Guidance

2. Definitions of the live EPA metrics

Published 15 October 2025

Applies to England and Wales

• Publication for Northern Ireland
• Publication for Scotland

For data collected from 1 January 2026 onwards live reporting of the total pollution incidents Environmental Performance Assessment (EPA) metric will follow the definition set out in section 2.1. However, a red, amber, green (RAG) status will not initially be applied, and metric performance will not contribute to the overall EPA rating. This is due to improvements in monitoring and changes in the way we assess incidents from 2026 data onwards. We will assess several years of data before reinstating RAG thresholds.

For 2026 data onwards (applied to data collected from the 1 January 2026) the 8 EPA metrics with live RAG thresholds, defined in sections 2.2 to 2.9 are:

• serious incidents affecting water (category 1 and 2 from sewerage and water supply assets)
• self-reporting of incidents affecting water (category 1 to 3 from sewerage and water supply assets)
• discharge permit compliance with numeric conditions
• discharge permit compliance with descriptive conditions
• storm overflows event duration monitor (EDM) operation
• satisfactory sludge use and disposal
• Water Industry National Environment Programme (WINEP) and National Environment Programme (NEP) in Wales scheme delivery
• water resources scheme delivery

2.1 Total pollution incidents affecting water (category 1 to 3 from sewerage assets per 10,000km sewer)

Background

The total pollution incidents metric has been part of the EPA since it was introduced for the 2011 data year. For data collected from 1 January 2026 onwards live reporting of the total pollution incidents EPA metric will follow the definition set out in this section. However, a RAG status will not be applied for 2026 and 2027 data, and metric performance will not contribute to the overall EPA rating. This is due to improvements in monitoring and changes in the way we assess incidents from 2026 data onwards. These include:

• addition of dry day spill data (when a storm overflow is used on a ‘dry day’)
• any changes to incident classification, which will be set out in new incident self-reporting and recording guidance

To reinstate RAG thresholds for this metric we intend to undertake an analysis of data in early 2028. This will involve data gathering and then an evidence based process and consultation.

This metric will be a core EPA metric when RAG thresholds are reinstated. More information on ratings including the core metric approach is in section 4.

Definition of metric

This metric includes incidents from the sewerage system and assets only. It does not include incidents from the water supply (clean water) service (for example from the water distribution system and water treatment works).

We use guidance to categorise all incidents as having a major (category 1), significant (category 2), minor (category 3) or no (category 4) impact on the water environment. The Environment Agency uses the common incident classification scheme (CICS) and Natural Resources Wales uses their triage and categorisation procedures. This metric assesses the total number of pollution incidents in a calendar year caused by discharges from a water company sewerage asset. It includes pollution incidents assessed as having category 1 to 3 impacts on the water environment. It does not include incidents impacting solely on air or land. Incidents affecting amenity of the water environment, for example bathing waters, and any incident affecting fish or ecology, are included.

Permitted storm overflows discharge dilute storm sewage due to rainfall or snowmelt from pumping stations (PS), waste water treatment works (WWTW) or combined sewer overflows (CSOs) on the sewerage network. If properly designed and operated in line with a permit, such discharges should have a negligible impact on the environment.

Sewerage assets included in this metric are:

• CSOs, excluding permitted storm overflows compliant with their permit resulting in a CICS category 3 incident
• foul sewers, including private sewers transferred to the water companies in October 2011 (used in the EPA from 1 January 2016)
• other water industry premises
• PS, including private PS transferred to the water companies in October 2016 (used in the EPA from 1 January 2021)
• rising mains, including private rising mains transferred to the water companies in October 2016 (used in the EPA from 1 January 2021)
• storm tanks
• surface water outfalls
• WWTW also known as sewage treatment works (STW)

This is not an exhaustive list. The ‘other water industry premises’ category is an optional categorisation used in the Environment Agency National Incident Recording System (NIRS) database. Natural Resources Wales uses an equivalent system called Wales Incident Recording System (WIRS). It is infrequently used to record incidents where the incident source does not fit any of the other categories.

Note that incidents reported to the Environment Agency as dry day spill incidents will be recorded on NIRS and be reported against this EPA metric from 1 January 2026. Natural Resources Wales will also report dry day spill figures on a yearly basis but will review the frequency and method of reporting.

Obligation

This metric is relevant to the Environmental Permitting (England & Wales) Regulations 2016. The 2016 Regulations apply to any incident from 1 January 2017 onwards. The Water Industry Act 1991, Section 94, states general duties of sewerage undertakers. They must maintain sewers and lateral drains to effectually drain its area, and to deal effectually with the contents of sewers.

Calculation

The total number of pollution incidents (categories 1 to 3) for which a water and sewerage company is responsible is normalised by 10,000km of sewer length. Incident data is as recorded on the Environment Agency NIRS or Natural Resources Wales WIRS database for a calendar year. The normalisation calculation accounts for the variation in sizes of water company networks and is a representative method of reporting on total pollution incidents. Ofwat have published the PR24 Performance Commitment Model for water and sewerage companies containing sewer length data. This is data we have agreed with Ofwat. We are using sewer lengths provided for the financial year ending 2023 for normalisation in the 5 year period from 2026 onwards. This data is listed in Table 1. The calculated result is rounded to 0 decimal places for assessment against the thresholds that we are developing and for reporting.

Table 1. Water and sewerage company sewer lengths for the EPA total pollution incidents metric 2026 to 2030

Water and sewerage company	Total length of sewers and rising mains (km) for the financial year ending 2023
Anglian Water	77,284
Northumbrian Water	30,237
Severn Trent Water (England)	92,576
Southern Water	39,973
South West Water	24,857
Thames Water	109,355
United Utilities	79,039
Wessex Water	35,089
Yorkshire Water	52,533
Dŵr Cymru (Welsh Water)	37,125
Hafren Dyfrdwy (for reference only)	495

Table note: data taken from the Ofwat PR24 Performance Commitment Model, provided to us in February 2024. Total length of sewers and rising mains includes the combined total of legacy sewers and private sewers transferred to the water and sewerage companies.

