Innovative repair to tricky triple sewer collapse

About the project

Danaher & Walsh APS was faced with a challenging sewer collapse in a residential area of Stamford, Lincolnshire.

The collapsed sewer ran along the length of a narrow access road, which is used by the residents of around forty houses.

Key details

Anglian Water
Project value
August 2018

Key aims and challenges

The 170m length of 225mm foul sewer presented a 50m long section of damaged pipework, including three separate collapses. What's more, the drain is at a depth of 3.6m under the narrow lane. 

Not only is the access road used constantly by residents, but excavation of the pipe would have necessitated demolition of numerous garden walls, driveways, outbuildings and even house extensions. Two road closures would also have been required to allow for safe working.

How did we do?

Working with Anglian Water's IMR Collections team, Danaher & Walsh APS carried out a full survey of the site before designing a tailor-made, no-dig solution for the troublesome sewer.

The first stage involved cleaning the pipe up to the point of the first collapse. Because of the precarious state of the damaged section of pipe, extra care was required so as to prevent complete collapse of the sewer.

In order to avoid this, a custom-designed 6m long packer was procured from a specialist manufacturer in Germany in order to 'bridge' the fragile sections. The patches were installed at high pressure, using a protective jean to prevent over-expansion and full collapse of the pipework.

The second collapse was further complicated by a disintegrated lateral connection and a void that had appeared around the collapse. Using a remotely-controlled cutting robot, the fragments of destroyed pipe were removed from the drain. Several patches were installed to line the damaged pipework and a 'top hat' joint was used to form the lateral connection. 

After the patches were fully cured, a small hole was drilled from surface level into the void. Resin was then injected into the cavity until full.

The third collapse was completed in a similar manner, using the custom packer to bridge the shattered pipework. In total, the project involved the installation of 65m of 225mm patches and the reconnection of eight laterals. 

Local residents were delighted that the complex works were successfully completed without any incursion onto their property at all and without any impact on their ability to access their driveways and gardens. 

Additionally, this method has saved the client around £100,000 versus the traditional excavation method.