Investment plans for storm discharge sites
Over the next two years, we’ll invest £1.12 billion in our sewage treatment works (STW). This includes £650 million on enhancing and upgrading over 135 sites to improve resilience and provide extra capacity. Over the same period, we’ll spend £470 million on the wider sewer network.
To 2025 and beyond, we're undertaking our largest ever upgrade of sewers and STW by upgrading more than 250 of our sites.
Please note that details will change as projects progress. This page was last updated on 16 November 2023.
Site names beginning with:
A
Abbey Mills
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Abingdon
An upgrade is planned for Abingdon STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
Acton and Stormworks
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Aldermaston STW
An upgrade is planned for Aldermaston STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Aldershot STW
An upgrade is planned for Aldershot STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Alton STW
An upgrade is planned for Alton STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed. We're also upgrading the storm tanks at the local Newmans Lane Pumping Station at a cost of over £5 million, which will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Alton.
Ampney St Peter STW
An upgrade is being planned for Ampney St Peter. It will include a substantial increase in treatment capacity, though the design hasn't been finalised. The project is likely to complete in 2026.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Ampney St Peter.
Appleton STW
Appleton STW is being upgraded at a cost of more than £5 million. This work will provide a major increase in treatment capacity, from 34 to 47.5 litres per second. This will reduce the need for untreated discharges in wet weather. This work is currently expected to complete in 2023.
We have additional work planned in 2027, which will improve the ability to treat the volumes of incoming sewage.
Arborfield STW
An upgrade is planned for Arborfield STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Ascot STW
Ascot STW is being upgraded at a cost of more than £11 million. This work will provide a major increase in treatment capacity, from 157 to 220 litres per second. This will reduce the need for untreated discharges in wet weather. It's due to complete in 2024. Additional work is planned and will be complete in 2026.
Aston Le Walls STW
Aston Le Walls STW has been upgraded to increase the capacity of the storm tanks at a cost of more than £0.5 million. This will reduce the need for untreated sewage discharges during storm conditions.
We're also planning to improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Aylesbury STW
Aylesbury STW is being upgraded at a cost of more than £15 million. This work will improve the treatment of sludge on the site.
We're also planning to improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2028.
B
Bampton STW
An upgrade is planned for Bampton STW. This work will provide a major increase in treatment capacity, from 23 to 36 litres per second. This will reduce the need for untreated discharges in wet weather. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Banbury STW
Upgrades are planned for Banbury STW. They'll include an increase in treatment capacity, from 266 to 490 litres per second. This will reduce the need for untreated discharges in wet weather, and provide a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Barford St Michael STW
An upgrade is planned for Barford St Michael STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Barkway STW
An upgrade is planned for Barkway STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Basingstoke STW
An upgrade is planned for Basingstoke STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Basingstoke.
Beckton STW
Beckton STW is being upgraded at a cost of over £181 million. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2023.
There is further investment planned between 2027 and 2030.
Beenham STW
An upgrade is planned for Beenham STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Beer Lane
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Bell Lane Creek and Frogmore Storm
These are two of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Bell Wharf
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Benson STW
Benson STW is being upgraded at a cost of more than £9 million. This work will provide a major increase in treatment capacity, from 58.7 to 74.9 litres per second. This will reduce the need for untreated discharges in wet weather. This work is currently expected to complete in 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Benson.
Bentley STW
Bentley STW is being upgraded at a cost of more than £6 million. This project will increase the capacity of the storm tanks, so reduce the need for untreated sewage discharges during storm conditions. We will also be improving the quality of treated effluent going to the river.
The storm tank scheme is due for completion in 2024. We plan to complete the phosphorus scheme in our next asset planning period (2025 to 2030) and will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Bentley.
Berkhamsted STW
Berkhamsted STW is being upgraded at a cost of more than £25 million. The upgrades comprise two schemes; the first completed in 2023 and provides a major increase in treatment capacity, from 247 to 316 litres per second. This reduces the need for untreated discharges in wet weather. The second scheme will upgrade our treatment processes to ensure higher quality of treated effluent going to the river. We expect to complete this scheme in 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Berkhamsted.
