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The vapor sample is then injected into an FID (Flame Ionizing <br /> Detector) chromatograph and the resulting chromatogram compared to <br /> standard chromatograms of known TFH (Total Fuel Hydrocarbons, <br /> gasoline) and BTEX (benzene, toluene, ethylbenzene, and xylenes) <br /> concentrations . A duel chromatograph comparison is also ran <br /> (Photovac 10550) to evaluate BTEX, TCE, PCE, and DCE. <br /> ON SITE ANALYSIS <br /> Besides bag samples collected for the WEGE laboratory some samples <br /> may be run on site using a Photovac lOS50 PID chromatograph. <br /> The influent and effluent samples are collected from the same ports <br /> as the bag samples but 60 cc syringes are used to collect the sample <br /> and 0 . 5 cc of the vapor sample are then injected directly into the <br /> PID chromatograph. The resulting chromatogram is then compared to a <br /> standard run on the same chromatograph prior to the sample run. <br /> During the initial month of operation, three effluent samples were <br /> obtained during the day and analyzed using the lOS50 chromatograph. <br /> The highest value is used to calculate the VOC poundage per day <br /> produced. Presently, an influent and an effluent sample are <br /> obtained upon arrival to the site . Adjustments are then made to the <br /> vapor extraction system: removal of liquids from the condensation <br /> traps; closing the air dilute valve to maximize vapor removal, <br /> without causing the REMOX Unit to shut down due to high temperature <br /> shut off (greater than 17500F) , and closing the pump bypass to <br /> create maximum flow and vacuum from the wells . Once, these <br /> ad3ustments have been completed and the system has stabilized, <br /> influent and effluent samples are again obtained, along with samples <br /> from the individual extraction orifices (wells) . The site is then <br /> secured until the next visit <br /> FLOW RATES <br /> Flow rates are measured at the site by use of orifice plates . A one <br /> inch orifice is placed in line for each well and a three inch <br /> orifice is used to measure the total flow. An orifice plate <br /> restricts the flow of air across it This restriction causes a <br /> pressure drop across the orifice By measuring the resulting <br /> pressure change across the orifice it is possible to calculate the <br /> air flow rate The flow rate is calculated by the pressure drop <br /> (millimeters (mm) water) across a square edge orifice plate . <br /> Ve = CK sgr (P) Q = AVe <br /> Where : <br /> Ve= velocity in feet per minute (fpm) <br /> C = Orifice Coefficient = 0 . 65 (for orifice used) <br /> K = Constant = 794 . 6 mm water <br /> P = Pressure differential across the orifice <br /> Q = Flow rate in cubic feet per minute (CFM) <br /> A = Area orifice in square feet . 1" = 0 . 00545 ft2 <br /> 3 " = 0 . 04909 ft2 <br /> Q = A X 0 . 65 X 794 . 6 X sgr(P) <br /> page 3 of R603 , 11/17/93 <br />