ISO 5667-18:2001
(Main)Water quality - Sampling - Part 18: Guidance on sampling of groundwater at contaminated sites
Water quality - Sampling - Part 18: Guidance on sampling of groundwater at contaminated sites
Qualité de l'eau — Échantillonnage — Partie 18: Lignes directrices pour l'échantillonnage des eaux souterraines sur des sites contaminés
Kakovost vode - 18. del: Navodilo za vzorčenje podzemne vode na onesnaženih mestih
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Frequently Asked Questions
ISO 5667-18:2001 is a standard published by the International Organization for Standardization (ISO). Its full title is "Water quality - Sampling - Part 18: Guidance on sampling of groundwater at contaminated sites". This standard covers: Water quality - Sampling - Part 18: Guidance on sampling of groundwater at contaminated sites
Water quality - Sampling - Part 18: Guidance on sampling of groundwater at contaminated sites
ISO 5667-18:2001 is classified under the following ICS (International Classification for Standards) categories: 13.060.10 - Water of natural resources; 13.060.45 - Examination of water in general. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 5667-18:2001 has the following relationships with other standards: It is inter standard links to ISO 5667-18:2001/Cor 1:2008, ISO 5667-11:2009; is excused to SIST ISO 5667-18:2001/Cor 1:2009, ISO 5667-18:2001/Cor 1:2008. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
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Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2001
.DNRYRVWYRGHGHO 1DYRGLOR]DY]RUþHQMHSRG]HPQHYRGHQDRQHVQDåHQLK
PHVWLK
Water quality -- Sampling -- Part 18: Guidance on sampling of groundwater at
contaminated sites
Qualité de l'eau -- Échantillonnage -- Partie 18: Lignes directrices pour l'échantillonnage
des eaux souterraines sur des sites contaminés
Ta slovenski standard je istoveten z: ISO 5667-18:2001
ICS:
13.060.10 Voda iz naravnih virov Water of natural resources
13.060.45 Preiskava vode na splošno Examination of water in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
INTERNATIONAL ISO
STANDARD 5667-18
First edition
2001-04-15
Water quality — Sampling —
Part 18:
Guidance on sampling of groundwater at
contaminated sites
Qualité de l'eau — Échantillonnage —
Partie 18: Lignes directrices pour l'échantillonnage des eaux souterraines
sur des sites contaminés
Reference number
©
ISO 2001
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ii © ISO 2001 – All rights reserved
Contents Page
Foreword.iv
Introduction.vi
1 Scope .1
2 Terms and definitions .1
3 Sampling strategy and programme design.3
3.1 General.3
3.2 Selection of sampling point location.3
3.3 Groundwater parameter selection .5
3.4 Sampling frequency.5
4 Types of monitoring installation .6
4.1 General.6
4.2 Unsaturated zone monitoring.6
4.3 Saturated zone .9
4.4 Construction materials for sampling installations.14
5 Sampling procedures .15
5.1 Well cleaning and development .15
5.2 Purging .16
5.3 Trial pits.19
5.4 Sampling of free-phase contaminants (DNAPLs and LNAPLs) .19
5.5 Materials for sampling equipment .19
5.6 Prevention of contamination .20
5.7 Preservation, stabilization and transport of samples.20
6 Safety precautions.21
7 Sample identification and records.21
8 Quality assurance/quality control.21
Annex A (normative) Calculation of sampling frequency using a nomogram.22
Bibliography.23
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 5667 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 5667-18 was prepared by Technical Committee ISO/TC 147, Water quality,
Subcommittee SC 6, Sampling (general methods).
ISO 5667 consists of the following parts, under the general title Water quality — Sampling:
— Part 1: Guidance on the design of sampling programmes
— Part 2: Guidance on sampling techniques
— Part 3: Guidance on the preservation and handling of samples
— Part 4: Guidance on sampling from lakes, natural and man-made
— Part 5: Guidance on sampling of drinking water and water used for food and beverage processing
— Part 6: Guidance on sampling of rivers and streams
— Part 7: Guidance on sampling of water and streams in boiler plants
— Part 8: Guidance on sampling of wet deposition
— Part 9: Guidance on sampling from marine waters
— Part 10: Guidance on sampling of waste waters
— Part 11: Guidance on sampling of groundwaters
— Part 12: Guidance on sampling of bottom sediments
— Part 13: Guidance on sampling of sludges from sewage and water-treatment works
— Part 14: Guidance on quality assurance of environmental water sampling and handling
— Part 15: Guidance on preservation and handling of sludge and sediment samples
— Part 16: Guidance on biotesting of samples
iv © ISO 2001 – All rights reserved
— Part 17: Guidance on sampling of suspended sediments
— Part 18: Guidance on sampling of groundwater at contaminated sites
— Part 19: Guidance on sampling of sediments in the marine environment
Annex A forms a normative part of this part of ISO 5667.
Introduction
The guidance in this part of ISO 5667 can be used in parallel with other guidance on investigating contaminated or
potentially contaminated sites as any groundwater sampling from such sites is likely to form part of a much wider
investigation programme.
Groundwater sampling, in general, is carried out to determine whether or not the groundwater in or beneath a site
is contaminated. It can also be used to satisfy the following additional objectives:
� to establish whether any migration of contaminants, derived from the site, is occurring and characterize the
spatial extent of any contamination and its form;
� to determine the direction and rate of groundwater flow and contaminant migration;
� to provide data for undertaking a risk assessment;
� to provide an early warning system for the impact of contaminants on the quality of groundwater resources,
surface waters and other potential receptors in the vicinity of the site;
� to monitor the performance and effectiveness of remedial measures or facility design.
� to demonstrate compliance with licence conditions, or collect evidence for regulatory purposes.
� to assist in the selection of remedial measures and remediation process design.
This guidance includes sampling of groundwater from both the saturated (below water table) zone and the
unsaturated (above the water table) zone.
Development of a groundwater sampling programme depends on the purposes of the investigation. This part of
ISO 5667 provides guidance to inform the user of the necessary considerations when planning and undertaking
groundwater sampling from potentially contaminated sites. Examples of typical sites include:
� present or former industrial sites with a history of potentially contaminatory activities;
� waste disposal (landfill) sites;
� sites where natural and/or artificial processes have led to potential land and groundwater contamination;
� sites where products have been spilled e.g. as a result of transportation accidents.
The guidance contained in this part of ISO 5667 covers selection of sampling points, the selection of sampling
installations and devices, groundwater parameter selection and sampling frequency.
Prescriptive guidance on methods and applications is not possible. Therefore, this guidance provides information
on the most commonly applied, and available, techniques and lists their advantages, disadvantages and limitations
of use where these are known. When considering design of sampling strategies, the properties of the contaminant
source, pathways for migration and the receptors need to be considered.
vi © ISO 2001 – All rights reserved
INTERNATIONAL STANDARD ISO 5667-18:2001(E)
Water quality — Sampling —
Part 18:
Guidance on sampling of groundwater at contaminated sites
1 Scope
This part of ISO 5667 provides guidance on the sampling of groundwater at potentially contaminated sites. It is
applicable to situations where contamination of the subsurface could exist as a result of downward migration of
pollutants whose source is at the surface or just below it, and when the guidance provided in ISO 5667-11 is
inappropriate.
2 Terms and definitions
For the purposes of this part of ISO 5667, the following terms and definitions apply.
2.1
piezometer
device consisting of a tube or pipe with a porous element or perforated section (surrounded by a filter) on the lower
part (piezometer tip), that is installed and sealed into the ground at an appropriate level within the saturated zone
for the purposes of water level measurement, hydraulic pressure measurement and/or groundwater sampling
2.2
nested piezometers
group of piezometers installed within a single larger-diameter borehole
NOTE In general, each piezometer should be designed to allow sampling over a specific depth interval within the aquifer.
Piezometer tips are isolated from each other by installing a permanent impermeable seal between them.
