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Glendoe recovery on track Aug 2011
TunnelTalk reporting
A major milestone was reached in the second week of July when BAM Nuttall completed breakthrough of the new bypass tunnel for Scottish and Southern Energy's (SEE) Glendoe hydro scheme in Scotland. The 600m long section of drill+blast work bypasses a zone of the headrace tunnel that suffered a major rockfall in August 2009 and caused shutdown of the newly-commissioned project.
Fig 1. Plan of the repair works

Fig 1. Plan of the repair works

Man-entry inspection of the dewatered system confirmed blockage of the 6.2km long headrace at about 2,000m from the reservoir intake. An estimated 20,000 tonne of debris covered a reach of up to 700-800m on the downstream side of the 5m diameter unlined TBM drive.
BAM Nuttall was awarded a recovery contract in early 2010 to excavate two new tunnels using drill+blast: a new 600m long section of headrace to bypass the collapsed zone and a new downstream access adit from which to clear the debris (Fig 1).
A bulletin released by Douglas Gilchrist, Project Community Liaison Officer for SEE, says that if good momentum is maintained the process of refilling the reservoir at Glendoe is expected to begin in Spring 2012 with electricity generation resuming in the first half of 2012.
Excavation of the 550m long access tunnel was completed in January 2011 and workers are making progress clearing the debris up through the headrace tunnel.
Bypass junction with the initial TBM-drive headrace

Bypass junction with the initial TBM-drive headrace

They are also taking the opportunity to repair erosion damage that occurred during the few months that the plant was in operation between December 2008 and the rockfall shutdown in August 2009.
The £150 million (US$250 million) scheme, which is built into the hills adjacent to Scotland's famous Loch Ness, collects water from a wide catchment to drive the single 100MW Pelton turbine in the underground powerhouse. The pumped-storage scheme is designed as a peak-demand rapid response installation with a loading rate of 0-100MW in a minute, and a start-up (through turbine and generator synchronisation) to full load in four minutes.
References
Rock falls shut down Glendoe power plant - TunnelTalk, Aug 2009
Glendoe rockfalls more serious than initial fears - TunnelTalk, Oct 2009
Recovery contract for failed headrace at Glendoe - TunnelTalk, Feb 2010

           

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