Area of Outstanding Natural Beauty

Clwydian Range & Dee Valley

Polluted by sewage 543 times in 2025 - lasting 2,887 hours

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Contains OS Data © Crown copyright & database right 2021-2024
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Totals for Clwydian Range & Dee Valley in 2025

22 Sites polluted by Dwr Cymru Welsh Water
543 sewage dumps
2,887 hours duration
Sewage pollution map of Clwydian Range & Dee Valley
Sewage pollution map of Clwydian Range & Dee Valley, showing 543 overflows in 2025
That's 4.01 months. On average 1.5 times a day

How does Clwydian Range & Dee Valley compare?

Clwydian Range & Dee Valley was the #23 most polluted Area of Outstanding Natural Beauty in England & Wales, by duration of sewage overflows, as reported by the water companies

Why the change?

Storm overflows spill when it rains, and 2025 was drier than 2024 - 90% of average annual rainfall against 105%.

So much of any drop is weather, not fixed pipes. The live page shows rainfall and sewage side by side, day by day.

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Pollution Summary 2025

Here are all the reported sewage overflow totals for Clwydian Range & Dee Valley in 2025.

How we count, and how accurate it is

A CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway counts towards Clwydian Range & Dee Valley when it sits inside the designated area, or within 200 metres of its boundary. An overflow close to two AONBs is counted in both.

We use data from the water companies, but we are seeing many anomalies that make us believe that location information is quite poor. The situation is likely far worse than reported here.

Other CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway s just outside the 200 metre boundary are not counted, though they may still affect water quality inside the area.

Company Waterway Site Sewage Dumps Duration (Hours) Reporting %
Dwr Cymru Welsh Water River Dee Corwen Wastewater Treatment Works 58 881 99.9
Dwr Cymru Welsh Water River Dee Llangollen Wastewater Treatment Works 50 455 99.9
Dwr Cymru Welsh Water Unnamed Stream CSO At Corwen Rear Of The Pavillion 73 329 97.9
Dwr Cymru Welsh Water River Dee Cefn Mawr Wastewater Treatment Works 48 318 99.9
Dwr Cymru Welsh Water River Cylflymen CSO at THE REAR OF THE TANNERY 54 208 99.9
Dwr Cymru Welsh Water River Alyn Llanarmon-yn-Ial Wastewater Treatment Works 59 177 99.9
Dwr Cymru Welsh Water Tref Y Nant Brook CSO and EO at Cefn PS 46 157 99.5
Dwr Cymru Welsh Water River Dee Abbey Road CSO 44 139 99.9
Dwr Cymru Welsh Water Alun Llanferres SPS 6 59 99.8
Dwr Cymru Welsh Water Dee Hand Hotel Gardens CSO 44 58 99.9
Dwr Cymru Welsh Water River Dee WEST STREET CSO 11 36 99.9
Dwr Cymru Welsh Water River Clywedog Gwynfryn CSO 14 19 99.9
Dwr Cymru Welsh Water River Alun Llandegla CSO 5 14 99.9
Dwr Cymru Welsh Water River Dee Newbridge SPS 7 14 99.7
Dwr Cymru Welsh Water River Dee Corwen Corner Station Yard CSO 4 7 99.6
Dwr Cymru Welsh Water River Dee Via Surface Water Sewer BERWYN STREET CSO 5 3 99.5
Dwr Cymru Welsh Water River Dee Royal Hotel CSO 3 1 99.9
Dwr Cymru Welsh Water River Dee Llangollen East St CSO 5 1 99.7
Dwr Cymru Welsh Water River Dee Llangollen Chruch St CSO 2 0 97.2
Dwr Cymru Welsh Water River Dee Llangollen Victoria Prom Riverside CSO 2 0 100
Dwr Cymru Welsh Water River Dee Llangollen Riverside Park Printing Works CSO 2 0 99.8
Dwr Cymru Welsh Water River Dee Park Avenue CSO 1 0 99.9

Data Sources & Accuracy

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

Annual figures up to and including 2025 come from official water company returns. The 2026 figure is our own estimate, derived continuously from the companies' live data feeds.

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.