Economic Model for Prioritizing Pipe Replacement Programs

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Courtesy of Weston Solutions, Inc


The condition of public infrastructure has become a common story in the United States media. Numerous newspaper, magazine, and television reports have described the need to upgrade the nation’s aging infrastructure. Estimated costs for these upgrades are staggering, typically in the hundreds of billions if not trillions of dollars. Despite these high estimates, there is no unified funding mechanism in place to finance these needed improvements. Thus, utilities must develop effective and rational plans for upgrading their infrastructure, and then obtain the funds necessary to implement those plans.

Water utilities have already begun to address their infrastructure needs and develop these progressive plans. In general, a typical water utility’s investment in the distribution/transmission system accounts for approximately 80% of all assets. It has been estimated that in the US between $100 and $325 billion will be required over the next 20 years to renew these water distribution systems. Here, the term renew includes both rehabilitation (cleaning and cement lining, for example, or other more innovative techniques for extending the life of the pipe) and replacement of pipe.

Currently, there are no standardized methodologies or tools available to water utilities for developing proactive distribution system renewal programs. Water utility operators, in general, manage and operate distribution systems in a reactive mode to respond to emergency water main leaks or breaks. As water mains age and are impacted by adverse environmental conditions, they become prone to more frequent breaks, leading to increasing disruption of service to customers and public health concerns. Some utilities recognize the need for the proactive renewal of distribution systems, but lack a systematic plan to address these infrastructure needs.

This paper describes the development of a prioritized water main replacement program for the St. Louis County Water Company (the Company). The Company’s infrastructure needs are similar to those facing other water utilities across the country. The Company has taken the initiative to address these problems, with the help of Roy F. Weston, Inc., in an innovative way described here within. The Company needed to develop a detailed replacement program in order to address an ever increasing number of water main breaks in the distribution system. The overall project approach was to compare the cumulative costs of continuing to repair individual pipes over time to the cost of replacement. The resulting computer model provides the utility with a prioritized short-term replacement program and a tool to evaluate and modify the replacement program, as necessary, as it progresses.

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