The Works for the Supply of Water to the City of Birmingham from Mid-Wales.” by ERNESTLAWSON MANSERGH and WALTERLEAHY MANSERCH, MM

Proceedings.] ELECTIONS. 3

dssociute ~~e.reslbe?.s-continued. IVORLLEWELLYN GRIFFITHS. GEQRGEPLUYMER. FREDERICKCHARLES HALL. ALFREDJOHN PRICE. ANDERSON CUNNINGHAM HILL. FAWCETTPUDSEY. JAMESHERBERT HILL, B.A.I. (Dubl.). GEORCETHOMSON PURVES. PERCIVALHOLT. CHARLESFRANCIS SATOW. JAYESHENRY HYDE, Stud. Inst. C.E. HERBERTSCROFIELD, B.&. (Lond.). LEONARDBENJAMIN WILLIAM JOLLEY, GEORCE MINARD SEELS. B.A. (Cantub.). JOSEPHGEORGE SHARF. HAROLDDUNIAM JONES, Stud. Inst. JOHNWOODHEAD SMITH. C.E. WILLIAMBOULTON SNITH. ROBERTOWEN JONES. JAMESEDWIN NORMANSNITHSON, GEORCEKENWORTHY. Stud. Inst. C.E. TVILLIAM GEORGE LANDALE. JOHNANDERSON STEWART. CHARLESFERCUSSON NASH LEAHY. ROBERTALEXANDER STURGEON. \i7ALTER LEIGH. HERBERT EDTVARDTASNAK. HUCHRoss LEWIS. DAYIDSTANLET THOXAS. M‘ILLIAM LONGBOTTOM. HERBERTJOE TONKS. VERNERWHITE LIVINGSTON MACASSBY.WILLIAM HOWARD SANDBERC TRIPP. HARRYCAMDEN MACEWAN. FRANCISANNESLEY WATKIN. IANSTUART MACKAY. WILLIAX CLEMENT WEST. THOMAS MAKINS. JOHNLETHAM WHITE, B.%. (Edi7~). ALFREDDE COURCYMEADE. ARTHUXCLAUDE WILLCOCKS. ARTHURMUDD. 1 ARCHIBALDEDG.4R iirILI,IAMS, Stud.

ROBERTHUTCHISON MURRAY, Stud. ~ Inst.C.E. Inst. C.E. l FREDERICK JOHNGIIEGSON WILLIAMS. STEPHENJOHN EORTON, Stud. 1nst.C.E. WILLIAXYATES. CHARLESRECINALD PALMER. CYRILlto~ MUSTON YOUNG.

(Paper No. 3963.) ‘‘ The Works for the Supply of Water to the City of Birmingham from Mid-Wales.” By ERNESTLAWSON MANSERGH and WALTERLEAHY MANSERCH, MM. Inst. C.E. THE city of Birmingham stands on high ground which forms the water-partingline between thestreams running northward and eastward to the River Trent and westward tothe River Severn. Within the boundariesof the borough the elevation above Ordnance Datum variesbetween 300 and 600 feet.The parliamentary district of supply (Fig. 1, Plate 1) embraces an area of 83,221 acres andsomewhat greater variations of elevation thanthe borough. According to the 1891 census it had a population of 648,000, and the demand for water was then approaching 15 million gallons per day. The local sources from which thecity and the surrounding districts were supplied before the Welsh water came into use were five streams, namely, Perry Brook, Plants’ Brook, Witton Brook B2

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 4 E. L. ASII W. L. MAKSEI:CII OS su1’pLy OP V-ATEI: [Miuutcs of the River Blythe, and the River Bourne, and six wells in the New RedSandstone, at Aston,King’s Vale, Shortheath, Perry, Selly Oak, and Longbridge. A supply of about 20 million gallons per day from these sources could be counted upon, but the quality of some of the water was not beyond reproach, and all had to be pumped- in some cases three times. In 1890 the late Mr. James Mansergh, Past-President Inst. C.E., wasconsulted by theWater Committee onthe question of an additional supply to the district, and full inquiries were then made as to the possibility of adding to the yield of the local sources ; but it as found impossible to recommend the Committee to adopt the hand-to-mouth policy of developing and improving-to the small extentthat was practicable-these local resources,which at best would have served for only a very few years. The recommendationmade tothe Committee w:ts that they should secure the control of the watershed of the Rivers Elan and Claerwen in Radnorshire (Fig. l), which is at a sufficient elevation to enable the water derived from it to be delivered into a serrice- reservoir near Birmingham at such a level that it could be supplied to a very large portionof the districtby gravitation (Fig. la, Plate l), and is of sufficient area to meet the requirements of the city and district for two or three generations. This schemewas approved by the Council, and a Bill was accordingly promoted in Parliament in theSession of 1892, whereby powers were sought to construct the works which form the subject, of this Paper. GENERALDESCRIPTIOS. Dminuge-Awu.-Thedrainage-area of theRivers Elan and Claerwenabove the Caban C8ch damis 45,562 acres, or 71.19 square miles, and the level of the river-bed at that dam is 700 feet above Ordnance Datum (Fig. 2). The hills around the basin rise to considerable elevations, the highest points being 1,721 on the north, 1,747 on the east, 2,115 on the south and 1,945 on the west: the average elevation is about 1,350 feet above Ordnance Datum. Geologically considered, the whole of this area consists of rocks of theLower Silurian order, slates, grits, and conglomerates.On some of the flatter tops of the hills peat occurs in places to a considerable depth, the drainage from which causes some discoloration of the water, especially in times of heavyrainfall following long summer droughts. Thedrainage-area actually available for the supply of water is less than the above-mentioned figure on account of a right having become establishedby long user to divertwater from about 800

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.1 TO CITY OF BIRMINGHAMFRON MID-WALES. 5 acres on the west side of the drainage-area into Cardiganshire for use in the Yspytty Ystwyth mines on the River Blaen Marchnant. The drainage-area was extremely sparsely populated at the time of the passing of the Act, there being not more than 300 people

Fig. 2.

PLANOF RESERVOIRS,ETC., AT ELAXVALLEY.

livingon the whole 71 square miles, andin consequence of the submersion of the low-lying farmlands in the Elan Valley, and a considerable portion of those in the ClaerwenValley, the population has since been much diminished, There cannot be on the drainage- area at thepresent time more than thirty inhabited dwelling-honses,

containing a population of perhaps 150, or, say,2 persons to the square mile. Themajor portion of the drainage-areaconsists of rough sheep-pasture-commonableland-and, in additionto pur- chasing all freehold lands, the Corporation havesecured the manorial rights over the commons, in orderto be in a position to protect their water from pollution at its source. These commons now carry about 24,000 sheep, and no cattle are allowed, so that the freedom of the water from animal pollution is beyond doubt. Rainfall.-Fortunately it happened that the owner of the Manor House of Nantgwyllt and the largest landowner on the drainage- area-&. Robert Lewis-Lloyd-had kept a rain-gaugethere for 20 yearsbefore investigations were commenced in 1890, and the returns from this gauge,checked by observations during1891 at three other gauges set up by the late Mr. G. J. Symons,F.R.S., enabled a close approximation to the average rainfallover the whole area to be arrived at. This was put for parliamentary purposes at 69 inches per annum, giving, after making the ordinary deduction of one-fifth, about 55 inches asthe average of three consecutive dry years. For the purpose of ascertaining the quantity of water available, the net drainage-area was taken as 44,000 acres, making a partial allowance forthe water-area of the reservoirs andthe 800 acres above alluded to ; and the collectable rain was taken as 36 inches per annum, involving a deduction of 19 inches per annum for loss by floods, evaporation, and absorption. This gave an arerage daily quantity of 99 million gallons, of which it was proposed to send out 224 million gallons for compensation, leaving 76& millions for the supply of the Birmingham district and the towns andvillages within 15 miles of the aqueduct. Some considerable opposition arose on the question of the compensation-water, and the normal quantity was eventually fixed at 27 million gdlons perday, with provision for freshets being sent down periodically-a matter which will be dealt with later. It may be interesting to state that on several occasions duringthe construction of the works the dry-weather flow fell to one-sixth of this compensation quantity. As soon as the necessary powers had been obtained, five monthly rain-gauges were established and a new gauge was also put down at Nantgwyllt, in a more open situation, as it was believed that owing to a certain amount of shelter the old gauge was registering low. Thisturned out to be the case. During a period of 14years, 1892-1905, inclusive, both gauges were observed, and the new one gave, for those14 years, an averagefall which was very nearly

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OR BIRMINGHAM FROM MID-WALES. 7 3 inches more than was recorded by the old gauge. Correcting the 14 years’ average of the new gauge for the periodof 35 years, 1871- 1905, inclusive, amean fall of 64-03 inches is obtained,which happens to be about the mean for the old gauge up to 1890. The yearly average of four out of the five monthly gauges already referred to showed during the same period of 14 years a marked agreementwith the figures for the new Nantgwylltgauge, the differencebeing only about inch. The fifth monthly gauge is situated about 2 miles to the north-east of the highest summit on thewater-parting line and the corrected average for this gauge is 81 28 inchesper annum, or 26 * 94 per cent. higher than the Nantgwyllt gauge. Pig. 3.

RAINFALLAT NANTGWYLLT,1871-1910.

Fig. 3 shows the actual rainfall gauged at Nantgwyllt from 1871 to the end of 1910. The Authors are of opinion that the probable true mean rainfall over the whole drainage-area may be taken as 65 inches.Deducting one-fifth (13 inches)to obtain the mean of three consecutive dry years, leaves 52 inches ; and again deducting 15 inchesfor evaporation, absorption, and loss by floods, leaves 37 inches collectable : 37 inches on 44,000 acres equals very nearly 102 milliongallons per day;and deducting compensation-water (27 million gallons per day) there is left 75 million gallons per day for the supply of Birmingham and district. It will be seen, therefore, that the River Wye receives a little more than onequarter of the collectablewater. Seeing that,

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 8 E. L. AND W. L. MAXSERGH ON SUPPLY OF WATER [Minutes of putting asidesalmon-fishing, thereis practically no user on the whole length-the supplies to ROSS,Hereford, and, to a very small extent,Monmouth, excepted-the Authors consider this a very ampleshare. Comparing it withtwo other works of the same character, namely, Manchester and Liverpool, the figures are :-

Manchester Liverpool Birmingham

By the courtesy of the Water Committee of the Corporation of Birmingham,and of Mr. F. W. Macaulay, M. Inst. C.E., the Engineer-in-Charge of the completed scheme,the Authors areenabled to give in the Table opposite the actual rainfall on the watershed as computed from the returns, the yield of the watershed, and the loss byevaporation and absorption, for the years 1908-1911, inclusive. Theaccompanying diagram (Figs. 4) shows for each month of these 4 years the relation between the precipitation on andthe flow off the watershed, andillustrates the principles of absorption ancl deferred flow. With regard to the figures given in the Table, the quantity of water used forsupply andsent to the river as compensation is accuratelymeasured, andthe additions to or deductions from storagecan alsobe determinedvery closely. Theother factor which goes tomake up the total yield of the watershed isthe quantity overflowing at Caban CGch dam. Whenever overflow occurs, theheight of thewater above thecrest of the weiris registered continuously by two recorders, one fixed at each end of the dam. The quantities of overflow given in the Table have been carefully worked out from the diagrams of these recorders, but the accuracy of theresult obviouslydepends upon the coefficient of dischargewhich is used. Different opinions are likelyto beheld as to the proper value to be assigned to the coefficient in the case of a. weir shaped like the crest of the Caban dam, and the Authors are of opinion that the same value should not be used for very small overflows asfor big floods. Theyhave worked out, on what they believe to be common-sense linea, a curve ratio for t811ecoefficient ;bt varying depths over the weir, but they are prepared to admit that, as this curve is necessarily an empirical one, the quantities can only be regarded as approximate.

0 0 0 0 0 0 do0 0 d. 22 0 I” N m W m dWm N h

0 0 0 0 0 m 0 01 La m N 3 N 3 m 3 0

W m0 3 9-

? 0 W

......

Figs. 4.

REFERENCE It TOTAL PRECIPITATION...... L~ l+l ADDITIONS TO STORAQE.... OVERFLOW a COMPENSATION DEDUCTIONS FROM STORAQE SUPPLY......

1909 1408 I

MONTHLYDISTRIBUTION OF WATER, 1908-1911.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 12 E. L. AND W. L. mmmGH ON SUPPLYOF WATER [SIinutes of In orderto utilize fullythe resources of the watershed, the scheme as laid before Parliament comprised the construction of six reservoirs, having a total available content of 17,174 million gallons. Some slight alterations in the levels of the dams at present constructed have increased this content to 17,250million gallons, which is169 times the estimated collectable water, namely, 102 million gallons per day. Checking this by the lateMr. Thomas Hawksley's figure of 500 - 500 - 150days; dcollectablein inches 3.3322

SO that ample provision has been made for the full utilization of the available rainfall on the drainage-area. The following is a summary in tabularform of theprincipal dimensions of the six reservoirs and their dams :-

- - - ~ i Level leigh of If Dar Top Length Length ' Top Water. Capacity. River- above Level. of of Watel Bed. River Dam. Weir. ' Area O.D. Bed. O.D. -___ - _- - i l Constructed. 1 Feet. Feet, Feet. Feet. Feet. Acre, Mill. Gall. Caban CBchl . 700 122 822 610 500566 7,815 (Fig. 7, Plate 1.) Pen-y-garegl . 822 123 945 528 4179 124 1,330 (Fig. 6, Plate 1.) Craig G8ch2 . 920 120 1,040 513 390 217 2,000 (Figs. 5 and 5a, (on -- Plate 1.) chord) 11,145 -~ Contemplated.

