The Holland Tunnel (1920–1924) was constructed by pneumatically forcing cylindrical shields through the river bottom. The shields not only dug through the muck, but also acted as the shell behind which the tunnel walls (made of iron rings filled with concrete) were created. This method proved successful for its time and is still used today in some deep-water ports around the world.
The Holland Tunnel opened on November 17, 1924. It was named after William W. Holland, who designed the original system of canals that now serve as underground drainage channels for the area surrounding New York City.
Construction began in 1918, and it took 13 months to complete. The tunnel is about 485 feet long and reaches a depth of 133 feet below sea level. Its width varies from 22 to 25 feet, depending on the section you are in. There are five traffic lanes plus a center divider, while the walking space is about 95 feet. Today the Holland Tunnel remains an important link in the transportation network for both passengers and freight between New Jersey and New York City.
As part of its ongoing efforts to improve safety and traffic flow inside the tunnel, NJ TRANSIT has conducted a rehabilitation project that started in October 2009. Work includes replacing electrical systems, installing signal lights, repairing bridges, and updating security cameras. The project is expected to be completed by May 2011.
The Holland Tunnel began construction in 1920 and opened in 1927. The Holland Tunnel was the world's longest continuous underwater vehicular tunnel at the time of its inauguration. The Hudson River Vehicular Tunnel or the Canal Street Tunnel were the initial names for the Holland Tunnel.
The city of New York is full of man-made wonders, and the sandhogs can lay claim to many of them. They excavated all of the subways, sewerage, water, and railroad tunnels in the city. The Lincoln, Holland, Queens-Midtown, and Brooklyn-Battery Tunnels were built. They assisted in the construction of the Brooklyn Bridge, the Woolworth Building, and several other projects.
The Holland Tunnel was the world's first mechanically ventilated underwater vehicle tunnel. It has a network of vents that run transversely, or perpendicularly, to the tubes. Each side of the Hudson River features two ventilation shaft structures, one on land and one in the river, around 1,000 feet (300 m) from the coastline. The tunnels are designed to remove excess moisture from the air inside the tube, as well as to prevent the accumulation of noxious gasses such as hydrogen sulfide.
The removal of excess moisture is important because water can cause damage to electrical equipment if it enters the tunnel through an electrical cable. The prevention of gas accumulation is crucial because many gases become toxic at low levels. For example, hydrogen sulfide is poisonous at concentrations as low as 2 parts per million (ppm), while carbon monoxide is deadly even at levels as low as 5 ppm.
There are also outdoor air intakes located near the entrances to both northbound and southbound lanes. These large openings, which are about 20 feet by 20 feet (6 m by 6 m), allow fresh air to flow into the tunnel. This helps reduce the buildup of harmful gases inside the tunnel.
Additionally, there are three more ventilation shafts along the length of the tunnel. These open spaces, which are about 30 feet by 30 feet (9 m by 9 m), provide additional means of removing excess moisture and preventing gas accumulation.