Video By Peter Reina
ENR's Peter Reina talks to Ailie MacAdam about her work as delivery director at Crossrail.


Major European contractors have flocked to London for a piece of the 21-kilometer Crossrail tunnel project now advancing at more than 40 sites across the city. Billed as Europe's largest infrastructure project, Crossrail survived the U.K.'s toughest austerity drive in generations, in part because officials pushed back its schedule by a year. That move cut the estimated cost by around $1.6 billion, to $23 billion.

The election of a new, budget-slashing U.K. government in May 2010 cast doubt on all state spending just as Crossrail was approaching its main procurement phase. "We spent a lot of time … looking at what we could do to make Crossrail the most attractive investment opportunity we could," says Andy Mitchell program director with Crossrail Ltd. (CRL), the city's project company.

Mitchell's team pulled it off and, within months of securing final approval in late 2010, signed $2 billion worth of contracts to build the 6.2-meter-dia bored tunnels and underground stations. To do so, U.K.-based contractors partnered with European and Irish firms.

"We knew that, with this project, there would be a strain on U.K. resources for tunneling," says Paul Glass, project director with the BFK joint venture. Spain's Ferrovial Agroman S.A. teamed with the U.K.'s BAM Nutall Ltd. and Kier Construction Ltd. to form BFK and win the 6.1-km-long west twin-tunnel contract, plus station excavations at Farringdon, Bond Street and Tottenham Court Road.

Spain's Dragados S.A. teamed with the Irish Republic's John Sisk & Sons to secure the contract for 11.9 km of the twin drives that form the east-running tunnels. Germany's Hochtief Construction A.G. and locally based J Murphy & Sons Ltd. won the final 2.64 km of tunnel on the east side, including the River Thames crossing. From France, Vinci Group landed the contract to upgrade the 550-m-long Victorian-era Connaught tunnel in the dock area.

International firms bring "top-class tunneling expertise," says Ailie MacAdam, a senior vice president with Bechtel Inc., San Francisco. MacAdam is CRL's delivery director for the new tunnel section, which accounts for about half the total investment, she estimates.

Teams are now busy working at the sites of seven new underground stations. The first of six earth-pressure-balance (EPB) tunnel-boring machines has driven over 700 m of the west tunnel and will soon be joined by its twin. The east tunnel's first EPB machine is under assembly at Limmo Peninsula, with a second being prepared for shipment from Germany. For the east tunnels, the remaining two EPBs and two slurry TBMs will launch between this winter and 2014 for a 2018 completion—a year later than planned.

Around 200 million passengers per year will use Crossrail when it opens, increasing by 10% the city's rail capacity, say CRL forecasters. The 118-km east-west line, between Shenfield and Abbey Maidenhead and Heathrow Airport, includes the tunnel section in central London and passes through underground stations being grafted onto existing large transportation hubs.

The U.K.'s rail infrastructure owner, Network Rail, is handling surface construction on either side of the city, accounting for 15% of overall investment. London Underground Ltd. is managing and financing upgrades to its metro stations serving Crossrail; CRL is handling all work in the central tunnel and stations.

Rapid Ramp-Up

The project secured conditional government support in 2007, followed by parliamentary approval in July 2008. CRL spent over $600 million to reach that point, says a spokesman.

With a 2017 completion deadline and $32.7 billion in funding, including contingencies and inflation, CRL began awarding contracts. It started by selecting 12 leading firms to bid for some 25 detailed design jobs. The first such contracts were awarded in May 2009. The co-located design workforce peaked at about 1,800 people in 2010, estimates Mitchell.

Among the most successful bidders for design work were locally based Arup Group Ltd. and W.S. Atkins. In an equal joint venture, the firms have largely completed designs for the entire running tunnels and also accumulated several station contracts, either in joint ventures or alone. "From what we've seen, the packages were keenly fought over," says Peter Chamley, Arup's project director.

