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bottom to the cribs and extending on both sides, before the rock was placed. The falling leaves, drifting into the pocket formed by the bank and the dike, were filling the crevices in the dike and rapidly making it tight at the time of leaving it. The resultant channel enters on the left of the point of the dike and follows it until deep water is reached.

The fall

Six hundred and seventy-five cubic yards of rock was used in this dike. here from pool to pool, a distance of 3,400 feet, was 2.5 feet, October 6, 1896. Stake Shoal, 9 miles above the mouth.-At this point the channel is straight. The water leaves the quiet pool above, enters between two gravel bars, and flows over the shoal at a width of 250 feet and for a length of 1,300 feet before the pool below is reached. The aim at this point was to narrow the entrance of the water onto the shoal and to train it along a longitudinal dike until the pool below was reached. A dike was begun on the right bank near the foot of the shoal, and carried upstream 200 feet, complete except as to backing. The project calls for 1,100 feet, which would carry the dike to the head of the shoal. There were logs prepared for 600 feet of crib work, and 100 cubic yards additional rock was quarried. The fall at this shoal from pool to pool, a distance of 1,300 feet, is 1.7 feet. Removal of snags.-Snags were removed during the season from Pryors Bend and points below. Bryors Bend is a stretch of river 3 miles in length, the lower end of which is 30 miles from the mouth of the river. It is difficult of navigation, particularly to rafts, on account of its circuitous course, the swift current, due to a fall of 7 feet in its length, and to the snags which lodge more easily in the bend than at any other point on the river.

The total number of snags removed was 91, of which 82 were taken from Pryors Bend. There were 10 overhanging trees cut and 20 drift trees cut.

The snagging party was in the field from October 20 to November 12, operating twenty-one working days.

Surveys were made at Bocks Bar, two; Stake Shoal, Woodpecker Island, Upper Turnpike, and Brandts Shoal.

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PROJECT FOR CONSTRUCTION OF LOCK AND DAM NO. 1, AT BREN-
NEKES SHOAL, OSAGE RIVER, MISSOURI.

MISSOURI RIVER COMMISSION,
OFFICE OF THE PRESIDENT,

St. Louis, Mo., May 18, 1897.

GENERAL: I have the honor to transmit herewith a complete project* for the construction of Lock and Dam No. 1, Osage River, Missouri, submitted by Capt. H. M. Chittenden, which has been approved by the Missouri River Commission in all of its general features, reserving decision upon the plans for operating machinery and the kind of cement to be used in concrete constructions until a later date, and leaving to Captain Chittenden's discretion the details of construction.

Approval is respectfully requested.

Very respectfully, your obedient servant,

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Respectfully referred to The Board of Engineers for examination, report, and recommendation. To be returned.

JOHN M. WILSON,

Brig. Gen., Chief of Engineers, U. S. Army.

[Second indorsement.]

THE BOARD OF ENGINEERS,
New York City, June 24, 1897.

Respectfully returned to the Chief of Engineers, with report of The Board of Engineers, dated June 23, 1897.

G. L. GILLESPIE,

Colonel, Corps of Engineers, Senior Member Present.

PROJECT OF CAPT. HIRAM M. CHITTENDEN, CORPS OF ENGINEERS.

The revised project for the construction of Lock and Dam No. 1, as at present approved by the Missouri River Commission and the Chief of Engineers, covers only the following points:

(1) Dimensions of lock, 220 by 42 feet.

(2) Use of concrete in construction.

(3) Lower miter sill fixed at reference 94 feet.

The completed project for the lock as herewith submitted covers the following additional points:

(4) Reference of upper miter sill 103 feet.

(5) Filling valves to be in miter sill wall under gate. (Pls. III, V, VI.) (6) Emptying valves in lower gate.

(7) Top of main walls at 120 feet.

Pl. VII.)

(8) Top of head walls at 128 feet (above flood height).

*Drawings not printed.

(9) Foundation on piles; timber grillage under walls; concrete floor 3 feet thick under chamber, with piles (4 feet centers) cut off even with top surface, and notched to make good contact with concrete. (Pl. III.)

(10) Underflow in river bed to be cut off by Wakefield piling under miter wall down to reference 75 feet, or by such other means as may be found most effective when work is done.

(11) Foundation to be drained so as to relieve any possible leakage from upper pool.

(12) Sections of walls, and all other details, as in drawings. (Pls. III to VII.)

PROJECT FOR DAM.

(13) The dam is to be built in ten 75-foot sections, separated by 9 piers, 10 by 30 feet at base, with tops at reference 120 feet. (Pl. II.) (14) The dam is to rest on a pile foundation and is to consist of a fixed weir and a movable crest. (Pl. VIII.)

(15) References: Top of foundation, 97.5 feet; top of fixed weir, 109 feet; crest of movable dam up, 116 feet.

(16) The underflow of the river is to be cut off, if possible, down to reference 75 feet, the same as under the lock.

(17) Materials are wood, iron, and concrete.

(18) Details and general plans as in drawings. (Pls. VIII to XIII.)

DETAILED DESCRIPTION OF LOCK.

Length over all, 275 feet 3 inches.
Length between quoins, 220 feet.
Breadth of foundation, 76 feet.
Width of lock chamber, 42 feet.

Height of main lock walls, 27 feet.

Height of head walls of lock, 35 feet.

Thickness of head walls, 16 feet.

Thickness of foot walls, 14 feet at base, 11 feet 9 inches at top.
Thickness of main walls, 14 feet at base, 5 feet at top.

