Thames Water EPA data report 2022
Published 12 July 2023
Applies to England
© Crown copyright 2023
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This publication is available at https://www.gov.uk/government/publications/water-and-sewerage-companies-in-england-environmental-performance-report-2022/thames-water-epa-data-report-2022
This report provides company specific data and information on the Environmental Performance Assessment (EPA) metrics. It contains current year and historic performance data (as published at the time, based on data provided in part by the water companies). For further information on what each EPA metric and performance star ratings mean see our EPA metric guide.
In addition to the EPA metrics, this report contains a section on event duration monitoring (EDM) of storm overflows. For a comparison between water companies and wider regulatory information see the Environmental performance of the water and sewerage companies in 2022 report.
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
We review and revise thresholds every 5 years.
1. EPA performance star rating
For 2022, Thames Water is 1 of 5 companies (out of 9) rated as requiring improvement (2 stars).
Annual performance star rating after assessment of Thames Water’s performance across all EPA metrics
| Year | Overall EPA star rating (out of 4) | Star rating description |
|---|---|---|
| 2011 | 3 stars | Above average company |
| 2012 | 3 stars | Above average company |
| 2013 | 2 stars | Below average company |
| 2014 | 3 stars | Above average company |
| 2015 | 3 stars | Above average company |
| 2016 | 2 stars | Company requires improvement |
| 2017 | 3 stars | Good company |
| 2018 | 3 stars | Good company |
| 2019 | 3 stars | Good company |
| 2020 | 3 stars | Good company |
| 2021 | 2 stars | Company requires improvement |
| 2022 | 2 stars | Company requires improvement |
2. Total pollution incidents (sewerage) metric (category 1 to 3)
Main facts
For 2022:
- 30 sewerage pollution incidents per 10,000km of sewer – this is rated as amber
- 331 actual incidents (needed 245 or fewer to be rated as green)
- 108,980km sewer length
- performance was better than the sector (31) for sewerage pollution incidents per 10,000km of sewer
- 1 of 5 companies (out of 9) not to be rated green
Annual number of pollution incidents (category 1 to 3) from Thames Water sewerage assets, with EPA status
2011 to 2015 data
| Year | 2011 | 2012 | 2013 | 2014 | 2015 |
|---|---|---|---|---|---|
| EPA status | green | amber | amber | amber | green |
| Incidents per 10,000km sewer | 38 | 68 | 90 | 76 | 38 |
| Actual incident numbers | 258 | 468 | 612 | 517 | 263 |
2016 to 2020 data
| Year | 2016 | 2017 | 2018 | 2019 | 2020 |
|---|---|---|---|---|---|
| EPA status | amber | amber | amber | amber | amber |
| Incidents per 10,000km sewer | 33 | 28 | 27 | 30 | 27 |
| Actual incident numbers | 357 | 303 | 297 | 325 | 292 |
2021 to 2025 data
| Year | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|
| EPA status | amber | amber | no data | no data | no data |
| Incidents per 10,000km sewer | 25 | 30 | no data | no data | no data |
| Actual incident numbers | 271 | 331 | no data | no data | no data |
Annual number of pollution incidents (category 1 to 3) from Thames Water sewerage assets, also showing EPA status and thresholds
Graph note: the EPA RAG status thresholds are set for normalised (per 10,000km sewer) numbers of sewerage incidents (see our EPA metric guide). We review and revise thresholds every 5 years. Equivalent thresholds for actual incident numbers are calculated using water company sewer length data – these are shown in the graph background and the table below.
