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Annotated translation of “Nota in verband met de voorgenomen putboring nabij Amsterdam [Note concerning the intended well drilling near Amsterdam]” by J. Drabbe and W. Badon Ghijben (1889)

Paper
Part of the following topical collections:
  1. Celebrating 50 years of SWIMs (Salt Water Intrusion Meetings)

Abstract

The famous report by engineers Drabbe and Badon Ghijben (1889), on an intended well drilling near Amsterdam (the Netherlands), was one of the key documents that contributed to the Ghijben-Herzberg formula, which links water-table elevation to the depth of the freshwater–saltwater interface in coastal aquifers. The report has been often cited but no English translation has appeared in the literature to date. The aim of this annotated translation of the report is to provide the international scientific community with easier access than was hitherto the case, plus electronic access to the original in Dutch. A brief introduction to the report is provided, followed by a translation that follows the original text as closely as possible.

Keywords

History of hydrogeology The Netherlands Salt-water/fresh-water relations Profile (eminent hydrogeologist) Salt-water intrusion 

Traduction annotée de “Nota in verband met de voorgenomen putboring nabij Amsterdam [Note concernant le projet de forage d’un puits près d’Amsterdam]” par J. Drabbe et W. Badon Ghijben (1889)

Résumé

Le célèbre rapport des ingénieurs Drabbe et Badon Ghijben sur le projet de forage d’un puits près d’Amsterdam (Pays Bas), publié en 1889, fut l’un des documents clés qui contribua à la formule de Ghijben-Herzberg qui lie l’altitude du niveau piézométrique à la profondeur de l’interface eau douce – eau salée dans les aquifères côtiers. Le rapport a souvent été cité mais, à la date d’aujourd’hui, aucune traduction n’était disponible dans la littérature. Le but de cette traduction annotée du rapport est. de fournir à la communauté scientifique internationale un accès plus facile que ce qui était le cas jusqu’à présent, ainsi qu’un accès électronique à l’original en hollandais. Une brève introduction au rapport est. fournie, suivie par une traduction, qui suit le texte original du plus près que possible.

Traducción comentada de “Nota in verband met de voorgenomen putboring nabij Amsterdam [Nota relativa a la perforación planificada de pozos cerca de Amsterdam]” por J. Drabbe y W. Badon Ghijben (1889)

Resumen

El famoso informe de los ingenieros Drabbe y Badon Ghijben publicado en 1889, sobre la perforación planificada de pozos cerca de Amsterdam (Países Bajos), fue uno de los documentos clave que contribuyeron a la fórmula Ghijben-Herzberg, que vincula la elevación de la capa freática con la profundidad de la interfaz agua dulce-agua salada en acuíferos costeros. El informe ha sido citado con frecuencia, pero hasta la fecha no ha aparecido ninguna traducción al inglés en la literatura. El objetivo de esta traducción comentada del informe es proporcionar a la comunidad científica internacional un acceso más fácil que hasta ahora, más el acceso electrónico al original en holandés. Se proporciona una breve introducción al informe, seguida de una traducción que sigue el texto original lo más fielmente posible.

对 J. Drabbe和 W. Badon Ghijben (1889) 的“Nota in verband met de voorgenomen putboring nabij Amsterdam [关于阿姆斯特丹附近钻井的报告]“翻译及注解

摘要

由工程师Drabbe 和Badon Ghijben于1889年发表的有关打算在(荷兰)阿姆斯特丹附近钻井的著名报告是对Ghijben-Herzberg公式做出贡献的关键文档之一,Ghijben-Herzberg公式把沿海含水层的水位高程与淡水咸水界面的深度联系在一起。报告经常被引用,但至今文献中仍没有英语翻译文本。带注解的翻译本报告目的就是以比过去更加容易获取的方式向国际科学界提供信息,并且可在网络上查询荷兰语的原文。先是对该报告做了简要的介绍,然后是尽可能地接近原文的翻译文本。

Tradução comentada de “Nota in verband met de voorgenomen putboring nabij Amsterdam [Nota a respeito da intenção de perfuração de poço próximo a Amsterdam]” por J. Drabbe e W. Badon Ghijben (1889)

Resumo

O famoso relatório dos engenheiros Drabbe e Badon Ghijben, lançado em 1889, a respeito da intenção de perfuração de poço próximo a Amsterdam (Países Baixos), foi um dos principais documentos que contribuíram para a fórmula de Ghijben-Herzberg, que liga a elevação do nível freático à profundidade da interface água doce e água salgada em aquíferos costeiros. O relatório foi frequentemente citado, mas nenhuma tradução em inglês apareceu na literatura até o momento. O objetivo desta tradução comentada do relatório é fornecer à comunidade científica internacional um acesso mais fácil do que previamente, além do acesso eletrônico ao original em holandês. Uma breve introdução ao relatório é fornecida, seguida de uma tradução que segue o texto original o mais próximo possível.

Introduction

The Ghijben-Herzberg principle relates water-table elevation to the depth of the freshwater–saltwater interface in a coastal aquifer, and is one of the best-known formulas in groundwater hydrology. The original articles by Drabbe and Badon Ghijben (1889) and Herzberg (1901), to which the formulation of the principle can be traced (Post et al. 2018), have become famous. Yet, because they are written in Dutch and German, respectively, few international scholars have had access to them, and moreover, the articles are not so easy to find. In the Netherlands, the issue of the Tijdschrift van het Koninklijk Instituut van Ingenieurs (Journal of the Royal Institute of Engineers) containing the report by Drabbe and Badon Ghijben (1889) only resides in two university libraries and no digital copy of the report and its figures was available prior to this translation. Since 2018 also marks the 50th anniversary of the Salt Water Intrusion Meeting conference series, it was decided to publish translated versions of the original articles into English.

What is rather unusual is that the original two-author report only brought fame to the second author, Badon Ghijben, and that the first author, Drabbe, received no more credit beyond authorship. As Carlston (1963) pointed out, the reason for this is that Drabbe was Badon Ghijben’s supervisor, and that it was merely by virtue of his military rank that he became the first author. It should be noted that the report format diverges from how we know it today as the author names do not appear at the top, but rather they dated and signed it at the end. It is not clear how Carlston (1963) arrived at his assumption, but it seems correct as Badon Ghijben’s peers gave full credit to him and only him around the start of the twentieth century (J. De Vries, emeritus professor, VU University Amsterdam, personal communication, 2018). This is clear from the minutes of a meeting held on 18 June 1904 (Pennink 1904), in which C.P.E. Ribbius insisted that the now famous principle should be named after Badon Ghijben instead of Herzberg. The “New Dutch bibliographic dictionary” published in 1911 (Molhuysen and Blok 1911) also gives all credit to Badon Ghijben and does not even mention Drabbe as an author of the report. When citing the work in the literature, it has become customary to date it to 1888/1889 instead of a single publication year. However, the combination of years was used in lieu of a volume number for the Journal of the Royal Institute of Engineers. Since the 1888/1889 volume was not printed until 1889, that latter year should be used for citing.

During the second half of the late nineteenth century, the Netherlands did not look anything like what it looks like today. At the time, Amsterdam was located near the shores of an inland sea (“Zuiderzee”) and a large estuary (named “het IJ”) still existed, which contained brackish water. The groundwater in and around the city also had a high salinity, and this, combined with a poor microbiological quality of the water, resulted in severe water supply problems. Freshwater was sourced from the dunes where it was captured using drainage canals and then piped to the city (De Vries 1994). This system was vulnerable during times of war and hence Badon Ghijben, a military engineer of the rank of captain, was commissioned to find a source of water to supply the city during an emergency.

Despite its fame, most of the information in the report by Drabbe and Badon Ghijben (1889) is unlikely to captivate the minds of an international audience in the twenty-first century. The reason is that the report is primarily a description and an interpretation of the geological and hydrochemical situation near Amsterdam. The main part of the discussion focusses on the origin and distribution of the Pleistocene sand layers, and this takes up about two-thirds of the report. At the time, very little was known about the geology, hydrostratigraphy, and the salinity distribution, and the report provided a systematic and up-to-date review of the state of knowledge. For this reason, Molhuysen and Blok (1911) characterised the report as “a work of lasting significance”.

The last third of the report is made up of a discussion of the hydrogeological conditions. This part starts with some observations about the iron content and the foul smell of some waters, found in abundant quantities in the coastal area within peat, under reducing conditions. This water is to be considered unfit for drinking, and then the discussion focusses on the high salinity of the groundwater. Three different possible sources are provided for the high chloride contents encountered. The first is connate seawater trapped in the clay and other marine deposits, which overlay the sand aquifers. The second is the high salinity of many of the surface-water bodies in the western part of the Netherlands. The third and last is the North Sea itself.

The actual equation that relates the elevation of the water table to the depth of the saltwater is not found until the second to last page. Badon Ghijben himself never felt that he had written anything remarkable (Post et al. 2018). In fact, a footnote in the original report actually alludes to the fact that he based his thinking on the analogy with seawater that intruded into river locks in contact with the sea. The footnote quotes J.F.W. Conrad (1825–1902, a well-known Dutch water engineer) who made a statement at a meeting held in April 1881 about the flow of water through locks (Conrad 1881). At the meeting, Conrad recounted an experiment he had conducted in a lock using three floats of different lengths. Upon opening the gates, the deepest float flowed inward, the shortest out to sea and the middle one stayed in position. He hypothesised that seawater intruded along the river bottom, thus partly driving the freshwater out of the lock. According to the minutes, a general by the name of Delprat had calculated that the inward flow of seawater occurred below a surface given by 40–50 times the “elevation of the slope”, by which he presumably meant the height of the water level above sea level in the lock.

Despite Badon Ghijben’s modesty, the analogy between the processes in a lock and the occurrence of freshwater on top of saline groundwater is a rather clever realisation and, as history has shown, formed an important step in the conceptual thinking of groundwater in coastal areas. He did not present his idea as conclusively as Herzberg (1901) did in his paper, but there can be no doubt that his understanding was correct. Moreover, and in more detail than Herzberg (1901), he discusses aspects of groundwater flow. He mentions for example the seaward flow of freshwater above the interface and the landward flow of seawater, and also correctly inferred that seawater must be intruding from the Zuiderzee because water levels in the polder area were kept below sea level.

