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National Grid prepares to tunnel under Thames

National Grid begin tunnelling project

Engineers have begun work on National Grid Gas Distribution’s largest civil engineering project – a 330m long tunnel under the River Thames.

The project involves sinking a 30m deep shaft at each of the land locations, before excavating the tunnel using a micro tunnel boring machine (TBM), which will be remotely operated from above ground.

Part of National Grid’s work to update London’s gas infrastructure, the work involves three of London’s most famous locations: the Royal Hospital Chelsea, Battersea Park and the River Thames.

Major events at the Royal Hospital Chelsea, most notably the Chelsea Flower Show, have been factored into the timetable of works.

Map of Thames tunnel

Map of National Grid’s tunnel underneath the River Thames

The first shaft, which will have a diameter of 7.5m, will be sunk in the grounds of the Royal Hospital Chelsea between January and March 2017. The site will then be cleared to avoid any disruption to the events over the summer. Work will then shift to Battersea Park where the second shaft – with a diameter of 6m – will be sunk between April and August 2017.

“This is National Grid Gas Distribution’s flagship civil engineering for the 2013-2021 regulatory period,” said project manager Andrew Hejdner. “We’re looking forward to getting started on the construction, which has taken almost 12 months of planning.

“Designing a 330m long tunnel that runs 30m under the River Thames is fairly straightforward in tunnelling terms; however, to secure so many permissions and factor in Thames Tideway’s works in such a short space of time is an impressive undertaking.

“Our project team have done a fantastic job in designing the river crossing and securing the necessary permissions.”

The project will be delivered by National Grid Gas Distribution’s strategic partner Triio, which also includes contractors Mott Macdonald and Skanska.

The tunnel forms part of National Grid’s £1bn investment in replacing ageing gas mains across the capital.

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