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Protection. The crest of the spillway and the downstream run- <br />down will be protected using concrete. The geometric configu- <br />ration of the concrete used to protect the spillway should ccn- <br />form to the dimensions shown on Figure 2.9. <br />Soil cement is also an acceptable form of protection for side <br />channel spillways. The river banks should be protected in <br />accordance with the requirements of Section 2.3 - Riverbank <br />Protection. The crest of the riverside berm will be protected <br />with a layer of riprap and vegetation. The layer of soil <br />cement on the spillway crest must be a minimiun of 2 feet thick. <br />The pitside slope is to be protected with soil cement placed in <br />horizontal layers not exceeding 8 inches in thickness and <br />between 8 and 12 feet wide. The soil cement should conform to <br />the requirements of Section 2.4.3 - Soil Cemerit. The geometric <br />configuration of soil cement for stabilizing side channel <br />spillways should conform to the dimensions shown on Figure <br />2.10. <br />2,5 LATERAL BERMS <br />Lateral berms are berms constructed, or left in place, between pits <br />and are perpendicular to the general direction of flow of the Sout!'. <br />Platte River. These lateral berms separate gravel mining pits from <br />one another. Lateral berms may be overtopped during major floods. <br />Ffien overtopped, the berms are subject to erosion due to the rela- <br />tively high velocity flow and, in time, may fail resulting in a rapid <br />release of water. This phenomenon can propagate in the downstream <br />direction potentially increasing with each successive failure. By <br />protecting lateral berms from catastrophic failure the likelihood of <br />such downstream propagation can be significantly decreased. <br />UD6FCD GRAVEL GUIDELINES 12,x17/87 <br />2-23 <br />