SAMPLING OF GROUNDWATER
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Sampling of Groundwater
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SAMPLING OF GROUNDWATER
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Sampler Education Volume X of 5
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CONTENTS
Sampling of Groundwater Sampler Education Volume X of 5
Chapter 1 ........................................................................................................... 1
Introduction ......................................................................................................... 1
1.1
Basic about groundwater sampling
1
1.2
Reasons for sampling
4
1.3
Legislation about groundwater sampling
5
Chapter 2 ........................................................................................................... 7
Basic knowledge about groundwater .................................................................. 7
10 .1
Terms about subsurface water
7
10 .2
The origin of groundwater and the water cycle
8
10 .3
Chemical components in groundwater
9
2.3
Geochemical processes in the groundwater
11
10 .4
Classification of groundwater
16
10 .5
Aquifers and their pressure levels
17
10 .6
Aquifer examples
21
Chapter 3 ......................................................................................................... 27
Decisions (sample situations) .......................................................................... 27
10 .1
Sampling related to water supply
27
10 .2
Groundwater monitoring
28
10 .3
Investigation of contaminated sites
29
10 .4
Monitoring wells at landfills
29
10 .5
Methods of drilling and well completion
30
Chapter 4 ......................................................................................................... 31
Planning of sampling ........................................................................................ 31
10 .1
Elements of a sampling plan
31
10 .2
Reading a well journal from Jupiter database
31
10 .3
Reading a chemical analysis from Jupiter
32
10 .4
Local conditions at sampling point
33
10 .5
Sampling methods for groundwater
33
10 .6
Type of analysis and contact to laboratory
34
Chapter 5 ......................................................................................................... 35
Pumps and other sampling equipments ........................................................... 35
10 .1
Centrifugal suction pump
35
10 .2
Peristaltic suction pump
35
10 .3
Vacuum suction pump
35
10 .4
Submerged pump with motor
36
10 .5
Submerged pump with batteries
36
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10 .6
10 .7
10 .8
10 .9
10 .10
Submerged diaphragm pump
Montejus pump
Inertia pump
Bailers
Equipment for on-line field measurement
36
36
36
37
37
Chapter 6 ......................................................................................................... 39
Sampling activities in the field ........................................................................... 39
10 .1
Identifying the sample locality
39
10 .2
Measuring the groundwater table
39
10 .3
Pre-pumping and field measurements
39
10 .4
Treatment of water samples – filtration and preservation
39
10 .5
Sterile sampling of drinking water
39
Chapter 7 ......................................................................................................... 41
Packing and sample handling ........................................................................... 41
10 .1
Ordering analysis from laboratory – logistic
41
10 .2
Main ions in groundwater – sample packing and handling
41
10 .3
Gasses in groundwater – sample packing and handling
41
10 .4
Organic substance – sample packing and handling
41
10 .5
Pesticides – sample packing and handling
41
10 .6
Volatile substances – sample packing and handling
41
10 .7
Oil – sample packing and handling
41
Chapter 8 ......................................................................................................... 42
documentation .................................................................................................. 42
10 .1
Sampling identification
42
10 .2
Sample labelling
42
10 .3
Analysis requisition
42
10 .4
Chain of custody report
42
10 .5
Sampling report
42
Chapter 9 ......................................................................................................... 44
Quality Control .................................................................................................. 44
10 .1
Contamination from sample equipment
44
10 .2
Maintenance and cleaning of pumps
44
10 .3
Critical situations during filling the sampler container
44
Chapter 10 ....................................................................................................... 45
HEALTH and safety .......................................................................................... 45
10 .1
Sampler friendly design of monitoring wells
45
10 .2
Physical working positions – heavy equipment handling
45
10 .3
Chemical used for preservation and field measurements
45
10 .4
Personal protection
45
References ....................................................................................................... 46
ii
Sampling of Groundwater
Appendices...................................................................................................... 48
A.1
Quality criteria for the main components in drinking-water
48
A.2
Parameter groups in water analysis
50
A.3
Common Minerals in Danish rocks
51
A.4
Well journals from Jupiter
54
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Sampling of Groundwater
Chapter 1 - Introduction
Chapter 1
INTRODUCTION
Aim of Learning





To be familiar with basic terms about groundwater and drinking water
To get an overview of sampling points for groundwater and drinking water
and how samples of groundwater are used
To be familiar with concentration concepts for substances dissolved in
groundwater
To realize the benefit from proper sampling of groundwater and drinking
water
To know the main principles of legislation about the item
First chapter in this textbook will provide you with basic knowledge about terms
and typical groundwater sampling situations. Also you will be introduced to use of
groundwater analysis and the main principles of legislation about groundwater
quality.
1.1
Basic about groundwater sampling
The term groundwater means that the water comes from the subsurface. However
the sampling in this book also include treated or purified water from a water work,
normally named drinking water or potable water. The term raw water is used for the
untreated water coming directly from the well.
Groundwater in the subsurface is “invisible” until you have raised it till the
ground surface by means of a pump or a bailer. Access to the groundwater is through
a borehole which is developed with certain installations so it becomes a well. Figure
1 shows a drawing of the subsurface part of a typical well with screen and casing.
The screen is a pipe with holes or slots positioned at the depth from where you want
to abstract the groundwater sample. In line with the screen is the pipe named casing.
The space between the casing and the surrounding rocks is filled with sealant of clay
or bentonite.
Around the screen is a filter pack of gravel in order to improve the inflow of
water, se Figure 1 b). In hard rocks such as sandstone or limestone it may not be
necessary to have a screen, because the rock is so solid, that the borehole can stay
open without collapse, see Figure 1 a).
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Figure 1
Typical wells in limestone a) and sand b)
The rocks from where it is possible to abstract groundwater are named aquifers.
Basically aquifer rock types consist of sand, gravel and fractured hard rocks. In
Figure 1 is shown a limestone aquifer in the bottom of the picture and a widespread
sand aquifer in the middle. Near the top of the section is shown two small sand
bodies which also are aquifers – if it is possible to abstract water from them. We do
not know if water abstraction is possible until we have carried out drillings and
equipped the boreholes with screens in order to see if sufficient water will appear in
the hole.
Each aquifer has a water level also named the groundwater table or pressure
level. In Figure 1 the limestone aquifer and the middle sand aquifer have different
pressure levels as seen from the levels of the blue water in the casings. The different
levels mean that the clay separating these two aquifers is tight and prevent hydraulic
contact between the sand and limestone.
The size of the aquifer determines if the aquifer is named primary or secondary.
In Figure 1 are shown two primary aquifers – the limestone and the middle sand. If
the two sand beds near the top are water bearing, we would name them secondary
aquifers.
When taking a groundwater sample it is essential to know which aquifer the water
comes from. Therefore well information about depth, screen level and water level
must always be known by the sampler. Also information about rock types is
2
Sampling of Groundwater
Chapter 1 - Introduction
important to identify the types of aquifer present. In Chapter 2 there are further
descriptions of the different types of aquifers.
Ground water looks typical clear and pure when the sample is taken – but it has
always different components dissolved in it. Other components may be suspended in
the water as small particles but are still practically invisible for the eye. Only after a
chemical analysis of the groundwater sample at a laboratory (or by help of field
measurements), we are able to identify the components.
The amount and types of the components determine the quality of the
groundwater. We measure this quality in concentrations of the different components
given in mg/l or in μg/l. Figure 2 illustrates concentration concepts exemplified with
dissolution of a sugar lump in different volumes of water. As 1 mg sugar/l water is
the same as 1 mg/kg , we can see that 1mg/l equals 1 ppm. This corresponds to one
lump of sugar dissolved in a road tank car. In the same way 1 μg/l is equal to 1 ppb
corresponding to a sugar lump dissolved in a tanker sailing in the oceans.
Because the quantity of substances is so extremely small, even a very slight
sampler contamination (from dirty hands or careless handling of sample equipment)
can cause severe impact on the analysis result.
1 lump of sugar - 2.7 gram
dissolved in:
dilution:
1 part per cent
1 o/o
0.27 litre
g/kg
10 g/kg
1 part per mille
1 o/oo
1 g/kg
1 part per million
1 ppm
0.001 g/kg
1 part per billion
1 ppb
0.000 001 g/kg
1 part per trillion
1 ppt
0.000 000 001 g/kg
1 part per quadrillion
1 ppq
0.000 000 000 001 g/kg
2.7 litre
2700 litre
2.7 million litre
Östertal bei Attendorn
2.7 billion litre
Starnberger See
2.7 trillion litre
Figure 2
textbooks).
Concentration examples. (figure may be altered – it could be a common one for all
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1.2
Reasons for sampling
In many situations it is essential to know the quality of groundwater and drinking
water. Health reasons are important, but also many environmental and technical
issues are related to the quality of groundwater.