Willem Badon Ghijben was born on 26 October 1845 and started his career as a military engineer in 1862 (Molhuysen and Blok 1911). He did a lot of work on the inundation defence system in Holland (the part of the Netherlands made up by the provinces of North and South-Holland, stretching along the western coast) and wrote a textbook on the subject during his time at the Royal Military Academy of the Netherlands where he started lecturing in 1873. He was promoted to the rank of captain in September 1875 and shortly after this he became the head of education in military engineering. He fulfilled this role until he was transferred to the military engineering department in Amsterdam in July 1882. He became the secretary of the technical committee for matters regarding artillery and engineering in the The Hague in June 1887, and in this role he wrote the famous report. He married Ms. W.J.J. Huysinga on 8 May 1890, and together they had four children. Problems with his health forced him to retire prematurely in 1902 (De Vries 1994). He passed away on 13 November 1907 (Molhuysen and Blok 1911).

Translation notes

The translation in this paper follows the original report’s text as closely as possible, except when doing so would result in overly complicated or unintelligible sentences in the modern English language. The punctuation used in the original text is unusual for modern standards, but has been adhered to as much as possible. The report contains many footnotes, which were indicated by (*), (†), (§), (**), (††), always in the same order and starting over again with the beginning of a new column. In this translation, all footnotes are consecutively numbered. Translator notes are recognisable as text in italic enclosed by square brackets and preceded by “tr:”. The Latin term “sic” means “just as it was written”.

Even for Dutch speakers, the text is not an easy read because of the antiquated terminology and the sometimes very long sentences. Many place names that are mentioned in the text, can be found in Fig. 1, which is a modified version of a figure from one of the plates in the original report. The plates are part of the reproduction of the original report, which is included as electronic supplementary material (ESM) to this paper. Frequent reference is made to “het IJ”, the former estuary that has largely been reclaimed. The reader may, by the way, note the double capitalisation of the word “IJ”, which is a feature of the Dutch language where the letter combination ij can substitute for y. This is also the reason that Badon Ghijben’s name is sometimes spelled Badon Ghyben. Another peculiar element of the Dutch language is found in town names like ′s Gravenhage, where the prefix ′s is shorthand for ‘des’ (and, translates into: the count’s hunting grounds).
Fig. 1

Map of the area around Amsterdam with the geographical names used by Drabbe and Badon Ghijben (1889)

The Defence Line of Amsterdam (in Dutch: Stelling van Amsterdam) mentioned in the report was an ingenious defence system that was in use until it became obsolete by the use of aircraft for warfare. The system worked by flooding the land around the city so that enemy troops could no longer pass. The strategic roads were built just higher than the flooding water levels for the Dutch troops to still be able to pass the area. At each of these passages, a fortress was built, and these are referred to a number of times in the report.

The geological term “dilivium” is used a lot in the translation. It is an antiquated term for the unconsolidated Pleistocene deposits that are found to depths of sometimes up to a few hundred metres in the Netherlands. Another term that is encountered a few times is “lage venen”. It is no longer in use but it refers to peat that has formed under the influence of groundwater. This peat is widespread in the coastal provinces of the Netherlands and is distinct from peat bogs that are fed by rainwater only. The latter are generally more abundant in the parts of the Netherlands located above mean sea level. The Dutch word “zakwater” is also used a few times, which has been presumed to indicate infiltrated rainwater.

All elevations are with respect to “Amsterdams Peil” (A.P. or AP.), which is the former national ordnance datum of the Netherlands; in the translation this has been changed to “AP”. It was based on the water levels in the canals of Amsterdam, which at the time still stood in direct connection to the sea. It was replaced by the Normaal Amsterdams Peil (N.A.P.) in 1891. The notation of units has been changed in this translation to contemporary conventions, so “M.” for “metres” has been replaced with “m”, and instead of “mG.” and “mG. per L.” (for solute concentrations) the translation uses “mg” and “mg/L”, respectively, except where they are within a quotation. Some geographical names are spelled differently from the modern spelling. The provinces Noordholland and Zuidholland, for example, are nowadays spelled as Noord-Holland and Zuid-Holland. The name “Holland op zijn Smalst” refers to a 7-km wide strip of land near IJmuiden where the province of Noord-Holland used to be at its narrowest (measured from east to west) between the North Sea and the IJ estuary. The reclamation of the IJ estuary in 1883 rendered the name obsolete.

The report contains several references to pioneers of earth sciences in the Netherlands. For example, W.C.H. Staring (1808–1877), J. Lorié (1852–1924) and P. Harting (1812–1885). The latter is best known internationally for defining the Eemian interglacial period. He based this on the identification of the shells of extinct marine organisms in a drilling in the “Gelderse Vallei” which is a shallow valley formed by the River Eem. There are many references to written works in Dutch in the footnotes. Their titles have been left untranslated.

Translation

Note concerning the intended well drilling near Amsterdam

Prepared in response to the written request by the sir Major General, inspector of the corps of engineers on 29 March 1887 no. 1073.1

(Plates 6 and 7.)

Regarding the to be initiated investigation into the possibility to, in the heart of the Defence Line of Amsterdam, through the drilling of deep wells, create the supply of drinking water of good quality, it is assumed in the letter by the sir major general, commander of the Defence Line of Amsterdam, dated March 28, no. 29, that for the test drilling, as meant in the writing of the Minister of War dated 24 March, Vth Department, Military engineering, no. 20, a site must be selected, located: within the perimeter of earlier works (2nd line), -- either in the vicinity of the pressure pipeline of one of the existing or to be constructed water supply lines, either near a waterway, -- furthermore within or near the town of Nieuweramstel, -- preferably on Crown land, -- and, considering the chance of obtaining good water, as far away as possible from the Zuiderzee and the former IJ, because the salinity of the water will generally be higher if the distance becomes smaller. Considering these factors, the aforementioned commander proposes the Crown lands of the military bases no. 12 near Ouderkerk and no. 13 at Amstelveen as sites for conducting a test drilling, and finally, given the available space and the opportunity to approach, chooses the former of these terrains.

With due observance of the aforementioned requirements and through closer study of the conditions, which can influence the success of the drilling, we have reached the conviction, that it is recommended, to select a different location instead, that is, preferably the Basis west of Sloten, near the Haarlemmermeer ring canal. This Note is mainly meant to motivate this view.

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Within the 2nd line of the Defence Line of Amsterdam, a well with sufficient yield of good drinking water can only be found in the sand, which makes up, covered by younger formations, the extension of the large “north German” diluvium, to which belong the westernmost, located above sea level, elevated areas, amongst others the connected series of hills stretching from the [tr: sic] Grebbe to the east of Naarden, and the associated hill of Muiderberg. Based on geological investigations, primarily into the nature of the rock types encountered, the elevated areas themselves are considered part of the so-called “mixed-diluvium”, which at an insignificant depth below the ground surface appears to transition into “Rhine diluvium” here. The latter is considered to be a weathered and crumbled residue of the mountain ridges of the so-called “lignite formation” in the western part of central Germany, transported from there by powerful pre-worldly currents in the direction of the current Rhine valley. The mixed diluvium consists here of a mixture of Rhine diluvium with mountain fragments from northern Germany and especially also from Scandinavia, as encountered in pure form in our northern provinces.

Both aforementioned geological formations together with those of a different origin, are summarised under the common name “gravel diluvium”, which is considered to comprise: finer and coarser sand, with gravel and occasional large boulders, sometimes mixed with, -- or alternated by loam.

To distinguish it from the “gravel diluvium” the flat sand terrain bordering the gravel-containing hills, that comprise the youngest diluvial formation or the transition to alluvial sediments, is generally called “sand diluvium”. It’s composition is: generally alternating finer and coarser sand, that often contains gravel and now and then loam; coarse gravel or larger boulders are only sporadically present.

This geological formation comprises amongst others the sand, that lies west of the aforementioned hills of the Gooi and Zeist regions, and that, sloping away from these, extend beneath Holland until the North Sea; the “marine sand” of the North Sea floor along the west coast of Holland is “merely a continuation of the diluvium”,2 eroded at the surface and partly displaced by waves, currents and tides, the action of which caused the finest marine sands to be blown from the beach to form dunes.

There are differences of opinion regarding the suspected origin of the sand diluvium: While Dr. W.C.H. Staring repeatedly argued,3 that one should regard the formation merely as a weathered and fragmented erosion product of the earlier-formed, adjacent gravel diluvium, displaced to depressions by rain and brooks during a long sequence of centuries, other authors contend, that it is more likely, that the sand diluvium has been directly deposited by large diluvial streams, in the same manner, as in which finer clay settled and is settling, along the less competent main rivers of historical times.

Without elaborating further, we believe that it can be assumed, that the former theory can pertain to the upper layers of the sand diluvium, but that more generally, the latter is truly appropriate for the actual bulk mass of that formation.

In this regard a number of relevant contradictions must be pointed out.

Already during a number of old well drillings (1837–1841 and 1849–1851) it has been found, that beneath Amsterdam, after repeated alternations of the rock type, continuous sand is generally not encountered until [tr: a depth] between 50 to 60 m below AP, which remains of the same nature until a depth reached during one of these drillings of 172 m below AP.

The results of these drillings and most of the samples obtained have been made subject of a very comprehensive investigation by the [tr: sic] professor P. Harting at the time. It was found, that the continuous sand layer beneath Amsterdam that was just mentioned, with respect to its constituent parts, does not show any significant differences with the sand layers, which have been penetrated up to a depth of 123 m below AP at the Zeisterheide,4 -- namely sand, mixed with debris from the mountain chains of the Rhine and without rock types, that must unmistakably originate from Scandinavia5; this assertion is supported by dr. Staring, but it is not consistent with his theory, according to which this sand diluvium is an erosion product of the adjacent gravel diluvium of Gooiland, that amongst others contains a lot of granite, of which a Scandinavian origin is not considered to be doubtful.

The report of the Commissie tot onderzoek van drinkwater enz. [tr: Commission for potable water supply etc.]6 contains, regarding a well drilling to a depth of 64 m below AP commissioned by that commission, completed in Vinkeveen in 1868, an account (Appendix XI), which has been most likely authored by dr. Staring or professor Harting, the most knowledgeable members on this subject of the commission, perhaps by the latter, as the samples of this drilling are part of the collection of the University in Utrecht. In that writing, the sand layers, which were penetrated between 7.8 and around 60 m below AP, are called “river deposits”, “upon which lie the peat bogs of the Vecht and Amstelland”, while one assumed, that only at a depth of well over 60 m below AP the “sand diluvium” had been reached, “that extends beneath these river sands with gravel, clay fragments and remnants of peat and wood.” Now there is, as will become clear, no doubt, that the sand west of the [tr: river] Vecht, of which the upper surface lies at 7.8 m below AP in Vinkeveen, forms one continuous unit with the sand, upon which east of the Vecht, rest the peat layers of Tienhoven, Loosdrecht and Ankeveen, -- the same that has been repeatedly called “sand diluvium” by Dr. Staring.7 There is a misconception or linguistic confusion here, that will in essence disappear, if one considers the sand diluvium as an “older river deposit”.

