Construction of the Olympic Stadium finished last week, ahead of schedule and under budget. Declan Lynch visited London 2012’s centrepiece attraction to find out why.
A real tug of war has broken out over who should use the Olympic Stadium in legacy. And you can see why - it’s a very impressive structure, in an ideal location, and built to high standards.
Team Stadium - Sir Robert McAlpine, Buro Happold and Populas constructed the Olympic Stadium to a tight three-year programme.
“It’s been conceived, designed and constructed in five years,” says Olympic Delivery Authority (ODA) project sponsor south Ian Crockford. “That’s half the typical timescale for a stadium of this size.”
Reduced after the Olympics
The stadium includes 25,000 permanent seats and 55,000 temporary ones so that capacity can be reduced after the Olympics when it is not expected to host such large events. This was the design decided on before West Ham United was chosen as preferred bidder to take over the stadium in legacy mode. It is not known what the football club’s ongoing capacity requirements are.
“We were given a great surface to work on,” says Sir Robert McAlpine project director Tony Aitkenhead. “The site was remediated during the enabling works.”
Team Stadium was selected as preferred bidder in January 2007 and began work on the foundations for site whilst finalising the roof structure design.
The stadium consists of a lower podium level, with a tier of 25,000 permanent seats, and appropriate facilities for Olympic use.
Above this are the 55,000 demountable seats and the roof. The roof and the seating stands are two separate structures, with the roof comprising a cable net supported by steel struts and the seating resting on concrete terracing .
The elegant lightweight roof structure involved plenty of hard work (NCE 15 January 2010). Most roof structures in the UK are a cantilever structure which is simpler but heavier. The Olympic Stadium roof is a cable net structure which supports a tension ring running around the roof’s internal circumference.
“This is the most sustainable option,” says Buro Happold project director Glyn Trippick. “Typically it uses half as much steel as the cantilever option.”
On top of the roof truss sit 14 lighting towers each 28m high and weighing 34t.
Team Stadium completed the superstructure in May 2010, and then began to turn the field of play from a crane area to an area suitable for Olympic track and field events.
“The foundation is similar to a typical trunk road,” says
Trippick. “There’s the sub-base, base then ground granulated blast furnace slag.”
Beneath the pitch are lots of services for all the requirements associated with the Games.
“Over 240 businesses have been engaged in the supply chain from across the UK,” says Crockfield.
“It’s been conceived, designed and constructed in five years. That’s half the typical timescale for a stadium of this size”
Ian Crockford, ODA
Contractor’s view: how we built the stadium
From concept design, through to detailed design and construction, no time could - or was - wasted, explains Team Stadium project director Tony Aikenhead.
We began Stage C concept design in June 2007 and by April 2008 had secured the first stage planning approval on behalf of the Olympic Delivery Authority (ODA). Permanent piling started in May 2008.
Typically, with a project of this nature and complexity, it would take around one and a half years to get from end concept to start of construction, but with the stadium we achieved this in just over six months. The design and procurement operation was fast tracked with us procuring major early subcontract packages, such as Byrne Bros for the concrete, Tarmac for precast terracing and steelwork contractor Watson Steel at the end of concept design.
Crucially we had the confidence in our design team, the McAlpine management team and our supply chain to back our ability to control the design development cost risk, technical challenges and programme surety.
To meet the client brief around demountability, we implemented a significant amount of prefabrication of concrete and steel elements. The early design and procurement, plus prefabrication, resulted in the stadium structure up to the roof compression truss being completed within 14 months, by July 2009.
By June 2010 the bowl work was substantially complete, the cable net roof and fabric were complete and fit-out works were well advanced in the west and south stands.
Landscaping and external works
Landscaping and external works continued unabated, with this being the area where we enjoyed the most interaction with others working on the Olympic Park.
Our early concerns about logistics of material delivery and getting workforce on to site were unfounded thanks to excellent management of logistics in the park by the ODA and its delivery partner CLM.
We were faced with a number of challenges in terms of the high targets set by the ODA around its priority themes of sustainability, carbon emissions, waste segregation, equality and inclusion, recycled content and potable water reduction. The bar had been significantly raised at the stadium, in comparison with other major projects, but I’m delighted that we met or exceeded all of these targets, learning a huge amount along the way.
“Steelworker Watson scored a big success in reusing gas pipeline found in a yard”
Tony Aikenhead, Sir Robert McAlpine
In particular, the sustainability successes were significant. For example, the embodied energy consumed in manufacturing the stadium’s elements was significantly lower than previous Olympic stadiums due to the compact design, and our structural steelwork subcontractor Watson Steel scored a big success in reusing unwanted gas pipeline found in a yard in Yorkshire.
Now, just two weeks before predicted completion, we have laid the turf on a carefully prepared drainage layer and rootzone. Our subcontractor Hewitt harvested the turf on the Sunday and by the following Wednesday morning it was laid and being watered in. The turf was grown in Scunthorpe from a blend of five different species of seed, which ensures density and full coverage at all times of the year.
The project has been exemplary, demonstrating collaborative working not only within our own design and construction team but also with our client and their stakeholders. Our extensive engagement with the workforce resulted in us all pushing the boundaries of health, safety and environmental performance. Well done to everyone!