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Work Plan for Additional Subsurface Assessment and Feasibility Study—Former Unocal Station#0187 <br /> September 14,2000 <br /> ADVANTAGES <br /> 1) Can remediate capillary fringe soils <br /> 2) Air sparge can strip petroleum compounds from soil and groundwater <br /> 3) Can reduce dissolved concentrations in groundwater <br /> 4) Requires no removal,treatment,storage, or discharge considerations for groundwater <br /> DISADVANTAGES <br /> I) The majority of the most significantly impacted soil and groundwater is well below the current <br /> groundwater level The effect of vapor extraction on the intermediate and deep zones may be <br /> minimal <br /> 2) Stratified soils may cause air sparging to be ineffective <br /> 3) Petroleum compounds stripped from the soil and groundwater in the intermediate and deep zones <br /> would be difficult to capture The variable lithology makes it difficult to predict air flow pathways <br /> from these zones <br /> 4) Construction and operation costs for an extraction system would be high <br /> 5) Abatement costs could be high <br /> CONCLUSION May not be a feasible remedial method for this site _ <br /> OPTION#4--OZONE MICROSPARGING (C-SPARGE) <br /> Ozone microsparging is a process where ozone in air is introduced into the groundwater through specially <br /> designed spargers to create small "microbubbles"As these microbubbles rise within the column of water, <br /> they strip VOCs from the groundwater Low flow rates (2-6 cfm) are used Upon entering the <br /> microbubbles, the VOCs are rapidly oxidized This patented C-Sparge process is available from K V <br /> Associates,Inc of Mashpee, Massachusetts(C-Spargen" literature included in Appendix C) <br /> Any ozone not consumed in the direct reaction with hydrocarbons rapidly decomposes to oxygen This <br /> has an added benefit of stimulating the natural biological degradation <br /> COST Relatively Low <br /> TIME FRAME Short term for impacts on and near the site, longer for off site impacts <br /> ADVANTAGES <br /> 1) Relatively low equipment and operating costs <br /> 2) Because of low flow rates,vapor extraction to capture off gassing is not required <br /> 3) Natural biodegradation rates may be enhanced by introduction of oxygen <br /> 4) Manufacturer's literature indicates cleanup times of 12 months or less under similar conditions <br /> DISADVANTAGES <br /> 1) Limited historical data on this process <br /> 2) Might be difficult to treat large areas <br /> CONCLUSION Potentially a feasible remedial technique for this site <br /> 240042 08 8 <br />