Old Elbe tunnel

Old Elbe Tunnel or St. Pauli Elbe Tunnel (German: Alter Elbtunnel (coll.) or St. Pauli Elbtunnel (official name)) which opened in 1911, is a pedestrian and vehicle tunnel in Hamburg, Germany. The 426 m (1,398 ft) long tunnel was a technical sensation; 24 m (80 ft) beneath the surface, two tubes with 6 m (20 ft) diameter connect central Hamburg with the docks and shipyards on the south side of the river Elbe. This meant a big improvement for tens of thousands of workers in one of the busiest harbours in the world.

Four huge lifts on either side of the tunnel carried pedestrians, carriages and motor vehicles to the bottom. They are still in operation, though due to the limited capacity by today's standards, other bridges and tunnels have been built and taken over most of the traffic.

In 2008 approx 300,000 cars, 63,000 bicycles and 700,000 pedestrians used the tunnel. The tunnel is opened 24 hours for pedestrians and bicycles. For motorized vehicles opening times are currently Monday to Friday from 5.20 AM to 8.00 PM, on Saturdays from 5.20 AM to 4.00 PM.

On 22 July 1907 the construction of the tunnel, which was undertaken by Philipp Holzmann, started to connect the quarters of St. Pauli near the Landungsbrücken and Steinwerder.

Work was done under pressure because the tunnel was below the water table of the Elbe. This type of building technique was used in the 19th century, in large engineering excavations, such as with the piers of bridges and with tunnels, where caissons under pressure were used to keep water from flooding the excavations, such as the foundations of the Brooklyn Bridge in New York City.

But workers who spend time in high-pressure atmospheric pressure conditions are at risk when they return to the lower pressure outside the caisson without slowly reducing the surrounding pressure. Due to the problems associated with decompression sickness, many of the men working on the Elbe tunnel were affected by, what was known at the time, Caisson's Disease. Three men died, 74 suffered severe cases and more than 600 came down with light symptoms among 4,400 workers.

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Wikipedia