What’s the longest underwater tunnel you’ve ever driven through? The Holland Tunnel into Manhattan, or maybe the Battery Tunnel into Brooklyn? Well, Norway laughs at your pitiful American underwater construction, because the country is now working on the longest undersea car tunnel in the world: A full 17 miles, stretching from the region of Stavanger in the south to Haugesund in the north. Yet, unusually, the tunnel actually connects a third location too — the island of Kvitsøy, which will tie in to the new tunnel with an undersea double roundabout.
The tunnel, called Rogfast, will have a fairly typical construction when it’s done: Two tunnels, each with two lanes going in one set direction. The roundabout, though, is anything but typical. Most Americans can’t figure out traffic circles when they’re at surface level, but apparently Norwegians can be trusted to navigate them when they’re 850 feet beneath the waves, according to CNN.
Not only long, but deep
The tunnel is meant to replace existing ferry routes, and will be the longest car tunnel to stretch between the sea. Its 17-mile length may pale in comparison to the Channel Tunnel, which connects Britain to France, but that tunnel only ferries cars via train — this one’s meant to be driven through. At its deepest, the tunnel will sit nearly a quarter mile beneath the North Sea.
That depth has proven a challenge, as the construction crew has faced saltwater leaks into the tunnel before it’s even hit 1,000 feet of depth. By the time the crew reaches the full 1,286 feet, the pressure of water on the tunnel will be even higher — jumping from 437 psi at the current depth to over 570 psi. Yet, not only are Norwegian authorities confident the tunnel will be a success, they’re confident enough to split the work. Two different teams are working on digging the tunnel, one starting from the north end and one from the south, with a goal of meeting in the middle with less than two inches of clearance on either side. Sorry, America, but our little tunnels have nothing on Norway.
