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Area of Outstanding Natural Beauty

Ynys Mon / Anglesey - 2025 Sewage

Polluted by sewage 16,691 hours in 2025 - That's 1.93 years

© OpenStreetMap contributors
Contains OS Data © Crown copyright & database right 2021-2024
© Top of the Poops 2021-2024

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Totals for 2025

Sewage16,691 hours
Monitoring offline0 hours
Potential pollution0 hours
Storm overflows54

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Daily Data - when it rained, and when they spilled

Square = rainfall none → heavy
Drop = sewage minutes → all day
Potential pollution Monitoring offline
Jan - 0 hours
Feb - 878 hours
Mar - 672 hours
Apr - 574 hours
May - 115 hours
Jun - 382 hours
Jul - 179 hours
Aug - 73 hours
Sept - 1,330 hours
Oct - 1,055 hours
Nov - 5,295 hours
Dec - 6,106 hours

Storm overflows in and around Ynys Mon / Anglesey

Company Site Name Receiving Waterway Overflow Days Total Duration (hours) Offline/Potential Pollution
Dwr Cymru Welsh Water Llanfachraeth WwTW Overflow River Alaw 319 4,497h 4m -
Dwr Cymru Welsh Water Brynsiencyn WwTW Storm Overflow Menai Strait 102 1,574h 12m -
Dwr Cymru Welsh Water Aberffraw WwTW Storm Overflow Aberffraw Bay 76 1,505h 19m -
Dwr Cymru Welsh Water Menai Llandegfan Storm Overflow Menai Strait 56 1,232h 46m -
Dwr Cymru Welsh Water Bangor Treborth WwTW Storm Overflow Menai Strait 69 966h 21m -
Dwr Cymru Welsh Water Bull Bay Storm Overflow Bull Bay 66 900h 30m -
Dwr Cymru Welsh Water Unknown Unknown 36 550h 2m -
Dwr Cymru Welsh Water Llanfair Pwllgwyngyll WwTW Storm Overflow Menai Strait 83 486h 41m -
Dwr Cymru Welsh Water Gorsllwyd Llanddona Storm Overflow Afon Cadnant 39 393h 55m -
Dwr Cymru Welsh Water Llanfaelog Storm Overflow Llyn Maelog 34 382h 4m -
Dwr Cymru Welsh Water Copperfield Close Four Mile Bridge Storm Overflow Holy Island Straits South 29 377h 16m -
Dwr Cymru Welsh Water Bae Trearthur Isallt Bach Overflow Caernarfon Bay North 25 364h 15m -
Dwr Cymru Welsh Water Llaneilian Storm Overflow Coastal Waters 34 362h 32m -
Dwr Cymru Welsh Water Hermon Malltraeth Storm Overflow Afon Frechwen 27 338h 27m -
Dwr Cymru Welsh Water Holyhead Bae Trearthur No2 Storm Overflow Unnamed Watercourse 27 316h 59m -
Dwr Cymru Welsh Water Holyhead Bae Trearthur No1 Storm Overflow Estuarial Waters of the Inland Sea 28 259h 30m -
Dwr Cymru Welsh Water Menai Ville Storm Overflow Menai Strait 47 242h 57m -
Dwr Cymru Welsh Water Menai Bridge Faelog Causeway 1 Overflow Menai Strait 44 238h 27m -
Dwr Cymru Welsh Water Holyhead WwTW Overflow Unnamed Watercourse 50 181h 27m -
Dwr Cymru Welsh Water Newborough WwTW Storm Overflow Afon Braint 24 180h 12m -
Dwr Cymru Welsh Water Gorad Beach Road Storm Overflow Estuarial Waters of Afon Alaw 21 159h 30m -
Dwr Cymru Welsh Water Fryars Bay Llanfaes Overflow Menai Strait 27 143h 50m -
Dwr Cymru Welsh Water Menai Bridge Suspension Storm Overflow Menai Strait 52 138h 28m -
Dwr Cymru Welsh Water Menai Suspension Bridge No 3 Overflow Menai Strait 48 131h 58m -
Dwr Cymru Welsh Water Brynsciencyn Overflow Menai Strait 12 98h -
Dwr Cymru Welsh Water Unknown Unknown 16 92h 16m -
Dwr Cymru Welsh Water Brynsiencyn Main Storm Overflow Menai Strait 12 88h 26m -
Dwr Cymru Welsh Water Malltraeth WwTW Storm Overflow Cefni Estuary 22 88h 9m -
Dwr Cymru Welsh Water Llangoed Lleiniog Overflow Menai Strait 27 86h 58m -
Dwr Cymru Welsh Water Moelfre Car Park Storm Overflow Coastal Waters of the Irish Sea 15 55h 54m -
Dwr Cymru Welsh Water Llandegfan Rhianfa Overflow Menai Strait 20 53h 27m -
Dwr Cymru Welsh Water Beaumaris West End Overflow Menai Strait 10 31h 50m -
Dwr Cymru Welsh Water Pont y Brenin Overflow Afon y Brenin 10 30h -
Dwr Cymru Welsh Water Beaumaris Green Overflow Estuarial Waters 11 29h 53m -
Dwr Cymru Welsh Water Beaumaris Green Storm Overflow Menai Strait 10 29h 23m -
Dwr Cymru Welsh Water Unknown Unknown 18 29h 12m -
Dwr Cymru Welsh Water Millbank Storm Overflow Unnamed Watercourse 10 16h 9m -
Dwr Cymru Welsh Water Treborth Bangor WwTW Overflow Menai Strait 8 14h 55m -
Dwr Cymru Welsh Water Malltraeth Overflow Afon Cefni 8 5h 42m -
Dwr Cymru Welsh Water High Street Malltraeth Storm Overflow Afon Cefni 6 5h 12m -
Dwr Cymru Welsh Water Benllech Old Tidal Tanks Storm Overflow Coastal Waters - Benllech 3 4h 54m -
Dwr Cymru Welsh Water Glyn Garth Overflow Menai Strait 5 3h 7m -
Dwr Cymru Welsh Water Malltraeth WwTW Inlet Storm Overflow Cefni Estuary 1 1h 13m -
Dwr Cymru Welsh Water Penrhos Beach Holyhead Storm Overflow Beddmanarch Bay 1 1h -
Dwr Cymru Welsh Water Pentraeth Tan Y Graig Storm Overflow River Nodwydd 2 0h 30m -
Dwr Cymru Welsh Water Arosfa Road Dwyran Storm Overflow Afon Braint 1 0h 15m -
Dwr Cymru Welsh Water Llyn Y Felin Storm Overflow Menai Strait 0 0h -
Dwr Cymru Welsh Water Llanfaes Overflow Unnamed Watercourse 0 0h -
Dwr Cymru Welsh Water Llangoed Cynlais Overflow Coastal Waters 0 0h -
Dwr Cymru Welsh Water Lon Fain Dwyran Storm Overflow River Braint 0 0h -
Dwr Cymru Welsh Water Aberffraw Storm Overflow River Ffraw 0 0h -
Dwr Cymru Welsh Water Llyn Y Felin Overflow Menai Strait 0 0h -
Dwr Cymru Welsh Water Gorwelion Road Newlands Beach Storm Overflow Estuary Afon Alaw 0 0h -
Dwr Cymru Welsh Water Bae Trearthur Lon Isallt Storm Overflow Adjacent Ditch 0 0h -

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.