Bicester STW
Bicester STW has been upgraded at a cost of more than £8 million. This work provided increased treatment capacity, reducing the need for untreated discharges in wet weather. This work was completed in 2022.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Bicester.
Bishop Stortford STW
An upgrade is planned for Bishop Stortford STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Blackbirds STW
An upgrade is planned for Blackbirds STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Bletchingdon STW
An upgrade is planned for Bletchingdon STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Bloxham STW
Bloxham STW is being upgraded at a cost of more than £6 million. This work will provide a major increase in treatment capacity, from 30.6 to 38 litres per second. This will reduce the need for untreated discharges in wet weather. This work will complete in 2023.
Blunsdon STW
An upgrade is planned for Blunsdon STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Boddington STW
An upgrade is planned for Boddington STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Bordon STW
An upgrade is planned for Bordon STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Bourton on the Water STW
An upgrade is planned for Bourton on the Water STW. This work will provide a major increase in treatment capacity, from 47 to 143 litres per second. This will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2024.
Work is also currently being carried out to reduce groundwater infiltration and other unwanted surface water entering the wastewater network in this area. This is due to complete by the end of 2025. Further investigation will continue in this area, which will help inform our long-term planning.
See our groundwater impacted system system plan for Bourton on the Water.
Boxford STW
An upgrade is planned for Boxford STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Bracknell STW
An upgrade is planned for Bracknell STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Braughing STW
An upgrade is planned for Braughing STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Brentwood (Nags Head Lane) STW
An upgrade is planned for Brentwood STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Brickendon STW
An upgrade is planned for Brickendon STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. We expect the project to complete in 2026.
Briff Lane (Bucklebury) STW
An upgrade is planned for Bucklebury STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. We expect the project, which is still being designed, to complete in 2026.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Briff Lane Bucklebury.
Brixton Storm Relief Sewer
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Broadwell STW
An upgrade is planned for Broadwell STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. We expect the project, which is still being designed, to complete in 2026.
Buntingford STW
Buntingford STW is being upgraded at a cost of more than £12 million. This work will provide a major increase in treatment capacity, from 40 to 48 litres per second. This ensures a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2024.
Burghfield STW
An upgrade is planned for Burghfield STW. This will include an increase in treatment capacity, as well as a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges.
We expect the £17m project to complete in the next asset management period (2025 to 2030) and we will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Burghfield.
Burstow STW
Burstow STW is being upgraded at a cost of more than £23 million. This will improve its ability to treat the volumes of incoming sewage and provide a higher quality of treated effluent going to the river. We expect the project to complete in 2024.
C
Caddington STW
An upgrade is planned for Caddington STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Camberley STW
An upgrade is planned for Camberley STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Carterton STW
An upgrade is planned for Carterton STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Carterton.
Cassington STW
An upgrade is planned for Cassington STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2025.
Chalgrove STW
Chalgrove STW is being upgraded at a cost of more than £1 million. This project will increase the capacity of the storm tanks, reducing the need for untreated sewage discharges during storm conditions. The scheme will complete in 2024.
Chapel Row STW
An upgrade is planned for Chapel Row STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Chapmore End STW
Chapmore End STW is being upgraded at a cost of over £3 million. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2023.
Charlbury STW
An upgrade is planned for Charlbury STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2025.
Charlton Storm Relief
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Chertsey STW
Chertsey STW is being upgraded at a cost of more than £15 million. This project will increase the capacity of the storm tanks and improve its ability to treat the volumes of incoming sewage. This will reduce the need for untreated sewage discharges during storm conditions. The storm tank scheme is due for completion in 2024, with other works completing in 2025.
Chesham STW
Chesham STW is being upgraded at a cost of more than £20 million. These projects will provide a major increase in treatment capacity to 353 litres per second. This will reduce the need for untreated discharges in wet weather and ensure a higher quality of treated effluent going to the river. The treatment capacity upgrade completed in early 2023 and we expect the effluent quality upgrade to complete in late 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Chesham.
