London landmark Westminster Bridge is undergoing an overhaul.
Andrew Barker went to see the new ironwork being lifted into place
COSMETIC surgery is not just for the rich and wrinkly.
Sometimes it is necessary to preserve a thing of beauty for posterity's sake. But in the case of Westminster Bridge, it wasn't a simple question of aesthetics, but rather a 'safety first' attitude from Transport for London that led to the operation.
Westminster Bridge has the lowest headroom clearance for river vessels of all the bridges on the Thames and in January 2001 two of the arch ribs and a fascia girder suffered heavy structural damage from a boat strike, affecting the loading on the footpath above.
'If it was hit as hard as Battersea was last September, almost certainly one span would have ended up in the river, ' says Ian Chapman, project manager for TfL.
The fascia lift is the latest stage in the renovation of the bridge, which began in 2003 as part of a £22.8 million programme by TfL. There is a total of 14 cast iron fascias, seven for each side, and all are in need of replacement. The 28 spandrels, triangular flourishes integral to the bridge's design, will be restored rather than replaced and inserted into new iron castings off-site.
Hyder Consulting was commissioned by Westminster City Council to carry out the design and supervision of the repairs and refurbishment of the fascia girders for all seven spans. The team is fresh off a road-over-rail bridge in Paddington, which opened in June this year.
The existing fascias are self-supporting, attached to nonstructural members at the footings. They are supported at their feet on either side and are tied to the bridge by lateral restraints.
By contrast, the new fascia panels are not self-supporting.
They are attached to curved steel beams and this frame is supported at the springing point and tied in via lateral restraints.
The new panels are simply attached to the new frame and held in place by steel hangers. So, should another collision occur, the risk of falling is dramat ically reduced.
There were so many unknown factors in the job that working on the first span took nine months in total as the fascia was removed one chunk at a time. Balbinder Chana, Hyder's technical manager, reckons the window for the remaining fascias will be close to approximately five weeks each.
'But other things, like the spandrels, have to be taken into account, ' he says.
The tired, 15-tonne fascias are accessed from temporary towers and platforms. They are cut out and lifted in one piece using a 35 m barge crane. They are then lowered onto a second barge and shipped off to Tilbury and consigned to the scrap heap. This work is undertaken by contractor Interserve. But the refurbishment doesn't stop there. All the shields, lamps and 700odd badges commemorating the original sponsors who made donations to the construction of the bridge are being reconditioned, and, where necessary, refashioned using the same materials and processes. The portcullis of Westminster and the interlocking V&As of the royal house of Queen Victoria and Prince Albert are among the emblems, gilded in gold leaf and illuminated by festoon lighting.
Standing on the temporary access platform, the cracks in the fascias, the result of thermal expansion and exposure to the elements, are very easy to see.
'We try to prop and brace as much as we can before we move each load, ' says Mr Chapman. Cover plates masking the scars of more than 150 years of use litter the original ironwork.
Everything is being cast anew. The chemical composition of the Victorian fascias, in particular the phosphorous content and the lead in the paint, pose too many problems for melting down to be cost-effective.
The bridge opened in 1862, 25 years after it had been commissioned. It has subsequently been painted in a chalky pale blue hue but the original colour, in fact, matched the leather seats of the commons benches. For this reason a bolder shade of glossy green has been used on the completed span 1 on the southern side. 'Theoretically we should have taken a swatch of leather from the commons and got it matched, but then they're not the originals, either, ' says project manager Phiroz Dalal.
'The new fascias will ref lect what the Victorians did. We've largely kept the same joint locations.'
One traffic lane and a footpath across the bridge have already been closed for three years but, in order to minimise disruption, the temporary offices were moved from the bridge onto a pontoon, replete with rooftop measures for nesting birds to keep the Environment Agency happy. As for the river traffic, the central three spans take turns to stay open for traffic. The contract is due for completion in Autumn 2007 and the total refurbishment of the bridge is due to be completed in autumn 2009. Lambeth Council and City of Westminster have cooperated on the project because the road bridge connects their two boroughs via the A302, which will also get a resurfacing.
'Transport for London is overcoming enormous challenges to replace the fascias on Westminster Bridge, one of London's iconic structures. We are keeping the bridge safe and stable for years to come, while staying true to its historic nature for all Londoners to enjoy, ' says Dana Skelley, Head of Road Network Management for Transport for London.
Because the bridge is listed, extensive consultation with English Heritage was necessary and a complex investigation into the design of the fascias required.
'Normally, we would have to use the original techniques, not just the materials only for a Grade I-listed structure. But we decided to do that here as well. Electrics have since been incorporated and a little plastic but, apart from that, the casting and carpentry are exactly the same as they were 100 years ago.'
Says Mr Dalal.
'It's important to keep these skills alive. We need these guys to be in business next t ime we come to do a Grade I structure.'
Key players on the Westminster Bridge team
DESIGN: TONY GEE & PARTNERS
TGP knows the stretch of the Thames well. The company designed the foundations and brows of the British Airways Millennium Wheel, which is a stone's throw from Westminster Bridge.
Interserve was acquired by the MacLellan Group in July this year.
CONSULTANT: HYDER CONSULTING
Hyder was commissioned by TfL to prepare design and build contracts for the replacement of the existing fascias on the bridge.
The work will be undertaken in two phases: a design and a construction phase. All the works are being carried out from the river using river-based plant to minimise any disruption to vehicular and pedestrian traffic.
FOUNDRYWORK: BALLANTINE BO'NESS IRON CO
Based in West Lothian, Scotland, this iron founder and metalworker has been running for 150 years. It has had contracts on a number of historical buildings including Buckingham Palace, Windsor Castle and the Scottish National Gallery. Its work covers pattern-making, fabricating and erecting and will remake original ironwork documented in photographs. The company will take on anything from cast iron gates to gilding work. At the Queen's official residence it restored the Mews Canopy using 25 per cent of the original castings. Work had to stop for 1.5 hours a day to allow the horses their exercise.