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American Government Special Collections Reference Desk


Silas Bent
The New York Times
December 10, 1922

Holland TunnelBirdseye View of Tunnel Plan, Looking Down Canal Street, Across the Hudson to Twelfth Street, Jersey City.  Arrow in Foreground Indicates Exit at Canal and Varick Streets, and Arrow to Right the Entrance in Broome Street.

Big Shields Bore Earth and Walls Rise on Insect Model


Population Problem Made Easier by New Auto Route—Inlet for Food.

By Silas Bent

Already New York and New Jersey are spliced together by underwater ties, but their latest groping to clasp hands beneath the Hudson is by all odds the most difficult and remarkable undertaking in that direction.  To complete the vehicular tunnel now being burrowed will require three years; but if it is used to capacity for the following three years, thrice the present population of the United States can pass through it, comfortably, safely and as complacently as though sweat and genius had not gone into the building of it.

Something more than gregarious neighborliness is back of this.  Economic forces are stronger than the herd instinct.  The tunnel will stretch invisibly to every pocket nerve for miles and miles around.  Even its construction is reflected in distant payrolls.  Ships replete with Oregon fir are waddling adown the coast and through the Panama Canal to bring timbers for the above-ground structures it involves.  Massachusetts granite will go into its roadways, Pennsylvania steel, iron and cement into its tubes and Brooklyn calking material will help make them watertight.

But the completed tunnel not only will be a step in unifying the Port of New York, it will help solve the living problem for millions.  Through it will flow from Jersey meadows milk and vegetables to the Manhattan consumer, and warehouses on the western bank of the river will relieve the congestion of railroad terminals.  The tunnel will mean the triumph of of the truck for short hauls hereabout, and it will be a triumph which the hard-presses railroads cannot begrudge.  Thousands of week-day delivery drivers and other thousands of Sunday motorists Jerseyward will be emancipated from the tedium of the ferries, and perhaps some day, when parking space is found above or below ground in New York, still other thousands may be emancipated from predatory landlords.

Emancipate!  Why, T. Albeus Adams, Chairman of the New Jersey Interstate Bridge and Tunnel Commission, has compared the tunnel to Lincoln's proclamation freeing the slaves.  It will reduce the excessive costs and delays caused by the river barrier.  It will save from waste the lettuce and celery and onions and potatoes which now rot in heaps on the Jersey side.

Being water-bound had cost New York a pretty penny.  The late George W. Perkins once told me casually of his investigations in this field.  He bought an ocean bay and set out to find why it was that fish, which cost nothing to feed, cost so much in New York.  And what he found was that the expense of moving a barrel of fish from the outskirts of New York to a market booth equaled the total expense of catching the fish, refrigerating them, supplying the barrel, moving it to a railroad way station and transporting it to town.

A Lesson from Insects.

As one way of meeting that condition, it was decided, for reasons of economy, to dig beneath, instead of hurdling the water.  The difficulties of bridging the Hudson need not be reiterated here; and as for moving the raw materials for Manhattan's dinner by airplane, that has not yet been found commercially practicable.  In the conquest of the air, it is worth noting, man has not learned as much from the birds as he has from certain insects about the business of mining and sapping.  The cricket, for instance, in that earth-bound stage before it becomes a songster, shores up its underground home while it burrows, plastering the walls neatly with moistened earth as it goes, that there may be no disastrous landslides behind it.  And men within the giant shield which has started under the Hudson River will build the tunnel-tube as the shield moves.

There are to be six of these shields, the largest ever constructed, in boring the two tubes which really go to make the tunnel, so called.  Two will dig through the Jersey shore and two beneath the river from the Jersey side.  One started more than three weeks ago from a concrete shaft at the foot of Canal Street in New York, and another will have started from the New York side before this appears.

