ARCHIVED REPORTS XR0008122 - Laserfiche WebLink

Home Browse Search

i R604 :UPDATE 10-JUNE, 1992 _ i ' INTRODUCTION This report includes the results of the'June, 1992 ground-water quarterly sampling, along with the events that have occurred at this—site-since- the 9th Update Status Report, that covered events up through April 14 , 1992 . As stated in our 8th Update Status report, the first phase of remediation to the above mentioned site, removing aged gasoline range hydrocarbons from the soil in the vadose zone beneath the tank field and pump island areas , has been completed. This finalized the clean-up of contaminated soil at this site. The following are the conclusions and recommendations from Update Status Report #9 : CONCLUSIONS AND DISCUSSION Vapor extraction has been successful in removing the degraded gasoline range petroleum hydrocarbons from the soil and for the most part ground water at this site. The vapor recovery system, operated under Variances #91-19 and 91-20 was turned off awaiting the Permit to Construct , Permit # AP 91-106 . During this "off Period" two periods of "re-equilibration" have occurred. Sample results from the vadose zone wells P1 , P3-Swarm and EX have indicated that these wells and the surrounding areas are now void of the contaminant. Upon start-up for the Permit to Construct P1 , P3-Swarm and EX exhibited minor vapor recovery, 0 . 04 , 0 .07 and 0 . 01 lbs/day respectively. As of April 14 , 1992 no detectable hydrocarbon vapors are being produced from these wells . Vapor extraction has greatly reduced the d3-ssolved contaminant found in the ground water. The most recent sampling occurred 80 days after the vapor recovery system was shut down and showed that since vapor recovery has been used at this site , MW1 has been reduced from 2 mg/L TPH to <0 . 05 mg/L TPH. MW5 , likewise has been reduced from 31 mg/L TPH to 0 . 08 mg/L TPH. The BTEX/s have also been removed from the ground water beneath the site to below the detection limits . Ground water gradients , corrected for vacuum influence, have shown potentiometric lows at the wells being used for vapor recovery, MW1 and MW5 . Once the vapor recovery is shut off, normal flow directions again take place to the east-southeast; 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 to the east of the site. Fecal coloform 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 coloform have been occasionally detected in any of the wells during those 3 months , this analysis will occur on a quarterly basis starting on the page 1