The Tunnel Through New York (1902)

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Preliminary work for the tunnel on Elm Street, one of the many points at which great care was necessary in excavating along the Croton water pipes. Munsey's Magazine, 1902.

Munsey's Magazine · 1902, pp. 226-234

By John B. McDonald, the contractor who is building the rapid transit road.

The interesting engineering feat of constructing an underground railway more than fourteen miles long beneath the streets of the metropolis without stopping surface traffic.

To build and equip New York's underground rapid transit railroad is truly a gigantic task. It is beset by almost countless complications. The problems growing out of it include many new ones, of much apparent difficulty, requiring the most expert skill and the highest practical judgment in their solving. Yet so far as the work has progressed there has been no obstacle that has not been foreseen, no task whose performance has not been thought out before the labor of digging and tunneling was begun. Nothing has been left to chance. The engineers of the Rapid Transit Commission and of the contractor have anticipated the methods and calculated the cost of every step that has been taken and that will be taken, to the day when trains begin to run on the road.

If you imagine an enormous capital letter Y, with its base resting at the City Hall Park, and the top of the main stem at One Hundred and Fourth Street; with its right prong ending at Bronx Park, and its left prong ending at Kingsbridge, you will have a rough outline picture of the route of the new road. The whole system will extend over twenty one linear miles on Manhattan Island and in the Bronx. What we will call the main line, from City Hall to One Hundred and Fourth Street, is about seven miles long, and each of the branches is of about the same length. In the far northern part of the city, where the lines cross valleys and low ground, the tracks will be carried on viaducts in the open air- an improved plan of elevated railroad structure. A little more than fourteen miles of the road will lie underground, and it is this part of the work; of course, which has given rise to practically all the problems. The road will be four tracked as far as One Hundred and Fourth Street, the outer tracks devoted to way trains and the inner ones to express trains. The express and way trains will continue to the eastern and western ends of the road, but with only two tracks on each branch.

As an engineering task, the building of the new road is practically without precedent. A great trench has to be carried through the heart of the most crowded city in the world without disturbing that city's traffic. It has to be led through a bewildering assortment of pipes that carry light, heat, water, power, and electric and pneumatic communication to all parts of New York. To do the work without disturbing the every day business of the people is the problem.

A Surgical Engineering Feat

Imagine a surgeon who has to direct a probe from the neck of a patient all the way to each heel. He must carry out the exploration thoroughly. He must not hurt a single nerve or break the wall of any vein or artery. Nerves, tendons, veins, and arteries must all be avoided, or pushed aside and protected, wherever the probe encounters them. Above all, the tranquility of the patient must not be upset. There you have a fair likeness of what had to be done in digging the rapid transit tunnel.

The rapid transit commissioners first made careful surveys, and a most exhaustive search of all the city maps, plans, and records, in order to select the route which would best serve the public, and along which the fewest obstacles would be encountered. They selected the City Hall Park as the ideal starting point, and Elm Street, Lafayette Place, and Fourth Avenue as the easiest route north. At Forty Second Street the line curves westward, cutting under the building on the corner, which happens to be a drug store. It runs west to Broadway, along which it continues to One Hundred and Fourth Street. Thence the western branch goes by tunnel and elevated viaduct along Broadway and Eleventh Avenue to Kingsbridge. The eastern branch runs under half a mile of Central Park and along Lenox Avenue, dives under the Harlem River, and thence proceeds along Westchester Avenue and the Southern Boulevard to the Bronx Park.

Having determined the route, the board's engineers, under the direction of their chief, William Barclay Parsons made a series of borings over the entire route to determine the precise nature of the ground in which the work was to be carried on. These borings went twenty-five feet below the surface, and they were only twenty feet apart- nearly six thousand of them altogether. Minute examinations of the city maps and records gave the exact location of every water pipe, gas main, sewer, pneumatic tube and wire conduit, every street car track, elevated railroad foundation, and building foundation that would be encountered on the route. The plan of the four track road, with stations a quarter of a mile apart, every sixth station being of double size to accommodate express traffic, was carefully worked out. It was determined that the four tracks should not be placed in pairs, one above the other, but that they should lie side by side in a broad, low tunnel. No motive power causing combustion in the tunnel should be used.

