Annual storm overflow discharge figures published

Wessex Water has published new figures on the number of storm overflow discharges near beaches and rivers in its region.

The UK water company provides overflow discharge alerts 365 days a year – not just during the summer bathing season – and with complete coverage around coasts. It supplies information that feeds into the Surfers Against Sewage SaferSeas app as well as local councils.

Data published in the company’s 2021 Coast and Rivers Watch report shows that 45 overflows operated between October 2020 and September 2021, with most occurring outside of the bathing season (15 May to 30 September) and releasing screened, highly diluted sewage into the sea or rivers to protect homes from flooding during heavy rainfall events when the sewerage network became overwhelmed due to the numerous roofs and highways connected to sewers.

The report shows all overflow notifications between October 2020 and September 2021 and specifically during this year’s bathing season, which will be assessed and audited by the Environment Agency.

Matt Wheeldon, Wessex Water’s Director of Assets and Compliance, said: “Most of these overflows discharge well out to sea or into rivers upstream and away of the bathing water, releasing screened and highly diluted sewage that is unlikely to have much impact on bathing water quality.

“Indeed, the majority of beaches in our region attain very high water quality classifications after sampling by the Environment Agency.

“However, we notify all overflow discharges on a precautionary basis because there is no real-time data that can help advise people of how water quality varies each day. However, our Warleigh Weir project is trialling sensors where the data, enhanced by AI algorithms will hopefully change that, providing actual real-time water quality notifications.”

Storm overflows have always been part of the sewerage network in the UK because the majority of properties were built with only one pipe draining them – carrying both rainwater and foul sewage. This historical infrastructure construction approach is common across Europe and nations such as the USA and Australia.

A need for change

Wessex Water said that it is calling on Government to help with addressing this legacy infrastructure issue by amending existing legislation so housing developers and property owners can’t connect surface water to sewers that carry foul water.

Furthermore, it is calling on Government for the powers to separate drains at property level and powers to discharge this rainwater as close to where it lands (such as via garden infiltration systems or soakaways) or straight into watercourses – solutions that cannot be easily delivered under current rules.

It is also calling on the industry’s economic regulator Ofwat to prioritise more investment rather than just focusing on bill reductions. Wessex Water has recently invested £181 million to improve nearly 600 storm overflows across its region since 2000, with a further £150 million being invested in improvements between 2020 and 2025.

Mr Wheeldon said: “Our aim should be for no negative impact to arise from storm overflows, including in carbon terms when solutions are weighed up.

“Upgrading the entire sewerage system is only feasible with massive and long-term roadworks disruption and significant investment. At the current rate of allowed investment, removing all overflows nationally would take several centuries. This is too slow.

“We totally support the Government’s ambition to reduce harm from overflows, but this will only happen with a realistic plan and targeted programme of improvement.”

Around 80% of Wessex Water’s storm overflows are monitored, rising to 100% coverage by 2023. All can be seen on an online map, along with their measured performance (number of discharges) in recent years and information about whether they contribute to any reasons why rivers do not meet good ecological status.

Read the 2021 Coast and Rivers Watch report.