Reporting thresholds
Published 20 May 2025
Applies to England and Wales
© Crown copyright 2025
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This publication is available at https://www.gov.uk/government/publications/guidelines-for-statutory-drainage-and-wastewater-management-plans-dwmps/reporting-thresholds
When you are preparing and publishing your DWMPs, in addition to meeting the performance indicators, you should adhere to the standardised reporting thresholds provided here as an additional reported output.
This ensures consistency in how you are reporting risk at each planning horizon over various spatial scales. It also enables you and stakeholders to better understand any spatial and temporal overlaps of risk, for example storm overflow spills and flooding.
1. Spatial scales
Asset based reporting (for example for storm overflows – not to miss ‘worst served’)
- level 1: company level
- level 2: river catchment or local authority level
- level 3: sewerage catchments level
2. Threshold description
- 0 green: low risk of not meeting performance indicator
- 1 amber: moderate risk of not meeting performance indicator
- 2 red: high risk of not meeting performance indicator
If a level 3 catchment falls within threshold ‘0’, you should still explore investment need as part of your asset management planning to avoid ignoring individual risk or worst served customers, for example individual property at sewer flood risk, a frequently spilling overflow.
The list below presents the only performance indicators where standardised reporting thresholds should apply and be presented as an output with your draft DWMP, and used as part of any ongoing engagement on scale of risk with stakeholders.
- storm overflow performance
- emergency overflow performance
- treatment works compliance
- treatment works compliance flow to full treatment FFT
- treatment works compliance dry weather flow DWF
- serious pollution incidents
- total pollution incidents
Descriptions of the performance indicators provided in the document How to form, publish and maintain your drainage and wastewater management plan (DWMP) under section 10.
| Performance indicator | Thresholds and reported scale |
|---|---|
| Storm overflow performance (for England) | Scale: Reported for every storm overflow for each planning (and reporting) horizon, upscaled to Level 3, Level 2 + Level 1 Thresholds on spills per annum for each overflow: 0 = less than, or equal to, 10 spills at Level 3 if 1 overflow is greater than 10 spills but less than 20 = threshold 1 1 = greater than 10 spills but less than 20 at Level 3 if 1 overflow greater than, or equal to, 20 spills = threshold 2 2 = greater than, or equal to, 20 spills Catchment thresholds: Total no. of spills / total no. of overflows |
| Emergency overflow performance | Scale: Reported at every emergency overflow for each planning (and reporting) horizon, upscaled to Level 3, Level 2 + Level 1 Thresholds on spills per annum for each overflow: 0 = 0 1 = 1 2 = 2 or more |
| Treatment works compliance (numeric) | Scale: Level 3, Level 2 + Level 1 Thresholds: To align with latest EPA methodology |
| Treatment works compliance (descriptive at numeric sites) | Scale: Level 3, Level 2 + Level 1 Thresholds: To align with latest EPA methodology |
| Total pollution incidents | Scale: reported at Level 3, Level 2 + Level 1 Thresholds: normalised incidents (by 10,000km sewer) To align with latest EPA methodology |
| Serious pollution incidents | Scale: reported at Level 3, Level 2 + Level 1 Thresholds: To align with latest EPA methodology |
| Treatment works compliance: flow (FFT and DWF) | Scale: reported at Level 3, Level 2 + Level 1 Thresholds: To align with latest EPA methodology |