LAND, PUBLIC WORKS AND UTILITIES
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Among structural measures which government has already put in hand are the construction of main drainage channels in the North-west New Territories flood plains and local works to protect low-lying villages which are difficult to drain. Construction of 6.5 kilometres of channels for the Tin Shui Wai hinterland has been completed and design is in hand for another 14 kilometres of channels in Yuen Long, Kam Tin and Ngau Tam Mei with a view to starting work on site in 1992. Two flood pumping stations together with other ancillary flood protection works were also completed at Tai O.
During the year the ground work for the creation of a new Land Drainage Ordinance was completed and it is expected that drafting of the ordinance will start shortly. The new ordinance will give the government much needed legal power to deal with the maintenance of natural streams in the New Territories. Comprehensive maintenance to ensure the efficient functioning of streams is an important part of the total effort to reduce the risk of flooding in the low-lying areas of the New Territories.
Geotechnical Control
The Geotechnical Engineering Office (GEO) of the Civil Engineering Department was established after the landslip disasters of the 1970s, and the control of geotechnical aspects of construction works in the interest of public safety continues to be one of its foremost duties. Checks were made on 6 007 design proposals in 1991. After the introduction of the prior approval system for reinforced fill structures in 1990, the first Endorsement - Certificate was issued to a reinforced fill proprietary product and assessment of two other
products is in progress.
The GEO operates the Landslip Warning System and a 24-hour emergency service to provide advice on landslips.
Landslip preventive work was carried out on 47 slopes and stabilisation work was carried out on four networks of disused air-raid precaution tunnels, requiring the expenditure of $80 million in the Landslip Preventive Measures Programme. In addition, the office completed the design and construction of works to improve the stability and reduce the environmental hazards from an old sanitary landfill at Sai Tso Wan at a cost of $38 million. A site formation design for a Housing Department project at Ho Man Tin South with an estimated cost of about $69 million and the design of stabilisation works to the slopes of an old landfill borrow area at Fung Shing Street, Ngau Chi Wan with an estimated cost of $15 million were also completed.
The presence of cavitous marble beneath sites in the north-western New Territories and around Ma On Shan has posed problems for development. Geological mapping to identify the extent of the buried marble in these areas has been completed and 10 new 1:5 000 scale geological maps were published for the area around Yuen Long. New legislation, enacted in July 1990, to empower the Building Authority with additional geotechnical controls to ensure safe development in these areas has been utilised.
The Hong Kong Geological Survey of the GEO continues to publish 1:20 000 scale geological maps and memoirs for the land and marine areas of the territory. During 1991, new geological maps for Sheung Shui, Kat O Chau and Silver Mine Bay were published. Geological maps at 1:20 000 scale are now available for more than 80 per cent of the territory. Large scale 1:5 000 geological survey work was completed in the Ma On Shan district and is well underway in the development areas of North Lantau. Engineering geology studies are also in progress in North Lantau, with the aim of identifying any