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• <br /> Total TPHg removed via groundwater treatment and discharge since system startup on December 19, 2002 <br /> ' 9 98 pounds of TPHg removed since the startup of the system <br /> Total BTEX removed via groundwater treatment and discharge since system startup on December 19, 2002 <br /> 164 pounds of BTEX removed since the startup of the system <br /> Air Sparge System Evaluation <br /> From June 28 to September 27, 2004, the air sparge system operated continuously The average injected air <br /> flow rate from July 26 to September 27, 2004 was approximately 28 cubic feet per minute (cfm) and the <br /> average influent pressure was approximately 2 5 pounds per square inch <br /> ICONCLUSIONS <br /> There are petroleum hydrocarbons remaining in the soil and groundwater The direction of groundwater <br /> flow and the magnitude of hydraulic gradient are generally consistent with the previous event <br /> Groundwater elevations have decreased approximately I I feet since June 2004 <br /> TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits in the <br /> groundwater samples collected from MW1, MW6, MW7, VWI, and VW2 The laboratory analytical <br /> results associated with the groundwater samples collected from MW 1 through MW10, and CW remain <br /> consistent with the results from previous sampling events Detectable concentrations of MTBE were <br /> present in samples collected from MW2, MW4, MWS, MW6, MW7, MW9, MW10, and CW The <br /> samples collected from MW2, MW4, MW5, MW9, MW10, and CW contained no detectable <br /> concentrations of petroleum hydrocarbons other than low concentrations of MTBE The samples <br />' collected from MW3 and MW8 and MW10 contained no detectable concentrations of petroleum <br /> hydrocarbons <br /> The vapor extraction system is operating at approximately 97 cfm Petroleum hydrocarbon vapor <br /> concentrations in VW1 generally increased and generally decreased in VW2 and VW4 during the third <br /> quarter 2004 with respect to the second quarter 2004 analytical results The vapor extraction system is <br />' collecting an average of approximately 26 gallons per hour of groundwater/condensate in the knockout <br /> tank from vapor VW 1, VW2, V W3, VW4, and MW I The air sparge system appears to be operating <br /> within design parameters <br />' RECOMMENDATIONS <br /> Based on the results of the Third Quarter 2004 monitoring event, we recommend the following <br />' • Conduct the Fourth Quarter 2004 groundwater monitoring and sampling of MW I through <br /> MW10, VW 1, VW2, and CW and analyze samples for TPHg and BTEX by EPA methods 8015B <br />' and 8021B, respectively, and MTBE, ETBE, TBA, TAME, and D1PE by EPA method 8260B <br /> s Ienvvo1625961quartEyl3gr-2004 doc 8 ATC Associates Inc <br />