A GENERAL VIEW OF THE NETHERLANDS
NUMBER XIII. WHAT TO SEE IN THE NETHERLANDS FROM AN ENGINEER'S POINT OP VIEW by R. P. J. TUTEIN NOLTHENIUS
CIVIL ENGINEEE
CIVIL ENGINEER



THE SERIES OF PAMPHLETS GIVING TOGETHER A GENERAL VIEW OF THE NETHERLANDS HAS BEEN PÜBLISHED FOR THE P. P. I. E. 1915 UNDER DIRECTION OF THE COMMERCIAL DEPARTMENT OF THE NETHERLANDS MINISTRY OF AGRICULTURE, INDUSTRY AND COMMERCE AT THE HAGUE
THL3 SERIES CONSISTS OF THE FOLLOWING NUMBERS:
i. aqricultuke and cattle
breeding.
ii. nursekies.
iii-vh. industries. - p. doyer. me'
chanical engineer. Vin. trade. -prop. dr. h.blink.
ix. pishekies. - dr. p. g. van
tienhoven.
x. currency and banking. -
paul sabel.
xi. holland on the seas. -
j. h. cohen stuart. xh. ports and waterways. v. j. p. de blocq van kuffeler. civil engineer.
xiii. wh at to see in the ne¬
therlands prom an engineer's point of view. - r. p. j tdtein nolthenius. civil engineer.
XIV. enginrers and contrac-
tors. - r. p. j. tutein nolthenius. civil engineer.
xv. education. -J.c. ligtvoet.
xvi. science.
1 dniversities. - dr. p. c. mol-
huysen.
2 theological in8truction.
prop. dr. l. knappert.
3 a revlew of the law. - dr. j.
van kuyk.
4 medical science. - prof. db.
e. c. van leersum. 6 facdlty of mathematicsand natubal science. - dr. J. a. vollgraff.
6 MATHEMATICS. - PROF. DR. J.
CARDINAAL. 1 PHYSICS - DR. J„ A. VOLLGRAFF.
8 a8tronomy. - PROF. DR. w. DE
SITTER.
9 MINERALOGY, GEOLOGY AND
RELATBD BRANCHES OF SCIENCE. - PROF. J. VAN BAKEN.
10 BOTANY. - DR. TH. VALETON.
11 ZOOLOGY. - DR. A. SCHIERBEEK.
12 chemi8try.- DR.W. P. JORISSEN.
13 clas8ical LITERATURE. - DR. P.
C. MOLHUYBEN.
14 ORIENTAL LITERATURE. - C. VAN
ARENDONK. 16 NETHERLANDS UTERATURE. -
DR. H. J. A. ruy8. 16 Hl STORY. - PROF. DR. P. J. BLOK. XVII. MENTAL, RELIGIOUS AND SOCIAL FORCKS. - PROF. DR. H. BAVINCK. XVni. LITERATURE. - JOH. DE MEESTER.
XIX. MUSIC. - S. VAN MILLIGEN.
XX. FINE ARTS. - C. VETH.
XXI. ARCHITKCTURE. - A. W.
WEISSMAN. ARCHITECT. XXEt. PUBLIC HEALTH. - DR. M. w. PIJNAPPEL.
XXIII. SPORT. - JONKHEER JAN
PEITH.
XXIV. THE WOMAN's MOVEMENT. -
DR. 'MIA BOISSEVAIN.
XXV. THE PEACE MOVEMENT. -
JONKHEER DR. B. DE JONG VAN BEEK EN DONK.



WHAT TO SBE IN THE NETHERLANDS PROM AN ENGINEER'S POINT OF VIEW
BY
R. P. J. TUTEIN NOLTHENIUS,
FORMERLY CHLEF ENGINEER IN THE ROYAL "WATERSTAAT" CORPS, M. AM. SOC. C. E., MEMBER ROYAL NETHERLANDS INST1TÜTE OF ENGINEERS.
CONTENTS.
I. How the Land was Reclaimed 4
II. Dikes and Defences Against the Sea ..... 23
III. Rivers, Canals and Harbours 37
IV. Fresh Water Supply and Sewage Disposal. . 52 V. Deep Foundations 60






WHAT TO SEE IN THE NETHERLANDS F ROM AN ENGINEER'S POINT OF VIEW.
INTRODUCTORY.
For the benefit of his American fellow-engineers, the author will try to condense into five short chapters the matter of as many volumes. This naturally calls for a merciless handling of the pruning-knife. But the writer knows that the American mind is as fertile as the American soil, and as a lopped tree sprouts with the more vigoür, so the natural genius of the reader will easily supply what is wanting.
Moreover, as this booklet is only intended to stimulate the reader to visit the Netherlands, more complete information might frustrate its purpose and, on the contrary, jnduce him to stay at home. *)
The author gratefully acknowledges the kindness of Mr. E. J. Labarbe, British Vice-Consul at Amsterdam, in correcting his English, and desires to thank Messrs. Bos, Jolles, de Blocq van Kcffeleb, Pennink, Bamaer and Wortman for revising data.
3



CHAPTER I.
HOW THE LAND WAS RECLAIMED.
1. Hydranlic Condition of Holland (Waterstaat).
2. Origin of the Polders.
8. The Conservancy Board (Polderbestuur).
4. Drained Lakes (Droogmakerijen).
5. A Peat Pit in Exploitation: the Bullewijker Polder.
6. Significance of Amsterdamsch Peil (AJP. and N.A.P.).
7. Drained Lakes nearBotterdam: Alexanderpolder and Zuid" plaspolder.
8. Haarlem Lake Polder.
9. Combination of Polders (Waterschap).
10. Larger Combinations (Hoogheemraadschap).
11. Bhineland (Bijnland).
12. Infiltration of Water (Kmet): Bijlmer Lake, Bethnne Polder, Naarden Lake, Betuwe.
18. The Passing of the Netherlands Windmill: the Hercules Motor.
14. Various Methods of Lifting Water (Bemalingswerktttigen),
Settling and Sinking of the Soil. 16. Scoop Wheels (Schepraderen).
16. Automatic Electric Plant.
17. Proposed Draining of the Zuyder Zee.
18. Proposed Draining of a Part of the Zuyder Zee, called the Wieringen Lake.
19. Parcelling ( Verkaveling).
1. HYDRAULIC CONDITION OF HOLLAND (Waterstaat).
The attention of the reader is first directed to the hydraulic condition of that part of the Netherlands which the inhabitants have wrested from the sea.
About 3,000 square miles (almost the entire western portion of the Kingdom) lies below the mean high water level of the sea. It required the incessant labour of countless generations of Netherlanders to change the fever-stricken fens and lonesome lakes into fertile pastures, world-famous 4



for their cattle-breeding qualities. Once the most desolate province of the Netherlands, Holland is now the most densely populated and the wealthiest. Itsfame eclipses so entirely that of the other parts of the Kingdom, that to most foreigners Holland is synonyrnous with the Netherlands.
This change in the fortunes of Holland is the outcome of Netherlands hydraulic engineering. But not only the engineer will here find ample matter for instruction. The historian and the legislator will also reap a rich harvest of information in the Netherlands polderland.
The struggle against Spain (so brillantly described by Motley) and against Louis XIV of France (in the XVII,h Century) would not have ended in victories if the hydraulic condition of the country had not proved a most powerful and reliable ally to the feebly-armed Republic.
Hence it is not surprising that the rules which our forefathers laid down for the maintenance of the hydraulic status of the country, are still living law and scrupulously followed.
Waterstaat signifies literally "Hydraulic status or condition." Rijkswaterstaat signifies "Hydraulic status of the Kingdom." Ingenieurs van den- Rijkswaterstaat (Royal Corps of the Waterstaat) are the civil engineers, in the service of the State, who control the general hydraulic condition of the Netherlands. In each of the eleven provinces a separate body of engineers supervises the hydraulic status in detail. They are called Ingenieurs van den Provincialen Waterstaat.
2. ORIGIN OF THE POLDERS.
The Roman author Pliny describes in the most vivid language the miserable condition of the first iuhabitants of Holland. In his times no dikes kept the fioods out; the natives housed on artificial knolls (Netherlands pol or potte, plural pollen) or on the top of low hills. Twice a day the environing plains were submerged. When the tide was in, their huts seemed to float, and they had the appearance of stranded vessels when the flood retired.
5



Christianity bringing civilisation, the inhabitants ameliorated their condition by embanking the land around their huts. Their dwelling on the knoll or pol naturally formed the centre of the reclamation, and this led them to give to the whole the name of polder (plur. polders1).
At first only small tracts of land were enclosed, and many polders still cover only a few acres. Larger polders were gradually formed by combining smaller ones. (The original boundaries can often be traeed). At last, emboldened by success, broader surfaces were embanked at one time.
3. THE CONSERVANCY BOARD (Polderbestuur).
By and by the Netherlands lowlands were covered by the present complete system of polders 2). These still boast their time-honoured administration, presided over by a Dijkgraaf (lit. Count of the Dike), while the other members of the board are called Heemraden (lit. Homestead Councillors)
The Conservancy Board not only looks after the hydraulic conditions of the polder, but often takes charge of the roads Sometimes seemingly incongruous tasks are laid on its shoulders — last vestiges of conditions obtaining in a period when no other political bodies were known on our soil. Even the choice of a Dominee (Protestant parish minister) is subject in some polders to the approval of the Board.
4. DRAINED LAKES — Droogmakerijen) — lit. dried lake or pool; the word lake or pool, which completes the sense, being dropped.
These are the most interesting polders from an engineer's point of view. They are generally drained peat-pits, often of considerable area.
As fuel was always scarce in Holland, the inhabitants
In the sequence the Netherlands plural will be indicated by brackets.
2) A vivid description of Netherlands polders and their products is given by Mr. J. W. Robertson Scott, in A Free Farmer in a Free State. London, W. Heineman, 1912.
6



