Storm overflow assessment framework 2025
How to assess the performance of and scope out improvements to storm overflows under Urban Waste Water Treatment Regulations requirements.
Applies to England
Documents
Details
This 2025 framework gives guidance for water companies in England. It replaces the storm overflow assessment framework published in 2018. It reflects:
- policy developments
- lessons learned from the 2018 framework
- the greater event duration monitoring (EDM) and data availability
- the Storm Overflow Discharge Reduction Plan
The framework references, links and is informed by other guidance and regulations.
Updates to this page
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The SOAF guidance has been updated to incorporate changes following the initial implementation of the guidance to improve clarity and consistency in its use. Updates include clarification on how spill data should be used when calculating the Valid Year Average (VYA), including how years with incomplete EDM data are treated and when a VYA reset may be applied following improvements. Updated the stage 2 water quality impact assessment for the UWWTR SOAF process and flowchart. Added a new appendix defining Population Equivalent and provided further clarification on the BTKNEEC cost-benefit assessment guidance.
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First published.
Update history
2026-08-18 10:00
The SOAF guidance has been updated to incorporate changes following the initial implementation of the guidance to improve clarity and consistency in its use. Updates include clarification on how spill data should be used when calculating the Valid Year Average (VYA), including how years with incomplete EDM data are treated and when a VYA reset may be applied following improvements. Updated the stage 2 water quality impact assessment for the UWWTR SOAF process and flowchart. Added a new appendix defining Population Equivalent and provided further clarification on the BTKNEEC cost-benefit assessment guidance.
2025-03-24 10:00
First published.