Join Us 3rd November 2024 - London

March for Clean Water

Dwyfor Meirionnydd was polluted by sewage 12,327 times in 2023
lasting 109,917 hours - that's 12.72 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 Dwyfor Meirionnydd in 2023

169 Sites polluted by Dwr Cymru Welsh Water

12,327 sewage dumps
109,917 h duration

That's 12.72 years! On average 33.8 times a day

Change Over Time

Take Action

Your local MP is Liz Saville-Roberts (Plaid Cymru) - Find out more about their interests, donors, and voting at They Work For You

Constituencies near Dwyfor Meirionnydd

Waterways in Dwyfor Meirionnydd

Pollution Summary 2023

Here are all the reported sewage overflow totals for Dwyfor Meirionnydd 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 183 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 Erch	Abererch WwTW Storm Overflow	238	4,697	96.6
Dwr Cymru Welsh Water	River Cadnant	BETHEL SEWAGE TRANSFER PS	235	4,377	99
Dwr Cymru Welsh Water	River Rhyd Hir	CSO at Llithfaen WwTW	215	4,269	100
Dwr Cymru Welsh Water	River Erch	CSO at Four Crosses STW	307	4,128	99.9
Dwr Cymru Welsh Water	Nant Brisgyll	CSO at Llan Ffestiniog Sewage Treatment Works	317	4,069	100
Dwr Cymru Welsh Water	River Goedol	BLAENAU FFESTINIOG WWTW (Settled STORM)	213	3,604	99.1
Dwr Cymru Welsh Water	River Llyfni	Settled Storm Sewage at Llanllyfni WwTW	260	3,483	99.9
Dwr Cymru Welsh Water	Tremadog Bay	Criccieth STW CSO to Settled Storm Sewage Tanks	200	3,381	100
Dwr Cymru Welsh Water	River Seiont	Llanrug WwTW Settled Storm	195	3,301	91.5
Dwr Cymru Welsh Water	River Wen	CSO at Chwilog STW	198	3,177	100
Dwr Cymru Welsh Water	Coastal Waters	FAIRBOURNE WWTW STORM TANKS	141	2,626	100
Dwr Cymru Welsh Water	Tyddyn Drain To Coastal Waters	TREFOR WWTW	175	2,572	100
Dwr Cymru Welsh Water	Dulas	LOWER CORRIS STW	157	2,547	100
Dwr Cymru Welsh Water	River Artro	LLANBEDR TERMINAL PS (STORM)	186	2,108	81.4
Dwr Cymru Welsh Water	Mawddach	Llanelltyd PS CSO	117	2,029	99
Dwr Cymru Welsh Water	River Gwyrfai	CSO at Waunfawr STW	123	1,807	100
Dwr Cymru Welsh Water	River Geirch	NEFYN WWTW	212	1,796	99.8
Dwr Cymru Welsh Water	River Llyfni	Nantlle PS	141	1,770	100
Dwr Cymru Welsh Water	Caernarfon Bay	NEFYN PUMPING STATION	156	1,718	100
Dwr Cymru Welsh Water	River Seiont	Pont Rhythallt Pumping Station	181	1,695	100
Dwr Cymru Welsh Water	Cwmllechen	BONTDDU STW	126	1,569	100
Dwr Cymru Welsh Water	River Tafarn Helyg	GELLILYDAN STW (SETTLED STORM)	138	1,486	99.1