In any case, the aforementioned statements will suffice to reveal:

1o. that the sand, in which the desired water supply wells must be found in Amsterdam, are most likely part of the deposits of a stream tube, that was bordered in the east by the hills along the line Grebbe-Zeisterheide-Naarden and here approximately came from the direction of Utrecht, so that the meant sands constitute one continuous mass with [tr: the sands], of which for example beneath Utrecht and west of Hilversum the upper surface is located approximately at AP.

and 2o. that on one side this sand mass extends into the Zuiderzee, including east of Naarden and at Muiderberg, where it is not covered by clay, and on the other side into the North Sea, where it, extending underneath the dunes, makes up the sandy coast.

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Upon reading the works by Dutch geologists cited above, that may be slightly outdated, one becomes of the impression, that the upper surface of the sand diluvium is characterised by a more or less gradual sloping surface being around AP near Utrecht, Loosdrecht and Naarden to 50 to 60 m below AP beneath Amsterdam,8 dipping to greater depth further to the north and west. After all, professor Harting even calculated from these data, that the “general sloping surface of the diluvium” could have dropped off to 146 m below AP at [tr: Den] Helder,9 an assumption though, which did not gain any probability, when in the same year, in which his treatise was published (1852), the same sand, that was found at 50 to 60 m below AP in Amsterdam, was found at a mere depth at 40 m below AP in Purmerend.10 Dr. Staring11 also compares the elevation of this sand with that of the upper surface of the sand layers with fine gravel at some locations in Zuidholland and Utrecht, and from this concludes, that the sand diluvium “beneath Noordholland lies much deeper than beneath Zuidholland”, a statement, which is also sometimes found in later written descriptions of the geology of our country. In this manner the view may arise, that in the deeper strata of the not large [tr: sic], part of Noordholland located within the second Defence Line of Amsterdam, there are no differences that can be located upfront, but that the best location for a well drilling probably has to be sought to the east or southeast of Amsterdam, that is: at a higher point than the assumed general sloping surface and closer to the places, where good drinking water has been found in the same sand at some locations. However, since at this point in time for a different, later to be mentioned reason a location to the south or west of the capital seemingly had to be selected, it appeared necessary, to first find some several [tr: sic] indications for the suspected nature of the deeper strata within the designated perimeter that is of interest from a defence point of view.

To this end, in a wider area, the available data of drillings and the samples held in the archive of the Corps of Engineers in Amsterdam have been studied and correlated.

For some of these drillings (Vinkeveen, Abcoude and Haarlem) the depth is large enough, to be able to assume with certainty, that one thus, just like in Amsterdam, has penetrated into the envisaged sand mass; in this regard the ordinary drillings at other locations yield less certainty of course; each on their own these do not have so much significance for the purpose here, -- jointly and correlated they nevertheless hold value owing to their large number and relatively close spacing, to correlate the deepest drillings both with each other as well as with the known diluvium and from this draw conclusions based on a reliable basis.

That investigation has yielded totally different findings than what one would suspect based on the aforementioned global concepts.

In plates 6 and 7 almost all available, relevant data have been collated into a continuous net of cross sections through the subsurface, oriented in such a way (plate 7, figure 1), that appeared to be the most suitable. With respect to this, we note the following.

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From plate 6 it becomes clear, how the sandy soil of the diluvium, “upon which rest the lower peats of Tienhoven, Loosdrecht and Ankeveen”, “veering off” beneath those peats from the direction of the Gooi region,12 the gentle slope of which can be traced virtually foot by foot, at least until Raasdorp, (east of Halfweg, figure 1), Hoofddorp (figure 3) and Kudelstaart (figure 5). The upper part of this formation consists of fine sand, stained blackbrown due to contaminations of plant origin and mixed with some clay or other binding materials, sufficient to create a very loose substance of the dry samples; during drilling it was sometimes considered as “loop- of klapzand” [tr: Left untranslated as the meaning is not clear. This probably indicates a runny, collapsible sand unit]. At a certain, not too dissimilar depth of some metres below the surface the sand becomes sharper, coarser, more pure and less clayey, and soon small pebbles appear, some of which can even be 1 cm thick; the heavy stippled lines in the cross sections, connecting the upper boundary of the first gravelly parts, display a certain regularity when viewed at large. At greater depths fine and coarse sand appear to be alternating, sometimes containing more and then again less clay or loam, always in such minor quantities that in drillings for the purpose of construction it is not considered.

The corresponding samples of the different drillings generally have the same appearance.

The conviction, that the subsurface of sand indicated in the figures of plate 6 constitutes a single continuous unit, is reinforced by the similar gradual variation of the overlying alluvial formations, of which a concise overview may follow.

In the central part of the area represented by the cross sections of plate 6 (for example: Hoeksjan in figure 1) one often finds on top of the sand three consecutively formed layers, namely: First “hard” or “dry” dark peat (often with wood fibres) with a sloping top surface and seldom thicker than 0.25 to 0.50 m, that forms an overlay of plant origin that covers the sand soil that drops off to the west and northwest; on top of this weak blue clay, settled from the brackish water of “an almost cut off inland sea, upon which the tides exerted little influence”13; finally the peat layer, that formed on top of this as normal laag veen [tr: sic] with a virtually horizontal surface [tr: “waterpas”, literally: the line indicated by a spirit level] in freshwater, after the depression became completely separated from the sea. The fact that this upper layer, mostly by mining or erosion, has disappeared largely or completely at many locations, as a result of which the clay removed of its peat layer is exposed in the reclaimed lakes of Holland, is irrelevant here, and has largely been left out of consideration in the plate, as well as other, mostly artificial, local changes at the surface.

East of the middle part meant above the clay layer pinches out, remaining of the same plastic [tr: “vette”, literally: “fat”] nature; the boundary to which it extends, has, based on the transects of the figures 1, 4 and 5 of plate 6 and 2 and 3 of plate 7, been approximately indicated with a stippled line a b c in figure 1 of plate 7, matching very well with the suspicion by dr. Staring, that it can be found near Wilnis.14 Here the marine deposit apparently encountered the peat already formed on the higher sand terrain (“marsh peat”? [tr: sic]).15 The transitional state west of this boundary appears: from below, from the alternation and admixture of clay and peat; from above, from the eastward decreasing elevation of the top of the clay layer, as a result of the decreasing amount that has settled. To the east of the meant boundary nothing but peat lies on the diluvium, formed partially before, partially after the formation of the clay deposit; it is remarkable that, amongst others during the expert investigation of the samples of the drilling at Vinkeveen16 a distinction was made between the “light peat” above 7.50 m below AP and the deepest 0.30 m thick layer “dark peat”, once again seemingly being the plant-derived cover on the sand, which is covered only by laag veen [tr: sic] here, and more to the west by clay.

As noted previously, the peat forms one continuous unit on both sides of the [tr: river] Vecht, terminating, where sand diluvium crops out in the Gooi region. The clay along the banks of the Vecht merely fills a channel in that peat (plate 6, figures 1, 4 and 5), possibly formed after an encroachment on the sea side; that is between Abcoude, Hinderdam and Geinbrug, as apparent from the shells, marine clay has certainly been deposited, that is bounded at amongst others the [tr: river] Gein between Abcoude and the Velterslaan [tr: road] by a sand bar, upon which the fortress at Abcoude has been built (plate 6, figure 5); later a layer of brown fluvial clay has been deposited over the deepest blue clay and the adjacent peat during the time, when the Vecht formed a branch of the Rhine (plate 6, figures, 1, 4 and 5; plate 7, figure 2).

Such young clay deposits can apparently also be found at some locations along the [tr: river] Amstel; however they do not crop out here, but have been covered again by continued peat formation (Vrouwenakker and Uithoorn in figure 5 of plate 6, Ouderkerk in figure 4 of plate 7); also in Amsterdam (Bickerseiland and Kadijk, figure 2 of plate 7) apparently younger marine clay has replaced a part of the eroded peat.

Also to the west of the part of the terrain initially considered does the soft blue clay layer slowly pinch out, however in a completely different fashion than to the east. Namely, starting between the [tr: river] Amstel and Haarlemmermeer it becomes, approaching the dunes, sandier, soon, except for only the relatively thin upper and lower parts, transitioning into very fine clay-containing runny sand. The lower surface of that, now consisting respectively of clay, sand and clay, marine deposit then starts to ascend east of Halfweg in the direction of the sea (plate 6, figures 1 and 2): it is within the undulating relief of the sand bar, behind which the entire layer has been deposited and of which the finest sand grains have thereby mixed up to a certain distance with the settling clay particles. That sand bar, with its numerous remains of shell-building organisms living in saline seawater,17 is regularly found everywhere along the line Spaarndam-Liebrug or Haarlem-Vijfhuizen-Cruquius, partially even also at the surface of the Haarlemmermeer18; previously originated in the open sea, it forms the base or origin of the present dune belt that formed later by aeolian deposition.19 In accordance with the explanation for the way, in which the layers considered here have presumably formed, the clay that still occurs in Liebrug and Vijfhuizen is ultimately no longer present in Haarlem, and furthermore the lower surface of the upper peat layer slightly rises in the direction of the sea.

Regarding the question, if the latter layer also ultimately pinches out, that is, whether the sand of the dune belt is separated by peat from the underlying deep continuous sand, there appears to be no decided opinion. Based on what is observed at or near the foot of the dunes,20 it is suggested multiple times, as if the entire dune mass, in a trenching [tr: sic] fashion, has moved to the interior over the normal laag veen [tr: sic]; at the same time, in that case one should have encountered that peat in the drilling drilled until 5 m below AP at the fortress at IJmuiden21; also during the excavation of “Holland op zijn Smalst” peat appears to have been encountered only sparsely at a limited number of locations.

We therefore believe that we may assume, that the rainwater infiltrating in the dunes, if not everywhere then across a large area, will encounter continuous sand, as a result of which it can reach the deeper sand layers.22

The deepest firm peat layer, -- the plant-derived cover on top of the diluvial sand, -- is still encountered at Raasdorp (figure 1), Hoofddorp (figure 3) and Kudelstaart (figure 5); more toward the west it has been eroded by the sea. In Haarlem (groote kazerne [tr: sic]; figure 1) on the other hand the sand and peat at 12.1 to 12.6 m below AP appear to form additional evidence, that it extended up until this point. Also with respect to the coarse sand located several metres deeper at Halfweg, Fort de Liede and Haarlem, the top surface of the sand diluvium can therefore be thought to extend up to 12.5 m below AP in Haarlem (plate 6, figure 1).

