The gate hoist is a unit consisting of a two-speed reversible electric motor driving a gear-reducer which acts through further reduction gearing to rotate a vertical stem supported on roller thrust bearings. The stem is threaded through a cross head which will raise or lower with the proper rotation of the stem. The cross head moves in guides anchored to the concrete structure. The upper end of a connecting link is pinconnected to the cross head and the lower end of the link is pinned to the lifting beam on the gate.

The hoist was designed to lift the dead weight of the gate, stem, cross head, and connecting link plus friction from the seals and gate pins for full water load. The forces at the hoist stem required to overcome dead weight and seal friction were estimated to be 35,000 and 5,000 pounds, respectively, or a total of 40, 000 pounds. The hoist was designed with a normal capacity of 80, 000 pounds. The motor starting and breakdown torques are 200 to 250 percent of the running torque; hence the hoist can exert a much larger force for a short time than its normal capacity. Normal working stresses for the material of the parts of the hoists and connections to the gate were used at the running torque of the motor. For the starting and breakdown torques the stresses were limited to two-thirds of the yield point of the material.

The hoist unit is equipped with a gate position indicator, limits which are to stop the hoist when the gate reaches the end of its travel, and a hand-operated grease injector system for lubricating the stem, cross-head guides, and bearings.

Three control cabinets contain the electrical equipment for operating the six hoists and are located on the concrete floor adjacent to the hoist units. An individual pushbutton station for each hoist is located in its respective control cabinet. The squared end on the motor shaft of the hoist unit is for hand-crank operation when necessary. About 26 minutes are required to open the gate and 13 minutes to close it.

The estimated weight of each gate is 35, 000 pounds, and its embedded metalwork weighs an additional 9, 300 pounds. The hoist for one gate, exclusive of the controls, weighs about 20, 000 pounds.

130. Approach Channel. The approach channel carries water from the Equalizing reservoir to the Main canal headworks structure. It is 120 feet wide at the base, with 1-1/2 to 1 side slopes. With water flowing at a depth of 23. 33 feet, the channel will deliver the maximum discharge of 13, 200 cubic feet per second at the low water surface elevation of 1540 in the reservoir. The section is excavated in earth and rock with the major part in rock. This canal was designed using n = 0.030 in Kutter's formula.

131. Main Canal. An unlined canal section beginning at station 2+33. 50 (the end of the canal headworks) extends to station 59+00. This section has a 50-foot base width with 1/2 to 1 side slopes, and is almost entirely in rock. For the maximum discharge of 13, 200 cubic feet per second the water flows at a depth of 35. 76 feet. A roughness coefficient of n = 0.035 in Kutter's formula was used to compute the hydraulics in this rock section.

CHAPTER IX--Dry Falls Dam--CONSTRUCTION62/

A. Contract Administration

132. Specifications No. 1231, "South Coulee Dam.'

Bids were opened on May 10, 1946, at Coulee Dam, Washington. The low bid of $2,771, 887.50 was submitted jointly by Roy L. Bair and Company and James Crick and Sons, of Spokane, Washington. Bids received were:

Contract No. 12r-16203 was awarded on June 18, 1946, and notice to proceed was received on August 28, 1946, fixing the completion date as February 13, 1949. Actual construction began on July 18, 1946. Three extensions of time, totaling 266 days, were granted the contractor. Order for changes No. 1, issued September 10, 1947, granted a 120-day extension because of increases in quantities. A 75-day extension was granted because of curtailment of operations on the Columbia Basin project during fiscal year 1947. "Findings of Fact", dated September 12, 1949, extended the completion date an additional 71 days, because of the unusually severe winter of 1948-1949. The work was accepted by the Government on September 9, 1949, 58 days ahead of the completion date. Appendix B shows the pay item breakdown for items in the specifications.

The principal features involved in the construction of the Dry Falls Dam were an earth- and rockfill dam across the Grand Coulee; the Main canal approach channel, headworks structure, control gates and transition, and the Main canal from canal station 2+29 to 24+00, inclusive; a drainage channel on the left abutment; relocation of a drainage channel for effluent from the Coulee City sewage treatment plant; and an 18inch pipe crossing over the canal at station 8+30. The principal items of work involved construction of a central or impervious portion of the dam consisting of a moistened and rolled embankment of selected clay, sand, and gravel; the portions of the embankment immediately upstream and downstream from the impervious portion, consisting of natural sand and minus 8-inch gravel with varying amounts of silt placed in 12-inch layers compacted by standard tamping rollers; and the upstream and downstream portions of the embankment consisting of rockfills. A concrete cutoff wall with footings extending into bedrock was constructed in a cutoff trench with sloping sides excavated in the foundation of the dam. A surfaced roadway was constructed on the crest of the dam with metal plate guardrails on each side. Work on the Main canal consisted of the approach channel approximately 4, 000 feet in length, the headworks structure including the approach and outlet transitions, and the canal section between stations 2+29 and 24+00. The discharge through the canal is controlled by six 12- by 18-foot radial gates installed in the headworks structure.

133. Orders for Changes. There were three orders for changes and seven extra work orders issued modifying the original work, as outlined in specifications No. 1231. Order for changes No. 1, issued September 10, 1947, directed the contractor to extend the excavation in the cutoff trench to bedrock between stations 26+50 and 29+50 in lieu of excavating to the limited depth, as shown on the original plans. The concrete cutoff was also extended through this section. The drawings also indicated elimination of

reinforcement steel from the embankment cutoff wall. A net increase in cost under order for changes No. 1 was $135, 912. 34.

