Dam Removal in Switzerland – Bally Dam is now history

Bally dam in Schönenwerd, which was built in 1888, constituted an obstacle to free passage and migration of fish along the course of the River Aare between Olten and Aarau. As part of a measure carried out by Alpiq’s Gösgen HPP, the dam was removed in 2017 incl. connections to the river bank. A temporary construction strip and bridge were set up to remove the 90m wide structure. Bally dam was then demolished in phases, with diversion dams providing protection. The river bank was stabilised using blocks and a biogenic mechanical bank protection system as well as individual trees. The removal of the Bally dam led to a 1.5m drop in the water level upstream of the dam. Current-loving fish species in the grayling and barbel regions have particularly benefitted from the demolition of the Bally dam. They are able to enjoy water flow rates typical for the River Aare, clean gravel banks and therefore better spawning conditions, more diverse habitats and more food.

Main Data

  • Concrete removed: 7,600 t
  • Installed supports : 4,800 t
  • Gravel used: 1,700 m3
  • Willow rods: 2,000 pcs.
  • Drop in water level: 1.5 m


Alpiq Hydro Aare AG


IUB Engineering AG

Construction period


Construction costs

CHF 1.1 million

Scope of services

  • Preliminary project
  • Construction project
  • Detailed project
  • Tendering
  • Implementation