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Improving Mississippi River, First District, etc.-Continued.

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Improving Mississippi River, Second District.

2, 979.51 2,979.52

Statement of expenditures at Hopefield

Bend, Arkansas, from September 1, 1891, to March 1, 1892.

693. 47
85.00

5.09

$2,699,55 119.55 19, 733. 43 4, 402.81 244.97 155.40 1,754. 41 503.22 3.50 546.03

3, 173. 81 9, 596, 01 4,744.44 1.716.97 63, 380, 34 1,252.30 16.01 31.89

5.921.66 57.818.43

2. 285. 17 18, 580.50

73.06 1,667. 48

36.53

36.54

7.306.78

205, 987. 18

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APPENDIX 6.

REPORT OF CAPT. C. M'D. TOWNSEND, CORPS OF ENGINEERS, ON OPERATIONS IN

THIRD DISTRICT.

UNITED STATES ENGINEER OFFICE,
Memphis, Tenn., May 31, 1892.

GENERAL: I have the honor to submit the following report of operations in the Third District, improving the Mississippi River, for the year ending May 31, 1892. This District extends from the month of White River to Warrenton, Miss., a distance of 220 miles. In its improvement, work has been undertaken at Lake Bolivar Front, Ashbrook Neck, Greenville, Lake Providence Reach, Delta Point, and Vicksburg Harbor, and the levees have been constructed and enlarged, in the Lower Mississippi Levee District, and in the Tensas Basin, Arkansas and Louisiana.

LAKE BOLIVAR FRONT,

The object of this improvement was to stop a caving of the bank, which was threatening the destruction of a large levee across the end of Lake Bolivar.

Four thousand, four hundred feet of revetment were built in 1888-'89, as described in the report of the Chief of Engineers for 1889, page 2704, along a portion of which the mats were but 180 feet wide. This section was strengthened in 1889–’90.

This work has accomplished the purpose for which it has been constructed. The caving has been checked at the end of the lake. Below the revetment the caving has continued, but the line of levees there threatened, has been replaced by a line further from the bank, erected by the Lower Mississippi Levee District.

An examination of the work during the low water of last season showed that the subaqueous mat was in good condition, but that at a number of places above the low-water line the brush revetment had rotted out, leaving portions of the bank exposed to the action of the river. It is proposed during the next season to repair these places, replacing the brush by a revetment of stone 10 inches thick.

ASHBROOK NECK.

The object of the work at this place is to prevent the river from cutting through the neck, and thus forming a cut-off, with its resultant disturbance of the regimen of the river. The neck at its narrowest section is but 2,300 feet wide.

The project adopted for this improvement in 1890 consisted in a continuous revetment of the upper side of the neck at its narrowest part, the subaqueous mats to have a width of from 250 to 300 feet, and the upper bank revetment to extend to a two-thirds stage. During the season 1890-'91, 2,820 feet of this revetment was thus constructed, the upper bank revetment being built of brush and stone, but due to a rapid rise in the river at the close of the season the subaqueous mat for the last 500 feet was only given a width of 180 feet.

After the flood of 1891 it was found that scouring had taken place at the foot of the mat 180 feet wide to such an extent as to endanger its stability.

The approved project for this season's work was to repair the portion of revetment of last year which had been undermined, and extend it 2,500 feet below the completed work and 3,500 feet above, substituting a riprap of 10 inches of stone for the upper bank revetmentment of brush and stone previously employed, and giving the upper bank a slope of 1 on 4 in place of 1 on 3.

Work was begun August 24, 1891, and suspended January 28, 1892, on account of the high stage of the river. Over the damaged mat was sunk a mat 300 feet wide, and 2,500 feet of revetment was completed below that of last season. Work was then begun on the upper portion of the project, but the rising of the river necessitated the suspension of operations when 1,300 feet of the bank had been revetted. The cost of the revetment was $30.83 per linear foot.

To prevent a flow of water across the neck, a levee was constructed parallel to the axis of the neck, as shown on the accompanying map. The levee was given an elevation equal to that of the main line of levees opposite to which it was located, with a crown of 4 feet and slopes of 1 on 24. Its length was 7,300 feet. This levee has been seriously injured during the existing flood. The extent of the damage will not be determined until the water subsides.

