Southern Water Targets an 80% Reduction in Sewer Overflows

By?Mark Coates MCIHT , International Director of Public Policy and Advocacy,?Bentley Systems

Water and sewage treatment utilities are now seeing?the environment as a benefit to progress

During the Victorian era, when much of the United Kingdom’s water infrastructure was first built, engineering was king.

If there was a question, the answer was usually to build better, and build bigger.

Nature took a back seat.

Times have changed, and so has the water industry. Now nature is seen not as an obstacle to progress, but as a key?part of the solution in providing a clean, secure, and sustainable service.

And thinking smarter is prized above thinking bigger – with the collection, sharing, and analysis of data playing an?increasingly vital role.

Just a little bit of smart thinking can make a huge difference.

Southern Water , for example, has calculated that preventing water from roads and roofs going into the system will have a significant impact on reducing storm overflow spillages (CSO). This is because only a minority of CSOs account for approaching half of spills.

The aim is to reduce the peak levels of water so the system is not overwhelmed – just as government’s spent the early months of the COVID-19 pandemic trying to “flatten the curve” of cases so that hospital admissions were spread out over a more manageable time-frame.

Some relatively simple interventions – swales alongside roads,?or smart butts that monitor rainfall and release contained water at safe times – can help achieve those goals.

In the long term, the aim is to make sure environmental considerations?around water supply and sewage are factored into new and existing developments removing hard surfaces from the built environment such as impermeable driveways, concrete play areas, paving over gardens, and extensions which create more roof run off. That requires close cooperation with external partners - whether local authorities or developers - as well as an understanding of water network that is both panoramic in scope and forensic in detail.

It is vital to know not just what the network looks like, but how it functions in different scenarios: to think of the network as an ecosystem rather than a static system of pipes.

Data is crucial - not just the ability to collect it and share it with partner organisations, but to analyse it in ways that yield genuine insight. Skills in these areas are now at a premium in the industry.

Keeping CSO spillages to a minimum is only one environmental objective. The modern water customer doesn't just expect reliable, clean, and relatively cheap water. Their concerns are far broader. That is particularly?true of the places covered by a company such as Southern Water. Hampshire, the isle of Wight, Kent, and Sussex all have not only highly-prized rural environments, but thriving tourism industries based around coastal areas, too. Protecting and enhancing those are an economic as well as an environmental concern.

If protecting nature is a significant challenge, working with nature provides at least some solutions. Sustainable drainage systems can, for example, directly run off to natural features or environments where it is beneficial. Nature seals can reduce the amount of wasted water. Farmers can be educated to make simple changes to their practices, which dramatically affect the amount of run off - cultivating against rather than with the slope, for example.?

The existing built environment is another matter. Roads, for example, represent a major challenge - they cannot simply be removed and replaced with alternatives with better drainage. Southern Water's approach is more targeted: identify the biggest problems and look for ways of retrofitting drainage solutions that make a real impact.

There is a thread of pragmatism and conservation running through a lot of physical work that southern is doing. While some things can be ripped out and built anew, such a Victorian approach can be impractical and have an excessive impact on the environment. CSOs, for example, may be decades old, but they still fulfill an important function that protects public health as well as property. When there are smart solutions to stop them overflowing, tearing them up and replacing them with a segregated system starts to seem not just unnecessary but wasteful.

Southern currently has five separate pathfinders where they are trailing new and innovative approaches. Each covers an area with distinct challenges, and in each, the approach is tailored to local circumstances. Deal in Kent has a specific challenge with surface water flooding; Margate requires a large, highly engineered urban drainage system. For the Isle of Wight, Southern Water is working on a whole-island system that aims to cut outfalls into the sea and rivers by up to 80% for 90% of the island. No two challenges are exactly alike, and therefore neither are the optimal solutions. What matters are results - and that is a sentiment even the Victorians would agree with.