Tunnel boring and station construction for Crossrail

With the announcement of programme and project delivery partners imminent, Europe's largest construction project is becoming a reality. James Stagg examines what the timing and scope of work will be for Crossrail.

It's been a long time coming, but the new railway set to link central London directly through to Maidenhead on its western fringes and Shenfield on its eastern is well on its way to actually being built. After years of argument and counter-argument for and against its construction, the joint venture team set up to deliver the railway, Crossrail Limited, is on the verge of announcing the winners of the bids to become its programme partner and project delivery partner for the £15.9bn scheme.

An announcement of those winning companies is imminent, but for the moment the shortlisted candidates for programme partner remain American giant Bechtel, Legacy 3 (a joint venture between Parsons Brinckerhoff and Balfour Beatty Management) and the Transcend joint venture company.

Legacy 3 and Bechtel also feature on the shortlist for project delivery partner alongside Laing O'Rourke and a Capita Symonds/NNN joint venture.

Bechtel and Legacy 3 have been heavily tipped to be the two most likely winners in what will become the UK and Europe's largest construction project. But this remains conjecture, confirms Steve Rowsell, Crossrail procurement director, who adds: "The final approvals are still required from Transport for London (TfL)."

According to industry insiders, the post most likely to enhance a company's reputation is the programme partner role, while that of project delivery partner will be the most immediately lucrative.

But there is no framework set up for the £400m project delivery role to oversee work on the twin-bore tunnels that will run under central London from Paddington in the west, to Stratford and Custom House in the east. For those subcontractors that have a close working relationship with the winning bidder, the scheme could prove to be a timely cash cow, as a Crossrail spokesman confirms.

"All the funding is now in place and there are no worries about the current economic climate causing any shortfall," he says. "The project delivery partner will have the relative power to start awarding its own contracts as soon as the winning bid is announced."

Construction methods will vary according to conditions in a particular area. Having examined data from site investigations and the analysis of ground samples, Crossrail's team has built up a picture of the best approach to take. In the west, where the soil is predominantly London clay, tunnels will be built using an open-face tunnel boring machine (TBM). To the east, with its different soil conditions, dual-mode Earth Pressure Balance Machines will provide the solution (see box). Conveyor belts will transport spoil back up to surface level.

Running alongside tunnelling work will be associated station redevelopment projects. Seven central stations will be constructed alongside existing stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street, Whitechapel, Canary Wharf and Woolwich.

"Enabling works are underway," says Rowsell. "Tenders are in and the results of the framework competitions for site facilities, demolition and civils are being finalised." CJ has learnt the shortlists for both the £20m demolition and £100m civils frameworks (see page 8), which include 13 and 10 hopeful contractors respectively.

It is thought that work will be shared as evenly as possible between the approved contractors. One demolition insider explains: "Especially in these tough times, we are all hoping that the work will be carved up like it was with Olympic contracts".

Rowsell says that engagement with the supply chain on the main construction contracts will begin in the Spring, shortly after Rob Holden (incoming Crossrail chief executive) takes up his post. "We will be hoping to get a consultation going with the industry on packaging, processes and programming for the main works," he adds. "We don't have to start the procurement until later in the year and won't begin on site until late 2010, so we have a little time to get ready."

Preparation work

At Tottenham Court Road station preparation work has already begun. The plan is to extend the station under the road to Centre Point making it six times larger. On its own the station upgrade will be worth £500m, but if the nearby tube and streetscape work is included, the bill will rise to £1bn.

A programme of utility diversions started in March 2007, which included diverting a local Victorian sewer and an Edwardian utilities tunnel alongside power, gas, water and telecommunications services. In all, up to 50 separate diversions at depths ranging from 300mm to 10m have been made and more than 1000m3 of material excavated.

Minimising disruption

To minimise local disruption, up to four utility companies have been using the same space at the same time. Engineers have also had to be mindful of the impact the station works would have on existing utilities infrastructure such as the Post Office tunnel railway and the Bazalgette sewers, which run directly above the busy Central line.

To facilitate the redevelopment of the station, a total of 13 properties have been compulsorily purchased and demolition will begin in Spring 2009.

"The utility diversion is now complete," a TfL spokesman confirms. "Buildings are now being prepared for the demolition, which will start in late March or early April." McGee is currently performing a soft strip, preparing the buildings. This is sensitive work, particularly as it's being carried out in one of the busiest areas of London, and to minimise impact, the buildings will be demolished floor by floor.

Following the demolition, construction can begin in earnest. The initial work will be to form a box for the new escalators to the Northern line. Then three new over bridges and staircases will be constructed to provide access to the southern end of the Northern line platforms and the new Crossrail platforms.

The direction of tunnel drives

• 2 TBMs from Royal Oak Portal, to the west end of Farringdon Station (6.16km)
• 2 TBMs from the Limmo Peninsula Shaft in a western direction, to the east end of Farringdon Station (8.30km)
• 2 drives from the Limmo Peninsula Shaft in an eastern direction, to Victoria Dock Portal (0.93km) constructed by one of the above TBMs
• 2 TBMs from Pudding Mill Lane Portal, to Stepney Green (2.72km) or vice versa
• 2 TBMs from Plumstead Portal under the River Thames, to the North Woolwich Portal (2.64km)

The tunnelling strategy is based on using earth pressure balance machines for construction of all the running tunnels within the central London area and slurry machines for the tunnel drives from Plumstead Portal to the North Woolwich Portal.

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Minimising the impact of construction

To minimise disruption to London during the construction of this mammoth project, DHL Excel Supply Chain has been contracted to perform a logistics study on the project. The firm performed a similar role for the Olympics and its work will inform Crossrail of the most efficient ways to deliver materials and equipment to the central London locations.

Jonathan Shortis, business development director at DHL, says the study will drive efficiency in terms of time and cost certainty, as well as having an opportunity to effect safety and waste. "Typically, the responsibility for logistics gets pushed down the tier of contractors to those working with a particular material," he says. "That is alright for smaller projects but a major project in central London is a vastly different environment."

DHL is to suggest Crossrail consider a 'control tower' to co-ordinate movements and consolidation centres to house materials. It will also look at opportunities for prefabrication.

"Complex projects in busy environments need a high level of control," Shortis adds. "We are used to working with contractors and see the delivery partner as a client too. Obviously things will change, but it's an issue of putting in place the flexibility and scalability. What we're giving Crossrail is a set of plans and strategies to run an efficient project and remove risk."