Mules-Fortezza hydraulic tunnel

Exploitation of Isarco's creek water for hydroelectric purposes
Owner/client Società Elettrica Altoatesina S.p.A.
Type of service Preliminary Design
Location Mules and Fortezza
Period 2006
Cost € 72.000.000

The study was about the boring of a hydraulic tunnel for the exploitation of the waters of the Isarco river for hydro-electric purposes, on the left of the Isarco Valley (Bozen).

Particular attention was placed on the analysis of the interaction between the hydraulic tunnel and the future Brenner Base Tunnel on the Verona - Innsbruck railway line, and of its complementary works that shall be performed, after the hydraulic tunnel, on the same slope but at lower levels. The area under study is located on the left of the Isarco river valley, between the residential areas of Fortezza and Mules, in the most northern area of the Southern Alps, and it extends south of the Periadriatic Fault, which consists of the so called 'Linea della Pusteria'.

The area is almost totally characterized by the presence of 'Brixen granite'; only the most northern strip is characterized by intrusive bodies attributable to the Periadriatic magmatism, with particular reference to the 'Lamella di Mules', for some kilometers starting from the water point.

The tunnel will mainly extend in the Brixen granite formation, through materials with good mechanical characteristics, except for the crossing of the tectonization cataclastic bands, which are mostly developed in the Rio Bianco incision. These zones are also preferred waterways, as well as important fixed potentials. Outside the cataclastic bands, water supply may be considered negligible. Due to the high percentage of quartz, granite shall be considered highly abrasive.

Tunnel type

Power tunnel at free surface


Excavation diameter: 4.4 meters; 12 km total length.

Altitude gap

Altitude gap: about 25 meters; constant slope: 1.5%.