The Grand'Maison Dam is an embankment dam on the Eau d'Olle, a tributary of the Romanche River. It is located in Vaujany of Isere within the French Alps. The primary purpose of the dam is to serve as the upper reservoir for a pumped-storage hydroelectric scheme where Lac du Verney located lower in the valley is the lower reservoir.
The dam was constructed between 1978 and 1985 with its power station being commissioned in 1987. With an installed capacity of 1,800 MW, it is the largest hydroelectric power station in France.The power station repeats the pumped-storage process as needed and acts as a peaking power plant. Power generation or pumping can be initiated within minutes. On an annual basis, the power station generates 1,420 GWh of electricity and consumes 1,720 GWh in pumping mode.