ENG-1972 — Page 175

124

PUBLIC WORKS AND UTILITIES

increasing supply by 3,500 million gallons a year on a continuing basis, bringing the total annual delivery to 18,500 million gallons.

Demand for water rose steadily, and a new daily peak of 234.9 million gallons was supplied, an increase of 9.3 per cent over the 1971 peak. Average consumption throughout the year was 195.5 million gallons a day, an increase of 8.0 per cent over the 1971 average. A total of 71,563 million gallons of potable water were consumed compared with 66,100 million gallons in 1971. In addition, 12,829 million gallons of salt water for flushing were supplied, 8.0 per cent less than 1971. Work continued on raising Plover Cove dams. By the end of 1972, the new siphon spillway system had been built and the main dam was almost up to its new level. In conjunction with this work, uprating of Tai Mei Tuk and Tai Po Tau pumping stations continued. Sha Tin treatment works, a focal point of Hong Kong's water supply, was steadily being enlarged, with new filters and settlement tanks being constructed to raise its capacity to 175 million gallons per day in early 1973.

The major contract in the High Island Water Scheme for the construction of the dams was awarded to the Italian firm of Vianini-Societa Per Azioni in August. The two main dams, which will form a fresh water reservoir between the mainland peninsula and High Island, will rise 210 feet above sea level and will be 2,500 feet and 1,500 feet long respectively. In addition to the two main dams, two smaller rock dams will be built higher up in two valleys. The reservoir thus formed will be 3.5 miles long and two miles wide, covering an area of 1,700 acres. About 16 million cubic yards of rock will be used to form the dams, while about 8.5 million cubic yards of material will be dredged from the seabed to form suitable foundations. Construc- tion of the tunnels and intakes to intercept water from the Sai Kung Peninsula catch- ment commenced at the end of 1971. Some 24 miles of tunnel ranging from seven to 13 feet in diameter are being driven, together with 18 stream intakes, each with a shaft of over 250 feet deep. Water from the catchment will flow to the reservoir by gravity and may be drawn from the reservoir into supply by gravity or pumping, depending on the level in the reservoir. There will be associated treatment works, service reservoirs and pipelines to bring the water to the public. The scheme is sched- uled for completion in 1978, but it is hoped to begin drawing water into supply in 1976.

The 50,000 gallons a day experimental desalting plant commissioned in 1971, proved the suitability of the site at Lok On Pai near Castle Peak for the construc- tion of a larger plant and in August 1972, a contract worth $337 million was awarded to the Sasakura Engineering Company of Osaka, Japan, for the supply and instal- lation of boilers, evaporators and ancillary equipment to produce 40 million gallons a day of desalted water from the sea, by a multi-stage flash evaporation process. A proportion of this cost is being met by a loan from the Asian Development Bank of US$21.5 million, repayable in 10 years from 1976. The first of the six units of the plant is expected to come into operation in mid-1974, the remaining five units coming into service successively at three-monthly intervals. When completed, it will be the largest desalting installation in the world.

In addition to these very large schemes, work continued on other projects bringing dependable supplies of fresh water to New Territories villages at Kat O