Water and sewerage companies in England: EPA metric guide for 2023
Published 23 July 2024
Applies to England
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The Environment Agency introduced the Environmental Performance Assessment (EPA) in 2011. It is a tool to compare performance between the 9 water and sewerage companies (called water companies in this report) and across years. Every 5 years we review the EPA metrics, aligning with the 5 year Asset Management Plan (AMP) investment cycles for water companies to make improvements and meet our expectations. In October 2017 we set out our performance expectations for 2020 to 2025 in the Water Industry Strategic Environmental Requirements (WISER).
This document provides guidance on each of the EPA metrics for 2023 data reporting. It explains the detail and importance of each metric. Our EPA targets for each metric apply to either calendar or financial years.
Please refer to the ‘environmental performance of the water and sewerage companies’ annual reports for the EPA and wider regulatory information.
1. EPA metric status and performance star rating
We set targets for each EPA metric. Company performance is then given a red, amber or green (RAG) status:
- red – significantly below target
- amber – below target
- green – achieved target or better
Based on performance across all of the metrics, EPA star ratings are then applied to each water company. This includes a new core metric requirement for 2022 data onwards. The core metric is discharge permit compliance which is required to be green for a water company to achieve a 4 star rating. Our expectation is that all water companies achieve 4 stars (the highest) rating.
EPA performance star rating descriptions for 2011 to 2025
| EPA star rating (out of 4) | Star rating description 2011 to 2015 | Star rating description 2016 to 2025 |
|---|---|---|
| 4 stars | Industry leading company | Industry leading company |
| 3 stars | Above average company | Good company |
| 2 stars | Below average company | Company requires improvement |
| 1 star | Poor performing company | Poor performing company |
Table note: ‘2011 to 2015’ and ‘2016 to 2025’ for EPA means 1 January to 31 December for calendar year metrics, and 1 April to 31 March for financial year metrics.
2. Total pollution incidents (sewerage) metric (category 1 to 3)
2.1 What this EPA metric means
This metric assesses how many category 1 to 3 pollution incidents from a water company sewerage asset were reported to us in a calendar year. This includes incidents affecting the water environment from sewerage assets. The number of pollution incidents is normalised per 10,000km of sewer length for which a water company is responsible so we can compare across the sector.
EPA thresholds for normalised (per 10,000km sewer) sewerage pollution incidents (category 1 to 3) for the calendar years 2011 to 2025
| Calendar year | Red status | Amber status | Green status |
|---|---|---|---|
| 2011 to 2015 | 130 or above | below 130 and above 50 | 50 or below |
| 2016 to 2020 | 50 or above | below 50 and above 25 | 25 or below |
| 2021 | 42 or above | below 42 and above 23 | 23 or below |
| 2022 | 40 or above | below 40 and above 22 | 22 or below |
| 2023 | 38 or above | below 38 and above 21 | 21 or below |
| 2024 | 37 or above | below 37 and above 20 | 20 or below |
| 2025 | 35 or above | below 35 and above 19 | 19 or below |
2.2 Sewerage pollution incidents
We record and investigate reports of pollution caused by discharges or escape of contaminants from water company sewerage assets, including:
- combined sewer overflows (CSOs)
- foul sewers, including transferred or adopted private sewers transferred to the water companies in 2011 (included in this EPA metric for 2016 onwards)
- other water industry premises
- pumping stations (PS), including transferred or adopted PS transferred to the water companies in 2016 (reported in the EPA for 2021 onwards)
- rising mains including transferred or adopted private rising mains transferred to the water companies in 2016 (included in this EPA metric for 2021 onwards)
- sewage treatment works (STW)
- storm tanks
- surface water outfalls
A category 1 incident has a serious, extensive or persistent impact on the environment, people or property and may, for example, result in a large number of fish deaths.
Category 2 incidents have a lesser, yet significant impact.
Category 3 incidents have a minor or minimal impact on the environment, people or property with only a limited or localised effect on water quality.
We assess impact according to the:
- persistence (time)
- extent (area affected)
- seriousness of effects
Effects of pollution include harm to:
- amenity
- aquatic life
- drinking water abstraction
- ecology
- fisheries
- human health
2.3 Importance of this metric
Discharges or escape of a contaminant from water company sewerage assets can cause environmental harm or pollution of surface waters or groundwater. We want water companies to reduce their impact on the environment and reduce the number of pollution incidents they cause.
