Multiattribute Utility Theory Deployment in Sewer Defects Assessment

Abstract

Assessing the condition of sewer pipelines is a backbone process to plan for rehabilitation and maintenance work. The closed circuit-television (CCTV) method is the widely adopted method to record the inner condition of the pipelines, which is then interpreted by a practitioner. This paper presents a condition assessment framework for sewer pipelines using multiattribute utility theory (MAUT). The condition assessment model utilizes MAUT to generate several utility functions for four sewer pipeline defects: deformation, settled deposits, infiltration, and surface damage. A proposed surface damage evaluation methodology is presented to assess the surface damage defect for three different materials: reinforced concrete, vitrified clay, and ductile iron. An aggregated condition index is computed based on the relative importance weights of the studied defects and tested with several rounding types. The rounding up type produced the optimum results, and the values were compared with the Concordia Sewer Protocol (CSP) suggested methodology yielding an average difference between the two approaches of 3.33%; and a mean absolute error (MAE) of 0.33. A sensitivity analysis was then carried out to check the impact of the change of the relative importance weights on the overall index. The proposed methodology aims to provide information for asset managers about the severity of some sewer defects existing in sewer pipelines. In addition, it reinforces their plans for rehabilitation and maintenance by suggesting the existing condition of the sewer pipelines.