The most rapid and economical handling of all excavated material to
scows was made possible by the Tunnel Company procuring from the New
York Central and Hudson River Railroad Company the pier at the foot of
32d Street, North River, known in the earlier stages of the work as Pier
No. 62, but subsequently changed to Pier No. 72, and thus referred to in
this paper. This pier was occupied by a freight-shed used by the New
York Central Railroad Company, under a long-term lease from the City,
and that Company had to make numerous changes in their tracks and
adjoining piers before No. 72 could be turned over; the contract for
the excavation, therefore, required the contractor to procure any piers
needed previous to and in addition to it. Under this clause of the
agreement, the contractor procured one-half of the pier at 35th Street,
North River, which was used for the disposal of all material excavated
previous to May 22d, 1905, on which date Pier No. 72 was first put in
service.
As the type of plant the contractor would elect to use could not be
determined, previous to the letting of the contract, a general plan for
Pier No. 72 and the trestle approach, suitable for either trains or
wagons, was attached to the contract, and the details were worked out
afterward. The method adopted was by train, and a two-track approach to
the pier was provided. Beginning on the east side of Ninth Avenue, at
the south line of 32d Street, at an elevation of 20 ft. below the
surface, crossing under Ninth Avenue and to the center line of 32d
Street, it rose on a 1.5% grade in open cut to the surface of 32d Street
at a point 500 ft. west of Tenth Avenue, from which point it rose above
the surface of the street on a timber trestle to Tenth Avenue, which was
crossed overhead. West of Tenth Avenue the line changed by a reverse
curve to the south sidewalk of 32d Street, and continued on a timber
trestle, practically level, to the New York Central Yard tracks near
Eleventh Avenue. These tracks and Eleventh Avenue were crossed overhead
on a through-truss, steel bridge, and a column-and-girder construction
on which the two tracks separated to a distance of 29 ft, between center
lines, so as to bring them directly over the posts of special timber
bents which spanned the two house tracks of the New York Central
south-bound freight shed, which the trestle here paralleled. This
position was held to a point 25 ft. west of the east house line of
Twelfth Avenue, where, by a system of cross-overs and turn-outs, access
was had from either track to six tracks on the pier. Four of these were
on upper decks, two on the north and two on the south edge of the pier,
at an elevation of 41 ft. above mean high tide, to carry earth and small
rock to chutes from which it was dumped into barges. The other two
tracks proceeded by a 5.3% grade down the center of the pier to the
lower deck where, at a distance of 540 ft. from the bulkhead, and beyond
the upper deck construction, they diverged into six, two on the north
and two on the south edge of the pier for standing tracks to serve
derricks, and two down the center for shifting purposes. A siding to the
north of the two running tracks just west of the bottom of the incline
served a bank of eight electric telphers. The arrangement of the pier is
shown by Fig. 4.
The trestle east of the steel structure at Eleventh Avenue had simple
four-post bents, as shown by Bent "_A_," on Fig. 5, all posts being
vertical, to save room at the street level; the outside posts and the
caps and sills were of 12 by 12-in. timber; the intermediate posts were
of 8 by 12-in. timber; and single or double decks of 3 by 8-in. bracing
were used, depending on the height of the bents. These bents were framed
on the ground in position and raised by hand. West of Tenth Avenue, the
sills of the bents rested on four 12 by 12-in. longitudinal timbers,
each spanning two bays and breaking joints, for convenience in
supporting the trestle while the tunnels were constructed in open cut
beneath. These bents were placed 12 ft. on centers, with one 8 by 16-in.
stringer under each rail, and one 6 by 16-in. jack-stringer supporting
the overhang of the floor on either side.
The bents along the New York Central freight shed had but two posts of
12 by 14-in. yellow pine varying from 26 ft, to 31 ft. 9 in. from center
to center; they had double caps of 12 by 14-in. yellow pine on edge, no
bottom sills or bracing, and the vibration and wind pressure were taken
care of by the top bracing and anchorage, as shown by Bent "_G_," on
Fig. 6.
[Illustration:
Fig. 4.
