Asset management (inspection, maintenance and repair or replacement) of infrastructures represents a complex multidimensional problem and constitutes a topical subject for many cities (constrained budget, environmental requirements, risk mitigation …). In this paper, we developed an innovative approach to sewer system management. The proposed approach is based on a multicriteria decision analysis (MCDA) which includes a degradation model considering uncertainties. The resulting tool, called AGORA, enables to assess a sewage system based on a set of technical, social, economic and environmental criteria, whereas considering uncertainties, and to compare different management strategies. The used probability multicriteria framework allows to consider different kinds of operational actions, and notably inspection (gain of information), and to have a rich vision on the system at different time horizon. AGORA is applied to a semi-virtual network.