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440 West Charter Way, Stockton, California September 16, 1992 <br /> Texaco Environmental Services Page 5 <br /> 5 Q SOI! VAPOR EXTRACTION AND TREATMENT <br /> The required flow rate for the sal vapor extraction system is 160 cfm (for 8 VI='s requiring a <br /> flow rate of 20 cfm each) A 5-hp regenerative blower (Rotron model 707), will provide 180 <br /> cfm when applying 50 inches of water vacuum This will allow for approximately 20 cfm of <br /> dilution air that can be routed into the system if needed <br /> Operating at a design flow rate of 160 cfm and an average concentration of 200 /fgll benzene <br /> and 11,500 TPH-G the daily mass emissions of benzene and TPH-G will be approximately 2 8 <br /> pounds per day benzene and 165 pounds TPH-G These emissions are in excess of the lifetime <br /> cancer risk as per (CAPCOA 1987) and the vapor extraction system will therefore require an <br /> emissions treatment device <br /> Because of the quantities of hydrocarbons to be extracted, and the removal rate, treatment by <br /> granular activated carbon (GAC) is not recommended for the Charter Way site Typically, <br /> carbon can be loaded by 20 percent before saturation, but the exact value depends on humidity <br /> and flow rate Based on the expected initial extraction rate of 165 lbs/day, approximately 800 <br /> lbs of carbon would be saturated each day <br /> Catalytic or thermal oxidization technologies are recommended for this site because of the high <br /> concentrations of hydrocarbons to be extracted Equipment selected for emission control must <br /> have a process flow rate of 180 cfm for the entire extraction system to work effectively <br /> However, if a 1 1 dilution of influent vapor is necessary to lower influent concentration, the <br /> process flow rate of the vapor abatement device must increase to 360 cfm in order to <br /> maximize vapor extraction Alternately, vapor extraction at the site can be performed in phases <br /> by extracting from the A levels initially and as concentrations decrease, additional vapors can <br /> be drawn from the B level VE's <br /> Prior to final equipment selection additional air sampling must be performed for tetraethyl lead, <br /> methane and carbon dioxide ,n the vapor stream Treatment by catalytic oxidization cannot be <br /> performed if lead concentrations are high unless vapors are pretreated for lead <br /> �L!�?� GROUNDWATER <br /> �� TECHNOLOGY <br />