Emma Kelly explains how Australia’s premier international gateway has completed a complex and expensive runway project.
Australia’s Sydney Airport recently completed a A$100 million (US$88m) runway safety project designed to bring it in line with international aviation safety requirements.
The project involved the construction of runway safety areas at each end of the airport’s three runways, designed to provide an extra margin of safety in the event an aircraft overruns or lands short of the runway.
But the final phase of the project, which saw the construction of a 295ft x 295ft (90m x 90m) paved safety area at the end of the east-west runway, was a significant engineering challenge as the new area had to be constructed over the city’s largest sewer, the M5 East motorway tunnel and a major electricity cable, not to mention having the Cooks River at its end.
The project required an extensive evaluation of options in order to meet the international requirements and overcome the infrastructure challenges. The solution was an 87,190 sq ft (8,100m2) land bridge over the sewer, the motorway tunnel and electricity cables to provide a cleared area measuring 295ft x 295ft (90m x 90m) from the end of the runway strip to assist in the deceleration of an aircraft. The construction involved more than 100 88ft (27m)-long pre-cast concrete structural beams, each weighing more than 25 tonnes. The area is designed to support nearly 600 tonnes – the weight of a fully-laden Airbus A380 – as well as emergency and rescue vehicles, says the airport.
The project involved extensive consultation with stakeholders and the community ahead of and during the construction. The Australian government imposed 22 conditions on the construction project in order to monitor construction progress, improve environmental and construction noise management and improve community consultation. Conditions included the installation of a Jet Blaster Barrier across the western end of the east-west runway to protect the worksite and allow the eastern end to continue to be used for take-offs.
The site for the Runway 25 runway end safety area (RESA) was: “significantly more complex” than the locations of the other five RESAs at the airport due to physical infrastructure at the runway end. The infrastructure includes Sydney Water Corporation’s Southern and Western Sydney Ocean Outfall Sewer (SWSOOS), which is a reinforced concrete twin box culvert sewer and a single box culvert sewer that merge into a three-cell culvert over the Cooks River. The airport thoroughly reviewed and investigated the risks and options for relocation of the SWSOOS, but the costs and risk were considered unacceptable.
In addition, the area was complicated by the M5 East motorway tunnel which carries two dual lane carriageways under the Cooks River and is located underneath the south-eastern corner of the RESA site.
The area also features the airport perimeter access road, which is part of the airside road network that connects all of the airside precincts on the airport. The section of the airport perimeter road at the western end of Runway 25 connects the international precinct with areas in the southwest sector of the airport. Some 787ft (240m) of the airside perimeter road had to be realigned to accommodate the RESA.
Furthermore, the site was complicated by the existence of other airport services infrastructure, all of which required relocation. These included airfield lighting cables; Airservices Australia’s copper and fibre optic communications cables; Airservices’ localiser and the power and signal cables serving it; a sewer line which connects from the International Terminal to the SWSOOS; two water tanks on top of the SWSOOS serving the airport; and red obstacle lights located on the south-west (approach) side of the SWSOOS.
Other utility services in the area required diversion for construction of the relocated airside perimeter road, including EnergyAustralia’s 132kV high voltage electricity cables, low voltage domestic supply cables, an Agility gas pipeline and fibre optic cables. The integrity of the high voltage electricity supply had to be maintained at all times which necessitated the cables to be slid across a 65ft (20m) path clear of the relocated airside perimeter road. Protection of the gas pipeline, meanwhile, was critical.
Design work on the project started way back in 2006, with Aurecon engaged as design engineer. Construction planning started in late 2007, with Baulderstone appointed managing contractor. Construction work started in October 2008 and the project was completed on March 31, 2010.
Despite the difficulties associated with the final phase of the project, the airport had little choice but to go ahead with it. The airport considered a number of options, including doing nothing, constructing an engineering material arrestor system (EMAS), extending the runway to the east, reducing runway length to facilitate compliant RESA as well as designing and constructing a RESA.
Doing nothing was not a viable option, says the airport. Without a compliant RESA, an incident on that runway end would be uninsurable and any accident could have serious consequences in the event of damage to the sewer. Without the RESA at Runway 07/25, it would not have complied with international safety requirements and would have to be closed to aircraft movements. That would have had a major environmental impact on the local community as it would have limited the implementation of the airport’s long term operating plan (LTOP), which sets the operational framework for noise sharing arrangements, says the airport. It would also have left the airport without cross-wind runway capacity which is required to maintain operations when the airport encounters strong winds from the east or west. “Given the significance of Runway 07/25 to the safe and efficient operation of both Sydney Airport and, in turn, the airport’s integral role in Australia’s overall aviation network, as well as the ability to appropriately implement LTOP modes to ensure noise sharing, the ‘do nothing’ option was rejected by Sydney Airport,” says the Major Development Plan for the project, which was required due to the project’s significant environmental impact as the runway had to be closed for certain operations between October 2008 and March 2010 which resulted in changes to aircraft noise exposure for local communities.
