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A S S O C I A T E S I N C <br /> ' <br /> 42 Groundwater Analytical Results <br /> esults <br /> ' A groundwater sample was not collected from well MW2 because of the presence of floating free <br /> k product in the well Groundwater samples collected from wells MW5 and DW contained low <br /> concentrations of BTEX constituents, but contained no detectable concentrations of TPHg, <br /> ' MTBE, TAME, ETBE, TBA, or DIPS Groundwater samples collected from wells MW4, MW7, <br /> and MW8 contained moderate concentrations of TPHg and BTEX constituents, but contained no <br /> detectable concentrations of MTBE, TAME, ETBE, TBA, or DIPE <br /> Groundwater samples collected from wells MW1, MW3, and MW6 contained elevated <br />' concentrations of TPHg and BTEX Concentrations of TPHg ranged from 170,000 parts per <br /> billion (ppb) in wells MWI and MW6 to 230,000 ppb in well MW3 Concentrations of benzene <br /> ranged from 4,200 ppb in well MW3 to 10,000 ppb in well MW6 Groundwater samples <br /> collected from wells MWI, MW3, and MW6 contained no detectable concentrations of MTBE, <br /> TAME, ETBE, TBA, or DIPE Analytical results of groundwater samples are summarized in <br /> Table 2 Isoconcentration maps showing TPHg and benzene concentrations in groundwater at <br />' the site are shown on Figures 4 and 5, respectively <br /> 5.0 DISCUSSION <br /> Based on the analytical results and field observations, soil and groundwater at the site are <br /> impacted by TPHg and BTEX None of the soil or groundwater samples collected from the site <br />' contained oxygenate fuel additives The lateral extent of impacted soil has been defined to the <br /> west and north, but has not been defined to the east or south The lateral extent of impacted <br />' groundwater has been defined to the west, but has not been defined to the north, east, or south <br /> In the judgment of ATC, additional site investigation activities are necessary ATC recommends <br /> installing additional soil borings south, east, and north of the existing groundwater monitoring <br /> wells to attempt to evaluate the lateral extent of impacted soil and groundwater ATC <br /> recommends collecting groundwater samples from each boring and submitting them for analysis <br /> Once the groundwater sampling and analysis have defined the lateral extent of impacted <br /> groundwater, groundwater monitoring wells should be installed at least south and east of the site <br /> to monitor the migration of the impacted groundwater Once the lateral extent of impacted soil <br />' and groundwater has been determined, remedial options for the site should be evaluated This <br /> may include pilot testing to determine the most effective remedial option for the site <br /> 1 <br /> w U63931reportslsumii doe 6 <br /> r <br />