The exploratory tunnelling for what could become the UK’s first large-scale pumped storage scheme in four decades has reached completion. This 1.2km tunnel represents the latest achievement in SSE’s ongoing efforts to advance the Coire Glas project in the Scottish Highlands.
Situated near Loch Lochy in the Great Glen, the planned Coire Glas project is designed to have an installed capacity of 1,300MW. It is expected to deliver 30GWh of long-duration electricity storage, sufficient to supply firm, flexible renewable power to three million British homes for up to 24 continuous hours.
SSE Renewables aims to reach a final investment decision on the Coire Glas project by late 2025 or early 2026, with the potential to begin main construction in the latter half of 2026. This timeline is contingent upon securing success in the administrative allocation of an investable cap and floor mechanism.
Exploratory work at Coire Glas began in December 2022 and is being carried out by STRABAG UK.
In early 2023, SSE announced a £100m investment to advance the Coire Glas project, including the construction of a significant exploratory tunnel as part of an extensive site investigation programme.
SSE’s technical partners, Stantec and COWI, have designed and supervised the complex ground investigation programme, which is being executed by STRABAG.
This work involved creating a tunnel approximately 5m high and 4.5m wide, cutting into the hillside near the proposed site of the underground powerhouse complex. The tunnel’s construction is crucial for gathering precise geological data to inform the detailed design of the main project works.
With the tunnel now complete, a three-month programme of exploratory drilling and testing will proceed to further assess the ground conditions in the area designated for the underground powerhouse excavations.
SSE Renewables Coire Glas director of development Mike Seaton said: “Completing the tunnelling is testament to the hard work and dedication of everyone involved and a positive step forward in de-risking the project.
“The works progressed to plan, and samples of the materials excavated from within the hillside are currently being analysed.
This phase of the project is an engineering challenge in itself and we are learning a huge amount as we progress the works. The findings of the tunnelling works, alongside our wider site ground investigation works completed by Fugro in December 2023, will be used to inform the final design, including the detailed design of underground structures, and will be a key consideration in any final decisions related to the project.”
