(3) Steel liners were desirable in the bellmouths and in the conduits leading to the gates to insure smooth, continuous flow boundaries free from surface irregularities that could cause local cavitation.

(4) Slide gates of the type developed for the Bureau's Palisades Dam outlet works provided

excellent, trouble-free regulation of flow through the outlet conduits. A guard gate and a service gate of this same basic design were placed one behind the other in each conduit.

ducts

(5) Twenty-four-inch-diameter connected to a 7-foot-wide by 5-foot-high passage

leading to the downstream face of the plug, and opening into the 41-foot-diameter tunnel supplied adequate air to the top of the conduits just downstream from the control gates.

(6) The conduits downstream from the gates were parallel, horizontal, 7 feet wide, 14.5 feet high, and free from surface irregularities that could produce cavitation. Steel lining extending across the floor and 13 feet up the walls was desirable.

(7) A deflector 6 feet long and 6 inches high, on the floor at the downstream end of the center conduit, directed that outlet's flow on a longer trajectory to produce better flow conditions in the downstream tunnel. (Note: To simplify fabrication of the conduits, this was not included in the prototype construction of the outlets.)

(8) Better flow conditions occurred in the tunnel when the keyway or conic tunnel plug section was replaced by a straight 41-foot-diameter tunnel. This alternative was costly and not justified by the moderate improvement in performance. The keyway section, which was needed for strength in the final tunnel closure, remained as originally proposed.

(9) Unsymmetrical flow releases from the three outlets resulted in side-to-side swinging flow in the circular tunnel. This swinging persisted to the outlet portal. No difficulty occurred in the tunnel due to this action.

(10) Swinging flow affected the direction in which water left the flip bucket at the tunnel portal, and under some operating conditions, water struck the lower portions of the left canyon wall.

(11) Deflecting the left wall of the deflector bucket to the right tended to prevent water from striking the canyon wall. A 20.5-foot deflection worked well for all symmetrical and unsymmetrical outlet flows, but was too severe for the large spillway flows. A sloped left wall of less deflection kept almost all the water off the canyon wall, but was unsatisfactory with spillway flows. A 12.5-foot deflection with a vertical wall allowed an appreciable portion of the water to strike the lower canyon wall during certain outlet flows, but is ideal for spillway flows.

(12) Constructing the deflector bucket in two stages, with only part of the curved invert present during outlet releases, did not significantly decrease

the amount or intensity of water impingement on the canyon wall with either symmetrical or unsymmetrical flows approaching the bucket.

(13) The full bucket with the left wall vertical and deflected 12.5 feet at the downstream end was used for both outlet works and spillway releases. Water will impinge on the lower canyon wall during small outlet releases. In the model the impingement was greatest with certain unsymmetrical flows, and such operation should be avoided wherever possible.

21. STRUCTURAL DESIGN OF DIVERSION TUNNELS. (a) Linings.-The tunnels were lined with a minimum thickness of 15 inches of concrete. The purpose of lining was twofold:

(1) To prevent destructive erosion of the sandstone; and

(2) To obtain the same capacity with the 41-foot-diameter tunnel as that of a larger unlined

tunnel.

The lining of the right tunnel was not reinforced except at the bottom of the construction raise. The lining of the left tunnel was reinforced at the following locations:

(1) The first 20 feet immediately downstream from the trashrack structure for possible water pressures during operation of tunnel plug outlet works.

(2) The high-pressure gate chamber lining; this lining was both rock-bolted and reinforced for grout pressures and gate hanger loads.

(3) The tunnel invert between station 23+68 and station 26+11.72 because of impact and turbulence of discharge from high-pressure gates during operation of tunnel-plug outlet works.

(4) At the bottom of the construction raise.

The lining for the right diversion tunnel is shown on figure 28. The lining for the left diversion tunnel was similar to that shown for the right diversion tunnel.

(b) Trashrack Structure.-The left diversion tunnel trashrack structure was designed for for a differential water load of 40 feet and temperature effects. The roof had a 2-foot 6-inch layer of gravel to

pressures were determined from the laboratory model.

22. 7.0- BY 10.5-FOOT OUTLET GATES AND CONTROLS. (a) Description.-Six 7.0- by 10.5-foot outlet gates were installed in the tunnel plug in the left diversion tunnel to regulate discharges through the three outlets. The gates were used from the time of closure of the right diversion tunnel until discharges could be made through the permanent outlet works at which time the outlet was taken out of service and plugged with concrete.

The gates were manufactured by Yuba Consolidated Industries, Inc., Benicia, Calif., under invitation No. DS-5216. The controls were manufactured by Kendo, Inc., Denver, Colo., under invitation No. DS-5364.

Two 7.0 by 10.5-foot outlet gates, which are identical, are installed in tandem in each of the three outlets; the upstream gate in each pair serves as a guard gate for the downstream regulating gate. Steel liners extend upstream to bellmouth entrances at the plug face, 40 feet from the guard gates, and downstream from the service gates distance of 68 feet to the end of the tunnel plug. Installation and assembly details are shown on figures 31 and 32.

(1) Gates.-Each gate has a steel body and bonnet, a flat, cast steel leaf and cast steel bonnet cover. An oil-operated hydraulic hoist is mounted on the bonnet cover and has a 32-inch-inside-diameter cylinder with a 10-foot 7-inch stroke for operating the leaf. The piston is connected to the leaf by a corrosion-resisting steel stem and bronze nut. Bronze seal bars on the gate leaf bear and slide on nickel-copper alloy seat surfaces in the body and bonnet. The leaf position is shown by a full-scale, direct-reading indicator mounted on the side of each hoist cylinder. The estimated weight of the six outlet gates with hoist cylinders, liners, and anchor bolts is 1,370,000 pounds.

(2) Controls.-A single control cabinet in the gate chamber contains the hydraulic and electrical equipment for operating all six gates and has a single oil tank mounted on the wall of the gate chamber directly above the cabinet. The estimated weight of the controls for the six gates is 4,500 pounds.

(b) Design.

(1) Outlet gates. -All six gates were designed to open or close with full flow under a maximum