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• A S S O C I A T E S I N C The groundwater samples collected from each well were submitted to State-certified Argon Laboratories, Inc (ELAP Cert No 2359) for chemical analysis of TPHg, benzene, toluene, ethylbenzene, xylenes (BTEX) utilizing EPA methods 8015/8020 and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA), tertiary amyl ether (TAME), and di-isopropyl ether (DIPS) utilizing EPA method 8260 ANALYTICAL RESULTS TPHg and/or BTEX were detected above laboratory method detection limits in the samples collected from wells MW1, MW3, MW5, MW6, and MW7 The groundwater samples collected from wells MW2, MW4, MW5, and MW6 contained low concentrations of MTBE ranging from 5 3 parts per billion (ppb) to 17 ppb by EPA method 8260 The groundwater samples collected from wells MW I, MW3, and MW7 did not contain detectable concentrations of MTBE, but the detection limits in the sample in wells MW 1 and MW3 were elevated due to dilutions factors None of the groundwater samples collected contained detectable concentrations of ETBE, TBA, TAME, or DIPE The sample collected from well CW contained no detectable concentrations of petroleum hydrocarbons Groundwater samples from wells MW1, MW3, and MW7 continue to contain elevated concentrations of TPHg and BTEX A summary of analytical results is presented in Table 1 Laboratory data sheets and chain-of-custody documentation are contained • in Attachment 2 GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW1 through MW7, and CW on October 12, 2001 Water levels ranged from 22 40 to 25 63 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 1 47 feet since June 2001 The water level data were used to develop the groundwater elevation contour map (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the northeast The average hydraulic gradient on October 12, 2001 was calculated to be 0 009 ft/ft or approximately 48 ft/mile A summary of groundwater monitoring data is presented in Table I CONCLUSIONS Concentrations of TPHg and BTEX in wells MW1 through MW7 and CW remain consistent with the results from previous sampling events Detectable concentrations of MTBE were present in wells MW2, MW4, MW5, and MW6 It appears there are petroleum hydrocarbons remaining in the soil and groundwater The direction of groundwater flow and the magnitude of hydraulic gradient are generally consistent with the previous event Groundwater elevations have decreased since June 2001 i w lwordpro1625961quart1yl3gr-2001 doe 3