Newspaper Extracts
Sheffield Flood
«ReturnInquest Resumed
The inquest on the bodies of Thomas Elston and others was resumed
at the Town Hall, Sheffield, on Wednesday, March 23rd.
The Coroner, John Webster, conducted the inquiry. Among
the professional and other gentlemen present were:
Robert Rawlinson, Civil Engineer, and Nathaniel Beardmore, Civil Engineer, from the Home Office
M. Mille, Engineer to the French Government
Robert W. Mylne, Civil Engineer, F.R.S. London
William Lindley, Civil Engineer, F.R.S.London, of the Hamburg Sewage and Water Works
Colonel Ford, of York
Perronet Thompson, barrister, instructed by Messrs. A. Smith
and Sons, solicitors to the Water Company
William Smith, Chairman of the Water Company
Thomas Jessop, Sheffield Mayor
Mr. Broadbent appeared for the friends of several of the
deceased.
Matthew B. Jackson of Sheffield, civil and
mechanical engineer said: 'I have been engaged in the construction of reservoirs in Australia. I was chief engineer of
the Melbourne Waterworks etc. I was on the embankment at Bradfield a few hours after the accident and 3 times since I
have examined it, in special reference to this enquiry. I am of the opinion there is no fault to be found with the
quantity of materials on the slopes. The material was ample and the slope sufficient. Perhaps in my own practice
I should have preferred a slope on 3 to 1 inside. The puddle was good and sufficient. I have put in a greater
proportion of puddle, but I do not think at all that any accident would have arisen from that. I have no fault to find
with the by-wash. I have examined the embankment. I should not have formed an embankment in the same way.
I should distinctly prohibit the use of railway wagons on a bank, more especially on the inside slope, because in the first
place, I should make the bank in layers of not more than 2 feet thick. Railway wagons always travel in the same line and
tend to consolidate the embankment unequally. Dobbins and carts, on the other hand, travel in different parts, and tend
to consolidate the bank equally. On the inside slope I should have insisted that layers not exceeding 2 feet each, should
have been carried over and through, each being perfectly finished before another was commenced. On the outside slope
I would not object to a tip of 3 feet, because it is not so necessary to have the outer slope so impervious to water.
It is better open, to let water have free exit. I mean by open, that it should be composed of more porous material.
The embankment had not been erected in that manner. There were always railway wagons on it now, showing that they have been used, and it is obvious the layers have put on a greater thickness than 2 feet. At the embankment at Agden, the layers are not being put down and completed consecutively; and if the one at Bradfield was constructed in the same way I should apprehend that there would be an unequal settlement. I did not measure the tips at Agden, I saw they very much exceeded the measurement I have given. Unequal settlement is dangerous, because it may cause a slip. It is peculiarly dangerous if there are pipes passing under the bank in trenches. It might be possible to pass them safely through in a culvert. The danger is that the unequal settlement may break the pipes or spring the joints, so as to produce a leakage. The depth of the tips I have mentioned is rather an extreme one. In constructing another bank, I should take the specifications of Mr. Leslie of Edinburgh, which are the best I have ever read. He restricts the tips to six inches, one layer to be finished before another is begun and wagons to be prohibited. They are safer than mine but more expensive. I approve Mr. Leslie's stipulation that the puddle wall should be brought up to and kept on a level of 6 inches, above the adjoining portion of the embankment. At my works in Melbourne, I had two fractured pipes. They were under the embankment in solid ground. They were laid on flags to the edge of the puddle trench and in passing through the puddle, each pipe of each main, which was only 6 foot 6 inch in length, was supported on an ashlar pillar. The pipes were puddled all round.
