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A S S O C I A T E S I N C <br /> CONCLUSIONS <br /> Concentrations from wells MWI through MWIO remain consistent with the results from the <br /> previous sampling event The direction of groundwater flow has reversed direction to the west <br /> from the previous monitoring event, though the gradient is almost flat at 0 002 ft/ft A slight <br /> groundwater mounding has occurred around wells MW3 and MW7 Groundwater elevations <br /> have decreased since September 2003 <br /> RECOMMENDATIONS <br /> Based on the results of the fourth quarter 2003 monitoring episode, we recommend the <br /> following <br /> • Conduct the first quarter 2004 groundwater monitoring and sampling of wells MW 1 <br /> through MW10 and DW and analyze samples for TPHg, BTEX, and MTBE by EPA <br /> method 8015B / 8021B Inspect well box conditions and maintain all well boxes in a <br /> water tight state <br /> • Request MTBE only be screened by EPA method 8020, and if positive, confirm with <br /> EPA method 8260B Because the previous eight (8) quarters results have consistently <br /> . contained no detectable concentrations of ETBE, DIPE, TBA, TAME, 1,2-DCA, and <br /> EDB, ATC requests to discontinue analyzing groundwater samples by 8260 except for <br /> MTBE confirmation analysis as described above <br /> ® Continue to monitor 1 CC and 2CC Effluents on a monthly basis If hydrocarbons are <br /> detected in either of the 1 CC or 2CC Effluents, the carbon will be replaced The Influent <br /> is the same as sample DW The Influent doesn't need to be sampled monthly, so it is <br /> sampled quarterly along with the other wells <br /> • ATC recommends sampling the three domestic wells across Munford Street to the south <br /> of the site This has been done on two prior occasions at approximately one-year <br /> intervals, and it has been approximately one year since the last off-site sampling event <br /> S IEnviromenta11163931REPORTS14gr-2003 doc 5 <br />