Defra reports mixed progress on storm spill plan

(by Karma Loveday)

A statutory report by Defra to Parliament on the progress of the Storm Overflow Discharge Reduction Plan (SODPR) shows mixed results in the first three years.

Between August 2022 when the plan was published (it was extended in 2023) until August 2025, progress against the targets was as follows: 

• The target for storm overflows discharging into or near ‘high priority sites’ (HPS) such as chalk streams not to cause local adverse ecological impact by 2045 – performance improved, with 22.6% of storm overflows near HPS in 2022/23 climbing to 33.7% in 2024/5 — meeting a proxy measure of no more than ten spills a year.

• The target to significantly improve discharges near designated bathing waters by 2035 –performance deteriorated, with 44.8% of relevant overflows meeting the required spill standards in 2024, down from 55.3% in 2022.

• That no overflow should discharge above an average of 10 times, over a 10-year period, per year by 2050 – performance improved; the 27.6% of storm overflows spilling 10 times a year or fewer in 2022/23 increased to 42.9% in 2024/25 across a 3-year dataset. Modelling indicated that, even after adjusting for rainfall and seasonality, the average number of spills per overflow has declined since 2022.

Elsewhere, the report charted progress on other developments, including a £3.1bn spend by the water industry on storm overflows in 2020-25; new Special Measures powers for regulators; full coverage of event duration monitoring (EDM) across all storm overflows since December 2023; and embedding the SODRP into other water planning frameworks.

Looking ahead, Defra said more than £10bn has been allocated in the 2025 to 2030 cycle 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. PR24 included a target to reduce average spills per storm overflow by 45% by 2029 compared to 2021 levels.

The next statutory progress report is due in 2030. 

• After announcing back in July that it was to conclude its investigation into the regulation of combined sewer overflows by Defra, the Environment Agency and Ofwat, the Office for Environmental Protection (OEP) has now published detailed reports setting out its findings. 

The OEP noted steps taken by the authorities in response to the its earlier recommendations.

These included:

• Defra has replaced outdated guidance with a new policy and guidance document that better reflects the legal duties of sewerage undertakers.

• Ofwat has revised its enforcement guidance and taken enforcement action against several water companies.  

• The Environment Agency has updated its Storm Overflow Assessment Framework and is progressing with plans to modernise permits and introduce spill limits.

However, the report also included additional recommendations to further strengthen regulation and prevent reoccurrence of the failures identified. It said:  

Defra should:  

1. Establish a process to monitor implementation of the new Storm Overflows Guidance and incorporate this into the five-yearly statutory review of the SODRP.  

2. Monitor the implementation of the SODRP requirements through Environment Agency permitting.  

3. Together with the Environment Agency and Ofwat, review the Memorandum of Understanding (MoU) in line with the SODRP review cycle and any reforms arising from the Independent Water Commission.

The Environment Agency should:

1. Update its document ‘Water companies: environmental permits for storm overflows and emergency overflows’ 13 September 2018 to properly and adequately set out the revised approach to regulating combined sewer overflows (CSOs) following updates to the Storms Overflow Assessment Framework (SOAF), spill frequency threshold permitting and Defra’s 1997 Guidance.  

2. Review the SOAF 2025 every five years, or earlier if appropriate.  

3. Together with Defra and Ofwat, review the MoU 12 months after the date of signature, or earlier if required.

4. Establish a robust and transparent methodology for consistent data collection and reporting. This framework should enable clear tracking of progress for each CSO and provide structured summaries at each stage of the SOAF process. It must also support accurate reporting of Best Technical Knowledge Not Entailing Excessive Cost (BTKNEEC) assessment outcomes, ensuring that data is both reliable and comparable across submissions.

5. Use better data to regularly monitor and review the proportion of CSOs that are not progressed for improvement following BTKNEEC assessments.  

6. Strengthen its regulatory oversight of BTKNEEC assessments and their outcomes. Greater scrutiny is needed to ensure that, in cases where CSOs are not improved, the concept of excessive costs is being correctly applied through robust cost-benefit analysis.

Ofwat (or any subsequent authority) should:

1. Together with Defra and the Environment Agency, review the storm overflows MoU 12 months after the date of signature, or earlier if required.

2. Collaborate with the Environment Agency on the above data collection and reporting methodology.