AWWA ACE58268

The deterioration of water mains is taking its toll on water utilities across the world. It is imperative that this deterioration be accurately quantified in order to implement effective renewal plans for water distribution systems. With hundreds and even thousands of buried pipes, it is often prohibitively expensive to directly inspect every water main in a distribution network. Identifying water main breakage patterns over time is an effective and inexpensive alternative to measuring the structural deterioration of a water distribution system. Breakage rates of water mains are affected by many factors that are pipe-intrinsic, environmental and operational. An effective water main renewal plan must consider future breakage rates and to forecast breakage rates one must identify the "true" background deterioration rates of the water mains, and quantify the impact of various environmental factors as well as operational strategies on future breakage rates. The National Research Council of Canada is developing a prototype computer application to help model the deterioration rates of water mains and subsequently plan their renewal. It considers time-dependent factors such as temperature (in the form of freezing index), soil moisture (in the form of rainfall deficit), main replacement rates and cathodic protection (CP) strategies, including hotspot CP as well as systematic retrofit CP. Non-time dependent (or static) factors such as pipe characteristics and soil type are considered through water main grouping. The background aging rates of water mains enable the projection of their future breakage rates. In addition, the impact of operational strategies such as schedules of cathodic protection (both hotspot and retrofit) and pipe replacement can be superimposed on this background aging. Subsequently, the life cycle costs of various scenarios of operational strategies can be evaluated and fine-tuned to achieve maximum efficiency in resource allocation. Further, because the impact of time-dependent climatic conditions is quantified as well, planners can obtain climate forecasts from the weather bureau (no more that 2-4 years recommended) to evaluate expected year to year variations in the breakage rates. Includes 6 references, figures.