Packing in the Piling
London's Tottenham Court Road is one of the West End's busiest Tube stations. It sits at corners of the not-so-nice end of Oxford Street and Charing Cross Road, and handles more than 150,000 passenger journeys daily. Congestion is reaching breaking point.

The station first opened in 1900 and it is surprising that it has survived in its current state for this long. The last time major expansion work took place was in the 1930s when the original lifts were removed and replaced with escalators. Since then, there has only been cosmetic work to improve its ambience.

By 2000 Tottenham Court Road had become an unwelcome addition to any Tube journey both for commuters and tourists. But now, under the powers of the Crossrail Act the station is set to be transformed for the 200,000 daily passengers expected to be using the station by 2017.

Just before Christmas a joint venture of BAM Nuttall and Taylor Woodrow (now Vinci) was awarded the £200M contract to upgrade the station, beating Balfour Beatty and a team of Laing O'Rourke and Costain.

During the six-year construction programme, the project will provide a new eastern ticket hall for access to the new Crossrail station as well as an extension to the existing basement level ticket hall beneath the plaza in front of the Centre Point tower and beneath Charing Cross Road. The existing Dominion Theatre entrance will be retained and three new entrances will be built, including two in front of Centre Point and one at the corner of Oxford Street and Charing Cross Road.

And one of the most important results of the transformation will be the separation of the escalators to the Northern and Central Lines platforms, dividing up passengers before they get to the narrower parts of the station.

Ralph Freeston, senior project manager for London Underground, explains: 'This is the first major part of the Crossrail project that's on the ground and it really is a catalyst for the whole area improving.'

Demolition contractor McGee began working on the site in 2009 on its 18 month programme. The firm's job was to clear sites at Denmark Place, Astoria and Goslett Yard, and in the process knocking down the original Tottenham Court Road station building on Oxford Street and the much-loved Astoria Theatre.

McGee has achieved a 98% recovery rate for the demolished materials, with the majority being used to fill in the basements of the buildings where necessary.

Now the hoardings are up and to passers by it looks like nothing is happening behind the scenes. But how wrong they are.

Freeston says piling work is going to plan, with the first piles installed at Denmark Place to ensure future over-site developments can easily be built.

'This was a requirement of the job demanded by the developer, that we had to put them in during the construction of the station because it couldn't have been done after the Crossrail tunnelling,' he explains. 'Piles with 2.1.m diameter have been installed up to 63m deep. The piles are so big because you have the Crossrail tunnels running through too.'

Altogether nearly 900 secant piles will have to be installed, ranging in diameter from 325mm to 2.1m. Those near the new railway route will need to be sleeved, so that no extra load is put on the tunnels running beneath. Once that is done the construction team will have to sink four large boxes.

Freeston explains: 'The first is the Northern Line escalator box, which sits on an incline and is a top-down construction where the piles go down to 32m.'

Work started in earnest this autumn with traffic on Charing Cross Road diverted around the back of Centre Point, past St Giles' Circus for four years to allow construction to begin.

'Then at the Centre Point plaza we'll be sinking the box for the ticket hall and the plant room. It's another top down, bottom up construction with secant piled walls,' continues Freeston. 'At Falconberg Court we are constructing a shaft that will give access for doing work on the Crossrail tunnels, and when it's done it will serve as the emergency access for the station. Lastly the Goslett Yard box is a similar depth to the Northern Line but will have a larger plan. It's also a top down construction with diaphragm and plunge walls.'

After the diversion of Charing Cross Road, the next major public milestone will be the closure of the Northern Line platforms for eight months from April to November 2011.

'We have to rework the platform tunnels to get the stairs between them and take out the curves and replace them with straight steel, and there just isn't enough room for us to work with passengers using it at the same time,' says Freeston.

The joint venture was challenged to do it differently by London Underground directors, but couldn't find the space on the constricted platforms.

'At King's Cross, when they built the new northern ticket hall, they were able to do it without closing the platforms,' explains Freeston. 'But they had room and it's just not possible here. We'll be doing the same on the Central Line in 2015.'

The tunnel boring machines for Crossrail will reach the bowels of the station in 2012, when they will go under the escalators and above the existing Northern Line tunnels.

Finally in 2014 the three new station entrances will be opened and everything, including the re-worked public realm designed by Stanton Williams, will be finished in 2016.

If everything goes to plan the following year will see the first Crossrail trains passing through the station no doubt giving people a transport experience that they can only begin to imagine now.

Article courtesy of New Civil Engineer- november 2010


Further Info
Peter Bishop - Head of Public Relations & Corporate Communication
BAM Nuttall Limited
St James House, Knoll Road, Camberley,
Surrey GU15 3XW
Tel: 01276 63484
Fax:01276 66060
peter.bishop@bamnuttall.co.uk