Failure Assessment Model to Prioritize Pipe Replacement in Water Utility Asset Management

The condition of a water distribution system has strong correlations with community health and economic development. However, studies indicate an urgent need to upgrade the nation's aging and deteriorating distribution systems if they are to continue to provide customers with reliable and safe water supplies. In response to this need, water utilities are applying various performance measurement initiatives including pipeline asset management. A key component of this process is condition assessment of each individual pipeline in order to identify failure-prone pipes and prioritize their renewal. However, the below ground location of pipes combined with lack of standard guidelines or tools to assist in assessment makes pipeline assessment and renewal decisions difficult. In this research, a pipe failure assessment model was developed to assist water utilities with their pipe renewal decisions. A conceptual model was created from a review of case studies, theories and asset management tools with careful consideration of the distinct properties of buried infrastructure and unique operating and maintenance characteristics of the industry. The model consists of several modules (components) written in Visual Basic for Application (VBA) within a Microsoft Excel platform. Excel was selected due to its commercial availability and the use of VBA user-forms simplifies the data entry and analysis features of the program. Rather than requiring extensive field data to determine the cause of breaks, the model's failure prediction and Multicriteria Decision Analysis (MCDA) modules use pipe inventory and break data compiled from the utility's existing operation and maintenance records. Recognizing that pipe renewal decisions are based on risk avoidance as well as on failure probabilities, a unique feature of the model is a consequence module so the decision maker can compare "what-if" infrastructure investment scenarios. The model was refined, through collaboration of water utility professionals. By drawing on the knowledge and experience of these experts, the review process added several features that facilitate the model's use and its responsiveness to the industry 's needs. Initial evaluations from the participating utilities indicate that the pipe failure assessment model will enhance the industry's ability to prioritize pipe renewal decisions and improve their return on investment. Utility personnel indicated that the model's use of routine pipeline operation and maintenance records, combined with its consequence modeling features, addresses the data limitations and risk avoidance characteristics of the industry in a way that is intuitive and understandable to utility staff. Utility personnel also commented that the model adds knowledge and transparency to the decision process, which is critical in an environment in which decisions will have to withstand scrutiny from various interest groups. Lastly, the investigation illustrates the need for better inventory and break data since this data plays such an important role in buried infrastructure planning programs. This paper was presented at the 8th Annual Water Distribution Systems Analysis Symposium which was held with the generous support of Awwa Research Foundation (AwwaRF).