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h x $ �[ R604 :UPDATE 16 2-23-1.993 CONCLUSIONS AND DISCUSSION II Estimates of petroleum hydrocarbons remaining in the soil after, the confirmation soil sampling that occurred on July 20, 21, 22, J 1992 was approximately 3027 pounds . Soil sample results from the SB4 confirmation sample boring and vapor samples from the vadosel zone well P1 have indicated that the former northeastern pump! island area and the surrounding area (AREA C) is now remediatedi, of the contaminant. The two remaining areas of ; impacted soilf are : AREA A - (S85) the area beneath the former; :.western pump'I k island and AREA B (SB3., SB9 and SB11) the area southeast of the former underground ''storage tanks .. Vapor extraction has removed the lighter fractions of gasoline; range hydrocarbons found in the soil and has greatly reduced they dissolved contaminant found in the ground water and the capillary[ fringe. Of the estimated 3027 pounds that remained in the soil after the July 22,1 1992 sampling, 129 out of and estimated 72 pounds have been ,; removed from AREA A and 2557 out of an'[ estimated 2946 . 5 pounds have been removed from AREA B. This leaves approximately 389 pounds of degraded gasoline ranget hydrocarbons to be removed from the soil in AREA B. If wed maintain our present vapor stream concentration, which removes; ' approximately 12 pounds per day, the majority of the estimated remaining 389 pounds will be removed from the soil by March 27,,' 1993 . Dual instrument -- GC FID and GC PID have confirmed that. benzene is no longer a component of the vapor streams . f ,F w Continual monitoring of the ground water indicates' that the once contaminated ground water associated with MW1 andEMW5 have been remediated and meet[ the Title 22 and DHS standards,. ' Ground water! I gradients, corrected for vacuum influence, 'F have shown ! potentiometric low's at the wells being used for vapor recovery i (MWS) . Once the ' vapor recovery is shut off, : normal flow directions again take place to the east-southeast' or northeast,,[ with the exception of ,the March 5, 1992 gradient, Yvhich flowed tap the north-northwest and may represent a recharge and/or a decline in water usage of the -municipal wells located east', of the site. ' Ff Fecal coliform haslbeen analyzed for monitoring wells MW3 , MW4 ,I MWS and MW6 on a monthly basis from December,: : 1991 through, February, 1992 . "!Only trace amounts of fecal coliform have been occasionally detected in any of the wells during those 3 months,, see Table 2 . RECOMMENDATIONS '! y 1 . Recommend this site for evaluation of: closure, see` Closure Evaluation Work Plan, UPDATE STATUS REPORT #15 .� 2 . Continuelivapor recovery on MW5 and the newly installed vadose wells VSB3 , VSBS, VSB9 and VSB11 .'' . 3 . Continuel'�to monitor this site on a quarterly basis . , i page 6 �I r