970
THE HONGKONG GOVERNMENT GAZETTE, 27TH SEPTEMBER, 1890.
REPORT ON THE DRAINAGE OF THE LOWER WESTERN AND CENTRAL DISTRICT OF VICTORIA.
SIR, The area the drainage of which, I now propose to discuss, is the zone between the Harbour and Caine Road, bounded to the west by Slaughter-house Point, and to the east by the Cricket Ground. Iti ncludes
District No. 1 Shek-tong Tsui
No. 2 Sai Ying-pun
No. 3 Taiping Shan
No. 4 Sheung Wan
"
No. 5 Chung Wan.
It therefore contains the bulk of the Chinese population.
2. In a previous report, it was recommended that the sewerage-system of the High-level District should be completely distinct from that of the lower districts.
The problem now to be solved is:-
(a.) The removal of the sewage from the lower zone, with the rain which falls upon it; to the sea.
(b.) The conveyance of storm-waters from the hill-sides above, through the district, to the sea.
3. The present arrangements for the sewage and storm-water of this district are practically those described in my report of 1882.
Briefly, the practice has been to cover in natural storm-water channels and connect to them branch-drains, conveying both sewage and storm-water. In many cases both main and lateral drains are in very bad condition.
4. In the report on the sewerage of the high level district the objections to the use of storm-water channels for the conveyance of sewage, were fully set forth. These objections apply with even greater force in the case of the low-level district, where, in many places, the storm-water channels are nearly level and accumulate, not only sewer-tainted air, but also sewage deposit.
5. The methods for the improvement of the drainage of this; and other districts, suggested in my report of 1882, have not been tried. This is fortunate, for my subsequent experience leads to the conclusion that they would not have remedied, completely, the evils which existed then; and which exist still.
6. As regards the construction of the branch-sewers no appreciable improvement has taken place. With a few exceptions, any extensions that have been carried out, have been made upon no definite principle.
It will now be necessary
to re-sewer the whole district with earthenware pipes; and to divert the sewage proper, or dry-weather-flow of the sewers from the storm-water channels, which are not; and cannot be made suitable for its reception. The existing stone-channels therefore, should revert to their legitimate use, the conveyance of storm-water from the surface of the district, and from the hills above it.
7. The first question that must be discussed is the number and position of the sewer out-falls. Now the sea must be the ultimate receptacle for the sewage of Victoria. When the system of self-cleansing sewers is complete, the sewage will be delivered into the harbour fresh, before putrefaction has commenced, assuming always that the house-drains are in order. In this condition, sewage is comparatively inoffensive, and is readily consumed by marine organisms, great and small.
8. The following are the leading considerations, which rule the selection of position for sewer out-falls. The sewage should be delivered into water, not less than six feet deep, at extreme low water, and at point where there is an uninterrupted flow of tide; so that the effluent may be removed and diluted, as quickly as possible. For this reason, salient angles are preferable to re-entering as the position of out-falls.
9. The existing Praya affords a very considerable range of choice, as to the position of out-falls. When the new reclamations are complete and the extraordinary irregularities in alignment, which disfigure the existing Praya, have disappeared; one position will be very nearly as good as another. Therefore there will be no necessity for constructing costly intercepting-sewers, to conduct the sewage to one or two great out-falls. Indeed, unless the sewage is wholly intercepted and carried, say, to an out-fall to Sulphur Channel, opposite Green Island, or to North Point; no appreciable benefit will result from its concentration, to any oue out-fall. Such complete interception cannot be effected, unless a con- siderable portion of the sewage is pumped; for the strip of land, between the Queen's Road and the Praya, is practically level; and no sewer, having a gradient sufficient to establish a self-cleansing velocity, could be constructed so as to convey the whole sewage, by gravity, to such a distant out-fall.
10. The complete interception of the sewage, from the harbour-frontage, would be exceedingly expensive, both as to first cost and maintenance. It would not effect any appreciable improvement in the sanitary condition of the city; nor, considering the mass of vessels which frequent the Praya, and the garbage which they throw overboard, would the amenity
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