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Construction of the Nant de Drance pumped storage power station progresses

Work on the construction of the largest hydroelectric power station project in the canton of Valais is continuing. Excavation of the machinery cavern, a veritable underground cathedral and the core component of the project, will be completed in 2014. With its capacity of 900 MW, the future Nant de Drance pumped storage power station will contribute significantly to the security of electricity supply in Switzerland and Europe. The power station will become operational in stages starting in 2018.

2014 promises to be a landmark year at the Nant de Drance construction site, highlighted by completion of drilling work on the machinery cavern in spring. Excavation of the machinery cavern has been underway since mid-2012 and will have lasted about two and a half years by the target date for its completion in spring 2014. The cavern dimensions are impressive: 194 metres long, 32 metres wide and 52 metres high. This structure will be the core component of the future plant. It will house six pump turbines linked to engine generators, each with a capacity of 150 MW, totalling 900 MW overall.

In 2014, workers from additional trades, in particular boilermakers, will join the Nant de Drance construction site work force and the first steel pipes will be dispatched to Châtelard (Valais). The pipes will be transported in parts and then assembled and welded directly at the Nant de Drance plant worksite. The imposing size of the pipe components will necessitate the mobilisation of several special convoys to transport this voluminous cargo. The distribution pipelines between the Vieux-Emosson reservoir supply galleries and the six hydroelectric pump turbines measure up to four metres in diameter and will be the first to be assembled at the Nant de Drance site. Another highlight of 2014 will see drilling completed on the second vertical shaft, which will be 430 metres deep and 8 metres in diameter.

Positive results and new visual identity for Nant de Drance SA in 2013

Nant de Drance SA can look back on positive results for 2013 as the year draws to a close. To date, both the Nant de Drance plant construction budget, totalling just under CHF 2 billion, and the site work schedule have been respected. This year was largely devoted to the excavation and concreting of the galleries. The drilling work is almost finished, with 95% of the caverns and 17 kilometres of gallery excavated thus far. Another highlight in 2013 was the work accomplished to raise the height of the Vieux-Emosson dam. Around 32,000 m3 of concrete were poured this year, enabling work to heighten the dam to reach the halfway mark. The concreting has now been interrupted due to the winter conditions and will resume next spring. The Vieux-Emosson dam will have gained 20 metres in height and doubled its capacity to 25 million m3 by autumn 2014.

Another key development in 2013 has been the marked increase in the number of workers on the construction site from 350 to nearly 450 persons. This increase has confronted Nant de Drance SA with new challenges, notably in relation to logistics and management of the coordination between personnel of different trades on the worksite. In response, its shareholder partners – Alpiq (39%), SBB (36%), IWB (15%) and FMV (10%) – have decided to reinforce this coordination, mainly through the deployment of additional staff assigned to this task. Nant de Drance SA is also developing its corporate culture, reflected in its new visual identity that includes a new logo and a new website,, highlighting images of this exceptional site.

An essential complement to new renewable energies

As part of the new energy policy set by the Federal Council, the Nant de Drance pumped storage plant will be one of the key resources for meeting the growing demand for energy supply that can be adjusted at any time to balance energy availability and consumer requirements from the electric power grid. The plant will have a constant stock of available renewable energy supply that can be fed into the grid at any time. Its role will therefore be crucial for the development of new renewable energy resources that are susceptible to irregular and variable production patterns. Furthermore, it will ensure a secure energy supply for both the Swiss electric power grid and the Swiss federal railway network.