THE New Zealand Herald AND DAILY SOUTHERN CROSS. TUESDAY, DECEMBER 9, 1924. WESTERN WHARF COLLAPSE.

New Zealand Herald, Volume LXI, Issue 18887, 9 December 1924, Page 8

THE New Zealand Herald AND DAILY SOUTHERN CROSS. TUESDAY, DECEMBER 9, 1924. WESTERN WHARF COLLAPSE.

A refoi t which must be taken very seriously indeed has been produced I)}' the two commissioners who inquired into the collapse of the Western Wharf. The document in itself is admirably shaped and phrased. Any intelligent layman who reads it with ordinary care and attention can follow the observations and conclusions of the inquiry. Be-

fore the wharf was built the ground on the Ponsonbv side of it was dredged in benches, or terraced formation. Afterwards, along this side, a rubble bank was deposited, rising to a point just above low water mark. It had a long slope down the terraced formation, under the wharf, about the pile's driven on that side. A shorter slope ran out the other way toward a corresponding slope of the tide deflector. On top of this rubble bank there was built a gravity retaining wall, again of rubble alongside the portion of the wharf still standing, but of con-j crete against the collapsed part. The intention, partly realised, was to fill in the space between the retaining wall and the tide deflector with spoil. A load was actually being tipped when the collapse began. The commission finds that the rubble bank under —partly by its own mass, partly because of the weight of the gravity walls of rubble and concrete, and partly because of the pressure from the spoil tipped between wharf and deflector —settled, moving downward and forward in | the direction of the long slope, that is the slope under the Western j Wharf. The retaining wall neces- j sarily moved with it, to an extent greater than the gap originally left between it and the upper works of the wharf structure. The stress caused by the concrete portion of the retaining wall settling against the wharf- forced the piles outward beyond the amount possible from their natural elasticity. The result was fracture and collapse. That is the crux 01 the report. The commissioners state that, when a bank of loose material is deposited in this fashion on sloping ground, it always settles, moving in the direction of the long slope. This they say is thoroughly well established, both by theory and observation. Therefore, they conclude, in designing a work including such a bank, with its possibilities of movement, and the development of the direct lateral thrust which' brought disaster, insufficient. foresight was displayed. Similar faults in design are observable at Prince's Wharf, Freeman's Bay, and the Calliope Dock Wharf, where tendencies identical with the happenings at Western Wharf have been observed.

The report so far is highly alarming- There is reassurance, however, in the opinion that the flaws in design are incidental, not fundamental. They are grave, but remediable. The sloping rubble bank is named as the whole source of weakness. It can be removed from the Western Wharf. In the opinion of the commissioners it should be taken away, the remaining portion of the wharf pulled back into position, suitably stayed, and repaired where necessary. It can then be utilised for shipping, and can safely be extended |in future. The scheme to fill in the space between the Western Wharf | and the tide deflector is approved, provided the type of retaining wall recommended, built cn secured foundations, is adopted. Fortu- | nately, the commissioners are also of opinion that with care and attention, disastrous results need not be apprehended at any of the three works they single out as suffering defects similar to that which did such serious damage at the Western Wharf. Constant watchfulness is enjoined, so that the movement already detected shall not proceed unchecked to an extent involving an extensive breakdown. Should the forward movement of the retaining walls accelerate to a degree constituting a menace to the structures toward which they are forced, the pressure behind must be relieved. These are the findings and recommendations of experts whose opinions must command respect. They have observed the ground, heard many witnesses, and sifted much evidence. They have shown an admirably judicial tone throughout, however hard the things they have l ad to say may be.

Following the finding there was a sequel as inevitable as the fall of the "Western Wharf once it began to collapse—the resignation of the board's engineer, Mr. Hamer. That has been tendered and accepted. The position would have become impossible otherwise; but with that, it must in common justice be said that Mr. Hamcr relinquishes his office with one error of judgment recorded against him. On the other side must be countcd a great mass of work done in the service of the board with which the commissioners have found no fault. In regard to the Western Wharf itself they have freely testified that apart from the flaw in design to which they attribute the trouble, everything was soundly planned and faithfully executed. Its strength would have been more than adequate for the loads it was expectcd to bear- Unhappily, owing to a strain it was never intended to bear, which no structure of the kind could have borne, it crashed into ruin. It was unsoundness in the planning of an accessory, not of the w ark itself, to which subsequent events must be attributed. The duplication of similar methods of bracing structures in three instances, elsewhere is the only defect the commissioners have found

in the great series of works fronting the Auckland Harbour, works which have all been planned by and executed under the supervision of Mr. Hamer. In the whole range of his achievements he has been found to have committed only the one error of judgment, even if it appears in more than one place. The commissioners have supplemented their report by expressing the opinion that had movement of the wall been detected and remedial measures taken, the Western Wharf need not have fallen. The general tenor of the findings, and this point in particular, remove much of the anxiety felt about other harbour works. Further emphasis is given the recommendation that the other points where movement has been detected should be subject to constant, rigid inspection, and that instant action to relieve stresses should be taken when the necessity arises- It

is stated by the commissioners —indeed it is fairly obvious from the report —that at the worst nothing approaching in gravity the collapse of the Western Wharf could happen at the wharves they have named. It is for the Harbour Board to see that nothing of the same kind, however much less in degree, is allowed to happen anywhere. The report has been accepted and approved. It recommends certain action. It is for the board, therefore, to take that action, in the determination to allow no further loss, since nothing can recover that occasioned by the collapse of the Western Wharf.