ENG-1965 — Page 210

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PUBLIC WORKS AND UTILITIES

Sha Tin and Tai Po Tau will gravitate by eight miles of tunnel to the same point. The combined flows can then gravitate through a further six miles of tunnel to Tai Mei Tuk for storage in Plover Cove. A reservoir of 900 million gallons capacity has been completed at Sha Tin to provide a balance for the flood flows in the Sha Tin-Tai Po Tau tunnel. The hydraulic gradient of the tunnel can be reversed by automatically closing a gate at Tai Po Tau, thereby forcing the flow into the balancing reservoir for temporary storage.

The River Indus yield, while non-existent during the driest periods of the winter, can exceed 200 million gallons a day under summer flood flow conditions and a pumping station of this capacity is being provided on its banks. Provision was also completed for the integration into the Plover Cove scheme of the water from Kwangtung province and the River Indus at the rate of 20 million gallons a day by means of a 36-inch diameter pipeline from Sha Tin to the outlet of Shing Mun Reservoir. Extraction from Plover Cove will be by pumping at Tai Mei Tuk against the fall of the Tai Po Tau-Tai Mei Tuk tunnel, which was 75 per cent complete. At Tai Po Tau the extract-together with the water from China and the River Indus-can be repumped against the fall of the Sha Tin-Tai Po Tau tunnel to the treatment works. These at present have a capacity of 80 million gallons a day, with site provision for extension to 160 million gallons a day. The treated water is pumped to service reservoirs through twin 48-inch and single 54-inch diameter mains laid below the two-lane road carriageway of the Lion Rock tunnel.

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The Tai Po Tau pumps, the eight-mile Sha Tin-Tai Po Tau tunnel, the Sha Tin treatment works and pumps, two of the Lion Rock tunnel pipelines, and the 900 million gallon balancing reservoir were all brought into service on 1st March to take delivery of water from Kwangtung province at the rate of 62 million gallons a day. The yields to Tai Po Tau and the River Indus pumping stations are impounded by inflating dams of neoprene-coated nylon under compressed air and water pressure, while the natural yield to Tai Po Tau is increased by a similar dam at Tau Pass which reverses the flow of a stream. These dams, on which installation work was completed during the year, deflate during periods of excess flow, and thus reduce the risk of flooding in the surrounding countryside.

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