What is TDRA?
What TDRA will mean:
- Construction of a large river water intake facility on Burnell Riverside (Ham Lands) above Teddington Weir
- Abstraction (intake) of millions of litres of water from the River Thames above Teddington Weir to send to the Lee Valley Reservoirs
- Construction of a new outfall (discharge) structure also on the Ham Lands riverside above Teddington Weir.
- Discharge of millions of litres of treated sewage into the River Thames at Teddington
- A 4 year construction time line, 14000 HGVs in the local Burnell Area roads and the open space hoarded off.
- Construction of a 3.5 metre tunnel 4km long under the streets of Isleworth, Twickenham, Teddington, Ham and Kingston to transfer the treated sewage to the outfall
- Construction of a 3.5 metre tunnel to join the abstraction structure to the existing Thames Lee Tunnel (TLT). The existing TLT transfers water to the Lee Valley reservoirs.
- Construction of a tertiary treatment facility within the Mogden sewage works and the launch shaft for the treated sewage tunnel (see more details here)
- Thames Water would have a multi million pound asset added to their balance sheet, but we do not think it is the solution for London's water needs.
Click to see the specific impact on Mogden and the new tertiary Treatment Plant and Burnell Riverside Open Space . To read more about this scheme in Thames Water's words, see their website here.
What is TDRA for?
- Thames Water describe TDRA as a 'contingency' asset for drought that will not be continuously in operation
- Thames Water suggests that TDRA may operate every 2 to 3 years and then almost entirely between July and November over their current 47-year outlook plan to 2075
- When not in use as a drought scheme the discharge of treated sewage will operate continually up to 15mld (mega litres a day) 365 days a year to ensure the mechanical systems and filters are kept operational. This is called a "sweetening flow.” The sweetening flow will be discharged from Mogden Sewage Treatment Works in Isleworth.
What is the planning process for TDRA?
In December 2023, Thames Water officially bypassed local planning authority to fast track the scheme through the National Infrastructure planning route. This means they will make the application for development via the Planning Inspectorate.
In Summer 2025 Thames Water launched their Statutory Consultation on TDRA.
In 2026 There was a supplementary consultation where Thames Water introduced significant changes to the Burnell Riverside Open Space worksite and suggested a second supplementary consultation may be held because of changes at Mogden site.
These changes mean that in "early 2027" Thames Water are expected to make their formal application to the Planning Inspectorate.
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Without action, this plan will go ahead.
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The ‘red line’ boundary shows the areas of land that will be impacted by TDRA during construction. The most significant sites of construction are Mogden and Burnell Riverside Open Space. (Note: in 2026 Thames Water removed a shaft in Ham Playing fields from their plans - but did not update the full red line boundary plan).
Works - Below and Above ground.
The treated effluent tunnel will be 3.5m in diameter and will be constructed under approximately 4Km of South West London. It will be approx 60m underground at Mogden and 20m at Ham Lands and Burnell. There will be significant above ground works in Mogden Sewage Works (Hounslow) and Burnell Riverside Open Space (Richmond and Kingston). The Burnell Riverside Open Space (Richmond and Kingston) site will be active for at least 4 years.
Read more about impact on those areas by clicking the links below