For discussion PWSC(96-97)73
on 4 December 1996

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Environmental Protection - Sewerage and sewage treatment
125DS - Tolo Harbour sewerage of unsewered areas

Members are invited to recommend to Finance Committee -

1. the upgrading of part of 125DS entitled "Tolo Harbour sewerage of unsewered areas, stage I phase IC" to Category A at an estimated cost of $36.7 million in money-of-the-day prices; and
2. the retention of the remainder of 125DS in Category B.

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PROBLEM
PROPOSAL
PROJECT SCOPE AND NATURE
JUSTIFICATION
FINANCIAL IMPLICATIONS
PUBLIC CONSULTATION
ENVIRONMENTAL IMPLICATIONS
LAND ACQUISITION
BACKGROUND INFORMATION
125DS - Tolo Harbour sewerage of unsewered areas Updated Cost Estimate and Implementation Plan
125DS - Tolo Harbour sewerage of unsewered areas Stage I Phase IC
125DS - Tolo Harbour sewerage of unsewered areas Names of unsewered areas of stage I phase I

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PROBLEM

Domestic sewage from unsewered areas in Sha Tin and Tai Po contributes to water pollution in the Tolo Harbour.

PROPOSAL

2. The Director of Drainage Services, with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade part of 125DS to Category A at an estimated cost of $36.7 million in money-of-the-day (MOD) prices for implementing necessary sewerage works at six unsewered areas in Sha Tin and Tai Po.

PROJECT SCOPE AND NATURE

3. The part of the project we propose to upgrade to Category A covers the six unsewered areas shown in the attached site plan. The scope of works comprises the construction of -

1. six kilometres of sewers, ranging from 150 millimetre to 300 millimetre in diameter;
2. one sewage pumping station at Heung Fan Liu;
3. three dry weather flow interceptors, two in Heung Fan Liu and one in Lai Chi Hang; and
4. 740 metres of footpath providing access for maintenance purposes.

4. The remaining works of 125DS for retention in Category B comprise detailed design, site investigation and environmental impact assessment for stage II works and construction of stage I phase ID, stage I phase II and stage II sewerage works.

JUSTIFICATION

5. In 1986, we established the Tolo Harbour Action Plan to reduce the pollutants entering the Tolo Harbour. One of the actions specified in the 1986 Tolo Harbour Action Plan is the provision of sewerage to unsewered areas. The consultancy study conducted under 95DS "Tolo Harbour catchment sewerage of unsewered areas - consultants’ fees and investigations" recommended short-term and long-term measures to prevent direct discharge of untreated domestic sewage into Tolo Harbour. We have implemented the short-term measures under 118DS "Tolo Harbour Catchment - first aid measures" for intercepting and diverting polluted flows into the existing sewerage system at seven locations in Sha Tin and Tai Po.

6. We included 125DS in Category C in August 1990 for the long-term water pollution abatement works in unsewered areas of the Tolo Harbour Catchment. The entire project aims at collecting sewage flows from unsewered developments at 165 locations into existing sewerage reticulated systems in Sha Tin and Tai Po and new communal septic tanks for remote locations. Details of the implementation programme are at Enclosure 1.

7. At present domestic sewage from unsewered areas in Sha Tin and Tai Po is partially treated by private septic tanks and discharged into Tolo Harbour via stormwater drainage systems and stream courses. Septic tanks can only remove large settleable solids. Floating materials in the sewage and the effluent from septic tanks still contain a high percentage of pollution matters. The materials detained in septic tanks need to be removed periodically and properly, otherwise the effluent will wash out the contaminated settled solids and floating materials. However, septic tank owners often fail to do this. In view of the limited functions and operational problems of septic tanks, the quality of the domestic sewage after treatment is below the standard required. The discharged sewage has become the major source of pollution in Tolo Harbour.

8. We propose to provide sewers up to the boundary of individual houses in San Uk Ka, Tai Po Kau, Shek Kwu Lung and Pan Chung. For Lai Chi Hang and Heung Fan Liu, we will provide dry weather flow interceptors to intercept the polluted flows in stream courses and convey them to public sewers. Due to a difference in height levels, we will construct a pumping station in Heung Fan Liu to uplift the sewage collected by the dry weather flow interceptors to the existing public sewers.

9. The proposed sewerage facilities in the six areas in Sha Tin and Tai Po will serve a total of 2 000 people. Upon completion, we will be able to reduce poorly treated sewage from entering into Tolo Harbour by 560m³ each day.

FINANCIAL IMPLICATIONS

10. We estimate the capital cost of the project to be $36.7 million in MOD prices, made up as follows -

A breakdown by man month of the estimates for consultants’ fees is at Enclosure 2.

