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Aerial view of the Coire Glas site with the forest and the bank of the loch
Aerial view of the Coire Glas site with the forest and the bank of the loch © John Zammit at Absolute Photography Ltd.

Client: 
SSE Renewables 

Location: 
Loch Lochy, Scotland 

Build time: 
2023 - 2024

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Coire Glas Exploratory Works

STRABAG UK delivered exploratory works on the site of a proposed large-scale pumped hydro storage scheme for SSE Renewables in a remote location 20 miles from Fort William, Scotland.

The project involves the construction of a 1.2km long and 4.5m wide tunnel using the drill and blast technique to better understand the geology and underlying strata of the site.

The exploratory works awarded to STRABAG UK involved cutting into the hillside towards the proposed location of the Coire Glas hydro scheme. 

Samples of the materials excavated from within the hillside will be analysed and, along with surveys and assessments, will provide information on the geological conditions of the site, which will inform the detailed design of the main works of the pumped hydro storage scheme.

STRABAG UK tunnelling experts used the drill and blast technique in the construction of this exploratory tunnel. The technique is rarely used in the UK, but it allowed the team to adapt to the variations in rock type and geological conditions. Holes are first meticulously drilled into the rock using advanced machinery tailored to the rock’s hardness and composition, followed by blasting, where the holes are filled with explosives and detonated in a controlled manner. The blast fractures the rock, facilitating its removal and allowing the tunnel to progress.

A fully operational tunnel construction site was established in this remote location near Fort William in Scotland. Several site compounds were constructed, including offices, workshops, group plant and water treatment, as well as a tunnel portal area with suitable containment.

Following the completion of the tunnel excavation, the team began a programme of extensive ground investigation. Further drilling and testing was carried out from the end of the tunnel, travelling even deeper into the mountain. The team drilled boreholes to a depth of up to 300m, using state-of-the-art investigative and testing methods rarely seen in the UK.

  • image inside the tunnel with STRABAG machinery © John Zammit at Absolute Photography Ltd.
    image inside the tunnel with STRABAG machinery © John Zammit at Absolute Photography Ltd.
  • Junction inside the tunnel with lighting © John Zammit at Absolute Photography Ltd.
    Junction inside the tunnel with lighting © John Zammit at Absolute Photography Ltd.
  • Image down the tunnel rounding a corner with lights along the way © John Zammit at Absolute Photography Ltd.
    Image down the tunnel rounding a corner with lights along the way © John Zammit at Absolute Photography Ltd.

Environmental and social responsibility

The project is part of a scheme to increase homegrown renewable energy within the UK. 

With works carried out in compounds surrounded by a nearby forest in the West Highlands, the steep hillside, and the shoreline of Loch Lochy, environmental protection was crucial to this project. Throughout the project, the site team worked in collaboration with the Scottish Environment Protection Agency (SEPA) to conduct meticulous monitoring and surveillance of both tunnel effluent and noise emissions to ensure a minimal impact on the natural environment. 

STRABAG UK’s preference for working with local construction partners and suppliers created several jobs in the region. Local schools were provided the opportunity to visit the site and apprentices, graduates, and young engineers from across the country also spent time on the site to learn about hard rock tunnelling.

Awards

In 2024, The Coire Glas Exploratory Works was awarded two New Civil Engineer Awards:

  • Tunnelling Project of the Year (up to $100m) (STRABAG UK) – Winner
  • Tunnelling Ground Investigation Project of the Year (STRABAG UK & SSE Renewables) – Winner