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This publication is available at https://www.gov.uk/government/publications/water-and-sewerage-companies-in-england-environmental-performance-report-2023/southern-water-epa-data-report-2023
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 2023 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 metric status and performance star rating
Main facts
For 2023:
red status for 2 metrics, amber status for 1 metric and green status for 4 metrics
1 of 5 companies (out of 9) rated as requires improvement (2 stars)
Annual performance star rating after assessment of Southern Water’s performance across all EPA metrics
Year
Overall EPA star rating (out of 4)
Star rating description
2011
2 stars
Below average company
2012
2 stars
Below average company
2013
1 star
Poor performing company
2014
2 stars
Below average company
2015
3 stars
Above average company
2016
3 stars
Good company
2017
3 stars
Good company
2018
2 stars
Company requires improvement
2019
1 star
Poor performing company
2020
2 stars
Company requires improvement
2021
1 star
Poor performing company
2022
2 stars
Company requires improvement
2023
2 stars
Company requires improvement
Annual percentage of red, amber or green (RAG) status EPA metric results for Southern Water
Graph note: there were 6 EPA metrics in the years 2011 to 2015 and 2018 to 2021. There were 7 EPA metrics in the years 2016, 2017, 2022 and 2023.
Annual number of EPA metrics and their RAG status results for Southern Water
Year
Number of metrics in EPA
Number of red metrics
Number of amber metrics
Number of green metrics
2011
6
2
1
3
2012
6
2
1
3
2013
6
3
0
3
2014
6
2
0
4
2015
6
0
3
3
2016
7
0
4
3
2017
7
0
4
3
2018
6
2
1
3
2019
6
3
1
2
2020
6
2
2
2
2021
6
4
1
1
2022
7
2
1
4
2023
7
2
1
4
2. Total pollution incidents (sewerage) metric (category 1 to 3)
Main facts
For 2023:
59 sewerage pollution incidents per 10,000km of sewer – this is rated as red
234 actual incidents (needed 85 or fewer to be rated as green)
39,729km sewer length
performance was worse than the sector (36) for sewerage pollution incidents per 10,000km of sewer
1 of 3 companies (out of 9) to be rated red, no companies rated green
Annual number of pollution incidents (category 1 to 3) from Southern Water sewerage assets, with EPA status
2011 to 2015 data
Year
2011
2012
2013
2014
2015
EPA status
red
red
red
red
amber
Incidents per 10,000km sewer
221
189
148
135
75
Actual incident numbers
479
409
320
292
163
2016 to 2020 data
Year
2016
2017
2018
2019
2020
EPA status
amber
amber
amber
red
red
Incidents per 10,000km sewer
35
31
39
110
102
Actual incident numbers
138
123
151
430
400
2021 to 2025 data
Year
2021
2022
2023
2024
2025
EPA status
red
red
red
no data
no data
Incidents per 10,000km sewer
94
90
59
no data
no data
Actual incident numbers
372
358
234
no data
no data
Annual number of pollution incidents (category 1 to 3) from Southern 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 Southern Water sewerage incidents for the calendar years 2011 to 2025
Calendar year
Red status
Amber status
Green status
2011 to 2015
281 or above
110 to 280
109 or below
2016
197 or above
101 to 196
100 or below
2017 to 2020
194 or above
100 to 193
99 or below
2021
165 or above
94 to 164
93 or below
2022
157 or above
90 to 156
89 or below
2023
149 or above
86 to 148
85 or below
2024
146 or above
82 to 145
81 or below
2025
138 or above
78 to 137
77 or below
Number of pollution incidents (total category 1 to 3) from Southern Water sewerage and water supply assets in 2023
Asset type
Number of pollution incidents (category 1 to 3)
Combined sewer overflow
3
Foul sewer
100
Other water industry premises
0
Pumping station
62
Rising main
29
Sewage treatment works
39
Storm tank
0
Surface water outfall
1
Water distribution system (water supply)
17
Water treatment works (water supply)
0
Note: water distribution system and water treatment works (both water supply assets) are not part of the EPA total pollution incidents (sewerage) metric.