were forced to delve for peat to burn. Peat was found in immense quantities to a considerable depth, in thestagnant waters eastward of the North Sea coast, which is formed by a row of sandy hills ordunes (Netherlands duinen). When all the peat was delved, and the subsoil laid bare, it paid to drain the pit, as the substratum was mostly fertile sea-clay. The new polder, formed in this way, only differs from those of earlier formation in its water-level lying on a lower pland This made the draining more difficult, and formerly, when only windmills drained the polders, a number of these built in an ascending row often proved necessary; the windmill in the polder lifting the water to the level of the next windmill and so on, till at last the water was lifted to the level of the adjoining river.
6. A PEAT PIT IN EXPLOITATION: THE BOLLEWIJKER POLDER.
A droogmakerij in formation may be visited in the proximity of Amsterdam. The Bullewijkerpolder near the village of Ouderkerk on the Amstel is being gradually changed into a peat-pit by the delving of the peat. This is done by machinery.
A certain sum per acre is laid aside in order eventually to defray the expenses of draining. The Government fixes this sum, and care is taken that this money, called veengeld or slikgeld (fen-money or mud-money), is prcperly administered. The money is deposited in instalments; nothing is paid if no peat is delved, but the total area must be stripped of peat within a certain number of years. Otherwise the ownership of the sub-soil would be of no value to the ingelanden ^at.: owners of land in the polder) who, having dug off their own peat, must await the clearing of the entire area before they can begin to exploit the subsoil.
6. SIGNIF1CANCE OF AMSTERDAMSCH PEIL (AMSTERDAM LEVEL).
Before proceeding, it is necessary to explain that in the Netherlands, and also in adjacent parts of Germany, the
7



datum-plan e or basis for the measurement of heights, is tbe mean high-water level at Amsterdam, as it was when the harbour on the Zuyder Zee was still in open communication with that sea (an inlet of the North Sea).
This level is called Amsterdamsen Peil, the mark being abbreviated: A.P. Some years ago it was observed that many of these marks, spread over the country, incorrectly indicated this plane, partly on account of disturbances in the subsoil, partly by carelessness in the renewal of wooden gauges. A general revision was therefore ordered, and now the new marks are distinguished froui the old ones by the letters N.A.P. (New Amsterdam Peil or Level).
7. DRAINED LAKES NE AR ROTTERDAM.
The Alexanderpolder is a fair example of a droogmakerij. It was drained in 1874, and has an area of 7,370 acres. The water level is kept at 21V2 feet below N.A.P. Four centrifugal pumps lift the water to an intermediary canal, from which it is discharged into the river by one centrifugal pump. The annual expenses of the polder are % 1.94 per acre.
Near to it — also within easy distance from the town of Gouda — lies another remarkable droogmakerij, drained in 1839, called the Zuidplaspolder (polder of the southern lake) of an area of 10,285 acres, where the water level is kept at 193/4 ft. below N.A.P. The polder is drained by twoplants: beneden stoomgemaalfenj (lit.: lower steam mills). These lift the water into an intermediary canal, drained by two other plants: bovenstoomgemaalfen) (upper steam mills). Formerly the lower steam mills were provided with Archimedean screws — Vijzel(s). These are now replaced by horizontal plunger-pumps. In the upper steam mills scoop wheels are installed which discharge the water into the river. The annual expenses of the polder work out at $ 1.78 per acre.
8



8. POLDER OF THE HAARLEM LAKE. (Haarlemmermeerpolder).
This is by far the most interesting droogmakerij. (See plate I).
PLATE I.
In ancient times three small lakes existed near the to wn of Haarlem. These gradually merged into one, their banks — consisting of peat — continually eroding. The large lake became a constant danger to the environing country, as the erosive power of the waves increased with the broadening of
9



its surface. Betweeu the 13th and the 19,h century 19,200 acres were devoured hy the waterwolf (a Netherlands word that needs no translation), so that the Government decided (in 1839) to drain the lake. This then assümed an oblong shape; its length being 14V2 miles, its greatest width ö1^ miles and total area 41,640 acres.
It was calculated that the draining of the lake and adjacent smaller surfaces, forming a total of 45,000 acres, by 114 windmills would cost a million dollars more than if the drainage were effected by three steam pumping plants of 400 I. H. P. each. The working expenses would also be heavier. Steam pumps were therefore installed, though pumping by steam on so large a scale was then a novelty.
An English firm contracted for the supply of three plants of 350 I. H. P. Each plant consisted of a vertical single-acting condeusing engine of the Cornish type; this was placed in the centre of the engine room, and surrounded by a ring of vertical pumps, lifting the water 15^2 foet. One plant still serves as emergency plant (it is called the Cruquius, after a famous Netherlands engineer). In one of the others (the Lyndbn) the machinery was replaced in 1913 by two steam engines of 600 I. H. P., each working a centrifugal pump. Centrifugal pumps were recently installed in the third power house (the Lekghwater) which are driven by Diesel engines *).
The lake was first surrounded by a drainage canal called the ringvaart (lit.: ring canal) in order to collect the water, which flowed freely into it from the surrounding country (dimensions: width 140 ft. on the surface, 95 ft. at the bottom, depth 10 ft.). The excavated soil (peat) served as an embankment on the inner side of the canal, to keep out the floods.
The bottom of Haarlem Lake lay 14 feet below N. A. P.
■•) A description, togeth er with drawings of the old engines, is to be found in " The Drainage of Fens and Low Cands" by W. H. Whekler, Spon, London & New York, 1888. Drawings ofthenewLynden plant are given in the second volume of the Netherlands work : "Polders en Droogmakerijen" by A. A. Beekman, the Hague, Van Cleef Bros, 1912. 10



The water level in the drained polder was fixed at 15i/2 below N.A.P. It contained 602,800,000 metric tons of water. To this were added by rainfall and infiltration 189,000,000 tons during the period of draining. It took 39 months to drain the lake, but the pumps actually worked during 191/2 months only, the engines being often stopped for cleaning the valves, etc. The draining was finally completed in 1852.
The expenses (including roads, etc.) amounted to $ 3,447,000, or $ 76.75 per acre. This was more than doublé the estimate, but fortunately the drained land (fertile seaclay) sold at higher figures than was expected, and left a deficit of only $ 1,103,000.
At present the population of the polder numbers 18,000, and the State taxes easily maker up the interest of that sum.
An exhaustive account of the vicissitudes of the polder during the period 1856 - 1906 was published by order of the Conservftncy Board. At first the drains and ditches formed a storage basin (boezem, lit.: bosom) of only 1/32 nd. part of the area of the drained land. This was insufficiënt to collect the rainfall and caused a rapid and injurious rising of the water in the ditches. The storage capacity has therefore been gradually increased to an area of 1/20 th. part of the polder surface.
The annual expenses of the draining of the polder are $ 1.46 per acre.
9. COMBINATIONS OF POLDERS [ Waterschappen)].
In this almost level country the same main drain, or ancient river, often serves as an outlet for a number of polders. The same substantial dike also frequently protects a number of polders against the sea or the river floods. This community of interests led to a special form of corporation, called waterschapfpen) (obsolete word, originally signifying drain, but at present applied to tbe corporation which takes care of the common drain or dike).
While the general interests of the combine are cared for by the Waterschap or Conservancy Board, the special
11



hydraulic requirements of each polder are attended to by special polder boards.
10. LARGER C0MBINATI0N8 [Hoogheemraadschappen)'] : lit., High Homestead Councillors' Corporation].
This is the title given to the most important combinations of polders. The President of the Board (Dijkgraaf) ia appointed by the Queen, which is also the case with the Presidents of Waterschappen, whose dikes defend the country against the floods of the principal rivers or against the sea.
Formerly these high and mighty Boards enjoyed extensive powers, and their gallows, whipping posts and pillories adorned the dikes in an ominous fashion. The Revolution of 1795, however, swept away those implements of rather arbitrary justice. The lower judicatory functions were retained by the Boards up .to 1841. At present infractions of the by-laws, keur(en), made by the Hoogheemraadschappen, are tried by the ordinary courts. And these corporations, once so powerful, are reduced to imposing fines of not more than ten dollars and inprisonment not exceeding three days. Even in order to inflict these small penalties the Board must call in the aid of ordinary justice. The criminal law of course now provides against the graver offences formerly punished by the keuren.
11. HOOGHEEMRAADSCHAP RIJNLAND (Rhineland because formerly the Rhine flowed through it).
This is by far the most important combination of polders. The Haarlem lake forms part of it. The combination is formed of two hundred and twenty-two polders, with an area of 190,763 acres. Of this area, 80,000 acres are still drained by wind-mills. Within its limits are found thetowns of Haarlem, Gouda and Leyden.
The polders discharge their water in the main drains of the combination. These form a storage basin of 6,520 acres (including the pools, lakes and ditches, which are in open communication with such drains). This basin discharges its waters by gravitation through outlet-sluices located at four 12



points of its circumference. When the natural outfiow is stopped, pumping engines take over the task. An almost constant water level is maintained in the basin, which only varies between 1 ft. 10 in. below N. A. P, and 2 ft. 3 in. below N. A. P. The pumping is effected by means of scoop wheels, as these are generallypreferred to centrifugal pumps when the lift is small, as is the case here.
The four pumping plants have a total capacity of 1,335 I. H. P. The most powerful plant is situated at Katwijk on the North Sea (near Leyden). It is seldom used, as it comes cheaper to discharge the waters in the North Sea Canal near Amsterdam, the Government being obliged to maintain a low water level on that canal.
Rhineland discharged in 1913,155 million tons of water by gravitation, and 338 million tons by pumping. This was a normal performance, as the total rainfall in that year amounted to 2 ft. 3*/2 in., which is a fair average. The previous year (1912) 802 million tons had to be discharged, the largest quantity for many years. In summer, fresh water is drawn from the River Ysel near Gouda, in order to replenish the drains and ditches, as evaporation lowers the water level too much in the polders
In 1911, an excessively dry year, 197 million tons of fresh water were drawn from the River Yssel.
The annual expenses of upkeep of Rhineland are 27 dollar cents per acre. This is rather a srnall sum, but each polder also pays its private expenses. These vary with their hydraulic conditions. Some disburse less than 30 cents per acre; in droogmakerijen, however, the annual expenses amount to almost % 4 per acre.
12. INFILTEATION WATER. (Kwel, i. e. well, spring).
The cost of draining the infiltration water often proves a heavy burden upon droogmakerijen. For instance, in the polder of Bijlmer Lake (near Amsterdam) the kwel amounts to ten times the rainfall. (Area 1,359 acres). The Betfanne droogmakerij near Utrecht was in an even worse condition. The subsoil being extremely porous, it
13



