Construction of the dam
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A technical and human performance ...
Started in 1955, the project was completed 54 months later. In June 1960, the dam is completed (the impoundment of the lake was completed in May 1961). The construction site brought 3,000 workers at the same time together, at the peak of the activity in July 1959.
Preliminary work began in 1955 with the establishment of construction facilities in the measure of the works: power plant of compressed air, washing-sifting station to prepare the aggregates used in the manufacture of concrete, concrete plant, 2,300 m² of workshops to maintain and repair a park of extremely important gear for public works. A dormitory town with 800 beds is built in Espinasses to host singles. Another 300 accommodations were built near the site.
The first real site is the one of the diversion of the Durance, prior to the construction of the dam. To do this, a temporary diversion composed of two tunnels of 900m long and 10.50m in diameter is dug in the rock, on the left bank of the future works . The derivation ends on the 29th of March 1957. Enormous resources are implemented for that time: a perforating unit with 3 " jumbo " (huge pneumatic drills on tracked machines), telescopic metallic coffering’s placed on rolling frames and a train for concrete.
Meanwhile, they need to think to restore the lines of communication that the impoundment of the lake will cut. They took the opportunity to modernize them. Over more than 14 km of railways and 3 viaducts S.N.C.F are constructed. Just as 50 km of roads and over more than 2.5km of bridges, including the viaduct of Savines with a length of 924 m. These projects will be more expensive than the construction of the dam itself ...
"Travaux sur la Durance" - Reportage régional pour le journal national - 04/04/1957 (archives INA)
The construction of the dam and factory
For 39 months, from March 1957 and the end of the construction in June 1960, 30 million tons of materials are moved and transported on the slopes of the site. The construction of the dam alone requires 14 million cubic meters of earthworks (6 times the volume of the Great Pyramid of Cheops). The dam is 600 meters wide and 650 meters thick at the base. To transport these huge amounts of rock, 35 semi-trailers "Euclid" imported from the United States are able to load 60 tons in their dumpster. There are, in one day, up to 1,500 vehicle 300 HP passages to set up per day 20,000 m³ of material compacted by 3 tire-rollers 35 to 45 tons and 2 rollers " on feet of sheep " 18 tons. The brush of the engines continues on the dam without interruption from 2 am to 22 pm. A Euclid driver earns about three times the salary of an office worker. But it is a hard and dangerous job ... While on the surface, shovels, dump trucks, tractors and rollers are turning non-stop, in the heart of the rock a huge underground cathedral gradually rises to form the factory.
Thanks to the very good quality of the granite all excavations can be realized without any support. By the end of 1958, the three caves built parallel to give shelter to the transformers, machinery and foot valves are available to the manufacturers of electromechanical equipment.
The site knows memorable moments. On the 14th of June 1957, a flood of 1700 m³ / s (the highest flood known after the one in May 1856 which reached 1,800 m³ / s) disturbs the works. At that time, only one temporary gallery of diversion is in operation. The cofferdam, built above the dam site to protect it, is overwhelmed, fortunately without too much damage. Another delicate operation is the transport of 4 rotors of alternators from the manufacturer's ateliers. The 260 tons of each rotor are transported by the road on a low profile vehicle.
The impoundment and the disappearance of Savines and Ubaye
On the 16th of November 1959, the dam gates are closed to begin the filling of the reservoir. 18 months later, on the 18th of May 1961, the lake is full for the first time. The impoundment of the reservoir has resulted by submerging the villages Savines and Ubaye, located under level 780.
It was decided to rebuild the village of Savines. Discussions are keen to know whether the new village will be built on the left bank or on the right bank with more sun. The left bank, the original side of the village, is chosen, resulting in the need to build a bridge of 920 meters long crossing the two shores of the lake. EDF finances the reconstruction of the municipal buildings and a new church symbolizes, by its modern originality, the revival of the village.
At Ubaye, the village is not rebuilt, but the cemetery is moved to the side of the lake. The impoundment of the dam obliges to move nearly 1,500 people ...
The war in Algeria prevents the opening
The dam of Serre-Ponçon was never officially opened. General de Gaulle was to preside over the ceremony, but the war in Algeria changed the program. The postponement will never be realized.
Cost of construction
- The dividing up of the total costs, estimated at 50 billion old francs , is as following:
- Dike and watertightness : 23%
- related works and factory: 21%
- hydro and electromechanical equipment : 13%
- Restoring communication : 27%
- Purchase of land : 13%
- Studies and trials : 3%