The 2.85m diameter concrete-lined tunnel will run from an existing shaft at Thames Water’s reservoir site in Stoke Newington and join the Ring Main at the New River Head pumping station, Finsbury.
AMEC’s engineers will have to deal with varying ground conditions, ranging from London clay to Thanet sands using a Lovat earth-balance tunnel boring machine (TBM). They will tunnel under Highbury and Islington, crossing under six London Underground tunnels, five Network Rail tunnels, a canal tunnel and two major sewers.
In addition to the tunnelling work, the contract involves a mechanical, electrical, instrumentation and communications upgrade and the sinking of two 50m deep launch and reception shafts for the TBM.
Detailed design begins immediately with work on site scheduled to start in July this year. Completion is planned for spring 2010.
The project forms part of a £90m strategic improvement to the Ring Main, which also includes the construction of a new tunnel from the Honor Oak reservoir, Forest Hill, to Brixton.
AMEC’s previous recent work for Thames Water includes a major transfer tunnel at High Wycombe and the award-winning Queen Mother Reservoir inlet tunnel recovery project, Datchet.