Dol-y-myna~h~.i 799 101 900 940 .. 147 1,680 i Ciloerwynt . . l 987 108 ,095 1,053 .. 281 3,150 Pant-y-beddau . ,077 1 98 ,175 720 .. 238 1,940 ____ 6,770 L Straieht. Curved. This darn has already been brought up to the level of 830 feet above O.D., i.e., 8 feet above top water of the Caban CBch reservoir, and is capable of holding back 150 million gallolls over an area of 26 acres.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. THE RAILVAY. Owing to the insuficiency of the roads in the neighbourhood of the reservoir-works and the enormous quantities of materials that hadnecessarily to be imported to the valleys, it was considered desirable totake parliamentary powers to make a shortbranch railway from the ;Mid-Wales line near Rhayader to the Caban C6ch dam. This line joins the Mid-Wales Railway at a point 125 yards sonth of the Rhayader tunnel, and has a total length of 29 miles ; and, in the 14 years during which the works were under construction, many thousand tons of cement, ironwork, stone, etc., were carried over it to the main yard, which was situated a few hundred yards below the site of the Caban dam, and from which the upper works were supplied. THE DAMS. As the three dams to be built for the first instalment were all of considerably greater height above river-bed level than any existing in this country previously, the cross section to be adopted was obviously a matter demanding the most careful consideration. It will be remembered that in April, 1895, the Bouzey dam, near Epinard in France, gave way, with very disastrous results, and in May, 1895, the late Mr. Jnmes Mansergh thought it advisable to obtain the opinion of Dr. W, C. Unwin, President Inst. C.E., as to the theoreticalstability of the profile as then designed. Dr. Unwin’s exhaustive report contains the followingsummary of his conclusions :-

‘l I am therefore of opinion that the dam is perfectly satisfactory so far as its design is concerned, and that, if well and carefully built, it will in fact have an unusually large margin of safety.”

The following broad principles were laid down for designing the profiles of the dams :- (l) That the lines of stress, with the reservoir either overflowing or empty, should fall within the middle fourth of the length of the base throughout. (2) Thatthe verticalcomponent of the pressureon thefoun- dations should nowhere exceed 10 tons per square foot. (3) That the factor of safety against overturning (reservoir overflowing) should nowhere be less than 3. The weight of the masonry was taken for the purpose of cnlcula- tion at 160 lbs. per cubic foot. This weight was tested in practice, and was found to be 157 lbs. per cubic foot. The quantities of solid

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 14 E. L. AND W. L. BIANSE1:GH ON SUPPLY OF WATEIZ [Minutes of stone and concretein the damswere aboutequal, the stone averaging in weight 168 lbs., and the concrete 146 lbs., per cubic foot. The ordinary graphical method was used for designing the profile of thedam, and the result corresponded closely withRankine's theoretical profile. Someslight variations werenecessarily made fromthe typical section so obtained, but, taking the Caban CBch dam as an example, the following theoretical data are of interest.

Maximum Pressures on Base per Factor of Square Foot. agan1stSafety Over- Reservoir Pull. ' Reservoir Empty., turning.

At one-third of height below crest . Under 3 tons ' About 39 tons 3.72 ,, two-thirds ,, ,, ,, . 1 About 5 ., ,, G$ ), 3.34 ,, river-bed level ...... ' ,, 6 ,, ,, sg ,, 3.5-1 ,, 20 feet below river-bed . . . ,, 6 ,, 1 ,, 94 ,, j 3.73

Manyother investigations of the theoreticalfactors of safety under various assumed conditions were made, but the Authors are of opinion that any dam which is properly built willbe perfectly safe and stable provided it satisfies theoretically the three conditions laiddown for these dams: because, first, a slice 1 foot thick only is taken into consideration, and no credit is taken either for the cohesion of the materials forming the structure or for the support of the adjoining parts ; and secondly, provided the lines of stress lie wholly within the middle third (or middle fourth, as in this case), no tension can be exerted on either face. Takingthe view setforth above, it wasdecided to leave out the counterforts which were shown on the section investigated by Dr. Unwin, although the culverts and valve-shafts remained. The leading dimensions of the standard profile of the water-dam as adopted in thecase of Caban CBch (Fig. 7, Plate 1)are as follows:- Themaximum depth of the foundationswas assumed to be 142 feet below the crest, and the bottom width at this level was 122feet 6inches, of which 14feet was up-stream and 108 feet 6 inches down-stream of what was called the centre-line of the dam but was really the up-streamface of the crest. Theup-stream facewas carried up verticallyfor a height of 40 feet, where there was a set-on of varying widths, from which a facebatter of 1 in 6 startedand was continued for a height of 70 feet (i.e., to 22 feet below thecrest), above which thebatter was 1 in 20.

The down-stream face had a curved batter, struck to a radius of 340 feet, from the assumed bottom of the foundations to 15 feet below the crest, at which point the down-stream face was 20 feet 3 inches from the centre-line, giving a total thickness of 21 feet at that level.Above thispoint, for a height of 10 feet l&inch, the curve wasreversed, and was struck to a radius of 38 feet; and above thatagain it wascontinued, to 6inches below the crest, at a radius of 12 feet. The crest stones were flat on the top and 5 feet wide. At the outer toe short curves of varying radii were introduced, which were tangential to the face-curve and to the horizontal floor of the flood-water channels. Mutatis mutandis, this profile was adopted in all the dams. The dams were built of cyclopean rubble faced with rock-faced block-in-course masonry. The rubble-which consisted of " plums " ranging in weight from 1 cwt. to more than 10 tons-was set in Portland-cementconcrete gauged generally 5 to 1. Thestones in the facingranged from 18 inches to 4 feet in width on the bed, and were backed with 4-to-1 concrete for a thickness of 5 feet at theup-stream face andwith 6-to-1 concrete 3 feetthick at the down-stream face. The concrete was allhand-mixed and of thoroughly cleanmaterials, and was well rammedbetween the plumsuntil the wholewas in a state of quiver,Plums were all washed and brushed perfectly clean, and their bases were roughly dressed toensure levelbedding. Practicallythe whole of the hearting for all the dams was local grit and conglomerate obtained from two quarries, one at each end of the Caban dam, but some of the facing-stone had to be imported from quarries near Pontypridd and Builth Wells.

DRAINAGEOF FOUXDATIONS. In orderto guard against the accumulation of water at the foundations of the dams,which, if in communicationwith the reservoir, would exert an overturning force on the structure, the same method of draining the foundations was adopted as was used in the case of the Vyrnwy dam of the Liverpool Waterworks. In each dam a main drain 6 feet 6 inches by 2 feet 3 inches was constructed, the bottom of the drain following approximately the level of theinvert of the flood-waterchannel. Atany places inthe foundations to which it was thought at all likely that water might travel from outside the foundations, pipe drains were built up in the hearting of the dam and discharged into the main drain. Themain drain in eachcase had an outletdischarging down-

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 16 F. L. AEU \V. L. MAKSR1;GII ON BU1’1’1,Y OF \VATEIc [Ifinutes of stream of thedam; thus at Caban CBch and Pen-y-gareg the culvertsformed the outlet,the stop being placed in theculvert up-stream of the drain ; whilst at Craig Gach, owing to the culvert being on one side of the valley, a separate outlet was built for the drain, discharging on to the apron below the clam above the top water-level of the Pen-y-gareg reservoir.

DAMS: METHODOF COSSTRUCTION. As the damswere to beessentially masonry and not concrete structures-that is to say, it wasdesired to have as large a per- centageof! solid stone as possible-it wasnecessary during construction that the whole of the working-area should be commanded by cranes to set not o~lythe facing-stones but also the big plums in the hearting. This necessitaOed a good deal of forethought in the arrangement of the temporary wagon-roads and crane-gantries, and it may be of interest to describe briefly the methods adopted in the case of the Cabnn C6ch dam, which are typical of those employed at the other dams. The plnnt in use consisted of :- Stenm derriclc-cranes with GO-foot jibs, capable of lifting 10 tons :rt a radius of 25 feet and less loads at proportionate radii. Hand derrick-cranes with &foot jibs, capable of lifting 4 tons at 16 feet radius. Steamtravelling cranes with 40-footjibs, capable of lifting 7 tons at 25 feet radius with the jib in line with the rails, or 5 tons at the same radius when “ across carriage.” Steamtravelling cranes with %-footjibs, tolift 5 tons at 16 feet radius. The handi derrick-cranes were used almost exclusively for setting the facing-stones. The block of the dam first built on the Brecon side, as hereafter described, was commanded by a cross road about 25 feet south of the: centre-line of the culvert, and by a crane-road built on the top of the temporary timber dam which shut out the river. With the aid of a steam-derrick fixed near the centre of the block on the up- stream side of the dam, and hand-derricks for fixing the stones in the clown-stream face and culvert-outlet, this block was brought up to a generallevel of 734 feet above Ordnancedatum. A similar arrangement was adoptedfor the block on theRadnor side. For building the central portion in the old bedof the river n steam- derrick was placed on the edge of each of the blocks already built, and-a Jow-level gantry was built out across the channel from the Radnor bank to the down-stream fnce. When all the lower portion

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 1’ror:oedinga.l TO CITY OF BIRA~IEGIIB~~FROX JIID-WAL~S. 17 of the structure had been brought up to the same general level, a crane-road was laid along the whole length of the damat an elevation of about 30 feet above the finishedwork. This road was formed of timberscarried on piersabout 20 feetapart. The piers were built of concrete and plums in the samemanner as the general body of the dam, and were incorpomted into the structure as the work proceeded. A turntable at oneend communicating with a cross ~~oadonthe hillside gave access tothe longitudinal crane-

gantry. ’ When the masonryreached the level of the crane-road thetimbers wereremoved and theoperation was repeated for another lift of 30 feet. For finishing the crest of the dam an outside gantry of timber waserected along the down-streamface about 15 feet below the top, corbel-stonesbeing builtout from the face to receive the feet of the trestles.

SUEMERGEDDAM AT CAREGDDU. A novel and, the Authors ventureto think, interesting feature of the scheme is the submerged dam constructed across the Caban CBch reservoir at a placecalled Caregddu, abont Ifmile higher up the River Elan than the Caban Cach dam itself. This dam is for the purpose of holding upthe water to the required level to chnrge the upper end of the aqueduct without involving the loss of storage for compensation purposes in the Caban reservoir. It was found that, in orderto give the most economical cross section andthe bestline, thefall required in the 74 miles of aqueduct between the Elan valley and the Prankley reservoir was approximately 170 feet. Top water-level of Frankley reservoir had to be at about 600 feet above O.D., and therefore the invert of the aqueduct at the Elan endwas necessarily about 770 O.D., or 70 feet above the bed of the river at the Caban CBch dam. The problem was to keep the water up at this level in the Caban COch reservoir so as to charge the aqueduct at all times, and at the same time to utilize to the fullest extentpossible the magnificent storage-capacity in the lower portion of that reservoir. Thefunction of the submergeddam is illustrated very clearly by Fig. 10. For example,assuming an absolutedrought of 169 days-which is whatthe storage provided is basedon-and that the daily quantity to he sent to supply is 35 million g:dlons, thd followingwill occur:-25 milliongallons per clay will be dischargedthrough the aqueduct, and 27 milliongallons perday will be discharged at the Caban darn for compensation, a total of [TIIE INST. C.E. VOL. csc.] C

52million gallons daily. Thelayer A B D Cwould thereforelast for 88 days. Thereafter, through theremainder of thedrought, waterfor supply to Birming- ham would be letdown from the upper reservoirs in the Elan Valley by way of the river, or else brought from the Claerwen Valley by way of the Dol-y- mynach tunnelhereafter described. Forthe remaining 81 days of the drought, as regards compensation-water, it will be seenfrom the figuresgiven on the diagram that there is more than sufficient water in the section D E F G H to satisfy the requirement of 27 million gallons per day. Without the submerged dam, this storage of nearly 2,500 milliongallons would have been lost, because it would have been impossible to lower thewater in the Cabanreservoir below 782 O.D. Thewater for supply is decanted out of a reservoir of not less than 660 milliongallons capacity,which is an obvious advantage,although it istrue thatthat amount of storage is unusable ; but it would have beenequally unusable if the submergeddam had not been constructed. The following is a brief de- scription in detail of the flood- works,etc., at each of the damsconstructed orpartially constructed.

CRAIGG~CH RESERVOIR.

