Norway eyes floating tunnel
The proposed under-water tunnel would halve travel time and be a world’s first
Sarah Bostock & Michael Sandelson
Sogn og Fjordane County’s Sognefjord in western Norway is over 4,000 feet deep and 3,000 feet wide. Measuring some 4,291 feet at its deepest point, the fjord’s length runs for about 128 miles through several western Norway municipalities.
It is the world’s second-longest fjord, beaten only by Greenland’s Scoresby Sund at some 220 miles long (approximately 350 km).
Using information and experience from deep sea foundations in connection with bridge constructions, The Norwegian Public Roads Administration (NPRA) announced the plans for their concrete Submerged Floating Tunnel (SFT) back in 2011.
Building curved tubes of some 4,000 feet in length would allow vehicles to travel on a road bridge 65 to 100 feet below the surface, it is thought. Each of them, one in each direction, would be held in place using a float system or pontoons on the surface.
According to Wired, Norwegian engineers are currently calculating what a submerged floating structure could handle and how the currents might affect movement.
Building them will prove very expensive too. It is believed this will cost around USD 25 billion to construct.
At the same time, the infrastructure will radically reduce journey times between southeastern Norway’s Kristiansand in the south and Trondheim in the north.
This some 680-mile trip currently takes about 21 hours and involves seven ferry crossings.
If built, the underwater tubes could cut this time almost in half, with a journey of less than 11 hours.
These form part of the government’s previously announced ferry-free initiative for western Norway’s E39 motorway route.
The idea of driving for periods of time underwater could sound quite daunting. But Kjersti Kvalheim Dunham, project manager overseeing the road revamp project, told Wired that “Norwegians are quite used to going underwater in tunnels.”
Norway has 1,150 tunnels, with 35 of them being subsea ones. One project currently under construction is Eiganes Tunnel/Ryfast.
The NPRA’s Submerged Floating Tunnels feasibility study can be found at www.vegvesen.no/_attachment/513909/binary/828610?fast_title=Feasibility+study+for+crossing+the+Sognefjord+-+Submerged+Floating+Tunnel+-+Drawings.pdf.
It also appeared in the Aug. 12, 2016, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.