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01 S s R <br /> gr <br /> • A S 5 0 C I A T E S I N C <br /> isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed generally towards <br /> the east with an apparent slight depression to the vicinity of the former UST area. The average hydraulic <br /> gradient on July 10, 2003 was calculated to be 0 0003 ft/ft or approximately 17 ftlmtle A summary of <br /> groundwater monitoring data is presented in Table 1 <br /> CONCLUSIONS <br /> Concentrations of petroleum hydrocarbon constituents decreased in the groundwater sample collected from <br /> MW-3 during the third quarter 2003 below levels detected dunng recent quarterly monitoring events The <br /> concentrations of petroleum hydrocarbon constituents detected to the groundwater sample collected from <br /> MW-3 during the third quarter 2003 represent hnstoncally low concentrations for groundwater samples <br /> collected from this well Low concentrations of toluene, ethylbenzene, total xylenes, and TPHg were <br /> detected in the groundwater sample collected from MW-2 Concentrations of petroleum hydrocarbons <br /> remained at nondetectable levels in groundwater samples collected from MW-1, MW-4, MW-5, and MW- <br /> 6 The direction of groundwater flow and magnitude of the hydraulic gradient are generally consistent with <br /> previous quarters <br /> RECOMMENDATIONS <br /> Based on the following, ATC recommends the site be considered for closure <br /> • Petroleum hydrocarbon constituents have never been detected in samples collected from MW4, <br /> MW-5, and MW-6 (downgradnent monitoring well) <br /> • Benzene has never been detected in samples collected from MW-1 and has not been detected in <br /> samples collected from MW-2 since September 1994 <br /> • MTBE has not been detected in samples collected from MW-1 and MW-2 since February 2001, <br /> and July 2001, respectively The concentrations of MTBE detected in samples collected from these <br /> wells have not exceeded the Maximum Contaminant Level for this constituent <br /> • Laboratory analytical results of groundwater samples collected from MW-3 indicate a decreasing <br /> trend in petroleum hydrocarbon concentrations MTBE has not been detected in samples collected <br /> from this well since April 1998 Additionally, the concentrations of benzene detected in samples <br /> collected from this well are low <br /> • It is ATC's understanding that the nearby municipal supply well has been taken out of service and <br /> therefore reduces the potential for impacted groundwater from the site to impact the local drinking <br /> water supply <br /> • <br /> w lwordpro1626051quart1y\3QR-2003 doc 3 <br />