Diploma of Environmental Monitoring & Technology
Study module 4
Groundwater sampling & testing
MSS025006A
Groundwater sampling
& analysis
Completion Record
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GSA Study module 4
Groundwater sampling & testing
INTRODUCTION
Site inspection
Determining site locations
Routine site inspection during sampling
2
2
3
4
GAS TESTING
4
MEASURING LEVELS & INTERFACES
6
Initial measurements
The depth of the bore
PURGING THE BORE
What volume do we purge?
Purge methods
SAMPLE COLLECTION
Types of sample collected
Collecting the sample
6
6
9
9
10
12
12
12
FIELD TESTING
13
QA/QC
14
ASSESSMENT & SUBMISSION
15
Knowledge questions
Assessment & submission rules
References & resources
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Introduction
This section deals with the practical aspects of the actual sampling process on site. Field
technicians are required to perform a lot of tasks in the field over a wide area and usually
with a significant time constraint.
Site inspection
Initial site visits by field technicians usually take place after the job is set up by project
managers and engineers associated with the project management side of things, although
this may not always be the case.
The technician is usually briefed by the project team as to the specifics of the job, and then,
after any appropriate site inductions, a site visit will take place so that some level of
familiarisation can occur.
The site inspection is a critical stage in the process as it allows the technician to gather
information about travel, access issues, organising keys, the equipment required and many
other factors. From this, the technician can be prepared which saves valuable time.
Also, the site visit is an essential task for the technician as it allows them to perform their
own assessment as to the safety of the site, any constraints or drivers that will affect the
efficiency and safety of the work, and allow any questions regarding the work or the site to
be asked and answered by appropriate personnel associated with the company or the client.
Common tasks during a site inspection by field technicians can include;
◗
Determining any safety issues that affect technicians
◗
Assessing the quality or condition of the sample points
◗
Determining the level of transportation or equipment that is required
◗
Assessing timeframes for the specific tasks
◗
Taking photos to aid navigation or site identification
◗
‘Ground truthing’ the GIS/GPS data provided by the client or company
◗
Assessing viable communication techniques (i.e mobile phone, two-way radio or
satellite phone)
◗
Determine the quality, state and type of bores on site
And the list goes on. This information will eventually end up in documented in a sampling
plan which the company will use to confirm the project requirements with both the client
and the field technician alike.
The sampling plan becomes part of the field technician’s field book and travels with the
technician on every site visit.
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Determining site locations
The site locations have been discussed in this and previous modules. The technician will
have been given maps of any type (i.e. topographic, GIS vectors or even ‘mud maps’) which
show the location of the bores as in the figure below;
Figure 4.1 – Example of a GIS vector showing location of bores.
The technician will also need a road map, or a map of trails so that they can arrive at each
location (especially without the need to ‘bush bash’ which puts the cars, equipment,
technician and the environment at risk).
Determining a route to access all bores in the required timeframe will be based on a blend
of the following two key criteria;
◗
‘Clean-to-dirty’ sampling
◗
‘Furthest-to-closest sampling
Generally speaking, the QA/QC requirements will require the technician to sample the
background site(s) first (aka baseline, control or reference site) as these are the least
contaminated sites. The route will then proceed either in accordance with the degree of
contamination, or based on the bores which are the furthest away for the site entrance as it
will always be more efficient to end the sampling at the borehole closest to the point at
which you exit the site as you will get back to ‘base’ quicker.
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Routine site inspection during sampling
Once the technician is at the site, they should always take the time to examine the site for
change. This could come in the form of changes to the bore itself but also changes to the
environment surrounding the bore. Examples of site aspects that may change over time
include;
◗
Quality of trails and tracks leading to site
◗
Earth works such as lakes, dams or ponds
◗
Utilities provisions for electricity, gas, water or telecommunications
◗
Removal of natural bushland
◗
Erosion, subsidence or slippage of land
Site specific changes about the bore and its protections include damage or removal of;
◗
the monument or flush plate
◗
security measures such as padlocks or bolts
◗
concrete foundations or supports
◗
The borehole cap
◗
The bore piping above or below ground
Any changes to the conditions in the field will be written into the field copy of the SAP or
other field sheets and communicated to either the company project team or the client so
that they are informed of the changes. This can save time and costs later if potential
problems are alerted to and dealt with promptly.
