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 thereby be regulated by lifts, according to circumstances, until the bank is thoroughly consolidated. It would be a great protection to a new bank. The by-wash might be ultimately raised to the height required by erecting sluices along the tip of it. If my reservoir at Melbourne had not had valves inside, it would have burst like this. It is better to have them inside, because then, if a leakage occurs in the pipe, the water can be shut off. I am of opinion that the accident has not occurred from the rising of the water under the outer slope of the embankment, because Mr. Gunson's evidence shows that the rock to which the puddle trench was sunk was impervious.
By Mr. B. Smith. - The works I constructed at Melbourne were 3,003 acres; the contents were 38,000,000 cubic yards and the depth 25ft. I have been an engineer since 1846. The waggons on the bank are not what is ordinarily understood as railway waggons; they are much smaller. They are, however, waggons running on rails. Leslie advises 6" layers, and I, 2ft layers. Engineers like lawyers, disagree. I have carried pipes under embankments. That has been the universal practice until now. There has been no great disaster from it until now. It has been an error of judgement committed by the most eminent engineers. I should not, after what has occurred here, again lay pipes under or through an embankment, by culverts or otherwise. I laid my pipes at Melbourne on stone, not on puddle, like Mr. Gunson. The two plans have their advantages and disadvantages. Neither of them are good jobs. I collared my pipes and bestowed great pains upon them. My plan was therefore not the right one; but I saved the embankment by having valves inside the reservoir. The pipes would be more liable to fracture on the stone than on puddle. The shields might cut the puddle, and prevent its adhesion to the pipe. I still think they are the best, but another engineer might think differently. After my experience at Melbourne and here, it seems to me foolish to think of placing pipes under an embankment again.
Mr. B. Smith suggested that the question for the jury was not so much what was to be done in future, but whether the servants of the Water Company had used reasonable care and skill in the construction of the reservoir. Mr. Rawlinson was there to attend to the other branch of the inquiry. He would find out the cause of the accident, no doubt, and his report to the Government would be published.
Mr. Prideaux suggested that if the outlet pipes were bared the jury would get at the information at once.
Mr. Jackson. - If that is done you will find it as I say, I have no doubt. What we want to know is, whether there is a leak outside the puddle, because that would settle it.
The Coroner. - We can shorten this inquiry if the Waterworks Company will be at the expense of baring their pipes, as we could arrive at a result at once. I, of course, have no means of paying for it.
Mr. B. Smith. - I cannot pledge the Water Company to do anything without consideration. They want, for their own satisfaction as well as that for the public, to ascertain the cause of the accident, and will take such means as are in their power to do so. At present, however, they are fighting in the dark, and I must again submit that the question for the jury is simply whether anybody is criminally responsible.
Mr. Jackson. - A few of the pipes at the end might be bared, and if they have started you might safely come to the conclusion that others have started too.
Mr. Rawlinson. - You might bare the outer end, plug up the pipes; then bare the inner end, plug up the pipes and use hydraulic pressure.
Mr. Beardmore. - But there was such a violent disturbance of the embankment when the bursting took place; the whole ground was shaken, and that may have done mischief to the pipes. If, therefore, you find that mischief has been done to the outlet pipes you won't know when it was done, or when the embankment gave way, whether it was done before. That is the real difficulty.
Mr. Smith. - Mr. Beardmore has anticipated what I was about to say. The bursting of the reservoir created a violent commotion of the ground, which may itself have broken the pipes, however perfect they were before. The fact of the pipes being broken or drawn now, therefore, is no proof that the accident arose from that.
Mr. Jackson said there could be no doubt that if the pipes were bared they would be found to be broken just outside the outer edge of the puddle wall. He was satisfied of this, because on visiting the dam the other day he found water bubbling up at the top of the fore bed. It was also bubbling up at a lower point. Whether, however, the leakage was from a fracture of the pipe or from a drawn joint he could not say. It was these appearances that made him express, on the same day, a positive opinion that the fracture or dislocation of the pipes had been the immediate cause of the accident.
Mr. Rawlinson explained that the present condition of the pipes under the embankment, supposing it was ascertained by baring them, could not be received as evidence of the condition in which they existed before the bursting of the embankment. He wished the jury distinctly to understand this. If a dozen joints were found to be drawn now, no human being could say that they were drawn before the flood.
Mr. Jackson's examination by Mr. B. Smith resumed. - I do not think there is any disadvantage in collars or shields round the outlet pipes when they are carefully puddled round. I am decidedly of opinion that the embankment has not burst in consequence of leakage arising from the baring of the rocks. If I had a dam to make tomorrow, I should not hesitate to bare the rocks, which is one of the commonest practices. The plan of keeping control of the water of a reservoir by making a culvert through the solid ground round the end of the embankment is now a new idea, but it is one which has not been much acted upon. The other plan I have named is in use at Manchester. When the crack was seen the mischief was done.