2.3
multiple boreholes
group of individual boreholes or piezometers installed separately to form a monitoring network adequate for the
purposes of an investigation
2.4
multi-level sampler
single installation for sampling groundwater from discrete depths within the sub-surface
NOTE The device can be driven directly into the ground, installed in a pre-existing borehole or installed in a purpose-drilled
hole. When installed in a borehole, integral packers are used to isolate individual sample ports.
2.5
aquifer
geological formation (bed or stratum) of permeable rock or unconsolidated material (e.g. sand and gravels) capable
of yielding significant quantities of water
2.6
aquitard
geologic stratum of formation of low permeability that impedes the flow of water between two aquifers
2.7
saturated zone
part of an aquifer in which the pore spaces of the formation are completely water-saturated
2.8
unsaturated zone
part of an aquifer in which the pore spaces of the formation are not totally water-saturated
2.9
groundwater
water in the saturated zone and/or unsaturated zone of an underground geological formation or artificial deposit
such as made ground
2.10
perched water table
isolated body of groundwater, which is limited in lateral and vertical extent, located within the unsaturated zone
overlying a much more extensive groundwater body
2.11
matrix potential
combination of forces, independent of gravity, acting on soil water (water contained within the pores of a soil/rock
matrix) that exist as a result of the attraction of solid surfaces to water and the attraction of water molecules to each
other
NOTE Generally, the smaller the particle size, the higher the matrix potential.
2.12
check valve
mechanical valve which allows fluids to pass in only one direction
NOTE The pressure of fluids flowing through the valve in one direction has the effect of opening the valve and in the other
of closing it.
2.13
receptor
entity that is vulnerable to the adverse effect(s) of a hazardous substance or agent
EXAMPLES Human, animal, water, vegetation, building services, etc.
2.14
packer
device or material for temporarily isolating specified vertical sections within boreholes in which to perform
groundwater sampling from discrete zones or locations within the borehole or aquifer
2.15
hydraulic conductivity
property of a water-bearing formation that relates to its capacity to transmit water through its internal,
interconnected pathways
2.16
effective porosity
proportion of saturated openings or pores within a water-bearing formation which contribute directly to the flow of
groundwater
NOTE Effective porosity is represented as the ratio of this volume of pore space to the total volume of rock.
2.17
field capacity
maximum amount of water that a soil or rock can retain after gravitational water has drained away
2 © ISO 2001 – All rights reserved
2.18
dense non-aqueous phase liquids
DNAPL
organic compounds that have a low water solubility and a density greater than that of water
EXAMPLES Chlorinated hydrocarbons such as trichloroethane.
2.19
light non-aqueous phase liquid
LNAPL
organic compounds that have a low water solubility and a density less than that of water
EXAMPLE Petroleum products.
3 Sampling strategy and programme design
3.1 General
Groundwater sampling can be carried out as a single exercise or as part of a larger site or environmental
investigation. Regardless of the purpose, a rational approach should be taken that clearly defines the objectives,
determines the level of information needed and identifies the various stages of the investigation.
It should be noted that, normally, groundwater sampling from the saturated zone alone cannot fully assess the level
of contamination of a site in situations where an unsaturated zone of considerable thickness exists. The potential
consequence of ignoring the unsaturated zone is that the unsaturated zone and groundwater system could become
extensively contaminated before any tangible evidence of leakage or contamination is evident in samples collected
from below the water table.
3.2 Selection of sampling point location
The location of monitoring installations and the design of the network for sampling groundwater from (potentially)
contaminated sites should take account of the following:
� the hydrogeological setting of the investigation site;
� the past and future use(s) of the site;
� the purpose of the exercise;
� the likely contaminants;
� the extent of contamination.
All of these factors should be considered during the preliminary stages of the site investigation programme to
enable the most appropriate and effective sampling programme to be designed. This information can be obtained
by examining all available information held by site owners (or their agents), local, regional and national regulatory
agencies and other data holders. Table 1 provides an overview of the steps involved in planning an investigation
strategy and for sampling groundwater from sites that are potentially contaminated.
In addition to the scientific requirements, other factors can influence the location of sampling points. These include
practical, environmental and safety considerations such as the ground slope, proximity of underground services
(gas pipes, electricity cables etc) and overhead clearance for drilling rigs and other sampling devices.
To establish whether migration of contaminants is occurring and determining the direction and rate of this
migration, monitoring points should be located inside and outside the contaminated area and both up and down the
hydraulic gradient. A greater number of sample points should be positioned down gradient, both inside and outside
of any contaminant plume.
Where site analysis indicates that the site is underlain by complex geology or that contaminants with a broad range
of physical and chemical properties are likely to be present, an increased number of monitoring points should be
installed for adequate characterization of the contaminant distribution. In addition to investigating the lateral
variation caused by heterogeneity, the sampling strategy should also be designed to investigate any vertical
variations.
[9]
Table 1 — Procedural steps for sampling groundwater (adapted from )
Step
(with reference to other ISO Procedure Essential elements Notes
standards)
Investigation/monitoring Collation of available data Identify data sources Geological, geochemical and
strategy (ISO 5667-1) hydrogeological characterization
Desk study
Develop conceptual model
See 3.2, 3.3 and 3.4
Design borehole/sampling point
Reconnaissance survey
network and sampling programme
Facility installation Installation of monitoring points Borehole design, material Seeclause4
by drilling selection and installation technique
See 5.1
Well cleaning and development
Well inspection Hydrologic measurements Water level measurements Hydrogeological characterization
Hydraulic testing
Well purging Removal or isolation of stagnant Representative groundwater See 5.1
water
Verification of representative See 5.2
Determination of well-purging
groundwater
parameters (e.g. EC, pH,
temperature, redox potential)
Sample collection Sample collection by appropriate See 4.2 and 4.3
Filtration mechanism
Field determinations
Unfiltered Field filtered Field determination of sensitive
(ISO 5667-2, ISO 5667-11,
sample sample parameters, pH, electrical
ISO 5667-3)
conductivity, temperature, redox
potential, dissolved oxygen as
appropriate
Organics (all) Alkalinity/pH Head-space free samples See 5.4, 5.5 and 5.6
Dissolved gases Dissolved trace Minimal aeration or de-
metals for pressurization
specific
geochemical
information
Sensitive Sulfide and other Minimal air contact Blanks and spiked samples
inorganic sensitive should be prepared in accordance
species, e.g. inorganics with ISO 5667-14
nitrite,
ammonium,
iron(II)
Tracer metals for Major cations Sample preservation
mobile (colloidal) and
loads anions
Storage and transport of Minimal loss of sample integrity See 5.7, clauses 6, 7 and 8
samples (ISO 5667-3) prior to analysis
Care should be taken when identifying the prevailing flow regime as localized recharge to the subsurface can alter
the regional hydraulic gradient. This can result in groundwater flow and contaminant transportation in a direction
that is contrary to flow imposed by the regional gradient. Dense non-aqueous phase liquids (DNAPLs) can also
move in a different direction and at a different rate to that of groundwater because their chemical properties are
4 © ISO 2001 – All rights reserved
different to those of water. Their migration is also affected by the geological structure of the low permeability layer
underlying the saturated aquifer.
Light non-aqueous phase liquids (LNAPLs) also have different chemical properties to those of water and their
migration and distribution will be affected by the geological structure and chemical interactions within the
unsaturated zone and zone of water table fluctuation.
Where sampling is aimed at providing an early warning of the impact of contaminants on receptors, monitoring
points should be located between the contaminant source (and plume) and the potential receptors as well as within
the zone of contamination, e.g. at landfill sites, monitoring points should be established around the outside of, but
close to, the landfill.
Sample points within the zone of contamination and outside (both up and down the hydraulic gradient) should be
installed to measure performance and effectiveness of remediation and for demonstrating compliance to licence
conditions.
3.3 Groundwater parameter selection
The parameters selected for analysis should reflect the nature of the investigation and/or the former, current and
proposed future use of the site. In some cases, certain contaminants will be the subject of national regulations.
