THE estimated cost to develop and construct undersea tunnels between mainland Shetland and four surrounding islands would be around £1 billion, it has been revealed.
Projections have been published by the engineering consultancy firm COWI, which has been working alongside Shetland Islands Council (SIC) and fellow consultants Stantec after community events on inter-island connectivity drew to a close.
The estimated cost of a tunnel between Yell and Unst has been quoted at £303 million, with a tunnel from mainland Shetland to Yell predicted at around £402 million and would take around eight years to complete.
Meanwhile, a proposed 8.2km tunnel, running under Linga Sound to Whalsay, would cost around £427.5m.
Proposed plans for Unst would also see a 5.3 km-long tunnel forming part of a 6km road corridor constructed, helping to connect areas near the Gutcher and Belmont ferry terminals.
The full project costs, including construction, pre-construction, and risk/contingency, total £487m for Whalsay, £402m for Yell, £345m for Unst, and £255m for Bressay.
Along with the projected build costs, an estimate for operating and maintenance of the tunnels over a 60-year period was also given, ranging from £44.4m for Bressay to £92.5m for Whalsay.
Tolls have reportedly been considered to help cover some of the maintenance costs for the likes of Yell.
Following the projections, Shetland Islands Council (SIC) and transport consultants said there is no cheaper option, even if a decision is made to keep with the island's ferries, according to Shetland News.
Council leader Emma Macdonald warned ahead of a crunch debate over the Shetland's transport infrastructure that “doing nothing is not an option”.
She said: “When islands have fixed links like causeways, bridges and tunnels, they experience repopulation, economic growth and a reduction in average age.
“Doing nothing is not an option in Shetland. We have islands depending on old, unreliable, carbon-heavy ferries, which are depopulating and continually at risk of ferry breakdowns.
“I look forward to the debate in the chamber later in June, where we’ll consider all the options before us.”
Ahead of a full council meeting on June 30, local communities on the islands were asked for their views on the proposed undersea tunnels.
The local authority will then decide on the options for future connectivity for Yell, Unst, Whalsay, Bressay, Fetlar, Skerries, Papa Stour and Foula.
Last June, the council agreed to commission a fixed link model study from consultants Stantec and COWI, using Yell Sound as a test case in a project comparing the cost of future ferry upgrades and investment in fixed links.
The study involved three international contractors, who consulted the financial community, and concluded that the tunnel is buildable and investable.
Andy Sloan, executive vice president UK and international at COWI, said: “We know that the tunnels can be built. From an engineering perspective it is relatively straightforward. The real challenge is whether we as a nation take a short-term or long-term view.
“As our global experience tells us, people will be attracted to live in remote and rural places if they are easy to get to, easy to get around, digitally connected and with job opportunities and an affordable standard of living.
“Fixed links can change how people in Scotland live, work and travel. They can reverse depopulation, provide vital services and support economic growth. Once Scotland builds its first tunnel, it will never stop.”
Proposed funding models for the projects include private investment, grant funding from both the Scottish and UK governments, and local authority borrowing.
Neil Grant, a director with SIC, said both governments had shown interest in the proposals, adding: “The Scottish government, in particular, has been supportive of the work to date.”
However, Grant added that “intense work” was needed to reach the stage of a full business case.
Separate pre-seismic studies were carried out by Norconsult, the engineering consultancy firm behind the Faroe Islands’ subsea tunnels, in 2025 and followed on from reviews of earlier investigations into the feasibility of subsea rock tunnels across Bluemull Sound and Yell Sound.
