Storm overflow register · 2025 annual return

Thames Water storm overflows, 2025

Thames Water reported 581 storm overflows in England for 2025. Together they recorded 9,189 spills over 107,822 hours, an average of 15.8 spills per overflow against 20.4 across England. That ranks 3 of 10 companies, where 1 is the fewest spills per overflow. Counting the same overflows in both years, spills were down 60% on 2024.

135 overflows did not spill · 28 spilled more than 60 times · 548 had monitors working for 90% of the year or more · 233 sewage treatment works with overflows

Hours spilling by month, 2025

Hours spilling, all Thames Water overflows, from the start/stop records. Spills running across a month end are split between the months.

All Thames Water storm overflows

Sorted by hours spilling. Open an overflow for its permit, location, reasons for high spills and improvement status.

Overflow	Discharges to	Spills 2025	Hours 2025	Spills vs 2024	Monitor uptime
Appleton Wastewater Treatment Works Storm tank at sewage works Sewage works Appleton Company site name Appleton STW EA ID / permit TWL00013 · CSSC.2453 Outlet location SU4368099790 (OS grid reference) · View on Apple Maps WFD catchment Frilford and Marcham Brook (GB106039023420) 2024 spills / hours 160 / 2,622 Long-term average 85.0 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 159 hours spilling →	Marcham Brook	17	159	down 89%	100%
Kintbury Storm tank at sewage works Sewage works Kintbury Company site name Kintbury STW EA ID / permit TWL00259 · TEMP.2706 Outlet location SU3950067101 (OS grid reference) · View on Apple Maps WFD catchment Kennet and Avon Canal, summit to Copse Lock (GB70610181) 2024 spills / hours 56 / 867 Long-term average 41.0 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 159 hours spilling →	Kennet & Avon Canal	11	159	down 80%	100%
Faringdon WwTW Inlet overflow at sewage works (with treatment) Sewage works Faringdon Company site name Faringdon STW EA ID / permit TWL00180 · CSSC.2343 Outlet location SU2794096510 (OS grid reference) · View on Apple Maps WFD catchment Thames (Leach to Evenlode) (GB106039030333) Treatment Reed bed 2024 spills / hours 138 / 790 Long-term average 81.2 spills a year (monitored since 2020) High-spill reason (company) Performance - SW Infiltration Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 159 hours spilling →	Faringdon Brook	50	159	down 64%	94%
Banbury Road Pumping Station Storm discharge at pumping station Company site name Banbury Road (Kings Sutton) SPS EA ID / permit TWL00479 · CNTW.0472 Outlet location SP4952041710 (OS grid reference) · View on Apple Maps WFD catchment Farthinghoe Stream (Source to Cherwell) and tributaries (GB106039037290) 2024 spills / hours 30 / 61 Long-term average 21.7 spills a year (monitored since 2023) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 155 hours spilling →	Middleton Brook	31	155	up 3%	97%
Burford Wastewater Treatment Works Storm tank at sewage works Sewage works Burford Company site name Burford STW EA ID / permit TWL00063 · CTCP.0026 Outlet location SP2565012270 (OS grid reference) · View on Apple Maps WFD catchment Windrush and tributaries (Little Rissington to Thames) (GB106039030440) 2024 spills / hours 25 / 338 Long-term average 5.3 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 153 hours spilling →	River Windrush	12	153	down 52%	100%
Middle Barton WwTW Storm tank at sewage works (with treatment) Sewage works Middle Barton Company site name Middle Barton STW EA ID / permit TWL00298 · CTCR.1850 Outlet location SP4473025410 (OS grid reference) · View on Apple Maps WFD catchment Dorn (Source to Glyme) (GB106039037380) Treatment Reed bed 2024 spills / hours 44 / 371 Long-term average 29.4 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 153 hours spilling →	River Dorn	15	153	down 66%	100%
