ARCHIVED REPORTS XR0006573 - Laserfiche WebLink

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Using benzene as an indicator, monitoring wells MW1, MW4 , MWS, MW6, MW7 and MW9 have been reduced to below detection limits while the wells being utilized for vapor extraction (MW2 , MW3 , and MW10) have been reduced by better than 95%, 99% and 99°s respectively MW8 increased from a reduced of approximately 56% (June-September, 1994) to a 2216 reduction as shown from the December 12 , 1994 sampling, this increase in contamination is most likely due to the down time of the REMOX unit during the months of October and November, 1994 Of the newly installed wells MW11 and MW12, MW12 has shown a significant (920) reduction in benzene concentration since the December 22 , 1993 sampling. MW11 has always tested below detection limits . On October 26 , 1993 , a sample of the water being treated by air stripping inside the "ConVault" was obtained for certified laboratory analysis This was accomplished to prove the suitability for dumping this cleaned water to the City of Stockton' s sanitary sewer. Also at this time a two hour source test performed on MW-8, indicated that a once a week two plus hour evacuation of this well will provide oxygen transfer to the area near the well and should help control migration of the ground water plume and enhance remediation of this site The "ConVault" stored/treated water was dumped to the sewer on Janaury 25, 1995 also at that time the weekly two hour venting of MW8 commenced As of January 12 , 1995 an estimated 11941 gallons of gasoline range hydrocarbons have been removed from the soil and ground water beneath this site Previously removed floating product (40 25 gallons) , condensation from vapor extraction (48 75 gallons) , pro3ected petroleum hydrocarbon vapor extraction- destruction (74079 pounds/6 25 = 11852 gallons) and venting of MWS (0 2 pounds/6 25 = 0 03 gallons) No chlorinated solvents were detected in chromatogram comparisons of the vapor (air) samples, "i e . " 1, 2 , -Dichloroethene (DCE) - retention time 2 . 079 minutes, Trichloroethylene (TCE) - retention time 3 . 023 minutes and Tetrachloroethylene (PCE) - retention time 3 75 minutes In the past, water samples from MW1 and MW6 were tested using EPA method 8240 and were below detection limits for these compounds, see Update Status Report 21, September, 1993 Water samples obtained on March 4, 1994 from MW1, MW6 , MW9 and MW11 were tested using EPA Method 8010 and were below detection limits for these compounds WEGE is also evaluating the need to change out BACT from Thermal Oxidation to Carbon Adsorbtion, in light of the lower amount of hydrocarbons found in the vapor stream and the cost savings of utilities, versus carbon change out PAGE 5