Sessional_Paper_1909 — Page 94

The obvious way of contracting the width of the northern entrance was to continue the breakwater northward for some distance; but I had to point out that, if that were done, the contracted entrance would be blocked by the rocky shoal which projects southward from K.M.L. 32 (the Asiatic Petroleum Co.'s Oil Works). The best way, therefore, and ultimately the most economical way, of narrowing the entrance would be to adhere to the position originally chosen for the north head of the break water, and extend the Oil Works point of land southward, by reclaiming the rocky shoal. I reckoned that the sale- able value of the area reclaimed would go a long way towards defraying the cost of carrying out the reclamation.

The southern entrance could easily be narrowed by curving in the south end of the breakwater sharply towards the shore; but I suggested that it would be preferable to adhere to the original plan entirely, as far as the breakwater was concerned, and narrow the southern entrance by building out a jetty from the shore, in line with Sixth Street. The jetty would be very useful as a public landing place, and the reduced entrance would occupy a position where vessels could easily make it without having to hug the shore.

The Consulting Engineers approved of these suggestions and recommended that the widths of the entrances should be reduced accordingly-the northern entrance from 900 feet to 300 feet, and the southern one from 840 feet to 390 feet. They considered that these widths would be quite sufficient for the traffic, and for the promotion of such a circulation of water within the sheltered area as would prevent stagnation and the serious deposit of silt. These opinions were based on the information which I was able to give regarding the nature of the traffic, and the strength and direction of the tidal currents.

With reference to the form of the breakwater: While approving of the general character of the original design, the Consulting Engineers were of opinion that certain alterations, which they considered of importauce, should be made in the details. They recommended that the slopes should be flattened; that a wide berm of five-ton boulders should be substituted for the ramp of ten-ton concrete blocks; and that the upper portion of the outer slope, which was originally intended to be covered with concrete in mass, faced with granite pitching set in cement mortar, should simply be covered with pitching consist- ing of two-ton concrete blocks set dry. The inner slope should be covered with dry stone pitching, in accordance with the original design; and the sizes and distribution of the materials in the rubble mound should, in the main, be in accordance with that design.

The Consulting Engineers entirely concurred in believing it to be necessary that a trench should be dredged in the mud, for the purpose of reducing the lateral spreading of the foundations, as the rubble is deposited.

Having regard to the nature of the bottom on which the breakwater has to be constructed, and the character of the local labour and materials available, the Consulting Engineers had no doubt that a rubble mound structure, such as I proposed. was the proper and most suitable one to adopt. It is true that during the construction of such a break- water its unfinished parts would be liable to damage from typhoons; but this unavoidable disadvantage would be more than compensated by the economy and convenience resulting from the adoption of a form of structure largely independent of skilled labour, and for which but comparatively little special plant and appliances would be required. The section recommended would also admit of the convenient rectification of such settlements of the work as would inevitably occur during construction and for some time after completion,

The complete scheme for the Boat-Shelter, as modified by the Consulting Engineers, was estimated to cost roughly $273,000 in excess of the estimate for the original scheme. The excess was due to the additional works which were recommended to be carried out at the entrances, the cost of the breakwater as modified being estimated to be practically equal to the same as designed. But as His Excellency the Governor had laid it down that no scheme could be accepted which would exceed in cost the amount of my estimate, namely $1,540,000, and as the Consulting Engineers considered that the additional works were absolutely essential, and that no cheaper type of breakwater could be devised, it became necessary to reduce the cost of the scheme by curtailing the length of the breakwater, and the area of the shelter.