For discussion PWSC(96-97)110
on 5 March 1997

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Environmental Protection - Sewerage and sewage treatment
204DS - Wan Chai East and North Point sewerage

Members are invited to recommend to Finance Committee -

1. the upgrading of part of 204DS entitled "Wan Chai East and North Point sewerage, stage 1 works" to Category A at an estimated cost of $504.7 million in money-of-the-day prices; and
2. the retention of the remainder of 204DS retitled "Wan Chai East and North Point sewerage, stage 2 works" in Category B.

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PROBLEM
PROPOSAL
PROJECT SCOPE AND NATURE
JUSTIFICATION
FINANCIAL IMPLICATIONS
PUBLIC CONSULTATION
ENVIRONMENTAL IMPLICATIONS
LAND ACQUISITION
BACKGROUND INFORMATION
204DS - Wan Chai East and North Point sewerage

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PROBLEM

The existing sewerage networks in Wan Chai East and North Point districts do not have adequate capacity to serve the areas.

PROPOSAL

2. The Director of Drainage Services , with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade part of 204DS to Category A at an estimated cost of $504.7 million in money-of-the-day (MOD) prices for the construction of Wan Chai East and North Point sewerage, stage 1 works.

PROJECT SCOPE AND NATURE

3. Project 204DS - "Wan Chai East and North Point sewerage" comprises two stages of works to be carried out according to a prioritised programme. The part of the project we now propose to upgrade to Category A is the stage 1 works. A plan showing the location of these works is at Enclosure 1. The scope of the works includes -

1. 2.3 kilometres of trunk sewers (with diameters ranging from 900 to 1 800 mm) along Causeway Road, Yee Wo Street, Hennessy Road, Percival Street and Gloucester Road to the Wan Chai East sewage screening plant;
2. 4 kilometres of branch sewers (with diameters ranging from 200 to 700 mm) in Wan Chai East including Happy Valley and So Kon Po;
3. 1 kilometre of branch sewers (with diameters ranging from 200 to 500 mm) in North Point;
4. structural rehabilitation of 1.3 kilometres of existing sewers (with diameters ranging from 525 to 1 500 mm) in Wan Chai East; and
5. five dry weather flow interceptors at market places in Wan Chai East and North Point.

4. The remaining works under 204DS to be retained in Category B as stage 2 works includes the construction of -

1. 3.5 kilometres of trunk sewers (with diameter ranging from 900 to 1 800 mm) along Electric Road, Java Road and King's Road in North Point;
2. 2.8 kilometres of branch sewers (with diameter ranging from 200 to 600 mm) in North Point;
3. a new pumping station and associated ancillary works in the existing North Point sewage screening plant;
4. structural rehabilitation of 1.9 kilometres of existing sewers (with diameter ranging from 825 to 1800 mm) in North Point; and
5. rectification of expedient connections in Wan Chai East and North Point.

5. We have divided the works under 204DS into two phases so that the works for Wan Chai East area can go ahead earlier.

JUSTIFICATION

6. The sewers covered by the project were designed and constructed before 1970. They suffer from siltation problems due to the velocity of the sewage throughput being insufficient to "self-cleanse" the system. The siltation problem is especially serious in downstream coastal areas and in areas such as Causeway Bay where the sewage carries a high content of grease and oil due to the high concentration of restaurants in the area.

7. Over the past three decades, much development has taken place in the Wan Chai and North Point areas. As a result, the total capacity of the sewerage network in these areas is overloaded by about 15%¹ . We estimate that about 25% of all existing sewers are overloaded and are affected by siltation problems.

8. In June 1993, we undertook a study of the sewerage connections at the existing markets in Wan Chai East and North Point areas. This revealed some expedient connections to the sewerage systems in these areas, which divert flows from the markets (including polluted flows) into the drainage system and thereafter into the sea without treatment.

9. To rectify this situation, we plan to increase the capacity of the existing sewers and to reconstruct (at steeper gradients) those parts of the main trunk and branch sewers which have siltation problems. We also plan to construct dry weather flow interceptors at the market areas to divert flows entering the drainage system into the sewerage system. Completion of these works, will provide a sustainable sewerage system which will have sufficient capacity to meet the demand up to year 2011² and will be less vulnerable to siltation than the existing system.

10. If we do not proceed with the project, we anticipate further overloading and blockage of the existing sewerage network. This will affect the system’s efficient operation and will impose planning constraints on further development in the areas in question.

11. We have obtained the agreement of Transport Department and the Police for temporary traffic schemes to be put in place during the implementation of the project. These will minimise traffic disruption during the construction phase, and maintain road access. In busy road sections, we will work only at night or at other non-peak hours. In addition, we will use the trenchless method³ of construction for the trunk sewers, where practicable.