Basically we can distinguish between the following types of sampling points and
locations, where knowledge about water quality is needed, see Figure 3.

Raw water sampling from wells for water supply

Sampling during treatment process at the water work

Sampling of water before delivery at customers

Sampling from special groundwater monitoring wells

Groundwater sampling from investigation of contaminated sites

Groundwater sampling from monitory wells at landfills
The first tree bullets are about sampling related to production of drinking water at
water works. You can regard every water work as a food industry – and the raw
water supply wells as the overall main input to this production. So it is quite
understandable that the quality of this main input must be carefully supervised and
controlled.
Figure 3
Red stars show sampling points for groundwater and drinking water
Sampling and analysis is always done before design of the treatment systems for a
new water work as ground water quality vary from place to place due to geological
conditions. So the type of treatment process will be designed special for the raw
water type existing in the actual place. There are no legislative rules for the quality
of the raw water used for the production – only the end product, the final drinking
water delivered to the consumers, has to comply with a set of requirements for
different parameters.
Because of the great public interest in pure and uncontaminated drinking water,
there is special legislation about how many samples, how often and which analysis
to make. Principally the number of samples and the frequency of sampling depend
4
Sampling of Groundwater
Chapter 1 - Introduction
on the amount of produced drinking water – the bigger amount – the more analyses
are required. Rules about this topic are described in Chapter 3.
Sampling from water supply wells and sampling for drinking water delivery
control must be carried out by certified persons and laboratories according to Danish
legislation.
Besides the control at the water work, groundwater is also sampled from specific
wells situated in selected monitoring areas. Sampling dedicated to monitor the
general ground water quality has taken place in Denmark since 1989. The reason
why groundwater monitoring is regarded so important is that Danish water supply
nearly 100 % is based on groundwater. Also groundwater quality influences the
water quality in surface waters as lakes and rivers.
Another reason for taking groundwater samples is related to soil contamination.
Investigation of contaminated sites always includes drilling and sampling of soil. If
water is present in the borehole, a screen will be placed in order to take water
samples from the well. The type of contamination determines which components
should be analysed. For nearly all types of old industries Danish “Videncenter for
jordforurening” has published a recommended list of chemical components to look
for depending on characteristic history and normal praxis for the industry in
question. (AVJ 2007).
Groundwater contamination is often related to upper aquifers situated only few
meters below ground surface. Sometimes the hydraulic conductivity is quite small in
these upper aquifers, and this may cause special care during sampling. We will
return to this later in Chapter 5.
The use of sampling and subsequent analysis during investigation of
contaminated sites is the risk evaluation. In order to determine if remediation is
relevant, ground water analysis is necessary to find out the character of the problem
and the spreading of the contamination.
Somewhat comparable to contaminated sites are groundwater sampling related to
landfills, as many old landfills can be regarded as contaminated sites. The reasons
for taking sampling at a landfill is to monitor the groundwater quality below and
downstream the landfill, to find out if there is any impact. In many cases the
monitoring is related to old landfills established without a permission – but also
many samples are taken from monitoring wells at new controlled landfills.
.
1.3
Legislation about groundwater sampling
GEUS has published technical directions for sampling in relation to the monitoring
programme. More information to be found at
http://www.geus.dk/publications/grundvandsovervaagning/
For quality of water intended for human consumption EC has adopted directive no
98/83/EC of 3. November 1998. Annex 1 in the directive have list of parameters and
parametric maximum values structured in 3 classes:
A) Microbiological parameters limiting values (regarded as potential danger)
B) Chemical parameters limiting values (regarded as potential danger)
C) Indicator parameters limiting values (no potential danger)
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In the corresponding Danish legislation, Statutory order no 1449 (11/12/2007)
about drinking water quality, the limit values for parameters are structured in the
following 4 groups:
1)
Quality limiting value for main components in drinking
2)
Quality limiting values for inorganic trace elements
3)
Quality limiting values for organic micro-pollutants
4)
Quality limiting values for micro-biological parameters
In appendix 1 of this textbook limit values for the main components in the Danish
Statutory Order is compared to limit values in the EC-directive.
Two kinds of monitoring are mentioned in annex 2 of the EC-directive. This is
check monitoring and audit monitoring.
Check monitoring is regularly in order to provide information on the organoleptic
and the microbiological quality of the water supply for human consumption. The
purpose of check monitoring is also to get information on the effectiveness of
drinking-water treatment – particularly when disinfection is used.
Audit monitoring is done to provide the information necessary to determine
whether or not the quality of the water comply with all parametric values set up in
the Directive.
The Danish legislation operates with four categories of monitoring points for
water supply. This is well monitoring (analysis of the raw water from the well),
extended monitoring and normal monitoring (analysis taken in the water supply
system) and finally restricted monitoring (analysis taken in the pipe system).
Appendix 2 show which parameters are included in each category.
6
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
Chapter 2
BASIC KNOWLEDGE ABOUT GROUNDWATER
Aim of Learning







To be familiar with terms used to characterize subsurface water
To know the interaction between groundwater and surface waters
To be familiar with the main chemical components in groundwater and
know their normal concentration levels in groundwater
To know the importance of pH and Eh-levels in groundwater
To be able to identify aquifer types given relevant well information
Be able to use potentiometric maps to get information about groundwater
level and flow direction
Know the hydraulic response when water is pumped from a well
This chapter describes how the groundwater is formed from precipitation and how it
is present in aquifers below the surface. Chemical components of groundwater as
well as main water types will be explained. Different types of aquifers are introduced
with figures and information about chemical characterization.
As sampling of groundwater is basically related to boreholes this chapter will also
include a section about borehole drilling and how to complete the well with suitable
filters, sealing and other installations.
10 .1 Terms about subsurface water
There is always a certain amount of water present in the ground, more or less filling
the voids between the soil grains and the fractures in the solid rock. If the voids and
fractures contain both air and water, the zone is said to be unsaturated,see Figure 4.
Other names for the unsaturated zone are vadose zone, soil moisture zone or zone of
aeration.
Below the unsaturated zone lies the saturated zone, where the voids and fractures
are completely filled with water.In Denmark the thickness of the unsaturated zone
does not exceed 70–80 metres. In areas with high mountains and dry deserts, in
contrast, it can be several hundred metres thick.
The term groundwater is used for the exchangeable part of water in the saturated
zone, i.e. the circulating part of water. Over the years this will be replaced by
precipitation infiltrating down from above.
Beneath the circulating groundwater lies the stationary water – also termed
stagnant water. This water is either not exchanged at all, or exchange is negligible.
The term residual water is used for water that was deposited at the same time as the
sediment was formed, i.e. several thousand or million years ago. Normally the
circulating groundwater is fresh water, whereas residual water or stagnant water may
be brackish. The boundary between the fresh groundwater and the brackish residual
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water may be located anywhere from a few metres to a couple of hundred metres
below ground surface depending on the rock type and precipitation in the area.
Figure 4
Subsurface water – saturated and unsaturated zones.
The boundary between the saturated and the unsaturated zone is the capillary
water table. This is always located at a higher level than the pressure level of the
groundwater (see GWT in Figure 4). The extent by which the capillary water table is
higher than the groundwater table depends on the capillarity of the soil type involved
– the more fine-grained the soil, the higher the water can be raised by capillary
forces. Thus clay and silt are able to raise the water several metres above the
groundwater table, typically up to surface level. In contrast, the more coarse
sediments such as sand and gravel have much lower capillarity and the capillary
water table is therefore virtually identical to the groundwater table or only a few
centimetres above it.
In Denmark the climate is normally so humid all year round that the pores of finegrained soils such as clay and silt are always saturated with water at depths
exceeding 1 m below ground surface.
10 .2 The origin of groundwater and the water cycle
All groundwater starts as precipitation that infiltrates down into the soil. Here the
water follows different routes leading to the sea, from where it will evaporate again
eventually generating new precipitation. This water cycle is shown in Figure 5.
The water remains in the various parts of the cycle for different lengths of time.
On average the water remains in the atmosphere, surface streams and drains for only
a period of weeks, whereas it can remain in the groundwater system for several
thousand years.
The fraction of the precipitation that seeps down to the groundwater through the
soil is termed the infiltration or net precipitation. This only comprises a small
fraction of the precipitation as about half evaporates from the ground surface and
some runs off via drainage systems and surface streams. During the summer period
8
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
nearly all the precipitation will evaporate and hence will not contribute to the
formation of new groundwater.
Exchange of water often takes place between the groundwater and the water in
lakes and surface streams. If the surface level of the stream or lake is below the
pressure level of the groundwater, groundwater will flow into the stream or lake.
