CO129-588-16 Water Supply- report on the Tai Lam Chung Valley Scheme 3-1-1941 - 3-1-1941 — Page 3

CROWN

AGENTS

FOR THE

ALL COMMUNICATIONS

TO BE ADDRESSED TO THE

CROWN AGENTS FOR THE COLONIES.

THE FOLLOWING REFERENCE AND THE

DATE OF THIS LETTER BEING QUOTED.

COLONIES

4, MILLBANK,

1.3

W/E.. 254/17.

RECEIVED

LONDON, S.W.I.

TELEGRAMS

TELEPHONE: ABBEY 7730.

INLAND: "CROWN SOWEST LONDON:" OVERSEAS: "CROWN LONDON."

4 JAN 1041 C.O. REG

3rd January, 1941.

дв

Sir,

4/-/40

I have the honour to refer to your letter No.53687/40 of the 23rd February regarding the proposed construction of a storage reservoir in the Tai Lam Chung valley, Hong Kong. Your letter requested us to arrange for a representative of Messrs. Binnie, Deacon & Gourley to visit Hong Kong to inspect and select the most suitable dam site, and report and advise on the general scheme, and upon any further surveys etc., which might be required.

2.

Mr. W.J.E. Binnie, the senior partner of the firm, visited Hong Kong in May last and spent three weeks in investigating conditions at the site and discussing the project with local officers. During the visit Mr. Binnie was asked to report on the problem as a whole, i.e. not only with regard to the dam

but also as to the best way in which the water could be distributed. We enclose two copies of the Consulting Engineers' report dated 27th December, 1940 which covers the layout of the complete scheme.

3.

Two sites had been suggested for a dam to impound water in the Tai Lam Chung Valley, and these two sites are referred to in the report as the "Upper" site and "Lower" site. The Upper site has the advantage that the water level of the reservoir would be at a higher elevation, and this would reduce the amount of pumping required. The Consulting Engineers have, however, reached the conclusion from the topographical features and the boreholes that the Upper dam site would be situated over a major geological fault which would make the dam very costly to construct, even assuming that its construction was practicable. The Consulting Engineers have no hesitation, therefore, in recommending that the dam should be built at the Lower site even though pumping costs will be greater.

4. Borings at the Lower site did not disclose the objections which were found at the Upper site and a gravity masonry dam is proposed which, with high water level at 190 ft., will permit the storage of 6,400 million gallons. The main dam would have a maximum height of about 190 ft., above the valley bottom and its length at road level would be about 940 ft. Small subsidiary dams would also be necessary at three depressions in the ridge which form part of the western boundary of the reservoir.

5.

Having regard to the minimum rainfall that may be expected in periods of drought, the anticipated run off from the ground, loss by evaporation etc., it is estimated that the natural catchment area of 4,200 acres will permit an average supply of 15 million gallons per day which can be increased to 30 million gallons per day when the run off from 8,000 acres is brought into the reservoir by catchwaters. The quantity of water supplied to Hong Kong in 1939 was 26.9 million gallons, but restrictions were in force during the year.

The Under Secretary of State,

COLONIAL OFFICE,

S.W.1.

6./

CA