Risk-Based and Condition-Based Assessment Framework for Large Diameter Sewers

Implementation of advanced and fit-for-purpose asset management strategies requires careful and thoughtful assessment of the physical conditions of buried, large diameter pipelines used within wastewater collection and conveyance systems. Knowledge of the structural integrity and hydraulic performance of these critical assets is therefore crucial. It provides guidance to municipalities and utilities on (1) prioritizing repair and replacement projects; (2) avoiding costly and disruptive emergency repairs; and (3) minimizing public and environmental impacts. The current work reports the development of a systematic methodology for conducting a condition assessment, for rehabilitation/replacement design, of large diameter sanitary and stormwater sewers. The methodology employs a risk-based asset management strategy coupled with risk management and condition assessment practices for prioritization of infrastructure assets based on criticality and direct and indirect impact of their potential failure on ‘Triple Bottom Line’. The proposed framework is based on sound engineering concepts and field experience. It is practical and simple to follow, and it has been successfully demonstrated to establish asset management and renewal/rehabilitation prioritization plans for different sewer rehabilitation projects across North America. The case study provided in this work demonstrated that integrating risk-based assessment approach into the conventional condition-based approach will not only capture the current structural integrity and hydraulic performance of these critical assets, but will, most importantly, account for the direct and indirect impact of their potential failure on ‘Triple Bottom Line’. This will help municipalities stretch their limited rehabilitation budgets and narrow the ‘infrastructure gap’ by enabling a ‘just-in-time’ investment strategy.