Chieveley STW
An upgrade is planned for Chieveley STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Chilton Foliat STW
Chilton Foliat STW was closed with all flows pumped to the Hungerford catchment, via a new 2km pipeline. The project cost more than £3 million and was completed in 2023.
Upgrade work (increasing storm tank storage capacity) was carried out at Hungerford STW to accommodate the additional flow.
Chinnor STW
Chinnor STW is being upgraded at a cost of more than £10 million. This project will provide a major increase in treatment capacity, from 47 to 73.8 litres per second This will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Chinnor.
Chipping Norton STW
Chipping Norton STW is being upgraded at a cost of more than £5 million.This will improve its ability to treat the volumes of incoming sewage reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Chipping Warden STW
An upgrade is planned for Chipping Warden STW. This will provide more reliable and accurate information relating to untreated discharges. The scheme is due to complete in 2024.
Chobham STW
Chobham STW is being upgraded at a cost of more than £12 million. This project will ensure a higher quality of treated effluent going to the river, and improve its ability to treat the volumes of incoming sewage. We expect the project to complete in 2024.
Cholsey STW
Cholsey STW is being upgraded at a cost of more than £5 million. It includes an increase in treatment capacity from 74 to 105 litres per second and an increase in storm tank capacity. This will reduce the need for untreated discharges in wet and stormy weather. We expect the scheme to complete in 2024.
Church Hanborough STW
An upgrade is planned for Church Hanborough STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Church Street Sewer
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Cirencester STW
Cirencester STW is being upgraded at a cost of more than £22 million. This project will provide a major increase in treatment capacity, from 269 to 484 litres per second. An increase in storm tank capacity, will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Cirencester.
Clanfield STW
An upgrade is planned for Clanfield STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Work is also currently being carried out to reduce groundwater infiltration and other unwanted surface water entering the wastewater network in this area. This is due to complete by end of 2025. Further investigation will continue in this area, which will help inform our long-term planning.
See our groundwater impacted system management plan for Clanfield.
Clapham Storm Relief Sewer, London
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Clavering STW
An upgrade is planned for Clavering STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Compton STW
An upgrade is planned for Compton STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Compton.
Cottered STW
Cottered STW has been upgraded at a cost of more than £2 million. This project has increased the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme was completed in 2023.
Counters Creek, Lots Road
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Cranleigh STW
An upgrade is planned for Cranleigh STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Cranleigh.
Crawley STW
Crawley STW is being upgraded at a cost of more than £34 million. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Cricklade STW
Cricklade STW is being upgraded at a cost of more than £5 million. This project will provide a major increase in treatment capacity, from 26 to 30 litres per second, reducing the need for untreated discharges in wet weather as well as including an increase in storm tank capacity. We expect the project to complete in 2024.
Crondall STW
An upgrade is planned for Crondall STW. This will improve its ability to treat the volumes of incoming sewage. The scheme is due to be complete in 2026.
See our groundwater impacted system management plan for Crondall.
Cropredy STW
An upgrade is planned for Cropredy STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Crossness STW
There’s a range of complex schemes underway at Crossness STW, including work to improve its ability to treat the volumes of incoming sewage. These schemes are likely to continue until 2030.
Croughton STW
An upgrade is planned for Croughton STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Cuddington STW
An upgrade is planned for Cuddington STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Culham STW
An upgrade is planned for Culham STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
Culworth STW
An upgrade is planned for Culworth STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
D
Dagnall STW
An upgrade is planned for Dagnall STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Deephams STW
There’s a range of complex schemes being planned at Deephams STW, including work to improve its ability to treat the volumes of incoming sewage. These schemes are likely to continue until 2030.
Deptford Creek Storm
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Deptford Storm Relief
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Didcot STW
An upgrade is planned for Didcot STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2028.
Dorchester STW
Dorchester STW is being upgraded at a cost of more than £2 million. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2023.
