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Hudson River Tunnel
Fifteenth Street in Jersey City to Morton Street in Manhattan, New York City, New York, USA
associated engineer
DeWitt Clinton Haskin
William H. Paine
Sir Benjamin Baker
Ernest William Moir
Charles Mattathias Jacobs
date  17th November 1874 - 25th February 1908, opened 1908
UK era  Modern  |  category  Tunnel  |  reference  HE077908
The Hudson River Tunnel was the first large-scale tunnelling project under a major American river. Intended to be the first trans-river rail link between Jersey City and Manhattan, the tunnel took more than 30 years to complete. Now part of a network of subaqueous river transport, the Hudson River Tunnel still in use as part of the Uptown Hudson Tubes.
The Hudson River divides New Jersey from New York state. It is tidal to Troy, some 240km from its mouth at Gravesend Bay, south of New York City. The closest fixed crossing was the Poughkeepsie rail bridge, opened in 1889, 120km upstream. All trade across the river at New York City had to be made by boat. Fleets of large steam-powered ferries, mostly operated by west-bank railway companies, transported vehicles, goods and passengers.
Clearly, a permanent crossing at New York City was needed but the difficulties of bridging a wide watercourse with a deep silty/sandy bed seemed to be beyond engineering expertise of the times. A tunnel was considered the best option. The route would run east from Hoboken in Jersey City to Greenwich Village in south-west Manhattan.
Colonel DeWitt Clinton Haskin (c.1824-1900), a former Union Army officer who had worked on the Union Pacific Railroad in California, realised the need for a tunnel. In the early 1870s, he undertook preliminary surveys and soundings at his own expense to investigate the alignment and feasibility of such a scheme. As a result, the Hudson Tunnel Railroad Company was incorporated on 26th May 1873, with $10m of funding ó apparently from an Englishman named Trevor Park (not Trevor William Park, who was associated with the Emma Silver Mine). The consulting engineer was another Union Army colonel, William H. Paine (1828-89).
Haskin, acting as chief project engineer, opposed the recommendations of other engineers and insisted that excavating the tunnel in a compressed air environment ó without using a tunnelling shield or some protection against collapse ó would be sufficient to uphold the tunnel walls long enough to install a structural brick lining.
Working under compressed air to repel water while sinking vertical shafts was not a new technique, though. On 20th October 1830, Admiral Lord Thomas Cochrane (1775-1860), a Royal Navy officer, had been granted a patent for Invented apparatus to facilitate excavating, sinking, and mining, or a pressurised airtight chamber.
However, using compressed air for supporting the excavation of a horizontal tunnel was another matter, and was first used in such a way here. In 1873, Haskin applied to patent his Improvement in the art of tunneling (patent No. 147,055, granted 3rd February 1874). He stated that the "distinguishing feature of my system, however, is, that instead of using temporary facings of timber or other rigid material, I rely upon the air pressure to resist the caving-in of the wall or the infiltration of water until the masonry wall is completed. This pressure is, of course, to be regulated by the exigencies of the occasion and may be varied from anything above that of the atmosphere to fifty pounds to the square inch [345kN per square metre], which is about as much as the human system will bear with safety".
He explained that to prevent water ingress from random springs, or air leaking out of the tunnel through fissures, he supplied "a temporary shield of canvas, leather, or other light flexible integument to the wall, against which the pressure instantly forces it and seals the leak". Furthermore, after completing the tunnel lining, he would allow working debris to accumulate in the bottom of the bore until "the tunnel is completed, leaving an opening only large enough for working purposes. By this means the area of the airlock, the surface exposed to pressure, and the consequent liability to leaks are materially diminished".
On 17th November 1874, Haskin began the west end of the Hudson tunnel by sinking a 9.1m diameter shaft 30m from the river bank near 15th Street, Jersey City. Less than one month after work began, on 15th December, the shaft was stopped halfway down its 20m depth. An injunction was brought concerning the tunnelís potential competition with the ferries operated by the Delaware, Lackawanna & Western Railroad Company, which were seeking financial compensation.
