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R603 UPDATE-14 3/25/93 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 . Before sampling the wells or the system, a calibrant made from fresh gasoline is in3ected into the GC-PID and GC-FID. The resulting chromatograms has numerous responses The microprocessor of the GC-PID and GC- FID computes the area per response in volt seconds and assigns a peak number 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 averaged with the preceding site visit' s pound per day value . This figure is then multiplied by the number of hours the system operated between visits , to estimate the total pounds each well and the system has removed for that time period This figure is added to the accumulated poundage of the previous visit to update the total pounds removed. The effluent sample is computed in the same fashion, but also includes natural gas flow along with the influent orifice flow rate . SAMPLING VAPOR STREAMS The vapor samples are obtained by attaching a dedicated air tight poly tubing to a sample port on the vapor recovery manifold (on the well side of the orifice plate) . The tubing is attached to a air tight fitting that connects a valved one liter tedlar bag which is placed inside a air tight sample box. The sample port is opened and a vacuum is placed on the tedlar bag inside the sample box, filling the tedlar bag with the vapor stream Once full the sample port is closed, the vacuum is withdrawn and the tedlar bag valve is closed, sealing the vapor stream sample inside the tedlar bag A small dedicated needle attached to a dedicated 1 cc syringe is then inserted into the septum of the tedlar bag to obtain the sample to be in3ected into the PID-GC and FID-GC The 1cc syringe is purged numerous times before filling it with the sample All but 0 5 cc of the sample is elected into the air before injecting the remaining 0 . 5 cc syringe sample into the chromatographs (the calibrant in3ection is 0 . 5 cc) Once the chromatogram is recorded an instrument blank is run prior to the next sample. The instrument blank indicates if residual peaks are being carried onto the next analysis . Prior to sampling an individual vapor stream, flow rates are recorded and vacuum influent readings are obtained from the wells by attaching a manometer calibrated in mm water to sample ports PAGE 6