The Westerville water distribution system was installed in the 1950s and consists of 205 miles of predominantly ductile iron and cast-iron pipes. A break rate that began a steady acceleration in 2006 caused the city to proactively identify and replace poor performing pipes to maintain reliability.
The city of Westerville chose not to rely on industry standard values for predicting pipe life because these values vary and can lead to inaccurate pipe break predictions. Instead, the city leveraged its pipe attribute data, empirical watermain break data, and information on pipe criticality to identify the riskiest pipes. Pipe and break data were imported into an asset management platform specifically designed to predict pipe failures called infraSOFT.
The software guides users through quality control steps to verify and improve data quality. InfraSOFT can predict year-by-year probability of a break for every pipe by using the Linear-Extended Yule Process with Weibull survival curves and Markov chain modeling of the progression of pipe deterioration. Predicted break data was coupled with consequence of failure data, which was generated based on each pipe’s size, proximity to roads, water, structures, and service to critical customers. This resulted in a quantitative understanding of risk.
With a list of pipes prioritized by risk, the city evaluated replacement investment levels and chose an affordable annual expenditure that will stabilize the break rate. Replacements were coordinated with other upcoming city street and utility projects to minimize disruption and costs. Proactive watermain replacement is underway with the expectations of reduced breaks and associated impacts, providing customers with a more reliable drinking water supply. The number of breaks in the system will now stay at or near current levels for the next 15 years instead of doubling in number.