1917: Engineer Olaf Hoff

We have two entries for Olaf Hoff, a pioneer in the creation of pre-fabricated sections that were sunk and connected to create underwater tunnels.

The first is from a 1917 issue of The American Magazine:


A Great Engineer Perfects A Good Plan


Time: A certain winter’s night, about twelve years ago.
Place: A bathroom in a cottage at Tarrytown, New York.

Kneeling on the floor before a tubful of water is a middle-aged man toying with a queer floating object. You may think he is trying to sail a boat and wonder that a man of his years should be so engaged. But you are mistaken; he is studying rather how to sink a boat.

The man turns a valve or two, and then smiles grimly as the tin model settles very slowly until it vanishes suddenly, leaving scarcely a ripple to mark the place where it sank. With a grunt of satisfaction he snatches the craft out of the water and hides it where no prying eyes may uncover his secret.

What evil plot is this? What mischief is brewing? .

This sounds like melodrama; but the honest, kindly face of the man is entirely out of keeping with popular notions of a fanatic or a villain.


Time: One year later.
Place: On the Detroit River.

Again the mysterious man with his queer, floating object; but now it has grown to enormous size. It is Olaf Hoff, about to put a tunnel under the river by a scheme that is little short of revolutionary. Great crowds have gathered around to witness the initial step, and among the crowd are engineers of the highest prominence.

It is no obscure inventor who has thus suddenly stepped into the limelight, but an experienced, practical engineer who has had a great deal to do with river crossings, although of a different kind. Ever since he arrived in New York, in 1879, a stalwart young Norwegian of twenty summers, one breast pocket bulging with the highest honors conferred up to that date by the famous Polytechnic Institute of Christiania, and the other throbbing with the ambition to make his mark in this land of wonderful engineering feats, he had had to do with bridge work. To be sure, his first job was not very promising. Despite his honors, he had to start at the bottom of the ladder. The best he could do in the beginning was to find a place in the fitting-up shop of a bridge company. But he showed his worth, and advanced rapidly, until a couple of years later he had climbed to the position of engineer of bridges of the Mexican Central Railway, and shortly after became locating engineer of the line. This gave him an excellent schooling in all-around work, and in a few years he had developed sufficient confidence in himself to hang up his own shingle as consulting and contracting engineer, in Minneapolis. There his most notable achievement was the building of a bridge across the Mississippi to St. Paul. Then, in 1910, he took charge of the bridge work of the New York Central and Hudson River Railroad, and, in four years, reconstructed over four hundred bridges.

All this work had been done out in the open; now, for the first time, he had contracted to build an underwater crossing. But he had a way of building even a tunnel in the open.

The situation at Detroit was a peculiar one: the ordinary method of procedure with a tunnel shield and compressed air could not be used, because the ground under the river was permeated by sulphurous fumes and poisonous gases, in which men could not work. If the tunnel was to be built at all, it would have to be by an entirely original method. That was Mr.Hoff’s chance. He had the necessary method.

Ordinarily we think of a tunnel as a hole dug through a mountain or under a river. But Mr. Hoff, with his new method, upset all previous notions of the term. For, like the man who dug a big hole in his back yard where it was handy to work on it, with the idea of cutting it up into sections and selling it to the neighboring farmers for post holes, so Mr. Hoff built the Detroit tunnel in the open, at a convenient point on the river bank; then he floated it out, a section at a time, and sank it into a deep ditch, previously dredged in the bed of the river.

The curtain rose for our second scene just as Mr. Hoff was about to reenact, on a full scale, the performance done in miniature in the bathtub. His tin model had now grown into a pair of enormous steel tubes, over twenty-three feet in diameter and two hundred and sixty feet long, which were boxed in at the sides, and braced with transverse webs, forming pockets to retain the concrete that was to be poured over the tunnel section after it was sunk. The ends of the tubes were closed by bulkheads, so that the structure floated like a big boat or Noah’s Ark, high out of the water. One would think that it would be a difficult task to align this clumsy vessel over the exact spot it was to occupy in the underwater trench; but that which gave Mr. Hoff the greatest concern at the moment was whether he could sink the monster successfully. If the unwieldy craft took a notion to plunge end first, could he check it before it dashed to the bottom and crumpled into a mass of junk?

Now we know what he was working at with his tin model in the bathtub. He was trying out a way of preventing the big brute from taking the bit in its teeth.

It was a critical moment, or, rather, two hours, for it took that long to fill the big tubes with enough water to sink them. At one time it looked as if the monster would surely get out of hand. One end of it began to sink faster and faster, until it was fifteen feet under water; but a buoyancy cylinder, provided for just this emergency, checked it and righted it. That was the only dangerous moment, and in due course the tunnel section rested on the bottom, just as Mr. Hoff had planned that it should. A few weeks later the concrete covering had been completed; then a second section was sunk and made fast to the first by divers. Thus the work proceeded until, eventually, the tunnel had been laid all the way across and weighted with sufficient concrete to keep it down; after which it was pumped clear of water.

A similar tunnel has just been constructed under the Harlem River, New York, to carry the tracks of the new Lexington Avenue subway. Here, profiting by the lessons learned at Detroit, the tunnel sections, although heavier and more unwieldy, because they consisted of four instead of two tubes, were sunk even more successfully.

