[Third indorsement.] WAR DEPARTMENT, A majority of the Board of Engineers reports that the main span of the bridge on the Memphis side of the river should be 1,000 feet in length; that the other two spans should be 600 feet in length, and the whole structure should be 75 feet above high water. Upon a careful examination of the evidence in this case, and the pe culiar methods of navigation by tows, it appears that the minimum width of 700 feet for the main span named in the act of Congress is more than ample and sufficient for all kinds of navigation on the river except the tows, which, of different lengths varying from 660 to 900 feet, pass down the main channel controlled by a single steam-boat. The usual length of these tows is 780 feet and the width 205 feet, and in one instance a tow of 1,032 feet in length is reported. When these tows are in line and under control they would have no difficulty in passing a bridge much less than 700 feet in width; but oecasionally, under existing methods, they can not be thus controlled, and may float down side on or, in other words, lengthwise across the stream. In this condition guidance is impossible, and it is difficult to see how any practicable length of span could insure safety. The obvious provision against such an accident is to increase the controlling power and insure safe guidance from the start, or to reduce the length and size of the tows. It may also be observed that a tow, thus floating helplessly down at right angles to the current, would be a serious and dangerous obstruction to all other methods of river navigation. While the rights of navigation in navigable rivers are to be jealously guarded and protected, the right to cross such streams by bridges to transport freight and passengers can not be disregarded. There must in such cases be mutual concession and such adjustments in the methods of transportation on the stream and in the construction of bridges over it, that the privileges of both may be enjoyed and preserved. To require such extreme length of bridge on the one hand as would permit navigation by tows in the same manner as if there was no bridge, would be as unreasonable as to construct the bridge in such a manner as practically to destroy all transportation by tows. . I am unable, therefore, to approve this report so far as the width of the main channel-span is concerned. It appears that the width of the river at the site selected and ap proved by the Board is 1,970 feet at low water. The width of the proposed piers is about 20 feet each. The minimum length of the main channel-span is fixed by law at 700 feet and the other two spaus at 600 feet each, to which add 40 feet for the width of the two piers, we have 1,940 feet, or 30 feet less than the width of the river at low water. One span 730 feet long and two spans 600 feet long in the clear will make, with 40 feet for the width of two piers, a bridge 1,970 feet long. It is better to add the 30 feet to the main span, rather than divide it between the shorter spans. Plans may be submitted by the railway and bridge company giving a main channel-span on the Memphis side of the river 730 feet long in the clear at low water, and two other spans 600 feet long in the clear at low water, the end piers to be placed at low water on either shore, so that the three spans will cover the entire width of the river at low water. All the necessary aids to navigation in passing under the bridge can not now be determined, but the railway and bridge company may consider the question of a guiding pier, with proper guards to the bridge pier on the Memphis side, for protection to navigation, or that of placing the pier on the Memphis side in 9 feet of water at the highest stage, making the long span 770 feet. The law requires that the bridge shall be so constructed as to provide for the passage of wagons and vehicles of all kinds and for the transit of animals. Drawings must be submitted in compliance with the law, showing a cross-section of the bridge and the roadways proposed. WILLIAM C. ENDICOTT, Secretary of War. REPORT OF BOARD OF ENGINEERS. MEMPHIS, TENN., May 26, 1888. SIR: The Board of Officers of the Corps of Engineers, U. S. Army, convened by Special Orders No. 26, dated Headquarters Corps of Engineers, U. S. Army, Washington, D. C., May 10, 1888, to examine and report upon the plans of the proposed bridge across the Mississippi River at Memphis, Tenn., submitted by the Kansas City and Memphis Railway and Bridge Company, would respectfully submit the following report: Before entering upon the details of the proposed bridge it is advis able to describe the locality. The city of Memphis is situated on a bluff on the left bank of the Mississippi River, at the confluence of Wolf River, and has a waterfront on the Mississippi of about 3 miles, beginning at the mouth of Wolf River and extending to near the head of President's Island. At this island the river divides into two channels of nearly equal size. The western channel was the main channel until within the last two years, since which time the best water has been found in the eastern channel, though the difference between the two in navigability is not great. On the shore opposite Memphis is the small village of Hopefield, mainly occupied by persons employed at the railroad transfer boats. Above the city there is a sharp bend in the river whose apex is about 4 miles above Wolf River. From this bend the current sets directly towards the Memphis shore, with a strong scour against the upper side of the Hopefield peninsula. Since 1877 half a mile in width of the point of this peninsula has washed away, and the present point is about a mile further down-stream than