Lin Au culvert, Hong Kong: taming the torrent

A major new water treatment plant on a mountainside overlooking Tai Po in Hong Kong sits on top of a steep flood-prone watercourse, 500 m of which has had to be buried deep under the works in a substantial culvert. This paper describes the challenging design and construction of the 8 m wide concrete-arch culvert, which for the past seven years has successfully contained and dissipated high-speed, boulder-laden storm flows of up to 80 m³/s. The Lin Au culvert incorporates a series of four chutes and stilling basins as well as providing overflow facilities for the treatment works above it using a variety of drop structures. The structural integrity of the culvert is critical, both to support the massive overlying fill platform of the new treatment works as well as to protect it from being washed out by up to 60 MW of hydraulic energy.