SEMAPA is designing and planning the development of Paris Rive Gauche. It is having part of the constructions built, particularly the public spaces, while coordinating implementation of the entire project. SEMAPA manages the process of acquiring land from its owners. The principal owner is the SNCF with which an agreement has been signed. As soon as a developer is identified, SEMAPA purchases the land from the SNCF for a price indexed to the average sale price. After purchasing building rights, the developer chooses an architect to design a building in accordance with the specifications drawn up by the coordinating town-planning architect in liaison with SEMAPA.

On the financial level, in view of the variation between expenditure (acquisition of land and development work) and revenues (sale of building rights), SEMAPA has taken out two loans for €259,163,000 (FF 1.7bn) in 1992 and €213,429,000 (FF 1.4bn) in 1996, which represent less than 15% of the total cost of the operation.