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6. If the sewers of the yellow district could reach the sea without traversing the districts tinted pink,--the case would be different, and something might then be said in favour of a complete dissociation of the two systems,but this is impos- sible as the pink section of the town interposes as a barrier along the whole length of the city between the yellow section and the harbour. Mr. Lagn's map does not represent correctly the two districts. The distribution of colours is erroneous; it should have been so made as to accord with the line of demarcation provided for in the European Reservation Ordinance which is the only true division. In the Central portion of his map Mr. LEIGH shews the yellow extending down the hill- slope as far as the water's edge, and also at the extreme right-hand of the inap shews a second yellow district stretching along the shore as far as Causeway Bay. Both these yellow sections excepting the comparatively small patch comprising the City Hall, the Cricket Ground, the Naval Yard, and the Military Cantonments, should have been shewn tinted pink between Queen's Road and the sea, because within their boundaries there is no legal restriction against native structures, and because there is every probability in view of the continued influx of Chinese from the mainland, of the ground being covered by such structures partially if not wholly. Nor are even the Military Cantonments themselves altogether safe from a similar fate, for there is actually a scheme under the consideration of the War Office for the sale of a portion of the Military lands for Chinese building purposes in order to raise funds for the erection of European Barracks on more important sites elsewhere. Mr. LEIGH should therefore have shewn one long littoral strip of pink colour embracing the whole of the lower city, except the patch above men- tioned, and if he had done so it would have been patent to anybody at the first glance of his map, that the Separate System sewers of the yellow portious having to be carried through the pink portions, had best be utilized by the Chinese as well, for the disposal of their foul waters.
7. At page 4 of his letter Mr. LEIGH states that his opposition to the Separate System is due to three different reasons. His first reason is that it will not be He says, possible to separate the rainfall from the sewage of native tenements.
in this connexion, that the rain from the roofs and backyards of houses cannot be led away as proposed by Mr. COOPER, by means of Surface-gutters passing from backyard to backyard because the owners of the houses will be likely to stop up the gutters at the communication-holes in the divisional walls between the back- yards, or else because leaves or sticks may choke up these communication-holes with the result that the ground floors would be flooded and trouble caused. There fore Mr. LEIGH proposes, in lieu, that the storm-waters should escape as at present through the foul-water drain of the house. But at page 13 of his letter Mr. LEIGH describes the foul-water drain of the house as being generally choked up with vegetable matter, fruit-skins and other solid refuse. On his own shewing therefore he takes us from the frying pan into the fire for it will be clear to the merest tyro in Sanitation that Mr. COOPER's open surface-gutter can be kept unobstructed far more easily for the escape of flood waters than Mr. LEIGN's varicose underground house-drain. But in fact there are no grounds whatsoever for Mr. LEIGH's appre- hensions that the house-owners will stop up the rain gutters. The Chinese are very neighbourly among themselves and would not be guilty of such silly acts of aggression towards each other, more especially as the passage of the surface gutter across a backyard does a tenement no harm. If any such abuse as that feared by Mr. LEIGH did prevail, it could readily be tnet by legislative enactment. From his recommendation that the heavy tropical rainfall of this climate should be conveyed away through the house drains it is clear Mr. LEIGH does not appreciate the main- advantage of the Separate System viz: the admissibility of small diameters for the house-drains. He attaches no importance to this, preferring to have in the sewage- conduits of the houses and of the streets diameters so large that they shall also be able to take in the heavy and deluging floods of Summer. Yet it is these large diameters, these capacious sizes, exposing so large a floor-surface of sewer and so large a surface of sewage for evaporation to which we attribute the sluggish flow in the east and west street sewers and the consequent undue exhalation of noxious air from them. Also in respect of the objection to surface gutters I should not forget to repeat here that Mr. COOPER'S scheme does provide for the admission into the house-drain of a sufficient quantity of the rainfall,-and that is only the excess which it is proposed to convey away in the surface gutters. This judicious arran- gement while on the one hand providing the house-drain with a sufficient volume of rain water, will so restrict that volume as to enable it to be carried off-by means of pipes of small diameter.