Gas testing
Depending upon the level or stage of the investigation of the groundwater, as well as the
complexity and nature of the contaminant, it may be that gas measurements of the static
bore at time of sample may also be required. This task is usually performed by a PhotoIonisation Detector (PID) for methane or non-methane hydrocarbons but similar meters
may also be used for H2S or similar inorganic gases.
When the monument (or cover plate) is opened (or removed), the first sight a technician
might see is the bore cap (assuming ants haven’t made a bloody nest in it!). If the bore
requires gas testing, then a cap designed to keep gases in will be used. There are quite a few
types of these caps on the market, but all will have an adjustable rubber flange that allows
the cap to be tightened when in position and provide an (relatively) gas tight seal, and also
usually have some sort of valve on them to allow gas sampling or testing without
introducing air to the bore which would contaminate the sample.
The gas or vapour sampling or testing task is usually completed by attaching a tube from the
PID to a cap with a valve on it, or simply inserted down the bore with the cap off. If gas
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sampling or testing is required, it is usually done prior to the water sampling so that the gas
is not displaced
Figure 4.2 – Valved cap for the collection or testing of vapours from boreholes. Note the
black rubber ‘flange’ which expands (upon twisting) inside the bore creating the seal. Also
not the valve, protective cap and steel padlock ring.
The difference between gas sampling and testing is that testing is done on site by way of a
variety of equipment and sampling is done by transferring (by either pumping or vacuum
filling) a sample bag which may be made of a variety of plastics or even stainless steel (and
yes, you can make a bag out of stainless steel!).
Figure 4.3 – Example of a gas/vapour testing meter (this one measures VOCs).
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Measuring levels & interfaces
Initial measurements
Once the bore has been located and the environmental condition recorded, and gas testing
(if required) is complete, the depths of waters and interfaces will be determined and
recorded on field sheets. This process will typically involve three measures;
◗
Measuring the levels of the standing level water
◗
Measuring the depth of the bore
◗
The or organic/water interfaces may also be measured if it is required
The depth of the bore
The level and depth of water and the bore are critical in piezometric studies as the
information is used in determining the flow of the groundwater. The depth of the bore is
mainly incorporated into historical data to check if the depth has changed. If the depth of
the bore has changed, it could mean two things;
◗
Sediment build-up has occurred, or,
◗
damage to the core has occurred
Either scenario could have drastic effects on data quality objectives and must be recorded
and reported appropriately to your supervisor.
Depending on the site, a bore could easily have more than two ‘depths’. Consider a bore
that is used in a contaminated site assessment where the site consisted of both halogenated
and un-halogenated organics, and both organic types have contaminated the groundwater.
These liquids are termed Light Non Aqueous Phase Liquids (LNAPL) and Dense Non
Aqueous Phase Liquids (DNAPL). The aqueous phase is called water!
In this case, assuming groundwater is also present there will be four measurements from
the top of the bore (which is a zero survey point). These measures are as follows;
◗
The Air-LNAPL interface (because they float on top of water)
◗
The LNAPL-Water interface (for the same reason)
◗
The Water-DNAPL interface (halogenated oil is denser than water and sinks)
◗
The bottom of the bore
Most of the time though, there will only be the depth of the air-water interface and the
depth to the bottom of the bore. For most interface meters sold today, the minimum depth
of oil that can be detected is about 1-5 mm depending on the model.
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These depths need to be measured with a special device called an interface meter. This
consists of a tape measure that has a special probe at the end of it which is effectively a
combination of a refractometer and a conductivity meter.
Figure 4.4 – Demonstration of the three different liquid phases in a groundwater bore.
The refractometer uses Snells law to determine the change in the speed of light as it
changes from one interface to another, usually by measuring the change in the angle of
incident Infra-Red light transmitted through a prism built into the probe.