EPA thresholds for actual number of Thames Water sewerage incidents for the calendar years 2011 to 2025
| Calendar year | Red status | Amber status | Green status |
|---|---|---|---|
| 2011 to 2015 | 885 or above | 346 to 884 | 345 or below |
| 2016 | 542 or above | 280 to 541 | 279 or below |
| 2017 to 2020 | 543 or above | 280 to 542 | 279 or below |
| 2021 | 453 or above | 257 to 452 | 256 or below |
| 2022 | 431 or above | 246 to 430 | 245 or below |
| 2023 | 409 or above | 235 to 408 | 234 or below |
| 2024 | 398 or above | 224 to 397 | 223 or below |
| 2025 | 376 or above | 213 to 375 | 212 or below |
Number of pollution incidents (category 1 to 3) from Thames Water sewerage and water supply assets in 2022
| Asset type | Number of pollution incidents (category 1 to 3) |
|---|---|
| Combined sewer overflow | 5 |
| Foul sewer | 178 |
| Other water industry premises | 1 |
| Pumping station | 19 |
| Rising main | 23 |
| Sewage treatment works | 79 |
| Storm tank | 1 |
| Surface water outfall | 25 |
| Water distribution system (water supply) | 65 |
| Water treatment works (water supply) | 1 |
Note: water distribution system and water treatment works (both water supply assets) are not part of the EPA total pollution incidents (sewerage) metric.
3. Serious pollution incidents (sewerage and water supply) metric (category 1 and 2)
Main facts
For 2022:
- 17 serious incidents – this is rated as red (needed 3 or fewer to be rated as green)
- 17 serious incidents from sewerage assets
- 0 serious incidents from water supply assets
- 1 of 4 companies (out of 9) to be rated red
Annual number of serious pollution incidents (category 1 and 2) from Thames Water assets (sewerage and from 2021 including water supply), with EPA status
2011 to 2015 data
| Year | 2011 | 2012 | 2013 | 2014 | 2015 |
|---|---|---|---|---|---|
| EPA status | amber | amber | amber | amber | amber |
| Serious incidents per 10,000km sewer | 2.9 | 2.2 | 3.2 | 2.3 | 1.8 |
| Actual serious incident numbers – sewerage | 20 | 15 | 22 | 16 | 12 |
2016 to 2020 data
| Year | 2016 | 2017 | 2018 | 2019 | 2020 |
|---|---|---|---|---|---|
| EPA status | amber | amber | amber | amber | amber |
| Serious incidents per 10,000km sewer | 0.9 | 0.9 | 0.8 | 1.4 | 1.2 |
| Actual serious incident numbers – sewerage | 10 | 10 | 9 | 15 | 13 |
2021 to 2025 data
| Year | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|
| EPA status | red | red | no data | no data | no data |
| Serious incident numbers – all assets | 12 | 17 | no data | no data | no data |
| Serious incident numbers – sewerage | 12 | 17 | no data | no data | no data |
| Serious incident numbers – water supply | 0 | 0 | no data | no data | no data |
Annual number of serious pollution incidents (category 1 and 2) from Thames Water assets (sewerage and from 2021 including water supply), also showing EPA status and thresholds
Graph note: for 2011 to 2020 EPA RAG status thresholds were set for normalised (per 10,000km sewer) numbers of serious sewerage incidents (see our EPA metric guide). Equivalent thresholds for actual serious sewerage incident numbers were calculated using water company sewer length data. We review and revise thresholds every 5 years. For 2021 to 2025 water companies are in one of two groups with different thresholds set for actual serious sewerage and water supply incident numbers. The thresholds for actual serious incident numbers are shown in the graph background and the table below.