By the Foreman. - We could not in an hour or two have drawn off sufficient water to prevent the accident. We might, if we were starting to construct a reservoir, have devised other means which would have done it - such as driving a tunnel as large as a railway tunnel; but that would have been an outrageous proceeding.
By Mr. Smith. - If I were planning a reservoir again, I should undoubtedly put in a culvert for the pipes. That has been suggested to me by this accident and that which I experience in Melbourne.
By The Foreman. - There was danger in having the rocks inside the dam. If they were covered in impervious material it would have been wise to have left that.
By Mr. Smith. - I think water got under the embankment, but after hearing Mr. Gunson's evidence, I think it was not a point of danger, but rather a loss of storage.
Another question being asked by a juryman as to the present condition of the pipes, the foreman (Mr. Pawson) interposed and said, the jury will give this point up if the water company will promise, for ulterior purposes, to have the pipes laid bare, and an examination made. The reason for this was that there were other dams in this locality constructed, and being constructed on the same principle.
Mr. Smith would undertake, on behalf of the company, that as to the baring of those pipes they should place themselves in the hands of Mr. Rawlinson. It was more important to the company than to anybody else.
The Foreman said the jury should take advantage of the power they had, because the examination sought had a bearing on the other works. Although they should endeavour to confine themselves strictly to their province, they could not forget that they were townsmen as well as jurymen.
Mr. Gunson was recalled, having expressed a wish to make some explanation. He was beginning to say that he had been misunderstood on the previous day in reference to the water seen behind the embankment. He did not think it had come from the reservoir.
The Coroner stated that he was quite satisfied with the note which he had taken on that point.
Mr. Gunson was then examined as to the variance which had taken place in the actual work from the specifications. These, it appeared, had been considerable. A specification, he said, was simply a guide; and when the specifications of the Bradfield Reservoir were drawn up, Mr. Leather was not aware of the materials to be got in the excavation of the reservoir.
By a Juryman. - Mr. Leather was more than twice - perhaps six times at Bradfield - during the construction of the work. I used to go over and see him. He had to come once a year at least to report.
The Coroner. - He is a "consulting engineer," an ornamental officer. He is expected to do nothing but simply present a report.
Examination continued. - We are not, as provided by the specifications, carrying up the puddle wall at Agden simultaneously with the embankment, because that was impossible. Stones may fall among the puddle if the embankment be carried up before the puddle wall, but I have taken every means to prevent it.
The Coroner strongly denounced the departure made from the specifications. A specification, he said, they would understand in future, was not a guide, but a farce and a deception. Here was one made for the purpose of not being carried out. He was out of all patience. If the reservoir at Bradfield had been constructed in the same way as this one was being made at Agden, he was not surprised at what had occurred. It would not be so bad if the water company would admit they had made a single mistake. They assumed that everything had been perfect.
The examination continued. - Mr. Gunson said Mr. Leather came over, and saw some of that work in progress where the specifications were departed from.
The Coroner. - Then he ought to be ashamed of himself.
A Juryman. - Mr. Coroner, take it more deliberately.
The Coroner. - It is difficult to do so when there is the broad fact that the work has destroyed nearly 300 of our fellow citizens. (To Mr. Smith) Have you any witnesses?
Mr. Smith. - I will say, if the jury are not satisfied, the company will be at the expense of calling the most eminent engineers in the world. The company court inquiry into the disaster. As to the evidence of Mr. Jackson, he had shown that the points questioned in the construction of the work were matters of doubt.
The Coroner. - If you cannot point out a reason for the embankment breaking, we have a right to assume that it has failed from bad management.
Mr. Smith. - I don't think that. One conjecture was that it arose from a natural failure of the ground.
The foreman, addressing the Coroner, said he had made a statement that morning which must have relieved Mr. Leather's mind, which was that the jury believed he had not been guilty of criminal neglect. Perhaps he would now ask Mr. Leather if he had formed any additional conjecture as to the cause of the disaster.
Mr. Leather. - I have heard the evidence this morning as to those pipes, and I think it possible such a thing may have happened as the drawing of the joints. At the same time, I think if such a thing took place the resultmust have shown itself long before, at the foot of the bank or in the valve-house. The theory seems very doubtful, but the gentleman spoke so confidently that it may be entitled to some credit. I still think that the accident has been caused by a slip of the land outside the bank. It may have taken place and been covered with the ruins of the embankment.
A juryman asked if there were any witnesses who had seen the crack before Mr. Gunson.
The Coroner. - It was seen about three hours before by a person who was here yesterday, but it was not thought necessary to call him.
