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AMERICAN SOCIETY OF CIVIL ENGINEERS

INSTITUTED 1852


TRANSACTIONS

Paper No. 1152


THE NEW YORK TUNNEL EXTENSION OF
THE PENNSYLVANIA RAILROAD.

THE EAST RIVER DIVISION.

BY ALFRED NOBLE, PAST-PRESIDENT, AM. SOC. C. E.




A general outline of the work included in this Division has been given
by General C. W. Raymond, M. Am. Soc. C. E., in the first paper of the
series. The few pages following are intended only as a note to connect
his paper with the more detailed descriptions of the execution of the
work, which will be supplied by the Resident Engineers in immediate
charge.

Soon after the Company's project was made public, in the latter part of
1901, borings were begun in the East River, and a few weeks later in
Manhattan and Long Island City. A preliminary base line was measured on
the Manhattan side, and temporary transit stations were established on
buildings from which all borings in the river were located. The river
borings were all wash-borings made from a pile-driver boat. After the
results were plotted on the map, contour lines were drawn to indicate
the rock surface, and profiles along the tunnel lines were plotted from
the contours; as the borings were preliminary to the final location of
the tunnels, and in many cases at some distance from the tunnel lines,
considerable divergence from the actual rock surface was expected, and
realized in a few places, yet on the whole the agreement was very good.
The borings revealed two depressions or channels where the rock surface
passed below the grade of the projected tunnels, these depressions being
separated by a rock reef which extends down stream from Blackwell's
Island. In 32d and 33d Streets in Manhattan, borings were made from the
river to the station site at intervals of about 100 ft., wash-borings
and core-borings alternating. In Long Island City, where the tunnel
lines were to pass diagonally under the passenger station building and
passenger yard of the Long Island Railroad and under streets and private
property, the arrangement of borings was less regular, although the
alternation of wash-borings and core-borings was carried out as far as
practicable. After the final location of the work, additional borings
were made, particularly on shaft sites and also along the approaches and
in the Sunnyside Yard, Long Island City.

A triangulation was carried across the river with a measured base on
each side. It was impossible to measure directly between the extremities
of either base. The bases were measured with 100-ft. steel tapes,
supported every 20 ft., stretched with a uniform pull, and frequently
compared with standardized tapes. On account of the crowded condition of
the streets during the hours of daylight and evening, most of the work
was done between 10 P. M. and 5 A. M. Similar measurements were made in
the streets along the tunnel lines. Angle readings were repeated many
times, as is usual in such work. Fig. 1 shows the triangulation, the
street measurements being omitted.

Levels were first transmitted across the river by simultaneous
observations of the river surface; then by several repetitions, across
Blackwell's Island and the narrow channels on each side, where the
longest sights were about 1100 ft.; and, finally, by several lines
through the tunnel of the East River Gas Company at 71st Street.

The franchise granted by the City of New York provided for the sale to
the Railroad Company of the portions of 32d Street between Seventh and
Eighth Avenues, and between Eighth and Ninth Avenues. Later, the Company
acquired by purchase the portion of 32d Street between Ninth and Tenth
Avenues. The franchise granted sub-surface rights under streets around
the station site to within 19 ft. of the street surface under Seventh,
Eighth, and Ninth Avenues; to within 30 in. of the street surface under
31st and 33d Streets, except that, under the sidewalks opposite the
station, that is to say, the south sidewalk in 31st Street and the north
sidewalk in 33d Street, the construction must be at least 5 ft. below
the street surface. In carrying out the work, full use of these rights
was made under Eighth Avenue, but only under such portions of Seventh
and Ninth Avenues as were indispensable for access by trains to the
station area. It was not practicable to make full use of the rights
granted under 31st and 33d Streets without incurring great expense for
supporting adjacent buildings or for injuries to them, and, after
careful consideration, the arrangement shown in the plans was decided
on, making about 45% of the sub-surface area under these streets
available at track level.

