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z s ~~ 2 ~~ ~~~ STATE OF COLORADO DNISION OF WATER RESOURCES OFFICE OF STATE ENGINEER TO GOVERN THE CONSTRUCTION OF AN EROSION CONTROL DAH Pteparatim of Famdatian fa Dam-All vegetable matter of every description, including toots ro a depth of two feet, shall be removed from the entire area upon which the dam wrll test, together with boggy or unstable materials and deposited outside the toes of the dam. The baalts of the stream channel shall be dressed ro a slope of about 1;:1. A curoff [teach, with sloping sides acrd a bottom witlth of not less than 5 feet and depth of 4 fee4 shag then be exnvated beneath the center line of the dam the full length thereof, which trench shall be tefr7led with the most impervious tnatetials avar7able. The foundation of the dam shall then be lightly plowed lengthwise of the dam, ro pnrvide proper contact between the (ouadation and the dam embanlmerrt. Ple®g of Dam Emh®Irmmt The materials shall be placed in the cutoff f[et]ch and is the ®banlmlmt of the dam is layers not ezoxdiag 6 inches in thirlmess, after which each layer shall be thoroughly compacted by a heavily loaded disc cultivator, a cornrgated or sheep's foot roller, the treads of a nterprTlar or [tor]ts, or by livestock used is the coastrvetioa During the coasttuction period, the top of the embanl®mt shall be maintained az a horizontal plane the full width acrd length thereof, and no side dumping of materials shall be pemtitted. The materials shall at ell times contain suffiden[ moisture ro provide proper compaction. Puddling of tnatexial with water shall not be permitted. No frorm material or large clods or stones shall be incorpotated in the darn. The upmeam face of the dam shall be coasaircted with a slope not steeper than 2;:1, acrd the downstream face oa a slope not steeper than 2:1. The nest or top of the furished dam shall be not lea than 8 feet in width. The upstream two-thirds of the dam shall be constnsted of the most impervious materials, such az clay loam, err a m+.n•w of clay acrd sand, and the downstream otu•-third of more pervious material, such as sand or gravel. 13e upstream fam of the dam shall be adequately protected agaimt wave action by stone riprap, or other suitable materials when required. Omlet-'lhae shall be looted beneath the dam an ungated outlet pipe not less than 12 inches in diameter and large enough ro drain within thirty-six bouts arty impourulatert[ in ercea of two acre-feet. Such outlet pipe shall be provided with cutoff collets. The pipe shall be placed is a trench bottomed in stable formation, and shall be completely surrounded with well compacted impervious ma[nia]s. Spillway-For the protection of the dam, an adequate sp171way shall be conae,....hri etouad one or both ends of the dam, of suffidmt width ro ptvvide a tapadty to carry the more discbarge from the drainage basin above the dam during periods of unusual ivnoff. The sprlway shall be to®ted in stable formations not east7y eroded, and shag extend to a point well downmeam from the dam. The following table shall be used to determine the treocaary width of spillway ro meet the above requirements. The top of the dam at all points shall be not lest than 4 feet above the bottom of the spillway. The following table shows the widths of spillways for corresponding dremaga areas with an allowance of a minimum freeboard between the maximum high water line and top of dam, of 2.3 feet, and maximum velodties of 35 feet per second of tune. AREAS OF LOW RAINFALL INIFJrSIIY AREAS OF H1GH RAINFALL IN)FNSfT}' AsFwoFavwAt;EeASx ~wsmwemloFrruwAr A1EAfftxW11CE6A71 f®tlt~MSm7W AtFwoFtstssw;Eeaai ts~ls~MOn+aF ABnYE aW Nw669 wAT NMii0wE4rFOMrM A90Y5 n11YNAtiei Bt1nAlArw AT W1ROWPrir Aa0YE n11Y NACIB{ 6PlrMArw AT lMrii0YlESt fi£r fOrr N f$7 rVlt M Flit e m X66 s b 0 b 0 t!0 M e0 11 EO 71 600 m eo a eo 1e abo ee 1m 1e 1m a em 1m Ib 21 120 26 7m 117 160 2! 1b >D em 1a4 z2o a9 1m 2a ea0 1N 2e0 11 16(1 27 1m0 160 2ao m 2ao u 11m 1e0 coo ~ 220 +e 12m lee X00 42 2q !0 1000 176 lt0 M 2e0 W 1N0 let ben t0 2m !7 1500 lee em !I 200 e0 1em 2m 7m SS 27D e2 17m 212 em se 2~0 ee 1em 210 em e2 2eo ro 1900 22! tom ea 2eo n tam w ALL AREAS EAST OF THE CONTINENCAL DNIDE BELOW AN ELEVATION OF 7000 FEET, ARE CONSB)ERHD AS BEING IN THE HIGH RAINFALL INTENSITY ZONE. The above spillway widths may be reduced at a point 50 feet below intake, by 25 per cent, where the spillway is located the full length thereof in hard clay or shale, and by 50 per cent when ]orated in hard rock formatiotss, if the slope or grade of the bottom is irlQeased accordingly. The grade for 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 mtram to the spillway must in all cases beone-third wider than shown in the table, and the bottom should slope from the lower end of the funnel section, toward the resnwir 1.0 foot in the distance of 50 feet, and the slope downstream should be 025 foot is a distance of 100 feet. Borrow Pits-Pits, from which materials are taken to build the dam, shall be cleared of all vegemble nutter, and tw material shall be borrowed within a distanre of 50 feet of any part of the dam without approval. Materials excavated from the spillway, whmlvimble, may be used in building the dam.