retested to the satisfaction of the Government. Since the rubber gaskets of each coupling may effectively insulate, electrically, each penstock section from the next, electrical connectors are used on the buried penstock sections so they may be protected against cathodic attack. The connectors, No. 6 stranded copper wire with plastic insulation, are fastened from section to section across the coupling and from the sections to the middle ring.

Except for the rings on the reducing bend of the wye branch which are 1-1/4 by 8 inches, the erection rings on the bend sections are 3/4 by 6 inches. The support rings on the penstock shell are 1 by 8 inches. All the rings were fabricated from steelplate, grade B, firebox quality, according to ASTM Designation A 201.

Manholes were placed along the penstocks to provide access to the interiors of the penstocks for maintenance and inspection. Each manhole is a nozzle whose design is a function of the internal pressure at its indicated location. Except for the 24-inch-inside-diameter manhole located immediately downstream from bend No. 8 to accommodate apparatus to be used in the turbine test program, the manholes are 20 inches inside diameter. Two 8-inch nozzles are furnished on each of the penstock makeup pieces as water supply and drain connections. Eight 1-1/2-inch half couplings and an 8-inch nozzle are furnished on each penstock downstream from anchor No. 8 for test connections. In addition, five 1-1/2-inch half couplings and two 3/4-inch half couplings are furnished on each penstock upstream from anchor No. 4 for test connections.

Combination air-inlet and air-release valve assemblies were installed just downstream of the penstock valve structure. They are actuated by metal floats. The air valves release air during the filling operations and admit air when the penstock is being drained.

188. Concrete Piers, Slabs, and Anchors. The concrete piers are of reinforced-concrete construction and carry the ring supports of adjoining sections of pipe, except where the pier is adjacent to an anchor. In the design of the piers, the forces resisted include the deadweight of the pipe full of water and transverse and longitudinal earthquake forces of 10 percent of the total deadweight. The design of the piers also considered the longitudinal forces in each section of pipe resulting from temperature change.

The concrete slabs extending from anchors No. 9 and 10 approximately 200 feet upstream are of reinforced-concrete construction. The slabs were designed to distribute the pier loads within this reach due to the questionable stability of the underlying material exposed during excavation.

The concrete anchors are encasements of the penstock bends and were designed to resist the vertical and horizontal components of the hydraulic forces. The coefficient of friction between the anchor and ground was assumed to be 0.4 with a safety factor of 1.25. The weight of the steel pipe length embedded in the anchor and the weight of the water volume associated with that pipe length were included in the anchor weight. Allowable bearing loads for anchors were normally 4, 000 pounds per square foot. Under extreme conditions concentrated loads of approximately 8,000 pounds per square foot maximum were allowed.

In all anchors, there are embedded two layers of reinforcement steel--an inner layer close to the pipe to resist cracking radially outward from the pipe and to tie the concrete below the pipe to that above the pipe, and an outer layer close to the outside surface of the anchor to hold all portions of the concrete within the anchor together in the event of cracking.

Each penstock trench from anchors No. 9 and 10 to the powerplant wall was excavated to the rock line. Since the structural strength and stability of this underlying material was uncertain, a concrete pad was placed in each trench to elevation 1188.50 and used to distribute and support the penstock load.

189. Installation and Coating. After installation of the penstocks in which all field joints were connected with sleeve-type couplings, any debris in the pipes was removed and the pipes were subjected to a leakage test. Upon satisfactory completion of the test, the pipes were drained.

Exterior

The interior surfaces of the penstocks were coated with coal-tar primer and coal-tar enamel. surfaces of the penstocks that were covered with backfill were coated and wrapped with coal-tar enamel, fibrous-glass matting, asbestos felt, and kraft paper. Exterior surfaces of the penstock that are exposed to public view or the atmosphere were treated with primer paint and phenolic-resin aluminum paint. The drainpiping was cleaned and painted with primer and coal-tar enamel.

8. Mechanical and Electrical Installations

190. Fishscreens. Forty fishscreens are required for the power conduit intake structure to prevent fish from entering the tunnel. Each of the 20 inlets is equipped with a set of guides, and 2 fishscreens. One lifting frame is required for lowering and raising the fishscreens in the guides.

(a) General Description. --The 40 fishscreens, guides, lifting frame, and appurtenant metalwork were furnished under invitation No. H-33, 409-A.