In planthe dam is an arc of a circle of 740 feetradius, and it carries a publicroad-bridge. The roadway, which was narrowed to the smallest feasible limit, is 9 feet 6 inches between theparapets ; andthe bridge consists of thirteen openings of 30 feet span, forming an overflow having a net length of 390 feet. In cross section thestandard profile was used (Figs. 5 and 5a, Plate l), set at right angles to the chord-line. The drainage-area above the dam is 13,700 acres, and provision was made in the culvert for carrying off waterduring construction at the rate of 30 cubic feet per minute per acre. To discharge this a circular culvert 17 feet 6inches in diameter was required, working under a few feet of head. Theculvert was, however, never called upon to discharge the full amount, though it was filled within 2 feet of the crown on several occasions. It was constructed on the left bank of the river, and its invert level was 937.4 O.D., or about 17 feet above the bed of the river. In planthere were threestraight lengths of culvertand two curves. Thestraight part actually under the dam consists of six rings of bluebrick, and was designed to be surroundedwith 4 feet of concrete;but, owing tothe fact that the foundations forthe dam had to be carried down below the level of the culvert-invert,the hearting masonry of thedam itself took the place of the concrete. That part which was driven outside the darn was concrete-lined throughout. The inlet end was bell-mouthed to 24 feet in diameter. In front of the bell-mouth a channel or inlet cut was formed, 24 feet wide at the bottom, and leading direct into the river gorge ; and clown-stream of this cuttinga concrete wall was built across the river to turn it through the culvert, and so pass it below the excavation for the foundations of the dam. Through this concretewall there was laid a 36-inch cast-iron pipe as near the bottom of the river as it could be got, and a similar pipe commanded by a sluice-valve at its upper end was laid through the dam foundations, discharging at the down-stream face of the apron at thetoe of thedam. These pipeswere forthe purpose of passing theriver through whilst the culvert was beingper- manently stopped. This was done by means of a block of concrete having an aggregatelength of 73 feeton the centre-line of the culvert, with its upper half omitted for a length of 12 feet under the valve-tower, whichstands at the intersectionof the two up-stream lengths of the culvert. c2

For a height of nearly 50 feet above the soffit of the culvert the tower consists of a projecting block of the masonry of the dam with a shaft through it 10 feet in internal diameter and lined with blue brick. Above, to top water, it is an octagonal masonry tower, the 10-foot shaft being continued in it; and there are openings 2 feet wide and 9 feethigh in the five water faces, protectedby steel gratings.The tower is surmounted at road-level by a handsome octagonal valve-house with a domed roof. The means of drawing off are the following :-In the upper part of the tower thewater has, of course, free access tothe shaft: in order to give it access at a lower level, an 18-inch cast-iron pipe is built in theupper portion of the stop just below the soffit of the culvert, and is carried on stanchions to the inlet end, where it is turned up and furnished with a horizontal bell-mouth with its lip at 963 O.D., or 77 feet below top water.Standing in the centre of the well, on a cast-iron bell-mouthed pipe leading through the main part of the stop, is a series of steelcylinders 3 feet in diameter, having plain ends faced with gun-metal. There are four steelguides erected outside them, and eachcylinder has four guide-wheels at the top and four at the bottom. There are in all eight cylinders, each 12 feet long ; and so truly were these cylinders faced that, when they were tested by being placed one on top of the otherforming a column 96 feethigh and filled withwater, the joints were absolutely watertight. The cylinders can be lifted vertically, so as to form an opening at any joint, by means of a central steel rod having three radial arms near the level of the top of each cylinder, the ends of which, whenthe rod is turned to the proper position, engage in small bracketson the inside of the cylinder.The raising is doneby hydraulic power, the pressure of 35 lbs.per squareinch being obtained from a small tank on the hillside which is kept constantly full by a small stream running throughit. The cast-iron bell-mouthed pipe alluded to above, on which the cylindersstand, diminishes to 27 inches in diameter,and bends into a horizontal line: it is laid in the concrete of the main stop, at the back of which thereis a valve-chamber, and an 18-inch sluice-valve isinserted on the pipe andis worked by hydraulic power, the water being obtained from the same source as that for thelifting-gear. The valve-chamber is formed by rz cross wall of concrete and blue brick, 11 feet thick, rising to a height of about 11 feet above the invert of the culvert ; and at a distance of 33 feet 6 inches below this again another crosswall or weir of concrete faced with masonry is built on the top of which is a. rectangular

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-WALES. 21 gauge-notch 10 feet wide, for the purpose of ascertaining roughly what volume of wateris being decanted from Craig GBch into Pen-y-gareg. The lip of the notch is a few inches only above top water of Pen-y-gareg reservoir, which heads up into this culvert. In additionto the 27-inchpipe, thereis a 12-inchpipe laid through the stop about 2 feet above the invert of the culvert, commandedby B geared sluice-valve in the aforesaidvalve-chamber. This pipe discharges, as the 27-inchpipe does, into the gauging- basin, andthere is another 12-inch pipe commandedby a valve through the gauge-weir wall so that the reservoir can be emptied.

PEN-P-GAREBRESERVOIR.

The middle of the dam is occupied by a valve-tower, immediately above a culvert whichpierces the base of the dam, theinvert being 123 feet below the crest (Fig. 6, Plate 1). The firstoperation in the construction of thisdam was the excavation of a temporary cut on the left bank of the river for the passage of the water whilst the excavationwas got out in the river- bed and right bank and the dam and culvert were built up to 850 O.D. onthe western side of the valley. Theculvert was 18 feet in diameter,straight in plan,with its invert-level at 822 O.D., andhad to provide for the discharge of flood-water from a drainage-area of about 16,000 acres. When the above-mentioned block had been completed the river was turned through the culvert, and excavation and building were takenin hand on the eastern portion, untilthe samelevel was arrived at, after which the work proceeded over the whole length of the dam in the manner described elsewhere. The culvert was lined with six 4&-inch rings of blue brickwork, the up-stream end projecting about 14 feet beyond the face of the dam in a block of masonry, 45 feet wide, upon which the valve-tower wasconstructed. The inlet end of theculvert wasfitted with a temporary cast-iron bell-mouth of segmental plates bolted to a cast- iron ring built into the masonry. When the time arrived for the stopping of the culvert, the bell-mouth was replaced by a steel curb fittedwith a gutta-percharing, against which a steelbulkhead waslowered toform a watertightstop to the culvert.The steel bulkhead is backed with 45 feet of concrete faced at the lower end withblue brickwork. Through thestop are two 24-inchwashout pipes controlled by geared sluice-valves worked in the culvert. Water is drawn from the Pen-y-gareg reservoir into the Caban CBch reservoirthrough avertical standpipe in the valve-tower

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 22 E. I,. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of 24 inches in diameter,having branches communicating with the reservoir at five different levels. Eachbranch is controlled by two sluice-valves, theouter ones 1 beingworked by hand-power and intended to be used only in case of emergency, whilst the inner ones are actuated by hydraulic power supplied from a tank on the hillside, in the same way as at Cr:xig GBch. Up to the level of 899 O.D. the valve-tower is formedby the projecting block on the face of the dam; above this level it is an octagonal shaft, on which is the valve-house. The tower was built of masonry backed with concrete, and in order to obtain a watertight well this was covered with 2 inch of asphalt, which in turn was lined with two rings of blue brickwork, forming a shaft 8 feet in diameter. At thebottom of the valve-shaft the standpipe tapers to36 inches in diameter,and is carried through the stop inthe culvert; passing under the flood-water channel, it discharges into a covered chamber situated on the right bank of the river, where the quantity of water is roughly gauged over a notch before it enters the Caban CBch reservoir. Access to the valve-house is either by way of the crest of the dam, if the circumstancespermit, or by means of a passagecon- structedthrough the dam, the floor of which isabout 17 feet 6 inches below the crest.This passage is lighted by openings in the down-stream face of the dam ; and, opposite, the valve-tower opens into a chamber from which steps lead to an elevated platform on a level with the floor of the valve-house. This platform forms a protection to the culvert immediately below it, by cutting off the overflow for a length of about 40 feet.

CAREGDDUDAM AND VIADUCT. The crest of this dam is at 782 O.D., or 40 feet below the top water-level of the Caban CBch reservoir. The river-bed was about 60 feet below the crest of the .dam, and the culvert was 19 feet in diameter, and had its invert-level at 725 O.D. (Figs. 9, Plate 3). The portion of the dam on the right bn.nB was constructed first, including the culvert, the river being allowed to flow down its old course for the time being ; and then, by means of an inlet cut and temporary stank, the culvert was brought into use and the dam was completed. Asthe up-streamface of thedam wouldnever be exposed to view when once th.e Caban Cdch reservoir was filled, it was built of bluebrickwork, finished with an ashlarcrest stone,

~~ ~ ~~ See p. 71.

The culvert was built in blue brickwork, except the central portion, which for a length of 8 feet 3 inches was of cast-ironsegmental plates,from the crown of whicha circular cast-iron shaft was carried to the crest of the dam and covered with a cast-iron plate. A temporary cast-iron bell-mouth was provided as at Pen-y-gareg. TWO36-inch washout pipes laid through the culvert served for the passage of the river whilst the stopping operationswere in hand, the pipes being controlled by sluice-valves worked by hydraulic power. Two stops were necessary in this case, the iron-lined portion of the culvertabove described being left as avalve-chamber. The up-stream stop consisted of a steel bulkhead of somewhat similar design to the one at Pen-y-gareg, and was hacked by about 32 feet of concrete. The down-stream stop was of concrete faced with blue brickwork.The washout pipes at theirinlet ends wereprovided with flaps which can, if necessary, be opened from the crest of the dam. Access to the valve-chamber is only possible when the Caban CBch reservoir is drawn down to 782 O.D. Above the crest of the dam a roadway, carried on piers and arches brought up toabove the topwater-level of the Caban reservoir, gives access to the Claerwen Valley. The roadway is 15 feet wide in the clear between the parapets, and the approaches at theends are built to railwaycurves, so that, when the time comes forconstructing further reservoirs in the Claerwen Valley, the carriage of materials fordoing so willbe facilitated. Over thestraight length of the dam the arches are elliptical, of 41 feet 3 inches span, the rise being one-fourth of the span. Under the cnrved :Lpproach on the north- east side there are five semi-circular arches of 15 feet span. At thedown-stream toe of the dam the groundwas only excavated to a good rock bottom to form a channel for flood-water, and the lined channels and masonry walls which have been provided in the case of theother clams were dispensed with,as only under very abnormalcircumstances would it belikely thatthe Caban C6ch reservoir ~vould be drawn down so low as to leave the toe of the Caregddu dam uncovered by water.

CABANC?CH RESERVOIR. The dam is situated about 7 furlongs below the confluence of the Rivers Elan and Claerwen, and when the reservoir is full top water tails out at about 48 miles up the Elan Valley, at the toe of the Pen-y-gareg dam, and 24 miles up the Claerwen Valley, at a point where thepartially-built Dol-y-mynach dam is situated. At this point the flood-water from the whole watershed of 45,562 acres had

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 24 E. L. AND W. L. MAA’SERGH ON SUPPLY OF WATER [Minutes of to be dealt with. In view of the large area, it wasnrsumed that provision should be made for a discharge of 15 cubic feet per minute per acre, representing a volume approaching 700,000 cubic feet per minute.During construction flood-water was carried off by two culverts, 16 feet in diameter, one on eachside of the river, with their inverts at 700 feet above O.D. (Fig. 7, Plate 1). In constructing thelower portion of the dam, the river-bed was first cleared of all loose boulders and stones on the site, anda temporary stank was then erected on the rigbt or Brecon bank, partly in the river-bed, to enclose the excavation for getting in the foundations andbuilding the soutl.1-west portion of the dam,including the Brecon culvert, LIP to the level of about 30 feet above the river-bed. The same procednre was then adopted on the left bankof the river, the Radnor culvert was constructed, and the north-east portion of the dam was built up to the same level as the block on the Radnor side, the river in the meantime following its usual course between these two portions. The two blocks were built with grooves, 9 feet by 9 feet in plan, to key in with the central portionwhich had then to be constructed. Toenable this to be done it was necessary to build a concrete- and-timber stank across theriver, just up-stream of the dam, to divert the water through the two culverts, and a timber stank was erected below thedam to prevent the water from backing up after it had passed through the culverts. This arrangement isolated thecentral portion, whichwas thenbuilt up tothe samelevel as the side blocks. After this the river was completely controlled and the dam could be built up over its entire length. One of the conditions fixed by Parliament was that the compensation-water should not be drawn out of the CabanCach reservoir below the level of 720 O.D. On the line of each of the culverts a block 30 feet wide was built, projecting 18 feet from the up-stream face of the dam and carried up to thislevel of 720 O.D. The culvert inthis block was constructed of cast-ironsegment plates, and a vertical branch5 feet 9 inches in diameter was brought through to the top of the block. The remainder of the culvert under the dam was lined with six rings of blue brick. As at Pen-y-gzareg and Caregddu the up-stream end of each culvert was provided with a temporary cast-ironbell-mouth, 22 feet 73 inches in horizontaldiameter, which, when the culvert was ready for stopping, was removed and replaced by aspecial curb ringwhich formed the seating for the steel bulk-head which was lowered in front of the entrance to the culvert. In the case of the Caban C6ch damthe steel bulkheads were backed by about 48 feet of concrete faced with blue brick, at the

down-stream ends. Through the stop in each culvert, two 24-inch washoutpipes were provided with their inverts 2 feet above the invert of theculvert, to pass theriver during the putting in of the stop. The compensation-water is drawnthrough 36-inchpipes laid through the culverts and under the main flood-water channel below thedam to the compensation-works oneither side of the river. The inlets are horizontal bell-mouth pipes, 5 feet in diameter, at the 720 O.D. levelbefore mentioned, brought through the vertical branchon the cast-iron portion of the culverts.Sluice-valves, 24 inches in diameter,are placed onall these pipesimmediately behind the stops, thoseon the compensation-watermains being operated by hydraulic pressure, those on the washout pipes by hand- power.Access tothe valves is obtainedeither by means of the culvertsfrom their lowerends, or, in theevent of this being impracticable, by lifts from the pmsage running through the dam; or yet again by way of the main drain.

