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4 <br />' A <br /> S S O C I A T E 5 I N C <br /> Air Sparge System <br />' From December 30, 2003 to March 26 2004 the air sparge s stem operated continuously The <br /> average injected air flowrate from December 30, 2003 to March 26, 2004 was approximately 939 <br />' cubic feet per minute (cfm) and the average influent pressure was approximately 2 9 pounds per <br /> square inch <br />' AdditionaI Site Activities <br />' On February 9 and 10, 2004 ATC trenched from well MW 1 to the main vapor extraction conduit <br /> and installed subsurface piping to connect well MW I to the vaper extraction system A "stinger" <br /> the same as the one in wells VW1 and VW2 was installed inside well MW to extract vapor and <br />' groundwater from the bottom of the well The trench area was backfilled and resurfaced <br /> On March 26, 2004, Cooper Controls and Electrical service calibrated the LEL and flow meters <br /> associated with the groundwater treatment system <br /> CONCLUSIONS <br /> TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits In <br /> the samples collected from wells MW5, MW6, and MW7 Petroleum hydrocarbon <br /> concentrations detected in groundwater samples collected from MW2 through MW10, and CW <br /> remain consistent with the results from previous sampling events Detectable concentrations of <br /> MTBE were present in samples collected from MW2, MW4, MW5, MW6, MW7, MW9, and <br /> CW The samples collected from MW2, MW4, MW9 and CW contained no detectable <br /> concentrations of petroleum hydrocarbons other than low concentrations of MTBE The samples <br />' collected from MW3, MWS and MW 10 contained no detectable concentrations of petroleum <br /> hydrocarbons There are petroleum hydrocarbons remaining in the soil and groundwater The <br /> direction of groundwater flow and the magnitude of hydraulic gradient are generally consistent <br />' with the previous event Groundwater elevations have increased slightly since December 2003 <br /> The vapor extraction system is operating at approximately 53 cfm and petroleum hydrocarbon <br /> vapor concentrations in vapor wells VW1 through VW4 decreased during the first quarter 2004 <br /> with respect to the fourth quarter 2003 analytical results The vapor extraction system is <br /> collecting an average of approximately 31 28 gallons per hour of groundwater/condensate in the <br /> knockout tank from vapor wells VWI, VW2, VW3, VW4, and well MW1 The air sparge <br /> system appears to be operating within design parameters <br />' RECOMMENDATIONS <br /> Based on the results of the First Quarter 2004 monitoring event, we recommend the following <br /> s Icnviro1625961quatEy\1gr-2004 doc 7 <br />