The Main Drainage of London." by JOHNEDWARD WORTH and WILLIAMSANTO CRIMP, MM
Total Page:16
File Type:pdf, Size:1020Kb
Proceedings.] WORTH AND CRIMP ON NAIN DRAINAGE OF LONDON. 49 23 February, 1897. JOHN WOLFE BARRY, C.B., F.R.S., President, in the Chair. (Paper No. 3029.) The Main Drainage of London." By JOHNEDWARD WORTH and WILLIAMSANTO CRIMP, MM. Inst. C.E. THEmain drainage of London was last broughtbefore the Institu- tion in a Paper by the late SirJ. W. Bazalgette, Past-President, in March, 1865,' and its past history maybe briefly referred to here. Prior to 1847 the sewers of London had been managed by eight distinct public bodies ; but in that year these were superseded by the Commission of Sewers, the members of which were nominated by the Government. Withinnine years of itsformation the Commission was reconstituted no fewer than six times, lastly in 1855 ; and during the period referred to, the question of main drainagewas discussed in all its phases, butwithout practical result. In thedrainage system in operation in 1854, themain sewers followed generally the valley lines, and discharged their contents into the Thamesat various points within themetropolitan area, at aboutmean-tide level. As thetide rose it closed the outletsand dammed back the sewage flowing from the higher ground,which accumulated inthe low-lyingportions of the sewers and remained stagnant for several hours daily. The fact that a gigantic system was subsequently carried out at a cost of several millions sterling, affords conclusive proof of the necessity which existed for dealing with the sewage upon comprehensive lines, and it is unnecessary to describe the state of the Thames withinthe metropolitan area further than to saythat it was notoriously bad. In 1556 a Metropolitan Board of Works was constituted, and formed thefirst authority elected underthe system of Local Government;and by and for the purposes of theAct which brought that body into existence, London was divided into thirty- Minutes of Proceedings Inst. C.E., vol. xxiv. p. 280. [TRE INST. C.E. VOL. CXXIX.] E Downloaded by [ UNIVERSITY OF BATH] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 50 WORTH AND CRIMP ON MAIN DRAINAGE OF LONDON. [Minutes Gf ninedistricts. Sir J. W. Bazalgettewas appointed Engineer to the Board, andwas instructed to prepare plans for theinter- ception from the Thames of the sewage of the metropolis. The objects soughtto be attained by the proposed workswere the interception of the sewage, as far as practicable, by gravitation, together with so much of the rainfall as could be reasonably dealt with,and its conveyance to points some distance below the metropolitan area. In designing the works, Sir J. W. Bazalgette, who was assisted by Messrs. Bidder and Thomas Hawksley, Past- Presidents, observed theprinciples of a constant flow inthe sewers, the abolition of tide-locking with its well-known disad- vantages, and the provision of improvedoutfalls, to enable the main-drainage system to deal with the sewage of districts pre- viously imperfectly drained. The system of sewers as designed and executed comprised, Plate 3, on the north side of the Thames, three large interceptingsewers, two of which, known as the high- level and themiddle-level, are gravitation sewersfrom their com- mencement, in the western and the north-western parts of the metropolitan area, to the outfall works at Barking; and a low- level sewer, which deals with the drainage area which is at too low a level to allow gravitation into the two intercepting sewers referred to. These sewers may be briefly described as- (A) Thehigh-level sewer, commencing withthe junction of the Fleet sewer at the foot of Hampstead Hill and proceeding to Old Ford. (B) The middle-level sewer, constructed generally in the lowest portion of the gravitation-area commencing at Harrow Road and joining the high-level sewer at Old Ford. (C) The low-level sewer, which follows generallythe north bank of the river. There is animportant exception tothe general rule in the route of the low-level sewer, by reason of the configuration of the Thames; for, instead of following its tortuous course, the sewer passes in aneasterly direction from BlackfriarsBridge to the Abbey Nills Pumping-Station,the large area lying between it and the riverbelow the point referred to, being drained by a sub- sidiary sewer, known as the Isle of Dogs branch. At the point of junction of the high-level and middle-level sewers at Old Ford, there is a large storm-overflow chamber for the purpose of relieving the outfa11 sewersbeyond from exces- sive volumes of storm-water into the River Lea ; because the two sewers continuing onwards from Old Ford to the outfall works at Downloaded by [ UNIVERSITY OF BATH] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proccdings.] NORTH AND CRIMP ON MAIN DNAINAUE OF LONDON. 