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Subject: Saga in Steel and Concrete - 191-202
Date: Sat, 3 May 2003 10:30:30 -0700


The following selection is taken from "Saga in Steel and Concrete:
Norwegian Engineers in America" by Kenneth Bjork published by the
Norwegian-American Historical Association (NAHA) in 1947. The volume is
still available from NAHA at where you will
also find the first 33 volumes of Studies and Records online. This
chapter is published with the kind permission of NAHA. The book this
selection is drawn from is under copyright and permission has been
granted for educational purposes and it is not to be used in any way for
any commercial venture.

The most serious gas thrown out by the gasoline motor is, of course,
carbon monoxide. Because of the great length of the tunnel this gas was a
problem to Singstad and his fellow engineers whether large or small
quantities of it were present. It was found that if the carbon monoxide
content were kept within safe limits, other gases would not be present in
sufficient amounts to be injurious to health. The researchers, however,
were handicapped by the fact that "only a small amount of experiments had
been made on engine gases, and these results did not give the information
necessary to serve as a basis for the planning of the ventilation of the
tunnel." There was nothing for Singstad to do but to conduct a series of
experiments to establish the necessary data.
With estimates at hand of traffic capacity and such information as was
available on the amount and composition of exhaust gases and their
physiological effects, Singstad and his associates were convinced that
the method of ventilating railroad tunnels --- of blowing fresh air from
one portal to the other --- was not adaptable to this case.
Such large quantities of air were required that the air velocities would
be excessive, causing not only discomfort to the traveling public but
also creating a hazard, particularly in case of fires in the tunnel. Many
modifications of such a plan were considered whereby intermediate shafts
were introduced and the tunnel was divided into several sections. There
were many practical objections to all of these plans, and it was
concluded that the only practicable method was to supply the fresh air
through an independent duct, feeding the air into the roadway from this
main duct at frequent intervals and to withdraw the vitiated air through
a similar duct also separated from the tunnel roadway, drawing the air
from the roadway through openings at frequent intervals throughout the
entire length of the tunnel.
By this method, the longitudinal flow of air in the tunnel would be
eliminated, the movement being instead a transverse one from the supply
duct toward the exhaust duct. Singstad explains further:
In a tunnel of circular cross-section with the roadway located at an
elevation giving maximum clearance for vehicles, there is space available
for ventilating ducts both below and above the roadway, one for the fresh
air and the other for the vitiated air.
The power required to move the large quantities of air is an important
factor, and it was found economical to divide the tunnel ducts into a
number of sections by locating the ventilation equipment in four shafts,
two on each side of the river. Navigation requirements did not permit the
location of any shafts beyond the pierhead lines, which at the site of
the tunnel are about 3,200 feet apart.
In designing the ventilation equipment it was necessary to know the
coefficient of friction for the flow of air in the concrete ducts such as
planned for the tunnel and the power losses where air is taken from or
supplied to a duct. No assurance could be found as to any reliable bases
for the existing formulas, and it was deemed necessary to verify them by
independent tests on large scale models before accepting them as a basis
for the design of the ventilation equipment for a project of this
The New York State Bridge and Tunnel Commission and the New Jersey
Interstate Bridge and Tunnel Commission accordingly entered into a
contract with the federal bureau of mines, to conduct these tests.
Studies to determine the amount and composition of exhaust gases from
motor vehicles were carried out at the bureau of mines experiment station
in Pittsburgh. A study of the effects of motor exhaust gases was made at
the bureau of mines experiment station at Yale University.
The conclusions drawn from the tests have been given by Singstad:
When an automobile engine with gasoline as a fuel is running properly,
the exhaust contains no substance which is toxic to any appreciable
extent other than carbon monoxide. Gasoline engines with cylinders
missing or when cold, oversupplied with oil or gasoline, or smoking from
any cause, may throw off disagreeable vapors irritating to the eyes and
nauseating to some persons.
