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G R604 :UPDATE 17 4-27-1993 CONCLUSIONS AND DISCUSSION �{ . Estimates of petroleum hydrocarbons remaining in the soil after the confirmation soil sampling that occurred on July 20, 21, 22, 1992 was approximately 3027 pounds . Soil sample results from the SB4 confirmation sample boring and vapor samples from the vadose i zone well P1 have indicated that the former northeastern pump island area and the surrounding area (AREA C) as now remedaated of the contaminant The two remaining areas of impacted soil are AREA A - (SB5) the area beneath the former western pump 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 the dissolved contaminant found an the ground water and the capillary fringe . Of the estimated 3027 pounds that remained in the soil after the July 22 , 1992 sampling, 141 out of an estimated 72 pounds have been removed from AREA A and 2746 out of an estimated 2946 5 pounds have been removed from AREA B. This leaves approximately 200 5 pounds of degraded gasoline range hydrocarbons to be removed from the soil an AREA B . If we maintain our present vapor stream concentration, which removes approximately 10 pounds per day, the maDoraty of the estimated remaining 200 pounds will be removed from the soil by April 5, 1993 . Dual instrument - GC FID and GC PID have confirmed that benzene is no longer a component of the vapor streams . . Continual monitoring of the ground water indicates that the once contaminated ground water associated with MW1 and MW5 have been remediated and meet the Title 22 and DHS standards . Ground water gradients, corrected for vacuum influence, have shown potentaometrac lows at the wells being used for vapor recovery (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, which flowed to the north-northwest and may represent a recharge and/or a decline in water usage of the municipal wells located east of the site Fecal coliform has been analyzed for monitoring wells MW3 , MW4, MW5 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 1 . Recommend this site for evaluation of closure, see Closure Evaluation Work Plan, UPDATE STATUS REPORT #15 2 Continue vapor recovery on MWS and the newly installed vadose wells VSB3 , VSB5 , VSB9 and VSB11 . 3 . Continue to monitor this site on a quarterly basis . page 6