Evaluation is increasingly important in decision-making processes for the sustainable planning and design of port plans. It acts as a support for plan preparation, for making values, interests and needs explicit, and for exploring the components of the decision-making process itself. Evaluation can be likened to an "implicit tool" that can integrate approaches, methodologies and models, adapting to the many needs revealed during the decision-making process. New sustainability challenges call for new approaches to creating frameworks for the analysis and evaluation of plans and projects that allow the integration of multidimensional goals and values. Utilizing some selected case studies of port plans in six Italian cities, this paper explores how environmental assessment can become a tool for dialog and interaction among different fields of expertise to support dynamic learning processes, knowledge management and the creation of shared choices, using suitable approaches and tools. In this view, Integrated Spatial Assessment (ISA) can be useful in supporting decision-making processes on different scales and institutional levels to stimulate dialog between technical and political evaluations, referring to complex values that are part of conflicting and changing realities in which it has become imperative to operate according to sustainability principles.