CONSTRUCTION methods being used to build the runway at Chek Lap Kok airport have been called into question by a top civil engineering expert. Leonhard Zanier, a senior engineer from the Technical University in Vienna said subsequent repairs to cracks could cost millions of dollars and lead to immense inconvenience for travellers when air services were suspended while the work was done. He said the rock being used for the base of the runway should be properly compacted instead of being allowed to settle by itself. ''It will cost peanuts [to compact the rock] compared with the overall cost of building the runway,'' said Mr Zanier, who is also an engineering expert for the United Nations. He is currently working on a compaction project for oil storage tanks on Tsing Yi island. Mr Zanier, who also works for the French soil compaction company Menard Soltraitement, said he had offered to do some tests at Chek Lap Kok to prove his claims but this was rejected by the Provisional Airport Authority (PAA). ''We had some of the PAA's soil mechanics people visit our site in Tsing Yi. I asked if we could do some tests at Chek Lap Kok, but they said: 'What for? It's not necessary','' he said. He believes that without compaction, settlement cracks from the continual pounding force of landing aircraft will appear in the runway soon after the airport opens in 1998. The runway is being built using rock excavated from the original Chek Lap Kok and Lam Chau islands. These islands are being incorporated into either end of the runway. The gap between is being filled with crushed rock. Engineering experts agree the runway will have a more solid foundation where it overlays the original islands. Mr Zanier, who admits he has a vested interest in advocating compaction, said the biggest problems will appear where the excavated rock meets the edge of the outline of both the islands. He said this area would be the most susceptible to settlement. He said two previous projects at Tsing Yi Island and in Singapore showed compaction was necessary to fill the gaps in between the boulders. It also reduced the risk of settlement from the clay and mud layers beneath the rock. The conditions at both locations were similar to those at Chek Lap Kok, where the PAA's contractors are removing soft marine mud and replacing it with rock, he said. Singapore's Changi airport authority used Mr Zanier's company to compact rock used to build the runway. The level of the rock dropped by 35 to 40 centimetres. Menard pounded the rock with a force of 1,400 tonnes using a 35-tonne steel cone dropped from a height of 40 metres. There has been zero settlement at Changi since the project was completed, Mr Zanier said. Similar figures were achieved at Tsing Yi, where a rock base was created for a network of oil storage tanks. The PAA said it used sophisticated monitoring devices to check the level of settlement. ''So far there are no major problems,'' said a spokesman. Tenders will be invited in December for a key part of the Central reclamation project at the former HMS Tamar naval base, according to the Territory Development Department. The scheme has been accelerated following the recent Sino-British defence lands agreement. Engineering consultants are about to be shortlisted for the design assignment, which the department hopes to award by October. Further along the Central waterfront outside Exchange Square, reclamation work is ahead of schedule and work is starting on the first two replacement piers. The Mass Transit Railway Corporation said work would take an important step forward next month when the first tube section for the airport railway immersed tunnel under the harbour is floated into position. ''We are about a quarter of the way through the contract, but about halfway through the first stage of reclamation work,'' said MTRC engineering manager, Bryan Reid. At Chek Lap Kok, reclamation work is also proceeding well with more than 67 per cent of the 1,248-hectare site having been formed.