Ynys Môn was polluted by sewage 4,452 times in 2023
lasting 36,008 hours - that's 4.17 years!
- but monitoring was disabled in some locations, so could be more

Select the constituency from the drop-down

Constituency

✔ means we have experimental daily data since 2023

Totals for Ynys Môn in 2023

81 Sites polluted by Dwr Cymru Welsh Water

4,452 sewage dumps
36,008 h duration

That's 4.17 years! On average 12.2 times a day

Change Over Time

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Constituencies near Ynys Môn

Waterways in Ynys Môn

Pollution Summary 2023

Here are all the reported sewage overflow totals for Ynys Môn in 2023. 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 constituency 4 of the total 91 CSO locations had reporting enabled for less than half the year, of which 4 had zero reporting.

Company	Waterway	Site	Sewage Dumps	Duration (Hours)	Reporting %
Dwr Cymru Welsh Water	River Goch	Craig Y Don SPS	290	4,436	98.1
Dwr Cymru Welsh Water	Unnamed Watercourse To River Goch	Rhosybol Gorslwyd PS	243	2,842	96.5
Dwr Cymru Welsh Water	Menai Strait	BRYNSCIENCYN STW	147	2,230	99.9
Dwr Cymru Welsh Water	Ditch	Hermon Malltraeth PS	131	2,016	94.4
Dwr Cymru Welsh Water	Cadnant	PONT LLANDEGFAN SEWAGE PUMPING STAT	110	1,844	100
Dwr Cymru Welsh Water	Menai Strait	LLANDEGFAN (MENAI) PUMPING STATION	104	1,779	100
Dwr Cymru Welsh Water	River Nodwydd	PENTRAETH STW	159	1,694	100
Dwr Cymru Welsh Water	Menai Strait	PS NO 3 (SUSPENSION BRIDGE) (EMERGE	131	1,510	99.9
Dwr Cymru Welsh Water	Menai Strait	PS NO 3 (SUSPENSION BRIDGE) (EMERGE	131	1,510	99.9
Dwr Cymru Welsh Water	Un-Named Watercourse	VALLEY STORM PS (GRAVITY DISCHARGE)	110	1,404	99.9
Dwr Cymru Welsh Water	River Meddanen	LLANFECHELL PUMPING STATION	96	1,206	100
Dwr Cymru Welsh Water	Unnamed Draining To New Harbour	Porth y Felin Sewage Pumping Station	88	1,103	100
Dwr Cymru Welsh Water	Braint	Gaerwen Station SPS	56	724	99.8
Dwr Cymru Welsh Water	Menai Strait	PS NO 1 (FAELOG CAUSEWAY) (EMERGENC	79	718	100
Dwr Cymru Welsh Water	Menai Strait	PS NO 1 (FAELOG CAUSEWAY) (EMERGENC	79	718	100
Dwr Cymru Welsh Water	Estuarial Waters Of Holy Island Strait South	Four Mile Bridge SPS Holyhead	48	698	100
Dwr Cymru Welsh Water	Menai Strait	Llanfair PG WwTW CSO	132	675	99.7
Dwr Cymru Welsh Water	Irish Sea	RHOSNEIGR SPS RHOSNEIGR	39	645	100
Dwr Cymru Welsh Water	Coastal Waters	BENLLECH WWTW (STW) LSO BENLLECH	88	633	100
Dwr Cymru Welsh Water	Un-Named Watercourse	HOLYHEAD WWTW FINAL EFFLUENT PS	142	610	100
Dwr Cymru Welsh Water	Bull Bay	Bull Bay P.S.	70	570	100
Dwr Cymru Welsh Water	Menai Strait	MOUNT FIELD P.S. BEAUMARIS ,	88	425	99.6
