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R604 :UPDATE 23 10-20-1993 <br /> Fecal Coliform: <br /> From December, 1991 through February, 1992, monthly fecal <br /> coliform samples were collected from monitor wells MW3, MW4, MW5 <br /> and MW6 . Samples were again collected in June, 1992, from <br /> monitoring wells MW3 , MW4 and MW6 . During the September 11, 1992 <br /> sampling, MW3 and MW6 were dry, no fecal coliform samples were <br /> obtained. Table 2 shows the results of these samples . the only <br /> wells that have tested positive for fecal coliform are MW4 and <br /> MW5 . As of June, 1992 all these wells are below detection <br /> limits, <2 2 MPN, for fecal coliform. <br /> VAPOR EXTRACTION <br /> Vapor Recovery Results: <br /> The vapor extraction system was shut down on November 21, 1991 on <br /> completion of operation under Initial Variance #91-19 and 90 day <br /> Variance #91-20 . A total of 13 , 116 pounds of gasoline range <br /> hydrocarbons were removed from the soils and ground water beneath <br /> this site by that time. <br /> The vadose zone vapor recovery wells (P1, P3-Swarm and EX) <br /> contributed little to the total recovered hydrocarbons during <br /> this time period. Pl = 1 3 pounds, P3-Swarm = 561 .4 pounds and <br /> EX = 127 pounds . <br /> The system was restarted under the Authority to Construct Permit <br /> (AP 91-106) on March 31, 1992 . <br /> On July 21, 22, and 23 , 1992, four new vadose zone vapor recovery <br /> wells were installed and manifolded to the recovery system. Pls <br /> of July 22 , 1992 the existing vapor extraction system (MW5, <br /> P3-Swarm and EX) had produced 13902 . 8 and the newly installed <br /> well VSB3 produced 3 6 pounds of gasoline range hydrocarbons. <br /> Since that time only the newly installed wells (VSB3 , VSB5, <br /> and VSB11) and MW5 have been used for vapor extraction. As of <br /> the latest sampling (October 6 , 1993) the new wells and MW5 have <br /> removed 4374 pounds of gasoline range hydrocarbons, for a total <br /> recovery of 18026 pounds, see Table 3 and Charts of vapor <br /> recovery. <br /> Vacuum Influence- <br /> As was stated earlier, vapor recovery has removed the lighter <br /> fractions of gasoline range (through ethylbenzene) petroleum <br /> hydrocarbons from the soil and has greatly reduced the petroleum <br /> hydrocarbons dissolved in the ground water beneath this site. <br /> Figure 3 represents the vacuum influence generated from the vapor <br /> recovery system, as measured on October 6, 1993 . <br /> page 3 <br />