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very soon force this on the common sense of the Corporation, and induce them to divert as much as possible of the surface water. I did not ask them to make duplicate drainage or separate sewers. However, I have been eleven years in enforcing that much on the Corporation, and at last had to resort to litigation to drive them to do it. I have just succeeded in getting what I originally proposed—that they should divert the surplus surface water into the brook, which, I think, is a perfectly good plan. This is not a manageable quantity to deal with on the sewage farm. As a consequence of arbitration I have compelled the Corporation to provide me with beautiful new depositing tanks of my own planning, which I shall be very pleased to show to any gentleman; and to show you the plan of taking the solids out of the sewage, which is an advantage on all irrigation farms, because in very few cases is it desirable to put sewage on mixed with sludge. I only mention this to show how long it takes to get practical ideas carried out. It was arrived at simply because of the foulness of the overflow, which Mr. Vawser thinks of no consequence after a shower has washed the streets clean; but if you take a small town, with a small stream made foul by the sewage-polluted storm-water of a large district getting into it, it becomes a great nuisance.
Mr. JERRAM : This is a most important matter, this question of separate sewerage, and what we want is to get at the results of our practical experience. Having a district of some 26,000 population, growing at the rate of 600 houses a year, it may be some advantage to give the results of the separate drainage system at Walthamstow, London. There is no doubt about it that, in laying out a system of drainage, very much must depend upon the physical circumstances of the district. If you have a district with a brook running through it which used to take the rainfall naturally from the surface of the ground, it must be self-evident that it must necessarily be much the cheapest way to have small surface drains to take the rain-water off the streets (and from that portion of the district more immediately under the control of the local board) as direct as possible into the brook, the natural drainage outfall. But where the river is far off—if the town is on the side of a hill and the river some little distance away, and you have to increase the size of your sewers considerably towards the outfall, it will then become a matter of calculation which will be the cheapestto have two sewers, one for sewerage, and another for surfacewater drainage, or one large sewer taking both rain-water and sewage. But where a brook runs through a district, there can be no question the cheapest method is to run your water drainage from the roads as direct, and in the smallest pipes possible, to the brook. This is the position we are in at Walthamstow. We have been carrying out the separate system in its entirety. We have not been content to take merely the drainage of the streets, but we have insisted there shall be two drains to each house, and I find enormous difficulties in carrying this out. When plans are sent in, in nine cases out of ten the drainage is shown wrong, and the sewage water is shown running into the surface-water drains. Although drains are inspected, and no drain is allowed to be covered up until it has been inspected by myself or my assistant, yet the result has been, after three years' experience, that I find all our inspection is in vain. Of course the surface-water drain is the shallower-only a foot or two from the surface — whilst the soil sewer is much deeper; and it is very natural, when the houses are out of our control, that when any man is sent to attend to the drains, he scratches the ground, finds the rain-water drain, and connects the sewerage drainage with it. What is the result? All the thousands of pounds we have spent in cleansing our brooks will be of no effect, as in a few years they will be almost as foul as they were before we started draining the district. Therefore I have come to the conclusion that it is very unwise indeed to attempt to separate the surface water entirely from the sewage, but only as far as you can have it under your entire controlfrom the fronts of the houses and the streets. This, I think, is the best possible plan to adopt; and that the rainfall from the back yard and stack-pipes should run into the soil sewers, and that there should only be one drain to each house. That is the conclusion I have come to after three years' experience, and I have frequently had great difficulty in finding where wrong connections have been made. The result then is, that I should say have only one drain and sewer, and no separate system, except under your own control. There is one matter that has not been gone thoroughly into, and that is the size of sewers for surface and sewage drainage. We all know how small the flow from real sewage is; a very small pipe indeed would take the sewage from houses, but for the storm-water we must have sewers large enough to take the most extensive storms, and in that way we get very large sewers. I think we are making a mistake, where we have a duplicate system, in making our soil sewers too large. They only become reservoirs for sewage gas, and I think a question which we should discuss at some future time should be the size of sewers where the duplicate system is adopted. This is my experience, and I think it would be an advantage if others who have tried the separate system would also give their experience. It is only a few years ago that the idea was started, but now we have actual results; let us know them, and then we shall get correct data to
Mr. J. LEMON : I was somewhat surprised to hear that this is a new system. So far as I know, the separate system has been discussed ever since the time when probably the oldest persons present in this room were boys. The General Board of Health first recommended the separate system, and Mr. Edwin Chadwick, the great sanitary reformer, was one of its strongest advocates. You know the old saying about the rainfall to the river, and the sewage to the land ; but even Mr. Chadwick, who was certainly as sanguine in his proposals as anybody I ever knew, did not go to the extent of an entirely separate system of drainage. Mr. Chadwick said : “I am in favour of admitting the roof-water from houses, and the water from paved surfaces, such as streets, mews, courts, alleys, and paved squares.” So even he was not in favour of the system in its entirety. I will go further, and say that there is no town in England where the separate system is carried out in its entirety, so far as I know, and I will go even further, and say that if it was carried out next week it would not last a month. I am an advocate of the separate system, and doing everything I can to enforce it, but I should be sorry to see the principle laid down that the separate system is applicable to all towns under all conditions. I think this is the mistake engineers make. We
