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APPENDIX 6.4.7-A2 <br /> values range from 0.05 to 0.08. Additionally, the road roughness used in the model is 0.016. <br /> The proposed conditions model used the same roughness values as the existing conditions <br /> model, apart from where the pits are in the cross sections. In these locations the roughness <br /> values were updated to be 0.035. <br /> Boundary Conditions <br /> The same boundary conditions were used for both the proposed and existing condition models. <br /> Hydrologic inputs for this project were obtained directly from the 2016 effective Flood Insurance <br /> Study. Downstream boundary conditions were obtained from a normal depth calculation based <br /> on slope. Table 1 lists all the boundary conditions and flow changes used in the analyses, <br /> which included the 100-year, 50-year, and 10-year events. <br /> Table 1: Boundary conditions shown for the analyses performed <br /> Recurrence Interval Upstream Boundary Flow Change at Downstream Boundary <br /> Condition —Total XS 81549 —Total Condition — Normal <br /> Flow cfs Flow cfs Depth (slope) <br /> 10- ear 3800 3,600 0.001500 <br /> 50-year 8800 7,600 0.001822 <br /> 100-year 11150 10,000 0.002087 <br /> To avoid potential errors in the hydraulic results at the project location from using the normal <br /> depth calculation method, the furthest downstream cross section was placed over 4000 feet and <br /> 10 cross sections away from WCR 54. To ensure the boundary was placed sufficiently far <br /> enough downstream a sensitivity analysis was performed. In the sensitivity analysis a maximum <br /> and minimum potential slope was input for the downstream boundary conditions normal depth <br /> calculation. The model was then ran and the results were checked to ensure that no changes <br /> could be seen in the hydraulic results at the project site. The maximum slope and minimum <br /> slopes used for the sensitivity analysis were 0.00459 and 0.00083, respectively. These values <br /> were chosen based on maximum and minimum friction slopes seen downstream of Weld <br /> County Road 54. The results of the sensitivity analysis revealed that the downstream boundary <br /> was sufficiently far enough away from the project site so that no changes in water surface <br /> elevation were seen at the area of interest. Profile lines from the sensitivity analysis can be seen <br /> below in Figure 7. <br />