DOL-Y-,MPNACH DAM. Originally, it was not intended that this dam should form part of the firstinstalment of the works. In view,however, of the fact that the top water of the Caban reservoir would back up in the Claerwen Valley to above the site of this dam, and that, in any case, some sort of weir would have had to be constructed to divert the dry-weather flow of the Claerwenthrough the Dol-y-mynach tunnelto aboveCaregddu, it was decided thatthe foundations shouldbe takenout, and the building of thedam carried up to 8 feet above the top water-level of the Caban reservoir. The drainage-area above this dam is 23,524 acres, and the culvert to pass the flood-waterwas 19feet in diameter,the same as at Caregddu, its invert-level being 800 O.D. The temporary cast-iron bell-mouth that had been used at Caregddu was utilized again here. Excavation had to be taken out across the valley over a length of 570 feet, and masonry was put in over 390 feet. A keying-groove about 15 feet wide and 6 feet deep was left longitudinally along the clam to serveas a bond tothe new masonrywhen the work is continued.Temporary walls atthe ends of the dam and flood- water channels now confine the overflow of flood-water to over the masonry, the culvert being plugged with a temporary timber stop. In connection withthe foregoing provisions for the temporary discharge of flood-water, it may be said that at no time were the culverts found to be inadequate for the fulfilment of their purpose,

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 26 E. L. AND W. L. MANSERGII ON SUPPLY OF WATER [Ifinutes of although on occasions they were called upon to deal with very large volumes of water.The heaviest rain-storm recordedoccurred in July, 1894, between 2 p.m. on the 24th July and 5 a.m. on the 25th July, i.e., 15 hours, when 3-57 inches were measured at Nantgwyllt newrain-gauge. On this occasion numerousobservations of floorl- heights, etc., were taken,and the flow off, as deduced fromthe investigation of allthese, was calculated at somethingbetween 12and 15 cubic feetper minute per acre, or a quantity, at the Caban dam, of not less than 540,000 cubic feet per minute.

DOL-Y-MYNACHTUNNEL. Thistunnel, which has its inletend situated in Dol-y-mynach reservoir about 225 feet above the dam, and its outlet in the Caban Cach reservoir about 250 feet above the Caregddu dam and on the opposite side of the valley to the Foel valve-tower, is a little more than l* mile in length and has a discharging-capacity of 50 million gallons perday. When the reservoirs in the ClaerwenValley are constructed, the water drawn from them for supplywill flow through this tunnel to the Foel valve-tower, and until that time the function of the tunnelis to divert the dry-weatherflow of the RiverCliterwen for supply to the aqueduct at times when the water in the Cabnn C6ch reservoir has been drawn down to the top of the submerged dam. In orderto enable thetunnel to be drivenfrom both ends economically, the invert gradient was varied, the upper portion of about 1,970 feethaving a fall of 1 in 1,000 andthe remaining length of about 4,725 feet a fall of 1 in 255. The cross sections of these two lengths are shown in Figs. 11, Plate 2. At the inletend of thetunnel there is an oct'agonalmasonry tower of which only the base has been built at present up to :L level of 848 O.D., but which will be raised eventually to its full height whenever Dol-y-mynach clam is completed. Water from the reservoir is admitted to the mouth of the tunnel through an opening, 7 feet 3 inches high and G feet wide, in one side of the tower at its base. The outer face of this opening is covered by a screen of steel bars, and the flow is controlled by :t couple of penstocks fitted a@& the inner face and worked from headstocks above. The invert-level at the tower is 823 O.D., and the total fall in the length of the tunnel is 20 feet. Thewater from the tunnel is discharged into the Caban CBch reservoir in such a way as to cause as little disturbance as possible to the slopes, the outlet being drowned at all times.

COMPENSATION-WORKS,ETC. Thevolume of compensation-water to bedischarged intothe RiverElan was fixed byParliament at 27 milliongallons per 24 hours in a regular and continuous tlow ; the point of discharge to be within 300 yards of the Caban C6ch dam. A clause was also inserted in the Corporation’sAct empowering the Board of Con- servators of the River Wye to require the Corporation tocreate freshets in the riverfrom time to time, upon due notice being given, byreducing the daily compensation-water to 22million gallons, and accumulating thedifference of 5 million gallons for any period not exceeding 21 days, and discharging thequantity so accumulated in a regular, equal, andcontinuous flow during 48 hours in addition to the daily compensation-water. It thus became necessary to provideapparatus for accurately measuringthree different rates of flow, andafter considerable discussion with the late Dr. G. F. Deacon, M. Inst. C.E., who was appointed to represent the Wye Conservators, and Mr. J. Parker, Assoc. M. Inst. C.E., representingthe City of Hereford, it was decided to adopt the principle of gauging the water by discharging it through rectangular orifices under a fixed head. Theworks for discharging and measuring the compensation- waterare in duplicate,identical installations having been placed on each side of the main channel about 120 yards below the toe of the dam, and the two sides are connected by a stonefootbridge, with three elliptical arches, built across the channel. The compensation-water main, which, as already described, is laid in each culvert of the Caban dam, passes through the stop and along the centre-line of the culvert to near the down-stream end, where it bends down below the invert, and is laid under the floor of the flood-water channel to a washout chamber behind the channel wall (Fig. 7, Plate 1). From here it rises again, and is carried horizontally, withits invert at 704 O.D., tothe receiving-tank,a brick-lined chamber 40 feet long and 32 feet wide. At the upper end of this tank the36-inch main is bentover to discharge vertically downwards through a steel spreader shaped like an inverted hopper, and having a bottomarea of 60square feet. The bottom of thisspreader is fixed 9 inches above the floor of the tank, Iwhich, for a length of 10 feet at the upper end, is at 694 O.D., or 16 feet below its top water-level, the remainder being at 701 O.D. Thewater discharged into the tank is thus effectivelystilled before reaching the gauging-orifices, which are built into the wall of the tank at itslower or eastern end.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 28 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of On eachside of theriver there are three of these gauging- orifices :-

(a) 49 inches by 12S 25 inches ; (b) 23 inches by 5.8 inches; (c) 37.28 inches by 9-32 inches.

They are all fixed with their centres ata level of 706 O.D. or 4 feet below top water-level of the tank ; and, under this constant head, they discharge, in round figures- (a) 22 million gallons ; (b) 5 million gallons ; (c) 123 milliongallons per 24 hours. The head of water over the orifices is registeredcontinuously by means of a float recorder with cylindrical diagram revolved by clockwork, and,in addition, a gun-metalpoint-gauge is fixed in each tank at the proper working level for the water, so that it can be seen at a glance whether there is sufficient depth to discharge the statutory quantity. In ordinary working, orifices (a)and (b) are open and (c) closed. When water is being accumulated for a freshet, orifice (a) alone is open. When accumulations are discharged for a freshet, both sets of works, with all orifices open, are required, the maximum to be reached being 794 million gallons per day. The closing and opening of the orifices called for special design, in order to preserve an absolutely plane surface on their uppersides and to give a perfectly free discharge. The orifices are formed in gun-metal plates fixed to cast-iron frames built flush with the end wall of the tank. On the back of each frame and well clear of the orifice, a projecting rib is formed witha machined face, against which a cast-iron cover can be fitted. This cover is in the form of a crosshead slidinghorizontally on Delta-metal rods at each side and actuated bya central rod, the other end of which is formed into thepiston of a hydraulic cylinder. To close the orifice, water underpressure is admitted behind the piston and the crosshead cover is pushed forward against the projecting rib on the frame. A watertight joint is formedby a gutta-percha ring resting in a V groove in the face of the cover, and when the cover has been pushedhome it can be locked in positionby means of a wedge actuated by a hand-wheel and screw. To open the orifice again, the wedge is removed, wateris admitted to the reverseside of the piston, and the caver slides back.

The compensation-water flowing through the orifices falls into a channel leading to a short culvert 5 feet high by 4 feet 6 inches wide throughthe channel-wall, and is discharged intothe main channel at an invert level of 695 O.D., the direction of discharge being at an angle of 45" with the centre-line of the channel.

POWER-HOUSES,ETC. Theconstant discharge of compensation-waterfrom the Caban Cbch reservoir provided a source of power which it was decided to utilize for various purposes in connection with the working of the scheme. In the original design power was needed €or working the hydraulicvalves upon the compensation-mains andthe draw-oft cylinders at the Foe1 valve-tower ; electric current was needed for the lifts in the Caban CBch dam and for lighting the valve-tower, the passage in the dam, the culverts,workshops, and various buildings. Arrangements were accordingly made for the erection of a 20-HP. vortex turbine upon the line of each compensation main just above the receiving-tank. Each turbine is designed to work on a fall of 26 feet, using 542 cubic feet of water, and making 280 revolutions, per minute; it drives a set of small high-pressure pumps working agninst an accumulator, and a dynamo for supplying current to the lift and for lighting. At a later stage of the work the addition of the roughing-filters near the head of the aqueduct necessitated the provision of a large increase in power to drive the pumps supplying filtered water under pressurefor sand-mashing, andto give thecurrent required for the electricconveyors andlarge arc-lights installed at the filters. As bhe bulk of the plant for the smaller installation had already been delivered at the site or was ready at the makers' shops, it was decided not to alter this arrangement, but to erect additional and morepowerful turbines above theothers, so thateither set or both couldbe used as desired.The larger plant consists of 75-HP. twin turbines, each being designed to develop its maximum power under a head of 24 feet, using 2,206 cubic feet of water per minute, at a speed of 350 revolutions per minute. Each turbine is coupled direct to a dynamo, which at the same speed is capable of giving 40 kilowatts at 500 volts. Ineach turbine-house is an overhead travelling craneto lift 2 tons. A doorway gives :~ccess to the adjoining compensation-gauge house builtover the receiving-tank. The walls of the buildingsare of stone in narrow courses, rock-facad, with deeper courses at all angles

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 30 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [MiIlutes of and quoins, and are lined with brickwork and rendered. The roofs are of pitch-pine, carried on steel principals, and slate-covered. The use of the electric current generated at these stations has been extended by Mr. Macaulay to drive the various tools in the fitters’ and blacksmiths’ shops, also to light all the staff houses in the Elanvillage ; and a system of storage-batteries has been installed by him in a chamber adjoining the turbine-house on the Radnorshire side of the river.

FOELVALVE-TOWER (Fig. 8, Plate 2). The Foel valve-tower at the head of the aqueduct is situated on the left bank of the Caban C6ch reservoir about 200 feet up-stream fromthe submergeddam. It iscircular in plan,the outer face being divided intoeight panelsby projectingbuttresses running fromtop to bottom. The lower portionis 42 feetin diameter outsidethe buttresses and 30 feet ininternal diameter. This portion is carried up to 836 O.D., where it is capped by a parapet wall 3 feet 6 inches high ; the upper portion which forms the valve- house is 29 feet 6 inches in external and25 feet in internal diameter. The domed roof is of timber covered with copper. The lower portion of thetower is divided internallyinto two semicircles, theouter of which forms a wet well containingthe draw-off pipes. Theother half is solid, withthe exception of SL circular shaft, 12 feet in internal diameter, up which are carried the valve-rods from the second system of valves and which also contains a spiral stairway giving access both to the valves and, through the discharge-chamber, tothe Foel tunnel. Communication between the reservoirand the wet well iseffected by archedopenings 12 feet high and 6 feet wide in the masonry of each of the four panels in the semicircle. The draw-off pipes inthe wet well consist of threevertical tiers of steel cylinders, 5 feet 6 inches in diameter, so arranged that any number of cylinders in any column can be lifted apart and water allowed to flow into the interiorof the column at any multiple of 2 feet below top water-level of the reservoir, down to 778 O.D. Each column is 48 feet high over all. The joints of the cylinders havegun-metal seatings accurately faced so asto form a per- fectlywatertight joint, and the cylinders are guided byrollers running against the flanges of vertical steel H beams. The lifting- rods are of Delta metal and are attached at the top to a cast-iron crosshead connected with the piston of a hydraulic cylinder having a stroke of 8 feet 2 inches. Each pipecolumn is capable of dis-

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-WALES. 31 charging the full quantity available for supply, namely, 75 million gallons per diem, with a head of 2 feet over the lip of the cylinder Eachcylinder can be lifted 2 feetfrom the cylinder below it. There are two sets of lifting-rods, one for the upper four cylinders and one for the lower four. The process of liftingthe cylinders in any one of thethree columns isas follows :-As soon as water is admittedinto the hydrauliccylinder below the piston the crosshead israised and carrieswith it thetop cylinder. After a travel of 2 feet,stop- blocks on the lifting-rods engage with lugs on the second cylinder, which then is raised in turn. At the end of 4 feet travel a second series of blocks catch the lugs on the third cylinder, and at the end of 6 feet travel the fourth cylinder is raised. When it is necessary to draw off by one of the lower four cylinders, the clips connecting the crosshead with the second set of lifting-rodsare moved into position, and the lower cylinders are raised in a similar manner. By means of a copper float moving in a vertical cast-iron float- pipe 12 inches in diameter,the water-level inthe reservoir is indicated on a dial in the valve-house, and the same dial shows the number of the cylinder which has to be raised,so that the water for supply is always decanted at a depth of 2 feet to 4 feet below the surface. The bottom cylinder of each column rests upon the lip of a cast- iron bell-mouth pipe built into the floor of the wet well. Immedi- ately below the bell-mouth each line of pipes is bent through an angle of 90" and laid horizontally, with the invert at 769 O.D., to the discharge-chamber at the head of thetunnel. After passing under the division-wall of the tower the pipes emerge into a valve- chamber at the foot of the dry well, where a 28-inch sluice-valve, with taper pipes on either side of it, is fixed on eachline. These valves form a second line of defenceupon the draw-off, andare worked by hydraulic power, the pressure-cylinders being fixed on a platform in the dry well; a vertical steel rod from the top of each cylinder is carried up to an indicator on the floor of the valve-house, so that the man in charge can see at a glance how far the valves are open.Small valves onthe by-passpipes to each mainvalve are worked by hand from headstocks on the valve-house floor. The discharge-chamber is separated from the valve-chamber by a wall of brickwork and concrete 6 feet thick carried up to 780 O.D., at whichlevel thereis a doorway formingthe means of inter- conmunication between the tower and the tunnel. In the valve-house there is an overhead travelling crane to lift 4 tons, revolving on a circular path laid on the top of the masonry

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 32 E. L, AND W. L. NANSBBGII ON swmr,y OF vxrm [Minutes d walls just below the dome, so that all the machinery in the tower is commanded. On the outside of the tower a bronze tablet above the entrance carries an inscription commemorating the pa.ssing of the Binning- ham Water Act of 1803, as well as the opening of the works by His late Majesty King Edward VII. on the 21st July, 1904, and recording the names of the engineers and of the principal members and officials of the Corporation connected with the scheme.

