An oil hydraulic system is provided for the control of high-pressure gates of the river outlets and canal outlet works. The system consists of an oil pump, electric motor, supply tank, 4-way valve (one for each gate), and piping. The oil piping is connected to the hydraulic gate hanger of the regulating gate in such a manner that the hanger releases the gate before oil is passed into the hoist cylinder, to raise or lower the gate.

A ventilation system is provided for the canal outlet works. This system consists of an air inlet, a fan unit, a duct from the fan to the emergency gate chamber, an air discharge head in the control gate chamber, and a starting switch for the fan motor. The fan unit draws air through an inlet in the roof of the control house and discharges it through a duct and discharge head into the gate chamber. The air from the gate chamber flows through the conduit and to the outside through a louver in the control house door. The fan has a capacity of 230 cubic feet per minute against 2 inches of static water pressure. The fan is started and stopped manually by a switch mounted in the control house. E. Railroad Structures

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34. Railroad Structures. - (a) Bridges and Culverts. Bridges were designed in accordance with the AREA "Specifications for Steel Railway Bridges" and "Specifications for Concrete and Reinforced Concrete Railroad Bridges. Concrete piles were designed for loads of 36 tons, steel piles for 50 tons, and timber piles for 27 tons. Culverts were designed in accordance with standards of the Chicago, Burlington and Quincy Railroad Co., employing rigid-frame design principles. Both the bridges and the culverts were designed for an E72 loading. Loadings were based on the "American Railway Engineering Manual, " 1948 edition. Allowable steel and concrete stresses are given in appendix F. In the design, the weight of embankment was taken as 105 pounds per cubic foot.

(b) Roadbed. To accommodate the weathering characteristics of the loess used in roadbed construction, the steepest embankment slope for normal conditions was established as 1-3/4 to 1. Subgrade was plowed or scarified, soaked by sprinkling if necessary, and compacted by a tamping roller. To stabilize the subgrade surface, a 6-inch layer of fine material from quarry waste was placed and rolled.

CHAPTER IV--CONTRACT ADMINISTRATION AND SURVEY WORK

35. Government Organization. The construction engineer's staff for Trenton Dam was generally similar to that used on most Bureau projects. During the relocation and dam construction work, dual organizations for field engineering, office engineering, inspection and surveying were set up. The staff of the two organizations were interchanged as the work loads required. An organization diagram is shown on figure 24.

Figure 24.--Government organization chart for Trenton Dam.

(a) Laboratory. -- A laboratory was provided and staffed with personnel for performing the required tests and inspections. These included tests on concrete materials and placements, inspection at mixing plants, and tests of earth materials during excavation and embankment placement. Laboratory forces supervised and assisted in installation of technical apparatus on the dam embankment. Settlement and piezometer readings were taken by the laboratory personnel during dam construction.

(b) Surveying. -- Survey parties started working in the Trenton Dam area during October 1947. A tentative dam axis was established soon afterwards for use in locating test drill holes. Topography for the general area was prepared on planetable sheets with a horizontal scale of 1 inch equals 100 feet and a contour interval of 5 feet. In the spring of 1949, the dam axis was established at a true bearing of N2°00'00"W. Permanent monuments consisting of brass caps set in concrete were placed in the ground so that approximately 4 inches protruded above ground. The station, offset from centerline or coordinate, and the elevation were stamped on the brass cap of each monument. permanent monuments were guarded with three fence posts to keep traffic away from the immediate area.

Those

Horizontal control for the dam was established from the dam axis. Brass cap monuments were set at stations 7+72.77, 20+00, 81+00, 90+00 and 92+00. All horizontal controls for the dam, structures, and borrow areas were established from these five

monuments. Permanent monuments were set every 500 feet, both 800 feet upstream and 800 feet downstream from the dam axis. As the work progressed, the permanent monuments were augmented by numerous temporary monuments which usually consisted either of 2- by 2-inch oak stakes or 3/4-inch round reinforcement bars driven flush with the ground surface. The temporary monuments were guarded with flags and guard stakes. Elevation and coordinate information was written on one of the guard stakes.

