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:

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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.

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.

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.

Bell Lane Creek and Frogmore Storm

These are two of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

Bell Wharf

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.

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.

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.

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.

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.

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.

Deptford Storm Relief

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.

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.

F

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.

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.

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.

G

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.

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.

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.

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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.

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.

Henley Road

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.

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.

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.

Isle of Dogs, London

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.

J

Jews Row Pumping Station (Falconbrook Storm Relief)

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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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.

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.

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.

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.

Norfolk Street

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.

(Northern) Low Level No 1 Brook Green

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.

O

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.

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.

Q

Queen Street

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

W

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.

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.

Western PS Low Lever Sewer

This is one of the 54 combined sewer overflows (CSOs) discharging to the tidal River Thames system.

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.