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R604 :UPDATE 19 5-19-1993 hose 2 inch union is placed between the tee and the 2 inch PVC flex hose that connects the well to the extraction manifold. At the manifold the individual wells are connected to their own 2 inch PVC riser (36 inch in height) with an orifice plate and a gate valve at the top of the riser Vacuum/pressure ports are located on either side of the orifice plate Each orifice (well) has its own manometer (calibrated in millimeters (mm) water) which are connected to the ports for continuous measurement of flow from a particular well All the extraction wells are manifolded together above the gate valve to a set of two orifice risers that are in parallel before the vacuum pumps After the vapor stream leaves the manifold, it is pulled into the pumps (two Rotron DR505 placed in series) and then into activated charcoal vapor scrubs If breakthrough occurs through the 1st carbon, this carbon is removed from the system The #2 carbon is then placed at the #1 position and a new carbon placed on the exhaust as the #2 carbon. A portable ambient air PID--GC (Photovac lOS50 packed column) was used at the site to sample for breakthrough of the carbon scrubs, the influent and effluent of the system, and the influent from the various vapor extraction wells Before sampling the wells or the system, a calibrant made from fresh gasoline is infected into the GC-PTD The resulting chromatogram has numerous responses. The microprocessor of the GC-PID 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. This factor as used to calculate mg/L as gasoline vapor from each analysis Pounds per day can be computed using these mg/L values, and the pressure differential created at the orifice (flow rate) for each well, and total influent . Since September 25 , 1992, tedlar bag samples are obtained and brought back to be analyzed in the WEGE portable laboratory This is necessary due to long eluting time (analysis time increased from 10 minutes per sample to 30 minutes per sample) needed per analysis using the 10s50 (all early eluding compounds have been removed by vapor extraction) The pounds per day values for each well and the influent are then averaged to the preceding site visit' s pound per day value and then multiplied by the number of days the system operated between visits to estimate the total pounds each well and the total 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, see Table 3 and Appendix C Sampling Vapor Streams: The vapor samples are obtained by attaching a dedicated air tight soft polytubing to a sample port on the well side of the orifice plate on the vapor recovery manifold The tubing is then connected to a tedlar bag placed inside a vacuum sampler. The sample port is then opened and the vacuum placed on the tedlar bag from the sample vessel allows the tedlar bag to fill with the vapor stream from that particular sample port Once the tedlar . bag is full the valve is closed and the vacuum removed from the sample vessel The tedlar bag contains an air tight locking page 5