Dwr Cymru Welsh Water	River Briant	LLANDDANIEL PONT Y CRUG SPS	45	393	100
Dwr Cymru Welsh Water	Menai Strait	LLANFAES WWTW STORM TANK	47	376	79.6
Dwr Cymru Welsh Water	Un-Named Watercourse	Valley Storm PS (Pumped Discharge)	83	324	99.9
Dwr Cymru Welsh Water	Unnamed Stream	Llangaffo STW CSO	118	293	100
Dwr Cymru Welsh Water	River Cadnant	Gorsllwyd Sewage Pumping Station	66	273	100
Dwr Cymru Welsh Water	Menai Strait	LLYN Y FELIN PS (EMERGENCY)	28	271	99.6
Dwr Cymru Welsh Water	Menai Strait	LLYN Y FELIN PS (EMERGENCY) , ,	28	271	99.6
Dwr Cymru Welsh Water	Abberffraw Bay	ABERFFRAW WASTE WATER TREATMENT WKS	219	266	72.1
Dwr Cymru Welsh Water	Menai Strait	LLEINIOG PS	59	257	99.9
Dwr Cymru Welsh Water	Llyn Maelog	BRYN DU SEWAGE PUMPING STATION	38	221	99.6
Dwr Cymru Welsh Water	Unnamed Stream	GWALCHMAI ISAF PS	25	218	100
Dwr Cymru Welsh Water	Esturial Waters Of Inland Sea	TREARDDUR BAY PS (PUMPED DISCHARGE)	61	215	97.7
Dwr Cymru Welsh Water	Menai Strait	GLYN GARTH PS LLANDEGFAN	43	213	100
Dwr Cymru Welsh Water	Old Harbour	Holyhead Wastewater Treatment Works SPS	70	213	100
Dwr Cymru Welsh Water	River Cefni	Llangefni Main Pumping Station	36	174	99.4
Dwr Cymru Welsh Water	Outer Harbour, Holyhead	Morawelon SPS	42	168	97.4
Dwr Cymru Welsh Water	New Harbour	Coastguard CSO	92	153	100
Dwr Cymru Welsh Water	Cefni - Cefni Reservoir West	Lon Sardis CSO (BODFFORDD OPP CAPEL SARDIS)	66	132	83.3
Dwr Cymru Welsh Water	River Goch	Storm Tank Army Cadet Centre CSO	36	131	100
Dwr Cymru Welsh Water	Estuarial Waters Of River Alaw	Gorad PS Gorad NR Valley Anglesey	39	125	100
Dwr Cymru Welsh Water	Un-Named Watercourse	TREARDDUR BAY PS (GRAVITY)	35	115	99.4
Dwr Cymru Welsh Water	Menai Strait	WEST END PS BEAUMARIS ANGLESEY	33	109	100
Dwr Cymru Welsh Water	Braint	LLANFAIR PG SPS	29	89	100
Dwr Cymru Welsh Water	Alan Catchment	RHOSYBOL PLAS Y FFRWD SPS	25	84	100
Dwr Cymru Welsh Water	Coastal Waters	MOELFRE PS MOELFRE	27	75	100
Dwr Cymru Welsh Water	River Braint	NEWBOROUGH STW	43	73	99.9
Dwr Cymru Welsh Water	Coastal Waters - Amlwch Harbour	Amlwch Port CSO	36	73	99.9
Dwr Cymru Welsh Water	Coastal Waters Of Irish Sea	CEMAES PS/BALANCING TANK CEMAES BAY	25	65	99.2
Dwr Cymru Welsh Water	Unnamed Ditch	TALWRN SPS	31	64	100
Dwr Cymru Welsh Water	Unnamed Watercourse	LLANFAES PS (EMERGENCY) , ,	5	57	99.9
Dwr Cymru Welsh Water	Menai Strait	RHIANFA PS LLANDEGFAN	30	57	99.9
Dwr Cymru Welsh Water	River Cefni	LLANGEFNI WWTW STORM OVERFLOW	78	50	99.7
Dwr Cymru Welsh Water	Cefni Estuary	MALLTRAETH WWTW - STORM	51	50	100
Dwr Cymru Welsh Water	Braint	DWYRAN BY SCHOOL - SSO	14	43	58.1
Dwr Cymru Welsh Water	Cefni	CSO Llangefni MH Front Ynys Mon Of	39	33	99.3