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In what has been mentioned so far with respect to the comparative investigation of the results of the drillings, there is nothing, that can be connected to the aforementioned depth of the diluvium in Amsterdam. This apparent contradiction is largely clarified by the figures 2–4 of plate 7.23

Here, one also encounters, starting from the top, the layers of peat and blue clay, while the latter pinches out again to the east in the same manner as indicated for the more southerly cross sections.24 Beneath these, another thin layer of “hard” or “dry” peat follows, which has been mixed with clay at some location in Amsterdam, but in other drillings it has been found here in the normal fashion as a distinctly marked separate layer25; according to the botanical investigation by professor Harting this peat consists “at least partially of plant remains, which originally grew on land”26; it is therefore not normal laag veen [tr: sic], which can also be inferred from its position more generally. This thin peat layer is also encountered on [tr: the island of] Pampus and north of het IJ,27 falling gently to 18 to 19 m below AP near Schardam, from where it rises again further to the north,28 presumably because of the influence of the Scandinavian dilivium; to the west of [tr: train] station Oostzaan and the fortress north of Purmerend it is, just like in the western part of the cross sections of plate 6, no longer encountered, except perhaps29 at the St. Aagtendijk.

This plant-derived crust [tr: sic], which in the cross sections of plate 6 appeared to form the cover of the sand diluvium, does so, in our opinion, in Amsterdam as well. From the figures 2 and 3 of plate 7 it follows, though, how the sand immediately beneath that thin peat layer near the [tr: the river] den Diemen and in Amsterdam forms the direct continuation of the upper part of the sand diluvium more to the east and to the south. A comparison of the samples further confirms this assertion.30 As an example hereof, it is further noted, that the brown sand, that during the well drilling at the Kadijk in Amsterdam was brought up from a depth of 13 m below AP, seemingly still completely matches with that from the sand quarries in Naarden; this sand layer, which in Amsterdam not entirely unjustified is called the “Muiderzand”, possesses springs in some parts of the city, of which the water was used for drinking water in former times.31

Elsewhere (plate 6) one can penetrate the sand to great depths without any change of the soil type; but the situation is completely different in Amsterdam (plate 7), where a clay layer follows again soon. The middle part of figure 2, further confirmed by figure 3 of plate 7, is of special significance, to comprehend this difference and trace the boundaries between both conditions.

From this it follows, that around 2500 m east of den Diemen at approximately 11.5 m below AP a sloping surface commences in the underlying diluvial sand, that can be traced regularly to around 24 m below AP. On this surface numerous remains of salt-water dwelling shell-building organisms are encountered, amongst which some, which nowadays are no longer encountered along our coasts.32 This same peculiar shell layer lies at a depth of 25 to 27 m below AP beneath Amsterdam and extends at roughly the same depth up to Edam, the town of Purmerend and other points in Noord-Holland north of het IJ. Beneath the present-day Gelderse Vallei it is – according to the investigations by professor Harting,33 continued by dr. J. Lorié, lecturer at the University in Utrecht,34 -- regularly encountered as the bottom of a sea arm during a part of the diluvial age; because of this professor Harting has named this sand layer with partially-extinct shellfish “Eemstelsel” [tr: sic] (or Eem formation). Based on a statement by dr. Lorié our suspicion is justified, that the aforementioned sloping surface is a part of the former coast of the sea of the Eem formation, and one can further assume, that the shell layer as meant above normally lies within the sand diluvium, that is: interbedded with consecutively formed layers of this dilivium. This latter fact is consistent with our belief mentioned above and based on other grounds, that in fact the sand, that beneath Amsterdam is found from 11.5 to 13 m below AP, should already be considered diluvial sand. The underlying clay layers are thus probably diluvial deposits,35 which have been covered by diluvial sand washed away from the surrounding areas during the last part of the diluvial age up until almost the same level at which this was present elsewhere.

The aforementioned old coast has also been found in the direction from Ouderkerk to Diemerdam (plate 7, figure 4); the fact that its slope appears to be a lot more gentle, is due to the very sharp direction [tr: sic] of the cross section. The upper part (at 11 m below AP) is located between Ouderkerk and Amstelveen just west of Post no. 12; and to the left of this point figure 4 of plate 7 further shows a similar condition as the corresponding part of figure 1 of plate 6.

From this it follows, that between Amsterdam on one side and Amstelveen-Sloten on the other side a sloping surface must exist in the deeper-seated diluvial sand of the same nature as the one, which near den Diemen[tr: has been] demonstrated by drillings and has been depicted in the figures 2 and 3 of plate 7; against this slope south and southwest of the capital, as well as to the southeast, the later deposited clay layer will pinch out, which in Amsterdam rests on the shell layer of the Eem formation that has been mentioned multiple times; that clay layer will therefore not be encountered in Amstelveen and Sloten.

In the meantime, -- underneath the sand layer with shells a new clay layer starts in Amsterdam at 27 to 28 m below AP, which only ends on average at 55 m below AP at most points. Because of the lack of drillings to the required depth between den Diemen and Amsterdam the manner in which this clay layer pinches out against the sand, portrayed by stippled lines with question marks in figure 2 of plate 7, is based on the mere guess, that the earlier mentioned sloping surface generally extends in roughly the same way below a depth of 24 m below AP as above it. It is thinkable, that this guess is incorrect; about the thick clay layer beneath Amsterdam meant here one only knows for a fact, that it does not occur in Abcoude and Haarlem, but does occur in Edam and Purmerend, where it is found with the lower surface at around 48 and 40 m below AP respectively. From the well drillings in the fortress on the eastern Beemsterringdijk [tr: dike] at the Middenweg and Jisperweg [tr: roads] we believe it can be inferred, that it does no longer occur there; perhaps it therefore does not extend much further to the north and to the west than Purmerend.

In any case, such a settling of sediment is not possible without the presence of a sandy strip of land, separating it from the open sea; that strip of land must be located between Amsterdam and Haarlem, because the indicated clay deposit is not found in Haarlem. If one further keeps in mind, that our land has subsided considerably since that time, it is then not unlikely, that this strip of land consisted amongst others partially of the sand diluvium at Sloten and Halfweg, and thus that this had already roughly formed, as indicated in figure 1 of plate 6, when the deeper clay layers beneath Amsterdam formed by the deposition of sediment.36 The contradicting fact, that the same sand diluvium lies on top of the Eem formation in Haarlem, while the latter is found in Amsterdam on top of the deep clay deposit, can only be overcome, by assuming, that the Eem formation in Haarlem is older than that in Amsterdam, and thus that the shell layer at both points does not form a continuous unit [tr: footnote 36 is repeated here]; this latter assumption would be consistent with the basic assumption of the reasoning, that an older sandy strip of land lies between both. The shell layer between 29 and 33.8 m below AP in Haarlem would then belong to a beach on the open sea, having existed, before the sand diluvium took the shape, which enabled the settling of clay behind it [tr: sic].

In addition to the previous remarks attention must finally be drawn to the left side of figure 3 of plate 6; it appears, that near Hoofddorp there is the start of a sloping surface in the sand diluvium covered by hard clay, of the same nature as found at 2500 m east of den Diemen as well as near Post n°. 12 and by extrapolation must exist amongst others to the north east of Sloten, yet nothing can be said about its further continuation. Perhaps this clay layer (which was found in only the two most south-westerly of 5 drillings near Hoofddorp) is of a local nature only. If not, then it would indicate, that Hoofddorp is located near the southern edge of the oldest part of the sand diluvium, just like Sloten near the northern edge; the diluvial river mentioned in the beginning of this Note, that carried sand masses, could then be conceived [tr: to run] in the direction from Utrecht to Haarlem.37 If one now focusses on the numbers in figure 1 of plate 7, indicating the position of the upper surface of the diluvium, immediately beneath the thin peat crust, one also finds a slope in that direction, and it even seems possible, that some rather too low numbers indicate, that the old channel has not fully disappeared by the levelling action of the water after the closing of the river mouth. Along that line of thought one would be on the north-easterly bank of the diluvial river deposits at Amstelveen and Sloten.

In any case, and even though some uncertainty still remains, if one shall encounter the deepest clay layers of Amsterdam in Sloten, we do not consider this likely; and there is certainty, that the geological makeup is completely different here than beneath Amsterdam. If we are not mistaken, then the following conclusion may be drawn from all the foregoing.

The “diluvium starting at a small depth below the alluvial clay and lage veen [tr: sic]” in Zuidholland of which dr. Staring38 speaks (in a most likely too general fashion) and into which one has penetrated from 9 to 51 m39 in Gouda and near Leiden from 15 to 81 m below AP,40 without finding in essence nothing but sand, in an alternating fashion finer and coarser or mixed with small pebbles, -- extends much further up until Amsterdam, than suggested by the well drillings in the capital itself; on the north side it is partially roughly bounded by the stippled line a d e in figure 1 of plate 7. South and southwest of the city it thus extends to within the 2nd line of the Defence line. Here, near Amstelveen, Nieuwe Meer, Schiphol and Sloten, most likely also still up until Halfweg and the gun powder store 1800 Roeden, one finds a subsurface, where the upper surface of the deep continuous diluvial sand is located a mere 5 m lower than at many locations located further to the east outside the 2nd line such as for example Abcoude; here (and even to a lesser extent still at points like Ouderkerk and the fortress near the Bijlmermeer), the geological nature of the deeper layers differs entirely from that beneath Amsterdam41; here finally, southwest of the capital, -- and not, as one would superficially expect, to the southeast, -- the continuous sand is reached the earliest as close as possible to Amsterdam and within the 2nd line of the Defence line.

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If in the foregoing an indication is contained, that a location southwest of Amsterdam does not have the disadvantages, which one could initially be tempted, to ascribe to it, the reasons, for which we consider the location to be the most favourable, with respect to the chance, to obtain good or at least useable water, are, although partially connected to the geological conditions, in essence however of a different kind. The conditions, which will complicate obtaining the desired result, must therefore be considered.

The diluvial sand regularly contains organic substances of a plant origin up until great depths, which not only stain the layers themselves, in which they occur, but also of which some, that is her degradation- or transformation products, can become dissolved in the water and thereby be carried to deeper, originally pristine layers; the occurrence of dissolved gases with an unpleasant smell, which certainly make the water unsuitable for use, could be a consequence of this.

