For discussion PWSC(96-97)76
on 18 December 1996

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Civil Engineering - Drainage and erosion protection
78CD - Stormwater drainage master plan study in Tuen Mun and Sham Tseng

Members are invited to recommend to Finance Committee the upgrading of 78CD to Category A at an estimated cost of $22.6 million in money-of-the-day prices.

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PROBLEM
PROPOSAL
PROJECT SCOPE AND NATURE
JUSTIFICATION
FINANCIAL IMPLICATIONS
PUBLIC CONSULTATION
ENVIRONMENTAL IMPLICATIONS
LAND ACQUISITION
BACKGROUND INFORMATION
78CD - Stormwater drainage master plan study in Tuen Mun and Sham Tseng

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PROBLEM

Many areas in the Tuen Mun and Sham Tseng drainage catchment basins are susceptible to serious and frequent flooding. The existing stormwater drainage system is inadequate to meet current flood protection standards.

PROPOSAL

2. The Director of Drainage Services (DDS), with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade 78CD to Category A at an estimated cost of $22.6 million in money-of-the-day (MOD) prices for the appointment of consultants to undertake a drainage master plan study in Tuen Mun and Sham Tseng. The area boundary of the study is shown at Enclosure 1.

PROJECT SCOPE AND NATURE

3. The scope of the project comprises the following -

1. preparing a computerised asset inventory and developing an asset management system for the stormwater drainage system to facilitate future system maintenance and development appraisal;
2. reviewing the capacity of the existing stormwater drainage system using hydrological/hydraulic modelling;
3. examining conditions and assessing performance of the existing stormwater drainage system to identify critical areas requiring improvements;
4. carrying out an environmental review to identify the various potential environmental concerns, the likely mitigation measures required, and the need for detailed environmental impact assessment on the improvements referred to at (c) above; and
5. developing cost-effective options with prioritised implementation programmes to improve the stormwater drainage system.

JUSTIFICATION

4. Tuen Mun and Sham Tseng are major residential and industrial areas with a population over 500, 000. Due to extensive urbanisation and rapid development in the areas, natural pervious uncultivated land and farm land have been paved and have become impermeable areas. During severe rainstorms, a large proportion of rainwater may remain on the ground surface instead of dissipating naturally as groundwater. The surface runoff then enters into the stormwater drainage system within a short period. Flooding will occur on occasions when the system is unable to cope with the sudden large amount of stormwater.

5. We built the main skeleton of the existing stormwater drainage system 15 to 30 years ago. Stormwater drainage systems have an average life span of about 25 years. Over the years, we have made numerous localised modifications and extensions to the drainage system. Nevertheless, these measures are not sufficient to prevent flooding. We therefore need to conduct a comprehensive study to identify the exact location of flood prone areas and dreaw up cost-effective methods to improve the capacity and reliability of the drainage system to redress the flooding problem.

6. The proposed study will examine the condition of the existing stormwater drainage system in Tuen Mun and Sham Tseng and assess its performance. After we have identified areas requiring improvement, we will recommend appropriate improvement measures and develop an asset inventory and asset management system for the efficient management of the drainage system and forward planning of extensions to the system.

7. DDS proposes to engage consultants to undertake the study because he has insufficient in-house staff resources.

FINANCIAL IMPLICATIONS

8. We estimate the cost of the proposed study to be $22.6 million in MOD prices (see paragraph 9 below), made up as follows -

A breakdown by man months of the estimate for consultants' fees is at Enclosure 2.

9. Subject to approval, we will phase expenditure as follows -

10. We have derived the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices for the period 1996 to 2000. We will tender the proposed consultancy on a lump-sum basis. The main consultants will in turn appoint contractors for specialist investigations through a tendering process. We will allow for inflation adjustment in the consultancy agreement as the project duration is more than 12 months.

11. The proposed consultancy will not give rise to any recurrent expenditure and would have no impact on sewage charges.

PUBLIC CONSULTATION

12. As the study involves investigation and analysis only, we consider public consultation unnecessary.

ENVIRONMENTAL IMPLICATIONS

13. The proposed consultancy will not have any adverse environmental impacts. The study will include an environmental review to identify potential environmental concerns, any mitigation measures required and the need for an Environmental Impact Assessment.

LAND ACQUISITION

14. The study does not require land acquisition.

BACKGROUND INFORMATION

15. The Governor’s 1995 Policy Address included a commitment to conduct seven drainage master plan studies covering all flood prone areas in the Territory. We upgraded 83CD "Yuen Long, Kam Tin, Ngau Tam Mei and Tin Shui Wai drainage master plan study", 75CD "Stormwater drainage master plan study on northern Hong Kong Island" and 76CD "Stormwater drainage master plan study in Tsuen Wan, Kwai Chung and Tsing Yi" to Category A in January 1996, May 1996 and July 1996 respectively. 78CD is the fourth in the series of the studies we plan to conduct. The implementation programme for the seven drainage master plan studies is set out on the map of the "Drainage Master Plan Areas" at Enclosure 3.

16. We upgraded 78CD to Category B in September 1995. We plan to commence the proposed study in February 1997 for completion in August 1998.

17. Subsequent to the completion of the study in August 1998, we will make the necessary arrangements to have the study results endorsed, prepare and obtain approval of the necessary preliminary project feasibility studies and employ consultants to complete the detailed design work for the project by mid 2000. We anticipate that the main construction works will start in mid 2000 for completion in late 2004.

(JJ141)

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Enclosure 2 to PWSC(96-97)76

78CD - Stormwater drainage master plan study in Tuen Mun and Sham Tseng

Breakdown of estimates for consultants' fees -

Notes

(1) A multiplier factor of 3 is applied to the average MPS point to arrive at the full staff costs including the consultant's’ overheads and profit as the staff will be employed in the consultant's’ offices. (At 1.4.95, MPS pt. 40 = $51,440 p.m. and MPS pt. 16 = $17,270 p.m.)

(2) Out-of-pocket expenses are the actual costs incurred. The consultants areis not entitled to any additional payment for overheads or profit in respect of these items.

(3) The figures given above are based on estimates prepared by the Director of Drainage Services. We will only know the actual man months and actual fees when we have selected the consultants through the usual competitive lump-sum fee bid system.

(JJ141)

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