New Integrated Condition-Assessment Model for Combined Storm-Sewer Systems

Optimal assessment of the overall state of the degradation affecting sewer systems requires consideration of both the hydraulic and the structural aspects. This work identifies a set of 15 factors-pertaining to both degradation aspects-as primary and constituting the framework for hierarchical structuring of the condition states. The relative importance of these factors was determined by the analytic hierarchy process (AHP). The proposed model was successfully applied to assess the current degradation state of the sewer network in Saint-Hyacinthe, Quebec. The relative significance effect, assessing prevalence of either the hydraulic or the structural criteria in the degradation process, was established through sensitivity analysis. The outcome indicates that hydraulic factors have to be integrated in the pipe-deterioration model as well as the structural factors. With a reference case set at w(s) = 0.5 (i.e., structural and hydraulic criteria having the same significance level), results remained conservative most of the time. Even if the AHP technique was already applied in sewers and water mains as shown in the literature, this paper is unique in that the AHP technique is used to combine a large number (fifteen) of structural and hydraulic criteria and subcriteria. The proposed model will enable researchers and municipal engineers to weigh the structural criterion against the hydraulic criterion to achieve adequate intervention that is carefully planned through a flexible tool outlaying a hierarchy of scores reflecting the infrastructure under consideration. DOI: 10.1061/(ASCE)WR.1943-5452.0000217. (C) 2013 American Society of Civil Engineers.