Conversely, water will flow to the groundwater from lakes and streams if their
surfaces are above the pressure level of the groundwater.
Figure 5
The water cycle
10 .3 Chemical components in groundwater
Groundwater components consist of dissolved substances (positive and negative
ions), gasses and other components as shown in Figure 6. In this overview-figure are
only seen the natural components – to this may be added contamination components
from human activities (anthropogenic substances). This could for instance be
fertilizer and pesticides spread in the field as well as solvents or other substances
spilled by industry.
When the groundwater slowly moves in the subsurface part of the water cycle
several processes will take place because the water always try to be in equilibrium
with the varying physical and chemical conditions in the subsurface. While
temperature in the groundwater system is rather constant in the interval 6-8 °C, the
pressure can vary considerable. The varying pressure impacts the chemical processes
and their equilibrium. At high pressure the water for instance is able to contain more
dissolved gasses than with lower pressure.
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Generally the pressure will be high in the deeper part of the groundwater system,
but this is related to the geological relations in the area. If we have tight
impermeable strata near the surface in for instance a valley, then the pressure in the
groundwater may be very high even at small depths.
Figure 6
Components
Species
Main components
positive ions – cations
Ca2+,
Na+,
Mg2+,
K+,
NH4+,
Fe2+,
Mn2+,
Main components
negative ions – anions
HCO3-, Hydrogen
carbonate
Cl-,
Chloride
SO42-, Sulphate
NO3-, Nitrate
PO43-, Phosphate
Trace components
(cations and anions)
Al3+, Aluminium
Ni2+, Nickel
Zn2+, Zink
F-,
Fluoride
and others
Organic components
Humic acids
Neutral (non-loaded) dissolved components
Silicic acid, H2SiO3
Gasses
O2,
CO2,
CH4,
H2S,
Calcium
Sodium
Magnesium
Potassium
Ammonium
Iron
Manganese
Oxygen
Carbon dioxide
Methane
Hydrogen sulphide
Classification of components in groundwater
The slowly movement of the groundwater will cause solution or precipitation of
substances from the minerals in the rocks where the groundwater moves. When
minerals are dissolved, they will release components to the groundwater – and
sometimes components from the groundwater will precipitate as solids and stay in
the subsurface.
On Figure 7 is shown which elements the mineral feldspar is build of and which
components this very common group of minerals can release to the groundwater. In
appendix 3 all other common minerals are shown in a similar table with their
formula or at least the elements included in their formula. Last column in the mineral
table is a short note describing the weathering condition for the mineral and the
significance for the groundwater chemistry.
10
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
MINERAL NAME
and chemical formula
FELDSPAR
K-feldspar
KAlSi3O8
Plagioclase
(Ca,Na)AlSi3O8.
Albite is the name for a pure
sodium plagioclase
NaAlSi3O8
Figure 7
APPEARANCE AND
OCCURRENCE
WEATHERING and significance
for the groundwater
Reddish skin-coloured (Kfeldspar). Light, grey or brown
(plagioclase feldspar)
Feldspar crumbles out of
basement rock.
Feldspar occurs as a constituent
of basement rock and as
angular grains in meltwater
sand.
Gradually weathers to clay
minerals and can thereby
release K+, Na+ and Ca2+ ions to
the groundwater.
Example of a common mineral group and elements released to groundwater.
Components in groundwater are seen in different levels of concentration. Main
components include substances with typical concentrations above 1 mg/l, while trace
elements are substances with typical concentration levels below 1 mg/l, see Figure 8.
Figure 8
Typical concentration levels of components in groundwater
2.3 Geochemical processes in the groundwater
Geochemical envirronment – pH and Eh
Every groundwater sample represents a specific geochemical environment and by
analysing the chemical components we can be informed about that environment.
Two important parameters characterise a geochemical environment and these are
acidity expressed by pH and redox potential expressed by Eh.
The acidity expressed as pH is a measure of the amount of hydrogen ions (H+) in
the water. pH is defined as the negative logarithm to the concentration of hydrogen
ions in the solution. Low values of pH means high concentrations of hydrogen ions,
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and thereby acid groundwater. On the opposite high pH values means low
concentrations of hydrogen ions and thereby basic groundwater. Water with pH =
7.0 is said to be neutral groundwater. Danish groundwater usually has pH in the
interval 4.5 – 8.0 meaning that you can find examples of acid as well as basic
groundwater in Denmark.
A redox process can be seen as a transfer of electrons. When a compound
receives electrons the compound is said to be reduced. The compound that delivers
the electrons is said to be oxidized.
A+ + e-  A
(reduction)
(1)
C+  C++ + e-
(oxidation)
(2)
The result of these two half reactions is a redox proeces:
A+ + C+  A + C++
(3)
(redox process)
The geochemical environment can be illustrated by drawing a diagram with pH as
X-axis and Eh as Y-axis, see Figure 9. Every groundwater sample represents a point
in this diagram. In Figure 9 are shown areas of stability for different minerals
according to pH and Eh. The mineral Calcit (CaCO3) is ex. seen to be stable at pH
above 7.8 and is independent of Eh. The mineral Pyrite on the contrary is only stable
at rather low Eh values and is nearly independent of pH (Pyrite is seen below the
“sulfate/sulfide fence” in the diagram).
Figure 9
12
Geochemical environment and related minerals characterized by Eh and pH
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
By measuring the voltage that is necessary to apply to the half reactions in
equations (1) and (2) it is possible to make a list of reduction potential values for
different substances. As a zero value is chosen the half reaction for hydrogen which
is assigned the redox potential of 0.00 Volt under standard conditions.
2H+ + 2e-  H2
(4)
Tables of standard potentials for half reactions of many substances can be found
in the literature.
The redox potential is also expressed as Eh with the unit Volt. Measurement of
redox potential in Volt is a standard field measurement during many groundwater
investigations as will be explained later in Chapter 6 of this text book. The field
measurements also include measurement of pH and the conductivity of the water. A
negative value of the Eh measurement means that the water is reduced while a
positive value means that the water is oxidized. The terms reduced and oxidized
water is also seen in the overview table Figure 14.
The redox potential can also be related to the equilibrium constant in the Nernst
equation:
Eh = Eho – (R•T/n•F) • ln K
(5)
Or written as
Eh = Eho – (0.0591/n) • log K
(6)
(Nernst equation)
where
R
= Gas Constant
T
= Temperature in degree Kelvin
n
= number of moles of electrons transferred in the reaction.
F
= Faradays number
K
= equilibrium constant for the reaction
o
Eh = the standard potential for the reaction
Redox processes and colour change
Redox processes can indirectly be studied in soil samples because of colour
change from reddish/yellowish in the zone with oxidizing water into dark or grey in
the zone with reducing water. The border zone between the two zones are named the
nitrate front, see Figure 10. When groundwater flow across this front, nitrate ions
(NO3-) are reduced to free nitrogen (N) and other components. The type of the other
components depends on which compounds were involved in the reaction as electron
donors. Theoretically, nitrate can be reduced by a number of different electron
donors such as hydrogen sulphide (H2S), methane (CH4), reduced iron (Fe++),
organic matter (C) or the mineral pyrite (FeS2).
In Figure 10 the colour change across the nitrate front is illustrated together with
characteristic water on both sides of the front. Water from the oxidizing zone always
have nitrate (NO3-) but no reduced iron (Fe++), while the opposite is the case, when
the groundwater sample is taken from the reduced zone. The upper nitrate containing
layers can range in thickness from a few metres to up to 50–75 metres below ground
surface.
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Figure 10
Nitrate front and colour changes in the groundwater system. Figure from the report
Water supply (2003)
The grey /black clay in the bottom of Figure 10 could be of the same kind as the
grey moraine clay shown in Figure 11 . Here we also see small white limestone
particles composed of the mineral calcium carbonate (CaCO3). Limestone particles
in Danish sediments are very common and originate from erosion processes, when
glaciers slipped over the solid limestone subsurface in Denmark..
14
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
Figure 11
Example of un-weathered gray clay with small white limestone particles. Often the lime
particles in clay are so fine grained, that you cannot see them with the naked eye
The limestone particles in sand and clay – as seen in Figure 11 – are very
important for the acidity (pH) of the water infiltrating from above. When water from
precipitation seeps down through the organic top layer, it will become slightly acid,
because CO2 (from decay of organic matter) combines with water to form carbonic
acid in the following way:
H2O + CO2  H+ + HCO3-  2H+ + CO3--
(7)
Dissolution of limestone particles in sediments will neutralize the slightly acid
groundwater thereby gradually raising pH consuming the limestone particles. The
border zone between sediments with and without limestone particles is named the
acid front, see Figure 12.