Two fishscreens are installed in vertical guides in each inlet of the intake structure. The screens are lowered and raised by means of a lifting frame attached to a 2-ton hoist. A circular crane rail was provided on top of the intake structure to accommodate the hoist.

The fishscreen frames are of welded construction, and are covered with No. 2-1/2 mesh, 0.092inch-diameter galvanized steel wire cloth. The steel wire cloth is held in place with clamp bars secured by steel carriage bolts with stainless steel nuts. The estimated weight of the 40 fishscreens is 103,000 pounds.

The estimated weight of the seats and guides is 35, 400 pounds, of the lifting frame 900 pounds, and of the appurtenant metalwork 10,000 pounds.

inch.

The fishscreens are designed for a 10-foot differential head at a stress of 20,000 pounds per square

191. Gantry Crane and Hoist. A 2-ton-capacity gantry crane is installed on the tunnel intake structure for handling the fishscreens during installation, maintenance, and washing operations.

(a) General Description. --The gantry crane was manufactured in accordance with the requirements of invitation No. (D) H-33, 442-B.

The gantry is pivoted on a column located at the center of the intake structure and is supported at the outer end on a two-wheel A-frame which travels 360° on a circular track of 29-foot, 2-inch radius. One wheel of the gantry is connected through a roller chain and sprockets to a 1/2-horsepower, 68-r.p.m. gear motor equipped with a motor-mounted disc brake. The gantry travels at a speed of 75 feet per minute. A 2-ton-capacity, single-line, base-mounted hoist is supported directly above the fishscreen slots by the gantry frame. The end of the hoist rope is equipped with a standard open-end wire-rope socket and a steel link for attaching to the lifting frame. The hoist is equipped with an electric brake, a mechanical load brake, and a limit switch which limits the travel in both the hoisting and lowering directions. The hoist has a lift of 38 feet and a lifting speed of 25 feet per minute. The hoist and gantry drive motors are single speed and are controlled from a pendant pushbutton station suspended from the gantry frame. Three-phase, 230-volt, 60-cycle power is supplied to the crane through a flexible cable loop fed from a connection box attached to the center column. The flexible cable will allow the crane to make three revolutions in one direction before the direction of travel must be reversed. All wiring and electrical equipment is in waterproof enclosures to protect against the spray water used in washing the fishscreens.

(b) Design. --A factor of safety of 5, based on the ultimate strength of the materials, was used in the design of the crane. The hoist is an item in regular commercial production and stresses are limited to the manufacturer's design criterion.

192. Cast-Iron Slide Gates. The ten 72- by 72-inch cast-iron slide gates_(fig. 128) are installed on the intake structure to shut off the flow of water through the Clear Creek Power Conduit and were furnished in accordance with invitation No. (D) H-33, 433-B. A motor-operated gate lift and control cabinet is installed on the deck for each gate. Each lift is equipped with a handwheel for emergency manual operation.

The estimated weight of gates, lifts, and controls is 49, 000 pounds.

The gates, lifts, and controls were designed by Waterman Industries Inc., to meet the requirements of 12 feet of head and operating speed of 6 inches per minute.

193. 156-Inch Butterfly Valves and Controls. One 156-inch butterfly valve is required in each of the two 11-foot, 6-inch diameter penstocks to shut off the flow of water for penstock maintenance and repair, or for emergency closure in case of turbine wicket failure or a penstock break for Clear Creek Powerplant.

The valves were manufactured by Nordberg Manufacturing Co., Milwaukee, Wis., under invitation No. DS-5455. The controls were manufactured by Hydraulic and Air Equipment Co., Portland, Oreg., under invitation No. DS-5604. Figure 155 shows the valve in the manufacturer's shop.

(a) Description. --The 156-inch butterfly valves are installed in the penstock valve structure as shown on figures 156 and 157.

Each valve consists of a body, split on the horizontal centerline, a leaf which pivots on horizontal trunnions, and an oil-operated hydraulic cylinder mounted on the valve body and connected to a crank on the leaf drive stem. The leaf has nonadjustable bronze seats with a rubber insert on the periphery. The valve body has a mating bronze seal which is externally adjustable. A position indicator on the drive stem side of the valve provides visual indication of the leaf position and actuates limit switches for remote indicator lights and other electrical features. Two 8-inch bypass lines, each containing a motor-operated valve, are provided.

The estimated weight of the two butterfly valves, complete with operators and handling equipment is 385,000 pounds. Weights of the major parts which might require handling during maintenance or repair are as follows: