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REG 603 UPDATE-8 7/17/92 • 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. Approximatell 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 MWl until September, 1991 when 0.02 feet of yellow-amber product was . discovered, and also wells MW3 has had up to 0.28 feet of yellow- amber product and MW10 have product sheens (showing up after the commencement of the vapor extraction source test on MW10 and the continuation of vapor extraction on MW1, MW2, MW3, MW10 and the tanks excavation area) 3.2 SITE CONDITIONS A. GROUND WATER A. 1 GROUND WATER March 10, 1992 The March, 1992 chemical results (sampled 3/10/92) indicate that dissolved benzene in monitor wells MW-2, MW-4 and MW-8 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 low levels of benzene (1.3 and 4 3 ppb respectively) and Monitor wells MW-5 and MW-7 are below the detection limit (<0.3) for benzene. Since the start up of vacuum Pxtraction from MW1 and MW10 the benzene levels in the monitor wells have dropped in all of the wells, see Figures 5A and 5B and Table 1 Monitoring wells MW2 and MW3 were added to the vapor extraction system on January 14, 1992 These wells are influencing the down gradient off site extent of the plume (MW7 and MWS) . Monitoring wells MW1, MW3 and MW10 contained floating proauct. Strang to moderate bio-odors were also noted along with a grey green coloration of the purged ground water from monitor wells MW2, MW4, MW7 and MW8 i PAGE 5