Dorking STW
Dorking STW is being upgraded at a cost of more than £14 million. This project will increase the capacity of the storm tanks and improve its ability to treat the volumes of incoming sewage. This will reduce the need for untreated sewage discharges during storm conditions. The storm tank scheme is due for completion in 2025, with further works to improve the sites ability to treat incoming flows completing in 2026.
Dorton STW
An upgrade is planned for Dorton STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Drayton STW
An upgrade is planned for Drayton STW. This project will provide a major increase in treatment capacity, from 43.3 to 57 litres per second. An increase in storm tank capacity will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2024.
E
Earl
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Earlswood STW
Upgrades are planned for Earlswood STW. These will include an increase in treatment capacity, from 340 to 400 litres per second, providing a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges in wet weather. We expect the projects to complete in 2025.
East Grafton STW
East Grafton STW has been upgraded at a cost of more than £0.4 million. This scheme increased the capacity of the storm tanks. This reduces the need for untreated sewage discharges during storm conditions. The scheme completed in 2023.
East Shefford STW
East Shefford STW is being upgraded at a cost of more than £10 million. This project will improve its ability to treat the volumes of incoming sewage, providing a higher quality of treated effluent going to the river. We expect the project to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for East Shefford.
Easthampstead Park STW
An upgrade is planned for Easthampstead Park STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Elstead STW
An upgrade is planned for Elstead STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Epping STW
An upgrade is planned for Epping STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Esher STW
An upgrade is planned for Esher STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
Eydon STW
An upgrade is planned for Eydon STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
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Fairford STW
An upgrade is planned for Fairford STW. This project will provide a major increase in treatment capacity, from 37.8 to 56.8 litres per second, reducing the need for untreated discharges in wet weather. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Fairford.
Falcon Brook
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Faringdon STW
Faringdon STW is being upgraded to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. We expect the scheme to complete in 2026.
Farnborough STW
An upgrade is planned for Farnborough STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Farnham STW
An upgrade is planned for Farnham STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Finstock STW
Finstock STW is being upgraded at a cost of over £1 million. We completed upgrades in 2023 to ensure a higher quality of treated effluent going to the river. Further upgrades are ongoing to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2024.
Fleet Main Line Sewer
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Fleet STW
An upgrade is planned for Fleet STW. This will include an increase in treatment capacity, as well as a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges in wet weather. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Forest Hill STW
An upgrade is planned for Forest Hill STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Fyfield STW
Fyfield has been upgraded at a cost of £2 million. This includes an increase in treatment capacity, providing a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges in wet weather. The project completed in 2023.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Fyfield.
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Gerrards Cross STW
An upgrade is planned for Gerrards Cross STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Godalming STW
An upgrade is planned for Godalming STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Goswell Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Greatworth STW
An upgrade is planned for Greatworth STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete by 2026.
Greenwich
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Grendon Underwood STW
An upgrade is planned for Grendon Underwood STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Guildford STW
We’re constructing a new sewage treatment works for Guildford at a cost of over £160 million. The scheme is due to complete in 2026.
Gun Wharf (Wapping Dock)
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
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Haddenham STW
An upgrade is planned for Haddenham STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Hammersmith
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Hampstead Norreys STW
An upgrade is planned for Hampstead Norreys STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Work is also currently being carried out to reduce groundwater infiltration and other unwanted surface water entering the wastewater network in this area. This is due to complete by end of 2025. Further investigation will continue in this area, which will help inform our long-term planning.
See our groundwater impacted system management plan for Hampstead Norreys.
Hanwell STW
Hanwell STW is being upgraded at a cost of over £1 million. The project will increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in late 2024.
Harpenden STW
An upgrade is planned for Harpenden STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Hartley Wintney STW
An upgrade is planned for Hartley Wintney STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Haslemere STW
An upgrade is planned for Haslemere STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Hatfield (Mill Green) STW
An upgrade is planned for Hatfield (Mill Green) STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Hatfield Heath STW
An upgrade is planned for Hatfield Heath STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Heath Wall Pumping Station
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Henley Road
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Henley STW
An upgrade is planned for Henley STW. This will provide a major increase in treatment capacity, from 67 to 82 litres per second. This will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2025.
