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One of the most important engineering problems
encountered in the building of the New York
rapid transit subway was the construction of the
two tunnels, or tubes, under the Harlem river.
These two tubes, through wliich the subway trains
are to run regularly from the Lenox avenue subway,
continuing to the Bronx subway, were constructed
on an entirely new engineering principle,
having been built of concrete above ground, and
then sunk to the bottom of the river, instead of
having been forced through the mud under the
river bottom, as had been done in such work heretofore.
These twin tubes are 641 feet in length
and are 16 feet in diameter, the top of the tunnel
being 20 feet below the low water mark. Before
the tubes were put in Jilace, the engineering department
of the "subway contractors devised a sys-
tern for the drainage of the seepage, or the water
percolating through the walls of the tubes, and
also in case of emergency arising from the sudden
inrush of water in the event of the breaking of
a water main. The drainage and pumping system
adopted, and me precautions taken to meet
the possible conditions, are graphically described
and explained in the accompanying illustrations.
Illustration Fig. I shows a sectional view of the
tunnel, looking southwest, and showing the arrangement
of the pumps which are in position in
both of the tubes at the function of the subway
and mouth of the tunnel at Harlem river. Special
pumps were adopted for this service, having been
especially designed and built at the A. S. Cameron
steam pump works, New York. A longitudinal
THE COAL TRADE BULLETIN. 47
arrangement of the piping and connections for the
pumps is shown on the right hand side of this
illustration.
Figs. II and III are reproductions of photographic
views taken in the tubes, and show the
inside construction of the tunnel with the pumps
in position. In the first of these two views a
portion of the end of the concrete archway is
shown, and it is at this point where the two tubes
are joined, and the double tracks continue in one
tunnel.
Fig. II shows two of the pumps in position on
concrete foundations, with the arrangement of
piping and connections. Four of these pumps
were installed, being of the size 12x12x18, and are
of the simplex single-cylinaer pattern, having the
Cameron regular pattern steam enu, which is
Fig. 1. Sectional View of Tunnel.