Frequency of assessment

This metric is assessed annually, based on a calendar year.

Expectation

Due to improvements in monitoring and changes in the way we assess incidents there will be no RAG status thresholds for 2026 and 2027 data years. In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the Water Industry Strategic Environmental Requirements (WISER) including a significant reduction in pollution incidents. This expectation and analysis of data in 2026 and 2027 will inform future thresholds.

RAG status thresholds

There will be no thresholds applied to the total pollution incidents metric for 2026 and 2027 data years. In early 2028 we intend to undertake an analysis of data collected. This will involve data gathering and then an evidence based process and consultation to determine RAG thresholds. The total pollution incident numbers (actual and normalised) will continue to be reported in the published EPA table with accompanying narrative for 2026 and 2027. However, the data will not contribute to the overall EPA rating until RAG thresholds are reinstated.

2.2 Serious incidents affecting water (category 1 and 2 from sewerage and water supply assets)

Background

The serious incidents metric has been part of the EPA since it was introduced for the 2011 data year. The WISER includes an expectation for zero serious incidents by 2030. The metric definition for the EPA 2026 to 2030 data years has been updated to include:

• removal of the two water and sewerage company asset base size groupings for RAG thresholds
• removal of the RAG threshold 5 year glide path (tighter thresholds each year) – there will instead be one set of thresholds for the 5 year period

This metric is a core EPA metric for the 2026 to 2030 data years. More information on ratings including the core metric approach is in section 4.

Definition of metric

This metric assesses the total number of serious incidents affecting water (categories 1 and 2) in a calendar year caused by a discharge or a release from a water company sewerage asset or water supply asset.

We use guidance to categorise all incidents as having a major (category 1), significant (category 2), minor (category 3) or no (category 4) impact on the water environment. The Environment Agency uses the common incident classification scheme (CICS) and Natural Resources Wales uses their triage and categorisation procedures. This metric includes pollution and non-pollution incidents assessed as having category 1 or 2 impacts on the water environment.

The metric incorporates water supply (clean water) incidents, as well as including sewerage incidents. This metric does not include incidents impacting solely on air or land. Incidents affecting amenity of the water environment, such as bathing waters, and any incident affecting fish or ecology, are included.

Assets included in this metric are:

• combined sewer overflows (CSOs)
• foul sewers, including private sewers transferred to the water companies in October 2011 (used in the EPA from 1 January 2016)
• other water industry premises
• PS, including private PS transferred to the water companies in October 2016 (used in the EPA from 1 January 2021)
• rising mains, including private rising mains transferred to the water companies in October 2016 (used in the EPA from 1 January 2021)
• storm tanks
• surface water outfalls
• WWTW also known as sewage treatment works (STW)
• water distribution system
• water treatment works (WTW)

This is not an exhaustive list. The ‘other water industry premises’ category is an optional categorisation used in the Environment Agency NIRS database. Natural Resources Wales uses an equivalent system called WIRS. It is infrequently used to record incidents where the incident source does not fit any of the other categories.

Obligation

This metric is relevant to the Environmental Permitting (England & Wales) Regulations 2016. The 2016 regulations apply to any incident from 1 January 2017 onwards. The Water Industry Act 1991, Section 94, states the general duty of sewerage undertakers to maintain sewers and lateral drains to effectually drain its area, and to deal effectually with the contents of sewers. The Water Industry Act 1991 states further duties of water undertakers – Section 37 to maintain an efficient and economical system of water supply, Section 52 for domestic supplies and Section 55 for non-domestic supplies.

Calculation

The total number of incidents (categories 1 and 2) from a discharge or release, that a water and sewerage company is responsible for in a calendar year is assessed. Incident data is as recorded on the Environment Agency NIRS and the Natural Resources Wales WIRS database.

The metric uses whole incident numbers (not normalised) for assessment against the thresholds below and for reporting.

Frequency of assessment

This metric is assessed annually, based on a calendar year.

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER. This includes an expectation for serious (category 1 and 2) pollution incidents to trend to zero by 2030. The EPA RAG status thresholds set align with this WISER expectation. All water and sewerage companies should achieve green EPA status for this metric.

RAG status thresholds

The RAG status thresholds for this metric are:

• red – 2 or more serious incidents
• amber – 1 serious incident
• green – zero serious incidents

2.3 Self-reporting of incidents affecting water (category 1 to 3 from sewerage and water supply assets)

Background 

The self-reporting of incidents metric has been part of the EPA since it was introduced for the 2011 data year. The metric definition for the EPA 2026 to 2030 data years has been updated to include:

• tighter RAG thresholds than the previous EPA period
• RAG thresholds tighten during the 5 year period – a glide path from 2026 to 2030

Self-reporting of incidents affecting water can contribute to each water and sewerage company’s proactive and predictive pollution prevention activities. This should lead to prevention of incidents and effective management of their responses when incidents do occur.

Definition of metric

This metric assesses the percentage of self-reporting by the water and sewerage company of incidents (category 1 to 3) affecting the water environment in a calendar year.

We use guidance to categorise all incidents as having a major (category 1), significant (category 2), minor (category 3) or no (category 4) impact on the water environment. The Environment Agency uses the common incident classification scheme (CICS) and Natural Resources Wales uses their triage and categorisation procedures.

This metric includes pollution incidents and non-pollution incidents caused by a discharge or a release from a sewerage asset or water supply asset affecting the water environment. This does not include incidents impacting solely on air or land. Incidents affecting amenity of the water environment, such as bathing waters, and any incident affecting fish or ecology, are included.

Assets included in this metric are:

• combined sewer overflows (CSOs) excluding CSOs compliant with their permit resulting in a CICS category 3 incident
• foul sewers, including private sewers transferred to the water companies in October 2011 (used in the EPA from 1 January 2016)
• other water industry premises
• PS, including private PS transferred to the water companies in October 2016 (used in the EPA from 1 January 2021)
• rising mains, including private rising mains transferred to the water companies in October 2016 (used in the EPA from 1 January 2021)
• storm tanks
• surface water outfalls
• WWTW also known as sewage treatment works (STW)
• water distribution system
• water treatment works (WTW)

Incidents arising from dry day spill retrospective data analysis will not be included within this metric as this metric assesses immediate self-reporting.

