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3^ 4^^ 
 
 
 DAWSON 
 
 ON 
 
 THE PAROY RESERVOIR. 
 
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 PAKOY RESEKVOIE. 
 
 nv 
 
 WI I.LI AM HELL DAWSON, M.A., 
 
 Assoc. M. Inst. C.IO. 
 
 By permission of tho Council. 
 
 Excorpt Minutes of Proceedings of Tho Institution of Civil Engineers. 
 
 Vol. Ixv. Session 1880-81. Part iii. 
 
 Edited by James Fouuest, Secretary. 
 
 LONDON: 
 
 JPuliItsljfli Ini thr Unstttutian, 
 
 25, GREAT (iEOIKJK STIlKlVr, WESTMINSTER, S.W. 
 
 1881. 
 
 [The right of I'tiblication and of Translation is r' saved.] 
 

 b 
 
 ' 
 
 ADVERTISEMENT. 
 
 The Institution as a body, is not rcsponsiWc, for the facts and 
 opinions advanced in tlio following pages. 
 
 
 r.ONDON: PBINTEl) BT WM. CLOWRS AND SONS, LIMITKD, STAMFOnU STUKKT AKU (-'IIAHIKO CU03S. 
 
THE INSTITUTION OF CIVIL ENGINEERS. 
 
 Sect. II.— OTHER SELECTED PAPERS. 
 
 {Paper No. 1767.) 
 
 " The Paroy Reservoir." 
 
 By William Bell Dawson, M.A., Assoc. M. Inst. C.E. 
 
 The Mamo-Rhine canal, which connects Paris with Strassbuvg, 
 has two summits on its course; one whore it passes from the 
 head-waters of the Mame to the valley of the Moselle, the other 
 in crossing the Vosges mountains before descending towards the 
 valley of the Rhine, The latter is lower and wider than tho 
 other, and the summit-reach is rather more than 18 miles in 
 length. This reach derives its supply from the head-waters of tho 
 Sarre, and from the Gondrexange pond, through which it passes, and 
 of which the level has been raised to increase its capacity. From 
 the summit-reach water is drawn off for tho supply of the canal 
 on both slopes, and also for a length of 12 miles on a branch from 
 this point northward, through the coalfields of the valley of tho 
 Sarre. On tho slope towards the Moselle the head- water has to do 
 duty as far as tho Rechicourt pond, of which the capacity has also 
 been artificially increased, to afibrd storage for any surplus from 
 the Gondrexange pond that may reach it along the canal, in ad- 
 dition to the rainfall of its own basin. Its capacity is 880,000,000 
 gallons, and it has to furnish the water necessary for tho working 
 of tho canal as far as Dombasle, a length of about 24 miles. 
 From this point an ample supply is derived from the Meurtho, 
 a tributary of the Moselle, near to which the canal runs for a 
 considerable distance. 
 
 The supply on this part of the canal was never more than 
 barely sufficient, and a scheme had been elaborated some twelve 
 years ago for supplementing it. The events of 1870-71 made a 
 fundamental change in the data of the problem, as the position of 
 the new frontier out off from France the summit-reach of the 
 Vosges, together with the Gondrexange and Rechicourt ponds, and 
 upon these the supply of the slope towards the Moselle depended, 
 of which the greater part still remained in France. By the Inter. 
 
DAWSON ON THE PAROY UESEIlVOin. 
 
