New Plymouth Harbor Board.

Opunake Times, Volume III, Issue 117, 16 August 1895, Page 2

New Plymouth Harbor Board.

The monthly meeting of thq Harbor Board was held on Tuesday. Present: Messrs E. Maxwell (chairman), F. Bluck, G. McLean, E, M. Smith (M.H.R.), R. H. Davies, L. Sarten, W. Shearer, J. Ward, and P. F. Ralfe. GOVERNMENT NOMINEES. The Marine Department notified that Messrs E. M. Smith (M.H.R.), L. Sarten and Joe Ward had been appointed members of the Board by the Government. WEIGHBRIDGE. Correspondence was read relative to the purchase of a weighbridge at the works. The Secretary said the bridge had been purchased and put in position at the works. FINANCIAL ACCOMMODATION. Mr W. H. Witchell, manager of the Bank of New Zealand, wrote stating that the Board’s application to overdraw as provided by the Act, viz., to the extent of one year’s revenue (£4000), had been considered, and he had much pleasure to inform them that the Board’s application had been granted.—The Chairman said that the Bank had met them in a liberal and prompt spirit, and it was very satisfactory to know that the requisite work could be now carried out. EXCHANGING NEWSPAPERS. The secretary of the Napier Harbor Board wrote forwarding* copies of newspapers containing reports of the Board’s meetings, and asking the New Plymouth Board to reciprocate.—The Chairman said that many Harbor Boards adopted this practice, and he thought that this Board might adopt the system with Boards constituted similarly to their own. On Mr Ralfe’s motion, it was decided to reciprocate with similar Boards. RUBBLE CONTRACT. Mr B. Pool, the contractor for the rubble work at the breakwater, wrote .stating that after a trial he had to give up the work, as owing to the faulty nature of the quarry he could not get sufficient stone out. He asked the Board to be as lenient with him as possible, as he was considerably out of pocket. He also asked that the Board might take over any surplus material, such as coal, &o.—The Chairman said that they had a deposit of £25 from Mr Pool, and some £l7 worth of work had been done, with some £4 in addition for material.—-Mr Shearer moved, That the deposit and the money for the work done be forfeited, and that he be allowed for any material that would be of use to the Board. —The Chairman thought they might forfeit the deposit, but allow him for work done. —Mr Shearer : That is all right if we were acting for ourselves, but we are acting for the ratepayers. —Mr Sarten said he would second the motion, as he held that Pool should forfeit. —Mr Bluck said he would move as an amendment, That the deposit be forfeited, but that Mr Pool be paid 75 per cent of £l7 3s, the net amount for work done.—The Chairman asked Mr Marchant’s opinion of the work done. —Mr Marchant said he was not in a position to judge of the work done. Pool had knocked off work the second day he was here, but he could say that the stones loaded up in the trucks that he saw were too small for rubble formation, and were not worth 6d a yard. Of the 188 yards of work done, he thought the Board might meet Pool by paying him for 100 yards. He did not wish to stand in the way of the man getting paid, but that was his opinion on the stone work done.—Mr Smith said that he would oppose the amendment proposed. He could sympathise with a man who had lost through bad weather or other unforseen accidents, but here was a man who gave a price, and said he was * satisfied with the same. The Board had been put to expense over the matter. Mr Ward seconded Mr Bluck’s amendment, and said that the stones had been passed when they were under specified size.—Mr Davies said the foreman was their representative, and stone had been put over that was not of specified size. He thought the Board was morally if not legally responsible to Pool. The amendment was put and carried on a show of hands, Messrs Smith and Shearer voting against it. ENGINEER’S REPORT. The Harbor Board went into Committee to consider Mr Marchant’s report, and also the terms on which be offered his services to the Board. The Board, on resuming, decided to engage Mr Marchant as consulting engineer for 12 months on the terms offered. Mr Marchant undertakes to put all the arrangements in order for repairing and dredging, and to personally advise the Board, or advise by letter. The report was adopted in its entirety, and tenders will be called for rubble protection work, the same to be dealt with at a special meeting to be held three -weeks hence. General Report on the Condition of the New Plymouth Breakwater, by Fredk. Wm. Marchant, Member of the Institute of Civil Engineers, London. BREAKWATER. This structure is 1950 feet in length, including approaches. About 800 ft of it from the root outwards is completely protected by sand accumulation on the weather side. ■ Of the remaining portion part has been protected by a rubble wave breaker, leaving about 4Goft standing exposed to the full break of the sea without any wave breaker on the sea face. Of this length about 860 ft presents a very dilapidated appearance when viewed from the weather side. Three gullets have been excavated in it by a recent storm, besides which there are subsidences, cavernous erosions, and disturbances in the set block work, which have existed for a greater or less time past. The gullets are not of any serious extent at present. The outer one js about 12ft x 12ft x. Bft, the middle pne of about the game dimensions, and the