autómatically drained the surrotmding older polders, wit! 1 a surface ten times its own. The discouraged proprietors of the droogmakerij decided to abandon the work, but the neighbours preferred to extend a helping hand, and now pay part óf the expenses 'of draining.
Most melancholy is the story of Naarden Lake (near Amsterdam). This lake of 1,482 acres was drained in the 17th century. Shortly afterwards the country was threatened with a Franco-German invasion, and the drained areaforming part of the defence system, it was flooded again. It remained in this condition till 1883, when a new company drained thé lake at the cost of $ 87,500.
The trials of the old company were imperfectly knowu, otherwise the new öne would have been less surprised when the bottom of the drained lake proved to leak like a sieve (only in the wrong direction) and let in the subterraneous water. The cost of maintaining the drainage proved excessive and the works were abandoned. The Society for the Preservation of Monuments of Nature bought the lake just in time to prevent Amsterdam from using it as a dumping ground. It now serves as a breeding place for wild waterfowl.
The kwel naturally varies with the conditions of the subsoil. Polders adjoining rivers suffer from it when the floods are high. An instance of this is seen in the island formed by the two branches of the Rhine, called the Betuwe. It is surrounded by dikes with atotallength of 111 statüte miles. Two tons of water per running foot of dike enter the Betuwe sübterraneously in twenty-four hours, when the level of the river rises to 8 feet above the level in the drains. In some parts of the Betuwe this rate is even doubled.
In the Haarlem Lake polder the kwel is rather small. Only one ton of water per running foot of dike, which is under a constant head of water of 14 ft. 10 in., enters the polder in twenty-four hours.
The kwel generally decreases in course of time. The subterraneous. veins are choked up with the mud and sand which the water carries.
14



13. THE PASSING OF THE NETHERLANDS WIN DMILL: THE NEW HERCULES MOTOR.
The typical Netherlands windmill is fast passing away. Np new ones are built, and the art of constructing these intricate wooden engines is almost lost.
The windmill of the ordinary type costs about $ 10,000 It develops 111/5 W.H.P. (Water horse-power measured in water actually lifted). It is estimated that one windmill suffices for draining 1,235 acres, when the lift is 4 ft. 2 in. However, as the wind blows with sufficiënt strength during 1,440 hours a year only, it is not always possible to maintain the desired water level.
Wind motors of the ordinary American type were introduced, but could not resisl the strong gales which often blow here. At present some sixty German Hercules motors — a heavier type — are succesfully used for the draining of small polders in the northern provinces, Friesland and Groningen. For this purpose these motors are coupled to Archimedean screws.
In this case screws, vijzel(s), are preferred to scoopwheels, because the ratio of efficiency is almost constant, althoügh the velocity of the motor varies. A good specimen of a Hercules motor is to be seen at Ulrum, a place not far from the town of Groningen. It drains 1,934 acres — rather a large surface for one mill, but the conditions are favourable, and the cost (including pile foundation) is $ 6,000.
14. VARIOUS METHODS OF LIFTING WATER [BemaUngswerJduigfen), lit. draining engines]. SETTL1NG ' AND SINKING OF THE SOIL.
As a rule the old Netherlands windmill was coupled to an Archimedean screw. When the lift was small, scoopwheels were also used. When steam was introduced, it only caused an increase of dimensions. Gradually, however, the centrifugal pump came into favour and now generally prevails.
One of the many reasons for its being preferred, is the ease with which the centrifugal pump accommodates itself
15



to permanent changes in the water level of the polder. In droogmakerijen and even in ordinary polders, the soil settles, becoming moi'e compact by draining. This leads to a permanent lowering of the water level in the polder.
In the Beemsterpolder (a lake drained in 1612) the water level was lowered in 1632 one foot, in 1694 again 1/2 ft, and in 1847 another */« ft, or in all 2 ft.
The sinking of the subsoil by geological process also causes some trouble. Fortunately this process is very slow. In the last six centuries the Zeeland polders have subsided three feet (1/2 ft per century). This seems to be the actual rate of the sinking of the Netherlands coast, as calculated by M. Ramaer, an Éngineer of the Royal Corps of the Waterstaat. (Transactions of the Netherlands Institute of Civil Engineers, 1907/08).
15. SCOOP-W HEELS \Scheprad{eren)~\.
A fair example of a Government scoop-wheel plant is found near Amsterdam at Schellingwoude, on the Zuyder Zee. (Small steamers ply hourly from Amsterdam to Schellingwoude). The plant consists of three wheels of 28 ft. diameter and 10 ft. broad. The quantity of water lifted in 24 hours is 770,000,000 gallons, when the lift is 4 ft., and 440,000,000
A more recent Government plant on a smaller scale is found near Keizersveer. (A branch line of the railway from Rotterdam to Breda passes the town of Geertruidenberg, from which it is easily reached on foot). In 1897 extensive reliability trials were made by M. Jolles of the Royal Corps of the Waterstaat. The following figures are extracted from a paper published in ude Ingenieur" :
gallons when the lift is 7*/2 to 8^ ft. Ratio
W. H.P ï H.P.
640
900'
Pumping Engines of the Southern Canal.
Greatest diameter of the wheel 24 ft. 7 in.
Width of scoop 8 ft. 2*/2 in
Mean dip of scoop 4 ft. 8 in.
Meanlift 3 ft. 8 in.
16



Mean number of reyolutionsof tandem-engineperminute 54
„ „ . „ „ wheel 4
(this proved to be the most favourable speed per minute)
Quantity of water lifted per minute 276 metric tons.
„ ,. horse power water lifted
Ratior . -,. , , = 581/,.
horse power gross mdicated 'z
Coal consumed per W. H. P. per hour 3673 lbs.
Total cost of plant $45,000.
16. AUTOMATIC ELECTRIC PLANTS.
The visitor to Keizersveer can at the same time easily inspect the Government electrical pumping plants on the River Donge.
Some years ago the Government dammed the river Meuse (Maas) near Woudrichem, where it mingled its waters with those of the principal branch of the Rhine (Waal). A new outlet for the Meuse was dug from the town of Heusden to the town of Geertruidenberg and named Bergsche Maas. The hydraulic condition of the environing polders was completely altered by this deviation. A great number of them, which formerly discharged their water freely by gravitation, were now unable to do this, and the Government was forced to put up, and to maintain, a large number of pumping plants at its own expense.
The polders near Geertruidenberg on the river Donge are small and not inhabited, as their lëvels do not keep out the more important floods. Their only produce is hay. These polders are isolated by tiny tidal streams, which together form the river called Donge. These peculiar conditions made it necessary to drain each polder separately, and as the installation of so large a number of complete pumping plants, with residences for attendants &c, would have proved expensive, it was decided to erect automatically working centrifugal pumps, driven by electricity. A central electric power station supplies the current required.
Each pump starts automatically when the water level in its polder surpasses a certain mark, and it also stops automatically when the water has fallen to its former plane. Thirtytwo pumps drain as many polders (a total area of9,240 acres;
17



the area of the largest polder is 2,005 acres, and of the
smallest 25 acres). The pumps are of the Neukirch type (a
German patent), and deliver 213 tons of water per minute.
The installation cost $119,400 (including the steam generat-
ing plant, the electrical transmissions and the buildings).
water horse-power
Ihe ratio ^—~-n— — = 50 to 60 % with a
gross mdicated horse-power
lift of 4 ft. 11 in. to 6 ft. 7 in.
A similar combine of 23 pumps, delivering 243 tons of
water per minute, was soon afterwards erected by the
Government on the northern side öf the Bergsche Maas.
17. PROPOSED DRAINING OF THE ZUYDER ZEE.
The draining of this large gulf of the North Sea has engaged the attention of Netherlands engineers for half a century or more. A great many plans were brought forward, and some were almost commenced upon. The most recent plan was prepared by Dr. Lely, the present Minister of the Department of Waterstaat. This scheme (Platell) embraces the greater part of the Zuyder Zee. It differs also from former projects by considerably enlarging the proposed lake in the northern part and feeding it with fresh water (358,150 acres). This will prove of great benefit to some of the environing provinces, which at present suffer much from summer droughts. In former schemes the river Ysel*) (a minor branch of the Rhine) was shut out; now it will supply the fresh water lake. This lake will be located in the northern part, where the bottom of the sea consists of sand, which is of far less agricultural value than the sea-clay, which forms in other parts the bottom of the Zuyder Zee.
According to Dr. Lely's project, four polders will be formed, having a total area of 494,000 acres. Some years ago this plan was approved by a Government Commission, which introduced slight modifications. Part of this project was embodied in a Bill, which a change of Ministry, however,
*) There is an other river Ysel (mentioned on page 14) which flows through the Netherlands; it is of small importance.
18



caüsed to be dropped. Dr. Lely now being again in powef, this Bill will once more be presented to the Chambers, after the project has been brought up to date.
plate ii.
The costs were estimated at $ 53,250,000 or at $ 81,500,000 if compound interest (on aS^/obasis)isadded to the outlay. The first polder will be saleable in the 17th. year after the commencement of the undertaking, the fourth in the 36th. year.
19



