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R604 :UPDATE 9-MARCH, 1992 . monitoring wells, see Table 1 . FECAL COLOFORM From December, 1991 through February, 1992 , monthly fecal coliform samples were being collected from monitor wells MW3 , MW4, MW5 and MW6 . Table 2 shows the results of these samples. Presently all these wells are below detection limits, <2 . 2 MPN, for fecal coloform, this analysis will no longer be obtained on a monthly basis, but will continue on a quarterly basis, see Appendix A- Laboratory Results. VAPOR EXTRACTION VAPOR RECOVERY SYSTEM AND MONITORING As stated in the Update Status Report #6 , wells P1, P3 , EX, MW1 and MW5 are manifolded to a vapor extraction system with individual valved orifices for flow control and measurement from the individual wells. The individual wells are fitted with a PVC "T" heads ( 4" reducing to 211 ) with a locking air tight cap, for well access. The "T" lateral (211 ) is fitted with a 1/4" pipe to tubing fatting for obtaining vacuum/pressure and temperature readings. A pipe to hose 2" union is placed between the "T" and the 2" PVC flex hose that goes from the well to the extraction manifold. At the manifold the individual wells are connected to • their own 2" PVC riser (36" in heigth) 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 monometer (calibrated in millimeters (mm) water) which are hooked 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 prior to the vacuum pumps. After the vapor stream leaves the manifold, it flows through a moisture drop out drum ( 55 gallon 17E ) and then is pulled into the pumps (two Rotron DR505 placed in series ) prior to entering a second moisture drop out drum and then onto activated charcoal vapor scrubs. If breakthrough was found to be occurring through the 1st carbon, this carbon was removed from the system, the #2 carbon was then placed into the #1 position and a new carbon placed on the exhaust as the #2 carbon To prevent the vapor extraction system from being shut down due to using up all of the carbon scrubs, a vapor stream - condensate unit was used (CYCLO-PURGE ) to re-Duvinate the spent carbons so that they could be placed back on line. This unit was able to remove approximately 20-25 percent of the absorbed hydrocarbons from the carbon scrubs as water and gasoline condensate, which was stored on site in 17H hazardous material drums along with the rinsates and purged well water. The recovered gasoline was eventually removed to Wicklands Terminal in Selby, CA. , for blending, see Table 4 Update Status Report #8 . Once the system was turned off all 10 carbon scrubs were sent to Cameron Yakima for rejuvenation, see Appendix D-Manifest. page 5