2.4 What we expect from water companies
We expect water companies to minimise all pollution incidents (category 1 to 3). The WISER sets out our performance expectations for pollution incidents in the period 2020 to 2025. Water companies must achieve at least a 40% reduction in incidents compared to numbers recorded in 2016. All water companies should achieve green EPA status for this metric. For 2023 this was equivalent to 21 or fewer pollution incidents per 10,000km of sewer length.
3. Serious pollution incidents (sewerage and water supply) metric (category 1 and 2)
3.1 What this EPA metric means
This metric assesses how many serious category 1 and 2 pollution incidents from a water company asset were reported to us in a calendar year. This includes serious incidents affecting the water environment, from sewerage assets, and from 1 January 2021 also water supply assets. Before 2021 the number of serious pollution incidents (sewerage only) was normalised per 10,000km of sewer length.
EPA thresholds for normalised (per 10,000km sewer) serious sewerage incidents (category 1 and 2) for the calendar years 2011 to 2020
| Calendar year | Red status | Amber status | Green status |
|---|---|---|---|
| 2011 to 2015 | 4 or above | below 4 and above 1.5 | 1.5 or below |
| 2016 to 2020 | 1.5 or above | below 1.5 and above 0.5 | 0.5 or below |
For 2021 to 2025 we have placed water companies into one of two groups for assessment of this metric. The 2 groups have different RAG thresholds for the actual number of serious incidents. The groupings were based on the size of their asset base (sewerage and water supply).
EPA thresholds for the actual number of serious incidents (category 1 and 2) from sewerage and water supply assets for 2021 to 2025
Group 1 (larger asset base size) – Anglian Water, Severn Trent Water, Thames Water and United Utilities
| Calendar year | Red status | Amber status | Green status |
|---|---|---|---|
| 2021 and 2022 | 6 or above | 4 or 5 | 3 or below |
| 2023 and 2024 | 5 or above | 3 or 4 | 2 or below |
| 2025 | 4 or above | 2 or 3 | 1 or below |
Group 2 (smaller asset base size) – Northumbrian Water, Southern Water, South West Water, Wessex Water and Yorkshire Water
| Calendar year | Red status | Amber status | Green status |
|---|---|---|---|
| 2021 and 2022 | 4 or above | 2 or 3 | 1 or below |
| 2023 and 2024 | 3 or above | 2 | 1 or below |
| 2025 | 2 or above | 1 | 0 |
3.2 Serious pollution incidents
We record and investigate reports of pollution caused by discharges or escape of contaminants from water company sewerage assets, including:
- CSOs
- foul sewers, including transferred or adopted private sewers transferred to the water companies in October 2011 (included in this EPA metric for 2016 onwards)
- other water industry premises
- PS (including transferred or adopted private PS transferred to the water companies in 2016, reported in the EPA for 2021 onwards)
- rising mains (including transferred or adopted private rising mains transferred to the water companies in 2016, reported in the EPA for 2021 onwards)
- STW
- storm tanks
- surface water outfalls
- water treatment works (WTW) for water supply (included in this EPA metric for 2021 onwards)
- water distribution system for water supply (included in this EPA metric for 2021 onwards)
A category 1 incident has a serious, extensive or persistent impact on the environment, people or property and may, for example, result in a large number of fish deaths. Category 2 incidents have a lesser, yet significant impact on water quality. We assess impact according to the:
- persistence (time)
- extent (area affected)
- seriousness of effects
Effects of pollution include harm to:
- amenity
- aquatic life
- drinking water abstraction
- ecology
- fisheries
- human health
3.3 Importance of this metric
Discharges or escape of a contaminant from water company sewerage or water supply assets can cause environmental harm or pollution of surface waters or groundwater. We want water companies to reduce their impact on the environment and reduce the number of serious pollution incidents they cause.
3.4 What we expect from water companies
We expect water companies to reduce serious pollution incidents (category 1 and category 2). The WISER sets out our performance expectations for serious incidents in the period 2020 to 2025. Water company serious pollution incidents must trend towards zero. All water companies should achieve green EPA status for this metric. For 2023 this was equivalent to 2 or fewer serious pollution incidents for the group 1 water companies and 1 or fewer for the group 2 water companies.
