Nant de Drance: Excavation of access tunnel completed

With yesterday’s completion of the drilling of the access tunnel to the future Nant de Drance pumped storage power station in Châtelard (canton of Vaud, VS), the partners of this project − Alpiq, the Swiss Federal Railways (SBB), and FMV – have achieved an important milestone. Hence an underground connection now exists between the lower and upper sections of the installation.

Yesterday, as the clock struck 15:00 hours, the final breakthrough took place between the access tunnel of the future Nant de Drance pumped storage power station and the tunnels of the upper section of the construction site. Hence the underground connection between Châtelard and Vieux Emosson is now complete. The boring machine, which started in October 2009, thus required a little less than three years to excavate the 5.6 kilometres of this tunnel to Châtelard. During this period it excavated some 400,000 m3 of material before reaching the future cavern for the machines, which is situated at a depth of 600 meters in the rock between the Emosson and Vieux Emosson reservoir dams. Due to the impressive dimensions of the boring machine, 9.45 meters in diameter and 142 meters long, it will take approximately three months to dismantle. The individual parts will then be transported to the valley by special convoys.

The completion of excavation of the access tunnel and the breakthrough between the lower and upper sections represents an important milestone for the three partners in this project, i.e., Alpiq (54%), Swiss Federal Railways (SBB) (36%) and FMV (10%). As of January 2013, the various construction sites between Emosson and Vieux Emosson will be connected underground to Châtelard via the access tunnel. Traffic on the road leading to the dam will thus be significantly reduced and furthermore, the upper construction site will remain accessible throughout the year, even in winter.

An important contribution to the energy policy Within the framework of the new energy policy defined by the Swiss Federal Council, the Nant de Drance pumped storage power station will make a significant contribution to meeting the increasing demand for balancing energy, i.e., the energy which is necessary to balance the planned exchange of electricity and to guarantee the reliable operation of the grid. As a store for renewable energy that can be injected into the grid at any time, Nant de Drance will be an ideal complement to new renewable energies, whose production is irregular. The power station will ensure the security of supply to the Swiss electricity grid, as well as to the railway network of the Swiss Federal Railways (SBB).