The physiological effects of carbon monoxide are wholly due to the union
of this gas with the hemoglobin. To whatever extent the hemoglobin is so
combined, by that amount it is rendered incapable to transport oxygen to
the organs and tissues of the body. The combination of carbon monoxide
and hemoglobin is a reversible reaction, so that when a person returns to
fresh air the carbon monoxide is gradually eliminated. Of all physical
signs and tests of carbon monoxide poisoning, headache proved the most
definite and reliable. Concentration of gas too weak or periods of
exposure too short to induce this sign are to be considered harmless. No
one had this symptom to an appreciable degree after a period of one hour
in the chamber with 4 parts of carbon monoxide in 10,000 parts of air.
With 6 parts the degree of effect, if any, was usually very slight, while
with 8 parts there was decided discomfort for some hours, although not
enough to interfere with the continuance of efficient work in the
laboratory or at the desk. . . .
Based on the investigations, a standard of ventilation was adopted
providing for a carbon monoxide content in the tunnel atmosphere not
exceeding 4 parts in 10,000 under capacity operation.
Tests were also conducted at the engineering experiment station at the
University of Illinois to determine the power required to supply and
exhaust the air under the adopted plan of ventilation. With data from the
three groups of investigations in hand, it was possible to proceed with
designs of the ventilating system.
Before actual construction of the system, it was considered advisable to
demonstrate it on a large-scale model of the tunnel. This investigation
was carried out under an agreement with the bureau of mines in the
bureau's experimental mine at Bruceton, Pennsylvania, part of which was
reconstructed for the purpose. There was a miniature tunnel, oval in
plan, with a roadway length of 400 feet; it was shut off from the outside
air except for a drift connecting it to a ventilation plant.
The results of the tests showed that "the methods of transverse air
movement investigated were practicable for tunnel ventilation and that
the best method from the standpoint of power saving and safety against
fire hazard was the one in which the air is introduced from the duct
under the roadway and exhausted through the duct above the ceiling."
The plan of ventilation finally adopted is described thus by Singstad:
Air is supplied to the tunnel from the fresh air duct located under the
roadway. The air is taken off from this duct through flues 10 feet to 15
feet apart, provided with adjustable dampers and leading into continuous
expansion chambers located just above the roadway, one on each side. From
these chambers, two continuous transverse fresh air streams sweep across
the roadway and dilute the exhaust gases. The air then slowly ascends to
the ceiling where it is drawn through adjustable openings, located from
10 to 15 feet apart, into the exhaust duct. In the four ventilation
buildings are located blower fans connecting through downcast ducts with
the fresh air ducts in the tunnel. These fans take air from the fan
rooms, the air entering the rooms through large louvred openings in the
sides of the buildings. In the same buildings the exhaust fans are
located in airtight rooms which are connected through ducts with the
exhaust duct in the tunnel. The exhaust fans connect to vertical
expanding stacks extending above the roofs of the buildings, through
which the vitiated air is expelled to the outside atmosphere. The
ventilation ducts in each tube are divided into seven sections by
transverse bulkheads, so that the equipment in each building ventilates
sections of the tunnel extending from the building to the portal or
half-way to the next building except in the case of the entrance
downgrade between the land and river buildings in each tube, which is
ventilated from the land building alone. Each duct section has three
fans, two of them required to be operated at full speed to supply the
normal maximum ventilation requirements, the third unit constituting the
The fans . . . are operated by electric motors through chain drives. The
ventilation equipment required about 4,000 horsepower at capacity
The Holland Tunnel was not planned and built without considerable doubt
and criticism from certain quarters, and there were those who were
unconvinced of its efficacy. The first year of its operation was
therefore of greatest interest, and Singstad, as engineer in charge of
operations, was called upon to report the results. Parts of his review
are of more than casual interest. {37}
During the first twelve-month period, ending in November, 1928, a total
of 8,517,689 vehicles used the tunnel. Of this number nearly 80 per cent
were passenger cars. The average daily traffic was 23,372, while the
average Sunday and holiday traffic was 36,391. The tunnel took about 43
per cent of the auto traffic crossing the Hudson, a figure far in excess
of the estimate made in the plans. There was no shutdown except for a few
hours on certain nights when the north tunnel was closed in order to take
accurate readings of the distribution of air in the various parts of the
tube. There was no serious accident, largely because of rigid enforcement
of traffic regulations, brilliant illumination, and prompt handling of
stoppages in the tunnel. Nearly 200 fires broke out in vehicles that were
going through the tunnel. All fires, however, were extinguished by
policemen using chemical fire extinguishers, and without the aid of a
special fire-fighting apparatus mounted on an emergency truck. Over 2,000
disabled vehicles were towed out of the tunnel, and a number of arrests
were made, summonses and warnings issued. {38}
The real test lay, however, in the performance of the ventilation system.
