AMEC Wins Thames Water Contract

AMEC has been awarded a £28m contract by Thames Water to construct a 4.5km tunnel that will connect a major water treatment works to the London Ring Main and help ensure security of water supply to the capital.

The 2.85m diameter concrete-lined tunnel will run from an existing shaft at Thames Water's reservoir site at Stoke Newington and join the Ring Main at the New River Head pumping station, Finsbury.

It is a challenging project. AMEC's engineers will have to deal with varying ground conditions, ranging from London clay to Thanet sands, as the Lovat earth-balance tunnel boring machine (TBM) drives its way under Highbury and Islington and crosses 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 50-metre-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.

The London Ring Main
The Ring Main was built to improve the speed and efficiency of transferring supplies of drinking water across the capital. At 50 miles long, the tunnel runs beneath the capital like an underground M25 at an average depth of 40 metres, deeper than most lines on the London Underground. The tunnel is wide enough to allow a car to pass through and is built in a ring so that water can flow in either direction. If a section is taken out of service for maintenance, supplies can still be delivered to every area of London. Water is moved under gravity, resulting in large energy savings as expensive overland pumping is reduced.

The Ring Main was officially opened in 1994 by HM the Queen and was completed two years ahead of schedule. It is the biggest capital project Thames Water has ever undertaken and is the longest tunnel ever built in this country.

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Posted 31/01/07

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