Contractor to carry out £20m of work on structure that collapsed eight months after official opening

BAM Nuttall is carrying out £20m of repairs on a tunnel originally built by Hochtief, following its collapse just eight months after being officially opened by the Queen.

Hochtief built the £150m Glendoe hydroelectric power station at Loch Ness for Scottish and Southern Energy, but the power station has been out of action since a tunnel partially collapsed in August 2009. BAM Nuttall has now been brought in to repair the tunnel, which carries water from a reservoir to the 100MW power station.

The repairs contract, which is worth about £20m, comprises two new tunnels - one is about 900 metres long and will divert water around the blockage; the other is a short access tunnel. The firm will use drilling and blasting.

The power station will not be functioning again until summer 2011. Scottish and Southern Energy is expected to seek damages from Hochtief over responsibility for the collapse, though neither firm would comment.