Optimizing small water main renewal using nondestructive examinations

Without good pipe-condition data, water main renewal cannot be optimized. Poor information about the integrity and life expectancy of water mains results in three basic asset management errors: (1) Comparatively strong mains are often discarded, because they are perceived to be weak. (2) Renewal of some mains occurs too late, resulting in repairs that were avoidable. (3) Rehabilitation methods are often inappropriately applied, either wasting money and producing an inferior product, or failing to use the residual strength of the host main and spending too much In-pipe nondestructive examination (NDE) tools have existed for many years, but these tools are seldom used for small-diameter mains, partly because they are considered too expensive. Many utilities would rather invest in new pipe than in testing old pipe. A large part of the cost of an in-pipe NDE assessment entails inserting and extracting these devices within an operating water system. Moreover, when these NDE tools are used, no guidelines exist for interpreting and applying the data. Instead of using NDE tools, the conditions of mains are usually inferred from indirect data: break history, age, soil conditions, and limited examinations of the pipes. Two Water Research Foundation (WaterRF) projects are underway, aimed at practical applications of current NDE technology on small water mains. Project 4471 proposes to use NDE in a nondisruptive manner to "sample" pipe in a system, then apply the information to infer the condition of similar pipes. Project 4473 goes a step further, proposing to combine the assessment, engineering, and rehabilitation of water mains into a single product delivery. This presentation will discuss the findings and recommendations of the research performed to date, including the results of side-by-side applications of several technologies along a main in Los Angeles.