Abstract: The disclosure relates to the field of the storage of toxic wastes, in solidified form, without the creation of any pollution, on appropriate artificial sites. Briefly, a concrete raft is cast on a ground stabilized in depth, said concrete raft being constituted by slabs having joints between them and being arranged in a diamond moulding. This raft can support a tight-sealing material. Wastes are then piled up on the raft in maintaining the shape of a tumulus-like mound, the positioning being done under the protection of a movable cover comprising a travelling crane provided with rolls of plastic film.