Although the Hudson tubes are supposed by tunnel engineers to have familiarized everybody with the nature of these shields, it may not be amiss to say that they are not disks such as ancient warriors buckled to their arms.  They are not at all that kind of shield.  They are cylinders.  Fancy a tomato can, if you will, more than thirty feet thick and eighteen feet long, with both ends knocked out and a partition or bulkhead dividing it into chambers, one twice as long as the other.  Picture this as made of steel, with a cutting edge in front and in its smaller rear chamber a titanic arm which lifts into place, inside the steel jacket, enormous segments of an iron ring.  This band, completed, is part of the tube.  Jacks fitted into the bulkhead, pounding and thrusting with incredible power against it, force the cylinder forward in readiness to repeat the operation.

Beneath the river a progress of fifteen feet a day is expected.  Now it is but a sixth of that.  Ultimately the blind steel shields westward bound will meet other cylinders eastward bound far beneath the river bed, and the vehicular joining of New York to New Jersey will be celebrated with much feasting and rejoicing.

In the forward section of the 400-ton shield the sandhogs work.  Under the ...{scan failure}... high air pressure required to keep back the water, sand and muck—usually thirty pounds or more to the inch—they are busy with shovel and pick, passing the loosened material into the maw of the shield, through shutters in the bulkhead.  Thence it goes out through the tunnel, is hoisted on to a gantry, so as not to interfere with street traffic below, and moves along to a dump where it is emptied into barges.  The gantrys, the pumping stations, the plants where air is compressed, the quarters for workers and engineers, constitute part of the open-air building which accompanies and facilitates the underground work.

The sandhogs in the forward chamber are one of three sets of men in the shield.  Another set handles the material loosened by the sandhogs' picks and the beveled forward edge of the cylinder.  Still another set manages that giant arm, operated by hydraulic power, which sets into place six-foot segments of cast iron, each weighing a ton and a half, with a key segment at the top weighing more than half a ton.  To feel the heft of one of the specially constructed ten-pound bolts used to rivet a section into place gives a notion of the size of the job.

Weight of the Roadways.

There are 100 of these bolts in each ring, and the contract for the quantity necessary in the whole tunnel was the largest of its kind ever let.  The cast iron circlet which makes up one thirty-inch segment of the tube weighs twenty-two tons, and the whole outer shell of the two highways—or should they be called low-ways?—will weigh 115,000 tons, which is but a part of the total; for at 800-foot intervals there will be huge concrete caissons and the tube itself will be lined with tile, reinforced with concrete and paved with granite.  Even so, it may not prove heavy enough.  It may be necessary to tie the whole thing down with additional poundage!

For the protection of the adventurous sandhogs at work in the forward chamber a blanket of clay has been laid over the river bottom above the tunnels.  It sometimes happens that the enormous air pressure necessary in this work brings what the sandhogs call a "blow."  An accident of that kind took place during the construction of one of the East River tubes, and three men were blown up into the river.  Marshall Navey was the only one of them who lived to tell the tale.  He was found swimming a bit aimlessly about the surface and taken ashore in a skiff.  Undeterred, he is at work on this tunnel.

The sandhogs work in pairs, a miner and his helper, and the peculiar qualification for their work is that they are constitutionally able to endure high air pressure.  The same qualification is required for the teams of men, usually Poles and Hungarians, who are busy in the rear chamber shoveling out the dirt and rock and sand sent through the orifices by the men beyond.  The iron work is done usually by negroes and cockney Englishmen; and these fellows may be found on construction work in England or the Orient, wherever high air pressure is required, a unique and hardy industrial type.

Sometimes changing from one air pressure to another too suddenly causes what underground workers call "the bends."  In more dignified phrase it is known as "caisson disease," caused by the presence in the blood of too much nitrogen.  The man attacked by it becomes as helpless as though dead drunk, and can be cured only by what hard drinkers call "the hair of the dog."  They must be put into a tank specially constructed and subjected to the same atmospheric pressure which brought the trouble.  Gradually the atmosphere is brought to normal, and "the bends," if the patient lives, are gone.

