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Power Plant Innertkirchen 3

Power Plant with Vertical Shaft, 3 Tunnels and Cavern

The 2.6 MW power plant utilizes the lowest incline of the of Urbach River at Innertkirchen for energy generation. From the above-ground Pfengli collection structure, the supply pipe is first directed into a vertical shaft and then into a pipe tunnel at a gradient of 22% before reaching the machine cavern. In the return tunnel, the turbinated water flows back into the Urbach River at a gradient of 2% via open channel flow.

The cavern is accessible via an access tunnel from the tunnel portal near Unterürbach. All tunneling and excavation works were carried out by drilling and blasting:

Preliminary cut access tunnel:  D = 11 m

Access tunnel: L = 157 m, A = 22.3 m², 2 %

Machine cavern: L = 17 m, W = 10 m, H = 15 m, A = 125 m²

Pipe tunnel: L = 490 m, A = 9.7 m², 22 %

Vertical shaft: H = 20 m, A = 4.9 m²

Return tunnel: L = 42 m, A = 11.2 m², 2 %


Project period: 2014 - 2016

Services as subplanner: Project author structural underground works for the phases design, submission and implementation, documentation