Focussing only on these, however, could be inadequate for providing the complete picture of contamination under
different geochemical and hydrogeological conditions. For example, where organic contaminants are susceptible to
degradation, the list of analytes should also include the degradation products, which in some cases can also be
hazardous. An example of this is the degradation of trichloroethylene (TCE), a DNAPL. One of its potential
degradation products is vinyl chloride, a relatively soluble and highly volatile compound.
Consideration should also be given to baseline or natural groundwater concentrations. Elevated concentrations can
already be present in the environment being investigated as a result of natural sources of contamination.
3.4 Sampling frequency
The frequency of sampling depends on the objectives of the investigation. If the investigation is designed to map an
established contaminant plume, a single-event sampling exercise may be used. In this case, sampling should be
completed as rapidly as possible to minimize the effects of temporal variation. Where the development of a plume
is to be monitored and/or the impacts on groundwater resources considered, the frequency should be based on the
prevailing hydrogeological and environmental conditions, the objectives of the study and the contaminants present.
Where monitoring is required to provide early warning, where there are compliance issues or for performance
assessment of remedial measures, in general, a recommended minimum sampling frequency is quarterly for most
chemical constituents (e.g. major ions, etc.) and monthly for those that are more mobile and reactive (e.g. VOCs
and dissolved gases).
However, where environmental conditions indicate that changes can occur more rapidly, more frequent sampling
should be carried out. In these cases, the exact frequency should be determined by examination of all influencing
natural and artificial factors. Examples of short-term influencing factors include tidal influences and localized rainfall
as well as ground disturbance caused by ground engineering activities.
One example of how sampling frequency can be determined using prevailing hydrogeological properties (including
hydraulic gradient, hydraulic conductivity and effective porosity) is shown in Figure 1. Relevant hydrogeological
[8]
parameters have been used to develop a nomogram, which has been adapted from to include the effects of
dispersion, for rapid estimation of sampling frequency. Dispersion has the effect of distributing the contaminant
both along the flow path and perpendicular to it. The modification applied leads to a 10 % increase in sample
frequency. A worked example is described in annex A.
Other environmental conditions can also influence the temporal distribution and concentration of contaminants in
groundwater and soil water and these should be considered during development of the sampling strategy.
Seasonal and more frequent variations in weather and climate can influence the rate of infiltration of contaminants
through the unsaturated zone. A rise in water table can also lead to the release (or re-release) of contaminants into
the groundwater and/or bring the contaminant source closer to the groundwater.
����
DN DN
F�� 0,1
����
��86 400Ki ��86 400Ki
[8]
Figure 1 — Nomogram for estimating sampling frequency (from )
4 Types of monitoring installation
4.1 General
Installations suitable for groundwater monitoring typically involve placement of access tubes for portable sampling
devices or burial of sensors or samplers in situ. These installations may be positioned within the saturated zone
(below the water table) or above it (unsaturated zone). In addition to sampling groundwater, installations below the
water table can be used to measure water levels and installations above the water table can measure soil gas and
soil moisture content.
4.2 Unsaturated zone monitoring
4.2.1 Introduction
Sampling techniques that are used for collection of groundwater from the unsaturated zone can be divided into two
types:
� solid sampling followed by extraction of groundwater (pore fluids);
� unsaturated pore fluid sampling.
4.2.2 Extraction from solid samples
4.2.2.1 General
The extraction of pore fluids from solid samples is the most widely used method for sampling groundwater in the
unsaturated zone. Collection of solid samples as part of this method can also allow useful geological information to
be obtained. There are two broad categories of solid sampling methods: hand-operated and power-operated.
Table 2 lists a range of suitable techniques that can be used for extracting solid samples for pore fluid collection.
6 © ISO 2001 – All rights reserved
The removal of solid samples from the ground is however a destructive form of sampling that, although necessary,
does not allow subsequent re-sampling from the same location. It therefore precludes taking samples at a later
date for analysis of trends.
Table 2 — A range of methods suitable for soil and rock sampling
Drilling
Method Soil/rock type Maximum depth Diameter range
a
fluid/flush
Trial pitting
Hand- All soil types and Maximum6m(but no Depends on depth of
powered unconsolidated rocks generally to 4 m) pit and soil/rock type
Tube Hand- Soils, clay and fine grained
sampling
powered unconsolidated geological Approximately 10 m no 25 mm to 75 mm
materials
Hand- Soils, clay and unconsolidated Approximately 5 m no 50 mm to 100 mm
Auger powered (e.g. geological materials
Approximately 30 m no 75 mm to 300 mm
“hollow stem”)
Cable tool
Soils, clay and unconsolidated no/yes
80 mto90m 150 mm to 300 mm
(e.g. “shell and auger”
geological materials water
drilling or “light
percussion” drilling)
Rotary yes
All types of geological
air, water,
>100 m 100 mm to 200 mm
(e.g. “direct” and “reverse
materials and made ground
mud, foam
rotary”)
etc.
a
Drilling fluids are required to lift drill cuttings, support the borehole whilst drilling, lubricate and cool the drill bit. Use of techniques where
drilling fluids are required may adversely affect sample quality.
4.2.2.2 Hand-operated samplers
These are typically tube-type or auger samplers. The tube samplers consist of a variable-length rod with hollow
sample chamber (of variable length and diameter). It is hammered into the ground to obtain a sample. Augers have
cutting bits at their lower end and a sample chamber (open at top and bottom) directly above. The sampler is
rotated into the ground by hand.
4.2.2.3 Power-operated sampling rigs
Standard drilling techniques can be used for sampling the unsaturated zone. However, drill rigs such as cable tool
and rotary units should not be used because of the need to use drilling fluids. Drilling fluids help to lift drill cuttings,
support the borehole whilst drilling and lubricate and cool the drill bit. The type of fluids include water, mud, foam
and air. However, the introduction of these fluids into the ground and their circulation, often under high pressure,
can potentially impact on the quality of the samples being collected or introduce extraneous contamination. The
use of air flush drilling should also be avoided where determinands include volatile organics and other sensitive
chemicals. Large diameter samples collected using these techniques can be sub-sampled to minimize the
problems of cross-contamination caused by drilling.
Solid- and hollow-stem augers can be used for sampling. For solid-stem auger methods, samples are collected
from the cuttings returned to the surface by the rotary action of the auger flights. This, however, can lead to
problems of cross-contamination and sample mixing. For hollow-stem methods, a central rod and cutting bit is
removed from within the auger column and replaced by a thin-walled sampler for collection of a relatively
undisturbed sample. Continuous-sampling tube samplers can also be used with hollow-stem auger drilling for
improved sample recovery.
Pore waters are then extracted from the recovered solid material by either centrifuging or mechanical squeezing as
soon as possible after collection. It is important that the groundwater extract be preserved in accordance with
ISO 5667-3 before analysis.
4.2.3 Pore-liquid sampling
4.2.3.1 General
Two types of method can be used to extract pore liquid directly from the subsurface, namely percolate soil water
samplers and vacuum soil water samplers. Both have advantages over solid sampling (see 5.2.2) in allowing
sequential sampling from fixed locations in the unsaturated zone to determine trends. The choice of sampler
depends on the objectives of the monitoring. Advantages and disadvantages of both types are shown in Table 3.
Table 3 — Advantages and disadvantages of pore liquid samplers
Sampler type Advantages Disadvantages
� Can be installed up to a depth of 15 m. � Excess pressure will damage samplers
without check-valves.
� Relatively easy to install. � Porous cup can become clogged
Vacuum samplers
and/or adsorb chemical constituents.
� Minimal ground disturbance required � Redox/pH changes can alter chemistry.
during installation.
� Multi-level installations are possible. � Vacuum/pressures required to extract
sample may affect sampling of volatile
compounds.
� Enables sampling of flow through � Difficult to install. Not always possible
macropores as well as interstitial water. in contaminated soils.
� Larger sample volumes possible. � Installation can alter natural flow.
� Less control over sample collection.
� Less potential for volatilization of
Percolate soil water samplers organic compounds.
� No need for continuous vacuum. � Pan-type samplers will only function
when field capacity is exceeded.
