MANIFOLD DESIGN Power Penstock and Outlets 78 8: Max. head 346 ft. 150 psi including waterhammer. pipes. Reinforcement around transitions and valves to be Nominal reinforcement required except for 26 ft. dia. Outlet Manifold and Outlets 1 to 6 inclusive: Max. head 238 ft. 103 psi. Pipes are designed for the full Reinforcement around transitions for outlets 1, 2, 5 and 6 Erection and Testing: Concrete ring supports designed as stiffeners to maintain cylindrical shape of pipes. TYPICAL CROSS SECTION 100 psf in two end panels (Outlets 1 & 2). 50 psf on remainder. Earthquake 5% of dead load applied horiz. at center of gravity of load. El. 53981 1-160*%! -320*% 5. Crane thrust upstr. on upstr. column 6. Earthquake forces acting upstream -and reverse. Structure assumed kept rigid longitudinally by brick walls. Add 15% impact Figure 71.--Structural design data for the outlet works control house and manifolds. 19-0° Min. 25-0 Max. 47. Superstructure. The superstructure of the control house is a concrete frame with reinforced grouted brick masonry walls and grouted brick veneer walls. The reinforced grouted brick masonry walls are 12-1/2 inches thick except for the west wall and approximately 20 feet of the west end of the south wall which are grouted brick veneer walls. The walls are similar to those of the powerhouse, except they are anchored to the concrete frame by stone anchors in metal slots. The brick walls are approximately 24 feet high with a maximum span of 19 feet. The grouted brick veneer walls are 13 inches thick, composed of an 8-inch concrete interior face and a 5-inch grouted brick exterior face. The grouted brick veneer is not reinforced. However, it is tied to the concrete with stone anchors in metal slots. Since the control house was close to and at the bottom of the steep canyon wall at the west end of the powerplant, the space between the canyon wall and the plant could become snowpacked. Therefore, the west wall was designed to withstand this additional load, which resulted in the requirement of the grouted brick veneer wall. Figures 65 and 72 show the control house. For additional details see drawings 456-D-128, 456-D-1025, and 456-D-1026.* 48. Heating and Ventilating System. The control house is equipped with natural convection and unit electric heaters with capacity to maintain the interior of the house above the freezing point. Portable heaters are also provided. The pump chamber is also equipped with portable heaters. E. River Diversion During Construction 49. Diversion Flows. Since the construction of Palisades Dam and appurtenances would extend over a period of several years, the design arrangement of the structures which were to bypass the river flows and the sequence of construction and interim river handling were dictated by the runoff characteristics of the river and by the downstream irrigation requirements from upstream irrigation storage reservoirs. Flood flows on the Snake River are limited to the spring and early summer. As noted in section 22e, the probable peak flows of floods up to the 25-year frequency could approach 50,000 second-feet, with accompanying flood volumes totaling up to 2,000,000 acre-feet. Irrigation releases from Jackson Lake Reservoir up to a maximum of 15,000 second-feet, which would need to be passed around the Palisades construction, were to be expected during the irrigation season from April 1 through October. At other times, normal river flows had to be passed around the construction site. From November through March, the normal flows were expected to average between 2,000 and 3,000 second-feet, although in past times flows up to 6,000 second-feet had been experienced. 50. Diversion Plan. - To effect diversion during the major period of the construction, the two 26-foot-diameter outlet and power tunnels were utilized for bypassing the river flows. These tunnels were constructed at the grade of the river and were provided with approach channels and tunnel adits to admit diversion from the river upstream. Temporary walls and guide channels were provided at the downstream end of the tunnels to direct the flows into the previously completed stilling basin and then back to the river. Prior to diversion through the tunnels, the contractor was permitted to pass the river flows over such portions of the dam embankment as already had been constructed in the cutoff trenches, and was allowed to utilize portions of the embankment as cofferdams. During diversion through the tunnels, the contractor was permitted to divert across temporary blockouts in the tunnel lining and through temporarily lined channels constructed downstream from the tunnels. During the nonirrigation season when both tunnels were not needed to pass diversion flows, the contractor was permitted to divert through only one tunnel so that he might install the manifold piping and embedments and certain of the gates and valves at the other tunnel exit. Finally, for closure operations, the contractor was permitted to divert through any of the already completed portions of the outlet works and power penstock installations. 