Laserfiche WebLink
<br />.-"-':'~" <br /> <br />;-~ <br /> <br />open channel spillway section would be constructed through the dune sand <br /> <br /> <br />adjacent to Riverside Dam. No channel armoring or grade control would be <br /> <br /> <br />constructed. <br /> <br />. <br /> <br />This alternative will provide for the safe passage of the inflow flood, although <br />significant erosion damage to the spillway channel and probable loss of a portion <br />of the reservoir storage may occur due to erosion and degradation of the spillway <br />channel. The expected depth of channel degradation has not been determined at <br />this time, and so the magnitude of the potential storage loss is unknown. This <br />alternative is the least costly, since no grade/erosion control structures are <br />envisioned. The feasibility of this alternative is dependent upon the result of a <br />scour/erosion analysis of the spillway channel under flood discharge conditions. At <br />this juncture, this is not the preferred alternative due to the unknown depth of <br />possible scour. <br /> <br />The Company's engineer provided technical engineering assistance in cooperation with <br />Riverside personnel in the evaluation of the above alternatives, particularly concerning the <br />size (width) of the spillway and configuration of the grade/erosion control wall(s). The <br />critical design issue is to keep the grade/erosion control walls in place with the event of <br />possibly severe scour of the spillway channel sands downstream from the control walls. <br /> <br />. <br /> <br />Alternative Designs and Construction Cost Estimates are found in Appendix B. <br /> <br />THE SELECTED PROJECT <br /> <br />The company has elected to construct Alternative 2b, an unlined emergency open channel <br />spillway with sheet piling grade/erosion control cutoff walls. A preliminary layout and <br />design is attached in Appendix B. <br /> <br />An open channel spillway would be constructed through the "blow" sand dune hills at the <br />southwest corner of the dam, extending from the normal lake level south to the control <br />crest, and then continuing at a downhill slope toward the South Platte River where the <br />channel would dayligh:. No channel armoring is proposed, although an incidental cover of <br /> <br />. <br /> <br />10 <br />