Dwr Cymru Welsh Water	River Dwyryd	Penrhyndeudraeth CSO	160	1,483	99.9
Dwr Cymru Welsh Water	Unnamed Stream	HARLECH TERMINAL PS (OUTFALL B)	132	1,475	99.6
Dwr Cymru Welsh Water	Nant Brisgyll	CSO at Llanffestiniog STW	149	1,388	100
Dwr Cymru Welsh Water	River Seiont	CAERNARFON WWTW STORM TANKS	153	1,336	99.9
Dwr Cymru Welsh Water	Coastal Waters Of Cardigan Bay	TYWYN STW MORFA GWYLLT TYWYN	106	1,306	99.9
Dwr Cymru Welsh Water	River Cedron	PENTREFELIN STW	141	1,258	99.9
Dwr Cymru Welsh Water	River Rhyd Hir	LLANNOR STW (SETTLED STORM)	146	1,257	99.9
Dwr Cymru Welsh Water	River Wnion	STAYLITTLE LANE CSO	85	1,216	100
Dwr Cymru Welsh Water	River Glaslyn	Settled Storm at Beddgelert Waste Water Treatment	69	1,172	100
Dwr Cymru Welsh Water	River Seiont	LLANBERIS WwTW	165	1,148	100
Dwr Cymru Welsh Water	River Mawddach	Penmaenpool PS	105	1,141	97.1
Dwr Cymru Welsh Water	River Ceunant Sych	CSO at Land Off A496 Manod Blaenau Ffesti	149	1,125	97.5
Dwr Cymru Welsh Water	Estuarial Waters Of River Dwyryd	MAENTWROG WWTW	109	1,119	100
Dwr Cymru Welsh Water	River Seiont	Storm Overflow at Penisarwaun Wastewater Treatment Works	147	1,032	99.4
Dwr Cymru Welsh Water	Gwyrfai	LLANFAGLAN WWTW FINAL EFFLUENT	91	959	100
Dwr Cymru Welsh Water	River Dyfi	ABERDYFI WHARF PS SEAVIEW TERRACE	60	950	99.9
Dwr Cymru Welsh Water	River Bowydd	CWM BOWYDD SSO BLAENAU FFESTINIOG	133	907	99.8
Dwr Cymru Welsh Water	River Barlwyd	LAND OPP GLANLLYN NR OAKLEY SQUARE CSO	152	895	100
Dwr Cymru Welsh Water	Cardigan Bay	BARMOUTH WWTW LONG SEA OUTFALL	223	839	100
Dwr Cymru Welsh Water	River Dee	BALA WWTW	80	836	100
Dwr Cymru Welsh Water	River Dyfrdwy	The Eagles CSO, Llanwchllyn	79	831	98.4
Dwr Cymru Welsh Water	River Goedol	CSO at Land Off Pencefn Road Tanygrisiau	120	791	98
Dwr Cymru Welsh Water	River Rhyd Hir	Settled Storm Overflow at Efailnewydd Wastewater Treatment Works	163	785	100
Dwr Cymru Welsh Water	Unnamed Stream	MYNYTHO STW - STORM OVERFLOW	134	770	97.8
Dwr Cymru Welsh Water	Dyffryn Main Drain	DYFFRYN ARDUDWY WWTW STORM	57	736	100
Dwr Cymru Welsh Water	Tremadog Bay	LLANDANWG TERMINAL PS	47	711	100
Dwr Cymru Welsh Water	River Llyfni	Pontllyfni STW-CSO Pontllyfni	49	702	100
Dwr Cymru Welsh Water	River Dwyfawr	Llanystumdwy (W Porthmadog) A (Settled Storm)	50	684	94.1
Dwr Cymru Welsh Water	River Caledffrwd	Llwyn Celyn CSO Deinolen	174	673	97
Dwr Cymru Welsh Water	River Dee	Bala WwTW Storm Tank	55	641	100