The conductivity meter measures the conductivity of the liquids by running a small current
through two or more electrodes positioned in the probe. Conductivity is a measure of the
dissolved ions (salts) and their ability to conduct electricity. It works on the inverse principle
to resistance. In this case, the conductivity measurement is not designed to be an absolute
quantitative measure, but a rather a relative, qualitative measure to differentiate between
the non-conductive organic phases and the conductive aqueous phase. The general principle
is as follows;
The top layer will be the LNAPL and have a low (near zero) conductivity, but a measureable
change in refraction from either air to oil, or oil to water, therefore, the refraction detector
will be active, and will be signalled to the technician by a tone or light. When the probe
enters water, the conductivity will be detected and takes precedence over the refraction
effect, and the tone or light behaviour changes. The reverse occurs (again) if the probe is
lowered into the DNAPL, with the appropriate change in signal.
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An example of an interface meter can be seen in the image below;
Figure 4.5 – Example of an interface meter for depth measurements in bores.
The technician will use the meter by lowering the probe into the well. When there is a
change in tone or light, the technician will raise and lower the probe to ensure they are
measuring the exact depth and then record the depth off the tape at the prescribed point
on the bore, usually the lip of the bore itself which is a benchmarked height determined by
surveyors.
This procedure occurs until all depths are measured and recorded. Once the task is
completed, the tape is wound up whilst being cleaned and decontaminated and the probe
head stored in the slot if provided.
Figure 4.6 – Example of one manufacturer’s instructions for positioning the meter to ensure a
correct reading of depth [source].
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Purging the bore
Purging literally means “to physically remove something”, and in this instance it means
physically removing groundwater.
Sampling (as you should know from previous studies) is actually a statistical phenomenon,
and the sample must be representative of the whole. The problem with groundwater is that
in between site visits and sampling events, the water that is in the bore can undergo an
innumerable amount of physical and chemical changes including;
◗
Chemical oxidation or reduction
◗
Changes in the relative amounts of constituents (either dilution or concentration)
◗
Settling (sedimentation) of particulates
◗
Separation or mixing of non-aqueous phases
◗
Gas phase changes as a result of physical or chemical disturbance
The list of possible changes could go on forever.
To ensure that a representative sample is obtained, it is absolutely essential that the bore
be purged in accordance with the standard method being applied.
What volume do we purge?
The Australian Standard stipulates that four to six times the bore volume should be purged
from the bore. Anecdotal evidence suggests that three bore volumes are adequate, but in
any case you will do as you are instructed by the SAP.
Calculating the bore volume
Consider a bore used for environmental monitoring of diffuse pollutants with the following
specifications;
ID
=
Aquifer depth =
51 mm
12 m
We calculate the volume using the following simple formula;
VL=π x r2 x h x 1000
Where;
r
=
Radius of the bore (in m)
h
=
Depth of the water column (in m)
So, in this case, we calculate the volume of the bore as;
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V
=
Pi x 0.025^2 x 12
=
24.5 L
Groundwater sampling & testing
Note that this just calculates the bore volume and not the volume to be purged, which is
found by multiplying the bore volume by the required volumes to be purged (which is
usually three, but can ranges from three to six).
Purge methods
Purging the bore can be achieved via many methods. The two most common methods
involve bailers and pumps. Either technique will ensure the removal of the appropriate
volume of water. Typical bailers can be seen in the figure below;
Figure 4.7 – Examples of plastic and stainless steel bailers used for purging and collecting
samples from ground water bores.
The bailer works using a very simple system based on gravity and the weight of the water.
Inside the bailer (which is hollow) there is a small ball. As the bailer is lowered into the
water, the ball is displaced from its seat at the bottom by the force of the water, and when
the bailer is raised, the ball falls to the bottom to take its seat, thereby trapping the water
sample in the body of the bailer.
When the technician removes the bailer from the bore, they use their finger or release
trigger (optional extra) to allow the sample of water to flow out of the bailer (or, if purging,
simply upend the bailer which allows for faster removal of water).
The second method for purging involves the use of a pump. This is an electrically (12V)
operated device that allows for rapid removal of water, the volume of which is measured by
either time (if the flow rate is accurate and constant) or by filling buckets of a known
volume. The pump is usually connected to the battery of a car or truck the technician is
using, or can have a separate power supply if required.
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The use of a pump can introduce some problems for the purging process. They are
notorious to decontaminate, and for sensitive jobs where decontamination is a potential
threat against quality, the pump is either not used, or is only used to purge and not sample.
