1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



Several houses by the side of the open part of the River Fleet at Kentish 

 Town, have drains from their privies emptying into the sewers ; these drains 

 were nearly filled with privy soil, which exuded and presented a most filthy 

 spectacle along the side of the open sewer. A wooden flushing gate was 

 constructed to pen up the water which rose gradually to such height as to 

 completely fill the drains. The gate being very large, was made to open 

 suddenly, by the simple principle on which the drag chain of a wagon is 

 loosened. When the head was up the gate was opened, and the water rushed 

 away. The effect upon the drains was, that the sudden withdrawal of the 

 water brought out with it, the soil with which they were nearly filled, and 

 left them in as clean a state as they were when first built. It also drew away 

 all the soil and filth from the open sewer, as far as the head of water ex- 

 tended. Since the flushing gates have been fixed, particular notice has been 

 taken what the effect is upon neighbouring districts, through which the 

 waters of these divisions pass before they reach the Thames. The depth of 

 the deposit was measured at every hundred feet length before using the gate ; 

 in one instance the length measured was 2440 feet before reaching the main 

 outlet to the river. The gate was then shut, and a head 2 ft. 6 in. in height 

 obtained, containing about 208 hogsheads of water; this head was let off, and 

 then the whole length of sewer was again examined, when it was found that 

 the deposit had been washed away in the whole length. In another instance 

 the head of water was 3 ft. in height ; and this was found to wash deposit away 

 for the whole length of 3250 feet, that being the length from the gate to the 

 main outlet. The total length of continuous sewer that a head of water at 

 one flushing gate would serve to keep free from accumulations, has not yet 

 been ascertained, the greatest length by experiment being 3250 feet, as just 

 stated ; but from the velocity of the current when it reached the extreme 

 end, and the depth of water the head furnished at that point, the surveyor 

 has not the slightest doubt but that more than a mile in length of continuous 

 sewer might be kept clear by the use of one flushing gate. 



But the washing away below the gate is not the only benefit derived from 

 heading up water by flushing gates, for the effect which took place, in the 

 manner named in the private drains at Kentish Town, is also beneficially 

 felt at the heads of sewers, and in other situations. The drains from the 

 houses in Eagle Street. Red Lion Square, enter the sewer near the bottom, 

 so that this sewer has required cleansing as often as twice in five years, the 

 depth of deposit being one foot and upwards ; this sewer is nearly on a dead 

 level for 300 feet. There is a flushing gate placed so as to head up water in 

 this sewer to a height of one foot eight inches, so that when there was 11 

 inches of deposit, there was nine inches of water standing over the soil. 

 The head of water was let off, and it was found that an average of 3i inches 

 in depth of deposit had been drawn away with the water from 300 feet of 

 sewer by this one head. 



The accumulation of deposit in this sewer is prevented by this process, 

 which occupies a man rather less than one day in the year. The East Long 

 Alley, and part of the Moor's Alley sewer, have bottoms of the most irre- 

 gular description ; the cleansing the deposit from these formerly cost on an 

 average 16?. per annum : the accumulations are now kept down by a flushing 

 gate of three feet in height, penning up the common run of water; to work 

 which, occupies a man rather less than three days in the year. 



The open sewer at the back of Glo'ster Street, Hoxton, was formerly so 

 offensive in the summer season, that one of the inhabitants, frum that cause 

 only, petitioned for leave to arch over, at his own expense, the portion op- 

 posite his premises, which was accordingly done. But since you have placed 

 a flushing gate in the covered sewer wdiich empties into this open sewer, the 

 use of that gate has not only kept down the accumulations in the covered 

 sewer, but has had the effect of keeping the open sewer in question clear for 

 its length of several hundred feet, thus preventing the dangerous nuisance 

 which formerly existed. The saving in this instance is greater than that 

 named as effected in the East Long Alley sewer. 



In regard to the effects of flushing the deposit into the river Thames, the 

 surveyor has made observations, and taken measurements, which enable him 

 to arrive at the conclusion, that rather more than 14-15ths of the soil and 

 impurities that entered the sewers in the Holborn and Finsbury divisions, 

 was washed to the Thames by occasional rains, and the common run of water 

 in the sewers. 



That much road drift is swept through the gully grates into the sewers is 

 certain. In Bedford Place, which has been lately flushed, the depth of de- 

 posit was nearly four feet ; and amongst this was found a layer of road drift 

 in one part, nine inches in thickness. 



In concluding this portion of the report, it may be in general ob- 

 served, that if there be running through a sewer, a sufficient body of water 

 with sufficient velocity to prevent deposits, that, of course, is the best ar- 

 rangement. But such an arrangement can only be obtained in main lines of 

 sewers, unless a considerable expense be incurred in the purchase of water ; 

 and this expense would far exceed the expense of cleansing by flushing. 

 But where there is not a run of water of sufficient body to keep the sewers 

 clear, there is, and must be, a deposit. 



