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spectively 15.4 and 12.7 feet, and this difference of mean depths is due to the difference of the widths of the two sections.

On the chart I have projected the lines of the jetties parallel to each other and 1,800 feet apart, with the following object in view: As there must be but little obstruction to the inflow of the tides, we must either build low (drowned) jetties or leave openings near the shore; but the same conditions which permit of easy inflow of the tides may permit the escape of so much of the ebb-tides as to destroy their scouring power. I therefore assume that the jetties to be built are high jetties, the inner portion of each jetty being drowned. We know that the flood-tides come in for two hours or more from the east or Louisiana shore before reaching the Texas side; therefore the east jetty should be a low one or else have a large opening near its shore end. The ebb-tides incline toward the Texas shore; therefore the west jetty should be a high one with a smaller opening near its shore end, to prevent as much as possible the escape of the ebb-tide.

If both jetties be built high with shore openings to permit the fullest inflow of flood-tides, we approximate more nearly to the condition of things in the pass. We have the funnel shape formed by the jetties and the shore lines, and we more certainly control the action of the ebb-currents than we could with low jetties; but the objection to high jetties is that they cost much more money to build and are more liable to injury by heavy seas than low jetties. Leaving out the question of differ ence of cost and maintenance of high and low jetties, let us see what we may expect with high jetties. We have already said that the mean area of the cross-sections in the pass was 27,744 square feet. If we leave openings near the shore ends of the jetties, protecting the openings by a sill (mattress) to prevent scour there, the aggregate area of the two openings below high-water, representing 20 per cent. of the mean area of the gorge above referred to, and make 15 per cent. of this aggregate opening on the Louisiana side or east jetty, I think we shall get nearly as full an inflow of tides as at present, but we shall get less discharge through the jetties than now, for the reason that fully 5 per cent., probably much more, must escape through the opening on the Texas side, and some, perhaps more than another 10 per cent., from the Louisiana opening. Therefore, with this loss of ebb volume through the jetties, they, to produce the same depth as we get in the gorge, should be closer together than the width of the pass at the gorge. We have shown, by a very rough calculation, that the volume of discharge of an ebb-tide, if flowing uniformly, would average about 77,727 cubic feet per second. The jetties at South Pass of Mississippi River have a volume of water flowing through them varying from 26,688 to 78,410 cubic feet per second, and though only 1,000 feet apart are not sufficient to produce and maintain a channel such as we have in the gorge at Sabine Pass. Many inferences may be drawn from this, but the most plausible one is that, assuming my calculation of discharge for Sabine Pass to be approximately correct, then, with jetties 1,800 feet apart, we shall not get such a channel as the South Pass jetties now have. With the Sabine Pass jetties 1,000 feet apart (both high jetties) we might get 26 feet and more of depth, but fortunately Sabine Pass bar does not require this depth. Whether the jetties be placed 1,800 feet apart or less, it will make but a very small difference in their aggregate cost. Neither will the direction taken by the jetties make much difference in their cost, as the bottom on the bar, to the eastward and westward of the lines projected, is of the same character and has the same depth of water on it as is found on the lines indicated. The line selected has some advantages;

it reaches deep water (the 20-foot curve) in about as short a distance as can be found. It covers or incloses what is left of the dredged chan nel, directs the ebb-discharge across, and very slightly with the littoral current; and during southeast storms, which are generally the most severe in that vicinity, the jetties would take the storm and consequent sea at an acute angle, instead of broadside on, as would be the case were they deflected more to the westward.

A single jetty at Sabine Pass would probably produce much deeper water over the bar than is now found. Such jetty, if built, should be on the west side of the present channel, and should follow approximately the line laid down for the proposed west jetty shown on the chart. The reason for this side being preferable to one on the east side of the channel, is in consequence of the pressure or inclination of the ebb-tides toward the west. In consequence of the jetty we might get a scour on the east side of it from both tides, and as it would check the spread of the ebb in a westerly direction, we should get increased velocity and probably scour.

At all events, in the construction of jetties at Sabine Pass, one jetty would have to be commenced first, for reasons given; in my judgment, it should be the west jetty. The foundation course of this jetty should be built nearly or quite its full length, before a second course is placed upon it. On the crest of the bar, where the water is only 6 feet in depth, the foundation course of the jetty will probably make some scour, which will continue to increase as the jetty is raised. As soon as a foundation mattress is laid and loaded with its stone to secure it, it should be covered with mud pumped on with a centrifugal pump. This will add to its weight, compact the stone, and possibly prevent the attack of the teredo; at all events, it will save quantities of stone, which is the most expensive ingredient of the jetty. When the jetty has been raised sufficiently high, the scour ought to be well remarked as well as the channel which it produces; this will then determine whether or not this jetty is to be raised higher or the other jetty to be commenced. As the difference between high and low water is only 1.4 feet, a high jetty will not very greatly exceed the cost of one reaching to low-water level.

