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10 June 1999 <br /> AGE-NC Protect No 97-0290 <br /> Page 13 of 26 <br /> I stockpiled on-site for treatment or transported off-site for disposal If soil is treated on-site and the <br /> hydrocarbon concentrations can be reduced to concentrations set by the lead agency or to non- <br /> detectable concentrations, the soil may be used to backfill the excavation If the hydrocarbon- <br /> impacted soil is disposed of off-site, material must be imported to backfill the excavation <br />' 7 2 2 Feasibility Of Excavation <br /> Excavation of hydrocarbon-impacted soil at the site, followed by ex-situ treatment and/or disposal <br />' has a low feasibility at the site Special excavating equipment and excavating techniques would be <br /> required to reach impacted soil at greater depth Excavation of hydrocarbon-impacted soil at depths <br /> greater than 43 feet bsg (estimated depth to ground water) would require a ground water pumping <br />' system to facilitate the dewatering of the excavation Site excavation activities would also require <br /> the destruction of on-site wells, which may or may not have to be replaced at another time Other <br />' disadvantages of site excavation include limited site space, excessive costs for deeper excavation, <br /> necessity for shoring, excessive backfilling costs, continued liability for landfill disposal and <br /> disruption of adjacent property businesses Future liability for off-site disposal can be reduced <br /> through indemnification offered by some soil recycling facilities <br /> Limited excavation within the core area at the site was reported to have been performed in 19$9 <br />' <br /> Prior to any future excavation of hydrocarbon-impacted soil at the site, it is likely that a substantial <br /> amount of"clean" soil would have to be removed for logistical reasons and either hauled off-site for <br /> disposal or hauled off-site for storage due to the limited space at the site <br />' 7 2 3 Estimated Costs For Excavation <br /> Once excavated, impacted soil would have to be transferred to an off-site disposal or recycling <br />' facility Replacement backfill material would be imported The cost for excavation, <br /> treatment/disposal and backfilling would likely be between $100 00 and $140 00 per cubic yard of <br /> impacted soil, depending upon actual hydrocarbon concentrations encountered during excavation <br />' Additional charges would apply for shoring and special equipment Additional soil remediation <br /> methods would have to be employed to remove hydrocarbons at greater depths and laterally <br />' <br /> 73 IN-SITU BIOREMEDIATION <br /> iAcceptance of this treatment technology within the regulatory community has grown recently, due <br /> to documented successful remediation of petroleum-hydrocarbon contaminants at numerous sites <br />' in California <br /> Advanced GeoEn-,iranmental,Inc <br /> 1 <br />