SITE INFORMATION AND CORRESPONDENCE FILE 1

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s. meter (49 ft) to 10.5 meter(35 ft). Wells were screened with larger intervals where contaminants were encountered higher in the vadose zone. 'Y Soil boring data indicated a volatile contamination in the vadose zone ranging from a depth of 5 m (16 ft) to 14 m (46 ft) with the zone of maximum contamination generally at 12 m (39 ft), However, as expected the vadose zone contamination was encountered at shallower depths closer to the reported spill site and only in the capillary zone at points distant from the spill. Previous investigations reported a light non-aqueous phase liquid(LNAPL) of up to 100 mm (4") thick, however by the time the authors conducted the project, the maximum apparent LNAPL thickness was observed to be 9 mm(.36" )thick. Remedial Technology Selection Previous investigations had detected hydrocarbon contaminant in all the four main phases: 1) in the vapor phase; 2) in the soil matrix (either sorbed to the soil, in soil pore space, or dissolved in soil moisture); 3) as a LNAPL or free product layer on the phreatic surface; and 4) as a dissolved phase in the groundwater. A complete remedial approach would address all of the four main phases in which the contaminant had been found. Previous consultants had suggested vapor extraction coupled with a dual pump LNAPL removal system. The client also indicated that the design must be an in-situ remedial technology with time —Ind economy playing a major selection role. Due to community pressures to begin cleanup no intermediate pilot study phase was funded. Therefore, the selected remedial approach must have the flexibility to be modified in the field. Due to the proven success rates of remediation using SVE technology (Johnston, 1990), the authors pursued SVE as a likely candidate for remediation. However, studies conducted at sites where the remediation system depended solely on vapor extraction was found to "weather" the contaminant-that is it will preferentially remove the volatile components leaving behind the less volatile compounds (Pedersen, 1991). The authors considered that a complete remedial approach would likely include in-situ bioremediation either naturally or enhanced in order to remediate the remaining less volatile compounds..Thus, the authors decided that bioventing which uses lower extraction rates, thereby limiting the weathering effects, should be an integral component of the design. Specific project remedial objectives were: • Remove the LNAPL layer floating on top of the shallow aquifer; • Remove and/or destroy the residual JP-4 fuel compounds in the vadose zone; • Complete the action in the most cost-effective manner, in the least time; • Utilize a system that provides the most flexibility, easiest maintenance, and least impact to base operations. 381