For discussion
on 3 February 1999



New Territories North Development
Civil Engineering - Drainage and erosion protection

81CD -North West New Territories development - main drainage channels for Yuen Long and Kam Tin - remainder

Members are invited to recommend to
Finance Committee -

  1. the upgrading of part of 81CD, entitled "Main drainage channels for Yuen Long and Kam Tin stage 2 - Kam Tin San Tsuen to Wang Toi Shan section", to Category A at an estimated cost of $419.3 million in money-of-the-day prices; and

  2. the retention of the remainder of 81CD,

    re-titled "Main drainage channels for Yuen Long and Kam Tin stage 2 - remainder", in Category B.


We need to improve the section of the Kam Tin River between Kam Tin San Tsuen and Wang Toi Shan to alleviate the flooding hazard to the low-lying areas of Yuen Long and Kam Tin.


2. The Director of Territory Development, with the support of the Secretary for Works, proposes to upgrade part of 81CD to Category A at an estimated cost of $419.3 million in money-of-the-day (MOD) prices for improvement to the section of Kam Tin River between Kam Tin San Tsuen and Wang Toi Shan.


3.The scope of 81CD comprises the construction of main drainage channels and associated works to improve the following sections of the tributaries of the Kam Tin River -

  1. from Kam Tin San Tsuen to Wang Toi Shan;

  2. from Kam Tin Road to Tai Kek; and

  3. from Ng Ka Tsuen to Kam Sheung Road near
    Shui Lau Tin and from Shek Tau Wai to
    Kam Sheung Road near Sheung Tsuen San Tsuen.

4.The part of 81CD we now propose to upgrade to Category A comprises the works described in paragraph 3(a) above, which include -

  1. a drainage channel of about 3.1 kilometres long along the section of Kam Tin River between
    Kam Tin San Tsuen and Wang Toi Shan;

  2. an inflatable dam, an air blower house, an irrigation water tank and a pumping chamber;

  3. a gauging station to replace the existing
    Kam Tin River Gauging Station;

  4. roads and ramps with associated drainage works;

  5. four vehicular bridges and five footbridges;

  6. environmental mitigation measures including landscaping works; and

  7. an environmental monitoring and audit programme for the works mentioned in paragraphs (a) to (f) above.

5.In recent years, extensive changes in land use and rapid development in Kam Tin and Yuen Long have significantly aggravated the flooding problem in this area which is already susceptible to flooding due to its low-lying topography. The "North West New Territories Base Strategy Studies" (the Study), completed in 1983, recommended a series of river training works to alleviate flooding hazards in the North West New Territories, including the low-lying areas of Yuen Long and Kam Tin. The "Territorial Land Drainage and Flood Control Strategy Study - Phase II", completed in 1993 under 52CD, also confirmed the recommendations of the Study. The river training works for the downstream sections of the Shan Pui River and the Kam Tin River under 43CD and 60CD commenced in 1993 and are still in progress. The proposed works under 81CD are the continuation of the downstream works aiming to alleviate flooding upstream of Kam Tin River and form part of the overall flood alleviation programme.

6.The existing section of the Kam Tin River between Kam Tin San Tsuen and Wang Toi Shan is narrow and meandering and can only accommodate moderate rain storms before flooding. The proposed works will turn the upper reaches of the section into a wider and deeper drainage channel. This new channel will substantially increase the hydraulic capacity of the river and will be capable of accommodating a 50-year return period rainstorm, thus significantly relieving the area from the risk of flooding.

7.As the new drainage channel will be wider and will follow new alignments at several locations, some areas of farm land that depend on water from the river for irrigation will be affected. In order to maintain an irrigation supply from the river to these areas, we will construct an inflatable dam and associated pumping facilities at the proposed drainage channel near Leung Uk Tsuen and a water pumping chamber at the furthest upstream reach of the drainage channel to replace an existing irrigation dam. Under normal weather conditions, we will deploy the inflatable dam to raise the upstream water level to that necessary to meet the irrigation demands. During heavy rainstorms when the upstream water level in the drainage channel is high, we will deflate the dam to allow flood water to flow downstream without obstruction. Air blowers in an air blower house at the dam will operate the inflatable dam automatically according to the required water levels.

