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(3) The thickness of the tunnel lining was determined by a rule of thumb providing 1 inch of thickness for each foot of internal diameter. In this instance slightly more thickness was provided. The tunnel lining was reinforced for a length of 120 feet upstream from the gate chamber. At the upstream end the hoop reinforcement and longitudinal reinforcement consisted of 1-inch-round bars spaced at 15 inches and 3/4-inch-round bars spaced at 19 inches, respectively. The amount of hoop reinforcement was increased in the downstream direction, while the longitudinal reinforcement remained constant. The spacing of the hoop reinforcement bars was uniformly decreased in steps from 15 inches to 6 inches at the end of the reinforced length of the tunnel lining. Also the tunnel was reinforced for a distance of 30 feet near the inlet and outlet portals. One-inch-round bars spaced at 12 inches and 3/4inch-round bars spaced at 12 inches were used for the hoop reinforcement and longitudinal reinforcement, respectively.

(4) The gate chamber and shaft were designed to withstand outside hydrostatic pressures at the maximum reservoir water level. The gate chamber plug was reinforced to resist water loads equivalent to 113 feet of head. An allowable stress of 13,000 pounds per square inch was used for the reinforcement around the gate frame, lining, and transition, Immediately upstream from the gate chamber, the allowable stress in the reinforcement was 18, 000 pounds per square inch.

(5) The valve house roof was designed to carry the dead weight and a snow load of 30 pounds per square foot. A spacing of 12 inches for the 1-inch-round bars was used in the valve house walls for the transverse reinforcement as well as the longitudinal reinforcement.

(6) The channel lining walls and floor were reinforced with two layers of reinforcement bars. A spacing of 12 inches was used for these bars. Each layer provided for transverse and longitudinal reinforcement. In the walls the transverse reinforcement was provided by 5/8-inch-round bars and 3/4-inch-round bars placed in the near and far face layers, respectively. The longitudinal reinforcement consisted of 5/8-inch-round bars placed in both the near and far face layers. The left wall of the channel lining was anchored to the rock with six 1-inch anchor bars. In the floor 3/4-inch-round bars were used in the top and bottom face layers for the transverse reinforcement. For the longitudinal reinforcement 3/4-inchround and 5/8-inch-round bars were used in the top and bottom face layers, respectively.

D. Modifications

20. General. - During construction it became necessary to change the requirements of the specifications and alter plans because of the revised flood hydrograph and because the excavated rock from the spillway would not meet riprap size requirements. Order for changes No. 1 (sec. 23) issued June 20, 1947, directed that the crest elevation of the dam and the line and grade of the spillway be changed from the original drawings and specifications. This change in grade reduced the quantity of suitable rock for dam construction. Accordingly, three sites, designated borrow areas 4, 5, and 6 (sec. 10 and fig. 4), were located that contained suitable rock and were within an economic haul distance. A price per cubic yard for stripping these borrow areas and a price for excavating the rock and transporting it to the dam were stipulated in the order for changes.

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Figure 10.--Gate chamber, shaft, and trashrack structure concrete outlines. (Sheet 1 of 2). -- From Drawings Nos. 222-D-10953 and 10397

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Figure 10. --Gate chamber, shaft, and trashrack structure concrete outlines. (Sheet 2 of 2). --From Drawings Nos. 222-D-10953 and 10397

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Figure 11. --Valve house and stilling basin concrete outline. -- From Drawing No. 222-D-10954

SCALE OF FEET

S-001645

16 Min 19'Av

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Figure 12. --Discharge curves for 4- by 4-foot outlet conduit.

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