TIMARU HARBOR BOARD.

Temuka Leader, Issue 2185, 7 April 1891, Page 4

TIMARU HARBOR BOARD.

A special meeting of the Harbor Board was held in Timaru on Friday to receive, the report of the Commissioners—Messrs 0. T. O'Connor and J. Goodall—appointed to report on the shjngle J question and make recommendations for dealing with it. Present —Messrs E. Acton (chairman), J Hill, G Stumbles, P It Platman, T Tegchemaker, J Manchester, J 8 Wilson, and I L Morris, and Captain "Woolloombe.

The secretary, Mr Tennent, read the reports. Mr O'Connor only signed the full report, Mr Goodall explaining in a separate report that he differed in some details from Mr O'Connor. Plans were attached to the report, showing the position recommended for the dredging stage. The reports having been read, the chairman said—l see Mr O'Connor makes an addition to the accumulation for ;a .quantity - ground up. Mr Goodall declines to admit that addition. Both agree that preparation .for is immediately necessary, but Mr Groodali is more moderate in his vjewa. '< I understand Mr O'Connor thinks that if we take away some shingle, there will be less sand to go round, The chairman: Tea; but Mr Goodall says though we do shift a quantity of shingle we still leave a sea-face, and there would be the same grinding. Mr Stumbles quite agreed with Mr Goodall there. The- Cdmmissionefs, were then invited to attend, and ..along conference was begun by Mr Teschemaker asking for an explanation of the difference, between their estimates of the quantity of shingle to be dealt with. Mr O'Connor said he reckoned on an average of 80,000 yards a year, Mr Goodall on 60,000. He (Mr O'Connor) derived his information from Mr Marchant, who made the,average over "a number of years 75,000 yards, and allowing a little margin, he made this a round number, 80,000. He did not know where Mr Goodall got his 60,000 yards from. 'J his was the chief difference between them. He (the it 80,000 yards on the average of the last 12 years.

Mr Goodall Baid he arrived at his figures by staking Mr Merchant's measurements for the last five years, as he did not consider the earlier measurements so trustworthy as the later ones, and five years was long .enough tirce to found an estimate on. , At the same time he was quite willing < to provide for a larger quantity.

Mr O'Connor said Mr Goodall took the'measures of year by year. But •these were only got by subtracting the measures of earlier years from the total at any time, and all were referred to Sir J.obn Coode's plan as the case. Starting from the state of things shown on that plan, they found 900,000 cubic yards accumulated in twelve years or 75,000 yards a year. The amount of accumulation fluctuated from year to year—in 1888 it was only 40,U)0 yards—so the average was taken over a long number of years. In reply to questions by members Mr O'Connor said in some years much larger quautities might arrive.—The calculations made in 1881 by Mr Btaekett and himself, were being , proved to be fairly accurate, and this showed that the accumulation was >Drocßediog steadily.—l be area of the gathering ground was overestimated in 1881; on the olher hand the rate of accumulation had not been quite so great as was then reckoned, and the two errors balanced, so that the progress of the shingle along the breakwater was just what was calculated. Mr Stumbles : Your prefer to shift the shiagle rather than extend the breakwater ?

Mr O'Connor: Tes, the figures in the report are in favor of that course. Mr Stumbles : But would it not be doing better with the money, to spend it in a work which would be useful in the couise of time, by sheltering the -harbor?

Mr O'Connor: This report deals with that question. You would have to go out 1000 feet before you increase the shelter at all. It is more than 1000 feet from the bend, and that 1000 feet giyes more shelter than if it were straight out. At all events that was the argument for putting the curve in the breakwater, In 188 Lhe (Mr O'Connor) advocated ju&t what Mr Stumbles was advocating now, ■carrying the breakwater straight out, for the reason that it would lengthen the time during , which the harbor would be free of shingle, but the .board at the 1 time did not adopt the suggestion, and the newspapers laughed at the reason given for it.

Mr Stumbles believed if the work was extended the back-wash would be

restored. ;:.."■ Mr O'Connor doubted it. The back-.<WMb-*ppe«ed~ta--be--Gonnected with the Bhore or shoal-water. There was less and less of it out to sea He said that it might not be necessary to go out 125 ft .per annum with a wall to: keep ahead of the shingle, but it might be necessary to go a great deal more. He would not be surprised to see the shingle form itself into a narrow spit and run along the mole very rapidly. That was what, he was afraid of at present. To Mr Wilson: Eubble would not be much cheaper than concrete at the price of stone here. To Captain Woollcom.be: The reflected wave, scarcely existed now; (be shingle had gone so far out.

Mr iStumbles pointed out that the shingle was a protection to the work on the inner part of the wharf. It would be a good thiug for the working if the breakwater were backed up all the way along. The chairman said the shingle was of value in that way, and they would like to be able to say " Thus far and no further." MrHillasked bad the Commissioners any data before them in regard to Caroline Bay. Mr O'Connor: Tes, we went and saw it. Mr Hill: Will it take long to accumulate so as to bring it reund into the harbor ? Mr O'Cannor could not say how long it would take, but it would take a pretty long time. I hey assumed that the deposit in Caroline Bay had gone round the harbor. Mr Goodall said that heavy seas running at the end of the mole would always keep the bottom disturbed, and at a uniform depth, the Caroline Bay deposit might come further out than it is yet, but when it came under the influence of the southerly seas the silt could settle no further. A limit would be reached where no further settlement could take place v and that limit, he believed was far to the north of the harbor. Perhaps the shingle in Caroline Bay. came from Waimataitai lagoon, where the beach was now pro: tected from the southerly gales but exposed to the north-eaaters. It could not be from Dashing Bocks, as there the baach was under the influence of the southerly seas. Mr O'Connor said if the shingle was shifted at all it would, of course, be discharged at some point where there would be no doubt it would travel north, not south. Mr IHatoian : If the amount stated is removed will that prevent the spit travelling along the work?

