Challenging Issues in Modeling Deterioration of Combined Sewers

The understanding of sewer deterioration mechanisms helps asset managers in developing deterioration models to estimate whether sewers have deteriorated sufficiently for likely collapses. While an accurate deterioration model is a significant component of an infrastructure management system, research in the area of deterioration modeling of sewer systems in the United States is still in its infancy. Research in the area of highways has matured and has become the basis for studies in sewer systems. Modeling the deterioration of highway systems involves methods that vary in complexity from Markov-chains-based models to econometric models. This paper presents the use of Markov-chains-based models in conjunction with nonlinear optimization for extending infrastructure management modeling to sewer systems. Modeling the structural condition of sewers using the Markov-chains-based model has its own challenges. This paper discusses the problems encountered in developing deterioration models for sewer management systems and suggests some possible improvements for deterioration modeling of combined sewer systems.