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R603 UPDATE-10 11/09/92 i prior to a filter in front of the vacuum pump. After the vapor stream leaves the vacuum pump, it is pushed into the thermal oxidizer (RXL 400 ) which oxidizes the gasoline range hydrocarbon vapors at no less than 1400°F and no greater than 15500F. Influent samples are obtained from the exit of the pump and effluent samples are obtained from the stack of the thermal oxidizer. The gasoline range hydrocarbons are oxidized into heat, CO2 and water vapor, see UPDATE STATUS REPORT #5 . A portable ambient air PID-GC (Photovac 10550 packed column) is used at the site to sample the influent and effluent of the REMOX oxidizer and the individual wells (MW1 , MW2-3 , MW10 and EX-411 ) , see Tables 2 , and 3. On October 22 , and 24, 1991, "Tedlar" bag samples were obtained of the influent and effluent of the REMOX incinerator. Also on January 20, May 21, June 22, July 15, August 26 , September 9 and September 11, 1992 influent samples were obtained. These samples were analyzed for TFH and BTEX along with screening for Tetrachloroethylene (PCE) , Trichloroethylene (TCE) and 1, 2, -Dichloroethane (DCE) using a Shimadzu GC-FID chromatograph mounted permanently in WEGE ' s portable laboratory. These compounds have the following retention times in the above • chromatograph, DCE = 2 . 079 minutes, TCE = 3 . 023 minutes and PCE = 3 . 75 minutes. Prior to sampling the wells or the system, a calibrant prepared from fresh gasoline is infected into the GC- PID. The resulting chromatogram has numerous responses. The microprocessor of the GC-PTD computes the area, per response, in volt seconds, and assigns a peak #, and retention time. The sum of all the responses are then used to obtain a mg/L per volt second calibrant factor, which is used to calculate mg/L as gasoline vapor from each analysis produced. Pounds per day can be computed using these mg/L values produced from the analysis of the different vapor recovery wells, the influent to the oxidizer, the pressure differential created at the orifice to determine flow rates for each well, and the influent to the oxidizer. The pounds per day values for each well and the influent are then averaged with the preceding site visit ' s pound per day value. This figure is then multiplied by the number of days the system operated between visits to estimate the total pounds each well and the system has removed for that time period. This poundage is then added to the accumulated poundage of the previous visit to update the total pounds removed to date. The effluent sample is computed in the same fashion, but also includes natural gas flow along with the .influent orifice flow rate. PAGE 6