LCQ7: Underground water main burst incidents

Following is a question by the Hon Pan Pey-chyou and a written reply by the Secretary for Development, Mrs Carrie Lam, in the Legislative Council today (November 2):

Question:

In recent years, a number of underground water main burst incidents occurred in Hong Kong, which not only caused inconvenience to members of the public, but also wasted valuable water resources. In this connection, will the Government inform this Council:

(a) of the details of the underground water mains replacement works which are currently in progress or have been planned to commence in the next three years in various districts on Hong Kong Island, broken down by District Council district; and the expected completion dates of the works currently in progress;

(b) of the respective numbers and exact locations of the underground water main burst incidents which occurred in various districts on Hong Kong Island in the past three years, broken down by District Council district; and

(c) in the past three years, of the average time required to handle water main bursts between receipt of reports of such incidents by the authorities and completion of the repair works and resumption of normal water supply, and among such incidents which occurred on Hong Kong Island, of the longest and shortest handling time?

Reply:

President,

The water distribution network of Hong Kong has gradually developed in accordance with the growing water demand. It is a massive and complex system, measuring 7,800 kilometres (km) in total length. With the ageing of the network, bursts and leaks are inevitable. We fully understand that suspension of water supplies would cause inconvenience to the public. To tackle the problem, the Water Supplies Department (WSD) is taking a multi-pronged approach, including proactive burst prevention by leakage detection, replacement or rehabilitation of aged water mains under the Water Mains Replacement and Rehabilitation Programme, and pressure management. With these measures in place, the number of water main burst incidents dropped from a peak of 2,500 in 2000-01 to 609 in 2010-11. In the first six months of 2011-12, the number dropped further to 212.

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

(a) The Replacement and Rehabilitation Programme for Hong Kong Island is implemented in four stages. Each stage involves replacement and rehabilitation (R & R) works at different locations. While works for Stage 1 and 2 have been substantially completed, we are pushing ahead with works for Stage 3 and 4. The total value of the five works contracts for Stage 3 amounts to $1.6 billion, two of which involve the replacement and rehabilitation of 71km of water mains in the Central and Western District. The remaining three contracts, one each for the Eastern District, Southern District and Wan Chai, involve replacement and rehabilitation of water mains measuring 52km, 39km and 51km respectively. All the works have commenced since 2009 and are expected to complete by the end of 2013. As for Stage 4, the works for the first two contracts with a total value of $1.1 billion commenced in the middle of this year. The work sites are scattered in four District Council (DC) areas on Hong Kong Island. These two contracts involve replacement and rehabilitation of 156km of water mains and are expected to complete by the end of 2015.

Details of the R & R works to be carried out in the coming three years in each District on Hong Kong Island are set out in Table 1.

We have been monitoring the progress of these works closely throughout the construction stage to ensure that they could be completed as soon as possible. We have also liaised regularly with departments and utilities companies concerned to overcome various constraints such as traffic, environmental constraints and densely packed underground utility services, so as to minimise the inconvenience caused by the works to the public.

(b) The number of underground water main burst incidents in each District on Hong Kong Island over the past three years are shown in Table 2.

(c) In the past three years, the average time required to handle fresh and salt water main burst incidents on Hong Kong Island (between receipt of reports of such incidents by the WSD and resumption of normal water supply) was about 8 hours and 12 hours respectively. The shortest and longest time for handling fresh water main burst incidents were about 2 hours and 46 hours respectively, whereas those involving salt water main burst incidents were about 3 hours and 76 hours respectively. Those incidents that required longer handling time were isolated cases mainly caused by the presence of densely packed underground utility services hindering the carrying out of repairing works; confined working time in non-peak hours; the need to remove the concrete surround that encased the burst water mains; the longer time required for setting of the concrete blocks for stabilising the new water mains before resumption of water supply.

After isolation of the burst fresh water mains, the WSD will maintain uninterrupted water supply for the affected areas by arranging alternative supply from other water supply zones as far as possible. If alternative supply from other supply zones is not viable, the WSD will provide temporary emergency fresh water supply to the affected consumers by provision of standpipes or deployment of water wagons and water tanks.

Ends/Wednesday, November 2, 2011
Issued at HKT 13:24

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