The thesis in question deals with the analysis of the impacts of the installation of the Simplício Hydroelectric Plant and its social, environmental and economic implications experienced by the population living in the municipality of Sapucaia, state of Rio de Janeiro, as it is the host city of the enterprise, as well as the surrounding areas. We started to investigate, assuming that the implantation of a Hydroelectric Plant, drives an important turn in the local development process, and this aspect, directly interferes in the dynamics of the life of the resident population. Therefore, we seek to know which listening mechanisms were put in place to guarantee popular participation at the time of the project s implementation, and what relationship has been established up to the present day with citizens, in guaranteeing a democratic practice and social participation, considering that the impacts promoted in the lives of the affected subjects are numerous, due to the economic, social, environmental, cultural, political changes, among others in the local reality. The study, in addition to the continuous documentary and bibliographic research, was based on a qualitative investigation that allows a better understanding and explanation of the dynamics of social relations, thereby bringing the researcher closer to the investigated reality. As data collection, questionnaires were used with the elected subjects and involved with the research object. The theoretical framework of the study, was based on the critical perspective that allowed analysis, interpretation and description of the data, considering that both the economic, social and environmental aspects present from the hydroelectric enterprise are due to the capitalist strategy, which contributes to the dismantling and retrogression of democratic conquests, with the elimination of instances of social control and incipient means of popular participation, elements that were present and impacted the investigated reality.