Assessment model of water main conditions

One of the greatest challenges facing municipal engineers is the condition assessment of buried infrastructure assets. It is a mandatory process to establish and employ management strategies for these assets. Condition assessment of water mains is challenging compared to other infrastructure assets because they are typically underground, operated under pressure, and mostly they are inaccessible. To assess the condition of water mains, current research considers physical, environmental, and operational factors and their effect on different types of water mains. A condition assessment model, using the analytic hierarchy process (AHP), is developed in order to set up rehabilitation priority for water mains. Various factors are incorporated in the developed model, such as physical (pipe type, size, age, breakage rate), environmental (Cathodic protection, ground water level, soil type, surface type, and road type), and operational (Hazen-Williams factor, operational pressure). Data, which are collected from municipal engineers who are experts in water system, include pair-wise comparison matrices among factors and their sub-factors. The AHP procedure is applied to these pair-wise comparison matrices in order to generate the relative weights of each factor on a scale out of 1.0. A model is developed to determine the condition of water main based on the AHP results. Each factor weight represents the relative importance of this factor among other factors that affect water main condition. Results show that pipe age has the highest relative contribution factor among others (20.95%); then pipe material (17.49%); however, the third factor is the breakage rate (13.13%). On the other hand, the least factor is type of service (2.85%). The developed model will assist municipal expertise to prioritise pipe inspection and rehabilitation planning for their existing water mains.