Obligation

This metric is relevant to the Environmental Permitting (England & Wales) Regulations 2016. The 2016 Regulations apply to any incident from 1 January 2017 onwards. The Water Industry Act 1991, Section 94, states the general duty of sewerage undertakers to maintain sewers and lateral drains to effectually drain its area, and to deal effectually with the contents of sewers). The Water Industry Act 1991 states further duties of water undertakers – Section 37 to maintain an efficient and economical system of water supply, Section 52 for domestic supplies and Section 55 for non-domestic supplies.

Calculation

The calculation for this metric is for category 1 to 3 incidents affecting water. For each water and sewerage company the calculation is: the total number of incidents self-reported as a percentage of total incidents for which they are considered responsible in a calendar year. This is as recorded on the Environment Agency NIRS and the Natural Resources Wales WIRS databases.

Note that the calculated % is rounded to 0 decimal places for assessment against the thresholds below and for reporting.

We also assess the incident self-reporting percentage for just WWTW and PS assets. We will report this figure in the EPA results table in brackets next to the overall self-reporting figure for clarity.

Frequency of assessment

This metric is assessed annually, based on calendar year, on a single year of results.

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER. For self-reporting of pollution incidents this includes expectations for self-reporting overall. It also includes a self-reporting expectation for WWTW and PS – these assets commonly either have staff on site or have alarms in place to provide early warning and hence reporting and action in the event of any problems. WISER states the expectations as ‘high levels of self-reporting of pollution incidents with at least 90 per cent of incidents self-reported by 2030’ and ‘more than 95% of incidents self-reported for WWTW and PS’. The EPA thresholds have been set to align with these expectations, using a 5 year glide path.

RAG status thresholds

The RAG status thresholds for this metric tighten during the 5 year EPA period (glide path for 2026 to 2030).

Table 2. EPA RAG thresholds for the self-reporting of incidents affecting water metric – 5 year glide path for 2026 to 2030

Year	Green threshold (self-reporting%) – all incidents	Green threshold self-reporting %) – just WWTW and PS combined	Amber threshold (self-reporting%) – all incidents	Amber threshold self-reporting%) – just WWTW and PS combined	Red threshold (self-reporting %) – all incidents and just WWTW and PS combined
Year 1 (2026 data)	86 or more	91 or more	Less than 86, more than 75	Less than 91, more than 75	75 or less
Year 2 (2027 data)	87 or more	92 or more	Less than 87, more than 75	Less than 92, more than 75	75 or less
Year 3 (2028 data)	88 or more	93 or more	Less than 88, more than 75	Less than 93, more than 75	75 or less
Year 4 (2029 data)	89 or more	94 or more	Less than 89, more than 75	Less than 94, more than 75	75 or less
Year 5 (2030 data)	90 or more	95 or more	Less than 90, more than 75	Less than 95, more than 75	75 or less

Table note: if the self-reporting percentage meets the green threshold for all incidents but not for just WWTW and PS combined, then the assessment result is amber status. If the self-reporting percentage meets the amber threshold for all incidents but not for just WWTW and PS combined, then the assessment result is red status.

2.4 Discharge permit compliance with numeric conditions

Background

The discharge permit compliance with numeric conditions metric has been part of the EPA since it was introduced for the 2011 data year. The metric definition for the EPA 2026 to 2030 data years has been updated with:

• inclusion of rolling year look-up table (LUT) compliance (where a limit cannot be exceeded more than a specified number of times in a 12 month period) – this is a change from reporting ‘calendar’ year LUT compliance in previous EPA cycles
• inclusion of rolling year compliance with annual average limits – this is a change from reporting ‘calendar’ year annual average compliance in previous EPA cycles
• inclusion of permit conditions covering failure to collect the required number of operator self-monitoring (OSM) samples
• inclusion of all permits with numeric quality discharge permit conditions except Environmental Permitting Regulations permitted emergency discharges from WTW – this is a change from excluding discharges less than 20m³ per day from WTW
• the compliance calculation now using the number of permits not number of sites

WTW emergency discharges consist of Environmental Permitting Regulations permitted emergency discharges from WTW and are not included in the OSM sample programme.

This metric is a core EPA metric for the 2026 to 2030 data years. It applied as a core metric for 2022 data onwards. More information on ratings including the core metric approach is in section 4.

Definition of metric

This metric applies to waste water treatment works (WWTW) that treat and dispose of sewage, and water treatment works (WTW) for the water supply service. It assesses compliance at WWTW and WTW that have numeric discharge permit conditions – these set numeric quality limits for discharging and monitoring treated waste water. All WWTW and WTW permits with numeric discharge permit conditions are included except Environmental Permitting Regulations permitted emergency discharges from WTW.

Permit conditions covering failure to collect the required number of OSM and Urban Waste Water Treatment Regulations (UWWTR) samples are included as well as permit conditions for numeric quality limits. Compliance with other discharge permit conditions are assessed by the descriptive conditions metric (section 2.5) and the shadow annual flow to full treatment metric (section 7.2).

Obligation

This metric is relevant to the Environmental Permitting (England & Wales) Regulations 2016 and the UWWTR 1994, requiring compliance with permits issued for water discharge activities and groundwater activities.

Calculation

The permits and discharges that are included in the assessment are agreed with water and sewerage companies each autumn.

The calculation for percentage compliance is (B – A) ÷ B × 100 where:

• A is the number of permits where one or more discharges are confirmed as failing in the calendar year
• B is the number of permits on the Environment Agency or Natural Resources Wales register during the calendar year

The calculation result is rounded to 1 decimal place for assessment against the thresholds below and for reporting.

