ARCHIVED REPORTS_XR0005088 - Laserfiche WebLink

Home Browse Search

r ' 11 February.2063 , AGE-NC Project No. 98-0520 ' Page 6 of 21 ' bioremediation are the appropriate site remediation technologies with the potential to address impacted soil and ground water that should be considered for this CAP. Natural attenuation is also , evaluated and discussed. 6.1. EX-SITU TREATMENT OF IMPACTED SOIL ' Hydrocarbon-impacted soil can be excavated and treated ex-situ on-site or transported-off-site for recycling/disposal.On-site treatment alternatives include aeration,bioremediation,vapor extraction, ' and thermal destruction;all are feasible methods for above-ground remediation of soil contaminated with gasoline. Off-site disposal generally involves transportation of the impacted soil to a licensed treatment/disposal facility. 6.1.1. Excavation 1 All of the above-mentioned methods of ex-situ treatment require excavation of the impacted soil, • which is generally the fastest and most effective method for soil remediation. Once'excavated, the ' impacted soil is generally-stockpiled on-site for treatment,or transported 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 can be' used to.backfill the excavation. If the ' -hydrocarbon-impacted soil is disposed off-site, fill material must be imported to backfill the excavation. 6.1.2. Feasibility of Excavation ' Excavation of impacted soil,followed by ex-situ treatment and/or disposal is a very effective method of remediation.Theoretically,all or at least the majority of the impacted soil is removed. In addition, ' longer-chain hydrocarbons are easily rernediated with excavation while in-situ methods are slower or are ineffective.However,excavation costs can be excessive if. 1)the volume of the impacted soil is significant, or 2) the vertical extent of soil impact exceeds 20 feet bsg or soil conditions require ' shoring, both resulting in the need for special equipment. AGE anticipates that special equipment for shoring would be required to excavate to the depth of ground water at the subject site due to the sandy soil encountered from surface grade to 20 feet bsg. TPH-g-impacted soil on the subject site extends to depths of approximately 20 feet bsg in the vicinity of the former USTs; however,the lateral extent of impacted vadose zone soil at the site is ' apparently extensive (Figure 5). Both of these assumptions will make excavation an expensive alternative. In-addition, if the contaminated soil assessed in the well borings are contiguous, contaminated soil extending beneath Moffat Boulevard also may have to be excavated. Advanced GeoEnvironmental,Inc.