A detailed description of the work will be found in the accompanying report of Mr. Arthur Hider, who was in local charge. Credit is due to Mr. Hider and the employés at Ashbrook Neck that so much revetment was constructed at this place and at so low a cost, especially when it is considered that the changes in plan necessitated the expenditure of nearly 2 cubic yards of stone per running foot more than was employed last season, and that plant, material, and labor were often diverted from it to insure the completion of the more urgent work at Greenville.

REPORT OF ASSISTANT ENGINEER ARTHUR HIDER.

The following report of work on the Ashbrook Neck improvement the past season gives a description of the work done, the quantity of material used, and the cost of the different items in detail. Work was begun August 24, 1891, and was suspended January 28, 1892, on account of the high stage of the water and the lateness of the

season.

Description. The project for the season's work, as approved, was the continuation of the revetment begun last year, both above and below the completed work; 3,500 feet above and 2,500 feet below, making a total length of 6,000 linear feet. Work was first begun at the lower end, where the wide 300-foot mats built last season terminated. After finishing this part of the project work was begun above, but only 1,300 feet of the 3,500 was completed before work had to be stopped on account of the high stage of the river.

The work here was identical with that done at Greenville, subaqueous mattresses from 250 to 300 feet in width, so as to extend out to the deepest water, upper bank graded to a slope of 1 or 4, and covered with 10 inches of riprap to the two-third full stage, which was taken at 32.8 feet on the Arkansas City gange, the height of the brush revetment being restricted to 5 feet above the stage of water existing at the time the mattresses were constructed.

Clearing. Before beginning the grading the upper bank was cleared of undergrowth, trees, and stumps, as the timber grew close to the river, in all 22.4 acres of clearing was done, at a cost of $71.50 per acre.

Grading.-Along the lower part of the work the bank was of hard material, and the rate of progress made was not so rapid as at the upper end, where the bank was composed of layers of sand and buckshot. Work was begun on August 24, and the grading finished January 5. Grader No. 3 was in service from the beginning, and Grader No. 77 from November 21 until the grading was finished. A single line of 4-inch hose was used on Grader No. 3, and a single line of 24-inch hose on Grader No. 77. The smaller grader, No. 77, gave good results where the bank was not excessively hard, and, considering the cost, was fairly economical. The pressure used on Grader No. 3 was steam 90 pounds, water 160 pounds per square inch; on Grader No. 77, steam 100 pounds, water 150 pounds. The length of bank graded was 5,155 linear feet; the average rate of progress made was 46.9 feet, the cost of hydraulic grading, $1.21 per foot, and the cost of dressing up and filling holes to bring the slope to an even grade was $0.46 cents, making the cost of a linear foot of completed grade $1.68.

Mattress construction was begun September 7, and the last mat sunk on January 16, 1892. Seven mats were built, the size of these varied from 475 to 1,200 feet in length, and from 250 to 300 feet in width. Two shore mats were constructed; one in front of the eddy just above the upper end of last season's work, to join the main mattress with the shore; this was 350 feet long by 974 feet wide; and the other 400 feet long by 140 feet wide; to cover the slope at the lower end of the work, in front of which the main mattress had been sunk before the upper bank had been graded.

Mattress No. 6 as built was 770 by 275 feet. In sinking this mat it broke in two about 150 feet from the head, and the lower 600 feet was lost. As great care had been taken in the construction of this, as well as all the other mats, and the usual precantions taken in sinking, the loss can not be attributed to any other cause than the fact that the mat had been ballasted ready to sink for nearly two days, which on account of heavy drenching rains could not be done, and that on the evening before the attempt to sink was made, a violent storm of wind and rain occurred, causing the waves and swells to break over the partly submerged mat. bringing into force abnormal strains that the mat was not designed to withstand, weakening the fastenings, and probably breaking some of the poles. The result was that after the head was sunk safely on the bottom, the construction after being subjected to this ordeal was not strong enough to endure the excessive strains which were then brought in play by the position of the mat, part on the bottom and the rest floating on the surface. The mat tore, apparently the longitudinal poles first breaking, and afterwards one after the other the longitudinal cables, of which there were fourteen in the width of the mat. The head lines and the first two cross cables held, and the upper 150 feet were sunk in place.

