974
THE HONGKONG GOVERNMENT GAZETTE, 27 SEPTEMBER, 1890.
REPORT ON THE DRAINAGE OF THE EASTERN DISTRICT OF VICTORIA
With a brief summary of recommendation made in the same, and in previous Reports on the subject of
Water-supply and Sewerage.
1. In this report the sewerage of the Eastern District will be discussed; and a recapitulation will be given of the propositions made in this and previous reports on sewerage.
2. The Eastern District, for the purposes of this report, comprises the strip of land between the bills and the harbour. It is bounded on the west by the Glenealy Nullah and on the east by Causeway Bay. The principle inhabited area is practically level. The only dwellings on high-ground are barracks, hospitals, and a few high-class tenements. The bulk of the population resides on the low flat ground.
3. The principles as to self-cleansing sewers, admission of rain-fall and ventilation, which have been laid down in previous reports, apply to this district with equal force. The main question to be decided is the number and position of the out-falls; and whether the sewage is to be discharged into the harbour, in front of the district, or whether it is to be con- veyed to some point outside it.
4. The out-fall question depends, to a considerable extent, on the future of the sea-frontage of this district; whether its area is to be extended by reclamation or not. The present frontage forms a bay, with shallow water for a considerable distance from the Praya wall. A wide strip of foreshore is exposed, at low tides which is very foul. It is possible, that on the completion of the New Praya Reclamation, the' tidal current may be altered in direction, so that silting-up may take place, with greater rapidity than heretofore, and that the deposit on the foreshore may become more offensive than at present. It secins probable that the reclamation of this foreshore will, in time, become an imperative necessity. The topographical conditions are favourable to economical reclamation. In framing a scheme for the sewerage of this district, the possibility of reclamation, must not be lost sight of.
5. The frontage of the foreshore, for the whole length of the district presents no really satisfactory position for an out-fall. The least objectionable point, as regards the hydrographical features of the harbour, would be the frontage of the property of Messrs. JARDINE, MATHESON & Co., near the sugar works, and opposite Kellett's Island. A strong tidal current passes through the channel, between the island and the Sugar Refinery wharf, and would rapidly remove the sewage from the immediate neighbourhood of the out-fall. But whether, after proceeding a short distance, the sewage would not accumulate in the shallow bays which exist, on both sides of the promontory, on which the Sugar Refinery stands, is a point which can only be decided by prolonged float observations. There are, however, many other objections to this point as a general out-let for the whole district. It is private property, and the proposition to place there the general out-fall for a whole district, would doubtless meet with strong opposition.
6. The inhabited area of the Eastern District is so nearly level that it is impracticable to concentrate the sewage, by self-cleansing sewers, at any point within its frontage, without pumping. If pumping be adopted, it would be unwise to fix the out-fall in a position, so open to objection, as that at East Point. A relatively small additional expense would convey the sewage to North Point; which, as an out-fall, leaves little to desire.
7. If the foreshore, in front of this district, were reclaimed to a line joining, with a sweeping curve, the eastern extremity of the Praya Extension, now in progress, with East Point; the Praya wall thus formed would be in relatively deep water, and would form an unobjectionable position for direct out-falls. On account of the increased extent of flat land that must drain to each these out-falls must be more numerous than if the present district alone were dealt with. To provide, in the present scheme, for a future extension of area, more out-falls must be provided and their inverts must be placed at a higher level than if the existing district only were to be treated, without regard to the future.
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8. Considering the uncertainty, as to the future condition of the foreshore, the best plan will be to provide for the strict requirements of the existing arca only, with the minimum number of out-lets. If reclamation is made, then it will be quite practicable to carry the sewage across it in pipes of small diameter, working under pressure, or as syphons; a separate set of sewers and out-falls being provided for the newly reclaimed land or the whole sewage may be intercepted: and pumped to North Point.
9. The project, now submitted, is designed on this principle. It is proposed to discharge the sewage, by a number of out-falls, carried out below low-water mark, into the harbour in front of the district. If the sewage be carried out to a suit- able distance, and discharged below low-water mark, it is certain that any nuisance which now arises from the state of the foreshore, will be abated, if not altogether remedied.
10. For the reasons given in a previous report, on the sewerage of the Central and Western Districts, the invert-level of the out-falls should be 2-75 above OD. Their number and position should be determined by the level and extent of the area draining to ench, and should be such as to give good self-cleansing gradient to the sewers, throughout the area contributing to each. One position being practically as good or as bad as the other, these conditions suffice to determine the question.
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