Heyford STW
An upgrade is planned for Heyford STW. This will provide a major increase in treatment capacity, from 17 to 22 litres per second. This will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2025.
Highworth STW
An upgrade is planned for Highworth STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Hockford STW
An upgrade is planned for Hockford STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Hogsmill STW
Hogsmill STW is being upgraded to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2026.
Holloway Storm Sewer
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Holmwood STW
An upgrade is planned for Holmwood STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Hook Norton STW
Hook Norton STW is being upgraded at a cost of over £11 million. This project will ensure a higher quality of treated effluent going to the river. We will also increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2024.
Horley (Oxon) STW
An upgrade is planned for Horley (Oxon) STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Horley (Surrey) STW
An upgrade is planned for Horley (Surrey) STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Horseferry Road
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Horton-Cum-Studley STW
An upgrade is planned for Horton-Cum-Studley STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Hungerford STW
Hungerford STW has been upgraded at a cost of over £5 million. This project has improved its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme completed in 2023.
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Iron Gate
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Isle of Dogs, London
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Islip STW
Islip STW has been upgraded at a cost of over £0.3 million. This scheme increased the capacity of the storm tanks. This reduces the need for untreated sewage discharges during storm conditions. The scheme was completed in 2023.
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Jews Row Pumping Station (Falconbrook Storm Relief)
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
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Kimpton STW
An upgrade is planned for Kimpton STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Kings Scholars Pond
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Kingsclere STW
An upgrade is planned for Kingsclere STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Kingsclere.
Kingston Bagpuize STW
Kingston Bagpuize STW is being upgraded at a cost of over £31 million. This project will increase the capacity of the storm tanks, reducing the need for untreated sewage discharges during storm conditions. We’ll be ensuring a higher quality of treated effluent going to the river. The schemes will be completing in 2024.
Kintbury STW
Kintbury STW is being upgraded at a cost of over £2 million. This project will improve its ability to treat the volumes of incoming sewage. This will reduce the need for untreated discharges in wet weather. The scheme is due to complete in 2023.
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Leatherhead STW
An upgrade is planned for Leatherhead STW. This will provide a major increase in treatment capacity, from 250 to 320 litres per second. This will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2026.
Lewknor STW
An upgrade is planned for Lewknor STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Lightwater STW
An upgrade is planned for Lightwater STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Little Compton STW
The scheme to increase the capacity of storm tanks, reducing the need for untreated sewage discharges during storm conditions, completed in 2023. A separate scheme due to complete in 2026 will also improve its ability to treat the volumes of incoming sewage.
Little Hallingbury STW
An upgrade is planned for Little Hallingbury STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Little Marlow STW
An upgrade is planned for Little Marlow STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is likely to complete in 2027.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Little Marlow.
London Bridge
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Long Reach STW
An upgrade is planned for Long Reach STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Low Level 1 N, Grosvenor Ditch, Millb
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Ludgershall STW
An upgrade is planned for Ludgershall STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Luton (East Hyde) STW
An upgrade is planned for Luton (East Hyde) STW. This scheme will ensure a higher quality of treated effluent going to the river and improve its ability to treat the volumes of incoming sewage. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
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Maidenhead STW
An upgrade is planned for Maidenhead STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Maidenhead.
Manuden STW
An upgrade is planned for Manuden STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Maple Lodge STW
Maple Lodge STW is being upgraded to ensure a higher quality of treated effluent going to the river, and to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. We can't yet confirm a completion date.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Maple Lodge.
Markyate STW
An upgrade is planned for Markyate STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Markyate.
Marlborough STW
An upgrade is planned for Marlborough STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Marlborough.
Marsh Gibbon STW
An upgrade is planned for Marsh Gibbon STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Marsh Gibbon.
Merstham STW
An upgrade is planned for Merstham STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Middle Barton STW
Middle Barton STW is being upgraded at a cost of over £1 million. This project will increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2025.
