For discussion PWSC(97-98)56
on 4 November 1997
ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE
HEAD 709 - WATERWORKS
Water Supplies - Salt water supplies
29WS - Improvement to Tsuen Wan/Kwai Chung salt water supply
Members are invited to recommend to Finance Committee the upgrading of 29WS to Category A at an estimated cost of $321.4 million in money-of-the-day prices for the construction of new salt water mains and the replacement of aged mains in Tsuen Wan and Kwai Chung districts.
The existing salt water supply system in Tsuen Wan and
Kwai Chung is not able to meet the growing demand from the districts and lacks operational flexibility to ensure a reliable supply for flushing.
2. The Director of Water Supplies (DWS), with the support of the Secretary for Works, proposes to upgrade 29WS to Category A at an estimated cost of $321.4 million in money-of-the-day (MOD) prices for the laying of new salt water mains and the replacement of aged mains in Tsuen Wan and Kwai Chung districts.
PROJECT SCOPE AND NATURE
3. The scope of the project comprises the laying of -
- approximately 2.1 kilometres of salt water mains of diameters ranging from 450 millimetres to 600 millimetres from Tsuen Wan central salt water pumping station to Tsuen King Circuit via Hoi Hing Road and Castle Peak Road;
- approximately 5.6 kilometres of salt water mains of diameters ranging from 800 millimetres to 900 millimetres from Tsuen Wan central salt water pumping station to Wo Yi Hop Road via Yeung Uk Road, Texaco Road, Kwai Shing Circuit and Castle Peak Road;
- approximately 400 metres of salt water mains of 1200 millimetres in diameter from Hoi Kwai Road to Yeung Uk Road;
- approximately 400 metres of salt water mains of 400 millimetres in diameter from Texaco Road to Peninsula low level salt water service reservoir via Shek Tau Street; and
- approximately 700 metres of salt water main of 450 millimetres in diameter in Yeung Uk Road.
4. We installed the existing salt water supply system in Tsuen Wan and Kwai Chung districts in the 1960s. Most of the salt water mains in this system are asbestos cement pipes which have reached the end of their useful life. The effects of aging have caused frequent bursts and leaks of these water mains in the past few years, causing traffic disruption and interruption of flushing water supply. The existing network lacks the flexibility necessary to avoid the suspension of supply to large areas when a burst occurs or when routine maintenance needs to be conducted.
5. The existing salt water system's carrying capacity has also become insufficient to cope with the increasing demand for flushing water arising from the redevelopment of older building blocks into high-rise residential and commercial blocks in Tsuen Wan and Kwai Chung districts. We need to enhance the existing system with more flexibility in the method of operation by laying new mains and replacing some of the aged mains. This will improve the reliability of the existing system. The new mains will also be able to meet the increase in salt water demand from the current level of 57 000 cubic metres per day to 71 000 cubic metres per day projected for 2011.
6. We estimate the capital cost of the project to be $321.4 million in MOD prices (see paragraph 7 below), made up as follows -
|(a) Pipe materials|| 28.9
|(b) Mainlaying by open cut method||120.1
|(c) Mainlaying by trenchless techniques||30.9
|(d) Consultants' fee for construction stage||0.6
|(e) Resident site staff expenses||34.5
|(g) Inflation allowance||84.9
(in MOD prices)
A breakdown by man months of the estimates for consultants' fees including resident site staff expenses is at the Enclosure.
7. Subject to approval, we will phase the expenditure as follows -
|1997 - 98||0.3||1.06750||0.3
|1998 - 99||27.3||1.16358 ||31.8
|1999 - 2000||89.4||1.26830 ||113.4
|2000 - 01||62.0||1.38244 ||85.7
|2001 - 02||31.0||1.50686 ||46.7
|2002 - 03||26.5||1.64248 ||43.5
8. We have derived the MOD estimates on the basis of the Government's forecast of trend labour and construction prices for the period between 1997 and 2003. As the quantities of mainlaying works may vary with the actual ground conditions, we will tender the works under a standard re-measurement contract. We will provide for adjustment due to inflation in the contracts because the construction period will last longer than 21 months.
9. We estimate the additional annually recurrent expenditure for the project to be $547,000.
10. This project, by itself, will lead to an increase in water charges by 0.1% in real terms by 20031.
11. We consulted the Environmental Affairs Committee of the Tsuen Wan District Board on 27 May 1997 and the Kwai Tsing District Board on
8 May 1997. Both of them supported the proposed project but expressed concern on the traffic arrangement during the construction period. We will address their concerns by incorporating relevant control clauses into the works contracts and closely supervising the construction activities of the contractors in order to ensure that the traffic flow in the vicinity of the work sites will not be adversely affected.
12. The Director of Environmental Protection completed an environmental review on 29WS in August 1993 and concluded that the project would have no long term environmental impacts and an Environmental Impact Assessment was not necessary. We will control noise, dust and site run-off during construction to comply with established standards and guidelines through the implementation of relevant mitigation measures in the works contract.
13. The project does not require land resumption. The Director of Lands however will clear 0.1347 hectare of Government land for the project but the clearance will not affect any households. We will charge the estimated clearance cost of $0.1 million to Head 701 - Land Acquisition.
14. We upgraded this project to Category B in September 1994. We have engaged consultants to carry out site investigation, traffic impact assessment and detailed design for the works at a cost of $3.5 million and have charged this amount to block allocation Subhead 9100WX "Waterworks, studies and investigations for items in Category D of the Public Works Programme"
15. The consultants have completed the traffic impact assessment and detailed design for the project. To keep the inconvenience to road users to a minimum, we will limit the number and length of traffic lanes to be occupied for the construction work in those roads where normal excavation methods are feasible. We will adopt trenchless techniques to lay the water mains at road junctions and will carry out the mainlaying works at other roads with heavy traffic outside peak periods. We have included all these requirements into the detailed design.
16. We plan to start the construction work in February 1998 for completion in February 2000.
1The increase in water charges is calculated on the assumption that the fresh water demand remains static during the period from 1997 to 2003 and that the amount of Governement subsidy to the waterworks operations is contained at the present level.
Enclosure to PWSC(97-98)56
29WS - Improvement to Tsuen Wan/Kwai Chung salt water supply
Breakdown of estimates for consultants' fees
DETAILS FOR CONSULTANTS' FEES
|Consultants' staff costs|| Estimated|
|(a) Consultants' fees for works in the construction stage ||Professional|
|(b) Site supervision by resident site staff employed by the consultants||Professional|
|Total consultants' staff cost||35.1
1. A multiplier factor of 3 is applied to the average MPS point to arrive at the full staff costs including the consultants' overheads and profit, as the staff will be employed in the consultants' offices. (at 1.4.96 MPS Pt. 40 = $55,390 and MPS Pt. 16 = $18,595 pm). A multiplier factor of 2.1 is applied to the average MPS in the case of site staff supplied by the consultants.
2. The figures given above are based on estimates prepared by the Director of Water Supplies. We will only know the actual consultants' fees upon finalisation of the account of the works contract.
Last Updated on 1 November 1997