Area of Outstanding Natural Beauty

Ynys Mon / Anglesey - Live Sewage

Polluted by sewage 6,090 hours in 2026 so far..

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Area of Outstanding Natural Beauty

Totals for Ynys Mon / Anglesey in 2026

Sewage6,090 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 - 1,703 hours

Feb - 1,527 hours

Mar - 997 hours

Apr - 673 hours

May - 234 hours

Jun - 0 hours

Jul - 0 hours

Aug - 164 hours

Sept - 282 hours

Oct - 503 hours

Nov - 2 hours

Daily data is experimental and data is not guaranteed to be accurate. Please inform us of any issue, we will fix.
We don't have rainfall data for Ynys Mon / Anglesey - the Welsh AONBs and the Isles of Scilly have no nearby rainfall station, so only sewage is shown. If you know where to source it please let us know!

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	177	2,946h 5m	-
Dwr Cymru Welsh Water	Bangor Treborth WwTW Storm Overflow	Menai Strait	59	728h 26m	-
Dwr Cymru Welsh Water	Brynsiencyn WwTW Storm Overflow	Menai Strait	99	601h 55m	-
Dwr Cymru Welsh Water	Menai Llandegfan Storm Overflow	Menai Strait	24	332h 48m	-
Dwr Cymru Welsh Water	Llaneilian Storm Overflow	Coastal Waters	22	289h 31m	-
Dwr Cymru Welsh Water	Bull Bay Storm Overflow	Bull Bay	39	211h 45m	-
Dwr Cymru Welsh Water	Llanfair Pwllgwyngyll WwTW Storm Overflow	Menai Strait	64	153h 12m	-
Dwr Cymru Welsh Water	Hermon Malltraeth Storm Overflow	Afon Frechwen	9	139h 30m	-
Dwr Cymru Welsh Water	Aberffraw WwTW Storm Overflow	Aberffraw Bay	9	99h 20m	-
Dwr Cymru Welsh Water	Gorsllwyd Llanddona Storm Overflow	Afon Cadnant	13	85h 42m	-
Dwr Cymru Welsh Water	Copperfield Close Four Mile Bridge Storm Overflow	Holy Island Straits South	7	65h 45m	-
Dwr Cymru Welsh Water	Llanfaelog Storm Overflow	Llyn Maelog	6	54h 28m	-
Dwr Cymru Welsh Water	Menai Ville Storm Overflow	Menai Strait	27	53h 43m	-
Dwr Cymru Welsh Water	Menai Bridge Faelog Causeway 1 Overflow	Menai Strait	27	53h 43m	-
Dwr Cymru Welsh Water	Menai Suspension Bridge No 3 Overflow	Menai Strait	27	48h 29m	-
Dwr Cymru Welsh Water	Menai Bridge Suspension Storm Overflow	Menai Strait	27	48h 15m	-
Dwr Cymru Welsh Water	Lon Fain Dwyran Storm Overflow	River Braint	6	45h 41m	-
Dwr Cymru Welsh Water	Gorad Beach Road Storm Overflow	Estuarial Waters of Afon Alaw	9	40h 57m	-
Dwr Cymru Welsh Water	Newborough WwTW Storm Overflow	Afon Braint	10	24h 53m	-
Dwr Cymru Welsh Water	Llangoed Lleiniog Overflow	Menai Strait	5	13h 12m	-
Dwr Cymru Welsh Water	Holyhead Bae Trearthur No1 Storm Overflow	Estuarial Waters of the Inland Sea	10	11h 58m	-
Dwr Cymru Welsh Water	Fryars Bay Llanfaes Overflow	Menai Strait	8	9h 1m	-
Dwr Cymru Welsh Water	Beaumaris West End Overflow	Menai Strait	6	3h 59m	-
Dwr Cymru Welsh Water	Llyn Y Felin Storm Overflow	Menai Strait	3	3h 30m	-
Dwr Cymru Welsh Water	Llyn Y Felin Overflow	Menai Strait	3	3h 30m	-
Dwr Cymru Welsh Water	Beaumaris Green Overflow	Estuarial Waters	4	3h 14m	-
Dwr Cymru Welsh Water	Llandegfan Rhianfa Overflow	Menai Strait	4	2h 45m	-
Dwr Cymru Welsh Water	Moelfre Car Park Storm Overflow	Coastal Waters of the Irish Sea	1	2h 45m	-
Dwr Cymru Welsh Water	Treborth Bangor WwTW Overflow	Menai Strait	3	2h 45m	-
Dwr Cymru Welsh Water	Holyhead WwTW Overflow	Unnamed Watercourse	3	2h 44m	-
Dwr Cymru Welsh Water	Bae Trearthur Isallt Bach Overflow	Caernarfon Bay North	2	1h 59m	-
Dwr Cymru Welsh Water	Pont y Brenin Overflow	Afon y Brenin	3	1h 29m	-
Dwr Cymru Welsh Water	Glyn Garth Overflow	Menai Strait	2	1h 11m	-
Dwr Cymru Welsh Water	Malltraeth WwTW Inlet Storm Overflow	Cefni Estuary	1	1h 2m	-
Dwr Cymru Welsh Water	Millbank Storm Overflow	Unnamed Watercourse	1	0h 30m	-
Dwr Cymru Welsh Water	Holyhead Bae Trearthur No2 Storm Overflow	Unnamed Watercourse	1	0h 27m	-
Dwr Cymru Welsh Water	Malltraeth WwTW Storm Overflow	Cefni Estuary	1	0h 15m	-
Dwr Cymru Welsh Water	Arosfa Road Dwyran Storm Overflow	Afon Braint	0	0h	-
Dwr Cymru Welsh Water	Llanfaes Overflow	Unnamed Watercourse	0	0h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0h	-
Dwr Cymru Welsh Water	Llangoed Cynlais Overflow	Coastal Waters	0	0h	-
Dwr Cymru Welsh Water	Brynsiencyn Main Storm Overflow	Menai Strait	0	0h	-
Dwr Cymru Welsh Water	Brynsciencyn Overflow	Menai Strait	0	0h	-
Dwr Cymru Welsh Water	Malltraeth Overflow	Afon Cefni	0	0h	-
Dwr Cymru Welsh Water	Aberffraw Storm Overflow	River Ffraw	0	0h	-
Dwr Cymru Welsh Water	Pentraeth Tan Y Graig Storm Overflow	River Nodwydd	0	0h	-
Dwr Cymru Welsh Water	High Street Malltraeth Storm Overflow	Afon Cefni	0	0h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0h	-
Dwr Cymru Welsh Water	Gorwelion Road Newlands Beach Storm Overflow	Estuary Afon Alaw	0	0h	-
Dwr Cymru Welsh Water	Benllech Old Tidal Tanks Storm Overflow	Coastal Waters - Benllech	0	0h	-
Dwr Cymru Welsh Water	Bae Trearthur Lon Isallt Storm Overflow	Adjacent Ditch	0	0h	-
Dwr Cymru Welsh Water	Penrhos Beach Holyhead Storm Overflow	Beddmanarch Bay	0	0h	-
Dwr Cymru Welsh Water	Unknown	Unknown	0	0h	-
Dwr Cymru Welsh Water	Beaumaris Green Storm Overflow	Menai Strait	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.

Analysing sewage pollution by the Water Industry

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Contains Water UK National Storm Overflow Hub Data CC-BY-SA 4.0 and analysis © 2025 Top-Of-The-Poops

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