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1 <br /> 27 December 1996 <br /> AGE-NC Project No 95-0143 <br />' Page 8 of 19 <br />' 5 2 2 FEASIBILITY OF EXCAVATION <br /> Excavation of impacted soil,followed by ex-situ treatment and/or disposal is a very effective method <br />' of remediation Theoretically, all or at least the majority of the impacted soil is removed However, <br /> excavation costs can be excessive if the volume of the impacted soil is significant or if the vertical <br /> extent of soil impact exceeds 20-25 feet, resulting in requirements for special equipment or shoring <br />' Impacted soil extends to ground water in the vicinity of former UST No 7 Hydrocarbon-impacted <br /> soil is also present beneath the small building Iocated on-site No special equipment would be <br />' required to reach ground water depth for excavation at the subject site However, impacted soil is <br /> present in the smear zone Excavation of the smear zone would require the extensive removal of <br /> overburden soil Impacted soil cannot be removed southwest of the former UST location without <br /> removal of the building <br /> The primary disadvantage of excavation is the disruption to site operations Automotive painting is <br />' performed in the building on the south side of the site Dust control would also be a concern Other <br /> disadvantages include air pollution control concerns, backfilling and compaction costs <br /> 5 2 3 ESTIMATED COSTS FOR EXCAVATION <br /> IAt the subject site, impacted soil in the vadose zone could be excavated with conventional <br /> equipment, such as a backhoe Approximately 1,000 cubic yards of soil would have to be excavated <br /> from the former UST location However, much of the impacted soil lies beneath the building on-site, <br /> and can not be removed The lateral extent of excavation would be determined by comparing the <br /> additional costs of removing o-.erburden soil with the benefits of the removal of additional impacted <br /> soil in the smear zone <br /> Once excavated, the soil will then be treated on-site or transferred to an off-site disposal facility <br /> Replacement backfill material must be imported if off-site disposal is chosen Space is available for <br /> on-site treatment of excavated soil However, permitting would be required for on-site treatment of <br /> impacted soil The cost for excavation, treatment/disposal and backfilling would likely be between <br /> $80 00 and $120 00 per cubic yard, depending upon hydrocarbon concentrations Total costs for <br /> excavation and treatment or disposal could therefore approach $150,000 00 <br /> r 5 3 IN-SITUBIOREMEDIATION <br /> 1 Acceptance of this treatment technology by the regulatory community has grown recently, due to <br />. documented success for remediation of petroleum hydrocarbon contaminants at a considerable <br /> I <br />