Orders were given to operate at a normal maximum capacity on the first
day. About 3,760,000 cubic feet of fresh air per minute was provided.
Nearly 52,000 vehicles, of which about 98 per cent were passenger cars,
went through the tube. The average carbon monoxide content in both
tunnels was .69 part per 10,000 parts of air. The highest was 1.60 parts
per 10,000. The permissible standard, previously mentioned, is 4 parts
per 10,000 parts of air. The longitudinal air draft caused by vehicular
movement at times reached 10 miles per hour. It was found, too, that
there was never enough fog or smoke to interfere with safe traffic, and,
in fact, the public and the press proclaimed air conditions were actually
better in the tube than in some streets of New York City. The general
cleanliness of the tunnel was also remarked by the traveling public and
the newspapers.
From a purely financial point of view, as well, the tunnel was a success.
Whereas its total cost, not including interest on the investment during
construction, was about $48,500,000, profit over operating costs was more
than $3,500,000 during the first year, one half going to each state. For
the first year the tunnel operated at about one half of estimated
capacity. Traffic has been at near capacity since the middle thirties. At
capacity operation the net annual earnings are about $7,000,000. The
tunnel was fully paid for out of toll charges at the end of 1940, or
after it had been in use for thirteen years. This was far beyond the
expectations of the legislatures of New York and New Jersey back in 1919.
Further tunneling did not, however, await the success of the New York
model. In March, 1925, contracts were let for the construction of the
George A. Posey Tunnel between Oakland and Alameda, California, which
when completed in 1928 was nearly a mile in total length and some 37 feet
in diameter. {40}
The cities of Oakland and Alameda, lying on the eastern shore of San
Francisco Bay, have grown in recent times to be, with Berkeley and
Richmond to the north, an important industrial center. Alameda, besides
having the traffic problems common to all dynamic American communities,
was cut off from direct connection with Oakland by an arm of San
Francisco Bay known as the San Antonio Estuary. Five miles long with an
average width of 1,000 feet and a depth of 30 feet over most of its
length, this estuary, while important commercially, presented a problem
to vehicular traffic that had been only partly met by four swinging
bridges fast becoming obsolete. Delays to motorists became unendurable;
and finally the federal government condemned the most westerly of the
bridges near the business center of Oakland. This action caused the
Alameda County board of supervisors to ask George A. Posey, county
engineer, to proceed with a study of the vehicular problem and to work
out a solution.
Since the country on either side of the estuary is low and flat, a
high-level bridge was considered uneconomical and a tunnel was decided
upon. In working out the designs, Posey and his associates adopted the
methods, somewhat modified, which had been worked out by Olaf Hoff, Ole
Singstad, and others. They decided to build 1,000 feet of tube for the
underwater section on the Oakland side, float the twelve units of precast
tubes, sink them in place, and cover them under water with tremie cement.
The tunnel plans called for two lines of traffic and sidewalks on both
sides, thus requiring an unusually efficient system of ventilation; the
Holland Tunnel system was adopted in all its important aspects. Ole
Singstad, its author, acted as consulting engineer for the Posey Tunnel.
The next important vehicular tunnel, which was the first international
tube of its kind, was built between Detroit and Windsor, Ontario, and is
generally called the Detroit-Windsor Tunnel. Designed by S. A. Thoresen,
another American engineer of Norwegian birth and training, this tunnel,
like the one at Oakland, borrowed heavily and wisely from the pioneer
work of Hoff and Singstad.
