What is TDRA?

What TDRA will mean:

  • Construction of a new abstraction (water removal) facility on Ham Lands riverside above Teddington Weir (see images)
  • Abstraction of millions of litres of water from the River Thames above Teddington Weir to send to the Lea Valley Reservoirs
  • Construction of a new outfall (discharge) facility also on the Ham Lands riverside above Teddington Weir (see images)
  • To use this discharge facility to pump millions of litres of treated sewage into the River Thames at Teddington
  • 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 2.2 metre tunnel to join the abstraction structure to the existing Thames Lee Tunnel (TLT). The existing TLT transfers water to the Lea Valley reservoirs.
  • Construction of a tertiary treatment facility on top of the storm tanks at Mogden sewage works
  • Construction of new shafts and other infrastructure at Ham Street car park, in Burnell open space and in Park Gate woods OR Tudor Drive pocket park

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 18mld (mega litres a day) 365 days a year to ensure the mechanical systems and filters are kept operational. This is called a "sweetening flow.” Thames Water say the sweetening flow may be discharged from Mogden Sewage Treatment Works as opposed to the new outfall above Teddington Weir.

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. Thames Water hope to make this application sometime in 2026
  • This scheme is called a 'contingency' asset. Thames Water claims it will not be operational daily.
  • In 2025 (possibly in the 2nd quarter) Thames Water expect to run a Statutory Consultation on TDRA. They will have to produce a lot more information on the possible impacts of the scheme at this consultation

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Without action, this plan will go ahead.

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Thames Water's Preferred Route for TDRA tunnels and Infrastructure locations

TW route

The map is based on Thames Water's documents in their Documents Library (expand Consultation documents and go to Map Book).

The original map provided by Thames Water is here.

The ABOVE GROUND WORKS

The treated effluent tunnel will be 3.5m in diameter and will be constructed under approximately 4Km of South West London. It will require an intermediate shaft at Ham / Playing fields or Ham Street carpark (Richmond). There will also be above ground works in Mogden Sewage Works (Hounslow), Burnell Open Space (Richmond and Kingston) and Royal Park Gate woods or Tudor Drive Pocket park (Kingston) .

The Richmond / North Kingston (Burnell Open Space) site will be active for at least 21 months. This is because it will be the site of construction of both the outfall and abstraction facilities and 2 shafts.

A typical building site for lowering shafts. The shaft sites will be active construction areas for 6 – 8 months each. (Image from Sennebogen.)

Another typical building site for lowering shafts. (Image from Donnegan Civil Engineering on a project for Scottish Water.)

Intermediate Shaft Ham Street Car Park near Ham House

Ham Car Park Shaft site
Ham Street Car Park for Ham House
Ham Street Car Park for Ham House

The abstraction facility

A new abstraction facility will be built on the riverside towpath on Burnell open space above Teddington Weir. The abstraction facility is likely to measure approximately 38m long and 3m to 4m in height above normal water level. The structure could be partially set into the riverbank but extend into the river by up to 3m. Thames Water indicates it could take 21 months to build this abstraction facility. A new tunnel will be made to carry the abstracted water to the existing Thames Lee Tunnel (TLT). The construction compound at Burnell Open Space will take up to half if not more of the area resulting in disruption to the thousands of people that use the towpath and open space regularly.

In a drought millions of litres of water would be taken from the river. In periods of drought, the river will be at its most stressed, and the possibility of ecological harm is ever present.

Abstracted water tunnel options

A pipeline is required to take the abstracted water from the abstraction facility to the existing Thames Lee Tunnel (TLT). Two shafts are required for the abstracted water pipeline.

Thames Water is deciding between two options for the TLT connection:

  • Park Gate woods (destroying areas of trees and wildlife habitat) or
  • Tudor Drive junction (where there is a "pocket park").

A 2.2m tunnel under Royal Gate Park Estate would be needed for the Tudor Drive option. It is not known what kind of pipeline works would be used for the Royal Park Gate woods option. It could be either a pipejacked tunnel or a trenched tunnel.

Burnell Site Abstraction

Location of the Burnell Avenue abstraction and outfall facilities.

TDRAAbstraction Location 2048

The photo shows the location of the proposed abstraction facility along the River Thames.

indicative image of abstraction structure

Thames Water has provided the image below to indicate what the abstraction facility will look like. This will be built on the Thames River Path in Teddington.

The abstraction / intake facility at Bessborough Walton Upon Thames, to show what we might expect at Teddington. (Click for larger photo.) See below for more real-life abstraction facilities.

Abstraction facility at Bessborough in Walton Upon Thames.

Abstraction facility at Bessborough in Walton Upon Thames.

Abstraction facility at Bessborough in Walton Upon Thames.

The abstraction / intake facility at Surbiton, taken from the river, to show what we might expect at Teddington.

The abstraction / intake facility at Bessborough Walton Upon Thames, to show what we might expect at Teddington.

The outfall (discharge) structure

The Outfall (Discharge) facility will be built on the riverside of Burnell Open Space. The last shaft of the treated effluent tunnel will be built a short distance away in the Open Space.

In a drought, millions of litres of treated sewage will be pumped into the river from the discharge facility, with a significant ecological impact on the river.

indicative image outfall facility

Thames Water has provided this image to indicate what the outfall (discharge) structure will look like. This will be built on the Thames River Path in Teddington.

Hogsmill STW Outfall

What an outfall (discharge) structure looks like in real life - this one at Hogsmill.

bluetits at abstraction point

The Blue Tit swimmers in the River Thames, near where the TDRA outfall (discharge) structure will be located in Teddington. (Photo courtesy of D Gwilliam)

Location of the discharge site along the riverside
Location of the discharge site along the riverside