4.9
The float tests were to determine the pattern and speeds of the existing currents in the vicinity of the proposed berths over the tidal cycle during a period of spring tides. The current-meter readings were to determine the likely maximum speeds and directions at selected points and depths.
These observations together with measurements of the silt load in the water would enable some idea of the likelihood of silting or scouring at the site to be assessed. Float-test results are shown on Drawing 11 and current-meter readings on Drawing 12.
Wave Observation
4.10
4.11
4.12
Wave observations are at the time of writing being carried out at the proposed terminal site for the following purposes:—
(a) To relate observed wind speeds with the height of waves at Kwai Chung.
(b) To compare the swell determined by calculation with that actually measured at the
site.
To enable these measurements to be taken, one of the test piles driven as part of the site-investigation programme has been left in place and marked in feet and inches on the length spanning the tidal range. Since it has been shown statistically that readings of wave heights taken over short periods at regular intervals give similar results to continuous readings, records are being kept by an observer who estimates the average and maximum height of waves together with their period for fifteen minutes each morning and afternoon. Arrangements are being made to continue recording waves throughout the 1969 south-west
monsoon season.
From the limited measurements so far obtained, it is nevertheless possible to determine wave heights at Kwai Chung produced by north and north-easterly winds and hence to estimate likely heights under the worst wind conditions from this quadrant in which containerships would be worked. Since observations began, practically no south-westerly winds have been recorded so that no comparison can be made at this juncture between calculated and recorded swell from that quarter.
4.13 Tabulated wind and wave observations are shown in Appendix 5.
Silt Load Measurement
4.14
To assist in assessing the likelihood of silting at the proposed berths, silt-load measurements were made in the vicinity of the site. These were taken in conjunction with the current measurements taken during spring tides in December 1968 and in January and February 1969.
4.15 These measurements are not considered to be truly representative as the silt load will vary seasonally and is likely to be increased when the Pearl River is in spate. They do however indicate that it would take a considerable time for any significant alteration in the seabed level to take place on account of any local precipitation of this source of material.
Borrow Area Investigations
4.17
4.16 Four borrow areas have been considered from which filling material may be obtained for reclamation purposes. One of these is on the Lai Chi Kok ridge, one on the Texaco peninsula and two on Tsing Yi Island. Their extent and positions are shown on Drawing 5. To ascertain the quantities of soft material and rock that would be available from the Lai Chi Kok site and to design a practical layout of platforms and access roads, 25 drillholes have been sunk covering the whole of this area. These augment the 60 probes taken in connection with the Kwai Chung Reclamation project. For the Texaco-peninsula site, the results of 2 boreholes and 147 probes were available from the Kwai Chung Reclamation project. Investigation results for these two areas are shown on Drawings 6 and 7.
4.18
In determining the fill available from Tsing Yi, the bores and probes carried out for the Tsing Yi Development Report have been relied upon.
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