No one who contemplates the difficulties of building a vehicular tunnel will sing with Walt Whitman the engineer's joys.  The greatest problem to be solved was mechanical ventilation, and it never before had been solved for a tunnel because none had been dug on this scale.  In solving it successfully several other problems were met as by-products of the research.  New discoveries in regard to poison gases were made and can be put to peacetime uses, in mines and other underground work; and I remember when the Bureau of Mines at Washington, which was helping in the investigation, announced as one of its by-products that motorists were wasting millions of dollars in gasoline every year because they used too rich a mixture in warm weather.

Ventilation Research.

In addition to the Bureau of Mines using mine shaft at Bruceton, Pa., for demonstration, the University of Illinois, using a miniature tunnel on the campus at Urbana, collaborated in the inquiry.  They made temperature measurements and smoke observations and took samples of dust; and Yale University gathered physiological data on the effect of carbon monoxide, which is the villain in this drama.  It is a deadly fume given off from internal combustion gas engines.  The reason it caused the engineers no trouble when the Pennsylvania tunnels under the Hudson and the Long Island Railroad tunnels under the East River were being constructed was that these trains are operated electrically.  Nor has it given serious trouble in tunnels through which steam locomotives pass.  In the case of the vehicular tunnel, the villain has been foiled, in effect, by cutting it into minute parts.

The largest quantity of carbon monoxide met with in the vehicular tunnel will be four parts in ten thousand.  If you were to take a grain of strychnine it would kill you, painfully but quickly, but if you were to take only 1-2,500 of a grain it would not even act, in all probability, as a mild tonic.  It would lack even so much as a homeopathic effect.  And if only 4-10,000 of the air you breathe is carbon monoxide it will not cause so much as a slight headache.  This is what will happen in the tunnel.  More than three and a half million cubic feet of fresh air will be pumped into it every minute by electric fans, while exhaust fans are pumping out the vitiated air.  Forty times every hour the atmosphere of the tunnel will be completely changed, every minute and a half.

"The experiments," says a report just issued, "have proved conclusively that the mechanical ventilation of the Hudson River Vehicular Tunnel as planned is assured of success."

The fresh air will be forced by blowers, housed in buildings over four ventilating shafts for each of the tunnels, into ducts beneath the tunnel roadways, pass through flues to continuous expansion chambers, out across the roadway through slots and slowly ascend to the ceiling.  It will remain in the tunnel, on an average, ninety seconds, and carry with it as it leaves the exhaust gases from automobile trucks and pleasure cars.  As the tunnel will have a maximum daily capacity of 46,000 vehicles, mostly motor-driven—two abreast each way—and will be nearly two miles long over all, a constant movement of the air into and out of it is imperative.

The shore ventilating shafts for each tunnel presented no special difficulty, nor did the river shafts on the New York side; but the two river shafts on the Jersey side brought a brand-new problem, because they must be placed where the rock foundation is 250 feet beneath the bed of the river.  This makes it necessary to drive down steel piling to be filled with reinforced concrete.  These are driven in twenty-foot sections, one screwed on to another, in a way which some engineers believed to be impossible.  They supposed that no thread could withstand the force which must be exercised, but this feat, nevertheless, is being accomplished.

The tunnel will be paved with granite blocks, and there will be a clear headroom of thirteen feet six inches between these and the ceiling slab.  At each side of the roadway there will be a granite curb, and at its centre a depressed concrete gutter with side inlet openings at frequent intervals.  At the low point of the tunnel the drain will connect with a sump, and a discharge pipe will run under the roadway of each tube to the shaft in the water, on the New York side.  In all the river and land shafts there will be pumping equipment.