If sold at $ 262 per acre,' the expenses will be entirely covered. They will probably make this price.
The enclosing dike or dam, running across the Zuyder Zee from the western coast of the pro vince of Friesland to the eastern border of North Holland, will measure 187a statute miles. (Estimated cost: $ 7,030,000. Including the outlet sluices, etc, $ 10,125,000). Its construction will take nine years.
(For further particulars see the next chapter).
18. PROPOSED DRAINING OF A PART OF THE ZUTDER ZEE, CALLED WIERINGEN LAKE.
With a view to acquiring experience in the reclamation of the Zuyder Zee, a former Ministry, in a Bill presented in 1907, suggested the draining of one of the above-mentioned polders. (The great dike across the Zuyder Zee was omitted in this project). The polder, situated between the coast of North Holland and the island of Wieringen, would cover 40,590 acres of saleable land, costing $ 348 per acre — or with compound interest added, $ 425 per acre — which would also be its selling value. The annual expenses were estimated at $ 2.09 per acre. It would take four years to construct the enclosing dike (10 '/2 miles, at $425 per running foot) Five steam pumping plants (2,125 W. H. P. at a cost of $ 563,000) discharging the water directly into the Zuyder Zee, would drain the polder in three years. The water level of the polder was to be fixed at 23 ft Vj2 in. below N. A. P. The engines were calculated in accordance with the customary rule that twelve water horse-power can drain 2,500 acres, when the water is to be lifted not more than three feet.
Three years after the completion of the draining,, the land would be ready for sale. Some time must then elapse before the soil is solid enough for digging ditches and tracing roads This work is called parcelling.
19. PARCELLING (Verkaveling).
The parcelling out of Wieringen polder was carefully planned by a commission of well-known experts, and differs 20



from former parcellings in so much as the proposed plots were reduced to half the usual size. Wieringen polder was to be divided into rectangular divisions of a length of 2,186 yards, and of a breadth of 1,093 yards, by a system of mainroads, hoofdwegfen), and country roads, landweg (en). All these roads were to be metalled (macadamed).
Each plot, Jcavel(s), was to be quartered (5461/2 yds X 546V2 yds) by a main drain or canal, hoofdtocht(eri), running parallel to the main road, and a cross drain, kruistochten), running parallel to the country road; each of these subdivisions in its turn to be halved by a ditch, sloot(en), running parallel to the main drain.
On either side of the roads ditches were to be dug, and every plot would also be divided by a ditch running parallel to the other ditches. In the Netherlands subterraneous draining is scarcely ever applied; open drains are preferred, as they also augment the capacity of the boezem (bosom: the emergency storage basin). This basin is of great importance, especially in polders with small pumping power, where otherwise a heavy rainfall would raise the water level in the ditches to an undesirable level*).
The parcelling-out proposed by the commission of experts, is shown on plate III. Principal dimensions: main roads 39*/3 ft., country roads 29*^ ft-, main drains or canals (measured at the water level) 401/3 ft., depth 6 ft. 11 in., slopes l*/2 :1. Cross drains: 29 ft. 2 in., depth 4 ft. 3 in , slopes IV2 :1) ditches 6y2 ft-, depth 3 ft. 3 in., slopes 8/4 : 1. Total emergency storage capacity 4.3 % of the total polder area.
As the draining of a larger part of the Zuyder Zee is now again being considered, this Wieringen scheme was dropped.
*) Formerly the pumping capacity was considered sufficientwhen the pumps could keep ahead of a daily rainfall of 21/, in. As a matter of fact snch delicate crops are now cultivated as demand a more constant water level, so the pumps must be able to keep ahead of a rainfall of 4 inches per day.
21



PLATE III.
p p
Eig. 2.
Taken from the work: Beekman, Waterbouwkunde. Published by Gebr. van Clkeff, The Hagu



CHAPTER II.
DIKES AND DEFENCES AGAINST THE SEA.
1. River Dikes.
2. Wells, wel(len); Why Dikes Subside; the Floating Sand in Zeeland Canses a Dijkval (fall of the dike).
3. Defence of the Slopes.
4 Sea Dikes: Petten Dike (Hondsbossche) near Alkmaar;
Westkappel Dike near Flnshing. B. System de Mtjralt.
6. Groynes or Sea Dams at Scheveningen, near The Hague.
7. The Proposed Dam in the Zuyder Zee.
1. RIVER DIKES.
As was pointed out in the first chapter, Netherlands dikes date from time immemorial. Their cross-section has, however, undergone many changes in the course of centuries. Formerly the floods were kept out more easily than is the case at present. In ancient times the German Rhine, when rising above its banks, flooded large tracts of land, which thus acted as a temporary storage basin. At present the German portion of the Rhine is well defended by levees, and the floods speed seawards as in a gutter. It was eventually found necessary to raise the crest of the Netherlands dikes and at the same time to augment their dimensions. A cross-section of the most important river dike in the Netherlands is shown on plate IV. The changes in profile and height effected in course of time are clearly shown.
This cross-section is taken at Vreeswijk on the Rhine (near Utrecht), where the canal to Amsterdam (called Merwede Canal) branches off from the Rhine, which in its lower course is called Lek. This dike is of vital importance. Ifa breach occurred near this spot, five hundred thousand acres
28



PLA.TE IV.
Hg. f.
Dike on the River Lek near Vreeswijk. Shaded cross-nise: dike in 1751. Finely shaded: dike in 1879.
Grossly shaded : reinforcement of 1880.
Very grossly shaded : reinforcement of 1884.
°—o—a- reinforcement proposed in the 18th centnry.
b- highest river level observed in 1761.
c- highest river level observed in 1885.
Dike on the river Lek near Vianen.
Fig. 2.



would be flooded, and eighteen cities and 180 villages would suffer more or less (Utrecht, Amsterdam, Leyden, etc). The only compensation would be the thorough scouring of the canals, gracht(en), of Amsterdam. This was the case in 1747, when the country was flooded for the last time. Fortunately the damage done was small, as the river subsided shortly after.
The cost of keeping dikes and levels in a state of repair, falls on the adjoining polders and is controlled by the Province and the State. These can order works, if judged necessary, and even execute them at the expense of the landowners, if the Conservancy Board of the polder delays in obeying orders.
In autumn ample material is stored along the dike for raising coffer-dams, kistingfenj, on its crest, if necessary. When the floods rise above a certain mark, the Conservancy Board stations sentinels on the dike, and the Government orders the engineers of the Rijkswaterstaat (see Chapter 1,1) to reside temporarily in the towns and villages adjoining the river. These report daily to the Government, a special letter carrier collecting these reports and those of the polder board. This is called river correspondence (rivier-correspondentie). The same precautions are taken in spring, when the ice breaks up.
The law gives the polder board and the State engineers full power to act in cases of emergency. They are authorized to deraolish dwellings, when bricks or other materials are required for nlling breaches or stopping the wells, which spring up near the inner toe of the dike,
2. WELLS \wel(lenj].
If the floods last, the dike becomes soaked, and the pressure of the river water causes the formation of small veins of water in the body of the dike. The material of which the dike is built (generally sandy clay) is easily carried away; the veins widen, and at last a well springs up, generally near the inner toe of the dike. This is considered dangerous, especially if much sand is thrown up by the well, as
25



this indicates large veins, and the hollowing out of the dike. It often happens that the crest of the dike suddenly subsides, and unless precautions are taken (by raising the crest temporarily by means of coffer-dams, etc.) the nood overtops it and the whole body of the dike is carried away.
If feasible, large masses of gravel are thrown on top of the wells. In this manner the veins are prevented from carrying away the sand, as this gravel forces the water to now more slowly. For the same reason all the ditches near the inner toe of the dike are filled up, and the inner slope of the dike is weighted with clay in order to compress the water veins.
The crest of the dikes generally serves as a road way, and is metalled. This facilitates the transport of materials to the imperilled spots. By the constant passing of heavy conveyances the dike itself is compressed to a solid mass. The crest of the dikes having been gradually raised in the course of centuries, each layer is in this way firmly trodden in. This explains the extraordinary solidity of Netherlands dikes. They seldom give way, even when thoroughly soaked by lasting floods, provided only the subsoil (staal) is firm enough to support the weight of the water-laden mass.
In some parts of Zeeland, the subsoil is very treacherous. Thin layers of loose sand, called drijfzand (floating sand) often cause great damage. Under certain hydrostatic conditions this sand suddenly slides into the river, and then a large part of the dike sinks below the water level. Such an oocurrence is called a dijkval (fall of the dike).
This only occurs on the tidal rivers of Zeeland, which are, properly speaking, inlets of the sea.
8. PROTECTION OF THE SLOPES.
The outer slope of river dikes is generally unprotected. The grass-grown surface forms a sufficiënt protection when the slope is a gradual one (the most important dikes have a slope of 3 :1). Grazing on the slopes is fortaddén.
I When the floods are expected to damage the slopes,
26



they are protected by a temporary matting of straw or of brushwood, covered with bricks.
4. SEA DIKES.
The Netherlands sea dikes are for the greater part to be found in land-locked inlets, and nature favours the country by protecting its coast line (171 miles) byafringe of sandhills or dunes, duin(eri). These rise with an easy slope from a broad sandy beach, on which the waves break without causing damage.
This natural protection is wanting only in the island of Walcheren near the village of Westkapelle, in the south of the country, for a distance of 4,100 yards (Westkappelle dike), and in the north of the province of Holland, near the village of Petten, over a length of 6,000 yards (Petten dike).
Petten is easily reached from Amsterdam by taking the railway to Alkmaar. Westkappelle can be visited from Flushing (Vlissingen) or Middelburg. The two dikes have many points in common; it will therefore be sufficiënt to describe the Pettemer Zeewering (Petten Sea Defence).
This dike consists of loose sand; the crest rises to 198/4 ft. above the ordinary high water level (indicatedby the letters: V. Z. vol zee, full sea). The outer toe is protected by a layer of carefully set stones, from 5feetbelow V. Z to77a feet above V. Z. with a slope of 4 :1 (see plate V). Parallel to the toe, three rows of oaken stakes are driven into this slope in order to break the force of the waves. Next comes a grass-grown berm of clay, dS1,^ ft. broad, sloping 40 in 1. This berm forms the basis of the dike proper. The dike has an outward slope of 5 :1, covered with a facing of carefully set stones, to lö1^ ft. above V. Z.
One quarter of the length of the Petten dike belongs to the Government, and the other three quarters of it are maintained by the Conservancy Board of the Waterschap called the "Hondsbossche". Here the protection slightly differs from the above given description. (See also plate V).
At Westkapelle the same system isapplied. The waves
27



PLATE V.
Fig. 2.
Maintained by the Conservancy Board of Hondsbossche.



there have a greater destructive force, the sea being deeper near this coast: hence the stone casing is of heavier construction.
5. SYSTEM DE MURALT.
Much attention is now paid to defence works of concrete, especially since Jonkheer de Muralt (formerly
PLATE VI.
Fig. 1.
Defence Works of Concrete.
engineer to the island of Schouwen) began his experiments with this material.
In 1913 Jhr. de Muralt published a profusely illustrated pamphlet in which he describes his numerous inventions *). '.'
1) Dyk- en oeverwerken. (Defence Works on Dikes and Coasts.) I. Waltman Jr., Delft, 1913.
29



