WHY RESERVOIR COLLAPSED

Sun (Auckland), Volume II, Issue 619, 22 March 1929, Page 16

WHY RESERVOIR COLLAPSED

Mr. Furkert Reveals Causes

FAULTY ORGANISATION IN COUNCIL STAFF

THAT responsibility for the bursting of the Mount Eden reservoir in the early morning of March 4 was chargeable to unsatisfactory organisation in the City Council’s staff and, more specifically, that the city engineer, the waterworks superintendent and the pump officer controlling the dam had erred conjointly, was the substance of the report presented at a special meeting of the council last evening by Mr. G. W. Furkert, engineer-in-chief and under-secretary of the Public Works Department, who had been appointed to investigate the disaster.

A FTER the council had considered and received Mr. Furkert’s findings, it passed a resolution expressing continued confidence in the officers involved and agreed that no action was necessary. “I viewed the damage to the old reservoir and inspected the remaining portion,” said Mr. Furkert. “I also examined all those persons who were likely to have any knowledge of the occurrence or of the past history of the old reservoir, and read the reports concerning the disaster prepared by the city engineer, the assistant city engineer, the clerk of works on the new dam, and the waterworks superintendent. Shortly, the position appears to be this: “In 1912 a reservoir was constructed from designs prepared in the office of the city engineer, which designs were alleged to require the outside support of the walls by an earth filling, but which on examination shew that even without this outside support, the reservoir would not burst while it remained in the condition in which it was when completed. “On completion a certain amount of leakage was discovered, and it was found that on all sides (particularly in the middle of the sides) there was a crack where the walls joined the floor. Certain remedial measures were taken with these cracks, and the reservoir | was still leaking when the city engineer j left for Australia. By memo, to j the then waterworks engineer he j asked that officer to act for him in I dealing with those leaks. The files I disclose that Mr. J. Carlaw (then waterworks engineer) reported that a bitumen treatment had completely stopped the leaks, and that he had taken over the reservoir. Apparently thereafter the city engineer’s staff had nothing to do with the reservoir, which passed into the hands of those responsible for the operation, as distinct from the construction, of the waterworks. “No tests appear to have been made at any subsequent date to ascertain if leakage continued. There is not the slightest doubt that very considerable leakage has been in progress for many years.” j Continuing, the report detailed the method of construction: the eoni dition of the break seemed to indicate

that tho floor had been laid first and the walls built round it. In the words of the city engineer, the reservoir had been designed principally as a lining to an excavated hole. . . .

CORROSION OF RODS “Although the bitumen treatment may have stopped the leaks at the time Mr. Carlaw took over, the leakage must have recommenced at a later date, and by its action upon the steel, which became exposed to water action as the result of the cracking, it gradually corroded the saic( steel until in many cases the rods were entirely severed before the accident occurred. “An examination of the severed ends shows that approximately 25 per cent, of the rods were gone altogether. A large number were reduced to approximately l-3in, and only a very few retained their original size. The number of rods which remained fairly efficient was not sufficient to carry the stresses due to a reservoir almost full. Had the floor rods remained in the condition in which they were when placed in 1912, the reservoir could have stood without support for a short time. It must be recollected that the city engineer’s staff, not having had anything to do with the reservoir since it was first constructed, would naturally have no reason to suppose that deterioration had taken place. “On March 1 last, having viewed the leakage appearing under the wall, the city engineer, after consultation with the assistant city engineer, and after having made fresh computations of th€* stresses, dispatched his assistant to the waterworks superintendent with a message that the water should be reduced to between seven and eight feet. When this message was received by Mr. Carr (waterworks superintendent) he made a demur on the ground that he could not efficiently keep up the supply of water to the high levels unless he kept a good supply of water in the storage tank, and he asked, ‘ls the reservoir going to collapse?’ Mr. Tyler’s reply was "Not if the water is kept down.’ THE WEAK POINT “We come now to the weak point in the arrangements. Nothing in writing was sent from the city engineer’s office. Mr. Tyler left Mr. Carr under the impression that his verbal request (it was not an order) would be complied with. On the other hand, Mr. Carr was left with the impression that if he kept the water at about 10ft things would be all right. Mr. Tyler was so concerned at the maintenance of the pro-

per level, that he offered the services of a man continuously to remain on the tank and see that the level did not exceed the pre-determined height. Mr. Carr, however, considered this unnecessary. He gave some verbal instructions to the man in charge of the pumping (Mr. Freeman), and those instructions appear to have been vague, because Mr. Freeman took no special steps to regulate the height, and on his early morning inspection, finding the level at lift, he did not consider it necessary to take any other steps. During Saturday the level fell in the ordinary way, as it does through use of water during the day, and those observing the leaks stated that they decreased, as one would naturally expect them to do.

