ARCHIVED REPORTS_XR0008413 - Laserfiche WebLink

Home Browse Search

1 ' 18 February 1997 AGE-NC Project No 95-0104 ' Page 10 of 22 ' excavation costs can be excessive if the volume of the impacted soil is significant or if the vertical extent of soil impact exceeds 20 to 25 feet, resulting in.requirements for special equipment or shoring ' Disadvantages of excavation include disruption to site activities, excessive costs for deeper excavations and continued liability for landfill disposal Additionally, if off-site disposal is performed, clean fill material must be imported and compaction engineered for backfilling I 6 2 3 ESTIMATED COSTS FOR EXCAVATION ' At the subject site, much of the impacted soil within the vadose zone could be excavated� p c ated with conventional equipment, such as a excavator Howevei, it is unlikely that excavation to depths greater than 20 to 25 feet is feasible at the site This would result in the removal of about 50% of the impacted soil at the site Approximately 100 to 125 cubic yards of impacted soil could be successfully excavated Additionally, it is likely that an additional 500 cubic yards of"clean" soil would have to be removed for logistical reasons �. Once excavated, the impacted soil can then be treated on-site or transferred to an off-site disposal facility Replacement backfill material must be imported if off-site disposal is chosen Based upon present site usage, it is unlikely that on-site 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 actual hydrocarbon concentrations encountered during excavation Total costs for excavation and treatment or disposal, based upon the removal of 200 to 250 cubic yards, would be between $18,000 and 530,000 However, additional soil remediation methods would have to be employed to remove hydrocarbons at greater depths 63 IN-SITU BIOREMEDIATION Acceptance of this treatment technology within the regulatory community has grown recently, due to documented success for remediation of petroleum hydrocarbon contaminants at numerous of sites in California I 6 3 1 PRINCIPLES For in-situ bioremediation, hydrocarbon-degrading bacteria are propagated in a liquid medium, which is then infected into inoculation wells screened through the interval of contaminated soil If ground water has been impacted, strategically located ground water monitoring wells can be used for ,• inoculation Once in the contaminant plume, the bacteria metabolize and therefore degrade hydrocarbons and spread laterally and vertically by migrating and reproducing, creating an advancing I