Dam on the Sessera Stream

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Client STECI s.r.l.

Location Piemonte

Status Completed

Interventions to overcome recurrent water crises, enhance and develop the environment

in the reclamation areas of the Dam on the Sessera stream

 Vams Ingegneria has drawn up the Environmental Impact Study of the project in question.

The project, which was subject to a National EIA procedure, has acquired a favourable opinion of environmental compatibility.

The intervention as a whole aimed at reducing the multi-sectoral water deficit (drinking, irrigation, hydroelectric) in a large area of the Baraggia Biellese and Vercelli in Piedmont, through the construction of a new reservoir on the Sessera stream with a useful capacity of 12,000,000 m3 and all the related works of adduction, distribution and hydroelectric use.

In consideration of the very high environmental sensitivity of both the site where the reservoir was built and the works for the derivation, transport and use of water resources (there are also 2 SCIs – IT 1120002 “Val Sessera” and IT1120004 “Baraggia di Rovasenda” for which the relevant Incidence Study has been drawn up) the numerous environmental analyses and investigations carried out (hydrological,  hydraulic, hydrobiological, fauna, floristic, with a particular focus on the ecosystem and the river habitat) in support of the Environmental Impact Study have directed many design choices (both construction and construction site) towards solutions to minimize environmental impacts on the most exposed components.

The works concerned:

New arch-gravity dam on the Sessera stream, with a height of 94.40 meters, located about 200 m downstream of the existing Mischie dam; – Primary adduction pipeline with a diameter of 1,600 mm and a length of 27.8 km from Piancone in the Municipality of Portula (BI) to the locality C.na Pavona in the Municipality of Rovasenda (VC); the pipeline in a natural tunnel for the first 3.6 km, then buried through the territories of the Municipalities of Pray, Crevacuore, Sostegno, Villa del Bosco in the Province of Biella and Roasio, Rovasenda in the Province of Vercelli; – No. 3 new hydroelectric power plants for the simultaneous energy exploitation of the flows conveyed downstream and biological release downstream of the new dam: “DMV” power plant located inside the dam choir to exploit the environmental release (no. 1 Pelton turbine 75 or KW – turbine flow rate 308÷1000 l/s; – “Ostola” power plant (Pelton turbine unit 6,200 KW – turbine flow rate 105÷750 l/s); – “Sesia” power plant (Pelton turbine unit 6,500 KW – average turbine flow rate 1455 l/s; turbine door maximum 4,000 l/s),

  1. Works for the drinking use of water reservoirs on the Sessera, Ravasanella, Ostola and Ingagna streams.

Particular attention was paid to the construction site of the intervention and to the management of materials (about 120,000 m3 of excavation, 14,000 m3 of stone material, 260,000 m3  of concrete batching), also through the solution of important operational problems (related precisely to the need for environmental protection of the territories) with the use of special conveyor belts, electric train, cableway.