For discussion PWSC(96-97)42
on 10 July 1996

ITEM FOR PUBLIC WORKS SUBCOMMITTEE
OF FINANCE COMMITTEE

HEAD 709 - WATERWORKS
Water Supplies - Fresh water supplies
170WF - Treatment and disposal of waterworks sludge from existing water treatment works - main works

Members are invited to recommend to Finance Committee the upgrading of 170WF to Category A at an estimated cost of $510.1 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
Details of cost estimate for the construction of sludge treatment and disposal facilities
Breakdown of estimates for consultant’s fees and resident site staff expenses
Details of cost contribution to Drainage Services Department
Public Consultation

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PROBLEM

The method of treatment and disposal of waterworks sludge discharged from nine water treatment works (WTWs) do not meet the requirements of the Water Pollution Control Ordinance for declared Water Control Zones. We need to improve the facilities at these nine WTWs.

PROPOSAL

2. The Director of Water Supplies (DWS), with the support of the Secretary for Works, proposes to upgrade 170WF to Category A at an estimated cost of $510.1 million in money-of-the-day (MOD) prices for the construction of the additional facilities for treatment and disposal of the waterworks sludge at nine existing WTWs.

PROJECT SCOPE AND NATURE

3. The scope of the project comprises -

1. Construction of additional facilities for treatment and disposal of waterworks sludge at nine existing WTWs under four packages -
   1. Package 1 - Aberdeen, Eastern and Red Hill WTWs

      This includes the construction of six sludge thickening tanks, three sludge holding tanks and ancillary works. We will transport the thickened sludge by road tankers to the Pak Kong WTW at Sai Kung where we shall use the existing filter presses to press this imported sludge, together with the sludge generated from the Pak Kong WTW itself, into dry cakes for disposal at landfill sites;

   2. Package 2 - Shek Lei Pui and Tai Po Road WTWs

      We will construct an inter-connected washwater transfer system for the two WTWs and a washwater recovery system at the respective WTWs to allow the discharge of sludge via public sewers to the sewage treatment works at Stonecutters Island for co-treatment and disposal with the sewage sludge. The main features include washwater and sludge pipes, two sludge thickening tanks, two sludge balancing tanks and ancillary works;

   3. Package 3 - Tsuen Wan WTW

      We will construct four washwater recovery tanks, three balancing tanks and ancillary works. We shall discharge the sludge via public sewers to the sewage treatment works at Stonecutters Island for co-treatment and disposal with the sewage sludge;

   4. Package 4 - Tai O, Silvermine Bay and Tuen Mun WTWs

      At Tai O, we will construct two washwater recovery tanks and a sludge storage tank together with ancillary works to facilitate the transportation of sludge to Silvermine Bay WTW for further treatment. At both Silvermine Bay and Tuen Mun, we will construct two sludge thickening tanks and install three filter presses at each of the WTWs to produce dry cakes for landfill disposal; and

2. Expansion of the proposed sewage disposal facilities at Stonecutters Island to cater for treatment of the additional sludge from the WTWs in packages 2 and 3.

4. Full details of the proposed work at each WTW are at Enclosure 1.

JUSTIFICATION

5. The Water Supplies Department treats raw water collected from the Territory’s catchment areas or received from China to remove impurities and render the treated water suitable for consumption. The treatment process produces sludge as a result of extracting these impurities from the raw water. The older WTWs provide little or no treatment of the sludge and discharge the sludge into the coastal waters of Hong Kong through nearby streams or storm water drains.

6. Under the Water Pollution Control Ordinance enacted in 1980, we declare areas of Hong Kong’s coastal waters as Water Control Zones. The discharge standards for Water Control Zones, commonly referred to as the Water Quality Objectives, limit various environmental parameters such as the aesthetics, suspended solids content and bacterial content of the discharges. Waterworks sludge fails to meet these standards. However, the Ordinance at the time, provided for exemption for discharges which existed before the declaration of an area as a Water Control Zone. This exemption applied to the discharge of sludge from the nine WTWs.

7. The Water Pollution Control (Amendment) Ordinance, enacted in December 1990, imposed tighter control on discharges and removed all previous exemptions. As a result, the exemptions covering the sludge discharges from the nine existing WTWs falling within the declared Water Control Zones no longer applied. However, the Director of Environmental Protection advised the DWS that a reasonable period of time would be allowed for completing the substantial improvement works required for the older WTWs to comply with the revised discharge standards.

8. DWS commenced a study in mid-1990 to determine the scope of the improvement works necessary to enable compliance with the statutory discharge standards. The study identified a number of technical and cost problems which required further detailed study. In 1993, DWS appointed an engineering consultant to carry out a detailed feasibility study to identify the best options for providing improvement works for individual WTWs from an environmental, engineering, costs and programming point of view. On completion of the feasibility study in 1994, DWS engaged an engineering consultant to undertake the detailed design and preparation of the tender documents for the sludge treatment and disposal facilities for the nine existing WTWs.

9. We now need to construct the sludge treatment and disposal facilities at the nine existing WTWs in order to provide an environmentally acceptable means of sludge disposal in compliance with the discharge standards for declared Water Control Zones under the Water Pollution Control Ordinance.

