Costain’s first drive for National Grid on its US$318M, 33km long London Cable Tunnels project has reached a significant milestone with the lowering down the shaft of the Herrenknecht EPBM ‘Cleopatra’ that will be used to bore the 4m i.d. approximately 8km long St John’s Wood Tunnel.
The EPBM is being lowered at National Grid’s site in Eade Road, Haringey. After the initial learning curve, it will start excavating at a planned rate of approximately 120m per week. Ground conditions are mostly through London Clay. The tunnel will be lined using a Buchan 6 plate trapezoidal gasketed and bolted ring, each 1.3m long, with muck removed via wagons and from the shaft by High Angle Conveyor.
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National Grid Project Manager David Luetchford said: “The arrival of ‘Cleopatra’ and the beginning of tunnelling marks a real landmark for the project. Once operational London Power Tunnels will help ensure homes, business, community and leisure facilities across the capital continue to receive the power supplies that make life as we know it possible.”
Explaining some of the advantages of the London Power Tunnels project, Mr Luetchford said: “By housing the cables deep underground we are avoiding digging up London’s road network, which would risk major disruption. It also means we can easily access the tunnels to carry out future maintenance work.”