ELANFILTERS, &c. The screening-arrangements and filters inst'alledat the outlet end of the Foe1 tunnel were not included in the original scheme, but were the result of information kindly furnished by Mr. J. Parry, M. Inst. C.E., theWaterworks Engineer to the Corporation of Liverpool, regardingthe serious diminution of the discharging- capacity of the main between Lake Vyrnwy and theOswestry filter- beds, owing to the coating of the pipes with a blanket-like deposit. This deposit did not occur on the Liverpool side of the filters ; and after consultation with the late Professor (Sir Rubert) Boyce, thelate Dr. CanlpbellBrown, and Mr. Parry,the Birmingham Corporation were advised to put in these works, whereby the mater would be screened and roughly filtered before it passed through any of the siphons where this deposit could accumulate. The only site available was a costly one, involving about 300,000 cubic yards of cutting in thehillside. The filters are thirty in number : each has an area of 450 square yards, being roughly 81 feet by 50 feet, the actual shape varying slightly to fit in with the configuration of the ground, as shown in Fig. 12, Plate 2. The inlet culvert is on the south-west or valley side of the filters, andthe inlets to the filters are controlledby sluices which adroit the water into chambers, on the top of wllich are fixed copper-gauzescreens in hingedframes, laid nearly horizontal ; the water passes vertically upwards through the screens and fallsover cast-iron weir-plates on to the filters(Figs. 12a and 12b). In orderto distribute the water as evenly as possible, perforated steel platesare fixed in the inlet chambers about 9 inches below the screens. Thescreens arc protectedabove from the weather by light steel sliding cover-plates fitted with wheels, which run on steel plntes. These covers can be housed under the gangway which runs along the filters,when it is necessary to get at the screens for cleansing or other purposes. Each inlet chamber has a separatewashout connection. To cleansea screen, the inlet-sluice

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-WALES. 3:i is closed, the washout-valve is opened,and the screen is then sprayed from above with a jet of water. The filters are constructedof concrete, the walls being faced with bluebrick above sand-level and finishedwith stone copings. The filtering medium is necessarily of a coarse nature and consists of rockcrushed to about 4. inchgauge. After passing through the filtering medium, the water is collected in the drains in the usual manner and brought to the outlet-chamber, which is controlled by sliding-gauge sluices over whichthe waterpasses to the outlet culvert (Figs. 12b and 12d). The outlet sluices can be adjusted to permit of the head on the filter being increased from nothing to 18 inches. The gauge-notch on the topof the sluices is 4 feet 6 inches wide and 6 inches deep, and the provision of a float indicator enables the ma,n in charge to see how much water is being passed through any filter. The water from all the filters is collected in the outlet-culvert, and is then gaugedthrough submerged orifices. Theculvert divides into two, and between the two branches there is a central chamber, thewater passing from one side or theother into the central chamber through orifices 3 feet 6 inches by 9 - 23 inches. Provision is made for six orifices, but at present two only are in use ; the remainder will be brought into use one by‘one as additional pipesare laid in the siphons on theaqueduct. The difference in head is recorded. WATER-HARDENING. The Elan water was found to have a slight action on lead, and, under the advice of Dr. Percy Frankland, F.R.S., it was decided to introduce into it, at the head of the aqueduct after filtration, chalk tothe extent of 1 to 1Qgrain per gallon, The works for this purpose were designed and carried out by Mr. Macaulay, and are as follows :- A chalk-store, holding about ZOO tons of chalk in bags, has been erectednear the west end of the filter-beds, and from it chalk iscarried as required byoverhead conveyors along theflter- beds to thechalking-house at theireast end. There it is lifted into a hopper on the upper floor, whichhas a capacity sufficient for3 or 4 days’chalking. From this hoppep it is carriedover a weighing-machine to shoots above the four mixers already installed, twobeing at presentin use n.t R time.These mixers are of the samedesign RS those used at Sheffield,’ except that they are without the second mixing-tank. -__ Minutes of Proceedings Inst. C.E., vol. clxxxi, p. S. [THE INST. C.E. VOL. cxc.] D

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 34 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of The elevator-buckets in the first tank deliver the chalking-mixture into a trough, into which the exhaust from the water-motor also discharges.The whole thendrops directly into the head of the aqueduct. The water for the motor is derived from a'reservoir on the hillsideabove the filter-beds. Thewater ispumped up into this reservoir by the pumps installed for filter-washing. Themixing-machinery works continuously day and night, and withoutattention except twice in the 24 hours,when the tanks require refilling with chalk.

THE AQUEDUCT. The total length of the aqueduct, from the Foe1 valve-tower in Caban CBch reservoir toFrankley service-reservoir, is 73 miles 658 yards. It consists of two main classes of work :- (a) Conduit-either in tunnel or cut and cover-designed to carrythe full quantity of wateravailable from the drainage-area. Of this conduit there is a total of 36 miles 1,248 yards. (b) Inverted siphons of cast-iron or steel, of which two pipes out of sixhave already been laid. The length of siphon is 36 miles 1,170 yards.

Class (U) embraces " tunnel " of an aggregate length of 12 miles 1,556 yards, and " cut and cover " of an aggregate lengthof 23 miles 1,452 yards.There are in all fifteen separatetunnels, nine over 500 yards in length and six not exceeding 500 yards each, on the whoie line, the longest being the Dolau tunnel between Doha and Bleddfa, 4 miles 464 yards in length ; and the shortest being the tunnelat Hagley, close to theSevern siphon-outlet, 183 yards in length. The general cross section of the tunnels is shown in Figs. 13. As :L generalrule, the thicknessesshown in theFigure were adhered to fairly closely, allowance being made for irregularities in the headings as driven, the whole, of course, being tightly packed withconcrete; but in bad or heavyground thicknesses were increasedgenerally to cut-and-coversection, andin somespecial cases through very heavy ground a barrel section with a brick arch was adopted. The ruling gradient adopted for the long tunnels was 1 in 3,0QQ, and the discharging-capacitywas calculated on Kutter'sformula, takingthe coeacient of roughness, n, as 0.014. Thiscoeficient was, of. course, applied to the cut and cover, whichhad a ruling

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITP OF BIRMINGHAM FROM MID-WALES. 35 gradient of 1 in 4,000 ; and so far as observations have gone, the actual depth of flow for varying quantities up to 25 million gallons per day corresponds very closely with the theoretical depth. Thecut-and-cover section is also illustratedin Fkp. 13. On the cut-and-coverlengths there were several places where the conduit had to cross comparatively narrow and shallow depressions

Figs. 13.

.-D'. 6"...... 4 COLLTUNN€L CUT AN0 COVER. ORDINARY SECTION

...... J GAUFRONCONDUIT ' Scale: I Inch - 6 Feet INCHES l2 6 0 l 2 3 4 5 10 FeEr TYPICALCONDUIT SECTIOXS.

and valleyswhere it wouldhave been uneconomical toput in siphons. On the whole length there are thirty-six such crossings, andthe total number embraces seven different methods, vary- ingfrom the simplepipe through an embankment covering a strengthened section of conduit carried on concrete foundations, at Dafarn Eithen on the Gaufron conduit, to the handsome aqueduct D2 Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 36 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of carried onstone piers and arches, at Deepwood Dingle,about 3 mileswest of Ludlow.The latter is 70 feet from the lowest

-*: Y

pointin the valley to coping-level,and consists of nine spans of 30 feet, with a total length above ground of 414 feet.

TWO different methods were adoptedfor the construction of these aqueducts carried on arches (Figs. l4),the second being a variation from the first due to the introduction of expanded metal, by which considerable economy in construction was effected. It was of course essential : (a)to make the whole structure as narrow as possible ; (6) to get the masonry facing as light as possible ; (c) to make the conduitthoroughly watertight; and (a) to obtain a good smooth surface inside for the water toflow over. In the earlier designs objects (a)and (b) were achieved by intro- ducing steel H-bar ribs, 2 feet apart, between which concrete was packed, arched fromthe outside outer flangesso far as thesides were concerned, and fiat at the roof and invert ; this formed the actual conduit. For (c) the inside of the concrete was lined with a $inch layer of asphalt, and for (d) a 4k-inch brick lining was laid over the asphalt across the invert and up the side walls. The outside facing of masonrywas only 12 to 14 inchesthick, with the smallspace between it and the concretearches between the joists filled with 8-to-l concrete ; the arches were gauged 4 to 1. In the later design the steel ribs were abandoned and the side walla were formed of slabs of reinforced concrete 3 feet in width, 6 inches thick, and 7 feet 6 inches high. These slabs were reinforced on the outer or tension side with a layer of expanded steel, and had V grooves in their abutting edges whichwere filled with cement grout to join the slabs. The lower edges of the slabs were placed in longitudinal 6-inch by 6-inch steel angle-bars, with their vertical flanges outside the slabs, and these angle-bars were tied together at intervals by flat steel bars 3 inches by 6 inch. Theresult of thisalteration was to cheapen and expedite the construction of these aqueducts. One or twoother forms of special constructionmay beof interest :- Steel Barrel Conduits.-At two points on the Nantmel conduit, about 5 and 7 mileseast of Rhayaderrespectively, theaqueduct had to be carried over a farmyard (in the case of Maes-y-gelli), and over a public road (in the case of Carmel). In both places it was impracticable to lower the surface in such a way as to obtain the necessary headroom under the aqueduct if carried on arches in the ordinary way, and steel barrels 8 feet 6 inches in internal diameter were adopted, between masonry abutments, The spans were 42 feet and 26 feetrespectively. The barrels were attached rigidly to one abutment, but were made free to move longitudinally at the other by means of a gland and stufting-box packed with two gutta-

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 38 E. L. AND W. L. YANSERGH ON DUPPLP OF WATER [Minutes of percharings. A lightsteel footbridge 3 feet 6 incheswide was attached to the barrels, and the floor of this was extended on each side to form a shelter. Gaufron Road.-Another place where a special form of construction had to be adopted was in the public road at Gaufron, about 2 miles east of Rhayader. Here the land abutting on the road was several feet lower than the road, and the ordinary construction of the conduit wouldhave involved a veryserious severance, whilst the road itself was not at U sufficient elevation to allow of the full cut-and-cover section being put under it. The arch of the ordinary section was omitted and a flat roof was put in, consisting of steel troughing bolted down to stone sills at springing-level (Figs. 13, p. 35). The spaces formedby the troughing atthe endswere carefully packed with corlcrete and caulked, the troughing was filled on the top with concrete, and a 2-inch layer of common asphalt was laid on the top of the concrete.

