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R603 UPDATE-22 11./11/93 <br /> Figure 4A, are measurements obtained during operation of the <br /> vacuum extraction system, September 29, 1993 . This figure shows <br /> a substantial low potentiomentrzc depression at the wells being <br /> utilized for vapor extraction (MW1, MW2, MW3 and MW10) . <br /> Figure 4B, November 5, 1993 shows a more normal gradient <br /> direction. Measurements were obtained dust prior to restarting <br /> the vapor extraction system after it had been off for <br /> approximately 1.84 hours . Of the wells being utilized for vapor <br /> extraction only MW2 shows evidence of vacuum depression. MW2 has <br /> the lowest hydraulic conductivity of the wells at this site . <br /> GROUND WATER UARTERLY SAMPLING <br /> Ground water samples were collected on September 29, 1993, see <br /> Table 1 These samples were collected by a WEGE geologist and <br /> "Chain of Custody" delivered on ice to a state certified testing <br /> laboratory (SUPERIOR PRECISION ANALYTICAL, INC. DHS#1332) for <br /> chemical analyses. These samples were analyzed for TPH and BTEX <br /> concentrations using EPA Methods 8015 and 602 respectively <br /> Since diesel has never shown up in the sample results, the <br /> samples obtained on 11/27/90 and later were analyzed using EPA <br /> methods 5030 and 602 for Total Fuel Hydrocarbons and BTEX. The <br /> next quarterly sampling will occur in December, 1993 <br /> 3 .0 RESULTS <br /> GROUND WATER SAMPLE RESULTS <br /> Ground water samples were obtained from all of the monitoring <br /> wells on September 29, 1993 <br /> The latest sample results showed a decline in contaminant levels <br /> associated with the ground water at MW1, MW2, and MW10 Of the <br /> other wells that have some degree of ground water contamination <br /> (MW3 , MW8 , and MW12) showed slight increases, see Table 1 <br /> The increase in contaminant concentrations found at MW3 , MW8 and <br /> MW12 is thought to be associated with the vacuum extraction <br /> system operating only 16k of the time due to equipment <br /> modifications (heat exchanger addition) and equipment check <br /> (increase noise from compressor) , see Tables 1 and 3 <br /> VAPOR RECOVERY OPERATIONS ANT] RFSTTT,TS <br /> Presently (November 5, 1993) the REMOX units have operated for a <br /> total of 10863 hours out of a total of 17303 hours (631c) The <br /> new replacement unit has operated 6861 hours out of 10656 hours <br /> (64%) , removing and destroying and estimated 71057 pounds of <br /> gasoline range hydrocarbons, see Tables 2, and 3 and Appendix C- <br /> Air Monitoring Report . <br /> Since February 18, 1993 the vapor recovery/destruction has been <br /> declining from an average above 200 pounds per day of gasoline <br /> range hydrocarbons to a low of 30 pounds per day of gasoline <br /> PAGE 2 <br />