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15 February 2000 AGE-NC Protect No 98-0448 Page 19 of 33 8 2 1 Excavation All of the mentioned methods of ex-situ treatment require excavation of the impacted soil, which is generally an effective method for soil remediation Once excavated,the impacted soil is generally stockpiled on-site for treatment or transported off-site for disposal If soil is treated on-site and the hydrocarbon concentrations can be reduced to concentrations set by the lead agency or to non- detectable concentrations, the soil may be used to backfill the excavation If the hydrocarbon- impacted soil is disposed of off-site, material must be-imported to backfill the excavation 8 2 2 Feasibility Of Excavation IThe site is currently utilized as a lumber manufacturing business and is occupied by several warehouse building structures Theoretically, the majority of the impacted soil could be excavated from the site However, excavation of hydrocarbon-impacted soil at the site, followed by ex-situ Itreatment and/or disposal would greatly disrupt the day to day business operation at the site, furthermore, excavation of impacted-soil could necessitate demolition of at least a portion of a warehouse building structure Excavation of impacted soil to depths greater than 25 feet bsg would require specialized excavating equipment and excavating techniques Excavation of hydrocarbon- impacted soil to depths greater than 19 feet bsg (estimated depth to ground water) would require a ground water pumping system to facilitate the dewatering of the excavation Site excavation activities would also require the destruction of on-site wells, which may or may not have to be replaced at another time Other potential disadvantages of site excavation include limited site space, excessive costs for deeper excavation, excessive backfilling costs and continued liability for landfill disposal Future liability for off-site disposal can be reduced through indemnification offered by some soil recycling facilities Prior to any excavation of hydrocarbon-impacted soil at the site, it is likely that a substantial amount of"clean" soil would have to be removed for logistical reasons and either hauled off-site for disposal or hauled off-site for storage due to the limited space at the site 8 2 3 Estimated Costs For Excavation _ Once excavated, impacted soil could be treated on-site or transferred to an off-site disposal or recycling facility Replacement backfill material must be imported if off-site disposal is chosen I Based upon limited site space, it is unlikely that onsite treatment would be acceptable The cost for excavation, treatment/disposal and backfilling would likely be between $80 00 and $120 00 per cubic yard, depending upon actual hydrocarbon concentrations encountered during excavation I Additional soil remediation methods would have to be employed to remove hydrocarbons at greater depths When the data collected at the site is plotted in both plan view and cross sectional views,the apparent volume of petroleum-impacted soil beneath the site yields approximately 1,340 cubic yards Advanced GeoEnvironmental,inc- 1