remedial Alternatives for Soil I6 2 1 Soil Excavation Excavation of contaminated soil is often the most effective remedial option in situations where the contamination is primarily restricted to areas at or above the water table, accessible from the surface and less than 30 feet bgs Excavating to depths greater than 30 feet bgs, or in saturated soils becomes increasingly cost prohibitive due to shoring necessities, equipment access to the excavation (ramping), and hauling and disposal or treatment costs of large volumes of potentially highly contaminated soil It should be noted that due to the fluctuation in groundwater table elevations at the site, excavation would be best performed during the summer or fall months ' when the water table is relatively low (i e approximately 12 feet bgs) Excavation would be impractical if executed during the periods of high water table (i a spring, approximately 7 feet bgs) At this site, excavation of the contaminated soil beneath the former UST pit would be a costly ' and not easily accomplished alternative because the sorbed-phase contamination resides in the saturated zone Excavation in this area would require extensive dewatering of the excavated area, necessitating water disposal or pretreatment prior to discharge, and probably shoring of the sidewalls Excavation would likely have a direct impact on future groundwater contamination, as I ZB171C CAP 12 November 20,2002