203
24
The two 18" pipes to be connected to a valve chamber somewhat similar to that on the Kowloon side, and the two 18" pipes brought up in the chamber and connected to a 24" pipe which shall be carried from the valve chamber above the level of the Harbour a distance of some 40 feet by approved gangway and let through the existing sea wall to the back, properly built in, sufficiently clear to allow a flanged connection to be made to the new 24" main which will continue the line from this point in the future.
The pipes in the valve chamber to be fitted with all the auxiliary fittings, bends, scour pipes and valves as shown on Drawing No. 7.
On both the Kowloon and Victoria sides the ends of the 24" pipes to be left with the flange faced, but not drilled, and temporarily stoppered, so that a connection of the 24" pipe may be made in the future.
The pipe line is to consist of two lines of 18" pipe laid in a trench excavated to such depths and widths below the bottom of the Harbour as will be sufficient to give a cover of refilled material of not less than 8′ 6′′ below the bottom of the Harbour, as shown on section, Drawing No. 3, excepting such length of pipes, near the Victoria shore, as shown to be laid into the hard strata, with less cover, but protected by concrete apron.
The pipe lines may be laid together or individually, and either in two trenches, one for each pipe, or in one trench for the two pipes, in which latter case the line of pipes would require to be laid not nearer than 4′ 6′′ from centres. The centres will be wider as the pipes diverge on approach to the valve chamber on either side, so as to get a convenient entrance through the walls of the chambers, and the Contractors must allow for all such additional width.
It is suggested, as a method of laying, that the pipes should be jointed on the shore in lengths of 200 feet, or such longer or shorter lengths as may be directed, and depth of water may allow, each length of 200 feet, or such other length, after being jointed, is to be tested for soundness of joints, bituminous lining, etc., under the direction of the Engineer, to such hydraulic pressure as he may direct, not exceeding 50% above the working pressure at the point where the connected length will be laid in position.
The Contractors must supply all water, apparatus, assistance, and everything necessary for carrying out these tests, and include all expenses. The length of pipe, as jointed together, to be floated into position either by its own buoyancy or other supplementary means as may be necessary, and joined up with the ball and socket joint between each 200 feet length before being immersed. It may be necessary for ball and socket joints to be at less distance than 200 feet so as to get a convenient entrance to the valve chamber, as before mentioned, in line.
The trench to be taken out to such cross section as shall give convenient space for properly laying and bedding the pipes, and the excavated material shall, so far as can conveniently be done, be returned as back fill, subject to any requirements of the Harbour Authorities as to the level over the trench, and all surplus material removed from the Works and deposited at such point in the Harbour, or within five miles of the Harbour, as the Harbour Authorities may direct.
Before laying the pipes the bottom of the trench is to be examined, and if necessary, levelled and adjusted, so that the pipe does not rest on the joints but on the body of the pipe itself.
Where a ball and socket joint is to be fitted, the additional excavation necessary to allow it to be properly bedded, to be included in the Tender together with the disposal of the additional surplus, and a provisional sum will be allowed in the Schedule for cement concrete, proportion 1—2—3 for bedding round, under and over the connection, as the Engineer shall direct. The rate given for the concrete to include all work in connection with it of every description wherever the disposal is below low level water of the Harbour.