Figure 12
Colour change in a normal glacial clay profile because of solution and oxidation.
To sum up the geochemical processes, two important geochemical fronts are
present in the groundwater system. This is the acid front and the redox front.
Location of the acid front depends on the presence of limestone particles in the
sediments, and location of the redox front depends on the presence of oxygen (or
other electron donors) in the groundwater system.
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10 .4 Classification of groundwater
Groundwater can be classified in many ways related to the values of the analysis
parameters. In this textbook will be introduced two very simple classification
systems, one based on the hardness of the water, see Figure 13, and the other based
on the redox conditions see Figure 14
Hardness
German
degrees
odH
pH
<8
HCO3-
Agg. CO2
<7
< 100
>5
8 – 18
7–8
100 – 300
<5
> 18
7–8
200 – 400
<5
Soft
Medium hard
Hard
Figure 13
mg/l
mg/l
Groundwater types divided after hardness criteria.
The hardness of the groundwater is a measure of the amount of Ca++ and Mg++
ions, and gives an indication of whether there is limestone in the sediments. Also the
hardness is a technical classification informing about how the water reacts with soap.
Hardness can be reported with a variety of units. In Denmark are used German
hardness degrees (odH) defined as
1 odH = 2,8 * ( [Ca++] + [Mg++] )
(1)
Where [Ca++] and [Mg++] are concentration given in meq/l.
Conversion factor from mg/l to meq/l can be calculated from atomic weight and
number of ionic charge. For Ca++ and Mg++ these factors are respectively 0,0499 and
0,0823.
Redox
criteria
Oxidized
O2
NO3-
0,5 –
10
mg/l
mg/l
Fe2+
mg/l
SO42mg/l
1 - 150
< 0,1
Reduced
<1
Strongly
reduced
<1
Figure 14
0,1 –
5
0,1 2
H2S
mg/l
CH4
mg/l
NH4+
20 – 120
< 0,05
<
0,05
< 0,1
20 – 250
< 0,1
< 0,1
< 0,1
< 20
0,1 - 5
0,1 5
0,1 - 5
mg/l
Approximately intervals for groundwater types divided after redox criteria
When groundwater is classified according to redox conditions, the intervals for
ionic values given in Figure 14 can be used. In the reduced and strongly reduced
water ideally there should be no oxygen present. However during pumping and
sampling of groundwater it can be rather difficult to avoid atmospheric air in the
system. If air has intruded during pumping a false oxygen value will appear in the
analysis report - in spite all other parameters may point at reduced or strongly
reduced water.
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Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
10 .5 Aquifers and their pressure levels
An aquifer can be defined as water-saturated rock from which it is possible to
abstract groundwater. This implies that the rock contains so many connected pores
or fractures that the groundwater can flow through it relatively unhindered. The
presence of a contiguous pore volume is expressed as the permeability of the rock.
An aquifer is thus a body of water-saturated, permeable rock or soil.
In sand or gravel sediments the permeability of an aquifer is related to the
contiguous pore volume that exists between individual grains. This is termed
intergranular permeability or primary permeability. In harder rocks like limestone
and granite the permeability is related to cracks and fractures. This is termed fracture
permeability or secondary permeability.
The size of an aquifer is determined by the extent of the permeable rock strata.
Aquifers can be isolated, i.e. surrounded by impermeable clay layers on all sides, or
widespread, for example solid limestone strata or large outwash plains. Examples of
isolated and widespread aquifers are shown in Figure 15.
Figure 15
Examples of aquifers. Blue line are groundwater table.
Each aquifer has a pressure level or a potentiometric surface. Another name for
the potentiometric surface is the groundwater table shown as GWT in Figure 4 in
Chapter 1. The location of the groundwater table relative to the upper boundary of
the aquifer determines whether the aquifer is unconfined, confined or artesian, see
Figure 15.
In an unconfined aquifer the potentiometric surface lies within the permeable
rock, and the voids just above the water comprise an unsaturated zone containing air.
The aquifer is not completely “filled up”. Figure 15 shows three examples of
unconfined aquifers – the two small sand lenses in the clay and the right part of the
primary sand aquifer.
In confined aquifers the potentiometric surface lies above the upper boundary of
the permeable rock that constitutes the aquifer. There are no air-filled voids just
above the aquifer, and confined aquifers are thus under pressure. In Figure 15 there
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are two confined aquifers – the limestone aquifer and the left part of the primary
sand aquifer.
An artesian aquifer is a confined aquifer in which the pressure level lies above
ground surface. In Figure 15 the far left part of the limestone aquifer is artesian as
the pressure level lies above ground surface. When a borehole is drilled into an
artesian aquifer the water will rise like a fountain. Artesian aquifers are often found
in valleys or lowlands, where the underlying rock consists of impermeable clay or
organic mud.Somewhere in the vicinity of an artesian aquifer there will always be
some higher-lying permeable rocks through which precipitation can infiltrate down
into the ground and build up the pressure.
A small aquifer from which only a limited amount of water can be abstracted and
which dries out periodically is termed a secondary aquifer. The corresponding
groundwater table is termed a secondary groundwater table. In contrast, the primary
aquifers are more extensive and receive a stable inflow of water that determines the
primary groundwater table.
In Figure 15 the geological conditions are clearly described, as are the
interrelationships between the different aquifers. In practice, however, the extent of
the individual aquifers and the boundary conditions pertaining are unknown due to a
lack of a detailed geological survey of the rocks.
Measurement of groundwater level
When a borehole reaches an aquifer, water will intrude into the bottom of the
borehole pipe and the water level will adjust to a level corresponding to the pressure
of the aquifer. Before a water sample can be taken, the well has to be developed for
use by installing a screen and a casing as was explained in Chapter 1 and illustrated
in Figure 1.
Once the well has been developed with a casing and screen the groundwater
potential can be measured. This is done by measuring the distance from a fixed point
on the surface to the surface of the water in the well pipe using a water level meter,
see Figure 16.
Figure 16
18
Water level meter with tape measure and indicator.
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
The water level meter consists of a long tape measure with an indicator at the end
that is lowered into the well. When the indicator reaches the water surface a weak
current passes between the ends of two thin wires running along the tape triggering a
visible or audible signal at the surface. The distance from the chosen measuring
point to the water surface can then be read on the tape measure.
In order to compare the groundwater potential in different wells the
measurements are expressed relative to sea level by subtracting the water level depth
from the ground level as shown on Figure 17.
Figure 17
Groundwater levels are calculated from measurements of water table below ground
surface using information about ground surface levels relative to sea-level.
An aquifer is not always reached when drilling for groundwater, however. If the
borehole only passes through fine-grained sediments such as silt or clay, the
groundwater will only seep into the well slowly. With such boreholes it will not be
possible to measure a representative water level until a long period of time has
passed, and it can be difficult or even impossible to get a water sample from this
well.
Potentiometric surface maps
When measurements have been obtained from a suitable number of wells with
screens in the same aquifer a potentiometric surface map can be prepared showing
the variation in pressure Figure 18. The curves on the map are drawn following the
same principle as for topographic contour lines except that far fewer points are
available for preparing the potentiometric surface maps. Moreover, the potential
curves are dynamic, i.e. they change as the pressure changes. Groundwater potential
is always affected by abstraction, but can also be affected by variation in
precipitation.
Under natural conditions the groundwater potential in Denmark is always above
sea level.
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Figure 18
Example of a potentiometric surface map from Odder, eastern Jutland. The topographic
contour lines and streams are also indicated.
In addition to the potentiometric curves the maps normally pin-points the location
of the wells where the water table was measured Figure 18. A relevant background
for the potentiometric curves are contour lines of the land surface and existing
streams and lakes in the area.
A potentiometric surface map is one of the most important elements of a hydrogeological survey. The map provides an overview of groundwater movement as the
latter usually takes place perpendicular to the potential curves. The curves also
provide information about the hydraulic gradient, defined as the slope of the
potentiometric surface (i.e. the distance between the curves divided by the
corresponding difference in elevation).
From the pattern of groundwater movement an area can be subdivided into
drainage basins. The boundaries between drainage basins are termed watersheds or
groundwater divides. As groundwater discharge varies with the time of year and the
magnitude of abstraction, watersheds are not stationary but are dynamic like
potential curves.
In some areas, several aquifers are located above each other separated by
impermeable rock strata. In principle, a separate potentiometric surface map should
be prepared for each of these aquifers. Usually, however, the number of well points
is insufficient to permit individual maps to be produced.
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Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
When water is pumped from a well the potentiometric level will drop, see Figure
19. Well journals often specify the magnitude of the drop corresponding to the
amount of water pumped up. This can give you an idea of the extent and
permeability of the aquifer. In Chapter 4 of this textbook will be explained how to
read a well journal and find the relevant information.