The arguments around these problems can go on forever – the point is that you will be told
a technique, and your job is to use that technique you are told!
Figure 4.8 – Example of a groundwater bore pump (12V).
The pump has Teflon based (if permanently installed) or disposable polyethylene plastic
tubing connected to it as it enters the bore, once it is lowered to an appropriate depth, the
pump is switched on and measurements (time or volume) are taken to determine the
appropriate point to stop purging.
Figure 4.9 – Example of Teflon tubing being used to purge water from bore (into a makeshift
flow through cell). Thinner cable (right) is 12V supply.
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Sample collection
Once the bore has been purged of the appropriate volume of water, the sampling regime
can be started. The types of samples to be collected will be confirmed by the Sampling &
Analysis Plan, and each project will have a unique sampling regime, in fact each bore can
sometimes have a different array of sample types to collect.
Types of sample collected
The types of sample collected can vary enormously. Sometimes a standard single use plastic
or glass bottle is used, whereas more complex assessments require sampling for every type
of sample the laboratory can perform analysis on (up to about twenty bottles per site!).
Generally peaking the types of samples that can be collected include;
◗
Water samples for typical dissolved analytes (e.g. anions and cations)
◗
Water samples for volatile substance sampling (i.e. VOC’s)
◗
Water samples for dissolved gas sampling (e.g. H2S)
◗
Water samples for gas evolution analysis (i.e. O2, N2, Ar)
◗
Bore headspace gas analysis (H2S, CH4 by pumping into tedlar bags or similar)
After reading some of the references, you will soon discover that there are some very
specialised samples and tests that can be performed on the bores, but we can’t discuss
everything here!
Collecting the sample
The SAP will dictate the samples required, and also the other factors associated with sample
collection including the appropriate preservatives, storage and transport requirements.
Sample bottle preparation has been covered in detail in earlier fieldwork modules. Please
refer to http://www.cffet.net/env/cert4/fieldwork/fw-1 for learner resources.
Filling techniques
The sample bottles can be filled using a variety of techniques including direct filling from the
pump or bailer, or filling a decontaminated stainless steel vessel and filling the bottles from
there (although this is less common).
It all depends on what equipment you have been supplied with and trained to use, but
always remember that whatever the technique, you must avoid cross contamination at all
costs.
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Field testing
Field testing is effectively the same as for surface waters (see Fieldwork notes) with the only
significant difference being the use of a flow through cell to ensure the water sample has
limited contact with air prior to the measurement of the parameters. The figure below
shows a typical flow through cell setup;
Figure 4.10 – Example of a flow through cell. The probe head sits inside.
Another difference is the potential use of ‘down bore’ probes or sonds. These are the same
as those used in surface water analysis, but are designed for use in the narrower bore
environment, and are typically only 40 mm in diameter.
Figure 4.11 – A ‘down bore’ water quality sond (probe) and meter.
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QA/QC
Remember that every groundwater monitoring investigation is being done to establish data
which must be representative of the groundwater population and therefore trusted, and the
only way that this can be achieved is if quality assurances and controls are put in place and
followed rigorously by the field technicians.
The quality assurance will have been managed by the project management and staff, and
implemented through the SAP by ensuring that Good Laboratory practice (GLP) has been
followed and that the requisite laboratory and field blanks are being used. Quality control
on the other hand is the collection of the aforementioned blanks.
QA/QC has been extensively covered in the Environmental fieldwork notes. Please refer to
the relevant section of those notes for details.
Another aspect of QC that needs to be addressed is that of the temperature associated with
the transporting of the samples. The samples are stored and transported in cooler boxes
(Esky’s and the like) and usually have cooler bricks or blocks to control the temperature. The
problem with this is that the temperature is sometimes not monitored, but these days there
are several cheap ways of monitoring the temperature including the use of data-loggers.
Figure 4.12 – A splash proof Tinytag™ temperature logger.
When the lab sends the sample bottles to the sampler, one of them will usually include a
temperature logger. Once the cooler box is received by the lab with the samples, the logger
is removed and the data is transferred to the computer where it is analysed to see if the
samples were transported properly and in accordance with the statutory or recommended
transporting temperatures.
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Assessment & Submission
This section provides formative assessment of the theory. Answer all questions by typing
the answer in the boxes provided. Speak to your teacher if you are having technical
problems with this document.
