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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.
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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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