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.�—.,.».. --,.. -- s'. � �... . ., � _G..« " -- '" __ _•• __..... � _ .. ..� ..., , ..lei:,l lL.t, �r,� ti'1�h�54&_.aL1 ix._;_ }- _ e i 15 February 2000 AGE-NC Protect No 98-0448 rPage 31 of 33 ' 10 1 REMEDIATION OF HYDROCARBON-RvIPACTED SOIL Petroleum hydrocarbon-Impacted soil in the vadose zone appears to be limited to the area containing ' wells MW-1, MW-2, MW-4, VW-1, VW-2, EW-1 and soil bonngs B-T and B-2 Impacted soil at the site has an estimated north-south diameter of approximately 70 feet, a east-west diameter of 50 feet and appears to extend downward to depths in excess of 50 bsg (See Figures 7, 8 and 9) The ' greatest concentrations of impacted soil is present at depths between 10 and 35 feet, while declining concentrations are present from 35 and 50 feet ' Because there appears to be a low feasibility for excavation,bioremediation and natural attenuation, then SVE appears to be the best remedial alternative for the site However, the majority of petroleum-impacted soil is submerged beneath the ground water table (saturated zone) Therefore, ' petroleum contaminants submerged beneath the ground water table will need to be mechanically stripped from the dissolved and adsorbed phases (air sparge) and vented into the vadose zone for recovery Soil remediation methods, estimated durations and associated costs are summarized on Table 11 AGE recommends the following actions for remediation of hydrocarbon-impacted soil at the site 1 Preparation of a Remedial Action Work Plan (RAWP) detailing the proposed SVE system ' 2 Design and install a SVE system 3 Soil-gas concentrations were detected between 170 and 1,880 ,ug/l, therefore an activated ' carbon SVE system should be installed to remediate the site to acceptable levels Operation of the SVE system at the site should be capable or removing between 70 and 80 percent of volatile contaminant by volume The SVE system will provide recovery and treatment of the "sparged" contaminants A ' thermal/catalytic system is not required at this time since there is a relatively small amount of impacted-soil within the present vadose zone A vacuurn/canmster-system will provide much higher efficiency with less supplemental fuel usage and lower energy cost ' The total duration of the remediation at the site will likely be approximately 12 to 24 months to allow for removal of the bulk of dissolved hydrocarbon from the ground water at the site 1 10 2 REMEDIATION OF HYDROCARBON-IMPACTED GROUND WATER ' would be more feasible from a cost and operation perspective, over An in-situ remediation method P p p an ex-situ remediation method (I a pump and treat) The in-situ method(air sparging in conjunction Advanced GeoEnvironmental,Inc w _