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R604 UPDATE 14 12-28-1992 <br /> INTRODUCTION <br /> This report includes the results of events occurring at this site <br /> ° since the 13th Update Status Report , from November 17, through <br /> December 9, 1992 The following are the conclusions and <br /> recommendations from Update Status Report #13 . <br /> UPDATE #13 <br /> CONCLUSIONS AND DISCUSSION <br /> Estimates of petroleum hydrocarbons remaining in the soil after <br /> the confirmation soil sampling that occurred on July 20 , 21, 22 , <br /> 1992 was estimated at 4345 pounds Soil sample results from SB4 <br /> confirmation sample boring and vapor samples from the vadose zone <br /> well P1 have indicated that the former northeastern pump island <br /> area and the surrounding area is now void of the contaminant <br /> The two remaining areas of impacted soil are area one (SB3 , SB9 <br /> and SB11) the area southeast of the former underground storage <br /> tank and area two - (SB5) the area beneath the former western <br /> pump island <br /> Vapor extraction has removed the lighter fractions of gasoline <br /> range hydrocarbons found in the soil and has greatly reduced the <br /> dissolved contaminant found in the ground water Of the <br /> estimated 4345 pounds that remained in the soil after the July <br /> 22 , 1992 sampling, 1597 pounds have been removed from area one <br /> and 14 pounds have been removed from area two Dual column - GC <br /> FID and GC PID have confirmed that benzene in no longer a <br /> component of the vapor streams <br /> Ground water gradients, corrected for vacuum influence, have <br /> shown potentiometrxc lows at the wells being used for vapor <br /> recovery (MW5) Once the vapor recovery is shut off, normal flow <br /> directions again take place to the east-southeast or northeast , <br /> with except the March 5 , 1992 gradient , which flowed to the <br /> north-northwest and may represent a recharge and/or a decline in <br /> water usage of the municipal wells to the east of the site . <br /> Fecal coliform has been analyzed for monitoring wells MW3 , MW4 , <br /> MW5 and MW6 on a monthly basis from December, 1991 through <br /> February, 1992 Only trace amounts of fecal coliform have been <br /> occasionally detected in any of the wells during those 3 months <br /> This analysis will be done on a quarterly basis starting on the <br /> June, 1992 ground water sampling, see Table 2 <br /> RECOMMENDATIONS <br /> 1 Continue vapor recovery on MW5 and the newly <br /> installed vadose wells VSB3 , VSB5 , VSB9 and VSB11 . <br /> 2 Continue to monitor this site on a quarterly basis . <br /> 3 Obtain depth to ground water and vacuum influence <br /> page 1 <br />