Sasso Bisolo – Valmasino Hydroelectric Power Plant

The Bisolo hydroelectric power station is located in the Bisolo Valley, a valley that begins at the Predarossa Glacier situated just outside Mount Disgrazia in the Municipality of Val Masino in the Province of Sondrio. The plant taps into the waters of the stream of the same name, a left tributary of the Masino stream. The station runs along the course of the stream at 1,404 m.a.s.l. up to the collection work at 980 m.a.s.l., the restitution point of the turbine waterfeed.
The station consists of a waterbed intake comprised of a collection crosspieces made of reinforced concrete for the derivation of the waters, two settling tanks and a surge tank for the conveyance of the waters coming from the penstock. The water intake flows entirely to the right of the stream and allows up to a maximum capacity of 2,800 l/s of the derivation of the water.
The steel penstock, used for the conveyance of the waters to the main building, has a DN of 1,100 mm and extends entirely to the right of the new bridge over the Bisolo stream at 1,352 m.a.s.l. From here, the penstock extends to the left and rests under the roadbed of the new Predarossa ski slope until reaching the main building. The total length is approximately 2,400 m. The layout of the penstock also includes a tunnel section.

The main building, located at approximately 980 m.a.s.l., was constructed entirely in reinforced concrete. Particular attention was given to the external finishing works, using local stones. The machine rooms, the panel room and the local transformers are housed inside. Two Pelton turbine-generator groups were installed, which produce an average of 20/22 Mw annually, with a nominal jump of 424.9 m.
The restitution of the turbine waterfeed to the Bisolo stream occurs thanks to an underground discharge channel, through which the main building reaches the streambed and extends upstream of the existing Enel penstock.

The delivery and connection to the national network of the electrical energy produced was implemented through an M.T. line and the relative delivery room, which from the main building reaches Ardenno along the adduction channel, which belongs to Enel. The contract involved the executive planning, the supervision of the job with the exception of planning regarding the aspect relative to the dimensioning of the electromechanical works. Particular diligence was given to identify the ideal layout of the penstock and the construction of the main building, which brought about important provisional support works in the excavations.