The council will probe storm overflows and sewage pollution in Portsmouth's coastal waters

Southern Water’s handling of sewage pollution will come under fresh scrutiny because a review into the city’s water quality has been launched.

Portsmouth City Council has launched an investigation into sewage pollution and water quality, inviting evidence from Southern Water, campaign groups and academics.

The review, being carried out by the council’s traffic, environment and community safety panel, will examine the impact of sewage discharges into local waters, the measures being taken to reduce them and whether further investment is needed.

Storm overflows remain key pollution source

Storm sewage overflows remain the biggest source of pollution affecting Portsmouth and Langstone harbours.

Many UK sewer systems carry both rainwater and sewage through the same pipes. During periods of heavy rainfall, storm overflows release excess wastewater into rivers or the sea to prevent flooding. While intended for emergency use, their increasing frequency has contributed to rising sewage pollution.

A report by the council’s assistant director of regulatory services, Richard Lee, summarises the latest Food Standards Agency sanitary surveys for Portsmouth Harbour (2022) and Langstone Harbour (2023), which assess pollution risks affecting shellfish waters.

For Portsmouth Harbour, the main pollution risks are storm overflows, urban surface water runoff, bird droppings and, to a lesser extent, waste discharged from recreational boats. Heavy rainfall can cause spikes in bacteria levels, with some shellfish harvesting areas remaining closed because of persistent contamination.

Although no major sewage treatment works discharge directly into Langstone Harbour following the diversion of treated wastewater from Budds Farm offshore in 2001, storm overflows during heavy rain continue to pose a significant pollution risk, particularly in the northern parts of the harbour.

Southern Water under scrutiny

As the region’s wastewater provider, Southern Water is responsible for treating and discharging wastewater.

The company has previously faced regulatory action, receiving a £126 million penalty in 2019 for serious sewerage failures and a £90 million fine in 2021 for polluting rivers and coastal waters. This week Southern was fined more than £7m after dumping sewage illegally off the Kent coast between 2019 and 2021.

The council’s review will examine the measures Southern Water is taking to reduce storm overflows, with the panel expected to present its findings and concerns to the company at the conclusion of the investigation.

A spokesperson for Southern Water said: “We welcome Portsmouth City Council’s review and the opportunity to discuss the work that is already underway to reduce storm overflows. We’re more than a year into a £170m investment programme across Portsmouth Harbour, which is already beginning to make a difference.

“This work includes upgrading our network, disconnecting homes and roof drainage from the foul sewer system, installing sustainable drainage schemes to reduce rainwater entering sewers, and upgrading pumping stations and treatment works. At our Budds Farm Wastewater Treatment Works, we’re increasing treatment capacity and building a new storm tank to provide additional storage during wet weather. Together, these improvements will help reduce storm overflows and create cleaner rivers and seas.”

Academics invited to contribute

The University of Portsmouth is among the organisations invited to contribute evidence to the review.

A university spokesperson said colleagues “would be happy to contribute to this important review” and highlighted the work of Professor Alex Ford, who has a “broad expertise in marine biology, ecotoxicology and parasitology” with a particular interest in “the effects of contaminants on crustaceans and their parasites”.

Other stakeholders, including campaign groups such as Surfers Against Sewage and local swimming groups, have also been invited to take part in the review.