Dwr Cymru Welsh Water	Tremadog Bay	MORFA BYCHAN WWTW	136	591	99.8
Dwr Cymru Welsh Water	River Dee	CSO at Cynwyd STW	124	570	100
Dwr Cymru Welsh Water	Llyfni	PONTLLYFNI PS	87	545	100
Dwr Cymru Welsh Water	Unnamed Stream	CSO At Corwen Rear Of The Pavillion	128	544	93.8
Dwr Cymru Welsh Water	River Glaslyn	CSO at Beddgelert East Bank Afon Glaslyn	84	530	96.3
Dwr Cymru Welsh Water	River Dysynni	Abergynolwyn STW (Settled Storm)	66	505	100
Dwr Cymru Welsh Water	River Prysor	CSO at Trawsfynydd WwTW	115	490	88.6
Dwr Cymru Welsh Water	Cyt Bach Surface Watercourse	SNOWDON STREET PS	130	479	98
Dwr Cymru Welsh Water	Coastal Waters	CRICCIETH EAST PS , ,	41	470	89.8
Dwr Cymru Welsh Water	River Llyfni	Talysarn No 4 - CSO	107	453	100
Dwr Cymru Welsh Water	River Gwyrfai	Bontnewydd CSO	119	426	97.3
Dwr Cymru Welsh Water	Tremadog Bay	Llanbedrog SPS	28	421	100
Dwr Cymru Welsh Water	River Rhydhir	LON COB BACH PS PWLLHELI	81	421	99.4
Dwr Cymru Welsh Water	River Geirch	Edern SPS CSO	51	421	100
Dwr Cymru Welsh Water	A Stream On Nw Boundary Of The Site	CSO at Talsarnau SPS	91	412	100
Dwr Cymru Welsh Water	Unnamed Stream	Clynnog Fawr CSO at PS	81	378	100
Dwr Cymru Welsh Water	Groundwater Via Infiltration System	SOUTH DISCHARGE	39	371	100
Dwr Cymru Welsh Water	Coastal Waters	Llwyngwril SPS	39	363	95.4
Dwr Cymru Welsh Water	Un-Named Stream Into Llifon	Dorlan Goch CSO	79	352	43.3
Dwr Cymru Welsh Water	Unnamed Ditch	ARTHOG TERRACE SEWAGE PUMPING ST	48	351	100
Dwr Cymru Welsh Water	River Gwyrfai	WAUNFAWR STW (FINAL EFFLUENT)	20	350	100
Dwr Cymru Welsh Water	River Carrog	CSO at Caernarfon Hen Gastell No5	94	346	99.2
Dwr Cymru Welsh Water	River Dwyfor	CSO at Garndolbenmaen STW	34	345	86.2
Dwr Cymru Welsh Water	Tremadog Bay	CRICCIETH WEST PS , ,	42	339	99.2
Dwr Cymru Welsh Water	River Seiont	CAERNARFON WWTW INLET PUMP ST 6MM	124	328	99.9
Dwr Cymru Welsh Water	Dysynni Low Level Drainage Cha	TYWYN STW MORFA GWYLLT TYWYN ,	83	309	99.9
Dwr Cymru Welsh Water	River Gwyrfai	Llanfaglan WwTW Settled Storm Overflow	30	301	99.2
Dwr Cymru Welsh Water	River Llyfni	Llanllyfni Glan Aber CSO	152	285	97.3
Dwr Cymru Welsh Water	River Dee	Corwen WwTW Settled Storm	29	259	100
Dwr Cymru Welsh Water	River Geirch	MORFA NEFYN PUMPING STATION CSO (B)	129	255	98.8
Dwr Cymru Welsh Water	Coastal Waters - River Daron	ABERDARON PS	37	242	100
Dwr Cymru Welsh Water	Rhyd	CAERNARFON - GLANRHYD SSO NO.	108	230	92