Soren A. Thoresen, an 1896 graduate of the Mechanical Trade School at
Porsgrund, studied electrical engineering at the technical institute in
Mittweida, Germany, before coming to the United States in 1903. After
working for a time in Minneapolis and later with Westinghouse at
Pittsburgh, he found his real opportunity with William Barclay Parsons of
New York City. Taking employment in 1905 as a draftsman, Thoresen rose to
become, in 1940, a member of the present distinguished firm of Parsons,
Klapp, Brinckerhoff, and Douglas, consulting engineers. Although his
training was along mechanical and electrical lines, Thoresen has
participated ably in many other branches of engineering. While his work
as an engineer has thus covered a variety of undertakings --- including
hydroelectric and defense projects --- he also made a successful
excursion into the field of tunneling and is therefore linked to our
story of transportation. {41}
In the early seventies of the last century the people of Detroit were
engaged in a heated debate over the relative merits of a bridge or tunnel
to cross the Detroit River to Canada. The struggle became tense when two
powerful and interested groups lined up on opposite sides in the battle.
The shipping interests favored a tunnel, because of their fear of what
bridges might do to the high masts of the ships which plied the river.
The railroads, on the other hand, favored bridges. It soon became clear,
however, that bridges high enough to clear the masts of ships would
require approaches a mile long at either end, and favorable opinion for a
tunnel thus gradually made headway.
Chesbrough's failure to tunnel under the Detroit River has already been
noted. A second venture in 1879, seeking to link Grosse Isle and the
Canadian mainland by a tube, was abandoned because limestone formations
made the cost prohibitive. When the Grand Trunk Railway tunnel under the
St. Clair River was completed at Port Huron in 1891, another flurry of
tunnel excitement swept over Detroit, whose citizens feared that shipping
might be diverted to Port Huron. In the meantime several renewed attempts
to push a bridge project through failed as miserably as the first
tunnels. Finally, the remarkable success of the Michigan Central project
settled the question of tunnel versus bridge in favor of the former, and
when automobile traffic became heavy, a vehicular tunnel under the
Detroit River was agreed upon. {42}
Formally opened on November 1, 1930, the Detroit-Windsor Tunnel met a
serious need in motor traffic between the two cities. Total crossings
both ways reported in 1929 were 17,000,000 passengers and 2,066,000 motor
vehicles. Up to 1929 two ferry systems, located about two and a half
miles apart, had to carry business and pleasure traffic, a strain
increasingly too great for that type of service. The new tunnel, 5,137
feet in length between portals, begins, on the American side, only a few
hundred feet from the center of Detroit's financial and shopping
district. At the Canadian end the entrance is located in the heart of
Windsor's business center. Two and a half years under construction, the
tunnel's underwater section of over half a mile was built in sections on
shore; these were towed into position, sunk, and concreted after the
manner of Hoff's earlier tunnel. The shield-driven sections at both shore
ends are about a quarter of a mile long, and the rest, built by the
cut-and-cover method, is over a quarter of a mile in length. The roadway,
which provides one lane of traffic each way as well as patrol sidewalks,
is ventilated in the Holland Tunnel tradition. {43}
While similar to earlier tunnels, the Detroit-Windsor tube nevertheless
was novel in several respects. Not least unusual was the financing method
used. Late in 1926, Thoresen writes, a man entered the New York offices
of Parsons, Klapp, Brinckerhoff, and Douglas, where Thoresen was
employed. The visitor put forward the idea of a tunnel under the Detroit
River, a project which he thought would be profitable as well as feasible
from a technical point of view. The tunnel, he said, would be financed by
private capital. This promoter, a captain in the Salvation Army, proved
to be something more than a visionary. A group of Detroit bankers
organized the Guardian Detroit Company, which, assisted by New York and
Chicago banking houses, took over the financing of the tunnel and engaged
Parsons, Klapp et al. as engineers of design and construction. To
Thoresen went the responsibility of design; Singstad acted as consulting
engineer for the whole tunnel and was responsible for the plan of its
ventilation system. {44}
As an international artery of travel the Detroit-Windsor Tunnel presented
an unusual problem in traffic regulation. Theoretically it can handle
1,000 vehicles per hour on each of its two lanes, but capacity is
regulated in fact by the speed with which customs and immigration
officials finish their duties at either end. At the two terminal plazas
are facilities for inspection, eight lanes on the American side and ten
on the Canadian side being kept busy when traffic is at a maximum. Lights
placed on the pavement help customs officials on the American side to
detect contraband. Bus passengers are discharged at the terminals and are
admitted to the streets after passing a routine inspection.
