Brenchley Trenchless Trial Lifts Sunken Sewer in Southern Water First

Why the pipe needed lifting

A gravity sewer relies on a steady downward slope to carry wastewater away. At Brenchley, a section of pipe leading to a pumping station had dropped. Water collected in the resulting dip, known as a belly, restricting flow and causing wastewater to back up at a manhole.

The original plan was to excavate and relay 18 metres of pipe. To get excavators into the wooded site, the team would have needed to remove a fence line and fell mature trees. Residents and road users faced a lane closure of around two weeks.

How the trial worked

Over several months, we worked with our supply chain partner to develop a way to lift the pipe from below. On site, small holes were drilled and expanding geopolymer was injected into the ground beneath the dropped section. As the material expanded, it raised the pipe.

Colleagues from Southern Water joined us to see the work first-hand. The team worked off the road and left the trees and fence line in place.

What we learned and what comes next

The trial demonstrated that the material could lift the pipe enough for some of the standing water to drain. Water remained in the dip at the end of the trial, so we’ll review the survey measurements before returning to complete the work.

On our return, we plan to use a camera to record the pipe’s profile before and after each lift. Comparing those measurements will show where the slope has changed and where further adjustment is needed to restore flow.