As part of the safety of the structure, it is necessary to carry out the maintenance of the Castet EVCs. This can only be done under the shelter of a construction cofferdam. The need is to build this cofferdam in accordance with the studies and documents provided.

1. Execution studies:

- Conduct surveys, measurements and assessments necessary to ensure a good understanding of the problems to be solved on the site

- Analyze existing plans and technical documents on the work

- Establish all execution studies for all work requiring it: calculation notes, overall plans and details,

- Drafting operating procedures and risk analysis of operations

2. Site facilities, means(s) of access and handling(s) necessary for the carrying out of the work

3. Works

- Creation of a construction cofferdam: construction of the fixed parts (threshold and lateral sealing) during the emptying of the reservoir, modification of the upstream balconies on the 3 piers, realization of the supports of the upper beam, realization of the moving elements (cofferdam deck) and adjustment in the workshop compatible with the geometry of the fixed parts

- Tests under hydraulic load of the cofferdam on the 2 passes and control: compliance with the maximum deformation of the upper beam and the deck, the installation and folding time, residual leaks under maximum hydraulic load

4. Waste management, site cleaning

5. General coordination of the site