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S. Mr. LEIGH's second reason for objecting to the Separate System is that the scheme divides the City into four drainage districts (page 4 of Mr. LEIGH's letter). I am not sure that I have seized the grounds or reasons of this objection quite correctly as the indictment is so rambling that it is difficult to follow the argu› ments, but I understand Mr. LEIGH to mean that he would prefer six drainage districts instead as shewn in his map, the out-falls being placed at points marked Mr. COOPER's contemplated division of L. 1, L. 2, L. 3, L. 4, L. 5, and L. 6. the City into four separate drainage areas is in accordance with the natural conti- guration of the hill-slope and of the spurs and ravines that intersect those areas. The division is a natural division governed purely by the topography of the ground Under this arrangement, the town sewage will and the gradients of the streets. he conveyed by easy inclines to certain points of ont-fall away from the more populous centres of Victoria and discharged where the tidal current will soonest disperse it. The proposed iuclines will be now here so flat as to incur the risk of undae deposits of silt in the pipe-sewers, more especially looking to the volume of descending sewage from the upper levels which will always maintain the flow through the lower town at a speed sufficient to be self-cleansing. In this respect Mr. LEIGH's Combined System proposes the creation of new main drains running straight down the hill ou steep inclines ranging from about one in four to one in ten, but this alternative is objectionable if only because it makes it difficult with such steep inclines to regulate and control the escape of the gases generated in such sewers,a difficulty that is not lessened by the necessarily large sizes to which these conduits would have to be built since Mr. LEIGH would destine them also for the escape of rain-water. Mr. LEIGU states also that in lieu of only four points of out-fall he would prefer many more and so avoid concentration of sewage matter at so few as four places. There might be something in this contention if the water in the harbour were stagnant, but as Mr. COOPER's proposed outlets of sewage-delivery are swept by tidal currents, Mr. LEIGH's multiplication of out- falls does not appear to me to be necessary. but whether necessary or not, the question is disposed of with regard to the Central and Western districts now that we are to have a general reclamation of the foreshore from Murray Pier to West Point; because it is certain that the erection of the new quay wall further out into the harbour along deeper water will tend to improve the velocity of the inshore currents and thus promote the more rapid dispersion of the effluent.
9. Mr. Leign's third and final objection is to the proposed intercepting sewers. In lieu of these intercepting sewers Mr. LEIGH recommends the direct consigning into the sea-of the contents of each descending main-sewer as soon as the latter has He impugns the been carried down to the Praya level-by the shortest route. propriety of collecting together the aggregate sewage of several knots or groups of foul water drains, and contends that this gathering in of converging foul waters into one trunk-pipe running parallel with the shore-line will not work, because the incline will be so flat as to preclude flow and thereby choke the trunk-pipe. In the previous paragraph I have already explained that there will be a self-cleansing velocity. and that as the trunk pipe has been designed to be self-cleansing, the But again here the new Reclaina- block anticipated by Mr. LEIGH will not occur. tion Scheme which was elaborated subsequently to the Drainage Project will neces- sitate a reconsideration of the latter in that branch of it which relates to the inter- cepting sewers, and as we shall now have in the central and western town a marine pre- embankment in deep water throughout, I am of opinion that it will be found ferable to adopt the modification set forth in the small alternative plan prepared by Mr. COOPER and dated the 29th of December, 1888, which plan together with a Report from Mr. COOPER in reply to Mr. LEIGH's criticismus is now submitted. In the Eastern portion of Victoria where no sea-reclamation is contemplated the first or original scheme prepared by Mr. COOPER would remain unaltered.
Mr. COOPER'S leport of 29th December 1888
and enclosure.
10. All those passages in Mr. LEIGH's letter wherein he urges the increased ventilation of the main sewers in connexion with his Combined Project, are, as stated before, concurred in by Mr. COOPER and myself provided the main sewers are continued in use as foul-water conduits. If sewage however is diverted from them into separate glazed stoneware pipe-drains as advocated by us it will obviously be unnecessary to embark in any system of increased ventilation for channels that The question of the adoption or the rejec- are destined to carry only rain-water. tion of the Separate System must therefore be settled first, and that of the ventila- tion of the present sewers second, and on this point I would like to point out that all the ventilation in the world will be useless so long as each private house-drain connected with such ventilated main continues to remain an elongated cesspool of Mr. COOPER and myself have pre- putrid sewage, without fall or without flow.
June
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