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260 them, varying in length from a few inches to a foot or more in the sig of large worst samples, and the galvanizing has not all disappeared even in eighteen-year-old wire. The corrosion at any one place varies in amount up to the complete destruction of the wire. Where a wire in a strand composed of several was found to be badly corroded most of the other wires adjacent to this bad piece were usually red labo found to be in fair condition, so that the strand still possessed a . fair measure of strength.
The greatest corrosion was found where the wires were tied or twisted together, due probably to the breaking of the galvanizing, which permitted earlier corrosion. While the galvanizing no doubt preserves the wire when intact, it is frequently broken when the wires are tied together by twisting and may soon be abraded by the moving sand, and when the steel is bared it is possible that corrosion is somewhat accelerated by a chemical or galvanic action set : ns han con ting up between the zinc and steel. Even without such aid, the Mint of th steel will corrode under water, and the manner in which the wirect Stone e corrodes in spots is somewhat similar to the pitting of the steel jut álb een plates of the hull of a Mississippi River steamboat.
Summing up the general condition of the old wire fastenings, it the river, may be said that some are so badly corroded that they are useless, siune rene? while others, often adjacent, are in fair condition and holding well, si the cost o and where the ties are composed of a number of wires they are in sigh water to their present condition more efficient than when the ties are of one awr's barga or two wires only. The ties as a whole still hold the brush work to- riuhtained in gether and offer a fair margin for further deterioration, but if their for uste a corrosion goes on as rapidly in the future as in the past it is be- miles he] lieved that their efficiency will cease before the efficiency of the . The brush ceases. It is, therefore, believed that the employment of sili- ** by rail. con bronze wire for tying the top pole grillage to the mat should per grow be continued and that as large poles as practicable be used for this grillage. The bronze wire will undoubtedly last much longer than of wire: any of the other materials and the corrosion of the clips will
in 1999, probably in nowise affect the durability of the mat.
Even should the entire efficiency of the wire fastenings be de- 2 galranize stroyed, the fascines will probably remain in place, because the
od 12 inch brush will be quite heavy from water soak and the spaces between the individual brush will be filled with sediment, so the revetment
och elips will still be effective in resisting erosion and would only fail by ses clipa... undermining or sloughing.
It is probably safe to estimate that a fascine mat built of small
wish will be effective for at least twenty-five years and that when good proportion of large brush is used its life will be considerably
All the revetment works in the First and Second districts have wn built by hired labor, the materials being usually purchased under contract.
Brush and poles are obtained from the bars along the river, the contractor delivering the material on Government barges, the Govrament doing its own towing. The usual price paid contractors is 11 per cord for brush and $1.50 per cord for poles, while the towing
the works costs from 25 to 50 cents per cord, depending upon the distance.
The stone used has come from two sources, from the upper rivers und by rail. Most of the stone used in the Firste district has come rom the river. Stone delivered on Government barges at the quares costs about 50 cents per cubic yard, and the towage from 50
eats to $1 per yard, depending upon the length of the towage and the stage of the river. The cost of towage is much less at high rater, but stone received then must be stored on the bank until reded, and the cost of handling is about equal to the difference in bw and high water towage. Some of the stone has been received
contractor's barges at the works, its cost not varying greatly irom that obtained in the other way. This has made the cost of stone ready for use at the works about $1.40 per cubic yard at New Madrid (70 miles below Cairo) and $1.50 at Plum Point (160 miles below Cairo). The stone used in the Second district has come in meent years by rail, the price loaded on barges at Memphis being shout $1.45 per gross ton, and the towage to Helena costs about 20
The cost of wire strand, etc., has varied rapidly with the market, the prices in 1899, when the last large lot was purchased, being :
No. 12 galvanized wire.
· per pound.. $0.0344
The material used in the building and sinking of one square (100
1 and bar
square feet) of fascine mattress and the cost is about as follows:
.12 0.70 cubie yards stone, at $1.50.
1.05 1.05 3 pounds No. 12 wire, at 314 cents.
.10 .10 512 pounds 14-inch wire strand, at 6 cents.
.33 4 pounds 5-16 inch wire strand, at 5 cents.
.20 142 pounds 12-inch wire strand, at 5 cents.
.08 .08 114 No. 5-16 inch clips, at 8 cents...
.10 .10 1.6 No. 12-inch clips, at 12 cents.
.02 .02 12 pound No. 9 silicon bronze wire, at 20 cents.
.10 Labor, including subsistence..
1.75 to 2:00 Towing
.10 to .25
d'hero] srtment a
'I spite of
Cost per square.
$5.70 to $6.50 The price of $6.50 per square is a maximum, but work has been she consis placed where the situation and conditions were favorable for less than $5.50 per square, and if the work were carried on extensively sche it is probable that the price would average about $6.00 per square, or $18 per linear foot of bank for fascine mats, 300 feet wide, built and sunk.
