HARBOUR ENGINEERING.—PORT OF AUCKLAND.

New Zealand Herald, Volume XI, Issue 3824, 13 February 1874, Page 3

HARBOUR ENGINEERING.—PORT OF AUCKLAND.

To the Editor of the Hbbald. Sie,—While we in Now Zealand are making great efforts, and. expending vast sums of money in the construction of railways and roads, and in the improvement of our internal communication generally, we appear to have lost eight of the equal requirements of our harbours and rivers, for with an expenditure which may bo called profuse and extravagant in the formation of railways, the majority of which, it is well ascertained, will not for many years to come cover their working expenses, but little, if any, money has been set apart for the equally important Biibject of the improvement of the lmrbours and porta of our extensive eea board. The matter is one of vital importance to the best interests of the colony generally, a:nd of Auckland in particular ; and the writer, while fully aware of his inability to discuss the subject in all its varied bearings, will be content for the present if he only succeeds in drawiDg public attention, and particularly that of the cDmmoreial classes, towards it. The position of the port and city of Auckland, on the Waitemata river, or rathor, estuary (as it is more properly an arm of the sea than a river), is, from its proximity to the neighbouring colonies of New South Wales, Victoria, and Queensland, together with New Caledonia, tbe Fijis, the Navigators' and the Society Islands, admirably adapted for becoming the seat of an extensive commerce with those countries, and there can bo little doubt that owing to this cause alone Auckland must, at no very distant day, become a great commercial city, and will be—as in fact it is now—the comrnorcial capital of the North Island of New Zealand. The subject of harbour engineering is perhaps of all the departments of civil engineering the one in which there exists the greatest uncertainty, owing chiefly to tlio antagonistic forces of the tides, winds, and currents. Thus there are hardly two harbours whose natural conditions are exactly similar, and it has sometimes happened that the engineer who bus been called upon to propose a plan for the improvement of a harbour has, without having made himself fully cognisant of the peculiar features, and sot of the tides of the locality in question, adopted some method which had been found to succeed at a totally dillerent locality, nnd the consequence has been that instead of improving the harbour, it has been made worse. In all such cases, both theory and practice must mutually bo brought to bear, and it may be asserted ae a fundamental rule that in all cases whatsoever, of the improvement of harboure, all engineering contrivances or appliances will be unavailing unless a strict attention has been paid to those natural causes which have produced that state of things which wo desire to remedy, while all hasty conclusions and generalisations must be carefully avoided if we desiro not to incur a great waste of time and of money. In the artificial formation of a harbour which is not naturally and securely laud-locked, the chief object of the engineer ie to provide deep water with good shelter and safe bertliage for vessels of all classes, at all times of the tide and in all weathers, and this object can only be attained by tho construction of a capacious wet dock, having nil these requisites. 'This is in truth the great want of the Port of Auckland ; and after the lamentable and destructive effects of the recent heavy gale upon the shipping in this port, no unprejudiced person will deny tho faet that the time has arrived when tho stigma of an unsafe harbour should be removed from the port of Auckland, by providing the means for enabling the vessels which frequent it to lie afloat at all times of the tide, in deop water and in perfect safety whilst discharging or taking in their cargoes. Our recent experience has proved that they are not in safety whilst doing so, and that under the prosent state of wharf accommodation they are liable to eerious injury while lying alongside tho Qiieon-street Wharf and its jetlios whenever uny atmospheric disturbance, resulting in a heary gale of wind, may occur; and considering that Auckland is the oldest town in New Zealund, and hue a large population estimated at about 25,000 inhabitants, the want of proper wharf accommodation iu view of the rapidly increasing shipping trade of the port, is, to say the least of it, remarkable.

Now the great advantages of a wot dock consist of its convenience in loading and unloading vessels at all times of the tide and of tho weather in a land-locked basin, affording the necessary wharfage room at a less cost than it can bo got for otherwise ; and with respect to the Queen-street Wharf, Mr. Carrutherß, the Kngineer-in-Cliief, in his report on harbour works of Auckland, dated July 16, 1872, stated that, " Tho works most pressingly required aro —first, a good durable jetty,—the present wharf at Queen-street, besides being 100 small for the traffic, is much decayed, and will shortly have to be replaced by a now structure." Mr. Carruthers proposed to provide the neceseary wharf room by contructing at once tho enclosing earthwork and masonry embankments of a wet dock between the breakwater nnd tho Queen-etreet Wharf, suitablo for vessels of the largest size, and on this point Mr. Carruthers says:—" Thero is no doubt in my mind that the wet dock should bo begun at once, and carried on vigorously, until at loaet the interior surrounding wall is finished." Tho wet dock qb proposed by Mr. Carruthers, was to be 26 feet deep, and the including embankment 06 feet wide at top, with basalt facing on outeido and metalled roadway. The interior masonry wall was to bo 2,600 feet in length, with fender piles; entrance gate masonry only. The estimated cost of tho wot dock was (leaving excavation of dock and gates to bo done hereafter) £145,000. This dock (with certain other works) wa3 recommended by Mr. Carrutliors to bo commenced at once, but no actio'i in this respect was takon by tho Harbour Hoard, nor does it appear, as nearly two years havo now elapsed sinco that gentleman reported on tho Auckland harbour works,

that any action is intended to be taken in the matter of a wet dock, the question of which appears to bo ono of thoso which, like the water supply, is to be indefinitely postponed. Tho general design submitted by Mr. Carruthei's for tlie improvement of the harbour of Auckland shewed an enclosing embankment or seawall extending on the western eido of Uio Queen-street wharf, crossing it inside of tho outer eastern jetty, and leaving an entrance, with an entrance gato nnd drawbridgo over, about half-way to tho breakwater pier, adupt.ed to tlio admittance and exit of veseels at high water. A largo amount of earthwork wus shewn wil>)>in tlie breakwater, and this was tho eile proposed by Mr. Curruthers for I lie construction of a largo dry dock, suitablo for vessels of tho largest class. This dry dock would therefore bo entered from the wet dock, and its enteranco would consequently havo tho inestimable advantage of being unaffected by the tidal action. But, with respect to this dock, Mr. Carruthers statod that it appeared to him to bo a work not much required at that time, but that when Auckland possessed lurgo ship-building yards aud othor works, and could therefore count on being able to put a a large gang of men to work at tho repair of any vessel in dock it would bo time enough to build a work, tho usefulness of which is dependent as much on the rapidity with which repairs can be made as on anything else. Mr. Carrutliers, however, suggested the construction of a small dry dock to the west of Uio Quecn-etreet Wharf, to bo 300 feet long, with gates 35 feet in the clear, and with 14 foot of water on the sill at high water. This site ie therefore about the eamo as that which has been recommended by Mr. Moriarty for the construction of a graving dock of somewhat larger dimensions, viz., 375 feet in length, 55 feet, width of entrance, and with 16 feot of wuler on tho sill at highwater (medium tido). Such a dock would undoubtedly accommodate the largest ships now trading to Auckland, but much difference of opinion exists as to the eligibility of the proposed site, which is much exposed to tbe force of the strong weeterly svhids which prevail for about six months out of tho twelve. Another objection that hue been raised to this site, ia the large amount of dredging that will be required in order to excavate a deep channel to the docl entrance, and whioh dredging must be con

tinued in order to prevent it from being silled up. It was denbtless for theee and other reasons that Mr. Carruthers recommended the western side of the breakwater as being better adapted for a 6rat-elass dock of largo dimensions. He did not, however, prepare plans or estimates of this work, the position and size of which ho only indicated on the general plan accompanying his report.—l am, &c, 1 , . S. PfiPPERCORNE, C.E.