Following is a question by the Dr Hon Priscilla Leung and a written reply by the Secretary for Development, Mr Paul Chan, in the Legislative Council today (March 16):
The Water Supplies Department commenced the Replacement and Rehabilitation Programme of Water Mains (the Programme) in 2000 to comprehensively replace and rehabilitate about 3 000 kilometres of aged water mains in phases. In reply to my written question on October 14 last year, the authorities indicated that the Programme would be substantially completed by the end of last year, and thereafter the condition of the water supply network would be significantly improved. However, a number of water main burst incidents occurred in Hong Kong within the past six months (e.g. three such incidents occurred in the vicinity of the Ma Tau Chung Fire Station in Kowloon City within three months), causing traffic congestion and serious nuisance to the daily lives of residents in the districts concerned. As such, some members of the public have queried the effectiveness of the Programme. In this connection, will the Government inform this Council:
(1) whether there are works under the Programme which have yet to be completed; if there are, set out the respective total lengths of the water mains concerned and the implementation schedules for the relevant works by District Council (DC) district;
(2) of the details of each of the fresh water main burst incident which occurred in September 2014 or after, including (i) the location of the burst water mains, (ii) the duration for which the fresh water supply was suspended as a result, and (iii) the number of years for which the water mains had been used before the burst, and set out such details by DC district; among such incidents, the respective numbers of those involving (i) water mains which had been used for less than 30 years and (ii) water mains which had been replaced and rehabilitated under the Programme;
(3) whether it has assessed the effectiveness of the Programme; if it has, of the details; if not, the reasons for that; and
(4) given that the authorities have indicated that "apart from the age of water mains, we will continue to consider other relevant factors, e.g. the pipe material, burst and leakage records, current conditions of the water mains, etc., to determine the probability of occurrence of burst failure of water mains and at the same time assess the seriousness of consequences arising from main bursts (e.g. the number of users affected, interruption to traffic, etc.) in identifying water mains with a relatively high risk of failure for replacement and rehabilitation", whether the authorities have drawn up a priority list for replacement and rehabilitation of water mains with a relatively high risk of failure; if they have, of the locations of such water mains and the relevant implementation schedules, and whether the several sections of water mains located in the vicinity of the Ma Tau Chung Fire Station which burst in the recent months were on the list; if they have not drawn up such a list, when the authorities will finish drawing up and publish the list?
The Replacement and Rehabilitation Programme of Water Mains (the Programme) involves the replacement and rehabilitation of some 3 000 kilometres (km) of aged water mains in stages. With the replacement and rehabilitation of 2 939 km (98 per cent) of aged water mains as at the end of December 2015, the whole Programme was substantially completed. My reply to the four parts of the question is as follows:
(1) Up to end January 2016, the respective total length of water mains of which relevant works are still in progress within each district of the District Council (DC) under the Programme are shown in Table 1. It is expected that the remaining works will be completed by the end of 2016.
(2) (i) Table 2 shows a breakdown of fresh water main burst incidents between September 2014 and January 2016 in the respective districts of the DC:
(ii) Of the 98 fresh water main burst incidents shown in Table 2, 64 cases (about 65 per cent) caused disruption to fresh water supply. Among these disruption cases, 45 cases (about 70 per cent) entailed suspension of water supply for eight hours or less and about 5.6 hours on average. For the remaining 19 cases, the duration of interruption averaged about 13.9 hours. Their repair works took longer time mainly because (a) the roads could only be closed on a limited scale in order to minimise the impact on road traffic; (b) only light weight equipment could be deployed for the repair works to avoid damaging the congested underground utilities; and (c) considerable time was needed to open up concrete structures.
(iii) Of the 98 water main burst incidents mentioned above, 15 incidents (about 15.3 per cent) involved water mains that have been in service for less than 30 years. Among them, nine cases were damaged or affected by road excavation works in the vicinity while the remaining six cases were caused by ground movement or subsidence, external loading or vibration. Of these 15 incidents, only one involved a water main that has been replaced and rehabilitated under the Programme. The incident was caused by road excavation works in the vicinity.
(3) Since its commencement in 2000, the Programme was substantially completed as at end December 2015. Its efficacy in reducing water mains burst incidents and leakage rates are demonstrated in:
(i) the significant drop in the number of water main bursts from around 2 500 cases in 2000 to 145 cases in 2015 (including both fresh and salt water mains); and
(ii) the reduction in leakage rates from over 25 per cent in 2000 to 15 per cent in 2015.
(4) Following the substantial completion of the Programme at end December 2015, the condition of the water supply network has improved significantly. Looking ahead, we will adopt a multi-pronged strategy to maintain the health conditions of the water supply network. With reference to overseas advanced technology and experience, we plan to progressively establish the Water Intelligent Network (WIN)(note). Upon its full implementation, we can use the WIN to analyse conditions of the water supply network and draw up the most cost-effective network management measures to optimise its health condition.
During the transitional period prior to the full implementation of the WIN, we will reprovision those aged water mains that are susceptible to failure. The first phase covers about 20 km of aged water mains that are mainly located in Kowloon City, Kwun Tong, Kwai Tsing and Tsuen Wan. We have commissioned a consultant to undertake the relevant investigations and design work. Upon completion of these works, we will proceed with the reprovisioning of these water mains as soon as possible. To identify the remaining water mains that need to be reprovisioned, we will continue to review the probability of occurrence of burst failure of water mains in the light of the relevant factors, such as pipe materials, burst and leakage records, current conditions of the water mains, etc., and assess the seriousness of consequences arising from main bursts (e.g. the number of consumers affected and interruption to traffic, etc.). We will then plan for reprovisioning of these water mains.
The recent incidents of water mains burst in the vicinity of Ma Tau Chung Fire Station in Kowloon City involved a salt water main of 900 mm in diameter, a fresh water distribution main of 250 mm in diameter and a salt water distribution main of 150 mm in diameter. All the distribution mains around the Ma Tau Chung Road, Shing Tak Street and Fu Ning Street were replaced at the end of December 2015 as part of the Programme and with the support and cooperation of the Kowloon City DC. Upon completion of the fresh water connection works for the remaining few consumers in the first quarter of this year, all these old distribution mains (including the distribution mains involved in the incidents) would be rendered obsolete. As regards the salt water main of 900 mm in diameter, rehabilitation work for this particular section of water main, measuring 400 metres in length, has been arranged and scheduled for completion by the middle of this year.
Note: Under the WIN, the whole water supply network will be divided into some 2 000 District Metering Areas for which monitoring and sensing equipment will be installed to collect relevant data for analysis by an intelligent network management system. The objective is to continuously monitor the conditions of the water supply network.
Ends/Wednesday, March 16, 2016
Issued at HKT 15:03