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Lago D'Idro (Italy)

ClientAgenzia Interregionale per il fiume Po

Work activitiesPreliminary and Detailed design



Period2022 - 2023


The new bypass tunnel represents the main intervention of the works for the hydraulic safety of the Lake, with the primary purpose of evacuating flows even in case of landslide collapse obstructing the outlet river.

The route of the tunnel develops along the right orographic bank for approximately 1316 meters, with the entrance located about 180 meters northeast of the entrance of the current spillway tunnel, in the Municipality of Idro, and the exit situated in the municipality of Lavenone approximately 460 meters downstream of the existing outlet.

The structure is entirely external to the perimeter of the landslide on the left orographic side.

The tunnel can be divided into 3 sections:

• Intake structures:

Intake structure with a width of 22 meters.

Rectangular-type connecting structure with a double arch, approximately 32 meters in length, with dimensions of 4.50 + 4.50 meters in width and 4.50 meters in height.

• Bypass tunnel: Approximately 1463 meters (of which approximately 1316 meters of natural tunnel, 51 meters of artificial tunnel on the Idro side, and 96 meters are artificial on the Lavenone side). 

The hydraulic tunnel has a polycentric internal section with an area of approximately 40 square meters and a constant slope of 0.85%.

• Discharge and return structure to the Chiese River consisting of:

• Reinforced concrete structure with two passageways, approximately 79 meters in length, constructed artificially and covered with soil to mitigate environmental impact.

• Diffuser structure, approximately 54 meters in length.

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