FUTURE OF GREY HARBOUR

Grey River Argus, 16 March 1944, Page 2

FUTURE OF GREY HARBOUR

BOARD’S DECISION j i < Recommendation by Engineer ' DEPUTATION TO APPROACH GOVERNMENT. ( Steps to place before the Govern- < ment a series of recommendations by 1 the Greymouth Harbour Board Eng-i < ineer (Mr. D. S. Kennedy) which con- i cern primarily the problem of the i bar were taken by the Board at a,. special meeting held yesterday after-1 ‘ noon The recommendations are in-1 ( eluded in a report prepared by the;: Engineer as a result of a resolution j, passed at the January meeting of the ( Board after the visit to Greymouth of f Mr. F. VZ. Furkert. The Board de- i cided yesterday thtft Mr. Kennedy, 1 with the Chairman of the Board (Mr. i J. B. Kent) and the Secretary (Mr. i W. B. Gilbert) should visit Welling- < ton at an early date to place this re- ; port before the Government. • The meeting was presided over by Mr. Kent, and there were also pre- ! sent Messrs F. Williams, W. B- , Pring, J Mulcare, E. W. Heenan, J ; A. Murdoch and J. Smeaton, also the . Secretary (Mr. W. B Gilbert), and the Engineer (Mr. D. S. Kennedy). DREDGING OF SOUTH LAGOONS j In the south lagoons, the report IJ states there is evidence of accretion [ £ in certain parts’of of the area .of tidal ij influence of one foot to four foot i ( above that found in the surveys ori] 1925-26, which were prepared for a | j report similar to the present one. j This 1925 report of Messrs Blair i r Mason, Ferguson, and Furkert re-' s commended, first, the extension oi 1. the North Breakwater by 221) i£ feet, which, it was considered, would c reduce the overlap of the . south £ breakwater, and by concentration ot ; the current give more scour in the t fairway and over the bar. Secondly, j it was maintained that increase ot; £ the tidal capacity of the south la- c goons was a work of importance and . early steps to form a channel across Preston Rd. between Karoro & Erua , Moana Lagoons and to provide a suitable bridge were advised. Thirdly, to carry out a scheme of dock and lagoon improveinent and reclamation of lands such as outlined a suction dredger of light draft to be arranged j r for pumping spoil from the lagoons to the flood line boundaries was considered necessary. Fourthly, it was ; believed that subsequent extensions, of the north and south breakwaters , would be found expedient after the leffect of the works proposed under ; headings 1 and 2 was felt and if th? t trade of the port then should warrant the expenditure. Finally, it was recommended that if, after the result on the bar of the lagoon works had been ascertained and the extensions to the breakwaters completed, the trade of the port demanded a greater'depth than had been obtained, the dredging of the area between the north training banks and the Cobden shore should be proceeded with, and the question of the deepening and enlargement of the Cobden Lagoon considered. BREAKWATER RESTORATION “On these recommendations,” Mr Kennedy’s report continues, “the north and south breakwater restoration works (erroneously called ex-| tensions, as the original walls were, built and extended between 18961906 and flattened out in later years to half-tide mark by the seas) were put in hand from 1926 onwards, that on the south side being finished in 1935, and now in process of further repair. On the north side a large sum of money (over £100,000) has been since spent in trying to hold the seaward end of the north mole in position and it had every appearance .of being a hopeless task—in fact, the stone apron would have threatened the very existence of the entrance if deposition of stone had gone on much longer. As the Board is now aware, I made changes in 1940 to use concrete blocks, etc. These have given satisfactory results at a fractional outlay, and to-day the Board is in a position to consider further improvements once more, due entirely to the improved method of consolidating the breakwater ends.” Mr. Kennedy adds a' recommendation that in any further breakwater extensions especially .on the north wall, a form of concrete construction be used. The report goes on to state that the estimate of £54,730 for the lagon work given in the 1925 report was revised in 1930 to £118,145. It was evident, further, that in these early reports no solution was offered to the problem of disposing of excess dredgings in Karoro Lagoon. The present report suggests the complete filling of Erua Moana above the Grey Harbour Board railway bridge eliminating the previous canal and bridging proposals and filling the whole lagoon in the Arney Street area;’ and a proposal is offered in regard to the connection between Karoro Lagoon and the dock area, by, a cut and a bridge through Presort Road and on to the area held by the Board in the railway loop. After dealing with other works made necessary by the scheme, the use for reclaimed land, and legal formalities involved, the report points out that the aerodrome construction involved a loss of appoximately 9,000,000 cubic feet, equal to 18 per cent of the estimated Lagoon dock water volume available for sluicing at high water, ordinary spring .tides. There then follows an estimate of the cost of the southern lagoon dredging and attendant works, the total being £184,984 Ils. Bd. The major items are:— Dredging £116,934 Ils Bd, dredging plant £36,080, channel from Karoro to the dock area £16090, and widening of entrance between the breakwaters (removal of aprons and repairs to old wave trap) £lO,OOO. In this estimate no allowance has been made for maintenance of the lagoons after dredging nor for maintenance of retaining walls. COBDEN LAGOONS The report states that an estimate of the cost of dredging the Cobden lagoons has been taken out so as to present a comprehensive idea of the possibilities in making extra tidal water available on the north side equal to about 12 million cubic feet or 27 per cent., of the ultimate capacity of the southern lagoons of 45,000,000 cubic feet. This would also provide a more effective wave trap to reduce the range entering the harbour. The whole of the areas affected are within the Board’s jurisdiction and walling would be only a nominal requirement. In these plans the possibility of the Cobden island scheme being further considered has been kept in mind, and it is, pointed out that dredging of the existing "river berthages, at the normal rate o f [expenditure, will cost over £200,000 in the next 50 vears. The cost of dredging and walling in the Cobden Lagoon area is estimated as £52,749.. ' HALF TIDE TRAINING WALL The -reconstruction of the half tide training wall is an extremely difficult work to estimate, the report continues, as it involves tidal work and

