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R603 UPDATE-23 12/27/93 just prior to restarting the vapor extraction system after it had been off for approximately 3.84 hours . Of the wells being utilized for vapor extraction only MW2 shows evidence of vacuum i depression. MW2 has the lowest hydraulic conductivity of the wells at this site. GROUND WATER QUARTERLY SAMPLING Ground water samples were collected on September 29, 1993, see Table 1 . These samples were collected by a WEGE geologist and k "Chain of Custody" delivered 'on ice to a state certified testing laboratory (SUPERIOR PRECISION ANALYTICAL, INC. DHS#1332) for chemical analyses. These samples were analyzed for TPH and BTEX M concentrations. using EPA Methods 8015 and 602 respectively. Since diesel has never shown up in the sample results, the samples obtained on 11/27/90 and later were analyzed using EPA methods 5030 and 602 for Total Fuel Hydrocarbons and BTEX. The i next quarterly sampling will occur in December, 1993 . f E 3 .0 RESULTS E 'F GROUND WATER SAMPLE RESULTS Ground water samples were obtained from all of the monitoring '. wells on September 29, 1993 . The latest sample results showed a decline in contaminant levels associated with the ground water at MW1, MW2, and MW10 . Of the k other wells that have some degree of ground water contamination } (MW3 , MW8, and MW12) showed slight increases, see Table 1 and Figure 5 . F The increase in contaminant concentrations found at MW3 , MW8 and MW12 is thought to be associated with the vacuum extraction system operating only 160 of the time due to equipment modifications (heat exchanger addition) and equipment check ' (increase noise from compressor) , see Tables 1 and 3 . VAPOR RECOVERY OPERATIONS AND RESULTS As of November 30, 1993 , the REMOX units have operated for a total of 11238 hours out of a total of 17902 hours (63%) . The new replacement operated 6859 hours out of 10628 hours (646) , prior to having the burner assembly replaced on November 5, 1993 . An estimated 71951 pounds of gasoline range hydrocarbons have been- destroyed, see Tables 2, and 3 and Appendix C-Air Monitoring Report . Since February 18, 1993 the vapor recovery/destruction has been declining from an average above 200 pounds per day of gasoline range hydrocarbons to a low of 30 9 Y pounds per day of gasoline range hydrocarbons on July 19, 1993 . With the addition of the k heat exchanger the pounds per day destruction was increased to �J nearly 70 pounds per day on August 23 , 1993 , just prior to } turning the system off for repair of the compressor and changing k PAGE 2 i