AMERICAN SOCIETY OF CIVIL ENGINEERS

INSTITUTED 1852

TRANSACTIONS

Paper No. 1154

THE NEW YORK TUNNEL EXTENSION OF THE PENNSYLVANIA RAILROAD.
THE BERGEN HILL TUNNELS.1

By F. Lavis, M. Am. Soc. C. E.

Location.—That section of the Pennsylvania Railroad’s New York Tunnels lying west of the Hudson River is designated Section “K,” and the tunnels are generally spoken of as the Bergen Hill Tunnels. Bergen Hill is a trap dike (diabase) forming the lower extension of the Hudson River Palisades.

There are two parallel single-track tunnels, cross-sections of which are shown on Plate VIII of the paper by Charles M. Jacobs, M. Am. Soc. C. E. The center line is a tangent, and nearly on the line of 32d Street, New York City, produced, its course being N. 50° 30' W. The elevation of the top of the rail at the Weehawken Shaft (a view of which is shown by Fig. 2, Plate XXII), on the west bank of the Hudson River, is about 64 ft. below mean high water; and at the Western Portal, or Hackensack end, the rail is about 17 ft. above; the grade throughout is 1.3%, ascending from east to west. The length of each tunnel between the portals is 5,920 ft.

A general plan and profile of these tunnels is shown on Plate I of the paper by Charles W. Raymond, M. Am. Soc. C. E. At

Central Avenue a shaft 212 ft. deep was sunk. It is 3,620 ft. from the Weehawken Shaft.

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History.—The contract for this work was let on March 6th, 1905, to the John Shields Construction Company; it was abandoned by the Receiver for that company on January 20th, 1906, and on March 20th, of that year, was re-let to William Bradley, who completed the work by December 31st, 1908.

The progress of excavation and lining in the North Tunnel is shown graphically on the progress diagram, Fig. 9, that of the South Tunnel being practically the same.

Geology.—Starting west from the Weehawken Shaft, the tunnels pass through a wide fault for a distance of nearly 400 ft., this fault being a continuation of that which forms the valley between the detached mass of trap and sandstone known as King’s Bluff, which lies north of the tunnels, and the main trap ridge of Bergen Hill.

The broken ground of the fault, which consists of decomposed sandstone, shale, feldspar, calcite, etc., interspersed with masses of harder sandstone and baked shale, gradually merges into a compact granular sandstone, which, at a distance of 460 ft. from the shaft, was self-supporting, and did not require timbering, which, of course, had been necessary up to this point.

A full face of sandstone continued to Station 274 + 60, 940 ft. from the shaft, where the main overlying body of trap appeared in the heading. The full face of the tunnel was wholly in trap at about Station 275 + 30, and continued in this through to the Western Portal, where the top of the trap was slightly below the roof of the tunnel, with hardpan above. The contact between the sandstone and the overlying trap was very clearly defined, the angle of dip being approximately 17° 40' toward the northwest.

The sandstone and trap are of the Triassic Period, and the trap of this vicinity is more particularly classified as diabase.

The character of the trap rock varied considerably. At the contact, at Station 275, and for a distance of approximately 200 ft. west, corresponding to a thickness of about 60 ft. measured at right