EPA thresholds for number of serious incidents from Thames Water assets (sewerage and from 2021 including water supply) for the calendar years 2011 to 2025
| Calendar year | Red status | Amber status | Green status |
|---|---|---|---|
| 2011 to 2015 | 27 or above | 11 to 26 | 10 or below |
| 2016 to 2020 | 16 or above | 7 to 15 | 6 or below |
| 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 0 |
Number of serious pollution incidents (category 1 and 2) from Thames Water sewerage and water supply assets in 2022
| Asset type | Number of serious pollution incidents (category 1 and 2) |
|---|---|
| Combined sewer overflow | 1 |
| Foul sewer | 7 |
| Other water industry premises | 0 |
| Pumping station | 0 |
| Rising main | 6 |
| Sewage treatment works | 2 |
| Storm tank | 0 |
| Surface water outfall | 1 |
| Water distribution system (water supply) | 0 |
| Water treatment works (water supply) | 0 |
4. Self-reporting of pollution incidents (sewerage and water supply) metric
Main facts
For 2022:
- 74% of all incidents self-reported, 94% from just pumping stations (PS) and sewage treatment works (STW) combined – this is rated as amber
- 293 self-reported incidents, 104 incidents reported by others
- needed 80% or higher self-reporting and 90% from just PS and STW combined to be rated as green
- performance was worse than the sector (82%) for self-reporting of all pollution incidents
- performance was better than the sector (92%) for self-reporting of just PS and STW pollution incidents combined
- 1 of 4 companies (out of 9) not to be green
Annual self-reporting of pollution incidents (category 1 to 3) from Thames Water sewerage and water supply assets, with EPA rating
2011 to 2015 data
| Year | 2011 | 2012 | 2013 | 2014 | 2015 |
|---|---|---|---|---|---|
| EPA status | amber | amber | amber | amber | amber |
| Percentage of incidents self-reported | 46 | 50 | 58 | 53 | 61 |
| Number of incidents self-reported | 123 | 240 | 359 | 280 | 164 |
2016 to 2020 data
| Year | 2016 | 2017 | 2018 | 2019 | 2020 |
|---|---|---|---|---|---|
| EPA status | amber | amber | green | green | amber |
| Percentage of incidents self-reported | 67 | 73 | 76 | 78 | 63 |
| Number of incidents self-reported | 244 | 235 | 254 | 290 | 209 |
2021 to 2025 data
| Year | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|
| EPA status | red | amber | no data | no data | no data |
| Percentage of incidents self-reported | 65 | 74 | no data | no data | no data |
| Number of incidents self-reported | 199 | 293 | no data | no data | no data |
| Percentage of PS and STW incidents self-reported | 81 | 94 | no data | no data | no data |
| Number of PS and STW incidents self-reported | 65 | 92 | no data | no data | no data |
Annual self-reporting of pollution incidents (category 1 to 3) from Thames Water sewerage and water supply assets, also showing EPA status and thresholds
Graph note: the EPA RAG status thresholds (for all sewerage and water supply assets) are shown in the graph background and in the EPA metric guide. We review and revise thresholds every 5 years. From 2021 the additional number in brackets is the self-reporting percentage for just PS and STW incidents combined. To achieve green status self-reporting for all assets must be 80% or above and for just STW and PS combined must be 90% or above.
Self-reporting of pollution incidents (category 1 to 3) from Thames Water sewerage and water supply assets in 2022
| Asset type | Number of pollution incidents self-reported (category 1 to 3) | Number of pollution incidents not self-reported (category 1 to 3) |
|---|---|---|
| Combined sewer overflow | 3 | 2 |
| Foul sewer | 128 | 50 |
| Other water industry premises | 0 | 1 |
| Pumping station | 18 | 1 |
| Rising main | 16 | 7 |
| Sewage treatment works | 74 | 5 |
| Storm tank | 1 | 0 |
| Surface water outfall | 5 | 20 |
| Water distribution system (water supply) | 47 | 18 |
| Water treatment works (water supply) | 1 | 0 |
5. Discharge permit compliance (numeric) metric
Main facts
For 2022:
- 99.5% numeric discharge permit compliance – this is rated as green
- 348 permitted discharge outlets from STW – 99.7% compliance (1 non-compliant STW)
- 36 permitted discharge outlets from water treatment works (WTW) – 97.2% compliance (1 non-compliant WTW)
- needed 4 or fewer non-compliant treatment works to be rated as green
- performance was better than the sector (99.0%) for numeric discharge permit compliance
- 1 of 5 companies (out of 9) to be rated green
