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1 v <br /> 0 <br /> 1 <br /> A s s O C I A T E s I N C <br /> Air Sparge System <br /> 1 From February 13, 2003 to March 27, 2003, the air sparge system operated continuously During <br /> that time, the average infected air flowrate was 44 cubic feet per minute (cfm) and the average <br /> influent pressure was 4 0 pounds per square inch <br />' CONCLUSIONS <br /> Concentrations of TPHg and BTEX in groundwater wells MW1 and MW3 have decreased by at <br /> least one order of magnitude since fourth quarter 2002 Concentrations of TPHg and BTEX in <br /> groundwater wells MW4 through MW10 and CW remain consistent with the results from <br /> 1 previous sampling events Detectable concentrations of MTBE were present in wells MW2, <br /> MW3, MW4, MW5, MW6, MW7, and CW It appears 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 /> increased since December 2002 <br /> The vapor extraction system is operating at approximately 79 cfm and petroleum hydrocarbon <br /> vapor concentrations in vapor wells V W 1 and V W2 decreased during the first quarter 2003 The <br /> vapor extraction system is extracting approximately 54 gallons per hour from vapor wells V W l <br /> and VW2 The air sparge system appears to be operating within design parameters <br /> RECOMMENDATIONS <br /> Based on the results of the First Quarter 2003 monitoring event, we recommend the following <br /> • Conduct the Second Quarter 2003 groundwater monitoring and sampling of wells MW1 <br /> through MW 10 and CW and analyze samples for TPHg and BTEX by EPA methods <br /> ' 8015/8020 and MTBE, ETBE, TBA, TAME, and DIPE by EPA method 8260 <br /> • Open vapor wells VW3 and VW4 gradually over the course of Second Quarter 2003 <br /> • Continue monthly monitoring of the vapor extraction, groundwater treatment and <br /> discharge system, and air sparge system <br /> i <br /> w lwordpro1625961quart1y\1gr-2003 doc 8 <br />