PWSC(97-98)120
For discussion
on 11 February 1998


ITEM FOR PUBLIC WORKS
SUBCOMMITTEE OF FINANCE COMMITTEE

HEAD 704 - DRAINAGE
Environmental Protection - Sewerage and sewage treatment
205DS - Aberdeen, Ap Lei Chau and Pok Fu Lam sewerage

Members are invited to recommend to Finance Committee -

  1. the upgrading of part of 205DS entitled "Aberdeen, Ap Lei Chau and Pok Fu Lam sewerage, stage 1A works" to Category A at an estimated cost of $71.8 million in
    money-of-the-day prices; and

  2. the retention of the remainder of 205DS in Category B.

PROBLEM

The existing sewerage systems in Aberdeen, Ap Lei Chau and Pok Fu Lam do not have adequate capacity to serve these districts.

PROPOSAL

2. The Director of Drainage Services, with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade part of 205DS to Category A at an estimated cost of $71.8 million in money-of-the-day (MOD) prices for the construction of the Aberdeen, Ap Lei Chau and Pok Fu Lam stage 1A sewerage works.

PROJECT SCOPE AND NATURE

3. Project 205DS "Aberdeen, Ap Lei Chau and Pok Fu Lam sewerage", comprising two stages of works, aims at improving the existing sewerage systems in the Aberdeen, Ap Lei Chau and Pok Fu Lam districts. The part of the project (i.e. stage 1A) we now propose to upgrade to Category A involves the construction of -

  1. 660-metre long trunk sewers (750 to 1 050 millimetres in diameter) and 480-metre long associated branch sewers (150 to 500 millimetres in diameter) in Wong Chuk Hang Road; and

  2. two-kilometre long sewers (225 to 450 millimetres in diameter) in Pok Fu Lam.

The site plan at Enclosure 1 shows the locations of the proposed works.

4. The remainder of 205DS comprising the remaining stage 1 works (i.e. stage 1B) and the surveys, site investigations, detailed design and construction for the stage 2 works will be retained in Category B. Details of the works are as follows -

  1. the stage 1B works -

    1. the upgrading of sewers in Ap Lei Chau Main Street;

    2. the refurbishment of sewers in the Aberdeen Reservoir water gathering ground;

    3. the reconstruction of sewers from Wong Chuk Hang to Aberdeen preliminary sewage treatment works (remaining part);

    4. the construction of a sewage pumping station at Aberdeen preliminary sewage treatment works; and

    5. modification works at the Aberdeen preliminary sewage treatment works.

  2. the stage 2 works -

    1. the upgrading of sewers and the construction of a pumping facility in Shum Wan Road; and

    2. the survey and rectification of expedient connections in Aberdeen, Ap Lei Chau and Pok Fu Lam as well as minor sewerage improvement works in these areas.

JUSTIFICATION

5. In June 1995, we completed the sewerage master plan study for Aberdeen, Ap Lei Chau and Pok Fu Lam under 149DS "Aberdeen, Ap Lei Chau and Pok Fu Lam sewerage - consultants' fees and investigation". This study identified deficiencies in the existing sewerage systems and recommended improvement measures.

6. The development of the area over the years has led to an increased amount of sewage requiring discharge. The study showed that the existing sewers in Wong Chuk Hang Road, which were built many years ago, do not have sufficient capacity to deal with the current sewage flow. The gradient of these sewers is not steep enough to carry sewage at a velocity sufficient to facilitate self-cleansing. This has resulted in the siltation of sewers, further reducing their capacity. More seriously, spillage of sewage through manholes may occur and cause flooding, environmental nuisance and inconvenience to road users.

7. We therefore propose to reconstruct the sewers at a steeper gradient to provide sufficient capacity to cater for the sewage flow demand up to 2011. Our original plan was to start construction in early 1999. As Highways Department plans to start the road works project B578TH "Wong Chuk Hang Road flyover and associated road widening" in June 1998, we have advanced the sewer re-construction works that fall within Highways Department's works site in order to implement these works under the road works contract. It is desirable to implement both the sewerage works and the road works under one contract to avoid repeated road openings.

8. Moreover, a part of the sewerage system in the Pok Fu Lam area cannot cope with the increasing demand for sewage discharge due to developments in the area. While the existing sewers in Pok Fu Lam Road are generally adequate, one section of the network near Queen Mary Hospital does not have sufficient capacity due to its flat gradient. We need to reconstruct this section by replacing the existing sewer with a wider sewer laid at a steeper gradient to provide the increased capacity needed to cater for future development. We also need to extend the existing sewers in Victoria Road, Sha Wan Drive and Sandy Bay Road to serve new developments in these areas. Upon completion of the works, sewage generated from various developments in the area will be conveyed to the new sewage screening plant at Sandy Bay for treatment and disposal. The plant is due to start operation in early 1998.