The fracture in that case I have no doubt arose from an unequal settlement of the embankment, though made with the limited tips I have mentioned. An embankment settles more in the centre from its length than at the sides, and, consequently, if the pipes were laid straight through the embankment, they would bend and break by the unequal settling. My plan of putting in the pipes at Melbourne was a bad one, but not so bad as the plan at Bradfield. There was no puddle between the flags and pipes at Melbourne, it would not have made any difference if there had been. I have not the least doubt that the structure of the Bradfield dam caused an unequal pressure, fractured the pipes, and so produced a leakage. There is this difference. The way my pipes were laid at Melbourne was more liable to cause a fracture. Mr. Gunson's plan was more likely to cause a drawn joint. I heard the mode described yesterday of keeping down the water in the puddle trench. The evidence of Mr. Gunson to a great extent dispelled a doubt I had previously entertained. The doubt was as to whether the water had got under the puddle trench and risen immediately under the outside slope, inducing a settlement and slip immediately before the burst. I am inclined to think that such was not the case, and that the puddle trench was a good job, though I scarcely think the evidence of Mr. Leather and Mr. Gunson showed the puddle trench was dry, as that would depend on the time of year and the weather. I am inclined to think that on the reservoir being filled the unequal settlement of the embankment occasioned a springing, or starting or drawing of the pipe joints. If a joint were once sprung, the internal pressure of the water itself would be sufficient to bow the lead out. Having the pipes cast narrower at the entrance to the socket is a good precaution. It is moreover, possible for the pressure of water on the valve which was outside the reservoir to have started a joint between the valves and the puddle wall. The opening or closing of the valves would increase the probability of this.
Mr. Leather was appealed to and he said he did not think there was such probability.
Mr. Jackson resumed - The probability of this would be diminished in proportion to the number of pipes below or outside the valve. There are four or five pipes below the valve at Bradfield. It is quite possible for the water to have crept along outside the outlet pipes, between the pipes and the puddle with fatal effect.
The Coroner here said it was the business of the jury to find out every possible fault in the construction of the dam. There had evidently been faults. According to the description of Mr. Leather and Mr. Gunson, the work was so perfect that it was almost impossible to improve it. But there was something fatal in the design of the puddle, or the reservoir would not have burst.
Mr. B. Smith begged to call the attention of the Coroner to the fact that the evidence on the previous day was that the bursting of the reservoir was caused, not by a fault in the embankment, but by a slip in the ground.
Mr. Jackson resumed - The outer surface of the pipe being cast iron would not unite with the puddle. At Melbourne I put shields round the pipes in order to prevent that. They would have the same effect as the collars spoken to by Mr. Rawlinson. The shields have to be put in 2 valves and bolted or otherwise fastened. I put 4 shields on each main. The shield was 7ft 6in in diameter. I have examined the stratification of the rock both inside and outside the Bradfield Reservoir. I do not see any objection to baring the rocks to make the embankment. I see nothing to lead me to conclude that that would be fatal to the bank, provided proper means were taken to drain away all water percolating under the outside slope of the bank. The question of baring the rocks inside the reservoir is more a possible cause of waste of water to the company, to be weighed against a certain economy in the construction of the bank than anything else. No damage from such a cause would result to the embankment by any water passing into the fissures of the rock, unless it flowed up under or immediately adjacent to the seat of the outside slope. That it would not necessarily do; it might flow up half a mile down the valley. If it flowed up under the seat of the embankment it would do no harm if drained away. It had been stated that it was not drained but that was not in evidence. I have not the least doubt the proximate cause of the bursting of the reservoir was the drawing of the joints of one or more of the pipes, a leakage along the side of the pipes, or both causes together. It is possible there might have been a leakage through a fissure inside coming out of the embankment.
In reply to the jury - I cannot say whether the joints were drawn or merely sprung. If the valves had been inside the dam, there would have been no tendency in the valves to draw the pipes. Moreover if a joint were drawn, and the water got to the middle, the embankment would be torn away before any means of preventing it could be adopted, even if the valves were inside the dam.
BY THE CORONER - It is possible for a leakage from the fissures of the rocks to have reappeared directly under the seat of the outside slope. That would be of itself a cause sufficient to burst the bank unless the water had free vent. That free vent can be obtained in one or two ways. It might be obtained by having the seat of the embankment under the outside slope efficiently drained by cutting trenches and filling them with large stones; that would admit of a free passage of the water. Another plan would be to collect all the water in a longitudinal drain at the bottom of the puddle trench, carried along all its length if necessary to the lowest point, and then transversely up to the surface of the ground, or to the bottom of the drain under the seat of the outside slope. That is a perfectly safe way of getting rid of water, provided the bottom of the puddle trench be all of rock. After hearing the evidence of Mr. Gunson yesterday, I do not think any precaution of this kind was necessary.
By the Jury - Is it possible for water to get under the outside slope without being observed; the ground might absorb it. I cannot tell whether the ground under the embankment at Bradfield would do so without seeing it.