Dwr Cymru Welsh Water	Dwyryd	PENRHYNDEUDRAETH OUTFALL-SCREE	21	221	100
Dwr Cymru Welsh Water	River Wnion	Marian Mawr CSO	68	217	100
Dwr Cymru Welsh Water	River Blaen-Y-Cae	BRYNCIR STW	64	204	100
Dwr Cymru Welsh Water	Carrog	CAERNARFON - RHOSTRYFAN CSO NO	94	185	100
Dwr Cymru Welsh Water	River Caledffwrd	BRYNREFAIL MAIN SPS	44	179	99.3
Dwr Cymru Welsh Water	River Glaslyn	CSO at Porthmadog Borth-Y-Gest SPS	31	165	98.3
Dwr Cymru Welsh Water	Dulas North	Minffordd St CSO, Corris	13	161	100
Dwr Cymru Welsh Water	Ffos Ddu	Marian Mawr Splitter Chamber CSO	32	161	99.8
Dwr Cymru Welsh Water	River Llifon	Caernarfon - Llwyn Gwalch CSO Groes	55	153	100
Dwr Cymru Welsh Water	Gwyrfai	CAERNARFON - RHOSTRYFAN CSO NO	88	151	96.2
Dwr Cymru Welsh Water	Tremadog Bay	CRICCIETH EAST PS	19	150	62.4
Dwr Cymru Welsh Water	Cadnant - Caernarfon	SSO AT MILL LANE CAERNARFON	97	144	100
Dwr Cymru Welsh Water	Desach	ABERDESACH PS	104	144	99.9
Dwr Cymru Welsh Water	Glaslyn Estuary Within Glaslyn	PORTHMADOG STW STORM STORAGE PORT	22	140	98
Dwr Cymru Welsh Water	River Dee	CORWEN WWTW FINAL EFFLUENT	9	136	100
Dwr Cymru Welsh Water	River Gwyrfai	CSO at Bontnewydd Glanrafon No10	64	130	95.8
Dwr Cymru Welsh Water	River Cyll-Y-Felin	CSO at Aberdaron WwTW	18	130	100
Dwr Cymru Welsh Water	River Henddol	FAIRBOURNE PUMPING STATION	24	128	99.2
Dwr Cymru Welsh Water	Llyn Nantlle Uchaf	Nantlle No 5-CSO	71	126	98.8
Dwr Cymru Welsh Water	River Dee	Corwen Corner Station Yard CSO	19	120	63
Dwr Cymru Welsh Water	Tremadog Bay	CRICCIETH WEST PS	29	107	98.3
Dwr Cymru Welsh Water	River Penrhos	CSO at Penrhos WwTW	47	102	100
Dwr Cymru Welsh Water	River Wen	AFONWEN WWTW PS	17	98	100
Dwr Cymru Welsh Water	Cegin	RHIWLAS STW	69	97	100
Dwr Cymru Welsh Water	Unknown	CSO at Tai Craig-y-don Cwymyglo	21	90	58.4
Dwr Cymru Welsh Water	River Prysor	Trawsfynydd Maesgwindy Est CSO	54	89	100
Dwr Cymru Welsh Water	River Eden	CSO at BRONABER STW	26	87	100
Dwr Cymru Welsh Water	River Y Llan	Llanfachreth STW (Storm) CSO	38	69	100
Dwr Cymru Welsh Water	Un-Named Watercourse	BRYNCOCH SEWAGE PUMPING STATION	9	68	99.1
Dwr Cymru Welsh Water	Menai Straits	CROSSVILLE CSO	72	65	100
Dwr Cymru Welsh Water	Unnamed Ditch	CASTELL PUMPING STATION	13	57	100
Dwr Cymru Welsh Water	River Cegin	RHIWLAS STW	28	51	100
Dwr Cymru Welsh Water	River Hwch	Llanberis CSO NO. 2	38	49	98.8
Dwr Cymru Welsh Water	Unnamed Watercourse	CAERNARFON MARGARET STREET SSO	83	46	99