 [R0l(M!t<Hl 
 
 nation:.! Convontion of May 1873 howovor, Germany agrocxl to 
 fun.iKh sufficiimt water to maintain tho depth of 5 feet 3 inches, 
 , which the canal had at that time. Subsequently, tho French 
 Government decided, hy the Decree of tho 8th of November, 1877, 
 to increase tho doi)th of water to 6 feet inches ; to carry this 
 into effect an additional (juantity of water had to be obtained. 
 From an examination of tho country, it was evident that no streams 
 of im])ortanco could be made available as a s(mrco of supply, and 
 that tho best means of securing it would be by the construction 
 of a reservoir which should depend entirely upon tho rainfall on 
 its own basin. Tliis solution had the additional advantage of 
 being independent of the political relations with a neighbouring 
 country. It was not difficult to obtain the site for such a reservoir. 
 At 4J^ miles from tho frontier, close to the canal, there was a mill- 
 pond of considerable extent, situated in a valley consisting entirely 
 of clay and marl, and whoso sides sloped up uniformly to a con- 
 siderable height. The east side of the valley, which is rather 
 steeper than tho other, consists of variegated marls lying almost 
 horizontally. Tho limo in these marls has separated from tho 
 general mass, and occurs as thin layers of calcite, 2 or 3 inches 
 in thickness, leaving between them beds of red, blue, and grey 
 clay, of a consistency not affected by contact with standing water, 
 and sufficiently compact and tenacious to form a good foundation 
 for masonry structures. On the west side of the valley there is a 
 heavy bed of rather soft red clay, which crumbles into flakes 
 when exposed to the air. In the central part of the valley a deposit 
 of black silt, 25 or 30 feet thick, occurs in the middle, thinning off 
 towards the sides. This silt is soft and compressible at the surface, 
 but firmer below. On exposure to the air it becomes as tough as 
 brick clay, and shrinks into little cubes as it dries. These aro 
 
 homogeneous and fine-grained, and while moist aro somewhat 
 greasy. 
 
 The mill-pond that existed here was retained by an embank- 
 ment of earth, which also served to carry across tho valley tho 
 road from Dombasle to Sarrebourg. The level of the water was 
 4 feet 5 inches above that of the surface of the canal opposite. 
 This level could be raised only 9 feet, otherwise the village of 
 Bures, at the upper end of the valley, would be inundated. Tho 
 volume contained between the level of tho water in the reach op- 
 posite and th^s new level was found to be 350,000,000 gallons. Tho 
 first point to be determined was, therefore, whether a reservoir with 
 this available capacity would bo sufficient to store the rainfall of 
 its own basin, and moot the demand on the length of canal which 
 
PrImtb.J 
 
 DAWSON ON THE PAROY RESERVOIR. 
 
 it would 1)0 rtMiuircd to supply. No direct oLsorvations of a satis- 
 factory character were available; but as the conditions of the 
 Gondrexangy pond had been studied for fourteen years, a com- 
 parison with it was thought admissible, as it is distant only 1 5 miles. 
 The rainfall and evaporation, respectively, were assumed to be 
 ocjual at the two places, and the diflerenees in the nature and cha- 
 racter of the two basins were taken into account. The volume of 
 water recpiiicd for the supply of the camil being known, the 
 problem i)rescnted no special difficulty. Tables were drawn up of 
 the receipts and expenditure of the reservoir as they would have 
 been during the fourteen years. From those it appeared that, 
 during the driest season, there would have l)een one week (in the 
 month of November, 1858), when the available (juantity would 
 have fallen to 3,000,000 gallons, after which the reservoir would 
 have been replenished by the winter lains. This result was con- 
 sidered satisfactory, and as affording sufficient guarantee for the 
 future. 
 
 Scale 2C)^ -Fat -Ihdi. 
 
 lUb 10 V 
 
 ■*«■« y,....* iLiT 
 
 40 lot 
 
 Cross Section of the Embankment. 
 
 A suitable position for the retaining dam was indicated by the 
 bank of the mill-pond. It was thought better to place the new 
 dam in front of the old one rather than to modify the profile and 
 height of the existing bank, to avoid the reconstruction of the 
 roadway on its summit, and the interruption to the traffic which 
 would necessarily result. The incorporation of a mass of earth- 
 work of uncertain quality in the body of the new work was also 
 obviated, and a much larger base was secured to the dam without 
 additional expense. The profile of the dam (Fig. 1) is one which 
 
 B 2 
 
■!— 
 
 DAWSON ON THE PAROY RESERVOIR. 
 
