Second-stage concrete was placed on January 30, 1961, after the installation of the tandem 4- by 4-foot gates. The forms were made in the contractor's carpenter shop. The same method of placement was used as in the first-stage concrete. Some grinding was required upon form removal to attain the required finish.

139. Miscellaneous Structures, (a) Control Houses and Manifold BLock.—Concreting operations at these features were started in September 1962, and completed in January 1963. Concrete was dry batched at the central batching plant, mixed by a pavement mixer at the jobsite, and placed by a crane and bucket. Forms were made in the contractor's carpenter shop and erected in place. The valve house for the 72-inch ring-follower gates and hollow-jet valves and their controls is shown in figure 96.

(b) Piezometer Terminal Wei/. —This feature, which is located 1,106 feet downstream from dam axis station 40+00, was placed in two lifts. The first placement was on May 19, 1959, and the second on June 16, 1959. The same methods were used as described above for the control houses. The outside of the well was coated with a black dampproofing compound to prevent seepage into the terminal well.

140. Reinforcement. All reinforcement steel for concrete was purchased by the contractor from the Colorado Builders Supply Co. of Denver, Colo. This company, using Bureau of Eeclamation drawings for reference, prepared detailed drawings of the steel and cutting lists for use in shop fabrication and jobsite placement.

Practically all the reinforcement steel as well as anchor bars and dowels were cut, bent, bundled, and tagged at the Pueblo, Colo. , plant of the company. The fabricated steel was hauled by truck to the jobsite. Ora E. Salyer of San Francisco, Calif. , subcontracted the placement of all reinforcement steel in the forms at the jobsite.

141. Anchor Bars. Anchor bars of 1-inch-diameter reinforcement steel were placed on 5-foot centers longitudinally and laterally under the spillway floor panels (fig. 86).

Anchor bars of 1-3/8-inch-diameter steel were used under the outlet channel floors and in back of the tunnel portal headwalls. After drilling holes 1-1/2 times the diameter of the size of the steel required and to a depth of 8 feet in rock, the anchor bars were grouted in place. A portable grout mixer was set up near the point of operations and the grout placed by hand methods. The mix used was 1 part of cement to 2-1/2 parts of sand.

There were a few locations where overexcavation of the rock in the foundation required replacement with longer anchor bars to bring the hook portion of the bar up into proper spacing in the floor concrete.

Pullout tests were made on several anchor bars, particularly in a few of the shale areas; two 15-ton jacks were unable to pull the anchor bars out of place, indicating that a good job of grouting had been obtained.

142. Tile Drains. A rather elaborate system of tile drains was incorporated in the construction of the spillway and the spillway and outlet works stilling basins to relieve any buildup of water pressure under the floors.

The drains range from 4 to 12 inches in diameter depending upon the area being drained and the size of the collection system. Drainage is through a system of small-size drains emptying into a larger-sized system, then through the walls to the floor of the spillway or into the drainage gallery on the spillway centerline, and then out onto the floors. In the stilling basins, discharge onto the floors is through the dentated sills. Some of the drains were laid with uncalked joints while others were of perforated pipe with calked joints.

Following excavation by line drilling with jackhammers and air spades, the lean concrete pads were placed. The tile drains were then installed, followed by the placing of the crushed rock or gravel; and finally the burlap and sand were placed, thus completing the drains.

CHAPTER VUL Construction—INSTALLATION OF METALWORK AND MACHINERY

143. General. As discussed in chapter IV, there are two separate outlet works at Navajo Dam, each with its own intake structure (including an elliptical bulkhead for the main outlet works), trashracks, conduit, regulating gates, and emergency gates. These and other mechanical items were furnished by the Government under procurement invitations and installed by the prime contractor, as discussed in this chapter.

144. Elliptical Intake Bulkhead. The elliptical intake bulkhead was supplied by the Pacific Coast Engineering Co., Alameda, Calif., under invitation No. DS-5292. The bulkhead was installed in the main outlet works intake structure during the month of January 1961. Its function is to close the intake section of the outlet works for maintenance or inspection. The elliptical bulkhead seats at elevation 5882. 5, but is normally suspended from the intake structure cover, which is at elevation 6000.0.

The elliptical bulkhead was raised to the intake structure with a 60-ton high-lift crane (see fig. 97). The bulkhead was suspended just above the seal seat where the contractor completed the field assembly. There were no unusual difficulties encountered in the assembly procedure. The bulkhead was raised to the storage position with a head frame and pulley arrangement, the line being controlled by the drums on the crane. The bulkhead functioned properly during a trial run and was suspended from the intake cover for normal operations.

During the initial operation of the 72-inch ring-foHower gates and hollow-jet valves, the bulkhead dropped to the closed position closing off the entry of water to the outlet works. As the rapidly rising water in the reservoir made it urgent that the bulkhead be raised immediately, the contractor was directed to proceed with this work and extra work order No. 1 was issued to cover the work (see subsec. 90(b)). Access for this extra work was provided by the contractor's and the Government's boats and a fabricated work barge. Only minor damage to the bulkhead guides was noted; the major part of the work consisted of rigging and lifting the bulkhead into position. Riggers were employed for the job and the bulkhead was raised, repaired, and relatched in position between April 12 and 20, 1963.

