Chek Lap Kok Airport 1

With his team of seventy surveyors, the Hong Kong Airport Authority’s fifty-plus-year-old chief surveyor defines, measures, computes, plots, and analyzes a vast collection of terrain and object data.

By discriminating use of the methods of classical and GPS surveying, photogrammetry, geographic land-information systems, seabed mapping, and ground-sensing technology, the Airport Authority’s surveyors provide fast, accurate, professional support on the vast airport platform for the work of up to fourteen thousand specialists at work on the site. Their tasks include keeping track of ground that may settle by up to 700mm or even more.

Ever since planning began, Ian Ayson has been responsible for one of the most challenging surveying projects of our time. His headquarters are an office on Chek Lap Kok, right amid the turbulent events on this vast site that changes at such incredible speed. If necessary, he can set up a meeting at short notice with colleagues in project management and engineering, with site supervisors and geotechnical engineers. They too have established their offices on the island, as have those in charge of the work for the various construction consortia and subcontractors with their own teams of surveyors.

A computer network and joint databases allow them to stay in constant touch with one another and with their colleagues at the Airport Authority’s head office in Hong Kong’s 374m tall Central Plaza tower. Every day, up to ten thousand construction workers and specialists arrive on the island by boat to reinforce the four thousand workers who, until the airport is complete, have taken up permanent residence there.

When Ian Ayson and his fellow pioneers arrived on Chek Lap Kok in 1992, the granite island’s area was only 302 hectares (746 acres), and the surf of the South China Sea could be heard everywhere on the island. Now, when the chief surveyor climbs into his site vehicle, he can only see a cloud of dust whirling into the air in the west. In just thirty-one months, 938 hectares (2318 acres) of new land have been wrested from the sea and the seashore has moved five kilometres further west.

A 13km-long seawall surrounds the levelled airport island, now four times its original size. Great blocks of granite weighing one, three, and five tons apiece form the protective seawall. They have been blasted out of the island’s rock to the seawall specifications, and are made to interlock tightly with one another in open fashion to dissipate the wave action of the sea.

How — as has been done at Chek Lap Kok — does one set about the task of wresting nearly nine and a half square kilometres of land from the sea, in some places to a depth of ninety metres, in only two and a half years? Where does one get the material? And how place it on the site so that, at minimum cost for removal and transport, one obtains maximum stability where one needs it: where planes will land and major structures stand? There are many such structures on Chek Lap Kok.

Apart from the gigantic platform itself, the most impressive structure on Chek Lap Kok is the eight-storeyed air-terminal building, 1.27 kilometres long, with a total floor area of 560’000 square metres (more than six million square feet) and an enormous, aerodynamically shaped roof that can resist typhoons. There must be no massive settlement of the supporting structure, nor must it begin to float in the heavy monsoon rains. Though it is built on Chek Lap Kok’s bedrock, piles up to 50m long have been rammed into the sometimes weathered rock and steel anchors fixed at many points, as the only way to ensure that the large structure will stand up to the tremendous forces of compression, lift, suction, and shear to which it will be exposed.

One of the first buildings completed on Chek Lap Kok is its air-traffic control centre and 84m tower, the tallest control tower in the world. Another major piece of construction is the south runway, one of a pair, each 60m wide and 3.8 kilometres long, with two road tunnels that pass under it. Among the building and civil-engineering structures there are also rail and motorway terminals, the world’s biggest air-freight centre, catering buildings and offices. These will include the future headquarters of the Airport Authority and of Hong Kong’s airline, Cathay Pacific.

To supply the kerosene for up to fifty aircraft an hour taking off and landing, nine giant fuel-storage tanks are being built next to the island’s own ocean-tanker terminal. They will hold a total of 180 billion litres of aircraft fuel — about 40 billion imperial (50 billion US) gallons! All that, please, with the least possible amount of noise and environmental impact, in order not to upset the white dolphins whose habitat is in the surrounding sea!

The contract cost of the buildings under construction on Chek Lap Kok is more than twenty billion Hong Kong dollars, about three billion US dollars. But this vast construction site is not just the world’s fastest, it’s probably also one of the most demanding survey projects of the 1990s. The airport’s completion and official opening are planned for April 1998. With all associated projects, the total cost will be over HK$150 billion, about US$20 billion.

For two years, great detonations kept shaking Chek Lap Kok daily during two time windows, 11.30am to 2pm and 4pm to 6pm. The shot-holes drilled by the mining engineers have a total length of 2700km. To remove most of the island’s granite, with an average height of 120m, they detonated 40’000 tons of explosive, and have turned the island into a platform about 5m above sea level. A similar fate was in store for the nearby island of Lam Chau, with a total area of only eight hectares (20 acres). This is now also part of the island airport and forms the natural foundation for the eastern third of the first of the two runways planned.

But not even all this material from the two rock islands was enough to fill the sea, an average 15m deep, or supply the land-fill needed for the airport’s vast area. An obvious solution was to level a couple of nearby islands — The Brothers — and take another seven million cubic metres from these. These two islands are in the direct line of approach to the runways. Two flight-radar stations have been built on them for greater flight safety. Yet that still was not enough to make a sufficiently large, stable foundation in the sea for Chek Lap Kok. So they sent great transport barges across to the nearby core projects and blasted the rest of the material they needed from approach roads under construction.

A complicating factor was that the upper strata of the seabed around Chek Lap Kok island were geotechnically too unstable a foundation for an airport. Up to thirteen giant dredgers, equipped with suction and gripper arms, were deployed to dredge up the masses of sludge, marine deposits, and limnic chalk deposited on the seabed. When the dredgers had finished, the specialists could at last start preparing the airport’s foundations by dumping rock from the granite islands into the sea, and sand dredged up from suitable marine locations.

By their combined efforts the contractors increased the island’s land area by a hectare (212 acres) a day; at peak time by as much as three hectares. To do that they had to dump 121 million cubic metres of rock and 76 million cubic metres of sand in the sea. Another 142 million cubic metres of waste material had to be moved from the sea to marine dump sites. A two-metre thick finishing layer of crushed granite aggregate and sea sand has been spread over the whole of the island’s surface. A layer of special geotechnical fabric, seven million square metres of it, separates this two-metre thick drainage layer from the much coarser land-fill substrate.