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APPENDIX 6.4.7-A2 <br /> d' <br /> :hV'* <br /> Figure 4: Model Extents <br /> Terrain Data <br /> The terrain used for the existing conditions model is unchanged from the CHAMP model except <br /> as previously noted in the CHAMP model modifications section. The CHAMP terrain data used <br /> for the existing condition model was developed from the best available survey and topographic <br /> data for the CWCB's Colorado Hazard Mapping Program. This includes post 2013 LiDAR, as <br /> well as bridge and river survey. For additional information please refer to the full CWCB <br /> hydraulic study documentation. <br /> The terrain data for the proposed conditions model used the existing conditions model terrain <br /> apart from the section of the model from WCR-13 to WCR-54. In this section of the model the <br /> overbanks were updated to reflect the proposed terrain of the final conditions of the Amen Pit <br /> area. The terrain surface used to cut cross sections from can be seen below in Figure 5. The <br /> channel geometry was not changed from existing to proposed condition because no channel <br /> work is proposed. To model conservatively, conveyance obstructions were used to fill the pits to <br /> the bankfull height of each pit shown at each cross section. In addition to the proposed gravel <br /> pits, a raised section of terrain was added to the proposed conditions model at cross section <br /> 81882. The determination of the raised surface elevation was part of a separate analysis and is <br /> detailed in Appendix C. Cross section 81882 is presented Figure 6 to show a comparison of <br /> existing to proposed cross sectional geometry, which include the modeled pits, the blocked <br /> obstructions, and the raised terrain created for the mixing plant. <br /> All data used for this model incorporated the following horizontal projection system: State Plane <br /> Coordinate System, Colorado North, NAD 83 (Feet). The vertical datum used was NAVD 88 (ft). <br />