� Theuse of awicktodrawwaterinto
the sampler can lead to chromato-
graphic effects that in turn can lead to
collection of chemically unrepre-
sentative groundwater samples.
4.2.3.2 Vacuum samplers
These samplers, installed in the ground, use a vacuum (applied at the surface) to draw porewater into the sample
collector. They consist of a porous cup (or similar) on the end of a sampling tube that is installed into a borehole. In
their simplest form they have a limited maximum installation depth, but a number of modifications can be made to
improve sampling and increase the depth range over which the samplers can be used. These modifications include
incorporating a gas-driven sampling device (see 4.3.3.5) above the porous cup.
4.2.3.3 Percolate soil water samplers
These samplers, which include pan and wick types, rely on gravity and/or capillary action to intercept both matrix
water and water flowing along preferential pathways (e.g. fissures) in the unsaturated zone. Installation of the
samplers requires excavation of a trench and tunnel and the installation of the sampler in the roof of the tunnel to
intercept soil water. The sampler is constructed of a suitable nonporous inert material which may have a wick
incorporated to draw water (which is under tension) into the sampler as well as intercepting its downward
movement.
8 © ISO 2001 – All rights reserved
4.3 Saturated zone monitoring
4.3.1 General
Any structure that provides a means of reaching the saturated zone can be used for groundwater sampling
purposes. The most commonly encountered means include supply boreholes, wells, and observation boreholes.
Trial pits and trenches can also be deep enough to reach groundwater where the water table is close to ground
level. In addition, discharging water at springs can be sampled.
Whilst existing wells can provide background information and evidence that contamination of groundwater has
occurred, the network available is unlikely to be adequate for characterizing the source and extent of
contamination. It is likely, therefore, that an additional monitoring installation will be required as part of a specific
site investigation.
Where perched groundwater is to be sampled, the methods described in this clause are generally applicable.
However, where shallow bodies of perched water are ephemeral, well sampling facilities should be combined with
suction (unsaturated zone) sampling devices.
When installing monitoring facilities in locations where perched groundwater is present, the techniques used for
investigation or installation of monitoring equipment should be chosen with care. To minimize the potential for
introducing artificial migration pathways (see 5.5), deep, open, fully penetrating screened boreholes should not be
installed.
The design of monitoring installations is also dependent on the nature of the contaminants being investigated.
Where free-phase contaminants such as DNAPLs and LNAPLs are present, the properties of these contaminants
and their potential distribution within the groundwater system should be considered during construction of
monitoring points.
4.3.2 Monitoring point installation
There are three major types of monitoring point installation for collection of groundwater samples (Figure 2). These
are:
a) single-screened/unscreened wells, boreholes or piezometers,
b) nested piezometers in a single borehole completion;
c) multi-level samplers.
The advantages and disadvantages of each are shown in Table 4.
Key
1 Open borehole 5 Sealing material 9 Well casing or piezometer pipe 13 Aquitard
2 Screened 6 Water table level 10 Gravel pack 14 Packer gas inflation line
borehole/piezometer
3 Nested piezometers 7 Casing pipe 11 Slotted well or piezometer screen 15 Packer
4 Borehole with packers 8 Open well or borehole 12 Piezometer 16 Isolated borehole section
Figure 2 — Major types of monitoring installation
10 © ISO 2001 – All rights reserved
Table 4 — Advantages and disadvantages of different monitoring point installations
Type Advantages Disadvantages
Single screened/unscreened
— Simple, can be designed for all types of —Canleadtoshort-circuitingofsystem
borehole/well/piezometer geological formation. and exacerbate problem.
— Easy to install. — Unable to provide information on
vertical variations in aquifer, e.g.
— No potential for vertical cross-
stratification.
contamination between sampling points.
— Incorrect placement of screen may lead
— Flexibility in well diameter.
to pollutants by-passing well.
— Sampler collection method not
— Concentrations represent means over
restricted.
screened length. Large purge volumes
may be required.
— With angled holes it is possible to get
beneath source and/or intercept vertical
fissures.
— A number of boreholes of different
depths may be installed in a small area to
establish a multiple borehole array
In addition to those described — Allows vertical variation to be — Can cause excessive ground
above, Multiple borehole investigated. disturbance in closely spaced arrays.
arrays have the following
— Simple design and operation. — Relatively expensive.
additional advantages and
disadvantages
— Potential for cross-contamination
between different levels eliminated.
— Diameter of well only limited by drilling
method.
— Array design can enable complete
vertical coverage.
Nested piezometers — Allow vertical variations to be — Poor installation and sealing can lead to
investigated. vertical leakage.
— Smaller diameters/internal diameters — Number of sampling points can be
require less purging. restricted by borehole diameter. Maximum
practical number is three per borehole.
— Sampling locations can be targeted.
— Smaller diameter of piezometers can
— Can allow variations in hydrogeological
restrict sampling options.
properties to be determined, e.g. head,
hydraulic conductivity. — In low hydraulic conductivity zones, low
storage volumes can make it difficult to
collect sufficient sample volume.
Multi-level samplers — Allow discrete sampling from specific — Installation difficult
points/horizons.
— Requires specialist knowledge and can
— Easier to operate than most other be expensive.
installations.
— Number of sampling points may be
— Minimal purge volumes. limited by borehole diameter.
— Minimal aquifer disturbance during — Poor installation may lead to cross-
sampling. contamination.
— Sampling method restricted to shallow
depth without incurring high costs.
4.3.3 Types of sampling equipment
4.3.3.1 General
A wide range of sampling devices is available for the sampling of groundwater from the saturated zone, including
portable devices which can be rapidly installed, operated and removed, and permanent installations for dedicated
sampling. The most commonly used systems are described below. A guide to their suitability for sampling different
chemical parameters is provided in Table 5. This table gives general guidance only and those methods indicated as
suitable may not be appropriate for all chemical parameters and in all environments. The user should consider
carefully the objectives of the study. In some cases it may be necessary to use more than one type of sampling
device.
Table 5 — A guide to the suitability of sampling methods for different groundwater parameters
a
Groundwater parameters
Sampling device a) b) c) d) e) f) g) h) i) j) k) l) m)
Depth sampler/bailer������� �
solidus (open)
Depth sampler/bailer ������������ �
solidus (closed) or
shut-in-sampler
Inertial pump ��� ��� � �
Bladder pump ������������ �
Gas-driven pump � ��� �
Gas-lift pump � ���
Submersible pump �� (�)(�) ��� (�) � (�)(�)(�)(�)
Suction (surface) ��� ��� � �
pumps
a
Groundwater parameters [� = suitable, (�) = limited suitability]
a) Electrical conductivity (�) h) Dissolved gases
b) pH i) Non-volatile organics
c) Alkalinity j) VOCs (volatile organic compounds)
d) Redox (E ) k) TOC (total organic carbon)
h
e) Major ions l) TOX (total organic halogen)
f) Trace metals m) Microbiological agents
g) Nitrates
NOTE This table is provided as a general guide only. The selection of an appropriate device will depend on the objectives of the study,
the performance and properties of the device and the environmental conditions. Under certain conditions a combination of sampling devices
should be considered, and some devices may not be appropriate for all determinands.
4.3.3.2 Depths samplers
Depth samplers are designed to sample groundwater at a specific depth within the borehole or piezometer. They
are available in a number of forms and are also commonly known as “grab samplers” or “bailers”.
The simplest device is a bottle or other sample container that is lowered down the borehole to below the water
surface. The sample container is allowed to fill and is then withdrawn from the borehole. This method only allows
samples of groundwater from the uppermost part of the saturated zone to be collected with any reliability. It should
only be used in exceptional circumstances for sampling groundwater.
An alternative device is one that consists of a tube (or cylinder) equipped with a check-valve at the lower end. This
device is lowered down the borehole to the required depth and then withdrawn with the sample. The action of
12 © ISO 2001 – All rights reserved
lowering and raising operates the check valve (open in downward travel and closed in upward travel) and enables
a sample from the required depth to be collected thereby allowing improved vertical resolution. More sophisticated
samplers are equipped with valves at both ends to improve sample integrity. Instead of a check valve, these valves
can be operated by electricity, gas pressure, vacuum or by mechanical messenger. For deeper boreholes, a
powered winch can be used for lowering the device. Sampler size should be chosen to enable adequate sample
volume and minimum disturbance of the borehole water.
