The Department for Environment, Food and Rural Affairs (DEFRA) launched the storm overflows discharge reduction plan in 2022, heralding tough new targets for water companies. Four years on, the strategy is now firmly in motion, with progress being reviewed against its long-term aim to crack down on sewage spills resulting from overflows caused by heavy rainfall.

What targets does the storm overflows discharge reduction plan set?

The plan requires water companies to deliver their largest ever environmental infrastructure investment – a £56 billion capital investment over 25 years – through a long-term programme to tackle storm sewage discharges by 2050. This frontloads action in particularly important and sensitive areas, including designated bathing waters and high-priority ecological sites.

The key targets are:

  • By 2035: to significantly improve storm overflows discharging into or near designated bathing waters
  • By 2045: to ensure storm overflows discharging into or near high-priority sites, such as chalk streams, do not cause local adverse ecological impact
  • By 2050: to ensure no storm overflow discharges more than an average of 10 times per year over a 10-year period, or causes adverse ecological harm

The SODRP has been embedded into:

  • Drainage and wastewater management plans
  • The Water Industry National Environment Programme
  • The price review process

Furthermore, updates to the National Planning Policy Framework now encourage the use of sustainable drainage systems (SuDS) in all new developments with drainage impacts or in flood risk areas. The Government is considering further reforms to enable ‘upstream’ pre-pipe interventions, including on rainwater management, sewer misuse and SuDS.

How are water companies impacted by the storm overflows discharge reduction plan?

The targets within the plan require water companies to take measures such as increasing the capacity of their networks and treating sewage before it’s discharged to protect public health and prevent pollution. They also have to massively reduce all discharges. Failure to meet these targets could see them face substantial fines or having to return money to customers.

The plan marked the first time water companies were required to act to address the discharges, and it continues to sit alongside ongoing work by the government, the Environment Agency and the regulator Ofwat to increase water companies’ performance, monitoring and accountability.

The plan sets out staged targets for water companies, focused on reducing the frequency and impact of storm overflow discharges over time:

  1. By 2035, water companies must improve all storm overflows discharging into or near every designated bathing water; and improve 75% of overflows discharging to high-priority nature sites
  2. By 2050, this will apply to all remaining storm overflows covered by the targets, regardless of location

The plan will be reviewed again in 2027 to consider the next steps, taking account of innovation and efficiencies.

The storm overflows discharge reduction plan also sets out that water companies are required to publish discharge information in near real-time, as well as commit to tackling the root causes of the issue by taking steps to improve surface water drainage.

In addition, the plan sets out broader expectations for the water industry to ensure infrastructure keeps pace with increasing external pressures, such as urban growth and climate change, to ensure water supplies remain clean and secure for the future.

At the time of the plan’s launch, former Environment Secretary George Eustice said:

“This is the first government to take action to end the environmental damage caused by sewage spills. We will require water companies to protect everyone who uses our water for recreation and ensure storm overflows pose no threat to the environment.

“Water companies will need to invest to stop unacceptable sewage spills so our rivers and coastlines can have greater protection than ever before.”

Measures have also been brought forward in the Environment Act to tackle sewage discharges, including the requirement for greater transparency from water companies on their storm overflow data.

What else is the Government doing to tackle sewage pollution?

Alongside this push, in 2021 the regulators – the Environment Agency and Ofwat – launched the largest criminal and civil investigations into water company sewage discharges ever, at over 2,200 wastewater treatment works (WWTWs).

To date, the investigation team has reviewed over 35,000 exhibits and produced over 1,050 statements from evidence handling, review and analysis.

The environmental offences under investigation are criminal offences, meaning it is a criminal investigation. Therefore, it must produce evidence to high standards that satisfy the criminal burden of proof, beyond reasonable doubt. The investigation team has now moved to the next phase and is gathering statements from external witnesses.

