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The existing outlet works access well would be capped with concrete <br />and sealed off with compacted fill. The two outlet conduits would be <br />separated from each other at the well by carrying the dividing wall through <br />the well. This would permit one conduit to be inspected while water was <br />carried in the other. <br />The writers wish to point out that the above conduit modifications <br />would permit steel pipe liners to be installed in the conduits at some <br />future date. Furthermore, the method of sealing the outlet works well <br />would permit future use as an inspection manhole or even a supplemental <br />overflow spillway, should either be desirable. <br />Spillway <br />The emergency spillway would be used very infrequently because of the <br />small natural drainage basin and relatively large outlet works capacity. <br />The potential inflow flood from drainage basin runoff is estimated to be no <br />more than 600 cfs for a return period of once in 200 years. <br />The spillway will be a side channel type with the overflow water reach- <br />ing the stream approximately 1,200 feet downstream from the primary dam <br />embankment. It will consist of a riprapped approach channel with bottom <br />elevation of 10,085 feet, a bottom width of 115 feet, and 3:1 side slopes. <br />A reinforced concrete cutoff and erosion control wall will act as a weir <br />having a crest length of 125 feet and a discharge coefficient of approxi- <br />mately 2.7. <br />The design flood could be passed with a head of 3.0 feet over the weir <br />crest, leaving 5.0 feet of freeboard on the dam for wave action resistance. <br />The cutoff wall will be sealed and protected with compacted fill and <br />grouted riprap. The downstream emergency channel will have a grade of <br />approximately 13 percent and be riprapped both on the bottom and sides. <br />Downstream from the riprapped spillway channel the natural drainage <br />way will not be modified in order to help retain the natural setting of <br />the area and for economy reasons. Some erosion would be experienced in <br />the natural side channel under flood conditions exceeding perhaps several <br />hundred cubic feet per second for one or two hours. <br />5 <br />