SIPHONS. The siphons, which have an aggregate lengthof nearly 362 miles, areeleven in number, the shortest, across the Lugg Valley, in Radnorshire,being 552 yardslong, and the longest, across the Valley of the Severn and its tributaries, 17 miles 234 yards. The shallowest siphon is that across the Dulas Valley, in Radnorshire, where the pressure barely exceeds 25 lbs. per square inch, as against a maximum of nearly ten times as much at the lowest point of the Severn siphon. When the full quantity of water procurable from the watershed is being delivered to Birmingham, the siphons will consist of six lines of pipes ; but, for the first insta,lmentof 25 million gallons per day,two lines only have been laid. The valve-chambers, bridges, etc.,have, however, been constructed for threelines of pipes in almost every instance. For pressures up to 400 feet of head cast-iron pipes were used, varying in thickness from 1 inch to 13 inch. For higher pressures andin special cases, suchas crossings of streamsand railways, welded steelpipes were employed. The internal diameter of the pipesranged from 414 inches to 42; inches,according to the hydraulicgradient that could be obtained.The ruling gradient adopted was 3 feet per mile, but small adjustments in the lengths, due to alterations of line, enabled slightly steeper gradients to be obtained in two cases of longsiphons, namely, the Temesiphon, where the gradient is 1 in 1,600, and the Severn siphon, where it is

1 in 1,570. The basis of the hydraulic calculations for the discharge of cast-iron and steel pipes was Kutter’s well-known formula, the value of n, the coefficient of roughness, being taken as 0.013. The pipes were laid in parallel lines, the distance between centres being 6 feetexcept at valve-chambersand crossings, where for economical reasonsthis dimension was slightlyreduced. All vertical bends on the cast-iron pipes were made by special curved pipes struck to a true radius, the straight pipes being laid to even gradients between the bends. In some cases of slight bends on the steel pipes skew flanges were employed. Long bends in plan were laid to a ruling radius of 600 feet, which was considered to be the limiting curve on whioh straight pipes of 42 inches diameter could be used without undue ‘‘ skew ” at each joint. The cast-iron pipes were of the ordinary socket-and-spigot type, 12 feet long, the joints being made with lead and yarnfor pressures up to 250 feet of head, and being run solid with lead for higher pressures.Double collars were used forjoining up where a cut pipe was necessary, and atvalve-chambers and other special lengths flange-joints were employed. In the case of steel pipes, where the gradient was flat, collar joints were used ; but on steeper gradients socket pipes, and at bends and chambers flanged pipes, were resorted to.Anchor-blocks andthrust-blocks of concretewere built upon the pipe-lines at each sharp bend to take up the displacing forces, which at some points assumed formidable dimensions. Sluice- Valves.-On the longer siphons sluice-valves were placed on the lines of pipes about every mile. In order to diminish the total pressure on the face, and to enable the valve to be worked by hand, the diameter of the valves in all cases wasreduced to 28 inches, taper pipes with air-valves on top being inserted on each side for a length of 10 feet 6 inches (Figs. 16, Plate 2). By-passes were not employed at the sluice-valves, which for pressures up to 150 feet head were of the single-door type ; for higher pressures a double-door valve was used, as illustrated in Fig. 16a, the smaller door,which is openediirst, being 12 inches in diameter.Both doors are worked by the samescrew, and the gearing for the highest pressures is 6 to 1. The sluice-valves and taper pipes were enclosed inchambers, lined throughout with blue brick. Arched openings inthe side walls, temporarily filled withred brickwork, were providedfor thethird line of pipes,These chambers were all brought up to about 2 feet above the surface of the ground, and covered with stone slabs, Hayward lights and the necessary entrance- and inspection-covers being provided. Outside each chamber concrete anchor-blocks were built around

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 40 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of the pipes to take up the longitudinal thrust due to the pressure on a valve-face when the pipes on one side are standing full and on the other side are empty. Air- VuZves.-In addition to those fixed against each sluice valve, air-valves (Fig. 19, Plate 2) were placed on the pipes at each summit and at places where there was a marked change of gradient. These were all enclosed in chambers similar in construction to those for sluice-valves. Wushouk-Washout-pipes were inserted at each stream-crossing and at thebottom of every depression in the line. They are 9 inches in internal diameter in all cases, the branch pipe being taken off horizontally at theinvert level of the main and a sluice-valve placed on thebranch immediately adjoining each main. Beyond each valve special bends and junctions lead into a common outlet- pipefor all the six lines.These outlet-pipesdischarge into the nearestconvenient stream, ditch, or pond. At river- and stream- crossings the washout-pipes and valves were as a rule placed in a chamber constructed in an abutment of the bridge, but in other cases they were enclosed in chambers of similarconstruction to those for air-valves. Inspection-Pipes, &.-The special pipe casting which carried the washoutbranch was alsoformed into an inspection-pipe, a short tlanged branch, 18 inches in diameter, being cast on the top of the pipe and closed by a cover securely bolted on. Similar inspection- pipes were placed on each side of every sluice-valve chamber. Details of the automatic stop-valves and also of the reflux-valves used on the aqueduct are shown in Figs. 17, 18, and 18a, Plate 2.

STPHONINLETS ASD OUTLETS. The inlet-chambers and outlets to siphons are shown in Figs. 15, Plate 2. In order to minimize the loss of water and the damage to property in case of a pipe bursting, the inlets of the siphons-with the exception of theshort Romsley siphon near the termination of the aqueduct-areprotected by automatic self-closingdoors. Similar doors to prevent a backflow from the adjoining length of conduit were placed on the outlets of the short siphons which have no sluice-valves in their length ; but in the cases of the three long siphons,namely, Downton, Teme, andSevern, as well as at the Lugg siphon, the lipsof the outlet-pipes were carried upwell above the invert of the conduit. Wherethe automatic doors were fixed, theside walls of the

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedinge.1 TO CITY OF BIRMINGHAM FROM MID-WALES. 41 conduit were splayed out at an angle of 35" to a width of 34 feet, anda rectangular chamber 34 feetby 8 feet wasformed at the ends of the pipes.This chamber was dividedby cross walls into six compartments, one for each line of pipes. Into the outer wall of each compartment the inlet- or outlet-pipe was built, and opposite it in each case there is an arched opening in the inner wall, which can be closed by a cast-iron sluice-door. Over each inlet- and outlet-chamber a rectangular house was built to contain the automatic gear.The chambers below ground were built of concrete faced withblue brickwork, but the houses were of redbrickwork with stone dressings. The automatic arrangement for working the doorn is shown in Figs. 15, Plate 2, and is arranged as follows :- 111 thecentre of eacharched opening and just behind the duice-doora rectangular steel plate is suspendedby means of a steelhanger swinging on a pivot fixed justabove the floor of the house and having a short right-angled arm at the top carry- inga counterbalance. Below thepivot the hanger is attached to a gun-metal trigger-bolt which engages with a specialshackle onthe lifting-chain of the sluice-door.To the upperend of thisshackle is attached a flexiblewire rope which passes over a cast-iron pulley carried on steel joists8 feet 6 inches abovethe floor, and down tothe piston-rod of avertical cast-iron air-cylinder standingon the floor. So longas the flow throughthe pipes is normal, the counterbalance keeps the hanger and plate in position withthe sluice-door suspended on the end of thetrigger-bolt. When a burst occurs, and the hydraulic gradient thereby becomes steepened, the pressure on the plate due to the increased velocity drives it backwards and causes the hanger to swing on its pivot, thuswithdrawing the trigger-bolt. The sluice-door then falls rapidly to within a few inches of its seat, coming to rest slowly as the air in the cylinder is forced out by the piston through a small hole in the cylinder-cover.The escaping air blows awhistle and at the same time an electric alarm is set going, so that the walks- manin charge of thelength is warned that a doorhas fallen. Whenrepairs have been effected, the sluice-dooris raised by means of a winch and suspended once more upon the trigger-bolt. The hanger and plate are forced back into position by means of a handwheel and screw fixed about halfway down and worked from a removable-grating platform in each compartment.

OVERFLOWS. When a sluice-door falls and the flow through a siphon is reduced, thewater necessarily becomes headed up in the aqueduct behind until such time as the rate of discharge of water into the aqueduct can be adjusted. In order torelieve the pressure upon the aqueduct undersuch circumstances seven overflows havebeen placed at various points to carry off the surplus water. Each of these overflows actsfor one or more siphons, and their positions are as follows :- l. At the head of the Elan conduit for the Caethon siphon. 2. At the Wye siphon-inlet for the Wye and Dulas siphons. 3. At Clywedog siphon-inlet for the Clywedog siphon. 4. On Bleddfa conduit for the Lugg siphon. 5. At Downton siphon-inlet for the Downton siphon. 6. On Hunstay conduit for the Deepwood and Teme siphons. 7. At Hopton Brook siphon-inlet for the Hopton Brook and Severn siphons.

The overflows consist of masonryweirs, varying inlength between 19 feet and 27 feet, over which in each case the water falls into a chamber at the head of a line of cast-iron pipes leading to thenearest stream capable of takingthe quantity overflowing without risk of damage to property. Where the overflow is situated on a length of the ordinary conduit section, the lip has been fixed level with the springing of the roof-arch, and in the other cases, where the overflow weir is built into the side wall of a siphon-inlet chamber, the lip hm been fixed at a level corresponding with a full aqueduct. Great care was takenand a good deal of money spent at the outlets into rivers and streams, in order to prevent any scourof the beds or banks.

RIVER-CROSSINGSAND BRIDGES. There were altogether twenty-six rivers and streams of a fair size to be crossed by the aqueduct where in siphon, and at all of these, with the exception of five, the pipes were carried over the stream above flood-level. As a rule, the streams were spanned by straight steelor cast-iron pipes laid between masonry abutments and carrying themselves and their contents, but in thecase of five rivers and onerailway, bridges were built to carry the pipes.These are over the River Teme at Leintwardine, Downton on the Rock,

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-WALES. 43 and Ludlow respectively, over the River Severn between Bewdley and Arley, over the Staffordshire and Worcestershire Canal near Cookley, andover the Oxford, Worcester, and Wolverhampton branch of the Great Western Railway near Hagley. At the first crossing of the River Teme near Leintwardine the total length between the masonry abutments on either side of the riveris 168 feet,which is divided into two spans by a central masonry pier ; and the bridge is formed of continuous steel lattice girders,each 171 feet 6 incheslong over all and 8 feet 6 inches deep. The abutments and central pier have been built wide enough to take the six lines of pipes, but only two girders are at present erected. The second crossing of the River Teme occurs near Downton on theRock, and the owner of DowntonCastle obtained, when the Bill was before the Parliamentary Committee, the insertion of a clauseproviding thatthe bridge should be astone structure in keepingwith the scenery of the neighbourhood.Accordingly, the bridge is formed by a segmental arch of masonry struck to a radius of 58 feet and having a clear span of 80 feet. On the east side of the bridgethere is asemicircular land arch of 15 feetspan to provide for an occupation road along the river-bank. Thethird crossing of theRiver Teme, south-east of Ludlow, consists of steel lattice girders of 110 feet span, as shown in Figs. 20, Plate 3. As in the case of No. 1 crossing at Leintwardine the abutments have been built to take all six lines of pipes, but only two of the four girders required have been fixed at present. The bridge over the Severn Valley and river is the largest bridge onthe aqueduct, being 624 feetlong over all, and constructed throughoutfor six lines of pipes, Figs. 22, Plate 3. It has five segmental land arches on the west side, built of #blue brick with stone facings ; a river span of 150 feet consisting of four segmental arched steel ribs ; and a heavy abutment on the east side. The steel ribs of the river span are fixed approximately 12 feet apart from centre to centre, and supported at each end upon steel pin-bearings, 8 inches in diameter, lying horizontally between cast- ironheel-shoes fixed tothe ends of theribs and cast-iron heel- plates bolted to granite blocks in the masonry abutments (Figs, 22a, Plate 3). They are segmental in form, the intrados of each being struck to a curve of 195 feet radius, and are 4 feet 9 inches deep between flange-plates. Above the level of the girders the bridge is divided into three galleries throughout its length, each gallery being arranged to take twolines of pipes.Removable hatchways arebuilt over each

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 44 E. L. AND W. L. MANSERGH Or SUPPLY OF WATER [Minutes of gallery, and rails are laid upon the decking to facilitate the trans- port of the pipes and other materials in case of repairs, or when laying a further line of pipes in the future. Any rise andfall in the steelwork of theriver span due to expansion and contraction is provided for by the hinged bearings at the ends of the ribs, and by thesliding bed-plates under the longitudinal stringers. An expansion-joint with a sliding gland of gun-metal is fixed upon each line of pipes over the land arch near the westend of theriver span, to take up any corresponding movement in the pipes themselves. In crossing the Stow Valley the actual length of the work above ground is greater than in the Severn Valley, measuring 694 feet in all, but the work is not so heavy as at the River Severn because the masonry piers and abutments are constructed for three lines of pipesonly. At the western end of this length the River Stow is crossed, as already described, by steel pipes 50 feet 6 inches in clear span, laid between two masonry abutments, which had to be somewhat massively built, because on the west bank it was necessary to provide a heavy block of concrete to form an anchorage sufficient to withstand the displacing force due to the verticalbend in the pipes, and on the east bank the abutment had to carry a chamber containing the expansion-joints on each line of pipes. Eastward from the river the pipes are carried for 395 feet across marshyground, being supported bymasonry piers 32 feetapart from centre to centre. The pipes rest in cast-iron chairs on roller bearings and are covered with an umbrella of steel plates. At the east side of the valley is the Staffordshire and Worcester- shire Canal, and an obligation had beenplaced upon the Corporation to construct a bridge having a clear span of not less than 100 feet over the canal and towing-path, with the soffit at the centre not less than 24 feetabove top water-level. The clearance above the towing-path was to be not less than 10 feet. It was decided to adopt the principle of the hydraulic arch, and the pipes themselves are laid to form the main ribs of a three-centre arch, the central portion being struck to a radius of 108 feet, and each of the two side portions to a radius of 120 feet, as shown in Figs. 21, Plate 3. The clear span between the masonry abutments is 106 feet 7 inches, and the rise at the centre is 13 feet 8& inches. The pipes are of steel, +:-inch thick, and in lengthsvarying between 7 feetand 8 feet, with skewed flanges accurately machined to the proper angle to give the required curve. Each pipe thus formed a voussoir of the arch. Light steel girders of the same curve as the pipes were attached to the latter bybrackets, and carried a platform which

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-WALES. 45 also formed a system of wind-bracing for the pipes. In each abutment heavy cast-iron pipes, with specialbody flanges to take the thrust of the arch, were embedded ,in a mass of concrete, and an air-valve was fixed on each line of pipes at the crown of the arch. In theother cases, wherethe aqueduct in siphon has to cross railways on its way from Wales to Birmingham, the pipes have been taken under the rails, but near Hagley the Great Western line runs in a cutting about 25 feet deep in the red sandstone, and it was necessaryto cross above the rails. Therailway-company insisted upon a bridge of sufficient span to enable the line to be doubled if necessary, and thepipes are accordingly carried across the cutting by a lattice-girder bridge of 50 feet clear span, at a height of 16 feet 9 inches above rail-level.

