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Mr Jeffrey Wong Page 9 of 10 6.0 CONCLUSIONS AND RECOMMENDATIONS 6.1 Conclusions • Groundwater, vadose soil and saturated soil in the vicinity of the former UST are significantly impacted by gasoline hydrocarbons No gasoline oxygenates were detected in the soil or groundwater However, the fuel additives EDB and 1,2 DCA are present in groundwater • The vertical extent of significant soil contamination has been defined Soil contamination of significance does not appear to exist below a depth of 80 feet bgs where only traces of BTEX compounds were previously detected in boring SB1/MW1 In boring SB6, hydrocarbons were not detected in the soil sample collected at 90 feet and only traces of toluene and xylenes were found in the sample from 105 feet The low levels of TPHg and BTEX detected in the samples from 100 feet and 110 feet in boring SB6 may be a result of the greater permeability of the soil at those depths and the effects of withdrawing the samples through the column of highly contaminated water in the drill string • Except in the northern portion of the site the lateral extent of soil contamination has been defined The presence of moderately low levels of gasoline hydrocarbons to soil samples collected from well MW4 at the depths of 20 and 30 feet is postulated to be a result of past elevation fluctuations of contaminated groundwater • Groundwater flow direction at the site appears to be highly variable, and the groundwater gradient appears to be relatively flat • The base of groundwater contamination is undefined Moderately high levels of petroleum \� hydrocarbons were found to extend to depths of 98 feet bgs although cross contamination of the, discrete samples cannot be ruled out • The lateral extent of groundwater contamination is not defined Peripheral wells MW2, MW3 and MW4 contain elevated levels of petroleum hydrocarbons • High concentrations of TPHg and BTEX in well MW1 suggest that free product may develop, however, none was observed during groundwater sampling 6.2 Recommendations Ground Zero recommends conducting a minimum of two quarters of groundwater monitoring and sampling in order to evaluate and confirm groundwater flow direction and contaminant levels Subsequent to data analysis from the events, additional monitoring well(s) may be advanced at the site in order to further delineate the extent of the groundwater contaminant plume datllgronnzelhvryslwe11repor1 doc