51 Barkingare of muchsmaller carrying-capacitythan the two sewers referred to. The two outfallsewers from Old Ford onwards are constructed side by side at thesame level, and are each 9 feet by 9 feet, constructed throughout in an embankmentconsiderably above the level of the ground, and pass through the site of the Abbey Nills pumping-station. At the latter place, the low-level intercepting sewer terminates;and the sewage is pumped into a third sewer of similar dimensions, the three sewers being then carried sideby side to the Barking outfall works. In order to obviate the necessity of constructing this low-levelsewer at a greatdepth, and of raisingall the sewage to a greatheight at Abbey Mills in one lift, a second pumping-station, known as the Western, was built at Grosvenor Road, Pimlico, for dealing withthe districts westward of that place. On arrivalat the outfall at Barking, the sewage could be discharged either into the river direct, or intoa tidal reservoir, of a capacity of 35 million gallons and covering an area of 9&acres, in order to admit of the sewage being discharged during ebbtide. Western Pumping-Station.-The western pumping-stationoccupies about 4 acres of land, and contains four single-actingbeam-engines, each of 90 HP., all placed in a rectangular building, witha pump- well occupying theentire basement dividedinto two compart- ments, one under each pair of engines. These compartments com- municate with each other, but means are provided for separating them for cleansing or other purposes, andthere is a separate inlet into each from the main sewer so that each pair of engines can work independently.There are also movable screens in order to interceptany solid substances which might interfere with the action of the pumps. These screens are in duplicate and are lifted out for cleansing-purposes when necessary. The engines are condensing rotative beam-engines, constructed by Messrs. James Watt and Company ; there are two pumps to each engine, one on either sideof the beam centre ; the steam-cylinders are 3 feet 1 inch in diameter, with a stroke of 8 feet ; the pumps have a diameter of 5 feet 3fr inches, with a stroke of 4 feet, and areof the single-acting plunger type. Steam is supplied by eight boilers, 6 feet 9 inches in diameter and 22 feet long, working at a pressure of 40 lbs. persquare inch. There are coal-vaults andother accessories necessary for the proper working of thestation. There is also acold-water reservoir for condensing purposes situatedin the grounds, capable of containing half-a-million gallons of water. In order to provide for the contingency of a breakdown of the principal engines, an auxiliary engine was erected in a separate E2 Downloaded by [ UNIVERSITY OF BATH] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 52 WORTH AND CRIMPON MAIN DRAINACtE OF LONDON. [Minutes of building at the rearof the principal buildings. It is a horizontal engine of 120 HP., supplied with steam from two boilers of the same dimensions as those in the main boiler-house. It works two pumps, each 4 feet in diameter, placed in LL separate well, and is provided with separate inlet- and outlet-channels distinct from those of the mainpumping-station. Buildings areprovided for the accommodation of the staff, which consists of eighteen men. The works were commenced in July, 1873, and the station was opened on the 5th of August, 1875. The cost was 5183,739, of which sum $56,879 was for enginesand pumping-machinery. Atthis station the lift is 18 feet, and about 54 milliongallons can be pumpedper day of twenty-four hours. The sewage atthis pumping-station is discharged into the head of the main low-level intercepting sewer, flowing in an easterly direction, asalready described, to Abbey Mills. Abbey Mills Pumping-Station.-The Abbey Millsstation is situated upon a site of 7 acres of ground, through which the northern out- fall sewer passes at a height of about 17 feet above the surface of theground. On the south-west side of theembankment stand the boiler- and engine-houses, chimney-shafts, coal stores and other accessories, whilst on the north-west side are the reservoirs for water forcondensing purposes andeight workmen’s cottages. The engine- andboiler-houses form one building, the engine-house being cruciform in plan. There are eight beam-engines, each of 142 HP., arranged in pairs, each arm of the structure containing one pair, parallel to one another. All the steam-cylinders are at theinner end of eacharm, SO thatthe cylinders are arranged symmetrically round tho centre of the building under the dome. The engines provided were condensing rotary beam-engines with cylinders 4 feet 6 inches in diameter and9 feet stroke ; the pumps being of the double-acting piston type, each engine working two of a diameter of 3 feet 104 inches, with a stroke of 4 feet 6 inches. The capacity of this station as designed was equal to 135 million gallons per day, and the lift was 36 feet.