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Following is a question by the Hon Ngan Kam-chuen and a written reply by the Acting Secretary for Works, Mr Lee Shing-see, in the Provisional Legislative Council today (Tuesday):
Question:
It has been reported that severe soil settlement has occurred in the Tseung Kwan O Industrial Estate which is situated in a reclamation area. In this connection, will the Government inform this Council:
(a) of the causes of the soil settlement in the Industrial Estate; and the party which will bear the responsibility for the losses arising from the soil settlement;
(b) of the reclamation areas which were reclaimed by the same method as that adopted for the Tseung Kwan O Industrial Estate;
(c) whether the authorities have prescribed in the reclamation contracts the specific reclamation methods that have to be used by contractors, and the responsibility of contractors for the maintenance work concerned should soil settlement occur within a certain period after the reclamation; and
(d) of the methods for stabilizing the sludge on the sea floor when reclamation is carried out?
Reply:
Madam President,
The land at Tseung Kwan O Industrial Estate was reclaimed by the Hong Kong Industrial Estates Corporation (HKIEC). The HKIEC appointed their own consultant for the design and supervision of the construction of the reclamation. They also directly employed the contractor for the reclamation works. The Territory Development Department, however, was engaged by the HKIEC to give advice in connection with their consultant management, and assisted in any necessary co-ordination with nearby government works projects.
The Administration's response to parts (a) to (d) of this question is as follows:
(a) As for all land formed from reclamation, settlement occurs both during and after construction as a result of consolidation of soil beneath the original seabed as water is squeezed out due to the weight of fill material placed on top, as well as consolidation of the fill material itself. Such consolidation is a long term process and may take many years to complete; and residual settlement is normally expected for some years after construction, the extent of which varies depending on the method of reclamation. Contractors cannot be held liable for such settlement or its effects if they have completed the reclamation in accordance with the contract specifications.
In the case of the Tseung Kwan O Industrial Estate reclamation, the measures that have been taken to accelerate the consolidation process include the placement of 600,000 sq. metres of geotextile fabric and the installation of vertical drains with a total length of some 5,400,000 metres. Land plots in industrial estates are granted to the companies which satisfy the selection criteria of the Hong Kong Industrial Estates Corporation. These companies are responsible for building their own premises to suit their purposes. We understand that all grantees are given data on the site conditions and are warned to adopt appropriate foundation and building design for works on the newly reclaimed estate prior to commencing their works.
(b) The following reclamation areas have been reclaimed using the same or similar reclamation method as that adopted in Tseung Kwan O Industrial Estate:
(i) all other reclamation in Tseung Kwan O;
(ii) about one third of the West Kowloon Reclamation area;
(iii) Aldrich Bay Reclamation;
(iv) Tuen Mun Area 38 Reclamation;
(v) Pak Shek Kok Reclamation; and
(vi) Tamar Basin, Central Reclamation
(c) The relevant reclamation method and the required standards have been specified in all of the above contracts including that for the Tseung Kwan O Industrial Estate reclamation works. The contractor is only liable for any settlement resulting from his non-compliance with the contract specifications. In such circumstances, he will be responsible for any remedy as provided under the terms of the contract. Maintenance is normally the responsibility of the land user or allocatee as stipulated under the relevant conditions of grant or allocation.
(d) In general, for reclamation works where the marine mud is not dredged away, a suitable geotextile fabric is placed on top of the marine mud to contain it in position while allowing water dissipation. It is then covered with a layer of sand to help control lateral displacement of the mud and to drain away the water dissipated from the marine mud. Fill material is then placed on the sand in layers of uniform thickness until the reclamation is complete.
Vertical settlement occurs as the great weight of the fill material squeezes the water out of the mud causing it to consolidate. We can speed up the consolidation process and hence settlement by inserting vertical drains through the marine mud to allow water to drain away more quickly. Placing temporary surcharge loads on the reclamation, say, for up to one year can further speed up the settlement. However, this is expensive and time consuming, and some noticeable minor residual settlement may still occur for a number of years. There is currently no practical method available to completely prevent such settlement.
End/Tuesday, April 7, 1998
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