PLATE VI.
Fig. 2



In Zeeland recent floods have shown that the crest of many sea dikes was too low. The most economie way of raising the crest proved to be the forming of a concrete shield or screen on the top of the dike. This invention by Jhr. de Muralt is shown on plate VI, fig it When travelling from Flushing to Rotterdam, a long stretch of dike where this system has been applied, will be seen on the left hand, near the station of Vlake. The raising of the crest by 3'/3 ft. costs $1.34 per running foot. When the crest is to be raised 5% ft., the cost amounts to $ 2.44 per running foot. Attention is called to the fact that wages are lower in the Netherlands than in the States. At Amsterdam, for instance, a bricklayer earns 14 to 19 dollar cents per hour, a carpenter 13 to 14 dollar cents. The working hours are 50 per week.
Jhr. de Muralt's system for protecting the outward slopes of dikes is also shown on plate VI, fig. 2. The concrete slabs are formed on the spot. They are kept in position by overlapping transverse beams of armoured concrete. The seams between the slabs are filled with asphalt (Cost approximately $ 1.33 per square yard).
On less exposed spots, slabs of concrete are laid down and kept in place by concrete bolts (plate VII).
A recent invention by Jhr. de Muralt aims at doing away with the world-renowned and widely-used Netherlands mattresses of brushwood. It is superfluous to describe these mattresses of brushwood, as they are well known in the States *).
The mattresses devised by Jhr. de Muralt consist of quadrangular concrete slabs measuring 3 ft. 2 in, and 5 to 6 inches thick, and weighing 550 to 660 lbs. apiece. They are armoured. An iron loop protrudes at each corner. The four loops of four adjoining slabs are screwed down together by an iron bolt The upper end of this bolt is eye-shaped.
When the mattress is ready (breadth 193/4 ft to 46 ft,
i) A detailed account of Netherlands mattresses is found in the Report on the North Sea Canal of Holland and the improvement of navigation from Rotterdam to the sea, by brevet Major-Q-eneral .1. Gr. Barnard (Professional Papers of the Corps of Engineers, U. S. Army, 1872, No. 22).
31



Mg. 2



length generally 72 ft.) two pontoons are floated over it at high tide. These coupled pontoons rest on a temporary framework when the tide subsides, and do not touch the mattress. As many sheaths are spared in these pontoons as the mattress possesses slabs. Through each of these sheaths a steel cable is lowered, ending in a hook. This hook catches the eye of the iron bolt at the corner of the slabs. When the tide comes in, the pontoons are floated to the spot where the mattresses are to be sunk. The inventor estimates the costs of these mattresses to be 2/3rds of the cost of ordinary mattresses. (These cost about $ 1.33 per square yard). Opinions differ widely as to the desirability of these concrete mattresses The time elapsed since the first application of the method is too short for a definitive verdict.
The Royal Netherlands Institute of Engineers awarded the Conrad Medal to Jhr. de Mubalt for his many inventions.
6. GROYNES OR SEA DAMS. [Hoofd{eri)].
To protect the sandy beach on the North Sea coast of the Netherlands from the action of the tides, groynes or sea dams have been constructed at fixed intervals. The tidal currents run parallel to the coast, and are rather feeble. The flood current, coming from the Channel, has a maximum velocity of 3 ft. per second. The ebb current is still weaker. These velocities however suffice (in combination with strong soüth-westerly gales) to gradually erode the sandy beach, which consists of extremelyfine sand. The groynes are made of brushwood, carefully covered with a layer of stones. Of late years concrete has also been applied, and specimens of it are to be found near Petten, while at Scheveningen (near The Hague) the visitor will find ample occasion to study the ordinary brushwood construction. A detailed account of the Netherlands shore and its protection is found in Stranden en Strandverdediging (Coasts and their Defence), by Dr. Wentholt, Eng. R. C. of the Waterstaat, Waltman, Delft. (A copy of this work was presented to the Am. Soc. of C.E.).
33



7. THE PROPOSED DAM IN THE ZUYDER ZEE.
Plate VIII, fig. 1, illustrates the cross section of the darn projected across the Zuyder Zee, which plan was approved in 1894 by the Committee appointed by the Government to report on the drainage of this inlet of the North Sea.
In the first place an artificial island will be dumped midway between the coast of North Holland and the coast of Friesland. This island will be provided with harbours for the working craft. The dam will then be started simultaneously from both sides of the island and from the two coasts. First a small dam. made of brushwood mattresses will be sunk. When raised over a certain length above ordinary high water level, powerful suction dredgers will form the body of a more substantial dike and raise the crest to 81/, ft above the highest floods known.
Eastward and westward of the island two gaps are to be left in the dikes (each of which is 9,000 yards long) and through these gaps the waters of the southern basin will be discharged when this is filled by northern storms, fiooding the low crested brushwood dams. Finally, the gaps are to be closed by means of brushwood mattresses.
This method of closing a dam or dike is usual in the Netherlands, but requires great foresight and skill.
Another method has been proposed by a Committee of eminent engineers and contractors, whom a society formed to promote actively the drainage of the Zuyder Zee had invited to reconsider the construction of this dam. The Committee proposes to use concrete caissons.1). (See Plate VIII, fig. 2). In the two gaps, to be left in the Zuyder Zee dam, a row of caissons will be placed at intervals of about the length of the caissons. These caissons are 164 feet long and 161/»
*) Iron caissons filled with concrete were recently used with great snccess at Scheveningen harbour. An illustrated description of these caissons is found in the paper of Mr. Wortman, Eng. R. C. Waterstaat, presented to the International Congress of St. Louis, 1904, which cover the crest of the snbjacent sand dam. (This snbmerged' sand dam is to be raised in the shortest possible time by powerful suction dredgers).
34



PLATE VHI.
Fig. 2.
Taken from the Work: "De Afsluiting en Drooglegging der Zuiderzee." Edited by the Zuiderzee-Vereeniging.



feet broad and also 16V2 feet high. They will be placed at intervals of 146 feet on layers of brushwood mattresses. When this row is put in place, a second row of caissons of the same dimensions placed backward of the first row will close the intervals.
A minority of the Committee did not approve of the proposed method and preferred the older one. It will, however, be possible to make a trial on a smaller scale. The draining of the Zuyder Zee also necessitates a dam between the coast of North Holland and the island of Wieringen, where the currents are rather strong Here a gap in the dam of a length of 654 yards will have to be closed in the same way. The cost of these caissons is estimated at $ 30.5 per running foot1;.
d) Similar caissons were constrncted for the quays of tbe harbonr of Rotterdam, and by a Netherlands firm of contractors for the harbonr of Talcahuanó (Chile).
36



CHAPjTER III.
RIVERS, CANALS AND HARBOURS.
1. The Three Principal Rivers: Rhine, Medse, and Schrldt. (Iljfn, Maas, Schelde).
2. The Principal Branch of the Rhine, called the Waal. 8. How the Formmg of Ice-jams is Prevented.
4. How the Depth of the Waal was Increased.
5. How Rotterdam is Reached from the Waal.
6. The Waterway from Rotterdam to the North Sea.
7. The Hook of Holland.
8. The Waterways of Amsterdam and the Port of Ymniden.
9. The Merwede Canal. The Poor Condition of the Subsoil.
10. The New River called the Bergsche Maas.
11. Canals through the Moors.
12. How the Moors are Attacked and the Subsoil turned into Arable Land.
1. THE THREE PRINCIPAL RIVERS.
The vital importance of the Netherlands network of rivers and canals is strikingly illustrated by the fact that the railways must content themselves with extremely low rates in order to compete with the waterways. The freight rates are a third of those charged in England, and are also much less than those of Belgium and Germany.
Three large rivers find their way to the sea through the Netherlands: the Rhine (Rijn), the Meuse (Maas) and the Scheldt (Schelde). The Rhine is by far the most important. Soon after passing the frontier, this river splits into three branches. Of these the Waal takes two-thirds of the waters
37



and nearly all the international traffic. For this reason only this branch will be considered in the following pages *).
2. THE PRINCIPAL BRANCH OF THE RHINE: THE WAAL.
The maximum discharge of the River Waal is 218,900 cubic feet per second and the minimum is 21,200 cubic ft. per second. The mean fall is about 0 58 ft. to the mile The rains in Germany cause the river to rise in winter, and the melting of Alpine snows cause summer floods, which often inundatè the uiterwaardfen) (lit. outlying lands). These are broad stretches of meadows, protected by low crested levels only, which are totally submerged in winter.
The mean velocity of the river varies fróin 2*/4 ft. per sec. to 5^2 ft- per sec.; the winter floods cause the water to rise 141/2 ft. above the lowest summer level The floods carry much gravel and sand, and deposits are formed by reason of the slowness of the current.
The number of vessels navigating the Waal and their tonnage are steadily increasing. In 1913 26,990 steam boats passed to and from Germany — mostly tugs — and 69,778 sailing vessels and barges, carrying 45 million tons of merchandise. By far the greater part of the goods are loaded at Rotterdam or destined to that port, this being the port of transhipment for sea-going vessels.
The largest quantity of goods is conveyed in barges, the dimensions of which arè steadily increasing. At present the maximum dimensions are: length 400 ft., beam 46'/4 ft., draught 9*/3 ft., dead-weight capacity, 3,583 tons. PracticaUy all the river craft are built in Netherlands yards, although a large number are owned by Germans.
To avoid the cost of transhipment, German shipowners
*) More complete information, also with regard to the other branches, will be found in the paper presented to the St. Louis Congress 1904, by Mr. Marinkellb, Eng. R. O of the Waterstaat. (Trans. Am. Soc. C. E.). Also in the papers presented to the Philadelphian Intern. Navigation Congress, 1912, by Messrs. Gockinga, Baucke, van Konijnenburg and van Panhüijs, Engineers of the Royal Corps of the Waterstaat. 38



have built sixty sea-going river steamers. These sail from Cologne to England and to German sea-ports. Their dimensions are: length 239V2 ft., beam 343/4 ft., draught 14V3 ft. Load (when on the river) 1,880 tons. Engines 600 I. H. P. When the river is low, up-going vessels partially unload at Rotterdam.
3. HOW THE FORMTNG OF ICE-JAMS IS PBEVENTED.
Before 1850 Netherlands rivers were in a bad condition and little was done to improve them. Numerous shoals, sharp river hen ds and the system of lateral overflows, zij deling sche overlaatfen), facilitated the forming of ice-jams.
These overflows were lateral gaps in the levees, allowing the floods to spread over large areas, in order to prevent the water rising to a dangerous level. Of course, such gaps were only made at spots were the floods could do small damage, and where the land could afterwards be drained by gravitation.
This system, however, had great disadvantages. It weakened the current in the river proper, and lessened the water pressure against the ice-jams. This caused ice-jams to settle and retarded their breaking-up. At present most of these overflows have been closed; the dikes are strengthened and their crests raised where necessary.
Ice-jams frequently formed where the river split into two channels, as this weakened the current. For this reason all doublé channels have been changed into single ones by damming up the less important one.
Sudden changes in the width of the river had the same effect, and this was also the case with sharp bends. The width of the river has therefore bëen regulated by groynes, made of brushwood and covered with rubble, and the sharp bends have been systematically eased. Experience has fully proved the efficacy of these measures; ice-jams are now things of the past.
39



