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v o <br /> A S S O C I A T E S I N C <br /> TPHg and BTEX removed from the groundwater at the site between December 19 and December <br /> 27, 2002 <br /> Concentration of TPHg in influent water sample <br /> = 61 000 ug TPHq x 1 kq x 3 78 L x 7,510 gallons since startup of system <br /> 1 L Water 1,000,000,000 ug i gallon <br /> 1 73 kg TPHg x 1 Ib = 0 79 pounds of TPHg removed since startup of system <br /> 22kg <br /> Concentration of total BTEX in influent water sample <br /> = 15.190 uci BTEX x 1 kq x 3 78 L x 7,510 gallons since startup of system <br /> 1 L Water 1,000,000,000 ug 1 gallon <br /> = 0 43 kg BTEX x 1 lb - 0 20 pounds of BTEX removed since startup of system <br /> 22kg <br /> CONCLUSIONS <br /> Concentrations of TPHg and BTEX in groundwater wells MW1 through MW10 and CW remain <br /> . consistent with the results from previous sampling events Detectable concentrations of MTBE <br /> were present in wells MW2, MW4, MWS, MW10, and CW It appears there are petroleum <br /> hydrocarbons remaining in the soil and groundwater The direction of groundwater flow and the <br /> magnitude of hydraulic gradient are generally consistent with the previous event Groundwater <br /> elevations have decreased since October 2002 <br /> The vapor extraction system is extracting approximately 38 gallons per hour from vapor wells <br /> V W 1, V W2, V W3, and V W4 Field measurements with a photoionization detector (PID) during <br /> the December 27, 2002 event yielded lower than expected VOCs concentrations in all vapor <br /> wells and the influent It is ATC's opinion that the high vacuum in the vapor wells could be <br /> causing a mounding effect of groundwater in the vapor wells and is blocking portions of the <br /> screen interval and preventing VOCs from being extracted from the vadose zone <br /> RECOMMENDATIONS <br /> Based on the results of the Fourth Quarter 2002 monitoring event, we recommend the following <br /> • Conduct the First Quarter 2003 groundwater monitoring and sampling of wells MW1 <br /> through MW10 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 /> • <br /> w lwordpro1625961quart1yl4gr-2002 doe 6 <br />