For discussion PWSC(95-96)105
on 15 March 1996


New Territories North Development
(Civil Engineering - Drainage and erosion protection)
35CD - Main drainage channels and poldered village protection schemes for San Tin, North West New Territories

Members are invited to recommend to Finance Committee the upgrading of 35CD to Category A, retitled “Village flood protection for the San Tin villages and Chau Tau Tsuen, North West New Territories”, at an estimated cost of $280.2 million in money-of-the-day prices.


The San Tin villages and Chau Tau Tsuen are in low-lying areas and are prone to frequent flooding during typhoons or heavy rainstorms.


2. The Director of Territory Development (DTD), with the support of the Secretary for Planning, Environment and Lands, proposes to upgrade 35CD to Category A at an estimated cost of $280.2 million in money-of-the-day (MOD) prices for carrying out flood protection works at the San Tin villages and Chau Tau Tsuen.


3. The scope of 35CD comprises the construction of flood protection works for Chau Tau Tsuen and seven other low-lying villages in San Tin. A list of these villages is at the Enclosure. The village flood protection works comprise -

  1. flood protection embankments around the eight village proper;
  2. flood storage ponds and pumping stations within the village proper;
  3. concrete-lined drainage channels together with concrete box culverts from pumping stations to existing streams; and
  4. roads for maintenance access to the proposed flood storage ponds and pumping stations.


4. In recent years, typhoons and heavy rainstorms have caused serious flooding in the San Tin villages and Chau Tau Tsuen, affecting some 3 950 villagers in 1 350 households. The flooding condition ranged from about 1.7 metres (under heavy rainstorm) to 2.5 metres (during the passage of typhoons). Upon completion of the proposed flood protection works, we expect that the villages will become less flood prone.

5. The proposed flood protection works for the San Tin villages and Chau Tau Tsuen are similar to those we have carried out for other villages in the North West New Territories, such as Kiu Tau Wai in Ping Shan and Lo Uk Tsuen in Ha Tsuen, both in Yuen Long. The completed works have effectively protected these villages from being flooded during typhoons or heavy rainstorms.

6. The proposed works will protect the San Tin villages and Chau Tau Tsuen from being flooded in the following ways -

  1. during typhoons or heavy rainstorms, the proposed flood storage ponds together with associated drains will collect the stormwater within the village boundary. Before the ponds start overflowing, the pumping stations will operate automatically to pump the water from the ponds into the proposed drainage channels for discharge into nearby streams; and
  2. the proposed embankments will prevent any external flood water from entering the village proper.

The completion of these works will significantly reduce the flooding risk for the San Tin villages and Chau Tau Tsuen.

7. As part of the works, we will construct roads for maintenance access to facilitate future maintenance of the proposed flood storage ponds and pumping stations.


8. We estimate the capital cost of the project to be $280.2 million in MOD prices (see paragraph 9 below), made up as follows -

$ million

(a) Flood protection embankments


(b) Flood storage ponds and drains


(c) Pumping stations


(d) Concrete-lined drainage channels and box culverts


(e) Associated roads for maintenance access with drainage and landscaping


(f) Contingencies


(at December 1994 prices)


(g) Inflation allowance


(in MOD prices)


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

Year $ million
(Dec 1994)
$ million

1996 - 97




1997 - 98




1998 - 99




1999 - 2000




2000 - 2001






10. We derive the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices for the period between 1996 and 2001. We will tender the civil engineering works under a standard re-measurement contract because the works involve extensive earthworks, the quantities of which are subject to variation during construction to suit the actual site conditions. As the construction period is more than 21 months, the contract will provide for adjustments to the tender price due to inflation. We will tender the purchase, installation, testing and commissioning of the electrical and mechanical works under a fixed-price lump-sum contract because we can clearly define the scope of the works in advance.

11. We estimate the annually recurrent expenditure of the proposed works to be $7.78 million.


12. We consulted the San Tin Rural Committee on the proposed works in February and March 1993. We also consulted the Yuen Long District Board in April and August 1993. Both the Rural Committee and the District Board supported the proposal.

13. We gazetted the proposed works for San Tin villages and Chau Tau Tsuen under the Roads (Works, Use and Compensation) Ordinance in August and December 1994 respectively. We also gazetted the proposed works for San Tin villages under the Foreshore and Sea-bed Ordinance in July 1994. We received no objection.


14. The Director of Environmental Protection (DEP) conducted an environmental review on the proposed works in 1993 and concluded that there should not be long-term environmental impacts and that an EIA study would not be necessary. As the scope of works and engineering conditions are similar to those of 71CD "Village flood protection for Sha Po Tsuen, Kam Tin, New Territories", DEP considers that we should adopt for this project the mitigation measures and environmental monitoring and audit requirements1 for 71CD which the Advisory Council on the Environment endorsed in February 1995. The mitigation measures include the use of close grab dredgers or excavators, proper disposal of dredged materials and no stockpiling of contaminated mud. The estimated cost of the mitigation measures is $4.5 million and that for the implementation of environmental monitoring and audit is $2.5 million. These costs are part of the overall project cost stated under items (a) and (b) of paragraph 8 above. The estimated cost of the measures during the maintenance dredging is about $0.2 million and is part of the recurrent expenditure stated in paragraph 11 above.

15. We have fully incorporated the mitigation measures, environmental monitoring and audit programmes into the detailed design and works contracts. We will ensure proper implementation of these measures during the construction and operation phases.


16. We will resume about 10.8 hectares of agricultural land. The clearance will affect 44 structures (including five domestic structures) and 15 residents. The Director of Housing will offer these families accommodation in line with the existing policy. We will charge the cost of land acquisition and clearance estimated at $220 million to Head 701 - Land Acquisition.


17. In 1987, we upgraded 35CD to Category B for the construction of main drainage channels to alleviate flooding in San Tin. In 1993, we revised the scope of 35CD to include two poldered village protection schemes in San Tin, North West New Territories.

18. The Director of Drainage Services has completed the detailed design and drawings and will supervise the implementation of the proposed works using in-house staff resources. We plan to start the proposed works in October 1996 for completion in April 1999.

1 -- The purpose of the environmental monitoring and audit programme is to monitor the environmental performance of the project and to ensure that the recommended mitigation measures will be implemented in a timely fashion. The programme will include an action plan which specifies necessary action to be undertaken to mitigate environmental effects to levels within established criteria. Water quality, noise and dust monitoring will be undertakenn for the construction phase and water quality and noise monitoring will be carried out for the operatioal phase.

Enclosure to PWSC(95-96)105

List of villages covered by 35CD - Main drainage channels and poldered village protection schemes for San Tin, North West New Territories

1. Chau Tau Tsuen

San Tin villages

1. Fan Tin Tsuen

2. On Lung Tsuen

3. San Lung Tsuen

4. Tsing Lung Tsuen

5. Tung Chun Wai

6. Wing Ping Tsuen

7. Yan Shau Wai

Last Updated on 8 December 1998