Innertkirchen 1 power plant
Underground Mining Power station construction
For the Kraftwerke Oberhasli (KWO) in the canton of Bern (CH), a consortium with JÄGER built an additional intake water channel for the existing power plant in Innertkirchen I. The main element of the first phase was the construction of a parallel shaft. This consists of a flat stretch of roughly 1,000 m in length with an excavated cross-section of 12 m2. The flat stretch was excavated using conventional tunnelling. There then followed the uphill tunnelling of a steep stretch of approx. 1,000 m in length. The excavation of the inclined shaft with an inclination of 70% was achieved with a tunnel boring machine with a diameter of 3.20 m. In addition to the parallel tunnel, the excavation of further small tunnels and caverns was required. A major challenge was presented by the construction site logistics. It was necessary to provide three attack points over three installation positions, one of which was reachable only via cable car.
Extension of central supporting cavern/underwater tunnel
In the spring of 2013, the AKI consortium (Strabag Tunnelbau - Gasser Felstechnik - Jäger Bau) was awarded another large contract section. This concerned a new power station control centre, a cavern (18 x 44 x 16 m) for an additional 150 MW unit, a 1.94 km underwater tunnel and a stilling basin on the outlet side (22,000 m³).
Due to its large storage capacity of 60,000 m³, the underwater tunnel was also pressed into service as a retention basin to prevent excessive discharge fluctuations (hydropeaking) from affecting the receiving water.
Overall, the order volume was 71 million Swiss francs.