Figure 19
Drop in potentiometric level caused by pumping.
10 .6 Aquifer examples
In the following section are shown some principal outline of aquifers from the
Danish geological sequence. The figures and text are all from (Sørensen, 2008).
Fractured basement rocks and sandstone aquifers
Figure 20
Diagrammatic cross-section through aquifers of fractured basement rock and younger
sand. Redrawn from (Olofsen, 2001).
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Aquifers like the one in Figure 20 is present in the Danish island Bornholm. The
geochemical conditions in fracture aquifers are characterised by the presence of
relatively young water. Groundwater containing oxygen and nitrate can thus be
detected deep down in the fractures, especially in the unconfined, unprotected
aquifers.
Water from fractured basement rock can contain raised levels of fluoride. The
fluoride is picked up when the water comes into contact with basement rock
containing small amounts of the fluoride-containing minerals fluorspar (CaF2) and
fluorapatite.
Limestone aquifers
Figure 21
Limestone aquifers – unconfined on the left and confined on the right.
Water flow in limestone aquifers mainly takes place in the fracture zones. As hard
limestone can be more fractured than soft limestone, limestone from the Danian Age
typically conducts more water than the soft limestone from the Late Cretaceous
Period. The location of the fracture zones is normally unknown or has not been
charted in detail.
Changes often take place in limestone deposits after they have been deposited
because limestone dissolves easily and re-precipitates, for example in step with
changes in pH. Dissolution of the limestone creates porosity – a factor that is
exploited when wells are renovated using acid treatment under pressure.
Well measurements (flow logs) of the rate of groundwater flow have shown that
inflow can vary markedly down through a limestone well – the majority of the water
often flows in very thin intervals of the stratification. Many limestone wells lack a
screen as the limestone is so stiff that the raw well can exist without collapsing. If
the limestone in a well is loose and crumbly, however, it may be necessary to install
a screen.
Groundwater from limestone aquifers is markedly affected by contact with the
limestone as its pH typically exceeds 7. The content of calcium, magnesium and
bicarbonate is usually high. The concentration of fluoride and strontium can also be
elevated, especially where the water is exchanged slowly and is in contact with old
hardening horizons in the limestone. Hardening horizons have developed over long
periods of time during which the seabed has not received new deposits or been
eroded deeper down, thereby allowing time for some of the trace elements, fluoride
and strontium in the seawater, to become incorporated into the surface of the
limestone.
In cases where the limestone is covered by plastic clay from the Early Tertiary
Period, ion-exchanged water is often present. This is due to the fact that plastic clay
22
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
is rich in the clay mineral smectite, which has a high cation exchange capacity.
Smectite can release Na+ ions to the groundwater by cation exchange with Ca++ ions
in the groundwater. The reason why Na+ ions are released – and not some of the
other ions in the mineral – is the relative weak electronic binding of Na+ ions to the
SiO2 lattice layer in clay.
In unconfined limestone aquifers, good quality groundwater suitable for
abstraction is sometimes found squeezed between overlying water containing
nitrate and underlying water containing fluoride and salt. This is the case in
Djursland and at several locations in northern Jutland. As the nitrate front slowly
migrates downwards the amount of good quality groundwater in these areas
gradually decreases.
Quartz and mica sand aquifers from Late Tertiary Period
Quartz sand is generally more suitable for groundwater abstraction than mica
sand because the grain size of quartz sand is medium to coarse, whereas that of mica
sand is finer. Quartz sand is usually very well sorted and pure, i.e. as much as 99%
of the grains consist of quartz. The Late Tertiary sand is typically surrounded by
mica silt and mica clay, and to some extent by lignite (see Figure 22)
Figure 22
Aquifers of quartz sand and mica sand below quaternary deposits.
The quality of the groundwater in Late Tertiary aquifers is often influenced by the
close contact with organic matter-rich deposits of mica clay and lignite. As a
consequence, the reduction capacity of the water is reasonably high. Thus the nitrate
content of the water is usually low if it is in contact with mica clay or lignite beds.
Abstraction from deep quartz sand sometimes stimulates movement of formerly
stagnant water, resulting in the inflow of so-called brown water to the groundwater.
The brown colouration is due to the dissolution of humus from the organic matterrich deposits that typically occur in the Late Tertiary beds. This process requires a
relatively high pH. Brown water problems are thus usually associated with marine
deposits, which are usually basic. In contrast, brown water problems rarely affect the
non-marine beds consisting of riverine deposits.
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Intensive abstraction and resultant lowering of the groundwater potential can lead
to oxidation of the pyrite in mica clay. Oxidation of pyrite (FeS2) typically results in
elevation of the sulphate concentration in the groundwater and lowering of the pH.
The non-marine Late Tertiary deposits do not naturally contain any lime, and their
capacity to neutralise the acid content of the water percolating into them is therefore
poor. The groundwater in unconfined quartz sand and mica sand aquifers is therefore
often acidic with a pH as low as 5 or 4, and it often contains aggressive carbon
dioxide.
Meltwater sand and gravel aquifers
Meltwater sand and gravel can be laid down in many way giving a variety of
geometrical aquifer forms and relations. The classical one is meltwater sand and
gravel spread out in an outwash plain, see Figure 23.
Figure 23
Aquifers formed as outwash plains and meltwater valleys a) without a confining layer
and b) with a confining layer, i.e. buried outwash plains.
Another rather classical form of meltwater aquifers is present in the prequaternary valleys, as seen in Figure 24.
The meltwater sand and gravel are composed of many different materials –
basement rock from Norway and Sweden and limestone, flint and Tertiary deposits
eroded from the Danish Prequaternary surface.
From the geochemical point of view the fragments of chalk and limestone from
the Prequaternary beds are of great significance for the quality of the groundwater.
When lime and chalk dissolve they neutralise the weekly acidic water seeping down
into the aquifers from above. In some areas of the country, for example in western
Jutland, all lime and chalk grains are completely dissolved, which makes the
groundwater relatively acidic.
Meltwater deposits do not normally contain any organic matter that can affect the
quality of the water.
24
Sampling of Groundwater
Chapter 2 - Basic knowledge about groundwater
Figure 24
Prequaternary valley at Brabrand, Aarhus. The steep southwestern side of the valley is
well documented from well data.
Due to the varying temperature conditions, meltwater deposits often alternate
between coarse-grained and fine-grained layers. An example of the variation in grain
size and structure of meltwater deposits is shown in Figure 25. The figure shows
four typical units deposited in a single episode that could for example have been an
early summer thaw.
• Gravel, stone and coarse sand with large-scale cross bedding
• Medium-grained sand with megaripple bedding
• Fine-grained sand with small ripple bedding
• Fine sand, silt and clay with horizontal bedding deposited in virtually stagnant
water.
Figure 25
Examples of variation in meltwater deposits
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Sampling of Groundwater
Chapter 3 - Decisions (sample situations)
Chapter 3
DECISIONS (SAMPLE SITUATIONS)
Aim of Learning


To know typical sample situations such as groundwater water
monitoring, quality control for water supply wells, investigation
and monitoring of contaminated sites and landfills
For each of the above mentioned situations - to know the role of
involved parties as well as critical conditions
Sample locations were introduced in Chapter 1 in the section about reasons for
sampling. In this Chapter 3 will be given more detailed descriptions of the parties
involved in sampling and critical conditions related to the sampling points.
10 .1 Sampling related to water supply
Figure 26 shows an example of a water supply system. During operation sampling
from the water supply well is done to monitor the quality of the raw water. This is
necessary because sometimes the quality may change over time as too strong
pumping may extract water from formerly remote parts of the aquifer. Also impact
from human activities at ground surface may change the quality of the groundwater
in the water supply well
Figure 26
Overview of a water supply system. Figure from report Water supply (2003).
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The monitoring of the raw water is carried out in a cycle related to the amount of
water extracted per year. The parameters to be analysed in the water include a large
number of substances that are naturally occurring in groundwater as well as
pesticides and organic solvents. In Appendix 2 is shown the parameters to be
analysed for in a well control according to Danish legislation. (Statutory Order
2002).
Before entering the pipe system for the customers the water quality must be
controlled to keep the quality demands for the different components. This delivery
control must also be done at selected points in the distribution systems, water towers
and storage tanks as well as at consumers.
Because of the great public interest in pure and uncontaminated drinking water,
there is special legislation about how many samples, how often and which analysis
to make. In Danish legislation there is a distinction between 4 groups of monitoring s
can be seen in Appendix 2:
• Well monitoring
• Extended monitoring
• Normal monitoring
• Restricted monitoring
Principally the number of samples and the frequency of sampling depend on the
amount of produced drinking water – the bigger amount – the more analyses are
required. Responsibility for the sampling of raw water is the owner of the water
supply plant or in practice – the person in charge of the daily operation of the supply.