PLANT FOR DISPOSAL OF EXCAVATED MATERIALS PIER NO. 72 N.R.]
The method of erection was as follows: An excavation was made on the
line of each post, 4 ft. deep and from 4 to 5 ft. square, depending on
whether it was for a single or reinforced post; 6 in. of concrete was
placed in the bottom, and on this were laid, at right angles to the
center of the trench, three 8 by 12-in. timbers varying in length with
the excavation from 3 to 4 ft. To these timbers was drifted one 12 by
12-in. timber of the same length as those in the bottom row, but at
right angles to them. Elevations were then taken on top of the 12 by
12-in. timber, and the bent was framed complete and of correct height.
The framing was done south of the line of the trestle and west of the
freight-house. The framed bents were picked up by a small two-boom
traveler carrying two double-drum, electric, hoisting engines, and run
forward into position. A hole had previously been made in the metal
gutter and canopy of the freight-house, by an experienced roofer, and
in the freight platform underneath, and, as soon as the bent had been
dropped into position, it was firmly drifted to the foot-blocks,
previously described, and the excavation made for them was filled with
concrete well rammed about the blocks and rounded off 6 in. above the
surface of the ground. Secure flashings, in two sections, were then made
about the posts to cover the holes made in the gutter and roof, the
bottom sections being firmly soldered to the roof or gutter, and the top
sections, which lapped over the bottom and cleared them 2 in. in all
directions, were firmly nailed to the posts and the joints leaded. This
arrangement allowed the bents to move slightly, and at the same time
made the roof and gutter water-tight. These bents were placed 16 ft. on
centers to correspond with the spacing of the doors of the freight shed.
Under the cross-overs near Eleventh Avenue, where the tracks had to
be supported in different positions on the caps, and could no longer
be kept over the posts, the caps were trussed and the posts were
reinforced, as shown on Bents "_J_," "_H_," and "_K_," Fig. 5.
[Illustration:
Fig. 5.
DETAIL OF BENTS FOR MATERIAL TRESTLE]
The trusses for the through bridge over the tracks were erected on
Sunday, April 16th. The two trusses, one 122 ft. and the other 165 ft. 8
in. from center to center of end posts, had been assembled and riveted,
lying flat on cribwork a few feet above the ground, south of the
permanent position and between the New York Central tracks and Eleventh
Avenue. On the date stated, the contractor, having been given permission
to block the Central's tracks from 5 a.m. to 9 p.m., erected a large
steel gin pole just south of the correct position of the center of the
north truss, which was then dragged, from the place where it had been
assembled, across the railroad tracks until the center of the bottom
chord was vertically under its true position, the truss still lying flat
and about at right angles to the center line of the bridge. Chains were
made fast to the top chord at the middle panel of the truss, which was
then turned up to a vertical plane, raised to its permanent position,
and guyed. The gin pole was then shifted and the operation repeated with
the longer truss, after which, half of the floor beams and a part of the
top laterals were bolted in position and the guys were removed, the
bridge being thus erected without the use of falsework of any kind.
During the lifting there was no sag in either truss that could be
noticed by the eye. Fig. 1, Plate LV, shows the bridge erected, with
the exception of the tight timber fence.
Pier No. 72 is directly over the North River Tunnels. When it was turned
over by the New York Central Railroad Company, the contractor for the
construction of those tunnels tore down the shed and removed the deck
and such piles as were in the path of the tubes. This left standing the
four northernmost, the four southernmost and two centers rows of piles
for the entire length of the pier. An additional row of piles was then
driven on either side of the two center rows, and battered so that at
the elevation of the tunnels they would be close to the center rows
and leave as much clear space as possible. The pier, therefore, was
constructed of three independent lines of four-post bents, which,
however, rested on sills which were continuous throughout the width of
the pier, as shown by Figs. 2 and 3, Plate LV.
[Illustration:
Fig. 6.
DETAIL OF BENTS FOR MATERIAL TRESTLE.]
