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Drainage Services Department - Sustainability Report 2012-2013

The Year's Highlights / Flood Prevention

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Sub-sections in The Year's Highlights

[Awards at-a-Glance] [Flood Prevention] [Sewage Collection, Treatment and Disposal]

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[highlight1.gif] 25 No. of Awards Received in 2012-13

Flood Prevention

Completion for River Improvement Works in Upper Lam Tsuen River, She Shan River and Upper Tai Po River

The commissioning ceremony of River Improvement Works in Upper Lam Tsuen River, She Shan River and Upper Tai Po River was held on 12 January 2013 which declared the rivers had attained a flood protection standard of 1 in 50 years.

In order to alleviate the flooding risk and cope with the future development in Tai Po area, we commenced construction of the river improvement works through straightening, widening and deepening of these rivers in September 2007. Apart from increasing their flood protection capacity, the ecological values of these natural rivers were also maintained. During construction, we encountered difficulties such as inclement weather, and limited site access, etc. With the joint efforts of our staff members and our contractor, the river improvement works was completed smoothly in December 2012. Most importantly, we developed mutual trust and understanding with the villagers and green groups in this project.

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The engineered She Shan River

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Commissioning Ceremony on 12 January 2013

Commissioning of Hong Kong West Drainage Tunnel, Lai Chi Kok Drainage Tunnel and Tsuen Wan Drainage Tunnel

To further enhance Hong Kong's overall flood protection capability, we have commissioned three large-scale drainage tunnels including Hong Kong West Drainage Tunnel (HKWDT), Lai Chi Kok Drainage Tunnel (LCKDT) and Tsuen Wan Drainage Tunnel (TWDT) in August 2012, October 2012 and March 2013 respectively. By adopting the interception approach at uphill catchment, the drainage tunnels provide effective and long-term flood protection to the urban downstream areas. Works were carried out on the urban fringes, reducing the need for road excavation in busy urban areas and thus minimising disruptions to the communities, traffic and commercial activities.

Hong Kong West Drainage Tunnel

HKWDT, running from Tai Hang to Cyberport, is about 11 kilometres long and of diameter varying from 6.25 metres to 7.25 metres. The project will relieve flooding in Northern Hong Kong Island, in particular the low-lying areas along Central, Admiralty, Wan Chai and Causeway Bay. One of the technological firsts of the project is the extensive use of Raise Boring Machines to excavate drop shafts of intakes from the bottom upwards. This method, which enabled transportation of excavated materials through the tunnel, had greatly reduced the construction nuisance and eliminate truck trips on narrow congested roads in delivery of spoil. With its exemplary achievements in overcoming various challenges during construction, the project was awarded with Tunnelling Project of the Year (US$100million to US$1billion category) in the "International Tunnelling Awards 2011", organised by British engineering magazines of "New Civil Engineer" and "Ground Engineering". The project was also elected as one of the top three projects in "The Hong Kong People Engineering Wonders in the 21st Century" election organised by The Hong Kong Institution of Engineers in 2013.

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The commissioning ceremony of the HKWDT was held on 22 August 2012 to celebrate the debut of a flood prevention masterpiece in Hong Kong history

Lai Chi Kok Drainage Tunnel

LCKDT, 3.7 kilometres in length and of diameter 4.9 metres, intercepts stormwater from the upland areas of Northwest Kowloon. It serves to raise the overall flood protection level of the downstream areas in Lai Chi Kok, Cheung Sha Wan and Sham Shui Po. One of the technological breakthroughs of the project is the first use in Hong Kong of a single Tunnel Boring Machine (TBM) for boring two sections of tunnel with distinct ground conditions, one in hard-rock and the other in soft-ground. When compared with conventional approach of using two TBMs, this results in significant savings in cost, plus knock-on saving in materials and associated energy input, leading to a reduction in carbon footprint. Besides, in order to protect the underground facilities, the construction workers have to work in a hyperbaric environment up to 4.2 bars, which breaks the record of Hong Kong tunnelling history. Safety performance of the hyperbaric operations was remarkable, attaining zero decompression illness. This successful experience in using hyperbaric operations paves a new way forward for the Hong Kong construction industry in using hyperbaric technology.

With achievements in technological breakthroughs and continuous improvement in service, the project was awarded "HKIE Innovation Award for the Engineering Industry" and "Civil Service Outstanding Service Award Scheme - Silver Prize in General Public Service" in 2013.

The commissioning ceremony of the LCKDT on 18 October 2012 declared the accomplishment of an engineering milestone to relieve the flooding problem in northwest Kowloon.

