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COST FEASIBILITY ANALYSES <br /> Thnfty Oil Co Station#172 <br /> 7647 Pacific Ave, Stockton, CA <br /> H drocarbon rm acted 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"H20 <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/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 ftlkg) <br /> 3 Averagelanticipated 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)1(2 2 Ib/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%)/(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 /> c* 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 /> a 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 5yatem <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 /> 60 OW <br /> a <br /> 500W <br /> CL <br /> 40 o00 <br /> 30 ow <br /> u <br /> C 20 ow <br /> O <br />. () 10 000 <br /> 0 <br /> Remediation Time <br /> 4 Estimated remediation time= 3 years <br /> Page 2 of 2 <br />