LCQ19: Water main burst incidents

Following is a question by the Hon Chan Kam-lam and a written reply by the Secretary for Development, Mr Mak Chai-kwong, in the Legislative Council today (July 4):

Question:

Recently, a number of water main burst incidents occurred in Kowloon East, and on each occasion the traffic was seriously affected and the residents were inconvenienced.  These incidents included the water main burst incident in Ping Shek Estate on May 3 this year, which led to the suspension of water supply to three blocks until 2am on the following day before water supply was resumed; on June 15 this year, a water main burst occurred at the entrance of the Jordan Valley Swimming Pool, which led to the complete closure of a section of the traffic lane leading from Choi Ha Road in Ngau Tau Kok towards Choi Ying Estate; and on May 21 this year, an underground water main burst occurred near Rhythm Garden, which led to serious disruption to the traffic at Prince Edward Road.  In this connection, will the Government inform this Council:

(a) of the respective numbers of reports of water main bursts (including fresh water pipes and flush water pipes) in Kwun Tong and Wong Tai Sin districts received by the Water Supplies Department (WSD) in each of the past three years; among such incidents, of the number of those caused by aged water mains or other aged parts;

(b) of the details of the notification mechanism adopted by WSD with regard to the handling of water main burst incidents at present; of the average time required for maintenance staff to isolate the burst mains; whether the entire sections of the water mains concerned will be replaced subsequently; and

(c) of the details and progress of the regular inspections of underground water mains, as well as the maintenance and replacement works of aged water mains carried out by the authorities at present?

Reply:

President,

The water distribution network of Hong Kong has been developing according to demand.  The system is massive and complex, measuring some 7,800 kilometres (km) in total length.  The hilly terrain of Hong Kong makes the water supply pressure relatively high.  Service reservoirs are often built at high level for the optimal use of precious land resources.  The high water pressure together with ground movements and external disturbances make bursts and leaks in our aged water distribution network inevitable.  We fully understand that the temporary suspension of water supply and, in some cases, the associated traffic disruption would cause inconvenience to the public.  To tackle the problem, the WSD is adopting a multi-pronged approach, including proactive burst prevention by leakage detection, replacement and rehabilitation of aged water mains under the Water Mains Replacement and Rehabilitation (R&R) Programme and implementation of water pressure management.

With the completion of some parts of the R&R Programme and the implementation of leakage control and pressure management measures, the number of water main burst incidents has dropped from the peak of about 2 500 in 2000/01 to about 320 in 2011/12.  The water main leakage rate has also declined from 25% in 2001 to 19% in 2011.  It is anticipated that the leakage rate will further decrease to 15% upon completion of the R&R Programme by end 2015.

My reply to the three parts of the question is as follows:

(a) The following table shows the numbers of water main burst incidents in the districts of Kwun Tong and Wong Tai Sin in the past three years：

Year   Kwun Tong District    Wong Tai Sin District
----   ------------------    ---------------------
       Fresh  Salt                 Fresh  Salt
       water  water   Total     water  water  Total
       -----  -----  -----    ------ -----  -----
09/10   33     129   162       12     37      49
10/11   39      61    100        4     10      14
11/12    6       20      26        5     14      19

Burst of water main is commonly due to a confluence of various factors.  The above-mentioned water main burst incidents were caused by aged water pipes or parts, ground movements and external disturbances.

(b) Upon receipt of a main burst report, the WSD's designated teams will immediately set off for the site to isolate the concerned water mains for carrying out repair works.  Should the incident affect the traffic around the site, the WSD will liaise with the concerned Government departments including the Police, Transport Department and Highways Department to make necessary traffic diversion arrangement to facilitate the repair works.  If the repair works affect other public utilities, the WSD will also liaise with relevant utility undertakers for protecting their facilities.

The public can obtain the latest information about water main burst incidents through the WSD's Customer and Telephone Enquiry Centre (CTEC) hotline.  For an incident affecting the water supply to a large numbers of consumers, the WSD will upload notifications onto the department's webpage.  In addition, radio announcements and press releases will be made for serious incidents.

Staff of the CTEC will also upload information of the water suspension arrangements implemented for emergencies to the Interactive Voice Recognition System of the WSD's hotline and the department's webpage for reference of customers.  The information includes the start time and anticipated end time of water suspension; areas affected; type of water supply affected; causes of suspension; as well as locations of standpipes installed, water tanks and water wagons.  Staff of the CTEC will also maintain close communication with the personnel on site to keep abreast of the latest developments of the incidents.

In the past three years (2009/10, 2010/11 and 2011/12), the average time taken to isolate the burst mains after receipt of main burst reports by the WSD were about 1.5, 2.1 and 1.5 hours respectively.

If a burst is found in a water mains, the WSD will isolate the water mains concerned and carry out emergency repairs of the water mains and road surface as soon as possible for resuming the water supply and traffic to normal.  After completion of the emergency repair works, the WSD will look into the causes of the bursts and, if necessary, replace or rehabilitate the whole section of the problematic mains.

The WSD regularly reviews the overall situation of water mains bursting and follows up the progress of the R&R works to coordinate the prioritisation of replacement and rehabilitation works for specific water mains.  Where necessary, water mains that are not included by the R&R Programme might be injected into the current or upcoming R&R works contracts to accord a higher priority of replacement and rehabilitation for the problematic water mains sections.  If timely adjustment to the works under the R&R Programme is not possible, the WSD will consider deploying district resources for early commencement of the R&R works for the problematic water mains sections.

(c) As mentioned above, the WSD is adopting a multi-pronged approach to tackle the problem of main bursts and leaks, including proactive burst prevention by leakage detection, replacement and rehabilitation of aged water mains under the R&R Programme and implementation of pressure management.

The WSD has enhanced leakage detection as a preventive measure to reduce main burst incidents.  With the advances in technology, the WSD has migrated from the traditional waste detection based leakage detection to the proactive burst prevention based leakage detection. Waste detection based leakage detection is the detection of water loss in a selected water supply zone with follow-up search for leakage spots within the supply zone. Proactive burst prevention based leakage detection is the direct checking of water mains for locating leakage points on the water mains.  Critical water main sections are often closely monitored under such an approach.  The more advanced technology also includes an appraisal of the general condition of the water mains inspected. GSM noise loggers with wireless data transmission capability have been installed at selected pipe sections for continuous monitoring of the flow condition and to provide alerts about possible leakage spots.  The WSD will keep pace with the technology advances around the world and explore new leakage detection technology to strengthen its leak detection capability.  The WSD is now trying out performance-based provisions in leakage detection contracts to incentivise contractors to take more positive steps and be more accurate in locating leaks.  The initial results are satisfactory.

Water main bursts and leaks are closely correlated to the water pressure in the mains.  As pressure management is a proven means to reduce water main bursts and leakage, the WSD has been actively implementing pressure management works in suitable locations over the whole territory.

The R&R Programme is a key element in the reduction of water main burst incidents and active leakage control.  It aims at replacing or rehabilitating 3,000 km of aged water mains of the water distribution network.  It was originally planned for implementation in four stages and for completion within a 20-year period by the end of 2020.  To bring about earlier improvement to the supply system and minimise inconvenience to the public due to frequent water main bursts, we decided in 2005 to compress the R&R Programme from a 20-year to a 15-year period, targeting for early completion by the end of 2015.

The staged implementation of the R&R Programme has made good progress.  Works under stages 1 and 2 have been completed while works under stage 3 and 4 are actively underway.  As at the end of May 2012, a total of about 1, 820 km of water mains have been replaced and rehabilitated.

Ends/Wednesday, July 4, 2012
Issued at HKT 13:07

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