4. Plant civil engineering

For coastal basins of just a few dozen km ² , plant construction can be carried out in the dry, protected by cofferdams, as in the case of the Rance and Shiwa rivers (Korea).

This may also be the case for some larger sites if the plants can be located close to the coast, but building cofferdams offshore exposed to storms may be more costly and time-consuming than using prefabricated reinforced concrete caisson plants built in series. This second solution can be standardized and can facilitate a short program. It applies very well to orthogonal turbines (figure 5 ). The turbines can then be placed in the caissons before towing, or in situ, the choice being linked to the caisson draught problem, the overall cost and the program.