SOIL SURVEY.

A soil survey, under the direction of the engineer of soils, was started in September and will be completed during the present year. The result of this survey will determine the size of the farm units.

SHOSHONE RESERVOIR.

A survey of the 5,370-foot contour, which is 10 feet above the crest of the spillway, has been completed, the original survey of the reservoir extending only to the 5,350-foot contour. The capacity of the reservoir to the 5,360-foot contour-the flow line-will be 456,000 acrefeet. Contracts, subject to the approval of the Secretary of the Interior, have been made for the purchase of 2,919 acres covered by the reservoir. Negotiations are in progress for the purchase of the remaining 1,320 acres.

BORINGS.

BORINGS AT DAM SITE.

Diamond-drill borings at the dam site continued from November 1, 1904, to May 31, 1905, two drills being used, one operated by steam, the other by hand. Great difficulty was experienced in getting the casing down through the gravel and large bowlders overlying the bed rock, the size of the bowlders passed through varying from a few feet up to 28 feet. On December 9, 1904, boring No. 4 entered bed rock at a depth of 88 feet below the bottom of the channel. The boring was continued into the bed rock for 83 feet, making a total depth of 171 feet from the bottom of the channel to the bottom of the boring. Other borings were made farther downstream, and a location was selected for the dam where the average indicated depth to bed rock is about 65 feet below the bottom of the channel. The bed rock encountered in all borings is a very hard granite. A total of 15 holes were put down from 26 feet to 83 feet into bed rock, the total distance through gravel and bowlders being 819 feet and into bed rock 408 feet.

BORINGS AT CORBETT DIVERSION.

Wash borings made at the Corbett diversion indicate that the material under the river channel is shale and sandstone in alternate layers, overlain with about 10 feet of gravel. This is satisfactory material for the foundation of the diverting weir.

BORINGS AT WILLWOOD DIVERSION.

The Willwood diversion is a point on Shoshone River about 6 miles below the Corbett diversion. Here it is proposed to divert water for the purpose of reclaiming the land on the south side of Shoshone River. The borings indicate that a suitable foundation on sandstone for a diverting weir exists a few feet below the bottom of the channel.

SHOSHONE DAM.

The location selected for the Shoshone dam is a gorge in solid granite, about 70 feet wide at the bottom of the river channel and 200 feet wide at an elevation of 250 feet above the channel (Pl. LXI). These conditions seem to call for a type of dam other than that of a gravity section. In order to control the entire flow of the stream it was found that a dam 240 feet in height above the bottom of the channel, or 305 feet in height above the lowest point of the foundation, as indicated by the borings, would be required. After a careful consideration of the problem by a board of engineers, an arched dam, the radius of the center of the top being 150 feet, was decided on. The cross section adopted is of the following dimensions: Top width, 10 feet; batter of upstream face from top of dam to stream bed (245 feet), 15 per cent; batter of downstream face for same vertical distance, 25 per cent;

from the stream bed to foundation (60 feet) both faces are vertical; width of bottom of section of dam, 108 feet (Pl. LXII). The dam will be constructed of concrete, in which pieces of granite rock weighing from 25 to 200 pounds will be placed by hand and rammed until well bedded. These rocks will be distributed uniformly throughout the dam and will form at least 25 per cent of its volume.

Plans and specifications for the construction of the Shoshone dam were prepared during the year under the direction of a board of engineers. On September 5, 1905, at Billings, Mont., bids for its construction were opened. Five bids were received, the lowest ($515,730) being that of Prendergast & Clarkson, of Chicago. On September 18, 1905, the contract was awarded to the above firm.

Bids received for the construction of Shoshone dam, Shoshone project, Montana.

A spillway 300 feet long, connected with a tunnel 20 by 20 feet in cross section and about 500 feet long, will be constructed on the left side of the river for the purpose of discharging surplus flood waters. The spillway tunnel will discharge into the river 100 feet below the lower toe of the dam, and will have a capacity of 20,000 second-feet.

An outlet tunnel 10 by 10 feet in cross section and about 480 feet long will be constructed around the dam on the right bank of the river. The elevation of the floor of the tunnel at its inlet will be 10 feet above the bottom of the reservoir. (Pl. LXIII., This tunnel will be constructed before work on the dam begins, and when completed will be used for conveying the water around the dam site during the construction of the dam. Designs of various types of gates for controlling the flow of water through the outlet tunnel are being made for the consideration of a board of engineers.

WAGON ROAD.

Work on the wagon road through Shoshone Canyon was continued from November 1, 1904, to July, 1905, when it was completed. For about one-half mile the construction involved very heavy rock work. On this portion of the road are two short tunnels. Over this road construction materials will be hauled to the dam site from Cody station, and after the construction of the dam it will be utilized as a portion of the road from Cody to the Yellowstone National Park, replacing the portion of the present road which will be covered by the reservoir.

EXPENDITURES.

The expenditures on the Shoshone project to September 30, 1905, for preliminary examination, final surveys, design of structures, construction of canyon road, construction of office buildings, quarters and storehouses, and administration were $162,944.39.

DE SMET PROJECT.

Since the last report no surveys have been made on this project, but stream gagings have been carried on continuously. At the time of the original surveys and report, sufficient stream gagings had not been made to determine the quantity of water available.