Providing award-winning storm water solutions for urban flooding challenges
Happy Valley in Hong Kong, China, is home to one of the city’s premier racecourses and several exclusive, high-rise residential buildings. Previously, the area was known as the Wong Nai Chung Valley and was dominated by rivers and a marsh-heavy environment. Despite development and investment in infrastructure, during the city’s rainy season, heavy rainstorms could lead to floods up to a metre deep. RSK company Binnies, known for its extensive technical expertise in this area, has a long history of working with the Hong Kong government’s Drainage Services Department on the Happy Valley Underground Stormwater Storage Scheme (HVUSSS): an innovative scheme designed to solve the historical flooding problem.
Almost 20 years ago, Binnies completed the first large-scale underground storage tank in Hong Kong, at Tai Hang Tung, for temporarily storing water during heavy rainstorms. The system effectively reduced flooding in Mong Kok, a major shopping area in Hong Kong and one of the busiest districts in the world. A major achievement was reducing the length of the drains upgraded from 94 km to about 48 km. These were laid under very busy roads with congestion of utilities and complex project interfaces.
More recently, Binnies designed a 2.4 ha, 60,000 m3 underground storage tank for Happy Valley, which featured innovative designs including a movable weir system; a foundation design with a peripheral sheet-pile wall and subsoil drainage system; and a water harvesting system. The robust nature of this scheme effectively reduced the required volume of the storage tank by 25%, thus shortening the time taken to construct the tank and thereby minimising public and environmental impacts. The movable weir system enables excess storm water to enter the tank at the optimal time. It also lets part of the stored water discharge back to the box culvert by gravity, instead of by pumping, achieving an impressive energy saving.
The hard work of all involved in the HVUSSS was recognised with a number of prestigious awards in Hong Kong and overseas, including the International Water Association Award that was received in 2012. The project showcases how Binnies and RSK can work with nature, applying smart and sustainable solutions to safeguard the general public from flooding risk in highly urbanised cities like Hong Kong.