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Polluted by sewage 1,552 hours in 2025
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We get information about overflowing CSOs since January 2025. Here is a chart of the last three months of data for Cardiff South and Penarth, here you can see overflows in red, the darker the red, the more the CSO overflowed that day.
Each CSO has a row, the most recent data is on the right hand side.
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Donate Now| Company | Site Name | Receiving Waterway | Overflow Days | Total Duration (hours) | Total Duration (days) |
|---|---|---|---|---|---|
| Dwr Cymru Welsh Water | Cardiff Central Storm Overflow | Severn Estuary | 61 | 276 h 15m | 11.5 |
| Dwr Cymru Welsh Water | Stonylands Storm Overflow | Sully Brook | 29 | 257 h 49m | 10.71 |
| Dwr Cymru Welsh Water | Penarth Head Storm Overflow | Severn Estuary | 39 | 167 h 9m | 6.96 |
| Dwr Cymru Welsh Water | Cardiff Eastern Long Sea Outfall Storm Overflow | Severn Estuary | 29 | 116 h | 4.83 |
| Dwr Cymru Welsh Water | Cardiff Eastern Short Sea Outfall Storm Overflow | Severn Estuary | 29 | 116 h | 4.83 |
| Dwr Cymru Welsh Water | Cog Moors WwTW Storm Overflow | Coastal Waters - Lavernock Point | 17 | 111 h | 4.62 |
| Dwr Cymru Welsh Water | Penarth Kymin Storm Overflow | Bristol Channel | 35 | 102 h 25m | 4.25 |
| Dwr Cymru Welsh Water | Penarth Marina Storm Overflow | Severn Estuary | 6 | 82 h 44m | 3.42 |
| Dwr Cymru Welsh Water | Cardiff Western District Storm Overflow | River Ely | 12 | 81 h 15m | 3.38 |
| Dwr Cymru Welsh Water | Brockhill Rise Storm Overflow | Bristol Channel | 28 | 80 h | 3.33 |
| Dwr Cymru Welsh Water | Sully Moors Road Storm Overflow | Tributary of Sully Brook | 13 | 37 h 45m | 1.54 |
| Dwr Cymru Welsh Water | St Cadoc's Avenue Dinas Powys Storm Overflow | Cadoxton River | 8 | 34 h 13m | 1.42 |
| Dwr Cymru Welsh Water | Grangetown Storm Overflow | River Taff | 9 | 31 h 45m | 1.29 |
| Dwr Cymru Welsh Water | Penarth Road Storm Overflow | River Ely | 9 | 15 h 59m | 0.62 |
| Dwr Cymru Welsh Water | Havelock Street Cardiff Storm Overflow | River Taff | 9 | 10 h 41m | 0.42 |
| Dwr Cymru Welsh Water | Maple Road Storm Overflow | Culvert to a Tributary of Sully Brook | 5 | 8 h 14m | 0.33 |
| Dwr Cymru Welsh Water | Cogan Flooding Relief Storm Overflow | River Ely via Cowslip | 1 | 6 h 30m | 0.25 |
| Dwr Cymru Welsh Water | Cornerswell Road Penarth Storm Overflow | The Sully Brook | 5 | 6 h 14m | 0.25 |
| Dwr Cymru Welsh Water | Park Street Cardiff Storm Overflow | River Taff | 4 | 4 h 30m | 0.17 |
| Dwr Cymru Welsh Water | Ocean Park Storm Overflow | Severn Estuary | 2 | 2 h 45m | 0.08 |
| Dwr Cymru Welsh Water | Penarth Cogan Storm Overflow | River Ely Estuary | 5 | 2 h | 0.08 |
| Dwr Cymru Welsh Water | Countess Place Penarth Overflow | The Sully Brook | 3 | 0 h 47m | 0 |
| Dwr Cymru Welsh Water | Harrowby Street Storm Overflow | River Taff Estuary | 1 | 0 h 15m | 0 |
| Dwr Cymru Welsh Water | Argae Lane Storm Overflow | Culvert Leading to Coldbrook | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Unknown | Unknown | 0 | 0 h | 0 |
EDM (Event Duration Monitoring) data and Consented Discharges to Controlled Waters with Conditions from Environment Agency & Data Map Wales, and Scottish Water
Experimental derived data from Thames Water API, Some data may be missing or inaccurate. Live sewage data from Stream Water API
Uses Environment Agency rainfall data from the real-time data API (Beta) - Rainfall data is delayed by up to two days.
This website is intended to provide an accurate representation of the Environment Agency data. The data is hard to use, and thus some errors may have been made. If you find something that is incorrect, please raise an issue at the GitHub issues page and we'll endeavour to fix it quickly.
This project is not associated, approved or endorsed by any of the companies whose logos you see here.
Get in touch if you have queries or want to discuss our data.
press [at] top-of-the-poops.org