In the shield-driven part of the tunnel, the distinguishing feature is
that for the primary lining structural steel was used instead of cast
iron, which had been commonly employed in the past. Greater economy,
lightness, ease of erection, and strength were the qualities mentioned in
defense of this choice.{45} It should be added that the steel lining was
planned by Thoresen.
Several other novel features characterized construction at Detroit. The
junction between the shield-driven section and the subaqueous tube was
effected without sinking a shaft at that point. The shield was driven
into a bell-shaped enlargement of the river tube near the shore. The
operation was performed under a clay blanket dumped in advance, the
shield being pushed blindly through the blanket. {46} In laying the giant
steel tube sections --- each measuring about 250 feet in length --- which
form the river section of the tunnel, sand was first placed in the bottom
of the trench at a correct grade by use of a specially designed leveling
device. Sand was lowered into the trench by means of clamshell buckets.
{47} All in all, the Detroit-Windsor Tunnel, in design and construction,
was no mere imitation.
On September 10, 1933; two tunnels --- one for vehicles and another,
about half a mile distant, for pedestrians and cyclists --- were opened
to traffic under the Scheldt River at Antwerp, Belgium. Behind this event
lies an interesting story of American collaboration and the eastward
movement of immigrant skills. In the spring of 1930, M. Frankinoul, a
prominent Belgian contractor, visited the United States in anticipation
of the Antwerp undertaking. The contractors were responsible for plans,
estimates, and bids, as well as for construction. The only tunnel work in
progress in this country at the time was at Detroit, where Frankinoul,
studied construction techniques and decided to employ the Parsons firm as
consultants. But before returning to his homeland he made further
inquiries and as a consequence asked Singstad to serve in a consulting
capacity. In the completed shield-driven tunnels at Antwerp, American
precedents were followed throughout, except for the escalators and
elevators serving the pedestrian tube. Cast-iron linings similar to those
in New York were adopted, on Singstad's recommendation. Singstad designed
not only this lining in all details but also the tunnel shield, and he
was wholly responsible for the ventilation system and the equipment
design. Thoresen, representing his firm, also participated as an active
consultant and has given an interesting record of the project. Both
Americans were decorated by King Albert for their services. {48}
In the meantime traffic across the Hudson between New York City and New
Jersey had continued to increase rapidly. The Port of New York Authority,
established in 1921 by the states of New York and New Jersey to promote
the commercial development of the New York port, with special regard to
improving terminal and transportation facilities, {49} was faced with the
fact that all vehicles crossing the Hudson in the vicinity of New York
City were borne by the George Washington Bridge (completed in 1931), the
Holland Tunnel, and nineteen ferries. Traffic had risen from 5,000,000
vehicles in 1915 to 31,500,000 in 1936 -an increase of over 500 per cent
in twenty-one years. A further increase to 40,000,000 was anticipated by
1941. {50} The Holland Tunnel and Washington Bridge left the large
mid-town section of Manhattan unprovided for. The result was that the
Port Authority planned what is called the Lincoln Tunnel to link New
Jersey with the central Manhattan business district and to form part of a
future through highway route to Long Island. {51}

<37> Ole Singstad, "A Year's Operating Experience with the Holland
Vehicular Tunnel," in Engineering News-Record, 101: 942-949 (December 27,
<38> For the technical operation of the tunnel, see also "Method of
Operating Holland Vehicular Tunnel," in Engineering News-Record,
99:700-702 (November 3, 1927).