[Illustration: FIG. 1.--Triangulation System East River Tunnel]

The work of the East River Division at this site embraced the excavation
to the depth necessary for railroad tracks, and the building of a
retaining wall extending in 31st Street from the east side of Ninth
Avenue to the west side of Seventh Avenue, thence northward along
Seventh Avenue for a distance of 155.5 ft.; also a retaining wall in 33d
Street from the west side of Seventh Avenue to the east side of Ninth
Avenue, and thence southward along Ninth Avenue for a distance of 136.3
ft. This work was placed under contract June 21st, 1904, with the New
York Contracting and Trucking Company, and later assigned by that
company to the New York Contracting Company-Pennsylvania Terminal, and
was carried out under the direction of George C. Clarke, M. Am. Soc.
C. E., as Resident Engineer, by whom it will be described in detail.

[Illustration: PLATE IX.--Map of Portion of Manhattan Island from 23d to
40th Streets, Showing Former Topography From Map Made by Gen. Egbert L.
Viele in 1865]

The station tracks leading eastward from the station will converge under
Seventh Avenue and for some distance farther east, and pass into two
three-track tunnels, one under 32d Street and the other under 33d
Street, at the respective distances of 192 and 402 ft. from Seventh
Avenue. A typical cross-section of the three-track tunnel is shown on
Plate XII. The converging sections were considered as easterly
extensions of the station, and were not included in the East River
Division. Within a few hundred feet (Plate XIV), the tracks are reduced
to two, each passing into a single tube, the two tunnels under each
street being formed in one excavation, the distance between center lines
of tunnels being 20 ft. 4 in. This construction has been termed a twin
tunnel, and a typical cross-section is shown on Plate XII. The tunnels
continue on tangents under the streets to Second Avenue where they curve
to the left by 1° 30' curves, passing under private property, gradually
diverging and passing through shafts just east of First Avenue. About
350 ft. west of the shaft, the divergence of the two lines from each
street becomes sufficient to leave a rock dividing wall between them,
and thence eastward each tunnel is formed in a separate excavation. A
typical cross-section of the two separated tunnels is shown on Plate
XII.

It thus appears that eastward from the station the lines constitute a
four-track railroad, each track being in a separate tunnel; for
convenience of the work these lines were designated _A_, _B_, _C_, and
_D_, from north to south.

[Illustration: PLATE X.--Manhattan Shaft, Lines _A_ and _B_]

At an early date, when the organization of the engineering staff was
taken up, Charles L. Harrison, M. Am. Soc. C. E., was appointed
Principal Assistant Engineer. He was directly in charge of all parts of
the work, and all Resident Engineers reported to him. George Leighton,
M. Am. Soc. C. E., was placed in charge as Resident Engineer of the 33d
Street lines from the west end of the three-track tunnel to the shaft
and also eastward from the shaft under East River. As he was not then
able to endure the effects of compressed air, the work under the river
was transferred to James H. Brace, M. Am. Soc. C. E., as Resident
Engineer. Before the completion of the land tunnels under 33d Street,
Mr. Leighton accepted more responsible employment elsewhere, and Mr.
Brace assumed charge of them also. Francis Mason, M. Am. Soc. C. E., was
in charge as Resident Engineer of the 32d Street lines during their
entire construction, and also of the tunnels extending these lines
eastward from the First Avenue shaft under the river.

The work just described as the 32d and 33d Street lines, terminating at
the easterly end at the First Avenue shafts, was placed under contract
on May 29th, 1905, with the United Engineering and Contracting Company.
The plans then provided for three-track tunnels from the west end of the
work under the contract eastward 1,628 ft. in 32d Street and 1,418 ft.
in 33d Street to the west line of Fifth Avenue, with a descending grade
of 0.4%; this was to constitute, in a degree, an extension of the
station, where trains could stand without brakes while awaiting signals
to proceed to or from the station. From Fifth Avenue eastward to the
lowest point under the river, the grade was to be 1.5% on all lines.
Later, during construction, when excavating westward under 33d Street
from Fifth Avenue, the surface of the rock was broken through,
disclosing quicksand; within the next few days trial drill holes through
the tunnel roof at 32d Street and Fifth Avenue showed a thin cover with
quicksand above it. The conditions had been indicated in a general way
by borings made before construction was begun, but they proved to be
rather worse than anticipated. On the topographical map of Manhattan
Island, made by General Egbert L. Viele in 1865, is shown a watercourse
which had its source near what is now Broadway and 44th Street, flowing
thence along the west side and south end of Murray Hill, passing under
the present site of the Waldorf-Astoria Hotel, crossing 33d Street at
the point where the rock surface was broken through in the tunnel
excavation, as above stated, crossing 32d Street at its intersection
with Fifth Avenue, where trial drilling showed thin rock cover over the
tunnel excavation, passing thence eastward a short distance south of 32d
Street, which it recrossed near Third Avenue, and finally discharging
into the East River near 34th Street, and a little west of the present
First Avenue. The ancient creek apparently followed the course of a
valley in the rock, the valley having become filled to a considerable
depth with very fine quicksand. This concurrence of depressions in the
rock surface with the watercourse shown on Viele's map was noted in so
many places and the difficulties of construction were so serious at
these places, that a section of the map showing the old topography along
and adjacent to the station and tunnel lines is reproduced in Plate IX.

