Hydropower Station Ötztaler Ache

Construction of a water tunnel

Client

Ötztaler Wasserkraftwerk GmbH / TIWAG-Tiroler Wasserkraft AG
Eduard-Wallnöfer-Platz 2, 6020 Innsbruck

Contractor

BeMo Tunnelling GmbH

Project location

Ötztal/ Tyrol, from Habichen (district Oetz) to Tumpen (district Umhausen)

Start of construction

2020

End of construction

2021

Project total value

8.661 million €

Geology

Main section: approx. 800 m SEM drive (drill and blast) in granite (hard rock with high UCS)
Soft ground sections of approx. 50 m

Technical Data

Construction of a 900 m water tunnel (Work-package 4) as part of the new built hydropower station “Wasserkraftanlage Ötztaler Ache”.
• Drill and blast in hard rock
• construction of a 20 m long “roofed” section: prior tunnel excavation a > 1.00 m tunnel shaped concrete slap was formed above the tunnel
• circular secondary lining (inner diameter = 3.80 m) with a 9 m long full-round shutter
• forming a pre-stressed secondary lining by conducting intense grouting after concrete works
• continuous gradient of 8,14 %
• Construction of a 150 m long steel-armoured conduit incl. concrete fill and grouting of the annular gap

Further project related information

The main challenges are the small cross-section of approx. 18 m² and the high UCS and abrasivity of the rock mass.
For the soft ground section at the north portal a tunnel-shaped concrete slab was formed to protect the tunnel-excavation works.
The excavation of the soft ground section was formed by a challenging combination of river sand (no cohesion) and large granite boulders with several meter diameter.