A discharge can be confirmed as failing for the following breaches of numeric discharge quality and monitoring permit conditions at WWTW and WTW:

• non-sanitary parameters numeric limits annual mean limits (rolling 12 months)
• non-sanitary parameters LUT numeric limits (rolling 12 months)
• non-sanitary parameters upper tier (UT) numeric limits
• nutrient parameters numeric limits annual mean limits (rolling 12 months)
• OSM failure to collect or analyse the required number of samples or parameters – includes failure to collect or analyse required number of ultraviolet (UV) samples or parameters
• sanitary parameters LUT numeric limits (rolling 12 months)
• sanitary parameters numeric limits
• sanitary parameters UT numeric limits
• UV disinfection dose (failure to meet the permitted rolling annual or daily dose requirements)
• UWWTR failure to collect or analyse the required number of samples or parameters
• UWWTR LUT parameters numeric limits
• UWWTR numeric parameters compliance
• UWWTR nutrients parameters numeric limits
• UWWTR UT parameters numeric limits

Note that sanitary parameters mean biochemical oxygen demand (BOD), ammonia and suspended solids. Non-sanitary parameters means all other parameters, such as nutrients and metals.

When a LUT exceedance occurs we will look back 12 whole months, including the month in which the exceedance occurs and count the collected number of pre-scheduled samples for the same parameter. If the number of samples that were also LUT exceedances for that parameter is more than the LUT allows we report a breach. A LUT breach will be reported in the EPA reporting year it occurs, regardless of which reporting year the preceding exceedances occurred. This is a change from reporting ‘calendar’ year LUT compliance in previous EPA cycles. For LUT exceedances during 2026, any LUT exceedance in the previous 12 month period that occurred in 2025 will be included in the assessment.

An annual average breach will be recorded where in any rolling 12 month assessment there is a breach of the annual average limit – we will take account of any confidence requirements specified for the parameter in the permit or guidance. This is a change from reporting ‘calendar’ year annual average compliance in previous EPA cycles. For 2026 rolling 12 month assessments we will include compliance data from 2025 to calculate the annual average compliance.

Failure to collect the required number of OSM samples will be reported where the required number of samples have not been collected in a calendar year. The OSM sample frequency for a discharge can change within year from ‘normal’ to ’reduced’ frequency, and the other way around, depending on discharge quality emission limit compliance and any relevant permit variations. Following a numeric limit breach, the sample frequency for sanitary parameters will increase back to the normal frequency. After 12 consecutive months of compliance the frequency can return to the reduced frequency. An annual OSM summary report is submitted by water and sewerage companies to us by the end of February each year – this should confirm all missed and rescheduled samples and frequency changes in the preceding calendar year.

The discharge permit compliance metric is reported as the number of failing permits, not the number of failing sites or discharges.

Frequency of assessment

This metric is assessed annually. It is based on permit breaches in a calendar year, looking back over a 12 month rolling year for LUT and annual average conditions. The reporting year is 1 January to 31 December each year. Data is recorded by us throughout the year in a compliance database, then extracted on the 28 February the following year as a final dataset for the EPA.

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER. The WISER performance expectation is 100% compliance – this means 100% of WWTW and WTW permits compliant with numeric quality limits and monitoring requirements for discharging treated waste water. The EPA RAG status thresholds set are informed by our WISER expectations.

RAG status thresholds

The RAG status thresholds are:

• red – the current year’s performance is equal to or less than 98%
• amber – the current year’s performance is greater than 98% and less than 99%
• green – the current year’s performance is equal to or more than 99%

2.5 Discharge permit compliance with descriptive conditions

Background

Discharge permit compliance with descriptive conditions is a new EPA metric for 2026 onwards. It applies to waste water treatment works (WWTW) and water treatment works (WTW) with discharge permit conditions that set numeric quality limits for discharging and monitoring treated waste water. This new metric is for descriptive permit conditions to reflect the performance and environmental risk of a site as a whole. It includes conditions which require control of flow to full treatment at a WWTW, and other storm and sewage in emergency discharges.

There is a separate EPA metric for discharge permit compliance with numeric conditions (which has been part of the EPA since it was introduced for the 2011 data year, section 2.4) – that metric is for compliance with numeric quality limits and monitoring requirements for discharging treated waste water. There is also a shadow EPA metric for WWTW compliance with numeric flow to full treatment annual limit conditions (section 7.2) – this is being developed with the intention of becoming live in the period 2026 to 2030.

Descriptive condition breaches have the potential to result in significant pollution or other significant impacts. Examples include:

• failure of the management condition that resulted in or had the potential to result in a poor quality discharge that could cause significant pollution
• failure to follow an operating technique as required by the permit which had the potential to result in significant pollution
• failure of a monitoring data quality condition which resulted in not being able to reliably check compliance with other conditions

Definition of metric

This metric applies to WWTW and WTW. It assesses compliance at WWTW and WTW that have numeric discharge permit conditions – these set numeric quality limits for discharging and monitoring treated waste water. This metric assesses compliance with descriptive conditions in those numeric discharge permits. All WWTW and WTW with numeric discharge permit conditions are included except Environmental Permitting Regulations permitted emergency discharges from WTW.

The Environment Agency uses the compliance classification scheme (CCS), and Natural Resources Wales an equivalent method, for assessing compliance with permit conditions. A CCS category 1 or 2 breach for a descriptive condition included in this EPA metric definition will result in a failing permit.

A descriptive condition breach may be associated with other breaches. For example, a sampled discharge that breaches a numeric quality limit (numeric condition) may following further investigation result in a management system breach (descriptive condition). Numeric condition breaches and descriptive condition breaches may not have the same category. But if the descriptive condition breach is CCS category 1 or 2 it will result in a failing WWTW or WTW permit under this descriptive condition metric.

Exclusions

We will not include any breaches of operating technique conditions in this metric if they relate to an investigation or innovative permitting scheme listed below:

• CNB – catchment nutrient balancing trials
• CP – catchment permitting trials
• CP and CNB hybrid scheme trials
• efficacy of treatment to remove specified pollutants (for example flexible chemicals permitting or phosphorus) trials
• ICW – integrated constructed wetlands trials
• perfluorooctanesulfonic acid (PFOS) and other chemical investigations or trials
• SSST – single site stretch target trials

For PFOS investigations the exclusion will be reviewed at the end of the AMP8 period (31 March 2030).