4. HOW THE DEPTH OF THE WAAL WAS 1NCREASED.
In the middle of the 19th century an international agreement fixed the general dimensions of the Rhine and its outlets. The mean water level of the river at its minimum discharge, düring a consecutive period of ten days, was taken as the basis for all improvements. It wasresolvedto improve the river to such an extent that at this level a depth of 9 ft. 10 in. of water would be available from Cologne to the North Sea. The German part of the Rhine did not fulfil these conditions, and in many places a depth of only 4/3t ft. to 58/t ft- was found in the channel. The Netherlands part of the Rhine and the Waal were also in an unsatisfactory condition.
In those days (1850) no accurate river maps existed, and the science of river improvement was still in its infancy. In consequence the first attempts to obtain the desired depth failed in some ways. It was then resolved to reduce the width of the Waal to 1,180 ft., but in 1889 the summer bed had to be narrowed to 1,017 ft. On part of the course the curves were modelled in accordance with the rules laid down by the famous French engineer M. Fargue.
These measures did not give entire satisfaction It was therefore decided (in 1909) to reduce the width of the sum mer bed to 863 ft., to ease the bends, etc. The direction of the groynes was also changed; formerly they were set perpendicularly to the axis of the river channel, at present they incline 70° to 80° in an upward direction. Their crest Hes 18 inches below the ordinary summer level.
B. HOW ROTTERDAM IS REACHED FROM THE WAAL.
The River Waal nominally ends near the small town of Woudrichem, where formerly its waters mingled with those of the Meuse. A short distance farther down the strearn divides, and only the north-westem branch is of importance for navigation. It flows past the towns of Gorinchem and Dordrecht. From the latter city a narrow but deep stream, called the Noord, leads to the branch of the Rhine which
40



flows past Rotterdam and there takes the name of Nieuwe Maas (New Meuse).
(This New Meuse does not contain a drop of water from the Meuse. Its name is however historically justified, as in ancient times the Meuse flowed in that channel).
From Woudrichem to Rotterdam the required depth of 9 ft. 10 in. is easily maintained, as here the scouring influence of the tides is feit.
6. THE WATERWAY FROM ROTTERDAM TO THE NORTH SEA.
A most dimcult problem awaited the Netherlands engineer westwards from Rotterdam. Eastwards from that town only rivercraft had to be provided for, but modern sea-going vessels required greater depth than the river could offer. One was at a loss how to meet the difficulty when, by a stroke of genius, a young and still unknown engineer of the Royal Corps of the "Waterstaat, P. Caland, found the solution. During his residence at the town of Brielle he was impressed by the amount of scouring power tidal currents acquire when guided in a proper manner. This is even the case when the tide range is small, as in the New Meuse, where the range is only 5 ft
In order to employ to the full the scouring capacity of the tides, M. Caland closed every byway of the stream, gave to its lower part a fan-like shape, and substituted for the crooked outlet near Brielle, a short cut through the immense shoal called the Hook of Holland.
M. Caland exposed his theory on the scouring power of tidal rivers in a paper presented to the Netherlands Institute of Civil Engineers. His idea still forms the basis of all tidal-river improvements.
7. THE HOOK OF HOLLAND CHANNEL.
The channel through .the shoal was extended into the North Sea by two low jetties formed of brushwood, reaching down to a depth of 23 ft. below low water. This depth was, in
41



PLATE IX.
16—20 feet tinder low water level. Over 24 vinder low water level.



1858, considered sufficiënt for the largest sea-going craft *).
The length of the northern jetty is at present 6,560 ft. The southern jetty was planned much shorter in order to force the flood current— running parallel to the coast in a northerly direction — to enter the river mouth. The width of the outlet was fixed at 2,952 ft. at the end of the jetties.
At first, however, the works at the Hook of Holland failed to a certain extent to give satisfaction The reason was a curious one. Fifty years ago Netherlanders were rather parsimonious, and M. Caland had to reckon with this propensity. So he estimated that the works would cost only two million of dollars and trusted to the scouring tides for the widening of his short cut through the shoal. He dug a channel of 164 ft. wide only, though the definite width was fixed at 2,300 feet.
Of course the tidal current in this narrow channel was very strong, for this channel formed the only outlet of the broad New Meuse. The current deepened the channel considerably, but refused to widen it. When the current reached the broad tranquil surface between the jetties, it slackened, and deposited the loose sand which it carried near the sea end of the piers. (Plate IX):
This deposit formed a bar of considerable dimensions, which was difficult to attack by dredging, the sea being very rough. In order to force the currents to scour away this bar, the southern jetty was gradually prolonged to a total length of 7,544 ft. (Cross sections of tbe jetties are shown on plate X).
This work proved a partial success only, and the same is to be said of the narrowing of the channel between the jetties by sinking a low dam at a distance of 700 ft. from, and parallel to, the southern pier.
Some years ago, M. Jolles, Eng. R. C. of the Waterstaat, then in charge of the works, called attention to the fact that by gradually prolonging the southern jetty, the original
A detailed account of this work is found in the report of Brigadier-General of the U. 8. A., J. Or. Barnard, already mentkmed. This eminent engineer fully approved of M. Calakd's plans.
43



idea of M. Caland had been abandoned, and that this explained the failure of the new improvements. The flood tide, instead of being intercepted by the northern jetty and forced to enter the river, was now deflected into the sea by the long southern jetty, which at present acts as a gigantic groyne, causing whirlpools in the river mouth.
In order to neutralise the effect of this extension of the southern jetty, M. Jolles proposed the construction of a low dam 2,300 ft. long, running parallel with the coast, at the sea-end of that pier. This would prevent the forming of secondary currents and normalize the influx of the tide. Actually a length of 950 ft. is raised till above the mark of high water, while the remainder lies about ten feet below low water mark. Various phases of the bar in the mouth of the river are shown on plate IX.
At the present day a depth is found between the jetties of 30 ft. 8 in., at ordinary low water, in a channel 4,000ft. wide, and the largest vessels ean enter the New Waterway at half-tide and sail up to Rotterdam ')•
8. THE WATERWAYS OF AMSTERDAM, AND THE PORT OF YMUIDEN.
To meet modern requirements, important changes were necessary in the communication between Amsterdam and the Rhine and the North Sea. A new canal, the Merwede Canal, connects Amsterdam with the Waal and also with the minor branch of the Rhine, called the Lek. A short cut through the sand-hiils connects Amsterdam with the North Sea near the village of Ymuiden.
The port of Amsterdam is described in N°. I of this series of booklets, while a detailed account of the harbour of Ymuiden was presented by M. Wortman, Eng. R. C. of
M. Jolles has written a paper on the waterway frorn the German frontier to the North Sea for the Congress to be held at San Francisco nnder the anspices of the Am. Soc. of C. E. The port of Rotterdam is described in N°. I of the present series of booklets.
44



PLATE X.



the Waterstaat, to the San Louis Congress 1904. (Trans. Am. Soc. C. E.).
The lock built at Ymuiden in 1891/95 is now considered insufficiënt, and a second lock of still larger dimensions is to be constructed. The length will be 1,312 ft., width 1472/3 ft., and depth on sill 49 ft. below N. A. P.
Por the same reason the width of the canal has been increased since 1904 to 164 ft. at the bottom and its depth to 327e ft- below the mean canal level (1 ft. 8 in.'below N.A.P.), while both railway swing-bridges have been replaced by new ones with spans of 180 ft. The only passenger bridge on the canal has been demolished and a steam ferry now conveys the traffic across.
9. THE MEE,WEDE CANAL.
The Merwede Canal, from Amsterdam to the Rhine, and which passes by the city of Utrecht, was ópenedin 1892.
Its length is 441/3 statute miles; width at the bottom, 66 ft., depth 10 ft., cost, $ 8,300,000. It is divided into four sectións, which are separated bylocks. The regulations allow the passage of vessels with a maximum length of 328 ft., a beam of 371/2 ft., and drawing 7d/4 ft. When their length is less than 279 ft. and the beam less than 331/2 ft., a draught of 9'/4ft. is allo wed ').
In many sections the subsoil was extremely poor. Therefore when constructing the lock near Amsterdam, the subsoil was first removed by dredging, to a considerable depth, and replaced by sand from the sea-dunes. In this compact mass the foundation pit was excavated without any trouble. The piles on which the construction rests, were then driven into the ground.
This poor condition of the subsoil also caused trouble when constructing the earthen accesses to the railway bridges on the canal. These bridges leave the vessels a free height of 21*1% ft., and the earthen inclines which lead to these bridges,
!) Details of the canal will be found in the paper presented to the Congress of St Louis by Messrs. van Hoogknhoyzb and de Lint.
46



weighing heavily on the subsoil, they partially settled as shown on plate XI, fig. 1. The layers of peat in the subsoil were compressed by the weight of the dam till pressure and counter-pressure balanced each other.
The same thing occurred in other parts of the country. A very bad case is shown on the same plate, fig. 2. This cross section is taken on the railway line from Hook of Holland to
PLATE XI.,
Fig. 2.
Schiedam. In some spots the road bed had to be laid on a wooden platform, supported by piles. By the same process a canal was recently changed into a paved road at Rotterdam The bad condition of the subsoil of the Merwede Canal
!) In former times a road bed often rested on layers of brushwood. Part of the railway between Amsterdam and Haarlem was constructed in this manner.
47



