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LCQ7: Incidents of water mains burst

Following is a question by the Dr Hon Junius Ho and a written reply by the Secretary for Development, Mr Michael Wong, in the Legislative Council today (July 5):

Question:

The Water Supplies Department (WSD) commenced the Replacement and Rehabilitation Programme of Water Mains (the Programme) in 2000 to replace and rehabilitate about 3 000 kilometres of aged water mains in phases. Although the Programme was substantially completed in December 2015, incidents of water mains burst have still occurred in Hong Kong from time to time in recent months (the incident locations included Wu Chui Road near Mei Lok Lane, Tuen Mun; Connaught Road West near Water Street, Western District; Tsuen Wan section of Castle Peak Road, Tsuen Wan; and Kwun Tong Road eastbound off Kai Yip Estate), causing traffic congestion and serious nuisance to the daily lives of the residents in the vicinity. In this connection, will the Government inform this Council:

(1) of the number of reports of water main burst received by the WSD since the beginning of this year (with a breakdown by District Council district);

(2) (i) of the total volume in cubic metres of fresh water lost during incidents of water mains burst, and the value of fresh water lost as calculated by its unit cost; and (ii) whether the authorities have assessed other relevant economic losses incurred due to water mains burst, since the beginning of this year; if so, of the outcome; if not, the reasons for that;

(3) of the details of the latest notification mechanism adopted by the WSD for handling incidents of water mains burst; and

(4) as the authorities have indicated that they will, following the completion of the Programme, progressively establish the Water Intelligent Network to continuously monitor the conditions of the water supply network, and will, prior to the completion of this work, commission a consultant to undertake the relevant investigations and design work for reprovisioning in phases those aged water mains that are susceptible to failure during the transitional period, of the progress of such work; how the authorities assess the conditions of the water mains and their probability of burst, so as to reduce the occurrence of incidents of water mains burst?

Reply:

President,

Given the hilly terrain of Hong Kong, the water pressure of our water supply networks generally ranges from 60 to 80 metres, higher than the 40 metres or so of Singapore and other places by a margin of 50 per cent to 100 per cent. High water pressure increases the risk of water mains bursts. The ageing of some water mains and disturbances to underground water mains caused by frequent roadworks, ground settlement, external loading and vibration also further exacerbate the risk of bursting.

To tackle the problem of ageing water mains, the Water Supplies Department (WSD) launched the Replacement and Rehabilitation Programme of Water Mains (the Programme) in 2000 to replace and rehabilitate about 3 000 kilometres of aged water mains in the territory. Following the substantial completion of the Programme at the end of 2015, the condition of the water supply networks has improved significantly. The number of water main burst incidents in Hong Kong also fell sharply, from about 2 500 cases in 2000 to some 170, 150 and 120 cases in 2014, 2015 and 2016 respectively. However, there are water mains that are not covered by the Programme but have become aged or worn out at present. Therefore, incidents of water main burst may continue to occur.

The WSD considers that another large-scale replacement and rehabilitation project modelled on the Programme is not the best way forward as it would entail high project costs. There are also associated social costs, such as traffic congestion caused by the works, that should not be overlooked. Riding on the technological advancements in the fields of sensors, telemetry, network management software and data analysis in recent years, the WSD is progressively implementing the Water Intelligent Network (WIN) to maintain the health of water distribution networks. Under the WIN project, the water distribution networks of Hong Kong will be divided into some 2 000 discrete District Metering Areas (DMAs) of manageable size, with monitoring and sensing equipment installed in the distribution network of each DMA. Pressure management will also be implemented in some areas, where feasible, to maintain a proper balance between stability of water supply and pressure of the water supply network. The WSD is also preparing to establish an intelligent network management computer system for analysing the tremendous amount of data collected from the DMAs in order to formulate the most effective network management measures and their respective priorities for individual DMAs. As at March this year, we have set up around 1 000 DMAs. We expect that the whole WIN will be put in place in five years' time.

Before the WIN comes into full operation, the WSD will deal with the aged water mains at high risk in a timely manner, such as reprovisioning these water mains in a risk-based approach, to maintain the health of the networks.

My reply to the four parts of the Dr Hon Junius Ho's question is as follows:

(1) The WSD has received a total of 36 water main burst reports between January and May this year. The following table shows a breakdown of the reports by District Council (DC) district:

No. of water main burst incidents that occurred
between January and May 2017
Central & Western District 1 Yau Tsim Mong 2
Eastern District 9 North District 0
Islands 1 Sai Kung 0
Southern District 0 Sha Tin 2
Wan Chai 3 Tai Po 3
Kowloon City 1 Kwai Tsing 5
Kwun Tong 1 Tuen Mun 4
Sham Shui Po 0 Tsuen Wan 2
Wong Tai Sin 1 Yuen Long 1

(2) The quantity of fresh water discharged as a result of fresh water main bursts between January and May this year accounted for less than 0.01 per cent of the fresh water supply over the same period. As mentioned above, the causes for water main bursts include high water pressure, ageing of water mains and other external factors. Therefore, water main burst should be regarded as an operational constraint instead of an economic loss.
 
However, the WSD understands that water main burst may cause nuisance to nearby residents. Hence, it will take appropriate measures to mitigate the resultant impact of each water main burst incident on the public. Upon receipt of a water main burst report, the WSD will release information about the incident and related emergency suspension of water supply as soon as possible. For cases involving fresh water, it will liaise with the DC members of the district or the management office concerned to identify suitable locations for the installation of temporary standpipes, water wagons or water tanks to provide emergency temporary water supply to affected customers. In addition, the WSD will co-ordinate with the Police to draw up temporary traffic arrangements to reduce the impact of water main burst on traffic. Under exceptional circumstances, the WSD will carry out immediate repair works for damaged road surface and reopen the road concerned while repair works for the burst water main will be scheduled for off-peak hours.
 
(3) Upon receipt of a water main burst report, the WSD will immediately deploy frontline staff to the site to turn off the relevant valve in order to isolate the defective section of water main for emergency repair. Details of the emergency suspension of water supply, including the water supply type, duration of suspension, affected areas, temporary fresh water supply arrangements, etc., will be released through the website and the mobile application, WSD Mobile App, to keep the affected public informed about the arrangements. The WSD mobile application has been updated since October 2016 to subdivide the concerned areas to be selected by the public from the 18 districts in the past to the 431 DC constituency areas over the territories, enabling members of the public to get hold of more accurate and latest information about the suspension of water supply. Members of the public may also call the WSD Enquiry Hotline for information about the emergency suspension of water supply. For particular groups of customers (such as hospitals), the WSD will contact them individually to enable them to implement emergency contingency measures as soon as possible.
 
(4) In a risk-based assessment exercise for all the water mains in the territory at the end of 2016, the WSD identified over 40 kilometres of water mains rated at high risk and requiring reprovisioning. The design work for reprovisioning of over 30 kilometres of these high risk water mains has been completed. A tender exercise for the works will be conducted within the year. As for the remaining 11 kilometres or so of these water mains, the WSD has also commissioned engineering consultants to carry out the design work.
 
The WSD would take into account a number of factors when assessing the condition and burst probability of water mains. They include water mains materials, years of service and past records of burst and leakage. With the progressive implementation of the WIN and by analysing the water flow and pressure data collected from the monitoring and sensing equipment installed at each DMA with an intelligent network management computer system, the WSD will assess the conditions of the water distribution networks and formulate appropriate network management measures to reduce the occurrence of water main burst.
 

Ends/Wednesday, July 5, 2017
Issued at HKT 12:00

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