World's Longest Undersea Tunnel Will Cut Travel Time Dramatically

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China, renowned for ambitious construction projects like the Great Wall and the world’s largest building, plans to build the world’s longest undersea tunnel. The Bohai strait, located off the coast of eastern China near the Korean peninsula, is one of the busiest seaways in the world due to its close proximity to Beijing. The country wants to build a rail tunnel across the strait that would cut travel times dramatically.

The 76-mile long tunnel, 56 miles of which will be underwater, would far surpass any efforts that came before it. The Channel Tunnel that joins the United Kingdom and France is currently the record holder of the world’s longest undersea section of any tunnel, but the section is only 23.5 miles. The Seikan tunnel in Japan, meanwhile, is the world’s longest undersea tunnel, at a length of 33.46 miles.

Above the sea, the Gotthard tunnel that runs through the Swiss Alps claimed the title of world’s longest rail tunnel when it opened in June, starting regular rail service in December. It’s 35.5 miles long.

The Bohai Strait tunnel would beat all of these by a long shot.

Here is the map of the route between the two:

Bohai Strait tunnel.

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Although only 101 miles apart point-to-point, it takes eight hours to travel between the port cities of Dalian and Yantai on either side of the strait. With high-speed trains powering through the new tunnel at speeds of 155 miles per hour, the travel time between the two towns will be reduced to just 45 minutes.

When first announced in 2013, the tunnel was given an approximate completion date of 2023 at a budget of 260 billion yuan ($37.8 billion). When opened, the China Railway Engineering Corporation will take over management, the holding company of the world’s largest construction firm. Even the company responsible for the tunnel has a “world’s largest” title to its name.

It’s impressive, but the project wouldn’t actually be the world’s longest continuous tunnel. That title would stay with the Delaware Aqueduct, an 85 mile long aqueduct constructed between 1939 and 1944. It carries over 500 million gallons of water per day from four reservoirs in upstate New York through to New York City and other counties. The tunnel is responsible for supplying around half of the city’s drinking water. The Bohai Strait tunnel plan is impressive, but it can’t quite claim all the “world’s longest” accolades.