Nant de Drance pumped-storage power station

Short description

Construction of an underground pumped-storage power station.

The project

The project involves the construction of a pumped-storage power station between the Emosson and Vieux Emosson dams. The new station is situated at an altitude of some 1,700 m. The underground facility is accessed  from below via a five-kilometre-long tunnel, and from above the surface via a system of tunnels measuring two kilometres in length. Vertical wells bring the water to the turbines. In addition to the structural work, the contract also includes management of the excavated material and increasing the height of the Vieux Emosson dam.

Services in detail

  • Main  tunnel: hard-rock boring machine with grippers.
  • Access tunnels and caverns: excavation via blasting. 
  • Shafts: raise drilling and blasting.
  • Lined tunnel: excavation via blasting.

Further information

  • Total volume of excavated material: 1.5 million m3
  • Total volume of concrete: 390,000 m3
  • Total quantity of steel: 20,000 t
  • Complex material preparation
  • Working at altitude 
  • Uphill trajectory for the tunnel boring machine: 11% gradient