Annual discharge permit compliance (numeric) for Thames Water (STW and from 2016 includes WTW), with EPA status
2011 to 2015 data
| Year | 2011 | 2012 | 2013 | 2014 | 2015 |
|---|---|---|---|---|---|
| EPA status | green | green | red | amber | green |
| Percentage permit compliance | 99.7 | 99.1 | 95.7 | 98.9 | 99.1 |
| Number of permitted discharge outlets from STW | 345 | 345 | 350 | 348 | 346 |
| Number of non-compliant STW | 1 | 3 | 15 | 4 | 3 |
2016 to 2020 data
| Year | 2016 | 2017 | 2018 | 2019 | 2020 |
|---|---|---|---|---|---|
| EPA status | amber | green | green | green | green |
| Percentage permit compliance | 97.9 | 99.5 | 99.0 | 99.7 | 99.7 |
| Number of permitted discharge outlets from STW | 349 | 348 | 349 | 349 | 349 |
| Number of permitted discharge outlets from WTW | 34 | 35 | 35 | 36 | 36 |
| Number of non-compliant STW | 6 | 2 | 4 | 1 | 1 |
| Number of non-compliant WTW | 2 | 0 | 0 | 0 | 0 |
2021 to 2025 data
| Year | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|
| EPA status | green | green | no data | no data | no data |
| Percentage permit compliance | 99.0 | 99.5 | no data | no data | no data |
| Number of permitted discharge outlets from STW | 348 | 348 | no data | no data | no data |
| Number of permitted discharge outlets from WTW | 36 | 36 | no data | no data | no data |
| Number of non-compliant STW | 3 | 1 | no data | no data | no data |
| Number of non-compliant WTW | 1 | 1 | no data | no data | no data |
Annual discharge permit compliance (numeric) for Thames Water (STW and from 2016 includes WTW), also showing EPA status and thresholds
Graph note: the EPA RAG status thresholds are shown in the graph background and in the EPA metric guide. We review and revise thresholds every 5 years.
6. Delivery of the Water Industry National Environment Programme (WINEP) metric
Main facts
For the financial year ending 2023 (cumulative year 1, year 2 and year 3 of the WINEP):
-
95.2% schemes completed within planned deadlines – this is rated as red (needed 100% to be rated as green)
- 236 schemes completed within planned deadlines
- 12 schemes (all water quality) did not meet requirements within planned deadline
- performance was worse than the sector (99.5%)
- worst performing company for this metric and only company (out of 9) to be rated red
Annual delivery of the NEP (WINEP from April 2020) by Thames Water, with EPA rating
Data for financial years ending 2012 to 2016
| Financial year ending | 2012 | 2013 | 2014 | 2015 | 2016 |
|---|---|---|---|---|---|
| Asset Management Plan (AMP) | AMP5 | AMP5 | AMP5 | AMP5 | AMP6 |
| EPA status | green | amber | green | green | green |
| Percentage of NEP complete to date (cumulative) | 109 | 96.8 | 102 | 102 | 100 |
| Cumulative number of schemes completed during AMP period | 49 | 60 | 87 | 130 | 10 |
Data for financial years ending 2017 to 2021
| Financial year ending | 2017 | 2018 | 2019 | 2020 | 2021 |
|---|---|---|---|---|---|
| Asset Management Plan (AMP) | AMP6 | AMP6 | AMP6 | AMP6 | AMP7 |
| EPA status | green | green | green | green | amber |
| Percentage of NEP complete to date (cumulative) | 100 | 100 | 100 | 99.3 | 98.0 |
| Cumulative number of schemes completed during AMP period | 64 | 133 | 172 | 265 | 48 |
Data for financial years ending 2022 to 2026
| Financial year ending | 2022 | 2023 | 2024 | 2025 | 2026 |
|---|---|---|---|---|---|
| Asset Management Plan (AMP) | AMP7 | AMP7 | AMP7 | AMP7 | AMP8 |
| EPA status | amber | red | no data | no data | no data |
| Percentage of WINEP complete within deadlines (to date) | 99.5 | 95.2 | no data | no data | no data |
| Cumulative number of schemes completed during AMP period | 191 | 236 | no data | no data | no data |
| Cumulative number of water quality schemes completed during AMP period | 179 | 219 | no data | no data | no data |
| Cumulative number of water resources schemes completed during AMP period | 5 | 5 | no data | no data | no data |
| Cumulative number of fisheries, biodiversity and geomorphology schemes completed during AMP period | 7 | 12 | no data | no data | no data |
Table note: AMP5 schemes that were completed early before their planned year were included in the cumulative delivery percentage (in some cases resulting in percentages over 100%). AMP6 and AMP7 schemes that were completed early before their planned year are not included in the cumulative delivery percentage until their planned year (cannot report over 100%). The EPA RAG status thresholds are in the EPA metric guide. We review and revise thresholds every 5 years.
