The Evening Star FRIDAY, DECEMBER 22, 1876.

Evening Star, Issue 4313, 22 December 1876, Page 2

The Evening Star FRIDAY, DECEMBER 22, 1876.

The Harbor Board should have no difficulty in deciding upon the course that should be adopted in view of the tenders before them. They have the choice of three methods which involve outlay that, so far as construction is concerned, may be pronounced non-repro-ductive ; while the fourth presents more than the self-evident advantage of reclaiming a large area ef valuable land at a light expense. For the more clearly comprehending the different plans, we append a short description of them published for the guidance of intending contractors : - Method No. 1 provides for the material dredged, being deposited at a dißtunce from the sonth side of the channel not less than 100 ft, except where shown otherwise at the lower end of the channel, and retained in position there by a temporary retaining wall—the top or sheet piling of whioh shall be proportioned to the height of the material deposited behind it, but in no case shall it le below half-iide level, or be carried up to a greater height than 2ft above hifch water. The entire erection is to be further braced and strengthened, if necessary, so that the material deposited behind shall not under any circumstances in the Engineer's opinion be washed by tidal notion or'other znvons into the harl or. AU material exposed and liable to t>e blown away, above high water level, must be protected by a substantial artificial covering. Method No. 2 is, in every respect, similar to No. 1, except that instead of timber the retaining wall shall be of rocky material, the wall to have a top width of at least 3ft, with side slopes ot 2 io 1. Method No. 3 provides for the dredged material being deposited three miles outside the Heads, and the erection of a half-tide wall of stone extending the whole length of the channel from Kilgonr's Point to the terminal point. The wall toDe6ft wide on top with side slopes of 2 to 1, and to be placed 200 ft distant from the seuth side of the channel. Method No. 4 provides that the dredged material is to be deposited in such parts of the reclamation area as the engineer may direct. The height of the reclamation levol is to be sft above high-water level. This method likewise includes the erection of a half-tide wall similar in extent, height, dimen. s*on», and position to that specified in Method No, 3. Each of the four methods embraces Mr Keid's idea ef providing a channel of sufficient width and depth to admit of vessels of the largest tonnage that can

enter the Port eommg up to Dnnedin. Hat the first two of the proposed plans include works that, besides being an tuorwous exper.su, phic* difficulties ir, the way of extending the width of the channel i he scheme of building walla to retain mud scooped oat from the channel as aides to it and to prevent its being washed back again, instead of removing it and utilising it for reclamation purposes, could only be justified were the difference of expense so great as to render all hope groundless of its being recouped within a reasonable time. It might then become a question whether it would be worth incurring the risk of spending the future time of the dredge in keeping a narrow channel open instead of employing it m extending the width to the full 300 ft It must not be forgotten that retaining walls present a practical impediment to extension, and that, should methods involving them be adopted, any extension of width, would be only effected at enormously-aggravated expense ; for not only would the retaining walls require removing, but the deposit would again have to be shifted, so that either the channel weuld practically be limited to the narrow width of 70ft at the bottom, or the cost of widening it at a future time would have to include that of undoing what would have been done. This doiDg and undoing is never any other than waste of time, money, and talent. It is the vice of small schemers ; it fritters away money, and is never satisfactory even for the purpose designed. For our own parts we should prefer method No. 4, which adopts the sensible idea of excavating without retaining walls, and using the dredged material as a means of reclaiming now useless areas of Pelichet Bay and the Upper Harbor. It must be remembered that the dredged material, thus utilised, provides a means of future revenue which wisely nursed would amount in value, in a very short' time when the trade of the Port becomes developed, to more than the whole cost of the work. It cannot, at any rate, wash back into the channel, and ■ therefore is done with at once and for ever. And if it be suggested that the channel will soon warp up if no retaining walls are built, perhaps, when it is considered that it has required unknown centuries to reduce the bed of the harbor to its present shallowness, and that there is no reason to imagine more, if so much, silt will be washed from slopes solidified by the pressure of thousands of years than would be likely to be returned into the channel from the loose material disintegrated by dredging and depo ited behind the retaining walls, it seems reasonable to conclude that the pro* posed No. 4 method is the proper one to adopt. JSot having the plans before us, we confine ourselves to what seem to us first principles. We regard it as essential that harbor improvement should not only contemplate present advantages but future; and that to purchase an immediate benefit by placing an impediment that is in all probability utterly needless in thje way of prospective development is unwise and improvident. Although all questions of the sort involve certain scientific considerations which none other than experts are thoroughly competent to decide, they resolve themselves ultimately into commercial considerations of profit and loss. Thus, when the question of retaining walls is placed before the Board, it becomes a question of' utility and. cost. It would appear that the difference between the lowest tender for No. 1 method and .for carrying out No. 4 method, which is Mr Simpson's plan in its entirety, is about £16,000 in actual money. While the latter _ contemplates utilising the dredged material and adding an indefinitely increasing value to the property of the the other merely proposes widening ' the channel and rendering its sides secure. Nor is it likely that any advantage in time would be gained; for it must at once be plain that excavating and building, though carried on simultaneously, will in all probability prove a slower process than excavating only ; and this probability is increased because of the necessity for securing the dredged stuff in its position, should it be deposited on the sides of the channel. An expert of no very extraordinary talent is well . able to say whether from the character of the bottom the channel would easily be kept open without retaining walls : and although there is confessedly at all times a risk of error in calculating upon tidal effects, those whose opportunities of observation are the most ample are at any rate the most likely to give a reliable opinion. A man who has a professional reputation is not likely to risk throwing it away for a mere crotchet; a man that has one to gain is equally unlikely to give a hasty and ill-founded opinion ; while a man having a professional reputation and a lucrative position involved, who has moreover had the advantage of conducting large works previously intimately connected with the Harbor, is still less likely to err. If, therefore, No. 4 plan is adopted, it seems to us to present the following probabilities of success:— First—The estimated cost is the lowest in proportion to the work to be done. Secondly : —lt ia likely to be completed in almost as short a time as any of them. Thirdly—lt presents no impediments to future extension of the width of the harbor. Fourthly—lt provides for repayment of its cost with immense interest upon the outlay. On these grounds, to which others might be added, which must recommend themselves to every member of the Board, we consider they will be justified in adopting it.