[Illustration: PLATE XI.--Long Island Shaft. Lines _A_ and _B_]

The unfavorable conditions developed at Fifth Avenue affected both the
construction of the tunnels and the maintenance of adjacent buildings.
It would be necessary to construct the tunnels in open cut for a large
part of the way westward, causing serious inconvenience to the public;
the buildings were mostly of the older class, founded in earth, but
there were several modern high buildings with foundations in the same
material; some of these had been built since the tunnels were planned.
In view of these added risks and the increased cost of construction, the
value of the three-track construction was reconsidered, and two
important changes were made in the plans. The first of these was to
continue the twin tunnel westward to Sixth Avenue in 32d Street, and to
a point 180 ft. west of Sixth Avenue in 33d Street; the twin tunnel
being 9-1/2 ft. less in height than the three-track tunnel and 9 ft.
narrower, the change reduced the difficulties considerably. Where the
three-track tunnel was thus eliminated, there was no longer objection to
a steeper grade, so that, going eastward from the station, a grade of
0.8% in 33d Street and 0.9% in 32d Street was substituted for the
original 0.4% grade. From the west line of Fifth Avenue eastward short
sections with descending grades of 0.3% connect with the original 1.5%
grade near Madison Avenue. The effect of these two changes--type of
tunnel and grade--was to lower the roof of the tunnels at Fifth Avenue
about 15 ft., which made it practicable to avoid open cutting east of
Sixth Avenue.

A full account of the construction of the cross-town tunnels will be
given by the Resident Engineers.

Permanent shafts were made on both sides of the East River, those in
Manhattan being located a few feet east of First Avenue, and those in
Long Island City being located, one in the so-called Annex Slip, the
other in the pier just south of it. The two railroad lines coming from
32d Street in Manhattan, and curving to the left at Second Avenue, are
about 34 ft. apart between centers at First Avenue, and it was
convenient to make the shaft large enough to cover both lines. Borings
had shown that the excavation for the tunnels would break out of the
rock about 200 ft. east of First Avenue. It was desirable to carry the
tunnel excavation eastward from the shaft in normal air far enough to
permit of building at least 50 ft. of tunnel and installing air-locks,
so that compressed air might be available when the rock surface was
broken through. The location adopted, and shown on Plate XIII, had the
further advantages that the rock surface was several feet above the
level of the top of the tunnels, and access to the river for receiving
and discharging materials could be had without crossing any street.
Similar reasons governed the location of the north shaft for the lines
from 33d Street. On the Long Island side of the river there were only
two feasible locations meeting these conditions, particularly in respect
to a safe thickness of rock above the tunnels, one near the pierhead
line, the other just outside the bulkhead line, and for many minor
reasons the latter was preferable. The center lines of each pair of
tunnels were 37 ft. apart, and each shaft, therefore, was made to cross
both lines of a pair, the same as on Manhattan side of the river. It was
not expected, however, that the Long Island shafts could be built
conveniently or the tunnels begun from them in normal air.

