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<br />Emergency Spillway <br /> <br />All emergency spillways shall be located on undis- <br />turbed earth and shall incorporate a longitudinal level <br />section at least 50 feet long. Side slopes shall be 2: I or <br />flatter. See Table 8 for spillway design. Widths shall be <br />such that Hp will not exceed 1.3 feet on silty or sandy <br />soils and 2 feet on other soils. <br /> <br />Embankment <br /> <br />The minimum top width shall be 10 feet for dams less <br />than 10 feet high, 12 feet for dams exceeding 10 feet. <br />The height is measured from the low point in valley <br />floor to the top of the dam. <br /> <br />Side slopes shall be 3: I both upstream and downstream. <br /> <br />A cutoff to relatively impervious material shall be pro- <br />vided under the dam except where such material exists <br />at the surface of the foundation. <br /> <br />The minimum cutoff trench bottom width shall be 10 <br />feet. Side slopes shall be stable and not steeper than I: I. <br />The embankment shall be constructed to a height 5 <br />percent greater than designed to allow for settlement. <br /> <br />TABLE 8 <br /> <br />Emergency Spillway Design <br /> <br />(based on 3:1 side slopes, level inlet channel, 100 feet <br />long <br /> <br />Bottom Q in ds <br />Width <br />(ft) H, = 1.0' Hp = 1.5' H, =2.0' <br />10 13 35 72 <br />20 24 64 128 <br />30 36 93 183 <br />40 47 122 238 <br />50 59 152 294 <br />"Ve" 3.35 4.55 5.6 <br />'In" .050 .045 0.040 <br /> <br />For inlet channel 50' long, subtract 0.1' from Hp value <br /> <br />For inlet channel 150' long, add 0.1' to Hp <br /> <br />"Vc" refers to velocity at the control section <br /> <br />"Hp" indicates depth of water measuredfrom crest of <br />emergency spillway to water/evel in pool. <br /> <br />Construction <br /> <br />The foundation area shan be cleared of an trees, <br />stumps, brush, roots, boulders, sod and debris and then <br />scarified. An channel banks and sharp breaks shan be <br />sloped to I: I or flatter. <br /> <br />The material used for fill shall be free of sod, roots, <br />frozen soil, stones over 6 inches in diameter and other <br />objectionable material. Suitable fill material at proper <br />moisture shan be placed in approximately horizontal <br />layers not exceeding 8 inches in thickness before com- <br />paction. The construction equipment shall be operated <br />over each layer in a way that will result in the required <br />compaction. Selected backfill material shall be placed <br />around the conduit in layers 4 inches thick and each <br />layer thoroughly compacted. <br /> <br />Construction operations shall be carried out in such a <br />manner that erosion and air and water pollution will be <br />minimized and held within legal limits. Safety measures <br />such as warning signs, required due to location will be <br />planned for. <br /> <br />62 <br />