2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference

Assessment Approach to Evaluate the Conditions of Ductile Iron (DI) Water Distribution Pipelines

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Dr. Khalid Kaddoura, AECOM
Mr. Alain Lalonde, Echologics
Mr. Rabia Mady, Cima+ (Presenter)

As any infrastructure component, watermains are prone to deterioration due to ageing and other influencing factors. Although periodic inspections and renewals are needed, many municipalities confront difficulties in preserving all deteriorated assets due to budget constraints. The use of proper and cost-effective condition assessment, part of asset management, methodologies will enhance the allocation of budgets toward sustainable systems.

This paper developed a desktop analysis scheme that is applicable to buried Ductile Iron (DI) watermains to understand the existing condition of watermains. Similar to the Cast Iron watermain approach developed by Rajani & Markar (2000),the methodology relied on calculating the residual factor of safety (FoS) that would enable decision-makers in understanding the current structural conditions of the water linear assets based on field measurements. As part of the study, a Non-Distractive acoustic inspection tool was used to inspect seven kilometers DI watermains to provide information about the average remaining wall thickness of each pipe segment within the seven kilometers of DI pipe segmens.  A comparison approach between the FoS approach and the inspection result were established to understand the difference between the two approaches pipe classification and/or condition grading. After categorizing the FoS outputs into three categories using the K-means clustering and establishing a confusion matrix for Good, Moderate, and Poor, the average accuracy was 81%. Besides, the study established a sensitivity analysis and considered the wall loss categorization of municipalities in Quebec by varying the wall thickness with a variety of operating pressures in the calculation of the residual FoS. As this study assesses existing conditions of watermains, decision-makers are able to prioritize and allocate municipal budgets to avoid catastrophic failure of linear assets