964
THE HONGKONG GOVERNMENT GAZETTE, 27TH SEPTEMBER, 1890.
REPORT ON THE SEWERAGE OF THE HIGH-LEVEL DISTRICT OF THE
CITY OF VICTORIA, HONGKONG.
SIR,-In continuation of the reports, which I have already submitted to you, with regard to the Recommendations made by the Commissioners appointed to enquire into the cause of the Fever, &c.; I have now the honour to lay before you, my recommendations as to the sewerage of that district.
1. In my previous reports I merely expressed concurrence with the statement, that the sewerage of the district, required improvement. Having made an examination of the district in question, and of that adjacent to it, eastward between the same altitudes; I find that many similar conditions obtain in both. The topographical features are such that the joint area may be treated as one sewerage scheme, which will be absolutely separate and distinct, from the sewerage of any other portion of the City of Victoria. I propose therefore to discuss, not merely the sewerage of the Western District; but that of what may be called the High-level District. The boundaries of the High-level District are, approximately, as follows. To the northward or below, Caine Road, as far as Ladder Street, thence westward by Bonham Road to its junction with Pokfoolum Road; and on, by Hill Road and Queen's Road to Belcher's Point. To the south or above, the present boundary is the Pokfoolum Aqueduct. To the east, the boundary is Shelley Street, though a few houses, east of this, may be connected to it. To the west, the boundary is at present undetermined, but may be taken as a line drawn in a southerly direction from Belcher's Point. The High-level District, therefore, comprises the greater portion of the arca, reserved for European dwellings. Its sewerage-system may be so arranged as to be wholly distinct from that of the City below. Indeed it will scarcely be an exaggeration to say, that no Chinese tenement will pour its sewage into this system.
2. The sewerage-system (if it merits the name), which has hitherto obtained in this and other districts, has been to drain tenements to the nearest natural storm-water channel, or nullah. When the open channel has become offensive, owing to the sewage poured into it, the nuisance has been abated, or rather hidden, by covering it over.
In this manner a number of large covered storm-water channels have come into existence, which follow the courses of natural water-courses, and which convey both rain-water and sewage to the harbour.
3. From the point where these combined channels cross Queen's Road, to their mouths at the Praya, they have but little fall, and they are filled up with sea water, on the rise of each tide. Excepting, therefore, during heavy rain, the current through them is checked in the lower and flatter parts, and a deposit of earth, stones and sand, mingled with sewage, takes place, giving off offensive emanations; which may, and often do, rise to the upper regions above.
4. In my original report on the Sanitary Condition of Hongkong, I proposed to remedy this, by diverting the sewage-proper and dry-weather flow from the combined sewer and storm-water channel, at the point where it enters the flat region, and conducting it by a separate pipe of small diameter to the sea. I further recommended certain improvements to the storm-water chaunels, in their steeper parts, so as to render them more suitable for the conveyance of sewage. These recommendations however, have not been carried out; nor, with the exception of a few lengths of pipe sewer, constructed since the arrival of Mr. COOPER, has any improvement been made in the construction of street-sewers, As far as sewerage is concerned, matters are now very much in the same condition, as they were in 1882. I now propose to effect the interception at an earlier period. All recent experience shews that a channel, suitable for the conveyance of a tropical rain-fall, is not a suitable conduit for sewage, in dry weather. The practice of converting storm-water channels into sewers has, not only here, but everywhere, beca weighed in the balance and found wanting.
5. This decision has been arrived at, principally by the consideration of recent experience, as to the ventilation of sewers. This question has received great attention of late years, and large additions have been made to the stock of knowledge on the subject. At the same time much misapprehension exists, as to the causes which necessitate it, its objects and effects. Before proceeding to describe the proposed sewerage of the High-level District, I propose to discuss, as briefly as possible, the principles of sewer-ventilation; and to define what it is intended to effect, what it can effect, and what it cannot do. These principles affect, not merely the High-level scheme; but every sewerage scheme whatsoever. To these general data, a brief discussion will be added of the general principles which have to be attended to, in the construction of sewers.
6. It is usual to speak of "sewer gas," as though it were some specific gaseous substance, such as oxygen or hydrogen, or ordinary coal gas; and to assume that sewage evolves this objectionable substance in large quantities. Now, as a matter of fact, sewage, even when containing the full amount of focal matter, and purposely retained in a stagnant and putrify- ing condition, is found to evolve but little, true gas. The gases which it does evolve are marsh-gas, carbonic acid and a little sulphurated hydrogen.* These gases are produced by the decay of all vegetable matters, in the presence of water. They are not intrinsically poisonous or disease-producing. In a large un-ventilated sewer, containing deposit, an elongated cosspool, in short, these gases may accumulate and make the air unfit to sustain life. A man entering such a sewer right loose his life by suffocation. He would not be poisoned, any more than a man who is drowned, on falling into the water, is poisoned by it.
* Fide Appendix Í. Appendix II.
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