This research aims to identify, through the Strategic Field of Action Theory, the rationalities encompassed in the environmental assessment of the UHE Tijuco Alto Hydropower Plant (Ribeira River Watershed, Brazil) and to characterize the strategies of the stakeholders in the decision-making process. An interpretative description based on documents and content analysis of the environmental assessment process was adopted as our research method. The evaluation of such documents demonstrates that the strategic actions designed by the skilled actor - in this case, the Vale do Ribeira Movement of People Threatened by Dams - was fundamental to unveil the rationality shared by local communities. This fact has changed the dominant order, which prioritizes the logic of development and often results in the release of projects that affect or violate human rights.