The cost of the upper bank revetment depends somewhat upon the amount of clearing and grading required, but usually 10 cents per square yard will cover this part of the cost. About three-tenths
See page cubic yards of stone will pave a square yard of bank, and the labor cost of placing this is from 20 to 25 cents. The cost per square yard will thus be:
son page For grading bank....
$0,10 $0.10 3-10 cubic yards stone, at $1.50.
.45 .45 Labor
.20 to .25 Miscellaneous
.10 Or from..
$0.80 to $0.90 and a This with banks about 35 feet high, graded to a slope of 1 to 3 5. weak an and paved to the top, makes the cost about $11 per linear foot of bank.
during w The above estimates thus make the cost of a completed revetment uth of the $18 per linear foot for the subaqueous work and $11 for the pav- min of wo ing, or a total of $29. In many cases, of course, the mattress need
the desig not be quite so wide and the bank may be lower, so that the cost will - utilizing be less, though, of course, it may at times exceed this price, so that
peration we may say that the cost of the present standard revetment is from $27 to $30 per linear foot, depending upon local conditions, or about $150,000 per mile.
*** is not . When ruult lend
" and th
The works required for the regulation of the river consist of contraction work and bank revetment. The histories of both of these have now been completed, but in these histories each has been conifered independently and almost without relation to the other, and it will be well to consider their relation to each other.
The works at Columbus, Hickman, New Madrid, Caruthersville, Helena, and the city of Memphis have consisted of revetment for the protection of the immediate banks and were not designed with any reference to the general regulation of the river; those at Point Pleasant and Cherokee also were intended for local objects only, and the revetment at Hopefield was designed only with reference pits effects on the river immediately below, so that none of these Torks can be considered as parts of a general plan for regulation. Indeed, the only works that can be so considered are those in Plum Point Reach,
PLUM POINT REACH
The systematic regulation of this reach was begun in 1882, the project being to effect this regulation by revetting all caving banks,
losing all side chutes, and contracting the main river at wide places. (See page 49 and Plate IV.) The work actually done and its local results have all been described in detail, the revetment vorks on pages 117 to 132, 165 to 176, and 199 to 220; the contraction work on pages 48 to 89 and 98 to 100.
But in spite of all this work, costing about five millions of dollars, the project is not yet complete and the desired effect has not been obtained. When the work began nothing was known as to how this river would lend itself to regulation; its power was greatly underistimated and a very large part of the first work was, in consequence, weak and inefficient and was soon destroyed. Just as the river was beginning to be understood, there came the delay of four rears, during which considerable changes took place in its regimen, and much of the good of the previous work was lost. Since the resumption of work operations have proceeded at a slower rate and with the design of ultimately completing the regulation of the reach, utilizing as much of the old work as possible. In the begin ning operations were carried on at somewhat widely separated places, and the intervals between being unregulated have allowed changes to take place that have almost done away with the usefulness of some of the work already done. At the present time sey
cetracted w iki both
of will conti eneral, the * veral manent! fumature
matematir and should
eral miles of bank are still unrevetted and caving and some contrac-sappear tion work remains to be done.
The object of all this work was, of course, an increase in the navigability of the river, and, as tending to this, the fixing of the channel in a permanent location.
The results have been as follows: Before the work began lowwater channel depths of 5 feet or less were not uncommon in the reach, but they have not been found since. As late as 1890 the depth at one of the crossings was but slightly over 6 feet, but since that time there has at all times been available a channel of several feet greater depth. Before the work began Plum Point Reach was known and dreaded as the worst part of the river, and it has been stated by residents of the locality that it was no uncommon sight to see as many as six steamboats aground at one time in different parts of the Reach, none of them drawing over 6 feet. At that time river men would reckon on not more than 8 or 9 feet in this Reach when the Cairo gage registered 20 feet. Now, even at the lowest stage, the river boats can find that depth without difficulty, and for many years navigation has been uninterrupted by lack of sufficient channel depths in the Reach, and Plum Point Reach no longer bears the womplete reputation of a bad piece of water.
In fixing the channel location the success has not been as marked, therefore, for in spite of the bank revetment the channel has continued to wander from place to place. Its location from time to time is its shown on the maps of the Reach. (Plates LVII to LXIX.)
From these maps it will be noted that in Ashport Bend the channel has always followed the caving bank, but beginning with Gold Dust Crossing, and from that point downstream, the variation in channel location and in the shape of the bars has been very marked. The change in location of Gold Dust Crossing seems to have been largely due to the changing shape of the bank in Ashport Bend and less directly to the growth of the head of Elmot Bar, due to the sudden widening of the river. Since Ashport Bend has been held in a fixed location by revetment, Gold Dust Crossing seems to have a tendency to become fixed; this tendency, however, being retarded by the hardness and consequent slowness in the erosion of the bar at the head of Elmot. The changes in Fletchers Bend and below have been due to the slight curvature of that bend, to change in the point of impingement of Gold Dust Crossing, and to caving of the bank at the point of impingement and the consequent changes in shape of the bank of this bend.