Since 1960 the importation of Chinese water into Hong Kong has played an important part in local water supply. With continued growth, consumption has risen leading to the need for major additional works including a fourth pumping station at Tai Po Tau, the heart of the raw water distribution system. Built in restricted site the D station will have a capacity of over 3000 million litres per day (Mld) (35 m~3/s) making it the largest water pumping station in Hong Kong, increasing capacity at Tai Po Tau to over 5100 Mld (64 m~3/s). An intricate arrangement of tunnels and shafts enables the raw water to be drawn from five sources at two distinct hydraulic levels. The two levels vary depending upon the time of year and also upon weather conditions which cause rapid increases in catchment flow. Water is pumped to two high head (110 m) and five low head (40 m) destinations. Because water is taken from local catchments it can contain large quantities of debris. The D station includes a screening facility which comprises raked bar and rotating band screens. Power supplies are provided from the local grid at 132 kV and the project includes construction of a substation. A major factor in the design and contract documentation for the project was the need to integrate construction of the new facilities, including connections, with minimal disruption to the existing system which the client continues to operate. These considerations influenced the contract strategy and required careful programming. Construction has involved traditional techniques but the large pumphouse sump, constructed mainly in bedrock, required special attention. The paper describes the development of the designs for permanent works and indicates how the implementation programme was developed.
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