What we did
Sections of sewer were repaired, replaced and renewed to increase capacity and efficiency, helping to reduce the risk of spills and pollution. Following a redesign of the scheme, modern sewer lining technology was used wherever possible to minimise disruption to the town.
Work that took place
Sewer improvement works in Modbury were carried out between January and September 2024.
The main phase of work took place from early January to February 2024. Sewer repairs, lining and associated works were completed across the town. Some sections of lining were delayed due to weather conditions and were completed later in the year.
The final lining works were completed in September 2024, bringing the project to completion.
How the work was carried out
Where possible, repairs were carried out from inside the existing sewer pipes. This meant the pipes could be fixed without digging up the road, reducing disruption in the town.
In areas where this was not suitable due to the age or condition of the sewers, more traditional excavation methods were used. This included digging down to the pipes, constructing new manholes where needed, and restoring the affected areas once the work was completed.
The completed improvements have strengthened the resilience and long‑term performance of Modbury’s sewer network.
Here's a bit more about how the lining process works:
1. Preparation
Before lining starts, the sewer is diverted using an overland pipe. The empty section is then cleaned and inspected with a CCTV camera. Pipes connecting into the sewer are accurately mapped so that the connections can be re-opened once the sewer has been lined.
2. Inserting the liner
A sliding foil is pulled through the pipe before the liner to reduce the amount of friction between the liner and the sewer. Then the liner sock is inserted using a 5-tonne winch. Air is pumped into the liner to expand it.
3. Curing
The liner is infused with polyester resin which is then dried by passing a UV light through it. The light reacts with the resin, curing it in place. Depending on the size of the pipe, the robot can dry between 0.5m and 1.5m per minute.
4. Reopening the connecting sewers
Once the liner is cured, flow through the sewer is restored. Then, the connecting sewers can be reopened. Our teams use a robot to do that too. The position of the connections are logged in the robots computer, and the robot cuts holes in the liner at exactly the right location.
5. The sewer is repaired
This method of repairing sewers means that the work can be completed much faster and with less disruption than traditional ‘open cut’ excavation. On average, 100 metres of pipe with a 225mm diameter can be repaired in just 1 day. And a liner like this is expected to last for decades.