The decision to make the shafts of permanent construction was based not
only on the desirability of having access to and egress from the tunnels
near the banks of the river for convenience of the workmen or exit for
passengers in case of accident, but to facilitate ventilation; these
locations divide the entire lengths of tunnels east of the station into
three parts, two of which were approximately 4,000 ft. each, and the
other about 5,500 ft. The accident risk was believed to be very small,
while much weight was given to the feature of facilitating ventilation.
Further studies have enhanced the importance attached to ventilation,
and it is now intended to provide appliances for mechanical ventilation
at all shafts. The plans of the shafts are shown on Plates X and XI. The
caissons for the shafts are of structural steel, with double walls,
filled between with concrete, including a cross-wall between and
parallel to the tunnels. All these structures were fitted for sinking
with compressed air, if that should prove necessary.

Although borings had shown that rock would be found at all the shaft
sites several feet above the tunnel level, it could not be determined in
advance of excavation whether the caissons would have to be sunk to full
depth; if sound, unfissured rock were found, the sinking could be
stopped above the tunnel level; but, if not, the caissons, in any case,
would have to be sunk far enough to permit placing a water-tight floor
below the tunnels, and the tunnels themselves begun through openings in
the side-walls of the caisson; such openings, therefore, closed by
removable bulkheads, were provided in all caissons.

[Illustration: PLATE XII.--Typical Tunnel Sections]

As already stated, the grade of 1.5% from Fifth Avenue eastward was
fixed with reference to the lowest point of the river bed in order to
give the requisite cover over the tunnels at the deepest point of the
channel on the west side of the reef, where the river bottom was about
60 ft. below mean high tide for a short distance. On the other hand, as
the use of compressed air in building the tunnels was anticipated, an
excessive depth below the water surface was to be avoided as far as
possible; it was necessary, however, to continue the descending grade
some further distance until the tunnels were mostly in rock, so that
drainage sumps under the tunnels could be made readily. Eastward from
the sumps the tunnels had a rising grade of 0.7% to the established
bulkhead line on the Long Island side, giving a cover at the points
where the tunnels enter rock, a short distance westward, of about 10 ft.
(if the dredging plane should be fixed at some future time at 40 ft.
below mean low tide, as may be reasonably anticipated). Eastward from
the bulkhead line, Tunnels _A_, _B_, and _D_ have ascending grades of
about 1.25%, while Tunnel _C_ rises at the rate of 1.9% in order to
effect a crossing over Tunnel _B_ west of the portals. This feature was
introduced in order to place the two west-bound tracks together through
the Sunnyside Yard, and the heavier grade, being downward with the
traffic, was not objectionable.

The arrangement of grades and tracks in the approaches and in Sunnyside
Yard would require the introduction of too much detail to be taken up
here, but will be dealt with in the paper on the Sunnyside Yard.

It was recognized from the inception of the project that the tunnels
under the East River would be the most difficult and expensive section
of the East River Division. The borings had shown a great variety of
materials to be passed through, embracing quicksand, coarse sand,
gravel, boulders, and bed-rock, as well as some clayey materials. (See
Plate XIII.) The rock was usually covered by a few feet of sand, gravel,
and boulders intermixed, but, in some places, where the rock surface was
at some distance below the tunnel grade, the material met in tunneling
was all quicksand; the nearest parallels in work previously done were
some of the tunnels under the Thames, particularly the Blackwall tunnel,
where open gravel was passed through. Before the plans for the East
River tunnels were completed, work had been resumed, after many years'
interruption, in the old Hudson River tunnels between 15th Street,
Jersey City, and Morton Street, Manhattan, and sand materials were
passed through for a short distance. These experiences satisfied nearly
all the engineers in any way connected with the work that the shield
method was the most suitable for the East River tunnels, and the plans
for the work were based on its adoption. (See Plate XII for
cross-sections, etc.) Other methods, as stated by General Raymond in the
introductory paper, were advocated, particularly caisson constructions
and the freezing process, the latter being urged very strongly, and,
when proposals were invited, in October, 1903, bidders were informed
that alternative methods would be taken into consideration.

Bids were received and opened on December 15th, 1903. Only one bidder
proposed to carry out the work on the basis of unit prices, but the
prices were so low that the acceptance of the proposal was deemed
inadmissible; no bid based on caisson methods was received; several
offers were made to perform the work by the shield method, in accordance
with the plans, for a percentage of its cost, and one was submitted, on
a similar basis, covering the use of the freezing method. The firm of S.
Pearson and Son, Limited, of London, England, submitted a proposal for
building the tunnels by the shield method, on a modification of the
percentage basis, and as this firm had built the Blackwall tunnel within
the estimates of cost and was the only bidder having such an experience
and record in work in any way similar to the East River tunnels,
negotiations were continued between that firm and the railroad company.