was the case eleven years ago. Formerly the current struck the left bank above the mouth of Wolf River, and followed the Memphis front tangentially. As the point of impact moved down-stream the angle of the current with the Memphis shore became more nearly a right angle, and the scouring effect on the bank became so great that expensive works of protection had to be built along a large part of the city front. To prevent this condition from getting worse it was also necessary to revet the upper side of the Hopefield peninsula. The Memphis revetment extends over about 2 miles of the city front, and has been very successful, but should be continued to the lower end of the bluffs. The Hopefield revetment extends over a distance of about 24 miles, and ought to have been carried to the point, a further distance of about a mile, but it was necessarily stopped by lack of funds. In passing the front of Memphis a floating object comes out of the Hopefield Bend heading straight for the upper end of the city wharf; it is then deflected to the right by the current, turning an angle of 100 degrees while passing the main part of the city, and turning another angle of about 25 degrees to the left while passing into the eastern or Tennessee chute of President's Island. Should it, however, be drawn into the western or Arkansas chute, it would turn an angle to the right of about 90 degrees. This is the course that all river craft must follow as they pass the city of Memphis, and the excessive curvature in a short distance, with its accompanying whirls and boils, is the reason why this part of the river is always dreaded by navigators. We have been informed that coal tows never attempt to run Memphis at night, and we know that the only tow of coal that passed Memphis while the Board was in session, towed by the W. W. O'Neil, laid up all night at a point above the mouth of Wolf River, although the stage of the river was only about 23 feet on the gauge, high water being 35.3 feet on the same gauge. On the other hand, we are informed by Captain Haarstick, president of the Mississippi Valley Transportation Company, that his tows, which are chiefly used to carry grain, flour, and merchandise, are forced by competition to run night and day, and that their pilots have standing orders to "flank" all sharp bends of the river, in which class the bend at Memphis is one of the chief. Accompanying this report are two diagrams, showing the actual posi tions at short intervals of several tows while passing the Memphis Bend, which indicate the method of "flanking" bends more clearly than can be described in words. These diagrams were furnished by officers of the Mississippi River Commission. It will be noted, however, that they refer to stages below high water, at which times the current of the river is considerably reduced, and the difficulty of flanking the bends is pro portionately lessened. In accordance with the requirements of the acts of Congress author izing the construction of this bridge, the engineers of the bridge company made current observations at the proposed site, and found the following velocities in the part of the river to be covered by the eastern or Tennessee span of the proposed bridge: The reading on the Memphis gauge of local highest water is 35.3 feet. The Board met at Memphis on the 24th instant, and on that day and the 25th held public sessions in the United States Engineer Office, and heard all parties who desired to present their views. They also in spected the entire front of Memphis from the head of the Hopefield revet ment to the head of President's Island, and floated along the city front with the boat in the position occupied by tows in flanking the Memphis Bend, the boat being under the control of one of the pilots of the Missis sippi Valley Transportation Company. In accordance with the special instructions to the Board, all parties who presented themselves were requested to give their views in writing. and all such statements and all letters received are appended to this report. No communication was received from the Coal Exchange of Pittsburgh, or from any coal operator. The only representations of the Ohio River coal interests who put in an appearance were two pilots, who belonged to a tow returning up-stream, which happened to reach Memphis while the Board was in session. After careful consideration of the facts before it, the Board has come to the unanimous conclusion that the site selected by the bridge engineers is the best that there is along the Memphis Front for the construction of a bridge, and that the clear height of 75 feet above highest water is all that should be required. The river interest is unanimous in requesting that the channel-span be placed next to the Tennessee shore, and the Board fully agrees with this view. It was also the opinion of the river men that the shore-pier on the Tennessee side should be at or near high-water mark, so that this pier might be out of water, and the shore be run as if no pier were there. The Board recommends that this pier be placed where it will be in 9 feet of water at the highest stage, because the barges that run at such stages draw 9 feet, and are therefore no more apt to hit the pier than the shore; moreover, 9 feet at extreme high water means less than 9 feet at ordinary high water, and it is deemed necessary to keep the outer channel-pier as far out in the river as circumstances will admit. The serious and difficult question before the Board is the clear width of water-way to be given under the channel-span. Major Ernst and Captain Kingman are in favor of a clear water-way of 1,000 feet, for the following reasons: The proposed location of the bridge, while