By Mr. Rawlinson - If the outlet pipes have been depressed by settlement of the embankment, is it possible the puddle might not have followed it. There may thus have been an open space left between the tip of the pipe and the puddle.
By the Jury - Could a vertical pressure press down the pipe and not the puddle?
By Mr. Rawlinson - The pressure would not be equal. The pressure on the top two sides may have depressed the pipe faster than the puddle, from the side pressure being more rapid than the centre pressure; and the water is there to avail itself of the least opening; and if water thus got in the consequences would be what we have seen. I have no desire to say a harsh word against those who made this dam, but the embankment has been destroyed; there must be a cause for its destruction, and it is our business to find out that cause. I do not go so far as to say the cause is a fault of some sort.
Mr. Pawson, foreman of the jury, said he concurred in the view of the desireableness of finding out the cause of the accident, and expressed his regret that the engineers of the Water Company, who necessarily knew most about it, had manifested so much reserve.
Mr. Jackson resumed in reply to the jury - It might have been advantageous to have had a better and more rapid discharge of water than the two pipes when danger was apprehended. I could have devised such a means. A tunnel might have been driven through the solid rock, round the end of the embankment. That in my opinion is by far the best way, and in any work I may have to do again, I should lay pipes in a tunnel through the solid and not under the embankment. Another mode is this: The stream supplying the reservoir might have been brought round to the by-wash by a channel, along the side of the reservoir, so as to have given complete control over the flood water. The pressure from the water could have been eased by the outlet pipes.
Mr. Gunson, recalled, said the water was carried along an artificial course during the whole time of the construction of the dam.
Mr. Jackson resumed in reply to the jury - I have constructed larger reservoirs than this in Australia, but none so deep, and it is depth that involves danger. Another suggestion for the safety of the dam is to construct the by-wash at a lower level than it was first intended ultimately that the water should stand. The plan was suggested to me last night by Colonel Ford, and is valuable, as the water might
pressible material. I think also that in the formation of the Agden embankment should be kept away from the puddle wall; that 3 feet layers are much too thick; and that 6 inch layers, as suggested by Mr. Lesley, are the only safe way of making the embankment.
By Mr. Smith - There are many instances, especially of late, in which pipes are not laid through the embankment. At Dublin, the culvert plan round the embankment is being made; I think also at the Culvington Reservoirs.
Nathaniel Beardmore, Civil Engineer, London. - I was requested by Sir George Grey to come down and assist Mr. Rawlinson in examining the reservoir, with the object of making a report. I have examined both the Bradfield and Agden reservoirs. I have heard the evidence of Mr's. Rawlinson, Jackson, Gunson and Leather. I agree substantially with the evidence of Mr. Rawlinson. I do not think the Agden embankment is being made in the secure manner necessary for such a work. In dealing with water, security should be taken against the remotest contingency of accidents. It would be very difficult to get everybody to agree as to the immediate cause of the bursting of the reservoir. The disruptions being so great, it will be difficult to discover the differences between causes and effects. My impression is that the puddle is the most excellent work. I think the immense depth excavated must have removed danger from the springs, and the probabilities must point to the pipes being the source, if not the cause of the accident. The description itself implies an immediate volume of water blowing up the material of the embankment. To my mind the most material conclusion is that the pipe leads the water to do that mischief. Telford, the great engineer, never, I believe, put pipes through the embankment of a dam. I agree generally with Mr. Rawlinon and Mr. Jackson as to the dangers arising from putting pipes under the embankments.
After retiring 20 minutes the jury returned into court and the Coroner said they had made up their minds. He was glad to have no occasion to sum up because he should have spoken in such a manner that would perhaps have been disagreeable to some persons.
The verdict was as follows:
'We find that Thomas Ellstone came to his death by drowning in the inundation caused by the bursting of the Bradfield Reservoir on the 12th inst. that in our opinion there has not been that engineering skill and that attention to the construction of the works which their magnitude and importance demanded; that in our opinion the Legislature ought to take such action as will result in a Governmental inspection of all works of this character, and that such inspection ought to be frequent, regular, and sufficient; and that we cannot separate without expressing our deep regret at the fearful loss of life which has occurred from the disruption of the Bradfield reservoir.'
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