A Thirty Five Million Dollar Contract

With all these details known, the board advertised for bids. The work to be done was not only to dig the tunnel, but to lay the tracks in it, to build and equip the stations, provide elevators in several of them, install the necessary terminal loops and side-tracks, and furnish the rolling stock. In other words, the contractor was to build and equip the road and stations in every detail, and to operate it for fifty years, with the privilege of renewal for an additional twenty five years. The rental to be paid will be equal to the interest on the bonds issued by the city for construction, and one per cent additional for a sinking fund which, before the expiration of the lease, will repay to the city its entire outlay for construction, thus giving, the railroad to the people of New York practically free of cost.

Chief Engineer Parsons informed the board, as it appeared by public record long after the contract was awarded, that this work should be done for about thirty-five millions of dollars. None of the bidders, of course, knew anything about his figures, or about the calculations of their competitors. My bid for the work was exactly thirty five millions. The nearest bid to it was one for thirty nine million, eight hundred thousand. It will be seen, then, that the board's own estimate and mine were practically the same. This feat of mathematics seems magical and mysterious until one remembers that in a general way the requirements of the contract were made known in advance, and that all engineers and contractors use about the same methods of calculation- so much for labor, so much for material, and when the total of these is known a given percentage added for profit.

As soon as the contract was awarded to me, I divided the road into fifteen sections, each of which was put in charge of a subcontractor. This added rapidity in the working. I have often been asked about the prodigious difficulties in the way of the tunnel. There are really none that cannot be overcome by intelligent and diligent labor. There has been, as long as I can remember, a popular impression that Manhattan Island consists generally of a mixture of granite and quicksand. That belief is not well founded. There certainly is a great deal of rock, especially in the upper portion. It is gneiss, really hard, but quite workable with the aid of pneumatic drills and blasting powder. The only thing resembling quicksand that we have thus far met is a bit of old swamp fifteen feet below the surface of Broadway at One Hundred and Fifteenth Street. There we found a quaking mixture of thin sand and bluish mud, in which a man would be quickly swallowed up. We dug it all out for the space of eighty feet in length and sixty feet in width. The quicksand was only eight feet in depth, and it was at the bottom of the tunnel. The vacant space was filled with gravel, thus making a firm, trustworthy roadbed.

The most arduous piece of work on the road is the boring of the Fort Washington tunnel, through the great hill of gneiss extending along Broadway and Eleventh Avenue from One Hundred and Fifty Eighth Street to a point near Fort George. This tunnel will be two miles long. Next to the Hoosac tunnel, it will, I believe, be the longest in the United States. Yet it excites little public attention. It is in the eye of the wayfaring man a mere incident of the whole rapid transit plan.

The boring is being done from headings at either end, and in both directions from intermediate shafts at One Hundred and Sixty Ninth and One Hundred and Eighty First Streets. On the shore of the Hudson River, half way between these points, is a large compressor plant, from which compressed air is conveyed in pipes to the drilling machines in the tunnel. Each of the shafts goes down one hundred feet to the floor of the tunnel. When the road is finished, elevators will carry passengers up and down. More men than would make a regiment have been at work here continuously during the last year. The drills never cease. The men work in three shifts of eight hours each. The tunnel will be carried forward in this way until it is finished.

Although the popular name for the underground road is the "Tunnel Route," this Fort Washington section is about the only one that deserves that title. For most of the way the road runs through a covered trench, its roof frequently touching the street surface. In very few cases will passengers have to walk more than fourteen feet down stairs from the street to the railroad platforms. At stations, the waiting rooms, tracks, and platforms will be roofed with thick glass at the street surface, so that sunlight will abound. The air in the tunnel will be as pure his in the lowest story of any house built under the best hygienic regulations. There will not be one whiff of what is known as cellar air, nor will there be steam, smoke, or cinders. The trains will be moved by electric motors, capable of a speed of fifty miles an hour. The tunnel will be thirteen feet high inside, and its width will be fifty feet, except where there are side tracks, which will make it eighteen feet wider.

So small is the amount of quicksand along the route of the great trench, that it does not appear in the calculations. All the excavation is estimated as earth and rock: 927,135 cubic yards of earth, and 921,182 cubic yards of rock, chiefly gneiss. From the Fort Washington tunnel, and from two or three other very short sections of similar boring, there will be drilled and blasted out 368,606 cubic yards of rock. During the past winter thirty five hundred men have been engaged in boring, excavating, and road building. The nature of the operations carried on can be seen by a glance at the occupations of this army- civil engineers, foremen (in drilling and steel construction), engineers, hoisters, pipe fitters, masons, caulkers, bracers, carpenters, blacksmiths, riveters, machinists, steam and air drill runners, and watchmen. As soon as the open season is well settled, this army will be increased to ten thousand men. In many sections besides the big tunnel work will be carried on day and night.