is dependent on weather conditions to a major degree. The use of a pun and towing launch is suggested, this being much more economical than a I railway system, which is liable to be washed away in heavy floods, and it is considered that heavier stone ana. concrete should be used in any future work Ths last work was done in July 1927 using small stones from an old wall on Cobden island but this work was ineffective and' the stone has now been washed away. The estimated cost, of restoring the training walls, upper and lower, is £16,546. THE BAR PROBLEM “As a result of several years’ close observation and. study of the difficult problem involved, I am unable to suggest any shortcut to a successful attack on the bar. There mav be the latent belief that merely by "dredging the lagoons and repairing the training walls, all the present bar troubles will be surmounted. I maintain that they will be still far from overcome. There will always be a bar but to keep it .at working. depth is the main consideration. The difficulties experienced are- being caused from outside influences —the river with the aid of the lagoons etc., merely having a certain effect on these 1 as also in time of floods and freshes. How to deal with this problem is not entirely a matter of imagination or mathematics, though both are frequently put into requistion for this purpose. I maintain that it is almost a purely physical problem and solvable, like all such problems, by experiment, at least to a greater and surer degree than by any. other known means. That to-day is the rational approach to solving most indeterminate hydraulic problems in harbour and river works throughout the world,—and it is my considered lopinion that to go ahead blindly, and | spend money on the contemplated ’ lagoon works without some such ■ experimental scale model work I being done beforehand, would |be sheer folly, akin to buildling a modern liner without [model tank studies. The result of such research would certainly give [tv more solid basis for opinion and a guide to plannning at a small cost compared to the money that would be spent in the hope that the contemplated works will come up to expectation. Though agreeing with the principle of the southern lagoons as [sluicing basins, I consider that until 'other aspects of the problem are I dealt with, consideration should be [given only to that on the Cobden side in the meantime.”

