|
in cubic yards | 263,000 | 238,995 | 517,000
Cast metal used in tunnel, including | | |
cast iron and cast steel, in tons | | 64,265 |
Steel bolts used, in tons | | 2,606 |
Cement used (concrete and grout), | | |
in barrels | 95,000 | 145,500 | 33,000
Concrete, in cubic yards | 95,000 | 75,400 | 18,500
Dynamite for blasting, in pounds | 600,000 | 100,400 | 206,000
Brickwork, in cubic yards | | 4,980 |
Structural steel (including Pier 72), | | |
in pounds | 50,000 | 3,141,000 | 1,475,000
------------------------------------------+---------+-----------+----------

The number of passengers carried on the Elevated Railroad and surface
lines of Ninth Avenue during the underpinning of these structures was
about 125,000,000.

The Board of Engineers, organized by the Pennsylvania Railroad Company
in January, 1902, immediately took up the matter of route and grade. The
center line, which had been assumed as the center line of 32d Street
extended westward, was slightly changed.

The grade adopted was approximately 2% descending westward from Ninth
Avenue, which would place the tunnel well below the Government dredging
plane of 40 ft. below mean low water at the pier head line; thence
westward on a lighter grade still descending until the deepest portion
of the river was reached where the top of the rail would be about 90 ft.
below mean high water, this location giving sufficient cover over the
tunnels to insure stability and guard against the possibility of
shipwrecks settling on the tunnels. From this point to the portal an
ascending grade of 1.30% was adopted, which gave the lines sufficient
elevation to cross over the tracks of the New York, Susquehanna and
Western and the Erie Railroads, which run along the westerly base of the
Palisades. Owing to the exigencies of construction, these grades in the
river were very slightly modified. Plate VII is a plan and profile of
the tunnels as constructed.

[Illustration: Plate VII.--Plan, Profile, and Triangulation, North River
Tunnels]

The Board of Engineers early in 1902 took up the question of supports
for the tunnels under the North River, and various plans and schemes
were considered.