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1 A r , 1 7 29 April AGE-NC Project No. 98'0446-' IPage 9 of 1'8 . in significant,,'or 2) the vertical extent of soil, impact exceeds 20 feet.or soil conditions require ' shoring, resulting inthe need for special equipment or shoring: TPHIgZiinpacted soil on the subject site extends to depths of approximately 17 feet bsg iri the vicinity ' of the former USTs and dispenser area and the site 'is unoccupied at the current time making excavation a viable alternative..AGE does not anticipate that special equipment would be required ' to excavate to the depth of ground water at the site. Potential disadvantages include air pollution control concerns,,backfilling and compaction'costs. ' 6.1.3. Estimated Costs For Excavation = _ ' At the site,-AGE anticipates that impacted'soil could be excavated with traditional earthmoving equipment(excavatorlbackhoe). Approximately 2,400 cubic yards of soil would-have to excavated, froin the former USTs and surrounding areas to mitigate the hydrocarbon adsorbed-to soil which may ' and has impacted ground water(Figure 9).Approximately 550 cubic yards of the excavated soil may not be disposed and could be,replaced into the upper portion of the excavation for isolated backfill above the water table, over a plastic bailer and clean backfill material. Soil at the UST area will be excavated'and stockpile for analysis. While`soil excavated above the highest water table depth of approximately 8 to 10 feet bsg down-gradient of the former UST area,' ' near MW-2 and MW-6,'willbe excavated in five-foot lift or layers and:stockpiled separately; this procedure will allow for the segregation of low concentration TPH-impacted soil away from the capillary fringe soil,water table soil and saturated soil.-Each soil zone will be piled for segregation -hydrocarbon-impact�and hydrocarbon mass evaluations. Soil excavated and separately analyzed for from below ten feet bsg will be piled separately for hydrocarbon'impact' and hydrocarbon mass evaluations; while any saturated soil will be stockpile within soil,berm'. Once excavated, the heavily impacted-soil or the targeted impacted soil would require transferred to an off-site disposal facility. Replacement backfillmaterialmust be-imported to-the site, with a „• ' volulnie likely greater than anticipated volume of soil to be removed for the 'Off site disposal. Compaction of the soil will require an additional volume of soil for backfilling purposes.. The cost for"excavation, treatment/disposal and backfilling would probably be between $150 and, ' $200 per cubic'yard, depending upon,-hydrocarbon concentrations. Total costs for-excavation and' ` ' treatment or disposal,plus permitting,fees, could therefore approach $250,000 to $350,000. Advanced GeoEnvironmentsl,Inc.