The first men arrived at the jobsite about April 15, 1953, set up temporary office and storage yard facilities downstream from the prime contractor's carpenter shop, and started bending Y-bars for outlet and power tunnels on April 22. The steel contractor set up a 1-1/4-inch alamo shear and a 1-1/4-inch alamo bender for use at the project site and started fabricating reinforcing steel for the cutoff walls and cable duct about May 1. The first steel was embedded on May 8, 1953. With the exception of cable duct, piezometer terminal well, cutoff walls and tunnels, all reinforcing steel was fabricated at San Jose, Calif.

Most of the reinforcing steel was shipped by rail from San Jose, Calif., to Ririe, Idaho, then hauled from Ririe to Palisades on a 20-ton truck and semitrailer. During the peak of construction in 1953 several truck loads of steel were shipped directly from San Jose to Palisades, and at this same time Teton Trading and Transporation Co. hauled several hundred tons from Ririe, Idaho, to Palisades.

A 2-ton crane and 2-1/2-ton flatbed truck were used for moving reinforcing steel around the jobsite.

Most of the reinforcing steel installed in the diversion channel and the outlet works stilling basin was supported on anchor bars that had been previously grouted into the rock (fig. 157). For supporting reinforcing steel in the powerplant, 2-inch angle iron or 1-3/8-inch reinforcing bars were set vertical and grouted into rock. Horizontal template bars were then welded to the vertical posts to support mats of steel. This method was also used for supporting reinforcing steel in the power and outlet tunnels.

After the 3/8-inch liner plates for the outlet and power tunnels were fabricated, the reinforcing steel was placed on the "cans" prior to moving them into the tunnels (fig. 158). The inner ring of reinforcing steel was supported by welding 5-foot template bars between the stiffener rings. The outer ring of steel was supported by welding short bars on stiffener rings at right angle to the 3/8-inch liner plate and then welding template bars parallel to the liner plate.

(h) Anchor Bars.--Anchor bars, placed in bedrock foundation, were used extensively in the outlet works stilling basin floor and left wall construction, between stations 19+00.25 and 23+05.75. Anchor bars were also installed in the diversion channel in both the right and left walls and floor bedrock foundation. Anchor bars were installed in the spillway inlet structure.

The first anchor bar holes in the stilling basin left wall were drilled to depths of 8 to 12 feet. Order for changes No. 1 provided that these holes and all future holes, for the left wall, be drilled to a depth of 15 feet. Drill-hole depth in the floor area was 8 feet. Most of the holes were drilled by jackhammer, though the contractor used two wagon drills for a short period in drilling some of the floor holes.

Final rock excavation lines were very erratic owing to the nature of the rock, causing much overbreak. This presented a problem in obtaining proper anchorage depth and also in having the anchor bars extend the correct distance into the concrete. To overcome this difficulty, the contractor cut anchor bars in increments of 6 inches, and was therefore able to pick bars of proper length from stock on hand, instead of spending time fabricating each bar individually as needed.

One and three-eighths inch A bars (hook shape) were put in the stilling basin left wall and that portion of the floor slab from station 20+14.25 to station 23+05.75. One and one-quarter inch A bars were put in the floor slab from station 19+00.25 to station 20+14.25. The bars put in the left wall of the diversion channel were 1-1/8-inch E bars (L shape).

site.

Mortar for grouting of the anchor bars was hand-mixed in small lots at the jobProportions were one part cement to two parts of concrete sand which was screened to a minus No. 8 fraction just before use. Vertical holes were filled with grout before inserting an anchor bar. The bars were then spotted to proper grade either by the use of a level or by means of a crosswire grid.

Anchor bars in wall rock were grouted in the same manner and alined properly from a wire grid. Later, and before rock was enclosed by reinforcing steel and forms, the open ends of holes were resealed with a stiff grout.

