Lee Tunnel Thames Tideway - Behind the project
The Lee Tunnel is a 6.9km long tunnel in East London for storage and conveyance of sewage mixed with rainwater. With a finished internal diameter of 7.2m and the length of 3 double-decker London busses, you can say that this is an impressive project.
The construction of this tunnel served multiple purposes. One of them was to improve the health of the Rivers Thames and Lee. The tunnel will receive stormwater flows from the Abbey Mills Pumping station complex and store until they can be pumped out at Beckton Sewage Treatment Works, which is now the largest sewer treatment plant in Western Europe. Other reasons for the construction of this tunnel were:
- The Bazelgette’s Victorian sewer system needs enlarging across London as the population continues to increase
- The storm discharges at combined stormwater overflow into the river Thames exceeded the permitted limits.
- The stormwater overflows from the Abbey Mills PS complex into the Lee river created 40% of the total stormwater overflows discharges alone.
- The Lee tunnel will eliminate the combined stormwater overflows discharges at Abbey Mills
Fibre reinforced concrete was used during the construction of this tunnel project in the major elements, the primary tunnel lining, the secondary tunnel lining and the permanent lining to all 5 shafts.
In the secondary lining to the tunnel, some 17000 tons of traditional reinforcement was replaced with >2.000 tons of the Dramix 5D6560BG fibre providing a much better-engineered solution in terms of crack width control and savings in embodied energy and costs.
Likewise, in the shafts where a double-sided slipform system was used to form the permanent linings and gave savings of about 4.000 tonnes of steel bar reinforcement, and again a much better-engineered solution and program savings.
In all large savings of steel bar reinforcement were made by adopting the SFRC tunnel and shaft linings solution.
After 6 years of construction, they finished the Lee Tunnel in 2016. It was an excavation of London’s deepest tunnel ever through chalk under full hydrostatic groundwater pressures.
If you would like to learn more about the process of constructing this tunnel, check out BBC's documentary about the project.
‘Engineering the Lee Tunnel and shafts through chalk at depth’ written by Peter Jewell and Matthew Bellhouse, gives you an insight in the complexity and scale of this tunnel.