Hong Kong 2003
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Civil Engineering

Geotechnical Engineering

The Civil Engineering Department (CED) manages a comprehensive slope safety system, which has brought about a substantial improvement in the safety of slopes in Hong Kong. This has been achieved by improving slope safety standards and technology, ensuring the safety of new slopes, improving the safety of existing slopes, and providing public warnings, information, education and community advisory services on slope safety.

The department audits the adequacy of the design and construction of all geotechnical works by the private sector, public authorities and government departments to ensure their long-term safety. In 2003, it audited 13 666 geotechnical design proposals and inspected 2 890 active construction sites.

The department maintains a continuing Landslip Preventive Measures (LPM) Programme to rectify the safety of existing slopes. In 2003, a total of about $920 million was spent on the LPM Programme. Upgrading works were completed on 260 government slopes, and all were landscaped to blend them with the surrounding environment. In addition, safety screening was completed on 320 private slopes.

The department inspects hillside squatter villages to identify huts vulnerable to landslides, recommends rehousing of the affected squatters and advises the occupants to seek safe shelter during heavy rain. In 2003, it inspected about 70 squatter villages.

With the availability of the Slope Maintenance Responsibility Information System on the Internet, members of the public can have ready access to information on slopes under their responsibility. Other slope-related information is also available in the Slope Information System. A bilingual version of the system has been uploaded to the Internet at the CED's Hong Kong Slope Safety website. The website has become an important source of reference for the public in obtaining slope-related information.

The Catalogue of Slopes has been made even more comprehensive. The department has done this by systematically examining the latest topographic plans and using aerial photograph interpretation techniques in order to identify and register slopes which meet the registration criteria but have not been included in the catalogue. The number of registered slopes in the catalogue has subsequently increased from 54 000 to 57 000.

In sustaining public awareness of slope safety, the department promotes and disseminates slope safety and slope maintenance messages to the public, and organises slope safety talks at schools and roving exhibitions in the community. In addition, a major exhibition will be held in the Central Library in April 2004 to show the history of landslide disasters in Hong Kong. A pamphlet on Maintenance of Buried Services Affecting Slopes is being prepared to remind slope owners to inspect and maintain underground water-carrying services. As part of efforts to improve the living environment, an open competition for the 'Best Landscaped Slope' was launched in June to encourage slope owners to maintain and beautify their slopes. The response was excellent.

The department's Community Advisory Unit provides useful advice to private slope owners to help them maintain and improve the condition and appearance of their slopes. In order to assist private slope owners to discharge their slope maintenance responsibility, a simple guide to 'Dangerous Hillside Orders' has been published to provide a step by step approach to undertaking the requirements of a Dangerous Hillside Order (an order issued under the Buildings Ordinance) promptly and effectively.

The Slope Maintenance Audit Section helps maintenance departments to improve their performance in discharging their slope maintenance responsibilities. Audits of government slope works indicate a continuous improvement in the overall state of maintenance.

The department maintains a 24-hour year-round emergency service to provide geotechnical advice to government departments on actions to be taken to protect the public against landslide danger. The computerised information system and telecommunication facilities have been upgraded to enhance efficiency in handling landslide information and emergency calls.

The department conducts various studies to improve the knowledge and methodology of dealing with natural terrain landslide hazards. It has developed techniques in dating natural terrain landslides, assessing the mobility of landslide debris and applying Geographic Information System technology to hazard studies. Natural terrain hazard mitigation works are being arranged for five sites in developed areas, while studies are being carried out in respect of four other sites.

During the year, the department continued to produce geotechnical guidance documents to disseminate new technological development findings and improved design and construction practice. In particular, the third edition of the Guide to Slope Maintenance and a revised Layman's Guide to Slope Maintenance were published. Guidance on new vegetation mixes and new planting techniques for greening slopes was also given.

The Geotechnical Information Unit in the Civil Engineering Library houses the largest collection of geotechnical data in Hong Kong. The library is open to the public, and served more than 26 500 users during 2003.

The department provides specialist geotechnical services to government departments, including the provision of ad hoc geotechnical advice and conducting feasibility studies, detailed investigations, design and construction supervision for a wide range of public works projects. The projects handled by the department during the year included site formation works at Kong Sin Wan Tsuen, Pok Fu Lam; slope upgrading works at the former Victoria Barracks, Kennedy Road; site formation works for the Yam O Tuk Fresh Water Service Reservoir on Lantau Island, and the Ping Che Fresh Water Service Reservoir in Fanling; geotechnical works for the drainage project at San Tin; and geotechnical works for Stage III of the Shenzhen River Regulation Project. In addition, the department also provides construction material testing and ground investigation services to support public works projects. The testing service is provided by the Public Works Laboratories. During the year, some 880 000 tests were carried out, and 20 000 metres of soil and rock were drilled.

Mining and Quarrying

The department enforces legislation relating to mining, quarrying and explosives, and administers quarrying contracts. It processes applications for the manufacture, storage, conveyance and use of explosives, and inspects stone quarries, blasting sites and explosives stores.

Hong Kong consumed 16.3 million tonnes of aggregates and other rock products in 2003. About 50 per cent of its demand for aggregates and rock products was met locally, with the balance imported from the Mainland.

One quarrying contract and two quarry rehabilitation contracts were in force during the year. The rehabilitation contracts require the operators to rehabilitate the quarries within a specified period, in return for the granting of rights to process and sell surplus rock excavated during the course of the works. The rehabilitation works involve recontouring and extensive planting to blend the quarries with the surrounding hillsides.

The department manages two government explosives depots (one at Kau Shat Wan on Lantau Island and the other at Piper's Hill, Sha Tin) which provide bulk storage facilities for imported explosives. It also undertakes the delivery of explosives from the depots to blasting sites and issues shotfirer certificates. About 2 100 tonnes of explosives were consumed in 2003, being used mostly for quarrying and site formation works.

The department also provides technical support to the Home Affairs Bureau and the Marine Department in assessing applications for fireworks displays.

Fill Supply and Mud Disposal

The Marine Fill Committee (MFC) is responsible for identifying and managing the supply of marine fill resources for development projects, and for managing disposal facilities for dredged and excavated sediment. The Public Fill Committee (PFC) has the duty to manage construction and demolition (C&D) materials and utilisation of 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.

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