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<br />, <br /> <br />4. The left bank levee would originate approximately 4,000 feet <br />upstream 9f the U.S. Highway 50 bridge across the Arkansas River. <br />The al ignment woulo parallel Colorado State Highway 194 on the south <br />side, cross U.S. Highway 50, and then curve to high ground approximately <br />1,200 feet east of the highway. An outlet structure would be provided <br />through the levee for the disposal of interior drainage waters but no <br />ponding area would be required. The engineering features of the plan <br />are discussed in greater detai I in the fol lowing paragraphs and are <br />listed in table I. The general plan is shown on plate I. Plans, pro- <br />fi les, sections, and other detai Is are shown on plates 2, 3, 4, and 5. <br /> <br />5. LEVEE DESIGN.- The levees would be constructed of random <br />earthfi I I to provide 4 feet of freeboard above the design water sur- <br />face for a discharge of 140,000 c.f.s. The cross section would be <br />trapezoidal with a 12-foot crown width and I on 2 side slopes. The <br />right bank levee would be surfaced with a 6-inch gravel course to <br />provide a maintenance road and to insure access by equipment to pos- <br />sible danger points during high river flows. The 12-foot crown width <br />is recommended because it would al low greater maneuverabi I ity and more <br />efficient operation of equipment than a narrower crown. Material for <br />the levee embankment would be excavated generally from the riverside <br />of the levee. There are ridges in the channel section where excavation <br />would be required to provide continuity of river channel waterway. <br />This material also would be uti I ized in the levee embankment. Pro- <br />tective works would be installed at curves in the levee alignment, at <br />locations where the levee would be adjacent to the existing river <br />channel, and also at the right bank bridge approaches. These works <br />would consist of double-row flexible steel jetties with anchors at <br />125-foot intervals. <br /> <br />6. HYDRAULIC DESIGN.- A study of the hydraul ic characteristics <br />of the Arkansas River channel indicated that with the right bank levee <br />in place, the capacity of the Arkansas Valley Branch line rai Iroad <br />bridge would not be adequate to pass the desisn f low of 140,000 c.f.s. <br />This deficiency would be corrected by improving the hydraul ic charac- <br />teristics of the channel and modifying the bridge. The existing deck <br />plate girder br i dge wou I d be reconstructed to prov ide. 3 feet of c lear- <br />ance above design water surface without changing the existing grade of <br />the track. Detai Is of the proposed bridge alteration are shown on <br />plate 4. <br /> <br />7. The capacity of the existing U.S. Highway 50 bridge across <br />the Arkansas River is not adequate to pass the design flow of 140,000 <br />c.f.s. However, the structure is considered obsolete from a traffic <br />standpoint by the Colorado Department of Highways and is to be replaced <br />as a part of its regular construction program. The Department has <br />advised that they wi I I design the new bridge to provide the required <br />waterway opening but that actual programming of construction is con- <br />tingent upon authorization of the proposed local protection project <br />and the actual starting and completion dates of construction. Since <br /> <br />A-2 <br /> <br />R 1/28/64 <br />