For all other innovative permitting approaches, the exclusion will no longer apply once the trial is complete and has been successful. At this point, the approach is either regulated conventionally and directly in the permit. Or it is regulated by use of a ‘business as usual’ operating techniques agreement (OTA) linked to the permit by the operating technique conditions.

Obligation

This metric is relevant to the Environmental Permitting (England and Wales) Regulations 2016 requiring compliance with permits issued for water discharge activities and groundwater activities.

Calculation

The permits that are included in the assessment are agreed with water and sewerage companies each autumn.

The calculation for percentage compliance is (B – A) ÷ B × 100 where:

• A is the number of permits that have CCS category 1 or 2 descriptive condition breaches
• B is the number of permits on the Environment Agency or Natural Resources Wales register during the calendar year

The calculation result is rounded to 1 decimal place for assessment against the thresholds below and for reporting.

We use the number of permits with numeric discharge quality limits in this metric, not the number of discharges associated with each WWTW. For example, a WWTW permit may have the following discharge activities associated with it: secondary treated sewage effluent, settled storm sewage, storm sewage and sewage in an emergency. A descriptive CCS category 1 or 2 condition breach relating to any of these discharges will result in a failing WWTW under this metric. Where several discharge activities are associated with the same permit, they may be located at the WWTW or at a last in line overflow which controls the flow to full treatment at the WWTW.

Some WTW discharges which are included in this metric occur intermittently and are not sampled or are sampled infrequently. CCS category 1 or 2 descriptive condition breaches for any of the WTW discharges in a permit which has been identified for use in the EPA will result in a failing permit.

Frequency of assessment

This metric is assessed annually, based on a calendar year. The reporting year is 1 January to 31 December each year. Data is recorded by us throughout the year in a compliance database, then extracted on the 28 February the following year as a final dataset for the EPA.

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER. The WISER performance expectation is 100% compliance – this means 100% of WWTW and WTW permits compliant with descriptive permit conditions. The EPA RAG status thresholds set are informed by our WISER expectations.

RAG status thresholds

The RAG status thresholds are:

• red – the current year’s performance is equal to or less than 98%
• amber – the current year’s performance is greater than 98% and less than 99%
• green – the current year’s performance is equal to or more than 99%

2.6 Storm overflows event duration monitor (EDM) operation

Background

Storm overflow EDM operation is a new EPA metric for the 2026 to 2030 reporting period. The metric was developed jointly by the Environment Agency and Natural Resources Wales. Storm overflow activations are a crucial issue for regulators and the general public, which necessitates performance reporting as part of the EPA. Data is provided by water and sewerage companies to the Environment Agency and Natural Resources Wales each year as part of their regulatory EDM annual return. The data used to support this metric is taken directly from the annual returns.

Definition of metric

This metric reports the percentage of EDM monitors reporting reliable storm overflow activation data with more than or equal to 90% operation during the annual reporting period. This is a robust metric for measuring water and sewerage companies progress towards meeting the Environment Act (2021) Section 81 requirement to report all discharges from storm overflows. This metric does not report on spill frequency or environmental impact, though our future ambition (post 2030) is to develop a metric assessing permit compliance or asset performance, likely utilising spill frequency.

At the end of December 2023 water and sewerage companies achieved 100% EDM installation, however data gaps and poor-quality data remain a significant concern. Whilst companies strive to improve spill monitoring, this metric will seek to ensure that the Section 81 requirement to report all storm overflow activations is met.

We are not asking water and sewerage companies to use the Monitoring Certification Scheme (MCERTS) for storm overflows as part of this metric at this time. However, they are required to provide reliable data as part of their permitted discharge conditions. The EDM good practice guide sets out the process and standards to follow, which includes a section on information validation.

Obligation

The requirement for water and sewerage companies to provide annual reports on discharges from storm overflows using EDM data is set out in the Environment Act (2021). The requirement to monitor and report storm overflow performance is secured through Environmental Permitting Regulation permit conditions, where applicable. We review EDM data prior to publication to ensure the data is complete. However, water and sewerage companies are responsible for quality assuring their own EDM data. They are required to submit a regulatory return as a statutory requirement and have a clear obligation to get this right.

Calculation data

The metric calculation is as defined below. It uses data provided within each water company’s annual EDM return to the Environment Agency or Natural Resources Wales each year. For companies operating in England, this EDM data is published by the Environment Agency in March each year. For companies operating in Wales companies are required to publish the annual return on their own websites with Natural Resources Wales publishing an annual storm overflow spill report.

Storm overflows are defined as including the following permitted storm discharge asset types:

• combined sewage overflows (CSOs) on the sewer network
• inlet CSOs at sewage treatment works
• storm discharges at pumping stations
• storm tanks at sewage treatment works

The annual EDM return is used to collect and calculate several figures set out below.

A. ‘Total number of storm overflows listed in the annual return’ which is the number of storm overflows included in each company’s annual EDM return – Natural Resources Wales receives separate EDM returns for permitted and unpermitted storm overflows which are combined to calculate the total, which is comparable to the Environment Agency approach.

B. ‘Total number of storm overflows with EDM commissioned’ which is the total number of storm overflows each company has declared to have EDM commissioned.

C. ‘Total number of storm overflows with spill data’ which is the number of storm overflows in the annual EDM return which have spill data reported – some storm overflows may have EDM commissioned but no data provided, either due to 0% EDM operation, or where no EDM spill data has been reported.

D. ‘Percentage of storm overflows with greater than or equal to 90% EDM operation during reporting period’ which is the percentage of monitored storm overflows that provided reliable data for 90% or more of the reporting period – this is published in the Environment Agency’s EDM annual return long-term trends.

Primary calculation for EDM operation

We calculate the ‘Percentage of storm overflows reporting greater than or equal to 90% EDM operation during annual reporting period’ – D above.

This is the reported percentage of storm overflows that provided reliable data for 90% or more of the reporting period. To calculate D, we count overflows with 90.0% and above EDM operation in the annual EDM return and divide by the total number of storm overflows with numeric spill data (C above), then multiply by 100.