The presence of clay or loam is not seldom associated with this, which, even if only occurring in a small amount, renders the water undrinkable. At the same time in all the clay, and even to some extent in sand, the occurrence of iron becomes a problem; sometimes this is present as a brown sludge (iron oxide), in other instances the iron oxides are reduced by rotting plants to ijzeroxydul [tr: ferrous iron], which is soluble in water with carbonic acid, being the carbonic acid that partially formed by the decay of organic substances. The latter case only occurs when there is a lack of oxygen in the subsurface; the pumped water then often clear upon reaching the surface, to soon, exposed to the air, as a result of the escape of carbonic acid and the uptake of oxygen, become opaque, followed by the precipitation of iron oxide.42 Iron makes the water, also in amounts, in which it is not unpalatable or harmful, less suitable for the preparation of several standard foodstuffs. More complex transformations do not need to be considered here; it appears though that the shortcomings of water from great depths, --where there can be no issue with the problem of normal waters sourced from shallow wells, the pollution with contaminants from faeces, -- bar one exception mentioned after this, can essentially all be attributed to the consequences of an incomplete rotting of plant-based materials caused by the limited supply of the oxygen of the atmospheric air and to the presence of loam and dissolved iron compounds, the latter in immediate connection to the plant decay. One can flatter oneself, to conquer these objections by extending the drilling deep enough within financially and technically feasible constraints; not only does the chance, to find a clean water source, increase if the investigation extends over a larger area,43 but at the same time the water, the greater depth at which it occurs, will have had more opportunity, to dispose itself of some of the pollutants discussed here by natural filtration; moreover artificial filtration remains as a last resort.

The lack of dissolved atmospheric air thus plays an important role for the water in the deeper layers; in this regards the conditions will be the most favourable, where in the water of those layers a steady natural flow exists; because in this way fresh air, dissolved in rainwater is continuously carried into the depths, [tr: and] the rotting of plants is brought to an end, and impurities are removed at the same time. Such a natural flow can only be the result of a difference in pressure head or groundwater level. Perhaps the higher water table in the range of hills of the Gooi and Zeist region does exert its influence up until close to Amsterdam in this regard, yet while it is know that amongst others the spring near Hilversum44 merely rises to 1 to 2 m above AP, we place less confidence in this than in the pressure exerted by the natural water tower, that is found west of Haarlem in the wide and high belt of dunes. Taking into consideration that the groundwater level in the dunes generally follows the undulating topography at a slight depth and is therefore elevated here by several metres above the surface of the Zuiderzee, then it appears to be certain, that there must be a continuous subsurface flow from the dunes toward the Zuiderzee. A very weak flow for sure, but one that has persisted for centuries and centuries; a flow, that will be stronger in the upper sand layers than in the deeper, but which also in the latter can not be absent. On these grounds, it is therefore considered to be preferable, to select a location within this presumed flow between the dunes and the Zuiderzee.

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This location additionally has other, perhaps more significant, advantages. Apart from the aforementioned objections, which can prevent the success of the test, there is another, which one could potentially encounter specifically during the deeper drilling, and that is: a too high a content of seawater-derived dissolved salts, mostly table salt. Artificial filtration will not even solve this problem; it may therefore be the most treacherous cliff, against which one must watch the most. Before indicating, the manner in which this, in our opinion, must occur, some statements need to be made beforehand.

During the previously-mentioned earlier well drillings in Amsterdam, conducted before the construction of the dune water supply line, it appeared, that the discharging water had a higher salt content, as it was sourced from a greater depth. The data on that collated from different sources45 are, with a number of newer [tr: data] of a similar nature,46 graphically displayed in figures 5 and 6 of plate 7.47 The results from older drillings in Amsterdam that are thereby connected by lines, could be summarised in the conclusion, that the salinity is approximately proportionate with the depth below 30 to 35 m below AP.

In one of these wells, on the Noordermarkt, the water level has been recorded five times a day during more than two weeks a while ago, and these were compared to the water levels in het IJ, which had not yet been closed off, and the nearby Prinsengracht. The report about these observations by dr. F.J. Stamkart and dr. C. J. Matthes48 contains a graphical depiction of the fluctuations of the water levels in the well and in het IJ; between them there appeared to exist some analogy, so that the observations give rise to “a not entirely improbable suspicion, that the water levels in the well can be in some connection to the changes in water level in het IJ”. In the well the fluctuation manifested themselves with a magnitude of about one tenth of, -- and 6 to 8 h later than, -- that in het IJ; meanwhile the water level in the well stayed at all times lower (on average just over 1 m) than that of het IJ.49 In the treatise by professor Harting, mentioned multiple times already, those facts were considered a proof, “the water from the sea or from het IJ provides a part of the well water”.50

Other observations of a similar nature complement these. In Purmerend (1852), the water at a depth of 50 m was drinkable, and found to be brackish at a depth of 75 m51; something similar seems to have been observed in Leiden52; even in Gorinchem one has found water with a chloride content of 1220 mg/L at a depth of 178 m below AP, yet after one had penetrated a “seawater formation” over a depth interval of more than 60 m.53 Tracing the original explanation by professor Harting,54 what later has also been written by both mentioned geologists about the described phenomenon can be summarised as follows.55

The increase of the salinity of the water with depth in our sea provinces is a general feature, which must be attributed to the water of the sea, that intrudes laterally in the soil of the coastal lands and mixes there with the downward flowing infiltrated rainwater; that lateral expansion of the seawater occurs up until a distance, which increases with depth; the seawater will contribute a greater proportion to the composition of the mixture, when the direction of the lateral movement deviates less from the vertical one, that is, when the depth is greater at any given point.

Based on this train of thought, rest the following, ever more powerful statements by dr. Staring, with which professor Harting seems to have agreed in essence. “There can be no doubt, if seawater intrudes our soil to a certain depth, which increases with the distance.”56 . . . . “That the sea extends far landward at some depth below our zee-aulluvien [tr: sea alluvium] is a known matter of fact”.57 . . . . “That the soil in our sea provinces is completely saturated with seawater in the subsurface is generally known”.58 Thus when the Commission of 1866 that was mentioned multiple times already decided for the purpose of drinking water investigation, to conduct test drillings in Vinkeveen and Zoetermeer, they immediately took the stance, that one “should not search for freshwater at depths greater than on average 50 m, because one reaches the seawater-saturated layer there, which is found to a still unknown distance from our coasts and to a still unknown depth in our sea provinces”.59 At the same time [tr: though], -- in Vinkeveen one found water at a depth of 64 m, which was not called brackish [tr: footnote 58 is repeated here], and about the water in Zoetermeer it was, after stating, that in it had been found (at a depth of 33.6 m) first 45 mg and later 36.5 mg chloride per litre, incomprehensibly remarked: “it thus appears, that one has stumbled upon a seawater layer in the subsurface” [tr: footnote 59 is repeated here]. Please note that chloride content was even lower than that of normal dune water (Amsterdam 38 mg; ′s Gravenhage 53.6 mg; [tr: Den] Helder 70 mg) and thereby did not insignificantly differ from that of water from the Zuiderzee (6000 mg) or from the North Sea (18,000 mg)!

Before raising some doubts against the previous, firm statements, which are apparently based on very few factual observations, we wish to immediately state, that in Haarlem in 1886,60 so close to the North Sea, at a depth of approximately 47 m below AP water has been found, that is regularly used for brewing beer and contains only 40 mg chloride per litre, so roughly as much as the nearby dune water; and even if the salt content should increase gradually there at greater depth, for example to the tenfold, then still the salt could not be detected by the taste,61 and therefore also not be harmful.

The salts from seawater can enter into the well water in three different ways.62,63 First, -- where one encounters sea deposits, like in Gorinchem, or conditions like in Amsterdam and in Purmerend, where the water-bearing sand layers are covered by layers of clay largely deposited in seawater, which have never had the opportunity, to lose the seawater that has been present since the onset, -- the source of the high salt content is not far to be found.

Should one wish to assume though, that the salt in the well water in Amsterdam, can derive from somewhere else than the clay laying over the sand, it is then not necessary, to look for this source just in het IJ. Much closer one finds the canals of Amsterdam and the dewatering canals of Amstelland, which at the time already, and just like now, contain water, with just about as much salt as the water of the former open IJ and the Zuiderzee.64 The answer to the question, what influence this water will exert on that of the subsurface, appears to be largely dependent on the nature of the intermediate layers and on the larger or smaller opportunity for water renewal of those layers. If one now considers, the enormous thickness of clay that is present between the canals of Amsterdam and the sand of the well water, the connection between the two can not be characterised as easy [tr: sic]; yet, on the other hand, that brackish canal water does make that, layers once saturated by seawater are maintained in that condition.

The same holds in the end for the water of the nearby sea itself, when one considers the wells in Amsterdam in relation to het IJ; also here there can not be a more or less direct connection, as the observations on the Noordermarkt may lead to suspect.

In relation to the increasing salt content with depth several other causes can still be conducive. First of all the law, that lighter fluids float on heavier ones; on the other hand the dilution of the intrinsically salt water with freshwater from elsewhere, since the dilution of downward flowing infiltrated rainwater will automatically have more influence in the higher layers than in deeper ones.65

Very worthy of attention is, that even at the greatest depth, for which the salt content has been determined in Amsterdam, the number still remained significantly below that of the Zuiderzee, het IJ and the canals of the city (see plate 7, figure 5). It is impossible to speak of a “seawater layer” or such expressions. At the same time it is thus certain, that from the one or the other side a rather powerful diluting freshwater supply must exist. One arrives at the same conclusion, when considering, that the water of the well in the Fortress north of Purmerend amongst others, deep 27 m below AP, has a salt content, which by chance was simultaneously investigated by three chemists and was still a bit smaller (35 mg, 24 mg and 31 mg chloride per litre) than that of the dune water of Amsterdam. How come this small quantity of salt, when the immediately bordering dewatering canal contains infinitely more saline water, and when the polder waters of the Beemster are hardly better?66

On the other hand water with a chloride content of 5180 mg was found at a depth of 60 m below AP in the fortress near Abcoude, which is approximately 5 times more than at the same depth in Amsterdam, which lies much closer to the sea. With this well drilling though the water had been found to have a salty taste almost from the start; if one considers, that the water of the nearby Angstel [tr: river] (part of Amstelland’s dewatering canal system) will not be much less saline in summer than the waters closer to Amsterdam of those dewatering canals,67 and that, as apparent some drillings in and near the mentioned fortress, near the Angstel [tr: river], beneath the clay layer, which is almost certainly fully penetrated by this water, not much else follows than sea sand on top of diluvial sand, then it is not improbable, that the saline water from the Angstel [tr: river] has found its way to the deep continuous sand diluvium right here, and that thus the water, which was pumped from 60 m below AP, was merely filtrated water from the Angstel [tr: river].68

Perhaps there is still another reason, and that is the intrusion of water from the Zuiderzee into the sand diluvium at locations, which form the easiest pathway, that is: where this sand without clay cover in the surrounds of Muiderberg is in direct contact with seawater.