The case wasn't resolved until 22nd September 1879. Work restarted soon afterwards. The Jersey City shaft was completed, with an enlarged chamber in the base from which parallel tunnel headings were to be driven under the river.
When Haskinís tunnelling technique was followed precisely ó using high enough air pressure, with leaks being detected and stopped quickly ó it worked. Tunnel workers, often called "sandhogs", dug out the soil by hand, working in pressures of up to 240kN per sq m. The tunnelís ceiling was then lined with 6mm thick iron plate and the remainder with 760mm of brickwork, giving a finished bore of 5.5m.
In mid 1880, for added safety, a "pilot-tunnel" (invented by Swedish engineer John Fracis Anderson [1848-1927]) was employed. This device (patent No. 241,272, granted 10th May 1881) consisted of a 1.8m diameter iron tube which was driven along the centre of the bore in advance of the main tunnel. It allowed any changes in the subsoil to be identified in advance of full excavation.
However, on 21st July 1880, a blow-out caused 20 deaths. A leak in the top of the north tunnel had allowed compressed air to escape into the 9m of silt above it, and water flooded the excavation. Because the tunnel could not be pumped dry, and a cofferdam had not worked, a rectangular caisson was sunk in October that year, which created a watertight chamber for the carrying out of repairs.
Tunnel construction resumed in January 1881, and at around the same time General William Sooy Smith (1830-1916) became the projectís chief engineer. For workforce safety in case of another blow-out, an airlocked bulkhead was installed near the tunnel heading. The tunnelís lining was changed from brick to concrete, and a pressurised discharge pipe carried away excavation arisings as slurry.
In July 1881, work on another vertical shaft began on the New York side of the river, at the west end of Morton Street. The shafts are some 1.7km apart, and with the approaches (1.2km in New Jersey, 1.4km in New York) the total length of the twin tunnels was planned at 4.3km. Between tunnel crown and the river bed above was to be at least 3.7m
Further tunnel blow-outs occurred on 20th and 30th August 1882, though fortunately nobody was killed on either occasion. Sources hint that there were probably other unreported non-fatal occurrences.
In 1882, Park died and finances dwindled. Operations were suspended on 4th November 1882. Over $1m had been spent, and 493m of the north tunnel and 171m of the south tunnel were complete.
Pumping stopped and the tunnels filled with water. On 20th March 1883, the pumps and compressors were restarted, and work began again on 22nd March. By 20th July, a further 22m of the north tunnel and 7m of the south tunnel had been constructed but work halted once more owing to lack of money. Haskin continued trying, unsuccessfully, to find funding until 1887 and eventually left the project in 1888.
Late in 1887, technical expertise was sought from British consulting engineers Sir John Fowler (1817-98) and Sir Benjamin Baker (1840-1907). They were asked whether it was possible to complete the tunnels for the $2.1m that had been estimated by American contractors. Baker visited the site, reporting in 1888, and their combined support for the project facilitated $1.5m of British investment.
In 1889, construction resumed with a contract let to British contractor S. Pearson & Son Ltd, founded in 1844. This time, the excavation was carried out from the safety of tunnelling shields ó a technique pioneered by Sir Mark Isambard Brunel (1769-1849) on the 1843 Thames Tunnel in London, and later developed by James Henry Greathead (1844-96).
Greatheadís former assistant, engineer Ernest William Moir (1862-1933), designed an 80 ton steel tunnelling shield for each tunnel at Baker's directions. Erection of the shields began in 1890. Moir was originally resident engineer for the project but, for various political reasons, transferred to the position of contractorís agent in January 1890.
Each shield consisted of a cylinder, 3.2m long and of 6.1m external diameter, formed from two concentric shells 430mm apart. The shield had an inclined cutting edge around its face, which was divided into nine compartments by vertical and horizontal bulkheads. The apparatus was jacked forward hydraulically from the existing tunnel lining by 16 jacks located between the cylindrical shells, pushing the subsoil through openings in the compartments. A ring of bolted cast iron lining plates 32mm thick was then installed behind the shield and the process repeated. The spoil was loaded manually onto wagons for removal.
