Subsurface engineering projects with high socio-environmental impacts raise strong controversies among stakeholders, which often affects the projects’ implementation. These controversies originate from a loss of public confidence in the decision-making process, lack of information about new technologies, and the desire of some promoters to avoid conflict. The lack of methodologies to structure each stage of the debate can, in this context, lead to the crystallization of the stakeholders’ positions and to the failure of the project. To promote mutual understanding and constructive exchanges, this article presents a combination of methods based on psychosocial engineering principles to support debate and encourage stakeholders to participate with an openness posture. The method is based on a set of studies conducted as part of the “Social Governance for Subsurface Engineering” project and includes three stages: (1) develop stakeholders’ knowledge so that they are able to participate in the debate with an informed viewpoint; (2) commit stakeholders to participate in the debate by adopting a posture conducive to constructive exchanges; and (3) structure exchanges between stakeholders through the use of cooperative methods facilitating the adoption of an openness posture.