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Hon. Director of Public Works,
3.0.
(
11861 200
ទ
IREC
Arc2 4. APR 08
PROPOSED BOAT-SHELTER AT MONGKONTSO1.
I beg to submit the accompanying plan and section, and the following report. I regret the delay in reporting, which has been due to my time being fully occupied with the routine work of the Department.
The plan shows, in red, the long breakwater originally pro- posed, and in green, a short breakwater now suggested, but not recommend -ed. The section shows a design which has been prepared after full con-
sideration of the effects of the 190€ typhoon.
The bulk of the work could be carried out by native contract- ors. The concrete blockwork is the only part of the structure which would have to be carried out departmentally, and very little special plant would be required for it. A dredger would have to be hired from the Dock Company or Messrs. Punchard, Lowther & Co., for the purpose of excavating the trench for the foundations.
The blockwork is expensive but necessary, because three tons is the maximum weight of the boulders to be got by junks, and such blocks are too small to withstand the action of the sea at or near low tide level. The concrete blocks would extend down to 7 feet below Ordnance Catum, at which depth the three-ton boulders would not be liable to disturbance by the waves.
I estimate the cost of this design at $370.00 per lineal foot, and the total cost of the long breakwater as follows:-
4,000 lineal feet at $370
Extra labour and materials at beads
$1,480,000
60,000
€
Total $1,540,000
The actual cross section of the long breakwater at any point would not differ materially from the average cross section shown; and judging by the borings taken in connection with the propos- ed work, and by the soundings on the Admiralty Charts, the average cross section of the short breakwater, or of any other breakwater in
the
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