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Southern Water unveils £1.5bn investment in Clean Rivers and Seas Plan to cut spills by 8,000 a year by 2035

Between 2025 – 2035 we’re planning to invest a record £1.5 billion to get to the root cause of storm overflows.

Southern Water has today published its Clean Rivers and Seas Plan, outlining proposals, underpinned by £1.5 billion investment between 2025-2035, to get to the root cause of storm overflows across our region. 

Storm overflows are part of the design of our combined sewer network, which captures both rainwater and wastewater. These emergency outlets are the last line of defence to stop homes and communities flooding when the sewer system becomes overwhelmed by large volumes of rain or groundwater entering the network – something we’re seeing more frequently due to erratic weather caused by climate change. 

Out of almost 1,000 storm overflows in our region, 50% of these are already hitting the government’s 2050 targets, releasing 10 times or less a year. This new plan will be the blueprint for how we’ll address the remaining overflows. By 2035, 75% of our high priority overflows will be meeting government targets, reducing spills by an average of 8,000 a year, and by 2050 100% will meet these targets.    

The first phase of this plan will be delivered between 2025 and 2030 and will see an investment of £700 million to focus on areas such as shellfish and bathing waters, and environmentally sensitive sites. This means by 2030, spills will reduce by 3,000 a year.  

The results are already astonishing – a staggering 70% reduction in spills at the nearest storm outfall on the Isle of Wight after we introduced water butts to most of the houses on a nearby street. These ‘Pathfinder’ projects show that we’re on the right track.    

The ‘Clean Rivers and Seas Task Force’ are a team of environmental scientists, engineers, and industry experts who have been leading on putting the plan together and testing nature-based solutions across the South-East. These solutions work in harmony with our natural environment, slowing the volume of rainwater going into the combined sewer, and making infrastructure improvements to increase our capacity. This includes rain gardens, wetlands, tree planting schemes, installing water butts in densely urbanised areas, and optimising our existing infrastructure.  

We understand our customers want to see change now. We face tough choices in striking a balance between environmental protection and minimising the impact on bills for customers. Although customers will notice the impact reflected in their bills, the average water bill is one of the lowest household bills. Some of the work will take a long time, but we are committed to investing the time and expertise to go as quickly as possible. This is why we are asking our customers for their feedback on our Clean Rivers and Seas Plan here so they can tell us if they agree with how we are prioritising overflows in our region before we agree it with Ofwat, our regulator.   

CEO of Southern Water, Lawrence Gosden, said:      

“I’ve heard our customers’ concerns, and we take our impact on the environment seriously. We have a long-term strategy to 2050 that will restore and protect our regions’ rivers and coastal habitats and a large part of that will be to get to the root cause of storm overflows.  

“We cannot simply switch storm overflows off. But by implementing this Clean Rivers and Seas Plan and tackling the root cause, slowing the flow of rainwater going into the combined sewer, whilst increasing capacity of our network, we can reduce their use.”  

“Collaboration is key, and we cannot achieve the results needed alone. That is why we are calling on our customers and local authorities to work with us and adopt solutions like water butts or sustainable drainage systems, to channel rainwater safely and slowly back into the environment. Together, we can go faster and further, protecting our communities and our environment.”