The Glendoe hydropower station generates 100MW through a head of 600m and peak flow of 18.6m3/s. The scheme includes a 905m long concrete faced rock fill dam 35m high, a 75km2catchment including supply pipes and tunnels, a 8.6km water supply tunnel, a 6km head race tunnel, a 0.4km tailrace tunnel, turbine hall and a 1.3km long access tunnel.

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The 5m diameter headrace tunnel was constructed using a TBM and was not lined, though rock support was provided where it was deemed required. A section of the headrace tunnel collapsed in August 2009 totally blocking the tunnel about 2km above the turbine. Unfortunately, it was not possible to remove the blockage and a new access tunnel and bypass tunnel were needed, as well as repairs to the remainder of the tunnel.

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The Board of Scottish and Southern Energy sought independent assurance as to the scope, cost and programme for the recovery works. OTB were given an investigatory remit to examine all aspects of the delivery of the recovery works including commercial, contractual and technical matters.