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The output timestep was set at 1 year and allows the user to view model output results on a yearly interval between zero and 100 years For the Initial Conditions table we selected the maximum MTBE concentrations of 34 nulligrams per kilogram(mg/kg)detected to sample P-9 at 8 fbg and 12 mg/kg detected to sample T-lE at fbg The starting MTBE concentration was 34 mg/kg (P-9 at 8 fbg) and concentrations were assumed to decrease by 3,142 mg/kg each foot below 8 fbg ending at a final concentration of 12 mg/kg (T-1E at 14 fbg) Using these values is very conservative and results in a much greater MTBE mass in both soil and groundwater than is actually present beneath the subject site Pro,file Structure: Tables 3 and 4 present the soil texture and soil physical and chemical parameters used in the model For the soil profile, a 15-foot thick layer of silt loam was selected as the soil texture because this appears to be the most representative soil based on the sandy silt and clayey silt identified in well boring MW-1,which is located near samples P-9 and T-1E-The input parameters for bulls density,effective porosity (total porosity m this model), water content, and fraction organic carbon value were based on actual values measured in soil samples collected from well boring MW-1 (see attached Table 2) h •s Chemical: Table 5 presents the chemicalp arameters information used in the model For the MTBE profile,standard MTBE properties were input into the model VLEACH Model Results MTBE Results: The maximum soil MTBE detections occurred during the August 1996 soil sampling activities Although no groundwater monitoring wells were present at that time, we assumed that groundwater was at a depth of approximately 15 fbg which was the actual depth to groundwater during 1998 The maximum MTBE concentration at 8 fbg was 34 mg/kg detected in sample P-9 and soil sample T-lE contained 12 mg/kg MTBE at 14 fbg Using these data we assumed impacted soil extended between 7 and 15 fbg and setup the initial conditions shown for profile I The VLEACH model results for MTBE leaching to groundwater is graphically shown on Figure 1 Note that the VLEACH model output uses soil water at 14 5 fbg to represent the groundwater surface and the resulting MTBE impact The model results for MTBE indicate that after one year, which would correspond to August 1997, the maximum MTBE concentration is observed to groundwater After 10 years the MTBE concentratton decreases by approximately • 0323 3