P.W.E. Hongkong.
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partment being used whilst the other is being cleaned out. The work also includes the necessary re-arrangements and extensions of mains to connect the new works with the West Point Filter Beds, the Pokfulam Road Pumping Station and the City mains.
The Contractor commenced work on the 19th October and by the end of the year the excavation was well advanced; the walls of the nullah crossing the site selected for the deposit of the excavated material were under construction and the diversion of the path to Pinewood Battery was practically completed.
1914 Estimates,.....$150,000.00 | Total Estimates, ........$310,000.00
1914 Expenditure,
4,502.62
Expenditure to, 31/12/14,...
15,211.85
120. Tytam Tuk Scheme, Second Section. In the early part of the year, whilst the cofferdams to enclose the site of the main dam where it crosses the stream-bed were still in course of construction, the excavations over the remaining portion of the length of 380 feet of foundation trench referred to in last year's Report were completed and concreting over this length was proceeded with. The cofferdams, which consisted of a single row of sheet piling, 6″ thick, V-grooved and tongued, driven down to the rock and backed up with earth in the case of the upstream dam and with stone in the case of the downstream dam, were completed in March and the work of excavating the foundations within the area enclosed by them was begun in April. The water percolating through and around the cofferdams was dealt with at first by a centrifugal pump driven by an oil engine. As the excavation deepened, more pumping-power was required and a steam-driven ram-pump and two additional centrifugal pumps were added, the latter being kept in reserve.
In excavating down to the rock-bottom, with the exception of a layer of small water-worn boulders overlying the rock, the material met with was entirely sand. Rock was encountered at about the estimated depths, the general level at the deepest part being 30 feet below the stream-bed. As the stream-bed itself was at about mean sea level, the cofferdams were called upon to withstand a very considerable pressure of water and it is satisfactory to be able to record that they successfully withstood it notwithstanding the unfavourable nature of the ground in which they were situated. On the upstream or reservoir side of the foundation-trench, a tongue, about 13 feet wide and 16 feet deep, was cut into the rock, the depth and width of the cutting varying with the soundness of the rock encountered. To admit of cutting the tongue and subsequently filling it in with concrete, it was necessary to make arrangements for carrying off the water leaking through the upstream cofferdams and so prevent it flooding the cutting. This was accomplished by constructing, parallel with the tongue and immediately clear of the base of the main dam, two concrete walls separated from each other by a distance of two feet, the upstream wall being on a foundation of dry rubble, and by laying a pipe from the space or channel so formed to lead the leakage-water away to the pump.
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