4. Self-reporting of pollution incidents (sewerage and water supply) metric
4.1 What this EPA metric means
This metric assesses the percentage of category 1 to 3 pollution incidents self-reported by a water company to the Environment Agency. For 2021 to 2025 we are also assessing the self-reporting percentage for incidents from just STW and PS combined. This must be 90% or above for a company to achieve a green rating as well as 80% or above for overall self-reporting.
EPA thresholds for percentage of incidents (from sewerage and water supply assets) self-reported for the calendar years 2011 to 2025
| Calendar year | Red status % | Amber status % | Green status % |
|---|---|---|---|
| 2011 to 2015 | 37 or below | above 37 and below 68 | 68 or above |
| 2016 to 2020 | 55 or below | above 55 and below 75 | 75 or above |
| 2021 to 2025 | 65 or below | above 65 and below 80 | 80 or above (and 90% or more for just STW and PS combined) |
4.2 Self-reporting of pollution incidents
Self-reporting is when a water company reports a pollution incident from one of their assets to us before a member of the public or third party does. This metric measures the percentage of pollution incidents from both sewerage and water supply assets that were self-reported to us in a calendar year. It applies to incidents that we have assessed as having a minor, significant or major (category 1 to 3) impact on the water environment.
4.3 Importance of this metric
Self-reporting of pollution incidents enables water companies to react quickly to reduce the impact and learn lessons to prevent future incidents. We encourage water companies to use telemetry and other technologies to manage their assets and improve self-reporting.
4.4 What we expect from water companies
The WISER sets out our performance expectations for the self-reporting of incidents in the period 2020 to 2025. Water companies must achieve high levels of self-reporting. This means at least 80% of incidents self-reported by 2025 and more than 90% for just STW and PS combined. All water companies should achieve green EPA status for this metric. For 2021 to 2025 this is equivalent to 80% or more of all incidents being self-reported and 90% or more for just STW and PS combined.
5. Discharge permit compliance (numeric) metric
5.1 What this EPA metric means
This metric assesses the percentage of STW and WTW that are compliant with the numeric water quality limits for treated wastewater in their discharge permits.
For 2022 data onwards this metric is a core metric and impacts overall EPA star rating. This metric is required to be green for a water company to achieve a 4 star rating (see section 1).
EPA thresholds for percentage permit compliance for the calendar years 2011 to 2025
| Calendar year | Red status % | Amber status % | Green status % |
|---|---|---|---|
| 2011 to 2015 | 96 or below | above 96 and below 99 | 99 or above |
| 2016 to 2020 | 97 or below | above 97 and below 99 | 99 or above |
| 2021 to 2025 | 98 or below | above 98 and below 99 | 99 or above |
5.2 Discharge permit compliance (numeric)
Water companies require an environmental permit to discharge treated wastewater from STW and WTW to surface water or to ground. This metric measures, for the number of permitted sites that each water company has, the percentage that are compliant with certain conditions in a calendar year. The permit conditions included in this metric are for discharge sampling requirements and discharge numeric quality limits.
5.3 Importance of this metric
We set permit conditions to prevent discharges causing environmental harm or pollution. We measure and report the percentage of sites that are compliant with their discharge permit conditions. We want water companies to reduce their impact on the environment by operating fully within the conditions of their permits.
5.4 What we expect from water companies
It is a statutory obligation for water companies to comply with their permits. The WISER sets out our performance expectations for discharge permit compliance in the period 2020 to 2025. Water companies must have a plan in place to achieve 100% compliance for all licences. They must also achieve 100% compliance with look up table conditions (where limits cannot be exceeded more than a specified number of times in 12 months). All water companies should achieve green EPA status for this metric. For 2021 to 2025 this is equivalent to compliance at 99% or more of their sites.
6. Delivery of the Water Industry National Environment Programme (WINEP) metric
6.1 What this EPA metric means
This metric assesses the percentage completion of planned schemes, investigations and monitoring in the Water Industry National Environment Programme (WINEP). The WINEP was known as the National Environment Programme (NEP) before April 2020. We also track percentage completion of additional WINEP schemes, which are not part of the EPA metric – the installation of EDM on storm overflows and investigations of flow monitors.