4.3.3.3 Inertial pumps
Inertial pumps consist of a continuous length of tube equipped with a non-return valve at the lower
...
INTERNATIONAL ISO
STANDARD 5667-18
First edition
2001-04-15
Water quality — Sampling —
Part 18:
Guidance on sampling of groundwater at
contaminated sites
Qualité de l'eau — Échantillonnage —
Partie 18: Lignes directrices pour l'échantillonnage des eaux souterraines
sur des sites contaminés
Reference number
©
ISO 2001
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ii © ISO 2001 – All rights reserved
Contents Page
Foreword.iv
Introduction.vi
1 Scope .1
2 Terms and definitions .1
3 Sampling strategy and programme design.3
3.1 General.3
3.2 Selection of sampling point location.3
3.3 Groundwater parameter selection .5
3.4 Sampling frequency.5
4 Types of monitoring installation .6
4.1 General.6
4.2 Unsaturated zone monitoring.6
4.3 Saturated zone .9
4.4 Construction materials for sampling installations.14
5 Sampling procedures .15
5.1 Well cleaning and development .15
5.2 Purging .16
5.3 Trial pits.19
5.4 Sampling of free-phase contaminants (DNAPLs and LNAPLs) .19
5.5 Materials for sampling equipment .19
5.6 Prevention of contamination .20
5.7 Preservation, stabilization and transport of samples.20
6 Safety precautions.21
7 Sample identification and records.21
8 Quality assurance/quality control.21
Annex A (normative) Calculation of sampling frequency using a nomogram.22
Bibliography.23
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 5667 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 5667-18 was prepared by Technical Committee ISO/TC 147, Water quality,
Subcommittee SC 6, Sampling (general methods).
ISO 5667 consists of the following parts, under the general title Water quality — Sampling:
— Part 1: Guidance on the design of sampling programmes
— Part 2: Guidance on sampling techniques
— Part 3: Guidance on the preservation and handling of samples
— Part 4: Guidance on sampling from lakes, natural and man-made
— Part 5: Guidance on sampling of drinking water and water used for food and beverage processing
— Part 6: Guidance on sampling of rivers and streams
— Part 7: Guidance on sampling of water and streams in boiler plants
— Part 8: Guidance on sampling of wet deposition
— Part 9: Guidance on sampling from marine waters
— Part 10: Guidance on sampling of waste waters
— Part 11: Guidance on sampling of groundwaters
— Part 12: Guidance on sampling of bottom sediments
— Part 13: Guidance on sampling of sludges from sewage and water-treatment works
— Part 14: Guidance on quality assurance of environmental water sampling and handling
— Part 15: Guidance on preservation and handling of sludge and sediment samples
— Part 16: Guidance on biotesting of samples
iv © ISO 2001 – All rights reserved
— Part 17: Guidance on sampling of suspended sediments
— Part 18: Guidance on sampling of groundwater at contaminated sites
— Part 19: Guidance on sampling of sediments in the marine environment
Annex A forms a normative part of this part of ISO 5667.
Introduction
The guidance in this part of ISO 5667 can be used in parallel with other guidance on investigating contaminated or
potentially contaminated sites as any groundwater sampling from such sites is likely to form part of a much wider
investigation programme.
Groundwater sampling, in general, is carried out to determine whether or not the groundwater in or beneath a site
is contaminated. It can also be used to satisfy the following additional objectives:
� to establish whether any migration of contaminants, derived from the site, is occurring and characterize the
spatial extent of any contamination and its form;
� to determine the direction and rate of groundwater flow and contaminant migration;
� to provide data for undertaking a risk assessment;
� to provide an early warning system for the impact of contaminants on the quality of groundwater resources,
surface waters and other potential receptors in the vicinity of the site;
� to monitor the performance and effectiveness of remedial measures or facility design.
� to demonstrate compliance with licence conditions, or collect evidence for regulatory purposes.
� to assist in the selection of remedial measures and remediation process design.
This guidance includes sampling of groundwater from both the saturated (below water table) zone and the
unsaturated (above the water table) zone.
Development of a groundwater sampling programme depends on the purposes of the investigation. This part of
ISO 5667 provides guidance to inform the user of the necessary considerations when planning and undertaking
groundwater sampling from potentially contaminated sites. Examples of typical sites include:
� present or former industrial sites with a history of potentially contaminatory activities;
� waste disposal (landfill) sites;
� sites where natural and/or artificial processes have led to potential land and groundwater contamination;
� sites where products have been spilled e.g. as a result of transportation accidents.
The guidance contained in this part of ISO 5667 covers selection of sampling points, the selection of sampling
installations and devices, groundwater parameter selection and sampling frequency.
Prescriptive guidance on methods and applications is not possible. Therefore, this guidance provides information
on the most commonly applied, and available, techniques and lists their advantages, disadvantages and limitations
of use where these are known. When considering design of sampling strategies, the properties of the contaminant
source, pathways for migration and the receptors need to be considered.
vi © ISO 2001 – All rights reserved
INTERNATIONAL STANDARD ISO 5667-18:2001(E)
Water quality — Sampling —
Part 18:
Guidance on sampling of groundwater at contaminated sites
1 Scope
This part of ISO 5667 provides guidance on the sampling of groundwater at potentially contaminated sites. It is
applicable to situations where contamination of the subsurface could exist as a result of downward migration of
pollutants whose source is at the surface or just below it, and when the guidance provided in ISO 5667-11 is
inappropriate.
2 Terms and definitions
For the purposes of this part of ISO 5667, the following terms and definitions apply.
2.1
piezometer
device consisting of a tube or pipe with a porous element or perforated section (surrounded by a filter) on the lower
part (piezometer tip), that is installed and sealed into the ground at an appropriate level within the saturated zone
for the purposes of water level measurement, hydraulic pressure measurement and/or groundwater sampling
2.2
nested piezometers
group of piezometers installed within a single larger-diameter borehole
NOTE In general, each piezometer should be designed to allow sampling over a specific depth interval within the aquifer.
Piezometer tips are isolated from each other by installing a permanent impermeable seal between them.
2.3
multiple boreholes
group of individual boreholes or piezometers installed separately to form a monitoring network adequate for the
purposes of an investigation
2.4
multi-level sampler
single installation for sampling groundwater from discrete depths within the sub-surface
NOTE The device can be driven directly into the ground, installed in a pre-existing borehole or installed in a purpose-drilled
hole. When installed in a borehole, integral packers are used to isolate individual sample ports.
2.5
aquifer
geological formation (bed or stratum) of permeable rock or unconsolidated material (e.g. sand and gravels) capable
of yielding significant quantities of water
2.6
aquitard
geologic stratum of formation of low permeability that impedes the flow of water between two aquifers
2.7
saturated zone
part of an aquifer in which the pore spaces of the formation are completely water-saturated
2.8
unsaturated zone
part of an aquifer in which the pore spaces of the formation are not totally water-saturated
2.9
groundwater
water in the saturated zone and/or unsaturated zone of an underground geological formation or artificial deposit
such as made ground
2.10
perched water table
isolated body of groundwater, which is limited in lateral and vertical extent, located within the unsaturated zone
overlying a much more extensive groundwater body
2.11
matrix potential
combination of forces, independent of gravity, acting on soil water (water contained within the pores of a soil/rock
matrix) that exist as a result of the attraction of solid surfaces to water and the attraction of water molecules to each
other
NOTE Generally, the smaller the particle size, the higher the matrix potential.
2.12
check valve
mechanical valve which allows fluids to pass in only one direction
NOTE The pressure of fluids flowing through the valve in one direction has the effect of opening the valve and in the other
of closing it.
