Pollution incidents - performance commitment data

What are performance commitments (PCs)?

The water regulator Ofwat sets targets called performance commitments (PCs) to ensure companies deliver the best possible service for customers, society and the environment. Wessex Water has a range of PCs for the 2020-25 period.

Each year we report our results against these commitments, in our Annual Performance Report.

Where appropriate we’re publishing the data underpinning calculation of the PCs – you can find our other PC datasets in the Performance Commitments section.

Pollution incidents PC

Many of the activities we carry out have the potential to cause pollution to the environment if something goes wrong, e.g., if a sewer collapses or if there is a failure at one of our Water Recycling Centres (WRCs). When sewage, or even clean water escapes from our systems, it can lead to environmental damage.

Pollution incidents are reported to the Environment Agency (EA), which is responsible for assessing their impact on the water environment, the land environment and the air environment. The EA assigns one of the following categories in line with the common incident classification scheme (CICS):

Category 1 - major impact
Category 2 - significant impact
Category 3 - minor impact
Category 4 - no impact

The pollution incidents PCs reports the total number of pollution incidents in a calendar year that are from wastewater assets and are classified as category 1-3 impact on water. Category 4 incidents are not included. The same definition is used for the ‘pollution incidents’ metric within the EA’s Environmental Performance Assessment (EPA) for water and sewerage companies.

We report the pollution incidents PC both as the absolute number of pollution incidents, and as a normalised figure (pollution incidents per 10,000 km of our sewer network).

The PC identifies how many times the water environment has been polluted as a result of our activities or assets. As such it incentivises us to improve the quality of the environment by reducing the number of pollution incidents that occur.

Dataset details

The dataset provides details of the pollution incidents that are from wastewater assets and are classified as category 1-3 impact on water in each calendar year.

Column position	Column heading	Description	Units
1	APR reporting year	The reporting year that this pollution incident contributes towards, e.g. 2020-2021, 2021-2022.	N/A
2	Event no	The National Incident Recording System (NIRS) event no. assigned by the EA that acts as a unique ID for the incident.	N/A
3	Observed date and time	The date and time that the pollution was first identified.	dd/mm/yyyy XX:XX (24hr clock format)
4	Reported date and time	The date and time that the pollution was reported to the EA.	dd/mm/yyyy XX:XX (24hr clock format)
5	Grid Ref (approximate)	The partial grid reference of the incident location. For anonymisation reasons, six figure grid references have been rounded to show only the first two figures for the easting and northing, e.g. ST5900041000.	N/A
6	Asset type	The type of asset that caused the pollution incident. There are eight possible entries: ‘Foul Sewer’ – A pipe that transfers wastewater by gravity from homes and businesses towards a Water Recycling Centre (WRC). ‘Rising Main’ – A pressurised pipe that transfers wastewater uphill towards a WRC, where the topography does not enable the wastewater to flow by gravity. ‘Pumping Station’ – Sites where we use pumps to move wastewater through rising mains. ‘Combined Sewer Overflow’ – Combined sewers carry foul water and rainwater in a single pipe. Combined sewer overflows act as ‘relief valves’ for periods of heavy rainfall, allowing excess heavily diluted sewage to be released to rivers or the sea. ‘Sewage Treatment Works’ – Sites for purifying wastewater ready for discharge back to the environment. Also known as Water Recycling Centres (WRCs). ‘Surface Water Outfall’ – Surface water networks take surface water flows such as run off from roofs and impermeable surfaces and discharge them to watercourses. These can sometimes also contain flows from combined sewer overflows. ‘Storm Tank’ – Similar to a CSO but with greater storage capacity, this asset allows excess heavily diluted sewage to be stored and if required discharged to the environment to provide relief during wet weather periods. ‘Other Water Industry Premises’	N/A
7	Water Env. Impact Level	The category assigned to the pollution incident by the Environment Agency (EA) in relation to impact on the water environment. There are three possible entries: ‘Category 1 (major)’ – major impact ‘Category 2 (significant)’ – significant impact ‘Category 3 (minor)’ – minor impact	N/A
8	Land Env. Impact Level	The category assigned to the pollution incident by the Environment Agency (EA) in relation to impact on the land environment. There are two different entries in this dataset: ‘Category 3 (minor)’ – minor impact ‘Category 4 (no impact)’ – no impact	N/A
9	Air Env. Impact Level	The category assigned to the pollution incident by the Environment Agency (EA) in relation to impact on the air environment. There are two different entries in this dataset: *‘Category 3 (minor)’* – minor impact *‘Category 4 (no impact)’* – no impact	N/A
10	Location	The approximate location of the pollution incident, taken from the EA database. In most cases this is the name of the village or town. For reasons of anonymisation, a more exact location is not provided.	N/A
11	Root cause	The outcome of our internal root cause analysis to understand why the pollution occurred. There are around forty different types of cause identified. This is not Environment Agency data and is not used as part of the pollution incidents PC or the EPA. The data is Wessex Water’s understanding of the root cause of the incident and is provided here for context only. We use the root cause analysis to consider how we can reduce the likelihood of similar pollution incidents occurring in future.	N/A

How was this data collated?

The EA sends us a copy of their pollutions database at the end of the calendar year. The published dataset is an extract from this database, with unnecessary detail removed and location information anonymised. We have also added the results of our internal root cause analysis.

Publish frequency

For the remaining years of the 2020-25 period, an additional year of data will be added after the annual reporting period.

Contact

If you have any questions or comments about this data set, please get in touch via opendata@wessexwater.co.uk

Terms of use

This dataset is licensed under CC BY, an open data licence, to make it freely available to other potential customers, stakeholders or interested organisations.

Supplementary information

For those keen to develop a deeper understanding of this dataset, the following additional reading is suggested:

Wessex Water’s Pollution Incident Reduction Plan, which summarises the pollution incidents each year (including cause) and sets out our plan for improvements: Our Pollution Incident Reduction Plan (PIRP)
Environment Agency information about the EPA: Environmental Performance Assessment (EPA) metric guide
Environment Agency 2023 EPA data report for Wessex Water: Wessex Water 2023 EPA
Discover Water’s environmental performance summary data from across the industry: DiscoverWater (en-GB)

Escape of sewage or clean water from our systems can cause environmental damage. The Environment Agency (EA) assesses the environmental impact of pollution incidents and assigns an impact category of 1 (major impact) to 4 (no impact). One of our ‘performance commitments’ (targets) seeks to minimise the total number of category 1-3 pollutions from wastewater assets each year.

Wastewater

Pollution Incidents PC Data 2020 2021 2021 2022 2022 2023 2023 2024 (69kb) /media/3dfkydjw/pollution-incidents-pc-data-2020-2021-2021-2022-2022-2023-2023-2024.csv

About this dataset

Last updated	1 week ago
Commitments	Pollution incidents Bathing water quality River water quality