For a man who has developed so novel a system of tunneling, Mr. Hoff is singularly modest, and insists on disclaiming most of the credit for the method.

“Why, as far back as 1840,” he says, “an engineer proposed that tunnels be built on land and sunk in a trench in the river bed. All I invented was the method of sinking the sections on an even keel and the method of strengthening the tubes with exterior webs or diaphragms to make pockets for concrete.”

That may be very true; nevertheless the world will rightly give Mr. Hoff credit for being the first man ever actually to build a tunnel of this type.

— A. Russell Bond

And the second is from a 1913 issue of The National Magazine:

Olaf Hoff — His Work

by Flynn Wayne

In a world growing busier every day the transportation problem is paramount. Quicker, safer and more convenient plans for getting from one point to another are ever unfolding in the brains of inventors and builders, whose thought is constantly centered upon the difficult problems of transportation.

Overhead construction has seen its greatest development in the present day. The age of steel has brought with it wonderful possibilities in structural work. Skyscrapers that have sent the sky-line of New York to dizzy heights; the colossal bridges that span the East River to Brooklyn, are notable instances of the wonderful development of the use of steel for expeditious transportation and the varied needs of a great city.

The builders of subways who delve like burrowing moles underneath the congested streets of the city are largely dependent on the use of steel, which, mined and molded, shaped and riveted again, returns to mother earth to aid man in conquering the congestion of city streets. Under men still bolder great caissons were sunk from each side of the historic Hudson to give “under river” transportation within three minutes instead of slow cumbersome fog-delayed ferries. It took faith to believe these things could be done, to get the money to prosecute the work. It took a heavy toll of human lives through ignorance and experiment. But advancement counts neither money nor lives in its measure of results for the general good, and the victims are indeed brave soldiers fallen in the relentless march of , progress. Tubes and tunnels were accepted as necessary, and the wonder was, how did the world get along without them? The problem still unsolved was a satisfactory method of building “under water” tubes and tunnels without the necessity of resorting to dangerous air caissons in which to carry on the work. Many problems of similar construction awaited the day when the building of tubes under the rivers should be robbed of its costly feature of accidents and .lives, and reduced to a comparatively simple problem of dollars and cents.

Olaf Hoff, a sandy-haired Norwegian-American in New York, was among those who were pondering this problem. A graduate of the Polytechnic School of Christiania, Norway, young Hoff came to America and entered the employ of the Keystone Bridge Company.

Two years later he went to Mexico and later his work — steadily bringing him to the forefront — took him to Minneapolis, where he built the first steel railroad bridge across the Mississippi River at that point. In 1901 he became engineer of bridges and buildings of the New York Central lines. Under his direction most of the rebuilding of the bridges of that great railway system was accomplished with little delay to its tremendous traffic. When the opportunity came to Mr. Hoff to go into business for himself he resigned his position, but hardly six months had passed when a problem of the Michigan Central Railway began to interest Olaf Hoff. The river at Detroit had to be kept open for navigation, a bridge was practically impossible, a tunnel built by old methods impracticable by reason of the tremendous expense, and yet the enforced use of ferries to carry the trains across the river greatly interfered with the efficiency of the road. Here was a difficulty that called forth the best ideas of the country’s most noted engineers.

The final solution of any problem is striking a balance between necessity and cost, and Olaf Hoff turned all his inventive genius into the work of building railway tunnels under water. His plans were accepted and the successful completion of the Detroit tunnel two years ago marks a hard struggle, gamely fought, and gloriously crowned. Mr. Hoff’s idea, stated briefly, was simple in the extreme. He built two great tubes of steel, laid them in huge cradles arranged in compartments for receiving concrete, launched them like barges into the river, towed them to their proper place and sank them to the bottom, which had been dredged to allow a forty foot clearance for the boats above. The sections of the tunnel were laid and joined together like the tubes of a water main. The concrete was poured into the compartments about the steel tubes and solidified in a few days — even under water. Encased in a shell of solid reinforced concrete the tubes will stand for ages. Not a life was lost in the work and the expense was considerably less.

In the further work of building tunnels under the rivers of New York City the success of Mr. Hoff’s method at Detroit attracted wide attention and he and his associates were successful in securing the contract to build the new four track tunnel under the Harlem River, connecting Manhattan with its fastest growing region, the Bronx. The dredging of the ditch across the river bed and the drilling of the rock for the approaches is now well under way. The big steel tubes for the tunnel are being built and some day, at the word of command, the fleet of steel tubes will sail forth to sink—sink gloriously to the bottom, there to become transformed into links of steel and concrete to bind closer than ever the busy life of a great metropolis.

And among its passengers when the tunnel is finally completed may be one, with sandy hair now streaked with gray, whose blue eyes behind rims of gold will calmly scan the morning paper. But who of his fellow-passengers would know, unless they were told, that it was Olaf Hoff, the builder of the tunnel — the man who has saved countless lives of future tunnel builders and toilers.

* * *

Oddly, there is no Wikipedia entry for Olaf Hoff. He is mentioned only in passing in the entry for engineer Ole Singstad.

Original page image from The American Magazine (a composite of two partial pages), click to enlarge:


Original page images from The National Magazine, click to enlarge:




Leave a comment

Filed under Engineering

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.