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Following is a question by the Hon Leung Che-cheung, and a written reply by the Secretary for Transport and Housing, Professor Anthony Cheung Bing-leung, in the Legislative Council today (21 November 2012):
Question:
It has recently been reported in the press that as the foundation works of the Home Ownership Scheme (HOS) project at Wang Yip Street West, Yuen Long (Wang Yip Street West project) have been affected by some cavern problems, it is necessary to reduce the scale of the housing estate. As a result, the number of flats to be provided in that housing estate will be 20% less than the original estimate, affecting the quantity of HOS flats to be supplied. Moreover, the building blocks in Kam Fung Court, Ma On Shan had cavern-induced unusual settlement after residents had moved in. In this connection, will the Government inform this Council:
(a) of the site identification process for HOS projects; apart from the six sites already announced, whether the Government has made any new progress in identifying sites for HOS projects;
(b) whether it has assessed if the aforesaid problem of the Wang Yip Street West project is attributable to the fact that the underground investigation work was not done thoroughly during the site identification process; in view of the exceptional circumstances of the HOS project, whether the Government will extend the structural guarantee period for the housing estate concerned; and
(c) of the measures adopted and the amount of resources deployed by the Hong Kong Housing Authority to tackle the aforesaid problem at Kam Fung Court?
Reply :
President,
My answer to the Hon Leung Che-cheung's three-part question is as follows:
(a) The Government has announced plans to provide about 17 000 Home Ownership Scheme (HOS) flats over four years from 2016/17 onwards. The resumption of HOS has been a regular part of the government's housing policy. Apart from the 6 announced sites, the Housing Authority (HA) is working with other government departments and bureaux to actively identify suitable sites for HOS development in different parts of the territory and from various medium and long term housing studies. We will consult the relevant district councils and the local community on individual HOS developments as appropriate.
(b) Most areas of Yuen Long district are located within the "Scheduled Area" in the Buildings Ordinance, meaning that there are complex ground condition with possible marble cavity at the locations. The Yuen Long HOS site at Wang Yip Street West is also within the "Scheduled Area". During site identification for the HOS development, the HA made reference to the Solid & Superficial Geology Map published by the Geotechnical Engineering Office (GEO), and the GI information from the adjacent developments, so as to identify possible geotechnical problems as early as possible. However, even with careful site identification, it should be noted that the extent and effect of marble cavity often vary greatly at different locations, and can only be ascertained by detailed ground investigation. Following the resumption of the HOS, the HA immediately commenced site specific GI works for the Yuen Long HOS site at Wang Yip Street West. The detailed GI results have subsequently revealed that the marble on the site has a karstic upper surface with solution features, and there are cavities within marble in some locations.
The karstic upper features and cavities in marble will affect the load carrying capacity of foundations and their design, and in turn would affect the architectural design and building disposition. In the foundation design, the HA will take into account the geological characteristic, including the occurrence of marble cavities, and will ensure full compliance with all the prevailing regulations and standards to ensure safety and quality. We have engaged expert consultants to provide advice, selected the most suitable foundation design and construction methodology and adopted enhanced superstructure design to maximise flat production under the overriding principle of safety and cost-effectiveness. The safety of the foundation and building structure of the Wang Yip Street West HOS project has been thoroughly addressed and upon completion, the foundations will be to the same standard as any other HOS development.
In order to provide assurance to HOS owners, the HA will continue to provide a 10-year structural guarantee to all newly completed HOS developments.
(c) Ground settlement usually occurs at newly reclaimed land due to the consolidation of underlying compressible marine mud deposits. In the case of Kam Fung Court in Ma On Shan, the problem of ground settlement is due to residual consolidation of compressible marine mud after reclamation, rather than the presence of karstic upper features and cavities in marble. As the buildings of Kam Fung Court rest on pile foundations carried down to competent bedrock, ground settlement at external areas will not affect the structural integrity of the buildings. Since the conditions on the site have stabilised and ground settlement reduced, minor maintenance works for the external areas and utility services are being carried out. As for the Tung Tau Yuen Long HOS Development, the site was formed in early 1980s. According to our geotechnical appraisal, there will not be significant ground settlement upon building completion.
Ends/Wednesday, November 21, 2012
Issued at HKT 14:01
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