It might still be an idea, but what an idea it is: a concrete tube submerged in the waters of a fjord with vehicles travelling inside it from one shore to another with little between their rolling tires and the deep blue abyss below.
It might seem outlandish but the idea has been deemed feasible by a group of engineers and architects commissioned by the Norwegian government to find a solution to the problem of crossing the country’s fjords without the use of a boat. Since these dramatic natural formations are often more than 1,000 metres deep, building bridges is out of the question.
The solution is found in a feasibility study that the Reinertsen Olav Olsen Group, a consortium of two firms, produced for the Norwegian Public Road Administration.
Entitled “Feasibility study for crossing Sognefjorden”, it recommends laying a concrete tube across the fjord, one of the deepest in the
Scandinavian country at 1,250 metres. Submerged under the surface of the water but supported by a chain of pontoons, it would facilitate the travel of vehicles between the towns of Lavik and Oppedal. The structure would be the first of its kind in the world, greatly reducing the travel time between the towns from 21 hours to 11.
Laying the tube, called a Submerged Floating Tunnel (SFT), across the fjord would be quite an undertaking because it would have to be anchored at either shore, kept 20 metres under the surface of the water and supported by pontoons with enough distance among them to allow ships to pass uninterrupted. Indeed, the two central pontoons would have to be 400 metres apart from each other to allow for their passage.
The feasibility study actually envisions the laying of two parallel tubes stretching for 3.7 kilometres with the support of 16 pontoons. The construction of these tubes would require 400,000 cubic metres of concrete and 61,000 of steel.
Each tube – or tunnel - would have two lanes: one for traffic and the other for maintenance and emergencies.
According to the study, it would take between seven and nine years to build at a cost of $25 billion.
«The structure is designed to withstand all functional and environmental loads with ample margins. Motions set up by wind, waves and currents are moderate and will not cause driving discomfort or traffic disruption», it reads.
The Norwegian government does not appear to have flinched at the cost of the project since it could apply it at fjords in other parts of the country.
The idea of a crossing dates back to 2011 when the government called out for proposals.
With 1,1990 fjords, Norway definitely needs a solution to its infrastructure challenge to reduce travel times for its people. An underwater tunnel would appear to be a good one since it would not change the natural scenery for which the country is know. It would also reduce the risk of driving along icy roads during winter.
If the Norwegian Public Road Administration were to go ahead with it, tunnels like the one proposed could be opened by 2035, according to estimates.
The government’s willingness to invest in infrastructure does not lie solely with ambitious projects like underwater tunnels. Its plan for the 2018-2029 period, approved by parliament earlier this year, calls for an investment of $72-117 billion on roads, highways, ports, railways, metros, airports and bridges.
THE NORWEGIAN PUBLIC ROAD ADMINISTRATION COMMISSIONED A FEASIBILITY STUDY FOR AN UNDERWATER TUNNEL IN SOGNEFJORD
THE CONCRETE TUNNEL, SUBMERGED UNDER THE SURFACE OF THE WATER, WOULD BE NEARLY FOUR KILOMETRES LONG, CONNECTING LAVIK AND OPPEDAL
THE PROJECT WOULD COST $25 BILLION AND TAKE SEVEN TO NINE YEARS TO ACCOMPLISH
THE TUNNEL WOULD BE NEARLY 20 METRES UNDER WATER AND SUPPORTED BY 16 PONTOONS
THE NORWEGIAN PUBLIC ROAD ADMINISTRATION COULD BUILD OTHER TUNNELS OF THIS KIND AT OTHER FJORDS BY 2035
THE 2018-2029 NATIONAL TRANSPORT PLAN FORESEES $72-117 BILLION WORTH OF INFRASTRUCTURE INVESTMENT