Constructing an EMAS would have involved the installation of frangible material at the runway end which would assist braking capacity for an overrunning aircraft. But this option was rejected as it would not have provided an equivalent level of safety to a RESA due to the short distance between the runway and the SWSOOS – only 193ft (59m). Even with an EMAS the distance would be too short to provide stopping distance for an aircraft. This option would also have required the runway to be shortened, which would have had an impact on arrivals operations.
Moving the operational runway to the east to provide sufficient room in front of the SWSOOS for the Runway 25 clearway and RESA was also considered, but there was not sufficient distance for compliant RESAs at both ends of the runway. Also, moving the runway to the east would require a steeper approach gradient which would create a permanent and adverse change to the approach path. This option would also have required considerable obstacle removal, significant airfield work and would not change the existing risks in relation to the SWSOOS and other structures at the end of the runway. As a result, it was also rejected.
Reducing runway length was not considered viable as this would result in considerable relocation work, would restrict the operation of larger aircraft, as well as not eliminating the risks associated with the SWSOOS and other infrastructure.
As a result, design and construction of a suitable RESA was the only viable option, and various design options were considered. These included Runway 07/25 end re-grading, raising by 4ft 7in (1.4m), decking over the SWSOOS and M5 tunnel and associated earthworks; re-grading, raising by 2 ft 6in (0.75m), decking over the SWSOOS and M5 tunnel and associated earthworks; and diverting the SWSOOS and airport perimeter road corridor, decking over the M5 tunnel and associated earthworks. The airport selected an option that did not require diversion of the SWSOOS.
What the project did involve was re-grading the surfaces within the plane of the existing clearway commencing at the runway end; re-grading the surface between the runway strip end and the SWSOOS; construction of a land bridge structure supporting the RESA where it goes over the SWSOOS; construction of a tunnel structure supporting the RESA where it spans the airport perimeter road; construction of a land bridge structure supporting the RESA where it goes over the M5 East motorway tunnel; construction of a 295ft x 295ft (90m x 90m) RESA; realignment of the airport perimeter road under the RESA and SWSOOS and installation of a pump station; construction of a bridge structure supporting the SWSOOS where it spans over the realigned airport perimeter road; diversion and protection of EnergyAustralia’s 132kV electricity mains and runway threshold and end lights; foundation works for the relocated localiser navigation aid aerial; installation of occupational health and safety barriers; and the demolition of redundant features.
All existing infrastructure in the area had to be diverted or protected prior to construction of the new RESA. The SWSOOS structure was protected by concrete decking that spans over it as a land bridge. The structure comprises contiguous flight auger (CFA) piles, cast in-situ headstocks and pre-cast concrete planks with a 7-in (18cm) continuous topping slab to tie all the planks together. The SWSOOS support structure is a reinforced, post tensioned concrete slab system that envelopes the existing headstocks and provides support for the SWSOOS over the airport perimeter road. As the top of the M5 East motorway tunnel was not designed to carry heavy loads, it has been protected with reinforced concrete pre-cast girders spanning over the tunnel, protecting the tunnel and providing part of the RESA surface. The land bridge structure comprises CFA piles with a cast in-situ headstock, pre-cast Super-T girders with a continuous toping slab.
The realigned airport perimeter road has a larger radius bend to accommodate more traffic lanes and a greater line of sight as it passes under the SWSOOS.
Airservices’ low voltage cable connecting obstruction lights, existing runway threshold and end lights, a localiser antenna and numerous communication cables were all relocated or protected.
Construction of the RESA required the closure of Runway 07/25 for certain periods. In the first phase of work, from mid-October 2008 to mid-June 2009, Runway 07 was not available to approaches from the west, while Runway 25 was not available for approaches from the east or departures to the west. In the second phase, from mid-June 2009 to October 2009, on Runway 07 approaches from the west were only allowed if required for aircraft safety or medical emergencies, while departures to the east were only allowed during set times. On Runway 25, approaches from the east were only available between 06:00hours and 07:00 hours as well as between 19:00hours and 23:00hours, with departures to the west available at the same times. In phase three, from the end of October 2009 to the end of March 2010, approaches from the west and departures to the east on Runway 07 were only available between 06:00-07:00 and 19:00-23:00, with approaches from the east and departures to the west on Runway 25 permitted during the same hours. During phases two and three, if required due to weather-related reasons, the runway was able to be brought back into operation between 07:00 and 19:00.
The project, which involved more than 700 construction workers, was completed as per outlined in the Major Development Plan and went ahead without any unforeseen problems, says the airport. In fact, it was completed ahead of schedule, finishing at the end of March instead of a June finish originally anticipated.
“In the air and at our airports, Australia’s aviation safety record is the envy of the world. We want to keep it that way. I want to congratulate all of Sydney Airport’s staff and contractors who were involved in delivering this vital piece of aviation infrastructure on schedule,” Russell Balding, Chief Executive of Sydney Airport said on completion of the project. He added: “Sydney Airport is investing to provide Sydney with the aviation infrastructure it needs.”
Emma Kelly explains how Australia’s premier international gateway has completed a complex and expensive runway project.