While taking on designers, CRL in early 2009 recruited a team of AECOM, CH2M Hill and Nichols Group Ltd. as its program manager with a contract estimated at $160 million. A larger, $630-million delivery partner contract went to Bechtel. "We'd manage the design contracts for the client and the procurement and construction," says MacAdam.

CRL's three-firm structure, the program and the delivery partners supported rapid ramp-up, believes Mitchell. But there were too many interfaces and some duplication, he adds. So, in April 2011, Mitchell merged the three entities into one team, which now has 850 staffers under his supervision. Bechtel's roughly 400-strong workforce is still there, but MacAdam now reports to Mitchell "directly as my boss, as opposed to as a client," she says.

Before awarding the main construction contracts, CRL had to ensure the project's survival through the new government's spending review in summer 2010.

Mitchell was already months into an effort to trim forecast costs to within the original $32.7 billion of available funding, and his review intensified. The new political mood for austerity "gave us the license to ask questions and challenge in a way that people had to take seriously," he says. Over $0.4 billion was saved by asking the project's ultimate owners and operators what could be eliminated with "no impairment to the service."

More savings were achieved by increasing procurement time for contracts and allowing BFK to deviate from the planned excavation sequence. Because of the then 2017 deadline, "we were already starting to make time-based, not cost- or value-based, decisions," says Mitchell. Instead of forming the roughly 11-m-dia, 250-m-long twin station tunnels with open-face excavations and sprayed concrete lining, BFK will drive the TBM straight through and then widen the bore. That removes "the massive risk" of not completing excavations in time, says Glass, project director. Also, driving the tunnel first reduces the amount of sprayed concrete lining needed and improves settlement control, he adds.

CRL further cut costs by inserting a three-month value engineering period in each contract. One result was to lengthen the west tunnels' precast concrete lining segments to 1.6 m from 1.5 m, says Glass.

The 18-month campaign led CRL in August 2010 to propose a reduced funding requirement of $23.2 billion and an extension of the line's tunneled-section completion date to late 2018. The government agreed to that plan in October 2010, and procurement took off with a succession of major contract awards.

Pushing Ahead

BFK launched Crossrail's first TBM from the western portal near Royal Oak this May. As with all the TBMs, CRL and Arup/Atkins specified it in detail and let contractors choose their own suppliers. Germany's Herrenknecht A.G. nabbed all eight orders.

Clays at the western section of tunnel mean "control of settlement is one of the biggest challenges," says Glass. "We've got a massive program of instrumentation and compensation grouting." Moving east, other TBMs will work in stiff clays with sands and then sandy material. Crossrail's two slurry TBMs will be used in chalk at the River Thames tunnel.

BFK will use its tunnels as pilot bores, to be widened into stations. But most of the other stations are being dug in open faces underground and lined with sprayed concrete to await the arrival of the TBMs. Those stations typically have two 11-m-dia platform tunnels and a smaller foot tunnel in between. Only two of the main stations, at Paddington and Canary Wharf, are being built from the surface.

In London's docklands area, a ceremony to sink the first station's pile at the Canary Wharf high-rise financial center launched Crossrail in May 2009. Having partially funded the station, Canary Wharf's owner used its subsidiary for the $780-million design-build contract.

Canary Wharf Contractors Ltd. had started work with the original 2017 completion deadline in mind. It kept that schedule and handed over the 250-long by 230-m-wide station box to CRL in March. The box will now wait until next summer to receive the first TBM from the Limmo portal.

Working to the new schedule's real deadline for Paddington station, the Costain-Skanska team is using top-down construction for the 260-m-long, 28-m-wide, 23-m-deep station box within slurry trench walls. The contractor got the walls done in time for BFK's first TBM arrival from Royal Oak this month, says Martin Quaid, project director.

With TBMs now on the move, sprayed-concrete work spreading across the system, slurry walls being completed, procurement of system-wide components starting and only one station contract to be awarded, "this year is huge" for Crossrail, says Becthel's MacAdam. "When we get this year under our belt, in my view, it sets us up for successful completion."