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Hon. D.P.'...
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MINUTE BY
MR. A. B. PURVES, M.INST.C.E.
I have little to add to the very full report prepared by Mr. Woodward: the figures given are indisputable and generally I agree with the report.
The consumption recorded during the past few months, with a constant supply,
is extraordinarily high and has entirely upset all previous estimates.
Mr. Woodward's estimates of future requirements cannot be regarded as high and if consumption continues to increase as forecasted, the present works will soon be inadequate to maintain a constant supply.
Filtration and distribution difficulties are increasing rapidly and it was just possible to avoid the introduction of restrictions last August when consumptions of 17.37 and 10.22 M.G.P.D). were recorded on the island and mainland respectively over a period of a fortnight.
As regards storage, the present position is relatively similar to that in 1920, when 2 years previously the island storage had been trebled by the completion of the Tytam Tuk Reservoir.
It was then thought and stated that Hong Kong water troubles were over for many years, but from 1922-1936, without a single exception, annual restriction of the island supply had to be imposed.
From 1920-1935 inclusive, approx. $20,000,000 had been spent on new Water Works, and already, despite the newly completed Jubilee Reservoir, the safety margin between resources and requirements for a constant supply is very small and by next year will have disappeared.
The programme of work outlined in Appendix VI is a formidable one and re- presents an outlay of probably $5,000,000. The time required to complete these works will depend on the staff provided. The present staff of the Water Works Construction Sub-department is quite inadequate to carry out this programme within a reasonable time and could deal only with the items of greatest urgency.
The following are the principal difficulties pertaining to the island supply which require immediate consideration.
1. Deficiency in raw water resources.
2. Increasing and safeguarding the delivery from the mainland to the island.
3. Lack of facilities on the island for taking fuller use of mainland water.
4. Additional filtration plant.
The deficiency in raw water resources can be met, temporarily, by constructing the Tai Mo Shan and other Catchwaters draining into the Shing Mun Valley, as shown in Appendix I and referred to in Paras. 32 and 33 of Report.
It is estimated that these Catchwaters, dealing with a total drainage area of 3888
acres, would increase the Shing Mun resources by 5 M.G.P.D.
As however about 4 years would be required to complete these works, the position on completion would be little better, relatively, than at present if the estimates of future consumption are borne out.
Further increases of the Shing Mun resources may be found economically possible, but at present it is considered that the works shewn on Appendix I re- present the final development of the Scheme.
It is accepted in Great Britain that water works resources should maintain a
5 years lead over requirements. If this practice is to be applied in Hong Kong, and there seems every reason why it should be, the only solution is to seek fresh sources of supply in the New Territories.
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The Tai Lam Chung Valley, lying a few miles East of Castle Peak is known to possess considerable water possibilities and to contain a basin which might be found suitable for a very large storage reservoir.
In view of the present position, the investigation of this valley, with a view to ascertaining its storage possibilities water value etc. is recommended.
Increasing and safeguarding the delivery from the mainland to the island,
Paras, 50 and 51 of Mr. Woodward's report deal with this matter and stress the vital importance of the cross harbour mains to the island supply.
I agree that a 2nd 18" main in substitution for the original 12" main should be provided as soon as possible and that a more permanent protection for both mains is very necessary.
The existing mains are much too vulnerable to corrosion from salt water action and also to damage from dragging anchors; whilst the Government diver reports that owing to corrosion it would be extremely difficult, if not impossible, to effect repairs to the 12" main were a length carried away.
Lack of facilities on the Island for taking fuller use of Mainland water.
At present, mainland water can only he delivered into the Gardens Service Reservoir, which is approx. 240 feet A. O D. Therefore only the low lying position of the City can he supplied from the mainland.
The middle levels of the City, e.g. below Caine Road level, are supplied from the Tytam Source via the Bowen Road Conduit which for a certain period of every year is worked to its utmost capacity.
For a good many years, difficulty has been experienced in delivering sufficient Tytam water to the central part of the City, owing to increasing demands in the Eastern district.
As the island resources are not capable of further development, the proposals outlined in Para. 52 of the Report shew the only course by which it is possible to deliver additional water to a higher level of the City.
Pumps capable of delivering 5 M. G. P. D. to the Albany Service Reservoir are contemplated but a portion of this delivery could be diverted westwards by convert- ing the existing unfiltered Albany-Elliot main to a filtered water main and connect- ing it to the proposed pumping main.
The question of augmenting the supply to the upper levels of the City, i.e. above Caine Road, is also one which cannot remain for long in abeyance and is referred to in Paras. 85 and 105 of the Report.
Additional Filtration Plant.
Not only are the existing filters on the island insufficient to cope with summer requirements, but the location of the various installations throughout the City is not ideal.
There is ample filtration capacity in the Western District and a reasonable amount in the Central District, which is augmented by filtered water from the main- land.
In the Eastern District, however, there is a deficiency and it is in this district that most future development is likely to occur.
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