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Following is a question on unusual site settlement occurring on the reclaimed land in Tseung Kwan O by Hon Fred LI and a oral reply by the Secretary for Works, Mr Lee Shing-see, in the Legislative Council meeting today (Wednesday) :

Question :

The Government is examining whether or not the unusual site settlement occurring on the reclaimed land in Tseung Kwan O is related to the construction works of the Strategic Sewage Disposal Scheme ("SSDS") Stage I currently in progress. In this connection, will the Government inform this Council:

(a) of the time when the authorities became aware of the unusual settlement occurring on the reclaimed land in Tseung Kwan O, the contingency measures they have subsequently taken to prevent the settlement from deteriorating, and whether they have given an account of this incident to the public;

(b) of the buildings and structures in Tseung Kwan O which have been affected by the unusual settlement; whether the authorities will conduct detailed inspections of these buildings to confirm that they are structurally safe; and whether they will take up the responsibility for solving the repair and maintenance problems caused to these buildings that have been affected by the unusual site settlement; and

(c) whether it has evaluated the other possible impacts of the SSDS construction works on the relevant districts throughout the territory; if it has, of the results of the evaluation; if it has not, of the reasons for that?

Reply:

Madam President,

(a) Concerning the time when the government became aware of unusual settlement issue in Tseung Kwan O reclaimed lands. Firstly, the Government knew about unusual settlement occurred at different areas of Tseung Kwan O at different times.

We were first verbally told by the Consultant in January 1999 that the rate of ground settlement at the site for the proposed road D4 which is situated at the south of Beverly Garden and Tong Ming Court in Tseung Kwan O Town Centre had not slowed down as anticipated. We immediately instructed the consultants to pay close attention on the ground settlement rate and to submit the ground settlement monitoring record. As revealed from the ground settlement monitoring record submitted by the consultants in April 1999, there were unusual ground settlement.

Regarding the unusual ground settlement and lowering of ground water level recorded by Mass Transit Railway Corporation (MTRC) at Area 86 of Tseung Kwan O, we knew about them in April 1999. Although, there are no buildings in this area, however we have been monitoring the situation of ground settlement in the area.

As regards the unusual settlement at Tseung Kwan O Industrial Estates firstly recorded in July 1999, the Government learnt about this from Hong Kong Industrial Estates Corporation's letter in August 1999. According to our preliminary investigation, there are no buildings in the area endangered at present.

TDD, in mid 1999, commissioned his consultant to conduct a desk-top study aiming to find out the cause(s) of the settlement, recommend further investigation work and estimate when the settlement would cease. TDD also asked the consultant to provide the ground settlement monitoring records in other areas, particularly those at the north of the proposed road D4. TDD received the first monitoring record for these areas in August 1999, which showed that slight settlement had also occurred at the monitoring stations near Tong Ming Court and Beverly Garden. The consultant, in its report submitted in September 1999, estimated that the settlement would slow down and stabilize progressively between November 1999 and March 2000. TDD, having received these preliminary findings, immediately notified other government departments of the situation and has discussed with them about these issues in detail. TDD has also arranged for further ground investigation works including drilling of boreholes to reach deep ground strata so as establish the relationship between groundwater drawdown and the unusual ground settlement.

After a high-level officals' meeting at the end of October, we decided that TDD should write and provide to the developers whose buildings being constructed, as well as the Housing Department (HD) with the records for monitoring the ground settlement and the groundwater level.

TDD had also convened a meeting with various utility companies, and briefed them on the situation and requested them to step up their inspection frequency for their own facilities.

At the same time, officials from TDD and HD had four public meetings (3, 4, 12 and 19 of November) with the residents of Tong Ming Court, Beverly Garden, etc. Officals of the Buildings Department (BD) also attended the first three meetings (3, 4, and 12 of November).

(b) Concerning the issues relating to which of the buildings and structures in Tseung Kwan O have been affected by the unusual settlement. Firstly, the Building Department has, in accordance with the Buildings Ordinance, conducted preliminary assessment and site inspection to those private buildings and structures (including those under Private Sector Participation Scheme) and found that they are structurally safe. As to buildings under construction, preliminary assessment of their foundations has not revealed that there is unsafe situation. If necessary, Building Department will coordinate with the flat owners and the developers regarding their building repairs and maintenance issues and provide appropriate assistance should situation require. Architectural Services Department has also made thorough inspections to the government buildings (mainly the schools) and do not find any signs of ground settlements occurred to these buildings except for some ground slabs. Housing Department will also conduct detailed investigation, maintenance and repairs for the properties of the Housing Authority (including public rental housing and Home Ownership Scheme flats).

(c) Before commencing the construction of the sewage tunnel works under Stage I of the Strategic Sewage Disposal Scheme (SSDS), a detailed assessment of the impact due to potential risk of ground settlement arising from the tunnel works on the affected districts has been made. Hence when the tunnel works are underneath the developed areas or districts with important structures, the contractor is required to strictly limit the water inflow in the tunnel so as to reduce the possibility of ground settlement resulting from groundwater drawdown. This is to ensure that the buildings, roads and public utilities at the districts concerned will not be affected. According to our assessment, when the tunnel works are proceeding underneath these districts, the settlement normally will not exceed 20 mm. Such an extent of settlement will not make any adverse impact on the buildings, roads and public utilities. For tunnel works underneath undeveloped areas or the seabed of Victoria Harbour, the works will not endanger any structures or utilities in areas with a distance from the tunnels, therefore the contractor is only required to limit the water inflow to a level that will not affect the progress and safety of the construction.

End/Wednesday, November 24, 1999

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