SCALE MODEL STUDIES The improvements to the rationing walls, the effectiveness of the lagoons as sluicing basins under present conditions and the design of wave traps, groynes at the hospital and breakwater extensions (straight or curved.) are among the problems which, lit is suggested should be the subject of research and the report states: “What ultimate effect these will have lon the bar problems is at present largely guess work.” It is considered that the proposed scale model should be constructed in Greymouth and the help of the School of Engineering at Canterbury University College sought. ■ • uti EXTENSION OF BREAKWATERS “The proximity of the present Blaketown low water mark fo the 1 end of the south breakwater is the most disturbing feature of all,” Mr. Kennedy goes on to say. “It seems apparent that the building of the groynes on the Blaketown Beach 'has brought about an advance of the fore shore in the space of a year or more that formerly extended over one or more decades. Their effect in holding the sand, etc., has been ' the same as that of the south breakwater but apparently more pronounced. “There appears only one remedy.subject to experimental investiga-' tion, and that is the extension of the two breakwaters into a more favourable depth to assist the various influences to deal with the sand deposits barring the harbour entrance. This work and tJ«e training wall, in my opinion, are the major undertakings, as the position at present is that the north breakwater work has been largely nullified by events on the south side. It is a fact that such l encroachment on the weather breaki water, may under certain recurring .periods, threaten the very existence . I of a harbour and continue to do so ’ 1 especially where bar dredging can|not be done as in Greymouth or with ithe equipment offering in New Zealand. “The building of breakwaters from , 1886-1906 produced results that have enabled the port to function with a fairly regular bar over many years and I am of the opinion that extensions would give the same again, I maybe even better, in the light of . existing knowledge. A 400 ft., extension in the first instance of both ' the north and south walls would en- | ter the northerly littoral, and if I slightly curved to the north-west, I believe that they would alter the | configuration of the bar from an , abrupt mound to an elongated bank [ on which the S. and W. gales would -have a better effect.” The estimated I cost of the the suggested breakwater . extensions is £140,500. ENGINEER’S RECOMMENt DATIONS. J The report concludes:— "My, recommendations to the Board are as follows:— (a) That the Board obtain a further opinion on this re- , port if an v doubt remains as to what 1 -should be done, (b) That the Board i I carry out the proposed scale model ‘ jstudies of the harbour as outlined in (| this report, (c) That on the results /of these tests a comprehensive ’■scheme be drawn up and works plac;|ed in order of priority, (d) In ad- , ivance of (b) and (c) I would recom/mend that the Board go into the matI |ter of arranging finance to carry out I the following:—■ (1) Extension of ■ the north and south breakwaters by I 400 feet each; (2) Half tide training wall restoration; (3) Excavation -of Cobden area as shown; (4) Restora- ; tion of wave traps and removal of aprons on breakwaters; (5) Construction of lagpon-railway bridge and repairs to south tip railway.-’ The total estimated cost of these ’ works is £227,295. It is also recommended that all major works be carried out by; contract. “As the present difficulty appears j to be one of raising finance and not ■ altogther an engineering one, Mr. j Kennedy adds, “there seems to be no ( point in going into further exhaustive j detail on any particular proposal un- ; til money can be made available.” h - BOARD’S DISCUSSION. I “No doubt you will agree that this ; is one of the most reports ■ that the Board has been called on to ’ consider,” said the Chairman in opening the discussion. A full picture of ; the affairs of the port was given, Mr. ; Kent said, and he thought thak on its 1 basis the Board would be able to J come to some conclusion. The whole r of the district depended on the port. 1 He 1 thought that the Engineer should . be congratulated on preparing such a . fine report, nnd moved that, togeth- > er with the report on the Cobden 3 scheme, id be printed and circulated to the Departments concerned —the Marine Department, the Public Works Department, and the Mines j Department, and also to ! the local - bodies concerned. « Mr. Mulcare seconded the motion. 1 He. thought that the more publicity

the matter got Mie better it would be for the Board and everyone concerned.

