Sessional_Paper_1892 — Page 457

453

No.

31

HONGKONG.

REPORT ON KOWLOON WATER SUPPLY.

Laid before the Legislative Council by Command of His Excellency the Governor, on the 16th November, 1892.

No. 521.

PUBLIC WORKS OFFICE,

KOWLOON WATER SUPPLY.

HONGKONG, 30th June, 1892.

SIR,I have the honour to report that in November last active operations were commenced for testing the yield of the well marked No. 1 on Plan* sunk under the direction of Mr. OSBERT CHADWICK, C.M.G., in 1890, and described in his report dated 14th of May, 1890, on the proposed water supply for British Kowloon.

2. From this well Mr. CHADWICK proposed to derive the water necessary for a complete supply to the Kowloon Peninsula, but as will be seen from his report in the event of sufficient water not being obtainable from it he proposed to supplement the supply by sinking further wells in the same locality but in different watersheds.

3. I now propose to briefly describe the experiments and further works that have been carried out during the last dry season with the object of ascertaining the quantity of water obtainable from this source during the dry season of the year.

4. A turbine pump capable of delivering 400,000 gallons per diem was obtained from England and erected in the well. This pump was actuated by a portable engine (a portion of the plant previously used in the construction of the Tytam water works). Every thing was in readiness and pumping commenced early in November.

5. It was soon found, however, that the brick steining of the well resting on a metal curb entering the impervious clayey stratum underlying the coarse silicious sand prevented the entry of water into the well. In fact, the well was practically a sump, and the supply of water to this sump must depend entirely (no springs existing in the bottom of it) on the measures adopted for intercepting the waters of the valley with which the ground for some distance around was more than saturated to the very surface, the surplus waters flowing by in a stream.

6. On piercing the steining of the well a few feet from the bottom a copious supply of water was immediately obtained, and the water in the well rapidly rose to the same level as that outside.

This flow of water into the well, as was to be expected, brought with it large quantities of sand, and it was evident that some less crude method must be resorted to before pumping for any length of time without endangering the staging carrying the pump and gear could be resorted to. Further, the sand contains a good deal of clayey matter, so that the cone of depression is of very limited area around any one point of abstraction.

7. The method adopted for diverting the water into the well and for taking the best advantage of the existence of a large comparatively flat bed of sand some 10 feet in depth and fully charged with water was as follows.

8. A line of 9-inch pipes commencing at the well 3 feet 6 inches above the bottom was laid with open joints in a south-easterly direction and provided with lateral branches as shewn on the Plan* in Drainage Area No. 1.

The pipes were laid on a bed of broken stone averaging 1 foot 6 inches thick and surrounded with 12 inches of the same material, on which was placed a layer of coarse screened sand 12 inches în thickness.

The trenches were then filled up and the ground restored to its original level.

The broken stones forming the foundation were deposited on the impervious clayey stratum so as to drain the sandy deposit at the lowest possible level.

9. Owing to the instability of the ground it was necessary to keep the water down in the excavation consequently pumping had to be resorted to day and night. However, by temporarily diverting the water near the point A, some pumping was saved.

Pumping commenced on the 27th of November, and was continued night and day till 4th of March, except for a short interval of three days. After the 4th of Marchi, al excavations being completed, the water was allowed to rise in the well at night and was pumped out during the following day.

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