8.As the existing Kam Tin River Gauging Station is located within the alignment of the proposed drainage channel, we need to demolish it and construct a new gauging station.

9.To facilitate future maintenance of the proposed drainage channel and to ensure its smooth functioning, we need to construct access roads and ramps. We will also construct four vehicular bridges and five footbridges to replace existing river-crossing facilities, which will need to be demolished under the proposed works.


10.We estimate the capital cost of the project to be $419.3 million in MOD prices (see paragraph 11 below), made up as follows -

$ million
(a)Drainage channel146.0
(b)Inflatable dam, air blower house, irrigation water tank, pumping chamber and gauging station17.0
(c)Roads and drainage works66.0
(d)Vehicular bridges and footbridges57.0
(e)Environmental mitigation measures8.0
(f)Environmental monitoring and audit (EM&A) programme5.0
(g)Resident site staff cost10.5
Sub-total340.5(at December
1997 prices)
(i)Provision for price adjustment78.8
Total419.3(in MOD prices)

While some on-site supervision will be provided by resident site staff from the Drainage Services Department, the Director of Drainage Services (DDS) has insufficient resources to provide the entire complement of site staff required. Consequently, he proposes to employ additional resident site staff through consultants for supervising the geotechnical and EM&A components of the works. A breakdown by man-months of the estimate for consultants’ resident site staff expenses is at the Enclosure.

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

Year$ million
(Dec 1997)
$ million
1999 - 0070.01.1289079.0
2000 - 01110.01.19663131.6
2001 - 02105.01.26843133.2
2002 - 0345.01.3445460.5
2003 - 0410.51.4252115.0

12.We have derived the MOD estimate on the basis of the Government's latest forecast of trend labour and construction prices for the period from 1999 to 2004. We will tender the proposed works under a standard remeasurement contract because the works involve extensive earthworks, the quantities of which may vary according to the actual ground conditions. The contract will make provision for price adjustments as the contract period will exceed 21 months.

13.We estimate the annually recurrent expenditure to be $4.64 million.


14.We consulted the Kam Tin Rural Committee, Pat Heung Rural Committee and Yuen Long District Board on the proposed works on 28March1994, 30 April 1994 and 23 June 1994, respectively. Members of the Committees and District Board supported the proposed project for the relief it would bring to the flooding problems in Yuen Long and Kam Tin.

15.We presented the findings and the environmental mitigation measures recommended in the EIA report to the Environmental Improvement Committee of the Yuen Long District Board on 13 June 1996. Members had no objection to the findings and the recommended mitigation measures. We then consulted the EIA Subcommittee of the Advisory Council on the Environment (ACE) on the EIA report on 1 July 1996. The ACE endorsed the report with the conditions described in paragraph 20 below.

16.We gazetted the proposed reclamation works under the Foreshore and Seabed (Reclamations) Ordinance on 10 March 1995 and received no objections.

17.We also gazetted the proposed road works ancillary to the drainage channel under the Roads (Works, Use and Compensation) Ordinance on 24 March1995. We received objections from twelve objectors. We had a series of discussions with the objectors. Ten objectors subsequently withdrew their objections, but we failed to persuade the remaining two to withdraw theirs. One objection was lodged on Fung Shui grounds and the other was based on the landowner's objection to the resumption of his land.

18.Subsequently, we made some amendments to a section of the road alignment in the proposed road scheme to accommodate the two objections. We gazetted the amendments under the Roads (Works, Use and Compensation) Ordinance on 11 April 1997. We received four objections to the amendments. After a series of discussions, we were able to persuade one objector to withdraw his objection and another to withdraw his objection on condition that the land resumption limit would be revised to avoid resumption of a portion of his land. The remaining two objectors refused to withdraw their objections. One objected to the resumption of his land and the other objected to the location of a replacement bridge.