The original plans and specifications contemplated that all tunnels
between the First Avenue shafts in Manhattan and East Avenue in Long
Island City would be shield-driven, and that work would proceed
simultaneously eastward from the First Avenue shafts and both eastward
and westward from the Long Island City shafts located west of Front
Street at the river, requiring twelve shields. When making their
proposal, S. Pearson and Son, Limited, suggested that shields might be
started from the east end of the work and arrive at the Front Street
shafts as soon as these shafts could be completed, and proposed sinking
a temporary shaft transversely across all four lines near the east end
of the work just west of East Avenue, from which, within a short time,
to drive toward Front Street by the use of shields. The railroad company
accepted the suggestion for the additional shaft, although the greater
part of the tunnels east of Front Street was built without shields.
After several months of negotiation, a contract was entered into on July
7th, 1904, with S. Pearson and Son, Incorporated, a corporation of the
State of New York organized by the English firm for the purpose of
entering into and carrying out this contract. The main features had been
agreed upon, and work had begun about two months before. The contract
embraced the permanent shafts in Manhattan and Long Island City, the
tunnels between these shafts, and their extension eastward in Long
Island City to East Avenue, including in all about 23,600 ft. of
single-track tunnels. The contract had novel features, and seemed to be
peculiarly suitable for the unknown risks and the unusual magnitude of
the work. A fixed amount was named as contractor's profit. If the actual
cost of the work when completed, including this sum named as
contractor's profit, should be less than a certain estimated amount
named in the contract, the contractor should have one-half of the
saving. If, on the other hand, the actual cost of the completed work,
including the fixed sum for contractor's profit, should exceed the
estimated cost named in the contract, the contractor should pay one-half
the excess and the railroad company the other half; the contractor's
liability was limited, however, to the amount named for profit plus
$1,000,000; or, in other words, his maximum money loss would be
$1,000,000. Any further excess of cost was to be borne wholly by the
railroad company. The management of the work, with some unimportant
restrictions, was placed with the contractor; the relations of the
engineer, as to plans, inspection, etc., were the same as in ordinary
work, and the interest of the contractor to reduce cost was the same in
kind as in ordinary work.

[Illustration: PLATE XIII.--Plan and Profile. East River Tunnels]

On account of the extent of the work embraced in this contract, and the
dangerous exposure to compressed air required in most of it, it was
divided into three residencies; two of these, including also the
cross-town tunnels, have been described; the third, with S. H. Woodard,
M. Am. Soc. C. E., as Resident Engineer, embraced all tunnels from the
easterly end of the work near East Avenue in Long Island City to the
meeting points under the river and also the permanent shafts in Long
Island City. A few months after the execution of the principal contract,
the work to be done was extended eastward 107.5 ft., across East Avenue.
The extensions of the tunnels were built without cast-iron linings and
with an interior cross-section of the same height as the tube tunnels,
but somewhat narrower. The work was also extended westward from the
First Avenue shafts to include the excavation of top headings in each
tunnel for a distance of 100 ft. and an enlargement to full size for 50
ft. The borings having shown that soft earth existed below the grade of
the tops of the tunnel under the passenger station building of the Long
Island Railroad on the east side of Front Street, and that earth of
varying character would be met in places beyond the station building
under the railroad tracks in the passenger yard and the street car
tracks in Borden Avenue, it had been decided, before proposals were
invited, to extend the metal lining eastward to East Avenue, at the east
end of the work embraced in the original contract, where the rising
tunnel grades approached the surface of the ground so closely that their
further extension would be in open cut. In places where the tunnels were
wholly in rock, the weight of the cast-iron tunnel lining was reduced
43%; where the surface of the rock was below the top of the tunnel, but
above the axis, the reduction of weight was somewhat less, about 25%;
notwithstanding these savings, the cost of the tunnels was probably
increased by the use of the cast-iron lining; on the other hand, when
passing through bad ground, a section of tunnel could be made absolutely
safe more quickly by erecting the lining as soon as a length of a few
feet of tunnel was ready; under a crowded passenger yard, this feature
had great value.