Marston St Lawrence SPS Storm discharge at pumping station EA ID / permit TWL00803 · Permit applied for Outlet location SP5364241713 (OS grid reference) · View on Apple Maps WFD catchment Farthinghoe Stream (Source to Cherwell) and tributaries (GB106039037290) 2024 spills / hours 66 / 654 Long-term average 31.7 spills a year (monitored since 2023) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 152 hours spilling →		29	152	down 56%	99%
Chinnor STW Storm tank at sewage works Sewage works Chinnor Company site name Chinnor STW EA ID / permit TWL00093 · CNTD.0028 Outlet location SP7602003240 (OS grid reference) · View on Apple Maps WFD catchment Kingsey Cuttle Brook and tributaries at Thame (GB106039030200) 2024 spills / hours 105 / 825 Long-term average 56.9 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 146 hours spilling →	Henton Stream	29	146	down 72%	99%
Middleton Stoney WwTW Storm tank at sewage works Sewage works Middleton Stoney Company site name Middleton Stoney STW EA ID / permit TWL00300 · TEMP.2773 Outlet location SP5381023580 (OS grid reference) · View on Apple Maps WFD catchment Langford Brook (Bicester to Ray inc Gagle Brook) (GB106039030140) 2024 spills / hours 55 / 694 Long-term average 24.8 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 145 hours spilling →	Gagle Brook	18	145	down 67%	100%
Finstock WwTW Storm tank at sewage works Sewage works Finstock Company site name Finstock STW EA ID / permit TWL00184 · CSSC.2347 Outlet location SP3681016960 (OS grid reference) · View on Apple Maps WFD catchment Evenlode (Bledington to Glyme confluence) (GB106039029960) 2024 spills / hours 38 / 363 Long-term average 24.9 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 144 hours spilling →	River Evenlode	13	144	down 66%	100%
Godalming Wastewater Treatment Work Storm tank at sewage works Sewage works Godalming Wastewater Treatment Work Company site name Godalming STW EA ID / permit TWL00197 · CNTW.0659 Outlet location SU9937045720 (OS grid reference) · View on Apple Maps WFD catchment Wey (Tilford to Shalford) (GB106039017820) 2024 spills / hours 25 / 234 Long-term average 12.0 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 143 hours spilling →	River Wey	10	143	down 60%	100%
Woodford Halse SPS Storm discharge at pumping station Company site name Woodford Halse (SPS) EA ID / permit TWL00461 · CTCR.1853 Outlet location SP5360052130 (OS grid reference) · View on Apple Maps WFD catchment Cherwell (Source to Trafford Bridge) (GB106039042650) 2024 spills / hours 52 / 493 Long-term average 23.2 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 142 hours spilling →	River Cherwell	15	142	down 71%	100%
Broome (Attenuation Tank) Overflow on sewer network Company site name Broome (attenuation tank) EA ID / permit TWL00060 · TEMP.2451 Outlet location SU1590082400 (OS grid reference) · View on Apple Maps WFD catchment Ray (Wiltshire) source to Lydiard Brook (GB106039023320) 2024 spills / hours 25 / 257 Long-term average 8.0 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 141 hours spilling →	Ray/Ditch	16	141	down 36%	99%
Colin Crescent, Colindale Overflow on sewer network EA ID / permit TWL00527 · Permit applied for Outlet location TQ2180289015 (OS grid reference) · View on Apple Maps WFD catchment Silk Stream and Edgware Brook (GB106039022970) 2024 spills / hours 48 / 327 Long-term average 40.3 spills a year (monitored since 2023) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 140 hours spilling →		31	140	down 35%	94%
Hogsmill A WwTW Storm tank at sewage works Sewage works Hogsmill A Company site name Hogsmill STW EA ID / permit TWL00229 · CASM.0042 Outlet location TQ1920068560 (OS grid reference) · View on Apple Maps WFD catchment Hogsmill (GB106039017440) 2024 spills / hours 24 / 194 Long-term average 20.4 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 139 hours spilling →	Hogsmill River	14	139	down 42%	100%
