South Canterbury Times. FRIDAY, NOVEMBER 4, 1881.

South Canterbury Times, Issue 2692, 4 November 1881, Page 2

South Canterbury Times. FRIDAY, NOVEMBER 4, 1881.

The Timaru Harbor Board yesterday decided that the reports of the Commissioners, Messrs O’Connor and Austin, appointed to report on the proposed deviations from the original and approved plans of the Breakwater, and other papers in connection witn this question, might be made public, and handed them to the Press for publication. They are too voluminous to admit, of our publishing them in full, and some of them have been so long in the hands of the Board that they have lost much of their interest, but we will endeavor to extract from them the most salient points. The original plans provided :—(1) For the turn being commenced at the present termination of the work, and (2) for the rest of the work being constructed in loose rubble, with slopes of one in one on each side, the seaward side to be faced with thirty-ton concrete blocks. The deviations proposed were (1) that the mole should be extended 400 ft farther in a straight line before the turn is made, and (2) that instead of loose rubble being used the work should be continued in packed concrete blocks, with cap-block, as hitherto. With regard to the latter deviation, the Commissioners had no difficulty in coming to a conclusion. A similar alteration had been previously made, and they recommended that the deviation should be allowed, providing more loose blocks were thrown over on the sea side than heretofore. With regard to the other and main deviation, the 400 ft extension, they reported that it could be securely constructed, and that the extra room such extension would give for shipping would make the whole work comparatively cheaper; but on the question whether theharbor works would be permanently successful, they gave an adverse opinion. They concluded that the shingle must overtake the present work in 12 years from January last, and reach 400 ft further in five and a-half years more, and then they assume in the first case that it would be six years, and in the second six years and a-half more before the shingle filled up or completely ruined the harbor. That is to say if the turn were made now the works would become useless in seventeen years from new, and if the mole is carried 400 ft further out, in 20 years from now. They then calculate which will yield the best return for the money, and find that to accommodate 192

ships a year for the longer terra would be better than accommodating ninety ships a year for the shorter term. They sum up their opinion on the supposed facts of the case as follows :—“ The prospects of the whole undertaking, however, seem very poor, the life being only anticipated to be 2 4 years, while the cost would be £25(5,000, being at the rate of £IO,OOO per annum, besides interest on loans for the temporary use of a harbor, which will not either be properly available for shipping for three years yet, and we think that it is a question for the serious consideration of the Harbor Board as to whether they should not allow the works to stand as they are for a few years, until the results to bo anticipated from the travelling shingle shall have become unmistakeable one way or other. The works as they stand are of great utility, not only to the landing service, but also to the ships, so that it could not be said that in the meantime nothing had been gained for the money expended, and if, after a few years, it could be demonstrated that the shingle would not ultimately destroy the works, then let them by all means proceed,” Then they point out that if the Board are not allowed to extend the straight mole, they cannot be prevented from putting on the turn, and as they report that if the work is to be gone on with at all, it would bo better to carry it further out before making the turn, they finally recommend the deviation from the original plan as “ the least of two evils.” They recommended, however, that the kant or arm should not he built at all, as if the shingle did overlap the work the arm would be useless, “ the shingle, when it gets out to the mole, would form in a short time the kant or arm which is estimated to cost the Board £10,000.” The second paper is the reply to or comment on the first, by Mr Goodall, the Harbor Board’s Engineer. In reference to the question of the time the shingle would require to overtake the works, he mentions the powerful effects of the waves reflected from the Breakwater in driving the shingle back, and meets the opinions of the Commissioners that all the shingle coming down the Waitaki must be stopped at Timafu, by saying that the greater portion must be ground to mud before it reaches this place. He shows, too, that the calculations of the Commissioners show that the farther the mole is carried seawards the less shingle it will retain, foot for foot/'dk they allow IGOO cubic yards per foot of the existing mole, but only 1300 cubic yards for each foot of the proposed 400 feet extension, whereas

“ contrary results should have been expected, for the outer ground is deeper, and the direction of the beach coming more at right angles to the stroke of the waves the travel of the shingle would be more retarded and the last section should retain more proportionately than what preceded it; besides which the back-wash, of which the Commissioners have taken no account, will further retard the shingle, and thus modify the line of travel.” Mr Goodall estimates that the quantity of shingle accumulating as estimated by the Commissioners, 8000 cubic yards per month, could, if necessary, be lifted over the Breakwater and allowed to go northward again for £I2OO a year. This would not need to be commenced for 17 years according to the Commissioners’ own showing,and at that time the cost would be a mere trifle to the port as it would then be one of the wealthiest in the colony. Those gentlemen showed that there would be about dO acres reclaimed, and the Board’s share of it would be worth £150,000, or £7500 a year. Mr Goodall makes the further suggestion for dealing with the shingle difficulty if the difficulty should ever arise,, that groins be built south of the works at suitable place, for retaining it. In reply to the suggestion that the arm should not be constructed at all, Mr Goodall says “ in that case the harbor would have to wait a very long while for the necessary shelter from the north-east and east. The kant formed by a shingle bank as suggested by their report, would not present a very convenient side to the harbor with long sloping banks, and the experiment would be dangerous, for the shingle once past the end of the mole would not merely form a spit, but would silt up the harbor as well.” The third paper is a summary of Messrs O l Connor and Austin’s report on Mr Goodall’s reply to their first report. Therein they say that they estimated the probable life of the harbor, not on the amonnt of shingle coming down the Waitaki, but upon the amount actually accumulated at the works. They consider the cost of lifting the shingle over the Breakwater, suggested by Mr Goodall, would be much more expensive than he estimated. They bad taken as a basis for their calculations, the fact that 214,000 cubic yards of shingle had accumulated in 27 months, and assumed that that accumulation represented the normal rate of travel, in the absence of proof that during that time the rate had been unusually rapid. They admit that they did not allow for the value of the land reclaimed, but they consider the value named by Mr Goodall questionable. Concerning the building of groins, they say that £ for £ it would probably be cheaper to go on extending the Breakwater, so as to collect the shingle in one mass. Respecting the arm, tiie Commissioners now say “ In our report alluded to we did not recommend that shingle should be allowed to overlap the works. We merely suggested that it might be impossible to prevent it doing so, and that if it did overlap them, then the cost of the kant would be lost, as it would add but very little to the life of the harbor. We therefore considered that construction of the kant should not be undertaken till effect of shingle travel

became certain. We were of course alive to the fact that if once the shingle got round the works the whole undertaking would be a failure ; but this would be equally the case, kant or no kant, so we saw no use in spending an additional £loo,oootill the possibility of contending with the shingle were proved beyond doubt one way or another.”

The question of the extension is now settled, and the mole is to be extended 400 feet further in a straight line. Whether any further modifications of plans now proposed to be carried out will be advisable, will probably be discovered during the progress of this work, but in the meantime there can be no two opinions, that if the Board’s request had not been acceded to a very great injury would have been done to this district.