2.13
receptor
entity that is vulnerable to the adverse effect(s) of a hazardous substance or agent
EXAMPLES Human, animal, water, vegetation, building services, etc.
2.14
packer
device or material for temporarily isolating specified vertical sections within boreholes in which to perform
groundwater sampling from discrete zones or locations within the borehole or aquifer
2.15
hydraulic conductivity
property of a water-bearing formation that relates to its capacity to transmit water through its internal,
interconnected pathways
2.16
effective porosity
proportion of saturated openings or pores within a water-bearing formation which contribute directly to the flow of
groundwater
NOTE Effective porosity is represented as the ratio of this volume of pore space to the total volume of rock.
2.17
field capacity
maximum amount of water that a soil or rock can retain after gravitational water has drained away
2 © ISO 2001 – All rights reserved
2.18
dense non-aqueous phase liquids
DNAPL
organic compounds that have a low water solubility and a density greater than that of water
EXAMPLES Chlorinated hydrocarbons such as trichloroethane.
2.19
light non-aqueous phase liquid
LNAPL
organic compounds that have a low water solubility and a density less than that of water
EXAMPLE Petroleum products.
3 Sampling strategy and programme design
3.1 General
Groundwater sampling can be carried out as a single exercise or as part of a larger site or environmental
investigation. Regardless of the purpose, a rational approach should be taken that clearly defines the objectives,
determines the level of information needed and identifies the various stages of the investigation.
It should be noted that, normally, groundwater sampling from the saturated zone alone cannot fully assess the level
of contamination of a site in situations where an unsaturated zone of considerable thickness exists. The potential
consequence of ignoring the unsaturated zone is that the unsaturated zone and groundwater system could become
extensively contaminated before any tangible evidence of leakage or contamination is evident in samples collected
from below the water table.
3.2 Selection of sampling point location
The location of monitoring installations and the design of the network for sampling groundwater from (potentially)
contaminated sites should take account of the following:
� the hydrogeological setting of the investigation site;
� the past and future use(s) of the site;
� the purpose of the exercise;
� the likely contaminants;
� the extent of contamination.
All of these factors should be considered during the preliminary stages of the site investigation programme to
enable the most appropriate and effective sampling programme to be designed. This information can be obtained
by examining all available information held by site owners (or their agents), local, regional and national regulatory
agencies and other data holders. Table 1 provides an overview of the steps involved in planning an investigation
strategy and for sampling groundwater from sites that are potentially contaminated.
In addition to the scientific requirements, other factors can influence the location of sampling points. These include
practical, environmental and safety considerations such as the ground slope, proximity of underground services
(gas pipes, electricity cables etc) and overhead clearance for drilling rigs and other sampling devices.
To establish whether migration of contaminants is occurring and determining the direction and rate of this
migration, monitoring points should be located inside and outside the contaminated area and both up and down the
hydraulic gradient. A greater number of sample points should be positioned down gradient, both inside and outside
of any contaminant plume.
Where site analysis indicates that the site is underlain by complex geology or that contaminants with a broad range
of physical and chemical properties are likely to be present, an increased number of monitoring points should be
installed for adequate characterization of the contaminant distribution. In addition to investigating the lateral
variation caused by heterogeneity, the sampling strategy should also be designed to investigate any vertical
variations.
[9]
Table 1 — Procedural steps for sampling groundwater (adapted from )
Step
(with reference to other ISO Procedure Essential elements Notes
standards)
Investigation/monitoring Collation of available data Identify data sources Geological, geochemical and
strategy (ISO 5667-1) hydrogeological characterization
Desk study
Develop conceptual model
See 3.2, 3.3 and 3.4
Design borehole/sampling point
Reconnaissance survey
network and sampling programme
Facility installation Installation of monitoring points Borehole design, material Seeclause4
by drilling selection and installation technique
See 5.1
Well cleaning and development
Well inspection Hydrologic measurements Water level measurements Hydrogeological characterization
Hydraulic testing
Well purging Removal or isolation of stagnant Representative groundwater See 5.1
water
Verification of representative See 5.2
Determination of well-purging
groundwater
parameters (e.g. EC, pH,
temperature, redox potential)
Sample collection Sample collection by appropriate See 4.2 and 4.3
Filtration mechanism
Field determinations
Unfiltered Field filtered Field determination of sensitive
(ISO 5667-2, ISO 5667-11,
sample sample parameters, pH, electrical
ISO 5667-3)
conductivity, temperature, redox
potential, dissolved oxygen as
appropriate
Organics (all) Alkalinity/pH Head-space free samples See 5.4, 5.5 and 5.6
Dissolved gases Dissolved trace Minimal aeration or de-
metals for pressurization
specific
geochemical
information
Sensitive Sulfide and other Minimal air contact Blanks and spiked samples
inorganic sensitive should be prepared in accordance
species, e.g. inorganics with ISO 5667-14
nitrite,
ammonium,
iron(II)
Tracer metals for Major cations Sample preservation
mobile (colloidal) and
loads anions
Storage and transport of Minimal loss of sample integrity See 5.7, clauses 6, 7 and 8
samples (ISO 5667-3) prior to analysis
Care should be taken when identifying the prevailing flow regime as localized recharge to the subsurface can alter
the regional hydraulic gradient. This can result in groundwater flow and contaminant transportation in a direction
that is contrary to flow imposed by the regional gradient. Dense non-aqueous phase liquids (DNAPLs) can also
move in a different direction and at a different rate to that of groundwater because their chemical properties are
4 © ISO 2001 – All rights reserved
different to those of water. Their migration is also affected by the geological structure of the low permeability layer
underlying the saturated aquifer.
Light non-aqueous phase liquids (LNAPLs) also have different chemical properties to those of water and their
migration and distribution will be affected by the geological structure and chemical interactions within the
unsaturated zone and zone of water table fluctuation.
Where sampling is aimed at providing an early warning of the impact of contaminants on receptors, monitoring
points should be located between the contaminant source (and plume) and the potential receptors as well as within
the zone of contamination, e.g. at landfill sites, monitoring points should be established around the outside of, but
close to, the landfill.
Sample points within the zone of contamination and outside (both up and down the hydraulic gradient) should be
installed to measure performance and effectiveness of remediation and for demonstrating compliance to licence
conditions.
3.3 Groundwater parameter selection
The parameters selected for analysis should reflect the nature of the investigation and/or the former, current and
proposed future use of the site. In some cases, certain contaminants will be the subject of national regulations.
Focussing only on these, however, could be inadequate for providing the complete picture of contamination under
different geochemical and hydrogeological conditions. For example, where organic contaminants are susceptible to
degradation, the list of analytes should also include the degradation products, which in some cases can also be
hazardous. An example of this is the degradation of trichloroethylene (TCE), a DNAPL. One of its potential
degradation products is vinyl chloride, a relatively soluble and highly volatile compound.
Consideration should also be given to baseline or natural groundwater concentrations. Elevated concentrations can
already be present in the environment being investigated as a result of natural sources of contamination.
3.4 Sampling frequency
The frequency of sampling depends on the objectives of the investigation. If the investigation is designed to map an
established contaminant plume, a single-event sampling exercise may be used. In this case, sampling should be
completed as rapidly as possible to minimize the effects of temporal variation. Where the development of a plume
is to be monitored and/or the impacts on groundwater resources considered, the frequency should be based on the
prevailing hydrogeological and environmental conditions, the objectives of the study and the contaminants present.
Where monitoring is required to provide early warning, where there are compliance issues or for performance
assessment of remedial measures, in general, a recommended minimum sampling frequency is quarterly for most
chemical constituents (e.g. major ions, etc.) and monthly for those that are more mobile and reactive (e.g. VOCs
and dissolved gases).
However, where environmental conditions indicate that changes can occur more rapidly, more frequent sampling
should be carried out. In these cases, the exact frequency should be determined by examination of all influencing
natural and artificial factors. Examples of short-term influencing factors include tidal influences and localized rainfall
as well as ground disturbance caused by ground engineering activities.