Note that the calculated results are rounded to 1 decimal place for assessment against the thresholds identified below and for reporting purposes.

Sub-measure calculation

We calculate the ’percentage of storm overflows listed with spill data’. 

This is the percentage of storm overflows listed in the return that have spill data reported. To calculate, we count the total number of storm overflows with spill data (C above). We divide this number by the total number of storm overflows listed in the annual EDM return (A above) and multiply by 100.

Note that the calculated results are rounded to 1 decimal place for assessment against the thresholds identified below and for reporting purposes.

Exemptions

There are a limited number of storm overflows where water and sewerage companies have deemed EDM installation unsafe, subject to agreement with regulators.

Natural Resources Wales position on emergency overflows

Where an emergency overflow is identified as reacting to rainfall events, Natural Resources Wales requires companies to investigate to determine the intended function of the overflow. These discharges will be included in the unpermitted storm overflow return for the purposes of this metric. Their inclusion does not impact this investigation process and pre-determine their status as a storm overflow for future permitting.

Frequency of assessment

This metric is assessed annually, based on a calendar year.

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER. This includes an expectation for companies to ‘reduce the frequency and volume of sewage discharges from storm overflows’ and ‘100% compliance for all licences and permits’. The EPA RAG status thresholds set for this metric are informed by these WISER expectations.

All storm overflows were required to have EDM commissioned by December 2023 with all EDM operational and providing reliable data. The purpose of EDM installation is to monitor storm overflow activations and progress towards meeting the storm overflow discharge reduction plan (SODRP) targets (England only). Wales has its own targets set by the Welsh Government.

RAG status thresholds

For the primary metric calculation, the percentage of storm overflows with greater than or equal to 90% EDM operation reported throughout reporting period, the metric thresholds are:

• red – less than 95%
• amber – equal to or less than 97.5% and equal to or greater than 95%
• green – greater than 97.5% in addition to meeting sub-measure requirements

For companies to achieve a green RAG status the primary metric calculation must be greater than 97.5% and the sub-measure (for percentage of storm overflows listed with spill data) must be greater than 99.5%. If the primary metric calculation is greater than 97.5% but the sub-measure is less than or equal to 99.5%, the RAG status is amber.

Forward look (2031 onwards)

We intend to develop the storm overflow metric further in future to focus on spill frequency or environmental impact. This could utilise developing areas of work including spill frequency threshold permitting (SFTP). At present however, these proposals are at a developmental stage. It would therefore be premature to use these measures prior to their implementation. As a result, the appropriate metric for 2026 to 2030 is storm overflow EDM operation. This live metric seeks to ensure that companies meet their statutory obligation to monitor and report all storm overflow activations.

2.7 Satisfactory sludge use and disposal

Background

The satisfactory sludge use and disposal metric was part of the EPA when it was introduced for the 2011 data year. The metric was suspended for the 2018 to 2021 data years and we did not report it publicly within the EPA. The following metric definition was developed between October 2020 and May 2022 by a Task and Finish group consisting of water and sewerage company members, Environment Agency and Natural Resources Wales. We reinstated it as a live metric (with a clarified definition) for the 2022 data year which was reported within the EPA published in 2023. There are no changes to the definition for the 2026 to 2030 data years.

Definition of metric

This metric assesses the percentage of sewage sludge production (overall tonnes of dry solids) that is dispatched and used or disposed of in a satisfactory manner. The water and sewerage company who is in control of the sludge when it is dispatched to its final outlet is the reporter of that sludge. This company may not be the producer of the residual sludge from the sewage plant treating the originally received domestic or urban waste water. This is accepted because there can be importations of sludge which includes trading between the water and sewerage companies. This sludge metric assesses performance of the water and sewerage company who holds the sludge that they dispatch for satisfactory use or disposal in England or Wales.

Obligation

The satisfactory sludge use and disposal metric includes compliance with the:

• Sludge (Use in Agriculture) Regulations
• Environmental Permitting (England and Wales) Regulations 2010 – where they apply to recycling to land (with field storage under S3 exemption only) and disposal of sewage sludge containing products and residual wastes
• Safe Sludge Matrix

Calculation

The metric requires completion of a template by each water and sewerage company. This return provides us with a sludge quantity and quality report. This is also used to report to the Department for Environment, Food and Rural Affairs (Defra) on the implementation of the Sludge (Use in Agriculture) Regulations.

Reporting is of tonnes of dry solids sent to any outlets in a compliant manner, when under the control of the sludge producer. This is reported in the return as two figures set out below.

1. Total satisfactory sludge, used by any route (to the nearest tonne of dry solids).

2. Percentage of total sludge dispatched for final use or disposal, used in a compliant manner. The calculation is:

(1 – (unsatisfactory sludge dispatched for final use or disposal ÷ total sludge dispatched for final use or disposal)) × 100 (% reported to 2 decimal places)

For non-agricultural outlets, sludge will be deemed compliant if at the point of entry an appropriate permit, exemption or regulatory position existed, allowing the sludge to be used in this manner.

Water and sewerage companies must report the input quantity for destruction technologies such as incineration, pyrolysis, gasification as well as restoration outlets. Amounts should be calculated at the point of storage prior to use, use and disposal.

Sludge dispatched includes solids added during the treatment process, for example lime.

Grit and screenings and water treatment sludge will be excluded.

Treatment related breaches that do not result in non-compliant sludges or residual products going to any outlets are not included. This is to avoid double counting.

Water and sewerage companies must include quantities in compliance (satisfactory) or non-compliance (unsatisfactory) with the Safe Sludge Matrix and the regulatory requirements of the Sludge (Use in Agriculture) Regulations and Environmental Permitting Regulations. This is in so far as these regulations apply to:

• recycling to land (with field storage)
• disposal of sewage sludge containing products and residual wastes

Unless agreed with the Environment Agency, sludge stored, used or disposed under a local enforcement position should be recorded as unsatisfactory sludge. Sludge stored, used or disposed under a regulatory position statement in England will be recorded as satisfactory. Natural Resources Wales classes sludge stored, used or disposed of in compliance with the conditions of a regulatory decision as satisfactory.