51. Diversion Capacity. - A diversion capacity curve showing the discharge versus upstream reservoir stage for each diversion tunnel is shown on figure 53. This *Not included. curve shows the discharge capacity of the tunnels with the closure plug omitted and with the temporary channel constructed beyond the downstream portals of the tunnels. Routing of the 25-year frequency flood noted in section 22e through the tunnels at this stage of construction resulted in a maximum upstream level at elevation 5450 and a maximum discharge of 47,000 second-feet. With the installation of the manifolds and controls the diversion capacities of the diversion tunnels would be reduced. The discharge capacities for the condition of flow after the downstream facilities have been installed are shown on figure 52. 52. Model Tests. Since the diversion tunnels were not positioned symmetrically with the downstream stilling basin, a temporary channel was needed to connect the tunnels to the basin. This channel required deflector and guide walls to adequately direct the flows into the basin. Hydraulic model tests 8/, 9/ were conducted to study the flow pattern through the connecting channel, to determine the positioning of the guide and deflector walls, and to evaluate the stilling action in the downstream basin. 8/"Hydraulic Model Study of the Penstock and Outlet Diversion Channels-- Palisades Dam," Hydraulic Laboratory Report No. HYD-345, January 25, 1952. 9/"Hydraulic Model Studies of the Palisades Dam Outlet Works and Spillway," Hydraulic Laboratory Report No. HYD-350, June 22, 1956. CHAPTER V--Design--POWER PENSTOCK AND OUTLET PIPES 53. General Description. The penstock system consists of a concrete-lined power tunnel 26 feet in diameter, and a steel pipe manifold with four 14-foot-diameter penstock branches and two 12-foot-diameter outlet pipe branches (outlets 7 and 8). The outlet pipe system consists of a similar concrete- and steel-lined outlet tunnel 26 feet in diameter, which runs parallel to the power tunnel, and a steel pipe manifold with six outlets numbered 1 through 6. The four penstock branches terminate in the powerhouse, and the eight outlets terminate in the outlet control house, as shown on figure 73. Water enters the tunnels at the intake structure on the upstream side of the dam. The tunnels are steel lined from station 10+12 to the portal, as shown on figure 182. The penstock and outlet pipe manifolds downstream from the tunnel portals are completely encased in concrete. The penstock and outlet pipe systems were installed under specifications No. DC-3675, and the fabrication of the penstock and outlet pipe manifold was performed under specifications No. DS-3839. The intakes of the power and outlet tunnels each have a fixed-wheel gate which serves as an emergency shutoff or as a service gate to permit unwatering of the penstock or outlet pipe system for inspection and maintenance; the intakes are protected by trashracks. Flow in each penstock branch is controlled by a 186-inch butterfly valve bolted to the downstream end. In each turbine inlet pipe between the butterfly valve and the turbine spiral case, a sleeve type coupling is installed to allow temperature movements and to permit the removal of the butterfly valve. Regulation of flow through outlets 1, 2, 5, and 6 of the outlet pipe system and outlets 7 and 8 of the penstock system is by means of 7-foot 6-inch by 9-foot outlet gates in the control house. Each regulating gate has a guard gate of the same size and type upstream from it. Outlets 3 and 4 of the outlet pipe system are equipped with 96-inch hollow-jet valves which are guarded by 96-inch ring-follower gates. An 18-inch drain and filling line, taking off from the bottom of the three-way wye of the outlet pipe manifold, connects with the bottom of the penstock manifold just upstream from the penstock branch for unit 1, as shown on drawing 456-D-309*. Where the 18-inch pipe passes through the pump sump in the outlet manifold anchor block, an 18- by 18- by 14-inch tee connects the drain and filling line with the suction side of a 3, 700-g. p. m. deep-well pump unit. A 14-inch gear gate valve is installed in the pump suction line. On each side of the pump suction tee connection, an 18-inch gear-operated gate valve is provided in the drain and filling line to permit shutting off the connections with the penstock or outlet pipe header, respectively. The pump discharges into the stilling basin through a 14-inch pipe. At the horizontal centerline of the penstock branch for unit 1 and in the 16-foot-diameter branch pipe of the outlet manifold, 8-inch nozzle connections are provided for a powerplant water supply system as shown on drawing 456-D-390*. A 30-inch-diameter air vent in the intake structures of the power and outlet tunnels admits or releases air during filling or unwatering. In addition, a 6-inch combination vacuum and automatic air release valve is provided upstream of the penstock branch for unit 1 and in the three-way wye of the outlet manifold for venting during filling and unwatering and to release air which may accumulate during operation in the pockets formed by the contours of the manifolds. The 6-inch blind-flanged nozzles and piezometer connections in the penstock branch for unit 2 are intended for testing purposes only. Access to the penstock branches and the header can be made through the 20-inch manholes at the bottom of the turbine inlet pipes in the powerhouse. The outlet manifold and the penstock header can also be entered through the outlet gates in the outlet control house. Figure 74 shows outlet pipe manifold wye W1. *Not included. |