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Following is a question by the Hon James To and a written reply by the Secretary for the Environment, Transport and Works, Dr Sarah Liao, at the Legislative Council meeting today (April 18) :
Question:
It has been learnt that the Water Supplies Department is implementing a 15-year comprehensive water mains improvement scheme to replace and rehabilitate the aged fresh water and salt water mains throughout the territory, and the Department has launched the scheme on Hong Kong Island first. The Government anticipates that with the implementation of the scheme, incidents of water mains burst and leakage can be substantially reduced in the future. In this connection, will the Government inform this Council:
(a) of the number of incidents of water mains burst in Kowloon and the New Territories in the past six months;
(b) for districts in which incidents of water mains burst occur before the implementation of water mains replacement works, whether the Government will advance the replacement of the water mains there, or it will only rehabilitate the burst water mains and replace the water mains in the districts later as scheduled; if the latter is the case, whether it will cause duplication of work processes and a waste of resources; and
(c) of the expected lifespan of the new water mains?
Reply:
Madam President,
(a) There were a total of 586 incidents of water mains burst in Kowloon and the New Territories in the past six months. The detailed breakdown is as follows:
2006 2007
Oct Nov Dec Jan Feb Mar
Total *** *** *** *** *** ***
Kowloon 306 53 53 52 57 35 56
New 280 59 47 63 36 28 47
Territories
Total 586 112 100 115 93 63 103
(b) When a water main bursts, the Water Supplies Department (WSD)'s emergency repair service staff and the contractor's emergency repair team will attend the incident immediately. The main task is to isolate the burst main from water sources as soon as possible and to repair the water main and resume water supply promptly. The aim is to minimise disruption to the traffic due to the burst and to alleviate any inconvenience caused to the public and business operators as a result of water supply suspension. The WSD attaches great importance to such repair work to fulfill its performance pledge. At present, the WSD's performance targets for emergency repair of burst water mains are as follows:
Services Performance Target
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Time for isolation of burst
water mains upon receipt of
report
- for pipe diameter up to 300mm 85% within 1.5 hours
- for pipe diameter above 85% within 2.5 hours
300mm to 600mm
Maximum duration of supply 85% within 8 hours
interruption due to fresh 95% within 12 hours
water main burst
The main objective of the comprehensive Replacement and Rehabilitation Programme of Water Mains is to systematically replace and rehabilitate about 3,000 kilometres of aged water mains. The programme is being launched in stages for completion by 2015. Given the scale of the undertaking, the WSD has to consult the respective District Councils and the Legislative Council, and to reach consensus with relevant departments such as the Highways Department, the Transport Department, the Police and the Environmental Protection Department before commencement of works. Staging of works is based on major considerations as follows:
1. Avoid the serious disruption of water supply to users that could be caused by extensive replacement and rehabilitation of water mains;
2. Avoid the traffic congestion that could be caused by extensive road excavation for the project; and
3. Accord priority to replacing and rehabilitating water mains that are in poorer condition and prone to leakage and bursting for enhancement of cost effectiveness.
The objectives and considerations of the Replacement and Rehabilitation Programme of Water Mains and of the emergency repair of burst water mains are entirely different. As such, there is no question of duplication of work processes and waste of resources. If replacement/rehabilitation of water mains is carried out as part of the emergency repair of burst water mains, there will be unnecessary delay in resuming water supply and unwarranted disruption to the public and the traffic.
(c) The types of pipes used in the Replacement and Rehabilitation Programme of Water Mains are mainly:
Diameter of Pipes (mm) Types of Material
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700 and above Mild steel
300 to 600 Ductile iron
Below 300 Polyethylene
Protective lining that offers high corrosion resistance is used in mild steel and ductile iron pipes. Their expected service life would be up to 60 years and 40 years for use as fresh water mains and salt water mains respectively.
Polyethylene pipes have good resistance to corrosion. Their average life expectancy can reach 50 years, whether for use as fresh water or salt water mains.
Ends/Wednesday, April 18, 2007
Issued at HKT 13:10
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