Knowledge questions
◗
Type brief answers to each of the questions posed below.
◗
All answers should come from the theory found in this document only unless the
question specifies other.
◗
Marks shown next to the question should act as a guide as to the relative length or
complexity of your answer.
1. List three tasks you might perform when assessing a site. 1mk
Click here to enter text.
Assessor feedback
2. How is the sampling route determined for the bores on a site? 3mk
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Assessor feedback
3. List five general or specific aspects you might inspect at a bore site 1mk
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Assessor feedback
4. Under what circumstances would gas or vapour sampling or testing be required? 2mk
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Assessor feedback
5. What is the difference between LNAPL and DNAPL? 2mk
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Assessor feedback
6. How does an interface meter work used in depth measurements? 4mk
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Assessor feedback
7. Why do we purge the water from a bore? List three of the physical or chemical
characteristics that purging helps keep representative. 3mk
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Assessor feedback
8. How much water is meant to be purged from a bore? 1mk
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Assessor feedback
9. Assuming three volumes required, calculate the purge volume for a 51 mm bore with an
aquifer height of 5.2 meters. 3mk
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Click here to enter text.
Assessor feedback
10. What equipment can be used for purging? 2mk
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Assessor feedback
11. Why is a flow through cell considered the best method of testing water quality from a
bore? 2mk
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Assessor feedback
12. Why are temperature loggers used during transportation of the samples? 1mk
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Assessment & submission rules
◗
Attempt all questions and tasks
◗
Write answers in the text-fields provided
Submission
◗
Use the documents ‘Save As…’ function to save the document to your computer using
the file name format of;
Yourname-APM-SM1
◗
email the document back to your teacher
Penalties
◗
If this assessment task is received greater than seven (7) days after the due date, it may
not be considered for marking without justification.
Results
◗
Your submitted work will be returned to you within 3 weeks of submission by email fully
graded with feedback.
◗
You have the right to appeal your results within 3 weeks of receipt of the marked work.
Problems
If you are having study related or technical problems with this document, make sure you
contact your assessor at the earliest convenience to get the problem resolved. The contact
details can be found at;
◗
www.cffet.net/env/contacts
References & resources
Resources
◗
Video resource on bore installation can be found here.
◗
Free groundwater modelling software can be found here.
◗
National Centre for Groundwater Research & Training here.
◗
NSW office of Water drilling pages can be found here.
References
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Note that some of these resources might be available from your teacher or library
Bates, G. (2010). Environmental Law in Australia. Australia: LexisNexis-Butterworths.
Burden, F. E. (2002). Environmental Monitoring Handbook. McGraw-Hill Professional.
Corporation, B. A. (2013). Procedure for installation of ground monitoring wells. Brisbane:
Brisbane Airport Corporation.
DIPNR. (2004). Guideline for the preapration of Environmental Management Plans. Sydney:
DIPNR.
EPA, U. (2013). Design and Installation of Monitoring Wells. America: US EPA.
Grammeno, Gaby (Ed). (2009). Planning Occupational Health and Safety, 8th Ed. Melbourne:
McPherson's Printing Group.
National Uniform Drillers Licensing Committee. (2012). Minimum Construction Requirements
for Water bores in Australia. 3rd Ed. Canberra: National Water Commission.
Nielsen, D. M. (2007). The Essential Handbook of Groundwater Sampling. Boca Raton: CRC
Press.
Quevauviller, P. E. (2009). Water Quality Measurements Series: Groundwater Monitoring.
West Sussex: John Wiley & Sons.
StandardsAustralia. (2004). AS/NZS ISO 14001:2004 Environmental Management Systems:
Requirements with guidance for use. Australia: Standards Australia.
Sundaram, B. E. (2009). Groundwater Sampling and Analysis: A Field Guide. Canberra:
Commonwealth of Australia.
vanLoon, G. W. (2011). Environmental Chemistry: a global perspective. New York: Oxford
University Press.
Workplace Health and Safety Act 2011. (n.d.).
Workplace Health and Safety Regulation 2011. (n.d.).
Younger, P. (2007). Goundwater in the Environment. Carlton, Victoria, Australia: Blackwell
Publishing.
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