Mr O'Connor took it that the dredging would take place alongside the breakwater, and would of course prevent such a spit being formed. 'The essential'difference between himself and Mr Goodall was that Mr Goodall assumed that the machinery could be worked with moderate uniformity on a great many days in the year. He (Mr O'Connor) did not think it safe to reckon on that. There would be many interruptions, many occasions when they could not work l just when they wanted to work. Mr. Goodall also assumed that the dredge would lift to its maximum capacity. Dredges never did that. If a dredge averaged 50 per cent of its capacity throughout the day it did very well. Even at Lyttelton they would often see the dredge buckets running empty, and with the particular form of dredge they proposed to adopt.it was more difficult to ensure working to full capacity. This was the only practicable form of dredge for the purpose. The maker m his circulars gave an example of a machine '•capable'' of lifting 400 tons per hour, but he gave as its average work 200 tons per hour. Ab to the difference between his estimate of cost and Mr Gobdall's, he did not know the maker's price for a 300-ton machine, but he saw that a 50-ton dredge cost £IOOO, and a 100-ton one £2OOO, so he thought it fair to assume that other prices would be proportionate to the power, so that a 300-ton dredge would cost £6OOO. Mr Goodall estimated only £4OOO. As to the barge, they could not reasonably expect to get a 300-ton barge for less than £3OOO and with the driving machinery £4OOO. He had other data on the subjoct in Sir John Coode and Mr BlaekeU's report to the New Plymouth board in 1889, in which they resommended a pump hopper dredge, and the description given of the dredge showed that it would only work up to half its maximum capacity. The cost of the dredge was put down at £II,OOO delivered, and the cost of working at £4OOO a year, or 7d a yard on the material shifted. Shingle would be more difficult to shift and therefore a larger margin should be nllowed. At New Plymouth there was 100,000 tons to shift, and Sir John Coode recommended a 400-ton dredge. Here there was not three-quarters of the quantity, but he (Mr O'Connor) proposed a machine of three-quarters of that power, because the material to be shifted was not sand but shingle, H»a figures were about three-fourths of Sir John Coode's.

Mr Teschemaker: Then you say ihat the harbor can be kept going for £B4OO a year ? Mr O'Connor: I think so, and if I were a landowner here I should think it a lavorable result.

In reply to Mr Wilson, Mr O'Connor explained the arrangement of the dredging machiuery, and to the chairman explained that a separate dredge and bargee do not answer so well as hopper dredges. In reply to a remark by the chairman

Mr Marchant said that he would like to explain that the putting down of the random blocks bad not been the cause of the shingle making up to the breakwater. Duriag the 12 months following October, 1885, the record plans showed that the shingle retreated 90 feet from the rock island and made .90 feet beside the breakwater, and that was before the random blocks were put down. At that time the breakwater was being underscoured ; 200 ft. of it had caverns in it, and other parts showed signs of weakness, Mr Goodall would tell them that there were after subsidences during construction, and that to cure

them he , put down random, blocks. Those settlements were threatening the existence of the breakwater, he considered, and he recommended the board to have some blocks put down, but only half the number the commissioners had recommended. Mr Blackett passed through after visiting Oamaru a,nd!,warned him not to ■ spare thei random blocks, as the want of them had ruined the Oamaru work. As the blocks - were put down it was found that they cut down the gorging wave which ran to the root of the breakwater, but they did not. reduce the reflected wave.. That was the history of the random blocks. Supposing that the shingle would have been kept back if they had not been put down, this breakwater would have been wrecked by underscour. But be did not think that the random blocks were the cause of the changes. Other explanations were the change in the direction of the work and the destruction of the kelp about the rock island.

.Mr Hill: Was your attention called to the "range " and the possibility of constructing! some slight work to prevent it?

Mr O'Connor said that was no part of the reference to them. He saw that there was a range, and be did not see how they were to stop it without narrowing the entrance. That was a question of navigation. The best thing at present seemed to be to make a wharf along the north mole.

Mr Manchester would like to know whether there was any danger of sandbanks being formed in front of the harbor entrance, and whether the removal of the shingle would be a safeguard against them. Mr O'Connor said that was one of the reasons why they recommended removal of the shingle instead of stopping it. Evidently a good deal was converted into sand and carried away in suspension, and some of it might be dropped in front of the harbor. At present there were not sufficient data to enable them to say whether there was such an accumulation there, and they recommended systematic sounding.

Mr Marcb'ant (to the chairman) said he had' reported that he found the water shoaled from 27ft to 24ft on a certain spot. The last sea had cut off Ihe top so that only 22ft was left. He had no doubt about the correctness -of,the soundings. No other questions being asked, Mr O'Connor briefly summarised the additional information he had given, and repeated,, after reference to Mr March ant's data, that they could not reckon having to shift less than 80,000 yards a year (1 yard equals 1-J tons). The chairman hoped every member would study the reports and make himself fully acquainted with the views of the Commission before next meeting. Mr Morris moved, and Mr Wilson seconded—" That the Harbor Board desire to acknowledge the skill, care, and attention which have evidently been devoted by the Commissioners to the question submitted to them."— Carried unanimously.

Mr O'Connor said he was much obliged to the board. He had simply done his duty: The subject happened to be rather an easy one for him, as he had bad a good deal to say about it before. Still he was obliged to the board for their resolution. Mc Goodall also returned thanks. He was obliged to the board for remembering him, and it was, and always would be, with him a labor of love to do anything for the Timaru harbor. The meeting then terminated.