A convincing proof of this appears in the sewer, in a part of Holborn, 

 which is in the Westminster district, and which is connected with the Essex 

 Street sewer, which has been lowered from its outfall at the Thames into 

 Holborn, and thence along Museum Street, Bloomsbury, to the boundary of 

 that district ; to which point it was completed in 1839. Yet with the ad- 

 vantage of a connexion with a sewer luwered from the Thames, and at a point 

 very little more than a mile from the river, this part of the llolburn sewer has 

 a considerable accumulation of deposit in it. 



The New River Company expressed their willingness to supply water at 

 certain seasons at a moderate expense to your Commission, where it might 

 be needed for flushing ; but at present, the common run of water, by being 

 penned up at intervals, has been found sufficient for the purpose. The use of 

 flushing gates, supplies the want of a sufficient fall in the sewers, and also 

 the want of a continuous and sufficient flow of water at a much less expense 

 than the cost of the prevalent filthy method of clearing the sewers from ac- 

 cumulations of deposit. 



Where there is not a sufficient fall and flow of water, then by damming up 

 the common run of water and letting it off suddenly, an artificial fill uf the 

 water is obtained, which answers the purpose. The ordinary fall at which it 

 is required that sewers shall be put in at, is about 51 feet for the half mile; 

 there are, however, cases where such a fall cannot begot: it is found at 

 Eton, for example, that a fall cannot be got of more than two feet in half a 

 mile, and m parts of Hamburgh not even of half that height. Under such 

 circumstances, unless there be a large body of water, with an adequate flow , 

 there must be a deposit. It is in such cases that the flushing apparatus, 

 collecting the common run of water supplies a remedy. If a continuous 

 line of sewer were formed on a dead level, and if the water be raised by a 

 dam 51 feet, then when the water is discharged, it has the effect of sweeping 

 away silt, or of keeping half a mile of continuous sewer clear from deposit, 

 producing the same effect as a fall of 5J feet in the half mile with a contin- 

 uous flow of water. 



When the surveyor first suggested the present method of application to 

 the principle of flushing, he asked your permission to take out a patent for 

 it ; but your opinion being that it should be left open for the use of any who 

 might wish to adopt it. he did not proceed therein ; as from its promising to 

 prove a saving of considerable amount to the public at large, you as a public 

 body did not wish a monopoly to be made of it ; and in accordance with this 

 spirit other Commissions of sewers were invited to inspect it. 



Many persons, interested in sewage, have looked at the flushing apparatus 

 used in these divisions, and the surveyor being desirous of the best possible 

 plan, has always expressed his wish that any one would suggest anything 

 that might answer the purpose better, but as yet he has not been favoured 

 with any suggestion on the subject. Much approbation was expressed by- 

 many, and one surveyor of sewers considered it clever ; Mr. Lindley, w ho is 

 employed to lay out the new sewage for Hamburgh, expressed his high satis- 

 faction with the plan, and at the clean state in which the sewers are kept by 

 its use; and considered the curved junctions as an excellent engineering 

 work : and the form of your gullies and shoots the one that should be gene- 

 rally used. Captain Vetch, who has been employed to lay out a plan of 

 sewage for Leeds, suggests Rushing for general use, and expresses his inten- 

 tion of using all the improvements you have adopted, in every place where 

 he has any influence. 



It is interesting to find that the principle of flushing has been in constant 

 practice for 400 years at Eton College, during which long period the sewers 

 have been kept free from accumulations of deposit by its use. > Sluice boards 

 are used to keep up a head of water ; these are drawn up with a windlass, 

 but the form of (lushing gates used by you is about to be adopted at Eton. 



In a communicatim, from a gentleman, the surveyor sent to France to 

 examine the sewers there, it is stated that there are In Paris about 80 miles 

 in length of covered sewers, the whole of which are constantly 

 flushed by the use of wooden dams, employing upwards ol 80 | 

 flushings with wooden dams, do not, however, clear the bottoms of the sewers 

 from a heavy black deposit which is thereftre scraped together, and got by 

 hand to the main line of sewer, where a sufficient head ol m 

 to wash it away. Now, if the method of flushing used in the Hi Iborn and 

 Finsbury divisions was adopted in Paris, six nun would be sufficient to 

 manage the whole of the gates; and from the very superior effect obtained 

 by the method you use, the whole of the deposit in every sewer would be 

 washed away without the labour at present used. 



The Surrey and Kent Commission have, I am informed, used side en 

 to some of their sew ers for years ; these were c rered ' > a sione, but since, 

 Mr. lanson, one of the surveyors to that Commission, has sew the 

 grating used in your divisions,' he has introduced -.bun lot the use of tlnir 

 side entrances, and, 1 believe, one or both of the other surveyors to that 

 Commission have done the same. 



' The same principle, upon a large scale, has also been in use for many 

 years for scouring harbours and removing bars, as may be seen at Dover, 

 Ramseate, See. — ho,' 