7. Sludge disposal and use metric
Main facts
For 2022:
-
100% satisfactory sludge disposal and use – this is rated as green
- 219,201t (tonnes dry solid) total volume dispatched
- 37,008ha (hectares) land used for spreading
-
84.5% of sludge produced was used in agriculture
- 1 of 5 companies (out of 9) to report 100% satisfactory sludge disposal and use – all companies rated green
Annual compliance with sludge disposal and use metric by Thames Water, with EPA ratings
2011 to 2015 data
| Year | 2011 | 2012 | 2013 | 2014 | 2015 |
|---|---|---|---|---|---|
| EPA status | green | green | green | green | green |
| Percentage of sludge compliant | 100 | 100 | 100 | 100 | 100 |
| Total volume of sludge dispatched (t thousands dry solid) | 259.4 | 236.4 | 233.6 | 257.4 | 256.7 |
2016 to 2020 data
| Year | 2016 | 2017 | 2018 | 2019 | 2020 |
|---|---|---|---|---|---|
| EPA status | green | green | no data | no data | no data |
| Percentage of sludge compliant | 100 | 100 | no data | no data | no data |
| Total volume of sludge dispatched (t thousands dry solid) | 260.0 | 230.9 | 222.4 | 203.1 | 211.0 |
2021 to 2025 data
| Year | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|
| EPA status | no data | green | no data | no data | no data |
| Percentage of sludge compliant | no data | 100 | no data | no data | no data |
| Total volume of sludge dispatched (t thousands dry solid) | 185.9 | 219.2 | no data | no data | no data |
Table note: for the 2018 to 2021 calendar years, we suspended the metric from the EPA whilst we reviewed our regulatory regime for sludge. The EPA RAG status thresholds are in the EPA metric guide.
Annual summary of sewage sludge disposal and use (dry matter) by Thames Water
| Year | Sewage sludge used in agriculture (t thousands) | Sewage sludge recovered non-agriculture (t thousands) | Sewage sludge disposed (t thousands) |
|---|---|---|---|
| 2021 | 184.5 | 1.4 | 0.0 |
| 2022 | 185.2 | 1.1 | 32.9 |
8. Supply Demand Balance Index (SDBI) metric
Main facts
For the financial year ending 2023:
- SDBI of 100 – this is rated as green
- 6 water resource zones
- 2,574 megalitres per day water distributed to the network
- 1 of 8 companies (out of 9) to be rated green
Annual compliance with SDBI by Thames Water, with EPA ratings
| Financial year ending | 2022 | 2023 | 2024 | 2025 | 2026 |
|---|---|---|---|---|---|
| EPA status | green | green | no data | no data | no data |
| SDBI score | 100 | 100 | no data | no data | no data |
Table note: the EPA RAG status thresholds are in the EPA metric guide.
9. Event Duration Monitoring (EDM) delivery
All water companies have investment in place to monitor all storm overflows by December 2023. 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 2022. The 2022 dataset also includes water company reasons for performance issues with monitors and reasons for high spill counts.
Thames Water storm overflows
| Year | 2022 |
|---|---|
| Total number of storm overflows listed in the annual return | 777 |
| Total number of storm overflows with EDM commissioned | 480 |
| Percentage of storm overflows listed with EDM commissioned | 61.8 |
| Total number of storm overflows with spill data | 472 |
| Percentage of storm overflows listed with spill data | 60.7 |
| Average number of spills per storm overflow with spill data | 17.0 |
| Average duration (hours) per monitored spill event | 9.3 |