ENG-1985 — Page 215

LAND, PUBLIC WORKS AND UTILITIES

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The Geotechnical Information Unit, which houses a large collection of geotechnical data, continued to provide an important service to the public as a reference centre for geotechnical information. As another service to the public, the Geotechnical Control Office published more reference publications with the aim of increasing the geological and geotechnical knowledge in Hong Kong. Publications during the year included: Review of Hong Kong Stratigraphy, Review of Superficial Deposits and Weathering in Hong Kong, Review of Tectonic History, Structure and Metamorphism of Hong Kong, and Bibliography on the Geology and Geotechnical Engineering of Hong Kong (2nd edition).

The long-term programme of 1:20 000 scale terrain evaluation mapping of the entire territory, to provide adequate geotechnical information for planning and engineering feasibility purposes, was completed during the year. This information will be made available to the public in due course. Good progress was also achieved with the detailed geological survey mapping programme, and the first 1:20 000 scale map and the accom- panying explanatory memoir will go on sale in early 1986. =

As part of the long-term programme of landslip preventive measures, stabilisation works were completed on 34 slopes and retaining walls at a cost of $27 million, and works commenced on a further 35 slopes and walls. Expenditure on stabilisation works is continuing at a rate of about $80 million per year. The Geotechnical Control Office also continued its routine work of exercising control over the geotechnical aspects of all public and private building and civil engineering works. All new design proposals for works which involved site formation, slopes, earth retaining structures and deep excavations were checked to ensure that they attained the necessary standards of safety. A total of 3 900 design proposals were processed.

Quarrying

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The total consumption of crushed rock aggregates in the territory amounted to approx- imately 15 million tonnes. Of the total tonnage of aggregate consumed, 60 per cent was obtained from six local contract quarries, and a further 20 per cent from the two government-operated quarries and a number of rock crushing plants associated with development works. The remaining 20 per cent was imported from China and consisted of both coarse aggregates and natural sand.

Water Supplies

Full supply was maintained throughout the year. At the beginning of 1985, there were 428 million cubic metres of water in storage, compared with 529 million cubic metres at the start of 1984. The combined storage of Hong Kong's largest reservoirs, High Island and Plover Cove, was 371 million cubic metres. Rainfall for the year was 2 191 millimetres compared with the average of 2 225 millimetres. Water piped from China during the year totalled 319 million cubic metres. The Lok On Pai desalting plant was not operated and continued to remain as a 'stand-by resource'. The salinity of water at High Island remained at about 13 milligrams per litre while at Plover Cove the salinity varied from 66 milligrams per litre in January to 46 milligrams per litre in December.

A peak consumption of 1.95 million cubic metres per day was experienced, compared with the 1984 peak of 1.99 million cubic metres per day. The average daily consumption throughout the year was 1.75 million cubic metres, an increase of 2.3 per cent over the 1984 average of 1.71 million cubic metres. The consumption of potable water totalled 637 million cubic metres compared with 627 million cubic metres. In addition, 101 million cubic metres of salt water for flushing were supplied, compared with 90 million cubic metres.