Project: Hydroelectric power plant at Pont Ventoux - Susa - Italy
Location: Piemonte Region, Italy
Client: Municipality electrical Authority of Turin (Italy) (AEM)
Cost of total Works: 62.000.000 euro (detail design)
Services: Feasibility study, preliminary and final design of the hydraulic works, surveys and investigations, tender documents
Period: 1992- 1993
The hydroelectric plant of Pont Ventoux- Susa was designed to satisfy the increasing demand of energy in Europe in the early nineteen-nineties. From the first phase of the design, this work was recognized to be one of the greatest hydroelectric works in Europe for its size and productive capacity.
The intervention was very complex, designed by various groups of companies. In particular, Technital was involved in the preliminary and detailed design carried out in association with Electricité de France and Coyne et Bellier of France for the Temporary Association of contractors (Spie Battignoles, Grandi Lavori Fincosit, Vianini, Società Italiana per Condotte d’Acqua).
The whole project was a combination of several projects requiring the presence of experts in different fields such as, for example, hydrodynamic, structural and electro-mechanical, geological and biological experts.
The main works designed by Technital were:
- the main diversion structure constituted by a dam on Dora Riparia River, a water intake structure and all ancillary works
- a free surface channel constructed in a tunnel 14 km long with a peak flow-rate of 30 m³/sec.
- ancillary works such as access roads and tunnels, restitution channel etc
- construction of buildings for the management and control of the dams and power plant
The dam was designed taking into account the presence of roads and railways and the need to avoid interference with them. An important aspect of the project was the environmental impact of the works, and the necessity to define appropriate mitigation measures.
The dam was designed to guarantee the following points:
- Hydraulic safety in case of the maximum discharge of about 900 m3/s
- The derivation of a discharge of at least 30 m3/s
- Avoidance of siltation at the mouth of the intake
- Handling between double security gates
The layout of tunnel was designed taking into account the costs of construction and maintenance of the system and the need to build in respect of security in the presence of some unstable areas from geologic point of view.
Today the works are completed and the plant is operative.
Further specific information
The dam 83.5 m wide, with three main openings 23 m wide closed by sector gates. On the left-hand side there is another opening which can close off the water intake. An automatic cleaning device located at the intake grid of the gates allows the regulation of the water levels and the elimination of any floating elements. To guarantee maximum security, all the gates are manoeuvred using electricity from the normal grid or a generator. The dissipation basin is 17.2 m long. Downstream of the dam the bottom is protected by stones of 700-1000 kg up to the level related to a flood event with a 10-year return period. A fish ladder has been included in the design to guarantee a constant flow and to allow the ascent of fish.
The water intake is located on the left side, about 13 m upper of the dam, and is 36.0 m long. The water intake has 5 openings divided by piers 1.23 m wide. A grid located in front of this structure prevents the ingress of coarse materials.
The grit chamber is scaled to prevent the entrance of sediments exceeding 0.2 mm in diameter.
The inner section of the tunnel is circular in shape with an internal radius of 2.1 m at the top, and the bottom has a polycentric shape.
The total thickness of the lining is 30 cm for the areas excavated by boring machine, and 35 cm for the areas excavated by traditional methods.