A gigantic five-storey basement took two years to excavate before construction could even start at UCLH.
Project: Proton Beam Therapy Centre, UCLH
Overall project value: £300m
Contract value: £195m
Contract type: Design and build
Main contractor: Bouygues UK
Demolition subcontractor: Cantillon
Start date: July 2015
Completion date: July 2020
There are big basement projects, and then there is UCLH’s proton beam therapy centre, being built in London’s West End.
This 28.5 m-deep excavation is not for the faint-hearted. That applies whether you’re looking down over the edge, or were intimately involved with calculating its design and retention. Put into context, UCLH says that at 87 m x 67 m wide, the L-shaped hole has a greater volume than the oft-quoted comparison of the Royal Albert Hall.
The funding for the job is actually split between two sites, with the other being delivered in the North-west, as UCLH director of estates Kieran McDaid explains.
“This is two projects combined into one,” he says. “UCLH and the Christie in Manchester were both successful in a national proton beam therapy award. It’s a UK facility that happens to be in two locations.”
Scarcity drives project downward
But whereas The Christie site for this emerging technology is, in the main, an above-ground project, the one at UCLH faced severe constraints that prevented this.
“One of the unique challenges of this site in London was how valuable and scarce a resource land happens to be,” Mr McDaid says. “But when we looked at it we thought this is the last opportunity in London to develop the UCLH campus. We have 43 buildings on a very constrained campus here and land is a scarce resource in London.”
“Today it’s like a tidal wave; the West End is washing over this part of town”
Kieran McDade, UCLH
He points out that the site is hemmed in by Euston station to the north and offices to the west. “Gone are the days when the hospital could rent extra space at £35 per sq ft,” he says. “Today it’s like a tidal wave; the West End is washing over this part of town; I can’t find office accommodation for less than £65 to £75 per sq ft. So as an NHS trust, the availability of land is a huge challenge for us.”
This saw the UCLH decision-makers opt to “push the proton facility five storeys below ground” (see box). “That allows us to build a six-storey hospital on top,” Mr McDaid explains. “We had the Rosenheim hospital cancer centre on this site. Let’s be kind, it was very 1920s: out of date, dilapidated stock that was beyond economic repair. The decision was to demolish the building and create a new asset.”
Bouygues UCLH basement site eye Dec 2015
Behind the Rosenheim was an old Odeon cinema on UCLH land, which occupied a site that had been bombed during the Second World War and had never been developed. “It’s probably one of the oldest undeveloped bomb sites in London,” Mr McDaid says. “So we’ve combined the Odeon site with the Rosenheim footprint and created this large project.”
With Cantillon carrying out the demolition and 18 months of enabling works having been completed, the main contract got under way in mid-2015 with a focus on diverting essential hospital utilities, such as the two main oxygen tanks that serve the main hospital.
These required relocation offsite next to the Jeremy Bentham (UCL’s spiritual founder) pub, all the while maintaining live services, before the site could be enabled for possession by main contractor Bouygues UK.
Proton beam therapy
Buried in the five-storey basement are three large gantries, a cyclotron particle accelerator and four treatment rooms, principally aimed at the treatment of children and young adults. The gantries allow the equipment to rotate 360 degrees around an anaesthetised patient.
The necessity for this rotation is driven by the systems flexibility for dealing with different kinds of tumours. While some private companies in the UK offer treatment for conditions like prostate cancer with a fixed beam setup for standard procedures, the UCLH and Christie sites must offer treatments “from every angle”, as Mr McDaid puts it. “That’s what makes this site so challenging,” he says.
He says the equipment is “probably the single largest purchase order for NHS equipment in the UK ever”, and including servicing came in at around £80m for both sites. “It’s a huge equipment order for the NHS,” he says, with UCLH due to receive its portion in June next year.
Proton beam therapy is a form of radiotherapy used to treat cancer which can be targeted precisely, causing minimal damage to surrounding tissue.
Together with the Department of Health, NHS England is funding the development of two centres, with the second being The Christie in Manchester. Patients are due to be treated at The Christie from summer next year, with UCLH following in summer 2020. When complete they will each treat up to 750 patients every year.
The Northern Line on the west side of the site runs less than 8 m from the deepest point of the large and complex excavation, which has required careful monitoring as the dig and build has progressed.
The excavation bottomed out on 14 July, a date not lost on the significant Gallic contingent in the French contractor’s team, with Bouygues UK production director Eric Pincemin not slow to point out its Bastille Day significance to his homeland.
“By next summer we’ll be back at street level, and by January-February 2019 we’ll have our topping out of the six floors [above ground],” he adds.
The propping has been a major undertaking.
“Every element is different. Every component, every corner, every tube. It took us two years to dig a hole,” says Bouygues UK project manager Pankaj Koul. “It took us two years because every component is customised for the job.”
“I have done a lot of deep excavations, but this is one of the most challenging in terms of the design”
Pankaj Koul, Bouygues
This is partly down to the irregular shape of the basement, and partly down to its sheer size. “When you’re talking about this kind of job, and because of the economies of scale, you don’t have people manufacturing them on a daily basis,” he says. “You have to find the right supplier.”
This forced Bouygues UK to look to an international supply chain rather than a national one. “We’ve got formwork suppliers from Germany, suppliers from France, Spain and the UK, and it takes time,” Mr Koul says.
Bouygues UCLH basement 2
“I have done a lot of deep excavations, but this is one of the most challenging in terms of the design. When you tell somebody you are doing an open basement five storeys deep, they say, ‘How are you going to do it? And who’s going to supply that [propping] strength and who’s going to supply you 15 types of different dimension struts’.”
The challenge is accentuated by the irregular shape and orientation of the L-shaped site, and by tolerances of as little as 2 mm on the vast project. “We’re talking about micro-precision,” Mr Koul says, before adding that this degree of quality comes with a certain price tag and timeframe.
Top down and bottom up
Another issue facing the scheme is the need for it to be delivered from entirely within its own footprint, as there is no room beyond the perimeter for vehicles and equipment to be operated from. It’s led to the unusual situation of the basement being delivered using both top down – to allow for a construction platform to be formed at the edge of the site – as well as bottom up construction.
But before this could happen the team had to install 78, 1 m thick diaphragm wall panels to depths ranging from 33 m to 36 m. Binding these together is a capping beam, which also serves to prop the king posts that in turn provide support for the excavation’s 1,500 tonnes of temporary strutting.
Bouygues UCLH basement site eye sept 17
The propping mainly functions in three vertical layers, 8 m apart, with the lower two levels fixed to horizontal waling beams. A fourth partial layer of struts supports the deepest corner of the site.
The fact that it’s taken two years to get to this stage is a testament to the difficulties faced when working on such a large excavation, without disrupting services on what is a live hospital site. Or indeed, as Mr Koul points out, the Jeremy Bentham pub. “Everything has been co-ordinated in BIM,” he says. “We had to deliver a full clash-free model and we’ve avoided a lot of potential re-work,” he says.
And re-work is something the team is keen to avoid, not just for cost reasons. With the six-storey building yet to be started on top and the first patient treatment date set for late summer 2020, it’s one of those projects that really must be delivered on time, something Bouygues remained confident of at the time of CN’s September visit.
Excavation facts and figures
- Two Mechanical and Electrical plant levels
- Two floors for patient proton beam therapy care
- Eight surgical theatres.
- Above ground there will be six floors which include Europe’s largest centre for the treatment of blood disorders
- 300 number of people have been involved in the excavation
- 3,000 people will have been involved in its construction
- Three multi-storey gantries for the proton beam therapy equipment