Figure 157.--View of stilling basin taken from station 24+00 looking south toward the outlet of the outlet tunnel. Various phases of construction are in progress, such as cleaning, installing of reinforcement, form construction, and finished concrete work. 456-108-1508, August 7, 1953.

Figure 158. --View looking upstream from station 18+50 of the outlet tunnel, showing

riggers readying can section 0-1 for entry into the tunnel. All reinforcing steel was placed on the can at the switchyard. This can was placed on the tracks and pushed into position at station 10+12 by the bulldozer. 456-108-1520, August 17, 1953.

(i) Drainage System and Air Vents.-- Six-inch-diameter concrete sewer pipe drains were installed on rock foundation under the concrete floor slabs of the stilling basin, and at approximate elevations 5360.0 and 5380.0 behind the left wall concrete slabs. The drains extended from station 19+01.25 to station 22+42.25. (See fig. 66.)

To serve as air vents, 8-inch-diameter concrete sewer pipe, was installed at approximately station 20+89.25, and connected to 8-inch-diameter metal pipe rising vertically in the right and left walls of the stilling basin (fig. 66). The tops of the 8-inchdiameter metal pipe were vented above water line through the wall concrete into the stilling basin. The bottom 8-inch-diameter concrete sewer pipe was vented by means of short risers into and out of the dentates at station 20+90.25.

The 6-inch-diameter longitudinal and cross drains were laid in excavated trenches in the final bedrock. The pipe was placed on a bed of gravel and covered with a minimum of 6 inches of screened gravel. To hold the loose gravel in position until covered with concrete, a layer of burlap was placed on the gravel. The burlap was then covered with approximately 2 inches of 3/4-inch-maximum concrete to stabilize the entire drain. All pipe joints were uncemented. Covering the completed drain with 2 inches of concrete prevented future disturbing of the loose gravel and sewer pipe during the erection of forms and reinforcing steel. Six-inch-diameter drains, in the left wall, were formed in place with blockouts, and gravel was placed around the pipe at a later time.

Eight-inch-diameter concrete sewer pipes with cemented joints eventually were cast in the concrete for the floor-slab placements. Job-fabricated tees connected the 6inch-diameter pipe and 8-inch-diameter dentate vent risers to the 8-inch-diameter sewer

pipe.

(j) Finishing.-- Most of the concrete placed received a floated (U2) finish as required by specifications No. DC-3675. There was also a small amount of screeded (U1) finish and troweled (U3) finish. All finish was applied by manual labor, except in the powerplant, where a power float aided in obtaining the U3 finish on the pipe gallery and service bay floors. In the stilling-basin area, a small, one-drum air tugger was used in the initial screeded strike-off of floor slabs. This eliminated considerable heavy and hard manual labor in getting the surface cut to grade line.

Tops of walls, curbs, etc., were sloped for drainage to eliminate detrimental pockets that might catch and hold surface water. All exposed sharp edges on wall tops, curbs, gutters, etc., were removed by tooling. In spite of certain operational difficulties including the hot weather problems of sun and hot winds and, at the beginning inexperienced help, the final finished surface was generally of a better texture than required.

(k) Curing.--All concrete placed in various structures received curing according to requirements of the specifications. In some cases water curing by sprinkling, flooding, or damp sand was used, but membrane curing was used wherever practical, and this method was preferred by the contractor.

Sealing compound, used for membrane curing, was gray in color and met requirements of color No. 3655 of Federal specifications TT-C-595. A self-agitating power sprayer was used to cover large areas and small orchard type sprayers to cover small areas and repairs. Water curing was used for the exposed top lifts of wall placements and slabs in the powerplant which were to receive succeeding lifts. Slabs above exposed interior walls of the powerplant were cured with damp sand to prevent water stain on the walls.

Some of the main problems encountered in obtaining proper curing were those inherent in getting a curing program organized, inexperienced help, and lack of water supply. All problems were ironed out early in the construction season so that the overall curing results were entirely satisfactory.

