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The area expected to be remediated using each respective approach was also <br /> evaluated This factor is important at this Site because the dissolved phase <br /> plume is contained in formations that are primarily silts and clays having low <br /> to moderate permeabilities <br /> Oxygen releasing compounds rely on diffusion in groundwater and natural <br /> groundwater movement to spread dissolved oxygen through an aquifer <br /> Effective coverage from an oxygen releasing compound infection point is <br /> particularly limited in less permeable formations and under conditions <br /> involving relatively flat groundwater gradients Effective coverage from a <br /> single infection point is estimated to be between 40 and 80 square feet <br /> Additionally, oxygen releasing compounds would not be expected to have an <br /> effect on potentially impacted soil above the groundwater table or to <br /> effectively volatilize contaminants in groundwater <br /> Air sparging utilizes physical injection of a readily soluble gaseous oxygen <br /> source into the aquifer The infection of compressed air into the subsurface <br /> enhances the mobility of the added oxygen and improves mixing and effective <br /> solubility Oxygen is added in quantities sufficient to volatilize dissolved <br /> phase petroleum hydrocarbons in groundwater and adsorbed petroleum <br /> hydrocarbons in the vadose zone, as well as promoting their aerobic <br /> biodegradation The radius of influence typically observed around a sparge <br /> point is on the order of 15 times the submerged depth <br /> Air sparging is expected to be more effective than oxygen releasing <br /> compounds because of soil permeability with respect to gases being <br /> significantly higher(typically 1,000 to 10,000 times higher)than those for <br /> liquids The effectiveness of oxygen releasing compounds is dependent on <br /> dissolution and groundwater migration and therefore would be expected to <br /> have limited effect at points more distant from injection points Air sparging <br /> over a period of time would introduce greater amounts of oxygen into the <br /> subsurface than even several liberal infections of oxygen releasing <br /> compounds, promoting not only aerobic biodegradation but volatilization as <br /> well <br /> Soil vapor extraction, combined with air sparging will be effective in <br /> removing contaminants in the soil column Soil vapor extraction will also help <br /> control migration of petroleum vapors throughout the subsurface <br /> 2.2 Feasibility <br /> Except for difficulties associated with the infection of oxygen releasing <br /> compounds beneath the Site building and the adjacent Center Street, both <br /> remedial methods appear to be feasible on an engineering basis Oxygen releasing <br /> compounds would likely be introduced by infection through a number of <br /> probeholes driven within the plume of impacted groundwater This plume appears <br /> g <br /> Picot Testing Work Plan <br /> 1717 South Center Street-Stockton,California <br /> Prepared by Philip Services Corp <br /> H\ENW2400I325121362EG1Prolecx\SkKkCentlptloucstpim doc July 23,2002 <br />