The jetty or jetties, built or to be built, should have a sufficiently broad foundation, depending upon the depth of water in which they are placed, to be able to withstand the pounding of the seas without danger of overturning. The foundation mats, at least the outer ones, should be partly flexible rather than stiff or rigid, so that in the event of a close scour the outer portion will drop, and modify and possibly prevent further scour. In the estimates and designs submitted, I have estimated for a top 15 feet wide, with side slopes of 1 on 2, and always a berme 15 feet in width at the foot of this slope.

With regard to the kind of mattresses to be used in the jetties, we have on the Sabine and Neches rivers, within 50 miles of the pass, any amount of brush and logs, and at about 100 miles distant from the pass there are immense quantities of hard sandstone in the vicinity and on the line of the Eastern Texas Railroad where it crosses the Neches River. We can, therefore, have a choice of mattress material. Those constructed by Mr. Eads in the jetties of the Mississippi River consisted of willows and brush, confined by parallel layers of plank at top and bottom, the Jumber being held together by hickory pins passing through the mattress and planks and then wedging the ends of the pins. This mattress is patented, and even were it not, it is probably no better and costs fully as much or more per cubic yard (in the history of the jetties by

Mr. Corthell it is given as $8.97 per cubic yard in place) than the Dutch mattress now being used by Colonel Mansfield on the Texas coast.

The next mattress to be considered is that designed by General Gillmore for use in the jetties at Charleston. Its detailed construction is not known to me, but taking the simple log raft composed of 12 inches diameter, logs each 30 feet long, and using poles for binders, and iron drift-pins for fastenings, taking the cost of the logs at the prices the mills are paying for them, we get the following as the cost of a mattress 30 by 60 feet in plan by 18 inches deep, loaded with stone:

60 logs, each 30 feet long = 1,800 feet, at 5 cents per foot .....

300 feet of 6" poles, at 3 cents

300 drift-pins=198 pounds, at 4 cents per pound, driven. 64.4 cubic yards of stone to sink it, at $4 per yard....

Total

$90 00

9.00

7.92

257 60

364 52

Making a volume of stone and logs of 3,600 cubic feet, or 133 cubic yards, at a cost of $2.73 per cubic yard.

The Dutch brush and fascine mattress, as constructed by Colonel Mansfield at Galveston, assuming the cane to cost $5.25 per cord, brush $4.50 per cord, and stone $4 per cubic yard, which, I believe, are the prices now being paid, would cost about, for—

Wiepens

Brush..

Labor and ropes..

44 cubic yards stone, at $4.

Volume=30 × 6 × 24 feet = 166.66 cubic yards=$2.16 per cubic yard.

$24 09

94 95

65 00

176 00

360 04

The length of the west jetty projected on the map is 18,120 feet, its cubic contents to mean high-water level = 374,141 cubic yards; if built to 6 inches below mean low-water its contents will be about 304,578 cubic yards. The east jetty, measured on the straight line, is 19,800 feet long; measured on the curved line, its length is 19,180 feet. Th contents of the straight jetty to mean high-water line=407,877 cubic yards; to 6 inches below mean low-water=336,468 cubic yards.

In the construction of jetties here it is probable that hearting mattresses can be used to within 3 or 4 feet of the surface of the water. If such be the case after the plant is available it is probable that they can be built in place at a cost of about $3 per cubic yard. At this price the

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To the above amounts, whether we build one or more jetties, should be added the cost of plant, consisting of a good tow-boat, scows, piledriver, powerful steam-pump and mattress-way, aggregating about $50,000. We shall also have to do considerable piling to compact the jetties, for which I estimate 3,103 piles, each 30 feet (average) in length, at $3 each, driven $9,309. It may also be necessary to dredge a channel between and above the jetties. The following estimate is for dreding so that the channel shall be 20 feet deep by 100 feet bottom width, with side slopes of 1 on 2, which will carry us into the 18-foot channel inside the bar. The estimate is only a rough approximation, and is about 800,000 cubic yards; this at 20 cents would cost $160,000.

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If we leave the dredging out of consideration, it would make the two high jetties cost at the rate of $3.85 per cubic yard. This is believed to be a little more than the actual cost per cubic yard of jetties thus far in place at Galveston; the material should cost less at Sabine than at Galveston, while the labor will cost fully as much or more. One jetty at Sabine Pass may produce 12 to 14 feet depth of water on the bar. Two jetties ought to produce much more, perhaps 24 feet, if placed less than 1,000 feet apart.

