LAND, PUBLIC WORKS AND UTILITIES
committee was set up in 1989 to make decisions on the reservation, allocation and efficient utilisation of fill resources for government and major private sector projects. It consists of representatives from a broad spectrum of government departments and policy branches involved in the development of the territory.
From the beginning of 1990 up to the end of 1996, about 260 million cubic metres of marine fill (about 10 per cent from China) and 152 million cubic metres of land- based fill had been used for reclamation projects. A further 310 million cubic metres of fill are likely to be required for reclamations over the next 10 years. Most of this is expected to come from Chinese waters where, with the agreement of Chinese authorities, GEO ground investigations have now identified considerable reserves of sand.
A second role of the committee is to plan the marine disposal of dredged mud, including contaminated mud, and to allocate disposal capacity at the gazetted marine disposal grounds. During the year under review, approximately 16 million cubic metres of uncontaminated mud were disposed of under licences issued by the Environmental Protection Department. The uncontaminated mud was dumped in submarine spoil grounds and in worked-out marine borrow pits, and the contaminated mud was disposed of in sea bed pits at East Sha Chau which were planned, designed and managed by the Fill Management Division and Port Works Division of the Civil Engineering Department. In 1996, additional work was undertaken to increase the disposal capacity of these pits from 3 million cubic metres to 10 million cubic metres. Another pit with a capacity of 30 million cubic metres was being planned.
Under the Fill Management Committee, the Public Dumping Sub-Committee was established to co-ordinate the public dumping activities which achieved the dual functions of recycled use of inert construction waste and supply of fill materials for reclamations. In 1996, the quantity of recycled inert construction waste used in reclamations reached a record figure of 5.0 million cubic metres.
In connection with the management of the territory's fill resources and mud disposal capacity, the GEO, on behalf of the Fill Management Committee, continued to undertake a series of environmental and ecological studies to examine the effects of the dredging and disposal activities, and to investigate possible ways to avoid or minimise adverse effects on the marine environment.
Hydraulic Studies
Large reclamation projects can have significant effects on the flow of water, sediment transport and wave activity in the harbour. Any adverse effects could be very costly or difficult to remedy. To avoid these problems, the Civil Engineering Department employs sophisticated hydraulic models to analyse the likely effects of proposed schemes and check that they are within acceptable limits. The facilities used include computer-based mathematical models and a large physical model housed in the Harbour Hydraulics Laboratory at Tuen Mun.
The assessments provided by these models are used for planning reclamation. layouts, the design of marine structures, navigation studies and the planning of future maintenance dredging requirements. In order to have a more comprehensive assessment of the hydraulic impact, the Civil Engineering Department is enhancing its physical and mathematical hydraulic models. The enhancement of the physical
227