AWWA INF52169

The effective planning of water distribution system renewal requires accurate quantification of the structural deterioration of water mains. As typical water distribution systems comprise hundreds and even thousands of buried pipes, direct inspection of all of them is often prohibitively expensive. Identifying water main breakage patterns over time is an effective and inexpensive alternative to measuring the structural deterioration of a water distribution system. Environmental and operational conditions exert stresses on the pipe. Pipe breakage occurs when these stresses exceed its structural resiliency. While the structural deterioration of the pipe is generally considered to be a steady, monotonous process, some of the environmental and operational stresses could be time-dependent, steady or transient. These stresses result in noisy breakage rate data sets that reduce the accuracy of establishing the underlying deterioration (aging) patterns, especially in small data sets. If the cause of these random stresses can be identified and attributed to a measurable phenomenon (e.g., temperatures, precipitation, etc.), their noisy effect can be neutralized to obtain a more accurate pipe deterioration pattern. A method is presented to analyze how breakage rate patterns in water mains are affected by time-dependent factors. The method is versatile enough to consider any number of underlying causes but the solution becomes more complex as the number of causes increases. The method is demonstrated with three case studies that examine the effect of temperature, soil moisture, main replacement rates and cathodic protection rates on pipe breakage patterns. Finding the true deterioration rates of buried water mains will inevitably lead to a more accurate prediction of their useful life, which in turn will lead to a more efficient allocation of resources for water main rehabilitation and renewal. Includes 26 references, figures.