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<br />e <br /> <br />e <br /> <br /> <br />OUTLET TUNNEL: The outlet tunnel would be extended about 70 feet <br />through the new embankment. 'rhe reservoir outlet works tower will <br />be removed and replaced with a gate structure. A hydraulic gate <br />mechanism that is operated from the dam crest will be included. <br /> <br />SPILLWAY: The present spillway size is not adequate to pass the <br />required flood, so the spillway for the enlarged dam will be <br />increased. The drainage area is about 32 square miles and based on <br />approximate estimates of runoff from thunderstorms from USBR <br />reconnaissance procedures, the PMP would result in a flood of about <br />15,000 cfs. Since the dam is presently an intermediate Class II <br />dam it must pass 50% of the PMP, or about 7500 cfs. Enlarging the <br />dam may change the classification to intermediate Class I which <br />requires 100% of the PMP. This would be addressed during the <br />design phase. <br /> <br />A concrete ogee crest is assumed for the spillway. Using the <br />equation: flow is equal to the length times a flow factor (C) of <br />2.7 times the water depth (freeboard of 7 feet) to the 1.5 power, <br />the spillway length must be 150 feet wide. <br /> <br />The spillway will be raised from the present elevation of 6896 feet <br />to 6925 feet (29 feet) and widened to about 150 feet. The spillway <br />will be constructed on the east abutment. A concrete ogee control <br />section is assumed. The sides of the spillway channel would be <br />vertical on both sides. About 100 feet of the existing spillway <br />channel will be filled to support the ogee concrete structure and <br />prevent erosion under the concrete. A layer of rip rap will be <br />placed over the fill to reduce erosion. <br /> <br />Red Mesa Dam <br /> <br />9 <br />