All sampling from water supply wells and sampling for drinking water delivery
control must be carried out by certified persons and laboratories according to Danish
legislation (Satutory Order, 2002).
At the water work uncertified staff may take special samples to monitor and
optimize the treatment process. This could be before and after aeration, before and
after a filter or before and after adding for instance lime to reduce acidity, see Figure
26.
10 .2 Groundwater monitoring
Sampling dedicated to monitor the general ground water quality has taken place in
Denmark since 1989. In all there are 1415 sampling points present in 70 different
catchment areas (GEUS 2007). The government is responsible for the operation of
these special monitoring wells for groundwater. (In practice the task is taken care of
by project managers in the 8 local “Miljøcentre” ????)
The reason why groundwater monitoring is regarded so important is that Danish
water supply nearly 100 % is based on groundwater. Besides groundwater quality
can influence the water quality in surface waters as lakes and rivers.
GEUS has published technical directions for sampling in relation to the
monitoring programme. More information to be found at
http://www.geus.dk/publications/grundvandsovervaagning/
28
Sampling of Groundwater
Chapter 3 - Decisions (sample situations)
10 .3 Investigation of contaminated sites
Investigation of contaminated sites nearly always includes drilling and sampling of
soil. If water is present in the drilled well a screen will be placed in order to take a
water sample from the well. The type of contamination determines which
components should be analysed. The project manager in charge of the investigation
is responsible for deciding which kind of analysis is relevant at the specific site.
Sampling and subsequent analysis will normally inform about if the groundwater
is contaminated due to the contaminated site. Basis for this evaluation is the ground
water quality criteria defined by Danish EPA. Normally they comply with the
drinking water requirements set by Danish EPA and EU. These criteria are first of all
health based – but sometimes they are also consider technical reasons such as
limitation of precipitated substances in washing machineries.
The result of the groundwater sampling and subsequent analysis can be very
important for the final risk evaluation of the site, where authorities decide if there
should be remediation or not at the site.
10 .4 Monitoring wells at landfills
Every landfill should have a groundwater monitoring programme in the operation,
closure and aftercare periods of the landfill. Monitoring wells should monitor
groundwater flow (velocity and direction) as well as natural groundwater quality in
the lower and, if relevant, upper aquifers below and around the landfill.
In the permit, conditions shall be laid down to the effect that a minimum of three
monitoring wells are established, including one upstream and two downstream from
the landfill (Statutory Order on Landfills, 2002). The monitoring wells must be
established as close to the boundaries of the landfill as possible. The competent
authority may increase the number of wells.
Analysis parameters for groundwater control at a landfill are determined on the
basis of expected composition and contamination of leachate as well as on
groundwater quality in the area. In the choice of analysis parameters the mobility of
substances in the groundwater zone shall be considered.
Trigger levels for the occurrence of a significant environmental damage in the
form of contamination of groundwater must be laid down in the permit. A significant
environmental damage is considered to have occurred when an analysis of a
groundwater sample shows that requirements for groundwater quality are not
complied with. In case of exceeding of a trigger level the result must be confirmed in
an additional sampling, and if the exceeding is confirmed it shall appear from a
condition in the permit which (remedial) actions the owner of the landfill must take.
Results of groundwater control samples shall be assessed by control charts with
fixed control rules and levels for each downstream sampling well. Based on
knowledge of local variations in groundwater quality, the control levels shall be laid
down in the permit.
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10 .5 Methods of drilling and well completion
(much text and figures can be put in here. This is available from old Chapter 6t in
the textbook Water Supply).
30
Sampling of Groundwater
Chapter 4 - Planning of sampling
Chapter 4
PLANNING OF SAMPLING
Aim of Learning
 To identify sample relevant information on well journals (such as
ground positions, depth, rock types, well design incl. screen
placement , groundwater levels and yields and corresponding head
loss).
 To identify sample relevant information from chemical analysis
(such as level for intake of water, type of analysis, redox relations,
values of pH, conductivity ect).
 To identify from maps local ground conditions and surroundings at
sample localities
 To know the different methods for taking water samples
10 .1 Elements of a sampling plan
(existing well journals, existing water analysis, locality maps and local
conditions, which parameters will be analysed in the sample)
10 .2 Reading a well journal from Jupiter database
(how to access Jupiter, important information on the different part of a
Jupiter well journal, calculating water volume in the well)
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Figure 27
Screen print of Jupiter Well Journal with translations (top par). See appendix 4 for the
whole well journal 1. and second view.
10 .3 Reading a chemical analysis from Jupiter
(how to find the chemical analysis via Internet, reading (and understanding)
information from chemical analysis)
DGU archive well no: 106.
screen: 98 m.b.g.
938
Intake no: 1
Top-screen: 88 m.b.g.
Bottom
Lund water work
Sample date:
01/04-2004
Parameter
Result
Well control
(raw water) l
Laboratorium
Method of Analysis
Sample Filtration
41 mS/m
Eurofins Danmark A/S
DS/EN 27888
Not filtrated
8.2 pH
Eurofins Danmark A/S
DS 287
Not filtrated
7.7 grader C
Eurofins Danmark A/S
Field measurement
Not filtrated
Laboratory
Method of analysis
Conductivity
pH
Temperature
Project:
Chemical main components
Parameter
32
Result
Sample Filtration
Sampling of Groundwater
Chapter 4 - Planning of sampling
Ammonium
Calcium
Carbondioxid, aggr.
Carbon,org,NVOC
Chloride
Fluoride
Hydrogen carbonat
Oxygen content
Evaporation residue I
Iron
Potassium
Magnesium
Manganese
Methane
Sodium
Nitrate
Nitrite
Phosphor, total-P
Sulfate
Hydrogene Sulphide
Figure 28
.17 mg/l
Eurofins Danmark A/S
DS 224
Filtreret i laborato
70 mg/l
Eurofins Danmark A/S
ICP
Ikke filtreret
<2 mg/l
Eurofins Danmark A/S
DS 236
Ikke filtreret
2.7 mg/l
Eurofins Danmark A/S
SM
Ikke filtreret
16 mg/l
Eurofins Danmark A/S
IC
Filtreret i laborato
.15 mg/l
Eurofins Danmark A/S
IC
Filtreret i laborato
240 mg/l
Eurofins Danmark A/S
DS 256
Ikke filtreret
3.4 mg/l
Eurofins Danmark A/S
DS 2206
Ikke filtreret
270 mg/l
Eurofins Danmark A/S
DS 204
Ikke filtreret
1.2 mg/l
Eurofins Danmark A/S
ICP
Ikke filtreret
1.9 mg/l
Eurofins Danmark A/S
ICP
Ikke filtreret
7.6 mg/l
Eurofins Danmark A/S
ICP
Ikke filtreret
.18 mg/l
Eurofins Danmark A/S
ICP
Ikke filtreret
.42 mg/l
Eurofins Danmark A/S
GC, FID
Ikke filtreret
10 mg/l
Eurofins Danmark A/S
ICP
Ikke filtreret
<.5 mg/l
Eurofins Danmark A/S
IC
Filtreret i laborato
<.01 mg/l
Eurofins Danmark A/S
DS 222
Filtreret i laborato
.15 mg/l
Eurofins Danmark A/S
DS 292
Ikke filtreret
22 mg/l
Eurofins Danmark A/S
IC
Filtreret i laborato
.035 mg/l
Eurofins Danmark A/S
DS 278
Ikke filtreret
Example of chemical analysis Jupiter. (Translated by IS)
10 .4 Local conditions at sampling point
Ground conditions around sampling point – what can be seen on different types of
maps (contour lines, surface geological maps, Danish Area Information)
(several possibilities for figures)
10 .5
Sampling methods for groundwater
(Pump principles, bailer principles)
8several possibilities for figures)
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10 .6 Type of analysis and contact to laboratory
(Ordering the right type of packing for the actual sampling)
Figure 29
34
Example of flasks and material received from laboratory for a well control analysis.
