Solving the problem

During heavy rainfall, homes in and around Long Close in Chippenham were susceptible to sewer flooding, caused by the high volume of water entering the system that carries both foul water from people's homes and rainwater runoff from buildings and surfaces.

This in turn could also lead to nearby storm overflows operating automatically, releasing water that hadn’t yet gone through the treatment process at a nearby water recycling centre back into the River Avon.

Our solution

From summer 2024, our team set about adding extra capacity to the sewer network to prevent the system from being overwhelmed and potentially spilling over on to nearby properties.

In a six-month project, a 10-metre-deep storage tank was sunk below ground on land off Long Close. Capable of holding an additional 250,000 litres of water, the tank holds the water back from the sewer system during storms and later releases it for onward travel to a water recycling centre for treatment.

In nearby streets, including London Road, Black Cross and Long Close itself, more than 200 metres of gravity sewer and nearly 300 metres of rising main were also upgraded and built to add capacity to the network.

Project manager Paul Delves explained: “By building this additional storage, we can help to ensure the sewer network’s ability to withstand the arrival of large volumes of water in a short space of time, such as during a heavy storm.

“The tank is able to hold an additional 250,000 litres of water back from the network to ensure the threat of the system becoming overwhelmed and causing flooding to nearby homes is diminished.

“This stormwater combines in the sewer with the foul water from homes and businesses and can also cause overflows to operate, but by retaining it in the tank, it can be returned to the sewer later, prior to being piped to a water recycling centre for treatment.’’

Working with the community

While the tank was built on land just off local roads, the construction of sewers within nearby streets meant our team spent a lot of time speaking with local customers and businesses before beginning the project.

As well as holding a community drop-in session to speak to local people directly about the scheme, they wrote to nearly 1,000 customers and businesses about it.

Working closely with Wiltshire Council, the on-road work was also timed to coincide with the school summer holidays to try to keep disruption to a minimum as much as possible.

Our team also stepped in to help local residents who did not have off-road parking with space to park their vehicles in the forecourt of a nearby business while the work was being carried out in London Road.

And the road on Black Cross was also improved by the team with updated resurfacing once we had completed that section of the work.

What else are we doing?

We’ve carried out other work to install storage tanks in Wiltshire, including in Bradford on Avon and Warminster. Further along the River Avon, we’ve also invested in projects in Bath, Saltford and Hanham.

We are proposing our largest ever investment in water and sewerage services to improve the health of rivers, reduce pollution and create around 2,000 extra jobs across the region, as part of a £3.5 billion package between 2025 and 2030.

Our business plan, which includes £400 million of investment towards reducing discharges from storm overflows through a programme of work that will include nature-boosting wetland creation, was being scrutinised for final decision at the end of 2024 by industry regulators.