 [Sflcctcd 
 
 hud boon adopted before iit the reservoirs of Montanbry and Mit- 
 terKlu'im. The earthwork is nteppod on the water side and faced 
 with masonry, ho desij^ned that if any settletncnt does oconr in the 
 i;arthwork, it can only cause the angles between tht> Huccessive 
 steps to become slightly more obtuse, without producinj; cr-ieks in 
 the masonry. The earthwork on the water side is thus enabled to 
 stand at an aveiajifo slope of al)Out IJ to 1, which reduces the 
 leu<i;th of the slope to nearly ono-half of what it would bo at the 
 ordinary inclination of .{ to 1. This ajjjain allows a layer of 
 puddle of suflicient thickness to bo idaced on the water slope, as 
 the reduction in its lenj^th brinj^s down the volumo of the ])uddle 
 t<» an admissible (juantity. It is protected by the masonry, and is 
 in a ])osition to perform its duty much nice certainly and effe(;tivoly 
 than if placed in the centre of the dam as a puddle wall. It can 
 also be carried down as far as necessary in a trench ulonj; the toe 
 of the slope. The. cost of the masonry facing is counterbalanced to 
 some extent by a corresponding saving in the volume of the earth- 
 work, and this becomes greater in proportion as tho dam is of 
 greater height. The crest of the dam rises 2 feet 3 inches above 
 the water level. 
 
 To take advantage of tho good foundation on tho east side of tho 
 valley, the waste weir and outlet works were combined into one 
 structure. According to observation tho maximum storm rainfall 
 amounts to 40,000 gallons per minute for tho basin. The length 
 of the overflow was calculated so that this (quantity of water 
 entering tho reservoir for a period of thirty-six hours would not 
 raise the water more than <S inches above the crest of the waste 
 weir, su])posing the outlet gates to remain closed. Tho water from 
 the reservoir passes into an intermediate basin, from which it can 
 be admitted to the canal or l)o turned into a waste-water channel. 
 This basin was placed on the site of an old borrow-pit made during 
 the construction of tho canal. 
 
 The material for the body of the dam was selected from among 
 the marls and clays at tlie sides of the valley. The puddle for tho 
 inner side of the work was obtained f.„ni a natural deposit of sandy 
 clay situated at a distance of 1000 yards from tho works. This 
 was mixed with one-tenth of its volumo of slaked lime before being 
 used. It was originally intended to carry up the earthwork as far 
 as possible during the first complete working season, to allow the 
 reservoir to fill with water during tho succeeding winter to com- 
 plete the settlement and consolidation of the work, and to construct 
 the masonry facing in the summer following. After the contract 
 was let it was abandoned, on account of the difficulties met with 
 
 Ji 
 
Paperfl-l 
 
 PAW80N ON THE PAROY RESERVOIB. 
 
 I 
 
 in oxcavating tho «ilt in the central part of tlio valley ; and tho 
 work was curriod on by day labour under tho HUpervision of tho 
 onginoer in charge. Tho delay occawionod in reorganizing the 
 work made it impracticable to conform to this plan without an 
 unwarrantable increase in the time occupied in its execution. To 
 secure the same advantagoH, it was decided to k(!ep the earthwork 
 constantly wot by a small force-jmnip, and to pay special attention 
 to its consolidation. 
 
 To prepare a seat for tho bank it was necessary to remove a 
 large quantity of tho silt occupying tho bottom of the valley. 
 After the water of tho mill-pond was let out, an excavation in the 
 silt, IG foot wide measured back from tho toe of the water slope, 
 was commenced at tho centre of tho valley. This was carried down 
 
 Fig. 2. 
 
 .too 
 
 )-00. 
 
 
 ! ' - 
 ! ' - 
 
 
 ^^-'^%':^^X^^ 
 
 II ! I 
 
 .17. 
 
 *''!!s ^ '^*^ ^*>: : "^fyKi 
 
 ll*K 
 
 Half elevation. 
 
 Transverse scctiwn. 
 
 Half section. 
 
 OlMlItESSloN-Rdt.LKR. 
 
