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With the 2012 Olympics in the bag a major building project is under way to deal with the expected increase in demand at London City Airport

This month, London City Airport (LCA) celebrates 20 years since its first flight taxied down the runway. A pioneering project, which many believed would never take off, LCA has certainly come a long way.

Today, it is one of Europe's fastest growing airports and with an increasing focus on east London and the Thames Gateway, following the award of the 2012 Olympic Games to the capital, the role of the airport has been further strengthened.

Its 20th anniversary will see the largest investment in the development of the airport since it was first built to support the growing demand.

Support services and construction company Carillion, which won the £19M contract to build additional aircraft parking stands, did not exist when the airport was built by Mowlem in 1987. However, in a twist of fate, Carillion, which now owns Mowlem, will be using its newly acquired in-house piling team – many of whom are ex-Mowlem – to carry the job forward.

The team has been on site since June. While the 2.8M passengers passing through the airport each year appreciate the quick access to London's Docklands that LCA offers them – it is only 5km from Canary Wharf – the turgid waters of the Royal Docks over which the new Apron Development will be built conceal some serious engineering challenges. Carillion Piling has overcome these using spud leg pontoon barges for the piling equipment, polymer mud for drilling fluid and pre-cast concrete components to support the in-situ topping slab.

Its project manager Jon Neale says: "We're installing 217 large diameter steel-cased piles into the dock floor, which will support the pre-cast concrete beam, and plank components, which support the in-situ concrete slab for the new Apron Development.

"The 1m diameter steel casings imported from the Netherlands are first positioned in the piling gate mounted on the spud barge with an 80t support crane. They are then driven through the dock bed into the bearing strata of Thanet Sands. The pile is drilled 3m to 4m into this very dense sand using polymer mud to support the bore.

"Once the pile bore has reached the design depth and been cleaned, the piling rig moves off-station to allow the support crane to install the reinforcement cage and then concrete the pile using tremie techniques through the polymer," says Neale.

The main challenge on this project is to complete the construction around an operational airport in close proximity to neighbouring communities.

Carillion Regional Civil Engineering (CRCE) operations director Steve Critchley says: "Because we are so near to residential areas we have to comply with strict Section 61 noise limits and National Air Traffic Services has imposed height restrictions on the works to safeguard ground radar systems, and the airspace.

This means all construction equipment has to be kept below a transitional surface inclined at 1:6 from the edge of the runway strip.
This means that most of the piling work will have to be carried out when the airport is not operational between 10.30pm and 5.30am during the week, and from 12.30pm on Saturday until 10.30am on Sunday.

To meet the noise and environmental constraints, auger piling and low-noise techniques are being used. Super-silenced equipment, including electric pumps, is helping to reduce noise levels.

During the planning stage, noise levels were analysed to ensure that the impact on the local community was minimised.

At the end of each shift all piling equipment has to be safeguarded below the transitional surface before the airport can be handed back to LCA Operations. Failure to comply would prevent the airport from opening and carries heavy financial penalties, which focuses the mind of management.

"You're very conscious of the time constraints and have to be certain as to what you can and cannot do within the time frame," says Piling contracts manager Robert Harris.

Obstructions on and below the King George V Dock bed needed to be dealt with as part of the project. Although Carillion Piling carried out magnetometer and visual inspections with divers before the works began, it has also had to deal with temporary works well below bed level and numerous objects and debris on the bed associated with the original dock construction.

Critchley says: "Working with the original owners and developers of the airport is especially rewarding because in 2003 we constructed a holding point for aircraft for LCA using the same techniques."

Work is due to finish on the project in 2008.

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