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REG 603 UPDATE-7 3/24/92 • 1. 26 ' and from 0 . 17 ' to 1 . 66 ' in MW-3 . Only a product sheen has been observed an MW10; during the March, ,Tune and September, 1991 and the March 10, 1992 samplings. The recovered gasoline is amber yellow and appears to be fresh (no apparent degradation) . Involved regulatory agencies suggested that product recovery commence before an aquifer pump test be performed. Temporary submersible pneumatic pumps were installed into monitor wells MW-1 and MW-3 for product recovery on October 10, 1989 . Approximately 40 gallons of gasoline was recovered. The product recovery system was removed in February, 1990, and the "ConVault" tank, until September, 1990 , was being used for the storage of the purged well water. On May 25, 1990 a water sample obtained from the "ConVault" indicated that the stored water was free of petroleum hydrocarbons (Table 1 Convault) . This water was later dumped to the sewer after permission was obtained by the Stockton Department of Municipal Utilities (approximately 250 gallons) . During the November 27 , 1990 monitoring round, 0 . 08 ' of a clear yellow floating product was again discovered in monitor well MW1 . This well was purged until depletion of the product was noted; approximately 1 quart of gasoline was recovered and placed into the 55 gallon drum storing the water "purged" prior to sampling the wells. Product thickness measurements obtained on subsequent site visits have shown only a sheen of product in MW1 until September, 1991 when 0 . 02 feet of yellow-amber product was discovered, and also wells MW3 and MW10 have product sheens (showing up after the vapor extraction source test on MW10 ) . 3 . 2 SITE CONDITIONS A. GROUND WATER A. 1. GROUND WATER: December 17, 1991 The December, 1991 chemical results (sampled 12/17/91) indicate that dissolved benzene in monitor wells MW-2, MW-3 , MW-4, MW-8, and MW-10 substantially exceeds the action level for drinking water of 1.0 ppb, set by the DHS, see Table 1. Monitor wells MW-6 and MW-9 have moderate levels of benzene ( 110 and 120 ppb respectively) and monlLor well VrW-7 contains a lower benzene Value of 4. 9 ppb. Monitor well MW5 is below the detection limit (<0 . 3 ) for benzene. Since the start up of vacuum extraction from MW1 and MW10 the benzene levels in the monitor wells have dropped in all of the wells with the exception of MW8 . Monitoring wells MW2 and MW3 were added to the vapor extraction system on January 14, 1992 . These wells have influence the down gradient off site extent of the plume (MW-7 and MW-8 ) . Monitor wells MW1, MW3 and MW10 ® contained a sheen of floating product (<0 .01 ' ) , see Figure 5A. Strong to moderate bio-odors were also noted along with a grey PAGE 5