A quantity of sludge will be recorded as unsatisfactory once per reporting year, regardless of the number of reasons it fails the metric. If for whatever reason sludge fails the metric in the first reporting year and the following reporting year, then it will be recorded as unsatisfactory in both reporting years. Any sludge reported as unsatisfactory in a reporting year that had been dispatched in the previous year can be accounted for in an additional calculation:

(1 – (unsatisfactory sludge dispatched for final use or disposal ÷ (total sludge dispatched for final disposal or use + the relevant unsatisfactory amount))) × 100

This accounts in the annual performance report for any distortion created by sludge being handled over more than one reporting year.

There may be sludge trading from one water and sewerage company to another water and sewerage company. This means a company may accept the import of sludge from another company to treat and dispatch for use. The receiving company is accountable for the reporting of all the sludge it sends to a final outlet in England or Wales against the metric. Water and sewerage companies must record a comment on this in the narrative of their sludge return to us.

There may be sludge trading from one water and sewerage company to a waste management company not in their control. Where sludge is passed for treatment to a waste management company this sludge should be reported as satisfactory by the water company – this is if at the point of entry an appropriate permit exists for the waste management company to accept the sludge. Water and sewerage companies must record a comment on this in the narrative of their sludge return to us.

Frequency of assessment

This metric is assessed annually, based on a calendar year. The reporting year is 1 January to 31 December each year.

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER. This includes an expectation for ‘100% compliance with satisfactory sludge use or disposal’. The EPA RAG status thresholds set are informed by this WISER expectation.

RAG status thresholds

The RAG status thresholds for percentage of sewage sludge production that is dispatched and used or disposed of in a satisfactory manner are:

• red – 98% or below satisfactory sludge use or disposal
• amber – below 98.2% but above 98% satisfactory sludge use or disposal
• green – 98.2% or above satisfactory sludge use or disposal

2.8 Water Industry National Environment Programme (WINEP) and National Environment Programme (NEP) in Wales scheme delivery

Background

The WINEP (England) or NEP (Wales) sets out the environmental measures or actions a water and sewerage company needs to invest in and complete during each 5 year AMP investment cycle. A WINEP driver links the statutory obligation or the non-statutory requirement to a water company’s actions.

The WINEP and NEP scheme delivery metric has been part of the EPA since it was introduced for the 2011 data year. The metric definition for the EPA 2026 to 2030 data years includes a change to the drivers included and excluded for EPA reporting.

The reason for this update is due to a new suite of drivers used for AMP8 compared to AMP7. In addition, the relative proportion of monitoring schemes (40% of the total programme) would have a disproportionate impact on WINEP and NEP EPA scoring. They would ‘dilute’ those schemes included in the EPA with more immediate environmental consequence or which are of greater effort to deliver.

This metric is a core EPA metric for the 2026 to 2030 data years. More information on ratings including the core metric approach is in section 4.

Definition of metric

This metric tracks the number of WINEP or NEP schemes delivered against the planned number of schemes. The metric reports scheme delivery as a percentage of the total number of schemes due to be delivered at that stage. This will be reported using the cumulative approach (that means cumulatively tracking the whole AMP 5 year programme). This metric will apply to AMP8 year 1 (starting 1 April 2025) to AMP8 year 5 (ending 31 March 2030) inclusive.

This metric will report on delivery of water quality, water resources, and natural environment, improvement (IMP), no deterioration (ND), and investigation (INV) schemes. It also includes schemes with the natural environment driver INNS_MON.

The EPA excludes all other monitoring (MON) drivers: EnvAct_MON1, EnvAct_MON2, EnvAct_MON3, EnvAct_MON4, EnvAct_MON5, EPR_MON1, U_MON3, U_MON4 and U_MON6. Schemes not delivered in AMP7 will be carried over into AMP8 tracker spreadsheets. For the EPA we will exclude schemes carried over from the previous AMP trackers with these driver codes. We will also exclude schemes with the U_MON1, U_MON2, BW_MON, SW_MON and the investigation driver code U_INV2.

Natural Resources Wales uses different driver codes for the NEP. Natural Resources Wales’s EPA calculations include schemes with a W_WFD_SHELL_MON1 or W_U_O_MON1 driver code.

Definitions for the AMP8 WINEP driver codes can be found within the ‘Driver Code Descriptions’ sheet in the published WINEP dataset.

Please note, we will continue to assess the delivery of actions with non-EPA driver codes. For English water and sewerage companies progress against these will be reported in the narrative of the annual performance report and will be used in the annual performance reviews with each water and sewerage company. Natural Resources Wales will report progress for all non-EPA drivers as part of overall end of year discussions with Dŵr Cymru Welsh Water and Welsh Government.

Obligation

This metric is relevant to the Environmental Permitting (England & Wales) Regulations 2016 which applied from 1 January 2017 onwards. The Water Industry Act 1991, Section 94, states a general sewerage duty – duty to provide, improve, extend sewers and to cleanse and maintain sewers and lateral drains to effectually drain its area, and to deal effectually with the contents of sewers.

The WINEP and NEP contain a wide range of schemes that the water company have committed to delivering. These schemes are driven by different requirements within various environmental legislation such as the Water Environment (Water Framework Directive) Regulations 2017, the Environment Act 2021, and the Urban Waste Water Treatment (England and Wales) Regulations (UWWTR) 1994.

