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R603 UPDATE-16 4/29/93 . 2_2 GROUND WATER QUARTERLY SAMPLING Ground water samples were collected on March 11, 1993 , see Table 1 These samples were collected by a WEGE geologist and "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 concentrations using EPA Methods 8015 and 602 respectively Since diesel has never shown up_..;.n 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 next quarterly sampling will occur in Tune, 1993 . 3 . 0 RESULTS 3 . 1 PRODUCT AND RECOVERY During the initial site assessment and subsequent site visits, floating product was observed in monitor wells MW-1, MW-3 and MW10 . Product thickness in MW-1 has ranged from 0 01' to 1 . 261 , and from 0 17' to 1 66' in MW-3 Only a product sheen has been observed in MW10 during the March, June and September, 1991 and the March 10, 1992 sampling. Since November 11, 1992 no product sheen has been observed in any of the wells at this site . The removal of the floating product can be attributed to the active vapor extraction at this site . 3 2 GROUND WATER SAMPLE RESULTS Ground water samples were obtained from all of the monitoring wells on March 11 and 15 , 1993 The latest sample results shows the continual decline in contaminant levels associated with the ground water at this site . of the wells that have some degree of ground water contamination (MW1, MW2 , MW3 , MW8, MW10 and MW12) MW2, MW8 and MW12 showed reductions . The increase in contaminant concentrations found at MW1 and MW3 is thought to be associated with the vacuum extraction at these wells, concentrating the contaminant from adaacent areas to the source of the vacuum, see Table 1 3 3 VAPOR RECOVERY VAPOR RECOVERY SYSTEM AND MONITORING As stated in Update Status Report #5, monitoring wells MW1, MW2 , MW3 , MW10 and the excavation 6 inch (EX-4) have been individually manifolded to a vapor extraction system with individual valved orifices for flow control sampling and vacuum and flow measurements from the individual wells . MW2 and MW3 are manifolded together with 2 inch tubing teed at the wells, but can be individually tested by placing a packer below the extraction tee of the well to seal that well from the vacuum system The PAGE 3