Building work at the pumped storage Nant de Drance hydrpower plant is progressing well. November 2019 saw the achievement of a further milestone with the flooding of both works water channels …

… connecting the upper Vieux Emosson reservoir with the lower Emosson dam. These also include two vertical shafts, each over 425 m high. The works water channels were then partially flooded after the final dry safety tests. The initial flooding served to test the relevant seals and functionality, and particularly the main gate valve. Once the two pressure shafts were flooded to the uppermost water level for the Vieux Emosson reservoir, and maintained for stability and safety tests several weeks, from the beginning of 2020 a variety of mechanical and electrical test programmes and wet-tests were then initiated on the six machine groups. In order to gua­rantee the smooth operation of all machinery, test and gauging series are due to last several months. Each of the six pump turbines is devised to produce 150 MW and will be switched online step by step.