TRENCHLESS SOLUTION IN NORFOLK

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Loddon Sewer Rehabilitation scheme

The Loddon Sewer Rehabilitation scheme for Anglian Water was designed to enable the repair of a 300mm diameter rising main that had experienced multiple bursts. The client engaged OnSite to quickly assess the site and provide a suitable solution. OnSite is a leading provider of specialist contracting services including water and wastewater.

Site of special scientific interest

The rising main partly ran through a site of special scientific interest (SSSI) meaning certain activities could not be undertaken without prior consent from Natural England. The land on such sites is protected by law for the conservation of its wildlife and in some cases geology. As a result, an open cut solution to repairing the rising main could not be considered. Another constraint was the difficulty of access to the pipeline.

A site meeting was organised between Anglian Water, OnSite and Claret Civil Engineering (the civils contractor) to discuss possible options and to target the problematic areas of the route. During the meeting, it was suggested that, due to the frequency of failure, any resolution needed to provide a standalone result, excluding the host pipe from the final structure. Additionally, there was a requirement for the internal operating pressure to be no more than 5 bar.

Alongside the existing rising main was a redundant rising main that was installed as a backup pipeline. It was decided that the backup line could be used to manage the rising main flows for the duration of the repair works.

Trenchless pipe rehabilitation

Due to the sensitive nature of the project, it was vitally important that the correct liner material was used. OnSite decided to introduce, for the first time in the UK, the NORDIPIPE TM system, from Austrian based firm NordiTube Technologies SE. The liner is made from a strong and flexible material able to withstand internal pressure and external pressure resulting from hydrostatic, soil and live load scenarios. Other advantages of this technology are the individual lengths up to 300metres and added resistance in case of pressure bumps. A combination of coated felt, glass fibre layers and felt made up the Liner for Loddon rising main.

Characteristics of glass fibre layers

  • Has its own intrinsic strength and stiffness
  • Independent – structural support does not depend on the host pipe
  • It does need close contact with the pipe in order to maximise the final lined pipes cross section and for the ends to be sealed off

Trenchless infographic