This study focuses on the public participation process that was implemented in the United States by the National Environmental Protection Act, which  , since the 1970s, has aimed to reconcile environmental concerns and the exploitation of natural resources. The conflict surrounding the open pit mining project in Rosemont, Arizona has continued for ten years due to this constraining legislative background. This study is therefore particularly revealing of the contradictions posed by these two differing approaches. It analyzes the stakeholders’ discourses, which were produced within institutional forums of participation in the case of the Rosemont mine proposal. Our results show that this kind of public participation reaches a socio-economically large and diverse public. However, the public is strongly controlled by interest groups. Therefore, the participation process can be defined in terms of “quantity” rather than of “quality.” This article reveals that analyzing public participation helps to assess environmental controversies.