Except in the contingencies in the estimate, no account has been made of the subsidence which may occur to the jetties; the bottom is very soft, and we shall certainly have some settling, but just how much it is impossible to say. The steamer Clifton was wrecked on the crest of the bar fifteen years or more ago, and she still remains there, without having settled much.

The worms (teredo) are particularly destructive at the pass, and for that reason I deem it well to cover the mattresses with inud as soon after being placed as is possible.

With the money now available for Sabine Pass, $153,000, it might be well as soon as the lines of the jetties are decided upon, to commence the construction of a single line of mattresses for foundation, commencing at the wreck of the Clifton and working outwards so far as the funds will permit. It is possible that with this money we can place one row of mats 40 feet wide with stone to sink and hold for a length of 7,000 feet, and would recommend that it, as well as subsequent work, be done by contract.

The commercial importance of the proposed work depends entirely on the railroads projected to terminate here. The grading for one road is partially completed to the town of Sabine Pass.

In 1872 it was reported that the value of domestic exports from Sabine Pass was $1,505,731.

The nearest port of entry is at Galveston, about 60 miles distaut.

Accompanying this report is one tracing containing results of surveys from 1872 to the present time, and extending from outside of Sabine Pass Bar to beyond the town of Sabine Pass. It also contains the tidal carves for December, 1881, and profiles through proposed jetty lines. A second tracing shows cross-sections of the pass at the town, and near the light-house, with current observations in each section.

In the event of appropriations being made for the jetties at this locality, the best and most economical results would be obtained by doing

the entire work within three years from the time of its commencement. Seven hundred thousand dollars could be expended in jetties during the fiscal year ending June 30, 1883.

The area of water-way inside the bar containing 18 feet or more of depth is about 340 acres.

Respectfully submitted.

The CHIEF OF ENGINEERS, U. S. A.

W. H. HEUER,

Captain of Engineers.

REPORT OF THE BOARD OF ENGINEERS.

OFFICE OF THE BOARD OF ENGINEERS FOR FORTIFICATIONS, AND FOR RIVER AND HARBOR IMPROVEMENTS, &C., New York, March 11, 1882.

GENERAL: This Board, to which was referred, by your letter of 6th instant, the report of Capt. W. H. Heuer, Corps of Engineers, relative to the improvement of Sabine Pass, Texas, has the honor to submit its views thereon as follows:

Sabine Pass, about 7 miles long, is the outlet of Sabine Lake, into which empty the waters of the Neches and Sabine rivers, depositing their mud sediment in the upper part of the lake in the form of bars. Navigation from Sabine Pass City to Beaumont, on the Neches, and to Orange on the Sabine River, to large-class vessels, is obstructed by the above bars and by shoal water of the lake. Sabine Pass itself, with the exception of a bar about 900 feet long, has a least depth of 18 feet. But beyond the shore line where it enters into the Gulf of Mexico is a bar 18,470 feet, or about 3 miles wide between the interior and exterior 18-foot bottom curves with little less than 7 feet water on its crest. As the waters of the rivers mentioned above deposit their sediment in Sabine Lake, this bar is evidently not made by deposit of material brought from those rivers, but is rather the natural coast formation of mud and fine material through which the inflowing and outflowing tides by reason of their dispersion have not the requisite velocity to cut and keep open a channel suitable for navigation by large vessels. Experiments have in fact shown that a channel cut through the bar fills rapidly by wave action in connection with that of the cross-currents.

It would seem, from Captain Heuer's estimate, that the body of water flowing into and out from Sabine Pass will prove sufficient to keep open a channel across the bar if it be contracted into a narrow passage-way. The same inference may be drawn from the present depth of water in the Sabine Pass, especially where it is narrow.

With the exception of an oyster bar about 900 feet wide just below the city, Sabine Pass may be said to have an unobstructed channel 18 feet deep and upwards from the outer bar nearly to the lake. Where the pass is wide this channel is somewhat narrowed, but generally it exceeds 500 feet in width. The chart shows that a width of pass of 2,000 feet secures a sufficient channel, both as to width and depth.

Now, if jetties are built from the shore 1,800 feet apart, as proposed, across the bar to deep water, the pass is virtually prolonged 31⁄2 miles and its mouth transferred to the same distance seaward. The funnel shape of the entrance-way will thus be lost and the surface slope of the channel of this elongated pass will be diminished, both of which changes

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