an instance of this in the remarks made by Mr. Gordon. He saw a discussion on the subject, and was misled by it in the report which he made to the authorities of Munich. I say the separate system is a system only applicable under certain conditions, which will depend upon the particular circumstances of each case. I classed them at one time, and stated where I thought the separate system applicable. I put them under these heads : (1) “Towns where it is necessary to pump the sewage to the land for purification or utilisation,” and (2) “where it is necessary to pump sewage for treatment by precipitation or intermittent filtration.” I would also say, when sewers are dead-locked in low-lying districts, it is necessary to keep out as much surface-water as practicable; but I
am not prepared to go further. I agree with Mr. Pritchard that there are towns where the separate system would be unadvisable. Some of the towns in the Midlands, for example, where the dry system is in operation, and large and densely populated towns. In these cases it is clear you had better only have one system of
Then, as regards its practical application, I think it is a great stretch of authority on the part of any governing body to compel an owner of property, after he has been called upon to drain his house into the sewer, to put in another surface drain, I think that is a most extraordinary stretch of authority, and if they did compel this to be done, no practical good would result from it. Take the case of an ordinary house-I will not refer to back yards and paved areas, because Mr. Parry says he does not include those—but take any ordinary house with back gardens. Take the house as 20 feet wide and 30 feet deep, and you have got 50 feet of depth to deal with, the remainder goes into the ground, sinks into the land. Supposing you go a little further and take in the back yards, what is the result ? Take my own house as an illustration; we have paved yards, as most such houses have, attached to the kitchen. In this paved yard we have got a yard gully, which is attached to the drain. Now, supposing that was connected with the rainfall sewer, according to Mr. Barry's system, what is there to prevent the servants throwing kitchen slops or anything else down this drain ? Of course they would do it; I believe they would do it in most cases. Then the cost of gullies for the separate system would simply result in failure. There are many houses in the metropolis and large towns with slop sinks common to many houses. I say in this case it is quite impossible to carry out the separate system, because the slops would constantly be thrown down so as to reach the rainfall drainage. It is important, however, where the sewage has to be purified, to do everything that can possibly be done to keep out the rainfall
. agree with Mr. Jerram that this should be restricted, as much as possible, to the area under the jurisdiction of the local authority, because that is the only district over which you can exercise efficient control. I have taken a great deal of trouble in this matter at the city of Winchester, where there are exceptional facilities for getting rid of the rainfall. We did there what is recommended by Mr. Jones. The rainfall went away long before the town existed, and I left it untouched, and it goes away into the nearest water
I simply laid down a separate system of sewers and took
away the sewage only; and the Corporation passed very elaborate bye-laws to prevent rainfall drainage being connected with the
What is the result? I find, where there is a shower of rain, that the quantity at the pumping station is enormously increased. Where does it come from? Not from the gullies in the streets, because there is not a single gully connected with the sewers. It comes from the back yards, where owners connect their stack-pipes and their drainage in the yard with the sewers. If the system recommended by Mr. Parry is carried out, it will be found, in less than ten years, that a great deal of the system of double drains will be carrying not merely surface water, but polluted water also.
Mr. PRITCHARD: The paper read by Mr. Parry is one of considerable interest, inasmuch as it has evolved lengthy discussion, and I am sure we must all feel obliged to Mr. Parry for having afforded this opportunity of considering the separate system. This subject has cropped up at both our district and annual meetings, whenever the disposal of sewage has been discussed. It has been thoroughly ventilated, but not too much ventilated, because this is a matter which requires grave consideration. I have not altered the opinion I expressed some years ago, and since then I have had many opportunities of putting my theories to the test of actual practice in the construction of works in different parts of the country. I agree with Colonel Jones, and endorse what was said by Mr. Jerram, that a great deal must depend upon the local circumstances connected with a town. It has been said, that although formerly in favour of the separate system, I am not
I am still in favour of the separate system, but it must be justified by the local circumstances--where the surface water may be fairly and readily turned into the natural streams. To say that I am not in favour of the separate system would be inconsistent, because in many towns I have constructed works turning the rainfall to the streams and natural watercourses. But there are considerable difficulties in the
way in some cases; for example, in such large towns as Birmingham, Leeds, or Manchester. To carry out the separate system there, would require, as I have before maintained, a triplicate system of drainage. The surface water from the streets in the towns I have named would be quite unfit to pass into the watercourses, which would have to be purified before it could be turned into the natural streams. In other instances the rain-water passes through street gullies, and in