Val d’Anniviers: new look for the Mottec power station
After works lasting seven years, the Mottec power station and the head at Tsarmette, the pillars of the Gougra hydroelectric complex, have been entirely renovated. HYDRO played a central part in this major project.
The Mottec power station underwent significant renovation from 2018 to 2025. The new plant was inaugurated on 26 May this year. This station represents the first pillar of the turbine unit of the Gougra SA hydroelectric complex (FMG), which is capable of supplying more than 140,000 households. Commissioned in 1959, it provides 20% of the output of Forces Motrices de la Gougra SA.
Optimised flow
Thanks to this total modernisation it was possible to increase the design flow from 12 to 15m3/s and installed capacity from 69 to 87MW, a boost of around 25%. The work affected the entire production chain: gates, turbines, alternators and transformers costing more than CHF 32 million, all paid for by FMG. HYDRO teams played a major part in this project.
Refurbishing the head at Tsarmette
The head at Tsarmette, situated between the Moiry dam and the Mottec power plant, also underwent major works.
Our engineering, operations and project management teams led the work on replacing the DN1800 butterfly valves at the mouth of the tunnel and the head of the well, and replacing all the electricity supply and control systems for the valves.
The anticorrosion protection on the penstock and all the high-pressure sections (8,650m2) was entirely renewed. All the sluice gates on the high-pressure side were replaced, as was the water settling system for controlling the valves.
The central workshops on the job
Our central workshops at Martigny carried out the full refurbishment of the three spherical valves (2xDN700 and 1xDN1000) located at the distributor at Mottec. They were dismantled, inspected, refurbished and reassembled with new components. The final pressure tests confirmed they were perfectly watertight. Our workshops also manufactured the new hydraulic controllers for these valves. The unit is now fit to run for decades to come.
Conditions at altitude
Completing the various works on the head at Moiry-Mottec involved coping with the problems you face when working at altitude in winter conditions. Special logistics arrangements were put in place, including winches, work platforms and helicopter transportation. Despite the challenging constraints, the project kept to schedule thanks to excellent coordination and the tireless commitment of the companies and our teams. More than 33,000 hours of work were put into this ambitious project by HYDRO to ensure the Mottec facility can operate safely over the long term.
The butterfly valve from Tsarmette was transported by Super Puma.
Lifting the new butterfly valve in the access tunnel to the valve chamber at Moiry.
Refurbishing the head at Tsarmette meant working in difficult conditions, in winter and with restricted access.
The new DN1800 butterfly valve is installed in Moiry, after putting in new brushes and anticorrosion protection on the downstream part of the penstock.
The HYDRO teams installed the rotary piston on valve no. 8, DN 1000.