Watlington Storm tank at sewage works Sewage works Watlington Company site name Watlington STW EA ID / permit TWL00433 · TEMP.2997 Outlet location SU6740095401 (OS grid reference) · View on Apple Maps WFD catchment Chalgrove Brook (GB106039023740) 2024 spills / hours 90 / 704 Long-term average 26.7 spills a year (monitored since 2020) High-spill reason (company) Performance - Asset configuration (e.g. PS/rising main/storm tanks) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 137 hours spilling →	Pyrton Stream	30	137	down 67%	100%
Lightwater WwTW Storm tank at sewage works Sewage works Lightwater Company site name Lightwater STW EA ID / permit TWL00266 · CNTD.0033 Outlet location SU9387062170 (OS grid reference) · View on Apple Maps WFD catchment Hale/Mill Bourne (Bagshot to Addlestone Bourne confluence near Chobham) (GB106039017930) 2024 spills / hours 14 / 100 Long-term average 16.9 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 136 hours spilling →	Hale Bourne	17	136	up 21%	100%
Wokingham (Ash Ridge) Storm tank at sewage works Sewage works Wokingham Company site name Ash Ridge (Wokingham) STW EA ID / permit TWL00459 · TEMP.3020 Outlet location SU8120070101 (OS grid reference) · View on Apple Maps WFD catchment Emm Brook (GB106039023130) 2024 spills / hours 74 / 472 Long-term average 37.6 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 136 hours spilling →	Ashridge Stream	11	136	down 85%	100%
Aylesbury WwTW Storm tank at sewage works Sewage works Aylesbury Company site name Aylesbury STW EA ID / permit TWL00478 · CSSC.0315 Outlet location SP7862014740 (OS grid reference) · View on Apple Maps WFD catchment Thame (Aylesbury to Scotsgrove Brook) (GB106039030370) 2024 spills / hours 54 / 664 Long-term average 20.3 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 135 hours spilling →	River Thame	13	135	down 76%	100%
Guildford STW Storm tank at sewage works Sewage works Guildford Company site name Guildford STW EA ID / permit TWL00206 · CTCR.1107 Outlet location TQ0040051850 (OS grid reference) · View on Apple Maps WFD catchment Wey (Shalford to River Thames confluence at Weybridge) (GB106039017630) 2024 spills / hours 46 / 554 Long-term average 17.9 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 133 hours spilling →	Wey	9	133	down 80%	100%
Beenham Wastewater Treatment Works Inlet overflow at sewage works Sewage works Beenham Company site name Beenham STW EA ID / permit TWL00031 · CSSC.1085 Outlet location SU5939069410 (OS grid reference) · View on Apple Maps WFD catchment Pang (GB106039023300) 2024 spills / hours 54 / 487 Long-term average 39.0 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 132 hours spilling →	Webbs Lane Stream	14	132	down 74%	100%
White Roding WwTW Storm tank at sewage works Sewage works White Roding Company site name White Roding STW EA ID / permit TWL00447 · CSSC.1455 Outlet location TL5693013680 (OS grid reference) · View on Apple Maps WFD catchment Upper Roding (to Cripsey Brook) (GB106037033500) 2024 spills / hours 69 / 447 Long-term average 60.3 spills a year (monitored since 2020) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 129 hours spilling →	White Roding Tributary	19	129	down 72%	100%
South Park, Overflow on sewer network Company site name South park, ilford EA ID / permit TWL00380 · CANM.0918 Outlet location TQ4515086450 (OS grid reference) · View on Apple Maps WFD catchment Seven Kings Water (GB106037028170) 2024 spills / hours 58 / 252 Long-term average 50.9 spills a year (monitored since 2019) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 126 hours spilling →	Loxford Water	42	126	down 28%	97%
Woking Wastewater Treatment Works Storm tank at sewage works Sewage works Woking Company site name Woking STW EA ID / permit TWL00458 · CASM.0308 Outlet location TQ0327057520 (OS grid reference) · View on Apple Maps WFD catchment Hoe Stream (Pirbright to River Wey confluence at Woking) (GB106039017900) 2024 spills / hours 35 / 359 Long-term average 18.7 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 125 hours spilling →	River Wey	10	125	down 71%	100%