If it satisfactorily follows from the foregoing, that the theory of a “fully by seawater” saturated subsurface does not hold in such a strict sense in several respects, -- we do not contest, that an action of such a kind at least on the side of the Zuiderzee is not only possible, but even likely. Everywhere where the interior waters are below AP, the pressure head on the subsurface water column is smaller on the inside than on outside, and water from the Zuiderzee must intrude, either in large or in small amounts. Even only then is there equilibrium, when the lighter interior water stands a little higher than the sea.

The situation is entirely different on the side of the North Sea, where in the dunes the water of the coast is always higher than in the sea. If one sets this difference = a and taking into consideration, that the specific weight of the water of the North Sea water is 1.0238, then at a depth of \( \frac{a}{0.0238} \) = 42 a there is equilibrium between the saline exterior water and the fresh interior water69; for a difference of 5 m that depth thus already becomes more that 200 m.

About half of the infiltrated rainwater on the dunes flows toward the sea; and is the reason, that freshwater wells are found even close to the North Sea; the other half flows landward through the sand layers connected to the dunes, and could perhaps be the cause, amongst others, that the well water in Amsterdam is not even more saline, and that the well in the fortress north of Purmerend has roughly the same salt content as the dune water. The fact already mentioned about the water in the well drilled in Haarlem in 1886 reinforces that view, and is also proof in the end, how powerful the prolonged weak flushing of sand can be: that completely fresh water has been found in continuous sand below a former seafloor.

It is therefore perhaps not far from the truth, to assume, that also in the deeper layers two flows exist and have existed for a long series of centuries. The one, the most powerful by far, of freshwater, going from the dunes to the Zuiderzee; beneath it on the coast of the Zuiderzee a weak brackish water flow to the interior, which mixes there with the deepest parts of the first-meant flow. In our opinion, the conclusion therefore must here be: to preserve freshwater at depth for as long as possible, one must, -- because of the dunes --, approach the North Sea as close as possible.70

This conclusion has the additional advantage, that it can be met for a location near the rather fresh71 dewatering canals of Rijnland; after all the Amstel [tr: river] near Ouderkerk will contain at least 15 times [tr: footnote 71 is repeated here] as much salt as the Haarlemmermeer-dewatering canal near Sloten. That this large difference will have a large positive influence on the deep well waters, is something that we do not dare to state firmly; yet there can be a difference. And even if this were not the case, then one would immediately have the advantage during drilling, to be able to use less saline water when working with the drilling fluid.

Conjunctively considering the various points discussed in this Note, we believe, that the Post west of Sloten may be mentioned as the most suitable location for a first test drilling. In comparison to Post n°. 12, this location has the additional benefit to be located: further behind the first defence line of the Defence works (8000 m instead of 5000 m), closer to the actual basin of Nieuwer-Amstel (de Overtoom) and on a navigation way suitable for larger ships.

Should the drilling not yield the desired results, then as a second location could seemingly be considered: either Schiphol, or the gun powder store de 1800 Roeden (east of Halfweg), the latter having the advantage to be located right by the pressure pipeline of the dune water supply company; the data that will be obtained during the drilling in Sloten will possibly make a closer deliberation of that choice easier.

Amsterdam, 8 July 1887.

The Lieutenant-Cornel,

First-attending Engineer,

J. Drabbe.

The Captain-Engineer,

W. Badon Ghijben.

Footnotes

  1. 1.

    Submitted to the institute for publication by His Excellency the Minister of War, via letter dated 23 July 1887, Vth Division Corps of Engineers, No. 87.

    Because of several facts that have since then become known and because of the publication of this note in the Journal of the Institute some notes and references have been added during the revision (see Minutes 1887–88, p. 28), in the form of footnotes, to the otherwise unmodified manuscript.

    The “intended” well drilling, meant in the header, has in the meantime been completed near Sloten; a findings report has been submitted to the Institute for publication by His Excellency the Minister of War.

  2. 2.

    W. C. H. Staring, De bodem van Nederland, 1ste deel, p. 246. In subsequent footnotes this publication will be indicated by the letters B. v. N.

  3. 3.

    B. v. N., II, p. 119–120, and Verslagen en mededelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde, 2de reeks, 1ste deel (1885) p 181–193.

  4. 4.

    Dr. P. Harting, De bodem onder Amsterdam in Verhandelingen van de eerste klasse van het Koninklijk Nederlands Instituut, 3de reeks, 5e deel (182) p 1752. In subsequent footnotes this publication will be indicated by the letters B. o. A.

  5. 5.

    B. v. N., II, p. 129–132.

  6. 6.

    Rapport aan den Koning van de Commissie, benoemd bij Zijner Majesteits besluit van den 16 Juli 1886, n°. 68, tot onderzoek van drinkwater in verband met de verspreiding van cholera en tot aanwijzing der middelen ter voorziening in zuiver drinkwater (1868, second print 1869.)

  7. 7.

    B. v. N.. I, p. 198 and II, p. 45.

  8. 8.

    See amongst others B. o. A., p. 173 and plate I, figure 3. When the above was written, it was still unknown to the writer, that professor Harting himself had pointed out the incorrectness of the depiction in the figure already in 1872 (Verslagen en Mededelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde, 2e reeks, 6e deel, p 182–183). That same depiction is also found in the recently published Waterstaatkundige beschrijving van Nederland, by W. Verwey Az. (Waterbouwkunde, 2e deel, afdeeling XIII), plate XX, figure d.

  9. 9.

    B. o. A p. 182.

  10. 10.

    B. v. N., II, p. 131.

  11. 11.

    B. v. N., I, p. 303–304 and II, p. 130–131.

  12. 12.

    B. v. N., I, p. 82 and II, p. 45.

  13. 13.

    B. v. N., I, p. 301.

  14. 14.

    B. v. N., I, p. 83.

  15. 15.

    Compare B. v. N., I, p. 85, 2nd paragraph.

  16. 16.

    Rapport van de Commissie tot onderzoek van drinkwater, p. 344.

  17. 17.

    B. v. N., I, p. 344–345.

  18. 18.

    B. v. N., I, p. 299 and Geological map of the Netherlands.

  19. 19.

    B. v. N., I, p. 215 and 324.

  20. 20.

    B. v. N., I, p. 81 and 324.

  21. 21.

    The same holds true for the drillings for the new lock in IJmuiden, where the peat layer meant here has also not been encountered. Peat was encountered there at an elevation of on average 3.0 to on average 2.4 m above AP, yet based on this elevation this can not be a continuation of Holland’s extensive laagveenformatie [tr: sic]; most likely this is peat from a marsh in a dune slack that later became covered (compare B. v. N., I, p. 52) and therefore of a very local nature. This is apparently also the case with the peat, that sometimes becomes exposed along the outer rim of the dunes by coastal erosion.

  22. 22.

    After this was written, clay and loam has been found in a well drilling near Vogelenzang (so nearly inside the dune body) between sand layers in the diluvium at depths from 45.0 to 51.4, from 51.9 to 52.6 and from 59.6 to 60.2 m below AP. In Haarlem, no diluvial clay had been encountered up until approximately 47.5 m below AP.

  23. 23.

    In figure 2 only some of the deep drillings in Amsterdam have been included, because the other available data do not yield differences of decisive significance with these. (See B. o. A., plate I, and Notulen K. Inst. v. Ing. 1886–87, plates IV and IVbis). The only thing is that clay layer VI seems to be hardly present near the Utrechtse Poort, according to a (in B. o. A. unused) report in Verhandelingen K. Inst. v. Ing., 1850, 6de stuk, p. 58–59. This last reference contains a more detailed depiction of the drilling on the Nieuwmarkt in Plate III, about which statements of a different nature are found in de Nieuwe Verhandelingen der 1ste klasse van het Koninklijk Nederlandsch Instituut, 8ste deel (1840).

    The Figures 2 and 3 have by the way been largely based on the borehole descriptions in the designs no. 66 from 1887 and no. 161 from 1886 regarding the construction of the channel Amsterdam-Merwede, with which the numbers indicated above the figures and in figure 1 of plate 7 correspond.

  24. 24.

    Here also does the clay layer in question become more sandy in a westerly direction in entirely the same manner as in the cross-sections of plate 6. In this manner, the old alluvial marine deposit in for example Amsterdam and Zeeburg, once more consists of 3 layers that transgrade into one another: at the top clay (II), in the middle more or less clay-containing sand (III) and at the bottom clay, partially mixed with peat of layer IV. Concerning layers II and III professor Harting already remarked, “that one can not consider them to be sharply separated, but that they can perhaps be more appropriately considered to form a single layer”. (B. o. A., p. 130.)

  25. 25.

    Namely: at the Utrechtse Poort, from 10.44 to 11.35 m below AP “dry peat with wood” (Verhandelingen K. Inst. v. I., 1850, 6de stuk, p. 58); on the Passeerdergracht, “a muck layer thick 0.25 m., entirely composed of plant remains in which fragments of linden wood are clearly recognisable” (B. o. A., p. 130); on the Bickerseiland [tr: isle], from 11.99 to 12.86 m below AP “peat” (B. o. A., p. 82).

  26. 26.

    B. o. A., p. 131, in which multiple botanical details about the nature of the plant remains

  27. 27.

    See figure 1 of plate 7, in which the numbers in italics font indicate, at which depth below AP the lower surface of the sloping thin peat crust is found.

  28. 28.

    According to the results of the drillings along the railway line Zaanstreek–Enkhuizen, kindly provided for consultation by the first engineer on duty of the State Railway Lines. At Enkuizen the lower surface of this peat layer has risen again to 12 m below AP.

  29. 29.

    In two drillings just south of the junction of the St. Aagtendijk and the Nieuwen dijk a thin layer with hard peat has been encountered with the lower surface at on average 19.5 m below AP, because this was not found in several drillings along the Zaan [tr: river] and the mentioned low level displayed so little resemblance with the position at other locations indicated in figure 1 of plate 7, it was considered possible, that one was dealing with a very local condition, without a connection with the other parts of this layer. Hence the word “perhaps”. That doubt raised can now be considered to be relieved, now that the three drillings for the new lock at IJ muiden have resulted in finding with a thickness of 0.25 m, 0.6 m and 0.25 m “peat with wood as well” at almost the same depth (lower surface 19 to 19.05 m below AP).