FINANCIAL IMPLICATIONS

12. We estimate the capital cost of the proposed works to be $504.7 million in MOD prices (see paragraph 13 below) made up as follows -

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

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

14. We have derived the MOD estimate on the basis of Government's forecasts of trend labour and construction prices for the period from 1997 to 2004. We will tender the trunk sewers works and the sewer rehabilitation works under a lump-sum contract, because we can ascertain the scope of a great part of the project works before we start construction. As the contract period will exceed 21 months, we will allow for adjustments to the tender price due to inflation.

15. We will tender the branch sewers works and the construction of the dry weather flow interceptors by means of a standard remeasurement contract because we are uncertain about the alignments of various utilities including electric cables, telephone lines, some stormwater drains and water mains. As the contract period will exceed 21 months, we will allow for adjustments to the tender price due to inflation.

16. We estimate the annually recurrent expenditure arising from the proposed sewerage works to be $6.2 million. This will be charged to the Sewage Services Trading Fund. Taking into account the current cost of $4.1 million in maintaining the existing sewerage networks in Wan Chai East and North Point, which is also charged to the Fund, the net additional recurrent expenditure chargeable to the Fund is $2.1 million. Subject to the Legislative Council passing a Resolution on appropriation of assets to the Trading Fund, the works under this project will, upon completion, become assets in the Fund valued at cost.

17. Based on the current level of sewage charges and water consumption, the proposed project by itself would lead to an increase in sewage charges by about 0.3%.

PUBLIC CONSULTATION

18. We consulted Eastern District Board and Wan Chai District Board in September 1996 on the proposed works including the temporary traffic arrangements and environmental mitigation measures during construction. Members of both District Boards supported the implementation of the proposed works.

ENVIRONMENTAL IMPLICATIONS

19. In September 1996, we completed an Environmental Impact Assessment (EIA). The EIA raised no concerns on the stage 1 works other than short term construction noise due to the proximity of some works to school and residential buildings. We will therefore require the contractors to employ a professional noise specialist and implement noise monitoring devices to ensure effective control over the construction noise impact of this project. We will control dust and site run-off nuisance through the implementation of mitigation measures in the contracts. The proposed sewerage works will improve the nearby coastal water quality by disposing into the sewerage system, untreated sewage currently discharged into the harbour via stormwater drains.

20. The Advisory Council on the Environment endorsed the EIA at its meeting on 28 October 1996.

LAND ACQUISITION

21. This project does not require land acquisition.

BACKGROUND INFORMATION

22. We completed the Wan Chai East and North Point sewerage master plan study under 141DS "Wan Chai East and North Point sewerage master plan study - consultants' fees and investigations" in August 1994. The study identified improvement works for the proper collection of sewage to treatment facilities.

23. We upgraded 204DS to Category B in October 1994. In June 1995, we upgraded part of 204DS to Category A as 195DS "Wan Chai East and North Point sewerage - consultants' fees and investigations" for employing consultants to carry out detailed design, investigation, environmental and traffic impact assessments for the whole project.

24. We have completed detailed design and tender documents for the stage 1 works. We intend to start the stage 1 works in September 1997 for completion in December 2001. We require a relatively long construction period because we need to complete the trunk sewers downstream before completing the branch sewers so that there will be sufficient capacity in the downstream trunk sewers when we commission the branch sewers. In addition, we will need to construct many sewers in short sections due to traffic considerations. We have to allow an additional nine months’ construction time because of this and the need to divert utilities along the sewer alignments.

25. The detailed design work and preparation of tender documents for the stage 2 works are in progress. We plan to start the stage 2 works in June 1998 for completion in December 2002.

Planning, Environment and Lands Branch
February 1997
(EE1063)

1 -- The capacity of the existing sewers in these areas is about 98000m³ per day.
2 -- According to the latest population forecast, we expect the Wan Chai East and North Point areas to have a population of about 371000 by 2011 which would generate a sewage flow of about 123000m³ per day.
3 -- The trenchless method refers to the use of micro-tunneling or boring techniques to construct underground sewers and drain pipes without opening up the road surface. The method, though more expensive, will greatly reduce road excavation and thus minimize disruption to traffic and underground utilities.

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Enclosure 2 to PWSC(96-97)110

204DS - Wan Chai East and North Point sewerage

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 consultants' overhead and profit, as the staff will be employed in the consultants' offices. A multiplier factor of 2.1 is applied in the case of site staff supplied by the consultants. (At 1.4.95, MPS pt. 40 = $51,440 p.m. and MPS pt. 16 = $17,270 p.m.)

(2) The figures given above are based on actual fee proposal from the consultants undertaking the investigations, design and construction supervision.

(EE1063)

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