THE ADJOURNED INQUEST.
WEDNESDAY, MARCH 23, 1864.
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, Esq.) conducted the inquiry. Among the professional and other gentlemen present were--Robert Rawlinson, Esq., C.E., and Nathaniel Beardmore, Esq., C.E., from the Home Office; M. Mille, member of the Legion of Honour, and engineer of bridges and roads to the French government, Robert W. Mylne C.E., F.R.S., of London; Wm. Lindley, Esq., C.E. (London), engineer of the Hamburg Sewage and Water Works; Colonel Ford, of York; Mr. Perronet Thompson, barrister, instructed by Messrs. A. Smith and Sons, solicitors to the Water Company; William Smith, Esq., chairman of the Water Company; the Mayor (Thomas Jessop, Esq.,) and the Town Clerk were present during a considerable part of the day; and Mr. Broadbent appeared for the friends of several of the deceased.
The CORONER in opening the proceedings, said the jury were met to inquire how Thomas Elston and others came to their deaths on the 12th inst. They would very likely hear very little about these people in the course of the proceedings. He proposed only to direct their attention to the death of Elston. Separate inquisitions could afterwards be made with regard to the other deceased without any particular inquiry. Having read the evidence taken on the previous occasion, the Coroner added that the course he proposed to take was to examine the engineer of the Company first, in order to get as far as possible a history of the embankment. If Mr. Leather could not give all the information deemed necessary, he (the Coroner) would examine Mr. Gunson, the resident engineer, Mr. Craven, the contractor, and such other witnesses as might be necessary. If their evidence was not satisfactory, he would call Mr. Rawlinson, the Government inspector, and one or two other witnesses who had been engaged in examining the reservoir, and who would give their opinions upon the cause of the disaster. That would be the most direct way of getting at what they wished.
The following evidence was then taken:--
EVIDENCE OF MR. J. T. LEATHER.
Mr. JOHN TOWLERTON LEATHER, Leventhorpe, near Leeds, civil engineer, said:-- I am the consulting engineer of the Sheffield Water Works Company. I was consulted by the company when they applied to Parliament for powers to make this Bradfield reservoir. I prepared the plans and specifications for the construction of the reservoir. That would be in the year 1858. Parliamentary plans and sections were deposited in 1852 for this and two other reservoirs, which we call the Bradfield scheme. I examined the country generally before depositing the plans, to see if water could be obtained. The contract for the Bradfield reservoir was let, I think, in 1858. Originally, the embankment was set out lower down the valley than where it is executed. That first embankment was never commenced, because it was found, on trial holes being sunk, that there had been a disturbance of the strata. I then altered my plans for the embankment to be where it now is. I examined the ground before we commenced making the embankment. The geological formation is just at the out crop of the coal measures, and the commencement of the mill stone grit. The strata consists of first--soil, then clay, then stone, then shale, with a gannister formation and a little coal in the centre of the valley. I had to deal with soil, clay, stone, and shale in the embankment. The only spring I ever saw in the valley was one in the site of the reservoir a little above the embankment. The first thing in forming an embankment is to sink the puddle trench in the centre of the base. The original plan provides for a puddle bank about ten feet below the surface. In sinking a trench we did not find a good foundation at that depth. It was not sufficiently water tight. It was therefore necessary to sink until we did get to a water--tight foundation. We sank to a depth varying from ten to sixty feet, and got a water tight foundation. A good deal of water came into the puddle trench during the working. We got rid of it by pumping. I do not remember what engine power the contractor had to pump the water. I came to see the trench, I think twice; but I cannot remember exactly. I came when I was wanted. I walked over the bottom of the trench when it was finished, and know it was water tight. I am not aware that in wet weather the quantity of water in the trench was so great that they could not pump it out. I saw the puddle trench in 1861, and in 1863 I saw the puddle wall. I did not see the puddling of the trench in its progress--at all events, not at the lowest point I did not see the whole of the puddle, but what I did see was well put in, and good work. The water was not cut off altogether from the trench. The trench simply divided the water courses. The water came into the trench so long as it was open. The bottom of the trench was impervious, but the sides were pervious. The water was not got rid of, but blocked out by the puddle) as is usual. When, therefore, the puddle wall got to a certain height, there would be water against it on the upper side. The water that would get through the rock to the puddle wall would not have a tendency to injure it, for it is made with water. The object of a puddle wall is to keep out water, and therefore water is always against it in a reservoir. The water rises against the puddle wall, but does not percolate through it. The water was not let off by any natural means; if it had the puddle wall would not be perfect. As the puddle wall was being constructed, the water rose with it, and was carried away. The embankment across the valley is 418 yards long.