Dwr Cymru Welsh Water	River Seiont	Peblig Industrial Estate CSO	31	46	99.5
Dwr Cymru Welsh Water	Groundwater Via Infiltration System	ST MARY'S SEWAGE PUMPING STATION	7	46	100
Dwr Cymru Welsh Water	Goch Bach	CSO Near Castle Gift Shop Llanberis	26	44	86.3
Dwr Cymru Welsh Water	River Dwyfawr	LLANYSTUMDWY PUMPING STATION	9	40	94.1
Dwr Cymru Welsh Water	Menai Strait	FELINHELI PS (QUAY COTTAGE) , ,	18	40	100
Dwr Cymru Welsh Water	River Llan	CAERNARFON - PENYGROES SSO NO.	44	38	99.9
Dwr Cymru Welsh Water	Cardigan Bay	BARMOUTH WWTW OUTFALL TO MLWS	22	28	100
Dwr Cymru Welsh Water	Un-Named Stream	PORTHMADOG - LOMBARD STREET SS	71	24	99.3
Dwr Cymru Welsh Water	River Ceidiog	Llandrillo STW PS CSO	29	22	100
Dwr Cymru Welsh Water	River Dysynni	Abergynolwyn SPS	27	21	99.9
Dwr Cymru Welsh Water	River Glaslyn	BORTH Y GES PS	30	21	100
Dwr Cymru Welsh Water	Esturial Waters Of River Erch	GIMBLET ROCK TIDAL TANK CSO	4	19	99.8
Dwr Cymru Welsh Water	River Mawddach	Llanelltyd CSO	13	19	99.7
Dwr Cymru Welsh Water	River Cadnant	BETHEL CSO BETHEL NEAR CAERNARFON	14	18	99.6
Dwr Cymru Welsh Water	Cadnant	BETHEL SSO NO. 3	8	16	100
Dwr Cymru Welsh Water	River Prysor	CSO at Trawsfynydd Near Bron Gwyndy	18	13	91.1
Dwr Cymru Welsh Water	Groundwater Via Infiltration System	WESLEYAN TERRACE SEWAGE PUMPING ST	2	13	95.7
Dwr Cymru Welsh Water	Llyn Padarn	LLANBERIS PS , ,	10	11	99.7
Dwr Cymru Welsh Water	Unnamed Stream	FRIOG SEWAGE PUMPING STATION	8	9	97.5
Dwr Cymru Welsh Water	River Seiont	Caernarfon WWTW Inlet Pump ST 6mm SPS	16	9	99.9
Dwr Cymru Welsh Water	River Glaslyn	BRITANNIA PS	2	9	91.3
Dwr Cymru Welsh Water	Cadnant	MIN-Y-NANT CSO	17	8	99.9
Dwr Cymru Welsh Water	Unnamed Ditch	GLASFRYN TERRACE STW ARTHOG	4	8	100
Dwr Cymru Welsh Water	Mawddach Estuary	BARMOUTH HARBOUR PUMPING STATION	10	7	96.1
Dwr Cymru Welsh Water	River Geirch	NEFYN WWTW (CONT. S/WATER OUTFALL)	14	7	10
Dwr Cymru Welsh Water	Unnamed Stream	CSO Rear Of Prysor Filling Station Traw	11	6	99.8
Dwr Cymru Welsh Water	Unnamed Stream	Trefor CSO	17	6	99.7
Dwr Cymru Welsh Water	River Mawddach	Dolgellau Main PS	3	5	100
Dwr Cymru Welsh Water	River Bowydd	Blaenau Ffestiniog WWTW Settled Storm (B)	4	5	99.1
Dwr Cymru Welsh Water	Un-Named Watercourse	LLANERCH CSO	12	4	99.8
Dwr Cymru Welsh Water	Barlwyd	BLAENAU FFESTINIOG NO2	13	4	49.9
Dwr Cymru Welsh Water	Nant Y Cyt	CHAPEL STREET/MADOG STREET PORTHM	5	3	38
Dwr Cymru Welsh Water	Stream Leading To Cyt Stre	TREMADOG SSO	3	3	99.9
