When an ageing water pipeline reached the end of its service life and needed replacing to prevent further water quality and pressure issues, 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 900m of the 8” and 6” sections located in Tilford Road and Tower Road in Hindhead, ran under a busy carriageway and through private gardens where access was difficult, bringing further challenges to this replacement project.

Tony Pipe, Project Manager at Radius Subterra explained: ‘These particular pipeline sections were in fact ideal to replace using a no-dig technique. We initially explored rehabilitation using our fast-setting spray-liner, Subcote® FLP, however, the number of excavations needed would have hampered entry to properties, which was required at all times. The location and the length of the 6” section in particular, was the main focus point. What’s more, it was critical for South East Water that the 6” section of the pipeline retained maximum capacity. That’s why we established that using Rolldown® to install a PE liner would be the best option.’ Working in partnership with partners White Utilities, Radius Subterra used their Rolldown® close-fit lining technology with 160mm SDR17 polyethylene pipe supplied by Radius Systems to rehabilitate the 6” pipe section.

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. 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.

Supplied in 12m lengths, Radius Systems PE100 pipe was butt-fused into one long 150m length and inserted in one pull into the host, then reverted to its original diameter. For the 8” section, Radius Subterra inserted the 160mm PE liner using the established slip-lining technique. The pipeline was then tested and commissioned successfully, and finally reconnected to the existing network.

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.”

The project which started in July with an estimated nine week to carry out, was completed a week ahead of schedule.