A reinforced-concrete fish ladder, designed and constructed to conform to the requirements of the Washington State Department of Fisheries, is located on the north shore of the river. The fishway has 20 bays 10 feet long by 6 feet wide and risers of 2 feet 1 inch. The bays are separated by 6-inch concrete baffle walls 3 feet 6 inches high.

To prevent the attempts of the fish to turn back after entering the fishway below the dam, an ingenious device, called a fish guard, is placed on top of the baffle walls of each bay. The fish guard is made up of a grid of short bars having a quarter of a circle bend at one end. Control of water through the fishway is obtained by the use of stop planks set in grooves at each end of the ladder. In conjunction with the stop planks on the lower end of the fishway a movable fish guard, operated by a hand hoist, is placed in a separate groove in the concrete. This device

may be raised or lowered to any desired river level. In a memorandum dated December 16, 1927, L. E. Mayhall, general superintendent of hatcheries, department of fisheries and game, Seattle, Wash., makes the following

statment:

Salmon ascend the rivers as a result of their instinct to reach their place of birth, the spawning beds in the upper reaches of the river, and when they meet an obstruction or dam they will make desperate efforts to get over, and on their way. By taking advantage of their desperation, they can be tricked into jumping small waterfalls into the entrance of the fishway, but when confined in a small place between the concrete walls of a fishway, they are quick to realize it is not their natural element, the big open river, so they become panicky and rush out, unless held in a fishway by the trapping device.

A gallery is placed inside the dam for convenience in

General authority for the construction of the Kittitas division is contained in a contract, dated December 19, 1925, between the United States and the Kittitas Reclamation District. The dam was built under a separate contract dated March 16, 1928, and awarded to C. F. Graff, of Seattle, Wash. The contractor commenced construction, but later, due to financial difficulties, relinquished the job to one of the sureties, Hans Pederson, who completed the work on October 11, 1929.

On September 20, 1928, the gates of the Kachess and Keechelus Reservoirs were closed and work was started on the building of two cofferdams. The upper cofferdam was first built as a rock-filled crib with timber sheeting extending a few feet into a 10-foot stratum of gravel and boulders. The lower cofferdam consisted of a rock-filled section. Notwithstanding the use of additional reinforcements consisting of sack dams, both cofferdams leaked badly through the gravel stratum. To unwater the foundations it became necessary to drive interlocking steel-sheet piling and to cover the cofferdams with clay blankets. The water in the river was first diverted by means of a 12-foot-wide by 9-foothigh timber flume placed on the north side of the river at elevation 2,142.5. Later the river was diverted through a temporary opening left in the dam. As construction progressed further, the opening was closed and the river allowed to pass through the sluice gates.

The foundation was excavated into solid rock to a depth of 3 to 4 feet, and the cut-off trench for the dam was excavated to an additional 5 feet. The excavated material was removed by stiff-leg derricks.

Grout holes were drilled on the center line of the cut-off trench at 5-foot centers. Drill holes were 25 feet deep in the river channel and tapered off to 10 feet on either river bank. Where the exposed foundation showed signs of seams, additional grout holes were drilled. In the south half of the spillway section, downstream from the cut-off trench, 20-foot grout holes were drilled on 10-foot centers,

both ways. The maximum amount of grout needed in any one hole was 381⁄2 cubic feet. The average requirement of grout per hole was 4.75 cubic feet. Before actual grouting was started, the foundation was covered with a 5-foot layer of concrete. When the concrete had partly set, the grout pipes were loosened and slightly raised above the top of the rock foundation. Grout under a maximum air pressure of 100 pounds per square inch was then forced into the seamy rock and into voids that existed between the original rock and the concrete blanket.

Concrete in the proportion of 1:2.75:6.25 was used for the interior portion of the dam. A richer mix of 1.5:2.75:6.25 was used in a 3-foot thickness at the exterior surface. This procedure was easily and quickly obtained by the addition of one sack of cement to the batch of the cubic-yard mixer. The concrete was chuted in place from a tower located on the south bank of the river. A concrete mix of 1:2.4:3.6 was used in the reinforced walls and slabs.

A concrete testing laboratory, established at Ellensburg, Wash., made numerous tests on strength, permeability, and economy of the mixes of concrete to be used in the dam. The sand and gravel used in the concrete was purchased from the Pioneer Sand & Gravel Co. and shipped from Steilacoom, Wash. The height of concrete pours varied from 4 to 10 feet. Keys were provided in all construction joints. Metal-lined forms were used on concrete surfaces exposed to view.

