REMOVAL OF MID-CHANNEL ROCK, BLUFF HARBOUR (REPORT OF THE COLONIAL MARINE ENGINEER ON PROPOSED).

Appendix to the Journals of the House of Representatives, 1887 Session I, D-07

D.—7

1887. NEW ZEALAND.

REMOVAL OF MID-CHANNEL ROCK, BLUFF HARBOUR (REPORT OF THE COLONIAL MARINE ENGINEER ON PROPOSED).

Presented to both Houses of the General Assembly by Command of His Excellency.

The Colonial Marine Engineer to the Minister having Charge of the Marine Department. Sir, — Marine Department, Wellington, 19th April, 1887. In accordance with instructions, I visited the Bluff Harbour in January last for the purpose of inspecting the Mid-channel Eock and gaining such information as would enable me to report on the proposal for its removal. 'Judging from the tenor of a letter of date 7th September, 1886, written to you by the Chairman of the Bluff Harbour Board, I inferred that the matter was considered one of importance and urgency ; but on my arrival I found very little evidence of this, as, from the Chairman downwards, all the officials appeared to take the slightest possible interest in the affair. However, after having made the necessary arrangements with the Harbourmaster as to boats and crews, I made an examination of the rock, and took such soundings and measurements as the weather and the short time available would allow. The size of the rock appears to be about 300 ft. by 250 ft., tolerably flat on the top, the depth of water on it varying from 14ft. to 17ft. at low water. The depth of water surrounding the rock at low water on the side next the navigable channel is about 21ft. or 22ft., and to this depth it would be necessary to remove nearly the whole of the rock to effect the desired improvements. Unfortunately, there is no very deep water near into which the fragments of it, when blasted, could be thrown, but every piece w 7ould require to be lifted into a punt or barge and conveyed away to a distance. The velocity of the tidal current, either ebb or flow, is so great that blasting operations would be carried on at a great disadvantage ; in fact, the time during which they could be carried on would most probably be confined to slack water at high and low tide. This slack water lasts a very short time, not more than fifteen to twenty minutes ; so that, unless some very expensive appliances were resorted to, ordinary blasting would be a slow and costly operation. In fact, this may be said of any plan that might be devised for removing this rock; and, although it is very difficult to give even an approximate estimate of the cost, I may say that it would not be worth while beginning the work without an available sum of at least £10,000 to £15,000, and it might cost very much more. It is not a work in which the execution of a portion would produce any benefit; it must be carried out in its entirety to be of any service. I may say, in conclusion, that, looking to the large expenditure necessary, it is a work the consideration of which may be postponed for a long time to come; and, from what I was able to gather, the presence of the rock is not such a serious bar to the navigation of the harbour as it might be thought to be, as, although the presence of the rock now necessitates a vessel to make an angle in her course in passing up or down the harbour, the removal of the rock would not allow of a straight course being taken, but there would still be a considerable angle in it, and the same amount of care would be required in the navigation of a vessel as at present. I may say also that the necessity for the removal of this rock would to a great extent be obviated if the arrangement of the buoys in its vicinity was altered : as they are now placed they have the effect of driving a vessel much nearer to the rock than is needed, although immediately opposite to the rock, or nearly so, there is a considerable width of deep water which the positions of the buoys as placed prevents vessels taking advantage of. I think this point should be brought before the notice of the Harbour Board officially, as, indeed, I believe it to have been already verbally by captains of the larger vessels. I attach a tracing (M.D. 1,325) showing the positions and approximate extent of the rock, &c. I have, &c, The Hon. the Minister having Charge of the Marine John Blackett, Department, Wellington. Marine Engineer. [Approximate Cost of Paper.— Preparation, nil; printing (1,275 copies), 17s.]

Authority : George Didsbuby, Government Printer, Wellington.—lBB7.

BLUFF HARBOUR