In compliance with the resolution of the Senate of December 14, 1870, the report of the Engineer Bureau on the proposed ship canal from Fort St. Philip to Breton Island. FEBRUARY 10, 1871.-Referred to the Committee on Commerce and ordered to be printed. WAR DEPARTMENT, February 9, 1871. The Secretary of War has the honor to submit to the Senate of the United States, in compliance with the resolution of December 14, 1870, the accompanying report of the Engineer Bureau upon the proposed ship canal from Fort St. Philip, in the Mississippi River, to Breton Island, in the Gulf of Mexico. WM. W. BELKNAP, IN THE SENATE OF THE UNITED STATES, On motion by Mr. Harris, Resolved, That the Committee on Commerce be instructed to inquire into the expediency of constructing and maintaining, at the expense and under the exclusive superintendence of the General Government, "a ship canal" from the Mississippi River, at or near Fort St. Philip, to a point near Breton Island, in the Gulf of Mexico; the canal to be open, a free way to all commerce entering or departing from the Mississippi River. Attest: Secretary. GEO. C. GORHAM, Chief Clerk. OFFICE OF THE CHIEF OF ENGINEERS, SIR: The communication from the Committee on Commerce of the Senate, referred to this office, inclosing a resolution of the Senate of the 14th December last, instructing that committee to inquire into the expediency of constructing a canal from the Mississippi River near Fort St. Philip to a point near Breton Island in the Gulf of Mexico, is herewith respectfully returned, and I also transmit a report from Capt. C. W. Howell, Corps of Engineers, in charge of the improvement of the mouth of the Mississippi, to whom the subject of this resolution was referred. The information in the possession of this office in regard to this project indicates the practicability of constructing and maintaining such a canal, but it does not admit of the preparation of a project with estimates of cost. It has had for years past many advocates and opponents. In 1837 Major Chase, Corps of Engineers, prepared careful estimates of its cost, upon a plan originating with Major Buisson of New Orleans. He concluded that a canal one hundred feet at surface and thirty feet deep would cost, all accessory works included, $10,000,000. Colonel Crozet, about the same time, advised a reduction of the depth to twenty feet, and believed that the cost would not then much exceed $5,000,000. Mr. Montaigu, in a memoir upon the subject printed in New Orleans in 1869, puts down the cost at $2,600,000, a sum, beyond question, entirely too low. Assuming the whole cost at $10,000,000, and it will probably not fall short of that sum, the yearly interest of this would be more than double the cost of maintaining two such dredge-boats as the one now successfully operating at the Southwest Pass in constant work during the year, and insure a continued depth of twenty feet over the bar. Still, the project of a canal is one which deserves careful examination. I would therefore suggest an appropriation of $10,000 for the purpose of making careful investigation of all questions bearing upon its location and construction and estimates of its probable cost. Very respectfully, your obedient servant, A. A. HUMPHREYS, Brigadier General and Chief of Engineers. Hon. W. W. BELKNAP, ` UNITED STATES ENGINEER OFFICE, New Orleans, Louisiana, December 22, 1870. GENERAL: In obedience to your instructions, contained in Engineer Department letter, prefixed hereto, I have to report as follows, viz: I have collected all information available regarding plans and surveys for the proposed ship canal, and have further made a hasty personal examination of Breton Island Pass. I am convinced that the project is one of more than ordinary merit and importance. It has, from time to time, for the past thirty years or more, attracted attention, and engineers have pronounced both in favor of and against it, on what appears to have been very insufficient data for forming professional opinions of weight enough to either condemn the project or authorize carrying it out. Of the same class must be any opinion I have formed from the evidence at my disposal, viz, the inclosed pamphlet containing the report of R. Montaigu, civil engineer, several charts of old and recent date, and the results of my own observations along the east coast of the Delta. It is probable that one or more official reports on this project are on file in the Engineer Department. Of these I have not sought to avail myself. The views called for are expressed as follows, viz: I consider that a permanent channel of communication between the Mississippi and the Gulf, adequate for the commerce of the Mississippi Valley, is extremely desirable; that such permanent channel can only be obtained through a canal, and that on or near the line indicated by Montaigu such canal can alone be advantageously located. Considering the project, viewed simply as a matter of construction and maintenance of the canal itself, it is undoubtedly feasible. For further consideration there are two questions presented, which, if decided in favor of the project, satisfy us as to the propriety of carrying it out, and assure the success of the work if undertaken by the General Government. These questions are stated as follows, viz: 1. Is shoaling (from natural causes) of the present deep entrance to, and channel through, Breton Island Pass, to be apprehended in the future? If so, will the rate of shoaling be such as to materially impair the usefulness of the canal within such reasonable period as to justify condemnation of the project? SHIP CANAL FROM FORT ST. PHILIP TO BRETON ISLAND. 3 2. Will the structures required to prolong the canal from the main land to the deep water of the pass necessarily cause such shoaling? Considering the first question, a comparison of the soundings displayed on several charts, viz: 1. Admiralty chart published in 1803 from surveys made in 1764, 1765, 1766, 1767, 1768, 1769, 1770, and 1771. 2. W. S. C. S. chart of 1844; revised in 1865. 