Polluted by sewage 13,647 hours in 2025 - That's 1.58 years
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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 Vale of Glamorgan, 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 | Ewenny No.2 Storm Overflow | River Ewenni | 106 | 2,130 h 45m | 88.75 |
| Dwr Cymru Welsh Water | Cowbridge Llanbethian WwTW Storm Overflow | River Thaw | 107 | 1,713 h 29m | 71.38 |
| Dwr Cymru Welsh Water | Llancarfan WwTW Overflow | Nant Llancarfan | 66 | 1,180 h 15m | 49.17 |
| Dwr Cymru Welsh Water | Wick WwTW Overflow | River Alyn | 107 | 1,179 h 30m | 49.12 |
| Dwr Cymru Welsh Water | Coslech WwTW Storm Overflow | River Ely | 104 | 1,153 h 30m | 48.04 |
| Dwr Cymru Welsh Water | Llandow Storm Overflow | Llandow Brook | 63 | 1,043 h 14m | 43.46 |
| Dwr Cymru Welsh Water | Llysworney Storm Overflow | Stembridge Brook | 42 | 833 h 24m | 34.71 |
| Dwr Cymru Welsh Water | Bonvilston East WwTW Overflow | Nant Llancarfan | 87 | 832 h 44m | 34.67 |
| Dwr Cymru Welsh Water | Trerhyngyll Overflow | Unnamed tributary of the River Thaw | 33 | 727 h 29m | 30.29 |
| Dwr Cymru Welsh Water | North Treoes Bridge Storm Overflow | Nant Ganna | 30 | 549 h 28m | 22.88 |
| Dwr Cymru Welsh Water | West Aberthaw WwTW Storm Overflow | Bristol Channel | 35 | 489 h | 20.38 |
| Dwr Cymru Welsh Water | Ystradowen Storm Overflow | unnamed tributary of Nant Dyfrygi | 20 | 310 h 51m | 12.92 |
| Dwr Cymru Welsh Water | Whitebridge Storm Overflow | River Ely | 22 | 203 h 15m | 8.46 |
| Dwr Cymru Welsh Water | B4265 Storm Overflow | River Thaw | 23 | 200 h 52m | 8.33 |
| Dwr Cymru Welsh Water | Barry Docks Pumped Storm Overflow | Barry No, 2 Dock | 102 | 127 h 37m | 5.29 |
| Dwr Cymru Welsh Water | Llantwit Major Beach Road Settled Storm Overflow | Coastal Waters - Severn Estuary | 11 | 111 h 4m | 4.62 |
| Dwr Cymru Welsh Water | Dyfrig Street Storm Overflow | Barry Dock No1 | 17 | 109 h 58m | 4.54 |
| Dwr Cymru Welsh Water | Llangan Storm Overflow | Canna Brook | 30 | 76 h 45m | 3.17 |
| Dwr Cymru Welsh Water | Unknown | Unknown | 18 | 76 h 39m | 3.17 |
| Dwr Cymru Welsh Water | Barry Town Long Sea Storm Overflow | Severn Estuary | 31 | 72 h | 3 |
| Dwr Cymru Welsh Water | Rock Road Storm Overflow | River Thaw | 14 | 61 h 49m | 2.54 |
| Dwr Cymru Welsh Water | Coldbrook Road Tank Storm Overflow | The Cold Brook | 8 | 53 h 45m | 2.21 |
| Dwr Cymru Welsh Water | Lower Fontygary Overflow | Bristol Channel | 5 | 47 h | 1.96 |
| Dwr Cymru Welsh Water | Peterston-super-Ely WwTW Storm Overflow | River Ely | 14 | 44 h 30m | 1.83 |
| Dwr Cymru Welsh Water | Wenvoe Overflow | Wrinstone Brook | 11 | 36 h | 1.5 |
| Dwr Cymru Welsh Water | Nant Talwg Storm Overflow | Nant Talwg | 7 | 33 h 10m | 1.38 |
| Dwr Cymru Welsh Water | Llantwit Major Beach Road Storm Overflow | River Colhuw | 4 | 31 h 30m | 1.29 |
| Dwr Cymru Welsh Water | Ewenny No.1 Overflow | River Ewenni | 6 | 30 h 45m | 1.25 |
| Dwr Cymru Welsh Water | Daniel Street 1 Storm Overflow | Culverted Section of Coldbrook | 7 | 28 h 15m | 1.17 |