Vertical control for all work on Trenton Dam was taken from permanent U. S. Coast and Geodetic Survey benchmarks located along the old Chicago, Burlington and Quincy Railroad right-of-way. From these benchmarks, vertical control circuits were extended to all permanent monuments in the dam and borrow areas.

The dam area was slope staked for stripping operations. After stripping, fill stakes were set for the downstream limits of the dam embankment and the upstream and downstream limits of the pervious zone. Detail cross sections were taken of the entire dam area after completion of stripping operations, to be used for determining excavated quantities. As the dam embankment progressed, the upstream and downstream slopes were maintained to line and grade by setting either slope or grade stakes. It was necessary to set these stakes for approximately every 5- or 10-foot vertical increment of embankment placed.

Control for line and grade of the spillway was maintained by four permanent monuments set outside of the working area. Two of these monuments were set on the centerline of the dam and the other two were set at right angles to the centerline of the dam and on the centerline of the spillway. From these monuments other monuments were set as the need arose.

Drift pins were driven into shale as control points for excavating for tile drains and cutoff trenches in the spillway chute. The forms for the floor cutoffs were also built and checked from drift pins. The upper portion of the spillway floor slabs was completed before much work was done in the gate structure area. This was advantageous in setting up control for the gate structure area. A number of offset lines were set in the spillway floor by using lead plugs and tacks. Control lines were established on the centerline of each spillway pier on offsets from construction joints, and on the centerline of the spillway. These controls were used for building and checking of forms. After outside forms of a placement were completed, line and grade work for all interior formwork, blockouts, curved sections, etc., was established.

Control for line and grade of the canal outlet works was similar to that used on the spillway structure. A set of lead plugs set on the centerline were used for control in placing the upstream section of conduit, which was placed into position as a unit.

36. Safety. The Government employed a full-time safety inspector for Trenton Dam. The safety program for the contractors was conducted by their supervisory personnel. Monthly safety meetings were conducted during the construction program.

A perfect safety record was achieved on the project by several contractors who completed their contract work without accident. These contractors with their work are listed below:

(1) American Bridge Company--Erection of high railroad bridge superstructure. (2) Nichols Construction Company--Relocation of county road.

(3) Asbell Brothers -- Reservoir clearing.

Government vehicles were operated throughout the entire job without accident.

The following is the safety record for the entire job, requiring approximately 3, 000, 000 man-hours:

Number of lost-time accidents, including
three fatalities

Total lost-time, man-days

21

18, 544

Frequency rate

Severity rate

7.0

6, 181

Circumstances under which the fatal accidents occurred are listed below:

(1) A truck overturning.

(2) A steel bin falling on a welder.

(3) A carpenter falling from a high form.

A. Contracts

37.

Major Construction Contracts. The construction of Trenton Dam and relocation of railroad and highway was accomplished by several major construction contracts. When it became apparent that relocation of the railroad and highway would require several months of negotiations and design work, it was considered advisable to issue two sets of specifications for construction of Trenton Dam, one for construction of that portion not traversed by either the railroad or highway and the other for completion of the work. The railroad and highway relocation work was performed by several contracts.

(a) Foundation Work. -- The foundation work for Trenton Dam was performed under specifications No. 2689. Bids submitted in response to advertising for these specifications were opened June 29, 1949, at Trenton, Nebr. Twelve bids were received. The low bid of $1, 626, 250.00, submitted by Marshall, Haas and Royce, San Mateo, Calif., was accepted and contract No. I2r-18601 was awarded July 15, 1949. Notice to proceed was acknowledged by the contractor on August 22, 1949, which established the completion date as July 18, 1950. The work was completed on July 18, 1950, and the final contract amount was $1,672, 397.64.

(b) Completion Work. -- Trenton Dam was completed under specifications No. 3047. Bids submitted in response to advertising for these specifications were opened June 23, 1950, at Trenton, Nebr. Twelve bids were received. The low bid of $4, 726, 557. 10, submitted by A. S. Vinnell Co., United Concrete Pipe Corp. and R. A. Bell, Alhambra, Calif., a joint venture, was accepted and contract No. 12r-19084 was awarded on June 30, 1950. The notice to proceed was acknowledged on August 7, 1950. The completion date was established as August 11, 1953.