“Mr. Carr states that he, happening to meet Mr. Tyler on the morning of Saturday, casually mentioned that the reservoir was at lift, and Mr. Tyler made no comment. Mr, Tyler, on the other hand, is emphatic that had he received any such message, he would have been so concerned that he would have immediately notified Mr. Bush,, so that steps might be taken to. have the water level lowered.

“Unfortunately there was no witness of this conversation, and as ‘7’ and ‘ll’ are easily confused, it may be that if any figure was mentioned, Mr. Tyler thought that it was ‘7.’

“On Sunday morning, March 3, the water was again recorded as being lift, which was higher than Mr. Carr’s instructions to his pumping staff permitted, but no action was taken. The reservoir was not inspected later in the day, and no alteration was made in the rate of pumping. It will be seen from the records of water pumped that more water was pumped on Sunday than for any day in the previous week, and exactly the same quantity as was pumped on February 22 and 23, which days were greater than any day subsequent to February 12. In view of these circumstances, the conclusion is inevitable that the water in the reservoir was at least up to its ordinary level when the burst occurred, and an examination of the walls of the reservoir by several officers after the catastrophe caused them to believe that the water was between 13 and 15ft deep. AT LEAST FIFTEEN FEET

“It may have been even more, because the damp marks on the walls and gauge board would dry from the top downwards owing to the fact that the lower parts are more frequently submerged and are consequently water soaked, while the upper part, being seldom submerged, would consequently dry out more quickly. As a further check on the quantity, I took evidence from those who saw the place immediately after the occurrence, and I carefully examined all undisturbed ground and partially completed walls around the area to be occupied by the new reservoir, and from the depth of water which filled this area, and making a reasonable allowance for splash, I am satisfied that there could not have been less than 15ft of water in the reservoir.

“The responsibility for the catastrophe must rest, to my mind, on the unsatisfactory organisation which exists in the City Council’s staff.

“By the council’s minut© of March 21, 1925, it appears that the city engineer l.as no control over the superintendent of waterworks (Mr. Carr). While Mr. Carr has the right to obtain advice from the city engineer, he is not called upon to submit any question to the city engineer if he does not think fit, nor has the city engineer any power to issue instructions to Mr. Carr. On the

day when alarm was first raised concerning the reservoir, Mr. Bush, influenced no doubt subconsciously by the anomalous position existing between himself and Mr. Carr, did not issue a definite order that the water' was to be reduced to 7-Bft. No doubt in working for a number of years in the peculiar relationship existing, he has found Mr. Carr willing to carry out verbal instructions, and has not therefore had occasion to ask the council for definite powers in case of emergency. At any rate, he did not issue, any order, either in writing or even verbally, but realising the gravity of the position, he sent his chief assistant to personally interview Mr. Carr. Mr. Carr, looking at the matter in the narrow way which, to him no doubt appeared all important, namely, as to how it would affect the consumers of water, did not openly refuse to reduce the level but, while listening to all Mr. Tyler said, made a mental decision to reduce the water to 10ft. At the same time, not wishing openly to disregard the request for a lower water level, he did not definitely advise Mr. Tyler that he -would not reduce the water to 7-Bft. VERBALLY PASSED ON “Later on Mr. Carr verbally passed the word on to Mr. Freeman that the water was to be kept down to about 10ft. Mr. Freeman, with the traditions of his establishment behind him, erred on what he considered the right side, and assumed that lift was near enough to 10. It is quite possible that Mr. Freeman did not understand that his instructions were to keep the level down to 10ft continuously, and may have assumed that it was only for that day. It is very difficult, in the absence of any system of keeping a log of orders and how they were obeyed, to arrive at exactly what did pass through his mind. "At any rate the water rose until it arrived at a stage that the wall, weakened by the corrosion of its reinforcement, and deprived of the support of the surrounding earth, finally gave way at the bottom, swung out on top of the escaping waters, tore loose from the roof, broke into three pieces, those pieces being carried to the position in which they now lie. “The question may be asked as to why the wall did not collapse on the Friday, when the water was at 15ft? The reply to that is that possibly the whole of the trench along the front of the reservoir was not excavated at the time the reservoir stood at 15ft early in the morning, and that when it was excavated completely during the afternoon, the water had fallen (as it usually does on week days in the afternoon). Also, the action of the escaping water on the scoria, deprived of its original overlying support, would cause a settlement which would render it less able to afford support on the Sunday night when the water rose again, than it had been on Friday. Again, when we are dealing with stresses which are so very close to the breaking point, tho application of the same stress a second time might cause a failure which one application of the same force would not necessarily cause. "It appears to me wrong that important, one might say vital, structures like city reservoirs, in which such forces of destruction are confined, should not be under the control constantly of those responsible for their construction, or, alternatively, under the control of a properly qualified engineer who would understand their designing and the fundamental basis of the designs, and whose duty it would be to bring a scientifically trained mind to bear on the problems of their maintenance.”