The Underground Tangle Of Pipes

The streets of New York have not been blocked at any place by the work of excavation for the tunnel. Of course some of them have been narrowed to half their normal width at several points, but there has been little or no obstruction of traffic. The route selected is not a pipe thoroughfare throughout, but important pipes run parallel with the road for at least two thirds of the way. Wherever pipe crossings are encountered, the underground structures have been readjusted; but troublesome as this work is, it has been done without any serious blocking of the streets.

A typical tangled puzzle of this kind is at Twenty Third Street and Fourth Avenue, where there is to be a large rapid transit station, and where surface car lines run along both avenue and street. Besides the obstacle their underground mechanism creates, gas, water, and sewer mains were encountered, in addition to pneumatic tubes through which mail is propelled, conduits for telegraph, telephone, high tension and low tension electric currents, and a few minor obstructions. These pipes, tubes, and conduits were piled upon one another like a lot of jackstraws- I had almost said like a mess of macaroni.

At such a point every pipe and conduit is charted and marked. As soon as the traction company has changed its motive power on the Lexington Avenue line, which is to be done this spring, the deep, broad cable pits will be abandoned, and we shall be at liberty to proceed. We shall take up, move aside, and relay each pipe, tube, or conduit. They will be replaced in an orderly arrangement just below the street pavement and alongside the rapid transit tunnel. Thus put down, the various pipes will form a pile nearly six feet in depth.

Throughout most of the sections below One Hundred and Fourth Street, the tunnel digging has involved a tremendous amount of delicate cutting away of earth. A slip of pickax or shovel might do great damage to any of the pipes which fill the space close under the surface. Thus far no accident of this kind has occurred. The men ply their tools as delicately as if they were scalpels. The pipes under and around which so much digging is done are supported in their proper positions by immense chains, which are swung from gigantic wooden girders and adjusted with scrupulous care. Similar girders are used to support street car tracks wherever the tunnel excavation is done from the surface. Owing to the great care that has been taken, no accident has occurred in these branches of the work.

How The Great Trench Is Dug

The general plan of street excavation is to make an opening four hundred feet long and one half the width of the street at a time. The tunnel is built along that section, the pipes and electric subways are replaced, and the street surface is restored. Then, as the pavement is relaid, new excavation is pushed forward. Meantime, work on the opposite half of the street, hitherto unopened, is carried on.

The trench dug is usually about twenty feet deep. On the bottom of the excavation is spread a solid floor of concrete. At intervals of five feet along this floor, frames of steel beams are erected, securely riveted together, and running transversely to the street. These frames are the ribs of the tunnel. They carry the load of the street above, and they sustain the thrust of the earth on either side. Between the frames there is built a concrete wall and roof thick enough to embed the steel skeleton and preserve it from rust or decay. Alternate layers of asphalt and roofing felt will be spread on the outside of the structure, so as to make it absolutely waterproof.

There were some special problems to be solved at certain points. The road crossed one or two sewers in places where, owing to the low elevation of the ground, it was not possible to carry them down beneath the railway bed. At Canal Street there was a sewer nine feet wide and six feet high, which drained an area of one hundred and twenty one acres lying east of the road, and ran across Broadway to the Hudson River. In this case a new channel, six feet in diameter, was built from the East River up James, Mulberry, and Center Streets to Canal Street, so that now the drainage of that district will be conveyed eastward instead of to the west.

In every branch the work is being hastened as rapidly as is consistent with safety, regard for public comfort, and the necessities of public travel. Chief Engineer Parsons has predicted that trains will be running before Christmas of 1903. I shall do all I can to fulfill the prophecy.

John B. McDonald was born in New York City in 1847. His father, Bartholomew McDonald, was alderman for the old Nineteenth district, and made a fortune as a contractor. John B. McDonald was his father's partner and is his successor. He has made extensive improvements in San Francisco harbor, and has constructed four hundred miles of the Canadian Pacific Railroad. He built one of the elevated lines in Chicago, and nine miles of tunnel through which the city gets water from Lake Michigan; also the tunnel through which electric motors haul freight trains of the Baltimore & Ohio railroad under and across the city of Baltimore. He is building the Jerome Park reservoir in New York. For more than twenty years Mr. McDonald studied the problem of rapid transit in New York, and he probably knows more about it than any other man. From the beginning he has been convinced that the true solution lay in an underground route, dry, brightly lighted with electricity, and with electric motive power, which avoids the vitiation of pure air and affords great speed. In building and equipping the present road he is realizing the ambition of his life.

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