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<br />- 23 - <br /> <br /> <br />0:2212 <br /> <br />.' <br /> <br />The principal spillways will be reinforced concrete pipe and <br />will be equipped with an ungated, reinforced concrete riser to the <br />height of the expected level of sediment deposition at the upstream <br />face of the dam as shown on Figure 3. Release rates of these spillways <br />are within the limits of Colorado State policies, Both structures <br />will release the maximum design storm volumes in less than 48 hours. <br /> <br />Criteria for the emergency spillways is in accordance with <br />Soil Conservation Service Engineering Memorandum No. 27, SCS <br />Technical Release No.2., and Section 3.21 of the Soil Conservation <br />Service National Engineering Handbook, Section 4, Supplement A. <br /> <br />The geologic and topographic conditions and "cut" and "fill" <br />relationships are suitable for earth spillways. <br /> <br />. <br /> <br />Liberal structural design and unit costs were used in estimating <br />floodwater-retarding structure costs. Embankment slopes of 3t:l and <br />2t:l were used for this evaluation. Berms and drains were included <br />in the planning cost estimates. Cost estimates for both the floodwater- <br />retarding structures and the diversion are based on current bid <br />prices and data supplied by the Lincoln Engineering and Watershed <br />Planning Unit. <br /> <br />Structural costs of removing and replacing the concrete floor <br />in the closed conduit structure FPC-l Chan., are based on current <br />bid prices of similar projects under contract by the Colorado State <br />Highway Department. The structural design for the stilling basin <br />located at the exit section of structure FPC-l Chan. was based on <br />criteria set forth in the Soil Conservation Service National Engineering <br />Handbook, Section 14. Structural quantity estimates were based on a <br />standard design for a St. Anthony Falls (SAF) stilling basin. <br /> <br />f' <br />