inshore one about BGi't x 22ft x 10ft. Thepresent damage is not assignable to any one cause in particular. Constructive details and arrangements contrary to the canons and experiences of marine engineering are altogetner responsible for it, such as the use of stretcher blocks, where none but headers should be used. Some of the stretchers have been worked out by the break of the sea as might and should have been anticipated. The concrete is of broken stone aggregate. It bas little or no admixture of sand, little assortment of sizes in the material employed, and is consequently excessively porous, especially in the monoliths. When once the sea can gain an entrance under any circumstances into the body of the concrete work, it can attack and destroy it in detail, stone by stone. . The set block work on top of the monolith is a very unsatisfactory method of construction as far as the permanent welfare of the work is concerned. No doubt it enabled the work to be expeditiously proceeded with during construction, but at the cost of the permanency of the finished structure. These particular blocks have their arrises broadly chamfered, and so present a series of trumpet mouths, into which a heavy breaking sea can inject air and water with almost explosive force. With few exceptions, all these blocks have been disturbed, and I understand some of them have occasionally been worked right out of their beds and rolled over the breakwater into the harbor, notwithstanding the fact that they are some 25 tons in weight and backed up by concrete in situ.

I am unable to assign a definite cause for the subsidences where the stretcher blocks have not been worked out. They may be due to settlement in the bag work foundation or to underscouring before the apron work was added.

These vcriticisms are made simply for the purpose of clearly showing in what direction a remedy may be found, and not for the purpose of finding fault with what has been done in the past.

It is evidently useless to attempt to patch up and restore the structure in its original details. The only remedy is to supplement the strength of the breakwater on the sea face, so as to prevent the storm wave attacking that part of the work, which is manifestly unable to withstand it.

I recommend that the gullets should be filled up with concrete blocks thrown in at random, and supported and defended on the 'sea side by a further sufficient quantity of such blocks. There are concrete blocks available for the purpose on the ground, and acting under instructions from the Works Committee, I am doing my best to make good the gullets in the manner recommended as fast as circumstances will permit. When these have been filled and protected in the manner suggested, the general strengthening of the work should be proceeded with as soon as possible. The rubble stone wave breaker which the Board has lately been adding to the breakwater should be continued on to the outer end—a distance of seven chains.

This rubble work should be covered over with random concrete blocks ; to be obtained partly from the stock in hand and partly from the chamfered block work on the sea side of the breakwater.

The quantity of rabble I consider to be amply sufficient for this work is 900 cubic yards per chain, bank measurement, having a height against the breakwater on an average of 15 feet above the top of the present apron work.

The very heaviest blocks of rubble obtained in the quarry should be reserved and tipped in among the concrete blocks of the wave breaker where considered desirable.

It is estimated that 170 concrete blocks can be obtained for use in the wave breaker on the length of seven chains requiring protection, which, together with the rubble, should afford an impregnable defence to the work. The double line railway for the block setting crane must be shifted over a few feet towards the harbor side to enable the foregoing recommendations to be carried out, but beyond this no alteration in working arrangements is necessary. Taking the cost of suitable rubble at 4s per cubic yard bank measurement, or at an equivalent rate per ton weight, the cost of the rubble protection necessary would be : 900 cubic yards, by 7 chains, at 4s, £1260; removal of tipping concrete blocks, shifting double line railway and contingencies, £600; or a total of £IB6O, the Board to provide all the plant and tools required in addition. QUARRY. To carry out the foregoing recommendations it is necessai’y to make proper _ arrangements with regard to quarrying. I recommend that a con tract be immediately let for the work ■at per ton, weighed on the Board’s weighbridge. It should be specified as minima, that of the total quantity required, one quarter should range from 1 cwfc to 1 ton, one quarter from 1 ton to 8 tons, five-sixteenths from 3 to 6 tons, one-eighth from 6 to 10 tons, and one-sixteenth over 10 tons. It would be desirable to divide the contract into two parts. Tenderers to state a price at per ton up to 5 tons weight, and another price for the heavier weights above 5 tons. Apparently there is an ample quantity of stone in the present quarry to yield the stones required up to 4 tons weight, • but it is doubtful if many heavier stones can be obtained without working the quarry at a much lower level. All the small stuff is to be used in the bottom of the wavebreaker and the larger sizes strictly set apart for fhg upper part and for admixture with the jcoucrete' blocks. I do not anticipate any difficulty in forking the quarry at a much lower

levelthanatprese.it, nor do I think the quarry road need be much altered beyond laying in the line to the northern side of the rock to be quarried, frooi which side it must be worked, both lor ease of quarrying and for yield of blocks of the maximum size. The question of providing increased cranage power for this work has been considered. The proposal to remove the block setting crane to the quarry 1 disapprove of for many reasons, and of which I have advised members of the Board. Probably the best way would be to approach the Westport Harbor Board through the Government, for the hire or purchase of a 20 ton quarry crane. If this falls through, other arrangements must be improvised for the purpose of lifting the heaviest weights. I do not like these makeshift appliances, they are clumsy and slow in use and necessarily very expensive to handle compared with a special and proper tool. DREDGING. I have carefully examined the dredger “ Thomas King,” with the object of forming an opinion whether a sand pump of power could be added to the vessel. This boat has an excellent compound surface condensing engine of, comparatively speaking, great power for the vessel’s size. The cylinders are 10 and 20 inches diameter, 12 inches stroke, making* 120 revolutions per minute with 601bs of steam. The boiler power is in duplicate, and not at all in good condition. The hull is of extremely strong build of very unhandy arrangements about her hopper, &c., and has never been properly maintained nor cared for. The hopper could carry about 50 cubic yards in fair weather, if a great quantity of coals was not aboard. This is a very small load, so the loss of time in conveying and dumping the spoil becomes a very serious matter. The engine is of sufficient power to drive a 12-inch sand pump easily, if it had only to discharge into the hopper.