(1) Repair.--Needed repairs to damaged concrete, eliminating of honeycomb caused by rock pockets, and she-bolt hole filling were performed according to specifications No. DC-3675. Where damage occurred, the concrete was chipped to a square or rectangular surface opening, with true edges, and to the required depth to expose solid concrete. The edge faces were chipped in a dovetail manner to provide a proper key. Before repairs were made, the fresh surface was packed with water-soaked burlap and given a precure of at least 4 hours. Chipped areas extending clear through a placement or exposing

reinforcement steel, or areas larger than 1 square foot, were formed and filled with concrete. Small holes, such as surface fractures and spalled she-bolt holes, were repaired by dry packing. Concrete used in large repairs contained the same mix proportions as the original placement. Repairs when finished and/or stripped were cured with sealing compound.

Repair of damaged concrete and truing of edges was performed with an air chipping gun. If the area was of large size, preliminary edge cuts were first made with a concrete saw, which prevented further spalling of the edges during chipping. Wherever possible, dry pack was put in place with the aid of a job-fabricated motor gun instead of hand tamping. This practice gave a well-compacted and tight repair.

(m) Control of Temperature. Specifications No. DC-3675 contains provisions requiring definite action to protect freshly placed concrete from freezing in case of cold weather: After the first frost, and until the mean daily temperature falls below 400 F. for more than 1 day, the concrete shall be protected from freezing for a period of 48 hours. When the mean daily temperature falls below 40° F. for more than 1 day, the concrete temperature shall be maintained at not lower than 500 F. for at least 72 hours. After the initial 72 hours of protection at 500 F. membrane-cured concrete shall be protected against freezing for an additional 72 hours, and water-cured concrete shall be protected against freezing for an additional 11 days.

To meet the specification requirements, the contractor cooperated fully for the concrete placements made during the period he operated in freezing or possible freezing weather. When temperatures dipped to 400 F., placements were well covered with canvas and electric light bulbs placed thereunder. As the weather became colder, fresh concrete was covered with a bedding of paper and later with straw. Oil burning heaters and orchard type oil heaters were also placed under the canvas canopies for best advantage. Care was taken to keep any direct heat from striking the fresh concrete and causing drying.

190. Concrete Structures.

(a) Cutoff Walls.--Forms to be used in concrete placement of the cutoff walls and trench foundations were fabricated at the jobsite. Trench forms were built to fit the rock contour. Wall forms were panels, which were handled with a crane during erection. Concrete placement was in two phases, the trench foundation and later the cutoff wall.

Before placement of concrete in the trench, foundation forms were built in a manner to reduce the amount of concrete yardage required to backfill the rock overbreak. The curtain of reinforcing steel for the walls was erected and also a 6-inch-high stub wall form. Lengths of 1-1/2-inch-diameter grout pipe nipples were installed for future foundation grouting, and vertical, wooden keys were nailed to the end of each placement form.

Concrete was placed directly in each trench form by means of a 2-cubic-yard, bottom-dump, concrete bucket, handled by a crane. The concrete was consolidated with internal vibration. Sealing compound was used for curing. Before erecting the wall panels, the top of the stub wall concrete and exposed reinforcing steel were cleaned with sandblasting, then washed to remove all loose material. To facilitate placing, a wooden hopper was used on top of the form to receive concrete dumped from the bucket; the hopper was slid along the form as placing progressed. On the steepest part of the abutment it was necessary to change from bucket placement to the use of a long, partially covered wooden chute with detachable elephant-trunk chutes in the form. This method worked very well. Concrete was kept to as dry a consistency as practicable, and no segregation occurred. Walls were internally vibrated, and curing was by sealing compound.

The first concrete was placed in the trench foundation for cutoff wall No. 2 on May 18, 1953, and placing was continued through the working season. The final placement of cutoff wall concrete was made on October 13 in cutoff wall No. 2. Two and onehalf-inch-maximum concrete, containing fly ash, and a water-cement ratio of 0.50, was used in both cutoff walls.

