Sessional_Paper_1905 — Page 755

677

3. Inverted syphon junction of Queen's Road Central and Peel Street

4.

Do.

5.

Do.

under nullah.

under nullah junction of Des Voeux Road Central

and Jubilee Street.

under nullan junction of Praya East and Tsing Kai

Lane.

16. Where overflow plates are fixed at the outfalls into the Harbour, they have a tendency to reduce the efficiency of a flush on account of the discharge pipe carried out into the Harbour being of a less diameter than the sewer; the water then has to back up to the level of the overflow plate, which is fixed well above the sewer and in consequence the sewer does not have a free discharge and the outlet is covered. I would suggest that this plate be either removed or that a moveable plate be inserted that could be lifted up when flushing is taking place.

EFFECT OF THE FLUSHING OF THE SEWERS BY THE GARDEN ROAD TANK.

17. A Flushing Tank has already been constructed in Garden Road below the Volunteer Headquarters, the capacity of which is 6,200 gallons and it has now been in operation for nearly 18 months.

18. Tests were made in February and April, 1904, as to the increase given to the velocity in the sewers compared with their normal flow, and it was found that the velocity approximately doubled when the sewers were being flushed (see Report dated April 25th, 1904). Since then flushing has been carried on regularly and it is found that though these sewers require less attention and cleaning than formerly, yet there is still a little deposit that settles in the portion between Queen Victoria Street and Ice House Street in Des Voeux Road, and along the Praya East and Queen's Road Central between Ship Street and Wellington Barracks. The former I attribute partly, to the overflow plates at the outfall, and to the effect of the flush being less the further away from the Tank that the sewer is, and that the flush in passing through a small pipe into a larger one, the depth of flow in the latter is reduced.

the

19. The portion in Queen's Road Central and Praya East is chiefly caused by very flat gradient of the 12" pipe sewer between Wellington Barracks and Arsenal store-yard which is 1 in 655. This could be greatly improved by re-laying this portion as far as Arsenal Street, a distance of 276 lineal yards which would then give the sewer a gradient of 1 in 375. I am informed that, this section is very rocky, but I cannot ascertain that there is any other obstacle in the way.

SITES FOR ADDITIONAL FLUSHING TANKS.

20. In proposing sites for additional Flushing Tanks, I presume that in view of the Garden Road Tank being supplied from the Albany Nullah, that Mr. CHAD- WICK's suggestion that the Low Level sewers might be flushed with sea water (see paras. 68 and 70, Mr. CHADWICK'S Report, 10th April, 1902), has been abandoned.

21. I. believe that there is ample water to be obtained from the nullahs and other sources without depleting them for their own cleansing, and the expense of pumping sea water would be very great compared with gravitating water from nullahs &c., to the Flushing Tanks.

22. The proposed sites are marked with a red circle on the attached plan and details are given in an attached list (Appendix B.).