Dwr Cymru Welsh Water	Cadnant	LLANSADWRN PS	27	33	99.9
Dwr Cymru Welsh Water	Adjacent Ditch	Llangefni Rhostrehwfa CSO	14	30	100
Dwr Cymru Welsh Water	Cefni Reservoir By-Pass Channel	Bodffordd STW Settled Storm	14	30	100
Dwr Cymru Welsh Water	Coastal Waters	RHOSNEIGR STW (SETTLED STORM/EMERGE	5	28	66.1
Dwr Cymru Welsh Water	Menai Strait	BRYNSCIENCYN PS , ,	7	27	100
Dwr Cymru Welsh Water	Menai Strait	BRYNSCIENCYN PS	7	27	100
Dwr Cymru Welsh Water	Y Brenin	PONT Y BRENIN PS	11	26	100
Dwr Cymru Welsh Water	Nant Cwyrtai	GWALCHMAI STW	19	14	99.9
Dwr Cymru Welsh Water	Unnamed Stream	VALLEY DYFFRYN AND PENDYFFRYN	5	9	100
Dwr Cymru Welsh Water	Via A Drainage To River Clai	CSO at Llangefni MH Rear of Burgess	9	7	99.9
Dwr Cymru Welsh Water	Cefni	MALLTRAETH VILLAGE CSO	5	6	72.4
Dwr Cymru Welsh Water	Eastuary - River Cefni	MALLTRAETH VILLAGE PUMPING STATION	5	6	72.4
Dwr Cymru Welsh Water	Menai Strait	PS NO 2 (PORTH WRACH) (EMERGENCY)	2	5	100
Dwr Cymru Welsh Water	Menai Strait	PS NO 2 (PORTH WRACH) (EMERGENCY)	2	5	100
Dwr Cymru Welsh Water	River Goch	Settled Storm Tank at Llanerchymedd STW	5	3	100
Dwr Cymru Welsh Water	Cefni Estuary	MALLTRAETH WWTW TERMINAL	1	2	100
Dwr Cymru Welsh Water	Unnamed Ditch	NEWBOROUGH MILLBANK SPS	1	2	35.2
Dwr Cymru Welsh Water	Of Braint	LLANFAIRPWLL SSO NO. 2	2	0	56.7
Dwr Cymru Welsh Water	Nodwydd	PENTRAETH TAN Y GRAIG SPS	3	0	99.9
Dwr Cymru Welsh Water	New Harbour, Holyhead	WATERSIDE PUMPING STATION	1	0	100
Dwr Cymru Welsh Water	New Harbour	Hibernia Row Pumping Station	1	0	99.9
Dwr Cymru Welsh Water	Adj Ditch	TREARDDUR BAY HAUL A MOR SPS	1	0	100
Dwr Cymru Welsh Water	Coastal Waters	CYNLAI PS LLANGOED ANGLESEY	1	0	100
Dwr Cymru Welsh Water	River Ffraw	ABERFFRAW SPS GLAN Y MOR ABERFFRAW	1	0	99.9
Dwr Cymru Welsh Water	Unnamed Ditch	FRYARS BAY P.S- SCREENED EMERG	0	0	100
Dwr Cymru Welsh Water	Coastal Waters	Llaneilian SPS	0	0	0
Dwr Cymru Welsh Water	Coastal Waters	WENDON CAR PARK PS BENLLECH , , ,	0	0	0
Dwr Cymru Welsh Water	River Cadnant	LLANSADWRN PS	0	0	100
Dwr Cymru Welsh Water	Beddmanarch Bay	PENRHOS BEACH PUMPING STATION	0	0	100
Dwr Cymru Welsh Water	River Alaw	Bodedern Sewage Pumping Station	0	0	100
Dwr Cymru Welsh Water	River Alaw	Newlands Beach PS Valley Angle	0	0	99.8
Dwr Cymru Welsh Water	River Cefni	Gaerwen WWTW Settled Storm	0	0	100
Dwr Cymru Welsh Water	Unnamed Ditch	LLANGAFFO CAE BERLLAN SPS	0	0	0
Dwr Cymru Welsh Water	Braint	DWYRAN RHYDWYN - SSO	0	0	0

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. This 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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