Delivery and tracking expectations

To record delivery of a WINEP or NEP scheme, water and sewerage companies must update their AMP8 tracker spreadsheet. These include columns for information on planned (indicative in Wales) delivery dates (‘Water Company Planned Delivery Date’) and final completion dates (‘Final Completion Date’) once a company claims delivery of the scheme. We expect water and sewerage companies to:

• manage delivery of their programmes effectively to ensure timely completion – accounting for any input that may be required from the Environment Agency or Natural Resources Wales to ensure completion in line with the planned or indicative delivery dates
• give advanced early warning where they suspect the scheme will not be delivered on time or to the expected standard
• report to us once the scheme has been delivered, providing any requested evidence to allow the regulator assurance process to occur

A scheme will count as a non-delivery in the EPA calculation where it has a date within the ‘Latest Allowable Delivery Date’ column which is within the current EPA reporting year, but we deem the scheme ‘not signed off’. This may be where:

• the water and sewerage company do not claim delivery of the scheme
• requested evidence has not been provided by the water and sewerage company to give assurance that delivery has occurred
• the evidence of delivery provided does not give the required assurance that the scheme has been delivered as expected
• evidence of delivery has been provided, but this is provided later than the sign-off guidance stipulates, which has compromised our assurance process
• the water and sewerage company claim delivery and provide the required evidence – however the scheme has been delivered later than the date within the ‘Latest Allowable Delivery Date’ column, albeit still delivered within the same AMP year

A water and sewerage company may claim to have delivered a scheme within the current EPA reporting year (based on their ‘Final Completion Date’ column), despite it not being due until a later AMP year (based on the date within the ‘Latest Allowable Delivery Date’ column). If we deem it ‘not signed-off’ (based on the decision in the ‘Sign Off’ column), this scheme will not be counted as a non-delivery for the EPA calculation. This is because the scheme is not technically due until a later AMP year. A revised planned delivery date (‘Water Company Planned Delivery Date’ column), to ensure delivery in time for the date within the ‘Latest Allowable Delivery Date’ column, will need to be agreed with us. The scheme will be assessed for EPA in the relevant future EPA reporting year.

A scheme may be delivered and signed off by us in the current EPA reporting year (based on the ‘Final Completion Date’ column and the decision in the ‘Sign Off’ decision column) despite having a statutory profiling date in a later AMP year. It will be counted as planned and delivered in the current EPA reporting year.

A water and sewerage company may provide the correct evidence of delivery, but we may not have finalised our decision in advance of EPA reporting. In this case, the scheme will be excluded from the current year’s EPA calculation and will be assessed in a future EPA reporting year. This will be marked as ‘pending’ within our ‘Sign Off’ column.

A water and sewerage company may fail to deliver a scheme on time to meet the date within the ‘Latest Allowable Delivery Date’ column. A new planned completion date (‘Water Company Planned Delivery Date’ column) will be agreed between us and the company. Where agreement is not reached, a date is set by us. This should be as soon as possible and should be no more than 12 months from the date within the ‘Latest Allowable Delivery Date’ column. Note this date change should not be treated as an extension to delivery. The date within the ‘Latest Allowable Delivery Date’ column should remain unchanged to reflect that delivery is overdue. In these cases, the water and sewerage company should provide regular delivery progress updates to us and Ofwat. Where the scheme is associated with a permitted or licenced activity, we may explore regulatory enforcement action.

For the reporting of a scheme that was reported as not delivered in the previous AMP year:

• if the scheme remains undelivered in the current AMP year, then we continue to report the scheme as not delivered within the AMP year it was expected to be delivered (based on the date within the ‘Latest Allowable Delivery Date’ column)
• if the scheme has been delivered by the new agreed date (that is the date in the ‘Water Company Planned Delivery Date’ column), then we report as delivered within the AMP year it was expected to be delivered (based on the date within the ‘Latest Allowable Delivery Date’ column)
• the exception to the above points is where a scheme was expected to be delivered in AMP7, but is rolled over to year 1 of AMP8 to ensure it continues to be tracked and counted as part of EPA assessment

Calculation

The metric reports scheme delivery percentage, based on the dataset within each water and sewerage company AMP8 WINEP or NEP tracker spreadsheet. The calculation includes schemes with a relevant driver code (see ‘definition of metric’ section). It assesses the number of schemes that should have been delivered at that stage in the AMP (based on the date within the ‘Latest Allowable Delivery Date’ column), against the number of schemes that have been delivered (based on the ‘Sign Off’ decision column).

The following example demonstrates the cumulative approach using AMP8 year 3. At the end of AMP8 year 3, the number of schemes not delivered in years 1, 2 and 3 combined (A), is recorded. This is then calculated as a percentage of the number of schemes planned in years 1, 2, and 3 combined (B).

Schemes not delivered (A) = any WINEP or NEP scheme with an applicable primary driver code, where the date within the ‘Latest Allowable Delivery Date’ column is between 1 April 2025 to 31 March 2028, but our sign-off decision is ‘not signed-off’.

Schemes planned (B) = any WINEP or NEP scheme with an applicable primary driver code where the date within the ‘Latest Allowable Delivery Date’ column is between 1 April 2025 to 31 March 2028 + any WINEP or NEP scheme with an applicable primary driver code where the date within the ‘Latest Allowable Delivery Date’ column is after 31 March 2028 but where the water and sewerage company have claimed delivery prior to 1 April 2028, and this has been assigned as ‘signed off’ by us.

The calculation is: (B – A) ÷ B × 100 = delivery percentage

Note that the calculated % is rounded to 1 decimal place for assessment against the thresholds below and for reporting.

Frequency of assessment

The frequency of assessment is annually in line with the WINEP and NEP delivery year (1 April to 31 March).

Expectation

In 2022 the Environment Agency set out its performance expectations for 2025 to 2030 in the WISER in England. This includes 100% WINEP delivery with all actions identified within the WINEP planned and completed to agreed timescales and specification. This expectation is reflected in the RAG status thresholds for this metric.

RAG status thresholds

The RAG status thresholds for this metric are:

• red – less than or equal to 98% scheme delivery
• amber – less than 100% and greater than 98% scheme delivery
• green – 100% scheme delivery

2.9 Water resources scheme delivery

As part of the ongoing EPA development we are implementing a new water resources delivery metric to replace the existing Supply Demand Balance Index (SDBI). Following the recent water resources scheme delivery metric consultation, the outcome will shortly be communicated separately, and will include details of the metric, however we expect these to be refined during 2025/2026. We intend to go live with the water resources delivery metric for the 2026/2027 data year for inclusion in the annual EPA report published in 2027.

Next: 3. RAG thresholds for EPA metrics.