For discussion PWSC(96-97)56
on 6 November 1996

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Environmental Protection - Sewerage and sewage treatment
132DS - Port Shelter sewerage
272DS - Port Shelter sewerage, stage 2

Members are invited to recommend to Finance Committee -

1. the upgrading of 132DS and part of 272DS, retitled "Port Shelter sewerage, stage 1 phase 2 and stage 2 phase 2 - Silverstrand, Tai Wan and Sha Ha sewerage", to Category A at an estimated total cost of $105 million in money-of-the-day prices; and
2. the retention of the remainder of 272DS in Category B.

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PROBLEM
PROPOSAL
PROJECT SCOPE AND NATURE
JUSTIFICATION
FINANCIAL IMPLICATIONS
PUBLIC CONSULTATION
ENVIRONMENTAL IMPLICATIONS
LAND ACQUISITION
BACKGROUND INFORMATION

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PROBLEM

The private septic tanks and sewage treatment plants in Silverstrand and in the villages in Tai Wan and Sha Ha at Port Shelter are ineffective in treating sewage generated in these areas. As a result, the poorly-treated sewage is polluting the stream courses and the surrounding water bodies.

PROPOSAL

2. The Director of Drainage Services, with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade 132DS and part of 272DS to Category A at an estimated total cost of $105 million ($80 million for 132DS and $25 million for part of 272DS) in money-of-the-day (MOD) prices for the construction of phase 2 of both stages 1 and 2 of the Port Shelter sewerage works.

PROJECT SCOPE AND NATURE

3. The works under 132DS include the construction of the following works in Silverstrand -

1. five sewage pumping stations;
2. about 4 000 metres of sewers (with diameters ranging from 225 to 450 millimetres) and about 1 500 metres of rising mains (with diameters ranging from 100 to 300 millimetres); and
3. house connection works¹ for about 85 private lots.

4. The part of works under 272DS which we propose to upgrade to Category A includes the construction of the following works in Tai Wan and Sha Ha -

1. one sewage pumping station;
2. about 2 500 metres of sewers (with diameters ranging from 225 to 300 millimetres) and about 600 metres of rising mains (150 millimetres in diameter); and
3. house connection works for 95 private lots.

5. The remaining works of 272DS for retention in Category B include the construction of -

1. 1 500 metres of sewers at Sha Kok Mei;
2. three sewage pumping stations, 8 250 metres of sewers and 800 metres of rising mains at Pak Kong, Wong Chuk Wan and in the environs of Sai Kung;
3. four sewage pumping stations, 6 000 metres of sewers and 2 000 metres of rising mains at Tai Chung Hau, Pak Sha Wan, Kau Sai San Tsuen and Ta Ho Tun; and
4. one sewage pumping station, 5 000 metres of sewers and 500 metres of rising mains at Tai Po Tsai and Mang Kung Uk.

JUSTIFICATION

6. The Port Shelter Sewerage Master Plan Study completed in March 1991 identified that a number of private sewage treatment facilities leading to Port Shelter had design or operation problems. The study recommended replacing these facilities by public sewerage systems in four stages having regard to cost and environmental effect criteria.

7. There is no public sewers in Silverstrand and the villages in Tai Wan and Sha Ha. The existing sewerage facilities in these areas are either private septic tanks or sewage treatment plants. Silverstrand is a popular bathing beach and is highly vulnerable to faecal contamination due to discharge from the private treatment facilities. We have been ranking the quality of the beach water as "acceptable", compared with "good" and "fair" in respect of other nearby beaches.

8. In order to achieve long term water quality improvement in Port Shelter, we need to provide sewerage systems including house connection works and sewage pumping stations in both Silverstrand and the villages in Tai Wan and Sha Ha. We will serve notice to owners of the concerned premises requiring them to construct corresponding terminal manholes within their private lots ² in line with the progress of the house connection works. Upon completion of the terminal manholes, we will be able to channel the sewage of concerned households in these two areas via the proposed sewerage systems to the Tseung Kwan O sewage treatment works and Sai Kung sewage treatment works respectively for proper treatment and disposal.

FINANCIAL IMPLICATIONS

9. We estimate the capital cost of the proposed works to be $105 million in MOD prices (see paragraph 10 below), made up as follows -

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

11. 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 2001. We will tender the civil engineering works of the project under a standard remeasurement contract because the exact alignments and invert levels of the sewers/rising mains laying works required under the proposed scheme may vary due to uncertain ground conditions. The tender price will be subject to adjustment for inflation because the contract period will be longer than 21 months. We will tender the electrical and mechanical works of the pumping stations under a fixed-price lump-sum contract because we can clearly define the scope of the relevant works in the contract.