  30. 30.

    Also, the coarser sand (sometimes with fine gravel), that in the indicated layer, going down the slope, is practically continuously encountered, namely: in Figure 2 of plate 7, in boring no. 10 at 10.6–10.9 m, at no. 9 at 12.6–13.6 m., at no. 8 at 12.2–14.3 m., at no. 7 at 12.6–14 m, and in Zeeburg at various depths between 13.5 and 15.5 m below AP; in Figure 3 of plate 7, in drilling no. 9 at 11.0–12.5 m, at no. 10 at 12.3–13.8 m. below AP. The same sand layer apparently continues also in a northwesterly direction; amongst others commences in Durgerdam and at the Blauwe hoofd, at around 16 to 18 and 19 m below AP sharp sand, at slightly greater depths mixed with small pebbles.

  31. 31.

    Details about this are found in: B. o. A., p. 216–217, G. J. Mulder Verhandeling over de wateren en lucht der stad Amsterdam (1827) p. 161–162 and Verhandelingen K. Inst. v. Ing 1850. 6de stuk, p. 64–67.

  32. 32.

    According to a communication by dr. Lorié. Also see the note [tr: the reference provided here is ambiguous and may be referring to footnotes 33, 36, 37 and 38] on p. 14 and 15.

  33. 33.

    Verslagen en mededeelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde, 2de reeks, 8ste deel (1874), p. 282 and 9de deel (1875), p. 42.

  34. 34.

    Archives du Musée Teyler, Série II. Vol. III, 1re partie (1887). Also see the note [tr: footnote 36] in the next column.

  35. 35.

    Compare: Verslagen en mededeelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde, 2de reeks, 8ste deel, p. 289 en 9de deel, p. 49.

  36. 36.

    The drilling at Sloten conducted since then appears to have confirmed these conclusions. Regarding the geological results of this drilling the Algemeen Handelsblad of 3 March 1888 contains a communication by dr. Lorié, to whom the soil samples were sent for investigation. In this one can read amongst others the following. “What makes this drilling of special interest to the geology, is the complete absence of the deeper and thus older marine formation with sea shells, which have been encountered by dr. Harting in various drillings in Amsterdam . . . . and were later referred to by him as the Eemstelsel[tr: Eemian formation] . . . . During the last years I found this Eemstelsel [tr: sic] also in some drillings east of Amsterdam along the Merwedekanaal, along the railway line Amsterdam–Hoorn, in Haarlem and in Vogelenzang. In it many shells occur, which no longer live along our shores, so that it is easy, to discern them from the shells on our coasts and the earth layers of the alluvium. The place where Sloten has now been built, just like Naarden, Weesp, and Muiden, must have been mainland during the North Sea (and not the Zuiderzee) waves ran at the location, where Amsterdam has now been built. Furthermore we consider the entire sand mass at Sloten below 13.3 m to 200 m” (beneath the area located at 1.10 m below AP) “as very old river sand. The land must therefore have been located just as much higher . . . .”

  37. 37.

    In relation to this consideration it may be worth remarking, that south of Kudelstaart and Aalsmeer, contrary to points located more east- and northward, traces of shells occur in the diluvial sand, so that the sand diluvium appears to be bordered by a sea beach there.

  38. 38.

    B. v. N., I., p. 304 and II p. 130.

  39. 39.

    B. v. N., I p. 377 and II p. 130.

  40. 40.

    Verhandelingen K. Inst. v. Ing., 1850, 6de stuk, p. 33–37, B. v. N., I, p. 303 and II p. 130.

  41. 41.

    See the note [tr: the reference provided here is ambiguous and may be referring to footnotes 27 or 32] on p. 13.

  42. 42.

    For more details see: B. o. A., p. 210, and especially Hon. mr. dr. A.D. van Riemsdijk, Dinkwateren grondboringen te Utrecht in 1870, p. 3, 20 and 24–27. In the latter work it is also demonstrated, that, for the assessment of such water from deeper layers, the presences of ammonia should not be associated with the usual negative connotation (see their p. 10–11, p. 27 note, and p. 69–75).

  43. 43.

    According to dr. Staring there are “examples of wells in diluvial soil, that can not contain infiltrated rainwater and that are separated by a mere few hundred metre from each other, but from which the one yields a completely clear and pure drinking water, the second a yellow, by iron oxide stained water, and the third water, that is impregnated with sulfurhydrogengas.” (Rapport van de Commissie tot onderzoek van drinkwater, p. 57.)

  44. 44.

    Prise d’eau of the Nieuweramstelsche waterleiding.

  45. 45.

    These sources are: for the well at the Nieuwmarkt, Het Instituut of Verslagen en mededeelingen van de vier klassen van het Koninklijk Nederlandsch Instituut, 1844, blz. 125–12; -- for the well on the Bickerseiland (Groote Bickersstraat; sugar refinery Java of B. Kooy) Verhandelingen K. Inst. v. I., 1850, 6de stuk, blz. 41; -- for the wells on the Noordermarkt (between the Noorderkert and the Prinsengracht), on the Muidergracht (Evangelisch-Luthersch Weeshuis, on one of the inner courtyards) and on the Passeerdergracht (at the “Huis van toevlucht voor behoeftigen”): B. o. A., p. 219–221.

  46. 46.

    Derived: for the well in Zoetermeer, from the Rapport van de Commissie tot onderzoek van drinkwater, p. 340; -- for the well in ‘s Gravenhage, behind the Department of War, from Tijdschrift K. Inst. v. I. 1870–71, blz. 110; − for the wells in Baambrugge and Abcoude (Raadhuis) from analyses of various experts, communicated in 1885 by the former mayor at the time; − for the wells on the Bakenassergracht in Haarlem (beer brewery of H. Lans en Zoon), on the De Wittenkade in Amsterdam (Kristal ice factory) and on the Singelgracht near the station of the Nederlandschen Rijnspoorweg in Amsterdam (beer brewery de Amstel), from analyses by various experts, communicated by our fellow member H. L. A. van den Wall Bake, member of the firm Mijnssen en Co., who installed these wells; -- for the wells in the fortress Spijkerboor, the battery on the Jisperweg, the fortress at Edam, the fortress at Abcoude and the Post no. 8 east of Abcoude, from analyses of mr. M.J.W.H. Muysers, military pharmacist 1st class; -- for the well in the fortress north of Purmerend from analyses of the same, the firm Schalkwijk en Pennink in Rotterdam and mister van Ark, pharmacist in Purmerend.

  47. 47.

    Regarding the remaining, in Figure 5 of plate 7 occurring data see the notes [tr: footnote 53] on p. 18, col. 1, [tr: footnote 61] on p. 19, col. 1 and [tr: footnote 64] on p. 20, col. 1.

  48. 48.

    Tijdschrift voor de Wis- en Natuurkundige Wetenschappen, published by the Eerste klasse van het Koninklijk Nederlandsch Instituut, 4th part (1851), p. 301–325.

  49. 49.

    Between the highest and the lowest water level in the well a difference existed of a mere 81 mm.

  50. 50.

    B. o. A., p. 222. Professor Harting has later also argued that the wells in Amsterdam are proof that there is a connection between the soil water and the water in het IJ (Rapport der Commissie tot onderzoek van drinkwater, p. 53). In the same spirit dr. Staring wrote that the observations by dr. Stamkart and dr. Matthes “prove that the water levels in het IJ and in the wells are related” (B. v. N., I, p. 309); when the same author stated a few years later, that the increasing salinity of the well water with depth in Amsterdam occurs “apparently by the influence of North Sea water” (Notulen K. Inst. v. I, 1859–60, p. 203), he hereby meant water, which via the Zuiderzee and het IJ originates from the North Sea. In the meantime it appears from the Report concerning the listed observations (from which the very carefully worded sentence paraphrased in the text was obtained), that the observers themselves absolutely do not consider it certain, that the water in the wells would be in communication with het IJ: a relation with the air pressure was also noted in the sense, that lower well water levels coincided with higher barometer readings and vice versa.

  51. 51.

    B. v. N., I, p. 309.

  52. 52.

    According to B. v. N., I, p. 309, the water of the well drilling near Leiden “did not become brackish until a significant depth”. Contrary to this, a statement by mr. D.A. Schretlen, who appears to have supervised the execution, contains amongst others the following: “the water from a depth of 16.6 M was brackish and stale in taste”; at a depth of 76.22 m it was “continuously brackish and bitter”; it appeared “that the water in the pipes stood at the same level as the open water” (water in the dewatering canals?) while “it can be assumed, that the water in the pipe should attain a connection to the open water” (Verhandelingen K. Inst. v. I. 1850, 6de stuk, p. 34 and 36.)

  53. 53.

    According to an analysis, reported in Verhandelingen, uitgegeven door de Commissie belast met het vevaardigen eene geologische beschrijving en kaart van Nederland, 1ste dee (1853), p. 140. Assuming that, the entire quantity of 1220 mg chloride is bound to sodium, one arrives at a table salt content of 2.02 per mille. For that analysis only a limited amount of water remaining was available; during an earlier investigation conducted during the drilling it was found, that the water contained “47 grein” (so 3060 mg) “pure sea salt to each Dutch pound” (Verhandelingen K. Inst. v. I. 1850, 6de stuk, p. 33.).

  54. 54.

    See B. o. A., p. 223.

  55. 55.

    Rapport der Commissie tot onderzoek van drinkwater, p. 52–53; B. v. N., I, p. 309.

  56. 56.

    B. v. N., I, p. 309. The sentence referenced there immediately follows with a here-omitted “thus” after the incorrect statement, that the water in Gorinchem at a depth of 178 m below AP had a table salt content of “over 2 to one hundred”, which according to note [tr: footnote 53] of the previous column must read per mille.

  57. 57.

    Notulen K. Inst. v. I. 1859–60, p. 203

  58. 58.

    Rapport der Commissie tot onderzoek van drinkwater, p. 58.

  59. 59.

    In there, p. 340.

  60. 60.

    Beer brewery of H. Lans and Son, Bakenessergracht near [the river] het Spaarne.

  61. 61.

