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R603 UPDATE-10 11/09/92 • Xylenes. Another water sample was obtained of the Convault water on October 13 , 1992 , and again analyzed by WEGE, non certified. The water was dramatically reduced .in hydrocarbons and showed the following concentrations: TFH 7 . 78 Mg/L, benzene 0 . 125 Mg/L, toluene 2. 953 Mg/L and xylenes 7 . 362 Mg/L. As of October 16 , 1992, a total of 5661 . 4 gallons of gasoline range hydrocarbons have been removed from the soil and ground water beneath this site with the condensation traps recovery, combined with previously removed floating product ( 40 . 25 gallons) and vapor extraction-destruction of hydrocarbons ( 35132 pounds/6. 25 = 5621 . 12 gallons) . No chlorinated solvents have been detected in chromatogram comparisons; ie. 1, 2, -Dichloroethane (DCE) - retention time 2 . 079 minutes, Trichloroethylene (TCE) - retention time 3 . 023 minutes and Tetrachloroethylene (PCE) - retention time 3 . 75 minutes. 4 .0 DISCUSSION AND CONCLUSIONS • As stated in earlier reports, the soil is contaminated with gasoline range hydrocarbons beneath the tank field (MW10 ) and along the capillary fringe of the ground water, (MW1, MW2, MW3 and MW10 ) , see Figure 6 . Ground water beneath the site contains the dissolved constituents of gasoline range hydrocarbons and has spread out from beneath the site to the north (MW-6 ) , to the south (MW-7 ) to the west (MW-9 ) and to the east (MW-8 ) . The latest ground water sampling, September 22, 1992, has shown a decline in the lateral extent of the plume, see Figure 5A ( 12--17-91 ) and Figure 5B ( 9-22-92 ) . Vapor extraction commenced on October 17 , 1991 and up until October 16 , 1992 has operated for 4864 hours out of a possible 8063 . 25 for a 60; run time, destroying 35 , 132 pounds of gasoline range hydrocarbons. Since the last status report, September 3, 1992, a total of 7578 pounds of gasoline range hydrocarbons have been removed/destroyed in 662 . 5 hours of operation ( 11 . 44 pounds per hour or 274. 52 pounds per day of operation) . DCE, TCE and PCE screening indicates that these compounds aida are not present- in the vapor stream at this site. Ground water elevation measurements show that the ground water is still in a discharge cycle with a valley forming from MW2 towards while the overall flaw direction is -co rhe souzheasL from rhe tank area towards newly .Installed monitoring well MW12 . • Ground water sample results obtained on December 17 , 1991, approximately 1473 hours after commencement of vapor extraction, PAGE 9