SEVERNTUNNEL.

Theportion of theaqueduct which, in relation CO itslength, involved the largest expenditure and some of the heaviest work, was that between 725 feet west and 1,100 feet east of the centre of the River Severn. At the western end of this length automatic valves were placed on the linesof pipes to protect the bridge works. These valves are of the balanced-disktype and are similar in general arrangement and action to those upon the siphonsof the Manchester Corporation’s aqueduct from Thirlmere.’ About 250 feet beyond the valve-chamber the land arches of the Severn Bridge, already described, commence. Immediately beyond the east abutment of the bridge, the pipes had to be laid under the Severn Valley branchof the Great Western Railway and then up a steep wooded bank on a gradient of 1 in 4. When the work came to be done and a start was made upon the excavation of thebridge-abutment, it was discovered thatthe surface of the hillside consisted of clay resting upon sandstone rock, ,and that this clay was full of waterand liable to movement. In fact, at thetime when the railway was under construction a serious slip had occurred at this point which had buried some of the rails and sleepers. The line had eventually been laid upon the “slipped ” material, and it was through this treacherous ground that thepipes had to be taken. At this point, also, the head of water upon the pipes attains its maximum, and any failure wouldbe attended by somewhat serious consequences. It was decided to carry the foundations of the bridge-abutment -

1 Minutes of Proceedings Inst. C.E., vol. cxxvi, p. 17.

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 46 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of and the chamber under the railway down to the solid rock, which involvedexcavating toa depth of 55 to 60 feet below rail-level. Longitudinaltrenches about 6 feetwide were sunk through the clay under the side walls and centre and were filled with concrete. The clay " dumplings " between these trenches were trimmed off to formthe centering of semicircularconcrete arches, of which the concrete inthe trenches formed the abutments. The haunches of these arches were filled up level with concrete, thus forming a solid platform upon which the superstructure of the bridge-abutment and the chamber under the railwaywere constructed. TheSevern Valley Railway at this point is asingle line, but previous to the discovery of the bad ground a siding had been put in for the use of the contractors, so that a double line had to be crossed under.The railway-company also insisted upon the work being carried out so as to provide for the future doubling of their line on the side opposite to the siding. The overall dimensions of the chamberwere 47 feet long by 54 feet 9 inches wide, with a central wall dividing it into two compartments, each to take three lines of pipes. Duringconstruction the rails weresupported on timber balks, the permanent roofing of the chamber being of steel troughing carried on steeljoists. Beyond the railway it was decided to lay the pipes up the slope in a tunnel drivenat a depthof between 40 feet and 50 feet beneath the surface, SO as to be below the influenceof any slip. This tunnel was made 15 feet in internal diameter and lined with cast-iron rings 3 feet wide, each ring consisting of fifteen segmental plates bolted together.The joints of the plateswere caulked internally with rust cement, and the space between the excavation and the lining was filled withcement grout under pressure. The tunnel was driven horizontally for a lengthof 115 feet, and then turned upwards on a gradient of 1 in 4, following approximately the surface slope, special angle-plates being inserted at the bend. Between the chamberunder therailway and the face of the tunnelthere was alength of 24 feet,in which the pipes were surrounded by concrete, forming a heavy anchor-block, 24 feet by 18 by 14 feet, to take up the longitudinal thrust of the tunnel and pipes.Provision was made in the tunnel for three lines of pipes, one along the centre at the invert andone on each side at springing- level, butat presentonly two lines are laid. Expansion in the pipes was takenup by corrugated-pipes, all the joints being flanged. An entrance-shaft, 6 feet in diameter, was placed on the tunnel atthe lowerend, and atthe upperend thecast-iron lining

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-WALES. 47 terminatesagainst aconcrete block throughwhich astepped passageleads to a reflux- and sluice-valve chamber at the top of the slope. The total length of the iron-lined tunnel is 634 feet, and it is partly in the clay and partly in the sandstone rock. Strong runs of water were tapped in several places, some of which it was found impossibleto exclude. Drain-pipes were therefore inserted, and the water was carried down the invert of the tunnel to a washout- pipe discharging into the river. Thecost of the works inthe length of 1,825 feet was approximately 2337,000.

RIVERWYE CROSSING. Withthe five exceptionsalready mentioned, wherever the siphon pipes cross a river or stream they are carried over it. These exceptions occur on the Wye, Dulas and Romsley siphons. In the first two of these cases the parliamentary plans showed overbridges, but exception was taken by some of the landowners when the Bill was in Committee, and a pledge was given that nothing should be done eitha tocause a severance in the fields adjoining the streams in question, or to injure the amenitiesof the scenery. The River Dnlas and the Black Brook, and the two streams in the Romsley Valley, are quite small, and there was no difficulty in laying the pipes underneath the beds and surrounding them with concrete. Atthe Wye,with its rapidcurrent and liability to sudden and heavy floods, the work was more troublesome, involving strong coffer-dams and costly pumping. Three parallel lines of pipes were laid in concrete, the top being 2 feet below the bed of the river at its deepest point. On the right bank of theriver a chamberwas built to contain the special washoutbranches and valves. The common outlet-pipefrom the three washouts discharges into a cast-iron stand-pipe, 21 inches in diameterand having a horizontal discharge branch 12 inchesin diameter, leading to the river just above ordinary water-level and protected by a flap valve. In orderto empty the pipes completely, should occasion arise, acentrifugal pump, belt-driven from a smallturbine, was fixed inthe chamber,with its 6-inchsuction-pipe going down to the bottom of thestand-pipe. The pressure-water for drivingthe turbine is taken off the mains, a 4-inch branch from each line of pipesleading into a commonfeed-pipe, so that if onemain is being emptied the turbine is driven by the water in the other.

RAILWAY-CROSSINGS. Of the six railway-crossings, two, namely, those over the Severn Valley branch of the Great Western Railway and over the Oxford, Worcester, and Wolverhampton branch of the same railway, have already been described ; and of two others, one over the Mid-Wales branch of theCambrian Railway near Rhayader, and one under the Central Wales branch of the London and North-Western Rail- way near Dolau station, it need only be said that the former was inordinary cut-and-cover, over a tunnel,and that in the case of the latter the concrete side walls of the aqueduct were thickened under the railway, and brickwork was substituted for the concrete in the arch. Over the Shrewsbury and Hereford branch of the London and North-Western and Great Western joint railway, near Ludlow, the aqueduct is in siphon and consists of two steel pipes, 412 inches in diameter. The railway at this place is on a low embankment, 11 feet high, and the companies concerned required that thepipes should be laid in a subway, which it was decided to build in two parts, each to take three lines of pipes. Only one part is at present constructed. The side walls are of red brickwork with an inner facing of blue brick ; the arch is of four rings of blue brickwork springing from stone skewbacks, andthe floors are4&-inch blue brick laid on 6 inches of concrete. The height from the floor to the soffit of the arch is 13 feet 74 inches andthe width 15 feet,the floor being raised 5 feet, forming a platform on each side of the central channel 4 feet 6 incheswide. The pipes, whichare in 8-foot lengths and jointed with double collars, are carried on stone bearers, and on the centre one a movable timber platform is fixed to give easy access throughout the length. Thesixth crossing is underthe Great Western and Midland jointrailway, near Northfield. Here the aqueduct is incut- and-cover andthe railwayis in embankment. The cut-and-cover section of the aqueduct was strengthened by making the side walls 2 feet 2 inohes thick at thespringing and the invert 2 feet thick at the centre, and the existing railway-which is a single line-was carried over on steel troughing laid on girder walls of brickwork built clear outside the aqueduct structure, provision being made for the doubling of the railway line in the future,

FRAXKLEYRESERVOIR (Figs. 23-26, Plate 3). Frankley service-reservoir, at the termination of the aqueduct, is situated on high ground about 6 miles south-west of the centre of Birmingham. Itstop water-level is at 603 O.D. and its capacity isjust over 200 million gallons. It is semicircular in plan, the radiusto the toe of the curved wall being 780 feet, and it is divided into two quadrantsby a central division wall. The side walls arecurved on the inner face to a radius of 31 feet 6 inches, the centre of the curve being vertically over the line of the toe and1 foot 6 inches above top water-level. These walls are built of 6-to-1 concrete covered with a layer of asphalt 3 inch thick and faced with blue brickwork 9 inches thick on the upper half and 44 inchesthick on the lower half of the curve. Where the walls were in the solid ground the back of the concretewas curved to follow the inner face, the total thicknessof the wall being 1 foot 9 inches (Fig. 25). Above the original surface of the ground the back of the wall was vertical, the thickness beingincreased from 3 feet at the top by set-offs of 9 inches every 4 feet in depth until a maximum width of 6 feet from the inner face line at the top was reached. In the lengths where the bulk of the side wall was above theoriginal ground-line the mass of concrete inthe backwas lightened considerably by the introduction of a system of piers and arches (Fig. 26). The floor of the reservoir was formed of 6-to-l concrete, 9 inches thick, covered with asphalt 3 inch thick, and had a general slope of 1 in 600 fromthe level toe of the curved side wall towardsthe centre,Pot-holes of soft material under the floor wereexcavated and refilled with 12-to-l concrete. Themain division-wall is also of 6-to-1 concrete faced with 9 inches of blue brickwork. In addition to the main division wall the floor was further sub- dividedby a dwarf wall of concrete in each quadrant, the top of which was at a level d 578 O.D., or 5 feet above the sill of the draw-offs. The reservoir-wallswere all broughtup to a height of 3 feet 3 inches above topwater, the side walls beingfinished with a moulded string-course,and the division-wall with a chamfered coping.All roundthe side walls a parapet-wall, 4 feet 3 inches high above the string-course, was built of red brickwork with stone coping, the level of the top being 610.5 O.D. Since the works were brought into operation a length of 100 feet [THE INST. C.E. VOL. cxc.] E

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 50 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER minutes of of the main division-wall has been cut down to 6 inches below top water-levelin order that the water may be decantedfrom one divisionto the other. This was foundto bedesirable in connec- tionwith the chalking of thewater already alluded to, for the purpose of allowingfor subsidence before thewater is takento the filters. Theexcavated material was formedinto banks around the reservoir-walls with a level berm at 607 O.D., and slopes of 24 to 1. A metalled roadway 16 feet wide was hid at the back of the walls, with approach-roads from the filters below joining it at the outlet- house in each half of the reservoir. The site of the reservoir and banks was carefully underdrained by tile drains laid in rubble, leading into open-jointed stoneware pipes, which inturn dischargedinto an open cut with pitched sides and bottomjoining up to the old watercourse below the works. Air-pipes weI*e broughtup off thedrains atthe back of the reservoir-walls. In order to providefor expansion and contraction in the long concrete walls, partingjoints were insertedevery 100 feet.The asphalt lining was continuous over these joints, and an asphalt key was fixed inthe centre of the wall across each joint.Each key consisted of arectangular plate, 6 inchesby 2 inches, runinto vertical recesses, 3 inches by 2 inches, left opposite one another in the concrete on each side of the joint. There was no asphalt lining to the maindivision-wall, but similarkeys were inserted at each straight joint and the floor asphalt was carried under the concrete in the wall on both sides to within 4 feet 6 inches of the centre and then turned up vertically for a height of 2 feet. Inlet Worlzs.-The aqueduct terminates in a gauge-ohamber built onthe west side of the reservoir and in linewith the main division-wall.This chamber consists of a, centralculvert 45 feet long, 9 feet wide, and 13 feet 8 inches high, with two side culverts each 5 feet wide and 13 feet high. Into each division-wall, between the culverts and just above the floor, six cast-iron gauge-plates with rectangular orifices 4 feet by 6 incheswere built. Out of the twelve orifices only four, two on each side, are in use for the present instalment.The water from the aqueduct passes through the orifices intothe sideculverts, in each of whichis a float pipe witha copper Boat actuating a differentialrecording apparatus fixed in a smallhouse over thecentral culvert. From the sideculverts the water Bows intothe inlet-basin, an open rectangulartank, 38 feetwide and 31 feetlong, immediately adjoining the gauge-chamber. Into the east end of this basin the

