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could be constructed at a more leisurely pace. The tentative programme calls for reduced dredging in these areas, leaving about 5 m of the weak stratum and capitalizing on the additional time available for consoli- dation. A third area close to the shore (designated as Phase Ib) can be filled without dredging.
One of the more costly aspects of the airport construction programme is the need to dispose of the dredged material at a distant site. The Consultants' Terms of Reference provided that a disposal site would be specified. Based on PWD direction (from a Working Party on Marine Dumping and Extraction), the cost of this operation is estimated on the assumption of ocean dumping disposal seaward of Cheung Chau Island. If a more convenient disposal site can be found, considerable savings would accrue in the cost of airport construction.
Figure 17 is a typical cross section through a portion of the airport site illustrating the layering of materials in the reclamation embankment. The cross section also indicates the preliminary construction plan for the protective seawall and the general fill area. Quantities of dredging, excavation, and placement of offshore fill required to construct the airport were developed from this and similar cross sections through the reclamation, constructed from data furnished by the PWD.
The scope of the replacement airport project can be appreciated by a review of the material quantities involved. Dredging of nearly 14 million m3 is required for
Phase I, and nearly 7 million m3 more would be dredged to complete the developed two-runway pilot scheme. The excavation of more than 100 million m3 of Chek Lap Kok Island and the smaller Lam Chau Island is required, and this operation is expected to pace the construction time span. Just over 56 million m3 of fill materials will be placed for Phase I (Ia and Ib) of the airport and another 21 million m3 will be placed in the area for Phase II.
As envisioned by the Consultants, excavation of the two islands would produce a surplus of material that could be made available for additional land reclamation. The material is characterized as "hard" and is not generally useful for fill under pile-supported structures. In the Consultants' view, however, it can be considered as a valuable resource to the Hong Kong Government for other reclamation purposes. The detailed report on civil engineering suggests alternative uses for this surplus material. These suggestions have not yet been evaluated by Government.
Construction of the airport at the selected site is an undertaking of major proportions, and an appreciation of its magnitude is essential to understand the construc- tion programming requirements. A tentative construction schedule is presented later in this summary. It should be remembered that the reclamation of approximately 530 hectares of land composed principally of granite will be a slow process. (Total airport land developed will be approximately 840 hectares.) In the Consultants' opinion, the time needed for this land reclamation is the pacing item in the programme for airport development.
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