Ofwat has announced proposals which, following a short consultation, would allow Southern Water to further accelerate its work in driving down the use of storm overflows, enabling an ambitious two-year programme to expand its nature-based and engineering solutions.

Following a number of successful pilot schemes, the water company has proposed to Ofwat the roll out of a range of innovative projects to stop and slow surface and groundwater reaching our sewer system, across three areas within its region:

• Isle of Wight
• Kent’s North and East coasts
• The Harbours and South Downs areas of West Sussex and Hampshire

These proposals would see Southern Water invest up to a further £50 million between now and spring 2025 - the utility said it has clear plans around how it will start the region-wide scaled-up approach.

As well as improving the existing network, and ensuring all sewer pipes are connected correctly, much of this funding will be spent on ‘greening’ communities by using nature to slow the flow, including:

• installing raingarden planters
• introducing swales and tree-pits to urban areas
• embarking upon new wetland schemes in the countryside

Storm overflows occur when the normal sewer levels rise due to surface and groundwater entering them – usually during or after a period of rainfall. The mechanism acts as a release valve, into the environment, so homes and communities are not flooded when pressure on the network builds. However, Southern Water says it agrees with customers that they are not acceptable.

Lawrence Gosden, Southern Water CEO, said:

“Reducing the use of storm overflows and their impact on water quality is a priority for me. To do this we have to get to the root of the problem and reduce the amount of surface water entering the sewerage system.

“The opportunity to accelerate our rollout of the innovative and sustainable drainage solutions we have already piloted, on a much larger scale in three specific areas, is a positive opportunity. These tactics have proven to help reduce volumes of surface water, stop sewage spills, and bring nature back to communities.

“This comes ahead of a much wider investment of billions of pounds over the coming decades, marking the beginning of the end for storm overflows.”

Work on the Isle of Wight will build on activity already taking place in Gurnard and Cowes, before moving onto Fishbourne, Wotton, Yarmouth and Freshwater. In Havenstreet, the company has already trialled the use of slow draining water butts, where two thirds of its customers took part in the scheme. Controlling the amount of water reaching the ground has resulted in a 70% reduction in local storm overflow activity.

Similar activity in Kent will expand on efforts ongoing in Deal, Margate and Whitstable – the company is hoping to achieve at least a 20 per cent reduction in total storm overflows in these areas by spring 2025. The team will expand on initial studies in nearby Fairlight in East Sussex, tackling legacy surface water flooding in the area.

Elsewhere, the focus in the Harbours and South Downs area is on tackling storm overflows driven by pressurised groundwater inundating both private and public sewers. The programme will involve sealing off sewers, including private stretches, and the rollout of wetlands in at least four sites by 2025. Benefits will also include biodiversity net gain and carbon reduction.