Following is a question by the Hon Gary Fan and a written reply by the Secretary for Development, Mr Paul Chan, in the Legislative Council today (April 15):
Question:
It has been reported that since July last year, some households in the housing estates along Sha Tin Wai (including Shatin Park Stages 1 to 3, Fung Shing Court, Greenfield Court, Garden Rivera and Greenwood Garden) have, one after another, found black particles in fresh water. Following laboratory tests, the Water Supplies Department (WSD) preliminarily confirmed that the particles were bitumen, which were suspected to be spalled fragments of anti-corrosive bitumen protective inner coatings of old-style fresh water pipes due to pipe ageing. WSD undertook to locate the problematic sections of the water pipes and install strainers to solve the problem. However, WSD has not given an account of the investigation results so far. Some households are worried that prolonged consumption of fresh water containing bitumen particles will affect their health or even cause cancer. Regarding the spalling of anti-corrosive bitumen protective inner coatings of fresh water pipes, will the Government inform this Council:
(1) whether WSD has located the sections of water pipes involved in the above incident; if it has, of their exact locations and age, and the reasons and remedies for the spalling of bitumen protective inner coatings; whether WSD has prepared an investigation report on the incident; if it has not, the reasons for that;
(2) whether WSD has formulated plans to comprehensively inspect all fresh water pipes in Shatin district for spalling of bitumen protective inner coatings in the light of the above incident; if it has, of the respective numbers of water pipes which have and have not been inspected; if not, the reasons for that;
(3) of the number of complaints about fresh water containing foreign objects received by WSD in each month of 2014, and the number of cases in which the foreign objects concerned were confirmed to be bitumen (with a breakdown by District Council district); and
(4) whether WSD has plans to inspect all fresh water pipes in Hong Kong for spalling of bitumen protective inner coatings, and whether it has formulated measures to prevent the recurrence of incidents of bitumen particles found in fresh water?
Reply:
President,
In designing water supply networks, the Water Supplies Department (WSD) uses different types of pipe materials to suit the need. Steel pipe is one of the major and commonly used pipe materials. As for the internal protective lining for fresh water steel pipes, bitumen was the most popular choice in the last century. The bitumen used had to comply with the requirements of BS4147, which precluded any harmful substance that might affect the safety of fresh water. Generally, the risk of the internal protective lining peeling off is not high. However, the possibility of tiny patches of bituminous lining peeling off from water mains after long years of service cannot be ruled out. Regarding the concerns of some customers about the organic compounds being leached from bituminous materials that might affect the quality of fresh water supplies, all the chemical test results for water samples taken regularly by WSD show that the fresh water is compliant with the Guidelines for Drinking-water Quality promulgated by the World Health Organization and is suitable for potable consumption.
Our reply to the four parts of the question is as follows:
(1) On receipt of complaints about fresh water supplies containing tiny bituminous particles lodged by some customers in the housing estates at Sha Tin Wai area in July 2014, the WSD conducted an investigation and found that the causes were related to the emergency repair works for a burst main at Che Kung Miu Road in Tai Wai on July 19, 2014 and the repair work for a water valve in Sha Tin on July 30, 2014. On resumption of water supply after the repair work, water pressure inside the network increased sharply, causing small patches of internal bituminous protective lining to peel off from the 800mm diameter fresh water main under Che Kung Miu Road and a 600mm diameter fresh water main under A Kung Kok Shan Road. These two water mains are steel pipes laid in 1983 and have been in use for over 30 years. The bituminous protective lining peeled off as a result of the sudden rise in water pressure and the ageing of pipes. The WSD has put these two water mains into the replacement and rehabilitation (R&R) programme. Relevant works are scheduled to commence this year. In the meantime, the WSD has installed six water strainers at the affected housing estates in order to prevent foreign particles from entering into the interior plumbing of the customers' premises. These strainers are also cleaned regularly.
(2) and (4) As mentioned above, the bituminous materials of the internal protective lining for fresh water steel pipes do not contain any harmful substance and, hence, will not affect the safety of fresh water. That said, the WSD has been taking water samples for tests from the supply networks regularly over the territories, including Sha Tin, and undertook regular flush cleansing of the water mains. On discovery of or receipt of a report about bituminous particles in water samples, the WSD will take immediate follow-up actions, including taking further water samples for tests and flush cleansing the water mains to ensure that the fresh water is compliant with the required standard. The WSD recorded two cases involving bituminous particles in the fresh water supplied by the government water supply system in 2014. Both of them occurred in the housing estates at Sha Tin Wai area. For details, please refer to part (1) above.
In fact, the WSD has begun to replace and rehabilitate the aged water mains under the R&R programme since 2000 and will continue the work as necessary. Since 2005, the WSD has replaced bitumen with epoxy as internal protective lining for pipes so as to prevent water quality from being affected by peeling bitumen.
(3) A breakdown by the constituency areas of the District Councils of the public complaints related to "fresh water supplies with foreign objects" arising from the government water supply system and the cases of "foreign objects confirmed to be bitumen" as received by the WSD in 2014 are shown in the Annex.
Attachment:
Ends/Wednesday, April 15, 2015
Issued at HKT 13:35
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