led the late M. Kluit, Eng. R. C. of the Waterstaat, to invent suspended siphons (see plate XII, fig. 1).
The iron plate siphon forms a kind of tubular bridge, resting at its ends on stone abutments. When the siphon needs repairing, the sluice-gates in the abutments are closed and the tube is floated to a repairing yard. In this manner repairs do not interfere with traffic on the canal.
10. THE NEW RIVER CALLED BERGSCHE MAAS.
Some years ago the Meuse still discharged into the Waal near Woudrichem.
In order to improve the hydraulic condition of the province of North Brabant it was resolved, in 1883, to form a separate outlet for the Meuse (the discharge of this river varies from 12,400 cubic ft. per sec. to 953,100 cubic feet per sec). The new river mouth is called the Bergsche Maas, because it flows near the city of Geertruidenberg. It has a total length of l33/4 statute miles. The width of the summer bed gradually increases from 135 yards to 250 yards; the levees are erected at distances of 545 yards. The total cost was £ 10,000,000. Of course many minor works (canals, pumping plants, etc.) are comprised in this sum. The new outlet was opened in 1904.
11. CANALS IN THE MOORS. [Kanaal (en) in het hooge veen].
No engineer visiting the Netherlands should fail to visit the north-eastern part of the country. While the western part, the polderland, was shaped by the inhabitants many centuries ago, modifications in the east are of recent date. In the north-eastern provinces of Overyssel, Drenthe and Groningen, and also in the south-east (North-Brabant and Limburg) we find a kind of fen totally different from the Holland fen. In Holland the fen, called low-fen (laag veen) is formed by successive layers of decaying water plants. This kind of fen is therefore found below the water level.
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PLATE XII.
11 l' ^^^-^^^^^^^^^^^^nfP lt * IT
Eig 1.
Section of the Merwede Canal.
On the contrary the high fen (hoog-veen) in the north-eastern parts consists of successive layers of moss, heather, dead bushes and trees. These materials decayed in the air and formed a loose peat, which produces an inferior fuel, burning easily, but containing less calorics than the solid Holland peat.
While the subsoil of the low fens generally consists of sea-clay, the high fen rests on a sandy soil, lying many feet above the sea-level.
12. HOW THE MOORS ARE RECLAIMED, AND THE SUBSOIL TURNED INTO ARABLE LAND.
First the high fen or moorland is drained by digging trenches in order to draw off the water. This canal system is completed by transverse ditches, and a main drain. (Plate XII, fig. 2). The moor or fen gradually shrinks to about twothirds of its volume, and after a couple of years is firm ënough to be cut, by hand or machinery. The turfs are then set in stacks to dry.
The uppermost layer, consisting of moss-litter peat, oxidized by the air and still fertile, is carefully laid aside and afterwards deposited on the sandy subsoil. It forms excellent arable land, as the permeable subsoil draws off all the superfluous water. The first year this layer is ploughed just deep enough
49



to mix a little bit of the sandy subsoil with the peat. In after years more and more sand is ploughed up and mixed with the peat. The water level in the canals is kept on a plane within easy reach of the roots of the crops, so that
Main Canals Subsidiary Canals Roads Bridges
DiTches Farmhouses
Cotfa^eSjtShopkeepers &c) with plots of land
Fig. 2.
The Doublé Canal, Fen Colony System. Fiom: Robertson Smith. A Free Farmer in a Free State.
the raising of vegetables proves a most profitable undertaking and a large export trade has sprang up.
About 250,000 acres of moorland have already been transformed into arable land. The digging of trenches and
50



canals, the cutting of the peat, etc, costs about $ 625 per acre. The peat sells at $ 960 to $ 1,250 per acre.
A visit to the fen colonies, veen-kolonie(en) in the southeastern part of the province of Groningen is specially recommended. The social organisation of these farmers also deserves attention. Large strawboard, starch and beetsugar mills have been started by them on a coöperative basis. The city of Groningen also owns vast tracts of cultivated moorland i).
*) A vivid description of fen colonies is to be found in Mr. Robertson Scott's book, already mentioned in chapter I. "Fig. 2, Flate XII reproduced one of its numerous illustrations.
Mr. W. A. Kkrr in his exhaustive study on Peat and its Products (Giïasgow, Besg, Eennedt & Elder, 1905) states: The systematic working of a peat-bog is best understood in the Netherlands, and lately some hundreds of Hollanders have been imported to work the moors at Thorne and Hatfield Chase near Doncaster. Also on that part of Chat Moss acquired from the Astley Estates Company by the Corporation of Manchester. The Dutch peat-cutter has a deservedly high reputation for skfll.
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CHAPTER IV.
FRESH WATER SUPPLY AND SEWAGE DISPOS AL.
1. Introductory.
2. The Underground Fresh Water Reservoir in the Sandhills (duinen).
3. The Troubles of Amsterdam With Regard to the Water Supply.
4. The Water Supply of Rotterdam and of other Netherlands Towns.
6. The Sewage Disposal of Amsterdam.
1. INTRODUCTORY.
In the western part of the Netherlands, where the land lies below the level of the sea, the fresh water supply and the disposal of sewage are most serious problems, especially as in latter years the population of the larger towns has increased considerably and more attention is paid to hygiëne. (Amsterdam had in 1869 a population of264,694, and in 1912 of 587,876; Rotterdam had in 1869 a population of 116,232, and in 1912 of 446,897).
Not long ago, only the rain falling on the roofs and collected in cisterns provided Amsterdam with drinking water. This is also the case in the country, for the water in the canals and ditches is brackish and is often not even fit for cattle.
The sewage system of Netherlands towns was very primitive. Cess-pools abounded, and as there are no running waters, the sewage which was delivered into the stagnant canals without being treated by chemical or other processes, formed an indescribable mass, offensive to sight and smell.
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2. THE UNDERGROUND FRESH WATER RESERVOIR IN THE DUNES OR SAND-HILLS. \Duin(enj\.
Fortunately the sand-hills bordering the North Sea coast form an underground water-reservoir of considerable dimensions. This, however, was not utilized till Jacob van Lennep, a popular novelist and poet, directed the attention of his fellow-townsmen to this mine of water, and induced them to form a company for the purpose of supplying Am. sterdam with pure water.
The present author, who then lived at Haarlem, remembers considering it a treat to drink this uduin" or dune water, when visiting the capital. For Haarlem, though situated at the foot of the hills, did not use duinwater, but was supplied with ordinary well water of indifferent taste. Imitating the camels, he would take his fill before returning home.
The death-rate of Amsterdam, which was 28.46 per thousand inhabitants, feil considerably after this freshwater supply had been laid in 1854. (It was in 1913 reduced to 11.11 per thousand, comparing favorably with New York's 13.76 and London's 14.39).
2. DIPFICULTIES WITH THE WATER SUPPLY AT AMSTERDAM.
Some years ago doubts were raised about the lasting capacity of this underground reservoir. Hydrological experts, however, did not agree, and so an expensive and thorough investigation was ordered by the city of Amsterdam.
The results of this investigation, which areofgeneral interest, will be briefly exposed here *).
The sand-hills which supply Amsterdam with fresh water are found westwards of Haarlem, and cover 6,400
1) Particulars are found in the paper presented to the St. Louis Congress 1904 hy M. Pennink, Director of the Amsterdam Municipal Waterworks.
53



acres. Their average height is twenty-two feet above the sea-level. They stretch from the North Sea coast to the polderland, a distance of 21/2 statute miles.
Only a f raction of the rainfall on this area is available. The rainfall partly evaporates and partly percolates into the low-lying Haarlem Lake polder. On an average, an acre of sand-hills yields 341,000 gallons of drinking water per year. As it will be possible to extend the total area to 6,810 acres, the annual supply can be increased to 2,320 million gallons per year.
This quantity is not sufficiënt. The population of Amsterdam consumed 3,430 million gallons in 1913, orabout a thousand millions more than the annual rainfall supplies.
This excess was drawn from the subjacent layers of sand by pumping. It formed part of the reserve accumulated there in the course of centuries. But this reservoir is not inexhaustible. The former director of the works, M. Van Hasselt, bored a great many wells on the sand-hills belonging to Amsterdam, and found that the total quantity of fresh water stored in these hills amounted to 66,000 millions of gallons only. If we take into consideration the yearly increase in population and the spreading habits of cleanliness, this reserve (even if totally available) would scarcely suffice for some sixty years. But long before the end of this period even the annual supply of rainfall will be worthless.
To understand this, it must be borne in mind that the sand-hills, through which the rain percolates, rest on layers of sand which are connected with the salt water of the North Sea. This seawater forms a subterraneous current, fiowing from west to east, from the sea to the low-lying Haarlem Lake polder.
The fresh water stored in the sand-hills floats on this salt water, which is of greater specific gravity. The salt water is forced downwards by this great mass of fresh water to a depth of 240 feet below the sea-level, as is shown on plate XIII, fig. 1.
The grade level of the salt water does not form a constant plane. When, by pumping, the mass of fresh water diminishes, its weight also decreases and the salt water
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PLATE XIII.
HYDROLOGICAL SECTION FROM THE NORTH SEA OVER TH£ DUNES INTO THE HAARLEMMER MEER POLDER (OBSERVATIONS ON OCTOBER 20TH AND 21ST, 1003.)
Pig. 1.
Cross Section of Sand Hills near Haarlem, forming the Subterraneous Water Reservoir ot Amsterdam.



ascends. When a certain part of the fresh water has been consumed, the sea water will rise to the level of the drains, and mix with the rain water which percolates through the sandhüls. This mixture will then be brackish and unpotable.
This danger is not imaginary. The towns of Delft and Leyden are supplied with water from the sand-hills in the same manner, and injudicious pumping has already led to trouble.
PLATE XIII.
Fig. 2.
Cross Section of Amsterdam Sewers.
The only way to avoid the difficulty is by artificially increasing the rainfall on the sand-hills. The present director of the works proposes to irrigate the hills by water from a branch of the Rhine (the River Lek). A pumping plant will be installed near the town of Schoonhoven, on that river, and the river-water then pumped to the sandhills near Haarlem. This will prove cheaper than the installation of a purifying plant at Schoonhoven and carrying the purified water directly to Amsterdam. No special artificial purifying will be required if the river water percolates through the sand-hills of Haarlem.
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4. THE WATER SUPPLY OF ROTTERDAM AND OTHER TOWNS.
Rotterdam is the only large city in the Netherlands which is supplied with purified river-water. At the present day many combines of country towns and villages are planned for supplying fresh water from the sand-hills or from the subterraneous layers of sand, which form the substratum of the Netherlands almost everywhere. The Government appointed a Board in 1913 which advises communities desirous of aineliorating their water supply. The Government also grants subsidies for making surveys, etc.
5. THE SEWAGE DISPOSAL OF AMSTERDAM.
Of all Netherlands towns, Amsterdam presents the most difficult problem with regard to its sewage disposal. Ithasby far the largest population, and disposal by gravitation, which was always difficult, is now almost impossible, since in 1870 a dam was built across the Y. (This is the landlocked inlet of the Zuyder Zee into which the water flows from the grachtfen) (canals) of Amsterdam. At the present time the Y forms part of the North Sea Canal, which connects Amsterdam directly with the North Sea by a short cut through the sand-hills fringing the coast. In this canal a constant water level of 1 ft. 8 in. below N. A. P. is maintained.
The sewage of the inner or ancient part of Amsterdam flows freely into the grachten. Many years ago it was proposed to fill up a number of the principal ones, and to establish a network of sewers, but the expenses proved too great. Moreover the death-rate of Amsterdam is low (as has already been observed) which proves that polluted canals are innocuous provided care is taken to supply pure water for drinking and household purposes. However, a certain degree of improvement was imperative, to prevent the smell becoming intolerable, so the canals are now flushed by pumping. The sluices and locks which connect the canals with the Y and with the River Amstel being closed, the water level in the canals is artificially lowered by pumps placed near the
57