Greatworth STW Storm tank at sewage works Sewage works Greatworth Company site name Greatworth STW EA ID / permit TWL00202 · CSSC.7686 Outlet location SP5494042120 (OS grid reference) · View on Apple Maps WFD catchment Farthinghoe Stream (Source to Cherwell) and tributaries (GB106039037290) 2024 spills / hours 48 / 637 Long-term average 18.4 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 123 hours spilling →	Farthinghoestream	12	123	down 75%	100%
Middleton Cheney WwTW Storm tank at sewage works Sewage works Middleton Cheney Company site name Middleton Cheney STW EA ID / permit TWL00299 · CAWM.0083 Outlet location SP5061041240 (OS grid reference) · View on Apple Maps WFD catchment Farthinghoe Stream (Source to Cherwell) and tributaries (GB106039037290) 2024 spills / hours 53 / 679 Long-term average 27.4 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 123 hours spilling →	Washle Brook	13	123	down 75%	100%
Dorchester WwTW Inlet overflow at sewage works Sewage works Dorchester Company site name Dorchester STW EA ID / permit TWL00157 · TEMP.2542 Outlet location SU5801093700 (OS grid reference) · View on Apple Maps WFD catchment Thame (Scotsgrove Brook to Thames) (GB106039030240) 2024 spills / hours 63 / 791 Long-term average 13.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 121 hours spilling →	Thame	15	121	down 76%	100%
Wargrave Wastewater Treatment Works Storm tank at sewage works Sewage works Wargrave Company site name Wargrave STW EA ID / permit TWL00428 · CTCR.2079 Outlet location SU7763077350 (OS grid reference) · View on Apple Maps WFD catchment Loddon (Swallowfield to River Thames confluence) (GB106039023160) 2024 spills / hours 46 / 519 Long-term average 18.1 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 121 hours spilling →	River Loddon	12	121	down 74%	100%
CSO at Crofton Road Overflow on sewer network Company site name Crofton road, sunnydale EA ID / permit TWL00125 · CSSA.0354 Outlet location TQ4350065850 (OS grid reference) · View on Apple Maps WFD catchment Quaggy (GB106039023290) 2024 spills / hours 53 / 224 Long-term average 31.6 spills a year (monitored since 2018) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 120 hours spilling →	Kyd Brook	31	120	down 42%	96%
SWS Overflow on sewer network Company site name South lane, ash EA ID / permit TWL00743 · CTCR.2000 Outlet location SU9860050300 (OS grid reference) · View on Apple Maps WFD catchment Wey (Shalford to River Thames confluence at Weybridge) (GB106039017630) 2024 spills / hours 36 / 245 Long-term average 16.3 spills a year (monitored since 2023) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 119 hours spilling →	Trib of Blackwater	12	119	down 67%	100%
Sandhurst Storm tank at sewage works Sewage works Sandhurst Company site name Sandhurst STW EA ID / permit TWL00359 · TEMP.2881 Outlet location SU8360060900 (OS grid reference) · View on Apple Maps WFD catchment Blackwater (Hawley to Whitewater confluence at Bramshill) (GB106039017290) 2024 spills / hours 37 / 315 Long-term average 23.0 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 115 hours spilling →	Blackwater	10	115	down 73%	100%
St Andrews Road, Black Horse Lane Overflow on sewer network Company site name St andrews road, black horse lane EA ID / permit TWL00383 · TEMP.2937 Outlet location TQ3587090050 (OS grid reference) · View on Apple Maps WFD catchment Lee (Tottenham Locks to Bow Locks/Three Mills Locks) (GB106038077852) 2024 spills / hours 9 / 13 Long-term average 12.6 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 114 hours spilling →	Dagenham Brook	6	114	down 33%	99%
Abingdon Sewage Treatment Works Storm tank at sewage works Sewage works Abingdon Company site name Abingdon STW EA ID / permit TWL00004 · CTCR.1804 Outlet location SU4933095090 (OS grid reference) · View on Apple Maps WFD catchment Thames (Evenlode to Thame) (GB106039030334) 2024 spills / hours 85 / 1,146 Long-term average 35.0 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 112 hours spilling →	Odhay Hill Ditch/River Thames	13	112	down 85%	100%
