« PreviousContinue »
which serves a dual purpose of grout cap and crestwall, was placed as an extention of the grout cap placement. Placing equipment consisted of a small crane and a 10-cubic-foot concrete mixer.
76. Valve House and Retaining Wall. - Concrete placing in the valve house structure was originally scheduled for initiation and completion during the 1949 construction season. However, delays in completing the tunnel lining made it impossible to complete the excava tion in sufficient time for any concrete placement prior to the winter shutdown.
Excavation operations were completed early in the 1950 season, and the foundation placement was made May 27. Prior to this placement, a small concrete wall was constructed adjacent to the excavation in an attempt to stop the flow of seepage water from the river into the foundation. This was not successful and it was necessary to use sandbags to maintain a dry foundation for placing.
Second-stage concrete, encasing the 56-inch-diameter pipe and connecting to the outlet portal, was placed during the period July 2 to 31, 1950. Concrete in the superstructure was placed in three separate lifts. The retaining wall was completed November 17, 1950.
The contractor elected to postpone placement of the machinery pedestals and crane rail beams until such time that he could employ an experienced cement finisher. He also delayed concreting operations in order to take advantage of the low stages of the river. As a result the concrete for the machinery pedestals and crane rail beams was not placed until the period August 9 to September 18, 1951.
Methods of batching, mixing, procurement and processing of aggregate, mixes used, and related information are discussed in sections 68 through 71.
G. Metalwork and Machinery
77. Outlet Pipe (56-Inch Inside Diameter). - Sandblasting of the 56-inch and 48-inch wye section of the outlet pipe, prior to painting, was started May 14, 1950. The specification paint schedule called for three coats of CA-50 coal-tar paint on pipe exteriors, and one coat of primer and one coat of hot-applied coal-tar enamel on the interior. Sandblasting and painting of the pipe sections to within the specified limit from the joints was completed by the end of the month. Concrete pipe pedestals were placed next in the outlet tunnel, and the outlet pipe installation was begun. The last painting, at the welded joints, completed the installation July 24, 1950.
78. High-Pressure Gate. - Installation of the high-pressure gate was performed, with the exception of gate control piping and apparatus, in November 1949. Control piping and apparatus in the tunnel and gate chamber were installed early in the 1950 construction season. The valve house installation was completed in September 1951.
The gate installation was tested by raising and lowering the gate several times, at 1-foot intervals, on July 15, 1950. No difficulties were encountered and the gate worked freely.
79. Butterfly Valves (48-Inch). - Because of delays in delivery it became necessary to omit the installation of the butterfly valves and butterfly valve hatch covers from the contract (see order for changes No. 6, in section 28). This installation was made by Government forces immediately upon delivery. Installation of the 5-ton traveling crane was completed August 21, 1951.
80. Other Metalwork. - The trashrack sections were sandblasted, painted, and installed during the period June 1 to June 23, 1950. Installation of the 8-inch thin-walled pipe for the gate-chamber ventilating system was performed during August 1950, after diversion of the Conejos River had been completed.
81. Cleaning and Painting Metalwork. - The prime contractor sublet the cleaning and painting of all metalwork and machinery in the gate chamber, the 8.5-foot horseshoe section of the tunnel, the valve house (except the butterfly valves), and the pipe handrailing for the spillway bridge, to Mr. M. J. Bowen of Monte Vista, Colo.
After cleaning the metal, a primer coat and two coats of paint were applied by brushing, as indicated in the painting schedule. A gasoline-soluble rust-preventive compound was applied to the track rails for the 5-ton hand-operated overhead traveling crane.
The subcontractor started painting the metalwork and machinery on September 12, 1951, and completed his contract in 10 days.
H. Factors Affecting Contractor Progress
82. Specifications No. 2594 (Prime Contract). - (a) Weather. --Adverse weather conditions were expected at this location, but were generally not as severe as anticipated. Because of frequent rainstorms which resulted in numerous temporary suspensions of embankment operations, suspension and resumption dates listed below are confined to seasonal shutdowns resulting from winter weather.
Work was initiated under this contract on June 6, 1949. Some embankment material was placed during the season, but placement was suspended November 1949 after severe frosts occurred. Concreting operations were continued in the outlet tunnel works until December 24, 1949, at which time all work was suspended for the season. Work was resumed May 4, 1950, and with the exception of the month of July, which was extremely wet and delayed fill operations, weather conditions permitted embankment operations to be continued until November 10, 1950. All operations were suspended for the season November 14, 1950, after heavy snows occurred Work was again resumed on May 7, 1951. An unseasonably dry year in 1951 was very favorable for embankment placement and work was completed under this contract on September 26, 1951. Only a few delays were caused by weather during the final construction season.
(b) Labor. --The quantity and quality of labor in most of the trades was generally adequate throughout the contract. There were no delays of any consequence caused by disputes between labor and management.
83. Specifications No. R5-13 (Reservoir Clearing). (a) Weather. --Weather, which was beneficial to operations under the prime contract, had the opposite effect on prosecution of this contract insofar as burning operations were concerned. This phase of the work was under rigid control and was suspended twice during the course of clearing, as previously noted. As there were 18 days allowable time remaining at the time of completion of the contract, no time extension was necessary because of inclement weather.
(b) Labor. --In general, the labor supply for prosecution of the work under this contract was adequate. However, during the early stages of clearing operations the contractor was reluctant to hire a large crew of laborers. As the work progressed this conditions was gradually rectified. Progress, was somewhat retarded throughout the duration of the job because of the insufficient number of supervisory personnel employed by the contractor.
I. Construction Equipment
84. Prime Contractor's Equipment. - The amount and condition of the major items of equipment was generally considered adequate. Operation of the separation plant could have been improved somewhat by design changes; however, the major delay was caused by wet material which failed to separate well regardless of plant conditions.
Equipment utilized directly and indirectly in the different phases of construction is listed as follows:
Capacity or type
12 cu. yd.
5 cu. yd.
Miscellaneous welding equipment *Owned by subcontractors
ON CRNA NA MWANA ANANANANNWNN
No pode parede
J. Initial Operational Problems
85. 48-Inch Butterfly Valves. - The butterfly control valves (sec. 79) were first placed in operation early in May 1952. With a reservoir head of less than 50 feet it was found to be extremely difficult to operate the valves with the handwheel, and trouble with the motor control relays and torque switch prevented reliable motor operation. Investigation revealed that the operating mechanism had been inadequately designed 2). (The valves were procured from the R-S Products Corporation under performance-type specifications and their design was not reviewed by the Bureau.) S. Morgan Smith Company, parent company to the R-S Products Corporation, constructed new valves and adequate operating mechanisms (fig. 34), which are scheduled for installation in the fall of 1954. Meanwhile, operation of the valves is according to a scale of partial openings which it is considered will not result in stresses exceeding 30 percent of the ultimate strength of the mechanisms, both valves being operated simultaneously. Figure 33 shows the completed outlet works with both valves of the original installation operating at full opening.