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LCQ20: Replacement and rehabilitation of public sewers
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     Following is a question by the Hon Kenneth Lau and a written reply by the Secretary for the Environment, Mr Wong Kam-sing, in the Legislative Council today (March 21):

Question:

     It has been reported that at present, the public sewers in quite a number of districts in the territory have been in service for several decades and rupture from time to time due to ageing. In addition, the volume of effluent discharge of some districts (e.g. Yuen Long) in recent years has increased substantially as a result of population growth, and exceeded the drainage capacity of the public sewers in the districts concerned, resulting in occasional occurrences of sewer blockage and backflow of sewage into properties, thereby causing nuisance to the shop operators and residents concerned. Regarding replacement and rehabilitation of public sewers, will the Government inform this Council:

(1) of the number of complaints about public sewer blockages received by the authorities in the past three years, with a breakdown by District Council (DC) district; whether the Drainage Services Department (DSD) looked into the causes of such sewer blockages, and what follow-up actions the DSD took;

(2) of the districts in which the public sewers have been in service for more than 30 years at present; the total length of public sewers throughout the territory at present, and among such sewers, the length of those identified as requiring expeditious replacement or rehabilitation after assessment and its percentage in the total length;

(3) of the length of the public sewers replaced or rehabilitated by the DSD in the past five years and the expenditures involved, with a breakdown by DC district; and

(4) as the DSD commenced a study on sewer rehabilitation in 2012 to develop a long-term and territory-wide replacement and rehabilitation strategy, of the outcome of the study; whether the DSD has drawn up a work schedule and set priorities for the territory-wide replacement and rehabilitation of sewers?

Reply:

President,

(1) In the past three years, the Drainage Services Department (DSD) has received around 61 900 complaints against the blockage of the public sewerage system. The distribution of those complaints among different District Council (DC) districts is as below:
 
Districts
(by District Council districts)
Number of complaints
in the past three years *
Central and Western 4 100
Wan Chai 6 300
Eastern 3 000
Southern 800
Yau Tsim Mong 13 900
Sham Shui Po 4 500
Kowloon City 6 800
Wong Tai Sin 1 500
Kwun Tong 1 700
Tsuen Wan 3 500
Tuen Mun 1 000
Yuen Long 7 000
North 1 600
Tai Po 1 400
Sai Kung 800
Sha Tin 2 700
Kwai Tsing 1 000
Islands 300

* The complaint numbers have been rounded to the nearest hundredth

     The common causes of sewer blockage include the presence of obstructing material, the building up of oils and grease and sewer collapse. The DSD has arranged regular sewer inspection and cleansing works with a view to reducing the inconvenience caused by sewer blockages.

(2) There are about 1 800 kilometre of sewers under the DSD's management, of which about 50km (around 3 per cent of the total length) of sewers have been initially assessed as sewers requiring urgent replacement and rehabilitation. About 830km of sewers in different parts of Hong Kong have been in service for 30 years or more as shown below:
 
Districts
(Based on DSD Administrative Regions)
Length of sewers in service for 30 years or more
Hong Kong Island and Islands (covering the following DC districts: Central and Western, Wan Chai, Eastern, Southern and Islands) 368km
Mainland South (covering the following DC districts: Yau Tsim Mong, Sham Shui Po, Kowloon City, Wong Tai Sin, Kwun Tong, Tsuen Wan, Sai Kung, Sha Tin and Kwai Tsing) 421km
Mainland North (covering the following DC districts: Tuen Mun, Yuen Long, North and Tai Po) 41km

(3) The DSD will arrange appropriate sewer replacement and rehabilitation works in different parts of Hong Kong taking account of factors such as sewer inspection results, structural conditions of sewers and complaint records. In the past five years, the DSD has rehabilitated around 107km of sewers at a cost of about $500 million in different districts as shown below:
 
Districts
(Based on DSD Administrative Regions)
Sewer rehabilitated in past five years Cost
Hong Kong Island and Islands (covering the following DC districts: Central and Western, Wan Chai, Eastern, Southern and Islands) 35km $28 million
Mainland South (covering the following DC districts: Yau Tsim Mong, Sham Shui Po, Kowloon City, Wong Tai Sin, Kwun Tong, Tsuen Wan, Sai Kung, Sha Tin and Kwai Tsing) 53km $377 million
Mainland North (covering the following DC districts: Tuen Mun, Yuen Long, North and Tai Po) 19km $95 million
 
(4) The DSD has been carrying out sewer rehabilitation works on an as-needed basis.  The demand for sewer rehabilitation works and the resource needed for these works will gradually increase as the sewers continue to age and deteriorate. As it would be more cost effective to deal with the problem in a holistic manner, the DSD commissioned a consultancy study in 2012 to carry out the risk assessment of all sewers and stormwater drains in Hong Kong and formulate the long-term replacement and rehabilitation (R&R) strategy. The consultancy study recommended the Government to adopt a risk-based approach to prioritise the R&R works for the ageing sewers with reference to their probability and consequence of pipe failure. To implement the recommendation in 2017, the DSD has initiated comprehensive planning for the inspection and rehabilitation of sewers that have been assessed to be of high risk. In terms of resource deployment, the department plans to seek funding support of the Legislative Council Finance Committee for two engineering projects at a total cost of about $1,250 million to rehabilitate the trunk sewers in Tuen Mun and those underground sewers with highest risk in different districts.
 
Ends/Wednesday, March 21, 2018
Issued at HKT 14:41
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