A water main will run throughout each tunnel, with hose connections for protection against flames, if necessary, and for flushing once in so often.  The sides and ceiling will be tiled, and there will be cross passages under water.  The tunnel will have electric lamps twenty feet apart on each side, interspersed with the fixtures on the opposite side.  There will be fire extinguishers and other operating facilities on both sides of the roadways, and, as a final touch, niches for telephones.

The outside diameter of the tunnel is twenty-nine and a half feet except for a section of the north tunnel west of the New Jersey land shaft, where the greater size is deemed advisable for the purpose of larger ventilation ducts.  Throughout its entire length the diameter of the tunnel was increased six inches as a precautionary measure after the earlier plans were drawn.

Clifford M. Holland who, though still under forty, is regarded as the greatest American tunnel engineer, observed when the work began on the New York side that every foot of progress was a new story.  This part of the tunnel is through "made" land, and the excavation revealed the steps by which during the last century Manhattan Island had been enlarged by human handiwork, and by the refuse from an old canal which once emptied into the river at the foot of Canal Street.  In other places cribbing of wood and stone had been erected and filled in with dirt and trash.  At times the tunneling brought to light timbers probably a hundred years old, preserved by reason of having been long underwater.

"Day by day," said one of Holland's assistants, "the shield is moving forward under the most complicated engineering conditions.  Above it is but a thin layer of earth and paved street.  Working with reduced air in these circumstances calls for extreme care.  Progress, slight to the uninformed, is great and important to the group of men constantly watching every element as the mass of steel creeps inch by inch out of its concrete home.

"Ordinarily we have experience which tells us what will happen in work like this, and ordinarily we know what we are working with and can make our assumptions accordingly.  But here we find the all-important working chamber nearly twice the size of its largest predecessor, passing through material which no one can accurately foretell, under pressures of shoving power never before used."

Similar Tunnels Abroad.

The first tunnel ever driven by the shield method was started in 1825 beneath the River Thames below the Tower Bridge, and completed in 1842.  London has a population almost half again as great as New York's, and the inner business section lies on both sides of the river.  Above London Bridge there are many such structures, but below it only one drawbridge has been found practicable, and the necessity arose of going beneath the water.  A tunnel was started as early as 1798, but the enterprise failed; and the roof of another, begun seven years later, collapsed.  The tube completed in 1842 was intended for vehicles, but no approaches were provided, and so it was used only for pedestrians until 1866, when it was sold to a railroad.  Later another pedestrian tunnel was opened, but discontinued; and still another was started but not completed.  At present, however, there are two vehicular tunnels.

Europe is ahead of this country in the construction of under-river highways.  Glasgow and Hamburg, Berlin and Paris have them, but none on any such scale as proposed here.  The two vehicular tunnels under the Thames are the Blackwell and the Rotherite, but neither of them is long enough to make mechanical ventilation necessary.  The volume of traffic in the larger of them amounts in a day only to as much as is expected hourly here.  In the last two years there have been half a dozen collapses of workmen who were paving or sweeping them, and in one instance a policeman was overcome, but none was seriously affected.

In Paris the tunneling under the Seine, and in Berlin under the River Spree, involved intricate engineering problems, but in no instance were the difficulties so great as must be overcome in the Hudson project.  Mr. Holland studied all the tunnels abroad, however, while he was planning the present work, and procured valuable information in regard to drainage, interior finish, paving, policing and such matters.

If Macaulay's imaginary New Zealander were to take his stand on a crumbling pier of Brooklyn Bridge instead of London Bridge, might he not meditate more wonderingly on what had gone on beneath the earth that on what had gone on up above it?  The slim and graceful tower of the Woolworth Building would be dust.  The placid dignity of the City Hall and the frowning arrogance of the Municipal Building alike would have vanished.  Diana would have toppled long since from her airy foothold atop Madison Square Garden.  Even the looped network of subways would be choked and ruined.  But might not that last man, brooding upon a vanished race, make his was finally into a spacious channel, impregnable against water and rust and time, beneath the Hudson River?

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