The Grono hydropower station in the Misox valley, canton of Graubünden, Switzerland, has returned to full operation following extensive repairs caused by a severe storm in June 2024.
The storm, which struck southern Graubünden, resulted in fatalities, injuries and significant infrastructure damage across the region. Several hydroelectric facilities operated by Axpo in the Misox valley were affected.
Most of the six plants in the valley resumed operation within days, having sustained only minor damage. These facilities include OIM (Officine Idroelettriche di Mesolcina SA), Calancasca SA, ELIN (Elettricità Industriale SA), a small plant operated by Tecnicama AG, and a small plant operated by Idro Arvigo AG on behalf of BKW and the municipality of Calanca.
The Grono plant, owned by Elettricità Industriale SA (ELIN), was the most severely impacted. The facility comprises the Roggiasca dam, the Grono power station and several water intakes. Flooding and debris caused extensive damage to civil works and electro-mechanical equipment.
Repair works involved Axpo specialists, plant personnel and external contractors. Two of the three turbine-generator units were recommissioned in early May 2025, following an outage of approximately 320 days. The third unit returned to service at the end of December 2025. After nearly 18 months of interruption, the plant is now fully operational.
Total repair costs amounted to approximately CHF 8m (US$10.3m) . In addition to direct repair expenses, the outage resulted in production losses. According to Axpo, these were largely offset by output from its broader generation portfolio.
Axpo operates around 60 hydropower plants across Switzerland. In Graubünden, the company operates approximately 20 facilities with a combined installed capacity of 1200MW, representing about one-third of its total hydropower production capacity
