The Industrial Canal and Inner Harbor of New Orleans Part 5

"The concrete work gives the impression of lightness, as well as strength, as though every yard of concrete was doing its special share of the work without overstraining, which is, of course, the characteristic of well-designed reinforced masonry.

"The outer surfaces are particularly smooth and well finished, more so than in any work I have recently seen.

"The erection of the gates, valves, operating machinery and the protective dam, has kept up closely with the concrete work, so that no delays need be apprehended at the close of the construction period.

"The shop and field work in the lock gates is excellent. The rivet holes match well and the rivet heads appear to be tight and well formed. The gate leaves seem very straight and true."

The lock was designed by George M. Wells of the George W. Goethals Company, a.s.sisted by R. O. Comer, designing engineer of the Dock Board, and approved by General Goethals. The methods employed to unwater the lock were devised by Mr. Wells. J. Devereux O'Reilly, chief engineer of the Dock Board, to November, 1919, had charge of the details of installing the unwatering and safety devices. He was succeeded by General a.r.s.ene Perrilliat, who supervised the final unwatering process.

Upon his death in October, 1920, he was succeeded by J. F. Coleman & Company, in charge of the engineering department, and H. M. Gallagher, chief engineer, under whom work is being brought to a conclusion.

From first to last, Tiley S. McChesney, a.s.sistant secretary and treasurer of the Dock Board, rendered intelligent and invaluable service, gathering together and holding the threads of the enterprise, and attending promptly to the mult.i.tude of details connected with the prosecution of the work.

The lock was formally dedicated May 2, 1921--a ceremony that was the feature of the Mississippi Valley a.s.sociation's convention in New Orleans.

With the dredging of the channel between the river and the lock, a work that should be finished before January, 1922, s.h.i.+ps will be able to pa.s.s from the Mississippi into Lake Pontchartrain. Then New Orleans can plan its next great development.

[Ill.u.s.tration: CROSS SECTION OF LOCK]

[Ill.u.s.tration: CROSS SECTION OF SIPHON]

NEW CHANNEL TO THE GULF.

George M. Wells, George R. Goethals, son of the General, Colonel E. J.

Dent, U.S. district engineer at New Orleans, and other engineers who have studied the problem, say that the dredging of a channel from the Industrial Ca.n.a.l to the gulf through Lake Pontchartrain, or the marshes, is feasible, comparatively cheap, and maintenance would be simple. This would shorten the distance from New Orleans to the sea by about 50 miles, and would be a vast saving for s.h.i.+ps. It is one of the objects towards which the Hudson Dock Board is working.

It is Uncle Sam's recognized duty to develop and maintain harbors and channels to the sea. Distance is obviously an important factor; furthermore, the proposed new outlet would be an important link in the Intracoastal Ca.n.a.l, connecting with the Warrior River section of Alabama, which the government is developing between the Atlantic and Gulf Coasts. A bill was introduced in the Senate in 1920 by Senator Ransdell of Louisiana, providing for the development of the proposed channel; it was not pressed because the ca.n.a.l was far from completed.

However, every effort will be made by the Dock Board from now on to have Uncle Sam take hold.

Colonel Dent has for a number of months been studying the feasible routes. He, by the way, is thoroughly convinced of the value of the Industrial Ca.n.a.l to the development of New Orleans, and the commerce of the nation, and has so expressed himself in public.

The Pontchartrain route has been laid off, by engineers, beginning at the Ca.n.a.l, paralleling the south sh.o.r.e of the Lake Pontchartrain to the south draw of the Southern Railway bridge, thence to the Rigolets to Cat Island Pa.s.s, from there to Cat Island Channel and so to the deep water of the Gulf, a total distance of 75 miles.

Soundings and surface probings have been taken at frequent intervals over the entire route. These have shown the engineers the following:

Three-quarters of a mile from the south sh.o.r.e of the lake, and as far as the railroad drawbridge, a hard bottom is found. The material is princ.i.p.ally packed sand, rather fine, with a small amount of clay, and occasionally some broken sh.e.l.ls. Beyond this distance from the sh.o.r.e, the bottom is softer, consisting of mud mixed with sand. From the bridge over the remainder of the route, the bottom, with the exception of a few sand pockets, is soft--a blue mud with a large percentage of sand. This soft material has so much tenacity, however, that current and wave wash, which tend to fill up artificially dredged channels, would affect only the surface.

The government is conducting large dredging operations in Mobile Bay, Gulfport Channel, Atchafalaya Bay and the Houston s.h.i.+p Channel. An outline of the results there will show how feasible the dredging of the Pontchartrain Channel would be, and how much cheaper in comparison.

The channel connecting Mobile Bay with the Gulf of Mexico has a bottom very soft for the most part, and with a small percentage of sand.

Towards the outer end, the material is black mud, about equal in consistency to the softest material found in the Pontchartrain route. A sounding pole with a 4-inch disc on the end can be easily pushed three or four feet into the mud and pulled out again. Wave and current action cause the channel to shoal at the rate of 78,000 to 132,000 cubic yards per mile per year, depending on the softness of the bottom and the depth. Where the highest rate obtains, the surrounding material consists of soft mud, without a trace of sand. Experience shows that where there is a fair percentage of sand in the material adjacent to the channel bed, the shoaling is lessened. In general, the material along the Pontchartrain route contains a greater percentage of sand and is far more tenacious than that along the Mobile Bay Channel.

Furthermore, the Pontchartrain route is not exposed to such strong cross currents.

