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COST FEASIBILITY ANALYSES <br /> Thrifty Oil Co. Station #172 <br /> 7647 Pacific Ave, Stockton, CA <br /> Hydrocarbon impacted soils: <br /> Estimated volume is 25,600 cu ft <br /> Impacted soil location is 20' - 55' bgs <br /> Areal extent of impacted soil is beneath the old and new tanks <br /> Average concentration is 1,300 ppm <br /> Estimated hydrocarbons is 3,660 lbs <br /> Vapor Extraction Test Results: <br /> Flow rate per well is about 16 cfm <br /> Radius of influence is 25 to 40 ft <br /> Inlet vapor concentration is up to 9,500 ppmv (34 mg/L) <br /> Extraction vacuum is up to 16 "H2O <br /> Oxygen levels in the extracted vapors were low and were limiting the <br /> performance of the VET unit <br /> Vapor Extraction may be a feasible remediation option <br /> Higher flow rate and influence may be achieved if the VE system is <br /> using equipment that is not using combustion (O2 demand) <br /> Vapor Extraction System: <br /> Assumptions: <br /> 1. If there is 500 ppm or more volatile hydrocarbons inthe soil structure, assume <br /> that the vapor extracted under ideal conditions is at saturation level. For gasoline <br /> the saturated vapor concentration is generally accepted to be 220 mg/I. <br /> 2. Researches by Shell Oil have indivcated that it takes approximately 200 liters of <br /> air to extract 1 g of TPH in the soil. (200 Ug = 7,060 cu fUkg) <br /> 3. Average/anticipated extraction flow rate is 75 cfm (4 wells) <br /> Calculations <br /> 1. Well extraction efficiency= (34 mg/L)/ (220 mg/L) = 15.5 % <br /> 2. Volume air needed to extract hydrocarbons = (3,660 lbs) /(2.2 Ib/kg) x(7,060 cu ft/kg) <br /> = 11.75x106 cu ft <br /> 3. Estimated time for remediation = (11.75x10° cu ft)/(75 cfm)/ (15.5%)/(1440 min/day) <br /> = 701 days <br /> = approx 2 years <br /> Page 2 of 2 <br />