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' 15 June 1999 AGE-NC Project No 98-0450 ' Page 7 of 27 ' 412 Feasibility Excavation of impacted soil is a very effective method of remediation Theoretically, all or a major 1 portion of impacted soil can be removed from the site However, excavation of the major portion of hydrocarbon impacted soil at the site does not appear feasible, due to the total depth of hydrocarbon impacted soil if a limited soil excavation were to be performed to remove the upper twenty five feet ' of hydrocarbon impacted soil special excavating and shoring or bracing techniques would be required along the northeast boundary of the site for removal of the upper impacted soil Sheet and/or pile shoring techniques would be feasible Alternative excavation techniques include benching and sloping along the southern edge of the ' impacted soils, which would reduce the volume of impacted soil that could be targeted for removal and result in a portion of impacted soil being left in-place at the site Due to the limited area of the site and the UST Iocated at the northern edge of the site, on-site ex-situ treatment methods would ' not be logistically feasible or cost effective,therefore impacted soil would be transported off-site to an appiopriate disposal facility M An excavation to remove the most of hydrocarbon-impacted soil would need to extend to the 35 feet bsg However, this depth would not allow for the removal of soil where the ground water table interfaces with the impacted soils, currently at 45 feet bsg ' Excavation of the major portion of the hydrocarbon-i npacted soil would require the removal of a significant volume of"clean"overburden soil The excavated "clean" overburden soil would have ' to be stockpiled at the site for subsequent use as excavation backfill or would need to be transported for offsite disposal Prior to backfilling, the "clean' soil stockpile material would require ' confirmatory laboratoiy analysis Disadvantages of site excavation include limited site space, excessive costs if shoring of the excavation is required, limited ainount of impacted soil remaining in-place if excavation sloping and benching is required, dust and air pollution control concerns, disruption of site use, continued liability for landfill disposal and disruption of adjacent property businesses Future liability for off- site disposal can be reduced through indemnification offered by some soil recycling facilities ' 413 Duration _ _ s I— The duration of soil removal operations is short in comparison to other remedial alternatives ' Excavation activities, including stockpiling soil, soil sampling and laboratory analysis, loading, transportation, disposal, excavation backfilling, and compaction is estimated to take approximately two to three weeks Arh-anced GeoEmlroninental,Inc 1