One example of how sampling frequency can be determined using prevailing hydrogeological properties (including
hydraulic gradient, hydraulic conductivity and effective porosity) is shown in Figure 1. Relevant hydrogeological
[8]
parameters have been used to develop a nomogram, which has been adapted from to include the effects of
dispersion, for rapid estimation of sampling frequency. Dispersion has the effect of distributing the contaminant
both along the flow path and perpendicular to it. The modification applied leads to a 10 % increase in sample
frequency. A worked example is described in annex A.
Other environmental conditions can also influence the temporal distribution and concentration of contaminants in
groundwater and soil water and these should be considered during development of the sampling strategy.
Seasonal and more frequent variations in weather and climate can influence the rate of infiltration of contaminants
through the unsaturated zone. A rise in water table can also lead to the release (or re-release) of contaminants into
the groundwater and/or bring the contaminant source closer to the groundwater.
����
DN DN
F�� 0,1
����
��86 400Ki ��86 400Ki
[8]
Figure 1 — Nomogram for estimating sampling frequency (from )
4 Types of monitoring installation
4.1 General
Installations suitable for groundwater monitoring typically involve placement of access tubes for portable sampling
devices or burial of sensors or samplers in situ. These installations may be positioned within the saturated zone
(below the water table) or above it (unsaturated zone). In addition to sampling groundwater, installations below the
water table can be used to measure water levels and installations above the water table can measure soil gas and
soil moisture content.
4.2 Unsaturated zone monitoring
4.2.1 Introduction
Sampling techniques that are used for collection of groundwater from the unsaturated zone can be divided into two
types:
� solid sampling followed by extraction of groundwater (pore fluids);
� unsaturated pore fluid sampling.
4.2.2 Extraction from solid samples
4.2.2.1 General
The extraction of pore fluids from solid samples is the most widely used method for sampling groundwater in the
unsaturated zone. Collection of solid samples as part of this method can also allow useful geological information to
be obtained. There are two broad categories of solid sampling methods: hand-operated and power-operated.
Table 2 lists a range of suitable techniques that can be used for extracting solid samples for pore fluid collection.
6 © ISO 2001 – All rights reserved
The removal of solid samples from the ground is however a destructive form of sampling that, although necessary,
does not allow subsequent re-sampling from the same location. It therefore precludes taking samples at a later
date for analysis of trends.
Table 2 — A range of methods suitable for soil and rock sampling
Drilling
Method Soil/rock type Maximum depth Diameter range
a
fluid/flush
Trial pitting
Hand- All soil types and Maximum6m(but no Depends on depth of
powered unconsolidated rocks generally to 4 m) pit and soil/rock type
Tube Hand- Soils, clay and fine grained
sampling
powered unconsolidated geological Approximately 10 m no 25 mm to 75 mm
materials
Hand- Soils, clay and unconsolidated Approximately 5 m no 50 mm to 100 mm
Auger powered (e.g. geological materials
Approximately 30 m no 75 mm to 300 mm
“hollow stem”)
Cable tool
Soils, clay and unconsolidated no/yes
80 mto90m 150 mm to 300 mm
(e.g. “shell and auger”
geological materials water
drilling or “light
percussion” drilling)
Rotary yes
All types of geological
air, water,
>100 m 100 mm to 200 mm
(e.g. “direct” and “reverse
materials and made ground
mud, foam
rotary”)
etc.
a
Drilling fluids are required to lift drill cuttings, support the borehole whilst drilling, lubricate and cool the drill bit. Use of techniques where
drilling fluids are required may adversely affect sample quality.
4.2.2.2 Hand-operated samplers
These are typically tube-type or auger samplers. The tube samplers consist of a variable-length rod with hollow
sample chamber (of variable length and diameter). It is hammered into the ground to obtain a sample. Augers have
cutting bits at their lower end and a sample chamber (open at top and bottom) directly above. The sampler is
rotated into the ground by hand.
4.2.2.3 Power-operated sampling rigs
Standard drilling techniques can be used for sampling the unsaturated zone. However, drill rigs such as cable tool
and rotary units should not be used because of the need to use drilling fluids. Drilling fluids help to lift drill cuttings,
support the borehole whilst drilling and lubricate and cool the drill bit. The type of fluids include water, mud, foam
and air. However, the introduction of these fluids into the ground and their circulation, often under high pressure,
can potentially impact on the quality of the samples being collected or introduce extraneous contamination. The
use of air flush drilling should also be avoided where determinands include volatile organics and other sensitive
chemicals. Large diameter samples collected using these techniques can be sub-sampled to minimize the
problems of cross-contamination caused by drilling.
Solid- and hollow-stem augers can be used for sampling. For solid-stem auger methods, samples are collected
from the cuttings returned to the surface by the rotary action of the auger flights. This, however, can lead to
problems of cross-contamination and sample mixing. For hollow-stem methods, a central rod and cutting bit is
removed from within the auger column and replaced by a thin-walled sampler for collection of a relatively
undisturbed sample. Continuous-sampling tube samplers can also be used with hollow-stem auger drilling for
improved sample recovery.
Pore waters are then extracted from the recovered solid material by either centrifuging or mechanical squeezing as
soon as possible after collection. It is important that the groundwater extract be preserved in accordance with
ISO 5667-3 before analysis.
4.2.3 Pore-liquid sampling
4.2.3.1 General
Two types of method can be used to extract pore liquid directly from the subsurface, namely percolate soil water
samplers and vacuum soil water samplers. Both have advantages over solid sampling (see 5.2.2) in allowing
sequential sampling from fixed locations in the unsaturated zone to determine trends. The choice of sampler
depends on the objectives of the monitoring. Advantages and disadvantages of both types are shown in Table 3.
Table 3 — Advantages and disadvantages of pore liquid samplers
Sampler type Advantages Disadvantages
� Can be installed up to a depth of 15 m. � Excess pressure will damage samplers
without check-valves.
� Relatively easy to install. � Porous cup can become clogged
Vacuum samplers
and/or adsorb chemical constituents.
� Minimal ground disturbance required � Redox/pH changes can alter chemistry.
during installation.
� Multi-level installations are possible. � Vacuum/pressures required to extract
sample may affect sampling of volatile
compounds.
� Enables sampling of flow through � Difficult to install. Not always possible
macropores as well as interstitial water. in contaminated soils.
� Larger sample volumes possible. � Installation can alter natural flow.
� Less control over sample collection.
� Less potential for volatilization of
Percolate soil water samplers organic compounds.
� No need for continuous vacuum. � Pan-type samplers will only function
when field capacity is exceeded.
� Theuse of awicktodrawwaterinto
the sampler can lead to chromato-
graphic effects that in turn can lead to
collection of chemically unrepre-
sentative groundwater samples.
4.2.3.2 Vacuum samplers
These samplers, installed in the ground, use a vacuum (applied at the surface) to draw porewater into the sample
collector. They consist of a porous cup (or similar) on the end of a sampling tube that is installed into a borehole. In
their simplest form they have a limited maximum installation depth, but a number of modifications can be made to
improve sampling and increase the depth range over which the samplers can be used. These modifications include
incorporating a gas-driven sampling device (see 4.3.3.5) above the porous cup.
4.2.3.3 Percolate soil water samplers
These samplers, which include pan and wick types, rely on gravity and/or capillary action to intercept both matrix
water and water flowing along preferential pathways (e.g. fissures) in the unsaturated zone. Installation of the
samplers requires excavation of a trench and tunnel and the installation of the sampler in the roof of the tunnel to
intercept soil water. The sampler is constructed of a suitable nonporous inert material which may have a wick
incorporated to draw water (which is under tension) into the sampler as well as intercepting its downward
movement.
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4.3 Saturated zone monitoring
4.3.1 General
Any structure that provides a means of reaching the saturated zone can be used for groundwater sampling
purposes. The most commonly encountered means include supply boreholes, wells, and observation boreholes.
Trial pits and trenches can also be deep enough to reach groundwater where the water table is close to ground
level. In addition, discharging water at springs can be sampled.
