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<br />u. S, AREY ENGINEBRS REPORT (CONT'D.) <br /> <br />. <br /> <br />spillway crest level), as governed by the capacity of the conduit through <br /> <br /> <br />the existing Sullivan Barrier. <br /> <br /> <br />Storage of the hypothetical flood that might originate in <br /> <br /> <br />the basin below Castlewood is provided by a storage capaoity of 36,800 <br /> <br /> <br />acre-feet (water depth 67.5 feet). Protection is provided on the assumption <br /> <br /> <br />that a flood of a magnitude equal to 125-percent of the reservoir design- <br /> <br /> <br />storm for the entire basin above the site, might occur with the reservoir <br /> <br /> <br />design flood waters already in the reservoir and the outlet conduit inoper- <br /> <br /> <br />ative. To protect the structure against the assumed conditions, 32,200 <br /> <br /> <br />acre-feet of additional storage is provided on top of the 36,800 acr&- feet <br /> <br /> <br />assumed to then be behind the barrier. This fixes the spillway crest level <br /> <br /> <br />at 56-feet above 1,;,e stream-bed, or IB-feet below the top of the dam, and <br /> <br /> <br />fixes the flood storage capacity, below spilbvay crest level, at 69,000 <br /> <br /> <br />acre- feet. <br /> <br />. <br /> <br />. <br /> <br />In addition, 2B,OOO aore-feet of surcharge storage would be <br /> <br /> <br />created before the freeboard to the top of the dam is reduoed to five <br /> <br /> <br />feet, at VIhich time the main overflow spillway would be discharging <br /> <br /> <br />16,000 sec. ft. The main overfl~l spillway, on the right abutment, <br /> <br /> <br />is a semi-ciroular overflow sill 157 feet long with a conduit IB-feet <br /> <br /> <br />in diameter consisting of a vertical shaft to stream-bed elevation and <br /> <br /> <br />a level-grade tunnel to the stilling basin in the stream bed below the <br /> <br /> <br />dam. On the left abutment is a second or emergency spillway at higher <br /> <br /> <br />elevation. It has a flat over-flow crest, 40D-feet wide, at .maximum <br /> <br /> <br />pool level under the hypothetical conditions as mentioned, and is included <br /> <br /> <br />in the plan to provide an additional factor of safety against overtopping <br /> <br />-25- <br />