THE HONGKONG GOVERNMENT GAZETTE, 27TH SEPTEMBER, 1890.
An experience of ten years in the Colony, and having had an office for six years on the Praya front, opposite Peddar's Wharf, and having always carefully observed the course of the numerous cargo boats and traffic by the side of the Praya, convinces me, that there is an almost equal strong current at any point along the Praya from Wellington Battery to Belcher's Point, and that there is very little difference in the speed of matter, either Eastward or Westward.
949
ments of Mr.
Mr. Cooper.
The float experiments of Mr. CHADWICK and Mr. COOPER were confined to particular points, and in no way Float experi- cause me to alter the above opinion. Therefore it would be far better to discharge smaller portions of sewage Chadwick and at a number of points, and thus diffuse the matter more thoroughly, than greater portions of sewage discharged at three or four points only.
opposite
quarter.
It would need but a very slight acquaintance with the Praya to see, that where the large population of Strong tide-way Chinese are, the Praya Wall has been constructed in the deepest water, and consequently in strong tidleway, Chinese which would effectually carry away any matters discharged by properly constructed and numerous outfalls. At a very little distance from the Praya Wall, (as will be seen from the length of the wharves), ocean steamers are
berthed.
at certain places
outfalls.
There are places, such as opposite the City Hall, Commissariat Pier and Bowrington, where the configura- Lesser tide-way tion of the Praya would naturally lead one to expect slack water; even at such places, I consider, that by not affecting suitable length of outfall, there is amply sufficient current to diffuse the small amount of sewage discharged at those places.
outfall at
Canal.
At Bowrington Canal especially, there exists a large foreshore caused by the deposit of silt washed down objection to the Wong-nei-cheong Valley. The outfall, proposed by Mr. COOPER at C. 4, is essentially wrongly placed for Bowrington a collecting sewer, as admitted in the report by the recommendation to carry this discharge by pumping to North
Point.
numerous
An advantage in having numerous direct outfalls is, that sewage would be more rapidly discharged into the Advantage of sea from its place of production. I estimate that from no part of the City would the sewage take longer than direct outfalls. two hours to be dispersed into the sea. Sir ROBERT RAWLINSON in his "Suggestions," says:
"All sewage should be disposed of, if practicable, on the day of its production." This would not be the case with low lying intercepting sewers; and in a tropical climate, it is essential to have the most speedy discharge.
exist.
An important fact which must not be forgotten in considering the discharge into the harbour of the sewage No focal matter of this City, is, that practically no focal matter exists. The disposal of night-soil being carried out by the bucket system.
of increased
I disapprove of any increase in the number of water-closets, which should only be allowed in the Hotels, Disapproval Clubs, or large Public Institutions. There is not therefore the liability of having floating matter brought down number of
by the sewers into the harbour.
Water Closets.
reclamation
to outfalls.
I have made no mention of the proposed reclamation from the Harbour in front of the City and shewn on Proposed new Plate No. 1, as it is obvious that the sea wall would project into deeper water, and greater tidal currents, there. advantageous by diffusing the discharge of outfalls still more rapidly. The work of constructing such outfalls would be a simple matter in building the new wall, which will be in from 15 to 40 feet depth of water.
The employment of four outfall points only, necessitates the construction of intercepting sewers, low-lying Intercepting and of very flat gradients, such as 1 in 1,000 to 1 in 1,700.
Sewers
necessary to Mr. Cooper's Scheme.
costly.
The construction of these sewers would be extremely costly, the soil is made ground, practically sand free Construction to the sea, the trenches would be continually flooded and heavy pumping would be required; in many places, without close piling, no pumping would contend with the sea.
Sewers
Besides, granted that the sewers were constructed, they would be "backwatered " every high tide. During Intercepting the South West Monsoon (especially when typhoons are in the neighbourhood) the sea level remains abuormally backwatered. high for days together, there being no rise and fall of the tide, and during such times the sewers may be called upon to work under pressure.
It must also be remembered, that these intercepting sewers by not having a free outfall, can never be sitting of
intercepting emptied; silting, in this case, must take place, necessitating, either very heavy flushing, or periodical cleaning Sewer." out of the silt pits.
Gas from
Sewer.
A source of danger is also created by the sewer becoming au elongated tank with slow velocity, constantly Discharge of giving off sewage gas, which must be discharged somewhere, and no doubt the tendency is for it to be distributed intercepting up the tributary sewers.
of Brighton
Sewer.
I would here like to give the experience at Brighton of the low level intercepting sewer. In a paper read Experience before the Institution of Civil Engineers, the Borough Surveyor of Brighton gives as his opinion, that, for a intercepting town like Brighton, the system of pipe outfalls into deep water was a good one, and that, from a sanitary point of view, they were not better off, after having built the seven miles of intercepting sewer, than they had been
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