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Commissioned Lai Chi Kok Drainage Tunnel at an adit and tunnel junction
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Chief Executive, Mr. C Y Leung, officiated the commissioning ceremony of the LCKDT on 18 October 2012

Tsuen Wan Drainage Tunnel

The 5.1 kilometres long TWDT, with diameter of 6.5 metres, intercepts surface runoff from the uphill catchment of Tsuen Wan and Kwai Chung for direct discharge into the sea near Yau Kom Tau, thereby relieving the loading of the existing drainage system in the downstream. The design capacity of TWDT is the highest among all the drainage tunnels in Hong Kong. The flow of floodwater at peak can fill up a Olympic-size swimming pool in 11 seconds. In order to maintain a certain amount of flow for downstream ecological needs, all intakes will intercept floodwater only when amber rainstorm signal or above is in force.

The commissioning ceremony of TWDT was held on 28 March 2013 which marked the launch of a drainage tunnel with the highest flow rate in Hong Kong.

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Permanent Secretary for Development (Works), Mr. Wai Chi-sing (fifth right), and Director of Drainage Services, Mr. Chan Chi-chiu (third left), officiated at the commissioning ceremony of the TWDT on 28 March 2013

Removal of Two More Flooding Blackspots

With the progressive completion of our flood prevention projects, we have removed all the remaining major or regional flooding blackspots in Hong Kong in 2010.

In 2012-13, we have further eliminated two flooding blackspots at Ha Wo Che Village in Sha Tin and Ling Tsui Tau Tsuen in Mui Wo, reducing the number of blackspots from 15 to 13 in 2013.

The remaining 13 flooding blackspots are being tackled in phases - drainage improvement works for six blackspots have been commissioned, and their effectiveness is being monitored; and drainage improvement works at various stages, namely planning, design and construction are being implemented for the other seven blackspots. We keep on closely monitoring these locations during rainy seasons and we expect to remove the remaining flooding blackspots progressively when we complete other improvement projects.

Change in Total Number of Flooding Blackspots

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Year 1995 Major or Regional Blackspots is 8, Medium, Small or Minor Blackspots is 82, Total Number of Flooding Blackspots is 90; Year 1996 Major or Regional Blackspots is 8, Medium, Small or Minor Blackspots is 66, Total Number of Flooding Blackspots is 74; Year 1997 Major or Regional Blackspots is 8, Medium, Small or Minor Blackspots is 63, Total Number of Flooding Blackspots is 71; Year 1998 Major or Regional Blackspots is 8, Medium, Small or Minor Blackspots is 76, Total Number of Flooding Blackspots is 84; Year 1999 Major or Regional Blackspots is 9, Medium, Small or Minor Blackspots is 65, Total Number of Flooding Blackspots is 74; Year 2000 Major or Regional Blackspots is 8, Medium, Small or Minor Blackspots is 64, Total Number of Flooding Blackspots is 72; Year 2001 Major or Regional Blackspots is 7, Medium, Small or Minor Blackspots is 64, Total Number of Flooding Blackspots is 71; Year 2002 Major or Regional Blackspots is 6, Medium, Small or Minor Blackspots is 59, Total Number of Flooding Blackspots is 65; Year 2003 Major or Regional Blackspots is 5, Medium, Small or Minor Blackspots is 57, Total Number of Flooding Blackspots is 62; Year 2004 Major or Regional Blackspots is 4, Medium, Small or Minor Blackspots is 49, Total Number of Flooding Blackspots is 53; Year 2005 Major or Regional Blackspots is 3, Medium, Small or Minor Blackspots is 40, Total Number of Flooding Blackspots is 43; Year 2006 Major or Regional Blackspots is 2, Medium, Small or Minor Blackspots is 36, Total Number of Flooding Blackspots is 38; Year 2007 Major or Regional Blackspots is 2, Medium, Small or Minor Blackspots is 33, Total Number of Flooding Blackspots is 35; Year 2008 Major or Regional Blackspots is 2, Medium, Small or Minor Blackspots is 30, Total Number of Flooding Blackspots is 32; Year 2009 Major or Regional Blackspots is 1, Medium, Small or Minor Blackspots is 21, Total Number of Flooding Blackspots is 22; Year 2010 Major or Regional Blackspots is 0, Medium, Small or Minor Blackspots is 18, Total Number of Flooding Blackspots is 18; Year 2011 Major or Regional Blackspots is 0, Medium, Small or Minor Blackspots is 16, Total Number of Flooding Blackspots is 16; Year 2012 Major or Regional Blackspots is 0, Medium, Small or Minor Blackspots is 15, Total Number of Flooding Blackspots is 15; Year 2013 Major or Regional Blackspots is 0, Medium, Small or Minor Blackspots is 13, Total Number of Flooding Blackspots is 13;
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