Norwegians may soon ford a fjord in an underwater floating tunnel
With any luck, Norwegians will be able to drive through fjords like never before. Specifically, they’ll do it in a big, floating tube, 70 to 100 feet below the ocean’s surface. If it’s successfully completed, the project will be an engineering first though, as this tunnel won’t be supported by anything but buoyancy, theoretically heading off problems that would be otherwise presented by more traditional bridge or tunnel designs.
Barriers to bridges
The goal is to get car traffic across a body of water called the Sognefjord, a long narrow fjord stretching 127 miles inland from the west coast of Norway. The fjord runs between steep slopes both above and below water, sometimes down to 4,000 foot depths. If that didn’t complicate logistics enough, the area is also prone to harsh weather conditions that can wear and corrode structures built over the water. Finally, ships, particularly from the Norwegian navy, require access in and out of the fjord.
The above factors basically rule out normal bridges and tunnels in some way or another. Ship access has even ruled out a floating bridge, which was offered as a flexible structure that wouldn’t require sinking pylons to the bottom of the deep water. Instead, the proposed tunnel will act a bit like an inverted floating bridge, being suspended from, rather than resting on, a series of pontoons across the water.
By being permanently underwater, the floating tunnel will still have to survive exposure to salt water, but with much less cold and wind. Cars will move through one of two tube-shaped tunnels, which when combined with worries about bad weather on the road, should actually be safer driving conditions than a normal bridge. The one thing a common pontoon bridge may have over this tunnel is the price— while the former are often built as cheaper alternatives to more permanent structures, this floating tunnel should cost around $25 billion. It also remains to be seen how successful construction will be, as other floating tunnels have been proposed, but none have been completed.
Source: Floating Underwater Tunnels Planned for Norway by Glenn McDonald, Live Science