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4.
RECLAMATION CONSIDERATIONS
To ensure stability and control settlement, it is assumed that marine deposits will be completely removed beneath the
the revetment zone and dredging will be carried out over the rest of the area with 3m of marine sediments remaining. Figure 8-1 shows a plan and typical section of the reclamation.
5.
5.1
SOURCE OF CONSTRUCTION MATERIALS
For the purpose of costing, two reclamation materials are considered:
combination of offshore and onshore
a
5.2
ONSHORE BORROW
sources of borrow for the (1) onshore borrow; and (2) borrow.
Table 8-1 is a summary of the quantities of the various materials required for the offshore embankment. The classification of the materials is the same as that developed for the Chek Lap Kok airport studies. It is assumed that materials for the bedding course, overfill, special fill and select fill are derived from topsoil and rippable materials. The remaining classes of materials would be from blasted rock. Bulking factors of 0.95 and 1.33 are assumed for materials of the above 2 origins, respectively. The amount of excavation from onshore borrow areas are shown in Table 8-2.
In the NTDC study, two potential borrow areas were identified in the vicinity of the proposed airport: one at Lau Fau Shan and the other at the northeastern boundary of the Castle Peak Firing Range. The NTDC report speculated that no borrowing from within the Firing Range will be allowed. The quantities of soil and rock from these two potential areas are estimated in the NTDC report to be 40 and 72 million cubic metres, respectively. The report has established the borrow requirement for the NW New Territories to be at 12 million cubic metres under the preferred strategy. Comparing these figures with those in Table
in Table 8-2, it is evident that additional borrow areas will have to be investigated. Such borrow areas exist within the Castle Peak Firing Range.
5.3
OFFSHORE & ONSHORE BORROW
Table 8-3 is a summary of the quantities for the offshore embankment, with marine sand substituted for quarry run and special fill below +2.23m P.D., together with additional dike material protection at the landward side of the reclamation.
According to the NTDC study, the quantity of marine sand found in Deep Bay is insignificant. However, potential sources do exist. For example, approximately 50 million cubic metres of silty sand is estimated to be found south of the Chinese Island of Nei Ling Ting to the SW of Deep Bay.
8-2
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