The Glendoe Hydro Scheme for the generation of hydro-electric power is located in the Monadhliath Mountains near Fort Augustus, above Loch Ness in the Highlands of Scotland.
Part of the main headrace tunnel collapsed in August 2009, and remedial work was not completed until 2012, with generation restarting in April.
The publication of the Renewables Obligation in 2001 made any new hydro-electric scheme eligible under the incentive, whereas previously only those under 10 Megawatts (MW) had qualified.
The smaller schemes were discarded because of the cost of transferring the water from the Glendoe plateau down to Loch Ness, while the pumped storage option was discarded because it would not qualify under the Renewable Obligation scheme, and because the difference in levels between the top reservoir and Loch Ness was sufficient that it would be extremely costly to overcome the issues this would introduce.
[6] A contract for the scheme was awarded to Hochtief in December 2005, and they began producing the detailed designs and starting construction from January 2006.
The bridge that carries the B862 road over the River Tarff near Fort Augustus had to be strengthened to cope with the weight of construction vehicles,[8] and this work was done in five weeks starting on 21 November 2005.
[14] The catchment for the reservoir is around 5.8 square miles (15 km2)[14] as it is fed by the upper reaches of the River Tarff, the Caochan Uilleim, and runoff from the A' Chraidhleag bog.
Some of it was cut by drill-and-blast, but the majority was created by a 16-foot (5 m) diameter tunnel boring machine,[18] 720 feet (220 m) long and named "Eliza Jane" after a competition by local schoolchildren.
The cost of building either scheme is therefore similar, and SSE took the decision to go with the larger size, as it also has significant operational benefits.
[23] They therefore chose to install an Andritz six-jet vertical-axis Pelton turbine which can generate up to 100 MW, from a peak flow of 660 cubic feet per second (18.6 m3/s).
[13] Hochtief completed the contract two months early,[25] and the station had been generating power since January 2009[26] when a formal opening of the scheme took place on 29 June 2009, at which Queen Elizabeth accompanied by Prince Philip, Duke of Edinburgh officiated.
[19] In August 2009 the station was shut down and the headrace tunnel drained because of internal rock falls near the upper end of it.
A contract for repair work was awarded to BAM Nuttall, who built a diversion tunnel around the rockfall by drill-and-blast.
[36] Glendoe has a hydraulic head of 600 m (2,000 ft), the highest of any hydro-electric scheme in the United Kingdom,[37] and is thus ideally suited to generating large amounts of energy from the stored water in the reservoir, especially when combined with the relatively high annual rainfall in the area of around 2,000 mm (79 in).
[24] At the time of its construction, it was the largest of Scotland's recent civil engineering projects, with Hochtief as the design and build contractor.
This is based on the amount of water falling on the catchment in an average year,[39] and is enough to provide approximately 5% of the electricity consumption of the city of Glasgow.