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v <br /> o <br /> A S S O C I A T E S I N c <br /> Total BTEX removed via groundwater treatment and discharge since system startup on December <br /> 19, 2002 <br /> 1 1 64 pounds of BTEX removed since the startup of the system <br /> Air Sparge System <br /> From March 26 to June 28, 2004, the air sparge system operated continuously The average <br /> 1 injected air flowrate from March 26, 2004 to June 28, 2004 was approximately 30 cubic feet per <br /> minute (cfm) and the average influent pressure was approximately 3 1 pounds per square inch <br />' CONCLUSIONS <br /> TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits in <br /> the groundwater samples collected from wells MW1, MW6, MW7, VWl, and VW2 Petroleum <br /> hydrocarbon concentrations detected in groundwater samples collected from MW1 through <br />' MW10, and CW remain consistent with the results from previous sampling events Detectable <br /> concentrations of MTBE were present in samples collected from wells MW2, MW4, MW5, <br /> MW6, MW7, MW9, CW, and VW2 The samples collected from wells MW2, MW4, MW5, <br /> MW9, and CW contained no detectable concentrations of petroleum hydrocarbons other than low <br /> concentrations of MTBE The samples collected from MW3, MW8 and MW10 contained no <br /> detectable concentrations of petroleum hydrocarbons There are petroleum hydrocarbons <br />' remaining in the soil and groundwater The direction of groundwater flow and the magnitude of <br /> hydraulic gradient are generally consistent with the previous event Groundwater elevations have <br /> decreased slightly since March 2004 <br />' The vapor extraction system is operating at approximately 72 cfm and petroleum hydrocarbon <br /> vapor concentrations in vapor wells V W 1 through V W4 increased during the second quarter <br /> 1 2004 with respect to the first quarter 2004 analytical results The vapor extraction system is <br /> collecting an average of approximately 23 gallons per hour of groundwater/condensate in the <br /> knockout tank from vapor wells V W 1, VW2, V W3, V W4, and well MW 1 The air sparge <br /> 1 system appears to be operating within design parameters <br /> RECOMMENDATIONS <br /> 1 Based on the results of the Second Quarter 2004 monitoringevent we recommend the following <br /> � g <br /> i • Conduct the Third Quarter 2004 groundwater monitoring and sampling of wells MW1 <br /> through MW10, VW 1, VW2, and CW and analyze samples for TPHg and BTEX by EPA <br /> methods 8015B and 8021B, respectively, and MTBE, ETBE, TBA, TAME, and DIPE by <br /> EPA method 8260B <br /> • Continue monthly monitoring of the vapor extraction system, groundwater treatment and <br /> discharge system, and air sparge system <br /> s lenviro1625961quartlyQcir-2004 doc 7 <br />