19.On 24 April 1998, the Chief Executive in Council overruled the objections (mentioned in paragraphs 17 and 18 above) in the public interest and authorised the proposed road works, subject to the modification to the resumption limit as requested by the objector who withdrew his objection, conditionally.


20.In May 1994, we employed consultants to carry out an environmental impact assessment (EIA) study to assess the environmental impact due to the construction and operation of a series of flood control projects in Yuen Long, Kam Tin and Ngau Tam Mei. Following completion of the EIA report in May 1996, we consulted the ACE in July 1996. ACE endorsed the report on condition that old river channels would be considered for restoration into wildlife habitats, the disposal of contaminated mud should be implemented to the satisfaction of the Fill Management Committee (FMC) and such implementation would have no adverse effects on the environment and the proponents should review the conceptual off-site compensation measures in the light of Government's latest policy on off-site compensation and report back to the EIA Sub-committee (EIASC) of the ACE their specific proposals for this project.

21.The EIA report concluded that the environmental impact of the proposed works could be controlled within established standards and guidelines through the implementation of the mitigation measures recommended in the EIA. We will implement these measures. As regards the conditions set by ACE, the Agriculture and Fisheries Department (AFD) is currently carrying out a study to address the restoration of the old river channels and the question of off-site compensation. We will report back to the EIASC the specific proposals for the restoration of the old river channels and off-site compensation measures once AFD has completed the study. We have also obtained the approval from FMC for the disposal method for contaminated mud. The key measures in respect of dredging works include the use of a closed mechanical grab, no stockpiling of contaminated mud, proper disposal of dredged materials and regular maintenance dredging. We estimate the cost of implementing the environmental mitigation measures ($8 million) and EM&A programme ($5 million) to be $13 million. These costs have been included in the overall project estimate.


22.We will resume about 11.5 hectares of agricultural land for the project. The land acquisition and clearance will affect 45 households involving 110 persons and 348 temporary structures. The Director of Housing will offer eligible families accommodation in public housing in line with the existing policy. We will charge the costs of land acquisition and clearance, estimated to be $260million, to Head 701 - Land Acquisition.


23.Stage 1 of the main drainage channels project for Yuen Long and Kam Tin is under construction under Public Works Programmes 60CD entitled "North West New Territories development - main drainage channels for Yuen Long and Kam Tin Stage 1 Phase 1" (which started in October 1993 for completion in April 1999) and 43CD entitled "North West New Territories development - main drainage channels for Yuen Long and Kam Tin Stage 1 Phase 2" (which started in October 1995 for completion in February 1999).

24.We upgraded 81CD to Category B in September 1995. DDS has completed the detailed design and drawings for the proposed works using in-house resources. We plan to start the works in June1999 for completion in May 2002. We will commence the remaining works under 81CD in October 1999 for completion by mid2003.


Works Bureau
January 1999

Enclosure to PWSC(98-99)63

81CD -North West New Territories development - main drainage channels
for Yuen Long and Kam Tin – remainder

Breakdown of the estimate for consultants' fees

Consultants' staff costsEstimated
($ million)
Site supervision by resident site staff employed by the consultantsProfessional
Total consultants' staff cost10.5

* MPS = Master Pay Scale


1.A multiplier factor of 1.7 is applied to the average MPS point to arrive at the full staff costs including the consultants’ overheads and profit, as the staff will be supplied by the consultants. (At 1.4.97, MPS pt. 40 = $59,210 p.m. and MPS pt. 16 = $19,860 p.m.)

2.The figures given above are based on estimates prepared by the Director of Drainage Services. We will only know the actual man months and fees when we have appointed the resident site staff.