3.
THE SITE
Geography
3.1
3.2
3.3
3.4
Kwai Chung lies on the Mainland some five miles north-west of the Kowloon peninsula and merges with the industrial town of Tsuen Wan. The site reserved in this area for the container terminal is situated between the former islands of Tsing Chau and Mong Chau at the mouth of Gin Drinker's Bay whose reclamation is now well advanced. This site is overlooked on the east by terraced hills from which material was obtained for the reclama- tion and which could be used as a source of further filling material for the terminal.
The drainage of the reclamation and the hinterland is by means of a large stormwater culvert which has its outfall just to the east of Mong Chau and the siting of this is a factor to be considered in planning the container berths. The area is well served by roads and a six-lane highway connects it with Kowloon to the south-east, while a similar highway to Castle Peak is under consideration.
The choice of the terminal site was largely influenced by the good sea approaches through the East Lamma Channel, there being already enough depth of water for containerships to approach within a few hundred feet of the proposed berths. The site is sheltered on the north and east by the mainland and on the west by Tsing Yi Island but is fairly exposed to the south-south-west with only limited shelter given by the San Men and Lema groups of Islands.
The position of the terminal site in relation to the surrounding area is shown on Drawings 1, 2 and 3.
Geology
3.5
3.6
3.7
3.8
Tides
3.9
The whole of the Kwai Chung area as far as Tsuen Wan is composed basically of Hong Kong granite, although Tsing Chau at the entrance of Gin Drinker's Bay also has intrusions of Tai Po granodiorite. The surrounding hills are of granite with varying degrees of de- composition on the surface.
The existing seabed between the former islands of Tsing Chau and Mong Chau is fairly flat except in the boundary regions and it slopes gently downwards in a south-easterly direction. The area is covered by a deep layer of soft grey marine clay. Shells are found in the top layer of this clay and the thickness of this varies considerably. The clay becomes less soft with depth and is underlaid by stiffer or more compact ground consisting of firm brown sandy clay or silt, or in some places compact brown clayey sand with or without a gravel content. This is probably a region of old alluvial deposits and residual soil.
The soft marine clay at the terminal site varies in thickness from a few feet to about 30 ft. and the level of the bedrock below the seabed from a few feet to more than 100 ft. Typical cross sections of the seabed are shown on Drawing 9.
Tsing Yi Island, a site for possible borrow areas, has similar geological characteristics to Kwai Chung but like Tsing Chau has a number of intrusions of igneous rock. The degree of decomposition of the granite at the sites chosen for borrow areas ensures that a good percentage of soft material would be available for reclamation purposes.
Hong Kong has a normal tidal range of about 8 feet. The tidal cycle is mixed in character being predominantly semi-diurnal with two high tides and two low tides each 24 hours approximately, but at certain times diurnal with only one high and one low tide in a similar period. The height of the tide is measured from Chart Datum which approximates to Lowest Astronomical Tide so that the water level rarely goes below zero.
3.10 Recording tide gauges are sited at North Point in Victoria Harbour and at Chi Ma Wan on Lantau Island. The records from the two are very similar when allowance has been made for phase difference and it can be assumed therefore, that these gauges will give a good indication of the tidal conditions at Kwai Chung which is sited more or less half way between the two.
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