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMISGHAM FROM MID-WALES. 51 main division-wall projects with a cut-water edge of masonry, and on each side an inlet-channel 16 feet wide leads to each half of the reservoir.The entrance to each channel is governedby three rectangular penstocks, 4 feet 6 inches wide and 4 feet high, worked by hydraulic pressure from headstocksfixed on the coping above. The water enters the reservoir over curved and stepped masonry weirsbuilt into each angleformed by thejunction of themain division-wall with the curved side of the reservoir. TO allow the water from the aqueduct to be sent directly on to the filters instead of through the reservoir, by-pass mains were laid fromeach side of theinlet-basin to the northern and southern outlet-houses.These willeach consist ultimately of two lines of cast-iron pipes 48 inches in diameter, but only one line on each side has beencompleted. The valves on these mains are 32 inches in diameter,and, like the adjoining penstocks, are worked by hydraulic gear. Outlet- Works.-For each half of the reservoir there are separate outlet-works which areidentical in arrangement. Each consists of a circular well and octagonal valve-houseabove, built in line with the subdivision wall. Eachoutlet-well has an outer chamber, 28 feet in internal diameter, built of concrete, with its floor at a level of 566 O.D. ; inside this there is a central tank of cast iron, 19 feet in diameter, to which are connected the 42-inch draw-off pipes, the 48-inch by-pass pipes from the inlet-basin andthe 54-inch supply-pipes to the filters. The sluice-valves on these lines of pipes are placed in the annular space between the concrete and cast iron, the diameter of the valves inall cases beingtwo-thirds of the diameter of the pipes they control. They are worked by hydraulic gear from headstocks bed on the floor of the valve-house above. The cast-iron tankis compossd of rings of segmental plates bolted together and carried up to 2 feet 6 inchesabove top water-level. Steeltie-rods connect the side plates with a central cast-iron column which also acts as a support for the floor-joists and carries thecentral pillar of a radialoverhead travelling crane which commands all the valves and gear. Thereare six draw-off pipes, three on each side of the subdivision wall, leading from eachhalf of the reservoir toits respective outlet-well.They were laid with their inverts horizontal at a level of 571 -08 O.D., andthe bell-mouths attheir headswere fixed about 20 feet back from the toe of the reservoir-wall, recesses beingformed in the curved side. Underthe reservoir-wall the pipes were laid in parallel straight lines and were then bent round to enter the outlet-well on radial lines, E2

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 52 E. L. AND W. L. MABSERGH ON SUPPLY OF WATER [Ninutes of OverJlozcs and ?Vashoz&-The overflow- and washout-pipeswere placed in the anglesbetween the main division-wall and the straight east wall of the reservoir, towards which corner the whole of the floor is sloped. The overflow-pipe for eachhalf, 18 inches in diameter,is built into a pieron the face of themain division- wall, the stone coping of the pierforming an overflow sill semicircular in plan and struck to a radius of 6 feet. The two overflow- pipes join together about 12 feet below top water-level, and their common outlet-pipe, to which the washout-pipes are also connected, was laid through the centre of the main division-wall and under the eastern wall and bank to the head of the open stream cut between the filters. As it is of importance that overflow should not take place from Frankleyreservoir, an electricarrangement was fixed in a small chamber in the main division-wall and was connected with an alarm bell in the engine-house, so as to give warning as soon as any water found its way over either of the overflow sills. The washout-pipes, of which thereare four, one for each subdivision of the floor, are also 18 inches in diameterand are controlled by sluice-valves fixed in chambers at the back of the east wall and worked by hand from headstocks above. In order to be able to pass water from one division to the other at any depth, a cast-iron pipe tapering from 48 inches to 32 inches in diameter was builtthrough the main division-wall underthe overflow lips,with its invert at 568 O.D., and is commanded by a 32-inch sluice-valve, worked by hydraulic gear in n. chamber formed in the body of the wall, access to which is obtained by a' manhole in the centre of the division-wall. Stairways of stone steps were built down the face of the main division-wall at each end and on both sides to give access to the bottom of the reservoir.Similar steps were also built down the face of the side walls at both the northern and soutllern ends of the reservoir, and ladders were fixed over the draw-off pipes opposite each outlet house. Iron gates in the parapet wall give access to the heads of the steps and ladders.

FILTER-BEDS. On the east side of Frankley reservoir eighteen sand filters were constructed, having a total sand area of more than 14 acres. The bedswere made of variousshapes and sizes to suit the site, the largest being 220 feet, and the smallest 150 feet square inside the walls. There is ampleroom for extending the filtering-areawhen

required,the positions of twenty-four morebeds having been provisionally determined (Fig. 23, Plate 3). The filters are of the ordinary type of " slow sand ".filters with arrangements for gauging the inflow to each bed, the rate of outflow being co~~trollerlby a sliding weir. The side wvitlls were built of 6-to-1 concrete, and faced with blue bricksabove sand-level. The copings are of stone 9 inchesthick. The floors are of concrete 12 inches thick, put in in two layers, with a fall of 12 inches across the bed towards the outlet well. The inlet-pipes are of cast-iron laid just above sand-level across the centre of the bed and supported by concretepiers. The pipes diminish in diameter as they get away from the inletgauge-chamber, and have vertical branches at the top with horizontal bell-mouthed outlets.Circular disks with openings of variousdiameters were placed in the pipes between the flanged joints in order to equalize the discharge from the bell-mouths. The average thickness of the filtering material is 5 feet, the top 2 feet 6 inchesbeing sand, andthe remainder gravel graded as follows :- No. l to pass $-inch ring and to be held by $-inch ring. No. 2 ,, ;-inch ,, 99 ,, &inch ,, No. 3 ,, l$-inch ,, 99 ,, $inch ,, No. 4 ,, 2 -inch ,, 97 ,, 13-inch ,, Thesand had all to be washed and screenedthrough a sieve of 64 meshes to the square inch. Practically all the filtering-material came from gravel and sand beds in the neighbourhood of Kidder- minster. The subsidiary drains below the filtering material are 6 inches by 6 inches in section and were built of red bricks laid dry with open joints i the main drains, which are 12 inches by 12 inches in the smaller and 15 inches by 15 inches in the larger beds, were built withbrick sides and covered withstone flags. The upper ends of all the subsidiary drains are connected with stoneware air-pipes laid in concrete berms along the side walls and terminating ina chamber at the head of the main drain. The working-depth of water over the sand at its full thickness is 2 feet 6 inches,and the top of the coping to the walls is 1 foot 6 inches above this water-led. The beds are designedfor R maximum rate of filtration of 450 gallons per square yard per 24 hours; i.e., a velocity through the sand of 4 inches per hour. Each filter is providedwith orertlow- and washout-pipeswhich

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. 54 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER minutes of discharge into the stream cut, and when the water has been drawn down in a be2 for scraping and washing the sand, the bed can be filled again with filtered water frombelow, so as to avoid disturbance of the surface. Pwe- Water Tank.-The outlet-mains from the filters discharged into the covered pure-water tank, which, as originally designed and constructed, had a capacity of 500,000 gallons, a quantity which was consideredsufficient to balance the hourly variations in the total rate of filtration caused by the laying on or off of a bed, and similar variations in the rate of pumping to the high-level districts. In actual working, however, owing to alterations in the method of working thedistributing-mains, coupled with a desire on the part of theauthorities to keep the service-reservoirs in the city always fairly full, so as to be capable of dealing with a bad fire in any part, the pure-water tank at Frankley had tofulfil the function of a service-reservoir, and its capacity had to be increased considerably. This was done by building another tank, to hold 74 million gallons, close to the first one and connected with it, so that the two formedpractically one reservoir. This second tank was designed by Mr. Macaulay, and constructed under his supervision. The original tank measured 99 feet 6 inches by 97 feet between the walls at top water-level (564.5 O.D.) and its draw-off level is 554.5 O.D. Eightoutlets from the tank were provided; namely, four 43-inch gravitation mains for the middle and high-level zones, of which only two were laid ; two 42-inch gravitation mains for the low-level zone, one of which is laid; and two 30-inch pipes to the suction-well of the engine-house, of whichonly one is completed. The valves on these mains are situated in a chamber immediately behind theeast wall of thepure-water tank and are worked by hydraulic gear. On each line of gravitation main a Venturi meter was placed, about 150 feet from the tank, wit8h the recorders in an underground chamber connected with the pump-floor of the engine- house. Provision WRS made for similar meters to be fixed on future lines of mains. Pumping-Stations, etc.-Although the bulk of the Welsh water is conveyed to the inhabitants of the district of supply by gravitation from Frankley, pumping has still to be resorted to for some small high-level areas. Two additional service-reservoirs were constructed, one at Warley, about 33 miles to the north of Frankley reservoir, and one at Northfield, about 2 mile to the south. Thepumping-station at Frankley is onthe eastern side of the pure-watertank, and the plant installed comprised threevertical triple-expansionsurface-condensing steam engines, working three

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRMINGHAM FROM MID-TALES. 55 sets of three-throwplunger pumps. Two of theseengines and pumpswere for pumping to Warley and Northfield respectively, and the third was a standby. In addition to the main engines and pumpswith their accessories, a good deal of auxiliarymachinery had to be installed, for working the numerous valves in connection withthe reservoir and filters, andfor electric lightingand other purposes. The covered service-reservoirs at Warleyand Northfield are verysimilar in size andgeneral construction. Warley reservoir measures 150 feet by 97 feet between the walls at top-water level, and Northfieldreservoir 128 feet by 114 feet.Both are 15 feet deep, the first-namedholding l$ milliongallons and Northfield about 100,000 gallons more. The side walls and floor were built of 6-to-lconcrete covered withcement rendering, and the walls- whichhave a face batter of 1 in 6 below top water-level-were lined with 9 inches of blue brickwork. The roofs are of concrete on expanded metal, laid between steel joists carried on cross walls of piers and arches. From each reservoir a gravitation main 20 inches in diameter was laid to join the city mains,

GENERAL. In addition to the waterworks,a considerable number of subsidiary and ancillary works had to be carriedout. On the watershed,in addition to the 36 miles of temporaryrailway, about 17 miles of permanent public highways had to be constructed, with numerous bridges, culverts, and fence-walls, wire and other fences, and also a large quantity of pitching and beaching of the sides of the reservoirs. A church, a Baptist chapel, and a school had to be built to take the place of those which were submerged in the Caban CBch reservoir. A house for a water-bailiff, appointed by the Wye Fishery Commissioners, has also been erected close to the Baptist chapel,and a house for the superintendent of theworks in the valleyhas also been built on the old villagesite, together with several smaller cottages for the staff, On the line of the aqueduct very few public roads were interfered with, and the total length of new road that had to be constructed amounted to about 700 yards. For the proper supervision of the aqueduct it was divided into eleven lengths, and a walksman was put in charge of each length ; and for the housing of these men ten neat cottages were built on smallplots of land at convenientspots. These houses, as well as the superintendent’s houseat the upper end, the Resident Engineer’s office-which is situated at Ludlow-the Frankley works, and the

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. ,?6 E. L. AND W. L. MANSERGH ON SUPPLY OF WATER [Minutes of office of the manager of the Water Department in Birmingham, are all in telephonic communication by means of a private telephone- line. Depots have also been established along the line of aqueduct in convenient positions where pipes and tools are stored for making good any breakdowns that may occur in the siphons. The whole of the works on the watershed and a length of about 2 miles of the aqueduct below the Elan filters were carried out by direct administration without contractors under the supervision, as Chief Resident Engineer, of Mr. George N. Yourdi, M. Inst. C.E. The following Table gives in round figures the quantities of the principal kinds of work which had to be done in the construction of the reservoirs, filters, aqueduct, etc., carried out by administration, the total cost of which amounted to X1,810,000. Excavation ...... 1,300,000 cubicyards. Cyclopean masonryand concrete in} 380,000 ,, ,, dams, etc...... Brickwork ...... 20,000 .... Masonry facing,including rubble work . 140,000 ,, ,, Pitchingand beachingonslopes, etc. . 425,000 ,, ,, Pitchingandballast, railways highways ...... 'lrd) 76,000 ,, ,, Fencing,mainly post andwire ... 32 miles.

The whole of the remainder of the aqueduct, the Frankley works, and mains into the city and district, were carried out by contract ; and the following Table gives the names of the various contractors, and the lengths andfinal amounts of their contracts.

Aqueduct. Co~ltract Contractor. Length in cost. No. Yards. f S. d. 3 JohnAnd and Sons ....23,612 387,960 17 7 a Morrigon and Mason, Ltd. ..18,480 292,49419 1 7 I? , . . 16,566 229,2248 'L 11 . . 25,608 488,27919 5 12 ,I . . 30,360 456,111 11 Y 13 Abram Kellett ..... 9,281 156,791146 10 Thos. Piggottand Co., (steel pipes) .....I 148,790 0 10 Frankley lrorks. 6 Abram Kellett ...... 367,9289 2 18 ...... 76,0864 6 20 Glenfield and Kennedy, Ltd. .... 13,91213 1 8 J. BlakeboroughandSons ..... 990 17 9

Ilistributiola. 15 John Aird and Sons ...... 144.404 13 6 17 , ...... 2165.876 3

Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [18/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TO CITY OF BIRXINGHAM FROMMID-WALES. 5’1 As mentioned previously, the works were inaugurated and water was turned into the aqueductfor the first time from the Elan filters on the 21st July, 1904, by His late Majesty King Edward VII., who was accompanied by Her Majesty Queen Alexandra, on which occasion the late Mr. James Mansergh, Past-President Inst. C.E., had the honour of conducting their Majesties over all the principal works and explaining the whole scheme to them, The works were handed over to the Water Departmentpractically complete at the end of October, 1906, but water had been supplied to the district from them formore than 2 years before that date.

The Paper is accompanied by twenty-four tracings, from which Plates 1-3 and the Figures in the text have been prepared.

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