Number of pollution incidents (total and breakdown of categories 1 to 3) from Southern Water sewerage and water supply assets in 2023
Asset type
Category 1 to 3
Category 1
Category 2
Category 3
Combined sewer overflow
3
0
0
3
Foul sewer
100
1
3
96
Other water industry premises
0
0
0
0
Pumping station
62
1
2
59
Rising main
29
1
3
25
Sewage treatment works
39
1
1
37
Storm tank
0
0
0
0
Surface water outfall
1
0
0
1
Water distribution system (water supply)
17
0
0
17
Water treatment works (water supply)
0
0
0
0
3. Serious pollution incidents (sewerage and water supply) metric (category 1 and 2)
Main facts
For 2023:
13 serious incidents – this is rated as red (needed 1 or 0 to be rated as green)
13 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 Southern Water assets (sewerage and from 2021 including water supply), with EPA status
2011 to 2015 data
Year
2011
2012
2013
2014
2015
EPA status
red
red
red
red
amber
Serious incidents per 10,000km sewer
9.7
4.6
4.2
5.5
3.2
Actual serious incident numbers – sewerage
21
10
9
12
7
2016 to 2020 data
Year
2016
2017
2018
2019
2020
EPA status
amber
amber
red
red
amber
Serious incidents per 10,000km sewer
0.8
1
1.8
1.8
1.0
Actual serious incident numbers – sewerage
3
4
7
7
4
2021 to 2025 data
Year
2021
2022
2023
2024
2025
EPA status
red
red
red
no data
no data
Serious incident numbers – all assets
12
5
13
no data
no data
Serious incident numbers – sewerage
12
5
13
no data
no data
Serious incident numbers – water supply
0
0
0
no data
no data
Annual number of serious pollution incidents (category 1 and 2) from Southern 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 Southern 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
9 or above
4 to 8
3 or below
2016 to 2020
6 or above
3 to 5
2 or below
2021 and 2022
4 or above
2 or 3
1 or 0
2023 and 2024
3 or above
2
1 or 0
2025
2 or above
1
0
Number of serious pollution incidents (category 1 and 2) from Southern Water sewerage and water supply assets in 2023
Asset type
Number of serious pollution incidents (category 1 and 2)
Combined sewer overflow
0
Foul sewer
4
Other water industry premises
0
Pumping station
3
Rising main
4
Sewage treatment works
2
Storm tank
0
Surface water outfall
0
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 2023:
69% of all incidents self-reported, 80% from just pumping stations (PS) and sewage treatment works (STW) combined – this is rated as amber
needed 80% or higher self-reporting and 90% from just PS and STW combined to be rated as green
174 self-reported incidents, 77 incidents reported by others
performance was worse than the sector (84%) for self-reporting of all pollution incidents
performance was worse than the sector (93%) for self-reporting of just PS and STW pollution incidents combined
worst performing company for self-reporting of all pollution incidents and for self-reporting of just PS and STW pollution incidents combined
1 of 3 companies (out of 9) not to be rated green
Annual self-reporting of pollution incidents (category 1 to 3) from Southern Water sewerage and water supply assets, with EPA rating
2011 to 2015 data
Year
2011
2012
2013
2014
2015
EPA status
green
green
green
green
amber
Percentage of incidents self-reported
84
86
77
69
59
Number of incidents self-reported
405
356
248
203
99
2016 to 2020 data
Year
2016
2017
2018
2019
2020
EPA status
amber
amber
green
green
green
Percentage of incidents self-reported
71
70
83
87
88
Number of incidents self-reported
103
94
156
400
360
2021 to 2025 data
Year
2021
2022
2023
2024
2025
EPA status
green
green
amber
no data
no data
Percentage of incidents self-reported
90
90
69
no data
no data
Number of incidents self-reported
353
352
174
no data
no data
Percentage of PS and STW incidents self-reported
96
95
80
no data
no data
Number of PS and STW incidents self-reported
259
213
81
no data
no data
Annual self-reporting of pollution incidents (category 1 to 3) from Southern 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 Southern Water sewerage and water supply assets in 2023
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
1
2
Foul sewer
52
48
Other water industry premises
0
0
Pumping station
51
11
Rising main
24
5
Sewage treatment works
30
9
Storm tank
0
0
Surface water outfall
1
0
Water distribution system (water supply)
15
2
Water treatment works (water supply)
0
0
Self-reporting of serious pollution incidents (category 1 to 2) from Southern Water sewerage and water supply assets in 2023
Asset type
Number of serious pollution incidents self-reported (category 1 to 2)
Number of serious pollution incidents not self-reported (category 1 to 2)
Combined sewer overflow
0
0
Foul sewer
3
1
Other water industry premises
0
0
Pumping station
2
1
Rising main
3
1
Sewage treatment works
0
2
Storm tank
0
0
Surface water outfall
0
0
Water distribution system (water supply)
0
0
Water treatment works (water supply)
0
0
5. Discharge permit compliance (numeric) metric
Main facts
For 2023:
99.4% numeric discharge permit compliance – this is rated as green