(b) Cable Duct.-- The electrical cable duct, extending from the powerplant to the electrical switchyards, was completed under specifications No. DC-3675 from station 1+51.78 to station 6+27.53, including seven of the required eight manholes. The structure is roughly square in end area, built of reinforced concrete, and extends along the downstream toe of the fill embankment for the dam.

Rough grading for the floor of the cable duct was performed with a bulldozer. All fine grading was by hand labor. The concrete was placed in two phases, the floor first and later the sidewalls and top. Reinforcing steel, extending from one sidewall through the bottom and up into the opposite wall, was erected previous to placing the floor concrete. A mobile crane and 2-cubic-yard concrete bucket were used for all placing. Floor panels were placed in alternate order.

The inside and exterior form panels for wall construction were fabricated at the jobsite. Expansion joints of 1/2-inch cork board and type F rubber water stop were installed at each manhole midpoint. Blockout construction was used to form the manhole openings, and the top portion of the reinforcing steel was erected in place.

In concrete placement, the walls were filled to the bottom of the top slab and the concrete then allowed to settle for approximately 1 hour, at the end of which period the concrete was revibrated and the top placed. Internal vibration was used to consolidate all concrete. Curing was at first by water, then was changed to sealing compound when a supply was obtained on the project. Necessary cleanup between floor concrete and walls was done by sandblasting.

(c) Power and Outlet Tunnels.--The contractor's work program called for considerable preliminary activity before mass concreting began. Forms for the curb rails were job built to fit the rock contour. Concrete was handplaced from trucks. In the outlet tunnel invert sections, the presence of running water presented a problem. The contractor elected to control the water by a system of concrete sewer pipe drains, constructed in a similar manner as used in the outlet works stilling basin. These drains were continuous, connecting between forms. Grout pipe at approximately 200-foot intervals, was installed into the drains to be used for backfill purposes when the grouting program begins. No concrete pipe drains were used in the power tunnel. Forms for invert placement and bulkheads were built at the site to fit the rock contour. Reinforcing steel was erected on pins anchored in the rock. For steel-liner placements, the reinforcing steel was placed around the liner before the liner was brought into the tunnel and then checked for quantity and spacing.

Except for two invert placements in the outlet tunnel, all concrete was placed by pumpcrete methods. The contractor used from two to four trucks transporting concrete to the two pumpcrete machines, with one elevating conveyor used whenever a pumpcrete machine was set up inside either tunnel. For a more detailed report on pumpcrete methods and difficulties, reference is made to section 188(f).

The first concrete placed in the tunnels was on May 28, 1953, in the curb rail of the outlet tunnel. Pumpcrete operations were started on July 15 for the outlet tunnel invert, and the first concrete for backfill behind the steel liner in the outlet tunnel was placed on August 27, 1953.

Steel-liner placements were carried on in three phases: sealing off the invert under the liner, placing the sidewall concrete, and sealing of the arch section. Methods on each phase improved with each new placement. All concrete was consolidated into place by internal vibration; also form vibrators mounted inside the steel liners furnished form vibration to provide dense consolidation of concrete.

Curb rail and concrete in the invert placements was cured by sealing compound. The exposed concrete, after stripping of bulkheads from the steel-liner placements, was water-cured.

The only areas in either tunnel requiring finishing were the invert sections upstream from station 10+12 in the outlet tunnel. These placements were given a U3, or troweled finish. Owing to the invert curvature, an excessive amount of labor was originally required in getting the finish completed for a placement. However, a program was worked out which reduced the overall finishing time to a minimum.

As the outside air temperature dropped in the fall, so did the air temperature in the tunnels. To protect fresh concrete from freezing, canvas bulkheads were erected in the tunnels, and oil heaters, of fan-driven and orchard type, were kept burning. The results were satisfactory.