The execution of the work under this contract will be described fully by
the Resident Engineers.

The plant assembled by the contractors is believed to be the most
extensive ever placed on a single piece of work, and will be described
in detail by their Managing Engineer, Henry Japp, M. Am. Soc. C. E.

For convenience in receiving materials to be used in construction, and
to facilitate the disposal of excavated materials, one pier was leased
on the east side of the Hudson River, two on the west side of the East
River and three on the east side. Excavated materials from the station,
the cross-town tunnels, and the river tunnels, were placed on barges
furnished by Mr. Henry Steers under several contracts embracing also
the disposal of the materials. In the earlier part of the work, they
were used as fill in the freight terminal of the Pennsylvania Railroad
at Greenville on the west side of the Upper Bay; when the fill at this
place was completed, the materials were sent to the tunnel company's
yard on the Passaic, at Harrison, N. J., and a small part to the
embankment in the Meadows Division. On account of the occasional closing
of the Passaic by ice, this involved the possibility of, and to some
extent resulted in, interruptions to the work of excavation. The
contract for the cross-town tunnels carried an option in favor of the
company to require the contractor for those tunnels to dispose of
materials at a stated price, and in the latter part of 1907, when the
excavation in these tunnels was being pushed rapidly, the railroad
company, unwilling to incur the responsibility for delays during the
winter, availed itself of this option. The disposal of materials was an
important part of the work, and will be dealt with more fully by the
Resident Engineers.

[Illustration: PLATE XIV.--Map and Profile, Cross-Town Tunnels]

At the time the contract was made with S. Pearson and Son, Incorporated,
it had not been determined whether mechanical ventilation would be
provided for the tunnels, and therefore the contract with that firm did
not include the final concrete lining at the shafts, above the inverts
of the tunnels. After the adoption of plans for mechanical ventilation,
in the latter part of 1908, the plans for lining the shafts with
concrete, including flues for conducting air to the tunnels, and
stairways for ingress and egress, were completed, and the work was
placed under contract; it will be described in detail by F. M. Green,
Assoc. M. Am. Soc. C. E.

At the east end of the work under the Pearson contract, the rising grade
of the tunnels brought them so near the surface of the ground that their
extension eastward could be carried out more readily in open cut than by
tunneling. The locations of the portals could be varied somewhat, and
they were built on rock which was found in rather narrow ridges at
convenient places. Tunnels _B_ and _D_ have a common portal; Tunnels _A_
and _C_ have separate ones, the portal for Tunnel _C_ being located
about 800 ft, west of the others as a result of its crossing over Tunnel
_B_, as already explained. Eastward from the portals, the track system
expands, in order to provide connections with the tracks of the Long
Island Railroad to and from Long Island City, with the New York
Connecting Railroad and New England lines, and with the storage and
cleaning yard known as the Sunnyside Yard extending to the west side of
Woodside Avenue, 2-3/4 miles east of the East River. (Plate XV.) The
yard and approaches are designed to avoid grade crossings by opposing
trains. The various general features of the yard and tunnel approaches,
bridge crossings, and street closings, have been described in sufficient
detail by General Raymond in the introductory paper.

[Illustration: PLATE XV.--Plan and Profile of Lines _A_ and _B_, and
Sunnyside Yards]

For convenience in placing the work under contract, a line was drawn 10
ft. west of Thomson Avenue, dividing the work east of that embraced in
the Pearson contract into two parts. The work west of the line was
placed under the immediate direction of George C. Clarke, M. Am. Soc.
C. E., as Resident Engineer, with Naughton Company and Arthur McMullen,
Contractors; Mr. Louis H. Barker was Resident Engineer of the part east
of the dividing line, with the Degnon Realty and Terminal Improvement
Company as the principal contractors. The substructures of the several
bridges in or across the yard were included in these contracts, but the
superstructures were carried out by various bridge companies, and other
minor features were executed by other contractors. More complete
descriptions of the plans and of the execution of the work will be given
by the Resident Engineers.