Southern Water’s ambitious £170 million programme to reduce storm overflows in Portsmouth Harbour is entering a new phase, with major works now beginning in Fareham and Havant.

The expansion marks a significant milestone in the company’s wider £1.5 billion Clean Rivers and Seas Plan, aimed at improving water quality across the South East.

In Portsmouth, extensive sewer surveys have paved the way for targeted engineering interventions. One key example is in Stamshaw, where investigations revealed a bottleneck in the sewer system at Stanley Road.

The solution is one of many taking shape as part of the wider £170 million scheme across Portsmouth Harbour and Gosport.

To ease pressure and reduce the risk of flooding during heavy rainfall, Southern Water and contractor Clancy are now diverting the sewer flow. This will allow stormwater to reach Budds Farm treatment works more efficiently, helping prevent overflows and protect local homes and businesses.

In Fareham, teams are identifying and disconnecting downpipes that wrongly feed into the foul water sewer, redirecting them to the surface water system. This simple fix significantly reduces the volume of water entering combined sewers, lowering the risk of overflows.

Across both towns, Southern Water will also be:

Installing sustainable drainage systems (SuDS) such as raingardens, swales, and permeable surfaces

Rolling out hundreds of smart and slow-draining water butts

Upgrading pumping stations and treatment works

Tackling roof runoff by disconnecting misconnected downpipes

Steven Reed from Southern Water’s Clean Rivers and Seas Task Force, said:

“Expanding into Fareham and Havant is a major step forward in our mission to reduce storm overflows and protect our coastal waters. Every downpipe we disconnect and every SuDS feature we install helps us build a more resilient sewer network for the future and more importantly helps improve water quality in Portsmouth Harbour for generations to come.”

Southern Water is also working with Portsmouth City Council to deliver roadside SuDS, building on successful partnerships with Isle of Wight Council and Kent County Council.