I recommend, however, that a smaller pump be used, perhaps about 11-inch, and that this pump shall discharge into a sludge pipe to convey away the commingled sand and water to a certain point on shore. The sludge pipe would be of wrought iron, No 10, 8.W.G., to be laid under the wharf and along the cattle race to a point about 1200 feet distant from the outer end of the wharf. From this point the pipe would descend to the sandy beach, and be laid underneath the sand at a level about 3ft above low water mark. In this manner. It would extend eastward along the beach for a distance of about 1100 feet.

Between the dredger afloat and the fixed sludge pipe under the wharf there would be a specially arranged length of pipe, allowing the vessel to move about at her work and still discharge into the sludge pipe. The would be branch connections all along the pipe, so that the vessel could dredge anywhere along the line, and still discharge in the manner above described.

The vessel then would never discharge into her hopper at all, except when doing some special work where the sludge pipe was out of reach, and so the loss of time in discharging would be avoided.

There is ample engine power to work the pump as I suggest, and discharge through the sludge pipe, 2300 feet long. No fear need be felt in depositing the sand on the beach in the manner suggested, that it will be brought out again by the wash of the sea. No doubt but that a large increase of the beach will occur about the point of deposit during fine weather. Should any inconvenience ever arise from this cause it will only be necessary to lengthen the sludge pipe another 800 ft or 400 ft farther to the eastward if the engine power seems competent to do it, as I think it easily will be. It has been suggested as an easy method of disposal that the pump might discharge over the breakwater. This would be dredging ad infinitum, as the sand would most certainly be drifted round into the harbor, and no decrease in quantity would take place. Mr Skinner kindly showed me his surveys of the sand banks both inside and outside the harbor, from which it appears that the average annual deposit of sand under the lee of the breakwater is but 19,500 cubic yards. This is really a very small quantity to deal with, given anything like fair dredging power. The worst of it is there is such a huge accumulation of sand in the harbor from the neglect of adequate dredging operations in the past, that it will take a long time with improved means to make any visible impression on it.

By working with the sand pump, and discharging through the sludge pipe, I think we might easily discharge 300 to 400 cubic yards of sand per day of eight hours—perhaps much more. As soon as the sand accumulation can be cleared awaj, there will be no difficulty in maintaining full depth of water at very small expense, with gear recommended.

It will not be necessary to stop the working of the dredge for more - than three weeks to fit the new gear. The construction and fitting of the gear should be let by contract, and tenders invited in Dunedin, Christchurch, and Wellington. I estimate the cost of the sand pump, pipes Ac., at about £I4OO.

The present condition of the port from sand accumulation is most serious. It is necessary to do everything possible to keep the present dredging gear running at top speed. The vessel should he worked overtime every hour she can be, and the men bo paid overtime wages. Necessary current repairs must bo effected by night if possible, so as not to stop her work during the day. On no account nu st she be taken for work other than her

legitimate emp'oymeut. The length of her run for dop-sit has been shortened by one half. By doing all this, and cordial assistance from all engaged, I hope to prevent the steamers being driven from the wharf by short water. It is necessary to make better arrangements for coaling than are in vogue at present. Four men are now employed on the dredge. ! have worked similar hut larger plant with three hands. Captain Holford informs that the mooring and other arrangements require four men to do the boat justice under the the particular circumstances of the port and plant. I, therefore, recommend that no change bo made in the crew employed at present, as economy in working is just now a secondary consideration, speed being everything. When the new gear is to be fitted to the vessel, it will be necessary to haul her up on the beach, and put her hull and boilers in good order. SUMMARY. Throughout my examination of the works ami consideration of schemes for their repair aud improvement, 1 have borne in mind the extreme poverty of the Board’s financial position, and that if my advice was to be of practical use it must be such that the works and remedies suggested came within the power of the Board to perform them. This has been no easy matter, and my position has been one of great anxiety and responsibility. Many arrangements and devices other than those herein described have been considered, but have been rejected on the score of expense. Immediate energetic action is necessary to prevent further damage to the breakwater and further shoaling inside the harbor. ESTIMATE. The approximate cost of the work recommended would be as under : Repairing aud strengthening £ breakwater 1860 Sand pump and pipes 1400 Repairing barge, say ... ... 200 Contingencies... ... ... 300 £3760 N.B.—The hire or purchase of a special quarry crane is not included in above estimate. Also the cost of repairs to breakwater now in band is not included. F. W. Marchant, M. Inst. C.E. August 10th, 1895.