Information Paper for Legislative Council
LegCo Panel on Planning, Lands and Works
Meeting on 13 May 1999
90WC - Replacement and Rehabilitation of
Watermains, Stage 1 Phase 1
1. This paper informs Members of the background on the strategy to replace or rehabilitate the aged watermains for solving the problem due to bursts and leaks of aged watermains. In June 1999, we will seek PWSC's approval for upgrading part of 90WC to Category A, entitled "Replacement and rehabilitation of watermains, stage 1 phase 1B - investigation", for engaging engineering consultants to carry out investigations and impact assessments for the phase 1B of the replacement and rehabilitation works under 90WC.
2. Hong Kong's fresh water and salt water supplies are provided through a network consisting of approximately 5 700 kilometres of underground watermains. In pace with the development of urban areas and new towns, about 45% of the watermains were laid 30 years or more ago and approaching the end of their service life. At present, Water Supplies Department (WSD) carries out piece-meal and small-scale replacement works for some aged watermains on an ad-hoc basis. However, they have become increasingly difficult and costly to maintain.
3. WSD is experiencing an increasing number of mains bursts and leaks due to the deteriorating condition of the watermains. During 1994 to 1997, there were about 19 000 pipe failures per year including 1 300 bursts and 17 700 leaks occurring in the water supply network. This number has increased by about 35% to 25 700 in 1998, comprising 1 800 bursts and 23 900 leaks. The loss of water due to such failures is estimated to be 232 million cubic metres per year.
4. In view of the considerable lengths and the deteriorating conditions of the watermains approaching the end of their service life in the years to come, WSD engaged consultants in February 1996 to carry out an Underground Asset Management Study (UAMS) to develop a comprehensive and cost-effective management plan for the water supply network. The Study was completed in end 1997 and concluded that if no improvement works are to be done on the water supply network, the reticulation system will continue to deteriorate and the number of pipe failures per year will increase to 40 000 in 20 years' time. The corresponding loss of fresh water will be about 629 million cubic metres per year at that time, which is obviously intolerable. Taking into account the capital cost of the replacement and rehabilitation works, savings in the maintenance cost and the implication of water lost through leakage and main bursts, the UAMS recommended that some 3 050 kilometres of aged watermains should be replaced or rehabilitated in stages in 20 years in order to prevent further deterioration of the water supply network. With the recommended replacement and rehabilitation works in place, the number of pipe failures per year will be reduced to 15 000 (900 bursts and 14 100 leaks) with a corresponding loss of fresh water of about 182 million cubic metres per year. An early implementation of the replacement and rehabilitation programme is advantageous.
Scope of Works
5. In order to tackle the most problematic areas at the earliest possible and to minimise disruption of water supply to consumers and traffic congestion caused by too much concurrent works, we plan to carry out the replacement and rehabilitation programme in stages. The first stage has two phases and covers the replacement or rehabilitation works which have the best value for money. As regards the subsequent stages, we will review the supply network and propose the improvement works with a view to completing all the works recommended in the UAMS.
6. The stage 1 phase 1 of the replacement and rehabilitation works were included in Category C in July 1998 as 90WC, which was upgraded to Category B in October 1998.
7. The full scope of works under 90WC comprises the replacement or rehabilitation of approximately 243 kilometres of fresh watermains and 107 kilometres of salt watermains, and the associated valves and fittings throughout the territory as shown in Sketches Nos. 03798/156/001 and 002 attached. The phasing of the works is as follows -
- Phase 1A
The phase 1A works comprise the replacement or rehabilitation of -
- approximately 29 kilometres of fresh watermains of diameter ranging from 150 millimetres to 450 millimetres in Yuen Long, Sheung Shui, Fanling, Tai Po and Sha Tin areas; and
- approximately 4 kilometres of salt watermains of diameter ranging from 150 millimetres to 400 millimetres in Tai Po and Sha Tin areas.
- Phase 1B
Phase 1B works comprise the replacement or rehabilitation of -
- approximately 219 kilometres of fresh watermains ranging in diameter from 150 millimetres to 1,400 millimetres throughout the territory; and
- approximately 98 kilometres of salt watermains ranging in diameter from 150 millimetres to 1,000 millimetres throughout the territory.
8. The part of 90WC we now propose to upgrade to Category A is for the investigations and impact assessments for the phase 1B works to be carried out by consultants. The scope of the proposed consultancy includes -
- site investigations and surveys;
- traffic impact assessments;
- drainage impact assessments;
- environmental reviews;
- preliminary design of the replacement or rehabilitation works; and
- pilot trials on the new replacement and rehabilitation techniques.
9. We plan to put forward the works of stage 1 phase 2 as a new project in 2000.
10. In view of the scale and the complexity of the works under phase 1, the proposed works demand considerable resources over a relatively short period. Having examined various ways and means of implementing the replacement and rehabilitation programme, we consider that WSD does not have adequate in-house resources to carry out all the works under this phase in addition to other planned projects. In order to achieve early improvement to the water supply network, WSD will redeploy existing in-house staff to carry out the phase 1A works but proposes to engage engineering consultants to deliver the phase 1B works.
11. As the phase 1B works, mostly situated in densely developed areas, involve works on busy roads, WSD needs to engage engineering consultants to carry out investigations and impact assessments for the proposed replacement and rehabilitation works so as to enable the detailed design to proceed. The consultants will carry out traffic impact assessments in the formulation of the preliminary design and recommend the use of the latest replacement and rehabilitation techniques to minimise road opening. As we do not have experience on such new techniques, the consultants will also be required to devise and supervise pilot trials to confirm the suitability of using the new techniques in Hong Kong.
12. We estimate the cost of the proposed consultancy for the investigations and impact assessments to be $69 million in MOD prices as follows -
|(a) Consultants' fees for
13. Subject to approval, we will phase the expenditure as follows -
|Price adjustment factor||$million
14. We derived the MOD estimates on the basis of Government's forecast of trend of labour and construction prices for the period 1999 to 2002. We will invite tender for the proposed consultancy on a lump sum basis. No price adjustment due to inflation will be allowed because of the short duration of the consultancy.
15. We will consult the relevant district boards during the consultancy and take into consideration the views expressed in the investigations and impact assessments consultancy of the project.
Programme of Works
16. Upon approval of this part upgrading of 90WC to Category A by Finance Committee, we will commence the investigations and impact assessments consultancy in November 1999 for completion in December 2000. We will then proceed with the detailed design for the phase 1B works in 2001 with a view to commencing the construction works in 2003 for completion in 2006.
17. As regards the phase 1A works of this project, detailed design is now in hand and we plan to upgrade this part of the works to Category A in June 2000 on completion of detailed design with a view to commencing the construction works in November 2000 for completion in 2005.