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R603 UPDATE-30 6/29/94 • Monitoring Report . Since February 18, 1993 the vapor recovery/destruction has been declining from an average above 200 pounds per day of gasoline range hydrocarbons to a present low of 9 9 pounds per day of gasoline range hydrocarbons on April 26, 1994 Presently the system is destroying a range from 14 to 7 pounds per day of gasoline range hydrocarbons, see Appendix C CONDENSATE REMOVAL BY LTT Condensation from vapor extraction is collected in moisture drop out tanks constructed of 12 " PVC pipe, before the manifold, to prevent moisture build up on the vacuum pump filter All fluids removed from the condensation traps are placed in the 1000 gallon "ConVault" As of June 27 , 1994 , 5250 gallons of water/condensate and 48 75 gallons of product have been removed from the subsurface of this site 4 . 0 SUMMARY There has been no evidence of floating product or product sheen on the ground water in 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 9901 MW8 has been reduced by approximately 880, since January 12 , 1990 Of the newly installed wells MW11 and MW12 , MW12 has shown a significant reduction in benzene concentration since the December 22 , 1993 sampling of 706 MW11 has always tested below detection limits On December 22 , 1993 , a sample of the water being treafpcj by a , r 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 June 24 , 1994 an esti mated 11907 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 (73860 pounds/6 25 = 1 .818 gallons) No chlorinated solvents were detected in chromatogram comparisons, "i e It 1 , 2 , -- Dichloroethane (DCE) - retention time 2 079 minutes, Trichloroethylene (TCE) - retention time 3 023 minutes and Tetrachloroethylene (PCE) - retention time 3 75 minutes Also water samples from MW1 and MW6 were tested using EPA method 8240 and were below detection limits for these compounds, see Update PAGE 3