Mud Mountain Outlet Structure: Hydraulic Model Investigation

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Mud Mountain Outlet Structure: Hydraulic Model Investigation

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Tate, Charles H. Jr.

Modifications to the outlet works at Mud Mountain Dam have been proposed to meet dam safety criteria. As part of the project, a new intake tower is proposed that will contain the entrances and transitions to the 9-ft-horseshoe and the 23-ft-diam flood control tunnels. The three fixed-cone flow control valves on the existing 23-ft-diam tunnel will be replaced with upstream tainter gates, and the tunnel will have open channel flow, A 1:30-scale model of the proposed 23-ft-diam tunnel was constructed to detennine the flow conditions associated with the proposed intake tower and the 23-ft-diam tunnel exit structure. The intake tower was modified several times based on value engineering suggestions and seismic constraints. Vortex conditions were documented for the various designs, and vortex suppression devices were developed for the worst conditions, Pressures were measured in the three bell-mouthed intakes to the tunnels. Flow conditions downstream of the tainter gates were documented, and the original design connecting curve between the new and existing sections of the 23-ft-diam tunnel was modified for improved flow conditions and a significant construction savings. Flow through the existing tunnel was documented. The exit structure was modified to direct the flow into the center of the exit channel. Pressures and water-surface profiles were documented through the recommended exit structure.