EPA thresholds for percentage of the WINEP completed in each of the financial years ending 2012 to 2026
| Financial year ending | Red status % | Amber status % | Green status % |
|---|---|---|---|
| 2012 to 2016 | 96 or below | above 96 and below 99 | 99 or above |
| 2017 to 2021 | 97 or below | above 97 and below 99 | 99 or above |
| 2022 to 2026 | 98 or below | above 98 and below 100 | 100 |
6.2 The WINEP
In 2019, the economic regulator Ofwat set the prices that water companies could charge their customers between April 2020 and March 2025. As part of that price review we developed and published a WINEP for each water company. These set out the environmental measures or actions each company needs to invest in and complete during the 5 year AMP7 investment cycle to make sure they meet environmental standards related to water. The measures include asset improvement schemes, investigations to inform future actions and monitoring designed to improve:
- fisheries
- biodiversity
- geomorphology
- water quality
- water resources
The AMP5 period ran from 1 April 2010 to 31 March 2015. The AMP6 period ran from 1 April 2015 to 31 March 2020.
6.3 Importance of this metric
The WINEP sets out the environmental measures that the water companies need to take to improve the water environment. Each financial year, we measure the cumulative number of WINEP schemes completed as a percentage against the planned schemes up to that point in the 5 year plan. This means we can assess if water companies are making improvements as planned. We want companies to improve company infrastructure and complete other required actions so that the impact of providing water supply and wastewater services is reduced.
6.4 What we expect from water companies
The WISER sets out our performance expectations for WINEP delivery in the period April 2020 to March 2025. Water company business plans must include all measures identified within the WINEP and these must be planned well and completed to agreed timescales and specification. All water companies should achieve green status for this metric. For the financial year ending 31 March 2024 this was equivalent to 100% of the WINEP being completed on time.
7. Satisfactory sludge use and disposal metric
7.1 What this EPA metric means
This metric assesses the percentage of sewage sludge production (overall tonnes dry solids) that is dispatched and used or disposed of in a satisfactory manner.
EPA thresholds for percentage sludge compliant for the 7 calendar years 2011 to 2017:
- red is 98 or below
- amber is above 98 and below 100
- green is 100
For the calendar years 2018 to 2021 we suspended the metric from the EPA whilst we reviewed the regulatory regime for sludge treatment, storage and use.
EPA thresholds for percentage satisfactory sludge use and disposal for the calendar years 2022 to 2025:
- red is 98.00 or below
- amber is above 98.00 and below 98.20
- green is 98.20 or above
7.2 Sewage sludge
Sewage sludge is a product of wastewater treatment. The majority of sludge is treated before being used in agriculture.
7.3 Importance of this metric
The metric measures the satisfactory use and disposal of sewage sludge dispatched by the water companies. We record and report the amount of sludge (tonnes of dry solids) that is disposed of or used in compliance with relevant environmental laws. These include the Sludge (Use in Agriculture) Regulations (SUiAR) and the Environmental Permitting (England and Wales) Regulations (EPR). Sludge use in ‘agriculture’ is allowed under the SUiAR. Sludge ‘recovered’ includes non-agricultural land reclamation, or other purposes permitted under EPR. Sludge can also be ‘disposed’ of by incineration, power generation or gasification and landfill.
Reporting also includes water company voluntary compliance with a Safe Sludge Matrix. We want water companies to comply with sludge regulations to maximise the benefit and reduce the environmental impact of sludge.
7.4 What we expect from water companies
The WISER sets out our performance expectations for sewage sludge treatment and re-use in the period 2020 to 2025. Water companies must manage sewage sludge treatment and re-use so as not to cause pollution to soil, surface water or groundwater. All water companies should achieve green status for this metric. Our strategy for safe and sustainable sludge use (published on GOV.UK in March 2020) explains our intention to move sludge regulation from the SUiAR to the EPR.
8. Supply Demand Balance Index (SDBI) metric
8.1 What this EPA metric means
This metric assesses how the supply demand balance (water available for supply compared to forecast dry year demands) compares to what is set out in a water company’s Water Resources Management Plan (WRMP).
EPA thresholds for SDBI in each of the 5 financial years ending 2022 to 2026:
- red is below 99
- amber is 99 or above and below 100
- green is 100
From the financial year ending 2024 onwards, the SDBI metric includes an assessment of the timeliness and quality of water company data submissions. A default amber status is applied either due to a lack of data assurance, data uncertainty or delayed submission limiting assessment. A red status is given when no data is made available in time for the EPA.
