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67. As mentioned in para. 49 the tendency will be for the areas supplied from the Eastern Source to move to the East and this movement will necessitate rearrangement of the sites of the filters.
68. With the proposed delivery of Mainland water (filtered) to Albany, and thence to Elliot when necessary, the Albany filters would not be required nor would those at Elliot for Tytam water. The Albany filters being very old would therefore be discarded.
69. Provision of filters of a capacity of 10 M.G./D. at Eastern to deal with the maximum quantity available from the Eastern source should therefore be made. This grouping of the filters at Eastern would materially facilitate the control of the filtration and also of distribution.
70. Filtration capacity for dealing with the Western resources is ample.
Proposed Extensions.
71. It is therefore proposed:-(a) that a 4 M.G./D. filtration plant be erected at Eastern now, (b) that one of 3 M.G./D. be erected there to supersede the Albany filters when Mainland water is supplied to that point and (c) that, to provide service reservoir space, the Bowen Road plant be dismantled and re-erected at Eastern.
Filters Mainland.
Existing Capacity.
72. The present normal capacity of the mainland slow sand filters is 2.9 M.G./D. although during 1936 the absolute limit of 4.08 M.G./D. had to be passed through them to satisfy the demand. The capacity of the Rapid Gravity filters is 10 M.G./D. making a present total of 12.9 M.G./D. A further 5 M.G./D. Rapid Gravity plant is now under construction and on completion of it (about June 1937) the total filter capacity of the mainland will be 17.9 M.G./D.
Filters Requirements.
73. The present resources of the Mainland supplies are 3.16 M.G./D. (Kowloon) and 9.25 M.G./D. (Shing Mun Valley) making a total of 12.41 M.G./D. Allowing an addition of 30% for the peak load, the required filter capacity for these resources should be 12.41+3.72=16.13 M.G./D. The 1937 filter capacity being 17.9 M.G./D. there will then be a favourable margin of 1.77 M.G./D.
74. With the addition of the catchment areas proposed in para. 34 the re- sources from the Mainland will be 12.41 +4.25-16.66 M.G./D. The required filter capacity for these resources after allowing 30% for peak load should be 16.66+ 5.00 21.66 M.G./D. There will thus be a deficit on the estimated requirements of 3.76 M.G./D. in 1941.
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Proposed Extension,
75. It is therefore proposed that the 4th 5 M.G./D. rapid gravity filtration plant be constructed in the lower Shek Lai Pui Valley by the end of 1939 in order to be available to utilize the proposed new resources. It is not practical to install a plant of smaller capacity as the uniformity of layout of the present plants would be destroyed and the balance of filtration capacity will most probably be required at an early date.
SERVICE RESERVOIRS
Island.
Existing Capacity.
76. The total capacity of the various service reservoirs in the City is 26.30 M.G. the working capacity of which is about 22.0 M.G. or approximate 12% above the estimated peak requirements of 1937. Details of the capacities of the various service reservoirs are shewn in Appendix V.
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