APPENDIX C
CONSTRUCTION STUDIES
CONFIDENTIAL
1.
ASSUMPTION
The findings of the Civil Engineering Studies are based on very limited geotechnical and oceanography information, outlined below, and the assumptions listed previously at Para 3.1.4.
2.
GEOTECHNICAL CONSIDERATIONS
2.1 The following information from the investigation carried out for the proposed Tin Shui Wai Urban Development was consulted:
Logs for 2 marine investigation holes located at 1 to 2km offshore in Deep Bay, to the NW of Nim Wan and west of Lau Fau Shan respectively, and
Results of vane shear tests performed in these 2 boreholes and summary of laboratory index properties tests on soil samples recovered.
2.2 Plans and several sections of the marine geophysical survey in South Deep Bay carried out for the proposed Tin Shui Wai Urban Development were also examined. The sections covered only the southern part of the proposed airport, and thickness of the marine deposits over the entire site was inferred from these
data.
2.3 The thickness of marine deposits under the proposed airport is estimated to range from 5 to 8 metres. The 2 boreholes indicated that these varied from very soft silty clay to medium sand.
The marine borehole off Lau Fau Shan revealed about 20m of alluvium beneath the proposed northern runway. Alluvial deposits ranged from firm silty clay to fine gravel. The alluvium is underlain by completely decomposed granite in which the boreholes were terminated.
3.
OCEANOGRAPHY
3.1 The Engineering Studies report (Appendix III) of the "Development Investigation of the NW New Territories" prepared by the New Territories Development Consultants (NTDC) was made available for the present study. Based on the NTDC's recommended design line, the minimum elevation for the seawall of the proposed airport was determined to be +5.1m P.D. (criterion for a 1000 year high water elevation which was established for the Chek Lap Kok airport studies).
3.2
smaller
Because of the more sheltered location of the site, sized armour rock protection may be provided at the most exposed southwestern tip of the airport.
8-1
CONFIDENTIAL
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