For discussion PWSC(95-96)72
on 10 January 1996

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Environmental Protection - sewerage and sewage treatment
208DS - Outlying Islands sewerage, stage 1, phase 1

Members are invited to recommend to Finance Committee -

1. the upgrading of part of 208DS, entitled "Outlying Islands sewerage, stage 1, phase 1 - consultants' fees and investigations" to Category A at an estimated cost of $24 million in money-of-the-day prices; and
2. the retention of the remainder of 208DS in Category B.

---

PROBLEM
PROPOSAL
PROJECT SCOPE AND NATURE
JUSTIFICATION
FINANCIAL IMPLICATIONS
PUBLIC CONSULTATION
ENVIRONMENTAL IMPLICATIONS
LAND ACQUISITION
BACKGROUND INFORMATION
208DS - Outlying Islands Sewerage Stage 1 Phase 1

---

PROBLEM

The existing sewerage facilities at Ngong Ping, Siu Ho Wan, Peng Chau, Yung Shue Wan, Cheung Chau and Mui Wo are inadequate to cope with the increasing sewage flows generated from existing developments and visitors.

PROPOSAL

2. The Director of Drainage Services (DDS), with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade part of 208DS to Category A at an estimated cost of $24 million in money-of-the-day (MOD) prices to engage consultants to undertake site investigations, an environmental impact assessment and detailed design for sewerage improvement works in the areas mentioned above.

PROJECT SCOPE AND NATURE

3. The sewerage improvement works under 208DS consist of construction of new and improved sewage treatment facilities at six locations - Ngong Ping, Siu Ho Wan, Peng Chau, Yung Shue Wan, Cheung Chau and Mui Wo. The works of the whole project comprise the following -

1. construction of trunk sewers and sewage treatment plant at Ngong Ping on Lantau Island to serve the large visitor population;
2. upgrading of the preliminary sewage treatment plant now being constructed under 2429CL - North Lantau Development phase 1 remaining works at Siu Ho Wan on Lantau Island to chemically enhanced primary level¹ ;
3. construction of a pumping station at Peng Chau and a submarine pipeline from Peng Chau to Discovery Bay;
4. construction of a sewage treatment plant and a submarine outfall at Yung Shue Wan on Lamma Island;
5. construction of a new submarine outfall for better dispersal of the treated sewage at Cheung Chau; and
6. upgrading of sewage sludge dewatering facilities for the existing sewage treatment plants at Cheung Chau and Mui Wo.

4. The part of the project which we now propose to upgrade to Category A comprises -

1. site investigations at the six locations mentioned in paragraph 3 above;
2. environmental impact assessment for the works under 208DS; and
3. detailed design (including preparation of tender documents and assessment of tenders) for the sewerage improvement works at Ngong Ping and Siu Ho Wan² mentioned in paragraph 3(a) and (b) above.

JUSTIFICATION

5. We completed 4146DS - Outlying Islands sewerage master plan study - consultants’ fees and investigations in December 1994. The study recommended inter alia a prioritised programme of works to improve the existing sewerage facilities at the six locations mentioned above to ensure that all wastewater generated in these areas is collected for proper treatment and disposal.

6. Ngong Ping, Siu Ho Wan, Peng Chau, Yung Shue Wan, Cheung Chau and Mui Wo are among those other areas of the outlying islands which either lack suitable sewerage facilities or sewage treatment plants with adequate capacity. Wastewater generated from existing developments and visitors during weekends or holidays pollutes the local streamcourses and the coastal waters. We estimate that the population of these areas will increase from the existing 45 000 to about 275 000 by 2011 and that the maximum number of day visitors to these areas will also increase from the existing 40 000 to 53 000 by 2011. We consider that the existing sewerage facilities are inadequate to cope with the increasing volumes of sewage generated from these areas.

7. The proposed new sewerage facilities at Ngong Ping, Peng Chau and Yung Shue Wan, as set out in paragraph 3(a), (c) and (d) above, will provide an additional sewage treatment capacity of 4 300 m³/day.

8. In carrying out the design for the Siu Ho Wan preliminary sewage treatment plant under 2429CL, we have already made provision for the possible upgrading of the treatment plant to chemically enhanced primary treatment level which is significantly more effective in the removal of all solids, in particular floatable solids. We consider it necessary to upgrade the treatment plant now because of the drift of floatable solids including oil and grease to the nearby swimming areas. The oil and grease also affect adversely the life of flora and fauna at the seabed.

9. After the upgrading of the existing sewage sludge dewatering facilities for the sewage treatment works at Cheung Chau and Mui Wo (paragraph 3(f) above refers), we will dewater the sludge collected to meet the Director of Environmental Protection’s latest standard with a minimum of 30% dry solids content³ . If we do not upgrade the sludge dewatering facilities, we estimate that the Government would need to pay an additional amount of $0.6 million a year to the landfill contractors to handle the wet sludge⁴ .

10. If we do not implement the proposed sewerage improvement works, existing developments will continue to discharge wastewater directly to streamcourses or the sea. The improved sewerage systems at the above locations will provide sufficient capacity with better treatment quality to meet future demand up to the year 2011.

