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The Obwalden parliament has to approve hefty additional costs for flood protection. The reason is the geology.
It is a project of the century for the canton of Obwalden. The canton is digging a flood relief tunnel between Sachseln and Alpnach over a length of 6.5 kilometers. In the event of flooding, the relief tunnel can absorb and drain water from Lake Sarnen. This leads to relief for the communities in the Sarneraatal – especially for the main town of Sarnen.
The project is well advanced. Around 80 percent of the entire route has now been excavated in the tunnel. The message that construction director Josef Hess had to announce a few weeks ago was all the more annoying: “The construction work is being delayed, because of water in the tunnel, tunneling is not progressing as desired. The project will cost 64 million francs more.”
“Bite the bullet”
64 million francs – that’s a lot of money for a small canton like Obwalden. Instead of the budgeted CHF 115 million, the flood relief tunnel will cost almost CHF 180 million. In order to be able to afford the tunnel, Obwalden has been levying a special tax for flood protection for several years.
Now the Obwalden cantonal parliament has dealt with the additional credit. Cantonal Councilor Marcel Durrer of the SVP said, gnashing his teeth: “We have to bite the bullet and bring the project to a good end.” It is a very important project for the protection of the valley. «We are always weaker against nature». And Canton Councilor Reto Wallimann from the FDP also agreed at the end: “There is actually no turning back. The work has already progressed far too far. We have to go through this.”
Legend:
The water is bubbling: in certain places, eight times the amount of water penetrates into the relief tunnel.
Canton of Obwalden
In fact, demolition of the project is practically no longer possible, as building director Josef Hess (independent) says: “We have already invested so much in this matter. The tunnel cannot be used until it is finished. We have to finish the project and we will finish it.”
Currently, however, the water flow is 400 instead of 50 liters per second.
Taking a look at the flood relief tunnel, construction manager Beat Ettlin shows where the problem lies with this Obwalden project of the century: The water gushes into the tunnel and in places where the experts would not have expected it. Site manager Beat Ettlin: “We assumed a residual water volume of 50 liters per second in the tunnel. Currently, however, the water flow is 400 liters per second.»
The geological conditions in the underground tunnel are very demanding and fault zones occur again and again. Those responsible are currently assuming that the construction period will take around two years longer – until 2025 instead of 2023.
“More staff, more security costs”
The longer construction time is also the main reason for the immensely higher costs. Josef Hess: “It’s a chain reaction: the inrush of water causes interruptions, and a complex dewatering system has to be installed for this”. The whole project needs more staff, more material and more means of security.
Legend:
Flood 2005: The impressive picture from the air shows how much parts of Sarnen were under water during the great flood.
keystone/ alessandro della valle
When it comes to flood protection, it’s worth taking a look back in Obwalden: Sarnen was severely affected by the great flood in 2005. The entire village center was under water and a quarter of a billion was damaged.
And that’s why – as the cantonal council concluded: a functioning flood protection system is even cheaper than another major event, despite the additional costs. The cantonal council has reluctantly approved the additional loan.