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.
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.
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.
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.
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.