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Innovation for an extraordinary project

December 8, 2023

Serpollet Agence HTB Grands Travaux was called in by RTE to replace six 400,000 volt oil cables at the EDF hydroelectric power station in Montézic (Aveyron), during the ten-yearly maintenance program. This was a project with very stringent technical and time constraints.

The project, managed at Serpollet Agence HTB Grands Travaux by Area Manager Alexandre Uson, as part of the GTSE* consortium, required more than two years of studies to implement operating procedures adapted to the physical constraints of the site.
The six oil cables to be renewed were deployed on both sides of a 700-meter-long narrow gallery - poorly lit, damp and permanently ventilated - and buried under 500 tons of sand within 2,800 channels covered with a concrete lid. These lines then passed through a 70-metre-high vertical shaft, before emerging in the plant section.

For Alexandre Uson, "this operation, carried out in eleven weeks, from April to June 2023, was a real challenge, which we were able to meet because we had prepared it extremely well with RTE, EDF and the consortium. We called on dedicated technical innovations and were able to count on committed and highly professional teams, led by Abdallah Samit, site foreman at Agence HTB Grands Travaux, even though working conditions were difficult. It was the combination of these three aspects - preparation, innovation and commitment - that made the project such a success.

Work in confined spaces

One of the major difficulties was the presence of very large quantities of sand in the gutters, which had to be cleared, stored and put back into place, while no existing mechanized solution was suited to the tunnel's narrowness and length. Two technical solutions were specially designed: a vacuum suction system to recover the sand from the first 350 meters of the tunnel; and then a custom-built electric two-bucket trailer to facilitate extraction and reuse of the sand from the remaining 350 meters. These two innovations greatly facilitated the work of the teams on site.

All in all, this project, which was carried out in fairly extreme conditions, went very well.
Patrice Coutenceau, project manager for RTE, emphasizes the extent to which the safety of all employees was assured: "No accidents occurred on a site where teams were very busy working in 2×8 or 3×8 shifts, and in particular on quite demanding manual tasks. I felt the cohesion of the teams on site, and I'd like to congratulate all the group's employees on their involvement"

*Groupe de Terrassement Serpollet ETPM