Mr. RAWLINSON here interposed in explanation. The effect of the explanation was that as the puddle trench was filled with puddle the fissures from which water had issued into it were closed, so that the water, while resting against so much of the puddle as covered the surface of the fissures could not penetrate the puddle, which was waterproof.
Examination of MR. LEATHER resumed: The embankment is 500 feet wide at the base, and 12 feet at the top. The inner slope is 2½ inches to 1 foot, and the outer slope the same. The greatest height is 95 feet. The puddle is 4 feet wide at the top, and gets wider by an inch and a half at every foot in depth. Thus, supposing the puddle wall is 95 feet high, it will be 16 feet wide at the base. There is 60 feet of puddle below the surface, making the total depth of the puddle wall 155 feet. The reservoir would contain a little over 114,000,000 cubic feet of water. The surface area of water was about 78 acres. The area of the gathering ground is about 43,000 acres. We got the material for making the embankment from the inside of the reservoir, and in doing so bared the rocks. In places, we got a good deal of stone. The embankment is made of stone, clay, shale, and earth. I cannot say how the material was put in Mr. Gunson was not my servant. He was the resident engineer. He had the superintendence of the works, occasionally consulting with me. He could not deviate from my plans. There are two 18 inch pipes from the inside to the outside of the reservoir underneath the embankment. The pipes are about 500 feet long, made of lengths of 9 feet. There would be 55 or 56 lengths. They are joined with sockets and lead in the ordinary way. They are laid in a trench 9 feet below the surface of the ground. They are wrapped round with clay puddle to the thickness of, I think, 18 inches, the trench being then filled in. The pipes are laid obliquely, not diagonally, across the embankment in a straight line. The valves are at the lower end of the pipe, outside the embankment. If one of the pipes were to burst in the centre, it would be difficult to get to it to repair it. It would have to be reached by excavations. An instance of that kind occurred in the great dam at Crookes. The pipes were originally of wood. I removed them by excavating, and substituted iron pipes. That would be thirty years ago. The breaking of one of those pipes would most likely cause serious damage to the embankment. The embankment might possibly fall before we could find out the damage; I can't tell what might happen. I never knew an instance of that. The pipes were made double the usual strength. I should think there could not be an unequal pressure upon the pipes from the embankment. Being laid in the solid ground the weight above could do them no harm, unless it was a crushing pressure. There would not be an unequal pressure upon the pipes so as to raise them at any of the joints, or cause them to leak. We can insure a sufficient equality of material along the whole length of the pipes for all practical purposes. The Water Company have other dams constructed on the same principle as this, which have been in operation for a great number of years. Possibly water from the sources blocked up in filling the puddle trench might get into the pipe trench. If it did it would show itself. If water got in below the puddle trench it might be dangerous; if above, it would not. It would show itself by percolating out at the lower end. Water mains in streets do not often give way under external pressure; I never knew one even break or yield at the joint from external pressure.
Mr. RAWLINSON: Is it not a common thing for a new line of mains to have blemished joints, and leak? ....... Mr. Leather: The pipes of the company are severely tested before they are put down ......... Mr. Rawlinson: I saw the testing apparatus, but nevertheless the question is a proper one. My experience is that they do give way.
Mr. LEATHER: My experience is the contrary; they scarcely ever do give way.
Examination of Mr. Leather by the Coroner resumed: I never heard of a pipe giving way because of water creeping along the pipe trench. I do not know that there was such a case at Birmingham. It would not have been better to have made a culvert for the pipes. Laying them in a trench is better, because in my judgement it is a more simple operation and more secure. In case of an accident a culvert would give readier access for repair, but with much greater liability to accident. I can hardly tell the pressure of water on the valve when the reservoir is full; I am not prepared with those calculations.