<39> Singstad to the author, October 16, 1946.
<40> For a valuable account of the Holland, George A. Posey, and
Detroit-Windsor vehicular tunnels by Ole Singstad, see his "Bau von
Unterwassertunneln in den Vereinigten Staaten von Amerika," in
Zeitschrift des Vereines deutscher Ingenieure, 77:265-270 (March 11,
1933). Competent studies of the Posey Tunnel are S. W. Gibbs,
"Construction Methods on Oakland Estuary Tube," in Engineering News
Record, 100:100-105 (January 19, 1928) ; A. R. Baker, "The
Oakland-Alameda Estuary Tube," in Engineering (London), 130:383-386,
449-451 (September 26, October 10, 1930); "Ventilating the World's
Largest Subway," in Domestic Engineer, 123:18-21, 38, 40-44 (May 12,
1928); Alvin A. Horwege, "Methods Used in the Construction of Twelve
Pre-cast Concrete Segments for the Alameda County, California, Estuary
Subway," in American Society of Civil Engineers, Proceedings, 53 (2) :
2675-2692 (December, 1927); and "Methods of Controlling Traffic in the
Oakland Estuary Tube," in Engineering News-Record, 102:710-712 (May 2,
1929) .
<41> Norwegian-American Technical Journal, vol. 11, no. 2, p. 7
(December, 1938); Wong, Norske utvandrere, 73; and information furnished
by Thoresen in an interview, May, 1941.
<42> "Detroit and Canada Vehicular Tunnel," in Canadian Engineer,
60:11-15, 53 (April 21, 1931).
<43> The Detroit-Windsor Tunnel," in Engineering (London), 130:605-609,
667669, 702-705 (November 14, 28, and December 5, 1930) ; S. A. Thoresen,
"Construction of Detroit-Canada Tunnel," in Canadian Engineer, 56:257-260
(February 26, 1929) ; "Detroit and Canada Vehicular Tunnel," in Canadian
Engineer, 60:11-15, 53; "The Detroit-Canada Vehicular Tunnel," in
Engineering News-Record, 103:600-606 (October 17, 1929); and S. A.
Thoresen, "Constructing the Detroit-Windsor Tunnel," in Civil
Engineering, 1:613-618 (April, 1931).
<44> Thoresen, in Civil Engineering, 1: 613-618.
<45> S. A. Thoresen, "Tunnel Lining of Welded Steel," in Iron Age,
125:985-989 (April 3, 1930). The question of steel versus cast iron for
tunnel lining is a highly controversial one, with respect both to merit
and economy. The chief objection made to steel lining is the difficulty
--- and expense --- of making it watertight in places like New York,
where this precaution is imperative. The tunnel at Detroit was cut
through generally impervious clay which, but for sand pockets, is nearly
ideal material for tunneling; as a consequence it was not designed to be
absolutely watertight. The only other tunnel built of structural steel
without provisions for watertightening is the one under Boston harbor,
where ground conditions are similar to those at Detroit.
<46> Thoresen, in Canadian Engineer, 56:257-260.
<47> Thoresen, in Civil Engineering, 1:613-618.
<48> Ole Singstad, "Vehicular and Pedestrian Tunnels at Antwerp," in
Civil Engineering, 4:1-5 (January, 1934); and S. A. Thoresen,
"Shield-driven Tunnels near Completion under the Schelde at Antwerp," in
Engineering News-Record, 110: 827-832 (June 49, 1933).
<49> "The Port of New York Authority," in Engineer (London), 162:2-4
(July 3, 1936).
<50> O. H. Ammann, "Planning the Lincoln Tunnel under the Hudson," in
Civil Engineering, 7:387-391 (June, 1937).
<51> "New Road under the Hudson," in Engineering News-Record, 118:901-907
(June 17, 1937).

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