Middleton Cheney STW
An upgrade is planned for Middleton Cheney STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Milton-Under-Wychwood STW
An upgrade is being planned for Milton-under-Wychwood STW. This will provide a major increase in treatment capacity, to 43 litres per second, reducing the need for untreated discharges in wet weather. The project is likely to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Milton-Under-Wychwood.
Mogden STW
There are a range of complex schemes underway at Mogden STW, including work to improve its ability to treat the volumes of incoming sewage. These schemes are likely to be ongoing until 2030.
Moreton in Marsh STW
Moreton in Marsh STW is being upgraded to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Moreton in Marsh.
Moreton STW
An upgrade is planned for Moreton STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Mortimer STW
An upgrade is planned for Mortimer STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
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Newbury STW
An upgrade is planned for Newbury STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Newmans Lane Pumping Station
Newmans Lane Pumping Station is being upgraded at a cost of over £5 million. This project will increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2025.
Nightingale Lane
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Norfolk Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
North Weald STW
An upgrade is planned for North Weald STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
North West Storm Relief
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
(Northern) Low Level No 1 Brook Green
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Northleach STW
An upgrade is planned for Northleach STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Northumberland Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
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Oxford STW
We're finalising plans for a major upgrade at Oxford STW, costing more than £130m. This will provide a significant increase in treatment capacity, larger storm tanks and a higher quality of treated effluent going to the river. We can't yet confirm a completion date.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Oxford.
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Pangbourne STW
Pangbourne STW is being upgraded at a cost of over £3 million. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Pauls Pier
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Princes Risborough STW
An upgrade is planned for Princes Risborough STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2027.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Princes Risborough.
Purton STW
An upgrade is planned for Purton STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Putney Bridge Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
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Queen Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
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Ramsbury STW
An upgrade is being planned for Ramsbury STW. This will provide a major increase in treatment capacity, from 27 to 53 litres per second. This will reduce the need for untreated discharges in wet weather. We expect the project to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Ramsbury.
Ratcliffe Highway Limekiln
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Reading STW
An upgrade is planned for Reading STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Reading.
Regent Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Ripley STW
An upgrade is planned for Ripley STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Riverside STW
An upgrade is planned for Riverside STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2027.
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Sandhurst STW
An upgrade is planned for Sandhurst STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2025.
Savoy Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Selborne STW
An upgrade is planned for Selbourne STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Shabbington STW
Shabbington STW is being upgraded at a cost of over £1 million. This will improve its ability to treat the volumes of incoming sewage and to increase the capacity of the storm tanks. This will reduce the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Shad, Thames
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Shamley Green STW
An upgrade is planned for Shamley Green STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Sherfield-On-Loddon STW
An upgrade is planned for Sherfield-on-Loddon STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
Shutford STW
An upgrade is planned for Shutford STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Silchester STW
An upgrade is planned for Silchester STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Silchester.
Sloane Street, Raneleigh Gardens
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Slough STW
Upgrades are planned for Slough STW. These will include an increase in treatment capacity, from 1150 to 1416 litres a second. This will provide a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges in wet weather. We can't yet confirm a completion date.
Smith Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Sonning Common STW
An upgrade is planned for Sonning Common STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
South Leigh STW
An upgrade is planned for South Leigh STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
South Moreton STW
An upgrade is planned for South Moreton STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Stamford Brook
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Standon STW
An upgrade is planned for Standon STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Stanford in the Vale STW
Stanford in the Vale STW is being upgraded at a cost of over £3 million. This project will increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2025.
Stanford Rivers STW
An upgrade is planned for Stanford Rivers STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Stansted Mountfitchet STW
An upgrade is planned for Stansted Mountfitchett STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Stanton Harcourt STW
An upgrade is planned for Stanton Harcourt STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Stewkley STW
An upgrade is planned for Stewkley STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2026.
Stone STW
Stone STW is being upgraded at a cost of over £1 million. This will increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2025.
SW Storm Relief Sewer, London
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Swindon STW
An upgrade at Swindon STW is planned to increase the capacity of the sludge stream, which will improve efficiency. The scheme is due for completion in 2030.
