The Pamphlet Collection of Sir Robert Stout: Volume 26
The only serious differences of opinions in these Reports are threefold:—
The only serious differences of opinions in these Reports are threefold:—
First—As to the creation of an artificial tidal current. Second—As to the construction of the retaining walls along the dredged channel. Third—As to the economy of utilising the stuff dredged from the channel as opposed to carrying it to sea.
First.—Mr. Blair endorses the principle laid down in Mr. Balfour's scheme of a central training wall up the centre of the Harbour to direct and control the tidal currents as a correct one, but would, instead of starting from the Portobello Peninsula, start it from the Quarantine island and close up the channel between the Island and the Peninsula. He would, also, extend it further up the Harbour. He also condemns the scheme which seems at present to be in operation—the simple cutting of a channel from Burke's to Dunedin, protected by a timber training wall, over which dredged material is thrown.
Mr. Barr also approves of the general principles laid down by Mr. Balfour "as established by long experience," but considers the estimate of cost inadequate, and suggests a modification of his scheme, which will cost less than his large scheme, while securing the same or nearly the same advantages. At the same time he considers it free from certain grave objections to Mr. Balfour's smaller scheme from an engineering point of view. His proposal is to construct the wall from Bare Head instead of either from Portobello or from Green Point.
It would be unfair, however, not to point out that neither Mr. Blair nor Mr. Barr propound schemes of their own for the improvement of the Harbour. They simply profess to state their opinions with regard to the scheme suggested by the late Mr. Balfour for Harbour Improvement, and give their views on the general question without reference to any scheme which, after thorough investigation, and procuring detailed information, they might recommend.
Mr. Thomson, on the other hand, advocates a dead water channel, and is strongly opposed to the creation of any tidal currents beyond those at present existing. He also considers no obstructions whatever should be placed against the easy influx and reflux of the tide. Mr. M'Gregor also makes the dredging of a deep water channel from Blanket Bay to the Head of the Harbour, widening out and sweeping round the foreshore of Dunedin, the salient feature of his scheme. He would prefer waiting to see the effects before interfering with the tidal currents, and would only propose utilising the first of the flood and last of the ebb towards scouring the artificial channel.
These two latter opinions the Committee consider worthy of great weight—especially as Mr. Balfour's training wall would be by far the most expensive portion of his scheme, and is not considered by any of the Engineers essential to the bringing of the largest ships to Dunedin at first, and might be altogether dispensed with ultimately; and also because the dispensing with the central training wall would remove the very grave page 8 objection of interfering with the water communication now existing between the Peninsula and Port Chalmers.
Second.—Mr. Blair would make the retaining walls along the dredged channel higher than high tide, and watertight, if constructed at all, so as to command and direct the tide. Mr. Barr would construct them higher than water-mark, but would make them at first not watertight, and seems to consider that the action of cross currents would not materially affect the success of the scheme. Mr. Thomson, on the other hand, considers cross currents such very formidable affairs, if attempted to be diverted in such a body of water as the Upper Harbour, that he would commence the works at the head of the Harbour and proceed downwards so as to prevent difficulties from them. And so much is he against any real or apparent obstruction to the tidal currents that he would restrict the height of the training walls to that only which may be necessary to guard the artificial channel from having the dug-out mud coming back upon it. He also advises that "nothing that is a mere experiment should be attempted."
Mr. M'Gregor would also keep the walls of the channel low, and would dispense with them altogether where the channel could be maintained without them, so as to offer as little obstruction as possible to the flood tide filling the Harbour. Where erected, he would only raise them a little above low water line, just sufficient to guide the low water through the artificial channel, and would mark out the channel by buoys on both sides.
Third.—As to the relative economy of utilising the dredge stuff in reclamation, or of carrying it out to sea. Mr. M'Gregor stands alone in his opinion, that it will be cheaper to carry the stuff to sea than to deposit it on the foreshore, or behind any wall. But this opinion is based upon the information he possesses as to the capabilities of the new combined Hopper Dredge; and certainly, if after careful investigation its powers are found to be equal to what they are represented, it is probable the other Engineers would modify their opinions somewhat. Indeed Mr. Blair in one part of his Report states that Mr. Balfour's plan of taking the stuff outside the Heads "is undoubtedly the cheapest way of getting rid of it"; though afterwards he modifies this by saying "that if reclamation can make it worth 4s. or 5s. per yard, there is a large balance on the other side," and recommends the employment of light punts, and machinery to haul them up for discharge at levels above water-mark. Both Mr. Thomson and Mr. Barr disapprove of sending the mud to sea on the ground of expense, and favour the employment of the travelling shoot that has already been in operation for the conveyance of the stuff.
In addition to the foregoing subjects treated of fully in these Reports (which the Committee would earnestly recommend to the perusal of every one), both Mr. Thomson and Mr. M'Gregor recommend the principle of deep water docks or basins for the accommodation of vessels loading or unloading; whilst Mr. Blair prefers, as a better plan, one large square basin, with short jetties at sides. He thinks that the Harbour is so well sheltered, and the tide so small, that it is not necessary to have basins enclosed.
Mr. Barr also points out an important fact, that "the tide rises about three feet higher on the Ocean Beach than at the head of the Harbour; and it is not unreasonable to expect that of this quantity some of it will be gained by the improvements contemplated, probably from one to two feet."
|By Mr. Thomson||£123,539||1||2|
|By Mr. M'Gregor||£125,000||0||0|
|By Mr. Barr||£152,862||0||0|
The extra walling accounting for the difference.page 9
Mr. Blair has not worked out in his Report any estimate of total cost. It may, however, be confidently asserted by the Committee that for a sum of £150,000 all the shipping at present frequenting the Port could be brought up to Dunedin and comfortably berthed there.
The Committee, in bringing their investigations at present to a close, would point out that there are four ways in which the contemplated improvements might be carried out. First—by the Provincial Government direct. This would no doubt be the simplest and quickest way, but from the multifarious duties devolving upon the Executive, and the frequent changes inseparable from political institutions, there is little doubt that this would prove in the long run the most expensive and most inefficient channel through which to effect the object desired. Second—the City Council. The benefit to the City, apart from the question of sewage, would fully justify the Corporation in taking the matter up, but the same objection applies to them as to the Provincial Government; besides, as the Harbour belongs to the Province as a whole, and as its proper management is a matter in which the country even more than the City is interested, it is questionable whether it would be wise to entrust its entire management to a body who would naturally view everything connected with it, merely from a City point of view. Third—a Private Company. There is no doubt were the necessary concessions made to such a body, the whole matter would soon be carried out expeditiously and profitably. In fact, it is well known that there are parties now ready to take it up on this footing. But, unless as a last resource, the Committee could not recommend this course. The principle that all such undertakings should be the property of the public and under their immediate control, is too well understood now to require any further comment, and the experience of the past few years in regard to similar public undertakings is sufficient warning against this lucrative enterprise being allowed to pass into the hands of any private individual or corporation. Fourth—a Harbour Trust composed of men representing the various sections of the community immediately interested, and who will devote their full attention and energies to this particular means of benefiting the Province. The Committee would therefore submit the following