CIVIL ENGINEERING AND PUBLIC WORKS
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HONG KONG
D
URING 1966 two 60 MW generat-
ing sets were commissioned for the North Point power station of the Hongkong Electric Co. Ltd. This brought the total installed generating capacity at North Point to 345 MW.
The demand for electricity supplied through the Hongkong Electric sys- tem had been growing at the rate of 13 per cent per annum and it had long been realised that there were limitations to the extent to which the North Point site could be redeveloped with maximum economy to meet this growing demand.
Already the original North Point station buildings, constructed in 1921. had been partially demolished to make space for the installation of the two latest 60 MW generating sets. In view of this, negotiations with the Hongkong Government took place in 1964, the outcome of which was that Hongkong Electric were granted a site of approximately 14 acres for a new power station on Ap Lei Chau, a small island opposite Aberdeen on the south west coast of Hong Kong Island.
The civil engineering works as- sociated with this new power station have been carried out under two con- tracts, one for site formation and the
Far East Architect & Builder June, 1967
AP LEI CHAU POWER STATION
by R. Boorman, planning engineer (civil)
Hongkong Electric Co. Ltd.
other for power station buildings
construction,
Site Formation
The Ap Lei Chau site, situated at the western tip of the island, was initially dominated by a steep-sided hill, 180 ft. high. Apart from some small quarry workings on the south shore the area was untouched. Also, as there was no road access, all plant and equipment had to be transported to the site by boat.
Preliminary earthworks (the forma- tion of access roads and preparation of areas for site offices, stores, workshops. etc.) were carried out between March and June, 1965, and bulk excavation commenced at the end of June, 1965.
It was decided that the site should be formed to a general level of + 20 ft. C.D. This involved the excavation of approximately 1 million cu, yd. of which 95 per cent was hard rhyo- lite rock. Samples of the rhyolite were tested at the University of Hong Kong and proved to be the hardest and most abrasive rock yet found in the Colony.
The bulk excavation was carried out in four stages. For the first stage
the crown of the hill was removed down to a level of + 125 ft. The remaining three stages consisted of almost equal volumes divided by lines running north to south; these stages were excavated in sequence from west to east, each stage being taken down to the + 20 ft. level.
Owing to the exceptionally hard nature of the rock primary blasting before excavation was essential. The main explosive used was made by mixing ammonium nitrate and fuel oil. For each blast the explosive was distributed through a pattern of 61⁄2 in. dia. and 3 in. dia. vertical holes and 3 in. dia. horizontal holes at the foot of the quarry face. The vertical holes were generally at a spacing of 15 ft. centre to centre.
Naturally, the quantity of explosive used per blast varied widely according to the particular circumstances, but on occasions weights in excess of 8,000 lb. per blast were used. Blast- ing ratios of the order of 3 cu. yd. per lb. of explosive were obtained.
The excavation was taken out in 35 ft. benches, an electric powered 150 RB face shovel fitted with a 6 cu. yd. bucket being used to dig out the loosened rock after blasting. The 150 RB loaded the excavated rock
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