The situation in the Blatten mountains in the Haut Valais is unique. The Gebidem dam, which usually collects water from the Aletsch glacier, is completely empty. It is a sure sign that major maintenance work is underway.
The Gebidem dam and the Bitsch powerhouse are the key elements of Electra-Massa. Commissioned in 1969, these facilities are about half-way through their service life. In order to ensure that they function correctly and to maintain them in good condition until the end of the concession in 2048 according to the concession-holder's obligations, Electra-Massa is undertaking major maintenance and renewal work. The shareholders will invest CHF 28 million between 2020 and 2025 to carry out this work.
The Gebidem dam was completely drained in October 2020. This step was necessary in order to renovate the bottom valve of the dam and to replace the butterfly valve located downstream of the wall. The anti-corrosion protection of the penstock connecting the dam to the power plant is also completely renewed. This is complicated and time-consuming work, which has to be done largely by hand. The old anti-corrosion protection must first be removed and the surface be perfectly clean before the new one can be applied.
The workers are also active in the lowlands at the Bitsch powerhouse. They are completely overhauling the main valve of one of the plant's three groups, as well as the transformer.
The facility will be operational again for the summer season as of May 2021. However, work will resume next winter to complete the anti-corrosion protection of the penstock and to carry out the annual maintenance work on the powerhouse's three machine groups.
While the Electra-Massa facility is out of service, Swissgrid, the national transmission grid operator, is taking the opportunity to renew the 220 kV substation at Bitsch, which connects the power plant to the extra-high-voltage transmission grid.
Multi-disciplinary complexity
The works underway at Electra-Massa are unique due to their scale and complexity. As asset manager, Alpiq is in charge of the entire project. The company is working closely with HYDRO Exploitation, which is responsible for managing the project and the works.
In addition to the technical aspects related to infrastructure, Electra-Massa attaches great importance to safety and the environment. Risk of landslides and avalanches, work in the immediate vicinity of the Jungfrau-Aletsch Nature Park, there are numerous challenges - in addition to the restrictions associated with the coronavirus pandemic. For this reason, an environmental office is supervising the work with natural hazard specialists to ensure that the safety and environmental concepts they have developed are being implemented.
David Jossen, Power Plant Manager at Electra-Massa, Hydro Exploitation
Access to the Gebidem dam is difficult in winter due to snow and cold weather. How do you carry out the work on the dam's valves?
In principle, the Gebidem dam is only accessible on foot in winter. However, due to the ongoing work, the access road to the dam is being cleared throughout the winter. If conditions become dangerous, the regional security service, with whom we are working closely, will close the access and the construction site. This was the case, for example, between 28 and 31 January 2021, as a result of the large amount of fresh snow and the mild temperatures that followed. An avalanche buried the two bottom valves of the dam.
We are also carefully observing the formation of ice stalactites on the crest of the dam, as some of the work is located just below it.
What are the main challenges you face?
The work being carried out is far from usual. This is the first time since the commissioning of the facility just over 50 years ago that we have replaced the dam's butterfly valve and renewed the penstock's anti-corrosion protection. We didn't know the exact condition that the facilities were going to be in. We are constantly faced with unforeseen events that need to be overcome.
With different works taking place at the same time, it was essential to plan them carefully in advance. Good communication and flexibility are also necessary because there are a lot of companies involved.
One of the biggest challenges, however, was draining Lake Gebidem. Because of the small amount of water in the Rhône, and because the waters of Lake Gebidem are very heavily laden with sediment, we had to pay particular attention to the concentration of suspended matter. Nevertheless, we managed to drain the lake while meeting all the specifications.
In addition to the technical aspects, it is also important to keep an eye on developments in the COVID-19 pandemic and the possible impact on ongoing work.
What does Electra-Massa's facility mean to you?
For me, Electra-Massa is not just a power plant, it is located in the middle of the mountains where I grew up. I discovered the watershed of Lake Gebidem, with the great Altesch Glacier and the Oberaletsch Glacier, as well as the Massa Gorge when I was a young boy.
Electra-Massa is an efficient and interesting power plant right on my doorstep. I am very proud and happy to be working for this facility.