 Scale 3',; of real si/.i'. 
 
 till tho silt was found sufficiently compact to resist a pressure of 
 21 tons on tho square foot (2*60 kilogrammes per square centimetre) 
 without yielding appreciably. A depth of 13 feet satisfied this 
 condition. From the lower side of this excavation the silt was 
 stepjMid back toward tho road. A small hand-pump was sufficient 
 to keep it free from^water. The earth, in filling in, was spread 
 in layers 1 inches in thickness, and was carried up so as to leave 
 a trench 5 feet in width between it and the upper side of tho exca- 
 vation. This trench was destined to receive the masonry wall 
 along tho toe of the water slope ; bat it was found necessary to fill 
 it temporarily with sand, which was carefully punned and brought 
 up to the natural surface of the ground to support the silt which 
 
 ■ ^.>.*fc.i(SK«iteffi?i4 
 
mmmmm 
 
 8 
 
 DAWSON ON Tlir PAROY RESERVOIR. 
 
 [Selected 
 
 would not stand alone. As the excavation extended from the 
 centre toward the sides of the valley, suflSciently firm ground was 
 found at a less depth ; and it soon became possiblo to remove 
 the silt entirely, and to seat the earthwork on the clay below. 
 After the excavation had been filled in to the natural surface 
 of the ground, the work presented less diflSculty. The puddle 
 on the water slope was carried up at the same time with the earth- 
 work of the body of the dam. The successive layers were partly 
 consolidated by the passage of the carts in w] h the material was 
 brouglit. In addition, a compression -roller was used. It was of 
 the design shown in Fig. 2, and weighed, when empty, 25 cwt. 
 An additional load of IG cwt. of stone could be placed in the 
 box. It v/as drawn by four horses, and the pole was attached 
 
 Fig. 3. 
 
 \ 
 
 Foundation of the masonry facing in tlie central part of the valley, as actually buili. 
 
 Scale , ;'„j of real size. 
 
 to an iron hoop running in guides at the four corners of the box, 
 to avoid turning the roller before commencing the return trip. 
 The final measurements showed that the earthwork had become so 
 thoroughly picked as to occupy nearly the same volume as that of 
 the borrow-pits from which it had been taken. This method of 
 consolidation cost ^d. per cubic yard of earthwork. Near the 
 masonry of the overflow and outlet wovks maidens of cast-iron, 
 
mi^mmirr 
 
 Pftpcrs.] DAWSON ON THE PAROY RESERVOIR. 9 
 
 weighing 35 lbs., wore used, and of hemispherical form below, to 
 prevent fouling. 
 
 As the dam rose in height, the toe of the watei-slope advanced 
 8li""htly. The amount nowhere exceeded 6 inches, and when the 
 full height was reached the movement ceased. During the latter 
 part of the same season in which the earthwork was completed, the 
 masonry facing was commenced. In building the wall along the 
 toe of the water-slope, light sheet piling was driven on the side 
 next the bank, and the temporary sand-filling was taken out to a 
 depth of 8 feet. The silt on t^e other side was sloped back and 
 the opening shored, as shown in Fig. 3. By the end of the season 
 the masonry wrs brought up to about one-half the height of the 
 dam, and during the following winter the reservoir was partially 
 filled. In the spring the facing was carried up to the full height 
 of the dam, and the whole of the works were completed by the 
 autumn of 1878. 
 
 Summary of Cost. 
 
 Tlic Paroy Mill Pond, including the old dam, thej g qqq 
 mill, &c. / ' 
 
 Land up to tho contour lino at 1 foot above tlicj g ^qq 
 normal watcr-lovel of the reservoir / ' 
 
 Indemnities "^^^ 
 
 Total purchases 13,000 
 
 Earthwork, and excavation in the foundations . . 3,320 
 
 Masonry facing 2, -100 
 
 Overflow and outlet works 1,340 
 
 14ft 
 Accossorea . . "" 
 
 Extras, estimated at scihcdulo prices <jOO 
 
 Total for construction .... 7,800 
 
 Grand total 21,400 
 
 'T?w^ 
 
LONDON : 
 PRINTED BY WILLIAM CLOWICS AND SONS, LIMITED, 
 
 STAUFORD STllEET AND CHARIKS C»086, 
 
Mill II '■iihi 
 
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