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i A S S O C I A T E 5 I N C wells MW2, MW4, MW5, and MW6 contained concentrations of methyl tertiary butyl ether (MTBE) ranging from 11 parts per billion (ppb) to 26 ppb by EPA method 8020 The presence of MTBE was not confirmed by EPA method 8260 The groundwater samples collected from wells MWI, MW3, and MW7 did not contain detectable concentrations of MTBE, but the detection limits in these samples were elevated due to high concentrations of TPHg and BTEX The sample collected from well CW contained no detectable concentrations of petroleum hydrocarbons Groundwater samples from wells MWI, 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 MWI through MW7, and CW on March 1, 2001 Water levels ranged from 21 35 to 24 12 feet below the tops of the well casing elevations, representing an average increase in the water table elevation of approximately 0 16 feet since November 2000 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 March 1, 2001 was calculated to be 0 006 ft/ft or approximately 32 ft/mile A summary of groundwater monitoring data is presented in Table I CONCLUSIONS Concentrations of TPHg and BTEX in wells MWI 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 although these results were not confirmed by EPA method 8260 It appears as though there are petroleum hydrocarbons remaining in the soil The direction of groundwater flow and the magnitude of hydraulic gradient are generally consistent with the previous event Groundwater elevations have increased since November 2000 RECOMMENDATIONS Based on the results of the First Quarter 2001 monitoring episode, we recommend the following Conduct the Second Quarter 2001 groundwater monitoring and sampling of wells MWI through MW7 and CW and analyze samples for TPHg, BTEX, and MTBE by EPA methods 8015/8020 Any detectable concentrations of MTBE will be confirmed by EPA method 8260 w\625961quardy%Igr-2001 duc 3