AWWA JAW68262

Many large-diameter cast-iron water pipelines do not have sufficient historical failure data to enable water authorities to confidently predict failure rates. Yet when these mains fail, the costs, both direct and indirect, can be extensive. This study was undertaken to develop an alternative approach for predicting failure and scheduling replacement. The methodology presented here combines asset condition with a physical probabilistic failure model to determine the expected lifetime of a large-diameter cast-iron pipeline. Net present-value calculations are used to determine the timing of both future inspections and replacement of the entire pipeline. A case study presented in the article provides insight into how this methodology can be applied to a drinking water distribution system. This modeling approach allows asset managers to maximize the usefulness of expensive inspection data and has the potential for improving the management of large-diameter water mains, a challenge that is compounded by an aging asset base and limited budgets. Utilities can apply these findings to help minimize the costs and consequences of failures in large-diameter cast-iron mains. Includes 25 references, table, figures.