The preliminary design was preceded by preparatory activities, including feasibility study and general cost estimation. The preliminary project has indentified the most appropriate design solutions. In particular it has defined the qualitative and functional characteristics of the works, the requirements to be met and the specific services to be provided. The proposed solution has been explained, also with regard to the environment and to administrative and technical feasibility. Compositional, dimensional, volumetric, typological, functional and technological features of the work, the time schedule of implementation, with an indication of the maximum duration of different phases: design, approval, contracting, construction and testing, as well as instructions for site preparation.