CO129-588-16 Water Supply- report on the Tai Lam Chung Valley Scheme 3-1-1941 - 3-1-1941 — Page 4

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6. The depth of the foundations for the dam at the Lower site will not be excessive as rock lies at an average depth of.36 ft. below the surface in the valley bottom. The material overlying the rock consists of sand and shingle and as these are pervious

to water it will be necessary to construct the foundations of the dam within steel pile coffer dams. Further, as the dam rests upon jointed rock it will be necessary to sink a cut-off wall below the base of the dam to prevent percolation. It is hoped that the material excavated from the foundations will be suitable for the concrete in the dam.

7.

The Consulting Engineers estimate that the works required to give an average of 15 million gallons per day would cost approximately $21,600,000. If, however, filter beds and pumping plant are installed in the first place to provide 71⁄2 million gallons only per day, then the cost of the works would be reduced to $20,850,000. These estimates are based on the actual costs incurred when constructing the Jubilee reservoir and on recent 'contracts for works in connection therewith; as it is impossible

to predict what the rates will be after the war. The above figures cover the cost of construction, supervision and Consulting Engineers fees, but not the cost of land, compensation, legal expenses, etc. which can be estimated more closely in the Colony. It is thought that the cost of the reservoir, including the main and subsidiary dams, will amount to $13, 300,000 or approximately ́ ́ ́ $2,100 per million gallons of available storage. The Jubilee reservoir cost about $2,700 per million gallons.

8.

It is expected that four years will be required to construct the reservoir and outlet tunnel, but the remainder of the works could probably be completed in two years. If it is the Colony's wish that the work should be proceeded with without undue delay, it is desirable that instructions should be sent to the Consulting Engineers to prepare detailed drawings, quantities, etc. They anticipate that with the depleted staff which they at present possess, this would occupy from twelve to eighteen months. If the proposals now submitted by the Consulting Engineers receive the approval of the Colonial Government we recommend that a start should be made with the detailed drawings.

9.

The Consulting Engineers consider that the reservoir with main and subsidiary dams and also the tunnels and connected works should be constructed by departmental administration as they do not think there are any contractors in Hong Kong with the requisite technical knowledge and plant to undertake works of the magnitude proposed. It will be remembered that the Gorge dam was built departmentally and, we believe, to the entire satisfaction of the Colonial Government. The filters, pumping stations, service reservoir and pipe lines could perhaps be undertaken by a local contractor.

I have the honour to be,

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Sir,

Your obedient Servant,

53687/41

Je lamont

for CROWN AGENTS.