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R603 UPDATE-33 9/30/94 I SUMMARY There has been no evidence of floating product or product sheen on the ground water an MW1 since April 14 , 1992 and MW3 and MW10 since November 11, 1992 . The last evidence of product, as a sheen in the condensate recovery system, was on March 1, 1993 Vapor recovery has reduced the hydrocarbons in ground water significantly since the May 25, 1990 sampling, see Table 1 Using benzene as an indicator, monitoring wells MW1, MW4 , MW5, 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 97%, 99% and 990 respectively MW8 has been reduced by approximately 56% Of the newly installed wells MW11 and MW12 , MW12 has shown a significant (92%) reduction in benzene concentration since the December 22 , 1993 sampling MW11 has always tested below detection limits On December 22 , 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 the approximately 800 gallons of this cleaned water to the City of Stockton' s sanitary sewer As of September 18 , 1994 an estimated 11912 7 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) , projected petroleum hydrocarbon vapor extraction- destruction (73898 pounds/6 25 = 11823 7 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 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 Marcn 4 , 1994 from MW! , Mi 6 , V1199 and Mligii were tested usury` EPA Method 8010 and were below detection limits for these compounds TIME FRAME October, 1994 Monthly air sampling and ground water gauging November, 1994 Monthly air sampling and ground water gauging December, 1994 Monthly air sampling and ground . water gauging with quarterly monitoring well sampling PAGE 2