Aare Canal between Winznau and Obergösgen (Photo Herbert Schibler)
Alpiq Hydro Aare AG is to start reinforcing several sections of the embankments of the over 100-year-old Aare Canal in Niederamt in the canton of Solothurn this year, to meet stricter seismic stability standards.
Starting in October 2022, four sections of the headrace for Alpiq’s Gösgen hydropower plant will be reinforced in the municipalities of Winznau and Obergösgen in the Solothurn Niederamt region by means of backfilling. The construction work is associated with the new concession for the Gösgen hydropower plant, which came into force on 1 January 2020, which include the reinforcement of several sections of the embankments of the 4.8km headrace. The embankments will be reinforced using a total of almost 20,000 tonnes of gravel sand. The costs of some CHF 1.2 million will be borne by Alpiq Hydro Aare AG.
The headrace of the Gösgen power plant was put into operation in 1917. The embankments are regularly inspected and are in a good condition. The reinforcement measures were triggered by higher seismic stability standards. To maintain the stability of the structure, individual sections have already been reinforced over the past years, most recently in 2013 and 2019.
Alpiq Hydro Aare will backfill a total of 2000m of the embankment with gravel sand; in Winznau in the Giessen and Schachen area on the south side of the canal and in Obergösgen upstream of the bridge on both sides. The additional material will broaden the crest and flatten the slope of the embankment, which will have a positive effect on its stability. At the same time as the backfilling, small amphibian ponds and hibernation structures for reptiles will be created as initial environmental compensation measures. Construction is scheduled for completion in May 2023.
The embankments of the Aare Canal will be reinforced in close consultation with the Solothurn Cantonal Environment Office and the Supervision of Dams Section of the Swiss Federal Office of Energy.
As a further element of the new concession for the Gösgen hydropower plant, the refurbishment of the weir in Winznau is scheduled for next year. Alpiq is currently drawing up the implementation plans and will provide information about the project, the construction process and the schedule towards the end of 2022.