24 permitted discharge outlets from water treatment works (WTW) – 100% compliance (0 non-compliant WTW)
performance was better than the sector (98.8.%) for numeric discharge permit compliance
1 of 6 companies (out of 9) to be rated green
Annual discharge permit compliance (numeric) for Southern Water (STW and from 2016 includes WTW), with EPA status
2011 to 2015 data
Year
2011
2012
2013
2014
2015
EPA status
red
amber
red
green
green
Percentage permit compliance
96.0
96.8
96.0
99.0
99.3
Number of permitted discharge outlets from STW
277
277
298
295
291
Number of non-compliant STW
11
9
12
3
2
2016 to 2020 data
Year
2016
2017
2018
2019
2020
EPA status
amber
amber
green
amber
amber
Percentage permit compliance
98.7
98.2
99.1
98.8
97.1
Number of permitted discharge outlets from STW
293
309
313
316
315
Number of permitted discharge outlets from WTW
11
19
20
20
25
Number of non-compliant STW
2
5
1
2
10
Number of non-compliant WTW
2
1
2
2
0
2021 to 2025 data
Year
2021
2022
2023
2024
2025
EPA status
red
amber
green
no data
no data
Percentage permit compliance
97.9
98.2
99.4
no data
no data
Number of permitted discharge outlets from STW
315
313
312
no data
no data
Number of permitted discharge outlets from WTW
25
24
24
no data
no data
Number of non-compliant STW
6
6
2
no data
no data
Percentage compliance STW
98.1
98.1
99.4
no data
no data
Number of non-compliant WTW
1
0
0
no data
no data
Percentage compliance WTW
96.0
100
100
no data
no data
Annual discharge permit compliance (numeric) for Southern 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 2024 (cumulative progress years 1 to 4 of the WINEP):
100% EPA schemes completed within planned deadlines – this is rated as green
258 EPA schemes completed within planned deadlines
performance was better than the sector (100%)
1 of 6 companies (out of 9) to be rated green
511 non-EPA WINEP schemes completed within planned deadlines
190 non-EPA WINEP schemes did not meet requirements within planned deadlines
Annual delivery of the NEP (WINEP from April 2020) by Southern 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
green
green
green
green
Percentage of NEP complete to date (cumulative)
124
109
100
100
100
Cumulative number of schemes completed during AMP period
124
190
200
267
2
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
red
red
Percentage of NEP complete to date (cumulative)
100
100
100
90.0
87.2
Cumulative number of schemes completed during AMP period
80
113
137
207
34
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
green
green
no data
no data
Percentage of WINEP to date complete within deadlines (to date)
98.4
100
100
no data
no data
Cumulative number of schemes completed during AMP period
127
255
258
no data
no data
Cumulative number of water quality schemes completed during AMP period
106
225
227
no data
no data
Cumulative number of water resources schemes completed during AMP period
3
4
5
no data
no data
Cumulative number of fisheries, biodiversity and geomorphology schemes completed during AMP period
18
26
26
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 2023:
99.28% satisfactory sludge disposal and use – this is rated as green
59,242t (tonnes dry solid) total volume dispatched
13,576ha (hectares) land used for spreading
100% of sludge produced was used in agriculture
1 of 4 companies (out of 9) to report less than 100% satisfactory sludge disposal and use – all companies rated green
Annual compliance with sludge disposal and use metric by Southern 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)
101.4
59.5
64.0
61.0
50.9
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)
60.4
53.2
53.8
50.7
58.1
2021 to 2025 data
Year
2021
2022
2023
2024
2025
EPA status
no data
green
green
no data
no data
Percentage of sludge compliant
no data
100
99.28
no data
no data
Total volume of sludge dispatched (t thousands dry solid)
59.0
60.0
59.2
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 Southern Water
565 megalitres per day water distributed to the network – above forecast
1 of 9 companies (out of 9) to be rated green
Annual compliance with SDBI by Southern Water, with EPA ratings
Financial year ending
2022
2023
2024
2025
2026
EPA status
red
green
green
no data
no data
SDBI score
97
100
100
no data
no data
Table note: the EPA RAG status thresholds are in the EPA metric guide.
9. Event Duration Monitoring (EDM) delivery
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.
Southern Water storm overflows
Year
2023
Total number of active storm overflows listed in the annual return
976
Total number of active storm overflows with EDM commissioned
976
Percentage of active storm overflows listed with EDM commissioned
100
Total number of storm overflows with spill data
962
Percentage of storm overflows listed with spill data
98.5
Average number of spills per storm overflow with spill data
30.7
Average duration (hours) per monitored spill event
10.8
Percentage storm overflows with ≥90% EDM operation during reporting period