Mr. Gunson said that, now the suggestion had been made as to a landslip, it was right to state he had been told there was a house opposite the reservoir, and which, though above the road considerably, showed some symptoms of giving way.
Mr. Leather recalled. - I did not disapprove the contract taken by the company for the construction of the work. Seven tenders were sent in; two were below my estimate; that of Mr. Craven, which was taken, was £900 more than my estimate. He is carrying out the work under the same contract, and has received a large sum of extras.
Mr. B. Smith said the original contract was £27,469. About £1,000 was added on the change of situation of the embankment. The extras are upwards of £6,000., and they are going on still. Mr. Leather certifies for the extras on the reports of Mr. Gunson, occasionally coming over to look at the work himself.
Mr. R. Rawlinson, Government engineer, was sworn and said. - I have had experience in the construction of waterworks. I have executed waterworks at Wigan, Berwick-on-Tweed, Swansea, and other places. As inspector, I have made myself acquainted with the great works erected during the last 20 years, and have personally inspected many of them, including those at Liverpool, designed and executed by Mr. Hawksley, and those at Manchester, designed and executed by Mr. Bateman. I have inspected carefully the Bradfield reservoir, which has failed, and other reservoirs of the company, and the reservoir at Agden now being constructed. I have also carefully looked over the specifications. As a practical engineer, I think no waterworks embankment ought to have pipes laid through it so as to prevent repair or renewal where necessary. The engineer should be master of his work, not let it be master of him. I know of many instances of failure where pipes and culverts have been laid through the main embankment. Cast-iron pipes having plain socket joints, although previously tested to four times the head of water they may have to carry, are occasionally found fractured and defective when the water is turned on, although in the street trenches in which they are laid they have only 4ft. of earth to bear. With the most careful jointing, the joints are sometimes found to be blown or defective. Pipes laid in the streets can be repaired without much damage. A defective pipe in this embankment may have worked the destruction we have witnessed, and no human ingenuity could prevent it under the circumstances in which those pipes exist. I did not say that it did so; I wish that to be clearly understood. That, therefore, is not a legitimate way in which to lay pipes for the making of a reservoir. In my own practice, I have formed a tunnel or culvert through the solid stratification on one side of the valley and perfectly free from the loose earth of the embankment. That culvert is executed in the very best possible manner with hydraulic lime, and puddled to make it perfectly watertight over the top. Within that culvert or tunnel the outlet pipes are ultimately laid. Provision is made for closing the pipes inside the reservoir. The centre portion of the tunnel - namely, that under the heaviest portion of the embankment - is closed by brickwork set in cement, so as to make a perfectly watertight plug at that point. Valves are placed at the outer end of the pipes in the usual way, to work the pipes. On the inner shaft arrangements are made to draw the water at various heights in the reservoir, or to exclude it from the shaft, so as to enable the pipes to be examined. Such an arrangement renders any accident to the pipe for mischief absolutely impossible. Where I have laid cast iron pipes through puddle under small heads of water, as pipes leading to a valley syphon, I have found it necessary, in order to prevent the water creeping along the outer surface of the pipe, to put on collar shields, as described by Mr. Jackson. I have done this because I found I could not make puddle adhere to the cast iron pipe so as to be watertight, even under only 5ft of pressure. Unless those precautions are taken the water does creep along the surface of the pipe. In land draining, where ordinary drainpipes are laid in a clay subsoil, the best drainers make no provision for an open substratum. They know that water will find its way to the pipes, and I believe the pipes drain as much by their outer subsoil as by the inner capacity. I believe there is an outer creep along every pipe.
The result of that experience teaches me that a smooth line of cast iron pipes, with joints such as described by Mr. Gunson, are not to be trusted as certain to be watertight in such an embankment, although lined the whole length with puddle. I heard Mr. Gunson's evidence as to the mode in which he had laid the pipes through the embankment. I expected to learn that the crossing of the puddle trench had been provided for, so as to give a bearing to the pipes uniform with that of the solid ground on either side. I was surprised to learn that in place of this an artificial trench had been excavated, at a flat slope from the bottom of the puddle trench, until at the surface line it exceeded 200ft. in length; that this had been filled with puddle to the depth of 20ft., in the puddle trench, thinning itself to 18" of puddle on the solid at either end, leaving upwards of 200ft. of pipes, in 9ft. lengths, with no bottom support other than the puddle beneath them. This would be in that portion of the embankment where there would be the greatest possible weight - namely, under the apex. I have had considerable experience on railway work. I have seen 60ft. embankments - and this was 90ft. - carried apparently over solid ground; I have executed bridges and culverts on such ground beneath those embankments. Serious fractures always, total destruction occasionally, resulted. I have known it settle so much as to move the grass surface 300ft away on either side. That occurring in a naturally compressible stratum, I should dread placing jointed pipes in an artificially formed compressible substratum. If that line of pipes has been depressed into the puddle, in all human probability it had not gone down equally in the puddle trench and under the loose embankment. But if it can be proved it has gone down equally as a bow would bend, and not drawn a joint, in my opinion it has left a cavity in the puddle trench above it, because the puddle is an artificially and carefully formed material, made so solid that if the puddle is as perfect as I believe, it could not follow the compression of the pipe equally on either side of the puddle wall. We have been told that the bank was formed on the same plan as the Agden reservoir in course of construction; the material not being watertight on each side. The inference is that the water as it rose would penetrate the bank, and search out its weakest point.