The motion was carried. The Chairman suggested that the Lagoon Dock scheme as set out in 1909-10 and of which plans had been prepared, be foi’mally abandoned as recommended by the Engineer and Borough Council and the Mines Department be advised of this decision. Mr. Smeaton formally moved along these lines, Mr. Pring seconding the motion. In reply to Mr. Mulcare. the Engineer said that the Lagoon Dock scheme provided for a wharf from the en d of the present wharf up to the present road bridge to Blaketown. To-day the wharf in this position was in a bad state of 'decay and practically useless, and the railway marshalling yards as suggested at the time the scheme was originally put forward would not now be acceptable to the Railway Department. The motion was carried. Mr. Murdoch moved that the legal formalities referred to in She report be cleared up. He remarked that when the Lagoon Dock scheme was advanced it was thought that the loading of coal should be separate from the loading of timber, but it seefned to him that with the improvee d facilities the argument for separate loading no longer applied. The motion was seconded by the Chairman and carried. In the course of an explanation to Board members, of >ihe various proposals, the Engineer said that a certain velocity was required in the river jo move sand. The present velocity was on the borderline, and the extra seven per cent, which would be provided if the Cobden Lagoon were dredged might be sufficient to make the difference. It was possible also that after a flood, the additional flow of water would slow up the rate of sand, accretion on the bar. The Cobden Island harbour scheme would give twice the amount of water provided by dredging the Cobden lagoons. In reply to Mr. Mulcare, the Engineer said that a scale model would not help him to. advise the Board, but would help any other Engineer. In his opinion such a model was absolutely essential. A similar model had recently been built in Tasmania. So much had been found out in recent years' that it was possible to make a model reproduce the life-size conditions. A model would settle all of the problems so far. as the bar was concerned. A, thousand pounds would go a long way towards the cost of such a model.

Mr. Murdoch said than the work on the southern lagoons had been Mr. Furkert’s recommendation, but it had been ruined by the aerodrome construction.

Mr. Williams said that if the lagoons were so important it was a wonder that they-had been allowed to fill in and that there had not been more water on the bar when they were operative. There had been a greater depth than at that 'time since the breakwaters were extended.

Mr. Pring said that it certainly looked as if the model would show which work was worthwhile. Mr. Heenan also agreed that a moael might be the wisest thing. It was possible, he said, that the walls had gone out too far. Mr. Murdoch said that if the walls had not gone out they would not have been able to get bigger ships into the port and the southerly drift might have smothered the whole bar up. Mr. Smeaton said thail Mr. Furkert had said that it might be necessary to extend the walls and this was supported by Mr Kennedy.. Mr. Muraoch asked for whom the money'necessary to construct a model would be spent. It was a national work. They should get the Government interested and unless it would put in substantially towards the cost of the model the Board should say that it could not do the job _ Mr Smeaton said that the Board should first approve of or reject the scheme and forward it to the Marine Department with a request for an earlv reply. If it had the approval of the Government they should 'then go on and make a model. The chairman said it was understood they could do nothing without the approval of the Marine Department. , ~ . . 3 Mr. Pring remarked that it had cost something like £2,000 for some of the reports, yet the model would give more information than any of them. He thought the Government would assist with the model. It was better to spend a little on that than a lot on something that might not be successful. The Engineer said that the alternate to the scale model was to- carry on with the dredging and the walls

and hope for the best. Mr. Mulcare _said that the Board would not get anywhere l ' if it did not offer Uo provide something towards the cost of the model. ' The Chairman said the Engineer had stated that the Board could provide the labour for constructing the model, which would be about 50 per cent, of tbe cost. In reply to a question by Mr. Murdoch as to whether the deep sea harbour scheme was being abandoned, the Engineer said that that too, could be tested on a scale model. Mr. Smeaton said that he would like to see the approval of the Government obtained and also a guarantee of Government assistance before anything was gone on with. The Chairman said that unless some improvements were proceeded with ’-he trade would go elsewhere. It was important for the South Island that there should be a permanent port here —otherwise the economy of the island was lopsided. On the - suggestion of Mr. Murdoch it was finally decided that the Chairman, the Engineer and the Secretary should form a deputation »o visit Wellington and place the report before the Government.