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t r <br /> 04 March 1996 <br /> ' AGE-NC Project No 95-0144 <br /> Page 10 of 18 <br /> concentrations set by the lead agency or to non-detectable concentrations, the soil can be used to <br /> backfill the excavation If the hydrocarbon-impacted soil is disposed of off-site, material must be <br /> imported to backfill the excavation <br /> 6 2 2 FEASIBILITY OF EXCAVATION 4 , <br /> Excavation of impacted soil, followed by ex-situ treatment and/or disposal is a very effective method <br /> of remediation, non-detect (ND) can usually be achieved by excavation since, theoretically, all <br /> contaminated soil is removed However, hydrocarbon-impacted soil may extend under the building r <br /> fiom UST No 1 Longer-chain hydrocarbons are also easily remediated with excavation, where rn- <br /> '' Asitu methods are slower or ineffective However, excavation is usually too costly, if the volume of <br /> Y impacted soil is very great or the impacted soil extends to depths requiring special equipment or <br /> extensive shoring No special equipment would be required for excavation at the subject site` <br /> The primary disadvantage of excavation is the disruptiontto a site Since the site is currently not in <br /> use, no other operations would be disturbed Other disadvantages include air pollution control <br /> concerns, backfilling and compaction costs <br /> ' 6 2 3 , ESTIMATED COSTS FOR EXCAVATION ' <br /> At the subject site, impacted soil could be excavated with traditional equipment Approximately 200 <br /> } cubic yards of soil would have to excavated from the former location of UST No '1 and } <br /> approximately 750 cubic yard of soil would have to be excavated from former location of UST No <br /> 8 location Very little "clean" overburden soil would need to be removed <br /> Once excavated, the soil must then be treated on-site of transferred to an off-site disposal facility <br /> ' Replacement backfill material must be imported if off-site disposal is chosen The cost for excavation, <br /> treatment/disposal and backfilling would likely be between $80 00 and $120 00 per-cubic yard, <br /> depending upon concentrations ofhydrocaibons Total costs for excavation and treatment or disposal <br /> t ' could therefore approach $100,000 00 <br /> 63 IN-SITU BIOREMEDIATION <br /> r - ' t ` <br /> Acceptance of this treatment,technology by the regulatory community has grown in recent years, as <br /> success has been achieved at sites in California and elsewhere <br /> 1 <br />