Positive construction progress on Unterer Tuxbach project

20.09.2017Tuxbach, Mayrhofen

Tunnel boring machine begins on connecting tunnel between Tuxbach Stream and Stillupp reservoir

The central element of the Unterer Tuxbach project, which VERBUND is carrying out in the Zillertal Valley in cooperation with Stadtwerke Schwaz, is an 8.6 km long connecting tunnel between Unterer Tuxbach and the Stillupp reservoir. Preliminary blasting work to prepare for use of a tunnel boring machine has been carried out over the last months. A little ceremony near the tunnel portal served as the kick-off for its operation, marked by hopes of successful and accident-free construction work.

The tunnel boring machine will start working on the tunnel from the Karlsteg end in the direction of Tuxbach. Then the machine will be retracted from the mountain and the connection from Karlsteg to the Stillup reservoir created. The total construction time for the Unterer Tuxbach project, the implementation of which was begun in early 2017, is estimated to be 3 years.

Michael Amerer, Managing Director of VERBUND Hydro Power GmbH: "The connection between Tuxbach and the Stillup reservoir is the heart of this project, in which we are investing 60 million euros. An investment which will trigger both local and regional added value. The Zillertal Valley Agreement ensures that the region will profit from the success of hydropower over the long term. Here in the Zillertal Valley it's obvious what other countries envy us for: Our long tradition and partnership-based style in using renewable hydropower."

Karl Heinz Gruber, Managing Director of VERBUND Hydro Power GmbH, spoke on the topic of the energy future: "For many years already we have been using hydropower in the Zillertal Valley. With the Unterer Tuxbach project, we are adapting the facilities to meet increasing challenges: more flexibility for the goal of integrating volatile forms of generation such as wind and photovoltaics. The Unterer Tuxbach project represents an efficient expansion of the green battery in the Zillertaler Alps for the coming decades."

Stadtwerke Schwaz was represented by Mayor Hans Lintner: "Stadtwerke Schwaz has been involved in hydropower since 1897 and is one of the electrification pioneers in Tyrol. VERBUND and Stadtwerke are not just partners in this project, but also share the conviction that hydropower will serve us well – as it has in the past – in terms of providing a clean, reliable and affordable power supply."

Vice Governor Josef Geisler highlighted the importance of hydropower for Tyrol: "The example of the Unterer Tuxbach project shows that here in Tyrol, we are actively working on implementing our energy strategy. We are taking steps to achieve our goal of being energy autonomous by 2050 and meeting our energy needs with renewable domestic energy sources. With the partnership-focussed approach we are taking, we are ensuring that we aren't just building bridges to our own future, but also to that of our children and grandchildren."

Unterer Tuxbach project

The water from the Stilluppbach, Tuxbach and Zemmbach streams has been used for clean electricity generation in the Bösdornau power plant for nearly 90 years. An ecologically and economically sound succession plan has been developed and approved for the time following expiration of the power plant's concession period in 2019. This involves creation of an underground connection between the Tuxbach Stream and the Stillupp reservoir and construction of a green power plant with an output of around 1.7 MW at the end of the passage where it flows into the reservoir. The unique combination of the new connecting passageway and linkage to the existing Mayrhofen power plant and the new Stillupp small hydropower plant can together generate a total of an additional 74 million kilowatt-hours of domestic hydropower electricity annually – to provide more than 20,000 households with CO2-free electricity. Implementation of the project will take approximately 3 years.

Commitments are being fulfilled

Numerous project-related agreements have been made with regard to the Unterer Tuxbach project. The Zillertal Valley Agreement was amended already in 2015 to ensure that the valley community will continue to profit from the success of clean hydropower, and that the towns' financial flexibility will be increased. In addition, numerous further commitments will be honoured, such as construction of a stretch of water for water sports in the course of dismantling the Zemm weirs in Mayrhofen. Flood protection measures in the Ufersiedlung area will also be improved. VERBUND's commitment to maintaining the Zillertal Valley central control station in Mayrhofen was renewed during negotiations.


The existing Tuxbach power plant facilities in the Finkenberg district will be shut down. Dismantling of the Grossdornau basin belonging to the power plant, as negotiated with the municipality, will free up space for other uses for the town. Moreover, the currently above-ground pipelines to the Bösdornau power plant will be relocated below grade in the area of Grossdornau.

It was also negotiated that VERBUND will in future forego usage of the Stillupp water catchment. And in future the existing water catchment on the Tuxbach River will also no longer be used. In the existing Bösdornau powerhouse, therefore, only one machine unit will be operated with the water of the Zemmbach Stream in order to meet the on-site power needs of the power plants and to ensure the cold start-up ability in the event of large-scale power outages. Thus it will remain possible to restore the supra-regional power supply step for step, starting from these facilities. This reduced continued usage of the Bösdornau power plant also ensures that the power plant building, built between 1928 and 1930 and attractive for reasons of industrial history, will be preserved as a part of Tyrol's and VERBUND's hydropower history.

More information on the Unterer Tuxbach project

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