perhaps as favorable as any that can be found within a reasonable distance from Memphis, 18 one that presents peculiar difficulties for the accommodation of navigation. All of those persons who have appeared before the Board in the defense of the navigation interest have declared that at this point it would frequently be necessary for heavy tows to pass under the bridge "broadside on;" that is, with the direction of their greatest length at right angles with the current and parallel with the bridge. As the ve locity of the current at high water is frequently as much as 8 miles per hour, there will often be great difficulty in "straightening out" before reaching the bridge, and sometimes this will be impossible. They think that the claim of the navigation interest in this respect is reasonable. The length of the tows of grain barges is about 660 feet; that of coal tows is sometimes as much as 900 feet. In one case a length of 1,032 feet is reported. To accommodate a tow 900 feet long a clear width of channel-way of 1,000 feet between piers will afford but scant margin. That width will afford only a safe margin for the more valuable tows of grain barges, which measure 660 feet in length. It is the width asked for by the navigation interest unanimously, and it should, in the judg ment of the officers mentioned, be accorded. The completion of the revetments in Hopefield and Memphis bends is essential to the preservation of a state of affairs even as favorable as that which now exists, as will be explained further on. No improvement is to be expected, but if for any reason the revetment should not succeed in preventing further movement of the Memphis Bend, the approach to the proposed location of the bridge will become less and less favorable as time advances. Any doubt as to the proper length of span should therefore be thrown in favor of the greater length. An increase of the water-way from 700 to 1,000 feet will no doubt increase the cost of the bridge, but even thus the cost may be much less than the sums expended upon some other bridges in the country, and it need not be prohibitory. The Board has therefore to state that a majority of its members report the clear width of channel-way required at Memphis to be 1,000 feet. The law requires that the side spans should not be less than 600 feet in length. In the judgment of the Board this provision is unnecessary, and could wisely be omitted in future laws for Mississippi bridges, as the great cost of piers in the Mississippi River compels the construction of side spans that must of necessity be wide enough for all ascending craft or for single boats descending the river, while all descending tows will of necessity take the channel. There is a positive objection to fixing the lengths of side spans by legislation, as the long channel-spans will almost necessarily be built on the cantilever system, and in such construction the length of the cantilever span fixes the length of the adjacent counterbalancing spans. Inasmuch as the law in the present case fixes the "other spans" at 600 feet, it is evident that the second span from the Tennessee shore must have this length. The third span will reach the Arkansas shore, and can not be made 600 feet over the water-way, as there is not water-way enough for a span of such length if the channel-space be 1,000 feet, the width of water-way at the se lected crossing being but 1,970 feet, out of which must be deducted the widths of the piers. The last pier of the bridge should therefore be on the edge of the Arkansas bank. It is recommended that the bridge company be required to protec the river banks for a reasonable distance above and below their bridge line, so as to preserve the present shore lines and prevent the forma tion of water-ways behind the shore piers. It is thought that such pro tection should extend from a point about 300 feet above the line of the bridge to a point about 50 feet below. The bank between high and low water lines should be paved. The Board is in serious doubt as to the expediency of permitting any bridge at all to be built in this stretch of river until it has received a fixed regimen. It is evidently vital to the navigation interests that the channel at the site of a bridge should be permanent; otherwise a change in channel might be an embargo to navigation. It therefore seems im perative that the work of fixing the river-front at Memphis should be completed, and this work seems essential whether the bridge be built or not. The completion and strengthening of the revetment in Hopefield Bend and the continuation of the Memphis revetment to the lower end of the bluffs seem vitally necessary to the successful maintenance of a naviga ble channel at the site of the proposed bridge, and the Board desires that its approval of the construction of the proposed bridge shall be considered as contingent on the completion of this collateral work. It is also the opinion of the Board that the proposed bridge, whatever its channel-span, would be in danger of becoming a menace to nav igation in case the main channel of the river should return to the Ar kansas side of President's Island. It is believed that the present favorable conditions should be assured by the construction of a sill across the Arkansas chute, and that any tendency for a return of the river to this chute should be vigorously repressed. The river-work above named is remote from the bridge, and its char acter and conditions are such that it should be done at the expense of the United States. Respectfully submitted. O. H. ERNST, Major of Engineers. DAN. C. KINGMAN, Captain of Engineers. CASSIUS E. GILLETTE, Recorder. The CHIEF OF ENGINEERS, U. S. A. |