The center portion, or spillway section, of the dam was constructed first and the abutments later. The drum gates were assembled in place. Alignment of the steel castings making up the gate hinges was obtained by placing the anchor-bolt nuts on each side of the casting. After the erection of the structural-steel sections of the gate, it was possible to set and grout the cast-iron wall plates to member correctly with the drum-gate side seals and to concrete around the gate hinges and seal castings.

Main items of the contractor's equipment consisted of one 4-yard steam shovel; forty 11⁄2-yard side dump cars; two steam dinky locomotives; one guy and two stiff-leg derricks; a stationary air compressor, 1,190 cubic feet per minute; one 200-horsepower motor; and one 1-cubic-yard concrete mixer.

For convenience in shipping materials a spur track was constructed from the Northern Pacific Railroad yards at Easton to the dam site. From 40 to 80 men were employed on the construction. The accompanying tabulation gives a detailed analysis of the cost of the work.

COST ANALYSIS

Cost of Dam. The accompanying table no. 1 shows the detail cost of Easton Dam, not including the cost of preliminary investigations, etc.

THE RIVERTON PROJECT, 100,000 acres irrigable, is located in Fremont County, west central Wyoming. The Wind River is a part of the Bighorn and Yellowstone River systems and drains the south slope of the Shoshone Mountains, and the northerly portion of the east slope of the Wind River Range, the latter a part of the Continental Divide. The drainage basin has an area of 1,860 square miles at the diversion dam. Of this area, a considerable portion has Alpine topography with peaks as high as 13,800 feet above sea level.

The average annual run-off is about 900,000 acre-feet, 80 percent of which comes from mid-May to early August, principally from melting snow. The maximum observed discharge is 12,300 second-feet, occurring in June 1906. While the irrigation demand synchronizes reasonably well with the flood wave, the full use of the water supply requires some seasonal storage as well as carry-over storage. The seasonal storage is required in late August and early September to finish off the potato, bean, and sugar-beet crops. Storage capacity of 155,000 acre-feet is now under construction at Bull Lake; and the Pilot Butte Reservoir, completed in 1926, provides 31,550 acre-feet of storage capacity.

The entire valley is youthful geologically. The irrigable lands are located, in part, on terraces of the main stream where there is a subsoil of cobble stones; and, in part, on the lower reaches of tributaries from lower lying lands of the drainage basin. Here the soils are mostly colluvial and aeolian in character and bedrock is not far removed. The main canal has an initial capacity of 2,200 second-feet. At mile post 9.25 a branch takes off the Pilot Butte Reservoir and the Pilot Canal. This is a first development of 20,000 acres on which irrigation began in 1925. A drop of 105 feet from the canal to the reservoir is utilized to produce electric power for use in further construction, especially excavation work with electric draglines, although electrical energy is furnished to nearby towns. The present installation consists of two 750 kilovolt-ampere units. The operation of the plant requires year-round operation of the canal, but the reservoir conserves the water so used for irrigation purposes in the following year.

DAM SITE

In the vicinity of the diversion dam the Wind River Valley has an average fall of 25 feet per mile. The recently workedover portion is 25,000 feet wide and is bordered by sandstone bluffs 40 to 100 feet high. The low-water channel is 120 feet wide and 2.5 feet deep and 8 feet to 10 feet lower than adjacent ground. Low-water surface is at elevation 5,552.0. Bedrock of rather soft sandstones and shales is generally at elevation 5,546 or higher, except in an old channel near the south abutment, where it is about elevation 5,536. lying the bedrock is a 7- to 15-foot thickness of granitic and andesitic cobblestones. These constitute the flood stage saltation load of the river. Except in the present stream bed these cobblestones are covered with 1 to 3 feet of sands carried higher in the river cross-section or brought in by winds and intermittent side streams.

DESIGN REQUIREMENTS

Over

It was required that the low water surface of the river be raised 17.75 feet to permit of diverting 2,200 second-feet into the canal with none passing down the river; that coarse materials carried by the river in flood be kept out of the canal; and that the diversion structure be able to safely pass a flood of 40,000 second-feet. It was also required that a means be provided for passing the saw logs and railroad tie. timbers annually driven down the river by a lumber company operating in the headwater forests; that a fish ladder be provided so that the mountain trout can continue their annual upstream run to spawning grounds; and that a roadway be provided across the valley for the benefit of future work on storage developments. The Wyoming State Highway Department cooperated in the last-mentioned matter, building a steel bridge over the spillway section, and more important, incorporating the highway from rail head at Riverton to the diversion dam in the highway U. S. No. 287, one of the principal entrances to the Yellowstone National Park. This cooperation, while highly valuable to the project, did not begin early enough to be of aid during the building of the dam.