Sampling of Groundwater
Chapter 5 - Pumps and other sampling equipments
Chapter 5
PUMPS AND OTHER SAMPLING EQUIPMENTS
Aim of Learning
 Be able to select appropriate sample equipment for a specific
borehole given information on well journals and given the type of
analysis to perform
 Know how pumps and bailers for sampling of groundwater are
operated and maintained
 Know how to operate, calibrate and maintain equipments used for
field measurements of conductivity, pH, temperature, oxygen and
redox conditions
 Know necessary equipments for taking a water sample for a
bacteriological analysis
10 .1 Centrifugal suction pump
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .2 Peristaltic suction pump
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .3 Vacuum suction pump
(mode of action, advantages and disadvantages)
Principal drawings and photo
Sampler Education Volume X of 5
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Sampler Education Volume X of 5
10 .4 Submerged pump with motor
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .5 Submerged pump with batteries
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .6 Submerged diaphragm pump
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .7 Montejus pump
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .8 Inertia pump
(mode of action, advantages and disadvantages)
Principal drawings and photo
36
Sampling of Groundwater
Chapter 5 - Pumps and other sampling equipments
10 .9 Bailers
(mode of action, advantages and disadvantages)
Principal drawings and photo
10 .10 Equipment for on-line field measurement
Operation and calibration for each of the following probes:
Conductivity, pH, oxygen, temperature and redox
Figure 30
Schematic outline of flow-through cells with probes
Sampler Education Volume X of 5
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Sampling of Groundwater
Chapter 6 - Sampling activities in the field
Chapter 6
SAMPLING ACTIVITIES IN THE FIELD
(instead of 6. Sub-sampling)
Aim of Learning
 To be able to pack the necessary equipment, tools and outfit for a
groundwater sampling task given the sampling locality and type of
analysis to perform
 Know which activities must be carried out at the locality to take the
water sample
 To be able to carry out the pre-pumping and know when to stop and
take the sample
 To be able to filtrate a water sample in the field
 To know how to take a sterile water sample
10 .1 Identifying the sample locality
10 .2 Measuring the groundwater table
(may be it should be part of 6.1)
10 .3 Pre-pumping and field measurements
(arrangement of equipment, measurements of indicator parameters)
10 .4 Treatment of water samples – filtration and preservation
10 .5 Sterile sampling of drinking water
(see suggestion for figures at next page)
Sampler Education Volume X of 5
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Sampler Education Volume X of 5
•
•
•
•
•
•
40
Figure 6.1 Outline of equipment during pre-pumping and sampling
Figure 6.2 Photo of flow through cells with probes (arrangement 1)
Figure 6.3 Photo of flow through cells with probes (arrangement 2)
Figure 6.4 Flush of tube before sampling (photo)
Figure 6.5 Filling of flask – tube down to the bottom (photo)
Figure 6.6 Filtering the sample in the field
Sampling of Groundwater
Chapter 7 - Packing and sample handling
Chapter 7
PACKING AND SAMPLE HANDLING
Aim of Learning

To communicate with the laboratory about appropriate packing and
sample amount for analysis of the following groups of parameters
-Inorganic main ions in ground water
-Dissolved gasses such as carbon dioxide, hydrogen sulfide and
methane
-Trace metals
-Organic substance
-Pesticides, organic solvents and micro-pollutants ect.



To be able to carry out preservation of samples in the field according
to specifications from the laboratory
To know how to store the samples until delivery at the laboratory
To organize and carry out sample transport logistic
10 .1 Ordering analysis from laboratory – logistic
10 .2 Main ions in groundwater – sample packing and handling
10 .3 Gasses in groundwater – sample packing and handling
10 .4 Organic substance – sample packing and handling
10 .5 Pesticides – sample packing and handling
10 .6 Volatile substances – sample packing and handling
10 .7 Oil – sample packing and handling
Figures: examples of flask and containers for the different type of analysis
Sampler Education Volume X of 5
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Sampler Education Volume X of 5
Chapter 8
DOCUMENTATION
Aim of Learning
 To be able to identify and register all relevant information about the
sampling point
 To be able to report groundwater level measurements, pre-pumping
results and readings from on-line measurements of water quality
 To know how to label the samples in an unambiguous way easy to
identify for others
 To be able to fill in analysis requisition for the laboratory in the
right way
10 .1 Sampling identification
(relevant information to identify the sample - to be coordinated with 6.1 –
identification of sample locality)
10 .2 Sample labelling
Which information – and the more technical part of the labelling
10 .3 Analysis requisition
10 .4 Chain of custody report
(more or less copy of the fine text in Ragnars “Sampling of wastewater
and sludge, section 10.2)
10 .5 Sampling report
(filled in forms with comments – or something more ? )
42
Sampling of Groundwater
Chapter 8 - documentation
Figure suggestions:
Examples of standard forms such as
Fig. 8.1 Well identification label in the field
Fig. 8.2 Pre-pump form with results
Fig. 8.3 Analysis requisistion
Fig. 8.4 Label on the water sample
NB – also relevant is Fig. 4.4
Sampler Education Volume X of 5
Packing for well monitoring analysis (photo)
Rev. 00
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Sampler Education Volume X of 5
Chapter 9
QUALITY CONTROL
Aim of Learning
• To be able to identify and report critical quality parameters in each step of
the sampling procedures such as - Possible false contribution of substances
from sampling equipment
• Maintenance of sensors for on-line measurements
10 .1 Contamination from sample equipment
(how to avoid this , arrangement of equipment, cleaning,and/or use of disposable
(throw away) equipment)
10 .2 Maintenance and cleaning of pumps
10 .3 Critical situations during filling the sampler container
hygiene conditions, no splasing ect)
Figure suggestions:
(pump separated in relevant parts for cleaning)
(eventually schematic picture of sensors and maintenance)
44
Sampling of Groundwater
Chapter 10 - HEALTH and safety
Chapter 10
HEALTH AND SAFETY
Aim of Learning



To identify personal risk elements during a given groundwater sampling
To know the risk from chemical substances used for preservation and field
analysis
To know which personal safety means is relevant to use during a given
groundwater sampling situation
10 .1 Sampler friendly design of monitoring wells
10 .2 Physical working positions – heavy equipment handling
(manholes, aids to avoid heavy lifts, work-positions during routine sampling)
10 .3 Chemical used for preservation and field measurements
10 .4 Personal protection
(gloves helmet ect)
Manhole with a sampler person
Examples of wrong and right working positions
(Photo of auger drilling – without helmet)
This ‘Section Break” (Next Page)’ MUST be kept at an EVEN page before
REFERENCES. This Section Breaks ends the CHAPTERS
Sampler Education Volume X of 5
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Sampler Education Volume X of 5
REFERENCES
EC 1998. COUNCIL DIRECTIVE 98/83/EC of 3 November 1998 on the quality of
water intended for human consumption. Down load from http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1998:330:0032:0054:EN:PDF
DANVA (2007). Download from http://www.danva.dk/sw160.asp . Web-page
visited 19 October 2007.
GEUS (2007) download from www.GEUS.dk 23-11-2007
(AVJ 2007) download from www.avjinfo.dk 23-11-2007.
Statutory Order on Landfills (Feb. 2002). Ministry of Environment and Energy.
Danish EPA. STATUTORY ORDER NO. 650 OF JUNE 29, 2001, ON
LANDFILLS
Olofsson, B., Jacjs, G., Knutsson, G. and Thunvik, R.: Grundvatten i hårdt berg – en
analys av kundskabsläget (Ground water in hard rock – a review). In Kunskapsläget
på kärnavfallsområdet. SOU 2001:35, Stockholm.
(more will come)
46
Sampling of Groundwater
Chapter 10 - References
This ‘Section Break” (Next Page)’ MUST be kept at the end of an EVEN page
ending the REFERENCES. With this “Section break” the APPENDICES begins.
