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R604 :UPDATE 17 4-27-1993 <br /> the GC-PID. The resulting chromatogram has numerous responses <br /> The microprocessor of the GC-PID computes the area per response <br /> in volt seconds, and assigns a peak number and retention time <br /> The sum of all the responses are then used to obtain a mg/L per <br /> volt second calibrant factor. This factor is used to calculate <br /> mg/L as gasoline vapor from each analysis . Pounds per day can <br /> be computed using these mg/L values, and the pressure <br /> differential created at the orifice (flow rate) for each well, <br /> and total influent Since September 25 , 1992 , tedlar bag samples <br /> are obtained and brought back to be analyzed in the WEGE portable <br /> laboratory. This is necessary due to long eluting time (analysis <br /> time increased from 10 minutes per sample to 30 minutes per <br /> sample) needed per analysis using the 10s50 (all early eluding <br /> compounds have been removed by vapor extraction) . The pounds per <br /> day values for each well and the influent are then averaged to <br /> the preceding site visit' s pound per day value and then <br /> multiplied by the number of days the system operated between <br /> visits to estimate the total pounds each well and the total <br /> system has removed for that time period. This poundage is then <br /> added to the accumulated poundage of the previous visit to update <br /> the total pounds removed to date, see Table 3 and Appendix B . <br /> Sampling vapor Streams <br /> The vapor samples are obtained by attaching a dedicated air tight <br /> soft polytubing to a sample port on the well side of the orifice <br /> plate on the vapor recovery manifold The tubing is then <br /> connected to a tedlar bag placed inside a vacuum sampler The <br /> sample port is then opened and the vacuum placed on the tedlar <br /> bag from the sample vessel allows the tedlar bag to fill with the <br /> vapor stream from that particular sample port . Once the tedlar <br /> bag is full the valve is closed and the vacuum removed from the <br /> sample vessel The tedlar bag contains an air tight locking <br /> septum valve which is then closed and locked to secure the vapor <br /> sample . A small dedicated needle attached to a dedicated 1 cc <br /> syringe is then inserted through the sample septum into the <br /> tedlar bag The 1cc syringe is purged numerous times before <br /> filling it with the sample . All but 0 5 cc of the sample is <br /> ejected into the air before injecting the remaining 0 . 5 cc <br /> syringe sample into the Shimadzu FID-GC (the calibrant injection <br /> is 0 . 5 cc) Once the chromatogram is recorded, an instrument <br /> blank is run prior to the next sample The instrument blank will <br /> indicate if residual peaks are being carried onto the next <br /> analysis <br /> Vacuum influent readings are obtained from the wells by attaching <br /> a manometer calibrated in mm water to sample ports at the well <br /> heads . These readings show the mm water pressure or vacuum that <br /> is being created at each well . <br /> page 5 <br />