Southern Water unveils £1.5bn CSO plan

Southern Water will spend £1.5 billion over the next decade to tackle spills from combined sewer overflows (CSOs).

The water company said it will spend the money between 2025 and 2035 to meet government-set targets decades ahead of the legally binding 2050 obligation.

Southern’s plan involves reducing discharges from c.1,000 CSOs below the target of 10 spills or fewer annually. This will bring 75% of high priority CSOs in line with government targets by 2035. Around half the CSO points in Southern’s region already meet the requirements.

The company will invest £700 million in the next asset management period (AMP8) to focus on bathing waters, coastal areas where shellfish live and environmentally sensitive locations.

It has launched an interactive map of all the CSOs across the region to inform customers and stakeholders of average spills of each point as well as the causes of problems, estimated cost and schedule to resolve.

The work, the company said, would lower spills by 3,000 each year. The next phase in AMP9 will focus on cutting spills by an average of 8,000 annually ahead of hitting 100% of targets by 2050.

Chief executive, Lawrence Gosden, explained the need to get to the root cause of storm overflows across the region. He said: “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.”

Preliminary work to slow volumes of water from entering the sewer networks on the Isle of Wight by giving water butts to residences close to a CSO has yielded a 70% reduction in spills.

Work is overseen by the Clean Rivers an Seas task force comprising environmental scientists and engineers who are developing how nature-based solutions can be used to stop sewers being overwhelmed. This will include rain gardens, wetlands, adding trees and installing water butts as well as optimising the current infrastructure.