145. Tandem Outlet Gate. The 4- by 4-foot tandem outlet gate was supplied by Moffett Engineering Co., Inc., Berkeley, Calif., under invitation No. DS-5203. The gate was installed during January and February of 1961. The function of this gate is to control the flow of water through the 7-foot-diameter horseshoe tunnel of the auxiliary outlet works. The gate is located in the auxiliary outlet works tunnel at station 11+18. 5.

Some difficulties were encountered before and during the installation of the gate. The gasket groove corners in the intermediate and downstream body sections were found to be overwidth and field corrective measures were required. The groove corners were filled with weld and ground smooth. The grease piping for the tandem gate was field installed after the gate body and reinforcement steel were in place. Because of the restricted working area, the pipe welds in the lower section were difficult to make and several rewelds were required before the piping would pass the pressure test.

The piezometer piping extends from all sections of the gate and terminates in a box which is recessed in the left side of the auxiliary gate chamber floor. The lines required some bending and threading to get through the reinforcement steel, and they were difficult to hold in position while placing concrete. The contractor used a wooden template drilled to the terminal box pattern to hold and position the lines during the concrete placing, When the contractor installed the piezometer piping, he found that there was considerable leakage between the gate body and the piezometer tips which was traced to defective threads in the gate body. To stop the leakage a stainless steel weld was run around the junction of the tip and the outside of the gate body.

The gate leaves and hoist cylinders were installed with a minimum of difficulty, but when the gate seals were checked, it was found that the upper left corner of the service gate had a 0.010-inch gap which tapered off both ways to less than 0.005 inch. By dressing the seals, the gap was reduced to 0. 007 inch under no head. The gate was accepted without further corrective measures. Water leakage past the gate is negligible. The control system was installed in September 1962 and the gate operated satisfactorily through several test runs.

146. 6- by 13-Foot Fixed-Wheel Gate. During the latter part of 1962 and early part of 1963, the contractor installed one 6- by 13-foot fixed-wheel gate in the main outlet works at station 10+38. 5 (fig. 98). The function of this gate is to close the outlet section of the outlet works for inspection and maintenance. The fixed-wheel gate is normally suspended below the gate bonnet which is located in the outlet works gate chamber between elevations 5755.0 and 5766.0, and seats in the gate frame and seals at elevation 5728. 5. The control for the fixed-wheel gate is situated at the top of the gate shaft above the erection chamber at elevation 6108. 0.

For repair and maintenance, the fixed-wheel gate is raised to the gate erection chamber which is located in the gate shaft between elevations 6080. 0 and 6108. 0. As the gate is raised, the gate stems are uncoupled and stored in the stem storage rack located adjacent to the gate shaft.

The fixed-wheel gate was supplied under invitation No. DS-5375 by The Delaney Co. of Houston, Tex., and was delivered to the project in two major sections on January 17, 1962. An onsite inspection of the gate sections revealed that the holes for assembling the gate seals required reaming and countersinking. The corrective work was performed by the Johnson Machine Works at their plant in Chariton, Iowa.

The construction contractor installed the gate guides and frames and assembled the stem storage rack during October 1962. The contractor completed the assembly of the fixed-wheel gate by attaching the rubber seals and installing the fixed wheels. It was impractical to set the spacing between the fixed wheels and the seals by measuring through the holes provided in the upstream gate skinplate, so only the four outside wheels were set by measuring through the holes. The inside wheels were set by stretching a piano wire between the top and bottom wheels on either side and adjusting the wheels to the wire with the aid of a 0. 005-inch feeler gage.

The gate stems and nuts were not bored and tapped when they arrived on the job, so the drilling and tapping was done in the field. After the stems and nuts were assembled, the stems were coupled together, stretched, and checked for total length.

When the gate was given a trial run, the left guide shoes on the gate forced the seals into a bind. Also, the wheel-to-seal dimensions were less than those on the embedded seals. The dimensions of the embedded seals were checked and found to be over the specified dimensions. Following the dimensional checks, the wheels were set to the dimensions of the embedded guides, and the gate was raised to the erection chamber where corrective measures were taken as discussed below.

All of the wheels were set to a system of stretched piano wire. The guide shoe holes were slotted and positioned in order to relieve the binding encountered on the trial run. Also, the tops and bottoms of the shoes were given more taper to facilitate going on and off the guides. The wheels were not fixed until after a second trial run was made. During the second trial run, the left seal was found to be 1/16 inch tight, so these wheels were adjusted in the gate chamber and then locked in position. During the leakage test, the amount of water passing the gate seals was approximately 85 gallons per minute, but this was expected to decrease considerably under a full head.

147. 72-Inch Ring-Follower Gates and 72-Inch Hollow-Jet Valves. The two 72-inch ring-follower gates and two 72-inch hollow-jet valves (fig. 99) were supplied by Acciaieria e Tubificio di Brescia, Brescia, Italy, under invitations No. DS-5315 and DS-5313, respectively. The gates and valves were installed in the main outlet works valve house in the early part of 1963. The function of the 72-inch valves is to regulate the flow through the outlet works during high runoff periods. The function of the ring-follower gates is to shut off the flow of water to the 72-inch hollow-jet valves when they are taken out of operation for maintenance or repair.

The 72-inch hoUow-jet valves, 72-inch ring-follower gates, and the 72-inch hoist cylinders (fig. 100) were received in the latter part of 1961 and stored in the contractor's yard until they were installed in January and February of 1963. After this rather long storage, the paint on the cylinders showed signs of excessive deterioration and the units had to be sandblasted and repainted before they could be installed. In addition, the cylinders had to be opened and cleaned because the wooden plugs that were used to seal the