Public decisions on plans and programs which are likely to have significant effects on the environment are increasingly the focus of important socio-technical controversies. These controversies are invariably charged with both epistemic and normative uncertainties. The spreading of controversies which is one of the main traits of the “risk society” is particularly salient in the field of environmental issues. In this paper we explore decision making devices (namely instruments and procedures) and their role in dealing with conflicts between (incommensurable) values as they arise in the process of public decision-making concerning the sustainability of projects with major impact on environment. In a Case Study, the Alqueva Multipurpose Project, the applied public decision support devices of the monistic and pluralistic approaches to incommensurability and value conflicts are identified. Points of strength and limitations are analyzed. A critical analysis of both the relevance of these devices in shaping public decision processes and the pros and cons of the specific way in which they help in dealing with uncertainty are also considered.

--