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R604 UPDATE 14 12--28-1992 hydrocarbons Figure 3 shows the outline of the soil contaminated after evaluation of the confirmation soil sample boring samples As was stated earlier, vapor recovery has removed the lighter fractions of g gasoline range petroleum hydrocarbons from the soil (through ethylbenzene) and has greatly reduced the petroleum hydrocarbons dissolved in the ground water beneath this site Figure 5 represents the vacuum influence generated from the vapor recovery system as measured before obtaining depth to ground water measurements on December 7, 1992 . System Operation Currently a flow rate that fluctuates between 70 cubic feet per minute and 88 cubic feet per minute is being maintained through the two blowers that are placed in series, prior to exhausting through 2 (in series) 110 activated carbon vapor scrub units These are serviced by Exceltran and Cameron Yakima for change out and rejuvenation From November 17, to December 9, 1992 the system has operated 526 hours and recovered 235 39 pounds of gasoline range hydrocarbons (10 74 pounds per day) CONCLUSIONS AND DISCUSSION Estimates of petroleum hydrocarbons remaining in the soil after the confirmation soil sampling that occurred on July 20, 21, 22 , 1992 was approximately 4345 pounds Soil sample results from the SB4 confirmation sample ]poring and vapor samples from the vadose zone well P1 have indicated that the former northeastern pump island area and the surrounding area is now void of the contaminant The two remaining areas of impacted soil are area one (SB3 , SB9 and SB11) the area southeast of the former underground storage tanks and area two - (SB5) the area beneath the former western pump island Vapor extraction has removed the lighter fractions of gasoline range hydrocarbons found in the soil and has greatly reduced the dissolved contaminant found in the ground water Of the estimated 4345 pounds that remained in the soil after the July 22 , 1992 sampling, 1886 pounds have been removed from area one and 60 pounds have been removed from area two . Dual column - GC FID and GC PTD have confirmed that benzene is no longer a component of the vapor streams Ground water gradients, corrected for vacuum influence, have shown potentiometric lows at the wells being used' for vapor recovery (MWS) . Once the vapor recovery is shut off, normal flow directions again take place to the east-southeast or northeast , with the exception of the March 5, 1992 gradient, which flowed to the north-northwest and may represent a recharge and/or a decline in water usage of the municipal wells located east of the site . Fecal coliform has been analyzed for monitoring wells MW3 , MW4 , MW5 and MW6 on a monthly basis from December, 1991 through February, 1992 Only trace amounts of fecal coliform have been page 7