12. We estimate the annual recurrent expenditure for the proposed works under 132DS and the part of 272DS to be $2.38 million and $0.47 million respectively. We will charge these expenditures to the Sewage Services Trading Fund. Subject to the Legislative Council passing a Resolution on appropriation of assets to the Trading Fund, the proposed sewerage works will, upon completion, become assets in the Fund valued at cost.

13. Based on the current level of sewage charges, the proposed project by itself would lead to an increase in sewage charges by about 0.4%.

PUBLIC CONSULTATION

14. We briefed the Sai Kung District Board on the works to be covered by Port Shelter sewerage stages 1 and 2 in September 1992 and January 1994 respectively. We completed consultation on the proposed sewerage works with residents of Silverstrand and village representatives of Tai Wan and Sha Ha in July 1992 and March 1995 respectively. They all supported the implementation of the proposed project.

ENVIRONMENTAL IMPLICATIONS

15. The Director of Environmental Protection completed the Environmental Reviews of the sewerage works in Silverstrand and the villages in Tai Wan and Sha Ha in December 1992 and May 1994 respectively. He concluded that the proposed sewerage works would not have any long term environmental impact and that an Environmental Impact Assessment study is not required. As there is no change in the scope of works since the completion of the Environmental Reviews, the findings are still valid.

16. The proposed sewerage works, when completed, will improve the water quality in the stream courses and in the surrounding water bodies. We will provide adequate odour removal equipment to control the potential odour emission arising from the pumping stations at an estimated cost of $3.8 million which has been included in the project estimate. For short term impacts, we will control noise, dust and site run-off nuisances during construction through the implementation of mitigation measures in the works contract.

LAND ACQUISITION

17. The proposed works do not require land acquisition.

BACKGROUND INFORMATION

18. The consultancy study commissioned in October 1989 under 102DS "Port Shelter sewerage master plan study - consultants’ fees and investigations" recommended measures for implementation in four stages for various locations to reduce water pollution at Port Shelter. The scopes of individual stages are as follows -

1. Stage 1 works comprise the upgrading of the Sai Kung sewage treatment works phase 1 and the provision of sewers at Tan Cheung, Po Lo Che, Tui Min Hoi and Silverstrand;
2. Stage 2 works comprise the provision of sewers at Sai Kung Old Town, Tai Wan, Sha Ha, Sha Kok Mei, Pak Kong, Wong Chuk Wan, the environs of Sai Kung, Tai Chung Hau, Pak Sha Wan, Kau Sai San Tsuen, Ta Ho Tun, Tai Po Tsai and Mang Kung Uk;
3. Stage 3 works comprise the provision of sewers at Ho Chung, Tseng Lan Shue and Tai Po Tsai San Tsuen; and
4. Stage 4 works comprise the upgrading of the Sai Kung sewage treatment works phase 2 and the provision of sewers at Tai Mong Tsai, Ta Ku Ling San Tsuen, Clear Water Bay Peninsula and the remote areas in Sai Kung, Ho Chung, Tseng Lan Shue and Silverstrand.

19. We upgraded 132DS to Category B in December 1991 for implementation of stages 1, 2 and 3 works. Subject to further review, we will implement stage 4 by taking into account the population growth in the area.

20. In June 1993, Members agreed to upgrade part of 132DS to Category A as 166DS, entitled "Port Shelter sewerage, stage 1 phase 1" at an estimated cost of $53 million for the construction of sewers at Tan Cheung, Po Lo Che and Tui Min Hoi and upgrading of the Sai Kung sewage treatment works phase 1. We started the works in November 1993 and completed them in February 1996.

21. In January 1995, Members agreed to upgrade another part of 132DS to Category A as 190DS, entitled "Port Shelter sewerage, stage 2 phase 1" at an estimated cost of $19 million for the construction of sewers at Sai Kung Old Town and Mang Kung Uk. We started the works in May 1995 for completion in April 1997.

22. In October 1995, we redesignated the remaining works under 132DS. Since then, 132DS is solely for the remainder of stage 1 works, while the remainder of stage 2 works and stage 3 works are renumbered 272DS and 273DS "Port Shelter sewerage stage 3" respectively.

23. We have completed the detailed design and working drawings for the works to be upgraded to Category A using in-house staffing resources. We plan to start the proposed works in February 1997 for completion in April 1999.

24. The detailed design of the works under the remaining part of 272DS and 273DS is in progress. In view of the limited staffing resources and the need to implement other high priority projects, we plan to start the remaining works of 272DS in June 1998 for completion in February 2002 and to start the works of 273DS in June 2000 for completion in February 2003.

1 -- House connection works refer to the laying of sewers between terminal manholes on private lots and the proposed main sewers.

2 -- Under the Water Pollution Control (Sewerage) Regulation enacted in June 1994, the landowners are obliged to lay internal sewers and construct terminal manholes within their lot boundaries.

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