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Takeley STW
An upgrade is planned for Takeley STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Temple Place Essex Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Tetsworth STW
An upgrade is planned for Tetsworth STW. This scheme will ensure a higher quality of treated effluent going to the river. We expect the project to complete in 2025/6.
Thame STW
An upgrade is planned for Thame STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Therfield STW
Therfield STW is being upgraded to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme will also ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Theydon Bois STW
An upgrade is planned for Theydon Bois STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Thornwood STW
An upgrade is planned for Thornwood STW. This will improve its ability to treat the volumes of incoming sewage as well as providing a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
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Uffington STW
An upgrade is planned for Uffington STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2025.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Uffington.
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Waddesdon STW
An upgrade is planned for Waddesdon STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Wanborough STW
An upgrade is planned for Wanborough STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Wandle Valley
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Wargrave STW
An upgrade is planned for Wargrave STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Warmington STW
An upgrade is planned for Warmington STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2026.
Wash Water STW
An upgrade is planned for Wash Water STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Wash Water.
Watlington STW
Upgrades are planned for Watlington STW. These will include an increase in treatment capacity to 60 litres per second, as well as providing a higher quality of treated effluent going to the river. This scheme will reduce the need for untreated discharges in wet weather. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Watlington.
West Putney S R, Horne Way
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Western PS Low Lever Sewer
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Weston (Herts) STW
An upgrade is planned for Weston STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Weston-On-The-Green STW
An upgrade is planned for Weston-On-The-Green STW. This scheme will ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
White Roding STW
White Roding STW is being upgraded at a cost of over £2 million. This will increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme is due for completion in 2025.
Whitwell STW
An upgrade is planned for Whitwell STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme is due to complete in 2024.
Willingale STW
Willingale STW has been upgraded at a cost of over £2 million. This scheme increases the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. This scheme was completed in early 2023.
Windsor STW
An upgrade is planned for Windsor STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2027.
Wingrave STW
An upgrade is planned for Wingrave STW. This scheme will ensure a higher quality of treated effluent going to the river, as well as improving its ability to treat the volumes of incoming sewage. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Wisley STW
An upgrade is planned for Wisley STW. This scheme will ensure a higher quality of treated effluent going to the river, as well as improving its ability to treat the volumes of incoming sewage. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Witney STW
Witney STW is being upgraded at a cost of more than £17 million. This work will provide a major increase in treatment capacity, from 240 to 399 litres per second. This will reduce the need for untreated discharges in wet weather. This work is running ahead of schedule and is currently expected to complete in 2024.
We're also investigating the impact of groundwater on the sewer network in this area. This will help inform our long-term planning.
See our groundwater impacted system management plan for Witney.
Woking STW
Woking STW is being upgraded to increase the capacity of the storm tanks. This will reduce the need for untreated sewage discharges during storm conditions. The scheme will also ensure a higher quality of treated effluent going to the river. We plan to complete this work in our next asset planning period (2025 - 2030) and will provide more detailed information once the work schedule is confirmed.
Wokingham (Ash Ridge) STW
An upgrade is planned for Wokingham STW. This will improve its ability to treat the volumes of incoming sewage, reducing the need for untreated discharges in wet weather. The scheme, which is still being designed, is due to complete in 2025.
Wood Street
This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.
The Thames Tideway Tunnel is the third and final stage of a program to improve the quality of the Tidal Thames. When complete, this final stage will reduce CSO overflows along the Thames by a further 40%. This 40% reduction will add to the 55% already achieved by the first two phases delivered by Thames Water. In total, the volume discharged to the Tidal Thames will be reduced by 95%, depending on the weather.
Woodstock STW
We completed a project at Woodstock STW to provide more reliable and accurate information relating to untreated discharges. This was completed in 2023.
Worminghall STW
Worminghall STW is being upgraded at a cost of over £7 million. This scheme will ensure a higher quality of treated effluent going to the river, improving its ability to treat the volumes of incoming sewage. We expect the project to complete in 2024.