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URS September 19, 2003 • Page 6 4.1 3 Soil Excavation Excavation is the removal of contaminated soils at the site by heavy equipment, then disposing of the contaminated soils at a landfill where they will be treated and stored The excavation required to remove most of the contaminated soil at the site would be at least 25-feet deep and 80-feet long by 100 feet wide Since the service station is active and there are no plans for line and tank upgrades, this alternative is not executable in the Immediate future 4 1 4 Air Injection Air infection is simply allowing air to enter into the ground above the water table and when combined with SVE offers benefits in operation such as reduction of "dead zones", mimmization of groundwater upwellmg, increasing pressure gradients, and creating a barrier to air flow towards sensitive locations Air infection can be either passive or active Active air infection is much more effective at Increasing air throughput in stagnant areas resulting in expedited remediation I4.2 Groundwater Remediation Technologies Groundwater extraction, dual-phase extraction, chemical oxidation, aquifer containment, air sparging, . and monitored natural attenuation remediation technologies are presented below 4.2.1 Groundwater Extraction Groundwater is extracted from extraction wells using pumps The extracted groundwater is then either treated before release to the environment or collected and transported off-site for disposal/treatment at a permitted storage/treatment facility Since most of the mass is most likely located in the soil above the ' groundwater table, groundwater extraction alone will not completely remediate the site 4 2 2 Dual-Phase Extraction ' DPE extracts both soil vapors and groundwater using high vacuum extraction The groundwater removal rate is much less than pumping, but the lowered groundwater level exposes contaminated soil that can ' be remediated by vacuum extraction DPE works better than standard SVE in tight soils because the high vacuum creates a greater radius of influence ' 4.2.3 Chemical Oxidation Chemical oxidation uses the addition of chemical to the aquifer to oxidize the hydrocarbons in place One method of chemical oxidation is ozone infection through specially built infection wells The ozone ' will oxidize the hydrocarbons into carbon dioxide and water, while increasing dissolved oxygen concentrations on the edge of the radius of influence of the infection point enhancing biodegradation 1 K\WproccssV5 BP ARC0102186\CAP Aug03\02186 CAP03 doe 1