TIMARU. HARBOR WORKS

Temuka Leader, Issue 2190, 18 April 1891, Page 1

TIMARU. HARBOR WORKS

(Oontinusd ) Mr Goodall’s Report, “ Timura 2nd April, 18S1. “ He Titnara Harbor Works.

“ Sir, —I have the bouoar to acknow. ledge tha receipt of the instructions, from the Secretary of the limaru Harbour Board appointing me a Commissioner along with Mr C, Y, O’Connor, to consider tha 'danger that exists to the harbour from travelling shingle’; to *n quire, examine, and report on the snbj mi and to state whether the danger can best ba averted by ‘ erection cf permanent works, or by the removal of shingle’ and beg to report as follows ; “ The subject has been thoroughly, and exhaustively discussed and considered, between your engineer, Mr Merchant Mr O’Connor and myseif and the result has been detailed in the report signed by Mr O’Connor, but, although Mr O’Connor and I agreed on main points, yet, necessarily, there are some points of difference between us, so 1 could not endorse 'he report. I, however, state that 1 agree in all that baa been said in the report named, except in so far as I shall now explain.

“I fully agree with Mr O’Connor that it would be advisable to take steps to avert the danger of the shingle overlapping the works, but sot from the consideration that there is imminent danger to the works for some years to come, hot aa there is a probability of danger at some fntnre time, and as it might be advantageous to resiore the beach to Timaru by allowing the shingle to travel northward from the breakwater, I consider it would be advtsab'e to at once initiates work for removing an average yearly quantity of shingle from the south of the breakwaUr to <ba north.

“ I cannot agree with Mr O’Connor tba 1 there is an average of 80,000 cubic yards of aocumalatiuu per annum, and although bis caicnlations'bave been based on figures taken from Sir John Code’s plan, I cannot consider that the result as arrived at gives an accurate amount. I consider that the records of Mr Merchant, who made the accumulation for the last five years 300,000 cubic yards to be more reliable. This will give an average of 60,000 cubic yards per annum equal to about 90,000 tons, “As for the rapidity with which the shingle may travel along the breakwater, I do not consider the circumstances cited at New Plymouth, can be taken in evidence as to what might occur at limarn, the two cases being so widely different, and the experiments of Mr Balfonr cannot give data to be relied upon, and the rate of progress of the shingle along the breakwater yearly may soon be changed for the tetter, for as the shingle creeps oat, the line of beach won d become more and more at right angles to the strike of the waves and so the travel of the shingle would be slackened.

; "I agree with Mr O’Connor that there are only two means of averting the danger to the harbonr from the growing accumulation of shingle (1) By extending the mole from the first kant in its original direction, or (2) by dredging the shingle accumulation ae it accrues, and 1 agree with him in the choice of the latter method, “ Alternative No. 1 by Extending Mole. I fnlly endorse all the reasons set forth for not recommending the extenson of the breakwater, but cannot agree with Mr O’Connor that, ‘ bad the straight ont kant been originally prolonged in its original line it would be a different matter, as the cost of the works as a whole would then have been much less than if such extension were made now,’ for bad (be k«a( (0 the

nor'h noi mirfe, and the straigb - out from the chore ex'euded inatead, a successful g rac are at a very lon pncsuch as the present north mole, oonid not possibly have been erected to enclose Mm* harbour, as it w< aid nut baye been sufficiently sheltered,—as there would nave been no shelter from the north-east and only-partial shelter from the southeast, a v*;ry expensive wall would have been required, and therefore the ex easioo of the etraigbi-oat kant coaid not have cheapened tbe work as a whole. Besides which, umess the kaul was made t<> the nor'h, adequate ahelter could not have be. n given to th • mouth of the harbour, and the" ocean range would have treey swept.in., ■ * Alternative No. 2 by Dbbdging. •‘ A though I oave already stated that there are' only 90,000 tons o( shingle per annum to con nd' with, yet, 1 to be quite safe, I am willing, te presume that the amount may be tons or to say an average of 500 tpns daily to be removed id 250 working days, which I take as a fair numberqf working days that may be got oat of 4 year. “Icannot agree to add 15,000 tons per annum for the abcnmalatidu of Caroline Bay, as it is not po-sible that the shifting of shingle at tbe south of the breakwater would prevent tbe nsual (juantity of sand from travelling round the breakwater and so increase the quantity to be shifted, for as soon as a ton of shingle is removed there win b j another to take its place, to be subjected to tbe sand making process ; and 'he base of oper aliens is so small that were it the case that it were so aft’-cted, the amount would be so insigificunt that it wou'd be inappreciable. “ Nor can I concur with Mr O,Connor that tbe dredging capacity should be 1600 tons per day of eight boars. One half that capacity should be enough, as any unusual necessity for clearing away the shingle could be met with by working extra hours. ' “ I would therefore recommend the adoption of a pump-hopper barge capable of lifting 300 ions per hour and baying hopper capacity for 150 tons of sand or shingle with the best and most Improved engines, indicating (50) fifty horse power. “ This vessel should be able to fill her hopper, proceed to opposite Dashing Rocks discharge and return in about on» boar and a half, including, all necessary stoppages. This would be rqual to five trips a day or 750 tons gross daily. Such a barge and pump would cost about £SOOO, and with staging, band crane for suction pipe add conliqgeocea included, the whole plant would not Exceed £SOOO. The cost of dredging dud damping the spoil, after taking into account every working cost, interest of capital, depreciation of plant, and contingencies, would be from to 3d per ton, and the total coat per annam for shifting 120,000 tons at 3d per ton would therefore be £2500 per annum, jand I am fuhy coevinced that this estimate is far in exo*se of the actual amount that wiil be incurred. “In all other matters I fully concur with Mr O’Connor's views. “ I have the honour etc, “ John Goodhall, M Inst C.E.”