| Dwr Cymru Welsh Water | Weycock Cross Storm Overflow | River Weycock | 5 | 23 h 45m | 0.96 |
| Dwr Cymru Welsh Water | Barry Town Short Sea Storm Overflow | Severn Estuary | 9 | 23 h 11m | 0.96 |
| Dwr Cymru Welsh Water | Whitewell Road 2 Storm Overflow | Coldbrook | 20 | 19 h 50m | 0.79 |
| Dwr Cymru Welsh Water | Robins Lane Storm Overflow | Culverted section of Cold brook | 8 | 18 h 41m | 0.75 |
| Dwr Cymru Welsh Water | Dyfan Road Storm Tank Storm Overflow | Culverted section of Coldbrook | 8 | 16 h 25m | 0.67 |
| Dwr Cymru Welsh Water | Cwm Barry Storm Overflow | Barry Brook | 9 | 11 h 42m | 0.46 |
| Dwr Cymru Welsh Water | Rhoose Storm Overflow | Bristol Channel | 8 | 11 h 22m | 0.46 |
| Dwr Cymru Welsh Water | Craig Penllyne Storm Overflow | River Thaw | 2 | 9 h | 0.38 |
| Dwr Cymru Welsh Water | Atlantic Trading Estate Storm Overflow | River Cadoxton | 1 | 3 h 58m | 0.12 |
| Dwr Cymru Welsh Water | Westward Rise Storm Overflow | Nant Talwg | 3 | 3 h 30m | 0.12 |
| Dwr Cymru Welsh Water | Pontypridd Road Storm Overflow | Barry Brook | 7 | 2 h 59m | 0.08 |
| Dwr Cymru Welsh Water | Coldbrook Road East 2 Storm Overflow | Coldbrook | 3 | 2 h 56m | 0.08 |
| Dwr Cymru Welsh Water | Torbay Terrace Junction Storm Overflow | The Rhoose Brook | 2 | 2 h 32m | 0.08 |
| Dwr Cymru Welsh Water | Harbour Road Barry Town Storm Overflow | Barry Harbour | 2 | 2 h 30m | 0.08 |
| Dwr Cymru Welsh Water | Station Road East Wenvoe Storm Overflow | Wrinstone Brook | 3 | 1 h 30m | 0.04 |
| Dwr Cymru Welsh Water | Broad Street Barry Storm Overflow | Unnamed Culvert leading to Barry Dock No, 1 | 3 | 1 h | 0.04 |
| Dwr Cymru Welsh Water | Whitewell Road 1 Storm Overflow | Coldbrook | 3 | 0 h 45m | 0 |
| Dwr Cymru Welsh Water | Junction of Claude Road West and Severn Avenue Barry Storm Overflow | Barry Brook | 2 | 0 h 45m | 0 |
| Dwr Cymru Welsh Water | Porthkerry Storm Overflow | The Whitelands Brook | 1 | 0 h 43m | 0 |
| Dwr Cymru Welsh Water | Price Avenue Storm Overflow | Coldbrook | 1 | 0 h 30m | 0 |
| Dwr Cymru Welsh Water | Coldbrook Road East 1 Storm Overflow | Culvert leading to Coldbrook | 1 | 0 h 29m | 0 |
| Dwr Cymru Welsh Water | Paget Road Barry Storm Overflow | Barry Old Harbour | 1 | 0 h 15m | 0 |
| Dwr Cymru Welsh Water | Cowbridge Street Barry Storm Overflow | Culverted Section of The Coldbrook | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Fontygary Fonmon Park Road Storm Overflow | Bristol Channel | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Colwinston Storm Overflow | Tributary of Colwinston Brook | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Cold Knap Storm Overflow | Bristol Channel | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Unknown | Unknown | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Millfield Drive Storm Overflow | River Thaw | 0 | 0 h | 0 |
| Dwr Cymru Welsh Water | Nant Talwg Way Storm Overflow | Nant Talwg | 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.