Caernarfon

Polluted by sewage 705 times in 2025 lasting 5,262 hours

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Totals for Caernarfon in 2025

12 Sites polluted by Dwr Cymru Welsh Water
705 sewage dumps
5,262 hours duration
Sewage pollution map of Caernarfon
Sewage pollution map of Caernarfon: 5,262 hours in 2025
That's 7.31 months. On average 1.9 times a day

Change Over Time

Constituency for Caernarfon

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Pollution Summary 2025

Here are all the reported sewage overflow totals for Caernarfon in 2025. Sometimes sewage can be being dumped for months at a time.

Reporting refers to how much of the time the monitoring was active. In this place all the declared CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway s appeared to have monitoring enabled for more than 50% of the year

Company Waterway Site Sewage Dumps Duration (Hours) Reporting %
Dwr Cymru Welsh Water Menai Strait BRYNSCIENCYN STW 184 2,785 99.9
Dwr Cymru Welsh Water River Seiont CAERNARFON STW 90 1,251 99.8
Dwr Cymru Welsh Water Seiont CAERNARFON PONT SEIONT PS 41 354 99.7
Dwr Cymru Welsh Water River Seiont CAERNARFON WWTW INLET PUMP ST 6MM 83 301 99.8
Dwr Cymru Welsh Water Cadnant - Caernarfon SSO AT MILL LANE CAERNARFON 87 194 99.9
Dwr Cymru Welsh Water Menai Strait BRYNSCIENCYN PS , , 13 103 99.9
Dwr Cymru Welsh Water River Seiont Peblig Industrial Estate CSO 37 97 98.2
Dwr Cymru Welsh Water Menai Straits CROSSVILLE CSO 67 95 99.9
Dwr Cymru Welsh Water Unnamed Watercourse CAERNARFON MARGARET STREET SSO 57 36 98.7
Dwr Cymru Welsh Water River Seiont Caernarfon WWTW Inlet Pump ST 6mm SPS 18 28 99.8
Dwr Cymru Welsh Water Cadnant MIN-Y-NANT CSO 27 14 99.7
Dwr Cymru Welsh Water Menai Straits BALACLAVA ROAD SEWAGE PUMPING ST 1 0 99.8
Dwr Cymru Welsh Water River Siont ANGLESEY ARMS PUMPING STATION 0 0 100
Dwr Cymru Welsh Water Menai Straits CAERNARFON BANK QUAY PS 0 0 99.9
Dwr Cymru Welsh Water Menai Strait WATERLOO PORT SEWAGE PUMPING ST 0 0 99.2

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.