The tunnel headings were accessed through a series of airlocks, through which all supplies and excavation arisings had to pass. The lock nearest the workings was an iron boiler shell, 1.8m in diameter and 4.6m long with a 900mm by 1.2m door at each end.
The tunnellers were working eight-hour shifts in air pressures of 240-275kN per sq m. They suffered severely from caisson disease ('the bends' or decompression sickness). From May 1890, Moir pioneered the use of an airlock chamber for treating the illness, returning suffers to a pressurised environment and reducing the pressure gradually. It proved successful in curing paralysis and other symptoms including those of the contractorís senior partner Weetman Dickinson Pearson (1856-1927).
The lack of fatalities was in stark contrast to the safety record under the earlier administration. According to Moir, the bends had killed 25% of Haskinís tunnellers a year. Paul Bert (1833-86), working in the 1870s in Paris, had identified nitrogen as the main culprit but this wasn't known to American engineers until the 1890s.
However, in July 1891, financial difficulties in the wake of the Barings bank crisis caused the British tunnelling effort to be suspended. At the time, the total length of tunnels was 1.24km for the north tube and 178m for the south. Work was abandoned in 1892.
In 1895, English engineer Charles Mattathias Jacobs (1850-1919) was invited to assess the practicality and cost of completing the tunnels, which by then were waterlogged to within 1.2m of the top of the Jersey City shaft. His feasibility report was well received, though no action was taken until the turn of the century. Jacobs had worked in America since 1889, becoming known for his tunnelling expertise. In 1891, he had established a consultancy in New York with Welsh engineer John Vipond Davies (1862-1939).
In October 1901, Jacobs visited the abandoned tunnels with lawyer and future politician William Gibbs McAdoo (1863-1941). McAdoo understood the projectís potential, and set up a package of funding. On 6th February 1902, the New York & Jersey Railroad Company was incorporated, with McAdoo as its president and Jacobs as chief engineer.
The earlier scheme had been intended for steam trains but this was now rejected in favour of an electrified line, partly because of air quality issues. The project scope was increased to extend the tunnels to a terminus on Christopher Street in Manhattan, adjoining the Ninth Avenue El (elevated railway, closed 1940) station. The New Jersey approach would be extended to a surface station, enabling electric tramcars to cross the river to an underground tramway station at Christopher Street. Apart from a short length of cut-and-cover tunnel in Manhattan built under contract, the whole project would be constructed by a direct labour force supervised by Jacobs.
Work commenced in February 1902. Moirís 1890s tunnelling shield was refurbished in order to complete the bore eastwards, and a new shield of similar design was made for the westward drive. A 213m rock outcrop had to be removed by drilling and blasting, adding 11 months to the programme. On 11th March 1904, the two parts of the north tunnel were holed through ó McAdoo and Jacobs were the first people to walk through it from New Jersey to New York.
Jacobs managed to triple the driving rate by increasing the number and capacity of the hydraulic jacks that moved the shields. The extra power also enabled the shields to be driven through the silt with their compartment doors closed, forcing the material into the surrounding subsoil and minimising arisings.
The south tunnel was holed through in September 1905. The tunnels have a finished internal diameter of 4.65m, and each tube is 1.72km long at a maximum depth of 29.6m below the river.
On 1st December 1906, the New York & Jersey Railroad Company became the Hudson & Manhattan Railroad Company. In 1907, the first trains ran through the Hudson River Tunnel, with one-way traffic in each bore.
On 25th February 1908, President Theodore Roosevelt (1858-1919) officially started the systemís electricity supply by depressing a button in the White House. The inaugural train was filled with dignitaries including New Jersey Governor John Franklin Fort (1852-1920), New York Governor Charles Evans Hughes (1862-1948), engineer George Westinghouse (1846-1914), financier August Belmont (1853-1924) and Cornelius Vanderbilt III (1873-1942). It took 10 and a half minutes to complete the east to west journey from Manhattan to Hoboken. The Hudson & Manhattan Railroad began its public service at midnight, and almost 100,000 passengers travelled on the first day.
