North Walsham Case Study
Comprehensive Brief
In April/May 2023, Radius Subterra embarked on discussions with Anglian Water’s IMR division to address issues with a 10″ PVC Potable Water pipeline, plagued by periodic significant leaks. The pipeline, situated in East Anglia amidst a mature wood, presented challenges due to limited access caused by trees and badger sets.
Traditional solutions like slip-lining were deemed inadequate, given the insufficient bore of a 225mm OD PE pipe to manage the required water throughput. To surmount these obstacles, Subterra proposed a tailored approach, the Rolldown methodology. This innovative technique involved reducing the OD of a 250mm PE100 pipe by 10%, enabling insertion into the host PVC main, then restoring it to its original size as a close-fit liner.
By adopting this method, the bore of the pipe was maximized, necessitating minimal excavations for launch/reception of sections and replacement of valves and services along the main. Radius Systems, as the AWS (Anglian Water Services) Framework PE pipe supplier, manufactured 13.5m sticks of the specified 250mm SDR21 PE100 8bar-rated pipe, minimising on-site welds.
Initially intended to line a 1200m section, the project’s scope expanded to 1500m upon the discovery of an IP gas main crossing the lower extent, ensuring no disruptive activity near the gas main.
Challenges
Challenging terrain and complex operational requirements demanded an unconventional approach. Radius Subterra tackled these obstacles with precision and expertise, providing a seamless solution where traditional methods fell short.
Problem #1: Limited access due to mature wood and environmental constraints.
Problem #2: Inadequate bore size for traditional slip-lining solutions.
Solution: Radius Systems’ 250mm SDR21 8bar-rated PE100 pipe installed using the Rolldown method, maximising bore size while minimising excavation, reinstatement, and carbon footprint.
What is Rolldown and Sliplining + benefits (Laymans terms)
Originally the proposed SDR to be used was SDR 26, however given the required bore would be met with an SDR21 PE main, it was agreed to proceed with slightly thicker pipe.
While traditional methods like Sliplining have their place, they wouldn’t have been suitable for the Anglian Water project. Here’s why:
Reduced Flow Rate: Sliplining often involves inserting a smaller diameter pipe inside the existing one. In this case, a smaller pipe wouldn’t have maintained the necessary flow rate for critical water delivery.
Limited Structural Reinforcement: Traditional Sliplining primarily creates a protective layer but doesn’t necessarily strengthen the original pipe itself. In the case of leaks due to potential weakness in the existing PVC main, this wouldn’t have addressed the root cause.
Precise Fit, Optimal Flow: Success Where Traditional Methods Fail
Addressing persistent leaks in a challenging environment, Anglian Water’s IMR division turned to Radius Subterra’s innovative rolldown pipeline repair technique. A 10″ PVC potable water pipeline in East Anglia, plagued by leaks and surrounded by mature woodland and delicate badger sets, posed significant challenges. Traditional slip-lining would have drastically reduced the internal diameter, compromising flow rates and requiring extensive excavations.
The Radius Subterra Rolldown Solution: Problem-Solving Beyond the Obvious
Maximised Bore: Radius Systems 250mm SDR21 PE100 8bar-rated pipe employs a “rolldown” technique for a secure, close-fitting connection within the host main. This minimises the annular space (gap between pipes), preserving a large internal diameter even within the original 10″ line.
Efficiency in Challenging Terrain: The rolldown process reduces the need for extensive excavations, ideal for areas with limited access or ecological sensitivities. This will also mean less carbon footprint due to the reduced number of excavations and re-instatement (Reduced Carbon Statistic to follow from Anglian Water). Traditional methods would have had to excavate 1,5km for the process along with reinstatement. It will be more expensive and would have a significantly higher carbon footprint.
Customised Pipe Design: Radius Systems, as Anglian Water Services’ preferred supplier, manufactured 13.5m PE100 pipe sticks tailored to the project, streamlining the repair process.
Anglian Water Case Study: Proof of Success at a glance
Challenge: Limited access, insufficient bore with slip-lining, need to protect sensitive environments.
Solution: Radius Subterra’s Rolldown method with 250mm SDR21 PE100 pipe maximised bore, minimised excavation, and reduced environmental impact.
Adaptive Approach: The project’s scope expanded successfully by 300m due to Rolldown’s flexibility and speed, even seamlessly navigating an unexpected gas main crossing.
Benefits of Minimal Bore Loss:
Maintains Flow Rate: Optimal flow for critical water delivery.
Cost-Effective Repairs: Reduced material needs and minimised excavation lower costs.
Long-Term Efficiency: Minimises potential for build-up, ensuring long-term pipeline health.
The Anglian Water project demonstrates how Radius Subterra’s can assist Utilities in their complex projects by capitalising on the thermoplastic properties of PE, adding a new dimension to plastic pipelines and the possibilities for their uses. where other methods fall short. It provides a secure, efficient, and ecologically sensitive way to repair and rehabilitate critical water infrastructure.
Q&A (Additional Technical Information provided by Garvan Kelly)
Why was the 225m OD inadequate?
The ID of 225mm PE100 SDR21 is c. 203mm – this would not allow the required flow of water for the main. Using a rolled and reverted 250mm SDR21 pipe within the PVC pipe gave an ID of 226mm, providing the crucial extra volume needed to supply the homes in the area.
Explain why traditional methods wouldn’t work with the constraints.
The traditional open cut and replacement methodology wasn’t suitable in these circumstances given the risk to the mature woodland through which the pipe passed, as well as the potential disturbance to wildlife in the area. Also, for the above reason, standard slip-lining with a smaller pipe was ruled out as insufficient in terms of usable bore within main.
Explain how roll down works
Rolldown involves pushing strings of welded PE pipe through a set of rollers that concentrically reduce the pipe by around 10%. The pipe remains stable in this rolled state and is then inserted into the host main. Once in place, the PE pipe is sealed and filled with water, then reverted via hydrostatic pressure back to its original OD, or as close as it is permitted to within the legacy host main.
Explain why roll down is such a specialist job
The combination of equipment used and the knowledge and experience of the characteristics of the PE pipe utilised in the process is something that is unique to Radius.
Explain why Radius Subterra in particular rather than any other contractor
As above
What is the CTA at the end
Subterra can assist Utilities in their complex projects by capitalising on the thermoplastic properties of PE, adding a new dimension to plastic pipelines and the possibilities for their uses.