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

12. We have derived the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices for the period 1997 to 2000. We will tender the proposed works as a standard remeasurement contract because we are uncertain about the existence and location of underground utilities such as electric cables, telephone cables, stormwater drains and water pipes. The contract will not allow for adjustments to the tender price due to inflation as the contract period will be less than 21 months.

13. We estimate the total annually recurrent expenditure to be $897,200, which includes $844,200 for the sewerage works and $53,000 for the footpaths. We will charge the expenditure of $844,200 to the Sewage Services Trading Fund and the expenditure of $53,000 to Head 63 Home Affairs Department Subhead 654 Local Public Works. Subject to the Legislative Council passing a Resolution on appropriation of assets to the Trading Fund, the sewerage works under the project, (except the footpaths) will, upon completion, become assets in the Fund valued at cost.

14. Based on the current level of sewage charges, the proposed project by itself would lead to an increase in sewage charges by about 0.1%.

PUBLIC CONSULTATION

15. We consulted Sha Tin District Board and Tai Po District Board on 4 July 1996 and 12 July 1996 respectively on the proposed stage I phase I works. Both supported the implementation of the proposed works.

ENVIRONMENTAL IMPLICATIONS

16. The proposed works will intercept polluted flows from the six unsewered areas in Sha Tin and Tai Po for delivery to the Sha Tin and Tai Po sewage treatment works for treatment before discharge, thus improving the water quality in Tolo Harbour.

17. We completed an Environmental Impact Assessment (EIA) in October 1993 under 137DS "Tolo Harbour sewerage of unsewered areas, stage I phase I - consultants’ fees and design". The EIA concludes that we will need mitigation devices such as deodorizers and filters for the sewage pumping station. We will install these at an estimated cost of $100,000 inside the underground station to control possible odour arising from its operation. We have included this cost in the overall project cost. For short term impacts caused by excavation works during construction, we shall control noise, dust and site run-off to within established standard and guidelines through implementation of mitigation measures in the relevant contracts.

LAND ACQUISITION

18. The project does not require land acquisition.

BACKGROUND INFORMATION

19. We included 125DS in Category C in August 1990 for the long-term water pollution abatement works in 165 unsewered areas of the Tolo Harbour Catchment. Stage I phase I covers works at 39 unsewered areas at which early implementation of the sewerage works will be most effective in terms of reduction of pollution into the Tolo Harbour. Stage I phase II covers works at 47 unsewered areas and stage II covers works at 79 unsewered areas.

20. Stage I phase I comprises four sub-phases, namely phases IA, IB, IC and ID. The unsewered areas covered in these various phases are at Enclosure 3.

21. In February 1991, we upgraded part of 125DS to Category A as 137DS for employing consultants to carry out the detailed design, site investigation and EIA for the stage I phase I works.

22. In January 1993, Members agreed to upgrade the stage I phase IA works to Category A as 163DS "Tolo Harbour sewerage of unsewered areas stage I phase IA". We have substantially completed the works in May 1995, with minor house connection works to be completed by August 1999.

23. In June 1994, we upgraded the stage I phase IB works to Category A as 177DS "Tolo Harbour sewerage of unsewered areas stage I phase IB". We have substantially completed the works in October 1996, with minor house connection works to be completed by August 1999.

24. We are now ready to proceed with stage I phase IC works. The consultants have completed site investigation, detailed design and tender documents for the works involved. We plan to start the proposed works in February 1997 for substantial completion in August 1998 with minor house connection works to be completed by August 1999.

25. Under our current programme, we plan to start work on stage I phase ID in late 1997. As regards stage I phase II works, these are now the subject of detailed design, site investigation and environmental impact assessment under 179DS "Tolo Harbour sewerage of unsewered areas stage I phase II - consultants’ fee and investigation".

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Enclosure 1 to PWSC(96-97)73

125DS - Tolo Harbour sewerage of unsewered areas Updated Cost Estimate and Implementation Plan

Legend : * Part of 125DS we now propose to upgrade to Category A

# The remainder of 125DS after upgrading

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Enclosure 2 to PWSC(96-97)73

125DS - Tolo Harbour sewerage of unsewered areas Stage I Phase IC

Details of Consultants’ Fees
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. (At 1.4.95, MPS pt. 40 = $51,440 p.m. and MPS pt.16 = $17,270 p.m.) A multiplier factor of 2.1 is applied in the case of site staff supplied by the consultants.

2. The consultants’ fees for construction stage are based on the scale fees calculated in accordance with the consultancy agreement the Director of Drainage Services has with the consultant undertaking the design and investigations of the stage I phase I project. The resident site staff costs are based on estimates prepared by the Director of Drainage Services. We will only know the actual man months and actual costs when the construction works have completed.

(LL152A)

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Enclosure 3 to PWSC(96-97)73

125DS - Tolo Harbour sewerage of unsewered areas Names of unsewered areas of stage I phase I

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