A stormwater drainage project beneath a famous racecourse in Hong Kong has won an award for demonstrating how cities around the world are rethinking the way they plan and manage intense rainfall in crowded urban spaces.
Black & Veatch and the Drainage Services Department of the Government of Hong Kong Special Administrative Region (DSD) received the 2012 Planning Award for the International Water Association’s East Asia region.
The winning HK$1 billion project, the Happy Valley Underground Stormwater Storage Scheme (HVUSSS), commenced construction in September 2011. The first phase is scheduled for completion by early 2015, the second by early 2018.
During historical heavy rainstorm events in August 2000, April 2006 and June 2008, severe flooding occurred in Happy Valley and its adjacent areas. With the new 60,000m3 capacity storage tank, stormwater will be temporarily stored in the storage tank during peak times of a rainstorm.
At the heart of the innovation is a movable crest weir system together with Supervisory and Data Acquisition (SCADA) real-time monitoring of water and tidal levels. The volume of water within the storage tank can be monitored and adjusted to prevent either pre-mature or late overspill of stormwater.
Major components include an inlet structure, twin cells diversion box culvert with overflow side weir system, an underground storage tank of 60,000m3 and a pump house with a pumping rate of 5,400 m3/hr.
During heavy rainstorms, excess runoff in the diversion box culvert will enter the storage tank via the overflow weir system. After rainstorms the storage tank will be emptied to prepare for upcoming rainstorm events.
Chan Chi-chiu, director of drainage services, said: “We put our best minds to work and have arrived at a solution that adopts the latest technology, takes into consideration future climatic change and reduces construction time, as well as cost. When planning, we were very aware of how this project could affect the community too, so we have paid close attention to accommodating their needs and minimizing the environmental and social impacts.”
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