Unst and Yell tunnel groups complete report
Tunnel action groups in the North Isles are celebrating today after completing an “important step”.
Unst and Yell Tunnel Action Groups have today published the pre-seismic report for proposed fixed links to both islands.
The pre-seismic work was carried out by Norconsult, the international engineering consultancy responsible for the design of all subsea tunnels in the Faroe Islands, as well as many of those in Norway.
This report also reviews previous geological studies, carried out between 2000 and 2002, which included seabed surveys and geological mapping.
Earlier studies identified potential challenges, including sediment layers, rock quality variations, and fault lines. However, based on updated international best practice and site visits, Norconsult has now produced new indicative alignments with a gentler slope of five per cent - compared to eight per cent in previous studies.
This change lengthens the tunnels but makes them “more suitable” for modern design standards and future transport use.
The report found that Bluemull Sound has “complex” geology, with ridges and troughs in the bedrock and variable sediment depths. As a result, “adjustments to alignments” may be required to find the best rock mass quality.
Yell Sound was described as having “deeper” rock structures and “significant fault zones”. The most promising alignment was likely under Bigga Island, though this still needs to be confirmed through further studies.
Alignments for possible tunnels are preliminary lines only, produced for technical assessment purposes. The next stage — a full seismic study — would provide the detailed geological data required to identify which alignments are feasible and to refine potential routes.
Unst Tunnel Action Group’s joint chairman Alec Priest said: “We are delighted to have completed this important step in the process. It shows how the money raised by our communities is being used, and gives everyone the chance to see how the project is progressing.
“Seismic surveys are the next crucial stage. They will give us the detailed data on the seabed and rock structures that we need before any firm decisions can be made about alignments and help refine costings for potential fixed links.”
He added: “Thanks to the amazing response so far, the majority of funds are already in place for consent support work and the seismic surveys. Just a small funding gap remains, which we hope to fill through continued community effort, local business support, and upcoming events.”