Glendoe Hydro Electric Scheme – Tunnelling
Poyry Energy JV Ltd (Formerly Electrowatt Ekono)
HOCHTIEF successfully delivered Glendoe Hydro Electric Scheme, a 100MW capacity hydroelectric power station south of Loch Ness. Water is collected in a new reservoir, impounded by a dam over 1km long, then transferred through an 8km power tunnel to a turbine housed in an underground cavern. The drop from the reservoir to the turbine is over 600m, making Glendoe the most efficient hydro scheme in the UK.
- 1km long, 35m high rock fill dam
- Aqueduct system: 8km tunnel, 4.5km pipeline
- 8km power tunnel
- 1.2km power station access tunnel
- Additional access and service tunnels
- Power Cavern, 38m long, 18m wide, 32m high, 250m underground
- Single 100MW Pelton Turbine
- 650km3 excavation
- 207km3 structural concrete
- 45km of access roads
We used a 200m long, 5m diameter Tunnel Boring Machine (TBM) to bore the 8km power tunnel, advancing 130m per week. A laser guidance system kept the tunnel on line, while drill and spray equipment fixed to the TBM enabled us to support the tunnel with rock bolts and sprayed concrete as we went. We used sprayed concrete to stabilise all underground works to minimise construction time, completing the power tunnel drive one month early.
Using sophisticated drilling jumbos and the latest explosives and detonation systems, we created the drill and blast aqueduct tunnels and power cavern. We modified the aqueduct tunnel programme so that we could advance up to seven faces concurrently. This enabled us to complete over 9km of tunnel on time, despite poor ground conditions. We continuously monitored the programme, resequencing operations and adopting continuous shift working to drive progress. We completed the scheme over two months early and achieved a CEEQUAL Excellent rating.