Initial technical details for the proposed €16bn (£14.2bn), 103km long rail tunnel connecting Finland to Estonia under the Gulf of Finland have been released, which includes two huge artificial islands and a tunnel 250m below the sea’s surface.
The mega-project will run between the capitals Tallinn and Helsinki at a maximum depth of 250m for the most part through solid crystalline bedrock under the channel, emerging into Estonia through softer sediments of Ediacara and Blue Clay.
To aid construction of the tunnel, FinEst Link said two, 400m x 300m artificial islands, located at places with water depths of 15m and 20m, would be built within the channel using the excavated material from the tunnel construction. These will provide ventilation, access and energy supplies to the tunnel below.
Under the plans, tunnelling will start from Helsinki using the drill and blast method to the first artificial island, Uppoluoto.
From Uppoluloto access to the tunnel for trucks will be provided by a spiralling 1.5km long, 9m diameter inclined tunnel. From the second island, Tallinnamatal, due to differing geological conditions, access will be created by two, 215m long vertical shafts to the tunnel below. At the end of both access points, large caves will be constructed and tunnel boring machines (TBMs) assembled.
The TBMs will then be used to bore two, single track, 10m diameter running tunnels about 70m apart with an 8m diameter maintenance tunnel between them. To minimise construction time, six tunnel drives from each island will take place simultaneously.
Tallinn Helsinki tunnel cross section
On completion of the tunnels, the track will be installed and a year of testing will take place before operation is due to start in 2040.
The details were published in the Helsinki-Tallinn Transport Link Feasibility Study – Final report by FinEst Link – a joint Finland and Estonia body set up to look into the possibility of a new connection.
Currently a ferry service connects the two countries, but it takes just over 2 hours and only runs 12 times a day. FinEst Link said the new tunnel would cut the time to only 30 minutes and allow it to run 40, 200km/h passenger trains, a total of 28, 160km/h car and truck trains and three, 120km/h freight trains each day.
The favoured tunnel alignment runs from Ulemiste just south of Tallinn on the Estonian side to one of three possible tunnel portals near Helsinki on the Finnish side.
The report says that on the Helsinki side the line would run in parallel with the planned airport rail line providing connections to the rest of Finland, Sweden and northern Russia. On the Estonian side, the link would connect directly to the airport which is already connected to the rest of the rail network and Rail Baltica – the new pan-Baltic rail project due to start construction in 2019.
Rail gauges differ between Finland and Estonia, so the line will be built to the European, 1435mm standard gauge to allow it to connect directly into Rail Baltica.
The tunnel is projected to cost £7.5bn to build, with rail costs adding a further £2.3bn. The report says the total cost would be around £14.2bn but this could rise to £17.8bn when more detailed designs had been produced.
Financing is due to come from a 40% EU grant, with a Public Private Partnership (PPP) contract, with a pay back cost of around £250M annually over 40 years. Revenue, it said, is set to far exceed the operational costs of the railway. It said viewed as simply as a transport project, the costs did not stack up, however taking into account the wider economic benefits it became viable.
FinEst Link said more work would need to be done to look at the wider benefits of the line.
“Further studies on the technical and economic feasibility are needed: logistics during the construction phase of an undersea mega-project, construction of artificial islands, environmental impact assessment, dynamic demand forecasts that take into account changes over time as the region repositions through better accessibility,” it said. “It has been concluded that a special focus needs to be set on wider economic impacts and to understanding the dynamics and wider impacts of regional development of twin cities.”
Despite this, FinEst Link project director Kari Ruohonen said the response to the tunnel was a positive one.
“Now it is a political question how and when to continue,” said Ruohonen. “Prime ministers will have a meeting in time of some weeks and governments will have a meeting this spring. The conversations from the panel were positive and same in the Finnish media. So it is hoped the project will continue.”
The project aims to start construction in 2025.