Order for changes No. 2, issued March 30, 1948, provided for a change in design of the side walls and the addition of 2-inch-diameter weep holes in the inlet and outlet transitions of the main canal headworks structure. The order also deleted the concrete parapet wall on the crest of the dam, substituting steel beam-type guard rails. The work under this order effected a net reduction in construction costs of $61, 053.73.

Order for changes No. 3, issued March 29, 1949, provided for construction of a 36-inch-diameter reinforced concrete pipe culvert in lieu of a 2.5-foot concrete culvert provided by the specifications. A net decrease in cost under order for changes No. 3 was $918.05.

Extra work order No. 1, issued November 18, 1946, directed the contractor to furnish the necessary labor and equipment to perform excavation and backfill for sewer and water lines, and to construct manholes, a septic tank, and footings for a water tower, all as directed by the contracting officer. The work was performed under an extra work order because of its urgency, the shortage of Government wage-hour personnel, and the distance of their headquarters from the jobsite.

Extra work order No. 2, issued March 6, 1947, provided for constructing a reinforced concrete catch basin near the southeast corner of the intersection of Fifth and Locust Streets in Coulee City and installing a 36-inch-diameter reinforced concrete pipe culvert extending diagonally across the intersection to empty into the head of the drainage channel near the east abutment of the dam, as described in the specifications. The work covered by this order was necessary to divert surface drainage from a natural channel to the drainage channel.

Extra work order No. 3, issued October 22, 1947, ordered the contractor to unwater the foundation of the dam between stations 26+50 and 29+50 below elevation 1520. The work order was issued in accordance with order for changes No. 1 which directed the contractor to extend the cutoff trench and concrete cutoff wall to bedrock between these stations, and provided that any unwatering would be paid as extra work.

Extra work order No. 4 was issued on June 9, 1947. In early blasting operations, the basalt rock broke in unusually small fragments undesirable for use in zone 3. Since the embankment quantities were increased under the work performed in order for changes No. 1, it was feared that a rock deficiency would develop, and the contractor was directed to load blasted rock fragments of sizes suitable for use in zone 3 embankment from spoiled banks along the canal. Subsequent to issuance of this order, the blasting resulted in large quantities of overbreak in main canal rock excavation, and the anticipated shortage did not materialize. Consequently, no work was performed under extra work order No. 4.

Extra work order No. 5, issued March 29, 1949, provided for miscellaneous

items of work under the prime contract as follows:

(1)

(2)

Straighten, rebend, or rehandle reinforcement bars.

Construct compacted earth-fill embankment between stations 2 and
7 of the drainage channel from Coulee City.

(3) Construct an approach road between approximately stations 0+25
and 6+09 from Dry Falls Dam to the existing county road.

(4)

(5)

Construct an access road across the outlet end of the barrel section
of the headworks structure.

Haul and place waste material from common excavation of dam
foundation for backfilling the headworks operating and maintenance

area.

Extra work order No. 6, issued April 6, 1949, directed the contractor to cut, mortise, and weld reinforcement bars, as required to secure them at proper positions in the horizontal beams of the headworks structure.

Extra work order No. 7, issued July 13, 1949, directed the contractor to install surface settlement points in the completed dam embankment. These are permanent points for observation of the behavior of the dam while in service and, as such, form a part of the completed structure.

The net increase in cost as a result of the six active extra work orders was $51, 172.81.

134. Government Administrative and Engineering Organization. - Contract administration, engineering, and inspection were assigned to an organization under the direction of the resident engineer. An office engineer was responsible for office activities, while an assistant resident engineer supervised and coordinated the work of surveying and inspection units. The office engineering unit handled clerical assignments, correspondence, and warehousing; prepared estimates, progress charts, and reports; made maps, drawings, and compiled data; and performed highway relocation and design, and other functions assigned to the job.

Two survey parties of three to eight men each, supervised by a chief of surveys, accomplished all required survey work. This unit established construction lines and grades, obtained measurements for estimates, checked layout for structures, and performed highway relocation surveys. Drilling, grouting, and detailed inspection duties were performed by one to four inspectors supervised by a construction engineer. Concrete control was assigned to one to four inspectors working under the direction of a materials engineer. Personnel of this unit operated the Coulee City concrete laboratory, performed routine control and materials tests, checked adequacy of forms, and inspected cleanup and mixing, placing, furnishing, and curing of concrete.

Inspection of all excavation activity was performed by one to three inspectors supervised by a public works inspector until May 1947. At this time, the Coulee City soils laboratory was established and an earthwork inspection unit was formed under the direction of a civil engineer. One to nine inspectors performed inspection of foundation excavation and cleanup, selected embankment materials, made supplemental investigations, inspected embankment construction, operated the soils laboratory, and were responsible for field sampling and testing.

135. Contractor's Forces. The contractor's organization was composed of office, earthwork, and concrete sections. The job was under the direction of a project manager, with the office section under the direction of an office manager. The earthwork and maintenance were under the direction of a superintendent of the earthworks section, assisted by two general foremen. The concrete superintendent also served as project engineer and was assisted by a carpenter superintendent and superintendents of labor and placing crews.

Subcontractors which were employed on the job are listed below: