Transmission Main and Plastic Pipe Leak Detection Using Advanced Correlation Technology: Case Studies

Interest in both condition assessment and leak detection on large diameter transmission mains is starting to increase as more and more utilities are recognizing the risk and need to plan financially for the maintenance of these critical pipes. With an increasing recognition of the importance of leakage from transmission mains, technologies have been developed to allow utilities to effectively survey their transmission mains for leakage. Until recently, most of these technologies involved inserting hydrophones [water microphones] directly into the water flow of the pipe and allowing this flow to carry them down the pipe. Recent advances in correlation technology have allowed a nonintrusive approach to be taken in finding leaks on large diameter transmission means. This paper will outline the experience from a project undertaken by East Bay Municipal Utility District (EBMUD), to evaluate two insertion technologies and a correlation technology. A final 65 mile survey project was undertaken using the correlation technology. This paper will outline the results of that survey and the challenges and lessons learned in undertaking a major correlation survey of transmission mains.