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:F R603 UPDATE-15 4/8/93 I Figure 4C, represents the gradient beneath the site from ground `-water measurements obtained March 11, 1993 . This figure shows a [ continued rise of the ground water beneath this site in the wells jilithat are not being purged by LTT. The dewatering valley. ' created by vapor extraction at MW1, MW2, MW3 and MW10, and the d{ purging of these wells along with MW8, is more pronounced and f ': indicates a larger area ofinfluence than previously shown in :,UPDATE REPORT 14, see Figures 4A, 4B and 4C. j f 2. 2 GROUND WATER OUARTERLY SAMPLING „Ground water samples were collected on March 11, 1.9.93, see Table h1 . These samples were- collected by a WEGE geologist and "Chain of Custody" delivered on ice to a state certified testing E l� laboratory (SUPERIOR PRECISION ANALYTICAL, INC. DHS#1332) for i chemical analyses . These samples were analyzed for TPH and BTEX concentrations using EPA Methods 8015 and 602 respectively. ' Since diesel has never shown up in the sample results, the 1 ! Esamples 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 June, 1993 . ; 3 . 0 RESULTS } M 3 . I 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..26' , a 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 E� vapor extraction at this site. 3 . 2 GROUND WATER SAMPLE RESULTS 'c 3 Ground water samples were obtained from all of the monitoring swells on March 11 and 15, 1993 . .! II 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 i! (MW1, MW2, MW3 , MW8, MW10 and MW12) MW2, MW8 and MW12 showed reductions . ; s The increase in contaminant concentrations found at MW1 and MW3 is y thought to be associated with the vacuum extraction at these wells, concentrating the contaminant form adjacent areas to the . source of the vacuum, see Table 1 and Figures 5A, 5B and 6'. . o PAGE 3 i � .