Canals, Tunnels and Penstocks

SSE reports exploratory tunnel completed at Coire Glas pumped storage site

SSE reports exploratory tunnel completed at Coire Glas pumped storage site
(photo courtesy SSE Renewables)

A 1.2-km-long exploratory tunnel is now complete at the site of what is anticipated to be the UK’s first large-scale pumped storage scheme to be developed in 40 years.

Completion of this tunnel is the latest milestone in SSE’s development of its 1,300 MW Coire Glas pumped storage project in the Scottish Highlands.

Located at Loch Lochy in the Great Glen, the proposed Coire Glas project would be capable of delivering 30 GWh of long-duration electricity storage.

SSE Renewables hopes to make a final investment decision on the project in late 2025 or early 2026, allowing for main construction to commence in the second half of 2026, subject to being successful in the administrative allocation of an investable cap and floor mechanism.

Exploratory work at Coire Glas began in December 2022 and is being conducted by STRABAG UK.

In early 2023, SSE announced a £100 million (US$127.6 million) investment boost to further develop Coire Glas, to include the construction of a major exploratory tunnel as part of a comprehensive package of site investigation works. SSE’s technical partners, Stantec and COWI, have designed and supervised the ground investigation program.

The works included creating a tunnel about 5 m high and 4.5 m wide, which cuts into the hillside around the proposed location of the underground powerhouse complex. Construction of the tunnel will allow the project team to gather accurate information on the geological conditions to inform the detailed design for the main works.

Now that tunnel construction is complete, a program of exploratory drilling and testing will continue for the next three months to further investigate the ground in the area of the proposed underground powerhouse excavations.

“Completing the tunnelling is testament to the hard work and dedication of everyone involved and a positive step forward in de-risking the project,” said Mike Seaton, director of development for Coire Glas with SSE Renewables. “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.”