In this article, the authors question the nature and effectiveness of the environmental impact assessment procedure in Québec by analysing some projects submitted by Hydro-Québec. The content of an impact study as required in the by-law is minimal : rather, its content takes shape from the interaction of various actors, through the steps of the procedure but also through learning from project to project. The procedure allows questioning and determination of project components to some extent, but its main emphasis is on designing mitigation and implementation measures. While the stated objective is to test the "social feasibility" of projects, feasibility as such is seldom tackled directly: thus, at a first level, the procedure would be one for the implementation of projects rather than for planning. At a second level, it must be interpreted in light of the paradoxical link between traditional planning and environmental planning.