The 'breakthrough' in campaign to build £500m subsea tunnels for Scottish islands

The Unst and Yell Tunnel Action groups said experts would also make recommendations for seismic survey locations that would contribute to the potential route of the tunnels under Yell Sound and Bluemull Sound, which are served by ferries.

The tunnels are expected to cost more than £500 million. Such tunnels are common in the Faroe Islands and Norway.

The groups said they had raised the money to commission the work from Norwegian consultancy Norconsult, with an online fundraising campaign reaching £13,000 over the past 18 months.

They had previously raised £100,000 from Unst Spaceport and North Yell Development Council to launch the project two years ago.

The survey work is expected to start on site at the end of this month and take up to three months to complete, with the results produced within six weeks. The campaigners said seismic surveys would be commissioned separately and are expected to be completed next year by Norwegian firm GeoPhysix, a sub-consultant of Norconsult.

Graham Hughson, joint chair of Yell Tunnel Action Group, said: “This is a huge step forward for the project, which we see as being absolutely vital for the long-term social and economic sustainability of our communities.

“Norconsult’s role will be to prepare the basis for carrying out seismic ground investigations using sonar technology, provide a follow up and report on the seismic investigations, prepare the tunnel alignments [choosing the most probable alignments using updated grade requirements] and prepare overviews and longitudinal sections for the tunnels.

“Should adjustments be needed following the seismic investigations, Norconsult will refine the alignments accordingly.”

The groups said the tunnels would “provide greater accessibility irrespective of weather conditions, eliminate geographical barriers, and open up endless possibilities for economic expansion and social integration”.

Duncan Gray, joint chair of Unst Tunnel Action Group, said: “We are delighted to have been able to engage such highly experienced industry experts. Norconsult will bring the skills and experience that they have gained from their work in areas where tunnelling is well established to our project and indeed the UK.”

Alice Mathewson, the group’s joint chair, said: “We are absolutely delighted to have reached this breakthrough stage in the project’s development, and to finally be laying the groundwork to make things happen.

“It is thanks to the many businesses and private individuals in our communities and beyond who have donated to the groups that we have been able to reach this milestone moment.

“It is the donators’ vision and generosity that has enabled us to move forward so significantly from planning to action. We are incredibly grateful for every contribution.”

Kristian Aunaas, director of infrastructure at Norconsult, said: “We look forward to working closely with the Unst and Yell Tunnel Action groups and contributing to the realisation of the project.”