Mr. RAWLINSON, after a calculation, said the pressure of water on each valve would be from four to five tons, when the reservoir was full.
Mr. LEATHER examination resumed: When the water flowed freely through the pipes they are not likely to sustain much injury. The opening of the valve would not have a tendency to wrench the joints of the pipes. The pressure lessens as the valve is opened.
The CORONER: One of those valves took half an hour in opening on the night of the inundation, and there was a shaking and straining of the pipe during the opening not felt before or after. That is the reason I ask the question. What I mean is, would there not be a greater pressure upon the valve when the water was in motion ?...... Mr. Leather: No. There would be a greater disturbance in the way of noise in opening the valve, but the pressure would diminish as the valve opened. The pipes would run off 10,000 cubic feet of water per minute. Every inch that the water lowered would diminish the pressure of the water upon the embankment. At this rate, 190 hours, or about nine days, would be required to let off the whole of the water, supposing there was no addition.. Don't you think it necessary to have had some more complete control over the water ? --I have not thought so hitherto. One cannot tell how such a thing as this may change one's views. There might be great damage in letting off the water too rapidly in order to relieve the embankment. ...... Not so much as in letting the whole off at once ? ---That depends on circumstances. There might not be so much. I did all that I thought necessary to provide against danger. I know of no means of providing against danger except the pipes and bye wash. There is a drain all round the Redmires dam, but that is for another purpose altogether.
The CORONER: Ought you not, as a practical engineer, to minimise the danger as much as possible in making these large reservoirs. There has been no attempt to minimise the danger here....... Mr. Leather: Oh yes, there has....... The Coroner: No there has not; and there is no use in having an engineer unless he does that. You have had the management of these dams. You have placed a great embankment there, and collected an immense body of water behind it. But even though there was a suspicion that the embankment might give way, you have provided no means of taking the water in any other direction, so as to avoid its coming down in one body upon the people of Sheffield. I ask you is it not desirable in such cases that some means should be taken of lessening the danger ? ...... Mr. Leather: I cannot conceive any other way than that adopted ...... The Coroner: Did you never think of any other way ? ..... Mr. Leather: No..... The Coroner: Cannot you conceive any mode of obviating the danger? ....... Mr. Leather: No other mode than that adopted ....... The Coroner: There was not the slightest arrangement made for doing away with the danger; that is what I complain of. Why, it would have taken eight days to have run off the water in the dam through outlet pipes if there had been no influx. The influx of water was so enormous that it would have taken three weeks to run off the water by the pipes........ Mr. Leather: I know of no means that could have been adopted to relieve such a difficulty......... The Coroner: I saw a large cutting near; could not that be made available, Mr Leather ? -- No: a cutting should be at the bottom of the embankment of a reservoir to relieve it under such circumstances, and I know of no means of having such a cutting ........ The Coroner: I am only sorry I am not an engineer: I would do it or give it up. Let me ask you further: Could you not have drawn away any water that reached the puddle without the puddle being injured--drawn away from the outside I mean ? ...... Mr. Leather: Yes........ Has anything of that sort been done ?----I do not know that is has ....... It was no part of your plan to drain the puddle trench ?--No, except during the working ......... I mean afterwards.--No; I did not suppose any water would get there afterwards ....... I am supposing it has. Could not the puddle trench be so drained as to prevent water getting there ? ..... No; any water that might get there would naturally percolate through the embankment on the lower side........ It would get away without doing any injury-Yes ........... I am told that water was seen coming from the bottom of the embankment sometimes, that might be the reason ?--It might be; that would be the natural result if any water did get into the embankment ....... Would there not be a greater weight upon the escape pipes in the centre of the embankment than at the edges of it ?--The pressure would be greater ...... The embankment was 90 feet high in the centre. If this weight pressed the pipes down at the centre through the puddle, would it not necessarily disjoint the pipes ? --No.
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