Foundation rests on piles. Beneath the walls the piles are 3 feet apart. Upon them is placed a timber grillage, consisting of 10 by 10 inch yellow pine timbers, surmounted by a floor of 4-inch oak plank. Between the walls, forming the floor of the lock, is a layer of concrete 3 feet thick. It extends 2 feet under the walls. The piles under the chamber are cut off level with the floor of the lock and the concrete is put in between them. The piles are notched in order to afford a more secure hold for the concrete. The concrete has a bearing surface of about 9 square feet on each pile and the piles are spaced 4 feet from center to center. It is believed that any upward pressure beneath the concrete would have to pull the piles before it could move the floor.

The necessity for this floor is to prevent leakage from the lock when the water within it stands above the level of the lower pool, and to prevent leakage into the lock should it become necessary to pump out the interior for repairs.

All leakage from the upper pool is cut off, as far as possible, by a row of Wakefield piling beneath the upper miter sill wall, extending down to reference 75 feet, the reference of the lock floor being 93 feet. But the nature of the river bed is such that water will find its way under considerable pressure to the ground under the lock. To prevent any evil effects from this pressure the foundation is thoroughly drained. Immediately below the concrete of the foundation is a natural layer of heavy clay from 1 to 2 feet thick. Beneath this is water-bearing gravel, which is the place where the water pressure will develop. To relieve

this pressure a trench will be let down into this layer just below the row of sheet piling (see drawing), and will be filled with broken stone. It will communicate with a drainpipe extending along the lock wall on the shore side and with the lower pool on the river side. Along each side of the lock, at intervals of 30 feet, holes about. 2 feet in diameter will be sunk into the gravel stratum and cased with sewer pipe. These will communicate on the shore side with the drainpipe and on the river side with the lower pool. By this means any tendency to develop pressure beneath the foundation is prevented, for relief is at once given through this connection with the lower pool.

The lock is to be filled through six culverts in the upper miter-sill wall. They are closed by wickets at their upper end, three being operated from each side on a single axis. The drawings make these details clear. The cross-section area of the filling culverts is about 61 square feet, calculated to fill the lock with a lift of 16 feet in three minutes, includ ing time of opening valves. The space above the culverts is protected from drift by a grating.

The lock is to be emptied through wickets in the lower gates similar to those now in use on the Kanawha River.

The head walls of the lock are carried up to 128 feet, so as to act as a guard in time of flood and prevent a current through the lock.

The gates are similar in general design to those in use on the Kanawha River, and present no features of special importance.

Through the upper miter sill wall are carried the pipes for operating the movable dam. (See description of dam.) The inlet culvert and valve for filling the chamber of the first section of the dam is in river wall of the lock opposite the upper gate. (See drawing.)

All other details, it is believed, are fully illustrated in the drawings. In the matter of the choice of cement for use in the concrete masonry, it is requested that the final decision be left open until certain experiments described below can be made. It is proposed to use both Portland and natural cements for this work. For all that portion of the

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masonry below standard low water (105 feet) a good natural cement will be used. This portion of the work, being subject neither to the action of frost nor to the abrasion of boats, nor, to any considerable

extent, to the action of currents, the qualities of hardness and strength are of secondary importance. Mass being here the desideratum, there is no reason to doubt that a natural cement concrete will answer every purpose.

For that portion of the walls above 105 feet one of the two arrangements shown in the accompanying cuts is proposed. If experiments now in progress show that a section along the general line of union of the two kinds of concrete possesses a strength equal to or greater than the weaker concrete, then the arrangement in Cut (1) is recommended. If, on the other hand, it results that such a joint is weaker than a similar section of natural cement concrete, the arrangement shown in Cut (2) is proposed. Very careful experiments with concrete blocks are now in progress, and will be continued until it is settled whether or not a good bond can be secured between contiguous masses of Portland and natural concretes when deposited at the same time.

The saving in cost by the use of natural cement will be considerable. If the lock were built all of Portland, it would cost $20,000 more than if all of natural cement. If built on the plan of Cut (2), it will cost $9,000 more than if all of natural cement. If built on the plan of cut (1), it will cost less than $3,000 more than if all of natural cement.

It is therefore recommended that the arrangement shown in Cut (1) be approved, subject to the results of pending investigations, and that, if these results are unfavorable, then the arrangement shown in Cut (2) be adopted.

THE DAM.

Necessity for a movable structure. The reason which led to the adoption of a movable dam for the site of Lock No. 1, Osage River, was that the high-water cross section at this point may be contracted as little as possible. In order to make the pool of the dam extend to the most favorable point for the construction of Lock No. 2, should such a lock ever be built, the crest of the dam should stand not lower than 116 feet. The contraction of waterway resulting from a fixed structure of this height would be such as to cause a rise in the flood plane above the lock of 3.08 feet above its level in the natural condition. (Pl. XV.) With a movable dam, as proposed, this rise in the flood plane is reduced to less than 1 foot. The topography of the valley above the dam is such that a difference of 2 feet in the flood plane of the river will represent a considerable acreage of overflow, and the damages which such an overflow would represent would probably be much greater than the extra cost of a movable dam over that of a fixed structure.

Detailed description of dam.-The dam rests on a pile foundation (Pl. VIII), surmounted by a timber grillage on which rests a watertight floor of 4-inch plank. The second row of piles on the upstream side consists of triple-thickness sheet piling reaching entirely across the river on a line with the sheet piling under the lock. It extends downward to reference 75 feet and will cut off the underflow of the river for 25 feet beneath the river bed. The foundation of the dam proper is 25.5 feet broad, and the structure forming the apron of the dam, also resting on piles and joined to the main foundation, is 16.5 feet wide, giving a total breadth of base of 42 feet.

The greatest possible relief of the dam, or difference in elevation between the upper and lower pools, is 16 feet. This, however, as explained in the discussion on the strains of the gate, can very rarely occur. In fact, when the present work of opening a direct connection between the Osage River and the Missouri near Cote Sans Dessein is finished, the lower pool can not fall below 105 feet during the naviga

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