942
THE HONGKONG GOVERNMENT GAZETTE, 27TH SEPTEMBER, 1890.
very variable and will no doubt very often be nil. In the latter case drain traps attached to sub-soil drains will prove ineffective and sewer air will freely course through such drains and issue through the interstices provided for the escape of sub-soil water.
Further, in the case of any stoppage occurring in a foul water sewer with which sub-soil drains happened to be in communication, sewage might back into the sub-soil drains and escape through the joints as just described. These objections will be got rid of if all foul waters are diverted from the existing drains of the town into special channels of their own sub-soil drainage then becomes possible and may be led without risk into the present existing drains.
I will now briefly describe the new Separate System of sewers proposed. On looking at the plans it will be seen the city is naturally divided into four drainage districts. Three of these districts are situated to the west of the Albany Nullah, and one to the east. There are thus, four proposed main intercepting sewers which for the convenience of reference I will allude to as numbers 1, 2, 3 and 4, draining districts Nos. 1, 2, 3 and 4 respectively as marked on the accompanying plan.
Main No. 1 providing for the drainage of district No. 1 (coloured red on plan sheet No. 1), will commence in Caine Road opposite Castle Road where it receives the sewage from Seymour Road, Castle Steps and Castle Road, it then takes a westerly course along the Caine Road, Bonham Road, Hill Road and Queen's Road West receiving the sewerage from Robinson and Richmond Roads, and ultimately discharging into the harbour at Belcher's Point.
The area of this district is 160 acres, and it is only thinly built over, but in order to allow for future extensions the sizes of the sewers have been calculated to discharge per 24 hours as much as 14 inches of rain-fall over the whole
area.
Main No. 2 providing for the sewerage of District No. 2 (coloured brown on plan sheet No. 1,) will commence in Queen's Road Central opposite Pottinger Street and takes a westerly course along Queen's Road receiving the sewerage from those portions of the Chung-wan, Tai-ping-shan and Sai-ying-pun districts which are situated south of the Queen's Road. On reaching Centre Street this main will take a northerly course down Centre Street, and arriving at the Praya will turn again to the west and follow the line of the Praya where it will receive the sewage of a portion of the Shek- tong-tsui District and ultimately discharge into the harbour at the proposed out-fall at Belcher's Point.
The area of this district is 233 acres and it is almost entirely built over. The sizes of the sewers have therefore been calculated to discharge 2.40 inches of rain-fall per 24 hours, or of an inch per hour, over the whole area.
Main No. 3 providing for the sewerage of District No. 3 (coloured yellow on plan sheets I and II,) will commence in Queen's Road Central, at the Corner of Murray Barracks, where it will receive the sewerage from Garden Road, and will pass down Murray Road to the Praya where it will turn along the Praya in a westerly direction as far as Winglok Street, which it will traverse and thence discharge into the harbour at Possession Point. This main is designed to provide for the portion of the city situated between Queen's Road Central and the Praya the area of which is 190 acres.
The circumstances prevailing in two portions of this District are so different that in calculating the sizes of the sewers I have sub-divided it into the area draining above Ice House Lane, which may be called Sub-district 3a com- prising 120 acres extent and the area draining below Ice House Lane to the west which I will call Sub-district 3B, 70 acres in extent.
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In sub-district 3A, are situated Government House, and the Botanical Gardens occupying extensive grounds and not likely ever to be closely built over, moreover the elevation and position of the Albany Nullah, admit of a free outlet being always obtained for storm waters in this neighbourhood. The size of the main sewer along the Praya has therefore been calculated to convey inch of rain-fall per 24 hours over this sub-district. The other sub-district 3B being closely built over, the sizes of the sewers have been calculated to discharge 2.4 inches of rain per 24 hours falling over the whole sub-district in addition to the inch contributed by sub-district 3a.
Main No. 4 providing for the sewerage of district No. 4 (coloured brown on plan sheet II,) will commence in Queen's Road Central opposite the Royal Naval Yard and will traverse Queen's Road in an easterly direction as far as the Eastern Guard House, where it turns down Arsenal Road to the Praya, and continues along the Praya as far as the Bowrington Canal and there discharges into the harbour. At this point also it receives the sewage of the Bowrington District.
Though the best available without pumping I cannot recommend the proposed position of this out-fall as a permanent measure and would strongly advise in perference, that the main be extended to the alternative point of out- fall at North Point.
The area of the eastern District is 247 acres. In it are situated the Barracks and Military and Naval Establish- ments but the higher levels are at present but little built over. The sizes of the sewers have been calculated to discharge 11⁄2 inches of the rain falling over the whole District. As just stated, I am only able to recommend the construction of the out-fall, at Bowrington as a temporary expedient and I therefore deem it desirable to submit herewith a plan (sheet No. III,) and also a section showing the necessary works that would have to be undertaken in order to extend the out-fall to North Point. Such an extension, if carried out, would provide also for the sewerage of the Causeway Bay Reclama tion and of Tung-lo-wau, giving a total area draining to North Point of 270 acres.
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