9. As Highways Department plans to start the road improvement works in Pok Fu Lam Road under project 577TH "Flyover at junction of Pok Fu Lam Road and Sassoon Road" in November 1998, we plan to incorporate the proposed sewerage works in Pok Fu Lam Road into the road works project so that we can implement both the road works and the sewerage works at the same location under one contract.

FINANCIAL IMPLICATIONS

10. We estimate the capital cost of the proposed works to be $71.8 million in MOD prices (see paragraph 11 below). This is made up as follows -

$ million


(a) Sewers in
Wong Chuk Hang Road


33.2


(b) Sewers in Pok Fu Lam


6.4


(c) Consultants' fees


8.6


(i) construction stage

2.0



(ii) resident site staff cost

6.6



(d) Contingencies


4.8




_____


Sub-total


53.0

(at
December
1996
prices)

(e) Inflation allowance


18.8




_____


Total


71.8

(in MOD
prices)


_____


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

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

Year

$ million
(Dec 1996)

Price
adjustment
factor

$ million
(MOD)

1998 - 99

4.3

1.16358

5.0

1999 - 2000

17.3

1.26830

21.9

2000 - 01

22.4

1.38244

31.0

2001 - 02

6.0

1.50686

9.0

2002 - 03

3.0

1.64248

4.9

_____


_____

53.0


71.8

_____


_____

12. We have derived the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices for the period 1998 to 2003. We will include the sewerage works in Wong Chuk Hang Road and Pok Fu Lam Road as remeasurement works in Highways Department's road works contracts under B578TH and 577TH. We will issue a works order to Drainage Services Department's term contractor to carry out the sewerage works in Victoria Road, Sha Wan Drive and Sandy Bay Road under a remeasurement contract. Remeasurement contracts will be adopted as we are uncertain about the existence and exact locations of underground utilities such as electric cables, telephone lines, stormwater drains and water mains. As the contract period will exceed 21 months, we will allow for adjustment to the tender price due to inflation.

13. We estimate the additional annually recurrent expenditure arising from the proposed works to be $110,000.

14. Based on the current level of sewage charges and water consumption, we consider that the additional recurrent expenditure will have negligible impact on sewage charges.

PUBLIC CONSULTATION

15. On 26 May 1997, the Director of Highways consulted the Traffic and Transport Committee of the Southern District Board on the project "Flyover at junction of Pok Fu Lam Road and Sassoon Road", which incorporates the proposed sewerage works along Pok Fu Lam Road. We consulted the Works Projects Committee of Southern Provisional District Board on 15 September 1997

on the whole stage 1 works, including the proposal for temporary traffic arrangements and environmental mitigation measures to be adopted during construction. Members supported the implementation of both projects.

ENVIRONMENTAL IMPLICATIONS

16. The Director of Environmental Protection completed an environmental review in 1995 and concluded that the project would have no major long term environmental impact. No environmental impact assessment is therefore necessary. We will control noise, dust and site run-off during construction to within established standards and guidelines through the implementation of mitigation measures in the relevant contracts.

LAND ACQUISITION

17. This project does not require land acquisition.

BACKGROUND INFORMATION

18. In September 1995, we upgraded 205DS to Category B for the sewerage improvement works for Aberdeen, Ap Lei Chau and Pok Fu Lam. We plan to carry out the works in two stages. To facilitate the implementation of the sewerage works in conjunction with the road works, we have further divided the stage 1 works into two sub-stages, namely the stage 1A works and the stage 1B works. We currently propose the upgrading of the stage 1A works to Category A.

19. To tie in with the implementation programme of B578TH, we plan to start the sewerage works in Wong Chuk Hang Road in June 1998 for completion in September 2001. As regards the proposed works in Pok Fu Lam, we plan to start the sewer reconstruction in Pok Fu Lam Road in November 1998 for completion in July 2001 in line with the implementation programme of 577TH. For the rest of the proposed sewerage works in Pok Fu Lam, we plan to start construction in August 1998 for completion in April 2000.

20. We plan to start the stage 1B works in January 1999 for completion in November 2001. We also plan to start the stage 2 works in early 2000 for completion in 2002.


Planning, Environment and Lands Bureau
January 1998

(JJ225)

Enclosure 2 to PWSC(97-98)120

205DS - Aberdeen, Ap Lei Chau and Pok Fu Lam sewerage

Breakdown of estimates for consultants' fees

Consultants' staff costs


Estimated
man
months

Average
MPS
salary
point

Multiplier
factor

Estimated
fee
($ million)

(a) Consultants' fees for construction stage

Professional

Technical

7

15

40

16

3.0

3.0

1.16

0.84

(b) Resident site staff cost

Professional

Technical

28

86

40

16

2.1

2.1

3.26

3.36





______

Total consultant's staff costs

8.62

______

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 1.4.96, MPS pt. 40 = $55,390 p.m. and MPS pt. 16 = $18,595 p.m.)

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


(JJ225)