    Regarding the question, at which chloride content the naturally occurring water is rendered unfit for drinking by a salty or brackish taste, the data diverge somewhat. E. A. Parkes, A. manual of practical hygiene, reports some data by De Chaumont on p. 57 of the 4th edition, concerning the quantities at which different dissolved inorganic substances become noticeable for an average palate; in that respect it is mentioned: 1070 mg chloridesodium, 285 mg chloridepotassium and 715 to 785 mg chloridemagnesium per litre. Supposing now, that these chloride salts are found in the well water in approximately the same mutual proportions as in seawater, then one could still consider potable water with 1050 mg chloridesodium, 35 mg chloridepotassium and 130 mg chloridemagnesium, together containing approximately 750 mg chloride per litre. If one on the other hand assumes that the chloride is bound to sodium, then the intended threshold is already reached at 650 mg chloride per litre.

    A report published by the 1ste klasse van het Koninklijk Nederlandsch Instituut about the water of the well on the Noordermarkt in Amsterdam, states at one point, that the taste “according to the findings of about one hundred persons [was] considered to be good”, and at another point: “the ample quantity of table salt, in relation to the small amount of other salts, renders the taste salt and less pleasant for many” (Tijdschrift voor de Wis- en Natuurkundige Wetenschappen, published by the eerste klasse van het Kon. Ned. Instituut, 4th editition, 1851, p. 294 and 295.) This water, which thus appears to be at the limit of drinkability, had a chloride content of (B. o. A., p. 219–221) a chloride content of 576 to 590 mg/L according to five different analyses.

    From a report in the Deutsche Bauzeitung 1879, p. 205, it follows, that the Stralsund wells of 55 to 59 m depth are made, of which the water is considered to be “relatively good”, though it contains 287.5 to 617.7 mg chloride per litre.

    It follows that a chloride content of 600 to 700 mg (plate 7, figure 5) must be considered the upper limit for drinkability, while a chloride content of 400 mg will presumable meet all the palates. One can easily convince oneself by the way, that this quantity (which corresponds to one teaspoon fine table salt to 2.5 to 3 L of water) does not bring about any changes in taste of the water. One of these is indicated in the aforementioned report about the well on the Noordermarkt in Amsterdam: “the large quantity of carbonic acid, that this water contains, does somewhat correct the taste; after boiling, which drives off the carbonic acid, the salty taste has become stronger”.

    Water from a Norton well at the post n°. 8 east of Abcoude, had, after the iron had precipitated, a pleasant taste and a chloride content of 333 mg/L. About the water from the well on the Bickerseiland [in Amsterdam] drilled in 1849 (with a chloride content of only 245 mg/L) on the other hand, it was testified that: “the first impression is very pleasant, hard and tasty; if one drinks small sips for a while, it leaves a silty aftertaste on the tongue” (Verhandelingen K. Inst. v. I., 1850, 6de stuk, p. 40). About this last well one reads in the Report by the drinking water commission (p. 66), cited several times, that it supplied the sugar refinery “of good water for years”, but that 4 years ago (so some 15 years after construction) it had become unusable.

    The aforementioned threshold figures for the chloride content from seawater or sea-alluves, at which the water becomes unsuitable for drinking, do not appear to apply to water from shallow wells, for which the relatively high chloride content is mostly a consequence of the admixture with infiltrated water from a contaminated soil. For according to analyses, conducted in the laboratory of professor J. W. Gunning, the chloride content of the contents of private wells can be taken on average as 5000 mg/L (Rapport der Commissie tot het ontwerpen of voordragen van een plan tot reiniging- en reinhouding van den bodem en de wateren van Amsterdam, 1873, p. 927 en 928.)

    If one isolates from the numerous water analyses, appearing in the Appendices VII and VIII of the Rapport der Commissie tot onderzoek van drinkwater, those, of which well water with respect to taste and external properties were considered to be favourable, it turns out, that the highest chloride contents were: 161, 178, 179, 183, 190, 202, 204, 207, 213, 215, 270 and 278 mg/L (sample nos. 14, 130, 26, 234, 129, 235, 227, 193, 138, 236, 195 and 52, respectively). This corresponds rather well with a report by Hon. mr. dr. Van Riemsdijk on p. 3 of the on p. 16 cited work, that a table salt content of 300 mg/L (so a chloride content of 182 mg/L) has to be considered as a maximum for good well water in Utrecht, the word “good” must apparently be interpreted here as “good visually and according to taste”. Based on this one can apparently assume, that a chloride content of 150 to 250 mg/L must be held for the threshold of drinkability for wells that are not deep (plate 7, figure 5).

  62. 62.

    For harmless drinking water it is often demanded, that the chloride content does not exceed a value of 20 to 30 or of 35 mg/L, since a larger amount of chloride compounds, consistent with the last part of the previous note, renders the water susceptible to contamination by infiltration water from the surface, in which germs of contaminants can be present; the water of our main rivers namely usually has a chloride content of between 10 and 17 mg/L up until close to the sea, an amount that is not seldom found in good rainwater. It goes without saying, that this demand (although completely justified for shallow wells outside our sea provinces, but which is not met even by the excellent water of our dune water supply), has no significance whatsoever when assessing water from deep wells, the high chloride content of which apparently originates from the sea. The passage stated in the text: “the salt is not harmful when it can not be tasted” only refers to this special case of course.

  63. 63.

    The three-pronged origin of the table salt stated here, namely the seawater originally present in the sea deposits, the water of the brackish dewatering canals and that of the sea itself, -- has also been presented in a slightly different form in B. v. N., p. 308–309.

  64. 64.

    According to Appendix N of the Memorie van Toelichting, belonging to the draft legislation for the reclamation of the southern part of the Zuiderzee (Bijlagen tot de Handelingen der Staten Generaal, 2de Kamer, zitting 1876–77, no. 174), the chloride content of the water in the intended part of the Zuiderzee can be taken as 6000 mg/L on average.

    During an investigation initiated in 1885 for State Medicinal Supervision it was found, that the water of the dewatering canals of Amstelland is saline everywhere and contains more table salt, as one approaches Amsterdam. In front of the Bijleveld it was found in Kokengen 2730 mg and in Harmelen 1395 mg chloride per litre (Verslag over den toestand der provincie Utrecht in 1885, Appendix VI, p. 41.)

    From the analyses by dr. G. J. Mulder, communicated in the Verhandeling over de wateren en lucht der stad Amsterdam, it can be calculated, that the chloride content of the water in 1825 was: in the Zuiderzee at Muiderberg 5624 mg/L; in het IJ at the Schreijerstoren 5294 mg/L; in the Amstel at het Kalfje north of Ouderkerk 5310 mg/L, and in the canals of Amsterdam approximately as the latter two figures.

    Based on those data and considering the changing water management and the frequent inlet of water from the Zuiderzee in Zeeburg, the figures on the right-hand side of figure 5 of plate 7 were estimated to give an indication. Since then it has been found that in doing so the chloride content of Amsterdam’s canals and the dewatering canals of Amstelland near Amsterdam has been estimated on the high side, and that at least after some rain does not exceed 4500 to 2500 mg/L.

  65. 65.

    The rainwater meant here, does not infiltrate into the ground in Amsterdam itself of course. The water in the upper soil of the capital is usually brackish and seldom contains less than circa 2500 to 3500 mg chloride per litre (Rapport der Commissie tot het ontwerpen van een plan tot reiniging, enz., p. 929); further compare the italicised citation in the next note.

  66. 66.

    According to a since then initiated investigation of two water samples, which were taken near the Fortress north of Purmerend on 17 October 1887, the chloride content of the Beemsterringvaart (Schermerboezem) is 2698 mg/L and in the Beemster 923 mg/L. If one assumes that a weak solution of table salt, is like this water, according to the experiments by professor Harting “does not lose absolutely anything of its chloridesodium content upon passing through the soil(B. o. A., p. 226; B. v. N., I p. 309), then the low chloride of the well water (on average 30 mg/L) contrasts starkly with the figures above.

  67. 67.

    Since then it has been found, that the dewatering canals of Amstelland at Abcoude, on the 3rd of September 1887, when after a summer drought some rain had fallen, had a chloride content of 2177 mg/L.

  68. 68.

    After the fact from the previous note this assumption becomes less plausible.

  69. 69.

    Above this depth of 42 a dune water would be flowing seaward, below it North Sea water would be encroaching landward in the same manner as the phenomena regarding locks, reported by mr. J. F. W. Conrad at the institute’s meeting on the 12th of April 1881 (Notulen K. Inst. v. I. 1880–81, p. 71); the numbers of 40 to 50 mentioned in there are apparently analogous to the coefficient of 42 calculated here.

  70. 70.

    At the since then completed well drilling in Sloten water with a salt content nearly as low as dune water has actually been found at a depth of circa 35 and 48 m below AP. Below this depth, at about 55 m below AP, the salt content suddenly starts to increase. At a depth of 200 m below AP the water of the well is 1.5 times as saline as the water from the Zuiderzee, so that it appears that one has to assume, that North Sea water encroaches beneath the dunes already at a depth less than what has been assumed.

  71. 71.

    This figure of 15 has been assumed by estimation, presuming, that the chloride content of the dewatering canals of Amstelland at Oudekerk probably would be 4500 to 5000, and that of the dewatering canals of Rijnland near Sloten would not exceed 300 to 350 mg/L. Since then it has been found though that the former figure presumably amounts usually to merely half of the assumed value, and that the latter on the other hand has to be assumed about 4 times higher; the proportionality factor of 15 is then reduced to somewhat less than 2. A brief clarification to explain this erroneous estimate: according to an analysis of water, which had been taken in November 1825 from the then lake Haarlemmermeer at Sloten, the chloride content was 393 mg/L at the time (dr. G. J. Mulder, Verhandeling etc., p. 66). Considering the improved water circulation in Rijnland it seemed that one could assume, that the figure would now be somewhat lower than then; other analyses of the dewatering canals of Rijnland appeared to confirm this; for example the Brouwersvaart at Overveen with 208 mg chloride per litre (Verhandelingen K. Inst. v. I. 1850, 6de stuk, p. 102); and also the waters in the surroundings of Leiderdorp and Leiden with merely 65 to 147 mg/L (sample nos. 49, 62, 64, 200 and 201 of Appendices VII and VIII of the Rapport der drinkwater-commissie cited multiple times). Contrary to this it has now become clear, that the northern part of the dewatering canals of Rijnland can at least not be considered to be “relatively fresh”.

Notes

Acknowledgements

The author would like to thank Sue Duncan for her assistance with the preparation of the translation for final publication.

Supplementary material

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References

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Federal Institute for Geosciences and Natural Resources (BGR)HannoverGermany

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