Construction of the northern tube under the Hudson River in 1905
Led by Chief Engineer Charles M. Jacobs, the tunnel design team worked between 1902 and 1904. The first task was digging two shafts, one just east of 11th Ave in Manhattan and a larger one a few hundred yards west of the river. The Weehawken Shaft was completed in September 1904 as a concrete-walled rectangular pit, 56 by 116 ft at the bottom and 76 ft deep. The PRR awarded the North River contract to O'Rourke Engineering Construction Company, which began work upon completion of the two shafts. (At the time, "North River Tunnels" referred to the tunnels east of the Weehawken Shaft; in later years the term has come to include the Bergen Hill tunnels as well.) The tunnels were built with drilling and blasting techniques and tunnelling shields, digging west from Manhattan, east and west from Weehawken, and east from the Bergen portals. The two ends of the northern tube under the river met in September 1906; at that time it was the longest underwater tunnel in the world. In 1905 the John Shields Construction Company received the contract to bore through Bergen Hill, the lower Hudson Palisades; William Bradley took over in 1906 and the tunnels to the Hackensack Meadows were completed in April 1908.
Except for a curve west of the west end of Pier 72 that totals just under a degree, the two tracks are straight 37 feet (11 m) apart, from west of 11th Avenue to the Bergen Hill portals; the tunnels are so straight that one can theoretically look down the tunnel and see the other side.
Although the tunnel is powered by third rail, the third rail ends just west of the Bergen Hill portals.
Since 2003 the tunnels have been operating near capacity during peak hours. Trains ordinarily travel west (to New Jersey) through the north tube and east (to Manhattan) through the south. During the morning rush about 24 trains are scheduled through the south tube in the busiest hour, and the same through the north tube in the afternoon.
The Access to the Region's Core project to build a set of parallel tunnels began construction in June 2009 to supplement the North River Tunnels, but that project was canceled in October 2010 by New Jersey Governor Chris Christie due to budget constraints. On February 7, 2011, Amtrak announced that it would spend $50-million on preliminary engineering and design work for a new tunnel project called Gateway, estimated to cost $13.5-billion.
^Hewett, B.H.M. (1912). "The North River Division". History of the Engineering Construction and Equipment of the Pennsylvania Railroad Company's New York Terminal and Approaches. New York: Isaac H. Blanchard Co. pp. 35–53.