Mays Lane Overflow Overflow on sewer network EA ID / permit TWL00648 · Permit applied for Outlet location TQ2467895229 (OS grid reference) · View on Apple Maps WFD catchment Dollis Brook and Upper Brent (GB106039022980) 2024 spills / hours 67 / 279 Long-term average 41.7 spills a year (monitored since 2023) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 112 hours spilling →		39	112	down 42%	100%
Ascot WwTW Storm tank at sewage works Sewage works Ascot Company site name Ascot STW EA ID / permit TWL00016 · CTCR.2048 Outlet location SU8917068230 (OS grid reference) · View on Apple Maps WFD catchment Bull Brook (GB106039017670) 2024 spills / hours 19 / 198 Long-term average 15.2 spills a year (monitored since 2020) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 109 hours spilling →	Trib of the Bull Brook	10	109	down 47%	100%
Moreton Pinkney WwTW Inlet overflow at sewage works Sewage works Moreton Pinkney Company site name Moreton Pinkney STW EA ID / permit TWL00305 · CNTD.0010 Outlet location SP5738049730 (OS grid reference) · View on Apple Maps WFD catchment Ashby Brook (Source to Cherwell) (GB106039037360) 2024 spills / hours 26 / 158 Long-term average 20.6 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 106 hours spilling →	Ashby Brook	26	106	no change	100%
Ash Vale Storm tank at sewage works Sewage works Ash Vale Company site name Ash Vale STW EA ID / permit TWL00017 · TEMP.2354 Outlet location SU8850054100 (OS grid reference) · View on Apple Maps WFD catchment Blackwater (Aldershot to Cove Brook confluence at Hawley) (GB106039017180) 2024 spills / hours 23 / 209 Long-term average 11.6 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 103 hours spilling →	Blackwater	9	103	down 61%	100%
Beech Hall Crescent CSO Overflow on sewer network Company site name Beech hall crescent, walthamstow EA ID / permit TWL00393 · CLCR.0032 Outlet location TQ3861091400 (OS grid reference) · View on Apple Maps WFD catchment Ching Brook (GB106038027930) 2024 spills / hours 56 / 242 Long-term average 64.7 spills a year (monitored since 2020) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 103 hours spilling →	Ching Brook	43	103	down 23%	100%
Bordon Wastewater Treatment Works Storm tank at sewage works Sewage works Bordon Company site name Bordon STW EA ID / permit TWL00048 · CTCR.1645 Outlet location SU8036036180 (OS grid reference) · View on Apple Maps WFD catchment South Wey (Bordon to River Slea confluence) (GB106039017720) 2024 spills / hours 21 / 166 Long-term average 43.1 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 98 hours spilling →	Wey (Southern Branch)	9	98	down 57%	100%
Pease Pottage Storm discharge at pumping station Company site name Pease Pottage SPS EA ID / permit TWL00328 · TEMP.2831 Outlet location TQ2630032301 (OS grid reference) · View on Apple Maps WFD catchment Stanford Brook (GB106039017450) 2024 spills / hours 19 / 196 Long-term average 11.9 spills a year (monitored since 2019) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 98 hours spilling →	Gatwick Stream	12	98	down 37%	92%
Brent Valley Golf Course , Lb Ealing Overflow on sewer network EA ID / permit TWL00489 · Permit applied for Outlet location TQ1453680771 (OS grid reference) · View on Apple Maps WFD catchment Lower Brent (GB106039023590) 2024 spills / hours 71 / 425 Long-term average 43.0 spills a year (monitored since 2023) High-spill reason (company) Performance - SW Infiltration Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 98 hours spilling →		39	98	down 45%	98%
High Wycombe 'a' Storm discharge at pumping station Company site name High Wycombe Transfer EA ID / permit TWL00224 · TEMP.2659 Outlet location SU8850092000 (OS grid reference) · View on Apple Maps WFD catchment Wye (High Wycombe fire station to Thames) (GB106039023880) 2024 spills / hours 0 / 0.0 Long-term average 0.7 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 98 hours spilling →	Wye	5	98	up from 0	100%
