For discussion PWSC(96-97)18
on 12 June 1996
ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE
HEAD 709 - WATERWORKS
Water Supplies - Salt water supplies
34WS - Reconstruction of Diamond Hill salt water service reservoir
Members are invited to recommend to Finance Committee the upgrading of 34WS to Category A at an estimated cost of $53.9 million in money-of-the-day prices.
The roof slabs, columns and floor slabs of the existing Diamond Hill salt water service reservoir (DHSR) have deteriorated to a poor state due to ageing and the corrosive effect of the saline environment. We need to reconstruct these parts of the reservoir to prevent disruption of the salt water supply to Kowloon City, Wang Tau Hom, Wong Tai Sin and Tze Wan Shan areas.
2. The Director of Water Supplies (DWS), with the support of the Secretary for Works, proposes to upgrade 34WS to Category A at an estimated cost of $53.9 million in money-of-the-day (MOD) prices for the reconstruction of the Diamond Hill salt water service reservoir and the reprovisioning of the public recreational facilities on the top of the reservoir.
3. The scope of the project comprises -
- demolition and reconstruction work at the reservoir; and
- reprovisioning of the public recreational facilities on the top of the reservoir.
4. The DHSR is an essential part of the salt water flushing supply system serving Kowloon City, Wang Tau Hom, Wong Tai Sin and Tze Wan Shan. The public makes use of the open space on the top of the DHSR for recreational purposes.
5. In recent years, the roof slabs, columns and floor slabs of DHSR have deteriorated to a poor state due to ageing and the corrosive effect of the saline environment despite regular maintenance. We have found concrete spalling, cracking, delamination and corroded reinforcement bars in many columns. Collapse of the currently deteriorating reservoir roof will disrupt the salt water supply to these areas. For safety reasons, we have not allowed public access to the open space on the top of the reservoir and erected temporary supports inside the service reservoir to reinforce support to the roof while the reservoir is still in service. We consider that the defects are beyond economic repair. Having regard to safety and the need to prevent disruption of flushing supply to the areas served by the reservoir, we plan to carry out the reconstruction of the reservoir and the reprovisioning of the public recreational facilities on the top of the reservoir as soon as possible.
6. We estimate the capital cost of the project to be $53.9 million in MOD prices (see paragraph 7 below), made up as follows -
| $ million
|
|---|
| (a) Demolition and reconstruction work | 35.1
|
| (b) Reprovisioning of recreational facilities | 1.0
|
| (c) Contingencies | 3.6
|
Sub-total
(at December 1995 prices) | 39.7
|
| (d) Inflation allowance | 14.2
|
Total
(in MOD prices) | 53.9
|
7. Subject to approval, we will phase the expenditure as follows -
|
Year
|
$million
(Dec 1995)
|
Price
Adjustment
factor
|
$million (MOD)
|
|---|
|
1996 - 97
|
0.2
|
1.07500
|
0.2
|
|
1997 - 98
|
9.9
|
1.18250
|
11.7
|
|
1998 - 99
|
11.2
|
1.30075
|
14.6
|
|
1999 - 2000
|
9.9
|
1.43083
|
14.2
|
|
2000 - 01
|
8.5
|
1.54708
|
13.2
|
|
39.7
|
|
53.9
|
8. We have derived the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices over the period 1996 to 2001. We will tender the civil engineering works as a lump sum contract with provision for inflation adjustment. We will allow inflation adjustment in the contract provision because the contract period exceeds 21 months.
9. The project will not give rise to any additional annually recurrent expenditure.
10. We consulted the Environment Committee of the Wong Tai Sin District Board on 26 March 1996. The Committee had no objection to the proposed works.
11. The Director of Environmental Protection (DEP) vetted a preliminary environmental review on this project completed by DWS in September 1995. Because of the location and nature of this project, DEP envisages that there is limited potential for adverse impacts on the environment associated with the operation of the service reservoir. He advises that there is no need to carry out an Environmental Impact Assessment. For the proper disposal of washwater arising from cleaning of the service reservoir during operation, DWS will implement mitigation measures as recommended by the Feasibility Study on Cleaning and Disinfection of Service Reservoirs and Disposal of the Effluent' to be completed by the end of 1996. For short term impacts, DWS will implement appropriate mitigation measures to contain construction noise, dust and site run-off within established standards and guidelines through the incorporation of standard pollution control clauses in the construction contract.
12. The project does not require land acquisition.
13. The existing DHSR is over 40 years old. It has a capacity of 22 000 cubic metres. It provides salt water supply for flushing to Kowloon City, Wang Tau Hom, Wong Tai Sin and Tze Wan Shan areas. We sub-allocate the open space on the top of the DHSR to the Urban Services Department for public recreational purposes.
14. The DHSR has two separate compartments. We will carry out the reconstruction work in phases such that at any one time only one compartment will be closed down while the other will remain in service so as to maintain the flushing supply to the areas served by the reservoir.
15. We upgraded this project to Category B in January 1996. We have completed the detailed design and preparation of drawings for the project. We plan to invite tenders for the works in September 1996 with a view to starting the site work in January 1997 for completion in December 1998.
(GG621)
Last Updated on 8 December 1998
