The
stairways of this station were directly over the open excavation for
the subway in the latter thoroughfare and were used by a large number
of people. The work was done in the same manner at each of the four
corners. Two narrow pits about 40 feet apart, were first sunk and
their bottoms covered with concrete at the elevation of the floor of
the subway. A trestle was built in each pit, and on these were placed
a pair of 3-foot plate girders, one on each side of the elevated
column, which was midway between the trestles. The column was then
riveted to the girders and was thus held independent of its original
foundations. Other pits were then sunk under the stairway and trestles
built in them to support it. When this work was completed it was
possible to carry out the remaining excavation without interfering
with the elevated railway traffic.
At 64th Street and Broadway, also, the whole elevated railway had to
be supported during construction. A temporary wooden bent was used to
carry the elevated structure. The elevated columns were removed until
the subway structure was completed at that point. (See photograph on
page 45.)
[Illustration: SMALL WATER MAINS BETWEEN STREET SURFACE AND SUBWAY
ROOF, SUBSTITUTED FOR ONE LARGE MAIN--125TH STREET AND LENOX AVE.]
[Illustration: SPECIAL CONSTRUCTION OF 6-1/2-FOOT SEWER, UNDER CHATHAM
SQUARE]
A feature of the construction which attracted considerable public
attention while it was in progress, was the underpinning of a part of
the Columbus Monument near the southwest entrance to Central Park.
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