Because of a delay in relocating the railroad, the contractor incurred additional costs. An amendatory agreement of April 1, 1952, provided for a payment of $490,000 to the contractor for rescheduling his work and for additional costs incurred because of the presence of the railroad through the dam site for about 10 months after the scheduled date for removal. Two extra work orders and four orders for changes were issued during the life of the contract. These involved, chiefly, rediversion of the river, stockpiling of a portion of riprap rock and rock blanket material, design changes, and cleaning and straightening about 500,000 pounds of partially bent and painted reinforcement bars. By findings of fact dated August 28, 1953, and supplemental findings of fact dated January 13, 1954, the completion date of the contract was extended to November 30, 1953, because of a delay in delivery of spillway radial gates. The contractor completed the work on November 30, 1953, at a final contract cost of $5, 570, 631.71.

(c) Railroad Earthwork, etc.-- Earthwork and structures, except bridge superstructures, for relocation of Chicago, Burlington and Quincy Railroad were constructed under specifications No. 3112. Bids submitted in response to advertising for these specifications were opened August 17, 1950 at Trenton, Nebr. Fifteen bids were received. Because of allegations of errors, misquoted freight rates, and other considerations, all bids were rejected and the work was readvertised.

Bids submitted in response to the readvertised specifications No. 3112 were opened September 1, 1950. Eight bids were received. The low bid of $2, 195, 467. 50, submitted by Perry McGlone Construction Co., Kansas City, Mo., was accepted and contract No. I2r-19157 was awarded on September 5, 1950. The notice to proceed was

acknowledged on September 12, 1950, and completion dates for various subdivisions of the contract established. One extra work order and two orders for changes involving minor changes, construction procedures, and extensions in completion time were issued during the life of the contract.

A findings of fact dated December 18, 1951, fixed dates for completion of various subdivisions of the contract. The final established dates for completion of all subdivisions of schedules No. 1 and 2 were September 30, 1951, and March 24, 1952, respectively. Schedule No. 1 was completed September 30, 1951, and schedule No. 2 was completed January 25, 1952.

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(d) Superstructure for Bridges. Superstructures for bridges for relocation of Chicago, Burlington and Quincy Railroad were constructed under specifications No. 3113. Bids submitted in response to advertising for these specifications were opened August 16, 1950, at Trenton, Nebr. Four bids were received. The low bid of $541, 305.00, submitted by the American Bridge Co., Denver, Colo., was accepted and contract No. I2r-19183 was awarded September 5, 1950. Notice to proceed was acknowledged by the contractor on September 23, 1950, and the completion date was established as December 7, 1951. Two orders for changes and one extra work order involving changes in design and construction were issued during the life of the contract. By a findings of fact dated February 2, 1953, the completion date was extended to November 14, 1952. The work was completed and accepted October 27, 1952.

(e) Tracklaying and Railroad Facilities. --Contract No. 181r-1322 was awarded to the Chicago, Burlington and Quincy Railroad Co. on August 1, 1950, for ballasting, laying of rails, installation of signal, telephone and telegraph systems, and construction of a new depot at Trenton, Nebr., at a cost not to exceed $2, 500,000. The work was started on November 21, 1951, and essentially completed on December 13, 1952. A supplemental contract which provided for a payment of $225, 000 by the railroad company to the Government for salvage value of the abandoned line was awarded at a later date.

(f) Highway Relocation.-- Contract No. 181r-1272 was awarded on June 16, 1950, to the State of Nebraska for relocation of U. S. Highway No. 34 around Trenton Dam and Swanson Reservoir (now Swanson Lake) at a cost not to exceed $1, 056, 000. The sum agreed represents the cost for rerouting and replacing in kind the existing highway. Work on the new highway started September 18, 1950, and completed in December 1951. Traffic was routed over the relocated highway January 2, 1952.

38. Principal Supply Contracts. The following is a listing of the principal supply contracts: