The Main Drainage of Working

Papers.] MAUGHAN ON THE NAIN DRAINAGE OF WOHING. 295

(Paper No. 3276.)

" The Main Drainage of Woking." By NICHOLASMAUQHAN. THEparish of Woking, in Surrey, is situated within 26 miles of the metropolis, and is divided into five wards, having a total area of 8,889 acres. These areknown as theWoking Station and Maybury Ward, of 753 acres; the Woking Village and Mayford Ward, of nearly 2,099 acres ; the St. Johns and Goldsworth Ward, of 1,338 acres; the Enaphill and Brookwood Ward, of 1,583 acres; andthe Sutton and Bridley Ward, of 3,116 acres. Whenthe scheme of main drainage described in the following Paper was definitely decided upon by the Urban DistrictCouncil, in 1897, the total population of the parish was 13,825, including 2,750 inmates of the Inkerman Barracks, Brookwood Asylum, and other publio institutions. The scheme includes the drainage of the whole of the parish, with the exception of the Sutton and Bridley Ward, which then hada population of only 1,100, of a rural character. In March, 1897, an inquiry was held by the Local Government Board into the applicationof the Urban DistrictCouncil, for sanc- tion to borrow the necessary funds for the construction of the work. Theengineers appointed todesign andcarry out the whole of the system were Messrs. John Taylor, Sons, and Santo Crimp, and they succeeded in perfecting a scheme by which about 80 percent. of the whole of the sewage is discharged at the outfall-works, by gravitation,at a level sufficiently high to irrigate the whole of the sewage-farm. It was found necessary to pump the remaining 20 per cent. of the sewage, and for this purpose the low-lying areas were divided into four separate districts, namely, Woking Village, Mayford, Maybury and Horsell Moor, each furnished with automatic pumps, driven by power generated at a central pumping-station situated at the outfall-works. The auto- maticpumps are driven by hydraulic power at apressure of 200 lbs. persquare inch, and arrangements have been made, whichwill be more fully described later,whereby the water, after it has done itswork, can be discharged intolarge cast-

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. 296 YAUGHAN ON THE YAIN DRAINAGE OF WOKING. [Selected irontanks and usedfor road-wateringand flushing purposes. The site selected for the outfall-works is situated in the valley of the Wey, near Woking Park Farm, and is naturally drained by several small streams and ditches, which ultimately discharge intothe River Wey. Thetop soil is of a light sandynature and extends toa depth varying between 3 feet and 4 feet, beneath which is a bed of gravel about 6 feet in depth; the total area of land acquiredfor the purposes of sewage-disposal is nearly 43 acres. The first contract,which was let by public tenderto Mr. H. Weldon, of Birmingham, comprised the construction of about 30 miles of sewers, with man-holes, lamp-holes and flushing-tanks, the buildings and tanks at the outfall-works, and also the buildings and sumps for the various pumping-stations for lifting the low-level sewage. The second contractwas let, also by.public tender, to Messrs. S. H. Johnson and Co., Stratford, London, for engines and boilers at the outfall-works and also for the sludge- pressingplant and centrifugal pumps for liftingthe low-level sewage from Woking Village. The third and final contract was let to the Hydraulic EngineeringCompany, Chester, for the automatic hydraulic pumps at the various pumping-stations and the steam-power pumps and accumulator at the central power-station. Work was commenced on the first contract inAugust, 1807, the main high-level intercepting-sewer being one of the first portions of the workto be dealtwith. This sewer is nearly 6 miles in length, and from theoutfall-works traverses the entire parish, finallyterminating at Brookwood. It is circularin section throughout,varying in diameter between 2 feet atthe outfall and 8 inches at the termination, and is constructed of concrete tubes,iron pipes with both lead andturned-and-bored joints, and stoneware pipes with Portland-cement joints, or, in the case of water-logged ground, with Hassalldouble-lined or Sutton flush joints. The collecting or branch sewers vary in diameter between 8 inches and 15 inches, and are constructed, as is the main sewer, of both iron and stoneware pipes, according to the nature of the ground and the depth at which they are laid. By far the greater part of the work had to be carried out inwaterlogged ground, and, the soil throughout the district being generally fine sand of the Bagshot series, great care had to be exercised in the construction of the sewers to ensure a sound foundation beingobtained. Tunnelling wasresorted to whenever possible, where the pipes had to be laid at a greater depth than 14 feet, and some miles of sewers were laid by this means; the greatest depth was attained in the case of the sewer taken through the Maybury Hill, which

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. papers.] MAUGHAN ON THE XAIN DRAINAGE OF WOKING. 297 for a short distance is at a depth of over 40 feet between ground- leveland invert-level. In a few cases, wherewater wasfound within a few inches of ground-level, it was considered advisable to carry up lateral drains, for the purposes of house-connections, from the main sewer to the boundary of the properties on either side of the road, duringthe construction of the sewer. These branch drains were all laid with pipes having patent joints and bedded on concrete, and, as the subsoil water was necessarily kept down for the construction of the main sewer, they could be laid in a practically dry trench, which would have been impossible at any other time. Storage-sewers, constructed of iron pipes,were laid for some distance from the pump-wells in the low-lying areas, in order to provide accommodation for the sewage, andthus avoid the necessity for running the pumps at night; and the branch sewers in these districts gravitating to the storage-sewer were kept at a sufficiently high level to prevent them becoming surcharged. The gradients of all sewers throughout thescheme were kept sufficiently sharp to ensure a minimum velocity in the sewers of 2 feet per second, and in setting out the works the following gradientswere strictly observed by the Author as being the flattest permissible. For 15-inchpipes, 1 in 800; for 12-inch pipes, 1 in 600 ; for 9-inch pipes, 1 in 350; and for8-inch pipes, 1 in 300. These gradients give a velocity in the sewer of approximately 2 feet per second, when running half full, andwere chosen as being numbers easily committed to memory. The main outfall gravitation-sewer is laid at a gradient of 1 in 1,000 where it is 2 feet in diameter, the gradient increasing as the diameter of the sewer decreases. At this gradientit is capable of discharging 2,900 gallons per minute, which is equivalent to upwards of 4,000,000 gallons in 24 hours. The man-holes were constructed of 9-inch brickwork, except in the case of those built in very bad ground, or at a considerable depth, when the thickness of the brickwork was increaEed to 14 inches. In order to guard against leakage through the brickwork, a l-inch space was left in the 14-inch walls, and was filled in with Portland-cement grout. The lamp-holes were constructed of 8-inch stoneware pipes surrounded with a block of cement concrete 2 feet 6 inches square. Both the man-hole and lamp-hole covers were provided with re- movable plates screwed to the under side, and could thus be kept sealed or used as fresh-air inlets ; galvanized iron dirt-pans were includedwith cvery cover, but were only necessary whenthe plates were removed. Flusl~ing tanks, havinga capacity of over

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. 298 MAU~HANON THE MAIN DRAINAGE OF WOEING. [Selected 600 gallons, were constructed at nearly all the high points of the system, orwhere the sewer had a dead end.” Theyare fitted withField automatic siphons which empty the tank in about 2 minutes. Disk-valves are also provided at several points along the main interceptingsewer, and furnish a means of flushing each section by allowing the sewage to head up, when it can be sud- denly released with a head of 3 feet or 4 feet ; overflows from the man-hole into the sewer below the disk-valve prevent anyaccident arising in the eventof a valve having been closed and forgotten. The automatic pumping-stations vary in size according to the quantity of sewage to be lifted. The largest station is that situated in Woking Village, which not only lifts the sewage from the district immediately surrounding it, but also receives the sewage from the Mayford pumping-station. Therising-main from the pumps at Woking Village discharges into a 12-inch sewer gravitating to the outfall-works and terminating in a 30-inch cast-iron storage-sewer, 440 feet in length. From this the sewage is lifted by centrifugal pumps into the settling-tanks. The pump-well at Woking Village is 11 feet 9 inches in diameter ; that atMaybury is 10 feet in diameter ; and those at Horsell Moor and Mayford are 8 feet 4inches in diameter. Thedepths vary according tothe level of the sewer discharging into the well, the average depth being 16 feet to 20 feet. All four wells are constructed of brickwork on a concrete foundation, are circular in plan, and are built of 18-inch walls up to the level of the main girders carrying the pump-barrels. Thesegirders, three in number,were built in as the work proceeded, special stone templates being inserted in the walls to distribute the weight. The thickness of the walls above this level is 14 inches, and a stone coping is fixed above the brickwork at a level with the 0oor of the pumping-station. At May- bury and at Horsell Moor thewalls of thesuperstructure are 1 foot 6 inches in thickness, in order to carry a cast-iron tank which forms the roof; the Woking Village and Mayford stations have 14-inch walls and are covered with a tiled roof on wooden rafters. Each building is 19 feet lO& inches by 15 feet 73 inches in interior dimensions, Fig. 1. At each station the pumps are in duplicate and entirely automatic, being actuated by means of counterbalanced floats, which start and stop the pumps according to the level of the sewage in the well, and are so arranged that the pumps do not start until the maximum quantity of sewage is in the well, and correspond- ingly do notstop until the sewage has beenreduced to its minimum level. The pumps are single-acting, the plungers being

forced downwards by means of a fixod operating-ram, within whichslides an operating cylinder. This ram is alternately placed in communication with the pressure-water and with the exhaust, by means of a slide-valve worked by hydraulic pressure.

Scale, + inch = 1 foot. SECTIOXOF PUMPIXQ-STATIOS. The upward stroke is accomplished by means of two side rams constantly open to the pressure. The suction- and delivery-valves are simpleflaps with indiarubber faces falling on gun-metal seats, and are not likely to get out of order or to be impeded in their

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. 300 MAUGHAN ON THE NAIN DRAINAGE OF WOKING. [Selected work by foreign matter in the sewage.Air-vessels are fixed on each delivery-pipe, and are supplied with an air-cock on the top. The Woking Village pumps have plungers 2 feet in diameter and 3 feet stroke, andl work at the rate of S$ strokes per minute; the ramsfor these pumps are 64- inches in diameter. The Maybury pumps have plungers 1 foot 4 inches in diameter and 3 feet stroke, and make 9fr strokesper minute;the rams are 52 inches in diameter. The Mayfordand Horsell Moor pumpshave plungers 1 foot in diameterand 3 feetstroke, and work at the rate of 85 strokesper minute. The rams at Mayford are43 inches in diameter and those at Horsell Moor 44 inches in diameter. The average lift is 16 feet, and the quantityof pressure-water required to raise 1,000 gallons of water through a height of 1 foot is about 8 gallons. At Woking Village and Mayford the exhaust water is discharged intothe pump-cylinder,where it mixes withthe sewage, but at Maybury and Horsell Moor it is discharged into the overheadcast-iron tanks already mentioned, from which it canbe drawn off asrequired for street-watering or flushing purposes. Abranch-pipe direct from the pressure-main is also furnished, so thatthe tanks can be rapidly filledshould the necessity at any timearise. Each tank is provided with an overflow, either directly into the pump-well or to a surface-water drain outside the building, and also with an outlet which passes downwards through the interior of the building, a valve being fixed at this point, and thence by a %inch pipe to a standpost in the street.Considerable saving is thus effected in theexpense of street-watering andflushing, as for either purpose it would otherwise be necessary to purchase water at the rate of IS. per 1,000 gallons. The machineryprovided for the purpose of generatingthe necessary pressure for these hydraulic pumps consists of a pair of horizontal compound steam-engines, drivinghydraulic pumps directlyin line behind the cylinders. Each of thesepumps delivers 94 gallons of water per minute against an accumulator pressure of 200 lbs. persquare inch. The engineswork at a boiler-pressure of 140 lbs. per square inch, and run at 90 revo- lutions per minute. The high-pressure cylinders are 6 inches in diameter, and the low-pressure cylinders lO& inches in diameter. The stroke in both cases is 1 foot. The force-pumps have 3-inch plungers and 45-inch pistons. The accumulator-ram is 11 inches in diameter, and the stroke is 10 feet. Steam is automatically admitted to the engines by means of an equilibrium-valve, to which is attached a wire rope passing over

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. Papers.] MAUGHAN ON THE MAIN DRAINAGE OF WOKING. 301 pulleys bolted tothe roof an3 endingin a weight suspended directly over the accumulator. When the accumulator is at, the bottom of its stroke, the weight keeps open the equilibrium-valve, and the engines at once start, and continuerunning until the accumulator is sufficiently high to engage the weight above it. when the valve closes. A relief-valve is provided at the foot of the accumulator, arranged to open, by means of a tappet-gear, when the accumulator is within G inches of the top of its stroke. This would only come into use in the rare eventof the automatic steam-valve failing to close.

F9.g. 2. I 0. &!Q

-___----_____ m-;-;;-. __-- --____ -s~-~~~~~~~~-~~~~~~~~~-~~----~~~~~~::~~~~~~ SCLIESN CHAMBER Scale, 1 inch = 50 feet. PLANOF SETTLING-TANKS. The water for supplying the hydraulic mains is obtained from a well outside the building, from which it is pumped by means of a two-throw pump,' to be described later, intoan overhead cast-iron tank, Pig. 3. The suction-pipes forthe hydraulicpumps are coupled directlyto the pipe leading from thispump to thetank. A considerable length of unjointed pipes have been laid from the well, through the gravelsubsoil, to act asa collecting-drain. The high-level outfall-sewer enters the farm at the north-west corner, and, passing under the buildings, discharges into a hexagonal chamber, into which thesewage from the low-level outfall is pumped, Fig. 2. The low-level sewerenters at the south-west corner, and discharges into a screening-tank near the buildings. After passing through a I-inch screen, the sewage from this sewer

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. 302 MAUGHAN ON THE MAIN DRAINAGE OF WOHING. [Selected flows into the pump-well in the engine-room, from which it is pumped into a brick tank outside the building, emptying into the hexagonal chamber. Three18-inch penstocks andontlets are built into this chamber, and deliver into three settling-tanks, the penstocks controlling the entry of the sewage into either tank as required. Each of these tanks measures 100 feet by 30 feet, the averagedepth being 5 feet. Thetotal tank capacity is nearly 300,000 gallons, which amply provides for 50 per cent. of the daily flow of 20,000 people. The floors of the tanks are constructed with a fall of 2 feet, towards the end at which the sewage enters, the sludge outlets being at thedeepest part. A length of two-thirds of the shallow endof each tank is covered in with galvanizedcorrugated-iron plates, supported on 7 inches by 33 inches wrought-ironjoists, and in these plates are drilled l-inch holes, at a distance of about 4 inches apart. The plates are fixed at a level of about 9 inches below the weir or overflow, and are covered with G inches of coarse gravel. At the end of this gravel- bed an iron joiet runs right across each tank, and is bolted to the girder carrying the galvanized plates. The top of this joist is at a higher level than theoverflow to theeffluent-channel. The sewage, on entering the tank, is thus obliged to pass upwards t,hrough the gravel filter, and thence to the overflow. The effect of this may be noticed in the analysis of the effluent given in theAppendix. The solid matter that falls to the bottom of the tank is partly liquefied, and the rest is retained until the tank is c!eaned out, when it passes into the sludge-culvert. At the present time, with a population of about 8,000 contributing to the works, and with only one tank in operation ata time, it. is found necessary to clean out this tank at the endof 10 days, but as house-connections are being made daily it will no doubt soon be more advantageous to use two tanks atonce, keeping the third in reserve. The sludge- outlets are covered with $-inch gratings, and deliver intoa sludge- chamber running along the endof the tanks, and then turning at rightangles and terminating in awell, constructed underthe buildings. The floors of the tanks are of concrete, and the walls of brickwork, 2 feet 3 inches in thickness. The effluent-weir at the end of the tanks is constructed of blue Staffordshire bricks, and is 2 feet 3 inches in width. The effluent-channel discharges into the maincarrier down thecentre of the farm. Fromthis channel there are three outlets, one opposite the centre of each tank, and each consisting of a6-inch pipepassing down andunder the channel and into the tank itself,where it branches into two 4-inch pipes carried along the top end of the tank, each being drilled

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. Papers.] MAUC~HANON THE MAIN DI~AINAGE OF WOKING. 303 with small holes at close intervals.By this means the effluent from one tank can be utilized for assisting to clean down the floor of either of the other tanks. Each of these wash-out pipes is con- trolledby adisk-valve fixed inthe effluent-channel. Another outlet is provided for each tank for the purpose of drawing off as much of the liquid from the sludge as possible before it leaves the tank. A narrow channel is built in the floor of each tank, falling slightly from the centre towards the shallow end, whence a pipe passes through the tank wall into a circular brick valve- chamber. Thethree inlet-pipes to this chamber, one from each tank, are each furnished with a valve, and an outlet-pipe andvalve communicate with the low-level sewer. The buildings are divided into four rooms as shown in Fig. 3. The first room, which is the engine- and boiler-room, contains two Robeylocomotive-type boilers, each having a single-cylinder, 15-HP. engineunderneath. The engines drive a S-inch shaft, which runs the whole length of the building, and in turn drivesa counter-shaftin the press-room. In the engine-room aretwo Bon accord”centrifugal pumps,each capable of raising 500 gallons of sewage per minute, the lift being about 15 feet. They are fixed on girders directly over the pump-well, into which the low-levelsewage is discharged. Thepumps are independent of each other, and, being provided with fast and loose pulleys, are driven by belts from the main shaft. In this room also is fixed a two-throw plunger-pump, which lifts the waterfrom the well outside the building and pumps it into a cast-iron tank ip the tank- room. This pump is capable of delivering 8,000 gallons of water per hour at a height not exceeding 28 feet. In the second room are fixed the engines and accumulator for the hydraulic pumps; the exhaust steam, both from these engines and from the Robey ” engines, can either be discharged through the roof into the atmosphere, or by branch pipes into a “ Blake ” condenser inthe boiler-room. This is a jet-condenser andair- pump, having a steam-cylinder 5& inches in diameter, the air-pump cylinder being 8 inches in diameter, and both having a stroke of 7 inches. Thethird or tank-room containsthe cast-iron tank already mentioned, and is also used as a lime store. The tank is carried on four girders built into the walls and strengthened bya cross-girder carried on two cast-iron columns. The capacity of the tank is 5,400 gallons. Thefourth or press-room contains the whole of the plant necessary for compressing the sludge intocake. This comprises two filter-presses, two sludge-receivers, from which the sludge is forced into the presses by compressed air, the air-

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. from the sludge-well anddischarging it intowrought-iron a mixing- tank. This chain-pump is 4 inches in diameter, and is supported

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. Papers.] MAUGHAN ox THE MAIN DRAINAGE OF TVOKING. 305 over the sludge-well on two wrought-iron joists. It is worked by means of a belt from the coanter-shaft, which also drives all the necessary machinery inthis room. Thesludge is discharged, about 10 feet above the floor-level, into a cast-iron shoot delivering into the mixing-tank. It is here mixed with milk of lime, added perfectly fresh. Revolvingstirring-rods are meanwhile kept constantly working. The sludge then gravitates into thereceivers, whichare below the floor-level. Each of these has an internal dip-pipe reaching to within 3 inches of the bottom, and, upon compressed air being admitted, thesludge is forced up these pipes into the presses. Both the presses and receiverscan be worked eithersimultaneously or separately. The receivers are 4 feet G inches in diameter and 9 feet in depth, and are constructed of mild steelplates, inch thick. The presses are supported on four cast-iron columnscarrying a frameworkof girders to which they are securely bolted. Each press consists of twenty-four plates, 3 feet square,capable of producing cakes l&inch in thickness. Side drainage-outlets are provided, discharging into cast-iron troughs, from which a4-inch cast-iron pipe conducts tothe high-level outfall. The cake from the presses is emptied into a wrought-iron tip-truck,running on rails,and the truck canbe rundirectly undereither press. The air-compressor hastwo water-jacketed cylinders, and is drivenby a belt from the counter-shaft. The compressed air is stored inan air-receiver, 3 feet 3 inches in diameter and 10 feet in height, constructed of $-inch steel plates. The air can be drawnoff as required. The land which has been acquired for the purpose of purifying

the sewageconsists of two fields known as the 'l upper" anti " lower "fields. At the present time the upperfield only has been laidout for sewage-disposal. This field hasan area of about 24 acres, 4 acres of which areoccupied by the tanks and buildings, and also by the cottages for the men in charge of the works. The remaining 20 acres have been laid out in level beds of G acres to 7 acres each, there being a fall of 3 inches between one bed ancl thenext, Fig. 4. A roadwayhas been constructed throughthe centre of the field, and the main carrier runsclose beside it ontthe south side. Cast-iron pipes are laid under the road at intervals of about 100 feet, in order to convey the sewage from the carrier to the land on the north side of the road. A drain has been laid for a distance of GO0 feet under the road at a depth of about 6 feet, and discharges the effluent into the rirer. A valvecontrols the rateat which the subsoil water is discharged intothe river through thig drain. A few branch-drainshave also been con- [THE INST. C.E. VOL. CXLIV.] S

Downloaded by [ University of Sussex] on [19/09/16]. Copyright © ICE Publishing, all rights reserved. 306 MAUGHAN ON THE MAIN DRAINAQE OF WOKING. [Selected nected to this main-drain, which are carried under the land at intervals of about 200 feet. At the present time about8,000 people are connected with the works, the quantity of sewage per head being well under 30 gallons per 24 hours. This is greatly due to the small amount of leakage in the sewers, which is considerably less than 1 gallon per head per 24 hours, and this rate will, of course, decrease as the population increases. The farm is, there fore, now dealing with the sewage of about 400 persons per acre, and the effluent obtained is remarkably good. The works were formally opened in July, 1899, the whole of the gravitationsystem being thencompleted, and manyconnections having been made. Since then house-connections have been steadily Fig. 4.

Scale, 1 inch = 800 feet.' PLANOF SEWAQE FA^. going on and have also been commenced on the sewers in thelow- level districts. The pumps have proved satisfactory in every way and require the minimum of attention. During the progress of the construction of the works several new streets were laid out, necessitating considerable additions to the sewers. This has, of course, added to the total cost of the scheme, which amounts' to 591,000. The cost of landhas amounted to over 510,000, and compensation and easements have been very heavy. The Author acted as Resident Engineer during the construction of the works, which are now completed and will amply provide forithe needs of the Parish of Woking for many years to come.

The Paper is accompanied by drawings, from which the Figures in the texthave been prepared.

APPENDIX.

ANALYSISOF SAHPLE8 OF~sEWAOEAND EFFLUENTTAKEN AT WOElNO ON 5 OCTOBER,1900.

crude Sewage Sewage flowing taken at over Weir Efaueut Iigh-Level from horn Farm. Outfall, Tanks, 10.46 a.m. 11.45 a.m. ?rains per 3rains per Grains per Gallon. Gallon. Gallon. Nitrogen as free ammonia ...... 3.920 5.110 0-1931 Nitrogen as albuminoidammonia ... 0.198 0.0705 0.0224 Oxygen absorbed in 4 hours ..... 1 a099 2.191 0.3780 Chlorine ...... 7-22 7-90 7.95

Nitrites ...... Nil Nil 0 * 1008 Nitrates ...... Nil Nil 2.0585 Total solid reaidue on clearwater ... 35.0 59.5 66.3 Suspended matter- Organic matter ...... 22.9 7.84 TraW.3 Mineralmatter ...... 3.4 0.56 ..

Total ...... 26.3 8.40 ..