Zuyder Zee. In the evening and duriugthe night, fresh water is let in from the Zuyder Zee at high tide, while the polluted waters are eyacuated on the Y. Twice a week the same is done in the ancient part of the town with water from the Amstel.
Sinee 1870 the population has doubled, and half the inhabitants of Amsterdam now live in the suburbs which have sprang up on the outer side of the semi-circular canal, called Singel, the ancient defence of the city. In these suburbs but few canals are found, so the sewage problem has assumed another form there.
The sanitary arrangement of the houses prevents the separation of the water for household purposes from the sewage. Many years ago the Ltkrntjr system was tried. This system proved satisfactory from a technical point of view, but too expensive. It was also a constant source of irritation to the residents, as flushing of water-closets was prohibited, this increasing the cost of the dryingup of the sewage, which formed part of the system.
M. van Hasselt, the former Director of Public Works, therefore suggested another solution, which was acceptedby the Town Council. In 1907 the sum of $ 1,200,000 was provisionally voted for its execution.
The project is based on the following data: Population per acre, 243. Consumption of water (sewage) per head and per 24 hours, 33 gallons. Maximum rainfall 8 inches. Of this rainfall 2/5ths to be drained while the shower lasts
To save expenses, the storm now is discharged into the canals, and the main se wer only collects the dry weather flow, which is about ^-nd. part of the storm flow. For this reason a diameter of 4 ft. 11 in. suffices tor the main sewer. The eastern or terminal part of this sewer will almost always be rail, so there was no objection togivingita circular shape.
This main sewer, the terminal part of which is calculated for a flow of 375 gallons per second, is laid along the outer embankment of the aforesaid Singel. From this main sewer secondary sewers branch off. These collect all the sewage and storm water. Automatic sluices have been constructed at the connecting points with the main drain. These allow the storm water to discharge into the canal. 58



From a sanitary point of view this system is not objectionable, as experience has proved in the older part of the city. One must also bear in mind that in the Amsterdam canals the water level is almost constant, and the sludge remains permanently submerged.
Most of the secondary sewers lie below the water level in the canals. They descend even to l41/4 ft. below N.A.P. At many places electrically-operated pumps are therefore inserted in the network of sewers, which deliver the sewage into the main drain. Finally the sewage is pumped from the main drain into the Zuyder Zee.
The sewers are made of concrete and rest on a pile foundation (see plate XIII, fig. 2).
The present Director of Amsterdam Public Works, M. A. W. Bos, is preparing a paper on this system for the Congress of San Francisco.
In the other towns the sewage generally flows freely into the canals, without purification. The almost constant water level in these canals permits the retention of this primitive method.
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CHAPTER V.
DEEP FOUNDATIONS.
1. Pile-driving.
2. Ancient Pile Foundations: Foundation of the Steeple of the Western Church at Amsterdam. The Settling of Foundations: Fissures: the old Western Railway Viaduct of Amsterdam.
3. Modern Foundations: the new Western Railway Viaduct at Amsterdam, tbe Quay of Delfzyl Harbour, the Jetties of Scheveningen Harbour.
1. PILE-DRIVING.
Foundations resting on piles are naturally most common in the western part of the Netherlands, where the soil consists of peat or soft clay. When ever possible, the piles are driven down to the level of the solid sand, which is generally found under the layers of clay or peat. This is not possible in cases where the sand lies too deep below the surface. In that case the engineer relies on the sucking power of the intermediate layers. These keep the pile suspended, provided care is taken not to put too heavy a load on the top of the pile. In order to prevent decay, the top of the pile always lies below the average water level.
Fir is generally used for piles, their length varying from 23 ft. to 50 ft., or more.
2. ANCIENT PILE FOUNDATIONS.
Formerly the alder tree flourished on the Netherlands low lands and was much used in pile-driving, though this wood decays under water. The common practice was to dig a hole, to place in this hole a bottomless barrel, and then to drive a sheaf of slender alder stakes through this barrel into 60



the subsoil. When the barrel was completely filled in this manner, it acted as a wooden ring, firmly holding the stakes together. Rows of these barrels formed the foundation, and on top beams were laid which supported the masonry. Later on, when the trade with Norway flourished, fir wasimported and used for piles. The more important buildings were founded on doublé rows of piles (diatance between the rows 3 ft.). When the building was of minor importance, the doublé rows alternated with single ones. The large churches and their steeples had to be treated in another way. For example, the steeple of the Western Church at Amsterdam, (Westerkerk) which attracts the attention by its graceful originality, was founded in 1619 by first excavating the soil down to 11 ft. 10 in. below A. P. and forming a hollow quadrangle of 641/* X 54 '/4 ft. Seven rows of piles were driven in in one direction, and seven other rows in a direction crossing the first at right angles. In this way the quadrangle was divided into 36 small ones. Beams and crossbeams (153/4 in. X 153/4 in.) were then laid on top of these rows, and solidly fastened to the tops of the piles. Round the quadrangle a sheet-piling was driven in, formed by boards, 16^2 long and 51/» in. thick.
The 36 small quadrangles were then entirely filled with pile work. The length of these piles varied between 26 ft. and 53 ft.; the number driven in in each quadrangle varied from 64 to 81 — according to their greater or smaller circumference. The total number of piles driven in was 3,624. The driving of this mass of piles, which was executed by two gangs of pile drivers, each numbering 70 men, is believed to have taken five months. Forty years ago it was estimated that such a foundation would at the present day cost $ 30,000, including the masonry to the level of the road way.
In the latter half of the 19th century the water level in the canals of Amsterdam was lowered by some inches. This has in many cases caused serious trouble, as the tops of the piles and the wooden superstructure on which the masonry rests, being no longer under water, soon began to decay. Many houses on the grachten had to be propped up in a most expensive manner.
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Nowadays, instead of the wooden platform, which rests on the piles and forms the base of the masonry, concrete is frequently used. The tops of the piles are imbedded in this mass. Concrete piles are also used now.
Even when the utmost care is taken, the masonry often shows fissures, caused by the settling of the foundations. This is specially the case with great masses of masonry. The late Inspector-General of the Waterstaat, M. Conrad, when visiting a newly-built lock, was in the habit of greeting the engineer in charge with the query, "Where is the fissure ?", being convinced that it was impossible to build a lock without such an accident. At the present time, at spots where fissures may be expected to form, small interstices are left, which — when the lock is completed — are filled with asphalt.
A most striking proof of the poor condition of the subsoil can still be seen at the viaduct on the east side of the Central Station of Amsterdam, which was built in 1874.
The former western viaduct was in still worse condition. The eastern abutment of this viaduct gradually inclined backwards, at the same time sinking about 5 ft. It was necessary to underprop the iron girders of the railway.
The cross-section of this viaduct is shown on plate XIV, fig. 1. On the top of piles 28 ft. long, rested a layer of concrete, only 73/4 ft. thick. Some years ago the viaduct was demolished and a new one was built on a foundation of pneumatic caissons. This gave an opportunity to examine the old foundations, and the piles proved to have been twisted and broken by lateral pressure of the subsoil.
In order to understand this, it is necessary to know how the Central Station was built. The foundation of the station and the viaduct on either side were laid in the Y. The bottom of this inlet of the Zuyder Zee consists of mud, resting on a subsoil of clay. This mud was removed by dredging to a depth of 20 ft. below A.P. and in its place sand was dumped. In this manner a dam of sand was formed with its crest at 18 ft. above A. P. This large mass of sand caused disturbances in the subsoil on.the spot where the viaduct had been built. The solid layer of clay, surrounding the <32



Fig. 1
Cross Section of Lower Pile Foundation of Railway Viaduct at Amsterdam.
Fig. 2.
Plan of Foundation of Amsterdam Railway Viaduct.



upper half of the piles, did not give way, but the less resistant layers of sand and clay, below this crust, moved in a lateral direction, and so the piles bent and snapped.
3. MODERN FOUNDATIONS.
a. Western viaduct at Amsterdam (Central Station).
The new western viaduct was built on a foundation of 35 caissons, reaching to an average depth of 63 ft. below N.A.P. These caissons are alternated as shown on plate XIV, fig. 2, forming solid blocks 230 ft. long and 69 ft. broad. The entire foundation cost the sum of % 856,000. It was described in 1907 by Mr. C. Lebmans in the weekly periodical "de Ingenieur" (published by the Royal Netherlands Inst. of Engineers. A copy is to be found in the library of the Am. Soc ofC.E.).
b. Harbour of Délfzyl (Province of Groningen).
The new quay in the harbour of Delfzyl was built by sinking hollow cylinders of concrete. Twenty-three of these, each 31 ft. 2 in. long, and 23 ft. wide, were sunk in a row, 41 ft below N. A. P. First the odd numbers were sunk, then the even numbers. Total cost $ 900 per yard of quay. The work is described in the paper presented to the St. Louis Congress, 1904, by M. Drüijvesteijn, Eng. R. C. of the Waterstaat.
c. Harbour of Scheveningen (near The Hague).
The sea end of the'jetties of this harbour is formed by concrete caissons, cast on the beach and floated to their destination.
A description of this work was presented to the St. Louis Congress, 1904, by M.Wortman, Eng. R.C. of the Waterstaat.
64