FINANCIAL IMPLICATIONS

10. We estimate the capital cost of the project to be $510.1 million in MOD prices (see paragraph 11 below), made up as follows -

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

12. We have derived the MOD estimates on the basis of the Government’s forecasts of trend labour and construction prices for the period 1996 to 2000. We will tender the works under a standard re-measurement contract because of uncertainties associated with the excavation works. The duration of the contract periods for Packages 1, 2 and 3 will be 12 months and we will not provide inflation adjustment for such contract works. The duration of the contract period for Package 4 is 21 months and we will provide inflation adjustment for this contract. The figure for consultant’s fees in paragraph 10(b) above represents an lump sum tender price provisionally included in a consultancy agreement for the design and construction of the project awarded under 203WF “Treatment and disposal of waterworks sludge from existing water treatment works - site investigations, consultants’ fees and advance works”.

13. We estimate the additional annually recurrent expenditure to be $16.0 million.

PUBLIC CONSULTATION

14. We consulted the relevant District Boards where necessary on the project in mid-1995 and did not receive any objections. Details of the consultation process are set out at Enclosure 4.

ENVIRONMENTAL IMPLICATIONS

15. We completed an Environmental Review (ER) as part of the project feasibility study for the proposed sludge treatment and disposal facilities in the nine existing WTWs in May 1994. The ER recommended that a detailed Environmental Impact Assessment (EIA) should be carried out for the proposed works in eight WTWs: Redhill, Tsuen Wan, Shek Lei Pui, Tai Po Road, Tuen Mun, Silvermine Bay, Tai O and Eastern. The ER concluded that no EIA was necessary in the case of the Aberdeen WTW and recommended that appropriate environmental mitigation measures be included in the detailed design of the proposed works at this WTW.

16. We engaged an engineering consultant to carry out a detailed study to examine the potential environmental impacts during the construction and operation of the proposed works at the eight WTWs. The consultant completed the EIA in October 1995. The EIA concluded that the proposed works would have no long term adverse impact on the environment provided we adopt the recommended environmental mitigation measures. For short term construction impact, we will incorporate adequate mitigation measures in the works contracts to control dust, noise impacts and ecological disturbances during the construction period as recommended in the EIA.

17. We submitted the EIA Report to the Advisory Council on the Environment on 18 December 1995. The Council endorsed the Report.

LAND ACQUISITION

18. The project does not require land resumption. We will require clearance of Government land at an estimated cost of $1 million. We will charge the costs to Head 701 “Land Acquisition”

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Background INFORMATION

19. We upgraded 170WF to Category B in November 1992. We engaged a consultant in 1993 to carry out feasibility studies on the treatment and disposal of waterworks sludge for 12 WTWs which included the nine WTWs in the above project scope and three other WTWs, namely Yau Kom Tau, Tai Po Tau and Elliot WTWs. We funded the study of 11 WTWs under 190WF “Treatment and disposal of waterworks sludge from existing water treatment works - feasibility study” in Category D at an estimated cost of $3.09 million and separately funded the study for Yau Kom Tau WTW under 128WF “Yau Kom Tau treatment works - stage II”.

20. The engineering consultants completed the feasibility study in December 1993 and identified the best option from the engineering, cost and environmental point of view for the 12 WTWs and recommended advanced works for Red Hill and Tai Po Tau WTWs. We consider that the advanced works at Tai Po Tau WTW will provide a satisfactory long term disposal arrangement and that further works are unnecessary. We decommissioned the Elliot WTW in December 1995 on economic grounds and no further improvement works were therefore necessary.

21. We upgraded the construction works for Yau Kom Tau WTW under 128WF “Yau Kom Tau treatment works - stage II” to Category A in July 1989 at an estimated cost of $127.0 million. The project scope included, among other items, improved sludge disposal facilities. The sludge treatment plant at this works included three sludge holding tanks and ancillary works. We completed the works in July 1995.

22. We upgraded part of 170WF to Category A as 203WF “Treatment and disposal of waterworks sludge from existing water treatment works - site investigations, consultants’ fees and advanced works” at an estimated cost of $22.0 million at March 1994 prices to pay for the consultant fees for the detailed design work and preparation of tender documents for the remaining nine WTWs. We intend to start the construction of the sludge treatment and disposal facilities under Package 1 in November 1996 for completion by November 1997. We will commence the works for Packages 2 and 3 in February 1997 for completion by February 1998. Package 4 will require a longer lead time for procurement of sludge de-watering filter presses. We will start the works for Package 4 in February 1997 for completion by November 1998.

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Enclosure 1 to PWSC(96-97)42

Details of cost estimate for the construction of sludge treatment and disposal facilities

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Enclosure 2 to PWSC(96-97)42

Breakdown of estimates for consultant’s fees and resident site staff expenses

Out-of-pocket expenses

The amount of out-of-pocket expenses is not significant.

Notes

1. The consultant’s fee for works in construction stage is the lump sum tender price provisionally included in the consultancy Agreement No. CE 30/94 for the design and construction of the project.
2. A multiplier factor of 2.1 is applied to the average MPS point to arrive at the full staff costs for resident site staff including the consultant’s overheads and profit, as the staff will be supplied by the consultant. (At 1.4.95, MPS pt. 40 = $51,440 p.m. and MPS pt. 16 = $17,270 p.m.)
3. The figures for the resident site staff given above are based on estimates prepared by the Director of Water Supplies. We will only know the actual man months and actual fees when we have appointed the resident site staff.

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Enclosure 3 to PWSC(96-97)42

Details of cost contribution to Drainage Services Department

Note

The above estimates are provided by the Director of Drainage Services as the portion of the contribution for receiving and co-treating sludge discharged from Shek Lei Pui, Tai Po Road and Tsuen Wan WTWs.

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Enclosure 4 to PWSC(96-97)42

Public Consultation