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REG 603 UPDATE-6 2/21/92 • vertically at the north corner and west corner of the excavation respectively and manifolded via underground to the treatment compound with SCH 40 2 inch and 4 inch PVC pipe. These pipes along with monitor wells MW1, MW2, MW3 and MW10 are being used for vapor extraction - soil and ground water remediation. On October 10, 1991 the vapor extraction system operated for 6 hours, to check the auto shut downs and percent destruction of the REMOX unit, utilizing monitor wells MW1, MW10 , and the excavation wells. The system was restarted on October 17, 1991 for the initial inspection and operation of the system. The unit operated until November 5, 1991, when it was shut down to replace a worn bearing. The system was restarted after the repairs on November 20, 1991 and operated until December 24, 1991. On this date someone turned off the main breaker that services the treatment compound. This breaker box has since been locked. The unit was restarted on January 3, 1992 and is running at the present (February 3, 1992) for a total run hours of 1869, removing and destroying 11273 pounds of gasoline range hydrocarbons ( 6 pounds per hour) , see Tables 2, 3 and 4 and Appendix C-Air Monitoring . Report. 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. Ground water beneath the site contains the disolved 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. Vapor extraction commenced on October 17, 1991 and up until February 3, 1992 has operared for 1869 hours our- of a possible 2615 .5 for a 71. 5% run time, destroying 11, 273 pounds of gasoline range hydrocarbons. DCE, TCE and PCE screening indicates that these compounds are not present in the vapor stream at this site. r_rrniinri water camel P nh+ta-inert nn Timm 77 1 991 pri cnr to vapor extraction, compared to ground water sample results obtained on December 17, 1991, approximately 826 hours of operation after commencement of vapor extraction show a decline in the extent of the floating product plume as well as a decline in the dissolved constituents in monitoring wells MW4 and MW6 (the two ground eater monitoring wells closest to the extraction wells) from the June sampling to the December sampling, see Figures 5A and 5B. It is felt that once the air dilute has been completely closed and all vacuum recovery can be directed to MW1, MW2, MW3, MW10 and EX- PAGE 10