3. Chart showing soundings taken by myself. December 1, 1870. Does not indicate any material change in depth of the pass, and its Gulf approach within the past hundred years. Montaigu reports that on comparison of soundings taken by himself in 1859 and 1860 with those noted on Blunt's chart of 1827, he observed a slight increase in depth to have occurred during the interval of time between the two surveys. The charts further indicate that changes have taken place in the bay at the head of the pass, which appear to have been caused more from shifting of the bottom than from addition of first deposit. The best information shows a very gradual filling of the lagoons and bayous around the head of this bay from deposit, and the growth of oyster reefs. If we consider the Mississippi as the source from which all this deposit has and must come, we find that above Fort St. Philip the levees have cut off all communication (except through several small canals, made and used by fishermen) between the river and Gulf. Any fresh deposit must then be brought from below the proposed canal, it is asserted, from Pass à Loutre. It is probably true that a very small quantity of deposit is thus obtained by the tide current setting into Breton Island Pass, that all or this is carried through the pass and deposited in what is already shoal water at the head of the bay. This bay, and the lagoons and bayous connected with it, forms a large reservoir to be daily filled and emptied by the tides through Breton Island Pass; the capacity of the reservoir determines the width and depth of the pass. As the reservoir slowly diminishes, so will the width and depth of the pass in proportion. If the reservoir fills so slowly that in a period of one hundred years no appreciable change is made in the pass, it appears that consideration of the time when the twenty-four-foot approach to the proposed canal may be filled, so as to give but twenty-three or twenty-two feet, is more a matter of speculation than of practical importance. In this connection I call attention to the past and present condition of several other passes on this coast, entirely similar to the one under consideration, viz: Ship and Cat Island Passes, opening into Mississippi Sound, and Chandaleur Pass, opening into Chandaleur Harbor and Bay, and remark that the charts to which I have before referred show soundings through these passes the same now as an hundred years ago. The same may be observed of the flats of St. Joseph Island; the tide-bore opposite this island; the flats opposite the mouth of Pearl River; the Rigolets, and the shoal at the head of the Rigolets. All these passes are tide-bores, opening into similar reservoirs, carrying little or no fresh deposit from the Gulf, and having but the simple effect of shifting back and forth, and leveling the light surface deposit on the shoals in which they terminate. If any confirmation were wanted of the permanency of these channels, the fact that all of them have remained to all appearances unchanged for so long a period, as shown, would seem to give it. As for the second question, I consider its favorable answer only dependent on a proper direction of jetties, which it is possible to give, and on a generous supply of money for the work. One thing which Mr. Montaigu has neglected to take into account in making his plans, and which I consider a very essential feature, is the protection of the face and west end of Breton Island, by construction of sea-walls or by some less expensive device if possible. It is evident that jetties extended one mile into the pass by contracting it must cause the washing away of this island until the original width of pass is obtained, or else a greater depth must be produced by scouring the bottom. As the bottom is of stiff clay and the island of sand, the latter will of course be acted on by the currents, thus widening the pass and probably transferring the line of deep water from the entrance to the canal. As to estimates for construction of this canal, &c., with such imperfect data as I have at command I cannot venture to present more than an opinion. I think it will only be safe to double the estimates made by Mr. Montaigu and stated in his report. In regard to the whole project, although my individual opinion is strongly in favor of it, yet I do not feel justified in recommending a work of such magnitude on the evidence now at command. I do recommend that a survey be made to furnish us with conclusive evidence either for or against the project. Such survey should be of the most exact and minute description, affording all information required for settling the questions I have suggested and for making final plans and estimates for the projected work. The cost of survey will probably be about $10,000. The time spent in making it, making plans and estimates, and in completing report, probably eight months. If the survey should prove beyond doubt the feasibility of the project, the following figures will show its economy to the Government; the benefit to commerce cannot be calculated: 1. To keep open the mouth of the Mississippi for one hundred years, $20,000,000 or $25,000,000. 2. To construct and care for this canal for one hundred years, (abont,) $6,000,000. I would close with an opinion, for entertaining which I may be thought visionary, viz: The successful completion of this canal may prove the first step toward founding a great commercial city seventy-five miles below the city of New Orleans. The sides of the canal will present room for ships and docks enough to accommodate the largest fleet that may ever be expected to engage in the commerce of the Mississippi; room enough for warehouses to receive, store, and distribute this commerce, and room for founderies, machine-shops, ship-yards, and all other industries of a great city, which are intimately or remotely connected with commerce. Ocean vessels need not enter the Mississippi. River steamers can enter the canal, and transfer of freights can be made directly into or from warehouses without one-tenth the expense, annoyance, and damage now sustained at New Orleans. In cheapness of freights no ports in this country could compete with this. In cheapness of merchandise no merchants in other cities could compete with those of this new city. It is only my intention to suggest this new Venice; the plausibility of the suggestion and the advantages which will arise from carrying it out will appear to thinking business men without having them further detailed here. The papers accompanying the letter ordering this report are herewith returned as requested. I have the honor to be, very respectfully, your obedient servant, C. W. HOWELL, Captain of Engineers United States Army. |