Sampler Education Volume X of 5
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Sampler Education Volume X of 5
Appendices
A.1
QUALITY CRITERIA FOR THE MAIN COMPONENTS IN
DRINKING-WATER
Translation of ANNEX 1a from the Danish BEK nr 1449 (11/12/2007)
Compared to values from EC-directive 98/83/EC
Parameters
Colour
Turbidity
Value at
Value at
Value at
outlet from
inlet to
consumer
water-work
consumer
s tap
mg Pt/l
5
15
15
Acceptable to
Consumers and no
abnormal change
FTU
0.3
1
1
Acceptable to
Consumers and no
abnormal change
Units
Values from Council
Directive 98/83/EC
Odour
Subjective
Acceptable to
Consumers and no
abnormal change
Taste
Subjective
Acceptable to
Consumers and no
abnormal change
Temperature
oC
7 – 8.5
pH
Not lower
≥ 6,5 og ≤ 9,5
= 3000 µS cm-1
Conductivity
mS/m
NVOC
mg C/l
4
4
4
mg/l
1500
1500
1500
50
50
50
mg Na/l
175
175
175
Potassium
mg K/l
10
10
10
Ammonium
mg NH4/l
0.05
0.05
0.05
mg Fe/l
0.1
0.2
0.2
mg Mn/l
0.02
0.05
0.05
Residue after evaporation
Calcium
mg Ca/l
Magnesium
mg Mg/l
Hardness, total
Sodium
Iron
Manganese
48
than 30 mS/m
Max
2 500 µS cm-1
odH
200 mg/l
(higher than DK)
0,50 mg/l
(higher than DK)
200 µg/l = 0,2mg/
(higher than DK) l
50 µg/l = 0,05mg/l
(higher than DK)
Sampling of Groundwater
Appendices - Quality criteria for the main components in drinking-water
Hydrogen carbonate
mg HCO3/l
Chloride
mg Cl/l
250
250
250
250 mg/l
Sulphate
mg SO4/l
250
250
250
250 mg/l
Nitrate
mg NO3/l
50
50
50
50 mg/l
Nitrite
mg NO2/l
0.01
0.1
0.1
0,50 mg/l
(higher than DK)
Total Phosphorous
mg P/l
0.15
0.15
0.15
Fluoride
mg F/l
1.5
1.5
1.5
Oxygen
mg O2 /l
Agg. carbon dioxide
mg CO2/l
2
2
2
Hydrogen sulphide
mg H2S/l
0.05
0.05
0.05
Methane
mg CH4/l
0.01
0.01
0.01
Chlorine, free and total
5
1,5 mg/l
5,0 mg/l
mg Cl/l
Sampler Education Volume X of 5
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A.2
50
PARAMETER GROUPS IN WATER ANALYSIS
Sampling of Groundwater
Appendices - Common Minerals in Danish rocks
A.3
COMMON MINERALS IN DANISH ROCKS
MINERAL NAME
and chemical formula
QUARTZ
SiO2 (with crystalline structure).
FLINT
SiO2 (like quartz, but flint is
amorphous, i.e. it lacks a crystal
structure).
FELDSPAR
K-feldspar
KAlSi3O8
Plagioclase
(Ca,Na)AlSi3O8.
Albite is the name for a pure
sodium plagioclase
NaAlSi3O8
DARK MINERALS
Silicates with formulas very like
those of the clay minerals, but
containing less water.
MICA
White mica (muscovite)
KAl2(AlSi3O10)(F,OH)2
Black mica (biotite)
K(Mg, Fe)3AlSi3O10(F,OH)2
APPEARANCE AND
OCCURRENCE
Mainly light, translucent or
white. Common in nearly all
types of sand. Quartz sand
consists virtually 100% of quartz
grains.
Black, grey or light, often with a
coating of calcite and found
together with chalk. Nodules
and layers in chalk and
limestone.
Also as finely distributed
cement. Common constituent of
beds from the glacial periods.
Reddish skin-coloured (Kfeldspar). Light, grey or brown
(plagioclase feldspar)
Feldspar occurs as a constituent
of basement rock and as
angular grains in meltwater
sand.
Typically hard in the fresh state.
Common as constituents of
basement rock and as sand
grains in very young sand, i.e.
immature sand.
Glittering appearance.
Sheets or flakes.
Common constituent of
basement rock.
White mica is found in all finegrained deposits from the Late
Tertiary Period (mica sand, mica
silt and mica clay)
Sampler Education Volume X of 5
Rev. 00
WEATHERING and significance
for the groundwater
Very stable – does not weather.
Great mechanical hardness and
chemical resistance.
Stable – does not weather.
Feldspar crumbles out of
basement rock.
Gradually weathers to clay
minerals and can thereby
release K+, Na+ and Ca2+ ions to
the groundwater.
Easily weather to clay minerals
while concomitantly taking up
water. This allows the release of
small amounts of Na+, K+, Ca2+,
Mg2+ and Fe2+ ions.
Released Fe2+ can act as a
reducing agent in groundwater.
White mica is relatively stable.
Black mica weathers easily to
clay minerals. The iron released
in the process can act as a
reducing agent in the
groundwater.
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Sampler Education Volume X of 5
MINERAL NAME
and chemical formula
CLAY MINERALS
4 groups – all contain Si ions,
Al ions and OH ions arranged in
a sheet structure
Additional constituents:
Iltite: K and Mg, Fe
Chlorite: Mg, Fe, Ni, Fe
Kaolinite: No other ions
Smectite: Ca, Na, Mg, Fe
GLAUCONITE
K(Fe,Mg,Al)2Si4O10(OH)2
CALCITE
CaCO3 = calcium carbonate
APATITE
Ca5(PO4)3(OH,F,Cl)
Mixture of the phosphate
minerals hydroxylapatite,
fluorapatite and chlorapatite.
PYRITE
FeS2
SIDERITE
FeCO3
52
APPEARANCE AND
OCCURRENCE
Grain size less than 0.002 mm.
Plastic (pliable) when wet.
Smectite has a great ability to
swell when wet and form
fractures when it dries out.
Early Tertiary clay consists
virtually 100% of clay minerals.
Moraine clay only contains
about 14–20% of clay minerals
by weight.
Olive green to dark green. Often
occurs as small rounded grains.
Only occurs in marine
deposits. Often occurs together
with apatite.
Always effervesces when in
contact with diluted hydrochloric
acid. Can resemble quartz, but
quartz is harder. Constitutes the
Pre-Quaternary chalk and
limestone beds. Occurs finely
distributed in unweathered beds
from the glacial periods.
Aggregates of phosphorite, the
impure massive form of apatite,
are often found in bottom layers
when new marine deposits
replace older eroded deposits.
Apatite is also found finely
distributed in basement rock.
Pyrite is also called fool’s gold.
The crystals are typically cuboid
or have the form of small
needles. Pyrite shines like gold.
It is very common in deposits
containing organic matter.
Siderite, or spathic iron ore.
Often mixed with clay and then
called clay ironstone.
Common as aggregates in
Tertiary clay, often as “fossilised
worm burrows”.
It is often found in meltwater
gravel (eroded out of Tertiary
clay).
WEATHERING and significance
for the groundwater
Clay minerals are a weathering
product of silicate minerals such
as feldspar, mica and dark
minerals. Clay containing Fe2+
becomes oxidised and hence
acts as a reducing agent in
groundwater. Oxidation of clay
causes a colour shift from bluegray to yellow or reddish, the
latter when the clay is free of
calcite.
Smectite, Na clay, can act as an
ion exchanger in groundwater.
Glauconite can weather to rustlike grains. Due to its Fe2+
content it can act as a reducing
agent in groundwater.
Readily soluble under acidic
conditions, and calcite therefore
eventually disappears from the
upper beds. Feeds the
groundwater with Ca2+ and
HCO3- and thereby affects
groundwater hardness.
Apatite can release fluoride into
the groundwater as F- in the
mine-ral can be exchanged with
Cl- and OH-.
Pyrite is easily oxidised, thereby
forming sulphuric acid and
ochre or rust.
Pyrite acts as a reducing agent
in groundwater.
In the weathered state it is often
observed as aggregates of rust
with a concentric structure.
Some of the iron can have been
replaced by manganese.
Acts as a reducing agent.
Sampling of Groundwater
Appendices - Common Minerals in Danish rocks
MINERAL NAME
and chemical formula
LIMONITE
Fe(OH)3 or Fe2O3, H2O
GIBBSITE
Al(OH)3
GYPSUM
CaSO4·2H2O
SALT
NaCl
(KCl can be present)
APPEARANCE AND
OCCURRENCE
WEATHERING and significance
for the groundwater
In loose form it is called ochre,
and in hardened form it is called
bog ore. Rust red or light brown
or yellow. Very common as a
precipitate from oxidised
groundwater in the form of a
coating on sand grains. Often
contains manganese
precipitates (blue-black)
Limonite is a weathering product
of minerals containing iron in the
form of Fe2+ (e.g. pyrite, apatite
and glauconite). Some of the
iron can have been replaced by
manganese.
Clay-like – difficult to distinguish
with the naked eye. Formed by
the weathering of silicates.
Low hardness. Is translucent or
white. Occurs as a cover layer
over salt domes. Also occurs as
small crystals in dunes with
black mica.
Tastes salty. Is translucent or
white. Can occur in deep well
samples from areas with salt
domes.
Sampler Education Volume X of 5
Rev. 00
Weathering of silicates to
gibbsite occurs when
percolating acidic water cannot
be neutralised by calcite.
Gibbsite can release Al3+
to the groundwater.
The mineral anhydrite (CaSO4)
is converted to gypsum in a
process involving the uptake of
water. Occurs when a uplifted
salt dome meets groundwater.
Gypsum can also be a
weathering product of pyrite.
Readily soluble in water, which
can render the groundwater
salty.
Salty mineral water is
groundwater affected by PreQuaternary salt domes.
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Sampler Education Volume X of 5
A.4
WELL JOURNALS FROM JUPITER
(5 pages with an example of a well journal from Jupiter – first view and second view
as pdf-file. All with translations of important text as is shown in Figure 27).
54
Sampling of Groundwater