The reason the embankment did not show signs of failure on the first admission of the 40ft of water would arise from the fact that the lower half, being upwards of 200ft. wide, may have been sufficiently tight to prevent any access of water to the puddle wall. As the water rose foot by foot in the reservoir it narrowed the intervening space between the water and the puddle wall two and a half feet.; and from my inspection of that bank, and from its state as it exists now, to be seen by anyone, it is obvious that the upper half of the bank is not made of watertight material, but contains a very large proportion of rubble stone. I measured some not on the surface more that 4ft. long, 2ft. wide, and 9" thick. The water would thus penetrate to the puddle wall, gradually creep vertically down the face of the puddle wall, and inevitably find out the weakest point. On the opposite side of the puddle wall there is the same defective arrangement of rubble stone, dangerously close to the puddle wall. That this was so through the deepest part of the bank is evidenced by the description of the ultimate breaking down of the top of the bank.
The first top water has been described as coming over in sheets and waves of foam. That water did not flow down the slope of the embankment, but was absorbed vertically into it. We have been told this reservoir embankment was made exactly as the Agden embankment. The mode of tipping the wagons and the material tipped I have no hesitation in coming to the conclusion that the substance of that bank is as porous as a sieve. The specification limits the tips to 3ft. each in thickness; the tips at present in work are at least double that height. This method of working rolls the largest stones continually to the foot of the tips, and makes, in fact, a rubble embankment open and porous inlayers. With regard to the mode of obtaining material to make the embankment, I hold it is most objectionable to take the material for making your embankment from within the reservoir and below the watermark, excepting a trial shaft has shown that that material is in its whole substance watertight. In the Bradfield reservoir several acres of surface have been bared by excavation. Many square yards of fissured rock have been bared. Into that rock I found by examination that surface water readily flows without pressure. With pressure the flow of water into them would be greater. No engineer can tell what is to become of that water. It may waste itself harmlessly below, but there is a possibility of its communicating with fissures beneath the external slope of the embankment. In such a case the engineer has no right to run the risk of letting water into the substrata, because the water will be beyond his control, and it will be impossible for him to tell what will become of it, except by experience. I do not undertake to say that water has done any injury. I have no evidence; neither can anybody say it has not done injury. I have examined the by-water, and do not think it adequate to convey away the flood water. I would have made a very much larger by-wash. In this case the by-wash has not been the cause of any injury, as the water never rose to it. I do not approve of a sloping by-wash such as the whole of the Sheffield Waterworks possess. I think it is always better to break your by-wash channel by a series of steps. I think for such a capacity of water and such a drainage area the two 18" pipes totally inadequate to give safety to the bank in the case of anticipated danger. To take away the incoming water of a flood from the reservoir the by-wash and pipes ought always to be equal to safely removing the greatest possible flood on a full reservoir. I have no wish to make statements away from this special question, but shall be glad to answer questions.
By the Jury. - I would not have put pipes in the embankment. Wherever put, the pipes should have been longer. It is a fatal objection to the scheme that there have not been valves to shut the water off from the pipes. The pipes and by-wash would not carry away a flood coming when the reservoir was full. There ought to be a goit to carry away the flood water when the dam was full. I am surprised that the engineers destroyed the one they used while the embankment was being made.
By the Coroner. - Several causes may have led to the catastrophe, - a fractured pipe, a blown or drawn joint, a creep along the pipes, a pressing down of the pipes in the puddle trench by the heavy material on both sides of it; or a washing away of the outer slope, as suggested by Mr. Leather; by a landslip, caused by undiscovered fissures and springs in communication with the interior of the reservoir, which fissures and springs, if they existed and had such communication, would become active for mischief as the water rose in the reservoir. Those are the methods which occur to my mind as agents which may have caused the destruction of the bank - one of them, or more of them combined, may have done it. My opinion is that it was the most fatal mistake to lay the pipes in the centre of the embankment upon an artificially formed com - the embankment the stones which are being dipped into the 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
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.' continued »