Whilst existing wells can provide background information and evidence that contamination of groundwater has
occurred, the network available is unlikely to be adequate for characterizing the source and extent of
contamination. It is likely, therefore, that an additional monitoring installation will be required as part of a specific
site investigation.
Where perched groundwater is to be sampled, the methods described in this clause are generally applicable.
However, where shallow bodies of perched water are ephemeral, well sampling facilities should be combined with
suction (unsaturated zone) sampling devices.
When installing monitoring facilities in locations where perched groundwater is present, the techniques used for
investigation or installation of monitoring equipment should be chosen with care. To minimize the potential for
introducing artificial migration pathways (see 5.5), deep, open, fully penetrating screened boreholes should not be
installed.
The design of monitoring installations is also dependent on the nature of the contaminants being investigated.
Where free-phase contaminants such as DNAPLs and LNAPLs are present, the properties of these contaminants
and their potential distribution within the groundwater system should be considered during construction of
monitoring points.
4.3.2 Monitoring point installation
There are three major types of monitoring point installation for collection of groundwater samples (Figure 2). These
are:
a) single-screened/unscreened wells, boreholes or piezometers,
b) nested piezometers in a single borehole completion;
c) multi-level samplers.
The advantages and disadvantages of each are shown in Table 4.
Key
1 Open borehole 5 Sealing material 9 Well casing or piezometer pipe 13 Aquitard
2 Screened 6 Water table level 10 Gravel pack 14 Packer gas inflation line
borehole/piezometer
3 Nested piezometers 7 Casing pipe 11 Slotted well or piezometer screen 15 Packer
4 Borehole with packers 8 Open well or borehole 12 Piezometer 16 Isolated borehole section
Figure 2 — Major types of monitoring installation
10 © ISO 2001 – All rights reserved
Table 4 — Advantages and disadvantages of different monitoring point installations
Type Advantages Disadvantages
Single screened/unscreened
— Simple, can be designed for all types of —Canleadtoshort-circuitingofsystem
borehole/well/piezometer geological formation. and exacerbate problem.
— Easy to install. — Unable to provide information on
vertical variations in aquifer, e.g.
— No potential for vertical cross-
stratification.
contamination between sampling points.
— Incorrect placement of screen may lead
— Flexibility in well diameter.
to pollutants by-passing well.
— Sampler collection method not
— Concentrations represent means over
restricted.
screened length. Large purge volumes
may be required.
— With angled holes it is possible to get
beneath source and/or intercept vertical
fissures.
— A number of boreholes of different
depths may be installed in a small area to
establish a multiple borehole array
In addition to those described — Allows vertical variation to be — Can cause excessive ground
above, Multiple borehole investigated. disturbance in closely spaced arrays.
arrays have the following
— Simple design and operation. — Relatively expensive.
additional advantages and
disadvantages
— Potential for cross-contamination
between different levels eliminated.
— Diameter of well only limited by drilling
method.
— Array design can enable complete
vertical coverage.
Nested piezometers — Allow vertical variations to be — Poor installation and sealing can lead to
investigated. vertical leakage.
— Smaller diameters/internal diameters — Number of sampling points can be
require less purging. restricted by borehole diameter. Maximum
practical number is three per borehole.
— Sampling locations can be targeted.
— Smaller diameter of piezometers can
— Can allow variations in hydrogeological
restrict sampling options.
properties to be determined, e.g. head,
hydraulic conductivity. — In low hydraulic conductivity zones, low
storage volumes can make it difficult to
collect sufficient sample volume.
Multi-level samplers — Allow discrete sampling from specific — Installation difficult
points/horizons.
— Requires specialist knowledge and can
— Easier to operate than most other be expensive.
installations.
— Number of sampling points may be
— Minimal purge volumes. limited by borehole diameter.
— Minimal aquifer disturbance during — Poor installation may lead to cross-
sampling. contamination.
— Sampling method restricted to shallow
depth without incurring high costs.
4.3.3 Types of sampling equipment
4.3.3.1 General
A wide range of sampling devices is available for the sampling of groundwater from the saturated zone, including
portable devices which can be rapidly installed, operated and removed, and permanent installations for dedicated
sampling. The most commonly used systems are described below. A guide to their suitability for sampling different
chemical parameters is provided in Table 5. This table gives general guidance only and those methods indicated as
suitable may not be appropriate for all chemical parameters and in all environments. The user should consider
carefully the objectives of the study. In some cases it may be necessary to use more than one type of sampling
device.
Table 5 — A guide to the suitability of sampling methods for different groundwater parameters
a
Groundwater parameters
Sampling device a) b) c) d) e) f) g) h) i) j) k) l) m)
Depth sampler/bailer������� �
solidus (open)
Depth sampler/bailer ������������ �
solidus (closed) or
shut-in-sampler
Inertial pump ��� ��� � �
Bladder pump ������������ �
Gas-driven pump � ��� �
Gas-lift pump � ���
Submersible pump �� (�)(�) ��� (�) � (�)(�)(�)(�)
Suction (surface) ��� ��� � �
pumps
a
Groundwater parameters [� = suitable, (�) = limited suitability]
a) Electrical conductivity (�) h) Dissolved gases
b) pH i) Non-volatile organics
c) Alkalinity j) VOCs (volatile organic compounds)
d) Redox (E ) k) TOC (total organic carbon)
h
e) Major ions l) TOX (total organic halogen)
f) Trace metals m) Microbiological agents
g) Nitrates
NOTE This table is provided as a general guide only. The selection of an appropriate device will depend on the objectives of the study,
the performance and properties of the device and the environmental conditions. Under certain conditions a combination of sampling devices
should be considered, and some devices may not be appropriate for all determinands.
4.3.3.2 Depths samplers
Depth samplers are designed to sample groundwater at a specific depth within the borehole or piezometer. They
are available in a number of forms and are also commonly known as “grab samplers” or “bailers”.
The simplest device is a bottle or other sample container that is lowered down the borehole to below the water
surface. The sample container is allowed to fill and is then withdrawn from the borehole. This method only allows
samples of groundwater from the uppermost part of the saturated zone to be collected with any reliability. It should
only be used in exceptional circumstances for sampling groundwater.
An alternative device is one that consists of a tube (or cylinder) equipped with a check-valve at the lower end. This
device is lowered down the borehole to the required depth and then withdrawn with the sample. The action of
12 © ISO 2001 – All rights reserved
lowering and raising operates the check valve (open in downward travel and closed in upward travel) and enables
a sample from the required depth to be collected thereby allowing improved vertical resolution. More sophisticated
samplers are equipped with valves at both ends to improve sample integrity. Instead of a check valve, these valves
can be operated by electricity, gas pressure, vacuum or by mechanical messenger. For deeper boreholes, a
powered winch can be used for lowering the device. Sampler size should be chosen to enable adequate sample
volume and minimum disturbance of the borehole water.
4.3.3.3 Inertial pumps
Inertial pumps consist of a continuous length of tube equipped with a non-return valve at the lower end. The tube is
lowered down the borehole to the required depth and then operated by successively lifting and lowering the tube
over a short distance (from 0,3 to 0,5 m). The movement can be achieved manually or by a mechanical lifting
device.
During the lowering part of the “lift-lower” cycle, the non-return valve is opened and this allows water to enter the
tube. The water is then lifted upwards during the lifting stage of the cycle. Successive cycles continue to lift the
water upward to the surface. The volume of liquid lifted depends on the diameter of the sampler and the length of
lift. Although there is no theoretical limitation on the maximum depth from which a sample can be taken, practical
limitations effectively restrict this method to lifting groundwater from a maximum of 60 m.
Inertial pumps are very simple in design and easy to assemble and so are often installed as dedicated pumps.
4.3.3.4 Bladder pumps
A bladder pump comprises a sample chamber that has a check valve at its base (inlet), another check valve at the
outlet and a gas-inflatable bladder inside. The pump is lowered to the required depth and the bladder successively
inflated and deflated using compressed gas. The action of inflation and deflation successively fills the sampler and
lifts the sample towa
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