8.2 SDBI
The SDBI assesses how the supply demand balance compares to what is set out in the WRMP. Water companies must provide commentary on their calculations and any differences from their WRMP. They should achieve an index of 100 if they are providing a secure supply of water.
We also ask the water companies to provide 3 pieces of additional information each year: per capita consumption, outage and leakage. These do not form part of the SDBI metric but support performance assessment.
8.3 Importance of this metric
Water companies write their WRMPs every 5 years to show how they will provide a secure supply of water to their customers over a 25 year period. These compare forecasts of demand and supply under dry year conditions and calculate a target headroom to protect customer supply. Comparison of these figures to actual availability of supply in the year allows security of supply to be assessed.
8.4 What we expect from companies
The WISER sets out our performance expectation for resilience of water supplies in the period 2020 to 2025. Water companies must assess resilience of their water supply system to predicted droughts and other non-drought water supply hazards. All water companies should achieve green EPA status for this metric. For the financial year ending 2024 this was equivalent to a SDBI of 100.
9. Event Duration Monitoring (EDM) delivery
Storm overflows are a necessary part of the current sewerage system. They are designed to discharge storm sewage (wastewater diluted with rainwater) to rivers or the sea at times of rainfall or snow melt. This is to prevent storm sewage backing up into homes and streets. Water companies have installed EDM on their storm overflows to capture performance information (how often and for how long they are used). Water companies met their obligation to monitor all storm overflows by December 2023. EDM coverage and data do not form part of the EPA WINEP delivery metric.
We have published the EDM storm overflow annual return dataset received from water companies. This shows how often and how long the monitored storm overflows operated during 2023. The 2023 dataset also includes water company reasons for performance issues with monitors and reasons for high spill counts.
Storm overflows include:
- CSOs on the sewerage network
- storm discharges at sewage pumping stations
- inlet CSOs at STW
- storm tanks at STW
10. EPA and reporting review 2021 to 2025
Every 5 years we review how we report on water company environmental performance and review the EPA. As a result of our last review, we revised the EPA to be broader and tighter from 1 January 2021. The changes reflect the performance expectations we set out in the WISER in 2017 for AMP7 (2020 to 2025). We have shared our EPA methodology with the water companies and have updated this EPA metric guide.
We set out our expectations and company legal obligations before a company business planning cycle starts. This enables companies to build requirements into their plans for investment, as regulated by Ofwat, the economic regulator of the water companies. We do not generally review the EPA more than every 5 years, as we wish to set clear targets for the 5 year period.
In 2022 we released a revised WISER document with our performance expectations for 2026 to 2030. During 2023 to 2025 we will review the EPA and how we report ready for the 2026 to 2030 data reporting years. The EPA and reporting review will include current EPA arrangements such as star ratings, or changes to existing metrics and their RAG thresholds. It will include development and the likely introduction of new metrics, and aspects of wider report narrative not included in the EPA.
11. Our regulation of water companies
We regulate and work in partnership with the 9 water companies that provide clean drinking water (water supply) and wastewater (sewerage) services in England, to make sure they:
- protect and improve the environment
- minimise the environmental impact of their assets and activities
- perform well and share good practice
- comply with licences and permits designed to protect people and the environment
Water companies provide an essential public service that underpins the social and economic health of the nation. We expect them to minimise the impact of taking clean water from the environment for water supply and returning used wastewater after treatment. Individually and collectively, however, these activities can and do affect the ecological health of rivers and their catchments. They also affect how water can be used downstream by others. It is the role of the Environment Agency to regulate this work.
By far the greatest potential environmental impact from the water companies’ activities is on the water and land environment. To regulate this impact, water companies have:
- abstraction licences which allow them to take water from the environment
- water discharge activity and groundwater activity permits which allow them to put treated wastewater back into the environment
- permits or other regulatory controls which allow them to dispose of, or use, sludge or other waste
- duties to manage their impact on flood and coastal risk and the environment
The licences and permits we issue control the level of impact water companies are allowed to have on the environment. It is vital that they meet the conditions we set in their licences and permits and meet their legal obligations.