The Gulfport Channel is dredged through very soft material, a grayish-blue mud of oozy consistency, into which the sounding pole penetrates six feet with very little exertion. On top, a small amount of sand is found, but practically none in the lower stratum. The material is considerably softer than any encountered on the Pontchartrain route, except for one small stretch. Yet the shoaling is not great. Where the shoaling is heaviest, between the end of the pier and Beacon 10, only about 700,000 cubic yards a mile has to be dredged out every year to maintain the channel. From Beacon 10 out, the average annual maintenance is less than 200,000 cubic yards a mile. Except for the four-mile stretch west of the inner entrance to the Cat Island Channel, the bottom, on the Pontchartrain route, is harder than that of the Gulfport Channel. Therefore, it is reasonable to conclude that the maintenance of the Pontchartrain Channel would not average as high as the outer portion of the Gulfport Channel.

The Atchafalaya Bay s.h.i.+p Channel, extending from the mouth of the Atchafalaya River across the shoal waters of Atchafalaya Bay, to about the 20-foot contour of the Gulf, a distance of fifteen miles, is through a material of slushy mud, with occasional thin pockets of sand.

The shoaling runs from 540,000 to 1,680,000 cubic yards a mile a year.

The highest rate is obtained in shallow water. Except in the stretch mentioned, the material on the Pontchartrain route is not as soft as on the Atchafalaya, nor are the depths as shoal, nor is there the exposure to cross currents.

In the Houston s.h.i.+p Channel, the material is composed of soft mud with a small amount of sand. A two-mile stretch through Red Fish Reef is practically self-maintaining. For the remainder of the channel, during the six years from 1915 to 1920, a total excavation of 13,574,000 cubic yards was necessary to maintain the depth. This is equivalent to 100,000 cubic yards a mile a year.

In summary, then:

1. The Lake Pontchartrain route is practically unexposed to cross currents, as is the case with the Mobile Bay, Gulfport, Atchafalaya, and, to a certain extent, the outer portion of the Houston s.h.i.+p Channels.

2. The material along and on the sides of the Pontchartrain route is, with the exception of a small stretch, more tenacious, and contains, in general, a greater proportion of sand than in the case of the neighboring channels mentioned.

The channel could therefore be more easily maintained.

Engineers estimate that a channel with a 300-foot bottom would be needed. On the south sh.o.r.e of the lake, the side slopes should be on the 1 to 3 ratio, with provision for a 1 to 5 ratio at the end of five years. Dumped on sh.o.r.e, the material would reclaim considerable frontage, and eliminate the re-deposit of this material in the channel.

Through the remainder of the route, the original excavation should be made with side slopes on the 1 to 5 ratio, with provision made for a 1 to 10 ratio in five years.

The dredging of the 75 miles of the Pontchartrain Channel would amount to 97,200,000 cubic yards, it is estimated by engineers. The cost would be around $10,000,000. The annual maintenance, during the first five years, would amount to 8,880,000 cubic yards--an estimate based on a comparison with the other channels into the Gulf, and the character of the material to be excavated. This estimate is considered large--but even at that, it is only 118,400 cubic yards a mile a year, and the cost would be about $750,000, according to Colonel Dent. After five years, it would be less.

Another proposed route, investigated by Colonel Dent, is through Lake Borgne. A ca.n.a.l some miles in length, through the marsh, would connect the lake with the Industrial Ca.n.a.l. This route has considerable maintenance advantages over the Pontchartrain route. The character of the bottom in Borgne is more or less the same as in Pontchartrain.

Sooner or later, one of these channels will be built by the government.

That it has not already been begun is due to the fact that the Ca.n.a.l has not yet been completed, and the expected development has not taken place. But there is no doubt that it will.

[Ill.u.s.tration: TYPICAL BRIDGE ON Ca.n.a.l]

[Ill.u.s.tration: EMERGENCY DAM CRANE]

WHY GOVERNMENT SHOULD OPERATE Ca.n.a.l.

It is the function of the state to provide port facilities in the form of docks, piers, warehouses, grain elevators, mechanical equipment, etc. But it is the duty of the national government to improve harbors, dredge streams, dig ca.n.a.ls for navigation and irrigation, erect levees to protect the back country, and build locks and dams when needed.

These are the premises from which the Hudson Dock Board reasons that the cost of construction and maintenance of the New Orleans Navigation Ca.n.a.l and Inner Harbor should be a.s.sumed by Uncle Sam. It will leave no stone unturned to have him a.s.sume the obligation.

The Navigation Ca.n.a.l is essentially a harbor improvement. It enables practically unlimited industrial development and commercial interchange. It is an important link in the Intracoastal Ca.n.a.l system which the government is developing to provide an inland waterway from Boston, Ma.s.s. to Brownsville, Tex., and, with the dredging of a channel through Lake Pontchartrain to the Gulf, a problem which U.S. engineers have been studying for some time and an undertaking which they have found feasible, it will put the nation's second port about fifty miles closer to the sea. It has considerable military value. Its purpose is, therefore, national; the local interests are secondary.

It is no new principle, this obligation of the government. That duty has been recognized by Congress since the United States was.

Any rivers and harbors bill will show great and useful expenditure for waterways improvement.

The Panama Ca.n.a.l, built by the government, is the greatest example.

Coming closer home, there is south pa.s.s at the mouth of the Mississippi. A bar, with a nine-foot depth of water, blocked the commerce of New Orleans. Under the rivers and harbors act of 1875, Captain James B. Eads was paid $8,000,000 for building the famous jetties to provide a 26-foot channel. Since then, the channel has been deepened to 33 feet.

In more recent years, the government began to improve southwest pa.s.s, the westernmost mouth of the Mississippi. A nine-foot bar was there, too. To increase the depth to 35 feet, the government spent, up to 1919, about $15,000,000, and is still spending.