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378-3 Pond <br />• <br />Geology. Sufficient soil and <br />foundation investigations shall be <br />made to determine the suitability <br />of the site for its intended <br />purpose. <br />grained materials for the upstrear <br />two-thirds of the dam and the <br />rocky so i 1 s on the clowrru Lrearn <br />slope. <br />Earth embankment. The minimum top <br />width for a dam is shown in table <br />1. If the embankment top is to be <br />used as a public road, the minimum <br />width shall be 16 ft. for one-way <br />traffic and 26 ft. for two-way <br />traffic. Guardrails or other <br />safety measures shall be used <br />where necessary and shall meet the <br />requirements of the responsible <br />road authority. <br />Table 1. Minimum top width for <br />dams <br />--------- ------------- <br />7otal height of Top width <br />• embankmen=_ _ <br />ft. ft. <br />10 - 15 8 <br />15 - 20 10 <br />20 - 25 12 <br />+Total height is the difference <br />between the top of the dam and the <br />lowest point on the dam <br />centerline. <br />The combined upstream and <br />downstream side slopes of the <br />settled embankments shall not be <br />steeper than five horizontal to <br />one vertical, and the upstream <br />slope shall not be sleeper than <br />2.5 horizontal to one vertical and <br />the downstream slope shall never <br />be steeper than 2 to 1. All <br />slopes must be designed to be <br />stable, even if flatter side <br />slopes are required. <br />When it becomes necessary to use <br />• rocky soils for the embankment, <br />the dam shall be desicned as a <br />"zoned fill," using the finer <br />If needed to protect the slopes of <br />the dam, special measures, such as <br />berms, rock riprap, sand-gravel, <br />soil cement, or special <br />vegetation, shall be provided <br />(Technical Release 56 and 69). <br />The minimum elevation of the top <br />of the settled embankment shall be <br />1 ft. above the water surface in <br />the reservoir with the emergency <br />spillway flowing at design depth. <br />The minimum difference in <br />elevation between the crest of the <br />emergency spillway and the settled <br />top of the dam shall be 4 feet. <br />The height of the dam shall be <br />increased by the amount needed to <br />insure that after settlement the <br />height of the dam equals or <br />exceeds the design height. This <br />increase shall not be less than 5 <br />percent, except where detailed <br />soil testing and laboratory <br />analyses show that a lesser amount <br />is adequate. <br />For dams other than livestock <br />water tanks and/or erosion <br />control, special plans and <br />specifications shall be prepared <br />if the dam is over 10 feet in <br />vertical height measured along the <br />centerline or has a surface area <br />in excess of twenty acres. The <br />plans must be approved by the <br />State Engineer of Colorado before <br />construction starts. <br />SCS. Colorado January 7989 <br />