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1 <br /> COST FEASIBILITY ANALYSES <br />' Thrifty Oil Co Station#172 <br /> 7647 Pacific Ave, Stockton, CA <br /> Hydr=2rbon 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 (02 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/l <br /> 2_ Researches by Shell Oil have indrvcated that it takes approximately 200 liters of <br /> air to extract 1 g of TPH in the soil (200 Ug=7,060 cu ft/kg) <br /> 3 Averagefantirapated extraction flow rate is 75 cfm (4 wells) <br /> Calculations <br /> 1 Well extraction efficiency= (34 mg/L)1(220 mg/L) = 15 5% <br /> 2 Volume air needed to extract hydrocarbons=(3 660 lbs)/(2 2 lb/kg)x(7,060 cu ft/kg) <br />' = 11 75x106 cu ft <br /> 3 Estimated time for remediation = (11 75x106 cu ft)/(75 cfm)/(15 5%)1 (1440 min/day) <br /> =701 days <br />' =approx 2 years <br /> Hydrocarbon impacted groundwater <br /> b Areal extent of impacted groundwater is around well MW-11 only <br />' d Impacted groundwater area is approx elliptical 65 ft and 80 ft <br /> b Assume 10 feet of groundwater is contaminated, <br /> Volume of groundwater contamination=40,820 cu ft <br />' Average concentration is approx 26 000 ug/L(52 000 ppb to 100 ppb) <br /> b Assume 25% saturation volume of water= 10,205 cu ft=289,000 L <br /> Estimated hydrocarbons is 7,514 g = 16 5 lbs <br />' Groundwater Remediation Svatem <br /> Assumptions <br /> 1 One pumping well (MW-11), pumping at 0 5 gpm= 720 gpd <br /> 2 Initial inlet concentration=52 000 ppb <br />' 3 Exponential reduction of concentration, down to 10 ppb through the duration of remediation <br /> WOW- <br /> 50=oW50om <br /> n.nan <br /> ao aoa <br /> (J 10 o00 <br /> 0 <br /> Remediation Time <br /> 4 Estimated remediation time=3 years <br /> Page 2 of 2 <br />