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Glendoe Hydro Scheme

At the end of 2005 Hochtief Construction as general contractor received the contract for planning and the turnkey production of a 100 MW hydro power station in Scotland. The project is located on the banks of Loch Ness near Fort Augustus right in the middle of a nature conservation area in the Scottish Highlands. During the design phase environmental aspects were taken into consideration and strict regulations devised for sustaining the region were applied during construction. The water needed to generate electricity is collected in a 75 km large catchment area and fed to the reservoir by means of a pipeline and tunnel system. From there it is transported to the power station cavern via the headrace tunnel and then transferred to Loch Ness through the tailrace tunnel. The reservoir is formed by a rock-filled embankment. A concrete apron protects it towards the water. A sealing screen prevents the dam being affected by undercurrents. A lower discharge tunnel and high-water relief were parts of the project. The 1,159 m long horseshoe- shaped access tunnel was driven by drill+blast and secured by shotcrete (NATM). The tunnel with an excavated cross-section of 43 m² served to provide access to the power station cavern during the construction phase. It now houses the 132 kV high-voltage cable. Five points of attack were used to produce the 8.5 km long diversion tunnel. Same 1.5 km was created by cut-and-cover. The remaining 7 km was driven using the NATM with a 19 m² horseshow cross-section. The diversion system was rounded off by 4 km of pipeline with 2 m diameter. Water is obtained from a total of 17 creeks. However, it had to be ensured that the region's rivers and creeks do not run dry at any time. The headrace and tailrace tunnels were excavated by a hard rock tunnel boring machine. The headrace covers a 600 m difference in height over its 6.2 km length. The maximum gradient amounts to 12 %. The drive takes place on the rise and provision of the TBM via rubber-tired vehicles operated within limits. Belt conveyors were employed to remove the muck. Electricity was already being produced during the construction phase: the conveyor drives acting as generators. The geology consists of quartzite, quartzite shale and meta conglomerate sandstone. The ground is by and large extremely compact and stable so that only parts of the tunnels had to be secured by shotcrete, in situ concrete and structuraI steel. To develop the individual construction yards some 50 km of roads had to be built or upgraded. Six bridges were either reinforced or built. The 100 MW Pelton turbine was installed before schedule so that electricity was already being produced as from December 2008 three months earlier than planned.


  • Country: United Kingdom
  • Region: United Kingdom/Scottland
  • Tunnel utilization: Utility
  • Type of utilization: Power Generation
  • Client: Scottish and Southern Energy
  • Consulting Engineer: Jacobs
  • Contractor: Hochtief Construction AG
  • Main construction method: Trenchless
  • Type of excavation: Drill-and-blast/Tunnel boring machine (TBM)
  • No. of tubes: 2
  • Tunnel total length: Power station cavern: 38 x 18m, 32 m high/Dam: 960 m, max. 35 m high/NATM tunnel: 8,200 m (19 x 43 m²); TBM tunnel: 8,100 m (bored diameter 6.00 m)
  • Contract Volume: approx. 180 mill. euros
  • Construction start/end: January 2006 till February 2009