Dwr Cymru Welsh Water	Unnamed Stream	HARLECH OUTSIDE LAUNDRY	7	3	58.7
Dwr Cymru Welsh Water	Tremadog Bay	CSO at Llandanwg SPS	3	2	99.6
Dwr Cymru Welsh Water	River Gwyrfai	Bontnewydd CSO Ysgol Gynradd Bontne	2	1	99.9
Dwr Cymru Welsh Water	River Siont	ANGLESEY ARMS PUMPING STATION	1	1	93.5
Dwr Cymru Welsh Water	Cadnant	BETHEL SSO NO. 2	4	1	99.9
Dwr Cymru Welsh Water	Glaslyn Estuary	PORTHMADOG STW STORM STORAGE PORT	1	1	98
Dwr Cymru Welsh Water	River Dwyryd	Harlech Rum Hole CSO	4	1	100
Dwr Cymru Welsh Water	Seiont	CAERNARFON PONT SEIONT PS	1	0	98.7
Dwr Cymru Welsh Water	Menai Strait	FELINHELI PS (ADJ TO QUAY TOILETS)	1	0	100
Dwr Cymru Welsh Water	Mawddach	MAWDDACH CRESCENT PUMPING STATION	1	0	99.8
Dwr Cymru Welsh Water	Esturial Waters River Erch	GLAN Y DON PS PWLLHELI	1	0	9.2
Dwr Cymru Welsh Water	Esturial Waters Of River Erch	MORFA GARREG PS PWLLHELI	2	0	100
Dwr Cymru Welsh Water	Menai Strait	FELINHELI PS (OPP SEA CADET CORPS)	1	0	100
Dwr Cymru Welsh Water	Un-Named Stream	MORFA BYCHAN WWTW	1	0	99.8
Dwr Cymru Welsh Water	Tremadog Bay	CSO ON SEWER (CRICCIETH BEACH)	1	0	100
Dwr Cymru Welsh Water	Menai Straits	BALACLAVA ROAD SEWAGE PUMPING ST	1	0	98.6
Dwr Cymru Welsh Water	Menai Straits	CAERNARFON BANK QUAY PS	1	0	98.1
Dwr Cymru Welsh Water	Menai Strait	WATERLOO PORT SEWAGE PUMPING ST	1	0	99.8
Dwr Cymru Welsh Water	Dee Via Surface Water Sewer And Culvert	Corwen Clawdd Poncen PS	0	0	100
Dwr Cymru Welsh Water	River Llyfni	Talysarn No 3 - CSO	0	0	94.8
Dwr Cymru Welsh Water	River Dwyryd	MAENTWROG CSO	0	0	0
Dwr Cymru Welsh Water	River Bowydd	Blaenau Ffestiniog CSO No 3	0	0	100
Dwr Cymru Welsh Water	River Soch Estuary	ABERSOCH HARBOUR PUMPING STATION	0	0	99.9
Dwr Cymru Welsh Water	Tremadog Bay	HARLECH TERMINAL PS (OUTFALL A)	0	0	0
Dwr Cymru Welsh Water	Angell	Aberangell No1 PS	0	0	0
Dwr Cymru Welsh Water	River Rhyd Hir Estuary	Y MAES CSO	0	0	100
Dwr Cymru Welsh Water	Unnamed Culvert To River Artro	Llanbedr CSO	0	0	98.5
Dwr Cymru Welsh Water	River Erch	BRIDGE GARAGE PWLLHELI	0	0	100
Dwr Cymru Welsh Water	River Glaslyn	AMMANDA TERRACE BORTH Y GEST PORTHM	0	0	58.4
Dwr Cymru Welsh Water	Ditch	Idris Villas Sewage Pumping Station	0	0	0
Dwr Cymru Welsh Water	River Caledffrwd	CSO at Pen yr Olchfa Clwt Y Bont Deiniolen	0	0	12.8
Dwr Cymru Welsh Water	Nant Y Cyt	BAKERS LANE/CHANDLERS PLACE PORTH	0	0	100

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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