The Government also introduced new powers under the Water (Special Measures) Act 2025, including giving Ofwat the ability to ban unfair bonuses for water company executives. This also enabled the Environment Agency to impose financial penalties using a lower, civil standard of proof, leading to the creation of new automatic penalties.

The Environment Agency now has the resources it needs to monitor storm overflows, investigate incidents and act when companies fail to meet the required standards. It achieved full coverage of event duration monitoring (EDM) across all storm overflows in December 2023, meaning near real-time public reporting of storm overflow discharges.

How are water companies performing against these new targets?

The Government publishes an annual progress report on the implementation of the plan, giving a clearer picture of how water companies are performing four years after it was first launched.

The 2025 report states that the reduction of local adverse ecological impact from storm overflow discharges improved from 22.6% in 2022 to 2023 to 33.7% in 2024 to 2025. Preliminary modelling also indicates progress against the 2050 rainfall target, with the average number of spills per overflow declining since 2022. Water companies invested over £3.1 billion during the 2020 to 2025 period (Price Review 19) to improve storm overflows.

However, water companies are not currently on track to meet the 2035 public health target, which focuses on reducing discharges of harmful pathogens near designated bathing waters. Only 44.8% of relevant overflows met the required spill standards in 2024, down from 55.3% in 2022.

“Most companies exceeded or achieved their individual commitments to reduce storm overflow discharges, although 2 companies failed to meet their targets,” the report says.

In addition, the Thames Tideway Tunnel was completed in May 2025, providing an estimated 95% reduction in sewage pollution entering the Thames.

Water companies have allocated more than £10 billion for the 2025 to 2030 cycle (Price Review 24) to upgrade approximately 2,500 overflows in England. This investment is prioritised at the most sensitive locations, including designated bathing waters and ecologically sensitive sites. Price Review 24 (PR24) includes a target to reduce average spills per storm overflow by 45% by 2029 compared to 2021 levels.

Are concrete pipes the solution to water companies achieving the storm overflows discharge reduction plan targets?

With water companies now under pressure to upgrade approximately 2,500 storm overflows by 2030, the need for proven, long-life drainage infrastructure has become increasingly urgent.

Made in the UK, Marshalls concrete flexible drainage pipes are designed to support this kind of long-term network upgrade. With a 120-year design life, they offer a durable, readily available solution for underground drainage, helping to safely store and convey wastewater and surface runoff through the network.

Concrete pipes can also be fitted with flow control and separation devices, supporting the movement and management of drainage during periods of heavy rainfall. This makes them particularly relevant as water companies work to increase network capacity, reduce discharge frequency and protect sensitive locations such as bathing waters and ecological sites.

Maintenance is another key consideration. Some flooding incidents occur because of blockages caused by inappropriate substances, such as wet wipes and fats, oils and greases, with water companies in England and Wales dealing with up to 300,000 sewer blockages a year, costing up to £100 million annually to clear them (Water UK, 2019). High-pressure water jetting is frequently used for blockage clearance, so pipeline strength and jetting resistance matter.

Following the publication of a new Manual for Drain & Sewer Cleaning and amendments to standards, including EN 14654-3 and BS 5911, as well as industry standards including the Design & Construction Guide adoption code, the MPA Precast Drainage Association carried out jetting resistance tests with both concrete and plastic drainage pipes, where concrete pipes proved the most successful.

Conforming to the exacting quality standards of the BSI and stringent industry specifications developed within the public domain, concrete pipes address the needs of water companies in terms of protection against pipeline ingress and leakage, as well as reducing maintenance costs.

With the plan now four years in and progress under review, could concrete prove the approved, readily available answer to upgrading the networks and meeting the targets of the storm overflow discharge reduction plan? We believe it will.

  • Storm overflows

  • Combined Sewer Overflow (CSO)

  • Water

Written By

Pete Tamblin

With 20 years’ experience across infrastructure and highway engineering, Pete Tamblin has delivered projects ranging from small housing developments to complex, multi‑million‑pound schemes.

Read Pete's full profile here.