ENG-2003 — Page 286

LAND, PUBLIC WORKS AND UTILITIES

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land-based fill reserves. Both committees are responsible to the Secretary for the Environment, Transport and Works.

About 10.9 million cubic metres of C&D materials were generated by local construction activities in 2003. Of this, about 9.6 million cubic metres of inert materials were re-used as fill in public filling areas including Tseung Kwan O Area 137, Tuen Mun Area 38, North Tsing Yi and Penny's Bay, or stockpiled at the fill banks in Tuen Mun Area 38 and Tseung Kan O Area 137.

The PFC explores ways to minimise the generation of C&D materials and reduce their disposal at landfills. The construction industry is encouraged to adopt construction methods and materials that reduce the generation of C&D materials at source. The temporary recycling facility at Tuen Mun Area 38 recycles suitable C&D materials into aggregates for re-use. In 2003, the recycling facility produced about 0.2 million tonnes of recycled aggregates for use in government projects.

The MFC maintains a Fill Management Database on fill requirements, mud disposal and surplus excavated materials from major public and private projects. Its purpose is to help the construction industry coordinate sources of fill materials and make the best use of surplus materials. All project data is available at the CED's home page.

The department manages mud disposal facilities. In 2003, about seven million cubic metres of uncontaminated mud and 0.5 million cubic metres of contaminated mud were generated from various works projects and maintenance works on navigational channels in the harbour. Uncontaminated mud was disposed of at open sea floor disposal grounds or exhausted marine sand borrow pits. Contaminated mud was placed in specially selected and closely monitored exhausted sand borrow pits, which were then capped with clean mud on completion of filling to isolate the contaminants from the environment. The use of exhausted sand borrow pits for mud disposal is preferred as it has the dual benefits of providing much needed disposal capacity and restoring the seabed to its natural profile and

state.

In connection with the management of Hong Kong's fill resources and mud disposal capacity, the department, on behalf of the MFC, continues to undertake a series of geotechnical, environmental and ecological studies and monitoring to examine the effect of the dredging and disposal activities, and to investigate possible ways to avoid or minimise the impact on the marine environment.

Hydraulic Studies

Coastal engineering projects may affect the flow of water, sediment transport and wave activity in the harbour. The department employs sophisticated computer hydraulic models to analyse the likely effects of proposed schemes, both during and after the construction phases, to ensure that their impacts are minimised to within acceptable limits. The models are used for reclamation layout planning, design of marine structures, waterway studies and assessment of future maintenance dredging requirements. A digital tidal stream atlas and a wave atlas were also developed by the department in 2001 to provide average tidal and extreme wave information. These atlases are being updated to reflect the latest shoreline and seabed profiles and to enhance the accuracy of the information.