Whitwell WwTW Storm tank at sewage works Sewage works Whitwell Company site name Whitwell STW EA ID / permit TWL00449 · TEMP.3008 Outlet location TL1916020740 (OS grid reference) · View on Apple Maps WFD catchment Mimram (Whitwell to Codicote Bottom) (GB106038033460) 2024 spills / hours 36 / 394 Long-term average 21.7 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 96 hours spilling →	River Mimram	13	96	down 64%	96%
Barkway Wastewater Treatment Works Storm tank at sewage works Sewage works Barkway Company site name Barkway STW EA ID / permit TWL00027 · CATM.3093 Outlet location TL3878034760 (OS grid reference) · View on Apple Maps WFD catchment Quin (GB106038040120) 2024 spills / hours 70 / 1,297 Long-term average 34.3 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 93 hours spilling →	The River Quin	7	93	down 90%	100%
Streatham & Balham Storm Relief C Overflow on sewer network Company site name Streatham & balham storm relief EA ID / permit TWL00728 · TEMP.2920 Outlet location TQ2712070900 (OS grid reference) · View on Apple Maps WFD catchment Wandle (Croydon to Wandsworth) and the Graveney (GB106039023460) 2024 spills / hours 74 / 133 Long-term average 55.7 spills a year (monitored since 2020) High-spill reason (company) Not asset maintenance - Hydraulic capacity Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 92 hours spilling →	Graveney	51	92	down 31%	95%
Avon Dassett WwTW Storm tank at sewage works Sewage works Avon Dassett Company site name Avon Dassett STW EA ID / permit TWL00020 · CSSC.1006 Outlet location SP4052049330 (OS grid reference) · View on Apple Maps WFD catchment Hanwell Brook (GB106039037340) 2024 spills / hours 36 / 343 Long-term average 25.4 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 91 hours spilling →	Hanwell Brook	12	91	down 67%	100%
East Grafton WwTW Storm tank at sewage works Sewage works East Grafton Company site name East Grafton STW EA ID / permit TWL00166 · CNTD.0031 Outlet location SU2589060960 (OS grid reference) · View on Apple Maps WFD catchment Upper Dun (GB106039017350) 2024 spills / hours 28 / 318 Long-term average 16.0 spills a year (monitored since 2018) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 90 hours spilling →	Tributary of River Dun	7	90	down 75%	100%
Woodstock STW Storm tank at sewage works Sewage works Woodstock Company site name Woodstock STW EA ID / permit TWL00462 · CSSC.2321 Outlet location SP4496017800 (OS grid reference) · View on Apple Maps WFD catchment Glyme (Dorn confluence to Evenlode) (GB106039029940) 2024 spills / hours 41 / 454 Long-term average 38.4 spills a year (monitored since 2019) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 89 hours spilling →	River Glyme	21	89	down 49%	99%
Clifton Wastewater Treatment Works Storm tank at sewage works Sewage works Clifton Company site name Clifton STW EA ID / permit TWL00105 · TEMP.0707 Outlet location SP4911031540 (OS grid reference) · View on Apple Maps WFD catchment Cherwell (Nell Bridge to Bletchingdon) (GB106039037431) 2024 spills / hours 36 / 213 Long-term average 15.9 spills a year (monitored since 2018) Investigation No investigation activity in reporting period Improvement No improvement action in reporting period Volume & pollution Estimate from 89 hours spilling →	Clifton Brook	12	89	down 67%	100%
Rous Road, Overflow on sewer network Company site name Rous road, buckhurst hill EA ID / permit TWL00701 · CANM.0921 Outlet location TQ4237594272 (OS grid reference) · View on Apple Maps WFD catchment Lower Roding (Loughton to Thames) (GB106037028181) 2024 spills / hours 51 / 246 Long-term average 30.0 spills a year (monitored since 2023) Investigation Env Act (SODRP) investigation ongoing Improvement No improvement action in reporting period Volume & pollution Estimate from 86 hours spilling →	Overflow Brook	19	86	down 63%	98%

Sewage treatment works

Storm tanks and inlet overflows at each Thames Water sewage works. The figures are 2025 spills.

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