It is not intended to give much length to the description of the Shafts
or the Land Tunnels, as more interest will probably center in the River
Tunnels.
The shafts did not form part of the regular tunnel contract, but were
built under contract by the United Engineering and Contracting Company
while the contract plans for the tunnel were being prepared. In this
way, when the tunnel contracts were let, the contractor found the shafts
ready, and he could get at his work at once.
Two shafts were provided, one on the New York side and one on the New
Jersey side. Their exact situation is shown on Plate XXVIII. They were
placed as near as possible to the point at which the disappearance of
the rock from the tunnels made it necessary to start the shield-driven
portion of the work.
The details of the shafts will now be described briefly.
_The Manhattan Shaft._--The Manhattan Shaft is located about 100 ft.
north of the tunnel center; there was nothing noticeable about its
construction. General figures relating to both shafts are given in Table
1.
_The Weehawken Shaft._--The Weehawken Shaft is shown in Fig. 1. This, as
will be seen from Table 1, was a comparatively large piece of work. The
shaft is over the tunnels, and includes both of them. In the original
design the wall of the shaft was intended to follow in plan the property
line shown in Fig. 2, and merely to extend down to the surface of the
rock, which, as disclosed by the preliminary borings, was here about 15
ft. below the surface. However, as the excavation proceeded, it was
found that this plan would not do, as the depth to the rock surface
varied greatly, and was often much lower than expected; the rock itself,
moreover, was very treacherous, the cause being that the line of
junction between the triassic sandstone, which is here the country rock,
and the intrusive trap of the Bergen Hill ridge, occurs about one-third
of the length of the shaft from its western end, causing more or less
disintegration of both kinds of rock. Therefore it was decided to line
the shaft with concrete throughout its entire depth, the shape being
changed to a rectangular plan, as shown in the drawings. At the same
time that the shaft was excavated, a length of 40 ft. of tunnels at each
end of it was taken out, also on account of the treacherous nature of
the ground, thus avoiding risk of injury to the shaft when the tunnel
contractors commenced work. There was much trouble with floods during
the fall of 1903, and numerous heavy falls of ground occurred, in spite
of extreme care and much heavy timbering. The greatest care was also
taken in placing the concrete lining, and the framing to support the
forms was carefully designed and of heavy construction; the forms were
of first-class workmanship, and great care was taken to keep them true
to line. A smooth surface was given to the concrete by placing a 3-in.
layer of mortar at the front of the walls and tamping this dry facing
mixture well down with the rest of the concrete. The east and west walls
act as retaining walls, while those on the north and south are facing
walls, and are tied to the rock with steel rods embedded and grouted
into the rock and into the concrete. Ample drainage for water at the
back of the wall was provided by upright, open-joint, vitrified drains
at frequent intervals, with dry-laid stone drains leading to them from
all wet spots in the ground. A general view of the finished work is
shown in Fig. 1, Plate XXIX, and Table 1 gives the most important dates
and figures relating to this shaft.
TABLE 1.--PARTICULARS OF SHAFTS ON THE NORTH RIVER TUNNELS OF THE
PENNSYLVANIA RAILROAD TUNNELS INTO NEW YORK CITY.
+===========+=====+======+======+==========+========+===========+========+
|Location. |Depth| Width|Length|Excavation|Concrete| Date| Date|
| | in| in| in|(including|in cubic|commenced.|finished.|
| |feet.| feet.| feet.| drifts),| yards.| | |
| | | | | in cubic| | | |
| | | | | yards. | | | |
+-----------+-----+------+------+----------+--------+----------+---------+
|Manhattan: | 55| 22| 32| 2,010| 209|June 10th,| December|
|11th Avenue| | | | | | 1903.| 11th,|
|and 32d | | | | | | | 1903.|
|Street. | | | | | | | |
| | | | | | | | |
|Weehawken: | 76| At| At| 55,315| 9,810|June 11th,|September|
|Baldwin | |bottom|bottom| | | 1903.|1st, |
|Avenue. | |56, at|115.75| | | |1904. |
| | | top|at top| | | | |
| | | 100.| 154.| | | | |
|===========+=====+======+======+==========+========+==========+=========+
+==========+====================+=============+============+===========+
|Location. |Ground met: |Lined with: | Cost to | Cost per |
| | | | Railroad |cubic foot.|
| | | | Company. | |
+----------+--------------------+-------------+------------+-----------+
|Manhattan:|Top 13 ft. filled; |Concrete | $12,943.75 | $0.335 |
|11th |red mica schist and |reinforced | | |
|Avenue and|granite. |with steel | | |
|32d | |beams down to| | |
|Street. | |rock. | | |
| | | | | |
|Weehawken:|Top 6 ft. filled, 30|Concrete with| 166,162,98 | 0.337 |
|Baldwin |ft. sand and |steel | | |
|Avenue. |hardpan, decomposed |tie-rods in | | |
| |rock (trap and |rock. | | |
| |sandstone) below. | | | |
+==========+====================+=============+============+===========+
[Illustration: FINAL DESIGN OF WEEHAWKEN SHAFT PLAN LONGITUDINAL SECTION
TRANSVERSE SECTION FIG. 1.]
After the tunnel work was finished, both shafts were provided with
stairs leading to the surface, a protective head-house was placed over
the New York Shaft, and a reinforced concrete fence, 8 ft. high, was
built around the Weehawken Shaft on the Company's property line, that
is, following the outline of the shaft as originally designed.