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the basis of site closure after application of selected best available technol- <br /> ogy has been supplied until no longer effective <br /> 5.3.2 Alternative 1: Soil Excavation and Air Spargmg <br /> This alternative will address hydrocarbon-impacted soil and groundwater beneath the site In <br /> addition to the common elements mentioned above, this alternative consists of soil excavation <br /> to 35 feet and proper off-site disposal The 35-foot depth interval was selected for economic <br /> evaluation because this is the minimum depth where unsaturated soils occur A shallower <br /> excavation would not be practical given that interim remedial measures effectively targeted <br /> shallower soil zones, leaving the targeted zone in the deeper interval Soils and groundwater <br /> at greater depth would be remediated through the air spargmg After removing any clean <br /> overburden, impacted soil would be excavated and trucked off site for disposal at an <br /> appropriate landfill Up to 3,000 cubic yards of soil would be excavated and some fraction <br /> transported to a landfill (space for on-site treatment is limited) Shoring may be required to <br /> prevent caving, and the excavation would be limited by surrounding improvements <br /> The United States Environmental Protection Agency(EPA) suggests that excavation with off- <br /> site landfill disposal should be considered for small soil volumes (less than 1,000 cubic yards) <br /> with high contaminant concentrations <br /> • Groundwater sparge could be implemented at monitoring wells where the perforated casing is <br /> known to be within the or under the water level Addition of air to the formation will increase <br /> the rate of biodegradation of hydrocarbon elements <br /> Benefits of this alternative are two-fold Excavation will remove much of the soil-source <br /> which is thought to be a potential source of groundwater contamination Spargmg will <br /> provide additional remediation of groundwater contamination and further facilitate <br /> remediation of any residuals in the soil zone <br /> This technology may be applied prior to site development, and will not interfere with the <br /> proposed development at the site <br /> 5.3.3 Alternative 2: Sail Vapor Extraction/Bioventing and Air Sparging <br /> SVE will provide an excellent alternative to excavation of contaminated soils This method <br /> has already been illustrated to be effective in the removal and delineation of hydrocarbon <br /> contaminants at this site Operational data have been presented within this report showing this <br /> effect Further operation of the SVE system will allow for additional remediation of deep <br /> soils <br /> 3201337E/CAP_AMD DOC 18 November 30, 1995 <br />