The bents for the upper floors of the pier were double-decked, with
12 by 12-in. posts, sills, intermediate and top caps, and 3 by 8-in.
longitudinal and cross-bracing. The bents for the incline were similar,
except that those below 16 ft. in height were of single-deck
construction. The spacing of the bents varied from 9 ft. 6 in. to 12
ft., except the three outer bays, which had a span of 23 ft., all to
agree with the position of the pile bents. The double-deck construction
extended for the full length of the original pier. A single-deck
extension, of full width and 180 ft. in length, was subsequently built
for the accommodation of four derricks for handling building material
and large rock. The piles for this extension were driven in three sets
of four rows each, similar to those in the old portion of the pier,
except that the bents were driven with a uniform spacing of 15 ft.
between centers. The three sets of bents were topped separately with
12 by 12-in. caps and 12 by 12-in. dock stringers; they were braced with
both cross and longitudinal low-water bracing, and were tied together by
a continuous 12 by 12-in. timber over the dock stringers and 12 by
12-in. packing pieces from stringer to stringer, each of these ties
being supported in the center of the span over the tunnels by two 2-in.
hog rods, Section "_A-A_," Fig. 4.
The south side of the upper deck of the pier carried three sets of nine
hoppers, each set covering 90 ft., a little less than the full length
between bulkheads of the largest deck scows, with 70 ft. clear between
sets, to allow for the length of a scow outside of the bulkhead and to
permit the free movement of boats. Each hopper occupied the full space
between two bents, and, as the caps were topped by strips of timber of
triangular section, with a width of 12 in. on the base and a height of
6 in., protected by a 6 by 6-in. steel angle, each set of hoppers
presented 90 lin. ft. of continuous dumping room. The bottoms of the
hoppers, set at an angle of 45°, were formed by 12 by 12-in. timbers
laid longitudinally, running continuously throughout each set, and
covered by 3-in. planking. The partitions were formed with 4-in. planks
securely spiked to uprights from the floor of the hoppers to the caps;
these partitions narrowed toward the front and bottom so as to fit
inside the chutes. Each hopper was lined on the bottom and sides with
½-in. steel plates, and the bottoms were subsequently armored with 2 by
1-in. square bars laid 3 in. on centers and bolted through the 12 by
12-in. flooring of the hoppers. The chutes, extending from the bottom of
the hoppers, were 20 ft. long and 7 ft. wide, in the clear; they were
formed entirely of steel plates, channels, and angles, and were
supported from the upper deck of the pier by chains; their lower ends
were 17 ft. above mean high tide and 14 ft. 6 in. from the string piece
of the pier. The hoppers and chutes are shown by Fig. 1, Plate LVI.
[Illustration:
Plate LV.
Material Trestle Over N.Y.C. & H.R.R.R. Co.'s Tracks;
and Construction of Pier No. 72, North River
Fig. 1.--Material Trestle Over N.Y.C. & H.R.R.R. Co.'s Tracks.
Fig. 2.--Material Trestle Under Construction on Pier No. 72,
North River, Showing Clear Water Over Tunnel Location.
Fig. 3.--Pier No. 72, North River, Showing Incline as Reconstructed
For Locomotives.]
A length of 150 ft. of the north side of the pier was for the use of the
contractor for the North River tunnels; it was equipped with a set of
nine chutes similar to those for the south side; they were used but
little, and were finally removed to make room for a cableway for
unloading sand and crushed stone.
At the foot of the incline there was a bank of eight telphers running
on rails securely bolted to the tops of 20-in. I-beams, which were hung
from stringers resting on the upper caps. The beams were erected in
pairs, each pair being securely braced together and to the trestle posts
to prevent swaying. Each telpher occupied the space between two bents,
about 10 ft., so that the entire bank commanded a length of 80 ft.,
which was approximately the length of a rock scow between bulkheads. All
supports for the telphers were provided as a part of the trestle, but
the machines themselves were a part of the contractor's plant.
Four derricks were erected on the extension, two on the north and two on
the south edge of the pier, supported on bents at a sufficient elevation
above the floor to clear a locomotive.
After most of the earth had been excavated, the out-bound set of hoppers
on the south side of the pier was removed, and two derricks were erected
in their place and used for unloading sand, crushed stone, and other
building material.