The Government has published a plan to work with water companies and regulators to stop the harm caused by raw sewage from storm overflows.

The storm overflows discharge reduction plan was published on 26 August, as a requirement of the Environment Act 2021 and sets policy for England only.

This Insight covers the main stages in developing the plan, its key targets and stakeholder reaction to it.

What are storm overflows?

In most of the UK, sewage from buildings is collected with water from roads, roofs, and other hard surfaces. During wet weather, the sewer network can be overwhelmed. To prevent sewer flooding, untreated sewage is discharged into waterways or the sea, via storm overflows, or combined sewer overflows.

While these mainly occur when the sewage system cannot cope with the excessive loads, misuse of the sewer system by disposing of items such as wet wipes or fat, oil and grease in drains can also add to the problem.

Risk to the environment and human health

The raw sewage released from storm overflows can contain high levels of pathogens, such as viruses and bacteria which pose a risk to human health. In August, swimmers were warned to stay away from beaches after heavy rain caused storm overflow discharges at numerous locations around the country.

Raw sewage may also contain organic pollutants (poisonous chemical substances), microplastics, pharmaceuticals, nutrients, and heavy metals, as well as litter and waste that is flushed down toilets. This can alter water chemistry and result in ecological harm and environmental damage.

Are storm overflow discharges legal?

Under certain conditions, yes. In England, the Environment Agency issues permits for individual storm overflows which set conditions for when they can be used and how they should be monitored and maintained.

There are around 15,000 storm overflows in England, their locations and discharge data are available to view on an interactive map from The Rivers Trust.

Storm overflows reduction plan

The Environment Act 2021 received Royal Assent on 9 November 2021. It imposed “a new duty on government to produce a statutory plan to reduce discharges from storm overflows and their adverse impact, and report to Parliament on progress”.


From 31 Mar 2022 to 12 May 2022, Defra ran a consultation on the storm overflow discharge reduction plan. It sought views how ambitious the plan was, which contained three headline targets for the environment, public health and reducing storm overflows.

Respondents were asked to what extent they agreed or disagreed with the level of ambition of the individual targets, as well as the overall ambition of the plan. They were also asked whether they would be willing to pay more for their monthly water bill for water companies to tackle sewage discharges.

The consultation received 21,831 responses. 59% of respondents felt the targets set out in the consultation did not address the key issues caused by storm overflows, while 46% said they would pay more in their water bills specifically to reduce the impact of sewage discharges.

The Government response to the consultation was published on 26 August, alongside the plan.

What’s in the plan?

The plan contains actions for water companies, the Government and the public to help reduce the impact of storm overflow discharges. The annexes contain further information on the Government’s legislative action, a feasibility study for getting rid of all storm overflows and a map of storm overflow investigation and improvements for 2020-2025.

The plan says:

  • by 2035, water companies will have to improve all storm overflows discharging into or near every designated bathing water; and improve 75% of overflows discharging into high priority nature sites
  • by 2050, this will apply to all remaining storm overflows covered by our targets, regardless of location

Under the plan, overflows that are causing the most harm will be addressed first, and it will be reviewed in 2027 to see where it can go further.

Stakeholder response

A Government press release, called the plan “the most significant investment and delivery programme ever undertaken by water companies to protect people and the environment”.

Chair of the Environmental Audit Committee, Phillip Dunne, issued a statement welcoming the increased investment committed by the plan. He also said the fact that “100% of overflows will have monitors installed by next year” was good news. However, he said it was “crucial that the data provided by these devices is actively assessed by the Environment Agency and Ofwat, and that firm action is taken immediately if the data demonstrates that permit conditions have been breached”.

The Rivers Trust was less positive in its assessment, reporting it was “appalled” the plan has “not taken into account the thousands of responses to the draft consultation which called for much more ambitious targets”. It also said the Government has stopped engaging with the Storm Overflows Taskforce, suggesting it was not “given the results of the consultation, nor invited to advise further on how the plan could have been strengthened”.

What happens next?

Under the Environment Act 2021, the Government must produce a report in 2025 on how the plan is being implemented and the effect of any progress. Reports will continue to be published every five years.

Further reading

About the author: Dominic Carver is a researcher at the House of Commons Library, specialising in water, the environment, and climate change.

Image: Discharge of sewage into a river by aquatarkus, Adobe Stock #300243119, Extended Licence

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