Meanwhile, a 1903 study of ferry traffic had indicated that a single pair of tunnels was not sufficient for the numbers of people commuting across the river, and that ferries south of the tunnels were used more heavily. To meet the need, in September 1905, McAdoo presided over the start of construction for a second pair of tunnels about 2km downstream ó the Downtown Tunnels.
The western terminus of the Downtown Tunnels is at Exchange Place in Jersey City. The Manhattan terminus was on land later used to build the twin towers of the World Trade Center (opened 1973), though the station has now been moved north of Ground Zero (as the site of the former twin towers is now called). The Downtown Tubes are 1.82km long at a maximum depth of 28m below the river. Passenger services commenced on 19th July 1909.
The four Hudson & Manhattan Railroad tunnels operated profitably and successfully ó in January 1910, more than 4 million people were carried through them. On 10th November 1910, the original uptown tunnels were extended northwards to a new terminus on 33rd Street. On 26th November 1911, they were completed westwards to Newark, New Jersey.
However, in the 1920s and 1930s road traffic was increasing and the Holland Tunnel (completed 1927) and the Lincoln Tunnel (1937) proved popular. The 1930s economic depression led to a lack of maintenance had caused the condition of the railways to deteriorate, impacting further on rail tunnel use.
The Hudson & Manhattan Railroad Company descended into bankruptcy in the 1950s and, in 1962, relinquished operation of both sets of tubes to the Port Authority of New York & New Jersey. The organisation improved the system and installed new rolling stock, operating the tunnels through a subsidiary, the Port Authority Trans-Hudson Corporation (PATH), which remains in operation. PATH now carries in excess of 240,000 passengers a day.
In April 1978, the American Society of Civil Engineers voted to designate the Hudson River Tunnelís uptown and downtown tubes a National Historic Civil Engineering Landmark. On 31st October 1978, bronze plaques were unveiled at PATH stations at the Hoboken terminal and the World Trade Center. The ceremony was attended by members of McAdooís family including his grandson, lawyer Brice McAdoo Clagett (1933-2008).
Chief engineer (1879-80): Spielmann & Brush
Chief engineer (1880-1): E.H. Burlingame
Chief engineer (1881-2): General William Sooy Smith
Chief engineer (1882-7): S.H. Finch
Chief engineer (1889-91): William Rich Hutton
Chief engineer (1902 onwards): Charles Mattathias Jacobs
Assistant engineer (1874-80): E.H. Burlingame
Assistant engineer (1880-2): S.H. Finch
Assistant engineer (1882-7): C.W. Raymond
Contractor's agent (1890-1): Ernest William Moir
Contractor (1889-91): S. Pearson & Son Ltd
Tunnelling shields: Sir William Arrol & Co (Glasgow)
Machinist (1874-87): C.W. Clift
Research: ECPK
"Engineers of Dreams: Great Bridge Builders and the Spanning of America" by Henry Petroski, Random House, December 2010
"Crossing the Hudson: Historic Bridges and Tunnels of the River" by Donald E. Wolf, Rutgers University Press, 2010
"Rails Under the Mighty Hudson: the Story of the Hudson Tubes, the Pennsy Tunnels, and Manhattan Transfer" by Brian J. Cudahy, Fordham University Press, 2002
"The Bends: Compressed Air in the History of Science, Diving, and Engineering" by John L. Phillips, Yale University Press, 1998
"The Hudson River Tunnels of the Hudson and Manhattan Railroad Company" by Charles Mattathias Jacobs, in Minutes of ICE Proceedings, paper and discussion, pp.169-243, London, January 1910
"Tunneling Under the Hudson River" by S.D.V. Burr, John Wiley & Sons, New York, 1885
"The Register of Arts, and Journal of Patent Inventions" edited by Luke Hebert, B. Steill, London, 1832

Hudson River Tunnel