The method of construction and the size of fastenings used, are fully described in the report of the Greenville Harbor improvement, with which it was identical. In all 12,587 squares of mat were built and sunk in place, at a cost of $1.69 per square, and 971 squares of shore mat, at a cost of $5.33 per square.

Upper bank work.-The riprap was carried up in advance of the rising water, except at the extreme lower end of the work, where it was necessary to build a connecting mat to join the main mat with the bank. As this was built near the close of the season, when the water was at a comparatively high stage, it was necessary to distribute the rock from barges to cover this part of the slope, which is about 400

feet in length. Care was taken to distribute this as nearly as possible to the required depth of 10 inches.

Material.-Brush and poles were obtained by contract. The average distance this was towed was 60 miles. Stone was procured from the reserve left over from last season's work, from Arkansas City, from Memphis, and two barges from the Ohio River. The progress of the work was much retarded on account of the uncertain and intermittent supply of stone, and as a consequence of this, the entire project could not be completed. There yet remains to be done 2,200 feet of revetment at the upper end.

In the beginning of the season the work suffered for want of sufficient plant. It was not until the latter end of October that a sufficient number of barges was available for the needs of the work. These causes, with the difficulty of adjusting the labor force economically to the above conditions, have rendered the cost of the work more expensive than it otherwise would have been.

Levee. The levee built parallel with the axis of the neck, to prevent the current at high water flowing across and precipitating a cut-off, which the revetment work was designed to prevent, was built by contract. The levee is 1 foot above the high water of 1890 (at the upper part of the bend, about 2 miles above the site of the work), crown 4 feet, slopes 1 on 24. The work was begun December 11, 1891, and finished February 20, 1892. The total length, 7,300 feet. The amount and cost was: 56,676.3 cubic yards of embankment, at 16g cents

. Extra work revetting ends .............

Total......

This amount is not included in the statement of cost of revetment.
The amount and value of material expended was as follows:

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$9,422.44 137.09

9,559.53

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Dividing this amount by the length of the bank revetment

cost per linear foot for this class of revetment, $30.83. The percentage of cost of the different items was:

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NOTE. The labor cost of loading stone is added to the value of material as the cost of stone.

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The actual length of bank covered with riprap, revetment, and subaqueous mattress, was 4,460 linear feet. The quantity of brush used per square of mat, was, brush, 0.661; poles, 0.132; total brush and poles per square, 0.793 cord. The quantity of stone used per square of subaqueous mat, was 0.688 cubic yard, on upper slope, and revetment 2.89 cubic yards. The average width of the work from top of slope paving to outer edge of mat is 418.7 feet. The quantity of brush and poles used per linear foot of completed work was 2.565 cords; stone, 5.136 cubic yards; wire cable, 14.8 pounds; wire, 19.517; spikes, 2.6 pounds. The average number of men employed was 144; the average cost of subsistence was 42.4 cents for each day's labor secured. A detailed list of expenditures, labor, cost, etc., is forwarded herewith (omitted); this gives an analysis in detail of the labor and material cost of the different items of work, a synopsis of which is embodied in the following statement:

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The object of the improvement at Greenville has been to prevent the caving of the bank at this locality, which was rapidly destroying the city. In 1887 and 1888 ten spur dikes were constructed in front of the town, which checked the caving along the city front. The caving, however, continued above, and threatened to flank and destroy the spurs completed. To check this tendency two spur dikes were constructed in 1889, at a distance of 1,500 and 2,000 feet, respectively, above the series of 1887. These spurs preserved those in front of Greenville during the flood of 1890, but the caving continuing above them, the spurs of 1889 formed a sharp salient, projecting into the river. The flood of 1891 cut across this salient, destroying these spars. The caving then rapidly extended down the river, eating into the bank from 800 to 900 feet, and flanked the two upper spurs of the series of 1887 and 1888.

The project as approved for this season's work was to revet the bank for about 6,000 feet above the upper remaining spur with a continuous revetment, similar in character to that adopted at Ashbrook Neck. The width of mat was 300 feet, and the height to which the stone riprap was carried was 30 feet on the Greenville gauge.

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