Project Appreciation and Objectives
Rising mains failures are typically responsible for about a third of all pollution incidents relating to pumping stations; there were over 800 such failures in 2006/7. Previous WRc work identified that often there was evidence of a defect in the rising main prior to its failure and so an inspection method that could locate such defects would significantly reduce the number of failures.
Several of the standard methods for water main and sewer inspection have been tried without very much success. Trials have, however, identified that an adaptation of the Sahara® leak detection technique can successfully deliver a probe up to 800m from the point of entry in a sewer rising main.
A new approach was needed, which both recognised the specific characteristics of rising mains, and built on the experience gained with other methods. This project reviewed a range of techniques that had the capacity to reliably and cost-effectively identify known defect types in sewer rising mains that could lead to failure.
Benefits to Clients
- Avoid major burst events and the associated expensive repercussions.
- Reduce risk of prosecution both by reducing pollution incidents from emergency overflow discharges and demonstrating to the regulator that procedures are in place to manage the risk.
- Reduce disruption and cost of repair from rising mains failures by a proactive approach.
- Ability to plan full or partial mains replacement based on information on the condition of the main either in advance of failure or following an initial failure.
Two phases are proposed as follows:
- Phase 1 - review potential techniques and bench scale trials, where necessary, to identify their ability to identify the expected defect types.
- Phase 2 - trial the best techniques in a series of pilot scale trials on short lengths of pipe at WRc.
Following completion of Phase 1 the Liaison Group would review the results to ensure that work on Phase 2 would commence only if there was a reasonable likelihood of success. Assuming that the project successfully identifies one or more suitable techniques then WRc would seek further funding to perform further field trials to implement and refine the successful techniques.
- Interim report on the feasibility of different techniques.
- Report on pilot scale testing.
- An implementation road map.
Related WRc Work
- Risk calculation tool for rising mains, CP053, 2001-2002
- Manual for the design, installation, operation and maintenance of sewer rising mains CP284, 2005-2006.
- WRc's Sahara® Leak Location system which pinpoints leaks in large diameter pipes, including pressurised sewer mains