11. In order to obtain the necessary information for carrying out the detailed design for the proposed sewerage improvement works, we have to carry out site investigations at the said locations including ground investigations as well as topographic and hydrological survey. We also need to conduct an environmental impact assessment for the works under 208DS to identify the visual, odour, noise and ecology impacts during the construction and operation stages so as to recommend appropriate mitigation measures to address any environmental problems identified. Having examined the in-house staff resources available, DDS considers it necessary to employ consultants to carry out the works mentioned in paragraph 4(a) and (b) above.

12. As regards the work mentioned in paragraph 4(c) above, DDS has already deployed all of his in-house resources available to design the sewerage improvement works at Peng Chau, Yung Shue Wan, Cheung Chau and Mui Wo. The improvement works at Siu Ho Wan and Ngong Ping also involve relatively large projects⁵ . DDS therefore proposes to also employ consultants to carry out the design.

FINANCIAL IMPLICATIONS

13. We estimate the cost of the proposed consultancy to be $24 million in MOD prices, made up as follows -

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

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

15. We derive the MOD prices on the basis of the Government's forecast of trend labour and construction prices over the period between 1995 and 1999. We will award the proposed consultancy on a lump-sum basis with provision for inflation adjustment. We allow inflation adjustment in the contract provision as the consultancy duration will exceed 12 months.

16. The proposed consultancy will not give rise to any recurrent expenditure.

PUBLIC CONSULTATION

17. The Director of Environmental Protection has presented the sewerage extension and improvement works project to the Islands District Board on 24 April 1995. The Board had no objection to the implementation of the sewerage extension and improvement works.

ENVIRONMENTAL IMPLICATIONS

18. We have conducted an environmental review under 4146DS. As recommended, we will employ consultants at an estimated cost of $3.5 million (included in the consultants' fees) to assess the environmental impacts and to recommend mitigation measures to address problems likely to arise during construction and operation of the sewerage improvement works.

LAND ACQUISITION

19. The proposed consultancy does not require land acquisition.

BACKGROUND INFORMATION

20. The study under 4146DS examined the inadequacy of the existing sewerage 7infrastructure and recommended the improvement works be implemented under two stages. The study recommended those items which have no major land problems to be implemented under 208DS.

21. We schedule the proposed investigations and consultancy for 208DS to start in February 1996 for completion in September 1998, and gazette in May 1997 works which are required to be gazetted under the Foreshore and Sea-bed (Reclamations) Ordinance. We plan to implement the stage 1, phase 1 work packages starting January 1997 for the upgrading of sewage sludge dewatering facilities at Cheung Chau and Mui Wo and October 1998 for other works in the packages. The works will be substantially completed by December 2000.

22. The remaining improvement works of Outlying Islands sewerage, stage 1 involve the construction of sewerage systems at Mui Wo, Peng Chau, Cheung Chau, Yung Shue Wan, Sok Kwu Wan and other North Lamma villages. We are currently identifying the land problems and any necessary solutions. We schedule this work to be completed in mid 1996.

23. Outlying Islands sewerage, stage 2 improvement works involve provision of trunk sewers and village sewerage systems to serve South Lantau, further improvements to sewerage systems at Mui Wo, Tai O, Peng Chau, Cheung Chau, Yung Shue Wan, Sok Kwu Wan and other North Lamma villages, and upgrading of existing sewage treatment works at Tai O. We shall carry out a review in late 1998 to determine an improvement programme for the stage 2 works.

Decision : withdrawn

1 -- Chemically enhanced primary level treatment refers to the addition of chemicals to sewage to alter the physical state of suspended and dissolved solids and to facilitate their removal byy sedimentation.
2 -- Drainage Services Department in-house staff will carry out detailed design for sewerage improvement works for Peng Chau, Yung Shue Wan, Cheung Chau and Mui Wo, with input from consultants on environmental impact assessment.
3 -- We have recently informed Members of the Director of Environmental Protection's latest standard with a minimum of 30% dry solids content by the PWSC paper on 200DS - Upgrading of sewage treatment works for sludge disposal (PWSC(95-96)65) issued for discussion on 6 December 1995.
4 -- The contracts for the strategic landfills are structured such that the wetter the sludge being deposited, the higher levy charged. If the sludge is dewatered to a higher dry solids content of 30%, we can avoid paying the landfall contractor a higher rate.
5 -- The construction costs of the improvement works at Siu Ho Wan and Ngong ping are estimated at $328 million and $21.5 million respectively at December 1994 prices.

---

Enclosure to PWSC(95-96)72

208DS - Outlying Islands Sewerage Stage 1 Phase 1

Breakdown of estimates for consultants' fees

Notes:

1. The average estimated cost per professional man-month is about equivalent to an Engineer on MPS point 44.
2. The average estimated cost per technical man-month is about equivalent to a Technical Officer on MPS point 20.
3. The figures given above are based on estimates prepared by the Drainage Services Department. We will only know the actual man-months and actual fees when we have selected the consultants through the usual competitive consultants selection procedure.

---