Articles & Case Studies

Fugro assists with rigorous tunnel checks at Glendoe Hydro Electric Scheme, UK

Posted: Monday 13th May 2013

A Fugro geophysical survey of concrete tunnel linings has helped return Scotland’s Glendoe Hydro Electric Scheme to service after a programme of repairs.

The 100MW hydro-electric scheme near Loch Ness is owned and operated by SSE plc and was officially opened by the Queen in June 2009. A rock fall in a tunnel carrying water from the scheme reservoir led to temporary closure for a rigorous programme of remedial work awarded to BAM Nuttall, including the construction of two new tunnels using drill and blast.

As part of QA checks of other site tunnels before station re-commissioning, BAM Nuttall undertook detailed assessment of reinforced concrete linings. An initial visual and tactile inspection revealed a number of voids in the lining of the lower outlet tunnel through the dam. Structural investigation specialists from Fugro were called in to carry out a detailed subsurface investigation.

Fugro project manager, Sam Brook, said: “The client requested a quick turnaround so we were on site within a few days of the enquiry and had delivered provisional results a week later to enable an early assessment of repair locations. We then completed a full, detailed report within a fortnight of visiting the site.”

Fugro collected a grid of GPR (ground penetrating radar) profiles along the 200m tunnel, with supplementary low frequency ultrasonic testing in targeted locations. The survey identified 23 voids with sufficient accuracy to enable targeted repairs.

Resin grout was injected into approximately 1000 drill holes, and the repair team found a very close correlation between the location and depth of features reported by Fugro and the uptake of grout. This underpinned confidence that quality issues had been thoroughly investigated and accurately treated to assure the power station’s long-term performance.

SSE found the survey results invaluable, praising Fugro’s fast response in mobilising to the site and delivering the required data.

Paul Smith, Managing Director, Generation, at SSE said: “The work to restore electricity generation at Glendoe has been undertaken in a very rigorous way to make sure that this strategic asset meets its original design criteria and is ready to play its full part in supporting the country’s electricity system for many decades to come.”

Glendoe is the first large-scale conventional hydro-electric station to be built in Scotland for over 50 years. It has the capability to start generating electricity at full capacity in just 90 seconds, providing power for some 53,000 homes.

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August 2021

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