Rehabilitation of 900 m of 8″ and 6″ sections of drinking water main
160 mm PE100 SDR17 PE100 drinking water pipe
An ageing water pipeline reached the end of its service life and needed replacing to prevent further water quality and pressure issues. The asset owner, South East Water and construction firm The Clancy Group engaged Radius Subterra to explore the feasibility of lining the main to restore its structural integrity and avoid disruption.
The cast iron raw water pipeline, which links a borehole to a service reservoir, was not only heavily encrusted with tuberculation, but also, 900 m of the 8” and 6” sections located in Tilford Road and Tower Road in Hindhead, ran under a busy carriageway and through gardens of private properties, where access was difficult, bringing further challenges to this replacement project.
The choice of renovation technique was strongly influenced by the need both to retain the maximum possible flow capacity of the pipeline, whilst at the same time keeping excavation and disruption to a minimum. With the above considerations in mind Radius Subterra’s Rolldown® close-fit polyethylene (PE) lining technique was chosen as the preferred solution.
A ground-breaking no-dig pipeline replacement technique, Rolldown® is used for the renovation of weakened and damaged steel, ductile iron, cast iron, asbestos cement and other pipelines to restore structural integrity and maintain pipe capacity and pressure requirements. It uses a PE pipe as a liner, which once inserted and pressurised, forms a close-fit inside the existing pipework.
PE pipe lengths are butt-fusion welded together into a long string. The pipe string is pushed through sets of specially-designed rollers that reduce the diameter of the PE liner by approximately 10%, which is subsequently retained without the application of any mechanical load. The prepared host main can then be lined with the reduced-diameter pipe by conventional slip-lining techniques. Once inserted, the PE liner pipe is reverted using cold water under pressure to revert it back towards its original diameter, enabling a close fit with the host pipe to be achieved. Compared to other lining techniques, longer lengths of pipe can be inserted in one pull with Rolldown®, making it the ideal solution for the renovation of pipelines crossing roads, rivers, lakes and designated nature sites or for pipework laid in urban areas or congested ground.
Radius Subterra initially explored rehabilitation of these sections of pipeline by using their fast-setting spray-liner, Subcote® FLP. However, the number of excavations needed would have hampered entry to the residents of the private properties, which was required at all times. The location and the length of the 6” section in particular, was the main focus point. It was also critical for South East Water that the 6” section of the pipeline retained maximum capacity. That’s why Radius Subterra established that using Rolldown® to install a PE liner would be the best option. Working in partnership with their partners White Utilities, Radius Subterra used their Rolldown® close-fit lining technology with 160 mm SDR17 polyethylene pipe supplied by Radius Systems to rehabilitate the 6” pipe section.
The PE100 drinking water pipe was supplied in 12 m lengths by Radius Systems. It was butt-fused into one long 150 m length and inserted in one pull into the host, then reverted to its original diameter. For the 8” section, Radius Subterra inserted the 160 mm PE liner using the established slip-lining technique. The pipeline was then tested and commissioned successfully, and finally reconnected to the existing network.
It was estimated that implementation time for the project would be nine weeks, it was however completed a week ahead of schedule.
Steve White, District Manager at The Clancy Group commented: ‘We are really pleased with the outcome of the project, which was undertaken by a team of not only skilled technicians, but also very helpful and hard working.’.
Jeremy Dufour, Project Manager at South East Water added: ‘This project has definitely been a success and on behalf of South East Water, I thank the Radius Subterra team for their work. This scheme was essential to ensuring reliability and longevity of this crucial part of our infrastructure that serves our customers.’