WELLINGTON DOCK'S FAILURE.

Dominion, Volume 4, Issue 1114, 29 April 1911, Page 14

WELLINGTON DOCK'S FAILURE.

[To tho Editor.] Sir,—As many of your readers are in-1 quiring of me upon what grounds Ibated my prophecy and open declarations of Wellington Dock's failure, with your kind permission I will give the information. Your readers will first understand that from the boatr-heds (Clyde IJiuiy) down to the far Thorndon end, the whole of the retaining wall around the water face is built upon made ground, which has a porous bottom. The whole of the dock site is made ground too, .to a much greater depth than the dredge lias ever touched. This being so, ami the dredge having cleared the site sufficiently deep !or tho dock, it was considered all I hat was needed to build the structure upon, and from this depth all calculations were made, hence the estimates, =£200,000, and the first move leading to the dock's failure. 1 knew before operations commenced that if the outer shell of the dock was

built upon tho bottom at th» depth which the'dredge had cleared, and the dock gates built in, all the pumps possible to apply on tho dock face could never empty the "basin. Failing to empty the basin, there could bo no graving dock. However, operations commenced, and as 1 had foreseen the method of proceeding with the work was altogether contrary to what experience would have dictated, and would eventuate in certain failure. Different circumstances need different methods, for any particular class of work, and only by" exporienco are wo taught how to adapt them successfully. It was a method that made no provision to ensure a sound and water-tight footing for the outer shell. That the outer shell was dumped upon a loose bottom, and built contiguously with the retaining wall, which, as stated above, has no sound foundation, and that the structure around the basin is open at tho foot to the full pressure of the outer sea, for the entire length of the water face. Therefore, under these conditions, it would be impossible to empty the basin. If the intention was to build the. dock complete from the inside of the basin, full of water and mud, makes the position appear the more pediculous—and no wonder at tho predicament. Assuming tho water could have been pumped out, as tho wall is now built, immediately tho inner pressure be removed the outer pressure of the sea would toppio over the whole structure, there being no sound footing to hold it in position. (Tho foot is crumbly, and rests on ii rotton bottom.) A similar thing happened in Auckland, when the sea wall collapsed, the same costing 4:25,000. What have Wellington experts to say to this? If my statements are not correct, 1 will ask one question:—When the contractors first failed to cause the cement to set, why did they not throw in the gates, pump out the water, and build tho bottom of tho basin in dry? This was known to be impossible. As I had stated through tho press would be the case, a fresh start had to be made. By continuing experimental work, the true position was veiled for many months, but eventually the failure of the dock was slowly, but surely, made known to the citizens as an impossible contract. Now, sir, having explained the cause of failure, with a little further tolerance 1 will givo a smattering of how I think the construction might have been a success, i and as a wrinkle can do no harm, may be of some little value to our exI perts, in so far that they may endeavour I to give tho citizens of Wellington value I for their money. First I wish to mention that I am in un way cancerned i with the money side of the question. The building of a dock on the present site. I and .the successful carrying out- of the I work is all 1 refer 10. From a commercial view, I repeat what I- stated four years 1 ago: That the present site is no place for a dock, it being the very key of flu i future Wellington. The theory and prac--1 tice is to carry all goods as near th< 3 centre of consumption as possible. The dock site would then be tho spot for om 0 of the largest wharves on tho waterfacc Tho destructor being in the way, time 1 will require its removal; otherwise, rates 0 will bo wasted in tho upkeep of street; 9 through heavy, traffic, wear and tear or 0 horses, vehicles, wages for labour' and 3 time, all to bo paid by the consumer This would be. altogether contrary to Dr. 8 Findlay's theory, expounded in a pampli- ; 3 lot, that waste should be avoided. But. in practice, the author's party have con- ! 3 taminatcd this country with a sense ol i 3 waste so that no country in the world il can compare witli New Zealand foi 13 waste in every respect.

To Aro site being chosen for the dock, and before going to the oxpenss of dredging, the first movo that ought to have been made was to put down bores, not a few, but many, in and around where the proposed structure was to be built, to pierce the loose ground right down into the solid. This operation would have proved how far down the outer portion of the structure had to bo built in order to" secure for it a sound and water-tight footing. This is of the first importance

to ensure stability, anil to effectually dam bock the outer sea. 'Die same operation

would have disclosed the nature of the ground. The number of cubic yards of earth to be removed (having the capacity or the dredge) would have given roughly the time and cost of dredging the basin to the required depth for the dock. The boring woidd also have shown the wisdom of building (ho outer shell first, before attempting the basin, and las', but not least, the base for tho estimates of the whole structure. AVith all the information possible to obtain, and submitted to the Harbour Board, they would then have been able to decide whether or not this city could have stood the cost, of the undertaking, and instead of .£200,000. I feel sure they would have had to consider an estimate of ,£300,000 or more. The dredging having been completed, and in order to expedite the work I would have started from a point at the Morgue end, casing a section of tho outer'wall right down into the solid to the'required depth of-.the dock, allowing a margin for the bottom inside the basin. From this section I would have continued tho wall both ways in sections, taking care that the foot of the wall was well grafted into tho solid, and made water-tight. In this way I would have continued, built, ami . completed tho outer shell of the dock, finishing up at (he gateway. The outer shell being completed, I would have then built in the gates, pumped out the water, and treated the basin dry, without the least difficulty. White treating tho basin, I would have connected up the retaining wall, finished tho reclamation, when tho dock and surrounding works would all have been completed and the dock ready use.

hi conclusion, sir, let me say (hat. lo build a dock on To Aro site requires no great amount of engineering skill. All that is- required is a little foresight, and with the method suggested iof sinking through water and loose earth, it is as easy to go down 100 fret as to go down 10 feet, without, the aid of n single pile, and every ounce of the material built in dry. T'lie rest is mine.—l am, etc., J. MTALE, M.M.C.E., M. South AVales Inst. Engineers. Pirio Street, April 18, 1911.