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STATE OF COLORADO DIVISION OF WATER RESOURCES OFFICE OF STATE ENGINEER SPECIFICATIONS TO GOVERN THE CONSTRUCTION OF A LIVESTOCK WATER TANK Preparation of Foundstioa for Dam--All vegetable matter of every description, including roots to a depth of two feet, shall be removed from the entire area upon which the dant wiL rest, together with boggy or unstable materials and deposited outride the toes of the dam. The banks of the stream channel shall be dressed to a slope of about l[fi:l. A bonding trench, with sloping sides and a bottom width of not less than 5 teat and depth of 4 feet, shall then be excavated beneath the center line of the dam the full length thereof, which trench shall be refilled with the most imper. vious materials available. The foundation of the dam shall then be lightly plowed lengthwise of the dam, to provide proper contact between the foundation and the dam embankment. Placing Df Dam Embaal[menL--The materials shall be placed in the bonding wench and in the embankment of the dam in layers not exceeding 6 inches in thickness, after which each layer shall be thoroughly compacted by a heavily loaded disc cultivator, a corrugated or sheep's foot roller, the treads of a caterpillar or trucks, or by livestock used in the construction. During the construction period, the top of the embankment shall be maintained as a horizontal plane the full width and length thereof, and no side dumping of materials shall be permitted. The materials shall at all times contain sufficient moisture to provide proper compaction. Puddling of material with water shall not be permitted. No frozen material or large clods or stones shall be incorporated in the dam. The upstream face o! the dam shall be constructed with a slope not steeper than 2if2:1, and the downstream face on a slope not steeper than 2:1. The crest or top of the finished dam shall be not less than 8 feet in width. The upstream two-thirds of the dam shall be constructed of the most impervious materials, such as clay loam, or a mixture of clay and sand, and the downstream one-third of more pervious material, such as sand or gravel. The up- stream face of the dam shall be adequately protected against wave action by stone riprap, or other suitable materials when required. Outlet-Should the stale engineer so require, there shall be located beneath the dam an outlet pipe not less than 8 inches in diameter, equipped with a control valve attached to the upstream end of the pipe, together with suitable mechanism for operating the valve. Such outlet pipe shall be provided with cutoff collars. The pipe shall be placed m a trench bottomed in stable formation, and shall be completely surrounded with well compacted impervious materials. Spltlway-For the protection of the dam, an adequate spillway shall be constructed around one or both ends of the dam, of sufficient width to provide a capacity to carry the enure discharge from the drainage basin above the dam during periods o1 unusual runoff. The spillway shall be located in stable formations not easily eroded, and shall extend to a point well downstream from the dam. The following table shall be rued to determine the necessary width of spill- way to meet the above requiremenu. The top of the dam at all poinu shall be not less than 4 feet above the bottom of the spillway. The following table shows the widths of spillways for corresponding drainage areas with an allowance of a mini- mum freeboard between the maximum high water line and top of dam, of 2.3 feet, and maximum velocities of 3.5 feet per second of time. AREAS OF LOW RAINFALL INTENSITY AREAS OF HIGH RAINFALL 7NTE*ISITY AREA OF REQUIRED WIDTX OF AREA OF RLQUIR[D WIDTX OF AR[A OF REQUIRED WIDTH OF DRAINAGE BASIN SPILLWAY"W"AT DRAINAGE BASI N SPILLWAY"W"AT DaA1NAGE BASIN SPILLWAY"W"AT ABOVE DAM NARROWEST POINT ABOVE DAM NARROWEST POINT ABOVE DAM NARROWEST POINT IN ACRES IN FEET In ACRES IN FEET IN ACRES IN FEET 20 8 20 8 100 76 10 9 /0 9 150 81 60 11 60 11 500 50 BO SI 80 16 550 96 lU0 ld 100 b00 105 110 21 120 26 700 117 160 25 110 30 800 129 220 29 160 31 900 110 260 33 160 Si 1000 150 300 35 200 /3 1100 160 350 36 220 16 7200 169 100 /2 210 50 1300 176 150 1/ 260 53 I/00 167 500 16 280 57 1500 196 600 51 300 60 1600 203 700 55 320 63 Ii00 212 F00 59 310 66 IB00 1I9 900 fit 360 70 1900 225 ]000 66 380 77 2000 233 ALL AREAS EAST OF THE CONTINENTAL DIVIDE BELOW AN ELEVATION OF 7000 FEET, ARE CONSID- ERED AS BEING IN THE HIGH RAINFALL INTENSITY ZONE. The above spillway widths ma.• be reduced at a point 50 feet below intake, by 25 per cent, where the spillway is • located tht full length thereof in hard clay or shale, and b5' 50 per cent when located in hard rock formations, if the slope or grade of the bottom is increased accordingly. The grade !or clay and shale formations should be 0.30 foot per 100 feet, and for rock formations 0.90 foot per 100 feet. The width of the entrance to the spillway must in all cases be I one-third wider than shown in the table, and Lhe bottom should slope from the lower end of the funnel section, toward the reservoir 1.0 foot in the distance of 50 feet, and the slope downstream should be 0.25 foot in a distance of ]00 feet. Bortow Pits--Piss, from which materials are taken to build the dam, shall be cleared of all vegetable matter, and no material shall be borrowed within a distance of 50 feet of any part of the dam. haterials excavated from the spill- way, when suitable, may be used in building the dam.